diff --git a/.gitattributes b/.gitattributes
index 42b01886c..683555503 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -5,4 +5,4 @@
 *.patch linguist-language=C++
 *.d.ts linguist-language=TypeScript
 
-src/zen/tests/*.js linguist-language=Test
+src/zen/tests/** linguist-language=C++
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 095a91134..5cd9cd53a 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -287,7 +287,7 @@ jobs:
     with:
       use-sccache: ${{ inputs.use-sccache }}
       build-version: ${{ needs.build-data.outputs.version }}
-      generate-gpo: true
+      generate-pgo: true
       profile-data-path-archive: zen-windows-profile-data-and-jarlog.zip
       release-branch: ${{ inputs.update_branch }}
       MOZ_BUILD_DATE: ${{needs.buildid.outputs.buildids}}
@@ -313,7 +313,7 @@ jobs:
     needs: [build-data, windows-step-2, start-self-host, buildid]
     with:
       build-version: ${{ needs.build-data.outputs.version }}
-      generate-gpo: false
+      generate-pgo: false
       release-branch: ${{ inputs.update_branch }}
       MOZ_BUILD_DATE: ${{needs.buildid.outputs.buildids}}
       use-sccache: ${{ inputs.use-sccache }}
@@ -331,15 +331,41 @@ jobs:
       MOZ_BUILD_DATE: ${{needs.buildid.outputs.buildids}}
       use-sccache: ${{ inputs.use-sccache }}
 
-  mac:
-    name: macOS build
+  mac-step-1:
+    name: macOS build step 1 (PGO build)
+    uses: ./.github/workflows/macos-release-build.yml
+    needs: [build-data, buildid]
+    permissions:
+      contents: write
+    secrets: inherit
+    with:
+      use-sccache: ${{ inputs.use-sccache }}
+      build-version: ${{ needs.build-data.outputs.version }}
+      generate-pgo: true
+      release-branch: ${{ inputs.update_branch }}
+      MOZ_BUILD_DATE: ${{needs.buildid.outputs.buildids}}
+
+  mac-step-2:
+    name: macOS build step 2 (Generate profile data)
+    uses: ./.github/workflows/macos-profile-build.yml
+    permissions:
+      contents: write
+    secrets: inherit
+    needs: [mac-step-1, build-data]
+    with:
+      build-version: ${{ needs.build-data.outputs.version }}
+      release-branch: ${{ inputs.update_branch }}
+
+  mac-step-3:
+    name: macOS build step 3 (build with profile data)
     uses: ./.github/workflows/macos-release-build.yml
     permissions:
       contents: write
     secrets: inherit
-    needs: [build-data, buildid]
+    needs: [build-data, mac-step-2, start-self-host, buildid]
     with:
       build-version: ${{ needs.build-data.outputs.version }}
+      generate-pgo: false
       release-branch: ${{ inputs.update_branch }}
       MOZ_BUILD_DATE: ${{needs.buildid.outputs.buildids}}
       use-sccache: ${{ inputs.use-sccache }}
@@ -350,7 +376,7 @@ jobs:
     permissions:
       contents: write
     secrets: inherit
-    needs: [build-data, mac]
+    needs: [build-data, mac-step-3]
     with:
       build-version: ${{ needs.build-data.outputs.version }}
       release-branch: ${{ inputs.update_branch }}
diff --git a/.github/workflows/linux-release-build.yml b/.github/workflows/linux-release-build.yml
index 5e5a32bff..baaea9dbf 100644
--- a/.github/workflows/linux-release-build.yml
+++ b/.github/workflows/linux-release-build.yml
@@ -105,6 +105,8 @@ jobs:
           SURFER_COMPAT: ${{ matrix.arch }}
           SURFER_CERT_PATCH_ISSUER: ${{ secrets.SURFER_CERT_PATCH_ISSUER }}
           SURFER_CERT_PATCH_NAME: ${{ secrets.SURFER_CERT_PATCH_NAME }}
+          SURFER_CERT_PATCH_NAME_PREV: ${{ secrets.SURFER_CERT_PATCH_NAME_PREV }}
+          SURFER_CERT_PATCH_ISSUER_PREV: ${{ secrets.SURFER_CERT_PATCH_ISSUER_PREV }}
         run: |
           . "$HOME/.cargo/env"
           npm run import
diff --git a/.github/workflows/macos-profile-build.yml b/.github/workflows/macos-profile-build.yml
new file mode 100644
index 000000000..43aa552b2
--- /dev/null
+++ b/.github/workflows/macos-profile-build.yml
@@ -0,0 +1,111 @@
+name: macOS PGO Builds
+
+permissions:
+  contents: read
+
+on:
+  workflow_call:
+    inputs:
+      build-version:
+        description: "The version to build"
+        required: true
+        type: string
+      release-branch:
+        description: "The branch to build"
+        required: true
+        type: string
+
+jobs:
+  macos-profile-build:
+    name: |
+      macOS Profile Build - ${{ matrix.arch }}
+    strategy:
+      fail-fast: false
+      matrix:
+        arch: [x86_64, aarch64]
+
+    runs-on: ${{ matrix.arch == 'x86_64' && 'macos-15-intel' || 'macos-26' }}
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version-file: ".nvmrc"
+
+      - name: Setup Python
+        uses: actions/setup-python@v5
+
+      - name: Setup Git
+        run: |
+          git config --global user.name "github-actions[bot]"
+          git config --global user.email "github-actions[bot]@users.noreply.github.com"
+
+      - name: Setup Rust
+        run: |
+          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain $(cat .rust-toolchain)
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Load Surfer CI setup
+        run: npm run surfer -- ci --brand ${{ inputs.release-branch }} --display-version ${{ inputs.build-version }}
+
+      - name: Download instrumented app
+        uses: actions/download-artifact@v4
+        with:
+          path: ~/instrumented
+          name: macos-pgo-stage1-${{ matrix.arch }}
+
+      - name: Download Firefox and dependencies
+        run: npm run download
+
+      - name: Import patches
+        env:
+          SURFER_NO_BRANDING_PATCH: true
+        run: |
+          . "$HOME/.cargo/env"
+          npm run import
+
+      - name: Bootstrap
+        run: |
+          cd engine
+          export SURFER_PLATFORM="darwin"
+          ./mach --no-interactive bootstrap --application-choice browser --exclude macos-sdk || true
+
+      - name: Extract instrumented app
+        run: |
+          set -ex
+          cd engine
+          ./mach python -m mozbuild.action.unpack_dmg \
+            "$HOME/instrumented/zen-macos-pgo-stage1-${{ matrix.arch }}.dmg" \
+            "$HOME/instrumented/app"
+          APP=$(find "$HOME/instrumented/app" -maxdepth 1 -name "*.app" -type d | head -1)
+          codesign --force --deep --sign - "$APP" || true
+
+      - name: Generate profile data
+        run: |
+          set -ex
+          export LLVM_PROFDATA="$HOME/.mozbuild/clang/bin/llvm-profdata"
+          export JARLOG_FILE=en-US.log
+          BINARY=$(find "$HOME/instrumented" -type f -path "*/Contents/MacOS/zen" | head -1)
+          test -n "$BINARY"
+          cd engine
+          ./mach python ../scripts/download_pgo_extended_corpus.py
+          ./mach python build/pgo/profileserver.py --binary "$BINARY" --extended-corpus ./pgo-extended-corpus
+
+      - name: Move profile data
+        run: |
+          mv engine/merged.profdata merged.profdata
+          mv engine/en-US.log en-US.log
+
+      - name: Upload artifacts
+        uses: actions/upload-artifact@v4
+        with:
+          retention-days: 1
+          path: |
+            merged.profdata
+            en-US.log
+          name: macos-profdata-${{ matrix.arch }}
diff --git a/.github/workflows/macos-release-build.yml b/.github/workflows/macos-release-build.yml
index b3395f0f1..0423c566e 100644
--- a/.github/workflows/macos-release-build.yml
+++ b/.github/workflows/macos-release-build.yml
@@ -1,10 +1,15 @@
 name: macOS Release Build
+
 permissions:
   contents: read
 
 on:
   workflow_call:
     inputs:
+      generate-pgo:
+        required: true
+        type: boolean
+        default: false
       build-version:
         description: "The version to build"
         required: true
@@ -26,17 +31,22 @@ on:
 jobs:
   mac-build:
     name: Build macOS - ${{ matrix.arch }}
-    runs-on: ${{ (inputs.release-branch == 'release') && 'blacksmith-6vcpu-macos-latest' || 'macos-26' }}
-
-    strategy:
-      fail-fast: false
-      matrix:
-        arch: [x86_64, aarch64]
+    runs-on: 'blacksmith-8vcpu-ubuntu-2404'
     env:
       SCCACHE_GHA_ENABLED: ${{ inputs.use-sccache && 'true' || 'false' }}
       CARGO_TERM_COLOR: always
       CARGO_INCREMENTAL: 0
+    strategy:
+      fail-fast: false
+      matrix:
+        arch: [x86_64, aarch64]
+
     steps:
+      - name: Free Disk Space (Ubuntu)
+        uses: jlumbroso/free-disk-space@main
+        with:
+          tool-cache: false
+
       - name: Checkout repository
         uses: actions/checkout@v4
         with:
@@ -44,16 +54,10 @@ jobs:
           token: ${{ secrets.DEPLOY_KEY }}
 
       - name: Setup Node.js
-        uses: actions/setup-node@v4
+        uses: useblacksmith/setup-node@v5
         with:
           node-version-file: ".nvmrc"
 
-      - name: Log SDK versions
-        run: |
-          ls /Library/Developer/CommandLineTools/SDKs/
-          xcrun --show-sdk-version
-          xcrun --show-sdk-path
-
       - name: Run sccache-cache
         uses: mozilla-actions/sccache-action@main
         if: ${{ inputs.use-sccache }}
@@ -67,157 +71,158 @@ jobs:
             core.exportVariable('ACTIONS_CACHE_URL', process.env['ACTIONS_CACHE_URL'])
             core.exportVariable('ACTIONS_RUNTIME_TOKEN', process.env['ACTIONS_RUNTIME_TOKEN'])
 
-      - name: Setup Python
-        uses: actions/setup-python@v5
-        # note: This will use the version defined in '.python-version' by default
-
       - name: Setup Git
         run: |
           git config --global user.name "github-actions[bot]"
           git config --global user.email "github-actions[bot]@users.noreply.github.com"
 
-      - name: Install system dependencies
+      - name: Install dependencies
         run: |
-          brew update
-          brew install cairo gnu-tar mercurial
-          sudo pip install setuptools
+          npm ci
+          sudo apt-get update
+          sudo apt-get install -y python3 python3-pip zstd yasm nasm build-essential libgtk2.0-dev libpython3-dev m4 uuid libasound2-dev libcurl4-openssl-dev libdbus-1-dev libdrm-dev libdbus-glib-1-dev libgtk-3-dev libpulse-dev libx11-xcb-dev libxt-dev xvfb --fix-missing
 
-          brew uninstall --ignore-dependencies python3.12 -f
+      - name: Load Surfer CI setup
+        run: npm run surfer -- ci --brand ${{ inputs.release-branch }} --display-version ${{ inputs.build-version }}
 
-          export PATH="$(python3 -m site --user-base)/bin":$PATH
-          python3 -m pip install --user mercurial
+      - name: Download Firefox and dependencies
+        run: npm run download
 
-          rm '/usr/local/bin/2to3-3.11' '/usr/local/bin/2to3-3.12' '/usr/local/bin/2to3'
-          rm '/usr/local/bin/idle3.11' '/usr/local/bin/idle3.12' '/usr/local/bin/idle3'
-          rm '/usr/local/bin/pydoc3.11' '/usr/local/bin/pydoc3.12' '/usr/local/bin/pydoc3'
-          rm '/usr/local/bin/python3.11' '/usr/local/bin/python3.12' '/usr/local/bin/python3'
-          rm '/usr/local/bin/python3.11-config' '/usr/local/bin/python3.12-config' '/usr/local/bin/python3-config'
+      - name: mac-cross Cache
+        env:
+          SEGMENT_DOWNLOAD_TIMEOUT_MINS: 5
+        id: cache-mac-cross
+        uses: useblacksmith/cache@v5
+        with:
+          path: ${HOME}/mac-cross
+          key: mac-cross
 
-          brew install watchman
+      - name: Setup for macOS (cctools and DMG tools)
+        if: steps.cache-mac-cross.outputs.cache-hit != 'true'
+        run: |
+          set -ex
+          mkdir -p ~/mac-cross
+          cd engine/
+          ./mach artifact toolchain --from-build linux64-cctools-port linux64-libdmg linux64-hfsplus
+          mv cctools dmg hfsplus ~/mac-cross/
+          ls ~/mac-cross/cctools/bin/x86_64-apple-darwin-ld ~/mac-cross/cctools/bin/aarch64-apple-darwin-ld ~/mac-cross/dmg/dmg ~/mac-cross/hfsplus/newfs_hfs
 
+      - name: Setup Rust
+        run: |
           curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain $(cat .rust-toolchain)
           source $HOME/.cargo/env
-
           if test "${{ matrix.arch }}" = "aarch64"; then
             rustup target add aarch64-apple-darwin
           else
             rustup target add x86_64-apple-darwin
           fi
 
-      - name: Force usage of gnu-tar
-        run: |
-          echo 'export PATH="/usr/local/opt/gnu-tar/libexec/gnubin:$PATH"' >> ~/.bash_profile
-          echo 'export PATH="/usr/local/opt/gnu-tar/libexec/gnubin:$PATH"' >> ~/.zsh
-          source ~/.bash_profile
-
-      - name: Install dependencies
-        run: |
-          npm ci
-
-      - name: Load surfer CI setup
-        run: npm run surfer -- ci --brand ${{ inputs.release-branch }} --display-version ${{ inputs.build-version }}
-
-      - name: Download Firefox source and dependencies
-        run: npm run download
-
       - name: Import
         env:
           SURFER_COMPAT: ${{ matrix.arch }}
           SURFER_CERT_PATCH_ISSUER: ${{ secrets.SURFER_CERT_PATCH_ISSUER }}
           SURFER_CERT_PATCH_NAME: ${{ secrets.SURFER_CERT_PATCH_NAME }}
-        run: npm run import
+          SURFER_CERT_PATCH_NAME_PREV: ${{ secrets.SURFER_CERT_PATCH_NAME_PREV }}
+          SURFER_CERT_PATCH_ISSUER_PREV: ${{ secrets.SURFER_CERT_PATCH_ISSUER_PREV }}
+          SURFER_PLATFORM: darwin
+        run: |
+          . "$HOME/.cargo/env"
+          npm run import -- --verbose
 
       - name: Bootstrap
         run: |
-          cd engine
+          set -x
           export SURFER_PLATFORM="darwin"
-          export PATH="$(python3 -m site --user-base)/bin":$PATH
-          # Always exist with 0, even if bootstrap fails
-          ./mach --no-interactive bootstrap --application-choice browser --exclude macos-sdk || true
-          cd ..
+          npm run bootstrap
 
       - name: Build language packs
         run: sh scripts/download-language-packs.sh
 
-      - name: Build Zen (PGO stage 1 - generate)
+      - name: Download artifact (if use profdata)
+        uses: actions/download-artifact@v4
+        if: ${{ !inputs.generate-pgo }}
+        with:
+          path: ~/artifact
+          name: macos-profdata-${{ matrix.arch }}
+
+      - name: Show artifact info
+        if: ${{ !inputs.generate-pgo }}
+        run: |
+          ls ~/artifact
+          ls ~/artifact/en-US.log
+          ls ~/artifact/merged.profdata
+
+      - name: Build
         env:
           SURFER_COMPAT: ${{ matrix.arch }}
           ZEN_RELEASE_BRANCH: ${{ inputs.release-branch }}
-          ZEN_GA_GENERATE_PROFILE: 1
           ZEN_SAFEBROWSING_API_KEY: ${{ secrets.ZEN_SAFEBROWSING_API_KEY }}
           ZEN_MOZILLA_API_KEY: ${{ secrets.ZEN_MOZILLA_API_KEY }}
           ZEN_GOOGLE_LOCATION_SERVICE_API_KEY: ${{ secrets.ZEN_GOOGLE_LOCATION_SERVICE_API_KEY }}
-        run: |
-          export SURFER_PLATFORM="darwin"
-          if [[ -n ${{ inputs.MOZ_BUILD_DATE }} ]];then
-            export MOZ_BUILD_DATE=${{ inputs.MOZ_BUILD_DATE }}
-          fi
-          bash .github/workflows/src/release-build.sh
-
-      - name: Generate PGO profile data
-        env:
-          SURFER_COMPAT: ${{ matrix.arch }}
         run: |
           set -x
-          export LLVM_PROFDATA="$HOME/.mozbuild/clang/bin/llvm-profdata"
-          export JARLOG_FILE=en-US.log
-          mkdir -p "$HOME/artifact"
-          cd engine
-          ./mach python ../scripts/download_pgo_extended_corpus.py
-          ./mach package
-          ./mach python build/pgo/profileserver.py --extended-corpus ./pgo-extended-corpus
-          mv merged.profdata "$HOME/artifact/merged.profdata"
-          mv en-US.log "$HOME/artifact/en-US.log"
-
-      - name: Build Zen
-        env:
-          SURFER_COMPAT: ${{ matrix.arch }}
-          ZEN_RELEASE_BRANCH: ${{ inputs.release-branch }}
-          ZEN_SAFEBROWSING_API_KEY: ${{ secrets.ZEN_SAFEBROWSING_API_KEY }}
-          ZEN_MOZILLA_API_KEY: ${{ secrets.ZEN_MOZILLA_API_KEY }}
-          ZEN_GOOGLE_LOCATION_SERVICE_API_KEY: ${{ secrets.ZEN_GOOGLE_LOCATION_SERVICE_API_KEY }}
-        run: |
           export SURFER_PLATFORM="darwin"
+          export ZEN_CROSS_COMPILING=1
+          if test ${{ inputs.generate-pgo }} = true; then
+            export ZEN_GA_GENERATE_PROFILE=1
+          fi
           if [[ -n ${{ inputs.MOZ_BUILD_DATE }} ]];then
             export MOZ_BUILD_DATE=${{ inputs.MOZ_BUILD_DATE }}
           fi
           bash .github/workflows/src/release-build.sh
 
+      - name: Package instrumented app (PGO stage 1)
+        if: ${{ inputs.generate-pgo }}
+        env:
+          SURFER_COMPAT: ${{ matrix.arch }}
+          ZEN_RELEASE: 1
+          SURFER_PLATFORM: darwin
+          ZEN_CROSS_COMPILING: 1
+          ZEN_GA_GENERATE_PROFILE: 1
+        run: |
+          set -ex
+          cd engine
+          ./mach package
+          mv obj-${{ matrix.arch }}-apple-darwin/dist/*.dmg "$GITHUB_WORKSPACE/zen-macos-pgo-stage1-${{ matrix.arch }}.dmg"
+
+      - name: Upload artifact (PGO stage 1)
+        uses: actions/upload-artifact@v4
+        if: ${{ inputs.generate-pgo }}
+        with:
+          retention-days: 2
+          name: macos-pgo-stage1-${{ matrix.arch }}
+          path: ./zen-macos-pgo-stage1-${{ matrix.arch }}.dmg
+
       - name: Package
+        if: ${{ !inputs.generate-pgo }}
         env:
           SURFER_COMPAT: ${{ matrix.arch }}
           ZEN_GA_DISABLE_PGO: true
         run: |
+          set -x
           export SURFER_PLATFORM="darwin"
+          export ZEN_CROSS_COMPILING=1
           export ZEN_RELEASE=1
           npm run package
 
       - name: Rename artifacts
+        if: ${{ !inputs.generate-pgo }}
         run: |
-          echo "Tarballing DMG"
           set -ex
           mv ./dist/*.dmg ./zen-${{ matrix.arch }}-apple-darwin-dist.dmg
-          mv ./engine/obj-${{ matrix.arch }}-apple-darwin/dist/host/bin/mar ./zen-macos-host-mar
           mv ./engine/obj-${{ matrix.arch }}-apple-darwin/dist/bin/platform.ini ./platform.ini
 
       - name: Upload dist dmg
         uses: actions/upload-artifact@v4
+        if: ${{ !inputs.generate-pgo }}
         with:
           retention-days: 1
           name: zen-${{ matrix.arch }}-apple-darwin-dist.dmg
           path: ./zen-${{ matrix.arch }}-apple-darwin-dist.dmg
 
-      - name: Upload host mar
-        uses: actions/upload-artifact@v4
-        if: matrix.arch == 'aarch64'
-        with:
-          retention-days: 1
-          name: zen-macos-host-mar
-          path: ./zen-macos-host-mar
-
       - name: Upload platform.ini
         uses: actions/upload-artifact@v4
-        if: matrix.arch == 'x86_64'
+        if: ${{ !inputs.generate-pgo && matrix.arch == 'x86_64' }}
         with:
           retention-days: 1
           name: platform.ini
diff --git a/.github/workflows/macos-universal-release-build.yml b/.github/workflows/macos-universal-release-build.yml
index 762a92a6d..101d39738 100644
--- a/.github/workflows/macos-universal-release-build.yml
+++ b/.github/workflows/macos-universal-release-build.yml
@@ -99,6 +99,16 @@ jobs:
           cd engine
           ./mach configure
 
+      - name: Build host mar tool
+        run: |
+          set -ex
+          cd engine
+          echo "ac_add_options --enable-project=tools/update-packaging" > mar-mozconfig
+          echo "mk_add_options MOZ_OBJDIR=@TOPSRCDIR@/obj-mar-tools" >> mar-mozconfig
+          MOZCONFIG=$PWD/mar-mozconfig ./mach build -v
+          cp obj-mar-tools/dist/host/bin/mar ../zen-macos-host-mar
+          rm -rf obj-mar-tools mar-mozconfig
+
       - name: Download x86_64 DMG from artifacts
         uses: actions/download-artifact@v4
         with:
@@ -213,11 +223,6 @@ jobs:
             --wait
           xcrun stapler staple "zen.macos-universal.dmg"
 
-      - name: Download host mar
-        uses: actions/download-artifact@v4
-        with:
-          name: zen-macos-host-mar
-
       - name: Upload build artifact
         uses: actions/upload-artifact@v4
         with:
diff --git a/.github/workflows/windows-release-build.yml b/.github/workflows/windows-release-build.yml
index 56bd977a0..e27d50589 100644
--- a/.github/workflows/windows-release-build.yml
+++ b/.github/workflows/windows-release-build.yml
@@ -6,7 +6,7 @@ permissions:
 on:
   workflow_call:
     inputs:
-      generate-gpo:
+      generate-pgo:
         required: true
         type: boolean
         default: false
@@ -35,7 +35,7 @@ jobs:
   windows-build:
     name: Build Windows - ${{ matrix.arch }}
     # aarch64 does not need full 16x, and we also dont use full LTO when generating GPO
-    runs-on: ${{ (inputs.release-branch == 'release' && !inputs.generate-gpo && matrix.arch == 'x86_64') && 'self-hosted' || 'blacksmith-8vcpu-ubuntu-2404' }}
+    runs-on: ${{ (inputs.release-branch == 'release' && !inputs.generate-pgo && matrix.arch == 'x86_64') && 'self-hosted' || 'blacksmith-8vcpu-ubuntu-2404' }}
     env:
       SCCACHE_GHA_ENABLED: ${{ inputs.use-sccache && 'true' || 'false' }}
       CARGO_TERM_COLOR: always
@@ -48,7 +48,7 @@ jobs:
     steps:
       - name: Free Disk Space (Ubuntu)
         uses: jlumbroso/free-disk-space@main
-        if: ${{ !(inputs.generate-gpo && matrix.arch == 'aarch64') }}
+        if: ${{ !(inputs.generate-pgo && matrix.arch == 'aarch64') }}
         with:
           tool-cache: false
 
@@ -91,7 +91,7 @@ jobs:
         run: npm run surfer -- ci --brand ${{ inputs.release-branch }} --display-version ${{ inputs.build-version }}
 
       - name: Download Firefox and dependencies
-        if: ${{ !(inputs.generate-gpo && matrix.arch == 'aarch64') }}
+        if: ${{ !(inputs.generate-pgo && matrix.arch == 'aarch64') }}
         run: npm run download
 
       - name: win-cross Cache
@@ -104,7 +104,7 @@ jobs:
           key: win-cross
 
       - name: Setup for Windows
-        if: steps.cache-win-cross.outputs.cache-hit != 'true' && !(inputs.generate-gpo && matrix.arch == 'aarch64')
+        if: steps.cache-win-cross.outputs.cache-hit != 'true' && !(inputs.generate-pgo && matrix.arch == 'aarch64')
         run: |
           set -x
           mkdir -p ~/win-cross
@@ -154,24 +154,26 @@ jobs:
             zlib1g-dev \
             aria2
           echo Setup wine
-          aria2c "https://firefox-ci-tc.services.mozilla.com/api/queue/v1/task/dQz_aHy8Rl-Lt0xf2WlrMw/artifacts/public/build/wine.tar.zst" -o wine.tar.zst
+          aria2c "https://firefox-ci-tc.services.mozilla.com/api/index/v1/task/gecko.cache.level-3.toolchains.v3.linux64-wine.latest/artifacts/public/build/wine.tar.zst" -o wine.tar.zst
           tar --zstd -xf wine.tar.zst -C ~/win-cross
           rm wine.tar.zst
           echo Setup Visual Studio
           ./mach python --virtualenv build taskcluster/scripts/misc/get_vs.py build/vs/vs2026.yaml ~/win-cross/vs2026
 
       - name: Import
-        if: ${{ !(inputs.generate-gpo && matrix.arch == 'aarch64') }}
+        if: ${{ !(inputs.generate-pgo && matrix.arch == 'aarch64') }}
         env:
           SURFER_COMPAT: ${{ matrix.arch }}
           SURFER_CERT_PATCH_ISSUER: ${{ secrets.SURFER_CERT_PATCH_ISSUER }}
           SURFER_CERT_PATCH_NAME: ${{ secrets.SURFER_CERT_PATCH_NAME }}
+          SURFER_CERT_PATCH_NAME_PREV: ${{ secrets.SURFER_CERT_PATCH_NAME_PREV }}
+          SURFER_CERT_PATCH_ISSUER_PREV: ${{ secrets.SURFER_CERT_PATCH_ISSUER_PREV }}
         run: |
           . "$HOME/.cargo/env"
           npm run import -- --verbose
 
       - name: Bootstrap
-        if: ${{ !(inputs.generate-gpo && matrix.arch == 'aarch64') }}
+        if: ${{ !(inputs.generate-pgo && matrix.arch == 'aarch64') }}
         run: |
           set -x
           cd engine/
@@ -189,7 +191,7 @@ jobs:
           ls ~/win-cross/vs2026 || true
 
       - name: Setup Rust
-        if: ${{ !(inputs.generate-gpo && matrix.arch == 'aarch64') }}
+        if: ${{ !(inputs.generate-pgo && matrix.arch == 'aarch64') }}
         run: |
           curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain $(cat .rust-toolchain)
           source $HOME/.cargo/env
@@ -208,18 +210,18 @@ jobs:
           echo "export MOZ_WINDOWS_RS_DIR=$(pwd)/windows-$WINDOWS_RS_VERSION" >> ../configs/common/mozconfig
 
       - name: Build language packs
-        if: ${{ !(inputs.generate-gpo && matrix.arch == 'aarch64') }}
+        if: ${{ !(inputs.generate-pgo && matrix.arch == 'aarch64') }}
         run: sh scripts/download-language-packs.sh
 
       - name: Download artifact (if use profdata)
         uses: actions/download-artifact@v4
-        if: ${{ !inputs.generate-gpo && matrix.arch == 'x86_64' }}
+        if: ${{ !inputs.generate-pgo && matrix.arch == 'x86_64' }}
         with:
           path: ~/artifact
           name: windows-profdata-${{ matrix.arch == 'aarch64' && 'arm64' || matrix.arch }}
 
       - name: Show artifact info
-        if: ${{ !inputs.generate-gpo && matrix.arch == 'x86_64' }}
+        if: ${{ !inputs.generate-pgo && matrix.arch == 'x86_64' }}
         run: |
           ls ~/artifact
           ls ~/artifact/en-US.log
@@ -228,7 +230,7 @@ jobs:
           chmod +x ~/artifact/merged.profdata
 
       - name: Build
-        if: ${{ !(inputs.generate-gpo && matrix.arch == 'aarch64') }}
+        if: ${{ !(inputs.generate-pgo && matrix.arch == 'aarch64') }}
         env:
           SURFER_COMPAT: ${{ matrix.arch }}
           ZEN_RELEASE_BRANCH: ${{ inputs.release-branch }}
@@ -241,7 +243,7 @@ jobs:
           dos2unix configs/windows/mozconfig
           export SURFER_PLATFORM="win32"
           export ZEN_CROSS_COMPILING=1
-          if test ${{ inputs.generate-gpo }} = true; then
+          if test ${{ inputs.generate-pgo }} = true; then
             export ZEN_GA_GENERATE_PROFILE=1
           fi
           if [[ -n ${{ inputs.MOZ_BUILD_DATE }} ]];then
@@ -250,7 +252,7 @@ jobs:
           bash .github/workflows/src/release-build.sh
 
       - name: Package
-        if: ${{ !(inputs.generate-gpo && matrix.arch == 'aarch64') }}
+        if: ${{ !(inputs.generate-pgo && matrix.arch == 'aarch64') }}
         env:
           SURFER_COMPAT: ${{ matrix.arch }}
           ZEN_GA_DISABLE_PGO: true
@@ -265,13 +267,13 @@ jobs:
           ls .
 
       - name: Move package for PGO upload
-        if: ${{ inputs.generate-gpo && matrix.arch == 'x86_64' }}
+        if: ${{ inputs.generate-pgo && matrix.arch == 'x86_64' }}
         run: |
           set -x
           mv ./zen.win64.zip ./zen.win64-pgo-stage-1.zip
 
       - name: Rename artifacts
-        if: ${{ !inputs.generate-gpo }}
+        if: ${{ !inputs.generate-pgo }}
         run: |
           mv ./zen.win64.zip zen.win-${{ matrix.arch == 'aarch64' && 'arm64' || matrix.arch }}.zip
           mv ./dist/output.mar windows${{ matrix.arch == 'aarch64' && '-arm64' || '' }}.mar
@@ -279,14 +281,14 @@ jobs:
 
       - name: Upload artifact (PGO)
         uses: actions/upload-artifact@v4
-        if: ${{ inputs.generate-gpo && matrix.arch == 'x86_64' }}
+        if: ${{ inputs.generate-pgo && matrix.arch == 'x86_64' }}
         with:
           retention-days: 2
           name: ${{ matrix.arch == 'aarch64' && 'arm64' || matrix.arch }}-${{ inputs.profile-data-path-archive }}
           path: ./zen.win64-pgo-stage-1.zip
 
       - name: Remove unnecessary files from obj
-        if: ${{ !inputs.generate-gpo }}
+        if: ${{ !inputs.generate-pgo }}
         run: |
           set -x
           mkdir obj-${{ matrix.arch }}-pc-windows-msvc/
@@ -301,7 +303,7 @@ jobs:
           cp -r --no-dereference engine/obj-${{ matrix.arch }}-pc-windows-msvc/* obj-${{ matrix.arch }}-pc-windows-msvc/ || true
 
       - name: Upload dist object
-        if: ${{ !inputs.generate-gpo }}
+        if: ${{ !inputs.generate-pgo }}
         uses: actions/upload-artifact@v4
         with:
           retention-days: 2
@@ -309,7 +311,7 @@ jobs:
           path: obj-${{ matrix.arch }}-pc-windows-msvc
 
       - name: Upload artifact (if Twilight branch, installer)
-        if: ${{ inputs.release-branch == 'twilight' && !inputs.generate-gpo }}
+        if: ${{ inputs.release-branch == 'twilight' && !inputs.generate-pgo }}
         uses: actions/upload-artifact@v4
         with:
           retention-days: 5
@@ -317,7 +319,7 @@ jobs:
           path: ./zen.installer${{ matrix.arch == 'aarch64' && '-arm64' || '' }}.exe
 
       - name: Upload artifact (if Twilight branch, .mar)
-        if: ${{ inputs.release-branch == 'twilight' && !inputs.generate-gpo }}
+        if: ${{ inputs.release-branch == 'twilight' && !inputs.generate-pgo }}
         uses: actions/upload-artifact@v4
         with:
           retention-days: 5
@@ -325,7 +327,7 @@ jobs:
           path: ./windows${{ matrix.arch == 'aarch64' && '-arm64' || '' }}.mar
 
       - name: Upload artifact (if Twilight branch, update manifests)
-        if: ${{ inputs.release-branch == 'twilight' && !inputs.generate-gpo }}
+        if: ${{ inputs.release-branch == 'twilight' && !inputs.generate-pgo }}
         uses: actions/upload-artifact@v4
         with:
           retention-days: 5
diff --git a/README.md b/README.md
index f3252b7ba..434e58315 100644
--- a/README.md
+++ b/README.md
@@ -34,8 +34,8 @@ Zen is a firefox-based browser with the aim of pushing your productivity to a ne
 
 ### Firefox Versions
 
-- [`Release`](https://zen-browser.app/download) - Is currently built using Firefox version `153.0.3`! 🚀
-- [`Twilight`](https://zen-browser.app/download?twilight) - Is currently built using Firefox version `RC 153.0.3`!
+- [`Release`](https://zen-browser.app/download) - Is currently built using Firefox version `154.0.1`!
+- [`Twilight`](https://zen-browser.app/download?twilight) - Is currently built using Firefox version `RC 154.0.1`!
 
 ### Contributing
 
diff --git a/build/firefox-cache/l10n-last-commit-hash b/build/firefox-cache/l10n-last-commit-hash
index 18180d8e5..2dbfec531 100644
--- a/build/firefox-cache/l10n-last-commit-hash
+++ b/build/firefox-cache/l10n-last-commit-hash
@@ -1 +1 @@
-8a0a534248f80d8c53a8997f24683521c3a50ebc
\ No newline at end of file
+bf4b57fd7fe94054457be7018e8e7beaf754c520
\ No newline at end of file
diff --git a/build/windows/sign.ps1 b/build/windows/sign.ps1
index 83f2ff040..4e0f345da 100644
--- a/build/windows/sign.ps1
+++ b/build/windows/sign.ps1
@@ -3,8 +3,6 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 param(
-    [string][Parameter(Mandatory=$true)]$SignIdentity,
-    [string][Parameter(Mandatory=$true)]$SignIdentityIssuer,
     [string][Parameter(Mandatory=$true)]$GithubRunId
 )
 
@@ -24,11 +22,15 @@ mkdir windsign-temp -ErrorAction SilentlyContinue
 #    echo "Downloaded git objects repo to"
 #} -Verbose -ArgumentList $PWD -Debug
 
+$token = gh auth token
+
 $env:SURFER_MOZCONFIG_ONLY="1"
 $env:SURFER_SIGNING_MODE=""
 
-$env:SURFER_CERT_PATCH_ISSUER=$SignIdentityIssuer
-$env:SURFER_CERT_PATCH_NAME=$SignIdentity
+get-content "$PSScriptRoot/../.env" | foreach {
+    $name, $value = $_.split('=')
+    set-content env:\$name $value
+}
 
 Start-Job -Name "DownloadGitl10n" -ScriptBlock {
     param($PWD)
@@ -46,7 +48,6 @@ npm run build
 
 echo "Downloading artifacts info"
 $artifactsInfo=gh api repos/zen-browser/desktop/actions/runs/$GithubRunId/artifacts
-$token = gh auth token
 
 function New-TemporaryDirectory {
     $tmp = [System.IO.Path]::GetTempPath() # Not $env:TEMP, see https://stackoverflow.com/a/946017
@@ -215,20 +216,12 @@ SignAndPackage x86_64
 $files = Get-ChildItem .\windsign-temp\windows-x64-signed-x86_64, .\windsign-temp\windows-x64-signed-arm64 -Recurse -Include *.exe
 signtool.exe sign /n "$SignIdentity" /t http://time.certum.pl/ /fd sha256 /v $files
 
-# Compress each signed bundle into a single gzip tarball (`-C <dir> .` so it has
-# no top-level directory) and upload it as a release asset on the windows-binaries
-# repo, keyed to this build's run id. Release assets keep the bundles out of git
-# (they were too large to commit) while still living in the windows-binaries repo.
-# The gated release job downloads and expands these from that repo's releases.
 $binariesRepo = "zen-browser/windows-binaries"
 $stagingTag = "windows-signed-$GithubRunId"
 echo "Ensuring staging release $stagingTag exists on $binariesRepo"
-gh release view $stagingTag --repo $binariesRepo *> $null
+gh release create $stagingTag --repo $binariesRepo --prerelease --title "Windows signed bundles ($GithubRunId)" --notes "Signed Windows bundles for run $GithubRunId, consumed by the release workflow. Safe to delete."
 if ($LASTEXITCODE -ne 0) {
-    gh release create $stagingTag --repo $binariesRepo --prerelease --title "Windows signed bundles ($GithubRunId)" --notes "Signed Windows bundles for run $GithubRunId, consumed by the release workflow. Safe to delete."
-    if ($LASTEXITCODE -ne 0) {
-        throw "Failed to create staging release $stagingTag on $binariesRepo"
-    }
+    throw "Failed to create staging release $stagingTag on $binariesRepo"
 }
 
 foreach ($name in @("x86_64", "arm64")) {
diff --git a/configs/branding/release/firefox.icns b/configs/branding/release/firefox.icns
new file mode 100644
index 000000000..87ec9d8b5
Binary files /dev/null and b/configs/branding/release/firefox.icns differ
diff --git a/configs/branding/twilight/firefox.icns b/configs/branding/twilight/firefox.icns
new file mode 100644
index 000000000..2698a9fad
Binary files /dev/null and b/configs/branding/twilight/firefox.icns differ
diff --git a/configs/common/mozconfig b/configs/common/mozconfig
index 22b8e95c5..2adf9d0eb 100644
--- a/configs/common/mozconfig
+++ b/configs/common/mozconfig
@@ -91,11 +91,6 @@ if test "$ZEN_RELEASE"; then
   export MOZ_PACKAGE_JSSHELL=1
 
   ac_add_options --disable-crashreporter
-
-  # Experimental flag, enabled only on nightly for Firefox.
-  # Should bring in some nice performance improvements, 
-  # but may cause stability issues.
-  ac_add_options --enable-replace-malloc
 fi
 
 ac_add_options --enable-jxl
diff --git a/configs/macos/mozconfig b/configs/macos/mozconfig
index c838095cd..889f89e74 100644
--- a/configs/macos/mozconfig
+++ b/configs/macos/mozconfig
@@ -7,7 +7,21 @@ unset MOZ_STDCXX_COMPAT
 ac_add_options --disable-dmd
 ac_add_options --enable-eme=widevine
 
-if test "$ZEN_RELEASE"; then
+if test "$ZEN_CROSS_COMPILING"; then
+  ZEN_MAC_CROSS="$HOME/mac-cross"
+
+  mk_add_options "export PATH=$ZEN_MAC_CROSS/cctools/bin:$PATH"
+  mk_add_options "export LD_LIBRARY_PATH=$HOME/.mozbuild/clang/lib:$LD_LIBRARY_PATH"
+
+  export MKFSHFS=$ZEN_MAC_CROSS/hfsplus/newfs_hfs
+  export DMG_TOOL=$ZEN_MAC_CROSS/dmg/dmg
+  export HFS_TOOL=$ZEN_MAC_CROSS/dmg/hfsplus
+
+  if test "$ZEN_RELEASE"; then
+    export MOZ_LD64_KNOWN_GOOD=1
+    ac_add_options --enable-linker=ld64
+  fi
+elif test "$ZEN_RELEASE"; then
   ALLOWED_SDKS="26.5 26.4"
   for SDK in $ALLOWED_SDKS; do
     if [ -d "/Library/Developer/CommandLineTools/SDKs/MacOSX${SDK}.sdk" ]; then
@@ -52,13 +66,3 @@ else
     export CXXFLAGS="$CXXFLAGS -mcpu=apple-m1"
   fi
 fi
-
-# Keep using ld64 on PGO/LTO builds because of performance regressions when using lld.
-# Mozilla sets "MOZ_LD64_KNOWN_GOOD" to true when they do automated builds with PGO/LTO on macOS.
-# See https://searchfox.org/firefox-main/rev/e61d59b5c9a651fd7bf28043f87c0dc669833496/build/moz.configure/lto-pgo.configure#261
-# export MOZ_LD64_KNOWN_GOOD=1
-# ac_add_options --enable-linker=ld64
-# 
-# if test "$ZEN_RELEASE"; then
-#   mk_add_options MOZ_MAKE_FLAGS="-j4"
-# fi
diff --git a/locales/ar/browser/browser/preferences/zen-preferences.ftl b/locales/ar/browser/browser/preferences/zen-preferences.ftl
index a7b2acc92..ab555b85f 100644
--- a/locales/ar/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/ar/browser/browser/preferences/zen-preferences.ftl
@@ -8,17 +8,17 @@ category-zen-looks =
 zen-warning-language = تغيير اللغة الافتراضية يمكن أن يجعل من الأسهل على المواقع أن تتبعك.
 zen-vertical-tabs-layout-header = تصميم المتصفح
 zen-vertical-tabs-layout-description = اختر التخطيط الذي يناسبك بشكل أفضل
-zen-layout-single-toolbar = Single toolbar
-zen-layout-multiple-toolbar = Multiple toolbars
-zen-layout-collapsed-toolbar = Collapsed toolbar
-sync-currently-syncing-workspaces = Other Workspaces
+zen-layout-single-toolbar = الشريط الجانبي فقط
+zen-layout-multiple-toolbar = الشريط الجانبي و العلوي
+zen-layout-collapsed-toolbar = الشريط الجانبي مطوي
+sync-currently-syncing-workspaces = مساحات العمل
 sync-engine-workspaces = 
-    .label = Other Workspaces
+    .label = مساحات العمل
     .tooltiptext = مزامنة مساحات العمل الخاصة بك عبر الأجهزة
     .accesskey = W
 zen-glance-title = لمحة
 zen-glance-header = الإعدادات العامة للنظرة
-zen-glance-description = احصل على نظرة عامة سريعة للروابط الخاصة بك دون فتحها في علامة تبويب جديدة
+zen-glance-description = احصل على نظرة عامة سريعة لروابطك دون فتحها في علامة تبويب جديدة
 zen-glance-trigger-label = طريقة المشغل
 zen-glance-enabled = 
     .label = تمكين اللمحة
@@ -27,17 +27,21 @@ zen-glance-trigger-ctrl-click =
 zen-glance-trigger-alt-click = 
     .label = Alt + انقر
 zen-glance-trigger-shift-click = 
-    .label = المناوبة + انقر
+    .label = Shift + اضغط
 zen-glance-trigger-meta-click = 
     .label = Meta (Command) + اضغط
 zen-look-and-feel-compact-view-header = إظهار في العرض المدمج
-zen-look-and-feel-compact-view-description = فقط إظهار أشرطة الأدوات التي تستخدمها!
+zen-look-and-feel-compact-view-description = فقط إظهار الأشرطة المستعملة!
 zen-look-and-feel-compact-view-enabled = 
     .label = تمكين الوضع المدمج لـ { -brand-short-name }
 zen-look-and-feel-compact-view-top-toolbar = 
     .label = إخفاء شريط الأدوات العلوي أيضا في الوضع المدمج
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = اجعل شريط الأدوات منبثقا عند التبديل أو فتح علامات تبويب جديدة في الوضع المدمج
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Allow dragging the window from web pages
 pane-zen-tabs-title = إدارة علامة التبويب
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -106,9 +110,9 @@ zen-theme-disable-all-enabled =
     .title = تعطيل جميع السمات
 zen-theme-disable-all-disabled = 
     .title = تمكين جميع السمات
-zen-theme-marketplace-description = البحث عن الثيمات وتثبيتها من المتجر.
+zen-theme-marketplace-description = ابحث عن مودات وتثبيتها من المتجر.
 zen-theme-marketplace-remove-button = 
-    .label = إزالة السمة
+    .label = إزالة المود
 zen-theme-marketplace-check-for-updates-button = 
     .label = التحقق من وجود تحديثات
 zen-theme-marketplace-import-button = 
@@ -125,7 +129,7 @@ zen-theme-marketplace-toggle-enabled-button =
     .title = تعطيل السمة
 zen-theme-marketplace-toggle-disabled-button = 
     .title = تمكين السمة
-zen-theme-marketplace-remove-confirmation = هل أنت متأكد من أنك تريد إزالة هذا الوضع؟
+zen-theme-marketplace-remove-confirmation = هل أنت متأكد من أنك تريد إزالة هذا المود؟
 zen-theme-marketplace-close-modal = أغلق
 zen-theme-marketplace-theme-header-title = 
     .title = محدد CSS: { $name }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = عرض معلومات الصفحة
 zen-find-shortcut = البحث في الصفحة
 zen-search-find-again-shortcut = البحث مرة أخرى
 zen-search-find-again-shortcut-prev = البحث عن السابق
-zen-search-find-again-shortcut-2 = ابحث مرة أخرى (بديل)
+zen-search-find-again-shortcut-alt = Find Again (Alt)
+zen-search-find-again-shortcut-prev-alt = Find Previous (Alt)
 zen-bookmark-this-page-shortcut = ضع إشارة مرجعية على هذه الصفحة
 zen-bookmark-show-library-shortcut = إظهار مكتبة الإشارات المرجعية
 zen-key-stop = إيقاف التحميل
@@ -281,7 +286,7 @@ zen-workspace-shortcut-switch-9 = التبديل إلى مساحة العمل 9
 zen-workspace-shortcut-switch-10 = التبديل إلى مساحة العمل 10
 zen-workspace-shortcut-forward = إلى الأمام فضاء العمل
 zen-workspace-shortcut-backward = مساحة العمل الخلفية
-zen-workspace-shortcut-create = Create New Workspace
+zen-workspace-shortcut-create = إنشاء مساحة عمل جديدة
 zen-sidebar-shortcut-toggle = تبديل عرض شريط العرض
 zen-pinned-tab-shortcut-reset = إعادة تعيين علامة التبويب المثبتة إلى عنوان URL المثبت
 zen-split-view-shortcut-grid = تبديل عرض تقسيم الشبكة
@@ -319,4 +324,4 @@ zen-devtools-toggle-accessibility-shortcut = قلب إمكانية الوصول
 zen-close-all-unpinned-tabs-shortcut = إغلاق جميع علامات التبويب الغير مثبتة
 zen-new-unsynced-window-shortcut = New Unsynced Window
 zen-duplicate-tab-shortcut = Duplicate Tab
-zen-key-find-selection = Find Selection
+zen-key-find-selection = البحث عن الاختيار
diff --git a/locales/ar/browser/browser/zen-boosts.ftl b/locales/ar/browser/browser/zen-boosts.ftl
index eb42026a7..2aad2425c 100644
--- a/locales/ar/browser/browser/zen-boosts.ftl
+++ b/locales/ar/browser/browser/zen-boosts.ftl
@@ -11,7 +11,7 @@ zen-boost-edit-reset =
 zen-boost-edit-delete = 
     .label = Delete Boost
 zen-boost-size = Size
-zen-boost-case = Case
+zen-boost-case = الحالة
 zen-boost-zap = Zap
 zen-boost-code = Code
 zen-boost-back = Back
@@ -48,9 +48,9 @@ zen-unzap-tooltip =
        *[other] { $elementCount } elements zapped
     }
 zen-boost-save = 
-    .label = Export Boost
+    .label = تصدير التعزيز
 zen-boost-load = 
-    .label = Import Boost
+    .label = استيراد التعزيز
 zen-panel-ui-boosts-exported-message = Boost exported!
 zen-site-data-boosts = Boosts
 zen-site-data-create-boost = 
diff --git a/locales/ar/browser/browser/zen-command-palette.ftl b/locales/ar/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..c8af413e2
--- /dev/null
+++ b/locales/ar/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Toggle Compact Mode
+zen-action-open-theme-picker = Open Theme Picker
+zen-action-new-split-view = New Split View
+zen-action-new-folder = New Folder
+zen-action-copy-current-url = Copy Current URL
+zen-action-settings = Settings
+zen-action-open-private-window = Open Private Window
+zen-action-open-new-window = Open New Window
+zen-action-new-blank-window = New Blank Window
+zen-action-pin-tab = Pin Tab
+zen-action-unpin-tab = Unpin Tab
+zen-action-open-space-routing = Open Space Routing
+zen-action-new-boost = New Boost
+zen-action-next-space = Next Space
+zen-action-previous-space = Previous Space
+zen-action-close-tab = Close Tab
+zen-action-reload-tab = Reload Tab
+zen-action-reload-tab-without-cache = Reload Tab Without Cache
+zen-action-next-tab = Next Tab
+zen-action-previous-tab = Previous Tab
+zen-action-capture-screenshot = Capture Screenshot
+zen-action-toggle-tabs-on-right = Toggle Tabs on right
+zen-action-add-to-essentials = Add to Essentials
+zen-action-remove-from-essentials = Remove from Essentials
+zen-action-find-in-page = Find in Page
+zen-action-manage-extensions = Manage Extensions
+zen-action-switch-to-automatic-appearance = Switch to Automatic Appearance
+zen-action-switch-to-light-mode = Switch to Light Mode
+zen-action-switch-to-dark-mode = Switch to Dark Mode
+zen-action-print = Print
+zen-action-focus-on = Focus on
+zen-action-extension = Extension
diff --git a/locales/ar/browser/browser/zen-general.ftl b/locales/ar/browser/browser/zen-general.ftl
index 688288f1b..8146c46a5 100644
--- a/locales/ar/browser/browser/zen-general.ftl
+++ b/locales/ar/browser/browser/zen-general.ftl
@@ -18,15 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max } مملؤة
 tab-context-zen-remove-essential = 
     .label = إزالة من الأساسيات
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] استبدل الرابط الأساسي بـ
-           *[false]
-                استبدل الرابط المثبت بـ
-                الحالي
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Replace with Current URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Edit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = تغيير الاسم...
 tab-context-zen-edit-icon = 
@@ -49,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = تأكيد
 zen-pinned-tab-replaced = Pinned tab URL has been replaced with the current URL.
+zen-pinned-tab-url-edited = Pinned tab URL has been updated!
+zen-pinned-tab-url-invalid = That doesn't look like a valid URL.
+zen-pinned-tab-edit-url-title = Edit Pinned URL
+zen-pinned-tab-edit-url-label = Enter the URL this pinned tab should point to:
 zen-tabs-renamed = تم تغيير اسم التبويب بنجاح!
 zen-background-tab-opened-toast = تم فتح علامة تبويب خلفية جديدة!
 zen-workspace-renamed-toast = تم تغيير اسم مساحة العمل بنجاح!
@@ -67,6 +75,8 @@ zen-icons-picker-emoji =
     .label = ايموجي
 zen-icons-picker-svg = 
     .label = الأيقونات
+zen-emojis-picker-search = 
+    .placeholder = Search emojis
 urlbar-search-mode-zen_actions = الإجراءات
 zen-site-data-settings = الاعدادات
 zen-generic-manage = إدارة
@@ -118,6 +128,9 @@ zen-sidebar-notification-updated-heading = اكتمل التحديث!
 zen-sidebar-notification-updated-label = ما الجديد في { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = عرض ملاحظات الإصدار
+zen-sidebar-notification-donate-label = Support { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donate to the project
 zen-sidebar-notification-restart-safe-mode-label = شيء معطل؟
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = إعادة التشغيل في الوضع الآمن
diff --git a/locales/ar/browser/browser/zen-space-routing.ftl b/locales/ar/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..d757144bb
--- /dev/null
+++ b/locales/ar/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Space Routing Settings
+zen-space-routing-rulepanel-placeholder = Routes let you choose where specific sites open inside Zen. For example, you can route YouTube links to always open inside your Personal space.
+zen-space-routing-dialog-title = Space Routing Settings
+zen-space-routing-external-default = Default route for external links
+zen-space-routing-new-route = New Route
+zen-space-routing-open-in-space = Open in Space
+zen-space-routing-most-recent-space = Most recent Space
+zen-space-routing-close-button = 
+    .aria-label = Close
+    .tooltiptext = Close
+zen-space-routing-contains = 
+    .label = Contains
+zen-space-routing-equal-to = 
+    .label = Is Equal To
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Open In
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/ar/browser/browser/zen-workspaces.ftl b/locales/ar/browser/browser/zen-workspaces.ftl
index cb267ae7e..c1a4932a3 100644
--- a/locales/ar/browser/browser/zen-workspaces.ftl
+++ b/locales/ar/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = الملف الشخصي
     .tooltiptext = تستخدم الملفات الشخصية لفصل ملفات تعريف الارتباط وبيانات الموقع بين المساحات.
 zen-workspace-creation-header = إنشاء مساحة
 zen-workspace-creation-label = يتم استخدام المساحات لتنظيم علامات التبويب والجلسات الخاصة بك.
+zen-workspace-default-profile = Default
 zen-workspaces-delete-workspace-title = حذف المساحة؟
 zen-workspaces-delete-workspace-body = هل أنت متأكد من رغبتك في حذف { $name }؟ لا يمكن التراجع عن هذا الإجراء.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/bg/browser/browser/preferences/zen-preferences.ftl b/locales/bg/browser/browser/preferences/zen-preferences.ftl
index a43ff8124..a6677a1da 100644
--- a/locales/bg/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/bg/browser/browser/preferences/zen-preferences.ftl
@@ -2,26 +2,26 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-pane-zen-looks-title = Look and Feel
+pane-zen-looks-title = Визия и усещане
 category-zen-looks = 
     .tooltiptext = { pane-zen-looks-title }
-zen-warning-language = Changing the default language could make it easier for Websites to track you.
-zen-vertical-tabs-layout-header = Browser Layout
-zen-vertical-tabs-layout-description = Choose the layout that suits you best
-zen-layout-single-toolbar = Only Sidebar
-zen-layout-multiple-toolbar = Sidebar and Top Toolbar
-zen-layout-collapsed-toolbar = Collapsed Sidebar
-sync-currently-syncing-workspaces = Workspaces
+zen-warning-language = Промяната на езика по подразбиране може да улесни уебсайтовете да те проследяват.
+zen-vertical-tabs-layout-header = Оформление на браузъра
+zen-vertical-tabs-layout-description = Избери оформлението, което най-добре ви подхожда
+zen-layout-single-toolbar = Само странична лента
+zen-layout-multiple-toolbar = Странична лента и горна лента с инструменти
+zen-layout-collapsed-toolbar = Скрита странична лента
+sync-currently-syncing-workspaces = Работни пространства
 sync-engine-workspaces = 
-    .label = Workspaces
-    .tooltiptext = Sync your workspaces across devices
+    .label = Работни пространства
+    .tooltiptext = Синхронизирай работните си пространства на всички устройства
     .accesskey = W
-zen-glance-title = Glance
-zen-glance-header = General settings for glance
-zen-glance-description = Get a quick overview of your links without opening them in a new tab
-zen-glance-trigger-label = Trigger method
+zen-glance-title = Бърз поглед
+zen-glance-header = Главни настройки за бърз поглед
+zen-glance-description = Получи бърз преглед на твоите линкове, без да ги отваряш в нов прозорец
+zen-glance-trigger-label = Метод на задействане
 zen-glance-enabled = 
-    .label = Enable Glance
+    .label = Включи бързия поглед
 zen-glance-trigger-ctrl-click = 
     .label = Ctrl + Click
 zen-glance-trigger-alt-click = 
@@ -30,22 +30,26 @@ zen-glance-trigger-shift-click =
     .label = Shift + Click
 zen-glance-trigger-meta-click = 
     .label = Meta (Command) + Click
-zen-look-and-feel-compact-view-header = Show in compact view
-zen-look-and-feel-compact-view-description = Only show the toolbars you use!
+zen-look-and-feel-compact-view-header = Покажи в компактен изглед
+zen-look-and-feel-compact-view-description = Показвай само лентите с инструменти, които използваш!
 zen-look-and-feel-compact-view-enabled = 
-    .label = Enable { -brand-short-name }'s compact mode
+    .label = Активирай компактния режим на { -brand-short-name }
 zen-look-and-feel-compact-view-top-toolbar = 
-    .label = Hide the top toolbar as well in compact mode
+    .label = Скрий и горната лента с инструменти в компактен режим
 zen-look-and-feel-compact-toolbar-flash-popup = 
-    .label = Briefly make the toolbar popup when switching or opening new tabs in compact mode
-pane-zen-tabs-title = Tab Management
+    .label = При превключване или отваряне на нови раздели в компактен режим лентата с инструменти да се показва за кратко
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Allow dragging the window from web pages
+pane-zen-tabs-title = Управление на табове
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
-pane-settings-workspaces-title = Workspaces
+pane-settings-workspaces-title = Работни пространства
 zen-tabs-select-recently-used-on-close = 
-    .label = When closing a tab, switch to the most recently used tab instead of the next tab
+    .label = При затваряне на раздел, преминавайте към най-скоро използвания, а не следващия
 zen-tabs-close-on-back-with-no-history = 
-    .label = Close tab and switch to its owner tab (or most recently used tab) when going back with no history
+    .label = Затваряне на раздела и преминаване към раздела на неговия собственик (или към най-скоро използвания раздел) при връщане назад без история
 zen-settings-workspaces-sync-unpinned-tabs = 
     .label = Sync only pinned tabs in workspaces
 zen-tabs-cycle-by-attribute = 
@@ -244,7 +248,8 @@ zen-page-info-shortcut = View Page Info
 zen-find-shortcut = Find on Page
 zen-search-find-again-shortcut = Find Again
 zen-search-find-again-shortcut-prev = Find Previous
-zen-search-find-again-shortcut-2 = Find Again (Alt)
+zen-search-find-again-shortcut-alt = Find Again (Alt)
+zen-search-find-again-shortcut-prev-alt = Find Previous (Alt)
 zen-bookmark-this-page-shortcut = Bookmark This Page
 zen-bookmark-show-library-shortcut = Show Bookmarks Library
 zen-key-stop = Stop Loading
diff --git a/locales/bg/browser/browser/zen-command-palette.ftl b/locales/bg/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..c8af413e2
--- /dev/null
+++ b/locales/bg/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Toggle Compact Mode
+zen-action-open-theme-picker = Open Theme Picker
+zen-action-new-split-view = New Split View
+zen-action-new-folder = New Folder
+zen-action-copy-current-url = Copy Current URL
+zen-action-settings = Settings
+zen-action-open-private-window = Open Private Window
+zen-action-open-new-window = Open New Window
+zen-action-new-blank-window = New Blank Window
+zen-action-pin-tab = Pin Tab
+zen-action-unpin-tab = Unpin Tab
+zen-action-open-space-routing = Open Space Routing
+zen-action-new-boost = New Boost
+zen-action-next-space = Next Space
+zen-action-previous-space = Previous Space
+zen-action-close-tab = Close Tab
+zen-action-reload-tab = Reload Tab
+zen-action-reload-tab-without-cache = Reload Tab Without Cache
+zen-action-next-tab = Next Tab
+zen-action-previous-tab = Previous Tab
+zen-action-capture-screenshot = Capture Screenshot
+zen-action-toggle-tabs-on-right = Toggle Tabs on right
+zen-action-add-to-essentials = Add to Essentials
+zen-action-remove-from-essentials = Remove from Essentials
+zen-action-find-in-page = Find in Page
+zen-action-manage-extensions = Manage Extensions
+zen-action-switch-to-automatic-appearance = Switch to Automatic Appearance
+zen-action-switch-to-light-mode = Switch to Light Mode
+zen-action-switch-to-dark-mode = Switch to Dark Mode
+zen-action-print = Print
+zen-action-focus-on = Focus on
+zen-action-extension = Extension
diff --git a/locales/bg/browser/browser/zen-general.ftl b/locales/bg/browser/browser/zen-general.ftl
index 3e7defe97..4ce02462c 100644
--- a/locales/bg/browser/browser/zen-general.ftl
+++ b/locales/bg/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = Запълнени слотове: { $num
 tab-context-zen-remove-essential = 
     .label = Премахване от Основни
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Replace Essential URL with Current
-           *[false] Replace Pinned URL with Current
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Replace with Current URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Edit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Промени етикета...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Потвърди
 zen-pinned-tab-replaced = Адресът на закачения раздел беше заменен с текущия адрес!
+zen-pinned-tab-url-edited = Pinned tab URL has been updated!
+zen-pinned-tab-url-invalid = That doesn't look like a valid URL.
+zen-pinned-tab-edit-url-title = Edit Pinned URL
+zen-pinned-tab-edit-url-label = Enter the URL this pinned tab should point to:
 zen-tabs-renamed = Разделът беше успешно преименуван!
 zen-background-tab-opened-toast = Отворен е нов раздел на заден план!
 zen-workspace-renamed-toast = Работното пространство беше преименувано успешно!
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = Емоджита
 zen-icons-picker-svg = 
     .label = Икони
+zen-emojis-picker-search = 
+    .placeholder = Search emojis
 urlbar-search-mode-zen_actions = Действия
 zen-site-data-settings = Настройки
 zen-generic-manage = Управление
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = Актуализацията е за
 zen-sidebar-notification-updated-label = Какво е ново в { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = Виж бележките към изданието
+zen-sidebar-notification-donate-label = Support { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donate to the project
 zen-sidebar-notification-restart-safe-mode-label = Има проблем?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Рестартирай в безопасен режим
diff --git a/locales/bg/browser/browser/zen-space-routing.ftl b/locales/bg/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..d757144bb
--- /dev/null
+++ b/locales/bg/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Space Routing Settings
+zen-space-routing-rulepanel-placeholder = Routes let you choose where specific sites open inside Zen. For example, you can route YouTube links to always open inside your Personal space.
+zen-space-routing-dialog-title = Space Routing Settings
+zen-space-routing-external-default = Default route for external links
+zen-space-routing-new-route = New Route
+zen-space-routing-open-in-space = Open in Space
+zen-space-routing-most-recent-space = Most recent Space
+zen-space-routing-close-button = 
+    .aria-label = Close
+    .tooltiptext = Close
+zen-space-routing-contains = 
+    .label = Contains
+zen-space-routing-equal-to = 
+    .label = Is Equal To
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Open In
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/bg/browser/browser/zen-workspaces.ftl b/locales/bg/browser/browser/zen-workspaces.ftl
index 7727a2ff2..01ef1f793 100644
--- a/locales/bg/browser/browser/zen-workspaces.ftl
+++ b/locales/bg/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Profile
     .tooltiptext = Profiles are used to separate cookies and site data between spaces.
 zen-workspace-creation-header = Create a Space
 zen-workspace-creation-label = Spaces are used to organize your tabs and sessions.
+zen-workspace-default-profile = Default
 zen-workspaces-delete-workspace-title = Delete Space?
 zen-workspaces-delete-workspace-body = Are you sure you want to delete { $name }? This action cannot be undone.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/bs/browser/browser/preferences/zen-preferences.ftl b/locales/bs/browser/browser/preferences/zen-preferences.ftl
index a43ff8124..0f0ccb122 100644
--- a/locales/bs/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/bs/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Hide the top toolbar as well in compact mode
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Briefly make the toolbar popup when switching or opening new tabs in compact mode
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Allow dragging the window from web pages
 pane-zen-tabs-title = Tab Management
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = View Page Info
 zen-find-shortcut = Find on Page
 zen-search-find-again-shortcut = Find Again
 zen-search-find-again-shortcut-prev = Find Previous
-zen-search-find-again-shortcut-2 = Find Again (Alt)
+zen-search-find-again-shortcut-alt = Find Again (Alt)
+zen-search-find-again-shortcut-prev-alt = Find Previous (Alt)
 zen-bookmark-this-page-shortcut = Bookmark This Page
 zen-bookmark-show-library-shortcut = Show Bookmarks Library
 zen-key-stop = Stop Loading
diff --git a/locales/bs/browser/browser/zen-command-palette.ftl b/locales/bs/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..c8af413e2
--- /dev/null
+++ b/locales/bs/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Toggle Compact Mode
+zen-action-open-theme-picker = Open Theme Picker
+zen-action-new-split-view = New Split View
+zen-action-new-folder = New Folder
+zen-action-copy-current-url = Copy Current URL
+zen-action-settings = Settings
+zen-action-open-private-window = Open Private Window
+zen-action-open-new-window = Open New Window
+zen-action-new-blank-window = New Blank Window
+zen-action-pin-tab = Pin Tab
+zen-action-unpin-tab = Unpin Tab
+zen-action-open-space-routing = Open Space Routing
+zen-action-new-boost = New Boost
+zen-action-next-space = Next Space
+zen-action-previous-space = Previous Space
+zen-action-close-tab = Close Tab
+zen-action-reload-tab = Reload Tab
+zen-action-reload-tab-without-cache = Reload Tab Without Cache
+zen-action-next-tab = Next Tab
+zen-action-previous-tab = Previous Tab
+zen-action-capture-screenshot = Capture Screenshot
+zen-action-toggle-tabs-on-right = Toggle Tabs on right
+zen-action-add-to-essentials = Add to Essentials
+zen-action-remove-from-essentials = Remove from Essentials
+zen-action-find-in-page = Find in Page
+zen-action-manage-extensions = Manage Extensions
+zen-action-switch-to-automatic-appearance = Switch to Automatic Appearance
+zen-action-switch-to-light-mode = Switch to Light Mode
+zen-action-switch-to-dark-mode = Switch to Dark Mode
+zen-action-print = Print
+zen-action-focus-on = Focus on
+zen-action-extension = Extension
diff --git a/locales/bs/browser/browser/zen-general.ftl b/locales/bs/browser/browser/zen-general.ftl
index 709b4575f..5c026accb 100644
--- a/locales/bs/browser/browser/zen-general.ftl
+++ b/locales/bs/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max } slots filled
 tab-context-zen-remove-essential = 
     .label = Remove from Essentials
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Replace Essential URL with Current
-           *[false] Replace Pinned URL with Current
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Replace with Current URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Edit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Change Label...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Confirm
 zen-pinned-tab-replaced = Pinned tab URL has been replaced with the current URL!
+zen-pinned-tab-url-edited = Pinned tab URL has been updated!
+zen-pinned-tab-url-invalid = That doesn't look like a valid URL.
+zen-pinned-tab-edit-url-title = Edit Pinned URL
+zen-pinned-tab-edit-url-label = Enter the URL this pinned tab should point to:
 zen-tabs-renamed = Tab has been successfully renamed!
 zen-background-tab-opened-toast = New background tab opened!
 zen-workspace-renamed-toast = Workspace has been successfully renamed!
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = Emojis
 zen-icons-picker-svg = 
     .label = Icons
+zen-emojis-picker-search = 
+    .placeholder = Search emojis
 urlbar-search-mode-zen_actions = Actions
 zen-site-data-settings = Settings
 zen-generic-manage = Manage
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = Update Complete!
 zen-sidebar-notification-updated-label = What's new in { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = View Release Notes
+zen-sidebar-notification-donate-label = Support { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donate to the project
 zen-sidebar-notification-restart-safe-mode-label = Something broke?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Restart in Safe Mode
diff --git a/locales/bs/browser/browser/zen-space-routing.ftl b/locales/bs/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..d757144bb
--- /dev/null
+++ b/locales/bs/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Space Routing Settings
+zen-space-routing-rulepanel-placeholder = Routes let you choose where specific sites open inside Zen. For example, you can route YouTube links to always open inside your Personal space.
+zen-space-routing-dialog-title = Space Routing Settings
+zen-space-routing-external-default = Default route for external links
+zen-space-routing-new-route = New Route
+zen-space-routing-open-in-space = Open in Space
+zen-space-routing-most-recent-space = Most recent Space
+zen-space-routing-close-button = 
+    .aria-label = Close
+    .tooltiptext = Close
+zen-space-routing-contains = 
+    .label = Contains
+zen-space-routing-equal-to = 
+    .label = Is Equal To
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Open In
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/bs/browser/browser/zen-workspaces.ftl b/locales/bs/browser/browser/zen-workspaces.ftl
index 7727a2ff2..01ef1f793 100644
--- a/locales/bs/browser/browser/zen-workspaces.ftl
+++ b/locales/bs/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Profile
     .tooltiptext = Profiles are used to separate cookies and site data between spaces.
 zen-workspace-creation-header = Create a Space
 zen-workspace-creation-label = Spaces are used to organize your tabs and sessions.
+zen-workspace-default-profile = Default
 zen-workspaces-delete-workspace-title = Delete Space?
 zen-workspaces-delete-workspace-body = Are you sure you want to delete { $name }? This action cannot be undone.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/ca/browser/browser/preferences/zen-preferences.ftl b/locales/ca/browser/browser/preferences/zen-preferences.ftl
index 853f16287..d8bc0dd54 100644
--- a/locales/ca/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/ca/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Amaga també la barra d'eines superior en el mode compacte
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Fa que la barra d'eines aparegui breument quan canvieu o obriu noves pestanyes en el mode compacte
+zen-look-and-feel-window-drag-header = Arrossegueu la finestra
+zen-look-and-feel-window-drag-description = Mou la finestra arrossegant l'espai buit a la part superior dels llocs web, igual que la barra de títol.
+zen-window-drag-enabled = 
+    .label = Permet arrossegar la finestra des de les pàgines web
 pane-zen-tabs-title = Gestió de pestanyes
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = Mostra la informació de la pàgina
 zen-find-shortcut = Cerca a la pàgina
 zen-search-find-again-shortcut = Cerca-ho un altre cop
 zen-search-find-again-shortcut-prev = Cerca l'anterior
-zen-search-find-again-shortcut-2 = Cerca-ho un altre cop (Alt)
+zen-search-find-again-shortcut-alt = Cerca-ho un altre cop (Alt)
+zen-search-find-again-shortcut-prev-alt = Cerca l'anterior (Alt)
 zen-bookmark-this-page-shortcut = Afegeix aquesta pàgina als marcadors
 zen-bookmark-show-library-shortcut = Mostra la biblioteca de marcadors
 zen-key-stop = Atura la càrrega
diff --git a/locales/ca/browser/browser/zen-command-palette.ftl b/locales/ca/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..c8af413e2
--- /dev/null
+++ b/locales/ca/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Toggle Compact Mode
+zen-action-open-theme-picker = Open Theme Picker
+zen-action-new-split-view = New Split View
+zen-action-new-folder = New Folder
+zen-action-copy-current-url = Copy Current URL
+zen-action-settings = Settings
+zen-action-open-private-window = Open Private Window
+zen-action-open-new-window = Open New Window
+zen-action-new-blank-window = New Blank Window
+zen-action-pin-tab = Pin Tab
+zen-action-unpin-tab = Unpin Tab
+zen-action-open-space-routing = Open Space Routing
+zen-action-new-boost = New Boost
+zen-action-next-space = Next Space
+zen-action-previous-space = Previous Space
+zen-action-close-tab = Close Tab
+zen-action-reload-tab = Reload Tab
+zen-action-reload-tab-without-cache = Reload Tab Without Cache
+zen-action-next-tab = Next Tab
+zen-action-previous-tab = Previous Tab
+zen-action-capture-screenshot = Capture Screenshot
+zen-action-toggle-tabs-on-right = Toggle Tabs on right
+zen-action-add-to-essentials = Add to Essentials
+zen-action-remove-from-essentials = Remove from Essentials
+zen-action-find-in-page = Find in Page
+zen-action-manage-extensions = Manage Extensions
+zen-action-switch-to-automatic-appearance = Switch to Automatic Appearance
+zen-action-switch-to-light-mode = Switch to Light Mode
+zen-action-switch-to-dark-mode = Switch to Dark Mode
+zen-action-print = Print
+zen-action-focus-on = Focus on
+zen-action-extension = Extension
diff --git a/locales/ca/browser/browser/zen-general.ftl b/locales/ca/browser/browser/zen-general.ftl
index d50b46e7c..a882b1c91 100644
--- a/locales/ca/browser/browser/zen-general.ftl
+++ b/locales/ca/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max }
 tab-context-zen-remove-essential = 
     .label = Elimina dels essencials
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Substitueix l'URL essencial per l'actual
-           *[false] Substitueix l'URL fixat per l'actual
+            [true] Edita l'URL essencial
+           *[false] Edita l'URL fixada
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Substitueix amb l'URL actual
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Edita…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Canvia l'etiqueta...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Confirma
 zen-pinned-tab-replaced = L'URL de la pestanya fixada s'ha substituït per l'URL actual.
+zen-pinned-tab-url-edited = L'URL de la pestanya fixada s'ha actualitzat!
+zen-pinned-tab-url-invalid = Això no sembla una URL vàlida.
+zen-pinned-tab-edit-url-title = Edita l'URL fixada
+zen-pinned-tab-edit-url-label = Introduïu l'URL a la qual ha d'apuntar aquesta pestanya fixada:
 zen-tabs-renamed = S'ha canviat el nom de la pestanya correctament
 zen-background-tab-opened-toast = S'ha obert una nova pestanya de fons
 zen-workspace-renamed-toast = S'ha canviat el nom de l'espai de treball correctament
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = Emojis
 zen-icons-picker-svg = 
     .label = Icones
+zen-emojis-picker-search = 
+    .placeholder = Cerca emojis
 urlbar-search-mode-zen_actions = Accions
 zen-site-data-settings = Configuració
 zen-generic-manage = Gestiona
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = Actualització completada!
 zen-sidebar-notification-updated-label = Novetats a { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = Mostra les notes de la versió
+zen-sidebar-notification-donate-label = Ajudeu-nos { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Feu una donació al projecte
 zen-sidebar-notification-restart-safe-mode-label = Alguna cosa no funciona?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Reinici en mode segur
diff --git a/locales/ca/browser/browser/zen-space-routing.ftl b/locales/ca/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..9ae2b8e50
--- /dev/null
+++ b/locales/ca/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Configuració de l'encaminament d'espais
+zen-space-routing-rulepanel-placeholder = Les rutes us permeten triar on s'obren llocs específics dins del Zen. Per exemple, podeu encaminar els enllaços del YouTube perquè sempre s'obrin dins del vostre espai personal.
+zen-space-routing-dialog-title = Configuració de l'encaminament d'espais
+zen-space-routing-external-default = Ruta per defecte per a enllaços externs
+zen-space-routing-new-route = Nova ruta
+zen-space-routing-open-in-space = Obre a l'espai
+zen-space-routing-most-recent-space = Espai més recent
+zen-space-routing-close-button = 
+    .aria-label = Tanca
+    .tooltiptext = Tanca
+zen-space-routing-contains = 
+    .label = Conté
+zen-space-routing-equal-to = 
+    .label = És igual a
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Obre a
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = Nova pestanya oberta a { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Afegeix una ruta per al domini
+           *[other] Afegeix una ruta per als dominis
+        }
diff --git a/locales/ca/browser/browser/zen-workspaces.ftl b/locales/ca/browser/browser/zen-workspaces.ftl
index d804b5bec..127c5fbc8 100644
--- a/locales/ca/browser/browser/zen-workspaces.ftl
+++ b/locales/ca/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Perfil
     .tooltiptext = Els perfils s'utilitzen per separar les galetes i les dades del lloc entre espais.
 zen-workspace-creation-header = Creació d'un espai
 zen-workspace-creation-label = Els espais s'utilitzen per organitzar les pestanyes i les sessions.
+zen-workspace-default-profile = Per defecte
 zen-workspaces-delete-workspace-title = Voleu suprimir l'espai de treball?
 zen-workspaces-delete-workspace-body = Esteu segur que voleu suprimir { $name }? Aquesta acció no es pot desfer.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/cs/browser/browser/preferences/zen-preferences.ftl b/locales/cs/browser/browser/preferences/zen-preferences.ftl
index b0194f747..1574529dc 100644
--- a/locales/cs/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/cs/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Skrýt horní panel nástrojů i v kompaktním režimu
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Krátce zobrazit vyskakovací panel nástrojů při přepínání nebo otevírání nových panelů v kompaktním režimu
+zen-look-and-feel-window-drag-header = Táhnutí okna
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Povolit přetahování okna z webových stránek
 pane-zen-tabs-title = Správa karet
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = Zobrazit informace o stránce
 zen-find-shortcut = Najít na stránce
 zen-search-find-again-shortcut = Najít znovu
 zen-search-find-again-shortcut-prev = Najít předchozí
-zen-search-find-again-shortcut-2 = Najít znovu (Alt)
+zen-search-find-again-shortcut-alt = Najít znovu (Alt)
+zen-search-find-again-shortcut-prev-alt = Najít předchozí (Alt)
 zen-bookmark-this-page-shortcut = Přidat záložku
 zen-bookmark-show-library-shortcut = Zobrazit knihovnu záložek
 zen-key-stop = Zastavit načítání
diff --git a/locales/cs/browser/browser/zen-boosts.ftl b/locales/cs/browser/browser/zen-boosts.ftl
index eb42026a7..5223dce6a 100644
--- a/locales/cs/browser/browser/zen-boosts.ftl
+++ b/locales/cs/browser/browser/zen-boosts.ftl
@@ -3,44 +3,44 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 zen-boost-edit-rename = 
-    .label = Rename Boost
+    .label = Přejmenovat Boost
 zen-boost-edit-shuffle = 
-    .label = Shuffle Vibes
+    .label = Zamíchat náladu
 zen-boost-edit-reset = 
-    .label = Reset All Edits
+    .label = Obnovit všechny úpravy
 zen-boost-edit-delete = 
-    .label = Delete Boost
-zen-boost-size = Size
+    .label = Odstranit Boost
+zen-boost-size = Velikost
 zen-boost-case = Case
 zen-boost-zap = Zap
 zen-boost-code = Code
-zen-boost-back = Back
+zen-boost-back = Zpět
 zen-boost-shuffle = 
     .tooltiptext = Shuffle Boost Settings
 zen-boost-invert = 
     .tooltiptext = Smart Invert Colors
 zen-boost-controls = 
-    .tooltiptext = Advanced Color Controls
+    .tooltiptext = Pokročilé nastavení barev
 zen-boost-disable = 
-    .tooltiptext = Disable Color Adjustments
+    .tooltiptext = Zakázat úpravy barev
 zen-boost-text-case-toggle = 
     .tooltiptext = Toggle Text Case
 zen-boost-css-picker = 
     .tooltiptext = Pick Selector
 zen-boost-css-inspector = 
-    .tooltiptext = Open Inspector
-zen-boost-color-contrast = Contrast
-zen-boost-color-brightness = Brightness
-zen-boost-color-original-saturation = Original Saturation
+    .tooltiptext = Otevřít inspektor
+zen-boost-color-contrast = Kontrast
+zen-boost-color-brightness = Jas
+zen-boost-color-original-saturation = Původní sytost
 zen-add-zap-helper = Click elements on the page to <b>Zap</b> them
 zen-remove-zap-helper = ← Click to Unzap
 zen-select-this = Insert selector for this
 zen-select-related = Insert selector for related
-zen-select-cancel = Cancel
+zen-select-cancel = Zrušit
 zen-zap-this = Zap this
 zen-zap-related = Zap all related elements
-zen-zap-cancel = Cancel
-zen-zap-done = Done
+zen-zap-cancel = Zrušit
+zen-zap-done = Hotovo
 zen-unzap-tooltip =
     { $elementCount ->
         [0] No elements zapped
@@ -48,11 +48,11 @@ zen-unzap-tooltip =
        *[other] { $elementCount } elements zapped
     }
 zen-boost-save = 
-    .label = Export Boost
+    .label = Exportovat Boost
 zen-boost-load = 
     .label = Import Boost
-zen-panel-ui-boosts-exported-message = Boost exported!
-zen-site-data-boosts = Boosts
+zen-panel-ui-boosts-exported-message = Boost exportován!
+zen-site-data-boosts = Boosty
 zen-site-data-create-boost = 
-    .tooltiptext = Create new boost
-zen-boost-rename-boost-prompt = Rename Boost?
+    .tooltiptext = Vytvořit nový Boost
+zen-boost-rename-boost-prompt = Přejmenovat Boost?
diff --git a/locales/cs/browser/browser/zen-command-palette.ftl b/locales/cs/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..799df2728
--- /dev/null
+++ b/locales/cs/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Přepnout kompaktní režim
+zen-action-open-theme-picker = Otevřít výběr motivu
+zen-action-new-split-view = Nové rozdělení zobrazení
+zen-action-new-folder = Nová složka
+zen-action-copy-current-url = Kopírovat aktuální URL adresu
+zen-action-settings = Nastavení
+zen-action-open-private-window = Otevřít nové anonymní okno
+zen-action-open-new-window = Otevřít nové okno
+zen-action-new-blank-window = Nové prázdné okno
+zen-action-pin-tab = Připnout panel
+zen-action-unpin-tab = Odepnout panel
+zen-action-open-space-routing = Open Space Routing
+zen-action-new-boost = Nový boost
+zen-action-next-space = Další prostor
+zen-action-previous-space = Předchozí prostor
+zen-action-close-tab = Zavřít panel
+zen-action-reload-tab = Obnovit panel
+zen-action-reload-tab-without-cache = Znovu načíst kartu bez mezipaměti
+zen-action-next-tab = Další karta
+zen-action-previous-tab = Předchozí karta
+zen-action-capture-screenshot = Pořídit snímek obrazovky
+zen-action-toggle-tabs-on-right = Přepnout panely vpravo
+zen-action-add-to-essentials = Přídat do Essentials
+zen-action-remove-from-essentials = Odstranit z Essentials
+zen-action-find-in-page = Najít na stránce
+zen-action-manage-extensions = Spravovat rozšíření
+zen-action-switch-to-automatic-appearance = Přepnout na automatický vzhled
+zen-action-switch-to-light-mode = Přepnout do světlého režimu
+zen-action-switch-to-dark-mode = Přepnout do tmavého režimu
+zen-action-print = Tisk
+zen-action-focus-on = Focus on
+zen-action-extension = Extension
diff --git a/locales/cs/browser/browser/zen-general.ftl b/locales/cs/browser/browser/zen-general.ftl
index ca6132599..666109bb0 100644
--- a/locales/cs/browser/browser/zen-general.ftl
+++ b/locales/cs/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max } zaplněných slotů
 tab-context-zen-remove-essential = 
     .label = Odstranit z Essentials
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Nahradit Essential URL aktuální
-           *[false] Nahradit připnutou URL aktuální
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Nahradit současnou URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Upravit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Změnit název...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Potvrdit
 zen-pinned-tab-replaced = Připnutá URL adresa panelu byla nahrazena aktuální URL adresou.
+zen-pinned-tab-url-edited = URL připnuté karty byla aktualizována!
+zen-pinned-tab-url-invalid = To nevypadá jako platná URL adresa.
+zen-pinned-tab-edit-url-title = Upravit připnutou adresu URL
+zen-pinned-tab-edit-url-label = Zadejte URL, na kterou by měl tento připnutý panel odkazovat:
 zen-tabs-renamed = Panel byl úspěšně přejmenován!
 zen-background-tab-opened-toast = Nový panel na pozadí byl otevřen!
 zen-workspace-renamed-toast = Pracovní prostor byl úspěšně přejmenován!
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = Emodži
 zen-icons-picker-svg = 
     .label = Ikony
+zen-emojis-picker-search = 
+    .placeholder = Vyhledat emoji
 urlbar-search-mode-zen_actions = Akce
 zen-site-data-settings = Nastavení
 zen-generic-manage = Spravovat
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = Aktualizace byla dokončena!
 zen-sidebar-notification-updated-label = Co je nového v prohlížeči { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = Zobrazit změny
+zen-sidebar-notification-donate-label = Podpořte { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Přispět na projekt
 zen-sidebar-notification-restart-safe-mode-label = Něco se rozbilo?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Restartovat v Nouzovém Režimu
diff --git a/locales/cs/browser/browser/zen-space-routing.ftl b/locales/cs/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..7d0f35e39
--- /dev/null
+++ b/locales/cs/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Space Routing Settings
+zen-space-routing-rulepanel-placeholder = Routes let you choose where specific sites open inside Zen. For example, you can route YouTube links to always open inside your Personal space.
+zen-space-routing-dialog-title = Space Routing Settings
+zen-space-routing-external-default = Default route for external links
+zen-space-routing-new-route = New Route
+zen-space-routing-open-in-space = Otevřít v prostoru
+zen-space-routing-most-recent-space = Nejnovější prostor
+zen-space-routing-close-button = 
+    .aria-label = Zavřít
+    .tooltiptext = Zavřít
+zen-space-routing-contains = 
+    .label = Obsahuje
+zen-space-routing-equal-to = 
+    .label = Je rovno
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Otevřít v
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/cs/browser/browser/zen-workspaces.ftl b/locales/cs/browser/browser/zen-workspaces.ftl
index 529d3514c..c4659c719 100644
--- a/locales/cs/browser/browser/zen-workspaces.ftl
+++ b/locales/cs/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Profil
     .tooltiptext = Profily se používají k oddělení cookies a údajů webových stránek mezi prostory.
 zen-workspace-creation-header = Vytvořte si prostor
 zen-workspace-creation-label = Prostory slouží k organizaci Vašich karet a relací.
+zen-workspace-default-profile = Výchozí
 zen-workspaces-delete-workspace-title = Odstranit prostor?
 zen-workspaces-delete-workspace-body = Opravdu chcete smazat { $name }? Tuto akci nelze vrátit zpět.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/cy/browser/browser/preferences/zen-preferences.ftl b/locales/cy/browser/browser/preferences/zen-preferences.ftl
index 2a24fed35..3ed1d9af4 100644
--- a/locales/cy/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/cy/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Cuddio'r bar offer uchaf hefyd yn y modd cryno
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Gwneud i'r bar offer ymddangos yn fyr wrth newid neu agor tabiau newydd yn y modd cryno
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Allow dragging the window from web pages
 pane-zen-tabs-title = Rheoli Tabiau
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = Gweld Manylion Tudalen
 zen-find-shortcut = Canfod ar y Dudalen
 zen-search-find-again-shortcut = Canfod Eto
 zen-search-find-again-shortcut-prev = Canfod y Blaenorol
-zen-search-find-again-shortcut-2 = Canfod Eto (Alt)
+zen-search-find-again-shortcut-alt = Find Again (Alt)
+zen-search-find-again-shortcut-prev-alt = Find Previous (Alt)
 zen-bookmark-this-page-shortcut = Gosod Nod Tudalen i'r Dudalen Hon
 zen-bookmark-show-library-shortcut = Dangos Llyfrgell Nodau Tudalen
 zen-key-stop = Stopio Llwytho
@@ -281,7 +286,7 @@ zen-workspace-shortcut-switch-9 = Symud i Gofod Gwaith 9
 zen-workspace-shortcut-switch-10 = Symud i Gofod Gwaith 10
 zen-workspace-shortcut-forward = Gofod Gwaith Ymlaen
 zen-workspace-shortcut-backward = Gofod Gwaith Nôl
-zen-workspace-shortcut-create = Create New Workspace
+zen-workspace-shortcut-create = Creu Gofod Gwaith Newydd
 zen-sidebar-shortcut-toggle = Toglo Lled y Bar Ochr
 zen-pinned-tab-shortcut-reset = Ailosod y Tab wedi'i Binio i URL wedi'i Binio
 zen-split-view-shortcut-grid = Toglo Grid Golwg Hollt
@@ -319,4 +324,4 @@ zen-devtools-toggle-accessibility-shortcut = Toglo Hygyrchedd
 zen-close-all-unpinned-tabs-shortcut = Cau Pob Tab Heb ei Binio
 zen-new-unsynced-window-shortcut = Ffenestr Wag Newydd
 zen-duplicate-tab-shortcut = Tab Dyblyg
-zen-key-find-selection = Find Selection
+zen-key-find-selection = Canfod y Dewis
diff --git a/locales/cy/browser/browser/zen-boosts.ftl b/locales/cy/browser/browser/zen-boosts.ftl
index eb42026a7..712ce96b2 100644
--- a/locales/cy/browser/browser/zen-boosts.ftl
+++ b/locales/cy/browser/browser/zen-boosts.ftl
@@ -3,56 +3,56 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 zen-boost-edit-rename = 
-    .label = Rename Boost
+    .label = Ailenwi Hwb
 zen-boost-edit-shuffle = 
-    .label = Shuffle Vibes
+    .label = Shyfflo Vibes
 zen-boost-edit-reset = 
-    .label = Reset All Edits
+    .label = Ailosod Pob Golygiad
 zen-boost-edit-delete = 
-    .label = Delete Boost
-zen-boost-size = Size
-zen-boost-case = Case
-zen-boost-zap = Zap
-zen-boost-code = Code
-zen-boost-back = Back
+    .label = Dileu Hwb
+zen-boost-size = Maint
+zen-boost-case = Maint Nod
+zen-boost-zap = Sap
+zen-boost-code = Côd
+zen-boost-back = Nôl
 zen-boost-shuffle = 
-    .tooltiptext = Shuffle Boost Settings
+    .tooltiptext = Syfflo Gosodiadau Hwb
 zen-boost-invert = 
-    .tooltiptext = Smart Invert Colors
+    .tooltiptext = Lliwiau Gwrthdroi Clyfar
 zen-boost-controls = 
-    .tooltiptext = Advanced Color Controls
+    .tooltiptext = Rheolyddion Lliw Uwch
 zen-boost-disable = 
-    .tooltiptext = Disable Color Adjustments
+    .tooltiptext = Analluogi Addasiadau Lliw
 zen-boost-text-case-toggle = 
-    .tooltiptext = Toggle Text Case
+    .tooltiptext = Toglo Priflythreniad Testun
 zen-boost-css-picker = 
-    .tooltiptext = Pick Selector
+    .tooltiptext = Dewis Dewisydd
 zen-boost-css-inspector = 
-    .tooltiptext = Open Inspector
-zen-boost-color-contrast = Contrast
-zen-boost-color-brightness = Brightness
-zen-boost-color-original-saturation = Original Saturation
-zen-add-zap-helper = Click elements on the page to <b>Zap</b> them
-zen-remove-zap-helper = ← Click to Unzap
-zen-select-this = Insert selector for this
-zen-select-related = Insert selector for related
-zen-select-cancel = Cancel
-zen-zap-this = Zap this
-zen-zap-related = Zap all related elements
-zen-zap-cancel = Cancel
-zen-zap-done = Done
+    .tooltiptext = Agor Arolygydd
+zen-boost-color-contrast = Cyferbyniad
+zen-boost-color-brightness = Disgleirdeb
+zen-boost-color-original-saturation = Dirlawnder Gwreiddiol
+zen-add-zap-helper = Cliciwch elfennau ar y dudalen <b>i'w</b> Sapio
+zen-remove-zap-helper = ← Clicio i Ddadsapio
+zen-select-this = Mewnosod dewisydd ar gyfer hwn
+zen-select-related = Mewnosod dewisydd ar gyfer cysylltiedig
+zen-select-cancel = Na
+zen-zap-this = Sapio hwn
+zen-zap-related = Sapio pob elfen gysylltiedig
+zen-zap-cancel = Na
+zen-zap-done = Gorffen
 zen-unzap-tooltip =
     { $elementCount ->
-        [0] No elements zapped
-        [1] { $elementCount } element zapped
-       *[other] { $elementCount } elements zapped
+        [0] Dim elfennau wedi'u sapio
+        [1] { $elementCount } elfen wedi'i sapio
+       *[other] { $elementCount } elfan wedi'u sapio
     }
 zen-boost-save = 
-    .label = Export Boost
+    .label = Allforio Hwb
 zen-boost-load = 
-    .label = Import Boost
-zen-panel-ui-boosts-exported-message = Boost exported!
-zen-site-data-boosts = Boosts
+    .label = Mewnforio Hwb
+zen-panel-ui-boosts-exported-message = Hwb wedi'i allforio!
+zen-site-data-boosts = Hybiau
 zen-site-data-create-boost = 
-    .tooltiptext = Create new boost
-zen-boost-rename-boost-prompt = Rename Boost?
+    .tooltiptext = Creu hwb newydd
+zen-boost-rename-boost-prompt = Ailenwi Hwb?
diff --git a/locales/cy/browser/browser/zen-command-palette.ftl b/locales/cy/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..c8af413e2
--- /dev/null
+++ b/locales/cy/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Toggle Compact Mode
+zen-action-open-theme-picker = Open Theme Picker
+zen-action-new-split-view = New Split View
+zen-action-new-folder = New Folder
+zen-action-copy-current-url = Copy Current URL
+zen-action-settings = Settings
+zen-action-open-private-window = Open Private Window
+zen-action-open-new-window = Open New Window
+zen-action-new-blank-window = New Blank Window
+zen-action-pin-tab = Pin Tab
+zen-action-unpin-tab = Unpin Tab
+zen-action-open-space-routing = Open Space Routing
+zen-action-new-boost = New Boost
+zen-action-next-space = Next Space
+zen-action-previous-space = Previous Space
+zen-action-close-tab = Close Tab
+zen-action-reload-tab = Reload Tab
+zen-action-reload-tab-without-cache = Reload Tab Without Cache
+zen-action-next-tab = Next Tab
+zen-action-previous-tab = Previous Tab
+zen-action-capture-screenshot = Capture Screenshot
+zen-action-toggle-tabs-on-right = Toggle Tabs on right
+zen-action-add-to-essentials = Add to Essentials
+zen-action-remove-from-essentials = Remove from Essentials
+zen-action-find-in-page = Find in Page
+zen-action-manage-extensions = Manage Extensions
+zen-action-switch-to-automatic-appearance = Switch to Automatic Appearance
+zen-action-switch-to-light-mode = Switch to Light Mode
+zen-action-switch-to-dark-mode = Switch to Dark Mode
+zen-action-print = Print
+zen-action-focus-on = Focus on
+zen-action-extension = Extension
diff --git a/locales/cy/browser/browser/zen-general.ftl b/locales/cy/browser/browser/zen-general.ftl
index 752f932a3..c86f50f2b 100644
--- a/locales/cy/browser/browser/zen-general.ftl
+++ b/locales/cy/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max } slotiau wedi'u llenwi
 tab-context-zen-remove-essential = 
     .label = Dileu o'r Hanfodion
     .accesskey = D
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Amnewid URL Hanfodol gyda'r Cyfredol
-           *[false] Amnewid URL wedi'i binio gyda'r Cyfredol
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
     .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Replace with Current URL
+    .accesskey = P
+tab-context-zen-edit-pinned-url = 
+    .label = Edit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Newid Label...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Cadarnhau
 zen-pinned-tab-replaced = Mae URL y tab wedi'i binio wedi'i newid i'r URL gyfredol!
+zen-pinned-tab-url-edited = Pinned tab URL has been updated!
+zen-pinned-tab-url-invalid = That doesn't look like a valid URL.
+zen-pinned-tab-edit-url-title = Edit Pinned URL
+zen-pinned-tab-edit-url-label = Enter the URL this pinned tab should point to:
 zen-tabs-renamed = Mae'r tab wedi cael ei ailenwi'n llwyddiannus!
 zen-background-tab-opened-toast = Tab cefndir newydd wedi'i agor!
 zen-workspace-renamed-toast = Mae'r Man Gwaith wedi cael ei ailenwi'n llwyddiannus!
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = Emojis
 zen-icons-picker-svg = 
     .label = Eiconau
+zen-emojis-picker-search = 
+    .placeholder = Search emojis
 urlbar-search-mode-zen_actions = Gweithredoedd
 zen-site-data-settings = Gosodiadau
 zen-generic-manage = Rheoli
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = Diweddariad Wedi'i Gwblhau!
 zen-sidebar-notification-updated-label = Beth sy'n newydd yn { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = Gweld Nodiadau Rhyddhau
+zen-sidebar-notification-donate-label = Support { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donate to the project
 zen-sidebar-notification-restart-safe-mode-label = Rhywbeth wedi torri?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Ailgychwyn yn y Modd Diogel
diff --git a/locales/cy/browser/browser/zen-space-routing.ftl b/locales/cy/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..0e45a7c83
--- /dev/null
+++ b/locales/cy/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Gosodiadau Llwybro Gofod
+zen-space-routing-rulepanel-placeholder = Mae Llwybrau yn gadael i chi ddewis lle mae wefannau penodol yn agor o fewn Zen. Er enghraifft, gallwch lywio dolenni YouTube i agor bob tro o fewn eich gofod Personol.
+zen-space-routing-dialog-title = Gosodiadau Llwybro Gofod
+zen-space-routing-external-default = Llwybr rhagosodedig ar gyfer dolenni allanol
+zen-space-routing-new-route = Llwybr Newydd
+zen-space-routing-open-in-space = Agor mewn Gofod
+zen-space-routing-most-recent-space = Gofod Diweddaraf
+zen-space-routing-close-button = 
+    .aria-label = Cau
+    .tooltiptext = Cau
+zen-space-routing-contains = 
+    .label = Yn cynnwys
+zen-space-routing-equal-to = 
+    .label = Yn Hafal i
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Yn Agor Yn
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/cy/browser/browser/zen-workspaces.ftl b/locales/cy/browser/browser/zen-workspaces.ftl
index 28f2adf99..cd4e3ebc2 100644
--- a/locales/cy/browser/browser/zen-workspaces.ftl
+++ b/locales/cy/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Proffil
     .tooltiptext = Mae proffiliau'n cael eu defnyddio i wahanu cwcis a data gwefan rhwng gofodau.
 zen-workspace-creation-header = Creu Gofod
 zen-workspace-creation-label = Mae gofodau'n cael eu defnyddio i drefnu eich tabiau a'ch sesiynau.
+zen-workspace-default-profile = Default
 zen-workspaces-delete-workspace-title = Dileu Gofod Gwaith?
 zen-workspaces-delete-workspace-body = Ydych chi'n siŵr eich bod chi eisiau dileu { $name }? Does dim modd dadwneud y weithred hon.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/da/browser/browser/preferences/zen-preferences.ftl b/locales/da/browser/browser/preferences/zen-preferences.ftl
index 9e90de776..3aa0feb0e 100644
--- a/locales/da/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/da/browser/browser/preferences/zen-preferences.ftl
@@ -38,23 +38,27 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Skjul også den øverste værktøjslinje i kompakt tilstand
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Vis kortvarigt værktøjslinjen ved skift eller åbning af nye faner i kompakt tilstand
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Allow dragging the window from web pages
 pane-zen-tabs-title = Fanehåndtering
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
 pane-settings-workspaces-title = Arbejdsområder
 zen-tabs-select-recently-used-on-close = 
-    .label = When closing a tab, switch to the most recently used tab instead of the next tab
+    .label = Når en fane lukkes, skift til den senest bruge fane i stedet for den næste fane
 zen-tabs-close-on-back-with-no-history = 
-    .label = Close tab and switch to its owner tab (or most recently used tab) when going back with no history
+    .label = Luk fanen og skift til dens ejerfane (eller den senest brugte fane), når du går tilbage uden historik
 zen-settings-workspaces-sync-unpinned-tabs = 
-    .label = Sync only pinned tabs in workspaces
+    .label = Synkroniser kun fastgjorte faner i arbejdsområder
 zen-tabs-cycle-by-attribute = 
     .label = Ctrl+Tab cycles within Essential or Workspace tabs only
 zen-tabs-cycle-ignore-pending-tabs = 
-    .label = Ignore Pending tabs when cycling with Ctrl+Tab
-zen-tabs-cycle-by-attribute-warning = Ctrl+Tab will cycle by recently used order, as it is enabled
+    .label = Ignorer Ventende faner, når du bruger Ctrl+Tab
+zen-tabs-cycle-by-attribute-warning = Ctrl+Tab cykler efter senest brugte rækkefølge, da det er aktiveret
 zen-look-and-feel-compact-toolbar-themed = 
-    .label = Use themed background for compact toolbar
+    .label = Brug temabaggrund til kompakt værktøjslinje
 zen-workspace-continue-where-left-off = 
     .label = Fortsæt, hvor du slap
 pane-zen-pinned-tab-manager-title = Fastgjorte Faner
@@ -85,7 +89,7 @@ zen-settings-workspaces-enabled =
 zen-settings-workspaces-hide-default-container-indicator = 
     .label = Skjul standardindikatoren for beholdere i fanelinjen
 zen-key-unsaved = Ikke-gemt genvej! Gem den ved at klikke på "Escape"-tasten efter at have indtastet den igen.
-zen-key-conflict = Conflicts with { $group } -> { $shortcut }
+zen-key-conflict = Konflikter med { $group } -> { $shortcut }
 pane-zen-theme-title = Temaindstillinger
 zen-vertical-tabs-title = Layout for sidepanel og faner
 zen-vertical-tabs-header = Lodrette Faner
@@ -234,7 +238,7 @@ zen-key-exit-full-screen = Afslut fuld skærm
 zen-ai-chatbot-sidebar-shortcut = Slå sidepanel for AI-chatbot til/fra
 zen-key-inspector-mac = Slå inspektør til/fra (Mac)
 zen-toggle-sidebar-shortcut = Slå Firefox-sidepanel til/fra
-zen-toggle-pin-tab-shortcut = Toggle Pin Tab
+zen-toggle-pin-tab-shortcut = Slå fanen Fastgør til/fra
 zen-reader-mode-toggle-shortcut-other = Slå Læsertilstand Til/Fra
 zen-picture-in-picture-toggle-shortcut = Slå Billede-i-Billede Til/Fra
 zen-nav-reload-shortcut-2 = Genindlæs side
@@ -244,7 +248,8 @@ zen-page-info-shortcut = Se sideoplysninger
 zen-find-shortcut = Find på side
 zen-search-find-again-shortcut = Find igen
 zen-search-find-again-shortcut-prev = Find forrige
-zen-search-find-again-shortcut-2 = Find igen (Alt)
+zen-search-find-again-shortcut-alt = Find Again (Alt)
+zen-search-find-again-shortcut-prev-alt = Find Previous (Alt)
 zen-bookmark-this-page-shortcut = Bogmærk denne side
 zen-bookmark-show-library-shortcut = Vis Bogmærkebibliotek
 zen-key-stop = Stop indlæsning
@@ -268,7 +273,7 @@ zen-close-tab-shortcut = Luk fane
 zen-compact-mode-shortcut-show-sidebar = Flydende sidepanel til/fra
 zen-compact-mode-shortcut-show-toolbar = Flydende værktøjslinje til/fra
 zen-compact-mode-shortcut-toggle = Kompakt tilstand til/fra
-zen-glance-expand = Expand Glance
+zen-glance-expand = Udvid Glance
 zen-workspace-shortcut-switch-1 = Skift til arbejdsområde 1
 zen-workspace-shortcut-switch-2 = Skift til arbejdsområde 2
 zen-workspace-shortcut-switch-3 = Skift til arbejdsområde 3
@@ -281,14 +286,14 @@ zen-workspace-shortcut-switch-9 = Skift til arbejdsområde 9
 zen-workspace-shortcut-switch-10 = Skift til arbejdsområde 10
 zen-workspace-shortcut-forward = Fremad Arbejdsområde
 zen-workspace-shortcut-backward = Bagudrettet Arbejdsrum
-zen-workspace-shortcut-create = Create New Workspace
+zen-workspace-shortcut-create = Opret Nyt Arbejdsrum
 zen-sidebar-shortcut-toggle = Skift sidepanelets bredde
 zen-pinned-tab-shortcut-reset = Nulstil fastgjort fane til fastgjort URL
 zen-split-view-shortcut-grid = Opdelt visning i gitter til/fra
 zen-split-view-shortcut-vertical = Lodret opdelt visning til/fra
 zen-split-view-shortcut-horizontal = Vandret opdelt visning til/fra
 zen-split-view-shortcut-unsplit = Luk opdelt visning
-zen-new-empty-split-view-shortcut = New Empty Split View
+zen-new-empty-split-view-shortcut = Ny Tom Delt Visning
 zen-key-select-tab-1 = Vælg fane #1
 zen-key-select-tab-2 = Vælg fane #2
 zen-key-select-tab-3 = Vælg fane #3
@@ -316,7 +321,7 @@ zen-devtools-toggle-performance-shortcut = Vis/skjul Ydeevne
 zen-devtools-toggle-storage-shortcut = Vis/skjul Lager
 zen-devtools-toggle-dom-shortcut = Vis/skjul DOM
 zen-devtools-toggle-accessibility-shortcut = Vis/skjul Tilgængelighed
-zen-close-all-unpinned-tabs-shortcut = Close All Unpinned Tabs
+zen-close-all-unpinned-tabs-shortcut = Luk Alle Ikke Fastgjorte Faner
 zen-new-unsynced-window-shortcut = New Unsynced Window
-zen-duplicate-tab-shortcut = Duplicate Tab
-zen-key-find-selection = Find Selection
+zen-duplicate-tab-shortcut = Dupliker Fane
+zen-key-find-selection = Find Valgte
diff --git a/locales/da/browser/browser/zen-boosts.ftl b/locales/da/browser/browser/zen-boosts.ftl
index eb42026a7..aa4dd0e0a 100644
--- a/locales/da/browser/browser/zen-boosts.ftl
+++ b/locales/da/browser/browser/zen-boosts.ftl
@@ -3,44 +3,44 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 zen-boost-edit-rename = 
-    .label = Rename Boost
+    .label = Omdøb Boost
 zen-boost-edit-shuffle = 
-    .label = Shuffle Vibes
+    .label = Bland Vibes
 zen-boost-edit-reset = 
     .label = Reset All Edits
 zen-boost-edit-delete = 
-    .label = Delete Boost
-zen-boost-size = Size
+    .label = Slet Boost
+zen-boost-size = Størrelse
 zen-boost-case = Case
 zen-boost-zap = Zap
 zen-boost-code = Code
-zen-boost-back = Back
+zen-boost-back = Tilbage
 zen-boost-shuffle = 
     .tooltiptext = Shuffle Boost Settings
 zen-boost-invert = 
-    .tooltiptext = Smart Invert Colors
+    .tooltiptext = Intelligent Invertering af Farver
 zen-boost-controls = 
-    .tooltiptext = Advanced Color Controls
+    .tooltiptext = Avanceret Farvekontroller
 zen-boost-disable = 
-    .tooltiptext = Disable Color Adjustments
+    .tooltiptext = Deaktiver Farvejusteringer
 zen-boost-text-case-toggle = 
     .tooltiptext = Toggle Text Case
 zen-boost-css-picker = 
     .tooltiptext = Pick Selector
 zen-boost-css-inspector = 
-    .tooltiptext = Open Inspector
-zen-boost-color-contrast = Contrast
-zen-boost-color-brightness = Brightness
+    .tooltiptext = Åben Inspektør
+zen-boost-color-contrast = Kontrast
+zen-boost-color-brightness = Lysstyrke
 zen-boost-color-original-saturation = Original Saturation
 zen-add-zap-helper = Click elements on the page to <b>Zap</b> them
 zen-remove-zap-helper = ← Click to Unzap
 zen-select-this = Insert selector for this
 zen-select-related = Insert selector for related
-zen-select-cancel = Cancel
+zen-select-cancel = Annuller
 zen-zap-this = Zap this
 zen-zap-related = Zap all related elements
-zen-zap-cancel = Cancel
-zen-zap-done = Done
+zen-zap-cancel = Annuller
+zen-zap-done = Færdig
 zen-unzap-tooltip =
     { $elementCount ->
         [0] No elements zapped
@@ -48,11 +48,11 @@ zen-unzap-tooltip =
        *[other] { $elementCount } elements zapped
     }
 zen-boost-save = 
-    .label = Export Boost
+    .label = Eksporter Boost
 zen-boost-load = 
-    .label = Import Boost
-zen-panel-ui-boosts-exported-message = Boost exported!
+    .label = Importer Boost
+zen-panel-ui-boosts-exported-message = Boost Eksporteret!
 zen-site-data-boosts = Boosts
 zen-site-data-create-boost = 
-    .tooltiptext = Create new boost
-zen-boost-rename-boost-prompt = Rename Boost?
+    .tooltiptext = Opret ny boost
+zen-boost-rename-boost-prompt = Omdøb Boost?
diff --git a/locales/da/browser/browser/zen-command-palette.ftl b/locales/da/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..c8af413e2
--- /dev/null
+++ b/locales/da/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Toggle Compact Mode
+zen-action-open-theme-picker = Open Theme Picker
+zen-action-new-split-view = New Split View
+zen-action-new-folder = New Folder
+zen-action-copy-current-url = Copy Current URL
+zen-action-settings = Settings
+zen-action-open-private-window = Open Private Window
+zen-action-open-new-window = Open New Window
+zen-action-new-blank-window = New Blank Window
+zen-action-pin-tab = Pin Tab
+zen-action-unpin-tab = Unpin Tab
+zen-action-open-space-routing = Open Space Routing
+zen-action-new-boost = New Boost
+zen-action-next-space = Next Space
+zen-action-previous-space = Previous Space
+zen-action-close-tab = Close Tab
+zen-action-reload-tab = Reload Tab
+zen-action-reload-tab-without-cache = Reload Tab Without Cache
+zen-action-next-tab = Next Tab
+zen-action-previous-tab = Previous Tab
+zen-action-capture-screenshot = Capture Screenshot
+zen-action-toggle-tabs-on-right = Toggle Tabs on right
+zen-action-add-to-essentials = Add to Essentials
+zen-action-remove-from-essentials = Remove from Essentials
+zen-action-find-in-page = Find in Page
+zen-action-manage-extensions = Manage Extensions
+zen-action-switch-to-automatic-appearance = Switch to Automatic Appearance
+zen-action-switch-to-light-mode = Switch to Light Mode
+zen-action-switch-to-dark-mode = Switch to Dark Mode
+zen-action-print = Print
+zen-action-focus-on = Focus on
+zen-action-extension = Extension
diff --git a/locales/da/browser/browser/zen-general.ftl b/locales/da/browser/browser/zen-general.ftl
index b8181d220..5372ff43b 100644
--- a/locales/da/browser/browser/zen-general.ftl
+++ b/locales/da/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max } slots filled
 tab-context-zen-remove-essential = 
     .label = Fjern fra Essentielle
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Replace Essential URL with Current
-           *[false] Replace Pinned URL with Current
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Replace with Current URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Edit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Change Label...
 tab-context-zen-edit-icon = 
@@ -41,16 +47,20 @@ pictureinpicture-minimize-btn =
     .tooltip = Minimer
 zen-panel-ui-gradient-generator-custom-color = Brugerdefineret Farve
 zen-copy-current-url-confirmation = Kopieret nuværende URL!
-zen-copy-current-url-as-markdown-confirmation = Copied current URL as Markdown!
+zen-copy-current-url-as-markdown-confirmation = Kopierede nuværende URL som Markdown!
 zen-general-cancel-label = 
     .label = Annuller
 zen-general-confirm = 
     .label = Bekræft
 zen-pinned-tab-replaced = Den fastgjorte fane-URL blev erstattet med den aktuelle.
+zen-pinned-tab-url-edited = Pinned tab URL has been updated!
+zen-pinned-tab-url-invalid = That doesn't look like a valid URL.
+zen-pinned-tab-edit-url-title = Edit Pinned URL
+zen-pinned-tab-edit-url-label = Enter the URL this pinned tab should point to:
 zen-tabs-renamed = Fanen blev omdøbt!
 zen-background-tab-opened-toast = Ny baggrundsfane åbnet!
 zen-workspace-renamed-toast = Arbejdsområde blev omdøbt!
-zen-split-view-limit-toast = Can't add more panels to the split view!
+zen-split-view-limit-toast = Kan ikke tilføje flere paneler til denne delte visning!
 zen-toggle-compact-mode-button = 
     .label = Kompakt tilstand
     .tooltiptext = Kompakt tilstand til/fra
@@ -65,18 +75,20 @@ zen-icons-picker-emoji =
     .label = Emojis
 zen-icons-picker-svg = 
     .label = Ikoner
+zen-emojis-picker-search = 
+    .placeholder = Search emojis
 urlbar-search-mode-zen_actions = Handlinger
 zen-site-data-settings = Indstillinger
 zen-generic-manage = Administrer
 zen-generic-more = Mere
 zen-generic-next = Næste
 zen-essentials-promo-label = Add to Essentials
-zen-essentials-promo-sublabel = Keep your favorite tabs just a click away
+zen-essentials-promo-sublabel = Hold dine yndlings faner et klik væk
 # These labels will be used for the site data panel settings
 zen-site-data-setting-allow = Tilladt
 zen-site-data-setting-block = Blokeret
-zen-site-data-protections-enabled = Enabled
-zen-site-data-protections-disabled = Disabled
+zen-site-data-protections-enabled = Aktiveret
+zen-site-data-protections-disabled = Deaktiveret
 zen-site-data-setting-cross-site = Cross-Site cookie
 zen-site-data-security-info-extension = 
     .label = Udvidelse
@@ -89,15 +101,15 @@ zen-site-data-manage-addons =
 zen-site-data-get-addons = 
     .label = Tilføj udvidelser
 zen-site-data-site-settings = 
-    .label = All Site Settings
+    .label = Alle Side Indstillinger
 zen-site-data-header-share = 
-    .tooltiptext = Share This Page
+    .tooltiptext = Del Denne Side
 zen-site-data-header-reader-mode = 
-    .tooltiptext = Enter Reader Mode
+    .tooltiptext = Åben Læsertilstand
 zen-site-data-header-screenshot = 
-    .tooltiptext = Take a Screenshot
+    .tooltiptext = Tag et Skærmbillede
 zen-site-data-header-bookmark = 
-    .tooltiptext = Bookmark This Page
+    .tooltiptext = Tilføj Side til Bogmærker
 zen-urlbar-copy-url-button = 
     .tooltiptext = Kopiér URL
 zen-site-data-setting-site-protection = Sporingsbeskyttelse
@@ -105,23 +117,26 @@ zen-site-data-setting-site-protection = Sporingsbeskyttelse
 # Section: Feature callouts
 
 zen-site-data-panel-feature-callout-title = Et nyt hjem for tilføjelser, tilladelser og mere
-zen-site-data-panel-feature-callout-subtitle = Click the icon to manage site settings, view security info, access extensions, and perform common actions.
+zen-site-data-panel-feature-callout-subtitle = Klik ikonet for at administrere side indstillinger, se sikkerhedsoplysninger, tilgå udvidelser, og udføre almindelige handlinger.
 zen-open-link-in-glance = 
     .label = Open Link in Glance
     .accesskey = G
-zen-sidebar-notification-updated-heading = Update Complete!
+zen-sidebar-notification-updated-heading = Opdatering Fuldført!
 
 # See ZenSidebarNotification.mjs to see how these would be used
 
-zen-sidebar-notification-updated-label = What's new in { -brand-short-name }
+zen-sidebar-notification-updated-label = Hvad er nyt i { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
-    .title = View Release Notes
-zen-sidebar-notification-restart-safe-mode-label = Something broke?
+    .title = Se Udgivelsesnoter
+zen-sidebar-notification-donate-label = Support { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donate to the project
+zen-sidebar-notification-restart-safe-mode-label = Noget der ikke virker?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
-    .title = Restart in Safe Mode
-zen-window-sync-migration-dialog-title = Keep Your Windows in Sync
-zen-window-sync-migration-dialog-message = Zen now syncs windows on the same device, so changes in one window are reflected across the others instantly.
-zen-window-sync-migration-dialog-learn-more = Learn More
-zen-window-sync-migration-dialog-accept = Got It
+    .title = Genstart i Beskyttet Tilstand
+zen-window-sync-migration-dialog-title = Hold Dine Vinduer Synkroniseret
+zen-window-sync-migration-dialog-message = Zen synkroniserer nu vinduer på samme enhed, så ændringer i et vindue afspejles øjeblikkeligt på tværs af de andre.
+zen-window-sync-migration-dialog-learn-more = Lær Mere
+zen-window-sync-migration-dialog-accept = Forstået
 zen-appmenu-new-blank-window = 
-    .label = New blank window
+    .label = Nyt tomt vindue
diff --git a/locales/da/browser/browser/zen-menubar.ftl b/locales/da/browser/browser/zen-menubar.ftl
index a24d50928..d9889d58b 100644
--- a/locales/da/browser/browser/zen-menubar.ftl
+++ b/locales/da/browser/browser/zen-menubar.ftl
@@ -9,14 +9,14 @@ zen-menubar-toggle-pinned-tabs =
            *[false] Collapse Pinned Tabs
         }
 zen-menubar-appearance = 
-    .label = Appearance
+    .label = Udseende
 zen-menubar-appearance-description = 
-    .label = Websites will use:
+    .label = Hjemmesider vil bruge:
 zen-menubar-appearance-auto = 
-    .label = Automatic
+    .label = Automatisk
 zen-menubar-appearance-light = 
-    .label = Light
+    .label = Lys
 zen-menubar-appearance-dark = 
-    .label = Dark
+    .label = Mørk
 zen-menubar-new-blank-window = 
-    .label = New Blank Window
+    .label = Nyt Tomt Vindue
diff --git a/locales/da/browser/browser/zen-space-routing.ftl b/locales/da/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..699599a41
--- /dev/null
+++ b/locales/da/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Space Routing Settings
+zen-space-routing-rulepanel-placeholder = Routes let you choose where specific sites open inside Zen. For example, you can route YouTube links to always open inside your Personal space.
+zen-space-routing-dialog-title = Space Routing Settings
+zen-space-routing-external-default = Default route for external links
+zen-space-routing-new-route = New Route
+zen-space-routing-open-in-space = Åben i Arbejdsområde
+zen-space-routing-most-recent-space = Seneste Arbejdsområde
+zen-space-routing-close-button = 
+    .aria-label = Luk
+    .tooltiptext = Luk
+zen-space-routing-contains = 
+    .label = Indeholder
+zen-space-routing-equal-to = 
+    .label = Is Equal To
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Åben i
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/da/browser/browser/zen-split-view.ftl b/locales/da/browser/browser/zen-split-view.ftl
index 5dd6024ab..a35d538dd 100644
--- a/locales/da/browser/browser/zen-split-view.ftl
+++ b/locales/da/browser/browser/zen-split-view.ftl
@@ -5,9 +5,9 @@
 tab-zen-split-tabs = 
     .label =
         { $tabCount ->
-            [-1] Split out tab
-            [1] Add split view...
-           *[other] Join { $tabCount } Tabs
+            [-1] Opdel fane
+            [1] Tilføj opdelt visning...
+           *[other] Sammenføj { $tabCount } Faner
         }
     .accesskey = S
 zen-split-link = 
diff --git a/locales/da/browser/browser/zen-vertical-tabs.ftl b/locales/da/browser/browser/zen-vertical-tabs.ftl
index 77325e82f..132ea277a 100644
--- a/locales/da/browser/browser/zen-vertical-tabs.ftl
+++ b/locales/da/browser/browser/zen-vertical-tabs.ftl
@@ -41,7 +41,7 @@ tabbrowser-reset-pin-button =
         }
 zen-tab-sublabel =
     { $tabSubtitle ->
-        [zen-default-pinned] Back to pinned url
-        [zen-default-pinned-cmd] Separate from pinned tab
+        [zen-default-pinned] Tilbage til fastgjort url
+        [zen-default-pinned-cmd] Adskil fra fastgjort fane
        *[other] { $tabSubtitle }
     }
diff --git a/locales/da/browser/browser/zen-workspaces.ftl b/locales/da/browser/browser/zen-workspaces.ftl
index f3208dc65..32be4a5aa 100644
--- a/locales/da/browser/browser/zen-workspaces.ftl
+++ b/locales/da/browser/browser/zen-workspaces.ftl
@@ -4,15 +4,15 @@
 
 zen-panel-ui-workspaces-text = Arbejdsområder
 zen-panel-ui-spaces-label = 
-    .label = Spaces
+    .label = Rum
 zen-panel-ui-workspaces-create = 
     .label = Opret rum
 zen-panel-ui-folder-create = 
     .label = Opret mappe
 zen-panel-ui-live-folder-create = 
-    .label = Live Folder
+    .label = Live Mappe
 zen-panel-ui-new-empty-split = 
-    .label = New Split
+    .label = Ny Opdeling
 zen-workspaces-panel-context-delete = 
     .label = Slet arbejdsområde
     .accesskey = D
@@ -23,9 +23,9 @@ zen-workspaces-panel-change-icon =
 zen-workspaces-panel-context-default-profile = 
     .label = Indstil profil
 zen-workspaces-panel-unload = 
-    .label = Unload Space
+    .label = Sæt Rum i Dvale
 zen-workspaces-panel-unload-others = 
-    .label = Unload All Other Spaces
+    .label = Sæt Alle Andre Rum i Dvale
 zen-workspaces-how-to-reorder-title = Sådan omarrangerer du rum
 zen-workspaces-how-to-reorder-desc = Træk rumikonerne nederst i sidepanelet for at omarrangere dem
 zen-workspaces-change-theme = 
@@ -37,7 +37,7 @@ zen-workspaces-panel-context-edit =
     .label = Rediger arbejdsområde
     .accesskey = E
 zen-bookmark-edit-panel-workspace-selector = 
-    .value = Spaces
+    .value = Rum
     .accesskey = W
 zen-panel-ui-gradient-generator-algo-complementary = 
     .label = Komplementær
@@ -54,22 +54,23 @@ zen-workspace-creation-name =
     .placeholder = Rumnavn
 zen-move-tab-to-workspace-button = 
     .label = Move To...
-    .tooltiptext = Move all tabs in this window to a Space
+    .tooltiptext = Bevæg alle faner i dette vindue til et Rum
 zen-workspaces-panel-context-reorder = 
     .label = Omarranger rum
 zen-workspace-creation-profile = Profil
     .tooltiptext = Profiler bruges til at adskille cookies og webstedsdata mellem forskellige rum.
 zen-workspace-creation-header = Opret et rum
 zen-workspace-creation-label = Rum bruges til at organisere dine faner og sessioner.
+zen-workspace-default-profile = Default
 zen-workspaces-delete-workspace-title = Slet arbejdsområde?
 zen-workspaces-delete-workspace-body = Er du sikker på, at du vil slette { $name }? Dette kan ikke fortrydes.
 # Note that the html tag MUST not be changed or removed, as it is used to better
 # display the shortcut in the toast notification.
-zen-workspaces-close-all-unpinned-tabs-toast = Tabs Closed! Use <span>{ $shortcut }</span> to undo.
+zen-workspaces-close-all-unpinned-tabs-toast = Faner Lukket! Brug <span>{ $shortcut }</span> for at fortryd.
 zen-workspaces-close-all-unpinned-tabs-title = 
-    .label = Clear
-    .tooltiptext = Close all unpinned tabs
+    .label = Ryd
+    .tooltiptext = Luk alle ikke-fastgjorte faner
 zen-panel-ui-workspaces-change-forward = 
-    .label = Next Space
+    .label = Nyt Rum
 zen-panel-ui-workspaces-change-back = 
-    .label = Previous Space
+    .label = Tidligere Rum
diff --git a/locales/de/browser/browser/preferences/zen-preferences.ftl b/locales/de/browser/browser/preferences/zen-preferences.ftl
index d58554d05..715672499 100644
--- a/locales/de/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/de/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Die obere Symbolleiste auch im Kompaktmodus ausblenden
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Symbolleiste im Kompaktmodus beim Wechseln oder Öffnen neuer Tabs kurz einblenden
+zen-look-and-feel-window-drag-header = Fenster ziehen
+zen-look-and-feel-window-drag-description = Verschiebe das Fenster, indem du leeren Platz an der Spitze der Webseite ziehst, genau wie die Titelleiste.
+zen-window-drag-enabled = 
+    .label = Erlaube das Ziehen des Fensters einer Webseite
 pane-zen-tabs-title = Tab-Verwaltung
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -54,7 +58,7 @@ zen-tabs-cycle-ignore-pending-tabs =
     .label = Ausstehende Tabs beim Wechseln mit Strg+Tab ignorieren
 zen-tabs-cycle-by-attribute-warning = Strg+Tab wechselt in der zuletzt verwendeten Reihenfolge, da diese Option aktiviert ist
 zen-look-and-feel-compact-toolbar-themed = 
-    .label = Theme-Hintergrund für kompakte Symbolleiste verwenden
+    .label = Design-Hintergrund für kompakte Symbolleiste verwenden
 zen-workspace-continue-where-left-off = 
     .label = Dort fortfahren, wo du aufgehört hast
 pane-zen-pinned-tab-manager-title = Angeheftete Tabs
@@ -64,7 +68,7 @@ zen-pinned-tab-manager-restore-pinned-tabs-to-pinned-url =
     .label = Angeheftete Tabs beim Start auf ihre ursprüngliche URL zurücksetzen
 zen-pinned-tab-manager-container-specific-essentials-enabled = 
     .label = Container-spezifische Essentials aktivieren
-zen-pinned-tab-manager-close-shortcut-behavior-label = Verhalten der Tastenkombination zum Schließen von Tabs
+zen-pinned-tab-manager-close-shortcut-behavior-label = Verhalten des Tastenkürzels zum Schließen von Tabs
 zen-pinned-tab-manager-reset-unload-switch-close-shortcut-option = 
     .label = URL zurücksetzen, entladen und zum nächsten Tab wechseln
 zen-pinned-tab-manager-unload-switch-close-shortcut-option = 
@@ -79,7 +83,7 @@ zen-pinned-tab-manager-close-close-shortcut-option =
     .label = Tab schließen
 pane-zen-workspaces-header = Arbeitsbereiche
 zen-settings-workspaces-header = Allgemeine Einstellungen für Arbeitsbereiche
-zen-settings-workspaces-description = Mit Arbeitsbereichen kannst du mehrere Browser-Sitzungen gleichzeitig haben
+zen-settings-workspaces-description = Mit Arbeitsbereichen kannst du mehrere Browser-Sitzungen gleichzeitig haben!
 zen-settings-workspaces-enabled = 
     .label = Arbeitsbereiche aktivieren (experimentell)
 zen-settings-workspaces-hide-default-container-indicator = 
@@ -91,16 +95,16 @@ zen-vertical-tabs-title = Seitenleiste und Tab-Layout
 zen-vertical-tabs-header = Vertikale Tabs
 zen-vertical-tabs-description = Verwalte deine Tabs in einem vertikalen Layout
 zen-vertical-tabs-show-expand-button = 
-    .label = Erweitern-Schaltfläche anzeigen
+    .label = Ausklapp-Button anzeigen
 zen-vertical-tabs-newtab-on-tab-list = 
     .label = „Neuer Tab“-Button in der Tab-Liste anzeigen
 zen-vertical-tabs-newtab-top-button-up = 
     .label = Schaltfläche „Neuer Tab“ nach oben verschieben
-zen-vertical-tabs-expand-tabs-by-default = Tabs standardmäßig erweitern
-zen-vertical-tabs-dont-expand-tabs-by-default = Tabs standardmäßig nicht erweitern
+zen-vertical-tabs-expand-tabs-by-default = Tabs standardmäßig ausklappen
+zen-vertical-tabs-dont-expand-tabs-by-default = Tabs standardmäßig nicht ausklappen
 zen-vertical-tabs-expand-tabs-on-hover = Tabs beim Drüberfahren erweitern (funktioniert nicht im Kompaktmodus)
-zen-vertical-tabs-expand-tabs-header = Wie Tabs erweitert werden sollen
-zen-vertical-tabs-expand-tabs-description = Wähle aus, wie Tabs in der Seitenleiste erweitert werden sollen
+zen-vertical-tabs-expand-tabs-header = Wie Tabs ausgeklappt werden
+zen-vertical-tabs-expand-tabs-description = Wähle aus, wie Tabs in der Seitenleiste ausgeklappt werden
 zen-theme-marketplace-header = Zen-Mods
 zen-theme-disable-all-enabled = 
     .title = Alle Mods deaktivieren
@@ -142,7 +146,7 @@ zen-theme-marketplace-link = Store besuchen
 zen-dark-theme-styles-header = Dunkles Design
 zen-dark-theme-styles-description = Passe das dunkle Design nach deinen Wünschen an
 zen-dark-theme-styles-amoled = Nacht-Design
-zen-dark-theme-styles-default = Standardmäßiges dunkles Design
+zen-dark-theme-styles-default = Dunkles Standard-Design
 zen-dark-theme-styles-colorful = Farbenfrohes dunkles Design
 zen-compact-mode-styles-left = Tab-Leiste ausblenden
 zen-compact-mode-styles-top = Obere Leiste ausblenden
@@ -208,7 +212,7 @@ zen-picture-in-picture-toggle-shortcut-mac = Bild-im-Bild umschalten (Mac)
 zen-picture-in-picture-toggle-shortcut-mac-alt = Bild-im-Bild umschalten (Mac Alternative)
 zen-page-source-shortcut-safari = Seitenquelltext (Safari)
 zen-nav-stop-shortcut = Navigation stoppen
-zen-history-sidebar-shortcut = Verlaufs-Seitenleiste
+zen-history-sidebar-shortcut = Verlaufs-Seitenleiste anzeigen
 zen-window-minimize-shortcut = Fenster minimieren
 zen-help-shortcut = Hilfe öffnen
 zen-preferences-shortcut = Einstellungen öffnen
@@ -238,13 +242,14 @@ zen-toggle-pin-tab-shortcut = Tab anheften/lösen
 zen-reader-mode-toggle-shortcut-other = Lesemodus umschalten
 zen-picture-in-picture-toggle-shortcut = Bild-im-Bild umschalten
 zen-nav-reload-shortcut-2 = Seite neu laden
-zen-key-about-processes = Über Prozesse
+zen-key-about-processes = Prozess-Manager öffnen
 zen-page-source-shortcut = Seitenquelltext anzeigen
 zen-page-info-shortcut = Seiteninformationen anzeigen
 zen-find-shortcut = Auf Seite suchen
 zen-search-find-again-shortcut = Weitersuchen
 zen-search-find-again-shortcut-prev = Vorheriges suchen
-zen-search-find-again-shortcut-2 = Weitersuchen (Alt)
+zen-search-find-again-shortcut-alt = Erneut suchen (Alt)
+zen-search-find-again-shortcut-prev-alt = Vorherigen suchen (Alt)
 zen-bookmark-this-page-shortcut = Diese Seite als Lesezeichen speichern
 zen-bookmark-show-library-shortcut = Lesezeichen-Bibliothek anzeigen
 zen-key-stop = Laden stoppen
@@ -255,7 +260,7 @@ zen-full-zoom-reset-shortcut-alt = Zoom zurücksetzen (Alt)
 zen-full-zoom-enlarge-shortcut-alt = Hineinzoomen (Alt)
 zen-full-zoom-enlarge-shortcut-alt2 = Hineinzoomen (Alt 2)
 zen-bidi-switch-direction-shortcut = Text-Richtung wechseln
-zen-private-browsing-shortcut = Privaten Modus öffnen
+zen-private-browsing-shortcut = Privates Fenster öffnen
 zen-screenshot-shortcut = Bildschirmfoto erstellen
 zen-key-sanitize = Browser-Daten löschen
 zen-quit-app-shortcut = Anwendung beenden
@@ -281,7 +286,7 @@ zen-workspace-shortcut-switch-9 = Zu Arbeitsbereich 9 wechseln
 zen-workspace-shortcut-switch-10 = Zu Arbeitsbereich 10 wechseln
 zen-workspace-shortcut-forward = Zum nächsten Arbeitsbereich wechseln
 zen-workspace-shortcut-backward = Zum vorherigen Arbeitsbereich wechseln
-zen-workspace-shortcut-create = Create New Workspace
+zen-workspace-shortcut-create = Neuen Arbeitsbereich erstellen
 zen-sidebar-shortcut-toggle = Seitenleisten-Breite umschalten
 zen-pinned-tab-shortcut-reset = Angehefteten Tab zurücksetzen
 zen-split-view-shortcut-grid = Raster-Layout für geteilte Ansicht umschalten
@@ -303,20 +308,20 @@ zen-key-goto-history = Zum Verlauf gehen
 zen-key-go-home = Zur Startseite gehen
 zen-bookmark-show-sidebar-shortcut = Lesezeichen-Seitenleiste anzeigen
 zen-bookmark-show-toolbar-shortcut = Lesezeichen-Symbolleiste anzeigen
-zen-devtools-toggle-shortcut = Entwicklertools umschalten
+zen-devtools-toggle-shortcut = Entwicklerwerkzeuge umschalten
 zen-devtools-toggle-browser-toolbox-shortcut = Browser-Toolbox umschalten
 zen-devtools-toggle-browser-console-shortcut = Browser-Konsole umschalten
 zen-devtools-toggle-responsive-design-mode-shortcut = Responsive-Design-Modus umschalten
 zen-devtools-toggle-inspector-shortcut = Inspektor umschalten
 zen-devtools-toggle-web-console-shortcut = Web-Konsole umschalten
 zen-devtools-toggle-js-debugger-shortcut = JavaScript-Debugger umschalten
-zen-devtools-toggle-net-monitor-shortcut = Netzwerk-Monitor umschalten
+zen-devtools-toggle-net-monitor-shortcut = Netzwerkanalyse umschalten
 zen-devtools-toggle-style-editor-shortcut = Stil-Editor umschalten
-zen-devtools-toggle-performance-shortcut = Performance umschalten
+zen-devtools-toggle-performance-shortcut = Leistung umschalten
 zen-devtools-toggle-storage-shortcut = Speicher umschalten
 zen-devtools-toggle-dom-shortcut = DOM umschalten
 zen-devtools-toggle-accessibility-shortcut = Barrierefreiheit umschalten
 zen-close-all-unpinned-tabs-shortcut = Alle nicht angehefteten Tabs schließen
 zen-new-unsynced-window-shortcut = Neues leeres Fenster
 zen-duplicate-tab-shortcut = Tab duplizieren
-zen-key-find-selection = Find Selection
+zen-key-find-selection = Auswahl suchen
diff --git a/locales/de/browser/browser/zen-boosts.ftl b/locales/de/browser/browser/zen-boosts.ftl
index 3dc0465ed..c2164344a 100644
--- a/locales/de/browser/browser/zen-boosts.ftl
+++ b/locales/de/browser/browser/zen-boosts.ftl
@@ -11,7 +11,7 @@ zen-boost-edit-reset =
 zen-boost-edit-delete = 
     .label = Boost löschen
 zen-boost-size = Größe
-zen-boost-case = Case
+zen-boost-case = Schreibweise
 zen-boost-zap = Zap
 zen-boost-code = Code
 zen-boost-back = Zurück
@@ -32,25 +32,25 @@ zen-boost-css-inspector =
 zen-boost-color-contrast = Kontrast
 zen-boost-color-brightness = Helligkeit
 zen-boost-color-original-saturation = Ausgangssättigung
-zen-add-zap-helper = Klicke auf Elemente auf der Seite, um sie mit <b>Zap</b> zu markieren
-zen-remove-zap-helper = ← Erneut klicken zum Wiederherstellen
+zen-add-zap-helper = Klicke auf Elemente der Seite, um sie zu <b>zappen</b>
+zen-remove-zap-helper = ← Klicken zum Entzappen
 zen-select-this = Selektor für dieses Element einfügen
 zen-select-related = Selektor für verwandte Elemente einfügen
 zen-select-cancel = Abbrechen
-zen-zap-this = Dieses entfernen
-zen-zap-related = Alle verwandten Elemente entfernen
+zen-zap-this = Dieses Element zappen
+zen-zap-related = Alle verwandten Elemente zappen
 zen-zap-cancel = Abbrechen
 zen-zap-done = Fertig
 zen-unzap-tooltip =
     { $elementCount ->
-        [0] Keine Elemente entfernt
-        [1] { $elementCount } Element entfernt
-       *[other] { $elementCount } Elemente entfernt
+        [0] Keine Elemente gezappt
+        [1] { $elementCount } Element gezappt
+       *[other] { $elementCount } Elemente gezappt
     }
 zen-boost-save = 
-    .label = Export Boost
+    .label = Boost exportieren
 zen-boost-load = 
-    .label = Import Boost
+    .label = Boost importieren
 zen-panel-ui-boosts-exported-message = Boost exportiert!
 zen-site-data-boosts = Boosts
 zen-site-data-create-boost = 
diff --git a/locales/de/browser/browser/zen-command-palette.ftl b/locales/de/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..e701fa447
--- /dev/null
+++ b/locales/de/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Kompakten Modus umschalten
+zen-action-open-theme-picker = Theme-Auswahl öffnen
+zen-action-new-split-view = Neue geteilte Ansicht
+zen-action-new-folder = Neuer Ordner
+zen-action-copy-current-url = Aktuelle URL kopieren
+zen-action-settings = Einstellungen
+zen-action-open-private-window = Privates Fenster öffnen
+zen-action-open-new-window = Neues Fenster öffnen
+zen-action-new-blank-window = Neues leeres Fenster
+zen-action-pin-tab = Tab anheften
+zen-action-unpin-tab = Tab lösen
+zen-action-open-space-routing = Arbeitsbereich-Routing öffnen
+zen-action-new-boost = Neuer Boost
+zen-action-next-space = Neuer Arbeitsbereich
+zen-action-previous-space = Vorheriger Arbeitsbereich
+zen-action-close-tab = Tab schließen
+zen-action-reload-tab = Tab neu laden
+zen-action-reload-tab-without-cache = Tab ohne Cache neu laden
+zen-action-next-tab = Nächster Tab
+zen-action-previous-tab = Vorherige Tab
+zen-action-capture-screenshot = Screenshot erstellen
+zen-action-toggle-tabs-on-right = Tab nach rechts umschalten
+zen-action-add-to-essentials = Zu Essentials hinzufügen
+zen-action-remove-from-essentials = Von Essentials entfernen
+zen-action-find-in-page = In Seite suchen
+zen-action-manage-extensions = Erweiterungen verwalten
+zen-action-switch-to-automatic-appearance = Zur automatischen Darstellung wechseln
+zen-action-switch-to-light-mode = Zum hellen Modus wechseln
+zen-action-switch-to-dark-mode = Zum dunklen Modus wechseln
+zen-action-print = Drucken
+zen-action-focus-on = Fokussieren auf
+zen-action-extension = Erweiterung
diff --git a/locales/de/browser/browser/zen-general.ftl b/locales/de/browser/browser/zen-general.ftl
index 66b8d4849..04c4f8472 100644
--- a/locales/de/browser/browser/zen-general.ftl
+++ b/locales/de/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max } Plätzen belegt
 tab-context-zen-remove-essential = 
     .label = Aus Essentials entfernen
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Essential-URL durch aktuelle ersetzen
-           *[false] Angeheftete URL durch aktuelle ersetzen
+            [true] Essentials URL bearbeiten
+           *[false] Angeheftete URL bearbeiten
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Mit aktueller URL ersetzen
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Bearbeiten...
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Titel ändern...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Bestätigen
 zen-pinned-tab-replaced = Die URL des angehefteten Tabs wurde aktualisiert!
+zen-pinned-tab-url-edited = Angeheftete URL wurde aktualisiert!
+zen-pinned-tab-url-invalid = Das sieht nicht nach einer gültigen URL aus.
+zen-pinned-tab-edit-url-title = Angeheftete URL bearbeiten
+zen-pinned-tab-edit-url-label = Gib die URL an, auf die der angeheftete Tab verweisen soll:
 zen-tabs-renamed = Tab umbenannt!
 zen-background-tab-opened-toast = Neuer Tab im Hintergrund geöffnet!
 zen-workspace-renamed-toast = Arbeitsbereich umbenannt!
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = Emojis
 zen-icons-picker-svg = 
     .label = Symbole
+zen-emojis-picker-search = 
+    .placeholder = Emojis durchsuchen
 urlbar-search-mode-zen_actions = Aktionen
 zen-site-data-settings = Einstellungen
 zen-generic-manage = Verwalten
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = Update abgeschlossen!
 zen-sidebar-notification-updated-label = Was in { -brand-short-name } neu ist
 zen-sidebar-notification-updated-tooltip = 
     .title = Versionshinweise anzeigen
+zen-sidebar-notification-donate-label = Unterstütze { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Spende für das Projekt
 zen-sidebar-notification-restart-safe-mode-label = Funktioniert etwas nicht?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Im abgesicherten Modus neu starten
diff --git a/locales/de/browser/browser/zen-space-routing.ftl b/locales/de/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..d8ab60f27
--- /dev/null
+++ b/locales/de/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Einstellungen für Arbeitsbereich-Routing
+zen-space-routing-rulepanel-placeholder = Mit Routen legst du fest, wo bestimmte Websites in Zen geöffnet werden. Du kannst zum Beispiel YouTube-Links immer in deinem privaten Arbeitsbereich öffnen lassen.
+zen-space-routing-dialog-title = Einstellungen für Arbeitsbereich-Routing
+zen-space-routing-external-default = Standardroute für externe Links
+zen-space-routing-new-route = Neue Route
+zen-space-routing-open-in-space = Im Arbeitsbereich öffnen
+zen-space-routing-most-recent-space = Zuletzt genutzter Arbeitsbereich
+zen-space-routing-close-button = 
+    .aria-label = Schließen
+    .tooltiptext = Schließen
+zen-space-routing-contains = 
+    .label = Enthält
+zen-space-routing-equal-to = 
+    .label = Ist gleich
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Öffnen in
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = Neuer Tab in { $targetWorkspace } geöffnet
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Route für Domain hinzufügen
+           *[other] Route für Domains hinzufügen
+        }
diff --git a/locales/de/browser/browser/zen-split-view.ftl b/locales/de/browser/browser/zen-split-view.ftl
index d230a24cb..9461629fb 100644
--- a/locales/de/browser/browser/zen-split-view.ftl
+++ b/locales/de/browser/browser/zen-split-view.ftl
@@ -6,13 +6,13 @@ tab-zen-split-tabs =
     .label =
         { $tabCount ->
             [-1] Tab abtrennen
-            [1] Split View hinzufügen...
+            [1] Geteilte Ansicht hinzufügen…
            *[other] { $tabCount } Tabs zusammenführen
         }
     .accesskey = S
 zen-split-link = 
-    .label = Link in geteiltem Tab öffnen
-    .accesskey = S
+    .label = Link in geteilter Ansicht öffnen
+    .accesskey = G
 zen-split-view-modifier-header = Geteilte Ansicht
 zen-split-view-modifier-activate-reallocation = 
     .label = Anordnung ändern
diff --git a/locales/de/browser/browser/zen-vertical-tabs.ftl b/locales/de/browser/browser/zen-vertical-tabs.ftl
index 633973af8..a2c3a7fde 100644
--- a/locales/de/browser/browser/zen-vertical-tabs.ftl
+++ b/locales/de/browser/browser/zen-vertical-tabs.ftl
@@ -16,10 +16,10 @@ zen-toolbar-context-compact-mode-just-toolbar =
     .label = Nur Symbolleiste ausblenden
 zen-toolbar-context-compact-mode-hide-both = 
     .label = Beides ausblenden
-    .accesskey = H
+    .accesskey = B
 zen-toolbar-context-move-to-folder = 
     .label = In Ordner verschieben...
-    .accesskey = M
+    .accesskey = O
 zen-toolbar-context-new-folder = 
     .label = Neuer Ordner
     .accesskey = N
diff --git a/locales/de/browser/browser/zen-welcome.ftl b/locales/de/browser/browser/zen-welcome.ftl
index d46b7759a..41757708e 100644
--- a/locales/de/browser/browser/zen-welcome.ftl
+++ b/locales/de/browser/browser/zen-welcome.ftl
@@ -2,24 +2,24 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-zen-welcome-title-line1 = Willkommen zu
+zen-welcome-title-line1 = Willkommen in
 zen-welcome-title-line2 = einem ruhigeren Internet
 zen-welcome-import-title = Ein neuer Anfang, dieselben Lesezeichen
 zen-welcome-import-description-1 = Deine Lesezeichen, dein Verlauf und deine Passwörter sind wie eine Spur durch das Internet – lass sie nicht zurück!
 zen-welcome-import-description-2 = Übertrage sie ganz einfach aus einem anderen Browser und mache genau dort weiter, wo du aufgehört hast.
 zen-welcome-import-button = Jetzt importieren
 zen-welcome-set-default-browser = { -brand-short-name } als Standardbrowser festlegen
-zen-welcome-dont-set-default-browser = { -brand-short-name } nicht als Standardbrowser festlegen
+zen-welcome-dont-set-default-browser = { -brand-short-name } NICHT als Standardbrowser festlegen
 zen-welcome-initial-essentials-title = Deine wichtigsten Tabs, immer in Reichweite
 zen-welcome-initial-essentials-description-1 = Halte deine wichtigsten Tabs leicht zugänglich und immer griffbereit, egal wie viele du öffnest.
-zen-welcome-initial-essentials-description-2 = Essential-Tabs sind immer sichtbar, unabhängig davon, in welchem Arbeitsbereich du dich befindest.
+zen-welcome-initial-essentials-description-2 = Essential-Tabs sind immer sichtbar, egal in welchem Arbeitsbereich du bist.
 zen-welcome-workspace-colors-title = Deine Arbeitsbereiche, deine Farben
 zen-welcome-workspace-colors-description = Personalisiere deinen Browser, indem du jedem Arbeitsbereich eine eigene Farbidentität gibst.
 zen-welcome-start-browsing-title =
     Alles bereit?<br/>
     Los geht's!
 zen-welcome-start-browsing-description-1 = Du bist startklar! Klicke auf den Button unten, um mit { -brand-short-name } loszulegen.
-zen-welcome-start-browsing = Los geht's!
+zen-welcome-start-browsing = Loslegen!
 zen-welcome-default-search-title = Deine Standard-Suchmaschine
 zen-welcome-default-search-description = Wähle deine Standard-Suchmaschine. Du kannst sie jederzeit später ändern!
 zen-welcome-skip-button = Überspringen
diff --git a/locales/de/browser/browser/zen-workspaces.ftl b/locales/de/browser/browser/zen-workspaces.ftl
index 829e1f606..bf18b4e89 100644
--- a/locales/de/browser/browser/zen-workspaces.ftl
+++ b/locales/de/browser/browser/zen-workspaces.ftl
@@ -12,10 +12,10 @@ zen-panel-ui-folder-create =
 zen-panel-ui-live-folder-create = 
     .label = Live-Ordner
 zen-panel-ui-new-empty-split = 
-    .label = Neuen Split erstellen
+    .label = Neue geteilte Ansicht
 zen-workspaces-panel-context-delete = 
     .label = Arbeitsbereich löschen
-    .accesskey = D
+    .accesskey = L
 zen-workspaces-panel-change-name = 
     .label = Namen ändern
 zen-workspaces-panel-change-icon = 
@@ -32,13 +32,13 @@ zen-workspaces-change-theme =
     .label = Design anpassen
 zen-workspaces-panel-context-open = 
     .label = Arbeitsbereich öffnen
-    .accesskey = O
+    .accesskey = ö
 zen-workspaces-panel-context-edit = 
     .label = Arbeitsbereich bearbeiten
     .accesskey = E
 zen-bookmark-edit-panel-workspace-selector = 
     .value = Arbeitsbereiche
-    .accesskey = W
+    .accesskey = A
 zen-panel-ui-gradient-generator-algo-complementary = 
     .label = Komplementär
 zen-panel-ui-gradient-generator-algo-splitComplementary = 
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Profil
     .tooltiptext = Profile trennen Cookies und Website-Daten zwischen verschiedenen Arbeitsbereichen.
 zen-workspace-creation-header = Arbeitsbereich erstellen
 zen-workspace-creation-label = Arbeitsbereiche helfen dir, deine Tabs und Sitzungen zu organisieren.
+zen-workspace-default-profile = Standard
 zen-workspaces-delete-workspace-title = Arbeitsbereich löschen?
 zen-workspaces-delete-workspace-body = Möchtest du { $name } wirklich löschen? Das lässt sich nicht rückgängig machen.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/el/browser/browser/preferences/zen-preferences.ftl b/locales/el/browser/browser/preferences/zen-preferences.ftl
index 61e2f7bdd..b39e2e77b 100644
--- a/locales/el/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/el/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Απόκρυψη και της επάνω γραμμής εργαλείων σε συμπαγή λειτουργία
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Σύντομη ανάδυση της γραμμής εργαλείων κατά την εναλλαγή ή το άνοιγμα νέων καρτελών σε συμπαγή λειτουργία
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Allow dragging the window from web pages
 pane-zen-tabs-title = Διαχείριση Καρτελών
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = Προβολή Πληροφοριών Σελίδας
 zen-find-shortcut = Εύρεση στη Σελίδα
 zen-search-find-again-shortcut = Εύρεση Ξανά
 zen-search-find-again-shortcut-prev = Εύρεση Προηγουμένου
-zen-search-find-again-shortcut-2 = Εύρεση Ξανά (Alt)
+zen-search-find-again-shortcut-alt = Find Again (Alt)
+zen-search-find-again-shortcut-prev-alt = Find Previous (Alt)
 zen-bookmark-this-page-shortcut = Σελιδοδείκτης στη Σελίδα
 zen-bookmark-show-library-shortcut = Εμφάνιση Βιβλιοθήκης Σελιδοδεικτών
 zen-key-stop = Διακοπή Φόρτωσης
diff --git a/locales/el/browser/browser/zen-command-palette.ftl b/locales/el/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..c8af413e2
--- /dev/null
+++ b/locales/el/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Toggle Compact Mode
+zen-action-open-theme-picker = Open Theme Picker
+zen-action-new-split-view = New Split View
+zen-action-new-folder = New Folder
+zen-action-copy-current-url = Copy Current URL
+zen-action-settings = Settings
+zen-action-open-private-window = Open Private Window
+zen-action-open-new-window = Open New Window
+zen-action-new-blank-window = New Blank Window
+zen-action-pin-tab = Pin Tab
+zen-action-unpin-tab = Unpin Tab
+zen-action-open-space-routing = Open Space Routing
+zen-action-new-boost = New Boost
+zen-action-next-space = Next Space
+zen-action-previous-space = Previous Space
+zen-action-close-tab = Close Tab
+zen-action-reload-tab = Reload Tab
+zen-action-reload-tab-without-cache = Reload Tab Without Cache
+zen-action-next-tab = Next Tab
+zen-action-previous-tab = Previous Tab
+zen-action-capture-screenshot = Capture Screenshot
+zen-action-toggle-tabs-on-right = Toggle Tabs on right
+zen-action-add-to-essentials = Add to Essentials
+zen-action-remove-from-essentials = Remove from Essentials
+zen-action-find-in-page = Find in Page
+zen-action-manage-extensions = Manage Extensions
+zen-action-switch-to-automatic-appearance = Switch to Automatic Appearance
+zen-action-switch-to-light-mode = Switch to Light Mode
+zen-action-switch-to-dark-mode = Switch to Dark Mode
+zen-action-print = Print
+zen-action-focus-on = Focus on
+zen-action-extension = Extension
diff --git a/locales/el/browser/browser/zen-general.ftl b/locales/el/browser/browser/zen-general.ftl
index 7e9c8c2ff..09c9dd9d4 100644
--- a/locales/el/browser/browser/zen-general.ftl
+++ b/locales/el/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max } γεμισμένες 
 tab-context-zen-remove-essential = 
     .label = Αφαίρεση από Απαραίτητα
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Αντικατάσταση Απαραίτητης διεύθυνσής με την τωρινή
-           *[false] Αντικατάσταση Καρφιτσωμένης διεύθυνσής με την τωρινή
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Replace with Current URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Edit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Αλλαγή Ετικέτας...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Επιβεβαίωση
 zen-pinned-tab-replaced = Το URL της καρφιτσωμένης καρτέλας έχει αντικατασταθεί από το τρέχον URL.
+zen-pinned-tab-url-edited = Pinned tab URL has been updated!
+zen-pinned-tab-url-invalid = That doesn't look like a valid URL.
+zen-pinned-tab-edit-url-title = Edit Pinned URL
+zen-pinned-tab-edit-url-label = Enter the URL this pinned tab should point to:
 zen-tabs-renamed = Η καρτέλα μετονομάστηκε επιτυχώς!
 zen-background-tab-opened-toast = Άνοιξε νέα καρτέλα στο παρασκήνιο!
 zen-workspace-renamed-toast = Ο χώρος εργασίας μετονομάστηκε επιτυχώς!
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = Εμότζι
 zen-icons-picker-svg = 
     .label = Εικονίδια
+zen-emojis-picker-search = 
+    .placeholder = Search emojis
 urlbar-search-mode-zen_actions = Ενέργειες
 zen-site-data-settings = Ρυθμίσεις
 zen-generic-manage = Διαχείριση
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = Η Ενημέρωση Ολοκληρ
 zen-sidebar-notification-updated-label = Τι νέο υπάρχει στο { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = Προβολή Σημειώσεων Έκδοσης
+zen-sidebar-notification-donate-label = Support { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donate to the project
 zen-sidebar-notification-restart-safe-mode-label = Χάλασε κάτι;
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Επανεκκίνηση σε Ασφαλή Λειτουργία
diff --git a/locales/el/browser/browser/zen-space-routing.ftl b/locales/el/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..d757144bb
--- /dev/null
+++ b/locales/el/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Space Routing Settings
+zen-space-routing-rulepanel-placeholder = Routes let you choose where specific sites open inside Zen. For example, you can route YouTube links to always open inside your Personal space.
+zen-space-routing-dialog-title = Space Routing Settings
+zen-space-routing-external-default = Default route for external links
+zen-space-routing-new-route = New Route
+zen-space-routing-open-in-space = Open in Space
+zen-space-routing-most-recent-space = Most recent Space
+zen-space-routing-close-button = 
+    .aria-label = Close
+    .tooltiptext = Close
+zen-space-routing-contains = 
+    .label = Contains
+zen-space-routing-equal-to = 
+    .label = Is Equal To
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Open In
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/el/browser/browser/zen-workspaces.ftl b/locales/el/browser/browser/zen-workspaces.ftl
index 320be140b..10c085bc2 100644
--- a/locales/el/browser/browser/zen-workspaces.ftl
+++ b/locales/el/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Προφίλ
     .tooltiptext = Τα προφίλ χρησιμοποιούνται για να διαχωρίζουν τα cookies και τα δεδομένα του ιστότοπου μεταξύ των χώρων.
 zen-workspace-creation-header = Δημιουργία Χώρου
 zen-workspace-creation-label = Οι χώροι χρησιμοποιούνται για την οργάνωση των καρτελών και των συνεδριών σας.
+zen-workspace-default-profile = Default
 zen-workspaces-delete-workspace-title = Διαγραφή Χώρου Εργασίας;
 zen-workspaces-delete-workspace-body = Είστε σίγουροι ότι Θέλετε να διαγράψετε το { $name }; Αυτή η πράξη δεν μπορεί να αναιρεθεί.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/en-GB/browser/browser/preferences/zen-preferences.ftl b/locales/en-GB/browser/browser/preferences/zen-preferences.ftl
index 295f8542e..c67ebbf74 100644
--- a/locales/en-GB/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/en-GB/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Hide the top toolbar as well in compact mode
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Briefly make the toolbar pop-up when switching or opening new tabs in compact mode
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Allow dragging the window from web pages
 pane-zen-tabs-title = Tab Management
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = View Page Info
 zen-find-shortcut = Find on Page
 zen-search-find-again-shortcut = Find Again
 zen-search-find-again-shortcut-prev = Find Previous
-zen-search-find-again-shortcut-2 = Find Again (Alt)
+zen-search-find-again-shortcut-alt = Find Again (Alt)
+zen-search-find-again-shortcut-prev-alt = Find Previous (Alt)
 zen-bookmark-this-page-shortcut = Bookmark This Page
 zen-bookmark-show-library-shortcut = Show Bookmarks Library
 zen-key-stop = Stop Loading
diff --git a/locales/en-GB/browser/browser/zen-command-palette.ftl b/locales/en-GB/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..c8af413e2
--- /dev/null
+++ b/locales/en-GB/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Toggle Compact Mode
+zen-action-open-theme-picker = Open Theme Picker
+zen-action-new-split-view = New Split View
+zen-action-new-folder = New Folder
+zen-action-copy-current-url = Copy Current URL
+zen-action-settings = Settings
+zen-action-open-private-window = Open Private Window
+zen-action-open-new-window = Open New Window
+zen-action-new-blank-window = New Blank Window
+zen-action-pin-tab = Pin Tab
+zen-action-unpin-tab = Unpin Tab
+zen-action-open-space-routing = Open Space Routing
+zen-action-new-boost = New Boost
+zen-action-next-space = Next Space
+zen-action-previous-space = Previous Space
+zen-action-close-tab = Close Tab
+zen-action-reload-tab = Reload Tab
+zen-action-reload-tab-without-cache = Reload Tab Without Cache
+zen-action-next-tab = Next Tab
+zen-action-previous-tab = Previous Tab
+zen-action-capture-screenshot = Capture Screenshot
+zen-action-toggle-tabs-on-right = Toggle Tabs on right
+zen-action-add-to-essentials = Add to Essentials
+zen-action-remove-from-essentials = Remove from Essentials
+zen-action-find-in-page = Find in Page
+zen-action-manage-extensions = Manage Extensions
+zen-action-switch-to-automatic-appearance = Switch to Automatic Appearance
+zen-action-switch-to-light-mode = Switch to Light Mode
+zen-action-switch-to-dark-mode = Switch to Dark Mode
+zen-action-print = Print
+zen-action-focus-on = Focus on
+zen-action-extension = Extension
diff --git a/locales/en-GB/browser/browser/zen-general.ftl b/locales/en-GB/browser/browser/zen-general.ftl
index 479798b15..f03e87ce2 100644
--- a/locales/en-GB/browser/browser/zen-general.ftl
+++ b/locales/en-GB/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max } slots filled
 tab-context-zen-remove-essential = 
     .label = Remove from Essentials
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Replace Essential URL with Current
-           *[false] Replace Pinned URL with Current
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Replace with Current URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Edit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Change Label...
 tab-context-zen-edit-icon = 
@@ -45,6 +51,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Confirm
 zen-pinned-tab-replaced = Pinned tab URL has been replaced with the current URL.
+zen-pinned-tab-url-edited = Pinned tab URL has been updated!
+zen-pinned-tab-url-invalid = That doesn't look like a valid URL.
+zen-pinned-tab-edit-url-title = Edit Pinned URL
+zen-pinned-tab-edit-url-label = Enter the URL this pinned tab should point to:
 zen-tabs-renamed = Tab has been successfully renamed!
 zen-background-tab-opened-toast = New background tab opened!
 zen-workspace-renamed-toast = Workspace has been successfully renamed!
@@ -63,6 +73,8 @@ zen-icons-picker-emoji =
     .label = Emojis
 zen-icons-picker-svg = 
     .label = Icons
+zen-emojis-picker-search = 
+    .placeholder = Search emojis
 urlbar-search-mode-zen_actions = Actions
 zen-site-data-settings = Settings
 zen-generic-manage = Manage
@@ -114,6 +126,9 @@ zen-sidebar-notification-updated-heading = Update Complete!
 zen-sidebar-notification-updated-label = What's new in { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = View Release Notes
+zen-sidebar-notification-donate-label = Support { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donate to the project
 zen-sidebar-notification-restart-safe-mode-label = Something broke?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Restart in Safe Mode
diff --git a/locales/en-GB/browser/browser/zen-space-routing.ftl b/locales/en-GB/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..d757144bb
--- /dev/null
+++ b/locales/en-GB/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Space Routing Settings
+zen-space-routing-rulepanel-placeholder = Routes let you choose where specific sites open inside Zen. For example, you can route YouTube links to always open inside your Personal space.
+zen-space-routing-dialog-title = Space Routing Settings
+zen-space-routing-external-default = Default route for external links
+zen-space-routing-new-route = New Route
+zen-space-routing-open-in-space = Open in Space
+zen-space-routing-most-recent-space = Most recent Space
+zen-space-routing-close-button = 
+    .aria-label = Close
+    .tooltiptext = Close
+zen-space-routing-contains = 
+    .label = Contains
+zen-space-routing-equal-to = 
+    .label = Is Equal To
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Open In
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/en-GB/browser/browser/zen-workspaces.ftl b/locales/en-GB/browser/browser/zen-workspaces.ftl
index dc52e03d1..55aaf4040 100644
--- a/locales/en-GB/browser/browser/zen-workspaces.ftl
+++ b/locales/en-GB/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Profile
     .tooltiptext = Profiles are used to separate cookies and site data between spaces.
 zen-workspace-creation-header = Create a Space
 zen-workspace-creation-label = Spaces are used to organise your tabs and sessions.
+zen-workspace-default-profile = Default
 zen-workspaces-delete-workspace-title = Delete Workspace?
 zen-workspaces-delete-workspace-body = Are you sure you want to delete { $name }? This action cannot be undone.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/en-US/browser/browser/preferences/zen-preferences.ftl b/locales/en-US/browser/browser/preferences/zen-preferences.ftl
index 62f8eebd9..473bfb740 100644
--- a/locales/en-US/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/en-US/browser/browser/preferences/zen-preferences.ftl
@@ -48,6 +48,11 @@ zen-look-and-feel-compact-view-top-toolbar =
 zen-look-and-feel-compact-toolbar-flash-popup =
     .label = Briefly make the toolbar popup when switching or opening new tabs in compact mode
 
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled =
+    .label = Allow dragging the window from web pages
+
 pane-zen-tabs-title = Tab Management
 category-zen-workspaces =
     .tooltiptext = { pane-zen-tabs-title }
diff --git a/locales/en-US/browser/browser/zen-general.ftl b/locales/en-US/browser/browser/zen-general.ftl
index d0ebc5f9d..31bdff0a4 100644
--- a/locales/en-US/browser/browser/zen-general.ftl
+++ b/locales/en-US/browser/browser/zen-general.ftl
@@ -164,5 +164,5 @@ zen-window-sync-migration-dialog-learn-more = Learn More
 zen-window-sync-migration-dialog-accept = Got It
 
 zen-appmenu-new-blank-window =
-    .label = New blank window
+    .label = New Blank Window
 
diff --git a/locales/en-US/browser/browser/zen-split-view.ftl b/locales/en-US/browser/browser/zen-split-view.ftl
index ee1e7081f..0a6176942 100644
--- a/locales/en-US/browser/browser/zen-split-view.ftl
+++ b/locales/en-US/browser/browser/zen-split-view.ftl
@@ -5,14 +5,14 @@
 tab-zen-split-tabs =
     .label =
         { $tabCount ->
-            [-1] Split out tab
-            [1] Add split view...
+            [-1] Split Out Tab
+            [1] Add Split View...
            *[other] Join { $tabCount } Tabs
         }
     .accesskey = S
 
 zen-split-link =
-    .label = Split link to new tab
+    .label = Split Link to New Tab
     .accesskey = S
 
 zen-split-view-modifier-header = Split View
diff --git a/locales/en-US/browser/browser/zen-workspaces.ftl b/locales/en-US/browser/browser/zen-workspaces.ftl
index a418f05fd..7274a6bcc 100644
--- a/locales/en-US/browser/browser/zen-workspaces.ftl
+++ b/locales/en-US/browser/browser/zen-workspaces.ftl
@@ -86,6 +86,8 @@ zen-workspace-default-profile = Default
 
 zen-workspaces-delete-workspace-title = Delete Space?
 zen-workspaces-delete-workspace-body = Are you sure you want to delete { $name }? This action cannot be undone.
+zen-workspaces-remote-delete-title = Delete Synced Space?
+zen-workspaces-remote-delete-body = { $name } was deleted on another device. Delete it here too? Keeping it will restore it on your other devices.
 
 # Note that the html tag MUST not be changed or removed, as it is used to better
 # display the shortcut in the toast notification.
diff --git a/locales/es-ES/browser/browser/preferences/zen-preferences.ftl b/locales/es-ES/browser/browser/preferences/zen-preferences.ftl
index 305e2f0b6..ba8bce037 100644
--- a/locales/es-ES/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/es-ES/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Ocultar también la barra de herramientas superior en el modo compacto
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Hacer emerger brevemente la barra de herramientas al cambiar o abrir nuevas pestañas en el modo compacto
+zen-look-and-feel-window-drag-header = Arrastrar ventana
+zen-look-and-feel-window-drag-description = Mueva la ventana arrastrando espacio vacío en la parte superior de los sitios web, al igual que la barra de título.
+zen-window-drag-enabled = 
+    .label = Permitir arrastrar la ventana desde páginas web
 pane-zen-tabs-title = Administración de pestañas
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = Ver información de la página
 zen-find-shortcut = Encontrar en la página
 zen-search-find-again-shortcut = Encontrar de nuevo
 zen-search-find-again-shortcut-prev = Encontrar anterior
-zen-search-find-again-shortcut-2 = Encontrar de nuevo (Alt)
+zen-search-find-again-shortcut-alt = Encontrar de nuevo (Alt)
+zen-search-find-again-shortcut-prev-alt = Encontrar anterior (Alt)
 zen-bookmark-this-page-shortcut = Añadir página a marcadores
 zen-bookmark-show-library-shortcut = Mostrar catálogo de marcadores
 zen-key-stop = Detener carga
diff --git a/locales/es-ES/browser/browser/zen-command-palette.ftl b/locales/es-ES/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..9104b6822
--- /dev/null
+++ b/locales/es-ES/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Alternar modo compacto
+zen-action-open-theme-picker = Abrir selector de temas
+zen-action-new-split-view = Nueva vista dividida
+zen-action-new-folder = Nueva carpeta
+zen-action-copy-current-url = Copiar URL actual
+zen-action-settings = Ajustes
+zen-action-open-private-window = Abrir ventana privada
+zen-action-open-new-window = Abrir nueva ventana
+zen-action-new-blank-window = Nueva ventana en blanco
+zen-action-pin-tab = Fijar pestaña
+zen-action-unpin-tab = Desfijar pestaña
+zen-action-open-space-routing = Abrir enrutamiento del espacio
+zen-action-new-boost = Nuevo Boost
+zen-action-next-space = Espacio siguiente
+zen-action-previous-space = Espacio anterior
+zen-action-close-tab = Cerrar pestaña
+zen-action-reload-tab = Recargar pestaña
+zen-action-reload-tab-without-cache = Recargar pestaña sin caché
+zen-action-next-tab = Pestaña siguiente
+zen-action-previous-tab = Pestaña anterior
+zen-action-capture-screenshot = Tomar captura de pantalla
+zen-action-toggle-tabs-on-right = Alternar pestañas a la derecha
+zen-action-add-to-essentials = Añadir a esenciales
+zen-action-remove-from-essentials = Quitar de esenciales
+zen-action-find-in-page = Encontrar en la página
+zen-action-manage-extensions = Administrar extensiones
+zen-action-switch-to-automatic-appearance = Cambiar a apariencia automática
+zen-action-switch-to-light-mode = Cambiar al modo claro
+zen-action-switch-to-dark-mode = Cambiar al modo oscuro
+zen-action-print = Imprimir
+zen-action-focus-on = Centrarse en
+zen-action-extension = Extensión
diff --git a/locales/es-ES/browser/browser/zen-general.ftl b/locales/es-ES/browser/browser/zen-general.ftl
index b9fb5237f..82fe9752b 100644
--- a/locales/es-ES/browser/browser/zen-general.ftl
+++ b/locales/es-ES/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max } huecos llenos
 tab-context-zen-remove-essential = 
     .label = Quitar de esenciales
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Reemplazar URL esencial con la actual
-           *[false] Reemplazar URL fijada con la actual
+            [true] Editar URL esencial
+           *[false] Editar URL fijada
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Reemplazar con la URL actual
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Editar…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Cambiar etiqueta...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Confirmar
 zen-pinned-tab-replaced = La URL de la pestaña fijada se ha reemplazado por la URL actual.
+zen-pinned-tab-url-edited = ¡La URL de la pestaña fijada ha sido actualizada!
+zen-pinned-tab-url-invalid = Eso no parece una URL válida.
+zen-pinned-tab-edit-url-title = Editar URL fijada
+zen-pinned-tab-edit-url-label = Introduzca la URL a la que debe apuntar esta pestaña fijada:
 zen-tabs-renamed = ¡La pestaña se ha renombrado con éxito!
 zen-background-tab-opened-toast = ¡Nueva pestaña abierta en segundo plano!
 zen-workspace-renamed-toast = ¡El espacio de trabajo ha sido renombrado con éxito!
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = Emojis
 zen-icons-picker-svg = 
     .label = Iconos
+zen-emojis-picker-search = 
+    .placeholder = Buscar emojis
 urlbar-search-mode-zen_actions = Acciones
 zen-site-data-settings = Ajustes
 zen-generic-manage = Administrar
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = ¡Actualización completada!
 zen-sidebar-notification-updated-label = Novedades en { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = Ver notas de la versión
+zen-sidebar-notification-donate-label = Soporte { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donar al proyecto
 zen-sidebar-notification-restart-safe-mode-label = ¿Algo dejó de funcionar?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Reiniciar en modo seguro
diff --git a/locales/es-ES/browser/browser/zen-space-routing.ftl b/locales/es-ES/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..4137fd958
--- /dev/null
+++ b/locales/es-ES/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Ajustes del enrutamiento del espacio
+zen-space-routing-rulepanel-placeholder = Las rutas le permiten elegir donde se abren sitios web específicos dentro de Zen. Por ejemplo, puede enrutar los enlaces de YouTube para que siempre se abran dentro de su espacio personal.
+zen-space-routing-dialog-title = Ajustes del enrutamiento del espacio
+zen-space-routing-external-default = Ruta por defecto para los enlaces externos
+zen-space-routing-new-route = Nueva ruta
+zen-space-routing-open-in-space = Abrir en espacio
+zen-space-routing-most-recent-space = Espacio más reciente
+zen-space-routing-close-button = 
+    .aria-label = Cerrar
+    .tooltiptext = Cerrar
+zen-space-routing-contains = 
+    .label = Contiene
+zen-space-routing-equal-to = 
+    .label = Es igual a
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Abrir en
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = Nueva pestaña abierta en { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Añadir ruta para el dominio
+           *[other] Añadir ruta para los dominios
+        }
diff --git a/locales/es-ES/browser/browser/zen-workspaces.ftl b/locales/es-ES/browser/browser/zen-workspaces.ftl
index 5e81b9307..e5e25c4c8 100644
--- a/locales/es-ES/browser/browser/zen-workspaces.ftl
+++ b/locales/es-ES/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Perfil
     .tooltiptext = Los perfiles se utilizan para separar las cookies y los datos de sitios entre espacios.
 zen-workspace-creation-header = Crear un espacio
 zen-workspace-creation-label = Los espacios se utilizan para organizar sus pestañas y sesiones.
+zen-workspace-default-profile = Predeterminado
 zen-workspaces-delete-workspace-title = ¿Eliminar espacio de trabajo?
 zen-workspaces-delete-workspace-body = ¿Seguro que quiere eliminar { $name }? Esta acción no se puede deshacer.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/et/browser/browser/preferences/zen-preferences.ftl b/locales/et/browser/browser/preferences/zen-preferences.ftl
index 9aa14af82..857e44c3b 100644
--- a/locales/et/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/et/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Peida ka ülemine tööriistariba kompaktses vaates
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Lühidalt kuva tööriistariba hüpikut kui lülitutakse kaartide vahel või avatakse uus kaart kompaktses režiimis
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Allow dragging the window from web pages
 pane-zen-tabs-title = Kaartide haldamine
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = Vaata veebilehe infot
 zen-find-shortcut = Otsi lehelt
 zen-search-find-again-shortcut = Otsi järgmist
 zen-search-find-again-shortcut-prev = Otsi eelmist
-zen-search-find-again-shortcut-2 = Otsi järgmist (alternatiivne)
+zen-search-find-again-shortcut-alt = Find Again (Alt)
+zen-search-find-again-shortcut-prev-alt = Find Previous (Alt)
 zen-bookmark-this-page-shortcut = Lisa järjehoidjatesse
 zen-bookmark-show-library-shortcut = Näita järjehoidjaid
 zen-key-stop = Peata laadimine
diff --git a/locales/et/browser/browser/zen-command-palette.ftl b/locales/et/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..c8af413e2
--- /dev/null
+++ b/locales/et/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Toggle Compact Mode
+zen-action-open-theme-picker = Open Theme Picker
+zen-action-new-split-view = New Split View
+zen-action-new-folder = New Folder
+zen-action-copy-current-url = Copy Current URL
+zen-action-settings = Settings
+zen-action-open-private-window = Open Private Window
+zen-action-open-new-window = Open New Window
+zen-action-new-blank-window = New Blank Window
+zen-action-pin-tab = Pin Tab
+zen-action-unpin-tab = Unpin Tab
+zen-action-open-space-routing = Open Space Routing
+zen-action-new-boost = New Boost
+zen-action-next-space = Next Space
+zen-action-previous-space = Previous Space
+zen-action-close-tab = Close Tab
+zen-action-reload-tab = Reload Tab
+zen-action-reload-tab-without-cache = Reload Tab Without Cache
+zen-action-next-tab = Next Tab
+zen-action-previous-tab = Previous Tab
+zen-action-capture-screenshot = Capture Screenshot
+zen-action-toggle-tabs-on-right = Toggle Tabs on right
+zen-action-add-to-essentials = Add to Essentials
+zen-action-remove-from-essentials = Remove from Essentials
+zen-action-find-in-page = Find in Page
+zen-action-manage-extensions = Manage Extensions
+zen-action-switch-to-automatic-appearance = Switch to Automatic Appearance
+zen-action-switch-to-light-mode = Switch to Light Mode
+zen-action-switch-to-dark-mode = Switch to Dark Mode
+zen-action-print = Print
+zen-action-focus-on = Focus on
+zen-action-extension = Extension
diff --git a/locales/et/browser/browser/zen-general.ftl b/locales/et/browser/browser/zen-general.ftl
index 7ba7cbd2d..9895e1a08 100644
--- a/locales/et/browser/browser/zen-general.ftl
+++ b/locales/et/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max } slots filled
 tab-context-zen-remove-essential = 
     .label = Eemalda olulistest
     .accesskey = o
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Replace Essential URL with Current
-           *[false] Replace Pinned URL with Current
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Replace with Current URL
     .accesskey = p
+tab-context-zen-edit-pinned-url = 
+    .label = Edit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Change Label...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Kinnita
 zen-pinned-tab-replaced = Pinned tab URL has been replaced with the current URL.
+zen-pinned-tab-url-edited = Pinned tab URL has been updated!
+zen-pinned-tab-url-invalid = That doesn't look like a valid URL.
+zen-pinned-tab-edit-url-title = Edit Pinned URL
+zen-pinned-tab-edit-url-label = Enter the URL this pinned tab should point to:
 zen-tabs-renamed = Kaart on edukalt ümber nimetatud!
 zen-background-tab-opened-toast = Taustal avati uus kaart!
 zen-workspace-renamed-toast = Tööruum on edukalt ümber nimetatud!
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = Emojid
 zen-icons-picker-svg = 
     .label = Ikoonid
+zen-emojis-picker-search = 
+    .placeholder = Search emojis
 urlbar-search-mode-zen_actions = Tegevused
 zen-site-data-settings = Sätted
 zen-generic-manage = Halda
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = Update Complete!
 zen-sidebar-notification-updated-label = What's new in { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = View Release Notes
+zen-sidebar-notification-donate-label = Support { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donate to the project
 zen-sidebar-notification-restart-safe-mode-label = Something broke?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Restart in Safe Mode
diff --git a/locales/et/browser/browser/zen-space-routing.ftl b/locales/et/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..d757144bb
--- /dev/null
+++ b/locales/et/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Space Routing Settings
+zen-space-routing-rulepanel-placeholder = Routes let you choose where specific sites open inside Zen. For example, you can route YouTube links to always open inside your Personal space.
+zen-space-routing-dialog-title = Space Routing Settings
+zen-space-routing-external-default = Default route for external links
+zen-space-routing-new-route = New Route
+zen-space-routing-open-in-space = Open in Space
+zen-space-routing-most-recent-space = Most recent Space
+zen-space-routing-close-button = 
+    .aria-label = Close
+    .tooltiptext = Close
+zen-space-routing-contains = 
+    .label = Contains
+zen-space-routing-equal-to = 
+    .label = Is Equal To
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Open In
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/et/browser/browser/zen-workspaces.ftl b/locales/et/browser/browser/zen-workspaces.ftl
index fafba2b1a..289f54969 100644
--- a/locales/et/browser/browser/zen-workspaces.ftl
+++ b/locales/et/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Profiil
     .tooltiptext = Profiile kasutatakse küpsiste ning saidi andmete eraldamiseks tööruumide vahel.
 zen-workspace-creation-header = Loo uus tööruum
 zen-workspace-creation-label = Tööruume kasutatakse kaartide ja sessioonide organiseerimiseks.
+zen-workspace-default-profile = Default
 zen-workspaces-delete-workspace-title = Delete Workspace?
 zen-workspaces-delete-workspace-body = Kas oled kindel, et soovid kustutada tööruumi { $name }? Seda tegevust ei saa tagasi võtta.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/eu/browser/browser/preferences/zen-preferences.ftl b/locales/eu/browser/browser/preferences/zen-preferences.ftl
index cc6082d37..fc091918e 100644
--- a/locales/eu/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/eu/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Hide the top toolbar as well in compact mode
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Briefly make the toolbar popup when switching or opening new tabs in compact mode
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Allow dragging the window from web pages
 pane-zen-tabs-title = Tab Management
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = View Page Info
 zen-find-shortcut = Find on Page
 zen-search-find-again-shortcut = Find Again
 zen-search-find-again-shortcut-prev = Find Previous
-zen-search-find-again-shortcut-2 = Find Again (Alt)
+zen-search-find-again-shortcut-alt = Find Again (Alt)
+zen-search-find-again-shortcut-prev-alt = Find Previous (Alt)
 zen-bookmark-this-page-shortcut = Bookmark This Page
 zen-bookmark-show-library-shortcut = Show Bookmarks Library
 zen-key-stop = Stop Loading
diff --git a/locales/eu/browser/browser/zen-command-palette.ftl b/locales/eu/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..c8af413e2
--- /dev/null
+++ b/locales/eu/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Toggle Compact Mode
+zen-action-open-theme-picker = Open Theme Picker
+zen-action-new-split-view = New Split View
+zen-action-new-folder = New Folder
+zen-action-copy-current-url = Copy Current URL
+zen-action-settings = Settings
+zen-action-open-private-window = Open Private Window
+zen-action-open-new-window = Open New Window
+zen-action-new-blank-window = New Blank Window
+zen-action-pin-tab = Pin Tab
+zen-action-unpin-tab = Unpin Tab
+zen-action-open-space-routing = Open Space Routing
+zen-action-new-boost = New Boost
+zen-action-next-space = Next Space
+zen-action-previous-space = Previous Space
+zen-action-close-tab = Close Tab
+zen-action-reload-tab = Reload Tab
+zen-action-reload-tab-without-cache = Reload Tab Without Cache
+zen-action-next-tab = Next Tab
+zen-action-previous-tab = Previous Tab
+zen-action-capture-screenshot = Capture Screenshot
+zen-action-toggle-tabs-on-right = Toggle Tabs on right
+zen-action-add-to-essentials = Add to Essentials
+zen-action-remove-from-essentials = Remove from Essentials
+zen-action-find-in-page = Find in Page
+zen-action-manage-extensions = Manage Extensions
+zen-action-switch-to-automatic-appearance = Switch to Automatic Appearance
+zen-action-switch-to-light-mode = Switch to Light Mode
+zen-action-switch-to-dark-mode = Switch to Dark Mode
+zen-action-print = Print
+zen-action-focus-on = Focus on
+zen-action-extension = Extension
diff --git a/locales/eu/browser/browser/zen-general.ftl b/locales/eu/browser/browser/zen-general.ftl
index c2754b4f4..a4c8a90ff 100644
--- a/locales/eu/browser/browser/zen-general.ftl
+++ b/locales/eu/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max } hutsune beteta
 tab-context-zen-remove-essential = 
     .label = Funtsezko fitxetatik Kendu
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Ordezkatu Funtsezko URLa Oraingoarekin
-           *[false] Ordezkatu Ainguratutako URLa Oraingoarekin
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Replace with Current URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Edit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Etiketa aldatu...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Baieztatu
 zen-pinned-tab-replaced = Oraingo estekak ordezkatu du ainguratutako fitxarena!
+zen-pinned-tab-url-edited = Pinned tab URL has been updated!
+zen-pinned-tab-url-invalid = That doesn't look like a valid URL.
+zen-pinned-tab-edit-url-title = Edit Pinned URL
+zen-pinned-tab-edit-url-label = Enter the URL this pinned tab should point to:
 zen-tabs-renamed = Fitxaren izena ongi aldatu da!
 zen-background-tab-opened-toast = Fitxa berri bat zabaldu da bigarren planoan!
 zen-workspace-renamed-toast = Lan-eremuaren izena ongi aldatu da!
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = Emojiak
 zen-icons-picker-svg = 
     .label = Ikonoak
+zen-emojis-picker-search = 
+    .placeholder = Search emojis
 urlbar-search-mode-zen_actions = Ekintzak
 zen-site-data-settings = Ezarpenak
 zen-generic-manage = Kudeatu
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = Update Complete!
 zen-sidebar-notification-updated-label = What's new in { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = View Release Notes
+zen-sidebar-notification-donate-label = Support { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donate to the project
 zen-sidebar-notification-restart-safe-mode-label = Something broke?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Restart in Safe Mode
diff --git a/locales/eu/browser/browser/zen-space-routing.ftl b/locales/eu/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..d757144bb
--- /dev/null
+++ b/locales/eu/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Space Routing Settings
+zen-space-routing-rulepanel-placeholder = Routes let you choose where specific sites open inside Zen. For example, you can route YouTube links to always open inside your Personal space.
+zen-space-routing-dialog-title = Space Routing Settings
+zen-space-routing-external-default = Default route for external links
+zen-space-routing-new-route = New Route
+zen-space-routing-open-in-space = Open in Space
+zen-space-routing-most-recent-space = Most recent Space
+zen-space-routing-close-button = 
+    .aria-label = Close
+    .tooltiptext = Close
+zen-space-routing-contains = 
+    .label = Contains
+zen-space-routing-equal-to = 
+    .label = Is Equal To
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Open In
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/eu/browser/browser/zen-workspaces.ftl b/locales/eu/browser/browser/zen-workspaces.ftl
index 7727a2ff2..01ef1f793 100644
--- a/locales/eu/browser/browser/zen-workspaces.ftl
+++ b/locales/eu/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Profile
     .tooltiptext = Profiles are used to separate cookies and site data between spaces.
 zen-workspace-creation-header = Create a Space
 zen-workspace-creation-label = Spaces are used to organize your tabs and sessions.
+zen-workspace-default-profile = Default
 zen-workspaces-delete-workspace-title = Delete Space?
 zen-workspaces-delete-workspace-body = Are you sure you want to delete { $name }? This action cannot be undone.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/fa/browser/browser/preferences/zen-preferences.ftl b/locales/fa/browser/browser/preferences/zen-preferences.ftl
index 7ed3131a5..a0115b82a 100644
--- a/locales/fa/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/fa/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = پنهان‌کردن نوار ابزار بالا در حالت فشرده
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Briefly make the toolbar popup when switching or opening new tabs in compact mode
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Allow dragging the window from web pages
 pane-zen-tabs-title = Tab Management
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = View Page Info
 zen-find-shortcut = Find on Page
 zen-search-find-again-shortcut = Find Again
 zen-search-find-again-shortcut-prev = Find Previous
-zen-search-find-again-shortcut-2 = Find Again (Alt)
+zen-search-find-again-shortcut-alt = Find Again (Alt)
+zen-search-find-again-shortcut-prev-alt = Find Previous (Alt)
 zen-bookmark-this-page-shortcut = Bookmark This Page
 zen-bookmark-show-library-shortcut = Show Bookmarks Library
 zen-key-stop = Stop Loading
diff --git a/locales/fa/browser/browser/zen-command-palette.ftl b/locales/fa/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..c8af413e2
--- /dev/null
+++ b/locales/fa/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Toggle Compact Mode
+zen-action-open-theme-picker = Open Theme Picker
+zen-action-new-split-view = New Split View
+zen-action-new-folder = New Folder
+zen-action-copy-current-url = Copy Current URL
+zen-action-settings = Settings
+zen-action-open-private-window = Open Private Window
+zen-action-open-new-window = Open New Window
+zen-action-new-blank-window = New Blank Window
+zen-action-pin-tab = Pin Tab
+zen-action-unpin-tab = Unpin Tab
+zen-action-open-space-routing = Open Space Routing
+zen-action-new-boost = New Boost
+zen-action-next-space = Next Space
+zen-action-previous-space = Previous Space
+zen-action-close-tab = Close Tab
+zen-action-reload-tab = Reload Tab
+zen-action-reload-tab-without-cache = Reload Tab Without Cache
+zen-action-next-tab = Next Tab
+zen-action-previous-tab = Previous Tab
+zen-action-capture-screenshot = Capture Screenshot
+zen-action-toggle-tabs-on-right = Toggle Tabs on right
+zen-action-add-to-essentials = Add to Essentials
+zen-action-remove-from-essentials = Remove from Essentials
+zen-action-find-in-page = Find in Page
+zen-action-manage-extensions = Manage Extensions
+zen-action-switch-to-automatic-appearance = Switch to Automatic Appearance
+zen-action-switch-to-light-mode = Switch to Light Mode
+zen-action-switch-to-dark-mode = Switch to Dark Mode
+zen-action-print = Print
+zen-action-focus-on = Focus on
+zen-action-extension = Extension
diff --git a/locales/fa/browser/browser/zen-general.ftl b/locales/fa/browser/browser/zen-general.ftl
index f4b3f238d..19dba2f76 100644
--- a/locales/fa/browser/browser/zen-general.ftl
+++ b/locales/fa/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max } slots filled
 tab-context-zen-remove-essential = 
     .label = Remove from Essentials
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Replace Essential URL with Current
-           *[false] Replace Pinned URL with Current
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Replace with Current URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Edit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Change Label...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = تایید
 zen-pinned-tab-replaced = Pinned tab URL has been replaced with the current URL.
+zen-pinned-tab-url-edited = Pinned tab URL has been updated!
+zen-pinned-tab-url-invalid = That doesn't look like a valid URL.
+zen-pinned-tab-edit-url-title = Edit Pinned URL
+zen-pinned-tab-edit-url-label = Enter the URL this pinned tab should point to:
 zen-tabs-renamed = Tab has been successfully renamed!
 zen-background-tab-opened-toast = New background tab opened!
 zen-workspace-renamed-toast = Workspace has been successfully renamed!
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = Emojis
 zen-icons-picker-svg = 
     .label = Icons
+zen-emojis-picker-search = 
+    .placeholder = Search emojis
 urlbar-search-mode-zen_actions = Actions
 zen-site-data-settings = Settings
 zen-generic-manage = Manage
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = Update Complete!
 zen-sidebar-notification-updated-label = What's new in { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = View Release Notes
+zen-sidebar-notification-donate-label = Support { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donate to the project
 zen-sidebar-notification-restart-safe-mode-label = Something broke?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Restart in Safe Mode
diff --git a/locales/fa/browser/browser/zen-space-routing.ftl b/locales/fa/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..d757144bb
--- /dev/null
+++ b/locales/fa/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Space Routing Settings
+zen-space-routing-rulepanel-placeholder = Routes let you choose where specific sites open inside Zen. For example, you can route YouTube links to always open inside your Personal space.
+zen-space-routing-dialog-title = Space Routing Settings
+zen-space-routing-external-default = Default route for external links
+zen-space-routing-new-route = New Route
+zen-space-routing-open-in-space = Open in Space
+zen-space-routing-most-recent-space = Most recent Space
+zen-space-routing-close-button = 
+    .aria-label = Close
+    .tooltiptext = Close
+zen-space-routing-contains = 
+    .label = Contains
+zen-space-routing-equal-to = 
+    .label = Is Equal To
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Open In
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/fa/browser/browser/zen-workspaces.ftl b/locales/fa/browser/browser/zen-workspaces.ftl
index b7ae488b2..2b5fe5d83 100644
--- a/locales/fa/browser/browser/zen-workspaces.ftl
+++ b/locales/fa/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Profile
     .tooltiptext = Profiles are used to separate cookies and site data between spaces.
 zen-workspace-creation-header = Create a Space
 zen-workspace-creation-label = Spaces are used to organize your tabs and sessions.
+zen-workspace-default-profile = Default
 zen-workspaces-delete-workspace-title = Delete Workspace?
 zen-workspaces-delete-workspace-body = Are you sure you want to delete { $name }? This action cannot be undone.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/fi/browser/browser/preferences/zen-preferences.ftl b/locales/fi/browser/browser/preferences/zen-preferences.ftl
index 08f86534f..52a4ec3dd 100644
--- a/locales/fi/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/fi/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Piilota työkalupalkki niin myös kompaktissa tilassa
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Tee työkalurivin ponnahdusikkuna lyhyesti, kun vaihdat tai avaat uusia välilehtiä kompaktitilassa
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Allow dragging the window from web pages
 pane-zen-tabs-title = Välilehtien Hallinta
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = Näytä Sivun Tiedot
 zen-find-shortcut = Etsi sivulta
 zen-search-find-again-shortcut = Etsi Uudelleen
 zen-search-find-again-shortcut-prev = Etsi Edellinen
-zen-search-find-again-shortcut-2 = Etsi Uudelleen (Alt)
+zen-search-find-again-shortcut-alt = Find Again (Alt)
+zen-search-find-again-shortcut-prev-alt = Find Previous (Alt)
 zen-bookmark-this-page-shortcut = Lisää Tämä Sivu Kirjanmerkkeihin
 zen-bookmark-show-library-shortcut = Näytä Kirjanmerkkikirjasto
 zen-key-stop = Lopeta Lataaminen
diff --git a/locales/fi/browser/browser/zen-command-palette.ftl b/locales/fi/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..c8af413e2
--- /dev/null
+++ b/locales/fi/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Toggle Compact Mode
+zen-action-open-theme-picker = Open Theme Picker
+zen-action-new-split-view = New Split View
+zen-action-new-folder = New Folder
+zen-action-copy-current-url = Copy Current URL
+zen-action-settings = Settings
+zen-action-open-private-window = Open Private Window
+zen-action-open-new-window = Open New Window
+zen-action-new-blank-window = New Blank Window
+zen-action-pin-tab = Pin Tab
+zen-action-unpin-tab = Unpin Tab
+zen-action-open-space-routing = Open Space Routing
+zen-action-new-boost = New Boost
+zen-action-next-space = Next Space
+zen-action-previous-space = Previous Space
+zen-action-close-tab = Close Tab
+zen-action-reload-tab = Reload Tab
+zen-action-reload-tab-without-cache = Reload Tab Without Cache
+zen-action-next-tab = Next Tab
+zen-action-previous-tab = Previous Tab
+zen-action-capture-screenshot = Capture Screenshot
+zen-action-toggle-tabs-on-right = Toggle Tabs on right
+zen-action-add-to-essentials = Add to Essentials
+zen-action-remove-from-essentials = Remove from Essentials
+zen-action-find-in-page = Find in Page
+zen-action-manage-extensions = Manage Extensions
+zen-action-switch-to-automatic-appearance = Switch to Automatic Appearance
+zen-action-switch-to-light-mode = Switch to Light Mode
+zen-action-switch-to-dark-mode = Switch to Dark Mode
+zen-action-print = Print
+zen-action-focus-on = Focus on
+zen-action-extension = Extension
diff --git a/locales/fi/browser/browser/zen-general.ftl b/locales/fi/browser/browser/zen-general.ftl
index 7ddce52f2..007d310df 100644
--- a/locales/fi/browser/browser/zen-general.ftl
+++ b/locales/fi/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max } täytetty paikka
 tab-context-zen-remove-essential = 
     .label = Poista olennaisista
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Replace Essential URL with Current
-           *[false] Replace Pinned URL with Current
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Replace with Current URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Edit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Change Label...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Vahvista
 zen-pinned-tab-replaced = Pinned tab URL has been replaced with the current URL.
+zen-pinned-tab-url-edited = Pinned tab URL has been updated!
+zen-pinned-tab-url-invalid = That doesn't look like a valid URL.
+zen-pinned-tab-edit-url-title = Edit Pinned URL
+zen-pinned-tab-edit-url-label = Enter the URL this pinned tab should point to:
 zen-tabs-renamed = Välilehti on nimetty uudelleen!
 zen-background-tab-opened-toast = Uusi taustavälilehti avattu!
 zen-workspace-renamed-toast = Työtila on nimetty uudelleen!
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = Emojit
 zen-icons-picker-svg = 
     .label = Kuvakkeet
+zen-emojis-picker-search = 
+    .placeholder = Search emojis
 urlbar-search-mode-zen_actions = Toiminnot
 zen-site-data-settings = Asetukset
 zen-generic-manage = Hallitse
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = Päivitys valmis!
 zen-sidebar-notification-updated-label = Mitä uutta { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = Katso Julkaisutiedot
+zen-sidebar-notification-donate-label = Support { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donate to the project
 zen-sidebar-notification-restart-safe-mode-label = Jotain rikki?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Käynnistä uudelleen vianmääritystilassa
diff --git a/locales/fi/browser/browser/zen-space-routing.ftl b/locales/fi/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..d757144bb
--- /dev/null
+++ b/locales/fi/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Space Routing Settings
+zen-space-routing-rulepanel-placeholder = Routes let you choose where specific sites open inside Zen. For example, you can route YouTube links to always open inside your Personal space.
+zen-space-routing-dialog-title = Space Routing Settings
+zen-space-routing-external-default = Default route for external links
+zen-space-routing-new-route = New Route
+zen-space-routing-open-in-space = Open in Space
+zen-space-routing-most-recent-space = Most recent Space
+zen-space-routing-close-button = 
+    .aria-label = Close
+    .tooltiptext = Close
+zen-space-routing-contains = 
+    .label = Contains
+zen-space-routing-equal-to = 
+    .label = Is Equal To
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Open In
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/fi/browser/browser/zen-workspaces.ftl b/locales/fi/browser/browser/zen-workspaces.ftl
index 3a02f6a80..6775d5e56 100644
--- a/locales/fi/browser/browser/zen-workspaces.ftl
+++ b/locales/fi/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Profiili
     .tooltiptext = Profiileja käytetään erottamaan evästeet ja sivustontiedot tiloihin.
 zen-workspace-creation-header = Luo työtila
 zen-workspace-creation-label = Työtiloja käytetään järjestämään sinun välilehtiä ja istuntoja.
+zen-workspace-default-profile = Default
 zen-workspaces-delete-workspace-title = Poista Työtila?
 zen-workspaces-delete-workspace-body = Oletko varma, että haluat poistaa { $name }? Tätä toimintoa ei voi peruuttaa.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/fr/browser/browser/preferences/zen-preferences.ftl b/locales/fr/browser/browser/preferences/zen-preferences.ftl
index d5828a59c..8e294eaf2 100644
--- a/locales/fr/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/fr/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Masquer aussi la barre d’outils du haut en mode compact
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = En mode compact, faire brièvement apparaitre la barre d’outils au changement ou à l’ouverture de nouveaux onglets
+zen-look-and-feel-window-drag-header = Déplacement de la fenêtre
+zen-look-and-feel-window-drag-description = Déplacer la fenêtre en faisant glisser un espace vide en haut des sites Web, comme la barre de titre.
+zen-window-drag-enabled = 
+    .label = Autoriser le déplacement de la fenêtre depuis les pages web
 pane-zen-tabs-title = Gestion des onglets
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = Voir les informations de la page
 zen-find-shortcut = Rechercher dans la page
 zen-search-find-again-shortcut = Retrouver
 zen-search-find-again-shortcut-prev = Rechercher le précédent
-zen-search-find-again-shortcut-2 = Rechercher à nouveau (alternatif)
+zen-search-find-again-shortcut-alt = Rechercher à nouveau (Alt)
+zen-search-find-again-shortcut-prev-alt = Rechercher le précédent (Alt)
 zen-bookmark-this-page-shortcut = Ajouter cette page aux favoris
 zen-bookmark-show-library-shortcut = Afficher la bibliothèque des favoris
 zen-key-stop = Arrêter le chargement
diff --git a/locales/fr/browser/browser/zen-command-palette.ftl b/locales/fr/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..85611e0f5
--- /dev/null
+++ b/locales/fr/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Activer/désactiver le mode compact
+zen-action-open-theme-picker = Ouvrir le sélecteur de thème
+zen-action-new-split-view = Nouvelle vue fractionnée
+zen-action-new-folder = Nouveau dossier
+zen-action-copy-current-url = Copier l’adresse actuelle
+zen-action-settings = Paramètres
+zen-action-open-private-window = Ouvrir une fenêtre privée
+zen-action-open-new-window = Ouvrir une nouvelle fenêtre
+zen-action-new-blank-window = Nouvelle fenêtre vide
+zen-action-pin-tab = Épingler l'onglet
+zen-action-unpin-tab = Désépingler l'onglet
+zen-action-open-space-routing = Ouvrir le routage des espaces
+zen-action-new-boost = Nouveau Boost
+zen-action-next-space = Espace suivant
+zen-action-previous-space = Espace précédent
+zen-action-close-tab = Fermer l’onglet
+zen-action-reload-tab = Recharger l'onglet
+zen-action-reload-tab-without-cache = Recharger l'onglet sans cache
+zen-action-next-tab = Onglet suivant
+zen-action-previous-tab = Onglet précédent
+zen-action-capture-screenshot = Prendre une capture d'écran
+zen-action-toggle-tabs-on-right = Activer/désactiver les onglets à droite
+zen-action-add-to-essentials = Ajouter aux Essentials
+zen-action-remove-from-essentials = Retirer des Essentials
+zen-action-find-in-page = Rechercher dans la page
+zen-action-manage-extensions = Gérer les extensions
+zen-action-switch-to-automatic-appearance = Passer à l'apparence automatique
+zen-action-switch-to-light-mode = Passer au mode clair
+zen-action-switch-to-dark-mode = Passer au mode sombre
+zen-action-print = Imprimer
+zen-action-focus-on = Focus sur
+zen-action-extension = Extension
diff --git a/locales/fr/browser/browser/zen-general.ftl b/locales/fr/browser/browser/zen-general.ftl
index 41d53b68f..26e45fd6f 100644
--- a/locales/fr/browser/browser/zen-general.ftl
+++ b/locales/fr/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max }
 tab-context-zen-remove-essential = 
     .label = Retirer des Essentials
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Remplacer l'URL de l'Essential par l'actuelle
-           *[false] Remplacer l'URL de l'onglet épinglé par l'actuelle
+            [true] Modifier l'URL de l'Essential
+           *[false] Modifier de l'URL de l'onglet épinglé
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Remplacer par l'URL actuelle
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Modifier…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Changer le libellé...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Confirmer
 zen-pinned-tab-replaced = L’adresse de l'onglet épinglé a été remplacée par l’adresse actuelle.
+zen-pinned-tab-url-edited = L'URL de l'onglet épinglé a été mise à jour !
+zen-pinned-tab-url-invalid = Cela ne ressemble pas à une URL valide.
+zen-pinned-tab-edit-url-title = Modifier l'URL épinglée
+zen-pinned-tab-edit-url-label = Entrer l'URL à laquelle cet onglet épinglé devrait pointer :
 zen-tabs-renamed = L’onglet a été renommé avec succès !
 zen-background-tab-opened-toast = Nouvel onglet ouvert en arrière-plan !
 zen-workspace-renamed-toast = L'espace de travail a été renommé avec succès !
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = Émojis
 zen-icons-picker-svg = 
     .label = Icônes
+zen-emojis-picker-search = 
+    .placeholder = Rechercher des émojis
 urlbar-search-mode-zen_actions = Actions
 zen-site-data-settings = Paramètres
 zen-generic-manage = Gérer
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = Mise à jour terminée !
 zen-sidebar-notification-updated-label = Quoi de neuf dans { -brand-short-name } ?
 zen-sidebar-notification-updated-tooltip = 
     .title = Voir les notes de version
+zen-sidebar-notification-donate-label = Soutenir { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Faire un don au projet
 zen-sidebar-notification-restart-safe-mode-label = Un problème est survenu ?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Redémarrer en mode de dépannage
diff --git a/locales/fr/browser/browser/zen-space-routing.ftl b/locales/fr/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..9719ffc7f
--- /dev/null
+++ b/locales/fr/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Paramètres de routage des espaces
+zen-space-routing-rulepanel-placeholder = Les routes vous permettent de choisir où s'ouvrent certains sites dans Zen. Par exemple, vous pouvez configurer les liens YouTube pour qu'ils s'ouvrent toujours dans votre espace personnel.
+zen-space-routing-dialog-title = Paramètres du routage des espaces
+zen-space-routing-external-default = Route par défaut pour les liens externes
+zen-space-routing-new-route = Nouvelle route
+zen-space-routing-open-in-space = Ouvrir dans l'espace
+zen-space-routing-most-recent-space = Espace le plus récent
+zen-space-routing-close-button = 
+    .aria-label = Fermer
+    .tooltiptext = Fermer
+zen-space-routing-contains = 
+    .label = Contient
+zen-space-routing-equal-to = 
+    .label = Est égal à
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Ouvrir dans
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = Nouvel onglet ouvert dans { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Ajouter une route pour le domaine
+           *[other] Ajouter une route pour les domaines
+        }
diff --git a/locales/fr/browser/browser/zen-workspaces.ftl b/locales/fr/browser/browser/zen-workspaces.ftl
index 0e64b9a29..0ea704098 100644
--- a/locales/fr/browser/browser/zen-workspaces.ftl
+++ b/locales/fr/browser/browser/zen-workspaces.ftl
@@ -58,9 +58,10 @@ zen-move-tab-to-workspace-button =
 zen-workspaces-panel-context-reorder = 
     .label = Réorganiser les espaces
 zen-workspace-creation-profile = Profil
-    .tooltiptext = Les profils sont utilisés pour séparer les cookies et les données des sites entre les Espaces.
+    .tooltiptext = Les profils sont utilisés pour séparer les cookies et les données des sites entre les espaces.
 zen-workspace-creation-header = Créer un espace
 zen-workspace-creation-label = Les espaces sont utilisés pour organiser vos onglets et sessions.
+zen-workspace-default-profile = Par défaut
 zen-workspaces-delete-workspace-title = Supprimer l’espace ?
 zen-workspaces-delete-workspace-body = Êtes-vous sûr de vouloir supprimer { $name } ? Cette action ne peut pas être annulée.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/ga-IE/browser/browser/preferences/zen-preferences.ftl b/locales/ga-IE/browser/browser/preferences/zen-preferences.ftl
index e370988ce..ff788191a 100644
--- a/locales/ga-IE/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/ga-IE/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Folaigh an barra uirlisí barr chomh maith i mód dlúth
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Déan preabfhuinneog an bharra uirlisí go hachomair agus cluaisíní nua á n-athrú nó á n-oscailt i mód dlúth
+zen-look-and-feel-window-drag-header = Tarraingt fuinneoige
+zen-look-and-feel-window-drag-description = Bog an fhuinneog trí spás folamh a tharraingt ag barr na suíomhanna gréasáin, díreach cosúil leis an mbarra teidil.
+zen-window-drag-enabled = 
+    .label = Ceadaigh an fhuinneog a tharraingt ó leathanaigh ghréasáin
 pane-zen-tabs-title = Bainistíocht Cluaisíní
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = Féach ar Fhaisnéis an Leathanaigh
 zen-find-shortcut = Aimsigh ar Leathanach
 zen-search-find-again-shortcut = Aimsigh Arís
 zen-search-find-again-shortcut-prev = Aimsigh Roimhe Seo
-zen-search-find-again-shortcut-2 = Aimsigh Arís (Alt)
+zen-search-find-again-shortcut-alt = Aimsigh Arís (Alt)
+zen-search-find-again-shortcut-prev-alt = Aimsigh Roimhe Seo (Alt)
 zen-bookmark-this-page-shortcut = Leabharmharc an Leathanach seo
 zen-bookmark-show-library-shortcut = Taispeáin Leabharlann Leabharmharcanna
 zen-key-stop = Stop ag Lódáil
diff --git a/locales/ga-IE/browser/browser/zen-command-palette.ftl b/locales/ga-IE/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..7f3aafb47
--- /dev/null
+++ b/locales/ga-IE/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Mód Dlúth a Athrú
+zen-action-open-theme-picker = Oscail an Roghnóir Téama
+zen-action-new-split-view = Radharc Scoilte Nua
+zen-action-new-folder = Fillteán Nua
+zen-action-copy-current-url = Cóipeáil an URL Reatha
+zen-action-settings = Socruithe
+zen-action-open-private-window = Oscail Fuinneog Phríobháideach
+zen-action-open-new-window = Oscail Fuinneog Nua
+zen-action-new-blank-window = Fuinneog Nua Bán
+zen-action-pin-tab = Cluaisín bioráin
+zen-action-unpin-tab = Díphionáil an Cluaisín
+zen-action-open-space-routing = Bealachú Spáis Oscailte
+zen-action-new-boost = Borradh Nua
+zen-action-next-space = An Chéad Spás Eile
+zen-action-previous-space = Spás Roimhe Seo
+zen-action-close-tab = Dún an Cluaisín
+zen-action-reload-tab = Athlódáil an cluaisín
+zen-action-reload-tab-without-cache = Athlódáil an Cluaisín Gan Taisce
+zen-action-next-tab = An Chluaisín Eile
+zen-action-previous-tab = Cluaisín Roimhe Seo
+zen-action-capture-screenshot = Gabh Seat Scáileán
+zen-action-toggle-tabs-on-right = Athraigh na cluaisíní ar dheis
+zen-action-add-to-essentials = Cuir leis na Bunriachtanais
+zen-action-remove-from-essentials = Bain de na Bunriachtanais
+zen-action-find-in-page = Aimsigh sa Leathanach
+zen-action-manage-extensions = Bainistigh Síneadh
+zen-action-switch-to-automatic-appearance = Athraigh go Dealramh Uathoibríoch
+zen-action-switch-to-light-mode = Athraigh go Mód Solais
+zen-action-switch-to-dark-mode = Athraigh go Mód Dorcha
+zen-action-print = Priontáil
+zen-action-focus-on = Dírigh ar
+zen-action-extension = Síneadh
diff --git a/locales/ga-IE/browser/browser/zen-general.ftl b/locales/ga-IE/browser/browser/zen-general.ftl
index 7b73f797e..d559d9a98 100644
--- a/locales/ga-IE/browser/browser/zen-general.ftl
+++ b/locales/ga-IE/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max } sliotán líonta
 tab-context-zen-remove-essential = 
     .label = Bain de na Bunriachtanais
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Cuir an URL Riachtanach in ionad an URL Reatha
-           *[false] Cuir an URL Priontáilte in ionad an URL Reatha
+            [true] Cuir URL Riachtanach in Eagar
+           *[false] Cuir URL Priontáilte in Eagar
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Ionadaigh leis an URL Reatha
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Cuir in eagar…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Athraigh Lipéad...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Deimhnigh
 zen-pinned-tab-replaced = Tá URL an chluaisín phinnáilte curtha in ionad an URL reatha!
+zen-pinned-tab-url-edited = Tá URL an chluaisín phinnáilte nuashonraithe!
+zen-pinned-tab-url-invalid = Ní cosúil gur URL bailí é sin.
+zen-pinned-tab-edit-url-title = Cuir URL bioráin in Eagar
+zen-pinned-tab-edit-url-label = Cuir isteach an URL ar cheart don chluaisín bioráilte seo a bheith ag pointeáil chuige:
 zen-tabs-renamed = Athainmníodh an cluaisín go rathúil!
 zen-background-tab-opened-toast = Tá cluaisín cúlra nua oscailte!
 zen-workspace-renamed-toast = Athainmníodh an spás oibre go rathúil!
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = Emojis
 zen-icons-picker-svg = 
     .label = Deilbhíní
+zen-emojis-picker-search = 
+    .placeholder = Cuardaigh emojis
 urlbar-search-mode-zen_actions = Gníomhartha
 zen-site-data-settings = Socruithe
 zen-generic-manage = Bainistigh
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = Nuashonrú críochnaithe!
 zen-sidebar-notification-updated-label = Cad atá nua i { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = Féach ar Nótaí Eisiúna
+zen-sidebar-notification-donate-label = Tacaíocht { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Tabhair síntiús don tionscadal
 zen-sidebar-notification-restart-safe-mode-label = Bhris rud éigin?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Atosaigh i Mód Sábháilte
diff --git a/locales/ga-IE/browser/browser/zen-space-routing.ftl b/locales/ga-IE/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..c0d91810d
--- /dev/null
+++ b/locales/ga-IE/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Socruithe Ródaithe Spáis
+zen-space-routing-rulepanel-placeholder = Le bealaí is féidir leat a roghnú cá n-osclaítear suíomhanna sonracha laistigh de Zen. Mar shampla, is féidir leat naisc YouTube a threorú chun go n-osclófar iad i gcónaí laistigh de do Spás Pearsanta.
+zen-space-routing-dialog-title = Socruithe Ródaithe Spáis
+zen-space-routing-external-default = Bealach réamhshocraithe le haghaidh naisc sheachtracha
+zen-space-routing-new-route = Bealach Nua
+zen-space-routing-open-in-space = Oscail sa Spás
+zen-space-routing-most-recent-space = Spás is déanaí
+zen-space-routing-close-button = 
+    .aria-label = Dún
+    .tooltiptext = Dún
+zen-space-routing-contains = 
+    .label = Tá
+zen-space-routing-equal-to = 
+    .label = Is Cothrom le
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Oscail Isteach
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = Osclaíodh cluaisín nua i { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Cuir Bealach leis don Fhearann
+           *[other] Cuir Bealach leis do Fhearainn
+        }
diff --git a/locales/ga-IE/browser/browser/zen-workspaces.ftl b/locales/ga-IE/browser/browser/zen-workspaces.ftl
index 789d9b5d7..70c80fa9b 100644
--- a/locales/ga-IE/browser/browser/zen-workspaces.ftl
+++ b/locales/ga-IE/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Próifíl
     .tooltiptext = Úsáidtear próifílí chun fianáin agus sonraí suímh a dheighilt idir spásanna.
 zen-workspace-creation-header = Cruthaigh Spás
 zen-workspace-creation-label = Úsáidtear spásanna chun do chluaisíní agus do sheisiúin a eagrú.
+zen-workspace-default-profile = Réamhshocrú
 zen-workspaces-delete-workspace-title = Scrios an spás?
 zen-workspaces-delete-workspace-body = An bhfuil tú cinnte gur mian leat { $name } a scriosadh? Ní féidir an gníomh seo a chealú.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/he/browser/browser/preferences/zen-preferences.ftl b/locales/he/browser/browser/preferences/zen-preferences.ftl
index 974be8fd7..28f5b5938 100644
--- a/locales/he/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/he/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = הסתרת סרגל עליון גם במצב מכווץ
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = הקפצה קצרה של סרגל הכלים במעבר או פתיחת לשוניות חדשות במצב מכווץ
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Allow dragging the window from web pages
 pane-zen-tabs-title = ניהול לשוניות
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = הצג מידע על עמוד
 zen-find-shortcut = חיפוש בעמוד
 zen-search-find-again-shortcut = מצא שוב
 zen-search-find-again-shortcut-prev = מצא קודם
-zen-search-find-again-shortcut-2 = מצא שוב (משני)
+zen-search-find-again-shortcut-alt = Find Again (Alt)
+zen-search-find-again-shortcut-prev-alt = Find Previous (Alt)
 zen-bookmark-this-page-shortcut = שים עמוד בסמניה
 zen-bookmark-show-library-shortcut = הצג ספריית סימניות
 zen-key-stop = עצור טעינה
@@ -281,7 +286,7 @@ zen-workspace-shortcut-switch-9 = מעבר למרחב עבודה 9
 zen-workspace-shortcut-switch-10 = מעבר למרחב עבודה 10
 zen-workspace-shortcut-forward = העברת מרחב העבודה קדימה
 zen-workspace-shortcut-backward = העברת מרחב העבודה אחורה
-zen-workspace-shortcut-create = Create New Workspace
+zen-workspace-shortcut-create = יצירת מרחב עבודה חדש
 zen-sidebar-shortcut-toggle = הפעל/כבה עובי של סרגל צד
 zen-pinned-tab-shortcut-reset = איפוס הלשונית המוצמדת לכתובת המוצמדת
 zen-split-view-shortcut-grid = הפעל/כבה תצוגה מפוצלת רשת
@@ -319,4 +324,4 @@ zen-devtools-toggle-accessibility-shortcut = הפעל/כבה נגישות
 zen-close-all-unpinned-tabs-shortcut = סגירת כל הלשוניות שאינן מוצמדות
 zen-new-unsynced-window-shortcut = חלון לא מסונכרן חדש
 zen-duplicate-tab-shortcut = שכפול לשונית
-zen-key-find-selection = Find Selection
+zen-key-find-selection = איתור בחירה
diff --git a/locales/he/browser/browser/zen-boosts.ftl b/locales/he/browser/browser/zen-boosts.ftl
index 66a825ec5..7688531b7 100644
--- a/locales/he/browser/browser/zen-boosts.ftl
+++ b/locales/he/browser/browser/zen-boosts.ftl
@@ -10,11 +10,11 @@ zen-boost-edit-reset =
     .label = Reset All Edits
 zen-boost-edit-delete = 
     .label = Delete Boost
-zen-boost-size = Size
+zen-boost-size = גודל
 zen-boost-case = Case
 zen-boost-zap = Zap
 zen-boost-code = Code
-zen-boost-back = Back
+zen-boost-back = חזרה
 zen-boost-shuffle = 
     .tooltiptext = Shuffle Boost Settings
 zen-boost-invert = 
diff --git a/locales/he/browser/browser/zen-command-palette.ftl b/locales/he/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..c8af413e2
--- /dev/null
+++ b/locales/he/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Toggle Compact Mode
+zen-action-open-theme-picker = Open Theme Picker
+zen-action-new-split-view = New Split View
+zen-action-new-folder = New Folder
+zen-action-copy-current-url = Copy Current URL
+zen-action-settings = Settings
+zen-action-open-private-window = Open Private Window
+zen-action-open-new-window = Open New Window
+zen-action-new-blank-window = New Blank Window
+zen-action-pin-tab = Pin Tab
+zen-action-unpin-tab = Unpin Tab
+zen-action-open-space-routing = Open Space Routing
+zen-action-new-boost = New Boost
+zen-action-next-space = Next Space
+zen-action-previous-space = Previous Space
+zen-action-close-tab = Close Tab
+zen-action-reload-tab = Reload Tab
+zen-action-reload-tab-without-cache = Reload Tab Without Cache
+zen-action-next-tab = Next Tab
+zen-action-previous-tab = Previous Tab
+zen-action-capture-screenshot = Capture Screenshot
+zen-action-toggle-tabs-on-right = Toggle Tabs on right
+zen-action-add-to-essentials = Add to Essentials
+zen-action-remove-from-essentials = Remove from Essentials
+zen-action-find-in-page = Find in Page
+zen-action-manage-extensions = Manage Extensions
+zen-action-switch-to-automatic-appearance = Switch to Automatic Appearance
+zen-action-switch-to-light-mode = Switch to Light Mode
+zen-action-switch-to-dark-mode = Switch to Dark Mode
+zen-action-print = Print
+zen-action-focus-on = Focus on
+zen-action-extension = Extension
diff --git a/locales/he/browser/browser/zen-general.ftl b/locales/he/browser/browser/zen-general.ftl
index dd85f9dc0..845498c57 100644
--- a/locales/he/browser/browser/zen-general.ftl
+++ b/locales/he/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max } מקומות מלאי
 tab-context-zen-remove-essential = 
     .label = הסרה מהחיוניות
     .accesskey = ר
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Replace Essential URL with Current
-           *[false] Replace Pinned URL with Current
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Replace with Current URL
     .accesskey = ב
+tab-context-zen-edit-pinned-url = 
+    .label = Edit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = שינוי תווית...
 tab-context-zen-edit-icon = 
@@ -45,6 +51,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = אישור
 zen-pinned-tab-replaced = כתובת הלשונית המוצמדת הוחלפה בכתובת הנוכחית!
+zen-pinned-tab-url-edited = Pinned tab URL has been updated!
+zen-pinned-tab-url-invalid = That doesn't look like a valid URL.
+zen-pinned-tab-edit-url-title = Edit Pinned URL
+zen-pinned-tab-edit-url-label = Enter the URL this pinned tab should point to:
 zen-tabs-renamed = שם הלשונית השתנה בהצלחה!
 zen-background-tab-opened-toast = לשונית נפתחה ברקע!
 zen-workspace-renamed-toast = שם מרחב העבודה השתנה בהצלחה!
@@ -63,6 +73,8 @@ zen-icons-picker-emoji =
     .label = אימוג׳י
 zen-icons-picker-svg = 
     .label = סמלים
+zen-emojis-picker-search = 
+    .placeholder = Search emojis
 urlbar-search-mode-zen_actions = פעולות
 zen-site-data-settings = הגדרות
 zen-generic-manage = ניהול
@@ -114,6 +126,9 @@ zen-sidebar-notification-updated-heading = העדכון הושלם!
 zen-sidebar-notification-updated-label = מה חדש ב־{ -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = צפייה בהערות שחרור הגרסה
+zen-sidebar-notification-donate-label = Support { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donate to the project
 zen-sidebar-notification-restart-safe-mode-label = משהו השתבש?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = הפעלה מחדש במצב בטוח
diff --git a/locales/he/browser/browser/zen-space-routing.ftl b/locales/he/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..308665eb4
--- /dev/null
+++ b/locales/he/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Space Routing Settings
+zen-space-routing-rulepanel-placeholder = Routes let you choose where specific sites open inside Zen. For example, you can route YouTube links to always open inside your Personal space.
+zen-space-routing-dialog-title = Space Routing Settings
+zen-space-routing-external-default = Default route for external links
+zen-space-routing-new-route = New Route
+zen-space-routing-open-in-space = Open in Space
+zen-space-routing-most-recent-space = Most recent Space
+zen-space-routing-close-button = 
+    .aria-label = סגירה
+    .tooltiptext = סגירה
+zen-space-routing-contains = 
+    .label = מכיל
+zen-space-routing-equal-to = 
+    .label = בדיוק
+zen-space-routing-regex = 
+    .label = ביטוי רגולרי
+zen-space-routing-open-in = פתיחה בתוך
+zen-space-routing-url = כתובת
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/he/browser/browser/zen-workspaces.ftl b/locales/he/browser/browser/zen-workspaces.ftl
index e35618442..b175e8cb3 100644
--- a/locales/he/browser/browser/zen-workspaces.ftl
+++ b/locales/he/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = פרופיל
     .tooltiptext = פרופילים משמשים להפרדת קובצי Cookie ונתוני אתר בין מרחבים שונים.
 zen-workspace-creation-header = יצירת מרחב
 zen-workspace-creation-label = המרחבים משמשים לסידור לשוניות והפעלות.
+zen-workspace-default-profile = Default
 zen-workspaces-delete-workspace-title = למחוק את המרחב?
 zen-workspaces-delete-workspace-body = למחוק את { $name }? לא ניתן לבטל פעולה זו.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/hu/browser/browser/preferences/zen-preferences.ftl b/locales/hu/browser/browser/preferences/zen-preferences.ftl
index d0cc5bbce..28a4a3bcd 100644
--- a/locales/hu/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/hu/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = A felső eszköztár is legyen elrejtve kompakt módban
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Eszköztár megjelenítése rövid ideig lap váltás vagy új megnyitása során kompakt módban
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Allow dragging the window from web pages
 pane-zen-tabs-title = Lap kezelés
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -222,7 +226,7 @@ zen-file-open-shortcut = Fájl megnyitása
 zen-save-page-shortcut = Oldal mentése
 zen-print-shortcut = Oldal nyomtatása
 zen-close-shortcut-2 = Lap bezárása
-zen-mute-toggle-shortcut = Némítás be-/kikapcsolása
+zen-mute-toggle-shortcut = Némítás kapcsolása
 zen-key-delete = Törlés gomb
 zen-key-go-back = Vissza
 zen-key-go-forward = Előre
@@ -231,12 +235,12 @@ zen-nav-fwd-shortcut-alt = Előrenavigálás (Alt)
 zen-history-show-all-shortcut = Minden előzmény megjelenítése
 zen-key-enter-full-screen = Belépés a teljes képernyőbe
 zen-key-exit-full-screen = Kilépés a teljes képernyőből
-zen-ai-chatbot-sidebar-shortcut = AI Chatbot oldalsáv ki-/bekapcsolása
-zen-key-inspector-mac = Vizsgáló ki-/bekapcsolása (Mac)
-zen-toggle-sidebar-shortcut = Firefox oldalsáv ki-/bekapcsolása
+zen-ai-chatbot-sidebar-shortcut = AI Chatbot oldalsáv kapcsolása
+zen-key-inspector-mac = Vizsgáló kapcsolása (Mac)
+zen-toggle-sidebar-shortcut = Firefox oldalsáv kapcsolása
 zen-toggle-pin-tab-shortcut = Lap rögzítése/feloldása
-zen-reader-mode-toggle-shortcut-other = Olvasó mód ki-/bekapcsolása
-zen-picture-in-picture-toggle-shortcut = Kép a képben mód ki-/bekapcsolása
+zen-reader-mode-toggle-shortcut-other = Olvasó mód kapcsolása
+zen-picture-in-picture-toggle-shortcut = Kép a képben mód kapcsolása
 zen-nav-reload-shortcut-2 = Oldal újratöltése
 zen-key-about-processes = A folyamatokról
 zen-page-source-shortcut = Oldal forrásának megtekintése
@@ -244,7 +248,8 @@ zen-page-info-shortcut = Oldal adatainak megtekintése
 zen-find-shortcut = Keresés az oldalon
 zen-search-find-again-shortcut = Keresés újra
 zen-search-find-again-shortcut-prev = Előző keresése
-zen-search-find-again-shortcut-2 = Keresés újra (Alt)
+zen-search-find-again-shortcut-alt = Find Again (Alt)
+zen-search-find-again-shortcut-prev-alt = Find Previous (Alt)
 zen-bookmark-this-page-shortcut = Oldal mentése a könyvjelzők közé
 zen-bookmark-show-library-shortcut = Könyvjelzőkönyvtár megtekintése
 zen-key-stop = Betöltés leállítása
@@ -260,14 +265,14 @@ zen-screenshot-shortcut = Képernyőkép-készítés
 zen-key-sanitize = Böngészési adatok törlése
 zen-quit-app-shortcut = Kilépés az alkalmazásból
 zen-key-wr-capture-cmd = WR rögzítési parancs
-zen-key-wr-toggle-capture-sequence-cmd = WR rögzítési szekvencia ki-/bekapcsolása
+zen-key-wr-toggle-capture-sequence-cmd = WR rögzítési szekvencia kapcsolása
 zen-nav-reload-shortcut = Oldal újratöltése
 zen-nav-reload-shortcut-skip-cache = Oldal újratöltése (Gyorsítótár átugrása)
 zen-close-shortcut = Ablak bezárása
 zen-close-tab-shortcut = Lap bezárása
-zen-compact-mode-shortcut-show-sidebar = Lebegő oldalsáv ki-/bekapcsolása
-zen-compact-mode-shortcut-show-toolbar = Lebegő eszköztár ki-/bekapcsolása
-zen-compact-mode-shortcut-toggle = Kompakt mód ki-/bekapcsolása
+zen-compact-mode-shortcut-show-sidebar = Lebegő oldalsáv kapcsolása
+zen-compact-mode-shortcut-show-toolbar = Lebegő eszköztár kapcsolása
+zen-compact-mode-shortcut-toggle = Kompakt mód kapcsolása
 zen-glance-expand = Bepillantás kiterjesztése
 zen-workspace-shortcut-switch-1 = Első munkakörnyezetre váltás
 zen-workspace-shortcut-switch-2 = Második munkakörnyezetre váltás
@@ -281,10 +286,10 @@ zen-workspace-shortcut-switch-9 = Kilencedik munkakörnyezetre váltás
 zen-workspace-shortcut-switch-10 = Tizedik munkakörnyezetre váltás
 zen-workspace-shortcut-forward = Következő munkakörnyezet
 zen-workspace-shortcut-backward = Előző munkakörnyezet
-zen-workspace-shortcut-create = Create New Workspace
+zen-workspace-shortcut-create = Új munkakörnyezet létrehozása
 zen-sidebar-shortcut-toggle = Oldalsáv szélességének váltása
 zen-pinned-tab-shortcut-reset = Rögzített lap visszaállítása rögzítéskori URL-re
-zen-split-view-shortcut-grid = Osztott nézet grid ki-/bekapcsolása
+zen-split-view-shortcut-grid = Osztott nézet grid kapcsolása
 zen-split-view-shortcut-vertical = Osztott nézet függőlegesen
 zen-split-view-shortcut-horizontal = Osztott nézet vízszintesen
 zen-split-view-shortcut-unsplit = Osztott nézet bezárása
@@ -319,4 +324,4 @@ zen-devtools-toggle-accessibility-shortcut = Hozzáférhetőség kapcsolása
 zen-close-all-unpinned-tabs-shortcut = Összes rögzítetlen lap bezárása
 zen-new-unsynced-window-shortcut = Új szinkronizálatlan ablak
 zen-duplicate-tab-shortcut = Lap duplikálása
-zen-key-find-selection = Find Selection
+zen-key-find-selection = Keresés kijelölésben
diff --git a/locales/hu/browser/browser/zen-boosts.ftl b/locales/hu/browser/browser/zen-boosts.ftl
index 30caaedb0..26c46b99c 100644
--- a/locales/hu/browser/browser/zen-boosts.ftl
+++ b/locales/hu/browser/browser/zen-boosts.ftl
@@ -5,18 +5,18 @@
 zen-boost-edit-rename = 
     .label = Boost átnevezése
 zen-boost-edit-shuffle = 
-    .label = Shuffle Vibes
+    .label = Hangulat keverése
 zen-boost-edit-reset = 
     .label = Minden módosítás visszaállítása
 zen-boost-edit-delete = 
     .label = Boost törlése
 zen-boost-size = Méret
-zen-boost-case = Case
-zen-boost-zap = Zap
+zen-boost-case = Kis-/nagybetű
+zen-boost-zap = Eltüntet
 zen-boost-code = Kód
 zen-boost-back = Vissza
 zen-boost-shuffle = 
-    .tooltiptext = Shuffle Boost Settings
+    .tooltiptext = Boost beállítások keverése
 zen-boost-invert = 
     .tooltiptext = Színek intelligens invertálása
 zen-boost-controls = 
@@ -24,28 +24,28 @@ zen-boost-controls =
 zen-boost-disable = 
     .tooltiptext = Színbeállítások letiltása
 zen-boost-text-case-toggle = 
-    .tooltiptext = Toggle Text Case
+    .tooltiptext = Kis- és nagybetűk váltása
 zen-boost-css-picker = 
-    .tooltiptext = Pick Selector
+    .tooltiptext = Szelektor kiválasztása
 zen-boost-css-inspector = 
     .tooltiptext = Vizsgáló megnyitása
 zen-boost-color-contrast = Kontraszt
 zen-boost-color-brightness = Fényerő
 zen-boost-color-original-saturation = Eredeti szaturáció
-zen-add-zap-helper = Click elements on the page to <b>Zap</b> them
-zen-remove-zap-helper = ← Click to Unzap
-zen-select-this = Insert selector for this
-zen-select-related = Insert selector for related
+zen-add-zap-helper = Kattints az oldal elemeire, hogy <b>Eltüntet</b>sd őket
+zen-remove-zap-helper = ← Visszaállításhoz kattints
+zen-select-this = Szelektor beillesztése ehhez
+zen-select-related = Szelektor beillesztése a kapcsolódó elemhez
 zen-select-cancel = Mégse
-zen-zap-this = Zap this
-zen-zap-related = Zap all related elements
+zen-zap-this = Tüntesd el ezt
+zen-zap-related = Összes kapcsolódó elem eltüntetése
 zen-zap-cancel = Mégse
 zen-zap-done = Kész
 zen-unzap-tooltip =
     { $elementCount ->
-        [0] No elements zapped
-        [1] { $elementCount } element zapped
-       *[other] { $elementCount } elements zapped
+        [0] Nincs eltüntetett elem
+        [1] { $elementCount } elem eltüntetve
+       *[other] { $elementCount } elem eltüntetve
     }
 zen-boost-save = 
     .label = Boost exportálása
diff --git a/locales/hu/browser/browser/zen-command-palette.ftl b/locales/hu/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..c8af413e2
--- /dev/null
+++ b/locales/hu/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Toggle Compact Mode
+zen-action-open-theme-picker = Open Theme Picker
+zen-action-new-split-view = New Split View
+zen-action-new-folder = New Folder
+zen-action-copy-current-url = Copy Current URL
+zen-action-settings = Settings
+zen-action-open-private-window = Open Private Window
+zen-action-open-new-window = Open New Window
+zen-action-new-blank-window = New Blank Window
+zen-action-pin-tab = Pin Tab
+zen-action-unpin-tab = Unpin Tab
+zen-action-open-space-routing = Open Space Routing
+zen-action-new-boost = New Boost
+zen-action-next-space = Next Space
+zen-action-previous-space = Previous Space
+zen-action-close-tab = Close Tab
+zen-action-reload-tab = Reload Tab
+zen-action-reload-tab-without-cache = Reload Tab Without Cache
+zen-action-next-tab = Next Tab
+zen-action-previous-tab = Previous Tab
+zen-action-capture-screenshot = Capture Screenshot
+zen-action-toggle-tabs-on-right = Toggle Tabs on right
+zen-action-add-to-essentials = Add to Essentials
+zen-action-remove-from-essentials = Remove from Essentials
+zen-action-find-in-page = Find in Page
+zen-action-manage-extensions = Manage Extensions
+zen-action-switch-to-automatic-appearance = Switch to Automatic Appearance
+zen-action-switch-to-light-mode = Switch to Light Mode
+zen-action-switch-to-dark-mode = Switch to Dark Mode
+zen-action-print = Print
+zen-action-focus-on = Focus on
+zen-action-extension = Extension
diff --git a/locales/hu/browser/browser/zen-general.ftl b/locales/hu/browser/browser/zen-general.ftl
index 93f887358..d45f52667 100644
--- a/locales/hu/browser/browser/zen-general.ftl
+++ b/locales/hu/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max } hely foglalt
 tab-context-zen-remove-essential = 
     .label = Eltávolítás az alapvetőkből
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Alapvető lap cseréje az aktuális URL-el
-           *[false] Rögzített lap cseréje az aktuális URL-el
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Replace with Current URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Edit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Címke módosítása...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Megerősítés
 zen-pinned-tab-replaced = A rögzített lap URL címe helyébe az aktuális URL cím lépett!
+zen-pinned-tab-url-edited = Pinned tab URL has been updated!
+zen-pinned-tab-url-invalid = That doesn't look like a valid URL.
+zen-pinned-tab-edit-url-title = Edit Pinned URL
+zen-pinned-tab-edit-url-label = Enter the URL this pinned tab should point to:
 zen-tabs-renamed = A lap sikeresen át lett nevezve!
 zen-background-tab-opened-toast = Új lap megnyitva!
 zen-workspace-renamed-toast = A munkakörnyezet sikeresen át lett nevezve!
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = Emojik
 zen-icons-picker-svg = 
     .label = Ikonok
+zen-emojis-picker-search = 
+    .placeholder = Search emojis
 urlbar-search-mode-zen_actions = Műveletek
 zen-site-data-settings = Beállítások
 zen-generic-manage = Kezelés
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = Frissítés befejezve!
 zen-sidebar-notification-updated-label = { -brand-short-name } újdonságai
 zen-sidebar-notification-updated-tooltip = 
     .title = Változások listájának megtekintése
+zen-sidebar-notification-donate-label = Support { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donate to the project
 zen-sidebar-notification-restart-safe-mode-label = Valami elromlott?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Újraindítás biztonságos módban
diff --git a/locales/hu/browser/browser/zen-space-routing.ftl b/locales/hu/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..7dd1e5178
--- /dev/null
+++ b/locales/hu/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Környezet útválasztási beállítások
+zen-space-routing-rulepanel-placeholder = Az útvonalakkal meghatározhatja, hogy az egyes webhelyek hol nyíljanak meg a Zen-ben. Beállíthatod például, hogy a YouTube-linkek mindig a Személyes környezetben nyíljanak meg.
+zen-space-routing-dialog-title = Környezet útválasztási beállítások
+zen-space-routing-external-default = Külső hivatkozások alapértelmezett útvonala
+zen-space-routing-new-route = Új útvonal
+zen-space-routing-open-in-space = Megnyitás környezetben
+zen-space-routing-most-recent-space = Legutóbbi környezet
+zen-space-routing-close-button = 
+    .aria-label = Bezárás
+    .tooltiptext = Bezárás
+zen-space-routing-contains = 
+    .label = Tartalmazza
+zen-space-routing-equal-to = 
+    .label = Megegyezik ezzel
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Megnyitás itt
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/hu/browser/browser/zen-workspaces.ftl b/locales/hu/browser/browser/zen-workspaces.ftl
index 00f7ead46..fdf2ca829 100644
--- a/locales/hu/browser/browser/zen-workspaces.ftl
+++ b/locales/hu/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Profil
     .tooltiptext = A profilok arra szolgálnak, hogy a sütiket és a webhelyadatokat elkülönítsék a munkakörnyezetek között.
 zen-workspace-creation-header = Környezet létrehozása
 zen-workspace-creation-label = A munkakörnyezetek a lapok és munkamenetek rendszerezésére szolgálnak.
+zen-workspace-default-profile = Default
 zen-workspaces-delete-workspace-title = Munkakörnyezet törlése?
 zen-workspaces-delete-workspace-body = Biztosan törölni szeretnéd ezt: { $name }? Ez a művelet visszafordíthatatlan.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/id/browser/browser/preferences/zen-preferences.ftl b/locales/id/browser/browser/preferences/zen-preferences.ftl
index 61fb563cf..9c35a6091 100644
--- a/locales/id/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/id/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Sembunyikan juga toolbar atas dalam mode ringkas
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Buat bilah tab muncul sebentar saat beralih atau membuka tab baru dalam mode ringkas
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Allow dragging the window from web pages
 pane-zen-tabs-title = Pengelolaan Tab
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = Lihat Info Halaman
 zen-find-shortcut = Temukan di Halaman
 zen-search-find-again-shortcut = Temukan Lagi
 zen-search-find-again-shortcut-prev = Cari Sebelumnya
-zen-search-find-again-shortcut-2 = Cari Lagi (Alt)
+zen-search-find-again-shortcut-alt = Find Again (Alt)
+zen-search-find-again-shortcut-prev-alt = Find Previous (Alt)
 zen-bookmark-this-page-shortcut = Markahi Laman Ini
 zen-bookmark-show-library-shortcut = Tampilkan Pustaka Markah
 zen-key-stop = Berhenti Memuat
@@ -281,7 +286,7 @@ zen-workspace-shortcut-switch-9 = Beralih ke Ruang Kerja 9
 zen-workspace-shortcut-switch-10 = Beralih ke Ruang Kerja 10
 zen-workspace-shortcut-forward = Ruang Kerja setelahnya
 zen-workspace-shortcut-backward = Ruang Kerja sebelumnya
-zen-workspace-shortcut-create = Create New Workspace
+zen-workspace-shortcut-create = Buat Ruang Kerja Baru
 zen-sidebar-shortcut-toggle = Peralihan lebar Bilah sisi
 zen-pinned-tab-shortcut-reset = Setel ulang Tab yang Disematkan ke URL awal
 zen-split-view-shortcut-grid = Beralih ke Panel terbagi
diff --git a/locales/id/browser/browser/zen-boosts.ftl b/locales/id/browser/browser/zen-boosts.ftl
index eb42026a7..c71740426 100644
--- a/locales/id/browser/browser/zen-boosts.ftl
+++ b/locales/id/browser/browser/zen-boosts.ftl
@@ -48,9 +48,9 @@ zen-unzap-tooltip =
        *[other] { $elementCount } elements zapped
     }
 zen-boost-save = 
-    .label = Export Boost
+    .label = Ekspor Boost
 zen-boost-load = 
-    .label = Import Boost
+    .label = Impor Boost
 zen-panel-ui-boosts-exported-message = Boost exported!
 zen-site-data-boosts = Boosts
 zen-site-data-create-boost = 
diff --git a/locales/id/browser/browser/zen-command-palette.ftl b/locales/id/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..c8af413e2
--- /dev/null
+++ b/locales/id/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Toggle Compact Mode
+zen-action-open-theme-picker = Open Theme Picker
+zen-action-new-split-view = New Split View
+zen-action-new-folder = New Folder
+zen-action-copy-current-url = Copy Current URL
+zen-action-settings = Settings
+zen-action-open-private-window = Open Private Window
+zen-action-open-new-window = Open New Window
+zen-action-new-blank-window = New Blank Window
+zen-action-pin-tab = Pin Tab
+zen-action-unpin-tab = Unpin Tab
+zen-action-open-space-routing = Open Space Routing
+zen-action-new-boost = New Boost
+zen-action-next-space = Next Space
+zen-action-previous-space = Previous Space
+zen-action-close-tab = Close Tab
+zen-action-reload-tab = Reload Tab
+zen-action-reload-tab-without-cache = Reload Tab Without Cache
+zen-action-next-tab = Next Tab
+zen-action-previous-tab = Previous Tab
+zen-action-capture-screenshot = Capture Screenshot
+zen-action-toggle-tabs-on-right = Toggle Tabs on right
+zen-action-add-to-essentials = Add to Essentials
+zen-action-remove-from-essentials = Remove from Essentials
+zen-action-find-in-page = Find in Page
+zen-action-manage-extensions = Manage Extensions
+zen-action-switch-to-automatic-appearance = Switch to Automatic Appearance
+zen-action-switch-to-light-mode = Switch to Light Mode
+zen-action-switch-to-dark-mode = Switch to Dark Mode
+zen-action-print = Print
+zen-action-focus-on = Focus on
+zen-action-extension = Extension
diff --git a/locales/id/browser/browser/zen-general.ftl b/locales/id/browser/browser/zen-general.ftl
index 860c3deed..04f2da7aa 100644
--- a/locales/id/browser/browser/zen-general.ftl
+++ b/locales/id/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max } slot terisi
 tab-context-zen-remove-essential = 
     .label = Hapus dari Esensial
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Perbarui URL awal Tab Esensial
-           *[false] Perbarui URL awal Tab Sematan
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Replace with Current URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Edit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Ubah Label...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Konfirmasi
 zen-pinned-tab-replaced = URL awal dari tab yang disematkan telah diganti dengan URL saat ini.
+zen-pinned-tab-url-edited = Pinned tab URL has been updated!
+zen-pinned-tab-url-invalid = That doesn't look like a valid URL.
+zen-pinned-tab-edit-url-title = Edit Pinned URL
+zen-pinned-tab-edit-url-label = Enter the URL this pinned tab should point to:
 zen-tabs-renamed = Tab telah berhasil diubah namanya!
 zen-background-tab-opened-toast = Tab baru telah terbuka di latar belakang!
 zen-workspace-renamed-toast = Ruang Kerja telah berhasil diubah namanya!
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = Emoji
 zen-icons-picker-svg = 
     .label = Ikon
+zen-emojis-picker-search = 
+    .placeholder = Search emojis
 urlbar-search-mode-zen_actions = Aksi
 zen-site-data-settings = Pengaturan
 zen-generic-manage = Kelola
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = Pembaruan Selesai!
 zen-sidebar-notification-updated-label = Apa yang baru di { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = Lihat Catatan Rilis
+zen-sidebar-notification-donate-label = Support { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donate to the project
 zen-sidebar-notification-restart-safe-mode-label = Ada yang rusak?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Mulai Ulang dalam Mode Aman
diff --git a/locales/id/browser/browser/zen-space-routing.ftl b/locales/id/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..d757144bb
--- /dev/null
+++ b/locales/id/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Space Routing Settings
+zen-space-routing-rulepanel-placeholder = Routes let you choose where specific sites open inside Zen. For example, you can route YouTube links to always open inside your Personal space.
+zen-space-routing-dialog-title = Space Routing Settings
+zen-space-routing-external-default = Default route for external links
+zen-space-routing-new-route = New Route
+zen-space-routing-open-in-space = Open in Space
+zen-space-routing-most-recent-space = Most recent Space
+zen-space-routing-close-button = 
+    .aria-label = Close
+    .tooltiptext = Close
+zen-space-routing-contains = 
+    .label = Contains
+zen-space-routing-equal-to = 
+    .label = Is Equal To
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Open In
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/id/browser/browser/zen-workspaces.ftl b/locales/id/browser/browser/zen-workspaces.ftl
index abc634e71..9e6ff7c87 100644
--- a/locales/id/browser/browser/zen-workspaces.ftl
+++ b/locales/id/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Profil
     .tooltiptext = Profil (Kontainer) digunakan untuk memisahkan cookie dan data situs antar Ruang.
 zen-workspace-creation-header = Buat sebuah Ruang
 zen-workspace-creation-label = Ruang digunakan untuk mengorganisasikan tab dan sesi Anda.
+zen-workspace-default-profile = Default
 zen-workspaces-delete-workspace-title = Hapus Ruang?
 zen-workspaces-delete-workspace-body = Apakah Anda yakin ingin menghapus { $name }? Tindakan ini tidak bisa dibatalkan.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/is/browser/browser/preferences/zen-preferences.ftl b/locales/is/browser/browser/preferences/zen-preferences.ftl
index 11ac037c8..32db43305 100644
--- a/locales/is/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/is/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Fela efstu verkfærastikuna einnig í þjöppuðu viðmóti
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Láta verkfærastikuna hoppa upp þegar skipt er um flipa eða nýir eru opnaðir í þjöppuðu viðmóti
+zen-look-and-feel-window-drag-header = Gluggadráttur
+zen-look-and-feel-window-drag-description = Færðu gluggann með því að draga autt svæði efst á vefsíðum, rétt eins og titilstikuna.
+zen-window-drag-enabled = 
+    .label = Leyfa að draga gluggann af vefsíðum
 pane-zen-tabs-title = Umsýsla flipa
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -49,7 +53,7 @@ zen-tabs-close-on-back-with-no-history =
 zen-settings-workspaces-sync-unpinned-tabs = 
     .label = Samstilla einungis festa flipa í vinnusvæðum
 zen-tabs-cycle-by-attribute = 
-    .label = Ctrl+Tab flettir aðeins innan flipa í þarfagripum eða vinnusvæðum
+    .label = Ctrl+Tab flettir aðeins innan flipa í Mikilvægt eða vinnusvæðum
 zen-tabs-cycle-ignore-pending-tabs = 
     .label = Hunsa flipa í bið þegar flett er í gegnum með Ctrl + Tab
 zen-tabs-cycle-by-attribute-warning = Ctrl+Tab mun fletta í gegnum röð eftir nýlega notuðum flipum, þegar það er virkjað
@@ -244,7 +248,8 @@ zen-page-info-shortcut = Skoða upplýsingar um síðu
 zen-find-shortcut = Finna á síðu
 zen-search-find-again-shortcut = Finna aftur
 zen-search-find-again-shortcut-prev = Finna fyrra
-zen-search-find-again-shortcut-2 = Finna aftur (Alt)
+zen-search-find-again-shortcut-alt = Finna aftur (Alt)
+zen-search-find-again-shortcut-prev-alt = Finna fyrra (Alt)
 zen-bookmark-this-page-shortcut = Bókamerkja þessa síðu
 zen-bookmark-show-library-shortcut = Birta bókamerkjasafn
 zen-key-stop = Stöðva hleðslu
diff --git a/locales/is/browser/browser/zen-command-palette.ftl b/locales/is/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..10a2da5be
--- /dev/null
+++ b/locales/is/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Víxla þjöppuðu viðmóti
+zen-action-open-theme-picker = Opna þemaval
+zen-action-new-split-view = Nýtt klofið yfirlit
+zen-action-new-folder = Ný mappa
+zen-action-copy-current-url = Afrita fyrirliggjandi slóð
+zen-action-settings = Stillingar
+zen-action-open-private-window = Opna huliðsglugga
+zen-action-open-new-window = Opna nýjan glugga
+zen-action-new-blank-window = Nýr auður gluggi
+zen-action-pin-tab = Festa flipa
+zen-action-unpin-tab = Losa flipa
+zen-action-open-space-routing = Opna Svæðabeiningar
+zen-action-new-boost = Ný endurhönnun
+zen-action-next-space = Næsta svæði
+zen-action-previous-space = Fyrra svæði
+zen-action-close-tab = Loka flipa
+zen-action-reload-tab = Endurhlaða flipa
+zen-action-reload-tab-without-cache = Endurhlaða flipa án skyndiminnis
+zen-action-next-tab = Næsta flipa
+zen-action-previous-tab = Fyrri flipa
+zen-action-capture-screenshot = Taka skjámynd
+zen-action-toggle-tabs-on-right = Víxla sýnileika flipa hægra megin
+zen-action-add-to-essentials = Bæta við Mikilvægt
+zen-action-remove-from-essentials = Fjarlægja úr Mikilvægt-flipum
+zen-action-find-in-page = Finna á síðu
+zen-action-manage-extensions = Sýsla með forritsauka
+zen-action-switch-to-automatic-appearance = Skipta yfir í sjálfvirkan útlitsham
+zen-action-switch-to-light-mode = Skipta yfir í ljósan ham
+zen-action-switch-to-dark-mode = Skipta yfir í dökkan ham
+zen-action-print = Prenta
+zen-action-focus-on = Skerpa
+zen-action-extension = Viðbót
diff --git a/locales/is/browser/browser/zen-general.ftl b/locales/is/browser/browser/zen-general.ftl
index 39f8aa763..05df7fdb8 100644
--- a/locales/is/browser/browser/zen-general.ftl
+++ b/locales/is/browser/browser/zen-general.ftl
@@ -7,24 +7,30 @@ unified-extensions-description = Forritsaukar eru notaðir til að auðga notagi
 tab-context-zen-reset-pinned-tab = 
     .label =
         { $isEssential ->
-            [true] Endurglæða þarfaflipa
-           *[false] Endurglæða festan flipa
+            [true] Endurlesa Mikilvægt-flipa
+           *[false] Endurlesa festan flipa
         }
     .accesskey = R
 tab-context-zen-add-essential = 
-    .label = Bæta við þarfaflipa
+    .label = Bæta við Mikilvægt
     .accesskey = F
 tab-context-zen-add-essential-badge = { $num } / { $max }
 tab-context-zen-remove-essential = 
-    .label = Fjarlægja úr þarfaflipum
+    .label = Fjarlægja úr Mikilvægt-flipum
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Skipta út vefslóð þarfaflipa fyrir fyrirliggjandi slóð
-           *[false] Skipta út vefslóð fests flipa fyrir fyrirliggjandi slóð
+            [true] Breyta vefslóð á Mikilvægt
+           *[false] Breyta vefslóð fests flipa
         }
     .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Skipta út fyrir fyrirliggjandi vefslóð
+    .accesskey = P
+tab-context-zen-edit-pinned-url = 
+    .label = Breyta…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Skipta um merkingu...
 tab-context-zen-edit-icon = 
@@ -45,6 +51,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Staðfesta
 zen-pinned-tab-replaced = URL-slóð festa flipans hefur verið skipt út með fyrirliggjandi slóð!
+zen-pinned-tab-url-edited = Vefslóð festa flipans hefur verið breytt!
+zen-pinned-tab-url-invalid = Þetta virðist ekki vera gild vefslóð.
+zen-pinned-tab-edit-url-title = Breyta festri vefslóð
+zen-pinned-tab-edit-url-label = Sláðu inn slóðina sem þessi festi flipi ætti að vísa á:
 zen-tabs-renamed = Tókst að endurnefna flipann!
 zen-background-tab-opened-toast = Nýr bakgrunnsflipi opnaður!
 zen-workspace-renamed-toast = Tókst að endurnefna vinnusvæðið!
@@ -63,12 +73,14 @@ zen-icons-picker-emoji =
     .label = Emoji-tákn
 zen-icons-picker-svg = 
     .label = Táknmyndir
+zen-emojis-picker-search = 
+    .placeholder = Leita að emoji-táknum
 urlbar-search-mode-zen_actions = Aðgerðir
 zen-site-data-settings = Stillingar
 zen-generic-manage = Sýsla
 zen-generic-more = Meira
 zen-generic-next = Næsta
-zen-essentials-promo-label = Bæta við þarfaflipa
+zen-essentials-promo-label = Bæta við Mikilvægt
 zen-essentials-promo-sublabel = Hafðu eftirlætisflipana þína við hendina
 # These labels will be used for the site data panel settings
 zen-site-data-setting-allow = Leyft
@@ -114,6 +126,9 @@ zen-sidebar-notification-updated-heading = Uppfærslu lokið!
 zen-sidebar-notification-updated-label = Nýtt á döfinni í { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = Skoða útgáfuupplýsingar
+zen-sidebar-notification-donate-label = Styrkja { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Styrkja verkefnið með framlagi
 zen-sidebar-notification-restart-safe-mode-label = Bilaði eitthvað?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Endurræsa í öruggum ham
diff --git a/locales/is/browser/browser/zen-space-routing.ftl b/locales/is/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..05226f6ff
--- /dev/null
+++ b/locales/is/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Stillingar beininga á svæði
+zen-space-routing-rulepanel-placeholder = Beiningar gera þér kleift að velja hvar ákveðin vefsvæði opnast inni í Zen. Til dæmis geturðu stillt það þannig að YouTube-tenglar opnist alltaf í persónulega svæðinu þínu.
+zen-space-routing-dialog-title = Stillingar beininga á svæði
+zen-space-routing-external-default = Sjálfgefin beining fyrir utanaðkomandi tengla
+zen-space-routing-new-route = Ný beining
+zen-space-routing-open-in-space = Opna í svæði
+zen-space-routing-most-recent-space = Nýjast notaða svæðið
+zen-space-routing-close-button = 
+    .aria-label = Loka
+    .tooltiptext = Loka
+zen-space-routing-contains = 
+    .label = Inniheldur
+zen-space-routing-equal-to = 
+    .label = Er jafnt og
+zen-space-routing-regex = 
+    .label = Regluleg segð
+zen-space-routing-open-in = Opna í
+zen-space-routing-url = Slóð
+zen-space-routing-tab-routed-toast = Nýr flipi opnaður innan { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Bæta við beiningu fyrir lén
+           *[other] Bæta við beiningu fyrir lén
+        }
diff --git a/locales/is/browser/browser/zen-welcome.ftl b/locales/is/browser/browser/zen-welcome.ftl
index d9d12a22d..f0bda4f48 100644
--- a/locales/is/browser/browser/zen-welcome.ftl
+++ b/locales/is/browser/browser/zen-welcome.ftl
@@ -12,7 +12,7 @@ zen-welcome-set-default-browser = Setja { -brand-short-name } sem sjálfgefna va
 zen-welcome-dont-set-default-browser = EKKI setja { -brand-short-name } sem sjálfgefna vafrann þinn
 zen-welcome-initial-essentials-title = Þörfustu fliparnir þinir, alltaf innan seilingar
 zen-welcome-initial-essentials-description-1 = Haltu mikilvægustu flipunum þínum við hendina, alveg sama hvað þeir eru margir.
-zen-welcome-initial-essentials-description-2 = Þarfafliparnir eru alltaf sjáanlegir, sama hvaða vinnusvæði þú ert á.
+zen-welcome-initial-essentials-description-2 = Mikilvægt-fliparnir eru alltaf sjáanlegir, sama hvaða vinnusvæði þú ert á.
 zen-welcome-workspace-colors-title = Vinnusvæðin þín, litirnir þínir
 zen-welcome-workspace-colors-description = Aðlagaðu vafrann að þínum þörfum með því að gefa hverju vinnusvæði sinn einstaka lit.
 zen-welcome-start-browsing-title =
diff --git a/locales/is/browser/browser/zen-workspaces.ftl b/locales/is/browser/browser/zen-workspaces.ftl
index 5fbf6d43f..69fc37cd8 100644
--- a/locales/is/browser/browser/zen-workspaces.ftl
+++ b/locales/is/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Notkunarsnið
     .tooltiptext = Notkunarsnið eru til þess að aðskilja vefkökur og gögn vefsvæða á milli vinnusvæða.
 zen-workspace-creation-header = Búa til vinnusvæði
 zen-workspace-creation-label = Vinnusvæði eru notuð til að skipuleggja flipana þína og vafurlotur.
+zen-workspace-default-profile = Sjálfgefið
 zen-workspaces-delete-workspace-title = Eyða svæði?
 zen-workspaces-delete-workspace-body = Ertu viss um að þú viljir eyða { $name }? Þessi aðgerð er ekki afturkallanleg.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/it/browser/browser/preferences/zen-preferences.ftl b/locales/it/browser/browser/preferences/zen-preferences.ftl
index 36a85b054..0935e3db2 100644
--- a/locales/it/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/it/browser/browser/preferences/zen-preferences.ftl
@@ -38,16 +38,20 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Nascondi anche la barra degli strumenti superiore in modalità compatta
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Fai comparire brevemente la barra degli strumenti quando si cambiano o si aprono nuove schede in modalità compatta
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Allow dragging the window from web pages
 pane-zen-tabs-title = Gestione Schede
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
 pane-settings-workspaces-title = Workspace
 zen-tabs-select-recently-used-on-close = 
-    .label = When closing a tab, switch to the most recently used tab instead of the next tab
+    .label = Quando si chiude una scheda, passa alla scheda usata più di recente invece della scheda successiva
 zen-tabs-close-on-back-with-no-history = 
     .label = Chiudi scheda e passa alla scheda proprietario (o scheda usata più di recente) quando si torna indietro senza cronologia
 zen-settings-workspaces-sync-unpinned-tabs = 
-    .label = Sync only pinned tabs in workspaces
+    .label = Sincronizza solo schede bloccate negli spazi di lavoro
 zen-tabs-cycle-by-attribute = 
     .label = Ctrl+Tab cicla solo tra le schede Essenziali o Spazi
 zen-tabs-cycle-ignore-pending-tabs = 
@@ -244,7 +248,8 @@ zen-page-info-shortcut = Visualizza Informazioni Pagina
 zen-find-shortcut = Trova nella pagina
 zen-search-find-again-shortcut = Trova Di Nuovo
 zen-search-find-again-shortcut-prev = Trova Precedente
-zen-search-find-again-shortcut-2 = Trova Ancora (Alt)
+zen-search-find-again-shortcut-alt = Find Again (Alt)
+zen-search-find-again-shortcut-prev-alt = Find Previous (Alt)
 zen-bookmark-this-page-shortcut = Aggiungi questa pagina ai segnalibri
 zen-bookmark-show-library-shortcut = Mostra Libreria Segnalibri
 zen-key-stop = Interrompi Caricamento
@@ -281,7 +286,7 @@ zen-workspace-shortcut-switch-9 = Passa allo spazio di lavoro 9
 zen-workspace-shortcut-switch-10 = Passa allo spazio di lavoro 10
 zen-workspace-shortcut-forward = Spazio Successivo
 zen-workspace-shortcut-backward = Spazio Precedente
-zen-workspace-shortcut-create = Create New Workspace
+zen-workspace-shortcut-create = Crea nuovo spazio di lavoro
 zen-sidebar-shortcut-toggle = Attiva/Disattiva Larghezza Barra Laterale
 zen-pinned-tab-shortcut-reset = Reimposta la scheda bloccata all'URL bloccata
 zen-split-view-shortcut-grid = Attiva/Disattiva Griglia Visualizzazione Dividi
@@ -318,5 +323,5 @@ zen-devtools-toggle-dom-shortcut = Attiva/Disattiva DOM
 zen-devtools-toggle-accessibility-shortcut = Attiva/Disattiva Accessibilità
 zen-close-all-unpinned-tabs-shortcut = Chiudi Tutte Le Schede Non Bloccate
 zen-new-unsynced-window-shortcut = New Unsynced Window
-zen-duplicate-tab-shortcut = Duplicate Tab
-zen-key-find-selection = Find Selection
+zen-duplicate-tab-shortcut = Duplica scheda
+zen-key-find-selection = Trova Selezione
diff --git a/locales/it/browser/browser/zen-boosts.ftl b/locales/it/browser/browser/zen-boosts.ftl
index eb42026a7..074013167 100644
--- a/locales/it/browser/browser/zen-boosts.ftl
+++ b/locales/it/browser/browser/zen-boosts.ftl
@@ -3,56 +3,56 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 zen-boost-edit-rename = 
-    .label = Rename Boost
+    .label = Rinomina Potenziamento
 zen-boost-edit-shuffle = 
-    .label = Shuffle Vibes
+    .label = Mischia Le Vibes
 zen-boost-edit-reset = 
-    .label = Reset All Edits
+    .label = Reimposta Tutte Le Modifiche
 zen-boost-edit-delete = 
-    .label = Delete Boost
-zen-boost-size = Size
-zen-boost-case = Case
+    .label = Elimina Potenziamento
+zen-boost-size = Dimensione
+zen-boost-case = Maiuscole/minuscole
 zen-boost-zap = Zap
-zen-boost-code = Code
-zen-boost-back = Back
+zen-boost-code = Codice
+zen-boost-back = Indietro
 zen-boost-shuffle = 
-    .tooltiptext = Shuffle Boost Settings
+    .tooltiptext = Impostazioni Boost Casuale
 zen-boost-invert = 
-    .tooltiptext = Smart Invert Colors
+    .tooltiptext = Inverti Colori Intelligente
 zen-boost-controls = 
-    .tooltiptext = Advanced Color Controls
+    .tooltiptext = Controlli Dei Colori Avanzati
 zen-boost-disable = 
-    .tooltiptext = Disable Color Adjustments
+    .tooltiptext = Disabilita Regolazioni Colore
 zen-boost-text-case-toggle = 
-    .tooltiptext = Toggle Text Case
+    .tooltiptext = Attiva/Disattiva Maiuscole
 zen-boost-css-picker = 
-    .tooltiptext = Pick Selector
+    .tooltiptext = Scegli Selettore
 zen-boost-css-inspector = 
-    .tooltiptext = Open Inspector
-zen-boost-color-contrast = Contrast
-zen-boost-color-brightness = Brightness
-zen-boost-color-original-saturation = Original Saturation
-zen-add-zap-helper = Click elements on the page to <b>Zap</b> them
-zen-remove-zap-helper = ← Click to Unzap
-zen-select-this = Insert selector for this
-zen-select-related = Insert selector for related
-zen-select-cancel = Cancel
-zen-zap-this = Zap this
-zen-zap-related = Zap all related elements
-zen-zap-cancel = Cancel
-zen-zap-done = Done
+    .tooltiptext = Apri Ispettore
+zen-boost-color-contrast = Contrasto
+zen-boost-color-brightness = Luminosità
+zen-boost-color-original-saturation = Saturazione Originale
+zen-add-zap-helper = Clicca gli elementi sulla pagina per <b>Zapparli</b>
+zen-remove-zap-helper = ← Clicca per Un-zappare
+zen-select-this = Inserisci un selettore per questo
+zen-select-related = Inserisci selettore per i correlati
+zen-select-cancel = Annulla
+zen-zap-this = Zappa questo
+zen-zap-related = Zappa tutti gli elementi correlati
+zen-zap-cancel = Annulla
+zen-zap-done = Fatto
 zen-unzap-tooltip =
     { $elementCount ->
-        [0] No elements zapped
-        [1] { $elementCount } element zapped
-       *[other] { $elementCount } elements zapped
+        [0] Nessun elemento zappato
+        [1] { $elementCount } elemento zappato
+       *[other] { $elementCount } elementi zappati
     }
 zen-boost-save = 
-    .label = Export Boost
+    .label = Esporta Potenziamento
 zen-boost-load = 
-    .label = Import Boost
-zen-panel-ui-boosts-exported-message = Boost exported!
-zen-site-data-boosts = Boosts
+    .label = Importa Potenziamento
+zen-panel-ui-boosts-exported-message = Potenziamento esportato!
+zen-site-data-boosts = Potenziamenti
 zen-site-data-create-boost = 
-    .tooltiptext = Create new boost
-zen-boost-rename-boost-prompt = Rename Boost?
+    .tooltiptext = Crea nuovo potenziamento
+zen-boost-rename-boost-prompt = Rinomina Potenziamento?
diff --git a/locales/it/browser/browser/zen-command-palette.ftl b/locales/it/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..d7240c602
--- /dev/null
+++ b/locales/it/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Toggle Compact Mode
+zen-action-open-theme-picker = Apri Selettore di Temi
+zen-action-new-split-view = New Split View
+zen-action-new-folder = Nuova Cartella
+zen-action-copy-current-url = Copia URL Corrente
+zen-action-settings = Impostazioni
+zen-action-open-private-window = Apri Finestra Privata
+zen-action-open-new-window = Apri Nuova Finestra
+zen-action-new-blank-window = Apri Finestra Vuota
+zen-action-pin-tab = Pin Tab
+zen-action-unpin-tab = Unpin Tab
+zen-action-open-space-routing = Open Space Routing
+zen-action-new-boost = Nuovo Boost
+zen-action-next-space = Spazio Successivo
+zen-action-previous-space = Spazio Precedente
+zen-action-close-tab = Chiudi Scheda
+zen-action-reload-tab = Ricarica Scheda
+zen-action-reload-tab-without-cache = Ricarica Scheda Senza Cache
+zen-action-next-tab = Scheda Successiva
+zen-action-previous-tab = Scheda Precedente
+zen-action-capture-screenshot = Cattura Schermata
+zen-action-toggle-tabs-on-right = Toggle Tabs on right
+zen-action-add-to-essentials = Aggiungi agli Essenziali
+zen-action-remove-from-essentials = Rimuovi dagli Essenziali
+zen-action-find-in-page = Trova nella Pagina
+zen-action-manage-extensions = Gestisci Estensioni
+zen-action-switch-to-automatic-appearance = Switch to Automatic Appearance
+zen-action-switch-to-light-mode = Switch to Light Mode
+zen-action-switch-to-dark-mode = Switch to Dark Mode
+zen-action-print = Stampa
+zen-action-focus-on = Focus on
+zen-action-extension = Estensione
diff --git a/locales/it/browser/browser/zen-general.ftl b/locales/it/browser/browser/zen-general.ftl
index b4b052db6..b14646b20 100644
--- a/locales/it/browser/browser/zen-general.ftl
+++ b/locales/it/browser/browser/zen-general.ftl
@@ -7,8 +7,8 @@ unified-extensions-description = Le estensioni sono usate per portare più funzi
 tab-context-zen-reset-pinned-tab = 
     .label =
         { $isEssential ->
-            [true] Reset Essential Tab
-           *[false] Reset Pinned Tab
+            [true] Resetta Scheda Essenziale
+           *[false] Resetta Scheda Bloccata
         }
     .accesskey = R
 tab-context-zen-add-essential = 
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max } slot riempiti
 tab-context-zen-remove-essential = 
     .label = Rimuovi dagli Essenziali
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Replace Essential URL with Current
-           *[false] Replace Pinned URL with Current
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Replace with Current URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Edit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Cambia Etichetta...
 tab-context-zen-edit-icon = 
@@ -39,16 +45,20 @@ pictureinpicture-minimize-btn =
     .tooltip = Minimizza
 zen-panel-ui-gradient-generator-custom-color = Colore personalizzato
 zen-copy-current-url-confirmation = L'URL corrente è stato copiato!
-zen-copy-current-url-as-markdown-confirmation = Copied current URL as Markdown!
+zen-copy-current-url-as-markdown-confirmation = URL corrente copiato come Markdown!
 zen-general-cancel-label = 
     .label = Annulla
 zen-general-confirm = 
     .label = Conferma
 zen-pinned-tab-replaced = L'URL della scheda bloccata è stato sostituito con l'URL attuale.
+zen-pinned-tab-url-edited = Pinned tab URL has been updated!
+zen-pinned-tab-url-invalid = That doesn't look like a valid URL.
+zen-pinned-tab-edit-url-title = Edit Pinned URL
+zen-pinned-tab-edit-url-label = Enter the URL this pinned tab should point to:
 zen-tabs-renamed = La scheda è stata rinominata con successo!
 zen-background-tab-opened-toast = Nuova scheda aperta in background!
 zen-workspace-renamed-toast = Il Workspace è stato rinominato con successo!
-zen-split-view-limit-toast = Can't add more panels to the split view!
+zen-split-view-limit-toast = Impossibile aggiungere altri pannelli alla vista divisa!
 zen-toggle-compact-mode-button = 
     .label = Modalità compatta
     .tooltiptext = Attiva/disattiva Modalità compatta
@@ -63,6 +73,8 @@ zen-icons-picker-emoji =
     .label = Emoji
 zen-icons-picker-svg = 
     .label = Icone
+zen-emojis-picker-search = 
+    .placeholder = Search emojis
 urlbar-search-mode-zen_actions = Azioni
 zen-site-data-settings = Impostazioni
 zen-generic-manage = Gestisci
@@ -114,6 +126,9 @@ zen-sidebar-notification-updated-heading = Aggiornamento completato!
 zen-sidebar-notification-updated-label = Cosa c'è di nuovo in { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = Vedi Note di Rilascio
+zen-sidebar-notification-donate-label = Support { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donate to the project
 zen-sidebar-notification-restart-safe-mode-label = Si è rotto qualcosa?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Riavvia in Modalità Provvisoria
@@ -122,4 +137,4 @@ zen-window-sync-migration-dialog-message = Zen ora sincronizza le finestre sullo
 zen-window-sync-migration-dialog-learn-more = Scopri di più
 zen-window-sync-migration-dialog-accept = Ho capito
 zen-appmenu-new-blank-window = 
-    .label = New blank window
+    .label = Nuova finestra vuota
diff --git a/locales/it/browser/browser/zen-menubar.ftl b/locales/it/browser/browser/zen-menubar.ftl
index feed1fb0b..044a0cb44 100644
--- a/locales/it/browser/browser/zen-menubar.ftl
+++ b/locales/it/browser/browser/zen-menubar.ftl
@@ -19,4 +19,4 @@ zen-menubar-appearance-light =
 zen-menubar-appearance-dark = 
     .label = Scuro
 zen-menubar-new-blank-window = 
-    .label = New Blank Window
+    .label = Nuova Finestra Vuota
diff --git a/locales/it/browser/browser/zen-space-routing.ftl b/locales/it/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..d757144bb
--- /dev/null
+++ b/locales/it/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Space Routing Settings
+zen-space-routing-rulepanel-placeholder = Routes let you choose where specific sites open inside Zen. For example, you can route YouTube links to always open inside your Personal space.
+zen-space-routing-dialog-title = Space Routing Settings
+zen-space-routing-external-default = Default route for external links
+zen-space-routing-new-route = New Route
+zen-space-routing-open-in-space = Open in Space
+zen-space-routing-most-recent-space = Most recent Space
+zen-space-routing-close-button = 
+    .aria-label = Close
+    .tooltiptext = Close
+zen-space-routing-contains = 
+    .label = Contains
+zen-space-routing-equal-to = 
+    .label = Is Equal To
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Open In
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/it/browser/browser/zen-split-view.ftl b/locales/it/browser/browser/zen-split-view.ftl
index 27af93a9b..59a4a13c9 100644
--- a/locales/it/browser/browser/zen-split-view.ftl
+++ b/locales/it/browser/browser/zen-split-view.ftl
@@ -5,9 +5,9 @@
 tab-zen-split-tabs = 
     .label =
         { $tabCount ->
-            [-1] Split out tab
-            [1] Add split view...
-           *[other] Join { $tabCount } Tabs
+            [-1] Dividi scheda
+            [1] Aggiungi vista divisa...
+           *[other] Combina { $tabCount } Schede
         }
     .accesskey = S
 zen-split-link = 
diff --git a/locales/it/browser/browser/zen-vertical-tabs.ftl b/locales/it/browser/browser/zen-vertical-tabs.ftl
index ca8bf28a1..1df678a3c 100644
--- a/locales/it/browser/browser/zen-vertical-tabs.ftl
+++ b/locales/it/browser/browser/zen-vertical-tabs.ftl
@@ -41,7 +41,7 @@ tabbrowser-reset-pin-button =
         }
 zen-tab-sublabel =
     { $tabSubtitle ->
-        [zen-default-pinned] Back to pinned url
-        [zen-default-pinned-cmd] Separate from pinned tab
+        [zen-default-pinned] Torna all'url bloccato
+        [zen-default-pinned-cmd] Separa dalla scheda bloccata
        *[other] { $tabSubtitle }
     }
diff --git a/locales/it/browser/browser/zen-workspaces.ftl b/locales/it/browser/browser/zen-workspaces.ftl
index 17c30a8c6..4302b2294 100644
--- a/locales/it/browser/browser/zen-workspaces.ftl
+++ b/locales/it/browser/browser/zen-workspaces.ftl
@@ -10,7 +10,7 @@ zen-panel-ui-workspaces-create =
 zen-panel-ui-folder-create = 
     .label = Crea Cartella
 zen-panel-ui-live-folder-create = 
-    .label = Live Folder
+    .label = Cartella Dinamica
 zen-panel-ui-new-empty-split = 
     .label = Nuova Divisione
 zen-workspaces-panel-context-delete = 
@@ -25,7 +25,7 @@ zen-workspaces-panel-context-default-profile =
 zen-workspaces-panel-unload = 
     .label = Scarica Spazio
 zen-workspaces-panel-unload-others = 
-    .label = Unload All Other Spaces
+    .label = Scarica Tutti Gli Altri Spazi
 zen-workspaces-how-to-reorder-title = Come riordinare gli spazi
 zen-workspaces-how-to-reorder-desc = Trascina le icone degli spazi in fondo alla barra laterale per riordinarle
 zen-workspaces-change-theme = 
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Profilo
     .tooltiptext = I profili vengono usati per separare i cookie e i dati dei siti tra gli spazi.
 zen-workspace-creation-header = Crea uno Spazio
 zen-workspace-creation-label = Gli Spazi sono usati per organizzare le tue schede e sessioni.
+zen-workspace-default-profile = Default
 zen-workspaces-delete-workspace-title = Eliminare Spazio?
 zen-workspaces-delete-workspace-body = Sei sicuro di voler cancellare { $name }? Questa azione non può essere annullata.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/ja/browser/browser/preferences/zen-preferences.ftl b/locales/ja/browser/browser/preferences/zen-preferences.ftl
index 63a8186a9..31dd01fdb 100644
--- a/locales/ja/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/ja/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = 上のツールバーをコンパクトモードで非表示にします
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = コンパクトモードでタブを切り替えたり新しいタブを開いたりするときに、ツールバーを一時的にポップアップ表示します
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Allow dragging the window from web pages
 pane-zen-tabs-title = タブ管理
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -47,7 +51,7 @@ zen-tabs-select-recently-used-on-close =
 zen-tabs-close-on-back-with-no-history = 
     .label = タブを閉じ、履歴がない状態で戻るときに所有者のタブ（または最近使用したタブ）に切り替えます
 zen-settings-workspaces-sync-unpinned-tabs = 
-    .label = ワークスペースのタブのうちピン留めされているタブのみを同期する
+    .label = ワークスペースにはピン留めされているタブのみを同期する
 zen-tabs-cycle-by-attribute = 
     .label = Ctrl+Tabキーを押してワークスペースタブ内または重要なタブ内のサイクルを切り替えます
 zen-tabs-cycle-ignore-pending-tabs = 
@@ -234,7 +238,7 @@ zen-key-exit-full-screen = 全画面表示を終了
 zen-ai-chatbot-sidebar-shortcut = AIチャットボットサイドバーの切り替え
 zen-key-inspector-mac = インスペクタの切り替え (Mac)
 zen-toggle-sidebar-shortcut = Firefoxサイドバーの切り替え
-zen-toggle-pin-tab-shortcut = ピンタブの切り替え
+zen-toggle-pin-tab-shortcut = ピン留めさせるタブの切り替え
 zen-reader-mode-toggle-shortcut-other = リーダーモードの切り替え
 zen-picture-in-picture-toggle-shortcut = ピクチャーインピクチャーの切り替え
 zen-nav-reload-shortcut-2 = ページを再読み込み
@@ -244,7 +248,8 @@ zen-page-info-shortcut = ページ情報を表示
 zen-find-shortcut = ページ上で検索
 zen-search-find-again-shortcut = 再検索
 zen-search-find-again-shortcut-prev = 前を検索
-zen-search-find-again-shortcut-2 = 再検索 (Alt)
+zen-search-find-again-shortcut-alt = Find Again (Alt)
+zen-search-find-again-shortcut-prev-alt = Find Previous (Alt)
 zen-bookmark-this-page-shortcut = このページをブックマーク
 zen-bookmark-show-library-shortcut = ブックマークライブラリを表示
 zen-key-stop = 読み込みを中止
@@ -281,7 +286,7 @@ zen-workspace-shortcut-switch-9 = ワークスペース9に切り替える
 zen-workspace-shortcut-switch-10 = ワークスペース10に切り替える
 zen-workspace-shortcut-forward = 次のワークスペースに移動
 zen-workspace-shortcut-backward = 前のワークスペースへ移動
-zen-workspace-shortcut-create = Create New Workspace
+zen-workspace-shortcut-create = 新しいワークスペースを作成する
 zen-sidebar-shortcut-toggle = サイドバーの幅を切り替える
 zen-pinned-tab-shortcut-reset = ピン留めされたタブをピン留めしたURLにリセット
 zen-split-view-shortcut-grid = 分割表示グリッドの切り替え
@@ -319,4 +324,4 @@ zen-devtools-toggle-accessibility-shortcut = アクセシビリティの切り
 zen-close-all-unpinned-tabs-shortcut = ピン留めされていないすべてのタブを閉じる
 zen-new-unsynced-window-shortcut = New Unsynced Window
 zen-duplicate-tab-shortcut = タブを複製
-zen-key-find-selection = Find Selection
+zen-key-find-selection = 選択を見つける
diff --git a/locales/ja/browser/browser/zen-boosts.ftl b/locales/ja/browser/browser/zen-boosts.ftl
index 6172b8b53..353231e92 100644
--- a/locales/ja/browser/browser/zen-boosts.ftl
+++ b/locales/ja/browser/browser/zen-boosts.ftl
@@ -11,7 +11,7 @@ zen-boost-edit-reset =
 zen-boost-edit-delete = 
     .label = ブーストを削除
 zen-boost-size = サイズ
-zen-boost-case = Case
+zen-boost-case = 大文字、小文字
 zen-boost-zap = ザップ
 zen-boost-code = コード
 zen-boost-back = 戻る
@@ -48,9 +48,9 @@ zen-unzap-tooltip =
        *[other] { $elementCount } elements zapped
     }
 zen-boost-save = 
-    .label = Export Boost
+    .label = ブーストをエキスポ―とする
 zen-boost-load = 
-    .label = Import Boost
+    .label = ブーストをインポートする
 zen-panel-ui-boosts-exported-message = ブーストがエクスポートされました！
 zen-site-data-boosts = ブースト
 zen-site-data-create-boost = 
diff --git a/locales/ja/browser/browser/zen-command-palette.ftl b/locales/ja/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..8384bf68d
--- /dev/null
+++ b/locales/ja/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = コンパクトモードを切り替える
+zen-action-open-theme-picker = テーマピッカーを開く
+zen-action-new-split-view = 新しく分割ビューを作成
+zen-action-new-folder = 新しいフォルダを作成
+zen-action-copy-current-url = 現在のURLをコピー
+zen-action-settings = 設定
+zen-action-open-private-window = プライベートウィンドウを開く
+zen-action-open-new-window = 新しいウィンドウを開く
+zen-action-new-blank-window = 新しい空のウィンドウを開く
+zen-action-pin-tab = タブをピン留め
+zen-action-unpin-tab = タブのピン留めを解除
+zen-action-open-space-routing = スペースルーティングを開く
+zen-action-new-boost = 新しいブースト
+zen-action-next-space = 次のスペースへ移動
+zen-action-previous-space = 前のスペースへ移動
+zen-action-close-tab = タブを閉じる
+zen-action-reload-tab = タブをリロード
+zen-action-reload-tab-without-cache = キャッシュをクリアしてタブをリロード
+zen-action-next-tab = 次のタブへ移動
+zen-action-previous-tab = 前のタブへ移動
+zen-action-capture-screenshot = スクリーンショットを撮る
+zen-action-toggle-tabs-on-right = 右のタブを切り替える
+zen-action-add-to-essentials = Essentialsに追加する
+zen-action-remove-from-essentials = Essentialsから削除する
+zen-action-find-in-page = ページ内を検索する
+zen-action-manage-extensions = 拡張機能を管理
+zen-action-switch-to-automatic-appearance = テーマの自動切り替えをオン
+zen-action-switch-to-light-mode = ライトモードに切り替える
+zen-action-switch-to-dark-mode = ダークモードに切り替える
+zen-action-print = 印刷
+zen-action-focus-on = フォーカスする
+zen-action-extension = 拡張機能
diff --git a/locales/ja/browser/browser/zen-folders.ftl b/locales/ja/browser/browser/zen-folders.ftl
index 1461393ab..e11c39586 100644
--- a/locales/ja/browser/browser/zen-folders.ftl
+++ b/locales/ja/browser/browser/zen-folders.ftl
@@ -3,7 +3,7 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 zen-folders-search-placeholder = 
-    .placeholder = { $folder-name } を検索
+    .placeholder = { $folder-name } を検索…
 zen-folders-panel-rename-folder = 
     .label = フォルダの名前を変更
 zen-folders-panel-unpack-folder = 
diff --git a/locales/ja/browser/browser/zen-general.ftl b/locales/ja/browser/browser/zen-general.ftl
index 81f90c814..08057a38a 100644
--- a/locales/ja/browser/browser/zen-general.ftl
+++ b/locales/ja/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max }スロットがいっ
 tab-context-zen-remove-essential = 
     .label = Essentialsから削除
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] EssentialタブのURLを今開いているURLで置き換える
-           *[false] ピン留めされたタブのURLを今開いているURLで置き換える
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Replace with Current URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Edit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = ラベルを変更する...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = 確定
 zen-pinned-tab-replaced = 固定したタブのURLが現在のURLに置き換えられました！
+zen-pinned-tab-url-edited = Pinned tab URL has been updated!
+zen-pinned-tab-url-invalid = That doesn't look like a valid URL.
+zen-pinned-tab-edit-url-title = Edit Pinned URL
+zen-pinned-tab-edit-url-label = Enter the URL this pinned tab should point to:
 zen-tabs-renamed = タブの名前は無事に変更されました！
 zen-background-tab-opened-toast = 新しい背景タブが開きました！
 zen-workspace-renamed-toast = ワークスペースの名前が変更されました！
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = 絵文字
 zen-icons-picker-svg = 
     .label = アイコン
+zen-emojis-picker-search = 
+    .placeholder = Search emojis
 urlbar-search-mode-zen_actions = アクション
 zen-site-data-settings = 設定
 zen-generic-manage = 管理
@@ -116,10 +128,13 @@ zen-sidebar-notification-updated-heading = アップデートが完了しまし
 zen-sidebar-notification-updated-label = { -brand-short-name }の新機能
 zen-sidebar-notification-updated-tooltip = 
     .title = リリースノートを表示する
+zen-sidebar-notification-donate-label = Support { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donate to the project
 zen-sidebar-notification-restart-safe-mode-label = 何か壊れましたか？
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = セーフモードで再起動する
-zen-window-sync-migration-dialog-title = Windowsを同期させておく
+zen-window-sync-migration-dialog-title = Windowsとの同期を維持
 zen-window-sync-migration-dialog-message = Zenは同一デバイス内のウィンドウを同期するようになり、１つのウィンドウでの操作が、他のウィンドウに、即座に反映されます。
 zen-window-sync-migration-dialog-learn-more = もっと詳しく
 zen-window-sync-migration-dialog-accept = わかりました
diff --git a/locales/ja/browser/browser/zen-menubar.ftl b/locales/ja/browser/browser/zen-menubar.ftl
index ca733f7ec..7a345c91d 100644
--- a/locales/ja/browser/browser/zen-menubar.ftl
+++ b/locales/ja/browser/browser/zen-menubar.ftl
@@ -5,8 +5,8 @@
 zen-menubar-toggle-pinned-tabs = 
     .label =
         { $pinnedAreCollapsed ->
-            [true] ピン留めされたタブ
-           *[false] ピン留めされたタブ
+            [true] ピン留めされたタブを表示する
+           *[false] ピン留めされたタブを表示しない
         }
 zen-menubar-appearance = 
     .label = 外観
diff --git a/locales/ja/browser/browser/zen-space-routing.ftl b/locales/ja/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..ff7fae4d2
--- /dev/null
+++ b/locales/ja/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = スペースルーティングの設定
+zen-space-routing-rulepanel-placeholder = ルートを使用すると、特定のサイトが「Zen」内でどこに開かれるかを選択できます。たとえば、YouTubeのリンクをあなたの個人的なスペース内に常に開くようにルーティングできます。
+zen-space-routing-dialog-title = スペースルーティングの設定
+zen-space-routing-external-default = 外部リンクのデフォルトルート
+zen-space-routing-new-route = 新しいルート
+zen-space-routing-open-in-space = スペースで開く
+zen-space-routing-most-recent-space = 直近のスペース
+zen-space-routing-close-button = 
+    .aria-label = 閉じる
+    .tooltiptext = 閉じる
+zen-space-routing-contains = 
+    .label = 含まれています
+zen-space-routing-equal-to = 
+    .label = に等しい
+zen-space-routing-regex = 
+    .label = 正規表現
+zen-space-routing-open-in = 開く
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/ja/browser/browser/zen-vertical-tabs.ftl b/locales/ja/browser/browser/zen-vertical-tabs.ftl
index dc726b4bb..acbc296aa 100644
--- a/locales/ja/browser/browser/zen-vertical-tabs.ftl
+++ b/locales/ja/browser/browser/zen-vertical-tabs.ftl
@@ -37,11 +37,11 @@ tabbrowser-reset-pin-button =
     .tooltiptext =
         { $tabCount ->
             [one] タブをリセットして固定する
-           *[other] タブをリセットして{ $tabCount }つのタブを固定する
+           *[other] タブをリセットして{ $tabCount }つのタブをピン留めする
         }
 zen-tab-sublabel =
     { $tabSubtitle ->
-        [zen-default-pinned] 固定された URL に戻る
-        [zen-default-pinned-cmd] 固定されたタブから切り離す
+        [zen-default-pinned] ピン留めされた URL に戻る
+        [zen-default-pinned-cmd] ピン留めされたタブから切り離す
        *[other] { $tabSubtitle }
     }
diff --git a/locales/ja/browser/browser/zen-workspaces.ftl b/locales/ja/browser/browser/zen-workspaces.ftl
index 5af1417c3..4adf7e749 100644
--- a/locales/ja/browser/browser/zen-workspaces.ftl
+++ b/locales/ja/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = プロファイル
     .tooltiptext = プロファイルはスペース間でクッキーとサイトデータを分離するために使用されます。
 zen-workspace-creation-header = スペースを作成する
 zen-workspace-creation-label = スペースはタブやセッションを整理するために使用されます。
+zen-workspace-default-profile = Default
 zen-workspaces-delete-workspace-title = スペースを削除しますか？
 zen-workspaces-delete-workspace-body = { $name }を削除してもよろしいですか？この操作は元に戻せません。
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/ko/browser/browser/preferences/zen-preferences.ftl b/locales/ko/browser/browser/preferences/zen-preferences.ftl
index 1a5b6544a..7b469cb06 100644
--- a/locales/ko/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/ko/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = 사이드바 축소 모드에서 상단 툴바 숨기기
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = 사이드바 축소 모드에서 새 탭을 전환하거나 열 때 툴바를 간략하게 팝업으로 표시합니다
+zen-look-and-feel-window-drag-header = 창 드래그
+zen-look-and-feel-window-drag-description = 타이틀바처럼, 웹사이트 위의 빈 공간을 드래그해 창을 움직이세요.
+zen-window-drag-enabled = 
+    .label = 웹 페이지에서 창 드래그 허용
 pane-zen-tabs-title = 탭 관리
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = 페이지 정보 보기
 zen-find-shortcut = 페이지에서 검색
 zen-search-find-again-shortcut = 재검색
 zen-search-find-again-shortcut-prev = 뒤로 검색
-zen-search-find-again-shortcut-2 = 재검색 (Alt)
+zen-search-find-again-shortcut-alt = 다시 찾기 (Alt)
+zen-search-find-again-shortcut-prev-alt = 이전 찾기 (Alt)
 zen-bookmark-this-page-shortcut = 이 페이지 북마크
 zen-bookmark-show-library-shortcut = 북마크 라이브러리 보기
 zen-key-stop = 로딩 멈추기
diff --git a/locales/ko/browser/browser/zen-command-palette.ftl b/locales/ko/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..061df31c3
--- /dev/null
+++ b/locales/ko/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = 축소 모드 전환
+zen-action-open-theme-picker = 테마 편집기 열기
+zen-action-new-split-view = 새 분할 화면
+zen-action-new-folder = 새 폴더
+zen-action-copy-current-url = 현재 URL 복사
+zen-action-settings = 설정
+zen-action-open-private-window = 사생활 보호 창 열기
+zen-action-open-new-window = 새 창 열기
+zen-action-new-blank-window = 새 빈 창
+zen-action-pin-tab = 탭 고정
+zen-action-unpin-tab = 탭 고정 해제
+zen-action-open-space-routing = 스페이스 경로 설정 열기
+zen-action-new-boost = 새 부스트
+zen-action-next-space = 다음 스페이스
+zen-action-previous-space = 이전 스페이스
+zen-action-close-tab = 탭 닫기
+zen-action-reload-tab = 탭 새로고침
+zen-action-reload-tab-without-cache = 캐시 없이 탭 새로고침
+zen-action-next-tab = 다음 탭
+zen-action-previous-tab = 이전 탭
+zen-action-capture-screenshot = 스크린샷 캡쳐
+zen-action-toggle-tabs-on-right = 우측 탭 표시 전환
+zen-action-add-to-essentials = 에센셜에 추가
+zen-action-remove-from-essentials = 에센셜에서 제거
+zen-action-find-in-page = 페이지에서 찾기
+zen-action-manage-extensions = 확장 프로그램 관리
+zen-action-switch-to-automatic-appearance = 자동으로 모양 변경
+zen-action-switch-to-light-mode = 밝은 모드로 변경
+zen-action-switch-to-dark-mode = 어두운 모드로 변경
+zen-action-print = 인쇄
+zen-action-focus-on = 집중
+zen-action-extension = 확장 프로그램
diff --git a/locales/ko/browser/browser/zen-general.ftl b/locales/ko/browser/browser/zen-general.ftl
index dd2018713..c72b683c9 100644
--- a/locales/ko/browser/browser/zen-general.ftl
+++ b/locales/ko/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max }개 추가됨
 tab-context-zen-remove-essential = 
     .label = 에센셜에서 제거하기
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] 에센셜 탭을 현재 URL로 초기화
-           *[false] 고정된 탭을 현재 URL로 초기화
+            [true] 에센셜 URL 편집
+           *[false] 고정된 탭 URL 편집
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = 현재 URL로 변경
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = 편집…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = 라벨 편집...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = 확인
 zen-pinned-tab-replaced = 고정 URL이 현재 URL로 변경되었습니다!
+zen-pinned-tab-url-edited = 고정된 탭 URL이 변경되었습니다!
+zen-pinned-tab-url-invalid = 올바른 URL 형식이 아닙니다.
+zen-pinned-tab-edit-url-title = 고정된 탭 URL 편집
+zen-pinned-tab-edit-url-label = 이 고정된 탭이 고정할 URL을 입력하세요:
 zen-tabs-renamed = 탭의 이름이 성공적으로 변경되었습니다!
 zen-background-tab-opened-toast = 새 백그라운드 탭이 열렸습니다!
 zen-workspace-renamed-toast = 워크스페이스 이름이 변경되었습니다!
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = 이모티콘
 zen-icons-picker-svg = 
     .label = 아이콘
+zen-emojis-picker-search = 
+    .placeholder = 이모지 검색
 urlbar-search-mode-zen_actions = 액션
 zen-site-data-settings = 설정
 zen-generic-manage = 관리
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = 업데이트 완료!
 zen-sidebar-notification-updated-label = { -brand-short-name }의 새로운 기능
 zen-sidebar-notification-updated-tooltip = 
     .title = 업데이트 기록 보기
+zen-sidebar-notification-donate-label = { -brand-short-name } 후원
+zen-sidebar-notification-donate-tooltip = 
+    .title = 프로젝트에 후원하기
 zen-sidebar-notification-restart-safe-mode-label = 무언가 고장났나요?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = 안전 모드로 다시 시작
diff --git a/locales/ko/browser/browser/zen-space-routing.ftl b/locales/ko/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..f503adb64
--- /dev/null
+++ b/locales/ko/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = 스페이스 경로 설정
+zen-space-routing-rulepanel-placeholder = 경로는 특정 사이트가 Zen의 어떤 곳으로 열릴지 설정할 수 있도록 합니다. 예를 들어, 유튜브 링크를 항상 "개인" 스페이스로 열리도록 할 수 있습니다.
+zen-space-routing-dialog-title = 스페이스 경로 설정
+zen-space-routing-external-default = 외부 링크의 기본 경로
+zen-space-routing-new-route = 새로운 경로
+zen-space-routing-open-in-space = 스페이스 안에서 열기
+zen-space-routing-most-recent-space = 가장 최근에 사용한 스페이스
+zen-space-routing-close-button = 
+    .aria-label = 닫기
+    .tooltiptext = 닫기
+zen-space-routing-contains = 
+    .label = 포함
+zen-space-routing-equal-to = 
+    .label = 일치
+zen-space-routing-regex = 
+    .label = 정규식
+zen-space-routing-open-in = ...에서 열기
+zen-space-routing-url = 주소
+zen-space-routing-tab-routed-toast = { $targetWorkspace }에 새 탭이 열렸습니다
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] 이 도메인을 경로로 추가
+           *[other] 이 도메인들을 경로로 추가
+        }
diff --git a/locales/ko/browser/browser/zen-workspaces.ftl b/locales/ko/browser/browser/zen-workspaces.ftl
index eaa6ea654..c2e611ce4 100644
--- a/locales/ko/browser/browser/zen-workspaces.ftl
+++ b/locales/ko/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = 프로필
     .tooltiptext = 프로필은 스페이스 간의 쿠키와 사이트 데이터를 분리하기 위해 사용됩니다.
 zen-workspace-creation-header = 스페이스 생성
 zen-workspace-creation-label = 스페이스는 탭과 세션을 정리하기 위해 사용됩니다.
+zen-workspace-default-profile = 기본
 zen-workspaces-delete-workspace-title = 워크스페이스를 삭제하시겠습니까?
 zen-workspaces-delete-workspace-body = 정말 { $name }을 삭제하시겠습니까? 이 작업은 되돌릴 수 없습니다.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/lt/browser/browser/preferences/zen-preferences.ftl b/locales/lt/browser/browser/preferences/zen-preferences.ftl
index e156f4da5..97ab02de0 100644
--- a/locales/lt/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/lt/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Slėpti viršutinę įrankių juostą ir kompaktiniu režimu
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Trumpai padaryti, kad įrankių juosta iškiltų perjungiant arba atidarant naujas korteles kompaktiniu režimu
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Allow dragging the window from web pages
 pane-zen-tabs-title = Kortelių tvarkymas
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -64,7 +68,7 @@ zen-pinned-tab-manager-restore-pinned-tabs-to-pinned-url =
     .label = Atkurti prisegtas korteles į jų originalų prisegtą URL paleidimo metu
 zen-pinned-tab-manager-container-specific-essentials-enabled = 
     .label = Įjungti konkrečiam konteineriui būtinuosius
-zen-pinned-tab-manager-close-shortcut-behavior-label = Užvėrimo kortelę sparčiųjų klavišų elgsena
+zen-pinned-tab-manager-close-shortcut-behavior-label = Užvėrimo kortelės sparčiųjų klavišų elgsena
 zen-pinned-tab-manager-reset-unload-switch-close-shortcut-option = 
     .label = Atkurti URL, iškelti ir perjungti į sekančią kortelę
 zen-pinned-tab-manager-unload-switch-close-shortcut-option = 
@@ -110,7 +114,7 @@ zen-theme-marketplace-description = Raskite ir įdiekite modifikacijas iš pardu
 zen-theme-marketplace-remove-button = 
     .label = Šalinti modifikaciją
 zen-theme-marketplace-check-for-updates-button = 
-    .label = Tikrinti, ar yra naujinimų
+    .label = Tikrinti dėl naujinimų
 zen-theme-marketplace-import-button = 
     .label = Importuoti modifikacijas
 zen-theme-marketplace-export-button = 
@@ -242,9 +246,10 @@ zen-key-about-processes = Apie procesus
 zen-page-source-shortcut = Peržiūrėti puslapio šaltinį
 zen-page-info-shortcut = Peržiūrėti puslapio informaciją
 zen-find-shortcut = Rasti puslapyje
-zen-search-find-again-shortcut = Rasti dar kartą
+zen-search-find-again-shortcut = Rasti vėl
 zen-search-find-again-shortcut-prev = Rasti ankstesnį
-zen-search-find-again-shortcut-2 = Rasti dar kartą (Alt)
+zen-search-find-again-shortcut-alt = Find Again (Alt)
+zen-search-find-again-shortcut-prev-alt = Find Previous (Alt)
 zen-bookmark-this-page-shortcut = Įtraukti šį puslapį į adresyną
 zen-bookmark-show-library-shortcut = Rodyti adresyno biblioteką
 zen-key-stop = Stabdyti įkėlimą
@@ -281,7 +286,7 @@ zen-workspace-shortcut-switch-9 = Perjungti į 9 darbo sritį
 zen-workspace-shortcut-switch-10 = Perjungti į 10 darbo sritį
 zen-workspace-shortcut-forward = Pirmyn darbo sritį
 zen-workspace-shortcut-backward = Atgal darbo sritį
-zen-workspace-shortcut-create = Create New Workspace
+zen-workspace-shortcut-create = Kurti naują darbo sritį
 zen-sidebar-shortcut-toggle = Perjungti šoninės juostos plotį
 zen-pinned-tab-shortcut-reset = Atkurti prisegtą kortelę į prisegtą URL
 zen-split-view-shortcut-grid = Perjungti skaidymo rodinį tinkleliu
@@ -319,4 +324,4 @@ zen-devtools-toggle-accessibility-shortcut = Perjungti prieinamumą
 zen-close-all-unpinned-tabs-shortcut = Užverti visas neprisegtas korteles
 zen-new-unsynced-window-shortcut = Naujas tuščias langas
 zen-duplicate-tab-shortcut = Dubliuoti kortelę
-zen-key-find-selection = Find Selection
+zen-key-find-selection = Rasti pasirinktus
diff --git a/locales/lt/browser/browser/zen-boosts.ftl b/locales/lt/browser/browser/zen-boosts.ftl
index 60b7619e8..3a0206659 100644
--- a/locales/lt/browser/browser/zen-boosts.ftl
+++ b/locales/lt/browser/browser/zen-boosts.ftl
@@ -3,56 +3,58 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 zen-boost-edit-rename = 
-    .label = Rename Boost
+    .label = Pervadinti apipavidalinimą
 zen-boost-edit-shuffle = 
-    .label = Shuffle Vibes
+    .label = Maišyti vaibus
 zen-boost-edit-reset = 
     .label = Atkurti visus redagavimus
 zen-boost-edit-delete = 
-    .label = Delete Boost
+    .label = Ištrinti apipavidalinimą
 zen-boost-size = Dydis
-zen-boost-case = Case
-zen-boost-zap = Zap
+zen-boost-case = Raidžių lygis
+zen-boost-zap = Šalinti
 zen-boost-code = Kodas
-zen-boost-back = Back
+zen-boost-back = Atgal
 zen-boost-shuffle = 
-    .tooltiptext = Shuffle Boost Settings
+    .tooltiptext = Maišymo apipavidalinimo nustatymai
 zen-boost-invert = 
-    .tooltiptext = Smart Invert Colors
+    .tooltiptext = Išmanusis spalvų inversija
 zen-boost-controls = 
-    .tooltiptext = Advanced Color Controls
+    .tooltiptext = Išplėstiniai spalvų valdymai
 zen-boost-disable = 
-    .tooltiptext = Disable Color Adjustments
+    .tooltiptext = Išjungti spalvų priderinimą
 zen-boost-text-case-toggle = 
-    .tooltiptext = Toggle Text Case
+    .tooltiptext = Perjungti teksto raidžių lygį
 zen-boost-css-picker = 
-    .tooltiptext = Pick Selector
+    .tooltiptext = Pasirinkimo parinkiklis
 zen-boost-css-inspector = 
-    .tooltiptext = Open Inspector
+    .tooltiptext = Atverti inspektorių
 zen-boost-color-contrast = Kontrastas
 zen-boost-color-brightness = Šviesumas
-zen-boost-color-original-saturation = Original Saturation
-zen-add-zap-helper = Click elements on the page to <b>Zap</b> them
-zen-remove-zap-helper = ← Click to Unzap
-zen-select-this = Insert selector for this
-zen-select-related = Insert selector for related
+zen-boost-color-original-saturation = Originali grynis
+zen-add-zap-helper = Spustelėkite elementus puslapyje, kad juos <b>pašalintumėte</b> („nutrūkčioti“).
+zen-remove-zap-helper = ← Spustelėkite, kad atkurtumėte
+zen-select-this = Įterpti pasirinkiklį šiam
+zen-select-related = Įterpti pasirinkiklį susijusiems
 zen-select-cancel = Atsisakyti
-zen-zap-this = Zap this
-zen-zap-related = Zap all related elements
-zen-zap-cancel = Cancel
-zen-zap-done = Done
+zen-zap-this = Šalinti šį
+zen-zap-related = Šalinti visus susijusius elementus
+zen-zap-cancel = Atsisakyti
+zen-zap-done = Atlikta
 zen-unzap-tooltip =
     { $elementCount ->
-        [0] No elements zapped
-        [1] { $elementCount } element zapped
-       *[other] { $elementCount } elements zapped
+        [0] Jokių elementų nepašalinta.
+        [1] { $elementCount } elementas pašalintas.
+        [few] { $elementCount } elementai pašalinti.
+        [many] { $elementCount } elemento pašalinta.
+       *[other] { $elementCount } elementų pašalinta.
     }
 zen-boost-save = 
-    .label = Export Boost
+    .label = Eksportuoti apipavidalinimą
 zen-boost-load = 
-    .label = Import Boost
-zen-panel-ui-boosts-exported-message = Boost exported!
-zen-site-data-boosts = Boosts
+    .label = Importuoti apipavidalinimą
+zen-panel-ui-boosts-exported-message = Apipavidalinimas eksportuotas.
+zen-site-data-boosts = Apipavidalinimai
 zen-site-data-create-boost = 
-    .tooltiptext = Create new boost
-zen-boost-rename-boost-prompt = Rename Boost?
+    .tooltiptext = Kurti naują apipavidalinimą
+zen-boost-rename-boost-prompt = Pervadinti apipavidalinimą?
diff --git a/locales/lt/browser/browser/zen-command-palette.ftl b/locales/lt/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..c8af413e2
--- /dev/null
+++ b/locales/lt/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Toggle Compact Mode
+zen-action-open-theme-picker = Open Theme Picker
+zen-action-new-split-view = New Split View
+zen-action-new-folder = New Folder
+zen-action-copy-current-url = Copy Current URL
+zen-action-settings = Settings
+zen-action-open-private-window = Open Private Window
+zen-action-open-new-window = Open New Window
+zen-action-new-blank-window = New Blank Window
+zen-action-pin-tab = Pin Tab
+zen-action-unpin-tab = Unpin Tab
+zen-action-open-space-routing = Open Space Routing
+zen-action-new-boost = New Boost
+zen-action-next-space = Next Space
+zen-action-previous-space = Previous Space
+zen-action-close-tab = Close Tab
+zen-action-reload-tab = Reload Tab
+zen-action-reload-tab-without-cache = Reload Tab Without Cache
+zen-action-next-tab = Next Tab
+zen-action-previous-tab = Previous Tab
+zen-action-capture-screenshot = Capture Screenshot
+zen-action-toggle-tabs-on-right = Toggle Tabs on right
+zen-action-add-to-essentials = Add to Essentials
+zen-action-remove-from-essentials = Remove from Essentials
+zen-action-find-in-page = Find in Page
+zen-action-manage-extensions = Manage Extensions
+zen-action-switch-to-automatic-appearance = Switch to Automatic Appearance
+zen-action-switch-to-light-mode = Switch to Light Mode
+zen-action-switch-to-dark-mode = Switch to Dark Mode
+zen-action-print = Print
+zen-action-focus-on = Focus on
+zen-action-extension = Extension
diff --git a/locales/lt/browser/browser/zen-general.ftl b/locales/lt/browser/browser/zen-general.ftl
index 5f91e697b..c6c9f0148 100644
--- a/locales/lt/browser/browser/zen-general.ftl
+++ b/locales/lt/browser/browser/zen-general.ftl
@@ -7,24 +7,30 @@ unified-extensions-description = Plėtiniai naudojami norint į „{ -brand-shor
 tab-context-zen-reset-pinned-tab = 
     .label =
         { $isEssential ->
-            [true] Atkurti butiniausią kortelę
+            [true] Atkurti būtiniausią kortelę
            *[false] Atkurti prisegtą kortelę
         }
     .accesskey = R
 tab-context-zen-add-essential = 
     .label = Įtraukti į būtiniausius
     .accesskey = E
-tab-context-zen-add-essential-badge = { $num } / { $max } užpildytų vietų
+tab-context-zen-add-essential-badge = { $num } / { $max }
 tab-context-zen-remove-essential = 
     .label = Šalinti iš būtiniausių
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Keisti būtiniausią URL su dabartiniu
-           *[false] Keisti prisegtą URL su dabartiniu
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Replace with Current URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Edit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Keisti žymę...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Patvirtinti
 zen-pinned-tab-replaced = Prisegtos kortelės URL pakeistas dabartiniu URL.
+zen-pinned-tab-url-edited = Pinned tab URL has been updated!
+zen-pinned-tab-url-invalid = That doesn't look like a valid URL.
+zen-pinned-tab-edit-url-title = Edit Pinned URL
+zen-pinned-tab-edit-url-label = Enter the URL this pinned tab should point to:
 zen-tabs-renamed = Kortelė sėkmingai pervadinta.
 zen-background-tab-opened-toast = Nauja fonos kortelė atverta.
 zen-workspace-renamed-toast = Darbo sritis sėkmingai pervadintas.
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = Jaustukai
 zen-icons-picker-svg = 
     .label = Piktogramos
+zen-emojis-picker-search = 
+    .placeholder = Search emojis
 urlbar-search-mode-zen_actions = Veiksmai
 zen-site-data-settings = Nustatymai
 zen-generic-manage = Tvarkyti
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = Naujinimas baigtas.
 zen-sidebar-notification-updated-label = Kas naujo naršyklėje „{ -brand-short-name }“
 zen-sidebar-notification-updated-tooltip = 
     .title = Peržiūrėti leidimo pastabas
+zen-sidebar-notification-donate-label = Support { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donate to the project
 zen-sidebar-notification-restart-safe-mode-label = Kažkas neveikia?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Paleisti iš naujo saugioje režime
diff --git a/locales/lt/browser/browser/zen-space-routing.ftl b/locales/lt/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..b1538d5a1
--- /dev/null
+++ b/locales/lt/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Erdvės nukreipimo nustatymai
+zen-space-routing-rulepanel-placeholder = Nukreipimai leidžia pasirinkti, kur konkrečios svetainės atveriamos naršyklėje „Zen“. Pavyzdžiui, galite nukreipti „YouTube“ nuorodas taip, kad jos visada būtų atveriamos jūsų asmeninėje erdvėje.
+zen-space-routing-dialog-title = Erdvės nukreipimo nustatymai
+zen-space-routing-external-default = Numatytasis nukreipimas išorės nuorodoms
+zen-space-routing-new-route = Naujas nukreipimas
+zen-space-routing-open-in-space = Atverti erdvėje
+zen-space-routing-most-recent-space = Naujausia erdvė
+zen-space-routing-close-button = 
+    .aria-label = Užverti
+    .tooltiptext = Užverti
+zen-space-routing-contains = 
+    .label = Turi
+zen-space-routing-equal-to = 
+    .label = Yra lygus
+zen-space-routing-regex = 
+    .label = Reguliarusis reiškinys
+zen-space-routing-open-in = Atverti per
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/lt/browser/browser/zen-workspaces.ftl b/locales/lt/browser/browser/zen-workspaces.ftl
index 3c7464e7c..8889194e1 100644
--- a/locales/lt/browser/browser/zen-workspaces.ftl
+++ b/locales/lt/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Profilis
     .tooltiptext = Profiliai naudojami atskirti slapukus ir svetainės duomenis tarp erdvių.
 zen-workspace-creation-header = Kurti erdvę
 zen-workspace-creation-label = Erdvės naudojamos tvarkyti jūsų korteles ir seansus.
+zen-workspace-default-profile = Default
 zen-workspaces-delete-workspace-title = Ištrinti erdvę?
 zen-workspaces-delete-workspace-body = Ar tikrai norite ištrinti „{ $name }“? Šio veiksmo anuliuoti negalima.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/nb/browser/browser/preferences/zen-preferences.ftl b/locales/nb/browser/browser/preferences/zen-preferences.ftl
index 38868994a..1188e137e 100644
--- a/locales/nb/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/nb/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Skjul også øvre verktøylinje i kompakt modus
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Få verktøylinjen til å komme opp momentert når du bytter til- eller åpner nye faner i kompakt modus
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Allow dragging the window from web pages
 pane-zen-tabs-title = Fanebehandling
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = Se sideinformasjon
 zen-find-shortcut = Finn på side
 zen-search-find-again-shortcut = Finn igjen
 zen-search-find-again-shortcut-prev = Finn forrige
-zen-search-find-again-shortcut-2 = Finn igjen (Alt)
+zen-search-find-again-shortcut-alt = Find Again (Alt)
+zen-search-find-again-shortcut-prev-alt = Find Previous (Alt)
 zen-bookmark-this-page-shortcut = Bokmerk denne siden
 zen-bookmark-show-library-shortcut = Vis Bokmerkebiblioteket
 zen-key-stop = Slutt å laste
diff --git a/locales/nb/browser/browser/zen-command-palette.ftl b/locales/nb/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..c8af413e2
--- /dev/null
+++ b/locales/nb/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Toggle Compact Mode
+zen-action-open-theme-picker = Open Theme Picker
+zen-action-new-split-view = New Split View
+zen-action-new-folder = New Folder
+zen-action-copy-current-url = Copy Current URL
+zen-action-settings = Settings
+zen-action-open-private-window = Open Private Window
+zen-action-open-new-window = Open New Window
+zen-action-new-blank-window = New Blank Window
+zen-action-pin-tab = Pin Tab
+zen-action-unpin-tab = Unpin Tab
+zen-action-open-space-routing = Open Space Routing
+zen-action-new-boost = New Boost
+zen-action-next-space = Next Space
+zen-action-previous-space = Previous Space
+zen-action-close-tab = Close Tab
+zen-action-reload-tab = Reload Tab
+zen-action-reload-tab-without-cache = Reload Tab Without Cache
+zen-action-next-tab = Next Tab
+zen-action-previous-tab = Previous Tab
+zen-action-capture-screenshot = Capture Screenshot
+zen-action-toggle-tabs-on-right = Toggle Tabs on right
+zen-action-add-to-essentials = Add to Essentials
+zen-action-remove-from-essentials = Remove from Essentials
+zen-action-find-in-page = Find in Page
+zen-action-manage-extensions = Manage Extensions
+zen-action-switch-to-automatic-appearance = Switch to Automatic Appearance
+zen-action-switch-to-light-mode = Switch to Light Mode
+zen-action-switch-to-dark-mode = Switch to Dark Mode
+zen-action-print = Print
+zen-action-focus-on = Focus on
+zen-action-extension = Extension
diff --git a/locales/nb/browser/browser/zen-general.ftl b/locales/nb/browser/browser/zen-general.ftl
index 97afeee60..826e42b25 100644
--- a/locales/nb/browser/browser/zen-general.ftl
+++ b/locales/nb/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max }
 tab-context-zen-remove-essential = 
     .label = Fjern fra Essentials
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Erstatt Essential nettadresse med gjeldende
-           *[false] Erstatt festet nettadresse med gjeldende
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Replace with Current URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Edit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Endre etikett...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Bekreft
 zen-pinned-tab-replaced = Festet fanes nettadresse har blit erstattet med gjeldende nettadresse!
+zen-pinned-tab-url-edited = Pinned tab URL has been updated!
+zen-pinned-tab-url-invalid = That doesn't look like a valid URL.
+zen-pinned-tab-edit-url-title = Edit Pinned URL
+zen-pinned-tab-edit-url-label = Enter the URL this pinned tab should point to:
 zen-tabs-renamed = Fanen har fått nytt navn!
 zen-background-tab-opened-toast = Ny bakgrunnsfane åpnet!
 zen-workspace-renamed-toast = Arbeidsområdet har fått nytt navn!
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = Emojier
 zen-icons-picker-svg = 
     .label = Ikoner
+zen-emojis-picker-search = 
+    .placeholder = Search emojis
 urlbar-search-mode-zen_actions = Handlinger
 zen-site-data-settings = Innstillinger
 zen-generic-manage = Behandle
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = Oppdatering fullført!
 zen-sidebar-notification-updated-label = Hva er nytt i { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = Se versjonsnotater
+zen-sidebar-notification-donate-label = Support { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donate to the project
 zen-sidebar-notification-restart-safe-mode-label = Er noe ødelagt?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Start på nytt i sikker modus
diff --git a/locales/nb/browser/browser/zen-space-routing.ftl b/locales/nb/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..d757144bb
--- /dev/null
+++ b/locales/nb/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Space Routing Settings
+zen-space-routing-rulepanel-placeholder = Routes let you choose where specific sites open inside Zen. For example, you can route YouTube links to always open inside your Personal space.
+zen-space-routing-dialog-title = Space Routing Settings
+zen-space-routing-external-default = Default route for external links
+zen-space-routing-new-route = New Route
+zen-space-routing-open-in-space = Open in Space
+zen-space-routing-most-recent-space = Most recent Space
+zen-space-routing-close-button = 
+    .aria-label = Close
+    .tooltiptext = Close
+zen-space-routing-contains = 
+    .label = Contains
+zen-space-routing-equal-to = 
+    .label = Is Equal To
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Open In
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/nb/browser/browser/zen-workspaces.ftl b/locales/nb/browser/browser/zen-workspaces.ftl
index 6cce57b33..dcce58ddf 100644
--- a/locales/nb/browser/browser/zen-workspaces.ftl
+++ b/locales/nb/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Profil
     .tooltiptext = Profiler er brukt til å separere informasjonskapsler og nettstedsdata mellom områder.
 zen-workspace-creation-header = Opprett et område
 zen-workspace-creation-label = Områder er brukt til å organisere fanene og øktene dine.
+zen-workspace-default-profile = Default
 zen-workspaces-delete-workspace-title = Slett Område?
 zen-workspaces-delete-workspace-body = Er du sikker på at du vil slette { $name }? Denne handlingen kan ikke angres.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/nl/browser/browser/preferences/zen-preferences.ftl b/locales/nl/browser/browser/preferences/zen-preferences.ftl
index ac7e8ac4b..6f06b3bb9 100644
--- a/locales/nl/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/nl/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Verberg de bovenste werkbalk ook in compacte modus
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Laat kort de werkbalk zien bij het wisselen of openen van nieuwe tabbladen in compacte modus
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Allow dragging the window from web pages
 pane-zen-tabs-title = Tabblad beheer
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = Pagina info bekijken
 zen-find-shortcut = Vinden op pagina
 zen-search-find-again-shortcut = Opnieuw zoeken
 zen-search-find-again-shortcut-prev = Vorige vinden
-zen-search-find-again-shortcut-2 = Opnieuw zoeken (alternatief)
+zen-search-find-again-shortcut-alt = Find Again (Alt)
+zen-search-find-again-shortcut-prev-alt = Find Previous (Alt)
 zen-bookmark-this-page-shortcut = Bladwijzer toevoegen voor deze pagina
 zen-bookmark-show-library-shortcut = Bladwijzerbibliotheek weergeven
 zen-key-stop = Laden stoppen
diff --git a/locales/nl/browser/browser/zen-command-palette.ftl b/locales/nl/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..c8af413e2
--- /dev/null
+++ b/locales/nl/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Toggle Compact Mode
+zen-action-open-theme-picker = Open Theme Picker
+zen-action-new-split-view = New Split View
+zen-action-new-folder = New Folder
+zen-action-copy-current-url = Copy Current URL
+zen-action-settings = Settings
+zen-action-open-private-window = Open Private Window
+zen-action-open-new-window = Open New Window
+zen-action-new-blank-window = New Blank Window
+zen-action-pin-tab = Pin Tab
+zen-action-unpin-tab = Unpin Tab
+zen-action-open-space-routing = Open Space Routing
+zen-action-new-boost = New Boost
+zen-action-next-space = Next Space
+zen-action-previous-space = Previous Space
+zen-action-close-tab = Close Tab
+zen-action-reload-tab = Reload Tab
+zen-action-reload-tab-without-cache = Reload Tab Without Cache
+zen-action-next-tab = Next Tab
+zen-action-previous-tab = Previous Tab
+zen-action-capture-screenshot = Capture Screenshot
+zen-action-toggle-tabs-on-right = Toggle Tabs on right
+zen-action-add-to-essentials = Add to Essentials
+zen-action-remove-from-essentials = Remove from Essentials
+zen-action-find-in-page = Find in Page
+zen-action-manage-extensions = Manage Extensions
+zen-action-switch-to-automatic-appearance = Switch to Automatic Appearance
+zen-action-switch-to-light-mode = Switch to Light Mode
+zen-action-switch-to-dark-mode = Switch to Dark Mode
+zen-action-print = Print
+zen-action-focus-on = Focus on
+zen-action-extension = Extension
diff --git a/locales/nl/browser/browser/zen-general.ftl b/locales/nl/browser/browser/zen-general.ftl
index 045faced3..0d741426f 100644
--- a/locales/nl/browser/browser/zen-general.ftl
+++ b/locales/nl/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max } plekken bezet
 tab-context-zen-remove-essential = 
     .label = Verwijderen uit Essentials
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Essential-URL vervangen door huidige
-           *[false] Vastgezette URL vervangen door huidige
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Replace with Current URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Edit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Naam veranderen...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Bevestigen
 zen-pinned-tab-replaced = Vastgemaakte tabblad URL is vervangen met de huidige URL!
+zen-pinned-tab-url-edited = Pinned tab URL has been updated!
+zen-pinned-tab-url-invalid = That doesn't look like a valid URL.
+zen-pinned-tab-edit-url-title = Edit Pinned URL
+zen-pinned-tab-edit-url-label = Enter the URL this pinned tab should point to:
 zen-tabs-renamed = Tabblad is succesvol hernoemd!
 zen-background-tab-opened-toast = Nieuw achtergrondtabblad geopend!
 zen-workspace-renamed-toast = Werkruimte succesvol is hernoemd!
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = Emoji's
 zen-icons-picker-svg = 
     .label = Iconen
+zen-emojis-picker-search = 
+    .placeholder = Search emojis
 urlbar-search-mode-zen_actions = Acties
 zen-site-data-settings = Instellingen
 zen-generic-manage = Beheren
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = Update voltooid!
 zen-sidebar-notification-updated-label = Wat is er veranderd in { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = Versie-informatie bekijken
+zen-sidebar-notification-donate-label = Support { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donate to the project
 zen-sidebar-notification-restart-safe-mode-label = Werkt er iets niet?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Herstarten in veilige modus
diff --git a/locales/nl/browser/browser/zen-space-routing.ftl b/locales/nl/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..d757144bb
--- /dev/null
+++ b/locales/nl/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Space Routing Settings
+zen-space-routing-rulepanel-placeholder = Routes let you choose where specific sites open inside Zen. For example, you can route YouTube links to always open inside your Personal space.
+zen-space-routing-dialog-title = Space Routing Settings
+zen-space-routing-external-default = Default route for external links
+zen-space-routing-new-route = New Route
+zen-space-routing-open-in-space = Open in Space
+zen-space-routing-most-recent-space = Most recent Space
+zen-space-routing-close-button = 
+    .aria-label = Close
+    .tooltiptext = Close
+zen-space-routing-contains = 
+    .label = Contains
+zen-space-routing-equal-to = 
+    .label = Is Equal To
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Open In
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/nl/browser/browser/zen-workspaces.ftl b/locales/nl/browser/browser/zen-workspaces.ftl
index 11ba1aad7..6f703abdb 100644
--- a/locales/nl/browser/browser/zen-workspaces.ftl
+++ b/locales/nl/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Profiel
     .tooltiptext = Profielen worden gebruikt om cookies en site-gegevens tussen ruimtes te scheiden.
 zen-workspace-creation-header = Maak een ruimte
 zen-workspace-creation-label = Ruimtes worden gebruikt om je tabbladen en sessies te organiseren.
+zen-workspace-default-profile = Default
 zen-workspaces-delete-workspace-title = Ruimte verwijderen?
 zen-workspaces-delete-workspace-body = Weet je zeker dat je { $name } wilt verwijderen? Deze actie kan niet ongedaan gemaakt worden.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/nn-NO/browser/browser/preferences/zen-preferences.ftl b/locales/nn-NO/browser/browser/preferences/zen-preferences.ftl
index 3b6670d6d..ff86b6c33 100644
--- a/locales/nn-NO/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/nn-NO/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Hide the top toolbar as well in compact mode
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Briefly make the toolbar popup when switching or opening new tabs in compact mode
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Allow dragging the window from web pages
 pane-zen-tabs-title = Tab Management
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = View Page Info
 zen-find-shortcut = Find on Page
 zen-search-find-again-shortcut = Find Again
 zen-search-find-again-shortcut-prev = Find Previous
-zen-search-find-again-shortcut-2 = Find Again (Alt)
+zen-search-find-again-shortcut-alt = Find Again (Alt)
+zen-search-find-again-shortcut-prev-alt = Find Previous (Alt)
 zen-bookmark-this-page-shortcut = Bookmark This Page
 zen-bookmark-show-library-shortcut = Show Bookmarks Library
 zen-key-stop = Stop Loading
diff --git a/locales/nn-NO/browser/browser/zen-command-palette.ftl b/locales/nn-NO/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..c8af413e2
--- /dev/null
+++ b/locales/nn-NO/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Toggle Compact Mode
+zen-action-open-theme-picker = Open Theme Picker
+zen-action-new-split-view = New Split View
+zen-action-new-folder = New Folder
+zen-action-copy-current-url = Copy Current URL
+zen-action-settings = Settings
+zen-action-open-private-window = Open Private Window
+zen-action-open-new-window = Open New Window
+zen-action-new-blank-window = New Blank Window
+zen-action-pin-tab = Pin Tab
+zen-action-unpin-tab = Unpin Tab
+zen-action-open-space-routing = Open Space Routing
+zen-action-new-boost = New Boost
+zen-action-next-space = Next Space
+zen-action-previous-space = Previous Space
+zen-action-close-tab = Close Tab
+zen-action-reload-tab = Reload Tab
+zen-action-reload-tab-without-cache = Reload Tab Without Cache
+zen-action-next-tab = Next Tab
+zen-action-previous-tab = Previous Tab
+zen-action-capture-screenshot = Capture Screenshot
+zen-action-toggle-tabs-on-right = Toggle Tabs on right
+zen-action-add-to-essentials = Add to Essentials
+zen-action-remove-from-essentials = Remove from Essentials
+zen-action-find-in-page = Find in Page
+zen-action-manage-extensions = Manage Extensions
+zen-action-switch-to-automatic-appearance = Switch to Automatic Appearance
+zen-action-switch-to-light-mode = Switch to Light Mode
+zen-action-switch-to-dark-mode = Switch to Dark Mode
+zen-action-print = Print
+zen-action-focus-on = Focus on
+zen-action-extension = Extension
diff --git a/locales/nn-NO/browser/browser/zen-general.ftl b/locales/nn-NO/browser/browser/zen-general.ftl
index f4cd42a80..9403e908a 100644
--- a/locales/nn-NO/browser/browser/zen-general.ftl
+++ b/locales/nn-NO/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max } slots filled
 tab-context-zen-remove-essential = 
     .label = Remove from Essentials
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Replace Essential URL with Current
-           *[false] Replace Pinned URL with Current
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Replace with Current URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Edit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Change Label...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Confirm
 zen-pinned-tab-replaced = Pinned tab URL has been replaced with the current URL.
+zen-pinned-tab-url-edited = Pinned tab URL has been updated!
+zen-pinned-tab-url-invalid = That doesn't look like a valid URL.
+zen-pinned-tab-edit-url-title = Edit Pinned URL
+zen-pinned-tab-edit-url-label = Enter the URL this pinned tab should point to:
 zen-tabs-renamed = Tab has been successfully renamed!
 zen-background-tab-opened-toast = New background tab opened!
 zen-workspace-renamed-toast = Workspace has been successfully renamed!
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = Emojis
 zen-icons-picker-svg = 
     .label = Icons
+zen-emojis-picker-search = 
+    .placeholder = Search emojis
 urlbar-search-mode-zen_actions = Actions
 zen-site-data-settings = Settings
 zen-generic-manage = Manage
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = Update Complete!
 zen-sidebar-notification-updated-label = What's new in { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = View Release Notes
+zen-sidebar-notification-donate-label = Support { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donate to the project
 zen-sidebar-notification-restart-safe-mode-label = Something broke?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Restart in Safe Mode
diff --git a/locales/nn-NO/browser/browser/zen-space-routing.ftl b/locales/nn-NO/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..d757144bb
--- /dev/null
+++ b/locales/nn-NO/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Space Routing Settings
+zen-space-routing-rulepanel-placeholder = Routes let you choose where specific sites open inside Zen. For example, you can route YouTube links to always open inside your Personal space.
+zen-space-routing-dialog-title = Space Routing Settings
+zen-space-routing-external-default = Default route for external links
+zen-space-routing-new-route = New Route
+zen-space-routing-open-in-space = Open in Space
+zen-space-routing-most-recent-space = Most recent Space
+zen-space-routing-close-button = 
+    .aria-label = Close
+    .tooltiptext = Close
+zen-space-routing-contains = 
+    .label = Contains
+zen-space-routing-equal-to = 
+    .label = Is Equal To
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Open In
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/nn-NO/browser/browser/zen-workspaces.ftl b/locales/nn-NO/browser/browser/zen-workspaces.ftl
index 41b6dc5ed..4a9650c22 100644
--- a/locales/nn-NO/browser/browser/zen-workspaces.ftl
+++ b/locales/nn-NO/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Profile
     .tooltiptext = Profiles are used to separate cookies and site data between spaces.
 zen-workspace-creation-header = Create a Space
 zen-workspace-creation-label = Spaces are used to organize your tabs and sessions.
+zen-workspace-default-profile = Default
 zen-workspaces-delete-workspace-title = Delete Workspace?
 zen-workspaces-delete-workspace-body = Are you sure you want to delete { $name }? This action cannot be undone.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/pl/browser/browser/preferences/zen-preferences.ftl b/locales/pl/browser/browser/preferences/zen-preferences.ftl
index bb0b0f05e..9d0830818 100644
--- a/locales/pl/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/pl/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Ukryj również górny pasek narzędzi w trybie kompaktowym
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Wyświetlaj na krótko pasek narzędzi podczas przełączania lub otwierania nowych kart w trybie kompaktowym
+zen-look-and-feel-window-drag-header = Przesuwanie okna
+zen-look-and-feel-window-drag-description = Przesuwaj okno, przeciągając pustą przestrzeń u góry stron internetowych, tak samo jak na pasku tytułu.
+zen-window-drag-enabled = 
+    .label = Zezwalaj na przeciąganie okna z poziomu stron internetowych
 pane-zen-tabs-title = Zarządzanie kartami
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = Zobacz informacje o stronie
 zen-find-shortcut = Znajdź na stronie
 zen-search-find-again-shortcut = Znajdź ponownie
 zen-search-find-again-shortcut-prev = Znajdź poprzedni
-zen-search-find-again-shortcut-2 = Znajdź ponownie (Alt)
+zen-search-find-again-shortcut-alt = Znajdź ponownie (Alt)
+zen-search-find-again-shortcut-prev-alt = Znajdź poprzedni (Alt)
 zen-bookmark-this-page-shortcut = Dodaj zakładkę do tej strony
 zen-bookmark-show-library-shortcut = Pokaż bibliotekę zakładek
 zen-key-stop = Zatrzymaj ładowanie
diff --git a/locales/pl/browser/browser/zen-boosts.ftl b/locales/pl/browser/browser/zen-boosts.ftl
index c2d9a4519..c7057e6c8 100644
--- a/locales/pl/browser/browser/zen-boosts.ftl
+++ b/locales/pl/browser/browser/zen-boosts.ftl
@@ -44,9 +44,9 @@ zen-zap-done = Gotowe
 zen-unzap-tooltip =
     { $elementCount ->
         [0] Nie ukryto żadnych elementów
-        [1] Ukryto {$elementCount} element
-        [few] Ukryto {$elementCount} elementy
-       *[other] Ukryto {$elementCount} elementów
+        [1] Ukryto { $elementCount } element
+        [few] Ukryto { $elementCount } elementy
+       *[other] Ukryto { $elementCount } elementów
     }
 zen-boost-save = 
     .label = Eksportuj Boosta
diff --git a/locales/pl/browser/browser/zen-command-palette.ftl b/locales/pl/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..355673562
--- /dev/null
+++ b/locales/pl/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Przełącz tryb kompaktowy
+zen-action-open-theme-picker = Otwórz wybór motywu
+zen-action-new-split-view = Nowy widok podzielony
+zen-action-new-folder = Nowy folder
+zen-action-copy-current-url = Skopiuj bieżący URL
+zen-action-settings = Ustawienia
+zen-action-open-private-window = Otwórz okno prywatne
+zen-action-open-new-window = Otwórz nowe okno
+zen-action-new-blank-window = Nowe puste okno
+zen-action-pin-tab = Przypnij kartę
+zen-action-unpin-tab = Odepnij kartę
+zen-action-open-space-routing = Otwórz reguły przestrzeni
+zen-action-new-boost = Nowy Boost
+zen-action-next-space = Następna przestrzeń
+zen-action-previous-space = Poprzednia przestrzeń
+zen-action-close-tab = Zamknij kartę
+zen-action-reload-tab = Odśwież kartę
+zen-action-reload-tab-without-cache = Odśwież kartę bez cache
+zen-action-next-tab = Następna karta
+zen-action-previous-tab = Poprzednia karta
+zen-action-capture-screenshot = Wykonaj zrzut ekranu
+zen-action-toggle-tabs-on-right = Przełącz karty na prawą stronę
+zen-action-add-to-essentials = Dodaj do niezbędnych
+zen-action-remove-from-essentials = Usuń z niezbędnych
+zen-action-find-in-page = Znajdź na stronie
+zen-action-manage-extensions = Zarządzaj rozszerzeniami
+zen-action-switch-to-automatic-appearance = Przełącz na wygląd automatyczny
+zen-action-switch-to-light-mode = Przełącz na tryb jasny
+zen-action-switch-to-dark-mode = Przełącz na tryb ciemny
+zen-action-print = Drukuj
+zen-action-focus-on = Przejdź do
+zen-action-extension = Rozszerzenie
diff --git a/locales/pl/browser/browser/zen-general.ftl b/locales/pl/browser/browser/zen-general.ftl
index 3d041a34f..562dd4153 100644
--- a/locales/pl/browser/browser/zen-general.ftl
+++ b/locales/pl/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max }
 tab-context-zen-remove-essential = 
     .label = Usuń z niezbędnych
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Zastąp adres URL niezbędnej karty bieżącym
-           *[false] Zastąp adres URL przypiętej karty bieżącym
+            [true] Edytuj niezbędny adres URL
+           *[false] Edytuj przypięty adres URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Zastąp bieżącym adresem URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Edytuj…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Zmień nazwę...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Potwierdź
 zen-pinned-tab-replaced = URL przypiętej karty został zastąpiony bieżącym adresem!
+zen-pinned-tab-url-edited = Adres URL przypiętej karty został zaktualizowany!
+zen-pinned-tab-url-invalid = To nie wygląda na prawidłowy adres URL.
+zen-pinned-tab-edit-url-title = Edytuj przypięty adres URL
+zen-pinned-tab-edit-url-label = Wprowadź adres URL, do którego ma prowadzić ta przypięta karta:
 zen-tabs-renamed = Nazwa karty została pomyślnie zmieniona!
 zen-background-tab-opened-toast = Nowa karta została otworzona w tle!
 zen-workspace-renamed-toast = Zmieniono nazwę przestrzeni roboczej!
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = Emotikony
 zen-icons-picker-svg = 
     .label = Ikony
+zen-emojis-picker-search = 
+    .placeholder = Szukaj emoji
 urlbar-search-mode-zen_actions = Akcje
 zen-site-data-settings = Ustawienia
 zen-generic-manage = Zarządzaj
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = Aktualizacja ukończona!
 zen-sidebar-notification-updated-label = Co nowego w { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = Zobacz informacje o aktualizacji
+zen-sidebar-notification-donate-label = Wesprzyj { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Wesprzyj projekt
 zen-sidebar-notification-restart-safe-mode-label = Coś się zepsuło?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Zrestartuj w trybie bezpiecznym
diff --git a/locales/pl/browser/browser/zen-space-routing.ftl b/locales/pl/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..314cabf25
--- /dev/null
+++ b/locales/pl/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Ustawienia przekierowywania przestrzeni
+zen-space-routing-rulepanel-placeholder = Reguły pozwalają wybrać, gdzie konkretne strony będą otwierane w przeglądarce Zen. Na przykład możesz przekierować linki do YouTube, aby zawsze otwierały się w Twojej prywatnej przestrzeni.
+zen-space-routing-dialog-title = Ustawienia przekierowywania przestrzeni
+zen-space-routing-external-default = Domyślne przekierowanie dla linków zewnętrznych
+zen-space-routing-new-route = Nowe przekierowanie
+zen-space-routing-open-in-space = Otwórz w przestrzeni
+zen-space-routing-most-recent-space = Ostatnio używana przestrzeń
+zen-space-routing-close-button = 
+    .aria-label = Zamknij
+    .tooltiptext = Zamknij
+zen-space-routing-contains = 
+    .label = Zawiera
+zen-space-routing-equal-to = 
+    .label = Jest równe
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Otwórz w
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = Nowa karta otwarta w { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Dodaj regułę dla domeny
+           *[other] Dodaj regułę dla domen
+        }
diff --git a/locales/pl/browser/browser/zen-workspaces.ftl b/locales/pl/browser/browser/zen-workspaces.ftl
index 143622b49..ccf5352dd 100644
--- a/locales/pl/browser/browser/zen-workspaces.ftl
+++ b/locales/pl/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Profil
     .tooltiptext = Profile służą do rozdzielania plików cookie i danych witryny między przestrzeniami.
 zen-workspace-creation-header = Utwórz przestrzeń
 zen-workspace-creation-label = Przestrzenie są wykorzystywane do zorganizowania kart i sesji.
+zen-workspace-default-profile = Domyślny
 zen-workspaces-delete-workspace-title = Usunąć przestrzeń?
 zen-workspaces-delete-workspace-body = Czy na pewno chcesz usunąć { $name }? Tej czynności nie można cofnąć.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/pt-BR/browser/browser/preferences/zen-preferences.ftl b/locales/pt-BR/browser/browser/preferences/zen-preferences.ftl
index 63e8299c6..19f1ed30a 100644
--- a/locales/pt-BR/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/pt-BR/browser/browser/preferences/zen-preferences.ftl
@@ -2,24 +2,24 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-pane-zen-looks-title = Aparência e Comportamento
+pane-zen-looks-title = Aparência
 category-zen-looks = 
     .tooltiptext = { pane-zen-looks-title }
-zen-warning-language = Alterar o idioma padrão pode facilitar o rastreamento por sites.
-zen-vertical-tabs-layout-header = Layout do Navegador
-zen-vertical-tabs-layout-description = Escolha o layout que melhor se adapta a você
-zen-layout-single-toolbar = Somente a barra lateral
+zen-warning-language = Alterar o idioma padrão talvez facilite que sites rastreiem você.
+zen-vertical-tabs-layout-header = Estilo do Navegador
+zen-vertical-tabs-layout-description = Defina o estilo que se encaixa melhor com você
+zen-layout-single-toolbar = Apenas a barra lateral
 zen-layout-multiple-toolbar = Barra lateral e barra de ferramentas superior
-zen-layout-collapsed-toolbar = Recolher Barra Lateral
+zen-layout-collapsed-toolbar = Barra lateral colapsada
 sync-currently-syncing-workspaces = Áreas de Trabalho
 sync-engine-workspaces = 
     .label = Áreas de Trabalho
     .tooltiptext = Sincronize suas áreas de trabalho entre dispositivos
     .accesskey = W
 zen-glance-title = Glance
-zen-glance-header = Configurações gerais do Glance
-zen-glance-description = Tenha uma visão geral rápida dos seus links sem abri-los em uma nova guia
-zen-glance-trigger-label = Método de acionamento
+zen-glance-header = Opções gerais do Glance
+zen-glance-description = Obtenha uma visão geral rápida dos seus links sem precisar abri-los em novas guias
+zen-glance-trigger-label = Modo de ativação
 zen-glance-enabled = 
     .label = Ativar Glance
 zen-glance-trigger-ctrl-click = 
@@ -31,59 +31,63 @@ zen-glance-trigger-shift-click =
 zen-glance-trigger-meta-click = 
     .label = Meta (Comando) + Clique
 zen-look-and-feel-compact-view-header = Exibir em modo compacto
-zen-look-and-feel-compact-view-description = Apenas mostre as barras de ferramentas que você usa!
+zen-look-and-feel-compact-view-description = Exiba apenas as barras de ferramentas que você usa!
 zen-look-and-feel-compact-view-enabled = 
-    .label = Ativar modo compacto de { -brand-short-name }s
+    .label = Ativar modo compacto de { -brand-short-name }
 zen-look-and-feel-compact-view-top-toolbar = 
     .label = Ocultar também a barra de ferramentas superior no modo compacto
 zen-look-and-feel-compact-toolbar-flash-popup = 
-    .label = Exibir a barra de ferramentas brevemente ao alternar ou abrir novas guias no modo compacto
+    .label = Exibir brevemente a barra de ferramentas ao trocar ou abrir novas abas no modo compacto
+zen-look-and-feel-window-drag-header = Arrastar janela
+zen-look-and-feel-window-drag-description = Mova a janela arrastando o espaço vazio no topo dos sites, assim como na barra de título.
+zen-window-drag-enabled = 
+    .label = Permitir arrastar a janela das páginas 
 pane-zen-tabs-title = Gerenciamento de Guias
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
 pane-settings-workspaces-title = Áreas de Trabalho
 zen-tabs-select-recently-used-on-close = 
-    .label = Quando a aba for fechada, troque para a aba usada por último ao invés da próxima aba
+    .label = Ao fechar uma aba, trocar para a aba mais usada recentemente ao invés da próxima aba
 zen-tabs-close-on-back-with-no-history = 
-    .label = Fechar a aba e mudar para a aba dona dela (ou para a mais recentemente usada) ao voltar sem histórico
+    .label = Fechar aba e trocar para a aba proprietária (ou para a mais usada recentemente) ao voltar sem histórico
 zen-settings-workspaces-sync-unpinned-tabs = 
-    .label = Sincronize apenas as abas fixadas nos espaços
+    .label = Sincronizar apenas abas fixadas na área de trabalho
 zen-tabs-cycle-by-attribute = 
-    .label = Ctrl+Tab alterna apenas entre as abas Essenciais ou Área de Trabalho
+    .label = Ctrl+Tab alterna apenas entre abas Essenciais ou da Área de Trabalho
 zen-tabs-cycle-ignore-pending-tabs = 
-    .label = Ignorar abas Pendentes ao alternar com Ctrl+Tab
-zen-tabs-cycle-by-attribute-warning = Ctrl+Tab vai alternar pela ordem de uso recente, já que está ativado
+    .label = Ignorar abas pendentes ao alternar com Ctrl+Tab
+zen-tabs-cycle-by-attribute-warning = Ctrl+Tab alternará em ordem de uso recente, já que está ativado
 zen-look-and-feel-compact-toolbar-themed = 
-    .label = Usar fundo temático na barra de ferramentas compacta
+    .label = Usar fundo temático para a barra de ferramentas compacta
 zen-workspace-continue-where-left-off = 
-    .label = Continue de onde você parou
-pane-zen-pinned-tab-manager-title = Guias Fixadas
-zen-pinned-tab-manager-header = Configurações gerais para guias fixadas
-zen-pinned-tab-manager-description = Gerencie o comportamento adicional das guias fixadas
+    .label = Continue de onde parou
+pane-zen-pinned-tab-manager-title = Abas Fixadas
+zen-pinned-tab-manager-header = Opções gerais para abas fixadas
+zen-pinned-tab-manager-description = Gerencie o comportamento adicional das abas fixadas
 zen-pinned-tab-manager-restore-pinned-tabs-to-pinned-url = 
-    .label = Restaurar guias fixadas para a URL original na inicialização
+    .label = Restaurar abas fixadas para seu URL original fixado na inicialização
 zen-pinned-tab-manager-container-specific-essentials-enabled = 
-    .label = Ativar essenciais específicos do contêiner
-zen-pinned-tab-manager-close-shortcut-behavior-label = Fechar Comportamento com Atalho Aba
+    .label = Ativar essenciais exclusivos de contêiner
+zen-pinned-tab-manager-close-shortcut-behavior-label = Atalho de fechar aba
 zen-pinned-tab-manager-reset-unload-switch-close-shortcut-option = 
-    .label = Redefina a URL, descarregue e mude para a próxima aba
+    .label = Redefinir o URL, descarregar e trocar para a próxima aba
 zen-pinned-tab-manager-unload-switch-close-shortcut-option = 
-    .label = Descarregar e alternar para a próxima aba
+    .label = Descarregar e trocar para a próxima aba
 zen-pinned-tab-manager-reset-switch-close-shortcut-option = 
-    .label = Redefinir o URL e mudar para a próxima aba
+    .label = Redefinir o URL e trocar para a próxima aba
 zen-pinned-tab-manager-switch-close-shortcut-option = 
-    .label = Mudar para a próxima aba
+    .label = Trocar para a próxima aba
 zen-pinned-tab-manager-reset-close-shortcut-option = 
     .label = Redefinir URL
 zen-pinned-tab-manager-close-close-shortcut-option = 
     .label = Fechar aba
-pane-zen-workspaces-header = Projetos
-zen-settings-workspaces-header = Configurações gerais para áreas de trabalho
-zen-settings-workspaces-description = Com espaços de trabalho, você pode ter várias sessões de navegação de uma vez!
+pane-zen-workspaces-header = Áreas de Trabalho
+zen-settings-workspaces-header = Opções gerais para áreas de trabalho
+zen-settings-workspaces-description = Com áreas de trabalho, você pode ter várias sessões de navegação de uma vez!
 zen-settings-workspaces-enabled = 
-    .label = Habilitar Área de Trabalho
+    .label = Ativar Áreas de Trabalho
 zen-settings-workspaces-hide-default-container-indicator = 
-    .label = Ocultar o indicador padrão do contêiner na barra de guias
+    .label = Ocultar o indicador padrão do contêiner na barra de abas
 zen-key-unsaved = Atalho não salvo! Proteja-o clicando na tecla "Escape" após digitá-lo novamente.
 zen-key-conflict = Conflitos com { $group } -> { $shortcut }
 pane-zen-theme-title = Opções de tema
@@ -244,7 +248,8 @@ zen-page-info-shortcut = Exibir informações da página
 zen-find-shortcut = Encontrar na Página
 zen-search-find-again-shortcut = Localizar novamente
 zen-search-find-again-shortcut-prev = Localizar Anterior
-zen-search-find-again-shortcut-2 = Pesquisar novamente (Alt)
+zen-search-find-again-shortcut-alt = Localizar Novamente (Alt)
+zen-search-find-again-shortcut-prev-alt = Localizar Anterior (Alt)
 zen-bookmark-this-page-shortcut = Adicionar aos favoritos
 zen-bookmark-show-library-shortcut = Mostrar Biblioteca de Favoritos
 zen-key-stop = Parar carregamento
diff --git a/locales/pt-BR/browser/browser/zen-boosts.ftl b/locales/pt-BR/browser/browser/zen-boosts.ftl
index cf906da64..471503d7f 100644
--- a/locales/pt-BR/browser/browser/zen-boosts.ftl
+++ b/locales/pt-BR/browser/browser/zen-boosts.ftl
@@ -37,7 +37,7 @@ zen-remove-zap-helper = Clique para Deszapar
 zen-select-this = Inserir seletor para isto
 zen-select-related = Inserir seletor para relacionados
 zen-select-cancel = Cancelar
-zen-zap-this = Zap isso
+zen-zap-this = Zap nisso
 zen-zap-related = Zap em todos os elementos relacionados
 zen-zap-cancel = Cancelar
 zen-zap-done = Pronto
diff --git a/locales/pt-BR/browser/browser/zen-command-palette.ftl b/locales/pt-BR/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..522ed1cbd
--- /dev/null
+++ b/locales/pt-BR/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Alternar Modo Compacto
+zen-action-open-theme-picker = Abrir Seletor de Temas
+zen-action-new-split-view = Nova Vista Dividida
+zen-action-new-folder = Nova Pasta
+zen-action-copy-current-url = Copiar URL Atual
+zen-action-settings = Configurações
+zen-action-open-private-window = Abrir Janela Privada
+zen-action-open-new-window = Abrir nova janela
+zen-action-new-blank-window = Nova Janela em Branco
+zen-action-pin-tab = Fixar Aba
+zen-action-unpin-tab = Desafixar Aba
+zen-action-open-space-routing = Abrir Roteamento de Espaço
+zen-action-new-boost = Novo Boost
+zen-action-next-space = Próximo Espaço
+zen-action-previous-space = Espaço Anterior
+zen-action-close-tab = Fechar Aba
+zen-action-reload-tab = Recarregar Aba
+zen-action-reload-tab-without-cache = Recarregar Aba sem Cache
+zen-action-next-tab = Próxima Aba
+zen-action-previous-tab = Aba Anterior
+zen-action-capture-screenshot = Captura de Tela
+zen-action-toggle-tabs-on-right = Alternar Abas à Direita
+zen-action-add-to-essentials = Adicionar aos Essenciais
+zen-action-remove-from-essentials = Remover dos Essenciais
+zen-action-find-in-page = Encontrar na Página
+zen-action-manage-extensions = Gerenciar Extensões
+zen-action-switch-to-automatic-appearance = Mudar para Modo Automático
+zen-action-switch-to-light-mode = Mudar para Modo Claro
+zen-action-switch-to-dark-mode = Mudar para Modo Escuro
+zen-action-print = Imprimir
+zen-action-focus-on = Focar em
+zen-action-extension = Extensão
diff --git a/locales/pt-BR/browser/browser/zen-general.ftl b/locales/pt-BR/browser/browser/zen-general.ftl
index d1a05e002..b803ce77b 100644
--- a/locales/pt-BR/browser/browser/zen-general.ftl
+++ b/locales/pt-BR/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max } Espaços preenchidos
 tab-context-zen-remove-essential = 
     .label = Remover dos Essenciais
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Substituir URL Essencial pela atual
-           *[false] Substituir URL Fixada pela atual
+            [true] Editar URL Essencial
+           *[false] Editar URL Fixada
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Substituir por URL atual
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Editar…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Alterar Rótulo...
 tab-context-zen-edit-icon = 
@@ -44,9 +50,13 @@ zen-general-cancel-label =
     .label = Cancelar
 zen-general-confirm = 
     .label = Confirmar
-zen-pinned-tab-replaced = A URL da guia fixada foi substituída pela URL atual!
-zen-tabs-renamed = A guia foi renomeada com sucesso!
-zen-background-tab-opened-toast = Nova guia em segundo plano aberta!
+zen-pinned-tab-replaced = A URL da aba fixada foi substituída pela URL atual!
+zen-pinned-tab-url-edited = A URL da aba fixada foi atualizada!
+zen-pinned-tab-url-invalid = Isso não parece ser uma URL válida.
+zen-pinned-tab-edit-url-title = Editar URL Fixada
+zen-pinned-tab-edit-url-label = Digite a URL que esta aba fixada deve apontar para:
+zen-tabs-renamed = A aba foi renomeada com sucesso!
+zen-background-tab-opened-toast = Nova aba em segundo plano aberta!
 zen-workspace-renamed-toast = A área de trabalho foi renomeada com sucesso!
 zen-split-view-limit-toast = Não é possível adicionar mais painéis à visualização dividida!
 zen-toggle-compact-mode-button = 
@@ -63,6 +73,8 @@ zen-icons-picker-emoji =
     .label = Emojis
 zen-icons-picker-svg = 
     .label = Ícones
+zen-emojis-picker-search = 
+    .placeholder = Procurar emojis
 urlbar-search-mode-zen_actions = Ações
 zen-site-data-settings = Configurações
 zen-generic-manage = Gerenciar
@@ -114,6 +126,9 @@ zen-sidebar-notification-updated-heading = Atualização Completa!
 zen-sidebar-notification-updated-label = O que há de novo em { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = Ver Notas da Versão
+zen-sidebar-notification-donate-label = Apoie { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Doe para o projeto
 zen-sidebar-notification-restart-safe-mode-label = Algo quebrou?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Reiniciar no Modo Seguro
diff --git a/locales/pt-BR/browser/browser/zen-space-routing.ftl b/locales/pt-BR/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..75ac6d7b1
--- /dev/null
+++ b/locales/pt-BR/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Opções de Roteamento de Espaço
+zen-space-routing-rulepanel-placeholder = As rotas permitem escolher onde sites específicos abrem no zen. Por exemplo, você pode encaminhar links do YouTube para sempre abrirem no seu Espaço Pessoal.
+zen-space-routing-dialog-title = Opções de Roteamento de Espaço
+zen-space-routing-external-default = Rota padrão para links externos
+zen-space-routing-new-route = Nova Rota
+zen-space-routing-open-in-space = Abrir no Espaço
+zen-space-routing-most-recent-space = Espaço mais recente
+zen-space-routing-close-button = 
+    .aria-label = Fechar
+    .tooltiptext = Fechar
+zen-space-routing-contains = 
+    .label = Contém
+zen-space-routing-equal-to = 
+    .label = É igual a
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Abrir em
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = Nova aba aberta em { $targetWorkspace}
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Adicionar Rota para Domínio
+           *[other] Adicionar Rota para Domínios
+        }
diff --git a/locales/pt-BR/browser/browser/zen-workspaces.ftl b/locales/pt-BR/browser/browser/zen-workspaces.ftl
index d8a2ed315..c61535b85 100644
--- a/locales/pt-BR/browser/browser/zen-workspaces.ftl
+++ b/locales/pt-BR/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Perfil
     .tooltiptext = Perfis são usados para separar cookies e dados de sites entre os espaços.
 zen-workspace-creation-header = Crie um Espaço
 zen-workspace-creation-label = Espaços são usados para organizar suas guias e sessões.
+zen-workspace-default-profile = Padrão
 zen-workspaces-delete-workspace-title = Excluir Espaço?
 zen-workspaces-delete-workspace-body = Tem certeza que deseja excluir { $name }? Esta ação não pode ser desfeita.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/pt-PT/browser/browser/preferences/zen-preferences.ftl b/locales/pt-PT/browser/browser/preferences/zen-preferences.ftl
index a501737b7..67554ef60 100644
--- a/locales/pt-PT/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/pt-PT/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Ocultar a barra de ferramentas superior também no modo compacto
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Fazer a barra de ferramentas saltar ligeiramente ao mudar ou ao abrir novos separadores no modo compacto
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Allow dragging the window from web pages
 pane-zen-tabs-title = Gestão de Separadores
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = Ver Informação da Página
 zen-find-shortcut = Procurar na Página
 zen-search-find-again-shortcut = Procurar Seguinte
 zen-search-find-again-shortcut-prev = Procurar Anterior
-zen-search-find-again-shortcut-2 = Procurar Seguinte (Alt)
+zen-search-find-again-shortcut-alt = Find Again (Alt)
+zen-search-find-again-shortcut-prev-alt = Find Previous (Alt)
 zen-bookmark-this-page-shortcut = Adicionar esta Página aos Favoritos
 zen-bookmark-show-library-shortcut = Mostrar Biblioteca de Favoritos
 zen-key-stop = Parar Carregamento
diff --git a/locales/pt-PT/browser/browser/zen-command-palette.ftl b/locales/pt-PT/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..1b2aecf75
--- /dev/null
+++ b/locales/pt-PT/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Alternar Modo Compacto
+zen-action-open-theme-picker = Abrir Seletor de Temas
+zen-action-new-split-view = Nova Vista Dividida
+zen-action-new-folder = Nova Pasta
+zen-action-copy-current-url = Copiar o URL atual
+zen-action-settings = Definições
+zen-action-open-private-window = Abrir Janela Privada
+zen-action-open-new-window = Abrir Nova Janela
+zen-action-new-blank-window = Nova Janela sem Sincronização
+zen-action-pin-tab = Fixar a Página
+zen-action-unpin-tab = Soltar a Página
+zen-action-open-space-routing = Abrir Roteamento de Espaços
+zen-action-new-boost = Novo Boost
+zen-action-next-space = Espaço seguinte
+zen-action-previous-space = Espaço anterior
+zen-action-close-tab = Fechar Separador
+zen-action-reload-tab = Recarregar separador
+zen-action-reload-tab-without-cache = Recarregar separador sem cache
+zen-action-next-tab = Separador seguinte
+zen-action-previous-tab = Separador anterior
+zen-action-capture-screenshot = Capturar o Ecrã
+zen-action-toggle-tabs-on-right = Alternar separadores à direita
+zen-action-add-to-essentials = Adicionar aos Essenciais
+zen-action-remove-from-essentials = Remover dos Essenciais
+zen-action-find-in-page = Localizar na página
+zen-action-manage-extensions = Gerir Extensões
+zen-action-switch-to-automatic-appearance = Alternar para Aparência Automática
+zen-action-switch-to-light-mode = Mudar para Modo Claro
+zen-action-switch-to-dark-mode = Mudar para Modo Escuro
+zen-action-print = Imprimir
+zen-action-focus-on = Focar em
+zen-action-extension = Extensão
diff --git a/locales/pt-PT/browser/browser/zen-general.ftl b/locales/pt-PT/browser/browser/zen-general.ftl
index c92bfecfe..40ffeef97 100644
--- a/locales/pt-PT/browser/browser/zen-general.ftl
+++ b/locales/pt-PT/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max } espaços preenchidos
 tab-context-zen-remove-essential = 
     .label = Remover dos Essenciais
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Substituir URL Essencial com o Atual
-           *[false] Substituir URL Fixado com o Atual
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Replace with Current URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Edit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Alterar etiqueta...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Confirmar
 zen-pinned-tab-replaced = O URL do separador fixado foi substituído pelo URL atual.
+zen-pinned-tab-url-edited = Pinned tab URL has been updated!
+zen-pinned-tab-url-invalid = That doesn't look like a valid URL.
+zen-pinned-tab-edit-url-title = Edit Pinned URL
+zen-pinned-tab-edit-url-label = Enter the URL this pinned tab should point to:
 zen-tabs-renamed = Nome do separador alterado com sucesso!
 zen-background-tab-opened-toast = Novo separador aberto em segundo plano!
 zen-workspace-renamed-toast = Nome do espaço de trabalho alterado com sucesso!
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = Emojis
 zen-icons-picker-svg = 
     .label = Ícones
+zen-emojis-picker-search = 
+    .placeholder = Search emojis
 urlbar-search-mode-zen_actions = Ações
 zen-site-data-settings = Definições
 zen-generic-manage = Gerir
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = Atualização Concluída!
 zen-sidebar-notification-updated-label = O que há de novo no { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = Ver Notas de Lançamento
+zen-sidebar-notification-donate-label = Support { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donate to the project
 zen-sidebar-notification-restart-safe-mode-label = Falhou alguma coisa?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Reiniciar em Modo de Segurança
diff --git a/locales/pt-PT/browser/browser/zen-space-routing.ftl b/locales/pt-PT/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..d757144bb
--- /dev/null
+++ b/locales/pt-PT/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Space Routing Settings
+zen-space-routing-rulepanel-placeholder = Routes let you choose where specific sites open inside Zen. For example, you can route YouTube links to always open inside your Personal space.
+zen-space-routing-dialog-title = Space Routing Settings
+zen-space-routing-external-default = Default route for external links
+zen-space-routing-new-route = New Route
+zen-space-routing-open-in-space = Open in Space
+zen-space-routing-most-recent-space = Most recent Space
+zen-space-routing-close-button = 
+    .aria-label = Close
+    .tooltiptext = Close
+zen-space-routing-contains = 
+    .label = Contains
+zen-space-routing-equal-to = 
+    .label = Is Equal To
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Open In
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/pt-PT/browser/browser/zen-workspaces.ftl b/locales/pt-PT/browser/browser/zen-workspaces.ftl
index 985a837c1..de19cb7dc 100644
--- a/locales/pt-PT/browser/browser/zen-workspaces.ftl
+++ b/locales/pt-PT/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Perfil
     .tooltiptext = Os perfis são usados para separar cookies e dados de sites entre espaços.
 zen-workspace-creation-header = Criar um Espaço
 zen-workspace-creation-label = Os espaços são usados para organizar os seus separadores e sessões.
+zen-workspace-default-profile = Default
 zen-workspaces-delete-workspace-title = Eliminar Espaço de Trabalho?
 zen-workspaces-delete-workspace-body = Tem certeza que deseja eliminar { $name }? Esta ação não pode ser desfeita.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/ro/browser/browser/preferences/zen-preferences.ftl b/locales/ro/browser/browser/preferences/zen-preferences.ftl
index a43ff8124..41abe1cd5 100644
--- a/locales/ro/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/ro/browser/browser/preferences/zen-preferences.ftl
@@ -2,26 +2,26 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-pane-zen-looks-title = Look and Feel
+pane-zen-looks-title = Aspect și Atmosferă
 category-zen-looks = 
     .tooltiptext = { pane-zen-looks-title }
-zen-warning-language = Changing the default language could make it easier for Websites to track you.
-zen-vertical-tabs-layout-header = Browser Layout
-zen-vertical-tabs-layout-description = Choose the layout that suits you best
-zen-layout-single-toolbar = Only Sidebar
-zen-layout-multiple-toolbar = Sidebar and Top Toolbar
-zen-layout-collapsed-toolbar = Collapsed Sidebar
-sync-currently-syncing-workspaces = Workspaces
+zen-warning-language = Schimbarea limbii implicite poate face ca Website-urile să te urmărească mai ușor.
+zen-vertical-tabs-layout-header = Aspect Browser
+zen-vertical-tabs-layout-description = Alege aspectul care ți se potrivește cel mai bine
+zen-layout-single-toolbar = Doar Bara Laterală
+zen-layout-multiple-toolbar = Bara Laterală și Bara de Unelte
+zen-layout-collapsed-toolbar = Bara Laterală Închisă
+sync-currently-syncing-workspaces = Spații de Lucru
 sync-engine-workspaces = 
-    .label = Workspaces
-    .tooltiptext = Sync your workspaces across devices
+    .label = Spații de Lucru
+    .tooltiptext = Sincronizează-ți Spațiile de Lucru pe toate dispozitivele
     .accesskey = W
 zen-glance-title = Glance
-zen-glance-header = General settings for glance
-zen-glance-description = Get a quick overview of your links without opening them in a new tab
-zen-glance-trigger-label = Trigger method
+zen-glance-header = Setări generale pentru Glance
+zen-glance-description = Vizualizează conținutul link-ului fără a deschide o filă nouă
+zen-glance-trigger-label = Metoda declanșării
 zen-glance-enabled = 
-    .label = Enable Glance
+    .label = Activează Glance
 zen-glance-trigger-ctrl-click = 
     .label = Ctrl + Click
 zen-glance-trigger-alt-click = 
@@ -30,293 +30,298 @@ zen-glance-trigger-shift-click =
     .label = Shift + Click
 zen-glance-trigger-meta-click = 
     .label = Meta (Command) + Click
-zen-look-and-feel-compact-view-header = Show in compact view
-zen-look-and-feel-compact-view-description = Only show the toolbars you use!
+zen-look-and-feel-compact-view-header = Afișează în Vizualizarea Compactă
+zen-look-and-feel-compact-view-description = Afișează doar Bara de Unelte pe care o folosești!
 zen-look-and-feel-compact-view-enabled = 
-    .label = Enable { -brand-short-name }'s compact mode
+    .label = Activează Modul Compact { -brand-short-name }
 zen-look-and-feel-compact-view-top-toolbar = 
-    .label = Hide the top toolbar as well in compact mode
+    .label = Ascunde Bara de Unelte și în Modul Compact
 zen-look-and-feel-compact-toolbar-flash-popup = 
-    .label = Briefly make the toolbar popup when switching or opening new tabs in compact mode
-pane-zen-tabs-title = Tab Management
+    .label = Arată temporar Bara de Unelte când schimbi sau deschizi file noi în Modul Compact
+zen-look-and-feel-window-drag-header = Tragerea ferestrei
+zen-look-and-feel-window-drag-description = Mută fereastra trăgând de spațiul liber din partea de sus a site-urilor, la fel cum tragi de bara de titlu.
+zen-window-drag-enabled = 
+    .label = Permite tragerea ferestrei de pe pagini web
+pane-zen-tabs-title = Gestionare File
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
-pane-settings-workspaces-title = Workspaces
+pane-settings-workspaces-title = Spații de Lucru
 zen-tabs-select-recently-used-on-close = 
-    .label = When closing a tab, switch to the most recently used tab instead of the next tab
+    .label = La închiderea unei file, comută la cea mai recent folosită filă în loc de fila următoare
 zen-tabs-close-on-back-with-no-history = 
-    .label = Close tab and switch to its owner tab (or most recently used tab) when going back with no history
+    .label = Închide fila și comută la fila părinte (sau cea mai recent folosită filă) când revii fără istoric
 zen-settings-workspaces-sync-unpinned-tabs = 
-    .label = Sync only pinned tabs in workspaces
+    .label = Sincronizează doar Filele Fixate din Spațiile de Lucru
 zen-tabs-cycle-by-attribute = 
-    .label = Ctrl+Tab cycles within Essential or Workspace tabs only
+    .label = Ctrl+Tab parcurge doar prin filele Esențiale sau ale Spațiului de Lucru
 zen-tabs-cycle-ignore-pending-tabs = 
-    .label = Ignore Pending tabs when cycling with Ctrl+Tab
-zen-tabs-cycle-by-attribute-warning = Ctrl+Tab will cycle by recently used order, as it is enabled
+    .label = Ignoră Filele în Așteptare când se parcurge cu Ctrl+Tab
+zen-tabs-cycle-by-attribute-warning = Cu această setare activată, Ctrl+Tab va comuta între file în ordinea accesării lor
 zen-look-and-feel-compact-toolbar-themed = 
-    .label = Use themed background for compact toolbar
+    .label = Folosește fundal tematic pentru Bara de Unelte compactă
 zen-workspace-continue-where-left-off = 
-    .label = Continue where you left off
-pane-zen-pinned-tab-manager-title = Pinned Tabs
-zen-pinned-tab-manager-header = General settings for pinned tabs
-zen-pinned-tab-manager-description = Manage additional behavior of pinned tabs
+    .label = Continuă de unde ai rămas
+pane-zen-pinned-tab-manager-title = File Fixate
+zen-pinned-tab-manager-header = Setări generale pentru File Fixate
+zen-pinned-tab-manager-description = Gestionează opțiuni suplimentare pentru Filele Fixate
 zen-pinned-tab-manager-restore-pinned-tabs-to-pinned-url = 
-    .label = Restore pinned tabs to their originally pinned URL on startup
+    .label = La pornire restaurează Filele Fixate la URL-ul fixat inițial
 zen-pinned-tab-manager-container-specific-essentials-enabled = 
-    .label = Enable container-specific essentials
-zen-pinned-tab-manager-close-shortcut-behavior-label = Close Tab Shortcut Behavior
+    .label = Activează Tab-uri Esențiale per container
+zen-pinned-tab-manager-close-shortcut-behavior-label = Comportamentul Scurtăturii la închiderea filei
 zen-pinned-tab-manager-reset-unload-switch-close-shortcut-option = 
-    .label = Reset URL, unload and switch to next tab
+    .label = Resetează URL-ul, închide și comută la file următoare
 zen-pinned-tab-manager-unload-switch-close-shortcut-option = 
-    .label = Unload and switch to next tab
+    .label = Închide și comută la fila următoare
 zen-pinned-tab-manager-reset-switch-close-shortcut-option = 
-    .label = Reset URL and switch to next tab
+    .label = Resetează URL-ul și comută la fila următoare
 zen-pinned-tab-manager-switch-close-shortcut-option = 
-    .label = Switch to next tab
+    .label = Comută la fila următoare
 zen-pinned-tab-manager-reset-close-shortcut-option = 
-    .label = Reset URL
+    .label = Resetează URL-ul
 zen-pinned-tab-manager-close-close-shortcut-option = 
-    .label = Close tab
-pane-zen-workspaces-header = Workspaces
-zen-settings-workspaces-header = General settings for workspaces
-zen-settings-workspaces-description = With workspaces, you can have multiple browsing sessions at once!
+    .label = Închide fila
+pane-zen-workspaces-header = Spații de Lucru
+zen-settings-workspaces-header = Setări generale pentru Spațiile de Lucru
+zen-settings-workspaces-description = Cu Spațiile de Lucru, poți avea mai multe sesiuni de navigare simultan!
 zen-settings-workspaces-enabled = 
-    .label = Enable Workspaces
+    .label = Activează Spațiile de Lucru
 zen-settings-workspaces-hide-default-container-indicator = 
-    .label = Hide the default container indicator in the tab bar
-zen-key-unsaved = Unsaved shortcut! Please save it by clicking the "Escape" key after retyping it.
-zen-key-conflict = Conflicts with { $group } -> { $shortcut }
-pane-zen-theme-title = Theme Settings
-zen-vertical-tabs-title = Sidebar and tabs layout
-zen-vertical-tabs-header = Vertical Tabs
-zen-vertical-tabs-description = Manage your tabs in a vertical layout
+    .label = Ascunde indicatorul containerului implicit în bara de file
+zen-key-unsaved = Scurtătură nesalvată! Te rugăm să o salvezi tastând "Escape" după ce a fost reintrodusă.
+zen-key-conflict = Conflict cu { $group } -> { $shortcut}
+pane-zen-theme-title = Setări Temă
+zen-vertical-tabs-title = Aspect bară laterală și file
+zen-vertical-tabs-header = File Verticale
+zen-vertical-tabs-description = Gestionează filele într-un aspect vertical
 zen-vertical-tabs-show-expand-button = 
-    .label = Show Expand Button
+    .label = Arată Butonul de Extindere
 zen-vertical-tabs-newtab-on-tab-list = 
-    .label = Show New Tab Button on Tab List
+    .label = Arată butonul pentru Filă Nouă în lista de tab-uri
 zen-vertical-tabs-newtab-top-button-up = 
-    .label = Move the new tab button to the top
-zen-vertical-tabs-expand-tabs-by-default = Expand Tabs by Default
-zen-vertical-tabs-dont-expand-tabs-by-default = Don't Expand Tabs by Default
-zen-vertical-tabs-expand-tabs-on-hover = Expand Tabs on Hover (Won't work on compact mode)
-zen-vertical-tabs-expand-tabs-header = How to expand tabs
-zen-vertical-tabs-expand-tabs-description = Choose how to expand tabs in the sidebar
-zen-theme-marketplace-header = Zen Mods
+    .label = Mută butonul pentru Filă Nouă în partea de sus
+zen-vertical-tabs-expand-tabs-by-default = Extinde filele în mod implicit
+zen-vertical-tabs-dont-expand-tabs-by-default = Nu extinde filele în mod implicit
+zen-vertical-tabs-expand-tabs-on-hover = Extinde filele la Survolare (Nu funcționează în Modul Compact)
+zen-vertical-tabs-expand-tabs-header = Cum se extind filele
+zen-vertical-tabs-expand-tabs-description = Alege cum să extinzi filele in bara laterală
+zen-theme-marketplace-header = Mod-uri Zen
 zen-theme-disable-all-enabled = 
-    .title = Disable all mods
+    .title = Dezactivează toate Mod-urile
 zen-theme-disable-all-disabled = 
-    .title = Enable all mods
-zen-theme-marketplace-description = Find and install mods from the store.
+    .title = Activează toate Mod-urile
+zen-theme-marketplace-description = Caută și instalează Mod-uri din magazin.
 zen-theme-marketplace-remove-button = 
-    .label = Remove mod
+    .label = Șterge Mod
 zen-theme-marketplace-check-for-updates-button = 
-    .label = Check for Updates
+    .label = Verifică dacă există Actualizări
 zen-theme-marketplace-import-button = 
-    .label = Import mods
+    .label = Importă Mod-uri
 zen-theme-marketplace-export-button = 
-    .label = Export Mods
-zen-theme-marketplace-import-success = Mods imported successfully
-zen-theme-marketplace-import-failure = There was an error importing the mods
-zen-theme-marketplace-export-success = Mods exported successfully
-zen-theme-marketplace-export-failure = There was an error exporting the mods
-zen-theme-marketplace-updates-success = Mods updated successfully
-zen-theme-marketplace-updates-failure = Couldn't find any updates!
+    .label = Exportă Mod-uri
+zen-theme-marketplace-import-success = Mod-uri importate cu succes
+zen-theme-marketplace-import-failure = A apărut o eroare la importarea Mod-urilor
+zen-theme-marketplace-export-success = Mod-uri exportate cu succes
+zen-theme-marketplace-export-failure = A apărut o eroare la exportarea Mod-urilor
+zen-theme-marketplace-updates-success = Mod-uri actualizate cu succes
+zen-theme-marketplace-updates-failure = Nu s-au găsit actualizări!
 zen-theme-marketplace-toggle-enabled-button = 
-    .title = Disable mod
+    .title = Dezactivează Mod
 zen-theme-marketplace-toggle-disabled-button = 
-    .title = Enable mod
-zen-theme-marketplace-remove-confirmation = Are you sure you want to remove this mod?
-zen-theme-marketplace-close-modal = Close
+    .title = Dezactivează Mod
+zen-theme-marketplace-remove-confirmation = Ești sigur că vrei să ștergi acest Mod?
+zen-theme-marketplace-close-modal = Închide
 zen-theme-marketplace-theme-header-title = 
-    .title = CSS Selector: { $name }
+    .title = Selector CSS: { $name }
 zen-theme-marketplace-dropdown-default-label = 
-    .label = None
+    .label = Nimic
 zen-theme-marketplace-input-default-placeholder = 
-    .placeholder = Type something...
-pane-zen-marketplace-title = Zen Mods
+    .placeholder = Scrie ceva...
+pane-zen-marketplace-title = Mod-uri Zen
 zen-themes-auto-update = 
-    .label = Automatically update installed mods on startup
+    .label = Actualizează automat Mod-urile instalate la pornire
 zen-settings-workspaces-force-container-tabs-to-workspace = 
-    .label = Switch to workspace where container is set as default when opening container tabs
-zen-theme-marketplace-link = Visit Store
-zen-dark-theme-styles-header = Dark Theme Styles
-zen-dark-theme-styles-description = Customize the dark theme to your liking
-zen-dark-theme-styles-amoled = Night Theme
-zen-dark-theme-styles-default = Default Dark Theme
-zen-dark-theme-styles-colorful = Colorful Dark Theme
-zen-compact-mode-styles-left = Hide Tab bar
-zen-compact-mode-styles-top = Hide Top bar
-zen-compact-mode-styles-both = Hide Both
-zen-urlbar-title = Zen URL Bar
-zen-urlbar-header = General settings for the URL bar
-zen-urlbar-description = Customize the URL bar to your liking
-zen-urlbar-behavior-label = Behavior
+    .label = Schimbă pe Spațiul de Lucru unde containerul este setat implicit când deschizi o filă container
+zen-theme-marketplace-link = Vizitează Magazinul
+zen-dark-theme-styles-header = Stiluri Temă Întunecată
+zen-dark-theme-styles-description = Personalizează tema întunecată după gustul tău
+zen-dark-theme-styles-amoled = Temă de Noapte
+zen-dark-theme-styles-default = Tema Întunecată Implicită
+zen-dark-theme-styles-colorful = Tema Întunecată Colorată
+zen-compact-mode-styles-left = Ascunde Bara de File
+zen-compact-mode-styles-top = Ascunde Bara de Sus
+zen-compact-mode-styles-both = Ascunde Ambele
+zen-urlbar-title = Bara URL Zen
+zen-urlbar-header = Setări generale pentru bara URL
+zen-urlbar-description = Personalizează bara URL după gustul tău
+zen-urlbar-behavior-label = Comportament
 zen-urlbar-behavior-normal = 
     .label = Normal
 zen-urlbar-behavior-floating-on-type = 
-    .label = Floating only when typing
+    .label = Plutitor doar când tastezi
 zen-urlbar-behavior-float = 
-    .label = Always floating
-pane-zen-CKS-title = Keyboard Shortcuts
+    .label = Întotdeauna plutitor
+pane-zen-CKS-title = Scurtături de Tastatură
 category-zen-CKS = 
     .tooltiptext = { pane-zen-CKS-title }
-pane-settings-CKS-title = { -brand-short-name } Keyboard Shortcuts
+pane-settings-CKS-title = Scurtături de Tastatură { -brand-short-name }
 category-zen-marketplace = 
-    .tooltiptext = Zen Mods
-zen-settings-CKS-header = Customize your keyboard shortcuts
-zen-settings-CKS-description = Change the default keyboard shortcuts to your liking and improve your browsing experience
+    .tooltiptext = Mod-uri Zen
+zen-settings-CKS-header = Personalizează-ți scurtăturile de tastatură
+zen-settings-CKS-description = Schimbă scurtăturile de tastatură implicite după gustul tău și îmbunătățește experiența de navigare
 zen-settings-CKS-disable-firefox = 
-    .label = Disable { -brand-short-name }'s default keyboard shortcuts
+    .label = Dezactivează scurtăturile de tastatură implicite { -brand-short-name }
 zen-settings-CKS-duplicate-shortcut = 
-    .label = Duplicate Shortcut
+    .label = Scurtătură Duplicată
 zen-settings-CKS-reset-shortcuts = 
-    .label = Reset to Default
-zenCKSOption-group-other = Other
-zenCKSOption-group-windowAndTabManagement = Window & Tab Management
-zenCKSOption-group-navigation = Navigation
-zenCKSOption-group-searchAndFind = Search & Find
-zenCKSOption-group-pageOperations = Page Operations
-zenCKSOption-group-historyAndBookmarks = History & Bookmarks
-zenCKSOption-group-mediaAndDisplay = Media & Display
-zenCKSOption-group-zen-compact-mode = Compact Mode
-zenCKSOption-group-zen-workspace = Workspaces
-zenCKSOption-group-zen-other = Other Zen Features
-zenCKSOption-group-zen-split-view = Split View
-zenCKSOption-group-devTools = Developer Tools
-zen-key-quick-restart = Quick Restart
-zen-window-new-shortcut = New Window
-zen-tab-new-shortcut = New Tab
-zen-key-redo = Redo
-zen-restore-last-closed-tab-shortcut = Restore Last Closed Tab
-zen-location-open-shortcut = Open Location
-zen-location-open-shortcut-alt = Open Location (Alt)
-zen-key-undo-close-window = Undo Close Window
-zen-text-action-undo-shortcut = Undo
-zen-text-action-redo-shortcut = Redo
-zen-text-action-cut-shortcut = Cut
-zen-text-action-copy-shortcut = Copy
-zen-text-action-copy-url-shortcut = Copy current URL
-zen-text-action-copy-url-markdown-shortcut = Copy current URL as Markdown
-zen-text-action-paste-shortcut = Paste
-zen-text-action-select-all-shortcut = Select All
-zen-text-action-delete-shortcut = Delete
-zen-history-show-all-shortcut-mac = Show All History (Mac)
-zen-full-screen-shortcut = Toggle Full Screen
-zen-reader-mode-toggle-shortcut-windows = Toggle Reader Mode (Windows)
-zen-picture-in-picture-toggle-shortcut-alt = Toggle Picture-in-Picture (Alt)
-zen-picture-in-picture-toggle-shortcut-mac = Toggle Picture-in-Picture (Mac)
-zen-picture-in-picture-toggle-shortcut-mac-alt = Toggle Picture-in-Picture (Mac Alt)
-zen-page-source-shortcut-safari = View Page Source (Safari)
-zen-nav-stop-shortcut = Stop Loading
-zen-history-sidebar-shortcut = Show History Sidebar
-zen-window-minimize-shortcut = Minimize Window
-zen-help-shortcut = Open Help
-zen-preferences-shortcut = Open Preferences
-zen-hide-app-shortcut = Hide Application
-zen-hide-other-apps-shortcut = Hide Other Applications
-zen-search-focus-shortcut = Focus Search
-zen-search-focus-shortcut-alt = Focus Search (Alt)
-zen-downloads-shortcut = Open Downloads
-zen-addons-shortcut = Open Add-ons
-zen-file-open-shortcut = Open File
-zen-save-page-shortcut = Save Page
-zen-print-shortcut = Print Page
-zen-close-shortcut-2 = Close Tab
-zen-mute-toggle-shortcut = Toggle Mute
-zen-key-delete = Delete Key
-zen-key-go-back = Go Back
-zen-key-go-forward = Go Forward
-zen-nav-back-shortcut-alt = Navigate Back (Alt)
-zen-nav-fwd-shortcut-alt = Navigate Forward (Alt)
-zen-history-show-all-shortcut = Show All History
-zen-key-enter-full-screen = Enter Full Screen
-zen-key-exit-full-screen = Exit Full Screen
-zen-ai-chatbot-sidebar-shortcut = Toggle AI Chatbot Sidebar
-zen-key-inspector-mac = Toggle Inspector (Mac)
-zen-toggle-sidebar-shortcut = Toggle Firefox Sidebar
-zen-toggle-pin-tab-shortcut = Toggle Pin Tab
-zen-reader-mode-toggle-shortcut-other = Toggle Reader Mode
-zen-picture-in-picture-toggle-shortcut = Toggle Picture-in-Picture
-zen-nav-reload-shortcut-2 = Reload Page
-zen-key-about-processes = About Processes
-zen-page-source-shortcut = View Page Source
-zen-page-info-shortcut = View Page Info
-zen-find-shortcut = Find on Page
-zen-search-find-again-shortcut = Find Again
-zen-search-find-again-shortcut-prev = Find Previous
-zen-search-find-again-shortcut-2 = Find Again (Alt)
-zen-bookmark-this-page-shortcut = Bookmark This Page
-zen-bookmark-show-library-shortcut = Show Bookmarks Library
-zen-key-stop = Stop Loading
-zen-full-zoom-reduce-shortcut = Zoom Out
-zen-full-zoom-enlarge-shortcut = Zoom In
-zen-full-zoom-reset-shortcut = Reset Zoom
-zen-full-zoom-reset-shortcut-alt = Reset Zoom (Alt)
-zen-full-zoom-enlarge-shortcut-alt = Zoom In (Alt)
-zen-full-zoom-enlarge-shortcut-alt2 = Zoom In (Alt 2)
-zen-bidi-switch-direction-shortcut = Switch Text Direction
-zen-private-browsing-shortcut = Private Browsing
-zen-screenshot-shortcut = Take Screenshot
-zen-key-sanitize = Clear Browsing Data
-zen-quit-app-shortcut = Quit Application
-zen-key-wr-capture-cmd = WR Capture Command
-zen-key-wr-toggle-capture-sequence-cmd = Toggle WR Capture Sequence
-zen-nav-reload-shortcut = Reload Page
-zen-nav-reload-shortcut-skip-cache = Reload Page (Skip Cache)
-zen-close-shortcut = Close Window
-zen-close-tab-shortcut = Close Tab
-zen-compact-mode-shortcut-show-sidebar = Toggle Floating Sidebar
-zen-compact-mode-shortcut-show-toolbar = Toggle Floating Toolbar
-zen-compact-mode-shortcut-toggle = Toggle Compact Mode
-zen-glance-expand = Expand Glance
-zen-workspace-shortcut-switch-1 = Switch to Workspace 1
-zen-workspace-shortcut-switch-2 = Switch to Workspace 2
-zen-workspace-shortcut-switch-3 = Switch to Workspace 3
-zen-workspace-shortcut-switch-4 = Switch to Workspace 4
-zen-workspace-shortcut-switch-5 = Switch to Workspace 5
-zen-workspace-shortcut-switch-6 = Switch to Workspace 6
-zen-workspace-shortcut-switch-7 = Switch to Workspace 7
-zen-workspace-shortcut-switch-8 = Switch to Workspace 8
-zen-workspace-shortcut-switch-9 = Switch to Workspace 9
-zen-workspace-shortcut-switch-10 = Switch to Workspace 10
-zen-workspace-shortcut-forward = Forward Workspace
-zen-workspace-shortcut-backward = Backward Workspace
-zen-workspace-shortcut-create = Create New Workspace
-zen-sidebar-shortcut-toggle = Toggle Sidebar's Width
-zen-pinned-tab-shortcut-reset = Reset Pinned Tab to Pinned URL
-zen-split-view-shortcut-grid = Toggle Split View Grid
-zen-split-view-shortcut-vertical = Toggle Split View Vertical
-zen-split-view-shortcut-horizontal = Toggle Split View Horizontal
-zen-split-view-shortcut-unsplit = Close Split View
-zen-new-empty-split-view-shortcut = New Empty Split View
-zen-key-select-tab-1 = Select tab #1
-zen-key-select-tab-2 = Select tab #2
-zen-key-select-tab-3 = Select tab #3
-zen-key-select-tab-4 = Select tab #4
-zen-key-select-tab-5 = Select tab #5
-zen-key-select-tab-6 = Select tab #6
-zen-key-select-tab-7 = Select tab #7
-zen-key-select-tab-8 = Select tab #8
-zen-key-select-tab-last = Select last tab
-zen-key-show-all-tabs = Show all tabs
-zen-key-goto-history = Go to history
-zen-key-go-home = Go Home
-zen-bookmark-show-sidebar-shortcut = Show Bookmarks Sidebar
-zen-bookmark-show-toolbar-shortcut = Show Bookmarks Toolbar
-zen-devtools-toggle-shortcut = Toggle DevTools
-zen-devtools-toggle-browser-toolbox-shortcut = Toggle Browser Toolbox
-zen-devtools-toggle-browser-console-shortcut = Toggle Browser Console
-zen-devtools-toggle-responsive-design-mode-shortcut = Toggle Responsive Design Mode
-zen-devtools-toggle-inspector-shortcut = Toggle Inspector
-zen-devtools-toggle-web-console-shortcut = Toggle Web Console
-zen-devtools-toggle-js-debugger-shortcut = Toggle JavaScript Debugger
-zen-devtools-toggle-net-monitor-shortcut = Toggle Network Monitor
-zen-devtools-toggle-style-editor-shortcut = Toggle Style Editor
-zen-devtools-toggle-performance-shortcut = Toggle Performance
-zen-devtools-toggle-storage-shortcut = Toggle Storage
-zen-devtools-toggle-dom-shortcut = Toggle DOM
-zen-devtools-toggle-accessibility-shortcut = Toggle Accessibility
-zen-close-all-unpinned-tabs-shortcut = Close All Unpinned Tabs
-zen-new-unsynced-window-shortcut = New Unsynced Window
-zen-duplicate-tab-shortcut = Duplicate Tab
-zen-key-find-selection = Find Selection
+    .label = Resetează la valoarea implicită
+zenCKSOption-group-other = Altceva
+zenCKSOption-group-windowAndTabManagement = Gestionarea Ferestrelor și Filelor
+zenCKSOption-group-navigation = Navigare
+zenCKSOption-group-searchAndFind = Caută și Găsește
+zenCKSOption-group-pageOperations = Operații pe Pagină
+zenCKSOption-group-historyAndBookmarks = Istoric și Marcaje
+zenCKSOption-group-mediaAndDisplay = Media și Afișare
+zenCKSOption-group-zen-compact-mode = Modul Compact
+zenCKSOption-group-zen-workspace = Spații de Lucru
+zenCKSOption-group-zen-other = Alte Funcții Zen
+zenCKSOption-group-zen-split-view = Vizualizare Împărțită
+zenCKSOption-group-devTools = Unelte pentru Dezvoltatori
+zen-key-quick-restart = Repornire Rapidă
+zen-window-new-shortcut = Fereastră Nouă
+zen-tab-new-shortcut = Filă Nouă
+zen-key-redo = Refă
+zen-restore-last-closed-tab-shortcut = Restaurează Ultima Filă Închisă
+zen-location-open-shortcut = Deschide Locația
+zen-location-open-shortcut-alt = Deschide Locația (Alt)
+zen-key-undo-close-window = Anulează Închiderea Ferestrei
+zen-text-action-undo-shortcut = Anulează
+zen-text-action-redo-shortcut = Refă
+zen-text-action-cut-shortcut = Decupează
+zen-text-action-copy-shortcut = Copiază
+zen-text-action-copy-url-shortcut = Copiază URL-ul curent
+zen-text-action-copy-url-markdown-shortcut = Copiază URL-ul curent ca Markdown
+zen-text-action-paste-shortcut = Lipește
+zen-text-action-select-all-shortcut = Selectează tot
+zen-text-action-delete-shortcut = Șterge
+zen-history-show-all-shortcut-mac = Arată tot istoricul (Mac)
+zen-full-screen-shortcut = Comută Ecran Complet
+zen-reader-mode-toggle-shortcut-windows = Comută Modul Cititor (Windows)
+zen-picture-in-picture-toggle-shortcut-alt = Comută Imaginea-în-Imagine (Alt)
+zen-picture-in-picture-toggle-shortcut-mac = Comută Imaginea-în-Imagine (Mac)
+zen-picture-in-picture-toggle-shortcut-mac-alt = Comută Imaginea-în-Imagine (Mac Alt)
+zen-page-source-shortcut-safari = Vezi Sursa Paginii (Safari)
+zen-nav-stop-shortcut = Oprește Încărcarea
+zen-history-sidebar-shortcut = Arată bara laterală a Istoricului
+zen-window-minimize-shortcut = Minimizează Fereastra
+zen-help-shortcut = Deschide Ajutor
+zen-preferences-shortcut = Deschide Preferințele
+zen-hide-app-shortcut = Ascunde Aplicația
+zen-hide-other-apps-shortcut = Ascunde Alte Aplicații
+zen-search-focus-shortcut = Focalizează pe Căutare
+zen-search-focus-shortcut-alt = Focalizează pe Căutare (Alt)
+zen-downloads-shortcut = Deschide Descărcările
+zen-addons-shortcut = Deschide Suplimentele
+zen-file-open-shortcut = Deschide Fișier
+zen-save-page-shortcut = Salvează Pagina
+zen-print-shortcut = Tipărește Pagina
+zen-close-shortcut-2 = Închide fila
+zen-mute-toggle-shortcut = Comută Sunet Mut
+zen-key-delete = Șterge Cheia
+zen-key-go-back = Mergi Înapoi
+zen-key-go-forward = Mergi Înainte
+zen-nav-back-shortcut-alt = Navighează Înapoi (Alt)
+zen-nav-fwd-shortcut-alt = Navighează Înainte (Alt)
+zen-history-show-all-shortcut = Arată tot istoricul
+zen-key-enter-full-screen = Intră în Ecran Complet
+zen-key-exit-full-screen = Ieși din Ecran Complet
+zen-ai-chatbot-sidebar-shortcut = Comută bara laterală a Robotului AI
+zen-key-inspector-mac = Comută Inspectorul (Mac)
+zen-toggle-sidebar-shortcut = Comută bara laterală Firefox
+zen-toggle-pin-tab-shortcut = Comută Fila Fixată
+zen-reader-mode-toggle-shortcut-other = Comută Modul Cititor
+zen-picture-in-picture-toggle-shortcut = Comută Imaginea-în-Imagine
+zen-nav-reload-shortcut-2 = Reîncarcă Pagina
+zen-key-about-processes = Despre Procese
+zen-page-source-shortcut = Vezi Sursa Paginii
+zen-page-info-shortcut = Vezi Informațiile Paginii
+zen-find-shortcut = Găsește în Pagină
+zen-search-find-again-shortcut = Găsește din nou
+zen-search-find-again-shortcut-prev = Găsește Anteriorul
+zen-search-find-again-shortcut-alt = Caută din nou (Alt)
+zen-search-find-again-shortcut-prev-alt = Caută anterior (Alt)
+zen-bookmark-this-page-shortcut = Marchează Această Pagină
+zen-bookmark-show-library-shortcut = Arată Librăria Marcajelor
+zen-key-stop = Oprește Încărcarea
+zen-full-zoom-reduce-shortcut = Micșorează
+zen-full-zoom-enlarge-shortcut = Mărește
+zen-full-zoom-reset-shortcut = Resetează Zoom
+zen-full-zoom-reset-shortcut-alt = Resetează Zoom (Alt)
+zen-full-zoom-enlarge-shortcut-alt = Mărește (Alt)
+zen-full-zoom-enlarge-shortcut-alt2 = Mărește (Alt 2)
+zen-bidi-switch-direction-shortcut = Schimbă Direcția Textului
+zen-private-browsing-shortcut = Navigare Anonimă
+zen-screenshot-shortcut = Fă o Captură de ecran
+zen-key-sanitize = Șterge Datele de Navigare
+zen-quit-app-shortcut = Închide Aplicația
+zen-key-wr-capture-cmd = Comanda de Captură WR
+zen-key-wr-toggle-capture-sequence-cmd = Comută Secvența de Captură WR
+zen-nav-reload-shortcut = Reîncarcă Pagina
+zen-nav-reload-shortcut-skip-cache = Reîncarcă Pagina (fără cache)
+zen-close-shortcut = Închide Fereastra
+zen-close-tab-shortcut = Închide fila
+zen-compact-mode-shortcut-show-sidebar = Comută Bara Laterală Plutitoare
+zen-compact-mode-shortcut-show-toolbar = Comută Bara de Unelte Plutitoare
+zen-compact-mode-shortcut-toggle = Comută Modul Compact
+zen-glance-expand = Extinde Glance
+zen-workspace-shortcut-switch-1 = Mergi la Spațiul de Lucru 1
+zen-workspace-shortcut-switch-2 = Mergi la Spațiul de Lucru 2
+zen-workspace-shortcut-switch-3 = Mergi la Spațiul de Lucru 3
+zen-workspace-shortcut-switch-4 = Mergi la Spațiul de Lucru 4
+zen-workspace-shortcut-switch-5 = Mergi la Spațiul de Lucru 5
+zen-workspace-shortcut-switch-6 = Mergi la Spațiul de Lucru 6
+zen-workspace-shortcut-switch-7 = Mergi la Spațiul de Lucru 7
+zen-workspace-shortcut-switch-8 = Mergi la Spațiul de Lucru 8
+zen-workspace-shortcut-switch-9 = Mergi la Spațiul de Lucru 9
+zen-workspace-shortcut-switch-10 = Mergi la Spațiul de Lucru 10
+zen-workspace-shortcut-forward = Spațiul de Lucru Următor
+zen-workspace-shortcut-backward = Spațiul de Lucru Anterior
+zen-workspace-shortcut-create = Creează un Spațiu de Lucru Nou
+zen-sidebar-shortcut-toggle = Comută Lățimea Barei Laterale
+zen-pinned-tab-shortcut-reset = Resetează Fila Fixată la URL-ul Fixat
+zen-split-view-shortcut-grid = Comută Vizualizarea Împărțită tip Grilă
+zen-split-view-shortcut-vertical = Comută Vizualizarea Împărțită Verticală
+zen-split-view-shortcut-horizontal = Comută Vizualizarea Împărțită Orizontală
+zen-split-view-shortcut-unsplit = Închide Vizualizarea Împărțită
+zen-new-empty-split-view-shortcut = Vizualizare Împărțită Nouă Goală
+zen-key-select-tab-1 = Selectează fila #1
+zen-key-select-tab-2 = Selectează fila #2
+zen-key-select-tab-3 = Selectează fila #3
+zen-key-select-tab-4 = Selectează fila #4
+zen-key-select-tab-5 = Selectează fila #5
+zen-key-select-tab-6 = Selectează fila #6
+zen-key-select-tab-7 = Selectează fila #7
+zen-key-select-tab-8 = Selectează fila #8
+zen-key-select-tab-last = Selectează ultima filă
+zen-key-show-all-tabs = Arată toate filele
+zen-key-goto-history = Mergi la istoric
+zen-key-go-home = Întoarce-te Acasă
+zen-bookmark-show-sidebar-shortcut = Arată Bara Laterală a Marcajelor
+zen-bookmark-show-toolbar-shortcut = Arată Bara de Unelte a Marcajelor
+zen-devtools-toggle-shortcut = Comută DevTools
+zen-devtools-toggle-browser-toolbox-shortcut = Comută Cutia de Unelte a Browser-ului
+zen-devtools-toggle-browser-console-shortcut = Comută Consola Browser-ului
+zen-devtools-toggle-responsive-design-mode-shortcut = Comută Modul de Design Receptiv
+zen-devtools-toggle-inspector-shortcut = Comută Inspectorul
+zen-devtools-toggle-web-console-shortcut = Comută Consola Web
+zen-devtools-toggle-js-debugger-shortcut = Comută Depănătorul JavaScript
+zen-devtools-toggle-net-monitor-shortcut = Comută Monitorul de Rețea
+zen-devtools-toggle-style-editor-shortcut = Comută Editorul de Stil
+zen-devtools-toggle-performance-shortcut = Comută Performanța
+zen-devtools-toggle-storage-shortcut = Comută Stocarea
+zen-devtools-toggle-dom-shortcut = Comută DOM
+zen-devtools-toggle-accessibility-shortcut = Comută Accesibilitatea
+zen-close-all-unpinned-tabs-shortcut = Închide toate filele nefixate
+zen-new-unsynced-window-shortcut = Fereastră Nouă Goală
+zen-duplicate-tab-shortcut = Duplică fila
+zen-key-find-selection = Găsește Selecția
diff --git a/locales/ro/browser/browser/zen-boosts.ftl b/locales/ro/browser/browser/zen-boosts.ftl
index eb42026a7..ca4cc4783 100644
--- a/locales/ro/browser/browser/zen-boosts.ftl
+++ b/locales/ro/browser/browser/zen-boosts.ftl
@@ -3,56 +3,56 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 zen-boost-edit-rename = 
-    .label = Rename Boost
+    .label = Redenumește Boost
 zen-boost-edit-shuffle = 
-    .label = Shuffle Vibes
+    .label = Amestecă Stilurile
 zen-boost-edit-reset = 
-    .label = Reset All Edits
+    .label = Resetează Toate Modificările
 zen-boost-edit-delete = 
-    .label = Delete Boost
-zen-boost-size = Size
-zen-boost-case = Case
-zen-boost-zap = Zap
-zen-boost-code = Code
-zen-boost-back = Back
+    .label = Șterge Boost
+zen-boost-size = Mărime
+zen-boost-case = Capitalizare
+zen-boost-zap = Șterge
+zen-boost-code = Cod
+zen-boost-back = Înapoi
 zen-boost-shuffle = 
-    .tooltiptext = Shuffle Boost Settings
+    .tooltiptext = Amestecă Setările Boost-ului
 zen-boost-invert = 
-    .tooltiptext = Smart Invert Colors
+    .tooltiptext = Culori Inversate Inteligent
 zen-boost-controls = 
-    .tooltiptext = Advanced Color Controls
+    .tooltiptext = Comenzi de Culoare Avansate
 zen-boost-disable = 
-    .tooltiptext = Disable Color Adjustments
+    .tooltiptext = Dezactivează Ajustările de Culoare
 zen-boost-text-case-toggle = 
-    .tooltiptext = Toggle Text Case
+    .tooltiptext = Schimbă Capitalizarea
 zen-boost-css-picker = 
-    .tooltiptext = Pick Selector
+    .tooltiptext = Alege Selectorul
 zen-boost-css-inspector = 
-    .tooltiptext = Open Inspector
+    .tooltiptext = Deschide Inspectorul
 zen-boost-color-contrast = Contrast
-zen-boost-color-brightness = Brightness
-zen-boost-color-original-saturation = Original Saturation
-zen-add-zap-helper = Click elements on the page to <b>Zap</b> them
-zen-remove-zap-helper = ← Click to Unzap
-zen-select-this = Insert selector for this
-zen-select-related = Insert selector for related
-zen-select-cancel = Cancel
-zen-zap-this = Zap this
-zen-zap-related = Zap all related elements
-zen-zap-cancel = Cancel
-zen-zap-done = Done
+zen-boost-color-brightness = Luminozitate
+zen-boost-color-original-saturation = Saturație Originală
+zen-add-zap-helper = Apasă pe elemente din pagină pentru a le <b>Șterge</b>
+zen-remove-zap-helper = ← Anulează Ștergerea
+zen-select-this = Inserează selector pentru acesta
+zen-select-related = Inserează selector pentru elemente asociate
+zen-select-cancel = Anulează
+zen-zap-this = Șterge element
+zen-zap-related = Șterge toate elementele asociate
+zen-zap-cancel = Anulează
+zen-zap-done = Gata
 zen-unzap-tooltip =
     { $elementCount ->
-        [0] No elements zapped
-        [1] { $elementCount } element zapped
-       *[other] { $elementCount } elements zapped
+        [0] Niciun element șters
+        [1] Un element șters
+       *[other] { $elementCount } elemente șterse
     }
 zen-boost-save = 
-    .label = Export Boost
+    .label = Exportă Boost
 zen-boost-load = 
-    .label = Import Boost
-zen-panel-ui-boosts-exported-message = Boost exported!
-zen-site-data-boosts = Boosts
+    .label = Importă Boost
+zen-panel-ui-boosts-exported-message = Boost exportat!
+zen-site-data-boosts = Boost-uri
 zen-site-data-create-boost = 
-    .tooltiptext = Create new boost
-zen-boost-rename-boost-prompt = Rename Boost?
+    .tooltiptext = Creează Boost nou
+zen-boost-rename-boost-prompt = Redenumește Boost?
diff --git a/locales/ro/browser/browser/zen-command-palette.ftl b/locales/ro/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..bc2bea0c6
--- /dev/null
+++ b/locales/ro/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Comută Modul Compact
+zen-action-open-theme-picker = Deschide selectorul de teme
+zen-action-new-split-view = Vizualizare împărțită nouă
+zen-action-new-folder = Folder nou
+zen-action-copy-current-url = Copiază URL-ul curent
+zen-action-settings = Setări
+zen-action-open-private-window = Deschide fereastră privată
+zen-action-open-new-window = Deschide o fereastră nouă
+zen-action-new-blank-window = Fereastră nouă goală
+zen-action-pin-tab = Fixează fila
+zen-action-unpin-tab = Anulează fixarea filei
+zen-action-open-space-routing = Deschide rutarea spațiilor
+zen-action-new-boost = Boost nou
+zen-action-next-space = Spațiul următor
+zen-action-previous-space = Spațiul anterior
+zen-action-close-tab = Închide fila
+zen-action-reload-tab = Reîncarcă fila
+zen-action-reload-tab-without-cache = Reîncarcă fila fără cache
+zen-action-next-tab = Fila următoare
+zen-action-previous-tab = Fila anterioară
+zen-action-capture-screenshot = Captură de ecran
+zen-action-toggle-tabs-on-right = Comută filele în dreapta
+zen-action-add-to-essentials = Adaugă la Esențiale
+zen-action-remove-from-essentials = Elimină din Esențiale
+zen-action-find-in-page = Găsește în pagină
+zen-action-manage-extensions = Gestionează extensiile
+zen-action-switch-to-automatic-appearance = Schimbă în modul Aparență Automată
+zen-action-switch-to-light-mode = Schimbă în modul luminos
+zen-action-switch-to-dark-mode = Schimbă în modul întunecat
+zen-action-print = Tipărește
+zen-action-focus-on = Focalizare pe
+zen-action-extension = Extensie
diff --git a/locales/ro/browser/browser/zen-folders.ftl b/locales/ro/browser/browser/zen-folders.ftl
index ebb7efe51..6acf2c4d2 100644
--- a/locales/ro/browser/browser/zen-folders.ftl
+++ b/locales/ro/browser/browser/zen-folders.ftl
@@ -3,21 +3,21 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 zen-folders-search-placeholder = 
-    .placeholder = Search { $folder-name }...
+    .placeholder = Caută { $folder-name }...
 zen-folders-panel-rename-folder = 
     .label = Rename Folder
 zen-folders-panel-unpack-folder = 
-    .label = Unpack Folder
+    .label = Despachetare Folder
 zen-folders-new-subfolder = 
     .label = New Subfolder
 zen-folders-panel-delete-folder = 
-    .label = Delete Folder
+    .label = Șterge Folder
 zen-folders-panel-convert-folder-to-space = 
-    .label = Convert folder to Space
+    .label = Convertește folderul în Spațiu
 zen-folders-panel-change-folder-space = 
     .label = Change Space...
 zen-folders-unload-all-tooltip = 
-    .tooltiptext = Unload active in this folder
+    .tooltiptext = Închide tab-urile active din folder
 zen-folders-unload-folder = 
-    .label = Unload All Tabs
-zen-folders-search-no-results = No tabs matching that search 🤔
+    .label = Închide toate filele
+zen-folders-search-no-results = Nicio filă nu se potrivește căutării 🤔
diff --git a/locales/ro/browser/browser/zen-general.ftl b/locales/ro/browser/browser/zen-general.ftl
index 709b4575f..2bbaf6840 100644
--- a/locales/ro/browser/browser/zen-general.ftl
+++ b/locales/ro/browser/browser/zen-general.ftl
@@ -2,126 +2,141 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-zen-panel-ui-current-profile-text = current profile
-unified-extensions-description = Extensions are used to bring more extra functionality into { -brand-short-name }.
+zen-panel-ui-current-profile-text = profilul curent
+unified-extensions-description = Extensiile sunt folosite pentru a aduce funcționalități suplimentare în { -brand-short-name }.
 tab-context-zen-reset-pinned-tab = 
     .label =
         { $isEssential ->
-            [true] Reset Essential Tab
-           *[false] Reset Pinned Tab
+            [true] Resetare Filă Esențială
+           *[false] Resetare Filă Fixată
         }
     .accesskey = R
 tab-context-zen-add-essential = 
-    .label = Add to Essentials
+    .label = Adaugă la Esențiale
     .accesskey = E
-tab-context-zen-add-essential-badge = { $num } / { $max } slots filled
+tab-context-zen-add-essential-badge = { $num } / { $max }
 tab-context-zen-remove-essential = 
-    .label = Remove from Essentials
+    .label = Elimină din Esențiale
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Replace Essential URL with Current
-           *[false] Replace Pinned URL with Current
+            [true] Editează URL-ul filei esențiale
+           *[false] Editează URL-ul filei fixate
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Înlocuiește cu URL-ul curent
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Editează…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Change Label...
 tab-context-zen-edit-icon = 
     .label = Change Icon...
-zen-themes-corrupted = Your { -brand-short-name } mods file is corrupted. They have been reset to the default theme.
-zen-shortcuts-corrupted = Your { -brand-short-name } shortcuts file is corrupted. They have been reset to the default shortcuts.
+zen-themes-corrupted = Fișierul tău de moduri { -brand-short-name } este corupt. Acestea au fost resetate la tema implicită.
+zen-shortcuts-corrupted = Fișierul tău de scurtături { -brand-short-name } este corupt. Acestea au fost resetate la scurtăturile implicite.
 # note: Do not translate the "<br/>" tags in the following string
 zen-new-urlbar-notification =
-    The new URL bar has been enabled, removing the need for new tab pages.<br/><br/>
-    Try opening a new tab to see the new URL bar in action!
-zen-disable = Disable
+    Noua bară URL a fost activată, eliminând necesitatea pentru paginile cu file noi.<br/><br/>
+    Încearcă să deschizi o filă nouă pentru a vedea noua bară URL în acțiune!
+zen-disable = Dezactivează
 pictureinpicture-minimize-btn = 
-    .aria-label = Minimize
-    .tooltip = Minimize
-zen-panel-ui-gradient-generator-custom-color = Custom Color
-zen-copy-current-url-confirmation = Copied current URL!
-zen-copy-current-url-as-markdown-confirmation = Copied current URL as Markdown!
+    .aria-label = Minimizează
+    .tooltip = Minimizează
+zen-panel-ui-gradient-generator-custom-color = Culoare Personalizată
+zen-copy-current-url-confirmation = URL-ul curent a fost copiat!
+zen-copy-current-url-as-markdown-confirmation = URL-ul curent a fost copiat ca Markdown!
 zen-general-cancel-label = 
-    .label = Cancel
+    .label = Anulează
 zen-general-confirm = 
-    .label = Confirm
-zen-pinned-tab-replaced = Pinned tab URL has been replaced with the current URL!
-zen-tabs-renamed = Tab has been successfully renamed!
-zen-background-tab-opened-toast = New background tab opened!
-zen-workspace-renamed-toast = Workspace has been successfully renamed!
-zen-split-view-limit-toast = Can't add more panels to the split view!
+    .label = Confirmă
+zen-pinned-tab-replaced = URL-ul filei fixate a fost înlocuit cu URL-ul curent!
+zen-pinned-tab-url-edited = URL-ul filei fixate a fost actualizat!
+zen-pinned-tab-url-invalid = Nu pare a fi un URL valid.
+zen-pinned-tab-edit-url-title = Editare URL fixat
+zen-pinned-tab-edit-url-label = Introdu URL-ul pe care această filă trebuie să-l indice:
+zen-tabs-renamed = Fila a fost redenumită cu succes!
+zen-background-tab-opened-toast = Filă nouă de fundal deschisă!
+zen-workspace-renamed-toast = Spațiul de Lucru a fost redenumit cu succes!
+zen-split-view-limit-toast = Nu se mai pot adăuga panouri noi la vizualizarea împărțită!
 zen-toggle-compact-mode-button = 
-    .label = Compact Mode
-    .tooltiptext = Toggle Compact Mode
+    .label = Modul Compact
+    .tooltiptext = Comută Modul Compact
 
 # note: Do not translate the "<br/>" tags in the following string
 
-zen-learn-more-text = Learn More
-zen-close-label = Close
+zen-learn-more-text = Află mai multe
+zen-close-label = Închide
 zen-singletoolbar-urlbar-placeholder-with-name = 
-    .placeholder = Search...
+    .placeholder = Caută...
 zen-icons-picker-emoji = 
-    .label = Emojis
+    .label = Emoji-uri
 zen-icons-picker-svg = 
-    .label = Icons
-urlbar-search-mode-zen_actions = Actions
-zen-site-data-settings = Settings
-zen-generic-manage = Manage
-zen-generic-more = More
-zen-generic-next = Next
-zen-essentials-promo-label = Add to Essentials
-zen-essentials-promo-sublabel = Keep your favorite tabs just a click away
+    .label = Iconițe
+zen-emojis-picker-search = 
+    .placeholder = Caută Emoji
+urlbar-search-mode-zen_actions = Acțiuni
+zen-site-data-settings = Setări
+zen-generic-manage = Gestionează
+zen-generic-more = Mai multe
+zen-generic-next = Următorul
+zen-essentials-promo-label = Adaugă la Esențiale
+zen-essentials-promo-sublabel = Ține filele tale preferate la un click distanță
 # These labels will be used for the site data panel settings
-zen-site-data-setting-allow = Allowed
-zen-site-data-setting-block = Blocked
-zen-site-data-protections-enabled = Enabled
-zen-site-data-protections-disabled = Disabled
-zen-site-data-setting-cross-site = Cross-Site cookie
+zen-site-data-setting-allow = Permis
+zen-site-data-setting-block = Blocat
+zen-site-data-protections-enabled = Activat
+zen-site-data-protections-disabled = Dezactivat
+zen-site-data-setting-cross-site = Cookie Cross-Site
 zen-site-data-security-info-extension = 
-    .label = Extension
+    .label = Extensie
 zen-site-data-security-info-secure = 
-    .label = Secure
+    .label = Securizat
 zen-site-data-security-info-not-secure = 
-    .label = Not Secure
+    .label = Nesecurizat
 zen-site-data-manage-addons = 
-    .label = Manage Extensions
+    .label = Gestionează Extensiile
 zen-site-data-get-addons = 
-    .label = Add Extensions
+    .label = Adaugă Extensii
 zen-site-data-site-settings = 
-    .label = All Site Settings
+    .label = Toate Setările Site-ului
 zen-site-data-header-share = 
-    .tooltiptext = Share This Page
+    .tooltiptext = Distribuie Această Pagină
 zen-site-data-header-reader-mode = 
-    .tooltiptext = Enter Reader Mode
+    .tooltiptext = Intră în Modul Cititor
 zen-site-data-header-screenshot = 
-    .tooltiptext = Take a Screenshot
+    .tooltiptext = Fă o Captură Ecran
 zen-site-data-header-bookmark = 
-    .tooltiptext = Bookmark This Page
+    .tooltiptext = Marchează Această Pagină
 zen-urlbar-copy-url-button = 
-    .tooltiptext = Copy URL
-zen-site-data-setting-site-protection = Tracking Protection
+    .tooltiptext = Copiază URL-ul
+zen-site-data-setting-site-protection = Protecție împotriva Urmăririi
 
 # Section: Feature callouts
 
-zen-site-data-panel-feature-callout-title = A new home for add-ons, permissions, and more
-zen-site-data-panel-feature-callout-subtitle = Click the icon to manage site settings, view security info, access extensions, and perform common actions.
+zen-site-data-panel-feature-callout-title = O casă nouă pentru Suplimente, Permisiuni și multe altele
+zen-site-data-panel-feature-callout-subtitle = Apasă pe iconiță pentru a gestiona setările site-ului, pentru a vizualiza informațiile de securitate, accesul extensiilor și pentru a efectua acțiuni comune.
 zen-open-link-in-glance = 
-    .label = Open Link in Glance
+    .label = Deschide link-ul în Glance
     .accesskey = G
-zen-sidebar-notification-updated-heading = Update Complete!
+zen-sidebar-notification-updated-heading = Actualizare finalizată!
 
 # See ZenSidebarNotification.mjs to see how these would be used
 
-zen-sidebar-notification-updated-label = What's new in { -brand-short-name }
+zen-sidebar-notification-updated-label = Ce este nou în { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
-    .title = View Release Notes
-zen-sidebar-notification-restart-safe-mode-label = Something broke?
+    .title = Vezi Notele de Lansare
+zen-sidebar-notification-donate-label = Suportă { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donează proiectului
+zen-sidebar-notification-restart-safe-mode-label = S-a stricat ceva?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
-    .title = Restart in Safe Mode
-zen-window-sync-migration-dialog-title = Keep Your Windows in Sync
-zen-window-sync-migration-dialog-message = Zen now syncs windows on the same device, so changes in one window are reflected across the others instantly.
-zen-window-sync-migration-dialog-learn-more = Learn More
-zen-window-sync-migration-dialog-accept = Got It
+    .title = Repornește în Modul Sigur
+zen-window-sync-migration-dialog-title = Păstrează-ți Ferestrele Sincronizate
+zen-window-sync-migration-dialog-message = Zen sincronizează ferestrele pe același dispozitiv, deci modificările dintr-o fereastră sunt reflectate instantaneu la celelalte ferestre.
+zen-window-sync-migration-dialog-learn-more = Află mai multe
+zen-window-sync-migration-dialog-accept = Am înțeles
 zen-appmenu-new-blank-window = 
-    .label = New blank window
+    .label = Fereastră Nouă Goală
diff --git a/locales/ro/browser/browser/zen-menubar.ftl b/locales/ro/browser/browser/zen-menubar.ftl
index a24d50928..1b029321f 100644
--- a/locales/ro/browser/browser/zen-menubar.ftl
+++ b/locales/ro/browser/browser/zen-menubar.ftl
@@ -5,18 +5,18 @@
 zen-menubar-toggle-pinned-tabs = 
     .label =
         { $pinnedAreCollapsed ->
-            [true] Expand Pinned Tabs
-           *[false] Collapse Pinned Tabs
+            [true] Extinde Filele Fixate
+           *[false] Restrânge Filele Fixate
         }
 zen-menubar-appearance = 
-    .label = Appearance
+    .label = Aspect
 zen-menubar-appearance-description = 
-    .label = Websites will use:
+    .label = Website-urile vor folosi:
 zen-menubar-appearance-auto = 
-    .label = Automatic
+    .label = Automat
 zen-menubar-appearance-light = 
-    .label = Light
+    .label = Luminos
 zen-menubar-appearance-dark = 
-    .label = Dark
+    .label = Întunecat
 zen-menubar-new-blank-window = 
-    .label = New Blank Window
+    .label = Fereastră Nouă Goală
diff --git a/locales/ro/browser/browser/zen-space-routing.ftl b/locales/ro/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..ec962ff32
--- /dev/null
+++ b/locales/ro/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Setări Rutare Spații
+zen-space-routing-rulepanel-placeholder = Rutele îți permit să alegi unde se deschid anumite site-uri în Zen. De exemplu, poți ruta link-urile de YouTube să fie deschide întotdeauna în Spațiul Personal.
+zen-space-routing-dialog-title = Setări Rutare Spații
+zen-space-routing-external-default = Rută implicită pentru link-uri externe
+zen-space-routing-new-route = Rută nouă
+zen-space-routing-open-in-space = Deschide în Spațiu
+zen-space-routing-most-recent-space = Cel mai recent Spațiu
+zen-space-routing-close-button = 
+    .aria-label = Închide
+    .tooltiptext = Închide
+zen-space-routing-contains = 
+    .label = Conține
+zen-space-routing-equal-to = 
+    .label = Este egal cu
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Deschide în
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = Filă nouă deschisă în { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Adaugă ruta pentru domeniu
+           *[other] Adaugă ruta pentru domenii
+        }
diff --git a/locales/ro/browser/browser/zen-split-view.ftl b/locales/ro/browser/browser/zen-split-view.ftl
index 4430fab34..d0a9453aa 100644
--- a/locales/ro/browser/browser/zen-split-view.ftl
+++ b/locales/ro/browser/browser/zen-split-view.ftl
@@ -5,14 +5,14 @@
 tab-zen-split-tabs = 
     .label =
         { $tabCount ->
-            [-1] Split out tab
-            [1] Add split view...
-           *[other] Join { $tabCount } Tabs
+            [-1] Desparte fila
+            [1] Împarte fila...
+           *[other] Îmbină { $tabCount } file
         }
     .accesskey = S
 zen-split-link = 
-    .label = Split link to new tab
+    .label = Împarte link-ul către o filă nouă
     .accesskey = S
-zen-split-view-modifier-header = Split View
+zen-split-view-modifier-header = Vizualizare Împărțită
 zen-split-view-modifier-activate-reallocation = 
-    .label = Activate reallocation
+    .label = Activează realocarea
diff --git a/locales/ro/browser/browser/zen-vertical-tabs.ftl b/locales/ro/browser/browser/zen-vertical-tabs.ftl
index 9989c7666..502de53ee 100644
--- a/locales/ro/browser/browser/zen-vertical-tabs.ftl
+++ b/locales/ro/browser/browser/zen-vertical-tabs.ftl
@@ -3,45 +3,45 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 zen-toolbar-context-tabs-right = 
-    .label = Tabs on the right
+    .label = File pe partea dreaptă
     .accesskey = R
 zen-toolbar-context-compact-mode = 
-    .label = Compact Mode
+    .label = Modul Compact
 zen-toolbar-context-compact-mode-enable = 
-    .label = Enable compact mode
+    .label = Activează modul compact
     .accesskey = D
 zen-toolbar-context-compact-mode-just-tabs = 
-    .label = Hide sidebar
+    .label = Ascunde bara laterală
 zen-toolbar-context-compact-mode-just-toolbar = 
-    .label = Hide toolbar
+    .label = Ascunde bara de unelte
 zen-toolbar-context-compact-mode-hide-both = 
-    .label = Hide both
+    .label = Ascunde ambele
     .accesskey = H
 zen-toolbar-context-move-to-folder = 
     .label = Move to Folder...
     .accesskey = M
 zen-toolbar-context-new-folder = 
-    .label = New Folder
+    .label = Folder Nou
     .accesskey = N
 sidebar-zen-expand = 
-    .label = Expand Sidebar
+    .label = Extinde bara laterală
 sidebar-zen-create-new = 
     .label = Create New...
 tabbrowser-unload-tab-button = 
     .tooltiptext =
         { $tabCount ->
-            [one] Unload and switch to tab
-           *[other] Unload { $tabCount } tabs and switch to the first
+            [one] Închide şi treci la filă
+           *[other] Închide { $tabCount } file şi treci la prima
         }
 tabbrowser-reset-pin-button = 
     .tooltiptext =
         { $tabCount ->
-            [one] Reset and pin tab
-           *[other] Reset and pin { $tabCount } tabs
+            [one] Resetează și Fixează fila
+           *[other] Resetează și Fixează { $tabCount } file
         }
 zen-tab-sublabel =
     { $tabSubtitle ->
-        [zen-default-pinned] Back to pinned url
-        [zen-default-pinned-cmd] Separate from pinned tab
+        [zen-default-pinned] Înapoi la url-ul fixat
+        [zen-default-pinned-cmd] Separă de filele fixate
        *[other] { $tabSubtitle }
     }
diff --git a/locales/ro/browser/browser/zen-welcome.ftl b/locales/ro/browser/browser/zen-welcome.ftl
index 063aff1e7..e5e8823f7 100644
--- a/locales/ro/browser/browser/zen-welcome.ftl
+++ b/locales/ro/browser/browser/zen-welcome.ftl
@@ -2,25 +2,25 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-zen-welcome-title-line1 = Welcome to
-zen-welcome-title-line2 = a calmer internet
-zen-welcome-import-title = A Fresh Start, Same Bookmarks
-zen-welcome-import-description-1 = Your bookmarks, history, and passwords are like a trail of breadcrumbs through the internet—don’t leave them behind!
-zen-welcome-import-description-2 = Easily bring them over from another browser and pick up right where you left off.
-zen-welcome-import-button = Import now
-zen-welcome-set-default-browser = Set { -brand-short-name } as your default browser
-zen-welcome-dont-set-default-browser = DON’T set { -brand-short-name } as your default browser
-zen-welcome-initial-essentials-title = Your Key Tabs, Always Within Reach
-zen-welcome-initial-essentials-description-1 = Keep your most important tabs easily accessible and always at hand, no matter how many you open.
-zen-welcome-initial-essentials-description-2 = Essential tabs are always visible, no matter what workspace you are in.
-zen-welcome-workspace-colors-title = Your Workspaces, Your Colors
-zen-welcome-workspace-colors-description = Personalize your browser by giving each workspace its own unique color identity.
+zen-welcome-title-line1 = Bine ai venit la
+zen-welcome-title-line2 = un internet mai calm
+zen-welcome-import-title = Un Început Proaspăt, Aceleași Marcaje
+zen-welcome-import-description-1 = Marcajele, istoricul și parolele tale sunt ca un șir de firimituri care îți dezvăluie traseul pe internet — nu le lăsa în urmă!
+zen-welcome-import-description-2 = Adu-le cu ușurință din alt browser și continuă exact de unde ai rămas.
+zen-welcome-import-button = Importă acum
+zen-welcome-set-default-browser = Setează { -brand-short-name } ca browser principal
+zen-welcome-dont-set-default-browser = NU seta { -brand-short-name } ca browser principal
+zen-welcome-initial-essentials-title = Filele tale cheie, întotdeauna la îndemână
+zen-welcome-initial-essentials-description-1 = Păstrează-ți cele mai importante file ușor de accesat, indiferent de câte ai deschise.
+zen-welcome-initial-essentials-description-2 = Filele Esențiale sunt mereu vizibile, indiferent de Spațiul de Lucru în care te afli.
+zen-welcome-workspace-colors-title = Spațiul Tău de Lucru, Culorile Tale
+zen-welcome-workspace-colors-description = Personalizează-ți browser-ul dând fiecărui Spațiu de Lucru o culoare de identitate unică.
 zen-welcome-start-browsing-title =
-    All set?<br/>
-    Let’s get rolling!
-zen-welcome-start-browsing-description-1 = You’re all set up and ready to go. Click the button below to start browsing with { -brand-short-name }.
-zen-welcome-start-browsing = Dive in!
-zen-welcome-default-search-title = Your Default Search Engine
-zen-welcome-default-search-description = Choose your default search engine. You can always change it later!
-zen-welcome-skip-button = Skip
-zen-welcome-finished = Your Zen has been set up correctly!
+    Totul este gata?<br/>
+    Haide să începem!
+zen-welcome-start-browsing-description-1 = Totul este pregătit. Dă click pe butonul de mai jos și începe navigarea cu { -brand-short-name }.
+zen-welcome-start-browsing = Începe acum!
+zen-welcome-default-search-title = Motorul Tău de Căutare Principal
+zen-welcome-default-search-description = Alege-ți motorul tău de căutare principal. Îl poți schimba oricând mai târziu!
+zen-welcome-skip-button = Treci peste
+zen-welcome-finished = Zen-ul tău a fost configurat corect!
diff --git a/locales/ro/browser/browser/zen-workspaces.ftl b/locales/ro/browser/browser/zen-workspaces.ftl
index 7727a2ff2..4a797e137 100644
--- a/locales/ro/browser/browser/zen-workspaces.ftl
+++ b/locales/ro/browser/browser/zen-workspaces.ftl
@@ -2,74 +2,75 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-zen-panel-ui-workspaces-text = Spaces
+zen-panel-ui-workspaces-text = Spații
 zen-panel-ui-spaces-label = 
-    .label = Spaces
+    .label = Spații
 zen-panel-ui-workspaces-create = 
-    .label = Create Space
+    .label = Creează Spațiu
 zen-panel-ui-folder-create = 
-    .label = Create Folder
+    .label = Creează Folder
 zen-panel-ui-live-folder-create = 
-    .label = Live Folder
+    .label = Folder Live
 zen-panel-ui-new-empty-split = 
-    .label = New Split
+    .label = Împărțire nouă
 zen-workspaces-panel-context-delete = 
-    .label = Delete Space
+    .label = Șterge Spațiu
     .accesskey = D
 zen-workspaces-panel-change-name = 
     .label = Change Name
 zen-workspaces-panel-change-icon = 
     .label = Change Icon
 zen-workspaces-panel-context-default-profile = 
-    .label = Set Profile
+    .label = Schimbă profilul
 zen-workspaces-panel-unload = 
-    .label = Unload Space
+    .label = Închide Spațiul
 zen-workspaces-panel-unload-others = 
-    .label = Unload All Other Spaces
-zen-workspaces-how-to-reorder-title = How to reorder spaces
-zen-workspaces-how-to-reorder-desc = Drag the space icons at the bottom of the sidebar to reorder them
+    .label = Închide Toate Celelalte Spații
+zen-workspaces-how-to-reorder-title = Cum să reordonezi spațiile
+zen-workspaces-how-to-reorder-desc = Trage iconițele spațiilor din josul barei laterale pentru a le reordone
 zen-workspaces-change-theme = 
     .label = Edit Theme
 zen-workspaces-panel-context-open = 
-    .label = Open Workspace
+    .label = Deschide Spațiul de Lucru
     .accesskey = O
 zen-workspaces-panel-context-edit = 
-    .label = Edit Space
+    .label = Modifică Spațiul
     .accesskey = E
 zen-bookmark-edit-panel-workspace-selector = 
-    .value = Spaces
+    .value = Spații
     .accesskey = W
 zen-panel-ui-gradient-generator-algo-complementary = 
-    .label = Complementary
+    .label = Complementar
 zen-panel-ui-gradient-generator-algo-splitComplementary = 
-    .label = Split
+    .label = Împărțire
 zen-panel-ui-gradient-generator-algo-analogous = 
-    .label = Analogous
+    .label = Analogic
 zen-panel-ui-gradient-generator-algo-triadic = 
     .label = Triadic
 zen-panel-ui-gradient-generator-algo-floating = 
-    .label = Floating
-zen-panel-ui-gradient-click-to-add = Click to add a color
+    .label = Plutitor
+zen-panel-ui-gradient-click-to-add = Apasă pentru a adăuga o culoare
 zen-workspace-creation-name = 
-    .placeholder = Space Name
+    .placeholder = Numele Spațiului
 zen-move-tab-to-workspace-button = 
     .label = Move To...
-    .tooltiptext = Move all tabs in this window to a Space
+    .tooltiptext = Mută toate filele din această fereastră într-un Spațiu
 zen-workspaces-panel-context-reorder = 
-    .label = Reorder Spaces
-zen-workspace-creation-profile = Profile
-    .tooltiptext = Profiles are used to separate cookies and site data between spaces.
-zen-workspace-creation-header = Create a Space
-zen-workspace-creation-label = Spaces are used to organize your tabs and sessions.
-zen-workspaces-delete-workspace-title = Delete Space?
-zen-workspaces-delete-workspace-body = Are you sure you want to delete { $name }? This action cannot be undone.
+    .label = Reordonează Spațiile
+zen-workspace-creation-profile = Profil
+    .tooltiptext = Profilurile sunt folosite pentru a separa cookie-urile și datele site-ului între spații.
+zen-workspace-creation-header = Creează un Spațiu
+zen-workspace-creation-label = Spațiile sunt folosite pentru a organiza filele și sesiunile tale.
+zen-workspace-default-profile = Implicit
+zen-workspaces-delete-workspace-title = Ștergi Spațiul?
+zen-workspaces-delete-workspace-body = Ești sigur că vrei să ștergi { $name }? Această acțiune nu poate fi anulată.
 # Note that the html tag MUST not be changed or removed, as it is used to better
 # display the shortcut in the toast notification.
-zen-workspaces-close-all-unpinned-tabs-toast = Tabs Closed! Use <span>{ $shortcut }</span> to undo.
+zen-workspaces-close-all-unpinned-tabs-toast = File închise! Apasă <span>{ $shortcut }</span> pentru a anula.
 zen-workspaces-close-all-unpinned-tabs-title = 
-    .label = Clear
-    .tooltiptext = Close all unpinned tabs
+    .label = Curăță
+    .tooltiptext = Închide toate filele nefixate
 zen-panel-ui-workspaces-change-forward = 
-    .label = Next Space
+    .label = Spațiul Următor
 zen-panel-ui-workspaces-change-back = 
-    .label = Previous Space
+    .label = Spațiul Anterior
diff --git a/locales/ru/browser/browser/preferences/zen-preferences.ftl b/locales/ru/browser/browser/preferences/zen-preferences.ftl
index bd2d72876..c4700086f 100644
--- a/locales/ru/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/ru/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Скрыть верхнюю панель инструментов в компактном виде
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Временно отображать панель инструментов при переключении или открытии новых вкладок в компактном виде
+zen-look-and-feel-window-drag-header = Перетаскивание окна
+zen-look-and-feel-window-drag-description = Перемещайте окно, перетаскивая пустое место в верхней части веб-сайтов, так же как и в заголовке.
+zen-window-drag-enabled = 
+    .label = Разрешить перетаскивание окна с веб-страниц
 pane-zen-tabs-title = Управление вкладками
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = Просмотр информации о страниц
 zen-find-shortcut = Найти на странице
 zen-search-find-again-shortcut = Найти следующее
 zen-search-find-again-shortcut-prev = Найти предыдущий
-zen-search-find-again-shortcut-2 = Найти снова (Alt)
+zen-search-find-again-shortcut-alt = Найти снова (Alt)
+zen-search-find-again-shortcut-prev-alt = Найти предыдущий (Alt)
 zen-bookmark-this-page-shortcut = Добавить эту страницу в закладки
 zen-bookmark-show-library-shortcut = Показать библиотеку закладок
 zen-key-stop = Остановить загрузку
@@ -281,7 +286,7 @@ zen-workspace-shortcut-switch-9 = Переключиться на простра
 zen-workspace-shortcut-switch-10 = Переключиться на пространство 10
 zen-workspace-shortcut-forward = Следующее пространство
 zen-workspace-shortcut-backward = Предыдущее пространство
-zen-workspace-shortcut-create = Create New Workspace
+zen-workspace-shortcut-create = Создать новое рабочее пространство
 zen-sidebar-shortcut-toggle = Ширина боковой панели
 zen-pinned-tab-shortcut-reset = Восстановить адрес закрепленной вкладки
 zen-split-view-shortcut-grid = Переключить разделение сетки вида
@@ -319,4 +324,4 @@ zen-devtools-toggle-accessibility-shortcut = Включить/выключить
 zen-close-all-unpinned-tabs-shortcut = Закрыть все не закреплённые вкладки
 zen-new-unsynced-window-shortcut = Новое пустое окно
 zen-duplicate-tab-shortcut = Дублировать вкладку
-zen-key-find-selection = Find Selection
+zen-key-find-selection = Найти выбранное
diff --git a/locales/ru/browser/browser/zen-boosts.ftl b/locales/ru/browser/browser/zen-boosts.ftl
index eb42026a7..d3b17d1c1 100644
--- a/locales/ru/browser/browser/zen-boosts.ftl
+++ b/locales/ru/browser/browser/zen-boosts.ftl
@@ -3,56 +3,57 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 zen-boost-edit-rename = 
-    .label = Rename Boost
+    .label = Переименовать стиль
 zen-boost-edit-shuffle = 
-    .label = Shuffle Vibes
+    .label = Сменить настроение
 zen-boost-edit-reset = 
-    .label = Reset All Edits
+    .label = Сбросить все изменения
 zen-boost-edit-delete = 
-    .label = Delete Boost
-zen-boost-size = Size
-zen-boost-case = Case
-zen-boost-zap = Zap
-zen-boost-code = Code
-zen-boost-back = Back
+    .label = Удалить стиль
+zen-boost-size = Размер
+zen-boost-case = Регистр
+zen-boost-zap = Ластик
+zen-boost-code = Код
+zen-boost-back = Назад
 zen-boost-shuffle = 
-    .tooltiptext = Shuffle Boost Settings
+    .tooltiptext = Перемешать настройки стиля
 zen-boost-invert = 
-    .tooltiptext = Smart Invert Colors
+    .tooltiptext = Умная инверсия цвета
 zen-boost-controls = 
-    .tooltiptext = Advanced Color Controls
+    .tooltiptext = Расширенные параметры цвета
 zen-boost-disable = 
-    .tooltiptext = Disable Color Adjustments
+    .tooltiptext = Отключить изменения цвета
 zen-boost-text-case-toggle = 
-    .tooltiptext = Toggle Text Case
+    .tooltiptext = Изменить регистр текста
 zen-boost-css-picker = 
-    .tooltiptext = Pick Selector
+    .tooltiptext = Выбрать селектор
 zen-boost-css-inspector = 
-    .tooltiptext = Open Inspector
-zen-boost-color-contrast = Contrast
-zen-boost-color-brightness = Brightness
-zen-boost-color-original-saturation = Original Saturation
-zen-add-zap-helper = Click elements on the page to <b>Zap</b> them
-zen-remove-zap-helper = ← Click to Unzap
-zen-select-this = Insert selector for this
-zen-select-related = Insert selector for related
-zen-select-cancel = Cancel
-zen-zap-this = Zap this
-zen-zap-related = Zap all related elements
-zen-zap-cancel = Cancel
-zen-zap-done = Done
+    .tooltiptext = Открыть инспектор
+zen-boost-color-contrast = Контраст
+zen-boost-color-brightness = Яркость
+zen-boost-color-original-saturation = Исходная насыщенность
+zen-add-zap-helper = Нажимайте по элементам на странице чтобы <b>стереть</b> их
+zen-remove-zap-helper = ← Нажмите, чтобы вернуть
+zen-select-this = Вставить селектор для этого
+zen-select-related = Вставить селектор для связанного
+zen-select-cancel = Отменить
+zen-zap-this = Стереть это
+zen-zap-related = Стереть всё связанное
+zen-zap-cancel = Отменить
+zen-zap-done = Готово
 zen-unzap-tooltip =
     { $elementCount ->
-        [0] No elements zapped
-        [1] { $elementCount } element zapped
-       *[other] { $elementCount } elements zapped
+        [0] Нет стёртых элементов
+        [1] Стёрт { $elementCount } элемент
+        [few] Стёрто { $elementCount } элемента
+       *[other] Стёрто { $elementCount } элементов
     }
 zen-boost-save = 
-    .label = Export Boost
+    .label = Экспортировать стиль
 zen-boost-load = 
-    .label = Import Boost
-zen-panel-ui-boosts-exported-message = Boost exported!
-zen-site-data-boosts = Boosts
+    .label = Импортировать стиль
+zen-panel-ui-boosts-exported-message = Стиль экспортирован!
+zen-site-data-boosts = Стили
 zen-site-data-create-boost = 
-    .tooltiptext = Create new boost
-zen-boost-rename-boost-prompt = Rename Boost?
+    .tooltiptext = Создать новый стиль
+zen-boost-rename-boost-prompt = Переименовать стиль?
diff --git a/locales/ru/browser/browser/zen-command-palette.ftl b/locales/ru/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..d20810455
--- /dev/null
+++ b/locales/ru/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Переключить компактный режим
+zen-action-open-theme-picker = Открыть выбор темы
+zen-action-new-split-view = Новая разделённая вкладка
+zen-action-new-folder = Новая папка
+zen-action-copy-current-url = Скопировать текущую ссылку
+zen-action-settings = Настройки
+zen-action-open-private-window = Открыть новое приватное окно
+zen-action-open-new-window = Открыть новое окно
+zen-action-new-blank-window = Новое пустое окно
+zen-action-pin-tab = Закрепить вкладку
+zen-action-unpin-tab = Открепить вкладку
+zen-action-open-space-routing = Открыть маршрутизацию пространств
+zen-action-new-boost = Новый стиль
+zen-action-next-space = Следующее пространство
+zen-action-previous-space = Предыдущее пространство
+zen-action-close-tab = Закрыть вкладку
+zen-action-reload-tab = Перезагрузить вкладку
+zen-action-reload-tab-without-cache = Перезагрузить вкладку без кэша
+zen-action-next-tab = Следующая вкладка
+zen-action-previous-tab = Предыдущая вкладка
+zen-action-capture-screenshot = Сделать скриншот
+zen-action-toggle-tabs-on-right = Переключить вкладки справа
+zen-action-add-to-essentials = Добавить в важное
+zen-action-remove-from-essentials = Удалить из важного
+zen-action-find-in-page = Найти на странице
+zen-action-manage-extensions = Управление расширениями
+zen-action-switch-to-automatic-appearance = Переключиться на автоматический вид
+zen-action-switch-to-light-mode = Переключиться на светлую тему
+zen-action-switch-to-dark-mode = Переключиться на темную тему
+zen-action-print = Печать
+zen-action-focus-on = Сфокусироваться на
+zen-action-extension = Расширения
diff --git a/locales/ru/browser/browser/zen-general.ftl b/locales/ru/browser/browser/zen-general.ftl
index d5d80ae37..2859b48d7 100644
--- a/locales/ru/browser/browser/zen-general.ftl
+++ b/locales/ru/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num }/{ $max } мест занято
 tab-context-zen-remove-essential = 
     .label = Удалить из важного
     .accesskey = К
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Заменить адрес важной вкладки на текущий
-           *[false] Заменить адрес закреплённой вкладки на текущий
+            [true] Изменить URL-адрес из важного
+           *[false] Изменить закрепленный URL-адрес
         }
+    .accesskey = З
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Заменить текущим URL-адресом
     .accesskey = С
+tab-context-zen-edit-pinned-url = 
+    .label = Редактировать…
+    .accesskey = У
 tab-context-zen-edit-title = 
     .label = Переименовать...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Подтвердить
 zen-pinned-tab-replaced = Адрес закреплённой вкладки заменён на текущий адрес!
+zen-pinned-tab-url-edited = Ссылка на закрепленную вкладку обновлена!
+zen-pinned-tab-url-invalid = Это не похоже на допустимый URL.
+zen-pinned-tab-edit-url-title = Редактировать прикрепленный URL
+zen-pinned-tab-edit-url-label = Введите URL на который должна вести эта вкладка:
 zen-tabs-renamed = Вкладка успешно переименована!
 zen-background-tab-opened-toast = Открыта новая фоновая вкладка!
 zen-workspace-renamed-toast = Пространство успешно переименовано!
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = Эмодзи
 zen-icons-picker-svg = 
     .label = Иконки
+zen-emojis-picker-search = 
+    .placeholder = Поиск эмодзи
 urlbar-search-mode-zen_actions = Действия
 zen-site-data-settings = Настройки
 zen-generic-manage = Изменить
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = Обновление завершен
 zen-sidebar-notification-updated-label = Что нового в { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = Примечания к выпуску
+zen-sidebar-notification-donate-label = Поддержать { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Поддержать проект
 zen-sidebar-notification-restart-safe-mode-label = Что-то пошло не так?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Перезапустить в безопасном режиме
diff --git a/locales/ru/browser/browser/zen-space-routing.ftl b/locales/ru/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..7cea799a2
--- /dev/null
+++ b/locales/ru/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Настройки маршрутизации
+zen-space-routing-rulepanel-placeholder = Маршруты позволяют настроить где каждый конкретный сайт будет открываться. Например, вы можете настроить чтобы ссылки на YouTube всегда открывались в пространстве "Личное".
+zen-space-routing-dialog-title = Маршрутизация пространств
+zen-space-routing-external-default = Стандартный маршрут для внешних ссылок
+zen-space-routing-new-route = Новый маршрут
+zen-space-routing-open-in-space = Открывать в пространстве
+zen-space-routing-most-recent-space = Последнее активное
+zen-space-routing-close-button = 
+    .aria-label = Закрыть
+    .tooltiptext = Закрыть
+zen-space-routing-contains = 
+    .label = Содержит
+zen-space-routing-equal-to = 
+    .label = Совпадает с
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Открывать в
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = Новая вкладка открыта в { $targetWorkspace}
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Добавить маршрутизацию для домена
+           *[other] Добавить маршрутизацию для доменов
+        }
diff --git a/locales/ru/browser/browser/zen-split-view.ftl b/locales/ru/browser/browser/zen-split-view.ftl
index b89b20b46..70be52875 100644
--- a/locales/ru/browser/browser/zen-split-view.ftl
+++ b/locales/ru/browser/browser/zen-split-view.ftl
@@ -5,9 +5,10 @@
 tab-zen-split-tabs = 
     .label =
         { $tabCount ->
-            [-1] Split out tab
-            [1] Add split view...
-           *[other] Join { $tabCount } Tabs
+            [-1] Убрать из разделения
+            [1] Добавить разделённую вкладку
+            [few] Объединить { $tabCount } вкладки
+           *[other] Объединить { $tabCount } вкладок
         }
     .accesskey = Ы
 zen-split-link = 
diff --git a/locales/ru/browser/browser/zen-workspaces.ftl b/locales/ru/browser/browser/zen-workspaces.ftl
index 6ec6134bf..ea5b5819e 100644
--- a/locales/ru/browser/browser/zen-workspaces.ftl
+++ b/locales/ru/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Профиль
     .tooltiptext = Профили используются для разделения файлов куки и данных сайта между пространствами.
 zen-workspace-creation-header = Создать пространство
 zen-workspace-creation-label = Пространства используются для организации ваших вкладок и сеансов.
+zen-workspace-default-profile = По умолчанию
 zen-workspaces-delete-workspace-title = Удалить пространство?
 zen-workspaces-delete-workspace-body = Вы уверены, что хотите удалить { $name }? Это действие необратимо.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/sk/browser/browser/preferences/zen-preferences.ftl b/locales/sk/browser/browser/preferences/zen-preferences.ftl
index ba3976eb2..17d8a7de1 100644
--- a/locales/sk/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/sk/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = V kompaktnom režime skryť aj horný panel nástrojov
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Pri prepínaní alebo otváraní nových kariet v kompaktnom režime nakrátko zobraziť panel nástrojov
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Allow dragging the window from web pages
 pane-zen-tabs-title = Správa kariet
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = Zobraziť zdroj stránky
 zen-find-shortcut = Hľadať na stránke
 zen-search-find-again-shortcut = Hľadať znova
 zen-search-find-again-shortcut-prev = Hľadať predchádzajúce
-zen-search-find-again-shortcut-2 = Hľadať znova (Alt)
+zen-search-find-again-shortcut-alt = Find Again (Alt)
+zen-search-find-again-shortcut-prev-alt = Find Previous (Alt)
 zen-bookmark-this-page-shortcut = Pridať stránku do záložiek
 zen-bookmark-show-library-shortcut = Zobraziť knižnicu záložiek
 zen-key-stop = Zastaviť načítanie
diff --git a/locales/sk/browser/browser/zen-boosts.ftl b/locales/sk/browser/browser/zen-boosts.ftl
index eb42026a7..919d84b9c 100644
--- a/locales/sk/browser/browser/zen-boosts.ftl
+++ b/locales/sk/browser/browser/zen-boosts.ftl
@@ -3,18 +3,18 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 zen-boost-edit-rename = 
-    .label = Rename Boost
+    .label = Premenovať Boost
 zen-boost-edit-shuffle = 
     .label = Shuffle Vibes
 zen-boost-edit-reset = 
     .label = Reset All Edits
 zen-boost-edit-delete = 
-    .label = Delete Boost
-zen-boost-size = Size
+    .label = Odstrániť Boost
+zen-boost-size = Velkosť
 zen-boost-case = Case
 zen-boost-zap = Zap
-zen-boost-code = Code
-zen-boost-back = Back
+zen-boost-code = Kód
+zen-boost-back = Späť
 zen-boost-shuffle = 
     .tooltiptext = Shuffle Boost Settings
 zen-boost-invert = 
@@ -36,7 +36,7 @@ zen-add-zap-helper = Click elements on the page to <b>Zap</b> them
 zen-remove-zap-helper = ← Click to Unzap
 zen-select-this = Insert selector for this
 zen-select-related = Insert selector for related
-zen-select-cancel = Cancel
+zen-select-cancel = Zrušiť
 zen-zap-this = Zap this
 zen-zap-related = Zap all related elements
 zen-zap-cancel = Cancel
@@ -55,4 +55,4 @@ zen-panel-ui-boosts-exported-message = Boost exported!
 zen-site-data-boosts = Boosts
 zen-site-data-create-boost = 
     .tooltiptext = Create new boost
-zen-boost-rename-boost-prompt = Rename Boost?
+zen-boost-rename-boost-prompt = Premenovať Boost?
diff --git a/locales/sk/browser/browser/zen-command-palette.ftl b/locales/sk/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..c8af413e2
--- /dev/null
+++ b/locales/sk/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Toggle Compact Mode
+zen-action-open-theme-picker = Open Theme Picker
+zen-action-new-split-view = New Split View
+zen-action-new-folder = New Folder
+zen-action-copy-current-url = Copy Current URL
+zen-action-settings = Settings
+zen-action-open-private-window = Open Private Window
+zen-action-open-new-window = Open New Window
+zen-action-new-blank-window = New Blank Window
+zen-action-pin-tab = Pin Tab
+zen-action-unpin-tab = Unpin Tab
+zen-action-open-space-routing = Open Space Routing
+zen-action-new-boost = New Boost
+zen-action-next-space = Next Space
+zen-action-previous-space = Previous Space
+zen-action-close-tab = Close Tab
+zen-action-reload-tab = Reload Tab
+zen-action-reload-tab-without-cache = Reload Tab Without Cache
+zen-action-next-tab = Next Tab
+zen-action-previous-tab = Previous Tab
+zen-action-capture-screenshot = Capture Screenshot
+zen-action-toggle-tabs-on-right = Toggle Tabs on right
+zen-action-add-to-essentials = Add to Essentials
+zen-action-remove-from-essentials = Remove from Essentials
+zen-action-find-in-page = Find in Page
+zen-action-manage-extensions = Manage Extensions
+zen-action-switch-to-automatic-appearance = Switch to Automatic Appearance
+zen-action-switch-to-light-mode = Switch to Light Mode
+zen-action-switch-to-dark-mode = Switch to Dark Mode
+zen-action-print = Print
+zen-action-focus-on = Focus on
+zen-action-extension = Extension
diff --git a/locales/sk/browser/browser/zen-general.ftl b/locales/sk/browser/browser/zen-general.ftl
index 2768b6852..a3ec4bd7a 100644
--- a/locales/sk/browser/browser/zen-general.ftl
+++ b/locales/sk/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = Využité pozície: { $num } / { $max }
 tab-context-zen-remove-essential = 
     .label = Odstrániť z hlavných
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Replace Essential URL with Current
-           *[false] Replace Pinned URL with Current
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Replace with Current URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Edit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Zmeniť Označenie...
 tab-context-zen-edit-icon = 
@@ -45,6 +51,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Potvrdiť
 zen-pinned-tab-replaced = URL pripnutej karty bola nahradená aktuálnou URL!
+zen-pinned-tab-url-edited = Pinned tab URL has been updated!
+zen-pinned-tab-url-invalid = That doesn't look like a valid URL.
+zen-pinned-tab-edit-url-title = Edit Pinned URL
+zen-pinned-tab-edit-url-label = Enter the URL this pinned tab should point to:
 zen-tabs-renamed = Karta bola úspešne premenovaná!
 zen-background-tab-opened-toast = Nová karta otvorená na pozadí!
 zen-workspace-renamed-toast = Pracovný priestor bol úspešne premenovaný!
@@ -63,6 +73,8 @@ zen-icons-picker-emoji =
     .label = Emoji
 zen-icons-picker-svg = 
     .label = Ikony
+zen-emojis-picker-search = 
+    .placeholder = Search emojis
 urlbar-search-mode-zen_actions = Akcie
 zen-site-data-settings = Nastavenia
 zen-generic-manage = Spravovať
@@ -114,6 +126,9 @@ zen-sidebar-notification-updated-heading = Aktualizácia Dokončená!
 zen-sidebar-notification-updated-label = Čo je nové v { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = Zobraziť Poznámky k Vydaniu
+zen-sidebar-notification-donate-label = Support { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donate to the project
 zen-sidebar-notification-restart-safe-mode-label = Niečo sa pokazilo?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Reštartovať v Núdzovom Režime
diff --git a/locales/sk/browser/browser/zen-space-routing.ftl b/locales/sk/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..d757144bb
--- /dev/null
+++ b/locales/sk/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Space Routing Settings
+zen-space-routing-rulepanel-placeholder = Routes let you choose where specific sites open inside Zen. For example, you can route YouTube links to always open inside your Personal space.
+zen-space-routing-dialog-title = Space Routing Settings
+zen-space-routing-external-default = Default route for external links
+zen-space-routing-new-route = New Route
+zen-space-routing-open-in-space = Open in Space
+zen-space-routing-most-recent-space = Most recent Space
+zen-space-routing-close-button = 
+    .aria-label = Close
+    .tooltiptext = Close
+zen-space-routing-contains = 
+    .label = Contains
+zen-space-routing-equal-to = 
+    .label = Is Equal To
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Open In
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/sk/browser/browser/zen-workspaces.ftl b/locales/sk/browser/browser/zen-workspaces.ftl
index 5b93a0502..af3539cfb 100644
--- a/locales/sk/browser/browser/zen-workspaces.ftl
+++ b/locales/sk/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Profil
     .tooltiptext = Profily sa používajú na oddelenie súborov cookie a údajov stránok medzi priestormi.
 zen-workspace-creation-header = Vytvoriť priestor
 zen-workspace-creation-label = Priestory sa používajú na organizáciu vašich kariet a relácií.
+zen-workspace-default-profile = Default
 zen-workspaces-delete-workspace-title = Odstrániť priestor?
 zen-workspaces-delete-workspace-body = Naozaj chcete odstrániť priestor { $name }? Túto akciu nie je možné vrátiť späť.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/sv-SE/browser/browser/preferences/zen-preferences.ftl b/locales/sv-SE/browser/browser/preferences/zen-preferences.ftl
index fca5ef3b3..bd3569ba1 100644
--- a/locales/sv-SE/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/sv-SE/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Dölj det övre verktygsfältet samt i kompakt läge
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Gör kort popup i verktygsfältet när du växlar eller öppnar nya flikar i kompakt läge
+zen-look-and-feel-window-drag-header = Fönsterdragning
+zen-look-and-feel-window-drag-description = Flytta fönstret genom att dra tomt utrymme högst upp på webbplatser, precis som titelfältet.
+zen-window-drag-enabled = 
+    .label = Tillåt att dra i fönstret från webbsidor
 pane-zen-tabs-title = Flikhantering
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = Visa sidinformation
 zen-find-shortcut = Hitta på sidan
 zen-search-find-again-shortcut = Hitta igen
 zen-search-find-again-shortcut-prev = Hitta föregående
-zen-search-find-again-shortcut-2 = Hitta igen (Alt)
+zen-search-find-again-shortcut-alt = Hitta igen (Alt)
+zen-search-find-again-shortcut-prev-alt = Hitta föregående (Alt)
 zen-bookmark-this-page-shortcut = Bokmärk denna sida
 zen-bookmark-show-library-shortcut = Visa bokmärkesbibliotek
 zen-key-stop = Sluta ladda
diff --git a/locales/sv-SE/browser/browser/zen-command-palette.ftl b/locales/sv-SE/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..188732cf2
--- /dev/null
+++ b/locales/sv-SE/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Växla kompakt läge
+zen-action-open-theme-picker = Öppna temaväljare
+zen-action-new-split-view = Ny delad vy
+zen-action-new-folder = Ny mapp
+zen-action-copy-current-url = Kopiera nuvarande URL
+zen-action-settings = Inställningar
+zen-action-open-private-window = Öppna privat fönster
+zen-action-open-new-window = Öppna nytt fönster
+zen-action-new-blank-window = Nytt blankt fönster
+zen-action-pin-tab = Fäst flik
+zen-action-unpin-tab = Avfäst flik
+zen-action-open-space-routing = Rutter med öppet utrymme
+zen-action-new-boost = Ny boost
+zen-action-next-space = Nästa arbetsyta
+zen-action-previous-space = Föregående arbetsyta
+zen-action-close-tab = Stäng flik
+zen-action-reload-tab = Ladda om flik
+zen-action-reload-tab-without-cache = Ladda om flik utan cache
+zen-action-next-tab = Nästa flik
+zen-action-previous-tab = Föregående flik
+zen-action-capture-screenshot = Fånga skärmdump
+zen-action-toggle-tabs-on-right = Växla flikar till höger
+zen-action-add-to-essentials = Lägg till Essentials
+zen-action-remove-from-essentials = Ta bort från Essentials
+zen-action-find-in-page = Hitta på sida
+zen-action-manage-extensions = Hantera tillägg
+zen-action-switch-to-automatic-appearance = Växla till automatiskt utseende
+zen-action-switch-to-light-mode = Växla till ljust läge
+zen-action-switch-to-dark-mode = Växla till mörkt läge
+zen-action-print = Skriv ut
+zen-action-focus-on = Fokus på
+zen-action-extension = Tillägg
diff --git a/locales/sv-SE/browser/browser/zen-general.ftl b/locales/sv-SE/browser/browser/zen-general.ftl
index db279ce9e..a16329b25 100644
--- a/locales/sv-SE/browser/browser/zen-general.ftl
+++ b/locales/sv-SE/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max } platser fyllda
 tab-context-zen-remove-essential = 
     .label = Ta bort från Essentials
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Ersätt Essential webbadress med nuvarande
-           *[false] Ersätt fäst webbadress med nuvarande
+            [true] Redigera Essential URL
+           *[false] Redigera fäst URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Ersätt med nuvarande URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Redigera…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Ändra etikett...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Bekräfta
 zen-pinned-tab-replaced = Den fästa flikens URL har ersatts med den aktuella URL!
+zen-pinned-tab-url-edited = Fäst flik URL har uppdaterats!
+zen-pinned-tab-url-invalid = Det ser inte ut som en giltig URL.
+zen-pinned-tab-edit-url-title = Redigera fäst URL
+zen-pinned-tab-edit-url-label = Ange den URL som den fästa fliken ska peka till:
 zen-tabs-renamed = Fliken har fått nytt namn!
 zen-background-tab-opened-toast = Ny bakgrundsflik öppnad!
 zen-workspace-renamed-toast = Arbetsytan har fått ett nytt namn!
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = Emojis
 zen-icons-picker-svg = 
     .label = Ikoner
+zen-emojis-picker-search = 
+    .placeholder = Sök emojis
 urlbar-search-mode-zen_actions = Åtgärder
 zen-site-data-settings = Inställningar
 zen-generic-manage = Hantera
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = Uppdatering slutförd!
 zen-sidebar-notification-updated-label = Vad är nytt i { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = Visa versionsfakta
+zen-sidebar-notification-donate-label = Stöd { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donera till projektet
 zen-sidebar-notification-restart-safe-mode-label = Har något gått sönder?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Starta om i felsäkert läge
diff --git a/locales/sv-SE/browser/browser/zen-space-routing.ftl b/locales/sv-SE/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..02b6dfd95
--- /dev/null
+++ b/locales/sv-SE/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Inställningar för ruttning av utrymme
+zen-space-routing-rulepanel-placeholder = Med rutter kan du välja var specifika webbplatser öppnas i Zen. Du kan till exempel dirigera YouTube-länkar så att de alltid öppnas i ditt personliga utrymme.
+zen-space-routing-dialog-title = Inställningar för ruttning av utrymme
+zen-space-routing-external-default = Standardrutt för externa länkar
+zen-space-routing-new-route = Ny rutt
+zen-space-routing-open-in-space = Öppna i utrymme
+zen-space-routing-most-recent-space = Mest senaste utrymme
+zen-space-routing-close-button = 
+    .aria-label = Stäng
+    .tooltiptext = Stäng
+zen-space-routing-contains = 
+    .label = Innehåller
+zen-space-routing-equal-to = 
+    .label = Är lika med
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Öppna i
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = Ny flik öppnad i { $targetWorkspace}
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Lägg till rutt för domän
+           *[other] Lägg till rutter för domäner
+        }
diff --git a/locales/sv-SE/browser/browser/zen-workspaces.ftl b/locales/sv-SE/browser/browser/zen-workspaces.ftl
index 6ad05c202..62a62cca6 100644
--- a/locales/sv-SE/browser/browser/zen-workspaces.ftl
+++ b/locales/sv-SE/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Profil
     .tooltiptext = Profiler används för att separera kakor och webbplatsdata mellan arbetsytor.
 zen-workspace-creation-header = Skapa en arbetsyta
 zen-workspace-creation-label = Arbetsytor används för att organisera dina flikar och sessioner.
+zen-workspace-default-profile = Standard
 zen-workspaces-delete-workspace-title = Ta bort arbetsyta?
 zen-workspaces-delete-workspace-body = Är du säker på att du vill radera { $name }? den här åtgärden kan inte ångras.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/th/browser/browser/preferences/zen-preferences.ftl b/locales/th/browser/browser/preferences/zen-preferences.ftl
index 4a8417a09..682177f3d 100644
--- a/locales/th/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/th/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = ซ่อนแถบเครื่องมือด้านบนด้วยในโหมดกะทัดรัด
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = แสดงแถบเครื่องมือชั่วขณะเมื่อสลับแท็บหรือเปิดแท็บใหม่ในโหมดกะทัดรัด
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Allow dragging the window from web pages
 pane-zen-tabs-title = การจัดการแท็บ
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = View Page Info
 zen-find-shortcut = ค้นหาในหน้านี้
 zen-search-find-again-shortcut = ค้นหาอีกครั้ง
 zen-search-find-again-shortcut-prev = ค้นหาก่อนหน้านี้
-zen-search-find-again-shortcut-2 = ค้นหาอีกครั้ง (Alt)
+zen-search-find-again-shortcut-alt = Find Again (Alt)
+zen-search-find-again-shortcut-prev-alt = Find Previous (Alt)
 zen-bookmark-this-page-shortcut = Bookmark This Page
 zen-bookmark-show-library-shortcut = Show Bookmarks Library
 zen-key-stop = หยุดการโหลด
diff --git a/locales/th/browser/browser/zen-command-palette.ftl b/locales/th/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..c8af413e2
--- /dev/null
+++ b/locales/th/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Toggle Compact Mode
+zen-action-open-theme-picker = Open Theme Picker
+zen-action-new-split-view = New Split View
+zen-action-new-folder = New Folder
+zen-action-copy-current-url = Copy Current URL
+zen-action-settings = Settings
+zen-action-open-private-window = Open Private Window
+zen-action-open-new-window = Open New Window
+zen-action-new-blank-window = New Blank Window
+zen-action-pin-tab = Pin Tab
+zen-action-unpin-tab = Unpin Tab
+zen-action-open-space-routing = Open Space Routing
+zen-action-new-boost = New Boost
+zen-action-next-space = Next Space
+zen-action-previous-space = Previous Space
+zen-action-close-tab = Close Tab
+zen-action-reload-tab = Reload Tab
+zen-action-reload-tab-without-cache = Reload Tab Without Cache
+zen-action-next-tab = Next Tab
+zen-action-previous-tab = Previous Tab
+zen-action-capture-screenshot = Capture Screenshot
+zen-action-toggle-tabs-on-right = Toggle Tabs on right
+zen-action-add-to-essentials = Add to Essentials
+zen-action-remove-from-essentials = Remove from Essentials
+zen-action-find-in-page = Find in Page
+zen-action-manage-extensions = Manage Extensions
+zen-action-switch-to-automatic-appearance = Switch to Automatic Appearance
+zen-action-switch-to-light-mode = Switch to Light Mode
+zen-action-switch-to-dark-mode = Switch to Dark Mode
+zen-action-print = Print
+zen-action-focus-on = Focus on
+zen-action-extension = Extension
diff --git a/locales/th/browser/browser/zen-general.ftl b/locales/th/browser/browser/zen-general.ftl
index c8f27e979..8ad5243d8 100644
--- a/locales/th/browser/browser/zen-general.ftl
+++ b/locales/th/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max } slots filled
 tab-context-zen-remove-essential = 
     .label = Remove from Essentials
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Replace Essential URL with Current
-           *[false] Replace Pinned URL with Current
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Replace with Current URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Edit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Change Label...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = ยืนยัน
 zen-pinned-tab-replaced = Pinned tab URL has been replaced with the current URL.
+zen-pinned-tab-url-edited = Pinned tab URL has been updated!
+zen-pinned-tab-url-invalid = That doesn't look like a valid URL.
+zen-pinned-tab-edit-url-title = Edit Pinned URL
+zen-pinned-tab-edit-url-label = Enter the URL this pinned tab should point to:
 zen-tabs-renamed = Tab has been successfully renamed!
 zen-background-tab-opened-toast = New background tab opened!
 zen-workspace-renamed-toast = Workspace has been successfully renamed!
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = อิโมจิ
 zen-icons-picker-svg = 
     .label = ไอคอน
+zen-emojis-picker-search = 
+    .placeholder = Search emojis
 urlbar-search-mode-zen_actions = Actions
 zen-site-data-settings = การตั้งค่า
 zen-generic-manage = จัดการ
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = อัปเดตเสร็จส
 zen-sidebar-notification-updated-label = มีอะไรใหม่ใน { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = View Release Notes
+zen-sidebar-notification-donate-label = Support { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donate to the project
 zen-sidebar-notification-restart-safe-mode-label = Something broke?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Restart in Safe Mode
diff --git a/locales/th/browser/browser/zen-space-routing.ftl b/locales/th/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..d757144bb
--- /dev/null
+++ b/locales/th/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Space Routing Settings
+zen-space-routing-rulepanel-placeholder = Routes let you choose where specific sites open inside Zen. For example, you can route YouTube links to always open inside your Personal space.
+zen-space-routing-dialog-title = Space Routing Settings
+zen-space-routing-external-default = Default route for external links
+zen-space-routing-new-route = New Route
+zen-space-routing-open-in-space = Open in Space
+zen-space-routing-most-recent-space = Most recent Space
+zen-space-routing-close-button = 
+    .aria-label = Close
+    .tooltiptext = Close
+zen-space-routing-contains = 
+    .label = Contains
+zen-space-routing-equal-to = 
+    .label = Is Equal To
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Open In
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/th/browser/browser/zen-workspaces.ftl b/locales/th/browser/browser/zen-workspaces.ftl
index ae5110fae..d5019ef48 100644
--- a/locales/th/browser/browser/zen-workspaces.ftl
+++ b/locales/th/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Profile
     .tooltiptext = Profiles are used to separate cookies and site data between spaces.
 zen-workspace-creation-header = Create a Space
 zen-workspace-creation-label = Spaces are used to organize your tabs and sessions.
+zen-workspace-default-profile = Default
 zen-workspaces-delete-workspace-title = Delete Workspace?
 zen-workspaces-delete-workspace-body = Are you sure you want to delete { $name }? This action cannot be undone.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/tr/browser/browser/preferences/zen-preferences.ftl b/locales/tr/browser/browser/preferences/zen-preferences.ftl
index 44f39df3c..9579823cd 100644
--- a/locales/tr/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/tr/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Kompakt modda üst araç çubuğunu gizle
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Kompakt modda yeni sekmeler arasında geçiş yaparken veya yeni sekmeler açarken araç çubuğunun açılır penceresini aktif edin
+zen-look-and-feel-window-drag-header = Pencere sürükleme
+zen-look-and-feel-window-drag-description = Web sitelerinin üst kısmındaki boş alanı tıpkı başlık çubuğu gibi sürükleyerek pencereyi taşıyın.
+zen-window-drag-enabled = 
+    .label = Pencerenin web sayfalarından sürüklenmesine izin ver
 pane-zen-tabs-title = Sekme Yönetimi
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = Sayfa detaylarını görüntüle
 zen-find-shortcut = Sayfada bul
 zen-search-find-again-shortcut = Tekrar ara
 zen-search-find-again-shortcut-prev = Öncekini ara
-zen-search-find-again-shortcut-2 = Tekrar ara (Alt)
+zen-search-find-again-shortcut-alt = Tekrar bul (Alt)
+zen-search-find-again-shortcut-prev-alt = Öncekini bul (Alt)
 zen-bookmark-this-page-shortcut = Sayfayı yer imlerine ekle
 zen-bookmark-show-library-shortcut = Yer imleri kütüphanesini göster
 zen-key-stop = Yüklemeyi durdur
diff --git a/locales/tr/browser/browser/zen-boosts.ftl b/locales/tr/browser/browser/zen-boosts.ftl
index 5e5e94f13..e1437331e 100644
--- a/locales/tr/browser/browser/zen-boosts.ftl
+++ b/locales/tr/browser/browser/zen-boosts.ftl
@@ -3,13 +3,13 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 zen-boost-edit-rename = 
-    .label = Boost’u yeniden adlandır
+    .label = Boostu yeniden adlandır
 zen-boost-edit-shuffle = 
     .label = Vibe'ları karıştır
 zen-boost-edit-reset = 
     .label = Tüm düzenlemeleri sıfırla
 zen-boost-edit-delete = 
-    .label = Boost’u sil
+    .label = Boostu sil
 zen-boost-size = Boyut
 zen-boost-case = Büyük/küçük harf
 zen-boost-zap = Zap
@@ -48,11 +48,11 @@ zen-unzap-tooltip =
        *[other] { $elementCount } öge Zap’lenmiş
     }
 zen-boost-save = 
-    .label = Boost’u dışa aktar
+    .label = Boostu dışa aktar
 zen-boost-load = 
-    .label = Boost’u içe aktar
+    .label = Boostu içe aktar
 zen-panel-ui-boosts-exported-message = Boost dışa aktarıldı!
-zen-site-data-boosts = Boost'lar
+zen-site-data-boosts = Boostlar
 zen-site-data-create-boost = 
-    .tooltiptext = Yeni Boost oluştur
+    .tooltiptext = Yeni boost oluştur
 zen-boost-rename-boost-prompt = Boost yeniden adlandırılsın mı?
diff --git a/locales/tr/browser/browser/zen-command-palette.ftl b/locales/tr/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..e7eb78b19
--- /dev/null
+++ b/locales/tr/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Kompakt modu aç/kapat
+zen-action-open-theme-picker = Tema seçiciyi aç
+zen-action-new-split-view = Yeni bölünmüş görünüm
+zen-action-new-folder = Yeni klasör
+zen-action-copy-current-url = Geçerli URL'yi kopyala
+zen-action-settings = Ayarlar
+zen-action-open-private-window = Gizli pencere aç
+zen-action-open-new-window = Yeni pencere aç
+zen-action-new-blank-window = Yeni boş pencere
+zen-action-pin-tab = Sekmeyi sabitle
+zen-action-unpin-tab = Sabitlemeyi kaldır
+zen-action-open-space-routing = Alan yönlendirmesini aç
+zen-action-new-boost = Yeni boost
+zen-action-next-space = Sonraki alan
+zen-action-previous-space = Önceli alan
+zen-action-close-tab = Sekmeyi kapat
+zen-action-reload-tab = Sekmeyi yenile
+zen-action-reload-tab-without-cache = Sekmeyi önbelleksiz yenile
+zen-action-next-tab = Sonraki sekme
+zen-action-previous-tab = Önceki sekme
+zen-action-capture-screenshot = Ekran görüntüsü al
+zen-action-toggle-tabs-on-right = Sekmeler sağda olsun
+zen-action-add-to-essentials = Temel sekmelere ekle
+zen-action-remove-from-essentials = Temel sekmelerden kaldır
+zen-action-find-in-page = Sayfada bul
+zen-action-manage-extensions = Uzantıları yönet
+zen-action-switch-to-automatic-appearance = Otomatik görünüme geç
+zen-action-switch-to-light-mode = Açık moda geç
+zen-action-switch-to-dark-mode = Koyu moda geç
+zen-action-print = Yazdır
+zen-action-focus-on = Odaklan
+zen-action-extension = Uzantı
diff --git a/locales/tr/browser/browser/zen-folders.ftl b/locales/tr/browser/browser/zen-folders.ftl
index a91c65ccf..650749081 100644
--- a/locales/tr/browser/browser/zen-folders.ftl
+++ b/locales/tr/browser/browser/zen-folders.ftl
@@ -5,17 +5,17 @@
 zen-folders-search-placeholder = 
     .placeholder = { $folder-name } Ara...
 zen-folders-panel-rename-folder = 
-    .label = Klasörü yeniden adlandır
+    .label = Klasörü yeniden adlandır…
 zen-folders-panel-unpack-folder = 
     .label = Klasörü çıkar
 zen-folders-new-subfolder = 
-    .label = Yeni alt klasör
+    .label = Yeni alt klasör…
 zen-folders-panel-delete-folder = 
     .label = Klasörü sil
 zen-folders-panel-convert-folder-to-space = 
     .label = Klasörü alana dönüştür
 zen-folders-panel-change-folder-space = 
-    .label = Alanı değiştir...
+    .label = Alanı değiştir
 zen-folders-unload-all-tooltip = 
     .tooltiptext = Klasörde aktif olanları boşalt
 zen-folders-unload-folder = 
diff --git a/locales/tr/browser/browser/zen-general.ftl b/locales/tr/browser/browser/zen-general.ftl
index 111178b6b..dbd486736 100644
--- a/locales/tr/browser/browser/zen-general.ftl
+++ b/locales/tr/browser/browser/zen-general.ftl
@@ -18,17 +18,23 @@ tab-context-zen-add-essential-badge = { $num } / { $max }
 tab-context-zen-remove-essential = 
     .label = Temel sekmelerden kaldır
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Temel sekmenin URL’sini geçerli olanla değiştir
-           *[false] Sabitlenmiş sekme URL’sini geçerli olanla değiştir
+            [true] Temel sekme adresini düzenle
+           *[false] Sabitlenmiş sekme adresini düzenle
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Mevcut adresle değiştir
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Düzenle…
+    .accesskey = E
 tab-context-zen-edit-title = 
-    .label = Etiketi Değiştir...
+    .label = Etiketi değiştir…
 tab-context-zen-edit-icon = 
-    .label = Simgeyi Değiştir...
+    .label = Simgeyi değiştir…
 zen-themes-corrupted = { -brand-short-name } adlı modun dosyaları hatalı. Varsayılan temaya sıfırlandılar.
 zen-shortcuts-corrupted = { -brand-short-name } kısayol dosyanız bozuldu. Varsayılan kısayollara sıfırlandı.
 # note: Do not translate the "<br/>" tags in the following string
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Onayla
 zen-pinned-tab-replaced = Sabitlenmiş sekmenin URL’si, mevcut URL ile değiştirildi!
+zen-pinned-tab-url-edited = Sabitlenmiş sekme adresi güncellendi!
+zen-pinned-tab-url-invalid = Bu geçerli bir adres gibi görünmüyor.
+zen-pinned-tab-edit-url-title = Sabitlenmiş sekme adresini düzenle
+zen-pinned-tab-edit-url-label = Bu sabitlenmiş sekmenin yönlendirileceği adresi girin:
 zen-tabs-renamed = Sekme başarıyla yeniden adlandırıldı!
 zen-background-tab-opened-toast = Yeni arka plan sekmesi açıldı!
 zen-workspace-renamed-toast = Çalışma alanı başarıyla yeniden adlandırıldı!
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = Emojiler
 zen-icons-picker-svg = 
     .label = Simgeler
+zen-emojis-picker-search = 
+    .placeholder = Emojilerde ara
 urlbar-search-mode-zen_actions = Eylemler
 zen-site-data-settings = Ayarlar
 zen-generic-manage = Yönet
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = Güncelleme tamamlandı!
 zen-sidebar-notification-updated-label = { -brand-short-name }'de neler yeni
 zen-sidebar-notification-updated-tooltip = 
     .title = Sürüm Notlarını Görüntüle
+zen-sidebar-notification-donate-label = { -brand-short-name } uygulamasını destekle
+zen-sidebar-notification-donate-tooltip = 
+    .title = Projeye bağış yap
 zen-sidebar-notification-restart-safe-mode-label = Bir sorun mu oluştu?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Güvenli Modda Yeniden Başlat
diff --git a/locales/tr/browser/browser/zen-space-routing.ftl b/locales/tr/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..090dae2b5
--- /dev/null
+++ b/locales/tr/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Alan yönlendirme ayarları
+zen-space-routing-rulepanel-placeholder = Yönlendirmeler, belirli sitelerin Zen içinde nerede açılacağını seçmenizi sağlar. Örneğin, YouTube bağlantılarının her zaman Kişisel alanınızda açılmasını sağlayabilirsiniz.
+zen-space-routing-dialog-title = Alan Yönlendirme Ayarları
+zen-space-routing-external-default = Harici bağlantılar için varsayılan yönlendirme
+zen-space-routing-new-route = Yeni yönlendirme
+zen-space-routing-open-in-space = Alanda aç
+zen-space-routing-most-recent-space = En son kullanılan alan
+zen-space-routing-close-button = 
+    .aria-label = Kapat
+    .tooltiptext = Kapat
+zen-space-routing-contains = 
+    .label = İçerir
+zen-space-routing-equal-to = 
+    .label = Şuna eşittir
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Şurada aç
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = { $targetWorkspace } alanında yeni sekme açıldı
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Alan adı için yönlendirme ekle
+           *[other] Alan adları için yönlendirme ekle
+        }
diff --git a/locales/tr/browser/browser/zen-vertical-tabs.ftl b/locales/tr/browser/browser/zen-vertical-tabs.ftl
index 47f635615..c4c3beced 100644
--- a/locales/tr/browser/browser/zen-vertical-tabs.ftl
+++ b/locales/tr/browser/browser/zen-vertical-tabs.ftl
@@ -18,7 +18,7 @@ zen-toolbar-context-compact-mode-hide-both =
     .label = İkisini de gizle
     .accesskey = H
 zen-toolbar-context-move-to-folder = 
-    .label = Klasöre taşı...
+    .label = Klasöre taşı
     .accesskey = M
 zen-toolbar-context-new-folder = 
     .label = Yeni klasör
@@ -26,7 +26,7 @@ zen-toolbar-context-new-folder =
 sidebar-zen-expand = 
     .label = Kenar çubuğunu genişlet
 sidebar-zen-create-new = 
-    .label = Yeni oluştur...
+    .label = Yeni oluştur
 tabbrowser-unload-tab-button = 
     .tooltiptext =
         { $tabCount ->
diff --git a/locales/tr/browser/browser/zen-workspaces.ftl b/locales/tr/browser/browser/zen-workspaces.ftl
index 39a66c11f..ba0f83ef7 100644
--- a/locales/tr/browser/browser/zen-workspaces.ftl
+++ b/locales/tr/browser/browser/zen-workspaces.ftl
@@ -17,9 +17,9 @@ zen-workspaces-panel-context-delete =
     .label = Çalışma alanını sil
     .accesskey = D
 zen-workspaces-panel-change-name = 
-    .label = Adı değiştir
+    .label = Adı değiştir…
 zen-workspaces-panel-change-icon = 
-    .label = Simgeyi değiştir
+    .label = Simgeyi değiştir…
 zen-workspaces-panel-context-default-profile = 
     .label = Profil ayarla
 zen-workspaces-panel-unload = 
@@ -29,7 +29,7 @@ zen-workspaces-panel-unload-others =
 zen-workspaces-how-to-reorder-title = Alanlar nasıl yeniden sıralanır
 zen-workspaces-how-to-reorder-desc = Alanları yeniden sıralamak için kenar çubuğunun altındaki alan simgelerini sürükleyin
 zen-workspaces-change-theme = 
-    .label = Temayı düzenle
+    .label = Temayı düzenle…
 zen-workspaces-panel-context-open = 
     .label = Çalışma alanı aç
     .accesskey = O
@@ -53,7 +53,7 @@ zen-panel-ui-gradient-click-to-add = Renk eklemek için tıkla
 zen-workspace-creation-name = 
     .placeholder = Alan adı
 zen-move-tab-to-workspace-button = 
-    .label = Şuraya taşı...
+    .label = Şuraya taşı
     .tooltiptext = Bu penceredeki tüm sekmeleri bir Alana taşı
 zen-workspaces-panel-context-reorder = 
     .label = Alanları yeniden sırala
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Profil
     .tooltiptext = Profiller, alanlar arasındaki çerezleri ve site verilerini ayırmak için kullanılır.
 zen-workspace-creation-header = Bir Alan Oluştur
 zen-workspace-creation-label = Alanlar, sekme ve oturumlarınızı düzenlemek için kullanılır.
+zen-workspace-default-profile = Varsayılan
 zen-workspaces-delete-workspace-title = Alan Silinsin mi?
 zen-workspaces-delete-workspace-body = { $name } ögesini silmek istediğinizden emin misiniz? Bu işlem geri alınamaz.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/uk/browser/browser/preferences/zen-preferences.ftl b/locales/uk/browser/browser/preferences/zen-preferences.ftl
index c2860504c..bab009e51 100644
--- a/locales/uk/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/uk/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Приховати верхню панель і в режимі компактного меню
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Коротко показувати, щоби панель інструментів спливала при перемиканні або відкритті нових вкладок у компактному режимі
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Allow dragging the window from web pages
 pane-zen-tabs-title = Керування вкладками
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = Інформація про сторінку
 zen-find-shortcut = Знайти на сторінці
 zen-search-find-again-shortcut = Знайти ще раз
 zen-search-find-again-shortcut-prev = Знайти попереднє
-zen-search-find-again-shortcut-2 = Знайти знову (Alt)
+zen-search-find-again-shortcut-alt = Find Again (Alt)
+zen-search-find-again-shortcut-prev-alt = Find Previous (Alt)
 zen-bookmark-this-page-shortcut = Додати цю сторінку в закладки
 zen-bookmark-show-library-shortcut = Показати бібліотеку закладок
 zen-key-stop = Зупинити завантаження
@@ -281,7 +286,7 @@ zen-workspace-shortcut-switch-9 = Перейти на робочу област
 zen-workspace-shortcut-switch-10 = Перейти на робочу область 10
 zen-workspace-shortcut-forward = Наступний робочий простір
 zen-workspace-shortcut-backward = Попередній робочий простір
-zen-workspace-shortcut-create = Create New Workspace
+zen-workspace-shortcut-create = Створити новий робочий простір
 zen-sidebar-shortcut-toggle = Перемкнути ширину бічної панелі
 zen-pinned-tab-shortcut-reset = Скинути прикріплену вкладку до закріпленої URL-адреси
 zen-split-view-shortcut-grid = Перемкнути розділену сітку
@@ -319,4 +324,4 @@ zen-devtools-toggle-accessibility-shortcut = Увімк. / Вимк. досту
 zen-close-all-unpinned-tabs-shortcut = Закрити всі відкріплені вкладки
 zen-new-unsynced-window-shortcut = Нове несинхронізоване вікно
 zen-duplicate-tab-shortcut = Дублювати вкладку
-zen-key-find-selection = Find Selection
+zen-key-find-selection = Знайти виділене
diff --git a/locales/uk/browser/browser/zen-boosts.ftl b/locales/uk/browser/browser/zen-boosts.ftl
index 37e88193d..1afd6576c 100644
--- a/locales/uk/browser/browser/zen-boosts.ftl
+++ b/locales/uk/browser/browser/zen-boosts.ftl
@@ -11,7 +11,7 @@ zen-boost-edit-reset =
 zen-boost-edit-delete = 
     .label = Видалити підсилення
 zen-boost-size = Розмір
-zen-boost-case = Case
+zen-boost-case = Регістр літер
 zen-boost-zap = Сховати
 zen-boost-code = Код
 zen-boost-back = Назад
@@ -44,14 +44,14 @@ zen-zap-done = Готово
 zen-unzap-tooltip =
     { $elementCount ->
         [0] Жоден елемент не сховано
-        [1] Сховано {$elementCount} елемент
-        [few] Сховано {$elementCount} елементи
-       *[other] Сховано {$elementCount} елементів
+        [1] Сховано { $elementCount } елемент
+        [few] Сховано { $elementCount } елементи
+       *[other] Сховано { $elementCount } елементів
     }
 zen-boost-save = 
-    .label = Export Boost
+    .label = Експортувати підсилення
 zen-boost-load = 
-    .label = Import Boost
+    .label = Імпортувати підсилення
 zen-panel-ui-boosts-exported-message = Підсилення експортовано!
 zen-site-data-boosts = Підсилення
 zen-site-data-create-boost = 
diff --git a/locales/uk/browser/browser/zen-command-palette.ftl b/locales/uk/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..c8af413e2
--- /dev/null
+++ b/locales/uk/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Toggle Compact Mode
+zen-action-open-theme-picker = Open Theme Picker
+zen-action-new-split-view = New Split View
+zen-action-new-folder = New Folder
+zen-action-copy-current-url = Copy Current URL
+zen-action-settings = Settings
+zen-action-open-private-window = Open Private Window
+zen-action-open-new-window = Open New Window
+zen-action-new-blank-window = New Blank Window
+zen-action-pin-tab = Pin Tab
+zen-action-unpin-tab = Unpin Tab
+zen-action-open-space-routing = Open Space Routing
+zen-action-new-boost = New Boost
+zen-action-next-space = Next Space
+zen-action-previous-space = Previous Space
+zen-action-close-tab = Close Tab
+zen-action-reload-tab = Reload Tab
+zen-action-reload-tab-without-cache = Reload Tab Without Cache
+zen-action-next-tab = Next Tab
+zen-action-previous-tab = Previous Tab
+zen-action-capture-screenshot = Capture Screenshot
+zen-action-toggle-tabs-on-right = Toggle Tabs on right
+zen-action-add-to-essentials = Add to Essentials
+zen-action-remove-from-essentials = Remove from Essentials
+zen-action-find-in-page = Find in Page
+zen-action-manage-extensions = Manage Extensions
+zen-action-switch-to-automatic-appearance = Switch to Automatic Appearance
+zen-action-switch-to-light-mode = Switch to Light Mode
+zen-action-switch-to-dark-mode = Switch to Dark Mode
+zen-action-print = Print
+zen-action-focus-on = Focus on
+zen-action-extension = Extension
diff --git a/locales/uk/browser/browser/zen-general.ftl b/locales/uk/browser/browser/zen-general.ftl
index a727b433b..ae390fb10 100644
--- a/locales/uk/browser/browser/zen-general.ftl
+++ b/locales/uk/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max } комірок зап
 tab-context-zen-remove-essential = 
     .label = Вилучити з основних елементів
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Замінити основну адресу на поточну
-           *[false] Замінити закріплену адресу на поточну
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Replace with Current URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Edit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Змінити мітку...
 tab-context-zen-edit-icon = 
@@ -47,6 +53,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Підтвердити
 zen-pinned-tab-replaced = URL-адресу закріпленої вкладки замінено на поточну URL-адресу.
+zen-pinned-tab-url-edited = Pinned tab URL has been updated!
+zen-pinned-tab-url-invalid = That doesn't look like a valid URL.
+zen-pinned-tab-edit-url-title = Edit Pinned URL
+zen-pinned-tab-edit-url-label = Enter the URL this pinned tab should point to:
 zen-tabs-renamed = Вкладку успішно перейменовано!
 zen-background-tab-opened-toast = Відкрито нову фонову вкладку!
 zen-workspace-renamed-toast = Робочий простір успішно перейменовано!
@@ -65,6 +75,8 @@ zen-icons-picker-emoji =
     .label = Емоджі
 zen-icons-picker-svg = 
     .label = Значки
+zen-emojis-picker-search = 
+    .placeholder = Search emojis
 urlbar-search-mode-zen_actions = Дії
 zen-site-data-settings = Налаштування
 zen-generic-manage = Керувати
@@ -116,6 +128,9 @@ zen-sidebar-notification-updated-heading = Оновлення завершено
 zen-sidebar-notification-updated-label = Що нового в { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = Переглянути примітки до випуску
+zen-sidebar-notification-donate-label = Support { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donate to the project
 zen-sidebar-notification-restart-safe-mode-label = Щось зламалося?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Перезапустити в безпечному режимі
diff --git a/locales/uk/browser/browser/zen-space-routing.ftl b/locales/uk/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..52f4e4fc7
--- /dev/null
+++ b/locales/uk/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Налаштування маршрутизації в просторі
+zen-space-routing-rulepanel-placeholder = За допомогою маршрутів ви можете вибрати, де саме в Zen будуть відкриватися певні сайти. Наприклад, ви можете налаштувати, щоби посилання на YouTube завжди відкривалися у вашому особистому просторі.
+zen-space-routing-dialog-title = Налаштування маршрутизації в просторі
+zen-space-routing-external-default = Типовий маршрут для зовнішніх посилань
+zen-space-routing-new-route = Новий маршрут
+zen-space-routing-open-in-space = Відкрити в просторі
+zen-space-routing-most-recent-space = Останній простір
+zen-space-routing-close-button = 
+    .aria-label = Закрити
+    .tooltiptext = Закрити
+zen-space-routing-contains = 
+    .label = Містить
+zen-space-routing-equal-to = 
+    .label = Це дорівнює
+zen-space-routing-regex = 
+    .label = Регулярний вираз
+zen-space-routing-open-in = Відкрити в
+zen-space-routing-url = URL-адреса
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/uk/browser/browser/zen-workspaces.ftl b/locales/uk/browser/browser/zen-workspaces.ftl
index bcb959308..1591cdf5e 100644
--- a/locales/uk/browser/browser/zen-workspaces.ftl
+++ b/locales/uk/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Профіль
     .tooltiptext = Профілі використовуються для розділення файлів cookie і даних сайту між просторами.
 zen-workspace-creation-header = Створити простір
 zen-workspace-creation-label = Простори використовуються для організації ваших вкладок та сеансів.
+zen-workspace-default-profile = Default
 zen-workspaces-delete-workspace-title = Видалити простір?
 zen-workspaces-delete-workspace-body = Упевнені, що хочете видалити { $name }? Цю дію неможливо скасувати.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/vi/browser/browser/preferences/zen-preferences.ftl b/locales/vi/browser/browser/preferences/zen-preferences.ftl
index 1158ff2aa..986708cf6 100644
--- a/locales/vi/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/vi/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = Ẩn thanh công cụ trên cùng trong chế độ thu gọn
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = Thanh bên hiện lên khi chuyển thẻ hoặc mở thẻ mới trong chế độ thu gọn
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Allow dragging the window from web pages
 pane-zen-tabs-title = Quản lí thẻ
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = Xem thông tin trang
 zen-find-shortcut = Tìm kiếm trên trang
 zen-search-find-again-shortcut = Tìm lại
 zen-search-find-again-shortcut-prev = Tìm trước đó
-zen-search-find-again-shortcut-2 = Tìm lại (Alt)
+zen-search-find-again-shortcut-alt = Find Again (Alt)
+zen-search-find-again-shortcut-prev-alt = Find Previous (Alt)
 zen-bookmark-this-page-shortcut = Đánh dấu trang này
 zen-bookmark-show-library-shortcut = Hiển thị thư viện dấu trang
 zen-key-stop = Dừng tải
diff --git a/locales/vi/browser/browser/zen-command-palette.ftl b/locales/vi/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..c8af413e2
--- /dev/null
+++ b/locales/vi/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = Toggle Compact Mode
+zen-action-open-theme-picker = Open Theme Picker
+zen-action-new-split-view = New Split View
+zen-action-new-folder = New Folder
+zen-action-copy-current-url = Copy Current URL
+zen-action-settings = Settings
+zen-action-open-private-window = Open Private Window
+zen-action-open-new-window = Open New Window
+zen-action-new-blank-window = New Blank Window
+zen-action-pin-tab = Pin Tab
+zen-action-unpin-tab = Unpin Tab
+zen-action-open-space-routing = Open Space Routing
+zen-action-new-boost = New Boost
+zen-action-next-space = Next Space
+zen-action-previous-space = Previous Space
+zen-action-close-tab = Close Tab
+zen-action-reload-tab = Reload Tab
+zen-action-reload-tab-without-cache = Reload Tab Without Cache
+zen-action-next-tab = Next Tab
+zen-action-previous-tab = Previous Tab
+zen-action-capture-screenshot = Capture Screenshot
+zen-action-toggle-tabs-on-right = Toggle Tabs on right
+zen-action-add-to-essentials = Add to Essentials
+zen-action-remove-from-essentials = Remove from Essentials
+zen-action-find-in-page = Find in Page
+zen-action-manage-extensions = Manage Extensions
+zen-action-switch-to-automatic-appearance = Switch to Automatic Appearance
+zen-action-switch-to-light-mode = Switch to Light Mode
+zen-action-switch-to-dark-mode = Switch to Dark Mode
+zen-action-print = Print
+zen-action-focus-on = Focus on
+zen-action-extension = Extension
diff --git a/locales/vi/browser/browser/zen-general.ftl b/locales/vi/browser/browser/zen-general.ftl
index 405d42a21..5e56d667c 100644
--- a/locales/vi/browser/browser/zen-general.ftl
+++ b/locales/vi/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max }
 tab-context-zen-remove-essential = 
     .label = Gỡ khỏi thẻ chính
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] Thay thế URL của thẻ chính bằng URL hiện tại
-           *[false] Thay thế URL của thẻ đã ghim bằng URL hiện tại
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Replace with Current URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Edit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = Đổi tên...
 tab-context-zen-edit-icon = 
@@ -45,6 +51,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = Xác nhận
 zen-pinned-tab-replaced = URL của thẻ đã ghim đã được thay thế bằng URL hiện tại!
+zen-pinned-tab-url-edited = Pinned tab URL has been updated!
+zen-pinned-tab-url-invalid = That doesn't look like a valid URL.
+zen-pinned-tab-edit-url-title = Edit Pinned URL
+zen-pinned-tab-edit-url-label = Enter the URL this pinned tab should point to:
 zen-tabs-renamed = Thẻ đã được đổi tên!
 zen-background-tab-opened-toast = Một thẻ mới đã được mở dưới nền!
 zen-workspace-renamed-toast = Không gian làm việc đã được đổi tên!
@@ -63,6 +73,8 @@ zen-icons-picker-emoji =
     .label = Biểu cảm
 zen-icons-picker-svg = 
     .label = Biểu tượng
+zen-emojis-picker-search = 
+    .placeholder = Search emojis
 urlbar-search-mode-zen_actions = Hành động
 zen-site-data-settings = Thiết lập
 zen-generic-manage = Quản lý
@@ -114,6 +126,9 @@ zen-sidebar-notification-updated-heading = Cập nhật hoàn tất!
 zen-sidebar-notification-updated-label = Có gì mới trong { -brand-short-name }
 zen-sidebar-notification-updated-tooltip = 
     .title = Xem ghi chú phát hành
+zen-sidebar-notification-donate-label = Support { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donate to the project
 zen-sidebar-notification-restart-safe-mode-label = Có lỗi xảy ra?
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = Khởi động lại ở Chế độ an toàn
diff --git a/locales/vi/browser/browser/zen-space-routing.ftl b/locales/vi/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..d757144bb
--- /dev/null
+++ b/locales/vi/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = Space Routing Settings
+zen-space-routing-rulepanel-placeholder = Routes let you choose where specific sites open inside Zen. For example, you can route YouTube links to always open inside your Personal space.
+zen-space-routing-dialog-title = Space Routing Settings
+zen-space-routing-external-default = Default route for external links
+zen-space-routing-new-route = New Route
+zen-space-routing-open-in-space = Open in Space
+zen-space-routing-most-recent-space = Most recent Space
+zen-space-routing-close-button = 
+    .aria-label = Close
+    .tooltiptext = Close
+zen-space-routing-contains = 
+    .label = Contains
+zen-space-routing-equal-to = 
+    .label = Is Equal To
+zen-space-routing-regex = 
+    .label = RegEx
+zen-space-routing-open-in = Open In
+zen-space-routing-url = URL
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/vi/browser/browser/zen-workspaces.ftl b/locales/vi/browser/browser/zen-workspaces.ftl
index c355cab68..14e71b03a 100644
--- a/locales/vi/browser/browser/zen-workspaces.ftl
+++ b/locales/vi/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = Hồ sơ
     .tooltiptext = Các hồ sơ sẽ không dùng chung dữ liệu giữa các không gian làm việc.
 zen-workspace-creation-header = Tạo không gian
 zen-workspace-creation-label = Không gian dùng để sắp xếp các thẻ và phiên làm việc của bạn.
+zen-workspace-default-profile = Default
 zen-workspaces-delete-workspace-title = Xóa không gian?
 zen-workspaces-delete-workspace-body = Bạn có chắc chắn muốn xóa { $name }? Thao tác này không thể hoàn tác.
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/zh-CN/browser/browser/preferences/zen-preferences.ftl b/locales/zh-CN/browser/browser/preferences/zen-preferences.ftl
index cc5014b4f..a29beed05 100644
--- a/locales/zh-CN/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/zh-CN/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = 在简洁模式下隐藏顶部工具栏
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = 简洁模式下，切换或打开新标签页时短暂弹出工具栏
+zen-look-and-feel-window-drag-header = 窗口拖动
+zen-look-and-feel-window-drag-description = 像拖动标题栏一样，通过拖动网站顶部的空白区域来移动窗口。
+zen-window-drag-enabled = 
+    .label = 允许从网页拖动窗口
 pane-zen-tabs-title = 标签页管理
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = 查看页面信息
 zen-find-shortcut = 在页面上查找
 zen-search-find-again-shortcut = 查找下一个
 zen-search-find-again-shortcut-prev = 查找上一个
-zen-search-find-again-shortcut-2 = 查找下一个（Alt）
+zen-search-find-again-shortcut-alt = 查找下一个（Alt）
+zen-search-find-again-shortcut-prev-alt = 查找上一个（Alt）
 zen-bookmark-this-page-shortcut = 将此页面加入书签
 zen-bookmark-show-library-shortcut = 显示书签库
 zen-key-stop = 停止加载
@@ -281,7 +286,7 @@ zen-workspace-shortcut-switch-9 = 切换到工作区 9
 zen-workspace-shortcut-switch-10 = 切换到工作区 10
 zen-workspace-shortcut-forward = 下一个工作区
 zen-workspace-shortcut-backward = 上一个工作区
-zen-workspace-shortcut-create = Create New Workspace
+zen-workspace-shortcut-create = 新建工作区
 zen-sidebar-shortcut-toggle = 折叠/展开侧边栏
 zen-pinned-tab-shortcut-reset = 重置固定标签页至其固定的 URL
 zen-split-view-shortcut-grid = 切换网格分屏视图
@@ -319,4 +324,4 @@ zen-devtools-toggle-accessibility-shortcut = 切换无障碍环境
 zen-close-all-unpinned-tabs-shortcut = 关闭所有未固定的标签页
 zen-new-unsynced-window-shortcut = 新建空白窗口
 zen-duplicate-tab-shortcut = 克隆标签页
-zen-key-find-selection = Find Selection
+zen-key-find-selection = 查找选中内容
diff --git a/locales/zh-CN/browser/browser/zen-boosts.ftl b/locales/zh-CN/browser/browser/zen-boosts.ftl
index 650ea1dc6..ef67d6da1 100644
--- a/locales/zh-CN/browser/browser/zen-boosts.ftl
+++ b/locales/zh-CN/browser/browser/zen-boosts.ftl
@@ -11,7 +11,7 @@ zen-boost-edit-reset =
 zen-boost-edit-delete = 
     .label = 删除 Boost
 zen-boost-size = 尺寸
-zen-boost-case = Case
+zen-boost-case = 大小写
 zen-boost-zap = 屏蔽
 zen-boost-code = 代码
 zen-boost-back = 返回
@@ -48,9 +48,9 @@ zen-unzap-tooltip =
        *[other] 已屏蔽 { $elementCount } 个元素
     }
 zen-boost-save = 
-    .label = Export Boost
+    .label = 导出 Boost
 zen-boost-load = 
-    .label = Import Boost
+    .label = 导入 Boost
 zen-panel-ui-boosts-exported-message = Boost 已导出！
 zen-site-data-boosts = Boost
 zen-site-data-create-boost = 
diff --git a/locales/zh-CN/browser/browser/zen-command-palette.ftl b/locales/zh-CN/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..da6fae139
--- /dev/null
+++ b/locales/zh-CN/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = 切换简洁模式
+zen-action-open-theme-picker = 打开主题选择器
+zen-action-new-split-view = 新建分屏视图
+zen-action-new-folder = 新建文件夹
+zen-action-copy-current-url = 复制当前网址
+zen-action-settings = 设置
+zen-action-open-private-window = 打开隐私窗口
+zen-action-open-new-window = 打开新窗口
+zen-action-new-blank-window = 新建空白窗口
+zen-action-pin-tab = 固定标签页
+zen-action-unpin-tab = 取消固定标签页
+zen-action-open-space-routing = 打开工作区路由
+zen-action-new-boost = 新建 Boost
+zen-action-next-space = 下一个工作区
+zen-action-previous-space = 上一个工作区
+zen-action-close-tab = 关闭标签页
+zen-action-reload-tab = 刷新标签页
+zen-action-reload-tab-without-cache = 刷新标签页并跳过缓存
+zen-action-next-tab = 下一个标签页
+zen-action-previous-tab = 上一个标签页
+zen-action-capture-screenshot = 截图
+zen-action-toggle-tabs-on-right = 切换右侧标签页
+zen-action-add-to-essentials = 添加到常驻标签页
+zen-action-remove-from-essentials = 从常驻标签页中移除
+zen-action-find-in-page = 在页面中查找
+zen-action-manage-extensions = 管理扩展
+zen-action-switch-to-automatic-appearance = 切换到自动外观模式
+zen-action-switch-to-light-mode = 切换到浅色模式
+zen-action-switch-to-dark-mode = 切换到深色模式
+zen-action-print = 打印
+zen-action-focus-on = 切换到
+zen-action-extension = 扩展
diff --git a/locales/zh-CN/browser/browser/zen-general.ftl b/locales/zh-CN/browser/browser/zen-general.ftl
index 0f2a108fc..d25b6f3b4 100644
--- a/locales/zh-CN/browser/browser/zen-general.ftl
+++ b/locales/zh-CN/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = 已使用 { $num } / { $max }
 tab-context-zen-remove-essential = 
     .label = 从常驻标签页中移除
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] 用当前内容替换常驻标签页URL
-           *[false] 用当前内容替换标签页URL
+            [true] 编辑常驻标签页
+           *[false] 编辑固定标签页
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = 替换为当前 URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = 编辑…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = 更改标签…
 tab-context-zen-edit-icon = 
@@ -45,6 +51,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = 确认
 zen-pinned-tab-replaced = 固定标签页的网址已更新为当前页面网址！
+zen-pinned-tab-url-edited = 固定标签页的 URL 已更新！
+zen-pinned-tab-url-invalid = URL 无效。
+zen-pinned-tab-edit-url-title = 编辑固定 URL
+zen-pinned-tab-edit-url-label = 请输入此固定标签页应指向的 URL：
 zen-tabs-renamed = 标签页重命名成功！
 zen-background-tab-opened-toast = 新的后台标签页已打开 ！
 zen-workspace-renamed-toast = 工作区重命名成功！
@@ -63,6 +73,8 @@ zen-icons-picker-emoji =
     .label = 表情符号
 zen-icons-picker-svg = 
     .label = 图标集
+zen-emojis-picker-search = 
+    .placeholder = 搜索表情符号
 urlbar-search-mode-zen_actions = 操作
 zen-site-data-settings = 设置
 zen-generic-manage = 管理
@@ -114,6 +126,9 @@ zen-sidebar-notification-updated-heading = 更新完成！
 zen-sidebar-notification-updated-label = 了解 { -brand-short-name } 的新版变化
 zen-sidebar-notification-updated-tooltip = 
     .title = 查看更新日志
+zen-sidebar-notification-donate-label = 支持 { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = 为此项目捐赠
 zen-sidebar-notification-restart-safe-mode-label = 出了什么问题吗？
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = 在排障模式下重启
diff --git a/locales/zh-CN/browser/browser/zen-space-routing.ftl b/locales/zh-CN/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..519842718
--- /dev/null
+++ b/locales/zh-CN/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = 工作区路由设置
+zen-space-routing-rulepanel-placeholder = 利用路由，您可以指定在哪里打开特定的站点；比方说，您可以将 YouTube 链接设置为始终在个人工作区中打开。
+zen-space-routing-dialog-title = 工作区路由设置
+zen-space-routing-external-default = 外部链接的默认路由
+zen-space-routing-new-route = 新建路由
+zen-space-routing-open-in-space = 打开于
+zen-space-routing-most-recent-space = 最近使用的工作区
+zen-space-routing-close-button = 
+    .aria-label = 关闭
+    .tooltiptext = 关闭
+zen-space-routing-contains = 
+    .label = 包含
+zen-space-routing-equal-to = 
+    .label = 等于
+zen-space-routing-regex = 
+    .label = 正则表达式
+zen-space-routing-open-in = 打开于
+zen-space-routing-url = 网址
+zen-space-routing-tab-routed-toast = 新标签页将打开于 { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] 为域名添加路由
+           *[other] 为多个域名添加路由
+        }
diff --git a/locales/zh-CN/browser/browser/zen-workspaces.ftl b/locales/zh-CN/browser/browser/zen-workspaces.ftl
index 219ccc4c1..c397c2812 100644
--- a/locales/zh-CN/browser/browser/zen-workspaces.ftl
+++ b/locales/zh-CN/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = 身份
     .tooltiptext = 身份用于在工作区之间分隔 Cookie 和站点数据。
 zen-workspace-creation-header = 创建工作区
 zen-workspace-creation-label = 工作区用于组织标签页和会话。
+zen-workspace-default-profile = 默认
 zen-workspaces-delete-workspace-title = 删除工作区？
 zen-workspaces-delete-workspace-body = 你确定要删除 { $name } 吗？这个操作无法撤销。
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/locales/zh-TW/browser/browser/preferences/zen-preferences.ftl b/locales/zh-TW/browser/browser/preferences/zen-preferences.ftl
index e47b873db..765aa9a76 100644
--- a/locales/zh-TW/browser/browser/preferences/zen-preferences.ftl
+++ b/locales/zh-TW/browser/browser/preferences/zen-preferences.ftl
@@ -38,6 +38,10 @@ zen-look-and-feel-compact-view-top-toolbar =
     .label = 在緊湊模式中也隱藏頂部的工具列
 zen-look-and-feel-compact-toolbar-flash-popup = 
     .label = 在緊湊模式下切換或開啟新分頁時短暫彈出工具列
+zen-look-and-feel-window-drag-header = Window dragging
+zen-look-and-feel-window-drag-description = Move the window by dragging empty space at the top of websites, just like the titlebar.
+zen-window-drag-enabled = 
+    .label = Allow dragging the window from web pages
 pane-zen-tabs-title = 分頁管理
 category-zen-workspaces = 
     .tooltiptext = { pane-zen-tabs-title }
@@ -244,7 +248,8 @@ zen-page-info-shortcut = 頁面資訊
 zen-find-shortcut = 尋找
 zen-search-find-again-shortcut = 找下一個
 zen-search-find-again-shortcut-prev = 找上一個
-zen-search-find-again-shortcut-2 = 再次尋找 (備用)
+zen-search-find-again-shortcut-alt = Find Again (Alt)
+zen-search-find-again-shortcut-prev-alt = Find Previous (Alt)
 zen-bookmark-this-page-shortcut = 將目前頁面加入書籤
 zen-bookmark-show-library-shortcut = 顯示書籤庫
 zen-key-stop = 停止載入
@@ -265,7 +270,7 @@ zen-nav-reload-shortcut = 重新整理頁面
 zen-nav-reload-shortcut-skip-cache = 重新整理頁面 (忽略快取)
 zen-close-shortcut = 關閉視窗
 zen-close-tab-shortcut = 關閉分頁
-zen-compact-mode-shortcut-show-sidebar = 切換浮動側邊欄
+zen-compact-mode-shortcut-show-sidebar = 叫出/收回浮動側邊欄
 zen-compact-mode-shortcut-show-toolbar = 切換浮動工具列
 zen-compact-mode-shortcut-toggle = 切換緊湊模式
 zen-glance-expand = 展開 Glance
diff --git a/locales/zh-TW/browser/browser/zen-command-palette.ftl b/locales/zh-TW/browser/browser/zen-command-palette.ftl
new file mode 100644
index 000000000..374ca610f
--- /dev/null
+++ b/locales/zh-TW/browser/browser/zen-command-palette.ftl
@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-action-toggle-compact-mode = 切換緊湊模式
+zen-action-open-theme-picker = 開啟主題編輯面板
+zen-action-new-split-view = 新增分割畫面
+zen-action-new-folder = 新增分頁夾
+zen-action-copy-current-url = 複製當前網址
+zen-action-settings = 設定
+zen-action-open-private-window = 開新隱私視窗
+zen-action-open-new-window = 開新視窗
+zen-action-new-blank-window = 開新簡白視窗
+zen-action-pin-tab = 釘選分頁
+zen-action-unpin-tab = 解除釘選分頁
+zen-action-open-space-routing = 開啟網址導航設定
+zen-action-new-boost = 建立新Boost
+zen-action-next-space = 下一工作區
+zen-action-previous-space = 上一工作區
+zen-action-close-tab = 關閉分頁
+zen-action-reload-tab = 重新整理頁面
+zen-action-reload-tab-without-cache = 重新整理頁面 (忽略快取)
+zen-action-next-tab = 下一分頁
+zen-action-previous-tab = 上一分頁
+zen-action-capture-screenshot = 拍攝畫面截圖
+zen-action-toggle-tabs-on-right = 切換右側分頁欄
+zen-action-add-to-essentials = 新增至 Essentials
+zen-action-remove-from-essentials = 從 Essentials 中移除
+zen-action-find-in-page = 在頁面中搜尋
+zen-action-manage-extensions = 管理擴充套件
+zen-action-switch-to-automatic-appearance = 切換為自動匹配亮暗色
+zen-action-switch-to-light-mode = 切換至亮色模式
+zen-action-switch-to-dark-mode = 切換為暗色模式
+zen-action-print = 列印
+zen-action-focus-on = 將焦點移至
+zen-action-extension = 擴充套件
diff --git a/locales/zh-TW/browser/browser/zen-general.ftl b/locales/zh-TW/browser/browser/zen-general.ftl
index 99476e47b..19aa7eb59 100644
--- a/locales/zh-TW/browser/browser/zen-general.ftl
+++ b/locales/zh-TW/browser/browser/zen-general.ftl
@@ -18,13 +18,19 @@ tab-context-zen-add-essential-badge = { $num } / { $max }
 tab-context-zen-remove-essential = 
     .label = 從 Essentials 中移除
     .accesskey = R
-tab-context-zen-replace-pinned-url-with-current = 
+tab-context-zen-edit-pinned-page = 
     .label =
         { $isEssential ->
-            [true] 以當前網址替換Essentials
-           *[false] 以當前網址替換釘選分頁
+            [true] Edit Essential URL
+           *[false] Edit Pinned URL
         }
+    .accesskey = P
+tab-context-zen-replace-pinned-url-with-current = 
+    .label = Replace with Current URL
     .accesskey = C
+tab-context-zen-edit-pinned-url = 
+    .label = Edit…
+    .accesskey = E
 tab-context-zen-edit-title = 
     .label = 重新命名
 tab-context-zen-edit-icon = 
@@ -45,6 +51,10 @@ zen-general-cancel-label =
 zen-general-confirm = 
     .label = 確認
 zen-pinned-tab-replaced = 釘選分頁網址已替換為當前網址！
+zen-pinned-tab-url-edited = Pinned tab URL has been updated!
+zen-pinned-tab-url-invalid = That doesn't look like a valid URL.
+zen-pinned-tab-edit-url-title = Edit Pinned URL
+zen-pinned-tab-edit-url-label = Enter the URL this pinned tab should point to:
 zen-tabs-renamed = 成功重新命名分頁！
 zen-background-tab-opened-toast = 新分頁已在背景開啟！
 zen-workspace-renamed-toast = 成功重新命名工作區！
@@ -58,18 +68,20 @@ zen-toggle-compact-mode-button =
 zen-learn-more-text = 瞭解更多
 zen-close-label = 關閉
 zen-singletoolbar-urlbar-placeholder-with-name = 
-    .placeholder = 搜尋...
+    .placeholder = 搜尋…
 zen-icons-picker-emoji = 
     .label = 表情符號
 zen-icons-picker-svg = 
     .label = 圖示
+zen-emojis-picker-search = 
+    .placeholder = Search emojis
 urlbar-search-mode-zen_actions = 操作
 zen-site-data-settings = 設定
 zen-generic-manage = 管理
 zen-generic-more = 更多
 zen-generic-next = 下一個
 zen-essentials-promo-label = 新增至 Essentials
-zen-essentials-promo-sublabel = 僅需點擊一下就能切換至您的最愛分頁
+zen-essentials-promo-sublabel = 僅需點擊一下就能切換至您的心儀分頁
 # These labels will be used for the site data panel settings
 zen-site-data-setting-allow = 允許
 zen-site-data-setting-block = 已封鎖
@@ -114,6 +126,9 @@ zen-sidebar-notification-updated-heading = 更新成功！
 zen-sidebar-notification-updated-label = { -brand-short-name } 更新了什麼
 zen-sidebar-notification-updated-tooltip = 
     .title = 查看版本資訊
+zen-sidebar-notification-donate-label = Support { -brand-short-name }
+zen-sidebar-notification-donate-tooltip = 
+    .title = Donate to the project
 zen-sidebar-notification-restart-safe-mode-label = 有東西壞掉了嗎？
 zen-sidebar-notification-restart-safe-mode-tooltip = 
     .title = 在安全模式下重新啟動
diff --git a/locales/zh-TW/browser/browser/zen-space-routing.ftl b/locales/zh-TW/browser/browser/zen-space-routing.ftl
new file mode 100644
index 000000000..c8351738e
--- /dev/null
+++ b/locales/zh-TW/browser/browser/zen-space-routing.ftl
@@ -0,0 +1,30 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+zen-space-routing-settings = 
+    .label = 網址導向設定
+zen-space-routing-rulepanel-placeholder = 讓您能選擇要將特定網站開啟在 Zen 的某個工作區。舉例來說，您可以設定將YouTube連結一律開啟在Personal工作區內。
+zen-space-routing-dialog-title = 網址導向設定
+zen-space-routing-external-default = 外部傳入網址的預設導向
+zen-space-routing-new-route = 新導向
+zen-space-routing-open-in-space = 開啟在
+zen-space-routing-most-recent-space = 最近使用的工作區
+zen-space-routing-close-button = 
+    .aria-label = 關閉
+    .tooltiptext = 關閉
+zen-space-routing-contains = 
+    .label = 包含
+zen-space-routing-equal-to = 
+    .label = 等同於
+zen-space-routing-regex = 
+    .label = 正規表達式
+zen-space-routing-open-in = 開啟在
+zen-space-routing-url = 網址
+zen-space-routing-tab-routed-toast = New tab opened in { $targetWorkspace }
+tab-context-zen-add-domain-to-sr = 
+    .label =
+        { $tabCount ->
+            [one] Add Route for Domain
+           *[other] Add Route for Domains
+        }
diff --git a/locales/zh-TW/browser/browser/zen-workspaces.ftl b/locales/zh-TW/browser/browser/zen-workspaces.ftl
index c0a20939b..feb561cd3 100644
--- a/locales/zh-TW/browser/browser/zen-workspaces.ftl
+++ b/locales/zh-TW/browser/browser/zen-workspaces.ftl
@@ -61,6 +61,7 @@ zen-workspace-creation-profile = 設定檔
     .tooltiptext = 設定檔用於隔離不同工作區的 Cookie 和網站資料。
 zen-workspace-creation-header = 建立工作區
 zen-workspace-creation-label = 工作區用於組織您的分頁與工作階段。
+zen-workspace-default-profile = Default
 zen-workspaces-delete-workspace-title = 刪除工作區？
 zen-workspaces-delete-workspace-body = 您確定要刪除 { $name } 嗎？此操作無法復原。
 # Note that the html tag MUST not be changed or removed, as it is used to better
diff --git a/package-lock.json b/package-lock.json
index 1224e4955..484c33d77 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -11,7 +11,7 @@
       "devDependencies": {
         "@babel/preset-typescript": "^7.27.0",
         "@zen-browser/prettier": "^3.9.3",
-        "@zen-browser/surfer": "^1.14.6",
+        "@zen-browser/surfer": "^1.14.8",
         "formal-git": "^1.2.9",
         "globals": "^16.3.0",
         "husky": "^9.1.7",
@@ -860,9 +860,9 @@
       }
     },
     "node_modules/@zen-browser/surfer": {
-      "version": "1.14.6",
-      "resolved": "https://registry.npmjs.org/@zen-browser/surfer/-/surfer-1.14.6.tgz",
-      "integrity": "sha512-hgTKadIJ/9/9dizHn4229ZZHQckd7D4OR6e7HVkcmtuq1Jke3OAn6SH7u7NjvzvYy35Mb2sXjVUvZEG1ITIfgg==",
+      "version": "1.14.8",
+      "resolved": "https://registry.npmjs.org/@zen-browser/surfer/-/surfer-1.14.8.tgz",
+      "integrity": "sha512-5HHcfibwHIK5n3huhJL2TLBX2+8odj6ebCMA6U2EcUj9ROSrcz7/bjY2n5MIa9oIRL9gtV3ott0jwJj6SlapxA==",
       "dev": true,
       "license": "MPL-2.0",
       "dependencies": {
diff --git a/package.json b/package.json
index c62853c08..c0ed6239c 100644
--- a/package.json
+++ b/package.json
@@ -49,7 +49,7 @@
   "devDependencies": {
     "@babel/preset-typescript": "^7.27.0",
     "@zen-browser/prettier": "^3.9.3",
-    "@zen-browser/surfer": "^1.14.6",
+    "@zen-browser/surfer": "^1.14.8",
     "formal-git": "^1.2.9",
     "globals": "^16.3.0",
     "husky": "^9.1.7",
diff --git a/prefs/firefox/browser.yaml b/prefs/firefox/browser.yaml
index 29eea1ac5..92032c989 100644
--- a/prefs/firefox/browser.yaml
+++ b/prefs/firefox/browser.yaml
@@ -102,3 +102,13 @@
 # Only enabled for windows, doesn't really fit inside Zen.
 - name: browser.startup.preXulSkeletonUI
   value: false
+
+- name: browser.preonboarding.enabled
+  value: false
+
+- name: browser.referrals.enabled
+  value: false
+  locked: true
+
+- name: browser.shell.customIcon.enabled
+  value: false # For now?
diff --git a/prefs/firefox/performance.yaml b/prefs/firefox/performance.yaml
index c58582064..e972fd471 100644
--- a/prefs/firefox/performance.yaml
+++ b/prefs/firefox/performance.yaml
@@ -2,18 +2,11 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-- name: browser.lowMemoryResponseMask
-  value: 3
-  condition: "defined(XP_MACOSX)"
-
-- name: network.predictor.enable-hover-on-ssl
-  value: true
-
 # See https://github.com/zen-browser/desktop/issues/11599, this pref seems to
 # have disabled itself on macos for some unknown reason.
 # Make sure its in sync with:
-# https://searchfox.org/firefox-main/rev/1477feb9706f4ccc5bd571c1c215832a6fbb7464/modules/libpref/init/StaticPrefList.yaml#7741-7748
+# https://searchfox.org/firefox-main/rev/dd2579cb6e7f1761a27ce64fb84d92c61d85c27f/modules/libpref/init/StaticPrefList.yaml#8396
 - name: gfx.webrender.compositor
-  condition: "defined(XP_WIN) || defined(XP_DARWIN)"
+  condition: "defined(XP_WIN) || defined(XP_DARWIN) || defined(MOZ_WIDGET_GTK)"
   value: "@cond"
   mirror: once
diff --git a/prefs/zen/macos.yaml b/prefs/zen/macos.yaml
index abca5c987..3f3fd2f18 100644
--- a/prefs/zen/macos.yaml
+++ b/prefs/zen/macos.yaml
@@ -2,10 +2,14 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-# Enable transparent background for macos
-- name: widget.macos.sidebar-blend-mode.behind-window
+# Give the whole window a translucent, blurred backdrop, using the material
+# below. See ZenWindowMaterialView in nsCocoaWindow.mm.
+- name: zen.widget.macos.window-vibrancy
   value: true
   condition: "defined(XP_MACOSX)"
+  cpptype: bool
+  mirror: always
+  type: static
 
 # 1. hudWindow
 # 2. fullScreenUI
diff --git a/prefs/zen/media.yaml b/prefs/zen/media.yaml
index abf40e5db..7402f3965 100644
--- a/prefs/zen/media.yaml
+++ b/prefs/zen/media.yaml
@@ -8,9 +8,5 @@
 - name: svg.context-properties.content.enabled
   value: true
 
-- name: image.avif.enabled
-  value: true
-  locked: true
-
 - name: media.eme.enabled
   value: true
diff --git a/prefs/zen/sync.yaml b/prefs/zen/sync.yaml
index dff75e481..9ed0efc35 100644
--- a/prefs/zen/sync.yaml
+++ b/prefs/zen/sync.yaml
@@ -10,3 +10,6 @@
   value: false
   locked: true
   condition: "!@IS_TWILIGHT@"
+
+- name: zen.spaces-sync.debug
+  value: false
diff --git a/prefs/zen/view.yaml b/prefs/zen/view.yaml
index fc433c617..3cb5c0338 100644
--- a/prefs/zen/view.yaml
+++ b/prefs/zen/view.yaml
@@ -50,7 +50,7 @@
   value: true
 
 - name: zen.view.drag-window-from-content.height-percentage
-  value: 10
+  value: 5
 
 - name: zen.view.borderless-fullscreen
   value: true
diff --git a/prefs/zen/workspaces.yaml b/prefs/zen/workspaces.yaml
index dfa8b7d6c..156672855 100644
--- a/prefs/zen/workspaces.yaml
+++ b/prefs/zen/workspaces.yaml
@@ -21,7 +21,7 @@
   value: 100
 
 - name: zen.workspaces.switch-animation-duration
-  value: 200
+  value: 250
 
 - name: zen.workspaces.wrap-around-navigation
   value: true
diff --git a/requirements.txt b/requirements.txt
index 03b71cd68..461f70773 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -8,4 +8,4 @@ packaging==24.2
 pathspec==0.12.1
 platformdirs==4.3.6
 pycodestyle==2.12.1
-requests==2.33.0
+requests==2.34.2
diff --git a/scripts/update_external_patches.py b/scripts/update_external_patches.py
index 341cb77f7..bb7a26626 100644
--- a/scripts/update_external_patches.py
+++ b/scripts/update_external_patches.py
@@ -83,7 +83,7 @@ def main():
       dest = patch.get("dest")
       if not url or not dest:
         die(f"Patch entry missing 'url' or 'dest': {patch}")
-      filename = url.split("/")[-1]
+      filename = patch.get("filename", url.split("/")[-1])
       output_file = os.path.join(OUTPUT_DIR, dest, filename)
       download_patch_from_url(url, output_file)
       replaces = patch.get("replaces", {})
diff --git a/src/-prettierignore.patch b/src/-prettierignore.patch
index ed444531d..3142c427a 100644
--- a/src/-prettierignore.patch
+++ b/src/-prettierignore.patch
@@ -1,8 +1,8 @@
 diff --git a/.prettierignore b/.prettierignore
-index 949896ff064ae0b54b6a657ea074bc88e12820f7..5249f420972667bece4d85fe8d35073afaebeb8a 100644
+index bd8ab46ff7175f5039b69b04c1afe53ab8efe746..7ae12a1ff3724e99aeec2e93518640a2fa9611e6 100644
 --- a/.prettierignore
 +++ b/.prettierignore
-@@ -1803,3 +1803,12 @@ tools/ts/test/baselines/
+@@ -1807,3 +1807,12 @@ tools/ts/test/baselines/
  try_task_config.json
  xpcom/idl-parser/xpidl/fixtures/xpctest.d.json
  **/package-lock.json
@@ -12,6 +12,6 @@ index 949896ff064ae0b54b6a657ea074bc88e12820f7..5249f420972667bece4d85fe8d35073a
 +*.min.js
 +*.min.mjs
 +*.inc
-+*/mochitests/*
++**/mochitests/**
 +*.svg
 +
diff --git a/src/browser/base/content/aboutDialog-js.patch b/src/browser/base/content/aboutDialog-js.patch
index 5ca9f1b12..b0bf35bf5 100644
--- a/src/browser/base/content/aboutDialog-js.patch
+++ b/src/browser/base/content/aboutDialog-js.patch
@@ -1,8 +1,8 @@
 diff --git a/browser/base/content/aboutDialog.js b/browser/base/content/aboutDialog.js
-index f6e1391baf12abb91c85a95107bb3923118746c0..cac04aa288e8a305d0c8b28e0c919abce87658e5 100644
+index a2fb4433c7044e7f5681d5762285314fa3e00a5c..dac1e79e86c534247a470ae062e59f7e7cba6e38 100644
 --- a/browser/base/content/aboutDialog.js
 +++ b/browser/base/content/aboutDialog.js
-@@ -52,7 +52,7 @@ function init() {
+@@ -58,7 +58,7 @@ function init() {
    ]);
    let versionIdKey = "base";
    let versionAttributes = {
@@ -11,7 +11,7 @@ index f6e1391baf12abb91c85a95107bb3923118746c0..cac04aa288e8a305d0c8b28e0c919abc
    };
  
    let arch = Services.sysinfo.get("arch");
-@@ -64,7 +64,7 @@ function init() {
+@@ -70,7 +70,7 @@ function init() {
    }
  
    let version = Services.appinfo.version;
@@ -20,7 +20,7 @@ index f6e1391baf12abb91c85a95107bb3923118746c0..cac04aa288e8a305d0c8b28e0c919abc
      versionIdKey += "-nightly";
      let buildID = Services.appinfo.appBuildID;
      let year = buildID.slice(0, 4);
-@@ -125,14 +125,6 @@ function init() {
+@@ -158,14 +158,6 @@ function init() {
        window.close();
      });
    if (AppConstants.MOZ_UPDATER) {
diff --git a/src/browser/base/content/aboutDialog-xhtml.patch b/src/browser/base/content/aboutDialog-xhtml.patch
index 3665d002a..db0836ebf 100644
--- a/src/browser/base/content/aboutDialog-xhtml.patch
+++ b/src/browser/base/content/aboutDialog-xhtml.patch
@@ -1,5 +1,5 @@
 diff --git a/browser/base/content/aboutDialog.xhtml b/browser/base/content/aboutDialog.xhtml
-index 3ffd464b960a4299a7dd0cd87e4fc2f781b9d593..7a831c8ee2b73bb89bf8a82ac24958b55c16a5aa 100644
+index 067eaf8d4e23f76a2423d01a1d9fa71d9ef3c65f..e0badae05d1da7e6de43e1d517539d4b09ec90f5 100644
 --- a/browser/base/content/aboutDialog.xhtml
 +++ b/browser/base/content/aboutDialog.xhtml
 @@ -102,10 +102,6 @@
@@ -13,7 +13,7 @@ index 3ffd464b960a4299a7dd0cd87e4fc2f781b9d593..7a831c8ee2b73bb89bf8a82ac24958b5
              </vbox>
  #endif
            </hbox>
-@@ -120,26 +116,22 @@
+@@ -120,12 +116,12 @@
            <vbox id="experimental" hidden="true">
              <description class="text-blurb" id="warningDesc" data-l10n-id="warningDesc-version"></description>
              <description class="text-blurb" id="communityExperimentalDesc" data-l10n-id="community-exp">
@@ -27,13 +27,8 @@ index 3ffd464b960a4299a7dd0cd87e4fc2f781b9d593..7a831c8ee2b73bb89bf8a82ac24958b5
 +            <label is="text-link" href="https://github.com/zen-browser/desktop" data-l10n-name="community-mozillaLink"/>
              <label is="text-link" useoriginprincipal="true" href="about:credits" data-l10n-name="community-creditsLink"/>
            </description>
--          <description class="text-blurb" id="contributeDesc" data-l10n-id="helpus">
--            <label is="text-link" href="https://foundation.mozilla.org/?form=firefox-about" data-l10n-name="helpus-donateLink"/>
--            <label is="text-link" href="https://www.mozilla.org/contribute/?utm_source=firefox-browser&#38;utm_medium=firefox-desktop&#38;utm_campaign=about-dialog" data-l10n-name="helpus-getInvolvedLink"/>
--          </description>
-         </vbox>
-       </vbox>
-     </hbox>
+           <description class="text-blurb" id="contributeDesc" data-l10n-id="helpus">
+@@ -144,8 +140,8 @@
      <vbox id="bottomBox">
        <hbox pack="center">
          <label is="text-link" class="bottom-link" useoriginprincipal="true" href="about:license" data-l10n-id="bottomLinks-license"/>
diff --git a/src/browser/base/content/browser-box-inc-xhtml.patch b/src/browser/base/content/browser-box-inc-xhtml.patch
index a45ec45a0..0fbb710dd 100644
--- a/src/browser/base/content/browser-box-inc-xhtml.patch
+++ b/src/browser/base/content/browser-box-inc-xhtml.patch
@@ -1,5 +1,5 @@
 diff --git a/browser/base/content/browser-box.inc.xhtml b/browser/base/content/browser-box.inc.xhtml
-index 4a16fe93daeefb88af024c1dac05bc1f518c3fcb..a420768e4047937c8becefb69c1017e13fc12231 100644
+index cf35762fdcc4716932c7af7cf4af4b2f72aea038..6c13e42806ce80accce464d7ec7e022a0d8e0078 100644
 --- a/browser/base/content/browser-box.inc.xhtml
 +++ b/browser/base/content/browser-box.inc.xhtml
 @@ -3,12 +3,22 @@
@@ -28,12 +28,12 @@ index 4a16fe93daeefb88af024c1dac05bc1f518c3fcb..a420768e4047937c8becefb69c1017e1
 @@ -25,7 +35,7 @@
      </stack>
    </vbox>
-   <splitter id="sidebar-splitter" class="chromeclass-extrachrome sidebar-splitter" resizebefore="sibling" resizeafter="none" hidden="true"/>
+   <splitter id="sidebar-splitter" class="chromeclass-extrachrome sidebar-splitter" resizebefore="sibling" resizeafter="none" hidden="true" role="separator" aria-controls="sidebar-box" data-l10n-id="sidebar-resize-splitter"/>
 -  <tabbox id="tabbrowser-tabbox" flex="1" tabcontainer="tabbrowser-tabs">
 +#include zen-tabbrowser-elements.inc.xhtml
      <tabpanels id="tabbrowser-tabpanels" flex="1" selectedIndex="0"/>
    </tabbox>
-   <splitter id="ai-window-splitter" class="chromeclass-extrachrome sidebar-splitter" resizebefore="none" resizeafter="sibling" collapsed="true"/>
+   <splitter id="ai-window-splitter" class="chromeclass-extrachrome sidebar-splitter" resizebefore="sibling" resizeafter="sibling" collapsed="true"/>
 @@ -34,3 +44,5 @@
      </stack>
    </vbox>
diff --git a/src/browser/base/content/browser-fullScreenAndPointerLock-js.patch b/src/browser/base/content/browser-fullScreenAndPointerLock-js.patch
index e3f016e80..06d8aa99b 100644
--- a/src/browser/base/content/browser-fullScreenAndPointerLock-js.patch
+++ b/src/browser/base/content/browser-fullScreenAndPointerLock-js.patch
@@ -1,5 +1,5 @@
 diff --git a/browser/base/content/browser-fullScreenAndPointerLock.js b/browser/base/content/browser-fullScreenAndPointerLock.js
-index d0d3b6fc57800b073bb1c75f6e55212749815b0a..f3d5790eed58f1cb9a36229582e0fa00f3668962 100644
+index 991cbab1fca19bc20adabb73c146c26a57db68eb..5c0debc58c9614b13916e758c7f64b522756c1d4 100644
 --- a/browser/base/content/browser-fullScreenAndPointerLock.js
 +++ b/browser/base/content/browser-fullScreenAndPointerLock.js
 @@ -502,8 +502,6 @@ var FullScreen = {
@@ -7,7 +7,7 @@ index d0d3b6fc57800b073bb1c75f6e55212749815b0a..f3d5790eed58f1cb9a36229582e0fa00
      let translate = shiftSize > 0 ? `0 ${shiftSize}px` : "";
      gNavToolbox.classList.toggle("fullscreen-floating-toolbox", shiftSize > 0);
 -    gNavToolbox.style.translate = translate;
--    gURLBar.style.translate = gURLBar.hasAttribute("breakout") ? translate : "";
-     let searchbar = document.getElementById("searchbar-new");
-     if (searchbar) {
-       searchbar.style.translate = searchbar.hasAttribute("breakout")
+-    gURLBar.style.setProperty("--toolbar-shift-translate", translate);
+     document
+       .getElementById("searchbar-new")
+       ?.style.setProperty("--toolbar-shift-translate", translate);
diff --git a/src/browser/base/content/browser-js.patch b/src/browser/base/content/browser-js.patch
index db7aaeba1..ad3e5b9a2 100644
--- a/src/browser/base/content/browser-js.patch
+++ b/src/browser/base/content/browser-js.patch
@@ -1,16 +1,16 @@
 diff --git a/browser/base/content/browser.js b/browser/base/content/browser.js
-index 1026474bb1bc026987be01a8c18fa0927cb911bc..60294e0587147d86ace8e6d6985d8c6eae8248b6 100644
+index 4960f4baed32a9e9f523262591eb93550ca9c4b0..9ee825057b1b3b5a08e1d2b2c1036f1be2088da6 100644
 --- a/browser/base/content/browser.js
 +++ b/browser/base/content/browser.js
 @@ -34,6 +34,7 @@ ChromeUtils.defineESModuleGetters(this, {
-     "resource://gre/modules/ContextualIdentityService.sys.mjs",
+     "moz-src:///toolkit/components/contextualidentity/ContextualIdentityService.sys.mjs",
    CustomizableUI:
      "moz-src:///browser/components/customizableui/CustomizableUI.sys.mjs",
 +  ZenCustomizableUI: "resource:///modules/ZenCustomizableUI.sys.mjs",
    DevToolsSocketStatus:
      "resource://devtools/shared/security/DevToolsSocketStatus.sys.mjs",
    DownloadUtils: "resource://gre/modules/DownloadUtils.sys.mjs",
-@@ -816,7 +817,12 @@ function UpdateBackForwardCommands(aWebNavigation) {
+@@ -831,7 +832,12 @@ function UpdateBackForwardCommands(aWebNavigation) {
  
    var backDisabled = backCommand.hasAttribute("disabled");
    var forwardDisabled = forwardCommand.hasAttribute("disabled");
@@ -24,7 +24,7 @@ index 1026474bb1bc026987be01a8c18fa0927cb911bc..60294e0587147d86ace8e6d6985d8c6e
      if (backDisabled) {
        backCommand.removeAttribute("disabled");
      } else {
-@@ -3719,7 +3725,7 @@ function warnAboutClosingWindow() {
+@@ -3973,7 +3979,7 @@ function warnAboutClosingWindow() {
  
    if (!isPBWindow && !toolbar.visible) {
      return gBrowser.warnAboutClosingTabs(
@@ -33,7 +33,7 @@ index 1026474bb1bc026987be01a8c18fa0927cb911bc..60294e0587147d86ace8e6d6985d8c6e
        gBrowser.closingTabsEnum.ALL
      );
    }
-@@ -3759,7 +3765,7 @@ function warnAboutClosingWindow() {
+@@ -4013,7 +4019,7 @@ function warnAboutClosingWindow() {
      return (
        isPBWindow ||
        gBrowser.warnAboutClosingTabs(
@@ -42,7 +42,7 @@ index 1026474bb1bc026987be01a8c18fa0927cb911bc..60294e0587147d86ace8e6d6985d8c6e
          gBrowser.closingTabsEnum.ALL
        )
      );
-@@ -3784,7 +3790,7 @@ function warnAboutClosingWindow() {
+@@ -4038,7 +4044,7 @@ function warnAboutClosingWindow() {
      AppConstants.platform != "macosx" ||
      isPBWindow ||
      gBrowser.warnAboutClosingTabs(
@@ -51,7 +51,7 @@ index 1026474bb1bc026987be01a8c18fa0927cb911bc..60294e0587147d86ace8e6d6985d8c6e
        gBrowser.closingTabsEnum.ALL
      )
    );
-@@ -4744,6 +4750,16 @@ var ConfirmationHint = {
+@@ -4998,6 +5004,16 @@ var ConfirmationHint = {
      }
  
      document.l10n.setAttributes(this._message, messageId, l10nArgs);
diff --git a/src/browser/base/content/navigator-toolbox-inc-xhtml.patch b/src/browser/base/content/navigator-toolbox-inc-xhtml.patch
index 6df802924..471dd604f 100644
--- a/src/browser/base/content/navigator-toolbox-inc-xhtml.patch
+++ b/src/browser/base/content/navigator-toolbox-inc-xhtml.patch
@@ -1,5 +1,5 @@
 diff --git a/browser/base/content/navigator-toolbox.inc.xhtml b/browser/base/content/navigator-toolbox.inc.xhtml
-index e7e94e13a990c154fb54bda4a3420ca00bdac009..8253b7d403734973729a5982cceafc12bab24f54 100644
+index dd2f391096968564086911c532f696dc7ffb8ae1..3de617bf4fb7fa35f7d4d7b618e4673b72b953ee 100644
 --- a/browser/base/content/navigator-toolbox.inc.xhtml
 +++ b/browser/base/content/navigator-toolbox.inc.xhtml
 @@ -2,7 +2,7 @@
@@ -26,7 +26,7 @@ index e7e94e13a990c154fb54bda4a3420ca00bdac009..8253b7d403734973729a5982cceafc12
    <toolbar id="TabsToolbar"
             class="browser-toolbar browser-titlebar"
             fullscreentoolbar="true"
-@@ -62,6 +66,8 @@
+@@ -54,6 +58,8 @@
            <html:sidebar-pins-promo id="drag-to-pin-promo-card"></html:sidebar-pins-promo>
            <arrowscrollbox id="pinned-tabs-container" orient="horizontal" clicktoscroll=""></arrowscrollbox>
            <splitter orient="vertical" id="vertical-pinned-tabs-splitter" resizebefore="sibling" resizeafter="none" hidden="true"/>
@@ -34,8 +34,8 @@ index e7e94e13a990c154fb54bda4a3420ca00bdac009..8253b7d403734973729a5982cceafc12
 +<html:div id="zen-tabs-wrapper">
            <hbox class="tab-drop-indicator" hidden="true"/>
            <arrowscrollbox id="tabbrowser-arrowscrollbox" orient="horizontal" flex="1" clicktoscroll="" scrolledtostart="" scrolledtoend="">
-             <tab is="tabbrowser-tab" class="tabbrowser-tab" selected="true" visuallyselected="" fadein=""/>
-@@ -81,6 +87,7 @@
+             <tab is="tabbrowser-tab" class="tabbrowser-tab" selected="" visuallyselected="" fadein=""/>
+@@ -73,6 +79,7 @@
                                tooltip="dynamic-shortcut-tooltip"
                                data-l10n-id="tabs-toolbar-new-tab"/>
            <html:span id="tabbrowser-tab-a11y-desc" hidden="true"/>
@@ -43,7 +43,7 @@ index e7e94e13a990c154fb54bda4a3420ca00bdac009..8253b7d403734973729a5982cceafc12
          </tabs>
  
          <toolbarbutton id="new-tab-button"
-@@ -115,9 +122,10 @@
+@@ -99,9 +106,10 @@
  
      <toolbarbutton class="content-analysis-indicator toolbarbutton-1 content-analysis-indicator-icon"/>
  
diff --git a/src/browser/components/aiwindow/ui/modules/AIWindow-sys-mjs.patch b/src/browser/components/aiwindow/ui/modules/AIWindow-sys-mjs.patch
index 22a419454..7f7063e78 100644
--- a/src/browser/components/aiwindow/ui/modules/AIWindow-sys-mjs.patch
+++ b/src/browser/components/aiwindow/ui/modules/AIWindow-sys-mjs.patch
@@ -1,12 +1,12 @@
 diff --git a/browser/components/aiwindow/ui/modules/AIWindow.sys.mjs b/browser/components/aiwindow/ui/modules/AIWindow.sys.mjs
-index 88c3545431cf1a300d968c296d9b171871b15fe5..754cd644f2e7b82db40d5c06618ac1764424484c 100644
+index e0b78c29ad081e6eb541eb2aeae4cb6d5cbb9b9b..ae56a624523bee66bc1d1343b455fc7cb65ebef1 100644
 --- a/browser/components/aiwindow/ui/modules/AIWindow.sys.mjs
 +++ b/browser/components/aiwindow/ui/modules/AIWindow.sys.mjs
-@@ -308,6 +308,7 @@ export const AIWindow = {
-   },
- 
-   _updateToolbarButtonPositions(win) {
+@@ -321,6 +321,7 @@ export const AIWindow = {
+    * @param {boolean} [options.isToggling]
+    */
+   _updateHamburgerMenuPosition(win, { isToggling = false } = {}) {
 +    return;
-     const modeSwitcherButton = win.document.getElementById("ai-window-toggle");
      const hamburgerMenu = win.document.getElementById("PanelUI-button");
-     const hamburgerMenuShouldBeAdjacent =
+     const targetToolbar = win.document.getElementById(
+       this.verticalTabsEnabled ? "nav-bar" : "TabsToolbar"
diff --git a/src/browser/components/asrouter/modules/FeatureCallout-sys-mjs.patch b/src/browser/components/asrouter/modules/FeatureCallout-sys-mjs.patch
index 3a890147a..cffa61439 100644
--- a/src/browser/components/asrouter/modules/FeatureCallout-sys-mjs.patch
+++ b/src/browser/components/asrouter/modules/FeatureCallout-sys-mjs.patch
@@ -1,8 +1,8 @@
 diff --git a/browser/components/asrouter/modules/FeatureCallout.sys.mjs b/browser/components/asrouter/modules/FeatureCallout.sys.mjs
-index c4638d2d557f05fa6638cd379be8e0076336f8dc..2e25f485aa94485d12ca9e98aa4eaf56a06cf1f8 100644
+index f6230d6f7ed589f4336387b6115ae4527cdb071b..a289f7b3a665154025121cc9184ab851a74ea33d 100644
 --- a/browser/components/asrouter/modules/FeatureCallout.sys.mjs
 +++ b/browser/components/asrouter/modules/FeatureCallout.sys.mjs
-@@ -778,6 +778,7 @@ export class FeatureCallout {
+@@ -812,6 +812,7 @@ export class FeatureCallout {
      ) {
        return false;
      }
@@ -10,3 +10,11 @@ index c4638d2d557f05fa6638cd379be8e0076336f8dc..2e25f485aa94485d12ca9e98aa4eaf56
  
      const style = this.win.getComputedStyle(el);
      return style?.visibility === "visible" && style?.display !== "none";
+@@ -1115,7 +1116,6 @@ export class FeatureCallout {
+             type="arrow"
+             consumeoutsideclicks="never"
+             norolluponanchor="true"
+-            nonnative=""
+             position="${panel_position?.panel_position_string}"
+             ${hide_arrow ? "" : 'show-arrow=""'}
+             ${autohide ? "" : 'noautohide="true"'}
diff --git a/src/browser/components/customizableui/CustomizableUI-sys-mjs.patch b/src/browser/components/customizableui/CustomizableUI-sys-mjs.patch
index ee13d11b3..15192e8c1 100644
--- a/src/browser/components/customizableui/CustomizableUI-sys-mjs.patch
+++ b/src/browser/components/customizableui/CustomizableUI-sys-mjs.patch
@@ -1,5 +1,5 @@
 diff --git a/browser/components/customizableui/CustomizableUI.sys.mjs b/browser/components/customizableui/CustomizableUI.sys.mjs
-index d5d4596739cde5d3d49d6294867f5da122c526b8..c206cfb374542c496be9bf0305a0a80bbcf503b2 100644
+index 491161e48044f75167a8e8a0348779cfa22fc40e..867d51b8a6b74f841afc6d84dcdfd8f2681652e5 100644
 --- a/browser/components/customizableui/CustomizableUI.sys.mjs
 +++ b/browser/components/customizableui/CustomizableUI.sys.mjs
 @@ -13,6 +13,7 @@ ChromeUtils.defineESModuleGetters(lazy, {
@@ -10,7 +10,7 @@ index d5d4596739cde5d3d49d6294867f5da122c526b8..c206cfb374542c496be9bf0305a0a80b
    HomePage: "resource:///modules/HomePage.sys.mjs",
    PanelMultiView:
      "moz-src:///browser/components/customizableui/PanelMultiView.sys.mjs",
-@@ -347,7 +348,7 @@ var CustomizableUIInternal = {
+@@ -348,7 +349,7 @@ var CustomizableUIInternal = {
        {
          type: CustomizableUI.TYPE_PANEL,
          defaultPlacements: [],
@@ -19,7 +19,7 @@ index d5d4596739cde5d3d49d6294867f5da122c526b8..c206cfb374542c496be9bf0305a0a80b
        },
        false
      );
-@@ -357,20 +358,15 @@ var CustomizableUIInternal = {
+@@ -358,27 +359,23 @@ var CustomizableUIInternal = {
        "back-button",
        "forward-button",
        "stop-reload-button",
@@ -41,27 +41,26 @@ index d5d4596739cde5d3d49d6294867f5da122c526b8..c206cfb374542c496be9bf0305a0a80b
      this.registerArea(
        CustomizableUI.AREA_NAVBAR,
        {
-@@ -378,8 +374,6 @@ var CustomizableUIInternal = {
+         type: CustomizableUI.TYPE_TOOLBAR,
          overflowable: true,
          defaultPlacements: navbarPlacements,
-         verticalTabsDefaultPlacements: [
--          "firefox-view-button",
--          "alltabs-button",
-         ],
+-        verticalTabsDefaultPlacements: ["alltabs-button", "ai-window-toggle"],
++        verticalTabsDefaultPlacements: [
++        ],
          defaultCollapsed: false,
        },
-@@ -403,10 +397,7 @@ var CustomizableUIInternal = {
-       {
+       true
+@@ -402,9 +399,6 @@ var CustomizableUIInternal = {
          type: CustomizableUI.TYPE_TOOLBAR,
          defaultPlacements: [
--          "firefox-view-button",
            "tabbrowser-tabs",
 -          "new-tab-button",
 -          "alltabs-button",
+-          "ai-window-toggle",
          ],
          verticalTabsDefaultPlacements: [],
          defaultCollapsed: null,
-@@ -486,6 +477,7 @@ var CustomizableUIInternal = {
+@@ -484,6 +478,7 @@ var CustomizableUIInternal = {
        CustomizableUI.AREA_NAVBAR,
        CustomizableUI.AREA_BOOKMARKS,
        CustomizableUI.AREA_TABSTRIP,
@@ -69,7 +68,7 @@ index d5d4596739cde5d3d49d6294867f5da122c526b8..c206cfb374542c496be9bf0305a0a80b
      ]);
      if (AppConstants.platform != "macosx") {
        toolbars.add(CustomizableUI.AREA_MENUBAR);
-@@ -1262,6 +1254,9 @@ var CustomizableUIInternal = {
+@@ -1285,6 +1280,9 @@ var CustomizableUIInternal = {
          placements = gPlacements.get(area);
        }
  
@@ -79,7 +78,7 @@ index d5d4596739cde5d3d49d6294867f5da122c526b8..c206cfb374542c496be9bf0305a0a80b
        // For toolbars that need it, mark as dirty.
        let defaultPlacements = areaProperties.get("defaultPlacements");
        if (
-@@ -1769,7 +1764,6 @@ var CustomizableUIInternal = {
+@@ -1793,7 +1791,6 @@ var CustomizableUIInternal = {
          lazy.log.info(
            "Widget " + aWidgetId + " not found, unable to remove from " + aArea
          );
@@ -87,7 +86,7 @@ index d5d4596739cde5d3d49d6294867f5da122c526b8..c206cfb374542c496be9bf0305a0a80b
        }
  
        this.notifyDOMChange(widgetNode, null, container, true, () => {
-@@ -1779,7 +1773,7 @@ var CustomizableUIInternal = {
+@@ -1803,7 +1800,7 @@ var CustomizableUIInternal = {
          // We also need to remove the panel context menu if it's there:
          this.ensureButtonContextMenu(widgetNode);
          if (gPalette.has(aWidgetId) || this.isSpecialWidget(aWidgetId)) {
@@ -96,7 +95,7 @@ index d5d4596739cde5d3d49d6294867f5da122c526b8..c206cfb374542c496be9bf0305a0a80b
          } else {
            window.gNavToolbox.palette.appendChild(widgetNode);
          }
-@@ -1947,16 +1941,16 @@ var CustomizableUIInternal = {
+@@ -1971,16 +1968,16 @@ var CustomizableUIInternal = {
          elem.setAttribute("skipintoolbarset", "true");
        }
      }
@@ -116,7 +115,7 @@ index d5d4596739cde5d3d49d6294867f5da122c526b8..c206cfb374542c496be9bf0305a0a80b
      // Handle initial state of vertical tabs.
      if (isVerticalTabs) {
        // Show the vertical tabs toolbar
-@@ -2198,6 +2192,10 @@ var CustomizableUIInternal = {
+@@ -2222,6 +2219,10 @@ var CustomizableUIInternal = {
     *   The identifier string of the area that aNode is being inserted into.
     */
    insertWidgetBefore(aNode, aNextNode, aContainer, aAreaId) {
@@ -127,7 +126,7 @@ index d5d4596739cde5d3d49d6294867f5da122c526b8..c206cfb374542c496be9bf0305a0a80b
      this.notifyDOMChange(aNode, aNextNode, aContainer, false, () => {
        this.setLocationAttributes(aNode, aAreaId);
        aContainer.insertBefore(aNode, aNextNode);
-@@ -4562,7 +4560,7 @@ var CustomizableUIInternal = {
+@@ -4592,7 +4593,7 @@ var CustomizableUIInternal = {
     * For all registered areas, builds those areas to reflect the current
     * placement state of all widgets.
     */
@@ -136,7 +135,7 @@ index d5d4596739cde5d3d49d6294867f5da122c526b8..c206cfb374542c496be9bf0305a0a80b
      for (let [areaId, areaNodes] of gBuildAreas) {
        let placements = gPlacements.get(areaId);
        let isFirstChangedToolbar = true;
-@@ -4573,7 +4571,7 @@ var CustomizableUIInternal = {
+@@ -4603,7 +4604,7 @@ var CustomizableUIInternal = {
          if (area.get("type") == CustomizableUI.TYPE_TOOLBAR) {
            let defaultCollapsed = area.get("defaultCollapsed");
            let win = areaNode.documentGlobal;
@@ -145,7 +144,7 @@ index d5d4596739cde5d3d49d6294867f5da122c526b8..c206cfb374542c496be9bf0305a0a80b
              win.setToolbarVisibility(
                areaNode,
                typeof defaultCollapsed == "string"
-@@ -5864,6 +5862,7 @@ export var CustomizableUI = {
+@@ -5899,6 +5900,7 @@ export var CustomizableUI = {
    unregisterArea(aName, aDestroyPlacements) {
      CustomizableUIInternal.unregisterArea(aName, aDestroyPlacements);
    },
@@ -153,7 +152,7 @@ index d5d4596739cde5d3d49d6294867f5da122c526b8..c206cfb374542c496be9bf0305a0a80b
    /**
     * Add a widget to an area.
     * If the area to which you try to add is not known to CustomizableUI,
-@@ -7827,7 +7826,9 @@ class OverflowableToolbar {
+@@ -7869,7 +7871,9 @@ class OverflowableToolbar {
          );
  
          if (webExtList && CustomizableUI.isWebExtensionWidget(child.id)) {
@@ -163,7 +162,7 @@ index d5d4596739cde5d3d49d6294867f5da122c526b8..c206cfb374542c496be9bf0305a0a80b
            webExtList.insertBefore(child, webExtList.firstElementChild);
          } else {
            child.setAttribute("cui-anchorid", this.#defaultListButton.id);
-@@ -7887,7 +7888,7 @@ class OverflowableToolbar {
+@@ -7929,7 +7933,7 @@ class OverflowableToolbar {
          ) {
            continue;
          }
@@ -172,7 +171,7 @@ index d5d4596739cde5d3d49d6294867f5da122c526b8..c206cfb374542c496be9bf0305a0a80b
          if (child != aExceptChild) {
            sum += getInlineSize(child);
          }
-@@ -7911,11 +7912,11 @@ class OverflowableToolbar {
+@@ -7953,11 +7957,11 @@ class OverflowableToolbar {
          parseFloat(style.paddingLeft) -
          parseFloat(style.paddingRight) -
          toolbarChildrenWidth;
@@ -186,7 +185,7 @@ index d5d4596739cde5d3d49d6294867f5da122c526b8..c206cfb374542c496be9bf0305a0a80b
      });
  
      lazy.log.debug(
-@@ -7930,7 +7931,39 @@ class OverflowableToolbar {
+@@ -7972,7 +7976,39 @@ class OverflowableToolbar {
        Math.max(targetWidth, targetChildrenWidth)
      );
      totalAvailWidth = Math.ceil(totalAvailWidth);
@@ -227,7 +226,7 @@ index d5d4596739cde5d3d49d6294867f5da122c526b8..c206cfb374542c496be9bf0305a0a80b
      return { isOverflowing, targetContentWidth, totalAvailWidth };
    }
  
-@@ -7991,7 +8024,11 @@ class OverflowableToolbar {
+@@ -8033,7 +8069,11 @@ class OverflowableToolbar {
              return;
            }
          }
@@ -240,7 +239,7 @@ index d5d4596739cde5d3d49d6294867f5da122c526b8..c206cfb374542c496be9bf0305a0a80b
            lazy.log.debug(
              `Need ${minSize} but width is ${totalAvailWidth} so bailing`
            );
-@@ -8024,7 +8061,7 @@ class OverflowableToolbar {
+@@ -8066,7 +8106,7 @@ class OverflowableToolbar {
          }
        }
        if (!inserted) {
@@ -249,7 +248,7 @@ index d5d4596739cde5d3d49d6294867f5da122c526b8..c206cfb374542c496be9bf0305a0a80b
        }
        child.removeAttribute("cui-anchorid");
        child.removeAttribute("overflowedItem");
-@@ -8150,6 +8187,9 @@ class OverflowableToolbar {
+@@ -8192,6 +8232,9 @@ class OverflowableToolbar {
     *   if no such list exists.
     */
    get #webExtList() {
@@ -259,7 +258,7 @@ index d5d4596739cde5d3d49d6294867f5da122c526b8..c206cfb374542c496be9bf0305a0a80b
      if (!this.#webExtListRef) {
        let targetID = this.#toolbar.getAttribute("addon-webext-overflowtarget");
        if (!targetID) {
-@@ -8161,6 +8201,9 @@ class OverflowableToolbar {
+@@ -8203,6 +8246,9 @@ class OverflowableToolbar {
        let win = this.#toolbar.documentGlobal;
        let { panel } = win.gUnifiedExtensions;
        this.#webExtListRef = panel.querySelector(`#${targetID}`);
@@ -269,7 +268,7 @@ index d5d4596739cde5d3d49d6294867f5da122c526b8..c206cfb374542c496be9bf0305a0a80b
      }
      return this.#webExtListRef;
    }
-@@ -8369,7 +8412,7 @@ class OverflowableToolbar {
+@@ -8411,7 +8457,7 @@ class OverflowableToolbar {
          break;
        }
        case "mousedown": {
diff --git a/src/browser/components/preferences/main-js.patch b/src/browser/components/preferences/main-js.patch
index 8e57adb8c..960d01ed7 100644
--- a/src/browser/components/preferences/main-js.patch
+++ b/src/browser/components/preferences/main-js.patch
@@ -1,8 +1,8 @@
 diff --git a/browser/components/preferences/main.js b/browser/components/preferences/main.js
-index fcbd421c99b24e53e46131a1e21ec690814cbf4f..fe3778a57aaeebc53f7f6763ea234cbb41816186 100644
+index 88675d1bcbf000b10d85a9c0980bc6069d88052c..ed3a1e809eb0fcccc5a957be7affb77be8978e32 100644
 --- a/browser/components/preferences/main.js
 +++ b/browser/components/preferences/main.js
-@@ -662,6 +662,11 @@ function createStartupConfig(hidden = false) {
+@@ -528,6 +528,11 @@ function createStartupConfig(hidden = false) {
            },
          ],
        },
@@ -14,16 +14,16 @@ index fcbd421c99b24e53e46131a1e21ec690814cbf4f..fe3778a57aaeebc53f7f6763ea234cbb
        {
          id: "windowsLaunchOnLogin",
          l10nId: "windows-launch-on-login",
-@@ -709,7 +714,7 @@ function createStartupConfig(hidden = false) {
+@@ -575,7 +580,7 @@ function createStartupConfig(hidden = false) {
  SettingGroupManager.registerGroups({
    defaultBrowser: createDefaultBrowserConfig(),
    startup: createStartupConfig(
--    Services.prefs.getBoolPref("browser-settings-redesign.enabled", false)
+-    Services.prefs.getBoolPref("browser.settings-redesign.enabled", false)
 +    false
    ),
  });
  
-@@ -762,7 +767,7 @@ function getBundleForLocales(newLocales) {
+@@ -628,7 +633,7 @@ function getBundleForLocales(newLocales) {
      ])
    );
    return new Localization(
diff --git a/src/browser/components/preferences/preferences-js.patch b/src/browser/components/preferences/preferences-js.patch
index 918e727ef..3e3ad8c86 100644
--- a/src/browser/components/preferences/preferences-js.patch
+++ b/src/browser/components/preferences/preferences-js.patch
@@ -1,8 +1,8 @@
 diff --git a/browser/components/preferences/preferences.js b/browser/components/preferences/preferences.js
-index c76a0647e14bac806d9428483bb565b3e10c31e7..2188f7808aca090f92574c7f5c55a28a9c5bb3f8 100644
+index a76699af75252bec31e17b562463c37236cbbfe5..6355a6ee92754846ffcdd123ac49545d520470c7 100644
 --- a/browser/components/preferences/preferences.js
 +++ b/browser/components/preferences/preferences.js
-@@ -131,6 +131,7 @@ ChromeUtils.defineLazyGetter(this, "gSubDialog", function () {
+@@ -132,6 +132,7 @@ ChromeUtils.defineLazyGetter(this, "gSubDialog", function () {
        styleSheets: [
          "chrome://browser/skin/preferences/dialog.css",
          "chrome://browser/skin/preferences/preferences.css",
@@ -10,7 +10,7 @@ index c76a0647e14bac806d9428483bb565b3e10c31e7..2188f7808aca090f92574c7f5c55a28a
        ],
        resizeCallback: async ({ title, frame }) => {
          // Search within main document and highlight matched keyword.
-@@ -437,6 +438,8 @@ const CONFIG_PANES = Object.freeze({
+@@ -462,6 +463,8 @@ const CONFIG_PANES = Object.freeze({
    tabsBrowsing: {
      l10nId: "tabs-browsing-section",
      groupIds: [
@@ -19,7 +19,7 @@ index c76a0647e14bac806d9428483bb565b3e10c31e7..2188f7808aca090f92574c7f5c55a28a
        "browserLayout",
        "tabs",
        "pageNavigation",
-@@ -483,7 +486,7 @@ function register_module(categoryName, categoryObject) {
+@@ -509,7 +512,7 @@ function register_module(categoryName, categoryObject) {
        }
        this._initted = true;
        let template = document.getElementById("template-" + categoryName);
@@ -28,7 +28,7 @@ index c76a0647e14bac806d9428483bb565b3e10c31e7..2188f7808aca090f92574c7f5c55a28a
          // Replace the template element with the nodes inside of it.
          template.replaceWith(template.content);
  
-@@ -527,6 +530,10 @@ function init_all() {
+@@ -553,6 +556,10 @@ function init_all() {
    register_module("paneHome", gHomePane);
    register_module("paneSearch", gSearchPane);
    register_module("panePrivacy", gPrivacyPane);
@@ -39,15 +39,3 @@ index c76a0647e14bac806d9428483bb565b3e10c31e7..2188f7808aca090f92574c7f5c55a28a
  
    // Restore the cached Firefox Labs nav button visibility so it shows
    // immediately when recipes are expected to be available, before
-@@ -656,9 +663,9 @@ async function gotoPref(
-   let redesignEnabled = srdSectionPrefs.all;
-   let categories = document.getElementById("categories");
-   const kDefaultCategoryInternalName = redesignEnabled
--    ? "paneSync"
-+    ? "paneTabsBrowsing"
-     : "paneGeneral";
--  const kDefaultCategory = redesignEnabled ? "sync" : "general";
-+  const kDefaultCategory = redesignEnabled ? "tabsBrowsing" : "general";
-   let hash = document.location.hash;
-   let category = aCategory || hash.substring(1) || kDefaultCategoryInternalName;
- 
diff --git a/src/browser/components/preferences/widgets/sync-engine-list/sync-engines-list-mjs.patch b/src/browser/components/preferences/widgets/sync-engine-list/sync-engines-list-mjs.patch
new file mode 100644
index 000000000..6bcfd56b9
--- /dev/null
+++ b/src/browser/components/preferences/widgets/sync-engine-list/sync-engines-list-mjs.patch
@@ -0,0 +1,15 @@
+diff --git a/browser/components/preferences/widgets/sync-engine-list/sync-engines-list.mjs b/browser/components/preferences/widgets/sync-engine-list/sync-engines-list.mjs
+index 9359a485ed6212c7df49a8d4b1e4a8febbc1c9b6..132fea440cfa535e78b35f706e7ef2d6881f9ba6 100644
+--- a/browser/components/preferences/widgets/sync-engine-list/sync-engines-list.mjs
++++ b/browser/components/preferences/widgets/sync-engine-list/sync-engines-list.mjs
+@@ -50,6 +50,10 @@ const engineTypeToMetadata = {
+     iconSrc: "chrome://global/skin/icons/settings.svg",
+     l10nId: "sync-currently-syncing-settings",
+   },
++  workspaces: {
++    iconSrc: "chrome://devtools/skin/images/tool-storage.svg",
++    l10nId: "sync-currently-syncing-workspaces",
++  },
+ };
+ 
+ /**
diff --git a/src/browser/components/preferences/zen-settings.js b/src/browser/components/preferences/zen-settings.js
index 73d5663cf..83f2fc3c4 100644
--- a/src/browser/components/preferences/zen-settings.js
+++ b/src/browser/components/preferences/zen-settings.js
@@ -1184,6 +1184,11 @@ Preferences.addAll([
     type: "bool",
     default: true,
   },
+  {
+    id: "zen.view.drag-window-from-content",
+    type: "bool",
+    default: true,
+  },
   {
     id: "zen.urlbar.behavior",
     type: "string",
diff --git a/src/browser/components/preferences/zenLooksAndFeel.inc.xhtml b/src/browser/components/preferences/zenLooksAndFeel.inc.xhtml
index 08b2c2ef7..8f004a3b5 100644
--- a/src/browser/components/preferences/zenLooksAndFeel.inc.xhtml
+++ b/src/browser/components/preferences/zenLooksAndFeel.inc.xhtml
@@ -61,6 +61,15 @@
                       data-l10n-id="zen-look-and-feel-compact-toolbar-flash-popup"
                       preference="zen.view.compact.toolbar-flash-popup"/>
       </vbox>
+
+      <label><html:h2 data-l10n-id="zen-look-and-feel-window-drag-header"/></label>
+      <description class="description-deemphasized" data-l10n-id="zen-look-and-feel-window-drag-description" />
+
+      <vbox class="indent">
+            <checkbox id="zenLooksAndFeelWindowDragEnabled"
+                  data-l10n-id="zen-window-drag-enabled"
+                  preference="zen.view.drag-window-from-content"/>
+      </vbox>
 </groupbox>
 
 <hbox id="zenGlanceCategory"
diff --git a/src/browser/components/sessionstore/SessionStore-sys-mjs.patch b/src/browser/components/sessionstore/SessionStore-sys-mjs.patch
index b421fd11b..f0131d9e7 100644
--- a/src/browser/components/sessionstore/SessionStore-sys-mjs.patch
+++ b/src/browser/components/sessionstore/SessionStore-sys-mjs.patch
@@ -1,18 +1,20 @@
 diff --git a/browser/components/sessionstore/SessionStore.sys.mjs b/browser/components/sessionstore/SessionStore.sys.mjs
-index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee4aa3be28 100644
+index 536e06eec9f35bad3b8366733b23b5a8697df9c8..631a16bc7518108641993836f0c52e2ab6e6c967 100644
 --- a/browser/components/sessionstore/SessionStore.sys.mjs
 +++ b/browser/components/sessionstore/SessionStore.sys.mjs
-@@ -129,6 +129,9 @@ const TAB_EVENTS = [
+@@ -129,6 +129,11 @@ const TAB_EVENTS = [
    "TabSplitViewActivate",
    "SplitViewRemoved",
    "SplitViewCreated",
 +  "TabAddedToEssentials",
 +  "TabRemovedFromEssentials",
++  "TabMove",
++  "TabGroupMoved",
 +  "ZenWorkspaceDataChanged",
  ];
  
  const XUL_NS = "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul";
-@@ -201,6 +204,8 @@ ChromeUtils.defineESModuleGetters(lazy, {
+@@ -201,6 +206,8 @@ ChromeUtils.defineESModuleGetters(lazy, {
    TabStateCache: "resource:///modules/sessionstore/TabStateCache.sys.mjs",
    TabStateFlusher: "resource:///modules/sessionstore/TabStateFlusher.sys.mjs",
    setTimeout: "resource://gre/modules/Timer.sys.mjs",
@@ -21,7 +23,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
  });
  
  ChromeUtils.defineLazyGetter(lazy, "blankURI", () => {
-@@ -1300,10 +1305,7 @@ var SessionStoreInternal = {
+@@ -1317,10 +1324,7 @@ var SessionStoreInternal = {
     */
    get willAutoRestore() {
      return (
@@ -33,17 +35,19 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
      );
    },
  
-@@ -1990,6 +1992,9 @@ var SessionStoreInternal = {
+@@ -2008,6 +2012,11 @@ var SessionStoreInternal = {
        case "TabPinned":
        case "TabUnpinned":
        case "SwapDocShells":
 +      case "TabRemovedFromEssentials":
 +      case "TabAddedToEssentials":
++      case "TabMove":
++      case "TabGroupMoved":
 +      case "ZenWorkspaceDataChanged":
          this.saveStateDelayed(win);
          break;
        case "TabGroupCreate":
-@@ -2099,6 +2104,10 @@ var SessionStoreInternal = {
+@@ -2117,6 +2126,10 @@ var SessionStoreInternal = {
        this._windows[aWindow.__SSi].isTaskbarTab = true;
      }
  
@@ -54,7 +58,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
      if (lazy.AIWindow.isAIWindowActiveAndEnabled(aWindow)) {
        this._windows[aWindow.__SSi].isAIWindow = true;
      }
-@@ -2135,7 +2144,7 @@ var SessionStoreInternal = {
+@@ -2153,7 +2166,7 @@ var SessionStoreInternal = {
      let isTaskbarTab = this._windows[aWindow.__SSi].isTaskbarTab;
      // A regular window is not a private window, taskbar tab window, or popup window
      let isRegularWindow =
@@ -63,7 +67,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
  
      // perform additional initialization when the first window is loading
      if (lazy.RunState.isStopped) {
-@@ -2147,7 +2156,7 @@ var SessionStoreInternal = {
+@@ -2165,7 +2178,7 @@ var SessionStoreInternal = {
          // to disk to NOW() to enforce a full interval before the next write.
          lazy.SessionSaver.updateLastSaveTime();
  
@@ -72,7 +76,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
            this._log.debug(
              "initializeWindow, the window is private or a web app. Saving SessionStartup.state for possibly restoring later"
            );
-@@ -2191,6 +2200,7 @@ var SessionStoreInternal = {
+@@ -2209,6 +2222,7 @@ var SessionStoreInternal = {
            null,
            "sessionstore-one-or-no-tab-restored"
          );
@@ -80,7 +84,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
          this._deferredAllWindowsRestored.resolve();
        }
        // this window was opened by _openWindowWithState
-@@ -2240,7 +2250,6 @@ var SessionStoreInternal = {
+@@ -2258,7 +2272,6 @@ var SessionStoreInternal = {
        if (closedWindowState) {
          let newWindowState;
          if (
@@ -88,7 +92,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
            !lazy.SessionStartup.willRestore()
          ) {
            // We want to split the window up into pinned tabs and unpinned tabs.
-@@ -2276,6 +2285,7 @@ var SessionStoreInternal = {
+@@ -2294,6 +2307,7 @@ var SessionStoreInternal = {
          }
  
          if (newWindowState) {
@@ -96,7 +100,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
            // Ensure that the window state isn't hidden
            this._restoreCount = 1;
            let state = { windows: [newWindowState] };
-@@ -2312,6 +2322,9 @@ var SessionStoreInternal = {
+@@ -2330,6 +2344,9 @@ var SessionStoreInternal = {
        });
        this._shouldRestoreLastSession = false;
      }
@@ -106,7 +110,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
  
      if (this._restoreLastWindow && aWindow.toolbar.visible) {
        // always reset (if not a popup window)
-@@ -2462,7 +2475,7 @@ var SessionStoreInternal = {
+@@ -2480,7 +2497,7 @@ var SessionStoreInternal = {
  
      var tabbrowser = aWindow.gBrowser;
  
@@ -115,7 +119,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
  
      TAB_EVENTS.forEach(function (aEvent) {
        tabbrowser.tabContainer.removeEventListener(aEvent, this, true);
-@@ -2513,7 +2526,7 @@ var SessionStoreInternal = {
+@@ -2531,7 +2548,7 @@ var SessionStoreInternal = {
  
        let isLastRegularWindow =
          Object.values(this._windows).filter(
@@ -124,7 +128,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
          ).length == 1;
        this._log.debug(
          `onClose, closing window isLastRegularWindow? ${isLastRegularWindow}`
-@@ -2570,8 +2583,8 @@ var SessionStoreInternal = {
+@@ -2588,8 +2605,8 @@ var SessionStoreInternal = {
        // 2) Flush the window.
        // 3) When the flush is complete, revisit our decision to store the window
        //    in _closedWindows, and add/remove as necessary.
@@ -135,7 +139,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
        }
  
        completionPromise = lazy.TabStateFlusher.flushWindow(aWindow).then(() => {
-@@ -2591,8 +2604,9 @@ var SessionStoreInternal = {
+@@ -2609,8 +2626,9 @@ var SessionStoreInternal = {
  
          // Save non-private windows if they have at
          // least one saveable tab or are the last window.
@@ -147,7 +151,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
  
            if (!isLastWindow && winData.closedId > -1) {
              this._addClosedAction(
-@@ -2668,7 +2682,7 @@ var SessionStoreInternal = {
+@@ -2686,7 +2704,7 @@ var SessionStoreInternal = {
     *        to call this method again asynchronously (for example, after
     *        a window flush).
     */
@@ -156,7 +160,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
      // Make sure SessionStore is still running, and make sure that we
      // haven't chosen to forget this window.
      if (
-@@ -2685,6 +2699,7 @@ var SessionStoreInternal = {
+@@ -2703,6 +2721,7 @@ var SessionStoreInternal = {
        // _closedWindows from a previous call to this function.
        let winIndex = this._closedWindows.indexOf(winData);
        let alreadyStored = winIndex != -1;
@@ -164,7 +168,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
        // If sidebar command is truthy, i.e. sidebar is open, store sidebar settings
        let shouldStore = hasSaveableTabs || isLastWindow;
  
-@@ -3507,7 +3522,7 @@ var SessionStoreInternal = {
+@@ -3525,7 +3544,7 @@ var SessionStoreInternal = {
      if (!isPrivateWindow && tabState.isPrivate) {
        return;
      }
@@ -173,7 +177,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
        return;
      }
  
-@@ -4246,6 +4261,12 @@ var SessionStoreInternal = {
+@@ -4264,6 +4283,12 @@ var SessionStoreInternal = {
          Math.min(tabState.index, tabState.entries.length)
        );
        tabState.pinned = false;
@@ -186,7 +190,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
  
        if (inBackground === false) {
          aWindow.gBrowser.selectedTab = newTab;
-@@ -4679,6 +4700,8 @@ var SessionStoreInternal = {
+@@ -4697,6 +4722,8 @@ var SessionStoreInternal = {
        // Append the tab if we're opening into a different window,
        tabIndex: aSource == aTargetWindow ? pos : Infinity,
        pinned: state.pinned,
@@ -195,7 +199,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
        userContextId: state.userContextId,
        skipLoad: true,
        preferredRemoteType,
-@@ -5176,9 +5199,10 @@ var SessionStoreInternal = {
+@@ -5194,9 +5221,10 @@ var SessionStoreInternal = {
        if (activePageData.title && activePageData.title != activePageData.url) {
          win.gBrowser.setInitialTabTitle(tab, activePageData.title, {
            isContentTitle: true,
@@ -207,7 +211,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
        }
      }
  
-@@ -5543,7 +5567,7 @@ var SessionStoreInternal = {
+@@ -5561,7 +5589,7 @@ var SessionStoreInternal = {
  
      for (let i = tabbrowser.pinnedTabCount; i < tabbrowser.tabs.length; i++) {
        let tab = tabbrowser.tabs[i];
@@ -216,7 +220,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
          removableTabs.push(tab);
        }
      }
-@@ -5656,7 +5680,7 @@ var SessionStoreInternal = {
+@@ -5674,7 +5702,7 @@ var SessionStoreInternal = {
  
      // collect the data for all windows
      for (ix in this._windows) {
@@ -225,7 +229,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
          // window data is still in _statesToRestore
          continue;
        }
-@@ -5800,11 +5824,12 @@ var SessionStoreInternal = {
+@@ -5818,11 +5846,12 @@ var SessionStoreInternal = {
      }
  
      let tabbrowser = aWindow.gBrowser;
@@ -239,7 +243,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
      // update the internal state data for this window
      for (let tab of tabs) {
        if (tab == aWindow.FirefoxViewHandler.tab) {
-@@ -5815,6 +5840,9 @@ var SessionStoreInternal = {
+@@ -5833,6 +5862,9 @@ var SessionStoreInternal = {
        tabsData.push(tabData);
      }
  
@@ -249,7 +253,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
      // update tab group state for this window
      winData.groups = [];
      for (let tabGroup of aWindow.gBrowser.tabGroups) {
-@@ -5831,7 +5859,7 @@ var SessionStoreInternal = {
+@@ -5849,7 +5881,7 @@ var SessionStoreInternal = {
      // a window is closed, point to the first item in the tab strip instead (it will never be the Firefox View tab,
      // since it's only inserted into the tab strip after it's selected).
      if (aWindow.FirefoxViewHandler.tab?.selected) {
@@ -258,7 +262,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
        winData.title = tabbrowser.tabs[0].label;
      }
      winData.selected = selectedIndex;
-@@ -6033,8 +6061,8 @@ var SessionStoreInternal = {
+@@ -6051,8 +6083,8 @@ var SessionStoreInternal = {
      // selectTab represents.
      let selectTab = 0;
      if (overwriteTabs) {
@@ -269,7 +273,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
        selectTab = Math.min(selectTab, winData.tabs.length);
      }
  
-@@ -6056,6 +6084,7 @@ var SessionStoreInternal = {
+@@ -6074,6 +6106,7 @@ var SessionStoreInternal = {
      if (overwriteTabs) {
        for (let i = tabbrowser.browsers.length - 1; i >= 0; i--) {
          if (!tabbrowser.tabs[i].selected) {
@@ -277,7 +281,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
            tabbrowser.removeTab(tabbrowser.tabs[i]);
          }
        }
-@@ -6090,6 +6119,12 @@ var SessionStoreInternal = {
+@@ -6108,6 +6141,12 @@ var SessionStoreInternal = {
          savedTabGroup => !openTabGroupIdsInWindow.has(savedTabGroup.id)
        );
      }
@@ -290,7 +294,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
  
      // Move the originally open tabs to the end.
      if (initialTabs) {
-@@ -6656,6 +6691,25 @@ var SessionStoreInternal = {
+@@ -6674,6 +6713,25 @@ var SessionStoreInternal = {
  
      // Most of tabData has been restored, now continue with restoring
      // attributes that may trigger external events.
@@ -316,7 +320,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
  
      if (tabData.pinned) {
        tabbrowser.pinTab(tab);
-@@ -6838,6 +6892,9 @@ var SessionStoreInternal = {
+@@ -6859,6 +6917,9 @@ var SessionStoreInternal = {
          aWindow.gURLBar.readOnly = false;
        }
      }
@@ -326,7 +330,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
  
      let promiseParts = Promise.withResolvers();
      aWindow.setTimeout(() => {
-@@ -7633,7 +7690,7 @@ var SessionStoreInternal = {
+@@ -7654,7 +7715,7 @@ var SessionStoreInternal = {
  
        let groupsToSave = new Map();
        for (let tIndex = 0; tIndex < window.tabs.length; ) {
@@ -335,7 +339,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
            // Adjust window.selected
            if (tIndex + 1 < window.selected) {
              window.selected -= 1;
-@@ -7648,7 +7705,7 @@ var SessionStoreInternal = {
+@@ -7669,7 +7730,7 @@ var SessionStoreInternal = {
            );
            // We don't want to increment tIndex here.
            continue;
@@ -344,7 +348,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
            // Convert any open groups into saved groups.
            let groupStateToSave = window.groups.find(
              groupState => groupState.id == window.tabs[tIndex].groupId
-@@ -8193,7 +8250,6 @@ var SessionStoreInternal = {
+@@ -8233,7 +8294,6 @@ var SessionStoreInternal = {
      timer.initWithCallback(
        function () {
          if (beats <= 0) {
@@ -352,7 +356,7 @@ index 11191a82a0f0dc6eee60f9de52a63bc6085c3981..f995c3b297c53aa6ee2219bfc09515ee
            Glean.sessionRestore.shutdownFlushAllOutcomes.timed_out.add(1);
            deferred.resolve();
          }
-@@ -8671,6 +8727,7 @@ var SessionStoreInternal = {
+@@ -8711,6 +8771,7 @@ var SessionStoreInternal = {
      if (
        !savedTabGroupState.tabs.length ||
        this.getSavedTabGroup(savedTabGroupState.id)
diff --git a/src/browser/components/sessionstore/TabState-sys-mjs.patch b/src/browser/components/sessionstore/TabState-sys-mjs.patch
index ea08f3598..e9b6ed2a6 100644
--- a/src/browser/components/sessionstore/TabState-sys-mjs.patch
+++ b/src/browser/components/sessionstore/TabState-sys-mjs.patch
@@ -1,8 +1,16 @@
 diff --git a/browser/components/sessionstore/TabState.sys.mjs b/browser/components/sessionstore/TabState.sys.mjs
-index 4ba4dda363b602cb6f4445ef056f2f9abb1b0e1e..6b4b407e05e26faca69d9d7ac6f31510620898fe 100644
+index a33deeb5b587d6a950960a1a4781176e4e730ad7..e96cfb9a5ffbe4feccdffa8b6d18ececb48d4c52 100644
 --- a/browser/components/sessionstore/TabState.sys.mjs
 +++ b/browser/components/sessionstore/TabState.sys.mjs
-@@ -99,10 +99,28 @@ class _TabState {
+@@ -8,6 +8,7 @@ ChromeUtils.defineESModuleGetters(lazy, {
+   PrivacyFilter: "resource://gre/modules/sessionstore/PrivacyFilter.sys.mjs",
+   TabAttributes: "resource:///modules/sessionstore/TabAttributes.sys.mjs",
+   TabStateCache: "resource:///modules/sessionstore/TabStateCache.sys.mjs",
++  UrlbarShared: "chrome://browser/content/urlbar/UrlbarShared.mjs",
+   sessionStoreLogger: "resource:///modules/sessionstore/SessionLogger.sys.mjs",
+ });
+ 
+@@ -103,10 +104,28 @@ class _TabState {
        }
      }
  
@@ -25,7 +33,7 @@ index 4ba4dda363b602cb6f4445ef056f2f9abb1b0e1e..6b4b407e05e26faca69d9d7ac6f31510
        browser,
        true
      );
-+    if (tabData.searchMode?.source === tab.documentGlobal.UrlbarUtils.RESULT_SOURCE.ZEN_ACTIONS) {
++    if (tabData.searchMode?.source === lazy.UrlbarShared.RESULT_SOURCE.ZEN_ACTIONS) {
 +      delete tabData.searchMode;
 +    }
  
diff --git a/src/browser/components/tabbrowser/content/tab-context-menu-js.patch b/src/browser/components/tabbrowser/content/tab-context-menu-js.patch
new file mode 100644
index 000000000..a99739423
--- /dev/null
+++ b/src/browser/components/tabbrowser/content/tab-context-menu-js.patch
@@ -0,0 +1,21 @@
+diff --git a/browser/components/tabbrowser/content/tab-context-menu.js b/browser/components/tabbrowser/content/tab-context-menu.js
+index 4a7cb33a4d9067d469bbe09d4cd8844581642f7a..d7f75471a207cccac6ca3dec49037ac30dd76163 100644
+--- a/browser/components/tabbrowser/content/tab-context-menu.js
++++ b/browser/components/tabbrowser/content/tab-context-menu.js
+@@ -839,13 +839,15 @@ var TabContextMenu = {
+     );
+     contextUnpinSelectedTabs.hidden =
+       !this.contextTab.pinned || !this.multiselected;
+-
++    gZenViewSplitter.updateContextMenuItems();
++    gZenPinnedTabManager.updatePinnedTabContextMenu(this.contextTab);
+     // Build Ask Chat items. The classic layout shows the full ask-chat submenu
+     // (#context_askChat); the alt layout shows only a flat "Summarize Page" item
+     // (#context_askChatSummarize). Hide whichever one this layout doesn't use so
+     // a pref toggle reverses cleanly.
+     if (!this._altTabContextMenu) {
+       document.getElementById("context_askChatSummarize").hidden = true;
++      document.getElementById("context_aiSeparator").hidden = true;
+       TabContextMenu.GenAI.buildTabMenu(
+         document.getElementById("context_askChat"),
+         this
diff --git a/src/browser/components/tabbrowser/content/tab-js.patch b/src/browser/components/tabbrowser/content/tab-js.patch
index a1aad36c5..f65f096c0 100644
--- a/src/browser/components/tabbrowser/content/tab-js.patch
+++ b/src/browser/components/tabbrowser/content/tab-js.patch
@@ -1,5 +1,5 @@
 diff --git a/browser/components/tabbrowser/content/tab.js b/browser/components/tabbrowser/content/tab.js
-index 8f2ebf3a0bd4e2af01cf41024b16bd491e8ed961..27721e26c3cd8cb066b462dedfa4ce785ca5c2c3 100644
+index 6fcef5bf0f4ac8c58515afd127c7065f26251c7c..0307d79923612b8f728bf41c13b39aa8c579171b 100644
 --- a/browser/components/tabbrowser/content/tab.js
 +++ b/browser/components/tabbrowser/content/tab.js
 @@ -21,6 +21,7 @@
@@ -52,7 +52,7 @@ index 8f2ebf3a0bd4e2af01cf41024b16bd491e8ed961..27721e26c3cd8cb066b462dedfa4ce78
          return;
        }
  
-@@ -220,11 +223,25 @@
+@@ -216,11 +219,25 @@
      }
  
      get visible() {
@@ -83,7 +83,7 @@ index 8f2ebf3a0bd4e2af01cf41024b16bd491e8ed961..27721e26c3cd8cb066b462dedfa4ce78
      }
  
      get hidden() {
-@@ -303,7 +320,7 @@
+@@ -299,7 +316,7 @@
          return false;
        }
  
@@ -92,7 +92,7 @@ index 8f2ebf3a0bd4e2af01cf41024b16bd491e8ed961..27721e26c3cd8cb066b462dedfa4ce78
      }
  
      get lastAccessed() {
-@@ -388,7 +405,18 @@
+@@ -384,7 +401,18 @@
      }
  
      get group() {
@@ -112,7 +112,7 @@ index 8f2ebf3a0bd4e2af01cf41024b16bd491e8ed961..27721e26c3cd8cb066b462dedfa4ce78
      }
  
      get splitview() {
-@@ -470,6 +498,10 @@
+@@ -466,6 +494,10 @@
          }
        }
  
@@ -123,7 +123,7 @@ index 8f2ebf3a0bd4e2af01cf41024b16bd491e8ed961..27721e26c3cd8cb066b462dedfa4ce78
        // If the previous target wasn't part of this tab then this is a mouseenter event.
        if (!this.contains(event.relatedTarget)) {
          this._mouseenter();
-@@ -499,6 +531,7 @@
+@@ -495,6 +527,7 @@
        if (!this.contains(event.relatedTarget)) {
          this._mouseleave();
        }
@@ -131,7 +131,15 @@ index 8f2ebf3a0bd4e2af01cf41024b16bd491e8ed961..27721e26c3cd8cb066b462dedfa4ce78
      }
  
      on_dragstart(event) {
-@@ -533,6 +566,8 @@
+@@ -506,6 +539,7 @@
+       if (event.eventPhase == Event.CAPTURING_PHASE) {
+         this.style.MozUserFocus = "";
+       } else if (
++        event.target.classList?.contains("tab-reset-button") ||
+         event.target.classList?.contains("tab-close-button") ||
+         gSharedTabWarning.willShowSharedTabWarning(this)
+       ) {
+@@ -529,6 +563,8 @@
          this.style.MozUserFocus = "ignore";
        } else if (
          event.target.classList.contains("tab-close-button") ||
@@ -140,7 +148,7 @@ index 8f2ebf3a0bd4e2af01cf41024b16bd491e8ed961..27721e26c3cd8cb066b462dedfa4ce78
          event.target.classList.contains("tab-icon-overlay") ||
          event.target.classList.contains("tab-audio-button")
        ) {
-@@ -567,7 +602,7 @@
+@@ -563,7 +599,7 @@
            }
          } else if (
            event.altKey &&
@@ -149,7 +157,7 @@ index 8f2ebf3a0bd4e2af01cf41024b16bd491e8ed961..27721e26c3cd8cb066b462dedfa4ce78
          ) {
            eventMaySelectTab = false;
          } else if (!this.selected && this.multiselected) {
-@@ -592,6 +627,10 @@
+@@ -600,6 +636,10 @@
        this.style.MozUserFocus = "";
      }
  
@@ -160,7 +168,7 @@ index 8f2ebf3a0bd4e2af01cf41024b16bd491e8ed961..27721e26c3cd8cb066b462dedfa4ce78
      on_click(event) {
        if (event.button != 0) {
          return;
-@@ -615,14 +654,31 @@
+@@ -623,14 +663,31 @@
              trigger: "alt_click",
            });
          }
@@ -193,7 +201,7 @@ index 8f2ebf3a0bd4e2af01cf41024b16bd491e8ed961..27721e26c3cd8cb066b462dedfa4ce78
          gBrowser.multiSelectedTabsCount > 0 &&
          !event.target.classList.contains("tab-close-button") &&
          !event.target.classList.contains("tab-icon-overlay") &&
-@@ -634,8 +690,9 @@
+@@ -642,8 +699,9 @@
        }
  
        if (
@@ -205,16 +213,16 @@ index 8f2ebf3a0bd4e2af01cf41024b16bd491e8ed961..27721e26c3cd8cb066b462dedfa4ce78
        ) {
          if (this.activeMediaBlocked) {
            if (this.multiselected) {
-@@ -653,7 +710,7 @@
+@@ -661,7 +719,7 @@
          return;
        }
  
 -      if (event.target.classList.contains("tab-close-button")) {
 +      if (!event.getModifierState("Accel") && event.target.classList.contains("tab-close-button")) {
          if (this.multiselected) {
-           gBrowser.removeMultiSelectedTabs(
-             lazy.TabMetrics.userTriggeredContext(
-@@ -673,6 +730,14 @@
+           gBrowser.removeMultiSelectedTabs({
+             metricsContext: lazy.TabMetrics.userTriggeredContext(
+@@ -681,6 +739,14 @@
          // (see tabbrowser-tabs 'click' handler).
          gBrowser.tabContainer._blockDblClick = true;
        }
@@ -229,9 +237,9 @@ index 8f2ebf3a0bd4e2af01cf41024b16bd491e8ed961..27721e26c3cd8cb066b462dedfa4ce78
      }
  
      on_dblclick(event) {
-@@ -696,6 +761,8 @@
-           animate: true,
-           triggeringEvent: event,
+@@ -707,6 +773,8 @@
+             lazy.TabMetrics.METRIC_SOURCE.TAB_STRIP
+           ),
          });
 +      } else if (this.hasAttribute('zen-essential') && !event.target.classList.contains("tab-icon-overlay")) {
 +        gZenPinnedTabManager._onTabResetPinButton(event, this, 'reset');
diff --git a/src/browser/components/tabbrowser/content/tabbrowser-js.patch b/src/browser/components/tabbrowser/content/tabbrowser-js.patch
index 9f38381f5..54ab76446 100644
--- a/src/browser/components/tabbrowser/content/tabbrowser-js.patch
+++ b/src/browser/components/tabbrowser/content/tabbrowser-js.patch
@@ -1,8 +1,8 @@
 diff --git a/browser/components/tabbrowser/content/tabbrowser.js b/browser/components/tabbrowser/content/tabbrowser.js
-index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645eb49d12e9 100644
+index 39b5babee5942427a82a7a64ad69e1b16efebcc1..32beac13dd4215a16de3a783db6c32da5504f9d8 100644
 --- a/browser/components/tabbrowser/content/tabbrowser.js
 +++ b/browser/components/tabbrowser/content/tabbrowser.js
-@@ -509,6 +509,7 @@
+@@ -513,6 +513,7 @@
       * @type {MozBrowser[]}
       */
      get splitViewBrowsers() {
@@ -10,7 +10,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        const browsers = [];
        if (this.#activeSplitView) {
          for (const tab of this.#activeSplitView.tabs) {
-@@ -578,15 +579,66 @@
+@@ -611,15 +612,66 @@
        return this.tabContainer.visibleTabs;
      }
  
@@ -76,10 +76,10 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
 +      return this.tabs.filter(tab => !tab.hasAttribute("zen-glance-tab"));
 +    }
 +
-     set selectedTab(val) {
-       if (
-         gSharedTabWarning.willShowSharedTabWarning(val) ||
-@@ -595,6 +647,9 @@
+     setSelectedTab(val, metricsContext = null) {
+       if (this.selectedTab === val) {
+         return;
+@@ -632,6 +684,9 @@
        ) {
          return;
        }
@@ -88,8 +88,8 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
 +      }
        // Update the tab
        this.tabbox.selectedTab = val;
-     }
-@@ -662,6 +717,10 @@
+ 
+@@ -708,6 +763,10 @@
          userContextId = parseInt(tabArgument.getAttribute("usercontextid"), 10);
        }
  
@@ -100,7 +100,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        if (openWindowInfo) {
          userContextId = openWindowInfo.originAttributes.userContextId;
        }
-@@ -763,6 +822,8 @@
+@@ -809,6 +868,8 @@
        this.tabpanels.appendChild(panel);
  
        let tab = this.tabs[0];
@@ -109,10 +109,10 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        tab.linkedPanel = uniqueId;
        this._selectedTab = tab;
        this._selectedBrowser = browser;
-@@ -1129,18 +1190,24 @@
-       aTab,
-       { telemetrySource = this.TabMetrics.METRIC_SOURCE.UNKNOWN } = {}
-     ) {
+@@ -1178,18 +1239,24 @@
+      *   The context for the operation for telemetry purposes, defaults to an unknown context.
+      */
+     pinTab(aTab, { metricsContext = this.TabMetrics.UNKNOWN_CONTEXT } = {}) {
 +      aTab = gZenGlanceManager.getTabOrGlanceParent(aTab);
        if (aTab.pinned || aTab == FirefoxViewHandler.tab) {
          return;
@@ -135,10 +135,10 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
  
        aTab.setAttribute("pinned", "true");
        this._updateTabBarForPinnedTabs();
-@@ -1148,16 +1215,25 @@
-     }
- 
-     unpinTab(aTab) {
+@@ -1206,16 +1273,25 @@
+      *   The context for the operation for telemetry purposes, defaults to an unknown context.
+      */
+     unpinTab(aTab, { metricsContext = this.TabMetrics.UNKNOWN_CONTEXT } = {}) {
 +      aTab = gZenGlanceManager.getTabOrGlanceParent(aTab);
        if (!aTab.pinned) {
          return;
@@ -162,7 +162,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        });
  
        aTab.style.marginInlineStart = "";
-@@ -1372,6 +1448,9 @@
+@@ -1430,6 +1506,9 @@
  
        let LOCAL_PROTOCOLS = ["chrome:", "about:", "resource:", "data:"];
  
@@ -172,7 +172,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        if (
          aIconURL &&
          !LOCAL_PROTOCOLS.some(protocol => aIconURL.startsWith(protocol))
-@@ -1381,6 +1460,9 @@
+@@ -1439,6 +1518,9 @@
          );
          return;
        }
@@ -182,7 +182,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
  
        let browser = this.getBrowserForTab(aTab);
        browser.mIconURL = aIconURL;
-@@ -1703,7 +1785,6 @@
+@@ -1761,7 +1843,6 @@
  
        // Preview mode should not reset the owner
        if (!this.#previewMode && !oldTab.selected) {
@@ -190,7 +190,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        }
  
        let lastRelatedTab = this.#lastRelatedTabMap.get(oldTab);
-@@ -1794,6 +1875,7 @@
+@@ -1852,6 +1933,7 @@
        if (!this.#previewMode) {
          newTab.recordTimeFromUnloadToReload();
          newTab.updateLastAccessed();
@@ -198,7 +198,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
          oldTab.updateLastAccessed();
          // if this is the foreground window, update the last-seen timestamps.
          if (this.documentGlobal == BrowserWindowTracker.getTopWindow()) {
-@@ -2008,6 +2090,9 @@
+@@ -2066,6 +2148,9 @@
        }
  
        let activeEl = document.activeElement;
@@ -208,7 +208,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        // If focus is on the old tab, move it to the new tab.
        if (activeEl == oldTab) {
          newTab.focus();
-@@ -2046,7 +2131,7 @@
+@@ -2104,7 +2189,7 @@
        // Focus the location bar if it was previously focused for that tab.
        // In full screen mode, only bother making the location bar visible
        // if the tab is a blank one.
@@ -217,7 +217,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
          let selectURL = () => {
            if (this._asyncTabSwitching) {
              // Set _awaitingSetURI flag to suppress popup notification
-@@ -2334,7 +2419,12 @@
+@@ -2392,7 +2477,12 @@
        return this._setTabLabel(aTab, aLabel);
      }
  
@@ -231,7 +231,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        if (!aLabel || (isURL && /^about:reader\?url=/.test(aLabel))) {
          return false;
        }
-@@ -2460,7 +2550,7 @@
+@@ -2518,7 +2608,7 @@
          newIndex = this.selectedTab._tPos + 1;
        }
  
@@ -240,7 +240,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
          if (this.isTabGroupLabel(targetTab)) {
            throw new Error(
              "Replacing a tab group label with a tab is not supported"
-@@ -2735,6 +2825,7 @@
+@@ -2793,6 +2883,7 @@
        uriIsAboutBlank,
        userContextId,
        skipLoad,
@@ -248,7 +248,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
      } = {}) {
        let b = document.createXULElement("browser");
        // Use the JSM global to create the permanentKey, so that if the
-@@ -2808,8 +2899,7 @@
+@@ -2866,8 +2957,7 @@
          // we use a different attribute name for this?
          b.setAttribute("name", name);
        }
@@ -258,7 +258,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
          b.setAttribute("transparent", "true");
        }
  
-@@ -2964,7 +3054,7 @@
+@@ -3022,7 +3112,7 @@
  
        let panel = this.getPanel(browser);
        let uniqueId = this._generateUniquePanelID();
@@ -267,7 +267,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        aTab.linkedPanel = uniqueId;
  
        // Inject the <browser> into the DOM if necessary.
-@@ -3024,8 +3114,8 @@
+@@ -3082,8 +3172,8 @@
        // If we transitioned from one browser to two browsers, we need to set
        // hasSiblings=false on both the existing browser and the new browser.
        if (this.tabs.length == 2) {
@@ -278,7 +278,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        } else {
          aTab.linkedBrowser.browsingContext.hasSiblings = this.tabs.length > 1;
        }
-@@ -3210,7 +3300,6 @@
+@@ -3268,7 +3358,6 @@
              this.selectedTab = this.addTrustedTab(BROWSER_NEW_TAB_URL, {
                tabIndex: tab._tPos + 1,
                userContextId: tab.userContextId,
@@ -286,7 +286,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
                focusUrlBar: true,
              });
              resolve(this.selectedBrowser);
-@@ -3320,6 +3409,10 @@
+@@ -3378,6 +3467,10 @@
          schemelessInput,
          hasValidUserGestureActivation = false,
          textDirectiveUserActivation = false,
@@ -297,7 +297,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        } = {}
      ) {
        // all callers of addTab that pass a params object need to pass
-@@ -3330,10 +3423,25 @@
+@@ -3388,10 +3481,25 @@
          );
        }
  
@@ -323,7 +323,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        // If we're opening a foreground tab, set the owner by default.
        ownerTab ??= inBackground ? null : this.selectedTab;
  
-@@ -3341,6 +3449,7 @@
+@@ -3399,6 +3507,7 @@
        if (this.selectedTab.owner) {
          this.selectedTab.owner = null;
        }
@@ -331,7 +331,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
  
        // Find the tab that opened this one, if any. This is used for
        // determining positioning, and inherited attributes such as the
-@@ -3393,6 +3502,22 @@
+@@ -3451,6 +3560,22 @@
            noInitialLabel,
            skipBackgroundNotify,
          });
@@ -354,7 +354,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
          if (insertTab) {
            // Insert the tab into the tab container in the correct position.
            this.#insertTabAtIndex(t, {
-@@ -3401,6 +3526,7 @@
+@@ -3459,6 +3584,7 @@
              ownerTab,
              openerTab,
              pinned,
@@ -362,7 +362,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
              bulkOrderedOpen,
              tabGroup: tabGroup ?? openerTab?.group,
            });
-@@ -3419,6 +3545,7 @@
+@@ -3477,6 +3603,7 @@
            openWindowInfo,
            skipLoad,
            triggeringRemoteType,
@@ -370,7 +370,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
          }));
  
          if (focusUrlBar) {
-@@ -3543,6 +3670,12 @@
+@@ -3601,6 +3728,12 @@
          }
        }
  
@@ -383,7 +383,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        // Additionally send pinned tab events
        if (pinned) {
          this.#notifyPinnedStatus(t);
-@@ -3553,6 +3686,15 @@
+@@ -3611,6 +3744,15 @@
        if (!inBackground) {
          this.selectedTab = t;
        }
@@ -399,15 +399,15 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        return t;
      }
  
-@@ -3785,6 +3927,7 @@
+@@ -3834,6 +3976,7 @@
+         insertBefore = null,
          isAdoptingGroup = false,
-         isUserTriggered = false,
-         telemetryUserCreateSource = "unknown",
+         metricsContext = this.TabMetrics.UNKNOWN_CONTEXT,
 +        forSplitView = false,
        } = {}
      ) {
        if (
-@@ -3795,9 +3938,6 @@
+@@ -3844,9 +3987,6 @@
              !this.isSplitViewWrapper(tabOrSplitView)
          )
        ) {
@@ -417,7 +417,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        }
  
        if (!color) {
-@@ -3818,9 +3958,14 @@
+@@ -3867,9 +4007,14 @@
          label,
          isAdoptingGroup
        );
@@ -432,9 +432,9 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
          group,
 -        insertBefore?.group ?? insertBefore
        );
-       group.addTabs(tabsAndSplitViews);
+       group.addTabs(tabsAndSplitViews, metricsContext);
  
-@@ -3941,7 +4086,7 @@
+@@ -3973,7 +4118,7 @@
        }
  
        this.#handleTabMove(tab, () =>
@@ -443,7 +443,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        );
      }
  
-@@ -4027,6 +4172,7 @@
+@@ -4059,6 +4204,7 @@
          color: group.color,
          insertBefore: newTabs[0],
          isAdoptingGroup: true,
@@ -451,7 +451,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        });
      }
  
-@@ -4237,6 +4383,7 @@
+@@ -4269,6 +4415,7 @@
          openWindowInfo,
          skipLoad,
          triggeringRemoteType,
@@ -459,7 +459,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        }
      ) {
        // If we don't have a preferred remote type (or it is `NOT_REMOTE`), and
-@@ -4297,6 +4444,7 @@
+@@ -4329,6 +4476,7 @@
            openWindowInfo,
            name,
            skipLoad,
@@ -467,7 +467,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
          });
        }
  
-@@ -4510,9 +4658,9 @@
+@@ -4542,9 +4690,9 @@
          }
  
          // Add a new tab if needed.
@@ -479,7 +479,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
  
            let url = "about:blank";
            if (tabData.entries?.length) {
-@@ -4545,8 +4693,10 @@
+@@ -4577,8 +4725,10 @@
              insertTab: false,
              skipLoad: true,
              preferredRemoteType,
@@ -491,7 +491,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
            if (select) {
              tabToSelect = tab;
            }
-@@ -4568,7 +4718,8 @@
+@@ -4600,7 +4750,8 @@
            this.pinTab(tab);
            // Then ensure all the tab open/pinning information is sent.
            this._fireTabOpen(tab, {});
@@ -501,7 +501,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
            let { groupId } = tabData;
            const tabGroup = tabGroupWorkingData.get(groupId);
            // if a tab refers to a tab group we don't know, skip any group
-@@ -4588,7 +4739,10 @@
+@@ -4620,7 +4771,10 @@
                  tabGroup.stateData.id,
                  tabGroup.stateData.color,
                  tabGroup.stateData.collapsed,
@@ -513,7 +513,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
                );
                tabsFragment.appendChild(tabGroup.node);
              }
-@@ -4643,9 +4797,21 @@
+@@ -4675,9 +4829,21 @@
        // to remove the old selected tab.
        if (tabToSelect) {
          let leftoverTab = this.selectedTab;
@@ -535,7 +535,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
  
        if (tabs.length > 1 || !tabs[0].selected) {
          this._updateTabsAfterInsert();
-@@ -4836,11 +5002,17 @@
+@@ -4882,11 +5048,17 @@
        if (ownerTab) {
          tab.owner = ownerTab;
        }
@@ -554,7 +554,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
          if (
            !bulkOrderedOpen &&
            ((openerTab &&
-@@ -4852,7 +5024,7 @@
+@@ -4898,7 +5070,7 @@
            let lastRelatedTab =
              openerTab && this.#lastRelatedTabMap.get(openerTab);
            let previousTab = lastRelatedTab || openerTab || this.selectedTab;
@@ -563,7 +563,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
              tabGroup = previousTab.group;
            }
            if (
-@@ -4868,7 +5040,7 @@
+@@ -4914,7 +5086,7 @@
                  previousTab.splitview
                ) + 1;
            } else if (previousTab.visible) {
@@ -572,7 +572,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
            } else if (previousTab == FirefoxViewHandler.tab) {
              elementIndex = 0;
            }
-@@ -4896,14 +5068,14 @@
+@@ -4942,14 +5114,14 @@
        }
        // Ensure index is within bounds.
        if (tab.pinned) {
@@ -591,7 +591,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
  
        if (pinned && !itemAfter?.pinned) {
          itemAfter = null;
-@@ -4920,7 +5092,7 @@
+@@ -4966,7 +5138,7 @@
  
        this.tabContainer._invalidateCachedTabs();
  
@@ -600,7 +600,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
          if (
            (this.isTab(itemAfter) && itemAfter.group == tabGroup) ||
            this.isSplitViewWrapper(itemAfter)
-@@ -4951,7 +5123,11 @@
+@@ -4997,7 +5169,11 @@
          const tabContainer = pinned
            ? this.tabContainer.pinnedTabsContainer
            : this.tabContainer;
@@ -612,7 +612,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        }
  
        if (tab.group?.collapsed) {
-@@ -4966,6 +5142,7 @@
+@@ -5012,6 +5188,7 @@
        if (pinned) {
          this._updateTabBarForPinnedTabs();
        }
@@ -620,23 +620,23 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
  
        TabBarVisibility.update();
      }
-@@ -5514,6 +5691,7 @@
-         telemetrySource,
+@@ -5568,6 +5745,7 @@
+         metricsContext,
        } = {}
      ) {
 +      tabs = tabs.filter(tab => !tab.hasAttribute("zen-empty-tab"));
        // When 'closeWindowWithLastTab' pref is enabled, closing all tabs
        // can be considered equivalent to closing the window.
        if (
-@@ -5603,6 +5781,7 @@
-         if (lastToClose) {
-           this.removeTab(lastToClose, aParams);
+@@ -5678,6 +5856,7 @@
+             closedTabCount -= 1;
+           }
          }
 +        gZenUIManager.onTabClose(undefined);
-       } catch (e) {
-         console.error(e);
-       }
-@@ -5648,6 +5827,14 @@
+ 
+         if (closedTabCount > 0) {
+           this.recordTabMetrics(
+@@ -5730,6 +5909,14 @@
          return;
        }
  
@@ -651,7 +651,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        let isVisibleTab = aTab.visible;
        // We have to sample the tab width now, since _beginRemoveTab might
        // end up modifying the DOM in such a way that aTab gets a new
-@@ -5655,6 +5842,9 @@
+@@ -5737,6 +5924,9 @@
        // state).
        let tabWidth = window.windowUtils.getBoundsWithoutFlushing(aTab).width;
        let isLastTab = this.#isLastTabInWindow(aTab);
@@ -661,8 +661,8 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        if (
          !this._beginRemoveTab(aTab, {
            closeWindowFastpath: true,
-@@ -5666,13 +5856,14 @@
-           telemetrySource,
+@@ -5747,13 +5937,14 @@
+           metricsContext,
          })
        ) {
 +        delete gZenWorkspaces._isClosingWindow;
@@ -677,7 +677,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        let lockTabSizing =
          !this.tabContainer.verticalMode &&
          !aTab.pinned &&
-@@ -5703,7 +5894,13 @@
+@@ -5784,7 +5975,13 @@
          // We're not animating, so we can cancel the animation stopwatch.
          Glean.browserTabclose.timeAnim.cancel(aTab._closeTimeAnimTimerId);
          aTab._closeTimeAnimTimerId = null;
@@ -692,7 +692,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
          return;
        }
  
-@@ -5746,7 +5943,7 @@
+@@ -5827,7 +6024,7 @@
       */
      #isLastTabInWindow(tab) {
        for (const otherTab of this.tabs) {
@@ -701,7 +701,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
            return false;
          }
        }
-@@ -5837,7 +6034,7 @@
+@@ -5917,7 +6114,7 @@
            closeWindowWithLastTab != null
              ? closeWindowWithLastTab
              : !window.toolbar.visible ||
@@ -710,7 +710,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
  
          if (closeWindow) {
            // We've already called beforeunload on all the relevant tabs if we get here,
-@@ -5861,6 +6058,7 @@
+@@ -5941,6 +6138,7 @@
  
          newTab = true;
        }
@@ -718,7 +718,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        aTab._endRemoveArgs = [closeWindow, newTab];
  
        // swapBrowsersAndCloseOther will take care of closing the window without animation.
-@@ -5901,13 +6099,7 @@
+@@ -5982,13 +6180,7 @@
        aTab._mouseleave();
  
        if (newTab) {
@@ -733,7 +733,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        } else {
          TabBarVisibility.update();
        }
-@@ -6040,6 +6232,7 @@
+@@ -6128,6 +6320,7 @@
          this.tabs[i]._tPos = i;
        }
  
@@ -741,7 +741,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        if (!this.#windowIsClosing) {
          // update tab close buttons state
          this.tabContainer._updateCloseButtons();
-@@ -6225,6 +6418,7 @@
+@@ -6313,6 +6506,7 @@
          memory_after: await getTotalMemoryUsage(),
          time_to_unload_in_ms: timeElapsed,
        });
@@ -749,7 +749,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
      }
  
      /**
-@@ -6270,6 +6464,7 @@
+@@ -6358,6 +6552,7 @@
        }
  
        let excludeTabs = new Set(aExcludeTabs);
@@ -757,7 +757,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
  
        // If this tab has a successor, it should be selectable, since
        // hiding or closing a tab removes that tab as a successor.
-@@ -6282,15 +6477,22 @@
+@@ -6370,13 +6565,13 @@
          !excludeTabs.has(aTab.owner) &&
          Services.prefs.getBoolPref("browser.tabs.selectOwnerOnClose")
        ) {
@@ -772,6 +772,11 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
 +        tab => !excludeTabs.has(tab) && gZenWorkspaces._shouldChangeToTab(tab) && tab !== aTab
        );
  
+       if (Services.prefs.getBoolPref("browser.tabs.selectMRUOnClose", false)) {
+@@ -6392,6 +6587,13 @@
+         }
+       }
+ 
 +      if (remainingTabs.length > 0 && Services.prefs.getBoolPref("zen.tabs.select-recently-used-on-close")) {
 +        let mostRecentTab = remainingTabs.reduce((a, b) =>
 +          b.lastAccessed > a.lastAccessed ? b : a
@@ -782,7 +787,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        let tab = this.tabContainer.findNextTab(aTab, {
          direction: 1,
          filter: _tab => remainingTabs.includes(_tab),
-@@ -6304,7 +6506,7 @@
+@@ -6405,7 +6607,7 @@
        }
  
        if (tab) {
@@ -791,7 +796,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        }
  
        // If no qualifying visible tab was found, see if there is a tab in
-@@ -6325,7 +6527,7 @@
+@@ -6426,7 +6628,7 @@
          });
        }
  
@@ -800,7 +805,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
      }
  
      _blurTab(aTab) {
-@@ -6336,7 +6538,7 @@
+@@ -6437,7 +6639,7 @@
       * @returns {boolean}
       *   False if swapping isn't permitted, true otherwise.
       */
@@ -809,7 +814,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        // Do not allow transfering a private tab to a non-private window
        // and vice versa.
        if (
-@@ -6390,6 +6592,7 @@
+@@ -6491,6 +6693,7 @@
        // fire the beforeunload event in the process.  Close the other
        // window if this was its last tab.
        if (
@@ -817,7 +822,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
          !remoteBrowser._beginRemoveTab(aOtherTab, {
            adoptedByTab: aOurTab,
            closeWindowWithLastTab: true,
-@@ -6401,7 +6604,7 @@
+@@ -6502,7 +6705,7 @@
        // If this is the last tab of the window, hide the window
        // immediately without animation before the docshell swap, to avoid
        // about:blank being painted.
@@ -826,7 +831,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        if (closeWindow) {
          let win = aOtherTab.documentGlobal;
          win.windowUtils.suppressAnimation(true);
-@@ -6535,11 +6738,13 @@
+@@ -6636,11 +6839,13 @@
        }
  
        // Finish tearing down the tab that's going away.
@@ -840,7 +845,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
  
        this.setTabTitle(aOurTab);
  
-@@ -6759,10 +6964,10 @@
+@@ -6860,10 +7065,10 @@
        SessionStore.deleteCustomTabValue(aTab, "hiddenBy");
      }
  
@@ -853,7 +858,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
          aTab.selected ||
          aTab.closing ||
          // Tabs that are sharing the screen, microphone or camera cannot be hidden.
-@@ -6822,7 +7027,8 @@
+@@ -6923,7 +7128,8 @@
       * @param {object} [aOptions={}]
       *   Key-value pairs that will be serialized into the features string.
       */
@@ -863,7 +868,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        if (this.tabs.length == 1) {
          return null;
        }
-@@ -6839,7 +7045,7 @@
+@@ -6940,7 +7146,7 @@
        // tell a new window to take the "dropped" tab
        let args = Cc["@mozilla.org/array;1"].createInstance(Ci.nsIMutableArray);
        args.appendElement(aTab.splitview ?? aTab);
@@ -872,7 +877,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
          private: PrivateBrowsingUtils.isWindowPrivate(window),
          features: Object.entries(aOptions)
            .map(([key, value]) => `${key}=${value}`)
-@@ -6847,6 +7053,8 @@
+@@ -6948,6 +7154,8 @@
          openerWindow: window,
          args,
        });
@@ -881,7 +886,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
      }
  
      /**
-@@ -6959,7 +7167,7 @@
+@@ -7074,7 +7282,7 @@
       *   `true` if element is a `<tab-group>`
       */
      isTabGroup(element) {
@@ -890,7 +895,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
      }
  
      /**
-@@ -7044,8 +7252,8 @@
+@@ -7146,8 +7354,8 @@
        }
  
        // Don't allow mixing pinned and unpinned tabs.
@@ -901,7 +906,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        } else {
          tabIndex = Math.max(tabIndex, this.pinnedTabCount);
        }
-@@ -7091,8 +7299,8 @@
+@@ -7193,8 +7401,8 @@
        this.#handleTabMove(
          element,
          () => {
@@ -912,7 +917,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
              neighbor = neighbor.group;
            }
            if (neighbor?.splitview) {
-@@ -7103,6 +7311,12 @@
+@@ -7205,6 +7413,12 @@
                return;
              }
            }
@@ -925,8 +930,8 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
  
            if (movingForwards && neighbor) {
              neighbor.after(element);
-@@ -7161,23 +7375,31 @@
-     #moveTabNextTo(element, targetElement, moveBefore = false, metricsContext) {
+@@ -7278,23 +7492,31 @@
+     ) {
        if (this.isTabGroupLabel(targetElement)) {
          targetElement = targetElement.group;
 -        if (!moveBefore && !targetElement.collapsed) {
@@ -963,7 +968,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        } else if (!element.pinned && targetElement && targetElement.pinned) {
          // If the caller asks to move an unpinned element next to a pinned
          // tab, move the unpinned element to be the first unpinned element
-@@ -7190,12 +7412,35 @@
+@@ -7307,12 +7529,35 @@
          //    move the tab group right before the first unpinned tab.
          // 4. Moving a tab group and the first unpinned tab is grouped:
          //    move the tab group right before the first unpinned tab's tab group.
@@ -1000,7 +1005,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
  
        // We want to include the splitview wrapper if it's the targetElement, but
        // not in the case where we want to reverse tabs within the same splitview.
-@@ -7204,6 +7449,7 @@
+@@ -7321,6 +7566,7 @@
        }
  
        let getContainer = () =>
@@ -1008,7 +1013,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
          element.pinned
            ? this.tabContainer.pinnedTabsContainer
            : this.tabContainer;
-@@ -7212,11 +7458,15 @@
+@@ -7329,11 +7575,15 @@
          element,
          () => {
            if (moveBefore) {
@@ -1024,11 +1029,11 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
 +            }
            }
          },
-         metricsContext
-@@ -7290,11 +7540,15 @@
-      * @param {TabMetricsContext} [metricsContext]
+         { metricsContext }
+@@ -7411,11 +7661,15 @@
+      *   The context for the operation for telemetry purposes.
       */
-     moveTabToExistingGroup(aTab, aGroup, metricsContext) {
+     moveTabToExistingGroup(aTab, aGroup, { metricsContext } = {}) {
 -      if (!this.isTab(aTab)) {
 +      if (!this.isTab(aTab) && !aTab.hasAttribute('split-view-group')) {
          throw new Error("Can only move a tab into a tab group");
@@ -1044,7 +1049,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        }
        if (aTab.group && aTab.group.id === aGroup.id) {
          return;
-@@ -7366,6 +7620,7 @@
+@@ -7489,6 +7743,7 @@
  
        let state = {
          tabIndex: tab._tPos,
@@ -1052,7 +1057,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        };
        if (tab.visible) {
          state.elementIndex = tab.elementIndex;
-@@ -7397,7 +7652,7 @@
+@@ -7527,7 +7782,7 @@
        let changedSplitView =
          previousTabState.splitViewId != currentTabState.splitViewId;
  
@@ -1061,7 +1066,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
          tab.dispatchEvent(
            new CustomEvent("TabMove", {
              bubbles: true,
-@@ -7444,6 +7699,10 @@
+@@ -7579,6 +7834,10 @@
  
        moveActionCallback();
  
@@ -1072,7 +1077,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        // Clear tabs cache after moving nodes because the order of tabs may have
        // changed.
        this.tabContainer._invalidateCachedTabs();
-@@ -7494,7 +7753,22 @@
+@@ -7626,7 +7885,22 @@
       * @returns {object}
       *    The new tab in the current window, null if the tab couldn't be adopted.
       */
@@ -1096,7 +1101,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        // Swap the dropped tab with a new one we create and then close
        // it in the other window (making it seem to have moved between
        // windows). We also ensure that the tab we create to swap into has
-@@ -7537,6 +7811,8 @@
+@@ -7669,6 +7943,8 @@
        }
        params.skipLoad = true;
        let newTab = this.addWebTab("about:blank", params);
@@ -1105,7 +1110,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
  
        aTab.container.tabDragAndDrop.finishAnimateTabMove();
  
-@@ -8247,7 +8523,7 @@
+@@ -8448,7 +8724,7 @@
          // preventDefault(). It will still raise the window if appropriate.
          return;
        }
@@ -1114,7 +1119,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        window.focus();
        aEvent.preventDefault();
      }
-@@ -8264,7 +8540,6 @@
+@@ -8465,7 +8741,6 @@
  
      on_TabGroupCollapse(aEvent) {
        aEvent.target.tabs.forEach(tab => {
@@ -1122,7 +1127,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
        });
      }
  
-@@ -8618,7 +8893,9 @@
+@@ -8819,7 +9094,9 @@
  
          let filter = this.#tabFilters.get(tab);
          if (filter) {
@@ -1132,7 +1137,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
  
            let listener = this.#tabListeners.get(tab);
            if (listener) {
-@@ -9423,6 +9700,7 @@
+@@ -9604,6 +9881,7 @@
              aWebProgress.isTopLevel
            ) {
              this._tab.setAttribute("busy", "true");
@@ -1140,7 +1145,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
              gBrowser._tabAttrModified(this._tab, ["busy"]);
              this._tab._notselectedsinceload = !this._tab.selected;
            }
-@@ -9503,6 +9781,7 @@
+@@ -9684,6 +9962,7 @@
          // known defaults. Note we use the original URL since about:newtab
          // redirects to a prerendered page.
          const shouldRemoveFavicon =
@@ -1148,7 +1153,7 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
            !this._browser.mIconURL &&
            !ignoreBlank &&
            !(originalLocation.spec in FAVICON_DEFAULTS);
-@@ -9677,13 +9956,6 @@
+@@ -9858,13 +10137,6 @@
              this._browser.originalURI = aRequest.originalURI;
            }
  
@@ -1162,13 +1167,3 @@ index c42b1a1a8df6b38886c17f71ea88e5aaa7eebc80..c741404ed973ee3ac246fe246c0f645e
          }
  
          let userContextId = this._browser.getAttribute("usercontextid") || 0;
-@@ -10532,7 +10804,8 @@ var TabContextMenu = {
-     );
-     contextUnpinSelectedTabs.hidden =
-       !this.contextTab.pinned || !this.multiselected;
--
-+    gZenViewSplitter.updateContextMenuItems();
-+    gZenPinnedTabManager.updatePinnedTabContextMenu(this.contextTab);
-     // Build Ask Chat items
-     TabContextMenu.GenAI.buildTabMenu(
-       document.getElementById("context_askChat"),
diff --git a/src/browser/components/tabbrowser/content/tabgroup-js.patch b/src/browser/components/tabbrowser/content/tabgroup-js.patch
index 98e1d9fe6..140b011c2 100644
--- a/src/browser/components/tabbrowser/content/tabgroup-js.patch
+++ b/src/browser/components/tabbrowser/content/tabgroup-js.patch
@@ -1,5 +1,5 @@
 diff --git a/browser/components/tabbrowser/content/tabgroup.js b/browser/components/tabbrowser/content/tabgroup.js
-index e78fa0dec83424c0059c081f83fda0d23bdb5a94..a7de584d9029ff9e55d809d50377593e398ee999 100644
+index 237950fb2c449ce088c204d33a70b1d95dae549b..af200a043dcd2e24393fcefe32493e356c9f8c6f 100644
 --- a/browser/components/tabbrowser/content/tabgroup.js
 +++ b/browser/components/tabbrowser/content/tabgroup.js
 @@ -14,11 +14,11 @@
@@ -129,7 +129,7 @@ index e78fa0dec83424c0059c081f83fda0d23bdb5a94..a7de584d9029ff9e55d809d50377593e
      }
  
      get color() {
-@@ -335,6 +366,9 @@
+@@ -330,6 +361,9 @@
      }
  
      set collapsed(val) {
@@ -139,7 +139,7 @@ index e78fa0dec83424c0059c081f83fda0d23bdb5a94..a7de584d9029ff9e55d809d50377593e
        if (!!val == this.collapsed) {
          return;
        }
-@@ -421,7 +455,6 @@
+@@ -416,7 +450,6 @@
            tabGroupName,
          })
          .then(result => {
@@ -147,7 +147,7 @@ index e78fa0dec83424c0059c081f83fda0d23bdb5a94..a7de584d9029ff9e55d809d50377593e
          });
      }
  
-@@ -496,13 +529,68 @@
+@@ -491,13 +524,68 @@
       * @returns {MozTabbrowserTab[]}
       */
      get tabs() {
@@ -221,15 +221,17 @@ index e78fa0dec83424c0059c081f83fda0d23bdb5a94..a7de584d9029ff9e55d809d50377593e
      }
  
      /**
-@@ -610,7 +698,6 @@
-           );
+@@ -617,9 +705,6 @@
+           });
          } else {
            if (tabOrSplitView.pinned) {
--            tabOrSplitView.documentGlobal.gBrowser.unpinTab(tabOrSplitView);
+-            tabOrSplitView.documentGlobal.gBrowser.unpinTab(tabOrSplitView, {
+-              metricsContext,
+-            });
            }
            let tabToMove =
              this.documentGlobal === tabOrSplitView.documentGlobal
-@@ -679,7 +766,7 @@
+@@ -682,7 +767,7 @@
       */
      on_click(event) {
        let isToggleElement =
@@ -238,7 +240,7 @@ index e78fa0dec83424c0059c081f83fda0d23bdb5a94..a7de584d9029ff9e55d809d50377593e
          event.target === this.#overflowCountLabel;
        if (isToggleElement && event.button === 0) {
          event.preventDefault();
-@@ -758,5 +845,6 @@
+@@ -761,5 +846,6 @@
      }
    }
  
diff --git a/src/browser/components/urlbar/UrlbarController-sys-mjs.patch b/src/browser/components/urlbar/UrlbarController-sys-mjs.patch
deleted file mode 100644
index 3db64fc48..000000000
--- a/src/browser/components/urlbar/UrlbarController-sys-mjs.patch
+++ /dev/null
@@ -1,21 +0,0 @@
-diff --git a/browser/components/urlbar/UrlbarController.sys.mjs b/browser/components/urlbar/UrlbarController.sys.mjs
-index a05894d593e4149097c473822a38f87b2220625f..1660106c2a6548920fdffd2656e5a1f12c2d548b 100644
---- a/browser/components/urlbar/UrlbarController.sys.mjs
-+++ b/browser/components/urlbar/UrlbarController.sys.mjs
-@@ -305,7 +305,6 @@ export class UrlbarController {
-     const isMac = AppConstants.platform == "macosx";
-     // Handle readline/emacs-style navigation bindings on Mac.
-     if (
--      isMac &&
-       this.view.isOpen &&
-       event.ctrlKey &&
-       (event.key == "n" || event.key == "p")
-@@ -494,6 +493,8 @@ export class UrlbarController {
-             });
-           }
-           event.preventDefault();
-+        } else if (!this.input.value && !(event.ctrlKey || event.altKey || event.shiftKey)) {
-+          this.browserWindow.gZenUIManager.enableCommandsMode(event);
-         }
-         break;
-       }
diff --git a/src/browser/components/urlbar/UrlbarMuxerStandard-sys-mjs.patch b/src/browser/components/urlbar/UrlbarMuxerStandard-sys-mjs.patch
index c45a18d70..ffa54d3ae 100644
--- a/src/browser/components/urlbar/UrlbarMuxerStandard-sys-mjs.patch
+++ b/src/browser/components/urlbar/UrlbarMuxerStandard-sys-mjs.patch
@@ -1,14 +1,14 @@
 diff --git a/browser/components/urlbar/UrlbarMuxerStandard.sys.mjs b/browser/components/urlbar/UrlbarMuxerStandard.sys.mjs
-index 16041c10755adced9d665539796737a9f55712de..2232bdcc02e20dbb384ca0529a8bd8ce73dc6284 100644
+index 65bd41b2ea14c26d490632d4a5348d6cf33ee9dd..80fbd685156949b6c7e93ed9d0ef56350dd1a0fe 100644
 --- a/browser/components/urlbar/UrlbarMuxerStandard.sys.mjs
 +++ b/browser/components/urlbar/UrlbarMuxerStandard.sys.mjs
-@@ -837,11 +837,16 @@ class MuxerUnifiedComplete extends UrlbarMuxer {
+@@ -925,11 +925,16 @@ class MuxerUnifiedComplete extends UrlbarMuxer {
        result.providerName == "UrlbarProviderHeuristicFallback" &&
        state.context.heuristicResult?.providerName !=
          "UrlbarProviderHeuristicFallback"
 +      && !(
-+        result.type == UrlbarUtils.RESULT_TYPE.SEARCH &&
-+        state.context.heuristicResult?.type == UrlbarUtils.RESULT_TYPE.URL
++        result.type == lazy.UrlbarShared.RESULT_TYPE.SEARCH &&
++        state.context.heuristicResult?.type == lazy.UrlbarShared.RESULT_TYPE.URL
 +      )
      ) {
        return false;
@@ -19,11 +19,11 @@ index 16041c10755adced9d665539796737a9f55712de..2232bdcc02e20dbb384ca0529a8bd8ce
        // Discard the result if a tab-to-search result was added already.
        if (!state.canAddTabToSearch) {
          return false;
-@@ -1491,7 +1496,9 @@ class MuxerUnifiedComplete extends UrlbarMuxer {
+@@ -1593,7 +1598,9 @@ class MuxerUnifiedComplete extends UrlbarMuxer {
        usedLimits.maxResultCount++;
      }
  
-+    if (!(result.heuristic && result.source == UrlbarUtils.RESULT_SOURCE.ZEN_ACTIONS)) {
++    if (!(result.heuristic && result.source == lazy.UrlbarShared.RESULT_SOURCE.ZEN_ACTIONS)) {
      state.usedResultSpan += span;
 +    }
      this._updateStatePostAdd(result, state);
diff --git a/src/browser/components/urlbar/UrlbarPrefs-sys-mjs.patch b/src/browser/components/urlbar/UrlbarPrefs-sys-mjs.patch
index 9b41ab880..9644cca42 100644
--- a/src/browser/components/urlbar/UrlbarPrefs-sys-mjs.patch
+++ b/src/browser/components/urlbar/UrlbarPrefs-sys-mjs.patch
@@ -1,8 +1,18 @@
 diff --git a/browser/components/urlbar/UrlbarPrefs.sys.mjs b/browser/components/urlbar/UrlbarPrefs.sys.mjs
-index 2d21248256c6c2bfb8dac958133c10e3251ef564..f788bd10ec2c08e4b27b77cd3bb0489fb04e8b7a 100644
+index 89f0d44d462de3d7d0f581d6371606f475443822..0d45ce5f6455e9c7276c54f504906bade5b3d286 100644
 --- a/browser/components/urlbar/UrlbarPrefs.sys.mjs
 +++ b/browser/components/urlbar/UrlbarPrefs.sys.mjs
-@@ -462,6 +462,7 @@ const PREF_URLBAR_DEFAULTS = /** @type {PreferenceDefinition[]} */ ([
+@@ -163,6 +163,9 @@ const PREF_URLBAR_DEFAULTS = /** @type {PreferenceDefinition[]} */ ([
+   // Feature gate pref for flight status suggestions in the urlbar.
+   ["flightStatus.featureGate", false],
+ 
++  // Whether to close the urlbar when blurring the window while the urlbar is focused.
++  ["closeOnWindowBlur", true],
++
+   // The minimum prefix length of a flight status keyword the user must type to
+   // trigger the suggestion. 0 means the min length should be taken from Nimbus
+   // or remote settings.
+@@ -482,6 +485,7 @@ const PREF_URLBAR_DEFAULTS = /** @type {PreferenceDefinition[]} */ ([
    ["shortcuts.tabs", true],
    ["shortcuts.history", true],
    ["shortcuts.actions", true],
@@ -10,7 +20,7 @@ index 2d21248256c6c2bfb8dac958133c10e3251ef564..f788bd10ec2c08e4b27b77cd3bb0489f
  
    // Boolean to determine if the providers defined in `exposureResults`
    // should be displayed in search results. This can be set by a
-@@ -799,6 +800,8 @@ function makeDefaultResultGroups({ showSearchSuggestionsFirst }) {
+@@ -840,6 +844,8 @@ function makeDefaultResultGroups({
     */
    let rootGroup = {
      children: [
diff --git a/src/browser/components/urlbar/UrlbarProvidersManager-sys-mjs.patch b/src/browser/components/urlbar/UrlbarProvidersManager-sys-mjs.patch
index d2f40925c..7a443b0b3 100644
--- a/src/browser/components/urlbar/UrlbarProvidersManager-sys-mjs.patch
+++ b/src/browser/components/urlbar/UrlbarProvidersManager-sys-mjs.patch
@@ -1,16 +1,16 @@
 diff --git a/browser/components/urlbar/UrlbarProvidersManager.sys.mjs b/browser/components/urlbar/UrlbarProvidersManager.sys.mjs
-index d2e2415e6b7c8833617dd1d4d01b16b110afbfa5..4a1e6e0940789b55144afd0566ecb91d88f7d590 100644
+index 67f51c7996c24549f39594c9a518bc5316350ce7..d66969f2411bb687c15448ad828b64ddf43c3389 100644
 --- a/browser/components/urlbar/UrlbarProvidersManager.sys.mjs
 +++ b/browser/components/urlbar/UrlbarProvidersManager.sys.mjs
 @@ -914,6 +914,7 @@ export class Query {
      if (
        result.heuristic &&
        this.context.searchMode &&
-+      !(this.context.searchMode.source === lazy.UrlbarUtils.RESULT_SOURCE.ZEN_ACTIONS && result.payload?.zenAction) &&
++      !(this.context.searchMode.source === lazy.UrlbarShared.RESULT_SOURCE.ZEN_ACTIONS && result.payload?.zenAction) &&
        (!this.context.trimmedSearchString ||
          (!this.context.searchMode.engineName && !result.autofill))
      ) {
-@@ -1044,6 +1045,7 @@ function updateSourcesIfEmpty(context) {
+@@ -1060,6 +1061,7 @@ function updateSourcesIfEmpty(context) {
              lazy.UrlbarShared.TOKEN_TYPE.RESTRICT_TITLE,
              lazy.UrlbarShared.TOKEN_TYPE.RESTRICT_URL,
              lazy.UrlbarShared.TOKEN_TYPE.RESTRICT_ACTION,
@@ -18,11 +18,11 @@ index d2e2415e6b7c8833617dd1d4d01b16b110afbfa5..4a1e6e0940789b55144afd0566ecb91d
            ].includes(t.type)
          );
  
-@@ -1103,6 +1105,14 @@ function updateSourcesIfEmpty(context) {
+@@ -1119,6 +1121,14 @@ function updateSourcesIfEmpty(context) {
            acceptedSources.push(source);
          }
          break;
-+      case lazy.UrlbarUtils.RESULT_SOURCE.WORKSPACES:
++      case lazy.UrlbarShared.RESULT_SOURCE.WORKSPACES:
 +        if (
 +          restrictTokenType === lazy.UrlbarShared.TOKEN_TYPE.RESTRICT_WORKSPACE ||
 +          !restrictTokenType
@@ -30,6 +30,6 @@ index d2e2415e6b7c8833617dd1d4d01b16b110afbfa5..4a1e6e0940789b55144afd0566ecb91d
 +          acceptedSources.push(source);
 +        }
 +        break;
-       case lazy.UrlbarUtils.RESULT_SOURCE.OTHER_LOCAL:
-       case lazy.UrlbarUtils.RESULT_SOURCE.ADDON:
+       case lazy.UrlbarShared.RESULT_SOURCE.OTHER_LOCAL:
+       case lazy.UrlbarShared.RESULT_SOURCE.ADDON:
        default:
diff --git a/src/browser/components/urlbar/UrlbarUtils-sys-mjs.patch b/src/browser/components/urlbar/UrlbarUtils-sys-mjs.patch
index 479b45005..630553ff9 100644
--- a/src/browser/components/urlbar/UrlbarUtils-sys-mjs.patch
+++ b/src/browser/components/urlbar/UrlbarUtils-sys-mjs.patch
@@ -1,8 +1,8 @@
 diff --git a/browser/components/urlbar/UrlbarUtils.sys.mjs b/browser/components/urlbar/UrlbarUtils.sys.mjs
-index aa7c67f2bfaa3f15d592a14b527a8721dfc9bc6f..d2fe012796ea3a5be05090a732011b3cf92b78be 100644
+index 78c76bde00b6b581184cee1cd0e1756e5f2da6a4..94c713470b1240729ef2350d090b0449f3801af4 100644
 --- a/browser/components/urlbar/UrlbarUtils.sys.mjs
 +++ b/browser/components/urlbar/UrlbarUtils.sys.mjs
-@@ -110,6 +110,8 @@ export var UrlbarUtils = {
+@@ -126,6 +126,8 @@ export var UrlbarUtils = {
      SEMANTIC_HISTORY: "semanticHistory",
      SUGGESTED_INDEX: "suggestedIndex",
      TAIL_SUGGESTION: "tailSuggestion",
@@ -11,22 +11,13 @@ index aa7c67f2bfaa3f15d592a14b527a8721dfc9bc6f..d2fe012796ea3a5be05090a732011b3c
    }),
  
    // Defines provider types.
-@@ -171,6 +173,8 @@ export var UrlbarUtils = {
-     OTHER_NETWORK: 6,
-     ADDON: 7,
-     ACTIONS: 8,
-+    ZEN_ACTIONS: 9,
-+    WORKSPACES: 10,
-   }),
- 
-   // Per-result exposure telemetry.
-@@ -320,6 +324,14 @@ export var UrlbarUtils = {
+@@ -274,6 +276,14 @@ export var UrlbarUtils = {
          telemetryLabel: "actions",
-         uiLabel: "urlbar-searchmode-actions2",
+         uiLabel: "urlbar-searchmode-actions3",
        },
 +      {
-+        source: this.RESULT_SOURCE.WORKSPACES,
-+        restrict: lazy.UrlbarShared.RESTRICT_TOKENS.WORKSPACE,
++        source: UrlbarShared.RESULT_SOURCE.WORKSPACES,
++        restrict: UrlbarShared.RESTRICT_TOKENS.WORKSPACE,
 +        icon: "chrome://browser/skin/zen-icons/selectable/layers.svg",
 +        pref: "shortcuts.workspaces",
 +        telemetryLabel: "workspaces",
@@ -35,12 +26,12 @@ index aa7c67f2bfaa3f15d592a14b527a8721dfc9bc6f..d2fe012796ea3a5be05090a732011b3c
      ]);
    },
  
-@@ -612,6 +624,12 @@ export var UrlbarUtils = {
+@@ -566,6 +576,12 @@ export var UrlbarUtils = {
            return this.RESULT_GROUP.HEURISTIC_FALLBACK;
          case "UrlbarProviderHistoryUrlHeuristic":
            return this.RESULT_GROUP.HEURISTIC_HISTORY_URL;
 +        case "ZenUrlbarProviderGlobalActions":
-+          if (result.source == this.RESULT_SOURCE.WORKSPACES) {
++          if (result.source == UrlbarShared.RESULT_SOURCE.WORKSPACES) {
 +            return this.RESULT_GROUP.ZEN_WORKSPACE;
 +          } else {
 +            return this.RESULT_GROUP.ZEN_ACTION;
diff --git a/src/browser/components/urlbar/content/UrlbarChildController-mjs.patch b/src/browser/components/urlbar/content/UrlbarChildController-mjs.patch
new file mode 100644
index 000000000..a7751f7ca
--- /dev/null
+++ b/src/browser/components/urlbar/content/UrlbarChildController-mjs.patch
@@ -0,0 +1,21 @@
+diff --git a/browser/components/urlbar/content/UrlbarChildController.mjs b/browser/components/urlbar/content/UrlbarChildController.mjs
+index a8e9d3093d046612650a17970330a8279f55833f..063a3e8adf009d6c0ddc60430bc0e7485e812b8a 100644
+--- a/browser/components/urlbar/content/UrlbarChildController.mjs
++++ b/browser/components/urlbar/content/UrlbarChildController.mjs
+@@ -258,7 +258,6 @@ export class UrlbarChildController {
+     const isMac = AppConstants.platform == "macosx";
+     // Handle readline/emacs-style navigation bindings on Mac.
+     if (
+-      isMac &&
+       this.view.isOpen &&
+       event.ctrlKey &&
+       (event.key == "n" || event.key == "p")
+@@ -450,6 +449,8 @@ export class UrlbarChildController {
+             });
+           }
+           event.preventDefault();
++        } else if (!this.input.value && !(event.ctrlKey || event.altKey || event.shiftKey)) {
++          this.window.gZenUIManager.enableCommandsMode(event);
+         }
+         break;
+       }
diff --git a/src/browser/components/urlbar/content/UrlbarInput-mjs.patch b/src/browser/components/urlbar/content/UrlbarInput-mjs.patch
index 13fc9f341..b6b5daebe 100644
--- a/src/browser/components/urlbar/content/UrlbarInput-mjs.patch
+++ b/src/browser/components/urlbar/content/UrlbarInput-mjs.patch
@@ -1,9 +1,9 @@
 diff --git a/browser/components/urlbar/content/UrlbarInput.mjs b/browser/components/urlbar/content/UrlbarInput.mjs
-index 0b1b4b2f0f8d6b0fb126aa1224409ab6f1ffb8d8..4405e1bf385477c2161ae3a5a62e32c1403a3630 100644
+index e7e9495e56076cd112beafb8297dece4ae4cea58..95e4333866a5f0d41fbdbe23910c396406a247e9 100644
 --- a/browser/components/urlbar/content/UrlbarInput.mjs
 +++ b/browser/components/urlbar/content/UrlbarInput.mjs
-@@ -98,6 +98,13 @@ const lazy = XPCOMUtils.declareLazy({
-   logger: () => lazy.UrlbarUtils.getLogger({ prefix: "Input" }),
+@@ -101,6 +101,13 @@ const lazy = XPCOMUtils.declareLazy({
+   logger: () => UrlbarShared.getLogger({ prefix: "Input" }),
  });
  
 +XPCOMUtils.defineLazyPreferenceGetter(
@@ -16,7 +16,7 @@ index 0b1b4b2f0f8d6b0fb126aa1224409ab6f1ffb8d8..4405e1bf385477c2161ae3a5a62e32c1
  const UNLIMITED_MAX_RESULTS = 99;
  
  let getBoundsWithoutFlushing = element =>
-@@ -770,7 +777,16 @@ ${
+@@ -769,7 +776,16 @@ ${
      // See _on_select().  HTMLInputElement.select() dispatches a "select"
      // event but does not set the primary selection.
      this._suppressPrimaryAdjustment = true;
@@ -33,7 +33,7 @@ index 0b1b4b2f0f8d6b0fb126aa1224409ab6f1ffb8d8..4405e1bf385477c2161ae3a5a62e32c1
      this._suppressPrimaryAdjustment = false;
    }
  
-@@ -844,6 +860,10 @@ ${
+@@ -843,6 +859,10 @@ ${
      hideSearchTerms = false,
      isSameDocument = false,
    } = {}) {
@@ -44,7 +44,7 @@ index 0b1b4b2f0f8d6b0fb126aa1224409ab6f1ffb8d8..4405e1bf385477c2161ae3a5a62e32c1
      if (!this.#isAddressbar) {
        throw new Error(
          "Cannot set URI for UrlbarInput that is not an address bar"
-@@ -1138,7 +1158,16 @@ ${
+@@ -1137,7 +1157,16 @@ ${
        this.searchModeSwitcher?.updateSearchIcon();
      }
  
@@ -61,7 +61,7 @@ index 0b1b4b2f0f8d6b0fb126aa1224409ab6f1ffb8d8..4405e1bf385477c2161ae3a5a62e32c1
    }
  
    /**
-@@ -1630,7 +1659,11 @@ ${
+@@ -1626,7 +1655,11 @@ ${
      openParams.avoidBrowserFocus = keepViewOpen;
  
      if (!this.#providesSearchMode(result) && !keepViewOpen) {
@@ -74,7 +74,7 @@ index 0b1b4b2f0f8d6b0fb126aa1224409ab6f1ffb8d8..4405e1bf385477c2161ae3a5a62e32c1
      }
  
      if (isCanonized) {
-@@ -2940,6 +2973,42 @@ ${
+@@ -2974,6 +3007,42 @@ ${
      await this.#updateLayoutBreakoutDimensions();
    }
  
@@ -117,7 +117,7 @@ index 0b1b4b2f0f8d6b0fb126aa1224409ab6f1ffb8d8..4405e1bf385477c2161ae3a5a62e32c1
    startLayoutExtend() {
      if (!this.#allowBreakout || this.hasAttribute("breakout-extend")) {
        // Do not expand if the Urlbar does not support being expanded or it is
-@@ -2957,6 +3026,13 @@ ${
+@@ -2988,6 +3057,13 @@ ${
      this.toggleAttribute("breakout-extend", true);
      this.#updateTextboxPosition();
  
@@ -131,7 +131,7 @@ index 0b1b4b2f0f8d6b0fb126aa1224409ab6f1ffb8d8..4405e1bf385477c2161ae3a5a62e32c1
      // Enable the animation only after the first extend call to ensure it
      // doesn't run when opening a new window.
      if (!this.hasAttribute("breakout-extend-animate")) {
-@@ -2984,6 +3060,29 @@ ${
+@@ -3011,6 +3087,29 @@ ${
        return;
      }
  
@@ -161,7 +161,7 @@ index 0b1b4b2f0f8d6b0fb126aa1224409ab6f1ffb8d8..4405e1bf385477c2161ae3a5a62e32c1
      this.toggleAttribute("breakout-extend", false);
      this.#updateTextboxPosition();
    }
-@@ -3031,7 +3130,7 @@ ${
+@@ -3049,7 +3148,7 @@ ${
      forceUnifiedSearchButtonAvailable = false
    ) {
      let prevState = this.getAttribute("pageproxystate");
@@ -170,7 +170,7 @@ index 0b1b4b2f0f8d6b0fb126aa1224409ab6f1ffb8d8..4405e1bf385477c2161ae3a5a62e32c1
      this.setAttribute("pageproxystate", state);
      this._inputContainer.setAttribute("pageproxystate", state);
      this._identityBox?.setAttribute("pageproxystate", state);
-@@ -3314,10 +3413,12 @@ ${
+@@ -3332,10 +3431,12 @@ ${
      }
  
      this.style.top = px(
@@ -183,7 +183,7 @@ index 0b1b4b2f0f8d6b0fb126aa1224409ab6f1ffb8d8..4405e1bf385477c2161ae3a5a62e32c1
      );
    }
  
-@@ -3376,9 +3477,10 @@ ${
+@@ -3394,9 +3495,10 @@ ${
            return;
          }
  
@@ -195,7 +195,7 @@ index 0b1b4b2f0f8d6b0fb126aa1224409ab6f1ffb8d8..4405e1bf385477c2161ae3a5a62e32c1
          );
          this.style.setProperty(
            "--urlbar-height",
-@@ -3883,6 +3985,7 @@ ${
+@@ -3902,6 +4004,7 @@ ${
    }
  
    _toggleActionOverride(event) {
@@ -203,7 +203,7 @@ index 0b1b4b2f0f8d6b0fb126aa1224409ab6f1ffb8d8..4405e1bf385477c2161ae3a5a62e32c1
      if (
        event.keyCode == KeyEvent.DOM_VK_SHIFT ||
        event.keyCode == KeyEvent.DOM_VK_ALT ||
-@@ -3995,8 +4098,8 @@ ${
+@@ -4014,8 +4117,8 @@ ${
      if (!this.#isAddressbar) {
        return val;
      }
@@ -214,7 +214,7 @@ index 0b1b4b2f0f8d6b0fb126aa1224409ab6f1ffb8d8..4405e1bf385477c2161ae3a5a62e32c1
        : val;
      // Only trim value if the directionality doesn't change to RTL and we're not
      // showing a strikeout https protocol.
-@@ -4298,6 +4401,7 @@ ${
+@@ -4317,6 +4420,7 @@ ${
      browser = this.window.gBrowser.selectedBrowser,
      keepViewOpen = false
    ) {
@@ -222,7 +222,7 @@ index 0b1b4b2f0f8d6b0fb126aa1224409ab6f1ffb8d8..4405e1bf385477c2161ae3a5a62e32c1
      if (this.#isAddressbar) {
        this.#prepareAddressbarLoad(
          url,
-@@ -4411,6 +4515,10 @@ ${
+@@ -4430,6 +4534,10 @@ ${
        }
        reuseEmpty = true;
      }
@@ -233,7 +233,7 @@ index 0b1b4b2f0f8d6b0fb126aa1224409ab6f1ffb8d8..4405e1bf385477c2161ae3a5a62e32c1
      if (
        where == "tab" &&
        reuseEmpty &&
-@@ -4418,6 +4526,9 @@ ${
+@@ -4437,6 +4545,9 @@ ${
      ) {
        where = "current";
      }
@@ -243,7 +243,7 @@ index 0b1b4b2f0f8d6b0fb126aa1224409ab6f1ffb8d8..4405e1bf385477c2161ae3a5a62e32c1
      return where;
    }
  
-@@ -4672,6 +4783,7 @@ ${
+@@ -4691,6 +4802,7 @@ ${
        this.setResultForCurrentValue(null);
        this.handleCommand();
        this.controller.clearLastQueryContextCache();
@@ -251,7 +251,7 @@ index 0b1b4b2f0f8d6b0fb126aa1224409ab6f1ffb8d8..4405e1bf385477c2161ae3a5a62e32c1
  
        this._suppressStartQuery = false;
      });
-@@ -4679,7 +4791,6 @@ ${
+@@ -4698,7 +4810,6 @@ ${
      contextMenu.addEventListener("popupshowing", () => {
        // Close the results pane when the input field contextual menu is open,
        // because paste and go doesn't want a result selection.
@@ -259,7 +259,7 @@ index 0b1b4b2f0f8d6b0fb126aa1224409ab6f1ffb8d8..4405e1bf385477c2161ae3a5a62e32c1
  
        let controller =
          this.document.commandDispatcher.getControllerForCommand("cmd_paste");
-@@ -4842,7 +4953,11 @@ ${
+@@ -4979,7 +5090,11 @@ ${
      if (!engineName && !source && !this.hasAttribute("searchmode")) {
        return;
      }
@@ -272,7 +272,7 @@ index 0b1b4b2f0f8d6b0fb126aa1224409ab6f1ffb8d8..4405e1bf385477c2161ae3a5a62e32c1
      if (this._searchModeIndicatorTitle) {
        this._searchModeIndicatorTitle.textContent = "";
        this._searchModeIndicatorTitle.removeAttribute("data-l10n-id");
-@@ -5159,6 +5274,7 @@ ${
+@@ -5297,6 +5412,7 @@ ${
  
      this.document.l10n.setAttributes(
        this.inputField,
@@ -280,7 +280,20 @@ index 0b1b4b2f0f8d6b0fb126aa1224409ab6f1ffb8d8..4405e1bf385477c2161ae3a5a62e32c1
        l10nId,
        l10nId == "urlbar-placeholder-with-name"
          ? { name: engineName }
-@@ -5282,6 +5398,11 @@ ${
+@@ -5347,6 +5463,12 @@ ${
+     }
+ 
+     lazy.logger.debug("Blur Event");
++    if (
++      this.document.commandDispatcher.focusedElement == this.inputField &&
++      !lazy.UrlbarPrefs.get("closeOnWindowBlur")
++    ) {
++      return;
++    }
+     // We cannot count every blur events after a missed engagement as abandoment
+     // because the user may have clicked on some view element that executes
+     // a command causing a focus change. For example opening preferences from
+@@ -5424,6 +5546,11 @@ ${
    }
  
    _on_click(event) {
@@ -292,10 +305,10 @@ index 0b1b4b2f0f8d6b0fb126aa1224409ab6f1ffb8d8..4405e1bf385477c2161ae3a5a62e32c1
      switch (event.target) {
        case this.inputField:
        case this._inputContainer:
-@@ -5371,10 +5492,11 @@ ${
+@@ -5513,10 +5640,11 @@ ${
        }
        if (untrim) {
-         this._setValue(this._untrimmedValue);
+         this.setValue(this._untrimmedValue);
 +        this.setSelectionRange(0, this.value.length);
        }
      }
@@ -305,7 +318,7 @@ index 0b1b4b2f0f8d6b0fb126aa1224409ab6f1ffb8d8..4405e1bf385477c2161ae3a5a62e32c1
        this.view.autoOpen({ event });
      } else {
        if (this._untrimOnFocusAfterKeydown) {
-@@ -5414,9 +5536,16 @@ ${
+@@ -5556,9 +5684,16 @@ ${
    }
  
    _on_mousedown(event) {
@@ -323,7 +336,7 @@ index 0b1b4b2f0f8d6b0fb126aa1224409ab6f1ffb8d8..4405e1bf385477c2161ae3a5a62e32c1
          if (
            event.composedTarget != this.inputField &&
            event.composedTarget != this._inputContainer
-@@ -5426,6 +5555,10 @@ ${
+@@ -5568,6 +5703,10 @@ ${
  
          this.focusedViaMousedown = !this.focused;
          this.#preventClickSelectsAll = this.focused;
@@ -334,21 +347,21 @@ index 0b1b4b2f0f8d6b0fb126aa1224409ab6f1ffb8d8..4405e1bf385477c2161ae3a5a62e32c1
  
          // Keep the focus status, since the attribute may be changed
          // upon calling this.focus().
-@@ -5461,7 +5594,7 @@ ${
-         }
-         // Don't close the view when clicking on a tab; we may want to keep the
+@@ -5605,7 +5744,7 @@ ${
          // view open on tab switch, and the TabSelect event arrived earlier.
--        if (event.target.closest?.("tab")) {
-+        if (event.target.closest?.("tab") || event.target.closest?.("#tabs-newtab-button")) {
+         // Also ignore mousedown on the urlbarView context menu: opening/closing the
+         // view is already handled by the result opening flow.
+-        if (event.target.closest?.("tab, #urlbarView-context-menu")) {
++        if (event.target.closest?.("tab, #urlbarView-context-menu") || event.target.closest?.("#tabs-newtab-button")) {
            break;
          }
  
-@@ -5750,7 +5883,7 @@ ${
+@@ -5894,7 +6033,7 @@ ${
      // When we are in actions search mode we can show more results so
      // increase the limit.
      let maxResults =
--      this.searchMode?.source != lazy.UrlbarUtils.RESULT_SOURCE.ACTIONS
-+      this.searchMode?.source != lazy.UrlbarUtils.RESULT_SOURCE.ZEN_ACTIONS
+-      this.searchMode?.source != UrlbarShared.RESULT_SOURCE.ACTIONS
++      this.searchMode?.source != UrlbarShared.RESULT_SOURCE.ZEN_ACTIONS
          ? lazy.UrlbarPrefs.get("maxRichResults")
          : UNLIMITED_MAX_RESULTS;
      let options = {
diff --git a/src/browser/components/urlbar/content/UrlbarShared-mjs.patch b/src/browser/components/urlbar/content/UrlbarShared-mjs.patch
index 08bbdf807..6a676136c 100644
--- a/src/browser/components/urlbar/content/UrlbarShared-mjs.patch
+++ b/src/browser/components/urlbar/content/UrlbarShared-mjs.patch
@@ -1,8 +1,8 @@
 diff --git a/browser/components/urlbar/content/UrlbarShared.mjs b/browser/components/urlbar/content/UrlbarShared.mjs
-index 5522d8a8c8d9549453c1700ff6fec40be52747ce..7b8ad33cc337907249749074057254bf7e316994 100644
+index 5b45afb747bfcdbd06782186737669aa2c4c634d..f68bd009f70415b5fb513abdfe19b4427ceefbfc 100644
 --- a/browser/components/urlbar/content/UrlbarShared.mjs
 +++ b/browser/components/urlbar/content/UrlbarShared.mjs
-@@ -32,6 +32,7 @@ export const UrlbarShared = {
+@@ -47,6 +47,7 @@ export const UrlbarShared = {
      // `looksLikeOrigin()` returned `LOOKS_LIKE_ORIGIN.OTHER` for this token.
      // It may or may not be an origin.
      POSSIBLE_ORIGIN_BUT_SEARCH_ALLOWED: 12,
@@ -10,19 +10,28 @@ index 5522d8a8c8d9549453c1700ff6fec40be52747ce..7b8ad33cc337907249749074057254bf
    }),
  
    /**
-@@ -52,6 +53,7 @@ export const UrlbarShared = {
+@@ -67,6 +68,7 @@ export const UrlbarShared = {
      TITLE: "#",
      URL: "$",
      ACTION: ">",
 +    WORKSPACE: "`",
    }),
  
+   // Defines UrlbarResult types.
+@@ -112,6 +114,8 @@ export const UrlbarShared = {
+     OTHER_NETWORK: 6,
+     ADDON: 7,
+     ACTIONS: 8,
++    ZEN_ACTIONS: 9,
++    WORKSPACES: 10,
+   }),
+ 
    /**
-@@ -68,6 +70,7 @@ export const UrlbarShared = {
+@@ -128,6 +132,7 @@ export const UrlbarShared = {
      if (lazy.UrlbarPrefs.get("scotchBonnet.enableOverride")) {
        keys.push(this.RESTRICT_TOKENS.ACTION);
      }
 +    keys.push(this.RESTRICT_TOKENS.WORKSPACE);
      return new Set(keys);
    },
- };
+ 
diff --git a/src/browser/components/urlbar/content/UrlbarView-mjs.patch b/src/browser/components/urlbar/content/UrlbarView-mjs.patch
index 21d69f2b0..7225a807e 100644
--- a/src/browser/components/urlbar/content/UrlbarView-mjs.patch
+++ b/src/browser/components/urlbar/content/UrlbarView-mjs.patch
@@ -1,8 +1,8 @@
 diff --git a/browser/components/urlbar/content/UrlbarView.mjs b/browser/components/urlbar/content/UrlbarView.mjs
-index 8afb2bf4a757b3ef7902f5a6e6eed6b70ca2845e..440dea1e66540ca1998cb7464b6695ac823fedcb 100644
+index e465806c4ae4fc372d9aa2b71aa7f0e74c65d026..c0b3781901298bedee2736819a93edbf545507a7 100644
 --- a/browser/components/urlbar/content/UrlbarView.mjs
 +++ b/browser/components/urlbar/content/UrlbarView.mjs
-@@ -674,7 +674,7 @@ export class UrlbarView {
+@@ -803,7 +803,7 @@ export class UrlbarView {
        !this.input.value ||
        this.input.getAttribute("pageproxystate") == "valid"
      ) {
@@ -11,7 +11,7 @@ index 8afb2bf4a757b3ef7902f5a6e6eed6b70ca2845e..440dea1e66540ca1998cb7464b6695ac
          // Try to reuse the cached top-sites context. If it's not cached, then
          // there will be a gap of time between when the input is focused and
          // when the view opens that can be perceived as flicker.
-@@ -812,10 +812,6 @@ export class UrlbarView {
+@@ -941,10 +941,6 @@ export class UrlbarView {
      }
  
      // If search mode isn't active, close the view.
@@ -22,7 +22,7 @@ index 8afb2bf4a757b3ef7902f5a6e6eed6b70ca2845e..440dea1e66540ca1998cb7464b6695ac
  
      // Search mode is active.  If the one-offs should be shown, make sure they
      // are enabled and show the view.
-@@ -3031,6 +3027,8 @@ export class UrlbarView {
+@@ -3203,6 +3199,8 @@ export class UrlbarView {
        if (row?.hasAttribute("row-selectable")) {
          row?.toggleAttribute("selected", true);
        }
@@ -31,7 +31,7 @@ index 8afb2bf4a757b3ef7902f5a6e6eed6b70ca2845e..440dea1e66540ca1998cb7464b6695ac
        if (element != row) {
          row?.toggleAttribute("descendant-selected", true);
        }
-@@ -3544,7 +3542,7 @@ export class UrlbarView {
+@@ -3715,7 +3713,7 @@ export class UrlbarView {
    }
  
    #enableOrDisableRowWrap() {
@@ -40,3 +40,16 @@ index 8afb2bf4a757b3ef7902f5a6e6eed6b70ca2845e..440dea1e66540ca1998cb7464b6695ac
      this.#rows.toggleAttribute("wrap", wrap);
      this.oneOffSearchButtons?.container.toggleAttribute("wrap", wrap);
    }
+@@ -4144,6 +4142,12 @@ export class UrlbarView {
+   }
+ 
+   on_blur() {
++    if (
++      this.document.commandDispatcher.focusedElement == this.input.inputField &&
++      !lazy.UrlbarPrefs.get("closeOnWindowBlur")
++    ) {
++      return;
++    }
+     // If the view is open without the input being focused, it will not close
+     // automatically when the window loses focus. We might be in this state
+     // after a Search Tip is shown on an engine homepage.
diff --git a/src/browser/themes/linux/browser-css.patch b/src/browser/themes/linux/browser-css.patch
index bc54b6b5d..4331385b9 100644
--- a/src/browser/themes/linux/browser-css.patch
+++ b/src/browser/themes/linux/browser-css.patch
@@ -1,11 +1,11 @@
 diff --git a/browser/themes/linux/browser.css b/browser/themes/linux/browser.css
-index 5e5d39787674d1d5ac8c39edccb04f8b8993fbb8..6c8b483ad19d9b26232592c68a7f2a6887161057 100644
+index e735ec80b56e1a2da4bc5bec29136ce60353277b..330ea62d220d9acd96a95a605888839388e97452 100644
 --- a/browser/themes/linux/browser.css
 +++ b/browser/themes/linux/browser.css
 @@ -14,7 +14,6 @@
      @media (-moz-gtk-theme-family) {
        --tabs-navbar-separator-style: none;
-       @media (prefers-color-scheme: light) {
+       @media (prefers-color-scheme: light) and (not -moz-pref("browser.nova.enabled")) {
 -        --urlbar-box-background-color: #fafafa;
        }
      }
diff --git a/src/browser/themes/shared/tabbrowser/tabs-css.patch b/src/browser/themes/shared/tabbrowser/tabs-css.patch
index ebd860758..28160af66 100644
--- a/src/browser/themes/shared/tabbrowser/tabs-css.patch
+++ b/src/browser/themes/shared/tabbrowser/tabs-css.patch
@@ -1,8 +1,8 @@
 diff --git a/browser/themes/shared/tabbrowser/tabs.css b/browser/themes/shared/tabbrowser/tabs.css
-index 24ad9ab050a67d4a375eb1d05261a7f7c267d7d1..b2f2ae8e765ad1f052aa07ab1d47f285062fbbcc 100644
+index 0820fa040642ee05c2a24f5d2cfa58da5c926647..2d93abcce1729744e5963f1c6ad47f253804576e 100644
 --- a/browser/themes/shared/tabbrowser/tabs.css
 +++ b/browser/themes/shared/tabbrowser/tabs.css
-@@ -33,7 +33,7 @@
+@@ -45,7 +45,7 @@
    --tab-group-line-thickness: 2px;
    --tab-group-line-toolbar-border-distance: 1px;
    /* Collapsed tabs should be square, so set width to match the min height */
@@ -11,7 +11,7 @@ index 24ad9ab050a67d4a375eb1d05261a7f7c267d7d1..b2f2ae8e765ad1f052aa07ab1d47f285
    --tab-collapsed-width: calc(var(--tab-collapsed-background-width) + 2 * var(--tab-inner-inline-margin));
    --tab-pinned-min-width-expanded: calc(var(--tab-pinned-expanded-background-width) + 2 * var(--tab-pinned-margin-inline-expanded));
    --tab-note-icon-end-margin: var(--dimension-4);
-@@ -282,7 +282,6 @@ tab-split-view-wrapper[dragtarget] {
+@@ -295,7 +295,6 @@ tab-split-view-wrapper[dragtarget] {
    }
  
    :root:not([uidensity="compact"], [sidebar-expand-on-hover]) &[pinned] {
@@ -19,7 +19,7 @@ index 24ad9ab050a67d4a375eb1d05261a7f7c267d7d1..b2f2ae8e765ad1f052aa07ab1d47f285
    }
  
    &:is([selected], [multiselected]) {
-@@ -296,6 +295,7 @@ tab-split-view-wrapper[dragtarget] {
+@@ -309,6 +308,7 @@ tab-split-view-wrapper[dragtarget] {
      border-radius: inherit;
      position: relative;
      overflow: hidden;
@@ -27,7 +27,7 @@ index 24ad9ab050a67d4a375eb1d05261a7f7c267d7d1..b2f2ae8e765ad1f052aa07ab1d47f285
  
      &::before {
        position: absolute;
-@@ -493,10 +493,6 @@ tab-split-view-wrapper[dragtarget] {
+@@ -506,10 +506,6 @@ tab-split-view-wrapper[dragtarget] {
  
    @media -moz-pref("browser.tabs.fadeOutUnloadedTabs") {
      &[pending] {
@@ -38,7 +38,7 @@ index 24ad9ab050a67d4a375eb1d05261a7f7c267d7d1..b2f2ae8e765ad1f052aa07ab1d47f285
        opacity: 0.5;
        /* Fade the favicon out */
        transition-property: filter, opacity;
-@@ -512,10 +508,6 @@ tab-split-view-wrapper[dragtarget] {
+@@ -525,10 +521,6 @@ tab-split-view-wrapper[dragtarget] {
  
    @media -moz-pref("browser.tabs.fadeOutExplicitlyUnloadedTabs") {
      &[pending][discarded] {
@@ -49,7 +49,7 @@ index 24ad9ab050a67d4a375eb1d05261a7f7c267d7d1..b2f2ae8e765ad1f052aa07ab1d47f285
        opacity: 0.5;
        /* Fade the favicon out */
        transition-property: filter, opacity;
-@@ -589,7 +581,7 @@ tab-split-view-wrapper[dragtarget] {
+@@ -602,7 +594,7 @@ tab-split-view-wrapper[dragtarget] {
    }
  
    #tabbrowser-tabs[orient="vertical"] & {
@@ -58,7 +58,7 @@ index 24ad9ab050a67d4a375eb1d05261a7f7c267d7d1..b2f2ae8e765ad1f052aa07ab1d47f285
    }
  
    &[crashed] {
-@@ -597,7 +589,7 @@ tab-split-view-wrapper[dragtarget] {
+@@ -610,7 +602,7 @@ tab-split-view-wrapper[dragtarget] {
    }
  
    #tabbrowser-tabs[orient="vertical"]:not([expanded]) &:not([crashed]),
@@ -67,7 +67,7 @@ index 24ad9ab050a67d4a375eb1d05261a7f7c267d7d1..b2f2ae8e765ad1f052aa07ab1d47f285
      &[soundplaying] {
        list-style-image: url("chrome://browser/skin/tabbrowser/tab-audio-playing-small.svg");
      }
-@@ -651,7 +643,7 @@ tab-split-view-wrapper[dragtarget] {
+@@ -664,7 +656,7 @@ tab-split-view-wrapper[dragtarget] {
      }
    }
  
@@ -76,7 +76,7 @@ index 24ad9ab050a67d4a375eb1d05261a7f7c267d7d1..b2f2ae8e765ad1f052aa07ab1d47f285
    &[crashed] {
      display: revert;
    }
-@@ -811,7 +803,7 @@ tab-split-view-wrapper[dragtarget] {
+@@ -824,7 +816,7 @@ tab-split-view-wrapper[dragtarget] {
        has not been added to root. There are certain scenarios when that attribute is temporarily
        removed from root such as when toggling the sidebar to expand with the toolbar button. */
      #tabbrowser-tabs[orient="horizontal"] &:not([pinned]):not([crashed]),
@@ -85,7 +85,7 @@ index 24ad9ab050a67d4a375eb1d05261a7f7c267d7d1..b2f2ae8e765ad1f052aa07ab1d47f285
        &:is([soundplaying], [muted], [activemedia-blocked]) {
          display: flex;
        }
-@@ -1031,7 +1023,6 @@ tab-split-view-wrapper[dragtarget] {
+@@ -1044,7 +1036,6 @@ tab-split-view-wrapper[dragtarget] {
  .tabbrowser-tab:is([image], [pinned]) > .tab-stack > .tab-content[attention]:not([selected]),
  .tabbrowser-tab > .tab-stack > .tab-content[pinned][titlechanged]:not([selected]),
  #tabbrowser-tabs[orient="vertical"] .tabbrowser-tab > .tab-stack > .tab-content[titlechanged]:not([selected]) {
@@ -93,7 +93,7 @@ index 24ad9ab050a67d4a375eb1d05261a7f7c267d7d1..b2f2ae8e765ad1f052aa07ab1d47f285
    background-position: center bottom 6.5px;
    background-size: 4px 4px;
    background-repeat: no-repeat;
-@@ -1780,7 +1771,7 @@ tab-group {
+@@ -1797,7 +1788,7 @@ tab-group {
  }
  
  #tabbrowser-tabs[orient="vertical"][expanded] {
@@ -102,7 +102,7 @@ index 24ad9ab050a67d4a375eb1d05261a7f7c267d7d1..b2f2ae8e765ad1f052aa07ab1d47f285
    &[movingtab][movingtab-addToGroup]:not([movingtab-group], [movingtab-ungroup]) .tabbrowser-tab:is(:active, [multiselected]) {
      margin-inline-start: var(--space-medium);
    }
-@@ -2335,7 +2326,7 @@ tab-group {
+@@ -2351,7 +2342,7 @@ tab-group {
    }
  }
  
@@ -111,7 +111,7 @@ index 24ad9ab050a67d4a375eb1d05261a7f7c267d7d1..b2f2ae8e765ad1f052aa07ab1d47f285
  #vertical-tabs-newtab-button {
    appearance: none;
    min-height: var(--tab-min-height);
-@@ -2346,7 +2337,7 @@ tab-group {
+@@ -2362,7 +2353,7 @@ tab-group {
    margin-inline: var(--tab-inner-inline-margin);
  
    #tabbrowser-tabs[orient="vertical"]:not([expanded]) & > .toolbarbutton-text {
@@ -120,16 +120,16 @@ index 24ad9ab050a67d4a375eb1d05261a7f7c267d7d1..b2f2ae8e765ad1f052aa07ab1d47f285
    }
  
    &:hover {
-@@ -2370,7 +2361,7 @@ tab-group {
+@@ -2386,7 +2377,7 @@ tab-group {
   * flex container. #tabs-newtab-button is a child of the arrowscrollbox where
   * we don't want a gap (between tabs), so we have to add some margin.
   */
 -#tabbrowser-arrowscrollbox[orient="vertical"] > #tabbrowser-arrowscrollbox-periphery > #tabs-newtab-button {
 +#tabbrowser-arrowscrollbox[orient="vertical"] #tabbrowser-arrowscrollbox-periphery > #tabs-newtab-button {
-   margin-block: var(--tab-block-margin);
+   margin-block: var(--tab-margin-block);
  }
  
-@@ -2560,7 +2551,6 @@ tab-group {
+@@ -2576,7 +2567,6 @@ tab-group {
  
    &:not([expanded]) {
      .tabbrowser-tab[pinned] {
@@ -137,7 +137,7 @@ index 24ad9ab050a67d4a375eb1d05261a7f7c267d7d1..b2f2ae8e765ad1f052aa07ab1d47f285
      }
  
      .tab-background {
-@@ -2599,8 +2589,8 @@ tab-group {
+@@ -2615,8 +2605,8 @@ tab-group {
        display: block;
        position: absolute;
        inset: auto;
@@ -148,7 +148,7 @@ index 24ad9ab050a67d4a375eb1d05261a7f7c267d7d1..b2f2ae8e765ad1f052aa07ab1d47f285
  
        &:-moz-window-inactive {
          background-image:
-@@ -2698,9 +2688,6 @@ tab-group {
+@@ -2714,9 +2704,6 @@ tab-group {
    ~ #tabbrowser-tabs[orient="horizontal"]::before {
      display: flex;
      content: "";
@@ -158,7 +158,7 @@ index 24ad9ab050a67d4a375eb1d05261a7f7c267d7d1..b2f2ae8e765ad1f052aa07ab1d47f285
    }
  }
  
-@@ -2733,7 +2720,6 @@ toolbar:not(#TabsToolbar) #firefox-view-button {
+@@ -2749,7 +2736,6 @@ toolbar:not(#TabsToolbar) #firefox-view-button {
    list-style-image: url(chrome://global/skin/icons/plus.svg);
  }
  
diff --git a/src/browser/themes/shared/urlbar-searchbar-css.patch b/src/browser/themes/shared/urlbar-searchbar-css.patch
index 148b7b911..fdc1f148d 100644
--- a/src/browser/themes/shared/urlbar-searchbar-css.patch
+++ b/src/browser/themes/shared/urlbar-searchbar-css.patch
@@ -1,5 +1,5 @@
 diff --git a/browser/themes/shared/urlbar-searchbar.css b/browser/themes/shared/urlbar-searchbar.css
-index cc595de7e3839f7e688122552bca95f9f9ad3988..da4b1e1b5013d7a1a9af3d45d94db7194a1826f7 100644
+index 22d624d718a289dd7b84ffc2f04dd35893dfbe95..4f57f7853f3043e3ad01d893aa928b9d2e6f3c16 100644
 --- a/browser/themes/shared/urlbar-searchbar.css
 +++ b/browser/themes/shared/urlbar-searchbar.css
 @@ -19,8 +19,8 @@
@@ -13,7 +13,7 @@ index cc595de7e3839f7e688122552bca95f9f9ad3988..da4b1e1b5013d7a1a9af3d45d94db719
    }
    @media (max-width: 770px) {
      --urlbar-container-min-width: 240px;
-@@ -114,7 +114,7 @@ toolbar[inactive="true"] .urlbar,
+@@ -126,7 +126,7 @@ toolbar[inactive="true"] .urlbar,
  .urlbar:not([usertyping]) > .urlbar-input-container > .urlbar-go-button,
  .urlbar:not(#searchbar-new, [focused]) > .urlbar-input-container > .urlbar-go-button,
  #urlbar-revert-button-container {
@@ -22,18 +22,18 @@ index cc595de7e3839f7e688122552bca95f9f9ad3988..da4b1e1b5013d7a1a9af3d45d94db719
  }
  
  /* Document Picture-in-Picture API window */
-@@ -350,6 +350,10 @@ toolbar[inactive="true"] .urlbar,
+@@ -403,6 +403,10 @@ toolbar[inactive="true"] .urlbar,
+   .urlbar:not([focused])[textoverflow="left"][domaindir="rtl"] > .urlbar-input-container > .urlbar-input-box > & {
      mask-image: linear-gradient(to right, transparent var(--urlbar-scheme-size), black calc(var(--urlbar-scheme-size) + 3ch));
    }
- 
++
 +  #navigator-toolbox[zen-has-implicit-hover="true"] .urlbar:not([focused])[textoverflow="left"] > .urlbar-input-container > .urlbar-input-box > & {
 +    mask-image: linear-gradient(to right, transparent, black 3ch, black calc(100% - 3ch), transparent);
 +  }
-+
-   &::selection {
-     border-radius: var(--urlbar-selection-border-radius);
-   }
-@@ -464,10 +468,14 @@ toolbar[inactive="true"] .urlbar,
+ }
+ 
+ #urlbar-scheme {
+@@ -492,10 +496,14 @@ toolbar[inactive="true"] .urlbar,
  
    .urlbar[breakout][breakout-extend] {
      height: auto;
@@ -46,5 +46,5 @@ index cc595de7e3839f7e688122552bca95f9f9ad3988..da4b1e1b5013d7a1a9af3d45d94db719
      > .urlbar-input-container {
 +      align-items: center;
        height: var(--urlbar-container-height);
-       padding-block: calc((var(--urlbar-container-height) - var(--urlbar-height)) / 2 + var(--urlbar-input-container-padding));
+       padding-block: calc((var(--urlbar-container-height) - var(--urlbar-height)) / 2);
        padding-inline: calc(var(--urlbar-margin-inline) + var(--urlbar-input-container-padding));
diff --git a/src/browser/themes/shared/urlbar/view-proton-css.patch b/src/browser/themes/shared/urlbar/view-proton-css.patch
index 9ae3d6c26..2ceb82290 100644
--- a/src/browser/themes/shared/urlbar/view-proton-css.patch
+++ b/src/browser/themes/shared/urlbar/view-proton-css.patch
@@ -1,18 +1,18 @@
 diff --git a/browser/themes/shared/urlbar/view-proton.css b/browser/themes/shared/urlbar/view-proton.css
-index 0b10c077a555e5d0fc488a3bb1b1b920f433204c..38e9d14e9838f2b8de6f654ff4e0700bb65506f0 100644
+index 3620b33cb11f2e6bba189cbaf7532cca0e97cd3b..346c318ed178fb77a217b3b992b94706db6bf0ee 100644
 --- a/browser/themes/shared/urlbar/view-proton.css
 +++ b/browser/themes/shared/urlbar/view-proton.css
-@@ -14,7 +14,7 @@
+@@ -12,7 +12,7 @@
  
    --urlbarView-small-font-size: 0.85em;
  
 -  --urlbarView-results-padding: 7px;
 +  --urlbarView-results-padding: 8px;
    --urlbarView-row-gutter: var(--space-xxsmall);
+   --urlbarview-row-padding-block: 6px;
    --urlbarView-row-padding-inline: var(--urlbar-icon-padding);
-   --urlbarView-row-padding-block: 6px;
-@@ -174,7 +174,6 @@
-       min-height: var(--urlbarView-row-min-height);
+@@ -165,7 +165,6 @@
+       min-height: var(--urlbarview-row-min-height);
      }
      :root[uidensity="touch"] & {
 -      padding-block: 11px;
diff --git a/src/dom/chrome-webidl/MediaController-webidl.patch b/src/dom/chrome-webidl/MediaController-webidl.patch
index 49307428f..3f0a31ddd 100644
--- a/src/dom/chrome-webidl/MediaController-webidl.patch
+++ b/src/dom/chrome-webidl/MediaController-webidl.patch
@@ -1,5 +1,5 @@
 diff --git a/dom/chrome-webidl/MediaController.webidl b/dom/chrome-webidl/MediaController.webidl
-index 790bc66a31253a861b21658e67c83796ae939298..0fb7e6cfbb1d1d35aeceb8d7b903cd86bf64403c 100644
+index 494ed7a424457dae822c86c0ef7f6d4e8685cd5e..a5a859cbdc76e0d79460780cfc41d7ed95e660e1 100644
 --- a/dom/chrome-webidl/MediaController.webidl
 +++ b/dom/chrome-webidl/MediaController.webidl
 @@ -23,6 +23,12 @@ enum MediaControlKey {
@@ -13,9 +13,9 @@ index 790bc66a31253a861b21658e67c83796ae939298..0fb7e6cfbb1d1d35aeceb8d7b903cd86
 +};
 +
  /**
-  * MediaController is used to control media playback for a tab, and each tab
-  * would only have one media controller, which can be accessed from the
-@@ -36,6 +42,7 @@ interface MediaController : EventTarget {
+  * The reason a chrome caller is pausing the controller. "user" preserves the
+  * existing user-initiated pause; the "system-*" values represent an
+@@ -49,6 +55,7 @@ interface MediaController : EventTarget {
    readonly attribute boolean isPlaying;
    readonly attribute boolean isAnyMediaBeingControlled;
    readonly attribute MediaSessionPlaybackState playbackState;
@@ -23,7 +23,7 @@ index 790bc66a31253a861b21658e67c83796ae939298..0fb7e6cfbb1d1d35aeceb8d7b903cd86
  
    // The effective audio-session type the tab is currently claiming. Chrome
    // consumers can use this to apply tab/application level audio-focus
-@@ -46,6 +53,9 @@ interface MediaController : EventTarget {
+@@ -59,6 +66,9 @@ interface MediaController : EventTarget {
    [Throws]
    MediaMetadataInit getMetadata();
  
diff --git a/src/dom/media/mediaelement/HTMLMediaElement-cpp.patch b/src/dom/media/mediaelement/HTMLMediaElement-cpp.patch
index 8fd51cb02..a00bb2656 100644
--- a/src/dom/media/mediaelement/HTMLMediaElement-cpp.patch
+++ b/src/dom/media/mediaelement/HTMLMediaElement-cpp.patch
@@ -1,16 +1,16 @@
 diff --git a/dom/media/mediaelement/HTMLMediaElement.cpp b/dom/media/mediaelement/HTMLMediaElement.cpp
-index b4ab1622d0e58781929aa6801dfd374f42567a7a..358f3d3cac3381ab9de3af65616095f69b9c7b23 100644
+index 912f2e08bd0d50e7ba012ed11b583127cf3e35e5..b60ec40f06f4e1a0f433eadebb1a18d40fd6d60f 100644
 --- a/dom/media/mediaelement/HTMLMediaElement.cpp
 +++ b/dom/media/mediaelement/HTMLMediaElement.cpp
-@@ -450,6 +450,7 @@ class HTMLMediaElement::MediaControlKeyListener final
-     // audible state. Therefore, in that case we would noitfy the audible state
-     // when media starts playing.
-     if (mState == MediaPlaybackState::ePlayed) {
+@@ -495,6 +495,7 @@ class HTMLMediaElement::MediaControlKeyListener final
+     // started, since they never reach the playing state.
+     if (mState == MediaPlaybackState::ePlayed ||
+         (IsStarted() && mControlType == ControlType::eUncontrollable)) {
 +      NotifyMediaPositionState();
-       NotifyAudibleStateChanged(mIsOwnerAudible
-                                     ? MediaAudibleState::eAudible
-                                     : MediaAudibleState::eInaudible);
-@@ -7450,6 +7451,9 @@ void HTMLMediaElement::FireTimeUpdate(TimeupdateType aType) {
+       NotifyAudibleStateChanged(newState);
+     }
+   }
+@@ -7738,6 +7739,9 @@ void HTMLMediaElement::FireTimeUpdate(TimeupdateType aType) {
      QueueTask(std::move(runner));
      mQueueTimeUpdateRunnerTime = TimeStamp::Now();
      mLastCurrentTime = CurrentTime();
diff --git a/src/external-patches/firefox/add_urlbar_closeonwindowblur_preference.patch b/src/external-patches/firefox/add_urlbar_closeonwindowblur_preference.patch
deleted file mode 100644
index e30eb8049..000000000
--- a/src/external-patches/firefox/add_urlbar_closeonwindowblur_preference.patch
+++ /dev/null
@@ -1,75 +0,0 @@
-diff --git a/browser/app/profile/firefox.js b/browser/app/profile/firefox.js
---- a/browser/app/profile/firefox.js
-+++ b/browser/app/profile/firefox.js
-@@ -411,10 +411,13 @@
- pref("browser.urlbar.maxRichResults", 10);
- 
- // The maximum number of historical search results to show.
- pref("browser.urlbar.maxHistoricalSearchSuggestions", 2);
- 
-+// Whether to close the urlbar when blurring the window while the urlbar is focused.
-+pref("browser.urlbar.closeOnWindowBlur", true);
-+
- // The default behavior for the urlbar can be configured to use any combination
- // of the match filters with each additional filter adding more results (union).
- pref("browser.urlbar.suggest.bookmark",             true);
- pref("browser.urlbar.suggest.clipboard",            true);
- pref("browser.urlbar.suggest.history",              true);
-diff --git a/browser/components/urlbar/UrlbarPrefs.sys.mjs b/browser/components/urlbar/UrlbarPrefs.sys.mjs
---- a/browser/components/urlbar/UrlbarPrefs.sys.mjs
-+++ b/browser/components/urlbar/UrlbarPrefs.sys.mjs
-@@ -152,10 +152,13 @@
-   ["filter.javascript", true],
- 
-   // Feature gate pref for flight status suggestions in the urlbar.
-   ["flightStatus.featureGate", false],
- 
-+  // Whether to close the urlbar when blurring the window while the urlbar is focused.
-+  ["closeOnWindowBlur", true],
-+
-   // The minimum prefix length of a flight status keyword the user must type to
-   // trigger the suggestion. 0 means the min length should be taken from Nimbus
-   // or remote settings.
-   ["flightStatus.minKeywordLength", 0],
- 
-diff --git a/browser/components/urlbar/content/UrlbarView.mjs b/browser/components/urlbar/content/UrlbarView.mjs
---- a/browser/components/urlbar/content/UrlbarView.mjs
-+++ b/browser/components/urlbar/content/UrlbarView.mjs
-@@ -3909,10 +3909,16 @@
-       }
-     }
-   }
- 
-   on_blur() {
-+    if (
-+      this.document.commandDispatcher.focusedElement == this.input.inputField &&
-+      !lazy.UrlbarPrefs.get("closeOnWindowBlur")
-+    ) {
-+      return;
-+    }
-     // If the view is open without the input being focused, it will not close
-     // automatically when the window loses focus. We might be in this state
-     // after a Search Tip is shown on an engine homepage.
-     if (!lazy.UrlbarPrefs.get("ui.popup.disable_autohide")) {
-       this.close();
-diff --git a/browser/components/urlbar/content/UrlbarInput.mjs b/browser/components/urlbar/content/UrlbarInput.mjs
---- a/browser/components/urlbar/content/UrlbarInput.mjs
-+++ b/browser/components/urlbar/content/UrlbarInput.mjs
-@@ -4783,10 +4783,16 @@
-     }
-   }
- 
-   _on_blur(event) {
-     lazy.logger.debug("Blur Event");
-+    if (
-+      this.document.commandDispatcher.focusedElement == this.inputField &&
-+      !lazy.UrlbarPrefs.get("closeOnWindowBlur")
-+    ) {
-+      return;
-+    }
-     // We cannot count every blur events after a missed engagement as abandoment
-     // because the user may have clicked on some view element that executes
-     // a command causing a focus change. For example opening preferences from
-     // the oneoff settings button.
-     // For now we detect that case by discarding the event on command, but we
-     // may want to figure out a more robust way to detect abandonment.
\ No newline at end of file
diff --git a/src/external-patches/firefox/bug_2011236.patch b/src/external-patches/firefox/bug_2011236.patch
new file mode 100644
index 000000000..a8764a3d4
--- /dev/null
+++ b/src/external-patches/firefox/bug_2011236.patch
@@ -0,0 +1,166 @@
+diff --git a/browser/components/sessionstore/test/browser.toml b/browser/components/sessionstore/test/browser.toml
+--- a/browser/components/sessionstore/test/browser.toml
++++ b/browser/components/sessionstore/test/browser.toml
+@@ -14,10 +14,12 @@
+   "browser_frame_history_c.html",
+   "browser_frame_history_c1.html",
+   "browser_frame_history_c2.html",
+   "browser_formdata_format_sample.html",
+   "browser_sessionHistory_slow.sjs",
++  "browser_policy_container_sample.html",
++  "browser_policy_container_sample_frame.html",
+   "browser_scrollPositions_sample.html",
+   "browser_scrollPositions_sample2.html",
+   "browser_scrollPositions_sample_frameset.html",
+   "browser_scrollPositions_readerModeArticle.html",
+   "browser_sessionStorage.html",
+@@ -226,10 +228,12 @@
+ ["browser_pinned_tabs.js"]
+ skip-if = [
+   "ccov", # Bug 1625525
+ ]
+ 
++["browser_policy_container_not_stored.js"]
++
+ ["browser_privatetabs.js"]
+ 
+ ["browser_purge_domaindata.js"]
+ 
+ ["browser_purge_shistory.js"]
+diff --git a/browser/components/sessionstore/test/browser_policy_container_not_stored.js b/browser/components/sessionstore/test/browser_policy_container_not_stored.js
+new file mode 100644
+--- /dev/null
++++ b/browser/components/sessionstore/test/browser_policy_container_not_stored.js
+@@ -0,0 +1,51 @@
++/* This Source Code Form is subject to the terms of the Mozilla Public
++ * License, v. 2.0. If a copy of the MPL was not distributed with this
++ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
++
++"use strict";
++
++/**
++ * A session history entry only needs to retain the policy container for loads
++ * that inherit their policies (about:blank, about:srcdoc, blob:, data:, ...).
++ * Anything fetched over the network gets its policies from the response again,
++ * so storing them would only bloat the session store (bug 2011236).
++ */
++
++const TEST_ROOT = getRootDirectory(gTestPath).replace(
++  "chrome://mochitests/content",
++  "https://example.com"
++);
++const PARENT_URL = TEST_ROOT + "browser_policy_container_sample.html";
++const FRAME_URL = TEST_ROOT + "browser_policy_container_sample_frame.html";
++
++add_task(async function test_policy_container_only_for_inheriting_loads() {
++  const tab = BrowserTestUtils.addTab(gBrowser, PARENT_URL);
++  gBrowser.selectedTab = tab;
++  await promiseBrowserLoaded(tab.linkedBrowser, true, PARENT_URL);
++  await TabStateFlusher.flush(tab.linkedBrowser);
++
++  const state = JSON.parse(ss.getTabState(tab));
++  const topEntry = state.entries.at(-1);
++  is(topEntry.url, PARENT_URL, "collected the parent entry");
++
++  const children = topEntry.children ?? [];
++  const networkFrame = children.find(child => child.url === FRAME_URL);
++  const blankFrame = children.find(child => child.url === "about:blank");
++
++  ok(networkFrame, "collected the network-scheme subframe entry");
++  ok(blankFrame, "collected the about:blank subframe entry");
++
++  // The parent has a CSP, so both subframes inherit a policy container onto
++  // their load state. Only the one that cannot recover it from a response
++  // should keep it in session history.
++  ok(
++    !("policyContainer" in networkFrame),
++    "https subframe entry does not store a policyContainer"
++  );
++  ok(
++    "policyContainer" in blankFrame,
++    "about:blank subframe entry still stores its inherited policyContainer"
++  );
++
++  await BrowserTestUtils.removeTab(tab);
++});
+diff --git a/browser/components/sessionstore/test/browser_policy_container_sample.html b/browser/components/sessionstore/test/browser_policy_container_sample.html
+new file mode 100644
+--- /dev/null
++++ b/browser/components/sessionstore/test/browser_policy_container_sample.html
+@@ -0,0 +1,12 @@
++<!DOCTYPE html>
++<html>
++<head>
++  <meta charset="utf-8">
++  <meta http-equiv="Content-Security-Policy" content="default-src * data: blob: 'unsafe-inline'">
++  <title>policyContainer session store sample</title>
++</head>
++<body>
++  <iframe id="network" src="browser_policy_container_sample_frame.html"></iframe>
++  <iframe id="blank" src="about:blank"></iframe>
++</body>
++</html>
+diff --git a/browser/components/sessionstore/test/browser_policy_container_sample_frame.html b/browser/components/sessionstore/test/browser_policy_container_sample_frame.html
+new file mode 100644
+--- /dev/null
++++ b/browser/components/sessionstore/test/browser_policy_container_sample_frame.html
+@@ -0,0 +1,10 @@
++<!DOCTYPE html>
++<html>
++<head>
++  <meta charset="utf-8">
++  <title>policyContainer session store sample frame</title>
++</head>
++<body>
++  frame
++</body>
++</html>
+diff --git a/docshell/shistory/SessionHistoryEntry.cpp b/docshell/shistory/SessionHistoryEntry.cpp
+--- a/docshell/shistory/SessionHistoryEntry.cpp
++++ b/docshell/shistory/SessionHistoryEntry.cpp
+@@ -41,10 +41,18 @@
+ extern mozilla::LazyLogModule gSHLog;
+ 
+ namespace mozilla {
+ namespace dom {
+ 
++// Only store policy container for loads that can't carry it themselves
++// (about:blank, about:srcdoc, blob:, data:, ...)
++// bug 1867137, bug 2011236
++static nsIPolicyContainer* PolicyContainerToStore(
++    nsIURI* aURI, nsIPolicyContainer* aPolicyContainer) {
++  return CSP_ShouldURIInheritCSP(aURI) ? aPolicyContainer : nullptr;
++}
++
+ SessionHistoryInfo::SessionHistoryInfo(nsDocShellLoadState* aLoadState,
+                                        nsIChannel* aChannel)
+     : mURI(aLoadState->URI()),
+       mOriginalURI(aLoadState->OriginalURI()),
+       mResultPrincipalURI(aLoadState->ResultPrincipalURI()),
+@@ -59,9 +67,10 @@
+       mLoadReplace(aLoadState->LoadReplace()),
+       mHasUserActivation(aLoadState->HasValidUserGestureActivation()),
+       mSharedState(SharedState::Create(
+           aLoadState->TriggeringPrincipal(), aLoadState->PrincipalToInherit(),
+           aLoadState->PartitionedPrincipalToInherit(),
+-          aLoadState->PolicyContainer(),
++          PolicyContainerToStore(aLoadState->URI(),
++                                 aLoadState->PolicyContainer()),
+           /* FIXME Is this correct? */
+           aLoadState->TypeHint())) {
+   // Pull the upload stream off of the channel instead of the load state, as
+@@ -124,11 +133,12 @@
+   loadInfo->GetPrincipalToInherit(
+       getter_AddRefs(mSharedState.Get()->mPrincipalToInherit));
+ 
+   mSharedState.Get()->mPartitionedPrincipalToInherit =
+       aPartitionedPrincipalToInherit;
+-  mSharedState.Get()->mPolicyContainer = aPolicyContainer;
++  mSharedState.Get()->mPolicyContainer =
++      PolicyContainerToStore(mURI, aPolicyContainer);
+   aChannel->GetContentType(mSharedState.Get()->mContentType);
+   aChannel->GetOriginalURI(getter_AddRefs(mOriginalURI));
+ 
+   uint32_t loadFlags;
+   aChannel->GetLoadFlags(&loadFlags);
+
diff --git a/src/external-patches/firefox/expose_tiled_attribute_to_all_platforms.patch b/src/external-patches/firefox/expose_tiled_attribute_to_all_platforms.patch
new file mode 100644
index 000000000..1b3e06b11
--- /dev/null
+++ b/src/external-patches/firefox/expose_tiled_attribute_to_all_platforms.patch
@@ -0,0 +1,72 @@
+diff --git a/widget/cocoa/nsCocoaWindow.mm b/widget/cocoa/nsCocoaWindow.mm
+--- a/widget/cocoa/nsCocoaWindow.mm
++++ b/widget/cocoa/nsCocoaWindow.mm
+@@ -70,10 +70,11 @@
+ #include "nsXULPopupManager.h"
+ 
+ #include "gfxPlatform.h"
+ #include "qcms.h"
+ 
++#import <objc/runtime.h>
+ #include <algorithm>
+ #include "mozilla/AutoRestore.h"
+ #include "mozilla/BasicEvents.h"
+ #include "mozilla/Maybe.h"
+ #include "mozilla/NativeKeyBindingsType.h"
+@@ -6948,10 +6949,31 @@
+     return nsSizeMode_Maximized;
+   }
+   return nsSizeMode_Normal;
+ }
+ 
++// The tiling state lives in a private NSWindow ivar "_tilingStateController"
++// (an _NSWMWindowTilingStateController). That controller's -tilingState returns
++// a non-nil _WMWindowTilingState only while the window is tiled by the system
++// window manager. None of this is public API, so it is all guarded and degrades
++// to false if the internals ever change.
++static bool WindowIsTiled(NSWindow* aWindow) {
++  if (!aWindow) {
++    return false;
++  }
++  static Ivar sControllerIvar =
++      class_getInstanceVariable([NSWindow class], "_tilingStateController");
++  if (!sControllerIvar) {
++    return false;
++  }
++  id controller = object_getIvar(aWindow, sControllerIvar);
++  if (![controller respondsToSelector:@selector(tilingState)]) {
++    return false;
++  }
++  return [controller performSelector:@selector(tilingState)] != nil;
++}
++
+ void nsCocoaWindow::ReportMoveEvent() {
+   NS_OBJC_BEGIN_TRY_IGNORE_BLOCK;
+ 
+   // Prevent recursion, which can become infinite (see bug 708278).  This
+   // can happen when the call to [NSWindow setFrameTopLeftPoint:] in
+@@ -6961,10 +6983,11 @@
+     return;
+   }
+   mInReportMoveEvent = true;
+ 
+   UpdateBounds();
++  SetIsTiled(WindowIsTiled(mWindow));
+ 
+   // The zoomed state can change when we're moving, in which case we need to
+   // update our internal mSizeMode. This can happen either if we're maximized
+   // and then moved, or if we're not maximized and moved back to zoomed state.
+   if (mWindow && (mSizeMode == nsSizeMode_Maximized) ^ mWindow.isZoomed) {
+@@ -7055,10 +7078,11 @@
+ 
+ void nsCocoaWindow::ReportSizeEvent() {
+   NS_OBJC_BEGIN_TRY_IGNORE_BLOCK;
+ 
+   UpdateBounds();
++  SetIsTiled(WindowIsTiled(mWindow));
+   LayoutDeviceIntRect innerBounds = GetClientBounds();
+   if (mWidgetListener) {
+     mWidgetListener->WindowResized(this, innerBounds.Size());
+   }
+   if (mAttachedWidgetListener) {
+
diff --git a/src/external-patches/firefox/gh-12979_clip_dirty_rect_to_device_size.patch b/src/external-patches/firefox/gh-12979_clip_dirty_rect_to_device_size.patch
deleted file mode 100644
index 4cd381da1..000000000
--- a/src/external-patches/firefox/gh-12979_clip_dirty_rect_to_device_size.patch
+++ /dev/null
@@ -1,21 +0,0 @@
-diff --git a/gfx/wr/webrender/src/renderer/composite.rs b/gfx/wr/webrender/src/renderer/composite.rs
---- a/gfx/wr/webrender/src/renderer/composite.rs
-+++ b/gfx/wr/webrender/src/renderer/composite.rs
-@@ -974,12 +974,15 @@
-                     .iter()
-                     .chain(self.layer_compositor_frame_state_in_prev_frame.as_ref().unwrap().rects_without_id.iter())  {
-                     combined_dirty_rect = combined_dirty_rect.union(&rect);
-                 }
- 
-+                let device_rect = DeviceRect::from_size(device_size.to_f32());
-+                let clipped_dirty_rect = combined_dirty_rect.intersection_unchecked(&device_rect);
-+
-                 partial_present_mode = Some(PartialPresentMode::Single {
--                    dirty_rect: combined_dirty_rect,
-+                    dirty_rect: clipped_dirty_rect,
-                 });
-             } else {
-                 partial_present_mode = None;
-             }
- 
-
diff --git a/src/external-patches/firefox/issue_14710.patch b/src/external-patches/firefox/issue_14710.patch
new file mode 100644
index 000000000..54e288ed8
--- /dev/null
+++ b/src/external-patches/firefox/issue_14710.patch
@@ -0,0 +1,55 @@
+diff --git a/toolkit/components/pictureinpicture/PictureInPicture.sys.mjs b/toolkit/components/pictureinpicture/PictureInPicture.sys.mjs
+--- a/toolkit/components/pictureinpicture/PictureInPicture.sys.mjs
++++ b/toolkit/components/pictureinpicture/PictureInPicture.sys.mjs
+@@ -119,10 +119,19 @@
+       }
+       case "PictureInPicture:VideoTabHidden": {
+         if (!lazy.PIP_ENABLED || !lazy.PIP_WHEN_SWITCHING_TABS) {
+           break;
+         }
++
++        // Suppress auto-toggle if the user deliberately closed this PiP window
++        if (
++          PictureInPicture.weakAutoPipBrowserClosedDeliberately.has(browser)
++        ) {
++          PictureInPicture.weakAutoPipBrowserClosedDeliberately.delete(browser);
++          break;
++        }
++
+         // If the tab is still selected, then we can ignore this event
+         if (browser.documentGlobal.gBrowser.selectedBrowser == browser) {
+           break;
+         }
+         let actor = browsingContext.currentWindowGlobal.getActor(
+@@ -261,10 +270,12 @@
+   maxConcurrentPlayerCount: 0,
+ 
+   // Maps auto pip browser to PictureInPictureParent actor
+   weakAutoPipBrowserToParent: new WeakMap(),
+ 
++  weakAutoPipBrowserClosedDeliberately: new WeakSet(),
++
+   /**
+    * Returns the player window if one exists and if it hasn't yet been closed.
+    *
+    * @param {PictureInPictureParent} pipActorRef
+    *   Reference to the calling PictureInPictureParent actor
+@@ -899,10 +910,17 @@
+     const { reason, actorRef } = closeData;
+     const win = this.getWeakPipPlayer(actorRef);
+     if (!win) {
+       return;
+     }
++
++    const browser = this.weakWinToBrowser.get(win);
++
++    if (reason === "CloseButton") {
++      PictureInPicture.weakAutoPipBrowserClosedDeliberately.add(browser);
++    }
++
+     this.removePiPBrowserFromWeakMap(this.weakWinToBrowser.get(win));
+     this.weakAutoPipBrowserToParent.delete(this.weakWinToBrowser.get(win));
+ 
+     Glean.pictureinpicture["closedMethod" + reason].record();
+     await this.closePipWindow(win);
+
diff --git a/src/external-patches/firefox/issue_14990.patch b/src/external-patches/firefox/issue_14990.patch
new file mode 100644
index 000000000..7f90b2a51
--- /dev/null
+++ b/src/external-patches/firefox/issue_14990.patch
@@ -0,0 +1,254 @@
+diff --git a/browser/components/sessionstore/SessionWriter.sys.mjs b/browser/components/sessionstore/SessionWriter.sys.mjs
+--- a/browser/components/sessionstore/SessionWriter.sys.mjs
++++ b/browser/components/sessionstore/SessionWriter.sys.mjs
+@@ -80,10 +80,14 @@
+       return await SessionWriterInternal.wipe();
+     } finally {
+       unlock();
+     }
+   },
++
++  get _jsonLengthHint() {
++    return SessionWriterInternal._lastJsonLength;
++  },
+ };
+ 
+ const SessionWriterInternal = {
+   // Path to the files used by the SessionWriter
+   Paths: null,
+@@ -104,10 +108,14 @@
+   /**
+    * Number of old upgrade backups that are being kept
+    */
+   maxUpgradeBackups: null,
+ 
++  // Estimated JSON string length from the previous write, used to pre-size
++  // the serialization buffer and avoid incremental reallocations.
++  _lastJsonLength: 0,
++
+   /**
+    * Initialize (or reinitialize) the writer.
+    *
+    * @param {string} origin Which of sessionstore.js or its backups
+    *   was used. One of the `STATE_*` constants defined above.
+@@ -201,48 +209,60 @@
+         }
+       }
+ 
+       let startWriteMs = Date.now();
+       let fileStat;
++      // Add 5% headroom to the hint so small growth between saves doesn't
++      // cause reallocs. The compressed-size-based estimate already has
++      // sufficient margin from the 4x multiplier.
++      let jsonLengthHint = Math.ceil(this._lastJsonLength * 1.05);
++
++      let uncompressedBytes;
+ 
+       if (options.isFinalWrite) {
+         // We are shutting down. At this stage, we know that
+         // $Paths.clean is either absent or corrupted. If it was
+         // originally present and valid, it has been moved to
+         // $Paths.cleanBackup a long time ago. We can therefore write
+         // with the guarantees that we erase no important data.
+-        await IOUtils.writeJSON(this.Paths.clean, state, {
++        uncompressedBytes = await IOUtils.writeJSON(this.Paths.clean, state, {
+           tmpPath: this.Paths.clean + ".tmp",
+           compress: true,
++          lengthHint: jsonLengthHint,
+         });
+         fileStat = await IOUtils.stat(this.Paths.clean);
+       } else if (this.state == STATE_RECOVERY) {
+         // At this stage, either $Paths.recovery was written >= 15
+         // seconds ago during this session or we have just started
+         // from $Paths.recovery left from the previous session. Either
+         // way, $Paths.recovery is good. We can move $Path.backup to
+         // $Path.recoveryBackup without erasing a good file with a bad
+         // file.
+-        await IOUtils.writeJSON(this.Paths.recovery, state, {
++        uncompressedBytes = await IOUtils.writeJSON(this.Paths.recovery, state, {
+           tmpPath: this.Paths.recovery + ".tmp",
+           backupFile: this.Paths.recoveryBackup,
+           compress: true,
++          lengthHint: jsonLengthHint,
+         });
+         fileStat = await IOUtils.stat(this.Paths.recovery);
+       } else {
+         // In other cases, either $Path.recovery is not necessary, or
+         // it doesn't exist or it has been corrupted. Regardless,
+         // don't backup $Path.recovery.
+-        await IOUtils.writeJSON(this.Paths.recovery, state, {
++        uncompressedBytes = await IOUtils.writeJSON(this.Paths.recovery, state, {
+           tmpPath: this.Paths.recovery + ".tmp",
+           compress: true,
++          lengthHint: jsonLengthHint,
+         });
+         fileStat = await IOUtils.stat(this.Paths.recovery);
+       }
+ 
+       telemetry.writeFileMs = Date.now() - startWriteMs;
+       telemetry.fileSizeBytes = fileStat.size;
++      // Use the actual pre-compression size from this write as the hint
++      // for the next write's buffer allocation.
++      this._lastJsonLength = uncompressedBytes.jsonLength;
+       lazy.sessionStoreLogger.debug(
+         `SessionWriter.write wrote ${telemetry.fileSizeBytes} bytes in ${telemetry.writeFileMs}ms`
+       );
+     } catch (ex) {
+       // Don't throw immediately
+@@ -375,10 +395,11 @@
+     } catch (ex) {
+       exn = exn || ex;
+     }
+ 
+     this.state = STATE_EMPTY;
++    this._lastJsonLength = 0;
+     if (exn) {
+       throw exn;
+     }
+ 
+     return { result: true };
+diff --git a/browser/components/sessionstore/test/unit/test_write_json_length_hint.js b/browser/components/sessionstore/test/unit/test_write_json_length_hint.js
+new file mode 100644
+--- /dev/null
++++ b/browser/components/sessionstore/test/unit/test_write_json_length_hint.js
+@@ -0,0 +1,73 @@
++/* Any copyright is dedicated to the Public Domain.
++   http://creativecommons.org/publicdomain/zero/1.0/ */
++
++"use strict";
++
++const { SessionWriter } = ChromeUtils.importESModule(
++  "resource:///modules/sessionstore/SessionWriter.sys.mjs"
++);
++
++const profd = do_get_profile();
++const { SessionFile } = ChromeUtils.importESModule(
++  "resource:///modules/sessionstore/SessionFile.sys.mjs"
++);
++
++const { updateAppInfo } = ChromeUtils.importESModule(
++  "resource://testing-common/AppInfo.sys.mjs"
++);
++updateAppInfo({
++  name: "SessionRestoreTest",
++  ID: "{230de50e-4cd1-11dc-8314-0800200c9a66}",
++  version: "1",
++  platformVersion: "",
++});
++
++add_setup(async function () {
++  let source = do_get_file("data/sessionstore_valid.js");
++  source.copyTo(profd, "sessionstore.js");
++  await writeCompressedFile(
++    SessionFile.Paths.clean.replace("jsonlz4", "js"),
++    SessionFile.Paths.clean
++  );
++  await SessionFile.read();
++});
++
++add_task(async function test_length_hint_updates_after_write() {
++  Assert.equal(
++    SessionWriter._jsonLengthHint,
++    0,
++    "Length hint starts at 0"
++  );
++
++  await SessionFile.write({});
++
++  let hintAfterSmall = SessionWriter._jsonLengthHint;
++  Assert.equal(
++    hintAfterSmall,
++    JSON.stringify({}).length,
++    "Hint matches the uncompressed JSON byte length"
++  );
++
++  let largerState = await IOUtils.readJSON(
++    PathUtils.join(do_get_cwd().path, "data", "sessionstore_complete.json")
++  );
++  await SessionFile.write(largerState);
++
++  Assert.greater(
++    SessionWriter._jsonLengthHint,
++    hintAfterSmall,
++    "Hint grows after writing a larger state"
++  );
++});
++
++add_task(async function test_length_hint_resets_on_wipe() {
++  await SessionFile.write({ windows: [{ tabs: [{ entries: [] }] }] });
++  Assert.greater(SessionWriter._jsonLengthHint, 0, "Hint is nonzero");
++
++  await SessionFile.wipe();
++  Assert.equal(
++    SessionWriter._jsonLengthHint,
++    0,
++    "Hint resets to 0 after wipe"
++  );
++});
+diff --git a/browser/components/sessionstore/test/unit/xpcshell.toml b/browser/components/sessionstore/test/unit/xpcshell.toml
+--- a/browser/components/sessionstore/test/unit/xpcshell.toml
++++ b/browser/components/sessionstore/test/unit/xpcshell.toml
+@@ -39,5 +39,10 @@
+ skip-if = [
+   "condprof", # Bug 1769154
+ ]
+ 
+ ["test_startup_session_async.js"]
++
++["test_write_json_length_hint.js"]
++support-files = [
++  "data/sessionstore_complete.json",
++]
+diff --git a/dom/chrome-webidl/IOUtils.webidl b/dom/chrome-webidl/IOUtils.webidl
+--- a/dom/chrome-webidl/IOUtils.webidl
++++ b/dom/chrome-webidl/IOUtils.webidl
+@@ -101,12 +101,12 @@
+    *
+    * @param path      An absolute file path
+    * @param value     The value to be serialized.
+    * @param options   Options for writing the file. The "append" mode is not supported.
+    *
+-   * @return Resolves with the number of bytes successfully written to the file,
+-   *         otherwise rejects with a DOMException.
++   * @return Resolves with the pre-compression size of the serialized JSON in
++   *         bytes (UTF-8), otherwise rejects with a DOMException.
+    */
+   [NewObject]
+   Promise<WriteJSONResult> writeJSON(DOMString path, any value, optional WriteJSONOptions options = {});
+   /**
+    * Moves the file from |sourcePath| to |destPath|, creating necessary parents.
+@@ -564,10 +564,16 @@
+   boolean flush = false;
+   /**
+    * If true, compress the data with LZ4-encoding before writing to the file.
+    */
+   boolean compress = false;
++  /**
++   * For |writeJSON|, a hint for the expected JSON string length in UTF-16 code
++   * units. When provided, the JSON serializer pre-allocates a buffer of this
++   * size to avoid incremental reallocations.
++   */
++  unsigned long long jsonLengthHint = 0;
+ };
+ 
+ /**
+  * Options to be passed to the |IOUtils.writeJSON| method.
+  */
+diff --git a/xpcom/ioutils/IOUtils.cpp b/xpcom/ioutils/IOUtils.cpp
+--- a/xpcom/ioutils/IOUtils.cpp
++++ b/xpcom/ioutils/IOUtils.cpp
+@@ -629,10 +629,13 @@
+         }
+ 
+         JSContext* cx = aGlobal.Context();
+         JS::Rooted<JS::Value> value(cx, aValue);
+         nsString string;
++        if (opts.mLengthHint) {
++          string.SetCapacity(opts.mLengthHint);
++        }
+         if (!JS_StringifyWithLengthHint(cx, &value, nullptr,
+                                         JS::NullHandleValue, AppendJSON,
+                                         &string, opts.mLengthHint)) {
+           JS::Rooted<JS::Value> exn(cx, JS::UndefinedValue());
+           if (JS_GetPendingException(cx, &exn)) {
+
diff --git a/src/external-patches/manifest.json b/src/external-patches/manifest.json
index 8f89a255f..7c794ef9c 100644
--- a/src/external-patches/manifest.json
+++ b/src/external-patches/manifest.json
@@ -7,14 +7,6 @@
     "id": "D299584",
     "name": "Native MacOS popovers fix"
   },
-  {
-    "type": "phabricator",
-    "id": "D284404",
-    "name": "Add urlbar closeOnWindowBlur preference",
-    "replaces": {
-      "\n\n": "\n     // may want to figure out a more robust way to detect abandonment."
-    }
-  },
   {
     "type": "local",
     // TODO: Convert into https://phabricator.services.mozilla.com/D298079
@@ -37,7 +29,32 @@
   },
   {
     "type": "phabricator",
-    "id": "D291714",
-    "name": "gh-12979 Clip dirty_rect to device_size"
+    "id": "D312091",
+    "name": "Expose tiled attribute to all platforms"
+  },
+  {
+    "type": "phabricator",
+    "id": "D298708",
+    "name": "Issue 14990",
+    "replaces": {
+      "this._lastJsonLength = uncompressedBytes;": "this._lastJsonLength = uncompressedBytes.jsonLength;",
+      "          jsonLengthHint,": "          lengthHint: jsonLengthHint,"
+    }
+  },
+  {
+    "type": "phabricator",
+    "id": "D320897",
+    "name": "Bug 2011236",
+    "replaces": {
+      // The upstream patch context includes a MOZ_DIAGNOSTIC_ASSERT that
+      // doesn't exist yet in our Firefox version.
+      "@@ -59,11 +67,12 @@": "@@ -59,9 +67,10 @@",
+      "aLoadState->TypeHint())) {\n   MOZ_DIAGNOSTIC_ASSERT(!mURI->SchemeIs(\"javascript\"));\n \n   // Pull": "aLoadState->TypeHint())) {\n   // Pull"
+    }
+  },
+  {
+    "type": "phabricator",
+    "id": "D321446",
+    "name": "Issue 14710"
   }
 ]
diff --git a/src/gfx/layers/AnimationInfo-cpp.patch b/src/gfx/layers/AnimationInfo-cpp.patch
index 83ce49a05..18032d367 100644
--- a/src/gfx/layers/AnimationInfo-cpp.patch
+++ b/src/gfx/layers/AnimationInfo-cpp.patch
@@ -1,16 +1,16 @@
 diff --git a/gfx/layers/AnimationInfo.cpp b/gfx/layers/AnimationInfo.cpp
-index b4941588bfbd94a337f2e848c659021723e1500d..8f91ca5b2fcca6ff04aa2c0af5ba26dd9fe7df0e 100644
+index 538808aa15d1902fc517f79e3a6d62f4d7fd9d37..4b0760b7be9d872a926f99716d16f3f64dcb2378 100644
 --- a/gfx/layers/AnimationInfo.cpp
 +++ b/gfx/layers/AnimationInfo.cpp
-@@ -14,6 +14,7 @@
- #include "mozilla/MotionPathUtils.h"
- #include "mozilla/PresShell.h"
- #include "mozilla/ScrollContainerFrame.h"
+@@ -18,6 +18,7 @@
+ #include "mozilla/layers/AnimationStorageData.h"
+ #include "mozilla/layers/CompositorThread.h"
+ #include "mozilla/layers/WebRenderLayerManager.h"
 +#include "mozilla/nsZenBoostsBackend.h"
  #include "nsIContent.h"
  #include "nsLayoutUtils.h"
  #include "nsRefreshDriver.h"
-@@ -341,9 +342,13 @@ static void SetAnimatable(NonCustomCSSPropertyId aProperty,
+@@ -367,9 +368,13 @@ static void SetAnimatable(NonCustomCSSPropertyId aProperty,
      case eCSSProperty_background_color: {
        // We don't support color animation on the compositor yet so that we can
        // resolve currentColor at this moment.
diff --git a/src/layout/generic/nsTextPaintStyle-cpp.patch b/src/layout/generic/nsTextPaintStyle-cpp.patch
index 2bd0f3b9b..3989cd21b 100644
--- a/src/layout/generic/nsTextPaintStyle-cpp.patch
+++ b/src/layout/generic/nsTextPaintStyle-cpp.patch
@@ -1,5 +1,5 @@
 diff --git a/layout/generic/nsTextPaintStyle.cpp b/layout/generic/nsTextPaintStyle.cpp
-index f741ab5eb83778ec2460a5d975757f09b3f2865e..f39a019c0d82db7ba9a122ce5269d0833ae04568 100644
+index 9dba72de611cd84ed07805f5ce40f882071240f0..782dea67f6d975ba5b7daa1e2e2ed862f7941952 100644
 --- a/layout/generic/nsTextPaintStyle.cpp
 +++ b/layout/generic/nsTextPaintStyle.cpp
 @@ -240,7 +240,7 @@ bool nsTextPaintStyle::GetTargetTextColor(nscolor* aForeColor) {
@@ -39,17 +39,14 @@ index f741ab5eb83778ec2460a5d975757f09b3f2865e..f39a019c0d82db7ba9a122ce5269d083
    return NS_GET_A(*aBackColor) != 0;
  }
  
-@@ -462,12 +463,12 @@ bool nsTextPaintStyle::InitSelectionColorsAndShadow() {
-     mSelectionPseudoStyle = std::move(style);
- 
-     if (nscolor bgColor = mSelectionPseudoStyle->GetVisitedDependentColor(
--            &nsStyleBackground::mBackgroundColor);
-+            &nsStyleBackground::mBackgroundColor, mFrame);
-         mSelectionPseudoStyle->HasAuthorSpecifiedTextColor() ||
-         NS_GET_A(bgColor) > 0) {
-       mSelectionBGColor = bgColor;
+@@ -463,9 +464,9 @@ bool nsTextPaintStyle::InitSelectionColorsAndShadow() {
+     if (mSelectionPseudoStyle->HasAuthorSpecifiedTextColor() ||
+         mSelectionPseudoStyle->HasAuthorSpecifiedBorderOrBackground()) {
+       mSelectionBGColor = mSelectionPseudoStyle->GetVisitedDependentColor(
+-          &nsStyleBackground::mBackgroundColor);
 -      mSelectionTextColor =
 -          mSelectionPseudoStyle->GetVisitedDependentColor(&nsStyleText::mColor);
++          &nsStyleBackground::mBackgroundColor, mFrame);
 +      mSelectionTextColor = mSelectionPseudoStyle->GetVisitedDependentColor(
 +          &nsStyleText::mColor, mFrame);
        return true;
diff --git a/src/layout/svg/SVGImageContext-cpp.patch b/src/layout/svg/SVGImageContext-cpp.patch
index 9a8fbd935..b83784c10 100644
--- a/src/layout/svg/SVGImageContext-cpp.patch
+++ b/src/layout/svg/SVGImageContext-cpp.patch
@@ -1,5 +1,5 @@
 diff --git a/layout/svg/SVGImageContext.cpp b/layout/svg/SVGImageContext.cpp
-index 384401ae2cb80a1bf438b1fb3d849254de100210..e5ef332bc529e6588c33b507993880ca9def51d1 100644
+index 4d43db157aa9447105eeb5459cad74de6cef01d6..327d8e4f7e21783824616800fa821218c8c848e8 100644
 --- a/layout/svg/SVGImageContext.cpp
 +++ b/layout/svg/SVGImageContext.cpp
 @@ -10,6 +10,7 @@
@@ -39,20 +39,17 @@ index 384401ae2cb80a1bf438b1fb3d849254de100210..e5ef332bc529e6588c33b507993880ca
    const nsStyleSVG* style = aStyle.StyleSVG();
    if (!style->ExposesContextProperties()) {
      // Content must have '-moz-context-properties' set to the names of the
-@@ -64,12 +80,14 @@ void SVGImageContext::MaybeStoreContextPaint(SVGImageContext& aContext,
+@@ -62,11 +78,11 @@ void SVGImageContext::MaybeStoreContextPaint(SVGImageContext& aContext,
+ 
    if ((style->mMozContextProperties.bits & StyleContextPropertyBits::FILL) &&
        style->mFill.kind.IsColor()) {
-     haveContextPaint = true;
--    contextPaint->SetFill(style->mFill.kind.AsColor().CalcColor(aStyle));
-+    contextPaint->SetFill(
-+        style->mFill.kind.AsColor().CalcColor(aStyle, nullptr));
+-    fill = Some(style->mFill.kind.AsColor().CalcColor(aStyle));
++    fill = Some(style->mFill.kind.AsColor().CalcColor(aStyle, nullptr));
    }
    if ((style->mMozContextProperties.bits & StyleContextPropertyBits::STROKE) &&
        style->mStroke.kind.IsColor()) {
-     haveContextPaint = true;
--    contextPaint->SetStroke(style->mStroke.kind.AsColor().CalcColor(aStyle));
-+    contextPaint->SetStroke(
-+        style->mStroke.kind.AsColor().CalcColor(aStyle, nullptr));
+-    stroke = Some(style->mStroke.kind.AsColor().CalcColor(aStyle));
++    stroke = Some(style->mStroke.kind.AsColor().CalcColor(aStyle, nullptr));
    }
-   if (style->mMozContextProperties.bits &
-       StyleContextPropertyBits::FILL_OPACITY) {
+   if ((style->mMozContextProperties.bits &
+        StyleContextPropertyBits::FILL_OPACITY) &&
diff --git a/src/services/sync/modules/service-sys-mjs.patch b/src/services/sync/modules/service-sys-mjs.patch
index daf57720d..3b616d60a 100644
--- a/src/services/sync/modules/service-sys-mjs.patch
+++ b/src/services/sync/modules/service-sys-mjs.patch
@@ -1,5 +1,5 @@
 diff --git a/services/sync/modules/service.sys.mjs b/services/sync/modules/service.sys.mjs
-index 4f4efe572909441abdd81909282936702c225621..81ab06a9414ed656b644a21b40b683f06a4f8dbf 100644
+index 4f4efe572909441abdd81909282936702c225621..2b47a2c9e97cf87641a0be9814f9a6be4d43f6ea 100644
 --- a/services/sync/modules/service.sys.mjs
 +++ b/services/sync/modules/service.sys.mjs
 @@ -99,6 +99,10 @@ function getEngineModules() {
@@ -7,8 +7,8 @@ index 4f4efe572909441abdd81909282936702c225621..81ab06a9414ed656b644a21b40b683f0
      whenFalse: "ExtensionStorageEngineBridge",
    };
 +  result.Spaces = {
-+    module: "resource:///modules/zen/ZenWorkspacesSync.sys.mjs",
-+    symbol: "ZenWorkspacesEngine",
++    module: "resource:///modules/zen/ZenSpacesSync.sys.mjs",
++    symbol: "ZenSpacesSyncEngine",
 +  };
    return result;
  }
diff --git a/src/testing/xpcshell/runxpcshelltests-py.patch b/src/testing/xpcshell/runxpcshelltests-py.patch
new file mode 100644
index 000000000..c0aaeea1b
--- /dev/null
+++ b/src/testing/xpcshell/runxpcshelltests-py.patch
@@ -0,0 +1,14 @@
+diff --git a/testing/xpcshell/runxpcshelltests.py b/testing/xpcshell/runxpcshelltests.py
+index 403401613189ffb758037850dc6bbb1d55f194ab..cad28e245155eb54775e551885532026e56c5fa9 100755
+--- a/testing/xpcshell/runxpcshelltests.py
++++ b/testing/xpcshell/runxpcshelltests.py
+@@ -2275,6 +2275,9 @@ class XPCShellTests:
+         appDirKey = None
+         if "appname" in self.mozInfo:
+             appDirKey = self.mozInfo["appname"] + "-appdir"
++            if appDirKey == "zen-appdir":
++                # Inherited manifests use firefox-appdir.
++                appDirKey = "firefox-appdir"
+ 
+         # We have to do this before we run tests that depend on having the node
+         # http/2 server.
diff --git a/src/toolkit/components/contextualidentity/ContextualIdentityService-sys-mjs.patch b/src/toolkit/components/contextualidentity/ContextualIdentityService-sys-mjs.patch
deleted file mode 100644
index 1b108254d..000000000
--- a/src/toolkit/components/contextualidentity/ContextualIdentityService-sys-mjs.patch
+++ /dev/null
@@ -1,37 +0,0 @@
-diff --git a/toolkit/components/contextualidentity/ContextualIdentityService.sys.mjs b/toolkit/components/contextualidentity/ContextualIdentityService.sys.mjs
-index 5702ff28cc22206f5ce16584dac8a78d816562ce..3d08ecc97ce5995b30d8a4af0c33df329b428008 100644
---- a/toolkit/components/contextualidentity/ContextualIdentityService.sys.mjs
-+++ b/toolkit/components/contextualidentity/ContextualIdentityService.sys.mjs
-@@ -270,11 +270,29 @@ _ContextualIdentityService.prototype = {
-     });
-   },
- 
--  create(name, icon, color) {
-+  create(name, icon, color, id = null) {
-     this.ensureDataReady();
- 
--    // Retrieve the next userContextId available.
--    let userContextId = ++this._lastUserContextId;
-+    if (id !== null) {
-+      id = typeof id == "string" ? Number(id) : id;
-+      if (!Number.isSafeInteger(id) || id <= 0) {
-+        throw new Error(`Invalid userContextId '${id}'`);
-+      }
-+    }
-+
-+    let userContextId;
-+    if (
-+      id !== null &&
-+      !this._identities.some(identity => identity.userContextId === id)
-+    ) {
-+      userContextId = id;
-+      this._lastUserContextId = Math.max(
-+        this._lastUserContextId,
-+        userContextId
-+      );
-+    } else {
-+      userContextId = ++this._lastUserContextId;
-+    }
- 
-     // Throw an error if the next userContextId available is invalid (the one associated to
-     // MAX_USER_CONTEXT_ID is already reserved to "userContextIdInternal.webextStorageLocal", which
diff --git a/src/toolkit/content/widgets/panel-list/panel-list-mjs.patch b/src/toolkit/content/widgets/panel-list/panel-list-mjs.patch
new file mode 100644
index 000000000..adde5f129
--- /dev/null
+++ b/src/toolkit/content/widgets/panel-list/panel-list-mjs.patch
@@ -0,0 +1,29 @@
+diff --git a/toolkit/content/widgets/panel-list/panel-list.mjs b/toolkit/content/widgets/panel-list/panel-list.mjs
+index 68ad2fafc8b31dfff541cf8381d9b9533e376d1c..fa62fec6bfb33338091fc06d3736fb76fd5c47c4 100644
+--- a/toolkit/content/widgets/panel-list/panel-list.mjs
++++ b/toolkit/content/widgets/panel-list/panel-list.mjs
+@@ -223,7 +223,12 @@ export class PanelList extends HTMLElement {
+     this.setAttribute("showing", "true");
+     // Tell the host element to hide any overflow in case the panel extends off
+     // the page before the alignment is set.
+-    hostElement.style.overflow = "hidden";
++    const hostHidesOverflow = !getComputedStyle(hostElement)
++      .overflow.split(" ")
++      .includes("visible");
++    if (!hostHidesOverflow) {
++      hostElement.style.overflow = "hidden";
++    }
+ 
+     // Wait for a layout flush, then find the bounds.
+     let {
+@@ -344,7 +349,9 @@ export class PanelList extends HTMLElement {
+       // Set the alignments and show the panel.
+       this.setAttribute("align", align);
+       this.setAttribute("valign", valign);
+-      hostElement.style.overflow = "";
++      if (!hostHidesOverflow) {
++        hostElement.style.overflow = "";
++      }
+       // Decide positioning based on where this panel will be rendered
+       const offsetParentIsBody =
+         this.supportsPopover() ||
diff --git a/src/toolkit/content/widgets/tabbox-js.patch b/src/toolkit/content/widgets/tabbox-js.patch
index 40f876dc8..8056fd11b 100644
--- a/src/toolkit/content/widgets/tabbox-js.patch
+++ b/src/toolkit/content/widgets/tabbox-js.patch
@@ -1,5 +1,5 @@
 diff --git a/toolkit/content/widgets/tabbox.js b/toolkit/content/widgets/tabbox.js
-index 9334120e818b609c6cb6792fd509e90c9b362551..2dde0c8698eb75bac0d0eb4d800d11b577e10a46 100644
+index 402fe6a74b5327a30199667de18f053ad75fe910..9bcbc827d18db2f996d964f7c7e3439e064c9e0d 100644
 --- a/toolkit/content/widgets/tabbox.js
 +++ b/toolkit/content/widgets/tabbox.js
 @@ -11,6 +11,23 @@
@@ -26,7 +26,7 @@ index 9334120e818b609c6cb6792fd509e90c9b362551..2dde0c8698eb75bac0d0eb4d800d11b5
    let imports = {};
    ChromeUtils.defineESModuleGetters(imports, {
      DeferredTask: "resource://gre/modules/DeferredTask.sys.mjs",
-@@ -225,7 +242,7 @@
+@@ -226,7 +243,7 @@
      ) {
        this._inAsyncOperation = false;
        if (oldPanel != this._selectedPanel) {
@@ -35,7 +35,7 @@ index 9334120e818b609c6cb6792fd509e90c9b362551..2dde0c8698eb75bac0d0eb4d800d11b5
          this._selectedPanel?.classList.add("deck-selected");
        }
        this.setAttribute("selectedIndex", val);
-@@ -924,7 +941,7 @@
+@@ -898,7 +915,7 @@
        if (!tab) {
          return;
        }
@@ -44,7 +44,7 @@ index 9334120e818b609c6cb6792fd509e90c9b362551..2dde0c8698eb75bac0d0eb4d800d11b5
          if (otherTab != tab && otherTab.selected) {
            otherTab._selected = false;
          }
-@@ -960,6 +977,7 @@
+@@ -934,6 +951,7 @@
       * @param {MozTab|null} [val]
       */
      set selectedItem(val) {
@@ -52,7 +52,7 @@ index 9334120e818b609c6cb6792fd509e90c9b362551..2dde0c8698eb75bac0d0eb4d800d11b5
        if (val && !val.selected) {
          // The selectedIndex setter ignores invalid values
          // such as -1 if |val| isn't one of our child nodes.
-@@ -1137,7 +1155,7 @@
+@@ -1111,7 +1129,7 @@
          if (tab == startTab) {
            return null;
          }
@@ -61,10 +61,10 @@ index 9334120e818b609c6cb6792fd509e90c9b362551..2dde0c8698eb75bac0d0eb4d800d11b5
            return tab;
          }
        }
-@@ -1199,13 +1217,30 @@
-      * @param {boolean} [aWrap]
+@@ -1175,13 +1193,30 @@
       */
-     advanceSelectedTab(aDir, aWrap) {
+     // eslint-disable-next-line no-unused-vars
+     advanceSelectedTab(aDir, aWrap, aEvent) {
 +      if (window?.gZenGlanceManager?._animating) return;
        let { ariaFocusedItem } = this;
        let startTab = ariaFocusedItem;
@@ -93,7 +93,7 @@ index 9334120e818b609c6cb6792fd509e90c9b362551..2dde0c8698eb75bac0d0eb4d800d11b5
        // Handle keyboard navigation for a hidden tab that can be selected, like the Firefox View tab,
        // which has a random placement in this.allTabs.
        if (startTab.hidden) {
-@@ -1218,7 +1253,7 @@
+@@ -1194,7 +1229,7 @@
          newTab = this.findNextTab(startTab, {
            direction: aDir,
            wrap: aWrap,
diff --git a/src/toolkit/modules/JSONFile-sys-mjs.patch b/src/toolkit/modules/JSONFile-sys-mjs.patch
index f289c4b40..ca27e90bc 100644
--- a/src/toolkit/modules/JSONFile-sys-mjs.patch
+++ b/src/toolkit/modules/JSONFile-sys-mjs.patch
@@ -1,5 +1,5 @@
 diff --git a/toolkit/modules/JSONFile.sys.mjs b/toolkit/modules/JSONFile.sys.mjs
-index 397991e4af8f49b6365d729fc11267b5c1113400..9b1d6fd3850b239000a3c4d2a2d5799a0989f4e3 100644
+index 397991e4af8f49b6365d729fc11267b5c1113400..599ed16981aa1f1e9abfee2ad6c1883efd88e0ba 100644
 --- a/toolkit/modules/JSONFile.sys.mjs
 +++ b/toolkit/modules/JSONFile.sys.mjs
 @@ -132,6 +132,7 @@ export function JSONFile(config) {
@@ -16,14 +16,14 @@ index 397991e4af8f49b6365d729fc11267b5c1113400..9b1d6fd3850b239000a3c4d2a2d5799a
      try {
 -      await IOUtils.writeJSON(
 +      if (this._useSizeHints && this._lastSavedSize) {
-+        this._options.jsonLengthHint = Math.ceil(this._lastSavedSize * 1.05);
++        this._options.lengthHint = Math.ceil(this._lastSavedSize * 1.05);
 +      }
 +      const result = await IOUtils.writeJSON(
          this.path,
          this._data,
          Object.assign({ tmpPath: this.path + ".tmp" }, this._options)
        );
-+      this._lastSavedSize = this._useSizeHints ? result : null;
++      this._lastSavedSize = this._useSizeHints ? result.jsonLength : null;
      } catch (ex) {
        if (typeof this._data.toJSONSafe == "function") {
          // If serialization fails, try fallback safe JSON converter.
diff --git a/src/toolkit/mozapps/update/updater/updater-cpp.patch b/src/toolkit/mozapps/update/updater/updater-cpp.patch
new file mode 100644
index 000000000..a2dcb66d2
--- /dev/null
+++ b/src/toolkit/mozapps/update/updater/updater-cpp.patch
@@ -0,0 +1,45 @@
+diff --git a/toolkit/mozapps/update/updater/updater.cpp b/toolkit/mozapps/update/updater/updater.cpp
+index 5042328c0ee521300a6897b21849abf8dcbd9d45..a7898bcf5f2a15119b8c5cf9ae71f2a1a749e56d 100644
+--- a/toolkit/mozapps/update/updater/updater.cpp
++++ b/toolkit/mozapps/update/updater/updater.cpp
+@@ -2436,15 +2436,37 @@ bool LaunchWinPostProcess(const WCHAR* installationDir,
+   // N.b.: two null terminating characters!  The first terminates a non-existent
+   // key-value pair, the second (automatically added) terminates the block of
+   // key-value pairs.
+-  const WCHAR* emptyEnvironment = L"\0";
++  // %SystemRoot% must be preserved, however.  Without it the NSIS post-update
++  // helper cannot load its plugin DLLs, so
++  // ServicesHelper::PathToUniqueRegistryPath returns an empty string and
++  // AddMaintCertKeys silently does nothing.  That leaves the maintenance
++  // service's allowed-certificate registry keys stale forever, which means a
++  // code signing certificate rotation can never complete through updates.
++  const WCHAR* environment = L"\0";
++  WCHAR environmentBlock[MAX_PATH + 16] = {L'\0'};
++  WCHAR systemRoot[MAX_PATH + 1] = {L'\0'};
++  DWORD systemRootLen =
++      GetEnvironmentVariableW(L"SystemRoot", systemRoot, MAX_PATH + 1);
++  if (systemRootLen > 0 && systemRootLen <= MAX_PATH) {
++    // environmentBlock is zero initialized and oversized relative to
++    // "SystemRoot=" plus a MAX_PATH value, so the second terminating null
++    // character is already present after the string's own terminator.
++    wcsncpy(environmentBlock, L"SystemRoot=",
++            sizeof(environmentBlock) / sizeof(environmentBlock[0]) - 1);
++    wcscat(environmentBlock, systemRoot);
++    environment = environmentBlock;
++  } else {
++    LOG(("LaunchWinPostProcess could not read SystemRoot; the post update "
++         "process will not be able to load its plugins"));
++  }
+ 
+   bool ok =
+       CreateProcessW(exefullpath, cmdline,
+                      nullptr,  // no special security attributes
+                      nullptr,  // no special thread attributes
+                      false,    // don't inherit filehandles
+-                     0,        // No special process creation flags
+-                     (LPVOID)emptyEnvironment, workingDirectory, &si, &pi);
++                     CREATE_UNICODE_ENVIRONMENT, (LPVOID)environment,
++                     workingDirectory, &si, &pi);
+   free(cmdline);
+   if (ok) {
+     LOG(("LaunchWinPostProcess - Waiting for process to complete"));
diff --git a/src/toolkit/themes/shared/menulist-css.patch b/src/toolkit/themes/shared/menulist-css.patch
index 427888eed..b89bfa0c4 100644
--- a/src/toolkit/themes/shared/menulist-css.patch
+++ b/src/toolkit/themes/shared/menulist-css.patch
@@ -1,13 +1,13 @@
 diff --git a/toolkit/themes/shared/menulist.css b/toolkit/themes/shared/menulist.css
-index 3b3e855f20c74f096324c42814e63cbdeb486051..f52e47fc8acea20a4e073b7f4a588d4d4e721aa8 100644
+index d763691ab48424aebd1f5152c8b60011445f2244..984b39f8a21c9460d316f8c0b77003a279aa2b6e 100644
 --- a/toolkit/themes/shared/menulist.css
 +++ b/toolkit/themes/shared/menulist.css
-@@ -53,7 +53,7 @@
+@@ -55,7 +55,7 @@
  
  :host(:not([native])) {
    appearance: none;
--  background-color: var(--button-background-color);
+-  background-color: var(--select-background-color);
 +  background-color: light-dark(rgba(0,0,0,.1), rgba(255,255,255,.1));
-   color: var(--button-text-color);
-   border-radius: var(--button-border-radius);
-   padding-block: var(--space-xsmall);
+   color: var(--select-text-color);
+   border: var(--select-border);
+   border-radius: var(--select-border-radius);
diff --git a/src/toolkit/xre/nsXREDirProvider-cpp.patch b/src/toolkit/xre/nsXREDirProvider-cpp.patch
index 963848a85..63b9c99ac 100644
--- a/src/toolkit/xre/nsXREDirProvider-cpp.patch
+++ b/src/toolkit/xre/nsXREDirProvider-cpp.patch
@@ -1,8 +1,8 @@
 diff --git a/toolkit/xre/nsXREDirProvider.cpp b/toolkit/xre/nsXREDirProvider.cpp
-index b54980f967ab8fe9b9c13bbad8fae6323ec84f1f..f1a5481fb3bd44c1f8f6e40f4163aa7842623325 100644
+index dcce3335e14f9f5d3c0b9fe6a86527be6011c143..ca788d6bd1db3a14d80bf571813e9c706456968f 100644
 --- a/toolkit/xre/nsXREDirProvider.cpp
 +++ b/toolkit/xre/nsXREDirProvider.cpp
-@@ -1333,9 +1333,11 @@ nsresult nsXREDirProvider::AppendFromAppData(nsIFile* aFile, bool aIsDotted) {
+@@ -1335,14 +1335,10 @@ nsresult nsXREDirProvider::AppendFromAppData(nsIFile* aFile, bool aIsDotted) {
    // Similar to nsXREDirProvider::AppendProfilePath.
    // TODO: Bug 1990407 - Evaluate if refactoring might be required there in the
    // future?
@@ -10,12 +10,17 @@ index b54980f967ab8fe9b9c13bbad8fae6323ec84f1f..f1a5481fb3bd44c1f8f6e40f4163aa78
 +  // Use aIsDotted for a different purpose here, will probably break in the future
 +  if (gAppData->profile && aIsDotted) {
      nsAutoCString profile;
-     profile = gAppData->profile;
+-#  if defined(MOZ_THUNDERBIRD)
+-    if (gAppData->profile[0] != '.') {
+-      profile.Assign('.');
+-    }
+-#  endif
+-    profile.Append(gAppData->profile);
 +    profile = "."_ns + nsDependentCString(gAppData->profile);
      MOZ_TRY(aFile->AppendRelativeNativePath(profile));
    } else {
      nsAutoCString vendor;
-@@ -1345,8 +1347,6 @@ nsresult nsXREDirProvider::AppendFromAppData(nsIFile* aFile, bool aIsDotted) {
+@@ -1352,8 +1348,6 @@ nsresult nsXREDirProvider::AppendFromAppData(nsIFile* aFile, bool aIsDotted) {
      ToLowerCase(vendor);
      ToLowerCase(appName);
  
@@ -24,11 +29,16 @@ index b54980f967ab8fe9b9c13bbad8fae6323ec84f1f..f1a5481fb3bd44c1f8f6e40f4163aa78
      MOZ_TRY(aFile->AppendRelativeNativePath(appName));
    }
  
-@@ -1514,13 +1514,8 @@ nsresult nsXREDirProvider::GetLegacyOrXDGHomePath(const char* aHomeDir,
- 
-     // If the build was made against a specific profile name, MOZ_APP_PROFILE=
-     // then make sure we respect this and dont move to XDG directory
--    if (gAppData->profile) {
+@@ -1530,18 +1524,8 @@ nsresult nsXREDirProvider::GetLegacyOrXDGHomePath(const char* aHomeDir,
+     // of a specific build where legacy needs to be forced, similar to the
+     // Firefox handling. Both casing are verified to account for systems where
+     // that matters.
+-    if (gAppData->profile
+-#  if defined(MOZ_THUNDERBIRD)
+-        && strcmp(gAppData->profile, "thunderbird") != 0 &&
+-        strcmp(gAppData->profile, "Thunderbird") != 0
+-#  endif
+-    ) {
 -      MOZ_TRY(NS_NewNativeLocalFile(nsDependentCString(aHomeDir),
 -                                    getter_AddRefs(localDir)));
 -    } else {
diff --git a/src/widget/SwipeTracker-cpp.patch b/src/widget/SwipeTracker-cpp.patch
index 965a670ea..39bceca6f 100644
--- a/src/widget/SwipeTracker-cpp.patch
+++ b/src/widget/SwipeTracker-cpp.patch
@@ -1,15 +1,15 @@
 diff --git a/widget/SwipeTracker.cpp b/widget/SwipeTracker.cpp
-index 887d06d3bd9cdaa934880e0ae7a11ec8b737fb61..979f93ddab0d661ac1a1d73e7a0ba27fa2c8f9b7 100644
+index 83b80a808261ce28e5c571dc802993556477f0c8..8de39d5c724e23f540a70f47e893e46bcf1112e6 100644
 --- a/widget/SwipeTracker.cpp
 +++ b/widget/SwipeTracker.cpp
-@@ -3,6 +3,7 @@
-  * You can obtain one at http://mozilla.org/MPL/2.0/. */
- 
- #include "SwipeTracker.h"
+@@ -10,6 +10,7 @@
+ #include "mozilla/PresShell.h"
+ #include "mozilla/StaticPrefs_browser.h"
+ #include "mozilla/StaticPrefs_widget.h"
 +#include "mozilla/StaticPrefs_zen.h"
- 
- #include "InputData.h"
- #include "mozilla/FlushType.h"
+ #include "mozilla/TimeStamp.h"
+ #include "mozilla/TouchEvents.h"
+ #include "mozilla/dom/SimpleGestureEventBinding.h"
 @@ -67,6 +68,9 @@ double SwipeTracker::SwipeSuccessTargetValue() const {
  }
  
diff --git a/src/widget/Theme-cpp.patch b/src/widget/Theme-cpp.patch
index 1b88b2c75..f8a79df1b 100644
--- a/src/widget/Theme-cpp.patch
+++ b/src/widget/Theme-cpp.patch
@@ -1,16 +1,16 @@
 diff --git a/widget/Theme.cpp b/widget/Theme.cpp
-index 766a8ca4bc6fcc98f719ad4f472b20bc1d198ac9..be4419cfafb55e5cac8f5de741185ee3cabc4722 100644
+index 0d9c9014dabfe7177c25d6f983ff823c4435a327..7995de05ed556fa6373b83e3e44bffc1b857dd73 100644
 --- a/widget/Theme.cpp
 +++ b/widget/Theme.cpp
-@@ -18,6 +18,7 @@
- #include "mozilla/RelativeLuminanceUtils.h"
- #include "mozilla/ScrollContainerFrame.h"
- #include "mozilla/StaticPrefs_widget.h"
+@@ -25,6 +25,7 @@
+ #include "mozilla/gfx/Filters.h"
+ #include "mozilla/gfx/Rect.h"
+ #include "mozilla/gfx/Types.h"
 +#include "mozilla/nsZenBoostsBackend.h"
  #include "mozilla/webrender/WebRenderAPI.h"
  #include "nsCSSColorUtils.h"
  #include "nsCSSRendering.h"
-@@ -670,10 +671,15 @@ template <typename PaintBackendData>
+@@ -671,10 +672,15 @@ template <typename PaintBackendData>
  void Theme::PaintTextField(PaintBackendData& aPaintData,
                             const LayoutDeviceRect& aRect,
                             const ElementState& aState, const Colors& aColors,
@@ -27,7 +27,7 @@ index 766a8ca4bc6fcc98f719ad4f472b20bc1d198ac9..be4419cfafb55e5cac8f5de741185ee3
    const CSSCoord radius = 2.0f;
  
    ThemeDrawing::PaintRoundedRectWithRadius(aPaintData, aRect, backgroundColor,
-@@ -690,9 +696,9 @@ template <typename PaintBackendData>
+@@ -691,9 +697,9 @@ template <typename PaintBackendData>
  void Theme::PaintListbox(PaintBackendData& aPaintData,
                           const LayoutDeviceRect& aRect,
                           const ElementState& aState, const Colors& aColors,
@@ -39,7 +39,7 @@ index 766a8ca4bc6fcc98f719ad4f472b20bc1d198ac9..be4419cfafb55e5cac8f5de741185ee3
  }
  
  template <typename PaintBackendData>
-@@ -1158,10 +1164,12 @@ bool Theme::DoDrawWidgetBackground(PaintBackendData& aPaintData,
+@@ -1159,10 +1165,12 @@ bool Theme::DoDrawWidgetBackground(PaintBackendData& aPaintData,
      case StyleAppearance::Textfield:
      case StyleAppearance::NumberInput:
      case StyleAppearance::PasswordInput:
diff --git a/src/widget/cocoa/VibrancyManager-mm.patch b/src/widget/cocoa/VibrancyManager-mm.patch
index 00ea2b670..52a41a5a9 100644
--- a/src/widget/cocoa/VibrancyManager-mm.patch
+++ b/src/widget/cocoa/VibrancyManager-mm.patch
@@ -1,16 +1,16 @@
 diff --git a/widget/cocoa/VibrancyManager.mm b/widget/cocoa/VibrancyManager.mm
-index 5df70a63afb235d2db11712276bb63f756222a0f..a2865aa2748433cbfd956ae46d197200fbbcfadd 100644
+index bc62ff28285691c605fe0680e7a98927f11d5882..c209b63179df298e9b43182813ba0045f08328cc 100644
 --- a/widget/cocoa/VibrancyManager.mm
 +++ b/widget/cocoa/VibrancyManager.mm
-@@ -11,6 +11,7 @@
+@@ -9,6 +9,7 @@
+ #import <objc/message.h>
  
- #include "nsCocoaWindow.h"
  #include "mozilla/StaticPrefs_widget.h"
 +#include "mozilla/StaticPrefs_zen.h"
+ #include "nsCocoaWindow.h"
  
  using namespace mozilla;
- 
-@@ -29,6 +30,9 @@ static NSVisualEffectState VisualEffectStateForVibrancyType(
+@@ -28,6 +29,9 @@ static NSVisualEffectState VisualEffectStateForVibrancyType(
      case VibrancyType::Sidebar:
        break;
    }
@@ -20,44 +20,3 @@ index 5df70a63afb235d2db11712276bb63f756222a0f..a2865aa2748433cbfd956ae46d197200
    return NSVisualEffectStateFollowsWindowActiveState;
  }
  
-@@ -36,7 +40,23 @@ static NSVisualEffectMaterial VisualEffectMaterialForVibrancyType(
-     VibrancyType aType) {
-   switch (aType) {
-     case VibrancyType::Sidebar:
--      return NSVisualEffectMaterialSidebar;
-+      switch (StaticPrefs::zen_widget_macos_window_material()) {
-+        case 1:
-+          return NSVisualEffectMaterialHUDWindow;
-+        case 2:
-+          return NSVisualEffectMaterialFullScreenUI;
-+        case 3:
-+          return NSVisualEffectMaterialPopover;
-+        case 4:
-+          return NSVisualEffectMaterialMenu;
-+        case 5:
-+          return NSVisualEffectMaterialToolTip;
-+        case 6:
-+          return NSVisualEffectMaterialHeaderView;
-+        case 7:
-+        default:
-+          return NSVisualEffectMaterialUnderWindowBackground;
-+      }
-     case VibrancyType::Titlebar:
-       return NSVisualEffectMaterialTitlebar;
-   }
-@@ -76,6 +96,7 @@ - (NSView*)hitTest:(NSPoint)aPoint {
- 
- - (void)prefChanged {
-   self.blendingMode = VisualEffectBlendingModeForVibrancyType(mType);
-+  self.material = VisualEffectMaterialForVibrancyType(mType);
- }
- @end
- 
-@@ -86,6 +107,7 @@ static void PrefChanged(const char* aPref, void* aClosure) {
- static constexpr nsLiteralCString kObservedPrefs[] = {
-     "widget.macos.sidebar-blend-mode.behind-window"_ns,
-     "widget.macos.titlebar-blend-mode.behind-window"_ns,
-+    "zen.widget.macos.window-material"_ns,
- };
- 
- VibrancyManager::VibrancyManager(const nsCocoaWindow& aCoordinateConverter,
diff --git a/src/widget/cocoa/nsCocoaWindow-h.patch b/src/widget/cocoa/nsCocoaWindow-h.patch
new file mode 100644
index 000000000..77f4033c0
--- /dev/null
+++ b/src/widget/cocoa/nsCocoaWindow-h.patch
@@ -0,0 +1,23 @@
+diff --git a/widget/cocoa/nsCocoaWindow.h b/widget/cocoa/nsCocoaWindow.h
+index 312011c1c2ac41e78affecbdef25d72766a7c882..e5865c7d6259f0a3df48edf7a26b1b75a23cdb3a 100644
+--- a/widget/cocoa/nsCocoaWindow.h
++++ b/widget/cocoa/nsCocoaWindow.h
+@@ -462,6 +462,10 @@ class nsCocoaWindow final : public nsIWidget {
+   void SetHideTitlebarSeparator(bool) override;
+   bool IsMacTitlebarDirectionRTL() override;
+   void SetCustomTitlebar(bool) override;
++  void SetWindowClass(const nsAString& aXulWinType,
++                      const nsAString& aXulWinClass,
++                      const nsAString& aXulWinName) override;
++  void UpdateWindowMaterial();
+   void UpdateThemeGeometries(
+       const nsTArray<ThemeGeometry>& aThemeGeometries) override;
+   void LockAspectRatio(bool aShouldLock) override;
+@@ -672,6 +676,7 @@ class nsCocoaWindow final : public nsIWidget {
+   bool mAspectRatioLocked = false;
+   bool mIsAlert = false;  // True if this is an non-native alert window.
+   bool mWasShown = false;
++  bool mIsBrowserWindow = false;
+ 
+   int32_t mNumModalDescendants = 0;
+ 
diff --git a/src/widget/cocoa/nsCocoaWindow-mm.patch b/src/widget/cocoa/nsCocoaWindow-mm.patch
new file mode 100644
index 000000000..983efe466
--- /dev/null
+++ b/src/widget/cocoa/nsCocoaWindow-mm.patch
@@ -0,0 +1,134 @@
+diff --git a/widget/cocoa/nsCocoaWindow.mm b/widget/cocoa/nsCocoaWindow.mm
+index 2efd02e4a92433fd29bbfdb707aa81cfec45031e..3b763c3927f07e529c826f8e4f62bc80a324b247 100644
+--- a/widget/cocoa/nsCocoaWindow.mm
++++ b/widget/cocoa/nsCocoaWindow.mm
+@@ -86,6 +86,7 @@
+ #include "mozilla/StaticPrefs_gfx.h"
+ #include "mozilla/StaticPrefs_ui.h"
+ #include "mozilla/StaticPrefs_widget.h"
++#include "mozilla/StaticPrefs_zen.h"
+ #include "mozilla/WritingModes.h"
+ #include "mozilla/dom/Document.h"
+ #include "mozilla/layers/CompositorBridgeChild.h"
+@@ -1332,6 +1333,110 @@ - (NSRect)_opaqueRectForWindowMoveWhenInTitlebar {
+ }
+ @end
+ 
++@interface ZenWindowMaterialView : NSVisualEffectView
++- (void)prefChanged;
++@end
++
++static void ZenWindowMaterialPrefChanged(const char* aPref, void* aClosure) {
++  [static_cast<ZenWindowMaterialView*>(aClosure) prefChanged];
++}
++
++static constexpr nsLiteralCString kZenWindowMaterialPrefs[] = {
++    "zen.widget.macos.window-material"_ns,
++    "zen.view.grey-out-inactive-windows"_ns,
++};
++
++static NSVisualEffectMaterial ZenWindowMaterial() {
++  switch (StaticPrefs::zen_widget_macos_window_material()) {
++    case 1:
++      return NSVisualEffectMaterialHUDWindow;
++    case 2:
++      return NSVisualEffectMaterialFullScreenUI;
++    case 3:
++      return NSVisualEffectMaterialPopover;
++    case 4:
++      return NSVisualEffectMaterialMenu;
++    case 5:
++      return NSVisualEffectMaterialToolTip;
++    case 6:
++      return NSVisualEffectMaterialHeaderView;
++    case 7:
++    default:
++      return NSVisualEffectMaterialUnderWindowBackground;
++  }
++}
++
++@implementation ZenWindowMaterialView
++- (instancetype)initWithFrame:(NSRect)aRect {
++  self = [super initWithFrame:aRect];
++  self.appearance = nil;
++  self.emphasized = NO;
++  self.blendingMode = NSVisualEffectBlendingModeBehindWindow;
++  [self prefChanged];
++  for (const auto& pref : kZenWindowMaterialPrefs) {
++    Preferences::RegisterCallback(ZenWindowMaterialPrefChanged, pref, self);
++  }
++  return self;
++}
++
++- (void)dealloc {
++  for (const auto& pref : kZenWindowMaterialPrefs) {
++    Preferences::UnregisterCallback(ZenWindowMaterialPrefChanged, pref, self);
++  }
++  [super dealloc];
++}
++
++- (void)prefChanged {
++  self.state = StaticPrefs::zen_view_grey_out_inactive_windows()
++                   ? NSVisualEffectStateFollowsWindowActiveState
++                   : NSVisualEffectStateActive;
++  self.material = ZenWindowMaterial();
++}
++@end
++
++static void ZenWindowVibrancyPrefChanged(const char* aPref, void* aClosure) {
++  static_cast<nsCocoaWindow*>(aClosure)->UpdateWindowMaterial();
++}
++
++void nsCocoaWindow::SetWindowClass(const nsAString& aXulWinType,
++                                   const nsAString& aXulWinClass,
++                                   const nsAString& aXulWinName) {
++  if (mWindowType != WindowType::TopLevel || mIsBrowserWindow ||
++      !aXulWinType.EqualsLiteral("navigator:browser")) {
++    return;
++  }
++  mIsBrowserWindow = true;
++  Preferences::RegisterCallback(ZenWindowVibrancyPrefChanged,
++                                "zen.widget.macos.window-vibrancy", this);
++  UpdateWindowMaterial();
++}
++
++void nsCocoaWindow::UpdateWindowMaterial() {
++  NS_OBJC_BEGIN_TRY_IGNORE_BLOCK;
++
++  if (!mWindow) {
++    return;
++  }
++  bool wanted = StaticPrefs::zen_widget_macos_window_vibrancy();
++  if (wanted ==
++      [mWindow.contentView isKindOfClass:[ZenWindowMaterialView class]]) {
++    return;
++  }
++
++  NSRect frame = mWindow.contentView.frame;
++  NSView* wrapper = wanted ? [[ZenWindowMaterialView alloc] initWithFrame:frame]
++                           : [[NSView alloc] initWithFrame:frame];
++  wrapper.wantsLayer = YES;
++  for (NSView* view in [mWindow contentViewContents]) {
++    [view removeFromSuperviewWithoutNeedingDisplay];
++    [wrapper addSubview:view];
++  }
++  mWindow.contentView = wrapper;
++  [wrapper release];
++
++  NS_OBJC_END_TRY_IGNORE_BLOCK;
++}
++
+ void nsCocoaWindow::UpdateWindowDraggingRegion(
+     const LayoutDeviceIntRegion& aRegion) {
+   // mChildView returns YES from mouseDownCanMoveWindow, so we need to put
+@@ -4919,6 +5024,10 @@ - (BOOL)wantsBestResolutionOpenGLSurface {
+ nsCocoaWindow::~nsCocoaWindow() {
+   NS_OBJC_BEGIN_TRY_IGNORE_BLOCK;
+ 
++  if (mIsBrowserWindow) {
++    Preferences::UnregisterCallback(ZenWindowVibrancyPrefChanged,
++                                    "zen.widget.macos.window-vibrancy", this);
++  }
+   RemoveAllChildren();
+   if (mWindow && mWindowMadeHere) {
+     CancelAllTransitions();
diff --git a/src/widget/cocoa/nsDragService-mm.patch b/src/widget/cocoa/nsDragService-mm.patch
index 8109f2625..8308e701c 100644
--- a/src/widget/cocoa/nsDragService-mm.patch
+++ b/src/widget/cocoa/nsDragService-mm.patch
@@ -1,16 +1,16 @@
 diff --git a/widget/cocoa/nsDragService.mm b/widget/cocoa/nsDragService.mm
-index 81fe6f749c1d046141003ad2413605b4d4acf9ed..f26c2556657ad683dad3fa712feca5965343175d 100644
+index 340a9ad81c5cb23bb7e5f927d11d5cffdde7ce70..32fc707ccfa56fa8c307860868d092c4a9050419 100644
 --- a/widget/cocoa/nsDragService.mm
 +++ b/widget/cocoa/nsDragService.mm
-@@ -22,6 +22,7 @@
- #include "mozilla/PresShell.h"
+@@ -10,6 +10,7 @@
  #include "mozilla/dom/Document.h"
  #include "mozilla/dom/DocumentInlines.h"
-+#include "mozilla/nsZenDragAndDrop.h"
- #include "nsIContent.h"
- #include "nsCocoaUtils.h"
  #include "mozilla/gfx/2D.h"
-@@ -146,6 +147,10 @@
++#include "mozilla/nsZenDragAndDrop.h"
+ #include "nsArrayUtils.h"
+ #include "nsCOMPtr.h"
+ #include "nsClipboard.h"
+@@ -145,6 +146,10 @@
                                              bitsPerPixel:32];
  
    uint8_t* dest = [imageRep bitmapData];
@@ -21,7 +21,7 @@ index 81fe6f749c1d046141003ad2413605b4d4acf9ed..f26c2556657ad683dad3fa712feca596
    for (uint32_t i = 0; i < height; ++i) {
      uint8_t* src = map.mData + i * map.mStride;
      for (uint32_t j = 0; j < width; ++j) {
-@@ -153,15 +158,15 @@
+@@ -152,15 +157,15 @@
        // is premultipled here. Also, Quartz likes RGBA, so do that translation
        // as well.
  #ifdef IS_BIG_ENDIAN
diff --git a/src/widget/gtk/nsDragService-cpp.patch b/src/widget/gtk/nsDragService-cpp.patch
new file mode 100644
index 000000000..85e9760e3
--- /dev/null
+++ b/src/widget/gtk/nsDragService-cpp.patch
@@ -0,0 +1,29 @@
+diff --git a/widget/gtk/nsDragService.cpp b/widget/gtk/nsDragService.cpp
+index f760a6bb887b321376761431886c771f14fd03af..d52110ba52a95ef7c7bfb915e120b8dd636c9448 100644
+--- a/widget/gtk/nsDragService.cpp
++++ b/widget/gtk/nsDragService.cpp
+@@ -23,6 +23,7 @@
+ #include "mozilla/StaticPrefs_widget.h"
+ #include "mozilla/WidgetUtils.h"
+ #include "mozilla/WidgetUtilsGtk.h"
++#include "mozilla/nsZenDragAndDrop.h"
+ #include "nsAppShell.h"
+ #include "nsArrayUtils.h"
+ #include "nsCRT.h"
+@@ -2304,11 +2305,15 @@ bool nsDragSession::SetAlphaPixmap(SourceSurface* aSurface,
+       cairo_image_surface_get_stride(surf), SurfaceFormat::B8G8R8A8);
+   if (!dt) return false;
+ 
++  auto drag_translucency = DRAG_IMAGE_ALPHA_LEVEL;
++  if (auto zenDragAndDrop = zen::nsZenDragAndDrop::GetZenDragAndDropInstance()) {
++    drag_translucency = zenDragAndDrop->GetDragImageOpacity();
++  }
+   dt->ClearRect(Rect(0, 0, dragRect.width, dragRect.height));
+   dt->DrawSurface(
+       aSurface, Rect(0, 0, dragRect.width, dragRect.height),
+       Rect(0, 0, dragRect.width, dragRect.height), DrawSurfaceOptions(),
+-      DrawOptions(DRAG_IMAGE_ALPHA_LEVEL, CompositionOp::OP_SOURCE));
++      DrawOptions(drag_translucency, CompositionOp::OP_SOURCE));
+ 
+   cairo_surface_mark_dirty(surf);
+   cairo_surface_set_device_offset(surf, -aXOffset, -aYOffset);
diff --git a/src/zen/boosts/ZenBoostStyles.sys.mjs b/src/zen/boosts/ZenBoostStyles.sys.mjs
index 88acf51c9..ac2a022f8 100644
--- a/src/zen/boosts/ZenBoostStyles.sys.mjs
+++ b/src/zen/boosts/ZenBoostStyles.sys.mjs
@@ -81,15 +81,8 @@ export class nsZenBoostStyles {
     }
 
     if (fontCase != "" || fontFamily != "") {
-      const ignoredElements = [
-        ".google-symbols",
-        "gf-load-icon-font",
-        "mat-icon",
-        ".google-material-icons",
-        "span",
-      ];
       style += `/* Text Format */\n`;
-      style += `body *:not(${ignoredElements.join(",")}) {\n`;
+      style += `body *:not(.google-symbols, gf-load-icon-font, mat-icon, .google-material-icons) {\n`;
       style += `${fontFamily}\n`;
       style += `${fontCase}\n`;
       style += `}\n`;
diff --git a/src/zen/common/modules/ZenSidebarNotification.mjs b/src/zen/common/modules/ZenSidebarNotification.mjs
index f5e134ffa..81d7fcade 100644
--- a/src/zen/common/modules/ZenSidebarNotification.mjs
+++ b/src/zen/common/modules/ZenSidebarNotification.mjs
@@ -22,27 +22,64 @@ class ZenSidebarNotification extends MozLitElement {
   static properties = {
     headingL10nId: { type: String, fluent: true },
     links: { type: Array },
+    autoHideMs: { type: Number },
   };
 
-  constructor({ headingL10nId = "", links = [] } = {}) {
+  #autoHideAnimation = null;
+
+  constructor({ headingL10nId = "", links = [], autoHideMs = 0 } = {}) {
     super();
     this.headingL10nId = headingL10nId;
     this.links = links;
+    this.autoHideMs = autoHideMs;
+    // Hold the countdown while the user is reading.
+    this.addEventListener("mouseenter", () => this.#autoHideAnimation?.pause());
+    this.addEventListener("mouseleave", () => this.#autoHideAnimation?.play());
   }
 
   connectedCallback() {
     super.connectedCallback();
     if (this.parentElement) {
-      this.#animateIn();
+      this.#animateIn().then(() => this.#startAutoHide());
     }
   }
 
   remove() {
+    if (this.#autoHideAnimation?.playState !== "finished") {
+      // Stop a running countdown; a finished one must keep its fill so
+      // the bar doesn't snap back to full during the fade-out.
+      this.#autoHideAnimation?.cancel();
+    }
+    this.#autoHideAnimation = null;
     this.#animateOut().then(() => {
       super.remove();
     });
   }
 
+  async #startAutoHide() {
+    if (!this.autoHideMs || !this.isConnected) {
+      return;
+    }
+    await this.updateComplete;
+    const bar = this.shadowRoot?.querySelector(
+      ".zen-sidebar-notification-progress-bar"
+    );
+    if (!bar || this.#autoHideAnimation) {
+      return;
+    }
+    this.#autoHideAnimation = bar.animate(
+      { transform: ["scaleX(1)", "scaleX(0)"] },
+      { duration: this.autoHideMs, easing: "linear", fill: "forwards" }
+    );
+    this.#autoHideAnimation.finished.then(
+      () => this.remove(),
+      () => {}
+    );
+    if (this.matches(":hover")) {
+      this.#autoHideAnimation.pause();
+    }
+  }
+
   render() {
     return html`
       <link
@@ -62,6 +99,15 @@ class ZenSidebarNotification extends MozLitElement {
           <img src="chrome://browser/skin/zen-icons/close.svg" />
         </div>
       </div>
+      ${
+        this.autoHideMs
+          ? html`
+              <div class="zen-sidebar-notification-progress">
+                <div class="zen-sidebar-notification-progress-bar"></div>
+              </div>
+            `
+          : null
+      }
       <div class="zen-sidebar-notification-body">
         ${this.links.map(
           link => html`
diff --git a/src/zen/common/modules/ZenStartup.mjs b/src/zen/common/modules/ZenStartup.mjs
index a1683d6ad..5766774df 100644
--- a/src/zen/common/modules/ZenStartup.mjs
+++ b/src/zen/common/modules/ZenStartup.mjs
@@ -4,6 +4,7 @@
 
 import checkForZenUpdates, {
   createWindowUpdateAnimation,
+  playWindowSweepAnimation,
 } from "chrome://browser/content/ZenUpdates.mjs";
 
 class ZenStartup {
@@ -195,6 +196,14 @@ class ZenStartup {
     checkForZenUpdates();
     return await createWindowUpdateAnimation();
   }
+
+  /**
+   * Entry point for privileged modules (e.g. the sync applier) to play the
+   * update sweep animation in this window.
+   */
+  playWindowSweepAnimation() {
+    return playWindowSweepAnimation();
+  }
 }
 
 window.gZenStartup = new ZenStartup();
diff --git a/src/zen/common/modules/ZenUIManager.mjs b/src/zen/common/modules/ZenUIManager.mjs
index 13434de29..dbb1bd2ca 100644
--- a/src/zen/common/modules/ZenUIManager.mjs
+++ b/src/zen/common/modules/ZenUIManager.mjs
@@ -4,6 +4,7 @@
 
 import { nsZenMultiWindowFeature } from "chrome://browser/content/zen-components/ZenCommonUtils.mjs";
 import { nsZenMenuBar } from "chrome://browser/content/zen-components/ZenMenubar.mjs";
+import { UrlbarShared } from "chrome://browser/content/urlbar/UrlbarShared.mjs";
 
 window.gZenUIManager = {
   _popupTrackingElements: [],
@@ -467,7 +468,7 @@ window.gZenUIManager = {
     let searchMode = null;
     if (!currentSearchMode) {
       searchMode = {
-        source: UrlbarUtils.RESULT_SOURCE.ZEN_ACTIONS,
+        source: UrlbarShared.RESULT_SOURCE.ZEN_ACTIONS,
         isPreview: true,
       };
     }
@@ -492,6 +493,13 @@ window.gZenUIManager = {
   _clearTimeout: null,
   _lastTab: null,
 
+  _urlbarSessionCounter: 0,
+  _urlbarOwner: null,
+
+  _isOwner(closeSeq) {
+    return this._urlbarOwner === closeSeq;
+  },
+
   // Check if browser elements are in a valid state for tab operations
   _validateBrowserState() {
     // Check if browser window is still open
@@ -516,8 +524,15 @@ window.gZenUIManager = {
     werePassedURL,
     searchClipboard,
     where,
-    overridePreferance = false
+    overridePreferance = false,
+    closeToken = {}
   ) {
+    // Keep this here. It's better to make sure every
+    // call has a different token rather then forgetting
+    // to increment it in one of the early returns.
+    const closeSeq = ++this._urlbarSessionCounter;
+    closeToken.id = closeSeq;
+
     // Validate browser state first
     if (!this._validateBrowserState()) {
       console.warn("Browser state invalid for new tab operation");
@@ -541,7 +556,13 @@ window.gZenUIManager = {
 
     // Close the new tab popup on cmd/ctrl + t
     if (!overridePreferance && gURLBar.hasAttribute("zen-newtab")) {
-      this.handleUrlbarClose();
+      // The _zenHandleUrlbarClose holds a token in it's closure.
+      // Call that instead.
+      if (gURLBar._zenHandleUrlbarClose) {
+        gURLBar._zenHandleUrlbarClose();
+      } else {
+        this.handleUrlbarClose(closeSeq);
+      }
       return true;
     }
 
@@ -567,7 +588,9 @@ window.gZenUIManager = {
     this._prevUrlbarLabel = gURLBar._untrimmedValue || "";
 
     // Set up URL bar for new tab
-    gURLBar._zenHandleUrlbarClose = this.handleUrlbarClose.bind(this);
+    gURLBar._zenHandleUrlbarClose = (onSwitch, onElementPicked) =>
+      this.handleUrlbarClose(closeSeq, onSwitch, onElementPicked);
+    this._urlbarOwner = closeSeq;
     gURLBar.setAttribute("zen-newtab", true);
 
     // Update newtab buttons
@@ -581,18 +604,33 @@ window.gZenUIManager = {
       document.getElementById("Browser:OpenLocation").doCommand();
     } catch (e) {
       console.error("Error opening location in new tab:", e);
-      this.handleUrlbarClose(false);
+      this.handleUrlbarClose(closeSeq, false, false);
       return false;
     }
     return true;
   },
 
+  /**
+   * Check whether the closeToken given by handleNewTab
+   * corresponds to a close event.
+   *
+   * @param {object} closeToken - Token previously passed to handleNewTab.
+   * @param {CustomEvent} event - A ZenURLBarClosed event.
+   * @returns {boolean}
+   */
+  matchesCloseToken(closeToken, event) {
+    return (
+      typeof closeToken?.id === "number" &&
+      event?.detail?.closeSeq === closeToken.id
+    );
+  },
+
   clearUrlbarData() {
     this._prevUrlbarLabel = null;
     this._lastSearch = "";
   },
 
-  handleUrlbarClose(onSwitch = false, onElementPicked = false) {
+  handleUrlbarClose(closeSeq, onSwitch = false, onElementPicked = false) {
     // Validate browser state first
     if (!this._validateBrowserState()) {
       console.warn("Browser state invalid for URL bar close operation");
@@ -606,59 +644,69 @@ window.gZenUIManager = {
 
     const isFocusedBefore = gURLBar.focused;
     setTimeout(() => {
-      // We use this attribute on Tabbrowser::addTab
-      gURLBar.removeAttribute("zen-newtab");
+      /* If someone else opened the url bar in the meantime don't be
+       * stingy and leave it open for them.*/
+      if (this._isOwner(closeSeq)) {
+        // We use this attribute on Tabbrowser::addTab
+        gURLBar.removeAttribute("zen-newtab");
 
-      // Safely restore tab visual state with proper validation
-      if (
-        this._lastTab &&
-        !this._lastTab.closing &&
-        this._lastTab.documentGlobal &&
-        !this._lastTab.documentGlobal.closed &&
-        gBrowser.selectedTab === this._lastTab
-      ) {
-        this._lastTab._visuallySelected = true;
-        this._lastTab = null;
-      }
-
-      // Reset newtab buttons
-      for (const button of this.newtabButtons) {
-        button.removeAttribute("in-urlbar");
-      }
-
-      // Handle search data
-      if (onSwitch) {
-        this.clearUrlbarData();
-      } else {
-        this._lastSearch = gURLBar._untrimmedValue || "";
-
-        if (this._clearTimeout) {
-          clearTimeout(this._clearTimeout);
+        // Safely restore tab visual state with proper validation
+        if (
+          this._lastTab &&
+          !this._lastTab.closing &&
+          this._lastTab.documentGlobal &&
+          !this._lastTab.documentGlobal.closed &&
+          gBrowser.selectedTab === this._lastTab
+        ) {
+          this._lastTab._visuallySelected = true;
+          this._lastTab = null;
         }
 
-        this._clearTimeout = setTimeout(() => {
+        // Reset newtab buttons
+        for (const button of this.newtabButtons) {
+          button.removeAttribute("in-urlbar");
+        }
+
+        // Handle search data
+        if (onSwitch) {
           this.clearUrlbarData();
-        }, this.urlbarWaitToClear);
-      }
+        } else {
+          this._lastSearch = gURLBar._untrimmedValue || "";
 
-      // Safely restore URL bar state with proper validation
-      if (this._prevUrlbarLabel) {
-        gURLBar.setURI({
-          uri: this._prevUrlbarLabel,
-          dueToTabSwitch: onSwitch,
-          isSameDocument: !onSwitch,
-        });
-      }
+          if (this._clearTimeout) {
+            clearTimeout(this._clearTimeout);
+          }
 
-      gURLBar.handleRevert();
+          this._clearTimeout = setTimeout(() => {
+            this.clearUrlbarData();
+          }, this.urlbarWaitToClear);
+        }
+
+        // Safely restore URL bar state with proper validation
+        if (this._prevUrlbarLabel) {
+          gURLBar.setURI({
+            uri: this._prevUrlbarLabel,
+            dueToTabSwitch: onSwitch,
+            isSameDocument: !onSwitch,
+          });
+        }
+
+        gURLBar.handleRevert();
+      }
 
       if (isFocusedBefore) {
         setTimeout(() => {
           window.dispatchEvent(
             new CustomEvent("ZenURLBarClosed", {
-              detail: { onSwitch, onElementPicked },
+              detail: { onSwitch, onElementPicked, closeSeq },
             })
           );
+
+          if (!this._isOwner(closeSeq)) {
+            return;
+          }
+          this._urlbarOwner = null;
+
           gURLBar.view.close({ elementPicked: onElementPicked });
           gURLBar.updateTextOverflow();
 
@@ -682,6 +730,8 @@ window.gZenUIManager = {
             }
           }
         }, 0);
+      } else if (this._isOwner(closeSeq)) {
+        this._urlbarOwner = null;
       }
     }, 0);
   },
diff --git a/src/zen/common/modules/ZenUpdates.mjs b/src/zen/common/modules/ZenUpdates.mjs
index c1f512fd6..94599bdee 100644
--- a/src/zen/common/modules/ZenUpdates.mjs
+++ b/src/zen/common/modules/ZenUpdates.mjs
@@ -7,6 +7,7 @@ import createSidebarNotification from "chrome://browser/content/zen-components/Z
 const ZEN_UPDATE_PREF = "zen.updates.last-version";
 const ZEN_BUILD_ID_PREF = "zen.updates.last-build-id";
 const ZEN_UPDATE_SHOW = "zen.updates.show-update-notification";
+const ZEN_UPDATE_NOTIFICATION_TIMEOUT_MS = 15000;
 
 export default function checkForZenUpdates() {
   const version = Services.appinfo.version;
@@ -25,6 +26,7 @@ export default function checkForZenUpdates() {
   );
   createSidebarNotification({
     headingL10nId: "zen-sidebar-notification-updated-heading",
+    autoHideMs: ZEN_UPDATE_NOTIFICATION_TIMEOUT_MS,
     links: [
       {
         url: Services.urlFormatter.formatURL(
@@ -59,6 +61,14 @@ export async function createWindowUpdateAnimation() {
     return;
   }
   Services.prefs.setStringPref(ZEN_BUILD_ID_PREF, appID);
+  await playWindowSweepAnimation();
+}
+
+/**
+ * Plays the full-window sweep shown after updates. Also used the first
+ * time incoming sync data is applied on this profile.
+ */
+export async function playWindowSweepAnimation() {
   await gZenWorkspaces.promiseInitialized;
   const appWrapper = document.getElementById("zen-main-app-wrapper");
   const element = document.createElement("div");
diff --git a/src/zen/common/styles/zen-browser-ui.css b/src/zen/common/styles/zen-browser-ui.css
index 01966ce3d..7308f9e58 100644
--- a/src/zen/common/styles/zen-browser-ui.css
+++ b/src/zen/common/styles/zen-browser-ui.css
@@ -113,15 +113,6 @@ body,
 }
 
 #zen-browser-background {
-  /* This is conceptually a background, but putting this on a pseudo-element
-    * avoids it from suppressing the chrome-content separator border, etc.
-    *
-    * See bugzilla's 1949528 and bug 1476281 (which would make this unnecessary). */
-  @media (-moz-platform: macos) {
-    -moz-default-appearance: -moz-sidebar;
-    appearance: auto;
-  }
-
   /*
    *  Important: We set the color to `AccentColor` so we can
    *  Compute the stylings and get the native accent color.
diff --git a/src/zen/common/styles/zen-omnibox.css b/src/zen/common/styles/zen-omnibox.css
index 6d6df9b2c..542e67de7 100644
--- a/src/zen/common/styles/zen-omnibox.css
+++ b/src/zen/common/styles/zen-omnibox.css
@@ -642,7 +642,7 @@
 
 .urlbarView-row {
   --urlbarView-row-padding-inline: 8px;
-  --urlbarView-row-padding-block: 10px;
+  --urlbarview-row-padding-block: 10px;
   color: light-dark(rgba(0, 0, 0, 0.7), rgba(255, 255, 255, 0.7)) !important;
 
   &:hover {
diff --git a/src/zen/common/styles/zen-sidebar-notification.css b/src/zen/common/styles/zen-sidebar-notification.css
index a5e15194d..529224f72 100644
--- a/src/zen/common/styles/zen-sidebar-notification.css
+++ b/src/zen/common/styles/zen-sidebar-notification.css
@@ -77,6 +77,18 @@
   }
 }
 
+.zen-sidebar-notification-progress {
+  height: 1px;
+  overflow: hidden;
+  transform: translateY(-1px);
+
+  & .zen-sidebar-notification-progress-bar {
+    height: 100%;
+    background: light-dark(color-mix(in srgb, var(--zen-primary-color) 50%, black), color-mix(in srgb, var(--zen-colors-primary) 15%, transparent 10%, #6b6b6b));
+    transform-origin: left center;
+  }
+}
+
 .zen-sidebar-notification-body {
   padding: 6px;
   display: flex;
diff --git a/src/zen/common/styles/zen-single-components.css b/src/zen/common/styles/zen-single-components.css
index 994c5a782..4b0a50231 100644
--- a/src/zen/common/styles/zen-single-components.css
+++ b/src/zen/common/styles/zen-single-components.css
@@ -46,8 +46,8 @@
   min-height: 30px;
 }
 
-/* Firefox View */
 #firefox-view-button,
+#ai-window-toggle,
 #wrapper-firefox-view-button {
   display: none !important;
 }
diff --git a/src/zen/common/styles/zen-theme.css b/src/zen/common/styles/zen-theme.css
index cd0e708fb..b676d6efc 100644
--- a/src/zen/common/styles/zen-theme.css
+++ b/src/zen/common/styles/zen-theme.css
@@ -92,7 +92,11 @@
   --in-content-accent-color-active: currentColor !important;
 
   /* This is like the secondary button */
-  --in-content-button-background: transparent !important;
+  --in-content-button-background: color-mix(
+    in srgb,
+    currentColor,
+    transparent 90%
+  ) !important;
   --in-content-button-text-color: var(--zen-secondary-btn-color) !important;
   --in-content-button-background-hover: color-mix(
     in srgb,
@@ -255,7 +259,7 @@
   --zen-active-tab-scale: 0.985;
 
   /* Define tab hover background color */
-  --tab-hover-background-color: var(--toolbarbutton-hover-background);
+  --tab-background-color-hover: var(--toolbarbutton-hover-background);
 
   /* Sidebar Notifications */
   --zen-sidebar-notification-bg: color-mix(
@@ -264,7 +268,7 @@
     light-dark(white, black)
   );
   --zen-sidebar-notification-shadow: 0 0 6px light-dark(rgba(0, 0, 0, 0.1), rgba(0, 0, 0, 0.3));
-  --zen-sidebar-notification-outline: 1px solid light-dark(transparent, rgba(255, 255, 255, 0.15));
+  --zen-sidebar-notification-outline: 1px solid light-dark(transparent, rgba(255, 255, 255, 0.1));
 
   --zen-sidebar-themed-icon-fill: light-dark(color-mix(in srgb, var(--zen-primary-color) 50%, black), color-mix(in srgb, var(--zen-colors-primary) 15%, #ebebeb));
 
diff --git a/src/zen/common/sys/ZenActorsManager.sys.mjs b/src/zen/common/sys/ZenActorsManager.sys.mjs
index 59cac7eba..4b3fc1471 100644
--- a/src/zen/common/sys/ZenActorsManager.sys.mjs
+++ b/src/zen/common/sys/ZenActorsManager.sys.mjs
@@ -29,6 +29,7 @@ let JSWINDOWACTORS = {
         DOMContentLoaded: {},
       },
     },
+    safeForUntrustedWebProcess: true,
     matches: [
       ...Services.prefs.getStringPref("zen.injections.match-urls").split(","),
       "about:preferences",
@@ -55,6 +56,7 @@ let JSWINDOWACTORS = {
     },
     allFrames: true,
     remoteTypes: ["web", "file"],
+    safeForUntrustedWebProcess: true,
     enablePreference: "zen.glance.enabled",
   },
   ZenWindowDrag: {
@@ -71,6 +73,7 @@ let JSWINDOWACTORS = {
     },
     messageManagerGroups: ["browsers"],
     remoteTypes: ["web", "file"],
+    safeForUntrustedWebProcess: true,
     enablePreference: "zen.view.drag-window-from-content",
   },
 };
@@ -88,6 +91,7 @@ if (!Services.appinfo.inSafeMode) {
         DOMWindowCreated: {},
       },
     },
+    safeForUntrustedWebProcess: true,
     allFrames: true,
     remoteTypes: ["web", "file"],
     enablePreference: "zen.boosts.enabled",
diff --git a/src/zen/common/sys/ZenUIMigration.sys.mjs b/src/zen/common/sys/ZenUIMigration.sys.mjs
index d025d97df..fd6bbe4f0 100644
--- a/src/zen/common/sys/ZenUIMigration.sys.mjs
+++ b/src/zen/common/sys/ZenUIMigration.sys.mjs
@@ -12,7 +12,7 @@ ChromeUtils.defineESModuleGetters(lazy, {
 
 class nsZenUIMigration {
   PREF_NAME = "zen.ui.migration.version";
-  MIGRATION_VERSION = 6;
+  MIGRATION_VERSION = 7;
 
   init(isNewProfile) {
     if (!isNewProfile) {
@@ -150,6 +150,20 @@ class nsZenUIMigration {
       }, 1000);
     });
   }
+
+  _migrateV7() {
+    if (
+      AppConstants.platform === "macosx" &&
+      Services.prefs.prefHasUserValue(
+        "widget.macos.sidebar-blend-mode.behind-window"
+      ) &&
+      !Services.prefs.getBoolPref(
+        "widget.macos.sidebar-blend-mode.behind-window"
+      )
+    ) {
+      Services.prefs.setBoolPref("zen.widget.macos.window-vibrancy", false);
+    }
+  }
 }
 
 export var gZenUIMigration = new nsZenUIMigration();
diff --git a/src/zen/compact-mode/ZenCompactMode.mjs b/src/zen/compact-mode/ZenCompactMode.mjs
index 9f85c4125..03ac69479 100644
--- a/src/zen/compact-mode/ZenCompactMode.mjs
+++ b/src/zen/compact-mode/ZenCompactMode.mjs
@@ -832,8 +832,9 @@ window.gZenCompactModeManager = {
 
       const onLeave = event => {
         if (AppConstants.platform == "macosx") {
-          const buttonRect =
-            gZenVerticalTabsManager.actualWindowButtons.getBoundingClientRect();
+          const buttonRect = window.windowUtils.getBoundsWithoutFlushing(
+            gZenVerticalTabsManager.actualWindowButtons
+          );
           const MAC_WINDOW_BUTTONS_X_BORDER = buttonRect.width + buttonRect.x;
           const MAC_WINDOW_BUTTONS_Y_BORDER = buttonRect.height + buttonRect.y;
           if (
diff --git a/src/zen/drag-and-drop/ZenDragAndDrop.js b/src/zen/drag-and-drop/ZenDragAndDrop.js
index c00e60543..355ba82a9 100644
--- a/src/zen/drag-and-drop/ZenDragAndDrop.js
+++ b/src/zen/drag-and-drop/ZenDragAndDrop.js
@@ -183,10 +183,10 @@
           if (tabClone.hasAttribute("visuallyselected")) {
             tabClone.style.transform = "translate(-50%, -50%)";
           }
-        } else if (AppConstants.platform !== "macosx" && !tab.isZenFolder) {
-          // On windows and linux, we still don't add some extra opaqueness
-          // for the tab to be more visible. This is a hacky workaround.
-          // TODO: Make windows and linux DnD use nsZenDragAndDrop::mDragImageOpacity
+        } else if (AppConstants.platform == "win" && !tab.isZenFolder) {
+          // On windows, the shell applies its own translucency to the drag
+          // image which we can't control, so force some extra contrast for
+          // the tab to be more visible. This is a hacky workaround.
           tabClone.style.colorScheme = "light";
           tabClone.style.setProperty("--tab-selected-textcolor", "black");
         }
diff --git a/src/zen/folders/zen-folders.css b/src/zen/folders/zen-folders.css
index f3ba4cdfd..a413d3445 100644
--- a/src/zen/folders/zen-folders.css
+++ b/src/zen/folders/zen-folders.css
@@ -60,7 +60,7 @@ zen-folder {
     }
   }
 
-  margin: 0 var(--tab-block-margin);
+  margin: 0 var(--tab-margin-block);
   margin-inline-end: 0;
 
   & > .tab-group-label-container {
@@ -70,7 +70,7 @@ zen-folder {
     --tab-group-color: transparent !important;
     padding-block-end: 0 !important;
     margin: 0 !important;
-    height: calc(var(--tab-block-margin) * 2 + var(--tab-min-height));
+    height: calc(var(--tab-margin-block) * 2 + var(--tab-min-height));
     padding-inline: var(--tab-group-label-padding);
 
     :root[zen-sidebar-expanded="true"] & {
@@ -161,7 +161,7 @@ zen-folder {
     }
 
     &:hover::before {
-      background-color: var(--tab-hover-background-color) !important;
+      background-color: var(--tab-background-color-hover) !important;
     }
 
     &:after {
diff --git a/src/zen/live-folders/ZenLiveFoldersManager.sys.mjs b/src/zen/live-folders/ZenLiveFoldersManager.sys.mjs
index c96b6eeb1..39f791b57 100644
--- a/src/zen/live-folders/ZenLiveFoldersManager.sys.mjs
+++ b/src/zen/live-folders/ZenLiveFoldersManager.sys.mjs
@@ -200,6 +200,50 @@ class nsZenLiveFoldersManager {
     return this.liveFolders.get(id);
   }
 
+  /**
+   * Returns the provider config needed to recreate this live folder on
+   * another device, or null for non-live folders. Fetch bookkeeping fields
+   * are stripped since they are device-local.
+   *
+   * @param {string} id - The folder ID.
+   */
+  getSyncableFolderData(id) {
+    const liveFolder = this.liveFolders.get(id);
+    if (!liveFolder) {
+      return null;
+    }
+    const state = { ...liveFolder.serialize().state };
+    delete state.lastFetched;
+    delete state.lastErrorId;
+    return { type: liveFolder.constructor.type, state };
+  }
+
+  /**
+   * Registers a live folder provider for a folder that arrived from
+   * Firefox Sync. The folder element must already exist.
+   *
+   * @param {string} id - The folder ID.
+   * @param {{ type: string, state: object }} config - Synced provider config.
+   */
+  async adoptSyncedFolder(id, { type, state } = {}) {
+    await this.stateRestored.promise;
+    if (this.liveFolders.has(id)) {
+      return;
+    }
+    const ProviderClass = this.registry.get(type);
+    if (!ProviderClass || !state) {
+      return;
+    }
+    const liveFolder = new ProviderClass({
+      id,
+      state: this.#applyDefaultStateValues({ ...state }),
+      manager: this,
+    });
+    this.liveFolders.set(id, liveFolder);
+    liveFolder.start();
+    this.saveState();
+  }
+
   async createFolder(type) {
     const [provider, providerType] = type.split(":");
     let ProviderClass = this.registry.get(provider);
@@ -324,7 +368,7 @@ class nsZenLiveFoldersManager {
               },
             ],
             content: {
-              width: "310px",
+              width: "312px",
               position: "callout",
               title_logo: {
                 imageURL: icon,
@@ -343,10 +387,6 @@ class nsZenLiveFoldersManager {
         ],
       },
     });
-
-    lazy.setTimeout(() => {
-      callout.endTour();
-    }, 10000);
   }
 
   deleteFolder(id, deleteFolder = true) {
@@ -623,6 +663,7 @@ class nsZenLiveFoldersManager {
   async #restoreState() {
     let data = await this.#readStateFromDisk();
     if (!Array.isArray(data)) {
+      this.stateRestored.resolve();
       return;
     }
 
diff --git a/src/zen/media/ZenMediaController.mjs b/src/zen/media/ZenMediaController.mjs
index 95ea84e72..fe0e927f1 100644
--- a/src/zen/media/ZenMediaController.mjs
+++ b/src/zen/media/ZenMediaController.mjs
@@ -12,7 +12,7 @@ XPCOMUtils.defineLazyPreferenceGetter(
 
 // Maximum number of cards shown in the stack; extra cards stay hidden until
 // a slot frees up.
-const MAX_STACKED_CARDS = 5;
+const MAX_STACKED_CARDS = 3;
 // How many background cards visually peek out at the top of the stack.
 // Deeper cards hide perfectly behind the last peeking one, so the stack
 // doesn't take more room with every extra card.
@@ -46,6 +46,10 @@ class ZenMediaCard {
     this.#initListeners();
 
     if (controller) {
+      // Queried before anything is wired up: it throws if the controller
+      // went away in the meantime, and the caller drops the card.
+      const positionState = controller.getPositionState();
+
       this.#controllerListeners = {
         positionstatechange: this.#onPositionstateChange.bind(this),
         playbackstatechange: this.#onPlaybackstateChange.bind(this),
@@ -62,7 +66,7 @@ class ZenMediaCard {
 
       this.element.classList.toggle("playing", controller.isPlaying);
       this.updateMetadata();
-      this.updatePositionState(controller.getPositionState());
+      this.updatePositionState(positionState);
       this.updateSupportedKeys();
     } else {
       this.element.setAttribute("media-sharing", "");
@@ -164,11 +168,33 @@ class ZenMediaCard {
   }
 
   setHidden(hidden) {
-    if (this.element.hidden === hidden) {
+    if (!hidden) {
+      // Showing cancels a hide that may still be animating.
+      this.element.removeAttribute("zen-hiding");
+      if (this.element.hidden) {
+        this.element.hidden = false;
+        this.manager.onCardVisibilityChanged();
+      }
       return;
     }
-    this.element.hidden = hidden;
-    this.manager.onCardVisibilityChanged();
+
+    if (this.element.hidden || this.element.hasAttribute("zen-hiding")) {
+      return;
+    }
+    this.element.setAttribute("zen-hiding", "true");
+    Promise.allSettled(
+      this.element.getAnimations().map(animation => animation.finished)
+    ).then(() => {
+      if (!this.element.hasAttribute("zen-hiding")) {
+        return;
+      }
+      this.element.removeAttribute("zen-hiding");
+      if (this.shouldBeVisible) {
+        return;
+      }
+      this.element.hidden = true;
+      this.manager.onCardVisibilityChanged();
+    });
   }
 
   // Mirrors the original bar behavior: hide instantly when the card's own
@@ -320,7 +346,7 @@ class ZenMediaCard {
 
   onToggle() {
     if (this.controller?.isPlaying) {
-      this.controller.pause();
+      this.controller.pause("user");
     } else {
       this.controller?.play();
     }
@@ -339,7 +365,7 @@ class ZenMediaCard {
   }
 
   onSeekDrag(event) {
-    this.controller?.pause();
+    this.controller?.pause("user");
     const newTime = (event.target.value / 100) * this.duration;
     this.currentTimeEl.textContent = this.formatSecondsToTime(newTime);
   }
@@ -382,7 +408,7 @@ class ZenMediaCard {
 
   onClose() {
     if (this.controller) {
-      this.controller.pause();
+      this.controller.pause("user");
     } else {
       const webRTC =
         this.browser.browsingContext.currentWindowGlobal.getActor("WebRTC");
@@ -412,7 +438,25 @@ class ZenMediaCard {
       this.#tabTimeout = null;
     }
 
-    this.element.remove();
+    const { element } = this;
+    if (element.hidden) {
+      element.remove();
+    } else {
+      // Animate the card out instead of popping it away. It leaves the
+      // flex flow immediately (so the remaining cards re-slot right away)
+      // but stays anchored where it currently is while it sinks and fades.
+      const barBottom =
+        this.manager.mediaControlBar.getBoundingClientRect().bottom;
+      element.style.bottom =
+        barBottom - element.getBoundingClientRect().bottom + "px";
+      element.setAttribute("zen-removing", "true");
+      // Resolves once the exit transitions finish or get cancelled, and
+      // immediately if they never start (e.g. reduced motion).
+      Promise.allSettled(
+        element.getAnimations().map(animation => animation.finished)
+      ).then(() => element.remove());
+    }
+
     this.manager.onCardDestroyed(this);
   }
 }
@@ -450,20 +494,49 @@ class nsZenMediaController {
     window.addEventListener("TabClose", onTabDiscardedOrClosed);
     window.addEventListener("TabBrowserDiscarded", onTabDiscardedOrClosed);
 
-    window.addEventListener("DOMAudioPlaybackStarted", event => {
-      this.activateMediaControls(
-        event.target.browsingContext.mediaController,
-        event.target
-      );
-    });
-
-    window.addEventListener("DOMAudioPlaybackStopped", () => {
-      for (const card of this.#cards.values()) {
-        card.updateMuteState();
+    window.addEventListener("TabAttrModified", event => {
+      if (!event.detail.changed.includes("soundplaying")) {
+        return;
       }
+      const tab = event.target;
+      if (!tab.hasAttribute("soundplaying")) {
+        this.onAudioPlaybackStopped();
+        return;
+      }
+      this.onAudioPlaybackStarted(tab.linkedBrowser);
     });
   }
 
+  onAudioPlaybackStarted(browser) {
+    // The card is created right away (while the controller is fresh) but
+    // only shown if the media is still playing a moment later, so short
+    // sounds (e.g. notification pings) never reveal it.
+    setTimeout(() => {
+      const card = this.#cardForBrowser(browser);
+      if (!card || card.isSharing) {
+        return;
+      }
+      if (card.controller.isPlaying) {
+        card.refreshVisibility();
+      } else if (card.element.hidden) {
+        // The sound was over before ever being shown (e.g. a notification
+        // ping): drop the card instead of keeping a ghost around.
+        card.destroy();
+      }
+    }, 1000);
+
+    this.activateMediaControls(
+      browser.browsingContext?.mediaController,
+      browser
+    );
+  }
+
+  onAudioPlaybackStopped() {
+    for (const card of this.#cards.values()) {
+      card.updateMuteState();
+    }
+  }
+
   get frontCard() {
     return this.#orderedCards.find(card => !card.element.hidden) ?? null;
   }
@@ -483,8 +556,23 @@ class nsZenMediaController {
     );
   }
 
+  #cardForBrowser(browser) {
+    return (
+      Array.from(this.#cards.values()).find(
+        card => card.browser.browserId === browser.browserId
+      ) ?? null
+    );
+  }
+
   activateMediaControls(mediaController, browser) {
-    if (!mediaController?.isActive || this.#cards.has(mediaController.id)) {
+    if (
+      !mediaController?.isActive ||
+      this.#cards.has(mediaController.id) ||
+      // Never stack more than one card for the same browser: sites that
+      // activate a fresh controller for every sound they play (e.g.
+      // notification pings) keep their one card.
+      this.#cardForBrowser(browser)
+    ) {
       return;
     }
 
@@ -570,9 +658,24 @@ class nsZenMediaController {
 
   #addCard(key, browser, controller = null) {
     const element = this.#createCardElement();
-    const card = new ZenMediaCard(this, element, browser, controller);
+    let card;
+    try {
+      card = new ZenMediaCard(this, element, browser, controller);
+    } catch (e) {
+      console.error("Failed to create media card", e);
+      // The controller went away while the card was being set up.
+      element.remove();
+      return null;
+    }
     this.#cards.set(key, card);
-    card.refreshVisibility();
+    if (controller) {
+      // Media cards start hidden and appear via the delayed check in
+      // onAudioPlaybackStarted or on tab switch, like the original bar;
+      // sharing cards show right away.
+      card.element.hidden = true;
+    } else {
+      card.refreshVisibility();
+    }
     this.onCardVisibilityChanged();
     return card;
   }
@@ -589,18 +692,31 @@ class nsZenMediaController {
       card => !card.element.hidden
     );
 
+    // Re-slot the indices without transitions first: the index transform
+    // only compensates the flex-order shift, so a reindexed card keeps
+    // its visual position through this step.
     visibleCards.forEach((card, index) => {
       card.element.toggleAttribute(
         "stack-overflow",
         index >= MAX_STACKED_CARDS
       );
       card.element.toggleAttribute("stacked-behind", index > 0);
+      card.element.setAttribute("zen-reindexing", "true");
       card.element.style.setProperty("--zen-media-card-index", index);
+      card.element.style.zIndex = 100 - index;
+    });
+
+    // Flush styles so the re-slotting lands instantly...
+    this.mediaControlBar.getBoundingClientRect();
+
+    // ...then animate only the peek level: demoted cards slide up from
+    // behind the front card instead of dropping in from above.
+    visibleCards.forEach((card, index) => {
+      card.element.removeAttribute("zen-reindexing");
       card.element.style.setProperty(
         "--zen-media-card-peek-level",
         Math.min(index, MAX_PEEK_LEVELS)
       );
-      card.element.style.zIndex = 100 - index;
     });
 
     const stackedCount = Math.min(visibleCards.length, MAX_STACKED_CARDS);
diff --git a/src/zen/media/zen-media-controls.css b/src/zen/media/zen-media-controls.css
index cd99f79d8..a3c0c9d7e 100644
--- a/src/zen/media/zen-media-controls.css
+++ b/src/zen/media/zen-media-controls.css
@@ -9,6 +9,7 @@
   --button-spacing: 2px;
   --zen-media-stack-peek: 8px;
   --zen-media-stack-gap: 6px;
+  --zen-media-stack-easing: cubic-bezier(0.25, 1, 0.5, 1);
 
   display: flex;
   min-width: 0;
@@ -88,7 +89,7 @@
       animation: zen-back-and-forth-text 10s infinite ease-in-out;
     }
 
-    & .zen-media-card {
+    & .zen-media-card:not([zen-removing], [zen-hiding]) {
       transform: none;
       opacity: 1;
     }
@@ -114,10 +115,10 @@
     padding: 0 6px;
     pointer-events: none;
     transition:
-      max-height 0.2s ease,
-      opacity 0.2s ease,
-      transform 0.2s ease,
-      padding 0.2s ease;
+      max-height 0.3s var(--zen-media-stack-easing),
+      opacity 0.3s var(--zen-media-stack-easing),
+      transform 0.3s var(--zen-media-stack-easing),
+      padding 0.3s var(--zen-media-stack-easing);
   }
 
   .zen-media-current-time,
@@ -137,6 +138,9 @@
   width: 100%;
   padding: 4px 6px;
   border-radius: var(--border-radius-medium);
+  @media (-moz-platform: macos) {
+    border-radius: calc(var(--border-radius-medium) - 2px);
+  }
   outline: var(--zen-sidebar-notification-outline);
   outline-offset: -1.5px;
   box-shadow: var(--zen-sidebar-notification-shadow);
@@ -149,12 +153,47 @@
       )
     )
     scale(calc(1 - 0.04 * var(--zen-media-card-peek-level, 0)));
-  opacity: calc(1 - 0.4 * var(--zen-media-card-peek-level, 0));
+  opacity: calc(1 - 0.3 * var(--zen-media-card-peek-level, 0));
+  filter: blur(0);
   transition:
-    transform 0.1s ease-out,
-    opacity 0.2s ease-out,
+    transform 0.35s var(--zen-media-stack-easing),
+    opacity 0.3s var(--zen-media-stack-easing),
+    filter 0.3s var(--zen-media-stack-easing),
     padding 0.3s ease-out;
 
+  @starting-style {
+    opacity: 0;
+    transform: translateY(0.5rem);
+    filter: blur(4px);
+  }
+
+  &[zen-reindexing] {
+    transition: none;
+  }
+
+  /* Removed and hiding cards sink down behind the stack while fading out */
+  &[zen-removing],
+  &[zen-hiding] {
+    translate: 0 0.5rem;
+    opacity: 0;
+    filter: blur(2px);
+    pointer-events: none;
+    transition:
+      translate 0.3s var(--zen-media-stack-easing),
+      opacity 0.3s var(--zen-media-stack-easing),
+      filter 0.3s var(--zen-media-stack-easing);
+  }
+
+  /* Removed cards additionally leave the flex flow instantly (bottom is
+     set inline to where the card was), so only translate/opacity/filter
+     animate; hiding cards stay in flow until the animation finishes. */
+  &[zen-removing] {
+    position: absolute;
+    left: 0;
+    width: 100%;
+    transform: none;
+  }
+
   &[stack-overflow] {
     display: none;
   }
@@ -249,7 +288,7 @@
     overflow: visible;
     position: relative;
     z-index: 2;
-    transition: height 0.2s ease-out;
+    transition: height 0.3s var(--zen-media-stack-easing);
   }
 }
 
diff --git a/src/zen/sessionstore/ZenSessionManager.sys.mjs b/src/zen/sessionstore/ZenSessionManager.sys.mjs
index 594ae490c..4b883ef02 100644
--- a/src/zen/sessionstore/ZenSessionManager.sys.mjs
+++ b/src/zen/sessionstore/ZenSessionManager.sys.mjs
@@ -10,7 +10,6 @@ const lazy = {};
 ChromeUtils.defineESModuleGetters(lazy, {
   ZenLiveFoldersManager:
     "resource:///modules/zen/ZenLiveFoldersManager.sys.mjs",
-  ZenSyncStore: "resource:///modules/zen/ZenSyncManager.sys.mjs",
   PrivateBrowsingUtils: "resource://gre/modules/PrivateBrowsingUtils.sys.mjs",
   SessionStore: "resource:///modules/sessionstore/SessionStore.sys.mjs",
   SessionStartup: "resource:///modules/sessionstore/SessionStartup.sys.mjs",
@@ -611,7 +610,9 @@ export class nsZenSessionManager {
       }
     );
     this.#collectWindowData(windows);
-    lazy.ZenSyncStore.notifyAboutChanges();
+    // Let interested consumers (e.g. Firefox Sync) know fresh sidebar data
+    // is available, without this module knowing anything about them.
+    Services.obs.notifyObservers(null, "zen-sidebar-data-collected");
     // This would save the data to disk asynchronously or when quitting the app.
     let sidebar = this.#sidebarWithoutCloning;
     this.#file.data = sidebar;
diff --git a/src/zen/sessionstore/ZenWindowSync.sys.mjs b/src/zen/sessionstore/ZenWindowSync.sys.mjs
index 452ab5fd8..f19316ab4 100644
--- a/src/zen/sessionstore/ZenWindowSync.sys.mjs
+++ b/src/zen/sessionstore/ZenWindowSync.sys.mjs
@@ -606,7 +606,9 @@ class nsZenWindowSync {
     if (isTab) {
       if (originalIsEssential !== targetIsEssential) {
         if (originalIsEssential) {
-          gZenPinnedTabManager.addToEssentials(aTargetItem);
+          gZenPinnedTabManager.addToEssentials(aTargetItem, {
+            replicating: true,
+          });
         } else {
           gZenPinnedTabManager.removeEssentials(
             aTargetItem,
@@ -1232,7 +1234,7 @@ class nsZenWindowSync {
       activeIndex = Math.min(activeIndex, entries.length - 1);
       activeIndex = Math.max(activeIndex, 0);
       let entryToUse = (entries[activeIndex] || entries[0]) ?? null;
-      this.#setPinnedInitialState(
+      this.setPinnedInitialState(
         aTab,
         { url: entryToUse?.url, title: entryToUse?.title },
         image
@@ -1250,14 +1252,22 @@ class nsZenWindowSync {
    */
   setPinnedUrl(aTab, aUrl, aImage) {
     this.log(`Setting pinned url for tab ${aTab.id}`);
-    this.#setPinnedInitialState(
+    this.setPinnedInitialState(
       aTab,
       { url: aUrl, title: aTab.zenStaticLabel },
       aImage
     );
   }
 
-  #setPinnedInitialState(aTab, aEntry, aImage) {
+  /**
+   * Sets the pinned initial state (canonical entry and icon) for a tab's
+   * instances across all windows.
+   *
+   * @param {object} aTab - Any window's instance of the tab.
+   * @param {object} aEntry - The canonical { url, title } entry.
+   * @param {string} [aImage] - Optional icon to store.
+   */
+  setPinnedInitialState(aTab, aEntry, aImage) {
     const initialState = { entry: aEntry, image: aImage };
     this.#runOnAllWindows(null, win => {
       const targetTab = this.getItemFromWindow(win, aTab.id);
@@ -1362,7 +1372,9 @@ class nsZenWindowSync {
       return;
     }
     tab._zenContentsVisible = true;
-    tab.id = this.#newTabSyncId;
+    if (!tab.id) {
+      tab.id = this.#newTabSyncId;
+    }
     if (lazy.gSyncOnlyPinnedTabs && !tab.pinned) {
       return;
     }
@@ -1373,6 +1385,7 @@ class nsZenWindowSync {
       const newTab = win.gBrowser.addTrustedTab("about:blank", {
         animate: true,
         createLazyBrowser: true,
+        userContextId: tab.userContextId,
         _forZenEmptyTab: tab.hasAttribute("zen-empty-tab"),
       });
       newTab.id = tab.id;
diff --git a/src/zen/space-routing/ZenSpaceRoutingManager.sys.mjs b/src/zen/space-routing/ZenSpaceRoutingManager.sys.mjs
index 7622417d8..0a0c70185 100644
--- a/src/zen/space-routing/ZenSpaceRoutingManager.sys.mjs
+++ b/src/zen/space-routing/ZenSpaceRoutingManager.sys.mjs
@@ -27,7 +27,7 @@ class nsZenSpaceRoutingManager {
     const element = window.MozXULElement.parseXULToFragment(`
         <menuseparator/>
         <menuitem id="context_zen-add-domain-to-routing"
-                  data-lazy-l10n-id="tab-context-zen-add-domain-to-sr"
+                  data-l10n-id="tab-context-zen-add-domain-to-sr"
                   data-l10n-args='{"tabCount": 1}'/>
       `);
     window.document.getElementById("context_undoCloseTab").after(element);
diff --git a/src/zen/spaces/ZenGradientGenerator.mjs b/src/zen/spaces/ZenGradientGenerator.mjs
index b73266457..28a47f31a 100644
--- a/src/zen/spaces/ZenGradientGenerator.mjs
+++ b/src/zen/spaces/ZenGradientGenerator.mjs
@@ -542,22 +542,22 @@ export class nsZenThemePicker extends nsZenMultiWindowFeature {
     const centerX = rect.width / 2;
     const centerY = rect.height / 2;
     const radius = (rect.width - padding) / 2;
-    const distance = Math.sqrt((x - centerX) ** 2 + (y - centerY) ** 2);
+    const distance = Math.sqrt((x - centerX) ** 2 + (y - centerY) ** 2) - 0.2;
     let angle = Math.atan2(y - centerY, x - centerX);
-    angle = (angle * 180) / Math.PI; // Convert to degrees
+    angle = (angle * 180) / Math.PI;
     if (angle < 0) {
-      angle += 360; // Normalize to [0, 360)
+      angle += 360;
     }
-    const normalizedDistance = 1 - Math.min(distance / radius, 1); // Normalize distance to [0, 1]
-    let hue = (angle / 360) * 360; // Normalize angle to [0, 360)
-    let saturation = normalizedDistance * 100; // stays high even in center
+    const normalizedDistance = 1 - Math.min(distance / radius, 1);
+    let hue = (angle / 360) * 360;
+    let saturation = normalizedDistance * 100;
     if (type !== EXPLICIT_LIGHTNESS_TYPE) {
       saturation = 90 + (1 - normalizedDistance) * 10;
       // Set the current lightness to how far we are from the center of the circle
       // For example, moving the dot outside will have higher lightness, while moving it inside will have lower lightness
       this.#currentLightness = Math.round((1 - normalizedDistance) * 100);
     }
-    let lightness = this.#currentLightness; // Fixed lightness for simplicity
+    let lightness = this.#currentLightness;
     if (type === EXPLICIT_BLACKWHITE_TYPE) {
       // We can only get grayscales from white to black
       saturation = 0;
@@ -1259,10 +1259,10 @@ export class nsZenThemePicker extends nsZenMultiWindowFeature {
     let colorToBlendOpacity;
     if (this.isMica) {
       colorToBlend = this.isDarkMode ? [0, 0, 0] : [255, 255, 255];
-      colorToBlendOpacity = 0.12;
+      colorToBlendOpacity = 0.3;
     } else if (AppConstants.platform === "macosx") {
       colorToBlend = [255, 255, 255];
-      colorToBlendOpacity = 0.18;
+      colorToBlendOpacity = 0.6;
     }
     if (colorToBlend) {
       const blendedAlpha = Math.min(
@@ -1495,9 +1495,17 @@ export class nsZenThemePicker extends nsZenMultiWindowFeature {
     return color;
   }
 
-  getToolbarColor(isDarkMode = false) {
-    const opacity = 0.8;
+  getToolbarColor(isDarkMode = false, accentColor = undefined) {
+    const opacity = 0.9;
     let baseColor = isDarkMode ? [255, 255, 255, opacity] : [0, 0, 0, opacity]; // Default toolbar
+    if (accentColor) {
+      // Blend a bit with the accent color to make it more visible
+      baseColor = this.blendColors(
+        accentColor,
+        baseColor.slice(0, 3),
+        this.canBeTransparent ? 15 : 5
+      ).concat(opacity);
+    }
     return baseColor;
   }
 
@@ -1763,7 +1771,7 @@ export class nsZenThemePicker extends nsZenMultiWindowFeature {
         docElement.style.setProperty("--zen-primary-color", primaryColor);
 
         // Set `--toolbox-textcolor` to have a contrast with the primary color
-        let textColor = this.getToolbarColor(isDarkMode);
+        let textColor = this.getToolbarColor(isDarkMode, dominantColor);
         docElement.style.setProperty(
           "--toolbox-textcolor",
           `rgba(${textColor[0]}, ${textColor[1]}, ${textColor[2]}, ${textColor[3]})`
@@ -2009,7 +2017,7 @@ export class nsZenThemePicker extends nsZenMultiWindowFeature {
       grain: theme.texture ?? 0,
       isDarkMode,
       isExplicitMode,
-      toolbarColor: this.getToolbarColor(isDarkMode),
+      toolbarColor: this.getToolbarColor(isDarkMode, dominantColor),
       primaryColor: this.getAccentColorForUI(dominantColor, isDarkMode),
     };
     this.currentOpacity = previousOpacity;
diff --git a/src/zen/spaces/ZenSpaceManager.mjs b/src/zen/spaces/ZenSpaceManager.mjs
index e4a31b5a8..6da584818 100644
--- a/src/zen/spaces/ZenSpaceManager.mjs
+++ b/src/zen/spaces/ZenSpaceManager.mjs
@@ -11,7 +11,6 @@ const lazy = {};
 
 ChromeUtils.defineESModuleGetters(lazy, {
   ZenSessionStore: "resource:///modules/zen/ZenSessionManager.sys.mjs",
-  ZenSyncStore: "resource:///modules/zen/ZenSyncManager.sys.mjs",
 });
 
 ChromeUtils.defineLazyGetter(lazy, "browserBackgroundElement", () => {
@@ -173,63 +172,6 @@ class nsZenWorkspaces {
     }
   }
 
-  /**
-   * Applies live sync changes: updates workspace cache, removes deleted items,
-   * then creates/updates pulled items.
-   *
-   * @param {{ spaces: Array}} pulled  Reconcile-pulled items.
-   * @param {{ spaces: Array}} removals  Items to remove.
-   */
-  async _applySyncChanges(pulled, removals = {}) {
-    if (!this.shouldHaveWorkspaces || this.privateWindowOrDisabled) {
-      return;
-    }
-    await this.promiseInitialized;
-
-    // 1. Update workspace cache (remove deleted, merge pulled)
-    const removedSpaceIds = new Set((removals.spaces || []).map(s => s.uuid));
-    if (removedSpaceIds.size || pulled.spaces?.length) {
-      const localMap = new Map(
-        this.getWorkspaces()
-          .filter(w => !removedSpaceIds.has(w.uuid))
-          .map(w => [w.uuid, w])
-      );
-      for (const space of pulled.spaces || []) {
-        if (!space?.uuid) {
-          continue;
-        }
-        const existing = localMap.get(space.uuid);
-        localMap.set(space.uuid, existing ? { ...existing, ...space } : space);
-      }
-      await this.propagateWorkspaces(
-        this.#getOrderedWorkspacesByPosition(Array.from(localMap.values()))
-      );
-      this.#propagateWorkspaceData();
-    }
-  }
-
-  #getOrderedWorkspacesByPosition(workspaces) {
-    return [...workspaces]
-      .map((workspace, index) => ({ workspace, index }))
-      .sort((a, b) => {
-        const aPosition =
-          typeof a.workspace.position === "number"
-            ? a.workspace.position
-            : a.index;
-        const bPosition =
-          typeof b.workspace.position === "number"
-            ? b.workspace.position
-            : b.index;
-        return aPosition - bPosition || a.index - b.index;
-      })
-      .map(({ workspace }) => {
-        // strip the position property that comes from pulled workspaces
-        const rest = { ...workspace };
-        delete rest.position;
-        return rest;
-      });
-  }
-
   #afterLoadInit() {
     const onResize = (...args) => {
       requestAnimationFrame(() => {
@@ -649,6 +591,7 @@ class nsZenWorkspaces {
         if (Math.abs(delta) < scrollThreshold) {
           return;
         }
+        event.preventDefault();
 
         // Determine scroll direction
         let rawDirection = delta > 0 ? 1 : -1;
@@ -861,13 +804,6 @@ class nsZenWorkspaces {
     })();
   }
 
-  #markWorkspaceChanged(workspaceId) {
-    lazy.ZenSyncStore.markItemChanged({
-      type: "space",
-      id: workspaceId,
-    });
-  }
-
   async selectStartPage() {
     if (!this.workspaceEnabled || gZenUIManager.testingEnabled) {
       return;
@@ -1296,8 +1232,6 @@ class nsZenWorkspaces {
     } else {
       workspacesData.push(workspaceData);
     }
-    // mark item as changed for sync
-    this.#markWorkspaceChanged(workspaceData.uuid);
 
     this.#propagateWorkspaceData();
   }
@@ -1306,9 +1240,6 @@ class nsZenWorkspaces {
     let { promise, resolve } = Promise.withResolvers();
     this.#deleteWorkspaceOwnedTabs(windowID);
 
-    // mark item as changed for sync
-    this.#markWorkspaceChanged(windowID);
-
     let workspacesData = this.getWorkspaces();
     // Remove the workspace from the cache
     workspacesData = workspacesData.filter(
@@ -1441,11 +1372,6 @@ class nsZenWorkspaces {
       return;
     }
     const workspaces = this.getWorkspaces();
-    // Track previous positions so we only notify observers for workspaces whose
-    // position changed during the reorder.
-    const previousPositions = new Map(
-      workspaces.map((workspace, index) => [workspace.uuid, index])
-    );
 
     const workspace = workspaces.find(w => w.uuid === id);
     if (!workspace) {
@@ -1474,15 +1400,6 @@ class nsZenWorkspaces {
     // Propagate the changes if the order has changed
     if (currentIndex !== newPosition) {
       this._workspaceCache = workspaces;
-
-      for (const [i, ws] of workspaces.entries()) {
-        if (previousPositions.get(ws.uuid) === i) {
-          continue;
-        }
-        // mark item as changed for sync
-        this.#markWorkspaceChanged(ws.uuid);
-      }
-
       this.#propagateWorkspaceData(workspaces);
     }
   }
@@ -1789,6 +1706,15 @@ class nsZenWorkspaces {
   }
 
   makeSureEmptyTabIsFirst() {
+    if (
+      gZenUIManager.testingEnabled &&
+      this._emptyTab &&
+      (this._emptyTab.closing || !this._emptyTab.isConnected)
+    ) {
+      this._emptyTab = gBrowser.tabs.find(
+        tab => tab.hasAttribute("zen-empty-tab") && !tab.closing
+      );
+    }
     const emptyTab = this._emptyTab;
     if (emptyTab) {
       emptyTab.setAttribute("zen-workspace-id", this.activeWorkspace);
@@ -1845,8 +1771,10 @@ class nsZenWorkspaces {
       )
     ) {
       delete this._alwaysAnimatePaddingTop;
-      const essentialsHeight =
-        window.windowUtils.getBoundsWithoutFlushing(essentialContainer).height;
+      const essentialsHeight = Math.max(
+        2,
+        window.windowUtils.getBoundsWithoutFlushing(essentialContainer).height
+      );
       requestAnimationFrame(() => {
         workspaceElement.style.paddingTop = essentialsHeight + "px";
       });
@@ -3317,8 +3245,10 @@ class nsZenWorkspaces {
       return width;
     }, 0);
 
-    // Check if the total width exceeds the parent's width
-    if (totalWidth > parent.clientWidth) {
+    // Check if the total width exceeds the parent's width.
+    const parentWidth =
+      window.windowUtils.getBoundsWithoutFlushing(parent).width;
+    if (totalWidth > parentWidth) {
       parent.setAttribute("icons-overflow", "true");
     } else {
       parent.removeAttribute("icons-overflow");
@@ -3326,7 +3256,7 @@ class nsZenWorkspaces {
 
     // Set the width of each icon to the maximum size they can fit on
     const widthPerButton = Math.max(
-      (parent.clientWidth - separation * (parent.children.length - 1)) /
+      (parentWidth - separation * (parent.children.length - 1)) /
         parent.children.length,
       minButtonSize
     );
diff --git a/src/zen/spaces/zen-workspaces.css b/src/zen/spaces/zen-workspaces.css
index 084afa712..b510c7d18 100644
--- a/src/zen/spaces/zen-workspaces.css
+++ b/src/zen/spaces/zen-workspaces.css
@@ -206,7 +206,7 @@
     &:hover,
     &[open='true'] {
       &::before {
-        background: var(--tab-hover-background-color);
+        background: var(--tab-background-color-hover);
       }
     }
   }
@@ -322,10 +322,10 @@ zen-workspace {
   position: absolute;
   height: 100%;
   overflow: hidden;
-  color: color-mix(in srgb, var(--toolbox-textcolor) 95%, var(--zen-primary-color));
+  color: var(--toolbox-textcolor);
 
   --tab-background-color-selected: color-mix(in srgb, light-dark(rgba(255, 255, 255, 0.8), rgba(255, 255, 255, 0.18)) 95%, var(--zen-primary-color)) !important;
-  --tab-selected-shadow: 0 0.8px 1.5px 0px light-dark(rgba(0, 0, 0, 0.15), rgba(0, 0, 0, 0.05)) !important;
+  --tab-box-shadow-selected: 0 0.8px 1.5px 0px light-dark(rgba(0, 0, 0, 0.15), rgba(0, 0, 0, 0.05)) !important;
   --tab-selected-textcolor: color-mix(in srgb, var(--toolbox-textcolor) 95%, var(--zen-primary-color)) !important;
 
   @media not (prefers-reduced-motion: reduce) {
diff --git a/src/zen/split-view/ZenViewSplitter.mjs b/src/zen/split-view/ZenViewSplitter.mjs
index bf8c489a9..f1b63c5de 100644
--- a/src/zen/split-view/ZenViewSplitter.mjs
+++ b/src/zen/split-view/ZenViewSplitter.mjs
@@ -230,7 +230,10 @@ class nsZenViewSplitter extends nsZenDOMOperatedFeature {
       }
       this.removeGroup(groupIndex);
       if (changeTab) {
-        gBrowser.selectedTab = remainingTabs[0];
+        const tabToSelect = remainingTabs.find(remaining => remaining !== tab);
+        if (tabToSelect) {
+          gBrowser.selectedTab = tabToSelect;
+        }
         document
           .getElementById("cmd_zenNewEmptySplit")
           .removeAttribute("disabled");
@@ -1398,7 +1401,12 @@ class nsZenViewSplitter extends nsZenDOMOperatedFeature {
     const tabIndexToUse = Math.max(0, initialIndex);
     return this.#withoutSplitViewTransition(() => {
       // TODO: Add support for splitting essential tabs
-      tabs = tabs.filter(t => !t.hidden && !t.hasAttribute("zen-empty-tab"));
+      tabs = tabs
+        .filter(t => !t.hidden && !t.hasAttribute("zen-empty-tab"))
+        // use glance parent tab instead of glance tab
+        .map(t => gZenGlanceManager.getTabOrGlanceParent(t))
+        // remove duplicates
+        .filter((t, i, arr) => arr.indexOf(t) === i);
       if (tabs.length < 2 || tabs.length > this.MAX_TABS) {
         return;
       }
@@ -1559,11 +1567,20 @@ class nsZenViewSplitter extends nsZenDOMOperatedFeature {
     if (reset) {
       this.removeSplitters();
     }
-    splitData.tabs.forEach(tab => {
-      if (tab.hasAttribute("pending")) {
-        gBrowser.getBrowserForTab(tab).reload();
-      }
-    });
+    const pendingTabs = splitData.tabs.filter(tab =>
+      tab.hasAttribute("pending")
+    );
+    if (pendingTabs.length) {
+      pendingTabs.forEach(tab => gBrowser._insertBrowser(tab));
+      // SessionStore listens for this on the tab container and restores each
+      // tab's saved history, scroll position and form data. Kept non-bubbling
+      // so it doesn't reach tabbrowser, which tracks Firefox's own split view.
+      gBrowser.tabContainer.dispatchEvent(
+        new CustomEvent("TabSplitViewActivate", {
+          detail: { tabs: pendingTabs },
+        })
+      );
+    }
 
     // Apply grid to tabs first to set zen-split attribute on containers
     // before setting zen-split-view on parents. This prevents the black flash
@@ -2516,22 +2533,33 @@ class nsZenViewSplitter extends nsZenDOMOperatedFeature {
       this.activateSplitView(data);
       gBrowser.selectedTab = emptyTab;
       setTimeout(() => {
+        const closeToken = {};
+        const controller = new AbortController();
+        const cleanup = (onSwitch = false, groupIndex = null) => {
+          if (groupIndex === null) {
+            groupIndex = this._data.findIndex(group =>
+              group.tabs.includes(emptyTab)
+            );
+          }
+          this.removeTabFromGroup(emptyTab, groupIndex, {
+            changeTab: !onSwitch,
+            forUnsplit: true,
+          });
+          const command = document.getElementById("cmd_zenNewEmptySplit");
+          command.removeAttribute("disabled");
+        };
         window.addEventListener(
           "ZenURLBarClosed",
           event => {
+            if (!gZenUIManager.matchesCloseToken(closeToken, event)) {
+              return;
+            }
+            controller.abort();
             const { onElementPicked, onSwitch } = event.detail;
             const groupIndex = this._data.findIndex(group =>
               group.tabs.includes(emptyTab)
             );
             const newSelectedTab = gBrowser.selectedTab;
-            const cleanup = () => {
-              this.removeTabFromGroup(emptyTab, groupIndex, {
-                changeTab: !onSwitch,
-                forUnsplit: true,
-              });
-              const command = document.getElementById("cmd_zenNewEmptySplit");
-              command.removeAttribute("disabled");
-            };
             if (onElementPicked) {
               if (
                 newSelectedTab === emptyTab ||
@@ -2539,7 +2567,7 @@ class nsZenViewSplitter extends nsZenDOMOperatedFeature {
                 selectedTab.getAttribute("zen-workspace-id") !==
                   newSelectedTab.getAttribute("zen-workspace-id")
               ) {
-                cleanup();
+                cleanup(onSwitch, groupIndex);
                 return;
               }
               this.removeTabFromGroup(emptyTab, groupIndex, {
@@ -2555,12 +2583,17 @@ class nsZenViewSplitter extends nsZenDOMOperatedFeature {
                 topOrLeft ? 0 : 1
               );
             } else {
-              cleanup();
+              cleanup(onSwitch, groupIndex);
             }
           },
-          { once: true }
+          { signal: controller.signal }
         );
-        gZenUIManager.handleNewTab(false, false, "tab", true);
+        if (
+          !gZenUIManager.handleNewTab(false, false, "tab", true, closeToken)
+        ) {
+          controller.abort();
+          cleanup();
+        }
       });
     });
   }
diff --git a/src/zen/split-view/zen-split-group.inc.css b/src/zen/split-view/zen-split-group.inc.css
index 420bfc9b1..1cf48c6ba 100644
--- a/src/zen/split-view/zen-split-group.inc.css
+++ b/src/zen/split-view/zen-split-group.inc.css
@@ -38,8 +38,8 @@ tab-group[split-view-group] {
 
     border-radius: var(--border-radius-medium);
     padding: 0 2px;
-    margin-inline: var(--tab-block-margin);
-    margin-block: var(--tab-block-margin);
+    margin-inline: var(--tab-margin-block);
+    margin-block: var(--tab-margin-block);
     min-height: var(--tab-min-height);
     outline: var(--tab-outline);
     outline-offset: var(--tab-outline-offset);
@@ -58,8 +58,8 @@ tab-group[split-view-group] {
 
     & > .tabbrowser-tab {
       --tab-background-color-selected: var(--zen-split-view-active-tab-bg);
-      --tab-hover-background-color: transparent;
-      --tab-selected-shadow: none;
+      --tab-background-color-hover: transparent;
+      --tab-box-shadow-selected: none;
       --border-radius-medium: var(--tab-border-radius);
       --zen-active-tab-scale: 1;
       --zen-folder-indent: 0 !important;
@@ -105,12 +105,12 @@ tab-group[split-view-group] {
     }
 
     tab-group[split-view-group]:where([hasactivetab]) &,
-    &:has(> tab:is([multiselected])) {
+    &:has(> tab:is([multiselected, visuallyselected])) {
       background-color: var(--tab-background-color-selected);
-      box-shadow: var(--tab-selected-shadow);
+      box-shadow: var(--tab-box-shadow-selected);
 
       & > .tabbrowser-tab {
-        --tab-hover-background-color: var(--zen-split-view-active-tab-bg);
+        --tab-background-color-hover: var(--zen-split-view-active-tab-bg);
         & .tab-background {
           background-color: var(--zen-split-view-active-tab-bg) !important;
         }
diff --git a/src/zen/split-view/zen-split-view.css b/src/zen/split-view/zen-split-view.css
index 6e856e9db..68543ca7e 100644
--- a/src/zen/split-view/zen-split-view.css
+++ b/src/zen/split-view/zen-split-view.css
@@ -261,6 +261,6 @@
 zen-split-fake-tab {
   border-radius: var(--border-radius-medium);
   background-color: color-mix(in srgb, var(--button-background-color-primary), transparent 40%);
-  margin: var(--tab-block-margin);
+  margin: var(--tab-margin-block);
   flex: 1;
 }
diff --git a/src/zen/sync/ZenSpacesSync.sys.mjs b/src/zen/sync/ZenSpacesSync.sys.mjs
new file mode 100644
index 000000000..e94e0c13d
--- /dev/null
+++ b/src/zen/sync/ZenSpacesSync.sys.mjs
@@ -0,0 +1,182 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+import {
+  Store,
+  SyncEngine,
+  Tracker,
+} from "resource://services-sync/engines.sys.mjs";
+import { CryptoWrapper } from "resource://services-sync/record.sys.mjs";
+import { SCORE_INCREMENT_XLARGE } from "resource://services-sync/constants.sys.mjs";
+import {
+  SIDEBAR_COLLECTED_TOPIC,
+  syncLog,
+  ZenSpacesSyncModel,
+} from "resource:///modules/zen/ZenSpacesSyncModel.sys.mjs";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  ZenSpacesSyncApplier: "resource:///modules/zen/ZenSpacesSyncApplier.sys.mjs",
+});
+
+const TRACKED_TOPICS = [
+  SIDEBAR_COLLECTED_TOPIC,
+  "contextual-identity-created",
+  "contextual-identity-updated",
+  "contextual-identity-deleted",
+];
+
+export class ZenSpacesSyncRecord extends CryptoWrapper {
+  _logName = "Sync.Record.ZenSpaces";
+}
+
+ZenSpacesSyncRecord.prototype.type = "spaces";
+
+/**
+ * Store for the Spaces engine. Outgoing records are pure projections of
+ * the session-store sidebar data; incoming batches are handed to the
+ * applier, which reconciles them into the live browser.
+ */
+class ZenSpacesSyncStore extends Store {
+  async getAllIDs() {
+    return ZenSpacesSyncModel.getAllRecordIds();
+  }
+
+  async itemExists(id) {
+    return ZenSpacesSyncModel.itemExists(id);
+  }
+
+  async createRecord(id, collection) {
+    const record = new ZenSpacesSyncRecord(collection, id);
+    const projected = ZenSpacesSyncModel.projectRecord(id);
+    if (!projected) {
+      record.deleted = true;
+      return record;
+    }
+    record.cleartext = { id, kind: projected.kind, data: projected.data };
+    return record;
+  }
+
+  async applyIncomingBatch(records, countTelemetry) {
+    const failed = await lazy.ZenSpacesSyncApplier.applyBatch(records);
+    for (const id of failed) {
+      countTelemetry?.addIncomingFailedReason(`failed to apply ${id}`);
+    }
+    return failed;
+  }
+
+  async wipe() {
+    // Never delete user data on an engine wipe.
+  }
+
+  async changeItemID() {}
+}
+
+/**
+ * Tracker for the Spaces engine. There is no per-event bookkeeping: every
+ * time fresh sidebar data is collected (or a container changes), the model
+ * diffs the current projections against the last-uploaded snapshot; the
+ * score is only bumped when something actually differs.
+ */
+class ZenSpacesSyncTracker extends Tracker {
+  _ignoreAll = false;
+
+  get ignoreAll() {
+    return this._ignoreAll;
+  }
+
+  set ignoreAll(value) {
+    this._ignoreAll = value;
+  }
+
+  onStart() {
+    for (const topic of TRACKED_TOPICS) {
+      Services.obs.addObserver(this, topic);
+    }
+  }
+
+  onStop() {
+    for (const topic of TRACKED_TOPICS) {
+      Services.obs.removeObserver(this, topic);
+    }
+  }
+
+  observe(subject, topic) {
+    if (this.ignoreAll) {
+      return;
+    }
+    if (topic !== SIDEBAR_COLLECTED_TOPIC) {
+      ZenSpacesSyncModel.invalidate();
+    }
+    try {
+      if (ZenSpacesSyncModel.hasPendingChanges()) {
+        syncLog(`tracker: pending changes after ${topic}, requesting sync`);
+        this.score += SCORE_INCREMENT_XLARGE;
+      }
+    } catch (e) {
+      console.error("ZenSpacesSync: change detection failed:", e);
+    }
+  }
+}
+
+export class ZenSpacesSyncEngine extends SyncEngine {
+  constructor(service) {
+    super("Spaces", service);
+  }
+
+  get _storeObj() {
+    return ZenSpacesSyncStore;
+  }
+
+  get _trackerObj() {
+    return ZenSpacesSyncTracker;
+  }
+
+  get _recordObj() {
+    return ZenSpacesSyncRecord;
+  }
+
+  get version() {
+    return 1;
+  }
+
+  get syncPriority() {
+    return 8;
+  }
+
+  get allowSkippedRecord() {
+    // A record that persistently fails to upload is skipped; the snapshot
+    // diff retries it on every following sync anyway.
+    return true;
+  }
+
+  async getChangedIDs() {
+    return ZenSpacesSyncModel.computeChangedIDs();
+  }
+
+  async _reconcile(item) {
+    // Incoming records always apply, and any local divergence re-uploads afterwards
+    // (see ZenSpacesSyncModel.noteApplied). The base reconciliation would
+    // instead drop incoming changes whenever the id is also in the local
+    // changed set, because the snapshot diff stamps its changes with "now"
+    // and the local side would always win the age comparison.
+    //
+    // An id we accept must also leave the outgoing set. Projections only
+    // reflect the applied state after the delayed session collection, so
+    // uploading the id later in this same sync would overwrite the record
+    // we just accepted with the stale pre-apply state (and the other
+    // device would then apply that, endlessly trading states back and
+    // forth). Divergence that survives the collection re-uploads on a
+    // later sync through the snapshot diff.
+    this._modified.delete(item.id);
+    return true;
+  }
+
+  async trackRemainingChanges() {}
+
+  async _onRecordsWritten(succeeded) {
+    ZenSpacesSyncModel.markUploaded(succeeded);
+  }
+}
diff --git a/src/zen/sync/ZenSpacesSyncApplier.sys.mjs b/src/zen/sync/ZenSpacesSyncApplier.sys.mjs
new file mode 100644
index 000000000..c1068b25b
--- /dev/null
+++ b/src/zen/sync/ZenSpacesSyncApplier.sys.mjs
@@ -0,0 +1,915 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+import {
+  canonicalJSON,
+  LAYOUT_RECORD_ID,
+  RECORD_KINDS,
+  syncableIconUrl,
+  syncLog,
+  ZenSpacesSyncModel,
+} from "resource:///modules/zen/ZenSpacesSyncModel.sys.mjs";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  SessionSaver: "resource:///modules/sessionstore/SessionSaver.sys.mjs",
+  E10SUtils: "resource://gre/modules/E10SUtils.sys.mjs",
+  TabStateCache: "resource:///modules/sessionstore/TabStateCache.sys.mjs",
+  ZenWindowSync: "resource:///modules/zen/ZenWindowSync.sys.mjs",
+  ZenLiveFoldersManager:
+    "resource:///modules/zen/ZenLiveFoldersManager.sys.mjs",
+  ContextualIdentityService:
+    "moz-src:///toolkit/components/contextualidentity/ContextualIdentityService.sys.mjs",
+});
+
+const FIRST_SYNC_ANIMATION_PREF = "zen.spaces-sync.first-sync-animation-shown";
+
+/**
+ * Applies batches of incoming Spaces records to the local browser.
+ */
+class nsZenSpacesSyncApplier {
+  #itemIn(win, id) {
+    return id ? win.document.getElementById(id) : null;
+  }
+
+  /**
+   * Maps a record's container guid to the local userContextId. A guid with
+   * no local mapping (its container record hasn't applied here yet) throws,
+   * failing the record so it redelivers once the container exists .
+   *
+   * @param {?string} containerGuid
+   * @returns {number}
+   */
+  #resolveContainerId(containerGuid) {
+    if (!containerGuid) {
+      return 0;
+    }
+    const mapped = ZenSpacesSyncModel.contextIdForGuid(containerGuid);
+    if (mapped === null) {
+      throw new Error(`unknown container guid ${containerGuid}`);
+    }
+    return mapped;
+  }
+
+  /**
+   * @param {Array} records - decrypted incoming records.
+   * @returns {Array<string>} ids of records that failed to apply.
+   */
+  async applyBatch(records) {
+    const incoming = {
+      containers: [],
+      spaces: [],
+      tabs: [],
+      folders: [],
+      splits: [],
+      layout: null,
+      deleted: [],
+    };
+    const handled = new Set();
+
+    for (const record of records) {
+      if (typeof record.id !== "string" || !record.id) {
+        continue;
+      }
+      if (record.deleted) {
+        if (record.id !== LAYOUT_RECORD_ID) {
+          incoming.deleted.push({ key: record.id, record });
+        }
+        handled.add(record);
+        continue;
+      }
+      const data = record.cleartext?.data;
+      if (!data) {
+        continue;
+      }
+      const entry = { key: record.id, data, record };
+      switch (record.cleartext.kind) {
+        case RECORD_KINDS.CONTAINER:
+          incoming.containers.push(entry);
+          break;
+        case RECORD_KINDS.SPACE:
+          incoming.spaces.push(entry);
+          break;
+        case RECORD_KINDS.TAB:
+          incoming.tabs.push(entry);
+          break;
+        case RECORD_KINDS.FOLDER:
+          incoming.folders.push(entry);
+          break;
+        case RECORD_KINDS.SPLIT:
+          incoming.splits.push(entry);
+          break;
+        case RECORD_KINDS.LAYOUT:
+          incoming.layout = entry;
+          break;
+        default:
+          // Unknown kind (newer client): leave untouched and unacknowledged.
+          continue;
+      }
+      handled.add(record);
+    }
+
+    syncLog(
+      `incoming batch: ${incoming.containers.length} containers, ` +
+        `${incoming.spaces.length} spaces, ${incoming.tabs.length} tabs, ` +
+        `${incoming.folders.length} folders, ${incoming.splits.length} splits, ` +
+        `layout=${!!incoming.layout}, ${incoming.deleted.length} tombstones`
+    );
+
+    const failed = new Set();
+    const fail = (record, e) => {
+      failed.add(record.id);
+      console.error(`ZenSpacesSync: failed to apply ${record.id}:`, e);
+    };
+
+    const deletions = this.#applyContainers(incoming, fail);
+
+    const win = lazy.ZenWindowSync.firstSyncedWindow;
+    if (!win) {
+      // Report the records as failed so the engine redelivers the batch on a later sync.
+      const noWindow = new Error("no synced window to apply into");
+      for (const entry of [
+        ...incoming.spaces,
+        ...incoming.folders,
+        ...incoming.tabs,
+        ...incoming.splits,
+        ...(incoming.layout ? [incoming.layout] : []),
+        ...deletions,
+      ]) {
+        fail(entry.record, noWindow);
+      }
+    } else {
+      await win.gZenWorkspaces.promiseInitialized;
+      this.#maybePlayFirstSyncAnimation(win);
+      const removals = this.#routeTombstones(win, deletions);
+      this.#deleteTabs(win, removals.tabs, fail);
+      this.#deleteSplits(win, removals.splits, fail);
+      await this.#applySpaces(win, incoming.spaces, fail);
+      await this.#applyFolders(win, incoming.folders, fail);
+      this.#applyTabs(win, incoming.tabs, fail);
+      this.#applySplits(win, incoming.splits, fail);
+      await this.#deleteFolders(win, removals.folders, fail);
+      await this.#deleteSpaces(win, removals.spaces, fail);
+      this.#applyOrdering(win, incoming, fail);
+      // Collect the session soon so the stored sidebar (and with it the
+      // sync projections) reflects the applied state instead of re-uploading
+      // the pre-apply one.
+      lazy.SessionSaver.runDelayed();
+    }
+
+    ZenSpacesSyncModel.invalidate();
+    for (const record of records) {
+      if (!handled.has(record) || failed.has(record.id)) {
+        continue;
+      }
+      ZenSpacesSyncModel.noteApplied(
+        record.id,
+        record.deleted ? null : record.cleartext
+      );
+    }
+    return [...failed];
+  }
+
+  /**
+   * Plays the update sweep animation over the window the first time
+   * incoming sync data lands on this profile.
+   *
+   * @param {Window} win
+   */
+  #maybePlayFirstSyncAnimation(win) {
+    if (Services.prefs.getBoolPref(FIRST_SYNC_ANIMATION_PREF, false)) {
+      return;
+    }
+    Services.prefs.setBoolPref(FIRST_SYNC_ANIMATION_PREF, true);
+    win.gZenStartup.playWindowSweepAnimation();
+  }
+
+  /**
+   * Tombstones have no payload. Whatever local thing owns the id decides
+   * what kind of deletion this is. Ids with no local counterpart need no
+   * work at all.
+   *
+   * @param {Window} win
+   * @param {Array<{key: string, record: object}>} deletions
+   */
+  #routeTombstones(win, deletions) {
+    const routed = { tabs: [], folders: [], splits: [], spaces: [] };
+    const spaces = win.gZenWorkspaces.getWorkspaces();
+    for (const entry of deletions) {
+      const el = this.#itemIn(win, entry.key);
+      if (win.gBrowser.isTab(el)) {
+        routed.tabs.push(entry);
+      } else if (el?.isZenFolder) {
+        routed.folders.push(entry);
+      } else if (el?.hasAttribute?.("split-view-group")) {
+        routed.splits.push(entry);
+      } else if (spaces.some(s => s.uuid === entry.key)) {
+        routed.spaces.push(entry);
+      }
+    }
+    if (deletions.length) {
+      const matched = new Set([
+        ...routed.tabs,
+        ...routed.folders,
+        ...routed.splits,
+        ...routed.spaces,
+      ]);
+      syncLog("tombstones routed:", {
+        tabs: routed.tabs.map(e => e.key),
+        folders: routed.folders.map(e => e.key),
+        splits: routed.splits.map(e => e.key),
+        spaces: routed.spaces.map(e => e.key),
+        unmatched: deletions.filter(e => !matched.has(e)).map(e => e.key),
+      });
+    }
+    return routed;
+  }
+
+  /* Mark: containers */
+
+  #applyContainers(incoming, fail) {
+    for (const { key: guid, data, record } of incoming.containers) {
+      try {
+        if (!data.name) {
+          continue;
+        }
+        const mapped = ZenSpacesSyncModel.contextIdForGuid(guid);
+        const existing =
+          mapped !== null
+            ? lazy.ContextualIdentityService.getPublicIdentityFromId(mapped)
+            : null;
+        if (existing) {
+          lazy.ContextualIdentityService.update(
+            mapped,
+            data.name,
+            data.icon,
+            data.color
+          );
+        } else {
+          const identity = lazy.ContextualIdentityService.create(
+            data.name,
+            data.icon,
+            data.color
+          );
+          ZenSpacesSyncModel.registerContainerGuid(
+            guid,
+            identity.userContextId
+          );
+        }
+      } catch (e) {
+        fail(record, e);
+      }
+    }
+
+    const rest = [];
+    for (const entry of incoming.deleted) {
+      const mapped = ZenSpacesSyncModel.contextIdForGuid(entry.key);
+      if (mapped === null) {
+        rest.push(entry);
+        continue;
+      }
+      try {
+        if (lazy.ContextualIdentityService.getPublicIdentityFromId(mapped)) {
+          lazy.ContextualIdentityService.remove(mapped);
+        }
+        ZenSpacesSyncModel.forgetContainerGuid(entry.key);
+      } catch (e) {
+        fail(entry.record, e);
+      }
+    }
+    return rest;
+  }
+
+  /* Mark: spaces */
+
+  async #applySpaces(win, spaces, fail) {
+    if (!spaces.length) {
+      return;
+    }
+    const list = win.gZenWorkspaces.getWorkspaces();
+    let changed = false;
+    const repaint = [];
+    for (const { data, record } of spaces) {
+      try {
+        if (!data.uuid) {
+          continue;
+        }
+        const fields = {
+          uuid: data.uuid,
+          name: data.name ?? "",
+          icon: data.icon ?? undefined,
+          theme: data.theme ?? null,
+          containerTabId: this.#resolveContainerId(data.containerGuid),
+        };
+        // A space record re-syncs whenever its child ordering changes, so
+        // only propagate (and especially repaint) when its own fields did.
+        const index = list.findIndex(s => s.uuid === data.uuid);
+        const current = index === -1 ? null : list[index];
+        const visualChanged =
+          !current ||
+          (current.name ?? "") !== fields.name ||
+          (current.icon ?? null) !== (fields.icon ?? null) ||
+          canonicalJSON(current.theme ?? null) !==
+            canonicalJSON(fields.theme ?? null);
+        const containerChanged =
+          !current || (current.containerTabId ?? 0) !== fields.containerTabId;
+        if (containerChanged) {
+          syncLog(
+            `space ${data.uuid} containerTabId ` +
+              `${current?.containerTabId ?? 0} -> ${fields.containerTabId} ` +
+              `(guid ${data.containerGuid ?? "none"})`
+          );
+        }
+        if (!current) {
+          list.push(fields);
+          changed = true;
+        } else if (visualChanged || containerChanged) {
+          list[index] = { ...current, ...fields };
+          changed = true;
+        }
+        if (visualChanged) {
+          repaint.push(data.uuid);
+        }
+      } catch (e) {
+        fail(record, e);
+      }
+    }
+    if (changed) {
+      await win.gZenWorkspaces.propagateWorkspaces(list);
+      win.gZenWindowSync.propagateWorkspacesToAllWindows(list);
+      for (const uuid of repaint) {
+        const updated = list.find(s => s.uuid === uuid);
+        if (updated) {
+          win.gZenThemePicker.onWorkspaceChange(updated);
+        }
+      }
+    }
+  }
+
+  async #deleteSpaces(win, removals, fail) {
+    for (const { key: uuid, record } of removals) {
+      try {
+        const spaces = win.gZenWorkspaces.getWorkspaces();
+        if (!spaces.some(s => s.uuid === uuid)) {
+          continue;
+        }
+        if (spaces.length <= 1) {
+          // Never delete the last space; the local copy revives it remotely.
+          continue;
+        }
+        if (!(await this.#confirmRemoteSpaceDelete(win, uuid))) {
+          continue;
+        }
+        await win.gZenWorkspaces.removeWorkspace(uuid);
+      } catch (e) {
+        fail(record, e);
+      }
+    }
+  }
+
+  /**
+   * @param {Window} win
+   * @param {string} uuid
+   * @returns {Promise<boolean>} Whether the user confirmed the deletion.
+   */
+  async #confirmRemoteSpaceDelete(win, uuid) {
+    const name = win.gZenWorkspaces.getWorkspaceFromId(uuid)?.name || uuid;
+    const [title, body] = await win.document.l10n.formatValues([
+      { id: "zen-workspaces-remote-delete-title" },
+      { id: "zen-workspaces-remote-delete-body", args: { name } },
+    ]);
+    const result = await Services.prompt.asyncConfirmEx(
+      win.browsingContext,
+      Services.prompt.MODAL_TYPE_WINDOW,
+      title,
+      body,
+      Services.prompt.STD_YES_NO_BUTTONS,
+      null,
+      null,
+      null,
+      null,
+      false
+    );
+    return result.get("buttonNumClicked") === 0;
+  }
+
+  /* Mark: folders */
+
+  async #applyFolders(win, folders, fail) {
+    // Parents before children so nesting targets exist.
+    const depths = new Map(folders.map(f => [f.key, f.data.parentFolderId]));
+    const depthOf = key => {
+      let depth = 0;
+      let parent = depths.get(key);
+      while (parent && depths.has(parent) && depth < 10) {
+        depth++;
+        parent = depths.get(parent);
+      }
+      return depth;
+    };
+    const ordered = [...folders].sort(
+      (a, b) => depthOf(a.key) - depthOf(b.key)
+    );
+
+    for (const { key: folderId, data, record } of ordered) {
+      try {
+        let folder = this.#itemIn(win, folderId);
+        if (!folder?.isZenFolder) {
+          folder = win.gZenFolders.createFolder([], {
+            id: folderId,
+            label: data.name || "Folder",
+            workspaceId:
+              data.workspaceUuid || win.gZenWorkspaces.activeWorkspace,
+            isLiveFolder: !!data.live,
+          });
+        } else if (data.name && folder.label !== data.name) {
+          folder.label = data.name;
+        }
+
+        if (data.live && !folder.isLiveFolder) {
+          // The folder synced before its provider config was available and
+          // materialized as a plain folder; upgrade it so this profile
+          // projects the config too instead of clobbering it with live: null.
+          folder.isLiveFolder = true;
+        }
+
+        if ((folder.iconURL || null) !== (data.icon || null)) {
+          win.gZenFolders.setFolderUserIcon(folder, data.icon || null);
+          // Window sync picks this up and mirrors the icon everywhere else.
+          folder.dispatchEvent(
+            new win.CustomEvent("TabGroupUpdate", { bubbles: true })
+          );
+        }
+
+        const desiredParent = data.parentFolderId
+          ? this.#itemIn(win, data.parentFolderId)
+          : null;
+        const currentParent = folder.group;
+        if ((currentParent?.id || null) !== (data.parentFolderId || null)) {
+          if (desiredParent?.isZenFolder) {
+            win.gBrowser.zenHandleTabMove(folder, () => {
+              if (desiredParent.tabs.length) {
+                desiredParent.tabs[0].after(folder);
+              } else {
+                desiredParent.appendChild(folder);
+              }
+            });
+          } else if (!data.parentFolderId && currentParent?.isZenFolder) {
+            const ws = data.workspaceUuid || win.gZenWorkspaces.activeWorkspace;
+            const container =
+              win.gZenWorkspaces.workspaceElement(ws)?.pinnedTabsContainer;
+            if (container) {
+              win.gBrowser.zenHandleTabMove(folder, () => {
+                container.insertBefore(
+                  folder,
+                  container.querySelector(".pinned-tabs-container-separator")
+                );
+              });
+            }
+          }
+        }
+        if (
+          data.workspaceUuid &&
+          folder.getAttribute("zen-workspace-id") !== data.workspaceUuid
+        ) {
+          if (!folder.group) {
+            win.gZenFolders.changeFolderToSpace(folder, data.workspaceUuid);
+          } else {
+            folder.setAttribute("zen-workspace-id", data.workspaceUuid);
+          }
+        }
+        if (data.live) {
+          await lazy.ZenLiveFoldersManager.adoptSyncedFolder(
+            folderId,
+            data.live
+          );
+        }
+      } catch (e) {
+        fail(record, e);
+      }
+    }
+  }
+
+  async #deleteFolders(win, removals, fail) {
+    for (const { key: folderId, record } of removals) {
+      try {
+        const folder = this.#itemIn(win, folderId);
+        if (!folder?.isZenFolder) {
+          continue;
+        }
+        // Members without their own tombstone survive: unpack, then delete
+        // the (now empty) folder.
+        await folder.unpackTabs();
+        await folder.delete();
+      } catch (e) {
+        fail(record, e);
+      }
+    }
+  }
+
+  /* Mark: tabs */
+
+  #applyTabs(win, tabs, fail) {
+    for (const { key: tabId, data, record } of tabs) {
+      try {
+        if (!data.url || data.url === "about:blank") {
+          continue;
+        }
+        const existing = this.#itemIn(win, tabId);
+        if (win.gBrowser.isTab(existing)) {
+          this.#updateTab(win, existing, data);
+        } else {
+          this.#createTab(win, tabId, data);
+        }
+      } catch (e) {
+        fail(record, e);
+      }
+    }
+  }
+
+  #createTab(win, tabId, data) {
+    const userContextId = this.#resolveContainerId(data.containerGuid);
+    syncLog(
+      `creating tab ${tabId} ` +
+        `(essential=${!!data.essential}, container=${userContextId})`,
+      data.url
+    );
+    const tab = win.gBrowser.addTrustedTab(data.url, {
+      createLazyBrowser: true,
+      inBackground: true,
+      skipAnimation: true,
+      skipBackgroundNotify: true,
+      lazyTabTitle: data.title || undefined,
+      userContextId,
+    });
+    // Setting the sync id before the queued TabOpen handler runs makes
+    // window sync treat this tab as already replicated.
+    tab.id = tabId;
+    tab._zenContentsVisible = true;
+    this.#updateTabIdentity(win, tab, data);
+    if (data.essential) {
+      win.gZenPinnedTabManager.addToEssentials(tab, { replicating: true });
+    } else {
+      if (data.workspaceUuid) {
+        tab.setAttribute("zen-workspace-id", data.workspaceUuid);
+      }
+      win.gBrowser.pinTab(tab);
+      if (data.workspaceUuid) {
+        win.gZenWorkspaces.moveTabToWorkspace(tab, data.workspaceUuid);
+      }
+      const folder = data.folderId && this.#itemIn(win, data.folderId);
+      if (folder?.isZenFolder) {
+        folder.addTabs([tab]);
+      }
+    }
+    lazy.ZenWindowSync.on_TabOpen({ target: tab }, { ignoreExistingId: true });
+  }
+
+  /**
+   * Reconciles the tab's synced identity: pinned initial state, static
+   * label/icon, the live icon and the default-container marker.
+   *
+   * @param {Window} win
+   * @param {MozTabbrowserTab} tab
+   * @param {object} data
+   */
+  #updateTabIdentity(win, tab, data) {
+    const icon = syncableIconUrl(data.icon);
+    const initial = tab._zenPinnedInitialState;
+    const identityChanged =
+      initial?.entry?.url !== data.url ||
+      (initial?.entry?.title || "") !== (data.title || "");
+    if (identityChanged || syncableIconUrl(initial?.image || "") !== icon) {
+      lazy.ZenWindowSync.setPinnedInitialState(
+        tab,
+        { url: data.url, title: data.title || "" },
+        icon || undefined
+      );
+    }
+    if (identityChanged && !tab.linkedPanel) {
+      // An unloaded tab has no live state to lose: retarget its lazy session
+      // state so the next activation loads the new canonical url directly
+      // instead of whatever the tab was created with.
+      this.#retargetUnloadedTab(win, tab, data, initial?.entry?.url);
+    }
+
+    const staticLabel =
+      typeof data.staticLabel === "string" ? data.staticLabel : null;
+    const localLabel =
+      typeof tab.zenStaticLabel === "string" ? tab.zenStaticLabel : null;
+    if (staticLabel !== localLabel) {
+      tab.zenStaticLabel = staticLabel ?? undefined;
+      if (staticLabel) {
+        tab._zenChangeLabelFlag = true;
+        try {
+          win.gBrowser._setTabLabel(tab, staticLabel);
+        } finally {
+          delete tab._zenChangeLabelFlag;
+        }
+      }
+    }
+    tab.zenStaticIcon = data.hasStaticIcon && icon ? icon : undefined;
+    const iconDiffers =
+      icon && syncableIconUrl(tab.getAttribute("image")) !== icon;
+    if (iconDiffers && (data.hasStaticIcon || !tab.linkedPanel)) {
+      try {
+        syncLog(
+          `setting synced${data.hasStaticIcon ? " static" : ""} ` +
+            `icon on tab ${tab.id}`
+        );
+        win.gBrowser.setIcon(tab, icon);
+        lazy.TabStateCache.update(tab.linkedBrowser.permanentKey, {
+          image: null,
+        });
+      } catch (e) {
+        console.error("ZenSpacesSync: failed to set tab icon", e);
+      }
+    }
+    if (data.defaultContainer) {
+      tab.setAttribute("zenDefaultUserContextId", "true");
+    } else {
+      tab.removeAttribute("zenDefaultUserContextId");
+    }
+  }
+
+  /**
+   * Points an unloaded tab's session state at the record's canonical url,
+   * mirroring ZenPinnedTabManager's reset-to-stored-state shape.
+   *
+   * @param {Window} win
+   * @param {MozTabbrowserTab} tab
+   * @param {object} data
+   * @param {?string} previousPinUrl - The pin url before this record applied.
+   */
+  #retargetUnloadedTab(win, tab, data, previousPinUrl) {
+    try {
+      const state = JSON.parse(win.SessionStore.getTabState(tab));
+      const entries = state.entries || [];
+      let currentUrl = null;
+      if (entries.length) {
+        const index = Math.min(
+          Math.max((state.index || entries.length) - 1, 0),
+          entries.length - 1
+        );
+        currentUrl = entries[index]?.url || null;
+      }
+      if (
+        currentUrl === data.url ||
+        (currentUrl && previousPinUrl && currentUrl !== previousPinUrl)
+      ) {
+        return;
+      }
+      state.entries = [
+        {
+          url: data.url,
+          title: data.title || "",
+          triggeringPrincipal_base64: lazy.E10SUtils.serializePrincipal(
+            Services.scriptSecurityManager.createContentPrincipal(
+              Services.io.newURI(data.url),
+              {}
+            )
+          ),
+        },
+      ];
+      state.index = 1;
+      state.image = syncableIconUrl(data.icon) || undefined;
+      delete state.scroll;
+      win.SessionStore.setTabState(tab, state);
+    } catch (e) {
+      console.error("ZenSpacesSync: failed to retarget unloaded tab", e);
+    }
+  }
+
+  /**
+   * Puts a tab or split group under the folder the record names, or back at
+   * top level when it names none.
+   *
+   * @param {Window} win
+   * @param {MozTabbrowserTab|MozTabbrowserTabGroup} item
+   * @param {?string} folderId
+   */
+  #applyFolderMembership(win, item, folderId) {
+    const currentFolder = item.group?.isZenFolder ? item.group.id : null;
+    const wantFolder = folderId || null;
+    if (currentFolder === wantFolder) {
+      return;
+    }
+    const target = wantFolder && this.#itemIn(win, wantFolder);
+    if (target?.isZenFolder) {
+      target.addTabs([item]);
+    } else if (!wantFolder && currentFolder) {
+      // ungroupTab pops a single nesting level. An item inside a subfolder
+      // lands inside the parent folder, so keep going until it is actually
+      // top-level.
+      while (win.gBrowser.isTabGroup(item.group) && item.group.isZenFolder) {
+        win.gBrowser.ungroupTab(item);
+      }
+    }
+  }
+
+  #updateTab(win, tab, data) {
+    this.#updateTabIdentity(win, tab, data);
+
+    const isEssential = tab.hasAttribute("zen-essential");
+    if (data.essential && !isEssential) {
+      syncLog(`incoming record promotes tab ${tab.id} to essential`);
+      win.gZenPinnedTabManager.addToEssentials(tab, { replicating: true });
+      return;
+    }
+    if (!data.essential && isEssential) {
+      console.warn(
+        `ZenSpacesSync: incoming record demotes essential tab ${tab.id}`
+      );
+      win.gZenPinnedTabManager.removeEssentials(tab, /* unpin */ false);
+    }
+    if (data.essential) {
+      return;
+    }
+
+    const inSplit = tab.group?.hasAttribute("split-view-group");
+    if (inSplit) {
+      // The split record governs placement of its members.
+      return;
+    }
+    this.#applyFolderMembership(win, tab, data.folderId);
+    if (
+      !data.folderId &&
+      data.workspaceUuid &&
+      tab.getAttribute("zen-workspace-id") !== data.workspaceUuid
+    ) {
+      win.gZenWorkspaces.moveTabToWorkspace(tab, data.workspaceUuid);
+    }
+  }
+
+  #removeTab(win, tab) {
+    if (tab.splitView) {
+      win.gZenViewSplitter.removeTabFromGroup(tab, undefined, {
+        forUnsplit: true,
+        changeTab: false,
+      });
+    }
+    win.gBrowser.removeTab(tab, { animate: true });
+  }
+
+  #deleteTabs(win, removals, fail) {
+    for (const { key: tabId, record } of removals) {
+      try {
+        const tab = this.#itemIn(win, tabId);
+        if (win.gBrowser.isTab(tab)) {
+          if (tab.hasAttribute("zen-essential")) {
+            console.warn(
+              `ZenSpacesSync: incoming tombstone removes essential tab ${tabId}`,
+              tab.linkedBrowser?.currentURI?.spec ?? ""
+            );
+          } else {
+            syncLog(`incoming tombstone removes tab ${tabId}`);
+          }
+          this.#removeTab(win, tab);
+        }
+      } catch (e) {
+        fail(record, e);
+      }
+    }
+  }
+
+  /* Mark: splits */
+
+  #applySplits(win, splits, fail) {
+    for (const { key: splitId, data, record } of splits) {
+      try {
+        const members = (data.tabs || [])
+          .map(id => this.#itemIn(win, id))
+          .filter(tab => win.gBrowser.isTab(tab));
+        const existing = this.#itemIn(win, splitId);
+        const hasGroup = existing?.hasAttribute?.("split-view-group");
+        if (hasGroup) {
+          const wanted = new Set(data.tabs || []);
+          for (const tab of [...existing.tabs]) {
+            if (tab.id && !wanted.has(tab.id)) {
+              win.gZenViewSplitter.removeTabFromGroup(tab, undefined, {
+                changeTab: false,
+              });
+            }
+          }
+        }
+        if (members.length >= 2) {
+          win.gZenViewSplitter.splitTabs(members, data.gridType, -1, {
+            groupFetchId: splitId,
+          });
+        }
+        const group = this.#itemIn(win, splitId);
+        if (group?.hasAttribute?.("split-view-group")) {
+          this.#applyFolderMembership(win, group, data.folderId);
+        }
+      } catch (e) {
+        fail(record, e);
+      }
+    }
+  }
+
+  #deleteSplits(win, removals, fail) {
+    for (const { key: splitId, record } of removals) {
+      try {
+        const index = win.gZenViewSplitter._data.findIndex(
+          group => group.groupId === splitId
+        );
+        if (index >= 0) {
+          win.gZenViewSplitter.removeGroup(index);
+        }
+      } catch (e) {
+        fail(record, e);
+      }
+    }
+  }
+
+  /* Mark: ordering */
+
+  #applyRelativeOrder(win, elements) {
+    let prev = null;
+    for (const el of elements) {
+      if (!el) {
+        continue;
+      }
+      if (
+        prev &&
+        prev.parentNode &&
+        prev.parentNode === el.parentNode &&
+        prev.nextElementSibling !== el
+      ) {
+        win.gBrowser.zenHandleTabMove(el, () => prev.after(el));
+      }
+      prev = el;
+    }
+  }
+
+  /**
+   * Ordering runs in the first synced window only: every move goes through
+   * zenHandleTabMove, whose TabMove events window sync replicates into the
+   * other windows.
+   *
+   * @param {Window} win
+   * @param {object} incoming
+   * @param {Function} fail
+   */
+  #applyOrdering(win, incoming, fail) {
+    for (const { key, data, record } of [
+      ...incoming.spaces,
+      ...incoming.folders,
+    ]) {
+      try {
+        if (Array.isArray(data.children) && data.children.length) {
+          // A folder's empty-tab placeholder anchors its first child: without
+          // it, relative ordering could never move anything to the start.
+          const folder = data.folderId ? this.#itemIn(win, key) : null;
+          const start = folder?.isZenFolder
+            ? folder.tabs.find(t => t.hasAttribute("zen-empty-tab"))
+            : null;
+          this.#applyRelativeOrder(win, [
+            start ?? null,
+            ...data.children.map(id => this.#itemIn(win, id)),
+          ]);
+        }
+      } catch (e) {
+        fail(record, e);
+      }
+    }
+    if (!incoming.layout) {
+      return;
+    }
+    const { data, record } = incoming.layout;
+    try {
+      for (const tabIds of Object.values(data.essentials || {})) {
+        if (Array.isArray(tabIds) && tabIds.length > 1) {
+          this.#applyRelativeOrder(
+            win,
+            tabIds.map(id => this.#itemIn(win, id))
+          );
+        }
+      }
+      if (Array.isArray(data.spaces) && data.spaces.length > 1) {
+        const current = win.gZenWorkspaces.getWorkspaces();
+        const byUuid = new Map(current.map(s => [s.uuid, s]));
+        const ordered = data.spaces
+          .map(uuid => byUuid.get(uuid))
+          .filter(Boolean);
+        for (const space of current) {
+          if (!data.spaces.includes(space.uuid)) {
+            ordered.push(space);
+          }
+        }
+        const changedOrder = ordered.some(
+          (space, i) => current[i]?.uuid !== space.uuid
+        );
+        if (changedOrder && ordered.length === current.length) {
+          win.gZenWindowSync.propagateWorkspacesToAllWindows(ordered);
+        }
+      }
+    } catch (e) {
+      fail(record, e);
+    }
+  }
+}
+
+export const ZenSpacesSyncApplier = new nsZenSpacesSyncApplier();
diff --git a/src/zen/sync/ZenSpacesSyncModel.sys.mjs b/src/zen/sync/ZenSpacesSyncModel.sys.mjs
new file mode 100644
index 000000000..27167bfa9
--- /dev/null
+++ b/src/zen/sync/ZenSpacesSyncModel.sys.mjs
@@ -0,0 +1,722 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+import { JSONFile } from "resource://gre/modules/JSONFile.sys.mjs";
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  ZenSessionStore: "resource:///modules/zen/ZenSessionManager.sys.mjs",
+  ZenLiveFoldersManager:
+    "resource:///modules/zen/ZenLiveFoldersManager.sys.mjs",
+  ContextualIdentityService:
+    "moz-src:///toolkit/components/contextualidentity/ContextualIdentityService.sys.mjs",
+});
+
+XPCOMUtils.defineLazyPreferenceGetter(
+  lazy,
+  "syncDebug",
+  "zen.spaces-sync.debug",
+  false
+);
+
+/**
+ * Debug logging for the whole Spaces sync pipeline.
+ *
+ * @param {string} message
+ * @param {...any} args
+ */
+export function syncLog(message, ...args) {
+  if (lazy.syncDebug) {
+    // eslint-disable-next-line no-console
+    console.debug(`ZenSpacesSync: ${message}`, ...args);
+  }
+}
+
+export const SIDEBAR_COLLECTED_TOPIC = "zen-sidebar-data-collected";
+
+export const RECORD_KINDS = Object.freeze({
+  CONTAINER: "container",
+  SPACE: "space",
+  TAB: "tab",
+  FOLDER: "folder",
+  SPLIT: "split",
+  LAYOUT: "layout",
+});
+
+export const LAYOUT_RECORD_ID = "layout";
+
+// Firefox ships four built-in containers with fixed userContextIds. They
+// exist on every device, so they map to well-known guids instead of the
+// per-profile generated ones.
+const BUILTIN_CONTAINER_MAX = 4;
+const BUILTIN_GUID_PREFIX = "builtin-";
+
+const STORE_FILE_NAME = "zen-spaces-sync.json";
+const STORE_VERSION = 1;
+
+// Everything setIcon accepts without a loading principal.
+const LOCAL_ICON_PROTOCOLS = ["data:", "chrome:", "about:", "resource:"];
+
+/**
+ * Normalizes a tab icon for syncing. The image attribute can hold a
+ * moz-remote-image: wrapper around the actual (svg data:) favicon, carrying
+ * a per-process contentParentId that means nothing on another device — sync
+ * the wrapped URL instead. Anything else setIcon would reject as remote is
+ * dropped.
+ *
+ * @param {?string} icon
+ * @returns {string}
+ */
+export function syncableIconUrl(icon) {
+  if (!icon || typeof icon !== "string") {
+    return "";
+  }
+  if (icon.startsWith("moz-remote-image:")) {
+    try {
+      const uri = Services.io.newURI(icon);
+      icon = new URLSearchParams(uri.query).get("url") || "";
+    } catch (e) {
+      return "";
+    }
+  }
+  return LOCAL_ICON_PROTOCOLS.some(protocol => icon.startsWith(protocol))
+    ? icon
+    : "";
+}
+
+function sortedClone(value) {
+  if (Array.isArray(value)) {
+    return value.map(sortedClone);
+  }
+  if (value && typeof value === "object") {
+    const out = {};
+    for (const key of Object.keys(value).sort()) {
+      out[key] = sortedClone(value[key]);
+    }
+    return out;
+  }
+  return value === undefined ? null : value;
+}
+
+/**
+ * Deterministic JSON serialization (recursively sorted keys), so that two
+ * structurally equal payloads always stringify identically.
+ *
+ * @param {object} value
+ */
+export function canonicalJSON(value) {
+  return JSON.stringify(sortedClone(value));
+}
+
+/**
+ * Digest of a record's canonical form. The uploaded-state snapshot only ever
+ * needs equality checks, so it stores these short digests instead of the
+ * full canonical strings, keeping the store file small and cheap to write.
+ *
+ * @param {string} kind
+ * @param {object} data
+ * @returns {string} base64 SHA-256 of the canonical record payload.
+ */
+const textEncoder = new TextEncoder();
+
+export function recordDigest(kind, data) {
+  const hasher = Cc["@mozilla.org/security/hash;1"].createInstance(
+    Ci.nsICryptoHash
+  );
+  hasher.init(Ci.nsICryptoHash.SHA256);
+  const bytes = textEncoder.encode(canonicalJSON({ kind, data }));
+  hasher.update(bytes, bytes.length);
+  return hasher.finish(/* base64 = */ true);
+}
+
+/**
+ * Owns the synced-data model for the Spaces engine.
+ */
+class nsZenSpacesSyncModel {
+  #file = null;
+  #cache = null;
+
+  #data() {
+    if (!this.#file) {
+      this.#file = new JSONFile({
+        path: PathUtils.join(PathUtils.profileDir, STORE_FILE_NAME),
+        dataPostProcessor: data => {
+          if (data.version !== STORE_VERSION) {
+            // Drop the uploaded snapshot so everything re-diffs against
+            // the (also wiped) server, but keep the container identity mappings.
+            data.uploaded = {};
+          }
+          data.version = STORE_VERSION;
+          data.uploaded ||= {};
+          data.containers ||= {};
+          // The container map used to be keyed by guid. It is keyed by
+          // userContextId now so that registering a guid replaces any
+          // previous one for the same container. Flip old stores over
+          // (old values are numeric ids, new values are guid strings).
+          for (const [key, value] of Object.entries(data.containers)) {
+            if (typeof value === "number") {
+              delete data.containers[key];
+              data.containers[value] = key;
+            }
+          }
+          return data;
+        },
+      });
+      this.#file.ensureDataReady();
+    }
+    return this.#file.data;
+  }
+
+  invalidate() {
+    this.#cache = null;
+  }
+
+  /* Mark: container identity */
+
+  guidForContextId(userContextId, { create = false } = {}) {
+    const id = Number(userContextId);
+    if (!Number.isSafeInteger(id) || id <= 0) {
+      return null;
+    }
+    if (id <= BUILTIN_CONTAINER_MAX) {
+      return `${BUILTIN_GUID_PREFIX}${id}`;
+    }
+    const data = this.#data();
+    const existing = data.containers[id];
+    if (existing) {
+      return existing;
+    }
+    if (!create) {
+      return null;
+    }
+    const guid = Services.uuid.generateUUID().toString().slice(1, -1);
+    data.containers[id] = guid;
+    this.#file.saveSoon();
+    return guid;
+  }
+
+  contextIdForGuid(guid) {
+    if (typeof guid !== "string" || !guid) {
+      return null;
+    }
+    if (guid.startsWith(BUILTIN_GUID_PREFIX)) {
+      const id = Number(guid.slice(BUILTIN_GUID_PREFIX.length));
+      return Number.isSafeInteger(id) && id > 0 && id <= BUILTIN_CONTAINER_MAX
+        ? id
+        : null;
+    }
+    for (const [id, mapped] of Object.entries(this.#data().containers)) {
+      if (mapped === guid) {
+        return Number(id);
+      }
+    }
+    return null;
+  }
+
+  /**
+   * Adopts an incoming guid as the identity's synced name.
+   *
+   * @param {string} guid
+   * @param {number} userContextId
+   */
+  registerContainerGuid(guid, userContextId) {
+    if (guid.startsWith(BUILTIN_GUID_PREFIX)) {
+      return;
+    }
+    this.#data().containers[userContextId] = guid;
+    this.#file.saveSoon();
+  }
+
+  forgetContainerGuid(guid) {
+    const data = this.#data();
+    for (const [id, mapped] of Object.entries(data.containers)) {
+      if (mapped === guid) {
+        delete data.containers[id];
+        this.#file.saveSoon();
+        return;
+      }
+    }
+  }
+
+  /* Mark: projections */
+
+  #isSyncableTab(tabData) {
+    return !!(
+      tabData &&
+      tabData.zenSyncId &&
+      (tabData.pinned || tabData.zenEssential) &&
+      !tabData.zenIsEmpty &&
+      !tabData.zenIsGlance &&
+      !tabData.zenLiveFolderItemId
+    );
+  }
+
+  #tabIdentity(tabData) {
+    const initial = tabData._zenPinnedInitialState;
+    let url = initial?.entry?.url;
+    let title = initial?.entry?.title;
+    if (!url || url === "about:blank") {
+      const entries = tabData.entries || [];
+      if (entries.length) {
+        let index = Math.min(
+          Math.max((tabData.index || entries.length) - 1, 0),
+          entries.length - 1
+        );
+        const entry = entries[index] || entries[0];
+        if (entry?.url && entry.url !== "about:blank") {
+          url = entry.url;
+          title ??= entry.title;
+        }
+      }
+    }
+    if (!url || url === "about:blank") {
+      return null;
+    }
+    const icon = syncableIconUrl(
+      (tabData.zenHasStaticIcon
+        ? tabData.image
+        : initial?.image || tabData.image) || ""
+    );
+    return { url, title: title || "", icon };
+  }
+
+  /**
+   * Builds the ordered child id list for one parent (a space's pinned
+   * section or a folder). Tabs and splits are ordered by their position in
+   * the collected tab list; folders are spliced in next to their recorded
+   * previous sibling.
+   *
+   * @param {object} root0
+   * @param {Array<object>} root0.tabs
+   * @param {Array<object>} root0.folders
+   * @param {Set<string>} root0.splitIds
+   * @param {Map<string, ?string>} root0.splitParents
+   * @param {Map<string, ?string>} root0.splitWs
+   * @param {object} root0.scope
+   */
+  #childSequence({ tabs, folders, splitIds, splitParents, splitWs, scope }) {
+    const seq = [];
+    const seenSplits = new Set();
+    for (const tab of tabs) {
+      const groupId = tab.groupId || null;
+      if (groupId && splitIds.has(groupId)) {
+        if (
+          !seenSplits.has(groupId) &&
+          scope.matchSplit(
+            splitParents.get(groupId) ?? null,
+            splitWs.get(groupId) ?? null
+          )
+        ) {
+          seenSplits.add(groupId);
+          seq.push(groupId);
+        }
+        continue;
+      }
+      if (scope.matchTab(tab, groupId)) {
+        seq.push(tab.zenSyncId);
+      }
+    }
+    for (const folder of folders) {
+      if (!scope.matchFolder(folder)) {
+        continue;
+      }
+      let index = seq.length;
+      const prev = folder.prevSiblingInfo;
+      if (!prev || prev.type === "start") {
+        // No stored sibling means the folder is the first child of its
+        // container (the section rebuild on startup places content before
+        // the fake start element, so the first item has no sibling at all).
+        index = 0;
+      } else if (prev.id) {
+        const at = seq.indexOf(prev.id);
+        if (at !== -1) {
+          index = at + 1;
+        } else if (prev.type === "tab") {
+          // An unsynced tab sibling (empty placeholders, live folder items)
+          // always sits at the start of its container.
+          index = 0;
+        }
+      }
+      seq.splice(index, 0, folder.id);
+    }
+    return seq;
+  }
+
+  /**
+   * Derives the shared projection context from one sidebar collection.
+   * Syncable tabs, folders, the syncable splits and their parents and
+   * workspaces, plus the folder-membership resolver.
+   *
+   * @param {object} sidebar
+   */
+  #projectionContext(sidebar) {
+    const tabs = (sidebar.tabs || []).filter(t => this.#isSyncableTab(t));
+    const folders = (sidebar.folders || []).filter(
+      f => f?.id && !f.splitViewGroup
+    );
+    const folderIds = new Set(folders.map(f => f.id));
+    const allSplits = (sidebar.splitViewData || []).filter(g => g?.groupId);
+    const splitParents = new Map();
+    for (const entry of sidebar.folders || []) {
+      if (entry?.splitViewGroup && entry.id) {
+        splitParents.set(entry.id, entry.parentId || null);
+      }
+    }
+
+    // Only splits whose members are all synced tabs are synced themselves.
+    const syncableTabIds = new Set(tabs.map(t => t.zenSyncId));
+    const splits = allSplits.filter(
+      g =>
+        Array.isArray(g.tabs) &&
+        g.tabs.length >= 2 &&
+        g.tabs.every(id => syncableTabIds.has(id))
+    );
+    const splitIds = new Set(splits.map(g => g.groupId));
+    const splitWs = new Map();
+    for (const tab of tabs) {
+      const groupId = tab.groupId || null;
+      if (groupId && splitIds.has(groupId) && !splitWs.has(groupId)) {
+        splitWs.set(groupId, tab.zenWorkspace || null);
+      }
+    }
+    const folderOf = groupId => {
+      if (!groupId) {
+        return null;
+      }
+      if (splitIds.has(groupId)) {
+        return splitParents.get(groupId) || null;
+      }
+      return folderIds.has(groupId) ? groupId : null;
+    };
+    return { tabs, folders, splits, splitIds, splitParents, splitWs, folderOf };
+  }
+
+  /**
+   * @param {Map} map
+   * @param {object} ctx - The projection context.
+   */
+  #projectTabs(map, ctx) {
+    for (const tab of ctx.tabs) {
+      const identity = this.#tabIdentity(tab);
+      if (!identity) {
+        continue;
+      }
+      const essential = !!tab.zenEssential;
+      map.set(tab.zenSyncId, {
+        kind: RECORD_KINDS.TAB,
+        data: {
+          tabId: tab.zenSyncId,
+          url: identity.url,
+          title: identity.title,
+          icon: identity.icon,
+          containerGuid: this.guidForContextId(tab.userContextId, {
+            create: true,
+          }),
+          essential,
+          workspaceUuid: essential ? null : tab.zenWorkspace || null,
+          folderId: ctx.folderOf(tab.groupId || null),
+          staticLabel:
+            typeof tab.zenStaticLabel === "string" ? tab.zenStaticLabel : null,
+          hasStaticIcon: !!tab.zenHasStaticIcon,
+          defaultContainer: !!tab.zenDefaultUserContextId,
+        },
+      });
+    }
+  }
+
+  projections() {
+    const sidebar = lazy.ZenSessionStore.getSidebarData() || {};
+    const stamp = sidebar.lastCollected || 0;
+    if (this.#cache && this.#cache.stamp === stamp) {
+      return this.#cache.map;
+    }
+
+    const map = new Map();
+    const pending = new Set();
+    const ctx = this.#projectionContext(sidebar);
+    const { tabs, folders, splits, splitIds, splitParents, splitWs } = ctx;
+
+    for (const identity of lazy.ContextualIdentityService.getPublicIdentities()) {
+      if (!identity.name) {
+        continue;
+      }
+      const guid = this.guidForContextId(identity.userContextId, {
+        create: true,
+      });
+      if (!guid) {
+        continue;
+      }
+      map.set(guid, {
+        kind: RECORD_KINDS.CONTAINER,
+        data: {
+          guid,
+          name: identity.name,
+          icon: identity.icon || "",
+          color: identity.color || "",
+        },
+      });
+    }
+
+    const spaces = sidebar.spaces || [];
+    for (const space of spaces) {
+      if (!space?.uuid) {
+        continue;
+      }
+      const uuid = space.uuid;
+      map.set(uuid, {
+        kind: RECORD_KINDS.SPACE,
+        data: {
+          uuid,
+          name: space.name ?? "",
+          icon: space.icon ?? null,
+          theme: space.theme ?? null,
+          containerGuid: this.guidForContextId(space.containerTabId, {
+            create: true,
+          }),
+          children: this.#childSequence({
+            tabs,
+            folders,
+            splitIds,
+            splitParents,
+            splitWs,
+            scope: {
+              matchTab: (t, groupId) =>
+                !groupId &&
+                !t.zenEssential &&
+                (t.zenWorkspace || null) === uuid,
+              matchSplit: (parent, ws) => !parent && ws === uuid,
+              matchFolder: f => !f.parentId && (f.workspaceId || null) === uuid,
+            },
+          }),
+        },
+      });
+    }
+
+    for (const folder of folders) {
+      const fid = folder.id;
+      let live = null;
+      if (folder.isLiveFolder) {
+        try {
+          live = lazy.ZenLiveFoldersManager.getSyncableFolderData(fid);
+        } catch (e) {
+          console.error("ZenSpacesSync: failed to project live folder", e);
+        }
+        if (!live) {
+          pending.add(fid);
+          continue;
+        }
+      }
+      map.set(fid, {
+        kind: RECORD_KINDS.FOLDER,
+        data: {
+          folderId: fid,
+          name: folder.name ?? "",
+          icon: folder.userIcon || null,
+          workspaceUuid: folder.workspaceId || null,
+          parentFolderId: folder.parentId || null,
+          live,
+          children: this.#childSequence({
+            tabs,
+            folders,
+            splitIds,
+            splitParents,
+            splitWs,
+            scope: {
+              matchTab: (t, groupId) => groupId === fid,
+              matchSplit: parent => parent === fid,
+              matchFolder: f => f.parentId === fid,
+            },
+          }),
+        },
+      });
+    }
+
+    this.#projectTabs(map, ctx);
+
+    for (const split of splits) {
+      map.set(split.groupId, {
+        kind: RECORD_KINDS.SPLIT,
+        data: {
+          splitId: split.groupId,
+          gridType: split.gridType || "grid",
+          tabs: [...split.tabs],
+          workspaceUuid: splitWs.get(split.groupId) ?? null,
+          folderId: splitParents.get(split.groupId) || null,
+        },
+      });
+    }
+
+    if (spaces.length) {
+      const essentials = {};
+      for (const tab of tabs) {
+        if (!tab.zenEssential) {
+          continue;
+        }
+        const key =
+          this.guidForContextId(tab.userContextId, { create: true }) ||
+          "default";
+        (essentials[key] ||= []).push(tab.zenSyncId);
+      }
+      map.set(LAYOUT_RECORD_ID, {
+        kind: RECORD_KINDS.LAYOUT,
+        data: {
+          spaces: spaces.map(s => s.uuid).filter(Boolean),
+          essentials,
+        },
+      });
+    }
+
+    this.#cache = { stamp, map, pending };
+    return map;
+  }
+
+  /**
+   * Ids that are locally present but deliberately not projected this cycle
+   * (live folders whose provider config isn't available yet). The diff must
+   * not read their absence as a deletion.
+   */
+  #pendingIds() {
+    this.projections();
+    return this.#cache.pending;
+  }
+
+  #digestCache = null;
+
+  /**
+   * Digests of all current projections. Change detection runs several times per
+   * sync cycle (tracker observe, changed-id computation, upload bookkeeping)
+   * and only needs to hash again after a fresh sidebar collection.
+   */
+  #digestAll() {
+    const map = this.projections();
+    if (this.#digestCache?.map === map) {
+      return this.#digestCache.digests;
+    }
+    const digests = new Map();
+    for (const [id, projected] of map) {
+      digests.set(id, recordDigest(projected.kind, projected.data));
+    }
+    this.#digestCache = { map, digests };
+    return digests;
+  }
+
+  /* Mark: engine-facing API */
+
+  getAllRecordIds() {
+    const ids = {};
+    for (const id of this.projections().keys()) {
+      ids[id] = true;
+    }
+    return ids;
+  }
+
+  itemExists(id) {
+    return this.projections().has(id);
+  }
+
+  projectRecord(id) {
+    return this.projections().get(id) ?? null;
+  }
+
+  /**
+   * Changes = diff between the current projections and the last state the
+   * server acknowledged. Ids present locally with different content are
+   * modified; ids only present in the uploaded snapshot are deletions.
+   */
+  computeChangedIDs() {
+    const uploaded = this.#data().uploaded;
+    const current = this.#digestAll();
+    const pending = this.#pendingIds();
+    const now = Date.now() / 1000;
+    const changes = {};
+    for (const [id, digest] of current) {
+      if (uploaded[id] !== digest) {
+        changes[id] = now;
+      }
+    }
+    for (const id of Object.keys(uploaded)) {
+      if (!current.has(id) && !pending.has(id)) {
+        changes[id] = now;
+      }
+    }
+    if (lazy.syncDebug && Object.keys(changes).length) {
+      const map = this.projections();
+      syncLog(
+        "outgoing diff:",
+        Object.keys(changes).map(id =>
+          current.has(id) ? `${map.get(id)?.kind} ${id}` : `TOMBSTONE ${id}`
+        )
+      );
+    }
+    return changes;
+  }
+
+  hasPendingChanges() {
+    const uploaded = this.#data().uploaded;
+    const current = this.#digestAll();
+    const pending = this.#pendingIds();
+    for (const [id, digest] of current) {
+      if (uploaded[id] !== digest) {
+        return true;
+      }
+    }
+    for (const id of Object.keys(uploaded)) {
+      if (!current.has(id) && !pending.has(id)) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  /**
+   * Called after records were successfully uploaded. Remember exactly what
+   * the server now holds for them.
+   *
+   * @param {Array<string>} ids
+   */
+  markUploaded(ids) {
+    const data = this.#data();
+    const current = this.#digestAll();
+    for (const id of ids) {
+      if (current.has(id)) {
+        data.uploaded[id] = current.get(id);
+      } else {
+        delete data.uploaded[id];
+      }
+    }
+    if (lazy.syncDebug && ids.length) {
+      syncLog(
+        "server acknowledged upload:",
+        ids.map(id => (current.has(id) ? id : `${id} (tombstone)`))
+      );
+    }
+    this.#file.saveSoon();
+  }
+
+  /**
+   * Called after an incoming record was applied locally. Storing the
+   * incoming payload as the uploaded state means a faithful local
+   * materialization produces no re-upload, while a divergent one re-uploads
+   * the local truth (self-healing).
+   *
+   * @param {string} id
+   * @param {?object} cleartext - null for tombstones.
+   */
+  noteApplied(id, cleartext) {
+    const data = this.#data();
+    if (!cleartext) {
+      delete data.uploaded[id];
+    } else {
+      data.uploaded[id] = recordDigest(cleartext.kind, cleartext.data);
+    }
+    syncLog(
+      `acknowledged incoming ${cleartext ? cleartext.kind : "tombstone"} ${id}`
+    );
+    this.#file.saveSoon();
+  }
+}
+
+export const ZenSpacesSyncModel = new nsZenSpacesSyncModel();
diff --git a/src/zen/sync/ZenSyncManager.sys.mjs b/src/zen/sync/ZenSyncManager.sys.mjs
deleted file mode 100644
index 1b454da81..000000000
--- a/src/zen/sync/ZenSyncManager.sys.mjs
+++ /dev/null
@@ -1,160 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-const lazy = {};
-
-ChromeUtils.defineESModuleGetters(lazy, {
-  ZenSessionStore: "resource:///modules/zen/ZenSessionManager.sys.mjs",
-  ContextualIdentityService:
-    "resource://gre/modules/ContextualIdentityService.sys.mjs",
-  ZenWindowSync: "resource:///modules/zen/ZenWindowSync.sys.mjs",
-});
-
-function normalizeUserContextId(value) {
-  const normalized = typeof value === "string" ? Number(value) : value;
-  if (!Number.isSafeInteger(normalized) || normalized <= 0) {
-    return null;
-  }
-  return normalized;
-}
-
-class ZenSyncManager {
-  getSidebarData() {
-    return lazy.ZenSessionStore.getSidebarData();
-  }
-
-  /**
-   * Whether to ignore changes to items. This is used to prevent
-   * infinite loops when applying incoming sync changes.
-   *
-   * @type {boolean}
-   */
-  #ignoreChanges = false;
-
-  #changedItems = new Map();
-
-  markItemChanged(item) {
-    if (item.type && item.id && !this.#ignoreChanges) {
-      const key = `${item.type}~${item.id}`;
-      this.#changedItems.set(key, { type: item.type, id: item.id });
-    }
-  }
-
-  #getChangedItems() {
-    return Array.from(this.#changedItems.values());
-  }
-
-  #clearChangedItems() {
-    this.#changedItems.clear();
-  }
-
-  notifyAboutChanges() {
-    const changedItems = this.#getChangedItems();
-
-    for (const item of changedItems) {
-      Services.obs.notifyObservers(
-        { wrappedJSObject: item },
-        "zen-workspace-item-changed"
-      );
-    }
-    this.#clearChangedItems();
-  }
-
-  async applyIncomingBatch(pulled, removals) {
-    try {
-      this.#ignoreChanges = true;
-      this.#applyIncomingContainers(
-        pulled.containers || [],
-        removals.containers || []
-      );
-
-      const win = lazy.ZenWindowSync.firstSyncedWindow;
-      if (win?.gZenWorkspaces) {
-        await win.gZenWorkspaces._applySyncChanges(pulled, removals);
-      }
-    } catch (e) {
-      console.error("ZenSyncManager: Failed to apply incoming sync data:", e);
-      throw e;
-    } finally {
-      this.#ignoreChanges = false;
-    }
-  }
-
-  #applyIncomingContainers(pulledContainers, removedContainers) {
-    const localContainersById = new Map(
-      lazy.ContextualIdentityService.getPublicIdentities().map(container => [
-        container.userContextId,
-        container,
-      ])
-    );
-
-    for (const container of pulledContainers) {
-      if (!container.name) {
-        continue;
-      }
-
-      const userContextId = normalizeUserContextId(container.userContextId);
-      if (userContextId === null) {
-        console.warn(
-          "ZenSyncManager: Ignoring incoming container with invalid userContextId",
-          { container }
-        );
-        continue;
-      }
-
-      const existsLocally = localContainersById.has(userContextId);
-
-      if (existsLocally) {
-        lazy.ContextualIdentityService.update(
-          userContextId,
-          container.name,
-          container.icon,
-          container.color
-        );
-        continue;
-      }
-
-      const createdIdentity = lazy.ContextualIdentityService.create(
-        container.name,
-        container.icon,
-        container.color,
-        userContextId
-      );
-      if (createdIdentity) {
-        localContainersById.set(createdIdentity.userContextId, createdIdentity);
-      }
-      if (createdIdentity && createdIdentity.userContextId !== userContextId) {
-        console.warn("ZenSyncManager: Container sync created unexpected ID", {
-          requestedId: userContextId,
-          createdId: createdIdentity.userContextId,
-          name: container.name,
-        });
-      }
-    }
-
-    for (const container of removedContainers) {
-      const userContextId = normalizeUserContextId(container.userContextId);
-      if (userContextId === null) {
-        console.warn(
-          "ZenSyncManager: Ignoring container removal with invalid userContextId",
-          { container }
-        );
-        continue;
-      }
-
-      if (!localContainersById.has(userContextId)) {
-        continue;
-      }
-
-      try {
-        lazy.ContextualIdentityService.remove(userContextId);
-        localContainersById.delete(userContextId);
-      } catch {
-        // Container may already be gone locally.
-      }
-    }
-  }
-}
-
-export const ZenSyncStore = new ZenSyncManager();
diff --git a/src/zen/sync/ZenWorkspacesSync.sys.mjs b/src/zen/sync/ZenWorkspacesSync.sys.mjs
deleted file mode 100644
index 0b0946ed4..000000000
--- a/src/zen/sync/ZenWorkspacesSync.sys.mjs
+++ /dev/null
@@ -1,404 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-import {
-  Store,
-  SyncEngine,
-  Tracker,
-} from "resource://services-sync/engines.sys.mjs";
-import { CryptoWrapper } from "resource://services-sync/record.sys.mjs";
-import { SCORE_INCREMENT_XLARGE } from "resource://services-sync/constants.sys.mjs";
-
-const lazy = {};
-
-ChromeUtils.defineESModuleGetters(lazy, {
-  ZenSyncStore: "resource:///modules/zen/ZenSyncManager.sys.mjs",
-  ContextualIdentityService:
-    "resource://gre/modules/ContextualIdentityService.sys.mjs",
-});
-
-const RECORD_ID_PREFIX_BY_TYPE = Object.freeze({
-  space: "s",
-  container: "c",
-});
-
-const RECORD_TYPE_BY_PREFIX = Object.freeze({
-  s: "space",
-  c: "container",
-});
-
-/**
- * Sync record wrapper for workspace and container items stored in the
- * Workspaces engine collection.
- */
-export class ZenWorkspacesRecord extends CryptoWrapper {
-  _logName = "Sync.Record.ZenSpaces";
-}
-
-ZenWorkspacesRecord.prototype.type = "spaces";
-
-function parseRecordId(id) {
-  const sep = id.indexOf("~");
-  if (sep === -1) {
-    return null;
-  }
-  const prefix = id.slice(0, sep);
-  const key = id.slice(sep + 1);
-  return { type: RECORD_TYPE_BY_PREFIX[prefix] || prefix, key };
-}
-
-function createRecordId(type, id) {
-  const prefix = RECORD_ID_PREFIX_BY_TYPE[type];
-  if (!prefix) {
-    throw new Error(`Unknown Spaces Sync record type: ${type}`);
-  }
-  return `${prefix}~${id}`;
-}
-
-function normalizeUserContextId(value) {
-  const normalized = typeof value === "string" ? Number(value) : value;
-  if (!Number.isSafeInteger(normalized) || normalized <= 0) {
-    return null;
-  }
-  return normalized;
-}
-
-/**
- * Strips the sync-envelope fields (`id` and `type`) from incoming record data
- * and restores the item's real identity key where needed
- *
- * @param {object} data
- */
-function stripSyncFields(data) {
-  const rest = { ...data };
-  delete rest.id;
-  delete rest.type;
-  return rest;
-}
-
-/**
- * Sync store implementation that serializes local workspace and container
- * state into records and applies incoming remote changes.
- */
-class ZenWorkspacesStore extends Store {
-  constructor(name, engine) {
-    super(name, engine);
-  }
-
-  async getAllIDs() {
-    const ids = {};
-    const sidebar = lazy.ZenSyncStore.getSidebarData();
-
-    for (const space of sidebar.spaces || []) {
-      if (space.uuid) {
-        ids[createRecordId("space", space.uuid)] = true;
-      }
-    }
-
-    for (const c of lazy.ContextualIdentityService.getPublicIdentities()) {
-      ids[createRecordId("container", c.userContextId)] = true;
-    }
-
-    return ids;
-  }
-
-  async itemExists(id) {
-    const parsed = parseRecordId(id);
-    if (!parsed) {
-      return false;
-    }
-    const sidebar = lazy.ZenSyncStore.getSidebarData();
-
-    switch (parsed.type) {
-      case "space":
-        return (sidebar.spaces || []).some(s => s.uuid === parsed.key);
-      case "container":
-        return lazy.ContextualIdentityService.getPublicIdentities().some(
-          c => String(c.userContextId) === parsed.key
-        );
-      default:
-        return false;
-    }
-  }
-
-  async createRecord(id, collection) {
-    const record = new ZenWorkspacesRecord(collection, id);
-    const parsed = parseRecordId(id);
-    if (!parsed) {
-      record.deleted = true;
-      return record;
-    }
-
-    const sidebar = lazy.ZenSyncStore.getSidebarData();
-
-    switch (parsed.type) {
-      case "space": {
-        const spaces = sidebar.spaces || [];
-        const idx = spaces.findIndex(s => s.uuid === parsed.key);
-        if (idx === -1) {
-          record.deleted = true;
-          return record;
-        }
-        const rest = { ...spaces[idx] };
-        delete rest.syncStatus;
-        record.cleartext = { id, type: "space", ...rest, position: idx };
-        break;
-      }
-
-      case "container": {
-        const container =
-          lazy.ContextualIdentityService.getPublicIdentities().find(
-            c => String(c.userContextId) === parsed.key
-          );
-        if (!container) {
-          record.deleted = true;
-          return record;
-        }
-        record.cleartext = {
-          id,
-          type: "container",
-          userContextId: container.userContextId,
-          name: container.name,
-          icon: container.icon,
-          color: container.color,
-        };
-        break;
-      }
-
-      default:
-        record.deleted = true;
-    }
-
-    return record;
-  }
-
-  async applyIncomingBatch(records, _countTelemetry) {
-    const pulled = { spaces: [], containers: [] };
-    const removals = { spaces: [], containers: [] };
-
-    for (const record of records) {
-      if (record.deleted) {
-        this._collectRemoval(record.id, removals);
-        continue;
-      }
-      const data = record.cleartext;
-      if (!data?.type) {
-        continue;
-      }
-      const clean = stripSyncFields(data);
-      switch (data.type) {
-        case "space":
-          pulled.spaces.push(clean);
-          break;
-        case "container":
-          pulled.containers.push(clean);
-          break;
-      }
-    }
-
-    // Suppress change tracking while applying incoming data to prevent
-    // feedback loops where applied items get re-uploaded immediately.
-    this.engine._tracker.ignoreAll = true;
-    try {
-      await lazy.ZenSyncStore.applyIncomingBatch(pulled, removals);
-    } finally {
-      this.engine._tracker.ignoreAll = false;
-    }
-    return [];
-  }
-
-  _collectRemoval(id, removals) {
-    const parsed = parseRecordId(id);
-    if (!parsed) {
-      return;
-    }
-    switch (parsed.type) {
-      case "space":
-        removals.spaces.push({ uuid: parsed.key });
-        break;
-      case "container": {
-        const userContextId = normalizeUserContextId(parsed.key);
-        if (userContextId === null) {
-          console.warn(
-            "ZenWorkspacesStore: Ignoring container removal with invalid userContextId",
-            { id }
-          );
-          break;
-        }
-        removals.containers.push({ userContextId });
-        break;
-      }
-    }
-  }
-
-  async create(record) {
-    await this._applySingle(record);
-  }
-
-  async update(record) {
-    await this._applySingle(record);
-  }
-
-  async _applySingle(record) {
-    this.engine._tracker.ignoreAll = true;
-    try {
-      if (record.deleted) {
-        const removals = { spaces: [], containers: [] };
-        this._collectRemoval(record.id, removals);
-        await lazy.ZenSyncStore.applyIncomingBatch(
-          { spaces: [], containers: [] },
-          removals
-        );
-        return;
-      }
-      const data = record.cleartext;
-      if (!data?.type) {
-        return;
-      }
-      const clean = stripSyncFields(data);
-      const pulled = { spaces: [], containers: [] };
-      switch (data.type) {
-        case "space":
-          pulled.spaces.push(clean);
-          break;
-        case "container":
-          pulled.containers.push(clean);
-          break;
-      }
-      await lazy.ZenSyncStore.applyIncomingBatch(pulled, {
-        spaces: [],
-        containers: [],
-      });
-    } finally {
-      this.engine._tracker.ignoreAll = false;
-    }
-  }
-
-  async remove() {
-    // No-op: never delete user data on wipe
-  }
-
-  async wipe() {
-    // No-op: never delete user data on wipe
-  }
-
-  changeItemID() {
-    // No-op
-  }
-}
-
-/**
- * Sync tracker that watches workspace and contextual identity observers and
- * marks the corresponding record IDs as changed.
- */
-class ZenWorkspacesTracker extends Tracker {
-  #changedIDs = {};
-  #ignoreAll = false;
-
-  get ignoreAll() {
-    return this.#ignoreAll;
-  }
-
-  set ignoreAll(value) {
-    this.#ignoreAll = value;
-  }
-
-  onStart() {
-    Services.obs.addObserver(this, "zen-workspace-item-changed");
-    Services.obs.addObserver(this, "contextual-identity-created");
-    Services.obs.addObserver(this, "contextual-identity-updated");
-    Services.obs.addObserver(this, "contextual-identity-deleted");
-  }
-
-  onStop() {
-    Services.obs.removeObserver(this, "zen-workspace-item-changed");
-    Services.obs.removeObserver(this, "contextual-identity-created");
-    Services.obs.removeObserver(this, "contextual-identity-updated");
-    Services.obs.removeObserver(this, "contextual-identity-deleted");
-  }
-
-  observe(subject, topic, _data) {
-    if (this.#ignoreAll) {
-      return;
-    }
-    if (topic === "zen-workspace-item-changed") {
-      const type = subject?.wrappedJSObject?.type;
-      const id = subject?.wrappedJSObject?.id;
-      if (type && id) {
-        this._trackChange({ type, id });
-      }
-    } else if (topic.startsWith("contextual-identity-")) {
-      const id = subject?.wrappedJSObject?.userContextId;
-      if (id && normalizeUserContextId(id) !== null) {
-        this._trackChange({ type: "container", id });
-      }
-    }
-  }
-
-  _trackChange(data) {
-    if (data.type && data.id) {
-      const id = createRecordId(data.type, data.id);
-      this.#changedIDs[id] = Date.now() / 1000;
-      this.score += SCORE_INCREMENT_XLARGE;
-    }
-  }
-
-  async getChangedIDs() {
-    return { ...this.#changedIDs };
-  }
-
-  async addChangedID(id, when) {
-    this.#changedIDs[id] = when;
-    return true;
-  }
-
-  async removeChangedID(...ids) {
-    for (const id of ids) {
-      delete this.#changedIDs[id];
-    }
-    return true;
-  }
-
-  clearChangedIDs() {
-    this.#changedIDs = {};
-  }
-}
-
-/**
- * Sync engine entrypoint that wires the Workspaces record, store, and tracker
- * implementations into Firefox Sync.
- */
-export class ZenWorkspacesEngine extends SyncEngine {
-  static get name() {
-    return "Spaces";
-  }
-
-  constructor(service) {
-    super("Spaces", service);
-  }
-
-  get _storeObj() {
-    return ZenWorkspacesStore;
-  }
-
-  get _trackerObj() {
-    return ZenWorkspacesTracker;
-  }
-
-  get _recordObj() {
-    return ZenWorkspacesRecord;
-  }
-
-  get version() {
-    return 2;
-  }
-
-  get syncPriority() {
-    return 8;
-  }
-
-  get allowSkippedRecord() {
-    return false;
-  }
-}
diff --git a/src/zen/sync/moz.build b/src/zen/sync/moz.build
index d10ad7a19..11868b8a0 100644
--- a/src/zen/sync/moz.build
+++ b/src/zen/sync/moz.build
@@ -3,6 +3,7 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 EXTRA_JS_MODULES.zen += [
-  "ZenSyncManager.sys.mjs",
-  "ZenWorkspacesSync.sys.mjs",
+    "ZenSpacesSync.sys.mjs",
+    "ZenSpacesSyncApplier.sys.mjs",
+    "ZenSpacesSyncModel.sys.mjs",
 ]
diff --git a/src/zen/tabs/ZenPinnedTabManager.mjs b/src/zen/tabs/ZenPinnedTabManager.mjs
index 7f4c48cf5..2313edd61 100644
--- a/src/zen/tabs/ZenPinnedTabManager.mjs
+++ b/src/zen/tabs/ZenPinnedTabManager.mjs
@@ -503,7 +503,7 @@ class nsZenPinnedTabManager extends nsZenDOMOperatedFeature {
     }
   }
 
-  addToEssentials(tab) {
+  addToEssentials(tab, { replicating = false } = {}) {
     // eslint-disable-next-line no-nested-ternary
     const tabs = tab
       ? // if it's already an array, dont make it [tab]
@@ -518,7 +518,12 @@ class nsZenPinnedTabManager extends nsZenDOMOperatedFeature {
       // eslint-disable-next-line no-shadow
       let tab = tabs[i];
       const section = gZenWorkspaces.getEssentialsSection(tab);
-      if (!this.canEssentialBeAdded(tab)) {
+      // canEssentialBeAdded gates user-initiated adds on the *active* space's
+      // container. A replicated add mirrors a decision already made in another
+      // window or on another device, always into the tab's own container
+      // section.
+      if (!replicating && !this.canEssentialBeAdded(tab)) {
+        this.log(`addToEssentials rejected for ${tab.id}`);
         movedAll = false;
         continue;
       }
@@ -570,6 +575,13 @@ class nsZenPinnedTabManager extends nsZenDOMOperatedFeature {
     for (let i = 0; i < tabs.length; i++) {
       // eslint-disable-next-line no-shadow
       const tab = tabs[i];
+      if (this._canLog) {
+        // eslint-disable-next-line no-console
+        console.trace(
+          `ZenPinnedTabManager: removing tab ${tab.id} from essentials ` +
+            `(unpin=${unpin})`
+        );
+      }
       tab.removeAttribute("zen-essential");
       if (
         gZenWorkspaces.workspaceEnabled &&
diff --git a/src/zen/tabs/zen-tabs/vertical-tabs.css b/src/zen/tabs/zen-tabs/vertical-tabs.css
index 9402bcf1d..9bd132ef6 100644
--- a/src/zen/tabs/zen-tabs/vertical-tabs.css
+++ b/src/zen/tabs/zen-tabs/vertical-tabs.css
@@ -302,7 +302,7 @@
   position: relative;
   border-bottom: 0 solid transparent !important;
 
-  --tab-block-margin: 2px;
+  --tab-margin-block: 2px;
   grid-gap: 0 !important;
 
   &[overflow]::after,
@@ -530,7 +530,7 @@
   }
 
   & #tabbrowser-arrowscrollbox-periphery {
-    margin-inline: var(--tab-block-margin);
+    margin-inline: var(--tab-margin-block);
   }
 
   & #nav-bar {
@@ -538,8 +538,7 @@
 
     :root[zen-single-toolbar="true"]:not([zen-has-empty-tab="true"]) & {
       & #urlbar:not([breakout-extend]) .urlbar-input-container {
-        padding-left: 8px;
-        padding-right: 4px;
+        padding-inline: 4px;
       }
     }
   }
@@ -631,7 +630,7 @@
       }
 
       & .tab-background {
-        margin-inline: var(--tab-block-margin);
+        margin-inline: var(--tab-margin-block);
         width: -moz-available;
       }
 
@@ -942,8 +941,8 @@
 .tab-reset-pin-button {
   display: flex;
   position: relative;
-  height: calc(100% - var(--tab-block-margin) * 2);
-  margin-left: calc(-1 * var(--tab-inline-padding) + var(--tab-block-margin));
+  height: calc(100% - var(--tab-margin-block) * 2);
+  margin-left: calc(-1 * var(--tab-inline-padding) + var(--tab-margin-block));
   margin-right: 8px;
   padding: 0 calc(var(--toolbarbutton-padding-inner) - 2px) 0 calc(var(--toolbarbutton-padding-inner) / 3 + var(--tab-inline-padding) - 2px);
   border-radius: 0;
@@ -1085,7 +1084,7 @@
 
     &[in-urlbar] {
       background: var(--tab-background-color-selected) !important;
-      box-shadow: var(--tab-selected-shadow);
+      box-shadow: var(--tab-box-shadow-selected);
     }
   }
 
@@ -1138,7 +1137,7 @@
   min-width: calc(100% + var(--zen-toolbox-padding) * 2);
   width: calc(100% + var(--zen-toolbox-padding) * 2);
   padding: 0 var(--zen-toolbox-padding);
-  display: grid;
+  display: grid !important; /* Override the hidden attribute */
 
   position: absolute;
 
diff --git a/src/zen/tests/manifest.toml b/src/zen/tests/manifest.toml
index c3f444157..c01ed3e6c 100644
--- a/src/zen/tests/manifest.toml
+++ b/src/zen/tests/manifest.toml
@@ -3,6 +3,36 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
+[alerts]
+source = "browser/base/content/test/alerts"
+is_direct_path = true
+
+[backforward]
+source = "browser/base/content/test/backforward"
+is_direct_path = true
+
+[caps]
+source = "browser/base/content/test/caps"
+is_direct_path = true
+
+[gesture]
+source = "browser/base/content/test/gesture"
+is_direct_path = true
+
+[gesture.replace-manifest]
+"[DEFAULT]" = '''[DEFAULT]
+prefs = [
+  "zen.window-sync.enabled=false",
+]'''
+
+[linkHandling]
+source = "browser/base/content/test/linkHandling"
+is_direct_path = true
+disable = [
+  # Glance opens with alt+click, firefox doesnt know that.
+  "browser_javascript_links.js",
+]
+
 [readermode]
 source = "toolkit/components/reader/tests/browser"
 is_direct_path = true
@@ -13,10 +43,88 @@ disable = [
   "browser_readerMode_colorSchemePref.js",
 ]
 
+[remote-settings]
+source = "services/settings/test/unit"
+is_direct_path = true
+xpcshell = true
+
+[remote-settings.replace-manifest]
+"../../../" = "../../../../services/"
+
 [safebrowsing]
 source = "browser/components/safebrowsing/content/test"
 is_direct_path = true
 
+[services-crypto]
+source = "services/crypto/tests/unit"
+is_direct_path = true
+xpcshell = true
+
+[services-crypto.replace-manifest]
+"../../../" = "../../../../services/"
+
+[sessionstore]
+source = "browser/components/sessionstore/test"
+is_direct_path = true
+disable = [
+  "browser_1933485_tab_groups_history.js",
+  "browser_1953801_tab_groups_history_close_other.js",
+  "browser_aboutSessionRestore.js",
+  "browser_bfcache_telemetry.js",
+  "browser_closedId.js",
+  "browser_closed_objects_changed_notifications_tabs.js",
+  "browser_closed_objects_changed_notifications_windows.js",
+  "browser_closed_tabs_closed_windows.js",
+  "browser_closed_tabs_windows.js",
+  "browser_cookies_partitioned.js",
+  "browser_crashedTabs.js",
+  "browser_dying_cache.js",
+  "browser_firefoxView_restore.js",
+  "browser_firefoxView_selected_restore.js",
+  "browser_forget_closed_tab_window_byId.js",
+  "browser_movePendingTabToNewWindow.js",
+  "browser_newtab_userTypedValue.js",
+  "browser_pinned_tabs.js",
+  "browser_purge_domaindata.js",
+  "browser_reopen_all_windows.js",
+  "browser_restoreLastActionCorrectOrder.js",
+  "browser_restoreLastClosedTabOrWindowOrSession.js",
+  "browser_restore_container_tabs_oa.js",
+  "browser_restore_tabless_window.js",
+  "browser_restore_verticalPinnedTabs.js",
+  "browser_restored_window_features.js",
+  "browser_scrollPositions.js",
+  "browser_scrollPositionsReaderMode.js",
+  "browser_searchModeSwitcher_restore.js",
+  "browser_speculative_connect.js",
+  "browser_splitview_integer_ids.js",
+  "browser_splitview_restore_in_closed_window.js",
+  "browser_splitview_string_migration.js",
+  "browser_swapDocShells.js",
+  "browser_tab_groups_restore_closed_in_closed_window.js",
+  "browser_tab_groups_restore_closed_in_open_window.js",
+  "browser_tab_groups_restore_closed_many_tabs.js",
+  "browser_tab_groups_closed.js",
+  "browser_tab_groups_restore_multiple.js",
+  "browser_tab_groups_restore_saved.js",
+  "browser_tab_groups_restore_simple.js",
+  "browser_tab_groups_save_on_removeAllTabsBut.js",
+  "browser_tab_groups_save_on_removeTabsToTheEnd.js",
+  "browser_tab_groups_save_on_removeTabsToTheStart.js",
+  "browser_tab_groups_save_on_window_close.js",
+  "browser_tab_groups_state.js",
+  "browser_tab_groups_undo.js",
+  "browser_tab_label_during_restore.js",
+  "browser_undoCloseById.js",
+  "browser_urlbarSearchMode.js",
+  "browser_windowStateContainer.js",
+  "browser_wireframe_basic.js",
+]
+
+[sessionstore.replace-manifest]
+'prefs = [' = '''prefs = [
+  "zen.window-sync.enabled=false",'''
+
 [shell]
 source = "browser/components/shell/test"
 is_direct_path = true
@@ -25,6 +133,15 @@ disable = [
   "browser_setDesktopBackgroundPreview.js",
 ]
 
+[sync]
+source = "services/sync/tests/unit"
+is_direct_path = true
+xpcshell = true
+
+[sync.replace-manifest]
+"../../../" = "../../../../services/"
+'"identity.fxaccounts.enabled=true"' = '"identity.fxaccounts.enabled=true", "browser.formfill.enable=true"'
+
 [tabMediaIndicator]
 source = "browser/components/tabbrowser/test/browser/tabMediaIndicator"
 is_direct_path = true
@@ -34,3 +151,10 @@ source = "toolkit/components/tooltiptext"
 disable = [
   "browser_input_file_tooltips.js",
 ]
+
+[zoom]
+source = "browser/base/content/test/zoom"
+is_direct_path = true
+
+[zoom.replace-manifest]
+"../general/" = "../../../../browser/base/content/test/general/"
diff --git a/src/zen/tests/media/head.js b/src/zen/tests/media/head.js
index de7674a1c..50dfaa974 100644
--- a/src/zen/tests/media/head.js
+++ b/src/zen/tests/media/head.js
@@ -30,7 +30,7 @@ async function playVideoIn(tab) {
     }
   );
   // Wait for the browser to actually consider the tab "playing" — this is
-  // what drives DOMAudioPlaybackStarted into the media controller.
+  // what drives the soundplaying TabAttrModified into the media controller.
   await BrowserTestUtils.waitForCondition(
     () => tab.soundPlaying,
     "tab reports soundplaying"
diff --git a/src/zen/tests/mochitests/alerts/browser.toml b/src/zen/tests/mochitests/alerts/browser.toml
new file mode 100644
index 000000000..6ac3bc4f1
--- /dev/null
+++ b/src/zen/tests/mochitests/alerts/browser.toml
@@ -0,0 +1,32 @@
+[DEFAULT]
+support-files = [
+  "head.js",
+  "file_dom_notifications.html",
+]
+
+["browser_notification_close.js"]
+https_first_disabled = true
+skip-if = [
+  "os == 'win'", # Bug 1227785
+]
+
+["browser_notification_do_not_disturb.js"]
+https_first_disabled = true
+
+["browser_notification_open_settings.js"]
+https_first_disabled = true
+skip-if = [
+  "os == 'win'", # Bug 1411118
+]
+
+["browser_notification_remove_permission.js"]
+https_first_disabled = true
+skip-if = [
+  "os == 'win'", # Bug 1411118
+]
+
+["browser_notification_tab_switching.js"]
+https_first_disabled = true
+skip-if = [
+  "os == 'win'", # Bug 1243263
+]
diff --git a/src/zen/tests/mochitests/alerts/browser_notification_close.js b/src/zen/tests/mochitests/alerts/browser_notification_close.js
new file mode 100644
index 000000000..7e9d43072
--- /dev/null
+++ b/src/zen/tests/mochitests/alerts/browser_notification_close.js
@@ -0,0 +1,78 @@
+"use strict";
+
+const { PlacesTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/PlacesTestUtils.sys.mjs"
+);
+
+const { PermissionTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/PermissionTestUtils.sys.mjs"
+);
+
+let notificationURL =
+  "https://example.org/browser/browser/base/content/test/alerts/file_dom_notifications.html";
+
+add_task(async function test_notificationClose() {
+  await addNotificationPermission(notificationURL);
+
+  await BrowserTestUtils.withNewTab(
+    {
+      gBrowser,
+      url: notificationURL,
+    },
+    async function dummyTabTask(aBrowser) {
+      await openNotification(aBrowser, "showNotification2");
+
+      info("Notification alert showing");
+
+      let alertWindow = Services.wm.getMostRecentWindow("alert:alert");
+      if (!alertWindow) {
+        ok(true, "Notifications don't use XUL windows on all platforms.");
+        await closeNotification(aBrowser);
+        return;
+      }
+
+      let alertTitleLabel =
+        alertWindow.document.getElementById("alertTitleLabel");
+      is(
+        alertTitleLabel.value,
+        "Test title",
+        "Title text of notification should be present"
+      );
+      let alertTextLabel =
+        alertWindow.document.getElementById("alertTextLabel");
+      is(
+        alertTextLabel.textContent,
+        "Test body 2",
+        "Body text of notification should be present"
+      );
+
+      let alertCloseButton = alertWindow.document.querySelector(".close-icon");
+      is(alertCloseButton.localName, "toolbarbutton", "close button found");
+      let promiseBeforeUnloadEvent = BrowserTestUtils.waitForEvent(
+        alertWindow,
+        "beforeunload"
+      );
+      let closedTime = alertWindow.Date.now();
+      alertCloseButton.click();
+      info("Clicked on close button");
+      await promiseBeforeUnloadEvent;
+
+      ok(true, "Alert should close when the close button is clicked");
+      let currentTime = alertWindow.Date.now();
+      // The notification will self-close at 12 seconds, so this checks
+      // that the notification closed before the timeout.
+      Assert.less(
+        currentTime - closedTime,
+        5000,
+        "Close requested at " +
+          closedTime +
+          ", actually closed at " +
+          currentTime
+      );
+    }
+  );
+});
+
+add_task(async function cleanup() {
+  PermissionTestUtils.remove(notificationURL, "desktop-notification");
+});
diff --git a/src/zen/tests/mochitests/alerts/browser_notification_do_not_disturb.js b/src/zen/tests/mochitests/alerts/browser_notification_do_not_disturb.js
new file mode 100644
index 000000000..852e0d1e2
--- /dev/null
+++ b/src/zen/tests/mochitests/alerts/browser_notification_do_not_disturb.js
@@ -0,0 +1,159 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/**
+ * Tests that notifications can be silenced using nsIAlertsDoNotDisturb
+ * on systems where that interface and its methods are implemented for
+ * the nsIAlertService.
+ */
+
+const ALERT_SERVICE = Cc["@mozilla.org/alerts-service;1"]
+  .getService(Ci.nsIAlertsService)
+  .QueryInterface(Ci.nsIAlertsDoNotDisturb);
+
+const PAGE =
+  "https://example.org/browser/browser/base/content/test/alerts/file_dom_notifications.html";
+
+// The amount of time in seconds that we will wait for a notification
+// to show up before we decide that it's not coming.
+const NOTIFICATION_TIMEOUT_SECS = 2000;
+
+add_setup(async function () {
+  await addNotificationPermission(PAGE);
+});
+
+/**
+ * Test that the manualDoNotDisturb attribute can prevent
+ * notifications from appearing.
+ */
+add_task(async function test_manualDoNotDisturb() {
+  try {
+    // Only run the test if the do-not-disturb
+    // interface has been implemented.
+    ALERT_SERVICE.manualDoNotDisturb;
+    ok(true, "Alert service implements do-not-disturb interface");
+  } catch (e) {
+    ok(
+      true,
+      "Alert service doesn't implement do-not-disturb interface, exiting test"
+    );
+    return;
+  }
+
+  // In the event that something goes wrong during this test, make sure
+  // we put the attribute back to the default setting when this test file
+  // exits.
+  registerCleanupFunction(() => {
+    ALERT_SERVICE.manualDoNotDisturb = false;
+  });
+
+  // Make sure that do-not-disturb is not enabled before we start.
+  ok(
+    !ALERT_SERVICE.manualDoNotDisturb,
+    "Alert service should not be disabled when test starts"
+  );
+
+  await BrowserTestUtils.withNewTab(PAGE, async browser => {
+    await openNotification(browser, "showNotification2");
+
+    info("Notification alert showing");
+
+    let alertWindow = Services.wm.getMostRecentWindow("alert:alert");
+
+    // For now, only the XUL alert backend implements the manualDoNotDisturb
+    // method for nsIAlertsDoNotDisturb, so we expect there to be a XUL alert
+    // window. If the method gets implemented by native backends in the future,
+    // we'll probably want to branch here and set the manualDoNotDisturb
+    // attribute manually.
+    ok(alertWindow, "Expected a XUL alert window.");
+
+    // We're using the XUL notification backend. This means that there's
+    // a menuitem for enabling manualDoNotDisturb. We exercise that
+    // menuitem here.
+    let doNotDisturbMenuItem = alertWindow.document.getElementById(
+      "doNotDisturbMenuItem"
+    );
+    is(doNotDisturbMenuItem.localName, "menuitem", "menuitem found");
+
+    let unloadPromise = BrowserTestUtils.waitForEvent(
+      alertWindow,
+      "beforeunload"
+    );
+
+    doNotDisturbMenuItem.click();
+    info("Clicked on do-not-disturb menuitem");
+    await unloadPromise;
+
+    // At this point, we should be configured to not display notifications
+    // to the user.
+    ok(
+      ALERT_SERVICE.manualDoNotDisturb,
+      "Alert service should be disabled after clicking menuitem"
+    );
+
+    // The notification should not appear, but there is no way from the
+    // client-side to know that it was blocked, except for waiting some time
+    // and realizing that the "onshow" event never fired.
+    await Assert.rejects(
+      openNotification(browser, "showNotification2", NOTIFICATION_TIMEOUT_SECS),
+      /timed out/,
+      "The notification should never display."
+    );
+
+    ALERT_SERVICE.manualDoNotDisturb = false;
+  });
+});
+
+/**
+ * Test that the suppressForScreenSharing attribute can prevent
+ * notifications from appearing.
+ */
+add_task(async function test_suppressForScreenSharing() {
+  try {
+    // Only run the test if the do-not-disturb
+    // interface has been implemented.
+    ALERT_SERVICE.suppressForScreenSharing;
+    ok(true, "Alert service implements do-not-disturb interface");
+  } catch (e) {
+    ok(
+      true,
+      "Alert service doesn't implement do-not-disturb interface, exiting test"
+    );
+    return;
+  }
+
+  // In the event that something goes wrong during this test, make sure
+  // we put the attribute back to the default setting when this test file
+  // exits.
+  registerCleanupFunction(() => {
+    ALERT_SERVICE.suppressForScreenSharing = false;
+  });
+
+  // Make sure that do-not-disturb is not enabled before we start.
+  ok(
+    !ALERT_SERVICE.suppressForScreenSharing,
+    "Alert service should not be suppressing for screen sharing when test " +
+      "starts"
+  );
+
+  await BrowserTestUtils.withNewTab(PAGE, async browser => {
+    await openNotification(browser, "showNotification2");
+
+    info("Notification alert showing");
+    await closeNotification(browser);
+    ALERT_SERVICE.suppressForScreenSharing = true;
+
+    // The notification should not appear, but there is no way from the
+    // client-side to know that it was blocked, except for waiting some time
+    // and realizing that the "onshow" event never fired.
+    await Assert.rejects(
+      openNotification(browser, "showNotification2", NOTIFICATION_TIMEOUT_SECS),
+      /timed out/,
+      "The notification should never display."
+    );
+  });
+
+  ALERT_SERVICE.suppressForScreenSharing = false;
+});
diff --git a/src/zen/tests/mochitests/alerts/browser_notification_open_settings.js b/src/zen/tests/mochitests/alerts/browser_notification_open_settings.js
new file mode 100644
index 000000000..4d25a357f
--- /dev/null
+++ b/src/zen/tests/mochitests/alerts/browser_notification_open_settings.js
@@ -0,0 +1,87 @@
+"use strict";
+
+var notificationURL =
+  "https://example.org/browser/browser/base/content/test/alerts/file_dom_notifications.html";
+// BrowserGlue passes "privacy-permissions" to openPreferences when the
+// notifications-open-settings observer fires; the Settings Redesign
+// LegacyPaneMappings shim routes that to the permissionsData pane.
+var expectedURL = Services.prefs.getBoolPref(
+  "browser.settings-redesign.enabled",
+  false
+)
+  ? "about:preferences#permissionsData"
+  : "about:preferences#privacy";
+
+add_task(async function test_settingsOpen_observer() {
+  info(
+    "Opening a dummy tab so openPreferences=>switchToTabHavingURI doesn't use the blank tab."
+  );
+  await BrowserTestUtils.withNewTab(
+    {
+      gBrowser,
+      url: "about:robots",
+    },
+    async function dummyTabTask() {
+      // Ensure preferences is loaded before removing the tab.
+      let syncPaneLoadedPromise = TestUtils.topicObserved(
+        "sync-pane-loaded",
+        () => true
+      );
+      let tabPromise = BrowserTestUtils.waitForNewTab(gBrowser, expectedURL);
+      info("simulate a notifications-open-settings notification");
+      let uri = NetUtil.newURI("https://example.com");
+      let principal = Services.scriptSecurityManager.createContentPrincipal(
+        uri,
+        {}
+      );
+      Services.obs.notifyObservers(principal, "notifications-open-settings");
+      let tab = await tabPromise;
+      ok(tab, "The notification settings tab opened");
+      await syncPaneLoadedPromise;
+      BrowserTestUtils.removeTab(tab);
+    }
+  );
+});
+
+add_task(async function test_settingsOpen_button() {
+  info("Adding notification permission");
+  await addNotificationPermission(notificationURL);
+
+  await BrowserTestUtils.withNewTab(
+    {
+      gBrowser,
+      url: notificationURL,
+    },
+    async function tabTask(aBrowser) {
+      info("Waiting for notification");
+      await openNotification(aBrowser, "showNotification2");
+
+      let alertWindow = Services.wm.getMostRecentWindow("alert:alert");
+      if (!alertWindow) {
+        ok(true, "Notifications don't use XUL windows on all platforms.");
+        await closeNotification(aBrowser);
+        return;
+      }
+
+      // Ensure preferences is loaded before removing the tab.
+      let syncPaneLoadedPromise = TestUtils.topicObserved(
+        "sync-pane-loaded",
+        () => true
+      );
+      let closePromise = promiseWindowClosed(alertWindow);
+      let tabPromise = BrowserTestUtils.waitForNewTab(gBrowser, expectedURL);
+      let openSettingsMenuItem = alertWindow.document.getElementById(
+        "openSettingsMenuItem"
+      );
+      openSettingsMenuItem.click();
+
+      info("Waiting for notification settings tab");
+      let tab = await tabPromise;
+      ok(tab, "The notification settings tab opened");
+
+      await syncPaneLoadedPromise;
+      await closePromise;
+      BrowserTestUtils.removeTab(tab);
+    }
+  );
+});
diff --git a/src/zen/tests/mochitests/alerts/browser_notification_remove_permission.js b/src/zen/tests/mochitests/alerts/browser_notification_remove_permission.js
new file mode 100644
index 000000000..ec6916e1b
--- /dev/null
+++ b/src/zen/tests/mochitests/alerts/browser_notification_remove_permission.js
@@ -0,0 +1,85 @@
+"use strict";
+
+const { PermissionTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/PermissionTestUtils.sys.mjs"
+);
+
+var tab;
+var notificationURL =
+  "https://example.org/browser/browser/base/content/test/alerts/file_dom_notifications.html";
+var alertWindowClosed = false;
+var permRemoved = false;
+
+function test() {
+  waitForExplicitFinish();
+
+  registerCleanupFunction(function () {
+    gBrowser.removeTab(tab);
+    window.restore();
+  });
+
+  addNotificationPermission(notificationURL).then(function openTab() {
+    tab = BrowserTestUtils.addTab(gBrowser, notificationURL);
+    gBrowser.selectedTab = tab;
+    BrowserTestUtils.browserLoaded(tab.linkedBrowser).then(() => onLoad());
+  });
+}
+
+function onLoad() {
+  openNotification(tab.linkedBrowser, "showNotification2").then(onAlertShowing);
+}
+
+function onAlertShowing() {
+  info("Notification alert showing");
+
+  let alertWindow = Services.wm.getMostRecentWindow("alert:alert");
+  if (!alertWindow) {
+    ok(true, "Notifications don't use XUL windows on all platforms.");
+    closeNotification(tab.linkedBrowser).then(finish);
+    return;
+  }
+  ok(
+    PermissionTestUtils.testExactPermission(
+      notificationURL,
+      "desktop-notification"
+    ),
+    "Permission should exist prior to removal"
+  );
+  let disableForOriginMenuItem = alertWindow.document.getElementById(
+    "disableForOriginMenuItem"
+  );
+  is(disableForOriginMenuItem.localName, "menuitem", "menuitem found");
+  Services.obs.addObserver(permObserver, "perm-changed");
+  alertWindow.addEventListener("beforeunload", onAlertClosing);
+  disableForOriginMenuItem.click();
+  info("Clicked on disable-for-origin menuitem");
+}
+
+function permObserver(subject, topic, data) {
+  if (topic != "perm-changed") {
+    return;
+  }
+
+  let permission = subject.QueryInterface(Ci.nsIPermission);
+  is(
+    permission.type,
+    "desktop-notification",
+    "desktop-notification permission changed"
+  );
+  is(data, "deleted", "desktop-notification permission deleted");
+
+  Services.obs.removeObserver(permObserver, "perm-changed");
+  permRemoved = true;
+  if (alertWindowClosed) {
+    finish();
+  }
+}
+
+function onAlertClosing(event) {
+  event.target.removeEventListener("beforeunload", onAlertClosing);
+
+  alertWindowClosed = true;
+  if (permRemoved) {
+    finish();
+  }
+}
diff --git a/src/zen/tests/mochitests/alerts/browser_notification_tab_switching.js b/src/zen/tests/mochitests/alerts/browser_notification_tab_switching.js
new file mode 100644
index 000000000..4e5a23f18
--- /dev/null
+++ b/src/zen/tests/mochitests/alerts/browser_notification_tab_switching.js
@@ -0,0 +1,116 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+"use strict";
+
+const { PermissionTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/PermissionTestUtils.sys.mjs"
+);
+
+var tab;
+var notification;
+var notificationURL =
+  "https://example.org/browser/browser/base/content/test/alerts/file_dom_notifications.html";
+var newWindowOpenedFromTab;
+
+add_task(async function test_notificationPreventDefaultAndSwitchTabs() {
+  await addNotificationPermission(notificationURL);
+
+  let originalTab = gBrowser.selectedTab;
+  await BrowserTestUtils.withNewTab(
+    {
+      gBrowser,
+      url: notificationURL,
+    },
+    async function dummyTabTask(aBrowser) {
+      // Put new tab in background so it is obvious when it is re-focused.
+      await BrowserTestUtils.switchTab(gBrowser, originalTab);
+      isnot(
+        gBrowser.selectedBrowser,
+        aBrowser,
+        "Notification page loaded as a background tab"
+      );
+
+      // First, show a notification that will be have the tab-switching prevented.
+      function promiseNotificationEvent(evt) {
+        return SpecialPowers.spawn(
+          aBrowser,
+          [evt],
+          async function (contentEvt) {
+            return new Promise(resolve => {
+              let contentNotification = content.wrappedJSObject._notification;
+              contentNotification.addEventListener(
+                contentEvt,
+                function (event) {
+                  resolve({ defaultPrevented: event.defaultPrevented });
+                },
+                { once: true }
+              );
+            });
+          }
+        );
+      }
+      await openNotification(aBrowser, "showNotification1");
+      info("Notification alert showing");
+      let alertWindow = Services.wm.getMostRecentWindow("alert:alert");
+      if (!alertWindow) {
+        ok(true, "Notifications don't use XUL windows on all platforms.");
+        await closeNotification(aBrowser);
+        return;
+      }
+      info("Clicking on notification");
+      let promiseClickEvent = promiseNotificationEvent("click");
+
+      // NB: This executeSoon is needed to allow the non-e10s runs of this test
+      // a chance to set the event listener on the page. Otherwise, we
+      // synchronously fire the click event before we listen for the event.
+      executeSoon(() => {
+        EventUtils.synthesizeMouseAtCenter(
+          alertWindow.document.getElementById("alertTitleLabel"),
+          {},
+          alertWindow
+        );
+      });
+      let clickEvent = await promiseClickEvent;
+      ok(
+        clickEvent.defaultPrevented,
+        "The event handler for the first notification cancels the event"
+      );
+      isnot(
+        gBrowser.selectedBrowser,
+        aBrowser,
+        "Notification page still a background tab"
+      );
+      let notificationClosed = promiseNotificationEvent("close");
+      await closeNotification(aBrowser);
+      await notificationClosed;
+
+      // Second, show a notification that will cause the tab to get switched.
+      await openNotification(aBrowser, "showNotification2");
+      alertWindow = Services.wm.getMostRecentWindow("alert:alert");
+      let promiseTabSelect = BrowserTestUtils.waitForEvent(
+        gBrowser.tabContainer,
+        "TabSelect"
+      );
+      EventUtils.synthesizeMouseAtCenter(
+        alertWindow.document.getElementById("alertTitleLabel"),
+        {},
+        alertWindow
+      );
+      await promiseTabSelect;
+      is(
+        gBrowser.selectedBrowser.currentURI.spec,
+        notificationURL,
+        "Clicking on the second notification should select its originating tab"
+      );
+      notificationClosed = promiseNotificationEvent("close");
+      await closeNotification(aBrowser);
+      await notificationClosed;
+    }
+  );
+});
+
+add_task(async function cleanup() {
+  PermissionTestUtils.remove(notificationURL, "desktop-notification");
+});
diff --git a/src/zen/tests/mochitests/alerts/file_dom_notifications.html b/src/zen/tests/mochitests/alerts/file_dom_notifications.html
new file mode 100644
index 000000000..6deede8fc
--- /dev/null
+++ b/src/zen/tests/mochitests/alerts/file_dom_notifications.html
@@ -0,0 +1,39 @@
+<html>
+<head>
+<meta charset="utf-8">
+<script>
+"use strict";
+
+function showNotification1() {
+  var options = {
+      dir: undefined,
+      lang: undefined,
+      body: "Test body 1",
+      tag: "Test tag",
+      icon: undefined,
+  };
+  var n = new Notification("Test title", options);
+  n.addEventListener("click", function(event) {
+    event.preventDefault();
+  });
+  return n;
+}
+
+function showNotification2() {
+  var options = {
+      dir: undefined,
+      lang: undefined,
+      body: "Test body 2",
+      tag: "Test tag",
+      icon: undefined,
+  };
+  return new Notification("Test title", options);
+}
+</script>
+</head>
+<body>
+<form id="notificationForm" onsubmit="showNotification();">
+  <input type="submit" value="Show notification" id="submit"/>
+</form>
+</body>
+</html>
diff --git a/src/zen/tests/mochitests/alerts/head.js b/src/zen/tests/mochitests/alerts/head.js
new file mode 100644
index 000000000..57b758483
--- /dev/null
+++ b/src/zen/tests/mochitests/alerts/head.js
@@ -0,0 +1,73 @@
+// Platforms may default to reducing motion. We override this to ensure the
+// alert slide animation is enabled in tests.
+SpecialPowers.pushPrefEnv({
+  set: [["ui.prefersReducedMotion", 0]],
+});
+
+async function addNotificationPermission(originString) {
+  return SpecialPowers.pushPermissions([
+    {
+      type: "desktop-notification",
+      allow: true,
+      context: originString,
+    },
+  ]);
+}
+
+/**
+ * Similar to `BrowserTestUtils.closeWindow`, but
+ * doesn't call `window.close()`.
+ */
+function promiseWindowClosed(window) {
+  return new Promise(function (resolve) {
+    Services.ww.registerNotification(function observer(subject, topic) {
+      if (topic == "domwindowclosed" && subject == window) {
+        Services.ww.unregisterNotification(observer);
+        resolve();
+      }
+    });
+  });
+}
+
+/**
+ * These two functions work with file_dom_notifications.html to open the
+ * notification and close it.
+ *
+ * |fn| can be showNotification1 or showNotification2.
+ * if |timeout| is passed, then the promise returned from this function is
+ * rejected after the requested number of miliseconds.
+ */
+function openNotification(aBrowser, fn, timeout) {
+  info(`openNotification: ${fn}`);
+  return SpecialPowers.spawn(
+    aBrowser,
+    [fn, timeout],
+    async function (contentFn, contentTimeout) {
+      await new Promise((resolve, reject) => {
+        let win = content.wrappedJSObject;
+        let notification = win[contentFn]();
+        win._notification = notification;
+
+        function listener() {
+          notification.removeEventListener("show", listener);
+          resolve();
+        }
+
+        notification.addEventListener("show", listener);
+
+        if (contentTimeout) {
+          content.setTimeout(() => {
+            notification.removeEventListener("show", listener);
+            reject("timed out");
+          }, contentTimeout);
+        }
+      });
+    }
+  );
+}
+
+function closeNotification(aBrowser) {
+  return SpecialPowers.spawn(aBrowser, [], function () {
+    content.wrappedJSObject._notification.close();
+  });
+}
diff --git a/src/zen/tests/mochitests/backforward/browser.toml b/src/zen/tests/mochitests/backforward/browser.toml
new file mode 100644
index 000000000..fd36247df
--- /dev/null
+++ b/src/zen/tests/mochitests/backforward/browser.toml
@@ -0,0 +1,7 @@
+[DEFAULT]
+
+["browser_history_menu.js"]
+fail-if = [
+  "a11y_checks", # Bug 1854233 navigator-toolbox may not be focusable
+]
+https_first_disabled = true
diff --git a/src/zen/tests/mochitests/backforward/browser_history_menu.js b/src/zen/tests/mochitests/backforward/browser_history_menu.js
new file mode 100644
index 000000000..8623d5405
--- /dev/null
+++ b/src/zen/tests/mochitests/backforward/browser_history_menu.js
@@ -0,0 +1,179 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// This test verifies that the back forward button long-press menu and context menu
+// shows the correct history items.
+
+add_task(async function mousedown_back() {
+  await testBackForwardMenu(false);
+});
+
+add_task(async function contextmenu_back() {
+  await testBackForwardMenu(true);
+});
+
+async function openHistoryMenu(useContextMenu) {
+  let backButton = document.getElementById("back-button");
+  let rect = backButton.getBoundingClientRect();
+
+  info("waiting for the history menu to open");
+
+  let popupShownPromise = BrowserTestUtils.waitForEvent(
+    useContextMenu ? document.getElementById("backForwardMenu") : backButton,
+    "popupshown"
+  );
+  if (useContextMenu) {
+    EventUtils.synthesizeMouseAtCenter(backButton, {
+      type: "contextmenu",
+      button: 2,
+    });
+  } else {
+    EventUtils.synthesizeMouseAtCenter(backButton, { type: "mousedown" });
+  }
+
+  EventUtils.synthesizeMouse(backButton, rect.width / 2, rect.height, {
+    type: "mouseup",
+  });
+  let popupEvent = await popupShownPromise;
+
+  ok(true, "history menu opened");
+
+  return popupEvent;
+}
+
+async function testBackForwardMenu(useContextMenu) {
+  let tab = await BrowserTestUtils.openNewForegroundTab(
+    gBrowser,
+    // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+    "http://example.com"
+  );
+
+  for (let iter = 2; iter <= 4; iter++) {
+    // Iterate three times. For the first two times through the loop, add a new history item.
+    // But for the last iteration, go back in the history instead.
+    await SpecialPowers.spawn(
+      gBrowser.selectedBrowser,
+      [iter],
+      async function (iterChild) {
+        if (iterChild == 4) {
+          let popStatePromise = new Promise(function (resolve) {
+            content.onpopstate = resolve;
+          });
+          content.history.back();
+          await popStatePromise;
+        } else {
+          // With the back-button intervention enabled, we need to make sure to
+          // trigger a user activation on each history entry, or they won't
+          // show in the menu.
+          content.document.notifyUserGestureActivation();
+          content.history.pushState({}, "" + iterChild, iterChild + ".html");
+        }
+      }
+    );
+
+    // Wait for the session data to be flushed before continuing the test
+    await new Promise(resolve =>
+      SessionStore.getSessionHistory(gBrowser.selectedTab, resolve)
+    );
+
+    let popupEvent = await openHistoryMenu(useContextMenu);
+
+    // Wait for the session data to be flushed before continuing the test
+    await new Promise(resolve =>
+      SessionStore.getSessionHistory(gBrowser.selectedTab, resolve)
+    );
+
+    is(
+      popupEvent.target.children.length,
+      iter > 3 ? 3 : iter,
+      "Correct number of history items"
+    );
+
+    let node = popupEvent.target.lastElementChild;
+    // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+    is(node.getAttribute("uri"), "http://example.com/", "'1' item uri");
+    is(node.getAttribute("index"), "0", "'1' item index");
+    is(
+      node.getAttribute("historyindex"),
+      iter == 3 ? "-2" : "-1",
+      "'1' item historyindex"
+    );
+
+    node = node.previousElementSibling;
+    // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+    is(node.getAttribute("uri"), "http://example.com/2.html", "'2' item uri");
+    is(node.getAttribute("index"), "1", "'2' item index");
+    is(
+      node.getAttribute("historyindex"),
+      iter == 3 ? "-1" : "0",
+      "'2' item historyindex"
+    );
+
+    if (iter >= 3) {
+      node = node.previousElementSibling;
+      // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+      is(node.getAttribute("uri"), "http://example.com/3.html", "'3' item uri");
+      is(node.getAttribute("index"), "2", "'3' item index");
+      is(
+        node.getAttribute("historyindex"),
+        iter == 4 ? "1" : "0",
+        "'3' item historyindex"
+      );
+    }
+
+    // Close the popup, but on the last iteration, click on one of the history items
+    // to ensure it opens in a new tab.
+    let popupHiddenPromise = BrowserTestUtils.waitForEvent(
+      popupEvent.target,
+      "popuphidden"
+    );
+
+    if (iter < 4) {
+      popupEvent.target.hidePopup();
+    } else {
+      let newTabPromise = BrowserTestUtils.waitForNewTab(
+        gBrowser,
+        // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+        url => url == "http://example.com/"
+      );
+
+      popupEvent.target.activateItem(popupEvent.target.children[2], {
+        button: 1,
+      });
+
+      let newtab = await newTabPromise;
+      gBrowser.removeTab(newtab);
+    }
+
+    await popupHiddenPromise;
+  }
+
+  gBrowser.removeTab(tab);
+}
+
+// Make sure that the history popup appears after navigating around in a preferences page.
+add_task(async function test_preferences_page() {
+  let tab = await BrowserTestUtils.openNewForegroundTab(
+    gBrowser,
+    "about:preferences"
+  );
+
+  openPreferences("search");
+  let popupEvent = await openHistoryMenu(true);
+
+  // Wait for the session data to be flushed before continuing the test
+  await new Promise(resolve =>
+    SessionStore.getSessionHistory(gBrowser.selectedTab, resolve)
+  );
+
+  is(popupEvent.target.children.length, 2, "Correct number of history items");
+
+  let popupHiddenPromise = BrowserTestUtils.waitForEvent(
+    popupEvent.target,
+    "popuphidden"
+  );
+  popupEvent.target.hidePopup();
+  await popupHiddenPromise;
+
+  gBrowser.removeTab(tab);
+});
diff --git a/src/zen/tests/mochitests/caps/browser.toml b/src/zen/tests/mochitests/caps/browser.toml
new file mode 100644
index 000000000..2afb307d4
--- /dev/null
+++ b/src/zen/tests/mochitests/caps/browser.toml
@@ -0,0 +1,10 @@
+[DEFAULT]
+
+["browser_principalSerialization_csp.js"]
+
+["browser_principalSerialization_json.js"]
+skip-if = [
+  "debug", # deliberately bypass assertions when deserializing. Bug 965637 removed the CSP from Principals, but the remaining bits in such Principals should deserialize correctly.
+]
+
+["browser_principalSerialization_version1.js"]
diff --git a/src/zen/tests/mochitests/caps/browser_principalSerialization_csp.js b/src/zen/tests/mochitests/caps/browser_principalSerialization_csp.js
new file mode 100644
index 000000000..909e72879
--- /dev/null
+++ b/src/zen/tests/mochitests/caps/browser_principalSerialization_csp.js
@@ -0,0 +1,106 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/*
+ * Within Bug 965637 we move the CSP away from the Principal. Serialized Principals however
+ * might still have CSPs serialized within them. This tests ensures that we do not
+ * encounter a memory corruption when deserializing. It's fine that the deserialized
+ * CSP is null, but the Principal itself should deserialize correctly.
+ */
+
+add_task(async function test_deserialize_principal_with_csp() {
+  /*
+  This test should be resilient to changes in principal serialization, if these are failing then it's likely the code will break session storage.
+  To recreate this for another version, copy the function into the browser console, browse some pages and printHistory.
+
+  Generated with:
+  function printHistory() {
+    let tests = [];
+    let entries = SessionStore.getSessionHistory(gBrowser.selectedTab).entries.map((entry) => { return entry.triggeringPrincipal_base64 });
+    entries.push(E10SUtils.serializePrincipal(gBrowser.selectedTab.linkedBrowser._contentPrincipal));
+    for (let entry of entries) {
+      console.log(entry);
+      let testData = {};
+      testData.input = entry;
+      let principal = E10SUtils.deserializePrincipal(testData.input);
+      testData.output = {};
+      if (principal.URI === null) {
+        testData.output.URI = false;
+      } else {
+        testData.output.URISpec = principal.URI.spec;
+      }
+      testData.output.originAttributes = principal.originAttributes;
+      testData.output.cspJSON = principal.cspJSON;
+
+      tests.push(testData);
+    }
+    return tests;
+  }
+  printHistory(); // Copy this into: serializedPrincipalsFromFirefox
+  */
+
+  let serializedPrincipalsFromFirefox = [
+    {
+      input:
+        "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",
+      output: {
+        // Within Bug 965637 we removed CSP from Principals. Already serialized Principals however should still deserialize correctly (just without the CSP).
+        // "cspJSON": "{\"csp-policies\":[{\"child-src\":[\"https://www.googletagmanager.com\",\"https://www.google-analytics.com\",\"https://www.youtube-nocookie.com\",\"https://trackertest.org\",\"https://www.surveygizmo.com\",\"https://accounts.firefox.com\",\"https://accounts.firefox.com.cn\",\"https://www.youtube.com\"],\"connect-src\":[\"'self'\",\"https://*.mozilla.net\",\"https://*.mozilla.org\",\"https://*.mozilla.com\",\"https://www.googletagmanager.com\",\"https://www.google-analytics.com\",\"https://accounts.firefox.com/\",\"https://accounts.firefox.com.cn/\"],\"default-src\":[\"'self'\",\"https://*.mozilla.net\",\"https://*.mozilla.org\",\"https://*.mozilla.com\"],\"frame-src\":[\"https://www.googletagmanager.com\",\"https://www.google-analytics.com\",\"https://www.youtube-nocookie.com\",\"https://trackertest.org\",\"https://www.surveygizmo.com\",\"https://accounts.firefox.com\",\"https://accounts.firefox.com.cn\",\"https://www.youtube.com\"],\"img-src\":[\"'self'\",\"https://*.mozilla.net\",\"https://*.mozilla.org\",\"https://*.mozilla.com\",\"data:\",\"https://mozilla.org\",\"https://www.googletagmanager.com\",\"https://www.google-analytics.com\",\"https://adservice.google.com\",\"https://adservice.google.de\",\"https://adservice.google.dk\",\"https://creativecommons.org\",\"https://ad.doubleclick.net\"],\"report-only\":false,\"script-src\":[\"'self'\",\"https://*.mozilla.net\",\"https://*.mozilla.org\",\"https://*.mozilla.com\",\"'unsafe-inline'\",\"'unsafe-eval'\",\"https://www.googletagmanager.com\",\"https://www.google-analytics.com\",\"https://tagmanager.google.com\",\"https://www.youtube.com\",\"https://s.ytimg.com\"],\"style-src\":[\"'self'\",\"https://*.mozilla.net\",\"https://*.mozilla.org\",\"https://*.mozilla.com\",\"'unsafe-inline'\"]}]}",
+        URISpec: "https://www.mozilla.org/en-US/",
+        originAttributes: {
+          firstPartyDomain: "",
+          inIsolatedMozBrowser: false,
+          privateBrowsingId: 0,
+          userContextId: 0,
+          geckoViewSessionContextId: "",
+          partitionKey: "",
+        },
+      },
+    },
+    {
+      input:
+        "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",
+      output: {
+        URISpec: "https://www.mozilla.org/en-US/firefox/accounts/",
+        originAttributes: {
+          firstPartyDomain: "",
+          inIsolatedMozBrowser: false,
+          privateBrowsingId: 0,
+          userContextId: 0,
+          geckoViewSessionContextId: "",
+          partitionKey: "",
+        },
+        // Within Bug 965637 we removed CSP from Principals. Already serialized Principals however should still deserialize correctly (just without the CSP).
+        // "cspJSON": "{\"csp-policies\":[{\"child-src\":[\"https://www.googletagmanager.com\",\"https://www.google-analytics.com\",\"https://www.youtube-nocookie.com\",\"https://trackertest.org\",\"https://www.surveygizmo.com\",\"https://accounts.firefox.com\",\"https://accounts.firefox.com.cn\",\"https://www.youtube.com\"],\"connect-src\":[\"'self'\",\"https://*.mozilla.net\",\"https://*.mozilla.org\",\"https://*.mozilla.com\",\"https://www.googletagmanager.com\",\"https://www.google-analytics.com\",\"https://accounts.firefox.com/\",\"https://accounts.firefox.com.cn/\"],\"default-src\":[\"'self'\",\"https://*.mozilla.net\",\"https://*.mozilla.org\",\"https://*.mozilla.com\"],\"frame-src\":[\"https://www.googletagmanager.com\",\"https://www.google-analytics.com\",\"https://www.youtube-nocookie.com\",\"https://trackertest.org\",\"https://www.surveygizmo.com\",\"https://accounts.firefox.com\",\"https://accounts.firefox.com.cn\",\"https://www.youtube.com\"],\"img-src\":[\"'self'\",\"https://*.mozilla.net\",\"https://*.mozilla.org\",\"https://*.mozilla.com\",\"data:\",\"https://mozilla.org\",\"https://www.googletagmanager.com\",\"https://www.google-analytics.com\",\"https://adservice.google.com\",\"https://adservice.google.de\",\"https://adservice.google.dk\",\"https://creativecommons.org\",\"https://ad.doubleclick.net\"],\"report-only\":false,\"script-src\":[\"'self'\",\"https://*.mozilla.net\",\"https://*.mozilla.org\",\"https://*.mozilla.com\",\"'unsafe-inline'\",\"'unsafe-eval'\",\"https://www.googletagmanager.com\",\"https://www.google-analytics.com\",\"https://tagmanager.google.com\",\"https://www.youtube.com\",\"https://s.ytimg.com\"],\"style-src\":[\"'self'\",\"https://*.mozilla.net\",\"https://*.mozilla.org\",\"https://*.mozilla.com\",\"'unsafe-inline'\"]}]}",
+      },
+    },
+  ];
+
+  for (let test of serializedPrincipalsFromFirefox) {
+    let principal = E10SUtils.deserializePrincipal(test.input);
+
+    for (let key in principal.originAttributes) {
+      is(
+        principal.originAttributes[key],
+        test.output.originAttributes[key],
+        `Ensure value of ${key} is ${test.output.originAttributes[key]}`
+      );
+    }
+
+    if ("URI" in test.output && test.output.URI === false) {
+      is(
+        principal.isContentPrincipal,
+        false,
+        "Should have not have a URI for system"
+      );
+    } else {
+      is(
+        principal.spec,
+        test.output.URISpec,
+        `Should have spec ${test.output.URISpec}`
+      );
+    }
+  }
+});
diff --git a/src/zen/tests/mochitests/caps/browser_principalSerialization_json.js b/src/zen/tests/mochitests/caps/browser_principalSerialization_json.js
new file mode 100644
index 000000000..f79f269fd
--- /dev/null
+++ b/src/zen/tests/mochitests/caps/browser_principalSerialization_json.js
@@ -0,0 +1,161 @@
+"use strict";
+
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/*
+  This test file exists to ensure whenever changes to principal serialization happens,
+  we guarantee that the data can be restored and generated into a new principal.
+
+  The tests are written to be brittle so we encode all versions of the changes into the tests.
+*/
+
+add_task(async function test_nullPrincipal() {
+  const nullId = "0";
+  // fields
+  const uri = 0;
+  const suffix = 1;
+
+  const nullReplaceRegex =
+    /moz-nullprincipal:{[a-f0-9]{8}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]{12}}/;
+  const NULL_REPLACE = "NULL_PRINCIPAL_URL";
+
+  /*
+   This test should NOT be resilient to changes in versioning,
+   however it exists purely to verify the code doesn't unintentionally change without updating versioning and migration code.
+  */
+  let tests = [
+    {
+      input: { OA: {} },
+      expected: `{"${nullId}":{"${uri}":"${NULL_REPLACE}"}}`,
+    },
+    {
+      input: { OA: {} },
+      expected: `{"${nullId}":{"${uri}":"${NULL_REPLACE}"}}`,
+    },
+    {
+      input: { OA: { userContextId: 0 } },
+      expected: `{"${nullId}":{"${uri}":"${NULL_REPLACE}"}}`,
+    },
+    {
+      input: { OA: { userContextId: 2 } },
+      expected: `{"${nullId}":{"${uri}":"${NULL_REPLACE}","${suffix}":"^userContextId=2"}}`,
+    },
+    {
+      input: { OA: { privateBrowsingId: 1 } },
+      expected: `{"${nullId}":{"${uri}":"${NULL_REPLACE}","${suffix}":"^privateBrowsingId=1"}}`,
+    },
+    {
+      input: { OA: { privateBrowsingId: 0 } },
+      expected: `{"${nullId}":{"${uri}":"${NULL_REPLACE}"}}`,
+    },
+  ];
+
+  for (let test of tests) {
+    let p = Services.scriptSecurityManager.createNullPrincipal(test.input.OA);
+    let sp = E10SUtils.serializePrincipal(p);
+    // Not sure why cppjson is adding a \n here
+    let spr = sp.replace(nullReplaceRegex, NULL_REPLACE);
+    is(
+      test.expected,
+      spr,
+      "Expected serialized object for " + JSON.stringify(test.input)
+    );
+    let dp = E10SUtils.deserializePrincipal(sp);
+
+    // Check all the origin attributes
+    for (let key in test.input.OA) {
+      is(
+        dp.originAttributes[key],
+        test.input.OA[key],
+        "Ensure value of " + key + " is " + test.input.OA[key]
+      );
+    }
+  }
+});
+
+add_task(async function test_contentPrincipal() {
+  const contentId = "1";
+  // fields
+  const content = 0;
+  // const domain = 1;
+  const suffix = 2;
+  // const csp = 3;
+
+  /*
+   This test should NOT be resilient to changes in versioning,
+   however it exists purely to verify the code doesn't unintentionally change without updating versioning and migration code.
+  */
+  let tests = [
+    {
+      // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+      input: { uri: "http://example.com/", OA: {} },
+      expected: `{"${contentId}":{"${content}":"http://example.com/"}}`,
+    },
+    {
+      // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+      input: { uri: "http://mozilla1.com/", OA: {} },
+      expected: `{"${contentId}":{"${content}":"http://mozilla1.com/"}}`,
+    },
+    {
+      // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+      input: { uri: "http://mozilla2.com/", OA: { userContextId: 0 } },
+      expected: `{"${contentId}":{"${content}":"http://mozilla2.com/"}}`,
+    },
+    {
+      // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+      input: { uri: "http://mozilla3.com/", OA: { userContextId: 2 } },
+      expected: `{"${contentId}":{"${content}":"http://mozilla3.com/","${suffix}":"^userContextId=2"}}`,
+    },
+    {
+      // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+      input: { uri: "http://mozilla4.com/", OA: { privateBrowsingId: 1 } },
+      expected: `{"${contentId}":{"${content}":"http://mozilla4.com/","${suffix}":"^privateBrowsingId=1"}}`,
+    },
+    {
+      // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+      input: { uri: "http://mozilla5.com/", OA: { privateBrowsingId: 0 } },
+      expected: `{"${contentId}":{"${content}":"http://mozilla5.com/"}}`,
+    },
+  ];
+
+  for (let test of tests) {
+    let uri = Services.io.newURI(test.input.uri);
+    let p = Services.scriptSecurityManager.createContentPrincipal(
+      uri,
+      test.input.OA
+    );
+    let sp = E10SUtils.serializePrincipal(p);
+    is(test.expected, sp, "Expected serialized object for " + test.input.uri);
+    let dp = E10SUtils.deserializePrincipal(sp);
+    is(dp.URI.spec, test.input.uri, "Ensure spec is the same");
+
+    // Check all the origin attributes
+    for (let key in test.input.OA) {
+      is(
+        dp.originAttributes[key],
+        test.input.OA[key],
+        "Ensure value of " + key + " is " + test.input.OA[key]
+      );
+    }
+  }
+});
+
+add_task(async function test_systemPrincipal() {
+  const systemId = "3";
+  /*
+   This test should NOT be resilient to changes in versioning,
+   however it exists purely to verify the code doesn't unintentionally change without updating versioning and migration code.
+  */
+  const expected = `{"${systemId}":{}}`;
+
+  let p = Services.scriptSecurityManager.getSystemPrincipal();
+  let sp = E10SUtils.serializePrincipal(p);
+  is(expected, sp, "Expected serialized object for system principal");
+  let dp = E10SUtils.deserializePrincipal(sp);
+  is(
+    dp,
+    Services.scriptSecurityManager.getSystemPrincipal(),
+    "Deserialized the system principal"
+  );
+});
diff --git a/src/zen/tests/mochitests/caps/browser_principalSerialization_version1.js b/src/zen/tests/mochitests/caps/browser_principalSerialization_version1.js
new file mode 100644
index 000000000..6c4a41e91
--- /dev/null
+++ b/src/zen/tests/mochitests/caps/browser_principalSerialization_version1.js
@@ -0,0 +1,159 @@
+"use strict";
+
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/*
+  This test file exists to ensure whenever changes to principal serialization happens,
+  we guarantee that the data can be restored and generated into a new principal.
+
+  The tests are written to be brittle so we encode all versions of the changes into the tests.
+*/
+
+add_task(function test_nullPrincipal() {
+  /*
+   As Null principals are designed to be non deterministic we just need to ensure that
+   a previous serialized version matches what it was generated as.
+
+   This test should be resilient to changes in versioning, however it should also be duplicated for a new serialization change.
+  */
+  // Principal created with: E10SUtils.serializePrincipal(Services.scriptSecurityManager.createNullPrincipal({ }));
+  let p = E10SUtils.deserializePrincipal(
+    "vQZuXxRvRHKDMXv9BbHtkAAAAAAAAAAAwAAAAAAAAEYAAAA4bW96LW51bGxwcmluY2lwYWw6ezU2Y2FjNTQwLTg2NGQtNDdlNy04ZTI1LTE2MTRlYWI1MTU1ZX0AAAAA"
+  );
+  is(
+    "moz-nullprincipal:{56cac540-864d-47e7-8e25-1614eab5155e}",
+    p.URI.spec,
+    "Deserialized principal doesn't have the correct URI"
+  );
+
+  // Principal created with: E10SUtils.serializePrincipal(Services.scriptSecurityManager.createNullPrincipal({ userContextId: 2 }));
+  let p2 = E10SUtils.deserializePrincipal(
+    "vQZuXxRvRHKDMXv9BbHtkAAAAAAAAAAAwAAAAAAAAEYAAAA4bW96LW51bGxwcmluY2lwYWw6ezA1ZjllN2JhLWIwODMtNDJhMi1iNDdkLTZiODRmNmYwYTM3OX0AAAAQXnVzZXJDb250ZXh0SWQ9Mg=="
+  );
+  is(
+    "moz-nullprincipal:{05f9e7ba-b083-42a2-b47d-6b84f6f0a379}",
+    p2.URI.spec,
+    "Deserialized principal doesn't have the correct URI"
+  );
+  is(p2.originAttributes.userContextId, 2, "Expected a userContextId of 2");
+});
+
+add_task(async function test_realHistoryCheck() {
+  /*
+  This test should be resilient to changes in principal serialization, if these are failing then it's likely the code will break session storage.
+  To recreate this for another version, copy the function into the browser console, browse some pages and printHistory.
+
+  Generated with:
+  function printHistory() {
+    let tests = [];
+    let entries = SessionStore.getSessionHistory(gBrowser.selectedTab).entries.map((entry) => { return entry.triggeringPrincipal_base64 });
+    entries.push(E10SUtils.serializePrincipal(gBrowser.selectedTab.linkedBrowser._contentPrincipal));
+    for (let entry of entries) {
+      console.log(entry);
+      let testData = {};
+      testData.input = entry;
+      let principal = E10SUtils.deserializePrincipal(testData.input);
+      testData.output = {};
+      if (principal.URI === null) {
+        testData.output.URI = false;
+      } else {
+        testData.output.URISpec = principal.URI.spec;
+      }
+      testData.output.originAttributes = principal.originAttributes;
+
+      tests.push(testData);
+    }
+    return tests;
+  }
+  printHistory(); // Copy this into: serializedPrincipalsFromFirefox
+  */
+
+  let serializedPrincipalsFromFirefox = [
+    {
+      input: "SmIS26zLEdO3ZQBgsLbOywAAAAAAAAAAwAAAAAAAAEY=",
+      output: {
+        URI: false,
+        originAttributes: {
+          firstPartyDomain: "",
+          inIsolatedMozBrowser: false,
+          privateBrowsingId: 0,
+          userContextId: 0,
+          geckoViewSessionContextId: "",
+          partitionKey: "",
+        },
+      },
+    },
+    {
+      input:
+        "ZT4OTT7kRfqycpfCC8AeuAAAAAAAAAAAwAAAAAAAAEYB3pRy0IA0EdOTmQAQS6D9QJIHOlRteE8wkTq4cYEyCMYAAAAC/////wAAAbsBAAAAe2h0dHBzOi8vZGV2ZWxvcGVyLm1vemlsbGEub3JnL2VuLVVTLz91dG1fc291cmNlPXd3dy5tb3ppbGxhLm9yZyZ1dG1fbWVkaXVtPXJlZmVycmFsJnV0bV9jYW1wYWlnbj1uYXYmdXRtX2NvbnRlbnQ9ZGV2ZWxvcGVycwAAAAAAAAAFAAAACAAAABUAAAAA/////wAAAAD/////AAAACAAAABUAAAAdAAAAXgAAAB0AAAAHAAAAHQAAAAcAAAAkAAAAAAAAAAD/////AAAAAP////8AAAAlAAAAVgAAAAD/////AQAAAAAAAAAAAAAAAA==",
+      output: {
+        URISpec:
+          "https://developer.mozilla.org/en-US/?utm_source=www.mozilla.org&utm_medium=referral&utm_campaign=nav&utm_content=developers",
+        originAttributes: {
+          firstPartyDomain: "",
+          inIsolatedMozBrowser: false,
+          privateBrowsingId: 0,
+          userContextId: 0,
+          geckoViewSessionContextId: "",
+          partitionKey: "",
+        },
+      },
+    },
+    {
+      input: "SmIS26zLEdO3ZQBgsLbOywAAAAAAAAAAwAAAAAAAAEY=",
+      output: {
+        URI: false,
+        originAttributes: {
+          firstPartyDomain: "",
+          inIsolatedMozBrowser: false,
+          privateBrowsingId: 0,
+          userContextId: 0,
+          geckoViewSessionContextId: "",
+          partitionKey: "",
+        },
+      },
+    },
+    {
+      input:
+        "vQZuXxRvRHKDMXv9BbHtkAAAAAAAAAAAwAAAAAAAAEYAAAA4bW96LW51bGxwcmluY2lwYWw6ezA0NWNhMThkLTQzNmMtNDc0NC1iYmI2LWIxYTE1MzY2ZGY3OX0AAAAA",
+      output: {
+        URISpec: "moz-nullprincipal:{045ca18d-436c-4744-bbb6-b1a15366df79}",
+        originAttributes: {
+          firstPartyDomain: "",
+          inIsolatedMozBrowser: false,
+          privateBrowsingId: 0,
+          userContextId: 0,
+          geckoViewSessionContextId: "",
+          partitionKey: "",
+        },
+      },
+    },
+  ];
+
+  for (let test of serializedPrincipalsFromFirefox) {
+    let principal = E10SUtils.deserializePrincipal(test.input);
+
+    for (let key in principal.originAttributes) {
+      is(
+        principal.originAttributes[key],
+        test.output.originAttributes[key],
+        `Ensure value of ${key} is ${test.output.originAttributes[key]}`
+      );
+    }
+
+    if ("URI" in test.output && test.output.URI === false) {
+      is(
+        principal.isContentPrincipal,
+        false,
+        "Should have not have a URI for system"
+      );
+    } else {
+      is(
+        principal.spec,
+        test.output.URISpec,
+        `Should have spec ${test.output.URISpec}`
+      );
+    }
+  }
+});
diff --git a/src/zen/tests/mochitests/gesture/browser.toml b/src/zen/tests/mochitests/gesture/browser.toml
new file mode 100644
index 000000000..4e9cc2e0d
--- /dev/null
+++ b/src/zen/tests/mochitests/gesture/browser.toml
@@ -0,0 +1,11 @@
+[DEFAULT]
+prefs = [
+  "zen.window-sync.enabled=false",
+]
+
+["browser_gesture_navigation.js"]
+
+["browser_gesture_scroll.js"]
+skip-if = [
+  "os == 'mac' && os_version == '15.30' && arch == 'aarch64'", # Bug 1988390
+]
diff --git a/src/zen/tests/mochitests/gesture/browser_gesture_navigation.js b/src/zen/tests/mochitests/gesture/browser_gesture_navigation.js
new file mode 100644
index 000000000..f92b070bb
--- /dev/null
+++ b/src/zen/tests/mochitests/gesture/browser_gesture_navigation.js
@@ -0,0 +1,231 @@
+"use strict";
+
+add_setup(async () => {
+  // Disable window occlusion. See bug 1733955 / bug 1779559.
+  if (navigator.platform.indexOf("Win") == 0) {
+    await SpecialPowers.pushPrefEnv({
+      set: [["widget.windows.window_occlusion_tracking.enabled", false]],
+    });
+  }
+});
+
+add_task(async () => {
+  // Open a new browser window to make sure there is no navigation history.
+  const newBrowser = await BrowserTestUtils.openNewBrowserWindow({});
+
+  let event = {
+    direction: SimpleGestureEvent.DIRECTION_LEFT,
+  };
+  ok(!newBrowser.gGestureSupport._shouldDoSwipeGesture(event));
+
+  event = {
+    direction: SimpleGestureEvent.DIRECTION_RIGHT,
+  };
+  ok(!newBrowser.gGestureSupport._shouldDoSwipeGesture(event));
+
+  await BrowserTestUtils.closeWindow(newBrowser);
+});
+
+function createSimpleGestureEvent(type, direction) {
+  let event = document.createEvent("SimpleGestureEvent");
+  event.initSimpleGestureEvent(
+    type,
+    false /* canBubble */,
+    false /* cancelableArg */,
+    window,
+    0 /* detail */,
+    0 /* screenX */,
+    0 /* screenY */,
+    0 /* clientX */,
+    0 /* clientY */,
+    false /* ctrlKey */,
+    false /* altKey */,
+    false /* shiftKey */,
+    false /* metaKey */,
+    0 /* button */,
+    null /* relatedTarget */,
+    0 /* allowedDirections */,
+    direction,
+    1 /* delta */
+  );
+  return event;
+}
+
+add_task(async () => {
+  await SpecialPowers.pushPrefEnv({
+    set: [["ui.swipeAnimationEnabled", false]],
+  });
+
+  // Open a new browser window and load two pages so that the browser can go
+  // back but can't go forward.
+  const newWindow = await BrowserTestUtils.openNewBrowserWindow({});
+
+  // gHistroySwipeAnimation gets initialized in a requestIdleCallback so we need
+  // to wait for the initialization.
+  await TestUtils.waitForCondition(() => {
+    return (
+      // There's no explicit notification for the initialization, so we wait
+      // until `isLTR` matches the browser locale state.
+      newWindow.gHistorySwipeAnimation.isLTR != Services.locale.isAppLocaleRTL
+    );
+  });
+
+  BrowserTestUtils.startLoadingURIString(
+    newWindow.gBrowser.selectedBrowser,
+    "about:mozilla"
+  );
+  await BrowserTestUtils.browserLoaded(
+    newWindow.gBrowser.selectedBrowser,
+    false,
+    "about:mozilla"
+  );
+  BrowserTestUtils.startLoadingURIString(
+    newWindow.gBrowser.selectedBrowser,
+    "about:about"
+  );
+  await BrowserTestUtils.browserLoaded(
+    newWindow.gBrowser.selectedBrowser,
+    false,
+    "about:about"
+  );
+
+  let event = createSimpleGestureEvent(
+    "MozSwipeGestureMayStart",
+    SimpleGestureEvent.DIRECTION_LEFT
+  );
+  newWindow.gGestureSupport._shouldDoSwipeGesture(event);
+
+  // Assuming we are on LTR environment.
+  is(
+    event.allowedDirections,
+    SimpleGestureEvent.DIRECTION_LEFT,
+    "Allows only swiping to left, i.e. backward"
+  );
+
+  event = createSimpleGestureEvent(
+    "MozSwipeGestureMayStart",
+    SimpleGestureEvent.DIRECTION_RIGHT
+  );
+  newWindow.gGestureSupport._shouldDoSwipeGesture(event);
+  is(
+    event.allowedDirections,
+    SimpleGestureEvent.DIRECTION_LEFT,
+    "Allows only swiping to left, i.e. backward"
+  );
+
+  await BrowserTestUtils.closeWindow(newWindow);
+});
+
+add_task(async () => {
+  await SpecialPowers.pushPrefEnv({
+    set: [["ui.swipeAnimationEnabled", true]],
+  });
+
+  // Open a new browser window and load two pages so that the browser can go
+  // back but can't go forward.
+  const newWindow = await BrowserTestUtils.openNewBrowserWindow({});
+
+  if (!newWindow.gHistorySwipeAnimation._isSupported()) {
+    await BrowserTestUtils.closeWindow(newWindow);
+    return;
+  }
+
+  function sendSwipeSequence(sendEnd) {
+    let event = createSimpleGestureEvent(
+      "MozSwipeGestureMayStart",
+      SimpleGestureEvent.DIRECTION_LEFT
+    );
+    newWindow.gGestureSupport.handleEvent(event);
+
+    event = createSimpleGestureEvent(
+      "MozSwipeGestureStart",
+      SimpleGestureEvent.DIRECTION_LEFT
+    );
+    newWindow.gGestureSupport.handleEvent(event);
+
+    event = createSimpleGestureEvent(
+      "MozSwipeGestureUpdate",
+      SimpleGestureEvent.DIRECTION_LEFT
+    );
+    newWindow.gGestureSupport.handleEvent(event);
+
+    event = createSimpleGestureEvent(
+      "MozSwipeGestureUpdate",
+      SimpleGestureEvent.DIRECTION_LEFT
+    );
+    newWindow.gGestureSupport.handleEvent(event);
+
+    if (sendEnd) {
+      sendSwipeEnd();
+    }
+  }
+  function sendSwipeEnd() {
+    let event = createSimpleGestureEvent(
+      "MozSwipeGestureEnd",
+      SimpleGestureEvent.DIRECTION_LEFT
+    );
+    newWindow.gGestureSupport.handleEvent(event);
+  }
+
+  // gHistroySwipeAnimation gets initialized in a requestIdleCallback so we need
+  // to wait for the initialization.
+  await TestUtils.waitForCondition(() => {
+    return (
+      // There's no explicit notification for the initialization, so we wait
+      // until `isLTR` matches the browser locale state.
+      newWindow.gHistorySwipeAnimation.isLTR != Services.locale.isAppLocaleRTL
+    );
+  });
+
+  BrowserTestUtils.startLoadingURIString(
+    newWindow.gBrowser.selectedBrowser,
+    "about:mozilla"
+  );
+  await BrowserTestUtils.browserLoaded(
+    newWindow.gBrowser.selectedBrowser,
+    false,
+    "about:mozilla"
+  );
+  BrowserTestUtils.startLoadingURIString(
+    newWindow.gBrowser.selectedBrowser,
+    "about:about"
+  );
+  await BrowserTestUtils.browserLoaded(
+    newWindow.gBrowser.selectedBrowser,
+    false,
+    "about:about"
+  );
+
+  // Start a swipe that's not enough to navigate
+  sendSwipeSequence(/* sendEnd = */ true);
+
+  // Wait two frames
+  await new Promise(r =>
+    window.requestAnimationFrame(() => window.requestAnimationFrame(r))
+  );
+
+  // The transition to fully stopped shouldn't have had enough time yet to
+  // become fully stopped.
+  ok(
+    newWindow.gHistorySwipeAnimation._isStoppingAnimation,
+    "should be stopping anim"
+  );
+
+  // Start another swipe.
+  sendSwipeSequence(/* sendEnd = */ false);
+
+  // Wait two frames
+  await new Promise(r =>
+    window.requestAnimationFrame(() => window.requestAnimationFrame(r))
+  );
+
+  // We should have started a new swipe, ie we shouldn't be stopping.
+  ok(
+    !newWindow.gHistorySwipeAnimation._isStoppingAnimation,
+    "should not be stopping anim"
+  );
+
+  sendSwipeEnd();
+
+  await BrowserTestUtils.closeWindow(newWindow);
+});
diff --git a/src/zen/tests/mochitests/gesture/browser_gesture_scroll.js b/src/zen/tests/mochitests/gesture/browser_gesture_scroll.js
new file mode 100644
index 000000000..ffe998a7b
--- /dev/null
+++ b/src/zen/tests/mochitests/gesture/browser_gesture_scroll.js
@@ -0,0 +1,43 @@
+/* Any copyright is dedicated to the Public Domain.
+   https://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const URL = `data:text/html,
+  <!doctype html>
+  <meta charset="utf-8">
+  <div style="height: 200vh"></div>
+  Some content
+  <div style="height: 200vh"></div>
+`;
+
+function getScrollPos(browser) {
+  return SpecialPowers.spawn(browser, [], () => {
+    return {
+      scrollY: Math.round(content.scrollY),
+      scrollMaxY: Math.round(content.scrollMaxY),
+    };
+  });
+}
+
+// Bug 1964901
+add_task(async function test_scroll_command() {
+  await BrowserTestUtils.withNewTab(URL, async function (browser) {
+    {
+      let { scrollY, scrollMaxY } = await getScrollPos(browser);
+      is(scrollY, 0, "Should be scrolled to the top");
+      isnot(scrollMaxY, 0, "Should be scrollable");
+    }
+    let scrollEvent = SpecialPowers.spawn(browser, [], async () => {
+      await new Promise(r => {
+        content.addEventListener("scrollend", r, { once: true });
+      });
+    });
+    goDoCommand("cmd_scrollBottom");
+    await scrollEvent;
+    {
+      let { scrollY, scrollMaxY } = await getScrollPos(browser);
+      is(scrollY, scrollMaxY, "Should be scrolled to the bottom");
+    }
+  });
+});
diff --git a/src/zen/tests/mochitests/linkHandling/browser.toml b/src/zen/tests/mochitests/linkHandling/browser.toml
new file mode 100644
index 000000000..72dd92d42
--- /dev/null
+++ b/src/zen/tests/mochitests/linkHandling/browser.toml
@@ -0,0 +1,12 @@
+[DEFAULT]
+
+["browser_contentAreaClick_subframe_javascript.js"]
+support-files = [
+  "file_contentAreaClick_subframe_javascript.html"
+]
+
+["browser_javascript_links.js"]
+disabled="Disabled by import_external_tests.py"
+support-files = [
+  "file_javascript_links_subframe.html"
+]
diff --git a/src/zen/tests/mochitests/linkHandling/browser_contentAreaClick_subframe_javascript.js b/src/zen/tests/mochitests/linkHandling/browser_contentAreaClick_subframe_javascript.js
new file mode 100644
index 000000000..b8236e073
--- /dev/null
+++ b/src/zen/tests/mochitests/linkHandling/browser_contentAreaClick_subframe_javascript.js
@@ -0,0 +1,49 @@
+const gExampleComRoot = getRootDirectory(gTestPath).replace(
+  "chrome://mochitests/content/",
+  "https://example.com/"
+);
+const IFRAME_FILE = "file_contentAreaClick_subframe_javascript.html";
+
+add_task(async function () {
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.link.alternative_click.block_javascript", false]],
+  });
+
+  await BrowserTestUtils.withNewTab(
+    `data:text/html,<iframe src="${gExampleComRoot + IFRAME_FILE}"></iframe>`,
+    async browser => {
+      let newTabPromise = BrowserTestUtils.waitForNewTab(
+        gBrowser,
+        "about:blank"
+      );
+      let javascriptRanPromise = TestUtils.topicObserved(
+        "contentAreaClick-javascriptRan"
+      );
+
+      // ctrl/cmd-click the link in the subframe. This should cause it to be
+      // loaded in a new tab.
+      info("Clicking link");
+      let expectedRemoteType =
+        browser.browsingContext.children[0].currentRemoteType;
+      await BrowserTestUtils.synthesizeMouseAtCenter(
+        "a",
+        { ctrlKey: true, metaKey: true },
+        browser.browsingContext.children[0]
+      );
+
+      info("Waiting for new tab");
+      let newTab = await newTabPromise;
+
+      info("Waiting to be notified that the javascript ran");
+      await javascriptRanPromise;
+      is(
+        newTab.linkedBrowser.remoteType,
+        expectedRemoteType,
+        "new tab was loaded in expected process"
+      );
+
+      info("Removing the tab");
+      BrowserTestUtils.removeTab(newTab);
+    }
+  );
+});
diff --git a/src/zen/tests/mochitests/linkHandling/browser_javascript_links.js b/src/zen/tests/mochitests/linkHandling/browser_javascript_links.js
new file mode 100644
index 000000000..891e17c17
--- /dev/null
+++ b/src/zen/tests/mochitests/linkHandling/browser_javascript_links.js
@@ -0,0 +1,88 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const TEST_PATH = getRootDirectory(gTestPath).replace(
+  "chrome://mochitests/content/",
+  "https://example.com/"
+);
+const IFRAME_PATH = TEST_PATH + "file_javascript_links_subframe.html";
+
+add_setup(async function () {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["browser.link.alternative_click.block_javascript", true],
+      ["browser.tabs.opentabfor.middleclick", true],
+      ["middlemouse.paste", false],
+      ["middlemouse.contentLoadURL", false],
+      ["general.autoScroll", false],
+    ],
+  });
+});
+
+add_task(async function () {
+  await BrowserTestUtils.withNewTab(
+    `data:text/html,<a href="javascript:alert(1);">click me`,
+    async browser => {
+      await BrowserTestUtils.synthesizeMouseAtCenter(
+        "a",
+        { button: 0, ctrlKey: true, metaKey: true },
+        browser
+      );
+      is(
+        gBrowser.tabs.length,
+        2,
+        "Accel+click on javascript: link shouldn't open a new tab"
+      );
+
+      await BrowserTestUtils.synthesizeMouseAtCenter(
+        "a",
+        { button: 1 },
+        browser
+      );
+      is(
+        gBrowser.tabs.length,
+        2,
+        "Middle click on javascript: link shouldn't open a new tab"
+      );
+
+      await BrowserTestUtils.synthesizeMouseAtCenter(
+        "a",
+        { button: 0, shiftKey: true },
+        browser
+      );
+      // This is fragile and might miss the new window, but the test will fail
+      // anyway when finishing with an extra window left behind.
+      // eslint-disable-next-line mozilla/no-arbitrary-setTimeout
+      await new Promise(resolve => setTimeout(resolve, 200));
+      is(
+        BrowserWindowTracker.windowCount,
+        1,
+        "Shift+click on javascript: link shouldn't open a new window"
+      );
+    }
+  );
+});
+
+add_task(async function iframe_link() {
+  await BrowserTestUtils.withNewTab(
+    `data:text/html,<iframe src="${IFRAME_PATH}"></iframe>`,
+    async browser => {
+      // ctrl/cmd-click the link in the subframe.
+      await BrowserTestUtils.synthesizeMouseAtCenter(
+        "a",
+        { ctrlKey: true, metaKey: true },
+        browser.browsingContext.children[0]
+      );
+
+      // eslint-disable-next-line mozilla/no-arbitrary-setTimeout
+      await new Promise(resolve => setTimeout(resolve, 200));
+      is(
+        gBrowser.tabs.length,
+        2,
+        "Click on javascript: link in iframe shouldn't open a new tab"
+      );
+    }
+  );
+});
diff --git a/src/zen/tests/mochitests/linkHandling/file_contentAreaClick_subframe_javascript.html b/src/zen/tests/mochitests/linkHandling/file_contentAreaClick_subframe_javascript.html
new file mode 100644
index 000000000..aa4ca9c75
--- /dev/null
+++ b/src/zen/tests/mochitests/linkHandling/file_contentAreaClick_subframe_javascript.html
@@ -0,0 +1,2 @@
+<!DOCTYPE html>
+<a href="javascript:SpecialPowers.notifyObserversInParentProcess(null, 'contentAreaClick-javascriptRan');">link</a>
diff --git a/src/zen/tests/mochitests/linkHandling/file_javascript_links_subframe.html b/src/zen/tests/mochitests/linkHandling/file_javascript_links_subframe.html
new file mode 100644
index 000000000..e52e169d2
--- /dev/null
+++ b/src/zen/tests/mochitests/linkHandling/file_javascript_links_subframe.html
@@ -0,0 +1,2 @@
+<!DOCTYPE html>
+<a href="javascript:alert(1)">click me
diff --git a/src/zen/tests/mochitests/moz.build b/src/zen/tests/mochitests/moz.build
index bbf85269c..377de8620 100644
--- a/src/zen/tests/mochitests/moz.build
+++ b/src/zen/tests/mochitests/moz.build
@@ -8,11 +8,21 @@
 
 
 BROWSER_CHROME_MANIFESTS += [
+	"alerts/browser.toml",
+	"backforward/browser.toml",
+	"caps/browser.toml",
+	"gesture/browser.toml",
+	"linkHandling/browser.toml",
 	"readermode/browser.toml",
 	"safebrowsing/browser.toml",
+	"sessionstore/browser.toml",
 	"shell/browser.toml",
 	"tabMediaIndicator/browser.toml",
 	"tooltiptext/browser.toml",
+	"zoom/browser.toml",
 ]
 XPCSHELL_TESTS_MANIFESTS += [
+	"remote-settings/xpcshell.toml",
+	"services-crypto/xpcshell.toml",
+	"sync/xpcshell.toml",
 ]
\ No newline at end of file
diff --git a/src/zen/tests/mochitests/remote-settings/head_settings.js b/src/zen/tests/mochitests/remote-settings/head_settings.js
new file mode 100644
index 000000000..f575f276c
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/head_settings.js
@@ -0,0 +1,86 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/* import-globals-from ../../../common/tests/unit/head_global.js */
+/* import-globals-from ../../../common/tests/unit/head_helpers.js */
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  AppConstants: "resource://gre/modules/AppConstants.sys.mjs",
+  Database: "resource://services-settings/Database.sys.mjs",
+  RemoteSettings: "resource://services-settings/remote-settings.sys.mjs",
+  RemoteSettingsClient:
+    "resource://services-settings/RemoteSettingsClient.sys.mjs",
+  RemoteSettingsWorker:
+    "resource://services-settings/RemoteSettingsWorker.sys.mjs",
+  setTimeout: "resource://gre/modules/Timer.sys.mjs",
+  SharedUtils: "resource://services-settings/SharedUtils.sys.mjs",
+  SyncHistory: "resource://services-settings/SyncHistory.sys.mjs",
+  TelemetryTestUtils: "resource://testing-common/TelemetryTestUtils.sys.mjs",
+  TestUtils: "resource://testing-common/TestUtils.sys.mjs",
+  UptakeTelemetry: "resource://services-settings/UptakeTelemetry.sys.mjs",
+  Utils: "resource://services-settings/Utils.sys.mjs",
+});
+
+const IS_ANDROID = AppConstants.platform == "android";
+
+function arrayEqual(a, b) {
+  return JSON.stringify(a) == JSON.stringify(b);
+}
+
+add_setup(function () {
+  Services.fog.initializeFOG();
+});
+
+function enableUptakeMetric() {
+  Services.fog.applyServerKnobsConfig(
+    JSON.stringify({
+      metrics_enabled: {
+        "uptake.remotecontent.result.uptake_remotesettings": true,
+      },
+    })
+  );
+}
+
+function assertTelemetryEvents(expectedEvents) {
+  if (IS_ANDROID) {
+    /*
+      Since `Services.fog.applyServerKnobsConfig()` has no effect on Android
+      https://searchfox.org/firefox-main/rev/e28b34ab33dbf49364999070168cbb7e11e8e5bd/toolkit/components/glean/xpcom/FOG.cpp#379-390
+      we skip assertions on events on this platform.
+      Alternatively we could have disabled the whole tests suites or introduced `if IS_ANDROID` on each
+      test involving telemetry, but this seems the most reasonable way.
+      See Bug 2028765 and Bug 2042499
+    */
+    Assert.ok(
+      true,
+      "Glean Uptake Telemetry assertions are ALWAYS true on Android"
+    );
+    return;
+  }
+  const events =
+    Glean.uptakeRemotecontentResult.uptakeRemotesettings.testGetValue() ?? [];
+  const receivedValues = events.map(e => e.extra.value);
+  Assert.equal(
+    events.length,
+    expectedEvents.length,
+    `number of uptake events (${receivedValues})`
+  );
+  for (let i = 0; i < expectedEvents.length; i++) {
+    for (const [key, expected] of Object.entries(expectedEvents[i])) {
+      if (typeof expected === "function") {
+        Assert.ok(
+          expected(events[i].extra[key]),
+          `event[${i}].extra.${key} passes validator`
+        );
+      } else {
+        Assert.equal(
+          events[i].extra[key],
+          expected,
+          `event[${i}].extra.${key}`
+        );
+      }
+    }
+  }
+}
diff --git a/src/zen/tests/mochitests/remote-settings/test_attachments_downloader.js b/src/zen/tests/mochitests/remote-settings/test_attachments_downloader.js
new file mode 100644
index 000000000..a2d1ca070
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_attachments_downloader.js
@@ -0,0 +1,896 @@
+const { Downloader } = ChromeUtils.importESModule(
+  "resource://services-settings/Attachments.sys.mjs"
+);
+
+const RECORD = {
+  id: "1f3a0802-648d-11ea-bd79-876a8b69c377",
+  attachment: {
+    hash: "f41ed47d0f43325c9f089d03415c972ce1d3f1ecab6e4d6260665baf3db3ccee",
+    size: 1597,
+    filename: "test_file.pem",
+    location:
+      "main-workspace/some-collection/65650a0f-7c22-4c10-9744-2d67e301f5f4.pem",
+    mimetype: "application/x-pem-file",
+  },
+};
+
+const RECORD_OF_DUMP = {
+  id: "filename-of-dump.txt",
+  attachment: {
+    filename: "filename-of-dump.txt",
+    hash: "4c46ef7e4f1951d210fe54c21e07c09bab265fd122580083ed1d6121547a8c6b",
+    size: 25,
+  },
+  last_modified: 1234567,
+  some_key: "some metadata",
+};
+
+let downloader;
+let server;
+
+add_setup(() => {
+  server = new HttpServer();
+  server.start(-1);
+  registerCleanupFunction(() => server.stop(() => {}));
+
+  server.registerDirectory(
+    "/cdn/main-workspace/some-collection/",
+    do_get_file("test_attachments_downloader")
+  );
+  server.registerDirectory(
+    "/cdn/bundles/",
+    do_get_file("test_attachments_downloader")
+  );
+
+  // For this test, we are using a server other than production. Force
+  // LOAD_DUMPS to true so that we can still load attachments from dumps.
+  delete Utils.LOAD_DUMPS;
+  Utils.LOAD_DUMPS = true;
+});
+
+async function clear_state() {
+  Services.fog.testResetFOG();
+  enableUptakeMetric();
+
+  Services.prefs.setStringPref(
+    "services.settings.server",
+    `http://localhost:${server.identity.primaryPort}/v1`
+  );
+
+  downloader = new Downloader("main", "some-collection");
+  downloader.cache = {};
+  const memCacheImpl = {
+    get: async id => {
+      return downloader.cache[id];
+    },
+    set: async (id, obj) => {
+      downloader.cache[id] = obj;
+    },
+    setMultiple: async idsObjs => {
+      idsObjs.forEach(([id, obj]) => (downloader.cache[id] = obj));
+    },
+    delete: async id => {
+      delete downloader.cache[id];
+    },
+    deleteMultiple: async ids => {
+      ids.forEach(id => delete downloader.cache[id]);
+    },
+    hasData: async () => {
+      return !!Object.keys(downloader.cache).length;
+    },
+  };
+  // The download() method requires a cacheImpl, but the Downloader
+  // class does not have one. Define a dummy no-op one.
+  Object.defineProperty(downloader, "cacheImpl", {
+    value: memCacheImpl,
+    // Writable to allow specific tests to override cacheImpl.
+    writable: true,
+  });
+  await downloader.deleteDownloaded(RECORD);
+
+  server.registerPathHandler("/v1/", (request, response) => {
+    response.write(
+      JSON.stringify({
+        capabilities: {
+          attachments: {
+            base_url: `http://localhost:${server.identity.primaryPort}/cdn/`,
+          },
+        },
+      })
+    );
+    response.setHeader("Content-Type", "application/json; charset=UTF-8");
+    response.setStatusLine(null, 200, "OK");
+  });
+
+  // For tests that use a real client and DB cache, clear the local DB too.
+  const client = RemoteSettings("some-collection");
+  await client.db.clear();
+  await client.db.pruneAttachments([]);
+}
+add_task(clear_state);
+
+add_task(
+  async function test_download_throws_server_info_error_if_invalid_response() {
+    server.registerPathHandler("/v1/", (request, response) => {
+      response.write("{bad json content");
+      response.setHeader("Content-Type", "application/json; charset=UTF-8");
+      response.setStatusLine(null, 200, "OK");
+    });
+
+    let error;
+    try {
+      await downloader.download(RECORD);
+    } catch (e) {
+      error = e;
+    }
+
+    Assert.ok(error instanceof Downloader.ServerInfoError);
+  }
+);
+add_task(clear_state);
+
+add_task(async function test_download_is_retried_3_times_if_download_fails() {
+  const record = {
+    id: "abc",
+    attachment: {
+      ...RECORD.attachment,
+      location: "404-error.pem",
+    },
+  };
+
+  let called = 0;
+  const _fetchAttachment = downloader._fetchAttachment;
+  downloader._fetchAttachment = async url => {
+    called++;
+    return _fetchAttachment(url);
+  };
+
+  let error;
+  try {
+    await downloader.download(record);
+  } catch (e) {
+    error = e;
+  }
+
+  Assert.equal(called, 4); // 1 + 3 retries
+  Assert.ok(error instanceof Downloader.DownloadError);
+});
+add_task(clear_state);
+
+add_task(async function test_download_as_bytes() {
+  const bytes = await downloader.downloadAsBytes(RECORD);
+
+  // See *.pem file in tests data.
+  Assert.greater(
+    bytes.byteLength,
+    1500,
+    `Wrong bytes size: ${bytes.byteLength}`
+  );
+});
+add_task(clear_state);
+
+add_task(async function test_download_is_retried_3_times_if_content_fails() {
+  const record = {
+    id: "abc",
+    attachment: {
+      ...RECORD.attachment,
+      hash: "always-wrong",
+    },
+  };
+  let called = 0;
+  downloader._fetchAttachment = async () => {
+    called++;
+    return new ArrayBuffer();
+  };
+
+  let error;
+  try {
+    await downloader.download(record);
+  } catch (e) {
+    error = e;
+  }
+
+  Assert.equal(called, 4); // 1 + 3 retries
+  Assert.ok(error instanceof Downloader.BadContentError);
+});
+add_task(clear_state);
+
+add_task(async function test_delete_all() {
+  const client = RemoteSettings("some-collection");
+  await client.db.create(RECORD);
+  await downloader.download(RECORD);
+
+  await client.attachments.deleteAll();
+
+  Assert.ok(!(await client.attachments.cacheImpl.get(RECORD.id)));
+});
+add_task(clear_state);
+
+add_task(async function test_downloader_reports_download_errors() {
+  const client = RemoteSettings("some-collection");
+
+  const record = {
+    attachment: {
+      ...RECORD.attachment,
+      location: "404-error.pem",
+    },
+  };
+
+  try {
+    await client.attachments.download(record, { retry: 0 });
+  } catch (e) {}
+
+  assertTelemetryEvents([
+    {
+      value: UptakeTelemetry.STATUS.DOWNLOAD_START,
+      source: client.identifier,
+    },
+    {
+      value: UptakeTelemetry.STATUS.DOWNLOAD_ERROR,
+      source: client.identifier,
+    },
+  ]);
+});
+add_task(clear_state);
+
+add_task(async function test_downloader_reports_offline_error() {
+  const backupOffline = Services.io.offline;
+  Services.io.offline = true;
+
+  try {
+    const client = RemoteSettings("some-collection");
+    const record = {
+      attachment: {
+        ...RECORD.attachment,
+        location: "will-try-and-fail.pem",
+      },
+    };
+    try {
+      await client.attachments.download(record, { retry: 0 });
+    } catch (e) {}
+
+    assertTelemetryEvents([
+      {
+        value: UptakeTelemetry.STATUS.DOWNLOAD_START,
+        source: client.identifier,
+      },
+      {
+        value: UptakeTelemetry.STATUS.NETWORK_OFFLINE_ERROR,
+        source: client.identifier,
+      },
+    ]);
+  } finally {
+    Services.io.offline = backupOffline;
+  }
+});
+add_task(clear_state);
+
+// Common code for test_download_cache_hit and test_download_cache_corruption.
+async function doTestDownloadCacheImpl({
+  simulateCorruption,
+  expectedReads = 1,
+  expectedWrites = 1,
+  downloadOptions = {},
+}) {
+  let readCount = 0;
+  let writeCount = 0;
+  const cacheImpl = {
+    async get(attachmentId) {
+      Assert.equal(attachmentId, RECORD.id, "expected attachmentId");
+      ++readCount;
+      if (simulateCorruption) {
+        throw new Error("Simulation of corrupted cache (read)");
+      }
+    },
+    async set(attachmentId, attachment) {
+      Assert.equal(attachmentId, RECORD.id, "expected attachmentId");
+      Assert.deepEqual(attachment.record, RECORD, "expected record");
+      ++writeCount;
+      if (simulateCorruption) {
+        throw new Error("Simulation of corrupted cache (write)");
+      }
+    },
+    async delete() {},
+  };
+  Object.defineProperty(downloader, "cacheImpl", { value: cacheImpl });
+
+  let downloadResult = await downloader.download(RECORD, downloadOptions);
+  Assert.equal(downloadResult._source, "remote_match", "expected source");
+  Assert.equal(downloadResult.buffer.byteLength, 1597, "expected result");
+  Assert.equal(readCount, expectedReads, "expected cache read attempts");
+  Assert.equal(writeCount, expectedWrites, "expected cache write attempts");
+}
+
+add_task(async function test_download_cache_hit() {
+  await doTestDownloadCacheImpl({ simulateCorruption: false });
+});
+add_task(clear_state);
+
+// Verify that the downloader works despite a broken cache implementation.
+add_task(async function test_download_cache_corruption() {
+  await doTestDownloadCacheImpl({ simulateCorruption: true });
+});
+add_task(clear_state);
+
+add_task(async function test_download_with_cache_enabled() {
+  await doTestDownloadCacheImpl({
+    simulateCorruption: false,
+    downloadOptions: {
+      cacheResult: true,
+    },
+  });
+});
+add_task(clear_state);
+
+add_task(async function test_download_with_cache_disabled() {
+  await doTestDownloadCacheImpl({
+    simulateCorruption: false,
+    expectedWrites: 0,
+    downloadOptions: {
+      cacheResult: false,
+    },
+  });
+});
+add_task(clear_state);
+
+add_task(async function test_download_cached() {
+  const client = RemoteSettings("main", "some-collection");
+  const attachmentId = "dummy filename";
+  const badRecord = {
+    attachment: {
+      ...RECORD.attachment,
+      hash: "non-matching hash",
+      location: "non-existing-location-should-fail.bin",
+    },
+  };
+  async function downloadWithCache(record, options) {
+    options = { ...options, useCache: true };
+    return client.attachments.download(record, options);
+  }
+  function checkInfo(downloadResult, expectedSource, msg) {
+    Assert.deepEqual(
+      downloadResult.record,
+      RECORD,
+      `${msg} : expected identical record`
+    );
+    // Simple check: assume that content is identical if the size matches.
+    Assert.equal(
+      downloadResult.buffer.byteLength,
+      RECORD.attachment.size,
+      `${msg} : expected buffer`
+    );
+    Assert.equal(
+      downloadResult._source,
+      expectedSource,
+      `${msg} : expected source of the result`
+    );
+  }
+
+  await Assert.rejects(
+    downloadWithCache(null, { attachmentId }),
+    /DownloadError: Could not download dummy filename/,
+    "Download without record or cache should fail."
+  );
+
+  // Populate cache.
+  const info1 = await downloadWithCache(RECORD, { attachmentId });
+  checkInfo(info1, "remote_match", "first time download");
+
+  await Assert.rejects(
+    downloadWithCache(null, { attachmentId }),
+    /DownloadError: Could not download dummy filename/,
+    "Download without record still fails even if there is a cache."
+  );
+
+  await Assert.rejects(
+    downloadWithCache(badRecord, { attachmentId }),
+    /DownloadError: Could not download .*non-existing-location-should-fail.bin/,
+    "Download with non-matching record still fails even if there is a cache."
+  );
+
+  // Download from cache.
+  const info2 = await downloadWithCache(RECORD, { attachmentId });
+  checkInfo(info2, "cache_match", "download matching record from cache");
+
+  const info3 = await downloadWithCache(RECORD, {
+    attachmentId,
+    fallbackToCache: true,
+  });
+  checkInfo(info3, "cache_match", "fallbackToCache accepts matching record");
+
+  const info4 = await downloadWithCache(null, {
+    attachmentId,
+    fallbackToCache: true,
+  });
+  checkInfo(info4, "cache_fallback", "fallbackToCache accepts null record");
+
+  const info5 = await downloadWithCache(badRecord, {
+    attachmentId,
+    fallbackToCache: true,
+  });
+  checkInfo(info5, "cache_fallback", "fallbackToCache ignores bad record");
+
+  // Bye bye cache.
+  await client.attachments.deleteDownloaded({ id: attachmentId });
+  await Assert.rejects(
+    downloadWithCache(null, { attachmentId, fallbackToCache: true }),
+    /DownloadError: Could not download dummy filename/,
+    "Download without cache should fail again."
+  );
+  await Assert.rejects(
+    downloadWithCache(badRecord, { attachmentId, fallbackToCache: true }),
+    /DownloadError: Could not download .*non-existing-location-should-fail.bin/,
+    "Download should fail to fall back to a download of a non-existing record"
+  );
+});
+add_task(clear_state);
+
+add_task(async function test_download_from_dump() {
+  const client = RemoteSettings("dump-collection", {
+    bucketName: "dump-bucket",
+  });
+
+  // Temporarily replace the resource:-URL with another resource:-URL.
+  const orig_RESOURCE_BASE_URL = Downloader._RESOURCE_BASE_URL;
+  Downloader._RESOURCE_BASE_URL = "resource://rs-downloader-test";
+  const resProto = Services.io
+    .getProtocolHandler("resource")
+    .QueryInterface(Ci.nsIResProtocolHandler);
+  resProto.setSubstitution(
+    "rs-downloader-test",
+    Services.io.newFileURI(do_get_file("test_attachments_downloader"))
+  );
+
+  function checkInfo(result, expectedSource, expectedRecord = RECORD_OF_DUMP) {
+    Assert.equal(
+      new TextDecoder().decode(new Uint8Array(result.buffer)),
+      "This would be a RS dump.\n",
+      "expected content from dump"
+    );
+    Assert.deepEqual(result.record, expectedRecord, "expected record for dump");
+    Assert.equal(result._source, expectedSource, "expected source of dump");
+  }
+
+  // If record matches, should happen before network request.
+  const dump1 = await client.attachments.download(RECORD_OF_DUMP, {
+    // Note: attachmentId not set, so should fall back to record.id.
+    fallbackToDump: true,
+  });
+  checkInfo(dump1, "dump_match");
+
+  // If no record given, should try network first, but then fall back to dump.
+  const dump2 = await client.attachments.download(null, {
+    attachmentId: RECORD_OF_DUMP.id,
+    fallbackToDump: true,
+  });
+  checkInfo(dump2, "dump_fallback");
+
+  // Fill the cache with the same data as the dump for the next part.
+  await client.db.saveAttachment(RECORD_OF_DUMP.id, {
+    record: RECORD_OF_DUMP,
+    blob: new Blob([dump1.buffer]),
+  });
+  // The dump should take precedence over the cache.
+  const dump3 = await client.attachments.download(RECORD_OF_DUMP, {
+    fallbackToCache: true,
+    fallbackToDump: true,
+  });
+  checkInfo(dump3, "dump_match");
+
+  // When the record is not given, the dump takes precedence over the cache
+  // as a fallback (when the cache and dump are identical).
+  const dump4 = await client.attachments.download(null, {
+    attachmentId: RECORD_OF_DUMP.id,
+    fallbackToCache: true,
+    fallbackToDump: true,
+  });
+  checkInfo(dump4, "dump_fallback");
+
+  // Store a record in the cache that is newer than the dump.
+  const RECORD_NEWER_THAN_DUMP = {
+    ...RECORD_OF_DUMP,
+    last_modified: RECORD_OF_DUMP.last_modified + 1,
+  };
+  await client.db.saveAttachment(RECORD_OF_DUMP.id, {
+    record: RECORD_NEWER_THAN_DUMP,
+    blob: new Blob([dump1.buffer]),
+  });
+
+  // When the record is not given, use the cache if it has a more recent record.
+  const dump5 = await client.attachments.download(null, {
+    attachmentId: RECORD_OF_DUMP.id,
+    fallbackToCache: true,
+    fallbackToDump: true,
+  });
+  checkInfo(dump5, "cache_fallback", RECORD_NEWER_THAN_DUMP);
+
+  // When a record is given, use whichever that has the matching last_modified.
+  const dump6 = await client.attachments.download(RECORD_OF_DUMP, {
+    fallbackToCache: true,
+    fallbackToDump: true,
+  });
+  checkInfo(dump6, "dump_match");
+  const dump7 = await client.attachments.download(RECORD_NEWER_THAN_DUMP, {
+    fallbackToCache: true,
+    fallbackToDump: true,
+  });
+  checkInfo(dump7, "cache_match", RECORD_NEWER_THAN_DUMP);
+
+  await client.attachments.deleteDownloaded(RECORD_OF_DUMP);
+
+  await Assert.rejects(
+    client.attachments.download(null, {
+      attachmentId: "filename-without-meta.txt",
+      fallbackToDump: true,
+    }),
+    /DownloadError: Could not download filename-without-meta.txt/,
+    "Cannot download dump that lacks a .meta.json file"
+  );
+
+  await Assert.rejects(
+    client.attachments.download(null, {
+      attachmentId: "filename-without-content.txt",
+      fallbackToDump: true,
+    }),
+    /Could not download resource:\/\/rs-downloader-test\/settings\/dump-bucket\/dump-collection\/filename-without-content\.txt(?!\.meta\.json)/,
+    "Cannot download dump that is missing, despite the existing .meta.json"
+  );
+
+  // Restore, just in case.
+  Downloader._RESOURCE_BASE_URL = orig_RESOURCE_BASE_URL;
+  resProto.setSubstitution("rs-downloader-test", null);
+});
+// Not really needed because the last test doesn't modify the main collection,
+// but added for consistency with other tests tasks around here.
+add_task(clear_state);
+
+add_task(
+  async function test_download_from_dump_fails_when_load_dumps_is_false() {
+    const client = RemoteSettings("dump-collection", {
+      bucketName: "dump-bucket",
+    });
+
+    // Temporarily replace the resource:-URL with another resource:-URL.
+    const orig_RESOURCE_BASE_URL = Downloader._RESOURCE_BASE_URL;
+    Downloader._RESOURCE_BASE_URL = "resource://rs-downloader-test";
+    const resProto = Services.io
+      .getProtocolHandler("resource")
+      .QueryInterface(Ci.nsIResProtocolHandler);
+    resProto.setSubstitution(
+      "rs-downloader-test",
+      Services.io.newFileURI(do_get_file("test_attachments_downloader"))
+    );
+
+    function checkInfo(
+      result,
+      expectedSource,
+      expectedRecord = RECORD_OF_DUMP
+    ) {
+      Assert.equal(
+        new TextDecoder().decode(new Uint8Array(result.buffer)),
+        "This would be a RS dump.\n",
+        "expected content from dump"
+      );
+      Assert.deepEqual(
+        result.record,
+        expectedRecord,
+        "expected record for dump"
+      );
+      Assert.equal(result._source, expectedSource, "expected source of dump");
+    }
+
+    // Download the dump so that we can use it to fill the cache.
+    const dump1 = await client.attachments.download(RECORD_OF_DUMP, {
+      // Note: attachmentId not set, so should fall back to record.id.
+      fallbackToDump: true,
+    });
+    checkInfo(dump1, "dump_match");
+
+    // Fill the cache with the same data as the dump for the next part.
+    await client.db.saveAttachment(RECORD_OF_DUMP.id, {
+      record: RECORD_OF_DUMP,
+      blob: new Blob([dump1.buffer]),
+    });
+
+    // Now turn off loading dumps, and check we no longer load from the dump,
+    // but use the cache instead.
+    Utils.LOAD_DUMPS = false;
+
+    const dump2 = await client.attachments.download(RECORD_OF_DUMP, {
+      // Note: attachmentId not set, so should fall back to record.id.
+      fallbackToDump: true,
+    });
+    checkInfo(dump2, "cache_match");
+
+    // When the record is not given, the dump would take precedence over the
+    // cache but we have disabled dumps, so we should load from the cache.
+    const dump4 = await client.attachments.download(null, {
+      attachmentId: RECORD_OF_DUMP.id,
+      fallbackToCache: true,
+      fallbackToDump: true,
+    });
+    checkInfo(dump4, "cache_fallback");
+
+    // Restore, just in case.
+    Utils.LOAD_DUMPS = true;
+    Downloader._RESOURCE_BASE_URL = orig_RESOURCE_BASE_URL;
+    resProto.setSubstitution("rs-downloader-test", null);
+  }
+);
+
+add_task(async function test_attachment_get() {
+  // Since get() is largely a wrapper around the same code as download(),
+  // we only test a couple of parts to check it functions as expected, and
+  // rely on the download() testing for the rest.
+
+  await Assert.rejects(
+    downloader.get(RECORD),
+    /NotFoundError: Could not find /,
+    "get() fails when there is no local cache nor dump"
+  );
+
+  const client = RemoteSettings("dump-collection", {
+    bucketName: "dump-bucket",
+  });
+
+  // Temporarily replace the resource:-URL with another resource:-URL.
+  const orig_RESOURCE_BASE_URL = Downloader._RESOURCE_BASE_URL;
+  Downloader._RESOURCE_BASE_URL = "resource://rs-downloader-test";
+  const resProto = Services.io
+    .getProtocolHandler("resource")
+    .QueryInterface(Ci.nsIResProtocolHandler);
+  resProto.setSubstitution(
+    "rs-downloader-test",
+    Services.io.newFileURI(do_get_file("test_attachments_downloader"))
+  );
+
+  function checkInfo(result, expectedSource, expectedRecord = RECORD_OF_DUMP) {
+    Assert.equal(
+      new TextDecoder().decode(new Uint8Array(result.buffer)),
+      "This would be a RS dump.\n",
+      "expected content from dump"
+    );
+    Assert.deepEqual(result.record, expectedRecord, "expected record for dump");
+    Assert.equal(result._source, expectedSource, "expected source of dump");
+  }
+
+  // When a record is given, use whichever that has the matching last_modified.
+  const dump = await client.attachments.get(RECORD_OF_DUMP);
+  checkInfo(dump, "dump_match");
+
+  await client.attachments.deleteDownloaded(RECORD_OF_DUMP);
+
+  await Assert.rejects(
+    client.attachments.get(null, {
+      attachmentId: "filename-without-meta.txt",
+      fallbackToDump: true,
+    }),
+    /NotFoundError: Could not find filename-without-meta.txt in cache or dump/,
+    "Cannot download dump that lacks a .meta.json file"
+  );
+
+  await Assert.rejects(
+    client.attachments.get(null, {
+      attachmentId: "filename-without-content.txt",
+      fallbackToDump: true,
+    }),
+    /Could not download resource:\/\/rs-downloader-test\/settings\/dump-bucket\/dump-collection\/filename-without-content\.txt(?!\.meta\.json)/,
+    "Cannot download dump that is missing, despite the existing .meta.json"
+  );
+
+  // Restore, just in case.
+  Downloader._RESOURCE_BASE_URL = orig_RESOURCE_BASE_URL;
+  resProto.setSubstitution("rs-downloader-test", null);
+});
+// Not really needed because the last test doesn't modify the main collection,
+// but added for consistency with other tests tasks around here.
+add_task(clear_state);
+
+add_task(async function test_obsolete_attachments_are_pruned() {
+  const RECORD2 = {
+    ...RECORD,
+    id: "another-id",
+  };
+  const client = RemoteSettings("some-collection");
+  // Store records and related attachments directly in the cache.
+  await client.db.importChanges({}, 42, [RECORD, RECORD2], { clear: true });
+  await client.db.saveAttachment(RECORD.id, {
+    record: RECORD,
+    blob: new Blob(["123"]),
+  });
+  await client.db.saveAttachment("custom-id", {
+    record: RECORD2,
+    blob: new Blob(["456"]),
+  });
+  // Store an extraneous cached attachment.
+  await client.db.saveAttachment("bar", {
+    record: { id: "bar" },
+    blob: new Blob(["789"]),
+  });
+
+  const recordAttachment = await client.attachments.cacheImpl.get(RECORD.id);
+  Assert.equal(
+    await recordAttachment.blob.text(),
+    "123",
+    "Record has a cached attachment"
+  );
+  const record2Attachment = await client.attachments.cacheImpl.get("custom-id");
+  Assert.equal(
+    await record2Attachment.blob.text(),
+    "456",
+    "Record 2 has a cached attachment"
+  );
+  const { blob: cachedExtra } = await client.attachments.cacheImpl.get("bar");
+  Assert.equal(await cachedExtra.text(), "789", "There is an extra attachment");
+
+  await client.attachments.prune([]);
+
+  Assert.ok(
+    await client.attachments.cacheImpl.get(RECORD.id),
+    "Record attachment was kept"
+  );
+  Assert.ok(
+    await client.attachments.cacheImpl.get("custom-id"),
+    "Record 2 attachment was kept"
+  );
+  Assert.ok(
+    !(await client.attachments.cacheImpl.get("bar")),
+    "Extra was deleted"
+  );
+});
+add_task(clear_state);
+
+add_task(
+  async function test_obsolete_attachments_listed_as_excluded_are_not_pruned() {
+    const client = RemoteSettings("some-collection");
+    // Store records and related attachments directly in the cache.
+    await client.db.importChanges({}, 42, [], { clear: true });
+    await client.db.saveAttachment(RECORD.id, {
+      record: RECORD,
+      blob: new Blob(["123"]),
+    });
+
+    const recordAttachment = await client.attachments.cacheImpl.get(RECORD.id);
+    Assert.equal(
+      await recordAttachment.blob.text(),
+      "123",
+      "Record has a cached attachment"
+    );
+
+    await client.attachments.prune([RECORD.id]);
+
+    Assert.ok(
+      await client.attachments.cacheImpl.get(RECORD.id),
+      "Record attachment was kept"
+    );
+  }
+);
+
+add_task(clear_state);
+
+add_task(async function test_cacheAll_happy_path() {
+  // verify bundle is downloaded succesfully
+  const allSuccess = await downloader.cacheAll();
+  Assert.ok(
+    allSuccess,
+    "Attachments cacheAll succesfully downloaded a bundle and saved all attachments"
+  );
+
+  // verify accuracy of attachments downloaded
+  Assert.equal(
+    downloader.cache["1"].record.title,
+    "test1",
+    "Test record 1 meta content appears accurate."
+  );
+  Assert.equal(
+    await downloader.cache["1"].blob.text(),
+    "test1\n",
+    "Test file 1 content is accurate."
+  );
+  Assert.equal(
+    downloader.cache["2"].record.title,
+    "test2",
+    "Test record 2 meta content appears accurate."
+  );
+  Assert.equal(
+    await downloader.cache["2"].blob.text(),
+    "test2\n",
+    "Test file 2 content is accurate."
+  );
+});
+
+add_task(async function test_cacheAll_using_real_db() {
+  const client = RemoteSettings("some-collection");
+
+  const allSuccess = await client.attachments.cacheAll();
+
+  Assert.ok(
+    allSuccess,
+    "Attachments cacheAll succesfully downloaded a bundle and saved all attachments"
+  );
+
+  Assert.equal(
+    (await client.attachments.cacheImpl.get("2")).record.title,
+    "test2",
+    "Test record 2 meta content appears accurate."
+  );
+  Assert.equal(
+    await (await client.attachments.cacheImpl.get("2")).blob.text(),
+    "test2\n",
+    "Test file 2 content is accurate."
+  );
+});
+
+add_task(clear_state);
+
+add_task(async function test_cacheAll_skips_with_existing_data() {
+  downloader.cache = {
+    1: "1",
+  };
+  const allSuccess = await downloader.cacheAll();
+  Assert.equal(
+    allSuccess,
+    null,
+    "Attachments cacheAll skips downloads if data already exists"
+  );
+});
+
+add_task(async function test_cacheAll_does_not_skip_if_force_is_true() {
+  downloader.cache = {
+    1: "1",
+  };
+  const allSuccess = await downloader.cacheAll(true);
+  Assert.equal(
+    allSuccess,
+    true,
+    "Attachments cacheAll does not skip downloads if force is true"
+  );
+});
+
+add_task(clear_state);
+
+add_task(async function test_cacheAll_failed_request() {
+  downloader.bucketName = "fake-bucket";
+  downloader.collectionName = "fake-collection";
+  const allSuccess = await downloader.cacheAll();
+  Assert.equal(
+    allSuccess,
+    false,
+    "Attachments cacheAll request failed to download a bundle and returned false"
+  );
+});
+
+add_task(clear_state);
+
+add_task(async function test_cacheAll_failed_unzip() {
+  downloader.bucketName = "error-bucket";
+  downloader.collectionName = "bad-zip";
+  const allSuccess = await downloader.cacheAll();
+  Assert.equal(
+    allSuccess,
+    false,
+    "Attachments cacheAll request failed to extract a bundle and returned false"
+  );
+});
+
+add_task(clear_state);
+
+add_task(async function test_cacheAll_failed_save() {
+  const client = RemoteSettings("some-collection");
+
+  const backup = client.db.saveAttachments;
+  client.db.saveAttachments = () => {
+    throw new Error("boom");
+  };
+
+  const allSuccess = await client.attachments.cacheAll();
+
+  Assert.equal(
+    allSuccess,
+    false,
+    "Attachments cacheAll failed to save entries in DB and returned false"
+  );
+  client.db.saveAttachments = backup;
+});
+
+add_task(clear_state);
diff --git a/src/zen/tests/mochitests/remote-settings/test_attachments_downloader/65650a0f-7c22-4c10-9744-2d67e301f5f4.pem b/src/zen/tests/mochitests/remote-settings/test_attachments_downloader/65650a0f-7c22-4c10-9744-2d67e301f5f4.pem
new file mode 100644
index 000000000..502e8c9ce
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_attachments_downloader/65650a0f-7c22-4c10-9744-2d67e301f5f4.pem
@@ -0,0 +1,26 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
\ No newline at end of file
diff --git a/src/zen/tests/mochitests/remote-settings/test_attachments_downloader/error-bucket--bad-zip.zip b/src/zen/tests/mochitests/remote-settings/test_attachments_downloader/error-bucket--bad-zip.zip
new file mode 100644
index 000000000..5b07782c9
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_attachments_downloader/error-bucket--bad-zip.zip
@@ -0,0 +1 @@
+not a zip
diff --git a/src/zen/tests/mochitests/remote-settings/test_attachments_downloader/main--some-collection.zip b/src/zen/tests/mochitests/remote-settings/test_attachments_downloader/main--some-collection.zip
new file mode 100644
index 000000000..8413ee7ab
Binary files /dev/null and b/src/zen/tests/mochitests/remote-settings/test_attachments_downloader/main--some-collection.zip differ
diff --git a/src/zen/tests/mochitests/remote-settings/test_attachments_downloader/settings/dump-bucket/dump-collection/filename-of-dump.txt b/src/zen/tests/mochitests/remote-settings/test_attachments_downloader/settings/dump-bucket/dump-collection/filename-of-dump.txt
new file mode 100644
index 000000000..77d7b4154
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_attachments_downloader/settings/dump-bucket/dump-collection/filename-of-dump.txt
@@ -0,0 +1 @@
+This would be a RS dump.
diff --git a/src/zen/tests/mochitests/remote-settings/test_attachments_downloader/settings/dump-bucket/dump-collection/filename-of-dump.txt.meta.json b/src/zen/tests/mochitests/remote-settings/test_attachments_downloader/settings/dump-bucket/dump-collection/filename-of-dump.txt.meta.json
new file mode 100644
index 000000000..de7681940
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_attachments_downloader/settings/dump-bucket/dump-collection/filename-of-dump.txt.meta.json
@@ -0,0 +1,10 @@
+{
+  "id": "filename-of-dump.txt",
+  "attachment": {
+    "filename": "filename-of-dump.txt",
+    "hash": "4c46ef7e4f1951d210fe54c21e07c09bab265fd122580083ed1d6121547a8c6b",
+    "size": 25
+  },
+  "last_modified": 1234567,
+  "some_key": "some metadata"
+}
diff --git a/src/zen/tests/mochitests/remote-settings/test_attachments_downloader/settings/dump-bucket/dump-collection/filename-without-content.txt.meta.json b/src/zen/tests/mochitests/remote-settings/test_attachments_downloader/settings/dump-bucket/dump-collection/filename-without-content.txt.meta.json
new file mode 100644
index 000000000..5867247dc
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_attachments_downloader/settings/dump-bucket/dump-collection/filename-without-content.txt.meta.json
@@ -0,0 +1,8 @@
+{
+  "fyi": "This .meta.json file describes an attachment, but that attachment is missing.",
+  "attachment": {
+    "filename": "filename-without-content.txt",
+    "hash": "...",
+    "size": "..."
+  }
+}
diff --git a/src/zen/tests/mochitests/remote-settings/test_attachments_downloader/settings/dump-bucket/dump-collection/filename-without-meta.txt b/src/zen/tests/mochitests/remote-settings/test_attachments_downloader/settings/dump-bucket/dump-collection/filename-without-meta.txt
new file mode 100644
index 000000000..5fbfd11c9
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_attachments_downloader/settings/dump-bucket/dump-collection/filename-without-meta.txt
@@ -0,0 +1 @@
+The filename-without-meta.txt.meta.json file is missing.
diff --git a/src/zen/tests/mochitests/remote-settings/test_remote_settings.js b/src/zen/tests/mochitests/remote-settings/test_remote_settings.js
new file mode 100644
index 000000000..9467ee79f
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_remote_settings.js
@@ -0,0 +1,1798 @@
+/* import-globals-from ../../../common/tests/unit/head_helpers.js */
+
+const { ObjectUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/ObjectUtils.sys.mjs"
+);
+
+let server;
+let client;
+let clientWithDump;
+
+async function clear_state() {
+  // Reset preview mode.
+  RemoteSettings.enablePreviewMode(undefined);
+  Services.prefs.clearUserPref("services.settings.preview_enabled");
+
+  client.verifySignature = false;
+  clientWithDump.verifySignature = false;
+
+  // Clear local DB.
+  await client.db.clear();
+  // Reset event listeners.
+  client._listeners.set("sync", []);
+
+  await clientWithDump.db.clear();
+
+  // Clear events snapshot.
+  Services.telemetry.snapshotEvents(Ci.nsITelemetry.DATASET_ALL_CHANNELS, true);
+  Services.fog.testResetFOG();
+  enableUptakeMetric();
+}
+
+add_task(() => {
+  // Set up an HTTP Server
+  server = new HttpServer();
+  server.start(-1);
+
+  // Point the blocklist clients to use this local HTTP server.
+  Services.prefs.setStringPref(
+    "services.settings.server",
+    `http://localhost:${server.identity.primaryPort}/v1`
+  );
+
+  Services.prefs.setStringPref("services.settings.loglevel", "debug");
+
+  client = RemoteSettings("password-fields");
+  clientWithDump = RemoteSettings("language-dictionaries");
+
+  server.registerPathHandler("/v1/", handleResponse);
+  server.registerPathHandler(
+    "/v1/buckets/monitor/collections/changes/changeset",
+    handleResponse
+  );
+  server.registerPathHandler(
+    "/v1/buckets/main/collections/password-fields/changeset",
+    handleResponse
+  );
+  server.registerPathHandler(
+    "/v1/buckets/main/collections/language-dictionaries/changeset",
+    handleResponse
+  );
+  server.registerPathHandler(
+    "/v1/buckets/main/collections/with-local-fields/changeset",
+    handleResponse
+  );
+  server.registerPathHandler("/fake-x5u", handleResponse);
+
+  registerCleanupFunction(() => {
+    server.stop(() => {});
+  });
+});
+add_task(clear_state);
+
+add_task(async function test_records_obtained_from_server_are_stored_in_db() {
+  // Test an empty db populates
+  await client.maybeSync(2000);
+
+  // Open the collection, verify it's been populated:
+  // Our test data has a single record; it should be in the local collection
+  const list = await client.get();
+  equal(list.length, 1);
+
+  const timestamp = await client.db.getLastModified();
+  equal(timestamp, 3000, "timestamp was stored");
+
+  const { signatures } = await client.db.getMetadata();
+  equal(signatures[0].signature, "abcdef", "metadata was stored");
+});
+add_task(clear_state);
+
+add_task(async function test_client_db_throws_if_not_synced() {
+  try {
+    await client.db.list();
+    Assert.ok(false, "db.list() should throw");
+  } catch (e) {
+    Assert.equal(
+      e.toString(),
+      'EmptyDatabaseError: "main/password-fields" has not been synced yet'
+    );
+  }
+
+  await client.maybeSync(2000);
+
+  const list = await client.db.list();
+  Assert.ok(Array.isArray(list), "data is an array");
+});
+add_task(clear_state);
+
+add_task(
+  async function test_records_from_dump_are_listed_as_created_in_event() {
+    if (IS_ANDROID) {
+      // Skip test: we don't ship remote settings dumps on Android (see package-manifest).
+      return;
+    }
+    let received;
+    clientWithDump.on("sync", ({ data }) => (received = data));
+    // Use a timestamp superior to latest record in dump.
+    const timestamp = 5000000000000; // Fri Jun 11 2128
+
+    await clientWithDump.maybeSync(timestamp);
+
+    const list = await clientWithDump.get();
+    Assert.greater(
+      list.length,
+      20,
+      `The dump was loaded (${list.length} records)`
+    );
+    equal(received.created[0].id, "xx", "Record from the sync come first.");
+
+    const createdById = received.created.reduce((acc, r) => {
+      acc[r.id] = r;
+      return acc;
+    }, {});
+
+    ok(
+      !(received.deleted[0].id in createdById),
+      "Deleted records are not listed as created"
+    );
+    equal(
+      createdById[received.updated[0].new.id],
+      received.updated[0].new,
+      "The records that were updated should appear as created in their newest form."
+    );
+
+    equal(
+      received.created.length,
+      list.length,
+      "The list of created records contains the dump"
+    );
+    equal(received.current.length, received.created.length);
+  }
+);
+add_task(clear_state);
+
+add_task(async function test_throws_when_network_is_offline() {
+  const backupOffline = Services.io.offline;
+  try {
+    Services.io.offline = true;
+    let error;
+    try {
+      await clientWithDump.maybeSync(2000);
+    } catch (e) {
+      error = e;
+    }
+    equal(error.name, "NetworkOfflineError");
+
+    assertTelemetryEvents([
+      {
+        value: UptakeTelemetry.STATUS.SYNC_START,
+      },
+      {
+        value: UptakeTelemetry.STATUS.NETWORK_OFFLINE_ERROR,
+      },
+    ]);
+  } finally {
+    Services.io.offline = backupOffline;
+  }
+});
+add_task(clear_state);
+
+add_task(async function test_sync_event_is_sent_even_if_up_to_date() {
+  if (IS_ANDROID) {
+    // Skip test: we don't ship remote settings dumps on Android (see package-manifest).
+    return;
+  }
+  // First, determine what is the dump timestamp. Sync will load it.
+  // Use a timestamp inferior to latest record in dump.
+  await clientWithDump._importJSONDump();
+  const uptodateTimestamp = await clientWithDump.db.getLastModified();
+  await clear_state();
+
+  // Now, simulate that server data wasn't changed since dump was released.
+  let received;
+  clientWithDump.on("sync", ({ data }) => (received = data));
+
+  await clientWithDump.maybeSync(uptodateTimestamp);
+
+  ok(!!received.current.length, "Dump records are listed as created");
+  equal(received.current.length, received.created.length);
+  assertTelemetryEvents([
+    {
+      value: UptakeTelemetry.STATUS.SYNC_START,
+    },
+    {
+      value: UptakeTelemetry.STATUS.UP_TO_DATE,
+    },
+  ]);
+});
+add_task(clear_state);
+
+add_task(async function test_records_can_have_local_fields() {
+  const c = RemoteSettings("with-local-fields", { localFields: ["accepted"] });
+  c.verifySignature = false;
+
+  await c.maybeSync(2000);
+
+  await c.db.update({
+    id: "c74279ce-fb0a-42a6-ae11-386b567a6119",
+    accepted: true,
+  });
+  await c.maybeSync(3000); // Does not fail.
+});
+add_task(clear_state);
+
+add_task(
+  async function test_records_changes_are_overwritten_by_server_changes() {
+    // Create some local conflicting data, and make sure it syncs without error.
+    await client.db.create({
+      website: "",
+      id: "9d500963-d80e-3a91-6e74-66f3811b99cc",
+    });
+
+    await client.maybeSync(2000);
+
+    const data = await client.get();
+    equal(data[0].website, "https://some-website.com");
+  }
+);
+add_task(clear_state);
+
+add_task(
+  async function test_get_returns_an_empty_list_when_database_is_empty() {
+    const data = await client.get({ syncIfEmpty: false });
+
+    ok(Array.isArray(data), "data is an array");
+    equal(data.length, 0, "data is empty");
+  }
+);
+add_task(clear_state);
+
+add_task(async function test_get_doesnt_affect_other_calls() {
+  const c1 = RemoteSettings("password-fields");
+  const c2 = RemoteSettings("password-fields");
+
+  const result1 = await c1.get({ syncIfEmpty: false });
+  Assert.deepEqual(result1, [], "data1 is empty");
+
+  try {
+    await c2.get({ syncIfEmpty: false, emptyListFallback: false });
+    Assert.ok(false, "get() should throw");
+  } catch (error) {
+    Assert.equal(
+      error.toString(),
+      'EmptyDatabaseError: "main/password-fields" has not been synced yet'
+    );
+  }
+});
+add_task(clear_state);
+
+add_task(async function test_get_throws_if_no_empty_fallback_and_no_sync() {
+  try {
+    await client.get({ syncIfEmpty: false, emptyListFallback: false });
+    Assert.ok(false, ".get() should throw");
+  } catch (error) {
+    Assert.equal(
+      error.toString(),
+      'EmptyDatabaseError: "main/password-fields" has not been synced yet'
+    );
+  }
+});
+add_task(clear_state);
+
+add_task(
+  async function test_get_loads_default_records_from_a_local_dump_when_database_is_empty() {
+    if (IS_ANDROID) {
+      // Skip test: we don't ship remote settings dumps on Android (see package-manifest).
+      return;
+    }
+
+    // When collection has a dump in services/settings/dumps/{bucket}/{collection}.json
+    const data = await clientWithDump.get();
+    notEqual(data.length, 0);
+    // No synchronization happened (responses are not mocked).
+  }
+);
+add_task(clear_state);
+
+add_task(async function test_get_loads_dump_only_once_if_called_in_parallel() {
+  const backup = clientWithDump._importJSONDump;
+  let callCount = 0;
+  clientWithDump._importJSONDump = async () => {
+    callCount++;
+    // eslint-disable-next-line mozilla/no-arbitrary-setTimeout
+    await new Promise(resolve => setTimeout(resolve, 100));
+    return 42;
+  };
+  await Promise.all([clientWithDump.get(), clientWithDump.get()]);
+  equal(callCount, 1, "JSON dump was called more than once");
+  clientWithDump._importJSONDump = backup;
+});
+add_task(clear_state);
+
+add_task(async function test_get_falls_back_to_dump_if_db_fails() {
+  if (IS_ANDROID) {
+    // Skip test: we don't ship remote settings dumps on Android (see package-manifest).
+    return;
+  }
+  const backup = clientWithDump.db.getLastModified;
+  clientWithDump.db.getLastModified = () => {
+    throw new Error("Unknown error");
+  };
+
+  const records = await clientWithDump.get({ dumpFallback: true });
+  ok(!!records.length, "dump content is returned");
+
+  // If fallback is disabled, error is thrown.
+  let error;
+  try {
+    await clientWithDump.get({ dumpFallback: false });
+  } catch (e) {
+    error = e;
+  }
+  equal(error.message, "Unknown error");
+
+  clientWithDump.db.getLastModified = backup;
+});
+add_task(clear_state);
+
+add_task(async function test_get_sorts_results_if_specified() {
+  await client.db.importChanges(
+    {},
+    42,
+    [
+      {
+        field: 12,
+        id: "9d500963-d80e-3a91-6e74-66f3811b99cc",
+      },
+      {
+        field: 7,
+        id: "d83444a4-f348-4cd8-8228-842cb927db9f",
+      },
+    ],
+    { clear: true }
+  );
+
+  const records = await client.get({ order: "field" });
+  Assert.less(
+    records[0].field,
+    records[records.length - 1].field,
+    "records are sorted"
+  );
+});
+add_task(clear_state);
+
+add_task(async function test_get_falls_back_sorts_results() {
+  if (IS_ANDROID) {
+    // Skip test: we don't ship remote settings dumps on Android (see package-manifest).
+    return;
+  }
+  const backup = clientWithDump.db.getLastModified;
+  clientWithDump.db.getLastModified = () => {
+    throw new Error("Unknown error");
+  };
+
+  const records = await clientWithDump.get({
+    dumpFallback: true,
+    order: "-id",
+  });
+
+  // eslint-disable-next-line mozilla/no-comparison-or-assignment-inside-ok
+  ok(records[0].id > records[records.length - 1].id, "records are sorted");
+
+  clientWithDump.db.getLastModified = backup;
+});
+add_task(clear_state);
+
+add_task(async function test_get_falls_back_to_dump_if_db_fails_later() {
+  if (IS_ANDROID) {
+    // Skip test: we don't ship remote settings dumps on Android (see package-manifest).
+    return;
+  }
+  const backup = clientWithDump.db.list;
+  clientWithDump.db.list = () => {
+    throw new Error("Unknown error");
+  };
+
+  const records = await clientWithDump.get({ dumpFallback: true });
+  ok(!!records.length, "dump content is returned");
+
+  // If fallback is disabled, error is thrown.
+  let error;
+  try {
+    await clientWithDump.get({ dumpFallback: false });
+  } catch (e) {
+    error = e;
+  }
+  equal(error.message, "Unknown error");
+
+  clientWithDump.db.list = backup;
+});
+add_task(clear_state);
+
+add_task(async function test_get_falls_back_to_dump_if_network_fails() {
+  if (IS_ANDROID) {
+    // Skip test: we don't ship remote settings dumps on Android (see package-manifest).
+    return;
+  }
+  const backup = clientWithDump.sync;
+  clientWithDump.sync = () => {
+    throw new Error("Sync error");
+  };
+
+  const records = await clientWithDump.get();
+  ok(!!records.length, "dump content is returned");
+
+  clientWithDump.sync = backup;
+});
+add_task(clear_state);
+
+add_task(async function test_get_does_not_sync_if_empty_dump_is_provided() {
+  if (IS_ANDROID) {
+    // Skip test: we don't ship remote settings dumps on Android (see package-manifest).
+    return;
+  }
+
+  const clientWithEmptyDump = RemoteSettings("example");
+  Assert.ok(!(await Utils.hasLocalData(clientWithEmptyDump)));
+
+  const data = await clientWithEmptyDump.get();
+
+  equal(data.length, 0);
+  Assert.ok(await Utils.hasLocalData(clientWithEmptyDump));
+});
+add_task(clear_state);
+
+add_task(async function test_get_synchronization_can_be_disabled() {
+  const data = await client.get({ syncIfEmpty: false });
+
+  equal(data.length, 0);
+});
+add_task(clear_state);
+
+add_task(
+  async function test_get_triggers_synchronization_when_database_is_empty() {
+    // The "password-fields" collection has no local dump, and no local data.
+    // Therefore a synchronization will happen.
+    const data = await client.get();
+
+    // Data comes from mocked HTTP response (see below).
+    equal(data.length, 1);
+    equal(data[0].selector, "#webpage[field-pwd]");
+  }
+);
+add_task(clear_state);
+
+add_task(async function test_get_ignores_synchronization_errors_by_default() {
+  // The monitor endpoint won't contain any information about this collection.
+  let data = await RemoteSettings("some-unknown-key").get();
+  equal(data.length, 0);
+  // The sync endpoints are not mocked, this fails internally.
+  data = await RemoteSettings("no-mocked-responses").get();
+  equal(data.length, 0);
+});
+add_task(clear_state);
+
+add_task(async function test_get_throws_if_no_empty_fallback() {
+  // The monitor endpoint won't contain any information about this collection.
+  try {
+    await RemoteSettings("some-unknown-key").get({
+      emptyListFallback: false,
+    });
+    Assert.ok(false, ".get() should throw");
+  } catch (error) {
+    Assert.ok(
+      error.message.includes("Response from server unparseable"),
+      "Server error was thrown"
+    );
+  }
+});
+add_task(clear_state);
+
+add_task(
+  async function test_get_throws_on_network_error_with_no_empty_fallback() {
+    const backup = Utils.fetch;
+    Utils.fetch = async () => {
+      throw new Error("Fake Network error");
+    };
+
+    const clientEmpty = RemoteSettings("no-dump-no-local-data");
+    let error;
+    try {
+      await clientEmpty.get({
+        emptyListFallback: false,
+        syncIfEmpty: true, // default value
+      });
+    } catch (exc) {
+      error = exc;
+    }
+
+    equal(error.toString(), "Error: Fake Network error");
+    Utils.fetch = backup;
+  }
+);
+
+add_task(async function test_get_verify_signature_empty_no_sync() {
+  client.verifySignature = true;
+  // No data, hence no signature in metadata, and no sync if empty.
+  let error;
+  try {
+    await client.get({
+      verifySignature: true,
+      syncIfEmpty: false,
+      emptyListFallback: false,
+    });
+    Assert.ok(false, "get() should throw");
+  } catch (e) {
+    error = e;
+  }
+  equal(
+    error.toString(),
+    'EmptyDatabaseError: "main/password-fields" has not been synced yet'
+  );
+});
+add_task(clear_state);
+
+add_task(async function test_get_verify_signature_no_metadata_no_sync() {
+  client.verifySignature = true;
+  // Store records but no metadata.
+  await client.db.importChanges(undefined, 42, []);
+  let error;
+  try {
+    await client.get({
+      verifySignature: true,
+      syncIfEmpty: false,
+      emptyListFallback: false,
+    });
+    Assert.ok(false, "get() should throw");
+  } catch (e) {
+    error = e;
+  }
+  equal(
+    error.toString(),
+    "MissingSignatureError: Missing signature (main/password-fields)"
+  );
+});
+add_task(clear_state);
+
+add_task(async function test_get_can_verify_signature_pulled() {
+  // Populate the local DB (only records, eg. loaded from dump previously)
+  await client._importJSONDump();
+
+  let calledSignature;
+  client._verifier = {
+    async asyncVerifyContentSignature(serialized, signature) {
+      calledSignature = signature;
+      return true;
+    },
+  };
+  client.verifySignature = true;
+
+  // No metadata in local DB, but gets pulled and then verifies.
+  ok(ObjectUtils.isEmpty(await client.db.getMetadata()), "Metadata is empty");
+
+  await client.get({ verifySignature: true });
+
+  ok(
+    !ObjectUtils.isEmpty(await client.db.getMetadata()),
+    "Metadata was pulled"
+  );
+  ok(calledSignature.endsWith("some-sig"), "Signature was verified");
+});
+add_task(clear_state);
+
+add_task(async function test_get_can_verify_signature() {
+  // Populate the local DB (record and metadata)
+  await client.maybeSync(2000);
+
+  client.verifySignature = true;
+
+  // It validates signature that was stored in local DB.
+  let calledSignature;
+  client._verifier = {
+    async asyncVerifyContentSignature(serialized, signature) {
+      calledSignature = signature;
+      return JSON.parse(serialized).data.length == 1;
+    },
+  };
+  ok(await Utils.hasLocalData(client), "Local data was populated");
+  await client.get({ verifySignature: true });
+
+  ok(calledSignature.endsWith("abcdef"), "Signature was verified");
+
+  // It throws when signature does not verify.
+  await client.db.delete("9d500963-d80e-3a91-6e74-66f3811b99cc");
+  let error = null;
+  try {
+    await client.get({ verifySignature: true });
+  } catch (e) {
+    error = e;
+  }
+  equal(
+    error.message,
+    "Invalid content signature (main/password-fields) using 'fake-x5u' and signer remote-settings.content-signature.mozilla.org"
+  );
+});
+add_task(clear_state);
+
+add_task(async function test_get_does_not_verify_signature_if_load_dump() {
+  if (IS_ANDROID) {
+    // Skip test: we don't ship remote settings dumps on Android (see package-manifest).
+    return;
+  }
+
+  let called;
+  clientWithDump._verifier = {
+    async asyncVerifyContentSignature() {
+      called = true;
+      return true;
+    },
+  };
+
+  // When dump is loaded, signature is not verified.
+  const records = await clientWithDump.get({ verifySignature: true });
+  ok(!!records.length, "dump is loaded");
+  ok(!called, "signature is missing but not verified");
+
+  // If metadata is missing locally, it is not fetched if `syncIfEmpty` is disabled.
+  clientWithDump.verifySignature = true;
+  let error;
+  try {
+    await clientWithDump.get({ verifySignature: true, syncIfEmpty: false });
+  } catch (e) {
+    error = e;
+  }
+  ok(!called, "signer was not called");
+  equal(
+    error.message,
+    "Missing signature (main/language-dictionaries)",
+    "signature is missing locally"
+  );
+
+  // If metadata is missing locally, it is fetched by default (`syncIfEmpty: true`)
+  await clientWithDump.get({ verifySignature: true });
+  const metadata = await clientWithDump.db.getMetadata();
+  ok(!!Object.keys(metadata).length, "metadata was fetched");
+  ok(called, "signature was verified for the data that was in dump");
+  clientWithDump.verifySignature = true;
+});
+add_task(clear_state);
+
+add_task(
+  async function test_get_does_verify_signature_if_json_loaded_in_parallel() {
+    const backup = clientWithDump._verifier;
+    let callCount = 0;
+    clientWithDump._verifier = {
+      async asyncVerifyContentSignature() {
+        callCount++;
+        return true;
+      },
+    };
+    await Promise.all([
+      clientWithDump.get({ verifySignature: true }),
+      clientWithDump.get({ verifySignature: true }),
+    ]);
+    equal(callCount, 0, "No need to verify signatures if JSON dump is loaded");
+    clientWithDump._verifier = backup;
+  }
+);
+add_task(clear_state);
+
+add_task(async function test_get_can_force_a_sync() {
+  const step0 = await client.db.getLastModified();
+  await client.get({ forceSync: true });
+  const step1 = await client.db.getLastModified();
+  await client.get();
+  const step2 = await client.db.getLastModified();
+  await client.get({ forceSync: true });
+  const step3 = await client.db.getLastModified();
+
+  equal(step0, null);
+  equal(step1, 3000);
+  equal(step2, 3000);
+  equal(step3, 3001);
+});
+add_task(clear_state);
+
+add_task(async function test_sync_runs_once_only() {
+  const backup = Utils.log.warn;
+  const messages = [];
+  Utils.log.warn = m => {
+    messages.push(m);
+  };
+
+  await Promise.all([client.maybeSync(2000), client.maybeSync(2000)]);
+
+  ok(
+    messages.includes("main/password-fields sync already running"),
+    "warning is shown about sync already running"
+  );
+  Utils.log.warn = backup;
+});
+add_task(clear_state);
+
+add_task(
+  async function test_sync_pulls_metadata_if_missing_with_dump_is_up_to_date() {
+    if (IS_ANDROID) {
+      // Skip test: we don't ship remote settings dumps on Android (see package-manifest).
+      return;
+    }
+
+    let called;
+    clientWithDump._verifier = {
+      async asyncVerifyContentSignature() {
+        called = true;
+        return true;
+      },
+    };
+    // When dump is loaded, signature is not verified.
+    const records = await clientWithDump.get({ verifySignature: true });
+    ok(!!records.length, "dump is loaded");
+    ok(!called, "signature is missing but not verified");
+
+    // Synchronize the collection (local data is up-to-date).
+    // Signature verification is disabled (see `clear_state()`), so we don't bother with
+    // fetching metadata.
+    const uptodateTimestamp = await clientWithDump.db.getLastModified();
+    await clientWithDump.maybeSync(uptodateTimestamp);
+    let metadata = await clientWithDump.db.getMetadata();
+    ok(!metadata, "metadata was not fetched");
+
+    // Synchronize again the collection (up-to-date, since collection last modified still > 42)
+    clientWithDump.verifySignature = true;
+    await clientWithDump.maybeSync(42);
+
+    // With signature verification, metadata was fetched.
+    metadata = await clientWithDump.db.getMetadata();
+    ok(!!Object.keys(metadata).length, "metadata was fetched");
+    ok(called, "signature was verified for the data that was in dump");
+
+    // Metadata is present, signature will now verified.
+    called = false;
+    await clientWithDump.get({ verifySignature: true });
+    ok(called, "local signature is verified");
+  }
+);
+add_task(clear_state);
+
+add_task(async function test_sync_event_provides_information_about_records() {
+  let eventData;
+  client.on("sync", ({ data }) => (eventData = data));
+
+  await client.maybeSync(2000);
+  equal(eventData.current.length, 1);
+
+  await client.maybeSync(3001);
+  equal(eventData.current.length, 2);
+  equal(eventData.created.length, 1);
+  equal(eventData.created[0].website, "https://www.other.org/signin");
+  equal(eventData.updated.length, 1);
+  equal(eventData.updated[0].old.website, "https://some-website.com");
+  equal(eventData.updated[0].new.website, "https://some-website.com/login");
+  equal(eventData.deleted.length, 0);
+
+  await client.maybeSync(4001);
+  equal(eventData.current.length, 1);
+  equal(eventData.created.length, 0);
+  equal(eventData.updated.length, 0);
+  equal(eventData.deleted.length, 1);
+  equal(eventData.deleted[0].website, "https://www.other.org/signin");
+});
+add_task(clear_state);
+
+add_task(async function test_inspect_method() {
+  // Synchronize the `password-fields` collection in order to have
+  // some local data when .inspect() is called.
+  await client.maybeSync(2000);
+
+  const inspected = await RemoteSettings.inspect();
+
+  // Assertion for global attributes.
+  const { mainBucket, serverURL, defaultSigner, collections, serverTimestamp } =
+    inspected;
+  const rsSigner = "remote-settings.content-signature.mozilla.org";
+  equal(mainBucket, "main");
+  equal(serverURL, `http://localhost:${server.identity.primaryPort}/v1`);
+  equal(defaultSigner, rsSigner);
+  equal(serverTimestamp, "5000");
+
+  // A collection is listed in .inspect() if it has local data or if there
+  // is a JSON dump for it.
+  // "password-fields" has no dump but was synchronized above and thus has local data.
+  let col = collections.pop();
+  equal(col.collection, "password-fields");
+  equal(col.serverTimestamp, 3000);
+  equal(col.localTimestamp, 3000);
+
+  if (!IS_ANDROID) {
+    // "language-dictionaries" has a local dump (not on Android)
+    col = collections.pop();
+    equal(col.collection, "language-dictionaries");
+    equal(col.serverTimestamp, 4000);
+    ok(!col.localTimestamp); // not synchronized.
+  }
+});
+add_task(clear_state);
+
+add_task(async function test_inspect_method_uses_a_random_cache_bust() {
+  const backup = Utils.fetchLatestChanges;
+  const cacheBusts = [];
+  Utils.fetchLatestChanges = (url, options) => {
+    cacheBusts.push(options.expected);
+    return { changes: [] };
+  };
+
+  await RemoteSettings.inspect();
+  await RemoteSettings.inspect();
+  await RemoteSettings.inspect();
+
+  notEqual(cacheBusts[0], cacheBusts[1]);
+  notEqual(cacheBusts[1], cacheBusts[2]);
+  notEqual(cacheBusts[0], cacheBusts[2]);
+  Utils.fetchLatestChanges = backup;
+});
+
+add_task(async function test_jexl_context_is_shown_in_inspect() {
+  const { jexlContext } = await RemoteSettings.inspect();
+  deepEqual(Object.keys(jexlContext).sort(), [
+    "appinfo",
+    "channel",
+    "country",
+    "formFactor",
+    "locale",
+    "os",
+    "version",
+  ]);
+  deepEqual(Object.keys(jexlContext.os).sort(), ["name", "version"]);
+  deepEqual(Object.keys(jexlContext.appinfo).sort(), ["ID", "OS"]);
+});
+
+add_task(async function test_clearAll_method() {
+  // Make sure we have some local data.
+  await client.maybeSync(2000);
+  await clientWithDump.maybeSync(2000);
+
+  await RemoteSettings.clearAll();
+
+  ok(!(await Utils.hasLocalData(client)), "Local data was deleted");
+  ok(!(await Utils.hasLocalData(clientWithDump)), "Local data was deleted");
+  ok(
+    !Services.prefs.prefHasUserValue(client.lastCheckTimePref),
+    "Pref was cleaned"
+  );
+
+  // Synchronization is not broken after resuming.
+  await client.maybeSync(2000);
+  await clientWithDump.maybeSync(2000);
+  ok(await Utils.hasLocalData(client), "Local data was populated");
+  ok(await Utils.hasLocalData(clientWithDump), "Local data was populated");
+});
+add_task(clear_state);
+
+add_task(async function test_listeners_are_not_deduplicated() {
+  let count = 0;
+  const plus1 = () => {
+    count += 1;
+  };
+
+  client.on("sync", plus1);
+  client.on("sync", plus1);
+  client.on("sync", plus1);
+
+  await client.maybeSync(2000);
+
+  equal(count, 3);
+});
+add_task(clear_state);
+
+add_task(async function test_listeners_can_be_removed() {
+  let count = 0;
+  const onSync = () => {
+    count += 1;
+  };
+
+  client.on("sync", onSync);
+  client.off("sync", onSync);
+
+  await client.maybeSync(2000);
+
+  equal(count, 0);
+});
+add_task(clear_state);
+
+add_task(async function test_all_listeners_are_executed_if_one_fails() {
+  let count = 0;
+  client.on("sync", () => {
+    count += 1;
+  });
+  client.on("sync", () => {
+    throw new Error("boom");
+  });
+  client.on("sync", () => {
+    count += 2;
+  });
+
+  let error;
+  try {
+    await client.maybeSync(2000);
+  } catch (e) {
+    error = e;
+  }
+
+  equal(count, 3);
+  equal(error.message, "boom");
+});
+add_task(clear_state);
+
+add_task(async function test_telemetry_reports_up_to_date() {
+  await client.maybeSync(2000);
+
+  const expectedTelemetry = [
+    {
+      value: UptakeTelemetry.STATUS.SYNC_START,
+    },
+    {
+      value: UptakeTelemetry.STATUS.SUCCESS,
+    },
+  ];
+  assertTelemetryEvents(expectedTelemetry);
+
+  await client.maybeSync(3000);
+
+  // No Telemetry was sent.
+  assertTelemetryEvents(
+    expectedTelemetry.concat([
+      {
+        value: UptakeTelemetry.STATUS.SYNC_START,
+      },
+      {
+        value: UptakeTelemetry.STATUS.UP_TO_DATE,
+      },
+    ])
+  );
+});
+add_task(clear_state);
+
+add_task(async function test_telemetry_if_sync_succeeds() {
+  // We test each client because Telemetry requires preleminary declarations.
+  await client.maybeSync(2000);
+
+  assertTelemetryEvents([
+    {
+      value: UptakeTelemetry.STATUS.SYNC_START,
+    },
+    {
+      value: UptakeTelemetry.STATUS.SUCCESS,
+    },
+  ]);
+});
+add_task(clear_state);
+
+add_task(
+  async function test_synchronization_duration_is_reported_in_uptake_status() {
+    await client.maybeSync(2000);
+
+    assertTelemetryEvents([
+      {
+        value: UptakeTelemetry.STATUS.SYNC_START,
+        source: client.identifier,
+        trigger: "manual",
+      },
+      {
+        value: UptakeTelemetry.STATUS.SUCCESS,
+        source: client.identifier,
+        trigger: "manual",
+        duration: d => parseInt(d) > 0,
+      },
+    ]);
+  }
+);
+add_task(clear_state);
+
+add_task(async function test_telemetry_reports_if_application_fails() {
+  client.on("sync", () => {
+    throw new Error("boom");
+  });
+
+  try {
+    await client.maybeSync(2000);
+  } catch (e) {}
+
+  assertTelemetryEvents([
+    {
+      value: UptakeTelemetry.STATUS.SYNC_START,
+    },
+    {
+      value: UptakeTelemetry.STATUS.APPLY_ERROR,
+    },
+  ]);
+});
+add_task(clear_state);
+
+add_task(async function test_telemetry_reports_if_sync_fails() {
+  await client.db.importChanges({}, 9999);
+
+  try {
+    await client.maybeSync(10000);
+  } catch (e) {}
+
+  assertTelemetryEvents([
+    {
+      value: UptakeTelemetry.STATUS.SYNC_START,
+    },
+    {
+      value: UptakeTelemetry.STATUS.SERVER_ERROR,
+    },
+  ]);
+});
+add_task(clear_state);
+
+add_task(async function test_telemetry_reports_if_parsing_fails() {
+  await client.db.importChanges({}, 10000);
+
+  try {
+    await client.maybeSync(10001);
+  } catch (e) {}
+
+  assertTelemetryEvents([
+    {
+      value: UptakeTelemetry.STATUS.SYNC_START,
+    },
+    {
+      value: UptakeTelemetry.STATUS.PARSE_ERROR,
+    },
+  ]);
+});
+add_task(clear_state);
+
+add_task(async function test_telemetry_reports_if_fetching_signature_fails() {
+  await client.db.importChanges({}, 11000);
+
+  try {
+    await client.maybeSync(11001);
+  } catch (e) {}
+
+  assertTelemetryEvents([
+    {
+      value: UptakeTelemetry.STATUS.SYNC_START,
+    },
+    {
+      value: UptakeTelemetry.STATUS.SERVER_ERROR,
+    },
+  ]);
+});
+add_task(clear_state);
+
+add_task(async function test_telemetry_reports_unknown_errors() {
+  const backup = client.db.getLastModified;
+  client.db.getLastModified = () => {
+    throw new Error("Internal");
+  };
+
+  try {
+    await client.maybeSync(2000);
+  } catch (e) {}
+
+  client.db.getLastModified = backup;
+  assertTelemetryEvents([
+    {
+      value: UptakeTelemetry.STATUS.SYNC_START,
+    },
+    {
+      value: UptakeTelemetry.STATUS.UNKNOWN_ERROR,
+    },
+  ]);
+});
+add_task(clear_state);
+
+add_task(async function test_telemetry_reports_indexeddb_as_custom_1() {
+  const backup = client.db.getLastModified;
+  const msg =
+    "IndexedDB getLastModified() The operation failed for reasons unrelated to the database itself";
+  client.db.getLastModified = () => {
+    throw new Error(msg);
+  };
+
+  try {
+    await client.maybeSync(2000);
+  } catch (e) {}
+
+  client.db.getLastModified = backup;
+  assertTelemetryEvents([
+    {
+      value: UptakeTelemetry.STATUS.SYNC_START,
+    },
+    {
+      value: UptakeTelemetry.STATUS.CUSTOM_1_ERROR,
+    },
+  ]);
+});
+add_task(clear_state);
+
+add_task(async function test_telemetry_reports_error_name_as_event_nightly() {
+  const backup = client.db.getLastModified;
+  client.db.getLastModified = () => {
+    const e = new Error("Some unknown error");
+    e.name = "ThrownError";
+    throw e;
+  };
+
+  try {
+    await client.maybeSync(2000);
+  } catch (e) {}
+
+  assertTelemetryEvents([
+    {
+      value: UptakeTelemetry.STATUS.SYNC_START,
+      source: client.identifier,
+      trigger: "manual",
+    },
+    {
+      value: UptakeTelemetry.STATUS.UNKNOWN_ERROR,
+      source: client.identifier,
+      trigger: "manual",
+      errorName: "ThrownError",
+      duration: d => parseInt(d) >= 0,
+    },
+  ]);
+
+  client.db.getLastModified = backup;
+});
+add_task(clear_state);
+
+add_task(async function test_bucketname_changes_when_preview_mode_is_enabled() {
+  equal(client.bucketName, "main");
+
+  RemoteSettings.enablePreviewMode(true);
+
+  equal(client.bucketName, "main-preview");
+});
+add_task(clear_state);
+
+add_task(
+  async function test_preview_mode_pref_affects_bucket_names_before_instantiated() {
+    Services.prefs.setBoolPref("services.settings.preview_enabled", true);
+
+    let clientWithDefaultBucket = RemoteSettings("other");
+    let clientWithBucket = RemoteSettings("coll", { bucketName: "buck" });
+
+    equal(clientWithDefaultBucket.bucketName, "main-preview");
+    equal(clientWithBucket.bucketName, "buck-preview");
+  }
+);
+add_task(clear_state);
+
+add_task(
+  async function test_preview_enabled_pref_ignored_when_mode_is_set_explicitly() {
+    Services.prefs.setBoolPref("services.settings.preview_enabled", true);
+
+    let clientWithDefaultBucket = RemoteSettings("other");
+    let clientWithBucket = RemoteSettings("coll", { bucketName: "buck" });
+
+    equal(clientWithDefaultBucket.bucketName, "main-preview");
+    equal(clientWithBucket.bucketName, "buck-preview");
+
+    RemoteSettings.enablePreviewMode(false);
+
+    equal(clientWithDefaultBucket.bucketName, "main");
+    equal(clientWithBucket.bucketName, "buck");
+  }
+);
+add_task(clear_state);
+
+add_task(
+  async function test_get_loads_default_records_from_a_local_dump_when_preview_mode_is_enabled() {
+    if (IS_ANDROID) {
+      // Skip test: we don't ship remote settings dumps on Android (see package-manifest).
+      return;
+    }
+    RemoteSettings.enablePreviewMode(true);
+    // When collection has a dump in services/settings/dumps/{bucket}/{collection}.json
+    const data = await clientWithDump.get();
+    notEqual(data.length, 0);
+    // No synchronization happened (responses are not mocked).
+  }
+);
+add_task(clear_state);
+
+add_task(async function test_local_db_distinguishes_preview_records() {
+  RemoteSettings.enablePreviewMode(true);
+  client.db.importChanges({}, Date.now(), [{ id: "record-1" }], {
+    clear: true,
+  });
+
+  RemoteSettings.enablePreviewMode(false);
+  client.db.importChanges({}, Date.now(), [{ id: "record-2" }], {
+    clear: true,
+  });
+
+  deepEqual(await client.get(), [{ id: "record-2" }]);
+});
+add_task(clear_state);
+
+add_task(
+  async function test_inspect_changes_the_list_when_preview_mode_is_enabled() {
+    if (IS_ANDROID) {
+      // Skip test: we don't ship remote settings dumps on Android (see package-manifest),
+      // and this test relies on the fact that clients are instantiated if a dump is packaged.
+      return;
+    }
+
+    // Register a client only listed in -preview...
+    RemoteSettings("crash-rate");
+
+    const { collections: before, previewMode: previewModeBefore } =
+      await RemoteSettings.inspect();
+
+    Assert.ok(!previewModeBefore, "preview is not enabled");
+
+    // These two collections are listed in the main bucket in monitor/changes (one with dump, one registered).
+    deepEqual(before.map(c => c.collection).sort(), [
+      "language-dictionaries",
+      "password-fields",
+    ]);
+
+    // Switch to preview mode.
+    RemoteSettings.enablePreviewMode(true);
+
+    const {
+      collections: after,
+      mainBucket,
+      previewMode,
+    } = await RemoteSettings.inspect();
+
+    Assert.ok(previewMode, "preview is enabled");
+
+    // These two collections are listed in the main bucket in monitor/changes (both are registered).
+    deepEqual(after.map(c => c.collection).sort(), [
+      "crash-rate",
+      "password-fields",
+    ]);
+    equal(mainBucket, "main-preview");
+  }
+);
+add_task(clear_state);
+
+add_task(async function test_sync_event_is_not_sent_from_get_when_no_dump() {
+  let called = false;
+  client.on("sync", () => {
+    called = true;
+  });
+
+  await client.get();
+
+  Assert.ok(!called, "sync event is not sent from .get()");
+});
+add_task(clear_state);
+
+add_task(async function test_get_can_be_called_from_sync_event_callback() {
+  let fromGet;
+  let fromEvent;
+
+  client.on("sync", async ({ data: { current } }) => {
+    // Before fixing Bug 1761953 this would result in a deadlock.
+    fromGet = await client.get();
+    fromEvent = current;
+  });
+
+  await client.maybeSync(2000);
+
+  Assert.ok(fromGet, "sync callback was called");
+  Assert.deepEqual(fromGet, fromEvent, ".get() gives current records list");
+});
+add_task(clear_state);
+
+add_task(async function test_attachments_are_pruned_when_sync_from_timer() {
+  await client.db.saveAttachment("bar", {
+    record: { id: "bar" },
+    blob: new Blob(["456"]),
+  });
+
+  await client.maybeSync(2000, { trigger: "broadcast" });
+
+  Assert.ok(
+    await client.attachments.cacheImpl.get("bar"),
+    "Extra attachment was not deleted on broadcast"
+  );
+
+  await client.maybeSync(3001, { trigger: "timer" });
+
+  Assert.ok(
+    !(await client.attachments.cacheImpl.get("bar")),
+    "Extra attachment was deleted on timer"
+  );
+});
+add_task(clear_state);
+
+function handleResponse(request, response) {
+  try {
+    const sample = getSampleResponse(request, server.identity.primaryPort);
+    if (!sample) {
+      do_throw(
+        `unexpected ${request.method} request for ${request.path}?${request.queryString}`
+      );
+    }
+
+    response.setStatusLine(
+      null,
+      sample.status.status,
+      sample.status.statusText
+    );
+    // send the headers
+    for (let headerLine of sample.sampleHeaders) {
+      let headerElements = headerLine.split(":");
+      response.setHeader(headerElements[0], headerElements[1].trimLeft());
+    }
+    response.setHeader("Date", new Date().toUTCString());
+
+    const body =
+      typeof sample.responseBody == "string"
+        ? sample.responseBody
+        : JSON.stringify(sample.responseBody);
+    response.write(body);
+    response.finish();
+  } catch (e) {
+    info(e);
+  }
+}
+
+function getSampleResponse(req, port) {
+  const responses = {
+    OPTIONS: {
+      sampleHeaders: [
+        "Access-Control-Allow-Headers: Content-Length,Expires,Backoff,Retry-After,Last-Modified,Total-Records,ETag,Pragma,Cache-Control,authorization,content-type,if-none-match,Alert,Next-Page",
+        "Access-Control-Allow-Methods: GET,HEAD,OPTIONS,POST,DELETE,OPTIONS",
+        "Access-Control-Allow-Origin: *",
+        "Content-Type: application/json; charset=UTF-8",
+        "Server: waitress",
+      ],
+      status: { status: 200, statusText: "OK" },
+      responseBody: null,
+    },
+    "GET:/v1/": {
+      sampleHeaders: [
+        "Access-Control-Allow-Origin: *",
+        "Access-Control-Expose-Headers: Retry-After, Content-Length, Alert, Backoff",
+        "Content-Type: application/json; charset=UTF-8",
+        "Server: waitress",
+      ],
+      status: { status: 200, statusText: "OK" },
+      responseBody: {
+        settings: {
+          batch_max_requests: 25,
+        },
+        url: `http://localhost:${port}/v1/`,
+        documentation: "https://kinto.readthedocs.org/",
+        version: "1.5.1",
+        commit: "cbc6f58",
+        hello: "kinto",
+      },
+    },
+    "GET:/v1/buckets/monitor/collections/changes/changeset": {
+      sampleHeaders: [
+        "Access-Control-Allow-Origin: *",
+        "Access-Control-Expose-Headers: Retry-After, Content-Length, Alert, Backoff",
+        "Content-Type: application/json; charset=UTF-8",
+        "Server: waitress",
+        `Date: ${new Date().toUTCString()}`,
+        'Etag: "5000"',
+      ],
+      status: { status: 200, statusText: "OK" },
+      responseBody: {
+        timestamp: 5000,
+        changes: [
+          {
+            id: "4676f0c7-9757-4796-a0e8-b40a5a37a9c9",
+            bucket: "main",
+            collection: "unknown-locally",
+            last_modified: 5000,
+          },
+          {
+            id: "4676f0c7-9757-4796-a0e8-b40a5a37a9c9",
+            bucket: "main",
+            collection: "language-dictionaries",
+            last_modified: 4000,
+          },
+          {
+            id: "0af8da0b-3e03-48fb-8d0d-2d8e4cb7514d",
+            bucket: "main",
+            collection: "password-fields",
+            last_modified: 3000,
+          },
+          {
+            id: "4acda969-3bd3-4074-a678-ff311eeb076e",
+            bucket: "main-preview",
+            collection: "password-fields",
+            last_modified: 2000,
+          },
+          {
+            id: "58697bd1-315f-4185-9bee-3371befc2585",
+            bucket: "main-preview",
+            collection: "crash-rate",
+            last_modified: 1000,
+          },
+        ],
+      },
+    },
+    "GET:/fake-x5u": {
+      sampleHeaders: ["Content-Type: application/octet-stream"],
+      status: { status: 200, statusText: "OK" },
+      responseBody: `-----BEGIN CERTIFICATE-----
+MIIGYTCCBEmgAwIBAgIBATANBgkqhkiG9w0BAQwFADB9MQswCQYDVQQGEwJVU
+ZARKjbu1TuYQHf0fs+GwID8zeLc2zJL7UzcHFwwQ6Nda9OJN4uPAuC/BKaIpxCLL
+26b24/tRam4SJjqpiq20lynhUrmTtt6hbG3E1Hpy3bmkt2DYnuMFwEx2gfXNcnbT
+wNuvFqc=
+-----END CERTIFICATE-----`,
+    },
+    "GET:/v1/buckets/main/collections/password-fields/changeset?_expected=2000":
+      {
+        sampleHeaders: [
+          "Access-Control-Allow-Origin: *",
+          "Access-Control-Expose-Headers: Retry-After, Content-Length, Alert, Backoff",
+          "Content-Type: application/json; charset=UTF-8",
+          "Server: waitress",
+          'Etag: "3000"',
+        ],
+        status: { status: 200, statusText: "OK" },
+        responseBody: {
+          timestamp: 3000,
+          metadata: {
+            id: "password-fields",
+            last_modified: 1234,
+            signatures: [
+              {
+                signature: "abcdef",
+                x5u: `http://localhost:${port}/fake-x5u`,
+              },
+            ],
+          },
+          changes: [
+            {
+              id: "9d500963-d80e-3a91-6e74-66f3811b99cc",
+              last_modified: 3000,
+              website: "https://some-website.com",
+              selector: "#user[password]",
+            },
+          ],
+        },
+      },
+    "GET:/v1/buckets/main/collections/password-fields/changeset?_expected=3001&_since=3000":
+      {
+        sampleHeaders: [
+          "Access-Control-Allow-Origin: *",
+          "Access-Control-Expose-Headers: Retry-After, Content-Length, Alert, Backoff",
+          "Content-Type: application/json; charset=UTF-8",
+          "Server: waitress",
+          'Etag: "4000"',
+        ],
+        status: { status: 200, statusText: "OK" },
+        responseBody: {
+          metadata: {
+            signatures: [{}],
+          },
+          timestamp: 4000,
+          changes: [
+            {
+              id: "aabad965-e556-ffe7-4191-074f5dee3df3",
+              last_modified: 4000,
+              website: "https://www.other.org/signin",
+              selector: "#signinpassword",
+            },
+            {
+              id: "9d500963-d80e-3a91-6e74-66f3811b99cc",
+              last_modified: 3500,
+              website: "https://some-website.com/login",
+              selector: "input#user[password]",
+            },
+          ],
+        },
+      },
+    "GET:/v1/buckets/main/collections/password-fields/changeset?_expected=4001&_since=4000":
+      {
+        sampleHeaders: [
+          "Access-Control-Allow-Origin: *",
+          "Access-Control-Expose-Headers: Retry-After, Content-Length, Alert, Backoff",
+          "Content-Type: application/json; charset=UTF-8",
+          "Server: waitress",
+          'Etag: "5000"',
+        ],
+        status: { status: 200, statusText: "OK" },
+        responseBody: {
+          metadata: {
+            signatures: [{}],
+          },
+          timestamp: 5000,
+          changes: [
+            {
+              id: "aabad965-e556-ffe7-4191-074f5dee3df3",
+              deleted: true,
+            },
+          ],
+        },
+      },
+    "GET:/v1/buckets/main/collections/password-fields/changeset?_expected=10000&_since=9999":
+      {
+        sampleHeaders: [
+          "Access-Control-Allow-Origin: *",
+          "Access-Control-Expose-Headers: Retry-After, Content-Length, Alert, Backoff",
+          "Content-Type: application/json; charset=UTF-8",
+          "Server: waitress",
+        ],
+        status: { status: 503, statusText: "Service Unavailable" },
+        responseBody: {
+          code: 503,
+          errno: 999,
+          error: "Service Unavailable",
+        },
+      },
+    "GET:/v1/buckets/main/collections/password-fields/changeset?_expected=10001&_since=10000":
+      {
+        sampleHeaders: [
+          "Access-Control-Allow-Origin: *",
+          "Access-Control-Expose-Headers: Retry-After, Content-Length, Alert, Backoff",
+          "Content-Type: application/json; charset=UTF-8",
+          "Server: waitress",
+          'Etag: "10001"',
+        ],
+        status: { status: 200, statusText: "OK" },
+        responseBody: "<invalid json",
+      },
+    "GET:/v1/buckets/main/collections/password-fields/changeset?_expected=11001&_since=11000":
+      {
+        sampleHeaders: [
+          "Access-Control-Allow-Origin: *",
+          "Access-Control-Expose-Headers: Retry-After, Content-Length, Alert, Backoff",
+          "Content-Type: application/json; charset=UTF-8",
+          "Server: waitress",
+        ],
+        status: { status: 503, statusText: "Service Unavailable" },
+        responseBody: {
+          changes: [
+            {
+              id: "c4f021e3-f68c-4269-ad2a-d4ba87762b35",
+              last_modified: 4000,
+              website: "https://www.eff.org",
+              selector: "#pwd",
+            },
+          ],
+        },
+      },
+    "GET:/v1/buckets/main/collections/password-fields?_expected=11001": {
+      sampleHeaders: [
+        "Access-Control-Allow-Origin: *",
+        "Access-Control-Expose-Headers: Retry-After, Content-Length, Alert, Backoff",
+        "Content-Type: application/json; charset=UTF-8",
+        "Server: waitress",
+      ],
+      status: { status: 503, statusText: "Service Unavailable" },
+      responseBody: {
+        code: 503,
+        errno: 999,
+        error: "Service Unavailable",
+      },
+    },
+    "GET:/v1/buckets/monitor/collections/changes/changeset?collection=password-fields&bucket=main&_expected=0":
+      {
+        sampleHeaders: [
+          "Access-Control-Allow-Origin: *",
+          "Access-Control-Expose-Headers: Retry-After, Content-Length, Alert, Backoff",
+          "Content-Type: application/json; charset=UTF-8",
+          "Server: waitress",
+          `Date: ${new Date().toUTCString()}`,
+          'Etag: "1338"',
+        ],
+        status: { status: 200, statusText: "OK" },
+        responseBody: {
+          timestamp: 1338,
+          changes: [
+            {
+              id: "fe5758d0-c67a-42d0-bb4f-8f2d75106b65",
+              bucket: "main",
+              collection: "password-fields",
+              last_modified: 1337,
+            },
+          ],
+        },
+      },
+    "GET:/v1/buckets/main/collections/password-fields/changeset?_expected=1337":
+      {
+        sampleHeaders: [
+          "Access-Control-Allow-Origin: *",
+          "Access-Control-Expose-Headers: Retry-After, Content-Length, Alert, Backoff",
+          "Content-Type: application/json; charset=UTF-8",
+          "Server: waitress",
+          'Etag: "3000"',
+        ],
+        status: { status: 200, statusText: "OK" },
+        responseBody: {
+          metadata: {
+            signatures: [
+              {
+                signature: "some-sig",
+                x5u: `http://localhost:${port}/fake-x5u`,
+              },
+            ],
+          },
+          timestamp: 3000,
+          changes: [
+            {
+              id: "312cc78d-9c1f-4291-a4fa-a1be56f6cc69",
+              last_modified: 3000,
+              website: "https://some-website.com",
+              selector: "#webpage[field-pwd]",
+            },
+          ],
+        },
+      },
+    "GET:/v1/buckets/main/collections/password-fields/changeset?_expected=1337&_since=3000":
+      {
+        sampleHeaders: [
+          "Access-Control-Allow-Origin: *",
+          "Access-Control-Expose-Headers: Retry-After, Content-Length, Alert, Backoff",
+          "Content-Type: application/json; charset=UTF-8",
+          "Server: waitress",
+          'Etag: "3001"',
+        ],
+        status: { status: 200, statusText: "OK" },
+        responseBody: {
+          metadata: {
+            signatures: [
+              {
+                signature: "some-sig",
+                x5u: `http://localhost:${port}/fake-x5u`,
+              },
+            ],
+          },
+          timestamp: 3001,
+          changes: [
+            {
+              id: "312cc78d-9c1f-4291-a4fa-a1be56f6cc69",
+              last_modified: 3001,
+              website: "https://some-website-2.com",
+              selector: "#webpage[field-pwd]",
+            },
+          ],
+        },
+      },
+    "GET:/v1/buckets/main/collections/language-dictionaries/changeset": {
+      sampleHeaders: [
+        "Access-Control-Allow-Origin: *",
+        "Access-Control-Expose-Headers: Retry-After, Content-Length, Alert, Backoff",
+        "Content-Type: application/json; charset=UTF-8",
+        "Server: waitress",
+        'Etag: "5000000000000"',
+      ],
+      status: { status: 200, statusText: "OK" },
+      responseBody: {
+        timestamp: 5000000000000,
+        metadata: {
+          id: "language-dictionaries",
+          last_modified: 1234,
+          signatures: [
+            {
+              signature: "xyz",
+              x5u: `http://localhost:${port}/fake-x5u`,
+            },
+          ],
+        },
+        changes: [
+          {
+            id: "xx",
+            last_modified: 5000000000000,
+            dictionaries: ["xx-XX@dictionaries.addons.mozilla.org"],
+          },
+          {
+            id: "fr",
+            last_modified: 5000000000000 - 1,
+            deleted: true,
+          },
+          {
+            id: "pt-BR",
+            last_modified: 5000000000000 - 2,
+            dictionaries: ["pt-BR@for-tests"],
+          },
+        ],
+      },
+    },
+    "GET:/v1/buckets/main/collections/with-local-fields/changeset?_expected=2000":
+      {
+        sampleHeaders: [
+          "Access-Control-Allow-Origin: *",
+          "Access-Control-Expose-Headers: Retry-After, Content-Length, Alert, Backoff",
+          "Content-Type: application/json; charset=UTF-8",
+          "Server: waitress",
+          'Etag: "2000"',
+        ],
+        status: { status: 200, statusText: "OK" },
+        responseBody: {
+          timestamp: 2000,
+          metadata: {
+            id: "with-local-fields",
+            last_modified: 1234,
+            signatures: [
+              {
+                signature: "xyz",
+                x5u: `http://localhost:${port}/fake-x5u`,
+              },
+            ],
+          },
+          changes: [
+            {
+              id: "c74279ce-fb0a-42a6-ae11-386b567a6119",
+              last_modified: 2000,
+            },
+          ],
+        },
+      },
+    "GET:/v1/buckets/main/collections/with-local-fields/changeset?_expected=3000&_since=2000":
+      {
+        sampleHeaders: [
+          "Access-Control-Allow-Origin: *",
+          "Access-Control-Expose-Headers: Retry-After, Content-Length, Alert, Backoff",
+          "Content-Type: application/json; charset=UTF-8",
+          "Server: waitress",
+          'Etag: "3000"',
+        ],
+        status: { status: 200, statusText: "OK" },
+        responseBody: {
+          timestamp: 3000,
+          metadata: {
+            signatures: [{}],
+          },
+          changes: [
+            {
+              id: "1f5c98b9-6d93-4c13-aa26-978b38695096",
+              last_modified: 3000,
+            },
+          ],
+        },
+      },
+    "GET:/v1/buckets/monitor/collections/changes/changeset?collection=no-mocked-responses&bucket=main&_expected=0":
+      {
+        sampleHeaders: [
+          "Access-Control-Allow-Origin: *",
+          "Access-Control-Expose-Headers: Retry-After, Content-Length, Alert, Backoff",
+          "Content-Type: application/json; charset=UTF-8",
+          "Server: waitress",
+          `Date: ${new Date().toUTCString()}`,
+          'Etag: "713705"',
+        ],
+        status: { status: 200, statusText: "OK" },
+        responseBody: {
+          data: [
+            {
+              id: "07a98d1b-7c62-4344-ab18-76856b3facd8",
+              bucket: "main",
+              collection: "no-mocked-responses",
+              last_modified: 713705,
+            },
+          ],
+        },
+      },
+  };
+  return (
+    responses[`${req.method}:${req.path}?${req.queryString}`] ||
+    responses[`${req.method}:${req.path}`] ||
+    responses[req.method]
+  );
+}
+
+add_task(clear_state);
+
+add_task(async function test_hasAttachments_works_as_expected() {
+  let res = await client.db.hasAttachments();
+  Assert.equal(res, false, "Should return false, no attachments at start");
+
+  await client.db.saveAttachment("foo", {
+    record: { id: "foo" },
+    blob: new Blob(["foo"]),
+  });
+
+  res = await client.db.hasAttachments();
+  Assert.equal(res, true, "Should return true, just saved an attachment");
+
+  await client.db.pruneAttachments([]);
+
+  res = await client.db.hasAttachments();
+  Assert.equal(res, false, "Should return false after attachments are pruned");
+});
+add_task(clear_state);
diff --git a/src/zen/tests/mochitests/remote-settings/test_remote_settings_dump_lastmodified.js b/src/zen/tests/mochitests/remote-settings/test_remote_settings_dump_lastmodified.js
new file mode 100644
index 000000000..6dd925281
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_remote_settings_dump_lastmodified.js
@@ -0,0 +1,55 @@
+"use strict";
+
+async function getLocalDumpLastModified(bucket, collection) {
+  let res;
+  try {
+    res = await fetch(
+      `resource://app/defaults/settings/${bucket}/${collection}.json`
+    );
+  } catch (e) {
+    return -1;
+  }
+  const { timestamp } = await res.json();
+  Assert.greaterOrEqual(
+    timestamp,
+    0,
+    `${bucket}/${collection} dump has timestamp`
+  );
+  return timestamp;
+}
+
+add_task(async function lastModified_of_non_existing_dump() {
+  ok(!Utils._dumpStats, "_dumpStats not initialized");
+  equal(
+    await Utils.getLocalDumpLastModified("did not", "exist"),
+    -1,
+    "A non-existent dump has value -1"
+  );
+  ok(Utils._dumpStats, "_dumpStats was initialized");
+
+  ok("did not/exist" in Utils._dumpStats, "cached non-existing dump result");
+  delete Utils._dumpStats["did not/exist"];
+});
+
+add_task(async function lastModified_summary_is_correct() {
+  ok(!!Object.keys(Utils._dumpStats).length, "Contains summary of dumps");
+
+  let checked = 0;
+  for (let [identifier, lastModified] of Object.entries(Utils._dumpStats)) {
+    let [bucket, collection] = identifier.split("/");
+    let actual = await getLocalDumpLastModified(bucket, collection);
+    if (actual < 0) {
+      info(`${identifier} has no dump, skip.`);
+      continue;
+    }
+    info(`Checking correctness of ${identifier}`);
+    equal(
+      await Utils.getLocalDumpLastModified(bucket, collection),
+      lastModified,
+      `Expected last_modified value for ${identifier}`
+    );
+    equal(lastModified, actual, `last_modified should match collection`);
+    checked++;
+  }
+  Assert.greater(checked, 0, "At least one dump was packaged and checked.");
+});
diff --git a/src/zen/tests/mochitests/remote-settings/test_remote_settings_jexl_filters.js b/src/zen/tests/mochitests/remote-settings/test_remote_settings_jexl_filters.js
new file mode 100644
index 000000000..032568db7
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_remote_settings_jexl_filters.js
@@ -0,0 +1,210 @@
+let client;
+
+async function createRecords(records) {
+  await client.db.importChanges(
+    {},
+    42,
+    records.map((record, i) => ({
+      id: `record-${i}`,
+      ...record,
+    })),
+    {
+      clear: true,
+    }
+  );
+}
+
+add_setup(() => {
+  client = RemoteSettings("some-key");
+});
+
+add_task(async function test_returns_all_without_target() {
+  await createRecords([
+    {
+      passwordSelector: "#pass-signin",
+    },
+    {
+      filter_expression: null,
+    },
+    {
+      filter_expression: "",
+    },
+  ]);
+
+  const list = await client.get();
+  equal(list.length, 3);
+});
+
+add_task(async function test_filters_can_be_disabled() {
+  const c = RemoteSettings("no-jexl", { filterCreator: null });
+  await c.db.importChanges({}, 42, [
+    {
+      id: "abc",
+      filter_expression: "1 == 2",
+    },
+  ]);
+
+  const list = await c.get();
+  equal(list.length, 1);
+});
+
+add_task(async function test_returns_entries_where_jexl_is_true() {
+  await createRecords([
+    {
+      willMatch: true,
+      filter_expression: "1",
+    },
+    {
+      willMatch: true,
+      filter_expression: "[42]",
+    },
+    {
+      willMatch: true,
+      filter_expression: "1 == 2 || 1 == 1",
+    },
+    {
+      willMatch: true,
+      filter_expression: 'env.appinfo.ID == "xpcshell@tests.mozilla.org"',
+    },
+    {
+      willMatch: false,
+      filter_expression: "env.version == undefined",
+    },
+    {
+      willMatch: true,
+      filter_expression: "env.unknown == undefined",
+    },
+    {
+      willMatch: false,
+      filter_expression: "1 == 2",
+    },
+  ]);
+
+  const list = await client.get();
+  equal(list.length, 5);
+  ok(list.every(e => e.willMatch));
+});
+
+add_task(async function test_ignores_entries_where_jexl_is_invalid() {
+  await createRecords([
+    {
+      filter_expression: "true === true", // JavaScript Error: "Invalid expression token: ="
+    },
+    {
+      filter_expression: "Objects.keys({}) == []", // Token ( (openParen) unexpected in expression
+    },
+  ]);
+
+  const list = await client.get();
+  equal(list.length, 0);
+});
+
+add_task(async function test_support_of_date_filters() {
+  await createRecords([
+    {
+      willMatch: true,
+      filter_expression: '"1982-05-08"|date < "2016-03-22"|date',
+    },
+    {
+      willMatch: false,
+      filter_expression: '"2000-01-01"|date < "1970-01-01"|date',
+    },
+  ]);
+
+  const list = await client.get();
+  equal(list.length, 1);
+  ok(list.every(e => e.willMatch));
+});
+
+add_task(async function test_support_of_preferences_filters() {
+  await createRecords([
+    {
+      willMatch: true,
+      filter_expression: '"services.settings.last_etag"|preferenceValue == 42',
+    },
+    {
+      willMatch: true,
+      filter_expression:
+        '"services.settings.poll_interval"|preferenceExists == true',
+    },
+    {
+      willMatch: true,
+      filter_expression:
+        '"services.settings.poll_interval"|preferenceIsUserSet == false',
+    },
+    {
+      willMatch: true,
+      filter_expression:
+        '"services.settings.last_etag"|preferenceIsUserSet == true',
+    },
+  ]);
+
+  // Set a pref for the user.
+  Services.prefs.setIntPref("services.settings.last_etag", 42);
+
+  const list = await client.get();
+  equal(list.length, 4);
+  ok(list.every(e => e.willMatch));
+});
+
+add_task(async function test_support_of_intersect_operator() {
+  await createRecords([
+    {
+      willMatch: true,
+      filter_expression: '{foo: 1, bar: 2}|keys intersect ["foo"]',
+    },
+    {
+      willMatch: true,
+      filter_expression: '(["a", "b"] intersect ["a", 1, 4]) == "a"',
+    },
+    {
+      willMatch: false,
+      filter_expression: '(["a", "b"] intersect [3, 1, 4]) == "c"',
+    },
+    {
+      willMatch: true,
+      filter_expression: `
+      [1, 2, 3]
+        intersect
+      [3, 4, 5]
+    `,
+    },
+  ]);
+
+  const list = await client.get();
+  equal(list.length, 3);
+  ok(list.every(e => e.willMatch));
+});
+
+add_task(async function test_support_of_samples() {
+  await createRecords([
+    {
+      willMatch: true,
+      filter_expression: '"always-true"|stableSample(1)',
+    },
+    {
+      willMatch: false,
+      filter_expression: '"always-false"|stableSample(0)',
+    },
+    {
+      willMatch: true,
+      filter_expression: '"turns-to-true-0"|stableSample(0.5)',
+    },
+    {
+      willMatch: false,
+      filter_expression: '"turns-to-false-1"|stableSample(0.5)',
+    },
+    {
+      willMatch: true,
+      filter_expression: '"turns-to-true-0"|bucketSample(0, 50, 100)',
+    },
+    {
+      willMatch: false,
+      filter_expression: '"turns-to-false-1"|bucketSample(0, 50, 100)',
+    },
+  ]);
+
+  const list = await client.get();
+  equal(list.length, 3);
+  ok(list.every(e => e.willMatch));
+});
diff --git a/src/zen/tests/mochitests/remote-settings/test_remote_settings_offline.js b/src/zen/tests/mochitests/remote-settings/test_remote_settings_offline.js
new file mode 100644
index 000000000..deea90601
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_remote_settings_offline.js
@@ -0,0 +1,139 @@
+// A collection with a dump that's packaged on all builds where this test runs,
+// including on Android at mobile/android/installer/package-manifest.in
+const TEST_BUCKET = "main";
+const TEST_COLLECTION = "password-recipes";
+
+let client;
+let DUMP_RECORDS;
+let DUMP_LAST_MODIFIED;
+
+add_setup(async () => {
+  // "services.settings.server" pref is not set.
+  // Test defaults to an unreachable server,
+  // and will only load from the dump if any.
+
+  client = new RemoteSettingsClient(TEST_COLLECTION, {
+    bucketName: TEST_BUCKET,
+  });
+
+  const dump = await SharedUtils.loadJSONDump(TEST_BUCKET, TEST_COLLECTION);
+  DUMP_RECORDS = dump.data;
+  DUMP_LAST_MODIFIED = dump.timestamp;
+
+  // Dumps are fetched via the following, which sorts the records, newest first.
+  // https://searchfox.org/mozilla-central/rev/5b3444ad300e244b5af4214212e22bd9e4b7088a/taskcluster/docker/periodic-updates/scripts/periodic_file_updates.sh#304
+  equal(
+    DUMP_LAST_MODIFIED,
+    DUMP_RECORDS[0].last_modified,
+    "records in dump ought to be sorted by last_modified"
+  );
+});
+
+async function importData(records) {
+  await RemoteSettingsWorker._execute("_test_only_import", [
+    TEST_BUCKET,
+    TEST_COLLECTION,
+    records,
+    records[0]?.last_modified || 0,
+  ]);
+}
+
+async function clear_state() {
+  await client.db.clear();
+}
+
+add_task(async function test_load_from_dump_when_offline() {
+  // Baseline: verify that the collection is empty at first,
+  // but non-empty after loading from the dump.
+  const beforeTimestamp = await client.db.getLastModified();
+  equal(beforeTimestamp, null, "collection empty when offline");
+
+  // should import from dump since collection was not initialized.
+  const after = await client.get();
+  equal(after.length, DUMP_RECORDS.length, "collection loaded from dump");
+  equal(await client.getLastModified(), DUMP_LAST_MODIFIED, "dump's timestamp");
+});
+add_task(clear_state);
+
+add_task(async function test_optional_skip_dump_after_empty_import() {
+  // clear_state should have wiped the database.
+  const beforeTimestamp = await client.db.getLastModified();
+  equal(beforeTimestamp, null, "collection empty after clearing");
+
+  // Verify that the dump is not imported again by client.get()
+  // when the database is initialized with an empty dump
+  // with `loadDumpIfNewer` disabled.
+  await importData([]); // <-- Empty set of records.
+
+  const after = await client.get({ loadDumpIfNewer: false });
+  equal(after.length, 0, "collection still empty due to import");
+  equal(await client.getLastModified(), 0, "Empty dump has no timestamp");
+});
+add_task(clear_state);
+
+add_task(async function test_optional_skip_dump_after_non_empty_import() {
+  await importData([{ last_modified: 1234, id: "dummy" }]);
+
+  const after = await client.get({ loadDumpIfNewer: false });
+  equal(after.length, 1, "Imported dummy data");
+  equal(await client.getLastModified(), 1234, "Expected timestamp of import");
+
+  await importData([]);
+  const after2 = await client.get({ loadDumpIfNewer: false });
+  equal(after2.length, 0, "Previous data wiped on duplicate import");
+  equal(await client.getLastModified(), 0, "Timestamp of empty collection");
+});
+add_task(clear_state);
+
+add_task(async function test_load_dump_after_empty_import() {
+  await importData([]); // <-- Empty set of records, i.e. last_modified = 0.
+
+  const after = await client.get();
+  equal(after.length, DUMP_RECORDS.length, "Imported dump");
+  equal(await client.getLastModified(), DUMP_LAST_MODIFIED, "dump's timestamp");
+});
+add_task(clear_state);
+
+add_task(async function test_load_dump_after_non_empty_import() {
+  // Dump is updated regularly, verify that the dump matches our expectations
+  // before running the test.
+  Assert.greater(
+    DUMP_LAST_MODIFIED,
+    1234,
+    "Assuming dump to be newer than dummy 1234"
+  );
+
+  await importData([{ last_modified: 1234, id: "dummy" }]);
+
+  const after = await client.get();
+  equal(after.length, DUMP_RECORDS.length, "Imported dump");
+  equal(await client.getLastModified(), DUMP_LAST_MODIFIED, "dump's timestamp");
+});
+add_task(clear_state);
+
+add_task(async function test_load_dump_after_import_from_broken_distro() {
+  // Dump is updated regularly, verify that the dump matches our expectations
+  // before running the test.
+  Assert.greater(
+    DUMP_LAST_MODIFIED,
+    1234,
+    "Assuming dump to be newer than dummy 1234"
+  );
+
+  // No last_modified time.
+  await importData([{ id: "dummy" }]);
+
+  const after = await client.get();
+  equal(after.length, DUMP_RECORDS.length, "Imported dump");
+  equal(await client.getLastModified(), DUMP_LAST_MODIFIED, "dump's timestamp");
+});
+add_task(clear_state);
+
+add_task(async function test_skip_dump_if_same_last_modified() {
+  await importData([{ last_modified: DUMP_LAST_MODIFIED, id: "dummy" }]);
+
+  const after = await client.get();
+  equal(after.length, 1, "Not importing dump when time matches");
+  equal(await client.getLastModified(), DUMP_LAST_MODIFIED, "Same timestamp");
+});
+add_task(clear_state);
diff --git a/src/zen/tests/mochitests/remote-settings/test_remote_settings_older_than_local.js b/src/zen/tests/mochitests/remote-settings/test_remote_settings_older_than_local.js
new file mode 100644
index 000000000..682849669
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_remote_settings_older_than_local.js
@@ -0,0 +1,149 @@
+const PREF_SETTINGS_SERVER = "services.settings.server";
+
+let server;
+let client;
+
+async function clear_state() {
+  await client.db.clear();
+}
+
+function setJSONResponse(response, changeset) {
+  response.setStatusLine(null, 200, "OK");
+  response.setHeader("Content-Type", "application/json; charset=UTF-8");
+  response.setHeader("Date", new Date().toUTCString());
+  response.write(JSON.stringify(changeset));
+}
+
+add_setup(() => {
+  Services.prefs.setStringPref("services.settings.loglevel", "debug");
+
+  // Set up an HTTP Server
+  server = new HttpServer();
+  server.start(-1);
+
+  Services.prefs.setStringPref(
+    PREF_SETTINGS_SERVER,
+    `http://localhost:${server.identity.primaryPort}/v1`
+  );
+
+  client = RemoteSettings("some-cid");
+
+  const bodies = {
+    // First successful sync at timestamp=333
+    "/v1/buckets/main/collections/some-cid/changeset?_expected=333": {
+      timestamp: 333,
+      metadata: {
+        signatures: [{ signature: "abc", x5u: "data:text/plain;base64,pem" }],
+      },
+      changes: [
+        { id: "rid2", last_modified: 22 },
+        { id: "rid1", last_modified: 11 },
+      ],
+    },
+    // Client fetches with _expected=222&_since=333
+    "/v1/buckets/main/collections/some-cid/changeset?_expected=222&_since=333":
+      {
+        timestamp: 222,
+        metadata: {
+          signatures: [{ signature: "ghi", x5u: "data:text/plain;base64,pem" }],
+        },
+        changes: [{ id: "rid1", last_modified: 11 }],
+      },
+    // Client refetches full collection with _expected=222 after signature fails.
+    "/v1/buckets/main/collections/some-cid/changeset?_expected=222": {
+      timestamp: 222,
+      metadata: {
+        signatures: [{ signature: "ghi", x5u: "data:text/plain;base64,pem" }],
+      },
+      changes: [{ id: "rid1", last_modified: 11 }],
+    },
+  };
+  const handler = (request, response) => {
+    const body = bodies[`${request.path}?${request.queryString}`];
+    if (!body) {
+      const err = new Error(
+        `Unexpected request ${request.path}?${request.queryString}`
+      );
+      console.error(err);
+      throw err;
+    }
+    setJSONResponse(response, body);
+  };
+  Object.keys(bodies).map(path =>
+    server.registerPathHandler(path.split("?")[0], handler)
+  );
+
+  // In this test suite, the only valid data is the one at timestamp=222 or timestamp=333, but not a mix of the two.
+  let backup = client._verifier;
+  client._verifier = {
+    asyncVerifyContentSignature: serialized => {
+      return (
+        serialized ==
+          '{"data":[{"id":"rid2","last_modified":22}],"last_modified":"444"}' ||
+        serialized ==
+          '{"data":[{"id":"rid1","last_modified":11},{"id":"rid2","last_modified":22}],"last_modified":"333"}' ||
+        serialized ==
+          '{"data":[{"id":"rid1","last_modified":11}],"last_modified":"222"}'
+      );
+    },
+  };
+
+  registerCleanupFunction(() => {
+    client._verifier = backup;
+    server.stop(() => {});
+    Services.prefs.clearUserPref(PREF_SETTINGS_SERVER);
+
+    Services.prefs.clearUserPref("services.settings.loglevel");
+  });
+});
+
+add_task(clear_state);
+
+add_task(async function test_ignores_if_local_signature_is_valid() {
+  await client.maybeSync(333);
+  Assert.deepEqual(
+    [
+      await client.db.getLastModified(),
+      (await client.get()).map(({ id }) => id),
+    ],
+    [333, ["rid1", "rid2"]]
+  );
+
+  await client.maybeSync(222);
+
+  // The client should detect that timestamp is older,
+  // but it ignores it because local data is good.
+  Assert.deepEqual(
+    [
+      await client.db.getLastModified(),
+      (await client.get()).map(({ id }) => id),
+    ],
+    [333, ["rid1", "rid2"]]
+  );
+});
+add_task(clear_state);
+
+add_task(async function test_uses_old_data_if_local_signature_is_invalid() {
+  // Import some data in the local DB. Signature will be bad.
+  await client.db.importChanges({}, 333, [{ id: "myid", last_modified: 1234 }]);
+  Assert.deepEqual(
+    [
+      await client.db.getLastModified(),
+      (await client.get()).map(({ id }) => id),
+    ],
+    [333, ["myid"]]
+  );
+
+  await client.maybeSync(222);
+
+  // The client should detect that timestamp is older,
+  // but will replace local data with this old data.
+  Assert.deepEqual(
+    [
+      await client.db.getLastModified(),
+      (await client.get()).map(({ id }) => id),
+    ],
+    [222, ["rid1"]]
+  );
+});
+add_task(clear_state);
diff --git a/src/zen/tests/mochitests/remote-settings/test_remote_settings_poll.js b/src/zen/tests/mochitests/remote-settings/test_remote_settings_poll.js
new file mode 100644
index 000000000..927342824
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_remote_settings_poll.js
@@ -0,0 +1,1287 @@
+const { pushBroadcastService } = ChromeUtils.importESModule(
+  "resource://gre/modules/PushBroadcastService.sys.mjs"
+);
+
+const { remoteSettingsBroadcastHandler, BROADCAST_ID } =
+  ChromeUtils.importESModule(
+    "resource://services-settings/remote-settings.sys.mjs"
+  );
+
+const PREF_SETTINGS_SERVER = "services.settings.server";
+const PREF_SETTINGS_SERVER_BACKOFF = "services.settings.server.backoff";
+const PREF_LAST_UPDATE = "services.settings.last_update_seconds";
+const PREF_LAST_ETAG = "services.settings.last_etag";
+const PREF_CLOCK_SKEW_SECONDS = "services.settings.clock_skew_seconds";
+
+// Telemetry report result.
+const TELEMETRY_SOURCE_POLL = "settings-changes-monitoring";
+const TELEMETRY_SOURCE_SYNC = "settings-sync";
+const CHANGES_PATH = "/v1" + Utils.CHANGES_PATH;
+
+var server;
+
+async function clear_state() {
+  // set up prefs so the kinto updater talks to the test server
+  Services.prefs.setStringPref(
+    PREF_SETTINGS_SERVER,
+    `http://localhost:${server.identity.primaryPort}/v1`
+  );
+
+  // set some initial values so we can check these are updated appropriately
+  Services.prefs.setIntPref(PREF_LAST_UPDATE, 0);
+  Services.prefs.setIntPref(PREF_CLOCK_SKEW_SECONDS, 0);
+  Services.prefs.clearUserPref(PREF_LAST_ETAG);
+
+  // Clear events snapshot.
+  Services.telemetry.snapshotEvents(Ci.nsITelemetry.DATASET_ALL_CHANNELS, true);
+  Services.fog.testResetFOG();
+  enableUptakeMetric();
+
+  // Clear sync history.
+  await new SyncHistory("").clear();
+}
+
+function serveChangesEntries(serverTime, entriesOrFunc) {
+  return (request, response) => {
+    response.setStatusLine(null, 200, "OK");
+    response.setHeader("Content-Type", "application/json; charset=UTF-8");
+    response.setHeader("Date", new Date(serverTime).toUTCString());
+    const entries =
+      typeof entriesOrFunc == "function" ? entriesOrFunc() : entriesOrFunc;
+    const latest = entries[0]?.last_modified ?? 42;
+    if (entries.length) {
+      response.setHeader("ETag", `"${latest}"`);
+    }
+    response.write(JSON.stringify({ timestamp: latest, changes: entries }));
+  };
+}
+
+add_setup(() => {
+  // Set up an HTTP Server
+  server = new HttpServer();
+  server.start(-1);
+
+  registerCleanupFunction(() => {
+    server.stop(() => {});
+  });
+});
+
+add_task(clear_state);
+
+add_task(async function test_an_event_is_sent_on_start() {
+  server.registerPathHandler(CHANGES_PATH, (request, response) => {
+    response.write(JSON.stringify({ timestamp: 42, changes: [] }));
+    response.setHeader("Content-Type", "application/json; charset=UTF-8");
+    response.setHeader("ETag", "42");
+    response.setHeader("Date", new Date().toUTCString());
+    response.setStatusLine(null, 200, "OK");
+  });
+  let notificationObserved = null;
+  const observer = {
+    observe(aSubject, aTopic, aData) {
+      Services.obs.removeObserver(this, "remote-settings:changes-poll-start");
+      notificationObserved = JSON.parse(aData);
+    },
+  };
+  Services.obs.addObserver(observer, "remote-settings:changes-poll-start");
+
+  await RemoteSettings.pollChanges({ expectedTimestamp: 13 });
+
+  Assert.equal(
+    notificationObserved.expectedTimestamp,
+    13,
+    "start notification should have been observed"
+  );
+});
+add_task(clear_state);
+
+add_task(async function test_offline_is_reported_if_relevant() {
+  const offlineBackup = Services.io.offline;
+  try {
+    Services.io.offline = true;
+
+    await RemoteSettings.pollChanges();
+
+    assertTelemetryEvents([
+      {
+        value: UptakeTelemetry.STATUS.NETWORK_OFFLINE_ERROR,
+      },
+    ]);
+  } finally {
+    Services.io.offline = offlineBackup;
+  }
+});
+add_task(clear_state);
+
+add_task(async function test_check_success() {
+  const serverTime = 8000;
+
+  server.registerPathHandler(
+    CHANGES_PATH,
+    serveChangesEntries(serverTime, [
+      {
+        id: "330a0c5f-fadf-ff0b-40c8-4eb0d924ff6a",
+        last_modified: 1100,
+        host: "localhost",
+        bucket: "some-other-bucket",
+        collection: "test-collection",
+      },
+      {
+        id: "254cbb9e-6888-4d9f-8e60-58b74faa8778",
+        last_modified: 1000,
+        host: "localhost",
+        bucket: "test-bucket",
+        collection: "test-collection",
+      },
+    ])
+  );
+
+  // add a test kinto client that will respond to lastModified information
+  // for a collection called 'test-collection'.
+  // Let's use a bucket that is not the default one (`test-bucket`).
+  const c = RemoteSettings("test-collection", {
+    bucketName: "test-bucket",
+  });
+  let maybeSyncCalled = false;
+  c.maybeSync = () => {
+    maybeSyncCalled = true;
+  };
+
+  // Ensure that the remote-settings:changes-poll-end notification works
+  let notificationObserved = false;
+  const observer = {
+    observe() {
+      Services.obs.removeObserver(this, "remote-settings:changes-poll-end");
+      notificationObserved = true;
+    },
+  };
+  Services.obs.addObserver(observer, "remote-settings:changes-poll-end");
+
+  await RemoteSettings.pollChanges();
+
+  // It didn't fail, hence we are sure that the unknown collection ``some-other-bucket/test-collection``
+  // was ignored, otherwise it would have tried to reach the network.
+
+  Assert.ok(maybeSyncCalled, "maybeSync was called");
+  Assert.ok(notificationObserved, "a notification should have been observed");
+  // Last timestamp was saved. An ETag header value is a quoted string.
+  Assert.equal(Services.prefs.getStringPref(PREF_LAST_ETAG), "1100");
+  // check the last_update is updated
+  Assert.equal(Services.prefs.getIntPref(PREF_LAST_UPDATE), serverTime / 1000);
+
+  // ensure that we've accumulated the correct telemetry
+  assertTelemetryEvents([
+    {
+      value: UptakeTelemetry.STATUS.SUCCESS,
+      source: TELEMETRY_SOURCE_POLL,
+      trigger: "manual",
+    },
+    {
+      value: UptakeTelemetry.STATUS.SUCCESS,
+      source: TELEMETRY_SOURCE_SYNC,
+      trigger: "manual",
+    },
+  ]);
+});
+add_task(clear_state);
+
+add_task(async function test_update_timer_interface() {
+  const remoteSettings = Cc["@mozilla.org/services/settings;1"].getService(
+    Ci.nsITimerCallback
+  );
+
+  const serverTime = 8000;
+  server.registerPathHandler(
+    CHANGES_PATH,
+    serveChangesEntries(serverTime, [
+      {
+        id: "028261ad-16d4-40c2-a96a-66f72914d125",
+        last_modified: 42,
+        host: "localhost",
+        bucket: "main",
+        collection: "whatever-collection",
+      },
+    ])
+  );
+
+  await new Promise(resolve => {
+    const e = "remote-settings:changes-poll-end";
+    const changesPolledObserver = {
+      observe() {
+        Services.obs.removeObserver(this, e);
+        resolve();
+      },
+    };
+    Services.obs.addObserver(changesPolledObserver, e);
+    remoteSettings.notify(null);
+  });
+
+  // Everything went fine.
+  Assert.equal(Services.prefs.getStringPref(PREF_LAST_ETAG), "42");
+  Assert.equal(Services.prefs.getIntPref(PREF_LAST_UPDATE), serverTime / 1000);
+});
+add_task(clear_state);
+
+add_task(async function test_check_up_to_date() {
+  // Simulate a poll with up-to-date collection.
+  const serverTime = 4000;
+  server.registerPathHandler(CHANGES_PATH, serveChangesEntries(serverTime, []));
+
+  Services.prefs.setStringPref(PREF_LAST_ETAG, "1100");
+
+  // Ensure that the remote-settings:changes-poll-end notification is sent.
+  let notificationObserved = false;
+  const observer = {
+    observe() {
+      Services.obs.removeObserver(this, "remote-settings:changes-poll-end");
+      notificationObserved = true;
+    },
+  };
+  Services.obs.addObserver(observer, "remote-settings:changes-poll-end");
+
+  // If server has no change, maybeSync() is not called.
+  let maybeSyncCalled = false;
+  const c = RemoteSettings("test-collection", {
+    bucketName: "test-bucket",
+  });
+  c.maybeSync = () => {
+    maybeSyncCalled = true;
+  };
+
+  await RemoteSettings.pollChanges();
+
+  Assert.ok(notificationObserved, "a notification should have been observed");
+  Assert.ok(!maybeSyncCalled, "maybeSync should not be called");
+  // Last update is overwritten
+  Assert.equal(Services.prefs.getIntPref(PREF_LAST_UPDATE), serverTime / 1000);
+
+  // ensure that we've accumulated the correct telemetry
+  assertTelemetryEvents([
+    {
+      value: UptakeTelemetry.STATUS.UP_TO_DATE,
+      source: TELEMETRY_SOURCE_POLL,
+    },
+    {
+      value: UptakeTelemetry.STATUS.SUCCESS,
+      source: TELEMETRY_SOURCE_SYNC,
+    },
+  ]);
+});
+add_task(clear_state);
+
+add_task(async function test_expected_timestamp() {
+  function withCacheBust(request, response) {
+    const entries = [
+      {
+        id: "695c2407-de79-4408-91c7-70720dd59d78",
+        last_modified: 1100,
+        host: "localhost",
+        bucket: "main",
+        collection: "with-cache-busting",
+      },
+    ];
+    if (
+      request.queryString.includes(`_expected=${encodeURIComponent('"42"')}`)
+    ) {
+      response.write(
+        JSON.stringify({
+          timestamp: 1110,
+          changes: entries,
+        })
+      );
+    }
+    response.setHeader("Content-Type", "application/json; charset=UTF-8");
+    response.setHeader("ETag", '"1100"');
+    response.setHeader("Date", new Date().toUTCString());
+    response.setStatusLine(null, 200, "OK");
+  }
+  server.registerPathHandler(CHANGES_PATH, withCacheBust);
+
+  const c = RemoteSettings("with-cache-busting");
+  let maybeSyncCalled = false;
+  c.maybeSync = () => {
+    maybeSyncCalled = true;
+  };
+
+  await RemoteSettings.pollChanges({ expectedTimestamp: '"42"' });
+
+  Assert.ok(maybeSyncCalled, "maybeSync was called");
+});
+add_task(clear_state);
+
+add_task(async function test_client_last_check_is_saved() {
+  server.registerPathHandler(CHANGES_PATH, (request, response) => {
+    response.write(
+      JSON.stringify({
+        timestamp: 42,
+        changes: [
+          {
+            id: "695c2407-de79-4408-91c7-70720dd59d78",
+            last_modified: 1100,
+            host: "localhost",
+            bucket: "main",
+            collection: "models-recipes",
+          },
+        ],
+      })
+    );
+    response.setHeader("Content-Type", "application/json; charset=UTF-8");
+    response.setHeader("ETag", '"42"');
+    response.setHeader("Date", new Date().toUTCString());
+    response.setStatusLine(null, 200, "OK");
+  });
+
+  const c = RemoteSettings("models-recipes");
+  c.maybeSync = () => {};
+
+  equal(
+    c.lastCheckTimePref,
+    "services.settings.main.models-recipes.last_check"
+  );
+  Services.prefs.setIntPref(c.lastCheckTimePref, 0);
+
+  await RemoteSettings.pollChanges({ expectedTimestamp: '"42"' });
+
+  notEqual(Services.prefs.getIntPref(c.lastCheckTimePref), 0);
+});
+add_task(clear_state);
+
+add_task(async function test_age_of_data_is_reported_in_uptake_status() {
+  const serverTime = 1552323900000;
+  const recordsTimestamp = serverTime - 3600 * 1000;
+  server.registerPathHandler(
+    CHANGES_PATH,
+    serveChangesEntries(serverTime, [
+      {
+        id: "b6ba7fab-a40a-4d03-a4af-6b627f3c5b36",
+        last_modified: recordsTimestamp,
+        host: "localhost",
+        bucket: "main",
+        collection: "some-entry",
+      },
+    ])
+  );
+
+  await RemoteSettings.pollChanges();
+
+  assertTelemetryEvents([
+    {
+      value: UptakeTelemetry.STATUS.SUCCESS,
+      source: TELEMETRY_SOURCE_POLL,
+      age: "3600",
+      trigger: "manual",
+    },
+    {
+      value: UptakeTelemetry.STATUS.SUCCESS,
+      source: TELEMETRY_SOURCE_SYNC,
+      trigger: "manual",
+      timestamp: `${recordsTimestamp}`,
+      duration: d => !!d,
+    },
+  ]);
+});
+add_task(clear_state);
+
+add_task(
+  async function test_synchronization_duration_is_reported_in_uptake_status() {
+    server.registerPathHandler(
+      CHANGES_PATH,
+      serveChangesEntries(10000, [
+        {
+          id: "b6ba7fab-a40a-4d03-a4af-6b627f3c5b36",
+          last_modified: 42,
+          host: "localhost",
+          bucket: "main",
+          collection: "some-entry",
+        },
+      ])
+    );
+    const c = RemoteSettings("some-entry");
+    // Simulate a synchronization that lasts 1 sec.
+    // eslint-disable-next-line mozilla/no-arbitrary-setTimeout
+    c.maybeSync = () => new Promise(resolve => setTimeout(resolve, 1000));
+
+    await RemoteSettings.pollChanges();
+
+    assertTelemetryEvents([
+      {
+        value: UptakeTelemetry.STATUS.SUCCESS,
+        source: TELEMETRY_SOURCE_POLL,
+        trigger: "manual",
+        age: a => !!a,
+      },
+      {
+        value: UptakeTelemetry.STATUS.SUCCESS,
+        source: TELEMETRY_SOURCE_SYNC,
+        trigger: "manual",
+        duration: d => parseInt(d) >= 1000,
+      },
+    ]);
+  }
+);
+add_task(clear_state);
+
+add_task(async function test_success_with_partial_list() {
+  function partialList(request, response) {
+    const entries = [
+      {
+        id: "028261ad-16d4-40c2-a96a-66f72914d125",
+        last_modified: 43,
+        host: "localhost",
+        bucket: "main",
+        collection: "cid-1",
+      },
+      {
+        id: "98a34576-bcd6-423f-abc2-1d290b776ed8",
+        last_modified: 42,
+        host: "localhost",
+        bucket: "main",
+        collection: "poll-test-collection",
+      },
+    ];
+    if (request.queryString.includes(`_since=42`)) {
+      response.write(
+        JSON.stringify({
+          timestamp: 43,
+          changes: entries.slice(0, 1),
+        })
+      );
+    } else {
+      response.write(
+        JSON.stringify({
+          timestamp: 42,
+          changes: entries,
+        })
+      );
+    }
+    response.setHeader("Content-Type", "application/json; charset=UTF-8");
+    response.setHeader("Date", new Date().toUTCString());
+    response.setStatusLine(null, 200, "OK");
+  }
+  server.registerPathHandler(CHANGES_PATH, partialList);
+
+  const c = RemoteSettings("poll-test-collection");
+  let maybeSyncCount = 0;
+  c.maybeSync = () => {
+    maybeSyncCount++;
+  };
+
+  await RemoteSettings.pollChanges();
+  await RemoteSettings.pollChanges();
+
+  // On the second call, the server does not mention the poll-test-collection
+  // and maybeSync() is not called.
+  Assert.equal(maybeSyncCount, 1, "maybeSync should not be called twice");
+});
+add_task(clear_state);
+
+add_task(async function test_full_polling() {
+  server.registerPathHandler(
+    CHANGES_PATH,
+    serveChangesEntries(10000, [
+      {
+        id: "b6ba7fab-a40a-4d03-a4af-6b627f3c5b36",
+        last_modified: 42,
+        host: "localhost",
+        bucket: "main",
+        collection: "poll-test-collection",
+      },
+    ])
+  );
+
+  const c = RemoteSettings("poll-test-collection");
+  let maybeSyncCount = 0;
+  c.maybeSync = () => {
+    maybeSyncCount++;
+  };
+
+  await RemoteSettings.pollChanges();
+  await RemoteSettings.pollChanges({ full: true });
+
+  // Since the second call is full, clients are called
+  Assert.equal(maybeSyncCount, 2, "maybeSync should be called twice");
+});
+add_task(clear_state);
+
+add_task(async function test_server_bad_json() {
+  function simulateBadJSON(request, response) {
+    response.setHeader("Content-Type", "application/json; charset=UTF-8");
+    response.write("<html></html>");
+    response.setStatusLine(null, 200, "OK");
+  }
+  server.registerPathHandler(CHANGES_PATH, simulateBadJSON);
+
+  let error;
+  try {
+    await RemoteSettings.pollChanges();
+  } catch (e) {
+    error = e;
+  }
+  Assert.ok(/JSON.parse: unexpected character/.test(error.message));
+
+  assertTelemetryEvents([
+    {
+      value: UptakeTelemetry.STATUS.PARSE_ERROR,
+    },
+  ]);
+});
+add_task(clear_state);
+
+add_task(async function test_server_bad_content_type() {
+  function simulateBadContentType(request, response) {
+    response.setHeader("Content-Type", "text/html");
+    response.write("<html></html>");
+    response.setStatusLine(null, 200, "OK");
+  }
+  server.registerPathHandler(CHANGES_PATH, simulateBadContentType);
+
+  let error;
+  try {
+    await RemoteSettings.pollChanges();
+  } catch (e) {
+    error = e;
+  }
+  Assert.ok(/Unexpected content-type/.test(error.message));
+
+  assertTelemetryEvents([
+    {
+      value: UptakeTelemetry.STATUS.CONTENT_ERROR,
+    },
+  ]);
+});
+add_task(clear_state);
+
+add_task(async function test_server_404_response() {
+  function simulateDummy404(request, response) {
+    response.setHeader("Content-Type", "text/html; charset=UTF-8");
+    response.write("<html></html>");
+    response.setStatusLine(null, 404, "OK");
+  }
+  server.registerPathHandler(CHANGES_PATH, simulateDummy404);
+
+  await RemoteSettings.pollChanges(); // Does not fail when running from tests.
+});
+add_task(clear_state);
+
+add_task(async function test_server_error() {
+  // Simulate a server error.
+  function simulateErrorResponse(request, response) {
+    response.setHeader("Date", new Date(3000).toUTCString());
+    response.setHeader("Content-Type", "application/json; charset=UTF-8");
+    response.write(
+      JSON.stringify({
+        code: 503,
+        errno: 999,
+        error: "Service Unavailable",
+      })
+    );
+    response.setStatusLine(null, 503, "Service Unavailable");
+  }
+  server.registerPathHandler(CHANGES_PATH, simulateErrorResponse);
+
+  let notificationObserved = false;
+  const observer = {
+    observe() {
+      Services.obs.removeObserver(this, "remote-settings:changes-poll-end");
+      notificationObserved = true;
+    },
+  };
+  Services.obs.addObserver(observer, "remote-settings:changes-poll-end");
+  Services.prefs.setIntPref(PREF_LAST_UPDATE, 42);
+
+  // pollChanges() fails with adequate error and no notification.
+  let error;
+  try {
+    await RemoteSettings.pollChanges();
+  } catch (e) {
+    error = e;
+  }
+
+  Assert.ok(
+    !notificationObserved,
+    "a notification should not have been observed"
+  );
+  Assert.ok(/Polling for changes failed/.test(error.message));
+  // When an error occurs, last update was not overwritten.
+  Assert.equal(Services.prefs.getIntPref(PREF_LAST_UPDATE), 42);
+  // ensure that we've accumulated the correct telemetry
+  assertTelemetryEvents([
+    {
+      value: UptakeTelemetry.STATUS.SERVER_ERROR,
+    },
+  ]);
+});
+add_task(clear_state);
+
+add_task(async function test_server_error_5xx() {
+  function simulateErrorResponse(request, response) {
+    response.setHeader("Date", new Date(3000).toUTCString());
+    response.setHeader("Content-Type", "text/html; charset=UTF-8");
+    response.write("<html></html>");
+    response.setStatusLine(null, 504, "Gateway Timeout");
+  }
+  server.registerPathHandler(CHANGES_PATH, simulateErrorResponse);
+
+  try {
+    await RemoteSettings.pollChanges();
+  } catch (e) {}
+
+  assertTelemetryEvents([
+    {
+      value: UptakeTelemetry.STATUS.SERVER_ERROR,
+    },
+  ]);
+});
+add_task(clear_state);
+
+add_task(async function test_server_error_4xx() {
+  function simulateErrorResponse(request, response) {
+    response.setHeader("Date", new Date(3000).toUTCString());
+    response.setHeader("Content-Type", "application/json; charset=UTF-8");
+    if (request.queryString.includes(`_since=${encodeURIComponent('"abc"')}`)) {
+      response.setStatusLine(null, 400, "Bad Request");
+      response.write(JSON.stringify({}));
+    } else {
+      response.setStatusLine(null, 200, "OK");
+      response.write(JSON.stringify({ changes: [] }));
+    }
+  }
+  server.registerPathHandler(CHANGES_PATH, simulateErrorResponse);
+
+  Services.prefs.setStringPref(PREF_LAST_ETAG, '"abc"');
+
+  let error;
+  try {
+    await RemoteSettings.pollChanges();
+  } catch (e) {
+    error = e;
+  }
+
+  Assert.ok(error.message.includes("400 Bad Request"), "Polling failed");
+  Assert.ok(
+    !Services.prefs.prefHasUserValue(PREF_LAST_ETAG),
+    "Last ETag pref was cleared"
+  );
+
+  await RemoteSettings.pollChanges(); // Does not raise.
+});
+add_task(clear_state);
+
+add_task(async function test_client_error() {
+  const collectionDetails = {
+    id: "b6ba7fab-a40a-4d03-a4af-6b627f3c5b36",
+    last_modified: 42,
+    host: "localhost",
+    bucket: "main",
+    collection: "some-entry",
+  };
+  server.registerPathHandler(
+    CHANGES_PATH,
+    serveChangesEntries(10000, [collectionDetails])
+  );
+  const c = RemoteSettings("some-entry");
+  c.maybeSync = () => {
+    throw new RemoteSettingsClient.CorruptedDataError("main/some-entry");
+  };
+
+  let notificationsObserved = [];
+  const observer = {
+    observe(aSubject, aTopic) {
+      Services.obs.removeObserver(this, aTopic);
+      notificationsObserved.push([aTopic, aSubject.wrappedJSObject]);
+    },
+  };
+  Services.obs.addObserver(observer, "remote-settings:changes-poll-end");
+  Services.obs.addObserver(observer, "remote-settings:sync-error");
+  Services.prefs.setIntPref(PREF_LAST_ETAG, 42);
+
+  // pollChanges() fails with adequate error and a sync-error notification.
+  let error;
+  try {
+    await RemoteSettings.pollChanges();
+  } catch (e) {
+    error = e;
+  }
+
+  Assert.equal(
+    notificationsObserved.length,
+    1,
+    "only the error notification should not have been observed"
+  );
+  console.log(notificationsObserved);
+  let [topicObserved, subjectObserved] = notificationsObserved[0];
+  Assert.equal(topicObserved, "remote-settings:sync-error");
+  Assert.ok(
+    subjectObserved.error instanceof RemoteSettingsClient.CorruptedDataError,
+    `original error is provided (got ${subjectObserved.error})`
+  );
+  Assert.deepEqual(
+    subjectObserved.error.details,
+    collectionDetails,
+    "information about collection is provided"
+  );
+
+  Assert.ok(/Corrupted/.test(error.message), "original client error is thrown");
+  // When an error occurs, last etag was not overwritten.
+  Assert.equal(Services.prefs.getIntPref(PREF_LAST_ETAG), 42);
+  // ensure that we've accumulated the correct telemetry
+  assertTelemetryEvents([
+    {
+      value: UptakeTelemetry.STATUS.SUCCESS,
+    },
+    {
+      value: UptakeTelemetry.STATUS.SYNC_ERROR,
+    },
+  ]);
+});
+add_task(clear_state);
+
+add_task(async function test_sync_success_is_stored_in_history() {
+  const collectionDetails = {
+    last_modified: 444,
+    bucket: "main",
+    collection: "desktop-manager",
+  };
+  server.registerPathHandler(
+    CHANGES_PATH,
+    serveChangesEntries(10000, [collectionDetails])
+  );
+  const c = RemoteSettings("desktop-manager");
+  c.maybeSync = () => {};
+  try {
+    await RemoteSettings.pollChanges({ expectedTimestamp: 555 });
+  } catch (e) {}
+
+  const { history } = await RemoteSettings.inspect();
+
+  Assert.deepEqual(history, {
+    [TELEMETRY_SOURCE_SYNC]: [
+      {
+        timestamp: 444,
+        status: "success",
+        infos: {},
+        datetime: new Date(444),
+      },
+    ],
+  });
+});
+add_task(clear_state);
+
+add_task(async function test_sync_error_is_stored_in_history() {
+  const collectionDetails = {
+    last_modified: 1337,
+    bucket: "main",
+    collection: "desktop-manager",
+  };
+  server.registerPathHandler(
+    CHANGES_PATH,
+    serveChangesEntries(10000, [collectionDetails])
+  );
+  const c = RemoteSettings("desktop-manager");
+  c.maybeSync = () => {
+    throw new RemoteSettingsClient.MissingSignatureError(
+      "main/desktop-manager"
+    );
+  };
+  try {
+    await RemoteSettings.pollChanges({ expectedTimestamp: 123456 });
+  } catch (e) {}
+
+  const { history } = await RemoteSettings.inspect();
+
+  Assert.deepEqual(history, {
+    [TELEMETRY_SOURCE_SYNC]: [
+      {
+        timestamp: 1337,
+        status: "sync_error",
+        infos: {
+          expectedTimestamp: 123456,
+          errorName: "MissingSignatureError",
+        },
+        datetime: new Date(1337),
+      },
+    ],
+  });
+});
+add_task(clear_state);
+
+add_task(
+  async function test_sync_broken_signal_is_sent_on_consistent_failure() {
+    // Wait for the "sync-broken-error" notification.
+    let notificationObserved = false;
+    const observer = {
+      observe() {
+        notificationObserved = true;
+      },
+    };
+    Services.obs.addObserver(observer, "remote-settings:broken-sync-error");
+    // Register a client with a failing sync method.
+    const c = RemoteSettings("desktop-manager");
+    c.maybeSync = () => {
+      throw new RemoteSettingsClient.InvalidSignatureError(
+        "main/desktop-manager"
+      );
+    };
+    // Simulate a response whose ETag gets incremented on each call
+    // (in order to generate several history entries, indexed by timestamp).
+    let timestamp = 1337;
+    server.registerPathHandler(
+      CHANGES_PATH,
+      serveChangesEntries(10000, () => {
+        return [
+          {
+            last_modified: ++timestamp,
+            bucket: "main",
+            collection: "desktop-manager",
+          },
+        ];
+      })
+    );
+
+    // Now obtain several failures in a row (less than threshold).
+    for (var i = 0; i < 9; i++) {
+      try {
+        await RemoteSettings.pollChanges();
+      } catch (e) {}
+    }
+    Assert.ok(!notificationObserved, "Not notified yet");
+
+    // Clear events snapshot.
+    Services.telemetry.snapshotEvents(
+      Ci.nsITelemetry.DATASET_ALL_CHANNELS,
+      true
+    );
+    Services.fog.testResetFOG();
+    enableUptakeMetric();
+
+    // Fail again once. Will now notify.
+    try {
+      await RemoteSettings.pollChanges();
+    } catch (e) {}
+    Assert.ok(notificationObserved, "Broken sync notified");
+    // Uptake event to notify broken sync is sent.
+    assertTelemetryEvents([
+      {
+        value: UptakeTelemetry.STATUS.SUCCESS,
+      },
+      {
+        value: UptakeTelemetry.STATUS.SYNC_ERROR,
+      },
+      {
+        value: UptakeTelemetry.STATUS.SYNC_BROKEN_ERROR,
+      },
+    ]);
+
+    // Synchronize successfully.
+    notificationObserved = false;
+    const failingSync = c.maybeSync;
+    c.maybeSync = () => {};
+    await RemoteSettings.pollChanges();
+
+    const { history } = await RemoteSettings.inspect();
+    Assert.equal(
+      history[TELEMETRY_SOURCE_SYNC][0].status,
+      UptakeTelemetry.STATUS.SUCCESS,
+      "Last sync is success"
+    );
+    Assert.ok(!notificationObserved, "Not notified after success");
+
+    // Now fail again. Broken sync isn't notified, we need several in a row.
+    c.maybeSync = failingSync;
+    try {
+      await RemoteSettings.pollChanges();
+    } catch (e) {}
+    Assert.ok(!notificationObserved, "Not notified on single error");
+    Services.obs.removeObserver(observer, "remote-settings:broken-sync-error");
+  }
+);
+add_task(clear_state);
+
+add_task(async function test_check_clockskew_is_updated() {
+  const serverTime = 2000;
+
+  function serverResponse(request, response) {
+    response.setHeader("Content-Type", "application/json; charset=UTF-8");
+    response.setHeader("Date", new Date(serverTime).toUTCString());
+    response.write(JSON.stringify({ timestamp: 42, changes: [] }));
+    response.setStatusLine(null, 200, "OK");
+  }
+  server.registerPathHandler(CHANGES_PATH, serverResponse);
+
+  let startTime = Date.now();
+
+  await RemoteSettings.pollChanges();
+
+  // How does the clock difference look?
+  let endTime = Date.now();
+  let clockDifference = Services.prefs.getIntPref(PREF_CLOCK_SKEW_SECONDS);
+  // we previously set the serverTime to 2 (seconds past epoch)
+  Assert.ok(
+    clockDifference <= endTime / 1000 &&
+      clockDifference >= Math.floor(startTime / 1000) - serverTime / 1000
+  );
+
+  // check negative clock skew times
+  // set to a time in the future
+  server.registerPathHandler(
+    CHANGES_PATH,
+    serveChangesEntries(Date.now() + 10000, [])
+  );
+
+  await RemoteSettings.pollChanges();
+
+  clockDifference = Services.prefs.getIntPref(PREF_CLOCK_SKEW_SECONDS);
+  // we previously set the serverTime to Date.now() + 10000 ms past epoch
+  Assert.ok(clockDifference <= 0 && clockDifference >= -10);
+});
+add_task(clear_state);
+
+add_task(async function test_check_clockskew_takes_age_into_account() {
+  const currentTime = Date.now();
+  const skewSeconds = 5;
+  const ageCDNSeconds = 3600;
+  const serverTime = currentTime - skewSeconds * 1000 - ageCDNSeconds * 1000;
+
+  function serverResponse(request, response) {
+    response.setHeader("Content-Type", "application/json; charset=UTF-8");
+    response.setHeader("Date", new Date(serverTime).toUTCString());
+    response.setHeader("Age", `${ageCDNSeconds}`);
+    response.write(JSON.stringify({ timestamp: 42, changes: [] }));
+    response.setStatusLine(null, 200, "OK");
+  }
+  server.registerPathHandler(CHANGES_PATH, serverResponse);
+
+  await RemoteSettings.pollChanges();
+
+  const clockSkew = Services.prefs.getIntPref(PREF_CLOCK_SKEW_SECONDS);
+  Assert.greaterOrEqual(clockSkew, skewSeconds, `clockSkew is ${clockSkew}`);
+});
+add_task(clear_state);
+
+add_task(async function test_backoff() {
+  function simulateBackoffResponse(request, response) {
+    response.setHeader("Content-Type", "application/json; charset=UTF-8");
+    response.setHeader("Backoff", "10");
+    response.write(JSON.stringify({ timestamp: 42, changes: [] }));
+    response.setStatusLine(null, 200, "OK");
+  }
+  server.registerPathHandler(CHANGES_PATH, simulateBackoffResponse);
+
+  // First will work.
+  await RemoteSettings.pollChanges();
+  // Second will fail because we haven't waited.
+  try {
+    await RemoteSettings.pollChanges();
+    // The previous line should have thrown an error.
+    Assert.ok(false);
+  } catch (e) {
+    Assert.ok(
+      /Server is asking clients to back off; retry in \d+s./.test(e.message)
+    );
+  }
+
+  // Once backoff time has expired, polling for changes can start again.
+  server.registerPathHandler(
+    CHANGES_PATH,
+    serveChangesEntries(12000, [
+      {
+        id: "6a733d4a-601e-11e8-837a-0f85257529a1",
+        last_modified: 1300,
+        host: "localhost",
+        bucket: "some-bucket",
+        collection: "some-collection",
+      },
+    ])
+  );
+  Services.prefs.setStringPref(
+    PREF_SETTINGS_SERVER_BACKOFF,
+    `${Date.now() - 1000}`
+  );
+
+  await RemoteSettings.pollChanges();
+
+  // Backoff tracking preference was cleared.
+  Assert.ok(!Services.prefs.prefHasUserValue(PREF_SETTINGS_SERVER_BACKOFF));
+
+  assertTelemetryEvents([
+    {
+      value: UptakeTelemetry.STATUS.UP_TO_DATE,
+    },
+    {
+      value: UptakeTelemetry.STATUS.SUCCESS,
+    },
+    {
+      value: UptakeTelemetry.STATUS.BACKOFF,
+    },
+    {
+      value: UptakeTelemetry.STATUS.SUCCESS,
+    },
+    {
+      value: UptakeTelemetry.STATUS.SUCCESS,
+    },
+  ]);
+});
+add_task(clear_state);
+
+add_task(async function test_network_error() {
+  // Simulate a network error (to check telemetry report).
+  Services.prefs.setStringPref(PREF_SETTINGS_SERVER, "http://localhost:42/v1");
+  try {
+    await RemoteSettings.pollChanges();
+  } catch (e) {}
+
+  // ensure that we've accumulated the correct telemetry
+  assertTelemetryEvents([
+    {
+      value: UptakeTelemetry.STATUS.NETWORK_ERROR,
+    },
+  ]);
+});
+add_task(clear_state);
+
+add_task(async function test_syncs_clients_with_local_database() {
+  server.registerPathHandler(
+    CHANGES_PATH,
+    serveChangesEntries(42000, [
+      {
+        id: "d4a14f44-601f-11e8-8b8a-030f3dc5b844",
+        last_modified: 10000,
+        host: "localhost",
+        bucket: "main",
+        collection: "some-unknown",
+      },
+      {
+        id: "39f57e4e-6023-11e8-8b74-77c8dedfb389",
+        last_modified: 9000,
+        host: "localhost",
+        bucket: "blocklists",
+        collection: "addons",
+      },
+      {
+        id: "9a594c1a-601f-11e8-9c8a-33b2239d9113",
+        last_modified: 8000,
+        host: "localhost",
+        bucket: "main",
+        collection: "recipes",
+      },
+    ])
+  );
+
+  // This simulates what remote-settings would do when initializing a local database.
+  // We don't want to instantiate a client using the RemoteSettings() API
+  // since we want to test «unknown» clients that have a local database.
+  new RemoteSettingsClient("addons", {
+    bucketName: "blocklists",
+  }).db.importChanges({}, 42);
+  new RemoteSettingsClient("recipes").db.importChanges({}, 43);
+
+  let error;
+  try {
+    await RemoteSettings.pollChanges();
+    Assert.ok(false, "pollChange() should throw when pulling recipes");
+  } catch (e) {
+    error = e;
+  }
+
+  // The `main/some-unknown` should be skipped because it has no local database.
+  // The `blocklists/addons` should be skipped because it is not the main bucket.
+  // The `recipes` has a local database, and should cause a network error because the test
+  // does not setup the server to receive the requests of `maybeSync()`.
+  Assert.ok(/HTTP 404/.test(error.message), "server will return 404 on sync");
+  Assert.equal(error.details.collection, "recipes");
+});
+add_task(clear_state);
+
+add_task(async function test_syncs_clients_with_local_dump() {
+  if (IS_ANDROID) {
+    // Skip test: we don't ship remote settings dumps on Android (see package-manifest).
+    return;
+  }
+  server.registerPathHandler(
+    CHANGES_PATH,
+    serveChangesEntries(42000, [
+      {
+        id: "d4a14f44-601f-11e8-8b8a-030f3dc5b844",
+        last_modified: 10000,
+        host: "localhost",
+        bucket: "main",
+        collection: "some-unknown",
+      },
+      {
+        id: "39f57e4e-6023-11e8-8b74-77c8dedfb389",
+        last_modified: 9000,
+        host: "localhost",
+        bucket: "blocklists",
+        collection: "addons",
+      },
+      {
+        id: "9a594c1a-601f-11e8-9c8a-33b2239d9113",
+        last_modified: 8000,
+        host: "localhost",
+        bucket: "main",
+        collection: "example",
+      },
+    ])
+  );
+
+  let error;
+  try {
+    await RemoteSettings.pollChanges();
+  } catch (e) {
+    error = e;
+  }
+
+  // The `main/some-unknown` should be skipped because it has no dump.
+  // The `blocklists/addons` should be skipped because it is not the main bucket.
+  // The `example` has a dump, and should cause a network error because the test
+  // does not setup the server to receive the requests of `maybeSync()`.
+  Assert.ok(/HTTP 404/.test(error.message), "server will return 404 on sync");
+  Assert.equal(error.details.collection, "example");
+});
+add_task(clear_state);
+
+add_task(async function test_adding_client_resets_polling() {
+  function serve200(request, response) {
+    const entries = [
+      {
+        id: "aa71e6cc-9f37-447a-b6e0-c025e8eabd03",
+        last_modified: 42,
+        host: "localhost",
+        bucket: "main",
+        collection: "a-collection",
+      },
+    ];
+    if (request.queryString.includes("_since")) {
+      response.write(
+        JSON.stringify({
+          timestamp: 42,
+          changes: [],
+        })
+      );
+    } else {
+      response.write(
+        JSON.stringify({
+          timestamp: 42,
+          changes: entries,
+        })
+      );
+    }
+    response.setStatusLine(null, 200, "OK");
+    response.setHeader("Content-Type", "application/json; charset=UTF-8");
+    response.setHeader("Date", new Date().toUTCString());
+  }
+  server.registerPathHandler(CHANGES_PATH, serve200);
+
+  // Poll once, without any client for "a-collection"
+  await RemoteSettings.pollChanges();
+
+  // Register a new client.
+  let maybeSyncCalled = false;
+  const c = RemoteSettings("a-collection");
+  c.maybeSync = () => {
+    maybeSyncCalled = true;
+  };
+
+  // Poll again.
+  await RemoteSettings.pollChanges();
+
+  // The new client was called, even if the server data didn't change.
+  Assert.ok(maybeSyncCalled);
+
+  // Poll again. This time maybeSync() won't be called.
+  maybeSyncCalled = false;
+  await RemoteSettings.pollChanges();
+  Assert.ok(!maybeSyncCalled);
+});
+add_task(clear_state);
+
+add_task(
+  async function test_broadcast_handler_passes_version_and_trigger_values() {
+    // The polling will use the broadcast version as cache busting query param.
+    let passedQueryString;
+    function serveCacheBusted(request, response) {
+      passedQueryString = request.queryString;
+      const entries = [
+        {
+          id: "b6ba7fab-a40a-4d03-a4af-6b627f3c5b36",
+          last_modified: 42,
+          host: "localhost",
+          bucket: "main",
+          collection: "from-broadcast",
+        },
+      ];
+      response.write(
+        JSON.stringify({
+          changes: entries,
+          timestamp: 42,
+        })
+      );
+      response.setHeader("ETag", "42");
+      response.setStatusLine(null, 200, "OK");
+      response.setHeader("Content-Type", "application/json; charset=UTF-8");
+      response.setHeader("Date", new Date().toUTCString());
+    }
+    server.registerPathHandler(CHANGES_PATH, serveCacheBusted);
+
+    let passedTrigger;
+    const c = RemoteSettings("from-broadcast");
+    c.maybeSync = (last_modified, { trigger }) => {
+      passedTrigger = trigger;
+    };
+
+    const version = "1337";
+
+    let context = { phase: pushBroadcastService.PHASES.HELLO };
+    await remoteSettingsBroadcastHandler.receivedBroadcastMessage(
+      version,
+      BROADCAST_ID,
+      context
+    );
+    Assert.equal(passedTrigger, "startup");
+    Assert.equal(passedQueryString, `_expected=${version}`);
+
+    clear_state();
+
+    context = { phase: pushBroadcastService.PHASES.REGISTER };
+    await remoteSettingsBroadcastHandler.receivedBroadcastMessage(
+      version,
+      BROADCAST_ID,
+      context
+    );
+    Assert.equal(passedTrigger, "startup");
+
+    clear_state();
+
+    context = { phase: pushBroadcastService.PHASES.BROADCAST };
+    await remoteSettingsBroadcastHandler.receivedBroadcastMessage(
+      version,
+      BROADCAST_ID,
+      context
+    );
+    Assert.equal(passedTrigger, "broadcast");
+  }
+);
+add_task(clear_state);
+
+add_task(async function test_stale_startup_timestamp() {
+  Services.prefs.setStringPref(PREF_LAST_ETAG, 42);
+
+  let error;
+  try {
+    await RemoteSettings.pollChanges({
+      trigger: "startup",
+      expectedTimestamp: "41",
+    });
+  } catch (e) {
+    error = e;
+  }
+
+  Assert.equal(error, undefined);
+  Assert.equal(Services.prefs.getStringPref(PREF_LAST_ETAG), "42");
+  assertTelemetryEvents([
+    {
+      value: UptakeTelemetry.STATUS.STALE_EXPECTED,
+    },
+  ]);
+});
+add_task(clear_state);
diff --git a/src/zen/tests/mochitests/remote-settings/test_remote_settings_recover_broken.js b/src/zen/tests/mochitests/remote-settings/test_remote_settings_recover_broken.js
new file mode 100644
index 000000000..5bb047c8a
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_remote_settings_recover_broken.js
@@ -0,0 +1,138 @@
+const PREF_SETTINGS_SERVER = "services.settings.server";
+const CHANGES_PATH = "/v1" + Utils.CHANGES_PATH;
+const BROKEN_SYNC_THRESHOLD = 10; // See default pref value
+
+let server;
+let client;
+let maybeSyncBackup;
+
+async function clear_state() {
+  // Disable logging output.
+  Services.prefs.setStringPref("services.settings.loglevel", "critical");
+  // Pull data from the test server.
+  Services.prefs.setStringPref(
+    PREF_SETTINGS_SERVER,
+    `http://localhost:${server.identity.primaryPort}/v1`
+  );
+
+  // Clear sync history.
+  await new SyncHistory("").clear();
+
+  // Simulate a response whose ETag gets incremented on each call
+  // (in order to generate several history entries, indexed by timestamp).
+  let timestamp = 1337;
+  server.registerPathHandler(CHANGES_PATH, (request, response) => {
+    response.setStatusLine(null, 200, "OK");
+    response.setHeader("Content-Type", "application/json; charset=UTF-8");
+    response.setHeader("Date", new Date(1000000).toUTCString());
+    response.setHeader("ETag", `"${timestamp}"`);
+    response.write(
+      JSON.stringify({
+        timestamp,
+        changes: [
+          {
+            last_modified: ++timestamp,
+            bucket: "main",
+            collection: "desktop-manager",
+          },
+        ],
+      })
+    );
+  });
+
+  // Restore original maybeSync() method between each test.
+  client.maybeSync = maybeSyncBackup;
+}
+
+function run_test() {
+  // Set up an HTTP Server
+  server = new HttpServer();
+  server.start(-1);
+
+  client = RemoteSettings("desktop-manager");
+  maybeSyncBackup = client.maybeSync;
+
+  run_next_test();
+
+  registerCleanupFunction(() => {
+    server.stop(() => {});
+    // Restore original maybeSync() method when test suite is done.
+    client.maybeSync = maybeSyncBackup;
+  });
+}
+
+add_task(clear_state);
+
+add_task(async function test_db_is_destroyed_when_sync_is_broken() {
+  // Simulate a successful sync.
+  client.maybeSync = async () => {
+    // Store some data in local DB.
+    await client.db.importChanges({}, 1515, []);
+  };
+  await RemoteSettings.pollChanges({ trigger: "timer" });
+
+  // Register a client with a failing sync method.
+  client.maybeSync = () => {
+    throw new RemoteSettingsClient.InvalidSignatureError(
+      "main/desktop-manager"
+    );
+  };
+
+  // Now obtain several failures in a row.
+  for (var i = 0; i < BROKEN_SYNC_THRESHOLD; i++) {
+    try {
+      await RemoteSettings.pollChanges({ trigger: "timer" });
+    } catch (e) {}
+  }
+
+  // Synchronization is in broken state.
+  Assert.equal(
+    await client.db.getLastModified(),
+    1515,
+    "Local DB was not destroyed yet"
+  );
+
+  // Synchronize again. Broken state will be detected.
+  try {
+    await RemoteSettings.pollChanges({ trigger: "timer" });
+  } catch (e) {}
+
+  // DB was destroyed.
+  Assert.equal(
+    await client.db.getLastModified(),
+    null,
+    "Local DB was destroyed"
+  );
+});
+
+add_task(clear_state);
+
+add_task(async function test_db_is_not_destroyed_when_state_is_server_error() {
+  // Since we don't mock the server endpoints to obtain the changeset of this
+  // collection, the call to `maybeSync()` will fail with network errors.
+
+  // Store some data in local DB.
+  await client.db.importChanges({}, 1515, []);
+
+  // Now obtain several failures in a row.
+  let lastError;
+  for (var i = 0; i < BROKEN_SYNC_THRESHOLD + 1; i++) {
+    try {
+      await RemoteSettings.pollChanges({ trigger: "timer" });
+    } catch (e) {
+      lastError = e;
+    }
+  }
+  Assert.ok(
+    /Cannot parse server content/.test(lastError.message),
+    "Error is about server"
+  );
+  // DB was not destroyed.
+  Assert.equal(
+    await client.db.getLastModified(),
+    1515,
+    "Local DB was not destroyed"
+  );
+});
+
+add_task(clear_state);
diff --git a/src/zen/tests/mochitests/remote-settings/test_remote_settings_release_prefs.js b/src/zen/tests/mochitests/remote-settings/test_remote_settings_release_prefs.js
new file mode 100644
index 000000000..3e1ae7c25
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_remote_settings_release_prefs.js
@@ -0,0 +1,252 @@
+"use strict";
+
+var nextUniqId = 0;
+function getNewUtils() {
+  const { Utils } = ChromeUtils.importESModule(
+    `resource://services-settings/Utils.sys.mjs?_${++nextUniqId}`
+  );
+  return Utils;
+}
+
+// A collection with a dump that's packaged on all builds where this test runs,
+// including on Android at mobile/android/installer/package-manifest.in
+const TEST_BUCKET = "main";
+const TEST_COLLECTION = "password-recipes";
+
+async function importData(records) {
+  await RemoteSettingsWorker._execute("_test_only_import", [
+    TEST_BUCKET,
+    TEST_COLLECTION,
+    records,
+    records[0]?.last_modified || 0,
+  ]);
+}
+
+async function clear_state() {
+  Services.env.set("MOZ_REMOTE_SETTINGS_DEVTOOLS", "0");
+  Services.prefs.clearUserPref("services.settings.server");
+  Services.prefs.clearUserPref("services.settings.preview_enabled");
+}
+
+add_setup(async function () {
+  // Set this env vars in order to test the code path where the
+  // server URL can only be overridden from Dev Tools.
+  // See `isRunningTests` in `services/settings/Utils.sys.mjs`.
+  const before = Services.env.get("MOZ_DISABLE_NONLOCAL_CONNECTIONS");
+  Services.env.set("MOZ_DISABLE_NONLOCAL_CONNECTIONS", "0");
+
+  registerCleanupFunction(() => {
+    clear_state();
+    Services.env.set("MOZ_DISABLE_NONLOCAL_CONNECTIONS", before);
+  });
+});
+
+add_task(clear_state);
+
+add_task(
+  {
+    skip_if: () => !AppConstants.RELEASE_OR_BETA,
+  },
+  async function test_server_url_cannot_be_toggled_in_release() {
+    Services.prefs.setStringPref(
+      "services.settings.server",
+      "http://localhost:8888/v1"
+    );
+
+    const Utils = getNewUtils();
+
+    Assert.equal(
+      Utils.SERVER_URL,
+      AppConstants.REMOTE_SETTINGS_SERVER_URLS[0],
+      "Server url pref was not read in release"
+    );
+  }
+);
+
+add_task(
+  {
+    skip_if: () => AppConstants.RELEASE_OR_BETA,
+  },
+  async function test_server_url_cannot_be_toggled_in_dev_nightly() {
+    Services.prefs.setStringPref(
+      "services.settings.server",
+      "http://localhost:8888/v1"
+    );
+
+    const Utils = getNewUtils();
+
+    Assert.notEqual(
+      Utils.SERVER_URL,
+      AppConstants.REMOTE_SETTINGS_SERVER_URLS[0],
+      "Server url pref was read in nightly/dev"
+    );
+  }
+);
+add_task(clear_state);
+
+add_task(
+  {
+    skip_if: () => !AppConstants.RELEASE_OR_BETA,
+  },
+  async function test_preview_mode_cannot_be_toggled_in_release() {
+    Services.prefs.setBoolPref("services.settings.preview_enabled", true);
+
+    const Utils = getNewUtils();
+
+    Assert.ok(!Utils.PREVIEW_MODE, "Preview mode pref was not read in release");
+  }
+);
+add_task(clear_state);
+
+add_task(
+  {
+    skip_if: () => AppConstants.RELEASE_OR_BETA,
+  },
+  async function test_preview_mode_cannot_be_toggled_in_dev_nightly() {
+    Services.prefs.setBoolPref("services.settings.preview_enabled", true);
+
+    const Utils = getNewUtils();
+
+    Assert.ok(Utils.PREVIEW_MODE, "Preview mode pref is read in dev/nightly");
+  }
+);
+add_task(clear_state);
+
+add_task(
+  {
+    skip_if: () => !AppConstants.RELEASE_OR_BETA,
+  },
+  async function test_load_dumps_will_always_be_loaded_in_release() {
+    Services.prefs.setStringPref(
+      "services.settings.server",
+      "http://localhost:8888/v1"
+    );
+
+    const Utils = getNewUtils();
+
+    Assert.equal(
+      Utils.SERVER_URL,
+      AppConstants.REMOTE_SETTINGS_SERVER_URLS[0],
+      "Server url pref was not read"
+    );
+    Assert.ok(Utils.LOAD_DUMPS, "Dumps will always be loaded");
+  }
+);
+
+add_task(
+  {
+    skip_if: () => AppConstants.RELEASE_OR_BETA,
+  },
+  async function test_load_dumps_can_be_disabled_in_dev_nightly() {
+    Services.prefs.setStringPref(
+      "services.settings.server",
+      "http://localhost:8888/v1"
+    );
+
+    const Utils = getNewUtils();
+
+    Assert.notEqual(
+      Utils.SERVER_URL,
+      AppConstants.REMOTE_SETTINGS_SERVER_URLS[0],
+      "Server url pref was read"
+    );
+    Assert.ok(!Utils.LOAD_DUMPS, "Dumps are not loaded if server is not prod");
+  }
+);
+add_task(clear_state);
+
+add_task(
+  async function test_server_url_can_be_changed_in_all_versions_if_running_for_devtools() {
+    Services.env.set("MOZ_REMOTE_SETTINGS_DEVTOOLS", "1");
+    Services.prefs.setStringPref(
+      "services.settings.server",
+      "http://localhost:8888/v1"
+    );
+
+    const Utils = getNewUtils();
+
+    Assert.notEqual(
+      Utils.SERVER_URL,
+      AppConstants.REMOTE_SETTINGS_SERVER_URLS[0],
+      "Server url pref was read"
+    );
+  }
+);
+add_task(clear_state);
+
+add_task(
+  async function test_preview_mode_can_be_changed_in_all_versions_if_running_for_devtools() {
+    Services.env.set("MOZ_REMOTE_SETTINGS_DEVTOOLS", "1");
+    Services.prefs.setBoolPref("services.settings.preview_enabled", true);
+
+    const Utils = getNewUtils();
+
+    Assert.ok(Utils.PREVIEW_MODE, "Preview mode pref was read");
+  }
+);
+add_task(clear_state);
+
+add_task(
+  async function test_dumps_are_not_loaded_if_server_is_not_prod_if_running_for_devtools() {
+    Services.env.set("MOZ_REMOTE_SETTINGS_DEVTOOLS", "1");
+    Services.prefs.setStringPref(
+      "services.settings.server",
+      "http://localhost:8888/v1"
+    );
+
+    const Utils = getNewUtils();
+    Assert.ok(!Utils.LOAD_DUMPS, "Dumps won't be loaded");
+
+    // The section below ensures that the LOAD_DUMPS flag properly takes effect.
+    // The client is set up here rather than add_setup to avoid triggering the
+    // lazy getters that are behind the global Utils.LOAD_DUMPS. If they are
+    // triggered too early, then they will potentially cache different values
+    // for the server urls and environment variables and this test then won't be
+    // testing what we expect it to.
+
+    let client = new RemoteSettingsClient(TEST_COLLECTION);
+
+    const dump = await SharedUtils.loadJSONDump(TEST_BUCKET, TEST_COLLECTION);
+    let DUMP_LAST_MODIFIED = dump.timestamp;
+
+    // Dump is updated regularly, verify that the dump matches our expectations
+    // before running the test.
+    Assert.greater(
+      DUMP_LAST_MODIFIED,
+      1234,
+      "Assuming dump to be newer than dummy 1234"
+    );
+
+    await client.db.clear();
+    await importData([{ last_modified: 1234, id: "dummy" }]);
+
+    const after = await client.get();
+    Assert.deepEqual(
+      after,
+      [{ last_modified: 1234, id: "dummy" }],
+      "Should have kept the original import"
+    );
+    Assert.equal(
+      await client.getLastModified(),
+      1234,
+      "Should have kept the import's timestamp"
+    );
+    await client.db.clear();
+  }
+);
+add_task(clear_state);
+
+add_task(
+  async function test_dumps_are_loaded_if_server_is_prod_if_running_for_devtools() {
+    Services.env.set("MOZ_REMOTE_SETTINGS_DEVTOOLS", "1");
+    Services.prefs.setStringPref(
+      "services.settings.server",
+      AppConstants.REMOTE_SETTINGS_SERVER_URLS[0]
+    );
+
+    const Utils = getNewUtils();
+
+    Assert.ok(Utils.LOAD_DUMPS, "dumps are loaded if prod");
+  }
+);
+add_task(clear_state);
diff --git a/src/zen/tests/mochitests/remote-settings/test_remote_settings_signatures.js b/src/zen/tests/mochitests/remote-settings/test_remote_settings_signatures.js
new file mode 100644
index 000000000..8b50c3519
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_remote_settings_signatures.js
@@ -0,0 +1,952 @@
+/* import-globals-from ../../../common/tests/unit/head_helpers.js */
+"use strict";
+
+const PREF_SETTINGS_SERVER = "services.settings.server";
+const SIGNER_NAME = "onecrl.content-signature.mozilla.org";
+
+const CERT_DIR = "test_remote_settings_signatures/";
+const CHAIN_FILES = ["collection_signing_ee.pem", "collection_signing_int.pem"];
+
+function getFileData(file) {
+  const stream = Cc["@mozilla.org/network/file-input-stream;1"].createInstance(
+    Ci.nsIFileInputStream
+  );
+  stream.init(file, -1, 0, 0);
+  const data = NetUtil.readInputStreamToString(stream, stream.available());
+  stream.close();
+  return data;
+}
+
+function getCertChain() {
+  const chain = [];
+  for (let file of CHAIN_FILES) {
+    chain.push(getFileData(do_get_file(CERT_DIR + file)));
+  }
+  return chain.join("\n");
+}
+
+let server;
+let client;
+
+add_setup(() => {
+  // Signature verification is enabled by default. We use a custom signer
+  // because these tests were originally written for OneCRL.
+  client = RemoteSettings("signed", { signerName: SIGNER_NAME });
+
+  Services.prefs.setStringPref("services.settings.loglevel", "debug");
+
+  // Set up an HTTP Server
+  server = new HttpServer();
+  server.start(-1);
+
+  registerCleanupFunction(() => {
+    Services.prefs.clearUserPref("services.settings.loglevel");
+    Services.prefs.clearUserPref(PREF_SETTINGS_SERVER);
+    server.stop(() => {});
+  });
+});
+
+add_task(async function test_check_signatures() {
+  // First, perform a signature verification with known data and signature
+  // to ensure things are working correctly
+  let verifier = Cc[
+    "@mozilla.org/security/contentsignatureverifier;1"
+  ].createInstance(Ci.nsIContentSignatureVerifier);
+
+  const emptyData = "[]";
+  const emptySignature =
+    "p384ecdsa=zbugm2FDitsHwk5-IWsas1PpWwY29f0Fg5ZHeqD8fzep7AVl2vfcaHA7LdmCZ28qZLOioGKvco3qT117Q4-HlqFTJM7COHzxGyU2MMJ0ZTnhJrPOC1fP3cVQjU1PTWi9";
+
+  ok(
+    await verifier.asyncVerifyContentSignature(
+      emptyData,
+      emptySignature,
+      getCertChain(),
+      SIGNER_NAME,
+      Ci.nsIX509CertDB.AppXPCShellRoot
+    )
+  );
+
+  const collectionData =
+    '[{"details":{"bug":"https://bugzilla.mozilla.org/show_bug.cgi?id=1155145","created":"2016-01-18T14:43:37Z","name":"GlobalSign certs","who":".","why":"."},"enabled":true,"id":"97fbf7c4-3ef2-f54f-0029-1ba6540c63ea","issuerName":"MHExKDAmBgNVBAMTH0dsb2JhbFNpZ24gUm9vdFNpZ24gUGFydG5lcnMgQ0ExHTAbBgNVBAsTFFJvb3RTaWduIFBhcnRuZXJzIENBMRkwFwYDVQQKExBHbG9iYWxTaWduIG52LXNhMQswCQYDVQQGEwJCRQ==","last_modified":2000,"serialNumber":"BAAAAAABA/A35EU="},{"details":{"bug":"https://bugzilla.mozilla.org/show_bug.cgi?id=1155145","created":"2016-01-18T14:48:11Z","name":"GlobalSign certs","who":".","why":"."},"enabled":true,"id":"e3bd531e-1ee4-7407-27ce-6fdc9cecbbdc","issuerName":"MIGBMQswCQYDVQQGEwJCRTEZMBcGA1UEChMQR2xvYmFsU2lnbiBudi1zYTElMCMGA1UECxMcUHJpbWFyeSBPYmplY3QgUHVibGlzaGluZyBDQTEwMC4GA1UEAxMnR2xvYmFsU2lnbiBQcmltYXJ5IE9iamVjdCBQdWJsaXNoaW5nIENB","last_modified":3000,"serialNumber":"BAAAAAABI54PryQ="}]';
+  const collectionSignature =
+    "p384ecdsa=f4pA2tYM5jQgWY6YUmhUwQiBLj6QO5sHLD_5MqLePz95qv-7cNCuQoZnPQwxoptDtW8hcWH3kLb0quR7SB-r82gkpR9POVofsnWJRA-ETb0BcIz6VvI3pDT49ZLlNg3p";
+
+  ok(
+    await verifier.asyncVerifyContentSignature(
+      collectionData,
+      collectionSignature,
+      getCertChain(),
+      SIGNER_NAME,
+      Ci.nsIX509CertDB.AppXPCShellRoot
+    )
+  );
+});
+
+add_task(async function test_bad_signature_does_not_lead_to_empty_list() {
+  Services.prefs.setStringPref(
+    PREF_SETTINGS_SERVER,
+    `http://localhost:${server.identity.primaryPort}/v1`
+  );
+  const x5u = `http://localhost:${server.identity.primaryPort}/x5u.pem`;
+
+  const networkCalls = [];
+
+  server.registerPathHandler(
+    "/v1/buckets/monitor/collections/changes/changeset",
+    (request, response) => {
+      response.write(
+        JSON.stringify({
+          changes: [
+            {
+              bucket: "main",
+              collection: "no-dump-no-local-data",
+              last_modified: 42,
+            },
+          ],
+        })
+      );
+      response.setHeader("Content-Type", "application/json; charset=UTF-8");
+      response.setStatusLine(null, 200, "OK");
+    }
+  );
+  server.registerPathHandler(
+    "/v1/buckets/monitor/collections/changes/changeset",
+    (request, response) => {
+      networkCalls.push(request);
+      response.write(
+        JSON.stringify({
+          changes: [
+            {
+              bucket: "main",
+              collection: "no-dump-no-local-data",
+              last_modified: 42,
+            },
+          ],
+        })
+      );
+      response.setHeader("Content-Type", "application/json; charset=UTF-8");
+      response.setStatusLine(null, 200, "OK");
+    }
+  );
+  server.registerPathHandler(
+    "/v1/buckets/main/collections/no-dump-no-local-data/changeset",
+    (request, response) => {
+      response.write(
+        JSON.stringify({
+          timestamp: 42,
+          changes: [],
+          metadata: {
+            signatures: [
+              {
+                signature: "bad-signature",
+                x5u,
+              },
+            ],
+          },
+        })
+      );
+      response.setHeader("Content-Type", "application/json; charset=UTF-8");
+      response.setStatusLine(null, 200, "OK");
+    }
+  );
+  server.registerPathHandler("/x5u.pem", (request, response) => {
+    response.write(getCertChain()); // At least cert will be valid.
+    response.setHeader("Content-Type", "text/plain; charset=UTF-8");
+    response.setStatusLine(null, 200, "OK");
+  });
+
+  const clientEmpty = RemoteSettings("no-dump-no-local-data");
+  clientEmpty.verifySignature = true; // default
+
+  // Check that client.get() will initiate a sync,
+  // and that it will throw since the signature is bad,
+  // and not return an empty list (`emptyListFallback: false`)
+  let error;
+  try {
+    await clientEmpty.get({
+      emptyListFallback: false,
+      syncIfEmpty: true, // default value
+    });
+  } catch (exc) {
+    error = exc;
+  }
+  equal(error.name, "InvalidSignatureError");
+
+  // Even running client.sync() will throw and won't leave
+  // anything in the database.
+  error = null;
+  try {
+    await clientEmpty.sync();
+  } catch (exc) {
+    error = exc;
+  }
+  equal(error.name, "InvalidSignatureError");
+  equal(await clientEmpty.db.getLastModified(), null);
+
+  // Call .get() again will initiate another sync.
+  networkCalls.length = 0;
+  try {
+    await clientEmpty.get({
+      emptyListFallback: false,
+      syncIfEmpty: true, // default value
+    });
+  } catch (exc) {
+    error = exc;
+  }
+  Assert.greater(networkCalls.length, 0, "Network calls were made");
+  equal(error.name, "InvalidSignatureError");
+});
+
+add_task(async function test_check_synchronization_with_signatures() {
+  const port = server.identity.primaryPort;
+
+  const x5u = `http://localhost:${port}/test_remote_settings_signatures/test_cert_chain.pem`;
+
+  // Telemetry reports.
+  const TELEMETRY_SOURCE = client.identifier;
+
+  function registerHandlers(responses) {
+    function handleResponse(serverTimeMillis, request, response) {
+      const key = `${request.method}:${request.path}?${request.queryString}`;
+      const available = responses[key];
+      const sampled = available.length > 1 ? available.shift() : available[0];
+      if (!sampled) {
+        do_throw(
+          `unexpected ${request.method} request for ${request.path}?${request.queryString}`
+        );
+      }
+
+      response.setStatusLine(
+        null,
+        sampled.status.status,
+        sampled.status.statusText
+      );
+      // send the headers
+      for (let headerLine of sampled.sampleHeaders) {
+        let headerElements = headerLine.split(":");
+        response.setHeader(headerElements[0], headerElements[1].trimLeft());
+      }
+
+      // set the server date
+      response.setHeader("Date", new Date(serverTimeMillis).toUTCString());
+
+      response.write(sampled.responseBody);
+    }
+
+    for (let key of Object.keys(responses)) {
+      const keyParts = key.split(":");
+      const valueParts = keyParts[1].split("?");
+      const path = valueParts[0];
+
+      server.registerPathHandler(path, handleResponse.bind(null, 2000));
+    }
+  }
+
+  // set up prefs so the kinto updater talks to the test server
+  Services.prefs.setStringPref(
+    PREF_SETTINGS_SERVER,
+    `http://localhost:${server.identity.primaryPort}/v1`
+  );
+
+  // These are records we'll use in the test collections
+  const RECORD1 = {
+    details: {
+      bug: "https://bugzilla.mozilla.org/show_bug.cgi?id=1155145",
+      created: "2016-01-18T14:43:37Z",
+      name: "GlobalSign certs",
+      who: ".",
+      why: ".",
+    },
+    enabled: true,
+    id: "97fbf7c4-3ef2-f54f-0029-1ba6540c63ea",
+    issuerName:
+      "MHExKDAmBgNVBAMTH0dsb2JhbFNpZ24gUm9vdFNpZ24gUGFydG5lcnMgQ0ExHTAbBgNVBAsTFFJvb3RTaWduIFBhcnRuZXJzIENBMRkwFwYDVQQKExBHbG9iYWxTaWduIG52LXNhMQswCQYDVQQGEwJCRQ==",
+    last_modified: 2000,
+    serialNumber: "BAAAAAABA/A35EU=",
+  };
+
+  const RECORD2 = {
+    details: {
+      bug: "https://bugzilla.mozilla.org/show_bug.cgi?id=1155145",
+      created: "2016-01-18T14:48:11Z",
+      name: "GlobalSign certs",
+      who: ".",
+      why: ".",
+    },
+    enabled: true,
+    id: "e3bd531e-1ee4-7407-27ce-6fdc9cecbbdc",
+    issuerName:
+      "MIGBMQswCQYDVQQGEwJCRTEZMBcGA1UEChMQR2xvYmFsU2lnbiBudi1zYTElMCMGA1UECxMcUHJpbWFyeSBPYmplY3QgUHVibGlzaGluZyBDQTEwMC4GA1UEAxMnR2xvYmFsU2lnbiBQcmltYXJ5IE9iamVjdCBQdWJsaXNoaW5nIENB",
+    last_modified: 3000,
+    serialNumber: "BAAAAAABI54PryQ=",
+  };
+
+  const RECORD3 = {
+    details: {
+      bug: "https://bugzilla.mozilla.org/show_bug.cgi?id=1155145",
+      created: "2016-01-18T14:48:11Z",
+      name: "GlobalSign certs",
+      who: ".",
+      why: ".",
+    },
+    enabled: true,
+    id: "c7c49b69-a4ab-418e-92a9-e1961459aa7f",
+    issuerName:
+      "MIGBMQswCQYDVQQGEwJCRTEZMBcGA1UEChMQR2xvYmFsU2lnbiBudi1zYTElMCMGA1UECxMcUHJpbWFyeSBPYmplY3QgUHVibGlzaGluZyBDQTEwMC4GA1UEAxMnR2xvYmFsU2lnbiBQcmltYXJ5IE9iamVjdCBQdWJsaXNoaW5nIENB",
+    last_modified: 4000,
+    serialNumber: "BAAAAAABI54PryQ=",
+  };
+
+  const RECORD1_DELETION = {
+    deleted: true,
+    enabled: true,
+    id: "97fbf7c4-3ef2-f54f-0029-1ba6540c63ea",
+    last_modified: 3500,
+  };
+
+  // Check that a signature on an empty collection is OK
+  // We need to set up paths on the HTTP server to return specific data from
+  // specific paths for each test. Here we prepare data for each response.
+
+  // A cert chain response (this the cert chain that contains the signing
+  // cert, the root and any intermediates in between). This is used in each
+  // sync.
+  const RESPONSE_CERT_CHAIN = {
+    comment: "RESPONSE_CERT_CHAIN",
+    sampleHeaders: ["Content-Type: text/plain; charset=UTF-8"],
+    status: { status: 200, statusText: "OK" },
+    responseBody: getCertChain(),
+  };
+
+  // A server settings response. This is used in each sync.
+  const RESPONSE_SERVER_SETTINGS = {
+    comment: "RESPONSE_SERVER_SETTINGS",
+    sampleHeaders: [
+      "Access-Control-Allow-Origin: *",
+      "Access-Control-Expose-Headers: Retry-After, Content-Length, Alert, Backoff",
+      "Content-Type: application/json; charset=UTF-8",
+      "Server: waitress",
+    ],
+    status: { status: 200, statusText: "OK" },
+    responseBody: JSON.stringify({
+      settings: {
+        batch_max_requests: 25,
+      },
+      url: `http://localhost:${port}/v1/`,
+      documentation: "https://kinto.readthedocs.org/",
+      version: "1.5.1",
+      commit: "cbc6f58",
+      hello: "kinto",
+    }),
+  };
+
+  // This is the initial, empty state of the collection. This is only used
+  // for the first sync.
+  const RESPONSE_EMPTY_INITIAL = {
+    comment: "RESPONSE_EMPTY_INITIAL",
+    sampleHeaders: [
+      "Content-Type: application/json; charset=UTF-8",
+      'ETag: "1000"',
+    ],
+    status: { status: 200, statusText: "OK" },
+    responseBody: JSON.stringify({
+      timestamp: 1000,
+      metadata: {
+        signatures: [
+          {
+            x5u,
+            signature:
+              "vxuAg5rDCB-1pul4a91vqSBQRXJG_j7WOYUTswxRSMltdYmbhLRH8R8brQ9YKuNDF56F-w6pn4HWxb076qgKPwgcEBtUeZAO_RtaHXRkRUUgVzAr86yQL4-aJTbv3D6u",
+          },
+        ],
+      },
+      changes: [],
+    }),
+  };
+
+  // Here, we map request method and path to the available responses
+  const emptyCollectionResponses = {
+    "GET:/test_remote_settings_signatures/test_cert_chain.pem?": [
+      RESPONSE_CERT_CHAIN,
+    ],
+    "GET:/v1/?": [RESPONSE_SERVER_SETTINGS],
+    "GET:/v1/buckets/main/collections/signed/changeset?_expected=1000": [
+      RESPONSE_EMPTY_INITIAL,
+    ],
+  };
+
+  //
+  // 1.
+  // - collection: undefined -> []
+  // - timestamp: undefined -> 1000
+  //
+
+  // .. and use this map to register handlers for each path
+  registerHandlers(emptyCollectionResponses);
+
+  // Clear events snapshot.
+  Services.telemetry.snapshotEvents(Ci.nsITelemetry.DATASET_ALL_CHANNELS, true);
+  Services.fog.testResetFOG();
+  enableUptakeMetric();
+
+  // With all of this set up, we attempt a sync. This will resolve if all is
+  // well and throw if something goes wrong.
+  await client.maybeSync(1000);
+
+  equal((await client.get()).length, 0);
+
+  assertTelemetryEvents([
+    {
+      value: UptakeTelemetry.STATUS.SYNC_START,
+      source: TELEMETRY_SOURCE,
+      trigger: "manual",
+    },
+    {
+      value: UptakeTelemetry.STATUS.SUCCESS,
+      source: TELEMETRY_SOURCE,
+      trigger: "manual",
+    },
+  ]);
+
+  //
+  // 2.
+  // - collection: [] -> [RECORD2, RECORD1]
+  // - timestamp: 1000 -> 3000
+  //
+  // Check that some additions (2 records) to the collection have a valid
+  // signature.
+
+  // This response adds two entries (RECORD1 and RECORD2) to the collection
+  const RESPONSE_TWO_ADDED = {
+    comment: "RESPONSE_TWO_ADDED",
+    sampleHeaders: [
+      "Content-Type: application/json; charset=UTF-8",
+      'ETag: "3000"',
+    ],
+    status: { status: 200, statusText: "OK" },
+    responseBody: JSON.stringify({
+      timestamp: 3000,
+      metadata: {
+        signatures: [
+          {
+            x5u,
+            signature:
+              "dwhJeypadNIyzGj3QdI0KMRTPnHhFPF_j73mNrsPAHKMW46S2Ftf4BzsPMvPMB8h0TjDus13wo_R4l432DHe7tYyMIWXY0PBeMcoe5BREhFIxMxTsh9eGVXBD1e3UwRy",
+          },
+        ],
+      },
+      changes: [RECORD2, RECORD1],
+    }),
+  };
+
+  const twoItemsResponses = {
+    "GET:/v1/buckets/main/collections/signed/changeset?_expected=3000&_since=1000":
+      [RESPONSE_TWO_ADDED],
+  };
+  registerHandlers(twoItemsResponses);
+  await client.maybeSync(3000);
+
+  equal((await client.get()).length, 2);
+
+  //
+  // 3.
+  // - collection: [RECORD2, RECORD1] -> [RECORD2, RECORD3]
+  // - timestamp: 3000 -> 4000
+  //
+  // Check the collection with one addition and one removal has a valid
+  // signature
+  const THREE_ITEMS_SIG =
+    "MIEmNghKnkz12UodAAIc3q_Y4a3IJJ7GhHF4JYNYmm8avAGyPM9fYU7NzVo94pzjotG7vmtiYuHyIX2rTHTbT587w0LdRWxipgFd_PC1mHiwUyjFYNqBBG-kifYk7kEw";
+
+  // Remove RECORD1, add RECORD3
+  const RESPONSE_ONE_ADDED_ONE_REMOVED = {
+    comment: "RESPONSE_ONE_ADDED_ONE_REMOVED ",
+    sampleHeaders: [
+      "Content-Type: application/json; charset=UTF-8",
+      'ETag: "4000"',
+    ],
+    status: { status: 200, statusText: "OK" },
+    responseBody: JSON.stringify({
+      timestamp: 4000,
+      metadata: {
+        signatures: [
+          {
+            x5u,
+            signature: THREE_ITEMS_SIG,
+          },
+        ],
+      },
+      changes: [RECORD3, RECORD1_DELETION],
+    }),
+  };
+
+  const oneAddedOneRemovedResponses = {
+    "GET:/v1/buckets/main/collections/signed/changeset?_expected=4000&_since=3000":
+      [RESPONSE_ONE_ADDED_ONE_REMOVED],
+  };
+  registerHandlers(oneAddedOneRemovedResponses);
+  await client.maybeSync(4000);
+
+  equal((await client.get()).length, 2);
+
+  //
+  // 4.
+  // - collection: [RECORD2, RECORD3] -> [RECORD2, RECORD3]
+  // - timestamp: 4000 -> 4100
+  //
+  // Check the signature is still valid with no operation (no changes)
+
+  // Leave the collection unchanged
+  const RESPONSE_EMPTY_NO_UPDATE = {
+    comment: "RESPONSE_EMPTY_NO_UPDATE ",
+    sampleHeaders: [
+      "Content-Type: application/json; charset=UTF-8",
+      'ETag: "4000"',
+    ],
+    status: { status: 200, statusText: "OK" },
+    responseBody: JSON.stringify({
+      timestamp: 4000,
+      metadata: {
+        signatures: [
+          {
+            x5u,
+            signature: THREE_ITEMS_SIG,
+          },
+        ],
+      },
+      changes: [],
+    }),
+  };
+
+  const noOpResponses = {
+    "GET:/v1/buckets/main/collections/signed/changeset?_expected=4100&_since=4000":
+      [RESPONSE_EMPTY_NO_UPDATE],
+  };
+  registerHandlers(noOpResponses);
+  await client.maybeSync(4100);
+
+  equal((await client.get()).length, 2);
+
+  //
+  // 5.
+  // - collection: [RECORD2, RECORD3] -> [RECORD2, RECORD3]
+  // - timestamp: 4000 -> 5000
+  //
+  // Check the collection is reset when the signature is invalid.
+  // Client will:
+  //   - Fetch metadata (with bad signature)
+  //   - Perform the sync (fetch empty changes)
+  //   - Refetch the metadata and the whole collection
+  //   - Validate signature successfully, but with no changes to emit.
+
+  const RESPONSE_COMPLETE_INITIAL = {
+    comment: "RESPONSE_COMPLETE_INITIAL ",
+    sampleHeaders: [
+      "Content-Type: application/json; charset=UTF-8",
+      'ETag: "4000"',
+    ],
+    status: { status: 200, statusText: "OK" },
+    responseBody: JSON.stringify({
+      timestamp: 4000,
+      metadata: {
+        signatures: [
+          {
+            x5u,
+            signature: THREE_ITEMS_SIG,
+          },
+        ],
+      },
+      changes: [RECORD2, RECORD3],
+    }),
+  };
+
+  const RESPONSE_EMPTY_NO_UPDATE_BAD_SIG = {
+    ...RESPONSE_EMPTY_NO_UPDATE,
+    responseBody: JSON.stringify({
+      timestamp: 4000,
+      metadata: {
+        signatures: [
+          {
+            x5u,
+            signature: "aW52YWxpZCBzaWduYXR1cmUK",
+          },
+        ],
+      },
+      changes: [],
+    }),
+  };
+
+  const badSigGoodSigResponses = {
+    // The first collection state is the three item collection (since
+    // there was sync with no updates before) - but, since the signature is wrong,
+    // another request will be made...
+    "GET:/v1/buckets/main/collections/signed/changeset?_expected=5000&_since=4000":
+      [RESPONSE_EMPTY_NO_UPDATE_BAD_SIG],
+    // Subsequent signature returned is a valid one for the three item
+    // collection.
+    "GET:/v1/buckets/main/collections/signed/changeset?_expected=5000": [
+      RESPONSE_COMPLETE_INITIAL,
+    ],
+  };
+
+  registerHandlers(badSigGoodSigResponses);
+  Services.telemetry.snapshotEvents(Ci.nsITelemetry.DATASET_ALL_CHANNELS, true);
+  Services.fog.testResetFOG();
+  enableUptakeMetric();
+
+  let syncEventSent = false;
+  client.on("sync", () => {
+    syncEventSent = true;
+  });
+
+  await client.maybeSync(5000);
+
+  equal((await client.get()).length, 2);
+
+  // since we only fixed the signature, and no data was changed, the sync event
+  // was not sent.
+  equal(syncEventSent, false);
+
+  // ensure that the failure count is incremented for a succesful sync with an
+  // (initial) bad signature - only SERVICES_SETTINGS_SYNC_SIG_FAIL should
+  // increment.
+  assertTelemetryEvents([
+    {
+      value: UptakeTelemetry.STATUS.SYNC_START,
+      source: TELEMETRY_SOURCE,
+      trigger: "manual",
+    },
+    {
+      value: UptakeTelemetry.STATUS.SIGNATURE_ERROR,
+      source: TELEMETRY_SOURCE,
+      trigger: "manual",
+    },
+  ]);
+
+  //
+  // 6.
+  // - collection: [RECORD2, RECORD3] -> [RECORD2, RECORD3]
+  // - timestamp: 4000 -> 5000
+  //
+  // Check the collection is reset when the signature is invalid.
+  // Client will:
+  //   - Fetch metadata (with bad signature)
+  //   - Perform the sync (fetch empty changes)
+  //   - Refetch the whole collection and metadata
+  //   - Sync will be no-op since local is equal to server, no changes to emit.
+
+  const badSigGoodOldResponses = {
+    // The first collection state is the current state (since there's no update
+    // - but, since the signature is wrong, another request will be made)
+    "GET:/v1/buckets/main/collections/signed/changeset?_expected=5000&_since=4000":
+      [RESPONSE_EMPTY_NO_UPDATE_BAD_SIG],
+    // The next request is for the full collection. This will be
+    // checked against the valid signature and last_modified times will be
+    // compared. Sync should be a no-op, even though the signature is good,
+    // because the local collection is newer.
+    "GET:/v1/buckets/main/collections/signed/changeset?_expected=5000": [
+      RESPONSE_EMPTY_INITIAL,
+    ],
+  };
+
+  // ensure our collection hasn't been replaced with an older, empty one
+  equal((await client.get()).length, 2, "collection was restored");
+
+  registerHandlers(badSigGoodOldResponses);
+
+  syncEventSent = false;
+  client.on("sync", () => {
+    syncEventSent = true;
+  });
+
+  await client.maybeSync(5000);
+
+  // Local data was unchanged, since it was never than the one returned by the server,
+  // thus the sync event is not sent.
+  equal(syncEventSent, false, "event was not sent");
+
+  //
+  // 7.
+  // - collection: [RECORD2, RECORD3] -> [RECORD2, RECORD3]
+  // - timestamp: 4000 -> 5000
+  //
+  // Check that a tampered local DB will be overwritten and
+  // sync event contain the appropriate data.
+
+  const RESPONSE_COMPLETE_BAD_SIG = {
+    ...RESPONSE_EMPTY_NO_UPDATE,
+    responseBody: JSON.stringify({
+      timestamp: 5000,
+      metadata: {
+        signatures: [
+          {
+            x5u,
+            signature: "aW52YWxpZCBzaWduYXR1cmUK",
+          },
+        ],
+      },
+      changes: [RECORD2, RECORD3],
+    }),
+  };
+
+  const badLocalContentGoodSigResponses = {
+    "GET:/v1/buckets/main/collections/signed/changeset?_expected=5000&_since=3900":
+      [RESPONSE_COMPLETE_BAD_SIG],
+    "GET:/v1/buckets/main/collections/signed/changeset?_expected=5000": [
+      RESPONSE_COMPLETE_INITIAL,
+    ],
+  };
+
+  registerHandlers(badLocalContentGoodSigResponses);
+
+  // we create a local state manually here, in order to test that the sync event data
+  // properly contains created, updated, and deleted records.
+  // the local DB contains same id as RECORD2 and a fake record.
+  // the final server collection contains RECORD2 and RECORD3
+  const localId = "0602b1b2-12ab-4d3a-b6fb-593244e7b035";
+  await client.db.importChanges(
+    { signatures: [{ x5u, signature: "abc" }] },
+    3900,
+    [
+      { ...RECORD2, last_modified: 1234567890, serialNumber: "abc" },
+      { id: localId },
+    ],
+    {
+      clear: true,
+    }
+  );
+
+  let syncData = null;
+  client.on("sync", ({ data }) => {
+    syncData = data;
+  });
+
+  // Clear events snapshot.
+  Services.telemetry.snapshotEvents(Ci.nsITelemetry.DATASET_ALL_CHANNELS, true);
+  Services.fog.testResetFOG();
+  enableUptakeMetric();
+
+  // Events telemetry is sampled on released, use fake channel.
+  await client.maybeSync(5000);
+
+  // We should report a corruption_error.
+  assertTelemetryEvents([
+    {
+      value: UptakeTelemetry.STATUS.SYNC_START,
+      source: client.identifier,
+      trigger: "manual",
+    },
+    {
+      value: UptakeTelemetry.STATUS.CORRUPTION_ERROR,
+      source: client.identifier,
+      trigger: "manual",
+      duration: d => parseInt(d) > 0,
+    },
+  ]);
+
+  // The local data was corrupted, and the Telemetry status reflects it.
+  // But the sync overwrote the bad data and was eventually a success.
+  // Since local data was replaced, we use records IDs to determine
+  // what was created and deleted. And bad local data will appear
+  // in the sync event as deleted.
+  equal(syncData.current.length, 2);
+  equal(syncData.created.length, 1);
+  equal(syncData.created[0].id, RECORD3.id);
+  equal(syncData.updated.length, 1);
+  equal(syncData.updated[0].old.serialNumber, "abc");
+  equal(syncData.updated[0].new.serialNumber, RECORD2.serialNumber);
+  equal(syncData.deleted.length, 1);
+  equal(syncData.deleted[0].id, localId);
+
+  //
+  // 8.
+  // - collection: [RECORD2, RECORD3] -> [RECORD2, RECORD3] (unchanged because of error)
+  // - timestamp: 4000 -> 6000
+  //
+  // Check that a failing signature throws after retry, and that sync changes
+  // are not applied.
+
+  const RESPONSE_ONLY_RECORD4_BAD_SIG = {
+    comment: "Create RECORD4",
+    sampleHeaders: [
+      "Content-Type: application/json; charset=UTF-8",
+      'ETag: "6000"',
+    ],
+    status: { status: 200, statusText: "OK" },
+    responseBody: JSON.stringify({
+      timestamp: 6000,
+      metadata: {
+        signatures: [
+          {
+            x5u,
+            signature: "aaaaaaaaaaaaaaaaaaaaaaaa", // sig verifier wants proper length or will crash.
+          },
+        ],
+      },
+      changes: [
+        {
+          id: "f765df30-b2f1-42f6-9803-7bd5a07b5098",
+          last_modified: 6000,
+        },
+      ],
+    }),
+  };
+  const RESPONSE_EMPTY_NO_UPDATE_BAD_SIG_6000 = {
+    ...RESPONSE_EMPTY_NO_UPDATE,
+    responseBody: JSON.stringify({
+      timestamp: 6000,
+      metadata: {
+        signatures: [
+          {
+            x5u,
+            signature: "aW52YWxpZCBzaWduYXR1cmUK",
+          },
+        ],
+      },
+      changes: [],
+    }),
+  };
+  const allBadSigResponses = {
+    "GET:/v1/buckets/main/collections/signed/changeset?_expected=6000&_since=4000":
+      [RESPONSE_EMPTY_NO_UPDATE_BAD_SIG_6000],
+    "GET:/v1/buckets/main/collections/signed/changeset?_expected=6000": [
+      RESPONSE_ONLY_RECORD4_BAD_SIG,
+    ],
+  };
+
+  // Reset telemetry capture.
+  Services.telemetry.snapshotEvents(Ci.nsITelemetry.DATASET_ALL_CHANNELS, true);
+  Services.fog.testResetFOG();
+  enableUptakeMetric();
+
+  registerHandlers(allBadSigResponses);
+  await Assert.rejects(
+    client.maybeSync(6000),
+    RemoteSettingsClient.InvalidSignatureError,
+    "Sync failed as expected (bad signature after retry)"
+  );
+
+  // Ensure that the failure is reflected in the accumulated telemetry:
+  assertTelemetryEvents([
+    {
+      value: UptakeTelemetry.STATUS.SYNC_START,
+      source: TELEMETRY_SOURCE,
+      trigger: "manual",
+    },
+    {
+      value: UptakeTelemetry.STATUS.SIGNATURE_RETRY_ERROR,
+      source: TELEMETRY_SOURCE,
+      trigger: "manual",
+    },
+  ]);
+
+  // When signature fails after retry, the local data present before sync
+  // should be maintained (if its signature is valid).
+  ok(
+    arrayEqual(
+      (await client.get()).map(r => r.id),
+      [RECORD3.id, RECORD2.id]
+    ),
+    "Local records were not changed"
+  );
+  // And local data should still be valid.
+  await client.get({ verifySignature: true }); // Not raising.
+
+  //
+  // 9.
+  // - collection: [RECORD2, RECORD3] -> [] (cleared)
+  // - timestamp: 4000 -> 6000
+  //
+  // Check that local data is cleared during sync if signature is not valid.
+
+  await client.db.create({
+    id: "c6b19c67-2e0e-4a82-b7f7-1777b05f3e81",
+    last_modified: 42,
+    tampered: true,
+  });
+
+  await Assert.rejects(
+    client.maybeSync(6000),
+    RemoteSettingsClient.InvalidSignatureError,
+    "Sync failed as expected (bad signature after retry)"
+  );
+
+  // Since local data was tampered, it was cleared.
+  equal((await client.get()).length, 0, "Local database is now empty.");
+
+  //
+  // 10.
+  // - collection: [RECORD2, RECORD3] -> [] (cleared)
+  // - timestamp: 4000 -> 6000
+  //
+  // Check that local data is cleared during sync if signature is not valid.
+
+  await client.db.create({
+    id: "c6b19c67-2e0e-4a82-b7f7-1777b05f3e81",
+    last_modified: 42,
+    tampered: true,
+  });
+
+  await Assert.rejects(
+    client.maybeSync(6000),
+    RemoteSettingsClient.InvalidSignatureError,
+    "Sync failed as expected (bad signature after retry)"
+  );
+  // Since local data was tampered, it was cleared.
+  equal((await client.get()).length, 0, "Local database is now empty.");
+
+  //
+  // 11.
+  // - collection: [RECORD2, RECORD3] -> [RECORD2, RECORD3]
+  // - timestamp: 4000 -> 6000
+  //
+  // Check that local data is restored if signature was valid before sync.
+  const sigCalls = [];
+  let i = 0;
+  client._verifier = {
+    async asyncVerifyContentSignature(serialized) {
+      sigCalls.push(serialized);
+      console.log(`verify call ${i}`);
+      return [
+        false, // After importing changes.
+        true, // When checking previous local data.
+        false, // Still fail after retry.
+        true, // When checking previous local data again.
+      ][i++];
+    },
+  };
+  // Create an extra record. It will have a valid signature locally
+  // thanks to the verifier mock.
+  await client.db.importChanges(
+    {
+      signatures: [{ x5u, signature: "aa" }],
+    },
+    4000,
+    [
+      {
+        id: "extraId",
+        last_modified: 42,
+      },
+    ]
+  );
+
+  equal((await client.get()).length, 1);
+
+  // Now sync, but importing changes will have failing signature,
+  // and so will retry (see `sigResults`).
+  await Assert.rejects(
+    client.maybeSync(6000),
+    RemoteSettingsClient.InvalidSignatureError,
+    "Sync failed as expected (bad signature after retry)"
+  );
+  equal(i, 4, "sync has retried as expected");
+
+  // Make sure that we retried on a blank DB. The extra record should
+  // have been deleted when we validated the signature the second time.
+  // Since local data was tampered, it was cleared.
+  ok(/extraId/.test(sigCalls[0]), "extra record when importing changes");
+  ok(/extraId/.test(sigCalls[1]), "extra record when checking local");
+  ok(!/extraId/.test(sigCalls[2]), "db was flushed before retry");
+  ok(/extraId/.test(sigCalls[3]), "when checking local after retry");
+});
diff --git a/src/zen/tests/mochitests/remote-settings/test_remote_settings_signatures/collection_signing_ee.pem b/src/zen/tests/mochitests/remote-settings/test_remote_settings_signatures/collection_signing_ee.pem
new file mode 100644
index 000000000..9392129f6
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_remote_settings_signatures/collection_signing_ee.pem
@@ -0,0 +1,16 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
diff --git a/src/zen/tests/mochitests/remote-settings/test_remote_settings_signatures/collection_signing_ee.pem.certspec b/src/zen/tests/mochitests/remote-settings/test_remote_settings_signatures/collection_signing_ee.pem.certspec
new file mode 100644
index 000000000..866c357c5
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_remote_settings_signatures/collection_signing_ee.pem.certspec
@@ -0,0 +1,5 @@
+issuer:collection-signer-int-CA
+subject:collection-signer-ee-int-CA
+subjectKey:secp384r1
+extension:extKeyUsage:codeSigning
+extension:subjectAlternativeName:onecrl.content-signature.mozilla.org
diff --git a/src/zen/tests/mochitests/remote-settings/test_remote_settings_signatures/collection_signing_int.pem b/src/zen/tests/mochitests/remote-settings/test_remote_settings_signatures/collection_signing_int.pem
new file mode 100644
index 000000000..de3c2ff3c
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_remote_settings_signatures/collection_signing_int.pem
@@ -0,0 +1,19 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
diff --git a/src/zen/tests/mochitests/remote-settings/test_remote_settings_signatures/collection_signing_int.pem.certspec b/src/zen/tests/mochitests/remote-settings/test_remote_settings_signatures/collection_signing_int.pem.certspec
new file mode 100644
index 000000000..2b3eb2d78
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_remote_settings_signatures/collection_signing_int.pem.certspec
@@ -0,0 +1,4 @@
+issuer:xpcshell signed apps test root
+subject:collection-signer-int-CA
+extension:basicConstraints:cA,
+extension:extKeyUsage:codeSigning
diff --git a/src/zen/tests/mochitests/remote-settings/test_remote_settings_startup_bundle.js b/src/zen/tests/mochitests/remote-settings/test_remote_settings_startup_bundle.js
new file mode 100644
index 000000000..ba93e2d33
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_remote_settings_startup_bundle.js
@@ -0,0 +1,152 @@
+const { Database } = ChromeUtils.importESModule(
+  "resource://services-settings/Database.sys.mjs"
+);
+const { RemoteSettings } = ChromeUtils.importESModule(
+  "resource://services-settings/remote-settings.sys.mjs"
+);
+
+let server;
+let startupClients;
+
+add_setup(async () => {
+  // Disable signature verification of collections listed in test startup.json.mzlz4
+  // since their metadata will eventually expire.
+  startupClients = [
+    "message-groups",
+    "nimbus-desktop-experiments",
+    "search-categorization",
+    "tracking-protection-lists",
+    "query-stripping",
+    "cfr",
+  ].map(id => {
+    const c = RemoteSettings(id);
+    c.verifySignature = false;
+    return c;
+  });
+
+  // Setup an HTTP server to serve the 'startup.json.mzlz4' bundle.
+  server = new HttpServer();
+  server.start(-1);
+  server.registerDirectory(
+    "/cdn/bundles/",
+    do_get_file("test_remote_settings_startup_bundle")
+  );
+  server.registerPathHandler("/v1/", (request, response) => {
+    response.write(
+      JSON.stringify({
+        capabilities: {
+          attachments: {
+            base_url: `http://localhost:${server.identity.primaryPort}/cdn/`,
+          },
+        },
+      })
+    );
+    response.setHeader("Content-Type", "application/json; charset=UTF-8");
+    response.setStatusLine(null, 200, "OK");
+  });
+  Services.prefs.setStringPref(
+    "services.settings.server",
+    `http://localhost:${server.identity.primaryPort}/v1`
+  );
+  registerCleanupFunction(() => {
+    server.stop(() => {});
+    Services.prefs.clearUserPref("services.settings.loglevel");
+  });
+});
+
+async function clear_state() {
+  await Database.destroy();
+  RemoteSettings._ongoingExtractBundlePromise = null;
+}
+
+add_task(async function test_bundle_is_pulled_when_get_needs_sync() {
+  const client = startupClients[0];
+
+  Assert.ok(
+    !(await Utils.hasLocalDump(client.bucketName, client.collectionName)),
+    "Client has no packaged dump"
+  );
+
+  const records = await client.get();
+
+  Assert.equal(records.length, 6, "Records were read from startup bundle");
+});
+add_task(clear_state);
+
+add_task(
+  async function test_signature_of_extracted_data_from_bundle_is_verified() {
+    const c = RemoteSettings("tracking-protection-lists"); // part of startup.json.mzlz4
+    c.verifySignature = true;
+
+    let called = null;
+    c.validateCollectionSignature = (records, timestamp, metadata) => {
+      called = { records, timestamp, metadata };
+    };
+
+    await c.get();
+
+    Assert.ok(!!called.records.length);
+    Assert.greaterOrEqual(called.timestamp, 1694684362860);
+    Assert.ok(called.metadata.flags.includes("startup"));
+  }
+);
+add_task(clear_state);
+
+add_task(async function test_bundle_is_not_importent_when_signature_fails() {
+  const c = RemoteSettings("tracking-protection-lists"); // part of startup.json.mzlz4
+  c.verifySignature = true;
+
+  let called = false;
+  c.validateCollectionSignature = () => {
+    called = true;
+    throw new Error("boom!");
+  };
+
+  let error;
+  try {
+    await c.get({ emptyListFallback: false });
+    Assert.ok(false, ".get() should fail without network");
+  } catch (e) {
+    error = e;
+  }
+  Assert.ok(called, "Signature was verified");
+  Assert.equal(
+    error.name,
+    "UnknownCollectionError",
+    ".get() fails without network and with bad startup bundle"
+  );
+});
+add_task(clear_state);
+
+add_task(async function test_sync_occurs_if_collection_not_part_of_bundle() {
+  const c = RemoteSettings("foo");
+
+  let error;
+  try {
+    await c.get({ emptyListFallback: false });
+    Assert.ok(false, ".get() should fail when bundle disabled");
+  } catch (e) {
+    error = e;
+  }
+  Assert.equal(
+    error.name,
+    "UnknownCollectionError",
+    ".get() fails to sync data"
+  );
+});
+add_task(clear_state);
+
+add_task(async function test_several_clients_wait_for_bundle() {
+  // several clients calling .get() in parallel will all take content from bundle.
+  const results = await Promise.allSettled(
+    startupClients.map(c => c.get({ emptyListFallback: false }))
+  );
+
+  Assert.deepEqual(
+    [6, 70, 5, "UnknownCollectionError", 3, 11],
+    results.map(({ status, value, reason }) =>
+      status == "fulfilled" ? value.length : reason.name
+    )
+  );
+});
+add_task(clear_state);
diff --git a/src/zen/tests/mochitests/remote-settings/test_remote_settings_startup_bundle/startup.json.mozlz4 b/src/zen/tests/mochitests/remote-settings/test_remote_settings_startup_bundle/startup.json.mozlz4
new file mode 100644
index 000000000..978459dde
Binary files /dev/null and b/src/zen/tests/mochitests/remote-settings/test_remote_settings_startup_bundle/startup.json.mozlz4 differ
diff --git a/src/zen/tests/mochitests/remote-settings/test_remote_settings_sync_history.js b/src/zen/tests/mochitests/remote-settings/test_remote_settings_sync_history.js
new file mode 100644
index 000000000..d0ef6cfc4
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_remote_settings_sync_history.js
@@ -0,0 +1,65 @@
+"use strict";
+
+async function clear_state() {
+  await new SyncHistory("").clear();
+}
+add_task(clear_state);
+
+add_task(async function test_entries_are_stored_by_source() {
+  const history = new SyncHistory();
+  await history.store(42, "success", { pi: "3.14" });
+  // Check that history is isolated by source.
+  await new SyncHistory("main/cfr").store(88, "error");
+
+  const l = await history.list();
+
+  Assert.deepEqual(l, [
+    {
+      timestamp: 42,
+      status: "success",
+      infos: { pi: "3.14" },
+      datetime: new Date(42),
+    },
+  ]);
+});
+add_task(clear_state);
+
+add_task(
+  async function test_old_entries_are_removed_keep_fixed_size_per_source() {
+    const history = new SyncHistory("settings-sync", { size: 3 });
+    const anotherHistory = await new SyncHistory("main/cfr");
+
+    await history.store(42, "success");
+    await history.store(41, "sync_error");
+    await history.store(43, "up_to_date");
+
+    let l = await history.list();
+    Assert.equal(l.length, 3);
+
+    await history.store(44, "success");
+    await anotherHistory.store(44, "success");
+
+    l = await history.list();
+    Assert.equal(l.length, 3);
+    Assert.ok(!l.map(e => e.timestamp).includes(41));
+
+    l = await anotherHistory.list();
+    Assert.equal(l.length, 1);
+  }
+);
+add_task(clear_state);
+
+add_task(async function test_entries_are_sorted_by_timestamp_desc() {
+  const history = new SyncHistory("settings-sync");
+  await history.store(42, "success");
+  await history.store(41, "sync_error");
+  await history.store(44, "up_to_date");
+
+  const l = await history.list();
+
+  Assert.deepEqual(
+    l.map(e => e.timestamp),
+    [44, 42, 41]
+  );
+});
+add_task(clear_state);
diff --git a/src/zen/tests/mochitests/remote-settings/test_remote_settings_utils.js b/src/zen/tests/mochitests/remote-settings/test_remote_settings_utils.js
new file mode 100644
index 000000000..fc4a73911
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_remote_settings_utils.js
@@ -0,0 +1,299 @@
+const BinaryOutputStream = Components.Constructor(
+  "@mozilla.org/binaryoutputstream;1",
+  "nsIBinaryOutputStream",
+  "setOutputStream"
+);
+
+const server = new HttpServer();
+server.start(-1);
+registerCleanupFunction(() => server.stop(() => {}));
+const SERVER_BASE_URL = `http://localhost:${server.identity.primaryPort}`;
+
+const proxyServer = new HttpServer();
+proxyServer.identity.add("http", "localhost", server.identity.primaryPort);
+proxyServer.start(-1);
+registerCleanupFunction(() => proxyServer.stop(() => {}));
+const PROXY_PORT = proxyServer.identity.primaryPort;
+
+// A sequence of bytes that would become garbage if it were to be read as UTF-8:
+// - 0xEF 0xBB 0xBF is a byte order mark.
+// - 0xC0 on its own is invalid (it's the first byte of a 2-byte encoding).
+const INVALID_UTF_8_BYTES = [0xef, 0xbb, 0xbf, 0xc0];
+
+server.registerPathHandler("/binary.dat", (request, response) => {
+  response.setStatusLine(null, 201, "StatusLineHere");
+  response.setHeader("headerName", "HeaderValue: HeaderValueEnd");
+  let binaryOut = new BinaryOutputStream(response.bodyOutputStream);
+  binaryOut.writeByteArray([0xef, 0xbb, 0xbf, 0xc0]);
+});
+
+// HTTPS requests are proxied with CONNECT, but our test server is HTTP,
+// which means that the proxy will receive GET http://localhost:port.
+var proxiedCount = 0;
+proxyServer.registerPrefixHandler("/", (request, response) => {
+  ++proxiedCount;
+  Assert.equal(request.path, "/binary.dat", `Proxy request ${proxiedCount}`);
+  // Close connection without sending any response.
+  response.seizePower();
+  response.finish();
+});
+
+add_task(async function test_utils_fetch_binary() {
+  let res = await Utils.fetch(`${SERVER_BASE_URL}/binary.dat`);
+
+  Assert.equal(res.status, 201, "res.status");
+  Assert.equal(res.statusText, "StatusLineHere", "res.statusText");
+  Assert.equal(
+    res.headers.get("headerName"),
+    "HeaderValue: HeaderValueEnd",
+    "Utils.fetch should return the header"
+  );
+
+  Assert.deepEqual(
+    Array.from(new Uint8Array(await res.arrayBuffer())),
+    INVALID_UTF_8_BYTES,
+    "Binary response body should be returned as is"
+  );
+});
+
+add_task(async function test_utils_fetch_binary_as_text() {
+  let res = await Utils.fetch(`${SERVER_BASE_URL}/binary.dat`);
+  Assert.deepEqual(
+    Array.from(await res.text(), c => c.charCodeAt(0)),
+    [65533],
+    "Interpreted as UTF-8, the response becomes garbage"
+  );
+});
+
+add_task(async function test_utils_fetch_binary_as_json() {
+  let res = await Utils.fetch(`${SERVER_BASE_URL}/binary.dat`);
+  await Assert.rejects(
+    res.json(),
+    /SyntaxError: JSON.parse: unexpected character/,
+    "Binary data is invalid JSON"
+  );
+});
+
+add_task(async function test_utils_fetch_has_conservative() {
+  let channelPromise = TestUtils.topicObserved("http-on-modify-request");
+  await Utils.fetch(`${SERVER_BASE_URL}/binary.dat`);
+
+  let channel = (await channelPromise)[0].QueryInterface(Ci.nsIHttpChannel);
+
+  Assert.equal(channel.URI.spec, `${SERVER_BASE_URL}/binary.dat`, "URL OK");
+
+  let internalChannel = channel.QueryInterface(Ci.nsIHttpChannelInternal);
+  Assert.ok(internalChannel.beConservative, "beConservative flag is set");
+});
+
+add_task(async function test_utils_fetch_has_conservative() {
+  let channelPromise = TestUtils.topicObserved("http-on-modify-request");
+  await Utils.fetch(`${SERVER_BASE_URL}/binary.dat`);
+
+  let channel = (await channelPromise)[0].QueryInterface(Ci.nsIHttpChannel);
+
+  Assert.equal(channel.URI.spec, `${SERVER_BASE_URL}/binary.dat`, "URL OK");
+
+  let internalChannel = channel.QueryInterface(Ci.nsIHttpChannelInternal);
+  Assert.ok(internalChannel.beConservative, "beConservative flag is set");
+});
+
+add_task(async function test_utils_fetch_with_bad_proxy() {
+  Services.prefs.setIntPref("network.proxy.type", 1);
+  Services.prefs.setStringPref("network.proxy.http", "127.0.0.1");
+  Services.prefs.setIntPref("network.proxy.http_port", PROXY_PORT);
+  Services.prefs.setBoolPref("network.proxy.allow_hijacking_localhost", true);
+
+  // The URL that we're going to request.
+  const DESTINATION_URL = `${SERVER_BASE_URL}/binary.dat`;
+
+  Assert.equal(proxiedCount, 0, "Proxy not used yet");
+  {
+    info("Bad proxy, default prefs");
+    let res = await Utils.fetch(DESTINATION_URL);
+    Assert.equal(res.status, 201, "Bypassed bad proxy");
+    // 10 instead of 1 because of reconnect attempts after a dropped request.
+    Assert.equal(proxiedCount, 10, "Proxy was used by HttpChannel");
+  }
+
+  // Disables the failover logic from HttpChannel.
+  Services.prefs.setBoolPref("network.proxy.failover_direct", false);
+  proxiedCount = 0;
+  {
+    info("Bad proxy, disabled network.proxy.failover_direct");
+    let res = await Utils.fetch(DESTINATION_URL);
+    Assert.equal(res.status, 201, "Bypassed bad proxy");
+    // 10 instead of 1 because of reconnect attempts after a dropped request.
+    Assert.equal(proxiedCount, 10, "Proxy was used by ServiceRequest");
+  }
+
+  proxiedCount = 0;
+  {
+    info("Using internal option of Utils.fetch: bypassProxy=true");
+    let res = await Utils.fetch(DESTINATION_URL, { bypassProxy: true });
+    Assert.equal(res.status, 201, "Bypassed bad proxy");
+    Assert.equal(proxiedCount, 0, "Not using proxy when bypassProxy=true");
+  }
+
+  // Disables the failover logic from ServiceRequest/Utils.fetch
+  Services.prefs.setBoolPref("network.proxy.allow_bypass", false);
+  proxiedCount = 0;
+
+  info("Bad proxy, disabled network.proxy.allow_bypass");
+  await Assert.rejects(
+    Utils.fetch(DESTINATION_URL),
+    /NetworkError/,
+    "Bad proxy request should fail without failover"
+  );
+  // 10 instead of 1 because of reconnect attempts after a dropped request.
+  Assert.equal(proxiedCount, 10, "Attempted to use proxy again");
+
+  Services.prefs.clearUserPref("network.proxy.type");
+  Services.prefs.clearUserPref("network.proxy.http");
+  Services.prefs.clearUserPref("network.proxy.http_port");
+  Services.prefs.clearUserPref("network.proxy.allow_hijacking_localhost");
+  Services.prefs.clearUserPref("network.proxy.failover_direct");
+  Services.prefs.clearUserPref("network.proxy.allow_bypass");
+});
+
+add_task(async function test_base_attachment_url_depends_on_server() {
+  Services.prefs.setStringPref(
+    "services.settings.server",
+    `http://localhost:${server.identity.primaryPort}/v1`
+  );
+  server.registerPathHandler("/v1/", (request, response) => {
+    response.write(
+      JSON.stringify({
+        capabilities: {
+          attachments: {
+            base_url: "http://default-url.com/",
+          },
+        },
+      })
+    );
+    response.setHeader("Content-Type", "application/json; charset=UTF-8");
+    response.setStatusLine(null, 200, "OK");
+  });
+  const before = await Utils.baseAttachmentsURL();
+  Assert.equal(before, "http://default-url.com/");
+
+  Services.prefs.setStringPref(
+    "services.settings.server",
+    `http://localhost:${server.identity.primaryPort}/v2`
+  );
+
+  Assert.equal(
+    Services.prefs.getStringPref("services.settings.server"),
+    Utils.SERVER_URL
+  );
+
+  server.registerPathHandler("/v2/", (request, response) => {
+    response.write(
+      JSON.stringify({
+        capabilities: {
+          attachments: {
+            base_url: "http://some-cdn-url.org/",
+          },
+        },
+      })
+    );
+    response.setHeader("Content-Type", "application/json; charset=UTF-8");
+    response.setStatusLine(null, 200, "OK");
+  });
+
+  const after = await Utils.baseAttachmentsURL();
+  Assert.equal(after, "http://some-cdn-url.org/");
+});
+
+add_task(async function test_base_attachment_url_reads_from_prefs() {
+  Services.prefs.setStringPref(
+    "services.settings.base_attachments_url",
+    `${Utils.SERVER_URL}|https://other/`
+  );
+  Assert.equal(await Utils.baseAttachmentsURL(), "https://other/");
+});
+
+add_task(async function test_base_attachment_url_is_robust_to_bad_saved_data() {
+  server.registerPathHandler("/v1/", (request, response) => {
+    response.write(
+      JSON.stringify({
+        capabilities: {
+          attachments: {
+            base_url: "http://some-cdn-url.org/",
+          },
+        },
+      })
+    );
+    response.setHeader("Content-Type", "application/json; charset=UTF-8");
+    response.setStatusLine(null, 200, "OK");
+  });
+
+  for (const badValue of [
+    "",
+    "|",
+    Utils.SERVER_URL,
+    `${Utils.SERVER_URL}|https://other`, // Missing trailing slash.
+    `${Utils.SERVER_URL}|https://other/path`, // Missing trailing slash.
+  ]) {
+    Services.prefs.setStringPref(
+      "services.settings.base_attachments_url",
+      badValue
+    );
+    Assert.equal(
+      await Utils.baseAttachmentsURL(),
+      "http://some-cdn-url.org/",
+      "Fallsback to server's"
+    );
+  }
+});
+
+add_task(async function test_base_attachment_url_does_not_retry_by_default() {
+  Services.prefs.clearUserPref("services.settings.base_attachments_url");
+  Services.prefs.setStringPref(
+    "services.settings.server",
+    `http://localhost:${server.identity.primaryPort}/v1`
+  );
+  let requests = 0;
+  server.registerPathHandler("/v1/", (request, response) => {
+    requests++;
+    response.setStatusLine(null, 503, "Service Unavailable");
+  });
+  try {
+    await Utils.baseAttachmentsURL({ retryWaitMsec: 10 });
+    Assert.ok(false, "should throw on error");
+  } catch (e) {}
+  Assert.equal(requests, 1);
+});
+
+add_task(async function test_base_attachment_url_can_retry() {
+  Services.prefs.clearUserPref("services.settings.base_attachments_url");
+  Services.prefs.setStringPref(
+    "services.settings.server",
+    `http://localhost:${server.identity.primaryPort}/v1`
+  );
+  let requests = 0;
+  server.registerPathHandler("/v1/", (request, response) => {
+    requests++;
+    if (requests < 4) {
+      response.setStatusLine(null, 503, "Service Unavailable");
+      return;
+    }
+
+    response.write(
+      JSON.stringify({
+        capabilities: {
+          attachments: {
+            base_url: "http://some-cdn-url.org/",
+          },
+        },
+      })
+    );
+    response.setHeader("Content-Type", "application/json; charset=UTF-8");
+    response.setStatusLine(null, 200, "OK");
+  });
+  Assert.equal(
+    await Utils.baseAttachmentsURL({ retries: 3, retryWaitMsec: 10 }),
+    "http://some-cdn-url.org/"
+  );
+  Assert.equal(requests, 4);
+});
diff --git a/src/zen/tests/mochitests/remote-settings/test_remote_settings_utils_telemetry.js b/src/zen/tests/mochitests/remote-settings/test_remote_settings_utils_telemetry.js
new file mode 100644
index 000000000..72fdb81b1
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_remote_settings_utils_telemetry.js
@@ -0,0 +1,79 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const server = new HttpServer();
+server.start(-1);
+registerCleanupFunction(() => server.stop(() => {}));
+const SERVER_BASE_URL = `http://localhost:${server.identity.primaryPort}`;
+
+const proxyServer = new HttpServer();
+proxyServer.start(-1);
+const PROXY_PORT = proxyServer.identity.primaryPort;
+proxyServer.stop();
+
+server.registerPathHandler("/destination", (request, response) => {
+  response.setStatusLine(null, 412);
+});
+
+function assertBypassTelemetryEvents(expectedEvents) {
+  const events = Glean.serviceRequest.bypassProxyInfo.testGetValue() ?? [];
+  Assert.equal(events.length, expectedEvents.length);
+  for (let i = 0; i < expectedEvents.length; i++) {
+    Assert.deepEqual(events[i].extra, {
+      value: expectedEvents[i].value,
+      ...expectedEvents[i].extra,
+    });
+  }
+  Services.fog.testResetFOG();
+}
+
+add_task(async function test_telemetry() {
+  const DESTINATION_URL = `${SERVER_BASE_URL}/destination`;
+
+  {
+    let res = await Utils.fetch(DESTINATION_URL);
+    Assert.equal(res.status, 412, "fetch without proxy succeeded");
+  }
+  assertBypassTelemetryEvents([]);
+
+  Services.prefs.setIntPref("network.proxy.type", 1);
+  Services.prefs.setStringPref("network.proxy.http", "127.0.0.1");
+  Services.prefs.setIntPref("network.proxy.http_port", PROXY_PORT);
+  Services.prefs.setBoolPref("network.proxy.allow_hijacking_localhost", true);
+
+  {
+    let res = await Utils.fetch(DESTINATION_URL);
+    Assert.equal(res.status, 412, "fetch with broken proxy succeeded");
+  }
+  // Note: failover handled by HttpChannel, hence no failover here.
+  assertBypassTelemetryEvents([]);
+
+  // Disable HttpChannel failover in favor of Utils.fetch's implementation.
+  Services.prefs.setBoolPref("network.proxy.failover_direct", false);
+  {
+    let res = await Utils.fetch(DESTINATION_URL);
+    Assert.equal(res.status, 412, "fetch succeeded with bypassProxy feature");
+  }
+  assertBypassTelemetryEvents([
+    {
+      category: "service_request",
+      method: "bypass",
+      object: "proxy_info",
+      value: "remote-settings",
+      extra: {
+        source: "prefs",
+        type: "manual",
+      },
+    },
+  ]);
+
+  Services.prefs.setBoolPref("network.proxy.allow_bypass", false);
+  await Assert.rejects(
+    Utils.fetch(DESTINATION_URL),
+    /NetworkError/,
+    "Request without failover fails"
+  );
+  assertBypassTelemetryEvents([]);
+});
diff --git a/src/zen/tests/mochitests/remote-settings/test_remote_settings_worker.js b/src/zen/tests/mochitests/remote-settings/test_remote_settings_worker.js
new file mode 100644
index 000000000..8fd5bf484
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_remote_settings_worker.js
@@ -0,0 +1,117 @@
+add_task(async function test_canonicaljson() {
+  const records = [
+    { id: "1", title: "title 1" },
+    { id: "2", title: "title 2" },
+  ];
+  const timestamp = 42;
+
+  const serialized = await RemoteSettingsWorker.canonicalStringify(
+    records,
+    timestamp
+  );
+
+  Assert.equal(
+    serialized,
+    '{"data":[{"id":"1","title":"title 1"},{"id":"2","title":"title 2"}],"last_modified":"42"}'
+  );
+});
+
+add_task(async function test_import_json_dump_into_idb() {
+  if (IS_ANDROID) {
+    // Skip test: we don't ship remote settings dumps on Android (see package-manifest).
+    return;
+  }
+  const client = new RemoteSettingsClient("language-dictionaries");
+  const before = await client.db.getLastModified();
+  Assert.equal(before, null);
+
+  await RemoteSettingsWorker.importJSONDump("main", "language-dictionaries");
+
+  const after = await client.get({ syncIfEmpty: false });
+  Assert.ok(!!after.length);
+  let lastModifiedStamp = await client.getLastModified();
+
+  Assert.equal(
+    lastModifiedStamp,
+    Math.max(...after.map(record => record.last_modified)),
+    "Should have correct last modified timestamp"
+  );
+
+  // Force a DB close for shutdown so we can delete the DB later.
+  Database._shutdownHandler();
+});
+
+add_task(async function test_throws_error_if_worker_fails() {
+  let error;
+  try {
+    await RemoteSettingsWorker.canonicalStringify(null, 42);
+  } catch (e) {
+    error = e;
+  }
+  Assert.equal(error.message.endsWith("records is null"), true);
+});
+
+add_task(async function test_throws_error_if_worker_fails_async() {
+  if (IS_ANDROID) {
+    // Skip test: we don't ship dump, so importJSONDump() is no-op.
+    return;
+  }
+  // Delete the Remote Settings database, and try to import a dump.
+  // This is not supported, and the error thrown asynchronously in the worker
+  // should be reported to the caller.
+  await new Promise((resolve, reject) => {
+    const request = indexedDB.deleteDatabase("remote-settings");
+    request.onsuccess = () => resolve();
+    request.onblocked = () => reject(new Error("Cannot delete DB"));
+    request.onerror = event => reject(event.target.error);
+  });
+  let error;
+  try {
+    await RemoteSettingsWorker.importJSONDump("main", "language-dictionaries");
+  } catch (e) {
+    error = e;
+  }
+  Assert.ok(/IndexedDB: Error accessing remote-settings/.test(error.message));
+});
+
+add_task(async function test_throws_error_if_worker_crashes() {
+  // This simulates a crash at the worker level (not within a promise).
+  let error;
+  try {
+    await RemoteSettingsWorker._execute("unknown_method");
+  } catch (e) {
+    error = e;
+  }
+  Assert.equal(error.message, "TypeError: Agent[method] is not a function");
+});
+
+add_task(async function test_stops_worker_after_timeout() {
+  // Change the idle time.
+  Services.prefs.setIntPref(
+    "services.settings.worker_idle_max_milliseconds",
+    1
+  );
+  // Run a task:
+  let serialized = await RemoteSettingsWorker.canonicalStringify([], 42);
+  Assert.equal(serialized, '{"data":[],"last_modified":"42"}', "API works.");
+  // Check that the worker gets stopped now the task is done:
+  await TestUtils.waitForCondition(() => !RemoteSettingsWorker.worker);
+  // Ensure the worker stays alive for 10 minutes instead:
+  Services.prefs.setIntPref(
+    "services.settings.worker_idle_max_milliseconds",
+    600000
+  );
+  // Run another task:
+  serialized = await RemoteSettingsWorker.canonicalStringify([], 42);
+  Assert.equal(
+    serialized,
+    '{"data":[],"last_modified":"42"}',
+    "API still works."
+  );
+  Assert.ok(RemoteSettingsWorker.worker, "Worker should stay alive a bit.");
+
+  // Clear the pref.
+  Services.prefs.clearUserPref(
+    "services.settings.worker_idle_max_milliseconds"
+  );
+});
diff --git a/src/zen/tests/mochitests/remote-settings/test_shutdown_handling.js b/src/zen/tests/mochitests/remote-settings/test_shutdown_handling.js
new file mode 100644
index 000000000..fbd9438a0
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_shutdown_handling.js
@@ -0,0 +1,132 @@
+/* Any copyright is dedicated to the Public Domain.
+http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_setup(() => {
+  Services.prefs.setStringPref("services.settings.loglevel", "debug");
+  registerCleanupFunction(() => {
+    Services.prefs.clearUserPref("services.settings.loglevel");
+  });
+});
+
+add_task(async function test_shutdown_abort_after_start() {
+  // Start a forever transaction:
+  let counter = 0;
+  let transactionStarted;
+  let startedPromise = new Promise(r => {
+    transactionStarted = r;
+  });
+  let promise = Database._executeIDB(
+    "records",
+    store => {
+      // Signal we've started.
+      transactionStarted();
+      function makeRequest() {
+        if (++counter > 1000) {
+          Assert.ok(
+            false,
+            "We ran 1000 requests and didn't get aborted, what?"
+          );
+          return;
+        }
+        dump("Making request " + counter + "\n");
+        const request = store
+          .index("cid")
+          .openCursor(IDBKeyRange.only("foopydoo/foo"));
+        request.onsuccess = () => {
+          makeRequest();
+        };
+      }
+      makeRequest();
+    },
+    { mode: "readonly" }
+  );
+
+  // Wait for the transaction to start.
+  await startedPromise;
+
+  Database._shutdownHandler(); // should abort the readonly transaction.
+
+  let rejection;
+  await promise.catch(e => {
+    rejection = e;
+  });
+  ok(rejection, "Promise should have rejected.");
+
+  // Now clear the shutdown flag and rejection error:
+  Database._cancelShutdown();
+  rejection = null;
+});
+
+add_task(async function test_shutdown_immediate_abort() {
+  // Now abort directly from the successful request.
+  let promise = Database._executeIDB(
+    "records",
+    store => {
+      let request = store
+        .index("cid")
+        .openCursor(IDBKeyRange.only("foopydoo/foo"));
+      request.onsuccess = () => {
+        // Abort immediately.
+        Database._shutdownHandler();
+        request = store
+          .index("cid")
+          .openCursor(IDBKeyRange.only("foopydoo/foo"));
+        Assert.ok(false, "IndexedDB allowed opening a cursor after aborting?!");
+      };
+    },
+    { mode: "readonly" }
+  );
+
+  let rejection;
+  // Wait for the abort
+  await promise.catch(e => {
+    rejection = e;
+  });
+  ok(rejection, "Directly aborted promise should also have rejected.");
+  // Now clear the shutdown flag and rejection error:
+  Database._cancelShutdown();
+});
+
+add_task(async function test_shutdown_worker() {
+  let client = new RemoteSettingsClient("language-dictionaries");
+  const before = await client.db.getLastModified();
+  Assert.equal(before, null);
+
+  let records = [{}];
+  let importPromise = RemoteSettingsWorker._execute(
+    "_test_only_import",
+    ["main", "language-dictionaries", records, 0],
+    { mustComplete: true }
+  );
+  let stringifyPromise = RemoteSettingsWorker.canonicalStringify(
+    [],
+    [],
+    Date.now()
+  );
+  // Change the idle time so we shut the worker down even though we can't
+  // set gShutdown from outside of the worker management code.
+  Services.prefs.setIntPref(
+    "services.settings.worker_idle_max_milliseconds",
+    1
+  );
+  RemoteSettingsWorker._abortCancelableRequests();
+  await Assert.rejects(
+    stringifyPromise,
+    /Shutdown/,
+    "Should have aborted the stringify request at shutdown."
+  );
+  await Assert.rejects(
+    importPromise,
+    /shutting down/,
+    "Ensure imports get aborted during shutdown"
+  );
+  const after = await client.db.getLastModified();
+  Assert.equal(after, null);
+  await TestUtils.waitForCondition(() => !RemoteSettingsWorker.worker);
+  Assert.ok(
+    !RemoteSettingsWorker.worker,
+    "Worker should have been terminated."
+  );
+});
diff --git a/src/zen/tests/mochitests/remote-settings/test_uptake_telemetry.js b/src/zen/tests/mochitests/remote-settings/test_uptake_telemetry.js
new file mode 100644
index 000000000..df7743414
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/test_uptake_telemetry.js
@@ -0,0 +1,68 @@
+const { UptakeTelemetry } = ChromeUtils.importESModule(
+  "resource://services-settings/UptakeTelemetry.sys.mjs"
+);
+
+add_setup(function () {
+  Services.fog.initializeFOG();
+});
+
+function enableUptakeMetric() {
+  Services.fog.applyServerKnobsConfig(
+    JSON.stringify({
+      metrics_enabled: {
+        "uptake.remotecontent.result.uptake_remotesettings": true,
+      },
+    })
+  );
+}
+
+add_task(async function test_unknown_status_is_not_reported() {
+  Services.fog.testResetFOG();
+  enableUptakeMetric();
+
+  try {
+    await UptakeTelemetry.report("unknown-status", { source: "update-source" });
+  } catch (e) {}
+
+  Assert.equal(
+    null,
+    Glean.uptakeRemotecontentResult.uptakeRemotesettings.testGetValue()
+  );
+});
+
+add_task(async function test_age_is_converted_to_string_and_reported() {
+  Services.fog.testResetFOG();
+  enableUptakeMetric();
+  const status = UptakeTelemetry.STATUS.SUCCESS;
+  const age = 42;
+
+  await UptakeTelemetry.report(status, { source: "s", age });
+
+  const events =
+    Glean.uptakeRemotecontentResult.uptakeRemotesettings.testGetValue();
+  Assert.equal(1, events.length);
+  Assert.deepEqual(events[0].extra, {
+    value: status,
+    source: "s",
+    age: `${age}`,
+  });
+});
+
+add_task(async function test_each_status_can_be_caught_in_snapshot() {
+  Services.fog.testResetFOG();
+  enableUptakeMetric();
+  const source = "some-source";
+
+  for (const status of Object.values(UptakeTelemetry.STATUS)) {
+    await UptakeTelemetry.report(status, { source });
+  }
+
+  const events =
+    Glean.uptakeRemotecontentResult.uptakeRemotesettings.testGetValue();
+  for (const status of Object.values(UptakeTelemetry.STATUS)) {
+    Assert.ok(
+      events.some(e => e.extra.value === status && e.extra.source === source),
+      `check events for ${status}`
+    );
+  }
+});
diff --git a/src/zen/tests/mochitests/remote-settings/xpcshell.toml b/src/zen/tests/mochitests/remote-settings/xpcshell.toml
new file mode 100644
index 000000000..06c149861
--- /dev/null
+++ b/src/zen/tests/mochitests/remote-settings/xpcshell.toml
@@ -0,0 +1,50 @@
+[DEFAULT]
+head = "../../../../services/common/tests/unit/head_global.js ../../../../services/common/tests/unit/head_helpers.js head_settings.js"
+firefox-appdir = "browser"
+tags = "remote-settings"
+support-files = ["test_remote_settings_signatures/**"]
+skip-if = [
+  "appname == 'thunderbird'", # Bug 1662758 - these tests don't pass if default bucket isn't "main".
+]
+
+["test_attachments_downloader.js"]
+support-files = ["test_attachments_downloader/**"]
+
+["test_remote_settings.js"]
+
+["test_remote_settings_dump_lastmodified.js"]
+
+["test_remote_settings_jexl_filters.js"]
+
+["test_remote_settings_offline.js"]
+
+["test_remote_settings_older_than_local.js"]
+
+["test_remote_settings_poll.js"]
+
+["test_remote_settings_recover_broken.js"]
+
+["test_remote_settings_release_prefs.js"]
+
+["test_remote_settings_signatures.js"]
+
+["test_remote_settings_startup_bundle.js"]
+support-files = ["test_remote_settings_startup_bundle/**"]
+
+["test_remote_settings_sync_history.js"]
+
+["test_remote_settings_utils.js"]
+
+["test_remote_settings_utils_telemetry.js"]
+skip-if = [
+  "os == 'android' && os_version == '14' && arch == 'x86_64'", # Bug 1739463
+]
+
+["test_remote_settings_worker.js"]
+
+["test_shutdown_handling.js"]
+
+["test_uptake_telemetry.js"]
+skip-if = [
+  "os == 'android'", # Bug 2042499
+]
diff --git a/src/zen/tests/mochitests/services-crypto/head_helpers.js b/src/zen/tests/mochitests/services-crypto/head_helpers.js
new file mode 100644
index 000000000..74d459b15
--- /dev/null
+++ b/src/zen/tests/mochitests/services-crypto/head_helpers.js
@@ -0,0 +1,68 @@
+/* import-globals-from ../../../common/tests/unit/head_helpers.js */
+
+var { XPCOMUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/XPCOMUtils.sys.mjs"
+);
+
+try {
+  // In the context of xpcshell tests, there won't be a default AppInfo
+  // eslint-disable-next-line mozilla/use-services
+  Cc["@mozilla.org/xre/app-info;1"].getService(Ci.nsIXULAppInfo);
+} catch (ex) {
+  // Make sure to provide the right OS so crypto loads the right binaries
+  var OS = "XPCShell";
+  if (mozinfo.os == "win") {
+    OS = "WINNT";
+  } else if (mozinfo.os == "mac") {
+    OS = "Darwin";
+  } else {
+    OS = "Linux";
+  }
+
+  const { updateAppInfo } = ChromeUtils.importESModule(
+    "resource://testing-common/AppInfo.sys.mjs"
+  );
+  updateAppInfo({
+    name: "XPCShell",
+    ID: "{3e3ba16c-1675-4e88-b9c8-afef81b3d2ef}",
+    version: "1",
+    platformVersion: "",
+    OS,
+  });
+}
+
+function base64UrlDecode(s) {
+  s = s.replace(/-/g, "+");
+  s = s.replace(/_/g, "/");
+
+  // Replace padding if it was stripped by the sender.
+  // See http://tools.ietf.org/html/rfc4648#section-4
+  switch (s.length % 4) {
+    case 0:
+      break; // No pad chars in this case
+    case 2:
+      s += "==";
+      break; // Two pad chars
+    case 3:
+      s += "=";
+      break; // One pad char
+    default:
+      throw new Error("Illegal base64url string!");
+  }
+
+  // With correct padding restored, apply the standard base64 decoder
+  return atob(s);
+}
+
+/**
+ * Print some debug message to the console. All arguments will be printed,
+ * separated by spaces.
+ *
+ * @param [arg0, arg1, arg2, ...]
+ *        Any number of arguments to print out
+ * Usage: _("Hello World") -> prints "Hello World"
+ * Usage: _(1, 2, 3) -> prints "1 2 3"
+ */
+var _ = function () {
+  print(Array.from(arguments).join(" "));
+};
diff --git a/src/zen/tests/mochitests/services-crypto/test_crypto_crypt.js b/src/zen/tests/mochitests/services-crypto/test_crypto_crypt.js
new file mode 100644
index 000000000..badf0ef4d
--- /dev/null
+++ b/src/zen/tests/mochitests/services-crypto/test_crypto_crypt.js
@@ -0,0 +1,226 @@
+const { WeaveCrypto } = ChromeUtils.importESModule(
+  "moz-src:///services/crypto/modules/WeaveCrypto.sys.mjs"
+);
+
+var cryptoSvc = new WeaveCrypto();
+
+add_task(async function test_key_memoization() {
+  let cryptoGlobal = cryptoSvc._getCrypto();
+  let oldImport = cryptoGlobal.subtle.importKey;
+  if (!oldImport) {
+    _("Couldn't swizzle crypto.subtle.importKey; returning.");
+    return;
+  }
+
+  let iv = cryptoSvc.generateRandomIV();
+  let key = await cryptoSvc.generateRandomKey();
+  let c = 0;
+  cryptoGlobal.subtle.importKey = function (
+    format,
+    keyData,
+    algo,
+    extractable,
+    usages
+  ) {
+    c++;
+    return oldImport.call(
+      cryptoGlobal.subtle,
+      format,
+      keyData,
+      algo,
+      extractable,
+      usages
+    );
+  };
+
+  // Encryption should cause a single counter increment.
+  Assert.equal(c, 0);
+  let cipherText = await cryptoSvc.encrypt("Hello, world.", key, iv);
+  Assert.equal(c, 1);
+  cipherText = await cryptoSvc.encrypt("Hello, world.", key, iv);
+  Assert.equal(c, 1);
+
+  // ... as should decryption.
+  await cryptoSvc.decrypt(cipherText, key, iv);
+  await cryptoSvc.decrypt(cipherText, key, iv);
+  await cryptoSvc.decrypt(cipherText, key, iv);
+  Assert.equal(c, 2);
+
+  // Un-swizzle.
+  cryptoGlobal.subtle.importKey = oldImport;
+});
+
+// Just verify that it gets populated with the correct bytes.
+add_task(async function test_makeUint8Array() {
+  ChromeUtils.importESModule("resource://gre/modules/ctypes.sys.mjs");
+
+  let item1 = cryptoSvc.makeUint8Array("abcdefghi", false);
+  Assert.ok(item1);
+  for (let i = 0; i < 8; ++i) {
+    Assert.equal(item1[i], "abcdefghi".charCodeAt(i));
+  }
+});
+
+add_task(async function test_encrypt_decrypt() {
+  // First, do a normal run with expected usage... Generate a random key and
+  // iv, encrypt and decrypt a string.
+  var iv = cryptoSvc.generateRandomIV();
+  Assert.equal(iv.length, 24);
+
+  var key = await cryptoSvc.generateRandomKey();
+  Assert.equal(key.length, 44);
+
+  var mySecret = "bacon is a vegetable";
+  var cipherText = await cryptoSvc.encrypt(mySecret, key, iv);
+  Assert.equal(cipherText.length, 44);
+
+  var clearText = await cryptoSvc.decrypt(cipherText, key, iv);
+  Assert.equal(clearText.length, 20);
+
+  // Did the text survive the encryption round-trip?
+  Assert.equal(clearText, mySecret);
+  Assert.notEqual(cipherText, mySecret); // just to be explicit
+
+  // Do some more tests with a fixed key/iv, to check for reproducable results.
+  key = "St1tFCor7vQEJNug/465dQ==";
+  iv = "oLjkfrLIOnK2bDRvW4kXYA==";
+
+  _("Testing small IV.");
+  mySecret = "YWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4eXo=";
+  let shortiv = "YWJj";
+  let err;
+  try {
+    await cryptoSvc.encrypt(mySecret, key, shortiv);
+  } catch (ex) {
+    err = ex;
+  }
+  Assert.ok(!!err);
+
+  _("Testing long IV.");
+  let longiv = "gsgLRDaxWvIfKt75RjuvFWERt83FFsY2A0TW+0b2iVk=";
+  try {
+    await cryptoSvc.encrypt(mySecret, key, longiv);
+  } catch (ex) {
+    err = ex;
+  }
+  Assert.ok(!!err);
+
+  // Test small input sizes
+  mySecret = "";
+  cipherText = await cryptoSvc.encrypt(mySecret, key, iv);
+  clearText = await cryptoSvc.decrypt(cipherText, key, iv);
+  Assert.equal(cipherText, "OGQjp6mK1a3fs9k9Ml4L3w==");
+  Assert.equal(clearText, mySecret);
+
+  mySecret = "x";
+  cipherText = await cryptoSvc.encrypt(mySecret, key, iv);
+  clearText = await cryptoSvc.decrypt(cipherText, key, iv);
+  Assert.equal(cipherText, "96iMl4vhOxFUW/lVHHzVqg==");
+  Assert.equal(clearText, mySecret);
+
+  mySecret = "xx";
+  cipherText = await cryptoSvc.encrypt(mySecret, key, iv);
+  clearText = await cryptoSvc.decrypt(cipherText, key, iv);
+  Assert.equal(cipherText, "olpPbETRYROCSqFWcH2SWg==");
+  Assert.equal(clearText, mySecret);
+
+  mySecret = "xxx";
+  cipherText = await cryptoSvc.encrypt(mySecret, key, iv);
+  clearText = await cryptoSvc.decrypt(cipherText, key, iv);
+  Assert.equal(cipherText, "rRbpHGyVSZizLX/x43Wm+Q==");
+  Assert.equal(clearText, mySecret);
+
+  mySecret = "xxxx";
+  cipherText = await cryptoSvc.encrypt(mySecret, key, iv);
+  clearText = await cryptoSvc.decrypt(cipherText, key, iv);
+  Assert.equal(cipherText, "HeC7miVGDcpxae9RmiIKAw==");
+  Assert.equal(clearText, mySecret);
+
+  // Test non-ascii input
+  // ("testuser1" using similar-looking glyphs)
+  mySecret = String.fromCharCode(355, 277, 349, 357, 533, 537, 101, 345, 185);
+  cipherText = await cryptoSvc.encrypt(mySecret, key, iv);
+  clearText = await cryptoSvc.decrypt(cipherText, key, iv);
+  Assert.equal(cipherText, "Pj4ixByXoH3SU3JkOXaEKPgwRAWplAWFLQZkpJd5Kr4=");
+  Assert.equal(clearText, mySecret);
+
+  // Tests input spanning a block boundary (AES block size is 16 bytes)
+  mySecret = "123456789012345";
+  cipherText = await cryptoSvc.encrypt(mySecret, key, iv);
+  clearText = await cryptoSvc.decrypt(cipherText, key, iv);
+  Assert.equal(cipherText, "e6c5hwphe45/3VN/M0bMUA==");
+  Assert.equal(clearText, mySecret);
+
+  mySecret = "1234567890123456";
+  cipherText = await cryptoSvc.encrypt(mySecret, key, iv);
+  clearText = await cryptoSvc.decrypt(cipherText, key, iv);
+  Assert.equal(cipherText, "V6aaOZw8pWlYkoIHNkhsP1JOIQF87E2vTUvBUQnyV04=");
+  Assert.equal(clearText, mySecret);
+
+  mySecret = "12345678901234567";
+  cipherText = await cryptoSvc.encrypt(mySecret, key, iv);
+  clearText = await cryptoSvc.decrypt(cipherText, key, iv);
+  Assert.equal(cipherText, "V6aaOZw8pWlYkoIHNkhsP5GvxWJ9+GIAS6lXw+5fHTI=");
+  Assert.equal(clearText, mySecret);
+
+  key = "iz35tuIMq4/H+IYw2KTgow==";
+  iv = "TJYrvva2KxvkM8hvOIvWp3==";
+  mySecret = "i like pie";
+
+  cipherText = await cryptoSvc.encrypt(mySecret, key, iv);
+  clearText = await cryptoSvc.decrypt(cipherText, key, iv);
+  Assert.equal(cipherText, "DLGx8BWqSCLGG7i/xwvvxg==");
+  Assert.equal(clearText, mySecret);
+
+  key = "c5hG3YG+NC61FFy8NOHQak1ZhMEWO79bwiAfar2euzI=";
+  iv = "gsgLRDaxWvIfKt75RjuvFW==";
+  mySecret = "i like pie";
+
+  cipherText = await cryptoSvc.encrypt(mySecret, key, iv);
+  clearText = await cryptoSvc.decrypt(cipherText, key, iv);
+  Assert.equal(cipherText, "o+ADtdMd8ubzNWurS6jt0Q==");
+  Assert.equal(clearText, mySecret);
+
+  key = "St1tFCor7vQEJNug/465dQ==";
+  iv = "oLjkfrLIOnK2bDRvW4kXYA==";
+  mySecret = "does thunder read testcases?";
+  cipherText = await cryptoSvc.encrypt(mySecret, key, iv);
+  Assert.equal(cipherText, "T6fik9Ros+DB2ablH9zZ8FWZ0xm/szSwJjIHZu7sjPs=");
+
+  var badkey = "badkeybadkeybadkeybadk==";
+  var badiv = "badivbadivbadivbadivbad=";
+  var badcipher = "crapinputcrapinputcrapinputcrapinputcrapinp=";
+  var failure;
+
+  try {
+    failure = false;
+    clearText = await cryptoSvc.decrypt(cipherText, badkey, iv);
+  } catch (e) {
+    failure = true;
+  }
+  Assert.ok(failure);
+
+  try {
+    failure = false;
+    clearText = await cryptoSvc.decrypt(cipherText, key, badiv);
+  } catch (e) {
+    failure = true;
+  }
+  Assert.ok(failure);
+
+  try {
+    failure = false;
+    clearText = await cryptoSvc.decrypt(cipherText, badkey, badiv);
+  } catch (e) {
+    failure = true;
+  }
+  Assert.ok(failure);
+
+  try {
+    failure = false;
+    clearText = await cryptoSvc.decrypt(badcipher, key, iv);
+  } catch (e) {
+    failure = true;
+  }
+  Assert.ok(failure);
+});
diff --git a/src/zen/tests/mochitests/services-crypto/test_crypto_random.js b/src/zen/tests/mochitests/services-crypto/test_crypto_random.js
new file mode 100644
index 000000000..55d0037b6
--- /dev/null
+++ b/src/zen/tests/mochitests/services-crypto/test_crypto_random.js
@@ -0,0 +1,52 @@
+const { WeaveCrypto } = ChromeUtils.importESModule(
+  "moz-src:///services/crypto/modules/WeaveCrypto.sys.mjs"
+);
+
+var cryptoSvc = new WeaveCrypto();
+
+add_task(async function test_crypto_random() {
+  if (this.gczeal) {
+    _("Running crypto random tests with gczeal(2).");
+    gczeal(2);
+  }
+
+  // Test salt generation.
+  var salt;
+
+  salt = cryptoSvc.generateRandomBytes(0);
+  Assert.equal(salt.length, 0);
+  salt = cryptoSvc.generateRandomBytes(1);
+  Assert.equal(salt.length, 4);
+  salt = cryptoSvc.generateRandomBytes(2);
+  Assert.equal(salt.length, 4);
+  salt = cryptoSvc.generateRandomBytes(3);
+  Assert.equal(salt.length, 4);
+  salt = cryptoSvc.generateRandomBytes(4);
+  Assert.equal(salt.length, 8);
+  salt = cryptoSvc.generateRandomBytes(8);
+  Assert.equal(salt.length, 12);
+
+  // sanity check to make sure salts seem random
+  var salt2 = cryptoSvc.generateRandomBytes(8);
+  Assert.equal(salt2.length, 12);
+  Assert.notEqual(salt, salt2);
+
+  salt = cryptoSvc.generateRandomBytes(1024);
+  Assert.equal(salt.length, 1368);
+  salt = cryptoSvc.generateRandomBytes(16);
+  Assert.equal(salt.length, 24);
+
+  // Test random key generation
+  var keydata, keydata2, iv;
+
+  keydata = await cryptoSvc.generateRandomKey();
+  Assert.equal(keydata.length, 44);
+  keydata2 = await cryptoSvc.generateRandomKey();
+  Assert.notEqual(keydata, keydata2); // sanity check for randomness
+  iv = cryptoSvc.generateRandomIV();
+  Assert.equal(iv.length, 24);
+
+  if (this.gczeal) {
+    gczeal(0);
+  }
+});
diff --git a/src/zen/tests/mochitests/services-crypto/test_jwcrypto.js b/src/zen/tests/mochitests/services-crypto/test_jwcrypto.js
new file mode 100644
index 000000000..04a30cd25
--- /dev/null
+++ b/src/zen/tests/mochitests/services-crypto/test_jwcrypto.js
@@ -0,0 +1,51 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  jwcrypto: "moz-src:///services/crypto/modules/jwcrypto.sys.mjs",
+});
+
+// Enable logging from jwcrypto.sys.mjs.
+Services.prefs.setStringPref("services.crypto.jwcrypto.log.level", "Debug");
+
+add_task(async function test_jwe_roundtrip_ecdh_es_encryption() {
+  const plaintext = crypto.getRandomValues(new Uint8Array(123));
+  const remoteKey = await crypto.subtle.generateKey(
+    {
+      name: "ECDH",
+      namedCurve: "P-256",
+    },
+    true,
+    ["deriveKey"]
+  );
+  const remoteJWK = await crypto.subtle.exportKey("jwk", remoteKey.publicKey);
+  delete remoteJWK.key_ops;
+  const jwe = await jwcrypto.generateJWE(remoteJWK, plaintext);
+  const decrypted = await jwcrypto.decryptJWE(jwe, remoteKey.privateKey);
+  Assert.deepEqual(plaintext, decrypted);
+});
+
+add_task(async function test_jwe_header_includes_key_id() {
+  const plaintext = crypto.getRandomValues(new Uint8Array(123));
+  const remoteKey = await crypto.subtle.generateKey(
+    {
+      name: "ECDH",
+      namedCurve: "P-256",
+    },
+    true,
+    ["deriveKey"]
+  );
+  const remoteJWK = await crypto.subtle.exportKey("jwk", remoteKey.publicKey);
+  delete remoteJWK.key_ops;
+  remoteJWK.kid = "key identifier";
+  const jwe = await jwcrypto.generateJWE(remoteJWK, plaintext);
+  let [header /* other items deliberately ignored */] = jwe.split(".");
+  header = JSON.parse(
+    new TextDecoder().decode(
+      ChromeUtils.base64URLDecode(header, { padding: "reject" })
+    )
+  );
+  Assert.equal(header.kid, "key identifier");
+});
diff --git a/src/zen/tests/mochitests/services-crypto/test_utils_hawk.js b/src/zen/tests/mochitests/services-crypto/test_utils_hawk.js
new file mode 100644
index 000000000..6faef5d68
--- /dev/null
+++ b/src/zen/tests/mochitests/services-crypto/test_utils_hawk.js
@@ -0,0 +1,346 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { CryptoUtils } = ChromeUtils.importESModule(
+  "moz-src:///services/crypto/modules/utils.sys.mjs"
+);
+
+function run_test() {
+  initTestLogging();
+
+  run_next_test();
+}
+
+add_task(async function test_hawk() {
+  let compute = CryptoUtils.computeHAWK;
+
+  let method = "POST";
+  let ts = 1353809207;
+  let nonce = "Ygvqdz";
+
+  let credentials = {
+    id: "123456",
+    key: "2983d45yun89q",
+  };
+
+  let uri_https = CommonUtils.makeURI(
+    "https://example.net/somewhere/over/the/rainbow"
+  );
+  let opts = {
+    credentials,
+    ext: "Bazinga!",
+    ts,
+    nonce,
+    payload: "something to write about",
+    contentType: "text/plain",
+  };
+
+  let result = await compute(uri_https, method, opts);
+  Assert.equal(
+    result.field,
+    'Hawk id="123456", ts="1353809207", nonce="Ygvqdz", ' +
+      'hash="2QfCt3GuY9HQnHWyWD3wX68ZOKbynqlfYmuO2ZBRqtY=", ' +
+      'ext="Bazinga!", ' +
+      'mac="q1CwFoSHzPZSkbIvl0oYlD+91rBUEvFk763nMjMndj8="'
+  );
+  Assert.equal(result.artifacts.ts, ts);
+  Assert.equal(result.artifacts.nonce, nonce);
+  Assert.equal(result.artifacts.method, method);
+  Assert.equal(result.artifacts.resource, "/somewhere/over/the/rainbow");
+  Assert.equal(result.artifacts.host, "example.net");
+  Assert.equal(result.artifacts.port, 443);
+  Assert.equal(
+    result.artifacts.hash,
+    "2QfCt3GuY9HQnHWyWD3wX68ZOKbynqlfYmuO2ZBRqtY="
+  );
+  Assert.equal(result.artifacts.ext, "Bazinga!");
+
+  let opts_noext = {
+    credentials,
+    ts,
+    nonce,
+    payload: "something to write about",
+    contentType: "text/plain",
+  };
+  result = await compute(uri_https, method, opts_noext);
+  Assert.equal(
+    result.field,
+    'Hawk id="123456", ts="1353809207", nonce="Ygvqdz", ' +
+      'hash="2QfCt3GuY9HQnHWyWD3wX68ZOKbynqlfYmuO2ZBRqtY=", ' +
+      'mac="HTgtd0jPI6E4izx8e4OHdO36q00xFCU0FolNq3RiCYs="'
+  );
+  Assert.equal(result.artifacts.ts, ts);
+  Assert.equal(result.artifacts.nonce, nonce);
+  Assert.equal(result.artifacts.method, method);
+  Assert.equal(result.artifacts.resource, "/somewhere/over/the/rainbow");
+  Assert.equal(result.artifacts.host, "example.net");
+  Assert.equal(result.artifacts.port, 443);
+  Assert.equal(
+    result.artifacts.hash,
+    "2QfCt3GuY9HQnHWyWD3wX68ZOKbynqlfYmuO2ZBRqtY="
+  );
+
+  /* Leaving optional fields out should work, although of course then we can't
+   * assert much about the resulting hashes. The resulting header should look
+   * roughly like:
+   * Hawk id="123456", ts="1378764955", nonce="QkynqsrS44M=", mac="/C5NsoAs2fVn+d/I5wMfwe2Gr1MZyAJ6pFyDHG4Gf9U="
+   */
+
+  result = await compute(uri_https, method, { credentials });
+  let fields = result.field.split(" ");
+  Assert.equal(fields[0], "Hawk");
+  Assert.equal(fields[1], 'id="123456",'); // from creds.id
+  Assert.ok(fields[2].startsWith('ts="'));
+  /* The HAWK spec calls for seconds-since-epoch, not ms-since-epoch.
+   * Warning: this test will fail in the year 33658, and for time travellers
+   * who journey earlier than 2001. Please plan accordingly. */
+  Assert.greater(result.artifacts.ts, 1000 * 1000 * 1000);
+  Assert.less(result.artifacts.ts, 1000 * 1000 * 1000 * 1000);
+  Assert.ok(fields[3].startsWith('nonce="'));
+  Assert.equal(fields[3].length, 'nonce="12345678901=",'.length);
+  Assert.equal(result.artifacts.nonce.length, "12345678901=".length);
+
+  let result2 = await compute(uri_https, method, { credentials });
+  Assert.notEqual(result.artifacts.nonce, result2.artifacts.nonce);
+
+  /* Using an upper-case URI hostname shouldn't affect the hash. */
+
+  let uri_https_upper = CommonUtils.makeURI(
+    "https://EXAMPLE.NET/somewhere/over/the/rainbow"
+  );
+  result = await compute(uri_https_upper, method, opts);
+  Assert.equal(
+    result.field,
+    'Hawk id="123456", ts="1353809207", nonce="Ygvqdz", ' +
+      'hash="2QfCt3GuY9HQnHWyWD3wX68ZOKbynqlfYmuO2ZBRqtY=", ' +
+      'ext="Bazinga!", ' +
+      'mac="q1CwFoSHzPZSkbIvl0oYlD+91rBUEvFk763nMjMndj8="'
+  );
+
+  /* Using a lower-case method name shouldn't affect the hash. */
+  result = await compute(uri_https_upper, method.toLowerCase(), opts);
+  Assert.equal(
+    result.field,
+    'Hawk id="123456", ts="1353809207", nonce="Ygvqdz", ' +
+      'hash="2QfCt3GuY9HQnHWyWD3wX68ZOKbynqlfYmuO2ZBRqtY=", ' +
+      'ext="Bazinga!", ' +
+      'mac="q1CwFoSHzPZSkbIvl0oYlD+91rBUEvFk763nMjMndj8="'
+  );
+
+  /* The localtimeOffsetMsec field should be honored. HAWK uses this to
+   * compensate for clock skew between client and server: if the request is
+   * rejected with a timestamp out-of-range error, the error includes the
+   * server's time, and the client computes its clock offset and tries again.
+   * Clients can remember this offset for a while.
+   */
+
+  result = await compute(uri_https, method, {
+    credentials,
+    now: 1378848968650,
+  });
+  Assert.equal(result.artifacts.ts, 1378848968);
+
+  result = await compute(uri_https, method, {
+    credentials,
+    now: 1378848968650,
+    localtimeOffsetMsec: 1000 * 1000,
+  });
+  Assert.equal(result.artifacts.ts, 1378848968 + 1000);
+
+  /* Search/query-args in URIs should be included in the hash. */
+  let makeURI = CommonUtils.makeURI;
+  result = await compute(makeURI("http://example.net/path"), method, opts);
+  Assert.equal(result.artifacts.resource, "/path");
+  Assert.equal(
+    result.artifacts.mac,
+    "WyKHJjWaeYt8aJD+H9UeCWc0Y9C+07ooTmrcrOW4MPI="
+  );
+
+  result = await compute(makeURI("http://example.net/path/"), method, opts);
+  Assert.equal(result.artifacts.resource, "/path/");
+  Assert.equal(
+    result.artifacts.mac,
+    "xAYp2MgZQFvTKJT9u8nsvMjshCRRkuaeYqQbYSFp9Qw="
+  );
+
+  result = await compute(
+    makeURI("http://example.net/path?query=search"),
+    method,
+    opts
+  );
+  Assert.equal(result.artifacts.resource, "/path?query=search");
+  Assert.equal(
+    result.artifacts.mac,
+    "C06a8pip2rA4QkBiosEmC32WcgFcW/R5SQC6kUWyqho="
+  );
+
+  /* Test handling of the payload, which is supposed to be a bytestring
+  (String with codepoints from U+0000 to U+00FF, pre-encoded). */
+
+  result = await compute(makeURI("http://example.net/path"), method, {
+    credentials,
+    ts: 1353809207,
+    nonce: "Ygvqdz",
+  });
+  Assert.equal(result.artifacts.hash, undefined);
+  Assert.equal(
+    result.artifacts.mac,
+    "S3f8E4hAURAqJxOlsYugkPZxLoRYrClgbSQ/3FmKMbY="
+  );
+
+  // Empty payload changes nothing.
+  result = await compute(makeURI("http://example.net/path"), method, {
+    credentials,
+    ts: 1353809207,
+    nonce: "Ygvqdz",
+    payload: null,
+  });
+  Assert.equal(result.artifacts.hash, undefined);
+  Assert.equal(
+    result.artifacts.mac,
+    "S3f8E4hAURAqJxOlsYugkPZxLoRYrClgbSQ/3FmKMbY="
+  );
+
+  result = await compute(makeURI("http://example.net/path"), method, {
+    credentials,
+    ts: 1353809207,
+    nonce: "Ygvqdz",
+    payload: "hello",
+  });
+  Assert.equal(
+    result.artifacts.hash,
+    "uZJnFj0XVBA6Rs1hEvdIDf8NraM0qRNXdFbR3NEQbVA="
+  );
+  Assert.equal(
+    result.artifacts.mac,
+    "pLsHHzngIn5CTJhWBtBr+BezUFvdd/IadpTp/FYVIRM="
+  );
+
+  // update, utf-8 payload
+  result = await compute(makeURI("http://example.net/path"), method, {
+    credentials,
+    ts: 1353809207,
+    nonce: "Ygvqdz",
+    payload: "andré@example.org", // non-ASCII
+  });
+  Assert.equal(
+    result.artifacts.hash,
+    "66DiyapJ0oGgj09IXWdMv8VCg9xk0PL5RqX7bNnQW2k="
+  );
+  Assert.equal(
+    result.artifacts.mac,
+    "2B++3x5xfHEZbPZGDiK3IwfPZctkV4DUr2ORg1vIHvk="
+  );
+
+  /* If "hash" is provided, "payload" is ignored. */
+  result = await compute(makeURI("http://example.net/path"), method, {
+    credentials,
+    ts: 1353809207,
+    nonce: "Ygvqdz",
+    hash: "66DiyapJ0oGgj09IXWdMv8VCg9xk0PL5RqX7bNnQW2k=",
+    payload: "something else",
+  });
+  Assert.equal(
+    result.artifacts.hash,
+    "66DiyapJ0oGgj09IXWdMv8VCg9xk0PL5RqX7bNnQW2k="
+  );
+  Assert.equal(
+    result.artifacts.mac,
+    "2B++3x5xfHEZbPZGDiK3IwfPZctkV4DUr2ORg1vIHvk="
+  );
+
+  // the payload "hash" is also non-urlsafe base64 (+/)
+  result = await compute(makeURI("http://example.net/path"), method, {
+    credentials,
+    ts: 1353809207,
+    nonce: "Ygvqdz",
+    payload: "something else",
+  });
+  Assert.equal(
+    result.artifacts.hash,
+    "lERFXr/IKOaAoYw+eBseDUSwmqZTX0uKZpcWLxsdzt8="
+  );
+  Assert.equal(
+    result.artifacts.mac,
+    "jiZuhsac35oD7IdcblhFncBr8tJFHcwWLr8NIYWr9PQ="
+  );
+
+  /* Test non-ascii hostname. HAWK (via the node.js "url" module) punycodes
+   * "ëxample.net" into "xn--xample-ova.net" before hashing. I still think
+   * punycode was a bad joke that got out of the lab and into a spec.
+   */
+
+  result = await compute(makeURI("http://ëxample.net/path"), method, {
+    credentials,
+    ts: 1353809207,
+    nonce: "Ygvqdz",
+  });
+  Assert.equal(
+    result.artifacts.mac,
+    "pILiHl1q8bbNQIdaaLwAFyaFmDU70MGehFuCs3AA5M0="
+  );
+  Assert.equal(result.artifacts.host, "xn--xample-ova.net");
+
+  result = await compute(makeURI("http://example.net/path"), method, {
+    credentials,
+    ts: 1353809207,
+    nonce: "Ygvqdz",
+    ext: 'backslash=\\ quote=" EOF',
+  });
+  Assert.equal(
+    result.artifacts.mac,
+    "BEMW76lwaJlPX4E/dajF970T6+GzWvaeyLzUt8eOTOc="
+  );
+  Assert.equal(
+    result.field,
+    'Hawk id="123456", ts="1353809207", nonce="Ygvqdz", ext="backslash=\\\\ quote=\\" EOF", mac="BEMW76lwaJlPX4E/dajF970T6+GzWvaeyLzUt8eOTOc="'
+  );
+
+  result = await compute(makeURI("http://example.net:1234/path"), method, {
+    credentials,
+    ts: 1353809207,
+    nonce: "Ygvqdz",
+  });
+  Assert.equal(
+    result.artifacts.mac,
+    "6D3JSFDtozuq8QvJTNUc1JzeCfy6h5oRvlhmSTPv6LE="
+  );
+  Assert.equal(
+    result.field,
+    'Hawk id="123456", ts="1353809207", nonce="Ygvqdz", mac="6D3JSFDtozuq8QvJTNUc1JzeCfy6h5oRvlhmSTPv6LE="'
+  );
+
+  /* HAWK (the node.js library) uses a URL parser which stores the "port"
+   * field as a string, but makeURI() gives us an integer. So we'll diverge
+   * on ports with a leading zero. This test vector would fail on the node.js
+   * library (HAWK-1.1.1), where they get a MAC of
+   * "T+GcAsDO8GRHIvZLeepSvXLwDlFJugcZroAy9+uAtcw=". I think HAWK should be
+   * updated to do what we do here, so port="01234" should get the same hash
+   * as port="1234".
+   */
+  result = await compute(makeURI("http://example.net:01234/path"), method, {
+    credentials,
+    ts: 1353809207,
+    nonce: "Ygvqdz",
+  });
+  Assert.equal(
+    result.artifacts.mac,
+    "6D3JSFDtozuq8QvJTNUc1JzeCfy6h5oRvlhmSTPv6LE="
+  );
+  Assert.equal(
+    result.field,
+    'Hawk id="123456", ts="1353809207", nonce="Ygvqdz", mac="6D3JSFDtozuq8QvJTNUc1JzeCfy6h5oRvlhmSTPv6LE="'
+  );
+});
+
+add_test(function test_strip_header_attributes() {
+  let strip = CryptoUtils.stripHeaderAttributes;
+
+  Assert.equal(strip(undefined), "");
+  Assert.equal(strip("text/plain"), "text/plain");
+  Assert.equal(strip("TEXT/PLAIN"), "text/plain");
+  Assert.equal(strip("  text/plain  "), "text/plain");
+  Assert.equal(strip("text/plain ; charset=utf-8  "), "text/plain");
+
+  run_next_test();
+});
diff --git a/src/zen/tests/mochitests/services-crypto/test_utils_httpmac.js b/src/zen/tests/mochitests/services-crypto/test_utils_httpmac.js
new file mode 100644
index 000000000..ced519b6a
--- /dev/null
+++ b/src/zen/tests/mochitests/services-crypto/test_utils_httpmac.js
@@ -0,0 +1,73 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { CryptoUtils } = ChromeUtils.importESModule(
+  "moz-src:///services/crypto/modules/utils.sys.mjs"
+);
+
+add_test(function setup() {
+  initTestLogging();
+  run_next_test();
+});
+
+add_task(async function test_sha1() {
+  _("Ensure HTTP MAC SHA1 generation works as expected.");
+
+  let id = "vmo1txkttblmn51u2p3zk2xiy16hgvm5ok8qiv1yyi86ffjzy9zj0ez9x6wnvbx7";
+  let key = "b8u1cc5iiio5o319og7hh8faf2gi5ym4aq0zwf112cv1287an65fudu5zj7zo7dz";
+  let ts = 1329181221;
+  let method = "GET";
+  let nonce = "wGX71";
+  let uri = CommonUtils.makeURI("http://10.250.2.176/alias/");
+
+  let result = await CryptoUtils.computeHTTPMACSHA1(id, key, method, uri, {
+    ts,
+    nonce,
+  });
+
+  Assert.equal(btoa(result.mac), "jzh5chjQc2zFEvLbyHnPdX11Yck=");
+
+  Assert.equal(
+    result.getHeader(),
+    'MAC id="vmo1txkttblmn51u2p3zk2xiy16hgvm5ok8qiv1yyi86ffjzy9zj0ez9x6wnvbx7", ' +
+      'ts="1329181221", nonce="wGX71", mac="jzh5chjQc2zFEvLbyHnPdX11Yck="'
+  );
+
+  let ext = "EXTRA DATA; foo,bar=1";
+
+  result = await CryptoUtils.computeHTTPMACSHA1(id, key, method, uri, {
+    ts,
+    nonce,
+    ext,
+  });
+  Assert.equal(btoa(result.mac), "bNf4Fnt5k6DnhmyipLPkuZroH68=");
+  Assert.equal(
+    result.getHeader(),
+    'MAC id="vmo1txkttblmn51u2p3zk2xiy16hgvm5ok8qiv1yyi86ffjzy9zj0ez9x6wnvbx7", ' +
+      'ts="1329181221", nonce="wGX71", mac="bNf4Fnt5k6DnhmyipLPkuZroH68=", ' +
+      'ext="EXTRA DATA; foo,bar=1"'
+  );
+});
+
+add_task(async function test_nonce_length() {
+  _("Ensure custom nonce lengths are honoured.");
+
+  function get_mac(length) {
+    let uri = CommonUtils.makeURI("http://example.com/");
+    return CryptoUtils.computeHTTPMACSHA1("foo", "bar", "GET", uri, {
+      nonce_bytes: length,
+    });
+  }
+
+  let result = await get_mac(12);
+  Assert.equal(12, atob(result.nonce).length);
+
+  result = await get_mac(2);
+  Assert.equal(2, atob(result.nonce).length);
+
+  result = await get_mac(0);
+  Assert.equal(8, atob(result.nonce).length);
+
+  result = await get_mac(-1);
+  Assert.equal(8, atob(result.nonce).length);
+});
diff --git a/src/zen/tests/mochitests/services-crypto/xpcshell.toml b/src/zen/tests/mochitests/services-crypto/xpcshell.toml
new file mode 100644
index 000000000..55529eb2c
--- /dev/null
+++ b/src/zen/tests/mochitests/services-crypto/xpcshell.toml
@@ -0,0 +1,20 @@
+[DEFAULT]
+head = "head_helpers.js ../../../../services/common/tests/unit/head_helpers.js"
+firefox-appdir = "browser"
+support-files = ["!/services/common/tests/unit/head_helpers.js"]
+
+["test_crypto_crypt.js"]
+
+["test_crypto_random.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_jwcrypto.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_utils_hawk.js"]
+
+["test_utils_httpmac.js"]
diff --git a/src/zen/tests/mochitests/sessionstore/SessionStoreTestUtils.sys.mjs b/src/zen/tests/mochitests/sessionstore/SessionStoreTestUtils.sys.mjs
new file mode 100644
index 000000000..889245172
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/SessionStoreTestUtils.sys.mjs
@@ -0,0 +1,197 @@
+const lazy = {};
+ChromeUtils.defineESModuleGetters(lazy, {
+  BrowserTestUtils: "resource://testing-common/BrowserTestUtils.sys.mjs",
+  SessionStore: "resource:///modules/sessionstore/SessionStore.sys.mjs",
+  TabStateFlusher: "resource:///modules/sessionstore/TabStateFlusher.sys.mjs",
+  TestUtils: "resource://testing-common/TestUtils.sys.mjs",
+});
+
+export var SessionStoreTestUtils = {
+  /**
+   * Running this init allows helpers to access test scope helpers, like Assert
+   * and SimpleTest.
+   * Tests should call this init() before using the helpers which rely on properties assign here.
+   *
+   * @param {object} scope The global scope where tests are being run.
+   * @param {DOMWindow} windowGlobal The global window object, for acessing gBrowser etc.
+   */
+  init(scope, windowGlobal) {
+    if (!scope) {
+      throw new Error(
+        "Must initialize SessionStoreTestUtils with a test scope"
+      );
+    }
+    if (!windowGlobal) {
+      throw new Error("this.windowGlobal must be defined when we init");
+    }
+    this._scopeRef = new WeakRef(scope);
+    this._windowGlobalRef = new WeakRef(windowGlobal);
+  },
+
+  get info() {
+    return this._scopeRef.deref()?.info;
+  },
+
+  get registerCleanupFunction() {
+    return this._scopeRef.deref()?.registerCleanupFunction;
+  },
+
+  get windowGlobal() {
+    return this._windowGlobalRef.deref();
+  },
+
+  async closeTab(tab) {
+    await lazy.TabStateFlusher.flush(tab.linkedBrowser);
+    let sessionUpdatePromise =
+      lazy.BrowserTestUtils.waitForSessionStoreUpdate(tab);
+    lazy.BrowserTestUtils.removeTab(tab);
+    await sessionUpdatePromise;
+  },
+
+  async openAndCloseTab(window, url) {
+    let { updatePromise } = await lazy.BrowserTestUtils.withNewTab(
+      { url, gBrowser: window.gBrowser },
+      async browser => {
+        return {
+          updatePromise: lazy.BrowserTestUtils.waitForSessionStoreUpdate({
+            linkedBrowser: browser,
+          }),
+        };
+      }
+    );
+    await updatePromise;
+    return lazy.TestUtils.topicObserved("sessionstore-closed-objects-changed");
+  },
+
+  // This assumes that tests will at least have some state/entries
+  waitForBrowserState(aState, aSetStateCallback) {
+    if (typeof aState == "string") {
+      aState = JSON.parse(aState);
+    }
+    if (typeof aState != "object") {
+      throw new TypeError(
+        "Argument must be an object or a JSON representation of an object"
+      );
+    }
+    if (!this.windowGlobal) {
+      throw new Error(
+        "no windowGlobal defined, please call init() first with the scope and window object"
+      );
+    }
+    let windows = [this.windowGlobal];
+    let tabsRestored = 0;
+    let expectedTabsRestored = 0;
+    let expectedWindows = aState.windows.length;
+    let windowsOpen = 1;
+    let listening = false;
+    let windowObserving = false;
+    let restoreHiddenTabs = Services.prefs.getBoolPref(
+      "browser.sessionstore.restore_hidden_tabs"
+    );
+    // This should match the |restoreTabsLazily| value that
+    // SessionStore.restoreWindow() uses.
+    let restoreTabsLazily =
+      Services.prefs.getBoolPref("browser.sessionstore.restore_on_demand") &&
+      Services.prefs.getBoolPref("browser.sessionstore.restore_tabs_lazily");
+
+    aState.windows.forEach(function (winState) {
+      winState.tabs.forEach(function (tabState) {
+        if (!restoreTabsLazily && (restoreHiddenTabs || !tabState.hidden)) {
+          expectedTabsRestored++;
+        }
+      });
+    });
+
+    // If there are only hidden tabs and restoreHiddenTabs = false, we still
+    // expect one of them to be restored because it gets shown automatically.
+    // Otherwise if lazy tab restore there will only be one tab restored per window.
+    if (!expectedTabsRestored) {
+      expectedTabsRestored = 1;
+    } else if (restoreTabsLazily) {
+      expectedTabsRestored = aState.windows.length;
+    }
+
+    function onSSTabRestored() {
+      if (++tabsRestored == expectedTabsRestored) {
+        // Remove the event listener from each window
+        windows.forEach(function (win) {
+          win.gBrowser.tabContainer.removeEventListener(
+            "SSTabRestored",
+            onSSTabRestored,
+            true
+          );
+        });
+        listening = false;
+        SessionStoreTestUtils.info("running " + aSetStateCallback.name);
+        lazy.TestUtils.executeSoon(aSetStateCallback);
+      }
+    }
+
+    // Used to add our listener to further windows so we can catch SSTabRestored
+    // coming from them when creating a multi-window state.
+    function windowObserver(aSubject, aTopic) {
+      if (aTopic == "domwindowopened") {
+        let newWindow = aSubject;
+        newWindow.addEventListener(
+          "load",
+          function () {
+            if (++windowsOpen == expectedWindows) {
+              Services.ww.unregisterNotification(windowObserver);
+              windowObserving = false;
+            }
+
+            // Track this window so we can remove the progress listener later
+            windows.push(newWindow);
+            // Add the progress listener
+            newWindow.gBrowser.tabContainer.addEventListener(
+              "SSTabRestored",
+              onSSTabRestored,
+              true
+            );
+          },
+          { once: true }
+        );
+      }
+    }
+
+    // We only want to register the notification if we expect more than 1 window
+    if (expectedWindows > 1) {
+      this.registerCleanupFunction(function () {
+        if (windowObserving) {
+          Services.ww.unregisterNotification(windowObserver);
+        }
+      });
+      windowObserving = true;
+      Services.ww.registerNotification(windowObserver);
+    }
+
+    this.registerCleanupFunction(function () {
+      if (listening) {
+        windows.forEach(function (win) {
+          win.gBrowser.tabContainer.removeEventListener(
+            "SSTabRestored",
+            onSSTabRestored,
+            true
+          );
+        });
+      }
+    });
+    // Add the event listener for this window as well.
+    listening = true;
+    this.windowGlobal.gBrowser.tabContainer.addEventListener(
+      "SSTabRestored",
+      onSSTabRestored,
+      true
+    );
+
+    // Ensure setBrowserState() doesn't remove the initial tab.
+    this.windowGlobal.gBrowser.selectedTab = this.windowGlobal.gBrowser.tabs[0];
+
+    // Finally, call setBrowserState
+    lazy.SessionStore.setBrowserState(JSON.stringify(aState));
+  },
+
+  promiseBrowserState(aState) {
+    return new Promise(resolve => this.waitForBrowserState(aState, resolve));
+  },
+};
diff --git a/src/zen/tests/mochitests/sessionstore/browser.toml b/src/zen/tests/mochitests/sessionstore/browser.toml
new file mode 100644
index 000000000..f6ab3d6e8
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser.toml
@@ -0,0 +1,483 @@
+[DEFAULT]
+support-files = [
+  "head.js",
+  "browser_formdata_sample.html",
+  "browser_formdata_xpath_sample.html",
+  "browser_frametree_sample.html",
+  "browser_frametree_sample_frameset.html",
+  "browser_frametree_sample_iframes.html",
+  "browser_frame_history_index.html",
+  "browser_frame_history_index2.html",
+  "browser_frame_history_index_blank.html",
+  "browser_frame_history_a.html",
+  "browser_frame_history_b.html",
+  "browser_frame_history_c.html",
+  "browser_frame_history_c1.html",
+  "browser_frame_history_c2.html",
+  "browser_formdata_format_sample.html",
+  "browser_sessionHistory_slow.sjs",
+  "browser_policy_container_sample.html",
+  "browser_policy_container_sample_frame.html",
+  "browser_scrollPositions_sample.html",
+  "browser_scrollPositions_sample2.html",
+  "browser_scrollPositions_sample_frameset.html",
+  "browser_scrollPositions_readerModeArticle.html",
+  "browser_sessionStorage.html",
+  "browser_speculative_connect.html",
+  "coopHeaderCommon.sjs",
+  "restore_redirect_http.html",
+  "restore_redirect_http.html^headers^",
+  "restore_redirect_js.html",
+  "restore_redirect_target.html",
+  "empty.html",
+  "coop_coep.html",
+  "coop_coep.html^headers^",
+]
+# remove this after bug 1628486 is landed
+prefs = [
+  "zen.window-sync.enabled=false",
+  "network.cookie.cookieBehavior=5",
+  "gfx.font_rendering.fallback.async=false",
+  "browser.sessionstore.closedTabsFromAllWindows=true",
+  "browser.sessionstore.closedTabsFromClosedWindows=true",
+  # Override the test default, allowing the session restore infobar to be shown if necessary
+  "browser.startup.couldRestoreSession.count=0",
+]
+
+["browser_1933485_tab_groups_history.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_1953801_tab_groups_history_close_other.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_aboutPrivateBrowsing.js"]
+
+["browser_aboutRestartrequired_noRestore.js"]
+
+["browser_aboutSessionRestore.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_async_duplicate_tab.js"]
+support-files = ["file_async_duplicate_tab.html"]
+
+["browser_async_flushes.js"]
+support-files = ["file_async_flushes.html"]
+run-if = [
+  "crashreporter",
+]
+
+["browser_async_remove_tab.js"]
+skip-if = [
+  "os == 'linux' && os_version == '24.04' && arch == 'x86_64' && display == 'x11' && opt", # Bug 1787024
+  "os == 'win' && os_version == '11.26100' && arch == 'x86_64' && asan", # Bug 1787024
+  "os == 'win' && os_version == '11.26200' && arch == 'x86_64' && asan", # Bug 1787024
+]
+
+["browser_async_window_flushing.js"]
+https_first_disabled = true
+skip-if = [
+  "os == 'mac' && os_version == '10.15' && arch == 'x86_64' && opt", # Bug 1775616
+  "os == 'win' && os_version == '11.26100' && arch == 'x86_64' && asan", # Bug 1775616
+  "os == 'win' && os_version == '11.26200' && arch == 'x86_64' && asan", # Bug 1775616
+  "os == 'win' && os_version == '11.26100' && arch == 'x86_64' && opt", # Bug 1775616
+  "os == 'win' && os_version == '11.26200' && arch == 'x86_64' && opt", # Bug 1775616
+]
+
+["browser_attributes.js"]
+
+["browser_background_tab_crash.js"]
+https_first_disabled = true
+run-if = [
+  "crashreporter",
+]
+tags = "os_integration"
+
+["browser_backup_recovery.js"]
+https_first_disabled = true
+tags = "os_integration"
+
+["browser_bfcache_telemetry.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_broadcast.js"]
+https_first_disabled = true
+
+["browser_capabilities.js"]
+
+["browser_cleaner.js"]
+
+["browser_closedId.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_closed_objects_changed_notifications_tabs.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_closed_objects_changed_notifications_windows.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_closed_tabs_closed_windows.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_closed_tabs_windows.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_cookies.js"]
+
+["browser_cookies_legacy.js"]
+
+["browser_cookies_partitioned.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_cookies_privacy.js"]
+
+["browser_cookies_sameSite.js"]
+
+["browser_crashedTabs.js"]
+disabled="Disabled by import_external_tests.py"
+https_first_disabled = true
+run-if = [
+  "crashreporter",
+]
+
+["browser_csp_policy_container_migration.js"]
+
+["browser_docshell_uuid_consistency.js"]
+
+["browser_duplicate_history.js"]
+
+["browser_duplicate_tab_in_new_window.js"]
+
+["browser_dying_cache.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_dynamic_frames.js"]
+
+["browser_firefoxView_restore.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_firefoxView_selected_restore.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_focus_after_restore.js"]
+tags = "os_integration"
+
+["browser_forget_async_closings.js"]
+
+["browser_forget_closed_tab_window_byId.js"]
+disabled="Disabled by import_external_tests.py"
+https_first_disabled = true
+
+["browser_formdata.js"]
+
+["browser_formdata_cc.js"]
+skip-if = [
+  "asan", # test runs too long
+]
+
+["browser_formdata_face.js"]
+
+["browser_formdata_format.js"]
+
+["browser_formdata_max_size.js"]
+
+["browser_formdata_password.js"]
+support-files = ["file_formdata_password.html"]
+
+["browser_formdata_xpath.js"]
+
+["browser_frame_history.js"]
+
+["browser_frametree.js"]
+https_first_disabled = true
+
+["browser_global_store.js"]
+
+["browser_history_persist.js"]
+
+["browser_ignore_updates_crashed_tabs.js"]
+https_first_disabled = true
+run-if = [
+  "crashreporter",
+]
+skip-if = [
+  "asan",
+]
+
+["browser_label_and_icon.js"]
+https_first_disabled = true
+skip-if = [
+  "os == 'mac' && os_version == '10.15' && arch == 'x86_64' && opt", # Bug 1638958
+  "os == 'mac' && os_version == '14.70' && arch == 'x86_64' && opt && socketprocess_networking", # Bug 1868915
+  "os == 'mac' && os_version == '15.30' && arch == 'aarch64'", # Disabled due to bleedover with other tests when run in regular suites; passes in "failures" jobs
+  "os == 'win' && os_version == '11.26100' && arch == 'x86_64' && opt", # Bug 1775605
+  "os == 'win' && os_version == '11.26200' && arch == 'x86_64' && opt", # Bug 1775605
+]
+
+["browser_movePendingTabToNewWindow.js"]
+disabled="Disabled by import_external_tests.py"
+https_first_disabled = true
+tags = "os_integration"
+
+["browser_multiple_navigateAndRestore.js"]
+
+["browser_multiple_select_after_load.js"]
+
+["browser_navigation_api_restore.js"]
+support-files = [
+  "empty_frame.html",
+  "entry1.html",
+  "entry2.html",
+  "entry3.html",
+]
+
+["browser_newtab_userTypedValue.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_not_collect_when_idle.js"]
+
+["browser_page_title.js"]
+
+["browser_parentProcessRestoreHash.js"]
+https_first_disabled = true
+tags = "openUILinkIn"
+
+["browser_pending_tabs.js"]
+
+["browser_pinned_tabs.js"]
+disabled="Disabled by import_external_tests.py"
+skip-if = [
+  "ccov", # Bug 1625525
+]
+
+["browser_policy_container_not_stored.js"]
+
+["browser_privatetabs.js"]
+
+["browser_purge_domaindata.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_purge_shistory.js"]
+
+["browser_remoteness_flip_on_restore.js"]
+
+["browser_reopen_all_windows.js"]
+disabled="Disabled by import_external_tests.py"
+https_first_disabled = true
+skip-if = [
+  "asan", # high memory
+]
+tags = "os_integration"
+
+["browser_replace_load.js"]
+skip-if = [
+  "true", # Bug 1646894
+]
+
+["browser_restoreLastActionCorrectOrder.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_restoreLastClosedTabOrWindowOrSession.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_restoreTabContainer.js"]
+
+["browser_restore_container_tabs_oa.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_restore_cookies_noOriginAttributes.js"]
+
+["browser_restore_pageProxyState.js"]
+
+["browser_restore_private_tab_os.js"]
+
+["browser_restore_redirect.js"]
+https_first_disabled = true
+
+["browser_restore_reversed_z_order.js"]
+skip-if = [
+  "true", # Bug 1455602
+]
+
+["browser_restore_srcdoc.js"]
+
+["browser_restore_tabless_window.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_restore_verticalPinnedTabs.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_restored_window_features.js"]
+disabled="Disabled by import_external_tests.py"
+skip-if = [
+  "os == 'win' && os_version == '11.26200' && asan", # Bug 2019745
+]
+
+["browser_revive_crashed_bg_tabs.js"]
+https_first_disabled = true
+run-if = [
+  "crashreporter",
+]
+
+["browser_scrollPositions.js"]
+disabled="Disabled by import_external_tests.py"
+https_first_disabled = true
+run-if = [
+  "fission",
+]
+
+["browser_scrollPositionsReaderMode.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_searchModeSwitcher_restore.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_sessionHistory.js"]
+https_first_disabled = true
+support-files = ["file_sessionHistory_hashchange.html"]
+
+["browser_sessionHistory_partitionedPrincipalToInherit.js"]
+
+["browser_sessionStorage.js"]
+tags = "os_integration"
+
+["browser_sessionStorage_size.js"]
+
+["browser_sessionStoreContainer.js"]
+
+["browser_should_restore_tab.js"]
+skip-if = [
+  "os == 'linux' && os_version == '24.04' && arch == 'x86_64' && display == 'x11' && debug && socketprocess_networking", # Bug 1848488
+  "os == 'win' && os_version == '11.26100' && arch == 'x86' && debug && verify-standalone",
+  "os == 'win' && os_version == '11.26200' && arch == 'x86' && debug && verify-standalone",
+  "os == 'win' && os_version == '11.26100' && arch == 'x86_64' && debug", # Bug 1848488
+  "os == 'win' && os_version == '11.26200' && arch == 'x86_64' && debug", # Bug 1848488
+]
+
+["browser_sizemodeBeforeMinimized.js"]
+skip-if = [
+  "os == 'win' && os_version == '11.26200' && asan", # Bug 2019745
+]
+
+["browser_speculative_connect.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_splitview_integer_ids.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_splitview_restore_in_closed_window.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_splitview_string_migration.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_swapDocShells.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_switch_remoteness.js"]
+
+["browser_tab_groups_closed.js"]
+disabled="Disabled by import_external_tests.py"
+skip-if = [
+  "os == 'linux' && os_version == '24.04' && arch == 'x86_64' && display == 'x11' && debug && socketprocess_networking", # Bug 1934803
+  "os == 'win' && os_version == '11.26100' && arch == 'x86_64' && debug", # Bug 1934803
+  "os == 'win' && os_version == '11.26200' && arch == 'x86_64' && debug", # Bug 1934803
+]
+
+["browser_tab_groups_closed_groups_in_closed_windows.js"]
+
+["browser_tab_groups_empty.js"]
+
+["browser_tab_groups_restore_closed_in_closed_window.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_tab_groups_restore_closed_in_open_window.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_tab_groups_restore_closed_many_tabs.js"]
+disabled="Disabled by import_external_tests.py"
+skip-if = [
+  "os == 'mac' && os_version == '15.30' && arch == 'aarch64' && opt", # Bug 1954300
+]
+
+["browser_tab_groups_restore_multiple.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_tab_groups_restore_saved.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_tab_groups_restore_simple.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_tab_groups_restore_to_group.js"]
+
+["browser_tab_groups_save_on_removeAllTabsBut.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_tab_groups_save_on_removeTabsToTheEnd.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_tab_groups_save_on_removeTabsToTheStart.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_tab_groups_save_on_window_close.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_tab_groups_saved.js"]
+skip-if = [
+  "os == 'linux' && os_version == '24.04' && arch == 'x86_64' && display == 'x11' && opt", # Bug 1945957
+]
+
+["browser_tab_groups_state.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_tab_groups_undo.js"]
+disabled="Disabled by import_external_tests.py"
+
+skip-if = [
+  "os == 'mac' && os_version == '15.30' && arch == 'aarch64'", # Bug 2023967
+]
+["browser_tab_label_during_restore.js"]
+disabled="Disabled by import_external_tests.py"
+https_first_disabled = true
+
+["browser_tab_notes_canonicalurl.js"]
+
+["browser_tabicon_after_bg_tab_crash.js"]
+run-if = [
+  "crashreporter",
+]
+
+["browser_tabs_in_urlbar.js"]
+https_first_disabled = true
+
+["browser_undoCloseById.js"]
+disabled="Disabled by import_external_tests.py"
+skip-if = [
+  "debug",
+]
+
+["browser_undoCloseById_targetWindow.js"]
+
+["browser_unrestored_crashedTabs.js"]
+run-if = [
+  "crashreporter",
+]
+
+["browser_upgrade_backup.js"]
+skip-if = [
+  "asan",
+  "tsan",
+]
+
+["browser_urlbarSearchMode.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_userTyped_restored_after_discard.js"]
+
+["browser_windowRestore_perwindowpb.js"]
+
+["browser_windowStateContainer.js"]
+disabled="Disabled by import_external_tests.py"
+
+["browser_wireframe_basic.js"]
+disabled="Disabled by import_external_tests.py"
diff --git a/src/zen/tests/mochitests/sessionstore/browser_1234021.js b/src/zen/tests/mochitests/sessionstore/browser_1234021.js
new file mode 100644
index 000000000..f6a95ad68
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_1234021.js
@@ -0,0 +1,22 @@
+"use strict";
+
+const PREF = "network.cookie.cookieBehavior";
+const PAGE_URL =
+  "http://mochi.test:8888/browser/" +
+  "browser/components/sessionstore/test/browser_1234021_page.html";
+const BEHAVIOR_REJECT = 2;
+
+add_task(async function test() {
+  await pushPrefs([PREF, BEHAVIOR_REJECT]);
+
+  await BrowserTestUtils.withNewTab(
+    {
+      gBrowser,
+      url: PAGE_URL,
+    },
+    async function handler(aBrowser) {
+      await TabStateFlusher.flush(aBrowser);
+      ok(true, "Flush didn't time out");
+    }
+  );
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_1234021_page.html b/src/zen/tests/mochitests/sessionstore/browser_1234021_page.html
new file mode 100644
index 000000000..0c3fca84d
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_1234021_page.html
@@ -0,0 +1,6 @@
+<!doctype html>
+<html>
+  <script>
+    sessionStorage;
+  </script>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_1284886_suspend_tab.html b/src/zen/tests/mochitests/sessionstore/browser_1284886_suspend_tab.html
new file mode 100644
index 000000000..ec3edbffd
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_1284886_suspend_tab.html
@@ -0,0 +1,12 @@
+<html>
+<head>
+  <script>
+    window.onbeforeunload = function() {
+      return true;
+    };
+  </script>
+</head>
+<body>
+TEST PAGE
+</body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_1284886_suspend_tab.js b/src/zen/tests/mochitests/sessionstore/browser_1284886_suspend_tab.js
new file mode 100644
index 000000000..3c6a2c1f2
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_1284886_suspend_tab.js
@@ -0,0 +1,95 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+add_task(async function test() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["dom.require_user_interaction_for_beforeunload", false]],
+  });
+
+  let url = "about:robots";
+  let tab0 = gBrowser.tabs[0];
+  let tab1 = await BrowserTestUtils.openNewForegroundTab(gBrowser, url);
+
+  const staleAttributes = [
+    "activemedia-blocked",
+    "busy",
+    "pendingicon",
+    "progress",
+    "soundplaying",
+  ];
+  for (let attr of staleAttributes) {
+    tab0.toggleAttribute(attr, true);
+  }
+  gBrowser.discardBrowser(tab0);
+  ok(!tab0.linkedPanel, "tab0 is suspended");
+  for (let attr of staleAttributes) {
+    ok(
+      !tab0.hasAttribute(attr),
+      `discarding browser removes "${attr}" tab attribute`
+    );
+  }
+
+  await BrowserTestUtils.switchTab(gBrowser, tab0);
+  ok(tab0.linkedPanel, "selecting tab unsuspends it");
+
+  // Test that active tab is not able to be suspended.
+  gBrowser.discardBrowser(tab0);
+  ok(tab0.linkedPanel, "active tab is not able to be suspended");
+
+  // Test that tab that is closing is not able to be suspended.
+  gBrowser._beginRemoveTab(tab1);
+  gBrowser.discardBrowser(tab1);
+
+  ok(tab1.linkedPanel, "cannot suspend a tab that is closing");
+
+  gBrowser._endRemoveTab(tab1);
+
+  // Open tab containing a page which has a beforeunload handler which shows a prompt.
+  url =
+    "http://example.com/browser/browser/components/sessionstore/test/browser_1284886_suspend_tab.html";
+  tab1 = await BrowserTestUtils.openNewForegroundTab(gBrowser, url);
+  await BrowserTestUtils.switchTab(gBrowser, tab0);
+
+  // Test that tab with beforeunload handler which would show a prompt cannot be suspended.
+  gBrowser.discardBrowser(tab1);
+  ok(
+    tab1.linkedPanel,
+    "cannot suspend a tab with beforeunload handler which would show a prompt"
+  );
+
+  // Test that tab with beforeunload handler which would show a prompt will be suspended if forced.
+  gBrowser.discardBrowser(tab1, true);
+  ok(
+    !tab1.linkedPanel,
+    "force suspending a tab with beforeunload handler which would show a prompt"
+  );
+
+  BrowserTestUtils.removeTab(tab1);
+
+  // Open tab containing a page which has a beforeunload handler which does not show a prompt.
+  url =
+    "http://example.com/browser/browser/components/sessionstore/test/browser_1284886_suspend_tab_2.html";
+  tab1 = await BrowserTestUtils.openNewForegroundTab(gBrowser, url);
+  await BrowserTestUtils.switchTab(gBrowser, tab0);
+
+  // Test that tab with beforeunload handler which would not show a prompt can be suspended.
+  gBrowser.discardBrowser(tab1);
+  ok(
+    !tab1.linkedPanel,
+    "can suspend a tab with beforeunload handler which would not show a prompt"
+  );
+
+  BrowserTestUtils.removeTab(tab1);
+
+  // Test that non-remote tab is not able to be suspended.
+  url = "about:robots";
+  tab1 = BrowserTestUtils.addTab(gBrowser, url, { forceNotRemote: true });
+  await promiseBrowserLoaded(tab1.linkedBrowser, true, url);
+  await BrowserTestUtils.switchTab(gBrowser, tab1);
+  await BrowserTestUtils.switchTab(gBrowser, tab0);
+
+  gBrowser.discardBrowser(tab1);
+  ok(tab1.linkedPanel, "cannot suspend a remote tab");
+
+  BrowserTestUtils.removeTab(tab1);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_1284886_suspend_tab_2.html b/src/zen/tests/mochitests/sessionstore/browser_1284886_suspend_tab_2.html
new file mode 100644
index 000000000..5c4291363
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_1284886_suspend_tab_2.html
@@ -0,0 +1,11 @@
+<html>
+<head>
+  <script>
+    window.onbeforeunload = function() {
+    };
+  </script>
+</head>
+<body>
+TEST PAGE
+</body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_1446343-windowsize.js b/src/zen/tests/mochitests/sessionstore/browser_1446343-windowsize.js
new file mode 100644
index 000000000..97f664a46
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_1446343-windowsize.js
@@ -0,0 +1,39 @@
+add_task(async function test() {
+  const win = await BrowserTestUtils.openNewBrowserWindow();
+
+  async function changeSizeMode(mode) {
+    let promise = BrowserTestUtils.waitForEvent(win, "sizemodechange");
+    win[mode]();
+    await promise;
+  }
+  if (win.windowState != win.STATE_NORMAL) {
+    await changeSizeMode("restore");
+  }
+
+  const { outerWidth, outerHeight, screenX, screenY } = win;
+  function checkCurrentState(sizemode) {
+    let state = ss.getWindowState(win);
+    let winState = state.windows[0];
+    let msgSuffix = ` should match on ${sizemode} mode`;
+    is(winState.width, outerWidth, "width" + msgSuffix);
+    is(winState.height, outerHeight, "height" + msgSuffix);
+    // The position attributes seem to be affected on macOS when the
+    // window gets maximized, so skip checking them for now.
+    if (AppConstants.platform != "macosx" || sizemode == "normal") {
+      is(winState.screenX, screenX, "screenX" + msgSuffix);
+      is(winState.screenY, screenY, "screenY" + msgSuffix);
+    }
+    is(winState.sizemode, sizemode, "sizemode should match");
+  }
+
+  checkCurrentState("normal");
+
+  await changeSizeMode("maximize");
+  checkCurrentState("maximized");
+
+  await changeSizeMode("minimize");
+  checkCurrentState("minimized");
+
+  // Clean up.
+  await BrowserTestUtils.closeWindow(win);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_1933485_tab_groups_history.js b/src/zen/tests/mochitests/sessionstore/browser_1933485_tab_groups_history.js
new file mode 100644
index 000000000..c4093127b
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_1933485_tab_groups_history.js
@@ -0,0 +1,43 @@
+"use strict";
+
+const ORIG_STATE = SessionStore.getBrowserState();
+
+registerCleanupFunction(async () => {
+  await SessionStoreTestUtils.promiseBrowserState(ORIG_STATE);
+});
+
+// This test ensures that closed tab groups are immediately stored in the
+// closedGroups array, even if their history was not stored in the tab state at
+// the time the tab group was closed.
+add_task(
+  async function test_browser_1933485_tabGroupImmediatelyStoredInClosedGroups() {
+    let win = await promiseNewWindowLoaded();
+
+    const urls = ["about:blank", "about:robots", "https://www.example.com/"];
+    const tabs = urls.map(url => BrowserTestUtils.addTab(win.gBrowser, url));
+    await Promise.all(
+      tabs.map((t, i) =>
+        BrowserTestUtils.browserLoaded(t.linkedBrowser, { wantLoad: urls[i] })
+      )
+    );
+
+    const tabGroup = win.gBrowser.addTabGroup(tabs);
+
+    let removePromise = BrowserTestUtils.waitForEvent(
+      tabGroup,
+      "TabGroupRemoved"
+    );
+    win.gBrowser.removeTabGroup(tabGroup);
+    await removePromise;
+
+    const closedGroupState = SessionStore.getClosedTabGroups(win);
+
+    Assert.equal(
+      closedGroupState.length,
+      1,
+      "Tab group is stored in closedGroups"
+    );
+
+    await BrowserTestUtils.closeWindow(win);
+  }
+);
diff --git a/src/zen/tests/mochitests/sessionstore/browser_1953801_tab_groups_history_close_other.js b/src/zen/tests/mochitests/sessionstore/browser_1953801_tab_groups_history_close_other.js
new file mode 100644
index 000000000..f1b2e2ae3
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_1953801_tab_groups_history_close_other.js
@@ -0,0 +1,55 @@
+"use strict";
+
+const ORIG_STATE = SessionStore.getBrowserState();
+
+registerCleanupFunction(async () => {
+  await SessionStoreTestUtils.promiseBrowserState(ORIG_STATE);
+});
+
+add_task(
+  async function test_browser_1953801_tabGroupImmediatelyStoredInSavedGroupsOnCloseOtherTabs() {
+    let savedGroupState;
+    let win = await promiseNewWindowLoaded();
+
+    savedGroupState = SessionStore.getSavedTabGroups(win);
+    Assert.equal(
+      savedGroupState.length,
+      0,
+      "Should start with no saved groups"
+    );
+
+    const tabs = [
+      BrowserTestUtils.addTab(win.gBrowser, "about:robots"),
+      BrowserTestUtils.addTab(win.gBrowser, "about:robots"),
+      BrowserTestUtils.addTab(win.gBrowser, "https://www.example.com"),
+    ];
+    await Promise.all(tabs.map(t => promiseBrowserLoaded(t.linkedBrowser)));
+
+    const tabGroup = win.gBrowser.addTabGroup([tabs[1], tabs[2]], {
+      label: "group-to-save",
+    });
+
+    await TestUtils.waitForCondition(
+      () => SessionStore.getWindowState(win).windows[0].groups.length == 1,
+      "Waiting for group to appear in session store"
+    );
+
+    let removePromise = BrowserTestUtils.waitForEvent(
+      tabGroup,
+      "TabGroupRemoved"
+    );
+    win.gBrowser.removeAllTabsBut(win.gBrowser.tabs[0]);
+    await removePromise;
+
+    savedGroupState = SessionStore.getSavedTabGroups(win);
+    Assert.equal(
+      savedGroupState.length,
+      1,
+      "Tab group is stored in saved groups"
+    );
+
+    await BrowserTestUtils.closeWindow(win);
+    forgetClosedWindows();
+    SessionStore.forgetSavedTabGroup(tabGroup.id);
+  }
+);
diff --git a/src/zen/tests/mochitests/sessionstore/browser_248970_b_perwindowpb.js b/src/zen/tests/mochitests/sessionstore/browser_248970_b_perwindowpb.js
new file mode 100644
index 000000000..ffddaf563
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_248970_b_perwindowpb.js
@@ -0,0 +1,199 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+function test() {
+  /** Test (B) for Bug 248970 */
+  waitForExplicitFinish();
+
+  let windowsToClose = [];
+  let file = Services.dirsvc.get("TmpD", Ci.nsIFile);
+  let filePath = file.path;
+  let fieldList = {
+    "//input[@name='input']": Date.now().toString(16),
+    "//input[@name='spaced 1']": Math.random().toString(),
+    "//input[3]": "three",
+    "//input[@type='checkbox']": true,
+    "//input[@name='uncheck']": false,
+    "//input[@type='radio'][1]": false,
+    "//input[@type='radio'][2]": true,
+    "//input[@type='radio'][3]": false,
+    "//select": 2,
+    "//select[@multiple]": [1, 3],
+    "//textarea[1]": "",
+    "//textarea[2]": "Some text... " + Math.random(),
+    "//textarea[3]": "Some more text\n" + new Date(),
+    "//input[@type='file']": filePath,
+  };
+
+  registerCleanupFunction(async function () {
+    for (let win of windowsToClose) {
+      await BrowserTestUtils.closeWindow(win);
+    }
+  });
+
+  function checkNoThrow(aLambda) {
+    try {
+      return aLambda() || true;
+    } catch (ex) {}
+    return false;
+  }
+
+  function getElementByXPath(aTab, aQuery) {
+    let doc = aTab.linkedBrowser.contentDocument;
+    let xptype = doc.defaultView.XPathResult.FIRST_ORDERED_NODE_TYPE;
+    return doc.evaluate(aQuery, doc, null, xptype, null).singleNodeValue;
+  }
+
+  function setFormValue(aTab, aQuery, aValue) {
+    let node = getElementByXPath(aTab, aQuery);
+    if (typeof aValue == "string") {
+      node.value = aValue;
+    } else if (typeof aValue == "boolean") {
+      node.checked = aValue;
+    } else if (typeof aValue == "number") {
+      node.selectedIndex = aValue;
+    } else {
+      Array.prototype.forEach.call(
+        node.options,
+        (aOpt, aIx) => (aOpt.selected = aValue.indexOf(aIx) > -1)
+      );
+    }
+  }
+
+  function compareFormValue(aTab, aQuery, aValue) {
+    let node = getElementByXPath(aTab, aQuery);
+    if (!node) {
+      return false;
+    }
+    if (ChromeUtils.getClassName(node) === "HTMLInputElement") {
+      return (
+        aValue ==
+        (node.type == "checkbox" || node.type == "radio"
+          ? node.checked
+          : node.value)
+      );
+    }
+    if (ChromeUtils.getClassName(node) === "HTMLTextAreaElement") {
+      return aValue == node.value;
+    }
+    if (!node.multiple) {
+      return aValue == node.selectedIndex;
+    }
+    return Array.prototype.every.call(
+      node.options,
+      (aOpt, aIx) => aValue.indexOf(aIx) > -1 == aOpt.selected
+    );
+  }
+
+  /**
+   * Test (B) : Session data restoration between windows
+   */
+
+  let rootDir = getRootDirectory(gTestPath);
+  const testURL = rootDir + "browser_248970_b_sample.html";
+  const testURL2 =
+    "http://mochi.test:8888/browser/" +
+    "browser/components/sessionstore/test/browser_248970_b_sample.html";
+
+  whenNewWindowLoaded({ private: false }, function (aWin) {
+    windowsToClose.push(aWin);
+
+    // get closed tab count
+    let count = ss.getClosedTabCountForWindow(aWin);
+    let max_tabs_undo = Services.prefs.getIntPref(
+      "browser.sessionstore.max_tabs_undo"
+    );
+    ok(
+      0 <= count && count <= max_tabs_undo,
+      "getClosedTabCountForWindow should return zero or at most max_tabs_undo"
+    );
+
+    // setup a state for tab (A) so we can check later that is restored
+    let value = "Value " + Math.random();
+    let state = { entries: [{ url: testURL }], extData: { key: value } };
+
+    // public session, add new tab: (A)
+    let tab_A = BrowserTestUtils.addTab(aWin.gBrowser, testURL);
+    ss.setTabState(tab_A, JSON.stringify(state));
+    promiseBrowserLoaded(tab_A.linkedBrowser).then(() => {
+      // make sure that the next closed tab will increase getClosedTabCountForWindow
+      Services.prefs.setIntPref(
+        "browser.sessionstore.max_tabs_undo",
+        max_tabs_undo + 1
+      );
+
+      // populate tab_A with form data
+      for (let i in fieldList) {
+        setFormValue(tab_A, i, fieldList[i]);
+      }
+
+      // public session, close tab: (A)
+      aWin.gBrowser.removeTab(tab_A);
+
+      // verify that closedTabCount increased
+      Assert.greater(
+        ss.getClosedTabCountForWindow(aWin),
+        count,
+        "getClosedTabCountForWindow has increased after closing a tab"
+      );
+
+      // verify tab: (A), in undo list
+      let tab_A_restored = checkNoThrow(() => ss.undoCloseTab(aWin, 0));
+      ok(tab_A_restored, "a tab is in undo list");
+      promiseTabRestored(tab_A_restored).then(() => {
+        is(
+          testURL,
+          tab_A_restored.linkedBrowser.currentURI.spec,
+          "it's the same tab that we expect"
+        );
+        aWin.gBrowser.removeTab(tab_A_restored);
+
+        whenNewWindowLoaded({ private: true }, function (win) {
+          windowsToClose.push(win);
+
+          // setup a state for tab (B) so we can check that its duplicated
+          // properly
+          let key1 = "key1";
+          let value1 = "Value " + Math.random();
+          let state1 = {
+            entries: [{ url: testURL2 }],
+            extData: { key1: value1 },
+          };
+
+          let tab_B = BrowserTestUtils.addTab(win.gBrowser, testURL2);
+          promiseTabState(tab_B, state1).then(() => {
+            // populate tab: (B) with different form data
+            for (let item in fieldList) {
+              setFormValue(tab_B, item, fieldList[item]);
+            }
+
+            // duplicate tab: (B)
+            let tab_C = win.gBrowser.duplicateTab(tab_B);
+            promiseTabRestored(tab_C).then(() => {
+              // verify the correctness of the duplicated tab
+              is(
+                ss.getCustomTabValue(tab_C, key1),
+                value1,
+                "tab successfully duplicated - correct state"
+              );
+
+              for (let item in fieldList) {
+                ok(
+                  compareFormValue(tab_C, item, fieldList[item]),
+                  'The value for "' + item + '" was correctly duplicated'
+                );
+              }
+
+              // private browsing session, close tab: (C) and (B)
+              win.gBrowser.removeTab(tab_C);
+              win.gBrowser.removeTab(tab_B);
+
+              finish();
+            });
+          });
+        });
+      });
+    });
+  });
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_248970_b_sample.html b/src/zen/tests/mochitests/sessionstore/browser_248970_b_sample.html
new file mode 100644
index 000000000..76c3ae1aa
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_248970_b_sample.html
@@ -0,0 +1,37 @@
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
+<meta charset="utf-8">
+<title>Test for bug 248970</title>
+
+<h3>Text Fields</h3>
+<input type="text" name="input">
+<input type="text" name="spaced 1">
+<input>
+
+<h3>Checkboxes and Radio buttons</h3>
+<input type="checkbox" name="check"> Check 1
+<input type="checkbox" name="uncheck" checked> Check 2
+<p>
+<input type="radio" name="group" value="1"> Radio 1
+<input type="radio" name="group" value="some"> Radio 2
+<input type="radio" name="group" checked> Radio 3
+
+<h3>Selects</h3>
+<select name="any">
+  <option value="1"> Select 1
+  <option value="some"> Select 2
+  <option>Select 3
+</select>
+<select multiple="multiple">
+  <option value=1> Multi-select 1
+  <option value=2> Multi-select 2
+  <option value=3> Multi-select 3
+  <option value=4> Multi-select 4
+</select>
+
+<h3>Text Areas</h3>
+<textarea name="testarea"></textarea>
+<textarea name="sized one" rows="5" cols="25"></textarea>
+<textarea></textarea>
+
+<h3>File Selector</h3>
+<input type="file">
diff --git a/src/zen/tests/mochitests/sessionstore/browser_339445.js b/src/zen/tests/mochitests/sessionstore/browser_339445.js
new file mode 100644
index 000000000..01e784439
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_339445.js
@@ -0,0 +1,39 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+add_task(async function test() {
+  /** Test for Bug 339445 */
+
+  let testURL =
+    "http://mochi.test:8888/browser/" +
+    "browser/components/sessionstore/test/browser_339445_sample.html";
+
+  let tab = BrowserTestUtils.addTab(gBrowser, testURL);
+  await promiseBrowserLoaded(tab.linkedBrowser, true, testURL);
+
+  await SpecialPowers.spawn(tab.linkedBrowser, [], function () {
+    let doc = content.document;
+    is(
+      doc.getElementById("storageTestItem").textContent,
+      "PENDING",
+      "sessionStorage value has been set"
+    );
+  });
+
+  let tab2 = gBrowser.duplicateTab(tab);
+  await promiseTabRestored(tab2);
+
+  await SpecialPowers.spawn(tab2.linkedBrowser, [], function () {
+    let doc2 = content.document;
+    is(
+      doc2.getElementById("storageTestItem").textContent,
+      "SUCCESS",
+      "sessionStorage value has been duplicated"
+    );
+  });
+
+  // clean up
+  BrowserTestUtils.removeTab(tab2);
+  BrowserTestUtils.removeTab(tab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_339445_sample.html b/src/zen/tests/mochitests/sessionstore/browser_339445_sample.html
new file mode 100644
index 000000000..ff5b4acd9
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_339445_sample.html
@@ -0,0 +1,18 @@
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
+<meta charset="utf-8">
+<title>Test for bug 339445</title>
+
+storageTestItem = <span id="storageTestItem">FAIL</span>
+
+<!--
+  storageTestItem's textContent will be one of the following:
+  * FAIL    : sessionStorage wasn't available
+  * PENDING : the test value has been initialized on first load
+  * SUCCESS : the test value was correctly retrieved
+-->
+
+<script type="application/javascript">
+  document.getElementById("storageTestItem").textContent =
+    sessionStorage.storageTestItem || "PENDING";
+  sessionStorage.storageTestItem = "SUCCESS";
+</script>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_345898.js b/src/zen/tests/mochitests/sessionstore/browser_345898.js
new file mode 100644
index 000000000..2a946ad28
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_345898.js
@@ -0,0 +1,69 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+function test() {
+  /** Test for Bug 345898 */
+
+  // all of the following calls with illegal arguments should throw NS_ERROR_ILLEGAL_VALUE
+  Assert.throws(
+    () => ss.getWindowState({}),
+    /NS_ERROR_ILLEGAL_VALUE/,
+    "Invalid window for getWindowState throws"
+  );
+  Assert.throws(
+    () => ss.setWindowState({}, "", false),
+    /NS_ERROR_ILLEGAL_VALUE/,
+    "Invalid window for setWindowState throws"
+  );
+  Assert.throws(
+    () => ss.getTabState({}),
+    /NS_ERROR_ILLEGAL_VALUE/,
+    "Invalid tab for getTabState throws"
+  );
+  Assert.throws(
+    () => ss.setTabState({}, "{}"),
+    /NS_ERROR_ILLEGAL_VALUE/,
+    "Invalid tab state for setTabState throws"
+  );
+  Assert.throws(
+    () => ss.setTabState({}, JSON.stringify({ entries: [] })),
+    /NS_ERROR_ILLEGAL_VALUE/,
+    "Invalid tab for setTabState throws"
+  );
+  Assert.throws(
+    () => ss.duplicateTab({}, {}),
+    /NS_ERROR_ILLEGAL_VALUE/,
+    "Invalid tab for duplicateTab throws"
+  );
+  Assert.throws(
+    () => ss.duplicateTab({}, gBrowser.selectedTab),
+    /NS_ERROR_ILLEGAL_VALUE/,
+    "Invalid window for duplicateTab throws"
+  );
+  Assert.throws(
+    () => ss.getClosedTabDataForWindow({}),
+    /NS_ERROR_ILLEGAL_VALUE/,
+    "Invalid window for getClosedTabData throws"
+  );
+  Assert.throws(
+    () => ss.undoCloseTab({}, 0),
+    /NS_ERROR_ILLEGAL_VALUE/,
+    "Invalid window for undoCloseTab throws"
+  );
+  Assert.throws(
+    () => ss.undoCloseTab(window, -1),
+    /NS_ERROR_ILLEGAL_VALUE/,
+    "Invalid index for undoCloseTab throws"
+  );
+  Assert.throws(
+    () => ss.getCustomWindowValue({}, ""),
+    /NS_ERROR_ILLEGAL_VALUE/,
+    "Invalid window for getCustomWindowValue throws"
+  );
+  Assert.throws(
+    () => ss.setCustomWindowValue({}, "", ""),
+    /NS_ERROR_ILLEGAL_VALUE/,
+    "Invalid window for setCustomWindowValue throws"
+  );
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_350525.js b/src/zen/tests/mochitests/sessionstore/browser_350525.js
new file mode 100644
index 000000000..190552a6b
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_350525.js
@@ -0,0 +1,136 @@
+"use strict";
+
+add_setup(async function () {
+  await SpecialPowers.pushPrefEnv({
+    set: [["dom.ipc.processCount", 1]],
+  });
+});
+
+add_task(async function () {
+  /** Test for Bug 350525 */
+
+  function test(aLambda) {
+    try {
+      return aLambda() || true;
+    } catch (ex) {}
+    return false;
+  }
+
+  /**
+   * setCustomWindowValue, et al.
+   */
+  let key = "Unique name: " + Date.now();
+  let value = "Unique value: " + Math.random();
+
+  // test adding
+  ok(
+    test(() => ss.setCustomWindowValue(window, key, value)),
+    "set a window value"
+  );
+
+  // test retrieving
+  is(
+    ss.getCustomWindowValue(window, key),
+    value,
+    "stored window value matches original"
+  );
+
+  // test deleting
+  ok(
+    test(() => ss.deleteCustomWindowValue(window, key)),
+    "delete the window value"
+  );
+
+  // value should not exist post-delete
+  is(ss.getCustomWindowValue(window, key), "", "window value was deleted");
+
+  // test deleting a non-existent value
+  ok(
+    test(() => ss.deleteCustomWindowValue(window, key)),
+    "delete non-existent window value"
+  );
+
+  /**
+   * setCustomTabValue, et al.
+   */
+  key = "Unique name: " + Math.random();
+  value = "Unique value: " + Date.now();
+  let tab = BrowserTestUtils.addTab(gBrowser);
+  tab.linkedBrowser.stop();
+
+  // test adding
+  ok(
+    test(() => ss.setCustomTabValue(tab, key, value)),
+    "store a tab value"
+  );
+
+  // test retrieving
+  is(ss.getCustomTabValue(tab, key), value, "stored tab value match original");
+
+  // test deleting
+  ok(
+    test(() => ss.deleteCustomTabValue(tab, key)),
+    "delete the tab value"
+  );
+
+  // value should not exist post-delete
+  is(ss.getCustomTabValue(tab, key), "", "tab value was deleted");
+
+  // test deleting a non-existent value
+  ok(
+    test(() => ss.deleteCustomTabValue(tab, key)),
+    "delete non-existent tab value"
+  );
+
+  // clean up
+  await promiseRemoveTabAndSessionState(tab);
+
+  /**
+   * getClosedTabCountForWindow, undoCloseTab
+   */
+
+  // get closed tab count
+  let count = ss.getClosedTabCountForWindow(window);
+  let max_tabs_undo = Services.prefs.getIntPref(
+    "browser.sessionstore.max_tabs_undo"
+  );
+  ok(
+    0 <= count && count <= max_tabs_undo,
+    "getClosedTabCountForWindow returns zero or at most max_tabs_undo"
+  );
+
+  // create a new tab
+  let testURL = "about:mozilla";
+  tab = BrowserTestUtils.addTab(gBrowser, testURL);
+  await promiseBrowserLoaded(tab.linkedBrowser);
+
+  // make sure that the next closed tab will increase getClosedTabCountForWindow
+  Services.prefs.setIntPref(
+    "browser.sessionstore.max_tabs_undo",
+    max_tabs_undo + 1
+  );
+  registerCleanupFunction(() =>
+    Services.prefs.clearUserPref("browser.sessionstore.max_tabs_undo")
+  );
+
+  // remove tab
+  await promiseRemoveTabAndSessionState(tab);
+
+  // getClosedTabCountForWindow
+  let newcount = ss.getClosedTabCountForWindow(window);
+  Assert.greater(
+    newcount,
+    count,
+    "after closing a tab, getClosedTabCountForWindow has been incremented"
+  );
+
+  // undoCloseTab
+  tab = test(() => ss.undoCloseTab(window, 0));
+  ok(tab, "undoCloseTab doesn't throw");
+
+  await promiseTabRestored(tab);
+  is(tab.linkedBrowser.currentURI.spec, testURL, "correct tab was reopened");
+
+  // clean up
+  gBrowser.removeTab(tab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_354894_perwindowpb.js b/src/zen/tests/mochitests/sessionstore/browser_354894_perwindowpb.js
new file mode 100644
index 000000000..0c5b97003
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_354894_perwindowpb.js
@@ -0,0 +1,490 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+/**
+ * Checks that restoring the last browser window in session is actually
+ * working.
+ *
+ * @see https://bugzilla.mozilla.org/show_bug.cgi?id=354894
+ * Note: It is implicitly tested that restoring the last window works when
+ * non-browser windows are around. The "Run Tests" window as well as the main
+ * browser window (wherein the test code gets executed) won't be considered
+ * browser windows. To achiveve this said main browser window has its windowtype
+ * attribute modified so that it's not considered a browser window any longer.
+ * This is crucial, because otherwise there would be two browser windows around,
+ * said main test window and the one opened by the tests, and hence the new
+ * logic wouldn't be executed at all.
+ * Note: Mac only tests the new notifications, as restoring the last window is
+ * not enabled on that platform (platform shim; the application is kept running
+ * although there are no windows left)
+ * Note: There is a difference when closing a browser window with
+ * BrowserCommands.tryToCloseWindow() as opposed to close(). The former will make
+ * nsSessionStore restore a window next time it gets a chance and will post
+ * notifications. The latter won't.
+ */
+
+// The rejection "BrowserWindowTracker.getTopWindow(...) is null" is left
+// unhandled in some cases. This bug should be fixed, but for the moment this
+// file allows a class of rejections.
+//
+// NOTE: Allowing a whole class of rejections should be avoided. Normally you
+//       should use "expectUncaughtRejection" to flag individual failures.
+const { PromiseTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/PromiseTestUtils.sys.mjs"
+);
+PromiseTestUtils.allowMatchingRejectionsGlobally(/getTopWindow/);
+
+// Some urls that might be opened in tabs and/or popups
+// Do not use about:blank:
+// That one is reserved for special purposes in the tests
+const TEST_URLS = ["about:mozilla", "about:buildconfig"];
+
+// Number of -request notifications to except
+// remember to adjust when adding new tests
+const NOTIFICATIONS_EXPECTED = 6;
+
+// Window features of popup windows
+const POPUP_FEATURES = "toolbar=no,resizable=no,status=no";
+
+// Window features of browser windows
+const CHROME_FEATURES = "chrome,all,dialog=no";
+
+const IS_MAC = navigator.platform.match(/Mac/);
+
+/**
+ * Returns an Object with two properties:
+ *   open (int):
+ *     A count of how many non-closed navigator:browser windows there are.
+ *   winstates (int):
+ *     A count of how many windows there are in the SessionStore state.
+ */
+function getBrowserWindowsCount() {
+  let open = 0;
+  for (let win of Services.wm.getEnumerator("navigator:browser")) {
+    if (!win.closed) {
+      ++open;
+    }
+  }
+
+  let winstates = JSON.parse(ss.getBrowserState()).windows.length;
+
+  return { open, winstates };
+}
+
+add_setup(async function () {
+  // Make sure we've only got one browser window to start with
+  let { open, winstates } = getBrowserWindowsCount();
+  is(open, 1, "Should only be one open window");
+  is(winstates, 1, "Should only be one window state in SessionStore");
+
+  // This test takes some time to run, and it could timeout randomly.
+  // So we require a longer timeout. See bug 528219.
+  requestLongerTimeout(3);
+
+  // Make the main test window not count as a browser window any longer
+  let oldWinType = document.documentElement.getAttribute("windowtype");
+  document.documentElement.setAttribute("windowtype", "navigator:testrunner");
+
+  registerCleanupFunction(() => {
+    document.documentElement.setAttribute("windowtype", oldWinType);
+  });
+});
+
+/**
+ * Sets up one of our tests by setting the right preferences, and
+ * then opening up a browser window preloaded with some tabs.
+ *
+ * @param options (Object)
+ *        An object that can contain the following properties:
+ *
+ *        private:
+ *          Whether or not the opened window should be private.
+ *
+ *        denyFirst:
+ *          Whether or not the first window that attempts to close
+ *          via closeWindowForRestoration should be denied.
+ *
+ * @param testFunction (Function*)
+ *        A generator function that yields Promises to be run
+ *        once the test has been set up.
+ *
+ * @returns Promise
+ *        Resolves once the test has been cleaned up.
+ */
+let setupTest = async function (options, testFunction) {
+  await pushPrefs(
+    ["browser.startup.page", 3],
+    ["browser.tabs.warnOnClose", false]
+  );
+  // SessionStartup caches pref values, but as this test tries to simulate a
+  // startup scenario, we'll reset them here.
+  SessionStartup.resetForTest();
+
+  // Observe these, and also use to count the number of hits
+  let observing = {
+    "browser-lastwindow-close-requested": 0,
+    "browser-lastwindow-close-granted": 0,
+  };
+
+  /**
+   * Helper: Will observe and handle the notifications for us
+   */
+  let hitCount = 0;
+  function observer(aCancel, aTopic) {
+    // count so that we later may compare
+    observing[aTopic]++;
+
+    // handle some tests
+    if (options.denyFirst && ++hitCount == 1) {
+      aCancel.QueryInterface(Ci.nsISupportsPRBool).data = true;
+    }
+  }
+
+  for (let o in observing) {
+    Services.obs.addObserver(observer, o);
+  }
+
+  let newWin = await promiseNewWindowLoaded({
+    private: options.private || false,
+  });
+
+  await injectTestTabs(newWin);
+
+  await testFunction(newWin, observing);
+
+  let count = getBrowserWindowsCount();
+  is(count.open, 0, "Got right number of open windows");
+  is(count.winstates, 1, "Got right number of stored window states");
+
+  for (let o in observing) {
+    Services.obs.removeObserver(observer, o);
+  }
+
+  await popPrefs();
+  // Act like nothing ever happened.
+  SessionStartup.resetForTest();
+};
+
+/**
+ * Loads a TEST_URLS into a browser window.
+ *
+ * @param win (Window)
+ *        The browser window to load the tabs in
+ */
+function injectTestTabs(win) {
+  let promises = TEST_URLS.map(url =>
+    BrowserTestUtils.addTab(win.gBrowser, url)
+  ).map(tab => BrowserTestUtils.browserLoaded(tab.linkedBrowser));
+  return Promise.all(promises);
+}
+
+/**
+ * Attempts to close a window via BrowserCommands.tryToCloseWindow so that
+ * we get the browser-lastwindow-close-requested and
+ * browser-lastwindow-close-granted observer notifications.
+ *
+ * @param win (Window)
+ *        The window to try to close
+ * @returns Promise
+ *        Resolves to true if the window closed, or false if the window
+ *        was denied the ability to close.
+ */
+function closeWindowForRestoration(win) {
+  return new Promise(resolve => {
+    let closePromise = BrowserTestUtils.windowClosed(win);
+    win.BrowserCommands.tryToCloseWindow();
+    if (!win.closed) {
+      resolve(false);
+      return;
+    }
+
+    closePromise.then(() => {
+      resolve(true);
+    });
+  });
+}
+
+/**
+ * Normal in-session restore
+ *
+ * Note: Non-Mac only
+ *
+ * Should do the following:
+ *  1. Open a new browser window
+ *  2. Add some tabs
+ *  3. Close that window
+ *  4. Opening another window
+ *  5. Checks that state is restored
+ */
+add_task(async function test_open_close_normal() {
+  if (IS_MAC) {
+    return;
+  }
+
+  await setupTest({ denyFirst: true }, async function (newWin, obs) {
+    let closed = await closeWindowForRestoration(newWin);
+    ok(!closed, "First close request should have been denied");
+
+    closed = await closeWindowForRestoration(newWin);
+    ok(closed, "Second close request should be accepted");
+
+    newWin = await promiseNewWindowLoaded();
+    is(
+      newWin.gBrowser.browsers.length,
+      TEST_URLS.length + 2,
+      "Restored window in-session with otherpopup windows around"
+    );
+
+    // Note that this will not result in the the browser-lastwindow-close
+    // notifications firing for this other newWin.
+    await BrowserTestUtils.closeWindow(newWin);
+
+    // setupTest gave us a window which was denied for closing once, and then
+    // closed.
+    is(
+      obs["browser-lastwindow-close-requested"],
+      2,
+      "Got expected browser-lastwindow-close-requested notifications"
+    );
+    is(
+      obs["browser-lastwindow-close-granted"],
+      1,
+      "Got expected browser-lastwindow-close-granted notifications"
+    );
+  });
+});
+
+/**
+ * PrivateBrowsing in-session restore
+ *
+ * Note: Non-Mac only
+ *
+ * Should do the following:
+ *  1. Open a new browser window A
+ *  2. Add some tabs
+ *  3. Close the window A as the last window
+ *  4. Open a private browsing window B
+ *  5. Make sure that B didn't restore the tabs from A
+ *  6. Close private browsing window B
+ *  7. Open a new window C
+ *  8. Make sure that new window C has restored tabs from A
+ */
+add_task(async function test_open_close_private_browsing() {
+  if (IS_MAC) {
+    return;
+  }
+
+  await setupTest({}, async function (newWin, obs) {
+    let closed = await closeWindowForRestoration(newWin);
+    ok(closed, "Should be able to close the window");
+
+    newWin = await promiseNewWindowLoaded({ private: true });
+    is(
+      newWin.gBrowser.browsers.length,
+      1,
+      "Did not restore in private browsing mode"
+    );
+
+    closed = await closeWindowForRestoration(newWin);
+    ok(closed, "Should be able to close the window");
+
+    newWin = await promiseNewWindowLoaded();
+    is(
+      newWin.gBrowser.browsers.length,
+      TEST_URLS.length + 2,
+      "Restored tabs in a new non-private window"
+    );
+
+    // Note that this will not result in the the browser-lastwindow-close
+    // notifications firing for this other newWin.
+    await BrowserTestUtils.closeWindow(newWin);
+
+    // We closed two windows with closeWindowForRestoration, and both
+    // should have been successful.
+    is(
+      obs["browser-lastwindow-close-requested"],
+      2,
+      "Got expected browser-lastwindow-close-requested notifications"
+    );
+    is(
+      obs["browser-lastwindow-close-granted"],
+      2,
+      "Got expected browser-lastwindow-close-granted notifications"
+    );
+  });
+});
+
+/**
+ * Open some popup window to check it isn't restored. Instead nothing at all
+ * should be restored
+ *
+ * Note: Non-Mac only
+ *
+ * Should do the following:
+ *  1. Open a popup
+ *  2. Add another tab to the popup (so that it gets stored) and close it again
+ *  3. Open a window
+ *  4. Check that nothing at all is restored
+ *  5. Open two browser windows and close them again
+ *  6. undoCloseWindow() one
+ *  7. Open another browser window
+ *  8. Check that nothing at all is restored
+ */
+add_task(async function test_open_close_only_popup() {
+  if (IS_MAC) {
+    return;
+  }
+
+  await setupTest({}, async function (newWin, obs) {
+    // We actually don't care about the initial window in this test.
+    await BrowserTestUtils.closeWindow(newWin);
+
+    // This will cause nsSessionStore to restore a window the next time it
+    // gets a chance.
+    let popupPromise = BrowserTestUtils.waitForNewWindow();
+    openDialog(location, "popup", POPUP_FEATURES, TEST_URLS[1]);
+    let popup = await popupPromise;
+
+    is(
+      popup.gBrowser.browsers.length,
+      1,
+      "Did not restore the popup window (1)"
+    );
+
+    let closed = await closeWindowForRestoration(popup);
+    ok(closed, "Should be able to close the window");
+
+    popupPromise = BrowserTestUtils.waitForNewWindow();
+    openDialog(location, "popup", POPUP_FEATURES, TEST_URLS[1]);
+    popup = await popupPromise;
+
+    BrowserTestUtils.addTab(popup.gBrowser, TEST_URLS[0]);
+    is(
+      popup.gBrowser.browsers.length,
+      2,
+      "Did not restore to the popup window (2)"
+    );
+
+    await BrowserTestUtils.closeWindow(popup);
+
+    newWin = await promiseNewWindowLoaded();
+    isnot(
+      newWin.gBrowser.browsers.length,
+      2,
+      "Did not restore the popup window"
+    );
+    is(
+      TEST_URLS.indexOf(newWin.gBrowser.browsers[0].currentURI.spec),
+      -1,
+      "Did not restore the popup window (2)"
+    );
+    await BrowserTestUtils.closeWindow(newWin);
+
+    // We closed one popup window with closeWindowForRestoration, and popup
+    // windows should never fire the browser-lastwindow notifications.
+    is(
+      obs["browser-lastwindow-close-requested"],
+      0,
+      "Got expected browser-lastwindow-close-requested notifications"
+    );
+    is(
+      obs["browser-lastwindow-close-granted"],
+      0,
+      "Got expected browser-lastwindow-close-granted notifications"
+    );
+  });
+});
+
+/**
+ * Open some windows and do undoCloseWindow. This should prevent any
+ * restoring later in the test
+ *
+ * Note: Non-Mac only
+ *
+ * Should do the following:
+ *  1. Open two browser windows and close them again
+ *  2. undoCloseWindow() one
+ *  3. Open another browser window
+ *  4. Make sure nothing at all is restored
+ */
+add_task(async function test_open_close_restore_from_popup() {
+  if (IS_MAC) {
+    return;
+  }
+
+  await setupTest({}, async function (newWin) {
+    let newWin2 = await promiseNewWindowLoaded();
+    await injectTestTabs(newWin2);
+
+    let closed = await closeWindowForRestoration(newWin);
+    ok(closed, "Should be able to close the window");
+    closed = await closeWindowForRestoration(newWin2);
+    ok(closed, "Should be able to close the window");
+
+    let counts = getBrowserWindowsCount();
+    is(counts.open, 0, "Got right number of open windows");
+    is(counts.winstates, 1, "Got right number of window states");
+
+    newWin = SessionWindowUI.undoCloseWindow(0);
+    await BrowserTestUtils.waitForEvent(newWin, "load");
+
+    // Make sure we wait until this window is restored.
+    await BrowserTestUtils.waitForEvent(
+      newWin.gBrowser.tabContainer,
+      "SSTabRestored"
+    );
+
+    newWin2 = await promiseNewWindowLoaded();
+
+    is(
+      TEST_URLS.indexOf(newWin2.gBrowser.browsers[0].currentURI.spec),
+      -1,
+      "Did not restore, as undoCloseWindow() was last called (2)"
+    );
+
+    counts = getBrowserWindowsCount();
+    is(counts.open, 2, "Got right number of open windows");
+    is(counts.winstates, 3, "Got right number of window states");
+
+    await BrowserTestUtils.closeWindow(newWin);
+    await BrowserTestUtils.closeWindow(newWin2);
+
+    counts = getBrowserWindowsCount();
+    is(counts.open, 0, "Got right number of open windows");
+    is(counts.winstates, 1, "Got right number of window states");
+  });
+});
+
+/**
+ * Test if closing can be denied on Mac.
+ *
+ * Note: Mac only
+ */
+add_task(async function test_mac_notifications() {
+  if (!IS_MAC) {
+    return;
+  }
+
+  await setupTest({ denyFirst: true }, async function (newWin, obs) {
+    let closed = await closeWindowForRestoration(newWin);
+    ok(!closed, "First close attempt should be denied");
+    closed = await closeWindowForRestoration(newWin);
+    ok(closed, "Second close attempt should be granted");
+
+    // We tried closing once, and got denied. Then we tried again and
+    // succeeded. That means 2 close requests, and 1 close granted.
+    is(
+      obs["browser-lastwindow-close-requested"],
+      2,
+      "Got expected browser-lastwindow-close-requested notifications"
+    );
+    is(
+      obs["browser-lastwindow-close-granted"],
+      1,
+      "Got expected browser-lastwindow-close-granted notifications"
+    );
+  });
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_367052.js b/src/zen/tests/mochitests/sessionstore/browser_367052.js
new file mode 100644
index 000000000..413794572
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_367052.js
@@ -0,0 +1,52 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+add_task(async function () {
+  // make sure that the next closed tab will increase getClosedTabCountForWindow
+  let max_tabs_undo = Services.prefs.getIntPref(
+    "browser.sessionstore.max_tabs_undo"
+  );
+  Services.prefs.setIntPref(
+    "browser.sessionstore.max_tabs_undo",
+    max_tabs_undo + 1
+  );
+  registerCleanupFunction(() =>
+    Services.prefs.clearUserPref("browser.sessionstore.max_tabs_undo")
+  );
+
+  forgetClosedTabs(window);
+
+  // restore a blank tab
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:mozilla");
+  await promiseBrowserLoaded(tab.linkedBrowser);
+
+  let count = await promiseSHistoryCount(tab.linkedBrowser);
+  Assert.greaterOrEqual(
+    count,
+    1,
+    "the new tab does have at least one history entry"
+  );
+
+  await promiseTabState(tab, { entries: [] });
+
+  // We may have a different sessionHistory object if the tab
+  // switched from non-remote to remote.
+  count = await promiseSHistoryCount(tab.linkedBrowser);
+  is(count, 0, "the tab was restored without any history whatsoever");
+
+  await promiseRemoveTabAndSessionState(tab);
+  is(
+    ss.getClosedTabCountForWindow(window),
+    0,
+    "The closed blank tab wasn't added to Recently Closed Tabs"
+  );
+});
+
+function promiseSHistoryCount(browser) {
+  return SpecialPowers.spawn(browser, [], async function () {
+    return docShell.QueryInterface(Ci.nsIWebNavigation).sessionHistory.count;
+  });
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_393716.js b/src/zen/tests/mochitests/sessionstore/browser_393716.js
new file mode 100644
index 000000000..383c25e38
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_393716.js
@@ -0,0 +1,103 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const URL = "about:config";
+
+add_setup(async function () {
+  // Make sure that the field of which we restore the state is visible on load.
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.aboutConfig.showWarning", false]],
+  });
+});
+
+/**
+ * Bug 393716 - Basic tests for getTabState(), setTabState(), and duplicateTab().
+ */
+add_task(async function test_set_tabstate() {
+  let key = "Unique key: " + Date.now();
+  let value = "Unique value: " + Math.random();
+
+  // create a new tab
+  let tab = BrowserTestUtils.addTab(gBrowser, URL);
+  ss.setCustomTabValue(tab, key, value);
+  await promiseBrowserLoaded(tab.linkedBrowser);
+
+  // get the tab's state
+  await TabStateFlusher.flush(tab.linkedBrowser);
+  let state = ss.getTabState(tab);
+  ok(state, "get the tab's state");
+
+  // verify the tab state's integrity
+  state = JSON.parse(state);
+  ok(
+    state instanceof Object &&
+      state.entries instanceof Array &&
+      !!state.entries.length,
+    "state object seems valid"
+  );
+  ok(
+    state.entries.length == 1 && state.entries[0].url == URL,
+    "Got the expected state object (test URL)"
+  );
+  ok(
+    state.extData && state.extData[key] == value,
+    "Got the expected state object (test manually set tab value)"
+  );
+
+  // clean up
+  gBrowser.removeTab(tab);
+});
+
+add_task(async function test_set_tabstate_and_duplicate() {
+  let key2 = "key2";
+  let value2 = "Value " + Math.random();
+  let value3 = "Another value: " + Date.now();
+  let state = {
+    entries: [{ url: URL, triggeringPrincipal_base64 }],
+    extData: { key2: value2 },
+  };
+
+  // create a new tab
+  let tab = BrowserTestUtils.addTab(gBrowser);
+  // set the tab's state
+  ss.setTabState(tab, JSON.stringify(state));
+  await promiseBrowserLoaded(tab.linkedBrowser);
+
+  // verify the correctness of the restored tab
+  ok(
+    ss.getCustomTabValue(tab, key2) == value2 &&
+      tab.linkedBrowser.currentURI.spec == URL,
+    "the tab's state was correctly restored"
+  );
+
+  // add text data
+  await setPropertyOfFormField(
+    tab.linkedBrowser,
+    "#about-config-search",
+    "value",
+    value3
+  );
+
+  // duplicate the tab
+  let tab2 = ss.duplicateTab(window, tab);
+  await promiseTabRestored(tab2);
+
+  // verify the correctness of the duplicated tab
+  ok(
+    ss.getCustomTabValue(tab2, key2) == value2 &&
+      tab2.linkedBrowser.currentURI.spec == URL,
+    "correctly duplicated the tab's state"
+  );
+  let textbox = await getPropertyOfFormField(
+    tab2.linkedBrowser,
+    "#about-config-search",
+    "value"
+  );
+  is(textbox, value3, "also duplicated text data");
+
+  // clean up
+  gBrowser.removeTab(tab2);
+  gBrowser.removeTab(tab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_394759_basic.js b/src/zen/tests/mochitests/sessionstore/browser_394759_basic.js
new file mode 100644
index 000000000..cc1c33516
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_394759_basic.js
@@ -0,0 +1,123 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const TEST_URL =
+  "data:text/html;charset=utf-8,<input%20id=txt>" +
+  "<input%20type=checkbox%20id=chk>";
+
+/**
+ * This test ensures that closing a window is a reversible action. We will
+ * close the the window, restore it and check that all data has been restored.
+ * This includes window-specific data as well as form data for tabs.
+ */
+function test() {
+  waitForExplicitFinish();
+
+  let uniqueKey = "bug 394759";
+  let uniqueValue = "unik" + Date.now();
+  let uniqueText = "pi != " + Math.random();
+
+  // Clear the list of closed windows.
+  forgetClosedWindows();
+
+  provideWindow(function onTestURLLoaded(newWin) {
+    BrowserTestUtils.addTab(newWin.gBrowser).linkedBrowser.stop();
+
+    // Mark the window with some unique data to be restored later on.
+    ss.setCustomWindowValue(newWin, uniqueKey, uniqueValue);
+    let [txt] = newWin.content.document.querySelectorAll("#txt");
+    txt.value = uniqueText;
+
+    let browser = newWin.gBrowser.selectedBrowser;
+
+    setPropertyOfFormField(browser, "#chk", "checked", true).then(() => {
+      BrowserTestUtils.closeWindow(newWin).then(() => {
+        is(
+          ss.getClosedWindowCount(),
+          1,
+          "The closed window was added to Recently Closed Windows"
+        );
+
+        let data = SessionStore.getClosedWindowData();
+
+        // Verify that non JSON serialized data is the same as JSON serialized data.
+        is(
+          JSON.stringify(data),
+          ss.getClosedWindowData(),
+          "Non-serialized data is the same as serialized data"
+        );
+
+        ok(
+          data[0].title == TEST_URL &&
+            JSON.stringify(data[0]).indexOf(uniqueText) > -1,
+          "The closed window data was stored correctly"
+        );
+
+        // Reopen the closed window and ensure its integrity.
+        let newWin2 = ss.undoCloseWindow(0);
+
+        ok(
+          newWin2.isChromeWindow,
+          "undoCloseWindow actually returned a window"
+        );
+        is(
+          ss.getClosedWindowCount(),
+          0,
+          "The reopened window was removed from Recently Closed Windows"
+        );
+
+        // SSTabRestored will fire more than once, so we need to make sure we count them.
+        let restoredTabs = 0;
+        let expectedTabs = data[0].tabs.length;
+        newWin2.addEventListener(
+          "SSTabRestored",
+          function sstabrestoredListener() {
+            ++restoredTabs;
+            info("Restored tab " + restoredTabs + "/" + expectedTabs);
+            if (restoredTabs < expectedTabs) {
+              return;
+            }
+
+            is(restoredTabs, expectedTabs, "Correct number of tabs restored");
+            newWin2.removeEventListener(
+              "SSTabRestored",
+              sstabrestoredListener,
+              true
+            );
+
+            is(
+              newWin2.gBrowser.tabs.length,
+              2,
+              "The window correctly restored 2 tabs"
+            );
+            is(
+              newWin2.gBrowser.currentURI.spec,
+              TEST_URL,
+              "The window correctly restored the URL"
+            );
+
+            let chk;
+            [txt, chk] =
+              newWin2.content.document.querySelectorAll("#txt, #chk");
+            ok(
+              txt.value == uniqueText && chk.checked,
+              "The window correctly restored the form"
+            );
+            is(
+              ss.getCustomWindowValue(newWin2, uniqueKey),
+              uniqueValue,
+              "The window correctly restored the data associated with it"
+            );
+
+            // Clean up.
+            BrowserTestUtils.closeWindow(newWin2).then(finish);
+          },
+          true
+        );
+      });
+    });
+  }, TEST_URL);
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_394759_behavior.js b/src/zen/tests/mochitests/sessionstore/browser_394759_behavior.js
new file mode 100644
index 000000000..01217f86c
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_394759_behavior.js
@@ -0,0 +1,93 @@
+/**
+ * Test helper function that opens a series of windows, closes them
+ * and then checks the closed window data from SessionStore against
+ * expected results.
+ *
+ * @param windowsToOpen (Array)
+ *        An array of Objects, where each object must define a single
+ *        property "isPopup" for whether or not the opened window should
+ *        be a popup.
+ * @param expectedResults (Array)
+ *        An Object with two properies: mac and other, where each points
+ *        at yet another Object, with the following properties:
+ *
+ *        popup (int):
+ *          The number of popup windows we expect to be in the closed window
+ *          data.
+ *        normal (int):
+ *          The number of normal windows we expect to be in the closed window
+ *          data.
+ * @returns Promise
+ */
+function testWindows(windowsToOpen, expectedResults) {
+  return (async function () {
+    let num = 0;
+    for (let winData of windowsToOpen) {
+      let features = "chrome,dialog=no," + (winData.isPopup ? "all=no" : "all");
+      let url = "http://example.com/?window=" + num;
+      num = num + 1;
+
+      let openWindowPromise = BrowserTestUtils.waitForNewWindow({ url });
+      openDialog(AppConstants.BROWSER_CHROME_URL, "", features, url);
+      let win = await openWindowPromise;
+      await BrowserTestUtils.closeWindow(win);
+    }
+
+    let closedWindowData = ss.getClosedWindowData();
+    let numPopups = closedWindowData.filter(function (el) {
+      return el.isPopup;
+    }).length;
+    let numNormal = ss.getClosedWindowCount() - numPopups;
+    // #ifdef doesn't work in browser-chrome tests, so do a simple regex on platform
+    let oResults = navigator.platform.match(/Mac/)
+      ? expectedResults.mac
+      : expectedResults.other;
+    is(
+      numPopups,
+      oResults.popup,
+      "There were " + oResults.popup + " popup windows to reopen"
+    );
+    is(
+      numNormal,
+      oResults.normal,
+      "There were " + oResults.normal + " normal windows to reopen"
+    );
+  })();
+}
+
+add_task(async function test_closed_window_states() {
+  // This test takes quite some time, and timeouts frequently, so we require
+  // more time to run.
+  // See Bug 518970.
+  requestLongerTimeout(2);
+
+  let windowsToOpen = [
+    { isPopup: false },
+    { isPopup: true },
+    { isPopup: true },
+    { isPopup: true },
+    { isPopup: true },
+    { isPopup: true },
+  ];
+  let expectedResults = {
+    mac: { popup: 5, normal: 0 },
+    other: { popup: 5, normal: 1 },
+  };
+
+  await testWindows(windowsToOpen, expectedResults);
+
+  let windowsToOpen2 = [
+    { isPopup: false },
+    { isPopup: false },
+    { isPopup: false },
+    { isPopup: false },
+    { isPopup: false },
+    { isPopup: false },
+  ];
+  let expectedResults2 = {
+    mac: { popup: 0, normal: 5 },
+    other: { popup: 0, normal: 5 },
+  };
+
+  await testWindows(windowsToOpen2, expectedResults2);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_394759_perwindowpb.js b/src/zen/tests/mochitests/sessionstore/browser_394759_perwindowpb.js
new file mode 100644
index 000000000..b79527d4c
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_394759_perwindowpb.js
@@ -0,0 +1,61 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const TESTS = [
+  { url: "about:config", key: "bug 394759 Non-PB", value: "uniq" + r() },
+  { url: "about:mozilla", key: "bug 394759 PB", value: "uniq" + r() },
+];
+
+function promiseTestOpenCloseWindow(aIsPrivate, aTest) {
+  return (async function () {
+    let win = await BrowserTestUtils.openNewBrowserWindow({
+      private: aIsPrivate,
+    });
+    BrowserTestUtils.startLoadingURIString(
+      win.gBrowser.selectedBrowser,
+      aTest.url
+    );
+    await promiseBrowserLoaded(win.gBrowser.selectedBrowser, true, aTest.url);
+    // Mark the window with some unique data to be restored later on.
+    ss.setCustomWindowValue(win, aTest.key, aTest.value);
+    await TabStateFlusher.flushWindow(win);
+    // Close.
+    await BrowserTestUtils.closeWindow(win);
+  })();
+}
+
+function promiseTestOnWindow(aIsPrivate, aValue) {
+  return (async function () {
+    let win = await BrowserTestUtils.openNewBrowserWindow({
+      private: aIsPrivate,
+    });
+    await TabStateFlusher.flushWindow(win);
+    let data = ss.getClosedWindowData()[0];
+    is(
+      ss.getClosedWindowCount(),
+      1,
+      "Check that the closed window count hasn't changed"
+    );
+    Assert.greater(
+      JSON.stringify(data).indexOf(aValue),
+      -1,
+      "Check the closed window data was stored correctly"
+    );
+    registerCleanupFunction(() => BrowserTestUtils.closeWindow(win));
+  })();
+}
+
+add_setup(async function () {
+  forgetClosedWindows();
+  forgetClosedTabs(window);
+});
+
+add_task(async function main() {
+  await promiseTestOpenCloseWindow(false, TESTS[0]);
+  await promiseTestOpenCloseWindow(true, TESTS[1]);
+  await promiseTestOnWindow(false, TESTS[0].value);
+  await promiseTestOnWindow(true, TESTS[0].value);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_394759_purge.js b/src/zen/tests/mochitests/sessionstore/browser_394759_purge.js
new file mode 100644
index 000000000..9665df0fe
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_394759_purge.js
@@ -0,0 +1,250 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+let { ForgetAboutSite } = ChromeUtils.importESModule(
+  "moz-src:///toolkit/components/forgetaboutsite/ForgetAboutSite.sys.mjs"
+);
+
+function promiseClearHistory() {
+  return new Promise(resolve => {
+    let observer = {
+      observe() {
+        Services.obs.removeObserver(
+          this,
+          "browser:purge-session-history-for-domain"
+        );
+        resolve();
+      },
+    };
+    Services.obs.addObserver(
+      observer,
+      "browser:purge-session-history-for-domain"
+    );
+  });
+}
+
+add_task(async function () {
+  // utility functions
+  function countClosedTabsByTitle(aClosedTabList, aTitle) {
+    return aClosedTabList.filter(aData => aData.title == aTitle).length;
+  }
+
+  function countOpenTabsByTitle(aOpenTabList, aTitle) {
+    return aOpenTabList.filter(aData =>
+      aData.entries.some(aEntry => aEntry.title == aTitle)
+    ).length;
+  }
+
+  // backup old state
+  let oldState = ss.getBrowserState();
+  let oldState_wins = JSON.parse(oldState).windows.length;
+  if (oldState_wins != 1) {
+    ok(
+      false,
+      "oldState in test_purge has " + oldState_wins + " windows instead of 1"
+    );
+  }
+
+  // create a new state for testing
+  const REMEMBER = Date.now(),
+    FORGET = Math.random();
+  let testState = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              { url: "http://example.com/", triggeringPrincipal_base64 },
+            ],
+          },
+        ],
+        selected: 1,
+      },
+    ],
+    _closedWindows: [
+      // _closedWindows[0]
+      {
+        tabs: [
+          {
+            entries: [
+              {
+                url: "http://example.com/",
+                triggeringPrincipal_base64,
+                title: REMEMBER,
+              },
+            ],
+          },
+          {
+            entries: [
+              {
+                url: "http://mozilla.org/",
+                triggeringPrincipal_base64,
+                title: FORGET,
+              },
+            ],
+          },
+        ],
+        selected: 2,
+        title: "mozilla.org",
+        _closedTabs: [],
+        closedGroups: [],
+      },
+      // _closedWindows[1]
+      {
+        tabs: [
+          {
+            entries: [
+              {
+                url: "http://mozilla.org/",
+                triggeringPrincipal_base64,
+                title: FORGET,
+              },
+            ],
+          },
+          {
+            entries: [
+              {
+                url: "http://example.com/",
+                triggeringPrincipal_base64,
+                title: REMEMBER,
+              },
+            ],
+          },
+          {
+            entries: [
+              {
+                url: "http://example.com/",
+                triggeringPrincipal_base64,
+                title: REMEMBER,
+              },
+            ],
+          },
+          {
+            entries: [
+              {
+                url: "http://mozilla.org/",
+                triggeringPrincipal_base64,
+                title: FORGET,
+              },
+            ],
+          },
+          {
+            entries: [
+              {
+                url: "http://example.com/",
+                triggeringPrincipal_base64,
+                title: REMEMBER,
+              },
+            ],
+          },
+        ],
+        selected: 5,
+        _closedTabs: [],
+        closedGroups: [],
+      },
+      // _closedWindows[2]
+      {
+        tabs: [
+          {
+            entries: [
+              {
+                url: "http://example.com/",
+                triggeringPrincipal_base64,
+                title: REMEMBER,
+              },
+            ],
+          },
+        ],
+        selected: 1,
+        _closedTabs: [
+          {
+            state: {
+              entries: [
+                {
+                  url: "http://mozilla.org/",
+                  triggeringPrincipal_base64,
+                  title: FORGET,
+                },
+                {
+                  url: "http://mozilla.org/again",
+                  triggeringPrincipal_base64,
+                  title: "doesn't matter",
+                },
+              ],
+            },
+            pos: 1,
+            title: FORGET,
+          },
+          {
+            state: {
+              entries: [
+                {
+                  url: "http://example.com",
+                  triggeringPrincipal_base64,
+                  title: REMEMBER,
+                },
+              ],
+            },
+            title: REMEMBER,
+          },
+        ],
+        closedGroups: [],
+      },
+    ],
+  };
+
+  // set browser to test state
+  ss.setBrowserState(JSON.stringify(testState));
+
+  // purge domain & check that we purged correctly for closed windows
+  let clearHistoryPromise = promiseClearHistory();
+  await ForgetAboutSite.removeDataFromBaseDomain("mozilla.org");
+  await clearHistoryPromise;
+
+  let closedWindowData = ss.getClosedWindowData();
+
+  // First set of tests for _closedWindows[0] - tests basics
+  let win = closedWindowData[0];
+  is(win.tabs.length, 1, "1 tab was removed");
+  is(countOpenTabsByTitle(win.tabs, FORGET), 0, "The correct tab was removed");
+  is(
+    countOpenTabsByTitle(win.tabs, REMEMBER),
+    1,
+    "The correct tab was remembered"
+  );
+  is(win.selected, 1, "Selected tab has changed");
+  is(win.title, REMEMBER, "The window title was correctly updated");
+
+  // Test more complicated case
+  win = closedWindowData[1];
+  is(win.tabs.length, 3, "2 tabs were removed");
+  is(
+    countOpenTabsByTitle(win.tabs, FORGET),
+    0,
+    "The correct tabs were removed"
+  );
+  is(
+    countOpenTabsByTitle(win.tabs, REMEMBER),
+    3,
+    "The correct tabs were remembered"
+  );
+  is(win.selected, 3, "Selected tab has changed");
+  is(win.title, REMEMBER, "The window title was correctly updated");
+
+  // Tests handling of _closedTabs
+  win = closedWindowData[2];
+  is(
+    countClosedTabsByTitle(win._closedTabs, REMEMBER),
+    1,
+    "The correct number of tabs were removed, and the correct ones"
+  );
+  is(
+    countClosedTabsByTitle(win._closedTabs, FORGET),
+    0,
+    "All tabs to be forgotten were indeed removed"
+  );
+
+  // restore pre-test state
+  ss.setBrowserState(oldState);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_423132.js b/src/zen/tests/mochitests/sessionstore/browser_423132.js
new file mode 100644
index 000000000..3a0113d4d
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_423132.js
@@ -0,0 +1,52 @@
+"use strict";
+
+/**
+ * Tests that cookies are stored and restored correctly
+ * by sessionstore (bug 423132).
+ */
+add_task(async function () {
+  const testURL =
+    "http://mochi.test:8888/browser/" +
+    "browser/components/sessionstore/test/browser_423132_sample.html";
+
+  Services.cookies.removeAll();
+  // make sure that sessionstore.js can be forced to be created by setting
+  // the interval pref to 0
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.sessionstore.interval", 0]],
+  });
+
+  let tab = BrowserTestUtils.addTab(gBrowser, testURL);
+  await BrowserTestUtils.browserLoaded(tab.linkedBrowser);
+  await TabStateFlusher.flush(tab.linkedBrowser);
+
+  // get the sessionstore state for the window
+  let state = ss.getBrowserState();
+
+  // verify our cookie got set during pageload
+  let i = 0;
+  for (var cookie of Services.cookies.cookies) {
+    i++;
+  }
+  Assert.equal(i, 1, "expected one cookie");
+
+  // remove the cookie
+  Services.cookies.removeAll();
+
+  // restore the window state
+  await setBrowserState(state);
+
+  // at this point, the cookie should be restored...
+  for (var cookie2 of Services.cookies.cookies) {
+    if (cookie.name == cookie2.name) {
+      break;
+    }
+  }
+  is(cookie.name, cookie2.name, "cookie name successfully restored");
+  is(cookie.value, cookie2.value, "cookie value successfully restored");
+  is(cookie.path, cookie2.path, "cookie path successfully restored");
+
+  // clean up
+  Services.cookies.removeAll();
+  BrowserTestUtils.removeTab(gBrowser.tabs[1]);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_423132_sample.html b/src/zen/tests/mochitests/sessionstore/browser_423132_sample.html
new file mode 100644
index 000000000..6ff7e7aa3
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_423132_sample.html
@@ -0,0 +1,14 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <script type="text/javascript">
+    // generate an enormous random number...
+    var r = Math.floor(Math.random() * Math.pow(2, 62)).toString();
+
+    // ... and use it to set a randomly named cookie
+    document.cookie = r + "=value; path=/ohai";
+  </script>
+<body>
+</body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_447951.js b/src/zen/tests/mochitests/sessionstore/browser_447951.js
new file mode 100644
index 000000000..9daf08268
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_447951.js
@@ -0,0 +1,86 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+function test() {
+  /** Test for Bug 447951 */
+
+  waitForExplicitFinish();
+  const baseURL =
+    "http://mochi.test:8888/browser/" +
+    "browser/components/sessionstore/test/browser_447951_sample.html#";
+
+  // Make sure the functionality added in bug 943339 doesn't affect the results
+  Services.prefs.setIntPref("browser.sessionstore.max_serialize_back", -1);
+  Services.prefs.setIntPref("browser.sessionstore.max_serialize_forward", -1);
+  registerCleanupFunction(function () {
+    Services.prefs.clearUserPref("browser.sessionstore.max_serialize_back");
+    Services.prefs.clearUserPref("browser.sessionstore.max_serialize_forward");
+  });
+
+  let tab = BrowserTestUtils.addTab(gBrowser);
+  BrowserTestUtils.browserLoaded(tab.linkedBrowser, {
+    wantLoad: "about:blank",
+  }).then(() => {
+    let tabState = { entries: [] };
+    let max_entries = Services.prefs.getIntPref(
+      "browser.sessionhistory.max_entries"
+    );
+    for (let i = 0; i < max_entries; i++) {
+      tabState.entries.push({ url: baseURL + i, triggeringPrincipal_base64 });
+    }
+
+    promiseTabState(tab, tabState)
+      .then(() => {
+        return TabStateFlusher.flush(tab.linkedBrowser);
+      })
+      .then(() => {
+        tabState = JSON.parse(ss.getTabState(tab));
+        is(
+          tabState.entries.length,
+          max_entries,
+          "session history filled to the limit"
+        );
+        is(tabState.entries[0].url, baseURL + 0, "... but not more");
+
+        // visit yet another anchor (appending it to session history)
+        SpecialPowers.spawn(tab.linkedBrowser, [], function () {
+          content.window.document.querySelector("a").click();
+        }).then(flushAndCheck);
+
+        function flushAndCheck() {
+          TabStateFlusher.flush(tab.linkedBrowser).then(check);
+        }
+
+        function check() {
+          tabState = JSON.parse(ss.getTabState(tab));
+          if (tab.linkedBrowser.currentURI.spec != baseURL + "end") {
+            // It may take a few passes through the event loop before we
+            // get the right URL.
+            executeSoon(flushAndCheck);
+            return;
+          }
+
+          is(
+            tab.linkedBrowser.currentURI.spec,
+            baseURL + "end",
+            "the new anchor was loaded"
+          );
+          is(
+            tabState.entries[tabState.entries.length - 1].url,
+            baseURL + "end",
+            "... and ignored"
+          );
+          is(
+            tabState.entries[0].url,
+            baseURL + 1,
+            "... and the first item was removed"
+          );
+
+          // clean up
+          gBrowser.removeTab(tab);
+          finish();
+        }
+      });
+  });
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_447951_sample.html b/src/zen/tests/mochitests/sessionstore/browser_447951_sample.html
new file mode 100644
index 000000000..00282f25e
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_447951_sample.html
@@ -0,0 +1,5 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>Testcase for bug 447951</title>
+
+<a href="#end">click me</a>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_454908.js b/src/zen/tests/mochitests/sessionstore/browser_454908.js
new file mode 100644
index 000000000..415930c32
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_454908.js
@@ -0,0 +1,65 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+if (gFissionBrowser) {
+  addCoopTask(
+    "browser_454908_sample.html",
+    test_dont_save_passwords,
+    HTTPSROOT
+  );
+}
+addNonCoopTask("browser_454908_sample.html", test_dont_save_passwords, ROOT);
+addNonCoopTask(
+  "browser_454908_sample.html",
+  test_dont_save_passwords,
+  HTTPROOT
+);
+addNonCoopTask(
+  "browser_454908_sample.html",
+  test_dont_save_passwords,
+  HTTPSROOT
+);
+
+const PASS = "pwd-" + Math.random();
+
+/**
+ * Bug 454908 - Don't save/restore values of password fields.
+ */
+async function test_dont_save_passwords(aURL) {
+  // Make sure we do save form data.
+  Services.prefs.clearUserPref("browser.sessionstore.privacy_level");
+
+  // Add a tab with a password field.
+  let tab = BrowserTestUtils.addTab(gBrowser, aURL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  // Fill in some values.
+  let usernameValue = "User " + Math.random();
+  await setPropertyOfFormField(browser, "#username", "value", usernameValue);
+  await setPropertyOfFormField(browser, "#passwd", "value", PASS);
+
+  // Close and restore the tab.
+  await promiseRemoveTabAndSessionState(tab);
+  tab = ss.undoCloseTab(window, 0);
+  browser = tab.linkedBrowser;
+  await promiseTabRestored(tab);
+
+  // Check that password fields aren't saved/restored.
+  let username = await getPropertyOfFormField(browser, "#username", "value");
+  is(username, usernameValue, "username was saved/restored");
+  let passwd = await getPropertyOfFormField(browser, "#passwd", "value");
+  is(passwd, "", "password wasn't saved/restored");
+
+  // Write to disk and read our file.
+  await forceSaveState();
+  await promiseForEachSessionRestoreFile((state, key) =>
+    // Ensure that we have not saved our password.
+    ok(!state.includes(PASS), "password has not been written to file " + key)
+  );
+
+  // Cleanup.
+  gBrowser.removeTab(tab);
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_454908_sample.html b/src/zen/tests/mochitests/sessionstore/browser_454908_sample.html
new file mode 100644
index 000000000..02f40bf20
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_454908_sample.html
@@ -0,0 +1,8 @@
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
+<title>Test for bug 454908</title>
+
+<h3>Dummy Login</h3>
+<form>
+<p>Username: <input type="text" id="username">
+<p>Password: <input type="password" id="passwd">
+</form>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_456342.js b/src/zen/tests/mochitests/sessionstore/browser_456342.js
new file mode 100644
index 000000000..68dbbbea1
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_456342.js
@@ -0,0 +1,90 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+addCoopTask(
+  "browser_456342_sample.xhtml",
+  test_restore_nonstandard_input_values,
+  HTTPSROOT
+);
+addNonCoopTask(
+  "browser_456342_sample.xhtml",
+  test_restore_nonstandard_input_values,
+  ROOT
+);
+addNonCoopTask(
+  "browser_456342_sample.xhtml",
+  test_restore_nonstandard_input_values,
+  HTTPROOT
+);
+addNonCoopTask(
+  "browser_456342_sample.xhtml",
+  test_restore_nonstandard_input_values,
+  HTTPSROOT
+);
+
+const EXPECTED_IDS = new Set(["searchTerm"]);
+
+const EXPECTED_XPATHS = new Set([
+  "/xhtml:html/xhtml:body/xhtml:form/xhtml:p[2]/xhtml:input",
+  "/xhtml:html/xhtml:body/xhtml:form/xhtml:p[3]/xhtml:input[@name='fill-in']",
+  "/xhtml:html/xhtml:body/xhtml:form/xhtml:p[4]/xhtml:input[@name='mistyped']",
+  "/xhtml:html/xhtml:body/xhtml:form/xhtml:p[5]/xhtml:textarea[@name='textarea_pass']",
+]);
+
+/**
+ * Bug 456342 - Restore values from non-standard input field types.
+ */
+async function test_restore_nonstandard_input_values(aURL) {
+  // Add tab with various non-standard input field types.
+  let tab = BrowserTestUtils.addTab(gBrowser, aURL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  // Fill in form values.
+  let expectedValue = Math.random();
+
+  await SpecialPowers.spawn(browser, [expectedValue], valueChild => {
+    for (let elem of content.document.forms[0].elements) {
+      elem.value = valueChild;
+      let event = elem.ownerDocument.createEvent("UIEvents");
+      event.initUIEvent("input", true, true, elem.documentGlobal, 0);
+      elem.dispatchEvent(event);
+    }
+  });
+
+  // Remove tab and check collected form data.
+  await promiseRemoveTabAndSessionState(tab);
+  let undoItems = ss.getClosedTabDataForWindow(window);
+  let savedFormData = undoItems[0].state.formdata;
+
+  let foundIds = 0;
+  for (let id of Object.keys(savedFormData.id)) {
+    ok(EXPECTED_IDS.has(id), `Check saved ID "${id}" was expected`);
+    is(
+      savedFormData.id[id],
+      "" + expectedValue,
+      `Check saved value for #${id}`
+    );
+    foundIds++;
+  }
+
+  let foundXpaths = 0;
+  for (let exp of Object.keys(savedFormData.xpath)) {
+    ok(EXPECTED_XPATHS.has(exp), `Check saved xpath "${exp}" was expected`);
+    is(
+      savedFormData.xpath[exp],
+      "" + expectedValue,
+      `Check saved value for ${exp}`
+    );
+    foundXpaths++;
+  }
+
+  is(foundIds, EXPECTED_IDS.size, "Check number of fields saved by ID");
+  is(
+    foundXpaths,
+    EXPECTED_XPATHS.size,
+    "Check number of fields saved by xpath"
+  );
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_456342_sample.xhtml b/src/zen/tests/mochitests/sessionstore/browser_456342_sample.xhtml
new file mode 100644
index 000000000..ea8704d17
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_456342_sample.xhtml
@@ -0,0 +1,46 @@
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
+"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml">
+
+<head><title>Test for bug 456342</title></head>
+
+<body>
+<form>
+<h3>Non-standard &lt;input&gt;s</h3>
+<p>Search        <input type="search"       id="searchTerm"/></p>
+<p>Image Search: <input type="image search" /></p>
+<p>Autocomplete: <input type="autocomplete" name="fill-in"/></p>
+<p>Mistyped:     <input type="txet"         name="mistyped"/></p>
+<p>Invalid attr: <textarea type="password" name="textarea_pass"/></p>
+
+<h3>Ignored types</h3>
+<input type="hidden" name="hideme"/>
+<input type="HIDDEN" name="hideme2"/>
+<input type="submit" name="submit"/>
+<input type="reset"  name="reset"/>
+<input type="image"  name="image"/>
+<input type="button" name="button"/>
+<input type="password" name="password"/>
+<input type="PassWord" name="password2"/>
+<input type="PASSWORD" name="password3"/>
+<input autocomplete="off" name="auto1"/>
+<input type="text" autocomplete="OFF" name="auto2"/>
+<input type="text" autocomplete="   OFF   " name="auto5"/>
+<input autocomplete="   off   " name="auto6"/>
+<input autocomplete=" cc-CSC " name="auto7"/>
+<input autocomplete=" NEW-password " name="auto8"/>
+<textarea autocomplete="off" name="auto3"/>
+<select autocomplete="off" name="auto4">
+  <option value="1" selected="true"/>
+  <option value="2"/>
+  <option value="3"/>
+</select>
+<select autocomplete="cc-CSC" name="CSC">
+  <option value="123" selected="true"/>
+  <option value="234"/>
+  <option value="345"/>
+</select>
+</form>
+
+</body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_459906.js b/src/zen/tests/mochitests/sessionstore/browser_459906.js
new file mode 100644
index 000000000..d5f138322
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_459906.js
@@ -0,0 +1,78 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+/* eslint-disable mozilla/no-arbitrary-setTimeout */
+
+function test() {
+  /** Test for Bug 459906 */
+
+  waitForExplicitFinish();
+
+  let testURL =
+    "http://mochi.test:8888/browser/" +
+    "browser/components/sessionstore/test/browser_459906_sample.html";
+  let uniqueValue = "<b>Unique:</b> " + Date.now();
+
+  var frameCount = 0;
+  let tab = BrowserTestUtils.addTab(gBrowser, testURL);
+  tab.linkedBrowser.addEventListener(
+    "load",
+    function listener() {
+      // wait for all frames to load completely
+      if (frameCount++ < 2) {
+        return;
+      }
+      tab.linkedBrowser.removeEventListener("load", listener, true);
+
+      let iframes = tab.linkedBrowser.contentWindow.frames;
+      iframes[1].document.body.innerHTML = uniqueValue;
+
+      frameCount = 0;
+      let tab2 = gBrowser.duplicateTab(tab);
+      tab2.linkedBrowser.addEventListener(
+        "load",
+        function loadListener() {
+          // wait for all frames to load (and reload!) completely
+          if (frameCount++ < 2) {
+            return;
+          }
+          tab2.linkedBrowser.removeEventListener("load", loadListener, true);
+
+          executeSoon(function innerHTMLPoller() {
+            let iframesTab2 = tab2.linkedBrowser.contentWindow.frames;
+            if (iframesTab2[1].document.body.innerHTML !== uniqueValue) {
+              // Poll again the value, since we can't ensure to run
+              // after SessionStore has injected innerHTML value.
+              // See bug 521802.
+              info("Polling for innerHTML value");
+              setTimeout(innerHTMLPoller, 100);
+              return;
+            }
+
+            is(
+              iframesTab2[1].document.body.innerHTML,
+              uniqueValue,
+              "rich textarea's content correctly duplicated"
+            );
+
+            let innerDomain = null;
+            try {
+              innerDomain = iframesTab2[0].document.domain;
+            } catch (ex) {
+              /* throws for chrome: documents */
+            }
+            is(innerDomain, "mochi.test", "XSS exploit prevented!");
+
+            // clean up
+            gBrowser.removeTab(tab2);
+            gBrowser.removeTab(tab);
+
+            finish();
+          });
+        },
+        true
+      );
+    },
+    true
+  );
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_459906_empty.html b/src/zen/tests/mochitests/sessionstore/browser_459906_empty.html
new file mode 100644
index 000000000..e01aaa339
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_459906_empty.html
@@ -0,0 +1,3 @@
+<title>Cross Domain File for bug 459906</title>
+
+cheers from localhost
diff --git a/src/zen/tests/mochitests/sessionstore/browser_459906_sample.html b/src/zen/tests/mochitests/sessionstore/browser_459906_sample.html
new file mode 100644
index 000000000..6f1c6a52e
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_459906_sample.html
@@ -0,0 +1,41 @@
+<!-- Testcase originally by David Bloom <bloom@google.com> -->
+
+<!DOCTYPE html>
+<title>Test for bug 459906</title>
+
+<body>
+<iframe src="data:text/html;charset=utf-8,not_on_localhost"></iframe>
+<iframe></iframe>
+
+<script type="application/javascript">
+  var loadCount = 0;
+  frames[0].addEventListener("DOMContentLoaded", handleLoad);
+  frames[1].addEventListener("DOMContentLoaded", handleLoad);
+  function handleLoad() {
+    if (++loadCount < 2)
+      return;
+    frames[0].removeEventListener("DOMContentLoaded", handleLoad);
+    frames[1].removeEventListener("DOMContentLoaded", handleLoad);
+    frames[0].document.designMode = "on";
+    frames[0].document.__defineGetter__("designMode", function() {
+      // inject a cross domain file ...
+      var documentInjected = false;
+      document.getElementsByTagName("iframe")[0].onload =
+        function() { documentInjected = true; };
+      frames[0].location = "browser_459906_empty.html";
+
+      // ... and ensure that it has time to load
+      for (var c = 0; !documentInjected && c < 20; c++) {
+        var r = new XMLHttpRequest();
+        r.open("GET", location.href, false);
+        r.overrideMimeType("text/plain");
+        r.send(null);
+      }
+
+      return "on";
+    });
+
+    frames[1].document.designMode = "on";
+  }
+</script>
+</body>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_461634.js b/src/zen/tests/mochitests/sessionstore/browser_461634.js
new file mode 100644
index 000000000..0e59d6e3f
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_461634.js
@@ -0,0 +1,133 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+add_task(async function testClosedTabData() {
+  /** Test for Bug 461634 */
+
+  const REMEMBER = Date.now(),
+    FORGET = Math.random();
+  let test_state = {
+    windows: [
+      {
+        tabs: [{ entries: [] }],
+        _closedTabs: [
+          {
+            state: { entries: [{ url: "http://www.example.net/" }] },
+            title: FORGET,
+          },
+          {
+            state: { entries: [{ url: "http://www.example.net/" }] },
+            title: REMEMBER,
+          },
+          {
+            state: { entries: [{ url: "http://www.example.net/" }] },
+            title: FORGET,
+          },
+          {
+            state: { entries: [{ url: "http://www.example.net/" }] },
+            title: REMEMBER,
+          },
+        ],
+      },
+    ],
+  };
+  let remember_count = 2;
+
+  function countByTitle(aClosedTabList, aTitle) {
+    return aClosedTabList.filter(aData => aData.title == aTitle).length;
+  }
+
+  function testForError(aFunction) {
+    try {
+      aFunction();
+      return false;
+    } catch (ex) {
+      return ex.name == "NS_ERROR_ILLEGAL_VALUE";
+    }
+  }
+
+  // Open a window and add the above closed tab list.
+  let newWin = openDialog(location, "", "chrome,all,dialog=no");
+  await promiseWindowLoaded(newWin);
+
+  Services.prefs.setIntPref(
+    "browser.sessionstore.max_tabs_undo",
+    test_state.windows[0]._closedTabs.length
+  );
+  await setWindowState(newWin, test_state, true);
+
+  let closedTabs = SessionStore.getClosedTabDataForWindow(newWin);
+
+  // Verify that non JSON serialized data is the same as JSON serialized data.
+  is(
+    JSON.stringify(closedTabs),
+    JSON.stringify(SessionStore.getClosedTabDataForWindow(newWin)),
+    "Non-serialized data is the same as serialized data"
+  );
+
+  is(
+    closedTabs.length,
+    test_state.windows[0]._closedTabs.length,
+    "Closed tab list has the expected length"
+  );
+  is(
+    countByTitle(closedTabs, FORGET),
+    test_state.windows[0]._closedTabs.length - remember_count,
+    "The correct amout of tabs are to be forgotten"
+  );
+  is(
+    countByTitle(closedTabs, REMEMBER),
+    remember_count,
+    "Everything is set up"
+  );
+
+  // All of the following calls with illegal arguments should throw NS_ERROR_ILLEGAL_VALUE.
+  ok(
+    testForError(() => ss.forgetClosedTab({}, 0)),
+    "Invalid window for forgetClosedTab throws"
+  );
+  ok(
+    testForError(() => ss.forgetClosedTab(newWin, -1)),
+    "Invalid tab for forgetClosedTab throws"
+  );
+  ok(
+    testForError(() =>
+      ss.forgetClosedTab(newWin, test_state.windows[0]._closedTabs.length + 1)
+    ),
+    "Invalid tab for forgetClosedTab throws"
+  );
+
+  // Remove third tab, then first tab.
+  ss.forgetClosedTab(newWin, 2);
+  ss.forgetClosedTab(newWin, null);
+
+  closedTabs = SessionStore.getClosedTabDataForWindow(newWin);
+
+  // Verify that non JSON serialized data is the same as JSON serialized data.
+  is(
+    JSON.stringify(closedTabs),
+    JSON.stringify(SessionStore.getClosedTabDataForWindow(newWin)),
+    "Non-serialized data is the same as serialized data"
+  );
+
+  is(
+    closedTabs.length,
+    remember_count,
+    "The correct amout of tabs was removed"
+  );
+  is(
+    countByTitle(closedTabs, FORGET),
+    0,
+    "All tabs specifically forgotten were indeed removed"
+  );
+  is(
+    countByTitle(closedTabs, REMEMBER),
+    remember_count,
+    "... and tabs not specifically forgetten weren't"
+  );
+
+  // Clean up.
+  Services.prefs.clearUserPref("browser.sessionstore.max_tabs_undo");
+  await BrowserTestUtils.closeWindow(newWin);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_461743.js b/src/zen/tests/mochitests/sessionstore/browser_461743.js
new file mode 100644
index 000000000..552947187
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_461743.js
@@ -0,0 +1,53 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+function test() {
+  /** Test for Bug 461743 */
+
+  waitForExplicitFinish();
+
+  let testURL =
+    "http://mochi.test:8888/browser/" +
+    "browser/components/sessionstore/test/browser_461743_sample.html";
+
+  let frameCount = 0;
+  let tab = BrowserTestUtils.addTab(gBrowser, testURL);
+  tab.linkedBrowser.addEventListener(
+    "load",
+    function loadListener(aEvent) {
+      // Wait for all frames to load completely.
+      if (frameCount++ < 2) {
+        return;
+      }
+      tab.linkedBrowser.removeEventListener("load", loadListener, true);
+      let tab2 = gBrowser.duplicateTab(tab);
+      tab2.linkedBrowser.addEventListener(
+        "461743",
+        function listener() {
+          tab2.linkedBrowser.removeEventListener("461743", listener, true);
+          is(aEvent.data, "done", "XSS injection was attempted");
+
+          executeSoon(function () {
+            let iframes = tab2.linkedBrowser.contentWindow.frames;
+            let innerHTML = iframes[1].document.body.innerHTML;
+            isnot(
+              innerHTML,
+              Cu.reportError.toString(),
+              "chrome access denied!"
+            );
+
+            // Clean up.
+            gBrowser.removeTab(tab2);
+            gBrowser.removeTab(tab);
+
+            finish();
+          });
+        },
+        true,
+        true
+      );
+    },
+    true
+  );
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_461743_sample.html b/src/zen/tests/mochitests/sessionstore/browser_461743_sample.html
new file mode 100644
index 000000000..a933ec5dc
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_461743_sample.html
@@ -0,0 +1,56 @@
+<!-- Testcase originally by <moz_bug_r_a4@yahoo.com> -->
+
+<!DOCTYPE html>
+<title>Test for bug 461743</title>
+
+<body>
+<iframe src="data:text/html;charset=utf-8,empty"></iframe>
+<iframe></iframe>
+
+<script type="application/javascript">
+  var chromeUrl = "chrome://global/content/mozilla.html";
+  var exploitUrl = "javascript:try { document.body.innerHTML = Components.utils.reportError; } catch (ex) { }";
+
+  var loadCount = 0;
+  frames[0].addEventListener("DOMContentLoaded", handleLoad);
+  frames[1].addEventListener("DOMContentLoaded", handleLoad);
+  function handleLoad() {
+    if (++loadCount < 2)
+      return;
+    frames[0].removeEventListener("DOMContentLoaded", handleLoad);
+    frames[1].removeEventListener("DOMContentLoaded", handleLoad);
+
+    var flip = 0;
+    MutationEvent.prototype.toString = function() {
+      return flip++ == 0 ? chromeUrl : exploitUrl;
+    };
+
+    var href = Object.getOwnPropertyDescriptor(Object.getPrototypeOf(frames[1].location), "href").get;
+    var loadChrome = { handleEvent: href };
+    var loadExploit = { handleEvent: href };
+
+    function delay() {
+      var xhr = new XMLHttpRequest();
+      xhr.open("GET", location.href, false);
+      xhr.send(null);
+    }
+    function done() {
+      var event = new MessageEvent("461743", { bubbles: true, cancelable: false,
+                                               data: "done", origin: location.href,
+                                               source: window });
+      document.dispatchEvent(event);
+      frames[0].document.removeEventListener("DOMNodeInserted", loadChrome, true);
+      frames[0].document.removeEventListener("DOMNodeInserted", delay, true);
+      frames[0].document.removeEventListener("DOMNodeInserted", loadExploit, true);
+      frames[0].document.removeEventListener("DOMNodeInserted", done, true);
+    }
+
+    frames[0].document.addEventListener("DOMNodeInserted", loadChrome, true);
+    frames[0].document.addEventListener("DOMNodeInserted", delay, true);
+    frames[0].document.addEventListener("DOMNodeInserted", loadExploit, true);
+    frames[0].document.addEventListener("DOMNodeInserted", done, true);
+
+    frames[0].document.designMode = "on";
+  }
+</script>
+</body>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_463205.js b/src/zen/tests/mochitests/sessionstore/browser_463205.js
new file mode 100644
index 000000000..dd3fc59b4
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_463205.js
@@ -0,0 +1,40 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const URL = ROOT + "browser_463205_sample.html";
+
+/**
+ * Bug 463205 - Check URLs before restoring form data to make sure a malicious
+ * website can't modify frame URLs and make us inject form data into the wrong
+ * web pages.
+ */
+add_task(async function test_check_urls_before_restoring() {
+  // Add a blank tab.
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:blank");
+  let browser = tab.linkedBrowser;
+  await BrowserTestUtils.browserLoaded(browser, { wantLoad: "about:blank" });
+
+  // Restore form data with a valid URL.
+  await promiseTabState(tab, getState(URL));
+
+  let value = await getPropertyOfFormField(browser, "#text", "value");
+  is(value, "foobar", "value was restored");
+
+  // Restore form data with an invalid URL.
+  await promiseTabState(tab, getState("http://example.com/"));
+
+  value = await getPropertyOfFormField(browser, "#text", "value");
+  is(value, "", "value was not restored");
+
+  // Cleanup.
+  gBrowser.removeTab(tab);
+});
+
+function getState(url) {
+  return JSON.stringify({
+    entries: [{ url: URL, triggeringPrincipal_base64 }],
+    formdata: { url, id: { text: "foobar" } },
+  });
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_463205_sample.html b/src/zen/tests/mochitests/sessionstore/browser_463205_sample.html
new file mode 100644
index 000000000..6591401b6
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_463205_sample.html
@@ -0,0 +1,7 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>bug 463205</title>
+
+<body>
+  <input type="text" id="text" />
+</body>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_463206.js b/src/zen/tests/mochitests/sessionstore/browser_463206.js
new file mode 100644
index 000000000..b760f1c76
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_463206.js
@@ -0,0 +1,120 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const MOCHI_ROOT = ROOT.replace(
+  "chrome://mochitests/content/",
+  "http://mochi.test:8888/"
+);
+if (gFissionBrowser) {
+  addCoopTask(
+    "browser_463206_sample.html",
+    test_restore_text_data_subframes,
+    HTTPSROOT
+  );
+}
+addNonCoopTask(
+  "browser_463206_sample.html",
+  test_restore_text_data_subframes,
+  HTTPSROOT
+);
+addNonCoopTask(
+  "browser_463206_sample.html",
+  test_restore_text_data_subframes,
+  HTTPROOT
+);
+addNonCoopTask(
+  "browser_463206_sample.html",
+  test_restore_text_data_subframes,
+  MOCHI_ROOT
+);
+
+async function test_restore_text_data_subframes(aURL) {
+  // Add a new tab.
+  let tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, aURL);
+
+  await setPropertyOfFormField(
+    tab.linkedBrowser,
+    "#out1",
+    "value",
+    Date.now().toString(16)
+  );
+
+  await setPropertyOfFormField(
+    tab.linkedBrowser,
+    "input[name='1|#out2']",
+    "value",
+    Math.random()
+  );
+
+  await setPropertyOfFormField(
+    tab.linkedBrowser.browsingContext.children[0].children[1],
+    "#in1",
+    "value",
+    new Date()
+  );
+
+  // Duplicate the tab.
+  let tab2 = gBrowser.duplicateTab(tab);
+  let browser2 = tab2.linkedBrowser;
+  await promiseTabRestored(tab2);
+
+  isnot(
+    await getPropertyOfFormField(browser2, "#out1", "value"),
+    await getPropertyOfFormField(
+      browser2.browsingContext.children[1],
+      "#out1",
+      "value"
+    ),
+    "text isn't reused for frames"
+  );
+
+  isnot(
+    await getPropertyOfFormField(browser2, "input[name='1|#out2']", "value"),
+    "",
+    "text containing | and # is correctly restored"
+  );
+
+  is(
+    await getPropertyOfFormField(
+      browser2.browsingContext.children[1],
+      "#out2",
+      "value"
+    ),
+    "",
+    "id prefixes can't be faked"
+  );
+
+  // Query a few values from the top and its child frames.
+  await SpecialPowers.spawn(tab2.linkedBrowser, [], async function () {
+    // Bug 588077
+    // XXX(farre): disabling this, because it started passing more heavily on Windows.
+    /*
+    let in1ValFrame0_1 = await SpecialPowers.spawn(
+      content.frames[0],
+      [],
+      async function() {
+        return SpecialPowers.spawn(content.frames[1], [], async function() {
+          return content.document.getElementById("in1").value;
+        });
+      }
+    );
+    todo_is(in1ValFrame0_1, "", "id prefixes aren't mixed up");
+    */
+  });
+
+  is(
+    await getPropertyOfFormField(
+      browser2.browsingContext.children[1].children[0],
+      "#in1",
+      "value"
+    ),
+    "",
+    "id prefixes aren't mixed up"
+  );
+  // Cleanup.
+  gBrowser.removeTab(tab2);
+  gBrowser.removeTab(tab);
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_463206_sample.html b/src/zen/tests/mochitests/sessionstore/browser_463206_sample.html
new file mode 100644
index 000000000..0d31f2906
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_463206_sample.html
@@ -0,0 +1,11 @@
+<!-- Testcase originally by <moz_bug_r_a4@yahoo.com> -->
+
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>Test for bug 463206</title>
+
+<iframe src="data:text/html;charset=utf-8,<iframe></iframe><iframe%20src='data:text/html;charset=utf-8,<input%2520id=%2522in1%2522>'></iframe>"></iframe>
+<iframe src="data:text/html;charset=utf-8,<input%20id='out1'><input%20id='out2'><iframe%20src='data:text/html;charset=utf-8,<input%2520id=%2522in1%2522>'>"></iframe>
+
+<input id="out1">
+<input name="1|#out2">
diff --git a/src/zen/tests/mochitests/sessionstore/browser_464199.js b/src/zen/tests/mochitests/sessionstore/browser_464199.js
new file mode 100644
index 000000000..5e0010b04
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_464199.js
@@ -0,0 +1,176 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+let { ForgetAboutSite } = ChromeUtils.importESModule(
+  "moz-src:///toolkit/components/forgetaboutsite/ForgetAboutSite.sys.mjs"
+);
+
+function promiseClearHistory() {
+  return new Promise(resolve => {
+    let observer = {
+      observe() {
+        Services.obs.removeObserver(
+          this,
+          "browser:purge-session-history-for-domain"
+        );
+        resolve();
+      },
+    };
+    Services.obs.addObserver(
+      observer,
+      "browser:purge-session-history-for-domain"
+    );
+  });
+}
+
+add_task(async function () {
+  /** Test for Bug 464199 */
+
+  const REMEMBER = Date.now(),
+    FORGET = Math.random();
+  let test_state = {
+    windows: [
+      {
+        tabs: [{ entries: [] }],
+        _closedTabs: [
+          {
+            state: { entries: [{ url: "http://www.example.net/" }] },
+            title: FORGET,
+          },
+          {
+            state: { entries: [{ url: "http://www.example.org/" }] },
+            title: REMEMBER,
+          },
+          {
+            state: {
+              entries: [
+                { url: "http://www.example.net/" },
+                { url: "http://www.example.org/" },
+              ],
+            },
+            title: FORGET,
+          },
+          {
+            state: { entries: [{ url: "http://example.net/" }] },
+            title: FORGET,
+          },
+          {
+            state: { entries: [{ url: "http://sub.example.net/" }] },
+            title: FORGET,
+          },
+          {
+            state: { entries: [{ url: "http://www.example.net:8080/" }] },
+            title: FORGET,
+          },
+          { state: { entries: [{ url: "about:license" }] }, title: REMEMBER },
+          {
+            state: {
+              entries: [
+                {
+                  url: "http://www.example.org/frameset",
+                  children: [
+                    { url: "http://www.example.org/frame" },
+                    { url: "http://www.example.org:8080/frame2" },
+                  ],
+                },
+              ],
+            },
+            title: REMEMBER,
+          },
+          {
+            state: {
+              entries: [
+                {
+                  url: "http://www.example.org/frameset",
+                  children: [
+                    { url: "http://www.example.org/frame" },
+                    { url: "http://www.example.net/frame" },
+                  ],
+                },
+              ],
+            },
+            title: FORGET,
+          },
+          {
+            state: {
+              entries: [
+                {
+                  url: "http://www.example.org/form",
+                  formdata: { id: { url: "http://www.example.net/" } },
+                },
+              ],
+            },
+            title: REMEMBER,
+          },
+          {
+            state: {
+              entries: [{ url: "http://www.example.org/form" }],
+              extData: { setCustomTabValue: "http://example.net:80" },
+            },
+            title: REMEMBER,
+          },
+        ],
+      },
+    ],
+  };
+  let remember_count = 5;
+
+  function countByTitle(aClosedTabList, aTitle) {
+    return aClosedTabList.filter(aData => aData.title == aTitle).length;
+  }
+
+  // open a window and add the above closed tab list
+  let newWin = openDialog(location, "", "chrome,all,dialog=no");
+  await promiseWindowLoaded(newWin);
+  Services.prefs.setIntPref(
+    "browser.sessionstore.max_tabs_undo",
+    test_state.windows[0]._closedTabs.length
+  );
+
+  let restoring = promiseWindowRestoring(newWin);
+  let restored = promiseWindowRestored(newWin);
+  ss.setWindowState(newWin, JSON.stringify(test_state), true);
+  await restoring;
+  await restored;
+
+  let closedTabs = ss.getClosedTabDataForWindow(newWin);
+  is(
+    closedTabs.length,
+    test_state.windows[0]._closedTabs.length,
+    "Closed tab list has the expected length"
+  );
+  is(
+    countByTitle(closedTabs, FORGET),
+    test_state.windows[0]._closedTabs.length - remember_count,
+    "The correct amout of tabs are to be forgotten"
+  );
+  is(
+    countByTitle(closedTabs, REMEMBER),
+    remember_count,
+    "Everything is set up."
+  );
+
+  let promise = promiseClearHistory();
+  await ForgetAboutSite.removeDataFromBaseDomain("example.net");
+  await promise;
+  closedTabs = ss.getClosedTabDataForWindow(newWin);
+  is(
+    closedTabs.length,
+    remember_count,
+    "The correct amout of tabs was removed"
+  );
+  is(
+    countByTitle(closedTabs, FORGET),
+    0,
+    "All tabs to be forgotten were indeed removed"
+  );
+  is(
+    countByTitle(closedTabs, REMEMBER),
+    remember_count,
+    "... and tabs to be remembered weren't."
+  );
+  // clean up
+  Services.prefs.clearUserPref("browser.sessionstore.max_tabs_undo");
+  await BrowserTestUtils.closeWindow(newWin);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_464620_a.html b/src/zen/tests/mochitests/sessionstore/browser_464620_a.html
new file mode 100644
index 000000000..5edb7e1a4
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_464620_a.html
@@ -0,0 +1,54 @@
+<!-- Testcase originally by <moz_bug_r_a4@yahoo.com> -->
+
+<title>Test for bug 464620 (injection on input)</title>
+
+<iframe></iframe>
+<iframe onload="setup()"></iframe>
+
+<script>
+  var targetUrl = "http://mochi.test:8888/browser/" +
+    "browser/components/sessionstore/test/browser_464620_xd.html";
+  var firstPass;
+
+  function setup() {
+    if (firstPass !== undefined)
+      return;
+    firstPass = frames[1].location.href == "about:blank";
+    if (firstPass) {
+      frames[0].location = 'data:text/html;charset=utf-8,<body onload="if (parent.firstPass) parent.step();"><input id="x" oninput="parent.xss()">XXX</body>';
+    }
+    frames[1].location = targetUrl;
+  }
+
+  function step() {
+    var x = frames[0].document.getElementById("x");
+    if (x.value == "")
+      x.value = "ready";
+    x.style.display = "none";
+    frames[0].document.designMode = "on";
+  }
+
+  function xss() {
+    step();
+
+    var documentInjected = false;
+    document.getElementsByTagName("iframe")[0].onload =
+      function() { documentInjected = true; };
+    frames[0].location = targetUrl;
+
+    for (var c = 0; !documentInjected && c < 20; c++) {
+      var r = new XMLHttpRequest();
+      r.open("GET", location.href, false);
+      r.overrideMimeType("text/plain");
+      r.send(null);
+    }
+    document.getElementById("state").textContent = "done";
+
+    var event = new MessageEvent("464620_a", { bubbles: true, cancelable: false,
+                                               data: "done", origin: location.href,
+                                               source: window });
+    document.dispatchEvent(event);
+  }
+</script>
+
+<p id="state">pending</p>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_464620_a.js b/src/zen/tests/mochitests/sessionstore/browser_464620_a.js
new file mode 100644
index 000000000..2ab0ca261
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_464620_a.js
@@ -0,0 +1,64 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+function test() {
+  /** Test for Bug 464620 (injection on input) */
+
+  waitForExplicitFinish();
+
+  let testURL =
+    "http://mochi.test:8888/browser/" +
+    "browser/components/sessionstore/test/browser_464620_a.html";
+
+  var frameCount = 0;
+  let tab = BrowserTestUtils.addTab(gBrowser, testURL);
+  tab.linkedBrowser.addEventListener(
+    "load",
+    function loadListener(aEvent) {
+      // wait for all frames to load completely
+      if (frameCount++ < 4) {
+        return;
+      }
+      this.removeEventListener("load", loadListener, true);
+
+      executeSoon(function () {
+        frameCount = 0;
+        let tab2 = gBrowser.duplicateTab(tab);
+        tab2.linkedBrowser.addEventListener(
+          "464620_a",
+          function listener() {
+            tab2.linkedBrowser.removeEventListener("464620_a", listener, true);
+            is(aEvent.data, "done", "XSS injection was attempted");
+
+            // let form restoration complete and take into account the
+            // setTimeout(..., 0) in sss_restoreDocument_proxy
+            executeSoon(function () {
+              setTimeout(function () {
+                let win = tab2.linkedBrowser.contentWindow;
+                isnot(
+                  win.frames[0].document.location,
+                  testURL,
+                  "cross domain document was loaded"
+                );
+                ok(
+                  !/XXX/.test(win.frames[0].document.body.innerHTML),
+                  "no content was injected"
+                );
+
+                // clean up
+                gBrowser.removeTab(tab2);
+                gBrowser.removeTab(tab);
+
+                finish();
+              }, 0);
+            });
+          },
+          true,
+          true
+        );
+      });
+    },
+    true
+  );
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_464620_b.html b/src/zen/tests/mochitests/sessionstore/browser_464620_b.html
new file mode 100644
index 000000000..e7fde55c2
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_464620_b.html
@@ -0,0 +1,57 @@
+<!-- Testcase originally by <moz_bug_r_a4@yahoo.com> -->
+
+<title>Test for bug 464620 (injection on DOM node insertion)</title>
+
+<iframe></iframe>
+<iframe></iframe>
+<iframe onload="setup()"></iframe>
+
+<script>
+  var targetUrl = "http://mochi.test:8888/browser/" +
+    "browser/components/sessionstore/test/browser_464620_xd.html";
+  var firstPass;
+
+  function setup() {
+    if (firstPass !== undefined)
+      return;
+    firstPass = frames[2].location.href == "about:blank";
+    if (firstPass) {
+      frames[0].location = 'data:text/html;charset=utf-8,<body onload="parent.step()">a</body>';
+      frames[1].location = 'data:text/html;charset=utf-8,<body onload="document.designMode=\'on\';">XXX</body>';
+    }
+    frames[2].location = targetUrl;
+  }
+
+  function step() {
+    frames[0].document.designMode = "on";
+    if (firstPass)
+      return;
+
+    var body = frames[0].document.body;
+    body.addEventListener("DOMNodeInserted", function() {
+      xss();
+    }, {capture: true, once: true});
+  }
+
+  function xss() {
+    var documentInjected = false;
+    document.getElementsByTagName("iframe")[1].onload =
+      function() { documentInjected = true; };
+    frames[1].location = targetUrl;
+
+    for (var c = 0; !documentInjected && c < 20; c++) {
+      var r = new XMLHttpRequest();
+      r.open("GET", location.href, false);
+      r.overrideMimeType("text/plain");
+      r.send(null);
+    }
+    document.getElementById("state").textContent = "done";
+
+    var event = new MessageEvent("464620_b", { bubbles: true, cancelable: false,
+                                               data: "done", origin: location.href,
+                                               source: window });
+    document.dispatchEvent(event);
+  }
+</script>
+
+<p id="state">pending</p>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_464620_b.js b/src/zen/tests/mochitests/sessionstore/browser_464620_b.js
new file mode 100644
index 000000000..a8aef26c5
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_464620_b.js
@@ -0,0 +1,64 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+function test() {
+  /** Test for Bug 464620 (injection on DOM node insertion) */
+
+  waitForExplicitFinish();
+
+  let testURL =
+    "http://mochi.test:8888/browser/" +
+    "browser/components/sessionstore/test/browser_464620_b.html";
+
+  var frameCount = 0;
+  let tab = BrowserTestUtils.addTab(gBrowser, testURL);
+  tab.linkedBrowser.addEventListener(
+    "load",
+    function loadListener(aEvent) {
+      // wait for all frames to load completely
+      if (frameCount++ < 6) {
+        return;
+      }
+      this.removeEventListener("load", loadListener, true);
+
+      executeSoon(function () {
+        frameCount = 0;
+        let tab2 = gBrowser.duplicateTab(tab);
+        tab2.linkedBrowser.addEventListener(
+          "464620_b",
+          function listener() {
+            tab2.linkedBrowser.removeEventListener("464620_b", listener, true);
+            is(aEvent.data, "done", "XSS injection was attempted");
+
+            // let form restoration complete and take into account the
+            // setTimeout(..., 0) in sss_restoreDocument_proxy
+            executeSoon(function () {
+              setTimeout(function () {
+                let win = tab2.linkedBrowser.contentWindow;
+                isnot(
+                  win.frames[1].document.location,
+                  testURL,
+                  "cross domain document was loaded"
+                );
+                ok(
+                  !/XXX/.test(win.frames[1].document.body.innerHTML),
+                  "no content was injected"
+                );
+
+                // clean up
+                gBrowser.removeTab(tab2);
+                gBrowser.removeTab(tab);
+
+                finish();
+              }, 0);
+            });
+          },
+          true,
+          true
+        );
+      });
+    },
+    true
+  );
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_464620_xd.html b/src/zen/tests/mochitests/sessionstore/browser_464620_xd.html
new file mode 100644
index 000000000..9ec51c4c7
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_464620_xd.html
@@ -0,0 +1,5 @@
+<title>Cross Document File for bug 464620</title>
+
+<body onload="document.designMode='on';" bgcolor="red">
+  This document is editable.
+</body>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_465215.js b/src/zen/tests/mochitests/sessionstore/browser_465215.js
new file mode 100644
index 000000000..bf16464fd
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_465215.js
@@ -0,0 +1,38 @@
+"use strict";
+
+var uniqueName = "bug 465215";
+var uniqueValue1 = "as good as unique: " + Date.now();
+var uniqueValue2 = "as good as unique: " + Math.random();
+
+add_task(async function () {
+  // set a unique value on a new, blank tab
+  let tab1 = BrowserTestUtils.addTab(gBrowser, "about:blank");
+  await BrowserTestUtils.browserLoaded(tab1.linkedBrowser, {
+    wantLoad: "about:blank",
+  });
+  ss.setCustomTabValue(tab1, uniqueName, uniqueValue1);
+
+  // duplicate the tab with that value
+  let tab2 = ss.duplicateTab(window, tab1);
+  await promiseTabRestored(tab2);
+  is(
+    ss.getCustomTabValue(tab2, uniqueName),
+    uniqueValue1,
+    "tab value was duplicated"
+  );
+
+  ss.setCustomTabValue(tab2, uniqueName, uniqueValue2);
+  isnot(
+    ss.getCustomTabValue(tab1, uniqueName),
+    uniqueValue2,
+    "tab values aren't sync'd"
+  );
+
+  // overwrite the tab with the value which should remove it
+  await promiseTabState(tab1, { entries: [] });
+  is(ss.getCustomTabValue(tab1, uniqueName), "", "tab value was cleared");
+
+  // clean up
+  gBrowser.removeTab(tab2);
+  gBrowser.removeTab(tab1);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_465223.js b/src/zen/tests/mochitests/sessionstore/browser_465223.js
new file mode 100644
index 000000000..f843e09dd
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_465223.js
@@ -0,0 +1,51 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+add_task(async function test_clearWindowValues() {
+  /** Test for Bug 465223 */
+
+  let uniqueKey1 = "bug 465223.1";
+  let uniqueKey2 = "bug 465223.2";
+  let uniqueValue1 = "unik" + Date.now();
+  let uniqueValue2 = "pi != " + Math.random();
+
+  // open a window and set a value on it
+  let newWin = openDialog(location, "_blank", "chrome,all,dialog=no");
+  await promiseWindowLoaded(newWin);
+  ss.setCustomWindowValue(newWin, uniqueKey1, uniqueValue1);
+
+  let newState = { windows: [{ tabs: [{ entries: [] }], extData: {} }] };
+  newState.windows[0].extData[uniqueKey2] = uniqueValue2;
+  await setWindowState(newWin, newState);
+
+  is(newWin.gBrowser.tabs.length, 2, "original tab wasn't overwritten");
+  is(
+    ss.getCustomWindowValue(newWin, uniqueKey1),
+    uniqueValue1,
+    "window value wasn't overwritten when the tabs weren't"
+  );
+  is(
+    ss.getCustomWindowValue(newWin, uniqueKey2),
+    uniqueValue2,
+    "new window value was correctly added"
+  );
+
+  newState.windows[0].extData[uniqueKey2] = uniqueValue1;
+  await setWindowState(newWin, newState, true);
+
+  is(newWin.gBrowser.tabs.length, 1, "original tabs were overwritten");
+  is(
+    ss.getCustomWindowValue(newWin, uniqueKey1),
+    "",
+    "window value was cleared"
+  );
+  is(
+    ss.getCustomWindowValue(newWin, uniqueKey2),
+    uniqueValue1,
+    "window value was correctly overwritten"
+  );
+
+  // clean up
+  await BrowserTestUtils.closeWindow(newWin);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_466937.js b/src/zen/tests/mochitests/sessionstore/browser_466937.js
new file mode 100644
index 000000000..cca45fec3
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_466937.js
@@ -0,0 +1,51 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const URL = ROOT + "browser_466937_sample.html";
+
+/**
+ * Bug 466937 - Prevent file stealing with sessionstore.
+ */
+add_task(async function test_prevent_file_stealing() {
+  // Add a tab with some file input fields.
+  let tab = BrowserTestUtils.addTab(gBrowser, URL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  // Generate a path to a 'secret' file.
+  let file = Services.dirsvc.get("TmpD", Ci.nsIFile);
+  file.append("466937_test.file");
+  file.createUnique(Ci.nsIFile.NORMAL_FILE_TYPE, 0o666);
+  let testPath = file.path;
+
+  // Fill in form values.
+  await setPropertyOfFormField(
+    browser,
+    "#reverse_thief",
+    "value",
+    "/home/user/secret2"
+  );
+  await setPropertyOfFormField(browser, "#bystander", "value", testPath);
+
+  // Duplicate and check form values.
+  let tab2 = gBrowser.duplicateTab(tab);
+  let browser2 = tab2.linkedBrowser;
+  await promiseTabRestored(tab2);
+
+  let thief = await getPropertyOfFormField(browser2, "#thief", "value");
+  is(thief, "", "file path wasn't set to text field value");
+  let reverse_thief = await getPropertyOfFormField(
+    browser2,
+    "#reverse_thief",
+    "value"
+  );
+  is(reverse_thief, "", "text field value wasn't set to full file path");
+  let bystander = await getPropertyOfFormField(browser2, "#bystander", "value");
+  is(bystander, testPath, "normal case: file path was correctly preserved");
+
+  // Cleanup.
+  gBrowser.removeTab(tab);
+  gBrowser.removeTab(tab2);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_466937_sample.html b/src/zen/tests/mochitests/sessionstore/browser_466937_sample.html
new file mode 100644
index 000000000..a05defa12
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_466937_sample.html
@@ -0,0 +1,20 @@
+<!-- Testcase originally by <moz_bug_r_a4@yahoo.com> -->
+
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>Test for bug 466937</title>
+
+<input id="thief" value="/home/user/secret">
+<input type="file" id="reverse_thief">
+<input type="file" id="bystander">
+
+<script>
+  window.addEventListener("DOMContentLoaded", function() {
+    if (!document.location.hash) {
+      document.location.hash = "#ready";
+    } else {
+      document.getElementById("thief").type = "file";
+      document.getElementById("reverse_thief").type = "text";
+    }
+  }, {once: true});
+</script>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_467409-backslashplosion.js b/src/zen/tests/mochitests/sessionstore/browser_467409-backslashplosion.js
new file mode 100644
index 000000000..bc6a4b18b
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_467409-backslashplosion.js
@@ -0,0 +1,88 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+// Test Summary:
+// 1.  Open about:sessionrestore where formdata is a JS object, not a string
+// 1a. Check that #sessionData on the page is readable after JSON.parse (skipped, checking formdata is sufficient)
+// 1b. Check that there are no backslashes in the formdata
+// 1c. Check that formdata doesn't require JSON.parse
+//
+// 2.  Use the current state (currently about:sessionrestore with data) and then open that in a new instance of about:sessionrestore
+// 2a. Check that there are no backslashes in the formdata
+// 2b. Check that formdata doesn't require JSON.parse
+//
+// 3.  [backwards compat] Use a stringified state as formdata when opening about:sessionrestore
+// 3a. Make sure there are nodes in the tree on about:sessionrestore (skipped, checking formdata is sufficient)
+// 3b. Check that there are no backslashes in the formdata
+// 3c. Check that formdata doesn't require JSON.parse
+
+const CRASH_STATE = {
+  windows: [
+    {
+      tabs: [
+        { entries: [{ url: "about:mozilla", triggeringPrincipal_base64 }] },
+      ],
+    },
+  ],
+};
+const STATE = createEntries(CRASH_STATE);
+const STATE2 = createEntries({ windows: [{ tabs: [STATE] }] });
+const STATE3 = createEntries(JSON.stringify(CRASH_STATE));
+
+function createEntries(sessionData) {
+  return {
+    entries: [{ url: "about:sessionrestore", triggeringPrincipal_base64 }],
+    formdata: { id: { sessionData }, url: "about:sessionrestore" },
+  };
+}
+
+add_task(async function test_nested_about_sessionrestore() {
+  // Prepare a blank tab.
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:blank");
+  let browser = tab.linkedBrowser;
+  await BrowserTestUtils.browserLoaded(browser, { wantLoad: "about:blank" });
+
+  // test 1
+  await promiseTabState(tab, STATE);
+  await checkState("test1", tab);
+
+  // test 2
+  await promiseTabState(tab, STATE2);
+  await checkState("test2", tab);
+
+  // test 3
+  await promiseTabState(tab, STATE3);
+  await checkState("test3", tab);
+
+  // Cleanup.
+  gBrowser.removeTab(tab);
+});
+
+async function checkState(prefix, tab) {
+  // Flush and query tab state.
+  await TabStateFlusher.flush(tab.linkedBrowser);
+  let { formdata } = JSON.parse(ss.getTabState(tab));
+
+  ok(
+    formdata.id.sessionData,
+    prefix + ": we have form data for about:sessionrestore"
+  );
+
+  let sessionData_raw = JSON.stringify(formdata.id.sessionData);
+  ok(
+    !/\\/.test(sessionData_raw),
+    prefix + ": #sessionData contains no backslashes"
+  );
+  info(sessionData_raw);
+
+  let gotError = false;
+  try {
+    JSON.parse(formdata.id.sessionData);
+  } catch (e) {
+    info(prefix + ": got error: " + e);
+    gotError = true;
+  }
+  ok(gotError, prefix + ": attempting to JSON.parse form data threw error");
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_477657.js b/src/zen/tests/mochitests/sessionstore/browser_477657.js
new file mode 100644
index 000000000..ae235d4f0
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_477657.js
@@ -0,0 +1,80 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+add_task(async function test_sizemodeDefaults() {
+  /** Test for Bug 477657 */
+  let newWin = openDialog(location, "_blank", "chrome,all,dialog=no");
+  await promiseWindowLoaded(newWin);
+  let newState = {
+    windows: [
+      {
+        tabs: [{ entries: [] }],
+        _closedTabs: [
+          {
+            state: { entries: [{ url: "about:" }] },
+            title: "About:",
+          },
+        ],
+        sizemode: "maximized",
+      },
+    ],
+  };
+
+  let uniqueKey = "bug 477657";
+  let uniqueValue = "unik" + Date.now();
+
+  ss.setCustomWindowValue(newWin, uniqueKey, uniqueValue);
+  is(
+    ss.getCustomWindowValue(newWin, uniqueKey),
+    uniqueValue,
+    "window value was set before the window was overwritten"
+  );
+
+  await setWindowState(newWin, newState, true);
+  // use newWin.setTimeout(..., 0) to mirror sss_restoreWindowFeatures
+  await new Promise(resolve => newWin.setTimeout(resolve, 0));
+
+  is(
+    ss.getCustomWindowValue(newWin, uniqueKey),
+    "",
+    "window value was implicitly cleared"
+  );
+
+  is(newWin.windowState, newWin.STATE_MAXIMIZED, "the window was maximized");
+
+  is(
+    ss.getClosedTabDataForWindow(newWin).length,
+    1,
+    "the closed tab was added before the window was overwritten"
+  );
+  delete newState.windows[0]._closedTabs;
+  delete newState.windows[0].sizemode;
+
+  await setWindowState(newWin, newState, true);
+  await new Promise(resolve => newWin.setTimeout(resolve, 0));
+
+  is(
+    ss.getClosedTabDataForWindow(newWin).length,
+    0,
+    "closed tabs were implicitly cleared"
+  );
+
+  is(
+    newWin.windowState,
+    newWin.STATE_MAXIMIZED,
+    "the window remains maximized"
+  );
+  newState.windows[0].sizemode = "normal";
+
+  await setWindowState(newWin, newState, true);
+  await new Promise(resolve => newWin.setTimeout(resolve, 0));
+
+  isnot(
+    newWin.windowState,
+    newWin.STATE_MAXIMIZED,
+    "the window was explicitly unmaximized"
+  );
+
+  await BrowserTestUtils.closeWindow(newWin);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_480893.js b/src/zen/tests/mochitests/sessionstore/browser_480893.js
new file mode 100644
index 000000000..e41b2efd9
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_480893.js
@@ -0,0 +1,45 @@
+"use strict";
+
+/**
+ * Tests that we get sent to the right page when the user clicks
+ * the "Close" button in about:sessionrestore
+ */
+add_task(async function () {
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.startup.page", 0]],
+  });
+
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:sessionrestore");
+  gBrowser.selectedTab = tab;
+  let browser = tab.linkedBrowser;
+  await BrowserTestUtils.browserLoaded(browser, false, "about:sessionrestore");
+
+  let doc = browser.contentDocument;
+
+  // Click on the "Close" button after about:sessionrestore is loaded.
+  doc.getElementById("errorCancel").click();
+
+  await BrowserTestUtils.browserLoaded(browser, false, "about:blank");
+
+  // Test that starting a new session loads the homepage (set to http://mochi.test:8888)
+  // if Firefox is configured to display a homepage at startup (browser.startup.page = 1)
+  let homepage = "http://mochi.test:8888/";
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["browser.startup.homepage", homepage],
+      ["browser.startup.page", 1],
+    ],
+  });
+
+  BrowserTestUtils.startLoadingURIString(browser, "about:sessionrestore");
+  await BrowserTestUtils.browserLoaded(browser, false, "about:sessionrestore");
+  doc = browser.contentDocument;
+
+  // Click on the "Close" button after about:sessionrestore is loaded.
+  doc.getElementById("errorCancel").click();
+  await BrowserTestUtils.browserLoaded(browser);
+
+  is(browser.currentURI.spec, homepage, "loaded page is the homepage");
+
+  BrowserTestUtils.removeTab(tab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_485482.js b/src/zen/tests/mochitests/sessionstore/browser_485482.js
new file mode 100644
index 000000000..f32523005
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_485482.js
@@ -0,0 +1,76 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+if (gFissionBrowser) {
+  addCoopTask(
+    "browser_485482_sample.html",
+    test_xpath_exp_for_strange_documents,
+    HTTPSROOT
+  );
+}
+addNonCoopTask(
+  "browser_485482_sample.html",
+  test_xpath_exp_for_strange_documents,
+  ROOT
+);
+addNonCoopTask(
+  "browser_485482_sample.html",
+  test_xpath_exp_for_strange_documents,
+  HTTPSROOT
+);
+addNonCoopTask(
+  "browser_485482_sample.html",
+  test_xpath_exp_for_strange_documents,
+  HTTPROOT
+);
+
+/**
+ * Bug 485482 - Make sure that we produce valid XPath expressions even for very
+ * weird HTML documents.
+ */
+async function test_xpath_exp_for_strange_documents(aURL) {
+  // Load a page with weird tag names.
+  let tab = BrowserTestUtils.addTab(gBrowser, aURL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  // Fill in some values.
+  let uniqueValue = Math.random();
+  await setPropertyOfFormField(
+    browser,
+    "input[type=text]",
+    "value",
+    uniqueValue
+  );
+  await setPropertyOfFormField(
+    browser,
+    "input[type=checkbox]",
+    "checked",
+    true
+  );
+
+  // Duplicate the tab.
+  let tab2 = gBrowser.duplicateTab(tab);
+  let browser2 = tab2.linkedBrowser;
+  await promiseTabRestored(tab2);
+
+  // Check that we generated valid XPath expressions to restore form values.
+  let text = await getPropertyOfFormField(
+    browser2,
+    "input[type=text]",
+    "value"
+  );
+  is("" + text, "" + uniqueValue, "generated XPath expression was valid");
+  let checkbox = await getPropertyOfFormField(
+    browser2,
+    "input[type=checkbox]",
+    "checked"
+  );
+  ok(checkbox, "generated XPath expression was valid");
+
+  // Cleanup.
+  gBrowser.removeTab(tab2);
+  gBrowser.removeTab(tab);
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_485482_sample.html b/src/zen/tests/mochitests/sessionstore/browser_485482_sample.html
new file mode 100644
index 000000000..c2097b593
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_485482_sample.html
@@ -0,0 +1,12 @@
+<!DOCTYPE html>
+<title>Test for bug 485482</title>
+
+<bad=name>
+  <input type="text">
+</bad=name>
+
+<worse=name>
+  <l0c@l+na~e"'�>
+    <input type="checkbox" name="check"> Check
+  </l0c@l+na~e"'�>
+</worse=name>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_485563.js b/src/zen/tests/mochitests/sessionstore/browser_485563.js
new file mode 100644
index 000000000..997b41560
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_485563.js
@@ -0,0 +1,35 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+function test() {
+  /** Test for Bug 485563 */
+
+  waitForExplicitFinish();
+
+  let uniqueValue =
+    Math.random() + "\u2028Second line\u2029Second paragraph\u2027";
+
+  let tab = BrowserTestUtils.addTab(gBrowser);
+  BrowserTestUtils.browserLoaded(tab.linkedBrowser, {
+    wantLoad: "about:blank",
+  }).then(() => {
+    ss.setCustomTabValue(tab, "bug485563", uniqueValue);
+    let tabState = JSON.parse(ss.getTabState(tab));
+    is(
+      tabState.extData.bug485563,
+      uniqueValue,
+      "unicode line separator wasn't over-encoded"
+    );
+    ss.deleteCustomTabValue(tab, "bug485563");
+    ss.setTabState(tab, JSON.stringify(tabState));
+    is(
+      ss.getCustomTabValue(tab, "bug485563"),
+      uniqueValue,
+      "unicode line separator was correctly preserved"
+    );
+
+    gBrowser.removeTab(tab);
+    finish();
+  });
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_490040.js b/src/zen/tests/mochitests/sessionstore/browser_490040.js
new file mode 100644
index 000000000..50cf0587c
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_490040.js
@@ -0,0 +1,107 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// Only windows with open tabs are restorable. Windows where a lone tab is
+// detached may have _closedTabs, but is left with just an empty tab.
+const STATES = [
+  {
+    shouldBeAdded: true,
+    windowState: {
+      windows: [
+        {
+          tabs: [
+            {
+              entries: [
+                {
+                  url: "http://example.com",
+                  triggeringPrincipal_base64,
+                  title: "example.com",
+                },
+              ],
+            },
+          ],
+          selected: 1,
+          _closedTabs: [],
+        },
+      ],
+    },
+  },
+  {
+    shouldBeAdded: false,
+    windowState: {
+      windows: [
+        {
+          tabs: [{ entries: [] }],
+          _closedTabs: [],
+        },
+      ],
+    },
+  },
+  {
+    shouldBeAdded: false,
+    windowState: {
+      windows: [
+        {
+          tabs: [{ entries: [] }],
+          _closedTabs: [
+            {
+              state: {
+                entries: [
+                  {
+                    url: "http://example.com",
+                    triggeringPrincipal_base64,
+                    index: 1,
+                  },
+                ],
+              },
+            },
+          ],
+        },
+      ],
+    },
+  },
+  {
+    shouldBeAdded: false,
+    windowState: {
+      windows: [
+        {
+          tabs: [{ entries: [] }],
+          _closedTabs: [],
+          extData: { keyname: "pi != " + Math.random() },
+        },
+      ],
+    },
+  },
+];
+
+add_task(async function test_bug_490040() {
+  for (let state of STATES) {
+    // Ensure we can store the window if needed.
+    let startingClosedWindowCount = ss.getClosedWindowCount();
+    await pushPrefs([
+      "browser.sessionstore.max_windows_undo",
+      startingClosedWindowCount + 1,
+    ]);
+
+    let curClosedWindowCount = ss.getClosedWindowCount();
+    let win = await BrowserTestUtils.openNewBrowserWindow();
+
+    await setWindowState(win, state.windowState, true);
+    if (state.windowState.windows[0].tabs.length) {
+      await BrowserTestUtils.browserLoaded(win.gBrowser.selectedBrowser, {
+        wantLoad: () => true,
+      });
+    }
+
+    await BrowserTestUtils.closeWindow(win);
+
+    is(
+      ss.getClosedWindowCount(),
+      curClosedWindowCount + (state.shouldBeAdded ? 1 : 0),
+      "That window should " +
+        (state.shouldBeAdded ? "" : "not ") +
+        "be restorable"
+    );
+  }
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_491168.js b/src/zen/tests/mochitests/sessionstore/browser_491168.js
new file mode 100644
index 000000000..7adb5a8b9
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_491168.js
@@ -0,0 +1,113 @@
+"use strict";
+
+const REFERRER1 = "http://example.org/?" + Date.now();
+const REFERRER2 = "http://example.org/?" + Math.random();
+const REFERRER3 = "http://example.org/?" + Math.random();
+
+add_task(async function () {
+  function getExpectedReferrer(referrer) {
+    let defaultPolicy = Services.prefs.getIntPref(
+      "network.http.referer.defaultPolicy"
+    );
+    Assert.greater(
+      [2, 3].indexOf(defaultPolicy),
+      -1,
+      "default referrer policy should be either strict-origin-when-cross-origin(2) or no-referrer-when-downgrade(3)"
+    );
+    if (defaultPolicy == 2) {
+      return referrer.match(/https?:\/\/[^\/]+\/?/i)[0];
+    }
+    return referrer;
+  }
+
+  async function checkDocumentReferrer(referrer, msg) {
+    await SpecialPowers.spawn(
+      gBrowser.selectedBrowser,
+      [{ referrer, msg }],
+      async function (args) {
+        Assert.equal(content.document.referrer, args.referrer, args.msg);
+      }
+    );
+  }
+
+  let ReferrerInfo = Components.Constructor(
+    "@mozilla.org/referrer-info;1",
+    "nsIReferrerInfo",
+    "init"
+  );
+  // Add a new tab.
+  let tab = (gBrowser.selectedTab = BrowserTestUtils.addTab(
+    gBrowser,
+    "about:blank"
+  ));
+  let browser = tab.linkedBrowser;
+  await BrowserTestUtils.browserLoaded(browser, { wantLoad: "about:blank" });
+
+  // Load a new URI with a specific referrer.
+  let referrerInfo1 = new ReferrerInfo(
+    Ci.nsIReferrerInfo.EMPTY,
+    true,
+    Services.io.newURI(REFERRER1)
+  );
+  browser.loadURI(Services.io.newURI("http://example.org"), {
+    referrerInfo: referrerInfo1,
+    triggeringPrincipal: Services.scriptSecurityManager.createNullPrincipal({}),
+  });
+  await promiseBrowserLoaded(browser);
+
+  await TabStateFlusher.flush(browser);
+  let tabState = JSON.parse(ss.getTabState(tab));
+  let actualReferrerInfo = E10SUtils.deserializeReferrerInfo(
+    tabState.entries[0].referrerInfo
+  );
+  is(
+    actualReferrerInfo.originalReferrer.spec,
+    REFERRER1,
+    "Referrer retrieved via getTabState matches referrer set via loadURI."
+  );
+
+  let referrerInfo2 = new ReferrerInfo(
+    Ci.nsIReferrerInfo.EMPTY,
+    true,
+    Services.io.newURI(REFERRER2)
+  );
+
+  tabState.entries[0].referrerInfo =
+    E10SUtils.serializeReferrerInfo(referrerInfo2);
+  await promiseTabState(tab, tabState);
+
+  await checkDocumentReferrer(
+    getExpectedReferrer(REFERRER2),
+    "document.referrer matches referrer set via setTabState using referrerInfo."
+  );
+  gBrowser.removeCurrentTab();
+
+  // Restore the closed tab.
+  tab = ss.undoCloseTab(window, 0);
+  await promiseTabRestored(tab);
+
+  await checkDocumentReferrer(
+    getExpectedReferrer(REFERRER2),
+    "document.referrer is still correct after closing and reopening the tab."
+  );
+
+  tabState.entries[0].referrerInfo = null;
+  tabState.entries[0].referrer = REFERRER3;
+  await promiseTabState(tab, tabState);
+
+  await checkDocumentReferrer(
+    getExpectedReferrer(REFERRER3),
+    "document.referrer matches referrer set via setTabState using referrer."
+  );
+  gBrowser.removeCurrentTab();
+
+  // Restore the closed tab.
+  tab = ss.undoCloseTab(window, 0);
+  await promiseTabRestored(tab);
+
+  await checkDocumentReferrer(
+    getExpectedReferrer(REFERRER3),
+    "document.referrer is still correct after closing and reopening the tab."
+  );
+  gBrowser.removeCurrentTab();
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_491577.js b/src/zen/tests/mochitests/sessionstore/browser_491577.js
new file mode 100644
index 000000000..ba64ab71f
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_491577.js
@@ -0,0 +1,212 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+add_task(async function test_deleteClosedWindow() {
+  /** Test for Bug 491577 */
+
+  const REMEMBER = Date.now(),
+    FORGET = Math.random();
+  let test_state = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              { url: "http://example.com/", triggeringPrincipal_base64 },
+            ],
+          },
+        ],
+        selected: 1,
+      },
+    ],
+    _closedWindows: [
+      // _closedWindows[0]
+      {
+        tabs: [
+          {
+            entries: [
+              {
+                url: "http://example.com/",
+                triggeringPrincipal_base64,
+                title: "title",
+              },
+            ],
+          },
+          {
+            entries: [
+              {
+                url: "http://mozilla.org/",
+                triggeringPrincipal_base64,
+                title: "title",
+              },
+            ],
+          },
+        ],
+        selected: 2,
+        title: FORGET,
+        _closedTabs: [],
+      },
+      // _closedWindows[1]
+      {
+        tabs: [
+          {
+            entries: [
+              {
+                url: "http://mozilla.org/",
+                triggeringPrincipal_base64,
+                title: "title",
+              },
+            ],
+          },
+          {
+            entries: [
+              {
+                url: "http://example.com/",
+                triggeringPrincipal_base64,
+                title: "title",
+              },
+            ],
+          },
+          {
+            entries: [
+              {
+                url: "http://mozilla.org/",
+                triggeringPrincipal_base64,
+                title: "title",
+              },
+            ],
+          },
+        ],
+        selected: 3,
+        title: REMEMBER,
+        _closedTabs: [],
+      },
+      // _closedWindows[2]
+      {
+        tabs: [
+          {
+            entries: [
+              {
+                url: "http://example.com/",
+                triggeringPrincipal_base64,
+                title: "title",
+              },
+            ],
+          },
+        ],
+        selected: 1,
+        title: FORGET,
+        _closedTabs: [
+          {
+            state: {
+              entries: [
+                {
+                  url: "http://mozilla.org/",
+                  triggeringPrincipal_base64,
+                  title: "title",
+                },
+                {
+                  url: "http://mozilla.org/again",
+                  triggeringPrincipal_base64,
+                  title: "title",
+                },
+              ],
+            },
+            pos: 1,
+            title: "title",
+          },
+          {
+            state: {
+              entries: [
+                {
+                  url: "http://example.com",
+                  triggeringPrincipal_base64,
+                  title: "title",
+                },
+              ],
+            },
+            title: "title",
+          },
+        ],
+      },
+    ],
+  };
+  let remember_count = 1;
+
+  function countByTitle(aClosedWindowList, aTitle) {
+    return aClosedWindowList.filter(aData => aData.title == aTitle).length;
+  }
+
+  function testForError(aFunction) {
+    try {
+      aFunction();
+      return false;
+    } catch (ex) {
+      return ex.name == "NS_ERROR_ILLEGAL_VALUE";
+    }
+  }
+
+  // open a window and add the above closed window list
+  let newWin = openDialog(location, "_blank", "chrome,all,dialog=no");
+  await promiseWindowLoaded(newWin);
+  Services.prefs.setIntPref(
+    "browser.sessionstore.max_windows_undo",
+    test_state._closedWindows.length
+  );
+  await setWindowState(newWin, test_state, true);
+
+  let closedWindows = ss.getClosedWindowData();
+  is(
+    closedWindows.length,
+    test_state._closedWindows.length,
+    "Closed window list has the expected length"
+  );
+  is(
+    countByTitle(closedWindows, FORGET),
+    test_state._closedWindows.length - remember_count,
+    "The correct amount of windows are to be forgotten"
+  );
+  is(
+    countByTitle(closedWindows, REMEMBER),
+    remember_count,
+    "Everything is set up."
+  );
+
+  // all of the following calls with illegal arguments should throw NS_ERROR_ILLEGAL_VALUE
+  ok(
+    testForError(() => ss.forgetClosedWindow(-1)),
+    "Invalid window for forgetClosedWindow throws"
+  );
+  ok(
+    testForError(() =>
+      ss.forgetClosedWindow(test_state._closedWindows.length + 1)
+    ),
+    "Invalid window for forgetClosedWindow throws"
+  );
+
+  // Remove third window, then first window
+  ss.forgetClosedWindow(2);
+  ss.forgetClosedWindow(null);
+
+  closedWindows = ss.getClosedWindowData();
+  is(
+    closedWindows.length,
+    remember_count,
+    "The correct amount of windows were removed"
+  );
+  is(
+    countByTitle(closedWindows, FORGET),
+    0,
+    "All windows specifically forgotten were indeed removed"
+  );
+  is(
+    countByTitle(closedWindows, REMEMBER),
+    remember_count,
+    "... and windows not specifically forgetten weren't."
+  );
+
+  // clean up
+  Services.prefs.clearUserPref("browser.sessionstore.max_windows_undo");
+  await BrowserTestUtils.closeWindow(newWin);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_495495.js b/src/zen/tests/mochitests/sessionstore/browser_495495.js
new file mode 100644
index 000000000..1bb2d1133
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_495495.js
@@ -0,0 +1,47 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+add_task(async function test_urlbarFocus() {
+  /** Test for Bug 495495 */
+
+  let newWin = openDialog(
+    location,
+    "_blank",
+    "chrome,all,dialog=no,toolbar=yes"
+  );
+  await promiseWindowLoaded(newWin);
+  let state1 = ss.getWindowState(newWin);
+  await BrowserTestUtils.closeWindow(newWin);
+
+  newWin = openDialog(
+    location,
+    "_blank",
+    "chrome,extrachrome,menubar,resizable,scrollbars,status,toolbar=no,location,personal,directories,dialog=no"
+  );
+  await promiseWindowLoaded(newWin);
+  let state2 = ss.getWindowState(newWin);
+
+  async function testState(state, expected) {
+    let win = openDialog(location, "_blank", "chrome,all,dialog=no");
+    await promiseWindowLoaded(win);
+
+    is(
+      win.gURLBar.readOnly,
+      false,
+      "URL bar should not be read-only before setting the state"
+    );
+    await setWindowState(win, state, true);
+    is(
+      win.gURLBar.readOnly,
+      expected.readOnly,
+      "URL bar read-only state should be restored correctly"
+    );
+
+    await BrowserTestUtils.closeWindow(win);
+  }
+
+  await BrowserTestUtils.closeWindow(newWin);
+  await testState(state1, { readOnly: false });
+  await testState(state2, { readOnly: true });
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_500328.js b/src/zen/tests/mochitests/sessionstore/browser_500328.js
new file mode 100644
index 000000000..06f53cd2a
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_500328.js
@@ -0,0 +1,132 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+async function checkState(browser) {
+  await SpecialPowers.spawn(browser, [], () => {
+    // Go back and then forward, and make sure that the state objects received
+    // from the popState event are as we expect them to be.
+    //
+    // We also add a node to the document's body when after going back and make
+    // sure it's still there after we go forward -- this is to test that the two
+    // history entries correspond to the same document.
+
+    // Set some state in the page's window.  When we go back(), the page should
+    // be retrieved from bfcache, and this state should still be there.
+    content.testState = "foo";
+  });
+
+  // Now go back.  This should trigger the popstate event handler.
+  let popstatePromise = SpecialPowers.spawn(browser, [], async () => {
+    let event = await ContentTaskUtils.waitForEvent(content, "popstate", true);
+    ok(event.state, "Event should have a state property.");
+
+    is(content.testState, "foo", "testState after going back");
+    is(
+      JSON.stringify(content.history.state),
+      JSON.stringify({ obj1: 1 }),
+      "first popstate object."
+    );
+
+    // Add a node with id "new-elem" to the document.
+    let doc = content.document;
+    ok(
+      !doc.getElementById("new-elem"),
+      "doc shouldn't contain new-elem before we add it."
+    );
+    let elem = doc.createElement("div");
+    elem.id = "new-elem";
+    doc.body.appendChild(elem);
+  });
+
+  // Ensure that the message manager has processed the previous task before
+  // going back to prevent racing with it in non-e10s mode.
+  await SpecialPowers.spawn(browser, [], () => {});
+  browser.goBack();
+
+  await popstatePromise;
+
+  popstatePromise = SpecialPowers.spawn(browser, [], async () => {
+    let event = await ContentTaskUtils.waitForEvent(content, "popstate", true);
+
+    // When content fires a PopStateEvent and we observe it from a chrome event
+    // listener (as we do here, and, thankfully, nowhere else in the tree), the
+    // state object will be a cross-compartment wrapper to an object that was
+    // deserialized in the content scope. And in this case, since RegExps are
+    // not currently Xrayable (see bug 1014991), trying to pull |obj3| (a RegExp)
+    // off of an Xrayed Object won't work. So we need to waive.
+    Assert.equal(
+      Cu.waiveXrays(event.state).obj3.toString(),
+      "/^a$/",
+      "second popstate object."
+    );
+
+    // Make sure that the new-elem node is present in the document.  If it's
+    // not, then this history entry has a different doc identifier than the
+    // previous entry, which is bad.
+    let doc = content.document;
+    let newElem = doc.getElementById("new-elem");
+    ok(newElem, "doc should contain new-elem.");
+    newElem.remove();
+    ok(!doc.getElementById("new-elem"), "new-elem should be removed.");
+  });
+
+  // Ensure that the message manager has processed the previous task before
+  // going forward to prevent racing with it in non-e10s mode.
+  await SpecialPowers.spawn(browser, [], () => {});
+  browser.goForward();
+  await popstatePromise;
+}
+
+add_task(async function test() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.navigation.requireUserInteraction", false]],
+  });
+
+  // Tests session restore functionality of history.pushState and
+  // history.replaceState().  (Bug 500328)
+
+  // We open a new blank window, let it load, and then load in
+  // http://example.com.  We need to load the blank window first, otherwise the
+  // docshell gets confused and doesn't have a current history entry.
+  let state;
+  await BrowserTestUtils.withNewTab(
+    { gBrowser, url: "about:blank" },
+    async function (browser) {
+      BrowserTestUtils.startLoadingURIString(browser, "http://example.com");
+      await BrowserTestUtils.browserLoaded(browser);
+
+      // After these push/replaceState calls, the window should have three
+      // history entries:
+      //   testURL        (state object: null)          <-- oldest
+      //   testURL        (state object: {obj1:1})
+      //   testURL?page2  (state object: {obj3:/^a$/})  <-- newest
+      function contentTest() {
+        let history = content.window.history;
+        history.pushState({ obj1: 1 }, "title-obj1");
+        history.pushState({ obj2: 2 }, "title-obj2", "?page2");
+        history.replaceState({ obj3: /^a$/ }, "title-obj3");
+      }
+      await SpecialPowers.spawn(browser, [], contentTest);
+      await TabStateFlusher.flush(browser);
+
+      state = ss.getTabState(gBrowser.getTabForBrowser(browser));
+    }
+  );
+
+  // Restore the state into a new tab.  Things don't work well when we
+  // restore into the old tab, but that's not a real use case anyway.
+  await BrowserTestUtils.withNewTab(
+    { gBrowser, url: "about:blank" },
+    async function (browser) {
+      let tab2 = gBrowser.getTabForBrowser(browser);
+
+      let tabRestoredPromise = promiseTabRestored(tab2);
+      ss.setTabState(tab2, state, true);
+
+      // Run checkState() once the tab finishes loading its restored state.
+      await tabRestoredPromise;
+      await checkState(browser);
+    }
+  );
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_506482.js b/src/zen/tests/mochitests/sessionstore/browser_506482.js
new file mode 100644
index 000000000..d93002d77
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_506482.js
@@ -0,0 +1,78 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+/* eslint-disable mozilla/no-arbitrary-setTimeout */
+
+function test() {
+  /** Test for Bug 506482 */
+
+  // test setup
+  waitForExplicitFinish();
+
+  // read the sessionstore.js mtime (picked from browser_248970_a.js)
+  let profilePath = Services.dirsvc.get("ProfD", Ci.nsIFile);
+  function getSessionstoreFile() {
+    let sessionStoreJS = profilePath.clone();
+    sessionStoreJS.append("sessionstore.jsonlz4");
+    return sessionStoreJS;
+  }
+  function getSessionstorejsModificationTime() {
+    let file = getSessionstoreFile();
+    if (file.exists()) {
+      return file.lastModifiedTime;
+    }
+    return -1;
+  }
+
+  // delete existing sessionstore.js, to make sure we're not reading
+  // the mtime of an old one initially.
+  let sessionStoreJS = getSessionstoreFile();
+  if (sessionStoreJS.exists()) {
+    sessionStoreJS.remove(false);
+  }
+
+  // test content URL
+  const TEST_URL =
+    "data:text/html;charset=utf-8," +
+    "<body style='width: 100000px; height: 100000px;'><p>top</p></body>";
+
+  // preferences that we use
+  const PREF_INTERVAL = "browser.sessionstore.interval";
+
+  // make sure sessionstore.js is saved ASAP on all events
+  Services.prefs.setIntPref(PREF_INTERVAL, 0);
+
+  // get the initial sessionstore.js mtime (-1 if it doesn't exist yet)
+  let mtime0 = getSessionstorejsModificationTime();
+
+  // create and select a first tab
+  let tab = BrowserTestUtils.addTab(gBrowser, TEST_URL);
+  promiseBrowserLoaded(tab.linkedBrowser).then(() => {
+    // step1: the above has triggered some saveStateDelayed(), sleep until
+    // it's done, and get the initial sessionstore.js mtime
+    setTimeout(function step1() {
+      let mtime1 = getSessionstorejsModificationTime();
+      isnot(mtime1, mtime0, "initial sessionstore.js update");
+
+      // step2: test sessionstore.js is not updated on tab selection
+      // or content scrolling
+      gBrowser.selectedTab = tab;
+      tab.linkedBrowser.contentWindow.scrollTo(1100, 1200);
+      setTimeout(function step2() {
+        let mtime2 = getSessionstorejsModificationTime();
+        is(
+          mtime2,
+          mtime1,
+          "tab selection and scrolling: sessionstore.js not updated"
+        );
+
+        // ok, done, cleanup and finish
+        if (Services.prefs.prefHasUserValue(PREF_INTERVAL)) {
+          Services.prefs.clearUserPref(PREF_INTERVAL);
+        }
+        gBrowser.removeTab(tab);
+        finish();
+      }, 3500); // end of sleep after tab selection and scrolling
+    }, 3500); // end of sleep after initial saveStateDelayed()
+  });
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_514751.js b/src/zen/tests/mochitests/sessionstore/browser_514751.js
new file mode 100644
index 000000000..bcb944c3e
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_514751.js
@@ -0,0 +1,41 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+add_task(async function test_malformedURI() {
+  /** Test for Bug 514751 (Wallpaper) */
+
+  let state = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              {
+                url: "about:mozilla",
+                triggeringPrincipal_base64,
+                title: "Mozilla",
+              },
+              {},
+            ],
+          },
+        ],
+      },
+    ],
+  };
+
+  var theWin = openDialog(location, "", "chrome,all,dialog=no");
+  await promiseWindowLoaded(theWin);
+
+  var gotError = false;
+  try {
+    await setWindowState(theWin, state, true);
+  } catch (e) {
+    if (/NS_ERROR_MALFORMED_URI/.test(e)) {
+      gotError = true;
+    }
+  }
+
+  ok(!gotError, "Didn't get a malformed URI error.");
+  await BrowserTestUtils.closeWindow(theWin);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_522375.js b/src/zen/tests/mochitests/sessionstore/browser_522375.js
new file mode 100644
index 000000000..07d04f933
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_522375.js
@@ -0,0 +1,25 @@
+function test() {
+  var startup_info = Services.startup.getStartupInfo();
+  // No .process info on mac
+
+  Assert.lessOrEqual(
+    startup_info.process,
+    startup_info.main,
+    "process created before main is run " + uneval(startup_info)
+  );
+
+  // on linux firstPaint can happen after everything is loaded (especially with remote X)
+  if (startup_info.firstPaint) {
+    Assert.lessOrEqual(
+      startup_info.main,
+      startup_info.firstPaint,
+      "main ran before first paint " + uneval(startup_info)
+    );
+  }
+
+  Assert.less(
+    startup_info.main,
+    startup_info.sessionRestored,
+    "Session restored after main " + uneval(startup_info)
+  );
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_522545.js b/src/zen/tests/mochitests/sessionstore/browser_522545.js
new file mode 100644
index 000000000..505cb6876
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_522545.js
@@ -0,0 +1,443 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+function test() {
+  /** Test for Bug 522545 */
+
+  waitForExplicitFinish();
+  requestLongerTimeout(4);
+
+  // This tests the following use case:
+  // User opens a new tab which gets focus. The user types something into the
+  // address bar, then crashes or quits.
+  function test_newTabFocused() {
+    let state = {
+      windows: [
+        {
+          tabs: [
+            { entries: [{ url: "about:mozilla", triggeringPrincipal_base64 }] },
+            { entries: [], userTypedValue: "example.com", userTypedClear: 0 },
+          ],
+          selected: 2,
+        },
+      ],
+    };
+
+    waitForBrowserState(state, function () {
+      let browser = gBrowser.selectedBrowser;
+      is(
+        browser.currentURI.spec,
+        "about:blank",
+        "No history entries still sets currentURI to about:blank"
+      );
+      is(
+        browser.userTypedValue,
+        "example.com",
+        "userTypedValue was correctly restored"
+      );
+      ok(
+        !browser.didStartLoadSinceLastUserTyping(),
+        "We still know that no load is ongoing"
+      );
+      is(
+        gURLBar.value,
+        "example.com",
+        "Address bar's value correctly restored"
+      );
+
+      // Change tabs to make sure address bar value gets updated.  If tab is
+      // lazy, wait for SSTabRestored to ensure address bar has time to update.
+      let tabToSelect = gBrowser.tabContainer.getItemAtIndex(0);
+      if (tabToSelect.linkedBrowser.isConnected) {
+        gBrowser.selectedTab = tabToSelect;
+        is(
+          gURLBar.value,
+          "about:mozilla",
+          "Address bar's value correctly updated"
+        );
+        runNextTest();
+      } else {
+        gBrowser.tabContainer.addEventListener(
+          "SSTabRestored",
+          function SSTabRestored(event) {
+            if (event.target == tabToSelect) {
+              gBrowser.tabContainer.removeEventListener(
+                "SSTabRestored",
+                SSTabRestored,
+                true
+              );
+              is(
+                gURLBar.value,
+                "about:mozilla",
+                "Address bar's value correctly updated"
+              );
+              runNextTest();
+            }
+          },
+          true
+        );
+        gBrowser.selectedTab = tabToSelect;
+      }
+    });
+  }
+
+  // This tests the following use case:
+  // User opens a new tab which gets focus. The user types something into the
+  // address bar, switches back to the first tab, then crashes or quits.
+  function test_newTabNotFocused() {
+    let state = {
+      windows: [
+        {
+          tabs: [
+            { entries: [{ url: "about:mozilla", triggeringPrincipal_base64 }] },
+            { entries: [], userTypedValue: "example.org", userTypedClear: 0 },
+          ],
+          selected: 1,
+        },
+      ],
+    };
+
+    waitForBrowserState(state, function () {
+      let browser = gBrowser.getBrowserAtIndex(1);
+      is(
+        browser.currentURI.spec,
+        "about:blank",
+        "No history entries still sets currentURI to about:blank"
+      );
+      is(
+        browser.userTypedValue,
+        "example.org",
+        "userTypedValue was correctly restored"
+      );
+      // didStartLoadSinceLastUserTyping does not exist on lazy tabs.
+      if (browser.didStartLoadSinceLastUserTyping) {
+        ok(
+          !browser.didStartLoadSinceLastUserTyping(),
+          "We still know that no load is ongoing"
+        );
+      }
+      is(
+        gURLBar.value,
+        "about:mozilla",
+        "Address bar's value correctly restored"
+      );
+
+      // Change tabs to make sure address bar value gets updated.  If tab is
+      // lazy, wait for SSTabRestored to ensure address bar has time to update.
+      let tabToSelect = gBrowser.tabContainer.getItemAtIndex(1);
+      if (tabToSelect.linkedBrowser.isConnected) {
+        gBrowser.selectedTab = tabToSelect;
+        is(
+          gURLBar.value,
+          "example.org",
+          "Address bar's value correctly updated"
+        );
+        runNextTest();
+      } else {
+        gBrowser.tabContainer.addEventListener(
+          "SSTabRestored",
+          function SSTabRestored(event) {
+            if (event.target == tabToSelect) {
+              gBrowser.tabContainer.removeEventListener(
+                "SSTabRestored",
+                SSTabRestored,
+                true
+              );
+              is(
+                gURLBar.value,
+                "example.org",
+                "Address bar's value correctly updated"
+              );
+              runNextTest();
+            }
+          },
+          true
+        );
+        gBrowser.selectedTab = tabToSelect;
+      }
+    });
+  }
+
+  // This tests the following use case:
+  // User is in a tab with session history, then types something in the
+  // address bar, then crashes or quits.
+  function test_existingSHEnd_noClear() {
+    let state = {
+      windows: [
+        {
+          tabs: [
+            {
+              entries: [
+                { url: "about:mozilla", triggeringPrincipal_base64 },
+                { url: "about:config", triggeringPrincipal_base64 },
+              ],
+              index: 2,
+              userTypedValue: "example.com",
+              userTypedClear: 0,
+            },
+          ],
+        },
+      ],
+    };
+
+    waitForBrowserState(state, function () {
+      let browser = gBrowser.selectedBrowser;
+      is(
+        browser.currentURI.spec,
+        "about:config",
+        "browser.currentURI set to current entry in SH"
+      );
+      is(
+        browser.userTypedValue,
+        "example.com",
+        "userTypedValue was correctly restored"
+      );
+      ok(
+        !browser.didStartLoadSinceLastUserTyping(),
+        "We still know that no load is ongoing"
+      );
+      is(
+        gURLBar.value,
+        "example.com",
+        "Address bar's value correctly restored to userTypedValue"
+      );
+      runNextTest();
+    });
+  }
+
+  // This tests the following use case:
+  // User is in a tab with session history, presses back at some point, then
+  // types something in the address bar, then crashes or quits.
+  function test_existingSHMiddle_noClear() {
+    let state = {
+      windows: [
+        {
+          tabs: [
+            {
+              entries: [
+                { url: "about:mozilla", triggeringPrincipal_base64 },
+                { url: "about:config", triggeringPrincipal_base64 },
+              ],
+              index: 1,
+              userTypedValue: "example.org",
+              userTypedClear: 0,
+            },
+          ],
+        },
+      ],
+    };
+
+    waitForBrowserState(state, function () {
+      let browser = gBrowser.selectedBrowser;
+      is(
+        browser.currentURI.spec,
+        "about:mozilla",
+        "browser.currentURI set to current entry in SH"
+      );
+      is(
+        browser.userTypedValue,
+        "example.org",
+        "userTypedValue was correctly restored"
+      );
+      ok(
+        !browser.didStartLoadSinceLastUserTyping(),
+        "We still know that no load is ongoing"
+      );
+      is(
+        gURLBar.value,
+        "example.org",
+        "Address bar's value correctly restored to userTypedValue"
+      );
+      runNextTest();
+    });
+  }
+
+  // This test simulates lots of tabs opening at once and then quitting/crashing.
+  function test_getBrowserState_lotsOfTabsOpening() {
+    gBrowser.stop();
+
+    let uris = [];
+    for (let i = 0; i < 25; i++) {
+      uris.push("http://example.com/" + i);
+    }
+
+    // We're waiting for the first location change, which should indicate
+    // one of the tabs has loaded and the others haven't. So one should
+    // be in a non-userTypedValue case, while others should still have
+    // userTypedValue and userTypedClear set.
+    gBrowser.addTabsProgressListener({
+      onLocationChange(aBrowser) {
+        if (uris.indexOf(aBrowser.currentURI.spec) > -1) {
+          gBrowser.removeTabsProgressListener(this);
+          firstLocationChange();
+        }
+      },
+    });
+
+    function firstLocationChange() {
+      let state = JSON.parse(ss.getBrowserState());
+      let hasUTV = state.windows[0].tabs.some(function (aTab) {
+        return (
+          aTab.userTypedValue && aTab.userTypedClear && !aTab.entries.length
+        );
+      });
+
+      ok(
+        hasUTV,
+        "At least one tab has a userTypedValue with userTypedClear with no loaded URL"
+      );
+
+      BrowserTestUtils.waitForMessage(
+        gBrowser.selectedBrowser.messageManager,
+        "SessionStore:update"
+      ).then(firstLoad);
+    }
+
+    function firstLoad() {
+      let state = JSON.parse(ss.getTabState(gBrowser.selectedTab));
+      let hasSH = !("userTypedValue" in state) && state.entries[0].url;
+      ok(hasSH, "The selected tab has its entry in SH");
+
+      runNextTest();
+    }
+
+    gBrowser.loadTabs(uris, {
+      triggeringPrincipal: Services.scriptSecurityManager.getSystemPrincipal(),
+    });
+  }
+
+  // This simulates setting a userTypedValue and ensures that just typing in the
+  // URL bar doesn't set userTypedClear as well.
+  function test_getBrowserState_userTypedValue() {
+    let state = {
+      windows: [
+        {
+          tabs: [{ entries: [] }],
+        },
+      ],
+    };
+
+    waitForBrowserState(state, function () {
+      let browser = gBrowser.selectedBrowser;
+      // Make sure this tab isn't loading and state is clear before we test.
+      is(browser.userTypedValue, null, "userTypedValue is empty to start");
+      ok(
+        !browser.didStartLoadSinceLastUserTyping(),
+        "Initially, no load should be ongoing"
+      );
+
+      let inputText = "example.org";
+      gURLBar.focus();
+      gURLBar.value = inputText.slice(0, -1);
+      EventUtils.sendString(inputText.slice(-1));
+
+      executeSoon(function () {
+        is(
+          browser.userTypedValue,
+          "example.org",
+          "userTypedValue was set when changing URLBar value"
+        );
+        ok(
+          !browser.didStartLoadSinceLastUserTyping(),
+          "No load started since changing URLBar value"
+        );
+
+        // Now make sure ss gets these values too
+        let newState = JSON.parse(ss.getBrowserState());
+        is(
+          newState.windows[0].tabs[0].userTypedValue,
+          "example.org",
+          "sessionstore got correct userTypedValue"
+        );
+        is(
+          newState.windows[0].tabs[0].userTypedClear,
+          0,
+          "sessionstore got correct userTypedClear"
+        );
+        runNextTest();
+      });
+    });
+  }
+
+  // test_getBrowserState_lotsOfTabsOpening tested userTypedClear in a few cases,
+  // but not necessarily any that had legitimate URIs in the state of loading
+  // (eg, "http://example.com"), so this test will cover that case.
+  function test_userTypedClearLoadURI() {
+    let state = {
+      windows: [
+        {
+          tabs: [
+            {
+              entries: [],
+              userTypedValue: "http://example.com",
+              userTypedClear: 2,
+            },
+          ],
+        },
+      ],
+    };
+
+    waitForBrowserState(state, function () {
+      let browser = gBrowser.selectedBrowser;
+      is(
+        browser.currentURI.spec,
+        "http://example.com/",
+        "userTypedClear=2 caused userTypedValue to be loaded"
+      );
+      is(
+        browser.userTypedValue,
+        null,
+        "userTypedValue was null after loading a URI"
+      );
+      ok(
+        !browser.didStartLoadSinceLastUserTyping(),
+        "We should have reset the load state when the tab loaded"
+      );
+      is(
+        gURLBar.value,
+        BrowserUIUtils.trimURL("http://example.com/"),
+        "Address bar's value set after loading URI"
+      );
+      runNextTest();
+    });
+  }
+
+  let tests = [
+    test_newTabFocused,
+    test_newTabNotFocused,
+    test_existingSHEnd_noClear,
+    test_existingSHMiddle_noClear,
+    test_getBrowserState_lotsOfTabsOpening,
+    test_getBrowserState_userTypedValue,
+    test_userTypedClearLoadURI,
+  ];
+  let originalState = JSON.parse(ss.getBrowserState());
+  let state = {
+    windows: [
+      {
+        tabs: [
+          { entries: [{ url: "about:blank", triggeringPrincipal_base64 }] },
+        ],
+      },
+    ],
+  };
+  function runNextTest() {
+    if (tests.length) {
+      waitForBrowserState(state, function () {
+        gBrowser.selectedBrowser.userTypedValue = null;
+        gURLBar.setURI();
+        tests.shift()();
+      });
+    } else {
+      waitForBrowserState(originalState, function () {
+        gBrowser.selectedBrowser.userTypedValue = null;
+        gURLBar.setURI();
+        finish();
+      });
+    }
+  }
+
+  // Run the tests!
+  runNextTest();
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_524745.js b/src/zen/tests/mochitests/sessionstore/browser_524745.js
new file mode 100644
index 000000000..c6dbda124
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_524745.js
@@ -0,0 +1,55 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+function test() {
+  /** Test for Bug 524745 */
+
+  let uniqKey = "bug524745";
+  let uniqVal = Date.now().toString();
+
+  waitForExplicitFinish();
+
+  whenNewWindowLoaded({ private: false }, function (window_B) {
+    waitForFocus(function () {
+      // Add identifying information to window_B
+      ss.setCustomWindowValue(window_B, uniqKey, uniqVal);
+      let state = JSON.parse(ss.getBrowserState());
+      let selectedWindow = state.windows[state.selectedWindow - 1];
+      is(
+        selectedWindow.extData && selectedWindow.extData[uniqKey],
+        uniqVal,
+        "selectedWindow is window_B"
+      );
+
+      // Now minimize window_B. The selected window shouldn't have the secret data
+      window_B.minimize();
+      waitForFocus(async function () {
+        state = JSON.parse(ss.getBrowserState());
+        selectedWindow = state.windows[state.selectedWindow - 1];
+        ok(
+          !selectedWindow.extData || !selectedWindow.extData[uniqKey],
+          "selectedWindow is not window_B after minimizing it"
+        );
+
+        // Now minimize the last open window (assumes no other tests left windows open)
+        let promiseSizeModeChange = BrowserTestUtils.waitForEvent(
+          window,
+          "sizemodechange"
+        );
+        window.minimize();
+        await promiseSizeModeChange;
+        state = JSON.parse(ss.getBrowserState());
+        is(
+          state.selectedWindow,
+          0,
+          "selectedWindow should be 0 when all windows are minimized"
+        );
+
+        // Cleanup
+        window.restore();
+        BrowserTestUtils.closeWindow(window_B).then(finish);
+      });
+    }, window_B);
+  });
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_526613.js b/src/zen/tests/mochitests/sessionstore/browser_526613.js
new file mode 100644
index 000000000..1b2ef48bb
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_526613.js
@@ -0,0 +1,86 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+function test() {
+  /** Test for Bug 526613 */
+
+  // test setup
+  waitForExplicitFinish();
+
+  function browserWindowsCount(expected) {
+    let count = 0;
+    for (let win of Services.wm.getEnumerator("navigator:browser")) {
+      if (!win.closed) {
+        ++count;
+      }
+    }
+    is(
+      count,
+      expected,
+      "number of open browser windows according to nsIWindowMediator"
+    );
+    let state = ss.getBrowserState();
+    info(state);
+    is(
+      JSON.parse(state).windows.length,
+      expected,
+      "number of open browser windows according to getBrowserState"
+    );
+  }
+
+  browserWindowsCount(1);
+
+  // backup old state
+  let oldState = ss.getBrowserState();
+  // create a new state for testing
+  let testState = {
+    windows: [
+      { tabs: [{ entries: [{ url: "http://example.com/" }] }], selected: 1 },
+      { tabs: [{ entries: [{ url: "about:mozilla" }] }], selected: 1 },
+    ],
+    // make sure the first window is focused, otherwise when restoring the
+    // old state, the first window is closed and the test harness gets unloaded
+    selectedWindow: 1,
+  };
+
+  let pass = 1;
+  function observer(aSubject, aTopic) {
+    is(
+      aTopic,
+      "sessionstore-browser-state-restored",
+      "The sessionstore-browser-state-restored notification was observed"
+    );
+
+    if (pass++ == 1) {
+      browserWindowsCount(2);
+
+      // let the first window be focused (see above)
+      function pollMostRecentWindow() {
+        if (Services.wm.getMostRecentWindow("navigator:browser") == window) {
+          ss.setBrowserState(oldState);
+        } else {
+          info("waiting for the current window to become active");
+          setTimeout(pollMostRecentWindow, 0);
+          window.focus(); // XXX Why is this needed?
+        }
+      }
+      pollMostRecentWindow();
+    } else {
+      browserWindowsCount(1);
+      ok(
+        !window.closed,
+        "Restoring the old state should have left this window open"
+      );
+      Services.obs.removeObserver(
+        observer,
+        "sessionstore-browser-state-restored"
+      );
+      finish();
+    }
+  }
+  Services.obs.addObserver(observer, "sessionstore-browser-state-restored");
+
+  // set browser to test state
+  ss.setBrowserState(JSON.stringify(testState));
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_528776.js b/src/zen/tests/mochitests/sessionstore/browser_528776.js
new file mode 100644
index 000000000..37b76a766
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_528776.js
@@ -0,0 +1,27 @@
+function browserWindowsCount(expected) {
+  var count = 0;
+  for (let win of Services.wm.getEnumerator("navigator:browser")) {
+    if (!win.closed) {
+      ++count;
+    }
+  }
+  is(
+    count,
+    expected,
+    "number of open browser windows according to nsIWindowMediator"
+  );
+  is(
+    JSON.parse(ss.getBrowserState()).windows.length,
+    expected,
+    "number of open browser windows according to getBrowserState"
+  );
+}
+
+add_task(async function () {
+  browserWindowsCount(1);
+
+  let win = await BrowserTestUtils.openNewBrowserWindow();
+  browserWindowsCount(2);
+  await BrowserTestUtils.closeWindow(win);
+  browserWindowsCount(1);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_579868.js b/src/zen/tests/mochitests/sessionstore/browser_579868.js
new file mode 100644
index 000000000..966a601e4
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_579868.js
@@ -0,0 +1,31 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+function test() {
+  waitForExplicitFinish();
+
+  let tab1 = BrowserTestUtils.addTab(gBrowser, "about:robots");
+  let tab2 = BrowserTestUtils.addTab(gBrowser, "about:mozilla");
+
+  promiseBrowserLoaded(tab1.linkedBrowser).then(() => {
+    // Tell the session storer that the tab is pinned
+    let newTabState =
+      '{"entries":[{"url":"about:robots"}],"pinned":true,"userTypedValue":"Hello World!"}';
+    ss.setTabState(tab1, newTabState);
+
+    // Undo pinning
+    gBrowser.unpinTab(tab1);
+
+    // Close and restore tab
+    gBrowser.removeTab(tab1);
+    let savedState = ss.getClosedTabDataForWindow(window)[0].state;
+    isnot(savedState.pinned, true, "Pinned should not be true");
+    tab1 = ss.undoCloseTab(window, 0);
+
+    isnot(tab1.pinned, true, "Should not be pinned");
+    gBrowser.removeTab(tab1);
+    gBrowser.removeTab(tab2);
+    finish();
+  });
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_579879.js b/src/zen/tests/mochitests/sessionstore/browser_579879.js
new file mode 100644
index 000000000..083f111a8
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_579879.js
@@ -0,0 +1,31 @@
+"use strict";
+
+add_task(async function () {
+  let tab1 = BrowserTestUtils.addTab(
+    gBrowser,
+    "data:text/plain;charset=utf-8,foo"
+  );
+  gBrowser.pinTab(tab1);
+
+  await promiseBrowserLoaded(tab1.linkedBrowser);
+  let tab2 = BrowserTestUtils.addTab(gBrowser);
+  gBrowser.pinTab(tab2);
+
+  is(
+    Array.prototype.indexOf.call(gBrowser.tabs, tab1),
+    0,
+    "pinned tab 1 is at the first position"
+  );
+  await promiseRemoveTabAndSessionState(tab1);
+
+  tab1 = SessionWindowUI.undoCloseTab(window);
+  ok(tab1.pinned, "pinned tab 1 has been restored as a pinned tab");
+  is(
+    Array.prototype.indexOf.call(gBrowser.tabs, tab1),
+    0,
+    "pinned tab 1 has been restored to the first position"
+  );
+
+  BrowserTestUtils.removeTab(tab1);
+  BrowserTestUtils.removeTab(tab2);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_580512.js b/src/zen/tests/mochitests/sessionstore/browser_580512.js
new file mode 100644
index 000000000..e27dc61ba
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_580512.js
@@ -0,0 +1,117 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const URIS_PINNED = ["about:license", "about:about"];
+const URIS_NORMAL_A = ["about:mozilla"];
+const URIS_NORMAL_B = ["about:buildconfig"];
+
+function test() {
+  waitForExplicitFinish();
+
+  isnot(
+    Services.prefs.getIntPref("browser.startup.page"),
+    3,
+    "pref to save session must not be set for this test"
+  );
+  ok(
+    !Services.prefs.getBoolPref("browser.sessionstore.resume_session_once"),
+    "pref to save session once must not be set for this test"
+  );
+
+  document.documentElement.setAttribute(
+    "windowtype",
+    "navigator:browsertestdummy"
+  );
+
+  openWinWithCb(closeFirstWin, URIS_PINNED.concat(URIS_NORMAL_A));
+}
+
+function closeFirstWin(win) {
+  win.gBrowser.pinTab(win.gBrowser.tabs[0]);
+  win.gBrowser.pinTab(win.gBrowser.tabs[1]);
+
+  let winClosed = BrowserTestUtils.windowClosed(win);
+  // We need to call BrowserCommands.tryToCloseWindow in order to trigger
+  // the machinery that chooses whether or not to save the session
+  // for the last window.
+  win.BrowserCommands.tryToCloseWindow();
+  ok(win.closed, "window closed");
+
+  winClosed.then(() => {
+    openWinWithCb(
+      checkSecondWin,
+      URIS_NORMAL_B,
+      URIS_PINNED.concat(URIS_NORMAL_B)
+    );
+  });
+}
+
+function checkSecondWin(win) {
+  is(
+    win.gBrowser.browsers[0].currentURI.spec,
+    URIS_PINNED[0],
+    "first pinned tab restored"
+  );
+  is(
+    win.gBrowser.browsers[1].currentURI.spec,
+    URIS_PINNED[1],
+    "second pinned tab restored"
+  );
+  ok(win.gBrowser.tabs[0].pinned, "first pinned tab is still pinned");
+  ok(win.gBrowser.tabs[1].pinned, "second pinned tab is still pinned");
+
+  BrowserTestUtils.closeWindow(win).then(() => {
+    // cleanup
+    document.documentElement.setAttribute("windowtype", "navigator:browser");
+    finish();
+  });
+}
+
+function openWinWithCb(cb, argURIs, expectedURIs) {
+  if (!expectedURIs) {
+    expectedURIs = argURIs;
+  }
+
+  var win = openDialog(
+    AppConstants.BROWSER_CHROME_URL,
+    "_blank",
+    "chrome,all,dialog=no",
+    argURIs.join("|")
+  );
+
+  win.addEventListener(
+    "load",
+    function () {
+      info("the window loaded");
+
+      var expectedLoads = expectedURIs.length;
+
+      win.gBrowser.addTabsProgressListener({
+        onStateChange(aBrowser, aWebProgress, aRequest, aStateFlags, _aStatus) {
+          if (
+            aRequest &&
+            aStateFlags & Ci.nsIWebProgressListener.STATE_STOP &&
+            aStateFlags & Ci.nsIWebProgressListener.STATE_IS_NETWORK &&
+            expectedURIs.indexOf(
+              aRequest.QueryInterface(Ci.nsIChannel).originalURI.spec
+            ) > -1 &&
+            --expectedLoads <= 0
+          ) {
+            win.gBrowser.removeTabsProgressListener(this);
+            info("all tabs loaded");
+            is(
+              win.gBrowser.tabs.length,
+              expectedURIs.length,
+              "didn't load any unexpected tabs"
+            );
+            executeSoon(function () {
+              cb(win);
+            });
+          }
+        },
+      });
+    },
+    { once: true }
+  );
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_581937.js b/src/zen/tests/mochitests/sessionstore/browser_581937.js
new file mode 100644
index 000000000..4d4fe9dfe
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_581937.js
@@ -0,0 +1,24 @@
+// Tests that an about:blank tab with no history will not be saved into
+// session store and thus, it will not show up in Recently Closed Tabs.
+
+"use strict";
+
+add_task(async function () {
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:blank");
+  await BrowserTestUtils.browserLoaded(tab.linkedBrowser, {
+    wantLoad: "about:blank",
+  });
+
+  is(
+    tab.linkedBrowser.currentURI.spec,
+    "about:blank",
+    "we will be removing an about:blank tab"
+  );
+
+  let r = `rand-${Math.random()}`;
+  ss.setCustomTabValue(tab, "foobar", r);
+
+  await promiseRemoveTabAndSessionState(tab);
+  let closedTabData = ss.getClosedTabDataForWindow(window);
+  ok(!closedTabData.includes(r), "tab not stored in _closedTabs");
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_586068-apptabs.js b/src/zen/tests/mochitests/sessionstore/browser_586068-apptabs.js
new file mode 100644
index 000000000..24878ba26
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_586068-apptabs.js
@@ -0,0 +1,104 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+requestLongerTimeout(2);
+
+const PREF_RESTORE_ON_DEMAND = "browser.sessionstore.restore_on_demand";
+
+add_task(async function test() {
+  Services.prefs.setBoolPref(PREF_RESTORE_ON_DEMAND, true);
+  registerCleanupFunction(function () {
+    Services.prefs.clearUserPref(PREF_RESTORE_ON_DEMAND);
+  });
+
+  let state = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              { url: "http://example.org/#1", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+            pinned: true,
+          },
+          {
+            entries: [
+              { url: "http://example.org/#2", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+            pinned: true,
+          },
+          {
+            entries: [
+              { url: "http://example.org/#3", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+            pinned: true,
+          },
+          {
+            entries: [
+              { url: "http://example.org/#4", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.org/#5", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.org/#6", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.org/#7", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+        ],
+        selected: 5,
+      },
+    ],
+  };
+
+  let loadCount = 0;
+  let promiseRestoringTabs = new Promise(resolve => {
+    gProgressListener.setCallback(function (aBrowser) {
+      loadCount++;
+
+      // We'll make sure that the loads we get come from pinned tabs or the
+      // the selected tab.
+
+      // get the tab
+      let tab;
+      for (let i = 0; i < window.gBrowser.tabs.length; i++) {
+        if (!tab && window.gBrowser.tabs[i].linkedBrowser == aBrowser) {
+          tab = window.gBrowser.tabs[i];
+        }
+      }
+
+      ok(tab.pinned || tab.selected, "load came from pinned or selected tab");
+
+      // We should get 4 loads: 3 app tabs + 1 normal selected tab
+      if (loadCount < 4) {
+        return;
+      }
+
+      gProgressListener.unsetCallback();
+      resolve();
+    });
+  });
+
+  let backupState = ss.getBrowserState();
+  ss.setBrowserState(JSON.stringify(state));
+  await promiseRestoringTabs;
+
+  // Cleanup.
+  await promiseBrowserState(backupState);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_586068-apptabs_ondemand.js b/src/zen/tests/mochitests/sessionstore/browser_586068-apptabs_ondemand.js
new file mode 100644
index 000000000..69416ecb8
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_586068-apptabs_ondemand.js
@@ -0,0 +1,102 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const PREF_RESTORE_ON_DEMAND = "browser.sessionstore.restore_on_demand";
+const PREF_RESTORE_PINNED_TABS_ON_DEMAND =
+  "browser.sessionstore.restore_pinned_tabs_on_demand";
+
+add_task(async function test() {
+  Services.prefs.setBoolPref(PREF_RESTORE_ON_DEMAND, true);
+  Services.prefs.setBoolPref(PREF_RESTORE_PINNED_TABS_ON_DEMAND, true);
+
+  registerCleanupFunction(function () {
+    Services.prefs.clearUserPref(PREF_RESTORE_ON_DEMAND);
+    Services.prefs.clearUserPref(PREF_RESTORE_PINNED_TABS_ON_DEMAND);
+  });
+
+  let state = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              { url: "http://example.org/#1", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+            pinned: true,
+          },
+          {
+            entries: [
+              { url: "http://example.org/#2", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+            pinned: true,
+          },
+          {
+            entries: [
+              { url: "http://example.org/#3", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+            pinned: true,
+          },
+          {
+            entries: [
+              { url: "http://example.org/#4", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.org/#5", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.org/#6", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.org/#7", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+        ],
+        selected: 5,
+      },
+    ],
+  };
+
+  let promiseRestoringTabs = new Promise(resolve => {
+    gProgressListener.setCallback(
+      function (aBrowser, aNeedRestore, aRestoring, aRestored) {
+        // get the tab
+        let tab;
+        for (let i = 0; i < window.gBrowser.tabs.length; i++) {
+          if (!tab && window.gBrowser.tabs[i].linkedBrowser == aBrowser) {
+            tab = window.gBrowser.tabs[i];
+          }
+        }
+
+        // Check that the load only comes from the selected tab.
+        ok(tab.selected, "load came from selected tab");
+        is(aNeedRestore, 6, "six tabs left to restore");
+        is(aRestoring, 1, "one tab is restoring");
+        is(aRestored, 0, "no tabs have been restored, yet");
+
+        gProgressListener.unsetCallback();
+        resolve();
+      }
+    );
+  });
+
+  let backupState = ss.getBrowserState();
+  ss.setBrowserState(JSON.stringify(state));
+  await promiseRestoringTabs;
+
+  // Cleanup.
+  await promiseBrowserState(backupState);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_586068-browser_state_interrupted.js b/src/zen/tests/mochitests/sessionstore/browser_586068-browser_state_interrupted.js
new file mode 100644
index 000000000..6ef18e2b3
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_586068-browser_state_interrupted.js
@@ -0,0 +1,207 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const PREF_RESTORE_ON_DEMAND = "browser.sessionstore.restore_on_demand";
+
+requestLongerTimeout(2);
+
+add_task(async function test() {
+  Services.prefs.setBoolPref(PREF_RESTORE_ON_DEMAND, false);
+  registerCleanupFunction(function () {
+    Services.prefs.clearUserPref(PREF_RESTORE_ON_DEMAND);
+  });
+
+  // The first state will be loaded using setBrowserState, followed by the 2nd
+  // state also being loaded using setBrowserState, interrupting the first restore.
+  let state1 = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              { url: "http://example.org#1", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.org#2", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.org#3", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.org#4", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+        ],
+        selected: 1,
+      },
+      {
+        tabs: [
+          {
+            entries: [
+              { url: "http://example.com#1", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.com#2", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.com#3", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.com#4", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+        ],
+        selected: 3,
+      },
+    ],
+  };
+  let state2 = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              { url: "http://example.org#5", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.org#6", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.org#7", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.org#8", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+        ],
+        selected: 3,
+      },
+      {
+        tabs: [
+          {
+            entries: [
+              { url: "http://example.com#5", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.com#6", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.com#7", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.com#8", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+        ],
+        selected: 1,
+      },
+    ],
+  };
+
+  // interruptedAfter will be set after the selected tab from each window have loaded.
+  let interruptedAfter = 0;
+  let loadedWindow1 = false;
+  let loadedWindow2 = false;
+  let numTabs = state2.windows[0].tabs.length + state2.windows[1].tabs.length;
+
+  let loadCount = 0;
+  let promiseRestoringTabs = new Promise(resolve => {
+    gProgressListener.setCallback(function (aBrowser, aNeedRestore) {
+      loadCount++;
+
+      if (
+        aBrowser.currentURI.spec == state1.windows[0].tabs[2].entries[0].url
+      ) {
+        loadedWindow1 = true;
+      }
+      if (
+        aBrowser.currentURI.spec == state1.windows[1].tabs[0].entries[0].url
+      ) {
+        loadedWindow2 = true;
+      }
+
+      if (!interruptedAfter && loadedWindow1 && loadedWindow2) {
+        interruptedAfter = loadCount;
+        ss.setBrowserState(JSON.stringify(state2));
+        return;
+      }
+
+      if (loadCount < numTabs + interruptedAfter) {
+        return;
+      }
+
+      // We don't actually care about load order in this test, just that they all
+      // do load.
+      is(loadCount, numTabs + interruptedAfter, "all tabs were restored");
+      is(aNeedRestore, 0, "there are no tabs left needing restore");
+
+      // Remove the progress listener.
+      gProgressListener.unsetCallback();
+      resolve();
+    });
+  });
+
+  // We also want to catch the extra windows (there should be 2), so we need to observe domwindowopened
+  Services.ww.registerNotification(function observer(aSubject, aTopic) {
+    if (aTopic == "domwindowopened") {
+      let win = aSubject;
+      win.addEventListener(
+        "load",
+        function () {
+          Services.ww.unregisterNotification(observer);
+          win.gBrowser.addTabsProgressListener(gProgressListener);
+        },
+        { once: true }
+      );
+    }
+  });
+
+  let backupState = ss.getBrowserState();
+  ss.setBrowserState(JSON.stringify(state1));
+  await promiseRestoringTabs;
+
+  // Cleanup.
+  await promiseAllButPrimaryWindowClosed();
+  await promiseBrowserState(backupState);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_586068-cascade.js b/src/zen/tests/mochitests/sessionstore/browser_586068-cascade.js
new file mode 100644
index 000000000..8f2b9e71b
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_586068-cascade.js
@@ -0,0 +1,104 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const PREF_RESTORE_ON_DEMAND = "browser.sessionstore.restore_on_demand";
+
+add_task(async function test() {
+  Services.prefs.setBoolPref(PREF_RESTORE_ON_DEMAND, false);
+  registerCleanupFunction(function () {
+    Services.prefs.clearUserPref(PREF_RESTORE_ON_DEMAND);
+  });
+
+  let state = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              { url: "http://example.com", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.com", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.com", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.com", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.com", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.com", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+        ],
+      },
+    ],
+  };
+
+  let expectedCounts = [
+    [3, 3, 0],
+    [2, 3, 1],
+    [1, 3, 2],
+    [0, 3, 3],
+    [0, 2, 4],
+    [0, 1, 5],
+  ];
+
+  let loadCount = 0;
+  let promiseRestoringTabs = new Promise(resolve => {
+    gProgressListener.setCallback(
+      function (aBrowser, aNeedRestore, aRestoring, aRestored) {
+        loadCount++;
+        let expected = expectedCounts[loadCount - 1];
+
+        is(
+          aNeedRestore,
+          expected[0],
+          "load " + loadCount + " - # tabs that need to be restored"
+        );
+        is(
+          aRestoring,
+          expected[1],
+          "load " + loadCount + " - # tabs that are restoring"
+        );
+        is(
+          aRestored,
+          expected[2],
+          "load " + loadCount + " - # tabs that has been restored"
+        );
+
+        if (loadCount == state.windows[0].tabs.length) {
+          gProgressListener.unsetCallback();
+          resolve();
+        }
+      }
+    );
+  });
+
+  let backupState = ss.getBrowserState();
+  ss.setBrowserState(JSON.stringify(state));
+  await promiseRestoringTabs;
+
+  // Cleanup.
+  await promiseBrowserState(backupState);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_586068-multi_window.js b/src/zen/tests/mochitests/sessionstore/browser_586068-multi_window.js
new file mode 100644
index 000000000..352c5bcef
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_586068-multi_window.js
@@ -0,0 +1,110 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const PREF_RESTORE_ON_DEMAND = "browser.sessionstore.restore_on_demand";
+
+add_task(async function test() {
+  Services.prefs.setBoolPref(PREF_RESTORE_ON_DEMAND, false);
+  registerCleanupFunction(function () {
+    Services.prefs.clearUserPref(PREF_RESTORE_ON_DEMAND);
+  });
+
+  // The first window will be put into the already open window and the second
+  // window will be opened with _openWindowWithState, which is the source of the problem.
+  let state = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              { url: "http://example.org#0", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+        ],
+        selected: 1,
+      },
+      {
+        tabs: [
+          {
+            entries: [
+              { url: "http://example.com#1", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.com#2", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.com#3", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.com#4", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.com#5", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.com#6", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+        ],
+        selected: 4,
+      },
+    ],
+  };
+  let numTabs = state.windows[0].tabs.length + state.windows[1].tabs.length;
+
+  let loadCount = 0;
+  let promiseRestoringTabs = new Promise(resolve => {
+    gProgressListener.setCallback(function (aBrowser, aNeedRestore) {
+      if (++loadCount == numTabs) {
+        // We don't actually care about load order in this test, just that they all
+        // do load.
+        is(loadCount, numTabs, "all tabs were restored");
+        is(aNeedRestore, 0, "there are no tabs left needing restore");
+
+        gProgressListener.unsetCallback();
+        resolve();
+      }
+    });
+  });
+
+  // We also want to catch the 2nd window, so we need to observe domwindowopened
+  Services.ww.registerNotification(function observer(aSubject, aTopic) {
+    if (aTopic == "domwindowopened") {
+      let win = aSubject;
+      win.addEventListener(
+        "load",
+        function () {
+          Services.ww.unregisterNotification(observer);
+          win.gBrowser.addTabsProgressListener(gProgressListener);
+        },
+        { once: true }
+      );
+    }
+  });
+
+  let backupState = ss.getBrowserState();
+  ss.setBrowserState(JSON.stringify(state));
+  await promiseRestoringTabs;
+
+  // Cleanup.
+  await promiseAllButPrimaryWindowClosed();
+  await promiseBrowserState(backupState);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_586068-reload.js b/src/zen/tests/mochitests/sessionstore/browser_586068-reload.js
new file mode 100644
index 000000000..b0b368824
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_586068-reload.js
@@ -0,0 +1,118 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const PREF_RESTORE_ON_DEMAND = "browser.sessionstore.restore_on_demand";
+
+add_task(async function test() {
+  Services.prefs.setBoolPref(PREF_RESTORE_ON_DEMAND, true);
+  registerCleanupFunction(function () {
+    Services.prefs.clearUserPref(PREF_RESTORE_ON_DEMAND);
+  });
+
+  let state = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              { url: "http://example.org/#1", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.org/#2", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.org/#3", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.org/#4", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.org/#5", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.org/#6", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.org/#7", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.org/#8", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.org/#9", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+        ],
+        selected: 1,
+      },
+    ],
+  };
+
+  let loadCount = 0;
+  let promiseRestoringTabs = new Promise(resolve => {
+    gBrowser.tabContainer.addEventListener(
+      "SSTabRestored",
+      function onRestored(event) {
+        let tab = event.target;
+        let browser = tab.linkedBrowser;
+        let tabData = state.windows[0].tabs[loadCount++];
+
+        // double check that this tab was the right one
+        is(
+          browser.currentURI.spec,
+          tabData.entries[0].url,
+          "load " + loadCount + " - browser loaded correct url"
+        );
+        is(
+          ss.getCustomTabValue(tab, "uniq"),
+          tabData.extData.uniq,
+          "load " + loadCount + " - correct tab was restored"
+        );
+
+        if (loadCount == state.windows[0].tabs.length) {
+          gBrowser.tabContainer.removeEventListener(
+            "SSTabRestored",
+            onRestored
+          );
+          resolve();
+        } else {
+          // reload the next tab
+          gBrowser.browsers[loadCount].reload();
+        }
+      }
+    );
+  });
+
+  let backupState = ss.getBrowserState();
+  ss.setBrowserState(JSON.stringify(state));
+  await promiseRestoringTabs;
+
+  // Cleanup.
+  await promiseBrowserState(backupState);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_586068-select.js b/src/zen/tests/mochitests/sessionstore/browser_586068-select.js
new file mode 100644
index 000000000..4d0f82487
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_586068-select.js
@@ -0,0 +1,125 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const PREF_RESTORE_ON_DEMAND = "browser.sessionstore.restore_on_demand";
+
+add_task(async function test() {
+  Services.prefs.setBoolPref(PREF_RESTORE_ON_DEMAND, true);
+  registerCleanupFunction(function () {
+    Services.prefs.clearUserPref(PREF_RESTORE_ON_DEMAND);
+  });
+
+  let state = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              { url: "http://example.org", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.org", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.org", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.org", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.org", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.org", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+        ],
+        selected: 1,
+      },
+    ],
+  };
+
+  let expectedCounts = [
+    [5, 1, 0],
+    [4, 1, 1],
+    [3, 1, 2],
+    [2, 1, 3],
+    [1, 1, 4],
+    [0, 1, 5],
+  ];
+  let tabOrder = [0, 5, 1, 4, 3, 2];
+
+  let loadCount = 0;
+  let promiseRestoringTabs = new Promise(resolve => {
+    gProgressListener.setCallback(
+      function (aBrowser, aNeedRestore, aRestoring, aRestored) {
+        loadCount++;
+        let expected = expectedCounts[loadCount - 1];
+
+        is(
+          aNeedRestore,
+          expected[0],
+          "load " + loadCount + " - # tabs that need to be restored"
+        );
+        is(
+          aRestoring,
+          expected[1],
+          "load " + loadCount + " - # tabs that are restoring"
+        );
+        is(
+          aRestored,
+          expected[2],
+          "load " + loadCount + " - # tabs that has been restored"
+        );
+
+        if (loadCount < state.windows[0].tabs.length) {
+          // double check that this tab was the right one
+          let expectedData =
+            state.windows[0].tabs[tabOrder[loadCount - 1]].extData.uniq;
+          let tab;
+          for (let i = 0; i < window.gBrowser.tabs.length; i++) {
+            if (!tab && window.gBrowser.tabs[i].linkedBrowser == aBrowser) {
+              tab = window.gBrowser.tabs[i];
+            }
+          }
+
+          is(
+            ss.getCustomTabValue(tab, "uniq"),
+            expectedData,
+            "load " + loadCount + " - correct tab was restored"
+          );
+
+          // select the next tab
+          window.gBrowser.selectTabAtIndex(tabOrder[loadCount]);
+        } else {
+          gProgressListener.unsetCallback();
+          resolve();
+        }
+      }
+    );
+  });
+
+  let backupState = ss.getBrowserState();
+  ss.setBrowserState(JSON.stringify(state));
+  await promiseRestoringTabs;
+
+  // Cleanup.
+  await promiseBrowserState(backupState);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_586068-window_state.js b/src/zen/tests/mochitests/sessionstore/browser_586068-window_state.js
new file mode 100644
index 000000000..25066a2db
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_586068-window_state.js
@@ -0,0 +1,115 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const PREF_RESTORE_ON_DEMAND = "browser.sessionstore.restore_on_demand";
+
+add_task(async function test() {
+  Services.prefs.setBoolPref(PREF_RESTORE_ON_DEMAND, false);
+  registerCleanupFunction(function () {
+    Services.prefs.clearUserPref(PREF_RESTORE_ON_DEMAND);
+  });
+
+  // We'll use 2 states so that we can make sure calling setWindowState doesn't
+  // wipe out currently restoring data.
+  let state1 = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              { url: "http://example.com#1", triggeringPrincipal_base64 },
+            ],
+          },
+          {
+            entries: [
+              { url: "http://example.com#2", triggeringPrincipal_base64 },
+            ],
+          },
+          {
+            entries: [
+              { url: "http://example.com#3", triggeringPrincipal_base64 },
+            ],
+          },
+          {
+            entries: [
+              { url: "http://example.com#4", triggeringPrincipal_base64 },
+            ],
+          },
+          {
+            entries: [
+              { url: "http://example.com#5", triggeringPrincipal_base64 },
+            ],
+          },
+        ],
+      },
+    ],
+  };
+  let state2 = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              { url: "http://example.org#1", triggeringPrincipal_base64 },
+            ],
+          },
+          {
+            entries: [
+              { url: "http://example.org#2", triggeringPrincipal_base64 },
+            ],
+          },
+          {
+            entries: [
+              { url: "http://example.org#3", triggeringPrincipal_base64 },
+            ],
+          },
+          {
+            entries: [
+              { url: "http://example.org#4", triggeringPrincipal_base64 },
+            ],
+          },
+          {
+            entries: [
+              { url: "http://example.org#5", triggeringPrincipal_base64 },
+            ],
+          },
+        ],
+      },
+    ],
+  };
+  let numTabs = state1.windows[0].tabs.length + state2.windows[0].tabs.length;
+
+  let loadCount = 0;
+  let promiseRestoringTabs = new Promise(resolve => {
+    gProgressListener.setCallback(function (aBrowser, aNeedRestore) {
+      // When loadCount == 2, we'll also restore state2 into the window
+      if (++loadCount == 2) {
+        ss.setWindowState(window, JSON.stringify(state2), false);
+      }
+
+      if (loadCount < numTabs) {
+        return;
+      }
+
+      // We don't actually care about load order in this test, just that they all
+      // do load.
+      is(
+        loadCount,
+        numTabs,
+        "test_setWindowStateNoOverwrite: all tabs were restored"
+      );
+      is(aNeedRestore, 0, "there are no tabs left needing restore");
+
+      gProgressListener.unsetCallback();
+      resolve();
+    });
+  });
+
+  let backupState = ss.getBrowserState();
+  ss.setWindowState(window, JSON.stringify(state1), true);
+  await promiseRestoringTabs;
+
+  // Cleanup.
+  await promiseBrowserState(backupState);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_586068-window_state_override.js b/src/zen/tests/mochitests/sessionstore/browser_586068-window_state_override.js
new file mode 100644
index 000000000..eb3d2c709
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_586068-window_state_override.js
@@ -0,0 +1,113 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const PREF_RESTORE_ON_DEMAND = "browser.sessionstore.restore_on_demand";
+
+add_task(async function test() {
+  Services.prefs.setBoolPref(PREF_RESTORE_ON_DEMAND, false);
+  registerCleanupFunction(function () {
+    Services.prefs.clearUserPref(PREF_RESTORE_ON_DEMAND);
+  });
+
+  // We'll use 2 states so that we can make sure calling setWindowState doesn't
+  // wipe out currently restoring data.
+  let state1 = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              { url: "http://example.com#1", triggeringPrincipal_base64 },
+            ],
+          },
+          {
+            entries: [
+              { url: "http://example.com#2", triggeringPrincipal_base64 },
+            ],
+          },
+          {
+            entries: [
+              { url: "http://example.com#3", triggeringPrincipal_base64 },
+            ],
+          },
+          {
+            entries: [
+              { url: "http://example.com#4", triggeringPrincipal_base64 },
+            ],
+          },
+          {
+            entries: [
+              { url: "http://example.com#5", triggeringPrincipal_base64 },
+            ],
+          },
+        ],
+      },
+    ],
+  };
+  let state2 = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              { url: "http://example.org#1", triggeringPrincipal_base64 },
+            ],
+          },
+          {
+            entries: [
+              { url: "http://example.org#2", triggeringPrincipal_base64 },
+            ],
+          },
+          {
+            entries: [
+              { url: "http://example.org#3", triggeringPrincipal_base64 },
+            ],
+          },
+          {
+            entries: [
+              { url: "http://example.org#4", triggeringPrincipal_base64 },
+            ],
+          },
+          {
+            entries: [
+              { url: "http://example.org#5", triggeringPrincipal_base64 },
+            ],
+          },
+        ],
+      },
+    ],
+  };
+  let numTabs = 2 + state2.windows[0].tabs.length;
+
+  let loadCount = 0;
+  let promiseRestoringTabs = new Promise(resolve => {
+    gProgressListener.setCallback(function (aBrowser, aNeedRestore) {
+      // When loadCount == 2, we'll also restore state2 into the window
+      if (++loadCount == 2) {
+        executeSoon(() =>
+          ss.setWindowState(window, JSON.stringify(state2), true)
+        );
+      }
+
+      if (loadCount < numTabs) {
+        return;
+      }
+
+      // We don't actually care about load order in this test, just that they all
+      // do load.
+      is(loadCount, numTabs, "all tabs were restored");
+      is(aNeedRestore, 0, "there are no tabs left needing restore");
+
+      gProgressListener.unsetCallback();
+      resolve();
+    });
+  });
+
+  let backupState = ss.getBrowserState();
+  ss.setWindowState(window, JSON.stringify(state1), true);
+  await promiseRestoringTabs;
+
+  // Cleanup.
+  await promiseBrowserState(backupState);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_586147.js b/src/zen/tests/mochitests/sessionstore/browser_586147.js
new file mode 100644
index 000000000..37c369c3a
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_586147.js
@@ -0,0 +1,52 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+function observeOneRestore(callback) {
+  let topic = "sessionstore-browser-state-restored";
+  Services.obs.addObserver(function onRestore() {
+    Services.obs.removeObserver(onRestore, topic);
+    callback();
+  }, topic);
+}
+
+function test() {
+  waitForExplicitFinish();
+
+  // There should be one tab when we start the test
+  let [origTab] = gBrowser.visibleTabs;
+  let hiddenTab = BrowserTestUtils.addTab(gBrowser);
+
+  is(gBrowser.visibleTabs.length, 2, "should have 2 tabs before hiding");
+  BrowserTestUtils.showOnlyTheseTabs(gBrowser, [origTab]);
+  is(gBrowser.visibleTabs.length, 1, "only 1 after hiding");
+  ok(hiddenTab.hidden, "sanity check that it's hidden");
+
+  BrowserTestUtils.addTab(gBrowser);
+  let state = ss.getBrowserState();
+  let stateObj = JSON.parse(state);
+  let tabs = stateObj.windows[0].tabs;
+  is(tabs.length, 3, "just checking that browser state is correct");
+  ok(!tabs[0].hidden, "first tab is visible");
+  ok(tabs[1].hidden, "second is hidden");
+  ok(!tabs[2].hidden, "third is visible");
+
+  // Make the third tab hidden and then restore the modified state object
+  tabs[2].hidden = true;
+
+  observeOneRestore(function () {
+    is(gBrowser.visibleTabs.length, 1, "only restored 1 visible tab");
+    let restoredTabs = gBrowser.tabs;
+
+    ok(!restoredTabs[0].hidden, "first is still visible");
+    ok(restoredTabs[1].hidden, "second tab is still hidden");
+    ok(restoredTabs[2].hidden, "third tab is now hidden");
+
+    // Restore the original state and clean up now that we're done
+    gBrowser.removeTab(gBrowser.tabs[1]);
+    gBrowser.removeTab(gBrowser.tabs[1]);
+
+    finish();
+  });
+  ss.setBrowserState(JSON.stringify(stateObj));
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_588426.js b/src/zen/tests/mochitests/sessionstore/browser_588426.js
new file mode 100644
index 000000000..e32867fc6
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_588426.js
@@ -0,0 +1,62 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+function test() {
+  let state = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [{ url: "about:mozilla", triggeringPrincipal_base64 }],
+            hidden: true,
+          },
+          {
+            entries: [{ url: "about:rights", triggeringPrincipal_base64 }],
+            hidden: true,
+          },
+        ],
+      },
+    ],
+  };
+
+  waitForExplicitFinish();
+
+  newWindowWithState(state, function (win) {
+    registerCleanupFunction(() => BrowserTestUtils.closeWindow(win));
+
+    is(win.gBrowser.tabs.length, 2, "two tabs were restored");
+    is(win.gBrowser.visibleTabs.length, 1, "one tab is visible");
+
+    let tab = win.gBrowser.visibleTabs[0];
+    is(
+      tab.linkedBrowser.currentURI.spec,
+      "about:mozilla",
+      "visible tab is about:mozilla"
+    );
+
+    finish();
+  });
+}
+
+function newWindowWithState(state, callback) {
+  let opts = "chrome,all,dialog=no,height=800,width=800";
+  let win = window.openDialog(AppConstants.BROWSER_CHROME_URL, "_blank", opts);
+
+  win.addEventListener(
+    "load",
+    function () {
+      executeSoon(function () {
+        win.addEventListener(
+          "SSWindowStateReady",
+          function () {
+            promiseTabRestored(win.gBrowser.tabs[0]).then(() => callback(win));
+          },
+          { once: true }
+        );
+
+        ss.setWindowState(win, JSON.stringify(state), true);
+      });
+    },
+    { once: true }
+  );
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_589246.js b/src/zen/tests/mochitests/sessionstore/browser_589246.js
new file mode 100644
index 000000000..e3e98f351
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_589246.js
@@ -0,0 +1,288 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// Mirrors WINDOW_ATTRIBUTES IN SessionStore.sys.mjs
+const WINDOW_ATTRIBUTES = ["width", "height", "screenX", "screenY", "sizemode"];
+
+var stateBackup = ss.getBrowserState();
+
+var originalWarnOnClose = Services.prefs.getBoolPref(
+  "browser.tabs.warnOnClose"
+);
+var originalStartupPage = Services.prefs.getIntPref("browser.startup.page");
+var originalWindowType = document.documentElement.getAttribute("windowtype");
+
+var gotLastWindowClosedTopic = false;
+var shouldPinTab = false;
+var shouldOpenTabs = false;
+var shouldCloseTab = false;
+var testNum = 0;
+var afterTestCallback;
+
+// Set state so we know the closed windows content
+var testState = {
+  windows: [{ tabs: [{ entries: [{ url: "http://example.org" }] }] }],
+  _closedWindows: [],
+};
+
+// We'll push a set of conditions and callbacks into this array
+// Ideally we would also test win/linux under a complete set of conditions, but
+// the tests for osx mirror the other set of conditions possible on win/linux.
+var tests = [];
+
+// the third & fourth test share a condition check, keep it DRY
+function checkOSX34Generator(num) {
+  return function (aPreviousState, aCurState) {
+    // In here, we should have restored the pinned tab, so only the unpinned tab
+    // should be in aCurState. So let's shape our expectations.
+    let expectedState = JSON.parse(aPreviousState);
+    expectedState[0].tabs.shift();
+    // size attributes are stripped out in _prepDataForDeferredRestore in SessionStore.sys.mjs.
+    // This isn't the best approach, but neither is comparing JSON strings
+    WINDOW_ATTRIBUTES.forEach(attr => delete expectedState[0][attr]);
+
+    is(
+      aCurState,
+      JSON.stringify(expectedState),
+      "test #" + num + ": closedWindowState is as expected"
+    );
+  };
+}
+function checkNoWindowsGenerator(num) {
+  return function (aPreviousState, aCurState) {
+    is(
+      aCurState,
+      "[]",
+      "test #" + num + ": there should be no closedWindowsLeft"
+    );
+  };
+}
+
+// The first test has 0 pinned tabs and 1 unpinned tab
+tests.push({
+  pinned: false,
+  extra: false,
+  close: false,
+  checkWinLin: checkNoWindowsGenerator(1),
+  checkOSX(aPreviousState, aCurState) {
+    is(aCurState, aPreviousState, "test #1: closed window state is unchanged");
+  },
+});
+
+// The second test has 1 pinned tab and 0 unpinned tabs.
+tests.push({
+  pinned: true,
+  extra: false,
+  close: false,
+  checkWinLin: checkNoWindowsGenerator(2),
+  checkOSX: checkNoWindowsGenerator(2),
+});
+
+// The third test has 1 pinned tab and 2 unpinned tabs.
+tests.push({
+  pinned: true,
+  extra: true,
+  close: false,
+  checkWinLin: checkNoWindowsGenerator(3),
+  checkOSX: checkOSX34Generator(3),
+});
+
+// The fourth test has 1 pinned tab, 2 unpinned tabs, and closes one unpinned tab.
+tests.push({
+  pinned: true,
+  extra: true,
+  close: "one",
+  checkWinLin: checkNoWindowsGenerator(4),
+  checkOSX: checkOSX34Generator(4),
+});
+
+// The fifth test has 1 pinned tab, 2 unpinned tabs, and closes both unpinned tabs.
+tests.push({
+  pinned: true,
+  extra: true,
+  close: "both",
+  checkWinLin: checkNoWindowsGenerator(5),
+  checkOSX: checkNoWindowsGenerator(5),
+});
+
+function test() {
+  /**
+   * Test for Bug 589246 - Closed window state getting corrupted when closing
+   * and reopening last browser window without exiting browser
+   */
+  waitForExplicitFinish();
+  // windows opening & closing, so extending the timeout
+  requestLongerTimeout(2);
+
+  // We don't want the quit dialog pref
+  Services.prefs.setBoolPref("browser.tabs.warnOnClose", false);
+  // Ensure that we would restore the session (important for Windows)
+  Services.prefs.setIntPref("browser.startup.page", 3);
+
+  runNextTestOrFinish();
+}
+
+function runNextTestOrFinish() {
+  if (tests.length) {
+    setupForTest(tests.shift());
+  } else {
+    // some state is cleaned up at the end of each test, but not all
+    ["browser.tabs.warnOnClose", "browser.startup.page"].forEach(function (p) {
+      if (Services.prefs.prefHasUserValue(p)) {
+        Services.prefs.clearUserPref(p);
+      }
+    });
+
+    ss.setBrowserState(stateBackup);
+    executeSoon(finish);
+  }
+}
+
+function setupForTest(aConditions) {
+  // reset some checks
+  gotLastWindowClosedTopic = false;
+  shouldPinTab = aConditions.pinned;
+  shouldOpenTabs = aConditions.extra;
+  shouldCloseTab = aConditions.close;
+  testNum++;
+
+  // set our test callback
+  afterTestCallback = /Mac/.test(navigator.platform)
+    ? aConditions.checkOSX
+    : aConditions.checkWinLin;
+
+  // Add observers
+  Services.obs.addObserver(
+    onLastWindowClosed,
+    "browser-lastwindow-close-granted"
+  );
+
+  // Set the state
+  Services.obs.addObserver(
+    onStateRestored,
+    "sessionstore-browser-state-restored"
+  );
+  ss.setBrowserState(JSON.stringify(testState));
+}
+
+function onStateRestored() {
+  info("test #" + testNum + ": onStateRestored");
+  Services.obs.removeObserver(
+    onStateRestored,
+    "sessionstore-browser-state-restored"
+  );
+
+  // change this window's windowtype so that closing a new window will trigger
+  // browser-lastwindow-close-granted.
+  document.documentElement.setAttribute("windowtype", "navigator:testrunner");
+
+  let newWin = openDialog(
+    location,
+    "_blank",
+    "chrome,all,dialog=no",
+    "http://example.com"
+  );
+  newWin.addEventListener(
+    "load",
+    function () {
+      promiseBrowserLoaded(newWin.gBrowser.selectedBrowser).then(() => {
+        // pin this tab
+        if (shouldPinTab) {
+          newWin.gBrowser.pinTab(newWin.gBrowser.selectedTab);
+        }
+
+        newWin.addEventListener(
+          "unload",
+          function () {
+            onWindowUnloaded();
+          },
+          { once: true }
+        );
+        // Open a new tab as well. On Windows/Linux this will be restored when the
+        // new window is opened below (in onWindowUnloaded). On OS X we'll just
+        // restore the pinned tabs, leaving the unpinned tab in the closedWindowsData.
+        if (shouldOpenTabs) {
+          let newTab = BrowserTestUtils.addTab(newWin.gBrowser, "about:config");
+          let newTab2 = BrowserTestUtils.addTab(
+            newWin.gBrowser,
+            "about:buildconfig"
+          );
+
+          newTab.linkedBrowser.addEventListener(
+            "load",
+            function () {
+              if (shouldCloseTab == "one") {
+                newWin.gBrowser.removeTab(newTab2);
+              } else if (shouldCloseTab == "both") {
+                newWin.gBrowser.removeTab(newTab);
+                newWin.gBrowser.removeTab(newTab2);
+              }
+              newWin.BrowserCommands.tryToCloseWindow();
+            },
+            { capture: true, once: true }
+          );
+        } else {
+          newWin.BrowserCommands.tryToCloseWindow();
+        }
+      });
+    },
+    { once: true }
+  );
+}
+
+// This will be called before the window is actually closed
+function onLastWindowClosed() {
+  info("test #" + testNum + ": onLastWindowClosed");
+  Services.obs.removeObserver(
+    onLastWindowClosed,
+    "browser-lastwindow-close-granted"
+  );
+  gotLastWindowClosedTopic = true;
+}
+
+// This is the unload event listener on the new window (from onStateRestored).
+// Unload is fired after the window is closed, so sessionstore has already
+// updated _closedWindows (which is important). We'll open a new window here
+// which should actually trigger the bug.
+function onWindowUnloaded() {
+  info("test #" + testNum + ": onWindowClosed");
+  ok(
+    gotLastWindowClosedTopic,
+    "test #" + testNum + ": browser-lastwindow-close-granted was notified prior"
+  );
+
+  let previousClosedWindowData = ss.getClosedWindowData();
+
+  // Now we want to open a new window
+  let newWin = openDialog(
+    location,
+    "_blank",
+    "chrome,all,dialog=no",
+    "about:mozilla"
+  );
+  newWin.addEventListener(
+    "load",
+    function () {
+      newWin.gBrowser.selectedBrowser.addEventListener(
+        "load",
+        function () {
+          // Good enough for checking the state
+          afterTestCallback(previousClosedWindowData, ss.getClosedWindowData());
+          afterTestCleanup(newWin);
+        },
+        { capture: true, once: true }
+      );
+    },
+    { once: true }
+  );
+}
+
+function afterTestCleanup(aNewWin) {
+  executeSoon(function () {
+    BrowserTestUtils.closeWindow(aNewWin).then(() => {
+      document.documentElement.setAttribute("windowtype", originalWindowType);
+      runNextTestOrFinish();
+    });
+  });
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_590268.js b/src/zen/tests/mochitests/sessionstore/browser_590268.js
new file mode 100644
index 000000000..086348b12
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_590268.js
@@ -0,0 +1,159 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const NUM_TABS = 12;
+
+var stateBackup = ss.getBrowserState();
+
+function test() {
+  /** Test for Bug 590268 - Provide access to sessionstore tab data sooner */
+  waitForExplicitFinish();
+  requestLongerTimeout(2);
+
+  // wasLoaded will be used to keep track of tabs that have already had SSTabRestoring
+  // fired for them.
+  let wasLoaded = {};
+  let restoringTabsCount = 0;
+  let restoredTabsCount = 0;
+  let uniq2 = {};
+  let uniq2Count = 0;
+  let state = { windows: [{ tabs: [] }] };
+  // We're going to put a bunch of tabs into this state
+  for (let i = 0; i < NUM_TABS; i++) {
+    let uniq = r();
+    let tabData = {
+      entries: [
+        { url: "http://example.com/#" + i, triggeringPrincipal_base64 },
+      ],
+      extData: { uniq, baz: "qux" },
+    };
+    state.windows[0].tabs.push(tabData);
+    wasLoaded[uniq] = false;
+  }
+
+  function onSSTabRestoring(aEvent) {
+    restoringTabsCount++;
+    let uniq = ss.getCustomTabValue(aEvent.originalTarget, "uniq");
+    wasLoaded[uniq] = true;
+
+    is(
+      ss.getCustomTabValue(aEvent.originalTarget, "foo"),
+      "",
+      "There is no value for 'foo'"
+    );
+
+    // On the first SSTabRestoring we're going to run the the real test.
+    // We'll keep this listener around so we can keep marking tabs as restored.
+    if (restoringTabsCount == 1) {
+      onFirstSSTabRestoring();
+    } else if (restoringTabsCount == NUM_TABS) {
+      onLastSSTabRestoring();
+    }
+  }
+
+  function onSSTabRestored() {
+    if (++restoredTabsCount < NUM_TABS) {
+      return;
+    }
+    cleanup();
+  }
+
+  function onTabOpen(aEvent) {
+    // To test bug 614708, we'll just set a value on the tab here. This value
+    // would previously cause us to not recognize the values in extData until
+    // much later. So testing "uniq" failed.
+    ss.setCustomTabValue(aEvent.originalTarget, "foo", "bar");
+  }
+
+  // This does the actual testing. SSTabRestoring should be firing on tabs from
+  // left to right, so we're going to start with the rightmost tab.
+  function onFirstSSTabRestoring() {
+    info("onFirstSSTabRestoring...");
+    for (let i = gBrowser.tabs.length - 1; i >= 0; i--) {
+      let tab = gBrowser.tabs[i];
+      let actualUniq = ss.getCustomTabValue(tab, "uniq");
+      let expectedUniq = state.windows[0].tabs[i].extData.uniq;
+
+      if (wasLoaded[actualUniq]) {
+        info("tab " + i + ": already restored");
+        continue;
+      }
+      is(actualUniq, expectedUniq, "tab " + i + ": extData was correct");
+
+      // Now we're going to set a piece of data back on the tab so it can be read
+      // to test setting a value "early".
+      uniq2[actualUniq] = r();
+      ss.setCustomTabValue(tab, "uniq2", uniq2[actualUniq]);
+
+      // Delete the value we have for "baz". This tests that deleteCustomTabValue
+      // will delete "early access" values (c.f. bug 617175). If this doesn't throw
+      // then the test is successful.
+      try {
+        ss.deleteCustomTabValue(tab, "baz");
+      } catch (e) {
+        ok(false, "no error calling deleteCustomTabValue - " + e);
+      }
+
+      // This will be used in the final comparison to make sure we checked the
+      // same number as we set.
+      uniq2Count++;
+    }
+  }
+
+  function onLastSSTabRestoring() {
+    let checked = 0;
+    for (let i = 0; i < gBrowser.tabs.length; i++) {
+      let tab = gBrowser.tabs[i];
+      let uniq = ss.getCustomTabValue(tab, "uniq");
+
+      // Look to see if we set a uniq2 value for this uniq value
+      if (uniq in uniq2) {
+        is(
+          ss.getCustomTabValue(tab, "uniq2"),
+          uniq2[uniq],
+          "tab " + i + " has correct uniq2 value"
+        );
+        checked++;
+      }
+    }
+    Assert.greater(
+      uniq2Count,
+      0,
+      "at least 1 tab properly checked 'early access'"
+    );
+    is(checked, uniq2Count, "checked the same number of uniq2 as we set");
+  }
+
+  function cleanup() {
+    // remove the event listener and clean up before finishing
+    gBrowser.tabContainer.removeEventListener(
+      "SSTabRestoring",
+      onSSTabRestoring
+    );
+    gBrowser.tabContainer.removeEventListener(
+      "SSTabRestored",
+      onSSTabRestored,
+      true
+    );
+    gBrowser.tabContainer.removeEventListener("TabOpen", onTabOpen);
+    // Put this in an executeSoon because we still haven't called restoreNextTab
+    // in sessionstore for the last tab (we'll call it after this). We end up
+    // trying to restore the tab (since we then add a closed tab to the array).
+    executeSoon(function () {
+      ss.setBrowserState(stateBackup);
+      executeSoon(finish);
+    });
+  }
+
+  // Add the event listeners
+  gBrowser.tabContainer.addEventListener("SSTabRestoring", onSSTabRestoring);
+  gBrowser.tabContainer.addEventListener(
+    "SSTabRestored",
+    onSSTabRestored,
+    true
+  );
+  gBrowser.tabContainer.addEventListener("TabOpen", onTabOpen);
+  // Restore state
+  ss.setBrowserState(JSON.stringify(state));
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_590563.js b/src/zen/tests/mochitests/sessionstore/browser_590563.js
new file mode 100644
index 000000000..86843d2e7
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_590563.js
@@ -0,0 +1,120 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+add_task(async function () {
+  let sessionData = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [{ url: "about:mozilla", triggeringPrincipal_base64 }],
+            hidden: true,
+          },
+          {
+            entries: [{ url: "about:blank", triggeringPrincipal_base64 }],
+            hidden: false,
+          },
+        ],
+      },
+    ],
+  };
+  let url = "about:sessionrestore";
+  let formdata = { id: { sessionData }, url };
+  let state = {
+    windows: [
+      { tabs: [{ entries: [{ url, triggeringPrincipal_base64 }], formdata }] },
+    ],
+  };
+
+  let win = await newWindowWithState(state);
+
+  registerCleanupFunction(() => BrowserTestUtils.closeWindow(win));
+
+  is(gBrowser.tabs.length, 1, "The total number of tabs should be 1");
+  is(
+    gBrowser.visibleTabs.length,
+    1,
+    "The total number of visible tabs should be 1"
+  );
+
+  await new Promise(resolve => executeSoon(resolve));
+  await new Promise(resolve => waitForFocus(resolve, win));
+  await middleClickTest(win);
+});
+
+async function middleClickTest(win) {
+  let browser = win.gBrowser.selectedBrowser;
+  let tabsToggle = browser.contentDocument.getElementById("tabsToggle");
+  EventUtils.synthesizeMouseAtCenter(
+    tabsToggle,
+    { button: 0 },
+    browser.contentWindow
+  );
+  let tree = browser.contentDocument.getElementById("tabList");
+  await TestUtils.waitForCondition(() => !tree.hasAttribute("hidden"));
+  // Force a layout flush before accessing coordinates.
+  tree.getBoundingClientRect();
+
+  is(tree.view.rowCount, 3, "There should be three items");
+
+  // click on the first tab item
+  var rect = tree.getCoordsForCellItem(1, tree.columns[1], "text");
+  EventUtils.synthesizeMouse(
+    tree.body,
+    rect.x,
+    rect.y,
+    { button: 1 },
+    browser.contentWindow
+  );
+  // click on the second tab item
+  rect = tree.getCoordsForCellItem(2, tree.columns[1], "text");
+  EventUtils.synthesizeMouse(
+    tree.body,
+    rect.x,
+    rect.y,
+    { button: 1 },
+    browser.contentWindow
+  );
+
+  is(
+    win.gBrowser.tabs.length,
+    3,
+    "The total number of tabs should be 3 after restoring 2 tabs by middle click."
+  );
+  is(
+    win.gBrowser.visibleTabs.length,
+    3,
+    "The total number of visible tabs should be 3 after restoring 2 tabs by middle click"
+  );
+}
+
+async function newWindowWithState(state) {
+  let opts = "chrome,all,dialog=no,height=800,width=800";
+  let win = window.openDialog(AppConstants.BROWSER_CHROME_URL, "_blank", opts);
+
+  await BrowserTestUtils.waitForEvent(win, "load");
+
+  // The form data will be restored before SSTabRestored, so we want to listen
+  // for that on the currently selected tab
+  await new Promise(resolve => {
+    win.gBrowser.tabContainer.addEventListener(
+      "SSTabRestored",
+      function onSSTabRestored(event) {
+        let tab = event.target;
+        if (tab.selected) {
+          win.gBrowser.tabContainer.removeEventListener(
+            "SSTabRestored",
+            onSSTabRestored,
+            true
+          );
+          resolve();
+        }
+      },
+      true
+    );
+
+    executeSoon(() => ss.setWindowState(win, JSON.stringify(state), true));
+  });
+
+  return win;
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_595601-restore_hidden.js b/src/zen/tests/mochitests/sessionstore/browser_595601-restore_hidden.js
new file mode 100644
index 000000000..220039442
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_595601-restore_hidden.js
@@ -0,0 +1,165 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+var windowState = {
+  windows: [
+    {
+      tabs: [
+        {
+          entries: [
+            { url: "http://example.com#1", triggeringPrincipal_base64 },
+          ],
+        },
+        {
+          entries: [
+            { url: "http://example.com#2", triggeringPrincipal_base64 },
+          ],
+        },
+        {
+          entries: [
+            { url: "http://example.com#3", triggeringPrincipal_base64 },
+          ],
+        },
+        {
+          entries: [
+            { url: "http://example.com#4", triggeringPrincipal_base64 },
+          ],
+        },
+        {
+          entries: [
+            { url: "http://example.com#5", triggeringPrincipal_base64 },
+          ],
+          hidden: true,
+        },
+        {
+          entries: [
+            { url: "http://example.com#6", triggeringPrincipal_base64 },
+          ],
+          hidden: true,
+        },
+        {
+          entries: [
+            { url: "http://example.com#7", triggeringPrincipal_base64 },
+          ],
+          hidden: true,
+        },
+        {
+          entries: [
+            { url: "http://example.com#8", triggeringPrincipal_base64 },
+          ],
+          hidden: true,
+        },
+      ],
+    },
+  ],
+};
+
+function test() {
+  waitForExplicitFinish();
+  requestLongerTimeout(2);
+
+  registerCleanupFunction(function () {
+    Services.prefs.clearUserPref("browser.sessionstore.restore_hidden_tabs");
+  });
+
+  // First stage: restoreHiddenTabs = true
+  // Second stage: restoreHiddenTabs = false
+  test_loadTabs(true, function () {
+    test_loadTabs(false, finish);
+  });
+}
+
+function test_loadTabs(restoreHiddenTabs, callback) {
+  Services.prefs.setBoolPref(
+    "browser.sessionstore.restore_hidden_tabs",
+    restoreHiddenTabs
+  );
+
+  let expectedTabs = restoreHiddenTabs ? 8 : 4;
+  let firstProgress = true;
+
+  newWindowWithState(windowState, function (win, needsRestore, isRestoring) {
+    if (firstProgress) {
+      firstProgress = false;
+      is(isRestoring, 3, "restoring 3 tabs concurrently");
+    } else {
+      Assert.less(isRestoring, 4, "restoring max. 3 tabs concurrently");
+    }
+
+    // We're explicity checking for (isRestoring == 1) here because the test
+    // progress listener is called before the session store one. So when we're
+    // called with one tab left to restore we know that the last tab has
+    // finished restoring and will soon be handled by the SS listener.
+    let tabsNeedingRestore = win.gBrowser.tabs.length - needsRestore;
+    if (isRestoring == 1 && tabsNeedingRestore == expectedTabs) {
+      is(win.gBrowser.visibleTabs.length, 4, "only 4 visible tabs");
+
+      TabsProgressListener.uninit();
+      executeSoon(callback);
+    }
+  });
+}
+
+var TabsProgressListener = {
+  init(win) {
+    this.window = win;
+    Services.obs.addObserver(this, "sessionstore-debug-tab-restored");
+  },
+
+  uninit() {
+    Services.obs.removeObserver(this, "sessionstore-debug-tab-restored");
+
+    delete this.window;
+    delete this.callback;
+  },
+
+  setCallback(callback) {
+    this.callback = callback;
+  },
+
+  observe(browser) {
+    TabsProgressListener.onRestored(browser);
+  },
+
+  onRestored(browser) {
+    if (
+      this.callback &&
+      ss.getInternalObjectState(browser) == TAB_STATE_RESTORING
+    ) {
+      this.callback.apply(null, [this.window].concat(this.countTabs()));
+    }
+  },
+
+  countTabs() {
+    let needsRestore = 0,
+      isRestoring = 0;
+
+    for (let i = 0; i < this.window.gBrowser.tabs.length; i++) {
+      let state = ss.getInternalObjectState(
+        this.window.gBrowser.tabs[i].linkedBrowser
+      );
+      if (state == TAB_STATE_RESTORING) {
+        isRestoring++;
+      } else if (state == TAB_STATE_NEEDS_RESTORE) {
+        needsRestore++;
+      }
+    }
+
+    return [needsRestore, isRestoring];
+  },
+};
+
+// ----------
+function newWindowWithState(state, callback) {
+  let opts = "chrome,all,dialog=no,height=800,width=800";
+  let win = window.openDialog(AppConstants.BROWSER_CHROME_URL, "_blank", opts);
+
+  registerCleanupFunction(() => BrowserTestUtils.closeWindow(win));
+
+  whenWindowLoaded(win, function onWindowLoaded(aWin) {
+    TabsProgressListener.init(aWin);
+    TabsProgressListener.setCallback(callback);
+
+    ss.setWindowState(aWin, JSON.stringify(state), true);
+  });
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_597071.js b/src/zen/tests/mochitests/sessionstore/browser_597071.js
new file mode 100644
index 000000000..953e46249
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_597071.js
@@ -0,0 +1,36 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/**
+ * Bug 597071 - Closed windows should only be resurrected when there is a single
+ * popup window
+ */
+add_task(async function test_close_last_nonpopup_window() {
+  // Purge the list of closed windows.
+  forgetClosedWindows();
+
+  let oldState = ss.getWindowState(window);
+
+  let popupState = {
+    windows: [{ tabs: [{ entries: [] }], isPopup: true, hidden: "toolbar" }],
+  };
+
+  // Set this window to be a popup.
+  ss.setWindowState(window, JSON.stringify(popupState), true);
+
+  // Open a new window with a tab.
+  let win = await BrowserTestUtils.openNewBrowserWindow({ private: false });
+  let tab = BrowserTestUtils.addTab(win.gBrowser, "http://example.com/");
+  await BrowserTestUtils.browserLoaded(tab.linkedBrowser);
+
+  // Make sure sessionstore sees this window.
+  let state = JSON.parse(ss.getBrowserState());
+  is(state.windows.length, 2, "sessionstore knows about this window");
+
+  // Closed the window and check the closed window count.
+  await BrowserTestUtils.closeWindow(win);
+  is(ss.getClosedWindowCount(), 1, "correct closed window count");
+
+  // Cleanup.
+  ss.setWindowState(window, oldState, true);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_600545.js b/src/zen/tests/mochitests/sessionstore/browser_600545.js
new file mode 100644
index 000000000..5b8315e00
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_600545.js
@@ -0,0 +1,123 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+requestLongerTimeout(2);
+
+var stateBackup = JSON.parse(ss.getBrowserState());
+
+function test() {
+  /** Test for Bug 600545 */
+  waitForExplicitFinish();
+  testBug600545();
+}
+
+function testBug600545() {
+  // Set the pref to false to cause non-app tabs to be stripped out on a save
+  Services.prefs.setBoolPref("browser.sessionstore.resume_from_crash", false);
+  Services.prefs.setIntPref("browser.sessionstore.interval", 2000);
+
+  registerCleanupFunction(function () {
+    Services.prefs.clearUserPref("browser.sessionstore.resume_from_crash");
+    Services.prefs.clearUserPref("browser.sessionstore.interval");
+  });
+
+  // This tests the following use case: When multiple windows are open
+  // and browser.sessionstore.resume_from_crash preference is false,
+  // tab session data for non-active window is stripped for non-pinned
+  // tabs.  This occurs after "sessionstore-state-write-complete"
+  // fires which will only fire in this case if there is at least one
+  // pinned tab.
+  let state = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              { url: "http://example.org#0", triggeringPrincipal_base64 },
+            ],
+            pinned: true,
+          },
+          {
+            entries: [
+              { url: "http://example.com#1", triggeringPrincipal_base64 },
+            ],
+          },
+          {
+            entries: [
+              { url: "http://example.com#2", triggeringPrincipal_base64 },
+            ],
+          },
+        ],
+        selected: 2,
+      },
+      {
+        tabs: [
+          {
+            entries: [
+              { url: "http://example.com#3", triggeringPrincipal_base64 },
+            ],
+          },
+          {
+            entries: [
+              { url: "http://example.com#4", triggeringPrincipal_base64 },
+            ],
+          },
+          {
+            entries: [
+              { url: "http://example.com#5", triggeringPrincipal_base64 },
+            ],
+          },
+          {
+            entries: [
+              { url: "http://example.com#6", triggeringPrincipal_base64 },
+            ],
+          },
+        ],
+        selected: 3,
+      },
+    ],
+  };
+
+  waitForBrowserState(state, function () {
+    // Need to wait for SessionStore's saveState function to be called
+    // so that non-pinned tabs will be stripped from non-active window
+    waitForSaveState(function () {
+      let expectedNumberOfTabs = getStateTabCount(state);
+      let retrievedState = JSON.parse(ss.getBrowserState());
+      let actualNumberOfTabs = getStateTabCount(retrievedState);
+
+      is(
+        actualNumberOfTabs,
+        expectedNumberOfTabs,
+        "Number of tabs in retreived session data, matches number of tabs set."
+      );
+
+      done();
+    });
+  });
+}
+
+function done() {
+  // Enumerate windows and close everything but our primary window. We can't
+  // use waitForFocus() because apparently it's buggy. See bug 599253.
+  let closeWinPromises = [];
+  for (let currentWindow of Services.wm.getEnumerator("navigator:browser")) {
+    if (currentWindow != window) {
+      closeWinPromises.push(BrowserTestUtils.closeWindow(currentWindow));
+    }
+  }
+
+  Promise.all(closeWinPromises).then(() => {
+    waitForBrowserState(stateBackup, finish);
+  });
+}
+
+// Count up the number of tabs in the state data
+function getStateTabCount(aState) {
+  let tabCount = 0;
+  for (let i in aState.windows) {
+    tabCount += aState.windows[i].tabs.length;
+  }
+  return tabCount;
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_601955.js b/src/zen/tests/mochitests/sessionstore/browser_601955.js
new file mode 100644
index 000000000..90cf6c182
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_601955.js
@@ -0,0 +1,54 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// This tests that pinning/unpinning a tab, on its own, eventually triggers a
+// session store.
+
+function test() {
+  waitForExplicitFinish();
+  // We speed up the interval between session saves to ensure that the test
+  // runs quickly.
+  Services.prefs.setIntPref("browser.sessionstore.interval", 2000);
+
+  // Loading a tab causes a save state and this is meant to catch that event.
+  waitForSaveState(testBug601955_1);
+
+  // Assumption: Only one window is open and it has one tab open.
+  BrowserTestUtils.addTab(gBrowser, "about:mozilla");
+}
+
+function testBug601955_1() {
+  // Because pinned tabs are at the front of |gBrowser.tabs|, pinning tabs
+  // re-arranges the |tabs| array.
+  ok(!gBrowser.tabs[0].pinned, "first tab should not be pinned yet");
+  ok(!gBrowser.tabs[1].pinned, "second tab should not be pinned yet");
+
+  waitForSaveState(testBug601955_2);
+  gBrowser.pinTab(gBrowser.tabs[0]);
+}
+
+function testBug601955_2() {
+  let state = JSON.parse(ss.getBrowserState());
+  ok(state.windows[0].tabs[0].pinned, "first tab should be pinned by now");
+  ok(!state.windows[0].tabs[1].pinned, "second tab should still not be pinned");
+
+  waitForSaveState(testBug601955_3);
+  gBrowser.unpinTab(window.gBrowser.tabs[0]);
+}
+
+function testBug601955_3() {
+  let state = JSON.parse(ss.getBrowserState());
+  ok(!state.windows[0].tabs[0].pinned, "first tab should not be pinned");
+  ok(!state.windows[0].tabs[1].pinned, "second tab should not be pinned");
+
+  done();
+}
+
+function done() {
+  gBrowser.removeTab(window.gBrowser.tabs[1]);
+
+  Services.prefs.clearUserPref("browser.sessionstore.interval");
+
+  executeSoon(finish);
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_607016.js b/src/zen/tests/mochitests/sessionstore/browser_607016.js
new file mode 100644
index 000000000..4d8254101
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_607016.js
@@ -0,0 +1,155 @@
+"use strict";
+
+var stateBackup = ss.getBrowserState();
+
+add_task(async function () {
+  /** Bug 607016 - If a tab is never restored, attributes (eg. hidden) aren't updated correctly */
+  ignoreAllUncaughtExceptions();
+
+  // Set the pref to true so we know exactly how many tabs should be restoring at
+  // any given time. This guarantees that a finishing load won't start another.
+  Services.prefs.setBoolPref("browser.sessionstore.restore_on_demand", true);
+  // Don't restore tabs lazily.
+  Services.prefs.setBoolPref("browser.sessionstore.restore_tabs_lazily", false);
+
+  let state = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              { url: "http://example.org#1", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          },
+          {
+            entries: [
+              { url: "http://example.org#2", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          }, // overwriting
+          {
+            entries: [
+              { url: "http://example.org#3", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          }, // hiding
+          {
+            entries: [
+              { url: "http://example.org#4", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          }, // adding
+          {
+            entries: [
+              { url: "http://example.org#5", triggeringPrincipal_base64 },
+            ],
+            extData: { uniq: r() },
+          }, // deleting
+          {
+            entries: [
+              { url: "http://example.org#6", triggeringPrincipal_base64 },
+            ],
+          }, // creating
+        ],
+        selected: 1,
+      },
+    ],
+  };
+
+  async function progressCallback() {
+    let curState = JSON.parse(ss.getBrowserState());
+    for (let i = 0; i < curState.windows[0].tabs.length; i++) {
+      let tabState = state.windows[0].tabs[i];
+      let tabCurState = curState.windows[0].tabs[i];
+      if (tabState.extData) {
+        is(
+          tabCurState.extData.uniq,
+          tabState.extData.uniq,
+          "sanity check that tab has correct extData"
+        );
+      } else {
+        // We aren't expecting there to be any data on extData, but panorama
+        // may be setting something, so we need to make sure that if we do have
+        // data, we just don't have anything for "uniq".
+        ok(
+          !("extData" in tabCurState) || !("uniq" in tabCurState.extData),
+          "sanity check that tab doesn't have extData or extData doesn't have 'uniq'"
+        );
+      }
+    }
+
+    // Now we'll set a new unique value on 1 of the tabs
+    let newUniq = r();
+    ss.setCustomTabValue(gBrowser.tabs[1], "uniq", newUniq);
+    let tabState = JSON.parse(ss.getTabState(gBrowser.tabs[1]));
+    is(
+      tabState.extData.uniq,
+      newUniq,
+      "(overwriting) new data is stored in extData"
+    );
+
+    // hide the next tab before closing it
+    gBrowser.hideTab(gBrowser.tabs[2]);
+    tabState = JSON.parse(ss.getTabState(gBrowser.tabs[2]));
+    ok(tabState.hidden, "(hiding) tab data has hidden == true");
+
+    // set data that's not in a conflicting key
+    let stillUniq = r();
+    ss.setCustomTabValue(gBrowser.tabs[3], "stillUniq", stillUniq);
+    tabState = JSON.parse(ss.getTabState(gBrowser.tabs[3]));
+    is(
+      tabState.extData.stillUniq,
+      stillUniq,
+      "(adding) new data is stored in extData"
+    );
+
+    // remove the uniq value and make sure it's not there in the closed data
+    ss.deleteCustomTabValue(gBrowser.tabs[4], "uniq");
+    tabState = JSON.parse(ss.getTabState(gBrowser.tabs[4]));
+    // Since Panorama might have put data in, first check if there is extData.
+    // If there is explicitly check that "uniq" isn't in it. Otherwise, we're ok
+    if ("extData" in tabState) {
+      ok(
+        !("uniq" in tabState.extData),
+        "(deleting) uniq not in existing extData"
+      );
+    } else {
+      ok(true, "(deleting) no data is stored in extData");
+    }
+
+    // set unique data on the tab that never had any set, make sure that's saved
+    let newUniq2 = r();
+    ss.setCustomTabValue(gBrowser.tabs[5], "uniq", newUniq2);
+    tabState = JSON.parse(ss.getTabState(gBrowser.tabs[5]));
+    is(
+      tabState.extData.uniq,
+      newUniq2,
+      "(creating) new data is stored in extData where there was none"
+    );
+
+    while (gBrowser.tabs.length > 1) {
+      BrowserTestUtils.removeTab(gBrowser.tabs[1]);
+    }
+  }
+
+  // Set the test state.
+  await setBrowserState(state);
+
+  // Wait until the selected tab is restored and all others are pending.
+  await Promise.all(
+    Array.from(gBrowser.tabs, tab => {
+      return tab == gBrowser.selectedTab
+        ? promiseTabRestored(tab)
+        : promiseTabRestoring(tab);
+    })
+  );
+
+  // Kick off the actual tests.
+  await progressCallback();
+
+  // Cleanup.
+  Services.prefs.clearUserPref("browser.sessionstore.restore_on_demand");
+  Services.prefs.clearUserPref("browser.sessionstore.restore_tabs_lazily");
+  await promiseBrowserState(stateBackup);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_615394-SSWindowState_events_duplicateTab.js b/src/zen/tests/mochitests/sessionstore/browser_615394-SSWindowState_events_duplicateTab.js
new file mode 100644
index 000000000..a94b056f5
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_615394-SSWindowState_events_duplicateTab.js
@@ -0,0 +1,69 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const testState = {
+  windows: [
+    {
+      tabs: [
+        { entries: [{ url: "about:blank", triggeringPrincipal_base64 }] },
+        { entries: [{ url: "about:robots", triggeringPrincipal_base64 }] },
+      ],
+    },
+  ],
+};
+
+function test() {
+  /** Test for Bug 615394 - Session Restore should notify when it is beginning and ending a restore */
+  waitForExplicitFinish();
+
+  waitForBrowserState(testState, test_duplicateTab);
+}
+
+function test_duplicateTab() {
+  let tab = gBrowser.tabs[1];
+  let busyEventCount = 0;
+  let readyEventCount = 0;
+  let newTab;
+
+  // We'll look to make sure this value is on the duplicated tab
+  ss.setCustomTabValue(tab, "foo", "bar");
+
+  function onSSWindowStateBusy() {
+    busyEventCount++;
+  }
+
+  function onSSWindowStateReady() {
+    newTab = gBrowser.tabs[2];
+    readyEventCount++;
+    is(ss.getCustomTabValue(newTab, "foo"), "bar");
+    ss.setCustomTabValue(newTab, "baz", "qux");
+  }
+
+  function onSSTabRestoring(aEvent) {
+    if (aEvent.target == newTab) {
+      is(busyEventCount, 1);
+      is(readyEventCount, 1);
+      is(ss.getCustomTabValue(newTab, "baz"), "qux");
+      is(newTab.linkedBrowser.currentURI.spec, "about:robots");
+
+      window.removeEventListener("SSWindowStateBusy", onSSWindowStateBusy);
+      window.removeEventListener("SSWindowStateReady", onSSWindowStateReady);
+      gBrowser.tabContainer.removeEventListener(
+        "SSTabRestoring",
+        onSSTabRestoring
+      );
+
+      gBrowser.removeTab(tab);
+      gBrowser.removeTab(newTab);
+      finish();
+    }
+  }
+
+  window.addEventListener("SSWindowStateBusy", onSSWindowStateBusy);
+  window.addEventListener("SSWindowStateReady", onSSWindowStateReady);
+  gBrowser.tabContainer.addEventListener("SSTabRestoring", onSSTabRestoring);
+
+  gBrowser._insertBrowser(tab);
+  newTab = ss.duplicateTab(window, tab);
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_615394-SSWindowState_events_setBrowserState.js b/src/zen/tests/mochitests/sessionstore/browser_615394-SSWindowState_events_setBrowserState.js
new file mode 100644
index 000000000..0392beef7
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_615394-SSWindowState_events_setBrowserState.js
@@ -0,0 +1,152 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const lameMultiWindowState = {
+  windows: [
+    {
+      tabs: [
+        {
+          entries: [
+            { url: "http://example.org#1", triggeringPrincipal_base64 },
+          ],
+          extData: { uniq: r() },
+        },
+        {
+          entries: [
+            { url: "http://example.org#2", triggeringPrincipal_base64 },
+          ],
+          extData: { uniq: r() },
+        },
+        {
+          entries: [
+            { url: "http://example.org#3", triggeringPrincipal_base64 },
+          ],
+          extData: { uniq: r() },
+        },
+        {
+          entries: [
+            { url: "http://example.org#4", triggeringPrincipal_base64 },
+          ],
+          extData: { uniq: r() },
+        },
+      ],
+      selected: 1,
+    },
+    {
+      tabs: [
+        {
+          entries: [
+            { url: "http://example.com#1", triggeringPrincipal_base64 },
+          ],
+          extData: { uniq: r() },
+        },
+        {
+          entries: [
+            { url: "http://example.com#2", triggeringPrincipal_base64 },
+          ],
+          extData: { uniq: r() },
+        },
+        {
+          entries: [
+            { url: "http://example.com#3", triggeringPrincipal_base64 },
+          ],
+          extData: { uniq: r() },
+        },
+        {
+          entries: [
+            { url: "http://example.com#4", triggeringPrincipal_base64 },
+          ],
+          extData: { uniq: r() },
+        },
+      ],
+      selected: 3,
+    },
+  ],
+};
+
+function getOuterWindowID(aWindow) {
+  return aWindow.docShell.outerWindowID;
+}
+
+function test() {
+  /** Test for Bug 615394 - Session Restore should notify when it is beginning and ending a restore */
+  waitForExplicitFinish();
+
+  // We'll track events per window so we are sure that they are each happening once
+  // pre window.
+  let windowEvents = {};
+  windowEvents[getOuterWindowID(window)] = {
+    busyEventCount: 0,
+    readyEventCount: 0,
+  };
+
+  // waitForBrowserState does it's own observing for windows, but doesn't attach
+  // the listeners we want here, so do it ourselves.
+  let newWindow;
+  function windowObserver(aSubject, aTopic) {
+    if (aTopic == "domwindowopened") {
+      Services.ww.unregisterNotification(windowObserver);
+
+      newWindow = aSubject;
+      newWindow.addEventListener(
+        "load",
+        function () {
+          windowEvents[getOuterWindowID(newWindow)] = {
+            busyEventCount: 0,
+            readyEventCount: 0,
+          };
+
+          newWindow.addEventListener("SSWindowStateBusy", onSSWindowStateBusy);
+          newWindow.addEventListener(
+            "SSWindowStateReady",
+            onSSWindowStateReady
+          );
+        },
+        { once: true }
+      );
+    }
+  }
+
+  function onSSWindowStateBusy(aEvent) {
+    windowEvents[getOuterWindowID(aEvent.originalTarget)].busyEventCount++;
+  }
+
+  function onSSWindowStateReady(aEvent) {
+    windowEvents[getOuterWindowID(aEvent.originalTarget)].readyEventCount++;
+  }
+
+  window.addEventListener("SSWindowStateBusy", onSSWindowStateBusy);
+  window.addEventListener("SSWindowStateReady", onSSWindowStateReady);
+  Services.ww.registerNotification(windowObserver);
+
+  waitForBrowserState(lameMultiWindowState, function () {
+    let checkedWindows = 0;
+    for (let id of Object.keys(windowEvents)) {
+      let winEvents = windowEvents[id];
+      is(
+        winEvents.busyEventCount,
+        1,
+        "window" + id + " busy event count correct"
+      );
+      is(
+        winEvents.readyEventCount,
+        1,
+        "window" + id + " ready event count correct"
+      );
+      checkedWindows++;
+    }
+    is(checkedWindows, 2, "checked 2 windows");
+    window.removeEventListener("SSWindowStateBusy", onSSWindowStateBusy);
+    window.removeEventListener("SSWindowStateReady", onSSWindowStateReady);
+    newWindow.removeEventListener("SSWindowStateBusy", onSSWindowStateBusy);
+    newWindow.removeEventListener("SSWindowStateReady", onSSWindowStateReady);
+
+    newWindow.close();
+    while (gBrowser.tabs.length > 1) {
+      gBrowser.removeTab(gBrowser.tabs[1]);
+    }
+
+    finish();
+  });
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_615394-SSWindowState_events_setTabState.js b/src/zen/tests/mochitests/sessionstore/browser_615394-SSWindowState_events_setTabState.js
new file mode 100644
index 000000000..99ada805b
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_615394-SSWindowState_events_setTabState.js
@@ -0,0 +1,61 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const testState = {
+  windows: [
+    {
+      tabs: [
+        { entries: [{ url: "about:blank", triggeringPrincipal_base64 }] },
+        { entries: [{ url: "about:policies", triggeringPrincipal_base64 }] },
+      ],
+    },
+  ],
+};
+
+function test() {
+  /** Test for Bug 615394 - Session Restore should notify when it is beginning and ending a restore */
+  waitForExplicitFinish();
+
+  waitForBrowserState(testState, test_setTabState);
+}
+
+function test_setTabState() {
+  let tab = gBrowser.tabs[1];
+  let newTabState = JSON.stringify({
+    entries: [{ url: "http://example.org", triggeringPrincipal_base64 }],
+    extData: { foo: "bar" },
+  });
+  let busyEventCount = 0;
+  let readyEventCount = 0;
+
+  function onSSWindowStateBusy() {
+    busyEventCount++;
+  }
+
+  function onSSWindowStateReady() {
+    readyEventCount++;
+    is(ss.getCustomTabValue(tab, "foo"), "bar");
+    ss.setCustomTabValue(tab, "baz", "qux");
+  }
+
+  function onSSTabRestoring() {
+    is(busyEventCount, 1);
+    is(readyEventCount, 1);
+    is(ss.getCustomTabValue(tab, "baz"), "qux");
+    is(tab.linkedBrowser.currentURI.spec, "http://example.org/");
+
+    window.removeEventListener("SSWindowStateBusy", onSSWindowStateBusy);
+    window.removeEventListener("SSWindowStateReady", onSSWindowStateReady);
+
+    gBrowser.removeTab(tab);
+    finish();
+  }
+
+  window.addEventListener("SSWindowStateBusy", onSSWindowStateBusy);
+  window.addEventListener("SSWindowStateReady", onSSWindowStateReady);
+  tab.addEventListener("SSTabRestoring", onSSTabRestoring, { once: true });
+  // Browser must be inserted in order to restore.
+  gBrowser._insertBrowser(tab);
+  ss.setTabState(tab, newTabState);
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_615394-SSWindowState_events_setWindowState.js b/src/zen/tests/mochitests/sessionstore/browser_615394-SSWindowState_events_setWindowState.js
new file mode 100644
index 000000000..80c521b1d
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_615394-SSWindowState_events_setWindowState.js
@@ -0,0 +1,65 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+function test() {
+  /** Test for Bug 615394 - Session Restore should notify when it is beginning and ending a restore */
+  waitForExplicitFinish();
+
+  let newState = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [{ url: "about:mozilla", triggeringPrincipal_base64 }],
+            extData: { foo: "bar" },
+          },
+          {
+            entries: [
+              { url: "http://example.org", triggeringPrincipal_base64 },
+            ],
+            extData: { baz: "qux" },
+          },
+        ],
+      },
+    ],
+  };
+
+  let busyEventCount = 0,
+    readyEventCount = 0,
+    tabRestoredCount = 0;
+
+  function onSSWindowStateBusy() {
+    busyEventCount++;
+  }
+
+  function onSSWindowStateReady() {
+    readyEventCount++;
+    is(ss.getCustomTabValue(gBrowser.tabs[0], "foo"), "bar");
+    is(ss.getCustomTabValue(gBrowser.tabs[1], "baz"), "qux");
+  }
+
+  function onSSTabRestored() {
+    if (++tabRestoredCount < 2) {
+      return;
+    }
+
+    is(busyEventCount, 1);
+    is(readyEventCount, 1);
+    is(gBrowser.tabs[0].linkedBrowser.currentURI.spec, "about:mozilla");
+    is(gBrowser.tabs[1].linkedBrowser.currentURI.spec, "http://example.org/");
+
+    window.removeEventListener("SSWindowStateBusy", onSSWindowStateBusy);
+    window.removeEventListener("SSWindowStateReady", onSSWindowStateReady);
+    gBrowser.tabContainer.removeEventListener("SSTabRestored", onSSTabRestored);
+
+    gBrowser.removeTab(gBrowser.tabs[1]);
+    finish();
+  }
+
+  window.addEventListener("SSWindowStateBusy", onSSWindowStateBusy);
+  window.addEventListener("SSWindowStateReady", onSSWindowStateReady);
+  gBrowser.tabContainer.addEventListener("SSTabRestored", onSSTabRestored);
+
+  ss.setWindowState(window, JSON.stringify(newState), true);
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_615394-SSWindowState_events_undoCloseTab.js b/src/zen/tests/mochitests/sessionstore/browser_615394-SSWindowState_events_undoCloseTab.js
new file mode 100644
index 000000000..e028cf6af
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_615394-SSWindowState_events_undoCloseTab.js
@@ -0,0 +1,65 @@
+"use strict";
+
+const testState = {
+  windows: [
+    {
+      tabs: [
+        { entries: [{ url: "about:blank", triggeringPrincipal_base64 }] },
+        { entries: [{ url: "about:robots", triggeringPrincipal_base64 }] },
+      ],
+    },
+  ],
+};
+
+// Test for Bug 615394 - Session Restore should notify when it is beginning and
+// ending a restore.
+add_task(async function test_undoCloseTab() {
+  await promiseBrowserState(testState);
+
+  let tab = gBrowser.tabs[1];
+  let busyEventCount = 0;
+  let readyEventCount = 0;
+  // This will be set inside the `onSSWindowStateReady` method.
+  let lastTab;
+
+  ss.setCustomTabValue(tab, "foo", "bar");
+
+  function onSSWindowStateBusy() {
+    busyEventCount++;
+  }
+
+  function onSSWindowStateReady() {
+    Assert.equal(gBrowser.tabs.length, 2, "Should only have 2 tabs");
+    lastTab = gBrowser.tabs[1];
+    readyEventCount++;
+    Assert.equal(ss.getCustomTabValue(lastTab, "foo"), "bar");
+    ss.setCustomTabValue(lastTab, "baz", "qux");
+  }
+
+  window.addEventListener("SSWindowStateBusy", onSSWindowStateBusy);
+  window.addEventListener("SSWindowStateReady", onSSWindowStateReady);
+
+  let restoredPromise = BrowserTestUtils.waitForEvent(
+    gBrowser.tabContainer,
+    "SSTabRestored"
+  );
+
+  await promiseRemoveTabAndSessionState(tab);
+  let reopenedTab = ss.undoCloseTab(window, 0);
+
+  await Promise.all([
+    restoredPromise,
+    BrowserTestUtils.browserLoaded(reopenedTab.linkedBrowser),
+  ]);
+
+  Assert.equal(reopenedTab, lastTab, "Tabs should be the same one.");
+  Assert.equal(busyEventCount, 1);
+  Assert.equal(readyEventCount, 1);
+  Assert.equal(ss.getCustomTabValue(reopenedTab, "baz"), "qux");
+  Assert.equal(reopenedTab.linkedBrowser.currentURI.spec, "about:robots");
+
+  window.removeEventListener("SSWindowStateBusy", onSSWindowStateBusy);
+  window.removeEventListener("SSWindowStateReady", onSSWindowStateReady);
+
+  BrowserTestUtils.removeTab(reopenedTab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_615394-SSWindowState_events_undoCloseWindow.js b/src/zen/tests/mochitests/sessionstore/browser_615394-SSWindowState_events_undoCloseWindow.js
new file mode 100644
index 000000000..7f9d72f49
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_615394-SSWindowState_events_undoCloseWindow.js
@@ -0,0 +1,146 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const lameMultiWindowState = {
+  windows: [
+    {
+      tabs: [
+        {
+          entries: [
+            { url: "http://example.org#1", triggeringPrincipal_base64 },
+          ],
+          extData: { uniq: r() },
+        },
+        {
+          entries: [
+            { url: "http://example.org#2", triggeringPrincipal_base64 },
+          ],
+          extData: { uniq: r() },
+        },
+        {
+          entries: [
+            { url: "http://example.org#3", triggeringPrincipal_base64 },
+          ],
+          extData: { uniq: r() },
+        },
+        {
+          entries: [
+            { url: "http://example.org#4", triggeringPrincipal_base64 },
+          ],
+          extData: { uniq: r() },
+        },
+      ],
+      selected: 1,
+    },
+    {
+      tabs: [
+        {
+          entries: [
+            { url: "http://example.com#1", triggeringPrincipal_base64 },
+          ],
+          extData: { uniq: r() },
+        },
+        {
+          entries: [
+            { url: "http://example.com#2", triggeringPrincipal_base64 },
+          ],
+          extData: { uniq: r() },
+        },
+        {
+          entries: [
+            { url: "http://example.com#3", triggeringPrincipal_base64 },
+          ],
+          extData: { uniq: r() },
+        },
+        {
+          entries: [
+            { url: "http://example.com#4", triggeringPrincipal_base64 },
+          ],
+          extData: { uniq: r() },
+        },
+      ],
+      selected: 3,
+    },
+  ],
+};
+
+function test() {
+  /** Test for Bug 615394 - Session Restore should notify when it is beginning and ending a restore */
+  waitForExplicitFinish();
+
+  let newWindow, reopenedWindow;
+
+  function firstWindowObserver(aSubject, aTopic) {
+    if (aTopic == "domwindowopened") {
+      newWindow = aSubject;
+      Services.ww.unregisterNotification(firstWindowObserver);
+    }
+  }
+  Services.ww.registerNotification(firstWindowObserver);
+
+  waitForBrowserState(lameMultiWindowState, function () {
+    // Close the window which isn't window
+    BrowserTestUtils.closeWindow(newWindow).then(() => {
+      // Now give it time to close
+      reopenedWindow = ss.undoCloseWindow(0);
+      reopenedWindow.addEventListener("SSWindowStateBusy", onSSWindowStateBusy);
+      reopenedWindow.addEventListener(
+        "SSWindowStateReady",
+        onSSWindowStateReady
+      );
+
+      reopenedWindow.addEventListener(
+        "load",
+        function () {
+          reopenedWindow.gBrowser.tabContainer.addEventListener(
+            "SSTabRestored",
+            onSSTabRestored
+          );
+        },
+        { once: true }
+      );
+    });
+  });
+
+  let busyEventCount = 0,
+    readyEventCount = 0,
+    tabRestoredCount = 0;
+  // These will listen to the reopened closed window...
+  function onSSWindowStateBusy() {
+    busyEventCount++;
+  }
+
+  function onSSWindowStateReady() {
+    readyEventCount++;
+  }
+
+  function onSSTabRestored() {
+    if (++tabRestoredCount < 4) {
+      return;
+    }
+
+    is(busyEventCount, 1);
+    is(readyEventCount, 1);
+
+    reopenedWindow.removeEventListener(
+      "SSWindowStateBusy",
+      onSSWindowStateBusy
+    );
+    reopenedWindow.removeEventListener(
+      "SSWindowStateReady",
+      onSSWindowStateReady
+    );
+    reopenedWindow.gBrowser.tabContainer.removeEventListener(
+      "SSTabRestored",
+      onSSTabRestored
+    );
+
+    reopenedWindow.close();
+    while (gBrowser.tabs.length > 1) {
+      gBrowser.removeTab(gBrowser.tabs[1]);
+    }
+
+    finish();
+  }
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_618151.js b/src/zen/tests/mochitests/sessionstore/browser_618151.js
new file mode 100644
index 000000000..4c4b2e482
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_618151.js
@@ -0,0 +1,67 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const stateBackup = ss.getBrowserState();
+const testState = {
+  windows: [
+    {
+      tabs: [
+        { entries: [{ url: "about:blank", triggeringPrincipal_base64 }] },
+        { entries: [{ url: "about:mozilla", triggeringPrincipal_base64 }] },
+      ],
+    },
+  ],
+};
+
+function test() {
+  /** Test for Bug 618151 - Overwriting state can lead to unrestored tabs */
+  waitForExplicitFinish();
+  runNextTest();
+}
+
+// Just a subset of tests from bug 615394 that causes a timeout.
+var tests = [test_setup, test_hang];
+function runNextTest() {
+  // set an empty state & run the next test, or finish
+  if (tests.length) {
+    // Enumerate windows and close everything but our primary window. We can't
+    // use waitForFocus() because apparently it's buggy. See bug 599253.
+    let closeWinPromises = [];
+    for (let currentWindow of Services.wm.getEnumerator("navigator:browser")) {
+      if (currentWindow != window) {
+        closeWinPromises.push(BrowserTestUtils.closeWindow(currentWindow));
+      }
+    }
+
+    Promise.all(closeWinPromises).then(() => {
+      let currentTest = tests.shift();
+      info("running " + currentTest.name);
+      waitForBrowserState(testState, currentTest);
+    });
+  } else {
+    ss.setBrowserState(stateBackup);
+    executeSoon(finish);
+  }
+}
+
+function test_setup() {
+  function onSSTabRestored() {
+    gBrowser.tabContainer.removeEventListener("SSTabRestored", onSSTabRestored);
+    runNextTest();
+  }
+
+  gBrowser.tabContainer.addEventListener("SSTabRestored", onSSTabRestored);
+  ss.setTabState(
+    gBrowser.tabs[1],
+    JSON.stringify({
+      entries: [{ url: "http://example.org", triggeringPrincipal_base64 }],
+      extData: { foo: "bar" },
+    })
+  );
+}
+
+function test_hang() {
+  ok(true, "test didn't time out");
+  runNextTest();
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_623779.js b/src/zen/tests/mochitests/sessionstore/browser_623779.js
new file mode 100644
index 000000000..ce6d1cde1
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_623779.js
@@ -0,0 +1,13 @@
+"use strict";
+
+add_task(async function () {
+  gBrowser.pinTab(gBrowser.selectedTab);
+
+  let newTab = gBrowser.duplicateTab(gBrowser.selectedTab);
+  await promiseTabRestored(newTab);
+
+  ok(!newTab.pinned, "duplicating a pinned tab creates unpinned tab");
+  BrowserTestUtils.removeTab(newTab);
+
+  gBrowser.unpinTab(gBrowser.selectedTab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_624727.js b/src/zen/tests/mochitests/sessionstore/browser_624727.js
new file mode 100644
index 000000000..57bb1e30c
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_624727.js
@@ -0,0 +1,33 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+var TEST_STATE = { windows: [{ tabs: [{ url: "about:blank" }] }] };
+
+add_task(async function () {
+  function assertNumberOfTabs(num, msg) {
+    is(gBrowser.tabs.length, num, msg);
+  }
+
+  function assertNumberOfPinnedTabs(num, msg) {
+    is(gBrowser.pinnedTabCount, num, msg);
+  }
+
+  // check prerequisites
+  assertNumberOfTabs(1, "we start off with one tab");
+  assertNumberOfPinnedTabs(0, "no pinned tabs so far");
+
+  // setup
+  BrowserTestUtils.addTab(gBrowser, "about:blank");
+  assertNumberOfTabs(2, "there are two tabs, now");
+
+  let [tab1, tab2] = gBrowser.tabs;
+  gBrowser.pinTab(tab1);
+  gBrowser.pinTab(tab2);
+  assertNumberOfPinnedTabs(2, "both tabs are now pinned");
+
+  // run the test
+  await promiseBrowserState(TEST_STATE);
+
+  assertNumberOfTabs(1, "one tab left after setBrowserState()");
+  assertNumberOfPinnedTabs(0, "there are no pinned tabs");
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_625016.js b/src/zen/tests/mochitests/sessionstore/browser_625016.js
new file mode 100644
index 000000000..afe5c1777
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_625016.js
@@ -0,0 +1,103 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+add_setup(async function () {
+  /** Test for Bug 625016 - Restore windows closed in succession to quit (non-OSX only) */
+
+  // We'll test this by opening a new window, waiting for the save
+  // event, then closing that window. We'll observe the
+  // "sessionstore-state-write-complete" notification and check that
+  // the state contains no _closedWindows. We'll then add a new tab
+  // and make sure that the state following that was reset and the
+  // closed window is now in _closedWindows.
+
+  requestLongerTimeout(2);
+
+  await forceSaveState();
+
+  // We'll clear all closed windows to make sure our state is clean
+  // forgetClosedWindow doesn't trigger a delayed save
+  forgetClosedWindows();
+  is(ss.getClosedWindowCount(), 0, "starting with no closed windows");
+});
+
+add_task(async function new_window() {
+  let newWin;
+  try {
+    newWin = await promiseNewWindowLoaded();
+    let tab = BrowserTestUtils.addTab(
+      newWin.gBrowser,
+      "http://example.com/browser_625016.js?" + Math.random()
+    );
+    await promiseBrowserLoaded(tab.linkedBrowser);
+
+    // Double check that we have no closed windows
+    is(ss.getClosedWindowCount(), 0, "no closed windows on first save");
+
+    await BrowserTestUtils.closeWindow(newWin);
+    newWin = null;
+
+    let state = JSON.parse(await promiseRecoveryFileContents());
+    is(state.windows.length, 1, "observe1: 1 window in data written to disk");
+    is(
+      state._closedWindows.length,
+      0,
+      "observe1: no closed windows in data written to disk"
+    );
+
+    // The API still treats the closed window as closed, so ensure that window is there
+    is(
+      ss.getClosedWindowCount(),
+      1,
+      "observe1: 1 closed window according to API"
+    );
+  } finally {
+    if (newWin) {
+      await BrowserTestUtils.closeWindow(newWin);
+    }
+    await forceSaveState();
+  }
+});
+
+// We'll open a tab, which should trigger another state save which would wipe
+// the _shouldRestore attribute from the closed window
+add_task(async function new_tab() {
+  let newTab;
+  try {
+    newTab = BrowserTestUtils.addTab(gBrowser, "about:mozilla");
+    await promiseBrowserLoaded(newTab.linkedBrowser);
+    await TabStateFlusher.flush(newTab.linkedBrowser);
+
+    let state = JSON.parse(await promiseRecoveryFileContents());
+    is(
+      state.windows.length,
+      1,
+      "observe2: 1 window in data being written to disk"
+    );
+    is(
+      state._closedWindows.length,
+      1,
+      "observe2: 1 closed window in data being written to disk"
+    );
+
+    // The API still treats the closed window as closed, so ensure that window is there
+    is(
+      ss.getClosedWindowCount(),
+      1,
+      "observe2: 1 closed window according to API"
+    );
+  } finally {
+    if (newTab) {
+      gBrowser.removeTab(newTab);
+    }
+  }
+});
+
+add_task(async function done() {
+  // The API still represents the closed window as closed, so we can clear it
+  // with the API, but just to make sure...
+  //  is(ss.getClosedWindowCount(), 1, "1 closed window according to API");
+  await promiseAllButPrimaryWindowClosed();
+  forgetClosedWindows();
+  Services.prefs.clearUserPref("browser.sessionstore.interval");
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_628270.js b/src/zen/tests/mochitests/sessionstore/browser_628270.js
new file mode 100644
index 000000000..ec91c1af2
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_628270.js
@@ -0,0 +1,43 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+async function test() {
+  let assertNumberOfTabs = function (num, msg) {
+    is(gBrowser.tabs.length, num, msg);
+  };
+
+  let assertNumberOfVisibleTabs = function (num, msg) {
+    is(gBrowser.visibleTabs.length, num, msg);
+  };
+
+  waitForExplicitFinish();
+
+  // check prerequisites
+  assertNumberOfTabs(1, "we start off with one tab");
+
+  // setup
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:mozilla");
+
+  await promiseBrowserLoaded(tab.linkedBrowser);
+
+  // hide the newly created tab
+  assertNumberOfVisibleTabs(2, "there are two visible tabs");
+  BrowserTestUtils.showOnlyTheseTabs(gBrowser, [gBrowser.tabs[0]]);
+  assertNumberOfVisibleTabs(1, "there is one visible tab");
+  ok(tab.hidden, "newly created tab is now hidden");
+
+  // close and restore hidden tab
+  await promiseRemoveTabAndSessionState(tab);
+  tab = ss.undoCloseTab(window, 0);
+
+  // check that everything was restored correctly, clean up and finish
+  await promiseBrowserLoaded(tab.linkedBrowser);
+  is(
+    tab.linkedBrowser.currentURI.spec,
+    "about:mozilla",
+    "restored tab has correct url"
+  );
+
+  gBrowser.removeTab(tab);
+  finish();
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_635418.js b/src/zen/tests/mochitests/sessionstore/browser_635418.js
new file mode 100644
index 000000000..c932a3b9f
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_635418.js
@@ -0,0 +1,58 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// This tests that hiding/showing a tab, on its own, eventually triggers a
+// session store.
+
+function test() {
+  waitForExplicitFinish();
+
+  // We speed up the interval between session saves to ensure that the test
+  // runs quickly.
+  Services.prefs.setIntPref("browser.sessionstore.interval", 2000);
+
+  // Loading a tab causes a save state and this is meant to catch that event.
+  waitForSaveState(testBug635418_1);
+
+  // Assumption: Only one window is open and it has one tab open.
+  BrowserTestUtils.addTab(gBrowser, "about:mozilla");
+}
+
+function testBug635418_1() {
+  ok(!gBrowser.tabs[0].hidden, "first tab should not be hidden");
+  ok(!gBrowser.tabs[1].hidden, "second tab should not be hidden");
+
+  waitForSaveState(testBug635418_2);
+
+  // We can't hide the selected tab, so hide the new one
+  gBrowser.hideTab(gBrowser.tabs[1]);
+}
+
+function testBug635418_2() {
+  let state = JSON.parse(ss.getBrowserState());
+  ok(!state.windows[0].tabs[0].hidden, "first tab should still not be hidden");
+  ok(state.windows[0].tabs[1].hidden, "second tab should be hidden by now");
+
+  waitForSaveState(testBug635418_3);
+  gBrowser.showTab(gBrowser.tabs[1]);
+}
+
+function testBug635418_3() {
+  let state = JSON.parse(ss.getBrowserState());
+  ok(
+    !state.windows[0].tabs[0].hidden,
+    "first tab should still still not be hidden"
+  );
+  ok(!state.windows[0].tabs[1].hidden, "second tab should not be hidden again");
+
+  done();
+}
+
+function done() {
+  gBrowser.removeTab(window.gBrowser.tabs[1]);
+
+  Services.prefs.clearUserPref("browser.sessionstore.interval");
+
+  executeSoon(finish);
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_636279.js b/src/zen/tests/mochitests/sessionstore/browser_636279.js
new file mode 100644
index 000000000..4842f145b
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_636279.js
@@ -0,0 +1,144 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+var stateBackup = ss.getBrowserState();
+
+var statePinned = {
+  windows: [
+    {
+      tabs: [
+        {
+          entries: [
+            { url: "http://example.com#1", triggeringPrincipal_base64 },
+          ],
+          pinned: true,
+        },
+      ],
+    },
+  ],
+};
+
+var state = {
+  windows: [
+    {
+      tabs: [
+        {
+          entries: [
+            { url: "http://example.com#1", triggeringPrincipal_base64 },
+          ],
+        },
+        {
+          entries: [
+            { url: "http://example.com#2", triggeringPrincipal_base64 },
+          ],
+        },
+        {
+          entries: [
+            { url: "http://example.com#3", triggeringPrincipal_base64 },
+          ],
+        },
+        {
+          entries: [
+            { url: "http://example.com#4", triggeringPrincipal_base64 },
+          ],
+        },
+      ],
+    },
+  ],
+};
+
+function test() {
+  waitForExplicitFinish();
+
+  registerCleanupFunction(function () {
+    TabsProgressListener.uninit();
+    ss.setBrowserState(stateBackup);
+  });
+
+  TabsProgressListener.init();
+
+  window.addEventListener(
+    "SSWindowStateReady",
+    function () {
+      let firstProgress = true;
+
+      TabsProgressListener.setCallback(function (needsRestore, isRestoring) {
+        if (firstProgress) {
+          firstProgress = false;
+          is(isRestoring, 3, "restoring 3 tabs concurrently");
+        } else {
+          Assert.lessOrEqual(
+            isRestoring,
+            3,
+            "restoring max. 2 tabs concurrently"
+          );
+        }
+
+        if (0 == needsRestore) {
+          TabsProgressListener.unsetCallback();
+          waitForFocus(finish);
+        }
+      });
+
+      ss.setBrowserState(JSON.stringify(state));
+    },
+    { once: true }
+  );
+
+  ss.setBrowserState(JSON.stringify(statePinned));
+}
+
+function countTabs() {
+  let needsRestore = 0,
+    isRestoring = 0;
+  for (let window of Services.wm.getEnumerator("navigator:browser")) {
+    if (window.closed) {
+      continue;
+    }
+
+    for (let i = 0; i < window.gBrowser.tabs.length; i++) {
+      let browserState = ss.getInternalObjectState(
+        window.gBrowser.tabs[i].linkedBrowser
+      );
+      if (browserState == TAB_STATE_RESTORING) {
+        isRestoring++;
+      } else if (browserState == TAB_STATE_NEEDS_RESTORE) {
+        needsRestore++;
+      }
+    }
+  }
+
+  return [needsRestore, isRestoring];
+}
+
+var TabsProgressListener = {
+  init() {
+    Services.obs.addObserver(this, "sessionstore-debug-tab-restored");
+  },
+
+  uninit() {
+    Services.obs.removeObserver(this, "sessionstore-debug-tab-restored");
+    this.unsetCallback();
+  },
+
+  setCallback(callback) {
+    this.callback = callback;
+  },
+
+  unsetCallback() {
+    delete this.callback;
+  },
+
+  observe(browser) {
+    TabsProgressListener.onRestored(browser);
+  },
+
+  onRestored(browser) {
+    if (
+      this.callback &&
+      ss.getInternalObjectState(browser) == TAB_STATE_RESTORING
+    ) {
+      this.callback.apply(null, countTabs());
+    }
+  },
+};
diff --git a/src/zen/tests/mochitests/sessionstore/browser_637020.js b/src/zen/tests/mochitests/sessionstore/browser_637020.js
new file mode 100644
index 000000000..d0c18305c
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_637020.js
@@ -0,0 +1,77 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const TEST_URL =
+  "http://mochi.test:8888/browser/browser/components/" +
+  "sessionstore/test/browser_637020_slow.sjs";
+
+const TEST_STATE = {
+  windows: [
+    {
+      tabs: [
+        { entries: [{ url: "about:mozilla", triggeringPrincipal_base64 }] },
+        { entries: [{ url: "about:robots", triggeringPrincipal_base64 }] },
+      ],
+    },
+    {
+      tabs: [
+        { entries: [{ url: TEST_URL, triggeringPrincipal_base64 }] },
+        { entries: [{ url: TEST_URL, triggeringPrincipal_base64 }] },
+      ],
+    },
+  ],
+};
+
+/**
+ * This test ensures that windows that have just been restored will be marked
+ * as dirty, otherwise _getCurrentState() might ignore them when collecting
+ * state for the first time and we'd just save them as empty objects.
+ *
+ * The dirty state acts as a cache to not collect data from all windows all the
+ * time, so at the beginning, each window must be dirty so that we collect
+ * their state at least once.
+ */
+
+add_task(async function test() {
+  // Wait until the new window has been opened.
+  let promiseWindow = new Promise(resolve => {
+    Services.obs.addObserver(function onOpened(subject) {
+      Services.obs.removeObserver(onOpened, "domwindowopened");
+      resolve(subject);
+    }, "domwindowopened");
+  });
+
+  // Set the new browser state that will
+  // restore a window with two slowly loading tabs.
+  let backupState = SessionStore.getBrowserState();
+  SessionStore.setBrowserState(JSON.stringify(TEST_STATE));
+  let win = await promiseWindow;
+  let delayedStartupFinished = new Promise(resolve =>
+    whenDelayedStartupFinished(win, resolve)
+  );
+  let restoring = promiseWindowRestoring(win);
+  let restored = promiseWindowRestored(win);
+  await restoring;
+  await restored;
+
+  // The window has now been opened. Check the state that is returned,
+  // this should come from the cache while the window isn't restored, yet.
+  info("the window has been opened");
+  checkWindows();
+
+  // The history has now been restored and the tabs are loading. The data must
+  // now come from the window, if it's correctly been marked as dirty before.
+  await delayedStartupFinished;
+  info("the delayed startup has finished");
+  checkWindows();
+
+  // Cleanup.
+  await BrowserTestUtils.closeWindow(win);
+  await promiseBrowserState(backupState);
+});
+
+function checkWindows() {
+  let state = JSON.parse(SessionStore.getBrowserState());
+  is(state.windows[0].tabs.length, 2, "first window has two tabs");
+  is(state.windows[1].tabs.length, 2, "second window has two tabs");
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_637020_slow.sjs b/src/zen/tests/mochitests/sessionstore/browser_637020_slow.sjs
new file mode 100644
index 000000000..abb1dee82
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_637020_slow.sjs
@@ -0,0 +1,22 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const DELAY_MS = "2000";
+
+let timer;
+
+function handleRequest(req, resp) {
+  resp.processAsync();
+  resp.setHeader("Cache-Control", "no-cache", false);
+  resp.setHeader("Content-Type", "text/html;charset=utf-8", false);
+
+  timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
+  timer.init(
+    () => {
+      resp.write("hi");
+      resp.finish();
+    },
+    DELAY_MS,
+    Ci.nsITimer.TYPE_ONE_SHOT
+  );
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_645428.js b/src/zen/tests/mochitests/sessionstore/browser_645428.js
new file mode 100644
index 000000000..3916c44a7
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_645428.js
@@ -0,0 +1,22 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const NOTIFICATION = "sessionstore-browser-state-restored";
+
+function test() {
+  waitForExplicitFinish();
+
+  function observe(subject, topic) {
+    if (NOTIFICATION == topic) {
+      finish();
+      ok(true, "TOPIC received");
+    }
+  }
+
+  Services.obs.addObserver(observe, NOTIFICATION);
+  registerCleanupFunction(function () {
+    Services.obs.removeObserver(observe, NOTIFICATION);
+  });
+
+  ss.setBrowserState(JSON.stringify({ windows: [] }));
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_659591.js b/src/zen/tests/mochitests/sessionstore/browser_659591.js
new file mode 100644
index 000000000..1020d2a39
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_659591.js
@@ -0,0 +1,39 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+function test() {
+  waitForExplicitFinish();
+
+  let eventReceived = false;
+
+  registerCleanupFunction(function () {
+    ok(eventReceived, "SSWindowClosing event received");
+  });
+
+  newWindow(function (win) {
+    win.addEventListener(
+      "SSWindowClosing",
+      function () {
+        eventReceived = true;
+      },
+      { once: true }
+    );
+
+    BrowserTestUtils.closeWindow(win).then(() => {
+      waitForFocus(finish);
+    });
+  });
+}
+
+function newWindow(callback) {
+  let opts = "chrome,all,dialog=no,height=800,width=800";
+  let win = window.openDialog(AppConstants.BROWSER_CHROME_URL, "_blank", opts);
+
+  win.addEventListener(
+    "load",
+    function () {
+      executeSoon(() => callback(win));
+    },
+    { once: true }
+  );
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_662743.js b/src/zen/tests/mochitests/sessionstore/browser_662743.js
new file mode 100644
index 000000000..c79388a56
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_662743.js
@@ -0,0 +1,138 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+// This tests that session restore component does restore the right <select> option.
+// Session store should not rely only on previous user's selectedIndex, it should
+// check its value as well.
+
+function test() {
+  /** Tests selected options */
+  requestLongerTimeout(2);
+  waitForExplicitFinish();
+
+  let testTabCount = 0;
+  let formData = [
+    // default case
+    {},
+
+    // new format
+    // index doesn't match value (testing an option in between (two))
+    { id: { select_id: { selectedIndex: 0, value: "val2" } } },
+    // index doesn't match value (testing an invalid value)
+    { id: { select_id: { selectedIndex: 4, value: "val8" } } },
+    // index doesn't match value (testing an invalid index)
+    { id: { select_id: { selectedIndex: 8, value: "val5" } } },
+    // index and value match position zero
+    { id: { select_id: { selectedIndex: 0, value: "val0" } }, xpath: {} },
+    // index doesn't match value (testing the last option (seven))
+    {
+      id: {},
+      xpath: {
+        "/xhtml:html/xhtml:body/xhtml:select[@name='select_name']": {
+          selectedIndex: 1,
+          value: "val7",
+        },
+      },
+    },
+    // index and value match the default option "selectedIndex":3,"value":"val3"
+    {
+      xpath: {
+        "/xhtml:html/xhtml:body/xhtml:select[@name='select_name']": {
+          selectedIndex: 3,
+          value: "val3",
+        },
+      },
+    },
+    // index matches default option however it doesn't match value
+    { id: { select_id: { selectedIndex: 3, value: "val4" } } },
+  ];
+
+  let expectedValues = [
+    null, // default value
+    "val2",
+    null, // default value (invalid value)
+    "val5", // value is still valid (even it has an invalid index)
+    "val0",
+    "val7",
+    null,
+    "val4",
+  ];
+  let callback = function () {
+    testTabCount--;
+    if (testTabCount == 0) {
+      finish();
+    }
+  };
+
+  for (let i = 0; i < formData.length; i++) {
+    testTabCount++;
+    testTabRestoreData(formData[i], expectedValues[i], callback);
+  }
+}
+
+function testTabRestoreData(aFormData, aExpectedValue, aCallback) {
+  let testURL = getRootDirectory(gTestPath) + "browser_662743_sample.html";
+  let tab = BrowserTestUtils.addTab(gBrowser, testURL);
+
+  aFormData.url = testURL;
+  let tabState = {
+    entries: [{ url: testURL, triggeringPrincipal_base64 }],
+    formdata: aFormData,
+  };
+
+  promiseBrowserLoaded(tab.linkedBrowser).then(() => {
+    promiseTabState(tab, tabState)
+      .then(() => {
+        // Flush to make sure we have the latest form data.
+        return TabStateFlusher.flush(tab.linkedBrowser);
+      })
+      .then(() => {
+        let doc = tab.linkedBrowser.contentDocument;
+        let select = doc.getElementById("select_id");
+        let value = select.options[select.selectedIndex].value;
+        let restoredTabState = JSON.parse(ss.getTabState(tab));
+
+        // If aExpectedValue=null we don't expect any form data to be collected.
+        if (!aExpectedValue) {
+          ok(
+            !restoredTabState.hasOwnProperty("formdata"),
+            "no formdata collected"
+          );
+          gBrowser.removeTab(tab);
+          aCallback();
+          return;
+        }
+
+        // test select options values
+        is(
+          value,
+          aExpectedValue,
+          "Select Option by selectedIndex &/or value has been restored correctly"
+        );
+
+        let restoredFormData = restoredTabState.formdata;
+        let selectIdFormData = restoredFormData.id.select_id;
+        value = restoredFormData.id.select_id.value;
+
+        // test format
+        ok(
+          "id" in restoredFormData || "xpath" in restoredFormData,
+          "FormData format is valid"
+        );
+        // test format
+        ok(
+          "selectedIndex" in selectIdFormData && "value" in selectIdFormData,
+          "select format is valid"
+        );
+        // test set collection values
+        is(value, aExpectedValue, "Collection has been saved correctly");
+
+        // clean up
+        gBrowser.removeTab(tab);
+
+        aCallback();
+      });
+  });
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_662743_sample.html b/src/zen/tests/mochitests/sessionstore/browser_662743_sample.html
new file mode 100644
index 000000000..0fd49417c
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_662743_sample.html
@@ -0,0 +1,15 @@
+<!DOCTYPE html>
+<title>Test 662743</title>
+
+<!-- Select events -->
+<h3>Select options</h3>
+<select id="select_id" name="select_name">
+  <option value="val0">Zero</option>
+  <option value="val1">One</option>
+  <option value="val2">Two</option>
+  <option value="val3" selected="selected">Three</option>
+  <option value="val4">Four</option>
+  <option value="val5">Five</option>
+  <option value="val6">Six</option>
+  <option value="val7">Seven</option>
+</select>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_662812.js b/src/zen/tests/mochitests/sessionstore/browser_662812.js
new file mode 100644
index 000000000..76de142a2
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_662812.js
@@ -0,0 +1,41 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+async function test() {
+  waitForExplicitFinish();
+
+  window.addEventListener(
+    "SSWindowStateBusy",
+    () => {
+      let state = ss.getWindowState(window);
+      ok(state.windows[0].busy, "window is busy");
+
+      window.addEventListener(
+        "SSWindowStateReady",
+        () => {
+          let state2 = ss.getWindowState(window);
+          ok(!state2.windows[0].busy, "window is not busy");
+
+          executeSoon(() => {
+            gBrowser.removeTab(gBrowser.tabs[1]);
+            finish();
+          });
+        },
+        { once: true }
+      );
+    },
+    { once: true }
+  );
+
+  // create a new tab
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:mozilla");
+  let browser = tab.linkedBrowser;
+  await BrowserTestUtils.browserLoaded(browser);
+  await TabStateFlusher.flush(browser);
+  const sessionStoreClosedObjectsChanged = TestUtils.topicObserved(
+    "sessionstore-closed-objects-changed"
+  );
+  gBrowser.removeTab(tab);
+  await sessionStoreClosedObjectsChanged;
+  ss.undoCloseTab(window, 0);
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_665702-state_session.js b/src/zen/tests/mochitests/sessionstore/browser_665702-state_session.js
new file mode 100644
index 000000000..fc024e224
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_665702-state_session.js
@@ -0,0 +1,26 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+function compareArray(a, b) {
+  if (a.length !== b.length) {
+    return false;
+  }
+  for (let i = 0; i < a.length; i++) {
+    if (a[i] !== b[i]) {
+      return false;
+    }
+  }
+  return true;
+}
+
+function test() {
+  let currentState = JSON.parse(ss.getBrowserState());
+  ok(currentState.session, "session data returned by getBrowserState");
+
+  let keys = Object.keys(currentState.session);
+  let expectedKeys = ["lastUpdate", "startTime", "recentCrashes"];
+  ok(
+    compareArray(keys.sort(), expectedKeys.sort()),
+    "session object from getBrowserState has correct keys"
+  );
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_682507.js b/src/zen/tests/mochitests/sessionstore/browser_682507.js
new file mode 100644
index 000000000..00a8ad4cd
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_682507.js
@@ -0,0 +1,22 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+function test() {
+  Services.prefs.setBoolPref("browser.sessionstore.restore_on_demand", true);
+  BrowserTestUtils.addTab(gBrowser, "about:mozilla");
+
+  ss.setTabState(gBrowser.tabs[1], ss.getTabState(gBrowser.tabs[1]));
+  ok(
+    gBrowser.tabs[1].hasAttribute("pending"),
+    "second tab should have 'pending' attribute"
+  );
+
+  gBrowser.selectedTab = gBrowser.tabs[1];
+  ok(
+    !gBrowser.tabs[1].hasAttribute("pending"),
+    "second tab should have not 'pending' attribute"
+  );
+
+  gBrowser.removeTab(gBrowser.tabs[1]);
+  Services.prefs.clearUserPref("browser.sessionstore.restore_on_demand");
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_687710.js b/src/zen/tests/mochitests/sessionstore/browser_687710.js
new file mode 100644
index 000000000..e90c74c88
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_687710.js
@@ -0,0 +1,58 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// Test that sessionrestore handles cycles in the shentry graph properly.
+//
+// These cycles shouldn't be there in the first place, but they cause hangs
+// when they mysteriously appear (bug 687710).  Docshell code assumes this
+// graph is a tree and tires to walk to the root.  But if there's a cycle,
+// there is no root, and we loop forever.
+
+var stateBackup = ss.getBrowserState();
+
+var state = {
+  windows: [
+    {
+      tabs: [
+        {
+          entries: [
+            {
+              docIdentifier: 1,
+              url: "http://example.com",
+              triggeringPrincipal_base64,
+              children: [
+                {
+                  docIdentifier: 2,
+                  url: "http://example.com",
+                  triggeringPrincipal_base64,
+                },
+              ],
+            },
+            {
+              docIdentifier: 2,
+              url: "http://example.com",
+              triggeringPrincipal_base64,
+              children: [
+                {
+                  docIdentifier: 1,
+                  url: "http://example.com",
+                  triggeringPrincipal_base64,
+                },
+              ],
+            },
+          ],
+        },
+      ],
+    },
+  ],
+};
+
+add_task(async function test() {
+  registerCleanupFunction(function () {
+    ss.setBrowserState(stateBackup);
+  });
+
+  /* This test fails by hanging. */
+  await setBrowserState(state);
+  ok(true, "Didn't hang!");
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_687710_2.js b/src/zen/tests/mochitests/sessionstore/browser_687710_2.js
new file mode 100644
index 000000000..7f2891e40
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_687710_2.js
@@ -0,0 +1,78 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// Test that the fix for bug 687710 isn't too aggressive -- shentries which are
+// cousins should be able to share bfcache entries.
+
+var stateBackup = ss.getBrowserState();
+
+var state = {
+  entries: [
+    {
+      docIdentifier: 1,
+      url: "http://example.com?1",
+      triggeringPrincipal_base64,
+      children: [
+        {
+          docIdentifier: 10,
+          url: "http://example.com?10",
+          triggeringPrincipal_base64,
+        },
+      ],
+    },
+    {
+      docIdentifier: 1,
+      url: "http://example.com?1#a",
+      triggeringPrincipal_base64,
+      children: [
+        {
+          docIdentifier: 10,
+          url: "http://example.com?10#aa",
+          triggeringPrincipal_base64,
+        },
+      ],
+    },
+  ],
+};
+
+add_task(async function test() {
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:blank");
+
+  // addTab sends a message to the child to load about:blank, which sends a
+  // message to the parent to add the SH entry.
+  // promiseTabState modifies the SH syncronously, so ensure it is settled.
+  await BrowserTestUtils.browserLoaded(tab.linkedBrowser, {
+    wantLoad: "about:blank",
+  });
+
+  await promiseTabState(tab, state);
+
+  function compareEntries(i, j, history) {
+    let e1 = history.getEntryAtIndex(i);
+    let e2 = history.getEntryAtIndex(j);
+
+    ok(e1.sharesDocumentWith(e2), `${i} should share doc with ${j}`);
+    is(e1.childCount, e2.childCount, `Child count mismatch (${i}, ${j})`);
+
+    for (let c = 0; c < e1.childCount; c++) {
+      let c1 = e1.GetChildAt(c);
+      let c2 = e2.GetChildAt(c);
+
+      ok(
+        c1.sharesDocumentWith(c2),
+        `Cousins should share documents. (${i}, ${j}, ${c})`
+      );
+    }
+  }
+
+  let history = tab.linkedBrowser.browsingContext.sessionHistory;
+
+  is(history.count, 2, "history.count");
+  for (let i = 0; i < history.count; i++) {
+    for (let j = 0; j < history.count; j++) {
+      compareEntries(i, j, history);
+    }
+  }
+
+  ss.setBrowserState(stateBackup);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_694378.js b/src/zen/tests/mochitests/sessionstore/browser_694378.js
new file mode 100644
index 000000000..fc6619b9a
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_694378.js
@@ -0,0 +1,41 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// Test Summary:
+// 1.  call ss.setWindowState with a broken state
+// 1a. ensure that it doesn't throw.
+
+add_task(async function test_brokenWindowState() {
+  let brokenState = {
+    windows: [
+      {
+        tabs: [
+          { entries: [{ url: "about:mozilla", triggeringPrincipal_base64 }] },
+        ],
+      },
+    ],
+    selectedWindow: 2,
+  };
+
+  let gotError = false;
+  try {
+    await setWindowState(window, brokenState, true);
+  } catch (ex) {
+    gotError = true;
+    info(ex);
+  }
+
+  ok(!gotError, "ss.setWindowState did not throw an error");
+
+  // Make sure that we reset the state. Use a full state just in case things get crazy.
+  let blankState = {
+    windows: [
+      {
+        tabs: [
+          { entries: [{ url: "about:blank", triggeringPrincipal_base64 }] },
+        ],
+      },
+    ],
+  };
+  await promiseBrowserState(blankState);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_701377.js b/src/zen/tests/mochitests/sessionstore/browser_701377.js
new file mode 100644
index 000000000..3f07aea6b
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_701377.js
@@ -0,0 +1,56 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+var state = {
+  windows: [
+    {
+      tabs: [
+        {
+          entries: [
+            { url: "http://example.com#1", triggeringPrincipal_base64 },
+          ],
+        },
+        {
+          entries: [
+            { url: "http://example.com#2", triggeringPrincipal_base64 },
+          ],
+          hidden: true,
+        },
+      ],
+    },
+  ],
+};
+
+function test() {
+  waitForExplicitFinish();
+
+  newWindowWithState(state, function (aWindow) {
+    let tab = aWindow.gBrowser.tabs[1];
+    ok(tab.hidden, "the second tab is hidden");
+
+    let tabShown = false;
+    let tabShowCallback = () => (tabShown = true);
+    tab.addEventListener("TabShow", tabShowCallback);
+
+    let tabState = ss.getTabState(tab);
+    ss.setTabState(tab, tabState);
+
+    tab.removeEventListener("TabShow", tabShowCallback);
+    ok(tab.hidden && !tabShown, "tab remains hidden");
+
+    finish();
+  });
+}
+
+// ----------
+function newWindowWithState(aState, aCallback) {
+  let opts = "chrome,all,dialog=no,height=800,width=800";
+  let win = window.openDialog(AppConstants.BROWSER_CHROME_URL, "_blank", opts);
+
+  registerCleanupFunction(() => BrowserTestUtils.closeWindow(win));
+
+  whenWindowLoaded(win, function onWindowLoaded(aWin) {
+    ss.setWindowState(aWin, JSON.stringify(aState), true);
+    executeSoon(() => aCallback(aWin));
+  });
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_705597.js b/src/zen/tests/mochitests/sessionstore/browser_705597.js
new file mode 100644
index 000000000..53d556e81
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_705597.js
@@ -0,0 +1,70 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+/* eslint-disable mozilla/no-arbitrary-setTimeout */
+
+const tabState = {
+  entries: [
+    {
+      url: "about:robots",
+      triggeringPrincipal_base64,
+      children: [{ url: "about:mozilla", triggeringPrincipal_base64 }],
+    },
+  ],
+};
+
+const blankState = {
+  windows: [
+    {
+      tabs: [
+        {
+          entries: [{ url: "about:blank", triggeringPrincipal_base64 }],
+        },
+      ],
+    },
+  ],
+};
+
+add_task(async function test() {
+  Services.prefs.setIntPref("browser.sessionstore.interval", 4000);
+  registerCleanupFunction(function () {
+    Services.prefs.clearUserPref("browser.sessionstore.interval");
+  });
+
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:blank");
+  let browser = tab.linkedBrowser;
+  await BrowserTestUtils.browserLoaded(browser, false, "about:blank");
+
+  await promiseTabState(tab, tabState);
+  let sessionHistory = browser.browsingContext.sessionHistory;
+  let entry = sessionHistory.getEntryAtIndex(0);
+
+  await whenChildCount(entry, 1);
+
+  // Create a dynamic subframe.
+  let doc = browser.contentDocument;
+  let iframe = doc.createElement("iframe");
+  iframe.setAttribute("src", "about:mozilla");
+  doc.body.appendChild(iframe);
+
+  await whenChildCount(entry, 2);
+
+  // Force reload the browser to discard the subframes.
+  browser.reloadWithFlags(Ci.nsIWebNavigation.LOAD_FLAGS_BYPASS_CACHE);
+
+  await BrowserTestUtils.browserLoaded(browser, false, "about:robots");
+  await TabStateFlusher.flush(browser);
+
+  let { entries } = JSON.parse(ss.getTabState(tab));
+  is(entries.length, 1, "tab has one history entry");
+  ok(!entries[0].children, "history entry has no subframes");
+
+  // Make sure that we reset the state.
+  waitForBrowserState(blankState, finish);
+});
+
+function whenChildCount(aEntry, aChildCount) {
+  return TestUtils.waitForCondition(
+    () => aEntry.childCount == aChildCount,
+    "wait for child count"
+  );
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_707862.js b/src/zen/tests/mochitests/sessionstore/browser_707862.js
new file mode 100644
index 000000000..2dab54a84
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_707862.js
@@ -0,0 +1,70 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+/* eslint-disable mozilla/no-arbitrary-setTimeout */
+
+const tabState = {
+  entries: [
+    {
+      url: "about:robots",
+      triggeringPrincipal_base64,
+      children: [{ url: "about:mozilla", triggeringPrincipal_base64 }],
+    },
+  ],
+};
+
+const blankState = {
+  windows: [
+    {
+      tabs: [
+        {
+          entries: [{ url: "about:blank", triggeringPrincipal_base64 }],
+        },
+      ],
+    },
+  ],
+};
+
+add_task(async function test() {
+  Services.prefs.setIntPref("browser.sessionstore.interval", 4000);
+  registerCleanupFunction(function () {
+    Services.prefs.clearUserPref("browser.sessionstore.interval");
+  });
+
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:blank");
+  let browser = tab.linkedBrowser;
+  await BrowserTestUtils.browserLoaded(browser, false, "about:blank");
+
+  await promiseTabState(tab, tabState);
+  let sessionHistory = browser.browsingContext.sessionHistory;
+  let entry = sessionHistory.getEntryAtIndex(0);
+
+  await whenChildCount(entry, 1);
+
+  // Create a dynamic subframe.
+  let doc = browser.contentDocument;
+  let iframe = doc.createElement("iframe");
+  iframe.setAttribute("src", "about:mozilla");
+  doc.body.appendChild(iframe);
+
+  await whenChildCount(entry, 2);
+
+  // Force reload the browser to deprecate the subframes.
+  browser.reloadWithFlags(Ci.nsIWebNavigation.LOAD_FLAGS_BYPASS_CACHE);
+
+  await BrowserTestUtils.browserLoaded(browser, false, "about:robots");
+  let newSessionHistory = browser.browsingContext.sessionHistory;
+  let newEntry = newSessionHistory.getEntryAtIndex(0);
+
+  await whenChildCount(newEntry, 0);
+  // Make sure that we reset the state.
+  waitForBrowserState(blankState, finish);
+
+  ok(true, "test passed");
+});
+
+function whenChildCount(aEntry, aChildCount) {
+  return TestUtils.waitForCondition(
+    () => aEntry.childCount == aChildCount,
+    "wait for child count"
+  );
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_739531.js b/src/zen/tests/mochitests/sessionstore/browser_739531.js
new file mode 100644
index 000000000..e02a94d9a
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_739531.js
@@ -0,0 +1,55 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// This test ensures that attempts made to save/restore ("duplicate") pages
+// using designmode AND make changes to document structure (remove body)
+// don't result in uncaught errors and a broken browser state.
+
+function test() {
+  waitForExplicitFinish();
+
+  let testURL =
+    "http://mochi.test:8888/browser/" +
+    "browser/components/sessionstore/test/browser_739531_sample.html";
+
+  let loadCount = 0;
+  let tab = BrowserTestUtils.addTab(gBrowser, testURL);
+
+  let removeFunc;
+  removeFunc = BrowserTestUtils.addContentEventListener(
+    tab.linkedBrowser,
+    "load",
+    function onLoad() {
+      // make sure both the page and the frame are loaded
+      if (++loadCount < 2) {
+        return;
+      }
+      removeFunc();
+
+      // executeSoon to allow the JS to execute on the page
+      executeSoon(function () {
+        let tab2;
+        let caughtError = false;
+        try {
+          tab2 = ss.duplicateTab(window, tab);
+        } catch (e) {
+          caughtError = true;
+          info(e);
+        }
+
+        is(gBrowser.tabs.length, 3, "there should be 3 tabs");
+
+        ok(!caughtError, "duplicateTab didn't throw");
+
+        // if the test fails, we don't want to try to close a tab that doesn't exist
+        if (tab2) {
+          gBrowser.removeTab(tab2);
+        }
+        gBrowser.removeTab(tab);
+
+        finish();
+      });
+    },
+    true
+  );
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_739531_frame.html b/src/zen/tests/mochitests/sessionstore/browser_739531_frame.html
new file mode 100644
index 000000000..10f045a39
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_739531_frame.html
@@ -0,0 +1 @@
+<body><html>1</html></body>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_739531_sample.html b/src/zen/tests/mochitests/sessionstore/browser_739531_sample.html
new file mode 100644
index 000000000..e6c48ff26
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_739531_sample.html
@@ -0,0 +1,23 @@
+<!-- originally a crash test for bug 713417
+     https://bug713417.bugzilla.mozilla.org/attachment.cgi?id=584240 -->
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<script>
+
+function boom() {
+  var w = document.getElementById("f").contentWindow;
+  var d = w.document;
+  d.designMode = "on";
+  var r = d.documentElement;
+  d.removeChild(r);
+  document.adoptNode(r);
+}
+
+</script>
+</head>
+<body onload="boom();">
+<iframe src="browser_739531_frame.html" id="f"></iframe>
+</body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_739805.js b/src/zen/tests/mochitests/sessionstore/browser_739805.js
new file mode 100644
index 000000000..d3b2b2e8c
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_739805.js
@@ -0,0 +1,51 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+var url = "data:text/html;charset=utf-8,<input%20id='foo'>";
+var tabState = {
+  entries: [{ url, triggeringPrincipal_base64 }],
+  formdata: { id: { foo: "bar" }, url },
+};
+
+function test() {
+  waitForExplicitFinish();
+  Services.prefs.setBoolPref("browser.sessionstore.restore_on_demand", true);
+
+  registerCleanupFunction(function () {
+    if (gBrowser.tabs.length > 1) {
+      gBrowser.removeTab(gBrowser.tabs[1]);
+    }
+    Services.prefs.clearUserPref("browser.sessionstore.restore_on_demand");
+  });
+
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:blank");
+  let browser = tab.linkedBrowser;
+
+  BrowserTestUtils.browserLoaded(browser, { wantLoad: "about:blank" }).then(
+    () => {
+      isnot(gBrowser.selectedTab, tab, "newly created tab is not selected");
+
+      ss.setTabState(tab, JSON.stringify(tabState));
+      is(
+        ss.getInternalObjectState(browser),
+        TAB_STATE_NEEDS_RESTORE,
+        "tab needs restoring"
+      );
+
+      let { formdata } = JSON.parse(ss.getTabState(tab));
+      is(formdata && formdata.id.foo, "bar", "tab state's formdata is valid");
+
+      promiseTabRestored(tab).then(() => {
+        SpecialPowers.spawn(browser, [], function () {
+          let input = content.document.getElementById("foo");
+          is(input.value, "bar", "formdata has been restored correctly");
+        }).then(() => {
+          finish();
+        });
+      });
+
+      // Restore the tab by selecting it.
+      gBrowser.selectedTab = tab;
+    }
+  );
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_819510_perwindowpb.js b/src/zen/tests/mochitests/sessionstore/browser_819510_perwindowpb.js
new file mode 100644
index 000000000..8dd41ef05
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_819510_perwindowpb.js
@@ -0,0 +1,152 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// Test opening default mochitest-normal-private-normal-private windows
+// (saving the state with last window being private)
+
+requestLongerTimeout(2);
+
+add_task(async function test_1() {
+  let win = await promiseNewWindowLoaded();
+  await promiseTabLoad(win, "http://www.example.com/#1");
+
+  win = await promiseNewWindowLoaded({ private: true });
+  await promiseTabLoad(win, "http://www.example.com/#2");
+
+  win = await promiseNewWindowLoaded();
+  await promiseTabLoad(win, "http://www.example.com/#3");
+
+  win = await promiseNewWindowLoaded({ private: true });
+  await promiseTabLoad(win, "http://www.example.com/#4");
+
+  let curState = JSON.parse(ss.getBrowserState());
+  is(curState.windows.length, 5, "Browser has opened 5 windows");
+  is(curState.windows[2].isPrivate, true, "Window is private");
+  is(curState.windows[4].isPrivate, true, "Last window is private");
+  is(curState.selectedWindow, 5, "Last window opened is the one selected");
+
+  let state = JSON.parse(await promiseRecoveryFileContents());
+
+  is(
+    state.windows.length,
+    2,
+    "sessionstore state: 2 windows in data being written to disk"
+  );
+  is(
+    state.selectedWindow,
+    2,
+    "Selected window is updated to match one of the saved windows"
+  );
+  ok(
+    state.windows.every(win2 => !win2.isPrivate),
+    "Saved windows are not private"
+  );
+  is(
+    state._closedWindows.length,
+    0,
+    "sessionstore state: no closed windows in data being written to disk"
+  );
+
+  // Cleanup.
+  await promiseAllButPrimaryWindowClosed();
+  forgetClosedWindows();
+});
+
+// Test opening default mochitest window + 2 private windows
+add_task(async function test_2() {
+  let win = await promiseNewWindowLoaded({ private: true });
+  await promiseTabLoad(win, "http://www.example.com/#1");
+
+  win = await promiseNewWindowLoaded({ private: true });
+  await promiseTabLoad(win, "http://www.example.com/#2");
+
+  let curState = JSON.parse(ss.getBrowserState());
+  is(curState.windows.length, 3, "Browser has opened 3 windows");
+  is(curState.windows[1].isPrivate, true, "Window 1 is private");
+  is(curState.windows[2].isPrivate, true, "Window 2 is private");
+  is(curState.selectedWindow, 3, "Last window opened is the one selected");
+
+  let state = JSON.parse(await promiseRecoveryFileContents());
+
+  is(
+    state.windows.length,
+    0,
+    "sessionstore state: no window in data being written to disk"
+  );
+  is(
+    state.selectedWindow,
+    0,
+    "Selected window updated to 0 given there are no saved windows"
+  );
+  is(
+    state._closedWindows.length,
+    0,
+    "sessionstore state: no closed windows in data being written to disk"
+  );
+
+  // Cleanup.
+  await promiseAllButPrimaryWindowClosed();
+  forgetClosedWindows();
+});
+
+// Test opening default-normal-private-normal windows and closing a normal window
+add_task(async function test_3() {
+  let normalWindow = await promiseNewWindowLoaded();
+  await promiseTabLoad(normalWindow, "http://www.example.com/#1");
+
+  let win = await promiseNewWindowLoaded({ private: true });
+  await promiseTabLoad(win, "http://www.example.com/#2");
+
+  win = await promiseNewWindowLoaded();
+  await promiseTabLoad(win, "http://www.example.com/#3");
+
+  let curState = JSON.parse(ss.getBrowserState());
+  is(curState.windows.length, 4, "Browser has opened 4 windows");
+  is(curState.windows[2].isPrivate, true, "Window 2 is private");
+  is(curState.selectedWindow, 4, "Last window opened is the one selected");
+
+  await BrowserTestUtils.closeWindow(normalWindow);
+
+  // Pin and unpin a tab before checking the written state so that
+  // the list of restoring windows gets cleared. Otherwise the
+  // window we just closed would be marked as not closed.
+  let tab = win.gBrowser.tabs[0];
+  win.gBrowser.pinTab(tab);
+  win.gBrowser.unpinTab(tab);
+
+  let state = JSON.parse(await promiseRecoveryFileContents());
+
+  is(
+    state.windows.length,
+    1,
+    "sessionstore state: 1 window in data being written to disk"
+  );
+  is(
+    state.selectedWindow,
+    1,
+    "Selected window is updated to match one of the saved windows"
+  );
+  ok(
+    state.windows.every(win2 => !win2.isPrivate),
+    "Saved windows are not private"
+  );
+  is(
+    state._closedWindows.length,
+    1,
+    "sessionstore state: 1 closed window in data being written to disk"
+  );
+  ok(
+    state._closedWindows.every(win2 => !win2.isPrivate),
+    "Closed windows are not private"
+  );
+
+  // Cleanup.
+  await promiseAllButPrimaryWindowClosed();
+  forgetClosedWindows();
+});
+
+async function promiseTabLoad(win, url) {
+  let tab = BrowserTestUtils.addTab(win.gBrowser, url);
+  await promiseBrowserLoaded(tab.linkedBrowser);
+  await TabStateFlusher.flush(tab.linkedBrowser);
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_906076_lazy_tabs.js b/src/zen/tests/mochitests/sessionstore/browser_906076_lazy_tabs.js
new file mode 100644
index 000000000..2fab82ca0
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_906076_lazy_tabs.js
@@ -0,0 +1,163 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const TEST_STATE = {
+  windows: [
+    {
+      tabs: [
+        {
+          entries: [{ url: "http://example.com", triggeringPrincipal_base64 }],
+        },
+        {
+          entries: [{ url: "http://example.com", triggeringPrincipal_base64 }],
+        },
+        {
+          entries: [{ url: "http://example.com", triggeringPrincipal_base64 }],
+        },
+        {
+          entries: [{ url: "http://example.com", triggeringPrincipal_base64 }],
+        },
+        {
+          entries: [{ url: "http://example.com", triggeringPrincipal_base64 }],
+        },
+        {
+          entries: [{ url: "http://example.com", triggeringPrincipal_base64 }],
+        },
+        {
+          entries: [{ url: "http://example.com", triggeringPrincipal_base64 }],
+        },
+        {
+          entries: [{ url: "http://example.com", triggeringPrincipal_base64 }],
+        },
+        {
+          entries: [{ url: "http://example.com", triggeringPrincipal_base64 }],
+        },
+        {
+          entries: [{ url: "http://example.com", triggeringPrincipal_base64 }],
+        },
+      ],
+    },
+  ],
+};
+
+const TEST_STATE_2 = {
+  windows: [
+    {
+      tabs: [
+        { entries: [{ url: "about:robots", triggeringPrincipal_base64 }] },
+        {
+          entries: [],
+          userTypedValue: "http://example.com",
+          userTypedClear: 1,
+        },
+      ],
+    },
+  ],
+};
+
+function countNonLazyTabs(win) {
+  win = win || window;
+  let count = 0;
+  for (let browser of win.gBrowser.browsers) {
+    if (browser.isConnected) {
+      count++;
+    }
+  }
+  return count;
+}
+
+/**
+ * Test that lazy browsers do not get prematurely inserted by
+ * code accessing browser bound properties on the unbound browser.
+ */
+
+add_task(async function test() {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["browser.sessionstore.restore_on_demand", true],
+      ["browser.sessionstore.restore_tabs_lazily", true],
+    ],
+  });
+
+  let backupState = SessionStore.getBrowserState();
+
+  await promiseBrowserState(TEST_STATE);
+
+  info(
+    "Check that no lazy browsers get unnecessarily inserted after session restore"
+  );
+  is(countNonLazyTabs(), 1, "Window has only 1 non-lazy tab");
+
+  await TestUtils.topicObserved("sessionstore-state-write-complete");
+
+  // When sessionstore write occurs, tabs are checked for state changes.
+  // Make sure none of them insert their browsers when this happens.
+  info("Check that no lazy browsers get inserted after sessionstore write");
+  is(countNonLazyTabs(), 1, "Window has only 1 non-lazy tab");
+
+  info("Check that lazy browser gets inserted properly");
+  ok(
+    !gBrowser.browsers[1].isConnected,
+    "The browser that we're attempting to insert is indeed lazy"
+  );
+  gBrowser._insertBrowser(gBrowser.tabs[1]);
+  is(countNonLazyTabs(), 2, "Window now has 2 non-lazy tabs");
+
+  // Check if any lazy tabs got inserted when window closes.
+  let newWindow = await promiseNewWindowLoaded();
+
+  SessionStore.setWindowState(newWindow, JSON.stringify(TEST_STATE));
+
+  await new Promise(resolve => {
+    newWindow.addEventListener(
+      "unload",
+      () => {
+        info("Check that no lazy browsers get inserted when window closes");
+        is(countNonLazyTabs(newWindow), 1, "Window has only 1 non-lazy tab");
+
+        info(
+          "Check that it is not possible to insert a lazy browser after the window closed"
+        );
+        ok(
+          !newWindow.gBrowser.browsers[1].isConnected,
+          "The browser that we're attempting to insert is indeed lazy"
+        );
+        newWindow.gBrowser._insertBrowser(newWindow.gBrowser.tabs[1]);
+        is(
+          countNonLazyTabs(newWindow),
+          1,
+          "Window still has only 1 non-lazy tab"
+        );
+
+        resolve();
+      },
+      { once: true }
+    );
+
+    newWindow.close();
+  });
+
+  // Bug 1365933.
+  info(
+    "Check that session with tab having empty entries array gets restored properly"
+  );
+  await promiseBrowserState(TEST_STATE_2);
+
+  is(gBrowser.tabs.length, 2, "Window has 2 tabs");
+  is(
+    gBrowser.selectedBrowser.currentURI.spec,
+    "about:robots",
+    "Tab has the expected URL"
+  );
+
+  gBrowser.selectedTab = gBrowser.tabs[1];
+  await BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser);
+  is(
+    gBrowser.selectedBrowser.currentURI.spec,
+    "http://example.com/",
+    "Tab has the expected URL"
+  );
+
+  // Cleanup.
+  await promiseBrowserState(backupState);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_911547_sample.html^headers^ b/src/zen/tests/mochitests/sessionstore/browser_911547_sample.html^headers^
new file mode 100644
index 000000000..4623dec30
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_911547_sample.html^headers^
@@ -0,0 +1 @@
+Content-Security-Policy: script-src 'self'
diff --git a/src/zen/tests/mochitests/sessionstore/browser_aboutPrivateBrowsing.js b/src/zen/tests/mochitests/sessionstore/browser_aboutPrivateBrowsing.js
new file mode 100644
index 000000000..8bb21620e
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_aboutPrivateBrowsing.js
@@ -0,0 +1,24 @@
+"use strict";
+
+// Tests that an about:privatebrowsing tab with no history will not
+// be saved into session store and thus, it will not show up in
+// Recently Closed Tabs.
+
+add_task(async function () {
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:privatebrowsing");
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  is(
+    gBrowser.browsers[1].currentURI.spec,
+    "about:privatebrowsing",
+    "we will be removing an about:privatebrowsing tab"
+  );
+
+  let r = `rand-${Math.random()}`;
+  ss.setCustomTabValue(tab, "foobar", r);
+
+  await promiseRemoveTabAndSessionState(tab);
+  let closedTabData = JSON.stringify(ss.getClosedTabDataForWindow(window));
+  ok(!closedTabData.includes(r), "tab not stored in _closedTabs");
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_aboutRestartrequired_noRestore.js b/src/zen/tests/mochitests/sessionstore/browser_aboutRestartrequired_noRestore.js
new file mode 100644
index 000000000..0b89f83ad
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_aboutRestartrequired_noRestore.js
@@ -0,0 +1,165 @@
+"use strict";
+
+function isEntriesMatchingOnURL(A, B) {
+  const AUrls = A.entries.map(e => e.url);
+  const BUrls = B.entries.map(e => e.url);
+
+  if (AUrls.entries.length !== BUrls.entries.length) {
+    return false;
+  }
+
+  for (let url of AUrls) {
+    if (!BUrls.includes(url)) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+function setState(aTab, aState) {
+  // Prepare the tab state.
+  let promise = promiseTabRestoring(aTab);
+  // setTabState will go through TabState.copyFromCache() from
+  // TabState.collect() triggered by saveStateAsyncWhenIdle()
+  ss.setTabState(aTab, JSON.stringify(aState));
+  return promise;
+}
+
+async function cleanup(aBrowser, aTab) {
+  // Flush to ensure the parent has all data.
+  await TabStateFlusher.flush(aBrowser);
+
+  // Cleanup.
+  gBrowser.removeTab(aTab);
+}
+
+async function getBrowserTab() {
+  // Create a background tab.
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:blank");
+  let browser = tab.linkedBrowser;
+  await BrowserTestUtils.browserLoaded(browser, { wantLoad: "about:blank" });
+  return [tab, browser];
+}
+
+add_setup(async function () {
+  // The tab shouldn't be restored right away.
+  Services.prefs.setBoolPref("browser.sessionstore.restore_on_demand", true);
+});
+
+add_task(async function only_about_restartrequired() {
+  const TAB_STATE = {
+    entries: [{ url: "about:restartrequired", triggeringPrincipal_base64 }],
+  };
+
+  let [tab, browser] = await getBrowserTab();
+
+  const previousTabState = TabState.collect(
+    tab,
+    ss.getInternalObjectState(tab)
+  );
+  is(previousTabState.entries.length, 0, "No entries before");
+
+  await setState(tab, TAB_STATE);
+
+  const collectedTabState = TabState.collect(
+    tab,
+    ss.getInternalObjectState(tab)
+  );
+  is(collectedTabState.entries.length, 0, "No entry found");
+
+  await cleanup(browser, tab);
+});
+
+add_task(async function one_and_about_restartrequired() {
+  const TAB_STATE = {
+    entries: [
+      { url: "https://www.mozilla.org", triggeringPrincipal_base64 },
+      { url: "about:restartrequired", triggeringPrincipal_base64 },
+    ],
+  };
+
+  let [tab, browser] = await getBrowserTab();
+
+  const previousTabState = TabState.collect(
+    tab,
+    ss.getInternalObjectState(tab)
+  );
+  is(previousTabState.entries.length, 0, "No entries before");
+
+  await setState(tab, TAB_STATE);
+
+  const collectedTabState = TabState.collect(
+    tab,
+    ss.getInternalObjectState(tab)
+  );
+  is(
+    collectedTabState.entries[0].url,
+    "https://www.mozilla.org",
+    "One entry found"
+  );
+
+  await cleanup(browser, tab);
+});
+
+add_task(async function about_restartrequired_with_params() {
+  const TAB_STATE = {
+    entries: [
+      {
+        url: "about:restartrequired?e=restartrequired&u=about%3Asupport&c=UTF-8&d=%20",
+        triggeringPrincipal_base64,
+      },
+    ],
+  };
+
+  let [tab, browser] = await getBrowserTab();
+
+  const previousTabState = TabState.collect(
+    tab,
+    ss.getInternalObjectState(tab)
+  );
+  is(previousTabState.entries.length, 0, "No entries before");
+
+  await setState(tab, TAB_STATE);
+
+  const collectedTabState = TabState.collect(
+    tab,
+    ss.getInternalObjectState(tab)
+  );
+  is(collectedTabState.entries[0].url, "about:support", "One entry found");
+
+  await cleanup(browser, tab);
+});
+
+add_task(async function about_restartrequired_evil() {
+  const TAB_STATE = {
+    entries: [
+      {
+        url: "https://www.mozilla.org/?u=http://evil.example.org&someParam=about:restartrequired",
+        triggeringPrincipal_base64,
+      },
+    ],
+  };
+
+  let [tab, browser] = await getBrowserTab();
+
+  const previousTabState = TabState.collect(
+    tab,
+    ss.getInternalObjectState(tab)
+  );
+  is(previousTabState.entries.length, 0, "No entries before");
+
+  await setState(tab, TAB_STATE);
+
+  const collectedTabState = TabState.collect(
+    tab,
+    ss.getInternalObjectState(tab)
+  );
+  is(
+    collectedTabState.entries[0].url,
+    TAB_STATE.entries[0].url,
+    "Original URL found"
+  );
+
+  await cleanup(browser, tab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_aboutSessionRestore.js b/src/zen/tests/mochitests/sessionstore/browser_aboutSessionRestore.js
new file mode 100644
index 000000000..df5a49d7b
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_aboutSessionRestore.js
@@ -0,0 +1,67 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const CRASH_URL = "about:mozilla";
+const CRASH_FAVICON = "chrome://branding/content/icon32.png";
+const CRASH_SHENTRY = { url: CRASH_URL, triggeringPrincipal_base64 };
+const CRASH_TAB = { entries: [CRASH_SHENTRY], image: CRASH_FAVICON };
+const CRASH_STATE = { windows: [{ tabs: [CRASH_TAB] }] };
+
+const TAB_URL = "about:sessionrestore";
+const TAB_FORMDATA = { url: TAB_URL, id: { sessionData: CRASH_STATE } };
+const TAB_SHENTRY = { url: TAB_URL, triggeringPrincipal_base64 };
+const TAB_STATE = { entries: [TAB_SHENTRY], formdata: TAB_FORMDATA };
+
+add_task(async function () {
+  // Prepare a blank tab.
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:blank");
+  let browser = tab.linkedBrowser;
+  await BrowserTestUtils.browserLoaded(browser, { wantLoad: "about:blank" });
+
+  // Fake a post-crash tab.
+  ss.setTabState(tab, JSON.stringify(TAB_STATE));
+  await promiseTabRestored(tab);
+
+  Assert.greater(gBrowser.tabs.length, 1, "we have more than one tab");
+
+  let tabsToggle = browser.contentDocument.getElementById("tabsToggle");
+  tabsToggle.click();
+  await TestUtils.waitForCondition(
+    () => browser.contentWindow.gTreeInitialized
+  );
+  let tree = browser.contentDocument.getElementById("tabList");
+  let view = tree.view;
+  ok(view.isContainer(0), "first entry is the window");
+  let titleColumn = tree.columns.title;
+  is(
+    view.getCellProperties(1, titleColumn),
+    "icon",
+    "second entry is the tab and has a favicon"
+  );
+
+  let newWindowOpened = BrowserTestUtils.waitForNewWindow();
+
+  SpecialPowers.spawn(browser.browsingContext, [], () => {
+    content.document.getElementById("errorTryAgain").click();
+  });
+
+  // Wait until the new window was restored.
+  let win = await newWindowOpened;
+
+  BrowserTestUtils.removeTab(tab);
+  await BrowserTestUtils.closeWindow(win);
+
+  let [
+    {
+      tabs: [
+        {
+          entries: [{ url }],
+        },
+      ],
+    },
+  ] = ss.getClosedWindowData();
+  is(url, CRASH_URL, "session was restored correctly");
+  ss.forgetClosedWindow(0);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_async_duplicate_tab.js b/src/zen/tests/mochitests/sessionstore/browser_async_duplicate_tab.js
new file mode 100644
index 000000000..e592df93e
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_async_duplicate_tab.js
@@ -0,0 +1,87 @@
+"use strict";
+
+const PATH = getRootDirectory(gTestPath).replace(
+  "chrome://mochitests/content/",
+  "http://example.com/"
+);
+const URL = PATH + "file_async_duplicate_tab.html";
+
+add_task(async function test_duplicate() {
+  // Create new tab.
+  let tab = BrowserTestUtils.addTab(gBrowser, URL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  // Flush to empty any queued update messages.
+  await TabStateFlusher.flush(browser);
+
+  // Click the link to navigate, this will add second shistory entry.
+  await SpecialPowers.spawn(browser, [], async function () {
+    return new Promise(resolve => {
+      docShell.chromeEventHandler.addEventListener(
+        "hashchange",
+        () => resolve(),
+        { once: true, capture: true }
+      );
+
+      // Click the link.
+      content.document.querySelector("a").click();
+    });
+  });
+
+  // Duplicate the tab.
+  let tab2 = ss.duplicateTab(window, tab);
+
+  // Wait until the tab has fully restored.
+  await promiseTabRestored(tab2);
+  await TabStateFlusher.flush(tab2.linkedBrowser);
+
+  // There should be two history entries now.
+  let { entries } = JSON.parse(ss.getTabState(tab2));
+  is(entries.length, 2, "there are two shistory entries");
+
+  // Cleanup.
+  BrowserTestUtils.removeTab(tab2);
+  BrowserTestUtils.removeTab(tab);
+});
+
+add_task(async function test_duplicate_remove() {
+  // Create new tab.
+  let tab = BrowserTestUtils.addTab(gBrowser, URL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  // Flush to empty any queued update messages.
+  await TabStateFlusher.flush(browser);
+
+  // Click the link to navigate, this will add second shistory entry.
+  await SpecialPowers.spawn(browser, [], async function () {
+    return new Promise(resolve => {
+      docShell.chromeEventHandler.addEventListener(
+        "hashchange",
+        () => resolve(),
+        { once: true, capture: true }
+      );
+
+      // Click the link.
+      content.document.querySelector("a").click();
+    });
+  });
+
+  // Duplicate the tab.
+  let tab2 = ss.duplicateTab(window, tab);
+
+  // Before the duplication finished, remove the tab.
+  await Promise.all([
+    promiseRemoveTabAndSessionState(tab),
+    promiseTabRestored(tab2),
+  ]);
+  await TabStateFlusher.flush(tab2.linkedBrowser);
+
+  // There should be two history entries now.
+  let { entries } = JSON.parse(ss.getTabState(tab2));
+  is(entries.length, 2, "there are two shistory entries");
+
+  // Cleanup.
+  BrowserTestUtils.removeTab(tab2);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_async_flushes.js b/src/zen/tests/mochitests/sessionstore/browser_async_flushes.js
new file mode 100644
index 000000000..d0bf039ff
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_async_flushes.js
@@ -0,0 +1,79 @@
+"use strict";
+
+const PATH = getRootDirectory(gTestPath).replace(
+  "chrome://mochitests/content/",
+  "http://example.com/"
+);
+const URL = PATH + "file_async_flushes.html";
+
+add_task(async function test_flush() {
+  // Create new tab.
+  let tab = BrowserTestUtils.addTab(gBrowser, URL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  // Flush to empty any queued update messages.
+  await TabStateFlusher.flush(browser);
+
+  // There should be one history entry.
+  let { entries } = JSON.parse(ss.getTabState(tab));
+  is(entries.length, 1, "there is a single history entry");
+
+  // Click the link to navigate, this will add second shistory entry.
+  await SpecialPowers.spawn(browser, [], async function () {
+    return new Promise(resolve => {
+      docShell.chromeEventHandler.addEventListener(
+        "hashchange",
+        () => resolve(),
+        { once: true, capture: true }
+      );
+
+      // Click the link.
+      content.document.querySelector("a").click();
+    });
+  });
+
+  // Flush to empty any queued update messages.
+  await TabStateFlusher.flush(browser);
+
+  // There should be two history entries now.
+  ({ entries } = JSON.parse(ss.getTabState(tab)));
+  is(entries.length, 2, "there are two shistory entries");
+
+  // Cleanup.
+  gBrowser.removeTab(tab);
+});
+
+add_task(async function test_remove() {
+  // Create new tab.
+  let tab = BrowserTestUtils.addTab(gBrowser, URL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  // Flush to empty any queued update messages.
+  await TabStateFlusher.flush(browser);
+
+  // There should be one history entry.
+  let { entries } = JSON.parse(ss.getTabState(tab));
+  is(entries.length, 1, "there is a single history entry");
+
+  // Click the link to navigate.
+  await SpecialPowers.spawn(browser, [], async function () {
+    return new Promise(resolve => {
+      docShell.chromeEventHandler.addEventListener(
+        "hashchange",
+        () => resolve(),
+        { once: true, capture: true }
+      );
+
+      // Click the link.
+      content.document.querySelector("a").click();
+    });
+  });
+
+  // Request a flush and remove the tab. The flush should still complete.
+  await Promise.all([
+    TabStateFlusher.flush(browser),
+    promiseRemoveTabAndSessionState(tab),
+  ]);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_async_remove_tab.js b/src/zen/tests/mochitests/sessionstore/browser_async_remove_tab.js
new file mode 100644
index 000000000..7d13d8476
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_async_remove_tab.js
@@ -0,0 +1,196 @@
+"use strict";
+
+async function createTabWithRandomValue(url) {
+  let tab = BrowserTestUtils.addTab(gBrowser, url);
+  let browser = tab.linkedBrowser;
+  await BrowserTestUtils.browserLoaded(browser, { wantLoad: url });
+
+  // Set a random value.
+  let r = `rand-${Math.random()}`;
+  ss.setCustomTabValue(tab, "foobar", r);
+
+  // Flush to ensure there are no scheduled messages.
+  await TabStateFlusher.flush(browser);
+
+  return { tab, r };
+}
+
+function isValueInClosedData(rval) {
+  return JSON.stringify(ss.getClosedTabDataForWindow(window)).includes(rval);
+}
+
+function restoreClosedTabWithValue(rval) {
+  let closedTabData = ss.getClosedTabDataForWindow(window);
+  let index = closedTabData.findIndex(function (data) {
+    return (data.state.extData && data.state.extData.foobar) == rval;
+  });
+
+  if (index == -1) {
+    throw new Error("no closed tab found for given rval");
+  }
+
+  return ss.undoCloseTab(window, index);
+}
+
+add_task(async function dont_save_empty_tabs() {
+  let { tab, r } = await createTabWithRandomValue("about:blank");
+
+  // Remove the tab before the update arrives.
+  let promise = promiseRemoveTabAndSessionState(tab);
+
+  // No tab state worth saving.
+  ok(!isValueInClosedData(r), "closed tab not saved");
+  await promise;
+
+  // Still no tab state worth saving.
+  ok(!isValueInClosedData(r), "closed tab not saved");
+});
+
+add_task(async function save_worthy_tabs_remote() {
+  let { tab, r } = await createTabWithRandomValue("https://example.com/");
+  ok(tab.linkedBrowser.isRemoteBrowser, "browser is remote");
+
+  // Remove the tab before the update arrives.
+  let promise = promiseRemoveTabAndSessionState(tab);
+
+  // Tab state deemed worth saving.
+  ok(isValueInClosedData(r), "closed tab saved");
+  await promise;
+
+  // Tab state still deemed worth saving.
+  ok(isValueInClosedData(r), "closed tab saved");
+});
+
+add_task(async function save_worthy_tabs_nonremote() {
+  let { tab, r } = await createTabWithRandomValue("about:robots");
+  ok(!tab.linkedBrowser.isRemoteBrowser, "browser is not remote");
+
+  // Remove the tab before the update arrives.
+  let promise = promiseRemoveTabAndSessionState(tab);
+
+  // Tab state deemed worth saving.
+  ok(isValueInClosedData(r), "closed tab saved");
+  await promise;
+
+  // Tab state still deemed worth saving.
+  ok(isValueInClosedData(r), "closed tab saved");
+});
+
+add_task(async function save_worthy_tabs_remote_final() {
+  let { tab, r } = await createTabWithRandomValue("about:blank");
+  let browser = tab.linkedBrowser;
+  ok(browser.isRemoteBrowser, "browser is remote");
+
+  // The subtest is racy, see bug 1787024. This is added as a sanity check,
+  // but the delay it introduces might also hide the race.
+  await TabStateFlusher.flush(browser);
+  let state = JSON.parse(ss.getTabState(tab));
+  is(state.entries.length, 1, "Should have one SH entry");
+  is(state.entries[0].url, "about:blank", "Should be about:blank SH entry");
+  ok(
+    state.entries[0].transient,
+    "Initial about:blank SH entry should be marked for replacement"
+  );
+
+  // Replace about:blank with a new remote page.
+  let entryReplaced = promiseOnHistoryReplaceEntry(browser);
+  browser.loadURI(Services.io.newURI("https://example.com/"), {
+    triggeringPrincipal: Services.scriptSecurityManager.getSystemPrincipal(),
+  });
+  await entryReplaced;
+
+  // Remotness shouldn't have changed.
+  ok(browser.isRemoteBrowser, "browser is still remote");
+
+  // Remove the tab before the update arrives.
+  await promiseRemoveTabAndSessionState(tab);
+
+  // Turns out there is a tab state worth saving.
+  ok(isValueInClosedData(r), "closed tab saved");
+});
+
+add_task(async function save_worthy_tabs_nonremote_final() {
+  let { tab, r } = await createTabWithRandomValue("about:blank");
+  let browser = tab.linkedBrowser;
+  ok(browser.isRemoteBrowser, "browser is remote");
+
+  // Replace about:blank with a non-remote entry.
+  BrowserTestUtils.startLoadingURIString(browser, "about:robots");
+  await BrowserTestUtils.browserLoaded(browser);
+  ok(!browser.isRemoteBrowser, "browser is not remote anymore");
+
+  // Remove the tab before the update arrives.
+  await promiseRemoveTabAndSessionState(tab);
+
+  // Turns out there is a tab state worth saving.
+  ok(isValueInClosedData(r), "closed tab saved");
+});
+
+add_task(async function dont_save_empty_tabs_final() {
+  let { tab, r } = await createTabWithRandomValue("https://example.com/");
+  let browser = tab.linkedBrowser;
+  ok(browser.isRemoteBrowser, "browser is remote");
+
+  // Replace the current page with an about:blank entry.
+  let entryReplaced = promiseOnHistoryReplaceEntry(browser);
+
+  // We're doing a cross origin navigation, so we can't reliably use a
+  // SpecialPowers task here. Instead we just emulate a location.replace() call.
+  browser.loadURI(Services.io.newURI("about:blank"), {
+    loadFlags:
+      Ci.nsIWebNavigation.LOAD_FLAGS_STOP_CONTENT |
+      Ci.nsIWebNavigation.LOAD_FLAGS_REPLACE_HISTORY,
+    triggeringPrincipal: Services.scriptSecurityManager.getSystemPrincipal(),
+  });
+
+  await entryReplaced;
+
+  // Remove the tab before the update arrives.
+  await promiseRemoveTabAndSessionState(tab);
+
+  // Turns out we don't want to save the tab state.
+  ok(!isValueInClosedData(r), "closed tab not saved");
+});
+
+add_task(async function undo_worthy_tabs() {
+  let { tab, r } = await createTabWithRandomValue("https://example.com/");
+  ok(tab.linkedBrowser.isRemoteBrowser, "browser is remote");
+
+  // Remove the tab before the update arrives.
+  let promise = promiseRemoveTabAndSessionState(tab);
+
+  // Tab state deemed worth saving.
+  ok(isValueInClosedData(r), "closed tab saved");
+
+  // Restore the closed tab before receiving its final message.
+  tab = restoreClosedTabWithValue(r);
+
+  // Wait for the final update message.
+  await promise;
+
+  // Check we didn't add the tab back to the closed list.
+  ok(!isValueInClosedData(r), "tab no longer closed");
+
+  // Cleanup.
+  BrowserTestUtils.removeTab(tab);
+});
+
+add_task(async function forget_worthy_tabs_remote() {
+  let { tab, r } = await createTabWithRandomValue("https://example.com/");
+  ok(tab.linkedBrowser.isRemoteBrowser, "browser is remote");
+
+  // Remove the tab before the update arrives.
+  let promise = promiseRemoveTabAndSessionState(tab);
+
+  // Tab state deemed worth saving.
+  ok(isValueInClosedData(r), "closed tab saved");
+
+  // Forget the closed tab.
+  ss.forgetClosedTab(window, 0);
+
+  // Wait for the final update message.
+  await promise;
+
+  // Check we didn't add the tab back to the closed list.
+  ok(!isValueInClosedData(r), "we forgot about the tab");
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_async_window_flushing.js b/src/zen/tests/mochitests/sessionstore/browser_async_window_flushing.js
new file mode 100644
index 000000000..42e24bdd8
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_async_window_flushing.js
@@ -0,0 +1,201 @@
+"use strict";
+
+const PAGE = "http://example.com/";
+
+/**
+ * Tests that if we initially discard a window as not interesting
+ * to save in the closed windows array, that we revisit that decision
+ * after a window flush has completed.
+ */
+add_task(async function test_add_interesting_window() {
+  // We want to suppress all non-final updates from the browser tabs
+  // so as to eliminate any racy-ness with this test.
+  await pushPrefs(["browser.sessionstore.debug.no_auto_updates", true]);
+
+  // Depending on previous tests, we might already have some closed
+  // windows stored. We'll use its length to determine whether or not
+  // the window was added or not.
+  let initialClosedWindows = ss.getClosedWindowCount();
+
+  // Make sure we can actually store another closed window
+  await pushPrefs([
+    "browser.sessionstore.max_windows_undo",
+    initialClosedWindows + 1,
+  ]);
+
+  // Create a new browser window. Since the default window will start
+  // at about:blank, SessionStore should find this tab (and therefore the
+  // whole window) uninteresting, and should not initially put it into
+  // the closed windows array.
+  let newWin = await BrowserTestUtils.openNewBrowserWindow();
+
+  let browser = newWin.gBrowser.selectedBrowser;
+
+  // Send a message that will cause the content to change its location
+  // to someplace more interesting. We've disabled auto updates from
+  // the browser, so the parent won't know about this
+  await SpecialPowers.spawn(browser, [PAGE], async function (newPage) {
+    content.location = newPage;
+  });
+
+  await promiseOnHistoryReplaceEntry(browser);
+
+  // Clear out the userTypedValue so that the new window looks like
+  // it's really not worth restoring.
+  browser.userTypedValue = null;
+
+  // Once this windowClosed Promise resolves, we should have finished
+  // the flush and revisited our decision to put this window into
+  // the closed windows array.
+  let windowClosed = BrowserTestUtils.windowClosed(newWin);
+
+  let handled = false;
+  whenDomWindowClosedHandled(() => {
+    // SessionStore's onClose handler should have just run.
+    let currentClosedWindows = ss.getClosedWindowCount();
+    is(
+      currentClosedWindows,
+      initialClosedWindows,
+      "We should not have added the window to the closed windows array"
+    );
+
+    handled = true;
+  });
+
+  // Ok, let's close the window.
+  newWin.close();
+
+  await windowClosed;
+
+  ok(handled, "domwindowclosed should already be handled here");
+
+  // The window flush has finished
+  let currentClosedWindows = ss.getClosedWindowCount();
+  is(
+    currentClosedWindows,
+    initialClosedWindows + 1,
+    "We should have added the window to the closed windows array"
+  );
+});
+
+/**
+ * Tests that if we initially store a closed window as interesting
+ * to save in the closed windows array, that we revisit that decision
+ * after a window flush has completed, and stop storing a window that
+ * we've deemed no longer interesting.
+ */
+add_task(async function test_remove_uninteresting_window() {
+  // We want to suppress all non-final updates from the browser tabs
+  // so as to eliminate any racy-ness with this test.
+  await pushPrefs(["browser.sessionstore.debug.no_auto_updates", true]);
+
+  // Depending on previous tests, we might already have some closed
+  // windows stored. We'll use its length to determine whether or not
+  // the window was added or not.
+  let initialClosedWindows = ss.getClosedWindowCount();
+
+  // Make sure we can actually store another closed window
+  await pushPrefs([
+    "browser.sessionstore.max_windows_undo",
+    initialClosedWindows + 1,
+  ]);
+
+  let newWin = await BrowserTestUtils.openNewBrowserWindow();
+
+  // Now browse the initial tab of that window to an interesting
+  // site.
+  let tab = newWin.gBrowser.selectedTab;
+  let browser = tab.linkedBrowser;
+  BrowserTestUtils.startLoadingURIString(browser, PAGE);
+
+  await BrowserTestUtils.browserLoaded(browser, false, PAGE);
+  await TabStateFlusher.flush(browser);
+
+  // Send a message that will cause the content to purge its
+  // history entries and make itself seem uninteresting.
+  await SpecialPowers.spawn(browser, [], async function () {
+    // Epic hackery to make this browser seem suddenly boring.
+    docShell.setCurrentURIForSessionStore(Services.io.newURI("about:blank"));
+  });
+
+  let { sessionHistory } = browser.browsingContext;
+  sessionHistory.purgeHistory(sessionHistory.count);
+
+  // Once this windowClosed Promise resolves, we should have finished
+  // the flush and revisited our decision to put this window into
+  // the closed windows array.
+  let windowClosed = BrowserTestUtils.windowClosed(newWin);
+
+  let handled = false;
+  whenDomWindowClosedHandled(() => {
+    // SessionStore's onClose handler should have just run.
+    let currentClosedWindows = ss.getClosedWindowCount();
+    is(
+      currentClosedWindows,
+      initialClosedWindows + 1,
+      "We should have added the window to the closed windows array"
+    );
+
+    handled = true;
+  });
+
+  // Ok, let's close the window.
+  newWin.close();
+
+  await windowClosed;
+
+  ok(handled, "domwindowclosed should already be handled here");
+
+  // The window flush has finished
+  let currentClosedWindows = ss.getClosedWindowCount();
+  is(
+    currentClosedWindows,
+    initialClosedWindows,
+    "We should have removed the window from the closed windows array"
+  );
+});
+
+/**
+ * Tests that when we close a window, it is immediately removed from the
+ * _windows array.
+ */
+add_task(async function test_synchronously_remove_window_state() {
+  // Depending on previous tests, we might already have some closed
+  // windows stored. We'll use its length to determine whether or not
+  // the window was added or not.
+  let state = JSON.parse(ss.getBrowserState());
+  ok(state, "Make sure we can get the state");
+  let initialWindows = state.windows.length;
+
+  // Open a new window and send the first tab somewhere
+  // interesting.
+  let newWin = await BrowserTestUtils.openNewBrowserWindow();
+  let browser = newWin.gBrowser.selectedBrowser;
+  BrowserTestUtils.startLoadingURIString(browser, PAGE);
+  await BrowserTestUtils.browserLoaded(browser, false, PAGE);
+  await TabStateFlusher.flush(browser);
+
+  state = JSON.parse(ss.getBrowserState());
+  is(
+    state.windows.length,
+    initialWindows + 1,
+    "The new window to be in the state"
+  );
+
+  // Now close the window, and make sure that the window was removed
+  // from the windows list from the SessionState. We're specifically
+  // testing the case where the window is _not_ removed in between
+  // the close-initiated flush request and the flush response.
+  let windowClosed = BrowserTestUtils.windowClosed(newWin);
+  newWin.close();
+
+  state = JSON.parse(ss.getBrowserState());
+  is(
+    state.windows.length,
+    initialWindows,
+    "The new window should have been removed from the state"
+  );
+
+  // Wait for our window to go away
+  await windowClosed;
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_attributes.js b/src/zen/tests/mochitests/sessionstore/browser_attributes.js
new file mode 100644
index 000000000..59cf6430d
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_attributes.js
@@ -0,0 +1,106 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/**
+ * This test makes sure that we correctly preserve tab attributes when storing
+ * and restoring tabs. It also ensures that we skip special attributes like
+ * 'image', 'muted', and 'pending' that need to be
+ * handled differently or internally.
+ */
+
+const PREF = "browser.sessionstore.restore_on_demand";
+
+add_task(async function test() {
+  Services.prefs.setBoolPref(PREF, true);
+  registerCleanupFunction(() => Services.prefs.clearUserPref(PREF));
+
+  // Add a new tab with a nice icon.
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:robots");
+  await promiseBrowserLoaded(tab.linkedBrowser);
+
+  // Because there is debounce logic in FaviconLoader.sys.mjs to reduce the
+  // favicon loads, we have to wait some time before checking that icon was
+  // stored properly.
+  await TestUtils.waitForCondition(
+    () => {
+      return gBrowser.getIcon(tab) != null;
+    },
+    "wait for favicon load to finish",
+    100,
+    5
+  );
+
+  // Check that the tab has an 'image' attribute.
+  ok(tab.hasAttribute("image"), "tab.image exists");
+
+  tab.toggleMuteAudio();
+  // Check that the tab has a 'muted' attribute.
+  ok(tab.hasAttribute("muted"), "tab.muted exists");
+
+  // Make sure we do not persist 'image' and 'muted' attributes.
+  let { attributes } = JSON.parse(ss.getTabState(tab));
+  ok(!("image" in attributes), "'image' attribute not saved");
+  ok(!("muted" in attributes), "'muted' attribute not saved");
+  ok(!("customizemode" in attributes), "'customizemode' attribute not saved");
+
+  // Test persisting a customizemode attribute.
+  {
+    let customizationReady = BrowserTestUtils.waitForEvent(
+      gNavToolbox,
+      "customizationready"
+    );
+    gCustomizeMode.enter();
+    await customizationReady;
+  }
+
+  let customizeIcon = gBrowser.getIcon(gBrowser.selectedTab);
+  ({ attributes } = JSON.parse(ss.getTabState(gBrowser.selectedTab)));
+  ok(!("image" in attributes), "'image' attribute not saved");
+  is(attributes.customizemode, "true", "'customizemode' attribute is correct");
+
+  {
+    let afterCustomization = BrowserTestUtils.waitForEvent(
+      gNavToolbox,
+      "aftercustomization"
+    );
+    gCustomizeMode.exit();
+    await afterCustomization;
+  }
+
+  // Test restoring a customizemode tab.
+  let state = {
+    entries: [],
+    attributes: { customizemode: "true", nonpersisted: "true" },
+  };
+
+  // Customize mode doesn't like being restored on top of a non-blank tab.
+  // For the moment, it appears it isn't possible to restore customizemode onto
+  // an existing non-blank tab outside of tests, however this may be a latent
+  // bug if we ever try to do that in the future.
+  let principal = Services.scriptSecurityManager.createNullPrincipal({});
+  tab.linkedBrowser.createAboutBlankDocumentViewer(principal, principal);
+
+  // Prepare a pending tab waiting to be restored.
+  let promise = promiseTabRestoring(tab);
+  ss.setTabState(tab, JSON.stringify(state));
+  await promise;
+
+  ok(tab.hasAttribute("pending"), "tab is pending");
+  ok(tab.hasAttribute("customizemode"), "tab is in customizemode");
+  ok(!tab.hasAttribute("nonpersisted"), "tab has no nonpersisted attribute");
+  is(gBrowser.getIcon(tab), customizeIcon, "tab has correct icon");
+  ok(!state.attributes.image, "'image' attribute not saved");
+
+  // Let the pending tab load.
+  gBrowser.selectedTab = tab;
+
+  // Ensure no 'image' or 'pending' attributes are stored.
+  ({ attributes } = JSON.parse(ss.getTabState(tab)));
+  ok(!("image" in attributes), "'image' attribute not saved");
+  ok(!("pending" in attributes), "'pending' attribute not saved");
+  ok(!("nonpersisted" in attributes), "'nonpersisted' attribute not saved");
+  is(attributes.customizemode, "true", "'customizemode' attribute is correct");
+
+  // Clean up.
+  gBrowser.removeTab(tab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_background_tab_crash.js b/src/zen/tests/mochitests/sessionstore/browser_background_tab_crash.js
new file mode 100644
index 000000000..b57360321
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_background_tab_crash.js
@@ -0,0 +1,262 @@
+"use strict";
+
+/**
+ * These tests the behaviour of the browser when background tabs crash,
+ * while the foreground tab remains.
+ *
+ * The current behavioural rule is this: if only background tabs crash,
+ * then only the first tab shown of that group should show the tab crash
+ * page, and subsequent ones should restore on demand.
+ */
+
+/**
+ * Makes the current browser tab non-remote, and then sets up two remote
+ * background tabs, ensuring that both belong to the same content process.
+ * Callers should pass in a testing function that will execute (and possibly
+ * yield Promises) taking the created background tabs as arguments. Once
+ * the testing function completes, this function will take care of closing
+ * the opened tabs.
+ *
+ * @param testFn (function)
+ *        A Promise-generating function that will be called once the tabs
+ *        are opened and ready.
+ * @return Promise
+ *        Resolves once the testing function completes and the opened tabs
+ *        have been completely closed.
+ */
+async function setupBackgroundTabs(testFn) {
+  const REMOTE_PAGE = "http://www.example.com";
+  const NON_REMOTE_PAGE = "about:mozilla";
+
+  // Browse the initial tab to a non-remote page, which we'll have in the
+  // foreground.
+  let initialTab = gBrowser.selectedTab;
+  let initialBrowser = initialTab.linkedBrowser;
+  BrowserTestUtils.startLoadingURIString(initialBrowser, NON_REMOTE_PAGE);
+  await BrowserTestUtils.browserLoaded(initialBrowser);
+  // Quick sanity check - the browser should be non remote.
+  Assert.ok(
+    !initialBrowser.isRemoteBrowser,
+    "Initial browser should not be remote."
+  );
+
+  // Open some tabs that should be running in the content process.
+  let tab1 = await BrowserTestUtils.openNewForegroundTab(gBrowser, REMOTE_PAGE);
+  let remoteBrowser1 = tab1.linkedBrowser;
+  await TabStateFlusher.flush(remoteBrowser1);
+
+  let tab2 = await BrowserTestUtils.openNewForegroundTab(gBrowser, REMOTE_PAGE);
+  let remoteBrowser2 = tab2.linkedBrowser;
+  await TabStateFlusher.flush(remoteBrowser2);
+
+  // Quick sanity check - the two browsers should be remote and share the
+  // same childID, or else this test is not going to work.
+  Assert.ok(
+    remoteBrowser1.isRemoteBrowser,
+    "Browser should be remote in order to crash."
+  );
+  Assert.ok(
+    remoteBrowser2.isRemoteBrowser,
+    "Browser should be remote in order to crash."
+  );
+  Assert.equal(
+    remoteBrowser1.frameLoader.childID,
+    remoteBrowser2.frameLoader.childID,
+    "Both remote browsers should share the same content process."
+  );
+
+  // Now switch back to the non-remote browser...
+  await BrowserTestUtils.switchTab(gBrowser, initialTab);
+
+  await testFn([tab1, tab2]);
+
+  BrowserTestUtils.removeTab(tab1);
+  BrowserTestUtils.removeTab(tab2);
+}
+
+/**
+ * Takes some set of background tabs that are assumed to all belong to
+ * the same content process, and crashes them.
+ *
+ * @param tabs (Array(<xul:tab>))
+ *        The tabs to crash.
+ * @return Promise
+ *        Resolves once the tabs have crashed and entered the pending
+ *        background state.
+ */
+async function crashBackgroundTabs(tabs) {
+  Assert.ok(!!tabs.length, "Need to crash at least one tab.");
+  for (let tab of tabs) {
+    Assert.ok(tab.linkedBrowser.isRemoteBrowser, "tab is remote");
+  }
+
+  let remotenessChangePromises = tabs.map(t => {
+    return BrowserTestUtils.waitForEvent(t, "TabRemotenessChange");
+  });
+
+  let tabsRevived = tabs.map(t => {
+    return promiseTabRestoring(t);
+  });
+
+  await BrowserTestUtils.crashFrame(tabs[0].linkedBrowser, false);
+  await Promise.all(remotenessChangePromises);
+  await Promise.all(tabsRevived);
+
+  // Both background tabs should now be in the pending restore
+  // state.
+  for (let tab of tabs) {
+    Assert.ok(!tab.linkedBrowser.isRemoteBrowser, "tab is not remote");
+    Assert.ok(!tab.linkedBrowser.hasAttribute("crashed"), "tab is not crashed");
+    Assert.ok(tab.hasAttribute("pending"), "tab is pending");
+  }
+}
+
+add_setup(async function () {
+  // We'll simplify by making sure we only ever one content process for this
+  // test.
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["dom.ipc.processCount", 1],
+      ["dom.ipc.processCount.webIsolated", 1],
+    ],
+  });
+
+  // On debug builds, crashing tabs results in much thinking, which
+  // slows down the test and results in intermittent test timeouts,
+  // so we'll pump up the expected timeout for this test.
+  requestLongerTimeout(5);
+});
+
+/**
+ * Tests that if a content process crashes taking down only
+ * background tabs, then the first of those tabs that the user
+ * selects will show the tab crash page, but the rest will restore
+ * on demand.
+ */
+add_task(async function test_background_crash_simple() {
+  await setupBackgroundTabs(async function ([tab1, tab2]) {
+    // Let's crash one of those background tabs now...
+    await crashBackgroundTabs([tab1, tab2]);
+
+    // Selecting the first tab should now send it to the tab crashed page.
+    let tabCrashedPagePromise = BrowserTestUtils.waitForContentEvent(
+      tab1.linkedBrowser,
+      "AboutTabCrashedReady",
+      false,
+      null,
+      true
+    );
+    await BrowserTestUtils.switchTab(gBrowser, tab1);
+    await tabCrashedPagePromise;
+
+    // Selecting the second tab should restore it.
+    let tabRestored = promiseTabRestored(tab2);
+    await BrowserTestUtils.switchTab(gBrowser, tab2);
+    await tabRestored;
+  });
+});
+
+/**
+ * Tests that if a content process crashes taking down only
+ * background tabs, and the user is configured to send backlogged
+ * crash reports automatically, that the tab crashed page is not
+ * shown.
+ */
+add_task(async function test_background_crash_autosubmit_backlogged() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.crashReports.unsubmittedCheck.autoSubmit2", true]],
+  });
+
+  await setupBackgroundTabs(async function ([tab1, tab2]) {
+    // Let's crash one of those background tabs now...
+    await crashBackgroundTabs([tab1, tab2]);
+
+    // Selecting the first tab should restore it.
+    let tabRestored = promiseTabRestored(tab1);
+    await BrowserTestUtils.switchTab(gBrowser, tab1);
+    await tabRestored;
+
+    // Selecting the second tab should restore it.
+    tabRestored = promiseTabRestored(tab2);
+    await BrowserTestUtils.switchTab(gBrowser, tab2);
+    await tabRestored;
+  });
+
+  await SpecialPowers.popPrefEnv();
+});
+
+/**
+ * Tests that if there are two background tab crashes in a row, that
+ * the two sets of background crashes don't interfere with one another.
+ *
+ * Specifically, if we start with two background tabs (1, 2) which crash,
+ * and we visit 1, 1 should go to the tab crashed page. If we then have
+ * two new background tabs (3, 4) crash, visiting 2 should still restore.
+ * Visiting 4 should show us the tab crashed page, and then visiting 3
+ * should restore.
+ */
+add_task(async function test_background_crash_multiple() {
+  let initialTab = gBrowser.selectedTab;
+
+  await setupBackgroundTabs(async function ([tab1, tab2]) {
+    // Let's crash one of those background tabs now...
+    await crashBackgroundTabs([tab1, tab2]);
+
+    // Selecting the first tab should now send it to the tab crashed page.
+    let tabCrashedPagePromise = BrowserTestUtils.waitForContentEvent(
+      tab1.linkedBrowser,
+      "AboutTabCrashedReady",
+      false,
+      null,
+      true
+    );
+    await BrowserTestUtils.switchTab(gBrowser, tab1);
+    await tabCrashedPagePromise;
+
+    // Now switch back to the original non-remote tab...
+    await BrowserTestUtils.switchTab(gBrowser, initialTab);
+
+    await setupBackgroundTabs(async function ([tab3, tab4]) {
+      await crashBackgroundTabs([tab3, tab4]);
+
+      // Selecting the second tab should restore it.
+      let tabRestored = promiseTabRestored(tab2);
+      await BrowserTestUtils.switchTab(gBrowser, tab2);
+      await tabRestored;
+
+      // Selecting the fourth tab should now send it to the tab crashed page.
+      tabCrashedPagePromise = BrowserTestUtils.waitForContentEvent(
+        tab4.linkedBrowser,
+        "AboutTabCrashedReady",
+        false,
+        null,
+        true
+      );
+      await BrowserTestUtils.switchTab(gBrowser, tab4);
+      await tabCrashedPagePromise;
+
+      // Selecting the third tab should restore it.
+      tabRestored = promiseTabRestored(tab3);
+      await BrowserTestUtils.switchTab(gBrowser, tab3);
+      await tabRestored;
+    });
+  });
+});
+
+// Tests that crashed preloaded tabs are removed and no unexpected errors are
+// thrown.
+add_task(async function test_preload_crash() {
+  if (!Services.prefs.getBoolPref("browser.newtab.preload")) {
+    return;
+  }
+
+  // Release any existing preloaded browser
+  NewTabPagePreloading.removePreloadedBrowser(window);
+
+  // Create a fresh preloaded browser
+  await BrowserTestUtils.maybeCreatePreloadedBrowser(gBrowser);
+
+  await BrowserTestUtils.crashFrame(gBrowser.preloadedBrowser, false);
+
+  Assert.ok(!gBrowser.preloadedBrowser);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_backup_recovery.js b/src/zen/tests/mochitests/sessionstore/browser_backup_recovery.js
new file mode 100644
index 000000000..238c41a41
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_backup_recovery.js
@@ -0,0 +1,308 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// This tests are for a sessionstore.js atomic backup.
+// Each test will wait for a write to the Session Store
+// before executing.
+
+const PREF_SS_INTERVAL = "browser.sessionstore.interval";
+const Paths = SessionFile.Paths;
+
+// Global variables that contain sessionstore.jsonlz4 and sessionstore.baklz4 data for
+// comparison between tests.
+var gSSData;
+var gSSBakData;
+
+function promiseRead(path) {
+  return IOUtils.readUTF8(path, { decompress: true });
+}
+
+async function reInitSessionFile() {
+  await SessionFile.wipe();
+  await SessionFile.read();
+}
+
+add_setup(async function () {
+  // Make sure that we are not racing with SessionSaver's time based
+  // saves.
+  Services.prefs.setIntPref(PREF_SS_INTERVAL, 10000000);
+  registerCleanupFunction(() => Services.prefs.clearUserPref(PREF_SS_INTERVAL));
+});
+
+add_task(async function test_creation() {
+  // Cancel all pending session saves so they won't get in our way.
+  SessionSaver.cancel();
+
+  // Create dummy sessionstore backups
+  let OLD_BACKUP = PathUtils.join(PathUtils.profileDir, "sessionstore.baklz4");
+  let OLD_UPGRADE_BACKUP = PathUtils.join(
+    PathUtils.profileDir,
+    "sessionstore.baklz4-0000000"
+  );
+
+  await IOUtils.writeUTF8(OLD_BACKUP, "sessionstore.bak");
+  await IOUtils.writeUTF8(OLD_UPGRADE_BACKUP, "sessionstore upgrade backup");
+
+  await reInitSessionFile();
+
+  // Ensure none of the sessionstore files and backups exists
+  for (let k of Paths.loadOrder) {
+    ok(
+      !(await IOUtils.exists(Paths[k])),
+      "After wipe " + k + " sessionstore file doesn't exist"
+    );
+  }
+  ok(
+    !(await IOUtils.exists(OLD_BACKUP)),
+    "After wipe, old backup doesn't exist"
+  );
+  ok(
+    !(await IOUtils.exists(OLD_UPGRADE_BACKUP)),
+    "After wipe, old upgrade backup doesn't exist"
+  );
+
+  // Open a new tab, save session, ensure that the correct files exist.
+  let URL_BASE =
+    "http://example.com/?atomic_backup_test_creation=" + Math.random();
+  let URL = URL_BASE + "?first_write";
+  let tab = BrowserTestUtils.addTab(gBrowser, URL);
+
+  info("Testing situation after a single write");
+  await promiseBrowserLoaded(tab.linkedBrowser);
+  await TabStateFlusher.flush(tab.linkedBrowser);
+  await SessionSaver.run();
+
+  ok(
+    await IOUtils.exists(Paths.recovery),
+    "After write, recovery sessionstore file exists again"
+  );
+  ok(
+    !(await IOUtils.exists(Paths.recoveryBackup)),
+    "After write, recoveryBackup sessionstore doesn't exist"
+  );
+  ok(
+    (await promiseRead(Paths.recovery)).includes(URL),
+    "Recovery sessionstore file contains the required tab"
+  );
+  ok(
+    !(await IOUtils.exists(Paths.clean)),
+    "After first write, clean shutdown " +
+      "sessionstore doesn't exist, since we haven't shutdown yet"
+  );
+
+  // Open a second tab, save session, ensure that the correct files exist.
+  info("Testing situation after a second write");
+  let URL2 = URL_BASE + "?second_write";
+  BrowserTestUtils.startLoadingURIString(tab.linkedBrowser, URL2);
+  await promiseBrowserLoaded(tab.linkedBrowser);
+  await TabStateFlusher.flush(tab.linkedBrowser);
+  await SessionSaver.run();
+
+  ok(
+    await IOUtils.exists(Paths.recovery),
+    "After second write, recovery sessionstore file still exists"
+  );
+  ok(
+    (await promiseRead(Paths.recovery)).includes(URL2),
+    "Recovery sessionstore file contains the latest url"
+  );
+  ok(
+    await IOUtils.exists(Paths.recoveryBackup),
+    "After write, recoveryBackup sessionstore now exists"
+  );
+  let backup = await promiseRead(Paths.recoveryBackup);
+  ok(!backup.includes(URL2), "Recovery backup doesn't contain the latest url");
+  ok(backup.includes(URL), "Recovery backup contains the original url");
+  ok(
+    !(await IOUtils.exists(Paths.clean)),
+    "After first write, clean shutdown " +
+      "sessionstore doesn't exist, since we haven't shutdown yet"
+  );
+
+  info("Reinitialize, ensure that we haven't leaked sensitive files");
+  await SessionFile.read(); // Reinitializes SessionFile
+  await SessionSaver.run();
+  ok(
+    !(await IOUtils.exists(Paths.clean)),
+    "After second write, clean shutdown " +
+      "sessionstore doesn't exist, since we haven't shutdown yet"
+  );
+  Assert.strictEqual(
+    Paths.upgradeBackup,
+    "",
+    "After second write, clean " +
+      "shutdown sessionstore doesn't exist, since we haven't shutdown yet"
+  );
+  ok(
+    !(await IOUtils.exists(Paths.nextUpgradeBackup)),
+    "After second write, clean " +
+      "shutdown sessionstore doesn't exist, since we haven't shutdown yet"
+  );
+
+  gBrowser.removeTab(tab);
+});
+
+var promiseSource = async function (name) {
+  let URL =
+    "http://example.com/?atomic_backup_test_recovery=" +
+    Math.random() +
+    "&name=" +
+    name;
+  let tab = BrowserTestUtils.addTab(gBrowser, URL);
+
+  await promiseBrowserLoaded(tab.linkedBrowser);
+  await TabStateFlusher.flush(tab.linkedBrowser);
+  await SessionSaver.run();
+  gBrowser.removeTab(tab);
+
+  let SOURCE = await promiseRead(Paths.recovery);
+  await SessionFile.wipe();
+  return SOURCE;
+};
+
+add_task(async function test_recovery() {
+  await reInitSessionFile();
+  info("Attempting to recover from the recovery file");
+
+  // Create Paths.recovery, ensure that we can recover from it.
+  let SOURCE = await promiseSource("Paths.recovery");
+  await IOUtils.makeDirectory(Paths.backups);
+  await IOUtils.writeUTF8(Paths.recovery, SOURCE, { compress: true });
+  is(
+    (await SessionFile.read()).source,
+    SOURCE,
+    "Recovered the correct source from the recovery file"
+  );
+
+  info("Corrupting recovery file, attempting to recover from recovery backup");
+  SOURCE = await promiseSource("Paths.recoveryBackup");
+  await IOUtils.makeDirectory(Paths.backups);
+  await IOUtils.writeUTF8(Paths.recoveryBackup, SOURCE, { compress: true });
+  await IOUtils.writeUTF8(Paths.recovery, "<Invalid JSON>", { compress: true });
+  is(
+    (await SessionFile.read()).source,
+    SOURCE,
+    "Recovered the correct source from the recovery file"
+  );
+});
+
+add_task(async function test_recovery_inaccessible() {
+  // Can't do chmod() on non-UNIX platforms, we need that for this test.
+  if (AppConstants.platform != "macosx" && AppConstants.platform != "linux") {
+    return;
+  }
+
+  await reInitSessionFile();
+  info(
+    "Making recovery file inaccessible, attempting to recover from recovery backup"
+  );
+  let SOURCE_RECOVERY = await promiseSource("Paths.recovery");
+  let SOURCE = await promiseSource("Paths.recoveryBackup");
+  await IOUtils.makeDirectory(Paths.backups);
+  await IOUtils.writeUTF8(Paths.recoveryBackup, SOURCE, { compress: true });
+
+  // Write a valid recovery file but make it inaccessible.
+  await IOUtils.writeUTF8(Paths.recovery, SOURCE_RECOVERY, { compress: true });
+  await IOUtils.setPermissions(Paths.recovery, 0);
+
+  is(
+    (await SessionFile.read()).source,
+    SOURCE,
+    "Recovered the correct source from the recovery file"
+  );
+  await IOUtils.setPermissions(Paths.recovery, 0o644);
+});
+
+add_task(async function test_clean() {
+  await reInitSessionFile();
+  let SOURCE = await promiseSource("Paths.clean");
+  await IOUtils.writeUTF8(Paths.clean, SOURCE, { compress: true });
+  await SessionFile.read();
+  await SessionSaver.run();
+  is(
+    await promiseRead(Paths.cleanBackup),
+    SOURCE,
+    "After first read/write, " +
+      "clean shutdown file has been moved to cleanBackup"
+  );
+});
+
+/**
+ * Tests loading of sessionstore when format version is known.
+ */
+add_task(async function test_version() {
+  info("Preparing sessionstore");
+  let SOURCE = await promiseSource("Paths.clean");
+
+  // Check there's a format version number
+  is(
+    JSON.parse(SOURCE).version[0],
+    "sessionrestore",
+    "Found sessionstore format version"
+  );
+
+  // Create Paths.clean file
+  await IOUtils.makeDirectory(Paths.backups);
+  await IOUtils.writeUTF8(Paths.clean, SOURCE, { compress: true });
+
+  info("Attempting to recover from the clean file");
+  // Ensure that we can recover from Paths.recovery
+  is(
+    (await SessionFile.read()).source,
+    SOURCE,
+    "Recovered the correct source from the clean file"
+  );
+});
+
+/**
+ * Tests fallback to previous backups if format version is unknown.
+ */
+add_task(async function test_version_fallback() {
+  await reInitSessionFile();
+  info("Preparing data, making sure that it has a version number");
+  let SOURCE = await promiseSource("Paths.clean");
+  let BACKUP_SOURCE = await promiseSource("Paths.cleanBackup");
+
+  is(
+    JSON.parse(SOURCE).version[0],
+    "sessionrestore",
+    "Found sessionstore format version"
+  );
+  is(
+    JSON.parse(BACKUP_SOURCE).version[0],
+    "sessionrestore",
+    "Found backup sessionstore format version"
+  );
+
+  await IOUtils.makeDirectory(Paths.backups);
+
+  info(
+    "Modifying format version number to something incorrect, to make sure that we disregard the file."
+  );
+  let parsedSource = JSON.parse(SOURCE);
+  parsedSource.version[0] = "bookmarks";
+  await IOUtils.writeJSON(Paths.clean, parsedSource, { compress: true });
+  await IOUtils.writeUTF8(Paths.cleanBackup, BACKUP_SOURCE, { compress: true });
+  is(
+    (await SessionFile.read()).source,
+    BACKUP_SOURCE,
+    "Recovered the correct source from the backup recovery file"
+  );
+
+  info(
+    "Modifying format version number to a future version, to make sure that we disregard the file."
+  );
+  parsedSource = JSON.parse(SOURCE);
+  parsedSource.version[1] = Number.MAX_SAFE_INTEGER;
+  await IOUtils.writeJSON(Paths.clean, parsedSource, { compress: true });
+  await IOUtils.writeUTF8(Paths.cleanBackup, BACKUP_SOURCE, { compress: true });
+  is(
+    (await SessionFile.read()).source,
+    BACKUP_SOURCE,
+    "Recovered the correct source from the backup recovery file"
+  );
+});
+
+add_task(async function cleanup() {
+  await reInitSessionFile();
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_bfcache_telemetry.js b/src/zen/tests/mochitests/sessionstore/browser_bfcache_telemetry.js
new file mode 100644
index 000000000..c1e987750
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_bfcache_telemetry.js
@@ -0,0 +1,44 @@
+const URL1 = "data:text/html;charset=utf-8,<body><p>Hello1</p></body>";
+const URL2 = "data:text/html;charset=utf-8,<body><p>Hello2</p></body>";
+
+async function getBFCacheComboTelemetry(probeInParent) {
+  let bfcacheCombo;
+  await TestUtils.waitForCondition(() => {
+    let histograms;
+    if (probeInParent) {
+      histograms = Services.telemetry.getSnapshotForHistograms(
+        "main",
+        false /* clear */
+      ).parent;
+    } else {
+      histograms = Services.telemetry.getSnapshotForHistograms(
+        "main",
+        false /* clear */
+      ).content;
+    }
+    bfcacheCombo = histograms.BFCACHE_COMBO;
+    return bfcacheCombo;
+  });
+  return bfcacheCombo;
+}
+
+async function test_bfcache_telemetry(probeInParent) {
+  Services.telemetry.getHistogramById("BFCACHE_COMBO").clear();
+
+  let tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, URL1);
+
+  BrowserTestUtils.startLoadingURIString(tab.linkedBrowser, URL2);
+  await BrowserTestUtils.browserLoaded(tab.linkedBrowser);
+
+  let bfcacheCombo = await getBFCacheComboTelemetry(probeInParent);
+
+  is(bfcacheCombo.values[0], 1, "1 bfcache success");
+
+  gBrowser.removeTab(tab);
+}
+
+add_task(async () => {
+  await test_bfcache_telemetry(
+    Services.prefs.getBoolPref("fission.bfcacheInParent")
+  );
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_broadcast.js b/src/zen/tests/mochitests/sessionstore/browser_broadcast.js
new file mode 100644
index 000000000..ed61fcb0c
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_broadcast.js
@@ -0,0 +1,162 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const INITIAL_VALUE = "browser_broadcast.js-initial-value-" + Date.now();
+
+/**
+ * This test ensures we won't lose tab data queued in the content script when
+ * closing a tab.
+ */
+add_task(async function flush_on_tabclose() {
+  let tab = await createTabWithStorageData(["http://example.com/"]);
+  let browser = tab.linkedBrowser;
+
+  await modifySessionStorage(browser, { test: "on-tab-close" });
+  await TabStateFlusher.flush(browser);
+  await promiseRemoveTabAndSessionState(tab);
+
+  let [
+    {
+      state: { storage },
+    },
+  ] = ss.getClosedTabDataForWindow(window);
+  is(
+    storage["http://example.com"].test,
+    "on-tab-close",
+    "sessionStorage data has been flushed on TabClose"
+  );
+});
+
+/**
+ * This test ensures we won't lose tab data queued in the content script when
+ * duplicating a tab.
+ */
+add_task(async function flush_on_duplicate() {
+  let tab = await createTabWithStorageData(["http://example.com/"]);
+  let browser = tab.linkedBrowser;
+
+  await modifySessionStorage(browser, { test: "on-duplicate" });
+  let tab2 = ss.duplicateTab(window, tab);
+  await promiseTabRestored(tab2);
+
+  await promiseRemoveTabAndSessionState(tab2);
+  let [
+    {
+      state: { storage },
+    },
+  ] = ss.getClosedTabDataForWindow(window);
+  is(
+    storage["http://example.com"].test,
+    "on-duplicate",
+    "sessionStorage data has been flushed when duplicating tabs"
+  );
+
+  gBrowser.removeTab(tab);
+});
+
+/**
+ * This test ensures we won't lose tab data queued in the content script when
+ * a window is closed.
+ */
+add_task(async function flush_on_windowclose() {
+  let win = await promiseNewWindow();
+  let tab = await createTabWithStorageData(["http://example.com/"], win);
+  let browser = tab.linkedBrowser;
+
+  await modifySessionStorage(browser, { test: "on-window-close" });
+  await BrowserTestUtils.closeWindow(win);
+
+  let [
+    {
+      tabs: [, { storage }],
+    },
+  ] = ss.getClosedWindowData();
+  is(
+    storage["http://example.com"].test,
+    "on-window-close",
+    "sessionStorage data has been flushed when closing a window"
+  );
+});
+
+/**
+ * This test ensures that stale tab data is ignored when reusing a tab
+ * (via e.g. setTabState) and does not overwrite the new data.
+ */
+add_task(async function flush_on_settabstate() {
+  let tab = await createTabWithStorageData(["http://example.com/"]);
+  let browser = tab.linkedBrowser;
+
+  // Flush to make sure our tab state is up-to-date.
+  await TabStateFlusher.flush(browser);
+
+  let state = ss.getTabState(tab);
+  await modifySessionStorage(browser, { test: "on-set-tab-state" });
+
+  // Flush all data contained in the content script but send it using
+  // asynchronous messages.
+  TabStateFlusher.flush(browser);
+
+  await promiseTabState(tab, state);
+
+  let { storage } = JSON.parse(ss.getTabState(tab));
+  is(
+    storage["http://example.com"].test,
+    INITIAL_VALUE,
+    "sessionStorage data has not been overwritten"
+  );
+
+  gBrowser.removeTab(tab);
+});
+
+/**
+ * This test ensures that we won't lose tab data that has been sent
+ * asynchronously just before closing a tab. Flushing must re-send all data
+ * that hasn't been received by chrome, yet.
+ */
+add_task(async function flush_on_tabclose_racy() {
+  let tab = await createTabWithStorageData(["http://example.com/"]);
+  let browser = tab.linkedBrowser;
+
+  // Flush to make sure we start with an empty queue.
+  await TabStateFlusher.flush(browser);
+
+  await modifySessionStorage(browser, { test: "on-tab-close-racy" });
+
+  // Flush all data contained in the content script but send it using
+  // asynchronous messages.
+  TabStateFlusher.flush(browser);
+  await promiseRemoveTabAndSessionState(tab);
+
+  let [
+    {
+      state: { storage },
+    },
+  ] = ss.getClosedTabDataForWindow(window);
+  is(
+    storage["http://example.com"].test,
+    "on-tab-close-racy",
+    "sessionStorage data has been merged correctly to prevent data loss"
+  );
+});
+
+function promiseNewWindow() {
+  return new Promise(resolve => {
+    whenNewWindowLoaded({ private: false }, resolve);
+  });
+}
+
+async function createTabWithStorageData(urls, win = window) {
+  let tab = BrowserTestUtils.addTab(win.gBrowser);
+  let browser = tab.linkedBrowser;
+
+  for (let url of urls) {
+    BrowserTestUtils.startLoadingURIString(browser, url);
+    await promiseBrowserLoaded(browser, true, url);
+    dump("Loaded url: " + url + "\n");
+    await modifySessionStorage(browser, { test: INITIAL_VALUE });
+  }
+
+  return tab;
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_capabilities.js b/src/zen/tests/mochitests/sessionstore/browser_capabilities.js
new file mode 100644
index 000000000..431cc36ab
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_capabilities.js
@@ -0,0 +1,90 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/**
+ * These tests ensures that disabling features by flipping nsIDocShell.allow*
+ * properties are (re)stored as disabled. Disallowed features must be
+ * re-enabled when the tab is re-used by another tab restoration.
+ */
+add_task(async function docshell_capabilities() {
+  let tab = await createTab();
+  let browser = tab.linkedBrowser;
+  let { browsingContext, docShell } = browser;
+
+  // Get the list of capabilities for docShells.
+  let flags = Object.keys(docShell).filter(k => k.startsWith("allow"));
+
+  // Check that everything is allowed by default for new tabs.
+  let state = JSON.parse(ss.getTabState(tab));
+  ok(!("disallow" in state), "everything allowed by default");
+  ok(
+    flags.every(f => docShell[f]),
+    "all flags set to true"
+  );
+
+  // Flip a couple of allow* flags.
+  docShell.allowImages = false;
+  docShell.allowMetaRedirects = false;
+  browsingContext.allowJavascript = false;
+
+  // Now reload the document to ensure that these capabilities
+  // are taken into account.
+  browser.reload();
+  await promiseBrowserLoaded(browser);
+
+  // Flush to make sure chrome received all data.
+  await TabStateFlusher.flush(browser);
+
+  // Check that we correctly save disallowed features.
+  let disallowedState = JSON.parse(ss.getTabState(tab));
+  let disallow = new Set(disallowedState.disallow.split(","));
+  ok(disallow.has("Images"), "images not allowed");
+  ok(disallow.has("MetaRedirects"), "meta redirects not allowed");
+  is(disallow.size, 2, "two capabilities disallowed");
+
+  // Reuse the tab to restore a new, clean state into it.
+  await promiseTabState(tab, {
+    entries: [{ url: "about:robots", triggeringPrincipal_base64 }],
+  });
+
+  // Flush to make sure chrome received all data.
+  await TabStateFlusher.flush(browser);
+
+  // After restoring disallowed features must be available again.
+  state = JSON.parse(ss.getTabState(tab));
+  ok(!("disallow" in state), "everything allowed again");
+  ok(
+    flags.every(f => docShell[f]),
+    "all flags set to true"
+  );
+
+  // Restore the state with disallowed features.
+  await promiseTabState(tab, disallowedState);
+
+  // Check that docShell flags are set.
+  ok(!docShell.allowImages, "images not allowed");
+  ok(!docShell.allowMetaRedirects, "meta redirects not allowed");
+
+  // Check that docShell allowJavascript flag is not set.
+  ok(browsingContext.allowJavascript, "Javascript still allowed");
+
+  // Check that we correctly restored features as disabled.
+  state = JSON.parse(ss.getTabState(tab));
+  disallow = new Set(state.disallow.split(","));
+  ok(disallow.has("Images"), "images not allowed anymore");
+  ok(disallow.has("MetaRedirects"), "meta redirects not allowed anymore");
+  ok(!disallow.has("Javascript"), "Javascript still allowed");
+  is(disallow.size, 2, "two capabilities disallowed");
+
+  // Clean up after ourselves.
+  gBrowser.removeTab(tab);
+});
+
+async function createTab() {
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:robots");
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+  return tab;
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_cleaner.js b/src/zen/tests/mochitests/sessionstore/browser_cleaner.js
new file mode 100644
index 000000000..b661591cb
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_cleaner.js
@@ -0,0 +1,252 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/*
+ * This test ensures that Session Restore eventually forgets about
+ * tabs and windows that have been closed a long time ago.
+ */
+
+"use strict";
+
+const LONG_TIME_AGO = 1;
+
+const URL_TAB1 =
+  "http://example.com/browser_cleaner.js?newtab1=" + Math.random();
+const URL_TAB2 =
+  "http://example.com/browser_cleaner.js?newtab2=" + Math.random();
+const URL_NEWGROUP =
+  "http://example.com/browser_cleaner.js?newgroup=" + Math.random();
+const URL_NEWWIN =
+  "http://example.com/browser_cleaner.js?newwin=" + Math.random();
+
+function isRecent(stamp) {
+  is(typeof stamp, "number", "This is a timestamp");
+  return Date.now() - stamp <= 60000;
+}
+
+function promiseCleanup() {
+  info("Cleaning up browser");
+
+  return promiseBrowserState(getClosedState());
+}
+
+function getClosedState() {
+  return Cu.cloneInto(CLOSED_STATE, {});
+}
+
+var CLOSED_STATE;
+
+add_setup(async function () {
+  forgetClosedWindows();
+  forgetClosedTabs(window);
+  forgetClosedTabGroups(window);
+});
+
+add_task(async function test_open_and_close() {
+  let newTab1 = BrowserTestUtils.addTab(gBrowser, URL_TAB1);
+  await promiseBrowserLoaded(newTab1.linkedBrowser);
+
+  let newTab2 = BrowserTestUtils.addTab(gBrowser, URL_TAB2);
+  await promiseBrowserLoaded(newTab2.linkedBrowser);
+
+  let newGroupTab = BrowserTestUtils.addTab(gBrowser, URL_NEWGROUP);
+  await promiseBrowserLoaded(newGroupTab.linkedBrowser);
+  let newGroup = gBrowser.addTabGroup([newGroupTab]);
+
+  let newWin = await promiseNewWindowLoaded();
+  let tab = BrowserTestUtils.addTab(newWin.gBrowser, URL_NEWWIN);
+
+  await promiseBrowserLoaded(tab.linkedBrowser);
+
+  await TabStateFlusher.flushWindow(window);
+  await TabStateFlusher.flushWindow(newWin);
+
+  info("1. Making sure that before closing, we don't have closedAt");
+  // For the moment, no "closedAt"
+  let state = JSON.parse(ss.getBrowserState());
+  is(
+    state.windows[0].closedAt || false,
+    false,
+    "1. Main window doesn't have closedAt"
+  );
+  is(
+    state.windows[1].closedAt || false,
+    false,
+    "1. Second window doesn't have closedAt"
+  );
+  is(
+    state.windows[0].tabs[0].closedAt || false,
+    false,
+    "1. First tab doesn't have closedAt"
+  );
+  is(
+    state.windows[0].tabs[1].closedAt || false,
+    false,
+    "1. Second tab doesn't have closedAt"
+  );
+  is(
+    state.windows[0].tabs[2].closedAt || false,
+    false,
+    "1. Grouped tab doesn't have closedAt"
+  );
+  is(
+    state.windows[0].groups[0].closedAt || false,
+    false,
+    "1. Group doesn't have closedAt"
+  );
+
+  info("2. Making sure that after closing, we have closedAt");
+
+  // Now close stuff, this should add closeAt
+  await BrowserTestUtils.closeWindow(newWin);
+  await promiseRemoveTabAndSessionState(newTab1);
+  await promiseRemoveTabAndSessionState(newTab2);
+
+  let removePromise = BrowserTestUtils.waitForEvent(
+    newGroup,
+    "TabGroupRemoved"
+  );
+  gBrowser.removeTabGroup(newGroup);
+  await removePromise;
+
+  state = CLOSED_STATE = JSON.parse(ss.getBrowserState());
+
+  is(
+    state.windows[0].closedAt || false,
+    false,
+    "2. Main window doesn't have closedAt"
+  );
+  ok(
+    isRecent(state._closedWindows[0].closedAt),
+    "2. Second window was closed recently"
+  );
+  ok(
+    isRecent(state.windows[0]._closedTabs[0].closedAt),
+    "2. First tab was closed recently"
+  );
+  ok(
+    isRecent(state.windows[0]._closedTabs[1].closedAt),
+    "2. Second tab was closed recently"
+  );
+  ok(
+    isRecent(state.windows[0].closedGroups[0].closedAt),
+    "2. Group was closed recently"
+  );
+});
+
+add_task(async function test_restore() {
+  info("3. Making sure that after restoring, we don't have closedAt");
+  await promiseBrowserState(CLOSED_STATE);
+
+  let newWin = ss.undoCloseWindow(0);
+  await promiseDelayedStartupFinished(newWin);
+
+  let newTab2 = ss.undoCloseTab(window, 0, window);
+  await promiseTabRestored(newTab2);
+
+  let newTab1 = ss.undoCloseTab(window, 0, window);
+  await promiseTabRestored(newTab1);
+
+  let state = JSON.parse(ss.getBrowserState());
+  is(
+    state.windows[0].closedAt || false,
+    false,
+    "3. Main window doesn't have closedAt"
+  );
+  is(
+    state.windows[1].closedAt || false,
+    false,
+    "3. Second window doesn't have closedAt"
+  );
+  is(
+    state.windows[0].tabs[0].closedAt || false,
+    false,
+    "3. First tab doesn't have closedAt"
+  );
+  is(
+    state.windows[0].tabs[1].closedAt || false,
+    false,
+    "3. Second tab doesn't have closedAt"
+  );
+
+  await BrowserTestUtils.closeWindow(newWin);
+  gBrowser.removeTab(newTab1);
+  gBrowser.removeTab(newTab2);
+});
+
+add_task(async function test_old_data() {
+  info(
+    "4. Removing closedAt from the sessionstore, making sure that it is added upon idle-daily"
+  );
+
+  let state = getClosedState();
+  delete state._closedWindows[0].closedAt;
+  delete state.windows[0]._closedTabs[0].closedAt;
+  delete state.windows[0]._closedTabs[1].closedAt;
+  delete state.windows[0].closedGroups[0].closedAt;
+  await promiseBrowserState(state);
+
+  info("Sending idle-daily");
+  Services.obs.notifyObservers(null, "idle-daily");
+  info("Sent idle-daily");
+
+  state = JSON.parse(ss.getBrowserState());
+  is(
+    state.windows[0].closedAt || false,
+    false,
+    "4. Main window doesn't have closedAt"
+  );
+  ok(
+    isRecent(state._closedWindows[0].closedAt),
+    "4. Second window was closed recently"
+  );
+  ok(
+    isRecent(state.windows[0]._closedTabs[0].closedAt),
+    "4. First tab was closed recently"
+  );
+  ok(
+    isRecent(state.windows[0]._closedTabs[1].closedAt),
+    "4. Second tab was closed recently"
+  );
+  ok(
+    isRecent(state.windows[0].closedGroups[0].closedAt),
+    "4. Group was closed recently"
+  );
+  await promiseCleanup();
+});
+
+add_task(async function test_cleanup() {
+  info(
+    "5. Altering closedAt to an old date, making sure that stuff gets collected, eventually"
+  );
+  await promiseCleanup();
+
+  let state = getClosedState();
+  state._closedWindows[0].closedAt = LONG_TIME_AGO;
+  state.windows[0]._closedTabs[0].closedAt = LONG_TIME_AGO;
+  state.windows[0].closedGroups[0].closedAt = LONG_TIME_AGO;
+  state.windows[0]._closedTabs[1].closedAt = Date.now();
+  let url = state.windows[0]._closedTabs[1].state.entries[0].url;
+
+  await promiseBrowserState(state);
+
+  info("Sending idle-daily");
+  Services.obs.notifyObservers(null, "idle-daily");
+  info("Sent idle-daily");
+
+  state = JSON.parse(ss.getBrowserState());
+  is(state._closedWindows[0], undefined, "5. Second window was forgotten");
+  is(state.windows[0].closedGroups[0], undefined, "5. Tab group was forgotten");
+
+  is(state.windows[0]._closedTabs.length, 1, "5. Only one closed tab left");
+  is(
+    state.windows[0]._closedTabs[0].state.entries[0].url,
+    url,
+    "5. The second tab is still here"
+  );
+
+  await promiseCleanup();
+
+  // Cleanup closed tab group
+  forgetClosedTabGroups(window);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_closedId.js b/src/zen/tests/mochitests/sessionstore/browser_closedId.js
new file mode 100644
index 000000000..4a993fe6d
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_closedId.js
@@ -0,0 +1,109 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const BACKUP_STATE = SessionStore.getBrowserState();
+
+async function add_new_tab(URL) {
+  let tab = BrowserTestUtils.addTab(gBrowser, URL);
+  await BrowserTestUtils.browserLoaded(tab.linkedBrowser);
+  return tab;
+}
+
+add_task(async function test_closedId_order() {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["browser.sessionstore.restore_on_demand", true],
+      ["browser.sessionstore.restore_tabs_lazily", true],
+    ],
+  });
+  // reset to 0
+  SessionStore.resetNextClosedId();
+  await promiseBrowserState({
+    windows: [
+      {
+        selected: 1, // SessionStore uses 1-based indexing.
+        tabs: [
+          {
+            entries: [],
+          },
+        ],
+        _closedTabs: [
+          {
+            state: {
+              entries: [
+                {
+                  url: "https://www.example.com/",
+                  triggeringPrincipal_base64,
+                },
+              ],
+              selected: 1,
+            },
+            closedId: 0,
+            closedAt: Date.now() - 100,
+            title: "Example",
+          },
+          {
+            state: {
+              entries: [
+                {
+                  url: "about:mozilla",
+                  triggeringPrincipal_base64,
+                },
+              ],
+            },
+            closedId: 1,
+            closedAt: Date.now() - 50,
+            title: "about:mozilla",
+          },
+          {
+            state: {
+              entries: [
+                {
+                  url: "https://www.example.net/",
+                  triggeringPrincipal_base64,
+                },
+              ],
+            },
+            closedId: 2,
+            closedAt: Date.now(),
+            title: "Example",
+          },
+        ],
+      },
+    ],
+  });
+
+  let tab = await add_new_tab("about:firefoxview");
+
+  is(
+    SessionStore.getClosedTabCountForWindow(window),
+    3,
+    "Closed tab count after restored session is 3"
+  );
+
+  let initialClosedId =
+    SessionStore.getClosedTabDataForWindow(window)[0].closedId;
+
+  // If this fails, that means one of the closedId's in the stubbed data in this test needs to be updated
+  // to reflect what the initial closedId is when a new tab is open and closed (which may change as more tests
+  // for session store are added here). You can manually verify a change to stubbed data by commenting out
+  // this._resetClosedTabsIds in SessionStore.sys.mjs temporarily and then the "Each tab has a unique closedId" case should fail.
+  is(initialClosedId, 0, "Initial closedId is 0");
+
+  await openAndCloseTab(window, "about:robots"); // closedId should be higher than the ones we just restored.
+
+  let closedData = SessionStore.getClosedTabDataForWindow(window);
+  is(closedData.length, 4, "Should have data for 4 closed tabs.");
+  is(
+    new Set(closedData.map(t => t.closedId)).size,
+    4,
+    "Each tab has a unique closedId"
+  );
+
+  BrowserTestUtils.removeTab(tab);
+
+  // Clean up for the next task.
+  await promiseBrowserState(BACKUP_STATE);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_closed_objects_changed_notifications_tabs.js b/src/zen/tests/mochitests/sessionstore/browser_closed_objects_changed_notifications_tabs.js
new file mode 100644
index 000000000..e6050998f
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_closed_objects_changed_notifications_tabs.js
@@ -0,0 +1,138 @@
+"use strict";
+
+/**
+ * This test is for the sessionstore-closed-objects-changed notifications.
+ */
+
+const MAX_TABS_UNDO_PREF = "browser.sessionstore.max_tabs_undo";
+const TOPIC = "sessionstore-closed-objects-changed";
+
+let notificationsCount = 0;
+
+async function openWindow(url) {
+  let win = await promiseNewWindowLoaded();
+  let flags = Ci.nsIWebNavigation.LOAD_FLAGS_REPLACE_HISTORY;
+  BrowserTestUtils.startLoadingURIString(win.gBrowser.selectedBrowser, url, {
+    flags,
+  });
+  await promiseBrowserLoaded(win.gBrowser.selectedBrowser, true, url);
+  return win;
+}
+
+async function closeWindow(win) {
+  await awaitNotification(() => BrowserTestUtils.closeWindow(win));
+}
+
+async function openAndCloseWindow(url) {
+  let win = await openWindow(url);
+  await closeWindow(win);
+}
+
+async function openTab(window, url) {
+  let tab = await BrowserTestUtils.openNewForegroundTab(window.gBrowser, url);
+  await TabStateFlusher.flush(tab.linkedBrowser);
+  return tab;
+}
+
+async function openAndCloseTab(window, url) {
+  let tab = await openTab(window, url);
+  await promiseRemoveTabAndSessionState(tab);
+}
+
+function countingObserver() {
+  notificationsCount++;
+}
+
+function assertNotificationCount(count) {
+  is(
+    notificationsCount,
+    count,
+    "The expected number of notifications was received."
+  );
+}
+
+async function awaitNotification(callback) {
+  let notification = TestUtils.topicObserved(TOPIC);
+  executeSoon(callback);
+  await notification;
+}
+
+add_task(async function test_closedObjectsChangedNotifications() {
+  // Create a closed window so that when we do the purge we can expect a notification.
+  await openAndCloseWindow("about:robots");
+
+  // Forget any previous closed windows or tabs from other tests that may have
+  // run in the same session.
+  await awaitNotification(() =>
+    Services.obs.notifyObservers(null, "browser:purge-session-history")
+  );
+
+  // Add an observer to count the number of notifications.
+  Services.obs.addObserver(countingObserver, TOPIC);
+
+  // Open a new window.
+  let win = await openWindow("about:robots");
+
+  info("Opening and closing a tab.");
+  await openAndCloseTab(win, "about:mozilla");
+  assertNotificationCount(1);
+
+  info("Opening and closing a second tab.");
+  await openAndCloseTab(win, "about:mozilla");
+  assertNotificationCount(2);
+
+  info(`Changing the ${MAX_TABS_UNDO_PREF} pref.`);
+  registerCleanupFunction(function () {
+    Services.prefs.clearUserPref(MAX_TABS_UNDO_PREF);
+  });
+  await awaitNotification(() =>
+    Services.prefs.setIntPref(MAX_TABS_UNDO_PREF, 1)
+  );
+  assertNotificationCount(3);
+
+  info("Undoing close of remaining closed tab.");
+  let tab = SessionStore.undoCloseTab(win, 0);
+  await promiseTabRestored(tab);
+  assertNotificationCount(4);
+
+  info("Closing tab again.");
+  await promiseRemoveTabAndSessionState(tab);
+  assertNotificationCount(5);
+
+  info("Purging session history.");
+  await awaitNotification(() =>
+    Services.obs.notifyObservers(null, "browser:purge-session-history")
+  );
+  assertNotificationCount(6);
+
+  info("Opening and closing another tab.");
+  await openAndCloseTab(win, "http://example.com/");
+  assertNotificationCount(7);
+
+  info("Purging domain data with no matches.");
+  Services.obs.notifyObservers(
+    null,
+    "browser:purge-session-history-for-domain",
+    "mozilla.com"
+  );
+  assertNotificationCount(7);
+
+  info("Purging domain data with matches.");
+  await awaitNotification(() =>
+    Services.obs.notifyObservers(
+      null,
+      "browser:purge-session-history-for-domain",
+      "example.com"
+    )
+  );
+  assertNotificationCount(8);
+
+  info("Opening and closing another tab.");
+  await openAndCloseTab(win, "http://example.com/");
+  assertNotificationCount(9);
+
+  await closeWindow(win);
+  assertNotificationCount(10);
+
+  Services.obs.removeObserver(countingObserver, TOPIC);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_closed_objects_changed_notifications_windows.js b/src/zen/tests/mochitests/sessionstore/browser_closed_objects_changed_notifications_windows.js
new file mode 100644
index 000000000..c2768ed24
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_closed_objects_changed_notifications_windows.js
@@ -0,0 +1,131 @@
+"use strict";
+
+/**
+ * This test is for the sessionstore-closed-objects-changed notifications.
+ */
+
+requestLongerTimeout(2);
+
+const MAX_WINDOWS_UNDO_PREF = "browser.sessionstore.max_windows_undo";
+const TOPIC = "sessionstore-closed-objects-changed";
+
+let notificationsCount = 0;
+
+async function openWindow(url) {
+  let win = await promiseNewWindowLoaded();
+  let flags = Ci.nsIWebNavigation.LOAD_FLAGS_REPLACE_HISTORY;
+  BrowserTestUtils.startLoadingURIString(win.gBrowser.selectedBrowser, url, {
+    flags,
+  });
+  await promiseBrowserLoaded(win.gBrowser.selectedBrowser, true, url);
+  return win;
+}
+
+async function closeWindow(win) {
+  await awaitNotification(() => BrowserTestUtils.closeWindow(win));
+}
+
+async function openAndCloseWindow(url) {
+  let win = await openWindow(url);
+  await closeWindow(win);
+}
+
+function countingObserver() {
+  notificationsCount++;
+}
+
+function assertNotificationCount(count) {
+  is(
+    notificationsCount,
+    count,
+    "The expected number of notifications was received."
+  );
+}
+
+async function awaitNotification(callback) {
+  let notification = TestUtils.topicObserved(TOPIC);
+  executeSoon(callback);
+  await notification;
+}
+
+add_task(async function test_closedObjectsChangedNotifications() {
+  // Create a closed window so that when we do the purge we know to expect a notification
+  await openAndCloseWindow("about:robots");
+
+  // Forget any previous closed windows or tabs from other tests that may have
+  // run in the same session.
+  await awaitNotification(() =>
+    Services.obs.notifyObservers(null, "browser:purge-session-history")
+  );
+
+  // Add an observer to count the number of notifications.
+  Services.obs.addObserver(countingObserver, TOPIC);
+
+  info("Opening and closing initial window.");
+  await openAndCloseWindow("about:robots");
+  assertNotificationCount(1);
+
+  // Store state with a single closed window for use in later tests.
+  let closedState = Cu.cloneInto(JSON.parse(ss.getBrowserState()), {});
+
+  info("Undoing close of initial window.");
+  let win = SessionStore.undoCloseWindow(0);
+  await promiseDelayedStartupFinished(win);
+  assertNotificationCount(2);
+
+  // Open a second window.
+  let win2 = await openWindow("about:mozilla");
+
+  info("Closing both windows.");
+  await closeWindow(win);
+  assertNotificationCount(3);
+  await closeWindow(win2);
+  assertNotificationCount(4);
+
+  info(`Changing the ${MAX_WINDOWS_UNDO_PREF} pref.`);
+  registerCleanupFunction(function () {
+    Services.prefs.clearUserPref(MAX_WINDOWS_UNDO_PREF);
+  });
+  await awaitNotification(() =>
+    Services.prefs.setIntPref(MAX_WINDOWS_UNDO_PREF, 1)
+  );
+  assertNotificationCount(5);
+
+  info("Forgetting a closed window.");
+  await awaitNotification(() => SessionStore.forgetClosedWindow());
+  assertNotificationCount(6);
+
+  info("Opening and closing another window.");
+  await openAndCloseWindow("about:robots");
+  assertNotificationCount(7);
+
+  info("Setting browser state to trigger change onIdleDaily.");
+  let state = Cu.cloneInto(JSON.parse(ss.getBrowserState()), {});
+  state._closedWindows[0].closedAt = 1;
+  await promiseBrowserState(state);
+  assertNotificationCount(8);
+
+  info("Sending idle-daily");
+  await awaitNotification(() =>
+    Services.obs.notifyObservers(null, "idle-daily")
+  );
+  assertNotificationCount(9);
+
+  info("Opening and closing another window.");
+  await openAndCloseWindow("about:robots");
+  assertNotificationCount(10);
+
+  info("Purging session history.");
+  await awaitNotification(() =>
+    Services.obs.notifyObservers(null, "browser:purge-session-history")
+  );
+  assertNotificationCount(11);
+
+  info("Setting window state.");
+  win = await openWindow("about:mozilla");
+  await awaitNotification(() => SessionStore.setWindowState(win, closedState));
+  assertNotificationCount(12);
+
+  Services.obs.removeObserver(countingObserver, TOPIC);
+  await BrowserTestUtils.closeWindow(win);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_closed_tabs_closed_windows.js b/src/zen/tests/mochitests/sessionstore/browser_closed_tabs_closed_windows.js
new file mode 100644
index 000000000..0a2f4194a
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_closed_tabs_closed_windows.js
@@ -0,0 +1,310 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+const { TelemetryTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/TelemetryTestUtils.sys.mjs"
+);
+const TEST_URLS = [
+  "http://mochi.test:8888/browser/",
+  "https://www.example.com/",
+  "https://example.net/",
+  "https://example.org/",
+  "about:mozilla",
+  "about:robots",
+];
+const TOPIC_CLOSED_OBJECTS_CHANGED = "sessionstore-closed-objects-changed";
+var preparedClosedIds;
+
+add_setup(async function testSetup() {
+  registerCleanupFunction(async () => {
+    await promiseAllButPrimaryWindowClosed();
+    Services.obs.notifyObservers(null, "browser:purge-session-history");
+  });
+  preparedClosedIds = await prepareClosedData();
+  SimpleTest.promiseFocus(window);
+});
+
+async function prepareClosedData() {
+  // prepare some closed state
+  let closedIds = {};
+  await openAndCloseTab(window, TEST_URLS[0]);
+  closedIds.tab0 = SessionStore.getClosedTabDataForWindow(window)[0].closedId;
+
+  const testWindow1 = await BrowserTestUtils.openNewBrowserWindow();
+  // open a non-transitory, worth-keeping tab to ensure window data is saved on close
+  await BrowserTestUtils.openNewForegroundTab(
+    testWindow1.gBrowser,
+    "about:mozilla"
+  );
+  await openAndCloseTab(testWindow1, TEST_URLS[1]);
+  closedIds.tab1 =
+    SessionStore.getClosedTabDataForWindow(testWindow1)[0].closedId;
+
+  const testWindow2 = await BrowserTestUtils.openNewBrowserWindow();
+  // open a non-transitory, worth-keeping tab to ensure window data is saved on close
+  await BrowserTestUtils.openNewForegroundTab(
+    testWindow2.gBrowser,
+    "about:mozilla"
+  );
+  await openAndCloseTab(testWindow2, TEST_URLS[2]);
+  closedIds.tab2 =
+    SessionStore.getClosedTabDataForWindow(testWindow2)[0].closedId;
+  await openAndCloseTab(testWindow2, TEST_URLS[3]);
+  closedIds.tab3 =
+    SessionStore.getClosedTabDataForWindow(testWindow2)[0].closedId;
+
+  const testWindow3 = await BrowserTestUtils.openNewBrowserWindow();
+  // open a non-transitory, worth-keeping tab to ensure window data is saved on close
+  await BrowserTestUtils.openNewForegroundTab(
+    testWindow3.gBrowser,
+    "about:mozilla"
+  );
+  await openAndCloseTab(testWindow3, TEST_URLS[4]);
+  closedIds.tab4 =
+    SessionStore.getClosedTabDataForWindow(testWindow3)[0].closedId;
+
+  // open a private window
+  const privateWin = await BrowserTestUtils.openNewBrowserWindow({
+    private: true,
+  });
+  // open a non-transitory, worth-keeping tab to ensure window data is saved on close
+  await BrowserTestUtils.openNewForegroundTab(
+    privateWin.gBrowser,
+    "about:mozilla"
+  );
+  await openAndCloseTab(privateWin, TEST_URLS[5]);
+  closedIds.tab5 =
+    SessionStore.getClosedTabDataForWindow(privateWin)[0].closedId;
+
+  const testWindow6 = await BrowserTestUtils.openNewBrowserWindow();
+
+  const testWindow7 = await BrowserTestUtils.openNewBrowserWindow();
+  await openAndCloseTab(testWindow7, TEST_URLS[4]);
+
+  await BrowserTestUtils.closeWindow(testWindow1);
+  closedIds.testWindow1 = SessionStore.getClosedWindowData()[0].closedId;
+  await BrowserTestUtils.closeWindow(testWindow2);
+
+  closedIds.testWindow2 = SessionStore.getClosedWindowData()[0].closedId;
+  await BrowserTestUtils.closeWindow(testWindow3);
+
+  closedIds.testWindow3 = SessionStore.getClosedWindowData()[0].closedId;
+  await BrowserTestUtils.closeWindow(privateWin);
+  Assert.greater(
+    closedIds.testWindow2,
+    closedIds.testWindow1,
+    "We got the closedIds in the expected order"
+  );
+
+  await BrowserTestUtils.closeWindow(testWindow6);
+  await BrowserTestUtils.closeWindow(testWindow7);
+  return closedIds;
+}
+
+// The tasks need to be run sequentially. They are broken up so the different functions
+// under test and any stack traces are easier to find
+
+add_task(async function get_closed_tabs_from_closed_windows() {
+  Assert.equal(
+    SessionStore.getClosedTabCount({ closedTabsFromClosedWindows: false }),
+    1,
+    "Expected closed tab count (in currently-open windows only)"
+  );
+  Assert.equal(
+    SessionStore.getClosedTabCount(),
+    5,
+    "Expected closed tab count (in currently-open and closed windows)"
+  );
+  // We dont keep the closed tab from the private window
+  Assert.equal(
+    SessionStore.getClosedTabCountFromClosedWindows(),
+    4,
+    "Expected closed tab count (from closed windows)"
+  );
+
+  // Closed tabs from closed windows aren't included in the list from getClosedTabData()
+  Assert.deepEqual(
+    SessionStore.getClosedTabData().map(td => td.state.entries[0].url),
+    ["http://mochi.test:8888/browser/"],
+    "Matched closed tab data from currently open windows"
+  );
+
+  // Closed tabs from open windows or closed private windows aren't included in the list
+  // from getClosedTabDataFromClosedWindows()
+  Assert.deepEqual(
+    SessionStore.getClosedTabDataFromClosedWindows().map(
+      td => td.state.entries[0].url
+    ),
+    [
+      "about:mozilla",
+      "https://example.org/",
+      "https://example.net/",
+      "https://www.example.com/",
+    ],
+    "Matched closed tab data from currently closed windows"
+  );
+});
+
+add_task(async function forget_closed_tabs_from_closed_windows() {
+  // forget the most recent tab we closed in testWindow1
+  let closedObjectsChanged = TestUtils.topicObserved(
+    TOPIC_CLOSED_OBJECTS_CHANGED
+  );
+  info(
+    "Calling forgetClosedTab with window sourceClosedId: " +
+      preparedClosedIds.testWindow1
+  );
+  SessionStore.forgetClosedTab(
+    { sourceClosedId: preparedClosedIds.testWindow1 },
+    0
+  );
+  await closedObjectsChanged;
+  Assert.deepEqual(
+    SessionStore.getClosedTabDataFromClosedWindows().map(
+      td => td.state.entries[0].url
+    ),
+    [
+      "about:mozilla",
+      "https://example.org/",
+      "https://example.net/",
+      // "https://www.example.com/" from testWindow1 was forgotten and should be removed
+    ],
+    "Closed tab forgotten"
+  );
+
+  // forget a closed window that had closed tabs
+  let closedTabCount = SessionStore.getClosedTabCountFromClosedWindows();
+  closedObjectsChanged = TestUtils.topicObserved(TOPIC_CLOSED_OBJECTS_CHANGED);
+  SessionStore.forgetClosedWindowById(preparedClosedIds.testWindow3);
+  await closedObjectsChanged;
+  Assert.equal(
+    SessionStore.getClosedTabCountFromClosedWindows(),
+    closedTabCount - 1,
+    "The closed tab is gone when we forget the closed window it was in"
+  );
+});
+
+add_task(async function expected_exceptions_closed_tabs_from_closed_windows() {
+  // testWindow3 was forgotten, attempting to undoClose its tabs should throw
+  Assert.throws(
+    () =>
+      SessionStore.undoClosedTabFromClosedWindow(
+        { sourceClosedId: preparedClosedIds.testWindow3 },
+        preparedClosedIds.tab4
+      ),
+    /NS_ERROR_ILLEGAL_VALUE/,
+    "Invalid window or source for undoClosedTabFromClosedWindow throws"
+  );
+  // tab1 was forgotten, attempting to undoClose it should throw
+  Assert.throws(
+    () =>
+      SessionStore.undoClosedTabFromClosedWindow(
+        { sourceClosedId: preparedClosedIds.testWindow1 },
+        preparedClosedIds.tab1
+      ),
+    /NS_ERROR_ILLEGAL_VALUE/,
+    "Invalid tab closedId for undoClosedTabFromClosedWindow throws"
+  );
+
+  // testWindow3 was forgotten, attempting to forget its tabs should throw
+  Assert.throws(
+    () =>
+      SessionStore.forgetClosedTab(
+        { sourceClosedId: preparedClosedIds.testWindow3 },
+        preparedClosedIds.tab4
+      ),
+    /NS_ERROR_ILLEGAL_VALUE/,
+    "Invalid window or source for forgetClosedTab throws"
+  );
+
+  // tab1 was forgotten, attempting to forget it again should throw
+  Assert.throws(
+    () =>
+      SessionStore.undoClosedTabFromClosedWindow(
+        { sourceClosedId: preparedClosedIds.testWindow3 },
+        preparedClosedIds.tab4
+      ),
+    /NS_ERROR_ILLEGAL_VALUE/,
+    "Invalid window for undoClosedTabFromClosedWindow throws"
+  );
+});
+
+add_task(async function undo_closed_tabs_from_closed_windows() {
+  const openTabsCount = gBrowser.tabs.length;
+
+  // undo most recently closed tab from a closed window using a window closedId
+  let closedObjectsChanged = TestUtils.topicObserved(
+    TOPIC_CLOSED_OBJECTS_CHANGED
+  );
+  let restoredTab1 = SessionStore.undoCloseTab(
+    { sourceClosedId: preparedClosedIds.testWindow2 },
+    0,
+    window
+  );
+  await BrowserTestUtils.waitForEvent(
+    window.gBrowser.tabContainer,
+    "SSTabRestored"
+  );
+  await closedObjectsChanged;
+  Assert.equal(
+    window.gBrowser.tabs.length,
+    openTabsCount + 1,
+    "The closed tab was restored"
+  );
+  Assert.equal(
+    restoredTab1.linkedBrowser.currentURI.spec,
+    "https://example.org/",
+    "The re-opened tab had the expected URL"
+  );
+  Assert.deepEqual(
+    SessionStore.getClosedTabDataFromClosedWindows().map(
+      td => td.state.entries[0].url
+    ),
+    [
+      "https://example.net/",
+      // "https://example.org/" from testWindow2 got reopened and should be removed
+    ],
+    "Re-opened tabs not listed in closed tabs"
+  );
+
+  // use undoClosedTabFromClosedWindows to reference the closed tab by closedId
+  closedObjectsChanged = TestUtils.topicObserved(TOPIC_CLOSED_OBJECTS_CHANGED);
+  let restoredTab2 = SessionStore.undoClosedTabFromClosedWindow(
+    { sourceClosedId: preparedClosedIds.testWindow2 },
+    preparedClosedIds.tab2,
+    window
+  );
+  await BrowserTestUtils.waitForEvent(
+    window.gBrowser.tabContainer,
+    "SSTabRestored"
+  );
+  await closedObjectsChanged;
+  Assert.equal(
+    window.gBrowser.tabs.length,
+    openTabsCount + 2,
+    "The closed tab was restored"
+  );
+  Assert.equal(
+    restoredTab2.linkedBrowser.currentURI.spec,
+    "https://example.net/",
+    "The re-opened tab had the expected URL"
+  );
+
+  Assert.deepEqual(
+    SessionStore.getClosedTabDataFromClosedWindows().map(
+      td => td.state.entries[0].url
+    ),
+    [
+      // "https://example.org/" from testWindow2 got reopened and should be removed
+    ],
+    "Re-opened tabs not listed in closed tabs"
+  );
+
+  // clean up the re-opened tabs
+  for (let tab of [restoredTab1, restoredTab2]) {
+    await TabStateFlusher.flush(tab.linkedBrowser);
+    let sessionUpdatePromise = BrowserTestUtils.waitForSessionStoreUpdate(tab);
+    BrowserTestUtils.removeTab(tab);
+    await sessionUpdatePromise;
+  }
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_closed_tabs_windows.js b/src/zen/tests/mochitests/sessionstore/browser_closed_tabs_windows.js
new file mode 100644
index 000000000..203c8c8d9
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_closed_tabs_windows.js
@@ -0,0 +1,337 @@
+const ORIG_STATE = ss.getBrowserState();
+
+const multiWindowState = {
+  windows: [
+    {
+      tabs: [
+        {
+          entries: [
+            {
+              url: "https://example.com#win-0-tab-0",
+              triggeringPrincipal_base64,
+            },
+          ],
+        },
+      ],
+      _closedTabs: [
+        {
+          state: {
+            entries: [
+              {
+                url: "https://example.com#win-0-closed-0",
+                triggeringPrincipal_base64,
+              },
+            ],
+          },
+        },
+        {
+          state: {
+            entries: [
+              {
+                url: "https://example.com#win-0-closed-1",
+                triggeringPrincipal_base64,
+              },
+            ],
+          },
+        },
+      ],
+      selected: 1,
+    },
+    {
+      tabs: [
+        {
+          entries: [
+            {
+              url: "https://example.org#win-1-tab-0",
+              triggeringPrincipal_base64,
+            },
+          ],
+        },
+        {
+          entries: [
+            {
+              url: "https://example.org#win-1-tab-1",
+              triggeringPrincipal_base64,
+            },
+          ],
+        },
+      ],
+      _closedTabs: [
+        {
+          state: {
+            entries: [
+              {
+                url: "https://example.org#win-1-closed-0",
+                triggeringPrincipal_base64,
+              },
+            ],
+          },
+        },
+      ],
+      selected: 1,
+    },
+  ],
+  _closedWindows: [
+    {
+      tabs: [
+        {
+          entries: [
+            {
+              url: "https://example.org#closedWin-0-tab-0",
+              triggeringPrincipal_base64,
+            },
+          ],
+        },
+      ],
+      _closedTabs: [
+        {
+          state: {
+            entries: [
+              {
+                url: "https://example.org##closedWin-0-closed-0",
+                triggeringPrincipal_base64,
+              },
+            ],
+          },
+        },
+      ],
+    },
+  ],
+};
+
+add_setup(async function testSetup() {
+  await SessionStoreTestUtils.promiseBrowserState(multiWindowState);
+});
+
+add_task(async function test_ClosedTabMethods() {
+  let sessionStoreUpdated;
+  const browserWindows = BrowserWindowTracker.orderedWindows;
+  Assert.equal(
+    browserWindows.length,
+    multiWindowState.windows.length,
+    `We expect ${multiWindowState.windows} open browser windows`
+  );
+  info(
+    `After setup, current tab URI: ${browserWindows[0].gBrowser.currentURI.spec}`
+  );
+  Assert.equal(
+    browserWindows[0].gBrowser.currentURI.spec,
+    "https://example.com/#win-0-tab-0",
+    "The first tab of the first window we restored is current"
+  );
+
+  for (let idx = 0; idx < browserWindows.length; idx++) {
+    const win = browserWindows[idx];
+    const winData = multiWindowState.windows[idx];
+    info(`window ${idx}: ${win.gBrowser.selectedBrowser.currentURI.spec}`);
+    Assert.equal(
+      winData._closedTabs.length,
+      SessionStore.getClosedTabDataForWindow(win).length,
+      `getClosedTabDataForWindow() for open window ${idx} returned the expected number of objects`
+    );
+  }
+
+  let closedCount;
+  closedCount = SessionStore.getClosedTabCountForWindow(browserWindows[0]);
+  Assert.equal(2, closedCount, "2 closed tab for this window");
+
+  closedCount = SessionStore.getClosedTabCountForWindow(browserWindows[1]);
+  Assert.equal(1, closedCount, "1 closed tab for this window");
+
+  closedCount = SessionStore.getClosedTabCount();
+  // 3 closed tabs from open windows, 1 closed tab from the closed window
+  Assert.equal(4, closedCount, "4 closed tab for all windows");
+
+  let allWindowsClosedTabs = SessionStore.getClosedTabData();
+  Assert.equal(
+    SessionStore.getClosedTabCount({ closedTabsFromClosedWindows: false }),
+    allWindowsClosedTabs.length,
+    "getClosedTabData returned the correct number of entries"
+  );
+  for (let tabData of allWindowsClosedTabs) {
+    Assert.ok(tabData.sourceWindowId, "each tab has a sourceWindowId property");
+  }
+
+  closedCount = SessionStore.getClosedTabCountFromClosedWindows();
+  Assert.equal(1, closedCount, "1 closed tabs from closed windows");
+
+  // ***********************************
+  info("check with the all-windows pref off");
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.sessionstore.closedTabsFromAllWindows", false]],
+  });
+
+  info("With this pref off, the closed tab count is that of the top window");
+  closedCount = SessionStore.getClosedTabCount({
+    closedTabsFromClosedWindows: false,
+  }); // Equivalent to SS.getClosedTabCountForWindow(browserWindows[0]),
+  Assert.equal(closedCount, 2, `2 closed tabs from the top (first) window`);
+  Assert.equal(
+    SessionStore.getClosedTabCount(), // includes closed tabs from closed windows, but only the top open window
+    3,
+    `3 closed tabs when counting the top window and the closed window`
+  );
+
+  allWindowsClosedTabs = SessionStore.getClosedTabData(); // Equivalent to SS.getClosedTabDataForWindow(browserWindows[0]),
+  Assert.equal(
+    allWindowsClosedTabs.length,
+    2,
+    "getClosedTabData returned the number of entries for the top window"
+  );
+  SpecialPowers.popPrefEnv();
+  await TestUtils.waitForTick();
+  //
+  // ***********************************
+
+  closedCount = SessionStore.getClosedTabCount();
+  Assert.equal(
+    4,
+    closedCount,
+    "Sanity-check, with the pref on, we're back to 4 closed tabs"
+  );
+
+  // ***********************************
+  info("check with the closed-tabs-from-closed-windows pref off");
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.sessionstore.closedTabsFromClosedWindows", false]],
+  });
+
+  info(
+    "With this pref off, the closed tab count is that of only the only windows"
+  );
+  closedCount = SessionStore.getClosedTabCount(); // Equivalent to SS.getClosedTabCountForWindow(browserWindows[0]),
+  Assert.equal(3, closedCount, `3 closed tabs from the open windows`);
+
+  allWindowsClosedTabs = SessionStore.getClosedTabData();
+  Assert.equal(
+    allWindowsClosedTabs.length,
+    3,
+    "getClosedTabData returned the number of entries for the top window"
+  );
+  SpecialPowers.popPrefEnv();
+  await TestUtils.waitForTick();
+  //
+  // ***********************************
+
+  info("forget the closed tab from the closed window");
+  sessionStoreUpdated = TestUtils.topicObserved(
+    "sessionstore-closed-objects-changed"
+  );
+  SessionStore.forgetClosedTab(
+    { sourceClosedId: SessionStore.getClosedWindowData()[0].closedId },
+    0
+  );
+  await sessionStoreUpdated;
+
+  closedCount = SessionStore.getClosedTabCountFromClosedWindows();
+  Assert.equal(
+    0,
+    closedCount,
+    "0 closed tabs from closed windows after forgetting them"
+  );
+  closedCount = SessionStore.getClosedTabCount();
+  Assert.equal(
+    3,
+    closedCount,
+    "3 closed tabs now that the closed tab from the closed window is forgotten"
+  );
+
+  info("restore one of the closed tabs from an open window");
+  sessionStoreUpdated = TestUtils.topicObserved(
+    "sessionstore-closed-objects-changed"
+  );
+
+  SessionStore.undoCloseTab(browserWindows[0], 0);
+  await sessionStoreUpdated;
+
+  Assert.equal(
+    1,
+    SessionStore.getClosedTabCountForWindow(browserWindows[0]),
+    "Now theres one closed tab in the first window"
+  );
+  Assert.equal(
+    1,
+    SessionStore.getClosedTabCountForWindow(browserWindows[1]),
+    "Theres still one closed tab in the 2nd window"
+  );
+
+  Assert.equal(
+    2,
+    SessionStore.getClosedTabCount(),
+    "Theres a total for 2 closed tabs"
+  );
+
+  // Bug 1836198 - sometimes this reports 1 not 2.
+  Assert.equal(
+    2,
+    SessionStore.getClosedTabData().length,
+    "We get the right number of tab entries from getClosedTabData()"
+  );
+
+  info("forget the last closed tab in the first window");
+  sessionStoreUpdated = TestUtils.topicObserved(
+    "sessionstore-closed-objects-changed"
+  );
+  SessionStore.forgetClosedTab(browserWindows[0], 0);
+  await sessionStoreUpdated;
+
+  Assert.equal(
+    0,
+    SessionStore.getClosedTabCountForWindow(browserWindows[0]),
+    "The first window has 0 closed tabs after forgetting the last tab"
+  );
+  Assert.equal(
+    1,
+    SessionStore.getClosedTabCountForWindow(browserWindows[1]),
+    "Theres still one closed tab in the 2nd window"
+  );
+
+  Assert.equal(
+    1,
+    SessionStore.getClosedTabCount(),
+    "Theres a total of one closed tabs"
+  );
+  Assert.equal(
+    1,
+    SessionStore.getClosedTabData().length,
+    "We get the right number of tab entries from getClosedTabData()"
+  );
+
+  info(
+    "Close the 2nd window. This makes its 1 closed tab a 'closed tab from closed window'"
+  );
+  await promiseAllButPrimaryWindowClosed();
+
+  Assert.equal(
+    0,
+    SessionStore.getClosedTabCountForWindow(browserWindows[0]),
+    "Closed tab count is unchanged after closing the other browser window"
+  );
+
+  Assert.equal(
+    0,
+    SessionStore.getClosedTabCount({ closedTabsFromClosedWindows: false }),
+    "Theres now 0 closed tabs from open windows after closing the other browser window which had the last one"
+  );
+
+  Assert.equal(
+    1,
+    SessionStore.getClosedTabCount({ closedTabsFromClosedWindows: true }),
+    "Theres now 1 closed tabs including closed windows after closing the other browser window which had the last one"
+  );
+
+  Assert.equal(
+    0,
+    SessionStore.getClosedTabData().length,
+    "We get the right number of tab entries from getClosedTabData()"
+  );
+
+  Assert.equal(
+    1,
+    SessionStore.getClosedTabCountFromClosedWindows(),
+    "There's 1 closed tabs from closed windows"
+  );
+
+  // Cleanup.
+  await promiseBrowserState(ORIG_STATE);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_cookies.js b/src/zen/tests/mochitests/sessionstore/browser_cookies.js
new file mode 100644
index 000000000..96244dda1
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_cookies.js
@@ -0,0 +1,81 @@
+"use strict";
+
+function promiseSetCookie(cookie) {
+  info(`Set-Cookie: ${cookie}`);
+  return Promise.all([
+    waitForCookieChanged(),
+    SpecialPowers.spawn(
+      gBrowser.selectedBrowser,
+      [cookie],
+      passedCookie => (content.document.cookie = passedCookie)
+    ),
+  ]);
+}
+
+function waitForCookieChanged() {
+  return new Promise(resolve => {
+    Services.obs.addObserver(function observer(subj, topic) {
+      Services.obs.removeObserver(observer, topic);
+      resolve();
+    }, "session-cookie-changed");
+  });
+}
+
+function cookieExists(host, name, value) {
+  let {
+    cookies: [c],
+  } = JSON.parse(ss.getBrowserState());
+  return c && c.host == host && c.name == name && c.value == value;
+}
+
+// Setup and cleanup.
+add_task(async function test_setup() {
+  registerCleanupFunction(() => {
+    Services.cookies.removeAll();
+  });
+});
+
+// Test session cookie storage.
+add_task(async function test_run() {
+  Services.cookies.removeAll();
+
+  // Add a new tab for testing.
+  gBrowser.selectedTab = BrowserTestUtils.addTab(
+    gBrowser,
+    "http://example.com/"
+  );
+  await promiseBrowserLoaded(gBrowser.selectedBrowser);
+
+  // Add a session cookie.
+  await promiseSetCookie("foo=bar");
+  ok(cookieExists("example.com", "foo", "bar"), "cookie was added");
+
+  // Modify a session cookie.
+  await promiseSetCookie("foo=baz");
+  ok(cookieExists("example.com", "foo", "baz"), "cookie was modified");
+
+  // Turn the session cookie into a normal one.
+  let expiry = new Date();
+  expiry.setDate(expiry.getDate() + 2);
+  await promiseSetCookie(`foo=baz; Expires=${expiry.toUTCString()}`);
+  ok(!cookieExists("example.com", "foo", "baz"), "no longer a session cookie");
+
+  // Turn it back into a session cookie.
+  await promiseSetCookie("foo=bar");
+  ok(cookieExists("example.com", "foo", "bar"), "again a session cookie");
+
+  // Remove the session cookie.
+  await promiseSetCookie("foo=; Expires=Thu, 01 Jan 1970 00:00:00 GMT");
+  ok(!cookieExists("example.com", "foo", ""), "cookie was removed");
+
+  // Add a session cookie.
+  await promiseSetCookie("foo=bar");
+  ok(cookieExists("example.com", "foo", "bar"), "cookie was added");
+
+  // Clear all session cookies.
+  Services.cookies.removeAll();
+  ok(!cookieExists("example.com", "foo", "bar"), "cookies were cleared");
+
+  // Cleanup.
+  BrowserTestUtils.removeTab(gBrowser.selectedTab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_cookies_legacy.js b/src/zen/tests/mochitests/sessionstore/browser_cookies_legacy.js
new file mode 100644
index 000000000..9c87b2e94
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_cookies_legacy.js
@@ -0,0 +1,77 @@
+"use strict";
+
+function createTestState() {
+  let r = Math.round(Math.random() * 100000);
+
+  let cookie = {
+    host: "http://example.com",
+    path: "/",
+    name: `name${r}`,
+    value: `value${r}`,
+    sameSite: Ci.nsICookie.SAMESITE_UNSET,
+  };
+
+  let state = {
+    windows: [
+      {
+        tabs: [
+          { entries: [{ url: "about:robots", triggeringPrincipal_base64 }] },
+        ],
+        cookies: [cookie],
+      },
+    ],
+  };
+
+  return [state, cookie];
+}
+
+function waitForNewCookie({ host, name, value }) {
+  info(`waiting for cookie ${name}=${value} from ${host}...`);
+
+  return new Promise(resolve => {
+    Services.obs.addObserver(function observer(subj, topic) {
+      let notification = subj.QueryInterface(Ci.nsICookieNotification);
+      if (notification.action != Ci.nsICookieNotification.COOKIE_ADDED) {
+        return;
+      }
+
+      let cookie = notification.cookie.QueryInterface(Ci.nsICookie);
+      if (cookie.host == host && cookie.name == name && cookie.value == value) {
+        ok(true, "cookie added by the cookie service");
+        Services.obs.removeObserver(observer, topic);
+        resolve();
+      }
+    }, "session-cookie-changed");
+  });
+}
+
+// Setup and cleanup.
+add_task(async function test_setup() {
+  Services.cookies.removeAll();
+
+  registerCleanupFunction(() => {
+    Services.cookies.removeAll();
+  });
+});
+
+// Test that calling ss.setWindowState() with a legacy state object that
+// contains cookies in the window state restores session cookies properly.
+add_task(async function test_window() {
+  let [state, cookie] = createTestState();
+  let win = await promiseNewWindowLoaded();
+
+  let promiseCookie = waitForNewCookie(cookie);
+  ss.setWindowState(win, JSON.stringify(state), true);
+  await promiseCookie;
+
+  await BrowserTestUtils.closeWindow(win);
+});
+
+// Test that calling ss.setBrowserState() with a legacy state object that
+// contains cookies in the window state restores session cookies properly.
+add_task(async function test_browser() {
+  let backupState = ss.getBrowserState();
+  let [state, cookie] = createTestState();
+  await Promise.all([waitForNewCookie(cookie), promiseBrowserState(state)]);
+  await promiseBrowserState(backupState);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_cookies_partitioned.js b/src/zen/tests/mochitests/sessionstore/browser_cookies_partitioned.js
new file mode 100644
index 000000000..4f0975a65
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_cookies_partitioned.js
@@ -0,0 +1,73 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/**
+ * Bug 1922193 - Test that session restore can restore partitioned cookies
+ * without the isPartitioned flag in the session cookie state. And verify the
+ * isPartitioned flag is correctly set on the restored cookie.
+ */
+
+const TEST_HOST = "example.com";
+const TEST_URL = `https://${TEST_HOST}`;
+const MAX_EXPIRY = Math.pow(2, 62);
+
+add_setup(async function () {
+  // Make sure that sessionstore.js can be forced to be created by setting
+  // the interval pref to 0.
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.sessionstore.interval", 0]],
+  });
+});
+
+add_task(async function runTest() {
+  Services.cookies.removeAll();
+
+  let tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, TEST_URL);
+
+  // Add a partitioned cookie.
+  const cv = Services.cookies.add(
+    TEST_HOST,
+    "/",
+    "foo",
+    "bar",
+    true,
+    false,
+    true,
+    MAX_EXPIRY,
+    { partitionKey: "(https,example.com)" },
+    Ci.nsICookie.SAMESITE_NONE,
+    Ci.nsICookie.SCHEME_HTTPS,
+    true
+  );
+  is(cv.result, Ci.nsICookieValidation.eOK, "Valid cookie");
+
+  await TabStateFlusher.flush(tab.linkedBrowser);
+
+  // Get the sessionstore state for the window.
+  let state = ss.getBrowserState();
+
+  // Remove the isPartitioned flag from the stored cookie.
+  state = JSON.parse(state);
+  delete state.cookies[0].isPartitioned;
+  state = JSON.stringify(state);
+
+  // Remove the cookie.
+  Services.cookies.removeAll();
+
+  // Restore the window state.
+  await setBrowserState(state);
+
+  // One cookie should be restored.
+  is(Services.cookies.cookies.length, 1, "One cookie should be restored.");
+
+  let cookie = Services.cookies.cookies[0];
+  is(cookie.name, "foo", "The cookie name should be foo.");
+  is(cookie.value, "bar", "The cookie value should be bar.");
+  ok(cookie.isPartitioned, "The isPartitioned flag should be set.");
+
+  // Clean up.
+  Services.cookies.removeAll();
+  BrowserTestUtils.removeTab(tab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_cookies_privacy.js b/src/zen/tests/mochitests/sessionstore/browser_cookies_privacy.js
new file mode 100644
index 000000000..a2c3c1d98
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_cookies_privacy.js
@@ -0,0 +1,126 @@
+"use strict";
+
+// MAX_EXPIRY should be 2^63-1, but JavaScript can't handle that precision.
+const MAX_EXPIRY = Math.pow(2, 62);
+
+function addCookie(scheme, secure = false) {
+  let cookie = createTestCookie(scheme, secure);
+  const cv = Services.cookies.add(
+    cookie.host,
+    cookie.path,
+    cookie.name,
+    cookie.value,
+    cookie.secure,
+    /* isHttpOnly = */ false,
+    /* isSession = */ true,
+    MAX_EXPIRY,
+    /* originAttributes = */ {},
+    Ci.nsICookie.SAMESITE_UNSET,
+    Ci.nsICookie.SCHEME_HTTPS
+  );
+  is(cv.result, Ci.nsICookieValidation.eOK, "Valid cookie");
+  return cookie;
+}
+
+function createTestCookie(scheme, secure = false) {
+  let r = Math.round(Math.random() * 100000);
+
+  let cookie = {
+    host: `${scheme}://example.com`,
+    path: "/",
+    name: `name${r}`,
+    value: `value${r}`,
+    secure,
+  };
+
+  return cookie;
+}
+
+function getCookie() {
+  let state = JSON.parse(ss.getBrowserState());
+  let cookies = state.cookies || [];
+  return cookies[0];
+}
+
+function compareCookies(a) {
+  let b = getCookie();
+  return a.host == b.host && a.name == b.name && a.value == b.value;
+}
+
+// Setup and cleanup.
+add_task(async function test_setup() {
+  Services.prefs.clearUserPref("browser.sessionstore.privacy_level");
+
+  registerCleanupFunction(() => {
+    Services.prefs.clearUserPref("browser.sessionstore.privacy_level");
+    Services.cookies.removeAll();
+  });
+});
+
+// Test privacy_level=none (default). We store all session cookies.
+add_task(async function test_level_none() {
+  Services.cookies.removeAll();
+
+  // Set level=none, store all cookies.
+  Services.prefs.setIntPref("browser.sessionstore.privacy_level", 0);
+
+  // With the default privacy level we collect all cookies.
+  ok(compareCookies(addCookie("http")), "non-secure http cookie stored");
+  Services.cookies.removeAll();
+
+  // With the default privacy level we collect all cookies.
+  ok(compareCookies(addCookie("https")), "non-secure https cookie stored");
+  Services.cookies.removeAll();
+
+  // With the default privacy level we collect all cookies.
+  ok(compareCookies(addCookie("https", true)), "secure https cookie stored");
+  Services.cookies.removeAll();
+});
+
+// Test privacy_level=encrypted. We store all non-secure session cookies.
+add_task(async function test_level_encrypted() {
+  Services.cookies.removeAll();
+
+  // Set level=encrypted, don't store any secure cookies.
+  Services.prefs.setIntPref("browser.sessionstore.privacy_level", 1);
+
+  // With level=encrypted, non-secure cookies will be stored.
+  ok(compareCookies(addCookie("http")), "non-secure http cookie stored");
+  Services.cookies.removeAll();
+
+  // With level=encrypted, non-secure cookies will be stored,
+  // even if sent by an HTTPS site.
+  ok(compareCookies(addCookie("https")), "non-secure https cookie stored");
+  Services.cookies.removeAll();
+
+  // With level=encrypted, non-secure cookies will be stored,
+  // even if sent by an HTTPS site.
+  ok(
+    addCookie("https", true) && !getCookie(),
+    "secure https cookie not stored"
+  );
+  Services.cookies.removeAll();
+});
+
+// Test privacy_level=full. We store no session cookies.
+add_task(async function test_level_full() {
+  Services.cookies.removeAll();
+
+  // Set level=full, don't store any cookies.
+  Services.prefs.setIntPref("browser.sessionstore.privacy_level", 2);
+
+  // With level=full we must not store any cookies.
+  ok(addCookie("http") && !getCookie(), "non-secure http cookie not stored");
+  Services.cookies.removeAll();
+
+  // With level=full we must not store any cookies.
+  ok(addCookie("https") && !getCookie(), "non-secure https cookie not stored");
+  Services.cookies.removeAll();
+
+  // With level=full we must not store any cookies.
+  ok(
+    addCookie("https", true) && !getCookie(),
+    "secure https cookie not stored"
+  );
+  Services.cookies.removeAll();
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_cookies_sameSite.js b/src/zen/tests/mochitests/sessionstore/browser_cookies_sameSite.js
new file mode 100644
index 000000000..ad81c98be
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_cookies_sameSite.js
@@ -0,0 +1,91 @@
+"use strict";
+
+const TEST_HTTP_URL = "http://example.com";
+const TEST_HTTPS_URL = "https://example.com";
+const MAX_EXPIRY = Math.pow(2, 62);
+
+function getSingleCookie() {
+  let cookies = Array.from(Services.cookies.cookies);
+  Assert.equal(cookies.length, 1, "expected one cookie");
+  return cookies[0];
+}
+
+async function verifyRestore(url, sameSiteSetting) {
+  Services.cookies.removeAll();
+
+  // Make sure that sessionstore.js can be forced to be created by setting
+  // the interval pref to 0.
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.sessionstore.interval", 0]],
+  });
+
+  let tab = BrowserTestUtils.addTab(gBrowser, url);
+  await BrowserTestUtils.browserLoaded(tab.linkedBrowser);
+
+  // Add a cookie with specific same-site setting.
+  let r = Math.floor(Math.random() * MAX_EXPIRY);
+  const cv = Services.cookies.add(
+    url,
+    "/",
+    "name" + r,
+    "value" + r,
+    false,
+    false,
+    true,
+    MAX_EXPIRY,
+    {},
+    sameSiteSetting,
+    url.startsWith("https:")
+      ? Ci.nsICookie.SCHEME_HTTPS
+      : Ci.nsICookie.SCHEME_HTTP
+  );
+  is(cv.result, Ci.nsICookieValidation.eOK, "Valid cookie");
+
+  await TabStateFlusher.flush(tab.linkedBrowser);
+
+  // Get the sessionstore state for the window.
+  let state = ss.getBrowserState();
+
+  // Verify our cookie got set.
+  let cookie = getSingleCookie();
+
+  // Remove the cookie.
+  Services.cookies.removeAll();
+
+  // Restore the window state.
+  await setBrowserState(state);
+
+  // At this point, the cookie should be restored.
+  let cookie2 = getSingleCookie();
+
+  is(
+    cookie2.sameSite,
+    cookie.sameSite,
+    "cookie same-site flag successfully restored"
+  );
+
+  is(
+    cookie2.schemeMap,
+    cookie.schemeMap,
+    "cookie schemeMap flag successfully restored"
+  );
+
+  // Clean up.
+  Services.cookies.removeAll();
+  BrowserTestUtils.removeTab(gBrowser.tabs[1]);
+}
+
+/**
+ * Tests that cookie.sameSite flag is stored and restored correctly by
+ * sessionstore.
+ */
+add_task(async function () {
+  // Test for various possible values of cookie.sameSite and schemeMap.
+  await verifyRestore(TEST_HTTP_URL, Ci.nsICookie.SAMESITE_UNSET);
+  await verifyRestore(TEST_HTTP_URL, Ci.nsICookie.SAMESITE_LAX);
+  await verifyRestore(TEST_HTTP_URL, Ci.nsICookie.SAMESITE_STRICT);
+
+  await verifyRestore(TEST_HTTPS_URL, Ci.nsICookie.SAMESITE_UNSET);
+  await verifyRestore(TEST_HTTPS_URL, Ci.nsICookie.SAMESITE_LAX);
+  await verifyRestore(TEST_HTTPS_URL, Ci.nsICookie.SAMESITE_STRICT);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_crashedTabs.js b/src/zen/tests/mochitests/sessionstore/browser_crashedTabs.js
new file mode 100644
index 000000000..25280ec77
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_crashedTabs.js
@@ -0,0 +1,503 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// This file spawns content tasks.
+
+"use strict";
+
+requestLongerTimeout(10);
+
+const PAGE_1 =
+  "data:text/html,<html><body>A%20regular,%20everyday,%20normal%20page.";
+const PAGE_2 =
+  "data:text/html,<html><body>Another%20regular,%20everyday,%20normal%20page.";
+
+// Turn off tab animations for testing and use a single content process
+// for these tests since we want to test tabs within the crashing process here.
+gReduceMotionOverride = true;
+
+// Allow tabs to restore on demand so we can test pending states
+Services.prefs.clearUserPref("browser.sessionstore.restore_on_demand");
+
+function clickButton(browser, id) {
+  info("Clicking " + id);
+  return SpecialPowers.spawn(browser, [id], buttonId => {
+    let button = content.document.getElementById(buttonId);
+    button.click();
+  });
+}
+
+/**
+ * Checks the documentURI of the root document of a remote browser
+ * to see if it equals URI.
+ *
+ * @param browser
+ *        The remote <xul:browser> to check the root document URI in.
+ * @param URI
+ *        A string to match the root document URI against.
+ * @return Promise
+ */
+async function promiseContentDocumentURIEquals(browser, URI) {
+  let contentURI = await SpecialPowers.spawn(browser, [], () => {
+    return content.document.documentURI;
+  });
+  is(
+    contentURI,
+    URI,
+    `Content has URI ${contentURI} which does not match ${URI}`
+  );
+}
+
+/**
+ * Checks the window.history.length of the root window of a remote
+ * browser to see if it equals length.
+ *
+ * @param browser
+ *        The remote <xul:browser> to check the root window.history.length
+ * @param length
+ *        The expected history length
+ * @return Promise
+ */
+async function promiseHistoryLength(browser, length) {
+  let contentLength = await SpecialPowers.spawn(browser, [], () => {
+    return content.history.length;
+  });
+  is(
+    contentLength,
+    length,
+    `Content has window.history.length ${contentLength} which does ` +
+      `not equal expected ${length}`
+  );
+}
+
+/**
+ * Returns a Promise that resolves when a browser has fired the
+ * AboutTabCrashedReady event.
+ *
+ * @param browser
+ *        The remote <xul:browser> that will fire the event.
+ * @return Promise
+ */
+function promiseTabCrashedReady(browser) {
+  return new Promise(resolve => {
+    browser.addEventListener(
+      "AboutTabCrashedReady",
+      function ready() {
+        browser.removeEventListener("AboutTabCrashedReady", ready, false, true);
+        resolve();
+      },
+      false,
+      true
+    );
+  });
+}
+
+/**
+ * Checks that if a tab crashes, that information about the tab crashed
+ * page does not get added to the tab history.
+ */
+add_task(async function test_crash_page_not_in_history() {
+  let newTab = BrowserTestUtils.addTab(gBrowser);
+  gBrowser.selectedTab = newTab;
+  let browser = newTab.linkedBrowser;
+  ok(browser.isRemoteBrowser, "Should be a remote browser");
+  await BrowserTestUtils.browserLoaded(browser, { wantLoad: "about:blank" });
+
+  BrowserTestUtils.startLoadingURIString(browser, PAGE_1);
+  await promiseBrowserLoaded(browser);
+  await TabStateFlusher.flush(browser);
+
+  // Crash the tab
+  await BrowserTestUtils.crashFrame(browser);
+
+  // Check the tab state and make sure the tab crashed page isn't
+  // mentioned.
+  let { entries } = JSON.parse(ss.getTabState(newTab));
+  is(entries.length, 1, "Should have a single history entry");
+  is(
+    entries[0].url,
+    PAGE_1,
+    "Single entry should be the page we visited before crashing"
+  );
+
+  gBrowser.removeTab(newTab);
+});
+
+/**
+ * Checks that if a tab crashes, that when we browse away from that page
+ * to a non-blacklisted site (so the browser becomes remote again), that
+ * we record history for that new visit.
+ */
+add_task(async function test_revived_history_from_remote() {
+  let newTab = BrowserTestUtils.addTab(gBrowser);
+  gBrowser.selectedTab = newTab;
+  let browser = newTab.linkedBrowser;
+  ok(browser.isRemoteBrowser, "Should be a remote browser");
+  await BrowserTestUtils.browserLoaded(browser, { wantLoad: "about:blank" });
+
+  BrowserTestUtils.startLoadingURIString(browser, PAGE_1);
+  await promiseBrowserLoaded(browser);
+  await TabStateFlusher.flush(browser);
+
+  // Crash the tab
+  await BrowserTestUtils.crashFrame(browser);
+
+  // Browse to a new site that will cause the browser to
+  // become remote again.
+  BrowserTestUtils.startLoadingURIString(browser, PAGE_2);
+  await promiseBrowserLoaded(browser);
+  ok(
+    !newTab.hasAttribute("crashed"),
+    "Tab shouldn't be marked as crashed anymore."
+  );
+  ok(browser.isRemoteBrowser, "Should be a remote browser");
+  await TabStateFlusher.flush(browser);
+
+  // Check the tab state and make sure the tab crashed page isn't
+  // mentioned.
+  let { entries } = JSON.parse(ss.getTabState(newTab));
+  is(entries.length, 2, "Should have two history entries");
+  is(
+    entries[0].url,
+    PAGE_1,
+    "First entry should be the page we visited before crashing"
+  );
+  is(
+    entries[1].url,
+    PAGE_2,
+    "Second entry should be the page we visited after crashing"
+  );
+
+  gBrowser.removeTab(newTab);
+});
+
+/**
+ * Checks that if a tab crashes, that when we browse away from that page
+ * to a blacklisted site (so the browser stays non-remote), that
+ * we record history for that new visit.
+ */
+add_task(async function test_revived_history_from_non_remote() {
+  let newTab = BrowserTestUtils.addTab(gBrowser);
+  gBrowser.selectedTab = newTab;
+  let browser = newTab.linkedBrowser;
+  ok(browser.isRemoteBrowser, "Should be a remote browser");
+  await BrowserTestUtils.browserLoaded(browser, { wantLoad: "about:blank" });
+
+  BrowserTestUtils.startLoadingURIString(browser, PAGE_1);
+  await promiseBrowserLoaded(browser);
+  await TabStateFlusher.flush(browser);
+
+  // Crash the tab
+  await BrowserTestUtils.crashFrame(browser);
+
+  // Browse to a new site that will not cause the browser to
+  // become remote again.
+  BrowserTestUtils.startLoadingURIString(browser, "about:mozilla");
+  await promiseBrowserLoaded(browser);
+  ok(
+    !newTab.hasAttribute("crashed"),
+    "Tab shouldn't be marked as crashed anymore."
+  );
+  ok(!browser.isRemoteBrowser, "Should not be a remote browser");
+  await TabStateFlusher.flush(browser);
+
+  // Check the tab state and make sure the tab crashed page isn't
+  // mentioned.
+  let { entries } = JSON.parse(ss.getTabState(newTab));
+  is(entries.length, 2, "Should have two history entries");
+  is(
+    entries[0].url,
+    PAGE_1,
+    "First entry should be the page we visited before crashing"
+  );
+  is(
+    entries[1].url,
+    "about:mozilla",
+    "Second entry should be the page we visited after crashing"
+  );
+
+  gBrowser.removeTab(newTab);
+});
+
+/**
+ * Checks that we can revive a crashed tab back to the page that
+ * it was on when it crashed.
+ */
+add_task(async function test_revive_tab_from_session_store() {
+  let newTab = BrowserTestUtils.addTab(gBrowser);
+  gBrowser.selectedTab = newTab;
+  let browser = newTab.linkedBrowser;
+  ok(browser.isRemoteBrowser, "Should be a remote browser");
+  await BrowserTestUtils.browserLoaded(browser, { wantLoad: "about:blank" });
+
+  BrowserTestUtils.startLoadingURIString(browser, PAGE_1);
+  await promiseBrowserLoaded(browser);
+
+  let newTab2 = BrowserTestUtils.addTab(gBrowser, "about:blank", {
+    remoteType: browser.remoteType,
+    initialBrowsingContextGroupId: browser.browsingContext.group.id,
+  });
+  let browser2 = newTab2.linkedBrowser;
+  ok(browser2.isRemoteBrowser, "Should be a remote browser");
+  await BrowserTestUtils.browserLoaded(browser2, { wantLoad: "about:blank" });
+
+  BrowserTestUtils.startLoadingURIString(browser, PAGE_1);
+  await promiseBrowserLoaded(browser);
+
+  BrowserTestUtils.startLoadingURIString(browser, PAGE_2);
+  await promiseBrowserLoaded(browser);
+
+  await TabStateFlusher.flush(browser);
+
+  // Crash the tab
+  await BrowserTestUtils.crashFrame(browser);
+  // Background tabs should not be crashed, but should be in the "to be restored"
+  // state.
+  ok(!newTab2.hasAttribute("crashed"), "Second tab should not be crashed.");
+  ok(newTab2.hasAttribute("pending"), "Second tab should be pending.");
+
+  // Use SessionStore to revive the first tab
+  let tabRestoredPromise = promiseTabRestored(newTab);
+  await clickButton(browser, "restoreTab");
+  await tabRestoredPromise;
+  ok(
+    !newTab.hasAttribute("crashed"),
+    "Tab shouldn't be marked as crashed anymore."
+  );
+  ok(newTab2.hasAttribute("pending"), "Second tab should still be pending.");
+
+  // We can't just check browser.currentURI.spec, because from
+  // the outside, a crashed tab has the same URI as the page
+  // it crashed on (much like an about:neterror page). Instead,
+  // we have to use the documentURI on the content.
+  await promiseContentDocumentURIEquals(browser, PAGE_2);
+
+  // We should also have two entries in the browser history.
+  await promiseHistoryLength(browser, 2);
+
+  gBrowser.removeTab(newTab);
+  gBrowser.removeTab(newTab2);
+});
+
+/**
+ * Checks that we can revive multiple crashed tabs back to the pages
+ * that they were on when they crashed.
+ */
+add_task(async function test_revive_all_tabs_from_session_store() {
+  let newTab = BrowserTestUtils.addTab(gBrowser);
+  gBrowser.selectedTab = newTab;
+  let browser = newTab.linkedBrowser;
+  ok(browser.isRemoteBrowser, "Should be a remote browser");
+  await BrowserTestUtils.browserLoaded(browser, { wantLoad: "about:blank" });
+
+  BrowserTestUtils.startLoadingURIString(browser, PAGE_1);
+  await promiseBrowserLoaded(browser);
+
+  // In order to see a second about:tabcrashed page, we'll need
+  // a second window, since only selected tabs will show
+  // about:tabcrashed.
+  let win2 = await BrowserTestUtils.openNewBrowserWindow();
+  let newTab2 = BrowserTestUtils.addTab(win2.gBrowser, PAGE_1, {
+    remoteType: browser.remoteType,
+    initialBrowsingContextGroupId: browser.browsingContext.group.id,
+  });
+  win2.gBrowser.selectedTab = newTab2;
+  let browser2 = newTab2.linkedBrowser;
+  ok(browser2.isRemoteBrowser, "Should be a remote browser");
+  await promiseBrowserLoaded(browser2);
+
+  BrowserTestUtils.startLoadingURIString(browser, PAGE_1);
+  await promiseBrowserLoaded(browser);
+
+  BrowserTestUtils.startLoadingURIString(browser, PAGE_2);
+  await promiseBrowserLoaded(browser);
+
+  await TabStateFlusher.flush(browser);
+  await TabStateFlusher.flush(browser2);
+
+  // Crash the tab
+  await BrowserTestUtils.crashFrame(browser);
+  // Both tabs should now be crashed.
+  is(newTab.getAttribute("crashed"), "true", "First tab should be crashed");
+  is(
+    newTab2.getAttribute("crashed"),
+    "true",
+    "Second window tab should be crashed"
+  );
+
+  // Use SessionStore to revive all the tabs
+  let tabRestoredPromises = Promise.all([
+    promiseTabRestored(newTab),
+    promiseTabRestored(newTab2),
+  ]);
+  await clickButton(browser, "restoreAll");
+  await tabRestoredPromises;
+
+  ok(
+    !newTab.hasAttribute("crashed"),
+    "Tab shouldn't be marked as crashed anymore."
+  );
+  ok(!newTab.hasAttribute("pending"), "Tab shouldn't be pending.");
+  ok(
+    !newTab2.hasAttribute("crashed"),
+    "Second tab shouldn't be marked as crashed anymore."
+  );
+  ok(!newTab2.hasAttribute("pending"), "Second tab shouldn't be pending.");
+
+  // We can't just check browser.currentURI.spec, because from
+  // the outside, a crashed tab has the same URI as the page
+  // it crashed on (much like an about:neterror page). Instead,
+  // we have to use the documentURI on the content.
+  await promiseContentDocumentURIEquals(browser, PAGE_2);
+  await promiseContentDocumentURIEquals(browser2, PAGE_1);
+
+  // We should also have two entries in the browser history.
+  await promiseHistoryLength(browser, 2);
+
+  await BrowserTestUtils.closeWindow(win2);
+  gBrowser.removeTab(newTab);
+});
+
+/**
+ * Checks that about:tabcrashed can close the current tab
+ */
+add_task(async function test_close_tab_after_crash() {
+  let newTab = BrowserTestUtils.addTab(gBrowser);
+  gBrowser.selectedTab = newTab;
+  let browser = newTab.linkedBrowser;
+  ok(browser.isRemoteBrowser, "Should be a remote browser");
+  await BrowserTestUtils.browserLoaded(browser, { wantLoad: "about:blank" });
+
+  BrowserTestUtils.startLoadingURIString(browser, PAGE_1);
+  await promiseBrowserLoaded(browser);
+
+  await TabStateFlusher.flush(browser);
+
+  // Crash the tab
+  await BrowserTestUtils.crashFrame(browser);
+
+  let promise = BrowserTestUtils.waitForEvent(
+    gBrowser.tabContainer,
+    "TabClose"
+  );
+
+  // Click the close tab button
+  await clickButton(browser, "closeTab");
+  await promise;
+
+  is(gBrowser.tabs.length, 1, "Should have closed the tab");
+});
+
+/**
+ * Checks that "restore all" button is only shown if more than one tab
+ * is showing about:tabcrashed
+ */
+add_task(async function test_hide_restore_all_button() {
+  let newTab = BrowserTestUtils.addTab(gBrowser);
+  gBrowser.selectedTab = newTab;
+  let browser = newTab.linkedBrowser;
+  ok(browser.isRemoteBrowser, "Should be a remote browser");
+  await BrowserTestUtils.browserLoaded(browser, { wantLoad: "about:blank" });
+
+  BrowserTestUtils.startLoadingURIString(browser, PAGE_1);
+  await promiseBrowserLoaded(browser);
+
+  await TabStateFlusher.flush(browser);
+
+  // Crash the tab
+  await BrowserTestUtils.crashFrame(browser);
+
+  let doc = browser.contentDocument;
+  let restoreAllButton = doc.getElementById("restoreAll");
+  let restoreOneButton = doc.getElementById("restoreTab");
+
+  let restoreAllStyles = window.getComputedStyle(restoreAllButton);
+  is(restoreAllStyles.display, "none", "Restore All button should be hidden");
+  ok(
+    restoreOneButton.classList.contains("primary"),
+    "Restore Tab button should have the primary class"
+  );
+
+  let newTab2 = BrowserTestUtils.addTab(gBrowser);
+  gBrowser.selectedTab = newTab;
+
+  BrowserTestUtils.startLoadingURIString(browser, PAGE_2);
+  await promiseBrowserLoaded(browser);
+
+  // Load up a second window so we can get another tab to show
+  // about:tabcrashed
+  let win2 = await BrowserTestUtils.openNewBrowserWindow();
+  let newTab3 = BrowserTestUtils.addTab(win2.gBrowser, PAGE_2, {
+    remoteType: browser.remoteType,
+    initialBrowsingContextGroupId: browser.browsingContext.group.id,
+  });
+  win2.gBrowser.selectedTab = newTab3;
+  let otherWinBrowser = newTab3.linkedBrowser;
+  await promiseBrowserLoaded(otherWinBrowser);
+  // We'll need to make sure the second tab's browser has finished
+  // sending its AboutTabCrashedReady event before we know for
+  // sure whether or not we're showing the right Restore buttons.
+  let otherBrowserReady = promiseTabCrashedReady(otherWinBrowser);
+
+  // Crash the first tab.
+  await BrowserTestUtils.crashFrame(browser);
+  await otherBrowserReady;
+
+  doc = browser.contentDocument;
+  restoreAllButton = doc.getElementById("restoreAll");
+  restoreOneButton = doc.getElementById("restoreTab");
+
+  restoreAllStyles = window.getComputedStyle(restoreAllButton);
+  isnot(
+    restoreAllStyles.display,
+    "none",
+    "Restore All button should not be hidden"
+  );
+  ok(
+    !restoreOneButton.classList.contains("primary"),
+    "Restore Tab button should not have the primary class"
+  );
+
+  await BrowserTestUtils.closeWindow(win2);
+  gBrowser.removeTab(newTab);
+  gBrowser.removeTab(newTab2);
+});
+
+add_task(async function test_aboutcrashedtabzoom() {
+  let newTab = BrowserTestUtils.addTab(gBrowser);
+  gBrowser.selectedTab = newTab;
+  let browser = newTab.linkedBrowser;
+  ok(browser.isRemoteBrowser, "Should be a remote browser");
+  await BrowserTestUtils.browserLoaded(browser, { wantLoad: "about:blank" });
+
+  BrowserTestUtils.startLoadingURIString(browser, PAGE_1);
+  await promiseBrowserLoaded(browser);
+
+  FullZoom.enlarge();
+  let zoomLevel = ZoomManager.getZoomForBrowser(browser);
+  Assert.notStrictEqual(zoomLevel, 1, "should have enlarged");
+
+  await TabStateFlusher.flush(browser);
+
+  // Crash the tab
+  await BrowserTestUtils.crashFrame(browser);
+
+  Assert.strictEqual(
+    ZoomManager.getZoomForBrowser(browser),
+    1,
+    "zoom should have reset on crash"
+  );
+
+  let tabRestoredPromise = promiseTabRestored(newTab);
+  await clickButton(browser, "restoreTab");
+  await tabRestoredPromise;
+
+  Assert.strictEqual(
+    ZoomManager.getZoomForBrowser(browser),
+    zoomLevel,
+    "zoom should have gone back to enlarged"
+  );
+  FullZoom.reset();
+
+  gBrowser.removeTab(newTab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_csp_policy_container_migration.js b/src/zen/tests/mochitests/sessionstore/browser_csp_policy_container_migration.js
new file mode 100644
index 000000000..0970e0dac
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_csp_policy_container_migration.js
@@ -0,0 +1,68 @@
+"use strict";
+
+// We use about:blank because CSP_ShouldURIInheritCSP requires the URL to be
+// about:blank, about:srcdoc, or be a blob, filesystem, data, or javascript
+// scheme. Top-level data: URI navigation is always blocked.
+const URL = "about:blank";
+
+const CSP_JSON = `{"csp-policies":[{"default-src":["'self'"],"report-only":false}]}`;
+
+const CSP_SERIALIZED =
+  "CdntGuXUQAS/4CfOuSPZrAAAAAAAAAAAwAAAAAAAAEYB3pRy0IA0EdOTmQAQS6D9QJIHOlRteE8wkTq4cYEyCMYAAAAC/////wAAAbsBAAAAKmh0dHBzOi8vYi5jb21wYXNzLWRlbW8uY29tL2NzcF9wbGF5Z3JvdW5kLwAAAAAAAAAFAAAACAAAABIAAAAI/////wAAAAj/////AAAACAAAABIAAAAaAAAAEAAAABoAAAAQAAAAGgAAABAAAAAqAAAAAAAAACr/////AAAAAP////8AAAAa/////wAAABr/////AQAAAAAAAAAAADh7IjEiOnsiMCI6Imh0dHBzOi8vYi5jb21wYXNzLWRlbW8uY29tL2NzcF9wbGF5Z3JvdW5kLyJ9fQAAAAEAAAASAGQAZQBmAGEAdQBsAHQALQBzAHIAYwAgACcAcwBlAGwAZgAnAAAA";
+
+// Same CSP, but serialized as a policy container
+const POLICY_CONTAINER_SERIALIZED =
+  "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";
+
+/*
+ * Tests that whether we pass a serialized CSP or policy container
+ * to the session store, it gets deserialized correctly and restored
+ * in the tab state.
+ */
+add_task(async function () {
+  // Sanity check: ensure that the CSP JSON and serialized CSP match
+  is(
+    E10SUtils.deserializeCSP(CSP_SERIALIZED).toJSON(),
+    CSP_JSON,
+    "CSP should deserialize correctly from serialized CSP string"
+  );
+
+  // Firefox 142 and earlier writes entry.csp;
+  await checkCSPWithSessionHistoryEntry({ url: URL, csp: CSP_SERIALIZED });
+  // Firefox 143 and later writes to policyContainer (bug 1974070).
+  await checkCSPWithSessionHistoryEntry({
+    url: URL,
+    policyContainer: POLICY_CONTAINER_SERIALIZED,
+  });
+});
+
+async function checkCSPWithSessionHistoryEntry(entry) {
+  const tab = await createTabWithSessionHistoryEntry(entry);
+
+  is(
+    tab.linkedBrowser.policyContainer.csp.toJSON(),
+    CSP_JSON,
+    "CSP should be restored correctly from session history entry"
+  );
+
+  BrowserTestUtils.removeTab(tab);
+}
+
+async function createTabWithSessionHistoryEntry(entry) {
+  const state = {
+    entries: [entry],
+  };
+
+  // Open a tab at a non-about:blank URL first. If the tab is already at
+  // about:blank, setTabState with url=about:blank won't trigger a real
+  // cross-document navigation, so the CSP from the session history entry
+  // would never be applied to the document's policyContainer.
+  const tab = BrowserTestUtils.addTab(gBrowser, "about:robots");
+  await promiseBrowserLoaded(tab.linkedBrowser, true, "about:robots");
+
+  const restored = promiseTabRestored(tab);
+  ss.setTabState(tab, JSON.stringify(state));
+  await restored;
+
+  return tab;
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_docshell_uuid_consistency.js b/src/zen/tests/mochitests/sessionstore/browser_docshell_uuid_consistency.js
new file mode 100644
index 000000000..6fc212eb2
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_docshell_uuid_consistency.js
@@ -0,0 +1,56 @@
+// First test - open a tab and duplicate it, using session restore to restore the history into the new tab.
+add_task(async function duplicateTab() {
+  const TEST_URL = "data:text/html,foo";
+  let tab = BrowserTestUtils.addTab(gBrowser, TEST_URL);
+  await BrowserTestUtils.browserLoaded(tab.linkedBrowser);
+
+  let historyID = tab.linkedBrowser.browsingContext.historyID;
+  let shEntry =
+    tab.linkedBrowser.browsingContext.sessionHistory.getEntryAtIndex(0);
+  is(shEntry.docshellID.toString(), historyID.toString());
+
+  let tab2 = gBrowser.duplicateTab(tab);
+  await BrowserTestUtils.browserLoaded(tab2.linkedBrowser);
+
+  historyID = tab2.linkedBrowser.browsingContext.historyID;
+  shEntry =
+    tab2.linkedBrowser.browsingContext.sessionHistory.getEntryAtIndex(0);
+  is(shEntry.docshellID.toString(), historyID.toString());
+
+  BrowserTestUtils.removeTab(tab);
+  BrowserTestUtils.removeTab(tab2);
+});
+
+// Second test - open a tab and navigate across processes, which triggers sessionrestore to persist history.
+add_task(async function contentToChromeNavigate() {
+  const TEST_URL = "data:text/html,foo";
+  let tab = BrowserTestUtils.addTab(gBrowser, TEST_URL);
+  await BrowserTestUtils.browserLoaded(tab.linkedBrowser);
+
+  let historyID = tab.linkedBrowser.browsingContext.historyID;
+  let sh = tab.linkedBrowser.browsingContext.sessionHistory;
+  is(sh.count, 1);
+  is(sh.getEntryAtIndex(0).docshellID.toString(), historyID.toString());
+
+  // Force the browser to navigate to the chrome process.
+  BrowserTestUtils.startLoadingURIString(tab.linkedBrowser, "about:config");
+  await BrowserTestUtils.browserLoaded(tab.linkedBrowser);
+
+  // Check to be sure that we're in the chrome process.
+  let docShell = tab.linkedBrowser.frameLoader.docShell;
+
+  // 'cause we're in the chrome process, we can just directly poke at the shistory.
+  sh = docShell.browsingContext.sessionHistory;
+
+  is(sh.count, 2);
+  is(
+    sh.getEntryAtIndex(0).docshellID.toString(),
+    docShell.historyID.toString()
+  );
+  is(
+    sh.getEntryAtIndex(1).docshellID.toString(),
+    docShell.historyID.toString()
+  );
+
+  BrowserTestUtils.removeTab(tab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_duplicate_history.js b/src/zen/tests/mochitests/sessionstore/browser_duplicate_history.js
new file mode 100644
index 000000000..6bb251139
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_duplicate_history.js
@@ -0,0 +1,30 @@
+ChromeUtils.defineESModuleGetters(this, {
+  SessionStore: "resource:///modules/sessionstore/SessionStore.sys.mjs",
+  TabStateCache: "resource:///modules/sessionstore/TabStateCache.sys.mjs",
+});
+
+add_task(async function () {
+  await BrowserTestUtils.withNewTab(
+    "http://example.com",
+    async function (aBrowser) {
+      let tab = gBrowser.getTabForBrowser(aBrowser);
+      await TabStateFlusher.flush(aBrowser);
+      let before = TabStateCache.get(aBrowser.permanentKey);
+
+      let newTab = SessionStore.duplicateTab(window, tab);
+      await Promise.all([
+        BrowserTestUtils.browserLoaded(newTab.linkedBrowser),
+        TestUtils.topicObserved("sessionstore-debug-tab-restored"),
+      ]);
+      let after = TabStateCache.get(newTab.linkedBrowser.permanentKey);
+
+      isnot(
+        before.history.entries,
+        after.history.entries,
+        "The entry objects should not be shared"
+      );
+
+      BrowserTestUtils.removeTab(newTab);
+    }
+  );
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_duplicate_tab_in_new_window.js b/src/zen/tests/mochitests/sessionstore/browser_duplicate_tab_in_new_window.js
new file mode 100644
index 000000000..d3baf1cd4
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_duplicate_tab_in_new_window.js
@@ -0,0 +1,37 @@
+ChromeUtils.defineESModuleGetters(this, {
+  SessionStore: "resource:///modules/sessionstore/SessionStore.sys.mjs",
+});
+
+add_task(async function () {
+  await BrowserTestUtils.withNewTab(
+    "https://example.com",
+    async function (aBrowser) {
+      BrowserTestUtils.startLoadingURIString(aBrowser, "https://example.org");
+      await BrowserTestUtils.browserLoaded(aBrowser);
+
+      let windowOpened = BrowserTestUtils.waitForNewWindow(
+        "https://example.org"
+      );
+      let newWindow = gBrowser.replaceTabWithWindow(
+        gBrowser.getTabForBrowser(aBrowser)
+      );
+      await windowOpened;
+      let newTab = SessionStore.duplicateTab(
+        newWindow,
+        newWindow.gBrowser.selectedTab
+      );
+
+      await BrowserTestUtils.browserLoaded(newTab.linkedBrowser);
+
+      await SpecialPowers.spawn(
+        newTab.linkedBrowser,
+        ["https://example.org"],
+        async ORIGIN => {
+          is(content.window.origin, ORIGIN);
+        }
+      );
+
+      BrowserTestUtils.closeWindow(newWindow);
+    }
+  );
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_dying_cache.js b/src/zen/tests/mochitests/sessionstore/browser_dying_cache.js
new file mode 100644
index 000000000..59357ae7c
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_dying_cache.js
@@ -0,0 +1,84 @@
+"use strict";
+
+/**
+ * This test ensures that after closing a window we keep its state data around
+ * as long as something keeps a reference to it. It should only be possible to
+ * read data after closing - writing should fail.
+ */
+
+add_task(async function test() {
+  // Open a new window.
+  let win = await promiseNewWindowLoaded();
+
+  // Load some URL in the current tab.
+  let flags = Ci.nsIWebNavigation.LOAD_FLAGS_REPLACE_HISTORY;
+  BrowserTestUtils.startLoadingURIString(
+    win.gBrowser.selectedBrowser,
+    "about:robots",
+    {
+      flags,
+    }
+  );
+  await promiseBrowserLoaded(win.gBrowser.selectedBrowser);
+
+  // Open a second tab and close the first one.
+  let tab = BrowserTestUtils.addTab(win.gBrowser, "about:mozilla");
+  await promiseBrowserLoaded(tab.linkedBrowser);
+  await TabStateFlusher.flush(tab.linkedBrowser);
+  await promiseRemoveTabAndSessionState(win.gBrowser.tabs[0]);
+
+  // Make sure our window is still tracked by sessionstore
+  // and the window state is as expected.
+  ok("__SSi" in win, "window is being tracked by sessionstore");
+  ss.setCustomWindowValue(win, "foo", "bar");
+  checkWindowState(win);
+
+  // Close our window.
+  await BrowserTestUtils.closeWindow(win);
+
+  // SessionStore should no longer track our window
+  // but it should still report the same state.
+  ok(!("__SSi" in win), "sessionstore does no longer track our window");
+  checkWindowState(win);
+
+  // Make sure we're not allowed to modify state data.
+  Assert.throws(
+    () => ss.setWindowState(win, {}),
+    /Window is not tracked/,
+    "we're not allowed to modify state data anymore"
+  );
+  Assert.throws(
+    () => ss.setCustomWindowValue(win, "foo", "baz"),
+    /Window is not tracked/,
+    "we're not allowed to modify state data anymore"
+  );
+});
+
+function checkWindowState(window) {
+  let {
+    windows: [{ tabs }],
+  } = ss.getWindowState(window);
+  is(tabs.length, 1, "the window has a single tab");
+  is(tabs[0].entries[0].url, "about:mozilla", "the tab is about:mozilla");
+
+  is(ss.getClosedTabCountForWindow(window), 1, "the window has one closed tab");
+  let [
+    {
+      state: {
+        entries: [{ url }],
+      },
+    },
+  ] = ss.getClosedTabDataForWindow(window);
+  is(url, "about:robots", "the closed tab is about:robots");
+
+  is(ss.getCustomWindowValue(window, "foo"), "bar", "correct extData value");
+}
+
+function shouldThrow(f) {
+  try {
+    f();
+  } catch (e) {
+    return true;
+  }
+  return null;
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_dynamic_frames.js b/src/zen/tests/mochitests/sessionstore/browser_dynamic_frames.js
new file mode 100644
index 000000000..0fadc1854
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_dynamic_frames.js
@@ -0,0 +1,107 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/**
+ * Ensure that static frames of framesets are serialized but dynamically
+ * inserted iframes are ignored.
+ */
+add_task(async function () {
+  // This URL has the following frames:
+  //  + data:text/html,A (static)
+  //  + data:text/html,B (static)
+  //  + data:text/html,C (dynamic iframe)
+  const URL =
+    "data:text/html;charset=utf-8," +
+    "<frameset cols=50%25,50%25><frame src='data:text/html,A'>" +
+    "<frame src='data:text/html,B'></frameset>" +
+    "<script>var i=document.createElement('iframe');" +
+    "i.setAttribute('src', 'data:text/html,C');" +
+    "document.body.appendChild(i);</script>";
+
+  // Add a new tab with two "static" and one "dynamic" frame.
+  let tab = BrowserTestUtils.addTab(gBrowser, URL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  await TabStateFlusher.flush(browser);
+  let { entries } = JSON.parse(ss.getTabState(tab));
+
+  // Check URLs.
+  ok(entries[0].url.startsWith("data:text/html"), "correct root url");
+  is(
+    entries[0].children[0].url,
+    "data:text/html,A",
+    "correct url for 1st frame"
+  );
+  is(
+    entries[0].children[1].url,
+    "data:text/html,B",
+    "correct url for 2nd frame"
+  );
+
+  // Check the number of children.
+  is(entries.length, 1, "there is one root entry ...");
+  is(entries[0].children.length, 2, "... with two child entries");
+
+  // Cleanup.
+  gBrowser.removeTab(tab);
+});
+
+/**
+ * Ensure that iframes created by the network parser are serialized but
+ * dynamically inserted iframes are ignored. Navigating a subframe should
+ * create a second root entry that doesn't contain any dynamic children either.
+ */
+add_task(async function () {
+  // This URL has the following frames:
+  //  + data:text/html,A (static)
+  //  + data:text/html,C (dynamic iframe)
+  const URL =
+    "data:text/html;charset=utf-8," +
+    "<iframe name=t src='data:text/html,A'></iframe>" +
+    "<a id=lnk href='data:text/html,B' target=t>clickme</a>" +
+    "<script>var i=document.createElement('iframe');" +
+    "i.setAttribute('src', 'data:text/html,C');" +
+    "document.body.appendChild(i);</script>";
+
+  // Add a new tab with one "static" and one "dynamic" frame.
+  let tab = BrowserTestUtils.addTab(gBrowser, URL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  await TabStateFlusher.flush(browser);
+  let { entries } = JSON.parse(ss.getTabState(tab));
+
+  // Check URLs.
+  ok(entries[0].url.startsWith("data:text/html"), "correct root url");
+  ok(!entries[0].children, "no children collected");
+
+  // Navigate the subframe by activating the link. Activate it directly in
+  // content rather than synthesizing a mouse click: the link sits inline
+  // between two asynchronously-loading iframes, so a coordinate-based click can
+  // intermittently miss it while layout is still reflowing. Set up the load
+  // listener before activating so the subframe load can't be missed either.
+  let loaded = promiseBrowserLoaded(
+    browser,
+    false /* don't ignore subframes */
+  );
+  await SpecialPowers.spawn(browser, [], () => {
+    content.document.getElementById("lnk").click();
+  });
+  await loaded;
+
+  await TabStateFlusher.flush(browser);
+  ({ entries } = JSON.parse(ss.getTabState(tab)));
+
+  // Check URLs.
+  ok(entries[0].url.startsWith("data:text/html"), "correct 1st root url");
+  ok(entries[1].url.startsWith("data:text/html"), "correct 2nd root url");
+  ok(!entries.children, "no children collected");
+  ok(!entries[0].children, "no children collected");
+  ok(!entries[1].children, "no children collected");
+
+  // Cleanup.
+  gBrowser.removeTab(tab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_firefoxView_restore.js b/src/zen/tests/mochitests/sessionstore/browser_firefoxView_restore.js
new file mode 100644
index 000000000..96533b85e
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_firefoxView_restore.js
@@ -0,0 +1,45 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const CLOSED_URI = "https://www.example.com/";
+
+const FirefoxViewTestUtils = ChromeUtils.importESModule(
+  "resource://testing-common/FirefoxViewTestUtils.sys.mjs"
+);
+FirefoxViewTestUtils.init(this);
+FirefoxViewTestUtils.enableFirefoxViewButton(window);
+
+add_task(async function test_TODO() {
+  let tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, CLOSED_URI);
+
+  Assert.equal(gBrowser.tabs[0].linkedBrowser.currentURI.filePath, "blank");
+
+  Assert.equal(gBrowser.tabs[1].linkedBrowser.currentURI.spec, CLOSED_URI);
+
+  Assert.equal(gBrowser.selectedTab, tab);
+
+  let state = ss.getCurrentState(true);
+
+  // SessionStore uses one-based indexes
+  Assert.equal(state.windows[0].selected, 2);
+
+  EventUtils.synthesizeMouseAtCenter(
+    window.document.getElementById("firefox-view-button"),
+    { type: "mousedown" },
+    window
+  );
+  Assert.ok(window.FirefoxViewHandler.tab.selected);
+
+  Assert.equal(gBrowser.tabs[2], window.FirefoxViewHandler.tab);
+
+  state = ss.getCurrentState(true);
+
+  // The FxView tab doesn't get recorded in the session state, but if it's the last selected tab when a window is closed
+  // we want to point to the first tab in the tab strip upon restore
+  Assert.equal(state.windows[0].selected, 1);
+
+  gBrowser.removeTab(window.FirefoxViewHandler.tab);
+  gBrowser.removeTab(tab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_firefoxView_selected_restore.js b/src/zen/tests/mochitests/sessionstore/browser_firefoxView_selected_restore.js
new file mode 100644
index 000000000..2538e444b
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_firefoxView_selected_restore.js
@@ -0,0 +1,94 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { _LastSession } = ChromeUtils.importESModule(
+  "resource:///modules/sessionstore/SessionStore.sys.mjs"
+);
+const { sinon } = ChromeUtils.importESModule(
+  "resource://testing-common/Sinon.sys.mjs"
+);
+const FirefoxViewTestUtils = ChromeUtils.importESModule(
+  "resource://testing-common/FirefoxViewTestUtils.sys.mjs"
+);
+
+const state = {
+  windows: [
+    {
+      tabs: [
+        {
+          entries: [
+            {
+              url: "https://example.org/",
+              triggeringPrincipal_base64,
+            },
+          ],
+        },
+      ],
+      selected: 2,
+    },
+  ],
+};
+
+FirefoxViewTestUtils.init(this);
+FirefoxViewTestUtils.enableFirefoxViewButton(window);
+
+add_task(async function test_firefox_view_selected_tab() {
+  let fxViewBtn = document.getElementById("firefox-view-button");
+  ok(fxViewBtn, "Got the Firefox View button");
+  fxViewBtn.click();
+
+  await BrowserTestUtils.browserLoaded(
+    window.FirefoxViewHandler.tab.linkedBrowser
+  );
+
+  let allTabsRestored = promiseSessionStoreLoads(1);
+
+  _LastSession.setState(state);
+
+  is(gBrowser.tabs.length, 2, "Number of tabs is 2");
+
+  ss.restoreLastSession();
+
+  await allTabsRestored;
+
+  ok(
+    window.FirefoxViewHandler.tab.selected,
+    "The Firefox View tab is selected and the browser window did not close"
+  );
+  is(gBrowser.tabs.length, 3, "Number of tabs is 3");
+
+  gBrowser.removeTab(window.FirefoxViewHandler.tab);
+  gBrowser.removeTab(gBrowser.selectedTab);
+});
+
+add_task(async function test_firefox_view_previously_selected() {
+  let fxViewBtn = document.getElementById("firefox-view-button");
+  ok(fxViewBtn, "Got the Firefox View button");
+  fxViewBtn.click();
+
+  await BrowserTestUtils.browserLoaded(
+    window.FirefoxViewHandler.tab.linkedBrowser
+  );
+
+  let tab = gBrowser.tabs[1];
+  gBrowser.selectedTab = tab;
+
+  let allTabsRestored = promiseSessionStoreLoads(1);
+
+  _LastSession.setState(state);
+
+  is(gBrowser.tabs.length, 2, "Number of tabs is 2");
+
+  ss.restoreLastSession();
+
+  await allTabsRestored;
+
+  ok(
+    window.FirefoxViewHandler.tab.selected,
+    "The Firefox View tab is selected and the browser window did not close"
+  );
+  is(gBrowser.tabs.length, 3, "Number of tabs is 3");
+
+  gBrowser.removeTab(window.FirefoxViewHandler.tab);
+  gBrowser.removeTab(gBrowser.selectedTab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_focus_after_restore.js b/src/zen/tests/mochitests/sessionstore/browser_focus_after_restore.js
new file mode 100644
index 000000000..220827657
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_focus_after_restore.js
@@ -0,0 +1,34 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+add_task(async function test() {
+  gURLBar.focus();
+  is(
+    document.activeElement,
+    gURLBar.inputField,
+    "urlbar is focused before restoring"
+  );
+
+  await promiseBrowserState({
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              {
+                url: "http://example.org/",
+                triggeringPrincipal_base64,
+              },
+            ],
+          },
+        ],
+        selected: 1,
+      },
+    ],
+  });
+  is(
+    document.activeElement,
+    gBrowser.selectedBrowser,
+    "content area is focused after restoring"
+  );
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_forget_async_closings.js b/src/zen/tests/mochitests/sessionstore/browser_forget_async_closings.js
new file mode 100644
index 000000000..89e9e9b17
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_forget_async_closings.js
@@ -0,0 +1,163 @@
+"use strict";
+
+const PAGE = "http://example.com/";
+
+/**
+ * Creates a tab in the current window worth storing in the
+ * closedTabs array, and then closes it. Runs a synchronous
+ * forgetFn passed in that should cause us to forget the tab,
+ * and then ensures that after the tab has sent its final
+ * update message that we didn't accidentally store it in
+ * the closedTabs array.
+ *
+ * @param forgetFn (function)
+ *        A synchronous function that should cause the tab
+ *        to be forgotten.
+ * @returns Promise
+ */
+let forgetTabHelper = async function (forgetFn) {
+  // We want to suppress all non-final updates from the browser tabs
+  // so as to eliminate any racy-ness with this test.
+  await pushPrefs(["browser.sessionstore.debug.no_auto_updates", true]);
+
+  // Forget any previous closed tabs from other tests that may have
+  // run in the same session.
+  Services.obs.notifyObservers(null, "browser:purge-session-history");
+
+  is(
+    ss.getClosedTabCountForWindow(window),
+    0,
+    "We should have 0 closed tabs being stored."
+  );
+
+  // Create a tab worth remembering.
+  let tab = BrowserTestUtils.addTab(gBrowser, PAGE);
+  let browser = tab.linkedBrowser;
+  await BrowserTestUtils.browserLoaded(browser, false, PAGE);
+  await TabStateFlusher.flush(browser);
+
+  // Now close the tab, and immediately choose to forget it.
+  let promise = promiseRemoveTabAndSessionState(tab);
+
+  // At this point, the tab will have closed, but the final update
+  // to SessionStore hasn't come up yet. Now do the operation that
+  // should cause us to forget the tab.
+  forgetFn();
+
+  is(
+    ss.getClosedTabCountForWindow(window),
+    0,
+    "Should have forgotten the closed tab"
+  );
+
+  // Now wait for the final update to come up.
+  await promise;
+
+  is(
+    ss.getClosedTabCountForWindow(window),
+    0,
+    "Should not have stored the forgotten closed tab"
+  );
+};
+
+/**
+ * Creates a new window worth storing in the closeWIndows array,
+ * and then closes it. Runs a synchronous forgetFn passed in that
+ * should cause us to forget the window, and then ensures that after
+ * the window has sent its final update message that we didn't
+ * accidentally store it in the closedWindows array.
+ *
+ * @param forgetFn (function)
+ *        A synchronous function that should cause the window
+ *        to be forgotten.
+ * @returns Promise
+ */
+let forgetWinHelper = async function (forgetFn) {
+  // We want to suppress all non-final updates from the browser tabs
+  // so as to eliminate any racy-ness with this test.
+  await pushPrefs(["browser.sessionstore.debug.no_auto_updates", true]);
+
+  // Forget any previous closed windows from other tests that may have
+  // run in the same session.
+  Services.obs.notifyObservers(null, "browser:purge-session-history");
+
+  is(
+    ss.getClosedWindowCount(),
+    0,
+    "We should have 0 closed windows being stored."
+  );
+
+  let newWin = await BrowserTestUtils.openNewBrowserWindow();
+
+  // Create a tab worth remembering.
+  let tab = newWin.gBrowser.selectedTab;
+  let browser = tab.linkedBrowser;
+  BrowserTestUtils.startLoadingURIString(browser, PAGE);
+  await BrowserTestUtils.browserLoaded(browser, false, PAGE);
+  await TabStateFlusher.flush(browser);
+
+  // Now close the window and immediately choose to forget it.
+  let windowClosed = BrowserTestUtils.windowClosed(newWin);
+
+  let handled = false;
+  whenDomWindowClosedHandled(() => {
+    // At this point, the window will have closed and the onClose handler
+    // has run, but the final update  to SessionStore hasn't come up yet.
+    // Now do the oepration that should cause us to forget the window.
+    forgetFn();
+
+    is(ss.getClosedWindowCount(), 0, "Should have forgotten the closed window");
+
+    handled = true;
+  });
+
+  newWin.close();
+
+  // Now wait for the final update to come up.
+  await windowClosed;
+
+  ok(handled, "domwindowclosed should already be handled here");
+
+  is(ss.getClosedWindowCount(), 0, "Should not have stored the closed window");
+};
+
+/**
+ * Tests that if we choose to forget a tab while waiting for its
+ * final flush to complete, we don't accidentally store it.
+ */
+add_task(async function test_forget_closed_tab() {
+  await forgetTabHelper(() => {
+    ss.forgetClosedTab(window, 0);
+  });
+});
+
+/**
+ * Tests that if we choose to forget a tab while waiting for its
+ * final flush to complete, we don't accidentally store it.
+ */
+add_task(async function test_forget_closed_window() {
+  await forgetWinHelper(() => {
+    ss.forgetClosedWindow(0);
+  });
+});
+
+/**
+ * Tests that if we choose to purge history while waiting for a
+ * final flush of a tab to complete, we don't accidentally store it.
+ */
+add_task(async function test_forget_purged_tab() {
+  await forgetTabHelper(() => {
+    Services.obs.notifyObservers(null, "browser:purge-session-history");
+  });
+});
+
+/**
+ * Tests that if we choose to purge history while waiting for a
+ * final flush of a window to complete, we don't accidentally
+ * store it.
+ */
+add_task(async function test_forget_purged_window() {
+  await forgetWinHelper(() => {
+    Services.obs.notifyObservers(null, "browser:purge-session-history");
+  });
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_forget_closed_tab_window_byId.js b/src/zen/tests/mochitests/sessionstore/browser_forget_closed_tab_window_byId.js
new file mode 100644
index 000000000..90f2227dd
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_forget_closed_tab_window_byId.js
@@ -0,0 +1,179 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const TEST_URLS = [
+  "http://mochi.test:8888/browser/",
+  "https://www.example.com/",
+  "https://example.net/",
+  "https://example.org/",
+];
+
+let window1, privateWin;
+let tab1, privateTab;
+
+async function openTab(window, url) {
+  let tab = BrowserTestUtils.addTab(window.gBrowser, url);
+  await promiseBrowserLoaded(tab.linkedBrowser, true, url);
+  return tab;
+}
+
+add_setup(async function testSetup() {
+  // prepare some closed state
+  window1 = await BrowserTestUtils.openNewBrowserWindow();
+  await openAndCloseTab(window1, TEST_URLS[0]);
+  // open another non-empty tab
+  tab1 = await openTab(window1, TEST_URLS[1]);
+
+  // open a private window
+  privateWin = await BrowserTestUtils.openNewBrowserWindow({ private: true });
+  // open another non-empty tab
+  privateTab = await openTab(privateWin, TEST_URLS[2]);
+  await openAndCloseTab(privateWin, TEST_URLS[3]);
+
+  registerCleanupFunction(async () => {
+    let windows = [];
+    for (let win of BrowserWindowTracker.orderedWindows) {
+      if (win != window) {
+        windows.push(win);
+      }
+    }
+    await Promise.all(windows.map(BrowserTestUtils.closeWindow));
+    Services.obs.notifyObservers(null, "browser:purge-session-history");
+  });
+});
+
+add_task(async function closeAndForgetTabs() {
+  // sanity check recently-closed tab data
+  Assert.equal(
+    SessionStore.getClosedTabCount(window1),
+    1,
+    "Only one tab closed in non-private windows"
+  );
+  Assert.equal(
+    SessionStore.getClosedTabCount(privateWin),
+    1,
+    "Only one tab closed in non-private windows"
+  );
+
+  // sanity check open tabs
+  Assert.equal(window1.gBrowser.tabs.length, 2, "Expected number of tabs open");
+  Assert.equal(
+    privateWin.gBrowser.tabs.length,
+    2,
+    "Expected number of tabs open"
+  );
+
+  let closedTabs = SessionStore.getClosedTabData(window1); // only non-private closed tabs
+  Assert.equal(typeof closedTabs[0].closedId, "number", "closedId is a number");
+  let sessionStoreUpdated = TestUtils.topicObserved(
+    "sessionstore-closed-objects-changed"
+  );
+  SessionStore.forgetClosedTabById(closedTabs[0].closedId);
+  await sessionStoreUpdated;
+  Assert.equal(
+    SessionStore.getClosedTabCount(window1),
+    0,
+    "There's no more records of closed tabs"
+  );
+
+  closedTabs = SessionStore.getClosedTabData(privateWin); // only private closed tabs
+  Assert.equal(typeof closedTabs[0].closedId, "number", "closedId is a number");
+
+  Assert.throws(
+    () => {
+      SessionStore.forgetClosedTabById(closedTabs[0].closedId, {
+        includePrivate: false,
+      });
+    },
+    /Invalid closedId/,
+    "forgetClosedWindowById should throw an exception when trying to match a closedId from a private window in non-private windows"
+  );
+
+  Assert.equal(
+    SessionStore.getClosedTabCount(privateWin),
+    1,
+    "Still one tab closed in non-private windows"
+  );
+
+  sessionStoreUpdated = TestUtils.topicObserved(
+    "sessionstore-closed-objects-changed"
+  );
+  SessionStore.forgetClosedTabById(closedTabs[0].closedId);
+  await sessionStoreUpdated;
+  Assert.equal(
+    SessionStore.getClosedTabCount(privateWin),
+    0,
+    "There's no more records of private closed tabs"
+  );
+});
+
+add_task(async function closeAndForgetTabsFromTabGroups() {
+  const newWin = await BrowserTestUtils.openNewBrowserWindow();
+
+  // sanity check recently-closed tab data
+  Assert.equal(SessionStore.getClosedTabCount(newWin), 0, "No tabs closed");
+
+  let groupedTab = await openTab(newWin, TEST_URLS[1]);
+  let group = newWin.gBrowser.addTabGroup([groupedTab]);
+  let removePromise = BrowserTestUtils.waitForEvent(group, "TabGroupRemoved");
+  newWin.gBrowser.removeTabGroup(group);
+  await removePromise;
+  await TabStateFlusher.flushWindow(newWin);
+
+  await TestUtils.waitForCondition(() => {
+    return SessionStore.getClosedTabCount(newWin) == 1;
+  }, "Grouped tab is closed");
+
+  let closedTabs = SessionStore.getClosedTabData(newWin);
+  let sessionStoreUpdated = TestUtils.topicObserved(
+    "sessionstore-closed-objects-changed"
+  );
+  SessionStore.forgetClosedTabById(closedTabs[0].closedId);
+  await sessionStoreUpdated;
+
+  Assert.equal(
+    SessionStore.getClosedTabCount(newWin),
+    0,
+    "Grouped tab was forgotten"
+  );
+});
+
+add_task(async function closeAndForgetWindows() {
+  let closedWindows;
+  await BrowserTestUtils.closeWindow(window1);
+  closedWindows = SessionStore.getClosedWindowData();
+  Assert.equal(
+    closedWindows.length,
+    1,
+    "There's one record for closed windows"
+  );
+
+  let sessionStoreUpdated = TestUtils.topicObserved(
+    "sessionstore-closed-objects-changed"
+  );
+  let closedWindowId = closedWindows[0].closedId;
+  SessionStore.forgetClosedWindowById(closedWindowId);
+  await sessionStoreUpdated;
+  Assert.equal(
+    SessionStore.getClosedWindowCount(),
+    0,
+    "There's no more records of closed windows"
+  );
+
+  await BrowserTestUtils.closeWindow(privateWin);
+  await TestUtils.waitForTick();
+  Assert.equal(
+    SessionStore.getClosedWindowCount(),
+    0,
+    "Closing the private window didn't add a closed window entry"
+  );
+  // check a non-matching closedId throws an exception
+  Assert.throws(
+    () => {
+      SessionStore.forgetClosedWindowById(closedWindowId);
+    },
+    /Invalid closedId/,
+    "forgetClosedWindowById should throw an exception when given an closedId that doesnt match any closed window"
+  );
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_formdata.js b/src/zen/tests/mochitests/sessionstore/browser_formdata.js
new file mode 100644
index 000000000..7e814e142
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_formdata.js
@@ -0,0 +1,227 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+requestLongerTimeout(2);
+
+/**
+ * This test ensures that form data collection respects the privacy level as
+ * set by the user.
+ */
+add_task(async function test_formdata() {
+  const URL =
+    "http://mochi.test:8888/browser/browser/components/" +
+    "sessionstore/test/browser_formdata_sample.html";
+
+  const OUTER_VALUE = "browser_formdata_" + Math.random();
+  const INNER_VALUE = "browser_formdata_" + Math.random();
+
+  // Creates a tab, loads a page with some form fields,
+  // modifies their values and closes the tab.
+  async function createAndRemoveTab() {
+    // Create a new tab.
+    let tab = BrowserTestUtils.addTab(gBrowser, URL);
+    let browser = tab.linkedBrowser;
+    await promiseBrowserLoaded(browser);
+
+    // Modify form data.
+    await setPropertyOfFormField(browser, "#txt", "value", OUTER_VALUE);
+    await setPropertyOfFormField(
+      browser.browsingContext.children[0],
+      "#txt",
+      "value",
+      INNER_VALUE
+    );
+
+    // Remove the tab.
+    await promiseRemoveTabAndSessionState(tab);
+  }
+
+  await createAndRemoveTab();
+  let [
+    {
+      state: { formdata },
+    },
+  ] = ss.getClosedTabDataForWindow(window);
+  is(formdata.id.txt, OUTER_VALUE, "outer value is correct");
+  is(formdata.children[0].id.txt, INNER_VALUE, "inner value is correct");
+
+  // Disable saving data for encrypted sites.
+  Services.prefs.setIntPref("browser.sessionstore.privacy_level", 1);
+
+  await createAndRemoveTab();
+  [
+    {
+      state: { formdata },
+    },
+  ] = ss.getClosedTabDataForWindow(window);
+  is(formdata.id.txt, OUTER_VALUE, "outer value is correct");
+  ok(!formdata.children, "inner value was *not* stored");
+
+  // Disable saving data for any site.
+  Services.prefs.setIntPref("browser.sessionstore.privacy_level", 2);
+
+  await createAndRemoveTab();
+  [
+    {
+      state: { formdata },
+    },
+  ] = ss.getClosedTabDataForWindow(window);
+  ok(!formdata, "form data has *not* been stored");
+
+  // Restore the default privacy level.
+  Services.prefs.clearUserPref("browser.sessionstore.privacy_level");
+});
+
+/**
+ * This test ensures that a malicious website can't trick us into restoring
+ * form data into a wrong website and that we always check the stored URL
+ * before doing so.
+ */
+add_task(async function test_url_check() {
+  const URL = "data:text/html;charset=utf-8,<input id=input>";
+  const VALUE = "value-" + Math.random();
+
+  // Create a tab with an iframe containing an input field.
+  let tab = BrowserTestUtils.addTab(gBrowser, URL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  // Restore a tab state with a given form data url.
+  async function restoreStateWithURL(url) {
+    let state = {
+      entries: [{ url: URL, triggeringPrincipal_base64 }],
+      formdata: { id: { input: VALUE } },
+    };
+
+    if (url) {
+      state.formdata.url = url;
+    }
+
+    await promiseTabState(tab, state);
+    return getPropertyOfFormField(browser, "#input", "value");
+  }
+
+  // Check that the form value is restored with the correct URL.
+  is(await restoreStateWithURL(URL), VALUE, "form data restored");
+
+  // Check that the form value is *not* restored with the wrong URL.
+  is(await restoreStateWithURL(URL + "?"), "", "form data not restored");
+  is(await restoreStateWithURL(), "", "form data not restored");
+
+  // Cleanup.
+  gBrowser.removeTab(tab);
+});
+
+/**
+ * This test ensures that collecting form data works as expected when having
+ * nested frame sets.
+ */
+add_task(async function test_nested() {
+  const URL =
+    "data:text/html;charset=utf-8," +
+    "<iframe src='data:text/html;charset=utf-8,<input/>'/>";
+
+  const FORM_DATA = {
+    children: [
+      {
+        url: "data:text/html;charset=utf-8,<input/>",
+        xpath: { "/xhtml:html/xhtml:body/xhtml:input": "m" },
+      },
+    ],
+  };
+
+  // Create a tab with an iframe containing an input field.
+  let tab = (gBrowser.selectedTab = BrowserTestUtils.addTab(gBrowser, URL));
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser, false /* don't ignore subframes */);
+
+  const iframe = await SpecialPowers.spawn(browser, [], () => {
+    return content.document.querySelector("iframe").browsingContext;
+  });
+  await SpecialPowers.spawn(iframe, [], async () => {
+    const input = content.document.querySelector("input");
+    const focusPromise = new Promise(resolve => {
+      input.addEventListener("focus", resolve, { once: true });
+    });
+    input.focus();
+    await focusPromise;
+  });
+
+  // Modify the input field's value.
+  await BrowserTestUtils.synthesizeKey("m", {}, browser);
+
+  // Remove the tab and check that we stored form data correctly.
+  await promiseRemoveTabAndSessionState(tab);
+  let [
+    {
+      state: { formdata },
+    },
+  ] = ss.getClosedTabDataForWindow(window);
+  is(
+    JSON.stringify(formdata),
+    JSON.stringify(FORM_DATA),
+    "formdata for iframe stored correctly"
+  );
+
+  // Restore the closed tab.
+  tab = ss.undoCloseTab(window, 0);
+  browser = tab.linkedBrowser;
+  await promiseTabRestored(tab);
+
+  // Check that the input field has the right value.
+  await TabStateFlusher.flush(browser);
+  ({ formdata } = JSON.parse(ss.getTabState(tab)));
+  is(
+    JSON.stringify(formdata),
+    JSON.stringify(FORM_DATA),
+    "formdata for iframe restored correctly"
+  );
+
+  // Cleanup.
+  gBrowser.removeTab(tab);
+});
+
+/**
+ * This test ensures that collecting form data for documents with
+ * designMode=on works as expected.
+ */
+add_task(async function test_design_mode() {
+  const URL =
+    "data:text/html;charset=utf-8,<h1>mozilla</h1>" +
+    "<script>document.designMode='on'</script>";
+
+  // Load a tab with an editable document.
+  let tab = (gBrowser.selectedTab = BrowserTestUtils.addTab(gBrowser, URL));
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  // Modify the document content.
+  await BrowserTestUtils.synthesizeKey("m", {}, browser);
+
+  // Close and restore the tab.
+  await promiseRemoveTabAndSessionState(tab);
+  tab = ss.undoCloseTab(window, 0);
+  browser = tab.linkedBrowser;
+  await promiseTabRestored(tab);
+
+  // Check that the innerHTML value was restored.
+  let html = await getPropertyOfFormField(browser, "body", "innerHTML");
+  let expected = "<h1>mmozilla</h1><script>document.designMode='on'</script>";
+  is(html, expected, "editable document has been restored correctly");
+
+  // Close and restore the tab.
+  await promiseRemoveTabAndSessionState(tab);
+  tab = ss.undoCloseTab(window, 0);
+  browser = tab.linkedBrowser;
+  await promiseTabRestored(tab);
+
+  // Check that the innerHTML value was restored.
+  html = await getPropertyOfFormField(browser, "body", "innerHTML");
+  expected = "<h1>mmozilla</h1><script>document.designMode='on'</script>";
+  is(html, expected, "editable document has been restored correctly");
+
+  // Cleanup.
+  gBrowser.removeTab(tab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_formdata_cc.js b/src/zen/tests/mochitests/sessionstore/browser_formdata_cc.js
new file mode 100644
index 000000000..7f0dac811
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_formdata_cc.js
@@ -0,0 +1,107 @@
+"use strict";
+
+const URL =
+  "http://mochi.test:8888/browser/browser/components/" +
+  "sessionstore/test/browser_formdata_sample.html";
+
+requestLongerTimeout(3);
+
+/**
+ * This test ensures that credit card numbers in form data will not be
+ * collected, while numbers that don't look like credit card numbers will
+ * still be collected.
+ */
+add_task(async function () {
+  const validCCNumbers = [
+    // 15 digits
+    "930771457288760",
+    "474915027480942",
+    "924894781317325",
+    "714816113937185",
+    "790466087343106",
+    "474320195408363",
+    "219211148122351",
+    "633038472250799",
+    "354236732906484",
+    "095347810189325",
+    // 16 digits
+    "3091269135815020",
+    "5471839082338112",
+    "0580828863575793",
+    "5015290610002932",
+    "9465714503078607",
+    "4302068493801686",
+    "2721398408985465",
+    "6160334316984331",
+    "8643619970075142",
+    "0218246069710785",
+  ];
+
+  const invalidCCNumbers = [
+    // 15 digits
+    "526931005800649",
+    "724952425140686",
+    "379761391174135",
+    "030551436468583",
+    "947377014076746",
+    "254848023655752",
+    "226871580283345",
+    "708025346034339",
+    "917585839076788",
+    "918632588027666",
+    // 16 digits
+    "9946177098017064",
+    "4081194386488872",
+    "3095975979578034",
+    "3662215692222536",
+    "6723210018630429",
+    "4411962856225025",
+    "8276996369036686",
+    "4449796938248871",
+    "3350852696538147",
+    "5011802870046957",
+  ];
+
+  // Creates a tab, loads a page with a form field, sets the value of the
+  // field, and then removes the tab to trigger data collection.
+  async function createAndRemoveTab(formValue) {
+    // Create a new tab.
+    let tab = BrowserTestUtils.addTab(gBrowser, URL);
+    let browser = tab.linkedBrowser;
+    await promiseBrowserLoaded(browser);
+
+    // Set form value.
+    await setInputValue(browser, formValue);
+
+    // Remove the tab.
+    await promiseRemoveTabAndSessionState(tab);
+  }
+
+  // Test that valid CC numbers are not collected.
+  for (let number of validCCNumbers) {
+    await createAndRemoveTab(number);
+    let [{ state }] = ss.getClosedTabDataForWindow(window);
+    ok(!("formdata" in state), "valid CC numbers are not collected");
+  }
+
+  // Test that non-CC numbers are still collected.
+  for (let number of invalidCCNumbers) {
+    await createAndRemoveTab(number);
+    let [
+      {
+        state: { formdata },
+      },
+    ] = ss.getClosedTabDataForWindow(window);
+    is(
+      formdata.id.txt,
+      number,
+      "numbers that are not valid CC numbers are still collected"
+    );
+  }
+});
+
+function setInputValue(browser, formValue) {
+  return SpecialPowers.spawn(browser, [formValue], async function (newValue) {
+    content.document.getElementById("txt").setUserInput(newValue);
+  });
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_formdata_face.js b/src/zen/tests/mochitests/sessionstore/browser_formdata_face.js
new file mode 100644
index 000000000..5c3833887
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_formdata_face.js
@@ -0,0 +1,168 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/**
+ * This test ensures that collecting form data for form-associated custom
+ * elements works as expected.
+ */
+add_task(async function test_face_restore() {
+  const URL = `data:text/html;charset=utf-8,<!DOCTYPE html>
+    <h1>mozilla</h1>
+    <script>
+      restoredStates = {};
+      customElements.define("c-e", class extends HTMLElement {
+        static formAssociated = true;
+        constructor() {
+          super();
+          this.internals = this.attachInternals();
+        }
+        formStateRestoreCallback(state, reason) {
+          if (reason == "restore") {
+            restoredStates[this.id] = state;
+          }
+        }
+      });
+    </script>
+    <form>
+      <c-e id="test1"></c-e>
+      <c-e id="test2"></c-e>
+      <c-e id="test3"></c-e>
+      <c-e id="test4"></c-e>
+      <c-e id="test5"></c-e>
+      <c-e id="test6"></c-e>
+    </form>`;
+
+  // Load a tab with a FACE.
+  let tab = (gBrowser.selectedTab = BrowserTestUtils.addTab(gBrowser, URL));
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  // Set the FACE state and value.
+  await SpecialPowers.spawn(browser, ["c-e"], selector => {
+    function formDataWith(...entries) {
+      const formData = new content.FormData();
+      for (let [key, value] of entries) {
+        formData.append(key, value);
+      }
+      return formData;
+    }
+    const states = [
+      "test state",
+      new content.File(["state"], "state.txt"),
+      formDataWith(["1", "state"], ["2", new content.Blob(["state_blob"])]),
+      null,
+      undefined,
+      null,
+    ];
+    const values = [
+      "test value",
+      new content.File(["value"], "value.txt"),
+      formDataWith(["1", "value"], ["2", new content.Blob(["value_blob"])]),
+      "null state",
+      "both value and state",
+      null,
+    ];
+
+    [...content.document.querySelectorAll(selector)].forEach((node, i) => {
+      node.internals.setFormValue(values[i], states[i]);
+    });
+  });
+
+  // Close and restore the tab.
+  await promiseRemoveTabAndSessionState(tab);
+
+  {
+    let [
+      {
+        state: { formdata },
+      },
+    ] = ss.getClosedTabDataForWindow(window);
+
+    is(formdata.id.test1.value, "test value", "String value should be stored");
+    is(formdata.id.test1.state, "test state", "String state should be stored");
+
+    let storedFile = formdata.id.test2.value;
+    is(storedFile.name, "value.txt", "File value name should be stored");
+    is(await storedFile.text(), "value", "File value text should be stored");
+    storedFile = formdata.id.test2.state;
+    is(storedFile.name, "state.txt", "File state name should be stored");
+    is(await storedFile.text(), "state", "File state text should be stored");
+
+    let storedFormData = formdata.id.test3.value;
+    is(
+      storedFormData.get("1"),
+      "value",
+      "FormData value string should be stored"
+    );
+    is(
+      await storedFormData.get("2").text(),
+      "value_blob",
+      "Form value blob should be stored"
+    );
+    storedFormData = formdata.id.test3.state;
+    is(
+      storedFormData.get("1"),
+      "state",
+      "FormData state string should be stored"
+    );
+    is(
+      await storedFormData.get("2").text(),
+      "state_blob",
+      "Form state blob should be stored"
+    );
+
+    is(formdata.id.test4.state, null, "Null state stored");
+    is(formdata.id.test4.value, "null state", "Value with null state stored");
+
+    is(
+      formdata.id.test5.value,
+      "both value and state",
+      "Undefined state should be set to value"
+    );
+    is(
+      formdata.id.test5.state,
+      "both value and state",
+      "Undefined state should be set to value"
+    );
+
+    ok(
+      !("test6" in formdata.id),
+      "Completely null values should not be stored"
+    );
+  }
+
+  tab = ss.undoCloseTab(window, 0);
+  browser = tab.linkedBrowser;
+  await promiseTabRestored(tab);
+
+  // Check that the FACE state was restored.
+  await SpecialPowers.spawn(browser, ["restoredStates"], async prop => {
+    let restoredStates = content.wrappedJSObject[prop];
+    is(restoredStates.test1, "test state", "String should be stored");
+
+    let storedFile = restoredStates.test2;
+    is(storedFile.name, "state.txt", "File name should be stored");
+    is(await storedFile.text(), "state", "File text should be stored");
+
+    const storedFormData = restoredStates.test3;
+    is(storedFormData.get("1"), "state", "Form data string should be stored");
+    is(
+      await storedFormData.get("2").text(),
+      "state_blob",
+      "Form data blob should be stored"
+    );
+
+    ok(!("test4" in restoredStates), "Null values don't get restored");
+
+    is(
+      restoredStates.test5,
+      "both value and state",
+      "Undefined state should be set to value"
+    );
+  });
+
+  // Cleanup.
+  gBrowser.removeTab(tab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_formdata_format.js b/src/zen/tests/mochitests/sessionstore/browser_formdata_format.js
new file mode 100644
index 000000000..841177d31
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_formdata_format.js
@@ -0,0 +1,172 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+function test() {
+  /** Tests formdata format */
+  waitForExplicitFinish();
+
+  let formData = [
+    {},
+    // old format
+    { "#input1": "value0" },
+    {
+      "#input1": "value1",
+      "/xhtml:html/xhtml:body/xhtml:input[@name='input2']": "value2",
+    },
+    { "/xhtml:html/xhtml:body/xhtml:input[@name='input2']": "value3" },
+    // new format
+    { id: { input1: "value4" } },
+    { id: { input1: "value5" }, xpath: {} },
+    {
+      id: { input1: "value6" },
+      xpath: { "/xhtml:html/xhtml:body/xhtml:input[@name='input2']": "value7" },
+    },
+    {
+      id: {},
+      xpath: { "/xhtml:html/xhtml:body/xhtml:input[@name='input2']": "value8" },
+    },
+    {
+      xpath: { "/xhtml:html/xhtml:body/xhtml:input[@name='input2']": "value9" },
+    },
+    // combinations
+    { "#input1": "value10", id: { input1: "value11" } },
+    {
+      "#input1": "value12",
+      id: { input1: "value13" },
+      xpath: {
+        "/xhtml:html/xhtml:body/xhtml:input[@name='input2']": "value14",
+      },
+    },
+    {
+      "#input1": "value15",
+      xpath: {
+        "/xhtml:html/xhtml:body/xhtml:input[@name='input2']": "value16",
+      },
+    },
+    {
+      "/xhtml:html/xhtml:body/xhtml:input[@name='input2']": "value17",
+      id: { input1: "value18" },
+    },
+    {
+      "/xhtml:html/xhtml:body/xhtml:input[@name='input2']": "value19",
+      id: { input1: "value20" },
+      xpath: {
+        "/xhtml:html/xhtml:body/xhtml:input[@name='input2']": "value21",
+      },
+    },
+    {
+      "/xhtml:html/xhtml:body/xhtml:input[@name='input2']": "value22",
+      xpath: {
+        "/xhtml:html/xhtml:body/xhtml:input[@name='input2']": "value23",
+      },
+    },
+    {
+      "#input1": "value24",
+      "/xhtml:html/xhtml:body/xhtml:input[@name='input2']": "value25",
+      id: { input1: "value26" },
+    },
+    {
+      "#input1": "value27",
+      "/xhtml:html/xhtml:body/xhtml:input[@name='input2']": "value28",
+      id: { input1: "value29" },
+      xpath: {
+        "/xhtml:html/xhtml:body/xhtml:input[@name='input2']": "value30",
+      },
+    },
+    {
+      "#input1": "value31",
+      "/xhtml:html/xhtml:body/xhtml:input[@name='input2']": "value32",
+      xpath: {
+        "/xhtml:html/xhtml:body/xhtml:input[@name='input2']": "value33",
+      },
+    },
+  ];
+  let expectedValues = [
+    ["", ""],
+    // old format
+    ["value0", ""],
+    ["value1", "value2"],
+    ["", "value3"],
+    // new format
+    ["value4", ""],
+    ["value5", ""],
+    ["value6", "value7"],
+    ["", "value8"],
+    ["", "value9"],
+    // combinations
+    ["value11", ""],
+    ["value13", "value14"],
+    ["", "value16"],
+    ["value18", ""],
+    ["value20", "value21"],
+    ["", "value23"],
+    ["value26", ""],
+    ["value29", "value30"],
+    ["", "value33"],
+  ];
+
+  let promises = [];
+  for (let i = 0; i < formData.length; i++) {
+    promises.push(testTabRestoreData(formData[i], expectedValues[i]));
+  }
+
+  Promise.all(promises).then(
+    () => finish(),
+    ex => ok(false, ex)
+  );
+}
+
+async function testTabRestoreData(aFormData, aExpectedValue) {
+  let URL = ROOT + "browser_formdata_format_sample.html";
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:blank");
+
+  aFormData.url = URL;
+  let tabState = {
+    entries: [{ url: URL, triggeringPrincipal_base64 }],
+    formdata: aFormData,
+  };
+
+  await BrowserTestUtils.browserLoaded(tab.linkedBrowser, {
+    wantLoad: "about:blank",
+  });
+  await promiseTabState(tab, tabState);
+
+  await TabStateFlusher.flush(tab.linkedBrowser);
+  let restoredTabState = JSON.parse(ss.getTabState(tab));
+  let restoredFormData = restoredTabState.formdata;
+
+  if (restoredFormData) {
+    let doc = tab.linkedBrowser.contentDocument;
+    let input1 = doc.getElementById("input1");
+    let input2 = doc.querySelector("input[name=input2]");
+
+    // test format
+    ok(
+      "id" in restoredFormData || "xpath" in restoredFormData,
+      "FormData format is valid: " + restoredFormData
+    );
+    // validate that there are no old keys
+    for (let key of Object.keys(restoredFormData)) {
+      if (!["id", "xpath", "url"].includes(key)) {
+        ok(false, "FormData format is invalid.");
+      }
+    }
+    // test id
+    is(
+      input1.value,
+      aExpectedValue[0],
+      "FormData by 'id' has been restored correctly"
+    );
+    // test xpath
+    is(
+      input2.value,
+      aExpectedValue[1],
+      "FormData by 'xpath' has been restored correctly"
+    );
+  }
+
+  // clean up
+  gBrowser.removeTab(tab);
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_formdata_format_sample.html b/src/zen/tests/mochitests/sessionstore/browser_formdata_format_sample.html
new file mode 100644
index 000000000..ed71702a1
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_formdata_format_sample.html
@@ -0,0 +1,7 @@
+<!DOCTYPE html>
+<title>Test formdata format</title>
+
+<!-- input events -->
+<h3>Input fields</h3>
+<input type="text" id="input1">
+<input type="text" name="input2">
diff --git a/src/zen/tests/mochitests/sessionstore/browser_formdata_max_size.js b/src/zen/tests/mochitests/sessionstore/browser_formdata_max_size.js
new file mode 100644
index 000000000..00b49985e
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_formdata_max_size.js
@@ -0,0 +1,131 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const URL =
+  "http://mochi.test:8888/browser/browser/components/" +
+  "sessionstore/test/browser_formdata_sample.html";
+
+const SHORT_VALUE = "abc";
+const LONG_VALUE = "abcdef";
+
+add_task(async function test_form_limit() {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      // "browser.sessionstore.dom_form_limit" limits the length of values in
+      // forms to 5. Here we have that SHORT_VALUE is less than 5 and
+      // LONG_VALUE is greater than 5.
+      ["browser.sessionstore.dom_form_limit", 5],
+      ["browser.sessionstore.debug.no_auto_updates", true],
+    ],
+  });
+
+  await BrowserTestUtils.withNewTab({ gBrowser, url: URL }, async browser => {
+    await setPropertyOfFormField(browser, "#txt", "value", SHORT_VALUE);
+    await TabStateFlusher.flush(browser);
+
+    let tab = gBrowser.getTabForBrowser(browser);
+    let state = JSON.parse(ss.getTabState(tab));
+    is(
+      state.formdata.id.txt,
+      SHORT_VALUE,
+      "values shorter than browser.sessionstore.dom_form_limit is ok."
+    );
+
+    await setPropertyOfFormField(browser, "#txt", "value", LONG_VALUE);
+    await TabStateFlusher.flush(browser);
+
+    state = JSON.parse(ss.getTabState(tab));
+    ok(
+      !state?.formdata?.id?.txt,
+      "values shorter than browser.sessionstore.dom_form_limit isn't ok."
+    );
+  });
+
+  await SpecialPowers.popPrefEnv();
+});
+
+add_task(async function test_form_max_limit() {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      // "browser.sessionstore.dom_form_max_limit" limits the total length
+      // of values AND length id/xpath collected from a form. Here we have
+      // that SHORT_VALUE + 'txt' is less than 7 and LONG_VALUE + 'txt' is
+      // greater than 7.
+      ["browser.sessionstore.dom_form_max_limit", 7],
+      ["browser.sessionstore.debug.no_auto_updates", true],
+    ],
+  });
+
+  await BrowserTestUtils.withNewTab({ gBrowser, url: URL }, async browser => {
+    await setPropertyOfFormField(browser, "#txt", "value", SHORT_VALUE);
+    await TabStateFlusher.flush(browser);
+
+    let tab = gBrowser.getTabForBrowser(browser);
+    let state = JSON.parse(ss.getTabState(tab));
+    is(
+      state.formdata.id.txt,
+      SHORT_VALUE,
+      "total length shorter than browser.sessionstore.dom_form_max_limit is ok."
+    );
+
+    await setPropertyOfFormField(browser, "#txt", "value", LONG_VALUE);
+    await TabStateFlusher.flush(browser);
+
+    state = JSON.parse(ss.getTabState(tab));
+    is(
+      state.formdata.id.txt,
+      SHORT_VALUE,
+      "total length shorter than browser.sessionstore.dom_form_max_limit isn't ok."
+    );
+  });
+
+  await SpecialPowers.popPrefEnv();
+});
+
+add_task(async function test_form_max_limit_many_fields() {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      // "browser.sessionstore.dom_form_max_limit" limits the total length
+      // of values AND length id/xpath collected from a form. Here we have
+      // that SHORT_VALUE * 2 + 'text' + 'txt' is less than 15 and LONG_VALUE
+      // + SHORT_VALUE + 'text' + 'txt' is greater than 15.
+      ["browser.sessionstore.dom_form_max_limit", 15],
+      ["browser.sessionstore.debug.no_auto_updates", true],
+    ],
+  });
+
+  await BrowserTestUtils.withNewTab({ gBrowser, url: URL }, async browser => {
+    await SpecialPowers.spawn(browser, [], () => {
+      let element = content.document.createElement("input");
+      element.id = "text";
+      element.type = "text";
+      content.document.body.appendChild(element);
+    });
+
+    await setPropertyOfFormField(browser, "#txt", "value", SHORT_VALUE);
+    await setPropertyOfFormField(browser, "#text", "value", SHORT_VALUE);
+    await TabStateFlusher.flush(browser);
+
+    let tab = gBrowser.getTabForBrowser(browser);
+    let state = JSON.parse(ss.getTabState(tab));
+    is(
+      state.formdata.id.txt,
+      SHORT_VALUE,
+      "total length shorter than browser.sessionstore.dom_form_max_limit is ok."
+    );
+
+    await setPropertyOfFormField(browser, "#txt", "value", LONG_VALUE);
+    await TabStateFlusher.flush(browser);
+
+    state = JSON.parse(ss.getTabState(tab));
+    is(
+      state.formdata.id.txt,
+      SHORT_VALUE,
+      "total length shorter than browser.sessionstore.dom_form_max_limit isn't ok."
+    );
+  });
+
+  await SpecialPowers.popPrefEnv();
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_formdata_password.js b/src/zen/tests/mochitests/sessionstore/browser_formdata_password.js
new file mode 100644
index 000000000..14abdb89f
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_formdata_password.js
@@ -0,0 +1,69 @@
+"use strict";
+
+/**
+ * Ensures that <input>s that are/were type=password are not saved.
+ */
+
+addCoopTask("file_formdata_password.html", test_hasBeenTypePassword, HTTPSROOT);
+
+addNonCoopTask(
+  "file_formdata_password.html",
+  test_hasBeenTypePassword,
+  HTTPROOT
+);
+addNonCoopTask(
+  "file_formdata_password.html",
+  test_hasBeenTypePassword,
+  HTTPSROOT
+);
+
+async function test_hasBeenTypePassword(aURL) {
+  let tab = BrowserTestUtils.addTab(gBrowser, aURL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  await SpecialPowers.spawn(browser, [], async function fillFields() {
+    let doc = content.document;
+
+    doc.getElementById("TextValue").setUserInput("abc");
+
+    doc.getElementById("TextValuePassword").setUserInput("def");
+    doc.getElementById("TextValuePassword").type = "password";
+
+    doc.getElementById("TextPasswordValue").type = "password";
+    doc.getElementById("TextPasswordValue").setUserInput("ghi");
+
+    doc.getElementById("PasswordValueText").setUserInput("jkl");
+    doc.getElementById("PasswordValueText").type = "text";
+
+    doc.getElementById("PasswordTextValue").type = "text";
+    doc.getElementById("PasswordTextValue").setUserInput("mno");
+
+    doc.getElementById("PasswordValue").setUserInput("pqr");
+  });
+
+  // Remove the tab.
+  await promiseRemoveTabAndSessionState(tab);
+
+  let [
+    {
+      state: { formdata },
+    },
+  ] = ss.getClosedTabDataForWindow(window);
+  let expected = [
+    ["TextValue", "abc"],
+    ["TextValuePassword", undefined],
+    ["TextPasswordValue", undefined],
+    ["PasswordValueText", undefined],
+    ["PasswordTextValue", undefined],
+    ["PasswordValue", undefined],
+  ];
+
+  for (let [id, expectedValue] of expected) {
+    is(
+      formdata.id[id],
+      expectedValue,
+      `Value should be ${expectedValue} for ${id}`
+    );
+  }
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_formdata_sample.html b/src/zen/tests/mochitests/sessionstore/browser_formdata_sample.html
new file mode 100644
index 000000000..d469f5751
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_formdata_sample.html
@@ -0,0 +1,20 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="utf-8">
+    <title>browser_formdata_sample.html</title>
+  </head>
+  <body>
+    <input id="txt" />
+    <iframe id="iframe"></iframe>
+
+    <script type="text/javascript">
+      let isOuter = window == window.top;
+
+      if (isOuter) {
+        let iframe = document.getElementById("iframe");
+        iframe.setAttribute("src", "https://example.com" + location.pathname);
+      }
+    </script>
+  </body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_formdata_xpath.js b/src/zen/tests/mochitests/sessionstore/browser_formdata_xpath.js
new file mode 100644
index 000000000..448e32746
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_formdata_xpath.js
@@ -0,0 +1,242 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const URL = ROOT + "browser_formdata_xpath_sample.html";
+
+/**
+ * Bug 346337 - Generic form data restoration tests.
+ */
+add_setup(function () {
+  // make sure we don't save form data at all (except for tab duplication)
+  Services.prefs.setIntPref("browser.sessionstore.privacy_level", 2);
+
+  registerCleanupFunction(() => {
+    Services.prefs.clearUserPref("browser.sessionstore.privacy_level");
+  });
+});
+
+const FILE1 = createFilePath("346337_test1.file");
+const FILE2 = createFilePath("346337_test2.file");
+
+const FIELDS = {
+  "//input[@name='input']": Date.now().toString(16),
+  "//input[@name='spaced 1']": Math.random().toString(),
+  "//input[3]": "three",
+  "//input[@type='checkbox']": true,
+  "//input[@name='uncheck']": false,
+  "//input[@type='radio'][1]": false,
+  "//input[@type='radio'][2]": true,
+  "//input[@type='radio'][3]": false,
+  "//select": 2,
+  "//select[@multiple]": [1, 3],
+  "//textarea[1]": "",
+  "//textarea[2]": "Some text... " + Math.random(),
+  "//textarea[3]": "Some more text\n" + new Date(),
+  "//input[@type='file'][1]": [FILE1],
+  "//input[@type='file'][2]": [FILE1, FILE2],
+};
+
+add_task(async function test_form_data_restoration() {
+  // Load page with some input fields.
+  let tab = BrowserTestUtils.addTab(gBrowser, URL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  // Fill in some values.
+  for (let xpath of Object.keys(FIELDS)) {
+    await setFormValue(browser, xpath);
+  }
+
+  // Duplicate the tab.
+  let tab2 = gBrowser.duplicateTab(tab);
+  let browser2 = tab2.linkedBrowser;
+  await promiseTabRestored(tab2);
+
+  // Check that all form values have been duplicated.
+  for (let xpath of Object.keys(FIELDS)) {
+    let expected = JSON.stringify(FIELDS[xpath]);
+    let actual = JSON.stringify(await getFormValue(browser2, xpath));
+    is(
+      actual,
+      expected,
+      'The value for "' + xpath + '" was correctly restored'
+    );
+  }
+
+  // Remove all tabs.
+  await promiseRemoveTabAndSessionState(tab2);
+  await promiseRemoveTabAndSessionState(tab);
+
+  // Restore one of the tabs again.
+  tab = ss.undoCloseTab(window, 0);
+  browser = tab.linkedBrowser;
+  await promiseTabRestored(tab);
+
+  // Check that none of the form values have been restored due to the privacy
+  // level settings.
+  for (let xpath of Object.keys(FIELDS)) {
+    let expected = FIELDS[xpath];
+    if (expected) {
+      let actual = await getFormValue(browser, xpath, expected);
+      isnot(
+        actual,
+        expected,
+        'The value for "' + xpath + '" was correctly discarded'
+      );
+    }
+  }
+
+  // Cleanup.
+  BrowserTestUtils.removeTab(tab);
+});
+
+function getPropertyOfXPath(browserContext, path, propName) {
+  return SpecialPowers.spawn(
+    browserContext,
+    [path, propName],
+    (pathChild, propNameChild) => {
+      let doc = content.document;
+      let xptype = doc.defaultView.XPathResult.FIRST_ORDERED_NODE_TYPE;
+      let node = doc.evaluate(
+        pathChild,
+        doc,
+        null,
+        xptype,
+        null
+      ).singleNodeValue;
+      return node[propNameChild];
+    }
+  );
+}
+
+function setPropertyOfXPath(browserContext, path, propName, newValue) {
+  return SpecialPowers.spawn(
+    browserContext,
+    [path, propName, newValue],
+    (pathChild, propNameChild, newValueChild) => {
+      let doc = content.document;
+      let xptype = doc.defaultView.XPathResult.FIRST_ORDERED_NODE_TYPE;
+      let node = doc.evaluate(
+        pathChild,
+        doc,
+        null,
+        xptype,
+        null
+      ).singleNodeValue;
+      node[propNameChild] = newValueChild;
+
+      let event = node.ownerDocument.createEvent("UIEvents");
+      event.initUIEvent("input", true, true, node.documentGlobal, 0);
+      node.dispatchEvent(event);
+    }
+  );
+}
+
+function execUsingXPath(browserContext, path, fnName, arg) {
+  return SpecialPowers.spawn(
+    browserContext,
+    [path, fnName, arg],
+    (pathChild, fnNameChild, argChild) => {
+      let doc = content.document;
+      let xptype = doc.defaultView.XPathResult.FIRST_ORDERED_NODE_TYPE;
+      let node = doc.evaluate(
+        pathChild,
+        doc,
+        null,
+        xptype,
+        null
+      ).singleNodeValue;
+
+      switch (fnNameChild) {
+        case "getMultipleSelected":
+          return Array.from(node.options, (opt, idx) => idx).filter(
+            idx => node.options[idx].selected
+          );
+        case "setMultipleSelected":
+          Array.prototype.forEach.call(
+            node.options,
+            (opt, idx) => (opt.selected = argChild.indexOf(idx) > -1)
+          );
+          break;
+        case "getFileNameArray":
+          return node.mozGetFileNameArray();
+        case "setFileNameArray":
+          node.mozSetFileNameArray(argChild, argChild.length);
+          break;
+      }
+
+      let event = node.ownerDocument.createEvent("UIEvents");
+      event.initUIEvent("input", true, true, node.documentGlobal, 0);
+      node.dispatchEvent(event);
+      return undefined;
+    }
+  );
+}
+
+function createFilePath(leaf) {
+  let file = Services.dirsvc.get("TmpD", Ci.nsIFile);
+  file.append(leaf);
+  return file.path;
+}
+
+function isArrayOfNumbers(value) {
+  return Array.isArray(value) && value.every(n => typeof n === "number");
+}
+
+function isArrayOfStrings(value) {
+  return Array.isArray(value) && value.every(n => typeof n === "string");
+}
+
+function getFormValue(browser, xpath) {
+  let value = FIELDS[xpath];
+
+  if (typeof value == "string") {
+    return getPropertyOfXPath(browser, xpath, "value");
+  }
+
+  if (typeof value == "boolean") {
+    return getPropertyOfXPath(browser, xpath, "checked");
+  }
+
+  if (typeof value == "number") {
+    return getPropertyOfXPath(browser, xpath, "selectedIndex");
+  }
+
+  if (isArrayOfNumbers(value)) {
+    return execUsingXPath(browser, xpath, "getMultipleSelected");
+  }
+
+  if (isArrayOfStrings(value)) {
+    return execUsingXPath(browser, xpath, "getFileNameArray");
+  }
+
+  throw new Error("unknown input type");
+}
+
+function setFormValue(browser, xpath) {
+  let value = FIELDS[xpath];
+
+  if (typeof value == "string") {
+    return setPropertyOfXPath(browser, xpath, "value", value);
+  }
+
+  if (typeof value == "boolean") {
+    return setPropertyOfXPath(browser, xpath, "checked", value);
+  }
+
+  if (typeof value == "number") {
+    return setPropertyOfXPath(browser, xpath, "selectedIndex", value);
+  }
+
+  if (isArrayOfNumbers(value)) {
+    return execUsingXPath(browser, xpath, "setMultipleSelected", value);
+  }
+
+  if (isArrayOfStrings(value)) {
+    return execUsingXPath(browser, xpath, "setFileNameArray", value);
+  }
+
+  throw new Error("unknown input type");
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_formdata_xpath_sample.html b/src/zen/tests/mochitests/sessionstore/browser_formdata_xpath_sample.html
new file mode 100644
index 000000000..682162d6a
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_formdata_xpath_sample.html
@@ -0,0 +1,37 @@
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
+<title>Test for bug 346337</title>
+
+<h3>Text Fields</h3>
+<input type="text" name="input">
+<input type="text" name="spaced 1">
+<input>
+
+<h3>Checkboxes and Radio buttons</h3>
+<input type="checkbox" name="check"> Check 1
+<input type="checkbox" name="uncheck" checked> Check 2
+<p>
+<input type="radio" name="group" value="1"> Radio 1
+<input type="radio" name="group" value="some"> Radio 2
+<input type="radio" name="group" checked> Radio 3
+
+<h3>Selects</h3>
+<select name="any">
+  <option value="1"> Select 1
+  <option value="some"> Select 2
+  <option>Select 3
+</select>
+<select multiple="multiple">
+  <option value=1> Multi-select 1
+  <option value=2> Multi-select 2
+  <option value=3> Multi-select 3
+  <option value=4> Multi-select 4
+</select>
+
+<h3>Text Areas</h3>
+<textarea name="testarea"></textarea>
+<textarea name="sized one" rows="5" cols="25"></textarea>
+<textarea></textarea>
+
+<h3>File Selector</h3>
+<input type="file">
+<input type="file" multiple>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_frame_history.js b/src/zen/tests/mochitests/sessionstore/browser_frame_history.js
new file mode 100644
index 000000000..4e281d261
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_frame_history.js
@@ -0,0 +1,247 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+/* eslint-disable mozilla/no-arbitrary-setTimeout */
+
+/**
+ Ensure that frameset history works properly when restoring a tab,
+ provided that the frameset is static.
+ */
+
+// Loading a toplevel frameset
+add_task(async function () {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["browser.navigation.requireUserInteraction", false],
+      ["dom.navigation.webidl.enabled", true],
+    ],
+  });
+
+  let testURL =
+    getRootDirectory(gTestPath) + "browser_frame_history_index.html";
+  let tab = BrowserTestUtils.addTab(gBrowser, testURL);
+  gBrowser.selectedTab = tab;
+
+  info("Opening a page with three frames, 4 loads should take place");
+  await waitForLoadsInBrowser(tab.linkedBrowser, 4);
+
+  let browser_b =
+    tab.linkedBrowser.contentDocument.getElementsByTagName("frame")[1];
+  let document_b = browser_b.contentDocument;
+  let links = document_b.getElementsByTagName("a");
+
+  // We're going to click on the first link, so listen for another load event
+  info("Clicking on link 1, 1 load should take place");
+  let promise = waitForLoadsInBrowser(tab.linkedBrowser, 1);
+  EventUtils.sendMouseEvent(
+    { type: "click" },
+    links[0],
+    browser_b.contentWindow
+  );
+  await promise;
+
+  info("Clicking on link 2, 1 load should take place");
+  promise = waitForLoadsInBrowser(tab.linkedBrowser, 1);
+  EventUtils.sendMouseEvent(
+    { type: "click" },
+    links[1],
+    browser_b.contentWindow
+  );
+  await promise;
+
+  info("Close then un-close page, 4 loads should take place");
+  await promiseRemoveTabAndSessionState(tab);
+  let newTab = ss.undoCloseTab(window, 0);
+  await waitForLoadsInBrowser(newTab.linkedBrowser, 4);
+
+  info("Go back in time, 1 load should take place");
+  gBrowser.goBack();
+  await waitForLoadsInBrowser(newTab.linkedBrowser, 1);
+
+  let expectedURLEnds = ["a.html", "b.html", "c1.html"];
+  let frames =
+    newTab.linkedBrowser.contentDocument.getElementsByTagName("frame");
+  for (let i = 0; i < frames.length; i++) {
+    is(
+      frames[i].contentDocument.location.href,
+      getRootDirectory(gTestPath) +
+        "browser_frame_history_" +
+        expectedURLEnds[i],
+      "frame " + i + " has the right url"
+    );
+  }
+
+  let expectedUrls = ["c", "c1", "c2"].map(
+    url => `${getRootDirectory(gTestPath)}browser_frame_history_${url}.html`
+  );
+  let entryUrls = frames[2].contentWindow.navigation
+    .entries()
+    .map(entry => entry.url);
+  for (const [entryUrl, expectedUrl] of expectedUrls.map((url, i) => [
+    entryUrls[i],
+    url,
+  ])) {
+    is(entryUrl, expectedUrl, "frame 2 NHE has correct url");
+  }
+
+  gBrowser.removeTab(newTab);
+});
+
+// Loading the frameset inside an iframe
+add_task(async function () {
+  let testURL =
+    getRootDirectory(gTestPath) + "browser_frame_history_index2.html";
+  let tab = BrowserTestUtils.addTab(gBrowser, testURL);
+  gBrowser.selectedTab = tab;
+
+  info(
+    "iframe: Opening a page with an iframe containing three frames, 5 loads should take place"
+  );
+  await waitForLoadsInBrowser(tab.linkedBrowser, 5);
+
+  let browser_b = tab.linkedBrowser.contentDocument
+    .getElementById("iframe")
+    .contentDocument.getElementsByTagName("frame")[1];
+  let document_b = browser_b.contentDocument;
+  let links = document_b.getElementsByTagName("a");
+
+  // We're going to click on the first link, so listen for another load event
+  info("iframe: Clicking on link 1, 1 load should take place");
+  let promise = waitForLoadsInBrowser(tab.linkedBrowser, 1);
+  EventUtils.sendMouseEvent(
+    { type: "click" },
+    links[0],
+    browser_b.contentWindow
+  );
+  await promise;
+
+  info("iframe: Clicking on link 2, 1 load should take place");
+  promise = waitForLoadsInBrowser(tab.linkedBrowser, 1);
+  EventUtils.sendMouseEvent(
+    { type: "click" },
+    links[1],
+    browser_b.contentWindow
+  );
+  await promise;
+
+  info("iframe: Close then un-close page, 5 loads should take place");
+  await promiseRemoveTabAndSessionState(tab);
+  let newTab = ss.undoCloseTab(window, 0);
+  await waitForLoadsInBrowser(newTab.linkedBrowser, 5);
+
+  info("iframe: Go back in time, 1 load should take place");
+  gBrowser.goBack();
+  await waitForLoadsInBrowser(newTab.linkedBrowser, 1);
+
+  let expectedURLEnds = ["a.html", "b.html", "c1.html"];
+  let frames = newTab.linkedBrowser.contentDocument
+    .getElementById("iframe")
+    .contentDocument.getElementsByTagName("frame");
+  for (let i = 0; i < frames.length; i++) {
+    is(
+      frames[i].contentDocument.location.href,
+      getRootDirectory(gTestPath) +
+        "browser_frame_history_" +
+        expectedURLEnds[i],
+      "frame " + i + " has the right url"
+    );
+  }
+  gBrowser.removeTab(newTab);
+});
+
+// Now, test that we don't record history if the iframe is added dynamically
+add_task(async function () {
+  // Start with an empty history
+  let blankState = JSON.stringify({
+    windows: [
+      {
+        tabs: [
+          { entries: [{ url: "about:blank", triggeringPrincipal_base64 }] },
+        ],
+        _closedTabs: [],
+      },
+    ],
+    _closedWindows: [],
+  });
+  await setBrowserState(blankState);
+
+  let testURL =
+    getRootDirectory(gTestPath) + "browser_frame_history_index_blank.html";
+  let tab = BrowserTestUtils.addTab(gBrowser, testURL);
+  gBrowser.selectedTab = tab;
+  await waitForLoadsInBrowser(tab.linkedBrowser, 1);
+
+  info(
+    "dynamic: Opening a page with an iframe containing three frames, 4 dynamic loads should take place"
+  );
+  let doc = tab.linkedBrowser.contentDocument;
+  let iframe = doc.createElement("iframe");
+  iframe.id = "iframe";
+  iframe.src = "browser_frame_history_index.html";
+  doc.body.appendChild(iframe);
+  await waitForLoadsInBrowser(tab.linkedBrowser, 4);
+
+  let browser_b = tab.linkedBrowser.contentDocument
+    .getElementById("iframe")
+    .contentDocument.getElementsByTagName("frame")[1];
+  let document_b = browser_b.contentDocument;
+  let links = document_b.getElementsByTagName("a");
+
+  // We're going to click on the first link, so listen for another load event
+  info("dynamic: Clicking on link 1, 1 load should take place");
+  let promise = waitForLoadsInBrowser(tab.linkedBrowser, 1);
+  EventUtils.sendMouseEvent(
+    { type: "click" },
+    links[0],
+    browser_b.contentWindow
+  );
+  await promise;
+
+  info("dynamic: Clicking on link 2, 1 load should take place");
+  promise = waitForLoadsInBrowser(tab.linkedBrowser, 1);
+  EventUtils.sendMouseEvent(
+    { type: "click" },
+    links[1],
+    browser_b.contentWindow
+  );
+  await promise;
+
+  info("Check in the state that we have not stored this history");
+  let state = ss.getBrowserState();
+  info(JSON.stringify(JSON.parse(state), null, "\t"));
+  is(
+    state.indexOf("c1.html"),
+    -1,
+    "History entry was not stored in the session state"
+  );
+  gBrowser.removeTab(tab);
+});
+
+// helper functions
+function waitForLoadsInBrowser(aBrowser, aLoadCount) {
+  return new Promise(resolve => {
+    let loadCount = 0;
+    aBrowser.addEventListener(
+      "load",
+      function listener() {
+        if (++loadCount < aLoadCount) {
+          info(
+            "Got " + loadCount + " loads, waiting until we have " + aLoadCount
+          );
+          return;
+        }
+
+        aBrowser.removeEventListener("load", listener, true);
+        resolve();
+      },
+      true
+    );
+  });
+}
+
+function timeout(delay, task) {
+  return new Promise((resolve, reject) => {
+    setTimeout(() => resolve(true), delay);
+    task.then(() => resolve(false), reject);
+  });
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_frame_history_a.html b/src/zen/tests/mochitests/sessionstore/browser_frame_history_a.html
new file mode 100644
index 000000000..8e7b35d7a
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_frame_history_a.html
@@ -0,0 +1,5 @@
+<html>
+  <body>
+    I'm A!
+  </body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_frame_history_b.html b/src/zen/tests/mochitests/sessionstore/browser_frame_history_b.html
new file mode 100644
index 000000000..38b43da21
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_frame_history_b.html
@@ -0,0 +1,10 @@
+<html>
+  <body>
+    I'm B!<br/>
+    <a target="c" href="browser_frame_history_c1.html">click me first</a><br/>
+    <a target="c" href="browser_frame_history_c2.html">then click me</a><br/>
+    Close this tab.<br/>
+    Restore this tab.<br/>
+    Click back.<br/>
+  </body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_frame_history_c.html b/src/zen/tests/mochitests/sessionstore/browser_frame_history_c.html
new file mode 100644
index 000000000..0efd7d902
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_frame_history_c.html
@@ -0,0 +1,5 @@
+<html>
+  <body>
+    I'm C!
+  </body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_frame_history_c1.html b/src/zen/tests/mochitests/sessionstore/browser_frame_history_c1.html
new file mode 100644
index 000000000..b55c1d45a
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_frame_history_c1.html
@@ -0,0 +1,5 @@
+<html>
+  <body>
+    I'm C1!
+  </body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_frame_history_c2.html b/src/zen/tests/mochitests/sessionstore/browser_frame_history_c2.html
new file mode 100644
index 000000000..aec504141
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_frame_history_c2.html
@@ -0,0 +1,5 @@
+<html>
+  <body>
+    I'm C2!
+  </body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_frame_history_index.html b/src/zen/tests/mochitests/sessionstore/browser_frame_history_index.html
new file mode 100644
index 000000000..04a44555a
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_frame_history_index.html
@@ -0,0 +1,9 @@
+<html>
+  <frameset cols="20%,80%">
+    <frameset rows="30%,70%">
+      <frame src="browser_frame_history_a.html"/>
+      <frame src="browser_frame_history_b.html"/>
+    </frameset>
+    <frame src="browser_frame_history_c.html" name="c"/>
+  </frameset>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_frame_history_index2.html b/src/zen/tests/mochitests/sessionstore/browser_frame_history_index2.html
new file mode 100644
index 000000000..d465abef6
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_frame_history_index2.html
@@ -0,0 +1,3 @@
+<html>
+  <iframe src="browser_frame_history_index.html" id="iframe" />
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_frame_history_index_blank.html b/src/zen/tests/mochitests/sessionstore/browser_frame_history_index_blank.html
new file mode 100644
index 000000000..4ddd1a7cf
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_frame_history_index_blank.html
@@ -0,0 +1,4 @@
+<html>
+ <body>
+ </body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_frametree.js b/src/zen/tests/mochitests/sessionstore/browser_frametree.js
new file mode 100644
index 000000000..06e0379c5
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_frametree.js
@@ -0,0 +1,134 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const URL = HTTPROOT + "browser_frametree_sample.html";
+const URL_FRAMESET = HTTPROOT + "browser_frametree_sample_frameset.html";
+const URL_IFRAMES = HTTPROOT + "browser_frametree_sample_iframes.html";
+
+/**
+ * Check that we correctly enumerate non-dynamic child frames.
+ */
+add_task(async function test_frametree() {
+  // Add an empty tab for a start.
+  let tab = BrowserTestUtils.addTab(gBrowser, URL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  // The page is a single frame with no children.
+  is(await countNonDynamicFrames(browser), 0, "no child frames");
+
+  // Navigate to a frameset.
+  BrowserTestUtils.startLoadingURIString(browser, URL_FRAMESET);
+  await promiseBrowserLoaded(browser);
+
+  // The frameset has two frames.
+  is(await countNonDynamicFrames(browser), 2, "two non-dynamic child frames");
+
+  // Go back in history.
+  let pageShowPromise = BrowserTestUtils.waitForContentEvent(
+    browser,
+    "pageshow",
+    true
+  );
+  browser.goBack();
+  await pageShowPromise;
+
+  // We're at page one again.
+  is(await countNonDynamicFrames(browser), 0, "no child frames");
+
+  // Append a dynamic frame.
+  await SpecialPowers.spawn(browser, [URL], async ([url]) => {
+    let frame = content.document.createElement("iframe");
+    frame.setAttribute("src", url);
+    content.document.body.appendChild(frame);
+    await ContentTaskUtils.waitForEvent(frame, "load");
+  });
+
+  // The dynamic frame should be ignored.
+  is(
+    await countNonDynamicFrames(browser),
+    0,
+    "we still have a single root frame"
+  );
+
+  // Cleanup.
+  BrowserTestUtils.removeTab(tab);
+});
+
+/**
+ * Check that we correctly enumerate non-dynamic child frames.
+ */
+add_task(async function test_frametree_dynamic() {
+  // Add an empty tab for a start.
+  let tab = BrowserTestUtils.addTab(gBrowser, URL_IFRAMES);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  // The page has two iframes.
+  is(await countNonDynamicFrames(browser), 2, "two non-dynamic child frames");
+  is(await enumerateIndexes(browser), "0,1", "correct indexes 0 and 1");
+
+  // Insert a dynamic frame.
+  await SpecialPowers.spawn(browser, [URL], async ([url]) => {
+    let frame = content.document.createElement("iframe");
+    frame.setAttribute("src", url);
+    content.document.body.insertBefore(
+      frame,
+      content.document.getElementsByTagName("iframe")[1]
+    );
+    await ContentTaskUtils.waitForEvent(frame, "load");
+  });
+
+  // The page still has two iframes.
+  is(await countNonDynamicFrames(browser), 2, "two non-dynamic child frames");
+  is(await enumerateIndexes(browser), "0,1", "correct indexes 0 and 1");
+
+  // Append a dynamic frame.
+  await SpecialPowers.spawn(browser, [URL], async ([url]) => {
+    let frame = content.document.createElement("iframe");
+    frame.setAttribute("src", url);
+    content.document.body.appendChild(frame);
+    await ContentTaskUtils.waitForEvent(frame, "load");
+  });
+
+  // The page still has two iframes.
+  is(await countNonDynamicFrames(browser), 2, "two non-dynamic child frames");
+  is(await enumerateIndexes(browser), "0,1", "correct indexes 0 and 1");
+
+  // Remopve a non-dynamic iframe.
+  await SpecialPowers.spawn(browser, [URL], async () => {
+    // Remove the first iframe, which should be a non-dynamic iframe.
+    content.document.body.removeChild(
+      content.document.getElementsByTagName("iframe")[0]
+    );
+  });
+
+  is(await countNonDynamicFrames(browser), 1, "one non-dynamic child frame");
+  is(await enumerateIndexes(browser), "1", "correct index 1");
+
+  // Cleanup.
+  BrowserTestUtils.removeTab(tab);
+});
+
+async function countNonDynamicFrames(browser) {
+  return SpecialPowers.spawn(browser, [], async () => {
+    let count = 0;
+    content.SessionStoreUtils.forEachNonDynamicChildFrame(
+      content,
+      () => count++
+    );
+    return count;
+  });
+}
+
+async function enumerateIndexes(browser) {
+  return SpecialPowers.spawn(browser, [], async () => {
+    let indexes = [];
+    content.SessionStoreUtils.forEachNonDynamicChildFrame(content, (frame, i) =>
+      indexes.push(i)
+    );
+    return indexes.join(",");
+  });
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_frametree_sample.html b/src/zen/tests/mochitests/sessionstore/browser_frametree_sample.html
new file mode 100644
index 000000000..dda129448
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_frametree_sample.html
@@ -0,0 +1,8 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="utf-8">
+    <title>browser_frametree_sample.html</title>
+  </head>
+  <body style='width: 100000px; height: 100000px;'>top</body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_frametree_sample_frameset.html b/src/zen/tests/mochitests/sessionstore/browser_frametree_sample_frameset.html
new file mode 100644
index 000000000..e1cd08735
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_frametree_sample_frameset.html
@@ -0,0 +1,11 @@
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Frameset//EN">
+<html lang="en">
+  <head>
+    <meta charset="utf-8">
+    <title>browser_frametree_sample_frameset.html</title>
+  </head>
+  <frameset id="frames" rows="50%, 50%">
+    <frame src="browser_frametree_sample.html">
+    <frame src="browser_frametree_sample.html">
+  </frameset>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_frametree_sample_iframes.html b/src/zen/tests/mochitests/sessionstore/browser_frametree_sample_iframes.html
new file mode 100644
index 000000000..aaffab8af
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_frametree_sample_iframes.html
@@ -0,0 +1,9 @@
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Frameset//EN">
+<html lang="en">
+  <head>
+    <meta charset="utf-8">
+    <title>browser_frametree_sample_iframes.html</title>
+  </head>
+  <iframe src="browser_frametree_sample.html"></iframe>
+  <iframe src="browser_frametree_sample.html"></iframe>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_global_store.js b/src/zen/tests/mochitests/sessionstore/browser_global_store.js
new file mode 100644
index 000000000..99aa67218
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_global_store.js
@@ -0,0 +1,53 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// Tests the API for saving global session data.
+add_task(async function () {
+  const key1 = "Unique name 1: " + Date.now();
+  const key2 = "Unique name 2: " + Date.now();
+  const value1 = "Unique value 1: " + Math.random();
+  const value2 = "Unique value 2: " + Math.random();
+
+  let global = {};
+  global[key1] = value1;
+
+  const testState = {
+    windows: [
+      {
+        tabs: [
+          { entries: [{ url: "about:blank", triggeringPrincipal_base64 }] },
+        ],
+      },
+    ],
+    global,
+  };
+
+  function testRestoredState() {
+    is(
+      ss.getCustomGlobalValue(key1),
+      value1,
+      "restored state has global value"
+    );
+  }
+
+  function testGlobalStore() {
+    is(ss.getCustomGlobalValue(key2), "", "global value initially not set");
+
+    ss.setCustomGlobalValue(key2, value1);
+    is(ss.getCustomGlobalValue(key2), value1, "retreived value matches stored");
+
+    ss.setCustomGlobalValue(key2, value2);
+    is(
+      ss.getCustomGlobalValue(key2),
+      value2,
+      "previously stored value was overwritten"
+    );
+
+    ss.deleteCustomGlobalValue(key2);
+    is(ss.getCustomGlobalValue(key2), "", "global value was deleted");
+  }
+
+  await promiseBrowserState(testState);
+  testRestoredState();
+  testGlobalStore();
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_history_persist.js b/src/zen/tests/mochitests/sessionstore/browser_history_persist.js
new file mode 100644
index 000000000..59f1a9445
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_history_persist.js
@@ -0,0 +1,140 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/**
+ * Ensure that history entries that should not be persisted are restored in the
+ * same state.
+ */
+add_task(async function check_history_not_persisted() {
+  // Create an about:blank tab
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:blank");
+  let browser = tab.linkedBrowser;
+  await BrowserTestUtils.browserLoaded(browser, { wantLoad: "about:blank" });
+
+  // Retrieve the tab state.
+  await TabStateFlusher.flush(browser);
+  let state = JSON.parse(ss.getTabState(tab));
+  is(
+    state.entries[0].transient,
+    true,
+    "Should have collected the transient state"
+  );
+  BrowserTestUtils.removeTab(tab);
+  browser = null;
+
+  // Open a new tab to restore into.
+  tab = BrowserTestUtils.addTab(gBrowser, "about:blank");
+  browser = tab.linkedBrowser;
+
+  {
+    let sessionHistory = browser.browsingContext.sessionHistory;
+
+    // addTab sends a message to the child to load about:blank, which sends a
+    // message to the parent to add the SH entry.
+    // promiseTabState modifies the SH syncronously, so ensure it is settled.
+    await BrowserTestUtils.browserLoaded(browser, { wantLoad: "about:blank" });
+    is(sessionHistory.count, 1, "Should have initial entry");
+  }
+
+  info("New about:blank loaded, restoring state");
+  await promiseTabState(tab, state);
+
+  {
+    let sessionHistory = browser.browsingContext.sessionHistory;
+    is(sessionHistory.count, 1, "Should be a single history entry");
+    is(
+      sessionHistory.getEntryAtIndex(0).URI.spec,
+      "about:blank",
+      "Should be the right URL"
+    );
+  }
+
+  // Load a new URL into the tab, it should replace the about:blank history entry
+  BrowserTestUtils.startLoadingURIString(browser, "about:robots");
+  await BrowserTestUtils.browserLoaded(browser, { wantLoad: "about:robots" });
+
+  {
+    let sessionHistory = browser.browsingContext.sessionHistory;
+
+    is(sessionHistory.count, 1, "Should be a single history entry");
+    is(
+      sessionHistory.getEntryAtIndex(0).URI.spec,
+      "about:robots",
+      "Should be the right URL"
+    );
+  }
+
+  // Cleanup.
+  BrowserTestUtils.removeTab(tab);
+});
+
+/**
+ * Check that entries default to being persisted when the attribute doesn't
+ * exist
+ */
+add_task(async function check_history_default_persisted() {
+  // Create an about:blank tab
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:blank");
+  let browser = tab.linkedBrowser;
+  await BrowserTestUtils.browserLoaded(browser, { wantLoad: "about:blank" });
+
+  // Retrieve the tab state.
+  await TabStateFlusher.flush(browser);
+  let state = JSON.parse(ss.getTabState(tab));
+  delete state.entries[0].transient;
+  BrowserTestUtils.removeTab(tab);
+  browser = null;
+
+  // Open a new tab to restore into.
+  tab = BrowserTestUtils.addTab(gBrowser, "about:blank");
+  browser = tab.linkedBrowser;
+
+  {
+    let sessionHistory = browser.browsingContext.sessionHistory;
+
+    // addTab sends a message to the child to load about:blank, which sends a
+    // message to the parent to add the SH entry.
+    // promiseTabState modifies the SH syncronously, so ensure it is settled.
+    await BrowserTestUtils.browserLoaded(browser, { wantLoad: "about:blank" });
+    is(sessionHistory.count, 1, "Should have initial entry");
+  }
+
+  info("New about:blank loaded, restoring state");
+  await promiseTabState(tab, state);
+
+  {
+    let sessionHistory = browser.browsingContext.sessionHistory;
+
+    is(sessionHistory.count, 1, "Should be a single history entry");
+    is(
+      sessionHistory.getEntryAtIndex(0).URI.spec,
+      "about:blank",
+      "Should be the right URL"
+    );
+  }
+
+  // Load a new URL into the tab, it should NOT replace the about:blank history entry
+  BrowserTestUtils.startLoadingURIString(browser, "about:robots");
+  await promiseBrowserLoaded(browser, false, "about:robots");
+
+  {
+    let sessionHistory = browser.browsingContext.sessionHistory;
+
+    is(sessionHistory.count, 2, "Should be two history entries");
+    is(
+      sessionHistory.getEntryAtIndex(0).URI.spec,
+      "about:blank",
+      "Should be the right URL"
+    );
+    is(
+      sessionHistory.getEntryAtIndex(1).URI.spec,
+      "about:robots",
+      "Should be the right URL"
+    );
+  }
+
+  // Cleanup.
+  BrowserTestUtils.removeTab(tab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_ignore_updates_crashed_tabs.js b/src/zen/tests/mochitests/sessionstore/browser_ignore_updates_crashed_tabs.js
new file mode 100644
index 000000000..b70a3aa39
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_ignore_updates_crashed_tabs.js
@@ -0,0 +1,108 @@
+// This test checks that browsers are removed from the SessionStore's
+// crashed browser set at a correct time, so that it can stop ignoring update
+// events coming from those browsers.
+
+/**
+ * Open a tab, crash it, navigate it to a remote uri, and check that it
+ * is removed from a crashed set.
+ */
+add_task(async function test_update_crashed_tab_after_navigate_to_remote() {
+  let tab = BrowserTestUtils.addTab(gBrowser, "https://example.com/");
+  let browser = tab.linkedBrowser;
+  gBrowser.selectedTab = tab;
+  await promiseBrowserLoaded(browser);
+  ok(
+    !SessionStore.isBrowserInCrashedSet(browser),
+    "browser is not in the crashed set"
+  );
+
+  await BrowserTestUtils.crashFrame(browser);
+  ok(
+    SessionStore.isBrowserInCrashedSet(browser),
+    "browser is in the crashed set"
+  );
+
+  BrowserTestUtils.startLoadingURIString(browser, "https://example.org/");
+  await BrowserTestUtils.browserLoaded(browser, false, "https://example.org/");
+  ok(
+    !SessionStore.isBrowserInCrashedSet(browser),
+    "browser is not in the crashed set"
+  );
+  ok(
+    !tab.hasAttribute("crashed"),
+    "Tab shouldn't be marked as crashed anymore."
+  );
+  gBrowser.removeTab(tab);
+});
+
+/**
+ * Open a tab, crash it, navigate it to a non-remote uri, and check that it
+ * is removed from a crashed set.
+ */
+add_task(async function test_update_crashed_tab_after_navigate_to_non_remote() {
+  let tab = BrowserTestUtils.addTab(gBrowser, "https://example.com/");
+  let browser = tab.linkedBrowser;
+  gBrowser.selectedTab = tab;
+  await promiseBrowserLoaded(browser);
+  ok(
+    !SessionStore.isBrowserInCrashedSet(browser),
+    "browser is not in the crashed set"
+  );
+
+  await BrowserTestUtils.crashFrame(browser);
+  ok(
+    SessionStore.isBrowserInCrashedSet(browser),
+    "browser is in the crashed set"
+  );
+
+  BrowserTestUtils.startLoadingURIString(browser, "about:mozilla");
+  await BrowserTestUtils.browserLoaded(browser, false, "about:mozilla");
+  ok(
+    !SessionStore.isBrowserInCrashedSet(browser),
+    "browser is not in the crashed set"
+  );
+  ok(
+    !gBrowser.selectedTab.hasAttribute("crashed"),
+    "Tab shouldn't be marked as crashed anymore."
+  );
+  gBrowser.removeTab(tab);
+});
+
+/**
+ * Open a tab, crash it, restore it from history, and check that it
+ * is removed from a crashed set.
+ */
+add_task(async function test_update_crashed_tab_after_session_restore() {
+  let tab = BrowserTestUtils.addTab(gBrowser, "https://example.com/");
+  let browser = tab.linkedBrowser;
+  gBrowser.selectedTab = tab;
+  await promiseBrowserLoaded(browser);
+  ok(
+    !SessionStore.isBrowserInCrashedSet(browser),
+    "browser is not in the crashed set"
+  );
+
+  await BrowserTestUtils.crashFrame(browser);
+  ok(
+    SessionStore.isBrowserInCrashedSet(browser),
+    "browser is in the crashed set"
+  );
+
+  let tabRestoredPromise = promiseTabRestored(tab);
+  // Click restoreTab button
+  await SpecialPowers.spawn(browser, [], () => {
+    let button = content.document.getElementById("restoreTab");
+    button.click();
+  });
+  await tabRestoredPromise;
+  ok(
+    !tab.hasAttribute("crashed"),
+    "Tab shouldn't be marked as crashed anymore."
+  );
+  ok(
+    !SessionStore.isBrowserInCrashedSet(browser),
+    "browser is not in the crashed set"
+  );
+
+  gBrowser.removeTab(tab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_label_and_icon.js b/src/zen/tests/mochitests/sessionstore/browser_label_and_icon.js
new file mode 100644
index 000000000..a76db891b
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_label_and_icon.js
@@ -0,0 +1,59 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_setup(async function () {
+  await SpecialPowers.pushPrefEnv({
+    set: [["test.wait300msAfterTabSwitch", true]],
+  });
+});
+
+/**
+ * Ensure that a pending tab has label and icon correctly set.
+ */
+add_task(async function test_label_and_icon() {
+  // Make sure that tabs are restored on demand as otherwise the tab will start
+  // loading immediately and we can't check its icon and label.
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.sessionstore.restore_on_demand", true]],
+  });
+
+  // Create a new tab.
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:robots");
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+  // Because there is debounce logic in FaviconLoader.sys.mjs to reduce the
+  // favicon loads, we have to wait some time before checking that icon was
+  // stored properly.
+  await TestUtils.waitForCondition(
+    () => {
+      return gBrowser.getIcon(tab) != null;
+    },
+    "wait for favicon load to finish",
+    100,
+    5
+  );
+
+  // Retrieve the tab state.
+  await TabStateFlusher.flush(browser);
+  let state = ss.getTabState(tab);
+  BrowserTestUtils.removeTab(tab);
+  browser = null;
+
+  // Open a new tab to restore into.
+  tab = BrowserTestUtils.addTab(gBrowser, "about:blank");
+  ss.setTabState(tab, state);
+  await promiseTabRestoring(tab);
+
+  // Check that label and icon are set for the restoring tab.
+  is(
+    gBrowser.getIcon(tab),
+    "chrome://browser/content/robot.ico",
+    "icon is set"
+  );
+  is(tab.label, "Gort! Klaatu barada nikto!", "label is set");
+
+  // Cleanup.
+  BrowserTestUtils.removeTab(tab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_movePendingTabToNewWindow.js b/src/zen/tests/mochitests/sessionstore/browser_movePendingTabToNewWindow.js
new file mode 100644
index 000000000..916426cda
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_movePendingTabToNewWindow.js
@@ -0,0 +1,124 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/**
+ * This tests the behaviour of moving pending tabs to a new window. These
+ * pending tabs have yet to be restored and should be restored upon opening
+ * in the new window. This test covers moving a single pending tab at once
+ * as well as multiple tabs at the same time (using tab multiselection).
+ */
+add_task(async function test_movePendingTabToNewWindow() {
+  const TEST_URIS = [
+    "http://www.example.com/1",
+    "http://www.example.com/2",
+    "http://www.example.com/3",
+    "http://www.example.com/4",
+  ];
+
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.sessionstore.restore_on_demand", true]],
+  });
+
+  let state = {
+    windows: [
+      {
+        tabs: [
+          { entries: [{ url: TEST_URIS[0], triggeringPrincipal_base64 }] },
+          { entries: [{ url: TEST_URIS[1], triggeringPrincipal_base64 }] },
+          { entries: [{ url: TEST_URIS[2], triggeringPrincipal_base64 }] },
+          { entries: [{ url: TEST_URIS[3], triggeringPrincipal_base64 }] },
+        ],
+        selected: 4,
+      },
+    ],
+  };
+
+  await promiseBrowserState(state);
+
+  is(
+    gBrowser.visibleTabs.length,
+    4,
+    "Three tabs are visible to start the test"
+  );
+
+  let tabToSelect = gBrowser.visibleTabs[1];
+  ok(tabToSelect.hasAttribute("pending"), "Tab should be pending");
+
+  gBrowser.addRangeToMultiSelectedTabs(gBrowser.selectedTab, tabToSelect);
+  ok(!gBrowser.visibleTabs[0].multiselected, "First tab not multiselected");
+  ok(gBrowser.visibleTabs[1].multiselected, "Second tab multiselected");
+  ok(gBrowser.visibleTabs[2].multiselected, "Third tab multiselected");
+  ok(gBrowser.visibleTabs[3].multiselected, "Fourth tab multiselected");
+
+  let promiseNewWindow = BrowserTestUtils.waitForNewWindow();
+  gBrowser.replaceTabsWithWindow(tabToSelect);
+
+  info("Waiting for new window");
+  let newWindow = await promiseNewWindow;
+  isnot(newWindow, gBrowser.documentGlobal, "Tab moved to new window");
+
+  let newWindowTabs = newWindow.gBrowser.visibleTabs;
+  await TestUtils.waitForCondition(() => {
+    return (
+      newWindowTabs.length == 3 &&
+      newWindowTabs[0].linkedBrowser.currentURI.spec == TEST_URIS[1] &&
+      newWindowTabs[1].linkedBrowser.currentURI.spec == TEST_URIS[2] &&
+      newWindowTabs[2].linkedBrowser.currentURI.spec == TEST_URIS[3]
+    );
+  }, "Wait for all three tabs to move to new window and load");
+
+  is(newWindowTabs.length, 3, "Three tabs should be in new window");
+  is(
+    newWindowTabs[0].linkedBrowser.currentURI.spec,
+    TEST_URIS[1],
+    "Second tab moved"
+  );
+  is(
+    newWindowTabs[1].linkedBrowser.currentURI.spec,
+    TEST_URIS[2],
+    "Third tab moved"
+  );
+  is(
+    newWindowTabs[2].linkedBrowser.currentURI.spec,
+    TEST_URIS[3],
+    "Fourth tab moved"
+  );
+
+  ok(
+    newWindowTabs[0].hasAttribute("pending"),
+    "First tab in new window should still be pending"
+  );
+  ok(
+    newWindowTabs[1].hasAttribute("pending"),
+    "Second tab in new window should still be pending"
+  );
+  newWindow.gBrowser.clearMultiSelectedTabs();
+  ok(
+    newWindowTabs.every(t => !t.multiselected),
+    "No multiselection should be present"
+  );
+
+  promiseNewWindow = BrowserTestUtils.waitForNewWindow();
+  newWindow.gBrowser.replaceTabsWithWindow(newWindowTabs[0]);
+
+  info("Waiting for second new window");
+  let secondNewWindow = await promiseNewWindow;
+  await TestUtils.waitForCondition(
+    () =>
+      secondNewWindow.gBrowser.selectedBrowser.currentURI.spec == TEST_URIS[1],
+    "Wait until the URI is updated"
+  );
+  is(
+    secondNewWindow.gBrowser.visibleTabs.length,
+    1,
+    "Only one tab in second new window"
+  );
+  is(
+    secondNewWindow.gBrowser.selectedBrowser.currentURI.spec,
+    TEST_URIS[1],
+    "First tab moved"
+  );
+
+  await BrowserTestUtils.closeWindow(secondNewWindow);
+  await BrowserTestUtils.closeWindow(newWindow);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_multiple_navigateAndRestore.js b/src/zen/tests/mochitests/sessionstore/browser_multiple_navigateAndRestore.js
new file mode 100644
index 000000000..e2ee1b9e3
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_multiple_navigateAndRestore.js
@@ -0,0 +1,45 @@
+"use strict";
+
+const PAGE_1 =
+  "data:text/html,<html><body>A%20regular,%20everyday,%20normal%20page.";
+const PAGE_2 =
+  "data:text/html,<html><body>Another%20regular,%20everyday,%20normal%20page.";
+
+add_task(async function () {
+  // Load an empty, non-remote tab at about:blank...
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:blank", {
+    forceNotRemote: true,
+  });
+  gBrowser.selectedTab = tab;
+  let browser = gBrowser.selectedBrowser;
+  ok(!browser.isRemoteBrowser, "Ensure browser is not remote");
+  // Load a remote page, and then another remote page immediately
+  // after.
+  BrowserTestUtils.startLoadingURIString(browser, PAGE_1);
+  browser.stop();
+  BrowserTestUtils.startLoadingURIString(browser, PAGE_2);
+  await BrowserTestUtils.browserLoaded(browser, false, PAGE_2);
+
+  ok(browser.isRemoteBrowser, "Should have switched remoteness");
+  await TabStateFlusher.flush(browser);
+  let state = JSON.parse(ss.getTabState(tab));
+  let entries = state.entries;
+  is(entries.length, 1, "There should only be one entry");
+  is(entries[0].url, PAGE_2, "Should have PAGE_2 as the sole history entry");
+  is(
+    browser.currentURI.spec,
+    PAGE_2,
+    "Should have PAGE_2 as the browser currentURI"
+  );
+
+  await SpecialPowers.spawn(browser, [PAGE_2], async function (expectedURL) {
+    docShell.QueryInterface(Ci.nsIWebNavigation);
+    Assert.equal(
+      docShell.currentURI.spec,
+      expectedURL,
+      "Content should have PAGE_2 as the browser currentURI"
+    );
+  });
+
+  BrowserTestUtils.removeTab(tab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_multiple_select_after_load.js b/src/zen/tests/mochitests/sessionstore/browser_multiple_select_after_load.js
new file mode 100644
index 000000000..dcb896e43
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_multiple_select_after_load.js
@@ -0,0 +1,54 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const URL = `data:text/html;charset=utf-8,
+<select id="select">
+  <option value="1"> 1
+  <option value="2"> 2
+  <option value="3"> 3
+</select>`;
+
+const VALUES = ["1", "3"];
+
+// Tests that a document that changes a <select> element's "multiple" attribute
+// *after* the load event (eg. perhaps in response to some user action) doesn't
+// crash the browser when being restored.
+add_task(async function () {
+  // Create new tab.
+  let tab = BrowserTestUtils.addTab(gBrowser, URL);
+  await promiseBrowserLoaded(tab.linkedBrowser);
+
+  // Change the "multiple" attribute of the <select> element and select some
+  // options.
+  await setPropertyOfFormField(tab.linkedBrowser, "select", "multiple", true);
+
+  for (let v of VALUES) {
+    await setPropertyOfFormField(
+      tab.linkedBrowser,
+      `option[value="${v}"]`,
+      "selected",
+      true
+    );
+  }
+
+  // Remove the tab.
+  await promiseRemoveTabAndSessionState(tab);
+
+  // Verify state of the closed tab.
+  let tabData = ss.getClosedTabDataForWindow(window);
+  Assert.deepEqual(
+    tabData[0].state.formdata.id.select,
+    VALUES,
+    "Collected correct formdata"
+  );
+
+  // Restore the close tab.
+  tab = ss.undoCloseTab(window, 0);
+  await promiseTabRestored(tab);
+  ok(true, "Didn't crash!");
+
+  // Cleanup.
+  gBrowser.removeTab(tab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_navigation_api_restore.js b/src/zen/tests/mochitests/sessionstore/browser_navigation_api_restore.js
new file mode 100644
index 000000000..51ffe1b8f
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_navigation_api_restore.js
@@ -0,0 +1,156 @@
+"use strict";
+
+const PATH = getRootDirectory(gTestPath).replace(
+  "chrome://mochitests/content/",
+  "https://example.com/"
+);
+const EMPTY_URL = PATH + "empty.html";
+const EMPTY_FRAME_URL = PATH + "empty_frame.html";
+
+add_setup(async () => {
+  await SpecialPowers.pushPrefEnv({
+    set: [["dom.navigation.webidl.enabled", true]],
+  });
+});
+
+async function checkNavigationEntries(browser, urls, inFrame = null) {
+  let entryUrls = await SpecialPowers.spawn(browser, [inFrame], aInFrame =>
+    (aInFrame ? content.frames[0].navigation : content.navigation)
+      .entries()
+      .map(entry => entry.url)
+  );
+  for (const [entryUrl, expectedUrl] of urls.map((expected, i) => [
+    entryUrls[i],
+    expected,
+  ])) {
+    is(entryUrl, expectedUrl);
+  }
+}
+
+add_task(async function test_toplevel_fragment_navigations() {
+  let tab = BrowserTestUtils.addTab(gBrowser, EMPTY_URL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  let hashes = ["#1", "#2", "#3"];
+  for (const hash of hashes) {
+    await SpecialPowers.spawn(browser, [hash], async url => {
+      content.history.pushState(null, "", url);
+    });
+  }
+  await SpecialPowers.spawn(browser, [], async () => {
+    content.history.back();
+  });
+
+  let expectedUrls = ["", ...hashes].map(hash => `${EMPTY_URL}${hash}`);
+  await checkNavigationEntries(browser, expectedUrls);
+
+  await TabStateFlusher.flush(browser);
+  let { entries } = JSON.parse(ss.getTabState(tab));
+  is(entries.length, 4);
+
+  await SessionStoreTestUtils.closeTab(tab);
+  tab = ss.undoCloseTab(window, 0);
+  await promiseTabRestored(tab);
+  browser = tab.linkedBrowser;
+
+  await checkNavigationEntries(browser, expectedUrls);
+
+  gBrowser.removeTab(tab);
+});
+
+add_task(async function test_frame_fragment_navigations() {
+  let tab = BrowserTestUtils.addTab(gBrowser, EMPTY_FRAME_URL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  let hashes = ["#1", "#2", "#3"];
+  for (const hash of hashes) {
+    await SpecialPowers.spawn(browser, [hash], async url => {
+      content.frames[0].history.pushState(null, "", url);
+    });
+  }
+  await SpecialPowers.spawn(browser, [], async () => {
+    content.history.back();
+  });
+
+  let expectedUrls = ["", ...hashes].map(hash => `${EMPTY_URL}${hash}`);
+  await checkNavigationEntries(browser, expectedUrls, true);
+
+  await TabStateFlusher.flush(browser);
+  let { entries } = JSON.parse(ss.getTabState(tab));
+  is(entries.length, 4);
+
+  await SessionStoreTestUtils.closeTab(tab);
+  tab = ss.undoCloseTab(window, 0);
+  await promiseTabRestored(tab);
+  browser = tab.linkedBrowser;
+
+  await checkNavigationEntries(browser, expectedUrls, true);
+
+  gBrowser.removeTab(tab);
+});
+
+add_task(async function test_mixed_fragment_navigations() {
+  let tab = BrowserTestUtils.addTab(gBrowser, EMPTY_FRAME_URL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  let hashes = ["#frame1", "#frame2", "#frame3"];
+
+  await SpecialPowers.spawn(browser, [], async () => {
+    content.frames[0].history.pushState(null, "", "#frame1");
+    content.frames[0].history.pushState(null, "", "#frame2");
+    content.history.pushState(null, "", "#top");
+    content.frames[0].history.pushState(null, "", "#frame3");
+  });
+
+  let expectedTopUrls = ["", "#top"].map(hash => `${EMPTY_FRAME_URL}${hash}`);
+  await checkNavigationEntries(browser, expectedTopUrls);
+  let expectedFrameUrls = ["", ...hashes].map(hash => `${EMPTY_URL}${hash}`);
+  await checkNavigationEntries(browser, expectedFrameUrls, true);
+
+  await TabStateFlusher.flush(browser);
+  let { entries } = JSON.parse(ss.getTabState(tab));
+  is(entries.length, 5, "Got expected number of history entries");
+
+  await SessionStoreTestUtils.closeTab(tab);
+  tab = ss.undoCloseTab(window, 0);
+  await promiseTabRestored(tab);
+  browser = tab.linkedBrowser;
+
+  await checkNavigationEntries(browser, expectedTopUrls);
+  await checkNavigationEntries(browser, expectedFrameUrls, true);
+
+  gBrowser.removeTab(tab);
+});
+
+add_task(async function test_toplevel_navigations() {
+  let tab = BrowserTestUtils.addTab(gBrowser, EMPTY_URL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  let urls = ["entry1.html", "entry2.html", "entry3.html"].map(
+    url => `${PATH}${url}`
+  );
+  for (const url of urls) {
+    BrowserTestUtils.startLoadingURIString(browser, url);
+    await BrowserTestUtils.browserLoaded(browser);
+  }
+
+  let expectedUrls = [EMPTY_URL, ...urls];
+  await checkNavigationEntries(browser, expectedUrls);
+
+  await TabStateFlusher.flush(browser);
+  let { entries } = JSON.parse(ss.getTabState(tab));
+  is(entries.length, 4);
+
+  await SessionStoreTestUtils.closeTab(tab);
+  tab = ss.undoCloseTab(window, 0);
+  await promiseTabRestored(tab);
+  browser = tab.linkedBrowser;
+
+  await checkNavigationEntries(browser, expectedUrls);
+
+  gBrowser.removeTab(tab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_newtab_userTypedValue.js b/src/zen/tests/mochitests/sessionstore/browser_newtab_userTypedValue.js
new file mode 100644
index 000000000..441652cb4
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_newtab_userTypedValue.js
@@ -0,0 +1,97 @@
+"use strict";
+
+requestLongerTimeout(4);
+
+/**
+ * Test that when restoring an 'initial page' with session restore, it
+ * produces an empty URL bar, rather than leaving its URL explicitly
+ * there as a 'user typed value'.
+ */
+add_task(async function () {
+  let win = await BrowserTestUtils.openNewBrowserWindow();
+  await BrowserTestUtils.openNewForegroundTab(
+    win.gBrowser,
+    "https://example.com/"
+  );
+  let tabOpenedAndSwitchedTo = BrowserTestUtils.switchTab(
+    win.gBrowser,
+    () => {}
+  );
+
+  // This opens about:newtab:
+  win.BrowserCommands.openTab();
+  let tab = await tabOpenedAndSwitchedTo;
+  is(win.gURLBar.value, "", "URL bar should be empty");
+  is(tab.linkedBrowser.userTypedValue, null, "userTypedValue should be null");
+  let state = JSON.parse(SessionStore.getTabState(tab));
+  ok(
+    !state.userTypedValue,
+    "userTypedValue should be undefined on the tab's state"
+  );
+  tab = null;
+
+  await BrowserTestUtils.closeWindow(win);
+
+  ok(SessionStore.getClosedWindowCount(), "Should have a closed window");
+
+  await forceSaveState();
+
+  win = SessionStore.undoCloseWindow(0);
+  await TestUtils.topicObserved(
+    "sessionstore-single-window-restored",
+    subject => subject == win
+  );
+  // Don't wait for load here because it's about:newtab and we may have swapped in
+  // a preloaded browser.
+  await TabStateFlusher.flush(win.gBrowser.selectedBrowser);
+
+  is(win.gURLBar.value, "", "URL bar should be empty");
+  tab = win.gBrowser.selectedTab;
+  is(tab.linkedBrowser.userTypedValue, null, "userTypedValue should be null");
+  state = JSON.parse(SessionStore.getTabState(tab));
+  ok(
+    !state.userTypedValue,
+    "userTypedValue should be undefined on the tab's state"
+  );
+
+  BrowserTestUtils.removeTab(tab);
+
+  for (let url of gInitialPages) {
+    if (url == BROWSER_NEW_TAB_URL || url === "about:opentabs") {
+      continue; // We tested about:newtab using BrowserCommands.openTab() above.
+    }
+    info("Testing " + url + " - " + new Date());
+    await BrowserTestUtils.openNewForegroundTab(win.gBrowser, url);
+    await BrowserTestUtils.closeWindow(win);
+
+    ok(SessionStore.getClosedWindowCount(), "Should have a closed window");
+
+    await forceSaveState();
+
+    win = SessionStore.undoCloseWindow(0);
+    await TestUtils.topicObserved(
+      "sessionstore-single-window-restored",
+      subject => subject == win
+    );
+    await BrowserTestUtils.browserLoaded(win.gBrowser.selectedBrowser, {
+      wantLoad: url,
+    });
+    await TabStateFlusher.flush(win.gBrowser.selectedBrowser);
+
+    is(win.gURLBar.value, "", "URL bar should be empty");
+    tab = win.gBrowser.selectedTab;
+    is(tab.linkedBrowser.userTypedValue, null, "userTypedValue should be null");
+    state = JSON.parse(SessionStore.getTabState(tab));
+    ok(
+      !state.userTypedValue,
+      "userTypedValue should be undefined on the tab's state"
+    );
+
+    info("Removing tab - " + new Date());
+    BrowserTestUtils.removeTab(tab);
+    info("Finished removing tab - " + new Date());
+  }
+  info("Removing window - " + new Date());
+  await BrowserTestUtils.closeWindow(win);
+  info("Finished removing window - " + new Date());
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_not_collect_when_idle.js b/src/zen/tests/mochitests/sessionstore/browser_not_collect_when_idle.js
new file mode 100644
index 000000000..ddb088813
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_not_collect_when_idle.js
@@ -0,0 +1,118 @@
+/** Test for Bug 1305950 */
+
+const { MockRegistrar } = ChromeUtils.importESModule(
+  "resource://testing-common/MockRegistrar.sys.mjs"
+);
+
+// The mock idle service.
+var idleService = {
+  _observers: new Set(),
+  _activity: {
+    addCalls: [],
+    removeCalls: [],
+    observerFires: [],
+  },
+
+  _reset() {
+    this._observers.clear();
+    this._activity.addCalls = [];
+    this._activity.removeCalls = [];
+    this._activity.observerFires = [];
+  },
+
+  _fireObservers(state) {
+    for (let observer of this._observers.values()) {
+      observer.observe(observer, state, null);
+      this._activity.observerFires.push(state);
+    }
+  },
+
+  QueryInterface: ChromeUtils.generateQI(["nsIUserIdleService"]),
+  idleTime: 19999,
+
+  addIdleObserver(observer, time) {
+    this._observers.add(observer);
+    this._activity.addCalls.push(time);
+  },
+
+  removeIdleObserver(observer, time) {
+    this._observers.delete(observer);
+    this._activity.removeCalls.push(time);
+  },
+};
+
+add_task(async function testIntervalChanges() {
+  const PREF_SS_INTERVAL = 2000;
+
+  // We speed up the interval between session saves to ensure that the test
+  // runs quickly.
+  Services.prefs.setIntPref("browser.sessionstore.interval", PREF_SS_INTERVAL);
+
+  // Increase `idleDelay` to 1 day to update the pre-registered idle observer
+  // in "real" idle service to avoid possible interference, especially for the
+  // CI server environment.
+  Services.prefs.setIntPref("browser.sessionstore.idleDelay", 86400);
+
+  // Mock an idle service.
+  let fakeIdleService = MockRegistrar.register(
+    "@mozilla.org/widget/useridleservice;1",
+    idleService
+  );
+  idleService._reset();
+
+  registerCleanupFunction(function () {
+    Services.prefs.clearUserPref("browser.sessionstore.interval");
+    MockRegistrar.unregister(fakeIdleService);
+  });
+
+  // Hook idle/active observer to mock idle service by changing pref `idleDelay`
+  // to a whatever value, which will not be used.
+  Services.prefs.setIntPref("browser.sessionstore.idleDelay", 5000);
+
+  // Wait a `sessionstore-state-write-complete` event from any previous
+  // scheduled state write. This is needed since the `_lastSaveTime` in
+  // runDelayed() should be set at least once, or the `_isIdle` flag will not
+  // become effective.
+  info("Waiting for sessionstore-state-write-complete notification");
+  await TestUtils.topicObserved("sessionstore-state-write-complete");
+
+  info(
+    "Got the sessionstore-state-write-complete notification, now testing idle mode"
+  );
+
+  // Enter the "idle mode" (raise the `_isIdle` flag) by firing idle
+  // observer of mock idle service.
+  idleService._fireObservers("idle");
+
+  // Cancel any possible state save, which is not related with this test to
+  // avoid interference.
+  SessionSaver.cancel();
+
+  let p1 = promiseSaveState();
+
+  // Schedule a state write, which is expeced to be postponed after about
+  // `browser.sessionstore.interval.idle` ms, since the idle flag was just set.
+  SessionSaver.runDelayed(0);
+
+  // We expect `p1` hits the timeout.
+  await Assert.rejects(
+    p1,
+    /Save state timeout/,
+    "[Test 1A] No state write during idle."
+  );
+
+  // Test again for better reliability. Same, we expect following promise hits
+  // the timeout.
+  await Assert.rejects(
+    promiseSaveState(),
+    /Save state timeout/,
+    "[Test 1B] Again: No state write during idle."
+  );
+
+  // Back to the active mode.
+  info("Start to test active mode...");
+  idleService._fireObservers("active");
+
+  info("[Test 2] Waiting for sessionstore-state-write-complete during active");
+  await TestUtils.topicObserved("sessionstore-state-write-complete");
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_oldformat.toml b/src/zen/tests/mochitests/sessionstore/browser_oldformat.toml
new file mode 100644
index 000000000..54842390e
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_oldformat.toml
@@ -0,0 +1,301 @@
+[DEFAULT]
+support-files = [
+  "head.js",
+  "browser_formdata_sample.html",
+  "browser_formdata_xpath_sample.html",
+  "browser_frametree_sample.html",
+  "browser_frametree_sample_frameset.html",
+  "browser_frametree_sample_iframes.html",
+  "browser_frame_history_index.html",
+  "browser_frame_history_index2.html",
+  "browser_frame_history_index_blank.html",
+  "browser_frame_history_a.html",
+  "browser_frame_history_b.html",
+  "browser_frame_history_c.html",
+  "browser_frame_history_c1.html",
+  "browser_frame_history_c2.html",
+  "browser_formdata_format_sample.html",
+  "browser_sessionHistory_slow.sjs",
+  "browser_scrollPositions_sample.html",
+  "browser_scrollPositions_sample2.html",
+  "browser_scrollPositions_sample_frameset.html",
+  "browser_scrollPositions_readerModeArticle.html",
+  "browser_sessionStorage.html",
+  "browser_speculative_connect.html",
+  "browser_248970_b_sample.html",
+  "browser_339445_sample.html",
+  "browser_423132_sample.html",
+  "browser_447951_sample.html",
+  "browser_454908_sample.html",
+  "browser_456342_sample.xhtml",
+  "browser_463205_sample.html",
+  "browser_463206_sample.html",
+  "browser_466937_sample.html",
+  "browser_485482_sample.html",
+  "browser_637020_slow.sjs",
+  "browser_662743_sample.html",
+  "browser_739531_sample.html",
+  "browser_739531_frame.html",
+  "coopHeaderCommon.sjs",
+  "restore_redirect_http.html",
+  "restore_redirect_http.html^headers^",
+  "restore_redirect_js.html",
+  "restore_redirect_target.html",
+  "browser_1234021_page.html",
+  "browser_1284886_suspend_tab.html",
+  "browser_1284886_suspend_tab_2.html",
+  "empty.html",
+  "coop_coep.html",
+  "coop_coep.html^headers^",
+]
+# remove this after bug 1628486 is landed
+prefs = [
+  "network.cookie.cookieBehavior=5",
+  "gfx.font_rendering.fallback.async=false",
+  "browser.sessionstore.closedTabsFromAllWindows=true",
+  "browser.sessionstore.closedTabsFromClosedWindows=true",
+]
+
+#NB: the following are disabled
+#  browser_464620_a.html
+#  browser_464620_b.html
+#  browser_464620_xd.html
+
+#disabled-for-intermittent-failures--bug-766044, browser_459906_empty.html
+#disabled-for-intermittent-failures--bug-766044, browser_459906_sample.html
+#disabled-for-intermittent-failures--bug-765389, browser_461743_sample.html
+
+["browser_1234021.js"]
+
+["browser_1284886_suspend_tab.js"]
+
+["browser_1446343-windowsize.js"]
+skip-if = [
+  "os == 'linux' && os_version == '22.04' && arch == 'x86_64' && display == 'wayland'", # Bug 1600180
+  "os == 'linux' && os_version == '24.04' && arch == 'x86_64' && display == 'x11'", # Bug 1600180
+]
+
+["browser_248970_b_perwindowpb.js"]
+# Disabled because of leaks.
+# Re-enabling and rewriting this test is tracked in bug 936919.
+skip-if = [
+  "true",
+]
+
+["browser_339445.js"]
+
+["browser_345898.js"]
+
+["browser_350525.js"]
+
+["browser_354894_perwindowpb.js"]
+skip-if = [
+  "os == 'win' && os_version == '11.26200' && asan", # Bug 2019745
+]
+
+["browser_367052.js"]
+
+["browser_393716.js"]
+skip-if = [
+  "debug", # Bug 1507747
+]
+
+["browser_394759_basic.js"]
+# Disabled for intermittent failures, bug 944372.
+skip-if = [
+  "true",
+]
+
+["browser_394759_behavior.js"]
+https_first_disabled = true
+
+["browser_394759_perwindowpb.js"]
+
+["browser_394759_purge.js"]
+
+["browser_423132.js"]
+
+["browser_447951.js"]
+
+["browser_454908.js"]
+
+["browser_456342.js"]
+skip-if = [
+  "verify-standalone",
+]
+
+["browser_461634.js"]
+
+["browser_463205.js"]
+
+["browser_463206.js"]
+
+["browser_464199.js"]
+# Disabled for frequent intermittent failures
+
+["browser_464620_a.js"]
+skip-if = [
+  "true",
+]
+
+["browser_464620_b.js"]
+skip-if = [
+  "true",
+]
+
+["browser_465215.js"]
+
+["browser_465223.js"]
+
+["browser_466937.js"]
+
+["browser_467409-backslashplosion.js"]
+
+["browser_477657.js"]
+skip-if = [
+  "os == 'linux' && os_version == '24.04' && arch == 'x86_64' && display == 'x11'", # Bug 1610668
+]
+
+["browser_480893.js"]
+
+["browser_485482.js"]
+
+["browser_485563.js"]
+
+["browser_490040.js"]
+
+["browser_491168.js"]
+
+["browser_491577.js"]
+
+["browser_495495.js"]
+
+["browser_500328.js"]
+
+["browser_514751.js"]
+
+["browser_522375.js"]
+
+["browser_522545.js"]
+skip-if = [
+  "true", # Bug 1380968
+]
+
+["browser_524745.js"]
+
+["browser_528776.js"]
+
+["browser_579868.js"]
+
+["browser_579879.js"]
+
+["browser_581937.js"]
+
+["browser_586068-apptabs.js"]
+
+["browser_586068-apptabs_ondemand.js"]
+
+["browser_586068-browser_state_interrupted.js"]
+
+["browser_586068-cascade.js"]
+
+["browser_586068-multi_window.js"]
+
+["browser_586068-reload.js"]
+https_first_disabled = true
+
+["browser_586068-select.js"]
+
+["browser_586068-window_state.js"]
+
+["browser_586068-window_state_override.js"]
+
+["browser_586147.js"]
+
+["browser_588426.js"]
+
+["browser_590268.js"]
+
+["browser_590563.js"]
+skip-if = [
+  "os == 'mac' && os_version == '15.30' && arch == 'aarch64'",
+]
+
+["browser_595601-restore_hidden.js"]
+
+["browser_597071.js"]
+
+["browser_600545.js"]
+
+["browser_601955.js"]
+
+["browser_607016.js"]
+
+["browser_615394-SSWindowState_events_duplicateTab.js"]
+
+["browser_615394-SSWindowState_events_setBrowserState.js"]
+
+["browser_615394-SSWindowState_events_setTabState.js"]
+
+["browser_615394-SSWindowState_events_setWindowState.js"]
+https_first_disabled = true
+
+["browser_615394-SSWindowState_events_undoCloseTab.js"]
+
+["browser_615394-SSWindowState_events_undoCloseWindow.js"]
+
+["browser_618151.js"]
+
+["browser_623779.js"]
+
+["browser_624727.js"]
+
+["browser_625016.js"]
+run-if = [
+  "os != 'mac'", # not running on macOS where closing all windows doesn't quit the application
+]
+
+["browser_628270.js"]
+
+["browser_635418.js"]
+
+["browser_636279.js"]
+
+["browser_637020.js"]
+
+["browser_645428.js"]
+
+["browser_659591.js"]
+
+["browser_662743.js"]
+
+["browser_662812.js"]
+
+["browser_665702-state_session.js"]
+
+["browser_682507.js"]
+
+["browser_687710.js"]
+
+["browser_687710_2.js"]
+https_first_disabled = true
+
+["browser_694378.js"]
+
+["browser_701377.js"]
+
+["browser_705597.js"]
+
+["browser_707862.js"]
+
+["browser_739531.js"]
+
+["browser_739805.js"]
+
+["browser_819510_perwindowpb.js"]
+skip-if = [
+  "true", # Bug 1284312, Bug 1341980, bug 1381451
+]
+
+["browser_906076_lazy_tabs.js"]
+https_first_disabled = true
diff --git a/src/zen/tests/mochitests/sessionstore/browser_page_title.js b/src/zen/tests/mochitests/sessionstore/browser_page_title.js
new file mode 100644
index 000000000..9f84e67a9
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_page_title.js
@@ -0,0 +1,54 @@
+"use strict";
+
+const URL = "data:text/html,<title>initial title</title>";
+
+add_task(async function () {
+  // Create a new tab.
+  let tab = BrowserTestUtils.addTab(gBrowser, URL);
+  await promiseBrowserLoaded(tab.linkedBrowser);
+
+  // Remove the tab.
+  await promiseRemoveTabAndSessionState(tab);
+
+  // Check the title.
+  let [
+    {
+      state: { entries },
+    },
+  ] = ss.getClosedTabDataForWindow(window);
+  is(entries[0].title, "initial title", "correct title");
+});
+
+add_task(async function () {
+  // Create a new tab.
+  let tab = BrowserTestUtils.addTab(gBrowser, URL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  // Flush to ensure we collected the initial title.
+  await TabStateFlusher.flush(browser);
+
+  // Set a new title.
+  await SpecialPowers.spawn(browser, [], async function () {
+    return new Promise(resolve => {
+      docShell.chromeEventHandler.addEventListener(
+        "DOMTitleChanged",
+        () => resolve(),
+        { once: true }
+      );
+
+      content.document.title = "new title";
+    });
+  });
+
+  // Remove the tab.
+  await promiseRemoveTabAndSessionState(tab);
+
+  // Check the title.
+  let [
+    {
+      state: { entries },
+    },
+  ] = ss.getClosedTabDataForWindow(window);
+  is(entries[0].title, "new title", "correct title");
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_parentProcessRestoreHash.js b/src/zen/tests/mochitests/sessionstore/browser_parentProcessRestoreHash.js
new file mode 100644
index 000000000..ad8144f86
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_parentProcessRestoreHash.js
@@ -0,0 +1,115 @@
+"use strict";
+
+const SELFCHROMEURL =
+  "chrome://mochitests/content/browser/browser/" +
+  "components/sessionstore/test/browser_parentProcessRestoreHash.js";
+
+const Cm = Components.manager;
+
+const TESTCLASSID = "78742c04-3630-448c-9be3-6c5070f062de";
+
+const TESTURL = "about:testpageforsessionrestore#foo";
+
+let TestAboutPage = {
+  QueryInterface: ChromeUtils.generateQI(["nsIAboutModule"]),
+  getURIFlags() {
+    // No CAN_ or MUST_LOAD_IN_CHILD means this loads in the parent:
+    return (
+      Ci.nsIAboutModule.ALLOW_SCRIPT |
+      Ci.nsIAboutModule.URI_SAFE_FOR_UNTRUSTED_CONTENT |
+      Ci.nsIAboutModule.HIDE_FROM_ABOUTABOUT
+    );
+  },
+
+  newChannel(aURI, aLoadInfo) {
+    // about: page inception!
+    let newURI = Services.io.newURI(SELFCHROMEURL);
+    let channel = Services.io.newChannelFromURIWithLoadInfo(newURI, aLoadInfo);
+    channel.originalURI = aURI;
+    return channel;
+  },
+
+  createInstance(iid) {
+    return this.QueryInterface(iid);
+  },
+
+  register() {
+    Cm.QueryInterface(Ci.nsIComponentRegistrar).registerFactory(
+      Components.ID(TESTCLASSID),
+      "Only here for a test",
+      "@mozilla.org/network/protocol/about;1?what=testpageforsessionrestore",
+      this
+    );
+  },
+
+  unregister() {
+    Cm.QueryInterface(Ci.nsIComponentRegistrar).unregisterFactory(
+      Components.ID(TESTCLASSID),
+      this
+    );
+  },
+};
+
+/**
+ * Test that switching from a remote to a parent process browser
+ * correctly clears the userTypedValue
+ */
+add_task(async function () {
+  await SpecialPowers.pushPrefEnv({
+    set: [["dom.security.skip_about_page_has_csp_assert", true]],
+  });
+
+  TestAboutPage.register();
+  let tab = await BrowserTestUtils.openNewForegroundTab(
+    gBrowser,
+    "http://example.com/",
+    true,
+    true
+  );
+  ok(tab.linkedBrowser.isRemoteBrowser, "Browser should be remote");
+
+  let resolveLocationChangePromise;
+  let locationChangePromise = new Promise(
+    r => (resolveLocationChangePromise = r)
+  );
+  let wpl = {
+    onStateChange(listener, request, state, _status) {
+      let location = request.QueryInterface(Ci.nsIChannel).originalURI;
+      // Ignore about:blank loads.
+      let docStop =
+        Ci.nsIWebProgressListener.STATE_STOP |
+        Ci.nsIWebProgressListener.STATE_IS_NETWORK;
+      if (location.spec == "about:blank" || (state & docStop) != docStop) {
+        return;
+      }
+      is(location.spec, TESTURL, "Got the expected URL");
+      resolveLocationChangePromise();
+    },
+  };
+  gBrowser.addProgressListener(wpl);
+
+  gURLBar.value = TESTURL;
+  gURLBar.select();
+  EventUtils.sendKey("return");
+
+  await locationChangePromise;
+
+  ok(!tab.linkedBrowser.isRemoteBrowser, "Browser should no longer be remote");
+
+  is(gURLBar.value, TESTURL, "URL bar visible value should be correct.");
+  is(gURLBar.untrimmedValue, TESTURL, "URL bar value should be correct.");
+  is(
+    gURLBar.getAttribute("pageproxystate"),
+    "valid",
+    "URL bar is in valid page proxy state"
+  );
+
+  ok(
+    !tab.linkedBrowser.userTypedValue,
+    "No userTypedValue should be on the browser."
+  );
+
+  BrowserTestUtils.removeTab(tab);
+  gBrowser.removeProgressListener(wpl);
+  TestAboutPage.unregister();
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_pending_tabs.js b/src/zen/tests/mochitests/sessionstore/browser_pending_tabs.js
new file mode 100644
index 000000000..20f3c4e8c
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_pending_tabs.js
@@ -0,0 +1,38 @@
+"use strict";
+
+const TAB_STATE = {
+  entries: [
+    { url: "about:mozilla", triggeringPrincipal_base64 },
+    { url: "about:robots", triggeringPrincipal_base64 },
+  ],
+  index: 1,
+};
+
+add_task(async function () {
+  // Create a background tab.
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:blank");
+  let browser = tab.linkedBrowser;
+  await BrowserTestUtils.browserLoaded(browser, { wantLoad: "about:blank" });
+
+  // The tab shouldn't be restored right away.
+  Services.prefs.setBoolPref("browser.sessionstore.restore_on_demand", true);
+
+  // Prepare the tab state.
+  let promise = promiseTabRestoring(tab);
+  ss.setTabState(tab, JSON.stringify(TAB_STATE));
+  ok(tab.hasAttribute("pending"), "tab is pending");
+  await promise;
+
+  // Flush to ensure the parent has all data.
+  await TabStateFlusher.flush(browser);
+
+  // Check that the shistory index is the one we restored.
+  let tabState = TabState.collect(tab, ss.getInternalObjectState(tab));
+  is(tabState.index, TAB_STATE.index, "correct shistory index");
+
+  // Check we don't collect userTypedValue when we shouldn't.
+  ok(!tabState.userTypedValue, "tab didn't have a userTypedValue");
+
+  // Cleanup.
+  gBrowser.removeTab(tab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_pinned_tabs.js b/src/zen/tests/mochitests/sessionstore/browser_pinned_tabs.js
new file mode 100644
index 000000000..7a51da7cc
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_pinned_tabs.js
@@ -0,0 +1,324 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const REMOTE_URL = "https://www.example.com/";
+const ABOUT_ROBOTS_URL = "about:robots";
+const NO_TITLE_URL = "data:text/plain,foo";
+
+const BACKUP_STATE = SessionStore.getBrowserState();
+registerCleanupFunction(() => promiseBrowserState(BACKUP_STATE));
+
+add_setup(async function () {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["browser.sessionstore.restore_on_demand", true],
+      ["browser.sessionstore.restore_tabs_lazily", true],
+    ],
+  });
+});
+
+/**
+ * When implementing batch insertion of tabs as part of session restore,
+ * we started reversing the insertion order of pinned tabs (bug 1607441).
+ * This test checks we don't regress that again.
+ */
+add_task(async function test_pinned_tabs_order() {
+  // we expect 3 pinned tabs plus the selected tab get content restored.
+  let allTabsRestored = promiseSessionStoreLoads(4);
+  await promiseBrowserState({
+    windows: [
+      {
+        selected: 4, // SessionStore uses 1-based indexing.
+        tabs: [
+          {
+            pinned: true,
+            entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }],
+          },
+          {
+            pinned: true,
+            entries: [{ url: ABOUT_ROBOTS_URL, triggeringPrincipal_base64 }],
+          },
+          {
+            pinned: true,
+            entries: [{ url: NO_TITLE_URL, triggeringPrincipal_base64 }],
+          },
+          { entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }] },
+          { entries: [{ url: "about:blank", triggeringPrincipal_base64 }] },
+        ],
+      },
+    ],
+  });
+  await allTabsRestored;
+  let [tab1, tab2, tab3, tab4, tab5] = gBrowser.tabs;
+  ok(tab1.pinned, "First tab is pinned");
+  ok(tab2.pinned, "Second tab is pinned");
+  ok(tab3.pinned, "Third tab is pinned");
+  ok(!tab4.pinned, "Fourth tab is not pinned");
+  ok(!tab5.pinned, "Fifth tab is not pinned");
+
+  ok(tab4.selected, "Fourth tab is selected");
+  is(
+    tab1.linkedBrowser.currentURI.spec,
+    REMOTE_URL,
+    "First tab has matching URL"
+  );
+  is(
+    tab2.linkedBrowser.currentURI.spec,
+    ABOUT_ROBOTS_URL,
+    "Second tab has matching URL"
+  );
+  is(
+    tab3.linkedBrowser.currentURI.spec,
+    NO_TITLE_URL,
+    "Third tab has matching URL"
+  );
+  // Clean up for the next task.
+  await promiseBrowserState(BACKUP_STATE);
+});
+
+/**
+ * When fixing the previous regression, pinned tabs started disappearing out
+ * of sessions with selected pinned tabs. This test checks that case.
+ */
+add_task(async function test_selected_pinned_tab_dataloss() {
+  // we expect 3 pinned tabs (one of which is selected) get content restored.
+  let allTabsRestored = promiseSessionStoreLoads(3);
+  await promiseBrowserState({
+    windows: [
+      {
+        selected: 1, // SessionStore uses 1-based indexing.
+        tabs: [
+          {
+            pinned: true,
+            entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }],
+          },
+          {
+            pinned: true,
+            entries: [{ url: ABOUT_ROBOTS_URL, triggeringPrincipal_base64 }],
+          },
+          {
+            pinned: true,
+            entries: [{ url: NO_TITLE_URL, triggeringPrincipal_base64 }],
+          },
+          { entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }] },
+          { entries: [{ url: "about:blank", triggeringPrincipal_base64 }] },
+        ],
+      },
+    ],
+  });
+  await allTabsRestored;
+  let [tab1, tab2, tab3, tab4, tab5] = gBrowser.tabs;
+  ok(tab5, "Should have 5 tabs");
+  ok(tab1.pinned, "First tab is pinned");
+  ok(tab2.pinned, "Second tab is pinned");
+  ok(tab3.pinned, "Third tab is pinned");
+  ok(tab4 && !tab4.pinned, "Fourth tab is not pinned");
+  ok(tab5 && !tab5.pinned, "Fifth tab is not pinned");
+
+  ok(tab1 && tab1.selected, "First (pinned) tab is selected");
+  is(
+    tab1.linkedBrowser.currentURI.spec,
+    REMOTE_URL,
+    "First tab has matching URL"
+  );
+  is(
+    tab2.linkedBrowser.currentURI.spec,
+    ABOUT_ROBOTS_URL,
+    "Second tab has matching URL"
+  );
+  is(
+    tab3.linkedBrowser.currentURI.spec,
+    NO_TITLE_URL,
+    "Third tab has matching URL"
+  );
+  // Clean up for the next task.
+  await promiseBrowserState(BACKUP_STATE);
+});
+
+/**
+ * While we're here, it seems useful to have a test for mixed pinned and
+ * unpinned tabs in session store state, as well as userContextId.
+ */
+add_task(async function test_mixed_pinned_unpinned() {
+  // we expect 3 pinned tabs plus the selected tab get content restored.
+  let allTabsRestored = promiseSessionStoreLoads(4);
+  await promiseBrowserState({
+    windows: [
+      {
+        selected: 4, // SessionStore uses 1-based indexing.
+        tabs: [
+          {
+            pinned: true,
+            entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }],
+          },
+          { entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }] },
+          {
+            pinned: true,
+            entries: [{ url: ABOUT_ROBOTS_URL, triggeringPrincipal_base64 }],
+          },
+          { entries: [{ url: "about:blank", triggeringPrincipal_base64 }] },
+          {
+            pinned: true,
+            entries: [{ url: NO_TITLE_URL, triggeringPrincipal_base64 }],
+          },
+        ],
+      },
+    ],
+  });
+  await allTabsRestored;
+  let [tab1, tab2, tab3, tab4, tab5] = gBrowser.tabs;
+  ok(tab1.pinned, "First tab is pinned");
+  ok(tab2.pinned, "Second tab is pinned");
+  ok(tab3.pinned, "Third tab is pinned");
+  ok(!tab4.pinned, "Fourth tab is not pinned");
+  ok(!tab5.pinned, "Fifth tab is not pinned");
+
+  // This is confusing to read - the 4th entry in the session data is
+  // selected. But the 5th entry is pinned, so it moves to the start of the
+  // tabstrip, so when we fetch `gBrowser.tabs`, the 4th entry in the list
+  // is actually the 5th tab.
+  ok(tab5.selected, "Fifth tab is selected");
+  is(
+    tab1.linkedBrowser.currentURI.spec,
+    REMOTE_URL,
+    "First tab has matching URL"
+  );
+  is(
+    tab2.linkedBrowser.currentURI.spec,
+    ABOUT_ROBOTS_URL,
+    "Second tab has matching URL"
+  );
+  is(
+    tab3.linkedBrowser.currentURI.spec,
+    NO_TITLE_URL,
+    "Third tab has matching URL"
+  );
+  // Clean up for the next task.
+  await promiseBrowserState(BACKUP_STATE);
+});
+
+/**
+ * After session restore, if we crash an unpinned tab, we noticed pinned tabs
+ * created in the same process would lose all data (Bug 1624511). This test
+ * checks that case.
+ */
+add_task(async function test_pinned_tab_dataloss() {
+  // We do not run if there are no crash reporters to avoid
+  // problems with the intentional crash.
+  if (!AppConstants.MOZ_CRASHREPORTER) {
+    return;
+  }
+  // If we end up increasing the process count limit in future,
+  // we want to ensure that we don't stop testing this case
+  // of pinned tab data loss.
+  if (SpecialPowers.getIntPref("dom.ipc.processCount") > 8) {
+    ok(
+      false,
+      "Process count is greater than 8, update the number of pinned tabs in test."
+    );
+  }
+
+  // We expect 17 pinned tabs plus the selected tab get content restored.
+  // Given that the default process count is currently 8, we need this
+  // number of pinned tabs to reproduce the data loss. If this changes,
+  // please add more pinned tabs.
+  let allTabsRestored = promiseSessionStoreLoads(18);
+  await promiseBrowserState({
+    windows: [
+      {
+        selected: 18, // SessionStore uses 1-based indexing.
+        tabs: [
+          {
+            pinned: true,
+            entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }],
+          },
+          {
+            pinned: true,
+            entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }],
+          },
+          {
+            pinned: true,
+            entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }],
+          },
+          {
+            pinned: true,
+            entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }],
+          },
+          {
+            pinned: true,
+            entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }],
+          },
+          {
+            pinned: true,
+            entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }],
+          },
+          {
+            pinned: true,
+            entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }],
+          },
+          {
+            pinned: true,
+            entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }],
+          },
+          {
+            pinned: true,
+            entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }],
+          },
+          {
+            pinned: true,
+            entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }],
+          },
+          {
+            pinned: true,
+            entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }],
+          },
+          {
+            pinned: true,
+            entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }],
+          },
+          {
+            pinned: true,
+            entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }],
+          },
+          {
+            pinned: true,
+            entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }],
+          },
+          {
+            pinned: true,
+            entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }],
+          },
+          {
+            pinned: true,
+            entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }],
+          },
+          {
+            pinned: true,
+            entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }],
+          },
+          { entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }] },
+        ],
+      },
+    ],
+  });
+  await allTabsRestored;
+
+  let tabs = gBrowser.tabs;
+  await BrowserTestUtils.crashFrame(tabs[17].linkedBrowser);
+
+  await TestUtils.topicObserved("sessionstore-state-write-complete");
+
+  for (let i = 0; i < tabs.length; i++) {
+    let tab = tabs[i];
+    is(
+      tab.linkedBrowser.currentURI.spec,
+      REMOTE_URL,
+      `Tab ${i + 1} should have matching URL`
+    );
+  }
+
+  // Clean up for the next task.
+  await promiseBrowserState(BACKUP_STATE);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_policy_container_not_stored.js b/src/zen/tests/mochitests/sessionstore/browser_policy_container_not_stored.js
new file mode 100644
index 000000000..9258e3d54
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_policy_container_not_stored.js
@@ -0,0 +1,51 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+/**
+ * A session history entry only needs to retain the policy container for loads
+ * that inherit their policies (about:blank, about:srcdoc, blob:, data:, ...).
+ * Anything fetched over the network gets its policies from the response again,
+ * so storing them would only bloat the session store (bug 2011236).
+ */
+
+const TEST_ROOT = getRootDirectory(gTestPath).replace(
+  "chrome://mochitests/content",
+  "https://example.com"
+);
+const PARENT_URL = TEST_ROOT + "browser_policy_container_sample.html";
+const FRAME_URL = TEST_ROOT + "browser_policy_container_sample_frame.html";
+
+add_task(async function test_policy_container_only_for_inheriting_loads() {
+  const tab = BrowserTestUtils.addTab(gBrowser, PARENT_URL);
+  gBrowser.selectedTab = tab;
+  await promiseBrowserLoaded(tab.linkedBrowser, true, PARENT_URL);
+  await TabStateFlusher.flush(tab.linkedBrowser);
+
+  const state = JSON.parse(ss.getTabState(tab));
+  const topEntry = state.entries.at(-1);
+  is(topEntry.url, PARENT_URL, "collected the parent entry");
+
+  const children = topEntry.children ?? [];
+  const networkFrame = children.find(child => child.url === FRAME_URL);
+  const blankFrame = children.find(child => child.url === "about:blank");
+
+  ok(networkFrame, "collected the network-scheme subframe entry");
+  ok(blankFrame, "collected the about:blank subframe entry");
+
+  // The parent has a CSP, so both subframes inherit a policy container onto
+  // their load state. Only the one that cannot recover it from a response
+  // should keep it in session history.
+  ok(
+    !("policyContainer" in networkFrame),
+    "https subframe entry does not store a policyContainer"
+  );
+  ok(
+    "policyContainer" in blankFrame,
+    "about:blank subframe entry still stores its inherited policyContainer"
+  );
+
+  await BrowserTestUtils.removeTab(tab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_policy_container_sample.html b/src/zen/tests/mochitests/sessionstore/browser_policy_container_sample.html
new file mode 100644
index 000000000..1b8ad8d29
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_policy_container_sample.html
@@ -0,0 +1,12 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <meta charset="utf-8">
+  <meta http-equiv="Content-Security-Policy" content="default-src * data: blob: 'unsafe-inline'">
+  <title>policyContainer session store sample</title>
+</head>
+<body>
+  <iframe id="network" src="browser_policy_container_sample_frame.html"></iframe>
+  <iframe id="blank" src="about:blank"></iframe>
+</body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_policy_container_sample_frame.html b/src/zen/tests/mochitests/sessionstore/browser_policy_container_sample_frame.html
new file mode 100644
index 000000000..4675a0cd4
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_policy_container_sample_frame.html
@@ -0,0 +1,10 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>policyContainer session store sample frame</title>
+</head>
+<body>
+  frame
+</body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_privatetabs.js b/src/zen/tests/mochitests/sessionstore/browser_privatetabs.js
new file mode 100644
index 000000000..237d9ff03
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_privatetabs.js
@@ -0,0 +1,60 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+add_task(function cleanup() {
+  info("Forgetting closed tabs");
+  forgetClosedTabs(window);
+});
+
+add_task(async function test_restore_pbm() {
+  // Clear the list of closed windows.
+  forgetClosedWindows();
+
+  // Create a new window to attach our frame script to.
+  let win = await promiseNewWindowLoaded({ private: true });
+
+  // Create a new tab in the new window that will load the frame script.
+  let tab = BrowserTestUtils.addTab(win.gBrowser, "about:mozilla");
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  // Check that we consider the tab as private.
+  let state = JSON.parse(ss.getTabState(tab));
+  ok(state.isPrivate, "tab considered private");
+
+  // Ensure that closed tabs in a private windows can be restored.
+  await SessionStoreTestUtils.closeTab(tab);
+  is(ss.getClosedTabCountForWindow(win), 1, "there is a single tab to restore");
+
+  // Ensure that closed private windows can never be restored.
+  await BrowserTestUtils.closeWindow(win);
+  is(ss.getClosedWindowCount(), 0, "no windows to restore");
+});
+
+/**
+ * Tests the purgeDataForPrivateWindow SessionStore method.
+ */
+add_task(async function test_purge_pbm() {
+  info("Clear the list of closed windows.");
+  forgetClosedWindows();
+
+  info("Create a new window to attach our frame script to.");
+  let win = await promiseNewWindowLoaded({ private: true });
+
+  info("Create a new tab in the new window that will load the frame script.");
+  let tab = BrowserTestUtils.addTab(win.gBrowser, "about:mozilla");
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  info("Ensure that closed tabs in a private windows can be restored.");
+  await SessionStoreTestUtils.closeTab(tab);
+  is(ss.getClosedTabCountForWindow(win), 1, "there is a single tab to restore");
+
+  info("Call purgeDataForPrivateWindow");
+  ss.purgeDataForPrivateWindow(win);
+
+  is(ss.getClosedTabCountForWindow(win), 0, "there is no tab to restore");
+
+  // Cleanup
+  await BrowserTestUtils.closeWindow(win);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_purge_domaindata.js b/src/zen/tests/mochitests/sessionstore/browser_purge_domaindata.js
new file mode 100644
index 000000000..662db006d
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_purge_domaindata.js
@@ -0,0 +1,196 @@
+/* Any copyright is dedicated to the Public Domain.
+   https://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const ORIG_STATE = SessionStore.getBrowserState();
+const SITE = "https://example.com/";
+
+registerCleanupFunction(async () => {
+  await SessionStoreTestUtils.promiseBrowserState(ORIG_STATE);
+});
+
+// Test for closed tabs and tab groups in an open window
+add_task(async function test_closedTabsPurgeDomainData() {
+  let win = await promiseNewWindowLoaded();
+
+  let tabs = [
+    BrowserTestUtils.addTab(win.gBrowser, "about:mozilla"),
+    BrowserTestUtils.addTab(win.gBrowser, "about:robots"),
+    BrowserTestUtils.addTab(win.gBrowser, SITE),
+  ];
+  let tabsInGroup = [
+    BrowserTestUtils.addTab(win.gBrowser, "about:robots"),
+    BrowserTestUtils.addTab(win.gBrowser, SITE),
+  ];
+
+  let allTabs = [...tabs, ...tabsInGroup];
+  await Promise.all(
+    allTabs.map(async t => {
+      await promiseBrowserLoaded(t.linkedBrowser);
+    })
+  );
+  let tabGroup = win.gBrowser.addTabGroup(tabsInGroup);
+
+  await TabStateFlusher.flushWindow(win);
+
+  tabs.forEach(t => {
+    win.gBrowser.removeTab(t);
+  });
+  let removePromise = BrowserTestUtils.waitForEvent(
+    tabGroup,
+    "TabGroupRemoved"
+  );
+  win.gBrowser.removeTabGroup(tabGroup);
+  await removePromise;
+
+  let state = ss.getWindowState(win).windows[0];
+  Assert.equal(
+    state._closedTabs.length,
+    3,
+    "Closed tabs state has all closed tabs"
+  );
+  Assert.equal(
+    state.closedGroups[0].tabs.length,
+    2,
+    "Closed tab group state has all closed tabs"
+  );
+
+  // Purge session history for domain
+  Services.obs.notifyObservers(
+    null,
+    "browser:purge-session-history-for-domain",
+    "example.com"
+  );
+
+  state = ss.getWindowState(win).windows[0];
+  Assert.equal(state._closedTabs.length, 2, "Closed tab list has one less tab");
+  Assert.equal(
+    state.closedGroups[0].tabs.length,
+    1,
+    "Closed tab group tab list has one less tab"
+  );
+
+  state._closedTabs.forEach((tab, index) => {
+    Assert.notEqual(
+      tab.state.entries[0].url,
+      SITE,
+      `Closed tab ${index} does not contain purged site`
+    );
+  });
+  state.closedGroups[0].tabs.forEach((tab, index) => {
+    Assert.notEqual(
+      tab.state.entries[0].url,
+      SITE,
+      `Closed tab ${index} in group does not contain purged site`
+    );
+  });
+
+  await BrowserTestUtils.closeWindow(win);
+});
+
+add_task(async function test_closedTabsInClosedWindowsPurgeDomainData() {
+  let win = await promiseNewWindowLoaded();
+
+  let openTabs = [
+    BrowserTestUtils.addTab(win.gBrowser, "about:mozilla"),
+    BrowserTestUtils.addTab(win.gBrowser, "about:robots"),
+    BrowserTestUtils.addTab(win.gBrowser, SITE),
+  ];
+  let tabsInOpenGroup = [
+    BrowserTestUtils.addTab(win.gBrowser, "about:robots"),
+    BrowserTestUtils.addTab(win.gBrowser, SITE),
+  ];
+  let closedTabs = [
+    BrowserTestUtils.addTab(win.gBrowser, "about:mozilla"),
+    BrowserTestUtils.addTab(win.gBrowser, "about:robots"),
+    BrowserTestUtils.addTab(win.gBrowser, SITE),
+  ];
+  let tabsInClosedGroup = [
+    BrowserTestUtils.addTab(win.gBrowser, "about:robots"),
+    BrowserTestUtils.addTab(win.gBrowser, SITE),
+  ];
+
+  let allTabs = [
+    ...openTabs,
+    ...tabsInOpenGroup,
+    ...closedTabs,
+    ...tabsInClosedGroup,
+  ];
+  await Promise.all(
+    allTabs.map(async t => {
+      await promiseBrowserLoaded(t.linkedBrowser);
+    })
+  );
+  win.gBrowser.addTabGroup(tabsInOpenGroup);
+  let closedTabGroup = win.gBrowser.addTabGroup(tabsInClosedGroup);
+
+  await TabStateFlusher.flushWindow(win);
+
+  closedTabs.forEach(t => {
+    win.gBrowser.removeTab(t);
+  });
+  let removePromise = BrowserTestUtils.waitForEvent(
+    closedTabGroup,
+    "TabGroupRemoved"
+  );
+  win.gBrowser.removeTabGroup(closedTabGroup);
+  await removePromise;
+
+  await BrowserTestUtils.closeWindow(win);
+
+  let state = ss.getClosedWindowData()[0];
+  Assert.equal(state.tabs.length, 6, "Open tabs state has all tabs");
+  Assert.equal(
+    state._closedTabs.length,
+    3,
+    "Closed tabs state has all closed tabs"
+  );
+  Assert.equal(
+    state.closedGroups[0].tabs.length,
+    2,
+    "Closed tab group state has all closed tabs"
+  );
+
+  // Purge session history for domain
+  Services.obs.notifyObservers(
+    null,
+    "browser:purge-session-history-for-domain",
+    "example.com"
+  );
+
+  state = ss.getClosedWindowData()[0];
+  Assert.equal(
+    state.tabs.length,
+    4,
+    "Open tabs state loses ungrouped and grouped site tab"
+  );
+  Assert.equal(state._closedTabs.length, 2, "Closed tabs state loses a tab");
+  Assert.equal(
+    state.closedGroups[0].tabs.length,
+    1,
+    "Closed tab group state loses a tab"
+  );
+
+  state.tabs.forEach((tab, index) => {
+    Assert.notEqual(
+      tab.entries[0].url,
+      SITE,
+      `Open tab ${index} does not contain purged site`
+    );
+  });
+  state._closedTabs.forEach((tab, index) => {
+    Assert.notEqual(
+      tab.state.entries[0].url,
+      SITE,
+      `Closed tab ${index} does not contain purged site`
+    );
+  });
+  state.closedGroups[0].tabs.forEach((tab, index) => {
+    Assert.notEqual(
+      tab.state.entries[0].url,
+      SITE,
+      `Closed tab ${index} in group does not contain purged site`
+    );
+  });
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_purge_shistory.js b/src/zen/tests/mochitests/sessionstore/browser_purge_shistory.js
new file mode 100644
index 000000000..617df0455
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_purge_shistory.js
@@ -0,0 +1,65 @@
+"use strict";
+
+/**
+ * This test checks that pending tabs are treated like fully loaded tabs when
+ * purging session history. Just like for fully loaded tabs we want to remove
+ * every but the current shistory entry.
+ */
+
+const TAB_STATE = {
+  entries: [
+    { url: "about:mozilla", triggeringPrincipal_base64 },
+    { url: "about:robots", triggeringPrincipal_base64 },
+  ],
+  index: 1,
+};
+
+function checkTabContents(browser) {
+  return SpecialPowers.spawn(browser, [], async function () {
+    let webNavigation = docShell.QueryInterface(Ci.nsIWebNavigation);
+    let history = webNavigation.sessionHistory;
+    Assert.ok(
+      history &&
+        history.count == 1 &&
+        content.document.documentURI == "about:mozilla",
+      "expected tab contents found"
+    );
+  });
+}
+
+add_task(async function () {
+  // Create a new tab.
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:blank");
+  let browser = tab.linkedBrowser;
+  await BrowserTestUtils.browserLoaded(browser, { wantLoad: "about:blank" });
+  await promiseTabState(tab, TAB_STATE);
+
+  // Create another new tab.
+  let tab2 = BrowserTestUtils.addTab(gBrowser, "about:blank");
+  let browser2 = tab2.linkedBrowser;
+  await BrowserTestUtils.browserLoaded(browser2, { wantLoad: "about:blank" });
+
+  // The tab shouldn't be restored right away.
+  Services.prefs.setBoolPref("browser.sessionstore.restore_on_demand", true);
+
+  // Prepare the tab state.
+  let promise = promiseTabRestoring(tab2);
+  ss.setTabState(tab2, JSON.stringify(TAB_STATE));
+  ok(tab2.hasAttribute("pending"), "tab is pending");
+  await promise;
+
+  // Purge session history.
+  Services.obs.notifyObservers(null, "browser:purge-session-history");
+  await checkTabContents(browser);
+  ok(tab2.hasAttribute("pending"), "tab is still pending");
+
+  // Kick off tab restoration.
+  gBrowser.selectedTab = tab2;
+  await promiseTabRestored(tab2);
+  await checkTabContents(browser2);
+  ok(!tab2.hasAttribute("pending"), "tab is not pending anymore");
+
+  // Cleanup.
+  gBrowser.removeTab(tab2);
+  gBrowser.removeTab(tab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_remoteness_flip_on_restore.js b/src/zen/tests/mochitests/sessionstore/browser_remoteness_flip_on_restore.js
new file mode 100644
index 000000000..fb799fc92
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_remoteness_flip_on_restore.js
@@ -0,0 +1,311 @@
+"use strict";
+
+/**
+ * This set of tests checks that the remoteness is properly
+ * set for each browser in a window when that window has
+ * session state loaded into it.
+ */
+
+/**
+ * Takes a SessionStore window state object for a single
+ * window, sets the selected tab for it, and then returns
+ * the object to be passed to SessionStore.setWindowState.
+ *
+ * @param state (object)
+ *        The state to prepare to be sent to a window. This is
+ *        state should just be for a single window.
+ * @param selected (int)
+ *        The 1-based index of the selected tab. Note that
+ *        If this is 0, then the selected tab will not change
+ *        from what's already selected in the window that we're
+ *        sending state to.
+ * @returns (object)
+ *        The JSON encoded string to call
+ *        SessionStore.setWindowState with.
+ */
+function prepareState(state, selected) {
+  // We'll create a copy so that we don't accidentally
+  // modify the caller's selected property.
+  let copy = {};
+  Object.assign(copy, state);
+  copy.selected = selected;
+
+  return {
+    windows: [copy],
+  };
+}
+
+const SIMPLE_STATE = {
+  tabs: [
+    {
+      entries: [
+        {
+          url: "http://example.com/",
+          triggeringPrincipal_base64,
+          title: "title",
+        },
+      ],
+    },
+    {
+      entries: [
+        {
+          url: "http://example.com/",
+          triggeringPrincipal_base64,
+          title: "title",
+        },
+      ],
+    },
+    {
+      entries: [
+        {
+          url: "http://example.com/",
+          triggeringPrincipal_base64,
+          title: "title",
+        },
+      ],
+    },
+  ],
+  title: "",
+  _closedTabs: [],
+};
+
+const PINNED_STATE = {
+  tabs: [
+    {
+      entries: [
+        {
+          url: "http://example.com/",
+          triggeringPrincipal_base64,
+          title: "title",
+        },
+      ],
+      pinned: true,
+    },
+    {
+      entries: [
+        {
+          url: "http://example.com/",
+          triggeringPrincipal_base64,
+          title: "title",
+        },
+      ],
+      pinned: true,
+    },
+    {
+      entries: [
+        {
+          url: "http://example.com/",
+          triggeringPrincipal_base64,
+          title: "title",
+        },
+      ],
+    },
+  ],
+  title: "",
+  _closedTabs: [],
+};
+
+/**
+ * This is where most of the action is happening. This function takes
+ * an Array of "test scenario" Objects and runs them. For each scenario, a
+ * window is opened, put into some state, and then a new state is
+ * loaded into that window. We then check to make sure that the
+ * right things have happened in that window wrt remoteness flips.
+ *
+ * The schema for a testing scenario Object is as follows:
+ *
+ * initialRemoteness:
+ *   an Array that represents the starting window. Each bool
+ *   in the Array represents the window tabs in order. A "true"
+ *   indicates that that tab should be remote. "false" if the tab
+ *   should be non-remote.
+ *
+ * initialSelectedTab:
+ *   The 1-based index of the tab that we want to select for the
+ *   restored window. This is 1-based to avoid confusion with the
+ *   selectedTab property described down below, though you probably
+ *   want to set this to be greater than 0, since the initial window
+ *   needs to have a defined initial selected tab. Because of this,
+ *   the test will throw if initialSelectedTab is 0.
+ *
+ * stateToRestore:
+ *   A JS Object for the state to send down to the window.
+ *
+ * selectedTab:
+ *   The 1-based index of the tab that we want to select for the
+ *   restored window. Leave this at 0 if you don't want to change
+ *   the selection from the initial window state.
+ *
+ * expectedRemoteness:
+ *   an Array that represents the window that we end up with after
+ *   restoring state. Each bool in the Array represents the window
+ *   tabs in order. A "true" indicates that the tab be remote, and
+ *   a "false" indicates that the tab should be "non-remote". We
+ *   need this Array in order to test pinned tabs which will also
+ *   be loaded by default, and therefore should end up remote.
+ *
+ */
+async function runScenarios(scenarios) {
+  for (let [scenarioIndex, scenario] of scenarios.entries()) {
+    info("Running scenario " + scenarioIndex);
+    Assert.greater(
+      scenario.initialSelectedTab,
+      0,
+      "You must define an initially selected tab"
+    );
+
+    // First, we need to create the initial conditions, so we
+    // open a new window to put into our starting state...
+    let win = await BrowserTestUtils.openNewBrowserWindow();
+    let tabbrowser = win.gBrowser;
+    Assert.ok(
+      tabbrowser.selectedBrowser.isRemoteBrowser,
+      "The initial browser should be remote."
+    );
+    // Now put the window into the expected initial state.
+    for (let i = 0; i < scenario.initialRemoteness.length; ++i) {
+      let tab;
+      if (i > 0) {
+        // The window starts with one tab, so we need to create
+        // any of the additional ones required by this test.
+        info("Opening a new tab");
+        tab = await BrowserTestUtils.openNewForegroundTab(tabbrowser);
+      } else {
+        info("Using the selected tab");
+        tab = tabbrowser.selectedTab;
+      }
+      let browser = tab.linkedBrowser;
+      let remotenessState = scenario.initialRemoteness[i]
+        ? E10SUtils.DEFAULT_REMOTE_TYPE
+        : E10SUtils.NOT_REMOTE;
+      tabbrowser.updateBrowserRemoteness(browser, {
+        remoteType: remotenessState,
+      });
+    }
+
+    // And select the requested tab.
+    let tabToSelect = tabbrowser.tabs[scenario.initialSelectedTab - 1];
+    if (tabbrowser.selectedTab != tabToSelect) {
+      await BrowserTestUtils.switchTab(tabbrowser, tabToSelect);
+    }
+
+    // Okay, time to test!
+    let state = prepareState(scenario.stateToRestore, scenario.selectedTab);
+
+    await setWindowState(win, state, true);
+
+    for (let i = 0; i < scenario.expectedRemoteness.length; ++i) {
+      let expectedRemoteness = scenario.expectedRemoteness[i];
+      let tab = tabbrowser.tabs[i];
+
+      Assert.equal(
+        tab.linkedBrowser.isRemoteBrowser,
+        expectedRemoteness,
+        "Should have gotten the expected remoteness " +
+          `for the tab at index ${i}`
+      );
+    }
+
+    await BrowserTestUtils.closeWindow(win);
+  }
+}
+
+/**
+ * Tests that if we restore state to browser windows with
+ * a variety of initial remoteness states. For this particular
+ * set of tests, we assume that tabs are restoring on demand.
+ */
+add_task(async function () {
+  // This test opens and closes windows, which might bog down
+  // a debug build long enough to time out the test, so we
+  // extend the tolerance on timeouts.
+  requestLongerTimeout(5);
+
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.sessionstore.restore_on_demand", true]],
+  });
+
+  const TEST_SCENARIOS = [
+    // Only one tab in the new window, and it's remote. This
+    // is the common case, since this is how restoration occurs
+    // when the restored window is being opened.
+    {
+      initialRemoteness: [true],
+      initialSelectedTab: 1,
+      stateToRestore: SIMPLE_STATE,
+      selectedTab: 3,
+      // All tabs should now be remote.
+      expectedRemoteness: [true, true, true],
+    },
+
+    // A single remote tab, and this is the one that's going
+    // to be selected once state is restored.
+    {
+      initialRemoteness: [true],
+      initialSelectedTab: 1,
+      stateToRestore: SIMPLE_STATE,
+      selectedTab: 1,
+      // All tabs should now be remote.
+      expectedRemoteness: [true, true, true],
+    },
+
+    // A single remote tab which starts selected. We set the
+    // selectedTab to 0 which is equivalent to "don't change
+    // the tab selection in the window".
+    {
+      initialRemoteness: [true],
+      initialSelectedTab: 1,
+      stateToRestore: SIMPLE_STATE,
+      selectedTab: 0,
+      // All tabs should now be remote.
+      expectedRemoteness: [true, true, true],
+    },
+
+    // An initially remote tab, but we're going to load
+    // some pinned tabs now, and the pinned tabs should load
+    // right away.
+    {
+      initialRemoteness: [true],
+      initialSelectedTab: 1,
+      stateToRestore: PINNED_STATE,
+      selectedTab: 3,
+      // Both pinned tabs and the selected tabs should all
+      // end up being remote.
+      expectedRemoteness: [true, true, true],
+    },
+
+    // A single non-remote tab.
+    {
+      initialRemoteness: [false],
+      initialSelectedTab: 1,
+      stateToRestore: SIMPLE_STATE,
+      selectedTab: 2,
+      // All tabs should now be remote.
+      expectedRemoteness: [true, true, true],
+    },
+
+    // A mixture of remote and non-remote tabs.
+    {
+      initialRemoteness: [true, false, true],
+      initialSelectedTab: 1,
+      stateToRestore: SIMPLE_STATE,
+      selectedTab: 3,
+      // All tabs should now be remote.
+      expectedRemoteness: [true, true, true],
+    },
+
+    // An initially non-remote tab, but we're going to load
+    // some pinned tabs now, and the pinned tabs should load
+    // right away.
+    {
+      initialRemoteness: [false],
+      initialSelectedTab: 1,
+      stateToRestore: PINNED_STATE,
+      selectedTab: 3,
+      // All tabs should now be remote.
+      expectedRemoteness: [true, true, true],
+    },
+  ];
+
+  await runScenarios(TEST_SCENARIOS);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_reopen_all_windows.js b/src/zen/tests/mochitests/sessionstore/browser_reopen_all_windows.js
new file mode 100644
index 000000000..6857d2af7
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_reopen_all_windows.js
@@ -0,0 +1,154 @@
+"use strict";
+
+const PATH = "browser/browser/components/sessionstore/test/empty.html";
+var URLS_WIN1 = [
+  "https://example.com/" + PATH,
+  "https://example.org/" + PATH,
+  "http://test1.mochi.test:8888/" + PATH,
+  "http://test1.example.com/" + PATH,
+];
+var EXPECTED_URLS_WIN1 = ["about:blank", ...URLS_WIN1];
+
+var URLS_WIN2 = [
+  "http://sub1.test1.mochi.test:8888/" + PATH,
+  "http://sub2.xn--lt-uia.mochi.test:8888/" + PATH,
+  "http://test2.mochi.test:8888/" + PATH,
+  "http://sub1.test2.example.org/" + PATH,
+  "http://sub2.test1.example.org/" + PATH,
+  "http://test2.example.com/" + PATH,
+];
+var EXPECTED_URLS_WIN2 = ["about:blank", ...URLS_WIN2];
+
+requestLongerTimeout(4);
+
+function allTabsRestored(win, expectedUrls) {
+  return new Promise(resolve => {
+    let tabsRestored = 0;
+    function handler(event) {
+      let spec = event.target.linkedBrowser.currentURI.spec;
+      if (expectedUrls.includes(spec)) {
+        tabsRestored++;
+      }
+      info(`Got SSTabRestored for ${spec}, tabsRestored=${tabsRestored}`);
+      if (tabsRestored === expectedUrls.length) {
+        win.gBrowser.tabContainer.removeEventListener(
+          "SSTabRestored",
+          handler,
+          true
+        );
+        resolve();
+      }
+    }
+    win.gBrowser.tabContainer.addEventListener("SSTabRestored", handler, true);
+  });
+}
+
+async function windowAndTabsRestored(win, expectedUrls) {
+  await TestUtils.topicObserved(
+    "browser-window-before-show",
+    subject => subject === win
+  );
+  return allTabsRestored(win, expectedUrls);
+}
+
+add_task(async () => {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      // Set the pref to true so we know exactly how many tabs should be restoring at
+      // any given time. This guarantees that a finishing load won't start another.
+      ["browser.sessionstore.restore_on_demand", false],
+    ],
+  });
+
+  forgetClosedWindows();
+  is(SessionStore.getClosedWindowCount(), 0, "starting with no closed windows");
+
+  // Open window 1, with different tabs
+  let win1 = await BrowserTestUtils.openNewBrowserWindow();
+  for (let url of URLS_WIN1) {
+    await BrowserTestUtils.openNewForegroundTab(win1.gBrowser, url);
+  }
+
+  // Open window 2, with different tabs
+  let win2 = await BrowserTestUtils.openNewBrowserWindow();
+  for (let url of URLS_WIN2) {
+    await BrowserTestUtils.openNewForegroundTab(win2.gBrowser, url);
+  }
+
+  await TabStateFlusher.flushWindow(win1);
+  await TabStateFlusher.flushWindow(win2);
+
+  // Close both windows
+  await BrowserTestUtils.closeWindow(win1);
+  await BrowserTestUtils.closeWindow(win2);
+  await forceSaveState();
+
+  // Verify both windows were accounted for by session store
+  is(
+    ss.getClosedWindowCount(),
+    2,
+    "The closed windows was added to Recently Closed Windows"
+  );
+
+  // We previously used to manually navigate the Library menu to click the
+  // "Reopen all Windows" button, but that reopens all windows at once without
+  // returning a reference to each window. Since we need to attach listeners to
+  // these windows *before* they start restoring tabs, we now manually call
+  // undoCloseWindow() here, which has the same effect, but also gives us the
+  // window references.
+  info("Reopening windows");
+  let restoredWindows = [];
+  while (SessionStore.getClosedWindowCount() > 0) {
+    restoredWindows.unshift(SessionWindowUI.undoCloseWindow());
+  }
+  is(restoredWindows.length, 2, "Reopened correct number of windows");
+
+  let win1Restored = windowAndTabsRestored(
+    restoredWindows[0],
+    EXPECTED_URLS_WIN1
+  );
+  let win2Restored = windowAndTabsRestored(
+    restoredWindows[1],
+    EXPECTED_URLS_WIN2
+  );
+
+  info("About to wait for tabs to be restored");
+  await Promise.all([win1Restored, win2Restored]);
+
+  const sessionRestoreInitialized =
+    Glean.sessionRestore.startupTimeline.sessionRestoreInitialized.testGetValue();
+  Assert.greater(
+    sessionRestoreInitialized,
+    0,
+    "Session store initialize recorded."
+  );
+
+  is(
+    restoredWindows[0].gBrowser.tabs.length,
+    EXPECTED_URLS_WIN1.length,
+    "All tabs restored"
+  );
+  is(
+    restoredWindows[1].gBrowser.tabs.length,
+    EXPECTED_URLS_WIN2.length,
+    "All tabs restored"
+  );
+
+  // Verify that tabs opened as expected
+  Assert.deepEqual(
+    restoredWindows[0].gBrowser.tabs.map(
+      tab => tab.linkedBrowser.currentURI.spec
+    ),
+    EXPECTED_URLS_WIN1
+  );
+  Assert.deepEqual(
+    restoredWindows[1].gBrowser.tabs.map(
+      tab => tab.linkedBrowser.currentURI.spec
+    ),
+    EXPECTED_URLS_WIN2
+  );
+
+  info("About to close windows");
+  await BrowserTestUtils.closeWindow(restoredWindows[0]);
+  await BrowserTestUtils.closeWindow(restoredWindows[1]);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_replace_load.js b/src/zen/tests/mochitests/sessionstore/browser_replace_load.js
new file mode 100644
index 000000000..21bec044a
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_replace_load.js
@@ -0,0 +1,56 @@
+"use strict";
+
+const STATE = {
+  entries: [{ url: "about:robots" }, { url: "about:mozilla" }],
+  selected: 2,
+};
+
+/**
+ * Bug 1100223. Calling browser.loadURI() while a tab is loading causes
+ * sessionstore to override the desired target URL. This test ensures that
+ * calling loadURI() on a pending tab causes the tab to no longer be marked
+ * as pending and correctly finish the instructed load while keeping the
+ * restored history around.
+ */
+add_task(async function () {
+  await testSwitchToTab("about:mozilla#fooobar", {
+    ignoreFragment: "whenComparingAndReplace",
+  });
+  await testSwitchToTab("about:mozilla?foo=bar", { replaceQueryString: true });
+});
+
+var testSwitchToTab = async function (url, options) {
+  // Create a background tab.
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:blank");
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  // The tab shouldn't be restored right away.
+  Services.prefs.setBoolPref("browser.sessionstore.restore_on_demand", true);
+
+  // Prepare the tab state.
+  let promise = promiseTabRestoring(tab);
+  ss.setTabState(tab, JSON.stringify(STATE));
+  ok(tab.hasAttribute("pending"), "tab is pending");
+  await promise;
+
+  options.triggeringPrincipal =
+    Services.scriptSecurityManager.getSystemPrincipal();
+
+  // Switch-to-tab with a similar URI.
+  switchToTabHavingURI(url, false, options);
+
+  // Tab should now restore
+  await promiseTabRestored(tab);
+  is(browser.currentURI.spec, url, "correct URL loaded");
+
+  // Check that we didn't lose any history entries.
+  await SpecialPowers.spawn(browser, [], async function () {
+    let webNavigation = docShell.QueryInterface(Ci.nsIWebNavigation);
+    let history = webNavigation.sessionHistory;
+    Assert.equal(history && history.count, 3, "three history entries");
+  });
+
+  // Cleanup.
+  gBrowser.removeTab(tab);
+};
diff --git a/src/zen/tests/mochitests/sessionstore/browser_restoreLastActionCorrectOrder.js b/src/zen/tests/mochitests/sessionstore/browser_restoreLastActionCorrectOrder.js
new file mode 100644
index 000000000..bd660a4bd
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_restoreLastActionCorrectOrder.js
@@ -0,0 +1,101 @@
+"use strict";
+
+const { _LastSession, _lastClosedActions } = ChromeUtils.importESModule(
+  "resource:///modules/sessionstore/SessionStore.sys.mjs"
+);
+
+/**
+ * Tests that the _lastClosedAction list is truncated correctly
+ * by removing oldest actions in SessionStore._addClosedAction
+ */
+add_task(async function test_undo_last_action_correct_order() {
+  SpecialPowers.pushPrefEnv({
+    set: [
+      ["browser.sessionstore.max_tabs_undo", 3],
+      ["browser.sessionstore.max_windows_undo", 1],
+    ],
+  });
+
+  gBrowser.removeAllTabsBut(gBrowser.tabs[0]);
+  await TabStateFlusher.flushWindow(window);
+
+  forgetClosedTabs(window);
+
+  const state = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              {
+                title: "example.org",
+                url: "https://example.org/",
+                triggeringPrincipal_base64,
+              },
+            ],
+          },
+          {
+            entries: [
+              {
+                title: "example.com",
+                url: "https://example.com/",
+                triggeringPrincipal_base64,
+              },
+            ],
+          },
+          {
+            entries: [
+              {
+                title: "mozilla",
+                url: "https://www.mozilla.org/",
+                triggeringPrincipal_base64,
+              },
+            ],
+          },
+          {
+            entries: [
+              {
+                title: "mozilla privacy policy",
+                url: "https://www.mozilla.org/privacy",
+                triggeringPrincipal_base64,
+              },
+            ],
+          },
+        ],
+        selected: 3,
+      },
+    ],
+  };
+
+  _LastSession.setState(state);
+  SessionStore.resetLastClosedActions();
+
+  let sessionRestored = promiseSessionStoreLoads(4 /* total restored tabs */);
+  SessionWindowUI.restoreLastClosedTabOrWindowOrSession(window);
+  await sessionRestored;
+
+  Assert.equal(window.gBrowser.tabs.length, 4, "4 tabs have been restored");
+
+  BrowserTestUtils.removeTab(window.gBrowser.tabs[3]);
+  BrowserTestUtils.removeTab(window.gBrowser.tabs[2]);
+  Assert.equal(window.gBrowser.tabs.length, 2, "Window has one open tab");
+
+  // open and close a window
+  let win2 = await BrowserTestUtils.openNewBrowserWindow();
+  Assert.equal(win2.gBrowser.tabs.length, 1, "Second window has one open tab");
+  BrowserTestUtils.startLoadingURIString(
+    win2.gBrowser.selectedBrowser,
+    "https://example.com/"
+  );
+  await BrowserTestUtils.browserLoaded(win2.gBrowser.selectedBrowser);
+  await BrowserTestUtils.closeWindow(win2);
+
+  // close one tab and reopen it
+  BrowserTestUtils.removeTab(window.gBrowser.tabs[1]);
+  Assert.equal(window.gBrowser.tabs.length, 1, "Window has one open tabs");
+  SessionWindowUI.restoreLastClosedTabOrWindowOrSession(window);
+  Assert.equal(window.gBrowser.tabs.length, 2, "Window now has two open tabs");
+
+  await SpecialPowers.popPrefEnv();
+  gBrowser.removeAllTabsBut(gBrowser.tabs[0]);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_restoreLastClosedTabOrWindowOrSession.js b/src/zen/tests/mochitests/sessionstore/browser_restoreLastClosedTabOrWindowOrSession.js
new file mode 100644
index 000000000..f7e2f38e4
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_restoreLastClosedTabOrWindowOrSession.js
@@ -0,0 +1,352 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { _LastSession, _lastClosedActions } = ChromeUtils.importESModule(
+  "resource:///modules/sessionstore/SessionStore.sys.mjs"
+);
+
+async function testLastClosedActionsEntries() {
+  SessionStore.resetLastClosedActions();
+
+  let win2 = await BrowserTestUtils.openNewBrowserWindow();
+  BrowserTestUtils.startLoadingURIString(
+    win2.gBrowser.selectedBrowser,
+    "https://www.mozilla.org/"
+  );
+
+  await BrowserTestUtils.browserLoaded(win2.gBrowser.selectedBrowser);
+  await openAndCloseTab(win2, "https://example.org/");
+
+  Assert.equal(
+    SessionStore.lastClosedActions.length,
+    1,
+    `1 closed action has been recorded`
+  );
+
+  await BrowserTestUtils.closeWindow(win2);
+
+  Assert.equal(
+    SessionStore.lastClosedActions.length,
+    2,
+    `2 closed actions have been recorded`
+  );
+}
+
+add_setup(() => {
+  forgetClosedTabs(window);
+  registerCleanupFunction(() => {
+    forgetClosedTabs(window);
+  });
+
+  // needed for verify tests so that forgetting tabs isn't recorded
+  SessionStore.resetLastClosedActions();
+});
+
+/**
+ * Tests that if the user invokes restoreLastClosedTabOrWindowOrSession it will
+ * result in either the last session will be restored, if possible, the last
+ * tab (or multiple selected tabs) that was closed is reopened, or the last
+ * window that is closed is reopened.
+ */
+add_task(async function test_undo_last_action() {
+  const state = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              {
+                title: "example.org",
+                url: "https://example.org/",
+                triggeringPrincipal_base64,
+              },
+            ],
+          },
+          {
+            entries: [
+              {
+                title: "example.com",
+                url: "https://example.com/",
+                triggeringPrincipal_base64,
+              },
+            ],
+          },
+          {
+            entries: [
+              {
+                title: "mozilla",
+                url: "https://www.mozilla.org/",
+                triggeringPrincipal_base64,
+              },
+            ],
+          },
+        ],
+        selected: 3,
+      },
+    ],
+  };
+
+  _LastSession.setState(state);
+
+  let sessionRestored = promiseSessionStoreLoads(3 /* total restored tabs */);
+  SessionWindowUI.restoreLastClosedTabOrWindowOrSession(window);
+  await sessionRestored;
+  Assert.equal(
+    window.gBrowser.tabs.length,
+    3,
+    "Window has three tabs after session is restored"
+  );
+
+  // open and close a window, then reopen it
+  let win2 = await BrowserTestUtils.openNewBrowserWindow();
+  Assert.equal(win2.gBrowser.tabs.length, 1, "Second window has one open tab");
+  BrowserTestUtils.startLoadingURIString(
+    win2.gBrowser.selectedBrowser,
+    "https://example.com/"
+  );
+  await BrowserTestUtils.browserLoaded(win2.gBrowser.selectedBrowser);
+  await BrowserTestUtils.closeWindow(win2);
+  let restoredWinPromise = BrowserTestUtils.waitForNewWindow({
+    url: "https://example.com/",
+  });
+  SessionWindowUI.restoreLastClosedTabOrWindowOrSession(window);
+  let restoredWin = await restoredWinPromise;
+  Assert.equal(
+    restoredWin.gBrowser.tabs.length,
+    1,
+    "First tab in the second window has been reopened"
+  );
+  await BrowserTestUtils.closeWindow(restoredWin);
+  SessionStore.forgetClosedWindow(restoredWin.index);
+  SessionWindowUI.restoreLastClosedTabOrWindowOrSession(window);
+
+  // close one tab and reopen it
+  BrowserTestUtils.removeTab(window.gBrowser.tabs[2]);
+  Assert.equal(window.gBrowser.tabs.length, 2, "Window has two open tabs");
+  SessionWindowUI.restoreLastClosedTabOrWindowOrSession(window);
+  Assert.equal(
+    window.gBrowser.tabs.length,
+    3,
+    "Window now has three open tabs"
+  );
+
+  // select 2 tabs and close both via the 'close 2 tabs' context menu option
+  let tab2 = window.gBrowser.tabs[1];
+  let tab3 = window.gBrowser.tabs[2];
+  await triggerClickOn(tab2, { ctrlKey: true });
+  Assert.equal(tab2.multiselected, true);
+  Assert.equal(tab3.multiselected, true);
+
+  let menu = await openTabMenuFor(tab3);
+  let menuItemCloseTab = document.getElementById("context_closeTab");
+  let tab2Closing = BrowserTestUtils.waitForTabClosing(tab2);
+  let tab3Closing = BrowserTestUtils.waitForTabClosing(tab3);
+  menu.activateItem(menuItemCloseTab);
+  await tab2Closing;
+  await tab3Closing;
+  Assert.equal(window.gBrowser.tabs[0].selected, true);
+  await TestUtils.waitForCondition(() => window.gBrowser.tabs.length == 1);
+  Assert.equal(
+    window.gBrowser.tabs.length,
+    1,
+    "Window now has one open tab after closing two multi-selected tabs"
+  );
+
+  // ensure both tabs are reopened with a single click
+  SessionWindowUI.restoreLastClosedTabOrWindowOrSession(window);
+  Assert.equal(
+    window.gBrowser.tabs.length,
+    3,
+    "Window now has three open tabs after reopening closed tabs"
+  );
+
+  // close one tab and forget it - it should not be reopened
+  BrowserTestUtils.removeTab(window.gBrowser.tabs[2]);
+  Assert.equal(window.gBrowser.tabs.length, 2, "Window has two open tabs");
+  SessionStore.forgetClosedTab(window, 0);
+  SessionWindowUI.restoreLastClosedTabOrWindowOrSession(window);
+  Assert.equal(
+    window.gBrowser.tabs.length,
+    2,
+    "Window still has two open tabs"
+  );
+
+  // create a tab group, delete it, and re-open it
+  const groupedTab = BrowserTestUtils.addTab(
+    window.gBrowser,
+    "https://example.com"
+  );
+  await BrowserTestUtils.browserLoaded(groupedTab.linkedBrowser);
+  const tabGroup = window.gBrowser.addTabGroup([groupedTab]);
+  Assert.equal(
+    window.gBrowser.tabs.length,
+    3,
+    "Window has three tabs after creating tab group"
+  );
+
+  await TabStateFlusher.flushWindow(window);
+  let removePromise = BrowserTestUtils.waitForEvent(
+    tabGroup,
+    "TabGroupRemoved"
+  );
+  window.gBrowser.removeTabGroup(tabGroup);
+  await removePromise;
+
+  SessionWindowUI.restoreLastClosedTabOrWindowOrSession(window);
+  Assert.equal(
+    window.gBrowser.tabs.length,
+    3,
+    "Window has three tabs after restoring tab group"
+  );
+  Assert.equal(
+    window.gBrowser.tabGroups.length,
+    1,
+    "Tab group exists on the tab strip after restore"
+  );
+
+  // Save and close the tab group, and then re-open it
+  const groupedTabToSave = BrowserTestUtils.addTab(
+    window.gBrowser,
+    "https://example.com"
+  );
+  await BrowserTestUtils.browserLoaded(groupedTabToSave.linkedBrowser);
+  const tabGroupToSave = window.gBrowser.addTabGroup([groupedTabToSave]);
+  Assert.equal(
+    window.gBrowser.tabs.length,
+    4,
+    "Window has four tabs after creating tab group"
+  );
+
+  await TabStateFlusher.flushWindow(window);
+  tabGroupToSave.save();
+  removePromise = BrowserTestUtils.waitForEvent(
+    tabGroupToSave,
+    "TabGroupRemoved"
+  );
+  window.gBrowser.removeTabGroup(tabGroupToSave);
+  await removePromise;
+
+  await TabStateFlusher.flushWindow(window);
+  SessionWindowUI.restoreLastClosedTabOrWindowOrSession(window);
+  Assert.equal(
+    window.gBrowser.tabs.length,
+    4,
+    "Window has four tabs after restoring tab group"
+  );
+  Assert.equal(
+    window.gBrowser.tabGroups.length,
+    2,
+    "Tab group exists on the tab strip after restore"
+  );
+
+  gBrowser.removeAllTabsBut(gBrowser.tabs[0], { animate: false });
+});
+
+add_task(async function test_forget_closed_window() {
+  await testLastClosedActionsEntries();
+  SessionStore.forgetClosedWindow();
+
+  // both the forgotten window and its closed tab has been removed from the list
+  Assert.ok(
+    !SessionStore.lastClosedActions.length,
+    `0 closed actions have been recorded`
+  );
+});
+
+add_task(async function test_user_clears_history() {
+  await testLastClosedActionsEntries();
+  Services.obs.notifyObservers(null, "browser:purge-session-history");
+
+  // both the forgotten window and its closed tab has been removed from the list
+  Assert.ok(
+    !SessionStore.lastClosedActions.length,
+    `0 closed actions have been recorded`
+  );
+});
+
+/**
+ * It the browser has restarted and the closed actions list is empty, we
+ * should fallback to re-opening the last closed tab if one exists.
+ */
+add_task(async function test_reopen_last_tab_if_no_closed_actions() {
+  await BrowserTestUtils.withNewTab(
+    {
+      gBrowser,
+      url: "about:blank",
+    },
+    async () => {
+      const TEST_URL = "https://example.com/";
+      let tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, TEST_URL);
+      let update = BrowserTestUtils.waitForSessionStoreUpdate(tab);
+      BrowserTestUtils.removeTab(tab);
+      await update;
+
+      SessionStore.resetLastClosedActions();
+
+      let promiseTab = BrowserTestUtils.waitForNewTab(gBrowser, TEST_URL);
+      SessionWindowUI.restoreLastClosedTabOrWindowOrSession(window);
+      let newTab = await promiseTab;
+      Assert.equal(newTab.linkedBrowser.currentURI.spec, TEST_URL);
+    }
+  );
+});
+
+/**
+ * It the browser has restarted and the closed actions list is empty, and
+ * no closed tabs exist for the window, we should fallback to re-opening
+ * the last session if one exists.
+ */
+add_task(async function test_reopen_last_session_if_no_closed_actions() {
+  gBrowser.removeAllTabsBut(gBrowser.tabs[0], { animate: false });
+  await TabStateFlusher.flushWindow(window);
+
+  forgetClosedTabs(window);
+
+  const state = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              {
+                title: "example.org",
+                url: "https://example.org/",
+                triggeringPrincipal_base64,
+              },
+            ],
+          },
+          {
+            entries: [
+              {
+                title: "example.com",
+                url: "https://example.com/",
+                triggeringPrincipal_base64,
+              },
+            ],
+          },
+          {
+            entries: [
+              {
+                title: "mozilla",
+                url: "https://www.mozilla.org/",
+                triggeringPrincipal_base64,
+              },
+            ],
+          },
+        ],
+        selected: 3,
+      },
+    ],
+  };
+
+  _LastSession.setState(state);
+  SessionStore.resetLastClosedActions();
+
+  let sessionRestored = promiseSessionStoreLoads(3 /* total restored tabs */);
+  SessionWindowUI.restoreLastClosedTabOrWindowOrSession(window);
+  await sessionRestored;
+  Assert.equal(gBrowser.tabs.length, 4, "Got the expected number of tabs");
+  gBrowser.removeAllTabsBut(gBrowser.tabs[0], { animate: false });
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_restoreTabContainer.js b/src/zen/tests/mochitests/sessionstore/browser_restoreTabContainer.js
new file mode 100644
index 000000000..a38dca386
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_restoreTabContainer.js
@@ -0,0 +1,81 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const TEST_PATH = getRootDirectory(gTestPath).replace(
+  "chrome://mochitests/content",
+  "https://example.com"
+);
+
+add_task(async function () {
+  const testUserContextId = 2;
+  const testCases = [
+    {
+      url: `${TEST_PATH}empty.html`,
+      crossOriginIsolated: false,
+    },
+    {
+      url: `${TEST_PATH}coop_coep.html`,
+      crossOriginIsolated: true,
+    },
+  ];
+
+  for (const testCase of testCases) {
+    let tab = BrowserTestUtils.addTab(gBrowser, testCase.url, {
+      userContextId: testUserContextId,
+    });
+    await promiseBrowserLoaded(tab.linkedBrowser);
+
+    is(
+      tab.userContextId,
+      testUserContextId,
+      `The tab was opened with the expected userContextId`
+    );
+
+    await SpecialPowers.spawn(
+      tab.linkedBrowser,
+      [testCase.crossOriginIsolated],
+      async expectedCrossOriginIsolated => {
+        is(
+          content.window.crossOriginIsolated,
+          expectedCrossOriginIsolated,
+          `The tab was opened in the expected crossOriginIsolated environment`
+        );
+      }
+    );
+
+    let sessionPromise = BrowserTestUtils.waitForSessionStoreUpdate(tab);
+    BrowserTestUtils.removeTab(tab);
+    await sessionPromise;
+
+    let restoredTab = SessionStore.undoCloseTab(window, 0);
+
+    // TODO: also check that `promiseTabRestored` is fulfilled. This currently
+    // doesn't happen correctly in some cases, as the content restore is aborted
+    // when the process switch occurs to load a cross-origin-isolated document
+    // into a different process.
+    await promiseBrowserLoaded(restoredTab.linkedBrowser);
+
+    is(
+      restoredTab.userContextId,
+      testUserContextId,
+      `The tab was restored with the expected userContextId`
+    );
+
+    await SpecialPowers.spawn(
+      restoredTab.linkedBrowser,
+      [testCase.crossOriginIsolated],
+      async expectedCrossOriginIsolated => {
+        is(
+          content.window.crossOriginIsolated,
+          expectedCrossOriginIsolated,
+          `The tab was restored in the expected crossOriginIsolated environment`
+        );
+      }
+    );
+
+    BrowserTestUtils.removeTab(restoredTab);
+  }
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_restore_container_tabs_oa.js b/src/zen/tests/mochitests/sessionstore/browser_restore_container_tabs_oa.js
new file mode 100644
index 000000000..5df11566b
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_restore_container_tabs_oa.js
@@ -0,0 +1,272 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { UrlbarProviderOpenTabs } = ChromeUtils.importESModule(
+  "moz-src:///browser/components/urlbar/UrlbarProviderOpenTabs.sys.mjs"
+);
+
+const PATH = "browser/browser/components/sessionstore/test/empty.html";
+
+/* import-globals-from ../../tabbrowser/test/browser/tabs/helper_origin_attrs_testing.js */
+loadTestSubscript(
+  "../../tabbrowser/test/browser/tabs/helper_origin_attrs_testing.js"
+);
+
+var TEST_CASES = [
+  "https://example.com/" + PATH,
+  "https://example.org/" + PATH,
+  "about:preferences",
+  "about:config",
+];
+
+var remoteTypes;
+
+var xulFrameLoaderCreatedCounter = {};
+
+function handleEventLocal(aEvent) {
+  if (aEvent.type != "XULFrameLoaderCreated") {
+    return;
+  }
+  // Ignore <browser> element in about:preferences and any other special pages
+  if ("gBrowser" in aEvent.target.documentGlobal) {
+    xulFrameLoaderCreatedCounter.numCalledSoFar++;
+  }
+}
+
+var NUM_DIFF_TAB_MODES = NUM_USER_CONTEXTS + 1; /** regular tab */
+
+add_setup(async function () {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      // Set the pref to true so we know exactly how many tabs should be restoring at
+      // any given time. This guarantees that a finishing load won't start another.
+      ["browser.sessionstore.restore_on_demand", true],
+      // Don't restore tabs lazily.
+      ["browser.sessionstore.restore_tabs_lazily", true],
+      // don't preload tabs so we don't have extra XULFrameLoaderCreated events
+      // firing
+      ["browser.newtab.preload", false],
+    ],
+  });
+
+  requestLongerTimeout(14);
+});
+
+function setupRemoteTypes(isolateEverything) {
+  if (isolateEverything) {
+    remoteTypes = [
+      "webIsolated=https://example.com",
+      "webIsolated=https://example.com^userContextId=1",
+      "webIsolated=https://example.com^userContextId=2",
+      "webIsolated=https://example.com^userContextId=3",
+      "webIsolated=https://example.org",
+      "webIsolated=https://example.org^userContextId=1",
+      "webIsolated=https://example.org^userContextId=2",
+      "webIsolated=https://example.org^userContextId=3",
+    ];
+  } else {
+    remoteTypes = [
+      "web",
+      "web=^userContextId=1",
+      "web=^userContextId=2",
+      "web=^userContextId=3",
+      "web",
+      "web=^userContextId=1",
+      "web=^userContextId=2",
+      "web=^userContextId=3",
+    ];
+  }
+  remoteTypes.push(...Array(NUM_DIFF_TAB_MODES * 2).fill(null)); // remote types for about: pages
+
+  forgetClosedWindows();
+  is(SessionStore.getClosedWindowCount(), 0, "starting with no closed windows");
+}
+
+/*
+ * 1. Open several tabs in different containers and in regular tabs
+ [page1, page2, page3] [ [(page1 - work) (page1 - home)] [(page2 - work) (page2 - home)] ]
+ * 2. Close the window
+ * 3. Restore session, window will have the following tabs
+ * [initial blank page, page1, page1-work, page1-home, page2, page2-work, page2-home] 
+ * 4. Verify correct remote types and that XULFrameLoaderCreated gets fired correct number of times
+ */
+async function testRestoreCommon(isolateEverything) {
+  await SpecialPowers.pushPrefEnv({
+    set: [["fission.webContentIsolationStrategy", isolateEverything ? 1 : 0]],
+  });
+  setupRemoteTypes(isolateEverything);
+
+  let newWin = await promiseNewWindowLoaded();
+  var regularPages = [];
+  var containerPages = {};
+  // Go through all the test cases and open same set of urls in regular tabs and in container tabs
+  for (const uri of TEST_CASES) {
+    // Open a url in a regular tab
+    let regularPage = await openURIInRegularTab(uri, newWin);
+    regularPages.push(regularPage);
+
+    // Open the same url in different user contexts
+    for (
+      var user_context_id = 1;
+      user_context_id <= NUM_USER_CONTEXTS;
+      user_context_id++
+    ) {
+      let containerPage = await openURIInContainer(
+        uri,
+        newWin,
+        user_context_id
+      );
+      containerPages[uri] = containerPage;
+    }
+  }
+  await TabStateFlusher.flushWindow(newWin);
+
+  // Close the window
+  await BrowserTestUtils.closeWindow(newWin);
+  await forceSaveState();
+
+  is(
+    SessionStore.getClosedWindowCount(),
+    1,
+    "Should have restore data for the closed window"
+  );
+
+  Assert.equal(
+    0,
+    (await UrlbarProviderOpenTabs.getDatabaseRegisteredOpenTabsForTests())
+      .length,
+    "No registered open pages should be left"
+  );
+
+  // Now restore the window
+  newWin = SessionStore.undoCloseWindow(0);
+
+  // Make sure to wait for the window to be restored.
+  await Promise.all([
+    BrowserTestUtils.waitForEvent(newWin, "SSWindowStateReady"),
+  ]);
+  await BrowserTestUtils.waitForEvent(
+    newWin.gBrowser.tabContainer,
+    "SSTabRestored"
+  );
+
+  var nonblank_pages_len =
+    TEST_CASES.length + NUM_USER_CONTEXTS * TEST_CASES.length;
+  is(
+    newWin.gBrowser.tabs.length,
+    nonblank_pages_len + 1 /* initial page */,
+    "Correct number of tabs restored"
+  );
+
+  // Now we have pages opened in the following manner
+  // [blank page, page1, page1-work, page1-home, page2, page2-work, page2-home]
+
+  info(`Number of tabs restored: ${newWin.gBrowser.tabs.length}`);
+  var currRemoteType, expectedRemoteType;
+  let loaded;
+  for (var tab_idx = 1; tab_idx < nonblank_pages_len; ) {
+    info(`Accessing regular tab at index ${tab_idx}`);
+    var test_page_data = regularPages.shift();
+    let regular_tab = newWin.gBrowser.tabs[tab_idx];
+    let regular_browser = regular_tab.linkedBrowser;
+
+    // I would have used browserLoaded but for about:config it doesn't work
+    let ready = TestUtils.waitForCondition(async () => {
+      // Catch an error because the browser might change remoteness in between
+      // calls, so we will just wait for the document to finish loadig.
+      return SpecialPowers.spawn(regular_browser, [], () => {
+        return content.document.readyState == "complete";
+      }).catch(console.error);
+    });
+    newWin.gBrowser.selectedTab = regular_tab;
+    await TabStateFlusher.flush(regular_browser);
+    await ready;
+
+    currRemoteType = regular_browser.remoteType;
+    expectedRemoteType = remoteTypes.shift();
+    is(
+      currRemoteType,
+      expectedRemoteType,
+      `correct remote type for regular tab with uri ${test_page_data.uri}`
+    );
+
+    let page_uri = regular_browser.currentURI.spec;
+    info(`Current uri = ${page_uri}`);
+
+    // Iterate over container pages, starting after the regular page and ending before the next regular page
+    var userContextId = 1;
+    for (
+      var container_tab_idx = tab_idx + 1;
+      container_tab_idx < tab_idx + 1 + NUM_USER_CONTEXTS;
+      container_tab_idx++, userContextId++
+    ) {
+      info(`Accessing container tab at index ${container_tab_idx}`);
+      let container_tab = newWin.gBrowser.tabs[container_tab_idx];
+
+      initXulFrameLoaderCreatedCounter(xulFrameLoaderCreatedCounter);
+      container_tab.documentGlobal.gBrowser.addEventListener(
+        "XULFrameLoaderCreated",
+        handleEventLocal
+      );
+
+      loaded = BrowserTestUtils.browserLoaded(
+        container_tab.linkedBrowser,
+        false,
+        test_page_data.uri
+      );
+
+      newWin.gBrowser.selectedTab = container_tab;
+      await TabStateFlusher.flush(container_tab.linkedBrowser);
+      await loaded;
+      let uri = container_tab.linkedBrowser.currentURI.spec;
+
+      // Verify XULFrameLoaderCreated was fired once
+      is(
+        xulFrameLoaderCreatedCounter.numCalledSoFar,
+        1,
+        `XULFrameLoaderCreated was fired once, when restoring ${uri} in container ${userContextId} `
+      );
+      container_tab.documentGlobal.gBrowser.removeEventListener(
+        "XULFrameLoaderCreated",
+        handleEventLocal
+      );
+
+      // Verify correct remote type for container tab
+      currRemoteType = container_tab.linkedBrowser.remoteType;
+      expectedRemoteType = remoteTypes.shift();
+      info(
+        `Remote type for container tab ${userContextId} is ${currRemoteType}`
+      );
+      is(
+        currRemoteType,
+        expectedRemoteType,
+        "correct remote type for container tab"
+      );
+    }
+    // Advance to the next regular page in our tabs list
+    tab_idx = container_tab_idx;
+  }
+
+  await BrowserTestUtils.closeWindow(newWin);
+
+  Assert.equal(
+    0,
+    (await UrlbarProviderOpenTabs.getDatabaseRegisteredOpenTabsForTests())
+      .length,
+    "No registered open pages should be left"
+  );
+}
+
+if (gFissionBrowser) {
+  // This will have no impact if fission is disabled, so we skip this test.
+  add_task(async function testRestoreIsolateEverything() {
+    await testRestoreCommon(/* isolateEverything */ true);
+  });
+}
+
+add_task(async function testRestoreIsolateNothing() {
+  await testRestoreCommon(/* isolateEverything */ false);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_restore_cookies_noOriginAttributes.js b/src/zen/tests/mochitests/sessionstore/browser_restore_cookies_noOriginAttributes.js
new file mode 100644
index 000000000..3973c7c73
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_restore_cookies_noOriginAttributes.js
@@ -0,0 +1,194 @@
+/*
+ * Bug 1267910 - The regression test case for session cookies.
+ */
+
+"use strict";
+
+const TEST_HOST = "www.example.com";
+const COOKIE = {
+  name: "test1",
+  value: "yes1",
+  path: "/browser/browser/components/sessionstore/test/",
+  sameSite: Ci.nsICookie.SAMESITE_UNSET,
+};
+const SESSION_DATA = JSON.stringify({
+  version: ["sessionrestore", 1],
+  windows: [
+    {
+      tabs: [
+        {
+          entries: [],
+          lastAccessed: 1463893009797,
+          hidden: false,
+          attributes: {},
+          image: null,
+        },
+        {
+          entries: [
+            {
+              url: "http://www.example.com/browser/browser/components/sessionstore/test/browser_1267910_page.html",
+              triggeringPrincipal_base64,
+              charset: "UTF-8",
+              ID: 0,
+              docshellID: 2,
+              originalURI:
+                "http://www.example.com/browser/browser/components/sessionstore/test/browser_1267910_page.html",
+              docIdentifier: 0,
+              persist: true,
+            },
+          ],
+          lastAccessed: 1463893009321,
+          hidden: false,
+          attributes: {},
+          userContextId: 0,
+          index: 1,
+          image: "http://www.example.com/favicon.ico",
+        },
+      ],
+      selected: 1,
+      _closedTabs: [],
+      busy: false,
+      width: 1024,
+      height: 768,
+      screenX: 4,
+      screenY: 23,
+      sizemode: "normal",
+      cookies: [
+        {
+          host: "www.example.com",
+          value: "yes1",
+          path: "/browser/browser/components/sessionstore/test/",
+          name: "test1",
+          sameSite: Ci.nsICookie.SAMESITE_UNSET,
+        },
+      ],
+    },
+  ],
+  selectedWindow: 1,
+  _closedWindows: [],
+  session: {
+    lastUpdate: 1463893009801,
+    startTime: 1463893007134,
+    recentCrashes: 0,
+  },
+  global: {},
+});
+
+const SESSION_DATA_OA = JSON.stringify({
+  version: ["sessionrestore", 1],
+  windows: [
+    {
+      tabs: [
+        {
+          entries: [],
+          lastAccessed: 1463893009797,
+          hidden: false,
+          attributes: {},
+          image: null,
+        },
+        {
+          entries: [
+            {
+              url: "http://www.example.com/browser/browser/components/sessionstore/test/browser_1267910_page.html",
+              triggeringPrincipal_base64,
+              charset: "UTF-8",
+              ID: 0,
+              docshellID: 2,
+              originalURI:
+                "http://www.example.com/browser/browser/components/sessionstore/test/browser_1267910_page.html",
+              docIdentifier: 0,
+              persist: true,
+            },
+          ],
+          lastAccessed: 1463893009321,
+          hidden: false,
+          attributes: {},
+          userContextId: 0,
+          index: 1,
+          image: "http://www.example.com/favicon.ico",
+        },
+      ],
+      selected: 1,
+      _closedTabs: [],
+      busy: false,
+      width: 1024,
+      height: 768,
+      screenX: 4,
+      screenY: 23,
+      sizemode: "normal",
+      cookies: [
+        {
+          host: "www.example.com",
+          value: "yes1",
+          path: "/browser/browser/components/sessionstore/test/",
+          name: "test1",
+          sameSite: Ci.nsICookie.SAMESITE_UNSET,
+          originAttributes: {
+            addonId: "",
+            inIsolatedMozBrowser: false,
+            userContextId: 0,
+          },
+        },
+      ],
+    },
+  ],
+  selectedWindow: 1,
+  _closedWindows: [],
+  session: {
+    lastUpdate: 1463893009801,
+    startTime: 1463893007134,
+    recentCrashes: 0,
+  },
+  global: {},
+});
+
+add_task(async function run_test() {
+  // Wait until initialization is complete.
+  await SessionStore.promiseInitialized;
+
+  // Clear cookies.
+  Services.cookies.removeAll();
+
+  // Open a new window.
+  let win = await promiseNewWindowLoaded();
+
+  // Restore window with session cookies that have no originAttributes.
+  await setWindowState(win, SESSION_DATA, true);
+
+  let cookieCount = 0;
+  for (var cookie of Services.cookies.getCookiesFromHost(TEST_HOST, {})) {
+    cookieCount++;
+  }
+
+  // Check that the cookie is restored successfully.
+  is(cookieCount, 1, "expected one cookie");
+  is(cookie.name, COOKIE.name, "cookie name successfully restored");
+  is(cookie.value, COOKIE.value, "cookie value successfully restored");
+  is(cookie.path, COOKIE.path, "cookie path successfully restored");
+
+  // Clear cookies.
+  Services.cookies.removeAll();
+
+  // In real usage, the event loop would get to spin between setWindowState
+  // uses.  Without a spin, we can defer handling the STATE_STOP that
+  // removes the progress listener until after the mozbrowser has been
+  // destroyed, causing a window leak.
+  await new Promise(resolve => win.setTimeout(resolve, 0));
+
+  // Restore window with session cookies that have originAttributes within.
+  await setWindowState(win, SESSION_DATA_OA, true);
+
+  cookieCount = 0;
+  for (cookie of Services.cookies.getCookiesFromHost(TEST_HOST, {})) {
+    cookieCount++;
+  }
+
+  // Check that the cookie is restored successfully.
+  is(cookieCount, 1, "expected one cookie");
+  is(cookie.name, COOKIE.name, "cookie name successfully restored");
+  is(cookie.value, COOKIE.value, "cookie value successfully restored");
+  is(cookie.path, COOKIE.path, "cookie path successfully restored");
+
+  // Close our window.
+  await BrowserTestUtils.closeWindow(win);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_restore_pageProxyState.js b/src/zen/tests/mochitests/sessionstore/browser_restore_pageProxyState.js
new file mode 100644
index 000000000..f98237c7e
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_restore_pageProxyState.js
@@ -0,0 +1,77 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const BACKUP_STATE = SessionStore.getBrowserState();
+registerCleanupFunction(() => promiseBrowserState(BACKUP_STATE));
+
+// The pageproxystate of the restored tab controls whether the identity
+// information in the URL bar will display correctly. See bug 1766951 for more
+// context.
+async function test_pageProxyState(url1, url2) {
+  info(`urls: "${url1}", "${url2}"`);
+
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["browser.sessionstore.restore_on_demand", true],
+      ["browser.sessionstore.restore_tabs_lazily", true],
+    ],
+  });
+
+  await promiseBrowserState({
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              {
+                url: url1,
+                triggeringPrincipal_base64,
+              },
+            ],
+          },
+          {
+            entries: [
+              {
+                url: url2,
+                triggeringPrincipal_base64,
+              },
+            ],
+          },
+        ],
+        selected: 1,
+      },
+    ],
+  });
+
+  // The first tab isn't lazy and should be initialized.
+  ok(gBrowser.tabs[0].linkedPanel, "first tab is not lazy");
+  is(gBrowser.selectedTab, gBrowser.tabs[0], "first tab is selected");
+  is(gBrowser.userTypedValue, null, "no user typed value");
+  is(
+    gURLBar.getAttribute("pageproxystate"),
+    "valid",
+    "has valid page proxy state"
+  );
+
+  // The second tab is lazy until selected.
+  ok(!gBrowser.tabs[1].linkedPanel, "second tab should be lazy");
+  gBrowser.selectedTab = gBrowser.tabs[1];
+  await promiseTabRestored(gBrowser.tabs[1]);
+  is(gBrowser.userTypedValue, null, "no user typed value");
+  is(
+    gURLBar.getAttribute("pageproxystate"),
+    "valid",
+    "has valid page proxy state"
+  );
+}
+
+add_task(async function test_system() {
+  await test_pageProxyState("about:support", "about:addons");
+});
+
+add_task(async function test_http() {
+  await test_pageProxyState(
+    "https://example.com/document-builder.sjs?html=tab1",
+    "https://example.com/document-builder.sjs?html=tab2"
+  );
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_restore_private_tab_os.js b/src/zen/tests/mochitests/sessionstore/browser_restore_private_tab_os.js
new file mode 100644
index 000000000..3041fe6f3
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_restore_private_tab_os.js
@@ -0,0 +1,59 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const TEST_URI =
+  "https://example.com/" +
+  "browser/browser/components/sessionstore/test/empty.html";
+
+add_setup(async function () {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      // Set the pref to true so we know exactly how many tabs should be restoring at
+      // any given time. This guarantees that a finishing load won't start another.
+      ["browser.sessionstore.restore_on_demand", true],
+      // Don't restore tabs lazily.
+      ["browser.sessionstore.restore_tabs_lazily", true],
+      // don't preload tabs so we don't have extra XULFrameLoaderCreated events
+      // firing
+      ["browser.newtab.preload", false],
+    ],
+  });
+});
+
+add_task(async function testRestore() {
+  // Clear the list of closed windows.
+  forgetClosedWindows();
+
+  // Create a new private window
+  let win = await promiseNewWindowLoaded({ private: true });
+
+  // Create a new private tab
+  let tab = BrowserTestUtils.addTab(win.gBrowser, TEST_URI);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+  await TabStateFlusher.flush(browser);
+
+  // Ensure that closed tabs in a private windows can be restored.
+  win.gBrowser.removeTab(tab);
+  is(ss.getClosedTabCountForWindow(win), 1, "there is a single tab to restore");
+
+  tab = SessionStore.undoCloseTab(win, 0);
+  info(`Undo close tab`);
+  browser = tab.linkedBrowser;
+  await promiseTabRestored(tab);
+  info(`Private tab restored`);
+
+  let expectedRemoteType = gFissionBrowser
+    ? "webIsolated=https://example.com^privateBrowsingId=1"
+    : "web";
+  is(browser.remoteType, expectedRemoteType, "correct remote type");
+
+  await BrowserTestUtils.closeWindow(win);
+
+  // Cleanup
+  info("Forgetting closed tabs");
+  forgetClosedTabs(window);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_restore_redirect.js b/src/zen/tests/mochitests/sessionstore/browser_restore_redirect.js
new file mode 100644
index 000000000..a1d4ae0a3
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_restore_redirect.js
@@ -0,0 +1,84 @@
+"use strict";
+
+const BASE = "http://example.com/browser/browser/components/sessionstore/test/";
+const TARGET = BASE + "restore_redirect_target.html";
+
+/**
+ * Ensure that a http redirect leaves a working tab.
+ */
+add_task(async function check_http_redirect() {
+  let state = {
+    entries: [
+      { url: BASE + "restore_redirect_http.html", triggeringPrincipal_base64 },
+    ],
+  };
+
+  // Open a new tab to restore into.
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:blank");
+  let browser = tab.linkedBrowser;
+
+  // addTab sends a message to the child to load about:blank, which sends a
+  // message to the parent to add the SH entry.
+  // promiseTabState modifies the SH syncronously, so ensure it is settled.
+  await BrowserTestUtils.browserLoaded(browser, { wantLoad: "about:blank" });
+
+  await promiseTabState(tab, state);
+
+  info("Restored tab");
+
+  await TabStateFlusher.flush(browser);
+  let data = TabState.collect(tab);
+  is(data.entries.length, 1, "Should be one entry in session history");
+  is(data.entries[0].url, TARGET, "Should be the right session history entry");
+
+  ok(
+    !ss.getInternalObjectState(browser),
+    "Temporary restore data should have been cleared"
+  );
+
+  // Cleanup.
+  BrowserTestUtils.removeTab(tab);
+});
+
+/**
+ * Ensure that a js redirect leaves a working tab.
+ */
+add_task(async function check_js_redirect() {
+  let state = {
+    entries: [
+      { url: BASE + "restore_redirect_js.html", triggeringPrincipal_base64 },
+    ],
+  };
+
+  // Open a new tab to restore into.
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:blank");
+  let browser = tab.linkedBrowser;
+
+  // addTab sends a message to the child to load about:blank, which sends a
+  // message to the parent to add the SH entry.
+  // promiseTabState modifies the SH syncronously, so ensure it is settled.
+  await BrowserTestUtils.browserLoaded(browser, { wantLoad: "about:blank" });
+
+  let loadPromise = BrowserTestUtils.browserLoaded(browser, true, url =>
+    url.endsWith("restore_redirect_target.html")
+  );
+
+  await promiseTabState(tab, state);
+
+  info("Restored tab");
+
+  await loadPromise;
+
+  await TabStateFlusher.flush(browser);
+  let data = TabState.collect(tab);
+  is(data.entries.length, 1, "Should be one entry in session history");
+  is(data.entries[0].url, TARGET, "Should be the right session history entry");
+
+  ok(
+    !ss.getInternalObjectState(browser),
+    "Temporary restore data should have been cleared"
+  );
+
+  // Cleanup.
+  BrowserTestUtils.removeTab(tab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_restore_reversed_z_order.js b/src/zen/tests/mochitests/sessionstore/browser_restore_reversed_z_order.js
new file mode 100644
index 000000000..69745148a
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_restore_reversed_z_order.js
@@ -0,0 +1,128 @@
+"use strict";
+
+const PRIMARY_WINDOW = window;
+
+let gTestURLsMap = new Map([
+  ["about:about", null],
+  ["about:license", null],
+  ["about:robots", null],
+  ["about:mozilla", null],
+]);
+let gBrowserState;
+
+add_setup(async function () {
+  let windows = [];
+  let count = 0;
+  for (let url of gTestURLsMap.keys()) {
+    let window = !count
+      ? PRIMARY_WINDOW
+      : await BrowserTestUtils.openNewBrowserWindow();
+    let browserLoaded = BrowserTestUtils.browserLoaded(
+      window.gBrowser.selectedBrowser
+    );
+    BrowserTestUtils.startLoadingURIString(
+      window.gBrowser.selectedBrowser,
+      url
+    );
+    await browserLoaded;
+    // Capture the title.
+    gTestURLsMap.set(url, window.gBrowser.selectedTab.label);
+    // Minimize the before-last window, to have a different window feature added
+    // to the test.
+    if (count == gTestURLsMap.size - 1) {
+      let activated = BrowserTestUtils.waitForEvent(
+        windows[count - 1],
+        "activate"
+      );
+      window.minimize();
+      await activated;
+    }
+    windows.push(window);
+    ++count;
+  }
+
+  // Wait until we get the lastest history from all windows.
+  await Promise.all(windows.map(window => TabStateFlusher.flushWindow(window)));
+
+  gBrowserState = ss.getBrowserState();
+
+  await promiseAllButPrimaryWindowClosed();
+});
+
+add_task(async function test_z_indices_are_saved_correctly() {
+  let state = JSON.parse(gBrowserState);
+  Assert.equal(
+    state.windows.length,
+    gTestURLsMap.size,
+    "Correct number of windows saved"
+  );
+
+  // Check if we saved state in correct order of creation.
+  let idx = 0;
+  for (let url of gTestURLsMap.keys()) {
+    Assert.equal(
+      state.windows[idx].tabs[0].entries[0].url,
+      url,
+      `Window #${idx} is stored in correct creation order`
+    );
+    ++idx;
+  }
+
+  // Check if we saved a valid zIndex (no null, no undefined or no 0).
+  for (let window of state.windows) {
+    Assert.ok(window.zIndex, "A valid zIndex is stored");
+  }
+
+  Assert.equal(
+    state.windows[0].zIndex,
+    3,
+    "Window #1 should have the correct z-index"
+  );
+  Assert.equal(
+    state.windows[1].zIndex,
+    2,
+    "Window #2 should have correct z-index"
+  );
+  Assert.equal(
+    state.windows[2].zIndex,
+    1,
+    "Window #3 should be the topmost window"
+  );
+  Assert.equal(
+    state.windows[3].zIndex,
+    4,
+    "Minimized window should be the last window to restore"
+  );
+});
+
+add_task(async function test_windows_are_restored_in_reversed_z_order() {
+  await promiseBrowserState(gBrowserState);
+
+  let indexedTabLabels = [...gTestURLsMap.values()];
+  let tabsRestoredLabels = BrowserWindowTracker.orderedWindows.map(
+    window => window.gBrowser.selectedTab.label
+  );
+
+  Assert.equal(
+    tabsRestoredLabels[0],
+    indexedTabLabels[2],
+    "First restored tab should be last used tab"
+  );
+  Assert.equal(
+    tabsRestoredLabels[1],
+    indexedTabLabels[1],
+    "Second restored tab is correct"
+  );
+  Assert.equal(
+    tabsRestoredLabels[2],
+    indexedTabLabels[0],
+    "Third restored tab is correct"
+  );
+  Assert.equal(
+    tabsRestoredLabels[3],
+    indexedTabLabels[3],
+    "Last restored tab should be a minimized window"
+  );
+
+  await promiseAllButPrimaryWindowClosed();
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_restore_srcdoc.js b/src/zen/tests/mochitests/sessionstore/browser_restore_srcdoc.js
new file mode 100644
index 000000000..9e670100e
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_restore_srcdoc.js
@@ -0,0 +1,44 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+function makeURL(srcdocValue) {
+  return `data:text/html;charset=utf-8,<iframe srcdoc="${srcdocValue}">`;
+}
+
+async function runTest(srcdocValue) {
+  forgetClosedWindows();
+
+  // Open a new tab.
+  let tab = BrowserTestUtils.addTab(gBrowser, makeURL(srcdocValue));
+  await promiseBrowserLoaded(tab.linkedBrowser);
+
+  // Close that tab.
+  await promiseRemoveTabAndSessionState(tab);
+
+  // Restore that tab.
+  tab = ss.undoCloseTab(window, 0);
+  await promiseTabRestored(tab);
+
+  // Verify contents were restored correctly.
+  let iframe = await SpecialPowers.spawn(
+    tab.linkedBrowser,
+    [],
+    () => content.document.querySelector("iframe").browsingContext
+  );
+  await SpecialPowers.spawn(iframe, [srcdocValue], text => {
+    Assert.equal(content.document.body.innerText, text, "Didn't load neterror");
+  });
+
+  // Cleanup.
+  gBrowser.removeTab(tab);
+}
+
+add_task(async function test_non_blank() {
+  await runTest("value");
+});
+
+add_task(async function test_blank() {
+  await runTest("");
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_restore_tabless_window.js b/src/zen/tests/mochitests/sessionstore/browser_restore_tabless_window.js
new file mode 100644
index 000000000..cffb2159f
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_restore_tabless_window.js
@@ -0,0 +1,56 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/**
+ * It's possible for us to restore windows without tabs,
+ * when on Windows/Linux the user closes the last tab as
+ * a means of closing the last window. That last tab
+ * would appear as a closed tab in session state for the
+ * window, with no open tabs (so the state would be resumed
+ * as showing the homepage). See bug 490136 for context.
+ * This test checks that in this case, the resulting window
+ * is functional and indeed has the required previously
+ * closed tabs available.
+ */
+add_task(async function test_restoring_tabless_window() {
+  let newWin = await BrowserTestUtils.openNewBrowserWindow();
+  let newState = {
+    windows: [
+      {
+        tabs: [],
+        _closedTabs: [
+          {
+            state: { entries: [{ url: "about:" }] },
+            title: "About:",
+          },
+        ],
+      },
+    ],
+  };
+
+  await setWindowState(newWin, newState, true);
+  let tab = await BrowserTestUtils.openNewForegroundTab(
+    newWin.gBrowser,
+    "https://example.com"
+  );
+  await TabStateFlusher.flush(tab.linkedBrowser);
+  let receivedState = SessionStore.getWindowState(newWin);
+  let { tabs, selected } = receivedState.windows[0];
+  is(tabs.length, 2, "Should have two tabs");
+  is(selected, 2, "Should have selected the new tab");
+  ok(
+    tabs[1]?.entries.some(e => e.url == "https://example.com/"),
+    "Should have found the new URL"
+  );
+
+  let closedTabData = SessionStore.getClosedTabDataForWindow(newWin);
+  is(closedTabData.length, 1, "Should have found 1 closed tab");
+  is(
+    closedTabData[0]?.state.entries[0].url,
+    "about:",
+    "Should have found the right URL for the closed tab"
+  );
+  await BrowserTestUtils.closeWindow(newWin);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_restore_verticalPinnedTabs.js b/src/zen/tests/mochitests/sessionstore/browser_restore_verticalPinnedTabs.js
new file mode 100644
index 000000000..187e062ae
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_restore_verticalPinnedTabs.js
@@ -0,0 +1,105 @@
+add_setup(() =>
+  SpecialPowers.pushPrefEnv({
+    set: [
+      ["sidebar.revamp", true],
+      ["sidebar.verticalTabs", true],
+    ],
+  })
+);
+const BACKUP_STATE = SessionStore.getBrowserState();
+const REMOTE_URL = "https://www.example.com/";
+const ABOUT_ROBOTS_URL = "about:robots";
+const ABOUT_HOME = "about:home";
+const ABOUT_MOZILLA = "about:mozilla";
+
+let tabs = [
+  {
+    entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }],
+    pinned: true,
+    userContextId: 0,
+    hidden: false,
+  },
+  {
+    entries: [{ url: ABOUT_MOZILLA, triggeringPrincipal_base64 }],
+    pinned: true,
+    userContextId: 0,
+    hidden: false,
+  },
+  {
+    entries: [{ url: ABOUT_ROBOTS_URL, triggeringPrincipal_base64 }],
+    pinned: true,
+    userContextId: 0,
+    hidden: false,
+  },
+  {
+    entries: [{ url: ABOUT_HOME, triggeringPrincipal_base64 }],
+    userContextId: 0,
+    hidden: false,
+  },
+];
+
+add_task(async function test_pinned_tabs_restored_position() {
+  let allTabsRestored = promiseSessionStoreLoads(3);
+  await setWindowState(
+    window,
+    {
+      windows: [
+        {
+          selected: 3, // SessionStore uses 1-based indexing.
+          tabs,
+        },
+      ],
+    },
+    true
+  );
+  await allTabsRestored;
+
+  const sidebar = document.querySelector("sidebar-main");
+  ok(sidebar, "Sidebar is shown.");
+
+  let tabStrip = document.getElementById("tabbrowser-tabs");
+  let verticalTabs = document.querySelector("#vertical-tabs");
+  let pinnedTabsContainer = document.querySelector("#pinned-tabs-container");
+
+  ok(BrowserTestUtils.isVisible(verticalTabs), "Vertical tabs slot is visible");
+  is(
+    tabStrip.parentNode,
+    verticalTabs,
+    "Tabstrip is slotted into the sidebar vertical tabs container"
+  );
+  ok(
+    BrowserTestUtils.isVisible(pinnedTabsContainer),
+    "Vertical pinned tabs container is visible"
+  );
+  is(
+    pinnedTabsContainer.children.length,
+    gBrowser.pinnedTabCount,
+    "Three tabs are in the vertical pinned tabs container"
+  );
+
+  let [tab1, tab2, tab3, tab4] = gBrowser.tabs;
+  ok(tab1.pinned, "First tab is pinned");
+  ok(tab2.pinned, "Second tab is pinned");
+  ok(tab3.pinned, "Third tab is pinned");
+  ok(!tab4.pinned, "Fourth tab is not pinned");
+  ok(tab3.selected, "Third tab is selected");
+
+  is(
+    tab1.linkedBrowser.currentURI.spec,
+    REMOTE_URL,
+    "First tab has matching URL"
+  );
+  is(
+    tab2.linkedBrowser.currentURI.spec,
+    ABOUT_MOZILLA,
+    "Second tab has matching URL"
+  );
+  is(
+    tab3.linkedBrowser.currentURI.spec,
+    ABOUT_ROBOTS_URL,
+    "Third tab has matching URL"
+  );
+
+  // cleanup
+  await promiseBrowserState(BACKUP_STATE);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_restored_window_features.js b/src/zen/tests/mochitests/sessionstore/browser_restored_window_features.js
new file mode 100644
index 000000000..20a1d7196
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_restored_window_features.js
@@ -0,0 +1,164 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const BARPROP_NAMES = [
+  "locationbar",
+  "menubar",
+  "personalbar",
+  "scrollbars",
+  "statusbar",
+  "toolbar",
+];
+
+function testFeatures(win, test) {
+  for (let name of BARPROP_NAMES) {
+    is(
+      win[name].visible,
+      !!test.barprops?.[name],
+      name + " should be " + (test.barprops?.[name] ? "visible" : "hidden")
+    );
+  }
+  let toolbar = win.document.getElementById("TabsToolbar");
+  is(
+    toolbar.collapsed,
+    !win.toolbar.visible,
+    win.toolbar.visible
+      ? "tabbar should not be collapsed"
+      : "tabbar should be collapsed"
+  );
+  let chromeFlags = win.docShell.treeOwner
+    .QueryInterface(Ci.nsIInterfaceRequestor)
+    .getInterface(Ci.nsIAppWindow).chromeFlags;
+  is(chromeFlags & test.chromeFlags, test.chromeFlags, "flags should be set");
+  if (test.unsetFlags) {
+    is(chromeFlags & test.unsetFlags, 0, "flags should be unset");
+  }
+}
+
+add_task(async function testRestoredWindowFeatures() {
+  const DUMMY_PAGE =
+    "browser/components/tabbrowser/test/browser/tabs/dummy_page.html";
+  const ALL_BARPROPS = {
+    locationbar: true,
+    menubar: true,
+    personalbar: true,
+    scrollbars: true,
+    statusbar: true,
+    toolbar: true,
+  };
+  const TESTS = [
+    {
+      url: "http://example.com/browser/" + DUMMY_PAGE,
+      features: "menubar=0,resizable",
+      barprops: { scrollbars: true },
+      chromeFlags: Ci.nsIWebBrowserChrome.CHROME_WINDOW_RESIZE,
+      unsetFlags: Ci.nsIWebBrowserChrome.CHROME_OPENAS_DIALOG,
+    },
+    {
+      url: "data:,", // title should be empty
+      checkContentTitleEmpty: true,
+      features: "location,resizable",
+      barprops: { locationbar: true, scrollbars: true },
+      chromeFlags: Ci.nsIWebBrowserChrome.CHROME_WINDOW_RESIZE,
+      unsetFlags: Ci.nsIWebBrowserChrome.CHROME_OPENAS_DIALOG,
+    },
+    {
+      url: "http://example.com/browser/" + DUMMY_PAGE,
+      features: "dialog,resizable",
+      barprops: { scrollbars: true },
+      chromeFlags:
+        Ci.nsIWebBrowserChrome.CHROME_OPENAS_DIALOG |
+        Ci.nsIWebBrowserChrome.CHROME_WINDOW_RESIZE,
+    },
+    {
+      chrome: true,
+      url: "http://example.com/browser/" + DUMMY_PAGE,
+      features: "chrome,all,dialog=no",
+      barprops: ALL_BARPROPS,
+      chromeFlags: Ci.nsIWebBrowserChrome.CHROME_ALL,
+      unsetFlags: Ci.nsIWebBrowserChrome.CHROME_OPENAS_DIALOG,
+    },
+    {
+      chrome: true,
+      url: "http://example.com/browser/" + DUMMY_PAGE,
+      features: "chrome,all,dialog=no,centerscreen",
+      barprops: ALL_BARPROPS,
+      chromeFlags: Ci.nsIWebBrowserChrome.CHROME_CENTER_SCREEN,
+    },
+    {
+      chrome: true,
+      url: "http://example.com/browser/" + DUMMY_PAGE,
+      features: "chrome,all,dialog=no,dependent",
+      barprops: ALL_BARPROPS,
+      chromeFlags: Ci.nsIWebBrowserChrome.CHROME_DEPENDENT,
+    },
+  ];
+  const TEST_URL_CHROME = "chrome://mochitests/content/browser/" + DUMMY_PAGE;
+
+  BrowserTestUtils.startLoadingURIString(
+    gBrowser.selectedBrowser,
+    TEST_URL_CHROME
+  );
+  await BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser);
+
+  for (let test of TESTS) {
+    let newWindowPromise = BrowserTestUtils.waitForNewWindow({
+      url: test.url,
+    });
+    let win;
+    if (test.chrome) {
+      win = window.openDialog(
+        AppConstants.BROWSER_CHROME_URL,
+        "_blank",
+        test.features,
+        test.url
+      );
+    } else {
+      await SpecialPowers.spawn(gBrowser.selectedBrowser, [test], t => {
+        content.window.open(t.url, "_blank", t.features);
+      });
+    }
+    win = await newWindowPromise;
+
+    let title = win.document.title;
+    if (test.checkContentTitleEmpty) {
+      let contentTitle = await SpecialPowers.spawn(
+        win.gBrowser.selectedBrowser,
+        [],
+        () => content.document.title
+      );
+      is(contentTitle, "", "title should be empty");
+    }
+
+    testFeatures(win, test);
+    let chromeFlags = win.docShell.treeOwner
+      .QueryInterface(Ci.nsIInterfaceRequestor)
+      .getInterface(Ci.nsIAppWindow).chromeFlags;
+
+    await BrowserTestUtils.closeWindow(win);
+
+    newWindowPromise = BrowserTestUtils.waitForNewWindow({
+      url: test.url,
+    });
+    SessionStore.undoCloseWindow(0);
+    win = await newWindowPromise;
+
+    is(title, win.document.title, "title should be preserved");
+    testFeatures(win, test);
+    is(
+      win.docShell.treeOwner
+        .QueryInterface(Ci.nsIInterfaceRequestor)
+        .getInterface(Ci.nsIAppWindow).chromeFlags,
+      // Use |>>> 0| to force unsigned.
+      (chromeFlags |
+        Ci.nsIWebBrowserChrome.CHROME_OPENAS_CHROME |
+        Ci.nsIWebBrowserChrome.CHROME_SUPPRESS_ANIMATION) >>>
+        0,
+      "unexpected chromeFlags"
+    );
+
+    await BrowserTestUtils.closeWindow(win);
+  }
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_revive_crashed_bg_tabs.js b/src/zen/tests/mochitests/sessionstore/browser_revive_crashed_bg_tabs.js
new file mode 100644
index 000000000..86f85503d
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_revive_crashed_bg_tabs.js
@@ -0,0 +1,59 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/**
+ * Tests that even if the user has set their tabs to restore
+ * immediately on session start, that background tabs after a
+ * content process crash restore on demand.
+ */
+
+"use strict";
+
+const PAGE_1 =
+  "data:text/html,<html><body>A%20regular,%20everyday,%20normal%20page.";
+const PAGE_2 =
+  "data:text/html,<html><body>Another%20regular,%20everyday,%20normal%20page.";
+
+add_setup(async function () {
+  await pushPrefs(
+    ["dom.ipc.processCount", 1],
+    ["browser.sessionstore.restore_on_demand", false]
+  );
+});
+
+add_task(async function test_revive_bg_tabs_on_demand() {
+  let newTab1 = BrowserTestUtils.addTab(gBrowser, PAGE_1);
+  let browser1 = newTab1.linkedBrowser;
+  await BrowserTestUtils.browserLoaded(browser1);
+
+  gBrowser.selectedTab = newTab1;
+
+  let newTab2 = BrowserTestUtils.addTab(gBrowser, PAGE_2);
+  let browser2 = newTab2.linkedBrowser;
+  await BrowserTestUtils.browserLoaded(browser2);
+
+  await TabStateFlusher.flush(browser2);
+
+  // Now crash the selected tab
+  let windowReady = BrowserTestUtils.waitForEvent(window, "SSWindowStateReady");
+  await BrowserTestUtils.crashFrame(browser1);
+
+  ok(newTab1.hasAttribute("crashed"), "Selected tab should be crashed");
+  ok(!newTab2.hasAttribute("crashed"), "Background tab should not be crashed");
+
+  // Wait until we've had a chance to restore all tabs immediately
+  await windowReady;
+
+  // But we should not have restored the background tab
+  ok(newTab2.hasAttribute("pending"), "Background tab should be pending");
+
+  // Now select newTab2 to make sure it restores.
+  let newTab2Restored = promiseTabRestored(newTab2);
+  gBrowser.selectedTab = newTab2;
+  await newTab2Restored;
+
+  ok(browser2.isRemoteBrowser, "Restored browser should be remote");
+
+  BrowserTestUtils.removeTab(newTab1);
+  BrowserTestUtils.removeTab(newTab2);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_scrollPositions.js b/src/zen/tests/mochitests/sessionstore/browser_scrollPositions.js
new file mode 100644
index 000000000..b6d8edec1
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_scrollPositions.js
@@ -0,0 +1,263 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const BASE = "http://example.com/browser/browser/components/sessionstore/test/";
+const URL2 = BASE + "browser_scrollPositions_sample2.html";
+const URL_FRAMESET = BASE + "browser_scrollPositions_sample_frameset.html";
+
+// Randomized set of scroll positions we will use in this test.
+const SCROLL_X = Math.round(100 * (1 + Math.random()));
+const SCROLL_Y = Math.round(200 * (1 + Math.random()));
+const SCROLL_STR = SCROLL_X + "," + SCROLL_Y;
+
+const SCROLL2_X = Math.round(300 * (1 + Math.random()));
+const SCROLL2_Y = Math.round(400 * (1 + Math.random()));
+const SCROLL2_STR = SCROLL2_X + "," + SCROLL2_Y;
+
+requestLongerTimeout(10);
+
+add_task(test_scroll_nested);
+
+if (gFissionBrowser) {
+  addCoopTask("browser_scrollPositions_sample.html", test_scroll, HTTPSROOT);
+}
+addNonCoopTask("browser_scrollPositions_sample.html", test_scroll, HTTPROOT);
+addNonCoopTask("browser_scrollPositions_sample.html", test_scroll, HTTPSROOT);
+
+addCoopTask(
+  "browser_scrollPositions_sample.html",
+  test_scroll_background_tabs,
+  HTTPSROOT
+);
+addNonCoopTask(
+  "browser_scrollPositions_sample.html",
+  test_scroll_background_tabs,
+  HTTPROOT
+);
+
+addNonCoopTask(
+  "browser_scrollPositions_sample.html",
+  test_scroll_background_tabs,
+  HTTPSROOT
+);
+
+function getScrollPosition(bc) {
+  return SpecialPowers.spawn(bc, [], () => {
+    let x = {},
+      y = {};
+    content.windowUtils.getVisualViewportOffset(x, y);
+    return { x: x.value, y: y.value };
+  });
+}
+
+/**
+ * This test ensures that we properly serialize and restore scroll positions
+ * for an average page without any frames.
+ */
+async function test_scroll(aURL) {
+  let tab = BrowserTestUtils.addTab(gBrowser, aURL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  // Scroll down a little.
+  await setScrollPosition(browser, SCROLL_X, SCROLL_Y);
+  await checkScroll(tab, { scroll: SCROLL_STR }, "scroll is fine");
+
+  // Duplicate and check that the scroll position is restored.
+  let tab2 = ss.duplicateTab(window, tab);
+  let browser2 = tab2.linkedBrowser;
+  await promiseTabRestored(tab2);
+
+  let scroll = await getScrollPosition(browser2);
+  is(
+    JSON.stringify(scroll),
+    JSON.stringify({ x: SCROLL_X, y: SCROLL_Y }),
+    "scroll position has been duplicated correctly"
+  );
+
+  // Check that reloading retains the scroll positions.
+  browser2.reload();
+  await promiseBrowserLoaded(browser2);
+  await checkScroll(
+    tab2,
+    { scroll: SCROLL_STR },
+    "reloading retains scroll positions"
+  );
+
+  // Check that a force-reload resets scroll positions.
+  browser2.reloadWithFlags(Ci.nsIWebNavigation.LOAD_FLAGS_BYPASS_CACHE);
+  await promiseBrowserLoaded(browser2);
+  await checkScroll(tab2, null, "force-reload resets scroll positions");
+
+  // Scroll back to the top and check that the position has been reset. We
+  // expect the scroll position to be "null" here because there is no data to
+  // be stored if the frame is in its default scroll position.
+  await setScrollPosition(browser, 0, 0);
+  await checkScroll(tab, null, "no scroll stored");
+
+  // Cleanup.
+  BrowserTestUtils.removeTab(tab);
+  BrowserTestUtils.removeTab(tab2);
+}
+
+/**
+ * This tests ensures that we properly serialize and restore scroll positions
+ * for multiple frames of pages with framesets.
+ */
+async function test_scroll_nested() {
+  let tab = BrowserTestUtils.addTab(gBrowser, URL_FRAMESET);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  // Scroll the first child frame down a little.
+  await setScrollPosition(
+    browser.browsingContext.children[0],
+    SCROLL_X,
+    SCROLL_Y
+  );
+  await checkScroll(
+    tab,
+    { children: [{ scroll: SCROLL_STR }] },
+    "scroll is fine"
+  );
+
+  // Scroll the second child frame down a little.
+  await setScrollPosition(
+    browser.browsingContext.children[1],
+    SCROLL2_X,
+    SCROLL2_Y
+  );
+  await checkScroll(
+    tab,
+    { children: [{ scroll: SCROLL_STR }, { scroll: SCROLL2_STR }] },
+    "scroll is fine"
+  );
+
+  // Duplicate and check that the scroll position is restored.
+  let tab2 = ss.duplicateTab(window, tab);
+  let browser2 = tab2.linkedBrowser;
+  await promiseTabRestored(tab2);
+
+  let scroll = await getScrollPosition(browser2.browsingContext.children[0]);
+  is(
+    JSON.stringify(scroll),
+    JSON.stringify({ x: SCROLL_X, y: SCROLL_Y }),
+    "scroll position #1 has been duplicated correctly"
+  );
+
+  scroll = await getScrollPosition(browser2.browsingContext.children[1]);
+  is(
+    JSON.stringify(scroll),
+    JSON.stringify({ x: SCROLL2_X, y: SCROLL2_Y }),
+    "scroll position #2 has been duplicated correctly"
+  );
+
+  // Check that resetting one frame's scroll position removes it from the
+  // serialized value.
+  await setScrollPosition(browser.browsingContext.children[0], 0, 0);
+  await checkScroll(
+    tab,
+    { children: [null, { scroll: SCROLL2_STR }] },
+    "scroll is fine"
+  );
+
+  // Check the resetting all frames' scroll positions nulls the stored value.
+  await setScrollPosition(browser.browsingContext.children[1], 0, 0);
+  await checkScroll(tab, null, "no scroll stored");
+
+  // Cleanup.
+  BrowserTestUtils.removeTab(tab);
+  BrowserTestUtils.removeTab(tab2);
+}
+
+/**
+ * Test that scroll positions persist after restoring background tabs in
+ * a restored window (bug 1228518).
+ * Also test that scroll positions for previous session history entries
+ * are preserved as well (bug 1265818).
+ */
+async function test_scroll_background_tabs(aURL) {
+  await pushPrefs(["browser.sessionstore.restore_on_demand", true]);
+
+  let newWin = await BrowserTestUtils.openNewBrowserWindow();
+  let tab = BrowserTestUtils.addTab(newWin.gBrowser, aURL);
+  let browser = tab.linkedBrowser;
+  await BrowserTestUtils.browserLoaded(browser);
+
+  // Add user interaction to the first entry.
+  await SpecialPowers.spawn(browser, [], () => {
+    content.document.notifyUserGestureActivation();
+  });
+
+  // Scroll down a little.
+  await setScrollPosition(browser, SCROLL_X, SCROLL_Y);
+  await checkScroll(
+    tab,
+    { scroll: SCROLL_STR },
+    "scroll on first page is fine"
+  );
+
+  // Navigate to a different page and scroll there as well.
+  let browser2loaded = BrowserTestUtils.browserLoaded(browser, false, URL2);
+  BrowserTestUtils.startLoadingURIString(browser, URL2);
+  await browser2loaded;
+
+  // Scroll down a little.
+  await setScrollPosition(browser, SCROLL2_X, SCROLL2_Y);
+  await checkScroll(
+    tab,
+    { scroll: SCROLL2_STR },
+    "scroll on second page is fine"
+  );
+
+  // Close the window
+  await BrowserTestUtils.closeWindow(newWin);
+
+  await forceSaveState();
+
+  // Now restore the window
+  newWin = ss.undoCloseWindow(0);
+
+  // Make sure to wait for the window to be restored.
+  await BrowserTestUtils.waitForEvent(newWin, "SSWindowStateReady");
+
+  is(newWin.gBrowser.tabs.length, 2, "There should be two tabs");
+
+  // The second tab should be the one we loaded aURL at still
+  tab = newWin.gBrowser.tabs[1];
+
+  ok(tab.hasAttribute("pending"), "Tab should be pending");
+  browser = tab.linkedBrowser;
+
+  // Ensure there are no pending queued messages in the child.
+  await TabStateFlusher.flush(browser);
+
+  // Now check to see if the background tab remembers where it
+  // should be scrolled to.
+  newWin.gBrowser.selectedTab = tab;
+  await promiseTabRestored(tab);
+
+  await checkScroll(
+    tab,
+    { scroll: SCROLL2_STR },
+    "scroll is correct for restored tab"
+  );
+
+  // Now go back in history and check that the scroll position
+  // is restored there as well.
+  is(browser.canGoBack, true, "can go back");
+  browser.goBack();
+
+  await BrowserTestUtils.browserLoaded(browser);
+  await TabStateFlusher.flush(browser);
+
+  await checkScroll(
+    tab,
+    { scroll: SCROLL_STR },
+    "scroll is correct after navigating back within the restored tab"
+  );
+
+  await BrowserTestUtils.closeWindow(newWin);
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_scrollPositionsReaderMode.js b/src/zen/tests/mochitests/sessionstore/browser_scrollPositionsReaderMode.js
new file mode 100644
index 000000000..c61b37c1a
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_scrollPositionsReaderMode.js
@@ -0,0 +1,76 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const BASE = "http://example.com/browser/browser/components/sessionstore/test/";
+const READER_MODE_URL =
+  "about:reader?url=" +
+  encodeURIComponent(BASE + "browser_scrollPositions_readerModeArticle.html");
+
+// Randomized set of scroll positions we will use in this test.
+const SCROLL_READER_MODE_Y = Math.round(400 * (1 + Math.random()));
+const SCROLL_READER_MODE_STR = "0," + SCROLL_READER_MODE_Y;
+
+requestLongerTimeout(2);
+
+/**
+ * Test that scroll positions of about reader page after restoring background
+ * tabs in a restored window (bug 1153393).
+ */
+add_task(async function test_scroll_background_about_reader_tabs() {
+  await pushPrefs(["browser.sessionstore.restore_on_demand", true]);
+
+  let newWin = await BrowserTestUtils.openNewBrowserWindow();
+  let tab = BrowserTestUtils.addTab(newWin.gBrowser, READER_MODE_URL);
+  let browser = tab.linkedBrowser;
+  await Promise.all([
+    BrowserTestUtils.browserLoaded(browser),
+    BrowserTestUtils.waitForContentEvent(browser, "AboutReaderContentReady"),
+  ]);
+
+  // Scroll down a little.
+  await setScrollPosition(browser, 0, SCROLL_READER_MODE_Y);
+  await checkScroll(tab, { scroll: SCROLL_READER_MODE_STR }, "scroll is fine");
+
+  // Close the window
+  await BrowserTestUtils.closeWindow(newWin);
+
+  await forceSaveState();
+
+  // Now restore the window
+  newWin = ss.undoCloseWindow(0);
+
+  // Make sure to wait for the window to be restored.
+  await BrowserTestUtils.waitForEvent(newWin, "SSWindowStateReady");
+
+  is(newWin.gBrowser.tabs.length, 2, "There should be two tabs");
+
+  // The second tab should be the one we loaded URL at still
+  tab = newWin.gBrowser.tabs[1];
+
+  ok(tab.hasAttribute("pending"), "Tab should be pending");
+  browser = tab.linkedBrowser;
+
+  // Ensure there are no pending queued messages in the child.
+  await TabStateFlusher.flush(browser);
+
+  // Now check to see if the background tab remembers where it
+  // should be scrolled to.
+  newWin.gBrowser.selectedTab = tab;
+  await Promise.all([
+    promiseTabRestored(tab),
+    BrowserTestUtils.waitForContentEvent(
+      tab.linkedBrowser,
+      "AboutReaderContentReady"
+    ),
+  ]);
+
+  await checkScroll(
+    tab,
+    { scroll: SCROLL_READER_MODE_STR },
+    "scroll is still fine"
+  );
+
+  await BrowserTestUtils.closeWindow(newWin);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_scrollPositions_readerModeArticle.html b/src/zen/tests/mochitests/sessionstore/browser_scrollPositions_readerModeArticle.html
new file mode 100644
index 000000000..55452e043
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_scrollPositions_readerModeArticle.html
@@ -0,0 +1,26 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Article title</title>
+<meta name="description" content="This is the article description." />
+</head>
+<body>
+<header>Site header</header>
+<div>
+<h1>Article title</h1>
+<h2 class="author">by Jane Doe</h2>
+<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a diam lectus. Sed sit amet ipsum mauris. Maecenas congue ligula ac quam viverra nec consectetur ante hendrerit. Donec et mollis dolor. Praesent et diam eget libero egestas mattis sit amet vitae augue. Nam tincidunt congue enim, ut porta lorem lacinia consectetur. Donec ut libero sed arcu vehicula ultricies a non tortor. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Aenean ut gravida lorem. Ut turpis felis, pulvinar a semper sed, adipiscing id dolor. Pellentesque auctor nisi id magna consequat sagittis. Curabitur dapibus enim sit amet elit pharetra tincidunt feugiat nisl imperdiet. Ut convallis libero in urna ultrices accumsan. Donec sed odio eros. Donec viverra mi quis quam pulvinar at malesuada arcu rhoncus. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. In rutrum accumsan ultricies. Mauris vitae nisi at sem facilisis semper ac in est.</p>
+<p>Vivamus fermentum semper porta. Nunc diam velit, adipiscing ut tristique vitae, sagittis vel odio. Maecenas convallis ullamcorper ultricies. Curabitur ornare, ligula semper consectetur sagittis, nisi diam iaculis velit, id fringilla sem nunc vel mi. Nam dictum, odio nec pretium volutpat, arcu ante placerat erat, non tristique elit urna et turpis. Quisque mi metus, ornare sit amet fermentum et, tincidunt et orci. Fusce eget orci a orci congue vestibulum. Ut dolor diam, elementum et vestibulum eu, porttitor vel elit. Curabitur venenatis pulvinar tellus gravida ornare. Sed et erat faucibus nunc euismod ultricies ut id justo. Nullam cursus suscipit nisi, et ultrices justo sodales nec. Fusce venenatis facilisis lectus ac semper. Aliquam at massa ipsum. Quisque bibendum purus convallis nulla ultrices ultricies. Nullam aliquam, mi eu aliquam tincidunt, purus velit laoreet tortor, viverra pretium nisi quam vitae mi. Fusce vel volutpat elit. Nam sagittis nisi dui.</p>
+<p>Vivamus fermentum semper porta. Nunc diam velit, adipiscing ut tristique vitae, sagittis vel odio. Maecenas convallis ullamcorper ultricies. Curabitur ornare, ligula semper consectetur sagittis, nisi diam iaculis velit, id fringilla sem nunc vel mi. Nam dictum, odio nec pretium volutpat, arcu ante placerat erat, non tristique elit urna et turpis. Quisque mi metus, ornare sit amet fermentum et, tincidunt et orci. Fusce eget orci a orci congue vestibulum. Ut dolor diam, elementum et vestibulum eu, porttitor vel elit. Curabitur venenatis pulvinar tellus gravida ornare. Sed et erat faucibus nunc euismod ultricies ut id justo. Nullam cursus suscipit nisi, et ultrices justo sodales nec. Fusce venenatis facilisis lectus ac semper. Aliquam at massa ipsum. Quisque bibendum purus convallis nulla ultrices ultricies. Nullam aliquam, mi eu aliquam tincidunt, purus velit laoreet tortor, viverra pretium nisi quam vitae mi. Fusce vel volutpat elit. Nam sagittis nisi dui.</p>
+<p>Vivamus fermentum semper porta. Nunc diam velit, adipiscing ut tristique vitae, sagittis vel odio. Maecenas convallis ullamcorper ultricies. Curabitur ornare, ligula semper consectetur sagittis, nisi diam iaculis velit, id fringilla sem nunc vel mi. Nam dictum, odio nec pretium volutpat, arcu ante placerat erat, non tristique elit urna et turpis. Quisque mi metus, ornare sit amet fermentum et, tincidunt et orci. Fusce eget orci a orci congue vestibulum. Ut dolor diam, elementum et vestibulum eu, porttitor vel elit. Curabitur venenatis pulvinar tellus gravida ornare. Sed et erat faucibus nunc euismod ultricies ut id justo. Nullam cursus suscipit nisi, et ultrices justo sodales nec. Fusce venenatis facilisis lectus ac semper. Aliquam at massa ipsum. Quisque bibendum purus convallis nulla ultrices ultricies. Nullam aliquam, mi eu aliquam tincidunt, purus velit laoreet tortor, viverra pretium nisi quam vitae mi. Fusce vel volutpat elit. Nam sagittis nisi dui.</p>
+<p>Vivamus fermentum semper porta. Nunc diam velit, adipiscing ut tristique vitae, sagittis vel odio. Maecenas convallis ullamcorper ultricies. Curabitur ornare, ligula semper consectetur sagittis, nisi diam iaculis velit, id fringilla sem nunc vel mi. Nam dictum, odio nec pretium volutpat, arcu ante placerat erat, non tristique elit urna et turpis. Quisque mi metus, ornare sit amet fermentum et, tincidunt et orci. Fusce eget orci a orci congue vestibulum. Ut dolor diam, elementum et vestibulum eu, porttitor vel elit. Curabitur venenatis pulvinar tellus gravida ornare. Sed et erat faucibus nunc euismod ultricies ut id justo. Nullam cursus suscipit nisi, et ultrices justo sodales nec. Fusce venenatis facilisis lectus ac semper. Aliquam at massa ipsum. Quisque bibendum purus convallis nulla ultrices ultricies. Nullam aliquam, mi eu aliquam tincidunt, purus velit laoreet tortor, viverra pretium nisi quam vitae mi. Fusce vel volutpat elit. Nam sagittis nisi dui.</p>
+<p>Vivamus fermentum semper porta. Nunc diam velit, adipiscing ut tristique vitae, sagittis vel odio. Maecenas convallis ullamcorper ultricies. Curabitur ornare, ligula semper consectetur sagittis, nisi diam iaculis velit, id fringilla sem nunc vel mi. Nam dictum, odio nec pretium volutpat, arcu ante placerat erat, non tristique elit urna et turpis. Quisque mi metus, ornare sit amet fermentum et, tincidunt et orci. Fusce eget orci a orci congue vestibulum. Ut dolor diam, elementum et vestibulum eu, porttitor vel elit. Curabitur venenatis pulvinar tellus gravida ornare. Sed et erat faucibus nunc euismod ultricies ut id justo. Nullam cursus suscipit nisi, et ultrices justo sodales nec. Fusce venenatis facilisis lectus ac semper. Aliquam at massa ipsum. Quisque bibendum purus convallis nulla ultrices ultricies. Nullam aliquam, mi eu aliquam tincidunt, purus velit laoreet tortor, viverra pretium nisi quam vitae mi. Fusce vel volutpat elit. Nam sagittis nisi dui.</p>
+<p>Vivamus fermentum semper porta. Nunc diam velit, adipiscing ut tristique vitae, sagittis vel odio. Maecenas convallis ullamcorper ultricies. Curabitur ornare, ligula semper consectetur sagittis, nisi diam iaculis velit, id fringilla sem nunc vel mi. Nam dictum, odio nec pretium volutpat, arcu ante placerat erat, non tristique elit urna et turpis. Quisque mi metus, ornare sit amet fermentum et, tincidunt et orci. Fusce eget orci a orci congue vestibulum. Ut dolor diam, elementum et vestibulum eu, porttitor vel elit. Curabitur venenatis pulvinar tellus gravida ornare. Sed et erat faucibus nunc euismod ultricies ut id justo. Nullam cursus suscipit nisi, et ultrices justo sodales nec. Fusce venenatis facilisis lectus ac semper. Aliquam at massa ipsum. Quisque bibendum purus convallis nulla ultrices ultricies. Nullam aliquam, mi eu aliquam tincidunt, purus velit laoreet tortor, viverra pretium nisi quam vitae mi. Fusce vel volutpat elit. Nam sagittis nisi dui.</p>
+<p>Vivamus fermentum semper porta. Nunc diam velit, adipiscing ut tristique vitae, sagittis vel odio. Maecenas convallis ullamcorper ultricies. Curabitur ornare, ligula semper consectetur sagittis, nisi diam iaculis velit, id fringilla sem nunc vel mi. Nam dictum, odio nec pretium volutpat, arcu ante placerat erat, non tristique elit urna et turpis. Quisque mi metus, ornare sit amet fermentum et, tincidunt et orci. Fusce eget orci a orci congue vestibulum. Ut dolor diam, elementum et vestibulum eu, porttitor vel elit. Curabitur venenatis pulvinar tellus gravida ornare. Sed et erat faucibus nunc euismod ultricies ut id justo. Nullam cursus suscipit nisi, et ultrices justo sodales nec. Fusce venenatis facilisis lectus ac semper. Aliquam at massa ipsum. Quisque bibendum purus convallis nulla ultrices ultricies. Nullam aliquam, mi eu aliquam tincidunt, purus velit laoreet tortor, viverra pretium nisi quam vitae mi. Fusce vel volutpat elit. Nam sagittis nisi dui.</p>
+<p>Vivamus fermentum semper porta. Nunc diam velit, adipiscing ut tristique vitae, sagittis vel odio. Maecenas convallis ullamcorper ultricies. Curabitur ornare, ligula semper consectetur sagittis, nisi diam iaculis velit, id fringilla sem nunc vel mi. Nam dictum, odio nec pretium volutpat, arcu ante placerat erat, non tristique elit urna et turpis. Quisque mi metus, ornare sit amet fermentum et, tincidunt et orci. Fusce eget orci a orci congue vestibulum. Ut dolor diam, elementum et vestibulum eu, porttitor vel elit. Curabitur venenatis pulvinar tellus gravida ornare. Sed et erat faucibus nunc euismod ultricies ut id justo. Nullam cursus suscipit nisi, et ultrices justo sodales nec. Fusce venenatis facilisis lectus ac semper. Aliquam at massa ipsum. Quisque bibendum purus convallis nulla ultrices ultricies. Nullam aliquam, mi eu aliquam tincidunt, purus velit laoreet tortor, viverra pretium nisi quam vitae mi. Fusce vel volutpat elit. Nam sagittis nisi dui.</p>
+<p>Vivamus fermentum semper porta. Nunc diam velit, adipiscing ut tristique vitae, sagittis vel odio. Maecenas convallis ullamcorper ultricies. Curabitur ornare, ligula semper consectetur sagittis, nisi diam iaculis velit, id fringilla sem nunc vel mi. Nam dictum, odio nec pretium volutpat, arcu ante placerat erat, non tristique elit urna et turpis. Quisque mi metus, ornare sit amet fermentum et, tincidunt et orci. Fusce eget orci a orci congue vestibulum. Ut dolor diam, elementum et vestibulum eu, porttitor vel elit. Curabitur venenatis pulvinar tellus gravida ornare. Sed et erat faucibus nunc euismod ultricies ut id justo. Nullam cursus suscipit nisi, et ultrices justo sodales nec. Fusce venenatis facilisis lectus ac semper. Aliquam at massa ipsum. Quisque bibendum purus convallis nulla ultrices ultricies. Nullam aliquam, mi eu aliquam tincidunt, purus velit laoreet tortor, viverra pretium nisi quam vitae mi. Fusce vel volutpat elit. Nam sagittis nisi dui.</p>
+<p>Vivamus fermentum semper porta. Nunc diam velit, adipiscing ut tristique vitae, sagittis vel odio. Maecenas convallis ullamcorper ultricies. Curabitur ornare, ligula semper consectetur sagittis, nisi diam iaculis velit, id fringilla sem nunc vel mi. Nam dictum, odio nec pretium volutpat, arcu ante placerat erat, non tristique elit urna et turpis. Quisque mi metus, ornare sit amet fermentum et, tincidunt et orci. Fusce eget orci a orci congue vestibulum. Ut dolor diam, elementum et vestibulum eu, porttitor vel elit. Curabitur venenatis pulvinar tellus gravida ornare. Sed et erat faucibus nunc euismod ultricies ut id justo. Nullam cursus suscipit nisi, et ultrices justo sodales nec. Fusce venenatis facilisis lectus ac semper. Aliquam at massa ipsum. Quisque bibendum purus convallis nulla ultrices ultricies. Nullam aliquam, mi eu aliquam tincidunt, purus velit laoreet tortor, viverra pretium nisi quam vitae mi. Fusce vel volutpat elit. Nam sagittis nisi dui.</p>
+<p>Vivamus fermentum semper porta. Nunc diam velit, adipiscing ut tristique vitae, sagittis vel odio. Maecenas convallis ullamcorper ultricies. Curabitur ornare, ligula semper consectetur sagittis, nisi diam iaculis velit, id fringilla sem nunc vel mi. Nam dictum, odio nec pretium volutpat, arcu ante placerat erat, non tristique elit urna et turpis. Quisque mi metus, ornare sit amet fermentum et, tincidunt et orci. Fusce eget orci a orci congue vestibulum. Ut dolor diam, elementum et vestibulum eu, porttitor vel elit. Curabitur venenatis pulvinar tellus gravida ornare. Sed et erat faucibus nunc euismod ultricies ut id justo. Nullam cursus suscipit nisi, et ultrices justo sodales nec. Fusce venenatis facilisis lectus ac semper. Aliquam at massa ipsum. Quisque bibendum purus convallis nulla ultrices ultricies. Nullam aliquam, mi eu aliquam tincidunt, purus velit laoreet tortor, viverra pretium nisi quam vitae mi. Fusce vel volutpat elit. Nam sagittis nisi dui.</p>
+</div>
+</body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_scrollPositions_sample.html b/src/zen/tests/mochitests/sessionstore/browser_scrollPositions_sample.html
new file mode 100644
index 000000000..0182783db
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_scrollPositions_sample.html
@@ -0,0 +1,8 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="utf-8">
+    <title>browser_scrollPositions_sample.html</title>
+  </head>
+  <body style='width: 100000px; height: 100000px;'>top</body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_scrollPositions_sample2.html b/src/zen/tests/mochitests/sessionstore/browser_scrollPositions_sample2.html
new file mode 100644
index 000000000..0182783db
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_scrollPositions_sample2.html
@@ -0,0 +1,8 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="utf-8">
+    <title>browser_scrollPositions_sample.html</title>
+  </head>
+  <body style='width: 100000px; height: 100000px;'>top</body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_scrollPositions_sample_frameset.html b/src/zen/tests/mochitests/sessionstore/browser_scrollPositions_sample_frameset.html
new file mode 100644
index 000000000..c7e363fa1
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_scrollPositions_sample_frameset.html
@@ -0,0 +1,11 @@
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Frameset//EN">
+<html lang="en">
+  <head>
+    <meta charset="utf-8">
+    <title>browser_scrollPositions_sample_frameset.html</title>
+  </head>
+  <frameset id="frames" rows="50%, 50%">
+    <frame src="browser_scrollPositions_sample.html">
+    <frame src="browser_scrollPositions_sample.html">
+  </frameset>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_searchModeSwitcher_restore.js b/src/zen/tests/mochitests/sessionstore/browser_searchModeSwitcher_restore.js
new file mode 100644
index 000000000..ef7deb707
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_searchModeSwitcher_restore.js
@@ -0,0 +1,105 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/* eslint-disable mozilla/no-arbitrary-setTimeout */
+"use strict";
+requestLongerTimeout(4);
+
+ChromeUtils.defineESModuleGetters(this, {
+  SearchService: "moz-src:///toolkit/components/search/SearchService.sys.mjs",
+  setTimeout: "resource://gre/modules/Timer.sys.mjs",
+  sinon: "resource://testing-common/Sinon.sys.mjs",
+});
+
+const BOOKMARKS_ICON_URL = "chrome://browser/skin/bookmark.svg";
+
+add_setup(async function () {
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.urlbar.scotchBonnet.enableOverride", true]],
+  });
+
+  forgetClosedWindows();
+});
+
+add_task(async function () {
+  let win = await BrowserTestUtils.openNewBrowserWindow();
+
+  await BrowserTestUtils.openNewForegroundTab(win.gBrowser, "about:mozilla");
+  await BrowserTestUtils.openNewForegroundTab(win.gBrowser, "about:home");
+
+  info("Set bookmarks search mode");
+  await win.gURLBar.setSearchMode(
+    { source: 1, isPreview: false },
+    win.gBrowser.selectedBrowser
+  );
+
+  await BrowserTestUtils.closeWindow(win);
+
+  ok(SessionStore.getClosedWindowCount(), "Should have a closed window");
+  await forceSaveState();
+
+  win = SessionStore.undoCloseWindow(0);
+
+  await TestUtils.topicObserved(
+    "sessionstore-single-window-restored",
+    subject => subject == win
+  );
+
+  let persistSandbox = sinon.createSandbox();
+  const originalUpdateSearchIcon =
+    win.gURLBar.searchModeSwitcher.updateSearchIcon;
+  let updateCalled = 0;
+
+  persistSandbox
+    .stub(win.gURLBar.searchModeSwitcher, "updateSearchIcon")
+    .callsFake(async function () {
+      await originalUpdateSearchIcon.call(this);
+      updateCalled++;
+    });
+
+  let defaultEngine = await SearchService.getDefault();
+  let defaultEngineIconURL = await defaultEngine.getIconURL();
+
+  let defaultEngineIconCallsStack = [];
+
+  persistSandbox.stub(defaultEngine, "getIconURL").callsFake(async function () {
+    const iconURL = defaultEngineIconURL;
+    defaultEngineIconURL = null;
+    defaultEngineIconCallsStack.push(true);
+    await new Promise(resolve => setTimeout(resolve, 200));
+    defaultEngineIconCallsStack.pop();
+    return Promise.resolve(iconURL);
+  });
+
+  registerCleanupFunction(async function () {
+    persistSandbox.restore();
+  });
+
+  await TabStateFlusher.flush(win.gBrowser.selectedBrowser);
+
+  is(win.gBrowser.tabs.length, 3, "The restored window should have 3 tabs");
+
+  // Search mode switcher icon update will trigger once.
+  await TestUtils.waitForCondition(() => updateCalled > 1);
+
+  let searchModeSwitcherIconUrl = win.gURLBar
+    .querySelector(".searchmode-switcher")
+    .getAttribute("iconsrc");
+
+  Assert.equal(
+    searchModeSwitcherIconUrl,
+    BOOKMARKS_ICON_URL,
+    "Search mode switcher should display bookmarks icon."
+  );
+
+  persistSandbox.restore();
+
+  // Wait for any ongoing calls to defaultEngine.getIconURL() to finish.
+  await TestUtils.waitForCondition(() => !defaultEngineIconCallsStack.length);
+
+  await BrowserTestUtils.closeWindow(win);
+
+  // Clean up
+  await promiseAllButPrimaryWindowClosed();
+  forgetClosedWindows();
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_sessionHistory.js b/src/zen/tests/mochitests/sessionstore/browser_sessionHistory.js
new file mode 100644
index 000000000..66afc64c3
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_sessionHistory.js
@@ -0,0 +1,294 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+requestLongerTimeout(2);
+
+/**
+ * Ensure that starting a load invalidates shistory.
+ */
+add_task(async function test_load_start() {
+  // Create a new tab.
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:blank");
+  let browser = tab.linkedBrowser;
+  await BrowserTestUtils.browserLoaded(browser, { wantLoad: "about:blank" });
+
+  const PAGE = "http://example.com/";
+
+  // Load a new URI.
+  let historyReplacePromise = promiseOnHistoryReplaceEntry(browser);
+  BrowserTestUtils.startLoadingURIString(browser, PAGE);
+
+  // Remove the tab before it has finished loading.
+  await historyReplacePromise;
+  await promiseRemoveTabAndSessionState(tab);
+
+  // Undo close the tab.
+  tab = ss.undoCloseTab(window, 0);
+  browser = tab.linkedBrowser;
+  await promiseTabRestored(tab);
+
+  // Check that the correct URL was restored.
+  is(browser.currentURI.spec, PAGE, "url is correct");
+
+  // Cleanup.
+  gBrowser.removeTab(tab);
+});
+
+/**
+ * Ensure that anchor navigation invalidates shistory.
+ */
+add_task(async function test_hashchange() {
+  const PATH = getRootDirectory(gTestPath).replace(
+    "chrome://mochitests/content/",
+    "http://example.com/"
+  );
+  const URL = PATH + "file_sessionHistory_hashchange.html";
+  // Create a new tab.
+  let tab = BrowserTestUtils.addTab(gBrowser, URL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  // Check that we start with a single shistory entry.
+  await TabStateFlusher.flush(browser);
+  let { entries } = JSON.parse(ss.getTabState(tab));
+  is(entries.length, 1, "there is one shistory entry");
+
+  // Click the link and wait for a hashchange event.
+  let eventPromise = BrowserTestUtils.waitForContentEvent(
+    browser,
+    "hashchange",
+    true
+  );
+  await SpecialPowers.spawn(browser, [], async function () {
+    content.document.querySelector("#a").click();
+  });
+  info("About to watch for a hash change event");
+  await eventPromise;
+  info("Got a hash change event");
+
+  // Check that we now have two shistory entries.
+  await TabStateFlusher.flush(browser);
+  ({ entries } = JSON.parse(ss.getTabState(tab)));
+  is(entries.length, 2, "there are two shistory entries");
+
+  // Cleanup.
+  gBrowser.removeTab(tab);
+});
+
+/**
+ * Ensure that loading pages from the bfcache invalidates shistory.
+ */
+add_task(async function test_pageshow() {
+  const URL = "data:text/html;charset=utf-8,<h1>first</h1>";
+  const URL2 = "data:text/html;charset=utf-8,<h1>second</h1>";
+
+  // Create a new tab.
+  let tab = BrowserTestUtils.addTab(gBrowser, URL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  // Create a second shistory entry.
+  BrowserTestUtils.startLoadingURIString(browser, URL2);
+  await promiseBrowserLoaded(browser);
+
+  // Wait until shistory changes.
+  let pageShowPromise = BrowserTestUtils.waitForContentEvent(
+    browser,
+    "pageshow",
+    true
+  );
+
+  // Go back to the previous url which is loaded from the bfcache.
+  browser.goBack();
+  await pageShowPromise;
+  is(browser.currentURI.spec, URL, "correct url after going back");
+
+  // Check that loading from bfcache did invalidate shistory.
+  await TabStateFlusher.flush(browser);
+  let { index } = JSON.parse(ss.getTabState(tab));
+  is(index, 1, "first history entry is selected");
+
+  // Cleanup.
+  gBrowser.removeTab(tab);
+});
+
+/**
+ * Ensure that subframe navigation invalidates shistory.
+ */
+add_task(async function test_subframes() {
+  const URL =
+    "data:text/html;charset=utf-8," +
+    "<iframe src=http%3A//example.com/ name=t></iframe>" +
+    "<a id=a1 href=http%3A//example.com/1 target=t>clickme</a>" +
+    "<a id=a2 href=http%3A//example.com/%23section target=t>clickme</a>";
+
+  // Create a new tab.
+  let tab = BrowserTestUtils.addTab(gBrowser, URL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  // Check that we have a single shistory entry.
+  await TabStateFlusher.flush(browser);
+  let { entries } = JSON.parse(ss.getTabState(tab));
+  is(entries.length, 1, "there is one shistory entry");
+  is(entries[0].children.length, 1, "the entry has one child");
+
+  // Navigate the subframe.
+  await SpecialPowers.spawn(browser, [], async function () {
+    content.document.notifyUserGestureActivation();
+    content.document.querySelector("#a1").click();
+  });
+  await promiseBrowserLoaded(
+    browser,
+    false /* wait for subframe load only */,
+    "http://example.com/1"
+  );
+
+  // Check shistory.
+  await TabStateFlusher.flush(browser);
+  ({ entries } = JSON.parse(ss.getTabState(tab)));
+  is(entries.length, 2, "there now are two shistory entries");
+  is(entries[1].children.length, 1, "the second entry has one child");
+
+  // Go back in history.
+  let goneBack = promiseBrowserLoaded(
+    browser,
+    false /* wait for subframe load only */,
+    "http://example.com/"
+  );
+  info("About to go back in history");
+  browser.goBack();
+  await goneBack;
+
+  // Navigate the subframe again.
+  let eventPromise = BrowserTestUtils.waitForContentEvent(
+    browser,
+    "hashchange",
+    true
+  );
+  await SpecialPowers.spawn(browser, [], async function () {
+    content.document.querySelector("#a2").click();
+  });
+  await eventPromise;
+
+  // Check shistory.
+  await TabStateFlusher.flush(browser);
+  ({ entries } = JSON.parse(ss.getTabState(tab)));
+  is(entries.length, 2, "there now are two shistory entries");
+  is(entries[1].children.length, 1, "the second entry has one child");
+
+  // Cleanup.
+  gBrowser.removeTab(tab);
+});
+
+/**
+ * Ensure that navigating from an about page invalidates shistory.
+ */
+add_task(async function test_about_page_navigate() {
+  // Create a new tab.
+  let tab = BrowserTestUtils.addTab(gBrowser, "about:blank");
+  let browser = tab.linkedBrowser;
+  await BrowserTestUtils.browserLoaded(browser, { wantLoad: "about:blank" });
+
+  // Check that we have a single shistory entry.
+  await TabStateFlusher.flush(browser);
+  let { entries } = JSON.parse(ss.getTabState(tab));
+  is(entries.length, 1, "there is one shistory entry");
+  is(entries[0].url, "about:blank", "url is correct");
+
+  // Verify that the title is also recorded.
+  is(entries[0].title, "about:blank", "title is correct");
+
+  BrowserTestUtils.startLoadingURIString(browser, "about:robots");
+  await promiseBrowserLoaded(browser);
+
+  // Check that we have changed the history entry.
+  await TabStateFlusher.flush(browser);
+  ({ entries } = JSON.parse(ss.getTabState(tab)));
+  is(entries.length, 1, "there is one shistory entry");
+  is(entries[0].url, "about:robots", "url is correct");
+
+  // Cleanup.
+  gBrowser.removeTab(tab);
+});
+
+/**
+ * Ensure that history.pushState and history.replaceState invalidate shistory.
+ */
+add_task(async function test_pushstate_replacestate() {
+  // Create a new tab.
+  let tab = BrowserTestUtils.addTab(gBrowser, "http://example.com/1");
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  // Check that we have a single shistory entry.
+  await TabStateFlusher.flush(browser);
+  let { entries } = JSON.parse(ss.getTabState(tab));
+  is(entries.length, 1, "there is one shistory entry");
+  is(entries[0].url, "http://example.com/1", "url is correct");
+
+  await SpecialPowers.spawn(browser, [], async function () {
+    content.window.history.pushState({}, "", "test-entry/");
+  });
+
+  // Check that we have added the history entry.
+  await TabStateFlusher.flush(browser);
+  ({ entries } = JSON.parse(ss.getTabState(tab)));
+  is(entries.length, 2, "there is another shistory entry");
+  is(entries[1].url, "http://example.com/test-entry/", "url is correct");
+
+  await SpecialPowers.spawn(browser, [], async function () {
+    content.window.history.replaceState({}, "", "test-entry2/");
+  });
+
+  // Check that we have modified the history entry.
+  await TabStateFlusher.flush(browser);
+  ({ entries } = JSON.parse(ss.getTabState(tab)));
+  is(entries.length, 2, "there is still two shistory entries");
+  is(
+    entries[1].url,
+    "http://example.com/test-entry/test-entry2/",
+    "url is correct"
+  );
+
+  // Cleanup.
+  gBrowser.removeTab(tab);
+});
+
+/**
+ * Ensure that slow loading subframes will invalidate shistory.
+ */
+add_task(async function test_slow_subframe_load() {
+  const SLOW_URL =
+    "http://mochi.test:8888/browser/browser/components/" +
+    "sessionstore/test/browser_sessionHistory_slow.sjs";
+
+  const URL =
+    "data:text/html;charset=utf-8," +
+    "<frameset cols=50%25,50%25>" +
+    "<frame src='" +
+    SLOW_URL +
+    "'>" +
+    "</frameset>";
+
+  // Add a new tab with a slow loading subframe
+  let tab = BrowserTestUtils.addTab(gBrowser, URL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  await TabStateFlusher.flush(browser);
+  let { entries } = JSON.parse(ss.getTabState(tab));
+
+  // Check the number of children.
+  is(entries.length, 1, "there is one root entry ...");
+  is(entries[0].children.length, 1, "... with one child entries");
+
+  // Check URLs.
+  ok(entries[0].url.startsWith("data:text/html"), "correct root url");
+  is(entries[0].children[0].url, SLOW_URL, "correct url for subframe");
+
+  // Cleanup.
+  gBrowser.removeTab(tab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_sessionHistory_partitionedPrincipalToInherit.js b/src/zen/tests/mochitests/sessionstore/browser_sessionHistory_partitionedPrincipalToInherit.js
new file mode 100644
index 000000000..5caf022d1
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_sessionHistory_partitionedPrincipalToInherit.js
@@ -0,0 +1,151 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_task(async function test_partitioned_principal_to_inherit() {
+  // Create a new tab.
+  let tab = await BrowserTestUtils.openNewForegroundTab(
+    gBrowser,
+    "https://example.com"
+  );
+  let browser = tab.linkedBrowser;
+
+  // Get the last entry in the session history.
+  let sh = browser.browsingContext.sessionHistory;
+  let entry = sh.getEntryAtIndex(sh.count - 1);
+  let partitionedPrincipalToInherit = entry.partitionedPrincipalToInherit;
+
+  // Check that the partitioned principal to inherit is properly set.
+  ok(partitionedPrincipalToInherit, "partitionedPrincipalToInherit is set");
+  is(
+    partitionedPrincipalToInherit.originAttributes.partitionKey,
+    "(https,example.com)",
+    "correct partitionKey"
+  );
+
+  BrowserTestUtils.removeTab(tab);
+});
+
+add_task(async function test_partitioned_Principal_to_inherit_in_iframe() {
+  // Create a new tab.
+  let tab = await BrowserTestUtils.openNewForegroundTab(
+    gBrowser,
+    "https://example.com"
+  );
+  let browser = tab.linkedBrowser;
+
+  // Load a same-origin iframe
+  await SpecialPowers.spawn(browser, [], async _ => {
+    let iframe = content.document.createElement("iframe");
+    iframe.src = "https://example.com";
+
+    await new content.Promise(resolve => {
+      iframe.onload = resolve;
+      content.document.body.appendChild(iframe);
+    });
+  });
+
+  // Get the last child entry in the session history for the same-origin iframe.
+  let sh = browser.browsingContext.sessionHistory;
+  let entry = sh.getEntryAtIndex(sh.count - 1);
+  let childEntry = entry.GetChildAt(entry.childCount - 1);
+  let partitionedPrincipalToInherit = childEntry.partitionedPrincipalToInherit;
+
+  // Check that the partitioned principal to inherit is properly set.
+  ok(partitionedPrincipalToInherit, "partitionedPrincipalToInherit is set");
+  is(
+    partitionedPrincipalToInherit.originNoSuffix,
+    "https://example.com",
+    "correct originNoSuffix in the same-origin iframe"
+  );
+  is(
+    partitionedPrincipalToInherit.originAttributes.partitionKey,
+    "(https,example.com)",
+    "correct partitionKey in the same-origin iframe"
+  );
+
+  // Load a cross-site iframe.
+  await SpecialPowers.spawn(browser, [], async _ => {
+    let iframe = content.document.createElement("iframe");
+    iframe.src = "https://example.net";
+
+    await new content.Promise(resolve => {
+      iframe.onload = resolve;
+      content.document.body.appendChild(iframe);
+    });
+  });
+
+  // Get the last child entry in the session history for the cross-site iframe.
+  entry = sh.getEntryAtIndex(sh.count - 1);
+  childEntry = entry.GetChildAt(entry.childCount - 1);
+  partitionedPrincipalToInherit = childEntry.partitionedPrincipalToInherit;
+
+  // Check that the partitioned principal to inherit is properly set.
+  ok(partitionedPrincipalToInherit, "partitionedPrincipalToInherit is set");
+  is(
+    partitionedPrincipalToInherit.originNoSuffix,
+    "https://example.net",
+    "correct originNoSuffix in the cross-site iframe"
+  );
+  is(
+    partitionedPrincipalToInherit.originAttributes.partitionKey,
+    "(https,example.com)",
+    "correct partitionKey in the cross-site iframe"
+  );
+
+  BrowserTestUtils.removeTab(tab);
+});
+
+add_task(async function test_partitioned_Principal_to_inherit_in_ABA_iframe() {
+  // Create a new tab.
+  let tab = await BrowserTestUtils.openNewForegroundTab(
+    gBrowser,
+    "https://example.com"
+  );
+  let browser = tab.linkedBrowser;
+
+  // Load a ABA iframe
+  await SpecialPowers.spawn(browser, [], async () => {
+    let iframe = content.document.createElement("iframe");
+    iframe.src = "https://example.net";
+
+    await new content.Promise(resolve => {
+      iframe.onload = resolve;
+      content.document.body.appendChild(iframe);
+    });
+
+    await SpecialPowers.spawn(iframe, [], async () => {
+      let nestedIframe = content.document.createElement("iframe");
+      nestedIframe.src = "https://example.com";
+
+      await new content.Promise(resolve => {
+        nestedIframe.onload = resolve;
+        content.document.body.appendChild(nestedIframe);
+      });
+    });
+  });
+
+  // Get the last child entry in the session history for the same-origin iframe.
+  let sh = browser.browsingContext.sessionHistory;
+  let entry = sh.getEntryAtIndex(sh.count - 1);
+  let childEntry = entry.GetChildAt(entry.childCount - 1);
+  let nestedChildEntry = childEntry.GetChildAt(childEntry.childCount - 1);
+  let partitionedPrincipalToInherit =
+    nestedChildEntry.partitionedPrincipalToInherit;
+
+  // Check that the partitioned principal to inherit is properly set.
+  ok(partitionedPrincipalToInherit, "partitionedPrincipalToInherit is set");
+  is(
+    partitionedPrincipalToInherit.originNoSuffix,
+    "https://example.com",
+    "correct originNoSuffix in the ABA iframe"
+  );
+  is(
+    partitionedPrincipalToInherit.originAttributes.partitionKey,
+    "(https,example.com,f)",
+    "correct partitionKey in the ABA iframe"
+  );
+
+  BrowserTestUtils.removeTab(tab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_sessionHistory_slow.sjs b/src/zen/tests/mochitests/sessionstore/browser_sessionHistory_slow.sjs
new file mode 100644
index 000000000..abb1dee82
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_sessionHistory_slow.sjs
@@ -0,0 +1,22 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const DELAY_MS = "2000";
+
+let timer;
+
+function handleRequest(req, resp) {
+  resp.processAsync();
+  resp.setHeader("Cache-Control", "no-cache", false);
+  resp.setHeader("Content-Type", "text/html;charset=utf-8", false);
+
+  timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
+  timer.init(
+    () => {
+      resp.write("hi");
+      resp.finish();
+    },
+    DELAY_MS,
+    Ci.nsITimer.TYPE_ONE_SHOT
+  );
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_sessionStorage.html b/src/zen/tests/mochitests/sessionstore/browser_sessionStorage.html
new file mode 100644
index 000000000..afc1cf1de
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_sessionStorage.html
@@ -0,0 +1,35 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="utf-8">
+    <title>browser_sessionStorage.html</title>
+  </head>
+  <body>
+    <iframe id="iframe"></iframe>
+
+    <script type="text/javascript">
+      let isOuter = window == window.top;
+      let args = window.location.search.slice(1).split("&");
+      let rand = args[0];
+
+      if (isOuter) {
+        let iframe = document.getElementById("iframe");
+        let isSecure = args.indexOf("secure") > -1;
+        let scheme = isSecure ? "https" : "http";
+        // WARNING This iframe might not finish loading before the top level document does
+        // See intermittent bug 1775609, bug 2001322
+        iframe.setAttribute("src", scheme + "://example.com" + location.pathname + "?" + rand);
+      }
+
+      if (sessionStorage.length === 0) {
+        sessionStorage.test = (isOuter ? "outer" : "inner") + "-value-" + rand;
+        document.title = sessionStorage.test;
+      }
+
+      // Log the load so that it becomes more obvious if intermittent failures reoccur
+      onload = () => {
+        dump(`browser_sessionStorage.html ${isOuter ? 'TOP LEVEL' : 'IFRAME'} loaded\n`);
+      }
+    </script>
+  </body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_sessionStorage.js b/src/zen/tests/mochitests/sessionstore/browser_sessionStorage.js
new file mode 100644
index 000000000..43af6c47e
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_sessionStorage.js
@@ -0,0 +1,308 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const RAND = Math.random();
+const URL =
+  "http://mochi.test:8888/browser/" +
+  "browser/components/sessionstore/test/browser_sessionStorage.html" +
+  "?" +
+  RAND;
+
+const HAS_FIRST_PARTY_DOMAIN = [
+  Ci.nsICookieService.BEHAVIOR_PARTITION_FOREIGN,
+].includes(Services.prefs.getIntPref("network.cookie.cookieBehavior"));
+const OUTER_ORIGIN = "http://mochi.test:8888";
+const FIRST_PARTY_DOMAIN = escape("(http,mochi.test)");
+const INNER_ORIGIN = HAS_FIRST_PARTY_DOMAIN
+  ? `http://example.com^partitionKey=${FIRST_PARTY_DOMAIN}`
+  : "http://example.com";
+const SECURE_INNER_ORIGIN = HAS_FIRST_PARTY_DOMAIN
+  ? `https://example.com^partitionKey=${FIRST_PARTY_DOMAIN}`
+  : "https://example.com";
+
+const OUTER_VALUE = "outer-value-" + RAND;
+const INNER_VALUE = "inner-value-" + RAND;
+
+/**
+ * This test ensures that setting, modifying and restoring sessionStorage data
+ * works as expected.
+ */
+add_task(async function session_storage() {
+  let tab = BrowserTestUtils.addTab(gBrowser, URL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  // Flush to make sure chrome received all data.
+  await TabStateFlusher.flush(browser);
+
+  let { storage } = JSON.parse(ss.getTabState(tab));
+  is(
+    storage[INNER_ORIGIN].test,
+    INNER_VALUE,
+    "sessionStorage data for example.com has been serialized correctly"
+  );
+  is(
+    storage[OUTER_ORIGIN].test,
+    OUTER_VALUE,
+    "sessionStorage data for mochi.test has been serialized correctly"
+  );
+
+  // Ensure that modifying sessionStore values works for the inner frame only.
+  await modifySessionStorage(browser, { test: "modified1" }, { frameIndex: 0 });
+  await TabStateFlusher.flush(browser);
+
+  ({ storage } = JSON.parse(ss.getTabState(tab)));
+  is(
+    storage[INNER_ORIGIN].test,
+    "modified1",
+    "sessionStorage data for example.com has been serialized correctly"
+  );
+  is(
+    storage[OUTER_ORIGIN].test,
+    OUTER_VALUE,
+    "sessionStorage data for mochi.test has been serialized correctly"
+  );
+
+  // Ensure that modifying sessionStore values works for both frames.
+  await modifySessionStorage(browser, { test: "modified" });
+  await modifySessionStorage(browser, { test: "modified2" }, { frameIndex: 0 });
+  await TabStateFlusher.flush(browser);
+
+  ({ storage } = JSON.parse(ss.getTabState(tab)));
+  is(
+    storage[INNER_ORIGIN].test,
+    "modified2",
+    "sessionStorage data for example.com has been serialized correctly"
+  );
+  is(
+    storage[OUTER_ORIGIN].test,
+    "modified",
+    "sessionStorage data for mochi.test has been serialized correctly"
+  );
+
+  // Test that duplicating a tab works.
+  let tab2 = gBrowser.duplicateTab(tab);
+  let browser2 = tab2.linkedBrowser;
+  // See bug 2001322, need to wait for iframe of tab2 to finish loading
+  const subframeLoaded = BrowserTestUtils.browserLoaded(tab2.linkedBrowser, {
+    includeSubFrames: true,
+    wantLoad: url => url.startsWith("http://example.com"),
+  });
+  await Promise.all([promiseTabRestored(tab2), subframeLoaded]);
+
+  // Flush to make sure chrome received all data.
+  await TabStateFlusher.flush(browser2);
+
+  ({ storage } = JSON.parse(ss.getTabState(tab2)));
+  is(
+    storage[INNER_ORIGIN].test,
+    "modified2",
+    "sessionStorage data for example.com has been duplicated correctly"
+  );
+  is(
+    storage[OUTER_ORIGIN].test,
+    "modified",
+    "sessionStorage data for mochi.test has been duplicated correctly"
+  );
+
+  // Ensure that the content script retains restored data
+  // (by e.g. duplicateTab) and sends it along with new data.
+  await modifySessionStorage(browser2, { test: "modified3" });
+  await TabStateFlusher.flush(browser2);
+
+  ({ storage } = JSON.parse(ss.getTabState(tab2)));
+  is(
+    storage[INNER_ORIGIN].test,
+    "modified2",
+    "sessionStorage data for example.com has been duplicated correctly"
+  );
+  is(
+    storage[OUTER_ORIGIN].test,
+    "modified3",
+    "sessionStorage data for mochi.test has been duplicated correctly"
+  );
+
+  // Check that loading a new URL discards data.
+  BrowserTestUtils.startLoadingURIString(browser2, "http://mochi.test:8888/");
+  await promiseBrowserLoaded(browser2);
+  await TabStateFlusher.flush(browser2);
+
+  ({ storage } = JSON.parse(ss.getTabState(tab2)));
+  is(
+    storage[OUTER_ORIGIN].test,
+    "modified3",
+    "navigating retains correct storage data"
+  );
+
+  is(
+    storage[INNER_ORIGIN].test,
+    "modified2",
+    "sessionStorage data for example.com wasn't discarded after top-level same-site navigation"
+  );
+
+  // Test that clearing the data in the first tab works properly within
+  // the subframe
+  await modifySessionStorage(browser, {}, { frameIndex: 0 });
+  await TabStateFlusher.flush(browser);
+  ({ storage } = JSON.parse(ss.getTabState(tab)));
+  is(
+    storage[INNER_ORIGIN],
+    undefined,
+    "sessionStorage data for example.com has been cleared correctly"
+  );
+
+  // Test that clearing the data in the first tab works properly within
+  // the top-level frame
+  await modifySessionStorage(browser, {});
+  await TabStateFlusher.flush(browser);
+  ({ storage } = JSON.parse(ss.getTabState(tab)));
+  ok(
+    storage === null || storage === undefined,
+    "sessionStorage data for the entire tab has been cleared correctly"
+  );
+
+  // Clean up.
+  BrowserTestUtils.removeTab(tab);
+  BrowserTestUtils.removeTab(tab2);
+});
+
+/**
+ * This test ensures that purging domain data also purges data from the
+ * sessionStorage data collected for tabs.
+ */
+add_task(async function purge_domain() {
+  let tab = BrowserTestUtils.addTab(gBrowser, URL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  // Purge data for "mochi.test".
+  await purgeDomainData(browser, "mochi.test");
+
+  // Flush to make sure chrome received all data.
+  await TabStateFlusher.flush(browser);
+
+  let { storage } = JSON.parse(ss.getTabState(tab));
+  ok(
+    !storage[OUTER_ORIGIN],
+    "sessionStorage data for mochi.test has been purged"
+  );
+  is(
+    storage[INNER_ORIGIN].test,
+    INNER_VALUE,
+    "sessionStorage data for example.com has been preserved"
+  );
+
+  BrowserTestUtils.removeTab(tab);
+});
+
+/**
+ * This test ensures that collecting sessionStorage data respects the privacy
+ * levels as set by the user.
+ */
+add_task(async function respect_privacy_level() {
+  let tab = BrowserTestUtils.addTab(gBrowser, URL + "&secure");
+  await promiseBrowserLoaded(tab.linkedBrowser);
+  await TabStateFlusher.flush(tab.linkedBrowser);
+  await promiseRemoveTabAndSessionState(tab);
+
+  let [
+    {
+      state: { storage },
+    },
+  ] = ss.getClosedTabDataForWindow(window);
+  is(
+    storage[OUTER_ORIGIN].test,
+    OUTER_VALUE,
+    "http sessionStorage data has been saved"
+  );
+  is(
+    storage[SECURE_INNER_ORIGIN].test,
+    INNER_VALUE,
+    "https sessionStorage data has been saved"
+  );
+
+  // Disable saving data for encrypted sites.
+  Services.prefs.setIntPref("browser.sessionstore.privacy_level", 1);
+
+  tab = BrowserTestUtils.addTab(gBrowser, URL + "&secure");
+  await promiseBrowserLoaded(tab.linkedBrowser);
+  await TabStateFlusher.flush(tab.linkedBrowser);
+  await promiseRemoveTabAndSessionState(tab);
+
+  [
+    {
+      state: { storage },
+    },
+  ] = ss.getClosedTabDataForWindow(window);
+  is(
+    storage[OUTER_ORIGIN].test,
+    OUTER_VALUE,
+    "http sessionStorage data has been saved"
+  );
+  ok(
+    !storage[SECURE_INNER_ORIGIN],
+    "https sessionStorage data has *not* been saved"
+  );
+
+  // Disable saving data for any site.
+  Services.prefs.setIntPref("browser.sessionstore.privacy_level", 2);
+
+  // Check that duplicating a tab copies all private data.
+  tab = BrowserTestUtils.addTab(gBrowser, URL + "&secure");
+  await promiseBrowserLoaded(tab.linkedBrowser);
+  let tab2 = gBrowser.duplicateTab(tab);
+  // See bug 2001322, need to wait for iframe of tab2 to finish loading
+  const subframeLoaded = BrowserTestUtils.browserLoaded(tab2.linkedBrowser, {
+    includeSubFrames: true,
+    wantLoad: url => url.startsWith("https://example.com"),
+  });
+  await Promise.all([promiseTabRestored(tab2), subframeLoaded]);
+  await promiseRemoveTabAndSessionState(tab);
+
+  // With privacy_level=2 the |tab| shouldn't have any sessionStorage data.
+  [
+    {
+      state: { storage },
+    },
+  ] = ss.getClosedTabDataForWindow(window);
+  ok(!storage, "sessionStorage data has *not* been saved");
+
+  // Remove all closed tabs before continuing with the next test.
+  // As Date.now() isn't monotonic we might sometimes check
+  // the wrong closedTabData entry.
+  forgetClosedTabs(window);
+
+  // Restore the default privacy level and close the duplicated tab.
+  Services.prefs.clearUserPref("browser.sessionstore.privacy_level");
+  await promiseRemoveTabAndSessionState(tab2);
+
+  // With privacy_level=0 the duplicated |tab2| should persist all data.
+  [
+    {
+      state: { storage },
+    },
+  ] = ss.getClosedTabDataForWindow(window);
+  is(
+    storage[OUTER_ORIGIN].test,
+    OUTER_VALUE,
+    "http sessionStorage data has been saved"
+  );
+  is(
+    storage[SECURE_INNER_ORIGIN].test,
+    INNER_VALUE,
+    "https sessionStorage data has been saved"
+  );
+});
+
+function purgeDomainData(browser, domain) {
+  return new Promise(resolve => {
+    Services.clearData.deleteDataFromHost(
+      domain,
+      true,
+      Services.clearData.CLEAR_HISTORY,
+      resolve
+    );
+  });
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_sessionStorage_size.js b/src/zen/tests/mochitests/sessionstore/browser_sessionStorage_size.js
new file mode 100644
index 000000000..104548281
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_sessionStorage_size.js
@@ -0,0 +1,34 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const RAND = Math.random();
+const URL =
+  "http://mochi.test:8888/browser/" +
+  "browser/components/sessionstore/test/browser_sessionStorage.html" +
+  "?" +
+  RAND;
+
+const OUTER_VALUE = "outer-value-" + RAND;
+
+// Lower the size limit for DOM Storage content. Check that DOM Storage
+// is not updated, but that other things remain updated.
+add_task(async function test_large_content() {
+  Services.prefs.setIntPref("browser.sessionstore.dom_storage_limit", 5);
+
+  let tab = BrowserTestUtils.addTab(gBrowser, URL);
+  let browser = tab.linkedBrowser;
+  await promiseBrowserLoaded(browser);
+
+  // Flush to make sure chrome received all data.
+  await TabStateFlusher.flush(browser);
+
+  let state = JSON.parse(ss.getTabState(tab));
+  info(JSON.stringify(state, null, "\t"));
+  Assert.equal(state.storage, null, "We have no storage for the tab");
+  Assert.equal(state.entries[0].title, OUTER_VALUE);
+  BrowserTestUtils.removeTab(tab);
+
+  Services.prefs.clearUserPref("browser.sessionstore.dom_storage_limit");
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_sessionStoreContainer.js b/src/zen/tests/mochitests/sessionstore/browser_sessionStoreContainer.js
new file mode 100644
index 000000000..c656df7ec
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_sessionStoreContainer.js
@@ -0,0 +1,166 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+add_task(async function () {
+  for (let i = 0; i < 3; ++i) {
+    let tab = BrowserTestUtils.addTab(gBrowser, "http://example.com/", {
+      userContextId: i,
+    });
+    let browser = tab.linkedBrowser;
+
+    await promiseBrowserLoaded(browser);
+
+    let tab2 = gBrowser.duplicateTab(tab);
+    Assert.equal(tab2.getAttribute("usercontextid") || "", i);
+    let browser2 = tab2.linkedBrowser;
+    await promiseTabRestored(tab2);
+
+    await SpecialPowers.spawn(
+      browser2,
+      [{ expectedId: i }],
+      async function (args) {
+        let loadContext = docShell.QueryInterface(Ci.nsILoadContext);
+        Assert.equal(
+          loadContext.originAttributes.userContextId,
+          args.expectedId,
+          "The docShell has the correct userContextId"
+        );
+      }
+    );
+
+    BrowserTestUtils.removeTab(tab);
+    BrowserTestUtils.removeTab(tab2);
+  }
+});
+
+add_task(async function () {
+  let tab = BrowserTestUtils.addTab(gBrowser, "http://example.com/", {
+    userContextId: 1,
+  });
+  let browser = tab.linkedBrowser;
+
+  await promiseBrowserLoaded(browser);
+
+  gBrowser.selectedTab = tab;
+
+  let tab2 = gBrowser.duplicateTab(tab);
+  let browser2 = tab2.linkedBrowser;
+  await promiseTabRestored(tab2);
+
+  await SpecialPowers.spawn(
+    browser2,
+    [{ expectedId: 1 }],
+    async function (args) {
+      Assert.equal(
+        docShell.getOriginAttributes().userContextId,
+        args.expectedId,
+        "The docShell has the correct userContextId"
+      );
+    }
+  );
+
+  BrowserTestUtils.removeTab(tab);
+  BrowserTestUtils.removeTab(tab2);
+});
+
+add_task(async function () {
+  let tab = BrowserTestUtils.addTab(gBrowser, "http://example.com/", {
+    userContextId: 1,
+  });
+  let browser = tab.linkedBrowser;
+
+  await promiseBrowserLoaded(browser);
+
+  gBrowser.removeTab(tab);
+
+  let tab2 = ss.undoCloseTab(window, 0);
+  Assert.equal(tab2.getAttribute("usercontextid"), 1);
+  await promiseTabRestored(tab2);
+  await SpecialPowers.spawn(
+    tab2.linkedBrowser,
+    [{ expectedId: 1 }],
+    async function (args) {
+      Assert.equal(
+        docShell.getOriginAttributes().userContextId,
+        args.expectedId,
+        "The docShell has the correct userContextId"
+      );
+    }
+  );
+
+  BrowserTestUtils.removeTab(tab2);
+});
+
+// Opens "uri" in a new tab with the provided userContextId and focuses it.
+// Returns the newly opened tab.
+async function openTabInUserContext(userContextId) {
+  // Open the tab in the correct userContextId.
+  let tab = BrowserTestUtils.addTab(gBrowser, "http://example.com", {
+    userContextId,
+  });
+
+  // Select tab and make sure its browser is focused.
+  gBrowser.selectedTab = tab;
+  tab.documentGlobal.focus();
+
+  let browser = gBrowser.getBrowserForTab(tab);
+  await BrowserTestUtils.browserLoaded(browser);
+  return { tab, browser };
+}
+
+function waitForNewCookie() {
+  return new Promise(resolve => {
+    Services.obs.addObserver(function observer(subj, topic) {
+      let notification = subj.QueryInterface(Ci.nsICookieNotification);
+      if (notification.action == Ci.nsICookieNotification.COOKIE_ADDED) {
+        Services.obs.removeObserver(observer, topic);
+        resolve();
+      }
+    }, "session-cookie-changed");
+  });
+}
+
+add_task(async function test() {
+  const USER_CONTEXTS = ["default", "personal", "work"];
+
+  // Make sure userContext is enabled.
+  await SpecialPowers.pushPrefEnv({
+    set: [["privacy.userContext.enabled", true]],
+  });
+
+  Services.cookies.removeAll();
+
+  for (let userContextId of Object.keys(USER_CONTEXTS)) {
+    // Load the page in 3 different contexts and set a cookie
+    // which should only be visible in that context.
+    let cookie = USER_CONTEXTS[userContextId];
+
+    // Open our tab in the given user context.
+    let { tab, browser } = await openTabInUserContext(userContextId);
+
+    await Promise.all([
+      waitForNewCookie(),
+      SpecialPowers.spawn(
+        browser,
+        [cookie],
+        passedCookie => (content.document.cookie = passedCookie)
+      ),
+    ]);
+
+    // Ensure the tab's session history is up-to-date.
+    await TabStateFlusher.flush(browser);
+
+    // Remove the tab.
+    gBrowser.removeTab(tab);
+  }
+
+  let state = JSON.parse(SessionStore.getBrowserState());
+  is(
+    state.cookies.length,
+    USER_CONTEXTS.length,
+    "session restore should have each container's cookie"
+  );
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_should_restore_tab.js b/src/zen/tests/mochitests/sessionstore/browser_should_restore_tab.js
new file mode 100644
index 000000000..07c699c31
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_should_restore_tab.js
@@ -0,0 +1,139 @@
+const NOTIFY_CLOSED_OBJECTS_CHANGED = "sessionstore-closed-objects-changed";
+
+add_setup(async () => {
+  registerCleanupFunction(async () => {
+    Services.obs.notifyObservers(null, "browser:purge-session-history");
+  });
+});
+
+async function check_tab_close_notification(openedTab, expectNotification) {
+  let tabUrl = openedTab.linkedBrowser.currentURI.spec;
+  let win = openedTab.documentGlobal;
+  let initialTabCount = SessionStore.getClosedTabCountForWindow(win);
+
+  let tabClosed = BrowserTestUtils.waitForTabClosing(openedTab);
+  let notified = false;
+  function topicObserver() {
+    notified = true;
+  }
+  Services.obs.addObserver(topicObserver, NOTIFY_CLOSED_OBJECTS_CHANGED);
+
+  BrowserTestUtils.removeTab(openedTab);
+  await tabClosed;
+  // SessionStore does a setTimeout(notify, 0) to notifyObservers when it handles TabClose
+  // We need to wait long enough to be confident the observer would have been notified
+  // if it was going to be.
+  let ticks = 0;
+  await TestUtils.waitForCondition(() => {
+    return ++ticks > 1;
+  });
+
+  Services.obs.removeObserver(topicObserver, NOTIFY_CLOSED_OBJECTS_CHANGED);
+  if (expectNotification) {
+    Assert.ok(
+      notified,
+      `Expected ${NOTIFY_CLOSED_OBJECTS_CHANGED} when the ${tabUrl} tab closed`
+    );
+    Assert.equal(
+      SessionStore.getClosedTabCountForWindow(win),
+      initialTabCount + 1,
+      "Expected closed tab count to have incremented"
+    );
+  } else {
+    Assert.ok(
+      !notified,
+      `Expected no ${NOTIFY_CLOSED_OBJECTS_CHANGED} when the ${tabUrl} tab closed`
+    );
+    Assert.equal(
+      SessionStore.getClosedTabCountForWindow(win),
+      initialTabCount,
+      "Expected closed tab count to have not changed"
+    );
+  }
+}
+
+add_task(async function test_control_case() {
+  let win = window;
+  let tabOpenedAndSwitchedTo = BrowserTestUtils.switchTab(
+    win.gBrowser,
+    () => {}
+  );
+  let tab = await BrowserTestUtils.openNewForegroundTab(
+    win.gBrowser,
+    "https://example.com/"
+  );
+  await tabOpenedAndSwitchedTo;
+  await check_tab_close_notification(tab, true);
+});
+
+add_task(async function test_about_new_tab() {
+  let win = window;
+  let tabOpenedAndSwitchedTo = BrowserTestUtils.switchTab(
+    win.gBrowser,
+    () => {}
+  );
+  // This opens about:newtab:
+  win.BrowserCommands.openTab();
+  let tab = await tabOpenedAndSwitchedTo;
+  await check_tab_close_notification(tab, false);
+});
+
+add_task(async function test_about_home() {
+  let win = window;
+  let tabOpenedAndSwitchedTo = BrowserTestUtils.switchTab(
+    win.gBrowser,
+    () => {}
+  );
+  let tab = await BrowserTestUtils.openNewForegroundTab(
+    win.gBrowser,
+    "about:home"
+  );
+  await tabOpenedAndSwitchedTo;
+  await check_tab_close_notification(tab, false);
+});
+
+add_task(async function test_navigated_about_home() {
+  let win = window;
+  let tabOpenedAndSwitchedTo = BrowserTestUtils.switchTab(
+    win.gBrowser,
+    () => {}
+  );
+  let tab = await BrowserTestUtils.openNewForegroundTab(
+    win.gBrowser,
+    "https://example.com/"
+  );
+  await tabOpenedAndSwitchedTo;
+  BrowserTestUtils.startLoadingURIString(tab.linkedBrowser, "about:home");
+  await BrowserTestUtils.browserLoaded(tab.linkedBrowser);
+  // even if we end up on an ignorable URL,
+  // if there's meaningful history, we should save this tab
+  await check_tab_close_notification(tab, true);
+});
+
+add_task(async function test_about_blank() {
+  let win = window;
+  let tabOpenedAndSwitchedTo = BrowserTestUtils.switchTab(
+    win.gBrowser,
+    () => {}
+  );
+  let tab = await BrowserTestUtils.openNewForegroundTab(
+    win.gBrowser,
+    "about:blank"
+  );
+  await tabOpenedAndSwitchedTo;
+  await check_tab_close_notification(tab, false);
+});
+
+add_task(async function test_about_privatebrowsing() {
+  let win = window;
+  let tabOpenedAndSwitchedTo = BrowserTestUtils.switchTab(
+    win.gBrowser,
+    () => {}
+  );
+  let tab = await BrowserTestUtils.openNewForegroundTab(
+    win.gBrowser,
+    "about:privatebrowsing"
+  );
+  await tabOpenedAndSwitchedTo;
+  await check_tab_close_notification(tab, false);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_sizemodeBeforeMinimized.js b/src/zen/tests/mochitests/sessionstore/browser_sizemodeBeforeMinimized.js
new file mode 100644
index 000000000..a832e71bc
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_sizemodeBeforeMinimized.js
@@ -0,0 +1,44 @@
+add_task(async function test() {
+  // Test for bugfix 384278. Confirms that sizemodeBeforeMinimized is set properly when window state is saved.
+  let win = await BrowserTestUtils.openNewBrowserWindow();
+
+  async function changeSizeMode(mode) {
+    let promise = BrowserTestUtils.waitForEvent(win, "sizemodechange");
+    win[mode]();
+    await promise;
+  }
+
+  function checkCurrentState(sizemodeBeforeMinimized) {
+    let state = ss.getWindowState(win);
+    let winState = state.windows[0];
+    is(
+      winState.sizemodeBeforeMinimized,
+      sizemodeBeforeMinimized,
+      "sizemodeBeforeMinimized should match"
+    );
+  }
+
+  // Note: Uses ss.getWindowState(win); as a more time efficient alternative to forceSaveState(); (causing timeouts).
+  // Simulates FF restart.
+
+  if (win.windowState != win.STATE_NORMAL) {
+    await changeSizeMode("restore");
+  }
+  ss.getWindowState(win);
+  await changeSizeMode("minimize");
+  checkCurrentState("normal");
+
+  // Need to create new window or test will timeout on linux.
+  await BrowserTestUtils.closeWindow(win);
+  win = await BrowserTestUtils.openNewBrowserWindow();
+
+  if (win.windowState != win.STATE_MAXIMIZED) {
+    await changeSizeMode("maximize");
+  }
+  ss.getWindowState(win);
+  await changeSizeMode("minimize");
+  checkCurrentState("maximized");
+
+  // Clean up.
+  await BrowserTestUtils.closeWindow(win);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_speculative_connect.html b/src/zen/tests/mochitests/sessionstore/browser_speculative_connect.html
new file mode 100644
index 000000000..a0fb88e0a
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_speculative_connect.html
@@ -0,0 +1,8 @@
+<html>
+<header>
+  <title>Dummy html page to test speculative connect</title>
+</header>
+<body>
+  Hello Speculative Connect
+</body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/browser_speculative_connect.js b/src/zen/tests/mochitests/sessionstore/browser_speculative_connect.js
new file mode 100644
index 000000000..01d2d0b61
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_speculative_connect.js
@@ -0,0 +1,145 @@
+const TEST_URLS = [
+  "about:buildconfig",
+  "http://mochi.test:8888/browser/browser/components/sessionstore/test/browser_speculative_connect.html",
+  "",
+];
+
+/**
+ * This will open tabs in browser. This will also make the last tab
+ * inserted to be the selected tab.
+ */
+async function openTabs(win) {
+  for (let i = 0; i < TEST_URLS.length; ++i) {
+    await BrowserTestUtils.openNewForegroundTab(win.gBrowser, TEST_URLS[i]);
+  }
+}
+
+add_task(async function speculative_connect_restore_on_demand() {
+  Services.prefs.setBoolPref("browser.sessionstore.restore_on_demand", true);
+  is(
+    Services.prefs.getBoolPref("browser.sessionstore.restore_on_demand"),
+    true,
+    "We're restoring on demand"
+  );
+  forgetClosedWindows();
+
+  // Open a new window and populate with tabs.
+  let win = await promiseNewWindowLoaded();
+  await openTabs(win);
+
+  // Close the window.
+  await BrowserTestUtils.closeWindow(win);
+
+  // Reopen a window.
+  let newWin = SessionWindowUI.undoCloseWindow(0);
+  // Make sure we wait until this window is restored.
+  await promiseWindowRestored(newWin);
+
+  let tabs = newWin.gBrowser.tabs;
+  is(tabs.length, TEST_URLS.length + 1, "Restored right number of tabs");
+
+  let e = new MouseEvent("mouseover");
+
+  // First tab should be ignored, since it's the default blank tab when we open a new window.
+
+  // Trigger a mouse enter on second tab.
+  tabs[1].dispatchEvent(e);
+  ok(
+    !tabs[1].__test_connection_prepared,
+    "Second tab doesn't have a connection prepared"
+  );
+  is(tabs[1].__test_connection_url, TEST_URLS[0], "Second tab has correct url");
+  ok(
+    SessionStore.getLazyTabValue(tabs[1], "connectionPrepared"),
+    "Second tab should have connectionPrepared flag after hovered"
+  );
+
+  // Trigger a mouse enter on third tab.
+  tabs[2].dispatchEvent(e);
+  ok(tabs[2].__test_connection_prepared, "Third tab has a connection prepared");
+  is(tabs[2].__test_connection_url, TEST_URLS[1], "Third tab has correct url");
+  ok(
+    SessionStore.getLazyTabValue(tabs[2], "connectionPrepared"),
+    "Third tab should have connectionPrepared flag after hovered"
+  );
+
+  // Last tab is the previously selected tab.
+  tabs[3].dispatchEvent(e);
+  is(
+    SessionStore.getLazyTabValue(tabs[3], "connectionPrepared"),
+    undefined,
+    "Previous selected tab shouldn't have connectionPrepared flag"
+  );
+  is(
+    tabs[3].__test_connection_prepared,
+    undefined,
+    "Previous selected tab should not have a connection prepared"
+  );
+  is(
+    tabs[3].__test_connection_url,
+    undefined,
+    "Previous selected tab should not have a connection prepared"
+  );
+
+  await BrowserTestUtils.closeWindow(newWin);
+});
+
+add_task(async function speculative_connect_restore_automatically() {
+  Services.prefs.setBoolPref("browser.sessionstore.restore_on_demand", false);
+  is(
+    Services.prefs.getBoolPref("browser.sessionstore.restore_on_demand"),
+    false,
+    "We're restoring automatically"
+  );
+  forgetClosedWindows();
+
+  // Open a new window and populate with tabs.
+  let win = await promiseNewWindowLoaded();
+  await openTabs(win);
+
+  // Close the window.
+  await BrowserTestUtils.closeWindow(win);
+
+  // Reopen a window.
+  let newWin = SessionWindowUI.undoCloseWindow(0);
+  // Make sure we wait until this window is restored.
+  await promiseWindowRestored(newWin);
+
+  let tabs = newWin.gBrowser.tabs;
+  is(tabs.length, TEST_URLS.length + 1, "Restored right number of tabs");
+
+  // First tab is ignored, since it's the default tab open when we open new window
+
+  // Second tab.
+  ok(
+    !tabs[1].__test_connection_prepared,
+    "Second tab doesn't have a connection prepared"
+  );
+  is(
+    tabs[1].__test_connection_url,
+    TEST_URLS[0],
+    "Second tab has correct host url"
+  );
+
+  // Third tab.
+  ok(tabs[2].__test_connection_prepared, "Third tab has a connection prepared");
+  is(
+    tabs[2].__test_connection_url,
+    TEST_URLS[1],
+    "Third tab has correct host url"
+  );
+
+  // Last tab is the previously selected tab.
+  is(
+    tabs[3].__test_connection_prepared,
+    undefined,
+    "Selected tab should not have a connection prepared"
+  );
+  is(
+    tabs[3].__test_connection_url,
+    undefined,
+    "Selected tab should not have a connection prepared"
+  );
+
+  await BrowserTestUtils.closeWindow(newWin);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_splitview_integer_ids.js b/src/zen/tests/mochitests/sessionstore/browser_splitview_integer_ids.js
new file mode 100644
index 000000000..4173f6d63
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_splitview_integer_ids.js
@@ -0,0 +1,178 @@
+/* Any copyright is dedicated to the Public Domain.
+   https://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const ORIG_STATE = SessionStore.getBrowserState();
+
+registerCleanupFunction(async () => {
+  await SessionStoreTestUtils.promiseBrowserState(ORIG_STATE);
+});
+
+add_task(async function test_fresh_session_sequential_integer_ids() {
+  SessionStore.resetNextClosedId();
+
+  let tab1 = gBrowser.tabs[0];
+  let tab2 = BrowserTestUtils.addTab(gBrowser, "about:robots");
+  await BrowserTestUtils.browserLoaded(tab2.linkedBrowser);
+
+  let splitview1 = gBrowser.addTabSplitView([tab1, tab2]);
+
+  Assert.strictEqual(
+    typeof splitview1.splitViewId,
+    "number",
+    "splitViewId should be a number"
+  );
+  Assert.strictEqual(
+    splitview1.splitViewId,
+    1,
+    "First split view ID should be 1"
+  );
+
+  let tab3 = BrowserTestUtils.addTab(gBrowser, "about:mozilla");
+  let tab4 = BrowserTestUtils.addTab(gBrowser, "about:about");
+  await Promise.all([
+    BrowserTestUtils.browserLoaded(tab3.linkedBrowser),
+    BrowserTestUtils.browserLoaded(tab4.linkedBrowser),
+  ]);
+
+  let splitview2 = gBrowser.addTabSplitView([tab3, tab4]);
+
+  Assert.strictEqual(
+    typeof splitview2.splitViewId,
+    "number",
+    "splitViewId should be a number"
+  );
+  Assert.strictEqual(
+    splitview2.splitViewId,
+    2,
+    "Second split view ID should be 2"
+  );
+
+  Assert.notEqual(
+    splitview1.splitViewId,
+    splitview2.splitViewId,
+    "Split view IDs should be unique"
+  );
+
+  gBrowser.removeTab(tab4);
+  gBrowser.removeTab(tab3);
+  gBrowser.removeTab(tab2);
+});
+
+add_task(async function test_counter_persists_across_sessions() {
+  let tab1 = gBrowser.tabs[0];
+  let tab2 = BrowserTestUtils.addTab(gBrowser, "about:robots");
+  await BrowserTestUtils.browserLoaded(tab2.linkedBrowser);
+
+  gBrowser.addTabSplitView([tab1, tab2]);
+
+  let tab3 = BrowserTestUtils.addTab(gBrowser, "about:mozilla");
+  let tab4 = BrowserTestUtils.addTab(gBrowser, "about:about");
+  await Promise.all([
+    BrowserTestUtils.browserLoaded(tab3.linkedBrowser),
+    BrowserTestUtils.browserLoaded(tab4.linkedBrowser),
+  ]);
+
+  let splitview2 = gBrowser.addTabSplitView([tab3, tab4]);
+  let secondId = splitview2.splitViewId;
+
+  await TabStateFlusher.flushWindow(window);
+
+  let state = JSON.parse(SessionStore.getBrowserState());
+
+  Assert.ok(state.maxSplitViewId, "maxSplitViewId should be in saved state");
+  Assert.strictEqual(
+    state.maxSplitViewId,
+    secondId,
+    "maxSplitViewId should match the highest ID used"
+  );
+
+  await SessionStoreTestUtils.promiseBrowserState(state);
+
+  let tab5 = BrowserTestUtils.addTab(gBrowser, "about:config");
+  let tab6 = BrowserTestUtils.addTab(gBrowser, "about:support");
+  await Promise.all([
+    BrowserTestUtils.browserLoaded(tab5.linkedBrowser),
+    BrowserTestUtils.browserLoaded(tab6.linkedBrowser),
+  ]);
+
+  let splitview3 = gBrowser.addTabSplitView([tab5, tab6]);
+
+  Assert.strictEqual(
+    typeof splitview3.splitViewId,
+    "number",
+    "New splitViewId should be a number"
+  );
+  Assert.strictEqual(
+    splitview3.splitViewId,
+    secondId + 1,
+    "New split view ID should be one more than persisted counter"
+  );
+
+  gBrowser.removeTab(tab6);
+  gBrowser.removeTab(tab5);
+});
+
+add_task(async function test_counter_initialized_from_persisted_value() {
+  let state = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              {
+                url: "about:mozilla",
+                triggeringPrincipal_base64,
+              },
+            ],
+            splitViewId: 42,
+          },
+          {
+            entries: [
+              {
+                url: "about:robots",
+                triggeringPrincipal_base64,
+              },
+            ],
+            splitViewId: 42,
+          },
+        ],
+        selected: 1,
+        splitViews: [
+          {
+            id: 42,
+            numberOfTabs: 2,
+          },
+        ],
+      },
+    ],
+    maxSplitViewId: 42,
+  };
+
+  await SessionStoreTestUtils.promiseBrowserState(state);
+
+  Assert.strictEqual(
+    gBrowser.tabs[0].splitview.splitViewId,
+    42,
+    "Restored split view should have ID 42"
+  );
+
+  let tab3 = BrowserTestUtils.addTab(gBrowser, "about:config");
+  let tab4 = BrowserTestUtils.addTab(gBrowser, "about:support");
+  await Promise.all([
+    BrowserTestUtils.browserLoaded(tab3.linkedBrowser),
+    BrowserTestUtils.browserLoaded(tab4.linkedBrowser),
+  ]);
+
+  let newSplitview = gBrowser.addTabSplitView([tab3, tab4]);
+
+  Assert.strictEqual(
+    newSplitview.splitViewId,
+    43,
+    "New split view ID should be maxSplitViewId + 1"
+  );
+
+  gBrowser.removeTab(tab4);
+  gBrowser.removeTab(tab3);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_splitview_restore_in_closed_window.js b/src/zen/tests/mochitests/sessionstore/browser_splitview_restore_in_closed_window.js
new file mode 100644
index 000000000..428050a74
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_splitview_restore_in_closed_window.js
@@ -0,0 +1,203 @@
+/* Any copyright is dedicated to the Public Domain.
+   https://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const ORIG_STATE = SessionStore.getBrowserState();
+forgetClosedWindows();
+
+registerCleanupFunction(async () => {
+  await SessionStoreTestUtils.promiseBrowserState(ORIG_STATE);
+});
+
+add_task(async function test_restoreSplitViewInClosedWindow() {
+  let win = await promiseNewWindowLoaded();
+  let tab1 = win.gBrowser.tabs[0];
+  let tab2 = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+  const splitview = win.gBrowser.addTabSplitView([tab1, tab2]);
+  const splitViewId = splitview.splitViewId;
+  await BrowserTestUtils.browserLoaded(
+    tab2.linkedBrowser,
+    false,
+    "about:robots"
+  );
+
+  Assert.equal(
+    splitview.tabs.length,
+    2,
+    "A splitview is present before closing the window."
+  );
+
+  await TabStateFlusher.flushWindow(win);
+  await BrowserTestUtils.closeWindow(win);
+
+  const closedWindowData = SessionStore.getClosedWindowData();
+  Assert.equal(closedWindowData.length, 1, "only `win` should be closed.");
+
+  const restoredWin = SessionStore.undoCloseWindow(0);
+  await promiseDelayedStartupFinished(restoredWin);
+
+  Assert.equal(
+    restoredWin.gBrowser.tabs.length,
+    2,
+    "There should be 2 tabs restored,"
+  );
+  Assert.equal(
+    restoredWin.gBrowser.tabs[1].splitview.tabs.length,
+    2,
+    "Both tabs in the splitview have been restored to the splitview."
+  );
+  Assert.equal(
+    restoredWin.gBrowser.tabs[1].splitview.splitViewId,
+    splitViewId,
+    "The correct splitview id is assigned."
+  );
+
+  await BrowserTestUtils.closeWindow(restoredWin);
+  forgetClosedWindows();
+});
+
+add_task(
+  async function test_restoreClosedTabGroupWithSplitViewFromClosedWindow() {
+    let win = await promiseNewWindowLoaded();
+    let aboutMozillaTab = BrowserTestUtils.addTab(
+      win.gBrowser,
+      "about:mozilla"
+    );
+    let aboutRobotsTab = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+    let aboutAboutTab = BrowserTestUtils.addTab(win.gBrowser, "about:about");
+    const splitview = win.gBrowser.addTabSplitView([
+      aboutRobotsTab,
+      aboutAboutTab,
+    ]);
+    const splitViewId = splitview.splitViewId;
+    const tabGroupToClose = win.gBrowser.addTabGroup([splitview], {
+      color: "blue",
+      label: "about pages",
+    });
+    const tabGroupToCloseId = tabGroupToClose.id;
+    await Promise.all([
+      BrowserTestUtils.browserLoaded(
+        aboutMozillaTab.linkedBrowser,
+        false,
+        "about:mozilla"
+      ),
+      BrowserTestUtils.browserLoaded(
+        aboutRobotsTab.linkedBrowser,
+        false,
+        "about:robots"
+      ),
+      BrowserTestUtils.browserLoaded(
+        aboutAboutTab.linkedBrowser,
+        false,
+        "about:about"
+      ),
+    ]);
+
+    await TabStateFlusher.flushWindow(win);
+
+    let removePromise = BrowserTestUtils.waitForEvent(
+      tabGroupToClose,
+      "TabGroupRemoved"
+    );
+    win.gBrowser.removeTabGroup(tabGroupToClose);
+    await removePromise;
+
+    Assert.ok(
+      !win.gBrowser.tabGroups.length,
+      "closed tab group should not be in the tab strip"
+    );
+    Assert.ok(
+      !win.gBrowser.tabs.includes(aboutRobotsTab),
+      "about:robots tab should not be in the tab strip"
+    );
+    Assert.ok(
+      !win.gBrowser.tabs.includes(aboutAboutTab),
+      "about:about tab should not be in the tab strip"
+    );
+
+    await TabStateFlusher.flushWindow(win);
+
+    const closedTabGroups = SessionStore.getClosedTabGroups(win);
+    Assert.equal(
+      closedTabGroups.length,
+      1,
+      "there should be a closed tab group"
+    );
+    Assert.equal(
+      closedTabGroups[0].id,
+      tabGroupToCloseId,
+      "the closed tab group should be the one we just closed"
+    );
+
+    let win2 = await promiseNewWindowLoaded();
+    await BrowserTestUtils.closeWindow(win);
+
+    const closedWindowData = SessionStore.getClosedWindowData();
+    Assert.equal(closedWindowData.length, 1, "only `win` should be closed");
+
+    let restorePromise = BrowserTestUtils.waitForEvent(
+      win2,
+      "SSWindowStateReady"
+    );
+    const restoredTabGroup = SessionStore.undoCloseTabGroup(
+      { sourceClosedId: closedWindowData[0].closedId },
+      tabGroupToCloseId,
+      win2
+    );
+    await restorePromise;
+
+    Assert.equal(
+      win2.gBrowser.tabs.length,
+      3,
+      "there should be 2 tabs restored + 1 initial tab from the new window"
+    );
+    Assert.equal(
+      win2.gBrowser.tabGroups.length,
+      1,
+      "there should be 1 tab group restored"
+    );
+    Assert.equal(
+      win2.gBrowser.selectedTab,
+      restoredTabGroup.tabs[0],
+      "first tab of the group is selected"
+    );
+    Assert.equal(
+      restoredTabGroup.tabs[0].splitview.tabs.length,
+      2,
+      "first tab of the group is should have a splitview with 2 tabs associated"
+    );
+    Assert.equal(
+      restoredTabGroup.tabs[0].splitview.splitViewId,
+      splitViewId,
+      "splitview ID should be restored"
+    );
+    Assert.equal(
+      restoredTabGroup.tabs.length,
+      2,
+      "the 2 restored tabs should be in the restored tab group"
+    );
+    Assert.equal(
+      restoredTabGroup.label,
+      "about pages",
+      "tab group name should be restored"
+    );
+    Assert.equal(
+      restoredTabGroup.id,
+      tabGroupToCloseId,
+      "tab group ID should be restored"
+    );
+    Assert.equal(
+      restoredTabGroup.color,
+      "blue",
+      "tab group color should be restored"
+    );
+    Assert.ok(
+      !restoredTabGroup.collapsed,
+      "tab group collapsed state should be restored"
+    );
+
+    await BrowserTestUtils.closeWindow(win2);
+    forgetClosedWindows();
+  }
+);
diff --git a/src/zen/tests/mochitests/sessionstore/browser_splitview_string_migration.js b/src/zen/tests/mochitests/sessionstore/browser_splitview_string_migration.js
new file mode 100644
index 000000000..7f1aef0e0
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_splitview_string_migration.js
@@ -0,0 +1,328 @@
+/* Any copyright is dedicated to the Public Domain.
+   https://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const ORIG_STATE = SessionStore.getBrowserState();
+forgetClosedWindows();
+
+registerCleanupFunction(async () => {
+  await SessionStoreTestUtils.promiseBrowserState(ORIG_STATE);
+});
+
+add_task(async function test_string_id_migration_preserves_grouping() {
+  let state = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              {
+                url: "about:mozilla",
+                triggeringPrincipal_base64,
+              },
+            ],
+            splitViewId: "1706789123456-42",
+          },
+          {
+            entries: [
+              {
+                url: "about:robots",
+                triggeringPrincipal_base64,
+              },
+            ],
+            splitViewId: "1706789123456-42",
+          },
+          {
+            entries: [
+              {
+                url: "about:about",
+                triggeringPrincipal_base64,
+              },
+            ],
+            splitViewId: "1706789123457-99",
+          },
+          {
+            entries: [
+              {
+                url: "about:config",
+                triggeringPrincipal_base64,
+              },
+            ],
+            splitViewId: "1706789123457-99",
+          },
+        ],
+        selected: 1,
+        splitViews: [
+          {
+            id: "1706789123456-42",
+            numberOfTabs: 2,
+          },
+          {
+            id: "1706789123457-99",
+            numberOfTabs: 2,
+          },
+        ],
+      },
+    ],
+  };
+
+  await SessionStoreTestUtils.promiseBrowserState(state);
+
+  info("State restored, checking tabs");
+  Assert.strictEqual(gBrowser.tabs.length, 4, "Should have 4 tabs");
+
+  let tab0 = gBrowser.tabs[0];
+  let tab1 = gBrowser.tabs[1];
+  let tab2 = gBrowser.tabs[2];
+  let tab3 = gBrowser.tabs[3];
+
+  info(`tab0.splitview: ${tab0.splitview}`);
+
+  if (!tab0.splitview) {
+    Assert.ok(false, "tab0 should have a splitview");
+    return;
+  }
+
+  Assert.strictEqual(
+    typeof tab0.splitview.splitViewId,
+    "number",
+    "Migrated splitViewId should be a number"
+  );
+  Assert.strictEqual(
+    typeof tab2.splitview.splitViewId,
+    "number",
+    "Migrated splitViewId should be a number"
+  );
+
+  Assert.strictEqual(
+    tab0.splitview.splitViewId,
+    tab1.splitview.splitViewId,
+    "Tabs with same string ID should have same integer ID"
+  );
+  Assert.strictEqual(
+    tab2.splitview.splitViewId,
+    tab3.splitview.splitViewId,
+    "Tabs with same string ID should have same integer ID"
+  );
+
+  Assert.notEqual(
+    tab0.splitview.splitViewId,
+    tab2.splitview.splitViewId,
+    "Different split views should have different integer IDs"
+  );
+
+  let tab4 = BrowserTestUtils.addTab(gBrowser, "about:preferences");
+  let tab5 = BrowserTestUtils.addTab(gBrowser, "about:addons");
+  await Promise.all([
+    BrowserTestUtils.browserLoaded(tab4.linkedBrowser),
+    BrowserTestUtils.browserLoaded(tab5.linkedBrowser),
+  ]);
+
+  let newSplitview = gBrowser.addTabSplitView([tab4, tab5]);
+
+  Assert.greater(
+    newSplitview.splitViewId,
+    tab0.splitview.splitViewId,
+    "New split view ID should be greater than migrated IDs"
+  );
+  Assert.greater(
+    newSplitview.splitViewId,
+    tab2.splitview.splitViewId,
+    "New split view ID should be greater than migrated IDs"
+  );
+
+  gBrowser.removeTab(tab5);
+  gBrowser.removeTab(tab4);
+});
+
+add_task(async function test_string_id_migration_in_closed_windows() {
+  let state = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              {
+                url: "about:blank",
+                triggeringPrincipal_base64,
+              },
+            ],
+          },
+        ],
+        selected: 1,
+      },
+    ],
+    _closedWindows: [
+      {
+        tabs: [
+          {
+            entries: [
+              {
+                url: "about:mozilla",
+                triggeringPrincipal_base64,
+              },
+            ],
+            splitViewId: "1706789123456-42",
+          },
+          {
+            entries: [
+              {
+                url: "about:robots",
+                triggeringPrincipal_base64,
+              },
+            ],
+            splitViewId: "1706789123456-42",
+          },
+        ],
+        splitViews: [
+          {
+            id: "1706789123456-42",
+            numberOfTabs: 2,
+          },
+        ],
+        selected: 1,
+        closedId: 1,
+        closedAt: Date.now(),
+        title: "Test Window",
+        _closedTabs: [],
+      },
+    ],
+  };
+
+  await SessionStoreTestUtils.promiseBrowserState(state);
+
+  let closedWindowData = SessionStore.getClosedWindowData();
+  Assert.strictEqual(closedWindowData.length, 1, "Should have 1 closed window");
+
+  let closedWinTabs = closedWindowData[0].tabs;
+  Assert.strictEqual(
+    closedWinTabs.length,
+    2,
+    "Closed window should have 2 tabs"
+  );
+
+  Assert.strictEqual(
+    typeof closedWinTabs[0].splitViewId,
+    "number",
+    "Closed window tab splitViewId should be migrated to number"
+  );
+  Assert.strictEqual(
+    typeof closedWinTabs[1].splitViewId,
+    "number",
+    "Closed window tab splitViewId should be migrated to number"
+  );
+
+  Assert.strictEqual(
+    closedWinTabs[0].splitViewId,
+    closedWinTabs[1].splitViewId,
+    "Closed window tabs with same string ID should have same integer ID"
+  );
+
+  let restoredWin = SessionStore.undoCloseWindow(0);
+  await promiseDelayedStartupFinished(restoredWin);
+
+  Assert.strictEqual(
+    restoredWin.gBrowser.tabs.length,
+    2,
+    "Restored window should have 2 tabs"
+  );
+
+  let restoredTab0 = restoredWin.gBrowser.tabs[0];
+  let restoredTab1 = restoredWin.gBrowser.tabs[1];
+
+  Assert.strictEqual(
+    typeof restoredTab0.splitview.splitViewId,
+    "number",
+    "Restored window tab should have integer splitViewId"
+  );
+  Assert.strictEqual(
+    restoredTab0.splitview.splitViewId,
+    restoredTab1.splitview.splitViewId,
+    "Restored split view should maintain grouping"
+  );
+
+  await BrowserTestUtils.closeWindow(restoredWin);
+  forgetClosedWindows();
+});
+
+add_task(async function test_old_session_without_maxSplitViewId() {
+  let state = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              {
+                url: "about:mozilla",
+                triggeringPrincipal_base64,
+              },
+            ],
+            splitViewId: "1706789123456-42",
+          },
+          {
+            entries: [
+              {
+                url: "about:robots",
+                triggeringPrincipal_base64,
+              },
+            ],
+            splitViewId: "1706789123456-42",
+          },
+        ],
+        selected: 1,
+        splitViews: [
+          {
+            id: "1706789123456-42",
+            numberOfTabs: 2,
+          },
+        ],
+      },
+    ],
+  };
+
+  await SessionStoreTestUtils.promiseBrowserState(state);
+
+  Assert.strictEqual(
+    typeof gBrowser.tabs[0].splitview.splitViewId,
+    "number",
+    "String ID should be migrated even without maxSplitViewId"
+  );
+  Assert.strictEqual(
+    gBrowser.tabs[0].splitview.splitViewId,
+    gBrowser.tabs[1].splitview.splitViewId,
+    "Grouping should be preserved"
+  );
+
+  let tab2 = BrowserTestUtils.addTab(gBrowser, "about:config");
+  let tab3 = BrowserTestUtils.addTab(gBrowser, "about:support");
+  await Promise.all([
+    BrowserTestUtils.browserLoaded(tab2.linkedBrowser),
+    BrowserTestUtils.browserLoaded(tab3.linkedBrowser),
+  ]);
+
+  let splitview = gBrowser.addTabSplitView([tab2, tab3]);
+
+  Assert.strictEqual(
+    typeof splitview.splitViewId,
+    "number",
+    "New split view should get integer ID"
+  );
+  Assert.greater(splitview.splitViewId, 0, "Counter should generate valid IDs");
+
+  await TabStateFlusher.flushWindow(window);
+  let newState = JSON.parse(SessionStore.getBrowserState());
+
+  Assert.ok(
+    newState.maxSplitViewId,
+    "maxSplitViewId should be persisted after first save"
+  );
+  Assert.strictEqual(
+    typeof newState.maxSplitViewId,
+    "number",
+    "Persisted maxSplitViewId should be a number"
+  );
+
+  gBrowser.removeTab(tab3);
+  gBrowser.removeTab(tab2);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_swapDocShells.js b/src/zen/tests/mochitests/sessionstore/browser_swapDocShells.js
new file mode 100644
index 000000000..047a36c51
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_swapDocShells.js
@@ -0,0 +1,40 @@
+"use strict";
+
+add_task(async function () {
+  let tab = (gBrowser.selectedTab = BrowserTestUtils.addTab(
+    gBrowser,
+    "about:mozilla"
+  ));
+  await promiseBrowserLoaded(gBrowser.selectedBrowser);
+
+  let win = gBrowser.replaceTabWithWindow(tab);
+  await promiseDelayedStartupFinished(win);
+  await promiseBrowserHasURL(win.gBrowser.browsers[0], "about:mozilla");
+
+  win.duplicateTabIn(win.gBrowser.selectedTab, "tab");
+  await promiseTabRestored(win.gBrowser.tabs[1]);
+
+  let browser = win.gBrowser.browsers[1];
+  is(browser.currentURI.spec, "about:mozilla", "tab was duplicated");
+
+  await BrowserTestUtils.closeWindow(win);
+});
+
+function promiseDelayedStartupFinished(win) {
+  return new Promise(resolve => {
+    whenDelayedStartupFinished(win, resolve);
+  });
+}
+
+function promiseBrowserHasURL(browser, url) {
+  let promise = Promise.resolve();
+
+  if (
+    browser.contentDocument.readyState === "complete" &&
+    browser.currentURI.spec === url
+  ) {
+    return promise;
+  }
+
+  return promise.then(() => promiseBrowserHasURL(browser, url));
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_switch_remoteness.js b/src/zen/tests/mochitests/sessionstore/browser_switch_remoteness.js
new file mode 100644
index 000000000..51c801d10
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_switch_remoteness.js
@@ -0,0 +1,57 @@
+"use strict";
+
+const URL = "http://example.com/browser_switch_remoteness_";
+
+function countHistoryEntries(browser, expected) {
+  return SpecialPowers.spawn(browser, [{ expected }], async function (args) {
+    let webNavigation = docShell.QueryInterface(Ci.nsIWebNavigation);
+    let history = webNavigation.sessionHistory;
+    Assert.equal(
+      history && history.count,
+      args.expected,
+      "correct number of shistory entries"
+    );
+  });
+}
+
+add_task(async function () {
+  // Open a new window.
+  let win = await promiseNewWindowLoaded();
+
+  // Add a new tab.
+  let tab = BrowserTestUtils.addTab(win.gBrowser, "about:blank");
+  let browser = tab.linkedBrowser;
+  await BrowserTestUtils.browserLoaded(browser, { wantLoad: "about:blank" });
+  ok(browser.isRemoteBrowser, "browser is remote");
+
+  // Get the maximum number of preceding entries to save.
+  const MAX_BACK = Services.prefs.getIntPref(
+    "browser.sessionstore.max_serialize_back"
+  );
+  Assert.greater(
+    MAX_BACK,
+    -1,
+    "check that the default has a value that caps data"
+  );
+
+  // Load more pages than we would save to disk on a clean shutdown.
+  for (let i = 0; i < MAX_BACK + 2; i++) {
+    BrowserTestUtils.startLoadingURIString(browser, URL + i);
+    await promiseBrowserLoaded(browser);
+    ok(browser.isRemoteBrowser, "browser is still remote");
+  }
+
+  // Check we have the right number of shistory entries.
+  await countHistoryEntries(browser, MAX_BACK + 2);
+
+  // Load a non-remote page.
+  BrowserTestUtils.startLoadingURIString(browser, "about:robots");
+  await promiseBrowserLoaded(browser);
+  ok(!browser.isRemoteBrowser, "browser is not remote anymore");
+
+  // Check that we didn't lose any shistory entries.
+  await countHistoryEntries(browser, MAX_BACK + 3);
+
+  // Cleanup.
+  await BrowserTestUtils.closeWindow(win);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_tab_groups_closed.js b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_closed.js
new file mode 100644
index 000000000..5a77264d9
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_closed.js
@@ -0,0 +1,197 @@
+"use strict";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  TabGroupTestUtils: "resource://testing-common/TabGroupTestUtils.sys.mjs",
+});
+
+const ORIG_STATE = SessionStore.getBrowserState();
+
+add_task(async function test_closingTabGroupAddsClosedGroup() {
+  let win = await promiseNewWindowLoaded();
+
+  let tabs = [
+    BrowserTestUtils.addTab(win.gBrowser, "https://example.com"),
+    BrowserTestUtils.addTab(win.gBrowser, "https://example.com"),
+    BrowserTestUtils.addTab(win.gBrowser, "https://example.com"),
+  ];
+  let group = win.gBrowser.addTabGroup(tabs);
+  await Promise.all(
+    tabs.map(async t => {
+      await BrowserTestUtils.browserLoaded(t.linkedBrowser);
+      await TabStateFlusher.flush(t.linkedBrowser);
+    })
+  );
+
+  let windowState = ss.getWindowState(win).windows[0];
+  Assert.equal(
+    windowState.closedGroups.length,
+    0,
+    "Window state starts with no closed groups"
+  );
+
+  await lazy.TabGroupTestUtils.removeTabGroup(group);
+
+  windowState = ss.getWindowState(win).windows[0];
+  Assert.equal(
+    windowState.closedGroups.length,
+    1,
+    "Window state gains a closed group"
+  );
+  Assert.equal(
+    windowState.closedGroups[0].tabs.length,
+    3,
+    "Closed group has 3 tabs"
+  );
+
+  await BrowserTestUtils.closeWindow(win);
+  forgetClosedWindows();
+  await SessionStoreTestUtils.promiseBrowserState(ORIG_STATE);
+});
+
+add_task(async function test_closedTabGroupSkipsNotWorthSavingTabs() {
+  let win = await promiseNewWindowLoaded();
+
+  const urls = ["https://example.com/", "about:blank"];
+  const tabs = urls.map(url => BrowserTestUtils.addTab(win.gBrowser, url));
+  let group = win.gBrowser.addTabGroup(tabs);
+  await Promise.all(
+    tabs.map(async (t, i) => {
+      await BrowserTestUtils.browserLoaded(t.linkedBrowser, {
+        wantLoad: urls[i],
+      });
+      await TabStateFlusher.flush(t.linkedBrowser);
+    })
+  );
+
+  let windowState = ss.getWindowState(win).windows[0];
+  Assert.equal(
+    windowState.closedGroups.length,
+    0,
+    "Window state starts with no closed groups"
+  );
+
+  await lazy.TabGroupTestUtils.removeTabGroup(group);
+
+  windowState = ss.getWindowState(win).windows[0];
+  Assert.equal(
+    windowState.closedGroups.length,
+    1,
+    "Window state gains a closed group"
+  );
+  Assert.equal(
+    windowState.closedGroups[0].tabs.length,
+    1,
+    "Closed group has only 1 tab"
+  );
+
+  await BrowserTestUtils.closeWindow(win);
+  forgetClosedWindows();
+  await SessionStoreTestUtils.promiseBrowserState(ORIG_STATE);
+});
+
+add_task(async function test_closedTabCountsRespectTabGroups() {
+  let win = await promiseNewWindowLoaded();
+
+  Assert.equal(
+    SessionStore.getClosedTabCount(),
+    0,
+    "Session store starts with 0 closed tabs"
+  );
+  Assert.equal(
+    SessionStore.getLastClosedTabCount(win),
+    0,
+    "Session store starts with 0 last closed tab count"
+  );
+
+  await SessionStoreTestUtils.openAndCloseTab(win, "https://example.com");
+
+  Assert.equal(
+    SessionStore.getClosedTabCount(),
+    1,
+    "Session store registers closed tab"
+  );
+  Assert.equal(
+    SessionStore.getLastClosedTabCount(win),
+    1,
+    "Session store reports last closed tab count as 1"
+  );
+
+  // We need to have at least one "worth saving" tab open in the window at time
+  // of close, or else the window will not be added to _closedWindows
+  BrowserTestUtils.addTab(win.gBrowser, "https://example.com");
+  let tabs = [
+    BrowserTestUtils.addTab(win.gBrowser, "https://example.com"),
+    BrowserTestUtils.addTab(win.gBrowser, "https://example.com"),
+    BrowserTestUtils.addTab(win.gBrowser, "https://example.com"),
+  ];
+  let group = win.gBrowser.addTabGroup(tabs);
+  await Promise.all(
+    tabs.map(async t => {
+      await BrowserTestUtils.browserLoaded(t.linkedBrowser);
+      await TabStateFlusher.flush(t.linkedBrowser);
+    })
+  );
+
+  await lazy.TabGroupTestUtils.removeTabGroup(group);
+
+  Assert.equal(
+    SessionStore.getClosedTabCount(),
+    4,
+    "Session store registers tabs from closed group"
+  );
+  Assert.equal(
+    SessionStore.getLastClosedTabCount(win),
+    3,
+    "Session store reports last closed tab count as 3"
+  );
+
+  Assert.equal(
+    SessionStore.getClosedTabCountForWindow(win),
+    4,
+    "Session store correctly reports closed tab count for window"
+  );
+
+  await BrowserTestUtils.closeWindow(win);
+
+  Assert.equal(
+    SessionStore.getClosedTabCountFromClosedWindows(),
+    4,
+    "Session store correctly reports closed tab count for closed windows"
+  );
+
+  forgetClosedWindows();
+  await SessionStoreTestUtils.promiseBrowserState(ORIG_STATE);
+});
+
+add_task(async function test_purgingSessionHistoryClearsClosedTabGroups() {
+  let win = await promiseNewWindowLoaded();
+
+  let tab = BrowserTestUtils.addTab(win.gBrowser, "https://example.com");
+  await BrowserTestUtils.browserLoaded(tab.linkedBrowser);
+  await TabStateFlusher.flush(tab.linkedBrowser);
+
+  let group = win.gBrowser.addTabGroup([tab]);
+  await lazy.TabGroupTestUtils.removeTabGroup(group);
+
+  let windowState = ss.getWindowState(win).windows[0];
+  Assert.equal(
+    windowState.closedGroups.length,
+    1,
+    "Window state gains a closed group"
+  );
+
+  Services.obs.notifyObservers(null, "browser:purge-session-history");
+
+  windowState = ss.getWindowState(win).windows[0];
+  Assert.equal(
+    windowState.closedGroups.length,
+    0,
+    "Session history purge removes closed groups"
+  );
+
+  await BrowserTestUtils.closeWindow(win);
+  forgetClosedWindows();
+  await SessionStoreTestUtils.promiseBrowserState(ORIG_STATE);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_tab_groups_closed_groups_in_closed_windows.js b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_closed_groups_in_closed_windows.js
new file mode 100644
index 000000000..0f1f288bb
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_closed_groups_in_closed_windows.js
@@ -0,0 +1,92 @@
+/* Any copyright is dedicated to the Public Domain.
+   https://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const ORIG_STATE = SessionStore.getBrowserState();
+
+registerCleanupFunction(async () => {
+  await SessionStoreTestUtils.promiseBrowserState(ORIG_STATE);
+});
+
+add_task(async function test_closedTabGroupsInClosedWindows() {
+  forgetClosedWindows();
+
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.sessionstore.closedTabsFromClosedWindows", true]],
+  });
+
+  let win = await promiseNewWindowLoaded();
+
+  // Window needs at least one worth-saving tab opened in order to be saved
+  BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+
+  let groupedTab1 = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+  let groupedTab2 = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+
+  let tabGroup = win.gBrowser.addTabGroup([groupedTab1, groupedTab2]);
+
+  await TabStateFlusher.flushWindow(win);
+
+  Assert.equal(
+    SessionStore.getClosedTabGroups(win).length,
+    0,
+    "should start with no closed tab groups"
+  );
+  Assert.equal(
+    SessionStore.getClosedTabDataForWindow(win).length,
+    0,
+    "should start with no closed tabs"
+  );
+  Assert.equal(
+    SessionStore.getClosedWindowData().length,
+    0,
+    "should start with no closed windows"
+  );
+
+  let removePromise = BrowserTestUtils.waitForEvent(
+    tabGroup,
+    "TabGroupRemoved"
+  );
+  win.gBrowser.removeTabGroup(tabGroup);
+  await removePromise;
+
+  await TabStateFlusher.flushWindow(win);
+
+  Assert.equal(
+    SessionStore.getClosedTabGroups().length,
+    1,
+    "should have one closed tab group"
+  );
+
+  await BrowserTestUtils.closeWindow(win);
+
+  Assert.equal(
+    SessionStore.getClosedWindowData().length,
+    1,
+    "should have one closed window"
+  );
+  Assert.equal(
+    SessionStore.getClosedTabGroups().length,
+    1,
+    "should still have one closed tab group, even when the window is closed"
+  );
+  Assert.equal(
+    SessionStore.getClosedTabDataFromClosedWindows().length,
+    2,
+    "should report 2 closed tabs from the closed tab group in the closed window"
+  );
+  await SpecialPowers.popPrefEnv();
+
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.sessionstore.closedTabsFromClosedWindows", false]],
+  });
+  Assert.equal(
+    SessionStore.getClosedTabGroups().length,
+    0,
+    "should report no closed tabs if closedTabsFromClosedWindows is false"
+  );
+  await SpecialPowers.popPrefEnv();
+
+  forgetClosedWindows();
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_tab_groups_empty.js b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_empty.js
new file mode 100644
index 000000000..5817c3a29
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_empty.js
@@ -0,0 +1,31 @@
+"use strict";
+
+const ORIG_STATE = SessionStore.getBrowserState();
+
+registerCleanupFunction(async () => {
+  await SessionStoreTestUtils.promiseBrowserState(ORIG_STATE);
+});
+
+add_task(async function test_ZeroTabGroups() {
+  let win = await promiseNewWindowLoaded();
+  const state = ss.getWindowState(win);
+
+  Assert.equal(state.windows.length, 1, "should have state from 1 window");
+  const windowState = state.windows[0];
+
+  Assert.ok(windowState.groups, "window state should have a `groups` property");
+  Assert.equal(
+    windowState.groups.length,
+    0,
+    "`groups` property should be 0 since there are no tab groups"
+  );
+
+  const countOfGroupedTabs = windowState.tabs.filter(tab => tab.groupId).length;
+  Assert.equal(
+    countOfGroupedTabs,
+    0,
+    "none of the tabs should refer to a tab group"
+  );
+  await BrowserTestUtils.closeWindow(win);
+  forgetClosedWindows();
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_tab_groups_restore_closed_in_closed_window.js b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_restore_closed_in_closed_window.js
new file mode 100644
index 000000000..6b3bb7ee8
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_restore_closed_in_closed_window.js
@@ -0,0 +1,135 @@
+/* Any copyright is dedicated to the Public Domain.
+   https://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const ORIG_STATE = SessionStore.getBrowserState();
+forgetClosedWindows();
+
+registerCleanupFunction(async () => {
+  await SessionStoreTestUtils.promiseBrowserState(ORIG_STATE);
+});
+
+add_task(async function test_restoreClosedTabGroupFromClosedWindow() {
+  let win = await promiseNewWindowLoaded();
+  let aboutMozillaTab = BrowserTestUtils.addTab(win.gBrowser, "about:mozilla");
+  let aboutRobotsTab = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+  let aboutAboutTab = BrowserTestUtils.addTab(win.gBrowser, "about:about");
+  const tabGroupToClose = win.gBrowser.addTabGroup(
+    [aboutRobotsTab, aboutAboutTab],
+    {
+      color: "blue",
+      label: "about pages",
+    }
+  );
+  const tabGroupToCloseId = tabGroupToClose.id;
+  await Promise.all([
+    BrowserTestUtils.browserLoaded(
+      aboutMozillaTab.linkedBrowser,
+      false,
+      "about:mozilla"
+    ),
+    BrowserTestUtils.browserLoaded(
+      aboutRobotsTab.linkedBrowser,
+      false,
+      "about:robots"
+    ),
+    BrowserTestUtils.browserLoaded(
+      aboutAboutTab.linkedBrowser,
+      false,
+      "about:about"
+    ),
+  ]);
+
+  await TabStateFlusher.flushWindow(win);
+
+  let removePromise = BrowserTestUtils.waitForEvent(
+    tabGroupToClose,
+    "TabGroupRemoved"
+  );
+  win.gBrowser.removeTabGroup(tabGroupToClose);
+  await removePromise;
+
+  Assert.ok(
+    !win.gBrowser.tabGroups.length,
+    "closed tab group should not be in the tab strip"
+  );
+  Assert.ok(
+    !win.gBrowser.tabs.includes(aboutRobotsTab),
+    "about:robots tab should not be in the tab strip"
+  );
+  Assert.ok(
+    !win.gBrowser.tabs.includes(aboutAboutTab),
+    "about:about tab should not be in the tab strip"
+  );
+
+  await TabStateFlusher.flushWindow(win);
+
+  const closedTabGroups = SessionStore.getClosedTabGroups(win);
+  Assert.equal(closedTabGroups.length, 1, "there should be a closed tab group");
+  Assert.equal(
+    closedTabGroups[0].id,
+    tabGroupToCloseId,
+    "the closed tab group should be the one we just closed"
+  );
+
+  let win2 = await promiseNewWindowLoaded();
+  await BrowserTestUtils.closeWindow(win);
+
+  const closedWindowData = SessionStore.getClosedWindowData();
+  Assert.equal(closedWindowData.length, 1, "only `win` should be closed");
+
+  let restorePromise = BrowserTestUtils.waitForEvent(
+    win2,
+    "SSWindowStateReady"
+  );
+  const restoredTabGroup = SessionStore.undoCloseTabGroup(
+    { sourceClosedId: closedWindowData[0].closedId },
+    tabGroupToCloseId,
+    win2
+  );
+  await restorePromise;
+
+  Assert.equal(
+    win2.gBrowser.tabs.length,
+    3,
+    "there should be 2 tabs restored + 1 initial tab from the new window"
+  );
+  Assert.equal(
+    win2.gBrowser.tabGroups.length,
+    1,
+    "there should be 1 tab group restored"
+  );
+  Assert.equal(
+    win2.gBrowser.selectedTab,
+    restoredTabGroup.tabs[0],
+    "first tab of the group is selected"
+  );
+  Assert.equal(
+    restoredTabGroup.tabs.length,
+    2,
+    "the 2 restored tabs should be in the restored tab group"
+  );
+  Assert.equal(
+    restoredTabGroup.label,
+    "about pages",
+    "tab group name should be restored"
+  );
+  Assert.equal(
+    restoredTabGroup.id,
+    tabGroupToCloseId,
+    "tab group ID should be restored"
+  );
+  Assert.equal(
+    restoredTabGroup.color,
+    "blue",
+    "tab group color should be restored"
+  );
+  Assert.ok(
+    !restoredTabGroup.collapsed,
+    "tab group collapsed state should be restored"
+  );
+
+  await BrowserTestUtils.closeWindow(win2);
+  forgetClosedWindows();
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_tab_groups_restore_closed_in_open_window.js b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_restore_closed_in_open_window.js
new file mode 100644
index 000000000..075438927
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_restore_closed_in_open_window.js
@@ -0,0 +1,105 @@
+/* Any copyright is dedicated to the Public Domain.
+   https://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const ORIG_STATE = SessionStore.getBrowserState();
+
+registerCleanupFunction(async () => {
+  await SessionStoreTestUtils.promiseBrowserState(ORIG_STATE);
+});
+
+add_task(async function test_restoreClosedTabGroupFromSameWindow() {
+  let win = await promiseNewWindowLoaded();
+  let aboutRobotsTab = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+  let aboutAboutTab = BrowserTestUtils.addTab(win.gBrowser, "about:about");
+  const tabGroupToClose = win.gBrowser.addTabGroup(
+    [aboutRobotsTab, aboutAboutTab],
+    {
+      color: "blue",
+      label: "about pages",
+    }
+  );
+  const tabGroupToCloseId = tabGroupToClose.id;
+
+  await TabStateFlusher.flushWindow(win);
+
+  Assert.equal(
+    win.gBrowser.tabs.length,
+    3,
+    "there should be 2 new tabs + 1 initial tab from the new window"
+  );
+
+  let removePromise = BrowserTestUtils.waitForEvent(
+    tabGroupToClose,
+    "TabGroupRemoved"
+  );
+  win.gBrowser.removeTabGroup(tabGroupToClose);
+  await removePromise;
+
+  Assert.ok(
+    !win.gBrowser.tabGroups.length,
+    "closed tab group should not be in the tab strip"
+  );
+  Assert.ok(
+    !win.gBrowser.tabs.includes(aboutRobotsTab),
+    "about:robots tab should not be in the tab strip"
+  );
+  Assert.ok(
+    !win.gBrowser.tabs.includes(aboutAboutTab),
+    "about:about tab should not be in the tab strip"
+  );
+
+  await TabStateFlusher.flushWindow(win);
+
+  let restorePromise = BrowserTestUtils.waitForEvent(win, "SSWindowStateReady");
+  const restoredTabGroup = SessionStore.undoCloseTabGroup(
+    win,
+    tabGroupToCloseId,
+    win
+  );
+  await restorePromise;
+
+  Assert.equal(
+    win.gBrowser.tabs.length,
+    3,
+    "there should be 2 tabs restored + 1 initial tab from the new window"
+  );
+  Assert.equal(
+    win.gBrowser.tabGroups.length,
+    1,
+    "there should be 1 tab group restored"
+  );
+  Assert.equal(
+    win.gBrowser.selectedTab,
+    restoredTabGroup.tabs[0],
+    "first tab of the group is selected"
+  );
+  Assert.equal(
+    restoredTabGroup.tabs.length,
+    2,
+    "the 2 restored tabs should be in the restored tab group"
+  );
+  Assert.equal(
+    restoredTabGroup.label,
+    "about pages",
+    "tab group name should be restored"
+  );
+  Assert.equal(
+    restoredTabGroup.id,
+    tabGroupToCloseId,
+    "tab group ID should be restored"
+  );
+  Assert.equal(
+    restoredTabGroup.color,
+    "blue",
+    "tab group color should be restored"
+  );
+  Assert.ok(
+    !restoredTabGroup.collapsed,
+    "tab group collapsed state should be restored"
+  );
+
+  await BrowserTestUtils.closeWindow(win);
+  forgetClosedWindows();
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_tab_groups_restore_closed_many_tabs.js b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_restore_closed_many_tabs.js
new file mode 100644
index 000000000..c671d6110
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_restore_closed_many_tabs.js
@@ -0,0 +1,202 @@
+/* Any copyright is dedicated to the Public Domain.
+   https://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { TabGroupTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/TabGroupTestUtils.sys.mjs"
+);
+
+// Ensure that a closed tab group will record all of its tabs into session state
+// without being constrained by the `browser.sessionstore.max_tabs_undo` pref
+// which normally limits the number of closed tabs that we retain in state.
+
+const ORIG_STATE = SessionStore.getBrowserState();
+
+const maxTabsUndo = Services.prefs.getIntPref(
+  "browser.sessionstore.max_tabs_undo"
+);
+const numberOfTabsToTest = maxTabsUndo + 5;
+
+registerCleanupFunction(async () => {
+  forgetClosedWindows();
+  forgetSavedTabGroups();
+  await SessionStoreTestUtils.promiseBrowserState(ORIG_STATE);
+});
+
+add_task(async function test_restoreClosedTabGroupWithManyTabs() {
+  let win = await promiseNewWindowLoaded();
+  let tabs = [];
+  let tabUrls = [];
+  for (let i = 1; i <= numberOfTabsToTest; i++) {
+    let tab = BrowserTestUtils.addTab(
+      win.gBrowser,
+      `https://example.com/?${i}`
+    );
+    tabUrls.push(`https://example.com/?${i}`);
+    tabs.push(tab);
+  }
+  await Promise.all(
+    tabs.map(tab => BrowserTestUtils.browserLoaded(tab.linkedBrowser))
+  );
+
+  const tabGroupToClose = win.gBrowser.addTabGroup(tabs, {
+    color: "blue",
+    label: "many tabs",
+  });
+  const tabGroupToCloseId = tabGroupToClose.id;
+
+  Assert.equal(
+    win.gBrowser.tabs.length,
+    numberOfTabsToTest + 1,
+    `there should be ${numberOfTabsToTest} new tabs + 1 initial tab from the new window`
+  );
+  for (let i = 1; i <= numberOfTabsToTest; i++) {
+    Assert.equal(
+      tabGroupToClose.tabs[i - 1].linkedBrowser.currentURI.spec,
+      tabUrls[i - 1],
+      `confirmed order of tab ${i} in the group`
+    );
+  }
+
+  await TabStateFlusher.flushWindow(win);
+
+  await TabGroupTestUtils.removeTabGroup(tabGroupToClose);
+
+  Assert.ok(
+    !win.gBrowser.tabGroups.length,
+    "closed tab group should not be in the tab strip"
+  );
+
+  let closedTabGroups = ss.getClosedTabGroups(win);
+  Assert.equal(
+    closedTabGroups.length,
+    1,
+    "one closed tab group should be in session state"
+  );
+  let closedTabGroup = closedTabGroups[0];
+  Assert.equal(
+    closedTabGroup.id,
+    tabGroupToCloseId,
+    "the tab group we closed should be in session state"
+  );
+  Assert.equal(
+    closedTabGroup.tabs.length,
+    numberOfTabsToTest,
+    "the closed tab group should contain all of the tabs"
+  );
+  for (let i = 1; i <= numberOfTabsToTest; i++) {
+    Assert.equal(
+      closedTabGroup.tabs[i - 1].state.entries[0].url,
+      tabUrls[i - 1],
+      `the closed tab group tab ${i} should preserve its order in the group`
+    );
+  }
+
+  let restorePromise = BrowserTestUtils.waitForEvent(win, "SSWindowStateReady");
+  let undoTabGroup = SessionStore.undoCloseTabGroup(
+    win,
+    tabGroupToCloseId,
+    win
+  );
+  await restorePromise;
+  await Promise.all(
+    undoTabGroup.tabs.map(tab =>
+      BrowserTestUtils.browserLoaded(tab.linkedBrowser)
+    )
+  );
+
+  Assert.equal(
+    win.gBrowser.tabs.length,
+    numberOfTabsToTest + 1,
+    `there should be ${numberOfTabsToTest} tabs restored + 1 initial tab from the new window`
+  );
+  for (let i = 1; i <= numberOfTabsToTest; i++) {
+    Assert.equal(
+      undoTabGroup.tabs[i - 1].linkedBrowser.currentURI.spec,
+      tabUrls[i - 1],
+      `the undo tab ${i} should preserve its order in the group`
+    );
+  }
+
+  await BrowserTestUtils.closeWindow(win);
+});
+
+add_task(async function test_restoreSavedTabGroupWithManyTabs() {
+  let win = await promiseNewWindowLoaded();
+  let tabs = [];
+  let tabUrls = [];
+  for (let i = 1; i <= numberOfTabsToTest; i++) {
+    let tab = BrowserTestUtils.addTab(
+      win.gBrowser,
+      `https://example.com/?${i}`
+    );
+    tabUrls.push(`https://example.com/?${i}`);
+    tabs.push(tab);
+  }
+  await Promise.all(
+    tabs.map(tab => BrowserTestUtils.browserLoaded(tab.linkedBrowser))
+  );
+
+  const tabGroupToSaveAndClose = win.gBrowser.addTabGroup(tabs, {
+    color: "blue",
+    label: "many tabs",
+  });
+  const tabGroupToSaveAndCloseId = tabGroupToSaveAndClose.id;
+
+  Assert.equal(
+    win.gBrowser.tabs.length,
+    numberOfTabsToTest + 1,
+    `there should be ${numberOfTabsToTest} new tabs + 1 initial tab from the new window`
+  );
+  for (let i = 1; i <= numberOfTabsToTest; i++) {
+    Assert.equal(
+      tabGroupToSaveAndClose.tabs[i - 1].linkedBrowser.currentURI.spec,
+      tabUrls[i - 1],
+      `confirmed order of tab ${i} in the group`
+    );
+  }
+
+  await TabGroupTestUtils.saveAndCloseTabGroup(tabGroupToSaveAndClose);
+
+  Assert.ok(
+    !win.gBrowser.tabGroups.length,
+    "closed tab group should not be in the tab strip"
+  );
+
+  let savedGroupData = SessionStore.getSavedTabGroup(tabGroupToSaveAndCloseId);
+  for (let i = 1; i <= numberOfTabsToTest; i++) {
+    Assert.equal(
+      savedGroupData.tabs[i - 1].state.entries[0].url,
+      tabUrls[i - 1],
+      `the saved tab group tab ${i} should preserve its order in the group`
+    );
+  }
+
+  let restorePromise = BrowserTestUtils.waitForEvent(win, "SSWindowStateReady");
+  let savedTabGroup = SessionStore.openSavedTabGroup(
+    tabGroupToSaveAndCloseId,
+    win
+  );
+  await restorePromise;
+  await Promise.all(
+    savedTabGroup.tabs.map(tab =>
+      BrowserTestUtils.browserLoaded(tab.linkedBrowser)
+    )
+  );
+
+  Assert.equal(
+    win.gBrowser.tabs.length,
+    numberOfTabsToTest + 1,
+    `there should be ${numberOfTabsToTest} tabs restored + 1 initial tab from the new window`
+  );
+  for (let i = 1; i <= numberOfTabsToTest; i++) {
+    Assert.equal(
+      savedTabGroup.tabs[i - 1].linkedBrowser.currentURI.spec,
+      tabUrls[i - 1],
+      `restored tab ${i} should preserve its order in the group`
+    );
+  }
+
+  await BrowserTestUtils.closeWindow(win);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_tab_groups_restore_multiple.js b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_restore_multiple.js
new file mode 100644
index 000000000..56ed6b643
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_restore_multiple.js
@@ -0,0 +1,135 @@
+"use strict";
+
+const ORIG_STATE = SessionStore.getBrowserState();
+
+registerCleanupFunction(async () => {
+  await SessionStoreTestUtils.promiseBrowserState(ORIG_STATE);
+});
+
+add_task(async function test_RestoreMultipleGroups() {
+  let win = await promiseNewWindowLoaded();
+  BrowserTestUtils.addTab(win.gBrowser, "about:about");
+
+  let aboutMozillaTab = BrowserTestUtils.addTab(win.gBrowser, "about:mozilla");
+  let aboutBlankTab = BrowserTestUtils.addTab(win.gBrowser, "about:blank");
+  let mozillaTabGroup = win.gBrowser.addTabGroup(
+    [aboutMozillaTab, aboutBlankTab],
+    { color: "red", label: "mozilla stuff" }
+  );
+  const mozillaTabGroupId = mozillaTabGroup.id;
+  BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+
+  let aboutAboutTab = BrowserTestUtils.addTab(win.gBrowser, "about:about");
+  let aboutMemoryTab = BrowserTestUtils.addTab(win.gBrowser, "about:memory");
+  let systemTabGroup = win.gBrowser.addTabGroup(
+    [aboutAboutTab, aboutMemoryTab],
+    { color: "blue", label: "system stuff" }
+  );
+  systemTabGroup.collapsed = true;
+  const systemTabGroupId = systemTabGroup.id;
+
+  BrowserTestUtils.addTab(win.gBrowser, "about:license");
+
+  await TabStateFlusher.flushWindow(win);
+  await BrowserTestUtils.closeWindow(win);
+
+  // Now restore the window
+  win = SessionStore.undoCloseWindow(0);
+  await BrowserTestUtils.waitForEvent(win, "SSWindowStateReady");
+  await BrowserTestUtils.waitForEvent(
+    win.gBrowser.tabContainer,
+    "SSTabRestored"
+  );
+
+  Assert.equal(
+    win.gBrowser.tabs.length,
+    8,
+    "there should be 7 tabs restored + 1 initial tab from the new window"
+  );
+  Assert.equal(
+    win.gBrowser.tabGroups.length,
+    2,
+    "there should be 2 tab groups restored"
+  );
+
+  Assert.ok(
+    !win.gBrowser.tabs[0].group,
+    "initial tab from the new window should not be in a group"
+  );
+  Assert.ok(
+    !win.gBrowser.tabs[1].group,
+    "about:about tab should not be in a group"
+  );
+  Assert.equal(
+    win.gBrowser.tabs[2].group.id,
+    mozillaTabGroupId,
+    "about:mozilla tab should be in the mozilla stuff group"
+  );
+  Assert.equal(
+    win.gBrowser.tabs[3].group.id,
+    mozillaTabGroupId,
+    "about:blank tab should be in the mozilla stuff group"
+  );
+  Assert.ok(
+    !win.gBrowser.tabs[4].group,
+    "about:robots tab should not be in a group"
+  );
+  Assert.equal(
+    win.gBrowser.tabs[5].group.id,
+    systemTabGroupId,
+    "about:about tab should be in the system stuff group"
+  );
+  Assert.equal(
+    win.gBrowser.tabs[6].group.id,
+    systemTabGroupId,
+    "about:memory tab should be in the system stuff group"
+  );
+  Assert.ok(
+    !win.gBrowser.tabs[7].group,
+    "about:license tab should not be in a group"
+  );
+
+  [mozillaTabGroup, systemTabGroup] = win.gBrowser.tabGroups;
+  Assert.equal(
+    mozillaTabGroup.label,
+    "mozilla stuff",
+    "tab group name should be restored"
+  );
+  Assert.equal(
+    mozillaTabGroup.id,
+    mozillaTabGroupId,
+    "tab group ID should be restored"
+  );
+  Assert.equal(
+    mozillaTabGroup.color,
+    "red",
+    "tab group color should be restored"
+  );
+  Assert.ok(
+    !mozillaTabGroup.collapsed,
+    "tab group collapsed state should be restored"
+  );
+
+  Assert.equal(
+    systemTabGroup.label,
+    "system stuff",
+    "tab group name should be restored"
+  );
+  Assert.equal(
+    systemTabGroup.id,
+    systemTabGroupId,
+    "tab group ID should be restored"
+  );
+  Assert.equal(
+    systemTabGroup.color,
+    "blue",
+    "tab group color should be restored"
+  );
+  Assert.ok(
+    systemTabGroup.collapsed,
+    "tab group collapsed state should be restored"
+  );
+
+  await BrowserTestUtils.closeWindow(win);
+  forgetClosedWindows();
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_tab_groups_restore_saved.js b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_restore_saved.js
new file mode 100644
index 000000000..a2cff8c05
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_restore_saved.js
@@ -0,0 +1,183 @@
+/* Any copyright is dedicated to the Public Domain.
+   https://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const ORIG_STATE = SessionStore.getBrowserState();
+
+registerCleanupFunction(async () => {
+  await SessionStoreTestUtils.promiseBrowserState(ORIG_STATE);
+});
+
+add_task(async function test_restoreSavedTabGroupToSameWindow() {
+  let win = await promiseNewWindowLoaded();
+  let aboutRobotsTab = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+  let aboutAboutTab = BrowserTestUtils.addTab(win.gBrowser, "about:about");
+  const tabGroupToSave = win.gBrowser.addTabGroup(
+    [aboutRobotsTab, aboutAboutTab],
+    {
+      color: "blue",
+      label: "about pages",
+    }
+  );
+  const tabGroupToSaveId = tabGroupToSave.id;
+
+  await TabStateFlusher.flushWindow(win);
+
+  tabGroupToSave.save();
+  let removePromise = BrowserTestUtils.waitForEvent(
+    tabGroupToSave,
+    "TabGroupRemoved"
+  );
+  win.gBrowser.removeTabGroup(tabGroupToSave);
+  await removePromise;
+
+  Assert.ok(
+    !win.gBrowser.tabGroups.length,
+    "saved tab group should not be in the tab strip"
+  );
+  Assert.ok(
+    !win.gBrowser.tabs.includes(aboutRobotsTab),
+    "about:robots tab should not be in the tab strip"
+  );
+  Assert.ok(
+    !win.gBrowser.tabs.includes(aboutAboutTab),
+    "about:about tab should not be in the tab strip"
+  );
+
+  await TabStateFlusher.flushWindow(win);
+
+  let restorePromise = BrowserTestUtils.waitForEvent(win, "SSWindowStateReady");
+  const restoredTabGroup = SessionStore.openSavedTabGroup(
+    tabGroupToSaveId,
+    win
+  );
+  await restorePromise;
+
+  Assert.equal(
+    win.gBrowser.tabs.length,
+    3,
+    "there should be 2 tabs restored + 1 initial tab from the new window"
+  );
+  Assert.equal(
+    win.gBrowser.tabGroups.length,
+    1,
+    "there should be 1 tab group restored"
+  );
+  Assert.equal(
+    win.gBrowser.selectedTab,
+    restoredTabGroup.tabs[0],
+    "first tab of the group is selected"
+  );
+  Assert.equal(
+    restoredTabGroup.tabs.length,
+    2,
+    "the 2 restored tabs should be in the restored tab group"
+  );
+  Assert.equal(
+    restoredTabGroup.label,
+    "about pages",
+    "tab group name should be restored"
+  );
+  Assert.equal(
+    restoredTabGroup.id,
+    tabGroupToSaveId,
+    "tab group ID should be restored"
+  );
+  Assert.equal(
+    restoredTabGroup.color,
+    "blue",
+    "tab group color should be restored"
+  );
+  Assert.ok(
+    !restoredTabGroup.collapsed,
+    "tab group collapsed state should be restored"
+  );
+
+  await BrowserTestUtils.closeWindow(win);
+  forgetSavedTabGroups();
+});
+
+add_task(async function test_restoreSavedTabGroupToAnotherWindow() {
+  let win = await promiseNewWindowLoaded();
+  let aboutRobotsTab = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+  let aboutAboutTab = BrowserTestUtils.addTab(win.gBrowser, "about:about");
+  const tabGroupToSave = win.gBrowser.addTabGroup(
+    [aboutRobotsTab, aboutAboutTab],
+    {
+      color: "blue",
+      label: "about pages",
+    }
+  );
+  const tabGroupToSaveId = tabGroupToSave.id;
+
+  await Promise.allSettled([
+    TabStateFlusher.flush(aboutRobotsTab.linkedBrowser),
+    TabStateFlusher.flush(aboutAboutTab.linkedBrowser),
+  ]);
+  tabGroupToSave.save();
+
+  await TabStateFlusher.flushWindow(win);
+
+  let removePromise = BrowserTestUtils.waitForEvent(
+    tabGroupToSave,
+    "TabGroupRemoved"
+  );
+  win.gBrowser.removeTabGroup(tabGroupToSave);
+  await removePromise;
+
+  await TabStateFlusher.flushWindow(win);
+
+  let win2 = await promiseNewWindowLoaded();
+
+  let restorePromise = BrowserTestUtils.waitForEvent(
+    win2,
+    "SSWindowStateReady"
+  );
+  const restoredTabGroup = SessionStore.openSavedTabGroup(
+    tabGroupToSaveId,
+    win2
+  );
+  await restorePromise;
+
+  Assert.equal(
+    win2.gBrowser.tabs.length,
+    3,
+    "there should be 2 tabs restored + 1 initial tab from the new window"
+  );
+  Assert.equal(
+    win2.gBrowser.tabGroups.length,
+    1,
+    "there should be 1 tab group restored"
+  );
+
+  Assert.equal(
+    restoredTabGroup.tabs.length,
+    2,
+    "the 2 restored tabs should be in the restored tab group"
+  );
+  Assert.equal(
+    restoredTabGroup.label,
+    "about pages",
+    "tab group name should be restored"
+  );
+  Assert.equal(
+    restoredTabGroup.id,
+    tabGroupToSaveId,
+    "tab group ID should be restored"
+  );
+  Assert.equal(
+    restoredTabGroup.color,
+    "blue",
+    "tab group color should be restored"
+  );
+  Assert.ok(
+    !restoredTabGroup.collapsed,
+    "tab group collapsed state should be restored"
+  );
+
+  await BrowserTestUtils.closeWindow(win2);
+  await BrowserTestUtils.closeWindow(win);
+  forgetSavedTabGroups();
+  forgetClosedWindows();
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_tab_groups_restore_simple.js b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_restore_simple.js
new file mode 100644
index 000000000..8c603645f
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_restore_simple.js
@@ -0,0 +1,68 @@
+"use strict";
+
+const ORIG_STATE = SessionStore.getBrowserState();
+
+registerCleanupFunction(async () => {
+  await SessionStoreTestUtils.promiseBrowserState(ORIG_STATE);
+});
+
+add_task(async function test_RestoreSingleGroup() {
+  let win = await promiseNewWindowLoaded();
+  let aboutRobotsTab = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+  let aboutAboutTab = BrowserTestUtils.addTab(win.gBrowser, "about:about");
+  const { id: originalTabGroupId } = win.gBrowser.addTabGroup(
+    [aboutRobotsTab, aboutAboutTab],
+    {
+      color: "blue",
+      label: "about pages",
+    }
+  );
+
+  await TabStateFlusher.flushWindow(win);
+  await BrowserTestUtils.closeWindow(win);
+
+  // Now restore the window
+  win = SessionStore.undoCloseWindow(0);
+  await BrowserTestUtils.waitForEvent(win, "SSWindowStateReady");
+  await BrowserTestUtils.waitForEvent(
+    win.gBrowser.tabContainer,
+    "SSTabRestored"
+  );
+
+  Assert.equal(
+    win.gBrowser.tabs.length,
+    3,
+    "there should be 2 tabs restored + 1 initial tab from the new window"
+  );
+  Assert.equal(
+    win.gBrowser.tabGroups.length,
+    1,
+    "there should be 1 tab group restored"
+  );
+
+  let tabGroup = win.gBrowser.tabGroups[0];
+  Assert.equal(
+    tabGroup.tabs.length,
+    2,
+    "the 2 restored tabs should be in the restored tab group"
+  );
+  Assert.equal(
+    tabGroup.label,
+    "about pages",
+    "tab group name should be restored"
+  );
+  Assert.equal(
+    tabGroup.id,
+    originalTabGroupId,
+    "tab group ID should be restored"
+  );
+  Assert.equal(tabGroup.color, "blue", "tab group color should be restored");
+  Assert.ok(
+    !tabGroup.collapsed,
+    "tab group collapsed state should be restored"
+  );
+
+  await win.gBrowser.removeTabGroup(tabGroup);
+  await BrowserTestUtils.closeWindow(win);
+  forgetClosedWindows();
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_tab_groups_restore_to_group.js b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_restore_to_group.js
new file mode 100644
index 000000000..6bb6a6e0d
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_restore_to_group.js
@@ -0,0 +1,62 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const ORIG_STATE = SessionStore.getBrowserState();
+
+registerCleanupFunction(async () => {
+  await SessionStoreTestUtils.promiseBrowserState(ORIG_STATE);
+});
+
+add_task(async function test_restoreTabToGroup() {
+  let groupedTabs = [
+    BrowserTestUtils.addTab(gBrowser, "about:mozilla"),
+    BrowserTestUtils.addTab(gBrowser, "about:robots"),
+  ];
+  let tabToRestore = groupedTabs[1];
+  await Promise.all(
+    groupedTabs.map(g => promiseBrowserLoaded(g.linkedBrowser))
+  );
+  let tabGroup = gBrowser.addTabGroup(groupedTabs);
+
+  await SessionStoreTestUtils.closeTab(tabToRestore);
+
+  Assert.equal(tabGroup.tabs.length, 1, "Tab group only has one tab");
+
+  await TabStateFlusher.flushWindow(window);
+
+  let tabRestoredEvent = BrowserTestUtils.waitForEvent(
+    gBrowser.tabContainer,
+    "SSTabRestored"
+  );
+  SessionStore.undoCloseTab(window);
+  await tabRestoredEvent;
+
+  Assert.equal(tabGroup.tabs.length, 2, "Tab group has two tabs");
+  let restoredTab = tabGroup.tabs.at(-1);
+  Assert.equal(
+    restoredTab.linkedBrowser.currentURI.spec,
+    "about:robots",
+    "Closed tab exists in group"
+  );
+  BrowserTestUtils.removeTab(restoredTab);
+
+  // remove the other tab in the group so it gets deleted
+  await SessionStoreTestUtils.closeTab(tabGroup.tabs[0]);
+
+  tabRestoredEvent = BrowserTestUtils.waitForEvent(
+    gBrowser.tabContainer,
+    "SSTabRestored"
+  );
+  SessionStore.undoCloseTab(window, 0);
+  await tabRestoredEvent;
+
+  restoredTab = gBrowser.tabs.at(-1);
+  Assert.ok(
+    !restoredTab.group,
+    "Tab was not restored to the group because the group was removed"
+  );
+
+  forgetClosedTabs(window);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_tab_groups_save_on_removeAllTabsBut.js b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_save_on_removeAllTabsBut.js
new file mode 100644
index 000000000..842f0a006
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_save_on_removeAllTabsBut.js
@@ -0,0 +1,127 @@
+/* Any copyright is dedicated to the Public Domain.
+   https://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const ORIG_STATE = SessionStore.getBrowserState();
+
+registerCleanupFunction(async () => {
+  await SessionStoreTestUtils.promiseBrowserState(ORIG_STATE);
+});
+
+add_task(async function test_removeAllTabsBut_default_save_tab_groups() {
+  let win = await promiseNewWindowLoaded();
+  let tab1 = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+  let tab2 = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+  let tab3 = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+
+  let tabGroup = win.gBrowser.addTabGroup([tab2, tab3]);
+  let tabGroupId = tabGroup.id;
+
+  await TabStateFlusher.flushWindow(win);
+
+  Assert.equal(
+    SessionStore.getSavedTabGroups().length,
+    0,
+    "should not be any saved tab groups to start"
+  );
+  Assert.equal(
+    SessionStore.getClosedTabGroups(win).length,
+    0,
+    "should not be any closed tab groups to start"
+  );
+  Assert.equal(
+    SessionStore.getClosedTabDataForWindow(win).length,
+    0,
+    "should not be any closed tabs"
+  );
+
+  win.gBrowser.removeAllTabsBut(tab1);
+
+  await TestUtils.waitForCondition(
+    () => win.gBrowser.tabs.length == 1,
+    "waiting for other tabs to close"
+  );
+
+  await TabStateFlusher.flushWindow(win);
+
+  Assert.equal(
+    SessionStore.getSavedTabGroups().length,
+    1,
+    "should have saved a tab group"
+  );
+  Assert.ok(
+    SessionStore.getSavedTabGroup(tabGroupId),
+    "should have saved the tab group that was closed"
+  );
+  Assert.equal(
+    SessionStore.getClosedTabGroups(win).length,
+    0,
+    "should only have saved the tab group, not deleted it"
+  );
+  Assert.equal(
+    SessionStore.getClosedTabDataForWindow(win).length,
+    0,
+    "should not be any closed tabs"
+  );
+
+  await BrowserTestUtils.closeWindow(win);
+  forgetClosedWindows();
+  forgetSavedTabGroups();
+});
+
+add_task(async function test_removeAllTabsBut_suppress_saving_tab_groups() {
+  let win = await promiseNewWindowLoaded();
+  let tab1 = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+  let tab2 = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+  let tab3 = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+
+  win.gBrowser.addTabGroup([tab2, tab3]);
+
+  await TabStateFlusher.flushWindow(win);
+
+  Assert.equal(
+    SessionStore.getSavedTabGroups().length,
+    0,
+    "should not be any saved tab groups to start"
+  );
+  Assert.equal(
+    SessionStore.getClosedTabGroups(win).length,
+    0,
+    "should not be any closed tab groups to start"
+  );
+  Assert.equal(
+    SessionStore.getClosedTabDataForWindow(win).length,
+    0,
+    "should not be any closed tabs"
+  );
+
+  win.gBrowser.removeAllTabsBut(tab1, { skipSessionStore: true });
+
+  await TestUtils.waitForCondition(
+    () => win.gBrowser.tabs.length == 1,
+    "waiting for other tabs to close"
+  );
+
+  await TabStateFlusher.flushWindow(win);
+
+  Assert.equal(
+    SessionStore.getSavedTabGroups().length,
+    0,
+    "should not have saved the tab group"
+  );
+  Assert.equal(
+    SessionStore.getClosedTabGroups(win),
+    0,
+    "should still not have any deleted tab groups"
+  );
+  Assert.equal(
+    SessionStore.getClosedTabDataForWindow(win).length,
+    0,
+    "should be 0 closed tabs"
+  );
+
+  await BrowserTestUtils.closeWindow(win);
+  forgetClosedWindows();
+  forgetSavedTabGroups();
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_tab_groups_save_on_removeTabsToTheEnd.js b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_save_on_removeTabsToTheEnd.js
new file mode 100644
index 000000000..44d97f93c
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_save_on_removeTabsToTheEnd.js
@@ -0,0 +1,112 @@
+/* Any copyright is dedicated to the Public Domain.
+   https://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const ORIG_STATE = SessionStore.getBrowserState();
+
+registerCleanupFunction(async () => {
+  await SessionStoreTestUtils.promiseBrowserState(ORIG_STATE);
+});
+
+add_task(async function test_removeTabsToTheEnd_saves_tab_groups() {
+  let win = await promiseNewWindowLoaded();
+  let tab1 = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+  let tab2 = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+  let tab3 = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+
+  let tabGroup = win.gBrowser.addTabGroup([tab2, tab3], { insertBefore: tab2 });
+  let tabGroupId = tabGroup.id;
+
+  await TabStateFlusher.flushWindow(win);
+
+  Assert.equal(
+    win.gBrowser.tabs.length,
+    4,
+    "should be 4 tabs: 1 tab from new window and 3 tabs just created"
+  );
+  Assert.equal(
+    SessionStore.getSavedTabGroups().length,
+    0,
+    "should not be any saved tab groups to start"
+  );
+
+  win.gBrowser.removeTabsToTheEndFrom(tab1);
+
+  await TestUtils.waitForCondition(
+    () => win.gBrowser.tabs.length == 2,
+    "waiting for tabs to the end to close"
+  );
+
+  await TabStateFlusher.flushWindow(win);
+
+  Assert.equal(
+    SessionStore.getSavedTabGroups().length,
+    1,
+    "should have saved a tab group"
+  );
+  Assert.ok(
+    SessionStore.getSavedTabGroup(tabGroupId),
+    "should have saved the tab group that was closed"
+  );
+
+  await BrowserTestUtils.closeWindow(win);
+  forgetClosedWindows();
+  forgetSavedTabGroups();
+});
+
+add_task(
+  async function test_removeTabsToTheEnd_only_saves_when_whole_tab_group_removed() {
+    let win = await promiseNewWindowLoaded();
+    let tab1 = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+    let tab2 = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+    BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+
+    let tabGroup = win.gBrowser.addTabGroup([tab1, tab2], {
+      insertBefore: tab1,
+    });
+
+    await TabStateFlusher.flushWindow(win);
+
+    Assert.equal(
+      win.gBrowser.tabs.length,
+      4,
+      "should be 4 tabs: 1 tab from new window and 3 tabs just created"
+    );
+    Assert.equal(
+      SessionStore.getSavedTabGroups().length,
+      0,
+      "should not be any saved tab groups to start"
+    );
+
+    win.gBrowser.removeTabsToTheEndFrom(tab1);
+
+    await TestUtils.waitForCondition(
+      () => win.gBrowser.tabs.length == 2,
+      "waiting for tabs to the end to close"
+    );
+
+    await TabStateFlusher.flushWindow(win);
+
+    Assert.equal(
+      SessionStore.getSavedTabGroups().length,
+      0,
+      "should not have saved a tab group because one did not close"
+    );
+    Assert.deepEqual(
+      win.gBrowser.tabGroups,
+      [tabGroup],
+      "tab group should still exist in the tab strip"
+    );
+    Assert.deepEqual(
+      tabGroup.tabs,
+      [tab1],
+      "tab group should just have one tab left"
+    );
+
+    await win.gBrowser.removeTabGroup(tabGroup);
+    await BrowserTestUtils.closeWindow(win);
+    forgetClosedWindows();
+    forgetSavedTabGroups();
+  }
+);
diff --git a/src/zen/tests/mochitests/sessionstore/browser_tab_groups_save_on_removeTabsToTheStart.js b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_save_on_removeTabsToTheStart.js
new file mode 100644
index 000000000..bcbf1538d
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_save_on_removeTabsToTheStart.js
@@ -0,0 +1,112 @@
+/* Any copyright is dedicated to the Public Domain.
+   https://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const ORIG_STATE = SessionStore.getBrowserState();
+
+registerCleanupFunction(async () => {
+  await SessionStoreTestUtils.promiseBrowserState(ORIG_STATE);
+});
+
+add_task(async function test_removeTabsToTheStart_saves_tab_groups() {
+  let win = await promiseNewWindowLoaded();
+  let tab1 = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+  let tab2 = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+  let tab3 = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+
+  let tabGroup = win.gBrowser.addTabGroup([tab1, tab2], { insertBefore: tab1 });
+  let tabGroupId = tabGroup.id;
+
+  await TabStateFlusher.flushWindow(win);
+
+  Assert.equal(
+    win.gBrowser.tabs.length,
+    4,
+    "should be 4 tabs: 1 tab from new window and 3 tabs just created"
+  );
+  Assert.equal(
+    SessionStore.getSavedTabGroups().length,
+    0,
+    "should not be any saved tab groups to start"
+  );
+
+  win.gBrowser.removeTabsToTheStartFrom(tab3);
+
+  await TestUtils.waitForCondition(
+    () => win.gBrowser.tabs.length == 1,
+    "waiting for other tabs to close"
+  );
+
+  await TabStateFlusher.flushWindow(win);
+
+  Assert.equal(
+    SessionStore.getSavedTabGroups().length,
+    1,
+    "should have saved a tab group"
+  );
+  Assert.ok(
+    SessionStore.getSavedTabGroup(tabGroupId),
+    "should have saved the tab group that was closed"
+  );
+
+  await BrowserTestUtils.closeWindow(win);
+  forgetClosedWindows();
+  forgetSavedTabGroups();
+});
+
+add_task(
+  async function test_removeTabsToTheStart_only_saves_when_whole_tab_group_removed() {
+    let win = await promiseNewWindowLoaded();
+    BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+    let tab2 = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+    let tab3 = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+
+    let tabGroup = win.gBrowser.addTabGroup([tab2, tab3], {
+      insertBefore: tab2,
+    });
+
+    await TabStateFlusher.flushWindow(win);
+
+    Assert.equal(
+      win.gBrowser.tabs.length,
+      4,
+      "should be 4 tabs: 1 tab from new window and 3 tabs just created"
+    );
+    Assert.equal(
+      SessionStore.getSavedTabGroups().length,
+      0,
+      "should not be any saved tab groups to start"
+    );
+
+    win.gBrowser.removeTabsToTheStartFrom(tab3);
+
+    await TestUtils.waitForCondition(
+      () => win.gBrowser.tabs.length == 1,
+      "waiting for tabs to the end to close"
+    );
+
+    await TabStateFlusher.flushWindow(win);
+
+    Assert.equal(
+      SessionStore.getSavedTabGroups().length,
+      0,
+      "should not have saved a tab group because one did not close"
+    );
+    Assert.deepEqual(
+      win.gBrowser.tabGroups,
+      [tabGroup],
+      "tab group should still exist in the tab strip"
+    );
+    Assert.deepEqual(
+      tabGroup.tabs,
+      [tab3],
+      "tab group should just have one tab left"
+    );
+
+    await win.gBrowser.removeTabGroup(tabGroup);
+    await BrowserTestUtils.closeWindow(win);
+    forgetClosedWindows();
+    forgetSavedTabGroups();
+  }
+);
diff --git a/src/zen/tests/mochitests/sessionstore/browser_tab_groups_save_on_window_close.js b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_save_on_window_close.js
new file mode 100644
index 000000000..04e7ae363
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_save_on_window_close.js
@@ -0,0 +1,254 @@
+/* Any copyright is dedicated to the Public Domain.
+   https://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const ORIG_STATE = SessionStore.getBrowserState();
+
+registerCleanupFunction(async () => {
+  await SessionStoreTestUtils.promiseBrowserState(ORIG_STATE);
+});
+
+forgetClosedWindows();
+forgetSavedTabGroups();
+
+add_task(async function test_saveOpenTabGroupsOnWindowClose() {
+  Assert.equal(
+    ss.getSavedTabGroups().length,
+    0,
+    "should start with no saved tab groups"
+  );
+  Assert.equal(
+    ss.getClosedWindowData().length,
+    0,
+    "should start with no closed windows"
+  );
+
+  info("open a new window with 1 standalone tab and 2 tabs in a tab group");
+  let win = await promiseNewWindowLoaded();
+  let aboutMozillaTab = BrowserTestUtils.addTab(win.gBrowser, "about:mozilla");
+  let aboutRobotsTab = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+  let aboutAboutTab = BrowserTestUtils.addTab(win.gBrowser, "about:about");
+  const tabGroupToClose = win.gBrowser.addTabGroup(
+    [aboutRobotsTab, aboutAboutTab],
+    {
+      color: "blue",
+      label: "about pages",
+    }
+  );
+  const tabGroupToCloseId = tabGroupToClose.id;
+  await Promise.all([
+    BrowserTestUtils.browserLoaded(
+      aboutMozillaTab.linkedBrowser,
+      false,
+      "about:mozilla"
+    ),
+    BrowserTestUtils.browserLoaded(
+      aboutRobotsTab.linkedBrowser,
+      false,
+      "about:robots"
+    ),
+    BrowserTestUtils.browserLoaded(
+      aboutAboutTab.linkedBrowser,
+      false,
+      "about:about"
+    ),
+  ]);
+
+  await TabStateFlusher.flushWindow(win);
+
+  info("close the window to make sure the tab group gets saved automatically");
+  await BrowserTestUtils.closeWindow(win);
+
+  const closedWindowData = SessionStore.getClosedWindowData();
+  Assert.equal(closedWindowData.length, 1, "`win` should now be closed");
+  Assert.equal(
+    closedWindowData[0].groups.length,
+    1,
+    "should be one tab group in the closed window"
+  );
+  const tabGroupInClosedWindow = closedWindowData[0].groups[0];
+  Assert.equal(
+    tabGroupInClosedWindow.id,
+    tabGroupToCloseId,
+    "closed window tab group should be the one that was in the window"
+  );
+  Assert.equal(ss.getSavedTabGroups().length, 1, "should be 1 saved tab group");
+  Assert.equal(
+    ss.getSavedTabGroup(tabGroupToCloseId).id,
+    tabGroupInClosedWindow.id,
+    "saved tab group should be the same as the tab group in the closed window"
+  );
+
+  info(
+    "reopen the closed window to make sure that the tab group reopens in the window and is no longer saved"
+  );
+  win = SessionStore.undoCloseWindow(0);
+  await BrowserTestUtils.waitForEvent(win, "SSWindowStateReady");
+  await BrowserTestUtils.waitForEvent(
+    win.gBrowser.tabContainer,
+    "SSTabRestored"
+  );
+
+  Assert.equal(
+    win.gBrowser.tabGroups.length,
+    1,
+    "tab group should have been restored"
+  );
+  Assert.equal(
+    win.gBrowser.tabGroups[0].id,
+    tabGroupToCloseId,
+    "restored tab group should be the one from the closed window"
+  );
+  Assert.equal(
+    ss.getSavedTabGroups().length,
+    0,
+    "saved tab group should no longer be saved because it should be restored into the reopened window"
+  );
+  Assert.equal(
+    ss.getClosedWindowData().length,
+    0,
+    "the closed window should have been reopened"
+  );
+
+  await TabStateFlusher.flushWindow(win);
+
+  info("close the window again");
+  await BrowserTestUtils.closeWindow(win);
+
+  Assert.equal(
+    ss.getClosedWindowData()[0].tabs.length,
+    4,
+    "re-closed window should have 1 new tab from the new window, 1 standalone tab, and 2 tabs in the tab group"
+  );
+  Assert.equal(
+    ss.getClosedWindowData()[0].groups.length,
+    1,
+    "tab group should still be in the closed window"
+  );
+
+  info(
+    "open the saved tab group into a different window, which should remove it from the closed window"
+  );
+  let savedGroupReopened = BrowserTestUtils.waitForEvent(
+    window,
+    "SSWindowStateReady"
+  );
+  await SessionStore.openSavedTabGroup(tabGroupToCloseId, window);
+  await savedGroupReopened;
+
+  await TabStateFlusher.flushWindow(window);
+
+  Assert.equal(
+    ss.getClosedWindowData()[0].tabs.length,
+    2,
+    "re-closed window should now just have 1 new tab from the new window and 1 standalone tab"
+  );
+  Assert.equal(
+    ss.getClosedWindowData()[0].groups.length,
+    0,
+    "re-closed window should no longer have tab groups because we opened the saved group into a different window"
+  );
+  Assert.equal(
+    ss.getSavedTabGroups().length,
+    0,
+    "saved tab group should no longer be saved because it should be restored into the main window"
+  );
+
+  info(
+    "reopen the closed window, which should no longer have the saved tab group in it since it moved into a different window"
+  );
+  win = SessionStore.undoCloseWindow(0);
+  await BrowserTestUtils.waitForEvent(win, "SSWindowStateReady");
+  await BrowserTestUtils.waitForEvent(
+    win.gBrowser.tabContainer,
+    "SSTabRestored"
+  );
+
+  Assert.equal(
+    win.gBrowser.openTabs.length,
+    2,
+    "the re-restored window should have 1 new tab and 1 standalone tab"
+  );
+  Assert.equal(
+    win.gBrowser.tabGroups.length,
+    0,
+    "the re-restored window should have no tab group"
+  );
+
+  info(
+    "move the tab group back into the window that we've been opening + closing"
+  );
+  let savedTabGroup = window.gBrowser.tabGroups[0];
+  let savedTabRemoval = BrowserTestUtils.waitForEvent(
+    savedTabGroup,
+    "TabGroupRemoved"
+  );
+  win.gBrowser.adoptTabGroup(window.gBrowser.tabGroups[0], { elementIndex: 2 });
+  await savedTabRemoval;
+
+  Assert.equal(
+    win.gBrowser.openTabs.length,
+    4,
+    "the re-restored window should have the tab group again after adopting it"
+  );
+
+  await TabStateFlusher.flushWindow(win);
+
+  info(
+    "close the window and forget it to make sure that the tab group will still be saved even if we forget about the closed window"
+  );
+  await BrowserTestUtils.closeWindow(win);
+  ss.forgetClosedWindow(0);
+
+  Assert.equal(
+    ss.getClosedWindowData().length,
+    0,
+    "the closed window should have been forgotten"
+  );
+  Assert.equal(
+    ss.getSavedTabGroups().length,
+    1,
+    "but the automatically saved tab group that was in the closed window should remain saved"
+  );
+
+  forgetClosedWindows();
+  forgetSavedTabGroups();
+});
+
+/**
+ * A closing window should not save its tab group if the window was closed
+ * in response to moving that tab group
+ */
+add_task(async function test_dontSaveAfterAdoptingGroup() {
+  let win = await promiseNewWindowLoaded();
+  let state = ss.getCurrentState();
+  Assert.ok(!state.savedGroups.length, "savedGroups starts empty");
+
+  let tab1 = BrowserTestUtils.addTab(win.gBrowser, "about:mozilla");
+  await BrowserTestUtils.browserLoaded(tab1.linkedBrowser);
+  await TabStateFlusher.flush(tab1.linkedBrowser);
+  let group1 = win.gBrowser.addTabGroup([tab1]);
+  await BrowserTestUtils.removeTab(win.gBrowser.tabs[0]);
+  let windowUnloaded = BrowserTestUtils.waitForEvent(win, "unload");
+  gBrowser.adoptTabGroup(group1);
+  await windowUnloaded;
+  state = ss.getCurrentState();
+  Assert.ok(!state.savedGroups.length, "savedGroups is still empty");
+});
+
+add_task(async function test_dontSaveAfterDeletingLastGroupInWindow() {
+  let win = await promiseNewWindowLoaded();
+  let state = ss.getCurrentState();
+  Assert.ok(!state.savedGroups.length, "savedGroups starts empty");
+  let tab1 = BrowserTestUtils.addTab(win.gBrowser, "about:mozilla");
+  await BrowserTestUtils.browserLoaded(tab1.linkedBrowser);
+  await TabStateFlusher.flush(tab1.linkedBrowser);
+  let group1 = win.gBrowser.addTabGroup([tab1]);
+  await BrowserTestUtils.removeTab(win.gBrowser.tabs[0]);
+  let windowUnloaded = BrowserTestUtils.waitForEvent(win, "unload");
+  win.gBrowser.removeTabGroup(group1);
+  await windowUnloaded;
+  state = ss.getCurrentState();
+  Assert.ok(!state.savedGroups.length, "savedGroups is still empty");
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_tab_groups_saved.js b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_saved.js
new file mode 100644
index 000000000..7a51e33f1
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_saved.js
@@ -0,0 +1,94 @@
+"use strict";
+
+const ORIG_STATE = SessionStore.getBrowserState();
+
+registerCleanupFunction(async () => {
+  await SessionStoreTestUtils.promiseBrowserState(ORIG_STATE);
+});
+
+add_task(async function test_SaveTabGroups() {
+  let win = await promiseNewWindowLoaded();
+  let state = ss.getCurrentState(win);
+  Assert.equal(
+    state.savedGroups.length,
+    0,
+    "savedGroups starts in initial state"
+  );
+
+  let tab1 = BrowserTestUtils.addTab(win.gBrowser, "about:mozilla?foo");
+  await BrowserTestUtils.browserLoaded(tab1.linkedBrowser);
+  await TabStateFlusher.flush(tab1.linkedBrowser);
+  let group1 = win.gBrowser.addTabGroup([tab1]);
+  ss.addSavedTabGroup(group1);
+
+  let tab2 = BrowserTestUtils.addTab(win.gBrowser, "about:mozilla?bar");
+  await BrowserTestUtils.browserLoaded(tab2.linkedBrowser);
+  await TabStateFlusher.flush(tab2.linkedBrowser);
+  let group2 = win.gBrowser.addTabGroup([tab2]);
+  ss.addSavedTabGroup(group2);
+
+  state = ss.getCurrentState();
+
+  Assert.equal(state.savedGroups.length, 2, "savedGroups has 2 groups");
+  Assert.equal(state.savedGroups[0].id, group1.id, "group1 is in savedGroups");
+  Assert.equal(state.savedGroups[0].tabs.length, 1, "group1 has 1 tab");
+  Assert.equal(state.savedGroups[1].id, group2.id, "group2 is in savedGroups");
+  Assert.equal(state.savedGroups[1].tabs.length, 1, "group2 has 1 tab");
+
+  ss.forgetSavedTabGroup(group1.id);
+  await win.gBrowser.removeTabGroup(group1);
+  state = ss.getCurrentState();
+
+  Assert.equal(state.savedGroups.length, 1, "savedGroups has 1 group");
+  Assert.equal(state.savedGroups[0].id, group2.id, "group2 is in savedGroups");
+  Assert.equal(state.savedGroups[0].tabs.length, 1, "group2 still has 1 tab");
+
+  ss.forgetSavedTabGroup(group2.id);
+  await win.gBrowser.removeTabGroup(group2);
+  await BrowserTestUtils.closeWindow(win);
+  forgetClosedWindows();
+});
+
+/**
+ * Newtabs with no history are considered unimportant and are ignored by
+ * sessionstore. Groups of unimportant tabs should also be ignored.
+ */
+add_task(async function test_ignoreUnimportantTabGroups() {
+  let win = await promiseNewWindowLoaded();
+  let state = ss.getCurrentState(win);
+  Assert.equal(state.savedGroups.length, 0, "savedGroups starts empty");
+
+  let tab1 = BrowserTestUtils.addTab(win.gBrowser, "about:newtab");
+  await BrowserTestUtils.browserLoaded(tab1.linkedBrowser);
+  await TabStateFlusher.flush(tab1.linkedBrowser);
+  let group1 = win.gBrowser.addTabGroup([tab1]);
+  ss.addSavedTabGroup(group1);
+
+  state = ss.getCurrentState();
+  Assert.equal(state.savedGroups.length, 0, "savedGroups is still empty");
+
+  await win.gBrowser.removeTabGroup(group1);
+  await BrowserTestUtils.closeWindow(win);
+  forgetClosedWindows();
+});
+
+add_task(async function test_refuseToSaveGroupsInPrivateWindows() {
+  const privateWin = await BrowserTestUtils.openNewBrowserWindow({
+    private: true,
+  });
+
+  let tab = BrowserTestUtils.addTab(privateWin.gBrowser, "about:newtab");
+  await BrowserTestUtils.browserLoaded(tab.linkedBrowser);
+  await TabStateFlusher.flush(tab.linkedBrowser);
+  let group = privateWin.gBrowser.addTabGroup([tab]);
+
+  Assert.throws(
+    () => {
+      ss.addSavedTabGroup(group);
+    },
+    /Refusing to save tab group/,
+    "addSavedTabGroup throws exception when trying to save a tab group from a private window"
+  );
+  await BrowserTestUtils.closeWindow(privateWin);
+  forgetClosedWindows();
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_tab_groups_state.js b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_state.js
new file mode 100644
index 000000000..0a645a86e
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_state.js
@@ -0,0 +1,101 @@
+"use strict";
+
+const ORIG_STATE = SessionStore.getBrowserState();
+
+registerCleanupFunction(async () => {
+  await SessionStoreTestUtils.promiseBrowserState(ORIG_STATE);
+});
+
+/**
+ * @param {WindowStateData} windowState
+ * @returns {TabStateData|undefined}
+ */
+function findTabStateByUrl(windowState, url) {
+  return windowState.tabs.find(tabState => tabState.userTypedValue == url);
+}
+
+add_task(async function test_TabGroupsInState() {
+  let win = await promiseNewWindowLoaded();
+  let aboutRobotsTab = BrowserTestUtils.addTab(win.gBrowser, "about:robots");
+  let aboutMozillaTab = BrowserTestUtils.addTab(win.gBrowser, "about:mozilla");
+  BrowserTestUtils.addTab(win.gBrowser, "about:about");
+
+  let group = win.gBrowser.addTabGroup([aboutRobotsTab, aboutMozillaTab], {
+    label: "non-meta about pages",
+  });
+
+  let state = ss.getWindowState(win);
+
+  Assert.equal(state.windows.length, 1, "should have state from 1 window");
+  let windowState = state.windows[0];
+
+  Assert.ok(windowState.groups, "window state should have a `groups` property");
+  Assert.equal(windowState.groups.length, 1, "there should be one tab group");
+  let groupState = windowState.groups[0];
+
+  Assert.equal(
+    groupState.id,
+    group.id,
+    "tab group ID should be recorded in state"
+  );
+  Assert.equal(
+    groupState.name,
+    group.label,
+    "tab group name should be recorded in state"
+  );
+  Assert.equal(
+    groupState.color,
+    group.color,
+    "tab group color should be recorded in state"
+  );
+  Assert.equal(
+    groupState.collapsed,
+    group.collapsed,
+    "tab group collapsed state should be recorded in state"
+  );
+
+  Assert.equal(
+    windowState.tabs.length,
+    4,
+    "there should be 3 tabs in session state + 1 initial tab"
+  );
+
+  const aboutRobotsTabState = findTabStateByUrl(windowState, "about:robots");
+  Assert.ok(aboutRobotsTabState, "about:robots tab should be in session state");
+  Assert.equal(
+    aboutRobotsTabState.groupId,
+    group.id,
+    "about:robots tab should be part of the tab group"
+  );
+
+  const aboutMozillaTabState = findTabStateByUrl(windowState, "about:mozilla");
+  Assert.ok(
+    aboutMozillaTabState,
+    "about:mozilla tab should be in session state"
+  );
+  Assert.equal(
+    aboutMozillaTabState.groupId,
+    group.id,
+    "about:mozilla tab should be part of the tab group"
+  );
+
+  const aboutAboutTabState = findTabStateByUrl(windowState, "about:about");
+  Assert.ok(aboutAboutTabState, "about:about tab should be in session state");
+  Assert.ok(
+    !aboutAboutTabState.groupId,
+    "about:about tab should NOT be part of the tab group"
+  );
+
+  // collapse the tab group and make sure the tab group data updates
+  group.collapsed = true;
+
+  state = ss.getWindowState(win);
+  groupState = state.windows[0].groups[0];
+  Assert.equal(
+    groupState.collapsed,
+    group.collapsed,
+    "updated tab group collapsed state should be recorded in state"
+  );
+  await BrowserTestUtils.closeWindow(win);
+  forgetClosedWindows();
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_tab_groups_undo.js b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_undo.js
new file mode 100644
index 000000000..c54d18287
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_tab_groups_undo.js
@@ -0,0 +1,117 @@
+/* Any copyright is dedicated to the Public Domain.
+   https://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const ORIG_STATE = SessionStore.getBrowserState();
+
+registerCleanupFunction(async () => {
+  await SessionStoreTestUtils.promiseBrowserState(ORIG_STATE);
+});
+
+add_task(async function test_tabGroupsUndo() {
+  Assert.equal(
+    SessionStore.getLastClosedTabGroupId(window),
+    null,
+    "Should start without a last closed tab group id"
+  );
+  Assert.equal(
+    window.gBrowser.tabGroups.length,
+    0,
+    "Should start with no tab groups"
+  );
+
+  let groupedTabs = [
+    BrowserTestUtils.addTab(gBrowser, "https://example.com"),
+    BrowserTestUtils.addTab(gBrowser, "https://example.com"),
+  ];
+  await Promise.all(
+    groupedTabs.map(g => promiseBrowserLoaded(g.linkedBrowser))
+  );
+
+  info("Adding to tab group");
+  let tabGroup = gBrowser.addTabGroup(groupedTabs);
+  let tabGroupId = tabGroup.id;
+
+  info("Waiting for tab group removed");
+  let removePromise = BrowserTestUtils.waitForEvent(
+    tabGroup,
+    "TabGroupRemoved"
+  );
+  await gBrowser.removeTabGroup(tabGroup);
+  await removePromise;
+
+  await TabStateFlusher.flushWindow(window);
+
+  info("Waiting for getLastClosedTabGroupId");
+  await TestUtils.waitForCondition(
+    () => SessionStore.getLastClosedTabGroupId(window) !== null
+  );
+
+  Assert.equal(
+    SessionStore.getLastClosedTabGroupId(window),
+    tabGroupId,
+    "SessionStore saves the ID of the last closed tab group"
+  );
+
+  SessionWindowUI.undoCloseTab(window);
+
+  Assert.equal(window.gBrowser.tabGroups.length, 1, "Tab group was restored");
+  Assert.equal(
+    SessionStore.getLastClosedTabGroupId(window),
+    null,
+    "SessionStore reset the ID of the last closed tab group"
+  );
+
+  BrowserTestUtils.removeTab(gBrowser.tabGroups[0].tabs[0]);
+  Assert.equal(
+    SessionStore.getLastClosedTabGroupId(window),
+    null,
+    "SessionStore last closed group ID is null after closing a tab within a group"
+  );
+
+  let ungroupedTab = BrowserTestUtils.addTab(gBrowser, "https://example.com");
+  await promiseBrowserLoaded(ungroupedTab.linkedBrowser);
+  BrowserTestUtils.removeTab(ungroupedTab);
+
+  Assert.equal(
+    SessionStore.getLastClosedTabGroupId(window),
+    null,
+    "SessionStore last closed group ID is null after closing a tab not in a group"
+  );
+
+  let savedGroupedTabs = [
+    BrowserTestUtils.addTab(gBrowser, "https://example.com"),
+    BrowserTestUtils.addTab(gBrowser, "https://example.com"),
+  ];
+  await Promise.all(
+    savedGroupedTabs.map(g => promiseBrowserLoaded(g.linkedBrowser))
+  );
+  info("Adding to tab group");
+  let savedTabGroup = gBrowser.addTabGroup(savedGroupedTabs);
+  let savedTabGroupId = savedTabGroup.id;
+
+  savedTabGroup.save();
+  info("Waiting for tab group removed");
+  removePromise = BrowserTestUtils.waitForEvent(
+    savedTabGroup,
+    "TabGroupRemoved"
+  );
+  await gBrowser.removeTabGroup(savedTabGroup);
+  await removePromise;
+
+  await TabStateFlusher.flushWindow(window);
+
+  info("Waiting for getLastClosedTabGroupId");
+  await TestUtils.waitForCondition(
+    () => SessionStore.getLastClosedTabGroupId(window) !== null
+  );
+
+  Assert.equal(
+    SessionStore.getLastClosedTabGroupId(window),
+    savedTabGroupId,
+    "SessionStore saves the ID of the last saved and closed tab group"
+  );
+
+  gBrowser.removeAllTabsBut(gBrowser.tabs[0]);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_tab_label_during_restore.js b/src/zen/tests/mochitests/sessionstore/browser_tab_label_during_restore.js
new file mode 100644
index 000000000..ef590b89e
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_tab_label_during_restore.js
@@ -0,0 +1,182 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/**
+ * Test that we don't do unnecessary tab label changes while restoring a tab.
+ */
+
+add_task(async function () {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["browser.sessionstore.restore_on_demand", true],
+      ["browser.sessionstore.restore_tabs_lazily", true],
+    ],
+  });
+
+  const BACKUP_STATE = SessionStore.getBrowserState();
+  const REMOTE_URL = "http://www.example.com/";
+  const ABOUT_ROBOTS_URI = "about:robots";
+  const ABOUT_ROBOTS_TITLE = "Gort! Klaatu barada nikto!";
+  const NO_TITLE_URL = "data:text/plain,foo";
+  const EMPTY_TAB_TITLE = gBrowser.tabContainer.emptyTabTitle;
+
+  function observeLabelChanges(tab, expectedLabels) {
+    let seenLabels = [tab.label];
+    function TabAttrModifiedListener(event) {
+      if (event.detail.changed.some(attr => attr == "label")) {
+        seenLabels.push(tab.label);
+      }
+    }
+    tab.addEventListener("TabAttrModified", TabAttrModifiedListener);
+    return async () => {
+      await TestUtils.waitForCondition(
+        () => seenLabels.length == expectedLabels.length,
+        "saw " + seenLabels.length + " TabAttrModified events"
+      );
+      tab.removeEventListener("TabAttrModified", TabAttrModifiedListener);
+      is(
+        JSON.stringify(seenLabels),
+        JSON.stringify(expectedLabels || []),
+        "observed tab label changes"
+      );
+    };
+  }
+
+  info("setting test browser state");
+  let browserLoadedPromise = BrowserTestUtils.firstBrowserLoaded(window, false);
+  await promiseBrowserState({
+    windows: [
+      {
+        tabs: [
+          { entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }] },
+          { entries: [{ url: ABOUT_ROBOTS_URI, triggeringPrincipal_base64 }] },
+          { entries: [{ url: REMOTE_URL, triggeringPrincipal_base64 }] },
+          { entries: [{ url: NO_TITLE_URL, triggeringPrincipal_base64 }] },
+          { entries: [{ url: "about:blank", triggeringPrincipal_base64 }] },
+        ],
+      },
+    ],
+  });
+  let [tab1, tab2, tab3, tab4, tab5] = gBrowser.tabs;
+  is(gBrowser.selectedTab, tab1, "first tab is selected");
+
+  await browserLoadedPromise;
+  const REMOTE_TITLE = tab1.linkedBrowser.contentTitle;
+  is(
+    tab1.linkedBrowser.currentURI.spec,
+    REMOTE_URL,
+    "correct URL loaded in first tab"
+  );
+  is(typeof REMOTE_TITLE, "string", "content title is a string");
+  isnot(REMOTE_TITLE.length, 0, "content title isn't empty");
+  isnot(REMOTE_TITLE, REMOTE_URL, "content title is different from the URL");
+  is(tab1.label, REMOTE_TITLE, "first tab displays content title");
+  ok(
+    document.title.startsWith(REMOTE_TITLE),
+    "title bar displays content title"
+  );
+  ok(tab2.hasAttribute("pending"), "second tab is pending");
+  ok(tab3.hasAttribute("pending"), "third tab is pending");
+  ok(tab4.hasAttribute("pending"), "fourth tab is pending");
+  is(tab5.label, EMPTY_TAB_TITLE, "fifth tab dislpays empty tab title");
+
+  info("selecting the second tab");
+  // The fix for bug 1364127 caused about: pages' initial tab titles to show
+  // their about: URIs until their actual page titles are known, e.g.
+  // "about:addons" -> "Add-ons Manager". This is bug 1371896. Previously,
+  // about: pages' initial tab titles were blank until the page title was known.
+  let finishObservingLabelChanges = observeLabelChanges(tab2, [
+    ABOUT_ROBOTS_URI,
+    ABOUT_ROBOTS_TITLE,
+  ]);
+  browserLoadedPromise = BrowserTestUtils.browserLoaded(
+    tab2.linkedBrowser,
+    false,
+    ABOUT_ROBOTS_URI
+  );
+  gBrowser.selectedTab = tab2;
+  await browserLoadedPromise;
+  ok(!tab2.hasAttribute("pending"), "second tab isn't pending anymore");
+  await finishObservingLabelChanges();
+  ok(
+    document.title.startsWith(ABOUT_ROBOTS_TITLE),
+    "title bar displays content title"
+  );
+
+  info("selecting the third tab");
+  finishObservingLabelChanges = observeLabelChanges(tab3, [
+    "example.com/",
+    REMOTE_TITLE,
+  ]);
+  browserLoadedPromise = BrowserTestUtils.browserLoaded(
+    tab3.linkedBrowser,
+    false,
+    REMOTE_URL
+  );
+  gBrowser.selectedTab = tab3;
+  await browserLoadedPromise;
+  ok(!tab3.hasAttribute("pending"), "third tab isn't pending anymore");
+  await finishObservingLabelChanges();
+  ok(
+    document.title.startsWith(REMOTE_TITLE),
+    "title bar displays content title"
+  );
+
+  info("selecting the fourth tab");
+  finishObservingLabelChanges = observeLabelChanges(tab4, [NO_TITLE_URL]);
+  browserLoadedPromise = BrowserTestUtils.browserLoaded(
+    tab4.linkedBrowser,
+    false,
+    NO_TITLE_URL
+  );
+  gBrowser.selectedTab = tab4;
+  await browserLoadedPromise;
+  ok(!tab4.hasAttribute("pending"), "fourth tab isn't pending anymore");
+  await finishObservingLabelChanges();
+  is(
+    document.title,
+    document.getElementById("bundle_brand").getString("brandFullName"),
+    "title bar doesn't display content title since page doesn't have one"
+  );
+
+  info("restoring the modified browser state");
+  gBrowser.selectedTab = tab3;
+  await TabStateFlusher.flushWindow(window);
+  await promiseBrowserState(SessionStore.getBrowserState());
+  [tab1, tab2, tab3, tab4, tab5] = gBrowser.tabs;
+  is(tab3, gBrowser.selectedTab, "third tab is selected after restoring");
+  ok(
+    document.title.startsWith(REMOTE_TITLE),
+    "title bar displays content title"
+  );
+  ok(tab1.hasAttribute("pending"), "first tab is pending after restoring");
+  ok(tab2.hasAttribute("pending"), "second tab is pending after restoring");
+  is(tab2.label, ABOUT_ROBOTS_TITLE, "second tab displays content title");
+  ok(!tab3.hasAttribute("pending"), "third tab is not pending after restoring");
+  is(
+    tab3.label,
+    REMOTE_TITLE,
+    "third tab displays content title in pending state"
+  );
+  ok(tab4.hasAttribute("pending"), "fourth tab is pending after restoring");
+  is(tab4.label, NO_TITLE_URL, "fourth tab displays URL");
+  is(tab5.label, EMPTY_TAB_TITLE, "fifth tab still displays empty tab title");
+
+  info("selecting the first tab");
+  finishObservingLabelChanges = observeLabelChanges(tab1, [REMOTE_TITLE]);
+  let tabContentRestored = TestUtils.topicObserved(
+    "sessionstore-debug-tab-restored"
+  );
+  gBrowser.selectedTab = tab1;
+  ok(
+    document.title.startsWith(REMOTE_TITLE),
+    "title bar displays content title"
+  );
+  await tabContentRestored;
+  ok(!tab1.hasAttribute("pending"), "first tab isn't pending anymore");
+  await finishObservingLabelChanges();
+
+  await promiseBrowserState(BACKUP_STATE);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_tab_notes_canonicalurl.js b/src/zen/tests/mochitests/sessionstore/browser_tab_notes_canonicalurl.js
new file mode 100644
index 000000000..18a44fc1b
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_tab_notes_canonicalurl.js
@@ -0,0 +1,98 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { TabNotes } = ChromeUtils.importESModule(
+  "moz-src:///browser/components/tabnotes/TabNotes.sys.mjs"
+);
+
+const BACKUP_STATE = SessionStore.getBrowserState();
+
+add_setup(async function () {
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.tabs.notes.enabled", true]],
+  });
+});
+
+registerCleanupFunction(async () => {
+  await TabNotes.reset();
+  await promiseBrowserState(BACKUP_STATE);
+});
+
+add_task(async function test_canonicalUrl_respects_privacy_level() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.sessionstore.privacy_level", 2]],
+  });
+
+  const CANONICAL_URL = "https://example.com/canonical-private";
+
+  let tab = BrowserTestUtils.addTab(gBrowser, "https://example.com/");
+  await BrowserTestUtils.browserLoaded(tab.linkedBrowser);
+  tab.canonicalUrl = CANONICAL_URL;
+
+  let state = JSON.parse(ss.getTabState(tab));
+  ok(
+    !("canonicalUrl" in state),
+    "canonicalUrl should not be saved when privacy level blocks it"
+  );
+
+  BrowserTestUtils.removeTab(tab);
+  await SpecialPowers.popPrefEnv();
+});
+
+add_task(async function test_canonicalUrl_saved_in_closed_tab_state() {
+  const CANONICAL_URL = "https://example.com/canonical-undoclose";
+
+  let tab = BrowserTestUtils.addTab(gBrowser, "https://example.com/");
+  await BrowserTestUtils.browserLoaded(tab.linkedBrowser);
+  tab.canonicalUrl = CANONICAL_URL;
+
+  let tabState = JSON.parse(ss.getTabState(tab));
+  is(
+    tabState.canonicalUrl,
+    CANONICAL_URL,
+    "canonicalUrl should be present in tab state before closing"
+  );
+
+  await promiseRemoveTabAndSessionState(tab);
+
+  let closedTabData = SessionStore.getClosedTabDataForWindow(window);
+  is(
+    closedTabData[0].state.canonicalUrl,
+    CANONICAL_URL,
+    "canonicalUrl should be preserved in closed tab data"
+  );
+
+  SessionStore.forgetClosedTab(window, 0);
+});
+
+add_task(async function test_canonicalUrl_in_session_state_on_navigation() {
+  const CANONICAL_URL = "https://example.com/canonical-nav";
+
+  let tab = BrowserTestUtils.addTab(gBrowser, "https://example.com/");
+  await BrowserTestUtils.browserLoaded(tab.linkedBrowser);
+  tab.canonicalUrl = CANONICAL_URL;
+
+  let tabState = JSON.parse(ss.getTabState(tab));
+  is(
+    tabState.canonicalUrl,
+    CANONICAL_URL,
+    "canonicalUrl should be in session state before navigation"
+  );
+
+  BrowserTestUtils.startLoadingURIString(
+    tab.linkedBrowser,
+    "https://example.org/"
+  );
+  await BrowserTestUtils.browserLoaded(tab.linkedBrowser);
+
+  tabState = JSON.parse(ss.getTabState(tab));
+  isnot(
+    tabState.canonicalUrl,
+    CANONICAL_URL,
+    "canonicalUrl should change after navigation to different URL"
+  );
+
+  BrowserTestUtils.removeTab(tab);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_tabicon_after_bg_tab_crash.js b/src/zen/tests/mochitests/sessionstore/browser_tabicon_after_bg_tab_crash.js
new file mode 100644
index 000000000..f33255867
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_tabicon_after_bg_tab_crash.js
@@ -0,0 +1,63 @@
+"use strict";
+
+const { ImageTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/ImageTestUtils.sys.mjs"
+);
+
+const FAVICON =
+  "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAsAAAALCAYAAACprHcmAAAARElEQVQYV2NkYLj3nwEnUGKEMxkYGBghilEFIQBTHKqYOIDFZHQ+DNz7j0MxdoDDGThNRgfoNsEATsXYARbFuAHtFAMAuvMbOrNomdAAAAAASUVORK5CYII=";
+const PAGE_URL = `data:text/html,
+<html>
+  <head>
+    <link rel="shortcut icon" href="${FAVICON}">
+  </head>
+  <body>
+    Favicon!
+  </body>
+</html>`;
+
+/**
+ * Tests that if a background tab crashes that it doesn't
+ * lose the favicon in the tab.
+ */
+add_task(async function test_tabicon_after_bg_tab_crash() {
+  let originalTab = gBrowser.selectedTab;
+
+  await BrowserTestUtils.withNewTab(
+    {
+      gBrowser,
+      url: PAGE_URL,
+    },
+    async function (browser) {
+      // Because there is debounce logic in FaviconLoader.sys.mjs to reduce the
+      // favicon loads, we have to wait some time before checking that icon was
+      // stored properly.
+      await TestUtils.waitForCondition(
+        () => {
+          return gBrowser.getIcon() != null;
+        },
+        "wait for favicon load to finish",
+        100,
+        5
+      );
+      await ImageTestUtils.assertEqualImage(
+        window,
+        browser.mIconURL,
+        FAVICON,
+        "Favicon is correctly set."
+      );
+
+      await BrowserTestUtils.switchTab(gBrowser, originalTab);
+      await BrowserTestUtils.crashFrame(
+        browser,
+        false /* shouldShowTabCrashPage */
+      );
+      await ImageTestUtils.assertEqualImage(
+        window,
+        browser.mIconURL,
+        FAVICON,
+        "Favicon is still set after crash."
+      );
+    }
+  );
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_tabs_in_urlbar.js b/src/zen/tests/mochitests/sessionstore/browser_tabs_in_urlbar.js
new file mode 100644
index 000000000..d971da6d6
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_tabs_in_urlbar.js
@@ -0,0 +1,151 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * Tests that tabs which aren't displayed yet (i.e. need to be reloaded) are
+ * still displayed in the address bar results.
+ */
+
+const RESTRICT_TOKEN_OPENPAGE = "%";
+
+const { PlacesTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/PlacesTestUtils.sys.mjs"
+);
+
+const { UrlbarProviderOpenTabs } = ChromeUtils.importESModule(
+  "moz-src:///browser/components/urlbar/UrlbarProviderOpenTabs.sys.mjs"
+);
+
+const { UrlbarTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/UrlbarTestUtils.sys.mjs"
+);
+
+var stateBackup = ss.getBrowserState();
+
+add_setup(async function () {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      // Set the pref to true so we know exactly how many tabs should be restoring at
+      // any given time. This guarantees that a finishing load won't start another.
+      ["browser.sessionstore.restore_on_demand", true],
+      // Don't restore tabs lazily.
+      ["browser.sessionstore.restore_tabs_lazily", false],
+    ],
+  });
+
+  registerCleanupFunction(() => {
+    ss.setBrowserState(stateBackup);
+  });
+
+  info("Waiting for the Places DB to be initialized");
+  await PlacesUtils.promiseLargeCacheDBConnection();
+  await UrlbarProviderOpenTabs.promiseDBPopulated;
+});
+
+add_task(async function test_unrestored_tabs_listed() {
+  const state = {
+    windows: [
+      {
+        tabs: [
+          {
+            entries: [
+              { url: "http://example.org/#1", triggeringPrincipal_base64 },
+            ],
+          },
+          {
+            entries: [
+              { url: "http://example.org/#2", triggeringPrincipal_base64 },
+            ],
+          },
+          {
+            entries: [
+              { url: "http://example.org/#3", triggeringPrincipal_base64 },
+            ],
+          },
+          {
+            entries: [
+              { url: "http://example.org/#4", triggeringPrincipal_base64 },
+            ],
+          },
+        ],
+        selected: 1,
+      },
+    ],
+  };
+
+  const tabsForEnsure = new Set();
+  state.windows[0].tabs.forEach(function (tab) {
+    tabsForEnsure.add(tab.entries[0].url);
+  });
+
+  let tabsRestoring = 0;
+  let tabsRestored = 0;
+
+  await new Promise(resolve => {
+    function handleEvent(aEvent) {
+      if (aEvent.type == "SSTabRestoring") {
+        tabsRestoring++;
+      } else {
+        tabsRestored++;
+      }
+
+      if (tabsRestoring < state.windows[0].tabs.length || tabsRestored < 1) {
+        return;
+      }
+
+      gBrowser.tabContainer.removeEventListener(
+        "SSTabRestoring",
+        handleEvent,
+        true
+      );
+      gBrowser.tabContainer.removeEventListener(
+        "SSTabRestored",
+        handleEvent,
+        true
+      );
+      executeSoon(resolve);
+    }
+
+    // currentURI is set before SSTabRestoring is fired, so we can sucessfully check
+    // after that has fired for all tabs. Since 1 tab will be restored though, we
+    // also need to wait for 1 SSTabRestored since currentURI will be set, unset, then set.
+    gBrowser.tabContainer.addEventListener("SSTabRestoring", handleEvent, true);
+    gBrowser.tabContainer.addEventListener("SSTabRestored", handleEvent, true);
+    ss.setBrowserState(JSON.stringify(state));
+  });
+
+  // Ensure any database statements started by UrlbarProviderOpenTabs are
+  // complete before continuing.
+  await PlacesTestUtils.promiseAsyncUpdates();
+
+  // Remove the current tab from tabsForEnsure, because switch to tab doesn't
+  // suggest it.
+  tabsForEnsure.delete(gBrowser.currentURI.spec);
+  info("Searching open pages.");
+  await UrlbarTestUtils.promiseAutocompleteResultPopup({
+    window,
+    waitForFocus,
+    value: RESTRICT_TOKEN_OPENPAGE,
+  });
+  const total = UrlbarTestUtils.getResultCount(window);
+  info(`Found ${total} matches`);
+
+  // Check to see the expected uris and titles match up (in any order)
+  for (let i = 0; i < total; i++) {
+    const result = await UrlbarTestUtils.getDetailsOfResultAt(window, i);
+    if (result.heuristic) {
+      info("Skip heuristic match");
+      continue;
+    }
+    const url = result.url;
+    Assert.ok(
+      tabsForEnsure.has(url),
+      `Should have the found result '${url}' in the expected list of entries`
+    );
+    // Remove the found entry from expected results.
+    tabsForEnsure.delete(url);
+  }
+  // Make sure there is no reported open page that is not open.
+  Assert.equal(tabsForEnsure.size, 0, "Should have found all the tabs");
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_undoCloseById.js b/src/zen/tests/mochitests/sessionstore/browser_undoCloseById.js
new file mode 100644
index 000000000..f1c49ae22
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_undoCloseById.js
@@ -0,0 +1,185 @@
+/* eslint-disable mozilla/no-arbitrary-setTimeout */
+"use strict";
+
+/**
+ * This test is for the undoCloseById function.
+ */
+
+async function openWindow(url) {
+  let win = await promiseNewWindowLoaded();
+  let flags = Ci.nsIWebNavigation.LOAD_FLAGS_REPLACE_HISTORY;
+  BrowserTestUtils.startLoadingURIString(win.gBrowser.selectedBrowser, url, {
+    flags,
+  });
+  await promiseBrowserLoaded(win.gBrowser.selectedBrowser, true, url);
+  return win;
+}
+
+async function closeWindow(win) {
+  await BrowserTestUtils.closeWindow(win);
+  // Wait 20 ms to allow SessionStorage a chance to register the closed window.
+  await new Promise(resolve => setTimeout(resolve, 20));
+}
+
+function getLastClosedTabData(win) {
+  const closedTabs = SessionStore.getClosedTabData(win);
+  return closedTabs[closedTabs.length - 1];
+}
+
+add_task(async function test_undoCloseById() {
+  // Clear the lists of closed windows and tabs.
+  forgetClosedWindows();
+  for (const win of SessionStore.getWindows()) {
+    while (SessionStore.getClosedTabCountForWindow(win)) {
+      SessionStore.forgetClosedTab(win, 0);
+    }
+  }
+  SessionStore.resetNextClosedId();
+
+  // Open a new window.
+  let win = await openWindow("about:robots");
+
+  // Open and close a tab.
+  await openAndCloseTab(win, "about:mozilla");
+  is(
+    SessionStore.lastClosedObjectType,
+    "tab",
+    "The last closed object is a tab"
+  );
+
+  // Record the first closedId created.
+  is(1, SessionStore.getClosedTabCount(), "We have 1 closed tab");
+  let initialClosedId = SessionStore.getClosedTabDataForWindow(win)[0].closedId;
+
+  // Open and close another window.
+  let win2 = await openWindow("about:mozilla");
+  await closeWindow(win2); // closedId == initialClosedId + 1
+  is(
+    SessionStore.lastClosedObjectType,
+    "window",
+    "The last closed object is a window"
+  );
+
+  // Open and close another tab in the first window.
+  await openAndCloseTab(win, "about:robots"); // closedId == initialClosedId + 2
+  is(
+    SessionStore.lastClosedObjectType,
+    "tab",
+    "The last closed object is a tab"
+  );
+
+  // Undo closing the second tab.
+  let tab = SessionStore.undoCloseById(initialClosedId + 2);
+  await promiseBrowserLoaded(tab.linkedBrowser);
+  is(
+    tab.linkedBrowser.currentURI.spec,
+    "about:robots",
+    "The expected tab was re-opened"
+  );
+
+  let notTab = SessionStore.undoCloseById(initialClosedId + 2);
+  is(notTab, undefined, "Re-opened tab cannot be unClosed again by closedId");
+
+  // Now the last closed object should be a window again.
+  is(
+    SessionStore.lastClosedObjectType,
+    "window",
+    "The last closed object is a window"
+  );
+
+  // Undo closing the first tab.
+  let tab2 = SessionStore.undoCloseById(initialClosedId);
+  await promiseBrowserLoaded(tab2.linkedBrowser);
+  is(
+    tab2.linkedBrowser.currentURI.spec,
+    "about:mozilla",
+    "The expected tab was re-opened"
+  );
+
+  // Close the two tabs we re-opened.
+  await promiseRemoveTabAndSessionState(tab); // closedId == initialClosedId + 3
+  is(
+    SessionStore.lastClosedObjectType,
+    "tab",
+    "The last closed object is a tab"
+  );
+  await promiseRemoveTabAndSessionState(tab2); // closedId == initialClosedId + 4
+  is(
+    SessionStore.lastClosedObjectType,
+    "tab",
+    "The last closed object is a tab"
+  );
+
+  // Open another new window.
+  let win3 = await openWindow("about:mozilla");
+
+  // Close both windows.
+  await closeWindow(win); // closedId == initialClosedId + 5
+  is(
+    SessionStore.lastClosedObjectType,
+    "window",
+    "The last closed object is a window"
+  );
+  await closeWindow(win3); // closedId == initialClosedId + 6
+  is(
+    SessionStore.lastClosedObjectType,
+    "window",
+    "The last closed object is a window"
+  );
+
+  // Undo closing the second window.
+  win = SessionStore.undoCloseById(initialClosedId + 6);
+  await BrowserTestUtils.waitForEvent(win, "load");
+
+  // Make sure we wait until this window is restored.
+  await BrowserTestUtils.waitForEvent(
+    win.gBrowser.tabContainer,
+    "SSTabRestored"
+  );
+
+  is(
+    win.gBrowser.selectedBrowser.currentURI.spec,
+    "about:mozilla",
+    "The expected window was re-opened"
+  );
+
+  let notWin = SessionStore.undoCloseById(initialClosedId + 6);
+  is(
+    notWin,
+    undefined,
+    "Re-opened window cannot be unClosed again by closedId"
+  );
+
+  // Close the window again.
+  await closeWindow(win);
+  is(
+    SessionStore.lastClosedObjectType,
+    "window",
+    "The last closed object is a window"
+  );
+
+  // Undo closing the first window.
+  win = SessionStore.undoCloseById(initialClosedId + 5);
+
+  await BrowserTestUtils.waitForEvent(win, "load");
+
+  // Make sure we wait until this window is restored.
+  await BrowserTestUtils.waitForEvent(
+    win.gBrowser.tabContainer,
+    "SSTabRestored"
+  );
+
+  is(
+    win.gBrowser.selectedBrowser.currentURI.spec,
+    "about:robots",
+    "The expected window was re-opened"
+  );
+
+  // Close the window again.
+  await closeWindow(win);
+  is(
+    SessionStore.lastClosedObjectType,
+    "window",
+    "The last closed object is a window"
+  );
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_undoCloseById_targetWindow.js b/src/zen/tests/mochitests/sessionstore/browser_undoCloseById_targetWindow.js
new file mode 100644
index 000000000..62e3da89e
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_undoCloseById_targetWindow.js
@@ -0,0 +1,93 @@
+"use strict";
+
+/**
+ * This test verifies SessionStore.undoCloseById behavior when passed the targetWindow argument
+ */
+
+async function openWindow(url) {
+  let win = await promiseNewWindowLoaded();
+  let flags = Ci.nsIWebNavigation.LOAD_FLAGS_REPLACE_HISTORY;
+  BrowserTestUtils.startLoadingURIString(win.gBrowser.selectedBrowser, url, {
+    flags,
+  });
+  await promiseBrowserLoaded(win.gBrowser.selectedBrowser, true, url);
+  return win;
+}
+
+async function closeWindow(win) {
+  TestUtils.waitForTick();
+  let sessionStoreUpdated = TestUtils.topicObserved(
+    "sessionstore-closed-objects-changed"
+  );
+  await BrowserTestUtils.closeWindow(win);
+  await sessionStoreUpdated;
+}
+
+function forgetTabsAndWindows() {
+  // Clear the lists of closed windows and tabs.
+  forgetClosedWindows();
+  while (SessionStore.getClosedTabCount(window)) {
+    SessionStore.forgetClosedTab(window, 0);
+  }
+}
+
+add_task(async function test_undoCloseById_with_targetWindow() {
+  forgetTabsAndWindows();
+  // Test that a tab closed in (currently open) window B, will correctly be opened in target window A.
+  // And that the closed record should be correctly removed from window B
+  const winA = window;
+  // Open a new window.
+  const winB = await openWindow("about:robots");
+  await SimpleTest.promiseFocus(winB);
+  // Open and close a tab in the 2nd window
+  await openAndCloseTab(winB, "about:mozilla");
+  is(
+    SessionStore.lastClosedObjectType,
+    "tab",
+    "The last closed object is a tab"
+  );
+  // Record the first closedId created.
+  const closedId = SessionStore.getClosedTabData(winB)[0].closedId;
+  let tabRestored = BrowserTestUtils.waitForNewTab(
+    winA.gBrowser,
+    "about:mozilla"
+  );
+
+  // Restore the tab into the first window, not the window it was closed in
+  SessionStore.undoCloseById(closedId, undefined, winA);
+  await tabRestored;
+  is(winA.gBrowser.selectedBrowser.currentURI.spec, "about:mozilla");
+
+  // Verify the closed tab data is removed from the source window
+  is(
+    SessionStore.getClosedTabData(winB).length,
+    0,
+    "Record removed from the source window's closed tab data"
+  );
+
+  BrowserTestUtils.removeTab(winA.gBrowser.selectedTab);
+  await closeWindow(winB);
+});
+
+add_task(async function test_undoCloseById_with_nonExistent_targetWindow() {
+  // Test that restoring a tab to a non-existent targetWindow throws
+  forgetTabsAndWindows();
+  await openAndCloseTab(window, "about:mozilla");
+  is(
+    SessionStore.lastClosedObjectType,
+    "tab",
+    "The last closed object is a tab"
+  );
+  // Record the first closedId created.
+  const closedId = SessionStore.getClosedTabData(window)[0].closedId;
+
+  // get a reference to a window that will be closed
+  const newWin = await BrowserTestUtils.openNewBrowserWindow();
+  await SimpleTest.promiseFocus(newWin);
+  await BrowserTestUtils.closeWindow(newWin);
+
+  // Expect an exception trying to restore a tab to a non-existent window
+  Assert.throws(() => {
+    SessionStore.undoCloseById(closedId, undefined, newWin);
+  }, /NS_ERROR_ILLEGAL_VALUE/);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_unrestored_crashedTabs.js b/src/zen/tests/mochitests/sessionstore/browser_unrestored_crashedTabs.js
new file mode 100644
index 000000000..51e54af12
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_unrestored_crashedTabs.js
@@ -0,0 +1,73 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/**
+ * Tests that if we have tabs that are still in the "click to
+ * restore" state, that if their browsers crash, that we don't
+ * show the crashed state for those tabs (since selecting them
+ * should restore them anyway).
+ */
+
+const PREF = "browser.sessionstore.restore_on_demand";
+const PAGE =
+  "data:text/html,<html><body>A%20regular,%20everyday,%20normal%20page.";
+
+add_task(async function test() {
+  await pushPrefs([PREF, true]);
+
+  await BrowserTestUtils.withNewTab(
+    {
+      gBrowser,
+      url: PAGE,
+    },
+    async function (browser) {
+      await TabStateFlusher.flush(browser);
+
+      // We'll create a second "pending" tab. This is the one we'll
+      // ensure doesn't go to about:tabcrashed. We start it non-remote
+      // since this is how SessionStore creates all browsers before
+      // they are restored.
+      let unrestoredTab = BrowserTestUtils.addTab(gBrowser, "about:blank", {
+        skipAnimation: true,
+        forceNotRemote: true,
+      });
+
+      let state = {
+        entries: [{ url: PAGE, triggeringPrincipal_base64 }],
+      };
+
+      ss.setTabState(unrestoredTab, JSON.stringify(state));
+
+      ok(!unrestoredTab.hasAttribute("crashed"), "tab is not crashed");
+      ok(unrestoredTab.hasAttribute("pending"), "tab is pending");
+
+      // Now crash the selected browser.
+      await BrowserTestUtils.crashFrame(browser);
+
+      ok(!unrestoredTab.hasAttribute("crashed"), "tab is still not crashed");
+      ok(unrestoredTab.hasAttribute("pending"), "tab is still pending");
+
+      // Selecting the tab should now restore it.
+      gBrowser.selectedTab = unrestoredTab;
+      await promiseTabRestored(unrestoredTab);
+
+      ok(!unrestoredTab.hasAttribute("crashed"), "tab is still not crashed");
+      ok(!unrestoredTab.hasAttribute("pending"), "tab is no longer pending");
+
+      // The original tab should still be crashed
+      let originalTab = gBrowser.getTabForBrowser(browser);
+      ok(originalTab.hasAttribute("crashed"), "original tab is crashed");
+      ok(!originalTab.isRemoteBrowser, "Should not be remote");
+
+      // We'd better be able to restore it still.
+      gBrowser.selectedTab = originalTab;
+      SessionStore.reviveCrashedTab(originalTab);
+      await promiseTabRestored(originalTab);
+
+      // Clean up.
+      BrowserTestUtils.removeTab(unrestoredTab);
+    }
+  );
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_upgrade_backup.js b/src/zen/tests/mochitests/sessionstore/browser_upgrade_backup.js
new file mode 100644
index 000000000..dd803a163
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_upgrade_backup.js
@@ -0,0 +1,161 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const Paths = SessionFile.Paths;
+const PREF_UPGRADE = "browser.sessionstore.upgradeBackup.latestBuildID";
+const PREF_MAX_UPGRADE_BACKUPS =
+  "browser.sessionstore.upgradeBackup.maxUpgradeBackups";
+
+/**
+ * Prepares tests by retrieving the current platform's build ID, clearing the
+ * build where the last backup was created and creating arbitrary JSON data
+ * for a new backup.
+ */
+function prepareTest() {
+  let result = {};
+
+  result.buildID = Services.appinfo.platformBuildID;
+  Services.prefs.setCharPref(PREF_UPGRADE, "");
+  result.contents = {
+    "browser_upgrade_backup.js": Math.random(),
+  };
+
+  return result;
+}
+
+/**
+ * Retrieves all upgrade backups and returns them in an array.
+ */
+async function getUpgradeBackups() {
+  let children = await IOUtils.getChildren(Paths.backups);
+
+  return children.filter(path => path.startsWith(Paths.upgradeBackupPrefix));
+}
+
+add_setup(async function () {
+  await SpecialPowers.pushPrefEnv({
+    set: [["test.wait300msAfterTabSwitch", true]],
+  });
+
+  // Wait until initialization is complete
+  await SessionStore.promiseInitialized;
+});
+
+add_task(async function test_upgrade_backup() {
+  let test = prepareTest();
+  info("Let's check if we create an upgrade backup");
+  await SessionFile.wipe();
+  await IOUtils.writeJSON(Paths.clean, test.contents, {
+    compress: true,
+  });
+  info("Call `SessionFile.read()` to set state to 'clean'");
+  await SessionFile.read();
+  await SessionFile.write(""); // First call to write() triggers the backup
+
+  Assert.equal(
+    Services.prefs.getCharPref(PREF_UPGRADE),
+    test.buildID,
+    "upgrade backup should be set"
+  );
+
+  Assert.ok(
+    await IOUtils.exists(Paths.upgradeBackup),
+    "upgrade backup file has been created"
+  );
+
+  let data = await IOUtils.readJSON(Paths.upgradeBackup, { decompress: true });
+  Assert.deepEqual(
+    test.contents,
+    data,
+    "upgrade backup contains the expected contents"
+  );
+
+  info("Let's check that we don't overwrite this upgrade backup");
+  let newContents = {
+    "something else entirely": Math.random(),
+  };
+  await IOUtils.writeJSON(Paths.clean, newContents, {
+    compress: true,
+  });
+  await SessionFile.write(""); // Next call to write() shouldn't trigger the backup
+  data = await IOUtils.readJSON(Paths.upgradeBackup, { decompress: true });
+  Assert.deepEqual(test.contents, data, "upgrade backup hasn't changed");
+});
+
+add_task(async function test_upgrade_backup_removal() {
+  let test = prepareTest();
+  let maxUpgradeBackups = Services.prefs.getIntPref(
+    PREF_MAX_UPGRADE_BACKUPS,
+    3
+  );
+  info("Let's see if we remove backups if there are too many");
+  await SessionFile.wipe();
+  await IOUtils.writeJSON(Paths.clean, test.contents, {
+    compress: true,
+  });
+  info("Call `SessionFile.read()` to set state to 'clean'");
+  await SessionFile.read();
+
+  // create dummy backups
+  await IOUtils.writeUTF8(Paths.upgradeBackupPrefix + "20080101010101", "", {
+    compress: true,
+  });
+  await IOUtils.writeUTF8(Paths.upgradeBackupPrefix + "20090101010101", "", {
+    compress: true,
+  });
+  await IOUtils.writeUTF8(Paths.upgradeBackupPrefix + "20100101010101", "", {
+    compress: true,
+  });
+  await IOUtils.writeUTF8(Paths.upgradeBackupPrefix + "20110101010101", "", {
+    compress: true,
+  });
+  await IOUtils.writeUTF8(Paths.upgradeBackupPrefix + "20120101010101", "", {
+    compress: true,
+  });
+  await IOUtils.writeUTF8(Paths.upgradeBackupPrefix + "20130101010101", "", {
+    compress: true,
+  });
+
+  // get currently existing backups
+  let backups = await getUpgradeBackups();
+
+  info("Write the session to disk and perform a backup");
+  await SessionFile.write(""); // First call to write() triggers the backup and the cleanup
+
+  // a new backup should have been created (and still exist)
+  is(
+    Services.prefs.getCharPref(PREF_UPGRADE),
+    test.buildID,
+    "upgrade backup should be set"
+  );
+  Assert.ok(
+    await IOUtils.exists(Paths.upgradeBackup),
+    "upgrade backup file has been created"
+  );
+
+  // get currently existing backups and check their count
+  let newBackups = await getUpgradeBackups();
+  is(
+    newBackups.length,
+    maxUpgradeBackups,
+    "expected number of backups are present after removing old backups"
+  );
+
+  // find all backups that were created during the last call to `SessionFile.write("");`
+  // ie, filter out all the backups that have already been present before the call
+  newBackups = newBackups.filter(function (backup) {
+    return !backups.includes(backup);
+  });
+
+  // check that exactly one new backup was created
+  is(newBackups.length, 1, "one new backup was created that was not removed");
+
+  await SessionFile.write(""); // Second call to write() should not trigger anything
+
+  backups = await getUpgradeBackups();
+  is(
+    backups.length,
+    maxUpgradeBackups,
+    "second call to SessionFile.write() didn't create or remove more backups"
+  );
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_urlbarSearchMode.js b/src/zen/tests/mochitests/sessionstore/browser_urlbarSearchMode.js
new file mode 100644
index 000000000..ffba47d98
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_urlbarSearchMode.js
@@ -0,0 +1,60 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/**
+ * This test makes sure that the urlbar's search mode is correctly preserved.
+ */
+
+ChromeUtils.defineESModuleGetters(this, {
+  UrlbarShared: "chrome://browser/content/urlbar/UrlbarShared.mjs",
+});
+
+ChromeUtils.defineLazyGetter(this, "UrlbarTestUtils", () => {
+  const { UrlbarTestUtils: module } = ChromeUtils.importESModule(
+    "resource://testing-common/UrlbarTestUtils.sys.mjs"
+  );
+  module.init(this);
+  return module;
+});
+
+add_task(async function test() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.urlbar.scotchBonnet.enableOverride", false]],
+  });
+  // Open the urlbar view and enter search mode.
+  await UrlbarTestUtils.promiseAutocompleteResultPopup({
+    window,
+    value: "test",
+  });
+  await UrlbarTestUtils.enterSearchMode(window, {
+    source: UrlbarShared.RESULT_SOURCE.HISTORY,
+  });
+
+  // The search mode should be in the tab state.
+  let state = JSON.parse(ss.getTabState(gBrowser.selectedTab));
+  Assert.ok(
+    "searchMode" in state,
+    "state.searchMode is present after entering search mode"
+  );
+  Assert.deepEqual(
+    state.searchMode,
+    {
+      source: UrlbarShared.RESULT_SOURCE.HISTORY,
+      entry: "oneoff",
+      isPreview: false,
+    },
+    "state.searchMode is correct"
+  );
+
+  // Exit search mode.
+  await UrlbarTestUtils.exitSearchMode(window);
+
+  // The search mode should not be in the tab state.
+  let newState = JSON.parse(ss.getTabState(gBrowser.selectedTab));
+  Assert.ok(
+    !newState.searchMode,
+    "state.searchMode is not present after exiting search mode"
+  );
+
+  await UrlbarTestUtils.promisePopupClose(window);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_userTyped_restored_after_discard.js b/src/zen/tests/mochitests/sessionstore/browser_userTyped_restored_after_discard.js
new file mode 100644
index 000000000..171197a74
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_userTyped_restored_after_discard.js
@@ -0,0 +1,47 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+add_task(async function testDiscardWithNotLoadedUserTypedValue() {
+  let tab1 = await BrowserTestUtils.openNewForegroundTab(
+    gBrowser,
+    "https://example.com"
+  );
+
+  // Make sure we flushed the state at least once (otherwise the fix
+  // for Bug 1422588 would make SessionStore.resetBrowserToLazyState
+  // to still store the user typed value into the tab state cache
+  // even when the user typed value was not yet being loading when
+  // the tab got discarded).
+  await TabStateFlusher.flush(tab1.linkedBrowser);
+
+  tab1.linkedBrowser.userTypedValue = "mockUserTypedValue";
+
+  let tab2 = await BrowserTestUtils.openNewForegroundTab(
+    gBrowser,
+    "about:robots"
+  );
+
+  let waitForTabDiscarded = BrowserTestUtils.waitForEvent(
+    tab1,
+    "TabBrowserDiscarded"
+  );
+  gBrowser.discardBrowser(tab1);
+  await waitForTabDiscarded;
+
+  const promiseTabLoaded = BrowserTestUtils.browserLoaded(
+    tab1.linkedBrowser,
+    false,
+    "https://example.com/"
+  );
+  await BrowserTestUtils.switchTab(gBrowser, tab1);
+  info("Wait for the restored tab to load https://example.com");
+  await promiseTabLoaded;
+  is(
+    tab1.linkedBrowser.currentURI.spec,
+    "https://example.com/",
+    "Restored discarded tab has loaded the expected url"
+  );
+
+  BrowserTestUtils.removeTab(tab2);
+  BrowserTestUtils.removeTab(tab1);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_windowRestore_perwindowpb.js b/src/zen/tests/mochitests/sessionstore/browser_windowRestore_perwindowpb.js
new file mode 100644
index 000000000..73568cb34
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_windowRestore_perwindowpb.js
@@ -0,0 +1,32 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// This test checks that closed private windows can't be restored
+
+function test() {
+  waitForExplicitFinish();
+
+  // Purging the list of closed windows
+  forgetClosedWindows();
+
+  // Load a private window, then close it
+  // and verify it doesn't get remembered for restoring
+  whenNewWindowLoaded({ private: true }, function (win) {
+    info("The private window got loaded");
+    win.addEventListener(
+      "SSWindowClosing",
+      function () {
+        executeSoon(function () {
+          is(
+            ss.getClosedWindowCount(),
+            0,
+            "The private window should not have been stored"
+          );
+        });
+      },
+      { once: true }
+    );
+    BrowserTestUtils.closeWindow(win).then(finish);
+  });
+}
diff --git a/src/zen/tests/mochitests/sessionstore/browser_windowStateContainer.js b/src/zen/tests/mochitests/sessionstore/browser_windowStateContainer.js
new file mode 100644
index 000000000..5b0fb6393
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_windowStateContainer.js
@@ -0,0 +1,168 @@
+"use strict";
+
+requestLongerTimeout(2);
+
+add_setup(async function () {
+  await SpecialPowers.pushPrefEnv({
+    set: [["dom.ipc.processCount", 1]],
+  });
+});
+
+function promiseTabsRestored(win, nExpected) {
+  return new Promise(resolve => {
+    let nReceived = 0;
+    function handler() {
+      if (++nReceived === nExpected) {
+        win.gBrowser.tabContainer.removeEventListener(
+          "SSTabRestored",
+          handler,
+          true
+        );
+        resolve();
+      }
+    }
+    win.gBrowser.tabContainer.addEventListener("SSTabRestored", handler, true);
+  });
+}
+
+add_task(async function () {
+  let win = await BrowserTestUtils.openNewBrowserWindow();
+
+  // Create 4 tabs with different userContextId.
+  for (let userContextId = 1; userContextId < 5; userContextId++) {
+    let tab = BrowserTestUtils.addTab(win.gBrowser, "http://example.com/", {
+      userContextId,
+    });
+    await promiseBrowserLoaded(tab.linkedBrowser);
+    await TabStateFlusher.flush(tab.linkedBrowser);
+  }
+
+  // Move the default tab of window to the end.
+  // We want the 1st tab to have non-default userContextId, so later when we
+  // restore into win2 we can test restore into an existing tab with different
+  // userContextId.
+  win.gBrowser.moveTabToEnd(win.gBrowser.tabs[0]);
+
+  let winState = ss.getWindowState(win);
+
+  for (let i = 0; i < 4; i++) {
+    Assert.equal(
+      winState.windows[0].tabs[i].userContextId,
+      i + 1,
+      "1st Window: tabs[" + i + "].userContextId should exist."
+    );
+  }
+
+  let win2 = await BrowserTestUtils.openNewBrowserWindow();
+
+  // Create tabs with different userContextId, but this time we create them with
+  // fewer tabs and with different order with win.
+  for (let userContextId = 3; userContextId > 0; userContextId--) {
+    let tab = BrowserTestUtils.addTab(win2.gBrowser, "http://example.com/", {
+      userContextId,
+    });
+    await promiseBrowserLoaded(tab.linkedBrowser);
+    await TabStateFlusher.flush(tab.linkedBrowser);
+  }
+
+  let tabsRestored = promiseTabsRestored(win2, 5);
+  await setWindowState(win2, winState, true);
+  await tabsRestored;
+
+  for (let i = 0; i < 4; i++) {
+    let browser = win2.gBrowser.tabs[i].linkedBrowser;
+    await SpecialPowers.spawn(browser, [i + 1], async function (expectedId) {
+      Assert.equal(
+        docShell.getOriginAttributes().userContextId,
+        expectedId,
+        "The docShell has the correct userContextId"
+      );
+
+      Assert.equal(
+        content.document.nodePrincipal.originAttributes.userContextId,
+        expectedId,
+        "The document has the correct userContextId"
+      );
+    });
+  }
+
+  // Test the last tab, which doesn't have userContextId.
+  let browser = win2.gBrowser.tabs[4].linkedBrowser;
+  await SpecialPowers.spawn(browser, [0], async function (expectedId) {
+    Assert.equal(
+      docShell.getOriginAttributes().userContextId,
+      expectedId,
+      "The docShell has the correct userContextId"
+    );
+
+    Assert.equal(
+      content.document.nodePrincipal.originAttributes.userContextId,
+      expectedId,
+      "The document has the correct userContextId"
+    );
+  });
+
+  await BrowserTestUtils.closeWindow(win);
+  await BrowserTestUtils.closeWindow(win2);
+});
+
+add_task(async function () {
+  let win = await BrowserTestUtils.openNewBrowserWindow();
+  await TabStateFlusher.flush(win.gBrowser.selectedBrowser);
+
+  let tab = BrowserTestUtils.addTab(win.gBrowser, "http://example.com/", {
+    userContextId: 1,
+  });
+  await promiseBrowserLoaded(tab.linkedBrowser);
+  await TabStateFlusher.flush(tab.linkedBrowser);
+
+  // win should have 1 default tab, and 1 container tab.
+  Assert.equal(win.gBrowser.tabs.length, 2, "win should have 2 tabs");
+
+  let winState = ss.getWindowState(win);
+
+  for (let i = 0; i < 2; i++) {
+    Assert.equal(
+      winState.windows[0].tabs[i].userContextId,
+      i,
+      "1st Window: tabs[" + i + "].userContextId should be " + i
+    );
+  }
+
+  let win2 = await BrowserTestUtils.openNewBrowserWindow();
+
+  let tab2 = BrowserTestUtils.addTab(win2.gBrowser, "http://example.com/", {
+    userContextId: 1,
+  });
+  await promiseBrowserLoaded(tab2.linkedBrowser);
+  await TabStateFlusher.flush(tab2.linkedBrowser);
+
+  // Move the first normal tab to end, so the first tab of win2 will be a
+  // container tab.
+  win2.gBrowser.moveTabToEnd(win2.gBrowser.tabs[0]);
+  await TabStateFlusher.flush(win2.gBrowser.tabs[0].linkedBrowser);
+
+  let tabsRestored = promiseTabsRestored(win2, 2);
+  await setWindowState(win2, winState, true);
+  await tabsRestored;
+
+  for (let i = 0; i < 2; i++) {
+    let browser = win2.gBrowser.tabs[i].linkedBrowser;
+    await SpecialPowers.spawn(browser, [i], async function (expectedId) {
+      Assert.equal(
+        docShell.getOriginAttributes().userContextId,
+        expectedId,
+        "The docShell has the correct userContextId"
+      );
+
+      Assert.equal(
+        content.document.nodePrincipal.originAttributes.userContextId,
+        expectedId,
+        "The document has the correct userContextId"
+      );
+    });
+  }
+
+  await BrowserTestUtils.closeWindow(win);
+  await BrowserTestUtils.closeWindow(win2);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/browser_wireframe_basic.js b/src/zen/tests/mochitests/sessionstore/browser_wireframe_basic.js
new file mode 100644
index 000000000..7e35aa257
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/browser_wireframe_basic.js
@@ -0,0 +1,48 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+add_setup(async function () {
+  await SpecialPowers.pushPrefEnv({
+    set: [["test.wait300msAfterTabSwitch", true]],
+  });
+});
+
+/**
+ * Ensure that document wireframes are persisted when enabled,
+ * and that we can generate previews for them.
+ */
+add_task(async function thumbnails_wireframe_basic() {
+  // Wireframes only works when Fission is enabled.
+  if (!Services.appinfo.fissionAutostart) {
+    ok(true, "Skipping test_wireframes when Fission is not enabled.");
+    return;
+  }
+
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.history.collectWireframes", true]],
+  });
+
+  let tab = await BrowserTestUtils.openNewForegroundTab(
+    gBrowser,
+    "https://www.example.com/"
+  );
+  await TabStateFlusher.flush(tab.linkedBrowser);
+  info("Checking a loaded tab");
+  checkWireframeForTab(tab);
+
+  await BrowserTestUtils.switchTab(gBrowser, gBrowser.tabs[0]);
+  gBrowser.discardBrowser(tab, true);
+
+  info("Checking a discarded tab");
+  checkWireframeForTab(tab);
+
+  gBrowser.removeTab(tab);
+});
+
+function checkWireframeForTab(tab) {
+  let wireframe = PageWireframes.getWireframeState(tab);
+  ok(wireframe, "After load: Got wireframe state");
+  Assert.greater(wireframe.rects.length, 0, "After load: Got wireframe rects");
+  let wireframeElement = PageWireframes.getWireframeElementForTab(tab);
+  is(wireframeElement.tagName, "svg", "Got wireframe element");
+}
diff --git a/src/zen/tests/mochitests/sessionstore/coopHeaderCommon.sjs b/src/zen/tests/mochitests/sessionstore/coopHeaderCommon.sjs
new file mode 100644
index 000000000..be4607b2c
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/coopHeaderCommon.sjs
@@ -0,0 +1,32 @@
+function handleRequest(request, response) {
+  let { NetUtil } = ChromeUtils.importESModule(
+    "resource://gre/modules/NetUtil.sys.mjs"
+  );
+  let query = new URLSearchParams(request.queryString);
+
+  response.setHeader("Cross-Origin-Opener-Policy", "same-origin", false);
+  response.setHeader("Cross-Origin-Embedder-Policy", "require-corp", false);
+
+  var fileRoot = query.get("fileRoot");
+
+  // Get the desired file
+  var file;
+  getObjectState("SERVER_ROOT", function (serverRoot) {
+    file = serverRoot.getFile(fileRoot);
+  });
+
+  // Set up the file streams to read in the file as UTF-8
+  let fstream = Cc["@mozilla.org/network/file-input-stream;1"].createInstance(
+    Ci.nsIFileInputStream
+  );
+
+  fstream.init(file, -1, 0, 0);
+
+  // Read the file
+  let available = fstream.available();
+  let data =
+    available > 0 ? NetUtil.readInputStreamToString(fstream, available) : "";
+  fstream.close();
+
+  response.write(data);
+}
diff --git a/src/zen/tests/mochitests/sessionstore/coop_coep.html b/src/zen/tests/mochitests/sessionstore/coop_coep.html
new file mode 100644
index 000000000..9fe6f7a03
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/coop_coep.html
@@ -0,0 +1,6 @@
+<!DOCTYPE html>
+
+<html>
+  <body>
+  </body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/coop_coep.html^headers^ b/src/zen/tests/mochitests/sessionstore/coop_coep.html^headers^
new file mode 100644
index 000000000..5f8621ef8
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/coop_coep.html^headers^
@@ -0,0 +1,2 @@
+Cross-Origin-Embedder-Policy: require-corp
+Cross-Origin-Opener-Policy: same-origin
diff --git a/src/zen/tests/mochitests/sessionstore/empty.html b/src/zen/tests/mochitests/sessionstore/empty.html
new file mode 100644
index 000000000..ba0056bc3
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/empty.html
@@ -0,0 +1,6 @@
+<!DOCTYPE html>
+<meta charset="UTF-8">
+<html>
+  <body>
+  </body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/empty_frame.html b/src/zen/tests/mochitests/sessionstore/empty_frame.html
new file mode 100644
index 000000000..9b65f2c24
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/empty_frame.html
@@ -0,0 +1,7 @@
+<!DOCTYPE html>
+<meta charset="UTF-8">
+<html>
+  <body>
+    <iframe src="empty.html" id="emptyFrame"></iframe>
+  </body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/entry1.html b/src/zen/tests/mochitests/sessionstore/entry1.html
new file mode 100644
index 000000000..ba0056bc3
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/entry1.html
@@ -0,0 +1,6 @@
+<!DOCTYPE html>
+<meta charset="UTF-8">
+<html>
+  <body>
+  </body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/entry2.html b/src/zen/tests/mochitests/sessionstore/entry2.html
new file mode 100644
index 000000000..ba0056bc3
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/entry2.html
@@ -0,0 +1,6 @@
+<!DOCTYPE html>
+<meta charset="UTF-8">
+<html>
+  <body>
+  </body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/entry3.html b/src/zen/tests/mochitests/sessionstore/entry3.html
new file mode 100644
index 000000000..ba0056bc3
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/entry3.html
@@ -0,0 +1,6 @@
+<!DOCTYPE html>
+<meta charset="UTF-8">
+<html>
+  <body>
+  </body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/file_async_duplicate_tab.html b/src/zen/tests/mochitests/sessionstore/file_async_duplicate_tab.html
new file mode 100644
index 000000000..76bf22127
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/file_async_duplicate_tab.html
@@ -0,0 +1 @@
+<a href=#section>clickme</a>
diff --git a/src/zen/tests/mochitests/sessionstore/file_async_flushes.html b/src/zen/tests/mochitests/sessionstore/file_async_flushes.html
new file mode 100644
index 000000000..76bf22127
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/file_async_flushes.html
@@ -0,0 +1 @@
+<a href=#section>clickme</a>
diff --git a/src/zen/tests/mochitests/sessionstore/file_formdata_password.html b/src/zen/tests/mochitests/sessionstore/file_formdata_password.html
new file mode 100644
index 000000000..0f072c31e
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/file_formdata_password.html
@@ -0,0 +1,17 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8">
+  </head>
+  <body>
+    <!-- Text/Password in the name indicates the type and the position of 'Value'
+         indicates when the value gets set relative to the type changes. -->
+    <input id="TextValue">
+    <input id="TextValuePassword">
+    <input id="TextPasswordValue">
+
+    <input id="PasswordValueText" type="password">
+    <input id="PasswordTextValue" type="password">
+    <input id="PasswordValue" type="password">
+  </body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/file_sessionHistory_hashchange.html b/src/zen/tests/mochitests/sessionstore/file_sessionHistory_hashchange.html
new file mode 100644
index 000000000..3cbe3e353
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/file_sessionHistory_hashchange.html
@@ -0,0 +1 @@
+<a id=a href=#section>clickme</a>
diff --git a/src/zen/tests/mochitests/sessionstore/head.js b/src/zen/tests/mochitests/sessionstore/head.js
new file mode 100644
index 000000000..78f777a42
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/head.js
@@ -0,0 +1,680 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const triggeringPrincipal_base64 = E10SUtils.SERIALIZED_SYSTEMPRINCIPAL;
+
+const TAB_STATE_NEEDS_RESTORE = 1;
+const TAB_STATE_RESTORING = 2;
+
+const ROOT = getRootDirectory(gTestPath);
+const HTTPROOT = ROOT.replace(
+  "chrome://mochitests/content/",
+  "http://example.com/"
+);
+const HTTPSROOT = ROOT.replace(
+  "chrome://mochitests/content/",
+  "https://example.com/"
+);
+
+const { SessionSaver } = ChromeUtils.importESModule(
+  "resource:///modules/sessionstore/SessionSaver.sys.mjs"
+);
+const { SessionFile } = ChromeUtils.importESModule(
+  "resource:///modules/sessionstore/SessionFile.sys.mjs"
+);
+const { TabState } = ChromeUtils.importESModule(
+  "resource:///modules/sessionstore/TabState.sys.mjs"
+);
+const { TabStateFlusher } = ChromeUtils.importESModule(
+  "resource:///modules/sessionstore/TabStateFlusher.sys.mjs"
+);
+const { SessionStoreTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/SessionStoreTestUtils.sys.mjs"
+);
+
+const { PageWireframes } = ChromeUtils.importESModule(
+  "resource:///modules/sessionstore/PageWireframes.sys.mjs"
+);
+
+const ss = SessionStore;
+SessionStoreTestUtils.init(this, window);
+
+// Some tests here assume that all restored tabs are loaded without waiting for
+// the user to bring them to the foreground. We ensure this by resetting the
+// related preference (see the "firefox.js" defaults file for details).
+Services.prefs.setBoolPref("browser.sessionstore.restore_on_demand", false);
+registerCleanupFunction(function () {
+  Services.prefs.clearUserPref("browser.sessionstore.restore_on_demand");
+});
+
+// Obtain access to internals
+Services.prefs.setBoolPref("browser.sessionstore.debug", true);
+registerCleanupFunction(function () {
+  Services.prefs.clearUserPref("browser.sessionstore.debug");
+});
+
+// This kicks off the search service used on about:home and allows the
+// session restore tests to be run standalone without triggering errors.
+Cc["@mozilla.org/browser/clh;1"].getService(Ci.nsIBrowserHandler).defaultArgs;
+
+function provideWindow(aCallback, aURL, aFeatures) {
+  function callbackSoon(aWindow) {
+    executeSoon(function executeCallbackSoon() {
+      aCallback(aWindow);
+    });
+  }
+
+  let win = openDialog(
+    AppConstants.BROWSER_CHROME_URL,
+    "",
+    aFeatures || "chrome,all,dialog=no",
+    aURL || "about:blank"
+  );
+  whenWindowLoaded(win, function onWindowLoaded(aWin) {
+    if (!aURL) {
+      info("Loaded a blank window.");
+      callbackSoon(aWin);
+      return;
+    }
+
+    aWin.gBrowser.selectedBrowser.addEventListener(
+      "load",
+      function () {
+        callbackSoon(aWin);
+      },
+      { capture: true, once: true }
+    );
+  });
+}
+
+// This assumes that tests will at least have some state/entries
+function waitForBrowserState(aState, aSetStateCallback) {
+  return SessionStoreTestUtils.waitForBrowserState(aState, aSetStateCallback);
+}
+
+function promiseBrowserState(aState) {
+  return SessionStoreTestUtils.promiseBrowserState(aState);
+}
+
+function promiseTabState(tab, state) {
+  if (typeof state != "string") {
+    state = JSON.stringify(state);
+  }
+
+  let promise = promiseTabRestored(tab);
+  ss.setTabState(tab, state);
+  return promise;
+}
+
+function promiseWindowRestoring(win) {
+  return new Promise(resolve =>
+    win.addEventListener("SSWindowRestoring", resolve, { once: true })
+  );
+}
+
+function promiseWindowRestored(win) {
+  return new Promise(resolve =>
+    win.addEventListener("SSWindowRestored", resolve, { once: true })
+  );
+}
+
+async function setBrowserState(state, win = window) {
+  ss.setBrowserState(typeof state != "string" ? JSON.stringify(state) : state);
+  await promiseWindowRestored(win);
+}
+
+async function setWindowState(win, state, overwrite = false) {
+  ss.setWindowState(
+    win,
+    typeof state != "string" ? JSON.stringify(state) : state,
+    overwrite
+  );
+  await promiseWindowRestored(win);
+}
+
+function waitForTopic(aTopic, aTimeout, aCallback) {
+  let observing = false;
+  function removeObserver() {
+    if (!observing) {
+      return;
+    }
+    Services.obs.removeObserver(observer, aTopic);
+    observing = false;
+  }
+
+  let timeout = setTimeout(function () {
+    removeObserver();
+    aCallback(false);
+  }, aTimeout);
+
+  function observer() {
+    removeObserver();
+    timeout = clearTimeout(timeout);
+    executeSoon(() => aCallback(true));
+  }
+
+  registerCleanupFunction(function () {
+    removeObserver();
+    if (timeout) {
+      clearTimeout(timeout);
+    }
+  });
+
+  observing = true;
+  Services.obs.addObserver(observer, aTopic);
+}
+
+/**
+ * Wait until session restore has finished collecting its data and is
+ * has written that data ("sessionstore-state-write-complete").
+ *
+ * @param {function} aCallback If sessionstore-state-write-complete is sent
+ * within buffering interval + 100 ms, the callback is passed |true|,
+ * otherwise, it is passed |false|.
+ */
+function waitForSaveState(aCallback) {
+  let timeout =
+    100 + Services.prefs.getIntPref("browser.sessionstore.interval");
+  return waitForTopic("sessionstore-state-write-complete", timeout, aCallback);
+}
+function promiseSaveState() {
+  return new Promise((resolve, reject) => {
+    waitForSaveState(isSuccessful => {
+      if (!isSuccessful) {
+        reject(new Error("Save state timeout"));
+      } else {
+        resolve();
+      }
+    });
+  });
+}
+function forceSaveState() {
+  return SessionSaver.run();
+}
+
+function promiseRecoveryFileContents() {
+  let promise = forceSaveState();
+  return promise.then(function () {
+    return IOUtils.readUTF8(SessionFile.Paths.recovery, {
+      decompress: true,
+    });
+  });
+}
+
+var promiseForEachSessionRestoreFile = async function (cb) {
+  for (let key of SessionFile.Paths.loadOrder) {
+    let data = "";
+    try {
+      data = await IOUtils.readUTF8(SessionFile.Paths[key], {
+        decompress: true,
+      });
+    } catch (ex) {
+      // Ignore missing files
+      if (!(DOMException.isInstance(ex) && ex.name == "NotFoundError")) {
+        throw ex;
+      }
+    }
+    cb(data, key);
+  }
+};
+
+function promiseBrowserLoaded(
+  aBrowser,
+  ignoreSubFrames = true,
+  wantLoad = null
+) {
+  return BrowserTestUtils.browserLoaded(aBrowser, !ignoreSubFrames, wantLoad);
+}
+
+function whenWindowLoaded(aWindow, aCallback) {
+  aWindow.addEventListener(
+    "load",
+    function () {
+      executeSoon(function executeWhenWindowLoaded() {
+        aCallback(aWindow);
+      });
+    },
+    { once: true }
+  );
+}
+function promiseWindowLoaded(aWindow) {
+  return new Promise(resolve => whenWindowLoaded(aWindow, resolve));
+}
+
+var gUniqueCounter = 0;
+function r() {
+  return Date.now() + "-" + ++gUniqueCounter;
+}
+
+function* BrowserWindowIterator() {
+  for (let currentWindow of Services.wm.getEnumerator("navigator:browser")) {
+    if (!currentWindow.closed) {
+      yield currentWindow;
+    }
+  }
+}
+
+var gWebProgressListener = {
+  _callback: null,
+
+  setCallback(aCallback) {
+    if (!this._callback) {
+      window.gBrowser.addTabsProgressListener(this);
+    }
+    this._callback = aCallback;
+  },
+
+  unsetCallback() {
+    if (this._callback) {
+      this._callback = null;
+      window.gBrowser.removeTabsProgressListener(this);
+    }
+  },
+
+  onStateChange(aBrowser, aWebProgress, aRequest, aStateFlags, _aStatus) {
+    if (
+      aStateFlags & Ci.nsIWebProgressListener.STATE_STOP &&
+      aStateFlags & Ci.nsIWebProgressListener.STATE_IS_NETWORK &&
+      aStateFlags & Ci.nsIWebProgressListener.STATE_IS_WINDOW
+    ) {
+      this._callback(aBrowser);
+    }
+  },
+};
+
+registerCleanupFunction(function () {
+  gWebProgressListener.unsetCallback();
+});
+
+var gProgressListener = {
+  _callback: null,
+
+  setCallback(callback) {
+    Services.obs.addObserver(this, "sessionstore-debug-tab-restored");
+    this._callback = callback;
+  },
+
+  unsetCallback() {
+    if (this._callback) {
+      this._callback = null;
+      Services.obs.removeObserver(this, "sessionstore-debug-tab-restored");
+    }
+  },
+
+  observe(browser) {
+    gProgressListener.onRestored(browser);
+  },
+
+  onRestored(browser) {
+    if (ss.getInternalObjectState(browser) == TAB_STATE_RESTORING) {
+      let args = [browser].concat(gProgressListener._countTabs());
+      gProgressListener._callback.apply(gProgressListener, args);
+    }
+  },
+
+  _countTabs() {
+    let needsRestore = 0,
+      isRestoring = 0,
+      wasRestored = 0;
+
+    for (let win of BrowserWindowIterator()) {
+      for (let i = 0; i < win.gBrowser.tabs.length; i++) {
+        let browser = win.gBrowser.tabs[i].linkedBrowser;
+        let state = ss.getInternalObjectState(browser);
+        if (browser.isConnected && !state) {
+          wasRestored++;
+        } else if (state == TAB_STATE_RESTORING) {
+          isRestoring++;
+        } else if (state == TAB_STATE_NEEDS_RESTORE || !browser.isConnected) {
+          needsRestore++;
+        }
+      }
+    }
+    return [needsRestore, isRestoring, wasRestored];
+  },
+};
+
+registerCleanupFunction(function () {
+  gProgressListener.unsetCallback();
+});
+
+// Close all but our primary window.
+function promiseAllButPrimaryWindowClosed() {
+  let windows = [];
+  for (let win of BrowserWindowIterator()) {
+    if (win != window) {
+      windows.push(win);
+    }
+  }
+
+  return Promise.all(windows.map(BrowserTestUtils.closeWindow));
+}
+
+// Forget all closed windows.
+function forgetClosedWindows() {
+  while (ss.getClosedWindowCount() > 0) {
+    ss.forgetClosedWindow(0);
+  }
+}
+
+// Forget all closed tabs for a window
+function forgetClosedTabs(win) {
+  const closedTabCount = ss.getClosedTabCountForWindow(win);
+  for (let i = 0; i < closedTabCount; i++) {
+    try {
+      ss.forgetClosedTab(win, 0);
+    } catch (err) {
+      // This will fail if there are tab groups in here
+    }
+  }
+}
+
+function forgetSavedTabGroups() {
+  const tabGroups = ss.getSavedTabGroups();
+  tabGroups.forEach(tabGroup => ss.forgetSavedTabGroup(tabGroup.id));
+}
+
+function forgetClosedTabGroups(win) {
+  const tabGroups = ss.getClosedTabGroups(win);
+  tabGroups.forEach(tabGroup => ss.forgetClosedTabGroup(win, tabGroup.id));
+}
+
+/**
+ * When opening a new window it is not sufficient to wait for its load event.
+ * We need to use whenDelayedStartupFinshed() here as the browser window's
+ * delayedStartup() routine is executed one tick after the window's load event
+ * has been dispatched. browser-delayed-startup-finished might be deferred even
+ * further if parts of the window's initialization process take more time than
+ * expected (e.g. reading a big session state from disk).
+ */
+function whenNewWindowLoaded(aOptions, aCallback) {
+  let features = "";
+  let url = "about:blank";
+
+  if ((aOptions && aOptions.private) || false) {
+    features = ",private";
+    url = "about:privatebrowsing";
+  }
+
+  let win = openDialog(
+    AppConstants.BROWSER_CHROME_URL,
+    "",
+    "chrome,all,dialog=no" + features,
+    url
+  );
+  let delayedStartup = promiseDelayedStartupFinished(win);
+
+  let browserLoaded = new Promise(resolve => {
+    if (url == "about:blank") {
+      resolve();
+      return;
+    }
+
+    win.addEventListener(
+      "load",
+      function () {
+        let browser = win.gBrowser.selectedBrowser;
+        promiseBrowserLoaded(browser).then(resolve);
+      },
+      { once: true }
+    );
+  });
+
+  Promise.all([delayedStartup, browserLoaded]).then(() => aCallback(win));
+}
+function promiseNewWindowLoaded(aOptions) {
+  return new Promise(resolve => whenNewWindowLoaded(aOptions, resolve));
+}
+
+/**
+ * This waits for the browser-delayed-startup-finished notification of a given
+ * window. It indicates that the windows has loaded completely and is ready to
+ * be used for testing.
+ */
+function whenDelayedStartupFinished(aWindow, aCallback) {
+  Services.obs.addObserver(function observer(aSubject, aTopic) {
+    if (aWindow == aSubject) {
+      Services.obs.removeObserver(observer, aTopic);
+      executeSoon(aCallback);
+    }
+  }, "browser-delayed-startup-finished");
+}
+function promiseDelayedStartupFinished(aWindow) {
+  return new Promise(resolve => whenDelayedStartupFinished(aWindow, resolve));
+}
+
+function promiseTabRestored(tab) {
+  return BrowserTestUtils.waitForEvent(tab, "SSTabRestored");
+}
+
+function promiseTabRestoring(tab) {
+  return BrowserTestUtils.waitForEvent(tab, "SSTabRestoring");
+}
+
+// Removes the given tab immediately and returns a promise that resolves when
+// all pending status updates (messages) of the closing tab have been received.
+function promiseRemoveTabAndSessionState(tab) {
+  let sessionUpdatePromise = BrowserTestUtils.waitForSessionStoreUpdate(tab);
+  BrowserTestUtils.removeTab(tab);
+  return sessionUpdatePromise;
+}
+
+// Write DOMSessionStorage data to the given browser.
+function modifySessionStorage(browser, storageData, storageOptions = {}) {
+  let browsingContext = browser.browsingContext;
+  if (storageOptions && "frameIndex" in storageOptions) {
+    browsingContext = browsingContext.children[storageOptions.frameIndex];
+  }
+
+  return SpecialPowers.spawn(
+    browsingContext,
+    [[storageData, storageOptions]],
+    async function ([data]) {
+      let frame = content;
+      let keys = new Set(Object.keys(data));
+      let isClearing = !keys.size;
+      let storage = frame.sessionStorage;
+
+      return new Promise(resolve => {
+        docShell.chromeEventHandler.addEventListener(
+          "MozSessionStorageChanged",
+          function onStorageChanged(event) {
+            if (event.storageArea == storage) {
+              keys.delete(event.key);
+            }
+
+            if (keys.size == 0) {
+              docShell.chromeEventHandler.removeEventListener(
+                "MozSessionStorageChanged",
+                onStorageChanged,
+                true
+              );
+              resolve();
+            }
+          },
+          true
+        );
+
+        if (isClearing) {
+          storage.clear();
+        } else {
+          for (let key of keys) {
+            frame.sessionStorage[key] = data[key];
+          }
+        }
+      });
+    }
+  );
+}
+
+function pushPrefs(...aPrefs) {
+  return SpecialPowers.pushPrefEnv({ set: aPrefs });
+}
+
+function popPrefs() {
+  return SpecialPowers.popPrefEnv();
+}
+
+function setScrollPosition(bc, x, y) {
+  return SpecialPowers.spawn(bc, [x, y], (childX, childY) => {
+    return new Promise(resolve => {
+      content.addEventListener(
+        "mozvisualscroll",
+        function onScroll(event) {
+          if (content.document.documentGlobal.visualViewport == event.target) {
+            content.removeEventListener("mozvisualscroll", onScroll, {
+              mozSystemGroup: true,
+            });
+            resolve();
+          }
+        },
+        { mozSystemGroup: true }
+      );
+      content.scrollTo(childX, childY);
+    });
+  });
+}
+
+async function checkScroll(tab, expected, msg) {
+  let browser = tab.linkedBrowser;
+  await TabStateFlusher.flush(browser);
+
+  let scroll = JSON.parse(ss.getTabState(tab)).scroll || null;
+  is(JSON.stringify(scroll), JSON.stringify(expected), msg);
+}
+
+function whenDomWindowClosedHandled(aCallback) {
+  Services.obs.addObserver(function observer(aSubject, aTopic) {
+    Services.obs.removeObserver(observer, aTopic);
+    aCallback();
+  }, "sessionstore-debug-domwindowclosed-handled");
+}
+
+function getPropertyOfFormField(browserContext, selector, propName) {
+  return SpecialPowers.spawn(
+    browserContext,
+    [selector, propName],
+    (selectorChild, propNameChild) => {
+      return content.document.querySelector(selectorChild)[propNameChild];
+    }
+  );
+}
+
+function setPropertyOfFormField(browserContext, selector, propName, newValue) {
+  return SpecialPowers.spawn(
+    browserContext,
+    [selector, propName, newValue],
+    (selectorChild, propNameChild, newValueChild) => {
+      let node = content.document.querySelector(selectorChild);
+      node[propNameChild] = newValueChild;
+
+      let event = node.ownerDocument.createEvent("UIEvents");
+      event.initUIEvent("input", true, true, node.documentGlobal, 0);
+      node.dispatchEvent(event);
+    }
+  );
+}
+
+function promiseOnHistoryReplaceEntry(browser) {
+  return new Promise((resolve, reject) => {
+    let sessionHistory = browser.browsingContext?.sessionHistory;
+    if (!sessionHistory) {
+      reject("No session history?");
+    }
+
+    var historyListener = {
+      OnHistoryNewEntry() {},
+      OnHistoryGotoIndex() {},
+      OnHistoryPurge() {},
+      OnHistoryReload() {
+        return true;
+      },
+
+      OnHistoryReplaceEntry() {
+        resolve();
+      },
+
+      QueryInterface: ChromeUtils.generateQI([
+        "nsISHistoryListener",
+        "nsISupportsWeakReference",
+      ]),
+    };
+
+    sessionHistory.addSHistoryListener(historyListener);
+  });
+}
+
+function loadTestSubscript(filePath) {
+  Services.scriptloader.loadSubScript(new URL(filePath, gTestPath).href, this);
+}
+
+function addCoopTask(aFile, aTest, aUrlRoot) {
+  async function taskToBeAdded() {
+    info(`File ${aFile} has COOP headers enabled`);
+    let filePath = `browser/browser/components/sessionstore/test/${aFile}`;
+    let url = aUrlRoot + `coopHeaderCommon.sjs?fileRoot=${filePath}`;
+    await aTest(url);
+  }
+  Object.defineProperty(taskToBeAdded, "name", { value: aTest.name });
+  add_task(taskToBeAdded);
+}
+
+function addNonCoopTask(aFile, aTest, aUrlRoot) {
+  async function taskToBeAdded() {
+    await aTest(aUrlRoot + aFile);
+  }
+  Object.defineProperty(taskToBeAdded, "name", { value: aTest.name });
+  add_task(taskToBeAdded);
+}
+
+function openAndCloseTab(window, url) {
+  return SessionStoreTestUtils.openAndCloseTab(window, url);
+}
+
+/**
+ * This is regrettable, but when `promiseBrowserState` resolves, we're still
+ * midway through loading the tabs. To avoid race conditions in URLs for tabs
+ * being available, wait for all the loads to finish:
+ */
+function promiseSessionStoreLoads(numberOfLoads) {
+  let loadsSeen = 0;
+  return new Promise(resolve => {
+    Services.obs.addObserver(function obs(browser) {
+      loadsSeen++;
+      if (loadsSeen == numberOfLoads) {
+        resolve();
+      }
+      // The typeof check is here to avoid one test messing with everything else by
+      // keeping the observer indefinitely.
+      if (typeof info == "undefined" || loadsSeen >= numberOfLoads) {
+        Services.obs.removeObserver(obs, "sessionstore-debug-tab-restored");
+      }
+      info("Saw load for " + browser.currentURI.spec);
+    }, "sessionstore-debug-tab-restored");
+  });
+}
+
+function triggerClickOn(target, options) {
+  let promise = BrowserTestUtils.waitForEvent(target, "click");
+  if (AppConstants.platform == "macosx") {
+    options.metaKey = options.ctrlKey;
+    delete options.ctrlKey;
+  }
+  EventUtils.synthesizeMouseAtCenter(target, options);
+  return promise;
+}
+
+async function openTabMenuFor(tab) {
+  let tabMenu = tab.ownerDocument.getElementById("tabContextMenu");
+
+  let tabMenuShown = BrowserTestUtils.waitForEvent(tabMenu, "popupshown");
+  EventUtils.synthesizeMouseAtCenter(
+    tab,
+    { type: "contextmenu" },
+    tab.documentGlobal
+  );
+  await tabMenuShown;
+
+  return tabMenu;
+}
diff --git a/src/zen/tests/mochitests/sessionstore/marionette/manifest.toml b/src/zen/tests/mochitests/sessionstore/marionette/manifest.toml
new file mode 100644
index 000000000..e66c364ca
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/marionette/manifest.toml
@@ -0,0 +1,65 @@
+[DEFAULT]
+subsuite = "integration"
+tags = "local os_integration"
+
+["test_log_files.py"]
+
+["test_new_tab_on_restore.py"]
+skip-if = [
+  "os == 'linux' && os_version == '24.04' && arch == 'x86_64' && display == 'x11'", # Bug 2054369
+]
+
+["test_persist_closed_tabs_restore_manually.py"]
+
+["test_restore_aiwindow.py"]
+
+["test_restore_loading_tab.py"]
+
+["test_restore_manually.py"]
+skip-if = [
+  "os == 'linux' && os_version == '24.04' && arch == 'x86_64' && display == 'x11'", # Bug 1968578
+]
+
+["test_restore_manually_with_pinned_tabs.py"]
+
+["test_restore_manually_with_tab_groups.py"]
+
+["test_restore_sidebar.py"]
+
+["test_restore_sidebar_automatic.py"]
+
+["test_restore_windows_after_close_last_tabs.py"]
+skip-if = [
+  "os == 'mac' && os_version == '10.15' && arch == 'x86_64'",
+  "os == 'mac' && os_version == '14.70' && arch == 'x86_64'",
+  "os == 'mac' && os_version == '15.30' && arch == 'aarch64'",
+]
+
+["test_restore_windows_after_restart_and_quit.py"]
+
+["test_restore_windows_after_windows_shutdown.py"]
+run-if = [
+  "os == 'win'",
+]
+skip-if = [
+  "os == 'win' && os_version == '11.26100' && arch == 'x86'", # Bug 1727691
+  "os == 'win' && os_version == '11.26100' && arch == 'x86_64'", # Bug 1727691
+  "os == 'win' && os_version == '11.26200' && arch == 'x86'", # Bug 1727691
+  "os == 'win' && os_version == '11.26200' && arch == 'x86_64'", # Bug 1727691
+]
+
+["test_splitview_restore.py"]
+
+["test_tabgroups_restore.py"]
+
+["test_tabnotes_canonicalurl_restore.py"]
+
+["test_taskbartab_restore.py"]
+run-if = [
+  "os == 'win'",
+]
+
+["test_taskbartab_sessionstate.py"]
+run-if = [
+  "os == 'win'",
+]
diff --git a/src/zen/tests/mochitests/sessionstore/marionette/session_store_test_case.py b/src/zen/tests/mochitests/sessionstore/marionette/session_store_test_case.py
new file mode 100644
index 000000000..8c76be10e
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/marionette/session_store_test_case.py
@@ -0,0 +1,473 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from urllib.parse import quote
+
+from marionette_driver import Wait, errors
+from marionette_driver.keys import Keys
+from marionette_harness import MarionetteTestCase, WindowManagerMixin
+
+
+def inline(doc):
+    return f"data:text/html;charset=utf-8,{quote(doc)}"
+
+
+# Each list element represents a window of tabs loaded at
+# some testing URL
+DEFAULT_WINDOWS = set([
+    # Window 1. Note the comma after the inline call -
+    # this is Python's way of declaring a 1 item tuple.
+    (inline("""<div">Lorem</div>"""),),
+    # Window 2
+    (
+        inline("""<div">ipsum</div>"""),
+        inline("""<div">dolor</div>"""),
+    ),
+    # Window 3
+    (
+        inline("""<div">sit</div>"""),
+        inline("""<div">amet</div>"""),
+    ),
+])
+
+
+class SessionStoreTestCase(WindowManagerMixin, MarionetteTestCase):
+    def setUp(
+        self,
+        startup_page=1,
+        include_private=True,
+        restore_on_demand=False,
+        no_auto_updates=True,
+        win_register_restart=False,
+        test_windows=DEFAULT_WINDOWS,
+        taskbartabs_enable=False,
+    ):
+        super().setUp()
+        self.marionette.set_context("chrome")
+
+        platform = self.marionette.session_capabilities["platformName"]
+        self.accelKey = Keys.META if platform == "mac" else Keys.CONTROL
+
+        self.test_windows = test_windows
+
+        self.private_windows = set([
+            (
+                inline("""<div">consectetur</div>"""),
+                inline("""<div">ipsum</div>"""),
+            ),
+            (
+                inline("""<div">adipiscing</div>"""),
+                inline("""<div">consectetur</div>"""),
+            ),
+        ])
+
+        self.marionette.enforce_gecko_prefs({
+            # Set browser restore previous session pref,
+            # depending on what the test requires.
+            "browser.startup.page": startup_page,
+            # Make the content load right away instead of waiting for
+            # the user to click on the background tabs
+            "browser.sessionstore.restore_on_demand": restore_on_demand,
+            # Avoid race conditions by having the content process never
+            # send us session updates unless the parent has explicitly asked
+            # for them via the TabStateFlusher.
+            "browser.sessionstore.debug.no_auto_updates": no_auto_updates,
+            # Whether to enable the register application restart mechanism.
+            "toolkit.winRegisterApplicationRestart": win_register_restart,
+            # Whether to enable taskbar tabs for this test
+            "browser.taskbarTabs.enabled": taskbartabs_enable,
+        })
+
+        self.all_windows = self.test_windows.copy()
+        self.open_windows(self.test_windows)
+
+        if include_private:
+            self.all_windows.update(self.private_windows)
+            self.open_windows(self.private_windows, is_private=True)
+
+    def tearDown(self):
+        try:
+            # Create a fresh profile for subsequent tests.
+            self.marionette.restart(in_app=False, clean=True)
+        finally:
+            super().tearDown()
+
+    def open_windows(self, window_sets, is_private=False):
+        """Open a set of windows with tabs pointing at some URLs.
+
+        @param window_sets (list)
+               A set of URL tuples. Each tuple within window_sets
+               represents a window, and each URL in the URL
+               tuples represents what will be loaded in a tab.
+
+               Note that if is_private is False, then the first
+               URL tuple will be opened in the current window, and
+               subequent tuples will be opened in new windows.
+
+               Example:
+
+               set(
+                   (self.marionette.absolute_url('layout/mozilla_1.html'),
+                    self.marionette.absolute_url('layout/mozilla_2.html')),
+
+                   (self.marionette.absolute_url('layout/mozilla_3.html'),
+                    self.marionette.absolute_url('layout/mozilla_4.html')),
+               )
+
+               This would take the currently open window, and load
+               mozilla_1.html and mozilla_2.html in new tabs. It would
+               then open a new, second window, and load tabs at
+               mozilla_3.html and mozilla_4.html.
+        @param is_private (boolean, optional)
+               Whether or not any new windows should be a private browsing
+               windows.
+        """
+        if is_private:
+            win = self.open_window(private=True)
+            self.marionette.switch_to_window(win)
+        else:
+            win = self.marionette.current_chrome_window_handle
+
+        for index, urls in enumerate(window_sets):
+            if index > 0:
+                win = self.open_window(private=is_private)
+                self.marionette.switch_to_window(win)
+            self.open_tabs(win, urls)
+
+    # Open a Firefox web app (taskbar tab) window
+    def open_taskbartab_window(self):
+        self.marionette.execute_async_script(
+            """
+            let [resolve] = arguments;
+            (async () => {
+                    let extraOptions = Cc["@mozilla.org/hash-property-bag;1"].createInstance(
+                        Ci.nsIWritablePropertyBag2
+                    );
+                    extraOptions.setPropertyAsBool("taskbartab", true);
+
+                    let args = Cc["@mozilla.org/array;1"].createInstance(Ci.nsIMutableArray);
+                    args.appendElement(null);
+                    args.appendElement(extraOptions);
+                    args.appendElement(null);
+
+                    // Simulate opening a taskbar tab window
+                    let win = Services.ww.openWindow(
+                        null,
+                        AppConstants.BROWSER_CHROME_URL,
+                        "_blank",
+                        "chrome,dialog=no,titlebar,close,toolbar,location,personalbar=no,status,menubar=no,resizable,minimizable,scrollbars",
+                        args
+                    );
+                    await new Promise(resolve => {
+                        win.addEventListener("load", resolve, { once: true });
+                    });
+                    await win.delayedStartupPromise;
+            })().then(resolve);
+        """
+        )
+
+    # Helper function for taskbar tabs tests, opens a taskbar tab window,
+    # closes the regular window, and reopens another regular window.
+    # Firefox will then be in a "ready to restore" state
+    def setup_taskbartab_restore_scenario(self):
+        self.open_taskbartab_window()
+        taskbar_tab_window_handle = self.marionette.close_chrome_window()[0]
+        self.marionette.switch_to_window(taskbar_tab_window_handle)
+        self.marionette.open(type="window")
+
+    def open_tabs(self, win, urls):
+        """Open a set of URLs inside a window in new tabs.
+
+        @param win (browser window)
+               The browser window to load the tabs in.
+        @param urls (tuple)
+               A tuple of URLs to load in this window. The
+               first URL will be loaded in the currently selected
+               browser tab. Subsequent URLs will be loaded in
+               new tabs.
+        """
+        # If there are any remaining URLs for this window,
+        # open some new tabs and navigate to them.
+        with self.marionette.using_context("content"):
+            if isinstance(urls, str):
+                self.marionette.navigate(urls)
+            else:
+                for index, url in enumerate(urls):
+                    if index > 0:
+                        tab = self.open_tab()
+                        self.marionette.switch_to_window(tab)
+                    self.marionette.navigate(url)
+
+    def wait_for_windows(self, expected_windows, message, timeout=5):
+        current_windows = None
+
+        def check(_):
+            nonlocal current_windows
+            current_windows = self.convert_open_windows_to_set()
+            return current_windows == expected_windows
+
+        try:
+            wait = Wait(self.marionette, timeout=timeout, interval=0.1)
+            wait.until(check, message=message)
+        except errors.TimeoutException as e:
+            # Update the message to include the most recent list of windows
+            message = (
+                f"{e.message}. Expected {expected_windows}, got {current_windows}."
+            )
+            raise errors.TimeoutException(message)
+
+    def get_urls_for_window(self, win):
+        orig_handle = self.marionette.current_chrome_window_handle
+
+        try:
+            with self.marionette.using_context("chrome"):
+                self.marionette.switch_to_window(win)
+                return self.marionette.execute_script(
+                    """
+                  return gBrowser.tabs.map(tab => {
+                    return tab.linkedBrowser.currentURI.spec;
+                  });
+                """
+                )
+        finally:
+            self.marionette.switch_to_window(orig_handle)
+
+    def convert_open_windows_to_set(self):
+        # There's no guarantee that Marionette will return us an
+        # iterator for the opened windows that will match the
+        # order within our window list. Instead, we'll convert
+        # the list of URLs within each open window to a set of
+        # tuples that will allow us to do a direct comparison
+        # while allowing the windows to be in any order.
+        opened_windows = set()
+        for win in self.marionette.chrome_window_handles:
+            urls = tuple(self.get_urls_for_window(win))
+            opened_windows.add(urls)
+
+        return opened_windows
+
+    def _close_window(self):
+        """Use as a callback to `marionette.quit` in order to close the
+        browser window.
+
+        `marionette.close`/`marionette.close_chrome_window` cannot
+        be used alone because they don't allow closing the last window.
+        """
+
+        self.marionette.execute_script("window.close()")
+
+    def close_all_tabs_and_restart(self):
+        self.close_all_tabs()
+        self.marionette.quit(callback=self._close_window)
+        self.marionette.start_session()
+
+    def simulate_os_shutdown(self):
+        """Simulate an OS shutdown.
+
+        :raises: Exception: if not supported on the current platform
+        :raises: WindowsError: if a Windows API call failed
+        """
+        if self.marionette.session_capabilities["platformName"] != "windows":
+            raise Exception("Unsupported platform for simulate_os_shutdown")
+
+        self._shutdown_with_windows_restart_manager(self.marionette.process_id)
+
+    def _shutdown_with_windows_restart_manager(self, pid):
+        """Shut down a process using the Windows Restart Manager.
+
+        When Windows shuts down, it uses a protocol including the
+        WM_QUERYENDSESSION and WM_ENDSESSION messages to give
+        applications a chance to shut down safely. The best way to
+        simulate this is via the Restart Manager, which allows a process
+        (such as an installer) to use the same mechanism to shut down
+        any other processes which are using registered resources.
+
+        This function starts a Restart Manager session, registers the
+        process as a resource, and shuts down the process.
+
+        :param pid: The process id (int) of the process to shutdown
+
+        :raises: WindowsError: if a Windows API call fails
+        """
+        import ctypes
+        from ctypes import POINTER, WINFUNCTYPE, Structure, WinError, pointer, windll
+        from ctypes.wintypes import BOOL, DWORD, HANDLE, LPCWSTR, UINT, ULONG, WCHAR
+
+        # set up Windows SDK types
+        OpenProcess = windll.kernel32.OpenProcess
+        OpenProcess.restype = HANDLE
+        OpenProcess.argtypes = [
+            DWORD,  # dwDesiredAccess
+            BOOL,  # bInheritHandle
+            DWORD,
+        ]  # dwProcessId
+        PROCESS_QUERY_INFORMATION = 0x0400
+
+        class FILETIME(Structure):
+            _fields_ = [("dwLowDateTime", DWORD), ("dwHighDateTime", DWORD)]
+
+        LPFILETIME = POINTER(FILETIME)
+
+        GetProcessTimes = windll.kernel32.GetProcessTimes
+        GetProcessTimes.restype = BOOL
+        GetProcessTimes.argtypes = [
+            HANDLE,  # hProcess
+            LPFILETIME,  # lpCreationTime
+            LPFILETIME,  # lpExitTime
+            LPFILETIME,  # lpKernelTime
+            LPFILETIME,
+        ]  # lpUserTime
+
+        ERROR_SUCCESS = 0
+
+        class RM_UNIQUE_PROCESS(Structure):
+            _fields_ = [("dwProcessId", DWORD), ("ProcessStartTime", FILETIME)]
+
+        RmStartSession = windll.rstrtmgr.RmStartSession
+        RmStartSession.restype = DWORD
+        RmStartSession.argtypes = [
+            POINTER(DWORD),  # pSessionHandle
+            DWORD,  # dwSessionFlags
+            POINTER(WCHAR),
+        ]  # strSessionKey
+
+        class GUID(ctypes.Structure):
+            _fields_ = [
+                ("Data1", ctypes.c_ulong),
+                ("Data2", ctypes.c_ushort),
+                ("Data3", ctypes.c_ushort),
+                ("Data4", ctypes.c_ubyte * 8),
+            ]
+
+        CCH_RM_SESSION_KEY = ctypes.sizeof(GUID) * 2
+
+        RmRegisterResources = windll.rstrtmgr.RmRegisterResources
+        RmRegisterResources.restype = DWORD
+        RmRegisterResources.argtypes = [
+            DWORD,  # dwSessionHandle
+            UINT,  # nFiles
+            POINTER(LPCWSTR),  # rgsFilenames
+            UINT,  # nApplications
+            POINTER(RM_UNIQUE_PROCESS),  # rgApplications
+            UINT,  # nServices
+            POINTER(LPCWSTR),
+        ]  # rgsServiceNames
+
+        RM_WRITE_STATUS_CALLBACK = WINFUNCTYPE(None, UINT)
+        RmShutdown = windll.rstrtmgr.RmShutdown
+        RmShutdown.restype = DWORD
+        RmShutdown.argtypes = [
+            DWORD,  # dwSessionHandle
+            ULONG,  # lActionFlags
+            RM_WRITE_STATUS_CALLBACK,
+        ]  # fnStatus
+
+        RmEndSession = windll.rstrtmgr.RmEndSession
+        RmEndSession.restype = DWORD
+        RmEndSession.argtypes = [DWORD]  # dwSessionHandle
+
+        # Get the info needed to uniquely identify the process
+        hProc = OpenProcess(PROCESS_QUERY_INFORMATION, False, pid)
+        if not hProc:
+            raise WinError()
+
+        creationTime = FILETIME()
+        exitTime = FILETIME()
+        kernelTime = FILETIME()
+        userTime = FILETIME()
+        if not GetProcessTimes(
+            hProc,
+            pointer(creationTime),
+            pointer(exitTime),
+            pointer(kernelTime),
+            pointer(userTime),
+        ):
+            raise WinError()
+
+        # Start the Restart Manager Session
+        dwSessionHandle = DWORD()
+        sessionKeyType = WCHAR * (CCH_RM_SESSION_KEY + 1)
+        sessionKey = sessionKeyType()
+        if RmStartSession(pointer(dwSessionHandle), 0, sessionKey) != ERROR_SUCCESS:
+            raise WinError()
+
+        try:
+            UProcs_count = 1
+            UProcsArrayType = RM_UNIQUE_PROCESS * UProcs_count
+            UProcs = UProcsArrayType(RM_UNIQUE_PROCESS(pid, creationTime))
+
+            # Register the process as a resource
+            if (
+                RmRegisterResources(
+                    dwSessionHandle, 0, None, UProcs_count, UProcs, 0, None
+                )
+                != ERROR_SUCCESS
+            ):
+                raise WinError()
+
+            # Shut down all processes using registered resources
+            if (
+                RmShutdown(
+                    dwSessionHandle, 0, ctypes.cast(None, RM_WRITE_STATUS_CALLBACK)
+                )
+                != ERROR_SUCCESS
+            ):
+                raise WinError()
+
+        finally:
+            RmEndSession(dwSessionHandle)
+
+    def windows_shutdown_with_variety(self, restart_by_os, expect_restore):
+        """Test restoring windows after Windows shutdown.
+
+        Opens a set of windows, both standard and private, with
+        some number of tabs in them. Once the tabs have loaded, shuts down
+        the browser with the Windows Restart Manager and restarts the browser.
+
+        This specifically exercises the Windows synchronous shutdown mechanism,
+        which terminates the process in response to the Restart Manager's
+        WM_ENDSESSION message.
+
+        If restart_by_os is True, the -os-restarted arg is passed when restarting,
+        simulating being automatically restarted by the Restart Manager.
+
+        If expect_restore is True, this ensures that the standard tabs have been
+        restored, and that the private ones have not. Otherwise it ensures that
+        no tabs and windows have been restored.
+        """
+        current_windows_set = self.convert_open_windows_to_set()
+        self.assertEqual(
+            current_windows_set,
+            self.all_windows,
+            msg=f"Not all requested windows have been opened. Expected {self.all_windows}, got {current_windows_set}.",
+        )
+
+        self.marionette.quit(callback=self.simulate_os_shutdown)
+
+        saved_args = self.marionette.instance.app_args
+        try:
+            if restart_by_os:
+                self.marionette.instance.app_args = ["-os-restarted"]
+
+            self.marionette.start_session()
+            self.marionette.set_context("chrome")
+        finally:
+            self.marionette.instance.app_args = saved_args
+
+        if expect_restore:
+            self.wait_for_windows(
+                self.test_windows,
+                "Non private browsing windows should have been restored",
+            )
+        else:
+            self.assertEqual(
+                len(self.marionette.chrome_window_handles),
+                1,
+                msg="Windows from last session shouldn`t have been restored.",
+            )
+            self.assertEqual(
+                len(self.marionette.window_handles),
+                1,
+                msg="Tabs from last session shouldn`t have been restored.",
+            )
diff --git a/src/zen/tests/mochitests/sessionstore/marionette/test_log_files.py b/src/zen/tests/mochitests/sessionstore/marionette/test_log_files.py
new file mode 100644
index 000000000..070fb252f
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/marionette/test_log_files.py
@@ -0,0 +1,176 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import os
+from urllib.parse import quote
+
+from marionette_driver import Wait, errors
+from marionette_harness import MarionetteTestCase, WindowManagerMixin
+
+
+def inline(doc):
+    return f"data:text/html;charset=utf-8,{quote(doc)}"
+
+
+class TestSessionRestoreLogging(WindowManagerMixin, MarionetteTestCase):
+    def setUp(self):
+        super().setUp()
+        self.marionette.enforce_gecko_prefs({
+            "browser.sessionstore.loglevel": "Debug",
+            "browser.sessionstore.log.appender.file.logOnSuccess": True,
+        })
+
+    def tearDown(self):
+        try:
+            # Create a fresh profile for subsequent tests.
+            self.marionette.restart(in_app=False, clean=True)
+        finally:
+            super().tearDown()
+
+    def getSessionFilePath(self):
+        profilePath = self.marionette.instance.profile.profile
+        assert profilePath is not None
+        return os.path.join(profilePath, "sessionstore.jsonlz4")
+
+    def getLogDirectoryPath(self):
+        profilePath = self.marionette.instance.profile.profile
+        assert profilePath is not None
+        return os.path.join(profilePath, "sessionstore-logs")
+
+    def cleanupLogDirectory(self):
+        dirPath = self.getLogDirectoryPath()
+        for fname in self.getLogFiles():
+            fpath = os.path.join(dirPath, fname)
+            os.remove(fpath)
+
+    def getLogFiles(self, matchstr=""):
+        dirPath = self.getLogDirectoryPath()
+        fileNames = []
+        if os.path.isdir(dirPath):
+            fileNames = [entry.name for entry in os.scandir(dirPath) if entry.is_file()]
+        # Optionally filter by substring
+        if len(matchstr) > 0 and len(fileNames) > 0:
+            fileNames = filter(lambda name: matchstr in name, fileNames)
+        return fileNames
+
+    def getMostRecentLogFile(self, matchstr=""):
+        dirPath = self.getLogDirectoryPath()
+        # Build full paths
+        files = [os.path.join(dirPath, f) for f in self.getLogFiles(matchstr)]
+        # Get the newest file by creation time
+        return max(files, key=os.path.getctime) if len(files) > 0 else None
+
+    def openAndCloseSaveworthyWindow(self):
+        urls = (
+            inline("""<div">ipsum</div>"""),
+            inline("""<div">dolor</div>"""),
+        )
+        self.marionette.set_context("chrome")
+        origWindow = self.marionette.current_window_handle
+        win = self.open_window(private=False)
+        self.marionette.switch_to_window(win)
+        with self.marionette.using_context("content"):
+            for index, url in enumerate(urls):
+                if index > 0:
+                    tab = self.open_tab()
+                    self.marionette.switch_to_window(tab)
+                self.marionette.navigate(url)
+        self.marionette.execute_script("window.close()")
+        self.marionette.switch_to_window(origWindow)
+
+    def getLineCount(self, logFile):
+        with open(logFile) as f:
+            return sum(1 for _ in f)
+
+    def test_per_startup_logfile_creation(self):
+        self.marionette.quit()
+        self.cleanupLogDirectory()
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+        self.marionette.quit()
+
+        # There were no errors so we just expect the success log file to have been created
+        self.assertEqual(
+            len(self.getLogFiles()),
+            1,
+            "Exactly one log file was created after a restart and quit",
+        )
+        self.marionette.start_session()
+
+    def test_errors_flush_to_disk(self):
+        self.marionette.enforce_gecko_prefs({
+            "browser.sessionstore.log.appender.file.logOnSuccess": False,
+        })
+        self.marionette.quit()
+        sessionFile = self.getSessionFilePath()
+        self.assertTrue(
+            os.path.isfile(sessionFile),
+            "The sessionstore.jsonlz4 file exists in the profile directory",
+        )
+        # replace the contents with nonsense so we get a not-readable error on startup
+        with open(sessionFile, "wb") as f:
+            f.write(b"\x00\xff\xabgarbageDATA")
+
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        errorLogFile = self.getMostRecentLogFile("error-")
+        self.assertTrue(errorLogFile, "We logged errors immediately")
+
+        if os.path.isfile(sessionFile):
+            os.remove(sessionFile)
+
+    def test_periodic_flush_to_disk(self):
+        # enable debug logging and verify that log messages are batched
+        # and only flush when the interval has passed
+        logFile = self.getMostRecentLogFile()
+        logFileCount = len(self.getLogFiles())
+        self.assertTrue(logFile, "A log file already exists")
+        self.assertEqual(logFileCount, 1, "A single 'success' log file exists")
+        startLineCount = self.getLineCount(logFile)
+
+        # open and close a window
+        self.openAndCloseSaveworthyWindow()
+
+        self.assertEqual(
+            self.getLineCount(logFile),
+            startLineCount,
+            "Log file line count unchanged; debug messages should be buffered and not yet flushed to disk",
+        )
+
+        # Set the flush interval to 1 second and open+close another window to trigger some
+        # debug log messages
+        self.marionette.set_pref("browser.sessionstore.logFlushIntervalSeconds", 1)
+        origWindow = self.marionette.current_window_handle
+        self.openAndCloseSaveworthyWindow()
+
+        try:
+            wait = Wait(self.marionette, timeout=5, interval=0.1)
+            wait.until(
+                lambda _: self.getLineCount(logFile) > startLineCount,
+                message="Waiting for line count in the log file to grow",
+            )
+            newLineCount = self.getLineCount(logFile)
+            self.assertTrue(
+                newLineCount > startLineCount,
+                f"{newLineCount - startLineCount} lines got flushed to the log file",
+            )
+        except errors.TimeoutException as e:
+            message = (
+                f"{e.message}. Line count didn't grow as expected in log file {logFile}"
+            )
+            raise errors.TimeoutException(message)
+        finally:
+            self.marionette.switch_to_window(origWindow)
+            self.marionette.clear_pref("browser.sessionstore.logFlushIntervalSeconds")
+
+        self.assertTrue(
+            self.getLineCount(logFile) > startLineCount,
+            "Debug log messages got flushed to disk",
+        )
+        self.assertEqual(
+            len(self.getLogFiles()),
+            logFileCount,
+            "We just appended to the one log file and didn't create any others",
+        )
diff --git a/src/zen/tests/mochitests/sessionstore/marionette/test_new_tab_on_restore.py b/src/zen/tests/mochitests/sessionstore/marionette/test_new_tab_on_restore.py
new file mode 100644
index 000000000..81543b746
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/marionette/test_new_tab_on_restore.py
@@ -0,0 +1,370 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import copy
+import os
+import sys
+
+# add this directory to the path
+sys.path.append(os.path.dirname(__file__))
+
+from marionette_driver import Wait
+from session_store_test_case import SessionStoreTestCase
+
+
+def inline(title):
+    return f"data:text/html;charset=utf-8,<html><head><title>{title}</title></head><body></body></html>"
+
+
+RESTORED_TAB_COUNT = 2
+
+
+class TestNewTabOnRestore(SessionStoreTestCase):
+    def setUp(self):
+        super().setUp(
+            startup_page=3,
+            include_private=False,
+            restore_on_demand=False,
+            test_windows=set([
+                (
+                    inline("Page 1"),
+                    inline("Page 2"),
+                ),
+            ]),
+        )
+
+    def _set_new_tab_on_restore_prefs(self, enabled, show_setting=True):
+        self.marionette.set_prefs({
+            "browser.sessionstore.newTabOnRestore": enabled,
+            "browser.sessionstore.newTabOnRestore.showSetting": show_setting,
+        })
+
+    def _quit_and_restore(self, expected_tab_count=None):
+        self.marionette.quit()
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+        if expected_tab_count is not None:
+            Wait(self.marionette, timeout=5, interval=0.1).until(
+                lambda _: self._get_tab_count() == expected_tab_count,
+                message=f"Expected {expected_tab_count} tabs after restore",
+            )
+
+    def _get_tab_count(self):
+        return self.marionette.execute_script(
+            """
+            let win = BrowserWindowTracker.getTopWindow();
+            return win.gBrowser.tabs.length;
+            """
+        )
+
+    def _get_selected_tab_url(self):
+        return self.marionette.execute_script(
+            """
+            let win = BrowserWindowTracker.getTopWindow();
+            return win.gBrowser.selectedBrowser.currentURI.spec;
+            """
+        )
+
+    def _is_selected_tab_hidden(self):
+        return self.marionette.execute_script(
+            """
+            let win = BrowserWindowTracker.getTopWindow();
+            return win.gBrowser.selectedTab.hidden;
+            """
+        )
+
+    def _get_telemetry_events(self):
+        return self.marionette.execute_script(
+            """
+            return Glean.sessionRestore.startupSessionAutoRestored.testGetValue();
+            """
+        )
+
+    def test_new_tab_opens_when_enabled(self):
+        self._set_new_tab_on_restore_prefs(enabled=True)
+        self._quit_and_restore(expected_tab_count=RESTORED_TAB_COUNT + 1)
+
+        selected_url = self._get_selected_tab_url()
+        self.assertIn(
+            "newtab",
+            selected_url.lower().replace("_", ""),
+            "Selected tab should be a new tab page",
+        )
+
+        events = self._get_telemetry_events()
+        self.assertEqual(len(events), 1, "One telemetry event recorded")
+        self.assertEqual(events[0]["extra"]["new_tab_action"], "opened")
+
+    def test_no_new_tab_when_disabled(self):
+        self._set_new_tab_on_restore_prefs(enabled=False)
+        self._quit_and_restore(expected_tab_count=RESTORED_TAB_COUNT)
+
+        events = self._get_telemetry_events()
+        self.assertEqual(len(events), 1, "One telemetry event recorded")
+        self.assertEqual(events[0]["extra"]["new_tab_action"], "disabled")
+
+    def test_no_new_tab_when_show_setting_false(self):
+        self._set_new_tab_on_restore_prefs(enabled=True, show_setting=False)
+        self._quit_and_restore(expected_tab_count=RESTORED_TAB_COUNT)
+
+        events = self._get_telemetry_events()
+        self.assertEqual(len(events), 1, "One telemetry event recorded")
+        self.assertEqual(events[0]["extra"]["new_tab_action"], "disabled")
+
+    def test_reuses_existing_newtab_rightmost(self):
+        self._set_new_tab_on_restore_prefs(enabled=True)
+
+        self.marionette.execute_script(
+            """
+            let win = BrowserWindowTracker.getTopWindow();
+            let { AboutNewTab } = ChromeUtils.importESModule(
+                "resource:///modules/AboutNewTab.sys.mjs"
+            );
+            win.gBrowser.addTrustedTab(AboutNewTab.newTabURL, {
+                triggeringPrincipal:
+                    Services.scriptSecurityManager.getSystemPrincipal(),
+            });
+            """
+        )
+
+        self._quit_and_restore(expected_tab_count=RESTORED_TAB_COUNT + 1)
+
+        events = self._get_telemetry_events()
+        self.assertEqual(len(events), 1, "One telemetry event recorded")
+        self.assertEqual(events[0]["extra"]["new_tab_action"], "reused")
+
+    def test_reuses_selected_newtab(self):
+        self._set_new_tab_on_restore_prefs(enabled=True)
+
+        self.marionette.execute_script(
+            """
+            let win = BrowserWindowTracker.getTopWindow();
+            let { AboutNewTab } = ChromeUtils.importESModule(
+                "resource:///modules/AboutNewTab.sys.mjs"
+            );
+            let tab = win.gBrowser.addTrustedTab(AboutNewTab.newTabURL, {
+                triggeringPrincipal:
+                    Services.scriptSecurityManager.getSystemPrincipal(),
+            });
+            win.gBrowser.selectedTab = tab;
+            """
+        )
+
+        self._quit_and_restore(expected_tab_count=RESTORED_TAB_COUNT + 1)
+
+        events = self._get_telemetry_events()
+        self.assertEqual(len(events), 1, "One telemetry event recorded")
+        self.assertEqual(events[0]["extra"]["new_tab_action"], "reused")
+
+    def test_no_new_tab_when_cmdline_url(self):
+        self._set_new_tab_on_restore_prefs(enabled=True)
+
+        orig_args = copy.copy(self.marionette.instance.app_args)
+        try:
+            self.marionette.quit()
+            self.marionette.instance.app_args.extend([
+                "-url",
+                "data:text/html,<title>cmdline</title>",
+            ])
+            self.marionette.start_session()
+            self.marionette.set_context("chrome")
+
+            Wait(self.marionette, timeout=5, interval=0.1).until(
+                lambda _: self._get_tab_count() >= RESTORED_TAB_COUNT,
+                message=f"Expected at least {RESTORED_TAB_COUNT} tabs after restore",
+            )
+
+            events = self._get_telemetry_events()
+            self.assertEqual(len(events), 1, "One telemetry event recorded")
+            self.assertEqual(events[0]["extra"]["new_tab_action"], "preempted")
+        finally:
+            self.marionette.instance.app_args = orig_args
+
+    def test_reuse_newtab_selects_visible_tab(self):
+        self._set_new_tab_on_restore_prefs(enabled=True)
+
+        self.marionette.execute_script(
+            """
+            let win = BrowserWindowTracker.getTopWindow();
+            let { AboutNewTab } = ChromeUtils.importESModule(
+                "resource:///modules/AboutNewTab.sys.mjs"
+            );
+            let visibleTab = win.gBrowser.addTrustedTab(AboutNewTab.newTabURL, {
+                triggeringPrincipal:
+                    Services.scriptSecurityManager.getSystemPrincipal(),
+            });
+            let hiddenTab = win.gBrowser.addTrustedTab(AboutNewTab.newTabURL, {
+                triggeringPrincipal:
+                    Services.scriptSecurityManager.getSystemPrincipal(),
+            });
+            win.gBrowser.hideTab(hiddenTab);
+            // Select first tab so neither newtab is selected
+            win.gBrowser.selectedTab = win.gBrowser.tabs[0];
+            """
+        )
+
+        self._quit_and_restore(expected_tab_count=RESTORED_TAB_COUNT + 2)
+
+        self.assertFalse(
+            self._is_selected_tab_hidden(),
+            "Selected tab should not be hidden",
+        )
+
+        events = self._get_telemetry_events()
+        self.assertEqual(len(events), 1, "One telemetry event recorded")
+        self.assertEqual(events[0]["extra"]["new_tab_action"], "reused")
+
+
+class TestNewTabOnRestoreNotSettingBased(SessionStoreTestCase):
+    """
+    Test that no new tab or telemetry is recorded when restore is not
+    triggered by the user's startup.page setting.
+    """
+
+    def setUp(self):
+        super().setUp(
+            startup_page=1,
+            include_private=False,
+            restore_on_demand=False,
+            test_windows=set([
+                (inline("Page 1"),),
+            ]),
+        )
+
+    def test_no_new_tab_on_non_setting_restore(self):
+        self.marionette.set_prefs({
+            "browser.sessionstore.newTabOnRestore": True,
+            "browser.sessionstore.newTabOnRestore.showSetting": True,
+        })
+
+        self.marionette.quit()
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        # Manually restore previous session (simulates non-setting-based restore)
+        self.marionette.execute_script(
+            """
+            const { SessionStore } = ChromeUtils.importESModule(
+                "resource:///modules/sessionstore/SessionStore.sys.mjs"
+            );
+            SessionStore.restoreLastSession();
+            """
+        )
+
+        events = self.marionette.execute_script(
+            """
+            return Glean.sessionRestore.startupSessionAutoRestored.testGetValue();
+            """
+        )
+        self.assertIsNone(
+            events,
+            "No telemetry when restore is not setting-based",
+        )
+
+
+class TestNewTabOnRestoreAfterCrash(SessionStoreTestCase):
+    """
+    A crash-triggered restore is not a user-configured restore, so the
+    new-tab-on-restore feature must not engage even when the setting is on.
+    Guards the `!ss.previousSessionCrashed` check in SessionStore's initSession.
+    """
+
+    def setUp(self):
+        super().setUp(
+            startup_page=3,
+            include_private=False,
+            restore_on_demand=False,
+            test_windows=set([
+                (
+                    inline("Page 1"),
+                    inline("Page 2"),
+                ),
+            ]),
+        )
+        self.marionette.set_prefs({
+            "browser.sessionstore.newTabOnRestore": True,
+            "browser.sessionstore.newTabOnRestore.showSetting": True,
+        })
+
+    def test_no_new_tab_after_crash(self):
+        # Persist prefs and the session to disk before the crash.
+        self.marionette.execute_async_script(
+            """
+            let [resolve] = arguments;
+            Services.prefs.savePrefFile(Services.dirsvc.get("PrefF", Ci.nsIFile));
+            const { TabStateFlusher } = ChromeUtils.importESModule(
+                "resource:///modules/sessionstore/TabStateFlusher.sys.mjs"
+            );
+            const { SessionSaver } = ChromeUtils.importESModule(
+                "resource:///modules/sessionstore/SessionSaver.sys.mjs"
+            );
+            (async () => {
+                for (let win of Services.wm.getEnumerator("navigator:browser")) {
+                    await TabStateFlusher.flushWindow(win);
+                }
+                await SessionSaver.run();
+            })().then(resolve);
+            """
+        )
+
+        # Simulate a crash: kill the process without a clean shutdown so the
+        # "final-state-write-complete" checkpoint is never recorded.
+        self.marionette.quit(in_app=False)
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        self.marionette.execute_async_script(
+            """
+            let [resolve] = arguments;
+            const { SessionStore } = ChromeUtils.importESModule(
+                "resource:///modules/sessionstore/SessionStore.sys.mjs"
+            );
+            SessionStore.promiseAllWindowsRestored.then(resolve);
+            """
+        )
+
+        # Validity check: the prefs must have actually persisted across the
+        # crash.
+        prefs = self.marionette.execute_script(
+            """
+            return {
+                enabled: Services.prefs.getBoolPref(
+                    "browser.sessionstore.newTabOnRestore", false
+                ),
+                showSetting: Services.prefs.getBoolPref(
+                    "browser.sessionstore.newTabOnRestore.showSetting", false
+                ),
+            };
+            """
+        )
+        self.assertTrue(
+            prefs["enabled"] and prefs["showSetting"],
+            "newTabOnRestore prefs should persist across the crash so the "
+            "feature is enabled; otherwise this test is not exercising the "
+            "previousSessionCrashed path",
+        )
+
+        # No new tab should be added: only the restored tabs are present.
+        tab_count = self.marionette.execute_script(
+            """
+            let win = BrowserWindowTracker.getTopWindow();
+            return win.gBrowser.tabs.length;
+            """
+        )
+        self.assertEqual(
+            tab_count,
+            RESTORED_TAB_COUNT,
+            "No new tab should be added after a crash restore",
+        )
+
+        events = self.marionette.execute_script(
+            """
+            return Glean.sessionRestore.startupSessionAutoRestored.testGetValue();
+            """
+        )
+        self.assertIsNone(
+            events,
+            "The new-tab-on-restore feature must not engage after a crash "
+            "restore (previousSessionCrashed)",
+        )
diff --git a/src/zen/tests/mochitests/sessionstore/marionette/test_persist_closed_tabs_restore_manually.py b/src/zen/tests/mochitests/sessionstore/marionette/test_persist_closed_tabs_restore_manually.py
new file mode 100644
index 000000000..1a58a92da
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/marionette/test_persist_closed_tabs_restore_manually.py
@@ -0,0 +1,221 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import os
+import sys
+
+# add this directory to the path
+sys.path.append(os.path.dirname(__file__))
+
+from marionette_driver import Wait, errors
+from session_store_test_case import SessionStoreTestCase
+
+
+def inline(title):
+    return f"data:text/html;charset=utf-8,<html><head><title>{title}</title></head><body></body></html>"
+
+
+class TestSessionRestoreClosedTabs(SessionStoreTestCase):
+    """
+    Test that closed tabs persist between sessions and
+    that any previously open tabs are added to the recently
+    closed tab list. When a previous session is restored,
+    an open tab is restored and removed from the closed tabs list.
+
+    If additional tabs are opened (and closed) before a previous
+    session is restored, those should be merged with the restored open
+    and closed tabs, preserving their state.
+    """
+
+    def setUp(self):
+        super().setUp(
+            startup_page=1,
+            include_private=False,
+            restore_on_demand=True,
+            test_windows=set([
+                # Window 1
+                (
+                    inline("lorem ipsom"),
+                    inline("dolor"),
+                ),
+            ]),
+        )
+
+    def test_restore(self):
+        self.marionette.execute_script(
+            """
+            Services.prefs.setBoolPref("browser.sessionstore.persist_closed_tabs_between_sessions", true);
+            """
+        )
+
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+        # Close the second tab leaving the first tab open
+        self.marionette.execute_async_script(
+            """
+            let resolve = arguments[0];
+            let tab = gBrowser.tabs[1];
+            gBrowser.removeTab(tab);
+            let { TabStateFlusher } = ChromeUtils.importESModule("resource:///modules/sessionstore/TabStateFlusher.sys.mjs");
+            TabStateFlusher.flush(tab).then(resolve);
+            """
+        )
+
+        self.marionette.quit()
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+            let { SessionStore } = ChromeUtils.importESModule("resource:///modules/sessionstore/SessionStore.sys.mjs");
+            let state = JSON.parse(SessionStore.getBrowserState());
+            return state.windows[0]._closedTabs.length;
+            """
+            ),
+            2,
+            msg="Should have 2 closed tabs after restart.",
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+            let { SessionStore } = ChromeUtils.importESModule("resource:///modules/sessionstore/SessionStore.sys.mjs");
+            let state = JSON.parse(SessionStore.getBrowserState());
+            return state.windows[0]._closedTabs[0].removeAfterRestore;
+            """
+            ),
+            True,
+            msg="Previously open tab that was added to closedTabs should have removeAfterRestore property.",
+        )
+
+        # open two new tabs, the second one will be closed
+        win = self.marionette.current_chrome_window_handle
+        self.open_tabs(win, (inline("sit"), inline("amet")))
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                return gBrowser.tabs[0].label
+                """
+            ),
+            "sit",
+            msg="First open tab should now be sit",
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                return gBrowser.tabs[1].label
+                """
+            ),
+            "amet",
+            msg="Second open tab should be amet",
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                return gBrowser.tabs.length
+                """
+            ),
+            2,
+            msg="should have 2 tabs open",
+        )
+
+        self.marionette.execute_async_script(
+            """
+            let resolve = arguments[0];
+            let tab = gBrowser.tabs[1];
+            gBrowser.removeTab(tab);
+            let { TabStateFlusher } = ChromeUtils.importESModule("resource:///modules/sessionstore/TabStateFlusher.sys.mjs");
+            TabStateFlusher.flush(tab).then(resolve);
+            """
+        )
+
+        self.wait_for_tabcount(1, "Waiting for 1 tabs")
+
+        # restore the previous session
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                const lazy = {};
+                ChromeUtils.defineESModuleGetters(lazy, {
+                    SessionStore: "resource:///modules/sessionstore/SessionStore.sys.mjs",
+                });
+                function observeClosedTabsChange() {
+                    return new Promise(resolve => {
+                        function observe(subject, topic, data) {
+                            if (topic == "sessionstore-closed-objects-changed") {
+                                Services.obs.removeObserver(this, "sessionstore-closed-objects-changed");
+                                resolve('observed closed objects changed');
+                            };
+                        }
+                        Services.obs.addObserver(observe, "sessionstore-closed-objects-changed");
+                    });
+                };
+
+                async function checkForClosedTabs() {
+                    let closedTabsObserver = observeClosedTabsChange();
+                    lazy.SessionStore.restoreLastSession();
+                    await closedTabsObserver;
+                    let state = JSON.parse(lazy.SessionStore.getBrowserState());
+                    return state.windows[0]._closedTabs.length;
+                }
+                return checkForClosedTabs();
+                """
+            ),
+            2,
+            msg="Should have 2 closed tab after restoring session.",
+        )
+
+        self.wait_for_tabcount(2, "Waiting for 2 tabs")
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                return gBrowser.tabs[0].label
+                """
+            ),
+            "sit",
+            msg="Newly opened tab should still exist",
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                return gBrowser.tabs[1].label
+                """
+            ),
+            "lorem ipsom",
+            msg="The open tab from the previous session should be restored",
+        )
+
+        # temporary until we remove this pref
+        self.marionette.execute_script(
+            """
+            Services.prefs.clearUserPref("browser.sessionstore.persist_closed_tabs_between_sessions");
+            """
+        )
+
+    def wait_for_tabcount(self, expected_tabcount, message, timeout=5):
+        current_tabcount = None
+
+        def check(_):
+            nonlocal current_tabcount
+            current_tabcount = self.marionette.execute_script(
+                "return gBrowser.tabs.length;"
+            )
+            return current_tabcount == expected_tabcount
+
+        try:
+            wait = Wait(self.marionette, timeout=timeout, interval=0.1)
+            wait.until(check, message=message)
+        except errors.TimeoutException as e:
+            # Update the message to include the most recent list of windows
+            message = (
+                f"{e.message}. Expected {expected_tabcount}, got {current_tabcount}."
+            )
+            raise errors.TimeoutException(message)
diff --git a/src/zen/tests/mochitests/sessionstore/marionette/test_restore_aiwindow.py b/src/zen/tests/mochitests/sessionstore/marionette/test_restore_aiwindow.py
new file mode 100644
index 000000000..530bfdecb
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/marionette/test_restore_aiwindow.py
@@ -0,0 +1,387 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import os
+import sys
+
+# add this directory to the path
+sys.path.append(os.path.dirname(__file__))
+
+from session_store_test_case import SessionStoreTestCase
+
+
+def inline(title):
+    return f"data:text/html;charset=utf-8,<html><head><title>{title}</title></head><body></body></html>"
+
+
+class AIWindowTestMixin:
+    def setUp(self, startup_page=1):
+        super().setUp(
+            startup_page=startup_page,
+            include_private=False,
+            restore_on_demand=True,
+            test_windows=set([
+                (
+                    inline("Tab 1"),
+                    inline("Tab 2"),
+                    inline("Tab 3"),
+                ),
+            ]),
+        )
+        self.marionette.set_context("chrome")
+        self.marionette.execute_script(
+            """
+            Services.prefs.setBoolPref("browser.smartwindow.enabled", true);
+            """
+        )
+
+    def is_ai_window(self):
+        return self.marionette.execute_script(
+            """
+            return window.document.documentElement.hasAttribute("ai-window");
+            """
+        )
+
+    def get_tab_count(self):
+        return self.marionette.execute_script(
+            """
+            return gBrowser.tabs.length;
+            """
+        )
+
+    def toggle_ai_window(self, enabled):
+        self.marionette.execute_script(
+            """
+            const { AIWindow } = ChromeUtils.importESModule(
+                "moz-src:///browser/components/aiwindow/ui/modules/AIWindow.sys.mjs"
+            );
+            AIWindow.toggleAIWindow(window, arguments[0]);
+            """,
+            script_args=[enabled],
+        )
+
+    def restore_last_session(self):
+        self.marionette.execute_script(
+            """
+            const lazy = {};
+            ChromeUtils.defineESModuleGetters(lazy, {
+                SessionStore: "resource:///modules/sessionstore/SessionStore.sys.mjs",
+            });
+            function observeClosedObjectsChange() {
+                return new Promise(resolve => {
+                    function observe(subject, topic, data) {
+                        if (topic == "sessionstore-closed-objects-changed") {
+                            Services.obs.removeObserver(observe, "sessionstore-closed-objects-changed");
+                            resolve();
+                        }
+                    }
+                    Services.obs.addObserver(observe, "sessionstore-closed-objects-changed");
+                });
+            }
+
+            async function restoreSession() {
+                let closedWindowsObserver = observeClosedObjectsChange();
+                lazy.SessionStore.restoreLastSession();
+                await closedWindowsObserver;
+            }
+            return restoreSession();
+            """
+        )
+
+
+class SmartWindowDefaultMixin(AIWindowTestMixin):
+    """Sets the prefs so the *next* startup opens a Smart Window.
+
+    Setting them after super().setUp() (which opened the Classic test windows)
+    means only the post-restart startup window is affected. The prefs flush to
+    prefs.js on the clean quit, so they apply at the restart startup.
+    """
+
+    def setUp(self, startup_page=1):
+        super().setUp(startup_page=startup_page)
+        self.marionette.execute_script(
+            """
+            Services.prefs.setBoolPref("browser.smartwindow.isDefaultWindow", true);
+            Services.prefs.setIntPref("browser.smartwindow.tos.consentTime", 1);
+            // Keep the Smart Window sign-in flow from navigating to the real
+            // accounts.firefox.com (non-local address crashes the test sandbox).
+            Services.prefs.setCharPref(
+                "identity.fxaccounts.remote.root",
+                "http://127.0.0.1/"
+            );
+            """
+        )
+
+    def can_restore_last_session(self):
+        return self.marionette.execute_script(
+            """
+            const { SessionStore } = ChromeUtils.importESModule(
+                "resource:///modules/sessionstore/SessionStore.sys.mjs"
+            );
+            return SessionStore.canRestoreLastSession;
+            """
+        )
+
+
+class TestAIWindowSessionRestore(AIWindowTestMixin, SessionStoreTestCase):
+    """
+    Test that AI Window state persists correctly across session restarts.
+    """
+
+    def test_window_mode_persists_across_restart(self):
+        """Test that both Classic and AI Window states persist across session restarts."""
+        self.marionette.execute_script(
+            """
+            Services.prefs.setBoolPref("browser.sessionstore.persist_closed_tabs_between_sessions", true);
+            """
+        )
+
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+
+        self.assertFalse(
+            self.is_ai_window(), msg="Window should start as Classic Window"
+        )
+
+        tab_count = self.get_tab_count()
+        self.assertEqual(tab_count, 3, msg="Should have 3 tabs")
+
+        self.toggle_ai_window(True)
+        self.assertTrue(
+            self.is_ai_window(), msg="Window should be AI Window after toggle"
+        )
+
+        self.marionette.quit()
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        self.restore_last_session()
+
+        self.assertEqual(
+            len(self.marionette.chrome_window_handles),
+            2,
+            msg="AI Window opened in new window due to type mismatch with startup window.",
+        )
+
+        # Switch to the AI window (the second window)
+        self.marionette.switch_to_window(self.marionette.chrome_window_handles[1])
+
+        self.assertTrue(
+            self.is_ai_window(),
+            msg="AI Window state should persist after restart",
+        )
+
+        self.assertEqual(
+            self.get_tab_count(),
+            tab_count,
+            msg="Tab count should be preserved after restart",
+        )
+
+    def test_aiwindow_not_restored_when_pref_disabled(self):
+        """Test that AI Windows revert to Classic when pref is disabled after restart."""
+        self.marionette.execute_script(
+            """
+            Services.prefs.setBoolPref("browser.sessionstore.persist_closed_tabs_between_sessions", true);
+            """
+        )
+
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+
+        self.toggle_ai_window(True)
+        self.assertTrue(self.is_ai_window(), msg="Window should be AI before restart")
+
+        self.marionette.quit()
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        self.marionette.execute_script(
+            """
+            Services.prefs.setBoolPref("browser.smartwindow.enabled", false);
+            """
+        )
+
+        self.restore_last_session()
+
+        self.assertEqual(
+            len(self.marionette.chrome_window_handles),
+            1,
+            msg="Window from last session has been restored.",
+        )
+
+        self.assertFalse(
+            self.is_ai_window(),
+            msg="AI Window should revert to Classic when pref is disabled",
+        )
+
+
+class TestAIWindowAutomaticRestore(AIWindowTestMixin, SessionStoreTestCase):
+    """Test AI Window persistence with automatic session restore."""
+
+    def setUp(self):
+        super().setUp(startup_page=3)
+
+    def test_single_window_stays_in_smart_window_on_automatic_restart(self):
+
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+
+        self.assertFalse(
+            self.is_ai_window(), msg="Window should start as Classic Window"
+        )
+
+        tab_count = self.get_tab_count()
+        self.assertEqual(tab_count, 3, msg="Should have 3 tabs")
+
+        self.toggle_ai_window(True)
+        self.assertTrue(
+            self.is_ai_window(), msg="Window should be AI Window after toggle"
+        )
+
+        # Restart with automatic session restore
+        self.marionette.quit()
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        self.assertEqual(
+            len(self.marionette.chrome_window_handles),
+            1,
+            msg="Should have exactly one window after automatic restore",
+        )
+
+        self.assertTrue(
+            self.is_ai_window(),
+            msg="Window should stay in Smart Window mode after restart",
+        )
+
+        self.assertEqual(
+            self.get_tab_count(),
+            tab_count,
+            msg="Tab count should be preserved after restart",
+        )
+
+
+class TestSmartWindowDefaultRestore(SmartWindowDefaultMixin, SessionStoreTestCase):
+    """
+    Regression test: "Restore previous session" must stay available when the
+    user's default is a Smart Window.
+
+    When Smart Window is the default, the first window opens as Smart at startup.
+    That startup path used to read the session restore state too early — before
+    the saved session had been loaded from disk — so the browser concluded there
+    was no session and disabled "Restore previous session". This test starts with
+    Smart Window as the default, restarts, and verifies the previous session is
+    still restorable and that the window stays Smart.
+    """
+
+    def test_restore_previous_session_available_with_smart_default(self):
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+        self.assertFalse(
+            self.is_ai_window(),
+            msg="Window opened during setUp should still be Classic",
+        )
+
+        self.marionette.quit()
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        # Startup window opens as Smart because Smart Window is the default, and
+        # it must stay Smart (no flash back to Classic).
+        self.assertTrue(
+            self.is_ai_window(),
+            msg="Startup window should open and stay Smart when it is the default",
+        )
+
+        # The actual regression: the previous session must not be discarded.
+        self.assertTrue(
+            self.can_restore_last_session(),
+            msg="Previous session should be restorable when Smart Window is default",
+        )
+
+
+class TestSmartWindowDefaultClassicAutomaticRestore(
+    SmartWindowDefaultMixin, SessionStoreTestCase
+):
+    """With Smart Window as default AND automatic restore (page=3), a window the
+    user kept as Classic must come back Classic — a full restore respects the
+    saved window type, even though new windows default to Smart."""
+
+    def setUp(self):
+        super().setUp(startup_page=3)
+
+    def test_classic_window_restored_as_classic_on_automatic_restore(self):
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+        self.assertFalse(self.is_ai_window(), msg="Window should start as Classic")
+
+        self.marionette.quit()
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        self.assertFalse(
+            self.is_ai_window(),
+            msg="Classic window must restore as Classic on automatic restore, "
+            "even when Smart Window is the default",
+        )
+
+
+class TestSmartWindowDefaultManualRestore(
+    SmartWindowDefaultMixin, SessionStoreTestCase
+):
+    """With Smart Window as default (startup.page=1), restoring a previously
+    Classic session via "Restore previous session" brings it back as Classic.
+    Smart-by-default only applies to the new startup window, not to windows
+    restored from a saved session."""
+
+    def test_classic_session_restored_as_classic_from_history_menu(self):
+        self.marionette.execute_script(
+            """
+            Services.prefs.setBoolPref("browser.sessionstore.persist_closed_tabs_between_sessions", true);
+            """
+        )
+
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+        self.assertFalse(
+            self.is_ai_window(), msg="Window opened during setUp should be Classic"
+        )
+        tab_count = self.get_tab_count()
+
+        self.marionette.quit()
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        # The new startup window opens Smart because Smart Window is the default.
+        self.assertTrue(
+            self.is_ai_window(),
+            msg="Startup window should open Smart when Smart Window is the default",
+        )
+
+        self.restore_last_session()
+
+        # The saved session was Classic, so restoring it opens its own window
+        # (its type doesn't match the Smart startup window).
+        self.assertEqual(
+            len(self.marionette.chrome_window_handles),
+            2,
+            msg="Restored Classic session should open in a separate window",
+        )
+
+        self.marionette.switch_to_window(self.marionette.chrome_window_handles[1])
+        self.assertFalse(
+            self.is_ai_window(),
+            msg="Restored window must stay Classic (restore respects the saved type)",
+        )
+        self.assertEqual(
+            self.get_tab_count(),
+            tab_count,
+            msg="Tab count should be preserved after restore",
+        )
diff --git a/src/zen/tests/mochitests/sessionstore/marionette/test_restore_loading_tab.py b/src/zen/tests/mochitests/sessionstore/marionette/test_restore_loading_tab.py
new file mode 100644
index 000000000..a7544184a
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/marionette/test_restore_loading_tab.py
@@ -0,0 +1,69 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from urllib.parse import quote
+
+from marionette_harness import MarionetteTestCase, WindowManagerMixin
+
+
+def inline(doc):
+    return f"data:text/html;charset=utf-8,{quote(doc)}"
+
+
+class TestRestoreLoadingPage(WindowManagerMixin, MarionetteTestCase):
+    def setUp(self):
+        super().setUp()
+        self.delayed_page = self.marionette.absolute_url("slow")
+
+    def do_test(self, html, is_restoring_expected):
+        self.marionette.navigate(inline(html.format(self.delayed_page)))
+        link = self.marionette.find_element("id", "link")
+        link.click()
+
+        self.marionette.restart(in_app=True)
+
+        with self.marionette.using_context("chrome"):
+            urls = self.marionette.execute_script(
+                "return gBrowser.tabs.map(t => t.linkedBrowser.currentURI.spec);"
+            )
+
+        if is_restoring_expected:
+            self.assertEqual(
+                len(urls),
+                2,
+                msg="The tab opened should be restored",
+            )
+            self.assertEqual(
+                urls[1],
+                self.delayed_page,
+                msg="The tab restored is correct",
+            )
+        else:
+            self.assertEqual(
+                len(urls),
+                1,
+                msg="The tab opened should not be restored",
+            )
+
+        self.close_all_tabs()
+
+    def test_target_blank(self):
+        self.do_test("<a id='link' href='{}' target='_blank'>click</a>", True)
+
+    def test_target_other(self):
+        self.do_test("<a id='link' href='{}' target='other'>click</a>", False)
+
+    def test_by_script(self):
+        self.do_test(
+            """
+            <a id='link'>click</a>
+            <script>
+            document.getElementById("link").addEventListener(
+                "click",
+                () => window.open("{}", "_blank");
+            )
+            </script>
+            """,
+            False,
+        )
diff --git a/src/zen/tests/mochitests/sessionstore/marionette/test_restore_manually.py b/src/zen/tests/mochitests/sessionstore/marionette/test_restore_manually.py
new file mode 100644
index 000000000..0f3291f2e
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/marionette/test_restore_manually.py
@@ -0,0 +1,140 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import os
+import sys
+
+# add this directory to the path
+sys.path.append(os.path.dirname(__file__))
+
+from session_store_test_case import SessionStoreTestCase
+
+
+def inline(title):
+    return f"data:text/html;charset=utf-8,<html><head><title>{title}</title></head><body></body></html>"
+
+
+class TestSessionRestoreManually(SessionStoreTestCase):
+    """
+    Test that window attributes for each window are restored
+    correctly (with manual session restore) in a new session.
+    """
+
+    def setUp(self):
+        super().setUp(
+            startup_page=1,
+            include_private=False,
+            restore_on_demand=True,
+            test_windows=set([
+                # Window 1
+                (
+                    inline("lorem ipsom"),
+                    inline("dolor"),
+                ),
+                # Window 2
+                (inline("sit"),),
+            ]),
+        )
+
+    def test_restore(self):
+        self.marionette.execute_script(
+            """
+            Services.prefs.setBoolPref("browser.sessionstore.persist_closed_tabs_between_sessions", true);
+            """
+        )
+
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+
+        self.assertEqual(
+            len(self.marionette.chrome_window_handles),
+            2,
+            msg="Should have 3 windows open.",
+        )
+        self.marionette.execute_async_script(
+            """
+            function getAllBrowserWindows() {
+                return Array.from(Services.wm.getEnumerator("navigator:browser"));
+            }
+            function promiseResize(value, win) {
+                let deferred = Promise.withResolvers();
+                let id;
+                function listener() {
+                    win.clearTimeout(id);
+                    if (win.innerWidth <= value) {
+                        id = win.setTimeout(() => {
+                            win.removeEventListener("resize", listener);
+                            deferred.resolve()
+                        }, 100);
+                    }
+                }
+                if (win.innerWidth > value) {
+                    win.addEventListener("resize", listener);
+                    win.resizeTo(value, value);
+                } else {
+                    deferred.resolve()
+                }
+                return deferred.promise;
+            }
+
+            let resolve = arguments[0];
+            let windows = getAllBrowserWindows();
+            let value = 500;
+            promiseResize(value, windows[1]).then(resolve);
+            """
+        )
+
+        self.marionette.quit()
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        # restore the previous session
+        self.marionette.execute_script(
+            """
+            const lazy = {};
+            ChromeUtils.defineESModuleGetters(lazy, {
+                SessionStore: "resource:///modules/sessionstore/SessionStore.sys.mjs",
+            });
+            function observeClosedObjectsChange() {
+                return new Promise(resolve => {
+                    function observe(subject, topic, data) {
+                        if (topic == "sessionstore-closed-objects-changed") {
+                            Services.obs.removeObserver(this, "sessionstore-closed-objects-changed");
+                            resolve('observed closed objects changed');
+                        };
+                    }
+                    Services.obs.addObserver(observe, "sessionstore-closed-objects-changed");
+                });
+            };
+
+            async function checkForWindowHeight() {
+                let closedWindowsObserver = observeClosedObjectsChange();
+                lazy.SessionStore.restoreLastSession();
+                await closedWindowsObserver;
+            }
+            checkForWindowHeight();
+            """
+        )
+
+        self.assertEqual(
+            len(self.marionette.chrome_window_handles),
+            2,
+            msg="Windows from last session have been restored.",
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                const lazy = {};
+                ChromeUtils.defineESModuleGetters(lazy, {
+                    SessionStore: "resource:///modules/sessionstore/SessionStore.sys.mjs",
+                });
+                let state = SessionStore.getCurrentState()
+                return state.windows[1]["height"]
+                """
+            ),
+            500,
+            "Second window has been restored to the correct height.",
+        )
diff --git a/src/zen/tests/mochitests/sessionstore/marionette/test_restore_manually_with_pinned_tabs.py b/src/zen/tests/mochitests/sessionstore/marionette/test_restore_manually_with_pinned_tabs.py
new file mode 100644
index 000000000..5e92dce2b
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/marionette/test_restore_manually_with_pinned_tabs.py
@@ -0,0 +1,106 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import os
+import sys
+from urllib.parse import quote
+
+# add this directory to the path
+sys.path.append(os.path.dirname(__file__))
+
+from marionette_driver import Wait, errors
+from session_store_test_case import SessionStoreTestCase
+
+
+def inline(doc):
+    return f"data:text/html;charset=utf-8,{quote(doc)}"
+
+
+class TestSessionRestoreWithPinnedTabs(SessionStoreTestCase):
+    def setUp(self):
+        super().setUp(
+            startup_page=1,
+            include_private=False,
+            restore_on_demand=True,
+            test_windows=set([
+                # Window 1
+                (
+                    inline("""<div">ipsum</div>"""),
+                    inline("""<div">dolor</div>"""),
+                    inline("""<div">amet</div>"""),
+                ),
+            ]),
+        )
+
+    def test_no_restore_with_quit(self):
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+        # add pinned tab in first window.
+        self.marionette.execute_async_script(
+            """
+            let resolve = arguments[0];
+            gBrowser.pinTab(gBrowser.tabs[0]);
+            let { TabStateFlusher } = ChromeUtils.importESModule("resource:///modules/sessionstore/TabStateFlusher.sys.mjs");
+            TabStateFlusher.flush(gBrowser.tabs[0]).then(resolve);
+        """
+        )
+
+        self.marionette.quit()
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        self.assertEqual(
+            self.marionette.execute_script("return gBrowser.tabs.length"),
+            2,
+            msg="Should have 2 tabs.",
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                "return gBrowser.tabs.filter(t => t.pinned).length"
+            ),
+            1,
+            msg="Pinned tab should have been restored.",
+        )
+
+        self.marionette.execute_script(
+            """
+            SessionStore.restoreLastSession();
+        """
+        )
+        self.wait_for_tabcount(3, "Waiting for 3 tabs")
+
+        self.assertEqual(
+            self.marionette.execute_script("return gBrowser.tabs.length"),
+            3,
+            msg="Should have 2 tabs.",
+        )
+        self.assertEqual(
+            self.marionette.execute_script(
+                "return gBrowser.tabs.filter(t => t.pinned).length"
+            ),
+            1,
+            msg="Should still have 1 pinned tab",
+        )
+
+    def wait_for_tabcount(self, expected_tabcount, message, timeout=5):
+        current_tabcount = None
+
+        def check(_):
+            nonlocal current_tabcount
+            current_tabcount = self.marionette.execute_script(
+                "return gBrowser.tabs.length;"
+            )
+            return current_tabcount == expected_tabcount
+
+        try:
+            wait = Wait(self.marionette, timeout=timeout, interval=0.1)
+            wait.until(check, message=message)
+        except errors.TimeoutException as e:
+            # Update the message to include the most recent list of windows
+            message = (
+                f"{e.message}. Expected {expected_tabcount}, got {current_tabcount}."
+            )
+            raise errors.TimeoutException(message)
diff --git a/src/zen/tests/mochitests/sessionstore/marionette/test_restore_manually_with_tab_groups.py b/src/zen/tests/mochitests/sessionstore/marionette/test_restore_manually_with_tab_groups.py
new file mode 100644
index 000000000..b3f727822
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/marionette/test_restore_manually_with_tab_groups.py
@@ -0,0 +1,325 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import os
+import sys
+from urllib.parse import quote
+
+# add this directory to the path
+sys.path.append(os.path.dirname(__file__))
+
+from marionette_driver import Wait, errors
+from session_store_test_case import SessionStoreTestCase
+
+
+def inline(doc):
+    return f"data:text/html;charset=utf-8,{quote(doc)}"
+
+
+class TestSessionRestoreWithTabGroups(SessionStoreTestCase):
+    def setUp(self):
+        super().setUp(
+            startup_page=1,
+            include_private=False,
+            restore_on_demand=True,
+            test_windows=set([
+                (
+                    inline("""<div">lorem</div>"""),
+                    inline("""<div">ipsum</div>"""),
+                    inline("""<div">dolor</div>"""),
+                    inline("""<div">sit</div>"""),
+                    inline("""<div">amet</div>"""),
+                ),
+            ]),
+        )
+
+    def test_no_restore_with_quit(self):
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+
+        self.marionette.execute_async_script(
+            """
+            let resolve = arguments[0];
+            gBrowser.addTabGroup([gBrowser.tabs[3], gBrowser.tabs[4]], { id: "group-left-open-1", label: "open-1" });
+            gBrowser.addTabGroup([gBrowser.tabs[2]], { id: "group-left-open-2", label: "open-2" });
+            let closedGroup = gBrowser.addTabGroup([gBrowser.tabs[1]], { id:"group-closed", label: "closed" });
+            gBrowser.removeTabGroup(closedGroup);
+
+            let { TabStateFlusher } = ChromeUtils.importESModule("resource:///modules/sessionstore/TabStateFlusher.sys.mjs");
+            TabStateFlusher.flushWindow(gBrowser.documentGlobal).then(resolve);
+        """
+        )
+
+        self.marionette.quit()
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                let closedGroupIds = SessionStore.getWindowState(gBrowser.documentGlobal).windows[0].closedGroups.map(g => g.id);
+                return !(closedGroupIds.includes("group-left-open-1") && closedGroupIds.includes("group-left-open-2"));
+                """
+            ),
+            True,
+            "Groups that were left open are NOT in closedGroups",
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                "return SessionStore.getWindowState(gBrowser.documentGlobal).windows[0].closedGroups.length"
+            ),
+            1,
+            msg="There is one closed group in the window",
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                "return SessionStore.getWindowState(gBrowser.documentGlobal).windows[0].closedGroups[0].id"
+            ),
+            "group-closed",
+            msg="Correct group appears in closedGroups",
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script("return SessionStore.savedGroups.length"),
+            2,
+            msg="There are two saved groups",
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                "return SessionStore.savedGroups.map(g => g.id)"
+            ),
+            ["group-left-open-1", "group-left-open-2"],
+            msg="The open groups from last session are now saved",
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                "return SessionStore.getWindowState(gBrowser.documentGlobal).windows[0].closedGroups[0].tabs.length"
+            ),
+            1,
+            msg="Closed group has 1 tab",
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                "return SessionStore.savedGroups.map(g => g.tabs.length)"
+            ),
+            [2, 1],
+            msg="Saved groups have 1 and 2 tabs respectively",
+        )
+
+        self.marionette.execute_script(
+            """
+            SessionStore.restoreLastSession();
+        """
+        )
+        self.wait_for_tabcount(4, "Waiting for 4 tabs")
+
+        self.assertEqual(
+            self.marionette.execute_script("return gBrowser.tabs.length"),
+            4,
+            msg="4 tabs was restored",
+        )
+        self.assertEqual(
+            self.marionette.execute_script("return gBrowser.tabGroups.length"),
+            2,
+            msg="2 tab groups were restored",
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script("return SessionStore.savedGroups?.length"),
+            0,
+            msg="We have no saved tab groups",
+        )
+
+    def test_no_redundant_saves(self):
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+
+        self.marionette.execute_script(
+            """
+            let group = gBrowser.addTabGroup([...gBrowser.tabs], { id: "group-to-save", label: "to-save" });
+            let { TabStateFlusher } = ChromeUtils.importESModule("resource:///modules/sessionstore/TabStateFlusher.sys.mjs");
+            TabStateFlusher.flushWindow(gBrowser.documentGlobal).then(() => {
+                group.saveAndClose();
+            });
+            """
+        )
+
+        self.marionette.quit()
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                return SessionStore.savedGroups.length;
+                """
+            ),
+            1,
+            "There is one and only one saved group",
+        )
+
+        self.marionette.execute_script(
+            """
+            SessionStore.forgetSavedTabGroup("group-to-save");
+            """
+        )
+
+    def test_open_groups_become_permanently_saved_after_two_quits_bug1954488(self):
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+
+        self.marionette.execute_async_script(
+            """
+            let resolve = arguments[0];
+            gBrowser.addTabGroup([gBrowser.tabs[3], gBrowser.tabs[4]], { id: "save-through-restore-1", label: "open-1" });
+            gBrowser.addTabGroup([gBrowser.tabs[1], gBrowser.tabs[2]], { id: "save-through-restore-2", label: "open-2" });
+
+            let { TabStateFlusher } = ChromeUtils.importESModule("resource:///modules/sessionstore/TabStateFlusher.sys.mjs");
+            TabStateFlusher.flushWindow(gBrowser.documentGlobal).then(resolve);
+        """
+        )
+
+        self.marionette.quit()
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                return SessionStore.savedGroups.length;
+                """
+            ),
+            2,
+            "There are two saved groups",
+        )
+
+        win = self.marionette.current_chrome_window_handle
+        self.open_tabs(win, (inline("sit"), inline("amet")))
+
+        self.marionette.quit()
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                return SessionStore.savedGroups.length;
+                """
+            ),
+            2,
+            "There are two saved groups",
+        )
+
+        self.marionette.execute_script(
+            """
+            SessionStore.restoreLastSession();
+        """
+        )
+        self.wait_for_tabcount(2, "Waiting for 2 tabs")
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                return SessionStore.savedGroups.length;
+                """
+            ),
+            2,
+            "There are still two saved groups after the second quit",
+        )
+
+        self.marionette.execute_script(
+            """
+            SessionStore.forgetSavedTabGroup("save-through-restore-1");
+            SessionStore.forgetSavedTabGroup("save-through-restore-2");
+            """
+        )
+
+    def test_saved_groups_no_longer_saved_if_restored_to_tab_strip_bug1956254(self):
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+
+        self.marionette.execute_async_script(
+            """
+            let resolve = arguments[0];
+            gBrowser.addTabGroup([gBrowser.tabs[3], gBrowser.tabs[4]], { id: "not-saved-after-restore-1", label: "open-1" });
+            gBrowser.addTabGroup([gBrowser.tabs[1], gBrowser.tabs[2]], { id: "not-saved-after-restore-2", label: "open-2" });
+
+            let { TabStateFlusher } = ChromeUtils.importESModule("resource:///modules/sessionstore/TabStateFlusher.sys.mjs");
+            TabStateFlusher.flushWindow(gBrowser.documentGlobal).then(resolve);
+            """
+        )
+
+        self.marionette.quit()
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                return SessionStore.savedGroups.length;
+                """
+            ),
+            2,
+            "There are two saved groups in the default state before restoration",
+        )
+
+        self.marionette.execute_script(
+            """
+            SessionStore.restoreLastSession();
+            """
+        )
+        self.wait_for_tabcount(5, "Waiting for 5 tabs")
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                return SessionStore.savedGroups.length;
+                """
+            ),
+            0,
+            "The two saved groups should no longer be saved because they were restored to the tab strip",
+        )
+
+        tab_group_ids = set(
+            self.marionette.execute_script(
+                """
+                return gBrowser.getAllTabGroups().map(tabGroup => tabGroup.id);
+                """
+            )
+        )
+        self.assertTrue(
+            "not-saved-after-restore-1" in tab_group_ids,
+            "the first saved tab group should now be in the tab strip",
+        )
+        self.assertTrue(
+            "not-saved-after-restore-2" in tab_group_ids,
+            "the second saved tab group should now be in the tab strip",
+        )
+
+    def wait_for_tabcount(self, expected_tabcount, message, timeout=5):
+        current_tabcount = None
+
+        def check(_):
+            nonlocal current_tabcount
+            current_tabcount = self.marionette.execute_script(
+                "return gBrowser.tabs.length;"
+            )
+            return current_tabcount == expected_tabcount
+
+        try:
+            wait = Wait(self.marionette, timeout=timeout, interval=0.1)
+            wait.until(check, message=message)
+        except errors.TimeoutException as e:
+            # Update the message to include the most recent list of windows
+            message = (
+                f"{e.message}. Expected {expected_tabcount}, got {current_tabcount}."
+            )
+            raise errors.TimeoutException(message)
diff --git a/src/zen/tests/mochitests/sessionstore/marionette/test_restore_sidebar.py b/src/zen/tests/mochitests/sessionstore/marionette/test_restore_sidebar.py
new file mode 100644
index 000000000..fcccf7c13
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/marionette/test_restore_sidebar.py
@@ -0,0 +1,304 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 0.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/0.0/.
+
+import os
+import sys
+
+# add this directory to the path
+sys.path.append(os.path.dirname(__file__))
+
+from session_store_test_case import SessionStoreTestCase
+
+
+def inline(title):
+    return f"data:text/html;charset=utf-8,<html><head><title>{title}</title></head><body></body></html>"
+
+
+class TestSessionRestore(SessionStoreTestCase):
+    """
+    Test that the sidebar and its attributes are restored on reopening of window.
+    """
+
+    def setUp(self):
+        super().setUp(
+            startup_page=1,
+            include_private=False,
+            restore_on_demand=True,
+            test_windows=set([
+                (
+                    inline("lorem ipsom"),
+                    inline("dolor"),
+                ),
+            ]),
+        )
+
+    def test_restore_sidebar_open(self):
+        self.assertEqual(
+            len(self.marionette.chrome_window_handles),
+            1,
+            msg="Should have 1 window open.",
+        )
+        self.marionette.execute_async_script(
+            """
+            const resolve = arguments[0];
+            let window = BrowserWindowTracker.getTopWindow()
+            window.SidebarController.show("viewHistorySidebar").then(() => {
+              let sidebarBox = window.document.getElementById("sidebar-box")
+              sidebarBox.style.width = "100px";
+            }).then(resolve);
+            """
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                let window = BrowserWindowTracker.getTopWindow()
+                return !window.document.getElementById("sidebar-box").hidden;
+                """
+            ),
+            True,
+            "Sidebar is open before window is closed.",
+        )
+
+        self.marionette.restart()
+        self.marionette.set_context("chrome")
+
+        self.assertEqual(
+            len(self.marionette.chrome_window_handles),
+            1,
+            msg="Windows from last session have been restored.",
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                let window = BrowserWindowTracker.getTopWindow()
+                return !window.document.getElementById("sidebar-box").hidden;
+                """
+            ),
+            True,
+            "Sidebar has been restored.",
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                let window = BrowserWindowTracker.getTopWindow()
+                return window.document.getElementById("sidebar-box").style.width;
+                """
+            ),
+            "100px",
+            "Sidebar width been restored.",
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                const lazy = {};
+                ChromeUtils.defineESModuleGetters(lazy, {
+                    SessionStore: "resource:///modules/sessionstore/SessionStore.sys.mjs",
+                });
+                let state = SessionStore.getCurrentState();
+                return state.windows[0].sidebar.command;
+                """
+            ),
+            "viewHistorySidebar",
+            "Correct sidebar category has been restored.",
+        )
+
+    def test_restore_sidebar_closed(self):
+        self.marionette.execute_async_script(
+            """
+            const resolve = arguments[0];
+            let window = BrowserWindowTracker.getTopWindow()
+            window.SidebarController.show("viewHistorySidebar").then(() => {
+             let sidebarBox = window.document.getElementById("sidebar-box")
+             sidebarBox.style.width = "100px";
+             window.SidebarController.toggle();
+            }).then(resolve);
+            """
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                let window = BrowserWindowTracker.getTopWindow()
+                return window.document.getElementById("sidebar-box").hidden;
+                """
+            ),
+            True,
+            "Sidebar is hidden before window is closed.",
+        )
+
+        self.marionette.restart()
+        self.marionette.set_context("chrome")
+
+        self.assertEqual(
+            len(self.marionette.chrome_window_handles),
+            1,
+            msg="Windows from last session have been restored.",
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                let window = BrowserWindowTracker.getTopWindow()
+                return window.document.getElementById("sidebar-box").hidden;
+                """
+            ),
+            True,
+            "Sidebar is hidden on session restore.",
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                let window = BrowserWindowTracker.getTopWindow()
+                return window.document.getElementById("sidebar-box").style.width;
+                """
+            ),
+            "100px",
+            "Sidebar width has been restored.",
+        )
+
+    def test_restore_for_always_show(self):
+        self.marionette.execute_script(
+            """
+            Services.prefs.setBoolPref("sidebar.revamp", true);
+            // Always show is only available with vertical tabs
+            Services.prefs.setBoolPref("sidebar.verticalTabs", true);
+            Services.prefs.setBoolPref("sidebar.animation.enabled", false);
+            Services.prefs.setStringPref("sidebar.visibility", "always-show");
+            """
+        )
+        self.marionette.restart()
+        self.marionette.set_context("chrome")
+
+        self.assertEqual(
+            len(self.marionette.chrome_window_handles),
+            1,
+            msg="Should have 1 window open.",
+        )
+        self.assertTrue(
+            self.marionette.execute_script(
+                """
+                const window = BrowserWindowTracker.getTopWindow();
+                return window.SidebarController.sidebarMain.expanded;
+                """
+            ),
+            "Sidebar is expanded before window is closed.",
+        )
+
+        self.marionette.restart()
+
+        self.marionette.execute_async_script(
+            """
+            let resolve = arguments[0];
+            let { BrowserInitState } = ChromeUtils.importESModule("resource:///modules/BrowserGlue.sys.mjs");
+            BrowserInitState.startupIdleTaskPromise.then(resolve);
+            """
+        )
+
+        self.assertTrue(
+            self.marionette.execute_script(
+                """
+                const window = BrowserWindowTracker.getTopWindow();
+                return window.SidebarController.sidebarMain.expanded;
+                """
+            ),
+            "Sidebar expanded state has been restored.",
+        )
+
+    def test_restore_for_hide_sidebar(self):
+        self.marionette.execute_script(
+            """
+            Services.prefs.setBoolPref("sidebar.revamp", true);
+            Services.prefs.setStringPref("sidebar.visibility", "hide-sidebar");
+            """
+        )
+        self.marionette.restart()
+        self.marionette.set_context("chrome")
+
+        self.assertEqual(
+            len(self.marionette.chrome_window_handles),
+            1,
+            msg="Should have 1 window open.",
+        )
+        self.assertTrue(
+            self.marionette.execute_script(
+                """
+                const window = BrowserWindowTracker.getTopWindow();
+                return window.SidebarController.sidebarContainer.hidden;
+                """
+            ),
+            "Sidebar is hidden before window is closed.",
+        )
+
+        self.marionette.restart()
+
+        self.assertTrue(
+            self.marionette.execute_script(
+                """
+                const window = BrowserWindowTracker.getTopWindow();
+                return window.SidebarController.sidebarContainer.hidden;
+                """
+            ),
+            "Sidebar visibility state has been restored.",
+        )
+
+    def test_restore_sidebar_open_from_backup_pref(self):
+        self.marionette.execute_script(
+            """
+            Services.prefs.setBoolPref("sidebar.revamp", true);
+            Services.prefs.setBoolPref("browser.privatebrowsing.autostart", true);
+            """
+        )
+        self.marionette.restart()
+        self.marionette.set_context("chrome")
+
+        # Open the history panel.
+        self.marionette.execute_async_script(
+            """
+            let resolve = arguments[0];
+            let window = BrowserWindowTracker.getTopWindow();
+            window.SidebarController.show("viewHistorySidebar").then(resolve);
+            """
+        )
+
+        # Restart the browser.
+        self.marionette.restart()
+        self.marionette.execute_async_script(
+            """
+            let resolve = arguments[0];
+            let { BrowserInitState } = ChromeUtils.importESModule("resource:///modules/BrowserGlue.sys.mjs");
+            BrowserInitState.startupIdleTaskPromise.then(resolve);
+            """
+        )
+
+        # Check to see if the history panel was restored.
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                let window = BrowserWindowTracker.getTopWindow();
+                return window.SidebarController.currentID;
+                """
+            ),
+            "viewHistorySidebar",
+            "Correct sidebar category has been restored.",
+        )
+
+    def test_upgrade_profile_and_restore_sidebar_from_backup_pref(self):
+        # Bug 1963549 - Sidebar bookmarks no longer open automatically since the last update.
+        self.marionette.execute_script(
+            """
+            Services.prefs.setIntPref("browser.migration.version", 154);
+            Services.xulStore.setValue(
+                AppConstants.BROWSER_CHROME_URL,
+                "sidebar-box",
+                "checked",
+                "true"
+            );
+            """
+        )
+        self.test_restore_sidebar_open_from_backup_pref()
diff --git a/src/zen/tests/mochitests/sessionstore/marionette/test_restore_sidebar_automatic.py b/src/zen/tests/mochitests/sessionstore/marionette/test_restore_sidebar_automatic.py
new file mode 100644
index 000000000..19c64844c
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/marionette/test_restore_sidebar_automatic.py
@@ -0,0 +1,106 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 0.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/0.0/.
+
+import os
+import sys
+
+# add this directory to the path
+sys.path.append(os.path.dirname(__file__))
+
+from session_store_test_case import SessionStoreTestCase
+
+
+def inline(title):
+    return f"data:text/html;charset=utf-8,<html><head><title>{title}</title></head><body></body></html>"
+
+
+class TestSessionRestore(SessionStoreTestCase):
+    """
+    Test that the sidebar and its attributes are restored on reopening of window.
+    """
+
+    def setUp(self):
+        super().setUp(
+            startup_page=3,
+            include_private=False,
+            restore_on_demand=False,
+            test_windows=set([
+                (
+                    inline("lorem ipsom"),
+                    inline("dolor"),
+                ),
+            ]),
+        )
+
+    def test_restore(self):
+        self.assertEqual(
+            len(self.marionette.chrome_window_handles),
+            1,
+            msg="Should have 1 window open.",
+        )
+        self.marionette.execute_script(
+            """
+            let window = BrowserWindowTracker.getTopWindow()
+            window.SidebarController.show("viewHistorySidebar");
+            let sidebarBox = window.document.getElementById("sidebar-box")
+            sidebarBox.style.width = "100px";
+            """
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                let window = BrowserWindowTracker.getTopWindow()
+                return !window.document.getElementById("sidebar-box").hidden;
+                """
+            ),
+            True,
+            "Sidebar is open before window is closed.",
+        )
+
+        self.marionette.restart()
+        self.marionette.set_context("chrome")
+
+        self.assertEqual(
+            len(self.marionette.chrome_window_handles),
+            1,
+            msg="Windows from last session have been restored.",
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                let window = BrowserWindowTracker.getTopWindow()
+                return !window.document.getElementById("sidebar-box").hidden;
+                """
+            ),
+            True,
+            "Sidebar has been restored.",
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                let window = BrowserWindowTracker.getTopWindow()
+                return window.document.getElementById("sidebar-box").style.width;
+                """
+            ),
+            "100px",
+            "Sidebar width been restored.",
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                const lazy = {};
+                ChromeUtils.defineESModuleGetters(lazy, {
+                    SessionStore: "resource:///modules/sessionstore/SessionStore.sys.mjs",
+                });
+                let state = SessionStore.getCurrentState();
+                return state.windows[0].sidebar.command;
+                """
+            ),
+            "viewHistorySidebar",
+            "Correct sidebar category has been restored.",
+        )
diff --git a/src/zen/tests/mochitests/sessionstore/marionette/test_restore_windows_after_close_last_tabs.py b/src/zen/tests/mochitests/sessionstore/marionette/test_restore_windows_after_close_last_tabs.py
new file mode 100644
index 000000000..48bc5447e
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/marionette/test_restore_windows_after_close_last_tabs.py
@@ -0,0 +1,57 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# add this directory to the path
+import os
+import sys
+
+sys.path.append(os.path.dirname(__file__))
+
+from session_store_test_case import SessionStoreTestCase
+
+
+class TestSessionStoreEnabledAllWindows(SessionStoreTestCase):
+    def setUp(self, include_private=True):
+        """Setup for the test, enabling session restore.
+
+        :param include_private: Whether to open private windows.
+        """
+        super().setUp(include_private=include_private, startup_page=3)
+
+    def test_with_variety(self):
+        """Test opening and restoring both standard and private windows.
+
+        Opens a set of windows, both standard and private, with
+        some number of tabs in them. Once the tabs have loaded, restarts
+        the browser, and then ensures that the standard tabs have been
+        restored, and that the private ones have not.
+        """
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+
+        self.marionette.quit()
+        self.marionette.start_session()
+
+        self.wait_for_windows(
+            self.test_windows, "Non private browsing windows should have been restored"
+        )
+
+    def test_close_tabs(self):
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+
+        self.close_all_tabs_and_restart()
+
+        self.assertEqual(
+            len(self.marionette.chrome_window_handles),
+            1,
+            msg="Windows from last session shouldn`t have been restored.",
+        )
+        self.assertEqual(
+            len(self.marionette.window_handles),
+            1,
+            msg="Tabs from last session shouldn`t have been restored.",
+        )
diff --git a/src/zen/tests/mochitests/sessionstore/marionette/test_restore_windows_after_restart_and_quit.py b/src/zen/tests/mochitests/sessionstore/marionette/test_restore_windows_after_restart_and_quit.py
new file mode 100644
index 000000000..2498a5f8c
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/marionette/test_restore_windows_after_restart_and_quit.py
@@ -0,0 +1,82 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# add this directory to the path
+import os
+import sys
+
+sys.path.append(os.path.dirname(__file__))
+
+from session_store_test_case import SessionStoreTestCase
+
+
+def inline(title):
+    return f"data:text/html;charset=utf-8,<html><head><title>{title}</title></head><body></body></html>"
+
+
+class TestSessionStoreEnabledAllWindows(SessionStoreTestCase):
+    def setUp(self, include_private=True):
+        """Setup for the test, enabling session restore.
+
+        :param include_private: Whether to open private windows.
+        """
+        super().setUp(include_private=include_private, startup_page=3)
+
+    def test_with_variety(self):
+        """Test opening and restoring both standard and private windows.
+
+        Opens a set of windows, both standard and private, with
+        some number of tabs in them. Once the tabs have loaded, restarts
+        the browser, and then ensures that the standard tabs have been
+        restored, and that the private ones have not.
+        """
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+
+        self.marionette.quit()
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        self.wait_for_windows(
+            self.test_windows, "Non private browsing windows should have been restored"
+        )
+
+
+class TestSessionStoreEnabledNoPrivateWindows(TestSessionStoreEnabledAllWindows):
+    def setUp(self):
+        super().setUp(include_private=False)
+
+
+class TestSessionStoreDisabled(SessionStoreTestCase):
+    def test_no_restore_with_quit(self):
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+
+        self.marionette.quit()
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        self.assertEqual(
+            len(self.marionette.chrome_window_handles),
+            1,
+            msg="Windows from last session shouldn`t have been restored.",
+        )
+        self.assertEqual(
+            len(self.marionette.window_handles),
+            1,
+            msg="Tabs from last session shouldn`t have been restored.",
+        )
+
+    def test_restore_with_restart(self):
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+
+        self.marionette.restart(in_app=True)
+
+        self.wait_for_windows(
+            self.test_windows, "Non private browsing windows should have been restored"
+        )
diff --git a/src/zen/tests/mochitests/sessionstore/marionette/test_restore_windows_after_windows_shutdown.py b/src/zen/tests/mochitests/sessionstore/marionette/test_restore_windows_after_windows_shutdown.py
new file mode 100644
index 000000000..cc7ac1673
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/marionette/test_restore_windows_after_windows_shutdown.py
@@ -0,0 +1,62 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# add this directory to the path
+import os
+import sys
+
+sys.path.append(os.path.dirname(__file__))
+
+from session_store_test_case import SessionStoreTestCase
+
+# We test the following combinations with simulated Windows shutdown:
+# - Start page = restore session (expect restore in all cases)
+#   - RAR (toolkit.winRegisterApplicationRestart) disabled
+#   - RAR enabled, restarted manually
+#
+# - Start page = home
+#   - RAR disabled (no restore)
+#   - RAR enabled:
+#     - restarted by OS (restore)
+#     - restarted manually (no restore)
+
+
+class TestWindowsShutdown(SessionStoreTestCase):
+    def setUp(self):
+        super().setUp(startup_page=3, no_auto_updates=False)
+
+    def test_with_variety(self):
+        """Test session restore selected by user."""
+        self.windows_shutdown_with_variety(restart_by_os=False, expect_restore=True)
+
+
+class TestWindowsShutdownRegisterRestart(SessionStoreTestCase):
+    def setUp(self):
+        super().setUp(startup_page=3, no_auto_updates=False, win_register_restart=True)
+
+    def test_manual_restart(self):
+        """Test that restore tabs works in case of register restart failure."""
+        self.windows_shutdown_with_variety(restart_by_os=False, expect_restore=True)
+
+
+class TestWindowsShutdownNormal(SessionStoreTestCase):
+    def setUp(self):
+        super().setUp(no_auto_updates=False)
+
+    def test_with_variety(self):
+        """Test that windows are not restored on a normal restart."""
+        self.windows_shutdown_with_variety(restart_by_os=False, expect_restore=False)
+
+
+class TestWindowsShutdownForcedSessionRestore(SessionStoreTestCase):
+    def setUp(self):
+        super().setUp(no_auto_updates=False, win_register_restart=True)
+
+    def test_os_restart(self):
+        """Test that register application restart restores the session."""
+        self.windows_shutdown_with_variety(restart_by_os=True, expect_restore=True)
+
+    def test_manual_restart(self):
+        """Test that OS shutdown is ignored on manual start."""
+        self.windows_shutdown_with_variety(restart_by_os=False, expect_restore=False)
diff --git a/src/zen/tests/mochitests/sessionstore/marionette/test_splitview_restore.py b/src/zen/tests/mochitests/sessionstore/marionette/test_splitview_restore.py
new file mode 100644
index 000000000..81239d34d
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/marionette/test_splitview_restore.py
@@ -0,0 +1,183 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# add this directory to the path
+import os
+import sys
+import unittest
+from urllib.parse import quote
+
+sys.path.append(os.path.dirname(__file__))
+
+from session_store_test_case import SessionStoreTestCase
+
+
+def inline(doc):
+    return f"data:text/html;charset=utf-8,{quote(doc)}"
+
+
+# Each list element represents a window of tabs loaded at
+# some testing URL
+DEFAULT_WINDOWS = set([
+    # Window 1. Note the comma after the inline call -
+    # this is Python's way of declaring a 1 item tuple.
+    (
+        inline("""<div">Lorem</div>"""),
+        inline("""<div">Ipsum</div>"""),
+        inline("""<div">Dolor</div>"""),
+        inline("""<div">sit</div>"""),
+        inline("""<div">amet</div>"""),
+    ),
+])
+
+
+class TestAutoRestoreWithSplitView(SessionStoreTestCase):
+    def setUp(self):
+        super().setUp(
+            startup_page=3,
+            include_private=False,
+            restore_on_demand=True,
+            test_windows=DEFAULT_WINDOWS,
+        )
+        self.marionette.set_context("chrome")
+
+    def test_splitview_restored_after_quit(self):
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+
+        self.marionette.execute_async_script(
+            """
+            let resolve = arguments[0];
+            gBrowser.addTabSplitView([gBrowser.tabs[0], gBrowser.tabs[1]], {
+            insertBefore: gBrowser.tabs[0],
+            });
+            let { TabStateFlusher } = ChromeUtils.importESModule("resource:///modules/sessionstore/TabStateFlusher.sys.mjs");
+            TabStateFlusher.flushWindow(gBrowser.documentGlobal).then(resolve);
+            """
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                "return gBrowser.tabs[1].splitview.tabs.length"
+            ),
+            2,
+            "There is a splitview with two tabs",
+        )
+
+        self.marionette.quit()
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                "return gBrowser.tabs[1].splitview.tabs.length"
+            ),
+            2,
+            "Splitview with two tabs restored",
+        )
+
+        self.assertIsNone(
+            self.marionette.execute_script("return gBrowser.activeSplitView"),
+            "Split view is not activated on restore when the selected tab is not in the split view",
+        )
+
+    def test_splitview_restored_multiple_after_quit(self):
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+
+        self.marionette.execute_async_script(
+            """
+            let resolve = arguments[0];
+            gBrowser.addTabSplitView([gBrowser.tabs[0], gBrowser.tabs[1]], {
+            insertBefore: gBrowser.tabs[0],
+            });
+            gBrowser.addTabSplitView([gBrowser.tabs[2], gBrowser.tabs[3]], {
+            insertBefore: gBrowser.tabs[2],
+            });
+            gBrowser.selectedTab = gBrowser.tabs[2];
+            let { TabStateFlusher } = ChromeUtils.importESModule("resource:///modules/sessionstore/TabStateFlusher.sys.mjs");
+            TabStateFlusher.flushWindow(gBrowser.documentGlobal).then(resolve);
+            """
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                "return gBrowser.tabs[2].splitview.tabs.length"
+            ),
+            2,
+            "There is a second splitview with two tabs",
+        )
+
+        self.marionette.quit()
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        self.assertTrue(
+            self.marionette.execute_script(
+                "return gBrowser.tabs[1].splitview.tabs.length && gBrowser.tabs[2].splitview.tabs.length"
+            ),
+            "Two split views have been restored",
+        )
+
+        self.assertTrue(
+            self.marionette.execute_script(
+                "return gBrowser.selectedTab == gBrowser.tabs[2]"
+            ),
+            "Third tab that's in a splitview is the selected tab",
+        )
+        self.assertTrue(
+            self.marionette.execute_script(
+                "return gBrowser.activeSplitView != gBrowser.tabs[0].splitview && gBrowser.activeSplitView == gBrowser.tabs[2].splitview"
+            ),
+            "Split view is not activated on restore when the selected tab does not belong to that split view",
+        )
+
+    @unittest.skipIf(
+        sys.platform.startswith("darwin"),
+        "macOS does not close Firefox when the last window closes",
+    )
+    def test_splitview_restored_after_closing_last_window(self):
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+
+        self.marionette.execute_async_script(
+            """
+            let resolve = arguments[0];
+            gBrowser.addTabSplitView([gBrowser.tabs[0], gBrowser.tabs[1]], {
+                insertBefore: gBrowser.tabs[0],
+            });
+            let { TabStateFlusher } = ChromeUtils.importESModule("resource:///modules/sessionstore/TabStateFlusher.sys.mjs");
+            TabStateFlusher.flushWindow(gBrowser.documentGlobal).then(resolve);
+            """
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                return gBrowser.tabs[0].splitview.tabs.length
+                """
+            ),
+            2,
+            "There is a splitview with two tabs",
+        )
+
+        self.marionette.quit(callback=self._close_window)
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                "return gBrowser.tabs[0].splitview.tabs.length"
+            ),
+            2,
+            "Splitview with two tabs restored",
+        )
+
+        self.assertIsNone(
+            self.marionette.execute_script("return gBrowser.activeSplitView"),
+            "Split view is not activated on restore when the selected tab is not in the split view",
+        )
diff --git a/src/zen/tests/mochitests/sessionstore/marionette/test_tabgroups_restore.py b/src/zen/tests/mochitests/sessionstore/marionette/test_tabgroups_restore.py
new file mode 100644
index 000000000..c4c13ea6a
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/marionette/test_tabgroups_restore.py
@@ -0,0 +1,185 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# add this directory to the path
+import os
+import sys
+import unittest
+from urllib.parse import quote
+
+sys.path.append(os.path.dirname(__file__))
+
+from session_store_test_case import SessionStoreTestCase
+
+
+def inline(doc):
+    return f"data:text/html;charset=utf-8,{quote(doc)}"
+
+
+# Each list element represents a window of tabs loaded at
+# some testing URL
+DEFAULT_WINDOWS = set([
+    # Window 1. Note the comma after the inline call -
+    # this is Python's way of declaring a 1 item tuple.
+    (inline("""<div">Lorem</div>"""), inline("""<div">Ipsum</div>""")),
+])
+
+
+class TestAutoRestoreWithTabGroups(SessionStoreTestCase):
+    def setUp(self):
+        super().setUp(
+            startup_page=3,
+            include_private=False,
+            restore_on_demand=True,
+            test_windows=DEFAULT_WINDOWS,
+        )
+        self.marionette.set_context("chrome")
+
+    def test_saved_groups_restored_after_quit(self):
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+
+        self.marionette.execute_async_script(
+            """
+            let resolve = arguments[0];
+            let group = gBrowser.addTabGroup([gBrowser.tabs[0]], { id: "test-group", label: "test-group" });
+            let { TabStateFlusher } = ChromeUtils.importESModule("resource:///modules/sessionstore/TabStateFlusher.sys.mjs");
+            TabStateFlusher.flushWindow(gBrowser.documentGlobal).then(resolve);
+            """
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script("return gBrowser.getAllTabGroups().length"),
+            1,
+            "There is one open group",
+        )
+
+        self.marionette.quit()
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        self.assertEqual(
+            self.marionette.execute_script("return gBrowser.getAllTabGroups().length"),
+            1,
+            "There is one open group",
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script("return SessionStore.savedGroups.length"),
+            0,
+            "The group was not saved because it was automatically restored",
+        )
+
+        self.marionette.execute_script(
+            """
+            let group = gBrowser.getTabGroupById("test-group");
+            group.documentGlobal.SessionStore.addSavedTabGroup(group);
+            group.documentGlobal.gBrowser.removeTabGroup(group, { animate: false });
+            """
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script("return SessionStore.savedGroups.length"),
+            1,
+            "The group is now saved",
+        )
+
+        self.marionette.quit()
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        self.assertEqual(
+            self.marionette.execute_script("return gBrowser.getAllTabGroups().length"),
+            0,
+            "The group was not automatically restored because it was manually saved",
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script("return SessionStore.savedGroups.length"),
+            1,
+            "The saved group persists after a second restart",
+        )
+
+        self.marionette.execute_script(
+            """
+            SessionStore.forgetSavedTabGroup("test-group");
+            """
+        )
+
+    @unittest.skipIf(
+        sys.platform.startswith("darwin"),
+        "macOS does not close Firefox when the last window closes",
+    )
+    def test_saved_groups_restored_after_closing_last_window(self):
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+
+        self.marionette.execute_async_script(
+            """
+            let resolve = arguments[0];
+            let group = gBrowser.addTabGroup([gBrowser.tabs[0]], { id: "test-group", label: "test-group" });
+            let { TabStateFlusher } = ChromeUtils.importESModule("resource:///modules/sessionstore/TabStateFlusher.sys.mjs");
+            TabStateFlusher.flushWindow(gBrowser.documentGlobal).then(resolve);
+            """
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script("return gBrowser.getAllTabGroups().length"),
+            1,
+            "There is one open group",
+        )
+
+        self.marionette.quit(callback=self._close_window)
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        self.assertEqual(
+            self.marionette.execute_script("return gBrowser.getAllTabGroups().length"),
+            1,
+            "There is one open group",
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script("return SessionStore.savedGroups.length"),
+            0,
+            "The group was not saved because it was automatically restored",
+        )
+
+        self.marionette.execute_script(
+            """
+            let group = gBrowser.getTabGroupById("test-group");
+            group.documentGlobal.SessionStore.addSavedTabGroup(group);
+            group.documentGlobal.gBrowser.removeTabGroup(group, { animate: false });
+            """
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script("return SessionStore.savedGroups.length"),
+            1,
+            "The group is now saved",
+        )
+
+        self.marionette.quit(callback=self._close_window)
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        self.assertEqual(
+            self.marionette.execute_script("return gBrowser.getAllTabGroups().length"),
+            0,
+            "The group was not automatically restored because it was manually saved",
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script("return SessionStore.savedGroups.length"),
+            1,
+            "The saved group persists after a second restart",
+        )
+
+        self.marionette.execute_script(
+            """
+            SessionStore.forgetSavedTabGroup("test-group");
+            """
+        )
diff --git a/src/zen/tests/mochitests/sessionstore/marionette/test_tabnotes_canonicalurl_restore.py b/src/zen/tests/mochitests/sessionstore/marionette/test_tabnotes_canonicalurl_restore.py
new file mode 100644
index 000000000..bfa41cc4d
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/marionette/test_tabnotes_canonicalurl_restore.py
@@ -0,0 +1,195 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import os
+import sys
+from urllib.parse import quote
+
+sys.path.append(os.path.dirname(__file__))
+
+from marionette_driver import Wait
+from session_store_test_case import SessionStoreTestCase
+
+
+def inline(doc):
+    return f"data:text/html;charset=utf-8,{quote(doc)}"
+
+
+CANONICAL_URL = "https://example.com/canonical"
+
+
+class TestCanonicalUrlRestore(SessionStoreTestCase):
+    """
+    Test that canonicalUrl and hasTabNote are properly restored on pending
+    tabs after browser restart with session restore enabled.
+
+    Uses two tabs with restore_on_demand=True:
+    - tabs[0]: pending tab (not selected, stays pending)
+    - tabs[1]: selected tab (the last one opened)
+    """
+
+    def setUp(self):
+        super().setUp(
+            startup_page=3,  # Restore previous session
+            include_private=False,
+            restore_on_demand=True,  # Keep non-selected tabs pending
+            test_windows=set([
+                # Two tabs - the last one opened will be selected
+                (
+                    inline("<div>Tab 1</div>"),
+                    inline("<div>Tab 2</div>"),
+                ),
+            ]),
+        )
+        self.marionette.set_context("chrome")
+        self.marionette.execute_script(
+            """
+            Services.prefs.setBoolPref("browser.tabs.notes.enabled", true);
+            """
+        )
+
+    def test_hasTabNote_set_after_restart(self):
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+
+        tab_count = self.marionette.execute_script("return gBrowser.tabs.length;")
+        self.assertEqual(tab_count, 2, "Should have 2 tabs")
+
+        # Set canonicalUrl and note on tabs[0] (will be pending after restart)
+        self.marionette.execute_async_script(
+            f"""
+            let resolve = arguments[0];
+            (async () => {{
+                const {{ TabNotes }} = ChromeUtils.importESModule(
+                    "moz-src:///browser/components/tabnotes/TabNotes.sys.mjs"
+                );
+
+                await TabNotes.init();
+
+                let pendingTab = gBrowser.tabs[0];
+                pendingTab.canonicalUrl = "{CANONICAL_URL}";
+                await TabNotes.set(pendingTab, "Note for pending tab");
+
+                let {{ TabStateFlusher }} = ChromeUtils.importESModule(
+                    "resource:///modules/sessionstore/TabStateFlusher.sys.mjs"
+                );
+                await TabStateFlusher.flushWindow(gBrowser.documentGlobal);
+            }})().then(resolve);
+            """
+        )
+
+        # Verify state before restart
+        result_before = self.marionette.execute_script(
+            """
+            return {
+                canonicalUrl: gBrowser.tabs[0].canonicalUrl,
+                hasTabNote: gBrowser.tabs[0].hasTabNote
+            };
+            """
+        )
+        self.assertEqual(
+            result_before["canonicalUrl"],
+            CANONICAL_URL,
+            "canonicalUrl should be set before restart",
+        )
+        self.assertTrue(
+            result_before["hasTabNote"],
+            "hasTabNote should be true before restart",
+        )
+
+        # Restart browser
+        self.marionette.quit()
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        # Wait for hasTabNote to be set on the pending tab (async due to database check)
+        Wait(self.marionette, timeout=10, interval=0.2).until(
+            lambda _: self.marionette.execute_script(
+                """
+                return gBrowser.tabs[0].hasTabNote === true;
+                """
+            ),
+            message="hasTabNote should be set on pending tab after restart",
+        )
+
+        # Verify state after restart
+        result = self.marionette.execute_script(
+            """
+            let pendingTab = gBrowser.tabs[0];
+            return {
+                isPending: pendingTab.hasAttribute("pending"),
+                canonicalUrl: pendingTab.canonicalUrl,
+                hasTabNote: pendingTab.hasTabNote
+            };
+            """
+        )
+
+        self.assertTrue(result["isPending"], "Tab should be pending after restore")
+        self.assertEqual(
+            result["canonicalUrl"],
+            CANONICAL_URL,
+            "canonicalUrl should be restored on pending tab",
+        )
+        self.assertTrue(
+            result["hasTabNote"],
+            "hasTabNote should be true for pending tab with existing note",
+        )
+
+    def test_canonicalUrl_cleared_when_feature_disabled(self):
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+
+        # Set canonicalUrl on a tab
+        self.marionette.execute_async_script(
+            f"""
+            let resolve = arguments[0];
+            (async () => {{
+                let tab = gBrowser.tabs[0];
+                tab.canonicalUrl = "{CANONICAL_URL}";
+
+                let {{ TabStateFlusher }} = ChromeUtils.importESModule(
+                    "resource:///modules/sessionstore/TabStateFlusher.sys.mjs"
+                );
+                await TabStateFlusher.flushWindow(gBrowser.documentGlobal);
+            }})().then(resolve);
+            """
+        )
+
+        canonicalUrl = self.marionette.execute_script(
+            "return gBrowser.tabs[0].canonicalUrl;"
+        )
+        self.assertEqual(
+            canonicalUrl, CANONICAL_URL, "canonicalUrl should be set before restart"
+        )
+
+        # Restart browser with tab notes disabled
+        self.marionette.execute_script(
+            """
+            Services.prefs.setBoolPref("browser.tabs.notes.enabled", false);
+            """
+        )
+        self.marionette.quit()
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        result = self.marionette.execute_script(
+            """
+            let tab = gBrowser.tabs[0];
+            return {
+                canonicalUrl: tab.canonicalUrl,
+                isPending: tab.hasAttribute("pending")
+            };
+            """
+        )
+
+        self.assertTrue(result["isPending"], "Tab should be pending after restore")
+        self.assertIsNone(
+            result["canonicalUrl"],
+            "canonicalUrl should be cleared when feature is disabled",
+        )
+
+    def test_hasTabNote_false_when_no_note(self):
+        self.skipTest("To be added in Bug 2014766 pending TabNotesController updates")
diff --git a/src/zen/tests/mochitests/sessionstore/marionette/test_taskbartab_restore.py b/src/zen/tests/mochitests/sessionstore/marionette/test_taskbartab_restore.py
new file mode 100644
index 000000000..e332fef87
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/marionette/test_taskbartab_restore.py
@@ -0,0 +1,132 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+
+import os
+import sys
+
+from marionette_driver import Wait
+
+# add this directory to the path
+sys.path.append(os.path.dirname(__file__))
+from session_store_test_case import SessionStoreTestCase
+
+
+def inline(title):
+    return f"data:text/html;charset=utf-8,<html><head><title>{title}</title></head><body></body></html>"
+
+
+class TestManualRestoreWithTaskbarTabs(SessionStoreTestCase):
+    def setUp(self):
+        super().setUp(
+            startup_page=1,
+            include_private=False,
+            restore_on_demand=False,
+            taskbartabs_enable=True,
+            test_windows=set([
+                # Window 1
+                (
+                    inline("lorem ipsom"),
+                    inline("dolor"),
+                ),
+            ]),
+        )
+
+    """
+    Close all regular windows except for a taskbar tab window. The
+    session should be over at this point. Opening another regular Firefox
+    window will open "restore previous session" in the hamburger menu.
+    And clicking it will restore the correct session.
+    """
+
+    def test_restore_without_closing_taskbartab(self):
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+
+        # See session_store_test_case.py
+        self.setup_taskbartab_restore_scenario()
+
+        # Verify that "restore previous session" button
+        # is visible in the hamburger menu
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                let newWindow = BrowserWindowTracker.getTopWindow({ allowTaskbarTabs: false });
+                return PanelMultiView.getViewNode(
+                    newWindow.document,
+                    "appMenu-restoreSession"
+                ).hasAttribute("disabled");
+            """
+            ),
+            False,
+            "The restore last session button should be visible",
+        )
+
+        # Simulate clicking "restore previous session"
+        self.marionette.execute_script(
+            """
+                SessionStore.restoreLastSession();
+            """
+        )
+
+        # Wait for the restore to be completed,
+        # meaning the window we opened should have
+        # two tabs again.
+        Wait(self.marionette).until(
+            lambda mn: (
+                mn.execute_script(
+                    """
+                let newWindow = BrowserWindowTracker.getTopWindow({ allowTaskbarTabs: false });
+                return newWindow.gBrowser.tabs.length;
+                """
+                )
+                == 2
+            )
+        )
+
+
+class TestAutoRestoreWithTaskbarTabs(SessionStoreTestCase):
+    def setUp(self):
+        super().setUp(
+            startup_page=3,
+            include_private=False,
+            restore_on_demand=False,
+            taskbartabs_enable=True,
+            test_windows=set([
+                # Window 1
+                (
+                    inline("lorem ipsom"),
+                    inline("dolor"),
+                ),
+            ]),
+        )
+
+    """
+    Close all regular windows except for a taskbar tab window. The
+    session should be over at this point. Opening another regular Firefox
+    window will open automatically restore the correct session
+    """
+
+    def test_restore_without_closing_taskbartab(self):
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+
+        self.setup_taskbartab_restore_scenario()
+
+        # Wait for the auto restore to be completed,
+        # meaning the window we opened should have
+        # the original two tabs plus the home page tab.
+        Wait(self.marionette).until(
+            lambda mn: (
+                mn.execute_script(
+                    """
+                let newWindow = BrowserWindowTracker.getTopWindow({ allowTaskbarTabs: false });
+                return newWindow.gBrowser.tabs.length;
+                """
+                )
+                == 3
+            )
+        )
diff --git a/src/zen/tests/mochitests/sessionstore/marionette/test_taskbartab_sessionstate.py b/src/zen/tests/mochitests/sessionstore/marionette/test_taskbartab_sessionstate.py
new file mode 100644
index 000000000..7f75f27df
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/marionette/test_taskbartab_sessionstate.py
@@ -0,0 +1,87 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+
+import os
+import sys
+
+# add this directory to the path
+sys.path.append(os.path.dirname(__file__))
+from session_store_test_case import SessionStoreTestCase
+
+
+def inline(title):
+    return f"data:text/html;charset=utf-8,<html><head><title>{title}</title></head><body></body></html>"
+
+
+class TestTaskbarTabSessionState(SessionStoreTestCase):
+    def setUp(self):
+        super().setUp(
+            startup_page=1,
+            include_private=False,
+            restore_on_demand=False,
+            taskbartabs_enable=True,
+            test_windows=set([
+                # Window 1
+                (
+                    inline("lorem ipsom"),
+                    inline("dolor"),
+                ),
+            ]),
+        )
+
+    """
+    Close all Firefox windows with the web app being closed last,
+    the session store state should include the last regular window
+    that's closed, but not the web app
+    """
+
+    def test_taskbartab_session_state(self):
+        self.wait_for_windows(
+            self.all_windows, "Not all requested windows have been opened"
+        )
+
+        self.marionette.enforce_gecko_prefs({"browser.taskbarTabs.enabled": True})
+
+        self.open_taskbartab_window()
+
+        # Close the original regular Firefox window
+        taskbar_tab_window_handle = self.marionette.close_chrome_window()[0]
+        self.marionette.switch_to_window(taskbar_tab_window_handle)
+
+        self.marionette.set_context("content")
+        dummy_html = self.marionette.absolute_url("empty.html")
+        self.marionette.navigate(dummy_html)
+        self.marionette.set_context("chrome")
+
+        self.marionette.quit()
+        self.marionette.start_session()
+        self.marionette.set_context("chrome")
+
+        # check for the session store state, it should have only two tabs and one window
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                const { _LastSession } = ChromeUtils.importESModule(
+                    "resource:///modules/sessionstore/SessionStore.sys.mjs"
+                    );
+                return _LastSession.getState().windows.length
+            """
+            ),
+            1,
+            "One window should be in the session state",
+        )
+
+        self.assertEqual(
+            self.marionette.execute_script(
+                """
+                const { _LastSession } = ChromeUtils.importESModule(
+                    "resource:///modules/sessionstore/SessionStore.sys.mjs"
+                    );
+                return _LastSession.getState().windows[0].tabs.length
+            """
+            ),
+            2,
+            "Two tabs should be in the session state",
+        )
diff --git a/src/zen/tests/mochitests/sessionstore/restore_redirect_http.html b/src/zen/tests/mochitests/sessionstore/restore_redirect_http.html
new file mode 100644
index 000000000..e69de29bb
diff --git a/src/zen/tests/mochitests/sessionstore/restore_redirect_http.html^headers^ b/src/zen/tests/mochitests/sessionstore/restore_redirect_http.html^headers^
new file mode 100644
index 000000000..533bda36f
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/restore_redirect_http.html^headers^
@@ -0,0 +1,2 @@
+HTTP 302 Moved Temporarily
+Location: restore_redirect_target.html
diff --git a/src/zen/tests/mochitests/sessionstore/restore_redirect_js.html b/src/zen/tests/mochitests/sessionstore/restore_redirect_js.html
new file mode 100644
index 000000000..f0130847b
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/restore_redirect_js.html
@@ -0,0 +1,10 @@
+<!DOCTYPE html>
+
+<html>
+<head>
+<script>
+var newLocation = window.location.toString().replace("restore_redirect_js.html", "restore_redirect_target.html");
+window.location.replace(newLocation);
+</script>
+</head>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/restore_redirect_target.html b/src/zen/tests/mochitests/sessionstore/restore_redirect_target.html
new file mode 100644
index 000000000..813af0550
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/restore_redirect_target.html
@@ -0,0 +1,8 @@
+<!DOCTYPE html>
+<meta charset="utf-8"/>
+<html>
+<head>
+<title>Test page</title>
+</head>
+<body>Test page</body>
+</html>
diff --git a/src/zen/tests/mochitests/sessionstore/unit/data/sessionCheckpoints_all.json b/src/zen/tests/mochitests/sessionstore/unit/data/sessionCheckpoints_all.json
new file mode 100644
index 000000000..e02c421c3
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/unit/data/sessionCheckpoints_all.json
@@ -0,0 +1,11 @@
+{
+  "profile-after-change": true,
+  "final-ui-startup": true,
+  "sessionstore-windows-restored": true,
+  "quit-application-granted": true,
+  "quit-application": true,
+  "sessionstore-final-state-write-complete": true,
+  "profile-change-net-teardown": true,
+  "profile-change-teardown": true,
+  "profile-before-change": true
+}
diff --git a/src/zen/tests/mochitests/sessionstore/unit/data/sessionstore_complete.json b/src/zen/tests/mochitests/sessionstore/unit/data/sessionstore_complete.json
new file mode 100644
index 000000000..92cb150ee
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/unit/data/sessionstore_complete.json
@@ -0,0 +1,907 @@
+{
+  "version": ["sessionrestore", 1],
+  "windows": [
+    {
+      "tabs": [
+        {
+          "entries": [
+            {
+              "url": "about:home",
+              "title": "New Tab",
+              "cacheKey": 0,
+              "ID": 889527166,
+              "docshellUUID": "{1c51a53b-d2b5-4484-8deb-aef7bd44abc4}",
+              "resultPrincipalURI": null,
+              "principalToInherit_base64": "{\"0\":{\"0\":\"moz-nullprincipal:{6ec4bec4-5873-4b33-b269-be6653e318d8}\"}}",
+              "hasUserInteraction": true,
+              "triggeringPrincipal_base64": "{\"3\":{}}",
+              "docIdentifier": 12,
+              "transient": false,
+              "navigationKey": "{d0185d51-bd9f-4f90-afb2-f40547ac08a8}",
+              "navigationId": "{08e9abae-27f4-4cbb-8eb6-1524776e7327}"
+            },
+            {
+              "url": "about:mozilla",
+              "title": "The Book of Mozilla, 6:27",
+              "cacheKey": 0,
+              "ID": 889527167,
+              "docshellUUID": "{1c51a53b-d2b5-4484-8deb-aef7bd44abc4}",
+              "resultPrincipalURI": null,
+              "principalToInherit_base64": "{\"0\":{\"0\":\"moz-nullprincipal:{b5d58330-101d-4601-9291-6435ebcb854e}\"}}",
+              "hasUserInteraction": true,
+              "triggeringPrincipal_base64": "{\"3\":{}}",
+              "docIdentifier": 13,
+              "transient": false,
+              "navigationKey": "{e546bd8d-4813-4a8a-8e90-0cdde6b5ab72}",
+              "navigationId": "{7fd8f06e-2863-4f78-85f4-a4684c635086}"
+            }
+          ],
+          "lastAccessed": 1770416063211,
+          "hidden": false,
+          "groupId": "1770415115529-1",
+          "searchMode": null,
+          "userContextId": 0,
+          "attributes": {},
+          "index": 2,
+          "requestedIndex": 0,
+          "image": null
+        },
+        {
+          "entries": [
+            {
+              "url": "about:newtab",
+              "title": "New Tab",
+              "cacheKey": 0,
+              "ID": 889527170,
+              "docshellUUID": "{739fd540-1ff5-4d46-8e55-896b64d6cfb3}",
+              "resultPrincipalURI": null,
+              "hasUserInteraction": true,
+              "triggeringPrincipal_base64": "{\"3\":{}}",
+              "docIdentifier": 14,
+              "transient": false,
+              "navigationKey": "{c3718cd7-fac1-4ca7-b728-73b028e8e26a}",
+              "navigationId": "{b0b9cd99-3b46-4b98-b032-2d9ab1d649c0}"
+            },
+            {
+              "url": "about:support",
+              "title": "Troubleshooting Information",
+              "cacheKey": 0,
+              "ID": 889527171,
+              "docshellUUID": "{739fd540-1ff5-4d46-8e55-896b64d6cfb3}",
+              "resultPrincipalURI": null,
+              "principalToInherit_base64": "{\"0\":{\"0\":\"moz-nullprincipal:{675de4b7-6fd5-47d4-a538-50bbcdca4c6c}\"}}",
+              "hasUserInteraction": true,
+              "triggeringPrincipal_base64": "{\"3\":{}}",
+              "docIdentifier": 15,
+              "transient": false,
+              "navigationKey": "{f8decd0b-ac89-4e55-892e-3e8ed627ba0e}",
+              "navigationId": "{ad8b07d9-29bf-4281-806a-c3534fc58d84}"
+            },
+            {
+              "url": "about:preferences",
+              "title": "Settings",
+              "cacheKey": 0,
+              "ID": 889527172,
+              "docshellUUID": "{739fd540-1ff5-4d46-8e55-896b64d6cfb3}",
+              "originalURI": "about:preferences",
+              "resultPrincipalURI": null,
+              "principalToInherit_base64": "{\"0\":{\"0\":\"moz-nullprincipal:{a6850bcd-5678-4594-9311-0affec22d009}\"}}",
+              "hasUserInteraction": true,
+              "triggeringPrincipal_base64": "{\"3\":{}}",
+              "docIdentifier": 16,
+              "structuredCloneState": "AgAAAAAA8f8LAACABAD//3BhbmVHZW5lcmFsAAAAAAA=",
+              "structuredCloneVersion": 8,
+              "children": [
+                {
+                  "url": "about:blank",
+                  "title": "about:blank",
+                  "cacheKey": 0,
+                  "ID": 889527173,
+                  "docshellUUID": "{5cdf1a82-9508-4a80-8884-312cb35c4b5a}",
+                  "resultPrincipalURI": null,
+                  "hasUserInteraction": true,
+                  "triggeringPrincipal_base64": "{\"3\":{}}",
+                  "policyContainer": "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",
+                  "docIdentifier": 17,
+                  "transient": true,
+                  "navigationKey": "{d292a0e0-a212-4147-a523-7196c1d82c09}",
+                  "navigationId": "{72db572a-c072-4aa9-b282-e22fdb01150d}"
+                },
+                {
+                  "url": "about:blank",
+                  "title": "about:blank",
+                  "cacheKey": 0,
+                  "ID": 20,
+                  "docshellUUID": "{99483b7c-4429-4610-970d-8e43b680cda6}",
+                  "resultPrincipalURI": null,
+                  "hasUserInteraction": true,
+                  "triggeringPrincipal_base64": "{\"3\":{}}",
+                  "policyContainer": "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",
+                  "docIdentifier": 22,
+                  "transient": true,
+                  "navigationKey": "{6dfc5997-9767-471e-a092-3d3cb72d5c18}",
+                  "navigationId": "{949e9fde-2b4d-4588-8bfe-807a46c38f02}"
+                }
+              ],
+              "transient": false,
+              "navigationKey": "{f8241c63-5204-446f-82f4-9a200b7a57eb}",
+              "navigationId": "{86153ed4-da40-4d2a-8017-8268fc40158f}"
+            }
+          ],
+          "lastAccessed": 1770416070546,
+          "hidden": false,
+          "splitViewId": 1,
+          "searchMode": null,
+          "userContextId": 0,
+          "attributes": {},
+          "index": 3,
+          "requestedIndex": 0,
+          "formdata": {
+            "url": "about:preferences",
+            "id": {
+              "searchInput": {
+                "state": "",
+                "value": ""
+              },
+              "browserRestoreSession": {
+                "state": "on",
+                "value": "on"
+              },
+              "windowsLaunchOnLogin": {
+                "state": "on",
+                "value": "on"
+              },
+              "alwaysCheckDefault": {
+                "state": "on",
+                "value": "on"
+              },
+              "linkTargeting": {
+                "state": "on",
+                "value": "on"
+              },
+              "switchToNewTabs": {
+                "state": "on",
+                "value": "on"
+              },
+              "openAppLinksNextToActiveTab": {
+                "state": "on",
+                "value": "on"
+              },
+              "warnOpenMany": {
+                "state": "on",
+                "value": "on"
+              },
+              "ctrlTabRecentlyUsedOrder": {
+                "state": "on",
+                "value": "on"
+              },
+              "tabPreviewShowThumbnails": {
+                "state": "on",
+                "value": "on"
+              },
+              "tabGroupSuggestions": {
+                "state": "on",
+                "value": "on"
+              },
+              "showTabsInTaskbar": {
+                "state": "on",
+                "value": "on"
+              },
+              "browserContainersCheckbox": {
+                "state": "on",
+                "value": "on"
+              },
+              "warnCloseMultiple": {
+                "state": "on",
+                "value": "on"
+              },
+              "warnOnQuitKey": {
+                "state": "on",
+                "value": "on"
+              },
+              "browserLayoutRadioGroup": {
+                "state": "false",
+                "value": "false"
+              },
+              "browserLayoutShowSidebar": {
+                "state": "on",
+                "value": "on"
+              },
+              "web-appearance-chooser": {
+                "state": "auto",
+                "value": "auto"
+              },
+              "contrastControlSettings": {
+                "state": "1",
+                "value": "1"
+              },
+              "contrastSettingsAuto": {
+                "state": "0",
+                "value": "0"
+              },
+              "contrastSettingsOff": {
+                "state": "1",
+                "value": "1"
+              },
+              "contrastSettingsOn": {
+                "state": "2",
+                "value": "2"
+              },
+              "defaultZoom": {
+                "state": "100",
+                "value": "100"
+              },
+              "zoomText": {
+                "state": "on",
+                "value": "on"
+              },
+              "chooseFolder": {
+                "state": "/home/sfoster/Downloads",
+                "value": "/home/sfoster/Downloads"
+              },
+              "alwaysAsk": {
+                "state": "on",
+                "value": "on"
+              },
+              "deletePrivate": {
+                "state": "on",
+                "value": "on"
+              },
+              "filter": {
+                "state": "",
+                "value": ""
+              },
+              "playDRMContent": {
+                "state": "on",
+                "value": "on"
+              },
+              "useRecommendedPerformanceSettings": {
+                "state": "on",
+                "value": "on"
+              },
+              "allowHWAccel": {
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+    {
+      "host": "addons.mozilla.org",
+      "value": "ef51d7121d46a4fd86e874d8a850d58e7ef917a047014268bf1d3be112b72b77",
+      "path": "/",
+      "name": "taarId",
+      "secure": true,
+      "httponly": true,
+      "originAttributes": {
+        "firstPartyDomain": "",
+        "geckoViewSessionContextId": "",
+        "partitionKey": "",
+        "privateBrowsingId": 0,
+        "userContextId": 3
+      },
+      "sameSite": 1,
+      "schemeMap": 2
+    },
+    {
+      "host": "addons.mozilla.org",
+      "value": "ef51d7121d46a4fd86e874d8a850d58e7ef917a047014268bf1d3be112b72b77",
+      "path": "/",
+      "name": "taarId",
+      "secure": true,
+      "httponly": true,
+      "originAttributes": {
+        "firstPartyDomain": "",
+        "geckoViewSessionContextId": "",
+        "partitionKey": "",
+        "privateBrowsingId": 0,
+        "userContextId": 4
+      },
+      "sameSite": 1,
+      "schemeMap": 2
+    },
+    {
+      "host": "addons.mozilla.org",
+      "value": "ef51d7121d46a4fd86e874d8a850d58e7ef917a047014268bf1d3be112b72b77",
+      "path": "/",
+      "name": "taarId",
+      "secure": true,
+      "httponly": true,
+      "originAttributes": {
+        "firstPartyDomain": "",
+        "geckoViewSessionContextId": "",
+        "partitionKey": "",
+        "privateBrowsingId": 0,
+        "userContextId": 0
+      },
+      "sameSite": 1,
+      "schemeMap": 2
+    },
+    {
+      "host": "addons.mozilla.org",
+      "value": "ef51d7121d46a4fd86e874d8a850d58e7ef917a047014268bf1d3be112b72b77",
+      "path": "/",
+      "name": "taarId",
+      "secure": true,
+      "httponly": true,
+      "originAttributes": {
+        "firstPartyDomain": "",
+        "geckoViewSessionContextId": "",
+        "partitionKey": "",
+        "privateBrowsingId": 0,
+        "userContextId": 1
+      },
+      "sameSite": 1,
+      "schemeMap": 2
+    },
+    {
+      "host": "addons.mozilla.org",
+      "value": "ef51d7121d46a4fd86e874d8a850d58e7ef917a047014268bf1d3be112b72b77",
+      "path": "/",
+      "name": "taarId",
+      "secure": true,
+      "httponly": true,
+      "originAttributes": {
+        "firstPartyDomain": "",
+        "geckoViewSessionContextId": "",
+        "partitionKey": "",
+        "privateBrowsingId": 0,
+        "userContextId": 2
+      },
+      "sameSite": 1,
+      "schemeMap": 2
+    }
+  ],
+  "browserConsole": false,
+  "browserToolbox": false
+}
diff --git a/src/zen/tests/mochitests/sessionstore/unit/data/sessionstore_invalid.js b/src/zen/tests/mochitests/sessionstore/unit/data/sessionstore_invalid.js
new file mode 100644
index 000000000..a8c3ff2ff
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/unit/data/sessionstore_invalid.js
@@ -0,0 +1,3 @@
+{
+  "windows": // invalid json
+}
diff --git a/src/zen/tests/mochitests/sessionstore/unit/data/sessionstore_valid.js b/src/zen/tests/mochitests/sessionstore/unit/data/sessionstore_valid.js
new file mode 100644
index 000000000..f9511f29f
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/unit/data/sessionstore_valid.js
@@ -0,0 +1,3 @@
+{
+  "windows": []
+}
\ No newline at end of file
diff --git a/src/zen/tests/mochitests/sessionstore/unit/head.js b/src/zen/tests/mochitests/sessionstore/unit/head.js
new file mode 100644
index 000000000..03f7e8239
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/unit/head.js
@@ -0,0 +1,37 @@
+ChromeUtils.defineESModuleGetters(this, {
+  SessionStartup: "resource:///modules/sessionstore/SessionStartup.sys.mjs",
+  SessionStore: "resource:///modules/sessionstore/SessionStore.sys.mjs",
+});
+
+// Call a function once initialization of SessionStartup is complete
+function afterSessionStartupInitialization(cb) {
+  info("Waiting for session startup initialization");
+  let observer = function () {
+    try {
+      info("Session startup initialization observed");
+      Services.obs.removeObserver(observer, "sessionstore-state-finalized");
+      cb();
+    } catch (ex) {
+      do_throw(ex);
+    }
+  };
+  Services.obs.addObserver(observer, "sessionstore-state-finalized");
+
+  // We need the Crash Monitor initialized for sessionstartup to run
+  // successfully.
+  const { CrashMonitor } = ChromeUtils.importESModule(
+    "resource://gre/modules/CrashMonitor.sys.mjs"
+  );
+  CrashMonitor.init();
+
+  // Start sessionstartup initialization.
+  SessionStartup.init();
+}
+
+// Compress the source file using lz4 and put the result to destination file.
+// After that, source file is deleted.
+async function writeCompressedFile(source, destination) {
+  let s = await IOUtils.read(source);
+  await IOUtils.write(destination, s, { compress: true });
+  await IOUtils.remove(source);
+}
diff --git a/src/zen/tests/mochitests/sessionstore/unit/test_backup_once.js b/src/zen/tests/mochitests/sessionstore/unit/test_backup_once.js
new file mode 100644
index 000000000..db566491d
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/unit/test_backup_once.js
@@ -0,0 +1,137 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { SessionWriter } = ChromeUtils.importESModule(
+  "resource:///modules/sessionstore/SessionWriter.sys.mjs"
+);
+
+// Make sure that we have a profile before initializing SessionFile.
+const profd = do_get_profile();
+const { SessionFile } = ChromeUtils.importESModule(
+  "resource:///modules/sessionstore/SessionFile.sys.mjs"
+);
+const Paths = SessionFile.Paths;
+
+// We need a XULAppInfo to initialize SessionFile
+const { updateAppInfo } = ChromeUtils.importESModule(
+  "resource://testing-common/AppInfo.sys.mjs"
+);
+updateAppInfo({
+  name: "SessionRestoreTest",
+  ID: "{230de50e-4cd1-11dc-8314-0800200c9a66}",
+  version: "1",
+  platformVersion: "",
+});
+
+add_setup(async function () {
+  let source = do_get_file("data/sessionstore_valid.js");
+  source.copyTo(profd, "sessionstore.js");
+  await writeCompressedFile(Paths.clean.replace("jsonlz4", "js"), Paths.clean);
+
+  // Finish initialization of SessionFile
+  await SessionFile.read();
+});
+
+function promise_check_exist(path, shouldExist) {
+  return (async function () {
+    info(
+      "Ensuring that " + path + (shouldExist ? " exists" : " does not exist")
+    );
+    if ((await IOUtils.exists(path)) != shouldExist) {
+      throw new Error(
+        "File" + path + " should " + (shouldExist ? "exist" : "not exist")
+      );
+    }
+  })();
+}
+
+function promise_check_contents(path, expect) {
+  return (async function () {
+    info("Checking whether " + path + " has the right contents");
+    let actual = await IOUtils.readJSON(path, {
+      decompress: true,
+    });
+    Assert.deepEqual(
+      actual,
+      expect,
+      `File ${path} contains the expected data.`
+    );
+  })();
+}
+
+function generateFileContents(id) {
+  let url = `http://example.com/test_backup_once#${id}_${Math.random()}`;
+  return { windows: [{ tabs: [{ entries: [{ url }], index: 1 }] }] };
+}
+
+// Write to the store, and check that it creates:
+// - $Path.recovery with the new data
+// - $Path.nextUpgradeBackup with the old data
+add_task(async function test_first_write_backup() {
+  let initial_content = generateFileContents("initial");
+  let new_content = generateFileContents("test_1");
+
+  info("Before the first write, none of the files should exist");
+  await promise_check_exist(Paths.backups, false);
+
+  await IOUtils.makeDirectory(Paths.backups);
+  await IOUtils.writeJSON(Paths.clean, initial_content, {
+    compress: true,
+  });
+  await SessionFile.write(new_content);
+
+  info("After first write, a few files should have been created");
+  await promise_check_exist(Paths.backups, true);
+  await promise_check_exist(Paths.clean, false);
+  await promise_check_exist(Paths.cleanBackup, true);
+  await promise_check_exist(Paths.recovery, true);
+  await promise_check_exist(Paths.recoveryBackup, false);
+  await promise_check_exist(Paths.nextUpgradeBackup, true);
+
+  await promise_check_contents(Paths.recovery, new_content);
+  await promise_check_contents(Paths.nextUpgradeBackup, initial_content);
+});
+
+// Write to the store again, and check that
+// - $Path.clean is not written
+// - $Path.recovery contains the new data
+// - $Path.recoveryBackup contains the previous data
+add_task(async function test_second_write_no_backup() {
+  let new_content = generateFileContents("test_2");
+  let previous_backup_content = await IOUtils.readJSON(Paths.recovery, {
+    decompress: true,
+  });
+
+  await IOUtils.remove(Paths.cleanBackup);
+
+  await SessionFile.write(new_content);
+
+  await promise_check_exist(Paths.backups, true);
+  await promise_check_exist(Paths.clean, false);
+  await promise_check_exist(Paths.cleanBackup, false);
+  await promise_check_exist(Paths.recovery, true);
+  await promise_check_exist(Paths.nextUpgradeBackup, true);
+
+  await promise_check_contents(Paths.recovery, new_content);
+  await promise_check_contents(Paths.recoveryBackup, previous_backup_content);
+});
+
+// Make sure that we create $Paths.clean and remove $Paths.recovery*
+// upon shutdown
+add_task(async function test_shutdown() {
+  let output = generateFileContents("test_3");
+
+  await IOUtils.writeUTF8(Paths.recovery, "I should disappear");
+  await IOUtils.writeUTF8(Paths.recoveryBackup, "I should also disappear");
+
+  await SessionWriter.write(output, {
+    isFinalWrite: true,
+    performShutdownCleanup: true,
+  });
+
+  Assert.ok(!(await IOUtils.exists(Paths.recovery)));
+  Assert.ok(!(await IOUtils.exists(Paths.recoveryBackup)));
+  await promise_check_contents(Paths.clean, output);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/unit/test_final_write_cleanup.js b/src/zen/tests/mochitests/sessionstore/unit/test_final_write_cleanup.js
new file mode 100644
index 000000000..b3fbd6b20
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/unit/test_final_write_cleanup.js
@@ -0,0 +1,116 @@
+"use strict";
+
+/**
+ * This test ensures that we correctly clean up the session state when
+ * writing with isFinalWrite, which is used on shutdown. It tests that each
+ * tab's shistory is capped to a maximum number of preceding and succeeding
+ * entries.
+ */
+
+const { SessionWriter } = ChromeUtils.importESModule(
+  "resource:///modules/sessionstore/SessionWriter.sys.mjs"
+);
+
+// Make sure that we have a profile before initializing SessionFile.
+do_get_profile();
+const {
+  SessionFile: { Paths },
+} = ChromeUtils.importESModule(
+  "resource:///modules/sessionstore/SessionFile.sys.mjs"
+);
+
+const MAX_ENTRIES = 9;
+const URL = "http://example.com/#";
+
+async function prepareWithLimit(back, fwd) {
+  SessionWriter.init("empty", false, Paths, {
+    maxSerializeBack: back,
+    maxSerializeForward: fwd,
+    maxUpgradeBackups: 3,
+  });
+  await SessionWriter.wipe();
+}
+
+add_setup(async function () {
+  registerCleanupFunction(() => SessionWriter.wipe());
+});
+
+function createSessionState(index) {
+  // Generate the tab state entries and set the one-based
+  // tab-state index to the middle session history entry.
+  let tabState = { entries: [], index };
+  for (let i = 0; i < MAX_ENTRIES; i++) {
+    tabState.entries.push({ url: URL + i });
+  }
+
+  return { windows: [{ tabs: [tabState] }] };
+}
+
+async function writeAndParse(state, path, options = {}) {
+  // We clone here because `write` can change the data passed.
+  let data = structuredClone(state);
+  await SessionWriter.write(data, options);
+  return IOUtils.readJSON(path, { decompress: true });
+}
+
+add_task(async function test_shistory_cap_none() {
+  let state = createSessionState(5);
+
+  // Don't limit the number of shistory entries.
+  await prepareWithLimit(-1, -1);
+
+  // Check that no caps are applied.
+  let diskState = await writeAndParse(state, Paths.clean, {
+    isFinalWrite: true,
+  });
+  Assert.deepEqual(state, diskState, "no cap applied");
+});
+
+add_task(async function test_shistory_cap_middle() {
+  let state = createSessionState(5);
+  await prepareWithLimit(2, 3);
+
+  // Cap is only applied on clean shutdown.
+  let diskState = await writeAndParse(state, Paths.recovery);
+  Assert.deepEqual(state, diskState, "no cap applied");
+
+  // Check that the right number of shistory entries was discarded
+  // and the shistory index updated accordingly.
+  diskState = await writeAndParse(state, Paths.clean, { isFinalWrite: true });
+  let tabState = state.windows[0].tabs[0];
+  tabState.entries = tabState.entries.slice(2, 8);
+  tabState.index = 3;
+  Assert.deepEqual(state, diskState, "cap applied");
+});
+
+add_task(async function test_shistory_cap_lower_bound() {
+  let state = createSessionState(1);
+  await prepareWithLimit(5, 5);
+
+  // Cap is only applied on clean shutdown.
+  let diskState = await writeAndParse(state, Paths.recovery);
+  Assert.deepEqual(state, diskState, "no cap applied");
+
+  // Check that the right number of shistory entries was discarded.
+  diskState = await writeAndParse(state, Paths.clean, { isFinalWrite: true });
+  let tabState = state.windows[0].tabs[0];
+  tabState.entries = tabState.entries.slice(0, 6);
+  Assert.deepEqual(state, diskState, "cap applied");
+});
+
+add_task(async function test_shistory_cap_upper_bound() {
+  let state = createSessionState(MAX_ENTRIES);
+  await prepareWithLimit(5, 5);
+
+  // Cap is only applied on clean shutdown.
+  let diskState = await writeAndParse(state, Paths.recovery);
+  Assert.deepEqual(state, diskState, "no cap applied");
+
+  // Check that the right number of shistory entries was discarded
+  // and the shistory index updated accordingly.
+  diskState = await writeAndParse(state, Paths.clean, { isFinalWrite: true });
+  let tabState = state.windows[0].tabs[0];
+  tabState.entries = tabState.entries.slice(3);
+  tabState.index = 6;
+  Assert.deepEqual(state, diskState, "cap applied");
+});
diff --git a/src/zen/tests/mochitests/sessionstore/unit/test_histogram_corrupt_files.js b/src/zen/tests/mochitests/sessionstore/unit/test_histogram_corrupt_files.js
new file mode 100644
index 000000000..2c469ed3b
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/unit/test_histogram_corrupt_files.js
@@ -0,0 +1,117 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/*
+ * The primary purpose of this test is to ensure that
+ * the sessionstore component records information about
+ * corrupted backup files into a histogram.
+ */
+
+"use strict";
+
+const Telemetry = Services.telemetry;
+const HistogramId = "FX_SESSION_RESTORE_ALL_FILES_CORRUPT";
+
+// Prepare the session file.
+do_get_profile();
+const { SessionFile } = ChromeUtils.importESModule(
+  "resource:///modules/sessionstore/SessionFile.sys.mjs"
+);
+
+/**
+ * A utility function for resetting the histogram and the contents
+ * of the backup directory. This will also compress the file using lz4 compression.
+ */
+function promise_reset_session(backups = {}) {
+  return (async function () {
+    // Reset the histogram.
+    Telemetry.getHistogramById(HistogramId).clear();
+
+    // Reset the contents of the backups directory
+    await IOUtils.makeDirectory(SessionFile.Paths.backups);
+    let basePath = do_get_cwd().path;
+    for (let key of SessionFile.Paths.loadOrder) {
+      if (backups.hasOwnProperty(key)) {
+        let path = backups[key];
+        const fullPath = PathUtils.join(basePath, ...path);
+        let s = await IOUtils.read(fullPath);
+        await IOUtils.write(SessionFile.Paths[key], s, {
+          compress: true,
+        });
+      } else {
+        await IOUtils.remove(SessionFile.Paths[key]);
+      }
+    }
+  })();
+}
+
+/**
+ * In order to use FX_SESSION_RESTORE_ALL_FILES_CORRUPT histogram
+ * it has to be registered in "toolkit/components/telemetry/Histograms.json".
+ * This test ensures that the histogram is registered and empty.
+ */
+add_task(async function test_ensure_histogram_exists_and_empty() {
+  let s = Telemetry.getHistogramById(HistogramId).snapshot();
+  Assert.equal(s.sum, 0, "Initially, the sum of probes is 0");
+});
+
+/**
+ * Makes sure that the histogram is negatively updated when no
+ * backup files are present.
+ */
+add_task(async function test_no_files_exist() {
+  // No session files are available to SessionFile.
+  await promise_reset_session();
+
+  await SessionFile.read();
+  // Checking if the histogram is updated negatively
+  let h = Telemetry.getHistogramById(HistogramId);
+  let s = h.snapshot();
+  Assert.equal(s.values[0], 1, "One probe for the 'false' bucket.");
+  Assert.equal(s.values[1], 0, "No probes in the 'true' bucket.");
+});
+
+/**
+ * Makes sure that the histogram is negatively updated when at least one
+ * backup file is not corrupted.
+ */
+add_task(async function test_one_file_valid() {
+  // Corrupting some backup files.
+  let invalidSession = ["data", "sessionstore_invalid.js"];
+  let validSession = ["data", "sessionstore_valid.js"];
+  await promise_reset_session({
+    clean: invalidSession,
+    cleanBackup: validSession,
+    recovery: invalidSession,
+    recoveryBackup: invalidSession,
+  });
+
+  await SessionFile.read();
+  // Checking if the histogram is updated negatively.
+  let h = Telemetry.getHistogramById(HistogramId);
+  let s = h.snapshot();
+  Assert.equal(s.values[0], 1, "One probe for the 'false' bucket.");
+  Assert.equal(s.values[1], 0, "No probes in the 'true' bucket.");
+});
+
+/**
+ * Makes sure that the histogram is positively updated when all
+ * backup files are corrupted.
+ */
+add_task(async function test_all_files_corrupt() {
+  // Corrupting all backup files.
+  let invalidSession = ["data", "sessionstore_invalid.js"];
+  await promise_reset_session({
+    clean: invalidSession,
+    cleanBackup: invalidSession,
+    recovery: invalidSession,
+    recoveryBackup: invalidSession,
+  });
+
+  await SessionFile.read();
+  // Checking if the histogram is positively updated.
+  let h = Telemetry.getHistogramById(HistogramId);
+  let s = h.snapshot();
+  Assert.equal(s.values[1], 1, "One probe for the 'true' bucket.");
+  Assert.equal(s.values[0], 0, "No probes in the 'false' bucket.");
+});
diff --git a/src/zen/tests/mochitests/sessionstore/unit/test_migration_lz4compression.js b/src/zen/tests/mochitests/sessionstore/unit/test_migration_lz4compression.js
new file mode 100644
index 000000000..4d9b700d8
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/unit/test_migration_lz4compression.js
@@ -0,0 +1,151 @@
+"use strict";
+
+const { SessionWriter } = ChromeUtils.importESModule(
+  "resource:///modules/sessionstore/SessionWriter.sys.mjs"
+);
+
+// Make sure that we have a profile before initializing SessionFile.
+const profd = do_get_profile();
+const { SessionFile } = ChromeUtils.importESModule(
+  "resource:///modules/sessionstore/SessionFile.sys.mjs"
+);
+const Paths = SessionFile.Paths;
+
+// We need a XULAppInfo to initialize SessionFile
+const { updateAppInfo } = ChromeUtils.importESModule(
+  "resource://testing-common/AppInfo.sys.mjs"
+);
+updateAppInfo({
+  name: "SessionRestoreTest",
+  ID: "{230de50e-4cd1-11dc-8314-0800200c9a66}",
+  version: "1",
+  platformVersion: "",
+});
+
+function promise_check_exist(path, shouldExist) {
+  return (async function () {
+    info(
+      "Ensuring that " + path + (shouldExist ? " exists" : " does not exist")
+    );
+    if ((await IOUtils.exists(path)) != shouldExist) {
+      throw new Error(
+        "File " + path + " should " + (shouldExist ? "exist" : "not exist")
+      );
+    }
+  })();
+}
+
+function promise_check_contents(path, expect) {
+  return (async function () {
+    info("Checking whether " + path + " has the right contents");
+    let actual = await IOUtils.readJSON(path, {
+      decompress: true,
+    });
+    Assert.deepEqual(
+      actual,
+      expect,
+      `File ${path} contains the expected data.`
+    );
+  })();
+}
+
+// Check whether the migration from .js to .jslz4 is correct.
+add_task(async function test_migration() {
+  let source = do_get_file("data/sessionstore_valid.js");
+  source.copyTo(profd, "sessionstore.js");
+
+  // Read the content of the session store file.
+  let parsed = await IOUtils.readJSON(Paths.clean.replace("jsonlz4", "js"));
+
+  // Read the session file with .js extension.
+  let result = await SessionFile.read();
+
+  // Check whether the result is what we wanted.
+  equal(result.origin, "clean");
+  equal(result.useOldExtension, true);
+  Assert.deepEqual(
+    result.parsed,
+    parsed,
+    "result.parsed contains expected data"
+  );
+
+  // Initiate a write to ensure we write the compressed version.
+  await SessionFile.write(parsed);
+  await promise_check_exist(Paths.backups, true);
+  await promise_check_exist(Paths.clean, false);
+  await promise_check_exist(Paths.cleanBackup, true);
+  await promise_check_exist(Paths.recovery, true);
+  await promise_check_exist(Paths.recoveryBackup, false);
+  await promise_check_exist(Paths.nextUpgradeBackup, true);
+  // The deprecated $Path.clean should exist.
+  await promise_check_exist(Paths.clean.replace("jsonlz4", "js"), true);
+
+  await promise_check_contents(Paths.recovery, parsed);
+});
+
+add_task(async function test_startup_with_compressed_clean() {
+  let state = { windows: [] };
+
+  // Mare sure we have an empty profile dir.
+  await SessionFile.wipe();
+
+  // Populate session files to profile dir.
+  await IOUtils.writeJSON(Paths.clean, state, {
+    compress: true,
+  });
+  await IOUtils.makeDirectory(Paths.backups);
+  await IOUtils.writeJSON(Paths.cleanBackup, state, {
+    compress: true,
+  });
+
+  // Initiate a read.
+  let result = await SessionFile.read();
+
+  // Make sure we read correct session file and its content.
+  equal(result.origin, "clean");
+  equal(result.useOldExtension, false);
+  Assert.deepEqual(
+    state,
+    result.parsed,
+    "result.parsed contains expected data"
+  );
+});
+
+add_task(async function test_empty_profile_dir() {
+  // Make sure that we have empty profile dir.
+  await SessionFile.wipe();
+  await promise_check_exist(Paths.backups, false);
+  await promise_check_exist(Paths.clean, false);
+  await promise_check_exist(Paths.cleanBackup, false);
+  await promise_check_exist(Paths.recovery, false);
+  await promise_check_exist(Paths.recoveryBackup, false);
+  await promise_check_exist(Paths.nextUpgradeBackup, false);
+  await promise_check_exist(Paths.backups.replace("jsonlz4", "js"), false);
+  await promise_check_exist(Paths.clean.replace("jsonlz4", "js"), false);
+  await promise_check_exist(Paths.cleanBackup.replace("lz4", ""), false);
+  await promise_check_exist(Paths.recovery.replace("jsonlz4", "js"), false);
+  await promise_check_exist(
+    Paths.recoveryBackup.replace("jsonlz4", "js"),
+    false
+  );
+  await promise_check_exist(
+    Paths.nextUpgradeBackup.replace("jsonlz4", "js"),
+    false
+  );
+
+  // Initiate a read and make sure that we are in empty state.
+  let result = await SessionFile.read();
+  equal(result.origin, "empty");
+  equal(result.noFilesFound, true);
+
+  // Create a state to store.
+  let state = { windows: [] };
+  await SessionWriter.write(state, { isFinalWrite: true });
+
+  // Check session files are created, but not deprecated ones.
+  await promise_check_exist(Paths.clean, true);
+  await promise_check_exist(Paths.clean.replace("jsonlz4", "js"), false);
+
+  // Check session file' content is correct.
+  await promise_check_contents(Paths.clean, state);
+});
diff --git a/src/zen/tests/mochitests/sessionstore/unit/test_session_schema.js b/src/zen/tests/mochitests/sessionstore/unit/test_session_schema.js
new file mode 100644
index 000000000..f14674037
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/unit/test_session_schema.js
@@ -0,0 +1,29 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_task(async function test_schema_smoke_test() {
+  let sessionData = await IOUtils.readJSON(
+    PathUtils.join(do_get_cwd().path, "data", "sessionstore_complete.json")
+  );
+  let result;
+
+  Assert.ok(
+    sessionData.version[0],
+    "Looks like we loaded up the session data ok"
+  );
+
+  try {
+    result = await SessionStore.validateState(sessionData);
+  } catch (ex) {
+    info("Exception validating session data:" + ex.message);
+  }
+
+  if (!result.valid) {
+    info(`Failed validation: ${JSON.stringify(result.errors)}`);
+  }
+  Assert.ok(result, "Got a validation result object");
+
+  Assert.ok(result.valid, "the session file was validated against the schema");
+});
diff --git a/src/zen/tests/mochitests/sessionstore/unit/test_startup_invalid_session.js b/src/zen/tests/mochitests/sessionstore/unit/test_startup_invalid_session.js
new file mode 100644
index 000000000..50960b1d4
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/unit/test_startup_invalid_session.js
@@ -0,0 +1,27 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+function run_test() {
+  let profd = do_get_profile();
+  var SessionFile = ChromeUtils.importESModule(
+    "resource:///modules/sessionstore/SessionFile.sys.mjs"
+  ).SessionFile;
+
+  let sourceSession = do_get_file("data/sessionstore_invalid.js");
+  sourceSession.copyTo(profd, "sessionstore.js");
+
+  let sourceCheckpoints = do_get_file("data/sessionCheckpoints_all.json");
+  sourceCheckpoints.copyTo(profd, "sessionCheckpoints.json");
+
+  // Compress sessionstore.js to sessionstore.jsonlz4
+  // and remove sessionstore.js
+  let oldExtSessionFile = SessionFile.Paths.clean.replace("jsonlz4", "js");
+  writeCompressedFile(oldExtSessionFile, SessionFile.Paths.clean).then(() => {
+    afterSessionStartupInitialization(function cb() {
+      Assert.equal(SessionStartup.sessionType, SessionStartup.NO_SESSION);
+      do_test_finished();
+    });
+  });
+
+  do_test_pending();
+}
diff --git a/src/zen/tests/mochitests/sessionstore/unit/test_startup_nosession_async.js b/src/zen/tests/mochitests/sessionstore/unit/test_startup_nosession_async.js
new file mode 100644
index 000000000..259c393e6
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/unit/test_startup_nosession_async.js
@@ -0,0 +1,19 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// Test SessionStartup.sessionType in the following scenario:
+// - no sessionstore.js;
+// - the session store has been loaded, so no need to go
+//    through the synchronous fallback
+
+function run_test() {
+  // Initialize the profile (the session startup uses it)
+  do_get_profile();
+
+  do_test_pending();
+
+  afterSessionStartupInitialization(function cb() {
+    Assert.equal(SessionStartup.sessionType, SessionStartup.NO_SESSION);
+    do_test_finished();
+  });
+}
diff --git a/src/zen/tests/mochitests/sessionstore/unit/test_startup_session_async.js b/src/zen/tests/mochitests/sessionstore/unit/test_startup_session_async.js
new file mode 100644
index 000000000..a61c9fe42
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/unit/test_startup_session_async.js
@@ -0,0 +1,32 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// Test SessionStartup.sessionType in the following scenario:
+// - valid sessionstore.js;
+// - valid sessionCheckpoints.json with all checkpoints;
+// - the session store has been loaded
+
+function run_test() {
+  let profd = do_get_profile();
+  var SessionFile = ChromeUtils.importESModule(
+    "resource:///modules/sessionstore/SessionFile.sys.mjs"
+  ).SessionFile;
+
+  let sourceSession = do_get_file("data/sessionstore_valid.js");
+  sourceSession.copyTo(profd, "sessionstore.js");
+
+  let sourceCheckpoints = do_get_file("data/sessionCheckpoints_all.json");
+  sourceCheckpoints.copyTo(profd, "sessionCheckpoints.json");
+
+  // Compress sessionstore.js to sessionstore.jsonlz4
+  // and remove sessionstore.js
+  let oldExtSessionFile = SessionFile.Paths.clean.replace("jsonlz4", "js");
+  writeCompressedFile(oldExtSessionFile, SessionFile.Paths.clean).then(() => {
+    afterSessionStartupInitialization(function cb() {
+      Assert.equal(SessionStartup.sessionType, SessionStartup.DEFER_SESSION);
+      do_test_finished();
+    });
+  });
+
+  do_test_pending();
+}
diff --git a/src/zen/tests/mochitests/sessionstore/unit/test_write_json_length_hint.js b/src/zen/tests/mochitests/sessionstore/unit/test_write_json_length_hint.js
new file mode 100644
index 000000000..fd4a44848
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/unit/test_write_json_length_hint.js
@@ -0,0 +1,73 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { SessionWriter } = ChromeUtils.importESModule(
+  "resource:///modules/sessionstore/SessionWriter.sys.mjs"
+);
+
+const profd = do_get_profile();
+const { SessionFile } = ChromeUtils.importESModule(
+  "resource:///modules/sessionstore/SessionFile.sys.mjs"
+);
+
+const { updateAppInfo } = ChromeUtils.importESModule(
+  "resource://testing-common/AppInfo.sys.mjs"
+);
+updateAppInfo({
+  name: "SessionRestoreTest",
+  ID: "{230de50e-4cd1-11dc-8314-0800200c9a66}",
+  version: "1",
+  platformVersion: "",
+});
+
+add_setup(async function () {
+  let source = do_get_file("data/sessionstore_valid.js");
+  source.copyTo(profd, "sessionstore.js");
+  await writeCompressedFile(
+    SessionFile.Paths.clean.replace("jsonlz4", "js"),
+    SessionFile.Paths.clean
+  );
+  await SessionFile.read();
+});
+
+add_task(async function test_length_hint_updates_after_write() {
+  Assert.equal(
+    SessionWriter._jsonLengthHint,
+    0,
+    "Length hint starts at 0"
+  );
+
+  await SessionFile.write({});
+
+  let hintAfterSmall = SessionWriter._jsonLengthHint;
+  Assert.equal(
+    hintAfterSmall,
+    JSON.stringify({}).length,
+    "Hint matches the uncompressed JSON byte length"
+  );
+
+  let largerState = await IOUtils.readJSON(
+    PathUtils.join(do_get_cwd().path, "data", "sessionstore_complete.json")
+  );
+  await SessionFile.write(largerState);
+
+  Assert.greater(
+    SessionWriter._jsonLengthHint,
+    hintAfterSmall,
+    "Hint grows after writing a larger state"
+  );
+});
+
+add_task(async function test_length_hint_resets_on_wipe() {
+  await SessionFile.write({ windows: [{ tabs: [{ entries: [] }] }] });
+  Assert.greater(SessionWriter._jsonLengthHint, 0, "Hint is nonzero");
+
+  await SessionFile.wipe();
+  Assert.equal(
+    SessionWriter._jsonLengthHint,
+    0,
+    "Hint resets to 0 after wipe"
+  );
+});
diff --git a/src/zen/tests/mochitests/sessionstore/unit/xpcshell.toml b/src/zen/tests/mochitests/sessionstore/unit/xpcshell.toml
new file mode 100644
index 000000000..01b0fe1f2
--- /dev/null
+++ b/src/zen/tests/mochitests/sessionstore/unit/xpcshell.toml
@@ -0,0 +1,48 @@
+[DEFAULT]
+run-if = [
+  "os != 'android'",
+]
+head = "head.js"
+tags = "condprof"
+firefox-appdir = "browser"
+support-files = [
+  "data/sessionCheckpoints_all.json",
+  "data/sessionstore_invalid.js",
+  "data/sessionstore_valid.js",
+]
+
+["test_backup_once.js"]
+skip-if = [
+  "condprof", # Bug 1769154
+]
+
+["test_final_write_cleanup.js"]
+
+["test_histogram_corrupt_files.js"]
+
+["test_migration_lz4compression.js"]
+skip-if = [
+  "condprof", # Bug 1769154
+]
+
+["test_session_schema.js"]
+support-files = [
+  "data/sessionstore_complete.json",
+]
+
+["test_startup_invalid_session.js"]
+skip-if = [
+  "condprof", # Bug 1769154
+]
+
+["test_startup_nosession_async.js"]
+skip-if = [
+  "condprof", # Bug 1769154
+]
+
+["test_startup_session_async.js"]
+
+["test_write_json_length_hint.js"]
+support-files = [
+  "data/sessionstore_complete.json",
+]
diff --git a/src/zen/tests/mochitests/shell/browser.toml b/src/zen/tests/mochitests/shell/browser.toml
index b3c5bb1ca..81688111f 100644
--- a/src/zen/tests/mochitests/shell/browser.toml
+++ b/src/zen/tests/mochitests/shell/browser.toml
@@ -104,6 +104,11 @@ skip-if = [
   "tsan", # Bug 1429950, Bug 1583315, Bug 1696109, Bug 1701449
 ]
 
+["browser_pinToTaskbarTelemetry.js"]
+run-if = [
+  "os == 'win'",
+]
+
 ["browser_processAUMID.js"]
 run-if = [
   "os == 'win'",
@@ -118,6 +123,12 @@ run-if = [
 ]
 tags = "os_integration"
 
+["browser_setDefaultPDFHandler_mac.js"]
+run-if = [
+  "os == 'mac'",
+]
+tags = "os_integration"
+
 ["browser_setDefaultProtocolHandler.js"]
 run-if = [
   "os == 'win'",
diff --git a/src/zen/tests/mochitests/shell/browser_1119088.js b/src/zen/tests/mochitests/shell/browser_1119088.js
index 2f466c92d..f79c70cd4 100644
--- a/src/zen/tests/mochitests/shell/browser_1119088.js
+++ b/src/zen/tests/mochitests/shell/browser_1119088.js
@@ -151,7 +151,7 @@ add_task(async function () {
       // Saves the file in ~/Pictures
       shellSvc.setDesktopBackground(image, 0, backgroundImage.leafName);
 
-      await BrowserTestUtils.waitForCondition(() => backgroundImage.exists());
+      await TestUtils.waitForCondition(() => backgroundImage.exists());
       info(`${backgroundImage.path} downloaded`);
       Assert.ok(
         FileUtils.File(backgroundImage.path).exists(),
diff --git a/src/zen/tests/mochitests/shell/browser_createWindowsShortcut.js b/src/zen/tests/mochitests/shell/browser_createWindowsShortcut.js
index 0b951bde2..d0fb56227 100644
--- a/src/zen/tests/mochitests/shell/browser_createWindowsShortcut.js
+++ b/src/zen/tests/mochitests/shell/browser_createWindowsShortcut.js
@@ -52,17 +52,23 @@ const gDirectoryServiceProvider = {
   QueryInterface: ChromeUtils.generateQI([Ci.nsIDirectoryServiceProvider]),
 };
 
-add_setup(() => {
+add_setup(async () => {
   Services.dirsvc
     .QueryInterface(Ci.nsIDirectoryService)
     .registerProvider(gDirectoryServiceProvider);
+
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.shell.shortcut.test", true]],
+  });
 });
 
-registerCleanupFunction(() => {
+registerCleanupFunction(async () => {
   gBase.remove(true);
   Services.dirsvc
     .QueryInterface(Ci.nsIDirectoryService)
     .unregisterProvider(gDirectoryServiceProvider);
+
+  await SpecialPowers.popPrefEnv();
 });
 
 add_task(async function test_CreateWindowsShortcut() {
diff --git a/src/zen/tests/mochitests/shell/browser_pinToTaskbarTelemetry.js b/src/zen/tests/mochitests/shell/browser_pinToTaskbarTelemetry.js
new file mode 100644
index 000000000..d111bc1a5
--- /dev/null
+++ b/src/zen/tests/mochitests/shell/browser_pinToTaskbarTelemetry.js
@@ -0,0 +1,81 @@
+/* Any copyright is dedicated to the Public Domain.
+ * https://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  ShellService: "moz-src:///browser/components/shell/ShellService.sys.mjs",
+});
+
+const kStubPref = "browser.shell.taskbar.test.pinWinRtStubResult";
+
+add_setup(function () {
+  Services.fog.initializeFOG();
+
+  registerCleanupFunction(() => {
+    Services.prefs.clearUserPref(kStubPref);
+  });
+});
+
+// Success outcomes: the WinRT stub returns Ok with no fallback, so the promise
+// resolves to the matching PinResult.
+add_task(async function successCases() {
+  const cases = [
+    ["success_pinned", Ci.nsIWindowsShellService.PINNED],
+    ["success_rejected", Ci.nsIWindowsShellService.REJECTED],
+    ["success_fire_and_forget", Ci.nsIWindowsShellService.UNKNOWN],
+  ];
+
+  for (let [stubValue, expected] of cases) {
+    Services.prefs.setCharPref(kStubPref, stubValue);
+
+    Assert.equal(undefined, Glean.taskbar.pinWinrt.testGetValue());
+
+    let result = await ShellService.pinCurrentAppToTaskbar(false);
+    Assert.equal(result, expected, `resolved PinResult for ${stubValue}`);
+
+    let events = Glean.taskbar.pinWinrt.testGetValue();
+    Assert.equal(events.length, 1, `one pin_winrt event for ${stubValue}`);
+    Assert.equal(
+      events[0].extra.result,
+      stubValue,
+      "result extra matches pref"
+    );
+
+    Services.fog.testResetFOG();
+  }
+});
+
+// Error outcomes: telemetry is recorded before the COM fallback runs. The
+// fallback's resolve/reject is environment-dependent, so only assert telemetry.
+add_task(async function errorCases() {
+  const errors = [
+    "error_get_aumid",
+    "error_set_aumid",
+    "error_get_taskbar_manager",
+    "error_schedule_request_pin",
+    "error_request_pin",
+  ];
+
+  for (let stubValue of errors) {
+    Services.prefs.setCharPref(kStubPref, stubValue);
+
+    Assert.equal(undefined, Glean.taskbar.pinWinrt.testGetValue());
+
+    try {
+      await ShellService.pinCurrentAppToTaskbar(false);
+    } catch (e) {
+      // The COM fallback may reject; the pin_winrt telemetry is already recorded.
+    }
+
+    let events = Glean.taskbar.pinWinrt.testGetValue();
+    Assert.equal(events.length, 1, `one pin_winrt event for ${stubValue}`);
+    Assert.equal(
+      events[0].extra.result,
+      stubValue,
+      "result extra matches pref"
+    );
+
+    Services.fog.testResetFOG();
+  }
+});
diff --git a/src/zen/tests/mochitests/shell/browser_processAUMID.js b/src/zen/tests/mochitests/shell/browser_processAUMID.js
index cf98316f8..5d54e645f 100644
--- a/src/zen/tests/mochitests/shell/browser_processAUMID.js
+++ b/src/zen/tests/mochitests/shell/browser_processAUMID.js
@@ -17,11 +17,11 @@ add_task(async function test_processAUMID() {
   // This function will trigger the relevant code paths that
   // incorrectly changes the process AUMID on MSIX, prior to
   // Bug 1950734 being fixed
-  await ShellService.checkPinCurrentAppToTaskbarAsync(false);
+  await ShellService.pinToTaskbar();
 
   is(
-    processAUMID,
     ShellService.checkCurrentProcessAUMIDForTesting(),
+    processAUMID,
     "The process AUMID should not be changed"
   );
 });
diff --git a/src/zen/tests/mochitests/shell/browser_setDefaultPDFHandler.js b/src/zen/tests/mochitests/shell/browser_setDefaultPDFHandler.js
index 3ffa6cb57..41a015e03 100644
--- a/src/zen/tests/mochitests/shell/browser_setDefaultPDFHandler.js
+++ b/src/zen/tests/mochitests/shell/browser_setDefaultPDFHandler.js
@@ -42,6 +42,9 @@ const launchModernSettingsDialogDefaultAppsStub = sinon.stub();
 const shellStub = sinon.stub(ShellService, "shellService").value({
   setDefaultBrowser: setDefaultStub,
   queryCurrentDefaultHandlerFor: queryCurrentDefaultHandlerForStub,
+  // setAsDefaultPDFHandler samples this for the recorded telemetry; the value
+  // doesn't matter for these assertions.
+  isDefaultHandlerFor: sinon.stub(),
   launchSetDefaultAppPicker: launchSetDefaultAppPickerStub,
   launchModernSettingsDialogDefaultApps:
     launchModernSettingsDialogDefaultAppsStub,
diff --git a/src/zen/tests/mochitests/shell/browser_setDefaultPDFHandler_mac.js b/src/zen/tests/mochitests/shell/browser_setDefaultPDFHandler_mac.js
new file mode 100644
index 000000000..dd7c1fc67
--- /dev/null
+++ b/src/zen/tests/mochitests/shell/browser_setDefaultPDFHandler_mac.js
@@ -0,0 +1,260 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// macOS-only checks for ShellService.setAsDefaultPDFHandler and the supporting
+// isDefaultHandlerFor / canSetAsDefaultPDFHandler branches. On macOS these go
+// through NSWorkspace; the native layer is mocked here.
+
+ChromeUtils.defineESModuleGetters(this, {
+  sinon: "resource://testing-common/Sinon.sys.mjs",
+});
+
+Assert.equal(AppConstants.platform, "macosx", "Platform is macOS");
+
+const setAsDefaultHandlerForStub = sinon.stub().resolves(false);
+const isDefaultHandlerForStub = sinon.stub().returns(false);
+const isDefaultHandlerAWebBrowserForStub = sinon.stub().returns(false);
+
+const fakeShellService = {
+  canSetAsDefaultHandler: true,
+  setAsDefaultHandlerFor: setAsDefaultHandlerForStub,
+  isDefaultHandlerFor: isDefaultHandlerForStub,
+  isDefaultHandlerAWebBrowserFor: isDefaultHandlerAWebBrowserForStub,
+  QueryInterface: ChromeUtils.generateQI([]),
+};
+
+const shellStub = sinon
+  .stub(ShellService, "shellService")
+  .value(fakeShellService);
+
+registerCleanupFunction(() => {
+  shellStub.restore();
+});
+
+function resetStubs() {
+  setAsDefaultHandlerForStub.resetHistory();
+  isDefaultHandlerForStub.resetHistory();
+  isDefaultHandlerAWebBrowserForStub.resetHistory();
+}
+
+function getAttemptEvent() {
+  const events = Glean.browser.setDefaultPdfHandlerAttempt.testGetValue();
+  Assert.ok(events?.length, "Recorded a set_default_pdf_handler_attempt event");
+  Assert.equal(events.length, 1, "Recorded exactly one attempt event");
+  return events[0];
+}
+
+add_task(async function test_canSetAsDefaultPDFHandler() {
+  fakeShellService.canSetAsDefaultHandler = true;
+  Assert.ok(
+    ShellService.canSetAsDefaultPDFHandler,
+    "canSetAsDefaultPDFHandler is true when the native value is true"
+  );
+
+  try {
+    fakeShellService.canSetAsDefaultHandler = false;
+    Assert.ok(
+      !ShellService.canSetAsDefaultPDFHandler,
+      "canSetAsDefaultPDFHandler is false when the native value is false"
+    );
+  } finally {
+    fakeShellService.canSetAsDefaultHandler = true;
+  }
+});
+
+add_task(async function test_isDefaultHandlerFor() {
+  isDefaultHandlerForStub.returns(true);
+  Assert.ok(
+    ShellService.isDefaultHandlerFor(".pdf"),
+    "isDefaultHandlerFor('.pdf') reflects the native result"
+  );
+  Assert.ok(
+    isDefaultHandlerForStub.calledWith(".pdf"),
+    "Forwarded '.pdf' to the native isDefaultHandlerFor"
+  );
+
+  isDefaultHandlerForStub.returns(false);
+  Assert.ok(
+    !ShellService.isDefaultHandlerFor(".pdf"),
+    "isDefaultHandlerFor('.pdf') is false when Firefox is not the default"
+  );
+
+  isDefaultHandlerForStub.returns(true);
+  Assert.ok(
+    ShellService.isDefaultHandlerFor("https"),
+    "isDefaultHandlerFor('https') reflects the native result"
+  );
+  Assert.ok(
+    isDefaultHandlerForStub.calledWith("https"),
+    "Forwarded 'https' to the native isDefaultHandlerFor"
+  );
+  resetStubs();
+});
+
+add_task(async function test_setAsDefaultPDFHandler_unsupported() {
+  Services.fog.testResetFOG();
+  try {
+    fakeShellService.canSetAsDefaultHandler = false;
+    setAsDefaultHandlerForStub.resolves(true);
+    isDefaultHandlerForStub.returns(true);
+
+    const result = await ShellService.setAsDefaultPDFHandler();
+    Assert.strictEqual(result, false, "Resolves false when unsupported");
+    Assert.ok(
+      setAsDefaultHandlerForStub.notCalled,
+      "Did not call the native setter when unsupported"
+    );
+    Assert.ok(
+      !Glean.browser.setDefaultPdfHandlerAttempt.testGetValue(),
+      "Did not record an attempt event when unsupported"
+    );
+  } finally {
+    fakeShellService.canSetAsDefaultHandler = true;
+    resetStubs();
+  }
+});
+
+add_task(async function test_setAsDefaultPDFHandler_confirmed() {
+  Services.fog.testResetFOG();
+  setAsDefaultHandlerForStub.resolves(true);
+  isDefaultHandlerForStub.returns(true);
+
+  const result = await ShellService.setAsDefaultPDFHandler();
+  Assert.strictEqual(result, true, "Resolves true when the user confirms");
+  Assert.ok(
+    setAsDefaultHandlerForStub.calledOnce,
+    "Called the native setAsDefaultHandlerFor once"
+  );
+  Assert.ok(
+    setAsDefaultHandlerForStub.calledWith(".pdf"),
+    "Forwarded '.pdf' to the native setAsDefaultHandlerFor"
+  );
+
+  const event = getAttemptEvent();
+  Assert.equal(
+    event.extra.method,
+    "launch_services",
+    "Event method is launch_services"
+  );
+  Assert.equal(event.extra.success, "true", "Event success is true");
+  Assert.equal(
+    event.extra.result_is_default,
+    "true",
+    "Event result_is_default reflects isDefaultHandlerFor"
+  );
+  resetStubs();
+});
+
+add_task(async function test_setAsDefaultPDFHandler_recordsIndependentState() {
+  Services.fog.testResetFOG();
+  // success (the native setter's result) and result_is_default (a separate
+  // isDefaultHandlerFor sample) come from different sources, so drive them to
+  // different values: a bug that conflated the two would pass every test where
+  // they happen to agree.
+  setAsDefaultHandlerForStub.resolves(true);
+  isDefaultHandlerForStub.returns(false);
+
+  const result = await ShellService.setAsDefaultPDFHandler();
+  Assert.strictEqual(result, true, "Resolves with the native setter's result");
+
+  const event = getAttemptEvent();
+  Assert.equal(
+    event.extra.success,
+    "true",
+    "success reflects the native setter"
+  );
+  Assert.equal(
+    event.extra.result_is_default,
+    "false",
+    "result_is_default reflects isDefaultHandlerFor, not success"
+  );
+  resetStubs();
+});
+
+add_task(async function test_setAsDefaultPDFHandler_declined() {
+  Services.fog.testResetFOG();
+  setAsDefaultHandlerForStub.resolves(false);
+  isDefaultHandlerForStub.returns(false);
+
+  const result = await ShellService.setAsDefaultPDFHandler();
+  Assert.strictEqual(result, false, "Resolves false when the user declines");
+
+  const event = getAttemptEvent();
+  Assert.equal(event.extra.success, "false", "Event success is false");
+  Assert.equal(
+    event.extra.result_is_default,
+    "false",
+    "Event result_is_default is false"
+  );
+  resetStubs();
+});
+
+add_task(async function test_setAsDefaultPDFHandler_error() {
+  Services.fog.testResetFOG();
+  setAsDefaultHandlerForStub.rejects(new Error("mock NSWorkspace failure"));
+  isDefaultHandlerForStub.returns(false);
+
+  const result = await ShellService.setAsDefaultPDFHandler();
+  Assert.strictEqual(
+    result,
+    false,
+    "Resolves false when the native call rejects"
+  );
+
+  const event = getAttemptEvent();
+  Assert.equal(event.extra.success, "false", "Event success is false on error");
+  resetStubs();
+  setAsDefaultHandlerForStub.resolves(false);
+});
+
+add_task(async function test_setAsDefaultPDFHandler_onlyIfKnownBrowser() {
+  setAsDefaultHandlerForStub.resolves(true);
+  isDefaultHandlerForStub.returns(true);
+
+  isDefaultHandlerAWebBrowserForStub.returns(true);
+  let result = await ShellService.setAsDefaultPDFHandler(true);
+  Assert.strictEqual(
+    result,
+    true,
+    "Resolves true when the handler is a browser"
+  );
+  Assert.ok(
+    setAsDefaultHandlerForStub.called,
+    "Set the default when the current handler is a browser"
+  );
+  Assert.ok(
+    isDefaultHandlerAWebBrowserForStub.calledWith(".pdf"),
+    "Forwarded '.pdf' to the native isDefaultHandlerAWebBrowserFor"
+  );
+  resetStubs();
+
+  isDefaultHandlerAWebBrowserForStub.returns(false);
+  result = await ShellService.setAsDefaultPDFHandler(true);
+  Assert.strictEqual(
+    result,
+    false,
+    "Resolves false when the handler is not a browser"
+  );
+  Assert.ok(
+    setAsDefaultHandlerForStub.notCalled,
+    "Did not set the default when the current handler is not a browser"
+  );
+  resetStubs();
+
+  isDefaultHandlerAWebBrowserForStub.returns(false);
+  result = await ShellService.setAsDefaultPDFHandler(false);
+  Assert.strictEqual(
+    result,
+    true,
+    "Resolves true and sets unconditionally when onlyIfKnownBrowser is false"
+  );
+  Assert.ok(
+    setAsDefaultHandlerForStub.called,
+    "Set the default unconditionally when onlyIfKnownBrowser is false"
+  );
+  Assert.ok(
+    isDefaultHandlerAWebBrowserForStub.notCalled,
+    "Did not consult the browser check when onlyIfKnownBrowser is false"
+  );
+  resetStubs();
+});
diff --git a/src/zen/tests/mochitests/shell/gtest/SetDefaultBrowserButtonTests.cpp b/src/zen/tests/mochitests/shell/gtest/SetDefaultBrowserButtonTests.cpp
deleted file mode 100644
index d28d077b9..000000000
--- a/src/zen/tests/mochitests/shell/gtest/SetDefaultBrowserButtonTests.cpp
+++ /dev/null
@@ -1,237 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#include <gtest/gtest.h>
-#include <gmock/gmock.h>
-
-#include <string_view>
-#include <string>
-#include <windows.h>
-#include <ole2.h>
-#include <tlhelp32.h>
-#include <uiautomation.h>
-
-#include "mozilla/Maybe.h"
-#include "mozilla/UniquePtr.h"
-#include "WindowsDefaultBrowser.h"
-
-static bool RegWriteStringValue(HKEY aRoot, std::wstring_view aKey,
-                                const mozilla::Maybe<std::wstring>& aName,
-                                std::wstring_view aValue) {
-  HKEY key;
-  LSTATUS ls{::RegCreateKeyExW(aRoot, aKey.data(), 0, nullptr,
-                               REG_OPTION_NON_VOLATILE, KEY_SET_VALUE, nullptr,
-                               &key, nullptr)};
-
-  if (ls != ERROR_SUCCESS) {
-    return false;
-  }
-
-  const BYTE* value{reinterpret_cast<const BYTE*>(aValue.data())};
-  const DWORD size{static_cast<DWORD>((aValue.size() + 1) * sizeof(WCHAR))};
-  ls = ::RegSetValueExW(key, aName ? aName->c_str() : nullptr, 0, REG_SZ, value,
-                        size);
-
-  ::RegCloseKey(key);
-
-  return (ls == ERROR_SUCCESS);
-}
-
-static bool RegDeleteValue(HKEY aRoot, std::wstring_view aKey,
-                           std::wstring_view aName) {
-  HKEY key;
-  LSTATUS ls{
-      ::RegOpenKeyExW(HKEY_CURRENT_USER, aKey.data(), 0, KEY_SET_VALUE, &key)};
-
-  if (ls == ERROR_SUCCESS) {
-    ::RegDeleteValueW(key, aName.data());
-    ::RegCloseKey(key);
-    return true;
-  }
-
-  return false;
-}
-
-static bool RegDeleteKey(HKEY aRoot, std::wstring_view aKey) {
-  LSTATUS ls{::RegDeleteTreeW(HKEY_CURRENT_USER, aKey.data())};
-
-  return (ls == ERROR_SUCCESS);
-}
-
-static void TerminateProcessById(DWORD aProcessId) {
-  HANDLE process{
-      ::OpenProcess(PROCESS_TERMINATE | SYNCHRONIZE, FALSE, aProcessId)};
-  if (process) {
-    ::TerminateProcess(process, 0);
-    ::WaitForSingleObject(process, INFINITE);
-    ::CloseHandle(process);
-  }
-}
-
-static void TerminateProcessByName(LPCWSTR aProcessName) {
-  HANDLE processes{::CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0)};
-  if (processes == INVALID_HANDLE_VALUE) {
-    return;
-  }
-
-  PROCESSENTRY32W process{};
-  process.dwSize = sizeof(PROCESSENTRY32W);
-  if (::Process32FirstW(processes, &process)) {
-    do {
-      if (::_wcsicmp(process.szExeFile, aProcessName) == 0) {
-        TerminateProcessById(process.th32ProcessID);
-      }
-    } while (::Process32NextW(processes, &process));
-  }
-  ::CloseHandle(processes);
-}
-
-static UIWindowElement WaitForSetDefaultBrowserButton() {
-  const int kMaxAttempts{40};
-  const DWORD kRetryDelayMs{500};
-  for (int i{0}; i < kMaxAttempts; ++i) {
-    auto [window, button]{FindSetDefaultBrowserButton()};
-    if (window && button) {
-      return {window, button};
-    }
-    Sleep(kRetryDelayMs);
-  }
-  return {};
-}
-
-static bool IsElementFocus(const UIElement& aElement) {
-  BOOL isFocus{FALSE};
-  aElement->get_CurrentHasKeyboardFocus(&isFocus);
-  return isFocus;
-}
-
-class SetDefaultBrowserButtonTests : public ::testing::Test {
- protected:
-  static void SetUpTestSuite() {
-    ASSERT_TRUE(GetAppRegName(sAppRegName));
-    RegisterAsBrowser();
-  }
-
-  static void TearDownTestSuite() { UnregisterAsBrowser(); }
-
-  void TearDown() override { TerminateSystemSettings(); }
-
-  void TerminateSystemSettings() {
-    LPCWSTR processName{L"SystemSettings.exe"};
-    TerminateProcessByName(processName);
-  }
-
- private:
-  static void RegisterAsBrowser() {
-    const std::wstring appRegName{sAppRegName.get()};
-
-    WCHAR exePath[MAX_PATH];
-    ::GetModuleFileNameW(nullptr, exePath, MAX_PATH);
-
-    const std::wstring appName{L"Firefox Test"};
-
-    // clang-format off
-    // HKEY_CURRENT_USER\Software\RegisteredApplications
-    {
-      const std::wstring key{L"Software\\RegisteredApplications"};
-      const std::wstring value{L"Software\\Clients\\StartMenuInternet\\" + appRegName + L"\\Capabilities"};
-      ASSERT_TRUE(RegWriteStringValue(HKEY_CURRENT_USER, key, mozilla::Some(appRegName), value));
-    }
-    // HKEY_CURRENT_USER\Software\Clients\StartMenuInternet\Firefox-XYZ
-    {
-      const std::wstring key{L"Software\\Clients\\StartMenuInternet\\" + appRegName};
-      ASSERT_TRUE(RegWriteStringValue(HKEY_CURRENT_USER, key, mozilla::Nothing(), appName));
-    }
-    // HKEY_CURRENT_USER\Software\Clients\StartMenuInternet\Firefox-XYZ\Capabilities
-    {
-      const std::wstring key{L"Software\\Clients\\StartMenuInternet\\" + appRegName + L"\\Capabilities"};
-      const std::wstring name{L"ApplicationDescription"};
-      ASSERT_TRUE(RegWriteStringValue(HKEY_CURRENT_USER, key, mozilla::Some(name), appName));
-    }
-    {
-      const std::wstring key{L"Software\\Clients\\StartMenuInternet\\" + appRegName + L"\\Capabilities"};
-      const std::wstring name{L"ApplicationIcon"};
-      const std::wstring value{std::wstring(exePath) + L",0"};
-      ASSERT_TRUE(RegWriteStringValue(HKEY_CURRENT_USER, key, mozilla::Some(name), value));
-    }
-    {
-      const std::wstring key{L"Software\\Clients\\StartMenuInternet\\" + appRegName + L"\\Capabilities"};
-      const std::wstring name{L"ApplicationName"};
-      ASSERT_TRUE(RegWriteStringValue(HKEY_CURRENT_USER, key, mozilla::Some(name), appName));
-    }
-    // HKEY_CURRENT_USER\Software\Clients\StartMenuInternet\Firefox-XYZ\Capabilities\URLAssociations
-    {
-      const std::wstring key{L"Software\\Clients\\StartMenuInternet\\" + appRegName + L"\\Capabilities\\URLAssociations"};
-      const std::wstring name{L"http"};
-      ASSERT_TRUE(RegWriteStringValue(HKEY_CURRENT_USER, key, mozilla::Some(name), appRegName));
-    }
-    {
-      const std::wstring key{L"Software\\Clients\\StartMenuInternet\\" + appRegName + L"\\Capabilities\\URLAssociations"};
-      const std::wstring name{L"https"};
-      ASSERT_TRUE(RegWriteStringValue(HKEY_CURRENT_USER, key, mozilla::Some(name), appRegName));
-    }
-    // HKEY_CURRENT_USER\Software\Clients\StartMenuInternet\Firefox-XYZ\DefaultIcon
-    {
-      const std::wstring key{L"Software\\Clients\\StartMenuInternet\\" + appRegName + L"\\DefaultIcon"};
-      const std::wstring value{std::wstring(exePath) + L",0"};
-      ASSERT_TRUE(RegWriteStringValue(HKEY_CURRENT_USER, key, mozilla::Nothing(), value));
-    }
-    // HKEY_CURRENT_USER\Software\Clients\StartMenuInternet\Firefox-XYZ\shell\open\command
-    {
-      const std::wstring key{L"Software\\Clients\\StartMenuInternet\\" + appRegName + L"\\shell\\open\\command"};
-      const std::wstring value{L"\"" + std::wstring(exePath) + L"\""};
-      ASSERT_TRUE(RegWriteStringValue(HKEY_CURRENT_USER, key, mozilla::Nothing(), value));
-    }
-    // HKEY_CURRENT_USER\Software\Classes\Firefox-XYZ\shell\open\command
-    {
-      const std::wstring key{L"Software\\Classes\\" + appRegName + L"\\shell\\open\\command"};
-      const std::wstring value{L"\"" + std::wstring(exePath) + L"\" -osint -url \"%1\""};
-      ASSERT_TRUE(RegWriteStringValue(HKEY_CURRENT_USER, key, mozilla::Nothing(), value));
-    }
-    // clang-format on
-  }
-
-  static void UnregisterAsBrowser() {
-    const std::wstring appRegName{sAppRegName.get()};
-
-    // clang-format off
-    // HKEY_CURRENT_USER\Software\RegisteredApplications
-    {
-      const std::wstring key{L"Software\\RegisteredApplications"};
-      ASSERT_TRUE(RegDeleteValue(HKEY_CURRENT_USER, key, appRegName));
-    }
-    // HKEY_CURRENT_USER\Software\Clients\StartMenuInternet\Firefox-XYZ
-    {
-      const std::wstring key{L"Software\\Clients\\StartMenuInternet\\" + appRegName};
-      ASSERT_TRUE(RegDeleteKey(HKEY_CURRENT_USER, key));
-    }
-    // HKEY_CURRENT_USER\Software\Classes\Firefox-XYZ
-    {
-      const std::wstring key{L"Software\\Classes\\" + appRegName};
-      ASSERT_TRUE(RegDeleteKey(HKEY_CURRENT_USER, key));
-    }
-    // clang-format on
-  }
-
-  inline static mozilla::UniquePtr<WCHAR[]> sAppRegName;
-};
-
-TEST_F(SetDefaultBrowserButtonTests, FindDefaultBrowserButton) {
-  ASSERT_TRUE(LaunchModernSettingsDialogDefaultApps());
-
-  auto [window, button]{WaitForSetDefaultBrowserButton()};
-  ASSERT_THAT(window, testing::NotNull());
-  ASSERT_THAT(button, testing::NotNull());
-}
-
-TEST_F(SetDefaultBrowserButtonTests, FocusDefaultBrowserButton) {
-  ASSERT_TRUE(LaunchModernSettingsDialogDefaultApps());
-
-  auto [window, button]{WaitForSetDefaultBrowserButton()};
-  ASSERT_THAT(window, testing::NotNull());
-  ASSERT_THAT(button, testing::NotNull());
-
-  FocusElement(window, button);
-  ASSERT_TRUE(IsElementFocus(button));
-}
diff --git a/src/zen/tests/mochitests/shell/gtest/WindowsDefaultBrowserTests.cpp b/src/zen/tests/mochitests/shell/gtest/WindowsDefaultBrowserTests.cpp
new file mode 100644
index 000000000..86759d7f8
--- /dev/null
+++ b/src/zen/tests/mochitests/shell/gtest/WindowsDefaultBrowserTests.cpp
@@ -0,0 +1,220 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "WindowsDefaultBrowserTests.h"
+
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+#include <string_view>
+#include <string>
+#include <windows.h>
+#include <ole2.h>
+#include <uiautomation.h>
+#include <tlhelp32.h>
+
+#include "mozilla/Maybe.h"
+#include "mozilla/UniquePtr.h"
+#include "WindowsDefaultBrowser.h"
+
+static bool RegDeleteKey(HKEY aRoot, std::wstring_view aKey) {
+  LSTATUS ls{::RegDeleteTreeW(HKEY_CURRENT_USER, aKey.data())};
+
+  return (ls == ERROR_SUCCESS);
+}
+
+static bool RegDeleteValue(HKEY aRoot, std::wstring_view aKey,
+                           std::wstring_view aName) {
+  HKEY key;
+  LSTATUS ls{
+      ::RegOpenKeyExW(HKEY_CURRENT_USER, aKey.data(), 0, KEY_SET_VALUE, &key)};
+
+  if (ls == ERROR_SUCCESS) {
+    ::RegDeleteValueW(key, aName.data());
+    ::RegCloseKey(key);
+    return true;
+  }
+
+  return false;
+}
+
+static bool RegWriteStringValue(HKEY aRoot, std::wstring_view aKey,
+                                const mozilla::Maybe<std::wstring>& aName,
+                                std::wstring_view aValue) {
+  HKEY key;
+  LSTATUS ls{::RegCreateKeyExW(aRoot, aKey.data(), 0, nullptr,
+                               REG_OPTION_NON_VOLATILE, KEY_SET_VALUE, nullptr,
+                               &key, nullptr)};
+
+  if (ls != ERROR_SUCCESS) {
+    return false;
+  }
+
+  const BYTE* value{reinterpret_cast<const BYTE*>(aValue.data())};
+  const DWORD size{static_cast<DWORD>((aValue.size() + 1) * sizeof(WCHAR))};
+  ls = ::RegSetValueExW(key, aName ? aName->c_str() : nullptr, 0, REG_SZ, value,
+                        size);
+
+  ::RegCloseKey(key);
+
+  return (ls == ERROR_SUCCESS);
+}
+
+static void TerminateProcessById(DWORD aProcessId) {
+  HANDLE process{
+      ::OpenProcess(PROCESS_TERMINATE | SYNCHRONIZE, FALSE, aProcessId)};
+  if (process) {
+    ::TerminateProcess(process, 0);
+    ::WaitForSingleObject(process, INFINITE);
+    ::CloseHandle(process);
+  }
+}
+
+static void TerminateProcessByName(LPCWSTR aProcessName) {
+  HANDLE processes{::CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0)};
+  if (processes == INVALID_HANDLE_VALUE) {
+    return;
+  }
+
+  PROCESSENTRY32W process{};
+  process.dwSize = sizeof(PROCESSENTRY32W);
+  if (::Process32FirstW(processes, &process)) {
+    do {
+      if (::_wcsicmp(process.szExeFile, aProcessName) == 0) {
+        TerminateProcessById(process.th32ProcessID);
+      }
+    } while (::Process32NextW(processes, &process));
+  }
+  ::CloseHandle(processes);
+}
+
+void FindSetDefaultBrowserButtonTests::SetUpTestSuite() {
+  ASSERT_TRUE(GetAppRegName(sAppRegName));
+  RegisterAsBrowser();
+}
+
+void FindSetDefaultBrowserButtonTests::TearDownTestSuite() {
+  UnregisterAsBrowser();
+}
+
+void FindSetDefaultBrowserButtonTests::TearDown() { TerminateSystemSettings(); }
+
+void FindSetDefaultBrowserButtonTests::TerminateSystemSettings() {
+  LPCWSTR processName{L"SystemSettings.exe"};
+  TerminateProcessByName(processName);
+}
+
+UIWindowElement
+FindSetDefaultBrowserButtonTests::WaitForSetDefaultBrowserButton() {
+  const int kMaxAttempts{40};
+  const DWORD kRetryDelayMs{500};
+  for (int i{0}; i < kMaxAttempts; ++i) {
+    auto [window, button]{FindSetDefaultBrowserButton()};
+    if (window && button) {
+      return {window, button};
+    }
+    Sleep(kRetryDelayMs);
+  }
+  return {};
+}
+
+void FindSetDefaultBrowserButtonTests::RegisterAsBrowser() {
+  const std::wstring appRegName{sAppRegName.get()};
+
+  WCHAR exePath[MAX_PATH];
+  ::GetModuleFileNameW(nullptr, exePath, MAX_PATH);
+
+  const std::wstring appName{L"Firefox Test"};
+
+  // clang-format off
+  // HKEY_CURRENT_USER\Software\RegisteredApplications
+  {
+    const std::wstring key{L"Software\\RegisteredApplications"};
+    const std::wstring value{L"Software\\Clients\\StartMenuInternet\\" + appRegName + L"\\Capabilities"};
+    ASSERT_TRUE(RegWriteStringValue(HKEY_CURRENT_USER, key, mozilla::Some(appRegName), value));
+  }
+  // HKEY_CURRENT_USER\Software\Clients\StartMenuInternet\Firefox-XYZ
+  {
+    const std::wstring key{L"Software\\Clients\\StartMenuInternet\\" + appRegName};
+    ASSERT_TRUE(RegWriteStringValue(HKEY_CURRENT_USER, key, mozilla::Nothing(), appName));
+  }
+  // HKEY_CURRENT_USER\Software\Clients\StartMenuInternet\Firefox-XYZ\Capabilities
+  {
+    const std::wstring key{L"Software\\Clients\\StartMenuInternet\\" + appRegName + L"\\Capabilities"};
+    const std::wstring name{L"ApplicationDescription"};
+    ASSERT_TRUE(RegWriteStringValue(HKEY_CURRENT_USER, key, mozilla::Some(name), appName));
+  }
+  {
+    const std::wstring key{L"Software\\Clients\\StartMenuInternet\\" + appRegName + L"\\Capabilities"};
+    const std::wstring name{L"ApplicationIcon"};
+    const std::wstring value{std::wstring(exePath) + L",0"};
+    ASSERT_TRUE(RegWriteStringValue(HKEY_CURRENT_USER, key, mozilla::Some(name), value));
+  }
+  {
+    const std::wstring key{L"Software\\Clients\\StartMenuInternet\\" + appRegName + L"\\Capabilities"};
+    const std::wstring name{L"ApplicationName"};
+    ASSERT_TRUE(RegWriteStringValue(HKEY_CURRENT_USER, key, mozilla::Some(name), appName));
+  }
+  // HKEY_CURRENT_USER\Software\Clients\StartMenuInternet\Firefox-XYZ\Capabilities\URLAssociations
+  {
+    const std::wstring key{L"Software\\Clients\\StartMenuInternet\\" + appRegName + L"\\Capabilities\\URLAssociations"};
+    const std::wstring name{L"http"};
+    ASSERT_TRUE(RegWriteStringValue(HKEY_CURRENT_USER, key, mozilla::Some(name), appRegName));
+  }
+  {
+    const std::wstring key{L"Software\\Clients\\StartMenuInternet\\" + appRegName + L"\\Capabilities\\URLAssociations"};
+    const std::wstring name{L"https"};
+    ASSERT_TRUE(RegWriteStringValue(HKEY_CURRENT_USER, key, mozilla::Some(name), appRegName));
+  }
+  // HKEY_CURRENT_USER\Software\Clients\StartMenuInternet\Firefox-XYZ\DefaultIcon
+  {
+    const std::wstring key{L"Software\\Clients\\StartMenuInternet\\" + appRegName + L"\\DefaultIcon"};
+    const std::wstring value{std::wstring(exePath) + L",0"};
+    ASSERT_TRUE(RegWriteStringValue(HKEY_CURRENT_USER, key, mozilla::Nothing(), value));
+  }
+  // HKEY_CURRENT_USER\Software\Clients\StartMenuInternet\Firefox-XYZ\shell\open\command
+  {
+    const std::wstring key{L"Software\\Clients\\StartMenuInternet\\" + appRegName + L"\\shell\\open\\command"};
+    const std::wstring value{L"\"" + std::wstring(exePath) + L"\""};
+    ASSERT_TRUE(RegWriteStringValue(HKEY_CURRENT_USER, key, mozilla::Nothing(), value));
+  }
+  // HKEY_CURRENT_USER\Software\Classes\Firefox-XYZ\shell\open\command
+  {
+    const std::wstring key{L"Software\\Classes\\" + appRegName + L"\\shell\\open\\command"};
+    const std::wstring value{L"\"" + std::wstring(exePath) + L"\" -osint -url \"%1\""};
+    ASSERT_TRUE(RegWriteStringValue(HKEY_CURRENT_USER, key, mozilla::Nothing(), value));
+  }
+  // clang-format on
+}
+
+void FindSetDefaultBrowserButtonTests::UnregisterAsBrowser() {
+  const std::wstring appRegName{sAppRegName.get()};
+
+  // clang-format off
+  // HKEY_CURRENT_USER\Software\RegisteredApplications
+  {
+    const std::wstring key{L"Software\\RegisteredApplications"};
+    ASSERT_TRUE(RegDeleteValue(HKEY_CURRENT_USER, key, appRegName));
+  }
+  // HKEY_CURRENT_USER\Software\Clients\StartMenuInternet\Firefox-XYZ
+  {
+    const std::wstring key{L"Software\\Clients\\StartMenuInternet\\" + appRegName};
+    ASSERT_TRUE(RegDeleteKey(HKEY_CURRENT_USER, key));
+  }
+  // HKEY_CURRENT_USER\Software\Classes\Firefox-XYZ
+  {
+    const std::wstring key{L"Software\\Classes\\" + appRegName};
+    ASSERT_TRUE(RegDeleteKey(HKEY_CURRENT_USER, key));
+  }
+  // clang-format on
+}
+
+mozilla::UniquePtr<WCHAR[]> FindSetDefaultBrowserButtonTests::sAppRegName;
+
+TEST_F(FindSetDefaultBrowserButtonTests, ButtonFound) {
+  ASSERT_TRUE(LaunchModernSettingsDialogDefaultApps());
+
+  auto [window, button]{WaitForSetDefaultBrowserButton()};
+  ASSERT_THAT(window, testing::NotNull());
+  ASSERT_THAT(button, testing::NotNull());
+}
diff --git a/src/zen/tests/mochitests/shell/gtest/WindowsDefaultBrowserTests.h b/src/zen/tests/mochitests/shell/gtest/WindowsDefaultBrowserTests.h
new file mode 100644
index 000000000..658fdf167
--- /dev/null
+++ b/src/zen/tests/mochitests/shell/gtest/WindowsDefaultBrowserTests.h
@@ -0,0 +1,30 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef WINDOWS_DEFAULT_BROWSER_TESTS_H_
+#define WINDOWS_DEFAULT_BROWSER_TESTS_H_
+
+#include <gtest/gtest.h>
+
+#include <windows.h>
+
+#include "mozilla/UniquePtr.h"
+#include "WindowsDefaultBrowser.h"
+
+class FindSetDefaultBrowserButtonTests : public ::testing::Test {
+ protected:
+  static void SetUpTestSuite();
+  static void TearDownTestSuite();
+  void TearDown() override;
+  void TerminateSystemSettings();
+  static UIWindowElement WaitForSetDefaultBrowserButton();
+
+ private:
+  static void RegisterAsBrowser();
+  static void UnregisterAsBrowser();
+
+  static mozilla::UniquePtr<WCHAR[]> sAppRegName;
+};
+
+#endif
diff --git a/src/zen/tests/mochitests/shell/gtest/WindowsUIElementTests.cpp b/src/zen/tests/mochitests/shell/gtest/WindowsUIElementTests.cpp
new file mode 100644
index 000000000..17fd1227c
--- /dev/null
+++ b/src/zen/tests/mochitests/shell/gtest/WindowsUIElementTests.cpp
@@ -0,0 +1,94 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <gtest/gtest.h>
+#include <gmock/gmock.h>
+
+#include <cstdint>
+#include <windows.h>
+#include <ole2.h>
+#include <uiautomation.h>
+
+#include "WindowsDefaultBrowser.h"
+#include "WindowsDefaultBrowserTests.h"
+#include "WindowsUIElement.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/SpinEventLoopUntil.h"
+#include "mozilla/WindowsVersion.h"
+#include "mozilla/gtest/MozAssertions.h"
+#include "nsCOMPtr.h"
+#include "nsISerialEventTarget.h"
+#include "nsITimer.h"
+#include "nsLiteralString.h"
+#include "nsThreadUtils.h"
+
+static bool IsElementFocus(const UIElement& aElement) {
+  BOOL isFocus{FALSE};
+  aElement->get_CurrentHasKeyboardFocus(&isFocus);
+  return isFocus;
+}
+
+class WindowsUIElementTests : public FindSetDefaultBrowserButtonTests {};
+
+TEST_F(WindowsUIElementTests, DefaultBrowserButtonFocused) {
+  ASSERT_TRUE(LaunchModernSettingsDialogDefaultApps());
+
+  auto [window, button]{WaitForSetDefaultBrowserButton()};
+  ASSERT_THAT(window, testing::NotNull());
+  ASSERT_THAT(button, testing::NotNull());
+
+  RefPtr<mozilla::WindowsUIElement> element{
+      new mozilla::WindowsUIElement(window, button)};
+  element->Focus();
+
+  ASSERT_TRUE(IsElementFocus(button));
+}
+
+TEST_F(WindowsUIElementTests, DefaultBrowserButtonStopsMoving) {
+  if (!mozilla::IsWin11OrLater()) {
+    // This test is intended to run only on Win11 since it's part of the feature
+    // that displays the Kit image behind the Set Default Browser button
+    return;
+  }
+
+  ASSERT_TRUE(LaunchModernSettingsDialogDefaultApps());
+
+  auto [window, button]{WaitForSetDefaultBrowserButton()};
+  ASSERT_THAT(window, testing::NotNull());
+  ASSERT_THAT(button, testing::NotNull());
+
+  RefPtr<mozilla::WindowsUIElement> element{
+      new mozilla::WindowsUIElement(window, button)};
+
+  nsCOMPtr<nsISerialEventTarget> queue;
+  ASSERT_NS_SUCCEEDED(NS_CreateBackgroundTaskQueue(
+      "WindowsUIElementTests::DefaultBrowserButtonStopsMovingQueue",
+      getter_AddRefs(queue)));
+
+  int ticks{0};
+  bool elementIsMoving{true};
+  bool done{false};
+  nsCOMPtr<nsITimer> timer;
+  auto callback{[element, &ticks, &elementIsMoving, &done](nsITimer* aTimer) {
+    elementIsMoving = element->IsMoving().valueOr(true);
+    constexpr int kMaxTicks{10};
+    if (!elementIsMoving || ++ticks >= kMaxTicks) {
+      aTimer->Cancel();
+      NS_DispatchToMainThread(NS_NewRunnableFunction(
+          "WindowsUIElementTests::DefaultBrowserButtonStopsMovingDone",
+          [&done] { done = true; }));
+    }
+  }};
+
+  const uint32_t kDelayMs{500};
+  ASSERT_NS_SUCCEEDED(NS_NewTimerWithCallback(
+      getter_AddRefs(timer), callback, kDelayMs, nsITimer::TYPE_REPEATING_SLACK,
+      "WindowsUIElementTests::DefaultBrowserButtonStopsMovingTimer"_ns, queue));
+
+  mozilla::SpinEventLoopUntil(
+      "WindowsUIElementTests::DefaultBrowserButtonStopsMovingLoop"_ns,
+      [&done] { return bool(done); });
+
+  ASSERT_FALSE(elementIsMoving);
+}
diff --git a/src/zen/tests/mochitests/shell/gtest/WindowsUIOverlayImageTests.cpp b/src/zen/tests/mochitests/shell/gtest/WindowsUIOverlayImageTests.cpp
new file mode 100644
index 000000000..e9c455a31
--- /dev/null
+++ b/src/zen/tests/mochitests/shell/gtest/WindowsUIOverlayImageTests.cpp
@@ -0,0 +1,275 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <gtest/gtest.h>
+#include <gmock/gmock.h>
+
+#include <cstdint>
+#include <vector>
+#include <windows.h>
+
+#include "WindowsUIOverlayImage.h"
+#include "WindowsDefaultBrowser.h"
+#include "WindowsDefaultBrowserTests.h"
+#include "WindowsUIElement.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/SpinEventLoopUntil.h"
+#include "mozilla/SyncRunnable.h"
+#include "mozilla/WindowsVersion.h"
+#include "mozilla/gtest/MozAssertions.h"
+#include "nsCOMPtr.h"
+#include "nsISerialEventTarget.h"
+#include "nsISupportsImpl.h"
+#include "nsITimer.h"
+#include "nsLiteralString.h"
+#include "nsThreadUtils.h"
+
+namespace {
+
+class CoverWindow final {
+ public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(CoverWindow)
+
+  static RefPtr<CoverWindow> Create(HWND aWindow) {
+    RECT rect{};
+    if (!GetWindowRect(aWindow, &rect)) {
+      return nullptr;
+    }
+
+    constexpr LPCWSTR kWindowClassName{L"CoverWindow"};
+    WNDCLASSEXW windowClass{sizeof(windowClass)};
+    windowClass.lpfnWndProc = DefWindowProcW;
+    windowClass.hInstance = GetModuleHandleW(nullptr);
+    windowClass.lpszClassName = kWindowClassName;
+    RegisterClassExW(&windowClass);
+
+    HWND window{nullptr};
+    mozilla::SyncRunnable::DispatchToThread(
+        mozilla::GetMainThreadSerialEventTarget(),
+        NS_NewRunnableFunction("CoverWindow::Create", [&window, rect] {
+          window = CreateWindowExW(
+              WS_EX_TOPMOST, kWindowClassName, nullptr, WS_POPUP, rect.left,
+              rect.top, rect.right - rect.left, rect.bottom - rect.top, nullptr,
+              nullptr, GetModuleHandleW(nullptr), nullptr);
+        }));
+    if (!window) {
+      return nullptr;
+    }
+
+    ShowWindow(window, SW_SHOWNOACTIVATE);
+
+    return RefPtr<CoverWindow>{new CoverWindow(window)};
+  }
+
+  // Non-copyable and non-movable
+  CoverWindow(const CoverWindow&) = delete;
+  CoverWindow(CoverWindow&&) = delete;
+  CoverWindow& operator=(const CoverWindow&) = delete;
+  CoverWindow& operator=(CoverWindow&&) = delete;
+
+ private:
+  explicit CoverWindow(HWND aWindow) : mWindow{aWindow} {}
+
+  ~CoverWindow() {
+    if (mWindow) {
+      NS_DispatchToMainThread(NS_NewRunnableFunction(
+          "CoverWindow::DestroyWindow",
+          [window = mWindow] { DestroyWindow(window); }));
+      mWindow = nullptr;
+    }
+  }
+
+  HWND mWindow;
+};
+
+}  // namespace
+
+class WindowsUIOverlayImageTests : public FindSetDefaultBrowserButtonTests {};
+
+TEST_F(WindowsUIOverlayImageTests, OverlayHiddenWhenCovered) {
+  if (!mozilla::IsWin11OrLater()) {
+    // This test is intended to run only on Win11 since it's part of the feature
+    // that displays the Kit image behind the Set Default Browser button
+    return;
+  }
+
+  ASSERT_TRUE(LaunchModernSettingsDialogDefaultApps());
+
+  auto [window, button]{WaitForSetDefaultBrowserButton()};
+  ASSERT_THAT(window, testing::NotNull());
+  ASSERT_THAT(button, testing::NotNull());
+
+  RefPtr<mozilla::WindowsUIElement> element{
+      new mozilla::WindowsUIElement(window, button)};
+
+  nsCOMPtr<nsISerialEventTarget> queue;
+  ASSERT_NS_SUCCEEDED(NS_CreateBackgroundTaskQueue(
+      "WindowsUIOverlayImageTests::OverlayHiddenWhenCoveredQueue",
+      getter_AddRefs(queue)));
+
+  bool elementIsMoving{true};
+  RefPtr<mozilla::WindowsUIOverlayImage> overlayImage;
+  bool overlayImageIsVisibleBefore{false};
+  RefPtr<CoverWindow> coverWindow;
+  bool overlayImageIsVisibleAfter{true};
+  bool done{false};
+  int ticks{0};
+  int state{0};
+  nsCOMPtr<nsITimer> timer;
+  auto callback{[element, &elementIsMoving, &overlayImage,
+                 &overlayImageIsVisibleBefore, window, &coverWindow,
+                 &overlayImageIsVisibleAfter, &done, &ticks,
+                 &state](nsITimer* aTimer) {
+    bool finished{false};
+    switch (state) {
+      case 0:
+        // Wait until the element stops moving
+        elementIsMoving = element->IsMoving().valueOr(true);
+        if (!elementIsMoving) {
+          ++state;
+        }
+        break;
+      case 1:
+        // Create the overlay image
+        overlayImage = element->CreateOverlayImage(
+            mozilla::WindowsUIOverlayImage::DisplayMode::Static);
+        finished = !overlayImage;
+        ++state;
+        break;
+      case 2:
+        // The overlay image is visible before anything covers it
+        overlayImageIsVisibleBefore = overlayImage->IsVisible();
+        if (overlayImageIsVisibleBefore) {
+          ++state;
+        }
+        break;
+      case 3:
+        // Cover the Windows Settings window
+        coverWindow = CoverWindow::Create(window);
+        finished = !coverWindow;
+        ++state;
+        break;
+      case 4:
+        // The overlay image shouldn't be visible
+        overlayImageIsVisibleAfter = overlayImage->IsVisible();
+        finished = true;
+        break;
+    }
+
+    constexpr int kMaxTicks{40};
+    if (finished || ++ticks >= kMaxTicks) {
+      aTimer->Cancel();
+      NS_DispatchToMainThread(NS_NewRunnableFunction(
+          "WindowsUIOverlayImageTests::OverlayHiddenWhenCoveredDone",
+          [&done] { done = true; }));
+    }
+  }};
+
+  const uint32_t kDelayMs{500};
+  ASSERT_NS_SUCCEEDED(NS_NewTimerWithCallback(
+      getter_AddRefs(timer), callback, kDelayMs, nsITimer::TYPE_REPEATING_SLACK,
+      "WindowsUIOverlayImageTests::OverlayHiddenWhenCoveredTimer"_ns, queue));
+
+  mozilla::SpinEventLoopUntil(
+      "WindowsUIOverlayImageTests::OverlayHiddenWhenCoveredLoop"_ns,
+      [&done] { return bool(done); });
+
+  ASSERT_FALSE(elementIsMoving);
+  ASSERT_THAT(overlayImage, testing::NotNull());
+  ASSERT_TRUE(overlayImageIsVisibleBefore);
+  ASSERT_THAT(coverWindow, testing::NotNull());
+  ASSERT_FALSE(overlayImageIsVisibleAfter);
+}
+
+TEST(GetFrameDurationTests, KitImageFirstFrameDurationIs40ms)
+{
+  nsCOMPtr<nsIFile> imageFile{mozilla::GetImageFile()};
+  ASSERT_THAT(imageFile, testing::NotNull());
+
+  RefPtr<IWICImagingFactory> factory{mozilla::CreateWICImagingFactory()};
+  ASSERT_THAT(factory, testing::NotNull());
+
+  RefPtr<IWICBitmapDecoder> decoder{
+      mozilla::CreateWICBitmapDecoder(factory, imageFile)};
+  ASSERT_THAT(decoder, testing::NotNull());
+
+  RefPtr<IWICBitmapFrameDecode> frame;
+  constexpr UINT kFrameNumber{0};
+  ASSERT_TRUE(
+      SUCCEEDED(decoder->GetFrame(kFrameNumber, getter_AddRefs(frame))));
+
+  const mozilla::TimeDuration kSentinelFrameDuration{
+      mozilla::TimeDuration::FromMilliseconds(999)};
+  const mozilla::TimeDuration duration{
+      mozilla::GetFrameDuration(frame, kSentinelFrameDuration)};
+
+  // Kit image (kit.gif) frame duration is 40 ms
+  const mozilla::TimeDuration kFrameDuration{
+      mozilla::TimeDuration::FromMilliseconds(40)};
+
+  EXPECT_EQ(duration, kFrameDuration);
+}
+
+class ComputeAdvancedFrameTests : public testing::Test {
+ protected:
+  const mozilla::TimeDuration mFrameDuration{
+      mozilla::TimeDuration::FromMilliseconds(25)};
+
+  const std::vector<mozilla::WindowsUIOverlayImage::Frame> mFrames{
+      4, mozilla::WindowsUIOverlayImage::Frame{{}, mFrameDuration}};
+};
+
+TEST_F(ComputeAdvancedFrameTests, DoesNotAdvanceWhenTimeBelowFrameDuration) {
+  mozilla::TimeDuration accumulated{
+      mozilla::TimeDuration::FromMilliseconds(20)};
+
+  size_t frame{mozilla::ComputeAdvancedFrame(mFrames, 0, accumulated)};
+
+  EXPECT_EQ(frame, 0u);
+  EXPECT_EQ(accumulated, mozilla::TimeDuration::FromMilliseconds(20));
+}
+
+TEST_F(ComputeAdvancedFrameTests, AdvancesSingleFrame) {
+  mozilla::TimeDuration accumulated{
+      mozilla::TimeDuration::FromMilliseconds(30)};
+
+  size_t frame{mozilla::ComputeAdvancedFrame(mFrames, 0, accumulated)};
+
+  EXPECT_EQ(frame, 1u);
+  EXPECT_EQ(accumulated,
+            mozilla::TimeDuration::FromMilliseconds(30) - mFrameDuration);
+}
+
+TEST_F(ComputeAdvancedFrameTests, AdvancesMultipleFramesInOneCall) {
+  mozilla::TimeDuration accumulated{
+      mozilla::TimeDuration::FromMilliseconds(60)};
+
+  size_t frame{mozilla::ComputeAdvancedFrame(mFrames, 0, accumulated)};
+
+  EXPECT_EQ(frame, 2u);
+  EXPECT_EQ(accumulated,
+            mozilla::TimeDuration::FromMilliseconds(60) - mFrameDuration * 2);
+}
+
+TEST_F(ComputeAdvancedFrameTests, DoesNotAdvancePastLastFrame) {
+  mozilla::TimeDuration accumulated{
+      mozilla::TimeDuration::FromMilliseconds(1000)};
+
+  size_t frame{mozilla::ComputeAdvancedFrame(mFrames, 0, accumulated)};
+
+  EXPECT_EQ(frame, 3u);
+  // The time for the frames not reached is left untouched
+  EXPECT_EQ(accumulated,
+            mozilla::TimeDuration::FromMilliseconds(1000) - mFrameDuration * 3);
+}
+
+TEST_F(ComputeAdvancedFrameTests, StaysOnLastFrame) {
+  mozilla::TimeDuration accumulated{
+      mozilla::TimeDuration::FromMilliseconds(1000)};
+
+  size_t frame{mozilla::ComputeAdvancedFrame(mFrames, 3, accumulated)};
+
+  EXPECT_EQ(frame, 3u);
+  EXPECT_EQ(accumulated, mozilla::TimeDuration::FromMilliseconds(1000));
+}
diff --git a/src/zen/tests/mochitests/shell/gtest/moz.build b/src/zen/tests/mochitests/shell/gtest/moz.build
index e8905d28f..ebf164e4a 100644
--- a/src/zen/tests/mochitests/shell/gtest/moz.build
+++ b/src/zen/tests/mochitests/shell/gtest/moz.build
@@ -1,14 +1,16 @@
-# This Source Code Form is subject to the terms of the Mozilla Public
-# License, v. 2.0. If a copy of the MPL was not distributed with this
-# file, You can obtain one at http://mozilla.org/MPL/2.0/.
-
-if CONFIG["MOZ_WIDGET_TOOLKIT"] == "windows":
-    LOCAL_INCLUDES += ["/browser/components/shell"]
-
-    UNIFIED_SOURCES += [
-        "LimitedAccessFeatureTests.cpp",
-        "SetDefaultBrowserButtonTests.cpp",
-        "ShellLinkTests.cpp",
-    ]
-
-FINAL_LIBRARY = "xul-gtest"
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+if CONFIG["MOZ_WIDGET_TOOLKIT"] == "windows":
+    LOCAL_INCLUDES += ["/browser/components/shell"]
+
+    UNIFIED_SOURCES += [
+        "LimitedAccessFeatureTests.cpp",
+        "ShellLinkTests.cpp",
+        "WindowsDefaultBrowserTests.cpp",
+        "WindowsUIElementTests.cpp",
+        "WindowsUIOverlayImageTests.cpp",
+    ]
+
+FINAL_LIBRARY = "xul-gtest"
diff --git a/src/zen/tests/mochitests/shell/unit/test_customIconManager.js b/src/zen/tests/mochitests/shell/unit/test_customIconManager.js
new file mode 100644
index 000000000..c3aa1fbae
--- /dev/null
+++ b/src/zen/tests/mochitests/shell/unit/test_customIconManager.js
@@ -0,0 +1,1128 @@
+/* Any copyright is dedicated to the Public Domain.
+ * https://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { MockRegistrar } = ChromeUtils.importESModule(
+  "resource://testing-common/MockRegistrar.sys.mjs"
+);
+const { sinon } = ChromeUtils.importESModule(
+  "resource://testing-common/Sinon.sys.mjs"
+);
+// This is an xpcshell test, but a sibling browser.toml makes eslint apply the
+// browser-test env, where TestUtils is a predefined global. It isn't one in
+// xpcshell (there's no head.js here to import it either), so the import is
+// required.
+// eslint-disable-next-line mozilla/no-redeclare-with-import-autofix
+const { TestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/TestUtils.sys.mjs"
+);
+const {
+  CustomIconManager,
+  ICON_CATALOG,
+  resolvePreview,
+  resolveResourceId,
+  OS_LIGHT,
+  OS_DARK,
+} = ChromeUtils.importESModule(
+  "moz-src:///browser/components/shell/CustomIconManager.sys.mjs"
+);
+// Importing this module constructs the toolkit profile service as a side effect,
+// which requires setupProfileService() to have run, so it must stay lazy and
+// only be touched from add_setup() onwards.
+const lazy = {};
+ChromeUtils.defineESModuleGetters(lazy, {
+  SelectableProfileService:
+    "resource:///modules/profiles/SelectableProfileService.sys.mjs",
+});
+
+const PREF_ICON_ID = "browser.shell.customIcon.id";
+const PREF_ENABLED = "browser.shell.customIcon.enabled";
+const PREF_PER_USER_START_MENU_SHORTCUT_CREATED =
+  "browser.shell.customIcon.perUserStartMenuShortcutCreated";
+const TEST_AUMID = "Test.Firefox.AUMID";
+const TEST_SHORTCUTS = ["C:\\fake\\Desktop\\Nightly.lnk"];
+const RETRO_RESOURCE_ID = ICON_CATALOG.retro2004.iconResourceId;
+
+// CustomIconManager.apply() refuses to run on MSIX (packaged) builds, so on the
+// MSIX CI job every task except the MSIX-specific one (which fakes the
+// condition itself and runs everywhere) is skipped.
+const ON_MSIX = Services.sysinfo.getProperty("hasWinPackageId");
+
+// add_task() mutates the options object it is handed (tagging it isTask), so
+// each call needs its own fresh object rather than a shared one.
+function skipOnMsix() {
+  return { skip_if: () => ON_MSIX };
+}
+
+function exePath() {
+  return Services.dirsvc.get("XREExeF", Ci.nsIFile).path;
+}
+
+// A shortcut path in the folder holding the user's pinned taskbar shortcuts.
+function pinnedShortcut() {
+  return PathUtils.join(
+    Services.dirsvc.get("AppData", Ci.nsIFile).path,
+    "Microsoft",
+    "Internet Explorer",
+    "Quick Launch",
+    "User Pinned",
+    "TaskBar",
+    "Nightly.lnk"
+  );
+}
+
+let shellServiceMock = {
+  QueryInterface: ChromeUtils.generateQI([Ci.nsIWindowsShellService]),
+  enumerateInstallShortcuts: sinon.stub(),
+  setShortcutsIcon: sinon.stub(),
+  createShortcut: sinon.stub(),
+};
+
+let winTaskbarMock = {
+  QueryInterface: ChromeUtils.generateQI([Ci.nsIWinTaskbar]),
+  setAllWindowIcons: sinon.stub(),
+  refreshTaskbarButtons: sinon.stub(),
+  get defaultGroupId() {
+    return TEST_AUMID;
+  },
+};
+
+// ensureAppliedOrRevert() awaits SelectableProfileService.init() on the startup
+// path so the shared custom-icon pref can finish loading from the profiles
+// database before it reconciles. We stub it here so these unit tests don't spin up
+// the real profiles machinery.
+let spsInitStub;
+
+// hasSystemWideStartMenuShortcut() does real filesystem/environment-variable
+// work so here we stub it to isolate maybeCreatePerUserStartMenuShortcut()'s
+// own branching logic from that.
+let hasSystemWideStartMenuShortcutStub;
+
+// Reset stub history + default behaviour, clear the prefs, and drop any
+// recorded Glean values before each task.
+function resetMocks() {
+  shellServiceMock.enumerateInstallShortcuts.reset();
+  shellServiceMock.enumerateInstallShortcuts.resolves(TEST_SHORTCUTS.slice());
+  shellServiceMock.setShortcutsIcon.reset();
+  shellServiceMock.setShortcutsIcon.resolves();
+  shellServiceMock.createShortcut.reset();
+  shellServiceMock.createShortcut.resolves();
+  winTaskbarMock.setAllWindowIcons.reset();
+  winTaskbarMock.refreshTaskbarButtons.reset();
+  spsInitStub.reset();
+  spsInitStub.resolves();
+  hasSystemWideStartMenuShortcutStub.reset();
+  hasSystemWideStartMenuShortcutStub.resolves(true);
+  Services.prefs.clearUserPref(PREF_ICON_ID);
+  Services.prefs.setBoolPref(PREF_ENABLED, true);
+  Services.prefs.clearUserPref(PREF_PER_USER_START_MENU_SHORTCUT_CREATED);
+  Services.fog.testResetFOG();
+}
+
+// The single "changed" event recorded since the last reset, or undefined if
+// none. Fails if more than one was recorded (each task exercises one change).
+function singleChangedEvent() {
+  let events = Glean.customIcon.changed.testGetValue() ?? [];
+  Assert.lessOrEqual(events.length, 1, "at most one changed event recorded");
+  return events[0];
+}
+
+// Since we're importing SelectableProfileService for this test, we lift some of
+// the setup from toolkit/profile/test/xpcshell/head.js which lets the service
+// be imported and executed in debug xpcshell tests.
+function setupProfileService() {
+  let profD = do_get_profile();
+
+  let dataHome = profD.clone();
+  dataHome.append("data");
+  dataHome.createUnique(Ci.nsIFile.DIRECTORY_TYPE, 0o755);
+
+  let dataHomeLocal = profD.clone();
+  dataHomeLocal.append("local");
+  dataHomeLocal.createUnique(Ci.nsIFile.DIRECTORY_TYPE, 0o755);
+
+  let xreDirProvider = Cc["@mozilla.org/xre/directory-provider;1"].getService(
+    Ci.nsIXREDirProvider
+  );
+  xreDirProvider.setUserDataDirectory(dataHome, false);
+  xreDirProvider.setUserDataDirectory(dataHomeLocal, true);
+}
+
+add_setup(function () {
+  setupProfileService();
+  Services.fog.initializeFOG();
+
+  let shellCid = MockRegistrar.register(
+    "@mozilla.org/browser/shell-service;1",
+    shellServiceMock
+  );
+  let taskbarCid = MockRegistrar.register(
+    "@mozilla.org/windows-taskbar;1",
+    winTaskbarMock
+  );
+
+  spsInitStub = sinon.stub(lazy.SelectableProfileService, "init").resolves();
+  hasSystemWideStartMenuShortcutStub = sinon.stub(
+    CustomIconManager,
+    "hasSystemWideStartMenuShortcut"
+  );
+
+  registerCleanupFunction(() => {
+    spsInitStub.restore();
+    hasSystemWideStartMenuShortcutStub.restore();
+    MockRegistrar.unregister(taskbarCid);
+    MockRegistrar.unregister(shellCid);
+    Services.prefs.clearUserPref(PREF_ICON_ID);
+    Services.prefs.clearUserPref(PREF_ENABLED);
+    Services.prefs.clearUserPref(PREF_PER_USER_START_MENU_SHORTCUT_CREATED);
+  });
+});
+
+/**
+ * This test verifies that apply() enumerates shortcuts by the default AUMID,
+ * writes the catalog resource ID (positive, un-negated) and the executable
+ * path to the matching shortcuts, sets the runtime window icon, and records
+ * the pref.
+ */
+add_task(
+  skipOnMsix(),
+  async function test_apply_updates_shortcuts_pref_and_runtime() {
+    resetMocks();
+
+    await CustomIconManager.apply("retro2004");
+
+    Assert.ok(
+      shellServiceMock.enumerateInstallShortcuts.calledOnceWithExactly(
+        TEST_AUMID
+      ),
+      "enumerateInstallShortcuts called once with the default AUMID"
+    );
+
+    Assert.ok(
+      shellServiceMock.setShortcutsIcon.calledOnce,
+      "setShortcutsIcon called once"
+    );
+    let [shortcuts, iconPath, resourceId] =
+      shellServiceMock.setShortcutsIcon.getCall(0).args;
+    Assert.deepEqual(
+      shortcuts,
+      TEST_SHORTCUTS,
+      "passed the enumerated shortcuts through"
+    );
+    Assert.equal(iconPath, exePath(), "icon source is the running executable");
+    Assert.equal(
+      resourceId,
+      RETRO_RESOURCE_ID,
+      "passed the catalog resource ID as-is (negation happens in C++, not JS)"
+    );
+
+    Assert.ok(
+      winTaskbarMock.setAllWindowIcons.calledOnceWithExactly(RETRO_RESOURCE_ID),
+      "runtime window icon set to the retro resource ID"
+    );
+    Assert.equal(
+      Services.prefs.getStringPref(PREF_ICON_ID, ""),
+      "retro2004",
+      "pref records the applied id"
+    );
+
+    let event = singleChangedEvent();
+    Assert.ok(event, "a changed event was recorded");
+    Assert.equal(event.category, "custom_icon", "event category");
+    Assert.equal(event.name, "changed", "event name");
+    Assert.equal(
+      event.extra.icon_id,
+      "retro2004",
+      "changed event carries the applied id"
+    );
+  }
+);
+
+/**
+ * This test verifies that apply() rejects when given an id absent from the
+ * catalog, without touching any shortcut or runtime state or the pref.
+ */
+add_task(skipOnMsix(), async function test_apply_unknown_id_throws() {
+  resetMocks();
+
+  await Assert.rejects(
+    CustomIconManager.apply("does-not-exist"),
+    /Unknown icon id/,
+    "apply rejects for an unknown catalog id"
+  );
+
+  Assert.ok(
+    shellServiceMock.setShortcutsIcon.notCalled,
+    "no shortcut work attempted for an unknown id"
+  );
+  Assert.ok(
+    winTaskbarMock.setAllWindowIcons.notCalled,
+    "no runtime work attempted for an unknown id"
+  );
+  Assert.equal(
+    Services.prefs.getStringPref(PREF_ICON_ID, ""),
+    "",
+    "pref left untouched"
+  );
+});
+
+/**
+ * This test verifies that apply() throws on MSIX (packaged) builds, where the
+ * feature is unsupported, without touching shortcuts, the runtime icon, or the
+ * pref.
+ */
+add_task(async function test_apply_throws_on_msix() {
+  resetMocks();
+
+  // Fake an MSIX build by flipping the sysinfo property the manager checks.
+  // nsSystemInfo is a writable property bag, so set it directly and restore it.
+  let bag = Services.sysinfo.QueryInterface(Ci.nsIWritablePropertyBag2);
+  let original = bag.getProperty("hasWinPackageId");
+  bag.setPropertyAsBool("hasWinPackageId", true);
+
+  try {
+    await Assert.rejects(
+      CustomIconManager.apply("retro2004"),
+      /MSIX/,
+      "apply rejects on an MSIX build"
+    );
+
+    Assert.ok(
+      shellServiceMock.setShortcutsIcon.notCalled,
+      "no shortcut work attempted on MSIX"
+    );
+    Assert.ok(
+      winTaskbarMock.setAllWindowIcons.notCalled,
+      "no runtime work attempted on MSIX"
+    );
+    Assert.equal(
+      Services.prefs.getStringPref(PREF_ICON_ID, ""),
+      "",
+      "pref left untouched on MSIX"
+    );
+  } finally {
+    bag.setPropertyAsBool("hasWinPackageId", original);
+  }
+});
+
+/**
+ * This test verifies that revert() resets matching shortcuts to the
+ * executable's default icon (resource ID 0), clears the runtime override, and
+ * clears the pref.
+ */
+add_task(
+  skipOnMsix(),
+  async function test_revert_resets_shortcuts_pref_and_runtime() {
+    resetMocks();
+    Services.prefs.setStringPref(PREF_ICON_ID, "retro2004");
+
+    await CustomIconManager.revert();
+
+    Assert.ok(
+      shellServiceMock.setShortcutsIcon.calledOnce,
+      "setShortcutsIcon called once"
+    );
+    let [, iconPath, resourceId] =
+      shellServiceMock.setShortcutsIcon.getCall(0).args;
+    Assert.equal(iconPath, exePath(), "reverts using the executable path");
+    Assert.equal(
+      resourceId,
+      0,
+      "resource ID 0 selects the executable's default icon"
+    );
+
+    Assert.ok(
+      winTaskbarMock.setAllWindowIcons.calledOnceWithExactly(0),
+      "runtime window icon cleared (0)"
+    );
+    Assert.ok(!Services.prefs.prefHasUserValue(PREF_ICON_ID), "pref cleared");
+
+    let event = singleChangedEvent();
+    Assert.ok(event, "reverting from a custom icon records a changed event");
+    Assert.equal(
+      event.extra.icon_id,
+      "default",
+      "revert records the default id as the new selection"
+    );
+  }
+);
+
+/**
+ * This test verifies that when enumeration matches no shortcuts, apply() skips
+ * setShortcutsIcon but still applies the runtime icon and records the pref, so
+ * the running window updates even though no shortcut could be changed.
+ */
+add_task(skipOnMsix(), async function test_apply_no_matching_shortcuts() {
+  resetMocks();
+  shellServiceMock.enumerateInstallShortcuts.resolves([]);
+
+  // Must not throw even though nothing matched.
+  await CustomIconManager.apply("retro2004");
+
+  Assert.ok(
+    shellServiceMock.setShortcutsIcon.notCalled,
+    "setShortcutsIcon not called when enumeration matched nothing"
+  );
+  Assert.ok(
+    winTaskbarMock.setAllWindowIcons.calledOnceWithExactly(RETRO_RESOURCE_ID),
+    "runtime icon still applied even though no shortcut changed"
+  );
+  Assert.equal(
+    Services.prefs.getStringPref(PREF_ICON_ID, ""),
+    "retro2004",
+    "pref still recorded"
+  );
+  Assert.equal(
+    singleChangedEvent()?.extra.icon_id,
+    "retro2004",
+    "changed event still recorded even though no shortcut matched"
+  );
+});
+
+/**
+ * This test verifies that when setShortcutsIcon rejects, apply() logs and
+ * swallows the failure rather than throwing, and still applies the runtime
+ * icon and pref.
+ */
+add_task(
+  skipOnMsix(),
+  async function test_apply_shortcut_write_failure_is_swallowed() {
+    resetMocks();
+    shellServiceMock.setShortcutsIcon.rejects(
+      Components.Exception(
+        "mock setShortcutsIcon failure",
+        Cr.NS_ERROR_NOT_AVAILABLE
+      )
+    );
+
+    // A shortcut-write failure is logged, not thrown.
+    await CustomIconManager.apply("retro2004");
+
+    Assert.ok(
+      shellServiceMock.setShortcutsIcon.calledOnce,
+      "setShortcutsIcon was attempted"
+    );
+    Assert.ok(
+      winTaskbarMock.setAllWindowIcons.calledOnceWithExactly(RETRO_RESOURCE_ID),
+      "runtime icon still applied despite the shortcut-write failure"
+    );
+    Assert.equal(
+      Services.prefs.getStringPref(PREF_ICON_ID, ""),
+      "retro2004",
+      "pref still recorded"
+    );
+    Assert.equal(
+      singleChangedEvent()?.extra.icon_id,
+      "retro2004",
+      "changed event still recorded despite the shortcut-write failure"
+    );
+  }
+);
+
+/**
+ * This test verifies that re-applying the icon that is already active (as the
+ * theme observer and startup reconcile do) records no changed event, so the
+ * probe only fires on a genuine change of icon.
+ */
+add_task(skipOnMsix(), async function test_apply_same_id_records_no_change() {
+  resetMocks();
+
+  await CustomIconManager.apply("retro2004");
+  Assert.ok(singleChangedEvent(), "first apply records a change");
+
+  Services.fog.testResetFOG();
+  await CustomIconManager.apply("retro2004");
+  Assert.equal(
+    Glean.customIcon.changed.testGetValue(),
+    undefined,
+    "re-applying the same id records no changed event"
+  );
+});
+
+/**
+ * This test verifies that revert() over the already-default state (no custom
+ * icon active) records no changed event.
+ */
+add_task(
+  skipOnMsix(),
+  async function test_revert_when_default_records_nothing() {
+    resetMocks();
+
+    await CustomIconManager.revert();
+
+    Assert.equal(
+      Glean.customIcon.changed.testGetValue(),
+      undefined,
+      "reverting when already default records no changed event"
+    );
+  }
+);
+
+/**
+ * This test verifies that a rejected apply() (unknown id) records no changed
+ * event.
+ */
+add_task(skipOnMsix(), async function test_unknown_id_records_no_change() {
+  resetMocks();
+
+  await Assert.rejects(
+    CustomIconManager.apply("does-not-exist"),
+    /Unknown icon id/,
+    "apply rejects for an unknown catalog id"
+  );
+
+  Assert.equal(
+    Glean.customIcon.changed.testGetValue(),
+    undefined,
+    "no changed event recorded for a rejected apply"
+  );
+});
+
+/**
+ * This test verifies that ensureAppliedOrRevert() records the current-icon
+ * string metric once at startup: the active id for a known custom icon, and
+ * "default" when no custom icon is set.
+ */
+add_task(
+  skipOnMsix(),
+  async function test_ensureAppliedOrRevert_records_current() {
+    resetMocks();
+    Services.prefs.setStringPref(PREF_ICON_ID, "retro2004");
+
+    await CustomIconManager.ensureAppliedOrRevert();
+    Assert.equal(
+      Glean.customIcon.current.testGetValue(),
+      "retro2004",
+      "current records the active custom icon id"
+    );
+
+    resetMocks();
+    await CustomIconManager.ensureAppliedOrRevert();
+    Assert.equal(
+      Glean.customIcon.current.testGetValue(),
+      "default",
+      "current records the default id when no custom icon is set"
+    );
+  }
+);
+
+/**
+ * This test verifies that ensureAppliedOrRevert() with a pref naming a known
+ * catalog id re-applies the runtime icon only, without rewriting shortcuts,
+ * and keeps the pref.
+ */
+add_task(
+  skipOnMsix(),
+  async function test_ensureAppliedOrRevert_applies_known_id() {
+    resetMocks();
+    Services.prefs.setStringPref(PREF_ICON_ID, "retro2004");
+
+    await CustomIconManager.ensureAppliedOrRevert();
+
+    Assert.ok(
+      winTaskbarMock.setAllWindowIcons.calledOnceWithExactly(RETRO_RESOURCE_ID),
+      "runtime icon applied for a known id"
+    );
+    Assert.ok(
+      shellServiceMock.setShortcutsIcon.notCalled,
+      "ensureAppliedOrRevert does not rewrite shortcuts for a known id"
+    );
+    Assert.equal(
+      Services.prefs.getStringPref(PREF_ICON_ID, ""),
+      "retro2004",
+      "pref retained"
+    );
+  }
+);
+
+/**
+ * This test verifies that ensureAppliedOrRevert() with a pref naming an id
+ * absent from the catalog (e.g. a newer build's icon, or one since retired)
+ * reverts the shortcuts and runtime icon to default and clears the pref.
+ */
+add_task(
+  skipOnMsix(),
+  async function test_ensureAppliedOrRevert_reverts_unknown_id() {
+    resetMocks();
+    Services.prefs.setStringPref(PREF_ICON_ID, "icon-from-a-newer-build");
+
+    await CustomIconManager.ensureAppliedOrRevert();
+
+    // Unknown id -> revert: shortcuts reset to default, runtime cleared, pref
+    // cleared.
+    Assert.ok(
+      shellServiceMock.setShortcutsIcon.calledOnce,
+      "revert rewrote shortcuts"
+    );
+    Assert.equal(
+      shellServiceMock.setShortcutsIcon.getCall(0).args[2],
+      0,
+      "shortcuts reset to the default icon"
+    );
+    Assert.ok(
+      winTaskbarMock.setAllWindowIcons.calledOnceWithExactly(0),
+      "runtime icon cleared"
+    );
+    Assert.ok(!Services.prefs.prefHasUserValue(PREF_ICON_ID), "pref cleared");
+    Assert.equal(
+      Glean.customIcon.changed.testGetValue(),
+      undefined,
+      "the startup reconcile of an unknown id is not a user change"
+    );
+  }
+);
+
+/**
+ * This test verifies that ensureAppliedOrRevert() does nothing when no custom
+ * icon pref is set.
+ */
+add_task(
+  skipOnMsix(),
+  async function test_ensureAppliedOrRevert_noop_without_pref() {
+    resetMocks();
+
+    await CustomIconManager.ensureAppliedOrRevert();
+
+    Assert.ok(
+      shellServiceMock.setShortcutsIcon.notCalled,
+      "no shortcut work when no custom icon is recorded"
+    );
+    Assert.ok(
+      winTaskbarMock.setAllWindowIcons.notCalled,
+      "no runtime work when no custom icon is recorded"
+    );
+  }
+);
+
+/**
+ * This test checks that ensureAppliedOrRevert() will run setShortcutsIcon
+ * even if no custom ID is set, but only if it's being called because a remote
+ * profile updated.
+ */
+add_task(
+  skipOnMsix(),
+  async function test_ensureAppliedOrRevert_when_remoteProfileUpdated() {
+    resetMocks();
+
+    await CustomIconManager.ensureAppliedOrRevert(
+      true /* remoteProfileUpdated */
+    );
+
+    Assert.ok(
+      shellServiceMock.setShortcutsIcon.notCalled,
+      "Shortcuts were not modified if a remote profile cleared the icon"
+    );
+    Assert.ok(
+      winTaskbarMock.setAllWindowIcons.calledOnce,
+      "Runtime icon was modified if a remote profile cleared the icon"
+    );
+  }
+);
+
+/**
+ * This test verifies that the startup reconcile (remoteProfileUpdated = false)
+ * awaits SelectableProfileService.init() before reading the pref, so a custom
+ * icon synced late from the selectable-profiles database is still applied
+ * rather than missed. init() stands in for that shared-pref load and only sets
+ * the pref after yielding, so a reconcile that read the pref without awaiting
+ * would see no icon and apply nothing.
+ */
+add_task(
+  skipOnMsix(),
+  async function test_ensureAppliedOrRevert_waits_for_shared_pref_load() {
+    resetMocks();
+
+    spsInitStub.callsFake(async () => {
+      await Promise.resolve();
+      Services.prefs.setStringPref(PREF_ICON_ID, "retro2004");
+    });
+
+    await CustomIconManager.ensureAppliedOrRevert();
+
+    Assert.ok(
+      spsInitStub.calledOnce,
+      "The startup reconcile awaited SelectableProfileService.init()."
+    );
+    Assert.ok(
+      winTaskbarMock.setAllWindowIcons.calledOnceWithExactly(RETRO_RESOURCE_ID),
+      "The icon synced during init() was applied to runtime windows."
+    );
+  }
+);
+
+/**
+ * This test verifies the theme-aware catalog shape: a theme-aware icon exposes
+ * distinct dark/light variants and resolveResourceId()/resolvePreview() pick the
+ * scheme-specific asset, while a flat icon ignores the scheme.
+ */
+add_task(async function test_theme_aware_catalog() {
+  let minimal = ICON_CATALOG.minimal;
+  Assert.ok(minimal.variants, "minimal is theme-aware");
+  Assert.notEqual(
+    minimal.variants.dark.iconResourceId,
+    minimal.variants.light.iconResourceId,
+    "dark and light variants use distinct resource IDs"
+  );
+  Assert.notEqual(
+    resolvePreview(minimal, "dark"),
+    resolvePreview(minimal, "light"),
+    "resolvePreview returns the scheme-specific preview for a theme-aware icon"
+  );
+  Assert.equal(
+    resolveResourceId(minimal, "dark"),
+    minimal.variants.dark.iconResourceId,
+    "resolveResourceId picks the dark variant's id under a dark scheme"
+  );
+  Assert.equal(
+    resolveResourceId(minimal, "light"),
+    minimal.variants.light.iconResourceId,
+    "resolveResourceId picks the light variant's id under a light scheme"
+  );
+
+  let retro = ICON_CATALOG.retro2004;
+  Assert.ok(!retro.variants, "retro2004 is theme-agnostic");
+  Assert.equal(
+    resolvePreview(retro, "dark"),
+    resolvePreview(retro, "light"),
+    "a flat entry returns the same preview regardless of scheme"
+  );
+  Assert.equal(
+    resolveResourceId(retro, "dark"),
+    retro.iconResourceId,
+    "a flat entry returns its single resource id regardless of scheme"
+  );
+});
+
+/**
+ * This test verifies the OS-theme runtime behaviour of a theme-aware icon:
+ * apply() picks the variant matching the OS taskbar theme, and a
+ * look-and-feel-changed notification re-applies the other variant when (and
+ * only when) the OS theme actually flips.
+ *
+ * osColorScheme() reads the Windows registry, so we mock nsIWindowsRegKey for
+ * the duration of this task only (to avoid disturbing other registry reads) and
+ * drive SystemUsesLightTheme directly.
+ */
+add_task(skipOnMsix(), async function test_theme_change_reapplies_variant() {
+  resetMocks();
+
+  // The test flips this between OS_LIGHT/OS_DARK to simulate the user
+  // changing their OS theme.
+  let osTheme = OS_LIGHT;
+  let regKeyMock = {
+    QueryInterface: ChromeUtils.generateQI([Ci.nsIWindowsRegKey]),
+    open() {},
+    close() {},
+    hasValue: name => name === "SystemUsesLightTheme",
+    readIntValue: name => (name === "SystemUsesLightTheme" ? osTheme : 0),
+  };
+  let regCid = MockRegistrar.register(
+    "@mozilla.org/windows-registry-key;1",
+    regKeyMock
+  );
+
+  let { dark, light } = ICON_CATALOG.minimal.variants;
+
+  try {
+    // Startup registers the look-and-feel-changed observer.
+    CustomIconManager.applyRuntimeOverrideForStartup();
+
+    // Light OS theme -> Minimal applies the light variant.
+    osTheme = OS_LIGHT;
+    await CustomIconManager.apply("minimal");
+    Assert.equal(
+      shellServiceMock.setShortcutsIcon.lastCall.args[2],
+      light.iconResourceId,
+      "Minimal applies the light variant under a light OS theme"
+    );
+    Assert.ok(
+      winTaskbarMock.setAllWindowIcons.calledWith(light.iconResourceId),
+      "runtime window icon set to the light variant"
+    );
+
+    // Flip the OS to dark and notify -> the active Minimal re-applies as dark.
+    osTheme = OS_DARK;
+    shellServiceMock.setShortcutsIcon.resetHistory();
+    winTaskbarMock.setAllWindowIcons.resetHistory();
+    Services.obs.notifyObservers(null, "look-and-feel-changed");
+    await TestUtils.waitForCondition(
+      () => shellServiceMock.setShortcutsIcon.called,
+      "icon re-applied after the OS theme flipped to dark"
+    );
+    Assert.equal(
+      shellServiceMock.setShortcutsIcon.lastCall.args[2],
+      dark.iconResourceId,
+      "the dark variant is applied after the theme flips to dark"
+    );
+
+    // A notification with no actual theme change is a no-op (the
+    // gLastAppliedScheme guard short-circuits before re-applying).
+    shellServiceMock.setShortcutsIcon.resetHistory();
+    Services.obs.notifyObservers(null, "look-and-feel-changed");
+    Assert.ok(
+      shellServiceMock.setShortcutsIcon.notCalled,
+      "no re-apply when the OS theme is unchanged"
+    );
+  } finally {
+    MockRegistrar.unregister(regCid);
+    Services.prefs.clearUserPref(PREF_ICON_ID);
+  }
+});
+
+/**
+ * This test verifies that maybeCreatePerUserStartMenuShortcut() does not create a
+ * shortcut when one already exists in the per-user Start Menu Programs folder.
+ */
+add_task(
+  skipOnMsix(),
+  async function test_maybeCreatePerUserStartMenuShortcut_already_exists() {
+    resetMocks();
+
+    let programsPath = Services.dirsvc.get("Progs", Ci.nsIFile).path;
+    shellServiceMock.enumerateInstallShortcuts.resolves([
+      programsPath + "\\Nightly.lnk",
+    ]);
+
+    await CustomIconManager.maybeCreatePerUserStartMenuShortcut();
+
+    Assert.ok(
+      shellServiceMock.createShortcut.notCalled,
+      "createShortcut not called when a per-user Start Menu shortcut already exists"
+    );
+    Assert.ok(
+      Services.prefs.getBoolPref(
+        PREF_PER_USER_START_MENU_SHORTCUT_CREATED,
+        false
+      ),
+      "the created pref is set once an existing shortcut is found"
+    );
+  }
+);
+
+/**
+ * This test verifies that maybeCreatePerUserStartMenuShortcut() creates a shortcut
+ * in the Programs folder when none is found among the enumerated shortcuts.
+ */
+add_task(
+  skipOnMsix(),
+  async function test_maybeCreatePerUserStartMenuShortcut_creates_shortcut() {
+    resetMocks();
+    // TEST_SHORTCUTS ("C:\\fake\\Desktop\\Nightly.lnk") does not live in
+    // the Programs dir, so the method must create the missing shortcut.
+
+    await CustomIconManager.maybeCreatePerUserStartMenuShortcut();
+
+    Assert.ok(
+      shellServiceMock.createShortcut.calledOnce,
+      "createShortcut called when no per-user Start Menu shortcut exists"
+    );
+    let [exeFile, args, , iconFile, iconIndex, aumid, location, name] =
+      shellServiceMock.createShortcut.getCall(0).args;
+    Assert.equal(
+      exeFile.path,
+      exePath(),
+      "shortcut targets the running executable"
+    );
+    Assert.deepEqual(args, [], "no extra arguments");
+    Assert.equal(iconFile.path, exePath(), "icon source is the executable");
+    Assert.equal(
+      iconIndex,
+      0,
+      "icon index 0 selects the executable's default icon"
+    );
+    Assert.equal(aumid, TEST_AUMID, "shortcut carries the install AUMID");
+    Assert.equal(
+      location,
+      "Programs",
+      "shortcut placed in the Programs location"
+    );
+    Assert.ok(name.endsWith(".lnk"), "shortcut filename ends with .lnk");
+    Assert.ok(
+      Services.prefs.getBoolPref(
+        PREF_PER_USER_START_MENU_SHORTCUT_CREATED,
+        false
+      ),
+      "the created pref is set once the shortcut is successfully created"
+    );
+  }
+);
+
+/**
+ * This test verifies that maybeCreatePerUserStartMenuShortcut() does nothing
+ * when the custom icon feature is disabled.
+ */
+add_task(
+  skipOnMsix(),
+  async function test_maybeCreatePerUserStartMenuShortcut_disabled_feature() {
+    resetMocks();
+    Services.prefs.setBoolPref(PREF_ENABLED, false);
+
+    await CustomIconManager.maybeCreatePerUserStartMenuShortcut();
+
+    Assert.ok(
+      shellServiceMock.createShortcut.notCalled,
+      "createShortcut not called when the feature is disabled"
+    );
+  }
+);
+
+/**
+ * This test verifies that maybeCreatePerUserStartMenuShortcut() is a no-op once
+ * the created pref has already been set by a prior run, even if the user has
+ * since deleted the shortcut.
+ */
+add_task(
+  skipOnMsix(),
+  async function test_maybeCreatePerUserStartMenuShortcut_skips_once_created() {
+    resetMocks();
+    Services.prefs.setBoolPref(PREF_PER_USER_START_MENU_SHORTCUT_CREATED, true);
+
+    await CustomIconManager.maybeCreatePerUserStartMenuShortcut();
+
+    Assert.ok(
+      shellServiceMock.createShortcut.notCalled,
+      "createShortcut not called once the created pref is set"
+    );
+  }
+);
+
+/**
+ * This test verifies that maybeCreatePerUserStartMenuShortcut() does not create
+ * a shortcut when there is no system-wide Start Menu shortcut to mirror.
+ */
+add_task(
+  skipOnMsix(),
+  async function test_maybeCreatePerUserStartMenuShortcut_no_system_wide_shortcut() {
+    resetMocks();
+    hasSystemWideStartMenuShortcutStub.resolves(false);
+
+    await CustomIconManager.maybeCreatePerUserStartMenuShortcut();
+
+    Assert.ok(
+      shellServiceMock.createShortcut.notCalled,
+      "createShortcut not called when there is no system-wide shortcut to mirror"
+    );
+  }
+);
+
+/**
+ * This test verifies that once a per-user shortcut has been successfully
+ * created, a later call does not attempt to create another one.
+ */
+add_task(
+  skipOnMsix(),
+  async function test_maybeCreatePerUserStartMenuShortcut_second_call_is_noop() {
+    resetMocks();
+
+    await CustomIconManager.maybeCreatePerUserStartMenuShortcut();
+    await CustomIconManager.maybeCreatePerUserStartMenuShortcut();
+
+    Assert.ok(
+      shellServiceMock.createShortcut.calledOnce,
+      "the second call does not attempt to recreate a user-deleted shortcut"
+    );
+  }
+);
+
+/**
+ * This test verifies that when enumerateInstallShortcuts rejects,
+ * maybeCreatePerUserStartMenuShortcut() swallows the error and does not attempt
+ * to create a shortcut.
+ */
+add_task(
+  skipOnMsix(),
+  async function test_maybeCreatePerUserStartMenuShortcut_enumeration_failure() {
+    resetMocks();
+    shellServiceMock.enumerateInstallShortcuts.rejects(
+      Components.Exception("mock enum failure", Cr.NS_ERROR_FAILURE)
+    );
+
+    await CustomIconManager.maybeCreatePerUserStartMenuShortcut();
+
+    Assert.ok(
+      shellServiceMock.createShortcut.notCalled,
+      "createShortcut not attempted when enumeration fails"
+    );
+  }
+);
+
+/**
+ * This test verifies that when createShortcut rejects,
+ * maybeCreatePerUserStartMenuShortcut() swallows the error and does not throw.
+ */
+add_task(
+  skipOnMsix(),
+  async function test_maybeCreatePerUserStartMenuShortcut_create_failure() {
+    resetMocks();
+    shellServiceMock.createShortcut.rejects(
+      Components.Exception("mock create failure", Cr.NS_ERROR_FAILURE)
+    );
+
+    await CustomIconManager.maybeCreatePerUserStartMenuShortcut();
+
+    Assert.ok(
+      shellServiceMock.createShortcut.calledOnce,
+      "createShortcut was attempted despite the eventual failure"
+    );
+    Assert.ok(
+      !Services.prefs.getBoolPref(
+        PREF_PER_USER_START_MENU_SHORTCUT_CREATED,
+        false
+      ),
+      "the created pref is left unset after a failed attempt"
+    );
+  }
+);
+
+/**
+ * This test verifies that maybeCreatePerUserStartMenuShortcut() is a no-op on
+ * MSIX (packaged) builds where shortcut creation is unsupported.
+ */
+add_task(
+  { skip_if: () => !ON_MSIX },
+  async function test_maybeCreatePerUserStartMenuShortcut_noop_on_msix() {
+    resetMocks();
+
+    await CustomIconManager.maybeCreatePerUserStartMenuShortcut();
+
+    Assert.ok(
+      shellServiceMock.enumerateInstallShortcuts.notCalled,
+      "no enumeration on MSIX"
+    );
+    Assert.ok(
+      shellServiceMock.createShortcut.notCalled,
+      "no shortcut creation on MSIX"
+    );
+  }
+);
+
+/**
+ * This test verifies that the feature stays enabled while our per-user Start
+ * Menu shortcut is still present: it shadows the system-wide one, so we can
+ * still write the shortcut the taskbar takes its icon from.
+ */
+add_task(skipOnMsix(), async function test_shouldDisable_shortcut_present() {
+  resetMocks();
+  Services.prefs.setBoolPref(PREF_PER_USER_START_MENU_SHORTCUT_CREATED, true);
+  hasSystemWideStartMenuShortcutStub.resolves(true);
+  shellServiceMock.enumerateInstallShortcuts.resolves([
+    Services.dirsvc.get("Progs", Ci.nsIFile).path + "\\Nightly.lnk",
+  ]);
+
+  Assert.ok(
+    !(await CustomIconManager.shouldDisableForMissingShortcut()),
+    "does not disable while the per-user Start Menu shortcut is present"
+  );
+});
+
+/**
+ * This test verifies that once our per-user Start Menu shortcut is gone, the
+ * feature is disabled when the system-wide shortcut governs the taskbar icon,
+ * since that lives in an all-users directory we cannot write.
+ */
+add_task(skipOnMsix(), async function test_shouldDisable_system_wide_governs() {
+  resetMocks();
+  Services.prefs.setBoolPref(PREF_PER_USER_START_MENU_SHORTCUT_CREATED, true);
+  hasSystemWideStartMenuShortcutStub.resolves(true);
+
+  Assert.ok(
+    await CustomIconManager.shouldDisableForMissingShortcut(),
+    "disables when the unwritable system-wide shortcut governs the taskbar"
+  );
+});
+
+/**
+ * This test verifies that a remaining taskbar pin keeps the feature enabled
+ * even alongside a system-wide shortcut, since we can still write the pin.
+ */
+add_task(skipOnMsix(), async function test_shouldDisable_pin_still_writable() {
+  resetMocks();
+  Services.prefs.setBoolPref(PREF_PER_USER_START_MENU_SHORTCUT_CREATED, true);
+  hasSystemWideStartMenuShortcutStub.resolves(true);
+  shellServiceMock.enumerateInstallShortcuts.resolves([pinnedShortcut()]);
+
+  Assert.ok(
+    !(await CustomIconManager.shouldDisableForMissingShortcut()),
+    "does not disable while a writable taskbar pin remains"
+  );
+});
+
+/**
+ * This test verifies that with no system-wide shortcut to take over, the
+ * feature stays enabled: the taskbar falls back to the window icon, which we
+ * set at runtime.
+ */
+add_task(
+  skipOnMsix(),
+  async function test_shouldDisable_window_icon_fallback() {
+    resetMocks();
+    Services.prefs.setBoolPref(PREF_PER_USER_START_MENU_SHORTCUT_CREATED, true);
+    hasSystemWideStartMenuShortcutStub.resolves(false);
+
+    Assert.ok(
+      !(await CustomIconManager.shouldDisableForMissingShortcut()),
+      "does not disable when the taskbar falls back to the window icon"
+    );
+  }
+);
+
+/**
+ * This test verifies that ensureAppliedOrRevert() acts on the decision above
+ * instead of reconciling as usual. With a custom icon recorded but the taskbar
+ * no longer overridable, it turns the feature off.
+ */
+add_task(
+  skipOnMsix(),
+  async function test_ensureAppliedOrRevert_disables_feature() {
+    resetMocks();
+    Services.prefs.setStringPref(PREF_ICON_ID, "retro2004");
+    Services.prefs.setBoolPref(PREF_PER_USER_START_MENU_SHORTCUT_CREATED, true);
+    hasSystemWideStartMenuShortcutStub.resolves(true);
+
+    await CustomIconManager.ensureAppliedOrRevert();
+
+    Assert.ok(
+      !Services.prefs.getBoolPref(PREF_ENABLED, false),
+      "the feature is disabled"
+    );
+    Assert.ok(
+      winTaskbarMock.setAllWindowIcons.calledOnceWithExactly(0),
+      "the runtime icon is reverted to the default rather than applied"
+    );
+    Assert.ok(!Services.prefs.prefHasUserValue(PREF_ICON_ID), "pref cleared");
+  }
+);
+
+/**
+ * This test verifies that refreshTaskbarButtons() delegates to
+ * WinTaskbar.refreshTaskbarButtons().
+ */
+add_task(function test_refreshTaskbarButtons_calls_wintaskbar() {
+  winTaskbarMock.refreshTaskbarButtons.reset();
+
+  CustomIconManager.refreshTaskbarButtons();
+
+  Assert.ok(
+    winTaskbarMock.refreshTaskbarButtons.calledOnce,
+    "refreshTaskbarButtons delegates to WinTaskbar"
+  );
+});
+
+/**
+ * This test verifies that refreshTaskbarButtons() swallows errors thrown by
+ * WinTaskbar.refreshTaskbarButtons() rather than propagating them.
+ */
+add_task(function test_refreshTaskbarButtons_swallows_errors() {
+  winTaskbarMock.refreshTaskbarButtons.reset();
+  winTaskbarMock.refreshTaskbarButtons.throws(
+    Components.Exception("mock failure", Cr.NS_ERROR_FAILURE)
+  );
+
+  CustomIconManager.refreshTaskbarButtons();
+
+  Assert.ok(
+    winTaskbarMock.refreshTaskbarButtons.calledOnce,
+    "refreshTaskbarButtons was attempted"
+  );
+});
diff --git a/src/zen/tests/mochitests/shell/unit/xpcshell.toml b/src/zen/tests/mochitests/shell/unit/xpcshell.toml
index 39bb48115..106c8565a 100644
--- a/src/zen/tests/mochitests/shell/unit/xpcshell.toml
+++ b/src/zen/tests/mochitests/shell/unit/xpcshell.toml
@@ -5,6 +5,11 @@ run-if = [
 firefox-appdir = "browser"
 tags = "os_integration"
 
+["test_customIconManager.js"]
+run-if = [
+  "os == 'win'",
+]
+
 ["test_desktopEntryStatus.js"]
 run-if = [
   "os == 'linux'",
diff --git a/src/zen/tests/mochitests/sync/addon1-search.json b/src/zen/tests/mochitests/sync/addon1-search.json
new file mode 100644
index 000000000..55f8af885
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/addon1-search.json
@@ -0,0 +1,21 @@
+{
+  "next": null,
+  "results": [
+    {
+      "name": "Non-Restartless Test Extension",
+      "type": "extension",
+      "guid": "addon1@tests.mozilla.org",
+      "current_version": {
+        "version": "1.0",
+        "files": [
+          {
+            "platform": "all",
+            "size": 485,
+            "url": "http://127.0.0.1:8888/addon1.xpi"
+          }
+        ]
+      },
+      "last_updated": "2011-09-05T20:42:09Z"
+    }
+  ]
+}
diff --git a/src/zen/tests/mochitests/sync/bootstrap1-search.json b/src/zen/tests/mochitests/sync/bootstrap1-search.json
new file mode 100644
index 000000000..8cd1cf43e
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/bootstrap1-search.json
@@ -0,0 +1,21 @@
+{
+  "next": null,
+  "results": [
+    {
+      "name": "Restartless Test Extension",
+      "type": "extension",
+      "guid": "bootstrap1@tests.mozilla.org",
+      "current_version": {
+        "version": "1.0",
+        "files": [
+          {
+            "platform": "all",
+            "size": 485,
+            "url": "http://127.0.0.1:8888/bootstrap1.xpi"
+          }
+        ]
+      },
+      "last_updated": "2011-09-05T20:42:09Z"
+    }
+  ]
+}
diff --git a/src/zen/tests/mochitests/sync/head_appinfo.js b/src/zen/tests/mochitests/sync/head_appinfo.js
new file mode 100644
index 000000000..79379ccea
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/head_appinfo.js
@@ -0,0 +1,58 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/* import-globals-from ../../../common/tests/unit/head_helpers.js */
+
+var { XPCOMUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/XPCOMUtils.sys.mjs"
+);
+
+// Required to avoid failures.
+do_get_profile();
+
+// Init FormHistoryStartup and pretend we opened a profile.
+var fhs = Cc["@mozilla.org/satchel/form-history-startup;1"].getService(
+  Ci.nsIObserver
+);
+fhs.observe(null, "profile-after-change", null);
+
+// An app is going to have some prefs set which xpcshell tests don't.
+Services.prefs.setStringPref(
+  "identity.sync.tokenserver.uri",
+  "http://token-server"
+);
+
+// Make sure to provide the right OS so crypto loads the right binaries
+function getOS() {
+  switch (mozinfo.os) {
+    case "win":
+      return "WINNT";
+    case "mac":
+      return "Darwin";
+    default:
+      return "Linux";
+  }
+}
+
+const { updateAppInfo } = ChromeUtils.importESModule(
+  "resource://testing-common/AppInfo.sys.mjs"
+);
+updateAppInfo({
+  name: "XPCShell",
+  ID: "xpcshell@tests.mozilla.org",
+  version: "1",
+  platformVersion: "",
+  OS: getOS(),
+});
+
+// Register resource aliases. Normally done in SyncComponents.manifest.
+function addResourceAlias() {
+  const resProt = Services.io
+    .getProtocolHandler("resource")
+    .QueryInterface(Ci.nsIResProtocolHandler);
+  for (let s of ["common", "sync", "crypto"]) {
+    let uri = Services.io.newURI("resource://gre/modules/services-" + s + "/");
+    resProt.setSubstitution("services-" + s, uri);
+  }
+}
+addResourceAlias();
diff --git a/src/zen/tests/mochitests/sync/head_errorhandler_common.js b/src/zen/tests/mochitests/sync/head_errorhandler_common.js
new file mode 100644
index 000000000..fcf44ec43
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/head_errorhandler_common.js
@@ -0,0 +1,195 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/* import-globals-from head_appinfo.js */
+/* import-globals-from ../../../common/tests/unit/head_helpers.js */
+/* import-globals-from head_helpers.js */
+/* import-globals-from head_http_server.js */
+
+// This file expects Service to be defined in the global scope when EHTestsCommon
+// is used (from service.js).
+/* global Service */
+
+var { Changeset, EngineManager, Store, SyncEngine, Tracker, LegacyTracker } =
+  ChromeUtils.importESModule("resource://services-sync/engines.sys.mjs");
+var {
+  ABORT_SYNC_COMMAND,
+  CLIENT_NOT_CONFIGURED,
+  CREDENTIALS_CHANGED,
+  DEFAULT_DOWNLOAD_BATCH_SIZE,
+  DEFAULT_GUID_FETCH_BATCH_SIZE,
+  DEFAULT_KEYBUNDLE_NAME,
+  DEVICE_TYPE_DESKTOP,
+  DEVICE_TYPE_MOBILE,
+  ENGINE_APPLY_FAIL,
+  ENGINE_BATCH_INTERRUPTED,
+  ENGINE_DOWNLOAD_FAIL,
+  ENGINE_SUCCEEDED,
+  ENGINE_UNKNOWN_FAIL,
+  ENGINE_UPLOAD_FAIL,
+  HMAC_EVENT_INTERVAL,
+  IDLE_OBSERVER_BACK_DELAY,
+  LOGIN_FAILED,
+  LOGIN_FAILED_INVALID_PASSPHRASE,
+  LOGIN_FAILED_LOGIN_REJECTED,
+  LOGIN_FAILED_NETWORK_ERROR,
+  LOGIN_FAILED_NO_PASSPHRASE,
+  LOGIN_FAILED_NO_USERNAME,
+  LOGIN_FAILED_SERVER_ERROR,
+  LOGIN_SUCCEEDED,
+  MASTER_PASSWORD_LOCKED,
+  MASTER_PASSWORD_LOCKED_RETRY_INTERVAL,
+  MAXIMUM_BACKOFF_INTERVAL,
+  MAX_ERROR_COUNT_BEFORE_BACKOFF,
+  MAX_HISTORY_DOWNLOAD,
+  MAX_HISTORY_UPLOAD,
+  METARECORD_DOWNLOAD_FAIL,
+  MINIMUM_BACKOFF_INTERVAL,
+  MULTI_DEVICE_THRESHOLD,
+  NO_SYNC_NODE_FOUND,
+  NO_SYNC_NODE_INTERVAL,
+  OVER_QUOTA,
+  PREFS_BRANCH,
+  RESPONSE_OVER_QUOTA,
+  SCORE_INCREMENT_MEDIUM,
+  SCORE_INCREMENT_SMALL,
+  SCORE_INCREMENT_XLARGE,
+  SCORE_UPDATE_DELAY,
+  SERVER_MAINTENANCE,
+  SINGLE_USER_THRESHOLD,
+  SQLITE_MAX_VARIABLE_NUMBER,
+  STATUS_DISABLED,
+  STATUS_OK,
+  STORAGE_VERSION,
+  SYNC_FAILED,
+  SYNC_FAILED_PARTIAL,
+  SYNC_KEY_DECODED_LENGTH,
+  SYNC_KEY_ENCODED_LENGTH,
+  SYNC_SUCCEEDED,
+  URI_LENGTH_MAX,
+  VERSION_OUT_OF_DATE,
+  WEAVE_VERSION,
+  kFirefoxShuttingDown,
+  kFirstSyncChoiceNotMade,
+  kSyncBackoffNotMet,
+  kSyncMasterPasswordLocked,
+  kSyncNetworkOffline,
+  kSyncNotConfigured,
+  kSyncWeaveDisabled,
+} = ChromeUtils.importESModule("resource://services-sync/constants.sys.mjs");
+var { BulkKeyBundle, SyncKeyBundle } = ChromeUtils.importESModule(
+  "resource://services-sync/keys.sys.mjs"
+);
+
+// Common code for test_errorhandler_{1,2}.js -- pulled out to make it less
+// monolithic and take less time to execute.
+const EHTestsCommon = {
+  service_unavailable(request, response) {
+    let body = "Service Unavailable";
+    response.setStatusLine(request.httpVersion, 503, "Service Unavailable");
+    response.setHeader("Retry-After", "42");
+    response.bodyOutputStream.write(body, body.length);
+  },
+
+  async sync_httpd_setup() {
+    let clientsEngine = Service.clientsEngine;
+    let clientsSyncID = await clientsEngine.resetLocalSyncID();
+    let catapultEngine = Service.engineManager.get("catapult");
+    let catapultSyncID = await catapultEngine.resetLocalSyncID();
+    let global = new ServerWBO("global", {
+      syncID: Service.syncID,
+      storageVersion: STORAGE_VERSION,
+      engines: {
+        clients: { version: clientsEngine.version, syncID: clientsSyncID },
+        catapult: { version: catapultEngine.version, syncID: catapultSyncID },
+      },
+    });
+    let clientsColl = new ServerCollection({}, true);
+
+    // Tracking info/collections.
+    let collectionsHelper = track_collections_helper();
+    let upd = collectionsHelper.with_updated_collection;
+
+    let handler_401 = httpd_handler(401, "Unauthorized");
+    return httpd_setup({
+      // Normal server behaviour.
+      "/1.1/johndoe/storage/meta/global": upd("meta", global.handler()),
+      "/1.1/johndoe/info/collections": collectionsHelper.handler,
+      "/1.1/johndoe/storage/crypto/keys": upd(
+        "crypto",
+        new ServerWBO("keys").handler()
+      ),
+      "/1.1/johndoe/storage/clients": upd("clients", clientsColl.handler()),
+
+      // Credentials are wrong or node reallocated.
+      "/1.1/janedoe/storage/meta/global": handler_401,
+      "/1.1/janedoe/info/collections": handler_401,
+
+      // Maintenance or overloaded (503 + Retry-After) at info/collections.
+      "/1.1/broken.info/info/collections": EHTestsCommon.service_unavailable,
+
+      // Maintenance or overloaded (503 + Retry-After) at meta/global.
+      "/1.1/broken.meta/storage/meta/global": EHTestsCommon.service_unavailable,
+      "/1.1/broken.meta/info/collections": collectionsHelper.handler,
+
+      // Maintenance or overloaded (503 + Retry-After) at crypto/keys.
+      "/1.1/broken.keys/storage/meta/global": upd("meta", global.handler()),
+      "/1.1/broken.keys/info/collections": collectionsHelper.handler,
+      "/1.1/broken.keys/storage/crypto/keys": EHTestsCommon.service_unavailable,
+
+      // Maintenance or overloaded (503 + Retry-After) at wiping collection.
+      "/1.1/broken.wipe/info/collections": collectionsHelper.handler,
+      "/1.1/broken.wipe/storage/meta/global": upd("meta", global.handler()),
+      "/1.1/broken.wipe/storage/crypto/keys": upd(
+        "crypto",
+        new ServerWBO("keys").handler()
+      ),
+      "/1.1/broken.wipe/storage": EHTestsCommon.service_unavailable,
+      "/1.1/broken.wipe/storage/clients": upd("clients", clientsColl.handler()),
+      "/1.1/broken.wipe/storage/catapult": EHTestsCommon.service_unavailable,
+    });
+  },
+
+  CatapultEngine: (function () {
+    function CatapultEngine() {
+      SyncEngine.call(this, "Catapult", Service);
+    }
+    CatapultEngine.prototype = {
+      exception: null, // tests fill this in
+      async _sync() {
+        if (this.exception) {
+          throw this.exception;
+        }
+      },
+    };
+    Object.setPrototypeOf(CatapultEngine.prototype, SyncEngine.prototype);
+
+    return CatapultEngine;
+  })(),
+
+  async generateCredentialsChangedFailure() {
+    // Make sync fail due to changed credentials. We simply re-encrypt
+    // the keys with a different Sync Key, without changing the local one.
+    let newSyncKeyBundle = new BulkKeyBundle("crypto");
+    await newSyncKeyBundle.generateRandom();
+    let keys = Service.collectionKeys.asWBO();
+    await keys.encrypt(newSyncKeyBundle);
+    return keys.upload(Service.resource(Service.cryptoKeysURL));
+  },
+
+  async setUp(server) {
+    syncTestLogging();
+    await configureIdentity({ username: "johndoe" }, server);
+    return EHTestsCommon.generateAndUploadKeys();
+  },
+
+  async generateAndUploadKeys() {
+    await generateNewKeys(Service.collectionKeys);
+    let serverKeys = Service.collectionKeys.asWBO("crypto", "keys");
+    await serverKeys.encrypt(Service.identity.syncKeyBundle);
+    let response = await serverKeys.upload(
+      Service.resource(Service.cryptoKeysURL)
+    );
+    return response.success;
+  },
+};
diff --git a/src/zen/tests/mochitests/sync/head_helpers.js b/src/zen/tests/mochitests/sync/head_helpers.js
new file mode 100644
index 000000000..d9383db21
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/head_helpers.js
@@ -0,0 +1,621 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/* import-globals-from head_appinfo.js */
+/* import-globals-from ../../../common/tests/unit/head_helpers.js */
+/* import-globals-from head_errorhandler_common.js */
+/* import-globals-from head_http_server.js */
+
+// This file expects Service to be defined in the global scope when EHTestsCommon
+// is used (from service.js).
+/* global Service */
+
+var { AddonTestUtils, MockAsyncShutdown } = ChromeUtils.importESModule(
+  "resource://testing-common/AddonTestUtils.sys.mjs"
+);
+var { Async } = ChromeUtils.importESModule(
+  "resource://services-common/async.sys.mjs"
+);
+var { CommonUtils } = ChromeUtils.importESModule(
+  "resource://services-common/utils.sys.mjs"
+);
+var { PlacesTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/PlacesTestUtils.sys.mjs"
+);
+var { sinon } = ChromeUtils.importESModule(
+  "resource://testing-common/Sinon.sys.mjs"
+);
+var { SerializableSet, Svc, Utils, getChromeWindow } =
+  ChromeUtils.importESModule("resource://services-sync/util.sys.mjs");
+var { XPCOMUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/XPCOMUtils.sys.mjs"
+);
+var { PlacesUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/PlacesUtils.sys.mjs"
+);
+var { PlacesSyncUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/PlacesSyncUtils.sys.mjs"
+);
+var { ObjectUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/ObjectUtils.sys.mjs"
+);
+var {
+  MockFxaStorageManager,
+  SyncTestingInfrastructure,
+  configureFxAccountIdentity,
+  configureIdentity,
+  encryptPayload,
+  getLoginTelemetryScalar,
+  makeFxAccountsInternalMock,
+  makeIdentityConfig,
+  promiseNamedTimer,
+  promiseZeroTimer,
+  sumHistogram,
+  syncTestLogging,
+  waitForZeroTimer,
+} = ChromeUtils.importESModule(
+  "resource://testing-common/services/sync/utils.sys.mjs"
+);
+ChromeUtils.defineESModuleGetters(this, {
+  AddonManager: "resource://gre/modules/AddonManager.sys.mjs",
+});
+
+add_setup(async function head_setup() {
+  // Initialize logging. This will sometimes be reset by a pref reset,
+  // so it's also called as part of SyncTestingInfrastructure().
+  syncTestLogging();
+  // If a test imports Service, make sure it is initialized first.
+  if (typeof Service !== "undefined") {
+    await Service.promiseInitialized;
+  }
+});
+
+// This is needed for loadAddonTestFunctions().
+var gGlobalScope = this;
+
+function ExtensionsTestPath(path) {
+  if (path[0] != "/") {
+    throw Error("Path must begin with '/': " + path);
+  }
+
+  return "../../../../toolkit/mozapps/extensions/test/xpcshell" + path;
+}
+
+function webExtensionsTestPath(path) {
+  if (path[0] != "/") {
+    throw Error("Path must begin with '/': " + path);
+  }
+
+  return "../../../../toolkit/components/extensions/test/xpcshell" + path;
+}
+
+/**
+ * Loads the WebExtension test functions by importing its test file.
+ */
+function loadWebExtensionTestFunctions() {
+  /* import-globals-from ../../../../toolkit/components/extensions/test/xpcshell/head_sync.js */
+  const path = webExtensionsTestPath("/head_sync.js");
+  let file = do_get_file(path);
+  let uri = Services.io.newFileURI(file);
+  Services.scriptloader.loadSubScript(uri.spec, gGlobalScope);
+}
+
+/**
+ * Installs an add-on from an addonInstall
+ *
+ * @param  install addonInstall instance to install
+ */
+async function installAddonFromInstall(install) {
+  await install.install();
+
+  Assert.notEqual(null, install.addon);
+  Assert.notEqual(null, install.addon.syncGUID);
+
+  return install.addon;
+}
+
+/**
+ * Convenience function to install an add-on from the extensions unit tests.
+ *
+ * @param  file
+ *         Add-on file to install.
+ * @param  reconciler
+ *         addons reconciler, if passed we will wait on the events to be
+ *         processed before resolving
+ * @return addon object that was installed
+ */
+async function installAddon(file, reconciler = null) {
+  let install = await AddonManager.getInstallForFile(file);
+  Assert.notEqual(null, install);
+  const addon = await installAddonFromInstall(install);
+  if (reconciler) {
+    await reconciler.queueCaller.promiseCallsComplete();
+  }
+  return addon;
+}
+
+/**
+ * Convenience function to uninstall an add-on.
+ *
+ * @param addon
+ *        Addon instance to uninstall
+ * @param reconciler
+ *        addons reconciler, if passed we will wait on the events to be
+ *        processed before resolving
+ */
+async function uninstallAddon(addon, reconciler = null) {
+  const uninstallPromise = new Promise(res => {
+    let listener = {
+      onUninstalled(uninstalled) {
+        if (uninstalled.id == addon.id) {
+          AddonManager.removeAddonListener(listener);
+          res(uninstalled);
+        }
+      },
+    };
+    AddonManager.addAddonListener(listener);
+  });
+  addon.uninstall();
+  await uninstallPromise;
+  if (reconciler) {
+    await reconciler.queueCaller.promiseCallsComplete();
+  }
+}
+
+async function generateNewKeys(collectionKeys, collections = null) {
+  let wbo = await collectionKeys.generateNewKeysWBO(collections);
+  let modified = new_timestamp();
+  collectionKeys.setContents(wbo.cleartext, modified);
+}
+
+// Helpers for testing open tabs.
+// These reflect part of the internal structure of TabEngine,
+// and stub part of Service.wm.
+
+function mockGetTabState(tab) {
+  return tab;
+}
+
+function mockGetOrderedNonPrivateWindows(urls) {
+  let tabs = [];
+  let win = {
+    gBrowser: {
+      tabs,
+    },
+  };
+
+  let lastAccessed = 2000;
+  for (let url of urls) {
+    tabs.push({
+      linkedBrowser: {
+        currentURI: Services.io.newURI(url),
+        contentTitle: "title",
+      },
+      lastAccessed,
+    });
+    lastAccessed += 1000;
+  }
+
+  return [win];
+}
+
+// Helper function to get the sync telemetry and add the typically used test
+// engine names to its list of allowed engines.
+function get_sync_test_telemetry() {
+  let { SyncTelemetry } = ChromeUtils.importESModule(
+    "resource://services-sync/telemetry.sys.mjs"
+  );
+  SyncTelemetry.tryRefreshDevices = function () {};
+  let testEngines = ["rotary", "steam", "sterling", "catapult", "nineties"];
+  for (let engineName of testEngines) {
+    SyncTelemetry.allowedEngines.add(engineName);
+  }
+  SyncTelemetry.submissionInterval = -1;
+  return SyncTelemetry;
+}
+
+function assert_valid_ping(record) {
+  if (record && (record.why != "shutdown" || !!record.syncs.length)) {
+    record.syncs.forEach(p => {
+      lessOrEqual(p.when, Date.now());
+    });
+  }
+}
+
+function assert_success_sync(record) {
+  ok(!record.failureReason, JSON.stringify(record.failureReason));
+  equal(undefined, record.status);
+  greater(record.engines.length, 0);
+  for (let e of record.engines) {
+    ok(!e.failureReason);
+    equal(undefined, e.status);
+    if (e.validation) {
+      equal(undefined, e.validation.problems);
+      equal(undefined, e.validation.failureReason);
+    }
+    if (e.outgoing) {
+      for (let o of e.outgoing) {
+        equal(undefined, o.failed);
+        notEqual(undefined, o.sent);
+      }
+    }
+    if (e.incoming) {
+      equal(undefined, e.incoming.failed);
+      equal(undefined, e.incoming.newFailed);
+      notEqual(undefined, e.incoming.applied || e.incoming.reconciled);
+    }
+  }
+}
+
+// Asserts that `ping` is a ping that doesn't contain any failure information
+function assert_success_ping(ping) {
+  ok(!!ping);
+  assert_valid_ping(ping);
+  ping.syncs.forEach(assert_success_sync);
+}
+
+// Hooks into telemetry to validate all pings after calling.
+function validate_all_future_pings() {
+  let telem = get_sync_test_telemetry();
+  telem.submit = assert_valid_ping;
+}
+
+function wait_for_pings(expectedPings) {
+  return new Promise(resolve => {
+    let telem = get_sync_test_telemetry();
+    let oldSubmit = telem.submit;
+    let pings = [];
+    telem.submit = function (record) {
+      pings.push(record);
+      if (pings.length == expectedPings) {
+        telem.submit = oldSubmit;
+        resolve(pings);
+      }
+    };
+  });
+}
+
+async function wait_for_ping(callback, allowErrorPings, getFullPing = false) {
+  let pingsPromise = wait_for_pings(1);
+  await callback();
+  let [record] = await pingsPromise;
+  if (allowErrorPings) {
+    assert_valid_ping(record);
+  } else {
+    assert_success_ping(record);
+  }
+  if (getFullPing) {
+    return record;
+  }
+  equal(record.syncs.length, 1);
+  return record.syncs[0];
+}
+
+// Perform a sync and validate all telemetry caused by the sync. If fnValidate
+// is null, we just check the ping records success. If fnValidate is specified,
+// then the sync must have recorded just a single sync, and that sync will be
+// passed to the function to be checked.
+async function sync_and_validate_telem(
+  fnValidate = null,
+  wantFullPing = false
+) {
+  let numErrors = 0;
+  let telem = get_sync_test_telemetry();
+  let oldSubmit = telem.submit;
+  try {
+    telem.submit = function (record) {
+      // This is called via an observer, so failures here don't cause the test
+      // to fail :(
+      try {
+        // All pings must be valid.
+        assert_valid_ping(record);
+        if (fnValidate) {
+          // for historical reasons most of these callbacks expect a "sync"
+          // record, not the entire ping.
+          if (wantFullPing) {
+            fnValidate(record);
+          } else {
+            Assert.equal(record.syncs.length, 1);
+            fnValidate(record.syncs[0]);
+          }
+        } else {
+          // no validation function means it must be a "success" ping.
+          assert_success_ping(record);
+        }
+      } catch (ex) {
+        print("Failure in ping validation callback", ex, "\n", ex.stack);
+        numErrors += 1;
+      }
+    };
+    await Service.sync();
+    Assert.equal(numErrors, 0, "There were telemetry validation errors");
+  } finally {
+    telem.submit = oldSubmit;
+  }
+}
+
+// Used for the (many) cases where we do a 'partial' sync, where only a single
+// engine is actually synced, but we still want to ensure we're generating a
+// valid ping. Returns a promise that resolves to the ping, or rejects with the
+// thrown error after calling an optional callback.
+async function sync_engine_and_validate_telem(
+  engine,
+  allowErrorPings,
+  onError,
+  wantFullPing = false
+) {
+  let telem = get_sync_test_telemetry();
+  let caughtError = null;
+  // Clear out status, so failures from previous syncs won't show up in the
+  // telemetry ping.
+  let { Status } = ChromeUtils.importESModule(
+    "resource://services-sync/status.sys.mjs"
+  );
+  Status._engines = {};
+  Status.partial = false;
+  // Ideally we'd clear these out like we do with engines, (probably via
+  // Status.resetSync()), but this causes *numerous* tests to fail, so we just
+  // assume that if no failureReason or engine failures are set, and the
+  // status properties are the same as they were initially, that it's just
+  // a leftover.
+  // This is only an issue since we're triggering the sync of just one engine,
+  // without doing any other parts of the sync.
+  let initialServiceStatus = Status._service;
+  let initialSyncStatus = Status._sync;
+
+  let oldSubmit = telem.submit;
+  let submitPromise = new Promise((resolve, reject) => {
+    telem.submit = function (ping) {
+      telem.submit = oldSubmit;
+      ping.syncs.forEach(record => {
+        if (record && record.status) {
+          // did we see anything to lead us to believe that something bad actually happened
+          let realProblem =
+            record.failureReason ||
+            record.engines.some(e => {
+              if (e.failureReason || e.status) {
+                return true;
+              }
+              if (e.outgoing && e.outgoing.some(o => o.failed > 0)) {
+                return true;
+              }
+              return e.incoming && e.incoming.failed;
+            });
+          if (!realProblem) {
+            // no, so if the status is the same as it was initially, just assume
+            // that its leftover and that we can ignore it.
+            if (record.status.sync && record.status.sync == initialSyncStatus) {
+              delete record.status.sync;
+            }
+            if (
+              record.status.service &&
+              record.status.service == initialServiceStatus
+            ) {
+              delete record.status.service;
+            }
+            if (!record.status.sync && !record.status.service) {
+              delete record.status;
+            }
+          }
+        }
+      });
+      if (allowErrorPings) {
+        assert_valid_ping(ping);
+      } else {
+        assert_success_ping(ping);
+      }
+      equal(ping.syncs.length, 1);
+      if (caughtError) {
+        if (onError) {
+          onError(ping.syncs[0], ping);
+        }
+        reject(caughtError);
+      } else if (wantFullPing) {
+        resolve(ping);
+      } else {
+        resolve(ping.syncs[0]);
+      }
+    };
+  });
+  // neuter the scheduler as it interacts badly with some of the tests - the
+  // engine being synced usually isn't the registered engine, so we see
+  // scored incremented and not removed, which schedules unexpected syncs.
+  let oldObserve = Service.scheduler.observe;
+  Service.scheduler.observe = () => {};
+  try {
+    Svc.Obs.notify("weave:service:sync:start");
+    try {
+      await engine.sync();
+    } catch (e) {
+      caughtError = e;
+    }
+    if (caughtError) {
+      Svc.Obs.notify("weave:service:sync:error", caughtError);
+    } else {
+      Svc.Obs.notify("weave:service:sync:finish");
+    }
+  } finally {
+    Service.scheduler.observe = oldObserve;
+  }
+  return submitPromise;
+}
+
+// Returns a promise that resolves once the specified observer notification
+// has fired.
+function promiseOneObserver(topic) {
+  return new Promise(resolve => {
+    let observer = function (subject, data) {
+      Svc.Obs.remove(topic, observer);
+      resolve({ subject, data });
+    };
+    Svc.Obs.add(topic, observer);
+  });
+}
+
+async function registerRotaryEngine() {
+  let { RotaryEngine } = ChromeUtils.importESModule(
+    "resource://testing-common/services/sync/rotaryengine.sys.mjs"
+  );
+  await Service.engineManager.clear();
+
+  await Service.engineManager.register(RotaryEngine);
+  let engine = Service.engineManager.get("rotary");
+  let syncID = await engine.resetLocalSyncID();
+  engine.enabled = true;
+
+  return { engine, syncID, tracker: engine._tracker };
+}
+
+// Set the validation prefs to attempt validation every time to avoid non-determinism.
+function enableValidationPrefs(engines = ["bookmarks"]) {
+  for (let engine of engines) {
+    Svc.PrefBranch.setIntPref(`engine.${engine}.validation.interval`, 0);
+    Svc.PrefBranch.setIntPref(
+      `engine.${engine}.validation.percentageChance`,
+      100
+    );
+    Svc.PrefBranch.setIntPref(`engine.${engine}.validation.maxRecords`, -1);
+    Svc.PrefBranch.setBoolPref(`engine.${engine}.validation.enabled`, true);
+  }
+}
+
+async function serverForEnginesWithKeys(users, engines, callback) {
+  // Generate and store a fake default key bundle to avoid resetting the client
+  // before the first sync.
+  let wbo = await Service.collectionKeys.generateNewKeysWBO();
+  let modified = new_timestamp();
+  Service.collectionKeys.setContents(wbo.cleartext, modified);
+
+  let allEngines = [Service.clientsEngine].concat(engines);
+
+  let globalEngines = {};
+  for (let engine of allEngines) {
+    let syncID = await engine.resetLocalSyncID();
+    globalEngines[engine.name] = { version: engine.version, syncID };
+  }
+
+  let contents = {
+    meta: {
+      global: {
+        syncID: Service.syncID,
+        storageVersion: STORAGE_VERSION,
+        engines: globalEngines,
+      },
+    },
+    crypto: {
+      keys: encryptPayload(wbo.cleartext),
+    },
+  };
+  for (let engine of allEngines) {
+    contents[engine.name] = {};
+  }
+
+  return serverForUsers(users, contents, callback);
+}
+
+async function serverForFoo(engine, callback) {
+  // The bookmarks engine *always* tracks changes, meaning we might try
+  // and sync due to the bookmarks we ourselves create! Worse, because we
+  // do an engine sync only, there's no locking - so we end up with multiple
+  // syncs running. Neuter that by making the threshold very large.
+  Service.scheduler.syncThreshold = 10000000;
+  return serverForEnginesWithKeys({ foo: "password" }, engine, callback);
+}
+
+// Places notifies history observers asynchronously, so `addVisits` might return
+// before the tracker receives the notification. This helper registers an
+// observer that resolves once the expected notification fires.
+async function promiseVisit(expectedType, expectedURI) {
+  return new Promise(resolve => {
+    function done(type, uri) {
+      if (uri == expectedURI.spec && type == expectedType) {
+        PlacesObservers.removeListener(
+          ["page-visited", "page-removed"],
+          observer.handlePlacesEvents
+        );
+        resolve();
+      }
+    }
+    let observer = {
+      handlePlacesEvents(events) {
+        Assert.equal(events.length, 1);
+
+        if (events[0].type === "page-visited") {
+          done("added", events[0].url);
+        } else if (events[0].type === "page-removed") {
+          Assert.ok(events[0].isRemovedFromStore);
+          done("removed", events[0].url);
+        }
+      },
+    };
+    PlacesObservers.addListener(
+      ["page-visited", "page-removed"],
+      observer.handlePlacesEvents
+    );
+  });
+}
+
+async function addVisit(
+  suffix,
+  referrer = null,
+  transition = PlacesUtils.history.TRANSITION_LINK
+) {
+  let uriString = "http://getfirefox.com/" + suffix;
+  let uri = CommonUtils.makeURI(uriString);
+  _("Adding visit for URI " + uriString);
+
+  let visitAddedPromise = promiseVisit("added", uri);
+  await PlacesTestUtils.addVisits({
+    uri,
+    visitDate: Date.now() * 1000,
+    transition,
+    referrer,
+  });
+  await visitAddedPromise;
+
+  return uri;
+}
+
+function bookmarkNodesToInfos(nodes) {
+  return nodes.map(node => {
+    let info = {
+      guid: node.guid,
+      index: node.index,
+    };
+    if (node.children) {
+      info.children = bookmarkNodesToInfos(node.children);
+    }
+    return info;
+  });
+}
+
+async function assertBookmarksTreeMatches(rootGuid, expected, message) {
+  let root = await PlacesUtils.promiseBookmarksTree(rootGuid, {
+    includeItemIds: true,
+  });
+  let actual = bookmarkNodesToInfos(root.children);
+
+  if (!ObjectUtils.deepEqual(actual, expected)) {
+    _(`Expected structure for ${rootGuid}`, JSON.stringify(expected));
+    _(`Actual structure for ${rootGuid}`, JSON.stringify(actual));
+    throw new Assert.constructor.AssertionError({ actual, expected, message });
+  }
+}
+
+function add_bookmark_test(task) {
+  const { BookmarksEngine } = ChromeUtils.importESModule(
+    "resource://services-sync/engines/bookmarks.sys.mjs"
+  );
+
+  add_task(async function () {
+    _(`Running bookmarks test ${task.name}`);
+    let engine = new BookmarksEngine(Service);
+    await engine.initialize();
+    await engine._resetClient();
+    try {
+      await task(engine);
+    } finally {
+      await engine.finalize();
+    }
+  });
+}
diff --git a/src/zen/tests/mochitests/sync/head_http_server.js b/src/zen/tests/mochitests/sync/head_http_server.js
new file mode 100644
index 000000000..35ea77203
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/head_http_server.js
@@ -0,0 +1,1268 @@
+/* import-globals-from head_appinfo.js */
+/* import-globals-from ../../../common/tests/unit/head_helpers.js */
+/* import-globals-from head_helpers.js */
+
+var Cm = Components.manager;
+
+// Shared logging for all HTTP server functions.
+var { Log } = ChromeUtils.importESModule("resource://gre/modules/Log.sys.mjs");
+var { CommonUtils } = ChromeUtils.importESModule(
+  "resource://services-common/utils.sys.mjs"
+);
+var { TestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/TestUtils.sys.mjs"
+);
+var {
+  MockFxaStorageManager,
+  SyncTestingInfrastructure,
+  configureFxAccountIdentity,
+  configureIdentity,
+  encryptPayload,
+  getLoginTelemetryScalar,
+  makeFxAccountsInternalMock,
+  makeIdentityConfig,
+  promiseNamedTimer,
+  promiseZeroTimer,
+  sumHistogram,
+  syncTestLogging,
+  waitForZeroTimer,
+} = ChromeUtils.importESModule(
+  "resource://testing-common/services/sync/utils.sys.mjs"
+);
+
+const SYNC_HTTP_LOGGER = "Sync.Test.Server";
+
+// While the sync code itself uses 1.5, the tests hard-code 1.1,
+// so we're sticking with 1.1 here.
+const SYNC_API_VERSION = "1.1";
+
+// Use the same method that record.js does, which mirrors the server.
+// The server returns timestamps with 1/100 sec granularity. Note that this is
+// subject to change: see Bug 650435.
+function new_timestamp() {
+  return round_timestamp(Date.now());
+}
+
+// Rounds a millisecond timestamp `t` to seconds, with centisecond precision.
+function round_timestamp(t) {
+  return Math.round(t / 10) / 100;
+}
+
+function return_timestamp(request, response, timestamp) {
+  if (!timestamp) {
+    timestamp = new_timestamp();
+  }
+  let body = "" + timestamp;
+  response.setHeader("X-Weave-Timestamp", body);
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  writeBytesToOutputStream(response.bodyOutputStream, body);
+  return timestamp;
+}
+
+function has_hawk_header(req) {
+  return (
+    req.hasHeader("Authorization") &&
+    req.getHeader("Authorization").startsWith("Hawk")
+  );
+}
+
+function basic_auth_header(user, password) {
+  return "Basic " + btoa(user + ":" + CommonUtils.encodeUTF8(password));
+}
+
+function basic_auth_matches(req, user, password) {
+  if (!req.hasHeader("Authorization")) {
+    return false;
+  }
+
+  let expected = basic_auth_header(user, CommonUtils.encodeUTF8(password));
+  return req.getHeader("Authorization") == expected;
+}
+
+function httpd_basic_auth_handler(body, metadata, response) {
+  if (basic_auth_matches(metadata, "guest", "guest")) {
+    response.setStatusLine(metadata.httpVersion, 200, "OK, authorized");
+    response.setHeader("WWW-Authenticate", 'Basic realm="secret"', false);
+  } else {
+    body = "This path exists and is protected - failed";
+    response.setStatusLine(metadata.httpVersion, 401, "Unauthorized");
+    response.setHeader("WWW-Authenticate", 'Basic realm="secret"', false);
+  }
+  writeBytesToOutputStream(response.bodyOutputStream, body);
+}
+
+/*
+ * Represent a WBO on the server
+ */
+function ServerWBO(id, initialPayload, modified) {
+  if (!id) {
+    throw new Error("No ID for ServerWBO!");
+  }
+  this.id = id;
+  if (!initialPayload) {
+    return;
+  }
+
+  if (typeof initialPayload == "object") {
+    initialPayload = JSON.stringify(initialPayload);
+  }
+  this.payload = initialPayload;
+  this.modified = modified || new_timestamp();
+  this.sortindex = 0;
+}
+ServerWBO.prototype = {
+  get data() {
+    return JSON.parse(this.payload);
+  },
+
+  get() {
+    return { id: this.id, modified: this.modified, payload: this.payload };
+  },
+
+  put(input) {
+    input = JSON.parse(input);
+    this.payload = input.payload;
+    this.modified = new_timestamp();
+    this.sortindex = input.sortindex || 0;
+  },
+
+  delete() {
+    delete this.payload;
+    delete this.modified;
+    delete this.sortindex;
+  },
+
+  // This handler sets `newModified` on the response body if the collection
+  // timestamp has changed. This allows wrapper handlers to extract information
+  // that otherwise would exist only in the body stream.
+  handler() {
+    let self = this;
+
+    return function (request, response) {
+      var statusCode = 200;
+      var status = "OK";
+      var body;
+
+      switch (request.method) {
+        case "GET":
+          if (self.payload) {
+            body = JSON.stringify(self.get());
+          } else {
+            statusCode = 404;
+            status = "Not Found";
+            body = "Not Found";
+          }
+          break;
+
+        case "PUT":
+          self.put(readBytesFromInputStream(request.bodyInputStream));
+          body = JSON.stringify(self.modified);
+          response.setHeader("Content-Type", "application/json");
+          response.newModified = self.modified;
+          break;
+
+        case "DELETE": {
+          self.delete();
+          let ts = new_timestamp();
+          body = JSON.stringify(ts);
+          response.setHeader("Content-Type", "application/json");
+          response.newModified = ts;
+          break;
+        }
+      }
+      response.setHeader("X-Weave-Timestamp", "" + new_timestamp(), false);
+      response.setStatusLine(request.httpVersion, statusCode, status);
+      writeBytesToOutputStream(response.bodyOutputStream, body);
+    };
+  },
+
+  /**
+   * Get the cleartext data stored in the payload.
+   *
+   * This isn't `get cleartext`, because `x.cleartext.blah = 3;` wouldn't work,
+   * which seems like a footgun.
+   */
+  getCleartext() {
+    return JSON.parse(JSON.parse(this.payload).ciphertext);
+  },
+
+  /**
+   * Setter for getCleartext(), but lets you adjust the modified timestamp too.
+   * Returns this ServerWBO object.
+   */
+  setCleartext(cleartext, modifiedTimestamp = this.modified) {
+    this.payload = JSON.stringify(encryptPayload(cleartext));
+    this.modified = modifiedTimestamp;
+    return this;
+  },
+};
+
+/**
+ * Represent a collection on the server. The '_wbos' attribute is a
+ * mapping of id -> ServerWBO objects.
+ *
+ * Note that if you want these records to be accessible individually,
+ * you need to register their handlers with the server separately, or use a
+ * containing HTTP server that will do so on your behalf.
+ *
+ * @param wbos
+ *        An object mapping WBO IDs to ServerWBOs.
+ * @param acceptNew
+ *        If true, POSTs to this collection URI will result in new WBOs being
+ *        created and wired in on the fly.
+ * @param timestamp
+ *        An optional timestamp value to initialize the modified time of the
+ *        collection. This should be in the format returned by new_timestamp().
+ *
+ * @return the new ServerCollection instance.
+ */
+function ServerCollection(wbos, acceptNew, timestamp) {
+  this._wbos = wbos || {};
+  this.acceptNew = acceptNew || false;
+
+  /*
+   * Track modified timestamp.
+   * We can't just use the timestamps of contained WBOs: an empty collection
+   * has a modified time.
+   */
+  this.timestamp = timestamp || new_timestamp();
+  this._log = Log.repository.getLogger(SYNC_HTTP_LOGGER);
+}
+ServerCollection.prototype = {
+  /**
+   * Convenience accessor for our WBO keys.
+   * Excludes deleted items, of course.
+   *
+   * @param filter
+   *        A predicate function (applied to the ID and WBO) which dictates
+   *        whether to include the WBO's ID in the output.
+   *
+   * @return an array of IDs.
+   */
+  keys: function keys(filter) {
+    let ids = [];
+    for (let [id, wbo] of Object.entries(this._wbos)) {
+      if (wbo.payload && (!filter || filter(id, wbo))) {
+        ids.push(id);
+      }
+    }
+    return ids;
+  },
+
+  /**
+   * Convenience method to get an array of WBOs.
+   * Optionally provide a filter function.
+   *
+   * @param filter
+   *        A predicate function, applied to the WBO, which dictates whether to
+   *        include the WBO in the output.
+   *
+   * @return an array of ServerWBOs.
+   */
+  wbos: function wbos(filter) {
+    let os = [];
+    for (let wbo of Object.values(this._wbos)) {
+      if (wbo.payload) {
+        os.push(wbo);
+      }
+    }
+
+    if (filter) {
+      return os.filter(filter);
+    }
+    return os;
+  },
+
+  /**
+   * Convenience method to get an array of parsed ciphertexts.
+   *
+   * @return an array of the payloads of each stored WBO.
+   */
+  payloads() {
+    return this.wbos().map(wbo => wbo.getCleartext());
+  },
+
+  // Just for syntactic elegance.
+  wbo: function wbo(id) {
+    return this._wbos[id];
+  },
+
+  payload: function payload(id) {
+    return this.wbo(id).payload;
+  },
+
+  cleartext(id) {
+    return this.wbo(id).getCleartext();
+  },
+
+  /**
+   * Insert the provided WBO under its ID.
+   *
+   * @return the provided WBO.
+   */
+  insertWBO: function insertWBO(wbo) {
+    this.timestamp = Math.max(this.timestamp, wbo.modified);
+    return (this._wbos[wbo.id] = wbo);
+  },
+
+  /**
+   * Update an existing WBO's cleartext using a callback function that modifies
+   * the record in place, or returns a new record.
+   */
+  updateRecord(id, updateCallback, optTimestamp) {
+    let wbo = this.wbo(id);
+    if (!wbo) {
+      throw new Error("No record with provided ID");
+    }
+    let curCleartext = wbo.getCleartext();
+    // Allow update callback to either return a new cleartext, or modify in place.
+    let newCleartext = updateCallback(curCleartext) || curCleartext;
+    wbo.setCleartext(newCleartext, optTimestamp);
+    // It is already inserted, but we might need to update our timestamp based
+    // on it's `modified` value, if `optTimestamp` was provided.
+    return this.insertWBO(wbo);
+  },
+
+  /**
+   * Insert a record, which may either an object with a cleartext property, or
+   * the cleartext property itself.
+   */
+  insertRecord(record, timestamp = Math.round(Date.now() / 10) / 100) {
+    if (typeof timestamp != "number") {
+      throw new TypeError("insertRecord: Timestamp is not a number.");
+    }
+    if (!record.id) {
+      throw new Error("Attempt to insert record with no id");
+    }
+    // Allow providing either the cleartext directly, or the CryptoWrapper-like.
+    let cleartext = record.cleartext || record;
+    return this.insert(record.id, encryptPayload(cleartext), timestamp);
+  },
+
+  /**
+   * Insert the provided payload as part of a new ServerWBO with the provided
+   * ID.
+   *
+   * @param id
+   *        The GUID for the WBO.
+   * @param payload
+   *        The payload, as provided to the ServerWBO constructor.
+   * @param modified
+   *        An optional modified time for the ServerWBO.
+   *
+   * @return the inserted WBO.
+   */
+  insert: function insert(id, payload, modified) {
+    return this.insertWBO(new ServerWBO(id, payload, modified));
+  },
+
+  /**
+   * Removes an object entirely from the collection.
+   *
+   * @param id
+   *        (string) ID to remove.
+   */
+  remove: function remove(id) {
+    delete this._wbos[id];
+  },
+
+  _inResultSet(wbo, options) {
+    return (
+      wbo.payload &&
+      (!options.ids || options.ids.includes(wbo.id)) &&
+      (!options.newer || wbo.modified > options.newer) &&
+      (!options.older || wbo.modified < options.older)
+    );
+  },
+
+  count(options) {
+    options = options || {};
+    let c = 0;
+    for (let wbo of Object.values(this._wbos)) {
+      if (wbo.modified && this._inResultSet(wbo, options)) {
+        c++;
+      }
+    }
+    return c;
+  },
+
+  get(options, request) {
+    let data = [];
+    for (let wbo of Object.values(this._wbos)) {
+      if (wbo.modified && this._inResultSet(wbo, options)) {
+        data.push(wbo);
+      }
+    }
+    switch (options.sort) {
+      case "newest":
+        data.sort((a, b) => b.modified - a.modified);
+        break;
+
+      case "oldest":
+        data.sort((a, b) => a.modified - b.modified);
+        break;
+
+      case "index":
+        data.sort((a, b) => b.sortindex - a.sortindex);
+        break;
+
+      default:
+        if (options.sort) {
+          this._log.error(
+            "Error: client requesting unknown sort order",
+            options.sort
+          );
+          throw new Error("Unknown sort order");
+        }
+        // If the client didn't request a sort order, shuffle the records
+        // to ensure that we don't accidentally depend on the default order.
+        TestUtils.shuffle(data);
+    }
+    if (options.full) {
+      data = data.map(wbo => wbo.get());
+      let start = options.offset || 0;
+      if (options.limit) {
+        let numItemsPastOffset = data.length - start;
+        data = data.slice(start, start + options.limit);
+        // use options as a backchannel to set x-weave-next-offset
+        if (numItemsPastOffset > options.limit) {
+          options.nextOffset = start + options.limit;
+        }
+      } else if (start) {
+        data = data.slice(start);
+      }
+
+      if (request && request.getHeader("accept") == "application/newlines") {
+        this._log.error(
+          "Error: client requesting application/newlines content"
+        );
+        throw new Error(
+          "This server should not serve application/newlines content"
+        );
+      }
+
+      // Use options as a backchannel to report count.
+      options.recordCount = data.length;
+    } else {
+      data = data.map(wbo => wbo.id);
+      let start = options.offset || 0;
+      if (options.limit) {
+        data = data.slice(start, start + options.limit);
+        options.nextOffset = start + options.limit;
+      } else if (start) {
+        data = data.slice(start);
+      }
+      options.recordCount = data.length;
+    }
+    return JSON.stringify(data);
+  },
+
+  post(input) {
+    input = JSON.parse(input);
+    let success = [];
+    let failed = {};
+
+    // This will count records where we have an existing ServerWBO
+    // registered with us as successful and all other records as failed.
+    for (let key in input) {
+      let record = input[key];
+      let wbo = this.wbo(record.id);
+      if (!wbo && this.acceptNew) {
+        this._log.debug(
+          "Creating WBO " + JSON.stringify(record.id) + " on the fly."
+        );
+        wbo = new ServerWBO(record.id);
+        this.insertWBO(wbo);
+      }
+      if (wbo) {
+        wbo.payload = record.payload;
+        wbo.modified = new_timestamp();
+        wbo.sortindex = record.sortindex || 0;
+        success.push(record.id);
+      } else {
+        failed[record.id] = "no wbo configured";
+      }
+    }
+    return { modified: new_timestamp(), success, failed };
+  },
+
+  delete(options) {
+    let deleted = [];
+    for (let wbo of Object.values(this._wbos)) {
+      if (this._inResultSet(wbo, options)) {
+        this._log.debug("Deleting " + JSON.stringify(wbo));
+        deleted.push(wbo.id);
+        wbo.delete();
+      }
+    }
+    return deleted;
+  },
+
+  // This handler sets `newModified` on the response body if the collection
+  // timestamp has changed.
+  handler() {
+    let self = this;
+
+    return function (request, response) {
+      var statusCode = 200;
+      var status = "OK";
+      var body;
+
+      // Parse queryString
+      let options = {};
+      for (let chunk of request.queryString.split("&")) {
+        if (!chunk) {
+          continue;
+        }
+        chunk = chunk.split("=");
+        if (chunk.length == 1) {
+          options[chunk[0]] = "";
+        } else {
+          options[chunk[0]] = chunk[1];
+        }
+      }
+      // The real servers return 400 if ids= is specified without a list of IDs.
+      if (options.hasOwnProperty("ids")) {
+        if (!options.ids) {
+          response.setStatusLine(request.httpVersion, "400", "Bad Request");
+          body = "Bad Request";
+          writeBytesToOutputStream(response.bodyOutputStream, body);
+          return;
+        }
+        options.ids = options.ids.split(",");
+      }
+      if (options.newer) {
+        options.newer = parseFloat(options.newer);
+      }
+      if (options.older) {
+        options.older = parseFloat(options.older);
+      }
+      if (options.limit) {
+        options.limit = parseInt(options.limit, 10);
+      }
+      if (options.offset) {
+        options.offset = parseInt(options.offset, 10);
+      }
+
+      switch (request.method) {
+        case "GET": {
+          body = self.get(options, request);
+          // see http://moz-services-docs.readthedocs.io/en/latest/storage/apis-1.5.html
+          // for description of these headers.
+          let { recordCount: records, nextOffset } = options;
+
+          self._log.info("Records: " + records + ", nextOffset: " + nextOffset);
+          if (records != null) {
+            response.setHeader("X-Weave-Records", "" + records);
+          }
+          if (nextOffset) {
+            response.setHeader("X-Weave-Next-Offset", "" + nextOffset);
+          }
+          response.setHeader("X-Last-Modified", "" + self.timestamp);
+          break;
+        }
+
+        case "POST": {
+          let res = self.post(
+            readBytesFromInputStream(request.bodyInputStream),
+            request
+          );
+          body = JSON.stringify(res);
+          response.newModified = res.modified;
+          break;
+        }
+
+        case "DELETE": {
+          self._log.debug("Invoking ServerCollection.DELETE.");
+          let deleted = self.delete(options, request);
+          let ts = new_timestamp();
+          body = JSON.stringify(ts);
+          response.newModified = ts;
+          response.deleted = deleted;
+          break;
+        }
+      }
+      response.setHeader("X-Weave-Timestamp", "" + new_timestamp(), false);
+
+      // Update the collection timestamp to the appropriate modified time.
+      // This is either a value set by the handler, or the current time.
+      if (request.method != "GET") {
+        self.timestamp =
+          response.newModified >= 0 ? response.newModified : new_timestamp();
+      }
+      response.setHeader("X-Last-Modified", "" + self.timestamp, false);
+
+      response.setStatusLine(request.httpVersion, statusCode, status);
+      writeBytesToOutputStream(response.bodyOutputStream, body);
+    };
+  },
+};
+
+/*
+ * Test setup helpers.
+ */
+function sync_httpd_setup(handlers) {
+  handlers["/1.1/foo/storage/meta/global"] = new ServerWBO(
+    "global",
+    {}
+  ).handler();
+  return httpd_setup(handlers);
+}
+
+/*
+ * Track collection modified times. Return closures.
+ *
+ * XXX - DO NOT USE IN NEW TESTS
+ *
+ * This code has very limited and very hacky timestamp support - the test
+ * server now has more complete and correct support - using this helper
+ * may cause strangeness wrt timestamp headers and 412 responses.
+ */
+function track_collections_helper() {
+  /*
+   * Our tracking object.
+   */
+  let collections = {};
+
+  /*
+   * Update the timestamp of a collection.
+   */
+  function update_collection(coll, ts) {
+    _("Updating collection " + coll + " to " + ts);
+    let timestamp = ts || new_timestamp();
+    collections[coll] = timestamp;
+  }
+
+  /*
+   * Invoke a handler, updating the collection's modified timestamp unless
+   * it's a GET request.
+   */
+  function with_updated_collection(coll, f) {
+    return function (request, response) {
+      f.call(this, request, response);
+
+      // Update the collection timestamp to the appropriate modified time.
+      // This is either a value set by the handler, or the current time.
+      if (request.method != "GET") {
+        update_collection(coll, response.newModified);
+      }
+    };
+  }
+
+  /*
+   * Return the info/collections object.
+   */
+  function info_collections(request, response) {
+    let body = "Error.";
+    switch (request.method) {
+      case "GET":
+        body = JSON.stringify(collections);
+        break;
+      default:
+        throw new Error("Non-GET on info_collections.");
+    }
+
+    response.setHeader("Content-Type", "application/json");
+    response.setHeader("X-Weave-Timestamp", "" + new_timestamp(), false);
+    response.setStatusLine(request.httpVersion, 200, "OK");
+    writeBytesToOutputStream(response.bodyOutputStream, body);
+  }
+
+  return {
+    collections,
+    handler: info_collections,
+    with_updated_collection,
+    update_collection,
+  };
+}
+
+// ===========================================================================//
+// httpd.js-based Sync server.                                               //
+// ===========================================================================//
+
+/**
+ * In general, the preferred way of using SyncServer is to directly introspect
+ * it. Callbacks are available for operations which are hard to verify through
+ * introspection, such as deletions.
+ *
+ * One of the goals of this server is to provide enough hooks for test code to
+ * find out what it needs without monkeypatching. Use this object as your
+ * prototype, and override as appropriate.
+ */
+var SyncServerCallback = {
+  onCollectionDeleted: function onCollectionDeleted() {},
+  onItemDeleted: function onItemDeleted() {},
+
+  /**
+   * Called at the top of every request.
+   *
+   * Allows the test to inspect the request. Hooks should be careful not to
+   * modify or change state of the request or they may impact future processing.
+   * The response is also passed so the callback can set headers etc - but care
+   * must be taken to not screw with the response body or headers that may
+   * conflict with normal operation of this server.
+   */
+  onRequest: function onRequest() {},
+};
+
+/**
+ * Construct a new test Sync server. Takes a callback object (e.g.,
+ * SyncServerCallback) as input.
+ */
+function SyncServer(callback) {
+  this.callback = callback || Object.create(SyncServerCallback);
+  this.server = new HttpServer();
+  this.started = false;
+  this.users = {};
+  this._log = Log.repository.getLogger(SYNC_HTTP_LOGGER);
+
+  // Install our own default handler. This allows us to mess around with the
+  // whole URL space.
+  let handler = this.server._handler;
+  handler._handleDefault = this.handleDefault.bind(this, handler);
+}
+SyncServer.prototype = {
+  server: null, // HttpServer.
+  users: null, // Map of username => {collections, password}.
+
+  /**
+   * Start the SyncServer's underlying HTTP server.
+   *
+   * @param port
+   *        The numeric port on which to start. -1 implies the default, a
+   *        randomly chosen port.
+   * @param cb
+   *        A callback function (of no arguments) which is invoked after
+   *        startup.
+   */
+  start: function start(port = -1, cb) {
+    if (this.started) {
+      this._log.warn("Warning: server already started on " + this.port);
+      return;
+    }
+    try {
+      this.server.start(port);
+      let i = this.server.identity;
+      this.port = i.primaryPort;
+      this.baseURI =
+        i.primaryScheme + "://" + i.primaryHost + ":" + i.primaryPort + "/";
+      this.started = true;
+      if (cb) {
+        cb();
+      }
+    } catch (ex) {
+      _("==========================================");
+      _("Got exception starting Sync HTTP server.");
+      _("Error: " + Log.exceptionStr(ex));
+      _("Is there a process already listening on port " + port + "?");
+      _("==========================================");
+      do_throw(ex);
+    }
+  },
+
+  /**
+   * Stop the SyncServer's HTTP server.
+   *
+   * @param cb
+   *        A callback function. Invoked after the server has been stopped.
+   */
+  stop: function stop(cb) {
+    if (!this.started) {
+      this._log.warn(
+        "SyncServer: Warning: server not running. Can't stop me now!"
+      );
+      return;
+    }
+
+    this.server.stop(cb);
+    this.started = false;
+  },
+
+  /**
+   * Return a server timestamp for a record.
+   * The server returns timestamps with 1/100 sec granularity. Note that this is
+   * subject to change: see Bug 650435.
+   */
+  timestamp: function timestamp() {
+    return new_timestamp();
+  },
+
+  /**
+   * Create a new user, complete with an empty set of collections.
+   *
+   * @param username
+   *        The username to use. An Error will be thrown if a user by that name
+   *        already exists.
+   * @param password
+   *        A password string.
+   *
+   * @return a user object, as would be returned by server.user(username).
+   */
+  registerUser: function registerUser(username, password) {
+    if (username in this.users) {
+      throw new Error("User already exists.");
+    }
+    this.users[username] = {
+      password,
+      collections: {},
+    };
+    return this.user(username);
+  },
+
+  userExists: function userExists(username) {
+    return username in this.users;
+  },
+
+  getCollection: function getCollection(username, collection) {
+    return this.users[username].collections[collection];
+  },
+
+  _insertCollection: function _insertCollection(collections, collection, wbos) {
+    let coll = new ServerCollection(wbos, true);
+    coll.collectionHandler = coll.handler();
+    collections[collection] = coll;
+    return coll;
+  },
+
+  createCollection: function createCollection(username, collection, wbos) {
+    if (!(username in this.users)) {
+      throw new Error("Unknown user.");
+    }
+    let collections = this.users[username].collections;
+    if (collection in collections) {
+      throw new Error("Collection already exists.");
+    }
+    return this._insertCollection(collections, collection, wbos);
+  },
+
+  /**
+   * Accept a map like the following:
+   * {
+   *   meta: {global: {version: 1, ...}},
+   *   crypto: {"keys": {}, foo: {bar: 2}},
+   *   bookmarks: {}
+   * }
+   * to cause collections and WBOs to be created.
+   * If a collection already exists, no error is raised.
+   * If a WBO already exists, it will be updated to the new contents.
+   */
+  createContents: function createContents(username, collections) {
+    if (!(username in this.users)) {
+      throw new Error("Unknown user.");
+    }
+    let userCollections = this.users[username].collections;
+    for (let [id, contents] of Object.entries(collections)) {
+      let coll =
+        userCollections[id] || this._insertCollection(userCollections, id);
+      for (let [wboID, payload] of Object.entries(contents)) {
+        coll.insert(wboID, payload);
+      }
+    }
+  },
+
+  /**
+   * Insert a WBO in an existing collection.
+   */
+  insertWBO: function insertWBO(username, collection, wbo) {
+    if (!(username in this.users)) {
+      throw new Error("Unknown user.");
+    }
+    let userCollections = this.users[username].collections;
+    if (!(collection in userCollections)) {
+      throw new Error("Unknown collection.");
+    }
+    userCollections[collection].insertWBO(wbo);
+    return wbo;
+  },
+
+  /**
+   * Delete all of the collections for the named user.
+   *
+   * @param username
+   *        The name of the affected user.
+   *
+   * @return a timestamp.
+   */
+  deleteCollections: function deleteCollections(username) {
+    if (!(username in this.users)) {
+      throw new Error("Unknown user.");
+    }
+    let userCollections = this.users[username].collections;
+    for (let name in userCollections) {
+      let coll = userCollections[name];
+      this._log.trace("Bulk deleting " + name + " for " + username + "...");
+      coll.delete({});
+    }
+    this.users[username].collections = {};
+    return this.timestamp();
+  },
+
+  /**
+   * Simple accessor to allow collective binding and abbreviation of a bunch of
+   * methods. Yay!
+   * Use like this:
+   *
+   *   let u = server.user("john");
+   *   u.collection("bookmarks").wbo("abcdefg").payload;  // Etc.
+   *
+   * @return a proxy for the user data stored in this server.
+   */
+  user: function user(username) {
+    let collection = this.getCollection.bind(this, username);
+    let createCollection = this.createCollection.bind(this, username);
+    let createContents = this.createContents.bind(this, username);
+    let modified = function (collectionName) {
+      return collection(collectionName).timestamp;
+    };
+    let deleteCollections = this.deleteCollections.bind(this, username);
+    return {
+      collection,
+      createCollection,
+      createContents,
+      deleteCollections,
+      modified,
+    };
+  },
+
+  /*
+   * Regular expressions for splitting up Sync request paths.
+   * Sync URLs are of the form:
+   *   /$apipath/$version/$user/$further
+   * where $further is usually:
+   *   storage/$collection/$wbo
+   * or
+   *   storage/$collection
+   * or
+   *   info/$op
+   * We assume for the sake of simplicity that $apipath is empty.
+   *
+   * N.B., we don't follow any kind of username spec here, because as far as I
+   * can tell there isn't one. See Bug 689671. Instead we follow the Python
+   * server code.
+   *
+   * Path: [all, version, username, first, rest]
+   * Storage: [all, collection?, id?]
+   */
+  pathRE:
+    /^\/([0-9]+(?:\.[0-9]+)?)\/([-._a-zA-Z0-9]+)(?:\/([^\/]+)(?:\/(.+))?)?$/,
+  storageRE: /^([-_a-zA-Z0-9]+)(?:\/([-_a-zA-Z0-9]+)\/?)?$/,
+
+  defaultHeaders: {},
+
+  /**
+   * HTTP response utility.
+   */
+  respond: function respond(req, resp, code, status, body, headers) {
+    resp.setStatusLine(req.httpVersion, code, status);
+    if (!headers) {
+      headers = this.defaultHeaders;
+    }
+    for (let header in headers) {
+      let value = headers[header];
+      resp.setHeader(header, value);
+    }
+    resp.setHeader("X-Weave-Timestamp", "" + this.timestamp(), false);
+    writeBytesToOutputStream(resp.bodyOutputStream, body);
+  },
+
+  /**
+   * This is invoked by the HttpServer. `this` is bound to the SyncServer;
+   * `handler` is the HttpServer's handler.
+   *
+   * TODO: need to use the correct Sync API response codes and errors here.
+   * TODO: Basic Auth.
+   * TODO: check username in path against username in BasicAuth.
+   */
+  handleDefault: function handleDefault(handler, req, resp) {
+    try {
+      this._handleDefault(handler, req, resp);
+    } catch (e) {
+      if (e instanceof HttpError) {
+        this.respond(req, resp, e.code, e.description, "", {});
+      } else {
+        throw e;
+      }
+    }
+  },
+
+  _handleDefault: function _handleDefault(handler, req, resp) {
+    this._log.debug(
+      "SyncServer: Handling request: " + req.method + " " + req.path
+    );
+
+    if (this.callback.onRequest) {
+      this.callback.onRequest(req, resp);
+    }
+
+    let parts = this.pathRE.exec(req.path);
+    if (!parts) {
+      this._log.debug("SyncServer: Unexpected request: bad URL " + req.path);
+      throw HTTP_404;
+    }
+
+    let [, version, username, first, rest] = parts;
+    // Doing a float compare of the version allows for us to pretend there was
+    // a node-reassignment - eg, we could re-assign from "1.1/user/" to
+    // "1.10/user" - this server will then still accept requests with the new
+    // URL while any code in sync itself which compares URLs will see a
+    // different URL.
+    if (parseFloat(version) != parseFloat(SYNC_API_VERSION)) {
+      this._log.debug("SyncServer: Unknown version.");
+      throw HTTP_404;
+    }
+
+    if (!this.userExists(username)) {
+      this._log.debug("SyncServer: Unknown user.");
+      throw HTTP_401;
+    }
+
+    // Hand off to the appropriate handler for this path component.
+    if (first in this.toplevelHandlers) {
+      let newHandler = this.toplevelHandlers[first];
+      return newHandler.call(
+        this,
+        newHandler,
+        req,
+        resp,
+        version,
+        username,
+        rest
+      );
+    }
+    this._log.debug("SyncServer: Unknown top-level " + first);
+    throw HTTP_404;
+  },
+
+  /**
+   * Compute the object that is returned for an info/collections request.
+   */
+  infoCollections: function infoCollections(username) {
+    let responseObject = {};
+    let colls = this.users[username].collections;
+    for (let coll in colls) {
+      responseObject[coll] = colls[coll].timestamp;
+    }
+    this._log.trace(
+      "SyncServer: info/collections returning " + JSON.stringify(responseObject)
+    );
+    return responseObject;
+  },
+
+  /**
+   * Collection of the handler methods we use for top-level path components.
+   */
+  toplevelHandlers: {
+    storage: function handleStorage(
+      handler,
+      req,
+      resp,
+      version,
+      username,
+      rest
+    ) {
+      let respond = this.respond.bind(this, req, resp);
+      if (!rest || !rest.length) {
+        this._log.debug(
+          "SyncServer: top-level storage " + req.method + " request."
+        );
+
+        // TODO: verify if this is spec-compliant.
+        if (req.method != "DELETE") {
+          respond(405, "Method Not Allowed", "[]", { Allow: "DELETE" });
+          return undefined;
+        }
+
+        // Delete all collections and track the timestamp for the response.
+        let timestamp = this.user(username).deleteCollections();
+
+        // Return timestamp and OK for deletion.
+        respond(200, "OK", JSON.stringify(timestamp));
+        return undefined;
+      }
+
+      let match = this.storageRE.exec(rest);
+      if (!match) {
+        this._log.warn("SyncServer: Unknown storage operation " + rest);
+        throw HTTP_404;
+      }
+      let [, collection, wboID] = match;
+      let coll = this.getCollection(username, collection);
+
+      let checkXIUSFailure = () => {
+        if (req.hasHeader("x-if-unmodified-since")) {
+          let xius = parseFloat(req.getHeader("x-if-unmodified-since"));
+          // Sadly the way our tests are setup, we often end up with xius of
+          // zero (typically when syncing just one engine, so the date from
+          // info/collections isn't used) - so we allow that to work.
+          // Further, the Python server treats non-existing collections as
+          // having a timestamp of 0.
+          let collTimestamp = coll ? coll.timestamp : 0;
+          if (xius && xius < collTimestamp) {
+            this._log.info(
+              `x-if-unmodified-since mismatch - request wants ${xius} but our collection has ${collTimestamp}`
+            );
+            respond(412, "precondition failed", "precondition failed");
+            return true;
+          }
+        }
+        return false;
+      };
+
+      switch (req.method) {
+        case "GET": {
+          if (!coll) {
+            if (wboID) {
+              respond(404, "Not found", "Not found");
+              return undefined;
+            }
+            // *cries inside*: - apparently the real sync server returned 200
+            // here for some time, then returned 404 for some time (bug 687299),
+            // and now is back to 200 (bug 963332).
+            respond(200, "OK", "[]");
+            return undefined;
+          }
+          if (!wboID) {
+            return coll.collectionHandler(req, resp);
+          }
+          let wbo = coll.wbo(wboID);
+          if (!wbo) {
+            respond(404, "Not found", "Not found");
+            return undefined;
+          }
+          return wbo.handler()(req, resp);
+        }
+        case "DELETE": {
+          if (!coll) {
+            respond(200, "OK", "{}");
+            return undefined;
+          }
+          if (checkXIUSFailure()) {
+            return undefined;
+          }
+          if (wboID) {
+            let wbo = coll.wbo(wboID);
+            if (wbo) {
+              wbo.delete();
+              this.callback.onItemDeleted(username, collection, wboID);
+            }
+            respond(200, "OK", "{}");
+            return undefined;
+          }
+          coll.collectionHandler(req, resp);
+
+          // Spot if this is a DELETE for some IDs, and don't blow away the
+          // whole collection!
+          //
+          // We already handled deleting the WBOs by invoking the deleted
+          // collection's handler. However, in the case of
+          //
+          //   DELETE storage/foobar
+          //
+          // we also need to remove foobar from the collections map. This
+          // clause tries to differentiate the above request from
+          //
+          //  DELETE storage/foobar?ids=foo,baz
+          //
+          // and do the right thing.
+          // TODO: less hacky method.
+          if (-1 == req.queryString.indexOf("ids=")) {
+            // When you delete the entire collection, we drop it.
+            this._log.debug("Deleting entire collection.");
+            delete this.users[username].collections[collection];
+            this.callback.onCollectionDeleted(username, collection);
+          }
+
+          // Notify of item deletion.
+          let deleted = resp.deleted || [];
+          for (let i = 0; i < deleted.length; ++i) {
+            this.callback.onItemDeleted(username, collection, deleted[i]);
+          }
+          return undefined;
+        }
+        case "PUT":
+          // PUT and POST have slightly different XIUS semantics - for PUT,
+          // the check is against the item, whereas for POST it is against
+          // the collection. So first, a special-case for PUT.
+          if (req.hasHeader("x-if-unmodified-since")) {
+            let xius = parseFloat(req.getHeader("x-if-unmodified-since"));
+            // treat and xius of zero as if it wasn't specified - this happens
+            // in some of our tests for a new collection.
+            if (xius > 0) {
+              let wbo = coll.wbo(wboID);
+              if (xius < wbo.modified) {
+                this._log.info(
+                  `x-if-unmodified-since mismatch - request wants ${xius} but wbo has ${wbo.modified}`
+                );
+                respond(412, "precondition failed", "precondition failed");
+                return undefined;
+              }
+              wbo.handler()(req, resp);
+              coll.timestamp = resp.newModified;
+              return resp;
+            }
+          }
+        // fall through to post.
+        case "POST":
+          if (checkXIUSFailure()) {
+            return undefined;
+          }
+          if (!coll) {
+            coll = this.createCollection(username, collection);
+          }
+
+          if (wboID) {
+            let wbo = coll.wbo(wboID);
+            if (!wbo) {
+              this._log.trace(
+                "SyncServer: creating WBO " + collection + "/" + wboID
+              );
+              wbo = coll.insert(wboID);
+            }
+            // Rather than instantiate each WBO's handler function, do it once
+            // per request. They get hit far less often than do collections.
+            wbo.handler()(req, resp);
+            coll.timestamp = resp.newModified;
+            return resp;
+          }
+          return coll.collectionHandler(req, resp);
+        default:
+          throw new Error("Request method " + req.method + " not implemented.");
+      }
+    },
+
+    info: function handleInfo(handler, req, resp, version, username, rest) {
+      switch (rest) {
+        case "collections": {
+          let body = JSON.stringify(this.infoCollections(username));
+          this.respond(req, resp, 200, "OK", body, {
+            "Content-Type": "application/json",
+          });
+          return;
+        }
+        case "collection_usage":
+        case "collection_counts":
+        case "quota":
+          // TODO: implement additional info methods.
+          this.respond(req, resp, 200, "OK", "TODO");
+          return;
+        default:
+          // TODO
+          this._log.warn("SyncServer: Unknown info operation " + rest);
+          throw HTTP_404;
+      }
+    },
+  },
+};
+
+/**
+ * Test helper.
+ */
+function serverForUsers(users, contents, callback) {
+  let server = new SyncServer(callback);
+  for (let [user, pass] of Object.entries(users)) {
+    server.registerUser(user, pass);
+    server.createContents(user, contents);
+  }
+  server.start();
+  return server;
+}
diff --git a/src/zen/tests/mochitests/sync/missing-sourceuri.json b/src/zen/tests/mochitests/sync/missing-sourceuri.json
new file mode 100644
index 000000000..dcd487726
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/missing-sourceuri.json
@@ -0,0 +1,20 @@
+{
+  "next": null,
+  "results": [
+    {
+      "name": "Restartless Test Extension",
+      "type": "extension",
+      "guid": "missing-sourceuri@tests.mozilla.org",
+      "current_version": {
+        "version": "1.0",
+        "files": [
+          {
+            "platform": "all",
+            "size": 485
+          }
+        ]
+      },
+      "last_updated": "2011-09-05T20:42:09Z"
+    }
+  ]
+}
diff --git a/src/zen/tests/mochitests/sync/missing-xpi-search.json b/src/zen/tests/mochitests/sync/missing-xpi-search.json
new file mode 100644
index 000000000..55f6432b2
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/missing-xpi-search.json
@@ -0,0 +1,21 @@
+{
+  "next": null,
+  "results": [
+    {
+      "name": "Non-Restartless Test Extension",
+      "type": "extension",
+      "guid": "missing-xpi@tests.mozilla.org",
+      "current_version": {
+        "version": "1.0",
+        "files": [
+          {
+            "platform": "all",
+            "size": 485,
+            "url": "http://127.0.0.1:8888/THIS_DOES_NOT_EXIST.xpi"
+          }
+        ]
+      },
+      "last_updated": "2011-09-05T20:42:09Z"
+    }
+  ]
+}
diff --git a/src/zen/tests/mochitests/sync/prefs_test_prefs_store.js b/src/zen/tests/mochitests/sync/prefs_test_prefs_store.js
new file mode 100644
index 000000000..63851a693
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/prefs_test_prefs_store.js
@@ -0,0 +1,47 @@
+// This is a "preferences" file used by test_prefs_store.js
+
+/* global pref, user_pref */
+
+// The prefs that control what should be synced.
+// Most of these are "default" prefs, so the value itself will not sync.
+pref("services.sync.prefs.sync.testing.int", true);
+pref("services.sync.prefs.sync.testing.string", true);
+pref("services.sync.prefs.sync.testing.bool", true);
+pref("services.sync.prefs.sync.testing.dont.change", true);
+// This is a default pref, but has the special "sync-seen" pref.
+pref("services.sync.prefs.sync.testing.seen", true);
+pref("services.sync.prefs.sync-seen.testing.seen", false);
+
+// this one is a user pref, so it *will* sync.
+user_pref("services.sync.prefs.sync.testing.turned.off", false);
+pref("services.sync.prefs.sync.testing.nonexistent", true);
+pref("services.sync.prefs.sync.testing.default", true);
+pref("services.sync.prefs.sync.testing.synced.url", true);
+// We shouldn't sync the URL, or the flag that says we should sync the pref
+// (otherwise some other client might overwrite our local value).
+user_pref("services.sync.prefs.sync.testing.unsynced.url", true);
+
+// The preference values - these are all user_prefs, otherwise their value
+// will not be synced.
+user_pref("testing.int", 123);
+user_pref("testing.string", "ohai");
+user_pref("testing.bool", true);
+user_pref("testing.dont.change", "Please don't change me.");
+user_pref("testing.turned.off", "I won't get synced.");
+user_pref("testing.not.turned.on", "I won't get synced either!");
+// Some url we don't want to sync
+user_pref(
+  "testing.unsynced.url",
+  "moz-extension://d5d31b00-b944-4afb-bd3d-d0326551a0ae"
+);
+user_pref("testing.synced.url", "https://www.example.com");
+
+// A pref that exists but still has the default value - will be synced with
+// null as the value.
+pref("testing.default", "I'm the default value");
+
+// A pref that has the default value - it will start syncing as soon as
+// we see a change, even if the change is to the default.
+pref("testing.seen", "the value");
+
+// A pref that shouldn't be synced
diff --git a/src/zen/tests/mochitests/sync/rewrite-search.json b/src/zen/tests/mochitests/sync/rewrite-search.json
new file mode 100644
index 000000000..740b6f2c3
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/rewrite-search.json
@@ -0,0 +1,21 @@
+{
+  "next": null,
+  "results": [
+    {
+      "name": "Rewrite Test Extension",
+      "type": "extension",
+      "guid": "rewrite@tests.mozilla.org",
+      "current_version": {
+        "version": "1.0",
+        "files": [
+          {
+            "platform": "all",
+            "size": 485,
+            "url": "http://127.0.0.1:8888/require.xpi?src=api"
+          }
+        ]
+      },
+      "last_updated": "2011-09-05T20:42:09Z"
+    }
+  ]
+}
diff --git a/src/zen/tests/mochitests/sync/systemaddon-search.json b/src/zen/tests/mochitests/sync/systemaddon-search.json
new file mode 100644
index 000000000..a81271491
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/systemaddon-search.json
@@ -0,0 +1,21 @@
+{
+  "next": null,
+  "results": [
+    {
+      "name": "System Add-on Test",
+      "type": "extension",
+      "guid": "system1@tests.mozilla.org",
+      "current_version": {
+        "version": "1.0",
+        "files": [
+          {
+            "platform": "all",
+            "size": 999,
+            "url": "http://127.0.0.1:8888/system.xpi"
+          }
+        ]
+      },
+      "last_updated": "2011-09-05T20:42:09Z"
+    }
+  ]
+}
diff --git a/src/zen/tests/mochitests/sync/test_412.js b/src/zen/tests/mochitests/sync/test_412.js
new file mode 100644
index 000000000..de0a2c087
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_412.js
@@ -0,0 +1,60 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { RotaryEngine } = ChromeUtils.importESModule(
+  "resource://testing-common/services/sync/rotaryengine.sys.mjs"
+);
+
+add_task(async function test_412_not_treated_as_failure() {
+  await Service.engineManager.register(RotaryEngine);
+  let engine = Service.engineManager.get("rotary");
+
+  let server = await serverForFoo(engine);
+
+  await SyncTestingInfrastructure(server);
+  await generateNewKeys(Service.collectionKeys);
+
+  // add an item to the server to the first sync advances lastModified.
+  let collection = server.getCollection("foo", "rotary");
+  let payload = encryptPayload({
+    id: "existing",
+    something: "existing record",
+  });
+  collection.insert("existing", payload);
+
+  let promiseObserved = promiseOneObserver("weave:engine:sync:finish");
+  try {
+    // Do sync.
+    _("initial sync to initialize the world");
+    await Service.sync();
+
+    // create a new record that should be uploaded and arrange for our lastSync
+    // timestamp to be wrong so we get a 412.
+    engine._store.items = { new: "new record" };
+    await engine._tracker.addChangedID("new", 0);
+
+    let saw412 = false;
+    let _uploadOutgoing = engine._uploadOutgoing;
+    engine._uploadOutgoing = async () => {
+      let lastSync = await engine.getLastSync();
+      await engine.setLastSync(lastSync - 2);
+      try {
+        await _uploadOutgoing.call(engine);
+      } catch (ex) {
+        saw412 = ex.status == 412;
+        throw ex;
+      }
+    };
+    _("Second sync - expecting a 412");
+    await Service.sync();
+    await promiseObserved;
+    ok(saw412, "did see a 412 error");
+    // But service status should be OK as the 412 shouldn't be treated as an error.
+    equal(Service.status.service, STATUS_OK);
+  } finally {
+    await promiseStopServer(server);
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_addon_utils.js b/src/zen/tests/mochitests/sync/test_addon_utils.js
new file mode 100644
index 000000000..e9e49fb9e
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_addon_utils.js
@@ -0,0 +1,156 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { AddonUtils } = ChromeUtils.importESModule(
+  "resource://services-sync/addonutils.sys.mjs"
+);
+
+const HTTP_PORT = 8888;
+const SERVER_ADDRESS = "http://127.0.0.1:8888";
+
+Services.prefs.setStringPref(
+  "extensions.getAddons.get.url",
+  SERVER_ADDRESS + "/search/guid:%IDS%"
+);
+
+AddonTestUtils.init(this);
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "1.9.2"
+);
+
+add_task(async function setup() {
+  await AddonTestUtils.promiseStartupManager();
+});
+
+function createAndStartHTTPServer(port = HTTP_PORT) {
+  try {
+    let server = new HttpServer();
+
+    server.registerFile(
+      "/search/guid:missing-sourceuri%40tests.mozilla.org",
+      do_get_file("missing-sourceuri.json")
+    );
+
+    server.registerFile(
+      "/search/guid:rewrite%40tests.mozilla.org",
+      do_get_file("rewrite-search.json")
+    );
+
+    server.start(port);
+
+    return server;
+  } catch (ex) {
+    _("Got exception starting HTTP server on port " + port);
+    _("Error: " + Log.exceptionStr(ex));
+    do_throw(ex);
+  }
+  return null; /* not hit, but keeps eslint happy! */
+}
+
+function run_test() {
+  syncTestLogging();
+
+  run_next_test();
+}
+
+add_task(async function test_handle_empty_source_uri() {
+  _("Ensure that search results without a sourceURI are properly ignored.");
+
+  let server = createAndStartHTTPServer();
+
+  const ID = "missing-sourceuri@tests.mozilla.org";
+
+  const result = await AddonUtils.installAddons([
+    { id: ID, requireSecureURI: false },
+  ]);
+
+  Assert.ok("installedIDs" in result);
+  Assert.equal(0, result.installedIDs.length);
+
+  Assert.ok("skipped" in result);
+  Assert.ok(result.skipped.includes(ID));
+
+  await promiseStopServer(server);
+});
+
+add_test(function test_ignore_untrusted_source_uris() {
+  _("Ensures that source URIs from insecure schemes are rejected.");
+
+  const bad = [
+    "http://example.com/foo.xpi",
+    "ftp://example.com/foo.xpi",
+    "silly://example.com/foo.xpi",
+  ];
+
+  const good = ["https://example.com/foo.xpi"];
+
+  for (let s of bad) {
+    let sourceURI = Services.io.newURI(s);
+    let addon = { sourceURI, name: "bad", id: "bad" };
+
+    let canInstall = AddonUtils.canInstallAddon(addon);
+    Assert.ok(!canInstall, "Correctly rejected a bad URL");
+  }
+
+  for (let s of good) {
+    let sourceURI = Services.io.newURI(s);
+    let addon = { sourceURI, name: "good", id: "good" };
+
+    let canInstall = AddonUtils.canInstallAddon(addon);
+    Assert.ok(canInstall, "Correctly accepted a good URL");
+  }
+  run_next_test();
+});
+
+add_task(async function test_source_uri_rewrite() {
+  _("Ensure that a 'src=api' query string is rewritten to 'src=sync'");
+
+  // This tests for conformance with bug 708134 so server-side metrics aren't
+  // skewed.
+
+  // We resort to monkeypatching because of the API design.
+  let oldFunction =
+    Object.getPrototypeOf(AddonUtils).installAddonFromSearchResult;
+
+  let installCalled = false;
+  Object.getPrototypeOf(AddonUtils).installAddonFromSearchResult =
+    async function testInstallAddon(addon) {
+      Assert.equal(
+        SERVER_ADDRESS + "/require.xpi?src=sync",
+        addon.sourceURI.spec
+      );
+
+      installCalled = true;
+
+      const install = await AddonUtils.getInstallFromSearchResult(addon);
+      Assert.equal(
+        SERVER_ADDRESS + "/require.xpi?src=sync",
+        install.sourceURI.spec
+      );
+      Assert.deepEqual(
+        install.installTelemetryInfo,
+        { source: "sync" },
+        "Got the expected installTelemetryInfo"
+      );
+
+      return { id: addon.id, addon, install };
+    };
+
+  let server = createAndStartHTTPServer();
+
+  let installOptions = {
+    id: "rewrite@tests.mozilla.org",
+    requireSecureURI: false,
+  };
+  await AddonUtils.installAddons([installOptions]);
+
+  Assert.ok(installCalled);
+  Object.getPrototypeOf(AddonUtils).installAddonFromSearchResult = oldFunction;
+
+  await promiseStopServer(server);
+});
diff --git a/src/zen/tests/mochitests/sync/test_addons_engine.js b/src/zen/tests/mochitests/sync/test_addons_engine.js
new file mode 100644
index 000000000..8c7b4ecc3
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_addons_engine.js
@@ -0,0 +1,277 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { AddonManager } = ChromeUtils.importESModule(
+  "resource://gre/modules/AddonManager.sys.mjs"
+);
+const { CHANGE_INSTALLED } = ChromeUtils.importESModule(
+  "resource://services-sync/addonsreconciler.sys.mjs"
+);
+const { AddonsEngine } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/addons.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+Services.prefs.setStringPref(
+  "extensions.getAddons.get.url",
+  "http://localhost:8888/search/guid:%IDS%"
+);
+Services.prefs.setBoolPref("extensions.install.requireSecureOrigin", false);
+
+let engine;
+let syncID;
+let reconciler;
+let tracker;
+
+AddonTestUtils.init(this);
+
+const ADDON_ID = "addon1@tests.mozilla.org";
+const XPI = AddonTestUtils.createTempWebExtensionFile({
+  manifest: {
+    name: "Test 1",
+    description: "Test Description",
+    browser_specific_settings: { gecko: { id: ADDON_ID } },
+  },
+});
+
+async function resetReconciler() {
+  reconciler._addons = {};
+  reconciler._changes = [];
+
+  await reconciler.saveState();
+
+  await tracker.clearChangedIDs();
+}
+
+add_task(async function setup() {
+  AddonTestUtils.createAppInfo(
+    "xpcshell@tests.mozilla.org",
+    "XPCShell",
+    "1",
+    "1.9.2"
+  );
+  AddonTestUtils.overrideCertDB();
+  await AddonTestUtils.promiseStartupManager();
+
+  await Service.engineManager.register(AddonsEngine);
+  engine = Service.engineManager.get("addons");
+  syncID = await engine.resetLocalSyncID();
+  reconciler = engine._reconciler;
+  tracker = engine._tracker;
+
+  reconciler.startListening();
+
+  // Don't flush to disk in the middle of an event listener!
+  // This causes test hangs on WinXP.
+  reconciler._shouldPersist = false;
+
+  await resetReconciler();
+});
+
+// This is a basic sanity test for the unit test itself. If this breaks, the
+// add-ons API likely changed upstream.
+add_task(async function test_addon_install() {
+  _("Ensure basic add-on APIs work as expected.");
+
+  let install = await AddonManager.getInstallForFile(XPI);
+  Assert.notEqual(install, null);
+  Assert.equal(install.type, "extension");
+  Assert.equal(install.name, "Test 1");
+
+  await resetReconciler();
+});
+
+add_task(async function test_find_dupe() {
+  _("Ensure the _findDupe() implementation is sane.");
+
+  // This gets invoked at the top of sync, which is bypassed by this
+  // test, so we do it manually.
+  await engine._refreshReconcilerState();
+
+  let addon = await installAddon(XPI, reconciler);
+
+  let record = {
+    id: Utils.makeGUID(),
+    addonID: ADDON_ID,
+    enabled: true,
+    applicationID: Services.appinfo.ID,
+    source: "amo",
+  };
+
+  let dupe = await engine._findDupe(record);
+  Assert.equal(addon.syncGUID, dupe);
+
+  record.id = addon.syncGUID;
+  dupe = await engine._findDupe(record);
+  Assert.equal(null, dupe);
+
+  await uninstallAddon(addon, reconciler);
+  await resetReconciler();
+});
+
+add_task(async function test_get_changed_ids() {
+  let timerPrecision = Services.prefs.getBoolPref(
+    "privacy.reduceTimerPrecision"
+  );
+  Services.prefs.setBoolPref("privacy.reduceTimerPrecision", false);
+
+  registerCleanupFunction(function () {
+    Services.prefs.setBoolPref("privacy.reduceTimerPrecision", timerPrecision);
+  });
+
+  _("Ensure getChangedIDs() has the appropriate behavior.");
+
+  _("Ensure getChangedIDs() returns an empty object by default.");
+  let changes = await engine.getChangedIDs();
+  Assert.equal("object", typeof changes);
+  Assert.equal(0, Object.keys(changes).length);
+
+  _("Ensure tracker changes are populated.");
+  let now = new Date();
+  let changeTime = now.getTime() / 1000;
+  let guid1 = Utils.makeGUID();
+  await tracker.addChangedID(guid1, changeTime);
+
+  changes = await engine.getChangedIDs();
+  Assert.equal("object", typeof changes);
+  Assert.equal(1, Object.keys(changes).length);
+  Assert.ok(guid1 in changes);
+  Assert.equal(changeTime, changes[guid1]);
+
+  await tracker.clearChangedIDs();
+
+  _("Ensure reconciler changes are populated.");
+  let addon = await installAddon(XPI, reconciler);
+  await tracker.clearChangedIDs(); // Just in case.
+  changes = await engine.getChangedIDs();
+  Assert.equal("object", typeof changes);
+  Assert.equal(1, Object.keys(changes).length);
+  Assert.ok(addon.syncGUID in changes);
+  _(
+    "Change time: " + changeTime + ", addon change: " + changes[addon.syncGUID]
+  );
+  Assert.greaterOrEqual(changes[addon.syncGUID], changeTime);
+
+  let oldTime = changes[addon.syncGUID];
+  let guid2 = addon.syncGUID;
+  await uninstallAddon(addon, reconciler);
+  changes = await engine.getChangedIDs();
+  Assert.equal(1, Object.keys(changes).length);
+  Assert.ok(guid2 in changes);
+  Assert.greater(changes[guid2], oldTime);
+
+  _("Ensure non-syncable add-ons aren't picked up by reconciler changes.");
+  reconciler._addons = {};
+  reconciler._changes = [];
+  let record = {
+    id: "DUMMY",
+    guid: Utils.makeGUID(),
+    enabled: true,
+    installed: true,
+    modified: new Date(),
+    type: "UNSUPPORTED",
+    scope: 0,
+    foreignInstall: false,
+  };
+  reconciler.addons.DUMMY = record;
+  await reconciler._addChange(record.modified, CHANGE_INSTALLED, record);
+
+  changes = await engine.getChangedIDs();
+  _(JSON.stringify(changes));
+  Assert.equal(0, Object.keys(changes).length);
+
+  await resetReconciler();
+});
+
+add_task(async function test_disabled_install_semantics() {
+  _("Ensure that syncing a disabled add-on preserves proper state.");
+
+  // This is essentially a test for bug 712542, which snuck into the original
+  // add-on sync drop. It ensures that when an add-on is installed that the
+  // disabled state and incoming syncGUID is preserved, even on the next sync.
+  const USER = "foo";
+  const PASSWORD = "password";
+
+  let server = new SyncServer();
+  server.start();
+  await SyncTestingInfrastructure(server, USER, PASSWORD);
+
+  await generateNewKeys(Service.collectionKeys);
+
+  let contents = {
+    meta: {
+      global: { engines: { addons: { version: engine.version, syncID } } },
+    },
+    crypto: {},
+    addons: {},
+  };
+
+  server.registerUser(USER, "password");
+  server.createContents(USER, contents);
+
+  let amoServer = new HttpServer();
+  amoServer.registerFile(
+    "/search/guid:addon1%40tests.mozilla.org",
+    do_get_file("addon1-search.json")
+  );
+
+  amoServer.registerFile("/addon1.xpi", XPI);
+  amoServer.start(8888);
+
+  // Insert an existing record into the server.
+  let id = Utils.makeGUID();
+  let now = Date.now() / 1000;
+
+  let record = encryptPayload({
+    id,
+    applicationID: Services.appinfo.ID,
+    addonID: ADDON_ID,
+    enabled: false,
+    deleted: false,
+    source: "amo",
+  });
+  let wbo = new ServerWBO(id, record, now - 2);
+  server.insertWBO(USER, "addons", wbo);
+
+  _("Performing sync of add-ons engine.");
+  await engine._sync();
+
+  // At this point the non-restartless extension should be staged for install.
+
+  // Don't need this server any more.
+  await promiseStopServer(amoServer);
+
+  // We ensure the reconciler has recorded the proper ID and enabled state.
+  let addon = reconciler.getAddonStateFromSyncGUID(id);
+  Assert.notEqual(null, addon);
+  Assert.equal(false, addon.enabled);
+
+  // We fake an app restart and perform another sync, just to make sure things
+  // are sane.
+  await AddonTestUtils.promiseRestartManager();
+
+  let collection = server.getCollection(USER, "addons");
+  engine.lastModified = collection.timestamp;
+  await engine._sync();
+
+  // The client should not upload a new record. The old record should be
+  // retained and unmodified.
+  Assert.equal(1, collection.count());
+
+  let payload = collection.payloads()[0];
+  Assert.notEqual(null, collection.wbo(id));
+  Assert.equal(ADDON_ID, payload.addonID);
+  Assert.ok(!payload.enabled);
+
+  await promiseStopServer(server);
+});
+
+add_test(function cleanup() {
+  // There's an xpcom-shutdown hook for this, but let's give this a shot.
+  reconciler.stopListening();
+  run_next_test();
+});
diff --git a/src/zen/tests/mochitests/sync/test_addons_reconciler.js b/src/zen/tests/mochitests/sync/test_addons_reconciler.js
new file mode 100644
index 000000000..c72b18b00
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_addons_reconciler.js
@@ -0,0 +1,209 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { AddonsReconciler, CHANGE_INSTALLED, CHANGE_UNINSTALLED } =
+  ChromeUtils.importESModule(
+    "resource://services-sync/addonsreconciler.sys.mjs"
+  );
+const { AddonsEngine } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/addons.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+AddonTestUtils.init(this);
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "1.9.2"
+);
+AddonTestUtils.overrideCertDB();
+
+const ADDON_ID = "addon1@tests.mozilla.org";
+const XPI = AddonTestUtils.createTempWebExtensionFile({
+  manifest: {
+    name: "Test 1",
+    description: "Test Description",
+    browser_specific_settings: { gecko: { id: ADDON_ID } },
+  },
+});
+
+function makeAddonsReconciler() {
+  const log = Service.engineManager.get("addons")._log;
+  const queueCaller = Async.asyncQueueCaller(log);
+  return new AddonsReconciler(queueCaller);
+}
+
+add_task(async function setup() {
+  await AddonTestUtils.promiseStartupManager();
+  Svc.PrefBranch.setBoolPref("engine.addons", true);
+  await Service.engineManager.register(AddonsEngine);
+});
+
+add_task(async function test_defaults() {
+  _("Ensure new objects have reasonable defaults.");
+
+  let reconciler = makeAddonsReconciler();
+  await reconciler.ensureStateLoaded();
+
+  Assert.ok(!reconciler._listening);
+  Assert.equal("object", typeof reconciler.addons);
+  Assert.equal(0, Object.keys(reconciler.addons).length);
+  Assert.equal(0, reconciler._changes.length);
+  Assert.equal(0, reconciler._listeners.length);
+});
+
+add_task(async function test_load_state_empty_file() {
+  _("Ensure loading from a missing file results in defaults being set.");
+
+  let reconciler = makeAddonsReconciler();
+  await reconciler.ensureStateLoaded();
+
+  let loaded = await reconciler.loadState();
+  Assert.ok(!loaded);
+
+  Assert.equal("object", typeof reconciler.addons);
+  Assert.equal(0, Object.keys(reconciler.addons).length);
+  Assert.equal(0, reconciler._changes.length);
+});
+
+add_task(async function test_install_detection() {
+  _("Ensure that add-on installation results in appropriate side-effects.");
+
+  let reconciler = makeAddonsReconciler();
+  await reconciler.ensureStateLoaded();
+  reconciler.startListening();
+
+  let before = new Date();
+  let addon = await installAddon(XPI);
+  let after = new Date();
+
+  Assert.equal(1, Object.keys(reconciler.addons).length);
+  Assert.ok(addon.id in reconciler.addons);
+  let record = reconciler.addons[ADDON_ID];
+
+  const KEYS = [
+    "id",
+    "guid",
+    "enabled",
+    "installed",
+    "modified",
+    "type",
+    "scope",
+    "foreignInstall",
+  ];
+  for (let key of KEYS) {
+    Assert.ok(key in record);
+    Assert.notEqual(null, record[key]);
+  }
+
+  Assert.equal(addon.id, record.id);
+  Assert.equal(addon.syncGUID, record.guid);
+  Assert.ok(record.enabled);
+  Assert.ok(record.installed);
+  Assert.ok(record.modified >= before && record.modified <= after);
+  Assert.equal("extension", record.type);
+  Assert.ok(!record.foreignInstall);
+
+  Assert.equal(1, reconciler._changes.length);
+  let change = reconciler._changes[0];
+  Assert.ok(change[0] >= before && change[1] <= after);
+  Assert.equal(CHANGE_INSTALLED, change[1]);
+  Assert.equal(addon.id, change[2]);
+
+  await uninstallAddon(addon);
+});
+
+add_task(async function test_uninstall_detection() {
+  _("Ensure that add-on uninstallation results in appropriate side-effects.");
+
+  let reconciler = makeAddonsReconciler();
+  await reconciler.ensureStateLoaded();
+  reconciler.startListening();
+
+  reconciler._addons = {};
+  reconciler._changes = [];
+
+  let addon = await installAddon(XPI);
+  let id = addon.id;
+
+  reconciler._changes = [];
+  await uninstallAddon(addon, reconciler);
+
+  Assert.equal(1, Object.keys(reconciler.addons).length);
+  Assert.ok(id in reconciler.addons);
+
+  let record = reconciler.addons[id];
+  Assert.ok(!record.installed);
+
+  Assert.equal(1, reconciler._changes.length);
+  let change = reconciler._changes[0];
+  Assert.equal(CHANGE_UNINSTALLED, change[1]);
+  Assert.equal(id, change[2]);
+});
+
+add_task(async function test_load_state_future_version() {
+  _("Ensure loading a file from a future version results in no data loaded.");
+
+  const FILENAME = "TEST_LOAD_STATE_FUTURE_VERSION";
+
+  let reconciler = makeAddonsReconciler();
+  await reconciler.ensureStateLoaded();
+
+  // First we populate our new file.
+  let state = { version: 100, addons: { foo: {} }, changes: [[1, 1, "foo"]] };
+
+  // jsonSave() expects an object with ._log, so we give it a reconciler
+  // instance.
+  await Utils.jsonSave(FILENAME, reconciler, state);
+
+  let loaded = await reconciler.loadState(FILENAME);
+  Assert.ok(!loaded);
+
+  Assert.equal("object", typeof reconciler.addons);
+  Assert.equal(0, Object.keys(reconciler.addons).length);
+  Assert.equal(0, reconciler._changes.length);
+});
+
+add_task(async function test_prune_changes_before_date() {
+  _("Ensure that old changes are pruned properly.");
+
+  let reconciler = makeAddonsReconciler();
+  await reconciler.ensureStateLoaded();
+  reconciler._changes = [];
+
+  let now = new Date();
+  const HOUR_MS = 1000 * 60 * 60;
+
+  _("Ensure pruning an empty changes array works.");
+  reconciler.pruneChangesBeforeDate(now);
+  Assert.equal(0, reconciler._changes.length);
+
+  let old = new Date(now.getTime() - HOUR_MS);
+  let young = new Date(now.getTime() - 1000);
+  reconciler._changes.push([old, CHANGE_INSTALLED, "foo"]);
+  reconciler._changes.push([young, CHANGE_INSTALLED, "bar"]);
+  Assert.equal(2, reconciler._changes.length);
+
+  _("Ensure pruning with an old time won't delete anything.");
+  let threshold = new Date(old.getTime() - 1);
+  reconciler.pruneChangesBeforeDate(threshold);
+  Assert.equal(2, reconciler._changes.length);
+
+  _("Ensure pruning a single item works.");
+  threshold = new Date(young.getTime() - 1000);
+  reconciler.pruneChangesBeforeDate(threshold);
+  Assert.equal(1, reconciler._changes.length);
+  Assert.notEqual(undefined, reconciler._changes[0]);
+  Assert.equal(young, reconciler._changes[0][0]);
+  Assert.equal("bar", reconciler._changes[0][2]);
+
+  _("Ensure pruning all changes works.");
+  reconciler._changes.push([old, CHANGE_INSTALLED, "foo"]);
+  reconciler.pruneChangesBeforeDate(now);
+  Assert.equal(0, reconciler._changes.length);
+});
diff --git a/src/zen/tests/mochitests/sync/test_addons_store.js b/src/zen/tests/mochitests/sync/test_addons_store.js
new file mode 100644
index 000000000..660b13e20
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_addons_store.js
@@ -0,0 +1,933 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { AddonsEngine } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/addons.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { SyncedRecordsTelemetry } = ChromeUtils.importESModule(
+  "resource://services-sync/telemetry.sys.mjs"
+);
+
+const HTTP_PORT = 8888;
+
+Services.prefs.setStringPref(
+  "extensions.getAddons.get.url",
+  "http://localhost:8888/search/guid:%IDS%"
+);
+// Note that all compat-override URLs currently 404, but that's OK - the main
+// thing is to avoid us hitting the real AMO.
+Services.prefs.setStringPref(
+  "extensions.getAddons.compatOverides.url",
+  "http://localhost:8888/compat-override/guid:%IDS%"
+);
+Services.prefs.setBoolPref("extensions.install.requireSecureOrigin", false);
+Services.prefs.setBoolPref("extensions.checkUpdateSecurity", false);
+
+AddonTestUtils.init(this);
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "1.9.2"
+);
+AddonTestUtils.overrideCertDB();
+
+Services.prefs.setBoolPref("extensions.experiments.enabled", true);
+
+const SYSTEM_ADDON_ID = "system1@tests.mozilla.org";
+const THEME_ID = "synctheme@tests.mozilla.org";
+
+add_setup(async function setupBuiltInAddon() {
+  // Enable SCOPE_APPLICATION for builtin testing.  Default in tests is only SCOPE_PROFILE.
+  let scopes = AddonManager.SCOPE_PROFILE | AddonManager.SCOPE_APPLICATION;
+  Services.prefs.setIntPref("extensions.enabledScopes", scopes);
+
+  const addon_version = "1.0";
+  const addon_res_url_path = "test-builtin-addon";
+
+  let xpi = await AddonTestUtils.createTempWebExtensionFile({
+    manifest: {
+      version: addon_version,
+      browser_specific_settings: { gecko: { id: SYSTEM_ADDON_ID } },
+    },
+  });
+
+  // The built-in location requires a resource: URL that maps to a
+  // jar: or file: URL.  This would typically be something bundled
+  // into omni.ja but for testing we just use a temp file.
+  let base = Services.io.newURI(`jar:file:${xpi.path}!/`);
+  let resProto = Services.io
+    .getProtocolHandler("resource")
+    .QueryInterface(Ci.nsIResProtocolHandler);
+  resProto.setSubstitution(addon_res_url_path, base);
+  let builtins = [
+    {
+      addon_id: SYSTEM_ADDON_ID,
+      addon_version,
+      res_url: `resource://${addon_res_url_path}/`,
+    },
+  ];
+  await AddonTestUtils.overrideBuiltIns({ builtins });
+  await AddonTestUtils.promiseStartupManager();
+});
+
+const ID1 = "addon1@tests.mozilla.org";
+const ID2 = "addon2@tests.mozilla.org";
+const ID3 = "addon3@tests.mozilla.org";
+
+const ADDONS = {
+  test_addon1: {
+    manifest: {
+      browser_specific_settings: {
+        gecko: {
+          id: ID1,
+          update_url: "http://example.com/data/test_install.json",
+        },
+      },
+    },
+  },
+
+  test_addon2: {
+    manifest: {
+      browser_specific_settings: { gecko: { id: ID2 } },
+    },
+  },
+
+  test_addon3: {
+    manifest: {
+      browser_specific_settings: {
+        gecko: {
+          id: ID3,
+          strict_max_version: "0",
+        },
+      },
+    },
+  },
+};
+
+const SEARCH_RESULT = {
+  next: null,
+  results: [
+    {
+      name: "Test Extension",
+      type: "extension",
+      guid: "addon1@tests.mozilla.org",
+      current_version: {
+        version: "1.0",
+        files: [
+          {
+            platform: "all",
+            size: 485,
+            url: "http://localhost:8888/addon1.xpi",
+          },
+        ],
+      },
+      last_updated: "2018-10-27T04:12:00.826Z",
+    },
+  ],
+};
+
+const MISSING_SEARCH_RESULT = {
+  next: null,
+  results: [
+    {
+      name: "Test",
+      type: "extension",
+      guid: "missing-xpi@tests.mozilla.org",
+      current_version: {
+        version: "1.0",
+        files: [
+          {
+            platform: "all",
+            size: 123,
+            url: "http://localhost:8888/THIS_DOES_NOT_EXIST.xpi",
+          },
+        ],
+      },
+    },
+  ],
+};
+
+const AMOSIGNED_SHA1_SEARCH_RESULT = {
+  next: null,
+  results: [
+    {
+      name: "Test Extension",
+      type: "extension",
+      guid: "amosigned-xpi@tests.mozilla.org",
+      current_version: {
+        version: "2.1",
+        files: [
+          {
+            platform: "all",
+            size: 4287,
+            url: "http://localhost:8888/amosigned-sha1only.xpi",
+          },
+        ],
+      },
+      last_updated: "2024-03-21T16:00:06.640Z",
+    },
+  ],
+};
+
+const XPIS = {};
+for (let [name, files] of Object.entries(ADDONS)) {
+  XPIS[name] = AddonTestUtils.createTempWebExtensionFile(files);
+}
+
+let engine;
+let store;
+let reconciler;
+
+const proxyService = Cc[
+  "@mozilla.org/network/protocol-proxy-service;1"
+].getService(Ci.nsIProtocolProxyService);
+
+const proxyFilter = {
+  proxyInfo: proxyService.newProxyInfo(
+    "http",
+    "localhost",
+    HTTP_PORT,
+    "",
+    "",
+    0,
+    4096,
+    null
+  ),
+
+  applyFilter(channel, defaultProxyInfo, callback) {
+    if (channel.URI.host === "example.com") {
+      callback.onProxyFilterResult(this.proxyInfo);
+    } else {
+      callback.onProxyFilterResult(defaultProxyInfo);
+    }
+  },
+};
+
+proxyService.registerChannelFilter(proxyFilter, 0);
+registerCleanupFunction(() => {
+  proxyService.unregisterChannelFilter(proxyFilter);
+});
+
+/**
+ * Create a AddonsRec for this application with the fields specified.
+ *
+ * @param  id       Sync GUID of record
+ * @param  addonId  ID of add-on
+ * @param  enabled  Boolean whether record is enabled
+ * @param  deleted  Boolean whether record was deleted
+ */
+function createRecordForThisApp(id, addonId, enabled, deleted) {
+  return {
+    id,
+    addonID: addonId,
+    enabled,
+    deleted: !!deleted,
+    applicationID: Services.appinfo.ID,
+    source: "amo",
+  };
+}
+
+function createAndStartHTTPServer(port) {
+  try {
+    let server = new HttpServer();
+
+    server.registerPathHandler(
+      "/search/guid:addon1%40tests.mozilla.org",
+      (req, resp) => {
+        resp.setHeader("Content-type", "application/json", true);
+        resp.write(JSON.stringify(SEARCH_RESULT));
+      }
+    );
+    server.registerPathHandler(
+      "/search/guid:missing-xpi%40tests.mozilla.org",
+      (req, resp) => {
+        resp.setHeader("Content-type", "application/json", true);
+        resp.write(JSON.stringify(MISSING_SEARCH_RESULT));
+      }
+    );
+    server.registerFile("/addon1.xpi", XPIS.test_addon1);
+
+    server.registerPathHandler(
+      "/search/guid:amosigned-xpi%40tests.mozilla.org",
+      (req, resp) => {
+        resp.setHeader("Content-type", "application/json", true);
+        resp.write(JSON.stringify(AMOSIGNED_SHA1_SEARCH_RESULT));
+      }
+    );
+    server.registerFile(
+      "/amosigned-sha1only.xpi",
+      do_get_file("amosigned-sha1only.xpi")
+    );
+
+    server.start(port);
+
+    return server;
+  } catch (ex) {
+    _("Got exception starting HTTP server on port " + port);
+    _("Error: " + Log.exceptionStr(ex));
+    do_throw(ex);
+  }
+  return null; /* not hit, but keeps eslint happy! */
+}
+
+// A helper function to ensure that the reconciler's current view of the addon
+// is the same as the addon itself. If it's not, then the reconciler missed a
+// change, and is likely to re-upload the addon next sync because of the change
+// it missed.
+async function checkReconcilerUpToDate(addon) {
+  let stateBefore = Object.assign({}, store.reconciler.addons[addon.id]);
+  await store.reconciler.rectifyStateFromAddon(addon);
+  let stateAfter = store.reconciler.addons[addon.id];
+  deepEqual(stateBefore, stateAfter);
+}
+
+add_setup(async function setup() {
+  await Service.engineManager.register(AddonsEngine);
+  engine = Service.engineManager.get("addons");
+  store = engine._store;
+  reconciler = engine._reconciler;
+
+  reconciler.startListening();
+
+  // Don't flush to disk in the middle of an event listener!
+  // This causes test hangs on WinXP.
+  reconciler._shouldPersist = false;
+});
+
+add_task(async function test_remove() {
+  _("Ensure removing add-ons from deleted records works.");
+
+  let addon = await installAddon(XPIS.test_addon1, reconciler);
+  let record = createRecordForThisApp(addon.syncGUID, ID1, true, true);
+  let countTelemetry = new SyncedRecordsTelemetry();
+  let failed = await store.applyIncomingBatch([record], countTelemetry);
+  Assert.equal(0, failed.length);
+  Assert.equal(null, countTelemetry.failedReasons);
+  Assert.equal(0, countTelemetry.incomingCounts.failed);
+
+  let newAddon = await AddonManager.getAddonByID(ID1);
+  Assert.equal(null, newAddon);
+});
+
+add_task(async function test_apply_enabled() {
+  let countTelemetry = new SyncedRecordsTelemetry();
+  _("Ensures that changes to the userEnabled flag apply.");
+
+  let addon = await installAddon(XPIS.test_addon1, reconciler);
+  Assert.ok(addon.isActive);
+  Assert.ok(!addon.userDisabled);
+
+  _("Ensure application of a disable record works as expected.");
+  let records = [];
+  records.push(createRecordForThisApp(addon.syncGUID, ID1, false, false));
+
+  let [failed] = await Promise.all([
+    store.applyIncomingBatch(records, countTelemetry),
+    AddonTestUtils.promiseAddonEvent("onDisabled"),
+  ]);
+  Assert.equal(0, failed.length);
+  Assert.equal(0, countTelemetry.incomingCounts.failed);
+  addon = await AddonManager.getAddonByID(ID1);
+  Assert.ok(addon.userDisabled);
+  await checkReconcilerUpToDate(addon);
+  records = [];
+
+  _("Ensure enable record works as expected.");
+  records.push(createRecordForThisApp(addon.syncGUID, ID1, true, false));
+  [failed] = await Promise.all([
+    store.applyIncomingBatch(records, countTelemetry),
+    AddonTestUtils.promiseWebExtensionStartup(ID1),
+  ]);
+  Assert.equal(0, failed.length);
+  Assert.equal(0, countTelemetry.incomingCounts.failed);
+  addon = await AddonManager.getAddonByID(ID1);
+  Assert.ok(!addon.userDisabled);
+  await checkReconcilerUpToDate(addon);
+  records = [];
+
+  _("Ensure enabled state updates don't apply if the ignore pref is set.");
+  records.push(createRecordForThisApp(addon.syncGUID, ID1, false, false));
+  Svc.PrefBranch.setBoolPref("addons.ignoreUserEnabledChanges", true);
+  failed = await store.applyIncomingBatch(records, countTelemetry);
+  Assert.equal(0, failed.length);
+  Assert.equal(0, countTelemetry.incomingCounts.failed);
+  addon = await AddonManager.getAddonByID(ID1);
+  Assert.ok(!addon.userDisabled);
+  records = [];
+
+  await uninstallAddon(addon, reconciler);
+  Svc.PrefBranch.clearUserPref("addons.ignoreUserEnabledChanges");
+});
+
+add_task(async function test_apply_enabled_appDisabled() {
+  _(
+    "Ensures that changes to the userEnabled flag apply when the addon is appDisabled."
+  );
+
+  // this addon is appDisabled by default.
+  let addon = await installAddon(XPIS.test_addon3);
+  Assert.ok(addon.appDisabled);
+  Assert.ok(!addon.isActive);
+  Assert.ok(!addon.userDisabled);
+
+  _("Ensure application of a disable record works as expected.");
+  store.reconciler.pruneChangesBeforeDate(Date.now() + 10);
+  store.reconciler._changes = [];
+  let records = [];
+  let countTelemetry = new SyncedRecordsTelemetry();
+  records.push(createRecordForThisApp(addon.syncGUID, ID3, false, false));
+  let failed = await store.applyIncomingBatch(records, countTelemetry);
+  Assert.equal(0, failed.length);
+  Assert.equal(0, countTelemetry.incomingCounts.failed);
+  addon = await AddonManager.getAddonByID(ID3);
+  Assert.ok(addon.userDisabled);
+  await checkReconcilerUpToDate(addon);
+  records = [];
+
+  _("Ensure enable record works as expected.");
+  records.push(createRecordForThisApp(addon.syncGUID, ID3, true, false));
+  failed = await store.applyIncomingBatch(records, countTelemetry);
+  Assert.equal(0, failed.length);
+  Assert.equal(0, countTelemetry.incomingCounts.failed);
+  addon = await AddonManager.getAddonByID(ID3);
+  Assert.ok(!addon.userDisabled);
+  await checkReconcilerUpToDate(addon);
+  records = [];
+
+  await uninstallAddon(addon, reconciler);
+});
+
+add_task(async function test_ignore_different_appid() {
+  _(
+    "Ensure that incoming records with a different application ID are ignored."
+  );
+
+  // We test by creating a record that should result in an update.
+  let addon = await installAddon(XPIS.test_addon1, reconciler);
+  Assert.ok(!addon.userDisabled);
+
+  let record = createRecordForThisApp(addon.syncGUID, ID1, false, false);
+  record.applicationID = "FAKE_ID";
+  let countTelemetry = new SyncedRecordsTelemetry();
+  let failed = await store.applyIncomingBatch([record], countTelemetry);
+  Assert.equal(0, failed.length);
+
+  let newAddon = await AddonManager.getAddonByID(ID1);
+  Assert.ok(!newAddon.userDisabled);
+
+  await uninstallAddon(addon, reconciler);
+});
+
+add_task(async function test_ignore_unknown_source() {
+  _("Ensure incoming records with unknown source are ignored.");
+
+  let addon = await installAddon(XPIS.test_addon1, reconciler);
+
+  let record = createRecordForThisApp(addon.syncGUID, ID1, false, false);
+  record.source = "DUMMY_SOURCE";
+  let countTelemetry = new SyncedRecordsTelemetry();
+  let failed = await store.applyIncomingBatch([record], countTelemetry);
+  Assert.equal(0, failed.length);
+
+  let newAddon = await AddonManager.getAddonByID(ID1);
+  Assert.ok(!newAddon.userDisabled);
+
+  await uninstallAddon(addon, reconciler);
+});
+
+add_task(async function test_apply_uninstall() {
+  _("Ensures that uninstalling an add-on from a record works.");
+
+  let addon = await installAddon(XPIS.test_addon1, reconciler);
+
+  let records = [];
+  let countTelemetry = new SyncedRecordsTelemetry();
+  records.push(createRecordForThisApp(addon.syncGUID, ID1, true, true));
+  let failed = await store.applyIncomingBatch(records, countTelemetry);
+  Assert.equal(0, failed.length);
+  Assert.equal(0, countTelemetry.incomingCounts.failed);
+
+  addon = await AddonManager.getAddonByID(ID1);
+  Assert.equal(null, addon);
+});
+
+add_task(async function test_addon_syncability() {
+  _("Ensure isAddonSyncable functions properly.");
+
+  Svc.PrefBranch.setStringPref(
+    "addons.trustedSourceHostnames",
+    "addons.mozilla.org,other.example.com"
+  );
+
+  Assert.ok(!(await store.isAddonSyncable(null)));
+
+  let addon = await installAddon(XPIS.test_addon1, reconciler);
+  Assert.ok(await store.isAddonSyncable(addon));
+
+  let dummy = {};
+  const KEYS = [
+    "id",
+    "syncGUID",
+    "type",
+    "scope",
+    "foreignInstall",
+    "isSyncable",
+  ];
+  for (let k of KEYS) {
+    dummy[k] = addon[k];
+  }
+
+  Assert.ok(await store.isAddonSyncable(dummy));
+
+  dummy.type = "UNSUPPORTED";
+  Assert.ok(!(await store.isAddonSyncable(dummy)));
+  dummy.type = addon.type;
+
+  dummy.scope = 0;
+  Assert.ok(!(await store.isAddonSyncable(dummy)));
+  dummy.scope = addon.scope;
+
+  dummy.isSyncable = false;
+  Assert.ok(!(await store.isAddonSyncable(dummy)));
+  dummy.isSyncable = addon.isSyncable;
+
+  dummy.foreignInstall = true;
+  Assert.ok(!(await store.isAddonSyncable(dummy)));
+  dummy.foreignInstall = false;
+
+  await uninstallAddon(addon, reconciler);
+
+  Assert.ok(!store.isSourceURITrusted(null));
+
+  let trusted = [
+    "https://addons.mozilla.org/foo",
+    "https://other.example.com/foo",
+  ];
+
+  let untrusted = [
+    "http://addons.mozilla.org/foo", // non-https
+    "ftps://addons.mozilla.org/foo", // non-https
+    "https://untrusted.example.com/foo", // non-trusted hostname`
+  ];
+
+  for (let uri of trusted) {
+    Assert.ok(store.isSourceURITrusted(Services.io.newURI(uri)));
+  }
+
+  for (let uri of untrusted) {
+    Assert.ok(!store.isSourceURITrusted(Services.io.newURI(uri)));
+  }
+
+  Svc.PrefBranch.setStringPref("addons.trustedSourceHostnames", "");
+  for (let uri of trusted) {
+    Assert.ok(!store.isSourceURITrusted(Services.io.newURI(uri)));
+  }
+
+  Svc.PrefBranch.setStringPref(
+    "addons.trustedSourceHostnames",
+    "addons.mozilla.org"
+  );
+  Assert.ok(
+    store.isSourceURITrusted(
+      Services.io.newURI("https://addons.mozilla.org/foo")
+    )
+  );
+
+  Svc.PrefBranch.clearUserPref("addons.trustedSourceHostnames");
+});
+
+add_task(async function test_get_all_ids() {
+  _("Ensures that getAllIDs() returns an appropriate set.");
+
+  _("Installing two addons.");
+  // XXX - this test seems broken - at this point, before we've installed the
+  // addons below, store.getAllIDs() returns all addons installed by previous
+  // tests, even though those tests uninstalled the addon.
+  // So if any tests above ever add a new addon ID, they are going to need to
+  // be added here too.
+  // Assert.equal(0, Object.keys(store.getAllIDs()).length);
+  let addon1 = await installAddon(XPIS.test_addon1, reconciler);
+  let addon2 = await installAddon(XPIS.test_addon2, reconciler);
+  let addon3 = await installAddon(XPIS.test_addon3, reconciler);
+
+  _("Ensure they're syncable.");
+  Assert.ok(await store.isAddonSyncable(addon1));
+  Assert.ok(await store.isAddonSyncable(addon2));
+  Assert.ok(await store.isAddonSyncable(addon3));
+
+  let ids = await store.getAllIDs();
+
+  Assert.equal("object", typeof ids);
+  Assert.equal(3, Object.keys(ids).length);
+  Assert.ok(addon1.syncGUID in ids);
+  Assert.ok(addon2.syncGUID in ids);
+  Assert.ok(addon3.syncGUID in ids);
+
+  await uninstallAddon(addon1, reconciler);
+  await uninstallAddon(addon2, reconciler);
+  await uninstallAddon(addon3, reconciler);
+});
+
+add_task(async function test_change_item_id() {
+  _("Ensures that changeItemID() works properly.");
+
+  let addon = await installAddon(XPIS.test_addon1, reconciler);
+
+  let oldID = addon.syncGUID;
+  let newID = Utils.makeGUID();
+
+  await store.changeItemID(oldID, newID);
+
+  let newAddon = await AddonManager.getAddonByID(ID1);
+  Assert.notEqual(null, newAddon);
+  Assert.equal(newID, newAddon.syncGUID);
+
+  await uninstallAddon(newAddon, reconciler);
+});
+
+add_task(async function test_create() {
+  _("Ensure creating/installing an add-on from a record works.");
+
+  let server = createAndStartHTTPServer(HTTP_PORT);
+
+  let guid = Utils.makeGUID();
+  let record = createRecordForThisApp(guid, ID1, true, false);
+  let countTelemetry = new SyncedRecordsTelemetry();
+  let failed = await store.applyIncomingBatch([record], countTelemetry);
+  Assert.equal(0, failed.length);
+
+  let newAddon = await AddonManager.getAddonByID(ID1);
+  Assert.notEqual(null, newAddon);
+  Assert.equal(guid, newAddon.syncGUID);
+  Assert.ok(!newAddon.userDisabled);
+
+  await uninstallAddon(newAddon, reconciler);
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_weak_signature_restrictions() {
+  _("Ensure installing add-ons with a weak signature fails when restricted.");
+
+  // Ensure restrictions on weak signatures are enabled (this should be removed when
+  // the new behavior is riding the train).
+  const resetWeakSignaturePref =
+    AddonTestUtils.setWeakSignatureInstallAllowed(false);
+  const server = createAndStartHTTPServer(HTTP_PORT);
+  const ID_TEST_SHA1 = "amosigned-xpi@tests.mozilla.org";
+
+  const guidKO = Utils.makeGUID();
+  const guidOK = Utils.makeGUID();
+  const recordKO = createRecordForThisApp(guidKO, ID_TEST_SHA1, true, false);
+  const recordOK = createRecordForThisApp(guidOK, ID1, true, false);
+  const countTelemetry = new SyncedRecordsTelemetry();
+
+  let failed;
+
+  const { messages } = await AddonTestUtils.promiseConsoleOutput(async () => {
+    failed = await store.applyIncomingBatch(
+      [recordKO, recordOK],
+      countTelemetry
+    );
+  });
+
+  Assert.equal(
+    1,
+    failed.length,
+    "Expect only 1 on the two synced add-ons to fail"
+  );
+
+  resetWeakSignaturePref();
+
+  let addonKO = await AddonManager.getAddonByID(ID_TEST_SHA1);
+  Assert.equal(null, addonKO, `Expect ${ID_TEST_SHA1} to NOT be installed`);
+  let addonOK = await AddonManager.getAddonByID(ID1);
+  Assert.notEqual(null, addonOK, `Expect ${ID1} to be installed`);
+
+  await uninstallAddon(addonOK, reconciler);
+  await promiseStopServer(server);
+
+  AddonTestUtils.checkMessages(messages, {
+    expected: [
+      {
+        message:
+          /Download of .*\/amosigned-sha1only.xpi failed: install rejected due to the package not including a strong cryptographic signature/,
+      },
+    ],
+  });
+});
+
+add_task(async function test_create_missing_search() {
+  _("Ensures that failed add-on searches are handled gracefully.");
+
+  let server = createAndStartHTTPServer(HTTP_PORT);
+
+  // The handler for this ID is not installed, so a search should 404.
+  const id = "missing@tests.mozilla.org";
+  let guid = Utils.makeGUID();
+  let record = createRecordForThisApp(guid, id, true, false);
+  let countTelemetry = new SyncedRecordsTelemetry();
+  let failed = await store.applyIncomingBatch([record], countTelemetry);
+  Assert.equal(1, failed.length);
+  Assert.equal(guid, failed[0]);
+  Assert.equal(
+    countTelemetry.incomingCounts.failedReasons[0].name,
+    "GET <URL> failed (status 404)"
+  );
+  Assert.equal(countTelemetry.incomingCounts.failedReasons[0].count, 1);
+
+  let addon = await AddonManager.getAddonByID(id);
+  Assert.equal(null, addon);
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_create_bad_install() {
+  _("Ensures that add-ons without a valid install are handled gracefully.");
+
+  let server = createAndStartHTTPServer(HTTP_PORT);
+
+  // The handler returns a search result but the XPI will 404.
+  const id = "missing-xpi@tests.mozilla.org";
+  let guid = Utils.makeGUID();
+  let record = createRecordForThisApp(guid, id, true, false);
+  let countTelemetry = new SyncedRecordsTelemetry();
+  /* let failed = */ await store.applyIncomingBatch([record], countTelemetry);
+  // This addon had no source URI so was skipped - but it's not treated as
+  // failure.
+  // XXX - this test isn't testing what we thought it was. Previously the addon
+  // was not being installed due to requireSecureURL checking *before* we'd
+  // attempted to get the XPI.
+  // With requireSecureURL disabled we do see a download failure, but the addon
+  // *does* get added to |failed|.
+  // FTR: onDownloadFailed() is called with ERROR_NETWORK_FAILURE, so it's going
+  // to be tricky to distinguish a 404 from other transient network errors
+  // where we do want the addon to end up in |failed|.
+  // This is being tracked in bug 1284778.
+  // Assert.equal(0, failed.length);
+
+  let addon = await AddonManager.getAddonByID(id);
+  Assert.equal(null, addon);
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_ignore_system() {
+  _("Ensure we ignore system addons");
+  // Our system addon should not appear in getAllIDs
+  await engine._refreshReconcilerState();
+  let num = 0;
+  let ids = await store.getAllIDs();
+  for (let guid in ids) {
+    num += 1;
+    let addon = reconciler.getAddonStateFromSyncGUID(guid);
+    Assert.notEqual(addon.id, SYSTEM_ADDON_ID);
+  }
+  Assert.greater(num, 1, "should have seen at least one.");
+});
+
+add_task(async function test_incoming_system() {
+  _("Ensure we handle incoming records that refer to a system addon");
+  // eg, loop initially had a normal addon but it was then "promoted" to be a
+  // system addon but wanted to keep the same ID. The server record exists due
+  // to this.
+
+  // before we start, ensure the system addon isn't disabled.
+  Assert.ok(!(await AddonManager.getAddonByID(SYSTEM_ADDON_ID).userDisabled));
+
+  // Now simulate an incoming record with the same ID as the system addon,
+  // but flagged as disabled - it should not be applied.
+  let server = createAndStartHTTPServer(HTTP_PORT);
+  // We make the incoming record flag the system addon as disabled - it should
+  // be ignored.
+  let guid = Utils.makeGUID();
+  let record = createRecordForThisApp(guid, SYSTEM_ADDON_ID, false, false);
+  let countTelemetry = new SyncedRecordsTelemetry();
+  let failed = await store.applyIncomingBatch([record], countTelemetry);
+  Assert.equal(0, failed.length);
+
+  // The system addon should still not be userDisabled.
+  Assert.ok(!(await AddonManager.getAddonByID(SYSTEM_ADDON_ID).userDisabled));
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_wipe() {
+  _("Ensures that wiping causes add-ons to be uninstalled.");
+
+  await installAddon(XPIS.test_addon1, reconciler);
+
+  await store.wipe();
+
+  let addon = await AddonManager.getAddonByID(ID1);
+  Assert.equal(null, addon);
+});
+
+add_task(async function test_wipe_and_install() {
+  _("Ensure wipe followed by install works.");
+
+  // This tests the reset sync flow where remote data is replaced by local. The
+  // receiving client will see a wipe followed by a record which should undo
+  // the wipe.
+  let installed = await installAddon(XPIS.test_addon1, reconciler);
+
+  let record = createRecordForThisApp(installed.syncGUID, ID1, true, false);
+
+  await store.wipe();
+
+  let deleted = await AddonManager.getAddonByID(ID1);
+  Assert.equal(null, deleted);
+
+  // Re-applying the record can require re-fetching the XPI.
+  let server = createAndStartHTTPServer(HTTP_PORT);
+
+  await store.applyIncoming(record);
+
+  let fetched = await AddonManager.getAddonByID(record.addonID);
+  Assert.ok(!!fetched);
+
+  // wipe again to we are left with a clean slate.
+  await store.wipe();
+
+  await promiseStopServer(server);
+});
+
+// STR for what this is testing:
+// * Either:
+//   * Install then remove an addon, then delete addons.json from the profile
+//     or corrupt it (in which case the addon manager will remove it)
+//   * Install then remove an addon while addon caching is disabled, then
+//     re-enable addon caching.
+// * Install the same addon in a different profile, sync it.
+// * Sync this profile
+// Before bug 1467904, the addon would fail to install because this profile
+// has a copy of the addon in our addonsreconciler.json, but the addon manager
+// does *not* have a copy in its cache, and repopulating that cache would not
+// re-add it as the addon is no longer installed locally.
+add_task(async function test_incoming_reconciled_but_not_cached() {
+  _(
+    "Ensure we handle incoming records our reconciler has but the addon cache does not"
+  );
+
+  // Make sure addon is not installed.
+  let addon = await AddonManager.getAddonByID(ID1);
+  Assert.equal(null, addon);
+
+  Services.prefs.setBoolPref("extensions.getAddons.cache.enabled", false);
+
+  addon = await installAddon(XPIS.test_addon1, reconciler);
+  Assert.notEqual(await AddonManager.getAddonByID(ID1), null);
+  await uninstallAddon(addon, reconciler);
+
+  Services.prefs.setBoolPref("extensions.getAddons.cache.enabled", true);
+
+  // now pretend it is incoming.
+  let server = createAndStartHTTPServer(HTTP_PORT);
+  let guid = Utils.makeGUID();
+  let record = createRecordForThisApp(guid, ID1, true, false);
+  let countTelemetry = new SyncedRecordsTelemetry();
+  let failed = await store.applyIncomingBatch([record], countTelemetry);
+  Assert.equal(0, failed.length);
+
+  Assert.notEqual(await AddonManager.getAddonByID(ID1), null);
+
+  await promiseStopServer(server);
+});
+
+// Helper for testing theme-specific addons
+function makeThemeSearchResult(id) {
+  return {
+    next: null,
+    results: [
+      {
+        name: "Sync Theme",
+        type: "theme",
+        guid: id,
+        current_version: {
+          version: "1.0",
+          files: [
+            {
+              platform: "all",
+              size: 1234,
+              url: `http://localhost:${HTTP_PORT}/synctheme.xpi`,
+            },
+          ],
+        },
+        last_updated: "2025-03-01T00:00:00.000Z",
+      },
+    ],
+  };
+}
+
+/**
+ * Incoming theme add-on record should
+ *   – install the theme
+ *   – enable it immediately
+ *   – clear the hand-off pref
+ */
+add_task(async function test_incoming_theme_gets_enabled() {
+  const xpiTheme = AddonTestUtils.createTempWebExtensionFile({
+    manifest: {
+      manifest_version: 2,
+      name: "Sync Theme",
+      version: "1.0",
+      applications: { gecko: { id: THEME_ID } },
+      theme: { colors: { frame: "#000000", tab_background_text: "#ffffff" } },
+    },
+  });
+
+  const server = createAndStartHTTPServer(HTTP_PORT);
+  server.registerFile("/synctheme.xpi", xpiTheme);
+  server.registerPathHandler(
+    `/search/guid:${encodeURIComponent(THEME_ID)}`,
+    (req, resp) => {
+      resp.setHeader("Content-Type", "application/json", true);
+      resp.write(JSON.stringify(makeThemeSearchResult(THEME_ID)));
+    }
+  );
+
+  // Pretend Prefs‑engine has just synced a new activeThemeID
+  Services.prefs.setStringPref("extensions.pendingActiveThemeID", THEME_ID);
+
+  // Feed an add-on record into the Addons engine.
+  const guid = Utils.makeGUID();
+  const record = createRecordForThisApp(guid, THEME_ID, true, false);
+  const telem = new SyncedRecordsTelemetry();
+
+  const onStartup = AddonTestUtils.promiseWebExtensionStartup(THEME_ID);
+  const failed = await store.applyIncomingBatch([record], telem);
+
+  Assert.equal(0, failed.length, "No records should fail to apply");
+  await onStartup;
+
+  const theme = await AddonManager.getAddonByID(THEME_ID);
+  Assert.ok(theme, "Theme is installed");
+  Assert.ok(theme.isActive, "Theme is active");
+  Assert.ok(!theme.userDisabled, "Theme is not user-disabled");
+
+  Assert.equal(
+    Services.prefs.getPrefType("extensions.pendingActiveThemeID"),
+    Ci.nsIPrefBranch.PREF_INVALID,
+    "Hand-off pref was cleared"
+  );
+
+  // Clean-up
+  await uninstallAddon(theme, reconciler);
+  await promiseStopServer(server);
+});
+
+// NOTE: The test above must be the last test run due to the addon cache
+// being trashed. It is probably possible to fix that by running, eg,
+// AddonRespository.backgroundUpdateCheck() to rebuild the cache, but that
+// requires implementing more AMO functionality in our test server
+
+add_task(async function cleanup() {
+  // There's an xpcom-shutdown hook for this, but let's give this a shot.
+  reconciler.stopListening();
+});
diff --git a/src/zen/tests/mochitests/sync/test_addons_tracker.js b/src/zen/tests/mochitests/sync/test_addons_tracker.js
new file mode 100644
index 000000000..f8473e4cf
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_addons_tracker.js
@@ -0,0 +1,174 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { AddonsEngine } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/addons.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+AddonTestUtils.init(this);
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "1.9.2"
+);
+AddonTestUtils.overrideCertDB();
+
+Services.prefs.setBoolPref("extensions.experiments.enabled", true);
+
+Svc.PrefBranch.setBoolPref("engine.addons", true);
+
+let reconciler;
+let tracker;
+
+const addon1ID = "addon1@tests.mozilla.org";
+
+const ADDONS = {
+  test_addon1: {
+    manifest: {
+      browser_specific_settings: { gecko: { id: addon1ID } },
+    },
+  },
+};
+
+const XPIS = {};
+
+async function cleanup() {
+  tracker.stop();
+
+  tracker.resetScore();
+  await tracker.clearChangedIDs();
+
+  reconciler._addons = {};
+  reconciler._changes = [];
+  await reconciler.saveState();
+}
+
+add_task(async function setup() {
+  await AddonTestUtils.promiseStartupManager();
+  for (let [name, data] of Object.entries(ADDONS)) {
+    XPIS[name] = AddonTestUtils.createTempWebExtensionFile(data);
+  }
+  await Service.engineManager.register(AddonsEngine);
+  let engine = Service.engineManager.get("addons");
+  reconciler = engine._reconciler;
+  tracker = engine._tracker;
+
+  await cleanup();
+});
+
+add_task(async function test_empty() {
+  _("Verify the tracker is empty to start with.");
+
+  Assert.equal(0, Object.keys(await tracker.getChangedIDs()).length);
+  Assert.equal(0, tracker.score);
+
+  await cleanup();
+});
+
+add_task(async function test_not_tracking() {
+  _("Ensures the tracker doesn't do anything when it isn't tracking.");
+
+  let addon = await installAddon(XPIS.test_addon1, reconciler);
+  await uninstallAddon(addon, reconciler);
+
+  Assert.equal(0, Object.keys(await tracker.getChangedIDs()).length);
+  Assert.equal(0, tracker.score);
+
+  await cleanup();
+});
+
+add_task(async function test_track_install() {
+  _("Ensure that installing an add-on notifies tracker.");
+
+  reconciler.startListening();
+
+  tracker.start();
+
+  Assert.equal(0, tracker.score);
+  let addon = await installAddon(XPIS.test_addon1, reconciler);
+  let changed = await tracker.getChangedIDs();
+
+  Assert.equal(1, Object.keys(changed).length);
+  Assert.ok(addon.syncGUID in changed);
+  Assert.equal(SCORE_INCREMENT_XLARGE, tracker.score);
+
+  await uninstallAddon(addon, reconciler);
+  await cleanup();
+});
+
+add_task(async function test_track_uninstall() {
+  _("Ensure that uninstalling an add-on notifies tracker.");
+
+  reconciler.startListening();
+
+  let addon = await installAddon(XPIS.test_addon1, reconciler);
+  let guid = addon.syncGUID;
+  Assert.equal(0, tracker.score);
+
+  tracker.start();
+
+  await uninstallAddon(addon, reconciler);
+  let changed = await tracker.getChangedIDs();
+  Assert.equal(1, Object.keys(changed).length);
+  Assert.ok(guid in changed);
+  Assert.equal(SCORE_INCREMENT_XLARGE, tracker.score);
+
+  await cleanup();
+});
+
+add_task(async function test_track_user_disable() {
+  _("Ensure that tracker sees disabling of add-on");
+
+  reconciler.startListening();
+
+  let addon = await installAddon(XPIS.test_addon1, reconciler);
+  Assert.ok(!addon.userDisabled);
+  Assert.ok(!addon.appDisabled);
+  Assert.ok(addon.isActive);
+
+  tracker.start();
+  Assert.equal(0, tracker.score);
+
+  _("Disabling add-on");
+  await addon.disable();
+  await reconciler.queueCaller.promiseCallsComplete();
+
+  let changed = await tracker.getChangedIDs();
+  Assert.equal(1, Object.keys(changed).length);
+  Assert.ok(addon.syncGUID in changed);
+  Assert.equal(SCORE_INCREMENT_XLARGE, tracker.score);
+
+  await uninstallAddon(addon, reconciler);
+  await cleanup();
+});
+
+add_task(async function test_track_enable() {
+  _("Ensure that enabling a disabled add-on notifies tracker.");
+
+  reconciler.startListening();
+
+  let addon = await installAddon(XPIS.test_addon1, reconciler);
+  await addon.disable();
+  await Async.promiseYield();
+
+  Assert.equal(0, tracker.score);
+
+  tracker.start();
+  await addon.enable();
+  await Async.promiseYield();
+  await reconciler.queueCaller.promiseCallsComplete();
+
+  let changed = await tracker.getChangedIDs();
+  Assert.equal(1, Object.keys(changed).length);
+  Assert.ok(addon.syncGUID in changed);
+  Assert.equal(SCORE_INCREMENT_XLARGE, tracker.score);
+
+  await uninstallAddon(addon, reconciler);
+  await cleanup();
+});
diff --git a/src/zen/tests/mochitests/sync/test_addons_validator.js b/src/zen/tests/mochitests/sync/test_addons_validator.js
new file mode 100644
index 000000000..91f3f7b31
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_addons_validator.js
@@ -0,0 +1,65 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { AddonValidator } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/addons.sys.mjs"
+);
+
+function getDummyServerAndClient() {
+  return {
+    server: [
+      {
+        id: "1111",
+        applicationID: Services.appinfo.ID,
+        addonID: "synced-addon@example.com",
+        enabled: true,
+        source: "amo",
+        understood: true,
+      },
+    ],
+    client: [
+      {
+        syncGUID: "1111",
+        id: "synced-addon@example.com",
+        type: "extension",
+        isSystem: false,
+        isSyncable: true,
+      },
+      {
+        syncGUID: "2222",
+        id: "system-addon@example.com",
+        type: "extension",
+        isSystem: true,
+        isSyncable: false,
+      },
+      {
+        // Plugins don't have a `syncedGUID`, but we don't sync them, so we
+        // shouldn't report them as client duplicates.
+        id: "some-plugin",
+        type: "plugin",
+      },
+      {
+        id: "another-plugin",
+        type: "plugin",
+      },
+    ],
+  };
+}
+
+add_task(async function test_valid() {
+  let { server, client } = getDummyServerAndClient();
+  let validator = new AddonValidator({
+    _findDupe() {
+      return null;
+    },
+    isAddonSyncable(item) {
+      return item.type != "plugin";
+    },
+  });
+  let { problemData, clientRecords, records, deletedRecords } =
+    await validator.compareClientWithServer(client, server);
+  equal(clientRecords.length, 4);
+  equal(records.length, 1);
+  equal(deletedRecords.length, 0);
+  deepEqual(problemData, validator.emptyProblemData());
+});
diff --git a/src/zen/tests/mochitests/sync/test_bookmark_batch_fail.js b/src/zen/tests/mochitests/sync/test_bookmark_batch_fail.js
new file mode 100644
index 000000000..9644d730e
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_bookmark_batch_fail.js
@@ -0,0 +1,25 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+_("Making sure a failing sync reports a useful error");
+// `Service` is used as a global in head_helpers.js.
+// eslint-disable-next-line no-unused-vars
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+add_bookmark_test(async function run_test(engine) {
+  await engine.initialize();
+  engine._syncStartup = async function () {
+    throw new Error("FAIL!");
+  };
+
+  try {
+    _("Try calling the sync that should throw right away");
+    await engine._sync();
+    do_throw("Should have failed sync!");
+  } catch (ex) {
+    _("Making sure what we threw ended up as the exception:", ex);
+    Assert.equal(ex.message, "FAIL!");
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_bookmark_decline_undecline.js b/src/zen/tests/mochitests/sync/test_bookmark_decline_undecline.js
new file mode 100644
index 000000000..12139dd16
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_bookmark_decline_undecline.js
@@ -0,0 +1,48 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+// A stored reference to the collection won't be valid after disabling.
+function getBookmarkWBO(server, guid) {
+  let coll = server.user("foo").collection("bookmarks");
+  if (!coll) {
+    return null;
+  }
+  return coll.wbo(guid);
+}
+
+add_task(async function test_decline_undecline() {
+  let engine = Service.engineManager.get("bookmarks");
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  try {
+    let { guid: bzGuid } = await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      url: "https://bugzilla.mozilla.org",
+      index: PlacesUtils.bookmarks.DEFAULT_INDEX,
+      title: "bugzilla",
+    });
+
+    ok(!getBookmarkWBO(server, bzGuid), "Shouldn't have been uploaded yet");
+    await Service.sync();
+    ok(getBookmarkWBO(server, bzGuid), "Should be present on server");
+
+    engine.enabled = false;
+    await Service.sync();
+    ok(
+      !getBookmarkWBO(server, bzGuid),
+      "Shouldn't be present on server anymore"
+    );
+
+    engine.enabled = true;
+    await Service.sync();
+    ok(getBookmarkWBO(server, bzGuid), "Should be present on server again");
+  } finally {
+    await PlacesSyncUtils.bookmarks.reset();
+    await promiseStopServer(server);
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_bookmark_engine.js b/src/zen/tests/mochitests/sync/test_bookmark_engine.js
new file mode 100644
index 000000000..e08847195
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_bookmark_engine.js
@@ -0,0 +1,1508 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { BookmarkHTMLUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/BookmarkHTMLUtils.sys.mjs"
+);
+const { BookmarkJSONUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/BookmarkJSONUtils.sys.mjs"
+);
+const { Bookmark, BookmarkFolder, BookmarksEngine, Livemark } =
+  ChromeUtils.importESModule(
+    "resource://services-sync/engines/bookmarks.sys.mjs"
+  );
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { SyncedRecordsTelemetry } = ChromeUtils.importESModule(
+  "resource://services-sync/telemetry.sys.mjs"
+);
+
+async function fetchAllRecordIds() {
+  let db = await PlacesUtils.promiseDBConnection();
+  let rows = await db.executeCached(`
+    WITH RECURSIVE
+    syncedItems(id, guid) AS (
+      SELECT b.id, b.guid FROM moz_bookmarks b
+      WHERE b.guid IN ('menu________', 'toolbar_____', 'unfiled_____',
+                       'mobile______')
+      UNION ALL
+      SELECT b.id, b.guid FROM moz_bookmarks b
+      JOIN syncedItems s ON b.parent = s.id
+    )
+    SELECT guid FROM syncedItems`);
+  let recordIds = new Set();
+  for (let row of rows) {
+    let recordId = PlacesSyncUtils.bookmarks.guidToRecordId(
+      row.getResultByName("guid")
+    );
+    recordIds.add(recordId);
+  }
+  return recordIds;
+}
+
+async function cleanupEngine(engine) {
+  await engine.resetClient();
+  await engine._store.wipe();
+  for (const pref of Svc.PrefBranch.getChildList("")) {
+    Svc.PrefBranch.clearUserPref(pref);
+  }
+  Service.recordManager.clearCache();
+  // Note we don't finalize the engine here as add_bookmark_test() does.
+}
+
+async function cleanup(engine, server) {
+  await promiseStopServer(server);
+  await cleanupEngine(engine);
+}
+
+add_setup(async function () {
+  await generateNewKeys(Service.collectionKeys);
+  await Service.engineManager.unregister("bookmarks");
+
+  do_get_profile(); // FOG needs a profile dir
+  Services.fog.initializeFOG();
+});
+
+add_task(async function test_buffer_timeout() {
+  await Service.recordManager.clearCache();
+  await PlacesSyncUtils.bookmarks.reset();
+  let engine = new BookmarksEngine(Service);
+  engine._newWatchdog = function () {
+    // Return an already-aborted watchdog, so that we can abort merges
+    // immediately.
+    let watchdog = Async.watchdog();
+    watchdog.controller.abort();
+    return watchdog;
+  };
+  await engine.initialize();
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+  let collection = server.user("foo").collection("bookmarks");
+
+  try {
+    info("Insert local bookmarks");
+    await PlacesUtils.bookmarks.insertTree({
+      guid: PlacesUtils.bookmarks.unfiledGuid,
+      children: [
+        {
+          guid: "bookmarkAAAA",
+          url: "http://example.com/a",
+          title: "A",
+        },
+        {
+          guid: "bookmarkBBBB",
+          url: "http://example.com/b",
+          title: "B",
+        },
+      ],
+    });
+
+    info("Insert remote bookmarks");
+    collection.insert(
+      "menu",
+      encryptPayload({
+        id: "menu",
+        type: "folder",
+        parentid: "places",
+        title: "menu",
+        children: ["bookmarkCCCC", "bookmarkDDDD"],
+      })
+    );
+    collection.insert(
+      "bookmarkCCCC",
+      encryptPayload({
+        id: "bookmarkCCCC",
+        type: "bookmark",
+        parentid: "menu",
+        bmkUri: "http://example.com/c",
+        title: "C",
+      })
+    );
+    collection.insert(
+      "bookmarkDDDD",
+      encryptPayload({
+        id: "bookmarkDDDD",
+        type: "bookmark",
+        parentid: "menu",
+        bmkUri: "http://example.com/d",
+        title: "D",
+      })
+    );
+
+    info("We expect this sync to fail");
+    await Assert.rejects(
+      sync_engine_and_validate_telem(engine, true),
+      ex => ex.name == "InterruptedError"
+    );
+  } finally {
+    await cleanup(engine, server);
+    await engine.finalize();
+  }
+});
+
+add_bookmark_test(async function test_maintenance_after_failure(engine) {
+  _("Ensure we try to run maintenance if the engine fails to sync");
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  try {
+    let syncStartup = engine._syncStartup;
+    let syncError = new Error("Something is rotten in the state of Places");
+    engine._syncStartup = function () {
+      throw syncError;
+    };
+
+    Services.prefs.clearUserPref("places.database.lastMaintenance");
+
+    _("Ensure the sync fails and we run maintenance");
+    await Assert.rejects(
+      sync_engine_and_validate_telem(engine, true),
+      ex => ex == syncError
+    );
+    Assert.equal(Glean.sync.maintenanceRunBookmarks.testGetValue().length, 1);
+    Services.fog.testResetFOG();
+
+    _("Sync again, but ensure maintenance doesn't run");
+    await Assert.rejects(
+      sync_engine_and_validate_telem(engine, true),
+      ex => ex == syncError
+    );
+    Assert.equal(Glean.sync.maintenanceRunBookmarks.testGetValue(), null);
+    Services.fog.testResetFOG();
+
+    _("Fast-forward last maintenance pref; ensure maintenance runs");
+    Services.prefs.setIntPref(
+      "places.database.lastMaintenance",
+      Date.now() / 1000 - 14400
+    );
+    await Assert.rejects(
+      sync_engine_and_validate_telem(engine, true),
+      ex => ex == syncError
+    );
+    Assert.equal(Glean.sync.maintenanceRunBookmarks.testGetValue().length, 1);
+    Services.fog.testResetFOG();
+
+    _("Fix sync failure; ensure we report success after maintenance");
+    engine._syncStartup = syncStartup;
+    await sync_engine_and_validate_telem(engine, false);
+    Assert.equal(Glean.sync.maintenanceFixBookmarks.testGetValue().length, 1);
+    Services.fog.testResetFOG();
+
+    await sync_engine_and_validate_telem(engine, false);
+    Assert.equal(Glean.sync.maintenanceFixBookmarks.testGetValue(), null);
+    Services.fog.testResetFOG();
+  } finally {
+    await cleanup(engine, server);
+  }
+});
+
+add_bookmark_test(async function test_delete_invalid_roots_from_server(engine) {
+  _("Ensure that we delete the Places and Reading List roots from the server.");
+
+  enableValidationPrefs();
+
+  let store = engine._store;
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  let collection = server.user("foo").collection("bookmarks");
+
+  engine._tracker.start();
+
+  try {
+    let placesRecord = await store.createRecord("places");
+    collection.insert("places", encryptPayload(placesRecord.cleartext));
+
+    let listBmk = new Bookmark("bookmarks", Utils.makeGUID());
+    listBmk.bmkUri = "https://example.com";
+    listBmk.title = "Example reading list entry";
+    listBmk.parentName = "Reading List";
+    listBmk.parentid = "readinglist";
+    collection.insert(listBmk.id, encryptPayload(listBmk.cleartext));
+
+    let readingList = new BookmarkFolder("bookmarks", "readinglist");
+    readingList.title = "Reading List";
+    readingList.children = [listBmk.id];
+    readingList.parentName = "";
+    readingList.parentid = "places";
+    collection.insert("readinglist", encryptPayload(readingList.cleartext));
+
+    // Note that we don't insert a record for the toolbar, so the  engine will
+    // report a parent-child disagreement, since Firefox's `parentid` is
+    // `toolbar`.
+    let newBmk = new Bookmark("bookmarks", Utils.makeGUID());
+    newBmk.bmkUri = "http://getfirefox.com";
+    newBmk.title = "Get Firefox!";
+    newBmk.parentName = "Bookmarks Toolbar";
+    newBmk.parentid = "toolbar";
+    collection.insert(newBmk.id, encryptPayload(newBmk.cleartext));
+
+    deepEqual(
+      collection.keys().sort(),
+      ["places", "readinglist", listBmk.id, newBmk.id].sort(),
+      "Should store Places root, reading list items, and new bookmark on server"
+    );
+
+    let ping = await sync_engine_and_validate_telem(engine, true);
+    // In a real sync, the engine is named `bookmarks-buffered`.
+    // However, `sync_engine_and_validate_telem` simulates a sync where
+    // the engine isn't registered with the engine manager, so the recorder
+    // doesn't see its `overrideTelemetryName`.
+    let engineData = ping.engines.find(e => e.name == "bookmarks");
+    ok(engineData.validation, "Bookmarks engine should always run validation");
+    equal(
+      engineData.validation.checked,
+      6,
+      "Bookmarks engine should validate all items"
+    );
+    deepEqual(
+      engineData.validation.problems,
+      [
+        {
+          name: "parentChildDisagreements",
+          count: 1,
+        },
+      ],
+      "Bookmarks engine should report parent-child disagreement"
+    );
+    deepEqual(
+      engineData.steps.map(step => step.name),
+      [
+        "fetchLocalTree",
+        "fetchRemoteTree",
+        "merge",
+        "apply",
+        "notifyObservers",
+        "fetchLocalChangeRecords",
+      ],
+      "Bookmarks engine should report all merge steps"
+    );
+
+    deepEqual(
+      collection.keys().sort(),
+      ["menu", "mobile", "toolbar", "unfiled", newBmk.id].sort(),
+      "Should remove Places root and reading list items from server; upload local roots"
+    );
+  } finally {
+    await cleanup(engine, server);
+  }
+});
+
+add_bookmark_test(
+  async function test_processIncoming_error_orderChildren(engine) {
+    _(
+      "Ensure that _orderChildren() is called even when _processIncoming() throws an error."
+    );
+
+    let store = engine._store;
+    let server = await serverForFoo(engine);
+    await SyncTestingInfrastructure(server);
+
+    let collection = server.user("foo").collection("bookmarks");
+
+    try {
+      let folder1 = await PlacesUtils.bookmarks.insert({
+        parentGuid: PlacesUtils.bookmarks.toolbarGuid,
+        type: PlacesUtils.bookmarks.TYPE_FOLDER,
+        title: "Folder 1",
+      });
+
+      let bmk1 = await PlacesUtils.bookmarks.insert({
+        parentGuid: folder1.guid,
+        url: "http://getfirefox.com/",
+        title: "Get Firefox!",
+      });
+      let bmk2 = await PlacesUtils.bookmarks.insert({
+        parentGuid: folder1.guid,
+        url: "http://getthunderbird.com/",
+        title: "Get Thunderbird!",
+      });
+
+      let toolbar_record = await store.createRecord("toolbar");
+      collection.insert("toolbar", encryptPayload(toolbar_record.cleartext));
+
+      let bmk1_record = await store.createRecord(bmk1.guid);
+      collection.insert(bmk1.guid, encryptPayload(bmk1_record.cleartext));
+
+      let bmk2_record = await store.createRecord(bmk2.guid);
+      collection.insert(bmk2.guid, encryptPayload(bmk2_record.cleartext));
+
+      // Create a server record for folder1 where we flip the order of
+      // the children.
+      let folder1_record = await store.createRecord(folder1.guid);
+      let folder1_payload = folder1_record.cleartext;
+      folder1_payload.children.reverse();
+      collection.insert(folder1.guid, encryptPayload(folder1_payload));
+
+      // Create a bogus record that when synced down will provoke a
+      // network error which in turn provokes an exception in _processIncoming.
+      const BOGUS_GUID = "zzzzzzzzzzzz";
+      let bogus_record = collection.insert(BOGUS_GUID, "I'm a bogus record!");
+      bogus_record.get = function get() {
+        throw new Error("Sync this!");
+      };
+
+      // Make the 10 minutes old so it will only be synced in the toFetch phase.
+      bogus_record.modified = new_timestamp() - 60 * 10;
+      await engine.setLastSync(new_timestamp() - 60);
+      engine.toFetch = new SerializableSet([BOGUS_GUID]);
+
+      let error;
+      try {
+        await sync_engine_and_validate_telem(engine, true);
+      } catch (ex) {
+        error = ex;
+      }
+      ok(!!error);
+
+      // Verify that the bookmark order has been applied.
+      folder1_record = await store.createRecord(folder1.guid);
+      let new_children = folder1_record.children;
+      Assert.deepEqual(
+        new_children.sort(),
+        [folder1_payload.children[0], folder1_payload.children[1]].sort()
+      );
+
+      let localChildIds = await PlacesSyncUtils.bookmarks.fetchChildRecordIds(
+        folder1.guid
+      );
+      Assert.deepEqual(localChildIds.sort(), [bmk2.guid, bmk1.guid].sort());
+    } finally {
+      await cleanup(engine, server);
+    }
+  }
+);
+
+add_bookmark_test(async function test_restorePromptsReupload(engine) {
+  await test_restoreOrImport(engine, { replace: true });
+});
+
+add_bookmark_test(async function test_importPromptsReupload(engine) {
+  await test_restoreOrImport(engine, { replace: false });
+});
+
+// Test a JSON restore or HTML import. Use JSON if `replace` is `true`, or
+// HTML otherwise.
+async function test_restoreOrImport(engine, { replace }) {
+  let verb = replace ? "restore" : "import";
+  let verbing = replace ? "restoring" : "importing";
+  let bookmarkUtils = replace ? BookmarkJSONUtils : BookmarkHTMLUtils;
+
+  _(`Ensure that ${verbing} from a backup will reupload all records.`);
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  let collection = server.user("foo").collection("bookmarks");
+
+  engine._tracker.start(); // We skip usual startup...
+
+  try {
+    let folder1 = await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.toolbarGuid,
+      type: PlacesUtils.bookmarks.TYPE_FOLDER,
+      title: "Folder 1",
+    });
+
+    _("Create a single record.");
+    let bmk1 = await PlacesUtils.bookmarks.insert({
+      parentGuid: folder1.guid,
+      url: "http://getfirefox.com/",
+      title: "Get Firefox!",
+    });
+    _(`Get Firefox!: ${bmk1.guid}`);
+
+    let backupFilePath = PathUtils.join(
+      PathUtils.tempDir,
+      `t_b_e_${Date.now()}.json`
+    );
+
+    _("Make a backup.");
+
+    await bookmarkUtils.exportToFile(backupFilePath);
+
+    _("Create a different record and sync.");
+    let bmk2 = await PlacesUtils.bookmarks.insert({
+      parentGuid: folder1.guid,
+      url: "http://getthunderbird.com/",
+      title: "Get Thunderbird!",
+    });
+    _(`Get Thunderbird!: ${bmk2.guid}`);
+
+    await PlacesUtils.bookmarks.remove(bmk1.guid);
+
+    let error;
+    try {
+      await sync_engine_and_validate_telem(engine, false);
+    } catch (ex) {
+      error = ex;
+      _("Got error: " + Log.exceptionStr(ex));
+    }
+    Assert.ok(!error);
+
+    _(
+      "Verify that there's only one bookmark on the server, and it's Thunderbird."
+    );
+    // Of course, there's also the Bookmarks Toolbar and Bookmarks Menu...
+    let wbos = collection.keys(function (id) {
+      return !["menu", "toolbar", "mobile", "unfiled", folder1.guid].includes(
+        id
+      );
+    });
+    Assert.equal(wbos.length, 1);
+    Assert.equal(wbos[0], bmk2.guid);
+
+    _(`Now ${verb} from a backup.`);
+    await bookmarkUtils.importFromFile(backupFilePath, { replace });
+
+    // If `replace` is `true`, we'll wipe the server on the next sync.
+    let bookmarksCollection = server.user("foo").collection("bookmarks");
+    _("Verify that we didn't wipe the server.");
+    Assert.ok(!!bookmarksCollection);
+
+    _("Ensure we have the bookmarks we expect locally.");
+    let recordIds = await fetchAllRecordIds();
+    _("GUIDs: " + JSON.stringify([...recordIds]));
+
+    let bookmarkRecordIds = new Map();
+    let count = 0;
+    for (let recordId of recordIds) {
+      count++;
+      let info = await PlacesUtils.bookmarks.fetch(
+        PlacesSyncUtils.bookmarks.recordIdToGuid(recordId)
+      );
+      // Only one bookmark, so _all_ should be Firefox!
+      if (info.type == PlacesUtils.bookmarks.TYPE_BOOKMARK) {
+        _(`Found URI ${info.url.href} for record ID ${recordId}`);
+        bookmarkRecordIds.set(info.url.href, recordId);
+      }
+    }
+    Assert.ok(bookmarkRecordIds.has("http://getfirefox.com/"));
+    if (!replace) {
+      Assert.ok(bookmarkRecordIds.has("http://getthunderbird.com/"));
+    }
+
+    _("Have the correct number of IDs locally, too.");
+    let expectedResults = [
+      "menu",
+      "toolbar",
+      "mobile",
+      "unfiled",
+      folder1.guid,
+      bmk1.guid,
+    ];
+    if (!replace) {
+      expectedResults.push("toolbar", folder1.guid, bmk2.guid);
+    }
+    Assert.equal(count, expectedResults.length);
+
+    _("Sync again. This'll wipe bookmarks from the server.");
+    try {
+      await sync_engine_and_validate_telem(engine, false);
+    } catch (ex) {
+      error = ex;
+      _("Got error: " + Log.exceptionStr(ex));
+    }
+    Assert.ok(!error);
+
+    _("Verify that there's the right bookmarks on the server.");
+    // Of course, there's also the Bookmarks Toolbar and Bookmarks Menu...
+    let payloads = server.user("foo").collection("bookmarks").payloads();
+    let bookmarkWBOs = payloads.filter(function (wbo) {
+      return wbo.type == "bookmark";
+    });
+
+    let folderWBOs = payloads.filter(function (wbo) {
+      return (
+        wbo.type == "folder" &&
+        wbo.id != "menu" &&
+        wbo.id != "toolbar" &&
+        wbo.id != "unfiled" &&
+        wbo.id != "mobile" &&
+        wbo.parentid != "menu"
+      );
+    });
+
+    let expectedFX = {
+      id: bookmarkRecordIds.get("http://getfirefox.com/"),
+      bmkUri: "http://getfirefox.com/",
+      title: "Get Firefox!",
+    };
+    let expectedTB = {
+      id: bookmarkRecordIds.get("http://getthunderbird.com/"),
+      bmkUri: "http://getthunderbird.com/",
+      title: "Get Thunderbird!",
+    };
+
+    let expectedBookmarks;
+    if (replace) {
+      expectedBookmarks = [expectedFX];
+    } else {
+      expectedBookmarks = [expectedTB, expectedFX];
+    }
+
+    doCheckWBOs(bookmarkWBOs, expectedBookmarks);
+
+    _("Our old friend Folder 1 is still in play.");
+    let expectedFolder1 = { title: "Folder 1" };
+
+    let expectedFolders;
+    if (replace) {
+      expectedFolders = [expectedFolder1];
+    } else {
+      expectedFolders = [expectedFolder1, expectedFolder1];
+    }
+
+    doCheckWBOs(folderWBOs, expectedFolders);
+  } finally {
+    await cleanup(engine, server);
+  }
+}
+
+function doCheckWBOs(WBOs, expected) {
+  Assert.equal(WBOs.length, expected.length);
+  for (let i = 0; i < expected.length; i++) {
+    let lhs = WBOs[i];
+    let rhs = expected[i];
+    if ("id" in rhs) {
+      Assert.equal(lhs.id, rhs.id);
+    }
+    if ("bmkUri" in rhs) {
+      Assert.equal(lhs.bmkUri, rhs.bmkUri);
+    }
+    if ("title" in rhs) {
+      Assert.equal(lhs.title, rhs.title);
+    }
+  }
+}
+
+function FakeRecord(constructor, r) {
+  this.defaultCleartext = constructor.prototype.defaultCleartext;
+  constructor.call(this, "bookmarks", r.id);
+  for (let x in r) {
+    this[x] = r[x];
+  }
+  // Borrow the constructor's conversion functions.
+  this.toSyncBookmark = constructor.prototype.toSyncBookmark;
+  this.cleartextToString = constructor.prototype.cleartextToString;
+}
+
+// Bug 632287.
+// (Note that `test_mismatched_folder_types()` in
+//  toolkit/components/places/tests/sync/test_bookmark_kinds.js is an exact
+// copy of this test, so it's fine to remove it as part of bug 1449730)
+add_task(async function test_mismatched_types() {
+  _(
+    "Ensure that handling a record that changes type causes deletion " +
+      "then re-adding."
+  );
+
+  let oldRecord = {
+    id: "l1nZZXfB8nC7",
+    type: "folder",
+    parentName: "Bookmarks Toolbar",
+    title: "Innerst i Sneglehode",
+    description: null,
+    parentid: "toolbar",
+  };
+
+  let newRecord = {
+    id: "l1nZZXfB8nC7",
+    type: "livemark",
+    siteUri: "http://sneglehode.wordpress.com/",
+    feedUri: "http://sneglehode.wordpress.com/feed/",
+    parentName: "Bookmarks Toolbar",
+    title: "Innerst i Sneglehode",
+    description: null,
+    children: [
+      "HCRq40Rnxhrd",
+      "YeyWCV1RVsYw",
+      "GCceVZMhvMbP",
+      "sYi2hevdArlF",
+      "vjbZlPlSyGY8",
+      "UtjUhVyrpeG6",
+      "rVq8WMG2wfZI",
+      "Lx0tcy43ZKhZ",
+      "oT74WwV8_j4P",
+      "IztsItWVSo3-",
+    ],
+    parentid: "toolbar",
+  };
+
+  let engine = new BookmarksEngine(Service);
+  await engine.initialize();
+  let store = engine._store;
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  try {
+    let oldR = new FakeRecord(BookmarkFolder, oldRecord);
+    let newR = new FakeRecord(Livemark, newRecord);
+    oldR.parentid = PlacesUtils.bookmarks.toolbarGuid;
+    newR.parentid = PlacesUtils.bookmarks.toolbarGuid;
+
+    await store.applyIncoming(oldR);
+    await engine._apply();
+    _("Applied old. It's a folder.");
+    let oldID = await PlacesTestUtils.promiseItemId(oldR.id);
+    _("Old ID: " + oldID);
+    let oldInfo = await PlacesUtils.bookmarks.fetch(oldR.id);
+    Assert.equal(oldInfo.type, PlacesUtils.bookmarks.TYPE_FOLDER);
+
+    await store.applyIncoming(newR);
+    await engine._apply();
+  } finally {
+    await cleanup(engine, server);
+    await engine.finalize();
+  }
+});
+
+add_bookmark_test(async function test_misreconciled_root(engine) {
+  _("Ensure that we don't reconcile an arbitrary record with a root.");
+
+  let store = engine._store;
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  // Log real hard for this test.
+  store._log.trace = store._log.debug;
+  engine._log.trace = engine._log.debug;
+
+  await engine._syncStartup();
+
+  // Let's find out where the toolbar is right now.
+  let toolbarBefore = await store.createRecord("toolbar", "bookmarks");
+  let toolbarIDBefore = await PlacesTestUtils.promiseItemId(
+    PlacesUtils.bookmarks.toolbarGuid
+  );
+  Assert.notEqual(-1, toolbarIDBefore);
+
+  let parentRecordIDBefore = toolbarBefore.parentid;
+  let parentGUIDBefore =
+    PlacesSyncUtils.bookmarks.recordIdToGuid(parentRecordIDBefore);
+  let parentIDBefore = await PlacesTestUtils.promiseItemId(parentGUIDBefore);
+  Assert.equal("string", typeof parentGUIDBefore);
+
+  _("Current parent: " + parentGUIDBefore + " (" + parentIDBefore + ").");
+
+  let to_apply = {
+    id: "zzzzzzzzzzzz",
+    type: "folder",
+    title: "Bookmarks Toolbar",
+    description: "Now you're for it.",
+    parentName: "",
+    parentid: "mobile", // Why not?
+    children: [],
+  };
+
+  let rec = new FakeRecord(BookmarkFolder, to_apply);
+
+  _("Applying record.");
+  let countTelemetry = new SyncedRecordsTelemetry();
+  await store.applyIncomingBatch([rec], countTelemetry);
+
+  // Ensure that afterwards, toolbar is still there.
+  // As of 2012-12-05, this only passes because Places doesn't use "toolbar" as
+  // the real GUID, instead using a generated one. Sync does the translation.
+  let toolbarAfter = await store.createRecord("toolbar", "bookmarks");
+  let parentRecordIDAfter = toolbarAfter.parentid;
+  let parentGUIDAfter =
+    PlacesSyncUtils.bookmarks.recordIdToGuid(parentRecordIDAfter);
+  let parentIDAfter = await PlacesTestUtils.promiseItemId(parentGUIDAfter);
+  Assert.equal(
+    await PlacesTestUtils.promiseItemGuid(toolbarIDBefore),
+    PlacesUtils.bookmarks.toolbarGuid
+  );
+  Assert.equal(parentGUIDBefore, parentGUIDAfter);
+  Assert.equal(parentIDBefore, parentIDAfter);
+
+  await cleanup(engine, server);
+});
+
+add_bookmark_test(async function test_invalid_url(engine) {
+  _("Ensure an incoming invalid bookmark URL causes an outgoing tombstone.");
+
+  let server = await serverForFoo(engine);
+  let collection = server.user("foo").collection("bookmarks");
+
+  await SyncTestingInfrastructure(server);
+  await engine._syncStartup();
+
+  // check the URL really is invalid.
+  let url = "https://www.42registry.42/";
+  Assert.throws(() => Services.io.newURI(url), /invalid/);
+
+  let guid = "abcdefabcdef";
+
+  let toolbar = new BookmarkFolder("bookmarks", "toolbar");
+  toolbar.title = "toolbar";
+  toolbar.parentName = "";
+  toolbar.parentid = "places";
+  toolbar.children = [guid];
+  collection.insert("toolbar", encryptPayload(toolbar.cleartext));
+
+  let item1 = new Bookmark("bookmarks", guid);
+  item1.bmkUri = "https://www.42registry.42/";
+  item1.title = "invalid url";
+  item1.parentName = "Bookmarks Toolbar";
+  item1.parentid = "toolbar";
+  item1.dateAdded = 1234;
+  collection.insert(guid, encryptPayload(item1.cleartext));
+
+  _("syncing.");
+  await sync_engine_and_validate_telem(engine, false);
+
+  // We should find the record now exists on the server as a tombstone.
+  let updated = collection.cleartext(guid);
+  Assert.ok(updated.deleted, "record was deleted");
+
+  let local = await PlacesUtils.bookmarks.fetch(guid);
+  Assert.deepEqual(local, null, "no local bookmark exists");
+
+  await cleanup(engine, server);
+});
+
+add_bookmark_test(async function test_sync_dateAdded(engine) {
+  await Service.recordManager.clearCache();
+  await PlacesSyncUtils.bookmarks.reset();
+  let store = engine._store;
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  let collection = server.user("foo").collection("bookmarks");
+
+  // TODO: Avoid random orange (bug 1374599), this is only necessary
+  // intermittently - reset the last sync date so that we'll get all bookmarks.
+  await engine.setLastSync(1);
+
+  engine._tracker.start(); // We skip usual startup...
+
+  // Just matters that it's in the past, not how far.
+  let now = Date.now();
+  let oneYearMS = 365 * 24 * 60 * 60 * 1000;
+
+  try {
+    let toolbar = new BookmarkFolder("bookmarks", "toolbar");
+    toolbar.title = "toolbar";
+    toolbar.parentName = "";
+    toolbar.parentid = "places";
+    toolbar.children = [
+      "abcdefabcdef",
+      "aaaaaaaaaaaa",
+      "bbbbbbbbbbbb",
+      "cccccccccccc",
+      "dddddddddddd",
+      "eeeeeeeeeeee",
+    ];
+    collection.insert("toolbar", encryptPayload(toolbar.cleartext));
+
+    let item1GUID = "abcdefabcdef";
+    let item1 = new Bookmark("bookmarks", item1GUID);
+    item1.bmkUri = "https://example.com";
+    item1.title = "asdf";
+    item1.parentName = "Bookmarks Toolbar";
+    item1.parentid = "toolbar";
+    item1.dateAdded = now - oneYearMS;
+    collection.insert(item1GUID, encryptPayload(item1.cleartext));
+
+    let item2GUID = "aaaaaaaaaaaa";
+    let item2 = new Bookmark("bookmarks", item2GUID);
+    item2.bmkUri = "https://example.com/2";
+    item2.title = "asdf2";
+    item2.parentName = "Bookmarks Toolbar";
+    item2.parentid = "toolbar";
+    item2.dateAdded = now + oneYearMS;
+    const item2LastModified = now / 1000 - 100;
+    collection.insert(
+      item2GUID,
+      encryptPayload(item2.cleartext),
+      item2LastModified
+    );
+
+    let item3GUID = "bbbbbbbbbbbb";
+    let item3 = new Bookmark("bookmarks", item3GUID);
+    item3.bmkUri = "https://example.com/3";
+    item3.title = "asdf3";
+    item3.parentName = "Bookmarks Toolbar";
+    item3.parentid = "toolbar";
+    // no dateAdded
+    collection.insert(item3GUID, encryptPayload(item3.cleartext));
+
+    let item4GUID = "cccccccccccc";
+    let item4 = new Bookmark("bookmarks", item4GUID);
+    item4.bmkUri = "https://example.com/4";
+    item4.title = "asdf4";
+    item4.parentName = "Bookmarks Toolbar";
+    item4.parentid = "toolbar";
+    // no dateAdded, but lastModified in past
+    const item4LastModified = (now - oneYearMS) / 1000;
+    collection.insert(
+      item4GUID,
+      encryptPayload(item4.cleartext),
+      item4LastModified
+    );
+
+    let item5GUID = "dddddddddddd";
+    let item5 = new Bookmark("bookmarks", item5GUID);
+    item5.bmkUri = "https://example.com/5";
+    item5.title = "asdf5";
+    item5.parentName = "Bookmarks Toolbar";
+    item5.parentid = "toolbar";
+    // no dateAdded, lastModified in (near) future.
+    const item5LastModified = (now + 60000) / 1000;
+    collection.insert(
+      item5GUID,
+      encryptPayload(item5.cleartext),
+      item5LastModified
+    );
+
+    let item6GUID = "eeeeeeeeeeee";
+    let item6 = new Bookmark("bookmarks", item6GUID);
+    item6.bmkUri = "https://example.com/6";
+    item6.title = "asdf6";
+    item6.parentName = "Bookmarks Toolbar";
+    item6.parentid = "toolbar";
+    const item6LastModified = (now - oneYearMS) / 1000;
+    collection.insert(
+      item6GUID,
+      encryptPayload(item6.cleartext),
+      item6LastModified
+    );
+
+    await sync_engine_and_validate_telem(engine, false);
+
+    let record1 = await store.createRecord(item1GUID);
+    let record2 = await store.createRecord(item2GUID);
+
+    equal(
+      item1.dateAdded,
+      record1.dateAdded,
+      "dateAdded in past should be synced"
+    );
+    equal(
+      record2.dateAdded,
+      item2LastModified * 1000,
+      "dateAdded in future should be ignored in favor of last modified"
+    );
+
+    let record3 = await store.createRecord(item3GUID);
+
+    ok(record3.dateAdded);
+    // Make sure it's within 24 hours of the right timestamp... This is a little
+    // dodgey but we only really care that it's basically accurate and has the
+    // right day.
+    Assert.less(Math.abs(Date.now() - record3.dateAdded), 24 * 60 * 60 * 1000);
+
+    let record4 = await store.createRecord(item4GUID);
+    equal(
+      record4.dateAdded,
+      item4LastModified * 1000,
+      "If no dateAdded is provided, lastModified should be used"
+    );
+
+    let record5 = await store.createRecord(item5GUID);
+    equal(
+      record5.dateAdded,
+      item5LastModified * 1000,
+      "If no dateAdded is provided, lastModified should be used (even if it's in the future)"
+    );
+
+    // Update item2 and try resyncing it.
+    item2.dateAdded = now - 100000;
+    collection.insert(
+      item2GUID,
+      encryptPayload(item2.cleartext),
+      now / 1000 - 50
+    );
+
+    // Also, add a local bookmark and make sure its date added makes it up to the server
+    let bz = await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      url: "https://bugzilla.mozilla.org/",
+      title: "Bugzilla",
+    });
+
+    // last sync did a POST, which doesn't advance its lastModified value.
+    // Next sync of the engine doesn't hit info/collections, so lastModified
+    // remains stale. Setting it to null side-steps that.
+    engine.lastModified = null;
+    await sync_engine_and_validate_telem(engine, false);
+
+    let newRecord2 = await store.createRecord(item2GUID);
+    equal(
+      newRecord2.dateAdded,
+      item2.dateAdded,
+      "dateAdded update should work for earlier date"
+    );
+
+    let bzWBO = collection.cleartext(bz.guid);
+    ok(bzWBO.dateAdded, "Locally added dateAdded lost");
+
+    let localRecord = await store.createRecord(bz.guid);
+    equal(
+      bzWBO.dateAdded,
+      localRecord.dateAdded,
+      "dateAdded should not change during upload"
+    );
+
+    item2.dateAdded += 10000;
+    collection.insert(
+      item2GUID,
+      encryptPayload(item2.cleartext),
+      now / 1000 - 10
+    );
+
+    engine.lastModified = null;
+    await sync_engine_and_validate_telem(engine, false);
+
+    let newerRecord2 = await store.createRecord(item2GUID);
+    equal(
+      newerRecord2.dateAdded,
+      newRecord2.dateAdded,
+      "dateAdded update should be ignored for later date if we know an earlier one "
+    );
+  } finally {
+    await cleanup(engine, server);
+  }
+});
+
+add_task(async function test_buffer_hasDupe() {
+  await Service.recordManager.clearCache();
+  await PlacesSyncUtils.bookmarks.reset();
+  let engine = new BookmarksEngine(Service);
+  await engine.initialize();
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+  let collection = server.user("foo").collection("bookmarks");
+  engine._tracker.start(); // We skip usual startup...
+  try {
+    let guid1 = Utils.makeGUID();
+    let guid2 = Utils.makeGUID();
+    await PlacesUtils.bookmarks.insert({
+      guid: guid1,
+      parentGuid: PlacesUtils.bookmarks.toolbarGuid,
+      url: "https://www.example.com",
+      title: "example.com",
+    });
+    await PlacesUtils.bookmarks.insert({
+      guid: guid2,
+      parentGuid: PlacesUtils.bookmarks.toolbarGuid,
+      url: "https://www.example.com",
+      title: "example.com",
+    });
+
+    await sync_engine_and_validate_telem(engine, false);
+    // Make sure we set hasDupe on outgoing records
+    Assert.ok(collection.payloads().every(payload => payload.hasDupe));
+
+    await PlacesUtils.bookmarks.remove(guid1);
+
+    await sync_engine_and_validate_telem(engine, false);
+
+    let tombstone = JSON.parse(
+      JSON.parse(collection.payload(guid1)).ciphertext
+    );
+    // We shouldn't set hasDupe on tombstones.
+    Assert.ok(tombstone.deleted);
+    Assert.ok(!tombstone.hasDupe);
+
+    let record = JSON.parse(JSON.parse(collection.payload(guid2)).ciphertext);
+    // We should set hasDupe on weakly uploaded records.
+    Assert.ok(!record.deleted);
+    Assert.ok(
+      record.hasDupe,
+      "Bookmarks bookmark engine should set hasDupe for weakly uploaded records."
+    );
+
+    await sync_engine_and_validate_telem(engine, false);
+  } finally {
+    await cleanup(engine, server);
+    await engine.finalize();
+  }
+});
+
+// Bug 890217.
+add_bookmark_test(async function test_sync_imap_URLs(engine) {
+  await Service.recordManager.clearCache();
+  await PlacesSyncUtils.bookmarks.reset();
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  let collection = server.user("foo").collection("bookmarks");
+
+  engine._tracker.start(); // We skip usual startup...
+
+  try {
+    collection.insert(
+      "menu",
+      encryptPayload({
+        id: "menu",
+        type: "folder",
+        parentid: "places",
+        title: "Bookmarks Menu",
+        children: ["bookmarkAAAA"],
+      })
+    );
+    collection.insert(
+      "bookmarkAAAA",
+      encryptPayload({
+        id: "bookmarkAAAA",
+        type: "bookmark",
+        parentid: "menu",
+        bmkUri:
+          "imap://vs@eleven.vs.solnicky.cz:993/fetch%3EUID%3E/" +
+          "INBOX%3E56291?part=1.2&type=image/jpeg&filename=" +
+          "invalidazPrahy.jpg",
+        title:
+          "invalidazPrahy.jpg (JPEG Image, 1280x1024 pixels) - Scaled (71%)",
+      })
+    );
+
+    await PlacesUtils.bookmarks.insert({
+      guid: "bookmarkBBBB",
+      parentGuid: PlacesUtils.bookmarks.toolbarGuid,
+      url:
+        "imap://eleven.vs.solnicky.cz:993/fetch%3EUID%3E/" +
+        "CURRENT%3E2433?part=1.2&type=text/html&filename=TomEdwards.html",
+      title: "TomEdwards.html",
+    });
+
+    await sync_engine_and_validate_telem(engine, false);
+
+    let aInfo = await PlacesUtils.bookmarks.fetch("bookmarkAAAA");
+    equal(
+      aInfo.url.href,
+      "imap://vs@eleven.vs.solnicky.cz:993/" +
+        "fetch%3EUID%3E/INBOX%3E56291?part=1.2&type=image/jpeg&filename=" +
+        "invalidazPrahy.jpg",
+      "Remote bookmark A with IMAP URL should exist locally"
+    );
+
+    let bPayload = collection.cleartext("bookmarkBBBB");
+    equal(
+      bPayload.bmkUri,
+      "imap://eleven.vs.solnicky.cz:993/" +
+        "fetch%3EUID%3E/CURRENT%3E2433?part=1.2&type=text/html&filename=" +
+        "TomEdwards.html",
+      "Local bookmark B with IMAP URL should exist remotely"
+    );
+  } finally {
+    await cleanup(engine, server);
+  }
+});
+
+add_task(async function test_resume_buffer() {
+  await Service.recordManager.clearCache();
+  let engine = new BookmarksEngine(Service);
+  await engine.initialize();
+  await engine._store.wipe();
+  await engine.resetClient();
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  let collection = server.user("foo").collection("bookmarks");
+
+  engine._tracker.start(); // We skip usual startup...
+
+  const batchChunkSize = 50;
+
+  engine._store._batchChunkSize = batchChunkSize;
+  try {
+    let children = [];
+
+    let timestamp = round_timestamp(Date.now());
+    // Add two chunks worth of records to the server
+    for (let i = 0; i < batchChunkSize * 2; ++i) {
+      let cleartext = {
+        id: Utils.makeGUID(),
+        type: "bookmark",
+        parentid: "toolbar",
+        title: `Bookmark ${i}`,
+        parentName: "Bookmarks Toolbar",
+        bmkUri: `https://example.com/${i}`,
+      };
+      let wbo = collection.insert(
+        cleartext.id,
+        encryptPayload(cleartext),
+        timestamp + 10 * i
+      );
+      // Something that is effectively random, but deterministic.
+      // (This is just to ensure we don't accidentally start using the
+      // sortindex again).
+      wbo.sortindex = 1000 + Math.round(Math.sin(i / 5) * 100);
+      children.push(cleartext.id);
+    }
+
+    // Add the parent of those records, and ensure its timestamp is the most recent.
+    collection.insert(
+      "toolbar",
+      encryptPayload({
+        id: "toolbar",
+        type: "folder",
+        parentid: "places",
+        title: "Bookmarks Toolbar",
+        children,
+      }),
+      timestamp + 10 * children.length
+    );
+
+    // Replace applyIncomingBatch with a custom one that calls the original,
+    // but forces it to throw on the 2nd chunk.
+    let origApplyIncomingBatch = engine._store.applyIncomingBatch;
+    engine._store.applyIncomingBatch = function (records) {
+      if (records.length > batchChunkSize) {
+        // Hacky way to make reading from the batchChunkSize'th record throw.
+        delete records[batchChunkSize];
+        Object.defineProperty(records, batchChunkSize, {
+          get() {
+            throw new Error("D:");
+          },
+        });
+      }
+      return origApplyIncomingBatch.call(this, records);
+    };
+
+    let caughtError;
+    _("We expect this to fail");
+    try {
+      await sync_engine_and_validate_telem(engine, true);
+    } catch (e) {
+      caughtError = e;
+    }
+    Assert.ok(caughtError, "Expected engine.sync to throw");
+    Assert.equal(caughtError.message, "D:");
+
+    // The buffer subtracts one second from the actual timestamp.
+    let lastSync = (await engine.getLastSync()) + 1;
+    // We poisoned the batchChunkSize'th record, so the last successfully
+    // applied record will be batchChunkSize - 1.
+    let expectedLastSync = timestamp + 10 * (batchChunkSize - 1);
+    Assert.equal(expectedLastSync, lastSync);
+
+    engine._store.applyIncomingBatch = origApplyIncomingBatch;
+
+    await sync_engine_and_validate_telem(engine, false);
+
+    // Check that all the children made it onto the correct record.
+    let toolbarRecord = await engine._store.createRecord("toolbar");
+    Assert.deepEqual(toolbarRecord.children.sort(), children.sort());
+  } finally {
+    await cleanup(engine, server);
+    await engine.finalize();
+  }
+});
+
+add_bookmark_test(async function test_livemarks(engine) {
+  _("Ensure we replace new and existing livemarks with tombstones");
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  let collection = server.user("foo").collection("bookmarks");
+  let now = Date.now();
+
+  try {
+    _("Insert existing livemark");
+    let modifiedForA = now - 5 * 60 * 1000;
+    await PlacesUtils.bookmarks.insert({
+      guid: "livemarkAAAA",
+      type: PlacesUtils.bookmarks.TYPE_FOLDER,
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      title: "A",
+      lastModified: new Date(modifiedForA),
+      dateAdded: new Date(modifiedForA),
+      source: PlacesUtils.bookmarks.SOURCE_SYNC,
+    });
+    collection.insert(
+      "menu",
+      encryptPayload({
+        id: "menu",
+        type: "folder",
+        parentName: "",
+        title: "menu",
+        children: ["livemarkAAAA"],
+        parentid: "places",
+      }),
+      round_timestamp(modifiedForA)
+    );
+    collection.insert(
+      "livemarkAAAA",
+      encryptPayload({
+        id: "livemarkAAAA",
+        type: "livemark",
+        feedUri: "http://example.com/a",
+        parentName: "menu",
+        title: "A",
+        parentid: "menu",
+      }),
+      round_timestamp(modifiedForA)
+    );
+
+    _("Insert remotely updated livemark");
+    await PlacesUtils.bookmarks.insert({
+      guid: "livemarkBBBB",
+      type: PlacesUtils.bookmarks.TYPE_FOLDER,
+      parentGuid: PlacesUtils.bookmarks.toolbarGuid,
+      title: "B",
+      lastModified: new Date(now),
+      dateAdded: new Date(now),
+    });
+    collection.insert(
+      "toolbar",
+      encryptPayload({
+        id: "toolbar",
+        type: "folder",
+        parentName: "",
+        title: "toolbar",
+        children: ["livemarkBBBB"],
+        parentid: "places",
+      }),
+      round_timestamp(now)
+    );
+    collection.insert(
+      "livemarkBBBB",
+      encryptPayload({
+        id: "livemarkBBBB",
+        type: "livemark",
+        feedUri: "http://example.com/b",
+        parentName: "toolbar",
+        title: "B",
+        parentid: "toolbar",
+      }),
+      round_timestamp(now)
+    );
+
+    _("Insert new remote livemark");
+    collection.insert(
+      "unfiled",
+      encryptPayload({
+        id: "unfiled",
+        type: "folder",
+        parentName: "",
+        title: "unfiled",
+        children: ["livemarkCCCC"],
+        parentid: "places",
+      }),
+      round_timestamp(now)
+    );
+    collection.insert(
+      "livemarkCCCC",
+      encryptPayload({
+        id: "livemarkCCCC",
+        type: "livemark",
+        feedUri: "http://example.com/c",
+        parentName: "unfiled",
+        title: "C",
+        parentid: "unfiled",
+      }),
+      round_timestamp(now)
+    );
+
+    _("Bump last sync time to ignore A");
+    await engine.setLastSync(round_timestamp(now) - 60);
+
+    _("Sync");
+    await sync_engine_and_validate_telem(engine, false);
+
+    deepEqual(
+      collection.keys().sort(),
+      [
+        "livemarkAAAA",
+        "livemarkBBBB",
+        "livemarkCCCC",
+        "menu",
+        "mobile",
+        "toolbar",
+        "unfiled",
+      ],
+      "Should store original livemark A and tombstones for B and C on server"
+    );
+
+    let payloads = collection.payloads();
+
+    deepEqual(
+      payloads.find(payload => payload.id == "menu").children,
+      ["livemarkAAAA"],
+      "Should keep A in menu"
+    );
+    ok(
+      !payloads.find(payload => payload.id == "livemarkAAAA").deleted,
+      "Should not upload tombstone for A"
+    );
+
+    deepEqual(
+      payloads.find(payload => payload.id == "toolbar").children,
+      [],
+      "Should remove B from toolbar"
+    );
+    ok(
+      payloads.find(payload => payload.id == "livemarkBBBB").deleted,
+      "Should upload tombstone for B"
+    );
+
+    deepEqual(
+      payloads.find(payload => payload.id == "unfiled").children,
+      [],
+      "Should remove C from unfiled"
+    );
+    ok(
+      payloads.find(payload => payload.id == "livemarkCCCC").deleted,
+      "Should replace C with tombstone"
+    );
+
+    await assertBookmarksTreeMatches(
+      "",
+      [
+        {
+          guid: PlacesUtils.bookmarks.menuGuid,
+          index: 0,
+          children: [
+            {
+              guid: "livemarkAAAA",
+              index: 0,
+            },
+          ],
+        },
+        {
+          guid: PlacesUtils.bookmarks.toolbarGuid,
+          index: 1,
+        },
+        {
+          guid: PlacesUtils.bookmarks.unfiledGuid,
+          index: 3,
+        },
+        {
+          guid: PlacesUtils.bookmarks.mobileGuid,
+          index: 4,
+        },
+      ],
+      "Should keep A and remove B locally"
+    );
+  } finally {
+    await cleanup(engine, server);
+  }
+});
+
+add_bookmark_test(async function test_unknown_fields(engine) {
+  let store = engine._store;
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+  let collection = server.user("foo").collection("bookmarks");
+  try {
+    let folder1 = await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.toolbarGuid,
+      type: PlacesUtils.bookmarks.TYPE_FOLDER,
+      title: "Folder 1",
+    });
+    let bmk1 = await PlacesUtils.bookmarks.insert({
+      parentGuid: folder1.guid,
+      url: "http://getfirefox.com/",
+      title: "Get Firefox!",
+    });
+    let bmk2 = await PlacesUtils.bookmarks.insert({
+      parentGuid: folder1.guid,
+      url: "http://getthunderbird.com/",
+      title: "Get Thunderbird!",
+    });
+    let toolbar_record = await store.createRecord("toolbar");
+    collection.insert("toolbar", encryptPayload(toolbar_record.cleartext));
+
+    let folder1_record_without_unknown_fields = await store.createRecord(
+      folder1.guid
+    );
+    collection.insert(
+      folder1.guid,
+      encryptPayload(folder1_record_without_unknown_fields.cleartext)
+    );
+
+    // First bookmark record has an unknown string field
+    let bmk1_record = await store.createRecord(bmk1.guid);
+    console.log("bmk1_record: ", bmk1_record);
+    bmk1_record.cleartext.unknownStrField =
+      "an unknown field from another client";
+    collection.insert(bmk1.guid, encryptPayload(bmk1_record.cleartext));
+
+    // Second bookmark record as an unknown object field
+    let bmk2_record = await store.createRecord(bmk2.guid);
+    bmk2_record.cleartext.unknownObjField = {
+      name: "an unknown object from another client",
+    };
+    collection.insert(bmk2.guid, encryptPayload(bmk2_record.cleartext));
+
+    // Sync the two bookmarks
+    await sync_engine_and_validate_telem(engine, true);
+
+    // Add a folder could also have an unknown field
+    let folder1_record = await store.createRecord(folder1.guid);
+    folder1_record.cleartext.unknownStrField =
+      "a folder could also have an unknown field!";
+    collection.insert(folder1.guid, encryptPayload(folder1_record.cleartext));
+
+    // sync the new updates
+    await engine.setLastSync(1);
+    await sync_engine_and_validate_telem(engine, true);
+
+    let payloads = collection.payloads();
+    // Validate the server has the unknown fields at the top level (and now unknownFields)
+    let server_bmk1 = payloads.find(payload => payload.id == bmk1.guid);
+    deepEqual(
+      server_bmk1.unknownStrField,
+      "an unknown field from another client",
+      "unknown fields correctly on the record"
+    );
+    Assert.equal(server_bmk1.unknownFields, null);
+
+    // Check that the mirror table has unknown fields
+    let db = await PlacesUtils.promiseDBConnection();
+    let rows = await db.executeCached(
+      `
+      SELECT guid, title, unknownFields from items WHERE guid IN 
+      (:bmk1, :bmk2, :folder1)`,
+      { bmk1: bmk1.guid, bmk2: bmk2.guid, folder1: folder1.guid }
+    );
+    // We should have 3 rows that came from the server
+    Assert.equal(rows.length, 3);
+
+    // Bookmark 1 - unknown string field
+    let remote_bmk1 = rows.find(
+      row => row.getResultByName("guid") == bmk1.guid
+    );
+    Assert.equal(remote_bmk1.getResultByName("title"), "Get Firefox!");
+    deepEqual(JSON.parse(remote_bmk1.getResultByName("unknownFields")), {
+      unknownStrField: "an unknown field from another client",
+    });
+
+    // Bookmark 2 - unknown object field
+    let remote_bmk2 = rows.find(
+      row => row.getResultByName("guid") == bmk2.guid
+    );
+    Assert.equal(remote_bmk2.getResultByName("title"), "Get Thunderbird!");
+    deepEqual(JSON.parse(remote_bmk2.getResultByName("unknownFields")), {
+      unknownObjField: {
+        name: "an unknown object from another client",
+      },
+    });
+
+    // Folder with unknown field
+
+    // check the server still has the unknown field
+    deepEqual(
+      payloads.find(payload => payload.id == folder1.guid).unknownStrField,
+      "a folder could also have an unknown field!",
+      "Server still has the unknown field"
+    );
+
+    let remote_folder = rows.find(
+      row => row.getResultByName("guid") == folder1.guid
+    );
+    Assert.equal(remote_folder.getResultByName("title"), "Folder 1");
+    deepEqual(JSON.parse(remote_folder.getResultByName("unknownFields")), {
+      unknownStrField: "a folder could also have an unknown field!",
+    });
+  } finally {
+    await cleanup(engine, server);
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_bookmark_order.js b/src/zen/tests/mochitests/sync/test_bookmark_order.js
new file mode 100644
index 000000000..fc182b81e
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_bookmark_order.js
@@ -0,0 +1,586 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+_(
+  "Making sure after processing incoming bookmarks, they show up in the right order"
+);
+const { Bookmark, BookmarkFolder } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/bookmarks.sys.mjs"
+);
+const { Weave } = ChromeUtils.importESModule(
+  "resource://services-sync/main.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+async function serverForFoo(engine) {
+  await generateNewKeys(Service.collectionKeys);
+
+  let clientsEngine = Service.clientsEngine;
+  let clientsSyncID = await clientsEngine.resetLocalSyncID();
+  let engineSyncID = await engine.resetLocalSyncID();
+  return serverForUsers(
+    { foo: "password" },
+    {
+      meta: {
+        global: {
+          syncID: Service.syncID,
+          storageVersion: STORAGE_VERSION,
+          engines: {
+            clients: {
+              version: clientsEngine.version,
+              syncID: clientsSyncID,
+            },
+            [engine.name]: {
+              version: engine.version,
+              syncID: engineSyncID,
+            },
+          },
+        },
+      },
+      crypto: {
+        keys: encryptPayload({
+          id: "keys",
+          // Generate a fake default key bundle to avoid resetting the client
+          // before the first sync.
+          default: [
+            await Weave.Crypto.generateRandomKey(),
+            await Weave.Crypto.generateRandomKey(),
+          ],
+        }),
+      },
+      [engine.name]: {},
+    }
+  );
+}
+
+async function resolveConflict(
+  engine,
+  collection,
+  timestamp,
+  buildTree,
+  message
+) {
+  let guids = {
+    // These items don't exist on the server.
+    fx: Utils.makeGUID(),
+    nightly: Utils.makeGUID(),
+    support: Utils.makeGUID(),
+    customize: Utils.makeGUID(),
+
+    // These exist on the server, but in a different order, and `res`
+    // has completely different children.
+    res: Utils.makeGUID(),
+    tb: Utils.makeGUID(),
+
+    // These don't exist locally.
+    bz: Utils.makeGUID(),
+    irc: Utils.makeGUID(),
+    mdn: Utils.makeGUID(),
+  };
+
+  await PlacesUtils.bookmarks.insertTree({
+    guid: PlacesUtils.bookmarks.menuGuid,
+    children: [
+      {
+        guid: guids.fx,
+        title: "Get Firefox!",
+        url: "http://getfirefox.com/",
+      },
+      {
+        guid: guids.res,
+        title: "Resources",
+        type: PlacesUtils.bookmarks.TYPE_FOLDER,
+        children: [
+          {
+            guid: guids.nightly,
+            title: "Nightly",
+            url: "https://nightly.mozilla.org/",
+          },
+          {
+            guid: guids.support,
+            title: "Support",
+            url: "https://support.mozilla.org/",
+          },
+          {
+            guid: guids.customize,
+            title: "Customize",
+            url: "https://mozilla.org/firefox/customize/",
+          },
+        ],
+      },
+      {
+        title: "Get Thunderbird!",
+        guid: guids.tb,
+        url: "http://getthunderbird.com/",
+      },
+    ],
+  });
+
+  let serverRecords = [
+    {
+      id: "menu",
+      type: "folder",
+      title: "Bookmarks Menu",
+      parentid: "places",
+      children: [guids.tb, guids.res],
+    },
+    {
+      id: guids.tb,
+      type: "bookmark",
+      parentid: "menu",
+      bmkUri: "http://getthunderbird.com/",
+      title: "Get Thunderbird!",
+    },
+    {
+      id: guids.res,
+      type: "folder",
+      parentid: "menu",
+      title: "Resources",
+      children: [guids.irc, guids.bz, guids.mdn],
+    },
+    {
+      id: guids.bz,
+      type: "bookmark",
+      parentid: guids.res,
+      bmkUri: "https://bugzilla.mozilla.org/",
+      title: "Bugzilla",
+    },
+    {
+      id: guids.mdn,
+      type: "bookmark",
+      parentid: guids.res,
+      bmkUri: "https://developer.mozilla.org/",
+      title: "MDN",
+    },
+    {
+      id: guids.irc,
+      type: "bookmark",
+      parentid: guids.res,
+      bmkUri: "ircs://irc.mozilla.org/nightly",
+      title: "IRC",
+    },
+  ];
+  for (let record of serverRecords) {
+    collection.insert(record.id, encryptPayload(record), timestamp);
+  }
+
+  engine.lastModified = collection.timestamp;
+  await sync_engine_and_validate_telem(engine, false);
+
+  let expectedTree = buildTree(guids);
+  await assertBookmarksTreeMatches(
+    PlacesUtils.bookmarks.menuGuid,
+    expectedTree,
+    message
+  );
+}
+
+async function get_engine() {
+  return Service.engineManager.get("bookmarks");
+}
+
+add_task(async function test_local_order_newer() {
+  let engine = await get_engine();
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  try {
+    let collection = server.user("foo").collection("bookmarks");
+    let serverModified = Date.now() / 1000 - 120;
+    await resolveConflict(
+      engine,
+      collection,
+      serverModified,
+      guids => [
+        {
+          guid: guids.fx,
+          index: 0,
+        },
+        {
+          guid: guids.res,
+          index: 1,
+          children: [
+            {
+              guid: guids.nightly,
+              index: 0,
+            },
+            {
+              guid: guids.support,
+              index: 1,
+            },
+            {
+              guid: guids.customize,
+              index: 2,
+            },
+            {
+              guid: guids.irc,
+              index: 3,
+            },
+            {
+              guid: guids.bz,
+              index: 4,
+            },
+            {
+              guid: guids.mdn,
+              index: 5,
+            },
+          ],
+        },
+        {
+          guid: guids.tb,
+          index: 2,
+        },
+      ],
+      "Should use local order as base if remote is older"
+    );
+  } finally {
+    await engine.wipeClient();
+    await Service.startOver();
+    await promiseStopServer(server);
+  }
+});
+
+add_task(async function test_remote_order_newer() {
+  let engine = await get_engine();
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  try {
+    let collection = server.user("foo").collection("bookmarks");
+    let serverModified = Date.now() / 1000 + 120;
+    await resolveConflict(
+      engine,
+      collection,
+      serverModified,
+      guids => [
+        {
+          guid: guids.tb,
+          index: 0,
+        },
+        {
+          guid: guids.res,
+          index: 1,
+          children: [
+            {
+              guid: guids.irc,
+              index: 0,
+            },
+            {
+              guid: guids.bz,
+              index: 1,
+            },
+            {
+              guid: guids.mdn,
+              index: 2,
+            },
+            {
+              guid: guids.nightly,
+              index: 3,
+            },
+            {
+              guid: guids.support,
+              index: 4,
+            },
+            {
+              guid: guids.customize,
+              index: 5,
+            },
+          ],
+        },
+        {
+          guid: guids.fx,
+          index: 2,
+        },
+      ],
+      "Should use remote order as base if local is older"
+    );
+  } finally {
+    await engine.wipeClient();
+    await Service.startOver();
+    await promiseStopServer(server);
+  }
+});
+
+add_task(async function test_bookmark_order() {
+  let engine = await get_engine();
+  let store = engine._store;
+  _("Starting with a clean slate of no bookmarks");
+  await store.wipe();
+  await assertBookmarksTreeMatches(
+    "",
+    [
+      {
+        guid: PlacesUtils.bookmarks.menuGuid,
+        index: 0,
+      },
+      {
+        guid: PlacesUtils.bookmarks.toolbarGuid,
+        index: 1,
+      },
+      {
+        // Index 2 is the tags root. (Root indices depend on the order of the
+        // `CreateRoot` calls in `Database::CreateBookmarkRoots`).
+        guid: PlacesUtils.bookmarks.unfiledGuid,
+        index: 3,
+      },
+      {
+        guid: PlacesUtils.bookmarks.mobileGuid,
+        index: 4,
+      },
+    ],
+    "clean slate"
+  );
+
+  function bookmark(name, parent) {
+    let bm = new Bookmark("http://weave.server/my-bookmark");
+    bm.id = name;
+    bm.title = name;
+    bm.bmkUri = "http://uri/";
+    bm.parentid = parent || "unfiled";
+    bm.tags = [];
+    return bm;
+  }
+
+  function folder(name, parent, children) {
+    let bmFolder = new BookmarkFolder("http://weave.server/my-bookmark-folder");
+    bmFolder.id = name;
+    bmFolder.title = name;
+    bmFolder.parentid = parent || "unfiled";
+    bmFolder.children = children;
+    return bmFolder;
+  }
+
+  async function apply(records) {
+    for (record of records) {
+      await store.applyIncoming(record);
+    }
+    await engine._apply();
+  }
+  let id10 = "10_aaaaaaaaa";
+  _("basic add first bookmark");
+  await apply([bookmark(id10, "")]);
+  await assertBookmarksTreeMatches(
+    "",
+    [
+      {
+        guid: PlacesUtils.bookmarks.menuGuid,
+        index: 0,
+      },
+      {
+        guid: PlacesUtils.bookmarks.toolbarGuid,
+        index: 1,
+      },
+      {
+        guid: PlacesUtils.bookmarks.unfiledGuid,
+        index: 3,
+        children: [
+          {
+            guid: id10,
+            index: 0,
+          },
+        ],
+      },
+      {
+        guid: PlacesUtils.bookmarks.mobileGuid,
+        index: 4,
+      },
+    ],
+    "basic add first bookmark"
+  );
+  let id20 = "20_aaaaaaaaa";
+  _("basic append behind 10");
+  await apply([bookmark(id20, "")]);
+  await assertBookmarksTreeMatches(
+    "",
+    [
+      {
+        guid: PlacesUtils.bookmarks.menuGuid,
+        index: 0,
+      },
+      {
+        guid: PlacesUtils.bookmarks.toolbarGuid,
+        index: 1,
+      },
+      {
+        guid: PlacesUtils.bookmarks.unfiledGuid,
+        index: 3,
+        children: [
+          {
+            guid: id10,
+            index: 0,
+          },
+          {
+            guid: id20,
+            index: 1,
+          },
+        ],
+      },
+      {
+        guid: PlacesUtils.bookmarks.mobileGuid,
+        index: 4,
+      },
+    ],
+    "basic append behind 10"
+  );
+
+  let id31 = "31_aaaaaaaaa";
+  let id30 = "f30_aaaaaaaa";
+  _("basic create in folder");
+  let b31 = bookmark(id31, id30);
+  let f30 = folder(id30, "", [id31]);
+  await apply([b31, f30]);
+  await assertBookmarksTreeMatches(
+    "",
+    [
+      {
+        guid: PlacesUtils.bookmarks.menuGuid,
+        index: 0,
+      },
+      {
+        guid: PlacesUtils.bookmarks.toolbarGuid,
+        index: 1,
+      },
+      {
+        guid: PlacesUtils.bookmarks.unfiledGuid,
+        index: 3,
+        children: [
+          {
+            guid: id10,
+            index: 0,
+          },
+          {
+            guid: id20,
+            index: 1,
+          },
+          {
+            guid: id30,
+            index: 2,
+            children: [
+              {
+                guid: id31,
+                index: 0,
+              },
+            ],
+          },
+        ],
+      },
+      {
+        guid: PlacesUtils.bookmarks.mobileGuid,
+        index: 4,
+      },
+    ],
+    "basic create in folder"
+  );
+
+  let id41 = "41_aaaaaaaaa";
+  let id40 = "f40_aaaaaaaa";
+  _("insert missing parent -> append to unfiled");
+  await apply([bookmark(id41, id40)]);
+  await assertBookmarksTreeMatches(
+    "",
+    [
+      {
+        guid: PlacesUtils.bookmarks.menuGuid,
+        index: 0,
+      },
+      {
+        guid: PlacesUtils.bookmarks.toolbarGuid,
+        index: 1,
+      },
+      {
+        guid: PlacesUtils.bookmarks.unfiledGuid,
+        index: 3,
+        children: [
+          {
+            guid: id10,
+            index: 0,
+          },
+          {
+            guid: id20,
+            index: 1,
+          },
+          {
+            guid: id30,
+            index: 2,
+            children: [
+              {
+                guid: id31,
+                index: 0,
+              },
+            ],
+          },
+          {
+            guid: id41,
+            index: 3,
+          },
+        ],
+      },
+      {
+        guid: PlacesUtils.bookmarks.mobileGuid,
+        index: 4,
+      },
+    ],
+    "insert missing parent -> append to unfiled"
+  );
+
+  let id42 = "42_aaaaaaaaa";
+
+  _("insert another missing parent -> append");
+  await apply([bookmark(id42, id40)]);
+  await assertBookmarksTreeMatches(
+    "",
+    [
+      {
+        guid: PlacesUtils.bookmarks.menuGuid,
+        index: 0,
+      },
+      {
+        guid: PlacesUtils.bookmarks.toolbarGuid,
+        index: 1,
+      },
+      {
+        guid: PlacesUtils.bookmarks.unfiledGuid,
+        index: 3,
+        children: [
+          {
+            guid: id10,
+            index: 0,
+          },
+          {
+            guid: id20,
+            index: 1,
+          },
+          {
+            guid: id30,
+            index: 2,
+            children: [
+              {
+                guid: id31,
+                index: 0,
+              },
+            ],
+          },
+          {
+            guid: id41,
+            index: 3,
+          },
+          {
+            guid: id42,
+            index: 4,
+          },
+        ],
+      },
+      {
+        guid: PlacesUtils.bookmarks.mobileGuid,
+        index: 4,
+      },
+    ],
+    "insert another missing parent -> append"
+  );
+
+  await engine.wipeClient();
+  await Service.startOver();
+  await engine.finalize();
+});
diff --git a/src/zen/tests/mochitests/sync/test_bookmark_places_query_rewriting.js b/src/zen/tests/mochitests/sync/test_bookmark_places_query_rewriting.js
new file mode 100644
index 000000000..e8dbbb48b
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_bookmark_places_query_rewriting.js
@@ -0,0 +1,57 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+_("Rewrite place: URIs.");
+const { BookmarkQuery, BookmarkFolder } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/bookmarks.sys.mjs"
+);
+// `Service` is used as a global in head_helpers.js.
+// eslint-disable-next-line no-unused-vars
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+function makeTagRecord(id, uri) {
+  let tagRecord = new BookmarkQuery("bookmarks", id);
+  tagRecord.queryId = "MagicTags";
+  tagRecord.parentName = "Bookmarks Toolbar";
+  tagRecord.bmkUri = uri;
+  tagRecord.title = "tagtag";
+  tagRecord.folderName = "bar";
+  tagRecord.parentid = PlacesUtils.bookmarks.toolbarGuid;
+  return tagRecord;
+}
+
+add_bookmark_test(async function run_test(engine) {
+  let store = engine._store;
+
+  let toolbar = new BookmarkFolder("bookmarks", "toolbar");
+  toolbar.parentid = "places";
+  toolbar.children = ["abcdefabcdef"];
+
+  let uri = "place:folder=499&type=7&queryType=1";
+  let tagRecord = makeTagRecord("abcdefabcdef", uri);
+
+  _("Type: " + tagRecord.type);
+  _("Folder name: " + tagRecord.folderName);
+  await store.applyIncoming(toolbar);
+  await store.applyIncoming(tagRecord);
+  await engine._apply();
+
+  let insertedRecord = await store.createRecord("abcdefabcdef", "bookmarks");
+  Assert.equal(insertedRecord.bmkUri, "place:tag=bar");
+
+  _("... but not if the type is wrong.");
+  let wrongTypeURI = "place:folder=499&type=2&queryType=1";
+  let wrongTypeRecord = makeTagRecord("fedcbafedcba", wrongTypeURI);
+  await store.applyIncoming(wrongTypeRecord);
+  toolbar.children = ["fedcbafedcba"];
+  await store.applyIncoming(toolbar);
+  let expected = wrongTypeURI;
+  await engine._apply();
+  // the mirror appends a special param to these.
+  expected += "&excludeItems=1";
+
+  insertedRecord = await store.createRecord("fedcbafedcba", "bookmarks");
+  Assert.equal(insertedRecord.bmkUri, expected);
+});
diff --git a/src/zen/tests/mochitests/sync/test_bookmark_record.js b/src/zen/tests/mochitests/sync/test_bookmark_record.js
new file mode 100644
index 000000000..9d160ee68
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_bookmark_record.js
@@ -0,0 +1,64 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Bookmark, BookmarkQuery, PlacesItem } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/bookmarks.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+function prepareBookmarkItem(collection, id) {
+  let b = new Bookmark(collection, id);
+  b.cleartext.stuff = "my payload here";
+  return b;
+}
+
+add_task(async function test_bookmark_record() {
+  await configureIdentity();
+
+  await generateNewKeys(Service.collectionKeys);
+  let keyBundle = Service.identity.syncKeyBundle;
+
+  _("Creating a record");
+
+  let placesItem = new PlacesItem("bookmarks", "foo", "bookmark");
+  let bookmarkItem = prepareBookmarkItem("bookmarks", "foo");
+
+  _("Checking getTypeObject");
+  Assert.equal(placesItem.getTypeObject(placesItem.type), Bookmark);
+  Assert.equal(bookmarkItem.getTypeObject(bookmarkItem.type), Bookmark);
+
+  await bookmarkItem.encrypt(keyBundle);
+  _("Ciphertext is " + bookmarkItem.ciphertext);
+  Assert.notEqual(bookmarkItem.ciphertext, null);
+
+  _("Decrypting the record");
+
+  let payload = await bookmarkItem.decrypt(keyBundle);
+  Assert.equal(payload.stuff, "my payload here");
+  Assert.equal(bookmarkItem.getTypeObject(bookmarkItem.type), Bookmark);
+  Assert.notEqual(payload, bookmarkItem.payload); // wrap.data.payload is the encrypted one
+});
+
+add_task(async function test_query_foldername() {
+  // Bug 1443388
+  let checks = [
+    ["foo", "foo"],
+    ["", undefined],
+  ];
+  for (let [inVal, outVal] of checks) {
+    let bmk1 = new BookmarkQuery("bookmarks", Utils.makeGUID());
+    bmk1.fromSyncBookmark({
+      url: Services.io.newURI("https://example.com"),
+      folder: inVal,
+    });
+    Assert.strictEqual(bmk1.folderName, outVal);
+
+    // other direction
+    let bmk2 = new BookmarkQuery("bookmarks", Utils.makeGUID());
+    bmk2.folderName = inVal;
+    let record = bmk2.toSyncBookmark();
+    Assert.strictEqual(record.folder, outVal);
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_bookmark_store.js b/src/zen/tests/mochitests/sync/test_bookmark_store.js
new file mode 100644
index 000000000..44fcc19aa
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_bookmark_store.js
@@ -0,0 +1,486 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Bookmark, BookmarkFolder, BookmarkQuery, PlacesItem } =
+  ChromeUtils.importESModule(
+    "resource://services-sync/engines/bookmarks.sys.mjs"
+  );
+// `Service` is used as a global in head_helpers.js.
+// eslint-disable-next-line no-unused-vars
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+const BookmarksToolbarTitle = "toolbar";
+
+// apply some test records without going via a test server.
+async function apply_records(engine, records) {
+  for (record of records) {
+    await engine._store.applyIncoming(record);
+  }
+  await engine._apply();
+}
+
+add_bookmark_test(async function test_ignore_specials(engine) {
+  _("Ensure that we can't delete bookmark roots.");
+  let store = engine._store;
+
+  // Belt...
+  let record = new BookmarkFolder("bookmarks", "toolbar", "folder");
+  record.deleted = true;
+  Assert.notEqual(
+    null,
+    await PlacesTestUtils.promiseItemId(PlacesUtils.bookmarks.toolbarGuid)
+  );
+
+  await apply_records(engine, [record]);
+
+  // Ensure that the toolbar exists.
+  Assert.notEqual(
+    null,
+    await PlacesTestUtils.promiseItemId(PlacesUtils.bookmarks.toolbarGuid)
+  );
+
+  await apply_records(engine, [record]);
+
+  Assert.notEqual(
+    null,
+    await PlacesTestUtils.promiseItemId(PlacesUtils.bookmarks.toolbarGuid)
+  );
+  await store.wipe();
+});
+
+add_bookmark_test(async function test_bookmark_create(engine) {
+  let store = engine._store;
+
+  try {
+    _("Ensure the record isn't present yet.");
+    let item = await PlacesUtils.bookmarks.fetch({
+      url: "http://getfirefox.com/",
+    });
+    Assert.equal(null, item);
+
+    _("Let's create a new record.");
+    let fxrecord = new Bookmark("bookmarks", "get-firefox1");
+    fxrecord.bmkUri = "http://getfirefox.com/";
+    fxrecord.title = "Get Firefox!";
+    fxrecord.tags = ["firefox", "awesome", "browser"];
+    fxrecord.keyword = "awesome";
+    fxrecord.parentName = BookmarksToolbarTitle;
+    fxrecord.parentid = "toolbar";
+    await apply_records(engine, [fxrecord]);
+
+    _("Verify it has been created correctly.");
+    item = await PlacesUtils.bookmarks.fetch(fxrecord.id);
+    Assert.equal(item.type, PlacesUtils.bookmarks.TYPE_BOOKMARK);
+    Assert.equal(item.url.href, "http://getfirefox.com/");
+    Assert.equal(item.title, fxrecord.title);
+    Assert.equal(item.parentGuid, PlacesUtils.bookmarks.toolbarGuid);
+    let keyword = await PlacesUtils.keywords.fetch(fxrecord.keyword);
+    Assert.equal(keyword.url.href, "http://getfirefox.com/");
+
+    _(
+      "Have the store create a new record object. Verify that it has the same data."
+    );
+    let newrecord = await store.createRecord(fxrecord.id);
+    Assert.ok(newrecord instanceof Bookmark);
+    for (let property of [
+      "type",
+      "bmkUri",
+      "title",
+      "keyword",
+      "parentName",
+      "parentid",
+    ]) {
+      Assert.equal(newrecord[property], fxrecord[property]);
+    }
+    Assert.ok(Utils.deepEquals(newrecord.tags.sort(), fxrecord.tags.sort()));
+
+    _("The calculated sort index is based on frecency data.");
+    Assert.greaterOrEqual(newrecord.sortindex, 150);
+
+    _("Create a record with some values missing.");
+    let tbrecord = new Bookmark("bookmarks", "thunderbird1");
+    tbrecord.bmkUri = "http://getthunderbird.com/";
+    tbrecord.parentName = BookmarksToolbarTitle;
+    tbrecord.parentid = "toolbar";
+    await apply_records(engine, [tbrecord]);
+
+    _("Verify it has been created correctly.");
+    item = await PlacesUtils.bookmarks.fetch(tbrecord.id);
+    Assert.equal(item.type, PlacesUtils.bookmarks.TYPE_BOOKMARK);
+    Assert.equal(item.url.href, "http://getthunderbird.com/");
+    Assert.equal(item.title, "");
+    Assert.equal(item.parentGuid, PlacesUtils.bookmarks.toolbarGuid);
+    keyword = await PlacesUtils.keywords.fetch({
+      url: "http://getthunderbird.com/",
+    });
+    Assert.equal(null, keyword);
+  } finally {
+    _("Clean up.");
+    await store.wipe();
+  }
+});
+
+add_bookmark_test(async function test_bookmark_update(engine) {
+  let store = engine._store;
+
+  try {
+    _("Create a bookmark whose values we'll change.");
+    let bmk1 = await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.toolbarGuid,
+      url: "http://getfirefox.com/",
+      title: "Get Firefox!",
+    });
+    await PlacesUtils.keywords.insert({
+      url: "http://getfirefox.com/",
+      keyword: "firefox",
+    });
+
+    _("Update the record with some null values.");
+    let record = await store.createRecord(bmk1.guid);
+    record.title = null;
+    record.keyword = null;
+    record.tags = null;
+    await apply_records(engine, [record]);
+
+    _("Verify that the values have been cleared.");
+    let item = await PlacesUtils.bookmarks.fetch(bmk1.guid);
+    Assert.equal(item.title, "");
+    let keyword = await PlacesUtils.keywords.fetch({
+      url: "http://getfirefox.com/",
+    });
+    Assert.equal(null, keyword);
+  } finally {
+    _("Clean up.");
+    await store.wipe();
+  }
+});
+
+add_bookmark_test(async function test_bookmark_createRecord(engine) {
+  let store = engine._store;
+
+  try {
+    _("Create a bookmark without a title.");
+    let bmk1 = await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.toolbarGuid,
+      url: "http://getfirefox.com/",
+    });
+
+    _("Verify that the record is created accordingly.");
+    let record = await store.createRecord(bmk1.guid);
+    Assert.equal(record.title, "");
+    Assert.equal(record.keyword, null);
+  } finally {
+    _("Clean up.");
+    await store.wipe();
+  }
+});
+
+add_bookmark_test(async function test_folder_create(engine) {
+  let store = engine._store;
+
+  try {
+    _("Create a folder.");
+    let folder = new BookmarkFolder("bookmarks", "testfolder-1");
+    folder.parentName = BookmarksToolbarTitle;
+    folder.parentid = "toolbar";
+    folder.title = "Test Folder";
+    await apply_records(engine, [folder]);
+
+    _("Verify it has been created correctly.");
+    let item = await PlacesUtils.bookmarks.fetch(folder.id);
+    Assert.equal(item.type, PlacesUtils.bookmarks.TYPE_FOLDER);
+    Assert.equal(item.title, folder.title);
+    Assert.equal(item.parentGuid, PlacesUtils.bookmarks.toolbarGuid);
+
+    _(
+      "Have the store create a new record object. Verify that it has the same data."
+    );
+    let newrecord = await store.createRecord(folder.id);
+    Assert.ok(newrecord instanceof BookmarkFolder);
+    for (let property of ["title", "parentName", "parentid"]) {
+      Assert.equal(newrecord[property], folder[property]);
+    }
+
+    _("Folders have high sort index to ensure they're synced first.");
+    Assert.equal(newrecord.sortindex, 1000000);
+  } finally {
+    _("Clean up.");
+    await store.wipe();
+  }
+});
+
+add_bookmark_test(async function test_folder_createRecord(engine) {
+  let store = engine._store;
+
+  try {
+    _("Create a folder.");
+    let folder1 = await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.toolbarGuid,
+      type: PlacesUtils.bookmarks.TYPE_FOLDER,
+      title: "Folder1",
+    });
+
+    _("Create two bookmarks in that folder without assigning them GUIDs.");
+    let bmk1 = await PlacesUtils.bookmarks.insert({
+      parentGuid: folder1.guid,
+      url: "http://getfirefox.com/",
+      title: "Get Firefox!",
+    });
+    let bmk2 = await PlacesUtils.bookmarks.insert({
+      parentGuid: folder1.guid,
+      url: "http://getthunderbird.com/",
+      title: "Get Thunderbird!",
+    });
+
+    _("Create a record for the folder and verify basic properties.");
+    let record = await store.createRecord(folder1.guid);
+    Assert.ok(record instanceof BookmarkFolder);
+    Assert.equal(record.title, "Folder1");
+    Assert.equal(record.parentid, "toolbar");
+    Assert.equal(record.parentName, BookmarksToolbarTitle);
+
+    _(
+      "Verify the folder's children. Ensures that the bookmarks were given GUIDs."
+    );
+    Assert.deepEqual(record.children, [bmk1.guid, bmk2.guid]);
+  } finally {
+    _("Clean up.");
+    await store.wipe();
+  }
+});
+
+add_bookmark_test(async function test_deleted(engine) {
+  let store = engine._store;
+
+  try {
+    _("Create a bookmark that will be deleted.");
+    let bmk1 = await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.toolbarGuid,
+      url: "http://getfirefox.com/",
+      title: "Get Firefox!",
+    });
+    // The engine needs to think we've previously synced it.
+    await PlacesTestUtils.markBookmarksAsSynced();
+
+    _("Delete the bookmark through the store.");
+    let record = new PlacesItem("bookmarks", bmk1.guid);
+    record.deleted = true;
+    await apply_records(engine, [record]);
+    _("Ensure it has been deleted.");
+    let item = await PlacesUtils.bookmarks.fetch(bmk1.guid);
+    let newrec = await store.createRecord(bmk1.guid);
+    Assert.equal(null, item);
+    Assert.equal(newrec.deleted, true);
+    _("Verify that the keyword has been cleared.");
+    let keyword = await PlacesUtils.keywords.fetch({
+      url: "http://getfirefox.com/",
+    });
+    Assert.equal(null, keyword);
+  } finally {
+    _("Clean up.");
+    await store.wipe();
+  }
+});
+
+add_bookmark_test(async function test_move_folder(engine) {
+  let store = engine._store;
+  store._childrenToOrder = {}; // *sob* - only needed for legacy.
+
+  try {
+    _("Create two folders and a bookmark in one of them.");
+    let folder1 = await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.toolbarGuid,
+      type: PlacesUtils.bookmarks.TYPE_FOLDER,
+      title: "Folder1",
+    });
+    let folder2 = await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.toolbarGuid,
+      type: PlacesUtils.bookmarks.TYPE_FOLDER,
+      title: "Folder2",
+    });
+    let bmk = await PlacesUtils.bookmarks.insert({
+      parentGuid: folder1.guid,
+      url: "http://getfirefox.com/",
+      title: "Get Firefox!",
+    });
+    // add records to the store that represent the current state.
+    await apply_records(engine, [
+      await store.createRecord(folder1.guid),
+      await store.createRecord(folder2.guid),
+      await store.createRecord(bmk.guid),
+    ]);
+
+    _("Now simulate incoming records reparenting it.");
+    let bmkRecord = await store.createRecord(bmk.guid);
+    Assert.equal(bmkRecord.parentid, folder1.guid);
+    bmkRecord.parentid = folder2.guid;
+
+    let folder1Record = await store.createRecord(folder1.guid);
+    Assert.deepEqual(folder1Record.children, [bmk.guid]);
+    folder1Record.children = [];
+    let folder2Record = await store.createRecord(folder2.guid);
+    Assert.deepEqual(folder2Record.children, []);
+    folder2Record.children = [bmk.guid];
+
+    await apply_records(engine, [bmkRecord, folder1Record, folder2Record]);
+
+    _("Verify the new parent.");
+    let movedBmk = await PlacesUtils.bookmarks.fetch(bmk.guid);
+    Assert.equal(movedBmk.parentGuid, folder2.guid);
+  } finally {
+    _("Clean up.");
+    await store.wipe();
+  }
+});
+
+add_bookmark_test(async function test_move_order(engine) {
+  let store = engine._store;
+  let tracker = engine._tracker;
+
+  // Make sure the tracker is turned on.
+  tracker.start();
+  try {
+    _("Create two bookmarks");
+    let bmk1 = await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.toolbarGuid,
+      url: "http://getfirefox.com/",
+      title: "Get Firefox!",
+    });
+    let bmk2 = await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.toolbarGuid,
+      url: "http://getthunderbird.com/",
+      title: "Get Thunderbird!",
+    });
+
+    _("Verify order.");
+    let childIds =
+      await PlacesSyncUtils.bookmarks.fetchChildRecordIds("toolbar");
+    Assert.deepEqual(childIds, [bmk1.guid, bmk2.guid]);
+    let toolbar = await store.createRecord("toolbar");
+    Assert.deepEqual(toolbar.children, [bmk1.guid, bmk2.guid]);
+
+    _("Move bookmarks around.");
+    store._childrenToOrder = {};
+    toolbar.children = [bmk2.guid, bmk1.guid];
+    await apply_records(engine, [
+      toolbar,
+      await store.createRecord(bmk1.guid),
+      await store.createRecord(bmk2.guid),
+    ]);
+    delete store._childrenToOrder;
+
+    _("Verify new order.");
+    let newChildIds =
+      await PlacesSyncUtils.bookmarks.fetchChildRecordIds("toolbar");
+    Assert.deepEqual(newChildIds, [bmk2.guid, bmk1.guid]);
+  } finally {
+    await tracker.stop();
+    _("Clean up.");
+    await store.wipe();
+  }
+});
+
+// Tests Bug 806460, in which query records arrive with empty folder
+// names and missing bookmark URIs.
+add_bookmark_test(async function test_empty_query_doesnt_die(engine) {
+  let record = new BookmarkQuery("bookmarks", "8xoDGqKrXf1P");
+  record.folderName = "";
+  record.queryId = "";
+  record.parentName = "Toolbar";
+  record.parentid = "toolbar";
+
+  // These should not throw.
+  await apply_records(engine, [record]);
+
+  delete record.folderName;
+  await apply_records(engine, [record]);
+});
+
+add_bookmark_test(async function test_calculateIndex_for_invalid_url(engine) {
+  let store = engine._store;
+
+  let folderIndex = await store._calculateIndex({
+    type: "folder",
+  });
+  equal(folderIndex, 1000000, "Should use high sort index for folders");
+
+  let toolbarIndex = await store._calculateIndex({
+    parentid: "toolbar",
+  });
+  equal(toolbarIndex, 150, "Should bump sort index for toolbar bookmarks");
+
+  let validURLIndex = await store._calculateIndex({
+    bmkUri: "http://example.com/a",
+  });
+  greaterOrEqual(validURLIndex, 0, "Should use frecency for index");
+
+  let invalidURLIndex = await store._calculateIndex({
+    bmkUri: "!@#$%",
+  });
+  equal(invalidURLIndex, 0, "Should not throw for invalid URLs");
+});
+
+// Test that applying incoming records uses the server's modified timestamp
+// for the local lastModified, not the current time. This is important because
+// using the current time causes non-deterministic behavior in the merge
+// algorithm when comparing local and remote ages.
+add_bookmark_test(async function test_incoming_lastModified(engine) {
+  let store = engine._store;
+
+  // The server's modified timestamp (in seconds).
+  const serverModified = 1770000000;
+
+  _("Create a folder record with a specific server modified time.");
+  let folderRecord = new BookmarkFolder("bookmarks", "BBBBBBBBBBBB");
+  folderRecord.title = "Test Folder";
+  folderRecord.parentName = BookmarksToolbarTitle;
+  folderRecord.parentid = "toolbar";
+  folderRecord.children = ["AAAAAAAAAAAA"];
+  folderRecord.modified = serverModified;
+
+  _("Create a bookmark record with a specific server modified time.");
+  let bmkRecord = new Bookmark("bookmarks", "AAAAAAAAAAAA");
+  bmkRecord.bmkUri = "http://example.com/test";
+  bmkRecord.title = "Test Bookmark";
+  bmkRecord.parentName = "Test Folder";
+  bmkRecord.parentid = "BBBBBBBBBBBB";
+  bmkRecord.modified = serverModified;
+
+  await apply_records(engine, [folderRecord, bmkRecord]);
+
+  _("Verify the bookmark's lastModified matches the server timestamp.");
+  let item = await PlacesUtils.bookmarks.fetch({ guid: "AAAAAAAAAAAA" });
+  Assert.ok(item, "Bookmark should exist");
+  // The server timestamp is in seconds, lastModified is in milliseconds.
+  Assert.equal(
+    item.lastModified.getTime(),
+    serverModified * 1000,
+    "lastModified should match the server's modified timestamp"
+  );
+
+  _("Verify the folder's lastModified also matches.");
+  let folder = await PlacesUtils.bookmarks.fetch("BBBBBBBBBBBB");
+  Assert.ok(folder, "Folder should exist");
+  Assert.equal(
+    folder.lastModified.getTime(),
+    serverModified * 1000,
+    "Folder lastModified should match the server's modified timestamp"
+  );
+
+  _("Update the bookmark with a newer server timestamp.");
+  const newerServerModified = 1780000000;
+  bmkRecord.title = "Updated Test Bookmark";
+  bmkRecord.modified = newerServerModified;
+  await apply_records(engine, [bmkRecord]);
+
+  item = await PlacesUtils.bookmarks.fetch("AAAAAAAAAAAA");
+  Assert.equal(
+    item.lastModified.getTime(),
+    newerServerModified * 1000,
+    "lastModified should be updated to the newer server timestamp"
+  );
+
+  await store.wipe();
+});
diff --git a/src/zen/tests/mochitests/sync/test_bookmark_tracker.js b/src/zen/tests/mochitests/sync/test_bookmark_tracker.js
new file mode 100644
index 000000000..c47b573e7
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_bookmark_tracker.js
@@ -0,0 +1,1264 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { PlacesTransactions } = ChromeUtils.importESModule(
+  "resource://gre/modules/PlacesTransactions.sys.mjs"
+);
+
+let engine;
+let store;
+let tracker;
+
+const DAY_IN_MS = 24 * 60 * 60 * 1000;
+
+add_task(async function setup() {
+  await Service.engineManager.switchAlternatives();
+  engine = Service.engineManager.get("bookmarks");
+  store = engine._store;
+  tracker = engine._tracker;
+});
+
+// Test helpers.
+async function verifyTrackerEmpty() {
+  await PlacesTestUtils.promiseAsyncUpdates();
+  let changes = await tracker.getChangedIDs();
+  deepEqual(changes, {});
+  equal(tracker.score, 0);
+}
+
+async function resetTracker() {
+  await PlacesTestUtils.markBookmarksAsSynced();
+  tracker.resetScore();
+}
+
+async function cleanup() {
+  await engine.setLastSync(0);
+  await store.wipe();
+  await resetTracker();
+  await tracker.stop();
+}
+
+// startTracking is a signal that the test wants to notice things that happen
+// after this is called (ie, things already tracked should be discarded.)
+async function startTracking() {
+  engine._tracker.start();
+  await PlacesTestUtils.markBookmarksAsSynced();
+}
+
+async function verifyTrackedItems(tracked) {
+  await PlacesTestUtils.promiseAsyncUpdates();
+  let changedIDs = await tracker.getChangedIDs();
+  let trackedIDs = new Set(Object.keys(changedIDs));
+  for (let guid of tracked) {
+    ok(guid in changedIDs, `${guid} should be tracked`);
+    Assert.greater(
+      changedIDs[guid].modified,
+      0,
+      `${guid} should have a modified time`
+    );
+    Assert.greaterOrEqual(
+      changedIDs[guid].counter,
+      -1,
+      `${guid} should have a change counter`
+    );
+    trackedIDs.delete(guid);
+  }
+  equal(
+    trackedIDs.size,
+    0,
+    `Unhandled tracked IDs: ${JSON.stringify(Array.from(trackedIDs))}`
+  );
+}
+
+async function verifyTrackedCount(expected) {
+  await PlacesTestUtils.promiseAsyncUpdates();
+  let changedIDs = await tracker.getChangedIDs();
+  do_check_attribute_count(changedIDs, expected);
+}
+
+// A debugging helper that dumps the full bookmarks tree.
+// Currently unused, but might come in handy
+// eslint-disable-next-line no-unused-vars
+async function dumpBookmarks() {
+  let columns = [
+    "id",
+    "title",
+    "guid",
+    "syncStatus",
+    "syncChangeCounter",
+    "position",
+  ];
+  return PlacesUtils.promiseDBConnection().then(connection => {
+    let all = [];
+    return connection
+      .executeCached(
+        `SELECT ${columns.join(", ")} FROM moz_bookmarks;`,
+        {},
+        row => {
+          let repr = {};
+          for (let column of columns) {
+            repr[column] = row.getResultByName(column);
+          }
+          all.push(repr);
+        }
+      )
+      .then(() => {
+        dump("All bookmarks:\n");
+        dump(JSON.stringify(all, undefined, 2));
+      });
+  });
+}
+
+add_task(async function test_tracking() {
+  _("Test starting and stopping the tracker");
+
+  // Remove existing tracking information for roots.
+  await startTracking();
+
+  let folder = await PlacesUtils.bookmarks.insert({
+    parentGuid: PlacesUtils.bookmarks.menuGuid,
+    title: "Test Folder",
+    type: PlacesUtils.bookmarks.TYPE_FOLDER,
+  });
+
+  // creating the folder should have made 2 changes - the folder itself and
+  // the parent of the folder.
+  await verifyTrackedCount(2);
+  // Reset the changes as the rest of the test doesn't want to see these.
+  await resetTracker();
+
+  function createBmk() {
+    return PlacesUtils.bookmarks.insert({
+      parentGuid: folder.guid,
+      url: "http://getfirefox.com",
+      title: "Get Firefox!",
+    });
+  }
+
+  try {
+    _("Tell the tracker to start tracking changes.");
+    await startTracking();
+    await createBmk();
+    // We expect two changed items because the containing folder
+    // changed as well (new child).
+    await verifyTrackedCount(2);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE);
+
+    _("Notifying twice won't do any harm.");
+    await createBmk();
+    await verifyTrackedCount(3);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE * 2);
+  } finally {
+    _("Clean up.");
+    await cleanup();
+  }
+});
+
+add_task(async function test_tracker_sql_batching() {
+  _(
+    "Test tracker does the correct thing when it is forced to batch SQL queries"
+  );
+
+  const SQLITE_MAX_VARIABLE_NUMBER = 999;
+  let numItems = SQLITE_MAX_VARIABLE_NUMBER * 2 + 10;
+
+  await startTracking();
+
+  let children = [];
+  for (let i = 0; i < numItems; i++) {
+    children.push({
+      url: "https://example.org/" + i,
+      title: "Sync Bookmark " + i,
+    });
+  }
+  let inserted = await PlacesUtils.bookmarks.insertTree({
+    guid: PlacesUtils.bookmarks.unfiledGuid,
+    children: [
+      {
+        type: PlacesUtils.bookmarks.TYPE_FOLDER,
+        children,
+      },
+    ],
+  });
+
+  Assert.equal(children.length, numItems);
+  Assert.equal(inserted.length, numItems + 1);
+  await verifyTrackedCount(numItems + 2); // The parent and grandparent are also tracked.
+  await resetTracker();
+
+  await PlacesUtils.bookmarks.remove(inserted[0]);
+  await verifyTrackedCount(numItems + 2);
+
+  await cleanup();
+});
+
+add_task(async function test_bookmarkAdded() {
+  _("Items inserted via the synchronous bookmarks API should be tracked");
+
+  try {
+    await startTracking();
+
+    _("Insert a folder using the sync API");
+    let totalSyncChanges = PlacesUtils.bookmarks.totalSyncChanges;
+    let syncFolder = await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      title: "Sync Folder",
+      type: PlacesUtils.bookmarks.TYPE_FOLDER,
+    });
+    await verifyTrackedItems(["menu", syncFolder.guid]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE);
+    Assert.equal(PlacesUtils.bookmarks.totalSyncChanges, totalSyncChanges + 2);
+
+    await resetTracker();
+    await startTracking();
+
+    _("Insert a bookmark using the sync API");
+    totalSyncChanges = PlacesUtils.bookmarks.totalSyncChanges;
+    let syncBmk = await PlacesUtils.bookmarks.insert({
+      parentGuid: syncFolder.guid,
+      url: "https://example.org/sync",
+      title: "Sync Bookmark",
+    });
+    await verifyTrackedItems([syncFolder.guid, syncBmk.guid]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE);
+    Assert.equal(PlacesUtils.bookmarks.totalSyncChanges, totalSyncChanges + 2);
+  } finally {
+    _("Clean up.");
+    await cleanup();
+  }
+});
+
+add_task(async function test_async_bookmarkAdded() {
+  _("Items inserted via the asynchronous bookmarks API should be tracked");
+
+  try {
+    await startTracking();
+
+    _("Insert a folder using the async API");
+    let totalSyncChanges = PlacesUtils.bookmarks.totalSyncChanges;
+    let asyncFolder = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_FOLDER,
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      title: "Async Folder",
+    });
+    await verifyTrackedItems(["menu", asyncFolder.guid]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE);
+    Assert.equal(PlacesUtils.bookmarks.totalSyncChanges, totalSyncChanges + 2);
+
+    await resetTracker();
+    await startTracking();
+
+    _("Insert a bookmark using the async API");
+    totalSyncChanges = PlacesUtils.bookmarks.totalSyncChanges;
+    let asyncBmk = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_BOOKMARK,
+      parentGuid: asyncFolder.guid,
+      url: "https://example.org/async",
+      title: "Async Bookmark",
+    });
+    await verifyTrackedItems([asyncFolder.guid, asyncBmk.guid]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE);
+    Assert.equal(PlacesUtils.bookmarks.totalSyncChanges, totalSyncChanges + 2);
+
+    await resetTracker();
+    await startTracking();
+
+    _("Insert a separator using the async API");
+    totalSyncChanges = PlacesUtils.bookmarks.totalSyncChanges;
+    let asyncSep = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_SEPARATOR,
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      index: asyncFolder.index,
+    });
+    await verifyTrackedItems(["menu", asyncSep.guid]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE);
+    Assert.equal(PlacesUtils.bookmarks.totalSyncChanges, totalSyncChanges + 2);
+  } finally {
+    _("Clean up.");
+    await cleanup();
+  }
+});
+
+add_task(async function test_async_onItemChanged() {
+  _("Items updated using the asynchronous bookmarks API should be tracked");
+
+  try {
+    await tracker.stop();
+
+    _("Insert a bookmark");
+    let fxBmk = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_BOOKMARK,
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      url: "http://getfirefox.com",
+      title: "Get Firefox!",
+    });
+    _(`Firefox GUID: ${fxBmk.guid}`);
+
+    await startTracking();
+
+    _("Update the bookmark using the async API");
+    let totalSyncChanges = PlacesUtils.bookmarks.totalSyncChanges;
+    await PlacesUtils.bookmarks.update({
+      guid: fxBmk.guid,
+      title: "Download Firefox",
+      url: "https://www.mozilla.org/firefox",
+      // PlacesUtils.bookmarks.update rejects last modified dates older than
+      // the added date.
+      lastModified: new Date(Date.now() + DAY_IN_MS),
+    });
+
+    await verifyTrackedItems([fxBmk.guid]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE * 3);
+    Assert.equal(PlacesUtils.bookmarks.totalSyncChanges, totalSyncChanges + 1);
+  } finally {
+    _("Clean up.");
+    await cleanup();
+  }
+});
+
+add_task(async function test_onItemChanged_itemDates() {
+  _("Changes to item dates should be tracked");
+
+  try {
+    await tracker.stop();
+
+    _("Insert a bookmark");
+    let fx_bm = await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      url: "http://getfirefox.com",
+      title: "Get Firefox!",
+    });
+    _(`Firefox GUID: ${fx_bm.guid}`);
+
+    await startTracking();
+
+    _("Reset the bookmark's added date, should not be tracked");
+    let totalSyncChanges = PlacesUtils.bookmarks.totalSyncChanges;
+    let dateAdded = new Date(Date.now() - DAY_IN_MS);
+    await PlacesUtils.bookmarks.update({
+      guid: fx_bm.guid,
+      dateAdded,
+    });
+    await verifyTrackedCount(0);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE);
+    Assert.equal(PlacesUtils.bookmarks.totalSyncChanges, totalSyncChanges);
+
+    await resetTracker();
+
+    _(
+      "Reset the bookmark's added date and another property, should be tracked"
+    );
+    totalSyncChanges = PlacesUtils.bookmarks.totalSyncChanges;
+    dateAdded = new Date();
+    await PlacesUtils.bookmarks.update({
+      guid: fx_bm.guid,
+      dateAdded,
+      title: "test",
+    });
+    await verifyTrackedItems([fx_bm.guid]);
+    Assert.equal(tracker.score, 2 * SCORE_INCREMENT_XLARGE);
+    Assert.equal(PlacesUtils.bookmarks.totalSyncChanges, totalSyncChanges + 1);
+
+    await resetTracker();
+
+    _("Set the bookmark's last modified date");
+    totalSyncChanges = PlacesUtils.bookmarks.totalSyncChanges;
+    let fx_id = await PlacesTestUtils.promiseItemId(fx_bm.guid);
+    let dateModified = Date.now() * 1000;
+    PlacesUtils.bookmarks.setItemLastModified(fx_id, dateModified);
+    await verifyTrackedItems([fx_bm.guid]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE);
+    Assert.equal(PlacesUtils.bookmarks.totalSyncChanges, totalSyncChanges + 1);
+  } finally {
+    _("Clean up.");
+    await cleanup();
+  }
+});
+
+add_task(async function test_onItemTagged() {
+  _("Items tagged using the synchronous API should be tracked");
+
+  try {
+    await tracker.stop();
+
+    _("Create a folder");
+    let folder = await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      title: "Parent",
+      type: PlacesUtils.bookmarks.TYPE_FOLDER,
+    });
+    _("Folder ID: " + folder);
+    _("Folder GUID: " + folder.guid);
+
+    _("Track changes to tags");
+    let uri = CommonUtils.makeURI("http://getfirefox.com");
+    let b = await PlacesUtils.bookmarks.insert({
+      parentGuid: folder.guid,
+      url: uri,
+      title: "Get Firefox!",
+    });
+    _("New item is " + b);
+    _("GUID: " + b.guid);
+
+    await startTracking();
+
+    _("Tag the item");
+    let totalSyncChanges = PlacesUtils.bookmarks.totalSyncChanges;
+    PlacesUtils.tagging.tagURI(uri, ["foo"]);
+
+    // bookmark should be tracked, folder should not be.
+    await verifyTrackedItems([b.guid]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE * 3);
+    Assert.equal(PlacesUtils.bookmarks.totalSyncChanges, totalSyncChanges + 6);
+  } finally {
+    _("Clean up.");
+    await cleanup();
+  }
+});
+
+add_task(async function test_onItemUntagged() {
+  _("Items untagged using the synchronous API should be tracked");
+
+  try {
+    await tracker.stop();
+
+    _("Insert tagged bookmarks");
+    let uri = CommonUtils.makeURI("http://getfirefox.com");
+    let fx1 = await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      url: uri,
+      title: "Get Firefox!",
+    });
+    // Different parent and title; same URL.
+    let fx2 = await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.toolbarGuid,
+      url: uri,
+      title: "Download Firefox",
+    });
+    PlacesUtils.tagging.tagURI(uri, ["foo"]);
+
+    await startTracking();
+
+    _("Remove the tag");
+    let totalSyncChanges = PlacesUtils.bookmarks.totalSyncChanges;
+    PlacesUtils.tagging.untagURI(uri, ["foo"]);
+
+    await verifyTrackedItems([fx1.guid, fx2.guid]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE * 4);
+    Assert.equal(PlacesUtils.bookmarks.totalSyncChanges, totalSyncChanges + 5);
+  } finally {
+    _("Clean up.");
+    await cleanup();
+  }
+});
+
+add_task(async function test_async_onItemUntagged() {
+  _("Items untagged using the asynchronous API should be tracked");
+
+  try {
+    await tracker.stop();
+
+    _("Insert tagged bookmarks");
+    let fxBmk1 = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_BOOKMARK,
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      url: "http://getfirefox.com",
+      title: "Get Firefox!",
+    });
+    let fxBmk2 = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_BOOKMARK,
+      parentGuid: PlacesUtils.bookmarks.toolbarGuid,
+      url: "http://getfirefox.com",
+      title: "Download Firefox",
+    });
+    let tag = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_FOLDER,
+      parentGuid: PlacesUtils.bookmarks.tagsGuid,
+      title: "some tag",
+    });
+    let fxTag = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_BOOKMARK,
+      parentGuid: tag.guid,
+      url: "http://getfirefox.com",
+    });
+
+    await startTracking();
+
+    _("Remove the tag using the async bookmarks API");
+    let totalSyncChanges = PlacesUtils.bookmarks.totalSyncChanges;
+    await PlacesUtils.bookmarks.remove(fxTag.guid);
+
+    await verifyTrackedItems([fxBmk1.guid, fxBmk2.guid]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE * 4);
+    Assert.equal(PlacesUtils.bookmarks.totalSyncChanges, totalSyncChanges + 5);
+  } finally {
+    _("Clean up.");
+    await cleanup();
+  }
+});
+
+add_task(async function test_async_onItemTagged() {
+  _("Items tagged using the asynchronous API should be tracked");
+
+  try {
+    await tracker.stop();
+
+    _("Insert untagged bookmarks");
+    let folder1 = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_FOLDER,
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      title: "Folder 1",
+    });
+    let fxBmk1 = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_BOOKMARK,
+      parentGuid: folder1.guid,
+      url: "http://getfirefox.com",
+      title: "Get Firefox!",
+    });
+    let folder2 = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_FOLDER,
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      title: "Folder 2",
+    });
+    // Different parent and title; same URL.
+    let fxBmk2 = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_BOOKMARK,
+      parentGuid: folder2.guid,
+      url: "http://getfirefox.com",
+      title: "Download Firefox",
+    });
+
+    await startTracking();
+
+    // This will change once tags are moved into a separate table (bug 424160).
+    // We specifically test this case because Bookmarks.sys.mjs updates tagged
+    // bookmarks and notifies observers.
+    _("Insert a tag using the async bookmarks API");
+    let tag = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_FOLDER,
+      parentGuid: PlacesUtils.bookmarks.tagsGuid,
+      title: "some tag",
+    });
+
+    _("Tag an item using the async bookmarks API");
+    let totalSyncChanges = PlacesUtils.bookmarks.totalSyncChanges;
+    await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_BOOKMARK,
+      parentGuid: tag.guid,
+      url: "http://getfirefox.com",
+    });
+
+    await verifyTrackedItems([fxBmk1.guid, fxBmk2.guid]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE * 4);
+    Assert.equal(PlacesUtils.bookmarks.totalSyncChanges, totalSyncChanges + 5);
+  } finally {
+    _("Clean up.");
+    await cleanup();
+  }
+});
+
+add_task(async function test_async_onItemKeywordChanged() {
+  _("Keyword changes via the asynchronous API should be tracked");
+
+  try {
+    await tracker.stop();
+
+    _("Insert two bookmarks with the same URL");
+    let fxBmk1 = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_BOOKMARK,
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      url: "http://getfirefox.com",
+      title: "Get Firefox!",
+    });
+    let fxBmk2 = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_BOOKMARK,
+      parentGuid: PlacesUtils.bookmarks.toolbarGuid,
+      url: "http://getfirefox.com",
+      title: "Download Firefox",
+    });
+
+    await startTracking();
+
+    _("Add a keyword for both items");
+    let totalSyncChanges = PlacesUtils.bookmarks.totalSyncChanges;
+    await PlacesUtils.keywords.insert({
+      keyword: "the_keyword",
+      url: "http://getfirefox.com",
+      postData: "postData",
+    });
+
+    await verifyTrackedItems([fxBmk1.guid, fxBmk2.guid]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE * 2);
+    Assert.equal(PlacesUtils.bookmarks.totalSyncChanges, totalSyncChanges + 2);
+  } finally {
+    _("Clean up.");
+    await cleanup();
+  }
+});
+
+add_task(async function test_async_onItemKeywordDeleted() {
+  _("Keyword deletions via the asynchronous API should be tracked");
+
+  try {
+    await tracker.stop();
+
+    _("Insert two bookmarks with the same URL and keywords");
+    let fxBmk1 = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_BOOKMARK,
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      url: "http://getfirefox.com",
+      title: "Get Firefox!",
+    });
+    let fxBmk2 = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_BOOKMARK,
+      parentGuid: PlacesUtils.bookmarks.toolbarGuid,
+      url: "http://getfirefox.com",
+      title: "Download Firefox",
+    });
+    await PlacesUtils.keywords.insert({
+      keyword: "the_keyword",
+      url: "http://getfirefox.com",
+    });
+
+    await startTracking();
+
+    _("Remove the keyword");
+    let totalSyncChanges = PlacesUtils.bookmarks.totalSyncChanges;
+    await PlacesUtils.keywords.remove("the_keyword");
+
+    await verifyTrackedItems([fxBmk1.guid, fxBmk2.guid]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE * 2);
+    Assert.equal(PlacesUtils.bookmarks.totalSyncChanges, totalSyncChanges + 2);
+  } finally {
+    _("Clean up.");
+    await cleanup();
+  }
+});
+
+add_task(async function test_bookmarkAdded_filtered_root() {
+  _("Items outside the change roots should not be tracked");
+
+  try {
+    await startTracking();
+
+    _("Create a new root");
+    let root = await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.rootGuid,
+      title: "New root",
+      type: PlacesUtils.bookmarks.TYPE_FOLDER,
+    });
+    _(`New root GUID: ${root.guid}`);
+
+    _("Insert a bookmark underneath the new root");
+    let untrackedBmk = await PlacesUtils.bookmarks.insert({
+      parentGuid: root.guid,
+      url: "http://getthunderbird.com",
+      title: "Get Thunderbird!",
+    });
+    _(`New untracked bookmark GUID: ${untrackedBmk.guid}`);
+
+    _("Insert a bookmark underneath the Places root");
+    let rootBmk = await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.rootGuid,
+      url: "http://getfirefox.com",
+      title: "Get Firefox!",
+    });
+    _(`New Places root bookmark GUID: ${rootBmk.guid}`);
+
+    _("New root and bookmark should be ignored");
+    await verifyTrackedItems([]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE * 3);
+  } finally {
+    _("Clean up.");
+    await cleanup();
+  }
+});
+
+add_task(async function test_onItemDeleted_filtered_root() {
+  _("Deleted items outside the change roots should not be tracked");
+
+  try {
+    await tracker.stop();
+
+    _("Insert a bookmark underneath the Places root");
+    let rootBmk = await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.rootGuid,
+      url: "http://getfirefox.com",
+      title: "Get Firefox!",
+    });
+    _(`New Places root bookmark GUID: ${rootBmk.guid}`);
+
+    await startTracking();
+
+    await PlacesUtils.bookmarks.remove(rootBmk);
+
+    await verifyTrackedItems([]);
+    // We'll still increment the counter for the removed item.
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE);
+  } finally {
+    _("Clean up.");
+    await cleanup();
+  }
+});
+
+add_task(async function test_onPageAnnoChanged() {
+  _("Page annotations should not be tracked");
+
+  try {
+    await tracker.stop();
+
+    _("Insert a bookmark without an annotation");
+    let pageURI = "http://getfirefox.com";
+    await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      url: pageURI,
+      title: "Get Firefox!",
+    });
+
+    await startTracking();
+
+    _("Add a page annotation");
+    await PlacesUtils.history.update({
+      url: pageURI,
+      annotations: new Map([[PlacesUtils.CHARSET_ANNO, "UTF-16"]]),
+    });
+    await verifyTrackedItems([]);
+    Assert.equal(tracker.score, 0);
+    await resetTracker();
+
+    _("Remove the page annotation");
+    await PlacesUtils.history.update({
+      url: pageURI,
+      annotations: new Map([[PlacesUtils.CHARSET_ANNO, null]]),
+    });
+    await verifyTrackedItems([]);
+    Assert.equal(tracker.score, 0);
+  } finally {
+    _("Clean up.");
+    await cleanup();
+  }
+});
+
+add_task(async function test_onFaviconChanged() {
+  _("Favicon changes should not be tracked");
+
+  try {
+    await tracker.stop();
+
+    let pageURI = CommonUtils.makeURI("http://getfirefox.com");
+    let iconURI = CommonUtils.makeURI("http://getfirefox.com/icon");
+    await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      url: pageURI,
+      title: "Get Firefox!",
+    });
+
+    await PlacesTestUtils.addVisits(pageURI);
+
+    await startTracking();
+
+    _("Favicon annotations should be ignored");
+    let iconURL =
+      "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAA" +
+      "AAAA6fptVAAAACklEQVQI12NgAAAAAgAB4iG8MwAAAABJRU5ErkJggg==";
+    await PlacesTestUtils.setFaviconForPage(pageURI, iconURI, iconURL);
+    await verifyTrackedItems([]);
+    Assert.equal(tracker.score, 0);
+  } finally {
+    _("Clean up.");
+    await cleanup();
+  }
+});
+
+add_task(async function test_async_onItemMoved_moveToFolder() {
+  _("Items moved via `moveToFolder` should be tracked");
+
+  try {
+    await tracker.stop();
+
+    await PlacesUtils.bookmarks.insertTree({
+      guid: PlacesUtils.bookmarks.menuGuid,
+      children: [
+        {
+          guid: "bookmarkAAAA",
+          title: "A",
+          url: "http://example.com/a",
+        },
+        {
+          guid: "bookmarkBBBB",
+          title: "B",
+          url: "http://example.com/b",
+        },
+        {
+          guid: "bookmarkCCCC",
+          title: "C",
+          url: "http://example.com/c",
+        },
+        {
+          guid: "bookmarkDDDD",
+          title: "D",
+          url: "http://example.com/d",
+        },
+      ],
+    });
+    await PlacesUtils.bookmarks.insertTree({
+      guid: PlacesUtils.bookmarks.toolbarGuid,
+      children: [
+        {
+          guid: "bookmarkEEEE",
+          title: "E",
+          url: "http://example.com/e",
+        },
+      ],
+    });
+
+    await startTracking();
+
+    _("Move (A B D) to the toolbar");
+    await PlacesUtils.bookmarks.moveToFolder(
+      ["bookmarkAAAA", "bookmarkBBBB", "bookmarkDDDD"],
+      PlacesUtils.bookmarks.toolbarGuid,
+      PlacesUtils.bookmarks.DEFAULT_INDEX
+    );
+
+    // Moving multiple bookmarks between two folders should track the old
+    // folder, new folder, and moved bookmarks.
+    await verifyTrackedItems([
+      "menu",
+      "toolbar",
+      "bookmarkAAAA",
+      "bookmarkBBBB",
+      "bookmarkDDDD",
+    ]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE * 3);
+    await resetTracker();
+
+    _("Reorder toolbar children: (D A B E)");
+    await PlacesUtils.bookmarks.moveToFolder(
+      ["bookmarkDDDD", "bookmarkAAAA", "bookmarkBBBB"],
+      PlacesUtils.bookmarks.toolbarGuid,
+      0
+    );
+
+    // Reordering bookmarks in a folder should only track the folder, not the
+    // bookmarks.
+    await verifyTrackedItems(["toolbar"]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE * 2);
+  } finally {
+    _("Clean up.");
+    await cleanup();
+  }
+});
+
+add_task(async function test_async_onItemMoved_update() {
+  _("Items moved via the asynchronous API should be tracked");
+
+  try {
+    await tracker.stop();
+
+    await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_BOOKMARK,
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      url: "http://getfirefox.com",
+      title: "Get Firefox!",
+    });
+    let tbBmk = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_BOOKMARK,
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      url: "http://getthunderbird.com",
+      title: "Get Thunderbird!",
+    });
+
+    await startTracking();
+
+    _("Repositioning a bookmark should track the folder");
+    let totalSyncChanges = PlacesUtils.bookmarks.totalSyncChanges;
+    await PlacesUtils.bookmarks.update({
+      guid: tbBmk.guid,
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      index: 0,
+    });
+    await verifyTrackedItems(["menu"]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE);
+    Assert.equal(PlacesUtils.bookmarks.totalSyncChanges, totalSyncChanges + 1);
+    await resetTracker();
+
+    _("Reparenting a bookmark should track both folders and the bookmark");
+    totalSyncChanges = PlacesUtils.bookmarks.totalSyncChanges;
+    await PlacesUtils.bookmarks.update({
+      guid: tbBmk.guid,
+      parentGuid: PlacesUtils.bookmarks.toolbarGuid,
+      index: PlacesUtils.bookmarks.DEFAULT_INDEX,
+    });
+    await verifyTrackedItems(["menu", "toolbar", tbBmk.guid]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE);
+    Assert.equal(PlacesUtils.bookmarks.totalSyncChanges, totalSyncChanges + 3);
+  } finally {
+    _("Clean up.");
+    await cleanup();
+  }
+});
+
+add_task(async function test_async_onItemMoved_reorder() {
+  _("Items reordered via the asynchronous API should be tracked");
+
+  try {
+    await tracker.stop();
+
+    _("Insert out-of-order bookmarks");
+    let fxBmk = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_BOOKMARK,
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      url: "http://getfirefox.com",
+      title: "Get Firefox!",
+    });
+    _(`Firefox GUID: ${fxBmk.guid}`);
+
+    let tbBmk = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_BOOKMARK,
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      url: "http://getthunderbird.com",
+      title: "Get Thunderbird!",
+    });
+    _(`Thunderbird GUID: ${tbBmk.guid}`);
+
+    let mozBmk = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_BOOKMARK,
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      url: "https://mozilla.org",
+      title: "Mozilla",
+    });
+    _(`Mozilla GUID: ${mozBmk.guid}`);
+
+    await startTracking();
+
+    _("Reorder bookmarks");
+    let totalSyncChanges = PlacesUtils.bookmarks.totalSyncChanges;
+    await PlacesUtils.bookmarks.reorder(PlacesUtils.bookmarks.menuGuid, [
+      mozBmk.guid,
+      fxBmk.guid,
+      tbBmk.guid,
+    ]);
+
+    // We only track the folder if we reorder its children, but we should
+    // bump the score for every changed item.
+    await verifyTrackedItems(["menu"]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE * 3);
+    Assert.equal(PlacesUtils.bookmarks.totalSyncChanges, totalSyncChanges + 1);
+  } finally {
+    _("Clean up.");
+    await cleanup();
+  }
+});
+
+add_task(async function test_onItemDeleted_removeFolderTransaction() {
+  _("Folders removed in a transaction should be tracked");
+
+  try {
+    await tracker.stop();
+
+    _("Create a folder with two children");
+    let folder = await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      title: "Test folder",
+      type: PlacesUtils.bookmarks.TYPE_FOLDER,
+    });
+    _(`Folder GUID: ${folder.guid}`);
+    let fx = await PlacesUtils.bookmarks.insert({
+      parentGuid: folder.guid,
+      url: "http://getfirefox.com",
+      title: "Get Firefox!",
+    });
+    _(`Firefox GUID: ${fx.guid}`);
+    let tb = await PlacesUtils.bookmarks.insert({
+      parentGuid: folder.guid,
+      url: "http://getthunderbird.com",
+      title: "Get Thunderbird!",
+    });
+    _(`Thunderbird GUID: ${tb.guid}`);
+
+    await startTracking();
+
+    let txn = PlacesTransactions.Remove({ guid: folder.guid });
+    // We haven't executed the transaction yet.
+    await verifyTrackerEmpty();
+
+    _("Execute the remove folder transaction");
+    await txn.transact();
+    await verifyTrackedItems(["menu", folder.guid, fx.guid, tb.guid]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE * 3);
+    await resetTracker();
+
+    _("Undo the remove folder transaction");
+    await PlacesTransactions.undo();
+
+    await verifyTrackedItems(["menu", folder.guid, fx.guid, tb.guid]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE * 3);
+    await resetTracker();
+
+    _("Redo the transaction");
+    await PlacesTransactions.redo();
+    await verifyTrackedItems(["menu", folder.guid, fx.guid, tb.guid]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE * 3);
+  } finally {
+    _("Clean up.");
+    await cleanup();
+  }
+});
+
+add_task(async function test_treeMoved() {
+  _("Moving an entire tree of bookmarks should track the parents");
+
+  try {
+    // Create a couple of parent folders.
+    let folder1 = await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      test: "First test folder",
+      type: PlacesUtils.bookmarks.TYPE_FOLDER,
+    });
+
+    // A second folder in the first.
+    let folder2 = await PlacesUtils.bookmarks.insert({
+      parentGuid: folder1.guid,
+      title: "Second test folder",
+      type: PlacesUtils.bookmarks.TYPE_FOLDER,
+    });
+
+    // Create a couple of bookmarks in the second folder.
+    await PlacesUtils.bookmarks.insert({
+      parentGuid: folder2.guid,
+      url: "http://getfirefox.com",
+      title: "Get Firefox!",
+    });
+    await PlacesUtils.bookmarks.insert({
+      parentGuid: folder2.guid,
+      url: "http://getthunderbird.com",
+      title: "Get Thunderbird!",
+    });
+
+    await startTracking();
+
+    // Move folder 2 to be a sibling of folder1.
+    let totalSyncChanges = PlacesUtils.bookmarks.totalSyncChanges;
+    await PlacesUtils.bookmarks.update({
+      guid: folder2.guid,
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      index: 0,
+    });
+
+    // the menu and both folders should be tracked, the children should not be.
+    await verifyTrackedItems(["menu", folder1.guid, folder2.guid]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE);
+    Assert.equal(PlacesUtils.bookmarks.totalSyncChanges, totalSyncChanges + 3);
+  } finally {
+    _("Clean up.");
+    await cleanup();
+  }
+});
+
+add_task(async function test_onItemDeleted() {
+  _("Bookmarks deleted via the synchronous API should be tracked");
+
+  try {
+    await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      url: "http://getfirefox.com",
+      title: "Get Firefox!",
+    });
+    let tb = await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      url: "http://getthunderbird.com",
+      title: "Get Thunderbird!",
+    });
+
+    await startTracking();
+
+    // Delete the last item - the item and parent should be tracked.
+    let totalSyncChanges = PlacesUtils.bookmarks.totalSyncChanges;
+    await PlacesUtils.bookmarks.remove(tb);
+
+    await verifyTrackedItems(["menu", tb.guid]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE);
+    Assert.equal(PlacesUtils.bookmarks.totalSyncChanges, totalSyncChanges + 2);
+  } finally {
+    _("Clean up.");
+    await cleanup();
+  }
+});
+
+add_task(async function test_async_onItemDeleted() {
+  _("Bookmarks deleted via the asynchronous API should be tracked");
+
+  try {
+    await tracker.stop();
+
+    let fxBmk = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_BOOKMARK,
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      url: "http://getfirefox.com",
+      title: "Get Firefox!",
+    });
+    await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_BOOKMARK,
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      url: "http://getthunderbird.com",
+      title: "Get Thunderbird!",
+    });
+
+    await startTracking();
+
+    _("Delete the first item");
+    let totalSyncChanges = PlacesUtils.bookmarks.totalSyncChanges;
+    await PlacesUtils.bookmarks.remove(fxBmk.guid);
+
+    await verifyTrackedItems(["menu", fxBmk.guid]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE);
+    Assert.equal(PlacesUtils.bookmarks.totalSyncChanges, totalSyncChanges + 2);
+  } finally {
+    _("Clean up.");
+    await cleanup();
+  }
+});
+
+add_task(async function test_async_onItemDeleted_eraseEverything() {
+  _("Erasing everything should track all deleted items");
+
+  try {
+    await tracker.stop();
+
+    let fxBmk = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_BOOKMARK,
+      parentGuid: PlacesUtils.bookmarks.mobileGuid,
+      url: "http://getfirefox.com",
+      title: "Get Firefox!",
+    });
+    _(`Firefox GUID: ${fxBmk.guid}`);
+    let tbBmk = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_BOOKMARK,
+      parentGuid: PlacesUtils.bookmarks.mobileGuid,
+      url: "http://getthunderbird.com",
+      title: "Get Thunderbird!",
+    });
+    _(`Thunderbird GUID: ${tbBmk.guid}`);
+    let mozBmk = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_BOOKMARK,
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      url: "https://mozilla.org",
+      title: "Mozilla",
+    });
+    _(`Mozilla GUID: ${mozBmk.guid}`);
+    let mdnBmk = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_BOOKMARK,
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      url: "https://developer.mozilla.org",
+      title: "MDN",
+    });
+    _(`MDN GUID: ${mdnBmk.guid}`);
+    let bugsFolder = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_FOLDER,
+      parentGuid: PlacesUtils.bookmarks.toolbarGuid,
+      title: "Bugs",
+    });
+    _(`Bugs folder GUID: ${bugsFolder.guid}`);
+    let bzBmk = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_BOOKMARK,
+      parentGuid: bugsFolder.guid,
+      url: "https://bugzilla.mozilla.org",
+      title: "Bugzilla",
+    });
+    _(`Bugzilla GUID: ${bzBmk.guid}`);
+    let bugsChildFolder = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_FOLDER,
+      parentGuid: bugsFolder.guid,
+      title: "Bugs child",
+    });
+    _(`Bugs child GUID: ${bugsChildFolder.guid}`);
+    let bugsGrandChildBmk = await PlacesUtils.bookmarks.insert({
+      type: PlacesUtils.bookmarks.TYPE_BOOKMARK,
+      parentGuid: bugsChildFolder.guid,
+      url: "https://example.com",
+      title: "Bugs grandchild",
+    });
+    _(`Bugs grandchild GUID: ${bugsGrandChildBmk.guid}`);
+
+    await startTracking();
+    // Simulate moving a synced item into a new folder. Deleting the folder
+    // should write a tombstone for the item, but not the folder.
+    await PlacesTestUtils.setBookmarkSyncFields({
+      guid: bugsChildFolder.guid,
+      syncStatus: PlacesUtils.bookmarks.SYNC_STATUS.NEW,
+    });
+    let totalSyncChanges = PlacesUtils.bookmarks.totalSyncChanges;
+    await PlacesUtils.bookmarks.eraseEverything();
+
+    // bugsChildFolder's sync status is still "NEW", so it shouldn't be
+    // tracked. bugsGrandChildBmk is "NORMAL", so we *should* write a
+    // tombstone and track it.
+    await verifyTrackedItems([
+      "menu",
+      mozBmk.guid,
+      mdnBmk.guid,
+      "toolbar",
+      bugsFolder.guid,
+      "mobile",
+      fxBmk.guid,
+      tbBmk.guid,
+      "unfiled",
+      bzBmk.guid,
+      bugsGrandChildBmk.guid,
+    ]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE * 8);
+    Assert.equal(PlacesUtils.bookmarks.totalSyncChanges, totalSyncChanges + 11);
+  } finally {
+    _("Clean up.");
+    await cleanup();
+  }
+});
+
+add_task(async function test_onItemDeleted_tree() {
+  _("Deleting a tree of bookmarks should track all items");
+
+  try {
+    // Create a couple of parent folders.
+    let folder1 = await PlacesUtils.bookmarks.insert({
+      parentGuid: PlacesUtils.bookmarks.menuGuid,
+      title: "First test folder",
+      type: PlacesUtils.bookmarks.TYPE_FOLDER,
+    });
+
+    // A second folder in the first.
+    let folder2 = await PlacesUtils.bookmarks.insert({
+      parentGuid: folder1.guid,
+      title: "Second test folder",
+      type: PlacesUtils.bookmarks.TYPE_FOLDER,
+    });
+
+    // Create a couple of bookmarks in the second folder.
+    let fx = await PlacesUtils.bookmarks.insert({
+      parentGuid: folder2.guid,
+      url: "http://getfirefox.com",
+      title: "Get Firefox!",
+    });
+    let tb = await PlacesUtils.bookmarks.insert({
+      parentGuid: folder2.guid,
+      url: "http://getthunderbird.com",
+      title: "Get Thunderbird!",
+    });
+
+    await startTracking();
+
+    // Delete folder2 - everything we created should be tracked.
+    let totalSyncChanges = PlacesUtils.bookmarks.totalSyncChanges;
+    await PlacesUtils.bookmarks.remove(folder2);
+
+    await verifyTrackedItems([fx.guid, tb.guid, folder1.guid, folder2.guid]);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE * 3);
+    Assert.equal(PlacesUtils.bookmarks.totalSyncChanges, totalSyncChanges + 4);
+  } finally {
+    _("Clean up.");
+    await cleanup();
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_bridged_engine.js b/src/zen/tests/mochitests/sync/test_bridged_engine.js
new file mode 100644
index 000000000..f0c49977b
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_bridged_engine.js
@@ -0,0 +1,230 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { BridgedEngine } = ChromeUtils.importESModule(
+  "resource://services-sync/bridged_engine.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+add_task(async function test_interface() {
+  class TestBridge {
+    constructor() {
+      this.storageVersion = 2;
+      this.syncID = "syncID111111";
+      this.clear();
+    }
+
+    clear() {
+      this.lastSyncMillis = 0;
+      this.wasSyncStarted = false;
+      this.incomingEnvelopes = [];
+      this.uploadedIDs = [];
+      this.wasSyncFinished = false;
+      this.wasReset = false;
+      this.wasWiped = false;
+    }
+
+    // `mozIBridgedSyncEngine` methods.
+
+    lastSync() {
+      return this.lastSyncMillis;
+    }
+
+    setLastSync(millis) {
+      this.lastSyncMillis = millis;
+    }
+
+    resetSyncId() {
+      return this.syncID;
+    }
+
+    ensureCurrentSyncId(newSyncId) {
+      equal(newSyncId, this.syncID, "Local and new sync IDs should match");
+      return this.syncID;
+    }
+
+    syncStarted() {
+      this.wasSyncStarted = true;
+    }
+
+    storeIncoming(envelopes) {
+      this.incomingEnvelopes.push(...envelopes.map(r => JSON.parse(r)));
+    }
+
+    apply() {
+      let outgoingEnvelopes = [
+        {
+          id: "hanson",
+          data: {
+            plants: ["seed", "flower 💐", "rose"],
+            canYouTell: false,
+          },
+        },
+        {
+          id: "sheryl-crow",
+          data: {
+            today: "winding 🛣",
+            tomorrow: "winding 🛣",
+          },
+        },
+      ].map(cleartext =>
+        JSON.stringify({
+          id: cleartext.id,
+          payload: JSON.stringify(cleartext),
+        })
+      );
+      return outgoingEnvelopes;
+    }
+
+    setUploaded(millis, ids) {
+      this.uploadedIDs.push(...ids);
+    }
+
+    syncFinished() {
+      this.wasSyncFinished = true;
+    }
+
+    reset() {
+      this.clear();
+      this.wasReset = true;
+    }
+
+    wipe() {
+      this.clear();
+      this.wasWiped = true;
+    }
+  }
+
+  let bridge = new TestBridge();
+  let engine = new BridgedEngine("Nineties", Service);
+  engine._bridge = bridge;
+  engine.enabled = true;
+
+  let server = await serverForFoo(engine);
+  try {
+    await SyncTestingInfrastructure(server);
+
+    info("Add server records");
+    let foo = server.user("foo");
+    let collection = foo.collection("nineties");
+    let now = new_timestamp();
+    collection.insert(
+      "backstreet",
+      encryptPayload({
+        id: "backstreet",
+        data: {
+          say: "I want it that way",
+          when: "never",
+        },
+      }),
+      now
+    );
+    collection.insert(
+      "tlc",
+      encryptPayload({
+        id: "tlc",
+        data: {
+          forbidden: ["scrubs 🚫"],
+          numberAvailable: false,
+        },
+      }),
+      now + 5
+    );
+
+    info("Sync the engine");
+    // Advance the last sync time to skip the Backstreet Boys...
+    bridge.lastSyncMillis = 1000 * (now + 2);
+    await sync_engine_and_validate_telem(engine, false);
+
+    let metaGlobal = foo.collection("meta").wbo("global").get();
+    deepEqual(
+      JSON.parse(metaGlobal.payload).engines.nineties,
+      {
+        version: 2,
+        syncID: "syncID111111",
+      },
+      "Should write storage version and sync ID to m/g"
+    );
+
+    greater(bridge.lastSyncMillis, 0, "Should update last sync time");
+    ok(
+      bridge.wasSyncStarted,
+      "Should have started sync before storing incoming"
+    );
+    deepEqual(
+      bridge.incomingEnvelopes
+        .sort((a, b) => a.id.localeCompare(b.id))
+        .map(({ payload, ...envelope }) => ({
+          cleartextAsObject: JSON.parse(payload),
+          ...envelope,
+        })),
+      [
+        {
+          id: "tlc",
+          modified: now + 5,
+          cleartextAsObject: {
+            id: "tlc",
+            data: {
+              forbidden: ["scrubs 🚫"],
+              numberAvailable: false,
+            },
+          },
+        },
+      ],
+      "Should stage incoming records from server"
+    );
+    deepEqual(
+      bridge.uploadedIDs.sort(),
+      ["hanson", "sheryl-crow"],
+      "Should mark new local records as uploaded"
+    );
+    ok(bridge.wasSyncFinished, "Should have finished sync after uploading");
+
+    deepEqual(
+      collection.keys().sort(),
+      ["backstreet", "hanson", "sheryl-crow", "tlc"],
+      "Should have all records on server"
+    );
+    let expectedRecords = [
+      {
+        id: "sheryl-crow",
+        data: {
+          today: "winding 🛣",
+          tomorrow: "winding 🛣",
+        },
+      },
+      {
+        id: "hanson",
+        data: {
+          plants: ["seed", "flower 💐", "rose"],
+          canYouTell: false,
+        },
+      },
+    ];
+    for (let expected of expectedRecords) {
+      let actual = collection.cleartext(expected.id);
+      deepEqual(
+        actual,
+        expected,
+        `Should upload record ${expected.id} from bridged engine`
+      );
+    }
+
+    await engine.resetClient();
+    ok(bridge.wasReset, "Should reset local storage for bridge");
+
+    await engine.wipeClient();
+    ok(bridge.wasWiped, "Should wipe local storage for bridge");
+
+    await engine.resetSyncID();
+    ok(
+      !foo.collection("nineties"),
+      "Should delete server collection after resetting sync ID"
+    );
+  } finally {
+    await promiseStopServer(server);
+    await engine.finalize();
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_clients_engine.js b/src/zen/tests/mochitests/sync/test_clients_engine.js
new file mode 100644
index 000000000..631819072
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_clients_engine.js
@@ -0,0 +1,2129 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { ClientEngine, ClientsRec } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/clients.sys.mjs"
+);
+const { CryptoWrapper } = ChromeUtils.importESModule(
+  "resource://services-sync/record.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+const MORE_THAN_CLIENTS_TTL_REFRESH = 691200; // 8 days
+const LESS_THAN_CLIENTS_TTL_REFRESH = 86400; // 1 day
+
+let engine;
+
+/**
+ * Unpack the record with this ID, and verify that it has the same version that
+ * we should be putting into records.
+ */
+async function check_record_version(user, id) {
+  let payload = user.collection("clients").wbo(id).data;
+
+  let rec = new CryptoWrapper();
+  rec.id = id;
+  rec.collection = "clients";
+  rec.ciphertext = payload.ciphertext;
+  rec.hmac = payload.hmac;
+  rec.IV = payload.IV;
+
+  let cleartext = await rec.decrypt(
+    Service.collectionKeys.keyForCollection("clients")
+  );
+
+  _("Payload is " + JSON.stringify(cleartext));
+  equal(Services.appinfo.version, cleartext.version);
+  equal(1, cleartext.protocols.length);
+  equal("1.5", cleartext.protocols[0]);
+}
+
+// compare 2 different command arrays, taking into account that a flowID
+// attribute must exist, be unique in the commands, but isn't specified in
+// "expected" as the value isn't known.
+function compareCommands(actual, expected, description) {
+  let tweakedActual = JSON.parse(JSON.stringify(actual));
+  tweakedActual.map(elt => delete elt.flowID);
+  deepEqual(tweakedActual, expected, description);
+  // each item must have a unique flowID.
+  let allIDs = new Set(actual.map(elt => elt.flowID).filter(fid => !!fid));
+  equal(allIDs.size, actual.length, "all items have unique IDs");
+}
+
+async function syncClientsEngine(server) {
+  engine._lastFxADevicesFetch = 0;
+  engine.lastModified = server.getCollection("foo", "clients").timestamp;
+  await engine._sync();
+}
+
+add_setup(async function () {
+  engine = Service.clientsEngine;
+
+  do_get_profile(); // FOG requires a profile directory.
+  Services.fog.initializeFOG();
+});
+
+async function cleanup() {
+  for (const pref of Svc.PrefBranch.getChildList("")) {
+    Svc.PrefBranch.clearUserPref(pref);
+  }
+  await engine._tracker.clearChangedIDs();
+  await engine._resetClient();
+  // un-cleanup the logs (the resetBranch will have reset their levels), since
+  // not all the tests use SyncTestingInfrastructure, and it's cheap.
+  syncTestLogging();
+  // We don't finalize storage at cleanup, since we use the same clients engine
+  // instance across all tests.
+}
+
+add_task(async function test_bad_hmac() {
+  _("Ensure that Clients engine deletes corrupt records.");
+  let deletedCollections = [];
+  let deletedItems = [];
+  let callback = {
+    onItemDeleted(username, coll, wboID) {
+      deletedItems.push(coll + "/" + wboID);
+    },
+    onCollectionDeleted(username, coll) {
+      deletedCollections.push(coll);
+    },
+  };
+  Object.setPrototypeOf(callback, SyncServerCallback);
+  let server = await serverForFoo(engine, callback);
+  let user = server.user("foo");
+
+  function check_clients_count(expectedCount) {
+    let coll = user.collection("clients");
+
+    // Treat a non-existent collection as empty.
+    equal(expectedCount, coll ? coll.count() : 0);
+  }
+
+  function check_client_deleted(id) {
+    let coll = user.collection("clients");
+    let wbo = coll.wbo(id);
+    return !wbo || !wbo.payload;
+  }
+
+  async function uploadNewKeys() {
+    await generateNewKeys(Service.collectionKeys);
+    let serverKeys = Service.collectionKeys.asWBO("crypto", "keys");
+    await serverKeys.encrypt(Service.identity.syncKeyBundle);
+    ok(
+      (await serverKeys.upload(Service.resource(Service.cryptoKeysURL))).success
+    );
+  }
+
+  try {
+    await configureIdentity({ username: "foo" }, server);
+    await Service.login();
+
+    await generateNewKeys(Service.collectionKeys);
+
+    _("First sync, client record is uploaded");
+    equal(engine.lastRecordUpload, 0);
+    ok(engine.isFirstSync);
+    check_clients_count(0);
+    await syncClientsEngine(server);
+    check_clients_count(1);
+    Assert.greater(engine.lastRecordUpload, 0);
+    ok(!engine.isFirstSync);
+
+    // Our uploaded record has a version.
+    await check_record_version(user, engine.localID);
+
+    // Initial setup can wipe the server, so clean up.
+    deletedCollections = [];
+    deletedItems = [];
+
+    _("Change our keys and our client ID, reupload keys.");
+    let oldLocalID = engine.localID; // Preserve to test for deletion!
+    engine.localID = Utils.makeGUID();
+    await engine.resetClient();
+    await generateNewKeys(Service.collectionKeys);
+    let serverKeys = Service.collectionKeys.asWBO("crypto", "keys");
+    await serverKeys.encrypt(Service.identity.syncKeyBundle);
+    ok(
+      (await serverKeys.upload(Service.resource(Service.cryptoKeysURL))).success
+    );
+
+    _("Sync.");
+    await syncClientsEngine(server);
+
+    _("Old record " + oldLocalID + " was deleted, new one uploaded.");
+    check_clients_count(1);
+    check_client_deleted(oldLocalID);
+
+    _(
+      "Now change our keys but don't upload them. " +
+        "That means we get an HMAC error but redownload keys."
+    );
+    Service.lastHMACEvent = 0;
+    engine.localID = Utils.makeGUID();
+    await engine.resetClient();
+    await generateNewKeys(Service.collectionKeys);
+    deletedCollections = [];
+    deletedItems = [];
+    check_clients_count(1);
+    await syncClientsEngine(server);
+
+    _("Old record was not deleted, new one uploaded.");
+    equal(deletedCollections.length, 0);
+    equal(deletedItems.length, 0);
+    check_clients_count(2);
+
+    _(
+      "Now try the scenario where our keys are wrong *and* there's a bad record."
+    );
+    // Clean up and start fresh.
+    user.collection("clients")._wbos = {};
+    Service.lastHMACEvent = 0;
+    engine.localID = Utils.makeGUID();
+    await engine.resetClient();
+    deletedCollections = [];
+    deletedItems = [];
+    check_clients_count(0);
+
+    await uploadNewKeys();
+
+    // Sync once to upload a record.
+    await syncClientsEngine(server);
+    check_clients_count(1);
+
+    // Generate and upload new keys, so the old client record is wrong.
+    await uploadNewKeys();
+
+    // Create a new client record and new keys. Now our keys are wrong, as well
+    // as the object on the server. We'll download the new keys and also delete
+    // the bad client record.
+    oldLocalID = engine.localID; // Preserve to test for deletion!
+    engine.localID = Utils.makeGUID();
+    await engine.resetClient();
+    await generateNewKeys(Service.collectionKeys);
+    let oldKey = Service.collectionKeys.keyForCollection();
+
+    equal(deletedCollections.length, 0);
+    equal(deletedItems.length, 0);
+    await syncClientsEngine(server);
+    equal(deletedItems.length, 1);
+    check_client_deleted(oldLocalID);
+    check_clients_count(1);
+    let newKey = Service.collectionKeys.keyForCollection();
+    ok(!oldKey.equals(newKey));
+  } finally {
+    await cleanup();
+    await promiseStopServer(server);
+  }
+});
+
+add_task(async function test_properties() {
+  _("Test lastRecordUpload property");
+  try {
+    equal(
+      Svc.PrefBranch.getPrefType("clients.lastRecordUpload"),
+      Ci.nsIPrefBranch.PREF_INVALID
+    );
+    equal(engine.lastRecordUpload, 0);
+
+    let now = Date.now();
+    engine.lastRecordUpload = now / 1000;
+    equal(engine.lastRecordUpload, Math.floor(now / 1000));
+  } finally {
+    await cleanup();
+  }
+});
+
+add_task(async function test_full_sync() {
+  _("Ensure that Clients engine fetches all records for each sync.");
+
+  let now = new_timestamp();
+  let server = await serverForFoo(engine);
+  let user = server.user("foo");
+
+  await SyncTestingInfrastructure(server);
+  await generateNewKeys(Service.collectionKeys);
+
+  let activeID = Utils.makeGUID();
+  user.collection("clients").insertRecord(
+    {
+      id: activeID,
+      name: "Active client",
+      type: "desktop",
+      commands: [],
+      version: "48",
+      protocols: ["1.5"],
+    },
+    now - 10
+  );
+
+  let deletedID = Utils.makeGUID();
+  user.collection("clients").insertRecord(
+    {
+      id: deletedID,
+      name: "Client to delete",
+      type: "desktop",
+      commands: [],
+      version: "48",
+      protocols: ["1.5"],
+    },
+    now - 10
+  );
+
+  try {
+    let store = engine._store;
+
+    _("First sync. 2 records downloaded; our record uploaded.");
+    strictEqual(engine.lastRecordUpload, 0);
+    ok(engine.isFirstSync);
+    await syncClientsEngine(server);
+    Assert.greater(engine.lastRecordUpload, 0);
+    ok(!engine.isFirstSync);
+    deepEqual(
+      user.collection("clients").keys().sort(),
+      [activeID, deletedID, engine.localID].sort(),
+      "Our record should be uploaded on first sync"
+    );
+    let ids = await store.getAllIDs();
+    deepEqual(
+      Object.keys(ids).sort(),
+      [activeID, deletedID, engine.localID].sort(),
+      "Other clients should be downloaded on first sync"
+    );
+
+    _("Delete a record, then sync again");
+    let collection = server.getCollection("foo", "clients");
+    collection.remove(deletedID);
+    // Simulate a timestamp update in info/collections.
+    await syncClientsEngine(server);
+
+    _("Record should be updated");
+    ids = await store.getAllIDs();
+    deepEqual(
+      Object.keys(ids).sort(),
+      [activeID, engine.localID].sort(),
+      "Deleted client should be removed on next sync"
+    );
+  } finally {
+    await cleanup();
+
+    try {
+      server.deleteCollections("foo");
+    } finally {
+      await promiseStopServer(server);
+    }
+  }
+});
+
+add_task(async function test_sync() {
+  _("Ensure that Clients engine uploads a new client record once a week.");
+
+  let server = await serverForFoo(engine);
+  let user = server.user("foo");
+
+  await SyncTestingInfrastructure(server);
+  await generateNewKeys(Service.collectionKeys);
+
+  function clientWBO() {
+    return user.collection("clients").wbo(engine.localID);
+  }
+
+  try {
+    _("First sync. Client record is uploaded.");
+    equal(clientWBO(), undefined);
+    equal(engine.lastRecordUpload, 0);
+    ok(engine.isFirstSync);
+    await syncClientsEngine(server);
+    ok(!!clientWBO().payload);
+    Assert.greater(engine.lastRecordUpload, 0);
+    ok(!engine.isFirstSync);
+
+    _(
+      "Let's time travel more than a week back, new record should've been uploaded."
+    );
+    engine.lastRecordUpload -= MORE_THAN_CLIENTS_TTL_REFRESH;
+    let lastweek = engine.lastRecordUpload;
+    clientWBO().payload = undefined;
+    await syncClientsEngine(server);
+    ok(!!clientWBO().payload);
+    Assert.greater(engine.lastRecordUpload, lastweek);
+    ok(!engine.isFirstSync);
+
+    _("Remove client record.");
+    await engine.removeClientData();
+    equal(clientWBO().payload, undefined);
+
+    _("Time travel one day back, no record uploaded.");
+    engine.lastRecordUpload -= LESS_THAN_CLIENTS_TTL_REFRESH;
+    let yesterday = engine.lastRecordUpload;
+    await syncClientsEngine(server);
+    equal(clientWBO().payload, undefined);
+    equal(engine.lastRecordUpload, yesterday);
+    ok(!engine.isFirstSync);
+  } finally {
+    await cleanup();
+    await promiseStopServer(server);
+  }
+});
+
+add_task(async function test_client_name_change() {
+  _("Ensure client name change incurs a client record update.");
+
+  let tracker = engine._tracker;
+
+  engine.localID; // Needed to increase the tracker changedIDs count.
+  let initialName = engine.localName;
+
+  tracker.start();
+  _("initial name: " + initialName);
+
+  // Tracker already has data, so clear it.
+  await tracker.clearChangedIDs();
+
+  let initialScore = tracker.score;
+
+  let changedIDs = await tracker.getChangedIDs();
+  equal(Object.keys(changedIDs).length, 0);
+
+  Services.prefs.setStringPref(
+    "identity.fxaccounts.account.device.name",
+    "new name"
+  );
+  await tracker.asyncObserver.promiseObserversComplete();
+
+  _("new name: " + engine.localName);
+  notEqual(initialName, engine.localName);
+  changedIDs = await tracker.getChangedIDs();
+  equal(Object.keys(changedIDs).length, 1);
+  ok(engine.localID in changedIDs);
+  Assert.greater(tracker.score, initialScore);
+  Assert.greaterOrEqual(tracker.score, SCORE_INCREMENT_XLARGE);
+
+  await tracker.stop();
+
+  await cleanup();
+});
+
+add_task(async function test_fxa_device_id_change() {
+  _("Ensure an FxA device ID change incurs a client record update.");
+
+  let tracker = engine._tracker;
+
+  engine.localID; // Needed to increase the tracker changedIDs count.
+
+  tracker.start();
+
+  // Tracker already has data, so clear it.
+  await tracker.clearChangedIDs();
+
+  let initialScore = tracker.score;
+
+  let changedIDs = await tracker.getChangedIDs();
+  equal(Object.keys(changedIDs).length, 0);
+
+  Services.obs.notifyObservers(null, "fxaccounts:new_device_id");
+  await tracker.asyncObserver.promiseObserversComplete();
+
+  changedIDs = await tracker.getChangedIDs();
+  equal(Object.keys(changedIDs).length, 1);
+  ok(engine.localID in changedIDs);
+  Assert.greater(tracker.score, initialScore);
+  Assert.greaterOrEqual(tracker.score, SINGLE_USER_THRESHOLD);
+
+  await tracker.stop();
+
+  await cleanup();
+});
+
+add_task(async function test_last_modified() {
+  _("Ensure that remote records have a sane serverLastModified attribute.");
+
+  let now = new_timestamp();
+  let server = await serverForFoo(engine);
+  let user = server.user("foo");
+
+  await SyncTestingInfrastructure(server);
+  await generateNewKeys(Service.collectionKeys);
+
+  let activeID = Utils.makeGUID();
+  user.collection("clients").insertRecord(
+    {
+      id: activeID,
+      name: "Active client",
+      type: "desktop",
+      commands: [],
+      version: "48",
+      protocols: ["1.5"],
+    },
+    now - 10
+  );
+
+  try {
+    let collection = user.collection("clients");
+
+    _("Sync to download the record");
+    await syncClientsEngine(server);
+
+    equal(
+      engine._store._remoteClients[activeID].serverLastModified,
+      now - 10,
+      "last modified in the local record is correctly the server last-modified"
+    );
+
+    _("Modify the record and re-upload it");
+    // set a new name to make sure we really did upload.
+    engine._store._remoteClients[activeID].name = "New name";
+    engine._modified.set(activeID, 0);
+    // The sync above also did a POST, so adjust our lastModified.
+    engine.lastModified = server.getCollection("foo", "clients").timestamp;
+    await engine._uploadOutgoing();
+
+    _("Local record should have updated timestamp");
+    Assert.greaterOrEqual(
+      engine._store._remoteClients[activeID].serverLastModified,
+      now
+    );
+
+    _("Record on the server should have new name but not serverLastModified");
+    let payload = collection.cleartext(activeID);
+    equal(payload.name, "New name");
+    equal(payload.serverLastModified, undefined);
+  } finally {
+    await cleanup();
+    server.deleteCollections("foo");
+    await promiseStopServer(server);
+  }
+});
+
+add_task(async function test_send_command() {
+  _("Verifies _sendCommandToClient puts commands in the outbound queue.");
+
+  let store = engine._store;
+  let tracker = engine._tracker;
+  let remoteId = Utils.makeGUID();
+  let rec = new ClientsRec("clients", remoteId);
+
+  await store.create(rec);
+  await store.createRecord(remoteId, "clients");
+
+  let action = "testCommand";
+  let args = ["foo", "bar"];
+  let extra = { flowID: "flowy" };
+
+  await engine._sendCommandToClient(action, args, remoteId, extra);
+
+  let newRecord = store._remoteClients[remoteId];
+  let clientCommands = (await engine._readCommands())[remoteId];
+  notEqual(newRecord, undefined);
+  equal(clientCommands.length, 1);
+
+  let command = clientCommands[0];
+  equal(command.command, action);
+  equal(command.args.length, 2);
+  deepEqual(command.args, args);
+  ok(command.flowID);
+
+  const changes = await tracker.getChangedIDs();
+  notEqual(changes[remoteId], undefined);
+
+  await cleanup();
+});
+
+// The browser UI might call _addClientCommand indirectly without awaiting on the returned promise.
+// We need to make sure this doesn't result on commands not being saved.
+add_task(async function test_add_client_command_race() {
+  let promises = [];
+  for (let i = 0; i < 100; i++) {
+    promises.push(
+      engine._addClientCommand(`client-${i}`, { command: "cmd", args: [] })
+    );
+  }
+  await Promise.all(promises);
+
+  let localCommands = await engine._readCommands();
+  for (let i = 0; i < 100; i++) {
+    equal(localCommands[`client-${i}`].length, 1);
+  }
+});
+
+add_task(async function test_command_validation() {
+  _("Verifies that command validation works properly.");
+
+  let store = engine._store;
+
+  let testCommands = [
+    ["resetAll", [], true],
+    ["resetAll", ["foo"], false],
+    ["resetEngine", ["tabs"], true],
+    ["resetEngine", [], false],
+    ["wipeEngine", ["tabs"], true],
+    ["wipeEngine", [], false],
+    ["logout", [], true],
+    ["logout", ["foo"], false],
+    ["__UNKNOWN__", [], false],
+  ];
+
+  for (let [action, args, expectedResult] of testCommands) {
+    let remoteId = Utils.makeGUID();
+    let rec = new ClientsRec("clients", remoteId);
+
+    await store.create(rec);
+    await store.createRecord(remoteId, "clients");
+
+    await engine.sendCommand(action, args, remoteId);
+
+    let newRecord = store._remoteClients[remoteId];
+    notEqual(newRecord, undefined);
+
+    let clientCommands = (await engine._readCommands())[remoteId];
+
+    if (expectedResult) {
+      _("Ensuring command is sent: " + action);
+      equal(clientCommands.length, 1);
+
+      let command = clientCommands[0];
+      equal(command.command, action);
+      deepEqual(command.args, args);
+
+      notEqual(engine._tracker, undefined);
+      const changes = await engine._tracker.getChangedIDs();
+      notEqual(changes[remoteId], undefined);
+    } else {
+      _("Ensuring command is scrubbed: " + action);
+      equal(clientCommands, undefined);
+
+      if (store._tracker) {
+        equal(engine._tracker[remoteId], undefined);
+      }
+    }
+  }
+  await cleanup();
+});
+
+add_task(async function test_command_duplication() {
+  _("Ensures duplicate commands are detected and not added");
+
+  let store = engine._store;
+  let remoteId = Utils.makeGUID();
+  let rec = new ClientsRec("clients", remoteId);
+  await store.create(rec);
+  await store.createRecord(remoteId, "clients");
+
+  let action = "resetAll";
+  let args = [];
+
+  await engine.sendCommand(action, args, remoteId);
+  await engine.sendCommand(action, args, remoteId);
+
+  let clientCommands = (await engine._readCommands())[remoteId];
+  equal(clientCommands.length, 1);
+
+  _("Check variant args length");
+  await engine._saveCommands({});
+
+  action = "resetEngine";
+  await engine.sendCommand(action, [{ x: "foo" }], remoteId);
+  await engine.sendCommand(action, [{ x: "bar" }], remoteId);
+
+  _("Make sure we spot a real dupe argument.");
+  await engine.sendCommand(action, [{ x: "bar" }], remoteId);
+
+  clientCommands = (await engine._readCommands())[remoteId];
+  equal(clientCommands.length, 2);
+
+  await cleanup();
+});
+
+add_task(async function test_command_invalid_client() {
+  _("Ensures invalid client IDs are caught");
+
+  let id = Utils.makeGUID();
+  let error;
+
+  try {
+    await engine.sendCommand("wipeEngine", ["tabs"], id);
+  } catch (ex) {
+    error = ex;
+  }
+
+  equal(error.message.indexOf("Unknown remote client ID: "), 0);
+
+  await cleanup();
+});
+
+add_task(async function test_process_incoming_commands() {
+  _("Ensures local commands are executed");
+
+  engine.localCommands = [{ command: "logout", args: [] }];
+
+  let ev = "weave:service:logout:finish";
+
+  let logoutPromise = new Promise(resolve => {
+    var handler = function () {
+      Svc.Obs.remove(ev, handler);
+
+      resolve();
+    };
+
+    Svc.Obs.add(ev, handler);
+  });
+
+  // logout command causes processIncomingCommands to return explicit false.
+  ok(!(await engine.processIncomingCommands()));
+
+  await logoutPromise;
+
+  await cleanup();
+});
+
+add_task(async function test_filter_duplicate_names() {
+  _(
+    "Ensure that we exclude clients with identical names that haven't synced in a week."
+  );
+
+  let now = new_timestamp();
+  let server = await serverForFoo(engine);
+  let user = server.user("foo");
+
+  await SyncTestingInfrastructure(server);
+  await generateNewKeys(Service.collectionKeys);
+
+  // Synced recently.
+  let recentID = Utils.makeGUID();
+  user.collection("clients").insertRecord(
+    {
+      id: recentID,
+      name: "My Phone",
+      type: "mobile",
+      commands: [],
+      version: "48",
+      protocols: ["1.5"],
+    },
+    now - 10
+  );
+
+  // synced recently, but not as recent as the phone.
+  let tabletID = Utils.makeGUID();
+  user.collection("clients").insertRecord(
+    {
+      id: tabletID,
+      name: "My Tablet",
+      type: "tablet",
+      commands: [],
+      version: "48",
+      protocols: ["1.5"],
+    },
+    now - 100
+  );
+
+  // Dupe of our client, synced more than 1 week ago.
+  let dupeID = Utils.makeGUID();
+  user.collection("clients").insertRecord(
+    {
+      id: dupeID,
+      name: engine.localName,
+      type: "desktop",
+      commands: [],
+      version: "48",
+      protocols: ["1.5"],
+    },
+    now - 604820
+  );
+
+  // Synced more than 1 week ago, but not a dupe.
+  let oldID = Utils.makeGUID();
+  user.collection("clients").insertRecord(
+    {
+      id: oldID,
+      name: "My old desktop",
+      type: "desktop",
+      commands: [],
+      version: "48",
+      protocols: ["1.5"],
+    },
+    now - 604820
+  );
+
+  try {
+    let store = engine._store;
+
+    _("First sync");
+    strictEqual(engine.lastRecordUpload, 0);
+    ok(engine.isFirstSync);
+    await syncClientsEngine(server);
+    Assert.greater(engine.lastRecordUpload, 0);
+    ok(!engine.isFirstSync);
+    deepEqual(
+      user.collection("clients").keys().sort(),
+      [recentID, tabletID, dupeID, oldID, engine.localID].sort(),
+      "Our record should be uploaded on first sync"
+    );
+
+    let ids = await store.getAllIDs();
+    deepEqual(
+      Object.keys(ids).sort(),
+      [recentID, tabletID, dupeID, oldID, engine.localID].sort(),
+      "Duplicate ID should remain in getAllIDs"
+    );
+    ok(
+      await engine._store.itemExists(dupeID),
+      "Dupe ID should be considered as existing for Sync methods."
+    );
+    ok(
+      !engine.remoteClientExists(dupeID),
+      "Dupe ID should not be considered as existing for external methods."
+    );
+
+    // dupe desktop should not appear in .deviceTypes.
+    equal(engine.deviceTypes.get("desktop"), 2);
+    equal(engine.deviceTypes.get("mobile"), 2);
+
+    // dupe desktop should not appear in stats
+    deepEqual(engine.stats, {
+      hasMobile: 1,
+      names: [engine.localName, "My Phone", "My Tablet", "My old desktop"],
+      numClients: 4,
+    });
+
+    ok(engine.remoteClientExists(oldID), "non-dupe ID should exist.");
+    ok(!engine.remoteClientExists(dupeID), "dupe ID should not exist");
+    equal(
+      engine.remoteClients.length,
+      3,
+      "dupe should not be in remoteClients"
+    );
+
+    // Check that a subsequent Sync doesn't report anything as being processed.
+    let counts;
+    Svc.Obs.add("weave:engine:sync:applied", function observe(subject) {
+      Svc.Obs.remove("weave:engine:sync:applied", observe);
+      counts = subject;
+    });
+
+    await syncClientsEngine(server);
+    equal(counts.applied, 0); // We didn't report applying any records.
+    equal(counts.reconciled, 5); // We reported reconcilliation for all records
+    equal(counts.succeeded, 0);
+    equal(counts.failed, 0);
+    equal(counts.newFailed, 0);
+
+    _("Broadcast logout to all clients");
+    await engine.sendCommand("logout", []);
+    await syncClientsEngine(server);
+
+    let collection = server.getCollection("foo", "clients");
+    let recentPayload = collection.cleartext(recentID);
+    compareCommands(
+      recentPayload.commands,
+      [{ command: "logout", args: [] }],
+      "Should send commands to the recent client"
+    );
+
+    let oldPayload = collection.cleartext(oldID);
+    compareCommands(
+      oldPayload.commands,
+      [{ command: "logout", args: [] }],
+      "Should send commands to the week-old client"
+    );
+
+    let dupePayload = collection.cleartext(dupeID);
+    deepEqual(
+      dupePayload.commands,
+      [],
+      "Should not send commands to the dupe client"
+    );
+
+    _("Update the dupe client's modified time");
+    collection.insertRecord(
+      {
+        id: dupeID,
+        name: engine.localName,
+        type: "desktop",
+        commands: [],
+        version: "48",
+        protocols: ["1.5"],
+      },
+      now - 10
+    );
+
+    _("Second sync.");
+    await syncClientsEngine(server);
+
+    ids = await store.getAllIDs();
+    deepEqual(
+      Object.keys(ids).sort(),
+      [recentID, tabletID, oldID, dupeID, engine.localID].sort(),
+      "Stale client synced, so it should no longer be marked as a dupe"
+    );
+
+    ok(
+      engine.remoteClientExists(dupeID),
+      "Dupe ID should appear as it synced."
+    );
+
+    // Recently synced dupe desktop should appear in .deviceTypes.
+    equal(engine.deviceTypes.get("desktop"), 3);
+
+    // Recently synced dupe desktop should now appear in stats
+    deepEqual(engine.stats, {
+      hasMobile: 1,
+      names: [
+        engine.localName,
+        "My Phone",
+        "My Tablet",
+        engine.localName,
+        "My old desktop",
+      ],
+      numClients: 5,
+    });
+
+    ok(
+      engine.remoteClientExists(dupeID),
+      "recently synced dupe ID should now exist"
+    );
+    equal(
+      engine.remoteClients.length,
+      4,
+      "recently synced dupe should now be in remoteClients"
+    );
+  } finally {
+    await cleanup();
+
+    try {
+      server.deleteCollections("foo");
+    } finally {
+      await promiseStopServer(server);
+    }
+  }
+});
+
+add_task(async function test_command_sync() {
+  _("Ensure that commands are synced across clients.");
+
+  await engine._store.wipe();
+  await generateNewKeys(Service.collectionKeys);
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  let user = server.user("foo");
+  let remoteId = Utils.makeGUID();
+
+  function clientWBO(id) {
+    return user.collection("clients").wbo(id);
+  }
+
+  _("Create remote client record");
+  user.collection("clients").insertRecord({
+    id: remoteId,
+    name: "Remote client",
+    type: "desktop",
+    commands: [],
+    version: "48",
+    protocols: ["1.5"],
+  });
+
+  try {
+    _("Syncing.");
+    await syncClientsEngine(server);
+
+    _("Checking remote record was downloaded.");
+    let clientRecord = engine._store._remoteClients[remoteId];
+    notEqual(clientRecord, undefined);
+    equal(clientRecord.commands.length, 0);
+
+    _("Send a command to the remote client.");
+    await engine.sendCommand("wipeEngine", ["tabs"]);
+    let clientCommands = (await engine._readCommands())[remoteId];
+    equal(clientCommands.length, 1);
+    await syncClientsEngine(server);
+
+    _("Checking record was uploaded.");
+    notEqual(clientWBO(engine.localID).payload, undefined);
+    Assert.greater(engine.lastRecordUpload, 0);
+    ok(!engine.isFirstSync);
+
+    notEqual(clientWBO(remoteId).payload, undefined);
+
+    Svc.PrefBranch.setStringPref("client.GUID", remoteId);
+    await engine._resetClient();
+    equal(engine.localID, remoteId);
+    _("Performing sync on resetted client.");
+    await syncClientsEngine(server);
+    notEqual(engine.localCommands, undefined);
+    equal(engine.localCommands.length, 1);
+
+    let command = engine.localCommands[0];
+    equal(command.command, "wipeEngine");
+    equal(command.args.length, 1);
+    equal(command.args[0], "tabs");
+  } finally {
+    await cleanup();
+
+    try {
+      let collection = server.getCollection("foo", "clients");
+      collection.remove(remoteId);
+    } finally {
+      await promiseStopServer(server);
+    }
+  }
+});
+
+add_task(async function test_clients_not_in_fxa_list() {
+  _("Ensure that clients not in the FxA devices list are marked as stale.");
+
+  await engine._store.wipe();
+  await generateNewKeys(Service.collectionKeys);
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  let remoteId = Utils.makeGUID();
+  let remoteId2 = Utils.makeGUID();
+  let collection = server.getCollection("foo", "clients");
+
+  _("Create remote client records");
+  collection.insertRecord({
+    id: remoteId,
+    name: "Remote client",
+    type: "desktop",
+    commands: [],
+    version: "48",
+    fxaDeviceId: remoteId,
+    protocols: ["1.5"],
+  });
+
+  collection.insertRecord({
+    id: remoteId2,
+    name: "Remote client 2",
+    type: "desktop",
+    commands: [],
+    version: "48",
+    fxaDeviceId: remoteId2,
+    protocols: ["1.5"],
+  });
+
+  let fxAccounts = engine.fxAccounts;
+  engine.fxAccounts = {
+    notifyDevices() {
+      return Promise.resolve(true);
+    },
+    device: {
+      getLocalId() {
+        return fxAccounts.device.getLocalId();
+      },
+      getLocalName() {
+        return fxAccounts.device.getLocalName();
+      },
+      getLocalType() {
+        return fxAccounts.device.getLocalType();
+      },
+      recentDeviceList: [{ id: remoteId }],
+      refreshDeviceList() {
+        return Promise.resolve(true);
+      },
+    },
+    _internal: {
+      now() {
+        return Date.now();
+      },
+    },
+  };
+
+  try {
+    _("Syncing.");
+    await syncClientsEngine(server);
+
+    ok(!engine._store._remoteClients[remoteId].stale);
+    ok(engine._store._remoteClients[remoteId2].stale);
+  } finally {
+    engine.fxAccounts = fxAccounts;
+    await cleanup();
+
+    try {
+      collection.remove(remoteId);
+    } finally {
+      await promiseStopServer(server);
+    }
+  }
+});
+
+add_task(async function test_dupe_device_ids() {
+  _(
+    "Ensure that we mark devices with duplicate fxaDeviceIds but older lastModified as stale."
+  );
+
+  await engine._store.wipe();
+  await generateNewKeys(Service.collectionKeys);
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  let remoteId = Utils.makeGUID();
+  let remoteId2 = Utils.makeGUID();
+  let remoteDeviceId = Utils.makeGUID();
+
+  let collection = server.getCollection("foo", "clients");
+
+  _("Create remote client records");
+  collection.insertRecord(
+    {
+      id: remoteId,
+      name: "Remote client",
+      type: "desktop",
+      commands: [],
+      version: "48",
+      fxaDeviceId: remoteDeviceId,
+      protocols: ["1.5"],
+    },
+    new_timestamp() - 3
+  );
+  collection.insertRecord({
+    id: remoteId2,
+    name: "Remote client",
+    type: "desktop",
+    commands: [],
+    version: "48",
+    fxaDeviceId: remoteDeviceId,
+    protocols: ["1.5"],
+  });
+
+  let fxAccounts = engine.fxAccounts;
+  engine.fxAccounts = {
+    notifyDevices() {
+      return Promise.resolve(true);
+    },
+    device: {
+      getLocalId() {
+        return fxAccounts.device.getLocalId();
+      },
+      getLocalName() {
+        return fxAccounts.device.getLocalName();
+      },
+      getLocalType() {
+        return fxAccounts.device.getLocalType();
+      },
+      recentDeviceList: [{ id: remoteDeviceId }],
+      refreshDeviceList() {
+        return Promise.resolve(true);
+      },
+    },
+    _internal: {
+      now() {
+        return Date.now();
+      },
+    },
+  };
+
+  try {
+    _("Syncing.");
+    await syncClientsEngine(server);
+
+    ok(engine._store._remoteClients[remoteId].stale);
+    ok(!engine._store._remoteClients[remoteId2].stale);
+  } finally {
+    engine.fxAccounts = fxAccounts;
+    await cleanup();
+
+    try {
+      collection.remove(remoteId);
+    } finally {
+      await promiseStopServer(server);
+    }
+  }
+});
+
+add_task(async function test_refresh_fxa_device_list() {
+  _("Ensure we refresh the fxa device list when we expect to.");
+
+  await engine._store.wipe();
+  engine._lastFxaDeviceRefresh = 0;
+  await generateNewKeys(Service.collectionKeys);
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  let numRefreshes = 0;
+  let now = Date.now();
+  let fxAccounts = engine.fxAccounts;
+  engine.fxAccounts = {
+    notifyDevices() {
+      return Promise.resolve(true);
+    },
+    device: {
+      getLocalId() {
+        return fxAccounts.device.getLocalId();
+      },
+      getLocalName() {
+        return fxAccounts.device.getLocalName();
+      },
+      getLocalType() {
+        return fxAccounts.device.getLocalType();
+      },
+      recentDeviceList: [],
+      refreshDeviceList() {
+        numRefreshes += 1;
+        return Promise.resolve(true);
+      },
+    },
+    _internal: {
+      now() {
+        return now;
+      },
+    },
+  };
+
+  try {
+    _("Syncing.");
+    await syncClientsEngine(server);
+    Assert.equal(numRefreshes, 1, "first sync should refresh");
+    now += 1000; // a second later.
+    await syncClientsEngine(server);
+    Assert.equal(numRefreshes, 1, "next sync should not refresh");
+    now += 60 * 60 * 2 * 1000; // 2 hours later
+    await syncClientsEngine(server);
+    Assert.equal(numRefreshes, 2, "2 hours later should refresh");
+    now += 1000; // a second later.
+    Assert.equal(numRefreshes, 2, "next sync should not refresh");
+  } finally {
+    await cleanup();
+    await promiseStopServer(server);
+  }
+});
+
+add_task(async function test_optional_client_fields() {
+  _("Ensure that we produce records with the fields added in Bug 1097222.");
+
+  const SUPPORTED_PROTOCOL_VERSIONS = ["1.5"];
+  let local = await engine._store.createRecord(engine.localID, "clients");
+  equal(local.name, engine.localName);
+  equal(local.type, engine.localType);
+  equal(local.version, Services.appinfo.version);
+  deepEqual(local.protocols, SUPPORTED_PROTOCOL_VERSIONS);
+
+  // Optional fields.
+  // Make sure they're what they ought to be...
+  equal(local.os, Services.appinfo.OS);
+  equal(local.appPackage, Services.appinfo.ID);
+
+  // ... and also that they're non-empty.
+  ok(!!local.os);
+  ok(!!local.appPackage);
+  ok(!!local.application);
+
+  // We don't currently populate device or formfactor.
+  // See Bug 1100722, Bug 1100723.
+
+  await cleanup();
+});
+
+add_task(async function test_merge_commands() {
+  _("Verifies local commands for remote clients are merged with the server's");
+
+  let now = new_timestamp();
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+  await generateNewKeys(Service.collectionKeys);
+
+  let collection = server.getCollection("foo", "clients");
+
+  let desktopID = Utils.makeGUID();
+  collection.insertRecord(
+    {
+      id: desktopID,
+      name: "Desktop client",
+      type: "desktop",
+      commands: [
+        {
+          command: "wipeEngine",
+          args: ["history"],
+          flowID: Utils.makeGUID(),
+        },
+      ],
+      version: "48",
+      protocols: ["1.5"],
+    },
+    now - 10
+  );
+
+  let mobileID = Utils.makeGUID();
+  collection.insertRecord(
+    {
+      id: mobileID,
+      name: "Mobile client",
+      type: "mobile",
+      commands: [
+        {
+          command: "logout",
+          args: [],
+          flowID: Utils.makeGUID(),
+        },
+      ],
+      version: "48",
+      protocols: ["1.5"],
+    },
+    now - 10
+  );
+
+  try {
+    _("First sync. 2 records downloaded.");
+    strictEqual(engine.lastRecordUpload, 0);
+    ok(engine.isFirstSync);
+    await syncClientsEngine(server);
+
+    _("Broadcast logout to all clients");
+    await engine.sendCommand("logout", []);
+    await syncClientsEngine(server);
+
+    let desktopPayload = collection.cleartext(desktopID);
+    compareCommands(
+      desktopPayload.commands,
+      [
+        {
+          command: "wipeEngine",
+          args: ["history"],
+        },
+        {
+          command: "logout",
+          args: [],
+        },
+      ],
+      "Should send the logout command to the desktop client"
+    );
+
+    let mobilePayload = collection.cleartext(mobileID);
+    compareCommands(
+      mobilePayload.commands,
+      [{ command: "logout", args: [] }],
+      "Should not send a duplicate logout to the mobile client"
+    );
+  } finally {
+    await cleanup();
+
+    try {
+      server.deleteCollections("foo");
+    } finally {
+      await promiseStopServer(server);
+    }
+  }
+});
+
+add_task(async function test_duplicate_remote_commands() {
+  _(
+    "Verifies local commands for remote clients are sent only once (bug 1289287)"
+  );
+
+  let now = new_timestamp();
+  let server = await serverForFoo(engine);
+
+  await SyncTestingInfrastructure(server);
+  await generateNewKeys(Service.collectionKeys);
+
+  let collection = server.getCollection("foo", "clients");
+
+  let desktopID = Utils.makeGUID();
+  collection.insertRecord(
+    {
+      id: desktopID,
+      name: "Desktop client",
+      type: "desktop",
+      commands: [],
+      version: "48",
+      protocols: ["1.5"],
+    },
+    now - 10
+  );
+
+  try {
+    _("First sync. 1 record downloaded.");
+    strictEqual(engine.lastRecordUpload, 0);
+    ok(engine.isFirstSync);
+    await syncClientsEngine(server);
+
+    _("Send command to client to wipe history engine");
+    await engine.sendCommand("wipeEngine", ["history"]);
+    await syncClientsEngine(server);
+
+    _(
+      "Simulate the desktop client consuming the command and syncing to the server"
+    );
+    collection.insertRecord(
+      {
+        id: desktopID,
+        name: "Desktop client",
+        type: "desktop",
+        commands: [],
+        version: "48",
+        protocols: ["1.5"],
+      },
+      now - 10
+    );
+
+    _("Send another command to the desktop client to wipe tabs engine");
+    await engine.sendCommand("wipeEngine", ["tabs"], desktopID);
+    await syncClientsEngine(server);
+
+    let desktopPayload = collection.cleartext(desktopID);
+    compareCommands(
+      desktopPayload.commands,
+      [
+        {
+          command: "wipeEngine",
+          args: ["tabs"],
+        },
+      ],
+      "Should only send the second command to the desktop client"
+    );
+  } finally {
+    await cleanup();
+
+    try {
+      server.deleteCollections("foo");
+    } finally {
+      await promiseStopServer(server);
+    }
+  }
+});
+
+add_task(async function test_upload_after_reboot() {
+  _("Multiple downloads, reboot, then upload (bug 1289287)");
+
+  let now = new_timestamp();
+  let server = await serverForFoo(engine);
+
+  await SyncTestingInfrastructure(server);
+  await generateNewKeys(Service.collectionKeys);
+
+  let collection = server.getCollection("foo", "clients");
+
+  let deviceBID = Utils.makeGUID();
+  let deviceCID = Utils.makeGUID();
+  collection.insertRecord(
+    {
+      id: deviceBID,
+      name: "Device B",
+      type: "desktop",
+      commands: [
+        {
+          command: "wipeEngine",
+          args: ["history"],
+          flowID: Utils.makeGUID(),
+        },
+      ],
+      version: "48",
+      protocols: ["1.5"],
+    },
+    now - 10
+  );
+  collection.insertRecord(
+    {
+      id: deviceCID,
+      name: "Device C",
+      type: "desktop",
+      commands: [],
+      version: "48",
+      protocols: ["1.5"],
+    },
+    now - 10
+  );
+
+  try {
+    _("First sync. 2 records downloaded.");
+    strictEqual(engine.lastRecordUpload, 0);
+    ok(engine.isFirstSync);
+    await syncClientsEngine(server);
+
+    _("Send command to client to wipe tab engine");
+    await engine.sendCommand("wipeEngine", ["tabs"], deviceBID);
+
+    const oldUploadOutgoing = SyncEngine.prototype._uploadOutgoing;
+    SyncEngine.prototype._uploadOutgoing = async () =>
+      engine._onRecordsWritten([], [deviceBID]);
+    await syncClientsEngine(server);
+
+    let deviceBPayload = collection.cleartext(deviceBID);
+    compareCommands(
+      deviceBPayload.commands,
+      [
+        {
+          command: "wipeEngine",
+          args: ["history"],
+        },
+      ],
+      "Should be the same because the upload failed"
+    );
+
+    _("Simulate the client B consuming the command and syncing to the server");
+    collection.insertRecord(
+      {
+        id: deviceBID,
+        name: "Device B",
+        type: "desktop",
+        commands: [],
+        version: "48",
+        protocols: ["1.5"],
+      },
+      now - 10
+    );
+
+    // Simulate reboot
+    SyncEngine.prototype._uploadOutgoing = oldUploadOutgoing;
+    engine = Service.clientsEngine = new ClientEngine(Service);
+    await engine.initialize();
+
+    await syncClientsEngine(server);
+
+    deviceBPayload = collection.cleartext(deviceBID);
+    compareCommands(
+      deviceBPayload.commands,
+      [
+        {
+          command: "wipeEngine",
+          args: ["tabs"],
+        },
+      ],
+      "Should only had written our outgoing command"
+    );
+  } finally {
+    await cleanup();
+
+    try {
+      server.deleteCollections("foo");
+    } finally {
+      await promiseStopServer(server);
+    }
+  }
+});
+
+add_task(async function test_keep_cleared_commands_after_reboot() {
+  _(
+    "Download commands, fail upload, reboot, then apply new commands (bug 1289287)"
+  );
+
+  let now = new_timestamp();
+  let server = await serverForFoo(engine);
+
+  await SyncTestingInfrastructure(server);
+  await generateNewKeys(Service.collectionKeys);
+
+  let collection = server.getCollection("foo", "clients");
+
+  let deviceBID = Utils.makeGUID();
+  let deviceCID = Utils.makeGUID();
+  collection.insertRecord(
+    {
+      id: engine.localID,
+      name: "Device A",
+      type: "desktop",
+      commands: [
+        {
+          command: "wipeEngine",
+          args: ["history"],
+          flowID: Utils.makeGUID(),
+        },
+        {
+          command: "wipeEngine",
+          args: ["tabs"],
+          flowID: Utils.makeGUID(),
+        },
+      ],
+      version: "48",
+      protocols: ["1.5"],
+    },
+    now - 10
+  );
+  collection.insertRecord(
+    {
+      id: deviceBID,
+      name: "Device B",
+      type: "desktop",
+      commands: [],
+      version: "48",
+      protocols: ["1.5"],
+    },
+    now - 10
+  );
+  collection.insertRecord(
+    {
+      id: deviceCID,
+      name: "Device C",
+      type: "desktop",
+      commands: [],
+      version: "48",
+      protocols: ["1.5"],
+    },
+    now - 10
+  );
+
+  try {
+    _("First sync. Download remote and our record.");
+    strictEqual(engine.lastRecordUpload, 0);
+    ok(engine.isFirstSync);
+
+    const oldUploadOutgoing = SyncEngine.prototype._uploadOutgoing;
+    SyncEngine.prototype._uploadOutgoing = async () =>
+      engine._onRecordsWritten([], [deviceBID]);
+    let commandsProcessed = 0;
+    engine.service.wipeClient = _engine => {
+      commandsProcessed++;
+    };
+
+    await syncClientsEngine(server);
+    await engine.processIncomingCommands(); // Not called by the engine.sync(), gotta call it ourselves
+    equal(commandsProcessed, 2, "We processed 2 commands");
+
+    let localRemoteRecord = collection.cleartext(engine.localID);
+    compareCommands(
+      localRemoteRecord.commands,
+      [
+        {
+          command: "wipeEngine",
+          args: ["history"],
+        },
+        {
+          command: "wipeEngine",
+          args: ["tabs"],
+        },
+      ],
+      "Should be the same because the upload failed"
+    );
+
+    // Another client sends a wipe command
+    collection.insertRecord(
+      {
+        id: engine.localID,
+        name: "Device A",
+        type: "desktop",
+        commands: [
+          {
+            command: "wipeEngine",
+            args: ["history"],
+            flowID: Utils.makeGUID(),
+          },
+          {
+            command: "wipeEngine",
+            args: ["tabs"],
+            flowID: Utils.makeGUID(),
+          },
+          {
+            command: "wipeEngine",
+            args: ["bookmarks"],
+            flowID: Utils.makeGUID(),
+          },
+        ],
+        version: "48",
+        protocols: ["1.5"],
+      },
+      now - 5
+    );
+
+    // Simulate reboot
+    SyncEngine.prototype._uploadOutgoing = oldUploadOutgoing;
+    engine = Service.clientsEngine = new ClientEngine(Service);
+    await engine.initialize();
+
+    commandsProcessed = 0;
+    engine.service.wipeClient = _engine => {
+      commandsProcessed++;
+    };
+    await syncClientsEngine(server);
+    await engine.processIncomingCommands();
+    equal(
+      commandsProcessed,
+      1,
+      "We processed one command (the other were cleared)"
+    );
+
+    localRemoteRecord = collection.cleartext(deviceBID);
+    deepEqual(localRemoteRecord.commands, [], "Should be empty");
+  } finally {
+    await cleanup();
+
+    // Reset service (remove mocks)
+    engine = Service.clientsEngine = new ClientEngine(Service);
+    await engine.initialize();
+    await engine._resetClient();
+
+    try {
+      server.deleteCollections("foo");
+    } finally {
+      await promiseStopServer(server);
+    }
+  }
+});
+
+add_task(async function test_deleted_commands() {
+  _("Verifies commands for a deleted client are discarded");
+
+  let now = new_timestamp();
+  let server = await serverForFoo(engine);
+
+  await SyncTestingInfrastructure(server);
+  await generateNewKeys(Service.collectionKeys);
+
+  let collection = server.getCollection("foo", "clients");
+
+  let activeID = Utils.makeGUID();
+  collection.insertRecord(
+    {
+      id: activeID,
+      name: "Active client",
+      type: "desktop",
+      commands: [],
+      version: "48",
+      protocols: ["1.5"],
+    },
+    now - 10
+  );
+
+  let deletedID = Utils.makeGUID();
+  collection.insertRecord(
+    {
+      id: deletedID,
+      name: "Client to delete",
+      type: "desktop",
+      commands: [],
+      version: "48",
+      protocols: ["1.5"],
+    },
+    now - 10
+  );
+
+  try {
+    _("First sync. 2 records downloaded.");
+    await syncClientsEngine(server);
+
+    _("Delete a record on the server.");
+    collection.remove(deletedID);
+
+    _("Broadcast a command to all clients");
+    await engine.sendCommand("logout", []);
+    await syncClientsEngine(server);
+
+    deepEqual(
+      collection.keys().sort(),
+      [activeID, engine.localID].sort(),
+      "Should not reupload deleted clients"
+    );
+
+    let activePayload = collection.cleartext(activeID);
+    compareCommands(
+      activePayload.commands,
+      [{ command: "logout", args: [] }],
+      "Should send the command to the active client"
+    );
+  } finally {
+    await cleanup();
+
+    try {
+      server.deleteCollections("foo");
+    } finally {
+      await promiseStopServer(server);
+    }
+  }
+});
+
+add_task(async function test_command_sync() {
+  _("Notify other clients when writing their record.");
+
+  await engine._store.wipe();
+  await generateNewKeys(Service.collectionKeys);
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  let collection = server.getCollection("foo", "clients");
+  let remoteId = Utils.makeGUID();
+  let remoteId2 = Utils.makeGUID();
+
+  _("Create remote client record 1");
+  collection.insertRecord({
+    id: remoteId,
+    name: "Remote client",
+    type: "desktop",
+    commands: [],
+    version: "48",
+    protocols: ["1.5"],
+  });
+
+  _("Create remote client record 2");
+  collection.insertRecord({
+    id: remoteId2,
+    name: "Remote client 2",
+    type: "mobile",
+    commands: [],
+    version: "48",
+    protocols: ["1.5"],
+  });
+
+  try {
+    equal(collection.count(), 2, "2 remote records written");
+    await syncClientsEngine(server);
+    equal(
+      collection.count(),
+      3,
+      "3 remote records written (+1 for the synced local record)"
+    );
+
+    await engine.sendCommand("wipeEngine", ["tabs"]);
+    await engine._tracker.addChangedID(engine.localID);
+    const getClientFxaDeviceId = sinon
+      .stub(engine, "getClientFxaDeviceId")
+      .callsFake(id => "fxa-" + id);
+    const engineMock = sinon.mock(engine);
+    let _notifyCollectionChanged = engineMock
+      .expects("_notifyCollectionChanged")
+      .withArgs(["fxa-" + remoteId, "fxa-" + remoteId2]);
+    _("Syncing.");
+    await syncClientsEngine(server);
+    _notifyCollectionChanged.verify();
+
+    engineMock.restore();
+    getClientFxaDeviceId.restore();
+  } finally {
+    await cleanup();
+    await engine._tracker.clearChangedIDs();
+
+    try {
+      server.deleteCollections("foo");
+    } finally {
+      await promiseStopServer(server);
+    }
+  }
+});
+
+add_task(async function ensureSameFlowIDs() {
+  // Clear events from other test cases.
+  Services.fog.testResetFOG();
+
+  let server = await serverForFoo(engine);
+  try {
+    // Setup 2 clients, send them a command, and ensure we get to events
+    // written, both with the same flowID.
+    await SyncTestingInfrastructure(server);
+    let collection = server.getCollection("foo", "clients");
+
+    let remoteId = Utils.makeGUID();
+    let remoteId2 = Utils.makeGUID();
+
+    _("Create remote client record 1");
+    collection.insertRecord({
+      id: remoteId,
+      name: "Remote client",
+      type: "desktop",
+      commands: [],
+      version: "48",
+      protocols: ["1.5"],
+    });
+
+    _("Create remote client record 2");
+    collection.insertRecord({
+      id: remoteId2,
+      name: "Remote client 2",
+      type: "mobile",
+      commands: [],
+      version: "48",
+      protocols: ["1.5"],
+    });
+
+    await syncClientsEngine(server);
+    await engine.sendCommand("wipeEngine", ["tabs"]);
+    await syncClientsEngine(server);
+    let wipeEvents = Glean.syncClient.sendcommand.testGetValue();
+    equal(wipeEvents.length, 2);
+    equal(wipeEvents[0].extra.flow_id, wipeEvents[1].extra.flow_id);
+    Services.fog.testResetFOG();
+    // Wipe remote clients to ensure deduping doesn't prevent us from adding the command.
+    for (let client of Object.values(engine._store._remoteClients)) {
+      client.commands = [];
+    }
+    // check it's correctly used when we specify a flow ID
+    let flowID = Utils.makeGUID();
+    await engine.sendCommand("wipeEngine", ["tabs"], null, { flowID });
+    await syncClientsEngine(server);
+    wipeEvents = Glean.syncClient.sendcommand.testGetValue();
+    equal(wipeEvents.length, 2);
+    equal(wipeEvents[0].extra.flow_id, flowID);
+    equal(wipeEvents[1].extra.flow_id, flowID);
+    Services.fog.testResetFOG();
+
+    // Wipe remote clients to ensure deduping doesn't prevent us from adding the command.
+    for (let client of Object.values(engine._store._remoteClients)) {
+      client.commands = [];
+    }
+
+    // and that it works when something else is in "extra"
+    await engine.sendCommand("wipeEngine", ["tabs"], null, {
+      reason: "testing",
+    });
+    await syncClientsEngine(server);
+    wipeEvents = Glean.syncClient.sendcommand.testGetValue();
+    equal(wipeEvents.length, 2);
+    equal(wipeEvents[0].extra.flow_id, wipeEvents[1].extra.flow_id);
+    equal(wipeEvents[0].extra.reason, "testing");
+    equal(wipeEvents[1].extra.reason, "testing");
+    Services.fog.testResetFOG();
+    // Wipe remote clients to ensure deduping doesn't prevent us from adding the command.
+    for (let client of Object.values(engine._store._remoteClients)) {
+      client.commands = [];
+    }
+
+    // and when both are specified.
+    await engine.sendCommand("wipeEngine", ["tabs"], null, {
+      reason: "testing",
+      flowID,
+    });
+    await syncClientsEngine(server);
+    wipeEvents = Glean.syncClient.sendcommand.testGetValue();
+    equal(wipeEvents.length, 2);
+    equal(wipeEvents[0].extra.flow_id, flowID);
+    equal(wipeEvents[1].extra.flow_id, flowID);
+    equal(wipeEvents[0].extra.reason, "testing");
+    equal(wipeEvents[1].extra.reason, "testing");
+    // Wipe remote clients to ensure deduping doesn't prevent us from adding the command.
+    for (let client of Object.values(engine._store._remoteClients)) {
+      client.commands = [];
+    }
+  } finally {
+    cleanup();
+    await promiseStopServer(server);
+  }
+});
+
+add_task(async function test_duplicate_commands_telemetry() {
+  // Clear events from other test cases.
+  Services.fog.testResetFOG();
+
+  let server = await serverForFoo(engine);
+  try {
+    await SyncTestingInfrastructure(server);
+    let collection = server.getCollection("foo", "clients");
+
+    let remoteId = Utils.makeGUID();
+    let remoteId2 = Utils.makeGUID();
+
+    _("Create remote client record 1");
+    collection.insertRecord({
+      id: remoteId,
+      name: "Remote client",
+      type: "desktop",
+      commands: [],
+      version: "48",
+      protocols: ["1.5"],
+    });
+
+    _("Create remote client record 2");
+    collection.insertRecord({
+      id: remoteId2,
+      name: "Remote client 2",
+      type: "mobile",
+      commands: [],
+      version: "48",
+      protocols: ["1.5"],
+    });
+
+    await syncClientsEngine(server);
+    // Make sure deduping works before syncing
+    await engine.sendCommand("wipeEngine", ["history"], remoteId);
+    await engine.sendCommand("wipeEngine", ["history"], remoteId);
+    equal(Glean.syncClient.sendcommand.testGetValue().length, 1);
+    await syncClientsEngine(server);
+    // And after syncing.
+    await engine.sendCommand("wipeEngine", ["history"], remoteId);
+    equal(Glean.syncClient.sendcommand.testGetValue().length, 1);
+    // Ensure we aren't deduping commands to different clients
+    await engine.sendCommand("wipeEngine", ["history"], remoteId2);
+    equal(Glean.syncClient.sendcommand.testGetValue().length, 2);
+  } finally {
+    cleanup();
+    await promiseStopServer(server);
+  }
+});
+
+add_task(async function test_other_clients_notified_on_first_sync() {
+  _(
+    "Ensure that other clients are notified when we upload our client record for the first time."
+  );
+
+  await engine.resetLastSync();
+  await engine._store.wipe();
+  await generateNewKeys(Service.collectionKeys);
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  const fxAccounts = engine.fxAccounts;
+  let calls = 0;
+  engine.fxAccounts = {
+    device: {
+      getLocalId() {
+        return fxAccounts.device.getLocalId();
+      },
+      getLocalName() {
+        return fxAccounts.device.getLocalName();
+      },
+      getLocalType() {
+        return fxAccounts.device.getLocalType();
+      },
+    },
+    notifyDevices() {
+      calls++;
+      return Promise.resolve(true);
+    },
+    _internal: {
+      now() {
+        return Date.now();
+      },
+    },
+  };
+
+  try {
+    engine.lastRecordUpload = 0;
+    _("First sync, should notify other clients");
+    await syncClientsEngine(server);
+    equal(calls, 1);
+
+    _("Second sync, should not notify other clients");
+    await syncClientsEngine(server);
+    equal(calls, 1);
+  } finally {
+    engine.fxAccounts = fxAccounts;
+    cleanup();
+    await promiseStopServer(server);
+  }
+});
+
+add_task(
+  async function device_disconnected_notification_updates_known_stale_clients() {
+    const spyUpdate = sinon.spy(engine, "updateKnownStaleClients");
+
+    Services.obs.notifyObservers(
+      null,
+      "fxaccounts:device_disconnected",
+      JSON.stringify({ isLocalDevice: false })
+    );
+    ok(spyUpdate.calledOnce, "updateKnownStaleClients should be called");
+    spyUpdate.resetHistory();
+
+    Services.obs.notifyObservers(
+      null,
+      "fxaccounts:device_disconnected",
+      JSON.stringify({ isLocalDevice: true })
+    );
+    ok(spyUpdate.notCalled, "updateKnownStaleClients should not be called");
+
+    spyUpdate.restore();
+  }
+);
+
+add_task(async function update_known_stale_clients() {
+  const makeFakeClient = id => ({ id, fxaDeviceId: `fxa-${id}` });
+  const clients = [
+    makeFakeClient("one"),
+    makeFakeClient("two"),
+    makeFakeClient("three"),
+  ];
+  const stubRemoteClients = sinon
+    .stub(engine._store, "_remoteClients")
+    .get(() => {
+      return clients;
+    });
+  const stubFetchFxADevices = sinon
+    .stub(engine, "_fetchFxADevices")
+    .callsFake(() => {
+      engine._knownStaleFxADeviceIds = ["fxa-one", "fxa-two"];
+    });
+
+  engine._knownStaleFxADeviceIds = null;
+  await engine.updateKnownStaleClients();
+  ok(clients[0].stale);
+  ok(clients[1].stale);
+  ok(!clients[2].stale);
+
+  stubRemoteClients.restore();
+  stubFetchFxADevices.restore();
+});
+
+add_task(async function test_create_record_command_limit() {
+  await engine._store.wipe();
+  await generateNewKeys(Service.collectionKeys);
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  const fakeLimit = 4 * 1024;
+
+  let maxSizeStub = sinon
+    .stub(Service, "getMemcacheMaxRecordPayloadSize")
+    .callsFake(() => fakeLimit);
+
+  let user = server.user("foo");
+  let remoteId = Utils.makeGUID();
+
+  _("Create remote client record");
+  user.collection("clients").insertRecord({
+    id: remoteId,
+    name: "Remote client",
+    type: "desktop",
+    commands: [],
+    version: "57",
+    protocols: ["1.5"],
+  });
+
+  try {
+    _("Initial sync.");
+    await syncClientsEngine(server);
+
+    _("Send a fairly sane number of commands.");
+
+    for (let i = 0; i < 5; ++i) {
+      await engine.sendCommand("wipeEngine", [`history: ${i}`], remoteId);
+    }
+
+    await syncClientsEngine(server);
+
+    _("Make sure they all fit and weren't dropped.");
+    let parsedServerRecord = user.collection("clients").cleartext(remoteId);
+
+    equal(parsedServerRecord.commands.length, 5);
+
+    await engine.sendCommand("wipeEngine", ["history"], remoteId);
+
+    _("Send a not-sane number of commands.");
+    // Much higher than the maximum number of commands we could actually fit.
+    for (let i = 0; i < 500; ++i) {
+      await engine.sendCommand("wipeEngine", [`tabs: ${i}`], remoteId);
+    }
+
+    await syncClientsEngine(server);
+
+    _("Ensure we didn't overflow the server limit.");
+    let wbo = user.collection("clients").wbo(remoteId);
+    less(wbo.payload.length, fakeLimit);
+
+    _(
+      "And that the data we uploaded is both sane json and containing some commands."
+    );
+    let remoteCommands = wbo.getCleartext().commands;
+    greater(remoteCommands.length, 2);
+    let firstCommand = remoteCommands[0];
+    _(
+      "The first command should still be present, since it had a high priority"
+    );
+    equal(firstCommand.command, "wipeEngine");
+    _("And the last command in the list should be the last command we sent.");
+    let lastCommand = remoteCommands[remoteCommands.length - 1];
+    equal(lastCommand.command, "wipeEngine");
+    deepEqual(lastCommand.args, ["tabs: 499"]);
+  } finally {
+    maxSizeStub.restore();
+    await cleanup();
+    try {
+      let collection = server.getCollection("foo", "clients");
+      collection.remove(remoteId);
+    } finally {
+      await promiseStopServer(server);
+    }
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_clients_escape.js b/src/zen/tests/mochitests/sync/test_clients_escape.js
new file mode 100644
index 000000000..62ffcf1ff
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_clients_escape.js
@@ -0,0 +1,57 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+add_task(async function test_clients_escape() {
+  _("Set up test fixtures.");
+
+  await configureIdentity();
+  let keyBundle = Service.identity.syncKeyBundle;
+
+  let engine = Service.clientsEngine;
+
+  try {
+    _("Test that serializing client records results in uploadable ascii");
+    engine.localID = "ascii";
+    engine.localName = "wéävê";
+
+    _("Make sure we have the expected record");
+    let record = await engine._createRecord("ascii");
+    Assert.equal(record.id, "ascii");
+    Assert.equal(record.name, "wéävê");
+
+    _("Encrypting record...");
+    await record.encrypt(keyBundle);
+    _("Encrypted.");
+
+    let serialized = JSON.stringify(record);
+    let checkCount = 0;
+    _("Checking for all ASCII:", serialized);
+    for (let ch of serialized) {
+      let code = ch.charCodeAt(0);
+      _("Checking asciiness of '", ch, "'=", code);
+      Assert.less(code, 128);
+      checkCount++;
+    }
+
+    _("Processed", checkCount, "characters out of", serialized.length);
+    Assert.equal(checkCount, serialized.length);
+
+    _("Making sure the record still looks like it did before");
+    await record.decrypt(keyBundle);
+    Assert.equal(record.id, "ascii");
+    Assert.equal(record.name, "wéävê");
+
+    _("Sanity check that creating the record also gives the same");
+    record = await engine._createRecord("ascii");
+    Assert.equal(record.id, "ascii");
+    Assert.equal(record.name, "wéävê");
+  } finally {
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_collection_getBatched.js b/src/zen/tests/mochitests/sync/test_collection_getBatched.js
new file mode 100644
index 000000000..f5425abe9
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_collection_getBatched.js
@@ -0,0 +1,187 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Collection, WBORecord } = ChromeUtils.importESModule(
+  "resource://services-sync/record.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+function recordRange(lim, offset, total) {
+  let res = [];
+  for (let i = offset; i < Math.min(lim + offset, total); ++i) {
+    res.push({ id: String(i), payload: "test:" + i });
+  }
+  return res;
+}
+
+function get_test_collection_info({
+  totalRecords,
+  batchSize,
+  lastModified,
+  throwAfter = Infinity,
+  interruptedAfter = Infinity,
+}) {
+  let coll = new Collection("http://example.com/test/", WBORecord, Service);
+  coll.full = true;
+  let requests = [];
+  let responses = [];
+  coll.get = async function () {
+    let limit = +this.limit;
+    let offset = 0;
+    if (this.offset) {
+      equal(this.offset.slice(0, 6), "foobar");
+      offset = +this.offset.slice(6);
+    }
+    requests.push({
+      limit,
+      offset,
+      spec: this.spec,
+      headers: Object.assign({}, this.headers),
+    });
+    if (--throwAfter === 0) {
+      throw new Error("Some Network Error");
+    }
+    let body = recordRange(limit, offset, totalRecords);
+    let response = {
+      obj: body,
+      success: true,
+      status: 200,
+      headers: {},
+    };
+    if (--interruptedAfter === 0) {
+      response.success = false;
+      response.status = 412;
+      response.body = "";
+    } else if (offset + limit < totalRecords) {
+      // Ensure we're treating this as an opaque string, since the docs say
+      // it might not be numeric.
+      response.headers["x-weave-next-offset"] = "foobar" + (offset + batchSize);
+    }
+    response.headers["x-last-modified"] = lastModified;
+    responses.push(response);
+    return response;
+  };
+  return { responses, requests, coll };
+}
+
+add_task(async function test_success() {
+  const totalRecords = 11;
+  const batchSize = 2;
+  const lastModified = "111111";
+  let { responses, requests, coll } = get_test_collection_info({
+    totalRecords,
+    batchSize,
+    lastModified,
+  });
+  let { response, records } = await coll.getBatched(batchSize);
+
+  equal(requests.length, Math.ceil(totalRecords / batchSize));
+
+  equal(records.length, totalRecords);
+  checkRecordsOrder(records);
+
+  // ensure we're returning the last response
+  equal(responses[responses.length - 1], response);
+
+  // check first separately since its a bit of a special case
+  ok(!requests[0].headers["x-if-unmodified-since"]);
+  ok(!requests[0].offset);
+  equal(requests[0].limit, batchSize);
+  let expectedOffset = 2;
+  for (let i = 1; i < requests.length; ++i) {
+    let req = requests[i];
+    equal(req.headers["x-if-unmodified-since"], lastModified);
+    equal(req.limit, batchSize);
+    if (i !== requests.length - 1) {
+      equal(req.offset, expectedOffset);
+    }
+
+    expectedOffset += batchSize;
+  }
+
+  // ensure we cleaned up anything that would break further
+  // use of this collection.
+  ok(!coll._headers["x-if-unmodified-since"]);
+  ok(!coll.offset);
+  ok(!coll.limit || coll.limit == Infinity);
+});
+
+add_task(async function test_total_limit() {
+  _("getBatched respects the (initial) value of the limit property");
+  const totalRecords = 100;
+  const recordLimit = 11;
+  const batchSize = 2;
+  const lastModified = "111111";
+  let { requests, coll } = get_test_collection_info({
+    totalRecords,
+    batchSize,
+    lastModified,
+  });
+  coll.limit = recordLimit;
+  let { records } = await coll.getBatched(batchSize);
+  checkRecordsOrder(records);
+
+  equal(requests.length, Math.ceil(recordLimit / batchSize));
+  equal(records.length, recordLimit);
+
+  for (let i = 0; i < requests.length; ++i) {
+    let req = requests[i];
+    if (i !== requests.length - 1) {
+      equal(req.limit, batchSize);
+    } else {
+      equal(req.limit, recordLimit % batchSize);
+    }
+  }
+
+  equal(coll._limit, recordLimit);
+});
+
+add_task(async function test_412() {
+  _("We shouldn't record records if we get a 412 in the middle of a batch");
+  const totalRecords = 11;
+  const batchSize = 2;
+  const lastModified = "111111";
+  let { responses, requests, coll } = get_test_collection_info({
+    totalRecords,
+    batchSize,
+    lastModified,
+    interruptedAfter: 3,
+  });
+  let { response, records } = await coll.getBatched(batchSize);
+
+  equal(requests.length, 3);
+  equal(records.length, 0); // we should not get any records
+
+  // ensure we're returning the last response
+  equal(responses[responses.length - 1], response);
+
+  ok(!response.success);
+  equal(response.status, 412);
+});
+
+add_task(async function test_get_throws() {
+  _("getBatched() should throw if a get() throws");
+  const totalRecords = 11;
+  const batchSize = 2;
+  const lastModified = "111111";
+  let { requests, coll } = get_test_collection_info({
+    totalRecords,
+    batchSize,
+    lastModified,
+    throwAfter: 3,
+  });
+
+  await Assert.rejects(coll.getBatched(batchSize), /Some Network Error/);
+
+  equal(requests.length, 3);
+});
+
+function checkRecordsOrder(records) {
+  ok(!!records.length);
+  for (let i = 0; i < records.length; i++) {
+    equal(records[i].id, String(i));
+    equal(records[i].payload, "test:" + i);
+  }
+}
diff --git a/src/zen/tests/mochitests/sync/test_collections_recovery.js b/src/zen/tests/mochitests/sync/test_collections_recovery.js
new file mode 100644
index 000000000..fd923bc27
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_collections_recovery.js
@@ -0,0 +1,95 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// Verify that we wipe the server if we have to regenerate keys.
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+add_task(async function test_missing_crypto_collection() {
+  enableValidationPrefs();
+
+  let johnHelper = track_collections_helper();
+  let johnU = johnHelper.with_updated_collection;
+  let johnColls = johnHelper.collections;
+
+  let empty = false;
+  function maybe_empty(handler) {
+    return function (request, response) {
+      if (empty) {
+        let body = "{}";
+        response.setStatusLine(request.httpVersion, 200, "OK");
+        response.bodyOutputStream.write(body, body.length);
+      } else {
+        handler(request, response);
+      }
+    };
+  }
+
+  let handlers = {
+    "/1.1/johndoe/info/collections": maybe_empty(johnHelper.handler),
+    "/1.1/johndoe/storage/crypto/keys": johnU(
+      "crypto",
+      new ServerWBO("keys").handler()
+    ),
+    "/1.1/johndoe/storage/meta/global": johnU(
+      "meta",
+      new ServerWBO("global").handler()
+    ),
+  };
+  let collections = [
+    "clients",
+    "bookmarks",
+    "forms",
+    "history",
+    "passwords",
+    "prefs",
+    "tabs",
+  ];
+  // Disable addon sync because AddonManager won't be initialized here.
+  await Service.engineManager.unregister("addons");
+  await Service.engineManager.unregister("extension-storage");
+
+  for (let coll of collections) {
+    handlers["/1.1/johndoe/storage/" + coll] = johnU(
+      coll,
+      new ServerCollection({}, true).handler()
+    );
+  }
+  let server = httpd_setup(handlers);
+  await configureIdentity({ username: "johndoe" }, server);
+
+  try {
+    let fresh = 0;
+    let orig = Service._freshStart;
+    Service._freshStart = async function () {
+      _("Called _freshStart.");
+      await orig.call(Service);
+      fresh++;
+    };
+
+    _("Startup, no meta/global: freshStart called once.");
+    await sync_and_validate_telem();
+    Assert.equal(fresh, 1);
+    fresh = 0;
+
+    _("Regular sync: no need to freshStart.");
+    await Service.sync();
+    Assert.equal(fresh, 0);
+
+    _("Simulate a bad info/collections.");
+    delete johnColls.crypto;
+    await sync_and_validate_telem();
+    Assert.equal(fresh, 1);
+    fresh = 0;
+
+    _("Regular sync: no need to freshStart.");
+    await sync_and_validate_telem();
+    Assert.equal(fresh, 0);
+  } finally {
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+    await promiseStopServer(server);
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_corrupt_keys.js b/src/zen/tests/mochitests/sync/test_corrupt_keys.js
new file mode 100644
index 000000000..7caea85d4
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_corrupt_keys.js
@@ -0,0 +1,248 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Weave } = ChromeUtils.importESModule(
+  "resource://services-sync/main.sys.mjs"
+);
+const { HistoryEngine } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/history.sys.mjs"
+);
+const { CryptoWrapper, WBORecord } = ChromeUtils.importESModule(
+  "resource://services-sync/record.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+add_task(async function test_locally_changed_keys() {
+  enableValidationPrefs();
+
+  let hmacErrorCount = 0;
+  function counting(f) {
+    return async function () {
+      hmacErrorCount++;
+      return f.call(this);
+    };
+  }
+
+  Service.handleHMACEvent = counting(Service.handleHMACEvent);
+
+  let server = new SyncServer();
+  let johndoe = server.registerUser("johndoe", "password");
+  johndoe.createContents({
+    meta: {},
+    crypto: {},
+    clients: {},
+  });
+  server.start();
+
+  try {
+    Svc.PrefBranch.setStringPref("registerEngines", "Tab");
+
+    await configureIdentity({ username: "johndoe" }, server);
+    // We aren't doing a .login yet, so fudge the cluster URL.
+    Service.clusterURL = Service.identity._token.endpoint;
+
+    await Service.engineManager.register(HistoryEngine);
+    // Disable addon sync because AddonManager won't be initialized here.
+    await Service.engineManager.unregister("addons");
+    await Service.engineManager.unregister("extension-storage");
+
+    async function corrupt_local_keys() {
+      Service.collectionKeys._default.keyPair = [
+        await Weave.Crypto.generateRandomKey(),
+        await Weave.Crypto.generateRandomKey(),
+      ];
+    }
+
+    _("Setting meta.");
+
+    // Bump version on the server.
+    let m = new WBORecord("meta", "global");
+    m.payload = {
+      syncID: "foooooooooooooooooooooooooo",
+      storageVersion: STORAGE_VERSION,
+    };
+    await m.upload(Service.resource(Service.metaURL));
+
+    _(
+      "New meta/global: " +
+        JSON.stringify(johndoe.collection("meta").wbo("global"))
+    );
+
+    // Upload keys.
+    await generateNewKeys(Service.collectionKeys);
+    let serverKeys = Service.collectionKeys.asWBO("crypto", "keys");
+    await serverKeys.encrypt(Service.identity.syncKeyBundle);
+    Assert.ok(
+      (await serverKeys.upload(Service.resource(Service.cryptoKeysURL))).success
+    );
+
+    // Check that login works.
+    Assert.ok(await Service.login());
+    Assert.ok(Service.isLoggedIn);
+
+    // Sync should upload records.
+    await sync_and_validate_telem();
+
+    // Tabs exist.
+    _("Tabs modified: " + johndoe.modified("tabs"));
+    Assert.greater(johndoe.modified("tabs"), 0);
+
+    // Let's create some server side history records.
+    let liveKeys = Service.collectionKeys.keyForCollection("history");
+    _("Keys now: " + liveKeys.keyPair);
+    let visitType = Ci.nsINavHistoryService.TRANSITION_LINK;
+    let history = johndoe.createCollection("history");
+    for (let i = 0; i < 5; i++) {
+      let id = "record-no--" + i;
+      let modified = Date.now() / 1000 - 60 * (i + 10);
+
+      let w = new CryptoWrapper("history", "id");
+      w.cleartext = {
+        id,
+        histUri: "http://foo/bar?" + id,
+        title: id,
+        sortindex: i,
+        visits: [{ date: (modified - 5) * 1000000, type: visitType }],
+        deleted: false,
+      };
+      await w.encrypt(liveKeys);
+
+      let payload = { ciphertext: w.ciphertext, IV: w.IV, hmac: w.hmac };
+      history.insert(id, payload, modified);
+    }
+
+    history.timestamp = Date.now() / 1000;
+    let old_key_time = johndoe.modified("crypto");
+    _("Old key time: " + old_key_time);
+
+    // Check that we can decrypt one.
+    let rec = new CryptoWrapper("history", "record-no--0");
+    await rec.fetch(
+      Service.resource(Service.storageURL + "history/record-no--0")
+    );
+    _(JSON.stringify(rec));
+    Assert.ok(!!(await rec.decrypt(liveKeys)));
+
+    Assert.equal(hmacErrorCount, 0);
+
+    // Fill local key cache with bad data.
+    await corrupt_local_keys();
+    _(
+      "Keys now: " + Service.collectionKeys.keyForCollection("history").keyPair
+    );
+
+    Assert.equal(hmacErrorCount, 0);
+
+    _("HMAC error count: " + hmacErrorCount);
+    // Now syncing should succeed, after one HMAC error.
+    await sync_and_validate_telem(ping => {
+      Assert.equal(
+        ping.engines.find(e => e.name == "history").incoming.applied,
+        5
+      );
+    });
+
+    Assert.equal(hmacErrorCount, 1);
+    _(
+      "Keys now: " + Service.collectionKeys.keyForCollection("history").keyPair
+    );
+
+    // And look! We downloaded history!
+    Assert.ok(
+      await PlacesUtils.history.hasVisits("http://foo/bar?record-no--0")
+    );
+    Assert.ok(
+      await PlacesUtils.history.hasVisits("http://foo/bar?record-no--1")
+    );
+    Assert.ok(
+      await PlacesUtils.history.hasVisits("http://foo/bar?record-no--2")
+    );
+    Assert.ok(
+      await PlacesUtils.history.hasVisits("http://foo/bar?record-no--3")
+    );
+    Assert.ok(
+      await PlacesUtils.history.hasVisits("http://foo/bar?record-no--4")
+    );
+    Assert.equal(hmacErrorCount, 1);
+
+    _("Busting some new server values.");
+    // Now what happens if we corrupt the HMAC on the server?
+    for (let i = 5; i < 10; i++) {
+      let id = "record-no--" + i;
+      let modified = 1 + Date.now() / 1000;
+
+      let w = new CryptoWrapper("history", "id");
+      w.cleartext = {
+        id,
+        histUri: "http://foo/bar?" + id,
+        title: id,
+        sortindex: i,
+        visits: [{ date: (modified - 5) * 1000000, type: visitType }],
+        deleted: false,
+      };
+      await w.encrypt(Service.collectionKeys.keyForCollection("history"));
+      w.hmac = w.hmac.toUpperCase();
+
+      let payload = { ciphertext: w.ciphertext, IV: w.IV, hmac: w.hmac };
+      history.insert(id, payload, modified);
+    }
+    history.timestamp = Date.now() / 1000;
+
+    _("Server key time hasn't changed.");
+    Assert.equal(johndoe.modified("crypto"), old_key_time);
+
+    _("Resetting HMAC error timer.");
+    Service.lastHMACEvent = 0;
+
+    _("Syncing...");
+    await sync_and_validate_telem(ping => {
+      Assert.equal(
+        ping.engines.find(e => e.name == "history").incoming.failed,
+        5
+      );
+    });
+
+    _(
+      "Keys now: " + Service.collectionKeys.keyForCollection("history").keyPair
+    );
+    _(
+      "Server keys have been updated, and we skipped over 5 more HMAC errors without adjusting history."
+    );
+    Assert.greater(johndoe.modified("crypto"), old_key_time);
+    Assert.equal(hmacErrorCount, 6);
+    Assert.equal(
+      false,
+      await PlacesUtils.history.hasVisits("http://foo/bar?record-no--5")
+    );
+    Assert.equal(
+      false,
+      await PlacesUtils.history.hasVisits("http://foo/bar?record-no--6")
+    );
+    Assert.equal(
+      false,
+      await PlacesUtils.history.hasVisits("http://foo/bar?record-no--7")
+    );
+    Assert.equal(
+      false,
+      await PlacesUtils.history.hasVisits("http://foo/bar?record-no--8")
+    );
+    Assert.equal(
+      false,
+      await PlacesUtils.history.hasVisits("http://foo/bar?record-no--9")
+    );
+  } finally {
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+    await promiseStopServer(server);
+  }
+});
+
+function run_test() {
+  Log.repository.rootLogger.addAppender(new Log.DumpAppender());
+  validate_all_future_pings();
+
+  run_next_test();
+}
diff --git a/src/zen/tests/mochitests/sync/test_declined.js b/src/zen/tests/mochitests/sync/test_declined.js
new file mode 100644
index 000000000..ccf663d0e
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_declined.js
@@ -0,0 +1,198 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { DeclinedEngines } = ChromeUtils.importESModule(
+  "resource://services-sync/stages/declined.sys.mjs"
+);
+const { EngineSynchronizer } = ChromeUtils.importESModule(
+  "resource://services-sync/stages/enginesync.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { Observers } = ChromeUtils.importESModule(
+  "resource://services-common/observers.sys.mjs"
+);
+
+function PetrolEngine() {}
+PetrolEngine.prototype.name = "petrol";
+
+function DieselEngine() {}
+DieselEngine.prototype.name = "diesel";
+
+function DummyEngine() {}
+DummyEngine.prototype.name = "dummy";
+
+function ActualEngine() {}
+ActualEngine.prototype.name = "actual";
+Object.setPrototypeOf(ActualEngine.prototype, SyncEngine.prototype);
+
+function getEngineManager() {
+  let manager = new EngineManager(Service);
+  Service.engineManager = manager;
+  manager._engines = {
+    petrol: new PetrolEngine(),
+    diesel: new DieselEngine(),
+    dummy: new DummyEngine(),
+    actual: new ActualEngine(),
+  };
+  return manager;
+}
+
+/**
+ * 'Fetch' a meta/global record that doesn't mention declined.
+ *
+ * Push it into the EngineSynchronizer to set enabled; verify that those are
+ * correct.
+ *
+ * Then push it into DeclinedEngines to set declined; verify that none are
+ * declined, and a notification is sent for our locally disabled-but-not-
+ * declined engines.
+ */
+add_task(async function testOldMeta() {
+  let meta = {
+    payload: {
+      engines: {
+        petrol: 1,
+        diesel: 2,
+        nonlocal: 3, // Enabled but not supported.
+      },
+    },
+  };
+
+  _("Record: " + JSON.stringify(meta));
+
+  let manager = getEngineManager();
+
+  // Update enabled from meta/global.
+  let engineSync = new EngineSynchronizer(Service);
+  await engineSync._updateEnabledFromMeta(meta, 3, manager);
+
+  Assert.ok(manager._engines.petrol.enabled, "'petrol' locally enabled.");
+  Assert.ok(manager._engines.diesel.enabled, "'diesel' locally enabled.");
+  Assert.ok(
+    !("nonlocal" in manager._engines),
+    "We don't know anything about the 'nonlocal' engine."
+  );
+  Assert.ok(!manager._engines.actual.enabled, "'actual' not locally enabled.");
+  Assert.ok(!manager.isDeclined("actual"), "'actual' not declined, though.");
+
+  let declinedEngines = new DeclinedEngines(Service);
+
+  function onNotDeclined(subject) {
+    Observers.remove("weave:engines:notdeclined", onNotDeclined);
+    Assert.ok(
+      subject.undecided.has("actual"),
+      "EngineManager observed that 'actual' was undecided."
+    );
+
+    let declined = manager.getDeclined();
+    _("Declined: " + JSON.stringify(declined));
+
+    Assert.ok(!meta.changed, "No need to upload a new meta/global.");
+    run_next_test();
+  }
+
+  Observers.add("weave:engines:notdeclined", onNotDeclined);
+
+  declinedEngines.updateDeclined(meta, manager);
+});
+
+/**
+ * 'Fetch' a meta/global that declines an engine we don't
+ * recognize. Ensure that we track that declined engine along
+ * with any we locally declined, and that the meta/global
+ * record is marked as changed and includes all declined
+ * engines.
+ */
+add_task(async function testDeclinedMeta() {
+  let meta = {
+    payload: {
+      engines: {
+        petrol: 1,
+        diesel: 2,
+        nonlocal: 3, // Enabled but not supported.
+      },
+      declined: ["nonexistent"], // Declined and not supported.
+    },
+  };
+
+  _("Record: " + JSON.stringify(meta));
+
+  let manager = getEngineManager();
+  manager._engines.petrol.enabled = true;
+  manager._engines.diesel.enabled = true;
+  manager._engines.dummy.enabled = true;
+  manager._engines.actual.enabled = false; // Disabled but not declined.
+
+  manager.decline(["localdecline"]); // Declined and not supported.
+
+  let declinedEngines = new DeclinedEngines(Service);
+
+  function onNotDeclined(subject) {
+    Observers.remove("weave:engines:notdeclined", onNotDeclined);
+    Assert.ok(
+      subject.undecided.has("actual"),
+      "EngineManager observed that 'actual' was undecided."
+    );
+
+    let declined = manager.getDeclined();
+    _("Declined: " + JSON.stringify(declined));
+
+    Assert.equal(
+      declined.indexOf("actual"),
+      -1,
+      "'actual' is locally disabled, but not marked as declined."
+    );
+
+    Assert.equal(
+      declined.indexOf("clients"),
+      -1,
+      "'clients' is enabled and not remotely declined."
+    );
+    Assert.equal(
+      declined.indexOf("petrol"),
+      -1,
+      "'petrol' is enabled and not remotely declined."
+    );
+    Assert.equal(
+      declined.indexOf("diesel"),
+      -1,
+      "'diesel' is enabled and not remotely declined."
+    );
+    Assert.equal(
+      declined.indexOf("dummy"),
+      -1,
+      "'dummy' is enabled and not remotely declined."
+    );
+
+    Assert.lessOrEqual(
+      0,
+      declined.indexOf("nonexistent"),
+      "'nonexistent' was declined on the server."
+    );
+
+    Assert.lessOrEqual(
+      0,
+      declined.indexOf("localdecline"),
+      "'localdecline' was declined locally."
+    );
+
+    // The meta/global is modified, too.
+    Assert.lessOrEqual(
+      0,
+      meta.payload.declined.indexOf("nonexistent"),
+      "meta/global's declined contains 'nonexistent'."
+    );
+    Assert.lessOrEqual(
+      0,
+      meta.payload.declined.indexOf("localdecline"),
+      "meta/global's declined contains 'localdecline'."
+    );
+    Assert.strictEqual(true, meta.changed, "meta/global was changed.");
+  }
+
+  Observers.add("weave:engines:notdeclined", onNotDeclined);
+
+  declinedEngines.updateDeclined(meta, manager);
+});
diff --git a/src/zen/tests/mochitests/sync/test_disconnect_shutdown.js b/src/zen/tests/mochitests/sync/test_disconnect_shutdown.js
new file mode 100644
index 000000000..1c0023824
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_disconnect_shutdown.js
@@ -0,0 +1,104 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { SyncDisconnect, SyncDisconnectInternal } = ChromeUtils.importESModule(
+  "resource://services-sync/SyncDisconnect.sys.mjs"
+);
+const { AsyncShutdown } = ChromeUtils.importESModule(
+  "resource://gre/modules/AsyncShutdown.sys.mjs"
+);
+const { PREF_LAST_FXA_USER_UID } = ChromeUtils.importESModule(
+  "resource://gre/modules/FxAccountsCommon.sys.mjs"
+);
+
+add_task(async function test_shutdown_blocker() {
+  let spySignout = sinon.stub(
+    SyncDisconnectInternal,
+    "doSyncAndAccountDisconnect"
+  );
+
+  // We don't need to check for the lock regularly as we end up aborting the wait.
+  SyncDisconnectInternal.lockRetryInterval = 1000;
+  // Force the retry count to a very large value - this test should never
+  // abort due to the retry count and we want the test to fail (aka timeout)
+  // should our abort code not work.
+  SyncDisconnectInternal.lockRetryCount = 10000;
+  // mock the "browser" sanitize function - it should not be called by
+  // this test.
+  let spyBrowser = sinon.stub(SyncDisconnectInternal, "doSanitizeBrowserData");
+  // mock Sync
+  let mockEngine1 = {
+    enabled: true,
+    name: "Test Engine 1",
+    wipeClient: sinon.spy(),
+  };
+  let mockEngine2 = {
+    enabled: false,
+    name: "Test Engine 2",
+    wipeClient: sinon.spy(),
+  };
+
+  // This weave mock never gives up the lock.
+  let Weave = {
+    Service: {
+      enabled: true,
+      lock: () => false, // so we never get the lock.
+      unlock: sinon.spy(),
+
+      engineManager: {
+        getAll: sinon.stub().returns([mockEngine1, mockEngine2]),
+      },
+      errorHandler: {
+        resetFileLog: sinon.spy(),
+      },
+    },
+  };
+  let weaveStub = sinon.stub(SyncDisconnectInternal, "getWeave");
+  weaveStub.returns(Weave);
+
+  Services.prefs.setStringPref(
+    PREF_LAST_FXA_USER_UID,
+    "dGVzdEBleGFtcGxlLmNvbQ=="
+  );
+
+  let promiseDisconnected = SyncDisconnect.disconnect(true);
+
+  // Pretend we hit the shutdown blocker.
+  info("simulating appShutdownConfirmed");
+  Services.prefs.setBoolPref("toolkit.asyncshutdown.testing", true);
+  AsyncShutdown.appShutdownConfirmed._trigger();
+  Services.prefs.clearUserPref("toolkit.asyncshutdown.testing");
+
+  info("waiting for disconnect to complete");
+  await promiseDisconnected;
+
+  Assert.ok(
+    !Services.prefs.prefHasUserValue(PREF_LAST_FXA_USER_UID),
+    "Should have reset different user warning pref"
+  );
+  Assert.equal(
+    Weave.Service.unlock.callCount,
+    0,
+    "should not have unlocked at the end"
+  );
+  Assert.ok(!Weave.Service.enabled, "Weave should be and remain disabled");
+  Assert.equal(
+    Weave.Service.errorHandler.resetFileLog.callCount,
+    1,
+    "should have reset the log"
+  );
+  Assert.equal(
+    mockEngine1.wipeClient.callCount,
+    1,
+    "enabled engine should have been wiped"
+  );
+  Assert.equal(
+    mockEngine2.wipeClient.callCount,
+    0,
+    "disabled engine should not have been wiped"
+  );
+  Assert.equal(spyBrowser.callCount, 1, "should not sanitize the browser");
+  Assert.equal(spySignout.callCount, 1, "should have signed out of FxA");
+});
diff --git a/src/zen/tests/mochitests/sync/test_engine.js b/src/zen/tests/mochitests/sync/test_engine.js
new file mode 100644
index 000000000..dc38c3626
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_engine.js
@@ -0,0 +1,246 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Observers } = ChromeUtils.importESModule(
+  "resource://services-common/observers.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+function SteamStore(engine) {
+  Store.call(this, "Steam", engine);
+  this.wasWiped = false;
+}
+SteamStore.prototype = {
+  async wipe() {
+    this.wasWiped = true;
+  },
+};
+Object.setPrototypeOf(SteamStore.prototype, Store.prototype);
+
+function SteamTracker(name, engine) {
+  LegacyTracker.call(this, name || "Steam", engine);
+}
+Object.setPrototypeOf(SteamTracker.prototype, LegacyTracker.prototype);
+
+function SteamEngine(name, service) {
+  SyncEngine.call(this, name, service);
+  this.wasReset = false;
+  this.wasSynced = false;
+}
+SteamEngine.prototype = {
+  _storeObj: SteamStore,
+  _trackerObj: SteamTracker,
+
+  async _resetClient() {
+    this.wasReset = true;
+  },
+
+  async _sync() {
+    this.wasSynced = true;
+  },
+};
+Object.setPrototypeOf(SteamEngine.prototype, SyncEngine.prototype);
+
+var engineObserver = {
+  topics: [],
+
+  observe(subject, topic, data) {
+    Assert.equal(data, "steam");
+    this.topics.push(topic);
+  },
+
+  reset() {
+    this.topics = [];
+  },
+};
+Observers.add("weave:engine:reset-client:start", engineObserver);
+Observers.add("weave:engine:reset-client:finish", engineObserver);
+Observers.add("weave:engine:wipe-client:start", engineObserver);
+Observers.add("weave:engine:wipe-client:finish", engineObserver);
+Observers.add("weave:engine:sync:start", engineObserver);
+Observers.add("weave:engine:sync:finish", engineObserver);
+
+async function cleanup(engine) {
+  for (const pref of Svc.PrefBranch.getChildList("")) {
+    Svc.PrefBranch.clearUserPref(pref);
+  }
+  engine.wasReset = false;
+  engine.wasSynced = false;
+  engineObserver.reset();
+  await engine._tracker.clearChangedIDs();
+  await engine.finalize();
+}
+
+add_task(async function test_members() {
+  _("Engine object members");
+  let engine = new SteamEngine("Steam", Service);
+  await engine.initialize();
+  Assert.equal(engine.Name, "Steam");
+  Assert.equal(engine.prefName, "steam");
+  Assert.ok(engine._store instanceof SteamStore);
+  Assert.ok(engine._tracker instanceof SteamTracker);
+});
+
+add_task(async function test_score() {
+  _("Engine.score corresponds to tracker.score and is readonly");
+  let engine = new SteamEngine("Steam", Service);
+  await engine.initialize();
+  Assert.equal(engine.score, 0);
+  engine._tracker.score += 5;
+  Assert.equal(engine.score, 5);
+
+  try {
+    engine.score = 10;
+  } catch (ex) {
+    // Setting an attribute that has a getter produces an error in
+    // Firefox <= 3.6 and is ignored in later versions.  Either way,
+    // the attribute's value won't change.
+  }
+  Assert.equal(engine.score, 5);
+});
+
+add_task(async function test_resetClient() {
+  _("Engine.resetClient calls _resetClient");
+  let engine = new SteamEngine("Steam", Service);
+  await engine.initialize();
+  Assert.ok(!engine.wasReset);
+
+  await engine.resetClient();
+  Assert.ok(engine.wasReset);
+  Assert.equal(engineObserver.topics[0], "weave:engine:reset-client:start");
+  Assert.equal(engineObserver.topics[1], "weave:engine:reset-client:finish");
+
+  await cleanup(engine);
+});
+
+add_task(async function test_invalidChangedIDs() {
+  _("Test that invalid changed IDs on disk don't end up live.");
+  let engine = new SteamEngine("Steam", Service);
+  await engine.initialize();
+  let tracker = engine._tracker;
+
+  await tracker._beforeSave();
+  await IOUtils.writeUTF8(tracker._storage.path, "5", {
+    tmpPath: tracker._storage.path + ".tmp",
+  });
+
+  ok(!tracker._storage.dataReady);
+  const changes = await tracker.getChangedIDs();
+  changes.placeholder = true;
+  deepEqual(
+    changes,
+    { placeholder: true },
+    "Accessing changed IDs should load changes from disk as a side effect"
+  );
+  ok(tracker._storage.dataReady);
+
+  Assert.ok(changes.placeholder);
+  await cleanup(engine);
+});
+
+add_task(async function test_wipeClient() {
+  _("Engine.wipeClient calls resetClient, wipes store, clears changed IDs");
+  let engine = new SteamEngine("Steam", Service);
+  await engine.initialize();
+  Assert.ok(!engine.wasReset);
+  Assert.ok(!engine._store.wasWiped);
+  Assert.ok(await engine._tracker.addChangedID("a-changed-id"));
+  let changes = await engine._tracker.getChangedIDs();
+  Assert.ok("a-changed-id" in changes);
+
+  await engine.wipeClient();
+  Assert.ok(engine.wasReset);
+  Assert.ok(engine._store.wasWiped);
+  changes = await engine._tracker.getChangedIDs();
+  Assert.equal(JSON.stringify(changes), "{}");
+  Assert.equal(engineObserver.topics[0], "weave:engine:wipe-client:start");
+  Assert.equal(engineObserver.topics[1], "weave:engine:reset-client:start");
+  Assert.equal(engineObserver.topics[2], "weave:engine:reset-client:finish");
+  Assert.equal(engineObserver.topics[3], "weave:engine:wipe-client:finish");
+
+  await cleanup(engine);
+});
+
+add_task(async function test_enabled() {
+  _("Engine.enabled corresponds to preference");
+  let engine = new SteamEngine("Steam", Service);
+  await engine.initialize();
+  try {
+    Assert.ok(!engine.enabled);
+    Svc.PrefBranch.setBoolPref("engine.steam", true);
+    Assert.ok(engine.enabled);
+
+    engine.enabled = false;
+    Assert.ok(!Svc.PrefBranch.getBoolPref("engine.steam"));
+  } finally {
+    await cleanup(engine);
+  }
+});
+
+add_task(async function test_sync() {
+  let engine = new SteamEngine("Steam", Service);
+  await engine.initialize();
+  try {
+    _("Engine.sync doesn't call _sync if it's not enabled");
+    Assert.ok(!engine.enabled);
+    Assert.ok(!engine.wasSynced);
+    await engine.sync();
+
+    Assert.ok(!engine.wasSynced);
+
+    _("Engine.sync calls _sync if it's enabled");
+    engine.enabled = true;
+
+    await engine.sync();
+    Assert.ok(engine.wasSynced);
+    Assert.equal(engineObserver.topics[0], "weave:engine:sync:start");
+    Assert.equal(engineObserver.topics[1], "weave:engine:sync:finish");
+  } finally {
+    await cleanup(engine);
+  }
+});
+
+add_task(async function test_disabled_no_track() {
+  _("When an engine is disabled, its tracker is not tracking.");
+  let engine = new SteamEngine("Steam", Service);
+  await engine.initialize();
+  let tracker = engine._tracker;
+  Assert.equal(engine, tracker.engine);
+
+  Assert.ok(!engine.enabled);
+  Assert.ok(!tracker._isTracking);
+  let changes = await tracker.getChangedIDs();
+  do_check_empty(changes);
+
+  Assert.ok(!tracker.engineIsEnabled());
+  Assert.ok(!tracker._isTracking);
+  changes = await tracker.getChangedIDs();
+  do_check_empty(changes);
+
+  let promisePrefChangeHandled = Promise.withResolvers();
+  const origMethod = tracker.onEngineEnabledChanged;
+  tracker.onEngineEnabledChanged = async (...args) => {
+    await origMethod.apply(tracker, args);
+    promisePrefChangeHandled.resolve();
+  };
+
+  engine.enabled = true; // Also enables the tracker automatically.
+  await promisePrefChangeHandled.promise;
+  Assert.ok(tracker._isTracking);
+  changes = await tracker.getChangedIDs();
+  do_check_empty(changes);
+
+  await tracker.addChangedID("abcdefghijkl");
+  changes = await tracker.getChangedIDs();
+  Assert.less(0, changes.abcdefghijkl);
+  promisePrefChangeHandled = Promise.withResolvers();
+  Svc.PrefBranch.setBoolPref("engine." + engine.prefName, false);
+  await promisePrefChangeHandled.promise;
+  Assert.ok(!tracker._isTracking);
+  changes = await tracker.getChangedIDs();
+  do_check_empty(changes);
+
+  await cleanup(engine);
+});
diff --git a/src/zen/tests/mochitests/sync/test_engine_abort.js b/src/zen/tests/mochitests/sync/test_engine_abort.js
new file mode 100644
index 000000000..a7c62afb4
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_engine_abort.js
@@ -0,0 +1,79 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { WBORecord } = ChromeUtils.importESModule(
+  "resource://services-sync/record.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { RotaryEngine } = ChromeUtils.importESModule(
+  "resource://testing-common/services/sync/rotaryengine.sys.mjs"
+);
+
+add_task(async function test_processIncoming_abort() {
+  _(
+    "An abort exception, raised in applyIncoming, will abort _processIncoming."
+  );
+  let engine = new RotaryEngine(Service);
+
+  let collection = new ServerCollection();
+  let id = Utils.makeGUID();
+  let payload = encryptPayload({ id, denomination: "Record No. " + id });
+  collection.insert(id, payload);
+
+  let server = sync_httpd_setup({
+    "/1.1/foo/storage/rotary": collection.handler(),
+  });
+
+  await SyncTestingInfrastructure(server);
+  await generateNewKeys(Service.collectionKeys);
+
+  _("Create some server data.");
+  let syncID = await engine.resetLocalSyncID();
+  let meta_global = Service.recordManager.set(
+    engine.metaURL,
+    new WBORecord(engine.metaURL)
+  );
+  meta_global.payload.engines = { rotary: { version: engine.version, syncID } };
+  _("Fake applyIncoming to abort.");
+  engine._store.applyIncoming = async function () {
+    let ex = {
+      code: SyncEngine.prototype.eEngineAbortApplyIncoming,
+      cause: "Nooo",
+    };
+    _("Throwing: " + JSON.stringify(ex));
+    throw ex;
+  };
+
+  _("Trying _processIncoming. It will throw after aborting.");
+  let err;
+  try {
+    await engine._syncStartup();
+    await engine._processIncoming();
+  } catch (ex) {
+    err = ex;
+  }
+
+  Assert.equal(err, "Nooo");
+  err = undefined;
+
+  _("Trying engine.sync(). It will abort without error.");
+  try {
+    // This will quietly fail.
+    await engine.sync();
+  } catch (ex) {
+    err = ex;
+  }
+
+  Assert.equal(err, undefined);
+
+  await promiseStopServer(server);
+  for (const pref of Svc.PrefBranch.getChildList("")) {
+    Svc.PrefBranch.clearUserPref(pref);
+  }
+  Service.recordManager.clearCache();
+
+  await engine._tracker.clearChangedIDs();
+  await engine.finalize();
+});
diff --git a/src/zen/tests/mochitests/sync/test_engine_changes_during_sync.js b/src/zen/tests/mochitests/sync/test_engine_changes_during_sync.js
new file mode 100644
index 000000000..891bea41e
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_engine_changes_during_sync.js
@@ -0,0 +1,611 @@
+const { FormHistory } = ChromeUtils.importESModule(
+  "resource://gre/modules/FormHistory.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { Bookmark, BookmarkFolder, BookmarkQuery } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/bookmarks.sys.mjs"
+);
+const { HistoryRec } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/history.sys.mjs"
+);
+const { FormRec } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/forms.sys.mjs"
+);
+const { LoginRec } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/passwords.sys.mjs"
+);
+const { PrefRec } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/prefs.sys.mjs"
+);
+
+const LoginInfo = Components.Constructor(
+  "@mozilla.org/login-manager/loginInfo;1",
+  Ci.nsILoginInfo,
+  "init"
+);
+
+/**
+ * We don't test the clients or tabs engines because neither has conflict
+ * resolution logic. The clients engine syncs twice per global sync, and
+ * custom conflict resolution logic for commands that doesn't use
+ * timestamps. Tabs doesn't have conflict resolution at all, since it's
+ * read-only.
+ */
+
+async function assertChildGuids(folderGuid, expectedChildGuids, message) {
+  let tree = await PlacesUtils.promiseBookmarksTree(folderGuid);
+  let childGuids = tree.children.map(child => child.guid);
+  deepEqual(childGuids, expectedChildGuids, message);
+}
+
+async function cleanup(engine, server) {
+  await engine._tracker.stop();
+  await engine._store.wipe();
+  for (const pref of Svc.PrefBranch.getChildList("")) {
+    Svc.PrefBranch.clearUserPref(pref);
+  }
+  Service.recordManager.clearCache();
+  await promiseStopServer(server);
+}
+
+add_task(async function test_history_change_during_sync() {
+  _("Ensure that we don't bump the score when applying history records.");
+
+  enableValidationPrefs();
+
+  let engine = Service.engineManager.get("history");
+  let server = await serverForEnginesWithKeys({ foo: "password" }, [engine]);
+  await SyncTestingInfrastructure(server);
+  let collection = server.user("foo").collection("history");
+
+  // Override `uploadOutgoing` to insert a record while we're applying
+  // changes. The tracker should ignore this change.
+  let uploadOutgoing = engine._uploadOutgoing;
+  engine._uploadOutgoing = async function () {
+    engine._uploadOutgoing = uploadOutgoing;
+    try {
+      await uploadOutgoing.call(this);
+    } finally {
+      _("Inserting local history visit");
+      await addVisit("during_sync");
+      await engine._tracker.asyncObserver.promiseObserversComplete();
+    }
+  };
+
+  engine._tracker.start();
+
+  try {
+    let remoteRec = new HistoryRec("history", "UrOOuzE5QM-e");
+    remoteRec.histUri = "http://getfirefox.com/";
+    remoteRec.title = "Get Firefox!";
+    remoteRec.visits = [
+      {
+        date: PlacesUtils.toPRTime(Date.now()),
+        type: PlacesUtils.history.TRANSITION_TYPED,
+      },
+    ];
+    collection.insert(remoteRec.id, encryptPayload(remoteRec.cleartext));
+
+    await sync_engine_and_validate_telem(engine, true);
+    strictEqual(
+      Service.scheduler.globalScore,
+      0,
+      "Should not bump global score for visits added during sync"
+    );
+
+    equal(
+      collection.count(),
+      1,
+      "New local visit should not exist on server after first sync"
+    );
+
+    await sync_engine_and_validate_telem(engine, true);
+    strictEqual(
+      Service.scheduler.globalScore,
+      0,
+      "Should not bump global score during second history sync"
+    );
+
+    equal(
+      collection.count(),
+      2,
+      "New local visit should exist on server after second sync"
+    );
+  } finally {
+    engine._uploadOutgoing = uploadOutgoing;
+    await cleanup(engine, server);
+  }
+});
+
+add_task(async function test_passwords_change_during_sync() {
+  _("Ensure that we don't bump the score when applying passwords.");
+
+  enableValidationPrefs();
+
+  let engine = Service.engineManager.get("passwords");
+  let server = await serverForEnginesWithKeys({ foo: "password" }, [engine]);
+  await SyncTestingInfrastructure(server);
+  let collection = server.user("foo").collection("passwords");
+
+  let uploadOutgoing = engine._uploadOutgoing;
+  engine._uploadOutgoing = async function () {
+    engine._uploadOutgoing = uploadOutgoing;
+    try {
+      await uploadOutgoing.call(this);
+    } finally {
+      _("Inserting local password");
+      let login = new LoginInfo(
+        "https://example.com",
+        "",
+        null,
+        "username",
+        "password",
+        "",
+        ""
+      );
+      await Services.logins.addLoginAsync(login);
+      await engine._tracker.asyncObserver.promiseObserversComplete();
+    }
+  };
+
+  engine._tracker.start();
+
+  try {
+    let remoteRec = new LoginRec(
+      "passwords",
+      "{765e3d6e-071d-d640-a83d-81a7eb62d3ed}"
+    );
+    remoteRec.formSubmitURL = "";
+    remoteRec.httpRealm = "";
+    remoteRec.hostname = "https://mozilla.org";
+    remoteRec.username = "username";
+    remoteRec.password = "sekrit";
+    remoteRec.timeCreated = Date.now();
+    remoteRec.timePasswordChanged = Date.now();
+    collection.insert(remoteRec.id, encryptPayload(remoteRec.cleartext));
+
+    await sync_engine_and_validate_telem(engine, true);
+    strictEqual(
+      Service.scheduler.globalScore,
+      0,
+      "Should not bump global score for passwords added during first sync"
+    );
+
+    equal(
+      collection.count(),
+      1,
+      "New local password should not exist on server after first sync"
+    );
+
+    await sync_engine_and_validate_telem(engine, true);
+    strictEqual(
+      Service.scheduler.globalScore,
+      0,
+      "Should not bump global score during second passwords sync"
+    );
+
+    equal(
+      collection.count(),
+      2,
+      "New local password should exist on server after second sync"
+    );
+  } finally {
+    engine._uploadOutgoing = uploadOutgoing;
+    await cleanup(engine, server);
+  }
+});
+
+add_task(async function test_prefs_change_during_sync() {
+  _("Ensure that we don't bump the score when applying prefs.");
+
+  const TEST_PREF = "test.duringSync";
+  // create a "control pref" for the pref we sync.
+  Services.prefs.setBoolPref("services.sync.prefs.sync.test.duringSync", true);
+
+  enableValidationPrefs();
+
+  let engine = Service.engineManager.get("prefs");
+  let server = await serverForEnginesWithKeys({ foo: "password" }, [engine]);
+  await SyncTestingInfrastructure(server);
+  let collection = server.user("foo").collection("prefs");
+
+  let uploadOutgoing = engine._uploadOutgoing;
+  engine._uploadOutgoing = async function () {
+    engine._uploadOutgoing = uploadOutgoing;
+    try {
+      await uploadOutgoing.call(this);
+    } finally {
+      _("Updating local pref value");
+      // Change the value of a synced pref.
+      Services.prefs.setStringPref(TEST_PREF, "hello");
+      await engine._tracker.asyncObserver.promiseObserversComplete();
+    }
+  };
+
+  engine._tracker.start();
+
+  try {
+    // All synced prefs are stored in a single record, so we'll only ever
+    // have one record on the server. This test just checks that we don't
+    // track or upload prefs changed during the sync.
+    let guid = CommonUtils.encodeBase64URL(Services.appinfo.ID);
+    let remoteRec = new PrefRec("prefs", guid);
+    remoteRec.value = {
+      [TEST_PREF]: "world",
+    };
+    collection.insert(remoteRec.id, encryptPayload(remoteRec.cleartext));
+
+    await sync_engine_and_validate_telem(engine, true);
+    strictEqual(
+      Service.scheduler.globalScore,
+      0,
+      "Should not bump global score for prefs added during first sync"
+    );
+    let payloads = collection.payloads();
+    equal(
+      payloads.length,
+      1,
+      "Should not upload multiple prefs records after first sync"
+    );
+    equal(
+      payloads[0].value[TEST_PREF],
+      "world",
+      "Should not upload pref value changed during first sync"
+    );
+
+    await sync_engine_and_validate_telem(engine, true);
+    strictEqual(
+      Service.scheduler.globalScore,
+      0,
+      "Should not bump global score during second prefs sync"
+    );
+    payloads = collection.payloads();
+    equal(
+      payloads.length,
+      1,
+      "Should not upload multiple prefs records after second sync"
+    );
+    equal(
+      payloads[0].value[TEST_PREF],
+      "hello",
+      "Should upload changed pref value during second sync"
+    );
+  } finally {
+    engine._uploadOutgoing = uploadOutgoing;
+    await cleanup(engine, server);
+    Services.prefs.clearUserPref(TEST_PREF);
+  }
+});
+
+add_task(async function test_forms_change_during_sync() {
+  _("Ensure that we don't bump the score when applying form records.");
+
+  enableValidationPrefs();
+
+  let engine = Service.engineManager.get("forms");
+  let server = await serverForEnginesWithKeys({ foo: "password" }, [engine]);
+  await SyncTestingInfrastructure(server);
+  let collection = server.user("foo").collection("forms");
+
+  let uploadOutgoing = engine._uploadOutgoing;
+  engine._uploadOutgoing = async function () {
+    engine._uploadOutgoing = uploadOutgoing;
+    try {
+      await uploadOutgoing.call(this);
+    } finally {
+      _("Inserting local form history entry");
+      await FormHistory.update([
+        {
+          op: "add",
+          fieldname: "favoriteDrink",
+          value: "cocoa",
+        },
+      ]);
+      await engine._tracker.asyncObserver.promiseObserversComplete();
+    }
+  };
+
+  engine._tracker.start();
+
+  try {
+    // Add an existing remote form history entry. We shouldn't bump the score when
+    // we apply this record.
+    let remoteRec = new FormRec("forms", "Tl9dHgmJSR6FkyxS");
+    remoteRec.name = "name";
+    remoteRec.value = "alice";
+    collection.insert(remoteRec.id, encryptPayload(remoteRec.cleartext));
+
+    await sync_engine_and_validate_telem(engine, true);
+    strictEqual(
+      Service.scheduler.globalScore,
+      0,
+      "Should not bump global score for forms added during first sync"
+    );
+
+    equal(
+      collection.count(),
+      1,
+      "New local form should not exist on server after first sync"
+    );
+
+    await sync_engine_and_validate_telem(engine, true);
+    strictEqual(
+      Service.scheduler.globalScore,
+      0,
+      "Should not bump global score during second forms sync"
+    );
+
+    equal(
+      collection.count(),
+      2,
+      "New local form should exist on server after second sync"
+    );
+  } finally {
+    engine._uploadOutgoing = uploadOutgoing;
+    await cleanup(engine, server);
+  }
+});
+
+add_task(async function test_bookmark_change_during_sync() {
+  _("Ensure that we track bookmark changes made during a sync.");
+
+  enableValidationPrefs();
+  let schedulerProto = Object.getPrototypeOf(Service.scheduler);
+  let syncThresholdDescriptor = Object.getOwnPropertyDescriptor(
+    schedulerProto,
+    "syncThreshold"
+  );
+  Object.defineProperty(Service.scheduler, "syncThreshold", {
+    // Trigger resync if any changes exist, rather than deciding based on the
+    // normal sync threshold.
+    get: () => 0,
+  });
+
+  let engine = Service.engineManager.get("bookmarks");
+  let server = await serverForEnginesWithKeys({ foo: "password" }, [engine]);
+  await SyncTestingInfrastructure(server);
+
+  // Already-tracked bookmarks that shouldn't be uploaded during the first sync.
+  let bzBmk = await PlacesUtils.bookmarks.insert({
+    parentGuid: PlacesUtils.bookmarks.menuGuid,
+    url: "https://bugzilla.mozilla.org/",
+    title: "Bugzilla",
+  });
+  _(`Bugzilla GUID: ${bzBmk.guid}`);
+
+  await PlacesTestUtils.setBookmarkSyncFields({
+    guid: bzBmk.guid,
+    syncChangeCounter: 0,
+    syncStatus: PlacesUtils.bookmarks.SYNC_STATUS.NORMAL,
+  });
+
+  let collection = server.user("foo").collection("bookmarks");
+
+  let bmk3; // New child of Folder 1, created locally during sync.
+
+  let uploadOutgoing = engine._uploadOutgoing;
+  engine._uploadOutgoing = async function () {
+    engine._uploadOutgoing = uploadOutgoing;
+    try {
+      await uploadOutgoing.call(this);
+    } finally {
+      _("Inserting bookmark into local store");
+      bmk3 = await PlacesUtils.bookmarks.insert({
+        parentGuid: folder1.guid,
+        url: "https://mozilla.org/",
+        title: "Mozilla",
+      });
+      await engine._tracker.asyncObserver.promiseObserversComplete();
+    }
+  };
+
+  // New bookmarks that should be uploaded during the first sync.
+  let folder1 = await PlacesUtils.bookmarks.insert({
+    type: PlacesUtils.bookmarks.TYPE_FOLDER,
+    parentGuid: PlacesUtils.bookmarks.toolbarGuid,
+    title: "Folder 1",
+  });
+  _(`Folder GUID: ${folder1.guid}`);
+
+  let tbBmk = await PlacesUtils.bookmarks.insert({
+    parentGuid: folder1.guid,
+    url: "http://getthunderbird.com/",
+    title: "Get Thunderbird!",
+  });
+  _(`Thunderbird GUID: ${tbBmk.guid}`);
+
+  engine._tracker.start();
+
+  try {
+    let bmk2_guid = "get-firefox1"; // New child of Folder 1, created remotely.
+    let folder2_guid = "folder2-1111"; // New folder, created remotely.
+    let tagQuery_guid = "tag-query111"; // New tag query child of Folder 2, created remotely.
+    let bmk4_guid = "example-org1"; // New tagged child of Folder 2, created remotely.
+    {
+      // An existing record changed on the server that should not trigger
+      // another sync when applied.
+      let remoteBzBmk = new Bookmark("bookmarks", bzBmk.guid);
+      remoteBzBmk.bmkUri = "https://bugzilla.mozilla.org/";
+      remoteBzBmk.description = "New description";
+      remoteBzBmk.title = "Bugzilla";
+      remoteBzBmk.tags = ["new", "tags"];
+      remoteBzBmk.parentName = "Bookmarks Menu";
+      remoteBzBmk.parentid = "menu";
+      collection.insert(bzBmk.guid, encryptPayload(remoteBzBmk.cleartext));
+
+      let remoteFolder = new BookmarkFolder("bookmarks", folder2_guid);
+      remoteFolder.title = "Folder 2";
+      remoteFolder.children = [bmk4_guid, tagQuery_guid];
+      remoteFolder.parentName = "Bookmarks Menu";
+      remoteFolder.parentid = "menu";
+      collection.insert(folder2_guid, encryptPayload(remoteFolder.cleartext));
+
+      let remoteFxBmk = new Bookmark("bookmarks", bmk2_guid);
+      remoteFxBmk.bmkUri = "http://getfirefox.com/";
+      remoteFxBmk.description = "Firefox is awesome.";
+      remoteFxBmk.title = "Get Firefox!";
+      remoteFxBmk.tags = ["firefox", "awesome", "browser"];
+      remoteFxBmk.keyword = "awesome";
+      remoteFxBmk.parentName = "Folder 1";
+      remoteFxBmk.parentid = folder1.guid;
+      collection.insert(bmk2_guid, encryptPayload(remoteFxBmk.cleartext));
+
+      // A tag query referencing a nonexistent tag folder, which we should
+      // create locally when applying the record.
+      let remoteTagQuery = new BookmarkQuery("bookmarks", tagQuery_guid);
+      remoteTagQuery.bmkUri = "place:type=7&folder=999";
+      remoteTagQuery.title = "Taggy tags";
+      remoteTagQuery.folderName = "taggy";
+      remoteTagQuery.parentName = "Folder 2";
+      remoteTagQuery.parentid = folder2_guid;
+      collection.insert(
+        tagQuery_guid,
+        encryptPayload(remoteTagQuery.cleartext)
+      );
+
+      // A bookmark that should appear in the results for the tag query.
+      let remoteTaggedBmk = new Bookmark("bookmarks", bmk4_guid);
+      remoteTaggedBmk.bmkUri = "https://example.org/";
+      remoteTaggedBmk.title = "Tagged bookmark";
+      remoteTaggedBmk.tags = ["taggy"];
+      remoteTaggedBmk.parentName = "Folder 2";
+      remoteTaggedBmk.parentid = folder2_guid;
+      collection.insert(bmk4_guid, encryptPayload(remoteTaggedBmk.cleartext));
+
+      collection.insert(
+        "toolbar",
+        encryptPayload({
+          id: "toolbar",
+          type: "folder",
+          title: "toolbar",
+          children: [folder1.guid],
+          parentName: "places",
+          parentid: "places",
+        })
+      );
+
+      collection.insert(
+        "menu",
+        encryptPayload({
+          id: "menu",
+          type: "folder",
+          title: "menu",
+          children: [bzBmk.guid, folder2_guid],
+          parentName: "places",
+          parentid: "places",
+        })
+      );
+
+      collection.insert(
+        folder1.guid,
+        encryptPayload({
+          id: folder1.guid,
+          type: "folder",
+          title: "Folder 1",
+          children: [bmk2_guid],
+          parentName: "toolbar",
+          parentid: "toolbar",
+        })
+      );
+    }
+
+    await assertChildGuids(
+      folder1.guid,
+      [tbBmk.guid],
+      "Folder should have 1 child before first sync"
+    );
+
+    let pingsPromise = wait_for_pings(2);
+
+    let changes = await PlacesSyncUtils.bookmarks.pullChanges();
+    deepEqual(
+      Object.keys(changes).sort(),
+      [folder1.guid, tbBmk.guid, "menu", "mobile", "toolbar", "unfiled"].sort(),
+      "Should track bookmark and folder created before first sync"
+    );
+
+    // Unlike the tests above, we can't use `sync_engine_and_validate_telem`
+    // because the bookmarks engine will automatically schedule a follow-up
+    // sync for us.
+    _("Perform first sync and immediate follow-up sync");
+    Service.sync({ engines: ["bookmarks"] });
+
+    let pings = await pingsPromise;
+    equal(pings.length, 2, "Should submit two pings");
+    ok(
+      pings.every(p => {
+        assert_success_ping(p);
+        return p.syncs.length == 1;
+      }),
+      "Should submit 1 sync per ping"
+    );
+
+    strictEqual(
+      Service.scheduler.globalScore,
+      0,
+      "Should reset global score after follow-up sync"
+    );
+    ok(bmk3, "Should insert bookmark during first sync to simulate change");
+    ok(
+      collection.wbo(bmk3.guid),
+      "Changed bookmark should be uploaded after follow-up sync"
+    );
+
+    let bmk2 = await PlacesUtils.bookmarks.fetch({
+      guid: bmk2_guid,
+    });
+    ok(bmk2, "Remote bookmark should be applied during first sync");
+    {
+      // We only check child GUIDs, and not their order, because the exact
+      // order is an implementation detail.
+      let folder1Children = await PlacesSyncUtils.bookmarks.fetchChildRecordIds(
+        folder1.guid
+      );
+      deepEqual(
+        folder1Children.sort(),
+        [bmk2_guid, tbBmk.guid, bmk3.guid].sort(),
+        "Folder 1 should have 3 children after first sync"
+      );
+    }
+    await assertChildGuids(
+      folder2_guid,
+      [bmk4_guid, tagQuery_guid],
+      "Folder 2 should have 2 children after first sync"
+    );
+    let taggedURIs = [];
+    await PlacesUtils.bookmarks.fetch({ tags: ["taggy"] }, b =>
+      taggedURIs.push(b.url)
+    );
+    equal(taggedURIs.length, 1, "Should have 1 tagged URI");
+    equal(
+      taggedURIs[0].href,
+      "https://example.org/",
+      "Synced tagged bookmark should appear in tagged URI list"
+    );
+
+    changes = await PlacesSyncUtils.bookmarks.pullChanges();
+    deepEqual(
+      changes,
+      {},
+      "Should have already uploaded changes in follow-up sync"
+    );
+
+    // First ping won't include validation data, since we've changed bookmarks
+    // and `canValidate` will indicate it can't proceed.
+    let engineData = pings.map(p => {
+      return p.syncs[0].engines.find(e => e.name == "bookmarks-buffered");
+    });
+    ok(engineData[0].validation, "Engine should validate after first sync");
+    ok(engineData[1].validation, "Engine should validate after second sync");
+  } finally {
+    Object.defineProperty(
+      schedulerProto,
+      "syncThreshold",
+      syncThresholdDescriptor
+    );
+    engine._uploadOutgoing = uploadOutgoing;
+    await cleanup(engine, server);
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_enginemanager.js b/src/zen/tests/mochitests/sync/test_enginemanager.js
new file mode 100644
index 000000000..3e366be54
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_enginemanager.js
@@ -0,0 +1,232 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+function PetrolEngine() {}
+PetrolEngine.prototype.name = "petrol";
+PetrolEngine.prototype.finalize = async function () {};
+
+function DieselEngine() {}
+DieselEngine.prototype.name = "diesel";
+DieselEngine.prototype.finalize = async function () {};
+
+function DummyEngine() {}
+DummyEngine.prototype.name = "dummy";
+DummyEngine.prototype.finalize = async function () {};
+
+class ActualEngine extends SyncEngine {
+  constructor(service) {
+    super("Actual", service);
+  }
+}
+
+add_task(async function test_basics() {
+  _("We start out with a clean slate");
+
+  let manager = new EngineManager(Service);
+
+  let engines = await manager.getAll();
+  Assert.equal(engines.length, 0);
+  Assert.equal(await manager.get("dummy"), undefined);
+
+  _("Register an engine");
+  await manager.register(DummyEngine);
+  let dummy = await manager.get("dummy");
+  Assert.ok(dummy instanceof DummyEngine);
+
+  engines = await manager.getAll();
+  Assert.equal(engines.length, 1);
+  Assert.equal(engines[0], dummy);
+
+  _("Register an already registered engine is ignored");
+  await manager.register(DummyEngine);
+  Assert.equal(await manager.get("dummy"), dummy);
+
+  _("Register multiple engines in one go");
+  await manager.register([PetrolEngine, DieselEngine]);
+  let petrol = await manager.get("petrol");
+  let diesel = await manager.get("diesel");
+  Assert.ok(petrol instanceof PetrolEngine);
+  Assert.ok(diesel instanceof DieselEngine);
+
+  engines = await manager.getAll();
+  Assert.equal(engines.length, 3);
+  Assert.notEqual(engines.indexOf(petrol), -1);
+  Assert.notEqual(engines.indexOf(diesel), -1);
+
+  _("Retrieve multiple engines in one go");
+  engines = await manager.get(["dummy", "diesel"]);
+  Assert.equal(engines.length, 2);
+  Assert.notEqual(engines.indexOf(dummy), -1);
+  Assert.notEqual(engines.indexOf(diesel), -1);
+
+  _("getEnabled() only returns enabled engines");
+  engines = await manager.getEnabled();
+  Assert.equal(engines.length, 0);
+
+  petrol.enabled = true;
+  engines = await manager.getEnabled();
+  Assert.equal(engines.length, 1);
+  Assert.equal(engines[0], petrol);
+
+  dummy.enabled = true;
+  diesel.enabled = true;
+  engines = await manager.getEnabled();
+  Assert.equal(engines.length, 3);
+
+  _("getEnabled() returns enabled engines in sorted order");
+  petrol.syncPriority = 1;
+  dummy.syncPriority = 2;
+  diesel.syncPriority = 3;
+
+  engines = await manager.getEnabled();
+
+  Assert.deepEqual(engines, [petrol, dummy, diesel]);
+
+  _("Changing the priorities should change the order in getEnabled()");
+
+  dummy.syncPriority = 4;
+
+  engines = await manager.getEnabled();
+
+  Assert.deepEqual(engines, [petrol, diesel, dummy]);
+
+  _("Unregister an engine by name");
+  await manager.unregister("dummy");
+  Assert.equal(await manager.get("dummy"), undefined);
+  engines = await manager.getAll();
+  Assert.equal(engines.length, 2);
+  Assert.equal(engines.indexOf(dummy), -1);
+
+  _("Unregister an engine by value");
+  // manager.unregister() checks for instanceof Engine, so let's make one:
+  await manager.register(ActualEngine);
+  let actual = await manager.get("actual");
+  Assert.ok(actual instanceof ActualEngine);
+  Assert.ok(actual instanceof SyncEngine);
+
+  await manager.unregister(actual);
+  Assert.equal(await manager.get("actual"), undefined);
+});
+
+class AutoEngine {
+  constructor(type) {
+    this.name = "automobile";
+    this.type = type;
+    this.initializeCalled = false;
+    this.finalizeCalled = false;
+    this.isActive = false;
+  }
+
+  async initialize() {
+    Assert.ok(!this.initializeCalled);
+    Assert.equal(AutoEngine.current, undefined);
+    this.initializeCalled = true;
+    this.isActive = true;
+    AutoEngine.current = this;
+  }
+
+  async finalize() {
+    Assert.equal(AutoEngine.current, this);
+    Assert.ok(!this.finalizeCalled);
+    Assert.ok(this.isActive);
+    this.finalizeCalled = true;
+    this.isActive = false;
+    AutoEngine.current = undefined;
+  }
+}
+
+class GasolineEngine extends AutoEngine {
+  constructor() {
+    super("gasoline");
+  }
+}
+
+class ElectricEngine extends AutoEngine {
+  constructor() {
+    super("electric");
+  }
+}
+
+add_task(async function test_alternates() {
+  let manager = new EngineManager(Service);
+  let engines = await manager.getAll();
+  Assert.equal(engines.length, 0);
+
+  const prefName = "services.sync.engines.automobile.electric";
+  Services.prefs.clearUserPref(prefName);
+
+  await manager.registerAlternatives(
+    "automobile",
+    prefName,
+    ElectricEngine,
+    GasolineEngine
+  );
+
+  let gasEngine = manager.get("automobile");
+  Assert.equal(gasEngine.type, "gasoline");
+
+  Assert.ok(gasEngine.isActive);
+  Assert.ok(gasEngine.initializeCalled);
+  Assert.ok(!gasEngine.finalizeCalled);
+  Assert.equal(AutoEngine.current, gasEngine);
+
+  _("Check that setting the controlling pref to false makes no difference");
+  Services.prefs.setBoolPref(prefName, false);
+  Assert.equal(manager.get("automobile"), gasEngine);
+  Assert.ok(gasEngine.isActive);
+  Assert.ok(gasEngine.initializeCalled);
+  Assert.ok(!gasEngine.finalizeCalled);
+
+  _("Even after the call to switchAlternatives");
+  await manager.switchAlternatives();
+  Assert.equal(manager.get("automobile"), gasEngine);
+  Assert.ok(gasEngine.isActive);
+  Assert.ok(gasEngine.initializeCalled);
+  Assert.ok(!gasEngine.finalizeCalled);
+
+  _("Set the pref to true, we still shouldn't switch yet");
+  Services.prefs.setBoolPref(prefName, true);
+  Assert.equal(manager.get("automobile"), gasEngine);
+  Assert.ok(gasEngine.isActive);
+  Assert.ok(gasEngine.initializeCalled);
+  Assert.ok(!gasEngine.finalizeCalled);
+
+  _("Now we expect to switch from gas to electric");
+  await manager.switchAlternatives();
+  let elecEngine = manager.get("automobile");
+  Assert.equal(elecEngine.type, "electric");
+  Assert.ok(elecEngine.isActive);
+  Assert.ok(elecEngine.initializeCalled);
+  Assert.ok(!elecEngine.finalizeCalled);
+  Assert.equal(AutoEngine.current, elecEngine);
+
+  Assert.ok(!gasEngine.isActive);
+  Assert.ok(gasEngine.finalizeCalled);
+
+  _("Switch back, and ensure we get a new instance that got initialized again");
+  Services.prefs.setBoolPref(prefName, false);
+  await manager.switchAlternatives();
+
+  // First make sure we deactivated the electric engine as we should
+  Assert.ok(!elecEngine.isActive);
+  Assert.ok(elecEngine.initializeCalled);
+  Assert.ok(elecEngine.finalizeCalled);
+
+  let newGasEngine = manager.get("automobile");
+  Assert.notEqual(newGasEngine, gasEngine);
+  Assert.equal(newGasEngine.type, "gasoline");
+
+  Assert.ok(newGasEngine.isActive);
+  Assert.ok(newGasEngine.initializeCalled);
+  Assert.ok(!newGasEngine.finalizeCalled);
+
+  _("Make sure unregister removes the alt info too");
+  await manager.unregister("automobile");
+  Assert.equal(manager.get("automobile"), null);
+  Assert.ok(newGasEngine.finalizeCalled);
+  Assert.deepEqual(Object.keys(manager._altEngineInfo), []);
+});
diff --git a/src/zen/tests/mochitests/sync/test_errorhandler_1.js b/src/zen/tests/mochitests/sync/test_errorhandler_1.js
new file mode 100644
index 000000000..f5e96ed44
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_errorhandler_1.js
@@ -0,0 +1,335 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { Status } = ChromeUtils.importESModule(
+  "resource://services-sync/status.sys.mjs"
+);
+
+const fakeServer = new SyncServer();
+fakeServer.start();
+const fakeServerUrl = "http://localhost:" + fakeServer.port;
+
+registerCleanupFunction(function () {
+  return promiseStopServer(fakeServer).finally(() => {
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+  });
+});
+
+let engine;
+add_task(async function setup() {
+  await Service.engineManager.clear();
+  await Service.engineManager.register(EHTestsCommon.CatapultEngine);
+  engine = Service.engineManager.get("catapult");
+});
+
+async function clean() {
+  let promiseLogReset = promiseOneObserver("weave:service:reset-file-log");
+  await Service.startOver();
+  await promiseLogReset;
+  Status.resetSync();
+  Status.resetBackoff();
+  // Move log levels back to trace (startOver will have reversed this), sicne
+  syncTestLogging();
+}
+
+add_task(async function test_401_logout() {
+  enableValidationPrefs();
+
+  let server = await EHTestsCommon.sync_httpd_setup();
+  await EHTestsCommon.setUp(server);
+
+  // By calling sync, we ensure we're logged in.
+  await sync_and_validate_telem();
+  Assert.equal(Status.sync, SYNC_SUCCEEDED);
+  Assert.ok(Service.isLoggedIn);
+
+  let promiseErrors = new Promise(res => {
+    Svc.Obs.add("weave:service:sync:error", onSyncError);
+    function onSyncError() {
+      _("Got weave:service:sync:error in first sync.");
+      Svc.Obs.remove("weave:service:sync:error", onSyncError);
+
+      // Wait for the automatic next sync.
+      Svc.Obs.add("weave:service:login:error", onLoginError);
+      function onLoginError() {
+        _("Got weave:service:login:error in second sync.");
+        Svc.Obs.remove("weave:service:login:error", onLoginError);
+        res();
+      }
+    }
+  });
+
+  // Make sync fail due to login rejected.
+  await configureIdentity({ username: "janedoe" }, server);
+  Service._updateCachedURLs();
+
+  _("Starting first sync.");
+  await sync_and_validate_telem(ping => {
+    deepEqual(ping.failureReason, { name: "httperror", code: 401 });
+  });
+  _("First sync done.");
+
+  await promiseErrors;
+  Assert.equal(Status.login, LOGIN_FAILED_NETWORK_ERROR);
+  Assert.ok(!Service.isLoggedIn);
+
+  // Clean up.
+  await Service.startOver();
+  await promiseStopServer(server);
+});
+
+add_task(async function test_credentials_changed_logout() {
+  enableValidationPrefs();
+
+  let server = await EHTestsCommon.sync_httpd_setup();
+  await EHTestsCommon.setUp(server);
+
+  // By calling sync, we ensure we're logged in.
+  await sync_and_validate_telem();
+  Assert.equal(Status.sync, SYNC_SUCCEEDED);
+  Assert.ok(Service.isLoggedIn);
+
+  await EHTestsCommon.generateCredentialsChangedFailure();
+
+  await sync_and_validate_telem(ping => {
+    equal(ping.status.sync, CREDENTIALS_CHANGED);
+    deepEqual(ping.failureReason, {
+      name: "unexpectederror",
+      error: "Error: Aborting sync, remote setup failed",
+    });
+  });
+
+  Assert.equal(Status.sync, CREDENTIALS_CHANGED);
+  Assert.ok(!Service.isLoggedIn);
+
+  // Clean up.
+  await Service.startOver();
+  await promiseStopServer(server);
+});
+
+add_task(async function test_login_non_network_error() {
+  enableValidationPrefs();
+
+  // Test non-network errors are reported
+  // when calling sync
+  let server = await EHTestsCommon.sync_httpd_setup();
+  await EHTestsCommon.setUp(server);
+  Service.identity._syncKeyBundle = null;
+
+  await Service.sync();
+  Assert.equal(Status.login, LOGIN_FAILED_NO_PASSPHRASE);
+
+  await clean();
+  await promiseStopServer(server);
+});
+
+add_task(async function test_sync_non_network_error() {
+  enableValidationPrefs();
+
+  // Test non-network errors are reported
+  // when calling sync
+  let server = await EHTestsCommon.sync_httpd_setup();
+  await EHTestsCommon.setUp(server);
+
+  // By calling sync, we ensure we're logged in.
+  await Service.sync();
+  Assert.equal(Status.sync, SYNC_SUCCEEDED);
+  Assert.ok(Service.isLoggedIn);
+
+  await EHTestsCommon.generateCredentialsChangedFailure();
+
+  await sync_and_validate_telem(ping => {
+    equal(ping.status.sync, CREDENTIALS_CHANGED);
+    deepEqual(ping.failureReason, {
+      name: "unexpectederror",
+      error: "Error: Aborting sync, remote setup failed",
+    });
+  });
+
+  Assert.equal(Status.sync, CREDENTIALS_CHANGED);
+  // If we clean this tick, telemetry won't get the right error
+  await Async.promiseYield();
+  await clean();
+  await promiseStopServer(server);
+});
+
+add_task(async function test_login_sync_network_error() {
+  enableValidationPrefs();
+
+  // Test network errors are reported when calling sync.
+  await configureIdentity({ username: "broken.wipe" });
+  Service.clusterURL = fakeServerUrl;
+
+  await Service.sync();
+  Assert.equal(Status.login, LOGIN_FAILED_NETWORK_ERROR);
+
+  await clean();
+});
+
+add_task(async function test_sync_network_error() {
+  enableValidationPrefs();
+
+  // Test network errors are reported when calling sync.
+  Services.io.offline = true;
+
+  await Service.sync();
+  Assert.equal(Status.sync, LOGIN_FAILED_NETWORK_ERROR);
+
+  Services.io.offline = false;
+  await clean();
+});
+
+add_task(async function test_login_non_network_error() {
+  enableValidationPrefs();
+
+  // Test non-network errors are reported
+  let server = await EHTestsCommon.sync_httpd_setup();
+  await EHTestsCommon.setUp(server);
+  Service.identity._syncKeyBundle = null;
+
+  await Service.sync();
+  Assert.equal(Status.login, LOGIN_FAILED_NO_PASSPHRASE);
+
+  await clean();
+  await promiseStopServer(server);
+});
+
+add_task(async function test_sync_non_network_error() {
+  enableValidationPrefs();
+
+  // Test non-network errors are reported
+  let server = await EHTestsCommon.sync_httpd_setup();
+  await EHTestsCommon.setUp(server);
+
+  // By calling sync, we ensure we're logged in.
+  await Service.sync();
+  Assert.equal(Status.sync, SYNC_SUCCEEDED);
+  Assert.ok(Service.isLoggedIn);
+
+  await EHTestsCommon.generateCredentialsChangedFailure();
+
+  await Service.sync();
+  Assert.equal(Status.sync, CREDENTIALS_CHANGED);
+
+  await clean();
+  await promiseStopServer(server);
+});
+
+add_task(async function test_login_network_error() {
+  enableValidationPrefs();
+
+  await configureIdentity({ username: "johndoe" });
+  Service.clusterURL = fakeServerUrl;
+
+  // Test network errors are not reported.
+
+  await Service.sync();
+  Assert.equal(Status.login, LOGIN_FAILED_NETWORK_ERROR);
+
+  Services.io.offline = false;
+  await clean();
+});
+
+add_task(async function test_sync_network_error() {
+  enableValidationPrefs();
+
+  // Test network errors are not reported.
+  Services.io.offline = true;
+
+  await Service.sync();
+  Assert.equal(Status.sync, LOGIN_FAILED_NETWORK_ERROR);
+
+  Services.io.offline = false;
+  await clean();
+});
+
+add_task(async function test_sync_server_maintenance_error() {
+  enableValidationPrefs();
+
+  // Test server maintenance errors are not reported.
+  let server = await EHTestsCommon.sync_httpd_setup();
+  await EHTestsCommon.setUp(server);
+
+  const BACKOFF = 42;
+  engine.enabled = true;
+  engine.exception = { status: 503, headers: { "retry-after": BACKOFF } };
+
+  Assert.equal(Status.service, STATUS_OK);
+
+  await sync_and_validate_telem(ping => {
+    equal(ping.status.sync, SERVER_MAINTENANCE);
+    deepEqual(ping.engines.find(e => e.failureReason).failureReason, {
+      name: "httperror",
+      code: 503,
+    });
+  });
+
+  Assert.equal(Status.service, SYNC_FAILED_PARTIAL);
+  Assert.equal(Status.sync, SERVER_MAINTENANCE);
+
+  await clean();
+  await promiseStopServer(server);
+});
+
+add_task(async function test_info_collections_login_server_maintenance_error() {
+  enableValidationPrefs();
+
+  // Test info/collections server maintenance errors are not reported.
+  let server = await EHTestsCommon.sync_httpd_setup();
+  await EHTestsCommon.setUp(server);
+
+  await configureIdentity({ username: "broken.info" }, server);
+
+  let backoffInterval;
+  Svc.Obs.add("weave:service:backoff:interval", function observe(subject) {
+    Svc.Obs.remove("weave:service:backoff:interval", observe);
+    backoffInterval = subject;
+  });
+
+  Assert.ok(!Status.enforceBackoff);
+  Assert.equal(Status.service, STATUS_OK);
+
+  await Service.sync();
+
+  Assert.ok(Status.enforceBackoff);
+  Assert.equal(backoffInterval, 42);
+  Assert.equal(Status.service, LOGIN_FAILED);
+  Assert.equal(Status.login, SERVER_MAINTENANCE);
+
+  await clean();
+  await promiseStopServer(server);
+});
+
+add_task(async function test_meta_global_login_server_maintenance_error() {
+  enableValidationPrefs();
+
+  // Test meta/global server maintenance errors are not reported.
+  let server = await EHTestsCommon.sync_httpd_setup();
+  await EHTestsCommon.setUp(server);
+
+  await configureIdentity({ username: "broken.meta" }, server);
+
+  let backoffInterval;
+  Svc.Obs.add("weave:service:backoff:interval", function observe(subject) {
+    Svc.Obs.remove("weave:service:backoff:interval", observe);
+    backoffInterval = subject;
+  });
+
+  Assert.ok(!Status.enforceBackoff);
+  Assert.equal(Status.service, STATUS_OK);
+
+  await Service.sync();
+
+  Assert.ok(Status.enforceBackoff);
+  Assert.equal(backoffInterval, 42);
+  Assert.equal(Status.service, LOGIN_FAILED);
+  Assert.equal(Status.login, SERVER_MAINTENANCE);
+
+  await clean();
+  await promiseStopServer(server);
+});
diff --git a/src/zen/tests/mochitests/sync/test_errorhandler_2.js b/src/zen/tests/mochitests/sync/test_errorhandler_2.js
new file mode 100644
index 000000000..2a7e6ba61
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_errorhandler_2.js
@@ -0,0 +1,529 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { Status } = ChromeUtils.importESModule(
+  "resource://services-sync/status.sys.mjs"
+);
+const { FileUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/FileUtils.sys.mjs"
+);
+
+const fakeServer = new SyncServer();
+fakeServer.start();
+
+registerCleanupFunction(function () {
+  return promiseStopServer(fakeServer).finally(() => {
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+  });
+});
+
+const logsdir = FileUtils.getDir("ProfD", ["weave", "logs"]);
+logsdir.create(Ci.nsIFile.DIRECTORY_TYPE, FileUtils.PERMS_DIRECTORY);
+
+function removeLogFiles() {
+  let entries = logsdir.directoryEntries;
+  while (entries.hasMoreElements()) {
+    let logfile = entries.getNext().QueryInterface(Ci.nsIFile);
+    logfile.remove(false);
+  }
+}
+
+function getLogFiles() {
+  let result = [];
+  let entries = logsdir.directoryEntries;
+  while (entries.hasMoreElements()) {
+    result.push(entries.getNext().QueryInterface(Ci.nsIFile));
+  }
+  return result;
+}
+
+let engine;
+add_task(async function setup() {
+  await Service.engineManager.clear();
+  await Service.engineManager.register(EHTestsCommon.CatapultEngine);
+  engine = Service.engineManager.get("catapult");
+});
+
+async function clean() {
+  let promiseLogReset = promiseOneObserver("weave:service:reset-file-log");
+  await Service.startOver();
+  await promiseLogReset;
+  Status.resetSync();
+  Status.resetBackoff();
+  removeLogFiles();
+  // Move log levels back to trace (startOver will have reversed this), sicne
+  syncTestLogging();
+}
+
+add_task(async function test_crypto_keys_login_server_maintenance_error() {
+  enableValidationPrefs();
+
+  Status.resetSync();
+  // Test crypto/keys server maintenance errors are not reported.
+  let server = await EHTestsCommon.sync_httpd_setup();
+  await EHTestsCommon.setUp(server);
+
+  await configureIdentity({ username: "broken.keys" }, server);
+
+  // Force re-download of keys
+  Service.collectionKeys.clear();
+
+  let backoffInterval;
+  Svc.Obs.add("weave:service:backoff:interval", function observe(subject) {
+    Svc.Obs.remove("weave:service:backoff:interval", observe);
+    backoffInterval = subject;
+  });
+
+  Assert.ok(!Status.enforceBackoff);
+  Assert.equal(Status.service, STATUS_OK);
+
+  let promiseObserved = promiseOneObserver("weave:service:reset-file-log");
+  await Service.sync();
+  await promiseObserved;
+
+  Assert.ok(Status.enforceBackoff);
+  Assert.equal(backoffInterval, 42);
+  Assert.equal(Status.service, LOGIN_FAILED);
+  Assert.equal(Status.login, SERVER_MAINTENANCE);
+
+  await clean();
+  await promiseStopServer(server);
+});
+
+add_task(async function test_lastSync_not_updated_on_complete_failure() {
+  enableValidationPrefs();
+
+  // Test info/collections prolonged server maintenance errors are reported.
+  let server = await EHTestsCommon.sync_httpd_setup();
+  await EHTestsCommon.setUp(server);
+
+  await configureIdentity({ username: "johndoe" }, server);
+
+  // Do an initial sync that we expect to be successful.
+  let promiseObserved = promiseOneObserver("weave:service:reset-file-log");
+  await sync_and_validate_telem();
+  await promiseObserved;
+
+  Assert.equal(Status.service, STATUS_OK);
+  Assert.equal(Status.sync, SYNC_SUCCEEDED);
+
+  let lastSync = Svc.PrefBranch.getStringPref("lastSync");
+
+  Assert.ok(lastSync);
+
+  // Report server maintenance on info/collections requests
+  server.registerPathHandler(
+    "/1.1/johndoe/info/collections",
+    EHTestsCommon.service_unavailable
+  );
+
+  promiseObserved = promiseOneObserver("weave:service:reset-file-log");
+  await sync_and_validate_telem(() => {});
+  await promiseObserved;
+
+  Assert.equal(Status.sync, SERVER_MAINTENANCE);
+  Assert.equal(Status.service, SYNC_FAILED);
+
+  // We shouldn't update lastSync on complete failure.
+  Assert.equal(lastSync, Svc.PrefBranch.getStringPref("lastSync"));
+
+  await clean();
+  await promiseStopServer(server);
+});
+
+add_task(
+  async function test_sync_syncAndReportErrors_server_maintenance_error() {
+    enableValidationPrefs();
+
+    // Test server maintenance errors are reported
+    // when calling syncAndReportErrors.
+    let server = await EHTestsCommon.sync_httpd_setup();
+    await EHTestsCommon.setUp(server);
+
+    const BACKOFF = 42;
+    engine.enabled = true;
+    engine.exception = { status: 503, headers: { "retry-after": BACKOFF } };
+
+    Assert.equal(Status.service, STATUS_OK);
+
+    let promiseObserved = promiseOneObserver("weave:service:reset-file-log");
+    await Service.sync();
+    await promiseObserved;
+
+    Assert.equal(Status.service, SYNC_FAILED_PARTIAL);
+    Assert.equal(Status.sync, SERVER_MAINTENANCE);
+
+    await clean();
+    await promiseStopServer(server);
+  }
+);
+
+add_task(
+  async function test_info_collections_login_syncAndReportErrors_server_maintenance_error() {
+    enableValidationPrefs();
+
+    // Test info/collections server maintenance errors are reported
+    // when calling syncAndReportErrors.
+    let server = await EHTestsCommon.sync_httpd_setup();
+    await EHTestsCommon.setUp(server);
+
+    await configureIdentity({ username: "broken.info" }, server);
+
+    let backoffInterval;
+    Svc.Obs.add("weave:service:backoff:interval", function observe(subject) {
+      Svc.Obs.remove("weave:service:backoff:interval", observe);
+      backoffInterval = subject;
+    });
+
+    Assert.ok(!Status.enforceBackoff);
+    Assert.equal(Status.service, STATUS_OK);
+
+    let promiseObserved = promiseOneObserver("weave:service:reset-file-log");
+    await Service.sync();
+    await promiseObserved;
+
+    Assert.ok(Status.enforceBackoff);
+    Assert.equal(backoffInterval, 42);
+    Assert.equal(Status.service, LOGIN_FAILED);
+    Assert.equal(Status.login, SERVER_MAINTENANCE);
+
+    await clean();
+    await promiseStopServer(server);
+  }
+);
+
+add_task(
+  async function test_meta_global_login_syncAndReportErrors_server_maintenance_error() {
+    enableValidationPrefs();
+
+    // Test meta/global server maintenance errors are reported
+    // when calling syncAndReportErrors.
+    let server = await EHTestsCommon.sync_httpd_setup();
+    await EHTestsCommon.setUp(server);
+
+    await configureIdentity({ username: "broken.meta" }, server);
+
+    let backoffInterval;
+    Svc.Obs.add("weave:service:backoff:interval", function observe(subject) {
+      Svc.Obs.remove("weave:service:backoff:interval", observe);
+      backoffInterval = subject;
+    });
+
+    Assert.ok(!Status.enforceBackoff);
+    Assert.equal(Status.service, STATUS_OK);
+
+    let promiseObserved = promiseOneObserver("weave:service:reset-file-log");
+    await Service.sync();
+    await promiseObserved;
+
+    Assert.ok(Status.enforceBackoff);
+    Assert.equal(backoffInterval, 42);
+    Assert.equal(Status.service, LOGIN_FAILED);
+    Assert.equal(Status.login, SERVER_MAINTENANCE);
+
+    await clean();
+    await promiseStopServer(server);
+  }
+);
+
+add_task(
+  async function test_download_crypto_keys_login_syncAndReportErrors_server_maintenance_error() {
+    enableValidationPrefs();
+
+    // Test crypto/keys server maintenance errors are reported
+    // when calling syncAndReportErrors.
+    let server = await EHTestsCommon.sync_httpd_setup();
+    await EHTestsCommon.setUp(server);
+
+    await configureIdentity({ username: "broken.keys" }, server);
+    // Force re-download of keys
+    Service.collectionKeys.clear();
+
+    let backoffInterval;
+    Svc.Obs.add("weave:service:backoff:interval", function observe(subject) {
+      Svc.Obs.remove("weave:service:backoff:interval", observe);
+      backoffInterval = subject;
+    });
+
+    Assert.ok(!Status.enforceBackoff);
+    Assert.equal(Status.service, STATUS_OK);
+
+    let promiseObserved = promiseOneObserver("weave:service:reset-file-log");
+    await Service.sync();
+    await promiseObserved;
+
+    Assert.ok(Status.enforceBackoff);
+    Assert.equal(backoffInterval, 42);
+    Assert.equal(Status.service, LOGIN_FAILED);
+    Assert.equal(Status.login, SERVER_MAINTENANCE);
+
+    await clean();
+    await promiseStopServer(server);
+  }
+);
+
+add_task(
+  async function test_upload_crypto_keys_login_syncAndReportErrors_server_maintenance_error() {
+    enableValidationPrefs();
+
+    // Test crypto/keys server maintenance errors are reported
+    // when calling syncAndReportErrors.
+    let server = await EHTestsCommon.sync_httpd_setup();
+
+    // Start off with an empty account, do not upload a key.
+    await configureIdentity({ username: "broken.keys" }, server);
+
+    let backoffInterval;
+    Svc.Obs.add("weave:service:backoff:interval", function observe(subject) {
+      Svc.Obs.remove("weave:service:backoff:interval", observe);
+      backoffInterval = subject;
+    });
+
+    Assert.ok(!Status.enforceBackoff);
+    Assert.equal(Status.service, STATUS_OK);
+
+    let promiseObserved = promiseOneObserver("weave:service:reset-file-log");
+    await Service.sync();
+    await promiseObserved;
+
+    Assert.ok(Status.enforceBackoff);
+    Assert.equal(backoffInterval, 42);
+    Assert.equal(Status.service, LOGIN_FAILED);
+    Assert.equal(Status.login, SERVER_MAINTENANCE);
+
+    await clean();
+    await promiseStopServer(server);
+  }
+);
+
+add_task(
+  async function test_wipeServer_login_syncAndReportErrors_server_maintenance_error() {
+    enableValidationPrefs();
+
+    // Test crypto/keys server maintenance errors are reported
+    // when calling syncAndReportErrors.
+    let server = await EHTestsCommon.sync_httpd_setup();
+
+    // Start off with an empty account, do not upload a key.
+    await configureIdentity({ username: "broken.wipe" }, server);
+
+    let backoffInterval;
+    Svc.Obs.add("weave:service:backoff:interval", function observe(subject) {
+      Svc.Obs.remove("weave:service:backoff:interval", observe);
+      backoffInterval = subject;
+    });
+
+    Assert.ok(!Status.enforceBackoff);
+    Assert.equal(Status.service, STATUS_OK);
+
+    let promiseObserved = promiseOneObserver("weave:service:reset-file-log");
+    await Service.sync();
+    await promiseObserved;
+
+    Assert.ok(Status.enforceBackoff);
+    Assert.equal(backoffInterval, 42);
+    Assert.equal(Status.service, LOGIN_FAILED);
+    Assert.equal(Status.login, SERVER_MAINTENANCE);
+
+    await clean();
+    await promiseStopServer(server);
+  }
+);
+
+add_task(
+  async function test_wipeRemote_syncAndReportErrors_server_maintenance_error() {
+    enableValidationPrefs();
+
+    // Test that we report prolonged server maintenance errors that occur whilst
+    // wiping all remote devices.
+    let server = await EHTestsCommon.sync_httpd_setup();
+
+    await configureIdentity({ username: "broken.wipe" }, server);
+    await EHTestsCommon.generateAndUploadKeys();
+
+    engine.exception = null;
+    engine.enabled = true;
+
+    let backoffInterval;
+    Svc.Obs.add("weave:service:backoff:interval", function observe(subject) {
+      Svc.Obs.remove("weave:service:backoff:interval", observe);
+      backoffInterval = subject;
+    });
+
+    Assert.ok(!Status.enforceBackoff);
+    Assert.equal(Status.service, STATUS_OK);
+
+    Svc.PrefBranch.setStringPref("firstSync", "wipeRemote");
+
+    let promiseObserved = promiseOneObserver("weave:service:reset-file-log");
+    await Service.sync();
+    await promiseObserved;
+
+    Assert.ok(Status.enforceBackoff);
+    Assert.equal(backoffInterval, 42);
+    Assert.equal(Status.service, SYNC_FAILED);
+    Assert.equal(Status.sync, SERVER_MAINTENANCE);
+    Assert.equal(Svc.PrefBranch.getStringPref("firstSync"), "wipeRemote");
+
+    await clean();
+    await promiseStopServer(server);
+  }
+);
+
+add_task(async function test_sync_engine_generic_fail() {
+  enableValidationPrefs();
+
+  equal(getLogFiles().length, 0);
+
+  let server = await EHTestsCommon.sync_httpd_setup();
+  engine.enabled = true;
+  engine.sync = async function sync() {
+    Svc.Obs.notify("weave:engine:sync:error", ENGINE_UNKNOWN_FAIL, "catapult");
+  };
+  let lastSync = Svc.PrefBranch.getStringPref("lastSync", null);
+  let log = Log.repository.getLogger("Sync.ErrorHandler");
+  Svc.PrefBranch.setBoolPref("log.appender.file.logOnError", true);
+
+  Assert.equal(Status.engines.catapult, undefined);
+
+  let promiseObserved = new Promise(res => {
+    Svc.Obs.add("weave:engine:sync:finish", function onEngineFinish() {
+      Svc.Obs.remove("weave:engine:sync:finish", onEngineFinish);
+
+      log.info("Adding reset-file-log observer.");
+      Svc.Obs.add("weave:service:reset-file-log", function onResetFileLog() {
+        Svc.Obs.remove("weave:service:reset-file-log", onResetFileLog);
+        res();
+      });
+    });
+  });
+
+  Assert.ok(await EHTestsCommon.setUp(server));
+  await sync_and_validate_telem(ping => {
+    deepEqual(ping.status.service, SYNC_FAILED_PARTIAL);
+    deepEqual(ping.engines.find(e => e.status).status, ENGINE_UNKNOWN_FAIL);
+  });
+
+  await promiseObserved;
+
+  _("Status.engines: " + JSON.stringify(Status.engines));
+  Assert.equal(Status.engines.catapult, ENGINE_UNKNOWN_FAIL);
+  Assert.equal(Status.service, SYNC_FAILED_PARTIAL);
+
+  // lastSync should update on partial failure.
+  Assert.notEqual(lastSync, Svc.PrefBranch.getStringPref("lastSync"));
+
+  // Test Error log was written on SYNC_FAILED_PARTIAL.
+  let logFiles = getLogFiles();
+  equal(logFiles.length, 1);
+  Assert.ok(
+    logFiles[0].leafName.startsWith("error-sync-"),
+    logFiles[0].leafName
+  );
+
+  await clean();
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_logs_on_sync_error() {
+  enableValidationPrefs();
+
+  _(
+    "Ensure that an error is still logged when weave:service:sync:error " +
+      "is notified, despite shouldReportError returning false."
+  );
+
+  let log = Log.repository.getLogger("Sync.ErrorHandler");
+  Svc.PrefBranch.setBoolPref("log.appender.file.logOnError", true);
+  log.info("TESTING");
+
+  // Ensure that we report no error.
+  Status.login = MASTER_PASSWORD_LOCKED;
+
+  let promiseObserved = promiseOneObserver("weave:service:reset-file-log");
+  Svc.Obs.notify("weave:service:sync:error", {});
+  await promiseObserved;
+
+  // Test that error log was written.
+  let logFiles = getLogFiles();
+  equal(logFiles.length, 1);
+  Assert.ok(
+    logFiles[0].leafName.startsWith("error-sync-"),
+    logFiles[0].leafName
+  );
+
+  await clean();
+});
+
+add_task(async function test_logs_on_login_error() {
+  enableValidationPrefs();
+
+  _(
+    "Ensure that an error is still logged when weave:service:login:error " +
+      "is notified, despite shouldReportError returning false."
+  );
+
+  let log = Log.repository.getLogger("Sync.ErrorHandler");
+  Svc.PrefBranch.setBoolPref("log.appender.file.logOnError", true);
+  log.info("TESTING");
+
+  // Ensure that we report no error.
+  Status.login = MASTER_PASSWORD_LOCKED;
+
+  let promiseObserved = promiseOneObserver("weave:service:reset-file-log");
+  Svc.Obs.notify("weave:service:login:error", {});
+  await promiseObserved;
+
+  // Test that error log was written.
+  let logFiles = getLogFiles();
+  equal(logFiles.length, 1);
+  Assert.ok(
+    logFiles[0].leafName.startsWith("error-sync-"),
+    logFiles[0].leafName
+  );
+
+  await clean();
+});
+
+// This test should be the last one since it monkeypatches the engine object
+// and we should only have one engine object throughout the file (bug 629664).
+add_task(async function test_engine_applyFailed() {
+  enableValidationPrefs();
+
+  let server = await EHTestsCommon.sync_httpd_setup();
+
+  engine.enabled = true;
+  delete engine.exception;
+  engine.sync = async function sync() {
+    Svc.Obs.notify("weave:engine:sync:applied", { newFailed: 1 }, "catapult");
+  };
+
+  Svc.PrefBranch.setBoolPref("log.appender.file.logOnError", true);
+
+  let promiseObserved = promiseOneObserver("weave:service:reset-file-log");
+
+  Assert.equal(Status.engines.catapult, undefined);
+  Assert.ok(await EHTestsCommon.setUp(server));
+  await Service.sync();
+  await promiseObserved;
+
+  Assert.equal(Status.engines.catapult, ENGINE_APPLY_FAIL);
+  Assert.equal(Status.service, SYNC_FAILED_PARTIAL);
+
+  // Test Error log was written on SYNC_FAILED_PARTIAL.
+  let logFiles = getLogFiles();
+  equal(logFiles.length, 1);
+  Assert.ok(
+    logFiles[0].leafName.startsWith("error-sync-"),
+    logFiles[0].leafName
+  );
+
+  await clean();
+  await promiseStopServer(server);
+});
diff --git a/src/zen/tests/mochitests/sync/test_errorhandler_filelog.js b/src/zen/tests/mochitests/sync/test_errorhandler_filelog.js
new file mode 100644
index 000000000..357049276
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_errorhandler_filelog.js
@@ -0,0 +1,473 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// `Service` is used as a global in head_helpers.js.
+// eslint-disable-next-line no-unused-vars
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { logManager } = ChromeUtils.importESModule(
+  "resource://gre/modules/FxAccountsCommon.sys.mjs"
+);
+const { FileUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/FileUtils.sys.mjs"
+);
+
+const logsdir = FileUtils.getDir("ProfD", ["weave", "logs"]);
+logsdir.create(Ci.nsIFile.DIRECTORY_TYPE, FileUtils.PERMS_DIRECTORY);
+
+// Delay to wait before cleanup, to allow files to age.
+// This is so large because the file timestamp granularity is per-second, and
+// so otherwise we can end up with all of our files -- the ones we want to
+// keep, and the ones we want to clean up -- having the same modified time.
+const CLEANUP_DELAY = 2000;
+const DELAY_BUFFER = 500; // Buffer for timers on different OS platforms.
+
+function run_test() {
+  validate_all_future_pings();
+  run_next_test();
+}
+
+add_test(function test_noOutput() {
+  // Ensure that the log appender won't print anything.
+  logManager._fileAppender.level = Log.Level.Fatal + 1;
+
+  // Clear log output from startup.
+  Svc.PrefBranch.setBoolPref("log.appender.file.logOnSuccess", false);
+  Svc.Obs.notify("weave:service:sync:finish");
+  Svc.Obs.add("weave:service:reset-file-log", function onResetFileLogOuter() {
+    Svc.Obs.remove("weave:service:reset-file-log", onResetFileLogOuter);
+    // Clear again without having issued any output.
+    Svc.PrefBranch.setBoolPref("log.appender.file.logOnSuccess", true);
+
+    Svc.Obs.add("weave:service:reset-file-log", function onResetFileLogInner() {
+      Svc.Obs.remove("weave:service:reset-file-log", onResetFileLogInner);
+
+      logManager._fileAppender.level = Log.Level.Trace;
+      for (const pref of Svc.PrefBranch.getChildList("")) {
+        Svc.PrefBranch.clearUserPref(pref);
+      }
+      run_next_test();
+    });
+
+    // Fake a successful sync.
+    Svc.Obs.notify("weave:service:sync:finish");
+  });
+});
+
+add_test(function test_logOnSuccess_false() {
+  Svc.PrefBranch.setBoolPref("log.appender.file.logOnSuccess", false);
+
+  let log = Log.repository.getLogger("Sync.Test.FileLog");
+  log.info("this won't show up");
+
+  Svc.Obs.add("weave:service:reset-file-log", function onResetFileLog() {
+    Svc.Obs.remove("weave:service:reset-file-log", onResetFileLog);
+    // No log file was written.
+    Assert.ok(!logsdir.directoryEntries.hasMoreElements());
+
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+    run_next_test();
+  });
+
+  // Fake a successful sync.
+  Svc.Obs.notify("weave:service:sync:finish");
+});
+
+function readFile(file, callback) {
+  NetUtil.asyncFetch(
+    {
+      uri: NetUtil.newURI(file),
+      loadUsingSystemPrincipal: true,
+    },
+    function (inputStream, statusCode) {
+      let data = NetUtil.readInputStreamToString(
+        inputStream,
+        inputStream.available()
+      );
+      callback(statusCode, data);
+    }
+  );
+}
+
+add_test(function test_logOnSuccess_true() {
+  Svc.PrefBranch.setBoolPref("log.appender.file.logOnSuccess", true);
+
+  let log = Log.repository.getLogger("Sync.Test.FileLog");
+  const MESSAGE = "this WILL show up";
+  log.info(MESSAGE);
+
+  Svc.Obs.add("weave:service:reset-file-log", function onResetFileLog() {
+    Svc.Obs.remove("weave:service:reset-file-log", onResetFileLog);
+
+    // Exactly one log file was written.
+    let entries = logsdir.directoryEntries;
+    Assert.ok(entries.hasMoreElements());
+    let logfile = entries.getNext().QueryInterface(Ci.nsIFile);
+    Assert.equal(logfile.leafName.slice(-4), ".txt");
+    Assert.ok(logfile.leafName.startsWith("success-sync-"), logfile.leafName);
+    Assert.ok(!entries.hasMoreElements());
+
+    // Ensure the log message was actually written to file.
+    readFile(logfile, function (error, data) {
+      Assert.ok(Components.isSuccessCode(error));
+      Assert.notEqual(data.indexOf(MESSAGE), -1);
+
+      // Clean up.
+      try {
+        logfile.remove(false);
+      } catch (ex) {
+        dump("Couldn't delete file: " + ex.message + "\n");
+        // Stupid Windows box.
+      }
+
+      for (const pref of Svc.PrefBranch.getChildList("")) {
+        Svc.PrefBranch.clearUserPref(pref);
+      }
+      run_next_test();
+    });
+  });
+
+  // Fake a successful sync.
+  Svc.Obs.notify("weave:service:sync:finish");
+});
+
+add_test(function test_sync_error_logOnError_false() {
+  Svc.PrefBranch.setBoolPref("log.appender.file.logOnError", false);
+
+  let log = Log.repository.getLogger("Sync.Test.FileLog");
+  log.info("this won't show up");
+
+  Svc.Obs.add("weave:service:reset-file-log", function onResetFileLog() {
+    Svc.Obs.remove("weave:service:reset-file-log", onResetFileLog);
+    // No log file was written.
+    Assert.ok(!logsdir.directoryEntries.hasMoreElements());
+
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+    run_next_test();
+  });
+
+  // Fake an unsuccessful sync.
+  Svc.Obs.notify("weave:service:sync:error");
+});
+
+add_test(function test_sync_error_logOnError_true() {
+  Svc.PrefBranch.setBoolPref("log.appender.file.logOnError", true);
+
+  let log = Log.repository.getLogger("Sync.Test.FileLog");
+  const MESSAGE = "this WILL show up";
+  log.info(MESSAGE);
+
+  Svc.Obs.add("weave:service:reset-file-log", function onResetFileLog() {
+    Svc.Obs.remove("weave:service:reset-file-log", onResetFileLog);
+
+    // Exactly one log file was written.
+    let entries = logsdir.directoryEntries;
+    Assert.ok(entries.hasMoreElements());
+    let logfile = entries.getNext().QueryInterface(Ci.nsIFile);
+    Assert.equal(logfile.leafName.slice(-4), ".txt");
+    Assert.ok(logfile.leafName.startsWith("error-sync-"), logfile.leafName);
+    Assert.ok(!entries.hasMoreElements());
+
+    // Ensure the log message was actually written to file.
+    readFile(logfile, function (error, data) {
+      Assert.ok(Components.isSuccessCode(error));
+      Assert.notEqual(data.indexOf(MESSAGE), -1);
+
+      // Clean up.
+      try {
+        logfile.remove(false);
+      } catch (ex) {
+        dump("Couldn't delete file: " + ex.message + "\n");
+        // Stupid Windows box.
+      }
+
+      for (const pref of Svc.PrefBranch.getChildList("")) {
+        Svc.PrefBranch.clearUserPref(pref);
+      }
+      run_next_test();
+    });
+  });
+
+  // Fake an unsuccessful sync.
+  Svc.Obs.notify("weave:service:sync:error");
+});
+
+add_test(function test_login_error_logOnError_false() {
+  Svc.PrefBranch.setBoolPref("log.appender.file.logOnError", false);
+
+  let log = Log.repository.getLogger("Sync.Test.FileLog");
+  log.info("this won't show up");
+
+  Svc.Obs.add("weave:service:reset-file-log", function onResetFileLog() {
+    Svc.Obs.remove("weave:service:reset-file-log", onResetFileLog);
+    // No log file was written.
+    Assert.ok(!logsdir.directoryEntries.hasMoreElements());
+
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+    run_next_test();
+  });
+
+  // Fake an unsuccessful login.
+  Svc.Obs.notify("weave:service:login:error");
+});
+
+add_test(function test_login_error_logOnError_true() {
+  Svc.PrefBranch.setBoolPref("log.appender.file.logOnError", true);
+
+  let log = Log.repository.getLogger("Sync.Test.FileLog");
+  const MESSAGE = "this WILL show up";
+  log.info(MESSAGE);
+
+  Svc.Obs.add("weave:service:reset-file-log", function onResetFileLog() {
+    Svc.Obs.remove("weave:service:reset-file-log", onResetFileLog);
+
+    // Exactly one log file was written.
+    let entries = logsdir.directoryEntries;
+    Assert.ok(entries.hasMoreElements());
+    let logfile = entries.getNext().QueryInterface(Ci.nsIFile);
+    Assert.equal(logfile.leafName.slice(-4), ".txt");
+    Assert.ok(logfile.leafName.startsWith("error-sync-"), logfile.leafName);
+    Assert.ok(!entries.hasMoreElements());
+
+    // Ensure the log message was actually written to file.
+    readFile(logfile, function (error, data) {
+      Assert.ok(Components.isSuccessCode(error));
+      Assert.notEqual(data.indexOf(MESSAGE), -1);
+
+      // Clean up.
+      try {
+        logfile.remove(false);
+      } catch (ex) {
+        dump("Couldn't delete file: " + ex.message + "\n");
+        // Stupid Windows box.
+      }
+
+      for (const pref of Svc.PrefBranch.getChildList("")) {
+        Svc.PrefBranch.clearUserPref(pref);
+      }
+      run_next_test();
+    });
+  });
+
+  // Fake an unsuccessful login.
+  Svc.Obs.notify("weave:service:login:error");
+});
+
+add_test(function test_noNewFailed_noErrorLog() {
+  Svc.PrefBranch.setBoolPref("log.appender.file.logOnError", true);
+  Svc.PrefBranch.setBoolPref("log.appender.file.logOnSuccess", false);
+
+  Svc.Obs.add("weave:service:reset-file-log", function onResetFileLog() {
+    Svc.Obs.remove("weave:service:reset-file-log", onResetFileLog);
+    // No log file was written.
+    Assert.ok(!logsdir.directoryEntries.hasMoreElements());
+
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+    run_next_test();
+  });
+  // failed is nonzero and newFailed is zero -- shouldn't write a log.
+  let count = {
+    applied: 8,
+    succeeded: 4,
+    failed: 5,
+    newFailed: 0,
+    reconciled: 4,
+  };
+  Svc.Obs.notify("weave:engine:sync:applied", count, "foobar-engine");
+  Svc.Obs.notify("weave:service:sync:finish");
+});
+
+add_test(function test_newFailed_errorLog() {
+  Svc.PrefBranch.setBoolPref("log.appender.file.logOnError", true);
+  Svc.PrefBranch.setBoolPref("log.appender.file.logOnSuccess", false);
+
+  let log = Log.repository.getLogger("Sync.Test.FileLog");
+  const MESSAGE = "this WILL show up 2";
+  log.info(MESSAGE);
+
+  Svc.Obs.add("weave:service:reset-file-log", function onResetFileLog() {
+    Svc.Obs.remove("weave:service:reset-file-log", onResetFileLog);
+
+    // Exactly one log file was written.
+    let entries = logsdir.directoryEntries;
+    Assert.ok(entries.hasMoreElements());
+    let logfile = entries.getNext().QueryInterface(Ci.nsIFile);
+    Assert.equal(logfile.leafName.slice(-4), ".txt");
+    Assert.ok(logfile.leafName.startsWith("error-sync-"), logfile.leafName);
+    Assert.ok(!entries.hasMoreElements());
+
+    // Ensure the log message was actually written to file.
+    readFile(logfile, function (error, data) {
+      Assert.ok(Components.isSuccessCode(error));
+      Assert.notEqual(data.indexOf(MESSAGE), -1);
+
+      // Clean up.
+      try {
+        logfile.remove(false);
+      } catch (ex) {
+        dump("Couldn't delete file: " + ex.message + "\n");
+        // Stupid Windows box.
+      }
+
+      for (const pref of Svc.PrefBranch.getChildList("")) {
+        Svc.PrefBranch.clearUserPref(pref);
+      }
+      run_next_test();
+    });
+  });
+  // newFailed is nonzero -- should write a log.
+  let count = {
+    applied: 8,
+    succeeded: 4,
+    failed: 5,
+    newFailed: 4,
+    reconciled: 4,
+  };
+
+  Svc.Obs.notify("weave:engine:sync:applied", count, "foobar-engine");
+  Svc.Obs.notify("weave:service:sync:finish");
+});
+
+add_test(function test_errorLog_dumpAddons() {
+  Svc.PrefBranch.setStringPref("log.logger", "Trace");
+  Svc.PrefBranch.setBoolPref("log.appender.file.logOnError", true);
+
+  Svc.Obs.add("weave:service:reset-file-log", function onResetFileLog() {
+    Svc.Obs.remove("weave:service:reset-file-log", onResetFileLog);
+
+    let entries = logsdir.directoryEntries;
+    Assert.ok(entries.hasMoreElements());
+    let logfile = entries.getNext().QueryInterface(Ci.nsIFile);
+    Assert.equal(logfile.leafName.slice(-4), ".txt");
+    Assert.ok(logfile.leafName.startsWith("error-sync-"), logfile.leafName);
+    Assert.ok(!entries.hasMoreElements());
+
+    // Ensure we logged some addon list (which is probably empty)
+    readFile(logfile, function (error, data) {
+      Assert.ok(Components.isSuccessCode(error));
+      Assert.notEqual(data.indexOf("Addons installed"), -1);
+
+      // Clean up.
+      try {
+        logfile.remove(false);
+      } catch (ex) {
+        dump("Couldn't delete file: " + ex.message + "\n");
+        // Stupid Windows box.
+      }
+
+      for (const pref of Svc.PrefBranch.getChildList("")) {
+        Svc.PrefBranch.clearUserPref(pref);
+      }
+      run_next_test();
+    });
+  });
+
+  // Fake an unsuccessful sync.
+  Svc.Obs.notify("weave:service:sync:error");
+});
+
+// Check that error log files are deleted above an age threshold.
+add_test(async function test_logErrorCleanup_age() {
+  _("Beginning test_logErrorCleanup_age.");
+  let maxAge = CLEANUP_DELAY / 1000;
+  let oldLogs = [];
+  let numLogs = 10;
+  let errString = "some error log\n";
+
+  Svc.PrefBranch.setBoolPref("log.appender.file.logOnError", true);
+  Svc.PrefBranch.setIntPref("log.appender.file.maxErrorAge", maxAge);
+
+  _("Making some files.");
+  const logsDir = PathUtils.join(PathUtils.profileDir, "weave", "logs");
+  await IOUtils.makeDirectory(logsDir);
+  for (let i = 0; i < numLogs; i++) {
+    let now = Date.now();
+    let filename = "error-sync-" + now + "" + i + ".txt";
+    let newLog = new FileUtils.File(PathUtils.join(logsDir, filename));
+    let foStream = FileUtils.openFileOutputStream(newLog);
+    foStream.write(errString, errString.length);
+    foStream.close();
+    _("  > Created " + filename);
+    oldLogs.push(newLog.leafName);
+  }
+
+  Svc.Obs.add(
+    "services-tests:common:log-manager:cleanup-logs",
+    function onCleanupLogs() {
+      Svc.Obs.remove(
+        "services-tests:common:log-manager:cleanup-logs",
+        onCleanupLogs
+      );
+
+      // Only the newest created log file remains.
+      let entries = logsdir.directoryEntries;
+      Assert.ok(entries.hasMoreElements());
+      let logfile = entries.getNext().QueryInterface(Ci.nsIFile);
+      Assert.ok(
+        oldLogs.every(function (e) {
+          return e != logfile.leafName;
+        })
+      );
+      Assert.ok(!entries.hasMoreElements());
+
+      // Clean up.
+      try {
+        logfile.remove(false);
+      } catch (ex) {
+        dump("Couldn't delete file: " + ex.message + "\n");
+        // Stupid Windows box.
+      }
+
+      for (const pref of Svc.PrefBranch.getChildList("")) {
+        Svc.PrefBranch.clearUserPref(pref);
+      }
+      run_next_test();
+    }
+  );
+
+  let delay = CLEANUP_DELAY + DELAY_BUFFER;
+
+  _("Cleaning up logs after " + delay + "msec.");
+  CommonUtils.namedTimer(
+    function onTimer() {
+      Svc.Obs.notify("weave:service:sync:error");
+    },
+    delay,
+    this,
+    "cleanup-timer"
+  );
+});
+
+add_task(async function test_remove_log_on_startOver() {
+  Svc.PrefBranch.setBoolPref("log.appender.file.logOnError", true);
+
+  let log = Log.repository.getLogger("Sync.Test.FileLog");
+  const MESSAGE = "this WILL show up";
+  log.info(MESSAGE);
+
+  let promiseLogWritten = promiseOneObserver("weave:service:reset-file-log");
+  // Fake an unsuccessful sync.
+  Svc.Obs.notify("weave:service:sync:error");
+
+  await promiseLogWritten;
+  // Should have at least 1 log file.
+  let entries = logsdir.directoryEntries;
+  Assert.ok(entries.hasMoreElements());
+
+  // Fake a reset.
+  let promiseRemoved = promiseOneObserver("weave:service:remove-file-log");
+  Svc.Obs.notify("weave:service:start-over:finish");
+  await promiseRemoved;
+
+  // should be no files left.
+  Assert.ok(!logsdir.directoryEntries.hasMoreElements());
+});
diff --git a/src/zen/tests/mochitests/sync/test_errorhandler_sync_checkServerError.js b/src/zen/tests/mochitests/sync/test_errorhandler_sync_checkServerError.js
new file mode 100644
index 000000000..d73d548cc
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_errorhandler_sync_checkServerError.js
@@ -0,0 +1,294 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { Status } = ChromeUtils.importESModule(
+  "resource://services-sync/status.sys.mjs"
+);
+const { FakeCryptoService } = ChromeUtils.importESModule(
+  "resource://testing-common/services/sync/fakeservices.sys.mjs"
+);
+
+var engineManager = Service.engineManager;
+
+function CatapultEngine() {
+  SyncEngine.call(this, "Catapult", Service);
+}
+CatapultEngine.prototype = {
+  exception: null, // tests fill this in
+  async _sync() {
+    throw this.exception;
+  },
+};
+Object.setPrototypeOf(CatapultEngine.prototype, SyncEngine.prototype);
+
+async function sync_httpd_setup() {
+  let collectionsHelper = track_collections_helper();
+  let upd = collectionsHelper.with_updated_collection;
+
+  let catapultEngine = engineManager.get("catapult");
+  let syncID = await catapultEngine.resetLocalSyncID();
+  let engines = { catapult: { version: catapultEngine.version, syncID } };
+
+  // Track these using the collections helper, which keeps modified times
+  // up-to-date.
+  let clientsColl = new ServerCollection({}, true);
+  let keysWBO = new ServerWBO("keys");
+  let globalWBO = new ServerWBO("global", {
+    storageVersion: STORAGE_VERSION,
+    syncID: Utils.makeGUID(),
+    engines,
+  });
+
+  let handlers = {
+    "/1.1/johndoe/info/collections": collectionsHelper.handler,
+    "/1.1/johndoe/storage/meta/global": upd("meta", globalWBO.handler()),
+    "/1.1/johndoe/storage/clients": upd("clients", clientsColl.handler()),
+    "/1.1/johndoe/storage/crypto/keys": upd("crypto", keysWBO.handler()),
+  };
+  return httpd_setup(handlers);
+}
+
+async function setUp(server) {
+  await configureIdentity({ username: "johndoe" }, server);
+  new FakeCryptoService();
+  syncTestLogging();
+}
+
+async function generateAndUploadKeys(server) {
+  await generateNewKeys(Service.collectionKeys);
+  let serverKeys = Service.collectionKeys.asWBO("crypto", "keys");
+  await serverKeys.encrypt(Service.identity.syncKeyBundle);
+  let res = Service.resource(
+    server.baseURI + "/1.1/johndoe/storage/crypto/keys"
+  );
+  return (await serverKeys.upload(res)).success;
+}
+
+add_task(async function setup() {
+  await engineManager.clear();
+  validate_all_future_pings();
+  await engineManager.register(CatapultEngine);
+});
+
+add_task(async function test_backoff500() {
+  enableValidationPrefs();
+
+  _("Test: HTTP 500 sets backoff status.");
+  let server = await sync_httpd_setup();
+  await setUp(server);
+
+  let engine = engineManager.get("catapult");
+  engine.enabled = true;
+  engine.exception = { status: 500 };
+
+  try {
+    Assert.ok(!Status.enforceBackoff);
+
+    // Forcibly create and upload keys here -- otherwise we don't get to the 500!
+    Assert.ok(await generateAndUploadKeys(server));
+
+    await Service.login();
+    await Service.sync();
+    Assert.ok(Status.enforceBackoff);
+    Assert.equal(Status.sync, SYNC_SUCCEEDED);
+    Assert.equal(Status.service, SYNC_FAILED_PARTIAL);
+  } finally {
+    Status.resetBackoff();
+    await Service.startOver();
+  }
+  await promiseStopServer(server);
+});
+
+add_task(async function test_backoff503() {
+  enableValidationPrefs();
+
+  _(
+    "Test: HTTP 503 with Retry-After header leads to backoff notification and sets backoff status."
+  );
+  let server = await sync_httpd_setup();
+  await setUp(server);
+
+  const BACKOFF = 42;
+  let engine = engineManager.get("catapult");
+  engine.enabled = true;
+  engine.exception = { status: 503, headers: { "retry-after": BACKOFF } };
+
+  let backoffInterval;
+  Svc.Obs.add("weave:service:backoff:interval", function (subject) {
+    backoffInterval = subject;
+  });
+
+  try {
+    Assert.ok(!Status.enforceBackoff);
+
+    Assert.ok(await generateAndUploadKeys(server));
+
+    await Service.login();
+    await Service.sync();
+
+    Assert.ok(Status.enforceBackoff);
+    Assert.equal(backoffInterval, BACKOFF);
+    Assert.equal(Status.service, SYNC_FAILED_PARTIAL);
+    Assert.equal(Status.sync, SERVER_MAINTENANCE);
+  } finally {
+    Status.resetBackoff();
+    Status.resetSync();
+    await Service.startOver();
+  }
+  await promiseStopServer(server);
+});
+
+add_task(async function test_overQuota() {
+  enableValidationPrefs();
+
+  _("Test: HTTP 400 with body error code 14 means over quota.");
+  let server = await sync_httpd_setup();
+  await setUp(server);
+
+  let engine = engineManager.get("catapult");
+  engine.enabled = true;
+  engine.exception = {
+    status: 400,
+    toString() {
+      return "14";
+    },
+  };
+
+  try {
+    Assert.equal(Status.sync, SYNC_SUCCEEDED);
+
+    Assert.ok(await generateAndUploadKeys(server));
+
+    await Service.login();
+    await Service.sync();
+
+    Assert.equal(Status.sync, OVER_QUOTA);
+    Assert.equal(Status.service, SYNC_FAILED_PARTIAL);
+  } finally {
+    Status.resetSync();
+    await Service.startOver();
+  }
+  await promiseStopServer(server);
+});
+
+add_task(async function test_service_networkError() {
+  enableValidationPrefs();
+
+  _(
+    "Test: Connection refused error from Service.sync() leads to the right status code."
+  );
+  let server = await sync_httpd_setup();
+  await setUp(server);
+  await promiseStopServer(server);
+  // Provoke connection refused.
+  Service.clusterURL = "http://localhost:12345/";
+
+  try {
+    Assert.equal(Status.sync, SYNC_SUCCEEDED);
+
+    Service._loggedIn = true;
+    await Service.sync();
+
+    Assert.equal(Status.sync, LOGIN_FAILED_NETWORK_ERROR);
+    Assert.equal(Status.service, SYNC_FAILED);
+  } finally {
+    Status.resetSync();
+    await Service.startOver();
+  }
+});
+
+add_task(async function test_service_offline() {
+  enableValidationPrefs();
+
+  _(
+    "Test: Wanting to sync in offline mode leads to the right status code but does not increment the ignorable error count."
+  );
+  let server = await sync_httpd_setup();
+  await setUp(server);
+
+  await promiseStopServer(server);
+  Services.io.offline = true;
+  Services.prefs.setBoolPref("network.dns.offline-localhost", false);
+
+  try {
+    Assert.equal(Status.sync, SYNC_SUCCEEDED);
+
+    Service._loggedIn = true;
+    await Service.sync();
+
+    Assert.equal(Status.sync, LOGIN_FAILED_NETWORK_ERROR);
+    Assert.equal(Status.service, SYNC_FAILED);
+  } finally {
+    Status.resetSync();
+    await Service.startOver();
+  }
+  Services.io.offline = false;
+  Services.prefs.clearUserPref("network.dns.offline-localhost");
+});
+
+add_task(async function test_engine_networkError() {
+  enableValidationPrefs();
+
+  _(
+    "Test: Network related exceptions from engine.sync() lead to the right status code."
+  );
+  let server = await sync_httpd_setup();
+  await setUp(server);
+
+  let engine = engineManager.get("catapult");
+  engine.enabled = true;
+  engine.exception = Components.Exception(
+    "NS_ERROR_UNKNOWN_HOST",
+    Cr.NS_ERROR_UNKNOWN_HOST
+  );
+
+  try {
+    Assert.equal(Status.sync, SYNC_SUCCEEDED);
+
+    Assert.ok(await generateAndUploadKeys(server));
+
+    await Service.login();
+    await Service.sync();
+
+    Assert.equal(Status.sync, LOGIN_FAILED_NETWORK_ERROR);
+    Assert.equal(Status.service, SYNC_FAILED_PARTIAL);
+  } finally {
+    Status.resetSync();
+    await Service.startOver();
+  }
+  await promiseStopServer(server);
+});
+
+add_task(async function test_resource_timeout() {
+  enableValidationPrefs();
+
+  let server = await sync_httpd_setup();
+  await setUp(server);
+
+  let engine = engineManager.get("catapult");
+  engine.enabled = true;
+  // Resource throws this when it encounters a timeout.
+  engine.exception = Components.Exception(
+    "Aborting due to channel inactivity.",
+    Cr.NS_ERROR_NET_TIMEOUT
+  );
+
+  try {
+    Assert.equal(Status.sync, SYNC_SUCCEEDED);
+
+    Assert.ok(await generateAndUploadKeys(server));
+
+    await Service.login();
+    await Service.sync();
+
+    Assert.equal(Status.sync, LOGIN_FAILED_NETWORK_ERROR);
+    Assert.equal(Status.service, SYNC_FAILED_PARTIAL);
+  } finally {
+    Status.resetSync();
+    await Service.startOver();
+  }
+  await promiseStopServer(server);
+});
diff --git a/src/zen/tests/mochitests/sync/test_extension_storage_engine.js b/src/zen/tests/mochitests/sync/test_extension_storage_engine.js
new file mode 100644
index 000000000..65194b858
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_extension_storage_engine.js
@@ -0,0 +1,259 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  Service: "resource://services-sync/service.sys.mjs",
+  extensionStorageSync: "resource://gre/modules/ExtensionStorageSync.sys.mjs",
+});
+
+const { ExtensionStorageEngineBridge, ExtensionStorageEngineKinto } =
+  ChromeUtils.importESModule(
+    "resource://services-sync/engines/extension-storage.sys.mjs"
+  );
+
+Services.prefs.setStringPref("webextensions.storage.sync.log.level", "debug");
+
+add_task(async function test_switching_between_kinto_and_bridged() {
+  function assertUsingKinto(message) {
+    let kintoEngine = Service.engineManager.get("extension-storage");
+    Assert.ok(kintoEngine instanceof ExtensionStorageEngineKinto, message);
+  }
+  function assertUsingBridged(message) {
+    let bridgedEngine = Service.engineManager.get("extension-storage");
+    Assert.ok(bridgedEngine instanceof ExtensionStorageEngineBridge, message);
+  }
+
+  let isUsingKinto = Services.prefs.getBoolPref(
+    "webextensions.storage.sync.kinto",
+    false
+  );
+  if (isUsingKinto) {
+    assertUsingKinto("Should use Kinto engine before flipping pref");
+  } else {
+    assertUsingBridged("Should use bridged engine before flipping pref");
+  }
+
+  _("Flip pref");
+  Services.prefs.setBoolPref("webextensions.storage.sync.kinto", !isUsingKinto);
+  await Service.engineManager.switchAlternatives();
+
+  if (isUsingKinto) {
+    assertUsingBridged("Should use bridged engine after flipping pref");
+  } else {
+    assertUsingKinto("Should use Kinto engine after flipping pref");
+  }
+
+  _("Clean up");
+  Services.prefs.clearUserPref("webextensions.storage.sync.kinto");
+  await Service.engineManager.switchAlternatives();
+});
+
+add_task(async function test_enable() {
+  const PREF = "services.sync.engine.extension-storage.force";
+
+  let addonsEngine = Service.engineManager.get("addons");
+  let extensionStorageEngine = Service.engineManager.get("extension-storage");
+
+  try {
+    Assert.ok(
+      addonsEngine.enabled,
+      "Add-ons engine should be enabled by default"
+    );
+    Assert.ok(
+      extensionStorageEngine.enabled,
+      "Extension storage engine should be enabled by default"
+    );
+
+    addonsEngine.enabled = false;
+    Assert.ok(
+      !extensionStorageEngine.enabled,
+      "Disabling add-ons should disable extension storage"
+    );
+
+    extensionStorageEngine.enabled = true;
+    Assert.ok(
+      !extensionStorageEngine.enabled,
+      "Enabling extension storage without override pref shouldn't work"
+    );
+
+    Services.prefs.setBoolPref(PREF, true);
+    Assert.ok(
+      extensionStorageEngine.enabled,
+      "Setting override pref should enable extension storage"
+    );
+
+    extensionStorageEngine.enabled = false;
+    Assert.ok(
+      !extensionStorageEngine.enabled,
+      "Disabling extension storage engine with override pref should work"
+    );
+
+    extensionStorageEngine.enabled = true;
+    Assert.ok(
+      extensionStorageEngine.enabled,
+      "Enabling extension storage with override pref should work"
+    );
+  } finally {
+    addonsEngine.enabled = true;
+    Services.prefs.clearUserPref(PREF);
+  }
+});
+
+add_task(async function test_notifyPendingChanges() {
+  let engine = new ExtensionStorageEngineBridge(Service);
+  await engine.initialize();
+
+  let extension = { id: "ext-1" };
+  let expectedChange = {
+    a: "b",
+    c: "d",
+  };
+
+  let lastSync = 0;
+  let syncID = Utils.makeGUID();
+  let error = null;
+  engine._rustStore = {
+    getSyncedChanges() {
+      if (error) {
+        throw new Error(error.message);
+      } else {
+        return [
+          { extId: extension.id, changes: JSON.stringify(expectedChange) },
+        ];
+      }
+    },
+  };
+
+  engine._bridge = {
+    ensureCurrentSyncId(id) {
+      if (syncID != id) {
+        syncID = id;
+        lastSync = 0;
+      }
+      return id;
+    },
+    resetSyncId() {
+      return syncID;
+    },
+    syncStarted() {},
+    lastSync() {
+      return lastSync;
+    },
+    setLastSync(lastSyncMillis) {
+      lastSync = lastSyncMillis;
+    },
+    apply() {
+      return [];
+    },
+    setUploaded(_modified, _ids) {},
+    syncFinished() {},
+  };
+
+  let server = await serverForFoo(engine);
+
+  let actualChanges = [];
+  let listener = changes => actualChanges.push(changes);
+  extensionStorageSync.addOnChangedListener(extension, listener);
+
+  try {
+    await SyncTestingInfrastructure(server);
+
+    info("Sync engine; notify about changes");
+    await sync_engine_and_validate_telem(engine, false);
+    deepEqual(
+      actualChanges,
+      [expectedChange],
+      "Should notify about changes during sync"
+    );
+
+    error = new Error("oops!");
+    actualChanges = [];
+    await sync_engine_and_validate_telem(engine, false);
+    deepEqual(
+      actualChanges,
+      [],
+      "Should finish syncing even if notifying about changes fails"
+    );
+  } finally {
+    extensionStorageSync.removeOnChangedListener(extension, listener);
+    await promiseStopServer(server);
+    await engine.finalize();
+  }
+});
+
+// It's difficult to know what to test - there's already tests for the bridged
+// engine etc - so we just try and check that this engine conforms to the
+// mozIBridgedSyncEngine interface guarantees.
+add_task(async function test_engine() {
+  // Forcibly set the bridged engine in the engine manager. the reason we do
+  // this, unlike the other tests where we just create the engine, is so that
+  // telemetry can get at the engine's `overrideTelemetryName`, which it gets
+  // through the engine manager.
+  await Service.engineManager.unregister("extension-storage");
+  await Service.engineManager.register(ExtensionStorageEngineBridge);
+  let engine = Service.engineManager.get("extension-storage");
+  Assert.equal(engine.version, 1);
+
+  Assert.deepEqual(await engine.getSyncID(), null);
+  await engine.resetLocalSyncID();
+  Assert.notEqual(await engine.getSyncID(), null);
+
+  Assert.equal(await engine.getLastSync(), 0);
+  // lastSync is seconds on this side of the world, but milli-seconds on the other.
+  await engine.setLastSync(1234.567);
+  // should have 2 digit precision.
+  Assert.equal(await engine.getLastSync(), 1234.57);
+  await engine.setLastSync(0);
+
+  // Set some data.
+  await extensionStorageSync.set({ id: "ext-2" }, { ext_2_key: "ext_2_value" });
+  // Now do a sync with out regular test server.
+  let server = await serverForFoo(engine);
+  try {
+    await SyncTestingInfrastructure(server);
+
+    info("Add server records");
+    let foo = server.user("foo");
+    let collection = foo.collection("extension-storage");
+    let now = new_timestamp();
+
+    collection.insert(
+      "fakeguid0000",
+      encryptPayload({
+        id: "fakeguid0000",
+        extId: "ext-1",
+        data: JSON.stringify({ foo: "bar" }),
+      }),
+      now
+    );
+
+    info("Sync the engine");
+
+    let ping = await sync_engine_and_validate_telem(engine, false);
+    Assert.ok(ping.engines.find(e => e.name == "rust-webext-storage"));
+    Assert.equal(
+      ping.engines.find(e => e.name == "extension-storage"),
+      null
+    );
+
+    // We should have applied the data from the existing collection record.
+    Assert.deepEqual(await extensionStorageSync.get({ id: "ext-1" }, null), {
+      foo: "bar",
+    });
+
+    // should now be 2 records on the server.
+    let payloads = collection.payloads();
+    Assert.equal(payloads.length, 2);
+    // find the new one we wrote.
+    let newPayload =
+      payloads[0].id == "fakeguid0000" ? payloads[1] : payloads[0];
+    Assert.equal(newPayload.data, `{"ext_2_key":"ext_2_value"}`);
+    // should have updated the timestamp.
+    greater(await engine.getLastSync(), 0, "Should update last sync time");
+  } finally {
+    await promiseStopServer(server);
+    await engine.finalize();
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_extension_storage_engine_kinto.js b/src/zen/tests/mochitests/sync/test_extension_storage_engine_kinto.js
new file mode 100644
index 000000000..1564e0b79
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_extension_storage_engine_kinto.js
@@ -0,0 +1,136 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+Services.prefs.setBoolPref("webextensions.storage.sync.kinto", true);
+
+const { ExtensionStorageEngineKinto: ExtensionStorageEngine } =
+  ChromeUtils.importESModule(
+    "resource://services-sync/engines/extension-storage.sys.mjs"
+  );
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { extensionStorageSyncKinto: extensionStorageSync } =
+  ChromeUtils.importESModule(
+    "resource://gre/modules/ExtensionStorageSyncKinto.sys.mjs"
+  );
+
+let engine;
+
+function mock(options) {
+  let calls = [];
+  let ret = function () {
+    calls.push(arguments);
+    return options.returns;
+  };
+  let proto = {
+    get calls() {
+      return calls;
+    },
+  };
+  Object.setPrototypeOf(proto, Function.prototype);
+  Object.setPrototypeOf(ret, proto);
+  return ret;
+}
+
+function setSkipChance(v) {
+  Services.prefs.setIntPref(
+    "services.sync.extension-storage.skipPercentageChance",
+    v
+  );
+}
+
+add_task(async function setup() {
+  await Service.engineManager.register(ExtensionStorageEngine);
+  engine = Service.engineManager.get("extension-storage");
+  do_get_profile(); // so we can use FxAccounts
+  loadWebExtensionTestFunctions();
+  setSkipChance(0);
+});
+
+add_task(async function test_calling_sync_calls__sync() {
+  let oldSync = ExtensionStorageEngine.prototype._sync;
+  let syncMock = (ExtensionStorageEngine.prototype._sync = mock({
+    returns: true,
+  }));
+  try {
+    // I wanted to call the main sync entry point for the entire
+    // package, but that fails because it tries to sync ClientEngine
+    // first, which fails.
+    await engine.sync();
+  } finally {
+    ExtensionStorageEngine.prototype._sync = oldSync;
+  }
+  equal(syncMock.calls.length, 1);
+});
+
+add_task(async function test_sync_skip() {
+  try {
+    // Do a few times to ensure we aren't getting "lucky" WRT Math.random()
+    for (let i = 0; i < 10; ++i) {
+      setSkipChance(100);
+      engine._tracker._score = 0;
+      ok(
+        !engine.shouldSkipSync("user"),
+        "Should allow explicitly requested syncs"
+      );
+      ok(!engine.shouldSkipSync("startup"), "Should allow startup syncs");
+      ok(
+        engine.shouldSkipSync("schedule"),
+        "Should skip scheduled syncs if skipProbability is 100"
+      );
+      engine._tracker._score = MULTI_DEVICE_THRESHOLD;
+      ok(
+        !engine.shouldSkipSync("schedule"),
+        "should allow scheduled syncs if tracker score is high"
+      );
+      engine._tracker._score = 0;
+      setSkipChance(0);
+      ok(
+        !engine.shouldSkipSync("schedule"),
+        "Should allow scheduled syncs if probability is 0"
+      );
+    }
+  } finally {
+    engine._tracker._score = 0;
+    setSkipChance(0);
+  }
+});
+
+add_task(async function test_calling_wipeClient_calls_clearAll() {
+  let oldClearAll = extensionStorageSync.clearAll;
+  let clearMock = (extensionStorageSync.clearAll = mock({
+    returns: Promise.resolve(),
+  }));
+  try {
+    await engine.wipeClient();
+  } finally {
+    extensionStorageSync.clearAll = oldClearAll;
+  }
+  equal(clearMock.calls.length, 1);
+});
+
+add_task(async function test_calling_sync_calls_ext_storage_sync() {
+  const extension = { id: "my-extension" };
+  let oldSync = extensionStorageSync.syncAll;
+  let syncMock = (extensionStorageSync.syncAll = mock({
+    returns: Promise.resolve(),
+  }));
+  try {
+    await withContext(async function (context) {
+      // Set something so that everyone knows that we're using storage.sync
+      await extensionStorageSync.set(extension, { a: "b" }, context);
+      let ping = await sync_engine_and_validate_telem(engine, false);
+      Assert.ok(ping.engines.find(e => e.name == "extension-storage"));
+      Assert.equal(
+        ping.engines.find(e => e.name == "rust-webext-storage"),
+        null
+      );
+    });
+  } finally {
+    extensionStorageSync.syncAll = oldSync;
+  }
+  Assert.greaterOrEqual(syncMock.calls.length, 1);
+});
diff --git a/src/zen/tests/mochitests/sync/test_extension_storage_tracker_kinto.js b/src/zen/tests/mochitests/sync/test_extension_storage_tracker_kinto.js
new file mode 100644
index 000000000..f09768287
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_extension_storage_tracker_kinto.js
@@ -0,0 +1,44 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+Services.prefs.setBoolPref("webextensions.storage.sync.kinto", true);
+
+const { ExtensionStorageEngine } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/extension-storage.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { extensionStorageSyncKinto: extensionStorageSync } =
+  ChromeUtils.importESModule(
+    "resource://gre/modules/ExtensionStorageSyncKinto.sys.mjs"
+  );
+
+let engine;
+
+add_task(async function setup() {
+  await Service.engineManager.register(ExtensionStorageEngine);
+  engine = Service.engineManager.get("extension-storage");
+  do_get_profile(); // so we can use FxAccounts
+  loadWebExtensionTestFunctions();
+});
+
+add_task(async function test_changing_extension_storage_changes_score() {
+  const tracker = engine._tracker;
+  const extension = { id: "my-extension-id" };
+  tracker.start();
+  await withContext(async function (context) {
+    await extensionStorageSync.set(extension, { a: "b" }, context);
+  });
+  Assert.equal(tracker.score, SCORE_INCREMENT_MEDIUM);
+
+  tracker.resetScore();
+  await withContext(async function (context) {
+    await extensionStorageSync.remove(extension, "a", context);
+  });
+  Assert.equal(tracker.score, SCORE_INCREMENT_MEDIUM);
+
+  await tracker.stop();
+});
diff --git a/src/zen/tests/mochitests/sync/test_form_validator.js b/src/zen/tests/mochitests/sync/test_form_validator.js
new file mode 100644
index 000000000..58ea8b855
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_form_validator.js
@@ -0,0 +1,86 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { FormValidator } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/forms.sys.mjs"
+);
+
+function getDummyServerAndClient() {
+  return {
+    server: [
+      {
+        id: "11111",
+        guid: "11111",
+        name: "foo",
+        fieldname: "foo",
+        value: "bar",
+      },
+      {
+        id: "22222",
+        guid: "22222",
+        name: "foo2",
+        fieldname: "foo2",
+        value: "bar2",
+      },
+      {
+        id: "33333",
+        guid: "33333",
+        name: "foo3",
+        fieldname: "foo3",
+        value: "bar3",
+      },
+    ],
+    client: [
+      {
+        id: "11111",
+        guid: "11111",
+        name: "foo",
+        fieldname: "foo",
+        value: "bar",
+      },
+      {
+        id: "22222",
+        guid: "22222",
+        name: "foo2",
+        fieldname: "foo2",
+        value: "bar2",
+      },
+      {
+        id: "33333",
+        guid: "33333",
+        name: "foo3",
+        fieldname: "foo3",
+        value: "bar3",
+      },
+    ],
+  };
+}
+
+add_task(async function test_valid() {
+  let { server, client } = getDummyServerAndClient();
+  let validator = new FormValidator();
+  let { problemData, clientRecords, records, deletedRecords } =
+    await validator.compareClientWithServer(client, server);
+  equal(clientRecords.length, 3);
+  equal(records.length, 3);
+  equal(deletedRecords.length, 0);
+  deepEqual(problemData, validator.emptyProblemData());
+});
+
+add_task(async function test_formValidatorIgnoresMissingClients() {
+  // Since history form records are not deleted from the server, the
+  // |FormValidator| shouldn't set the |missingClient| flag in |problemData|.
+  let { server, client } = getDummyServerAndClient();
+  client.pop();
+
+  let validator = new FormValidator();
+  let { problemData, clientRecords, records, deletedRecords } =
+    await validator.compareClientWithServer(client, server);
+
+  equal(clientRecords.length, 2);
+  equal(records.length, 3);
+  equal(deletedRecords.length, 0);
+
+  let expected = validator.emptyProblemData();
+  deepEqual(problemData, expected);
+});
diff --git a/src/zen/tests/mochitests/sync/test_forms_store.js b/src/zen/tests/mochitests/sync/test_forms_store.js
new file mode 100644
index 000000000..716487865
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_forms_store.js
@@ -0,0 +1,176 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+_(
+  "Make sure the form store follows the Store api and correctly accesses the backend form storage"
+);
+const { FormEngine } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/forms.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { SyncedRecordsTelemetry } = ChromeUtils.importESModule(
+  "resource://services-sync/telemetry.sys.mjs"
+);
+
+add_task(async function run_test() {
+  let engine = new FormEngine(Service);
+  await engine.initialize();
+  let store = engine._store;
+
+  async function applyEnsureNoFailures(records) {
+    let countTelemetry = new SyncedRecordsTelemetry();
+    Assert.equal(
+      (await store.applyIncomingBatch(records, countTelemetry)).length,
+      0
+    );
+  }
+
+  _("Remove any existing entries");
+  await store.wipe();
+  if ((await store.getAllIDs()).length) {
+    do_throw("Shouldn't get any ids!");
+  }
+
+  _("Add a form entry");
+  await applyEnsureNoFailures([
+    {
+      id: Utils.makeGUID(),
+      name: "name!!",
+      value: "value??",
+    },
+  ]);
+
+  _("Should have 1 entry now");
+  let id = "";
+  for (let _id in await store.getAllIDs()) {
+    if (id == "") {
+      id = _id;
+    } else {
+      do_throw("Should have only gotten one!");
+    }
+  }
+  Assert.ok(store.itemExists(id));
+
+  _("Should be able to find this entry as a dupe");
+  Assert.equal(
+    await engine._findDupe({ name: "name!!", value: "value??" }),
+    id
+  );
+
+  let rec = await store.createRecord(id);
+  _("Got record for id", id, rec);
+  Assert.equal(rec.name, "name!!");
+  Assert.equal(rec.value, "value??");
+
+  _("Create a non-existent id for delete");
+  Assert.ok((await store.createRecord("deleted!!")).deleted);
+
+  _("Try updating.. doesn't do anything yet");
+  await store.update({});
+
+  _("Remove all entries");
+  await store.wipe();
+  if ((await store.getAllIDs()).length) {
+    do_throw("Shouldn't get any ids!");
+  }
+
+  _("Add another entry");
+  await applyEnsureNoFailures([
+    {
+      id: Utils.makeGUID(),
+      name: "another",
+      value: "entry",
+    },
+  ]);
+  id = "";
+  for (let _id in await store.getAllIDs()) {
+    if (id == "") {
+      id = _id;
+    } else {
+      do_throw("Should have only gotten one!");
+    }
+  }
+
+  _("Change the id of the new entry to something else");
+  await store.changeItemID(id, "newid");
+
+  _("Make sure it's there");
+  Assert.ok(store.itemExists("newid"));
+
+  _("Remove the entry");
+  await store.remove({
+    id: "newid",
+  });
+  if ((await store.getAllIDs()).length) {
+    do_throw("Shouldn't get any ids!");
+  }
+
+  _("Removing the entry again shouldn't matter");
+  await store.remove({
+    id: "newid",
+  });
+  if ((await store.getAllIDs()).length) {
+    do_throw("Shouldn't get any ids!");
+  }
+
+  _("Add another entry to delete using applyIncomingBatch");
+  let toDelete = {
+    id: Utils.makeGUID(),
+    name: "todelete",
+    value: "entry",
+  };
+  await applyEnsureNoFailures([toDelete]);
+  id = "";
+  for (let _id in await store.getAllIDs()) {
+    if (id == "") {
+      id = _id;
+    } else {
+      do_throw("Should have only gotten one!");
+    }
+  }
+  Assert.ok(store.itemExists(id));
+  // mark entry as deleted
+  toDelete.id = id;
+  toDelete.deleted = true;
+  await applyEnsureNoFailures([toDelete]);
+  if ((await store.getAllIDs()).length) {
+    do_throw("Shouldn't get any ids!");
+  }
+
+  _("Add an entry to wipe");
+  await applyEnsureNoFailures([
+    {
+      id: Utils.makeGUID(),
+      name: "towipe",
+      value: "entry",
+    },
+  ]);
+
+  await store.wipe();
+
+  if ((await store.getAllIDs()).length) {
+    do_throw("Shouldn't get any ids!");
+  }
+
+  _("Ensure we work if formfill is disabled.");
+  Services.prefs.setBoolPref("browser.formfill.enable", false);
+  try {
+    // a search
+    if ((await store.getAllIDs()).length) {
+      do_throw("Shouldn't get any ids!");
+    }
+    // an update.
+    await applyEnsureNoFailures([
+      {
+        id: Utils.makeGUID(),
+        name: "some",
+        value: "entry",
+      },
+    ]);
+  } finally {
+    Services.prefs.clearUserPref("browser.formfill.enable");
+    await store.wipe();
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_forms_tracker.js b/src/zen/tests/mochitests/sync/test_forms_tracker.js
new file mode 100644
index 000000000..aee74381a
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_forms_tracker.js
@@ -0,0 +1,78 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { FormEngine } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/forms.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+add_task(async function run_test() {
+  _("Verify we've got an empty tracker to work with.");
+  let engine = new FormEngine(Service);
+  await engine.initialize();
+  let tracker = engine._tracker;
+
+  let changes = await tracker.getChangedIDs();
+  do_check_empty(changes);
+  Log.repository.rootLogger.addAppender(new Log.DumpAppender());
+
+  async function addEntry(name, value) {
+    await engine._store.create({ name, value });
+    await engine._tracker.asyncObserver.promiseObserversComplete();
+  }
+  async function removeEntry(name, value) {
+    let guid = await engine._findDupe({ name, value });
+    await engine._store.remove({ id: guid });
+    await engine._tracker.asyncObserver.promiseObserversComplete();
+  }
+
+  try {
+    _("Create an entry. Won't show because we haven't started tracking yet");
+    await addEntry("name", "John Doe");
+    changes = await tracker.getChangedIDs();
+    do_check_empty(changes);
+
+    _("Tell the tracker to start tracking changes.");
+    tracker.start();
+    await removeEntry("name", "John Doe");
+    await addEntry("email", "john@doe.com");
+    changes = await tracker.getChangedIDs();
+    do_check_attribute_count(changes, 2);
+
+    _("Notifying twice won't do any harm.");
+    tracker.start();
+    await addEntry("address", "Memory Lane");
+    changes = await tracker.getChangedIDs();
+    do_check_attribute_count(changes, 3);
+
+    _("Check that ignoreAll is respected");
+    await tracker.clearChangedIDs();
+    tracker.score = 0;
+    tracker.ignoreAll = true;
+    await addEntry("username", "johndoe123");
+    await addEntry("favoritecolor", "green");
+    await removeEntry("name", "John Doe");
+    tracker.ignoreAll = false;
+    changes = await tracker.getChangedIDs();
+    do_check_empty(changes);
+    equal(tracker.score, 0);
+
+    _("Let's stop tracking again.");
+    await tracker.clearChangedIDs();
+    await tracker.stop();
+    await removeEntry("address", "Memory Lane");
+    changes = await tracker.getChangedIDs();
+    do_check_empty(changes);
+
+    _("Notifying twice won't do any harm.");
+    await tracker.stop();
+    await removeEntry("email", "john@doe.com");
+    changes = await tracker.getChangedIDs();
+    do_check_empty(changes);
+  } finally {
+    _("Clean up.");
+    await engine._store.wipe();
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_fxa_node_reassignment.js b/src/zen/tests/mochitests/sync/test_fxa_node_reassignment.js
new file mode 100644
index 000000000..0fa7ee922
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_fxa_node_reassignment.js
@@ -0,0 +1,399 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+_("Test that node reassignment happens correctly using the FxA identity mgr.");
+// The node-reassignment logic is quite different for FxA than for the legacy
+// provider.  In particular, there's no special request necessary for
+// reassignment - it comes from the token server - so we need to ensure the
+// Fxa cluster manager grabs a new token.
+
+const { RESTRequest } = ChromeUtils.importESModule(
+  "resource://services-common/rest.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { Status } = ChromeUtils.importESModule(
+  "resource://services-sync/status.sys.mjs"
+);
+const { SyncAuthManager } = ChromeUtils.importESModule(
+  "resource://services-sync/sync_auth.sys.mjs"
+);
+
+add_task(async function setup() {
+  // Disables all built-in engines. Important for avoiding errors thrown by the
+  // add-ons engine.
+  await Service.engineManager.clear();
+
+  // Setup the sync auth manager.
+  Status.__authManager = Service.identity = new SyncAuthManager();
+});
+
+// API-compatible with SyncServer handler. Bind `handler` to something to use
+// as a ServerCollection handler.
+function handleReassign(handler, req, resp) {
+  resp.setStatusLine(req.httpVersion, 401, "Node reassignment");
+  resp.setHeader("Content-Type", "application/json");
+  let reassignBody = JSON.stringify({ error: "401inator in place" });
+  resp.bodyOutputStream.write(reassignBody, reassignBody.length);
+}
+
+var numTokenRequests = 0;
+
+function prepareServer(cbAfterTokenFetch) {
+  syncTestLogging();
+  let config = makeIdentityConfig({ username: "johndoe" });
+  // A server callback to ensure we don't accidentally hit the wrong endpoint
+  // after a node reassignment.
+  let callback = {
+    onRequest(req) {
+      let full = `${req.scheme}://${req.host}:${req.port}${req.path}`;
+      let expected = config.fxaccount.token.endpoint;
+      Assert.ok(
+        full.startsWith(expected),
+        `request made to ${full}, expected ${expected}`
+      );
+    },
+  };
+  Object.setPrototypeOf(callback, SyncServerCallback);
+  let server = new SyncServer(callback);
+  server.registerUser("johndoe");
+  server.start();
+
+  // Set the token endpoint for the initial token request that's done implicitly
+  // via configureIdentity.
+  config.fxaccount.token.endpoint = server.baseURI + "1.1/johndoe/";
+  // And future token fetches will do magic around numReassigns.
+  let numReassigns = 0;
+  return configureIdentity(config).then(() => {
+    Service.identity._tokenServerClient = {
+      getTokenUsingOAuth() {
+        return new Promise(res => {
+          // Build a new URL with trailing zeros for the SYNC_VERSION part - this
+          // will still be seen as equivalent by the test server, but different
+          // by sync itself.
+          numReassigns += 1;
+          let trailingZeros = new Array(numReassigns + 1).join("0");
+          let token = config.fxaccount.token;
+          token.endpoint = server.baseURI + "1.1" + trailingZeros + "/johndoe";
+          token.uid = config.username;
+          _(`test server saw token fetch - endpoint now ${token.endpoint}`);
+          numTokenRequests += 1;
+          res(token);
+          if (cbAfterTokenFetch) {
+            cbAfterTokenFetch();
+          }
+        });
+      },
+    };
+    return server;
+  });
+}
+
+function getReassigned() {
+  try {
+    return Services.prefs.getBoolPref("services.sync.lastSyncReassigned");
+  } catch (ex) {
+    if (ex.result != Cr.NS_ERROR_UNEXPECTED) {
+      do_throw(
+        "Got exception retrieving lastSyncReassigned: " + Log.exceptionStr(ex)
+      );
+    }
+  }
+  return false;
+}
+
+/**
+ * Make a test request to `url`, then watch the result of two syncs
+ * to ensure that a node request was made.
+ * Runs `between` between the two. This can be used to undo deliberate failure
+ * setup, detach observers, etc.
+ */
+async function syncAndExpectNodeReassignment(
+  server,
+  firstNotification,
+  between,
+  secondNotification,
+  url
+) {
+  _("Starting syncAndExpectNodeReassignment\n");
+  let deferred = Promise.withResolvers();
+  async function onwards() {
+    let numTokenRequestsBefore;
+    function onFirstSync() {
+      _("First sync completed.");
+      Svc.Obs.remove(firstNotification, onFirstSync);
+      Svc.Obs.add(secondNotification, onSecondSync);
+
+      Assert.equal(Service.clusterURL, "");
+
+      // Track whether we fetched a new token.
+      numTokenRequestsBefore = numTokenRequests;
+
+      // Allow for tests to clean up error conditions.
+      between();
+    }
+    function onSecondSync() {
+      _("Second sync completed.");
+      Svc.Obs.remove(secondNotification, onSecondSync);
+      Service.scheduler.clearSyncTriggers();
+
+      // Make absolutely sure that any event listeners are done with their work
+      // before we proceed.
+      waitForZeroTimer(function () {
+        _("Second sync nextTick.");
+        Assert.equal(
+          numTokenRequests,
+          numTokenRequestsBefore + 1,
+          "fetched a new token"
+        );
+        Service.startOver().then(() => {
+          server.stop(deferred.resolve);
+        });
+      });
+    }
+
+    Svc.Obs.add(firstNotification, onFirstSync);
+    await Service.sync();
+  }
+
+  // Make sure that we really do get a 401 (but we can only do that if we are
+  // already logged in, as the login process is what sets up the URLs)
+  if (Service.isLoggedIn) {
+    _("Making request to " + url + " which should 401");
+    let request = new RESTRequest(url);
+    await request.get();
+    Assert.equal(request.response.status, 401);
+    CommonUtils.nextTick(onwards);
+  } else {
+    _("Skipping preliminary validation check for a 401 as we aren't logged in");
+    CommonUtils.nextTick(onwards);
+  }
+  await deferred.promise;
+}
+
+// Check that when we sync we don't request a new token by default - our
+// test setup has configured the client with a valid token, and that token
+// should be used to form the cluster URL.
+add_task(async function test_single_token_fetch() {
+  enableValidationPrefs();
+
+  _("Test a normal sync only fetches 1 token");
+
+  let numTokenFetches = 0;
+
+  function afterTokenFetch() {
+    numTokenFetches++;
+  }
+
+  // Set the cluster URL to an "old" version - this is to ensure we don't
+  // use that old cached version for the first sync but prefer the value
+  // we got from the token (and as above, we are also checking we don't grab
+  // a new token). If the test actually attempts to connect to this URL
+  // it will crash.
+  Service.clusterURL = "http://example.com/";
+
+  let server = await prepareServer(afterTokenFetch);
+
+  Assert.ok(!Service.isLoggedIn, "not already logged in");
+  await Service.sync();
+  Assert.equal(Status.sync, SYNC_SUCCEEDED, "sync succeeded");
+  Assert.equal(numTokenFetches, 0, "didn't fetch a new token");
+  // A bit hacky, but given we know how prepareServer works we can deduce
+  // that clusterURL we expect.
+  let expectedClusterURL = server.baseURI + "1.1/johndoe/";
+  Assert.equal(Service.clusterURL, expectedClusterURL);
+  await Service.startOver();
+  await promiseStopServer(server);
+});
+
+add_task(async function test_momentary_401_engine() {
+  enableValidationPrefs();
+
+  _("Test a failure for engine URLs that's resolved by reassignment.");
+  let server = await prepareServer();
+  let john = server.user("johndoe");
+
+  _("Enabling the Rotary engine.");
+  let { engine, syncID, tracker } = await registerRotaryEngine();
+
+  // We need the server to be correctly set up prior to experimenting. Do this
+  // through a sync.
+  let global = {
+    syncID: Service.syncID,
+    storageVersion: STORAGE_VERSION,
+    rotary: { version: engine.version, syncID },
+  };
+  john.createCollection("meta").insert("global", global);
+
+  _("First sync to prepare server contents.");
+  await Service.sync();
+
+  _("Setting up Rotary collection to 401.");
+  let rotary = john.createCollection("rotary");
+  let oldHandler = rotary.collectionHandler;
+  rotary.collectionHandler = handleReassign.bind(this, undefined);
+
+  // We want to verify that the clusterURL pref has been cleared after a 401
+  // inside a sync. Flag the Rotary engine to need syncing.
+  john.collection("rotary").timestamp += 1000;
+
+  function between() {
+    _("Undoing test changes.");
+    rotary.collectionHandler = oldHandler;
+
+    function onLoginStart() {
+      // lastSyncReassigned shouldn't be cleared until a sync has succeeded.
+      _("Ensuring that lastSyncReassigned is still set at next sync start.");
+      Svc.Obs.remove("weave:service:login:start", onLoginStart);
+      Assert.ok(getReassigned());
+    }
+
+    _("Adding observer that lastSyncReassigned is still set on login.");
+    Svc.Obs.add("weave:service:login:start", onLoginStart);
+  }
+
+  await syncAndExpectNodeReassignment(
+    server,
+    "weave:service:sync:finish",
+    between,
+    "weave:service:sync:finish",
+    Service.storageURL + "rotary"
+  );
+
+  await tracker.clearChangedIDs();
+  await Service.engineManager.unregister(engine);
+});
+
+// This test ends up being a failing info fetch *after we're already logged in*.
+add_task(async function test_momentary_401_info_collections_loggedin() {
+  enableValidationPrefs();
+
+  _(
+    "Test a failure for info/collections after login that's resolved by reassignment."
+  );
+  let server = await prepareServer();
+
+  _("First sync to prepare server contents.");
+  await Service.sync();
+
+  _("Arrange for info/collections to return a 401.");
+  let oldHandler = server.toplevelHandlers.info;
+  server.toplevelHandlers.info = handleReassign;
+
+  function undo() {
+    _("Undoing test changes.");
+    server.toplevelHandlers.info = oldHandler;
+  }
+
+  Assert.ok(Service.isLoggedIn, "already logged in");
+
+  await syncAndExpectNodeReassignment(
+    server,
+    "weave:service:sync:error",
+    undo,
+    "weave:service:sync:finish",
+    Service.infoURL
+  );
+});
+
+// This test ends up being a failing info fetch *before we're logged in*.
+// In this case we expect to recover during the login phase - so the first
+// sync succeeds.
+add_task(async function test_momentary_401_info_collections_loggedout() {
+  enableValidationPrefs();
+
+  _(
+    "Test a failure for info/collections before login that's resolved by reassignment."
+  );
+
+  let oldHandler;
+  let sawTokenFetch = false;
+
+  function afterTokenFetch() {
+    // After a single token fetch, we undo our evil handleReassign hack, so
+    // the next /info request returns the collection instead of a 401
+    server.toplevelHandlers.info = oldHandler;
+    sawTokenFetch = true;
+  }
+
+  let server = await prepareServer(afterTokenFetch);
+
+  // Return a 401 for the next /info request - it will be reset immediately
+  // after a new token is fetched.
+  oldHandler = server.toplevelHandlers.info;
+  server.toplevelHandlers.info = handleReassign;
+
+  Assert.ok(!Service.isLoggedIn, "not already logged in");
+
+  await Service.sync();
+  Assert.equal(Status.sync, SYNC_SUCCEEDED, "sync succeeded");
+  // sync was successful - check we grabbed a new token.
+  Assert.ok(sawTokenFetch, "a new token was fetched by this test.");
+  // and we are done.
+  await Service.startOver();
+  await promiseStopServer(server);
+});
+
+// This test ends up being a failing meta/global fetch *after we're already logged in*.
+add_task(async function test_momentary_401_storage_loggedin() {
+  enableValidationPrefs();
+
+  _(
+    "Test a failure for any storage URL after login that's resolved by" +
+      "reassignment."
+  );
+  let server = await prepareServer();
+
+  _("First sync to prepare server contents.");
+  await Service.sync();
+
+  _("Arrange for meta/global to return a 401.");
+  let oldHandler = server.toplevelHandlers.storage;
+  server.toplevelHandlers.storage = handleReassign;
+
+  function undo() {
+    _("Undoing test changes.");
+    server.toplevelHandlers.storage = oldHandler;
+  }
+
+  Assert.ok(Service.isLoggedIn, "already logged in");
+
+  await syncAndExpectNodeReassignment(
+    server,
+    "weave:service:sync:error",
+    undo,
+    "weave:service:sync:finish",
+    Service.storageURL + "meta/global"
+  );
+});
+
+// This test ends up being a failing meta/global fetch *before we've logged in*.
+add_task(async function test_momentary_401_storage_loggedout() {
+  enableValidationPrefs();
+
+  _(
+    "Test a failure for any storage URL before login, not just engine parts. " +
+      "Resolved by reassignment."
+  );
+  let server = await prepareServer();
+
+  // Return a 401 for all storage requests.
+  let oldHandler = server.toplevelHandlers.storage;
+  server.toplevelHandlers.storage = handleReassign;
+
+  function undo() {
+    _("Undoing test changes.");
+    server.toplevelHandlers.storage = oldHandler;
+  }
+
+  Assert.ok(!Service.isLoggedIn, "already logged in");
+
+  await syncAndExpectNodeReassignment(
+    server,
+    "weave:service:login:error",
+    undo,
+    "weave:service:sync:finish",
+    Service.storageURL + "meta/global"
+  );
+});
diff --git a/src/zen/tests/mochitests/sync/test_fxa_service_cluster.js b/src/zen/tests/mochitests/sync/test_fxa_service_cluster.js
new file mode 100644
index 000000000..0203d01ef
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_fxa_service_cluster.js
@@ -0,0 +1,58 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { initializeIdentityWithTokenServerResponse } =
+  ChromeUtils.importESModule(
+    "resource://testing-common/services/sync/fxa_utils.sys.mjs"
+  );
+
+add_task(async function test_findCluster() {
+  _("Test FxA _findCluster()");
+
+  _("_findCluster() throws on 500 errors.");
+  initializeIdentityWithTokenServerResponse({
+    status: 500,
+    headers: [],
+    body: "",
+  });
+
+  await Assert.rejects(
+    Service.identity._findCluster(),
+    /TokenServerClientServerError/
+  );
+
+  _("_findCluster() returns null on authentication errors.");
+  initializeIdentityWithTokenServerResponse({
+    status: 401,
+    headers: { "content-type": "application/json" },
+    body: "{}",
+  });
+
+  let cluster = await Service.identity._findCluster();
+  Assert.strictEqual(cluster, null);
+
+  _("_findCluster() works with correct tokenserver response.");
+  let endpoint = "http://example.com/something";
+  initializeIdentityWithTokenServerResponse({
+    status: 200,
+    headers: { "content-type": "application/json" },
+    body: JSON.stringify({
+      api_endpoint: endpoint,
+      duration: 300,
+      id: "id",
+      key: "key",
+      uid: "uid",
+    }),
+  });
+
+  cluster = await Service.identity._findCluster();
+  // The cluster manager ensures a trailing "/"
+  Assert.strictEqual(cluster, endpoint + "/");
+
+  for (const pref of Svc.PrefBranch.getChildList("")) {
+    Svc.PrefBranch.clearUserPref(pref);
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_glean.js b/src/zen/tests/mochitests/sync/test_glean.js
new file mode 100644
index 000000000..ffa768ffa
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_glean.js
@@ -0,0 +1,1387 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { WBORecord } = ChromeUtils.importESModule(
+  "resource://services-sync/record.sys.mjs"
+);
+const { RotaryEngine } = ChromeUtils.importESModule(
+  "resource://testing-common/services/sync/rotaryengine.sys.mjs"
+);
+const { getFxAccountsSingleton } = ChromeUtils.importESModule(
+  "resource://gre/modules/FxAccounts.sys.mjs"
+);
+const fxAccounts = getFxAccountsSingleton();
+
+function SteamStore(engine) {
+  Store.call(this, "Steam", engine);
+}
+Object.setPrototypeOf(SteamStore.prototype, Store.prototype);
+
+function SteamTracker(name, engine) {
+  LegacyTracker.call(this, name || "Steam", engine);
+}
+Object.setPrototypeOf(SteamTracker.prototype, LegacyTracker.prototype);
+
+function SteamEngine(service) {
+  SyncEngine.call(this, "steam", service);
+}
+
+SteamEngine.prototype = {
+  _storeObj: SteamStore,
+  _trackerObj: SteamTracker,
+  _errToThrow: null,
+  problemsToReport: null,
+  async _sync() {
+    if (this._errToThrow) {
+      throw this._errToThrow;
+    }
+  },
+  getValidator() {
+    return new SteamValidator();
+  },
+};
+Object.setPrototypeOf(SteamEngine.prototype, SyncEngine.prototype);
+
+function BogusEngine(service) {
+  SyncEngine.call(this, "bogus", service);
+}
+
+BogusEngine.prototype = Object.create(SteamEngine.prototype);
+
+class SteamValidator {
+  async canValidate() {
+    return true;
+  }
+
+  async validate(engine) {
+    return {
+      problems: new SteamValidationProblemData(engine.problemsToReport),
+      version: 1,
+      duration: 0,
+      recordCount: 0,
+    };
+  }
+}
+
+class SteamValidationProblemData {
+  constructor(problemsToReport = []) {
+    this.problemsToReport = problemsToReport;
+  }
+
+  getSummary() {
+    return this.problemsToReport;
+  }
+}
+
+async function cleanAndGo(engine, server) {
+  await engine._tracker.clearChangedIDs();
+  for (const pref of Svc.PrefBranch.getChildList("")) {
+    Svc.PrefBranch.clearUserPref(pref);
+  }
+  syncTestLogging();
+  Service.recordManager.clearCache();
+  await promiseStopServer(server);
+}
+
+async function sync_engine(engine, errorRegex = undefined) {
+  // Clear out status so failures from previous syncs won't show in the record.
+  let { Status } = ChromeUtils.importESModule(
+    "resource://services-sync/status.sys.mjs"
+  );
+  Status._engines = {};
+  Status.partial = false;
+  // Neuter the scheduler as it interacts badly with some of the tests - the
+  // engine being synced usually isn't the registered engine, so we see
+  // scored incremented and not removed, which schedules unexpected syncs.
+  let oldObserve = Service.scheduler.observe;
+  Service.scheduler.observe = () => {};
+  try {
+    Svc.Obs.notify("weave:service:sync:start");
+    let caughtError;
+    try {
+      await engine.sync();
+    } catch (e) {
+      caughtError = e;
+    }
+    if (caughtError) {
+      ok(
+        errorRegex.test(JSON.stringify(caughtError)),
+        "Engine sync error expected."
+      );
+      Svc.Obs.notify("weave:service:sync:error", caughtError);
+    } else {
+      ok(!errorRegex, "No engine sync error expected.");
+      Svc.Obs.notify("weave:service:sync:finish");
+    }
+  } finally {
+    Service.scheduler.observe = oldObserve;
+  }
+}
+
+add_setup(async function () {
+  // Avoid addon manager complaining about not being initialized
+  await Service.engineManager.unregister("addons");
+  await Service.engineManager.unregister("extension-storage");
+
+  do_get_profile(); // FOG requires a profile dir.
+  Services.fog.initializeFOG();
+
+  // We're not using `wait_for_ping` which means we aren't implicitly calling
+  // get_sync_test_telemetry() so often. So call it here for its side effects.
+  let telem = get_sync_test_telemetry();
+  // Unlike the telemetry tests, we actually want the Glean APIs to be called.
+  // So pretend we're in production.
+  telem.isProductionSyncUser = () => true;
+});
+
+add_task(async function test_basic() {
+  enableValidationPrefs();
+
+  let helper = track_collections_helper();
+  let upd = helper.with_updated_collection;
+
+  let handlers = {
+    "/1.1/johndoe/info/collections": helper.handler,
+    "/1.1/johndoe/storage/crypto/keys": upd(
+      "crypto",
+      new ServerWBO("keys").handler()
+    ),
+    "/1.1/johndoe/storage/meta/global": upd(
+      "meta",
+      new ServerWBO("global").handler()
+    ),
+  };
+
+  let collections = [
+    "clients",
+    "bookmarks",
+    "forms",
+    "history",
+    "passwords",
+    "prefs",
+    "tabs",
+  ];
+
+  for (let coll of collections) {
+    handlers["/1.1/johndoe/storage/" + coll] = upd(
+      coll,
+      new ServerCollection({}, true).handler()
+    );
+  }
+
+  let server = httpd_setup(handlers);
+  await configureIdentity({ username: "johndoe" }, server);
+
+  // Test that a basic batch can make it.
+  await GleanPings.sync.testSubmission(
+    reason => {
+      equal(reason, "schedule");
+      Glean.syncs.syncs.testGetValue().forEach(assert_success_sync);
+    },
+    async () => {
+      await Service.sync();
+    }
+  );
+
+  for (const pref of Svc.PrefBranch.getChildList("")) {
+    Svc.PrefBranch.clearUserPref(pref);
+  }
+  await promiseStopServer(server);
+});
+
+add_task(async function test_processIncoming_error() {
+  let engine = Service.engineManager.get("bookmarks");
+  await engine.initialize();
+  let store = engine._store;
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+  let collection = server.user("foo").collection("bookmarks");
+  try {
+    // Create a bogus record that when synced down will provoke a
+    // network error which in turn provokes an exception in _processIncoming.
+    const BOGUS_GUID = "zzzzzzzzzzzz";
+    let bogus_record = collection.insert(BOGUS_GUID, "I'm a bogus record!");
+    bogus_record.get = function get() {
+      throw new Error("Sync this!");
+    };
+    // Make it 10 minutes old so it will only be synced in the toFetch phase.
+    bogus_record.modified = Date.now() / 1000 - 60 * 10;
+    await engine.setLastSync(Date.now() / 1000 - 60);
+    engine.toFetch = new SerializableSet([BOGUS_GUID]);
+
+    await GleanPings.sync.testSubmission(
+      reason => {
+        equal(reason, "schedule");
+        equal(Glean.syncs.hashedFxaUid.testGetValue(), "f".repeat(32));
+
+        const syncs = Glean.syncs.syncs.testGetValue();
+        equal(syncs.length, 1);
+
+        const sync = syncs[0];
+        deepEqual(sync.failureReason, { name: "httperror", code: 500 });
+        equal(sync.engines.length, 1);
+
+        const e = sync.engines[0];
+        equal(e.name, "bookmarks-buffered");
+        deepEqual(e.failureReason, { name: "httperror", code: 500 });
+      },
+      async () => {
+        await sync_engine(engine, /500 Internal Server Error/);
+      }
+    );
+  } finally {
+    await store.wipe();
+    await cleanAndGo(engine, server);
+  }
+});
+
+add_task(async function test_uploading() {
+  // Clear out status, so failures from previous syncs won't show up in the
+  // telemetry ping.
+  let { Status } = ChromeUtils.importESModule(
+    "resource://services-sync/status.sys.mjs"
+  );
+  Status._engines = {};
+  Status.partial = false;
+
+  let engine = Service.engineManager.get("bookmarks");
+  await engine.initialize();
+  let store = engine._store;
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  let bmk = await PlacesUtils.bookmarks.insert({
+    parentGuid: PlacesUtils.bookmarks.toolbarGuid,
+    url: "http://getfirefox.com/",
+    title: "Get Firefox!",
+  });
+
+  try {
+    await GleanPings.sync.testSubmission(
+      reason => {
+        equal(reason, "schedule");
+        equal(Glean.syncs.hashedFxaUid.testGetValue(), "f".repeat(32));
+
+        const syncs = Glean.syncs.syncs.testGetValue();
+        equal(syncs.length, 1);
+
+        const sync = syncs[0];
+        equal(sync.engines.length, 1);
+
+        const e = sync.engines[0];
+        equal(e.name, "bookmarks-buffered");
+        greater(e.outgoing[0].sent, 0);
+        ok(!e.incoming);
+      },
+      async () => {
+        await sync_engine(engine);
+      }
+    );
+
+    await PlacesUtils.bookmarks.update({
+      guid: bmk.guid,
+      title: "New Title",
+    });
+
+    await store.wipe();
+    await engine.resetClient();
+    // We don't sync via the service, so don't re-hit info/collections, so
+    // lastModified remaning at zero breaks things subtly...
+    engine.lastModified = null;
+
+    await GleanPings.sync.testSubmission(
+      reason => {
+        equal(reason, "schedule");
+        equal(Glean.syncs.hashedFxaUid.testGetValue(), "f".repeat(32));
+
+        const syncs = Glean.syncs.syncs.testGetValue();
+        equal(syncs.length, 1);
+
+        const sync = syncs[0];
+        equal(sync.engines.length, 1);
+
+        const e = sync.engines[0];
+        equal(e.name, "bookmarks-buffered");
+        equal(e.outgoing.length, 1);
+        ok(!!e.incoming);
+      },
+      async () => {
+        await sync_engine(engine);
+      }
+    );
+  } finally {
+    // Clean up.
+    await store.wipe();
+    await cleanAndGo(engine, server);
+  }
+});
+
+add_task(async function test_upload_failed() {
+  let collection = new ServerCollection();
+  collection._wbos.flying = new ServerWBO("flying");
+
+  let server = sync_httpd_setup({
+    "/1.1/foo/storage/rotary": collection.handler(),
+  });
+
+  await SyncTestingInfrastructure(server);
+  await configureIdentity({ username: "foo" }, server);
+
+  let engine = new RotaryEngine(Service);
+  engine._store.items = {
+    flying: "LNER Class A3 4472",
+    scotsman: "Flying Scotsman",
+    peppercorn: "Peppercorn Class",
+  };
+  const FLYING_CHANGED = 12345;
+  const SCOTSMAN_CHANGED = 23456;
+  const PEPPERCORN_CHANGED = 34567;
+  await engine._tracker.addChangedID("flying", FLYING_CHANGED);
+  await engine._tracker.addChangedID("scotsman", SCOTSMAN_CHANGED);
+  await engine._tracker.addChangedID("peppercorn", PEPPERCORN_CHANGED);
+
+  let syncID = await engine.resetLocalSyncID();
+  let meta_global = Service.recordManager.set(
+    engine.metaURL,
+    new WBORecord(engine.metaURL)
+  );
+  meta_global.payload.engines = { rotary: { version: engine.version, syncID } };
+
+  try {
+    await engine.setLastSync(123); // needs to be non-zero so that tracker is queried
+    let changes = await engine._tracker.getChangedIDs();
+    _(
+      `test_upload_failed: Rotary tracker contents at first sync: ${JSON.stringify(
+        changes
+      )}`
+    );
+    engine.enabled = true;
+    await GleanPings.sync.testSubmission(
+      reason => {
+        equal(reason, "schedule");
+        equal(Glean.syncs.hashedFxaUid.testGetValue(), "f".repeat(32));
+
+        const syncs = Glean.syncs.syncs.testGetValue();
+        equal(syncs.length, 1);
+
+        const sync = syncs[0];
+        equal(sync.engines.length, 1);
+
+        const e = sync.engines[0];
+        equal(e.incoming, null);
+        deepEqual(e.outgoing, [
+          {
+            sent: 3,
+            failed: 2,
+            failedReasons: [
+              { name: "scotsman", count: 1 },
+              { name: "peppercorn", count: 1 },
+            ],
+          },
+        ]);
+      },
+      async () => {
+        await sync_engine(engine);
+      }
+    );
+
+    await engine.setLastSync(123);
+
+    changes = await engine._tracker.getChangedIDs();
+    _(
+      `test_upload_failed: Rotary tracker contents at second sync: ${JSON.stringify(
+        changes
+      )}`
+    );
+    await GleanPings.sync.testSubmission(
+      reason => {
+        equal(reason, "schedule");
+        equal(Glean.syncs.hashedFxaUid.testGetValue(), "f".repeat(32));
+
+        const syncs = Glean.syncs.syncs.testGetValue();
+        equal(syncs.length, 1);
+
+        const sync = syncs[0];
+        equal(sync.engines.length, 1);
+
+        const e = sync.engines[0];
+        deepEqual(e.outgoing, [
+          {
+            sent: 2,
+            failed: 2,
+            failedReasons: [
+              { name: "scotsman", count: 1 },
+              { name: "peppercorn", count: 1 },
+            ],
+          },
+        ]);
+      },
+      async () => {
+        await sync_engine(engine);
+      }
+    );
+  } finally {
+    await cleanAndGo(engine, server);
+    await engine.finalize();
+  }
+});
+
+add_task(async function test_sync_partialUpload() {
+  let collection = new ServerCollection();
+  let server = sync_httpd_setup({
+    "/1.1/foo/storage/rotary": collection.handler(),
+  });
+  await SyncTestingInfrastructure(server);
+  await generateNewKeys(Service.collectionKeys);
+
+  let engine = new RotaryEngine(Service);
+  await engine.setLastSync(123);
+
+  // Create a bunch of records (and server side handlers)
+  for (let i = 0; i < 234; i++) {
+    let id = "record-no-" + i;
+    engine._store.items[id] = "Record No. " + i;
+    await engine._tracker.addChangedID(id, i);
+    // Let two items in the first upload batch fail.
+    if (i != 23 && i != 42) {
+      collection.insert(id);
+    }
+  }
+
+  let syncID = await engine.resetLocalSyncID();
+  let meta_global = Service.recordManager.set(
+    engine.metaURL,
+    new WBORecord(engine.metaURL)
+  );
+  meta_global.payload.engines = { rotary: { version: engine.version, syncID } };
+
+  try {
+    let changes = await engine._tracker.getChangedIDs();
+    _(
+      `test_sync_partialUpload: Rotary tracker contents at first sync: ${JSON.stringify(
+        changes
+      )}`
+    );
+    engine.enabled = true;
+    await GleanPings.sync.testSubmission(
+      reason => {
+        equal(reason, "schedule");
+        equal(Glean.syncs.hashedFxaUid.testGetValue(), "f".repeat(32));
+
+        const syncs = Glean.syncs.syncs.testGetValue();
+        equal(syncs.length, 1);
+
+        const sync = syncs[0];
+        ok(!sync.failureReason);
+        equal(sync.engines.length, 1);
+
+        const e = sync.engines[0];
+        equal(e.name, "rotary");
+        ok(!e.incoming);
+        ok(!e.failureReason);
+        deepEqual(e.outgoing, [
+          {
+            sent: 234,
+            failed: 2,
+            failedReasons: [
+              { name: "record-no-23", count: 1 },
+              { name: "record-no-42", count: 1 },
+            ],
+          },
+        ]);
+      },
+      async () => {
+        await sync_engine(engine);
+      }
+    );
+
+    collection.post = function () {
+      throw new Error("Failure");
+    };
+
+    engine._store.items["record-no-1000"] = "Record No. 1000";
+    await engine._tracker.addChangedID("record-no-1000", 1000);
+    collection.insert("record-no-1000", 1000);
+
+    await engine.setLastSync(123);
+
+    changes = await engine._tracker.getChangedIDs();
+    _(
+      `test_sync_partialUpload: Rotary tracker contents at second sync: ${JSON.stringify(
+        changes
+      )}`
+    );
+    // It would be nice if we had a more descriptive error for this...
+    const uploadFailureError = {
+      name: "httperror",
+      code: 500,
+    };
+    await GleanPings.sync.testSubmission(
+      reason => {
+        equal(reason, "schedule");
+        equal(Glean.syncs.hashedFxaUid.testGetValue(), "f".repeat(32));
+
+        const syncs = Glean.syncs.syncs.testGetValue();
+        equal(syncs.length, 1);
+
+        const sync = syncs[0];
+        deepEqual(sync.failureReason, uploadFailureError);
+        equal(sync.engines.length, 1);
+
+        const e = sync.engines[0];
+        equal(e.name, "rotary");
+        deepEqual(e.incoming, {
+          failed: 1,
+          failedReasons: [
+            { name: "No ciphertext: nothing to decrypt?", count: 1 },
+          ],
+        });
+        ok(!e.outgoing);
+        deepEqual(e.failureReason, uploadFailureError);
+      },
+      async () => {
+        await sync_engine(engine, /500 Internal Server Error/);
+      }
+    );
+  } finally {
+    await cleanAndGo(engine, server);
+    await engine.finalize();
+  }
+});
+
+add_task(async function test_generic_engine_fail() {
+  enableValidationPrefs();
+
+  await Service.engineManager.register(SteamEngine);
+  let engine = Service.engineManager.get("steam");
+  engine.enabled = true;
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+  let e = new Error("generic failure message");
+  engine._errToThrow = e;
+
+  try {
+    const changes = await engine._tracker.getChangedIDs();
+    _(
+      `test_generic_engine_fail: Steam tracker contents: ${JSON.stringify(
+        changes
+      )}`
+    );
+    await GleanPings.sync.testSubmission(
+      reason => {
+        equal(reason, "schedule");
+        equal(Glean.syncs.hashedFxaUid.testGetValue(), "f".repeat(32));
+
+        const syncs = Glean.syncs.syncs.testGetValue();
+        equal(syncs.length, 1);
+
+        const sync = syncs[0];
+        equal(sync.status.service, SYNC_FAILED_PARTIAL);
+        deepEqual(
+          sync.engines.find(err => err.name === "steam").failureReason,
+          {
+            name: "unexpectederror",
+            error: String(e),
+          }
+        );
+      },
+      async () => {
+        await Service.sync();
+      }
+    );
+  } finally {
+    await cleanAndGo(engine, server);
+    await Service.engineManager.unregister(engine);
+  }
+});
+
+add_task(async function test_engine_fail_weird_errors() {
+  enableValidationPrefs();
+  await Service.engineManager.register(SteamEngine);
+  let engine = Service.engineManager.get("steam");
+  engine.enabled = true;
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+  try {
+    let msg = "Bad things happened!";
+    engine._errToThrow = { message: msg };
+    await GleanPings.sync.testSubmission(
+      reason => {
+        equal(reason, "schedule");
+        equal(Glean.syncs.hashedFxaUid.testGetValue(), "f".repeat(32));
+
+        const syncs = Glean.syncs.syncs.testGetValue();
+        equal(syncs.length, 1);
+
+        const sync = syncs[0];
+        equal(sync.status.service, SYNC_FAILED_PARTIAL);
+        deepEqual(
+          sync.engines.find(err => err.name === "steam").failureReason,
+          {
+            name: "unexpectederror",
+            error: msg,
+          }
+        );
+      },
+      async () => {
+        await Service.sync();
+      }
+    );
+    let e = { msg };
+    engine._errToThrow = e;
+    await GleanPings.sync.testSubmission(
+      reason => {
+        equal(reason, "schedule");
+        equal(Glean.syncs.hashedFxaUid.testGetValue(), "f".repeat(32));
+
+        const syncs = Glean.syncs.syncs.testGetValue();
+        equal(syncs.length, 1);
+
+        const sync = syncs[0];
+        equal(sync.status.service, SYNC_FAILED_PARTIAL);
+        deepEqual(
+          sync.engines.find(err => err.name === "steam").failureReason,
+          {
+            name: "unexpectederror",
+            error: JSON.stringify(e),
+          }
+        );
+      },
+      async () => {
+        await Service.sync();
+      }
+    );
+  } finally {
+    await cleanAndGo(engine, server);
+    Service.engineManager.unregister(engine);
+  }
+});
+
+add_task(async function test_overrideTelemetryName() {
+  enableValidationPrefs(["steam"]);
+
+  await Service.engineManager.register(SteamEngine);
+  let engine = Service.engineManager.get("steam");
+  engine.overrideTelemetryName = "steam-but-better";
+  engine.enabled = true;
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  const problemsToReport = [
+    { name: "someProblem", count: 123 },
+    { name: "anotherProblem", count: 456 },
+  ];
+
+  try {
+    info("Sync with validation problems");
+    engine.problemsToReport = problemsToReport;
+    await GleanPings.sync.testSubmission(
+      reason => {
+        equal(reason, "schedule");
+        equal(Glean.syncs.hashedFxaUid.testGetValue(), "f".repeat(32));
+
+        const syncs = Glean.syncs.syncs.testGetValue();
+        equal(syncs.length, 1);
+
+        const sync = syncs[0];
+        ok(!sync.engines.find(e => e.name === "steam"));
+        const eng = sync.engines.find(e => e.name === "steam-but-better");
+        ok(eng);
+        delete eng.validation.took; // can't compare real times.
+        deepEqual(
+          eng.validation,
+          {
+            version: 1,
+            checked: 0,
+            problems: problemsToReport,
+          },
+          "Should include validation report with overridden name"
+        );
+      },
+      async () => {
+        await Service.sync();
+      }
+    );
+
+    info("Sync without validation problems");
+    engine.problemsToReport = null;
+    await GleanPings.sync.testSubmission(
+      reason => {
+        equal(reason, "schedule");
+        equal(Glean.syncs.hashedFxaUid.testGetValue(), "f".repeat(32));
+
+        const syncs = Glean.syncs.syncs.testGetValue();
+        equal(syncs.length, 1);
+
+        const sync = syncs[0];
+        ok(!sync.engines.find(e => e.name === "steam"));
+        const eng = sync.engines.find(e => e.name === "steam-but-better");
+        ok(eng);
+        ok(
+          !eng.validation,
+          "Should not include validation report when there are no problems"
+        );
+      },
+      async () => {
+        await Service.sync();
+      }
+    );
+  } finally {
+    await cleanAndGo(engine, server);
+    await Service.engineManager.unregister(engine);
+  }
+});
+
+add_task(async function test_engine_fail_ioerror() {
+  enableValidationPrefs();
+
+  await Service.engineManager.register(SteamEngine);
+  let engine = Service.engineManager.get("steam");
+  engine.enabled = true;
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+  // create an IOError to re-throw as part of Sync.
+  try {
+    // (Note that fakeservices.js has replaced Utils.jsonMove etc, but for
+    // this test we need the real one so we get real exceptions from the
+    // filesystem.)
+    await Utils._real_jsonMove("file-does-not-exist", "anything", {});
+  } catch (ex) {
+    engine._errToThrow = ex;
+  }
+  ok(engine._errToThrow, "expecting exception");
+
+  try {
+    const changes = await engine._tracker.getChangedIDs();
+    _(
+      `test_engine_fail_ioerror: Steam tracker contents: ${JSON.stringify(
+        changes
+      )}`
+    );
+    await GleanPings.sync.testSubmission(
+      reason => {
+        equal(reason, "schedule");
+        equal(Glean.syncs.hashedFxaUid.testGetValue(), "f".repeat(32));
+
+        const syncs = Glean.syncs.syncs.testGetValue();
+        equal(syncs.length, 1);
+
+        const sync = syncs[0];
+        equal(sync.status.service, SYNC_FAILED_PARTIAL);
+        const failureReason = sync.engines.find(
+          e => e.name === "steam"
+        ).failureReason;
+        equal(failureReason.name, "unexpectederror");
+        // ensure the profile dir in the exception message has been stripped.
+        ok(
+          !failureReason.error.includes(PathUtils.profileDir),
+          failureReason.error
+        );
+        ok(failureReason.error.includes("[profileDir]"), failureReason.error);
+      },
+      async () => {
+        await Service.sync();
+      }
+    );
+  } finally {
+    await cleanAndGo(engine, server);
+    await Service.engineManager.unregister(engine);
+  }
+});
+
+add_task(async function test_clean_urls() {
+  enableValidationPrefs();
+
+  await Service.engineManager.register(SteamEngine);
+  let engine = Service.engineManager.get("steam");
+  engine.enabled = true;
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+  engine._errToThrow = new TypeError(
+    "http://www.google .com is not a valid URL."
+  );
+
+  try {
+    const changes = await engine._tracker.getChangedIDs();
+    _(`test_clean_urls: Steam tracker contents: ${JSON.stringify(changes)}`);
+    await GleanPings.sync.testSubmission(
+      reason => {
+        equal(reason, "schedule");
+        equal(Glean.syncs.hashedFxaUid.testGetValue(), "f".repeat(32));
+
+        const syncs = Glean.syncs.syncs.testGetValue();
+        equal(syncs.length, 1);
+
+        const sync = syncs[0];
+        equal(sync.status.service, SYNC_FAILED_PARTIAL);
+        const failureReason = sync.engines.find(
+          e => e.name === "steam"
+        ).failureReason;
+        equal(failureReason.name, "unexpectederror");
+        equal(failureReason.error, "<URL> is not a valid URL.");
+      },
+      async () => {
+        await Service.sync();
+      }
+    );
+    // Handle other errors that include urls.
+    engine._errToThrow =
+      "Other error message that includes some:url/foo/bar/ in it.";
+    await GleanPings.sync.testSubmission(
+      reason => {
+        equal(reason, "schedule");
+        equal(Glean.syncs.hashedFxaUid.testGetValue(), "f".repeat(32));
+
+        const syncs = Glean.syncs.syncs.testGetValue();
+        equal(syncs.length, 1);
+
+        const sync = syncs[0];
+        equal(sync.status.service, SYNC_FAILED_PARTIAL);
+        const failureReason = sync.engines.find(
+          e => e.name === "steam"
+        ).failureReason;
+        equal(failureReason.name, "unexpectederror");
+        equal(
+          failureReason.error,
+          "Other error message that includes <URL> in it."
+        );
+      },
+      async () => {
+        await Service.sync();
+      }
+    );
+  } finally {
+    await cleanAndGo(engine, server);
+    await Service.engineManager.unregister(engine);
+  }
+});
+
+// Arrange for a sync to hit a "real" OS error during a sync and make sure it's sanitized.
+add_task(async function test_clean_real_os_error() {
+  enableValidationPrefs();
+
+  // Simulate a real error.
+  await Service.engineManager.register(SteamEngine);
+  let engine = Service.engineManager.get("steam");
+  engine.enabled = true;
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+  let path = PathUtils.join(PathUtils.profileDir, "no", "such", "path.json");
+  try {
+    await IOUtils.readJSON(path);
+    throw new Error("should fail to read the file");
+  } catch (ex) {
+    engine._errToThrow = ex;
+  }
+
+  try {
+    const changes = await engine._tracker.getChangedIDs();
+    _(`test_clean_urls: Steam tracker contents: ${JSON.stringify(changes)}`);
+    await GleanPings.sync.testSubmission(
+      reason => {
+        equal(reason, "schedule");
+        equal(Glean.syncs.hashedFxaUid.testGetValue(), "f".repeat(32));
+
+        const syncs = Glean.syncs.syncs.testGetValue();
+        equal(syncs.length, 1);
+
+        const sync = syncs[0];
+        equal(sync.status.service, SYNC_FAILED_PARTIAL);
+        const failureReason = sync.engines.find(
+          e => e.name === "steam"
+        ).failureReason;
+        equal(failureReason.name, "unexpectederror");
+        equal(
+          failureReason.error,
+          "OS error [File/Path not found] Could not open `[profileDir]/no/such/path.json': file does not exist"
+        );
+      },
+      async () => {
+        await Service.sync();
+      }
+    );
+  } finally {
+    await cleanAndGo(engine, server);
+    await Service.engineManager.unregister(engine);
+  }
+});
+
+add_task(async function test_initial_sync_engines() {
+  enableValidationPrefs();
+
+  await Service.engineManager.register(SteamEngine);
+  let engine = Service.engineManager.get("steam");
+  engine.enabled = true;
+  // These are the only ones who actually have things to sync at startup.
+  let telemetryEngineNames = ["clients", "prefs", "tabs", "bookmarks-buffered"];
+  let server = await serverForEnginesWithKeys(
+    { foo: "password" },
+    ["bookmarks", "prefs", "tabs"].map(name => Service.engineManager.get(name))
+  );
+  await SyncTestingInfrastructure(server);
+  try {
+    const changes = await engine._tracker.getChangedIDs();
+    _(
+      `test_initial_sync_engines: Steam tracker contents: ${JSON.stringify(
+        changes
+      )}`
+    );
+    await GleanPings.sync.testSubmission(
+      reason => {
+        equal(reason, "schedule");
+        equal(Glean.syncs.hashedFxaUid.testGetValue(), "f".repeat(32));
+
+        const syncs = Glean.syncs.syncs.testGetValue();
+        equal(syncs.length, 1);
+
+        const sync = syncs[0];
+        equal(sync.engines.find(e => e.name === "clients").outgoing[0].sent, 1);
+        equal(sync.engines.find(e => e.name === "tabs").outgoing[0].sent, 1);
+
+        sync.engines
+          .filter(e => telemetryEngineNames.includes(e.name))
+          .forEach(e => {
+            greaterOrEqual(e.took, 0);
+            ok(!!e.outgoing);
+            equal(e.outgoing.length, 1);
+            notEqual(e.outgoing[0].sent, undefined);
+            equal(e.outgoing[0].failed, undefined);
+            equal(e.outgoing[0].failedReasons, undefined);
+          });
+      },
+      async () => {
+        await Service.sync();
+      }
+    );
+  } finally {
+    await cleanAndGo(engine, server);
+    await Service.engineManager.unregister(engine);
+  }
+});
+
+add_task(async function test_nserror() {
+  enableValidationPrefs();
+
+  await Service.engineManager.register(SteamEngine);
+  let engine = Service.engineManager.get("steam");
+  engine.enabled = true;
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+  engine._errToThrow = Components.Exception(
+    "NS_ERROR_UNKNOWN_HOST",
+    Cr.NS_ERROR_UNKNOWN_HOST
+  );
+  try {
+    const changes = await engine._tracker.getChangedIDs();
+    _(`test_nserror: Steam tracker contents: ${JSON.stringify(changes)}`);
+    await GleanPings.sync.testSubmission(
+      reason => {
+        equal(reason, "schedule");
+        equal(Glean.syncs.hashedFxaUid.testGetValue(), "f".repeat(32));
+
+        const syncs = Glean.syncs.syncs.testGetValue();
+        equal(syncs.length, 1);
+
+        const sync = syncs[0];
+        deepEqual(sync.status, {
+          service: SYNC_FAILED_PARTIAL,
+          sync: LOGIN_FAILED_NETWORK_ERROR,
+        });
+        const eng = sync.engines.find(e => e.name === "steam");
+        deepEqual(eng.failureReason, {
+          name: "httperror",
+          code: Cr.NS_ERROR_UNKNOWN_HOST,
+        });
+      },
+      async () => {
+        await Service.sync();
+      }
+    );
+  } finally {
+    await cleanAndGo(engine, server);
+    await Service.engineManager.unregister(engine);
+  }
+});
+
+add_task(async function test_sync_why() {
+  enableValidationPrefs();
+
+  await Service.engineManager.register(SteamEngine);
+  let engine = Service.engineManager.get("steam");
+  engine.enabled = true;
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+  let e = new Error("generic failure message");
+  engine._errToThrow = e;
+
+  try {
+    const changes = await engine._tracker.getChangedIDs();
+    _(
+      `test_generic_engine_fail: Steam tracker contents: ${JSON.stringify(
+        changes
+      )}`
+    );
+    await GleanPings.sync.testSubmission(
+      reason => {
+        equal(reason, "schedule");
+        equal(Glean.syncs.hashedFxaUid.testGetValue(), "f".repeat(32));
+
+        const syncs = Glean.syncs.syncs.testGetValue();
+        equal(syncs.length, 1);
+
+        const sync = syncs[0];
+        equal(sync.why, "user");
+      },
+      async () => {
+        await Service.sync({ why: "user" });
+      }
+    );
+  } finally {
+    await cleanAndGo(engine, server);
+    await Service.engineManager.unregister(engine);
+  }
+});
+
+add_task(async function test_discarding() {
+  enableValidationPrefs();
+
+  let helper = track_collections_helper();
+  let upd = helper.with_updated_collection;
+  let telem = get_sync_test_telemetry();
+  telem.maxPayloadCount = 2;
+  telem.submissionInterval = Infinity;
+
+  let server;
+  try {
+    let handlers = {
+      "/1.1/johndoe/info/collections": helper.handler,
+      "/1.1/johndoe/storage/crypto/keys": upd(
+        "crypto",
+        new ServerWBO("keys").handler()
+      ),
+      "/1.1/johndoe/storage/meta/global": upd(
+        "meta",
+        new ServerWBO("global").handler()
+      ),
+    };
+
+    let collections = [
+      "clients",
+      "bookmarks",
+      "forms",
+      "history",
+      "passwords",
+      "prefs",
+      "tabs",
+    ];
+
+    for (let coll of collections) {
+      handlers["/1.1/johndoe/storage/" + coll] = upd(
+        coll,
+        new ServerCollection({}, true).handler()
+      );
+    }
+
+    server = httpd_setup(handlers);
+    await configureIdentity({ username: "johndoe" }, server);
+    GleanPings.sync.testBeforeNextSubmit(() => {
+      ok(false, "Submitted telemetry ping when we should not have.");
+    });
+
+    for (let i = 0; i < 5; ++i) {
+      await Service.sync();
+    }
+    telem.submissionInterval = -1;
+
+    await GleanPings.sync.testSubmission(
+      reason => {
+        equal(reason, "schedule");
+        equal(Glean.syncs.discarded.testGetValue(), 4);
+        const syncs = Glean.syncs.syncs.testGetValue();
+        equal(syncs.length, 2);
+        syncs.forEach(assert_success_sync);
+      },
+      async () => {
+        await Service.sync(); // Sixth time's the charm.
+      }
+    );
+  } finally {
+    telem.maxPayloadCount = 500;
+    telem.submissionInterval = -1;
+    if (server) {
+      await promiseStopServer(server);
+    }
+  }
+});
+
+add_task(async function test_no_foreign_engines_in_error_ping() {
+  enableValidationPrefs();
+
+  await Service.engineManager.register(BogusEngine);
+  let engine = Service.engineManager.get("bogus");
+  engine.enabled = true;
+  let server = await serverForFoo(engine);
+  engine._errToThrow = new Error("Oh no!");
+  await SyncTestingInfrastructure(server);
+  try {
+    await GleanPings.sync.testSubmission(
+      reason => {
+        equal(reason, "schedule");
+        const syncs = Glean.syncs.syncs.testGetValue();
+        equal(syncs.length, 1);
+        const sync = syncs[0];
+        equal(sync.status.service, SYNC_FAILED_PARTIAL);
+        ok(sync.engines.every(e => e.name !== "bogus"));
+      },
+      async () => {
+        await Service.sync();
+      }
+    );
+  } finally {
+    await cleanAndGo(engine, server);
+    await Service.engineManager.unregister(engine);
+  }
+});
+
+add_task(async function test_no_foreign_engines_in_success_ping() {
+  enableValidationPrefs();
+
+  await Service.engineManager.register(BogusEngine);
+  let engine = Service.engineManager.get("bogus");
+  engine.enabled = true;
+  let server = await serverForFoo(engine);
+
+  await SyncTestingInfrastructure(server);
+  try {
+    await GleanPings.sync.testSubmission(
+      reason => {
+        equal(reason, "schedule");
+        const syncs = Glean.syncs.syncs.testGetValue();
+        equal(syncs.length, 1);
+        const sync = syncs[0];
+        ok(sync.engines.every(e => e.name !== "bogus"));
+      },
+      async () => {
+        await Service.sync();
+      }
+    );
+  } finally {
+    await cleanAndGo(engine, server);
+    await Service.engineManager.unregister(engine);
+  }
+});
+
+add_task(async function test_no_node_type() {
+  let server = sync_httpd_setup({});
+  await configureIdentity(null, server);
+
+  await GleanPings.sync.testSubmission(
+    reason => {
+      equal(reason, "schedule");
+      Assert.strictEqual(Glean.syncs.syncNodeType.testGetValue(), null);
+    },
+    async () => {
+      await Service.sync();
+    }
+  );
+  await promiseStopServer(server);
+});
+
+add_task(async function test_node_type() {
+  Service.identity.logout();
+  let server = sync_httpd_setup({});
+  await configureIdentity({ node_type: "the-node-type" }, server);
+
+  await GleanPings.sync.testSubmission(
+    reason => {
+      equal(reason, "schedule");
+      equal(Glean.syncs.syncNodeType.testGetValue(), "the-node-type");
+    },
+    async () => {
+      await Service.sync();
+    }
+  );
+  await promiseStopServer(server);
+});
+
+add_task(async function test_node_type_change() {
+  Service.identity.logout();
+  let server = sync_httpd_setup({});
+  await configureIdentity({ node_type: "first-node-type" }, server);
+  // Default to submitting each hour - we should still submit on node change.
+  let telem = get_sync_test_telemetry();
+  telem.submissionInterval = 60 * 60 * 1000;
+  // reset the node type from previous test or our first sync will submit.
+  telem.lastSyncNodeType = null;
+  // do 2 syncs with the same node type.
+  await Service.sync();
+  await Service.sync();
+  // then another with a different node type.
+  Service.identity.logout();
+  await configureIdentity({ node_type: "second-node-type" }, server);
+  await GleanPings.sync.testSubmission(
+    () => {
+      equal(
+        Glean.syncs.syncs.testGetValue().length,
+        2,
+        "2 syncs in first ping"
+      );
+      equal(Glean.syncs.syncNodeType.testGetValue(), "first-node-type");
+    },
+    async () => {
+      await Service.sync();
+    }
+  );
+  await GleanPings.sync.testSubmission(
+    () => {
+      equal(
+        Glean.syncs.syncs.testGetValue().length,
+        1,
+        "1 sync in second ping"
+      );
+      equal(Glean.syncs.syncNodeType.testGetValue(), "second-node-type");
+    },
+    async () => {
+      telem.finish();
+    }
+  );
+  await promiseStopServer(server);
+});
+
+add_task(async function test_uid_change() {
+  enableValidationPrefs();
+
+  await Service.engineManager.register(BogusEngine);
+  let engine = Service.engineManager.get("bogus");
+  engine.enabled = true;
+  let server = await serverForFoo(engine);
+
+  await SyncTestingInfrastructure(server);
+  let telem = get_sync_test_telemetry();
+  telem.maxPayloadCount = 500;
+  telem.submissionInterval = Infinity;
+
+  // a sync with the "old" uid.
+  await Service.sync();
+
+  fxAccounts.telemetry._setHashedUID("deadbeef");
+
+  try {
+    await GleanPings.sync.testSubmission(
+      reason => {
+        equal(reason, "idchange");
+        equal(
+          Glean.syncs.syncs.testGetValue().length,
+          1,
+          "first sync in its own ping"
+        );
+      },
+      async () => {
+        await Service.sync();
+      }
+    );
+    await GleanPings.sync.testSubmission(
+      () => {
+        equal(
+          Glean.syncs.syncs.testGetValue().length,
+          1,
+          "second sync in its own ping"
+        );
+      },
+      async () => {
+        telem.finish();
+      }
+    );
+  } finally {
+    await cleanAndGo(engine, server);
+    await Service.engineManager.unregister(engine);
+  }
+});
+
+add_task(async function test_deletion_request_ping() {
+  async function assertRecordedSyncDeviceID(expected) {
+    // `onAccountInitOrChange` sets the id asynchronously, so wait a tick.
+    await Promise.resolve();
+    equal(Glean.deletionRequest.syncDeviceId.testGetValue(), expected);
+  }
+  Services.fog.testResetFOG();
+
+  const MOCK_HASHED_UID = "00112233445566778899aabbccddeeff";
+  const MOCK_DEVICE_ID1 = "ffeeddccbbaa99887766554433221100";
+  const MOCK_DEVICE_ID2 = "aabbccddeeff99887766554433221100";
+
+  // Calculated by hand using SHA256(DEVICE_ID + HASHED_UID)[:32]
+  const SANITIZED_DEVICE_ID1 = "dd7c845006df9baa1c6d756926519c8c";
+  const SANITIZED_DEVICE_ID2 = "0d06919a736fc029007e1786a091882c";
+
+  let currentDeviceID = null;
+  sinon.stub(fxAccounts.device, "getLocalId").callsFake(() => {
+    return Promise.resolve(currentDeviceID);
+  });
+  let telem = get_sync_test_telemetry();
+  sinon.stub(telem, "isProductionSyncUser").callsFake(() => true);
+  fxAccounts.telemetry._setHashedUID(false);
+
+  try {
+    // The scalar should start out undefined, since no user is actually logged in.
+    await assertRecordedSyncDeviceID(null);
+
+    // If we start up without knowing the hashed UID, it should stay undefined.
+    telem.observe(null, "weave:service:ready");
+    await assertRecordedSyncDeviceID(null);
+
+    // But now let's say we've discovered the hashed UID from the server.
+    fxAccounts.telemetry._setHashedUID(MOCK_HASHED_UID);
+    currentDeviceID = MOCK_DEVICE_ID1;
+
+    // Now when we load up, we'll record the sync device id.
+    telem.observe(null, "weave:service:ready");
+    await assertRecordedSyncDeviceID(SANITIZED_DEVICE_ID1);
+
+    // When the device-id changes we'll update it.
+    currentDeviceID = MOCK_DEVICE_ID2;
+    telem.observe(null, "fxaccounts:new_device_id");
+    await assertRecordedSyncDeviceID(SANITIZED_DEVICE_ID2);
+
+    // When the user signs out we'll clear it.
+    telem.observe(null, "fxaccounts:onlogout");
+    await assertRecordedSyncDeviceID("");
+  } finally {
+    fxAccounts.telemetry._setHashedUID(false);
+    telem.isProductionSyncUser.restore();
+    fxAccounts.device.getLocalId.restore();
+  }
+});
+
+// TODO: Is the topic `"weave:telemetry:migration"` presently hooked up?
+add_task(async function test_migration() {
+  let telem = get_sync_test_telemetry();
+  const migrationInfo = {
+    entries: 42,
+    entries_successful: 42,
+    extensions: 84,
+    extensions_successful: 83,
+    openFailure: false,
+  };
+  telem._addMigrationRecord("webext-storage", migrationInfo);
+  await GleanPings.sync.testSubmission(
+    () => {
+      const migrations = Glean.syncs.migrations.testGetValue();
+      equal(migrations.length, 1);
+      deepEqual(migrations[0], {
+        migration_type: "webext-storage",
+        entries: 42,
+        entriesSuccessful: 42,
+        extensions: 84,
+        extensionsSuccessful: 83,
+        openFailure: false,
+      });
+    },
+    () => {
+      telem.finish();
+    }
+  );
+});
diff --git a/src/zen/tests/mochitests/sync/test_history_engine.js b/src/zen/tests/mochitests/sync/test_history_engine.js
new file mode 100644
index 000000000..15c10c987
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_history_engine.js
@@ -0,0 +1,429 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { HistoryEngine } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/history.sys.mjs"
+);
+
+// Use only for rawAddVisit.
+XPCOMUtils.defineLazyServiceGetter(
+  this,
+  "asyncHistory",
+  "@mozilla.org/browser/history;1",
+  Ci.mozIAsyncHistory
+);
+async function rawAddVisit(id, uri, visitPRTime, transitionType) {
+  return new Promise(resolve => {
+    let results = [];
+    let handler = {
+      handleResult(result) {
+        results.push(result);
+      },
+      handleError(resultCode) {
+        do_throw(`updatePlaces gave error ${resultCode}!`);
+      },
+      handleCompletion(count) {
+        resolve({ results, count });
+      },
+    };
+    asyncHistory.updatePlaces(
+      [
+        {
+          guid: id,
+          uri: typeof uri == "string" ? CommonUtils.makeURI(uri) : uri,
+          visits: [{ visitDate: visitPRTime, transitionType }],
+        },
+      ],
+      handler
+    );
+  });
+}
+
+add_task(async function test_history_download_limit() {
+  let engine = new HistoryEngine(Service);
+  await engine.initialize();
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  let lastSync = new_timestamp();
+
+  let collection = server.user("foo").collection("history");
+  for (let i = 0; i < 15; i++) {
+    let id = "place" + i.toString(10).padStart(7, "0");
+    let wbo = new ServerWBO(
+      id,
+      encryptPayload({
+        id,
+        histUri: "http://example.com/" + i,
+        title: "Page " + i,
+        visits: [
+          {
+            date: Date.now() * 1000,
+            type: PlacesUtils.history.TRANSITIONS.TYPED,
+          },
+          {
+            date: Date.now() * 1000,
+            type: PlacesUtils.history.TRANSITIONS.LINK,
+          },
+        ],
+      }),
+      lastSync + 1 + i
+    );
+    wbo.sortindex = 15 - i;
+    collection.insertWBO(wbo);
+  }
+
+  // We have 15 records on the server since the last sync, but our download
+  // limit is 5 records at a time. We should eventually fetch all 15.
+  await engine.setLastSync(lastSync);
+  engine.downloadBatchSize = 4;
+  engine.downloadLimit = 5;
+
+  // Don't actually fetch any backlogged records, so that we can inspect
+  // the backlog between syncs.
+  engine.guidFetchBatchSize = 0;
+
+  let ping = await sync_engine_and_validate_telem(engine, false);
+  deepEqual(ping.engines[0].incoming, { applied: 5 });
+
+  let backlogAfterFirstSync = Array.from(engine.toFetch).sort();
+  deepEqual(backlogAfterFirstSync, [
+    "place0000000",
+    "place0000001",
+    "place0000002",
+    "place0000003",
+    "place0000004",
+    "place0000005",
+    "place0000006",
+    "place0000007",
+    "place0000008",
+    "place0000009",
+  ]);
+
+  // We should have fast-forwarded the last sync time.
+  equal(await engine.getLastSync(), lastSync + 15);
+
+  engine.lastModified = collection.modified;
+  ping = await sync_engine_and_validate_telem(engine, false);
+  ok(!ping.engines[0].incoming);
+
+  // After the second sync, our backlog still contains the same GUIDs: we
+  // weren't able to make progress on fetching them, since our
+  // `guidFetchBatchSize` is 0.
+  let backlogAfterSecondSync = Array.from(engine.toFetch).sort();
+  deepEqual(backlogAfterFirstSync, backlogAfterSecondSync);
+
+  // Now add a newer record to the server.
+  let newWBO = new ServerWBO(
+    "placeAAAAAAA",
+    encryptPayload({
+      id: "placeAAAAAAA",
+      histUri: "http://example.com/a",
+      title: "New Page A",
+      visits: [
+        {
+          date: Date.now() * 1000,
+          type: PlacesUtils.history.TRANSITIONS.TYPED,
+        },
+      ],
+    }),
+    lastSync + 20
+  );
+  newWBO.sortindex = -1;
+  collection.insertWBO(newWBO);
+
+  engine.lastModified = collection.modified;
+  ping = await sync_engine_and_validate_telem(engine, false);
+  deepEqual(ping.engines[0].incoming, { applied: 1 });
+
+  // Our backlog should remain the same.
+  let backlogAfterThirdSync = Array.from(engine.toFetch).sort();
+  deepEqual(backlogAfterSecondSync, backlogAfterThirdSync);
+
+  equal(await engine.getLastSync(), lastSync + 20);
+
+  // Bump the fetch batch size to let the backlog make progress. We should
+  // make 3 requests to fetch 5 backlogged GUIDs.
+  engine.guidFetchBatchSize = 2;
+
+  engine.lastModified = collection.modified;
+  ping = await sync_engine_and_validate_telem(engine, false);
+  deepEqual(ping.engines[0].incoming, { applied: 5 });
+
+  deepEqual(Array.from(engine.toFetch).sort(), [
+    "place0000005",
+    "place0000006",
+    "place0000007",
+    "place0000008",
+    "place0000009",
+  ]);
+
+  // Sync again to clear out the backlog.
+  engine.lastModified = collection.modified;
+  ping = await sync_engine_and_validate_telem(engine, false);
+  deepEqual(ping.engines[0].incoming, { applied: 5 });
+
+  deepEqual(Array.from(engine.toFetch), []);
+
+  await engine.wipeClient();
+  await engine.finalize();
+});
+
+add_task(async function test_history_visit_roundtrip() {
+  let engine = new HistoryEngine(Service);
+  await engine.initialize();
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  engine._tracker.start();
+
+  let id = "aaaaaaaaaaaa";
+  let oneHourMS = 60 * 60 * 1000;
+  // Insert a visit with a non-round microsecond timestamp (e.g. it's not evenly
+  // divisible by 1000). This will typically be the case for visits that occur
+  // during normal navigation.
+  let time = (Date.now() - oneHourMS) * 1000 + 555;
+  // We use the low level history api since it lets us provide microseconds
+  let { count } = await rawAddVisit(
+    id,
+    "https://www.example.com",
+    time,
+    PlacesUtils.history.TRANSITIONS.TYPED
+  );
+  equal(count, 1);
+  // Check that it was inserted and that we didn't round on the insert.
+  let visits = await PlacesSyncUtils.history.fetchVisitsForURL(
+    "https://www.example.com"
+  );
+  equal(visits.length, 1);
+  equal(visits[0].date, time);
+
+  let collection = server.user("foo").collection("history");
+
+  // Sync the visit up to the server.
+  await sync_engine_and_validate_telem(engine, false);
+
+  collection.updateRecord(
+    id,
+    cleartext => {
+      // Double-check that we didn't round the visit's timestamp to the nearest
+      // millisecond when uploading.
+      equal(cleartext.visits[0].date, time);
+      // Add a remote visit so that we get past the deepEquals check in reconcile
+      // (otherwise the history engine will skip applying this record). The
+      // contents of this visit don't matter, beyond the fact that it needs to
+      // exist.
+      cleartext.visits.push({
+        date: (Date.now() - oneHourMS / 2) * 1000,
+        type: PlacesUtils.history.TRANSITIONS.LINK,
+      });
+    },
+    new_timestamp() + 10
+  );
+
+  // Force a remote sync.
+  await engine.setLastSync(new_timestamp() - 30);
+  await sync_engine_and_validate_telem(engine, false);
+
+  // Make sure that we didn't duplicate the visit when inserting. (Prior to bug
+  // 1423395, we would insert a duplicate visit, where the timestamp was
+  // effectively `Math.round(microsecondTimestamp / 1000) * 1000`.)
+  visits = await PlacesSyncUtils.history.fetchVisitsForURL(
+    "https://www.example.com"
+  );
+  equal(visits.length, 2);
+
+  await engine.wipeClient();
+  await engine.finalize();
+});
+
+add_task(async function test_history_visit_dedupe_old() {
+  let engine = new HistoryEngine(Service);
+  await engine.initialize();
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  let initialVisits = Array.from({ length: 25 }, (_, index) => ({
+    transition: PlacesUtils.history.TRANSITION_LINK,
+    date: new Date(Date.UTC(2017, 10, 1 + index)),
+  }));
+  initialVisits.push({
+    transition: PlacesUtils.history.TRANSITION_LINK,
+    date: new Date(),
+  });
+  await PlacesUtils.history.insert({
+    url: "https://www.example.com",
+    visits: initialVisits,
+  });
+
+  let recentVisits = await PlacesSyncUtils.history.fetchVisitsForURL(
+    "https://www.example.com"
+  );
+  equal(recentVisits.length, 20);
+  let { visits: allVisits, guid } = await PlacesUtils.history.fetch(
+    "https://www.example.com",
+    {
+      includeVisits: true,
+    }
+  );
+  equal(allVisits.length, 26);
+
+  let collection = server.user("foo").collection("history");
+
+  await sync_engine_and_validate_telem(engine, false);
+
+  collection.updateRecord(
+    guid,
+    data => {
+      data.visits.push(
+        // Add a couple remote visit equivalent to some old visits we have already
+        {
+          date: Date.UTC(2017, 10, 1) * 1000, // Nov 1, 2017
+          type: PlacesUtils.history.TRANSITIONS.LINK,
+        },
+        {
+          date: Date.UTC(2017, 10, 2) * 1000, // Nov 2, 2017
+          type: PlacesUtils.history.TRANSITIONS.LINK,
+        },
+        // Add a couple new visits to make sure we are still applying them.
+        {
+          date: Date.UTC(2017, 11, 4) * 1000, // Dec 4, 2017
+          type: PlacesUtils.history.TRANSITIONS.LINK,
+        },
+        {
+          date: Date.UTC(2017, 11, 5) * 1000, // Dec 5, 2017
+          type: PlacesUtils.history.TRANSITIONS.LINK,
+        }
+      );
+    },
+    new_timestamp() + 10
+  );
+
+  await engine.setLastSync(new_timestamp() - 30);
+  await sync_engine_and_validate_telem(engine, false);
+
+  allVisits = (
+    await PlacesUtils.history.fetch("https://www.example.com", {
+      includeVisits: true,
+    })
+  ).visits;
+
+  equal(allVisits.length, 28);
+  ok(
+    allVisits.find(x => x.date.getTime() === Date.UTC(2017, 11, 4)),
+    "Should contain the Dec. 4th visit"
+  );
+  ok(
+    allVisits.find(x => x.date.getTime() === Date.UTC(2017, 11, 5)),
+    "Should contain the Dec. 5th visit"
+  );
+
+  await engine.wipeClient();
+  await engine.finalize();
+});
+
+add_task(async function test_history_unknown_fields() {
+  let engine = new HistoryEngine(Service);
+  await engine.initialize();
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  engine._tracker.start();
+
+  let id = "aaaaaaaaaaaa";
+  let oneHourMS = 60 * 60 * 1000;
+  // Insert a visit with a non-round microsecond timestamp (e.g. it's not evenly
+  // divisible by 1000). This will typically be the case for visits that occur
+  // during normal navigation.
+  let time = (Date.now() - oneHourMS) * 1000 + 555;
+  // We use the low level history api since it lets us provide microseconds
+  let { count } = await rawAddVisit(
+    id,
+    "https://www.example.com",
+    time,
+    PlacesUtils.history.TRANSITIONS.TYPED
+  );
+  equal(count, 1);
+
+  let collection = server.user("foo").collection("history");
+
+  // Sync the visit up to the server.
+  await sync_engine_and_validate_telem(engine, false);
+
+  collection.updateRecord(
+    id,
+    cleartext => {
+      equal(cleartext.visits[0].date, time);
+
+      // Add unknown fields to an instance of a visit
+      cleartext.visits.push({
+        date: (Date.now() - oneHourMS / 2) * 1000,
+        type: PlacesUtils.history.TRANSITIONS.LINK,
+        unknownVisitField: "an unknown field could show up in a visit!",
+      });
+      cleartext.title = "A page title";
+      // Add unknown fields to the payload for this URL
+      cleartext.unknownStrField = "an unknown str field";
+      cleartext.unknownObjField = { newField: "a field within an object" };
+    },
+    new_timestamp() + 10
+  );
+
+  // Force a remote sync.
+  await engine.setLastSync(new_timestamp() - 30);
+  await sync_engine_and_validate_telem(engine, false);
+
+  // Add a new visit to ensure we're actually putting things back on the server
+  let newTime = (Date.now() - oneHourMS) * 1000 + 555;
+  await rawAddVisit(
+    id,
+    "https://www.example.com",
+    newTime,
+    PlacesUtils.history.TRANSITIONS.LINK
+  );
+
+  // Sync again
+  await engine.setLastSync(new_timestamp() - 30);
+  await sync_engine_and_validate_telem(engine, false);
+
+  let placeInfo = await PlacesSyncUtils.history.fetchURLInfoForGuid(id);
+
+  // Found the place we're looking for
+  Assert.equal(placeInfo.title, "A page title");
+  Assert.equal(placeInfo.url, "https://www.example.com/");
+
+  // It correctly returns any unknownFields that might've been
+  // stored in the moz_places_extra table
+  deepEqual(JSON.parse(placeInfo.unknownFields), {
+    unknownStrField: "an unknown str field",
+    unknownObjField: { newField: "a field within an object" },
+  });
+
+  // Getting visits via SyncUtils also will return unknownFields
+  // via the moz_historyvisits_extra table
+  let visits = await PlacesSyncUtils.history.fetchVisitsForURL(
+    "https://www.example.com"
+  );
+  equal(visits.length, 3);
+
+  // fetchVisitsForURL is a sync method that gets called during upload
+  // so unknown field should already be at the top-level
+  deepEqual(
+    visits[0].unknownVisitField,
+    "an unknown field could show up in a visit!"
+  );
+
+  // Remote history record should have the fields back at the top level
+  let remotePlace = collection.payloads().find(rec => rec.id === id);
+  deepEqual(remotePlace.unknownStrField, "an unknown str field");
+  deepEqual(remotePlace.unknownObjField, {
+    newField: "a field within an object",
+  });
+
+  await engine.wipeClient();
+  await engine.finalize();
+});
diff --git a/src/zen/tests/mochitests/sync/test_history_store.js b/src/zen/tests/mochitests/sync/test_history_store.js
new file mode 100644
index 000000000..a6d9a181e
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_history_store.js
@@ -0,0 +1,560 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { HistoryEngine } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/history.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { SyncedRecordsTelemetry } = ChromeUtils.importESModule(
+  "resource://services-sync/telemetry.sys.mjs"
+);
+
+const TIMESTAMP1 = (Date.now() - 103406528) * 1000;
+const TIMESTAMP2 = (Date.now() - 6592903) * 1000;
+const TIMESTAMP3 = (Date.now() - 123894) * 1000;
+
+function isDateApproximately(actual, expected, skewMillis = 1000) {
+  let lowerBound = expected - skewMillis;
+  let upperBound = expected + skewMillis;
+  return actual >= lowerBound && actual <= upperBound;
+}
+
+let engine, store, fxuri, fxguid, tburi, tbguid;
+
+async function applyEnsureNoFailures(records) {
+  let countTelemetry = new SyncedRecordsTelemetry();
+  Assert.equal(
+    (await store.applyIncomingBatch(records, countTelemetry)).length,
+    0
+  );
+}
+
+add_task(async function setup() {
+  engine = new HistoryEngine(Service);
+  await engine.initialize();
+  store = engine._store;
+});
+
+add_task(async function test_store() {
+  _("Verify that we've got an empty store to work with.");
+  do_check_empty(await store.getAllIDs());
+
+  _("Let's create an entry in the database.");
+  fxuri = CommonUtils.makeURI("http://getfirefox.com/");
+
+  await PlacesTestUtils.addVisits({
+    uri: fxuri,
+    title: "Get Firefox!",
+    visitDate: TIMESTAMP1,
+  });
+  _("Verify that the entry exists.");
+  let ids = Object.keys(await store.getAllIDs());
+  Assert.equal(ids.length, 1);
+  fxguid = ids[0];
+  Assert.ok(await store.itemExists(fxguid));
+
+  _("If we query a non-existent record, it's marked as deleted.");
+  let record = await store.createRecord("non-existent");
+  Assert.ok(record.deleted);
+
+  _("Verify createRecord() returns a complete record.");
+  record = await store.createRecord(fxguid);
+  Assert.equal(record.histUri, fxuri.spec);
+  Assert.equal(record.title, "Get Firefox!");
+  Assert.equal(record.visits.length, 1);
+  Assert.equal(record.visits[0].date, TIMESTAMP1);
+  Assert.equal(record.visits[0].type, Ci.nsINavHistoryService.TRANSITION_LINK);
+
+  _("Let's modify the record and have the store update the database.");
+  let secondvisit = {
+    date: TIMESTAMP2,
+    type: Ci.nsINavHistoryService.TRANSITION_TYPED,
+  };
+  let onVisitObserved = PlacesTestUtils.waitForNotification(["page-visited"]);
+  let updatedRec = await store.createRecord(fxguid);
+  updatedRec.cleartext.title = "Hol Dir Firefox!";
+  updatedRec.cleartext.visits.push(secondvisit);
+  await applyEnsureNoFailures([updatedRec]);
+  await onVisitObserved;
+  let queryres = await PlacesUtils.history.fetch(fxuri.spec, {
+    includeVisits: true,
+  });
+  Assert.equal(queryres.title, "Hol Dir Firefox!");
+  Assert.deepEqual(queryres.visits, [
+    {
+      date: new Date(TIMESTAMP2 / 1000),
+      transition: Ci.nsINavHistoryService.TRANSITION_TYPED,
+    },
+    {
+      date: new Date(TIMESTAMP1 / 1000),
+      transition: Ci.nsINavHistoryService.TRANSITION_LINK,
+    },
+  ]);
+  await PlacesUtils.history.clear();
+});
+
+add_task(async function test_store_create() {
+  _("Create a brand new record through the store.");
+  tbguid = Utils.makeGUID();
+  tburi = CommonUtils.makeURI("http://getthunderbird.com");
+  let onVisitObserved = PlacesTestUtils.waitForNotification(["page-visited"]);
+  let record = await store.createRecord(tbguid);
+  record.cleartext = {
+    id: tbguid,
+    histUri: tburi.spec,
+    title: "The bird is the word!",
+    visits: [
+      { date: TIMESTAMP3, type: Ci.nsINavHistoryService.TRANSITION_TYPED },
+    ],
+  };
+  await applyEnsureNoFailures([record]);
+  await onVisitObserved;
+  Assert.ok(await store.itemExists(tbguid));
+  do_check_attribute_count(await store.getAllIDs(), 1);
+  let queryres = await PlacesUtils.history.fetch(tburi.spec, {
+    includeVisits: true,
+  });
+  Assert.equal(queryres.title, "The bird is the word!");
+  Assert.deepEqual(queryres.visits, [
+    {
+      date: new Date(TIMESTAMP3 / 1000),
+      transition: Ci.nsINavHistoryService.TRANSITION_TYPED,
+    },
+  ]);
+  await PlacesUtils.history.clear();
+});
+
+add_task(async function test_null_title() {
+  _(
+    "Make sure we handle a null title gracefully (it can happen in some cases, e.g. for resource:// URLs)"
+  );
+  let resguid = Utils.makeGUID();
+  let resuri = CommonUtils.makeURI("unknown://title");
+  let record = await store.createRecord(resguid);
+  record.cleartext = {
+    id: resguid,
+    histUri: resuri.spec,
+    title: null,
+    visits: [
+      { date: TIMESTAMP3, type: Ci.nsINavHistoryService.TRANSITION_TYPED },
+    ],
+  };
+  await applyEnsureNoFailures([record]);
+  do_check_attribute_count(await store.getAllIDs(), 1);
+
+  let queryres = await PlacesUtils.history.fetch(resuri.spec, {
+    includeVisits: true,
+  });
+  Assert.equal(queryres.title, "");
+  Assert.deepEqual(queryres.visits, [
+    {
+      date: new Date(TIMESTAMP3 / 1000),
+      transition: Ci.nsINavHistoryService.TRANSITION_TYPED,
+    },
+  ]);
+  await PlacesUtils.history.clear();
+});
+
+add_task(async function test_invalid_records() {
+  _("Make sure we handle invalid URLs in places databases gracefully.");
+  await PlacesUtils.withConnectionWrapper(
+    "test_invalid_record",
+    async function (db) {
+      await db.execute(
+        "INSERT INTO moz_places " +
+          "(url, url_hash, title, rev_host, visit_count, last_visit_date) " +
+          "VALUES ('invalid-uri', hash('invalid-uri'), 'Invalid URI', '.', 1, " +
+          TIMESTAMP3 +
+          ")"
+      );
+      // Add the corresponding visit to retain database coherence.
+      await db.execute(
+        "INSERT INTO moz_historyvisits " +
+          "(place_id, visit_date, visit_type, session) " +
+          "VALUES ((SELECT id FROM moz_places WHERE url_hash = hash('invalid-uri') AND url = 'invalid-uri'), " +
+          TIMESTAMP3 +
+          ", " +
+          Ci.nsINavHistoryService.TRANSITION_TYPED +
+          ", 1)"
+      );
+    }
+  );
+  do_check_attribute_count(await store.getAllIDs(), 1);
+
+  _("Make sure we report records with invalid URIs.");
+  let invalid_uri_guid = Utils.makeGUID();
+  let countTelemetry = new SyncedRecordsTelemetry();
+  let failed = await store.applyIncomingBatch(
+    [
+      {
+        id: invalid_uri_guid,
+        histUri: ":::::::::::::::",
+        title: "Doesn't have a valid URI",
+        visits: [
+          { date: TIMESTAMP3, type: Ci.nsINavHistoryService.TRANSITION_EMBED },
+        ],
+      },
+    ],
+    countTelemetry
+  );
+  Assert.equal(failed.length, 1);
+  Assert.equal(failed[0], invalid_uri_guid);
+  Assert.equal(
+    countTelemetry.incomingCounts.failedReasons[0].name,
+    "<URL> is not a valid URL."
+  );
+  Assert.equal(countTelemetry.incomingCounts.failedReasons[0].count, 1);
+
+  _("Make sure we handle records with invalid GUIDs gracefully (ignore).");
+  await applyEnsureNoFailures([
+    {
+      id: "invalid",
+      histUri: "http://invalid.guid/",
+      title: "Doesn't have a valid GUID",
+      visits: [
+        { date: TIMESTAMP3, type: Ci.nsINavHistoryService.TRANSITION_EMBED },
+      ],
+    },
+  ]);
+
+  _(
+    "Make sure we handle records with invalid visit codes or visit dates, gracefully ignoring those visits."
+  );
+  let no_date_visit_guid = Utils.makeGUID();
+  let no_type_visit_guid = Utils.makeGUID();
+  let invalid_type_visit_guid = Utils.makeGUID();
+  let non_integer_visit_guid = Utils.makeGUID();
+  countTelemetry = new SyncedRecordsTelemetry();
+  failed = await store.applyIncomingBatch(
+    [
+      {
+        id: no_date_visit_guid,
+        histUri: "http://no.date.visit/",
+        title: "Visit has no date",
+        visits: [{ type: Ci.nsINavHistoryService.TRANSITION_EMBED }],
+      },
+      {
+        id: no_type_visit_guid,
+        histUri: "http://no.type.visit/",
+        title: "Visit has no type",
+        visits: [{ date: TIMESTAMP3 }],
+      },
+      {
+        id: invalid_type_visit_guid,
+        histUri: "http://invalid.type.visit/",
+        title: "Visit has invalid type",
+        visits: [
+          {
+            date: TIMESTAMP3,
+            type: Ci.nsINavHistoryService.TRANSITION_LINK - 1,
+          },
+        ],
+      },
+      {
+        id: non_integer_visit_guid,
+        histUri: "http://non.integer.visit/",
+        title: "Visit has non-integer date",
+        visits: [
+          { date: 1234.567, type: Ci.nsINavHistoryService.TRANSITION_EMBED },
+        ],
+      },
+    ],
+    countTelemetry
+  );
+  Assert.equal(failed.length, 0);
+
+  // Make sure we can apply tombstones (both valid and invalid)
+  countTelemetry = new SyncedRecordsTelemetry();
+  failed = await store.applyIncomingBatch(
+    [
+      { id: no_date_visit_guid, deleted: true },
+      { id: "not-a-valid-guid", deleted: true },
+    ],
+    countTelemetry
+  );
+  Assert.deepEqual(failed, ["not-a-valid-guid"]);
+  Assert.equal(
+    countTelemetry.incomingCounts.failedReasons[0].name,
+    "<URL> is not a valid URL."
+  );
+
+  _("Make sure we handle records with javascript: URLs gracefully.");
+  await applyEnsureNoFailures(
+    [
+      {
+        id: Utils.makeGUID(),
+        histUri: "javascript:''",
+        title: "javascript:''",
+        visits: [
+          { date: TIMESTAMP3, type: Ci.nsINavHistoryService.TRANSITION_EMBED },
+        ],
+      },
+    ],
+    countTelemetry
+  );
+
+  _("Make sure we handle records without any visits gracefully.");
+  await applyEnsureNoFailures([
+    {
+      id: Utils.makeGUID(),
+      histUri: "http://getfirebug.com",
+      title: "Get Firebug!",
+      visits: [],
+    },
+  ]);
+});
+
+add_task(async function test_unknowingly_invalid_records() {
+  _("Make sure we handle rejection of records by places gracefully.");
+  let oldCAU = store._canAddURI;
+  store._canAddURI = () => true;
+  try {
+    _("Make sure that when places rejects this record we record it as failed");
+    let guid = Utils.makeGUID();
+    let countTelemetry = new SyncedRecordsTelemetry();
+    let invalidRecord = await store.createRecord(guid);
+    invalidRecord.cleartext = {
+      id: guid,
+      histUri: "javascript:''",
+      title: "javascript:''",
+      visits: [
+        {
+          date: TIMESTAMP3,
+          type: Ci.nsINavHistoryService.TRANSITION_EMBED,
+        },
+      ],
+    };
+    let result = await store.applyIncomingBatch(
+      [invalidRecord],
+      countTelemetry
+    );
+    deepEqual(result, [guid]);
+  } finally {
+    store._canAddURI = oldCAU;
+  }
+});
+
+add_task(async function test_clamp_visit_dates() {
+  let futureVisitTime = Date.now() + 5 * 60 * 1000;
+  let recentVisitTime = Date.now() - 5 * 60 * 1000;
+
+  let recordA = await store.createRecord("visitAAAAAAA");
+  recordA.cleartext = {
+    id: "visitAAAAAAA",
+    histUri: "http://example.com/a",
+    title: "A",
+    visits: [
+      {
+        date: "invalidDate",
+        type: Ci.nsINavHistoryService.TRANSITION_LINK,
+      },
+    ],
+  };
+  let recordB = await store.createRecord("visitBBBBBBB");
+  recordB.cleartext = {
+    id: "visitBBBBBBB",
+    histUri: "http://example.com/b",
+    title: "B",
+    visits: [
+      {
+        date: 100,
+        type: Ci.nsINavHistoryService.TRANSITION_TYPED,
+      },
+      {
+        date: 250,
+        type: Ci.nsINavHistoryService.TRANSITION_TYPED,
+      },
+      {
+        date: recentVisitTime * 1000,
+        type: Ci.nsINavHistoryService.TRANSITION_TYPED,
+      },
+    ],
+  };
+  let recordC = await store.createRecord("visitCCCCCCC");
+  recordC.cleartext = {
+    id: "visitCCCCCCC",
+    histUri: "http://example.com/c",
+    title: "D",
+    visits: [
+      {
+        date: futureVisitTime * 1000,
+        type: Ci.nsINavHistoryService.TRANSITION_BOOKMARK,
+      },
+    ],
+  };
+  let recordD = await store.createRecord("visitDDDDDDD");
+  recordD.cleartext = {
+    id: "visitDDDDDDD",
+    histUri: "http://example.com/d",
+    title: "D",
+    visits: [
+      {
+        date: recentVisitTime * 1000,
+        type: Ci.nsINavHistoryService.TRANSITION_DOWNLOAD,
+      },
+    ],
+  };
+  await applyEnsureNoFailures([recordA, recordB, recordC, recordD]);
+
+  let visitsForA = await PlacesSyncUtils.history.fetchVisitsForURL(
+    "http://example.com/a"
+  );
+  deepEqual(visitsForA, [], "Should ignore visits with invalid dates");
+
+  let visitsForB = await PlacesSyncUtils.history.fetchVisitsForURL(
+    "http://example.com/b"
+  );
+  deepEqual(
+    visitsForB,
+    [
+      {
+        date: recentVisitTime * 1000,
+        type: Ci.nsINavHistoryService.TRANSITION_TYPED,
+      },
+      {
+        // We should clamp visit dates older than original Mosaic release.
+        date: PlacesSyncUtils.bookmarks.EARLIEST_BOOKMARK_TIMESTAMP * 1000,
+        type: Ci.nsINavHistoryService.TRANSITION_TYPED,
+      },
+    ],
+    "Should record clamped visit and valid visit for B"
+  );
+
+  let visitsForC = await PlacesSyncUtils.history.fetchVisitsForURL(
+    "http://example.com/c"
+  );
+  equal(visitsForC.length, 1, "Should record clamped future visit for C");
+  let visitDateForC = PlacesUtils.toDate(visitsForC[0].date);
+  ok(
+    isDateApproximately(visitDateForC, Date.now()),
+    "Should clamp future visit date for C to now"
+  );
+
+  let visitsForD = await PlacesSyncUtils.history.fetchVisitsForURL(
+    "http://example.com/d"
+  );
+  deepEqual(
+    visitsForD,
+    [
+      {
+        date: recentVisitTime * 1000,
+        type: Ci.nsINavHistoryService.TRANSITION_DOWNLOAD,
+      },
+    ],
+    "Should not clamp valid visit dates"
+  );
+});
+
+add_task(async function test_remove() {
+  _("Remove an existent record and a non-existent from the store.");
+  await applyEnsureNoFailures([
+    { id: fxguid, deleted: true },
+    { id: Utils.makeGUID(), deleted: true },
+  ]);
+  Assert.equal(false, await store.itemExists(fxguid));
+  let queryres = await PlacesUtils.history.fetch(fxuri.spec, {
+    includeVisits: true,
+  });
+  Assert.equal(null, queryres);
+
+  _("Make sure wipe works.");
+  await store.wipe();
+  do_check_empty(await store.getAllIDs());
+  queryres = await PlacesUtils.history.fetch(fxuri.spec, {
+    includeVisits: true,
+  });
+  Assert.equal(null, queryres);
+  queryres = await PlacesUtils.history.fetch(tburi.spec, {
+    includeVisits: true,
+  });
+  Assert.equal(null, queryres);
+});
+
+add_task(async function test_chunking() {
+  let mvpi = store.MAX_VISITS_PER_INSERT;
+  store.MAX_VISITS_PER_INSERT = 3;
+  let checkChunks = function (input, expected) {
+    let chunks = Array.from(store._generateChunks(input));
+    deepEqual(chunks, expected);
+  };
+  try {
+    checkChunks([{ visits: ["x"] }], [[{ visits: ["x"] }]]);
+
+    // 3 should still be one chunk.
+    checkChunks([{ visits: ["x", "x", "x"] }], [[{ visits: ["x", "x", "x"] }]]);
+
+    // 4 should still be one chunk as we don't split individual records.
+    checkChunks(
+      [{ visits: ["x", "x", "x", "x"] }],
+      [[{ visits: ["x", "x", "x", "x"] }]]
+    );
+
+    // 4 in the first and 1 in the second should be 2 chunks.
+    checkChunks(
+      [{ visits: ["x", "x", "x", "x"] }, { visits: ["x"] }],
+      // expected
+      [[{ visits: ["x", "x", "x", "x"] }], [{ visits: ["x"] }]]
+    );
+
+    // we put multiple records into chunks
+    checkChunks(
+      [
+        { visits: ["x", "x"] },
+        { visits: ["x"] },
+        { visits: ["x"] },
+        { visits: ["x", "x"] },
+        { visits: ["x", "x", "x", "x"] },
+      ],
+      // expected
+      [
+        [{ visits: ["x", "x"] }, { visits: ["x"] }],
+        [{ visits: ["x"] }, { visits: ["x", "x"] }],
+        [{ visits: ["x", "x", "x", "x"] }],
+      ]
+    );
+  } finally {
+    store.MAX_VISITS_PER_INSERT = mvpi;
+  }
+});
+
+add_task(async function test_getAllIDs_filters_file_uris() {
+  let uri = CommonUtils.makeURI("file:///Users/eoger/tps/config.json");
+  let visitAddedPromise = promiseVisit("added", uri);
+  await PlacesTestUtils.addVisits({
+    uri,
+    visitDate: Date.now() * 1000,
+    transition: PlacesUtils.history.TRANSITION_LINK,
+  });
+  await visitAddedPromise;
+
+  do_check_attribute_count(await store.getAllIDs(), 0);
+
+  await PlacesUtils.history.clear();
+});
+
+add_task(async function test_applyIncomingBatch_filters_file_uris() {
+  const guid = Utils.makeGUID();
+  let uri = CommonUtils.makeURI("file:///Users/eoger/tps/config.json");
+  await applyEnsureNoFailures([
+    {
+      id: guid,
+      histUri: uri.spec,
+      title: "TPS CONFIG",
+      visits: [
+        { date: TIMESTAMP3, type: Ci.nsINavHistoryService.TRANSITION_TYPED },
+      ],
+    },
+  ]);
+  Assert.equal(false, await store.itemExists(guid));
+  let queryres = await PlacesUtils.history.fetch(uri.spec, {
+    includeVisits: true,
+  });
+  Assert.equal(null, queryres);
+});
+
+add_task(async function cleanup() {
+  _("Clean up.");
+  await PlacesUtils.history.clear();
+});
diff --git a/src/zen/tests/mochitests/sync/test_history_tracker.js b/src/zen/tests/mochitests/sync/test_history_tracker.js
new file mode 100644
index 000000000..64433574b
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_history_tracker.js
@@ -0,0 +1,251 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { PlacesDBUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/PlacesDBUtils.sys.mjs"
+);
+const { HistoryEngine } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/history.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+let engine;
+let tracker;
+
+add_task(async function setup() {
+  await Service.engineManager.clear();
+  await Service.engineManager.register(HistoryEngine);
+  engine = Service.engineManager.get("history");
+  tracker = engine._tracker;
+});
+
+async function verifyTrackerEmpty() {
+  let changes = await engine.pullNewChanges();
+  do_check_empty(changes);
+  equal(tracker.score, 0);
+}
+
+async function verifyTrackedCount(expected) {
+  let changes = await engine.pullNewChanges();
+  do_check_attribute_count(changes, expected);
+}
+
+async function verifyTrackedItems(tracked) {
+  let changes = await engine.pullNewChanges();
+  let trackedIDs = new Set(Object.keys(changes));
+  for (let guid of tracked) {
+    ok(guid in changes, `${guid} should be tracked`);
+    Assert.greater(changes[guid], 0, `${guid} should have a modified time`);
+    trackedIDs.delete(guid);
+  }
+  equal(
+    trackedIDs.size,
+    0,
+    `Unhandled tracked IDs: ${JSON.stringify(Array.from(trackedIDs))}`
+  );
+}
+
+async function resetTracker() {
+  await tracker.clearChangedIDs();
+  tracker.resetScore();
+}
+
+async function cleanup() {
+  await PlacesUtils.history.clear();
+  await resetTracker();
+  await tracker.stop();
+}
+
+add_task(async function test_empty() {
+  _("Verify we've got an empty, disabled tracker to work with.");
+  await verifyTrackerEmpty();
+  Assert.ok(!tracker._isTracking);
+
+  await cleanup();
+});
+
+add_task(async function test_not_tracking() {
+  _("Create history item. Won't show because we haven't started tracking yet");
+  await addVisit("not_tracking");
+  await verifyTrackerEmpty();
+
+  await cleanup();
+});
+
+add_task(async function test_start_tracking() {
+  _("Add hook for save completion.");
+  let savePromise = new Promise((resolve, reject) => {
+    let save = tracker._storage._save;
+    tracker._storage._save = async function () {
+      try {
+        await save.call(this);
+        resolve();
+      } catch (ex) {
+        reject(ex);
+      } finally {
+        tracker._storage._save = save;
+      }
+    };
+  });
+
+  _("Tell the tracker to start tracking changes.");
+  tracker.start();
+  let scorePromise = promiseOneObserver("weave:engine:score:updated");
+  await addVisit("start_tracking");
+  await scorePromise;
+
+  _("Score updated in test_start_tracking.");
+  await verifyTrackedCount(1);
+  Assert.equal(tracker.score, SCORE_INCREMENT_SMALL);
+
+  await savePromise;
+
+  _("changedIDs written to disk. Proceeding.");
+  await cleanup();
+});
+
+add_task(async function test_start_tracking_twice() {
+  _("Verifying preconditions.");
+  tracker.start();
+  await addVisit("start_tracking_twice1");
+  await verifyTrackedCount(1);
+  Assert.equal(tracker.score, SCORE_INCREMENT_SMALL);
+
+  _("Notifying twice won't do any harm.");
+  tracker.start();
+  let scorePromise = promiseOneObserver("weave:engine:score:updated");
+  await addVisit("start_tracking_twice2");
+  await scorePromise;
+
+  _("Score updated in test_start_tracking_twice.");
+  await verifyTrackedCount(2);
+  Assert.equal(tracker.score, 2 * SCORE_INCREMENT_SMALL);
+
+  await cleanup();
+});
+
+add_task(async function test_track_delete() {
+  _("Deletions are tracked.");
+
+  // This isn't present because we weren't tracking when it was visited.
+  await addVisit("track_delete");
+  let uri = CommonUtils.makeURI("http://getfirefox.com/track_delete");
+  let guid = await engine._store.GUIDForUri(uri.spec);
+  await verifyTrackerEmpty();
+
+  tracker.start();
+  let visitRemovedPromise = promiseVisit("removed", uri);
+  let scorePromise = promiseOneObserver("weave:engine:score:updated");
+  await PlacesUtils.history.remove(uri);
+  await Promise.all([scorePromise, visitRemovedPromise]);
+
+  await verifyTrackedItems([guid]);
+  Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE);
+
+  await cleanup();
+});
+
+add_task(async function test_dont_track_expiration() {
+  _("Expirations are not tracked.");
+  let uriToRemove = await addVisit("to_remove");
+  let guidToRemove = await engine._store.GUIDForUri(uriToRemove.spec);
+
+  await resetTracker();
+  await verifyTrackerEmpty();
+
+  tracker.start();
+  let visitRemovedPromise = promiseVisit("removed", uriToRemove);
+  let scorePromise = promiseOneObserver("weave:engine:score:updated");
+
+  // Observe expiration.
+  Services.obs.addObserver(function onExpiration(aSubject, aTopic) {
+    Services.obs.removeObserver(onExpiration, aTopic);
+    // Remove the remaining page to update its score.
+    PlacesUtils.history.remove(uriToRemove);
+  }, PlacesUtils.TOPIC_EXPIRATION_FINISHED);
+
+  // Force expiration of 1 entry.
+  Services.prefs.setIntPref("places.history.expiration.max_pages", 0);
+  Cc["@mozilla.org/places/expiration;1"]
+    .getService(Ci.nsIObserver)
+    .observe(null, "places-debug-start-expiration", 1);
+
+  await Promise.all([scorePromise, visitRemovedPromise]);
+  await verifyTrackedItems([guidToRemove]);
+
+  await cleanup();
+});
+
+add_task(async function test_stop_tracking() {
+  _("Let's stop tracking again.");
+  await tracker.stop();
+  await addVisit("stop_tracking");
+  await verifyTrackerEmpty();
+
+  await cleanup();
+});
+
+add_task(async function test_stop_tracking_twice() {
+  await tracker.stop();
+  await addVisit("stop_tracking_twice1");
+
+  _("Notifying twice won't do any harm.");
+  await tracker.stop();
+  await addVisit("stop_tracking_twice2");
+  await verifyTrackerEmpty();
+
+  await cleanup();
+});
+
+add_task(async function test_filter_file_uris() {
+  tracker.start();
+
+  let uri = CommonUtils.makeURI("file:///Users/eoger/tps/config.json");
+  let visitAddedPromise = promiseVisit("added", uri);
+  await PlacesTestUtils.addVisits({
+    uri,
+    visitDate: Date.now() * 1000,
+    transition: PlacesUtils.history.TRANSITION_LINK,
+  });
+  await visitAddedPromise;
+
+  await verifyTrackerEmpty();
+  await tracker.stop();
+  await cleanup();
+});
+
+add_task(async function test_filter_hidden() {
+  tracker.start();
+
+  _("Add visit; should be hidden by the redirect");
+  let hiddenURI = await addVisit("hidden");
+  let hiddenGUID = await engine._store.GUIDForUri(hiddenURI.spec);
+  _(`Hidden visit GUID: ${hiddenGUID}`);
+
+  _("Add redirect visit; should be tracked");
+  let trackedURI = await addVisit(
+    "redirect",
+    hiddenURI.spec,
+    PlacesUtils.history.TRANSITION_REDIRECT_PERMANENT
+  );
+  let trackedGUID = await engine._store.GUIDForUri(trackedURI.spec);
+  _(`Tracked visit GUID: ${trackedGUID}`);
+
+  _("Add visit for framed link; should be ignored");
+  let embedURI = await addVisit(
+    "framed_link",
+    null,
+    PlacesUtils.history.TRANSITION_FRAMED_LINK
+  );
+  let embedGUID = await engine._store.GUIDForUri(embedURI.spec);
+  _(`Framed link visit GUID: ${embedGUID}`);
+
+  _("Run Places maintenance to mark redirect visit as hidden");
+  await PlacesDBUtils.maintenanceOnIdle();
+
+  await verifyTrackedItems([trackedGUID]);
+
+  await cleanup();
+});
diff --git a/src/zen/tests/mochitests/sync/test_hmac_error.js b/src/zen/tests/mochitests/sync/test_hmac_error.js
new file mode 100644
index 000000000..df1998d64
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_hmac_error.js
@@ -0,0 +1,250 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+// Track HMAC error counts.
+var hmacErrorCount = 0;
+(function () {
+  let hHE = Service.handleHMACEvent;
+  Service.handleHMACEvent = async function () {
+    hmacErrorCount++;
+    return hHE.call(Service);
+  };
+})();
+
+async function shared_setup() {
+  enableValidationPrefs();
+  syncTestLogging();
+
+  hmacErrorCount = 0;
+
+  let clientsEngine = Service.clientsEngine;
+  let clientsSyncID = await clientsEngine.resetLocalSyncID();
+
+  // Make sure RotaryEngine is the only one we sync.
+  let { engine, syncID, tracker } = await registerRotaryEngine();
+  await engine.setLastSync(123); // Needs to be non-zero so that tracker is queried.
+  engine._store.items = {
+    flying: "LNER Class A3 4472",
+    scotsman: "Flying Scotsman",
+  };
+  await tracker.addChangedID("scotsman", 0);
+  Assert.equal(1, Service.engineManager.getEnabled().length);
+
+  let engines = {
+    rotary: { version: engine.version, syncID },
+    clients: { version: clientsEngine.version, syncID: clientsSyncID },
+  };
+
+  // Common server objects.
+  let global = new ServerWBO("global", { engines });
+  let keysWBO = new ServerWBO("keys");
+  let rotaryColl = new ServerCollection({}, true);
+  let clientsColl = new ServerCollection({}, true);
+
+  return [engine, rotaryColl, clientsColl, keysWBO, global, tracker];
+}
+
+add_task(async function hmac_error_during_404() {
+  _("Attempt to replicate the HMAC error setup.");
+  let [engine, rotaryColl, clientsColl, keysWBO, global, tracker] =
+    await shared_setup();
+
+  // Hand out 404s for crypto/keys.
+  let keysHandler = keysWBO.handler();
+  let key404Counter = 0;
+  let keys404Handler = function (request, response) {
+    if (key404Counter > 0) {
+      let body = "Not Found";
+      response.setStatusLine(request.httpVersion, 404, body);
+      response.bodyOutputStream.write(body, body.length);
+      key404Counter--;
+      return;
+    }
+    keysHandler(request, response);
+  };
+
+  let collectionsHelper = track_collections_helper();
+  let upd = collectionsHelper.with_updated_collection;
+  let handlers = {
+    "/1.1/foo/info/collections": collectionsHelper.handler,
+    "/1.1/foo/storage/meta/global": upd("meta", global.handler()),
+    "/1.1/foo/storage/crypto/keys": upd("crypto", keys404Handler),
+    "/1.1/foo/storage/clients": upd("clients", clientsColl.handler()),
+    "/1.1/foo/storage/rotary": upd("rotary", rotaryColl.handler()),
+  };
+
+  let server = sync_httpd_setup(handlers);
+  // Do not instantiate SyncTestingInfrastructure; we need real crypto.
+  await configureIdentity({ username: "foo" }, server);
+  await Service.login();
+
+  try {
+    _("Syncing.");
+    await sync_and_validate_telem();
+
+    _(
+      "Partially resetting client, as if after a restart, and forcing redownload."
+    );
+    Service.collectionKeys.clear();
+    await engine.setLastSync(0); // So that we redownload records.
+    key404Counter = 1;
+    _("---------------------------");
+    await sync_and_validate_telem();
+    _("---------------------------");
+
+    // Two rotary items, one client record... no errors.
+    Assert.equal(hmacErrorCount, 0);
+  } finally {
+    await tracker.clearChangedIDs();
+    await Service.engineManager.unregister(engine);
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+    Service.recordManager.clearCache();
+    await promiseStopServer(server);
+  }
+});
+
+add_task(async function hmac_error_during_node_reassignment() {
+  _("Attempt to replicate an HMAC error during node reassignment.");
+  let [engine, rotaryColl, clientsColl, keysWBO, global, tracker] =
+    await shared_setup();
+
+  let collectionsHelper = track_collections_helper();
+  let upd = collectionsHelper.with_updated_collection;
+
+  // We'll provide a 401 mid-way through the sync. This function
+  // simulates shifting to a node which has no data.
+  function on401() {
+    _("Deleting server data...");
+    global.delete();
+    rotaryColl.delete();
+    keysWBO.delete();
+    clientsColl.delete();
+    delete collectionsHelper.collections.rotary;
+    delete collectionsHelper.collections.crypto;
+    delete collectionsHelper.collections.clients;
+    _("Deleted server data.");
+  }
+
+  let should401 = false;
+  function upd401(coll, handler) {
+    return function (request, response) {
+      if (should401 && request.method != "DELETE") {
+        on401();
+        should401 = false;
+        let body = '"reassigned!"';
+        response.setStatusLine(request.httpVersion, 401, "Node reassignment.");
+        response.bodyOutputStream.write(body, body.length);
+        return;
+      }
+      handler(request, response);
+    };
+  }
+
+  let handlers = {
+    "/1.1/foo/info/collections": collectionsHelper.handler,
+    "/1.1/foo/storage/meta/global": upd("meta", global.handler()),
+    "/1.1/foo/storage/crypto/keys": upd("crypto", keysWBO.handler()),
+    "/1.1/foo/storage/clients": upd401("clients", clientsColl.handler()),
+    "/1.1/foo/storage/rotary": upd("rotary", rotaryColl.handler()),
+  };
+
+  let server = sync_httpd_setup(handlers);
+  // Do not instantiate SyncTestingInfrastructure; we need real crypto.
+  await configureIdentity({ username: "foo" }, server);
+
+  _("Syncing.");
+  // First hit of clients will 401. This will happen after meta/global and
+  // keys -- i.e., in the middle of the sync, but before RotaryEngine.
+  should401 = true;
+
+  // Use observers to perform actions when our sync finishes.
+  // This allows us to observe the automatic next-tick sync that occurs after
+  // an abort.
+  function onSyncError() {
+    do_throw("Should not get a sync error!");
+  }
+  let onSyncFinished = function () {};
+  let obs = {
+    observe: function observe(subject, topic) {
+      switch (topic) {
+        case "weave:service:sync:error":
+          onSyncError();
+          break;
+        case "weave:service:sync:finish":
+          onSyncFinished();
+          break;
+      }
+    },
+  };
+
+  Svc.Obs.add("weave:service:sync:finish", obs);
+  Svc.Obs.add("weave:service:sync:error", obs);
+
+  // This kicks off the actual test. Split into a function here to allow this
+  // source file to broadly follow actual execution order.
+  async function onwards() {
+    _("== Invoking first sync.");
+    await Service.sync();
+    _("We should not simultaneously have data but no keys on the server.");
+    let hasData = rotaryColl.wbo("flying") || rotaryColl.wbo("scotsman");
+    let hasKeys = keysWBO.modified;
+
+    _("We correctly handle 401s by aborting the sync and starting again.");
+    Assert.equal(!hasData, !hasKeys);
+
+    _("Be prepared for the second (automatic) sync...");
+  }
+
+  _("Make sure that syncing again causes recovery.");
+  let callbacksPromise = new Promise(resolve => {
+    onSyncFinished = function () {
+      _("== First sync done.");
+      _("---------------------------");
+      onSyncFinished = function () {
+        _("== Second (automatic) sync done.");
+        let hasData = rotaryColl.wbo("flying") || rotaryColl.wbo("scotsman");
+        let hasKeys = keysWBO.modified;
+        Assert.equal(!hasData, !hasKeys);
+
+        // Kick off another sync. Can't just call it, because we're inside the
+        // lock...
+        (async () => {
+          await Async.promiseYield();
+          _("Now a fresh sync will get no HMAC errors.");
+          _(
+            "Partially resetting client, as if after a restart, and forcing redownload."
+          );
+          Service.collectionKeys.clear();
+          await engine.setLastSync(0);
+          hmacErrorCount = 0;
+
+          onSyncFinished = async function () {
+            // Two rotary items, one client record... no errors.
+            Assert.equal(hmacErrorCount, 0);
+
+            Svc.Obs.remove("weave:service:sync:finish", obs);
+            Svc.Obs.remove("weave:service:sync:error", obs);
+
+            await tracker.clearChangedIDs();
+            await Service.engineManager.unregister(engine);
+            for (const pref of Svc.PrefBranch.getChildList("")) {
+              Svc.PrefBranch.clearUserPref(pref);
+            }
+            Service.recordManager.clearCache();
+            server.stop(resolve);
+          };
+
+          Service.sync();
+        })().catch(console.error);
+      };
+    };
+  });
+  await onwards();
+  await callbacksPromise;
+});
diff --git a/src/zen/tests/mochitests/sync/test_httpd_sync_server.js b/src/zen/tests/mochitests/sync/test_httpd_sync_server.js
new file mode 100644
index 000000000..0cc489082
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_httpd_sync_server.js
@@ -0,0 +1,250 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+add_test(function test_creation() {
+  // Explicit callback for this one.
+  let server = new SyncServer(Object.create(SyncServerCallback));
+  Assert.ok(!!server); // Just so we have a check.
+  server.start(null, function () {
+    _("Started on " + server.port);
+    server.stop(run_next_test);
+  });
+});
+
+add_test(function test_url_parsing() {
+  let server = new SyncServer();
+
+  // Check that we can parse a WBO URI.
+  let parts = server.pathRE.exec("/1.1/johnsmith/storage/crypto/keys");
+  let [all, version, username, first, rest] = parts;
+  Assert.equal(all, "/1.1/johnsmith/storage/crypto/keys");
+  Assert.equal(version, "1.1");
+  Assert.equal(username, "johnsmith");
+  Assert.equal(first, "storage");
+  Assert.equal(rest, "crypto/keys");
+  Assert.equal(null, server.pathRE.exec("/nothing/else"));
+
+  // Check that we can parse a collection URI.
+  parts = server.pathRE.exec("/1.1/johnsmith/storage/crypto");
+  [all, version, username, first, rest] = parts;
+  Assert.equal(all, "/1.1/johnsmith/storage/crypto");
+  Assert.equal(version, "1.1");
+  Assert.equal(username, "johnsmith");
+  Assert.equal(first, "storage");
+  Assert.equal(rest, "crypto");
+
+  // We don't allow trailing slash on storage URI.
+  parts = server.pathRE.exec("/1.1/johnsmith/storage/");
+  Assert.equal(parts, undefined);
+
+  // storage alone is a valid request.
+  parts = server.pathRE.exec("/1.1/johnsmith/storage");
+  [all, version, username, first, rest] = parts;
+  Assert.equal(all, "/1.1/johnsmith/storage");
+  Assert.equal(version, "1.1");
+  Assert.equal(username, "johnsmith");
+  Assert.equal(first, "storage");
+  Assert.equal(rest, undefined);
+
+  parts = server.storageRE.exec("storage");
+  let collection;
+  [all, , collection] = parts;
+  Assert.equal(all, "storage");
+  Assert.equal(collection, undefined);
+
+  run_next_test();
+});
+
+const { RESTRequest } = ChromeUtils.importESModule(
+  "resource://services-common/rest.sys.mjs"
+);
+function localRequest(server, path) {
+  _("localRequest: " + path);
+  let url = server.baseURI.substr(0, server.baseURI.length - 1) + path;
+  _("url: " + url);
+  return new RESTRequest(url);
+}
+
+add_task(async function test_basic_http() {
+  let server = new SyncServer();
+  server.registerUser("john", "password");
+  Assert.ok(server.userExists("john"));
+  server.start();
+  _("Started on " + server.port);
+
+  let req = localRequest(server, "/1.1/john/storage/crypto/keys");
+  _("req is " + req);
+  // Shouldn't reject, beyond that we don't care.
+  await req.get();
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_info_collections() {
+  let server = new SyncServer(Object.create(SyncServerCallback));
+  function responseHasCorrectHeaders(r) {
+    Assert.equal(r.status, 200);
+    Assert.equal(r.headers["content-type"], "application/json");
+    Assert.ok("x-weave-timestamp" in r.headers);
+  }
+
+  server.registerUser("john", "password");
+  server.start();
+
+  let req = localRequest(server, "/1.1/john/info/collections");
+  await req.get();
+  responseHasCorrectHeaders(req.response);
+  Assert.equal(req.response.body, "{}");
+
+  let putReq = localRequest(server, "/1.1/john/storage/crypto/keys");
+  let payload = JSON.stringify({ foo: "bar" });
+  let putResp = await putReq.put(payload);
+
+  responseHasCorrectHeaders(putResp);
+
+  let putResponseBody = putResp.body;
+  _("PUT response body: " + JSON.stringify(putResponseBody));
+
+  // When we PUT something to crypto/keys, "crypto" appears in the response.
+  req = localRequest(server, "/1.1/john/info/collections");
+
+  await req.get();
+  responseHasCorrectHeaders(req.response);
+  let expectedColl = server.getCollection("john", "crypto");
+  Assert.ok(!!expectedColl);
+  let modified = expectedColl.timestamp;
+  Assert.greater(modified, 0);
+  Assert.equal(putResponseBody, modified);
+  Assert.equal(JSON.parse(req.response.body).crypto, modified);
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_storage_request() {
+  let keysURL = "/1.1/john/storage/crypto/keys?foo=bar";
+  let foosURL = "/1.1/john/storage/crypto/foos";
+  let storageURL = "/1.1/john/storage";
+
+  let server = new SyncServer();
+  let creation = server.timestamp();
+  server.registerUser("john", "password");
+
+  server.createContents("john", {
+    crypto: { foos: { foo: "bar" } },
+  });
+  let coll = server.user("john").collection("crypto");
+  Assert.ok(!!coll);
+
+  _("We're tracking timestamps.");
+  Assert.greaterOrEqual(coll.timestamp, creation);
+
+  async function retrieveWBONotExists() {
+    let req = localRequest(server, keysURL);
+    let response = await req.get();
+    _("Body is " + response.body);
+    _("Modified is " + response.newModified);
+    Assert.equal(response.status, 404);
+    Assert.equal(response.body, "Not found");
+  }
+
+  async function retrieveWBOExists() {
+    let req = localRequest(server, foosURL);
+    let response = await req.get();
+    _("Body is " + response.body);
+    _("Modified is " + response.newModified);
+    let parsedBody = JSON.parse(response.body);
+    Assert.equal(parsedBody.id, "foos");
+    Assert.equal(parsedBody.modified, coll.wbo("foos").modified);
+    Assert.equal(JSON.parse(parsedBody.payload).foo, "bar");
+  }
+
+  async function deleteWBONotExists() {
+    let req = localRequest(server, keysURL);
+    server.callback.onItemDeleted = function () {
+      do_throw("onItemDeleted should not have been called.");
+    };
+
+    let response = await req.delete();
+
+    _("Body is " + response.body);
+    _("Modified is " + response.newModified);
+    Assert.equal(response.status, 200);
+    delete server.callback.onItemDeleted;
+  }
+
+  async function deleteWBOExists() {
+    let req = localRequest(server, foosURL);
+    server.callback.onItemDeleted = function (username, collection, wboID) {
+      _("onItemDeleted called for " + collection + "/" + wboID);
+      delete server.callback.onItemDeleted;
+      Assert.equal(username, "john");
+      Assert.equal(collection, "crypto");
+      Assert.equal(wboID, "foos");
+    };
+    await req.delete();
+    _("Body is " + req.response.body);
+    _("Modified is " + req.response.newModified);
+    Assert.equal(req.response.status, 200);
+  }
+
+  async function deleteStorage() {
+    _("Testing DELETE on /storage.");
+    let now = server.timestamp();
+    _("Timestamp: " + now);
+    let req = localRequest(server, storageURL);
+    await req.delete();
+
+    _("Body is " + req.response.body);
+    _("Modified is " + req.response.newModified);
+    let parsedBody = JSON.parse(req.response.body);
+    Assert.greaterOrEqual(parsedBody, now);
+    do_check_empty(server.users.john.collections);
+  }
+
+  async function getStorageFails() {
+    _("Testing that GET on /storage fails.");
+    let req = localRequest(server, storageURL);
+    await req.get();
+    Assert.equal(req.response.status, 405);
+    Assert.equal(req.response.headers.allow, "DELETE");
+  }
+
+  async function getMissingCollectionWBO() {
+    _("Testing that fetching a WBO from an on-existent collection 404s.");
+    let req = localRequest(server, storageURL + "/foobar/baz");
+    await req.get();
+    Assert.equal(req.response.status, 404);
+  }
+
+  server.start(null);
+
+  await retrieveWBONotExists();
+  await retrieveWBOExists();
+  await deleteWBOExists();
+  await deleteWBONotExists();
+  await getStorageFails();
+  await getMissingCollectionWBO();
+  await deleteStorage();
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_x_weave_records() {
+  let server = new SyncServer();
+  server.registerUser("john", "password");
+
+  server.createContents("john", {
+    crypto: { foos: { foo: "bar" }, bars: { foo: "baz" } },
+  });
+  server.start();
+
+  let wbo = localRequest(server, "/1.1/john/storage/crypto/foos");
+  await wbo.get();
+  Assert.equal(false, "x-weave-records" in wbo.response.headers);
+  let col = localRequest(server, "/1.1/john/storage/crypto");
+  await col.get();
+  // Collection fetches do.
+  Assert.equal(col.response.headers["x-weave-records"], "2");
+
+  await promiseStopServer(server);
+});
diff --git a/src/zen/tests/mochitests/sync/test_interval_triggers.js b/src/zen/tests/mochitests/sync/test_interval_triggers.js
new file mode 100644
index 000000000..a2a35fb3f
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_interval_triggers.js
@@ -0,0 +1,472 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+Svc.PrefBranch.setStringPref("registerEngines", "");
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+let scheduler;
+let clientsEngine;
+
+async function sync_httpd_setup() {
+  let clientsSyncID = await clientsEngine.resetLocalSyncID();
+  let global = new ServerWBO("global", {
+    syncID: Service.syncID,
+    storageVersion: STORAGE_VERSION,
+    engines: {
+      clients: { version: clientsEngine.version, syncID: clientsSyncID },
+    },
+  });
+  let clientsColl = new ServerCollection({}, true);
+
+  // Tracking info/collections.
+  let collectionsHelper = track_collections_helper();
+  let upd = collectionsHelper.with_updated_collection;
+
+  return httpd_setup({
+    "/1.1/johndoe/storage/meta/global": upd("meta", global.handler()),
+    "/1.1/johndoe/info/collections": collectionsHelper.handler,
+    "/1.1/johndoe/storage/crypto/keys": upd(
+      "crypto",
+      new ServerWBO("keys").handler()
+    ),
+    "/1.1/johndoe/storage/clients": upd("clients", clientsColl.handler()),
+  });
+}
+
+async function setUp(server) {
+  syncTestLogging();
+  await configureIdentity({ username: "johndoe" }, server);
+  await generateNewKeys(Service.collectionKeys);
+  let serverKeys = Service.collectionKeys.asWBO("crypto", "keys");
+  await serverKeys.encrypt(Service.identity.syncKeyBundle);
+  await serverKeys.upload(Service.resource(Service.cryptoKeysURL));
+}
+
+add_task(async function setup() {
+  scheduler = Service.scheduler;
+  clientsEngine = Service.clientsEngine;
+
+  // Don't remove stale clients when syncing. This is a test-only workaround
+  // that lets us add clients directly to the store, without losing them on
+  // the next sync.
+  clientsEngine._removeRemoteClient = async () => {};
+});
+
+add_task(async function test_successful_sync_adjustSyncInterval() {
+  enableValidationPrefs();
+
+  _("Test successful sync calling adjustSyncInterval");
+  let syncSuccesses = 0;
+  function onSyncFinish() {
+    _("Sync success.");
+    syncSuccesses++;
+  }
+  Svc.Obs.add("weave:service:sync:finish", onSyncFinish);
+
+  let server = await sync_httpd_setup();
+  await setUp(server);
+
+  // Confirm defaults
+  Assert.ok(!scheduler.idle);
+  Assert.equal(false, scheduler.numClients > 1);
+  Assert.equal(scheduler.syncInterval, scheduler.singleDeviceInterval);
+  Assert.ok(!scheduler.hasIncomingItems);
+
+  _("Test as long as numClients <= 1 our sync interval is SINGLE_USER.");
+  // idle == true && numClients <= 1 && hasIncomingItems == false
+  scheduler.idle = true;
+  await Service.sync();
+  Assert.equal(syncSuccesses, 1);
+  Assert.ok(scheduler.idle);
+  Assert.equal(false, scheduler.numClients > 1);
+  Assert.ok(!scheduler.hasIncomingItems);
+  Assert.equal(scheduler.syncInterval, scheduler.singleDeviceInterval);
+
+  // idle == false && numClients <= 1 && hasIncomingItems == false
+  scheduler.idle = false;
+  await Service.sync();
+  Assert.equal(syncSuccesses, 2);
+  Assert.ok(!scheduler.idle);
+  Assert.equal(false, scheduler.numClients > 1);
+  Assert.ok(!scheduler.hasIncomingItems);
+  Assert.equal(scheduler.syncInterval, scheduler.singleDeviceInterval);
+
+  // idle == false && numClients <= 1 && hasIncomingItems == true
+  scheduler.hasIncomingItems = true;
+  await Service.sync();
+  Assert.equal(syncSuccesses, 3);
+  Assert.ok(!scheduler.idle);
+  Assert.equal(false, scheduler.numClients > 1);
+  Assert.ok(scheduler.hasIncomingItems);
+  Assert.equal(scheduler.syncInterval, scheduler.singleDeviceInterval);
+
+  // idle == true && numClients <= 1 && hasIncomingItems == true
+  scheduler.idle = true;
+  await Service.sync();
+  Assert.equal(syncSuccesses, 4);
+  Assert.ok(scheduler.idle);
+  Assert.equal(false, scheduler.numClients > 1);
+  Assert.ok(scheduler.hasIncomingItems);
+  Assert.equal(scheduler.syncInterval, scheduler.singleDeviceInterval);
+
+  _(
+    "Test as long as idle && numClients > 1 our sync interval is idleInterval."
+  );
+  // idle == true && numClients > 1 && hasIncomingItems == true
+  await Service.clientsEngine._store.create({
+    id: "foo",
+    cleartext: { name: "bar", type: "mobile" },
+  });
+  await Service.sync();
+  Assert.equal(syncSuccesses, 5);
+  Assert.ok(scheduler.idle);
+  Assert.greater(scheduler.numClients, 1);
+  Assert.ok(scheduler.hasIncomingItems);
+  Assert.equal(scheduler.syncInterval, scheduler.idleInterval);
+
+  // idle == true && numClients > 1 && hasIncomingItems == false
+  scheduler.hasIncomingItems = false;
+  await Service.sync();
+  Assert.equal(syncSuccesses, 6);
+  Assert.ok(scheduler.idle);
+  Assert.greater(scheduler.numClients, 1);
+  Assert.ok(!scheduler.hasIncomingItems);
+  Assert.equal(scheduler.syncInterval, scheduler.idleInterval);
+
+  _("Test non-idle, numClients > 1, no incoming items => activeInterval.");
+  // idle == false && numClients > 1 && hasIncomingItems == false
+  scheduler.idle = false;
+  await Service.sync();
+  Assert.equal(syncSuccesses, 7);
+  Assert.ok(!scheduler.idle);
+  Assert.greater(scheduler.numClients, 1);
+  Assert.ok(!scheduler.hasIncomingItems);
+  Assert.equal(scheduler.syncInterval, scheduler.activeInterval);
+
+  _("Test non-idle, numClients > 1, incoming items => immediateInterval.");
+  // idle == false && numClients > 1 && hasIncomingItems == true
+  scheduler.hasIncomingItems = true;
+  await Service.sync();
+  Assert.equal(syncSuccesses, 8);
+  Assert.ok(!scheduler.idle);
+  Assert.greater(scheduler.numClients, 1);
+  Assert.ok(!scheduler.hasIncomingItems); // gets reset to false
+  Assert.equal(scheduler.syncInterval, scheduler.immediateInterval);
+
+  Svc.Obs.remove("weave:service:sync:finish", onSyncFinish);
+  await Service.startOver();
+  await promiseStopServer(server);
+});
+
+add_task(async function test_unsuccessful_sync_adjustSyncInterval() {
+  enableValidationPrefs();
+
+  _("Test unsuccessful sync calling adjustSyncInterval");
+
+  let syncFailures = 0;
+  function onSyncError() {
+    _("Sync error.");
+    syncFailures++;
+  }
+  Svc.Obs.add("weave:service:sync:error", onSyncError);
+
+  _("Test unsuccessful sync calls adjustSyncInterval");
+  // Force sync to fail.
+  Svc.PrefBranch.setStringPref("firstSync", "notReady");
+
+  let server = await sync_httpd_setup();
+  await setUp(server);
+
+  // Confirm defaults
+  Assert.ok(!scheduler.idle);
+  Assert.equal(false, scheduler.numClients > 1);
+  Assert.equal(scheduler.syncInterval, scheduler.singleDeviceInterval);
+  Assert.ok(!scheduler.hasIncomingItems);
+
+  _("Test as long as numClients <= 1 our sync interval is SINGLE_USER.");
+  // idle == true && numClients <= 1 && hasIncomingItems == false
+  scheduler.idle = true;
+  await Service.sync();
+  Assert.equal(syncFailures, 1);
+  Assert.ok(scheduler.idle);
+  Assert.equal(false, scheduler.numClients > 1);
+  Assert.ok(!scheduler.hasIncomingItems);
+  Assert.equal(scheduler.syncInterval, scheduler.singleDeviceInterval);
+
+  // idle == false && numClients <= 1 && hasIncomingItems == false
+  scheduler.idle = false;
+  await Service.sync();
+  Assert.equal(syncFailures, 2);
+  Assert.ok(!scheduler.idle);
+  Assert.equal(false, scheduler.numClients > 1);
+  Assert.ok(!scheduler.hasIncomingItems);
+  Assert.equal(scheduler.syncInterval, scheduler.singleDeviceInterval);
+
+  // idle == false && numClients <= 1 && hasIncomingItems == true
+  scheduler.hasIncomingItems = true;
+  await Service.sync();
+  Assert.equal(syncFailures, 3);
+  Assert.ok(!scheduler.idle);
+  Assert.equal(false, scheduler.numClients > 1);
+  Assert.ok(scheduler.hasIncomingItems);
+  Assert.equal(scheduler.syncInterval, scheduler.singleDeviceInterval);
+
+  // idle == true && numClients <= 1 && hasIncomingItems == true
+  scheduler.idle = true;
+  await Service.sync();
+  Assert.equal(syncFailures, 4);
+  Assert.ok(scheduler.idle);
+  Assert.equal(false, scheduler.numClients > 1);
+  Assert.ok(scheduler.hasIncomingItems);
+  Assert.equal(scheduler.syncInterval, scheduler.singleDeviceInterval);
+
+  _(
+    "Test as long as idle && numClients > 1 our sync interval is idleInterval."
+  );
+  // idle == true && numClients > 1 && hasIncomingItems == true
+  Svc.PrefBranch.setIntPref("clients.devices.mobile", 2);
+  scheduler.updateClientMode();
+
+  await Service.sync();
+  Assert.equal(syncFailures, 5);
+  Assert.ok(scheduler.idle);
+  Assert.greater(scheduler.numClients, 1);
+  Assert.ok(scheduler.hasIncomingItems);
+  Assert.equal(scheduler.syncInterval, scheduler.idleInterval);
+
+  // idle == true && numClients > 1 && hasIncomingItems == false
+  scheduler.hasIncomingItems = false;
+  await Service.sync();
+  Assert.equal(syncFailures, 6);
+  Assert.ok(scheduler.idle);
+  Assert.greater(scheduler.numClients, 1);
+  Assert.ok(!scheduler.hasIncomingItems);
+  Assert.equal(scheduler.syncInterval, scheduler.idleInterval);
+
+  _("Test non-idle, numClients > 1, no incoming items => activeInterval.");
+  // idle == false && numClients > 1 && hasIncomingItems == false
+  scheduler.idle = false;
+  await Service.sync();
+  Assert.equal(syncFailures, 7);
+  Assert.ok(!scheduler.idle);
+  Assert.greater(scheduler.numClients, 1);
+  Assert.ok(!scheduler.hasIncomingItems);
+  Assert.equal(scheduler.syncInterval, scheduler.activeInterval);
+
+  _("Test non-idle, numClients > 1, incoming items => immediateInterval.");
+  // idle == false && numClients > 1 && hasIncomingItems == true
+  scheduler.hasIncomingItems = true;
+  await Service.sync();
+  Assert.equal(syncFailures, 8);
+  Assert.ok(!scheduler.idle);
+  Assert.greater(scheduler.numClients, 1);
+  Assert.ok(!scheduler.hasIncomingItems); // gets reset to false
+  Assert.equal(scheduler.syncInterval, scheduler.immediateInterval);
+
+  await Service.startOver();
+  Svc.Obs.remove("weave:service:sync:error", onSyncError);
+  await promiseStopServer(server);
+});
+
+add_task(async function test_back_triggers_sync() {
+  enableValidationPrefs();
+
+  let server = await sync_httpd_setup();
+  await setUp(server);
+
+  // Single device: no sync triggered.
+  scheduler.idle = true;
+  scheduler.observe(
+    null,
+    "active",
+    Svc.PrefBranch.getIntPref("scheduler.idleTime")
+  );
+  Assert.ok(!scheduler.idle);
+
+  // Multiple devices: sync is triggered.
+  Svc.PrefBranch.setIntPref("clients.devices.mobile", 2);
+  scheduler.updateClientMode();
+
+  let promiseDone = promiseOneObserver("weave:service:sync:finish");
+
+  scheduler.idle = true;
+  scheduler.observe(
+    null,
+    "active",
+    Svc.PrefBranch.getIntPref("scheduler.idleTime")
+  );
+  Assert.ok(!scheduler.idle);
+  await promiseDone;
+
+  Service.recordManager.clearCache();
+  for (const pref of Svc.PrefBranch.getChildList("")) {
+    Svc.PrefBranch.clearUserPref(pref);
+  }
+  scheduler.setDefaults();
+  await clientsEngine.resetClient();
+
+  await Service.startOver();
+  await promiseStopServer(server);
+});
+
+add_task(async function test_adjust_interval_on_sync_error() {
+  enableValidationPrefs();
+
+  let server = await sync_httpd_setup();
+  await setUp(server);
+
+  let syncFailures = 0;
+  function onSyncError() {
+    _("Sync error.");
+    syncFailures++;
+  }
+  Svc.Obs.add("weave:service:sync:error", onSyncError);
+
+  _("Test unsuccessful sync updates client mode & sync intervals");
+  // Force a sync fail.
+  Svc.PrefBranch.setStringPref("firstSync", "notReady");
+
+  Assert.equal(syncFailures, 0);
+  Assert.equal(false, scheduler.numClients > 1);
+  Assert.equal(scheduler.syncInterval, scheduler.singleDeviceInterval);
+
+  Svc.PrefBranch.setIntPref("clients.devices.mobile", 2);
+  await Service.sync();
+
+  Assert.equal(syncFailures, 1);
+  Assert.greater(scheduler.numClients, 1);
+  Assert.equal(scheduler.syncInterval, scheduler.activeInterval);
+
+  Svc.Obs.remove("weave:service:sync:error", onSyncError);
+  await Service.startOver();
+  await promiseStopServer(server);
+});
+
+add_task(async function test_bug671378_scenario() {
+  enableValidationPrefs();
+
+  // Test scenario similar to bug 671378. This bug appeared when a score
+  // update occurred that wasn't large enough to trigger a sync so
+  // scheduleNextSync() was called without a time interval parameter,
+  // setting nextSync to a non-zero value and preventing the timer from
+  // being adjusted in the next call to scheduleNextSync().
+  let server = await sync_httpd_setup();
+  await setUp(server);
+
+  let syncSuccesses = 0;
+  function onSyncFinish() {
+    _("Sync success.");
+    syncSuccesses++;
+  }
+  Svc.Obs.add("weave:service:sync:finish", onSyncFinish);
+
+  // After first sync call, syncInterval & syncTimer are singleDeviceInterval.
+  await Service.sync();
+  Assert.equal(syncSuccesses, 1);
+  Assert.equal(false, scheduler.numClients > 1);
+  Assert.equal(scheduler.syncInterval, scheduler.singleDeviceInterval);
+  Assert.equal(scheduler.syncTimer.delay, scheduler.singleDeviceInterval);
+
+  let promiseDone = new Promise(resolve => {
+    // Wrap scheduleNextSync so we are notified when it is finished.
+    scheduler._scheduleNextSync = scheduler.scheduleNextSync;
+    scheduler.scheduleNextSync = function () {
+      scheduler._scheduleNextSync();
+
+      // Check on sync:finish scheduleNextSync sets the appropriate
+      // syncInterval and syncTimer values.
+      if (syncSuccesses == 2) {
+        Assert.notEqual(scheduler.nextSync, 0);
+        Assert.equal(scheduler.syncInterval, scheduler.activeInterval);
+        Assert.lessOrEqual(scheduler.syncTimer.delay, scheduler.activeInterval);
+
+        scheduler.scheduleNextSync = scheduler._scheduleNextSync;
+        Svc.Obs.remove("weave:service:sync:finish", onSyncFinish);
+        Service.startOver().then(() => {
+          server.stop(resolve);
+        });
+      }
+    };
+  });
+
+  // Set nextSync != 0
+  // syncInterval still hasn't been set by call to updateClientMode.
+  // Explicitly trying to invoke scheduleNextSync during a sync
+  // (to immitate a score update that isn't big enough to trigger a sync).
+  Svc.Obs.add("weave:service:sync:start", function onSyncStart() {
+    // Wait for other sync:start observers to be called so that
+    // nextSync is set to 0.
+    CommonUtils.nextTick(function () {
+      Svc.Obs.remove("weave:service:sync:start", onSyncStart);
+
+      scheduler.scheduleNextSync();
+      Assert.notEqual(scheduler.nextSync, 0);
+      Assert.equal(scheduler.syncInterval, scheduler.singleDeviceInterval);
+      Assert.equal(scheduler.syncTimer.delay, scheduler.singleDeviceInterval);
+    });
+  });
+
+  await Service.clientsEngine._store.create({
+    id: "foo",
+    cleartext: { name: "bar", type: "mobile" },
+  });
+  await Service.sync();
+  await promiseDone;
+});
+
+add_task(async function test_adjust_timer_larger_syncInterval() {
+  _(
+    "Test syncInterval > current timout period && nextSync != 0, syncInterval is NOT used."
+  );
+  Svc.PrefBranch.setIntPref("clients.devices.mobile", 2);
+  scheduler.updateClientMode();
+  Assert.equal(scheduler.syncInterval, scheduler.activeInterval);
+
+  scheduler.scheduleNextSync();
+
+  // Ensure we have a small interval.
+  Assert.notEqual(scheduler.nextSync, 0);
+  Assert.equal(scheduler.syncTimer.delay, scheduler.activeInterval);
+
+  // Make interval large again
+  await clientsEngine._wipeClient();
+  Svc.PrefBranch.clearUserPref("clients.devices.mobile");
+  scheduler.updateClientMode();
+  Assert.equal(scheduler.syncInterval, scheduler.singleDeviceInterval);
+
+  scheduler.scheduleNextSync();
+
+  // Ensure timer delay remains as the small interval.
+  Assert.notEqual(scheduler.nextSync, 0);
+  Assert.lessOrEqual(scheduler.syncTimer.delay, scheduler.activeInterval);
+
+  // SyncSchedule.
+  await Service.startOver();
+});
+
+add_task(async function test_adjust_timer_smaller_syncInterval() {
+  _(
+    "Test current timout > syncInterval period && nextSync != 0, syncInterval is used."
+  );
+  scheduler.scheduleNextSync();
+
+  // Ensure we have a large interval.
+  Assert.notEqual(scheduler.nextSync, 0);
+  Assert.equal(scheduler.syncTimer.delay, scheduler.singleDeviceInterval);
+
+  // Make interval smaller
+  Svc.PrefBranch.setIntPref("clients.devices.mobile", 2);
+  scheduler.updateClientMode();
+  Assert.equal(scheduler.syncInterval, scheduler.activeInterval);
+
+  scheduler.scheduleNextSync();
+
+  // Ensure smaller timer delay is used.
+  Assert.notEqual(scheduler.nextSync, 0);
+  Assert.lessOrEqual(scheduler.syncTimer.delay, scheduler.activeInterval);
+
+  // SyncSchedule.
+  await Service.startOver();
+});
diff --git a/src/zen/tests/mochitests/sync/test_keys.js b/src/zen/tests/mochitests/sync/test_keys.js
new file mode 100644
index 000000000..58453bfba
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_keys.js
@@ -0,0 +1,242 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Weave } = ChromeUtils.importESModule(
+  "resource://services-sync/main.sys.mjs"
+);
+const { CollectionKeyManager, CryptoWrapper } = ChromeUtils.importESModule(
+  "resource://services-sync/record.sys.mjs"
+);
+
+var collectionKeys = new CollectionKeyManager();
+
+function do_check_keypair_eq(a, b) {
+  Assert.equal(2, a.length);
+  Assert.equal(2, b.length);
+  Assert.equal(a[0], b[0]);
+  Assert.equal(a[1], b[1]);
+}
+
+add_test(function test_set_invalid_values() {
+  _("Ensure that setting invalid encryption and HMAC key values is caught.");
+
+  let bundle = new BulkKeyBundle("foo");
+
+  let thrown = false;
+  try {
+    bundle.encryptionKey = null;
+  } catch (ex) {
+    thrown = true;
+    Assert.equal(ex.message.indexOf("Encryption key can only be set to"), 0);
+  } finally {
+    Assert.ok(thrown);
+    thrown = false;
+  }
+
+  try {
+    bundle.encryptionKey = ["trollololol"];
+  } catch (ex) {
+    thrown = true;
+    Assert.equal(ex.message.indexOf("Encryption key can only be set to"), 0);
+  } finally {
+    Assert.ok(thrown);
+    thrown = false;
+  }
+
+  try {
+    bundle.hmacKey = Utils.generateRandomBytesLegacy(15);
+  } catch (ex) {
+    thrown = true;
+    Assert.equal(ex.message.indexOf("HMAC key must be at least 128"), 0);
+  } finally {
+    Assert.ok(thrown);
+    thrown = false;
+  }
+
+  try {
+    bundle.hmacKey = null;
+  } catch (ex) {
+    thrown = true;
+    Assert.equal(ex.message.indexOf("HMAC key can only be set to string"), 0);
+  } finally {
+    Assert.ok(thrown);
+    thrown = false;
+  }
+
+  try {
+    bundle.hmacKey = ["trollolol"];
+  } catch (ex) {
+    thrown = true;
+    Assert.equal(ex.message.indexOf("HMAC key can only be set to"), 0);
+  } finally {
+    Assert.ok(thrown);
+    thrown = false;
+  }
+
+  try {
+    bundle.hmacKey = Utils.generateRandomBytesLegacy(15);
+  } catch (ex) {
+    thrown = true;
+    Assert.equal(ex.message.indexOf("HMAC key must be at least 128"), 0);
+  } finally {
+    Assert.ok(thrown);
+    thrown = false;
+  }
+
+  run_next_test();
+});
+
+add_task(async function test_ensureLoggedIn() {
+  let log = Log.repository.getLogger("Test");
+  Log.repository.rootLogger.addAppender(new Log.DumpAppender());
+
+  await configureIdentity();
+
+  let keyBundle = Weave.Service.identity.syncKeyBundle;
+
+  /*
+   * Build a test version of storage/crypto/keys.
+   * Encrypt it with the sync key.
+   * Pass it into the CollectionKeyManager.
+   */
+
+  log.info("Building storage keys...");
+  let storage_keys = new CryptoWrapper("crypto", "keys");
+  let default_key64 = await Weave.Crypto.generateRandomKey();
+  let default_hmac64 = await Weave.Crypto.generateRandomKey();
+  let bookmarks_key64 = await Weave.Crypto.generateRandomKey();
+  let bookmarks_hmac64 = await Weave.Crypto.generateRandomKey();
+
+  storage_keys.cleartext = {
+    default: [default_key64, default_hmac64],
+    collections: { bookmarks: [bookmarks_key64, bookmarks_hmac64] },
+  };
+  storage_keys.modified = Date.now() / 1000;
+  storage_keys.id = "keys";
+
+  log.info("Encrypting storage keys...");
+
+  // Use passphrase (sync key) itself to encrypt the key bundle.
+  await storage_keys.encrypt(keyBundle);
+
+  // Sanity checking.
+  Assert.equal(null, storage_keys.cleartext);
+  Assert.notEqual(null, storage_keys.ciphertext);
+
+  log.info("Updating collection keys.");
+
+  // updateContents decrypts the object, releasing the payload for us to use.
+  // Returns true, because the default key has changed.
+  Assert.ok(await collectionKeys.updateContents(keyBundle, storage_keys));
+  let payload = storage_keys.cleartext;
+
+  _("CK: " + JSON.stringify(collectionKeys._collections));
+
+  // Test that the CollectionKeyManager returns a similar WBO.
+  let wbo = collectionKeys.asWBO("crypto", "keys");
+
+  _("WBO: " + JSON.stringify(wbo));
+  _("WBO cleartext: " + JSON.stringify(wbo.cleartext));
+
+  // Check the individual contents.
+  Assert.equal(wbo.collection, "crypto");
+  Assert.equal(wbo.id, "keys");
+  Assert.equal(undefined, wbo.modified);
+  Assert.equal(collectionKeys.lastModified, storage_keys.modified);
+  Assert.ok(!!wbo.cleartext.default);
+  do_check_keypair_eq(payload.default, wbo.cleartext.default);
+  do_check_keypair_eq(
+    payload.collections.bookmarks,
+    wbo.cleartext.collections.bookmarks
+  );
+
+  Assert.ok("bookmarks" in collectionKeys._collections);
+  Assert.equal(false, "tabs" in collectionKeys._collections);
+
+  _("Updating contents twice with the same data doesn't proceed.");
+  await storage_keys.encrypt(keyBundle);
+  Assert.equal(
+    false,
+    await collectionKeys.updateContents(keyBundle, storage_keys)
+  );
+
+  /*
+   * Test that we get the right keys out when we ask for
+   * a collection's tokens.
+   */
+  let b1 = new BulkKeyBundle("bookmarks");
+  b1.keyPairB64 = [bookmarks_key64, bookmarks_hmac64];
+  let b2 = collectionKeys.keyForCollection("bookmarks");
+  do_check_keypair_eq(b1.keyPair, b2.keyPair);
+
+  // Check key equality.
+  Assert.ok(b1.equals(b2));
+  Assert.ok(b2.equals(b1));
+
+  b1 = new BulkKeyBundle("[default]");
+  b1.keyPairB64 = [default_key64, default_hmac64];
+
+  Assert.ok(!b1.equals(b2));
+  Assert.ok(!b2.equals(b1));
+
+  b2 = collectionKeys.keyForCollection(null);
+  do_check_keypair_eq(b1.keyPair, b2.keyPair);
+
+  /*
+   * Checking for update times.
+   */
+  let info_collections = {};
+  Assert.ok(collectionKeys.updateNeeded(info_collections));
+  info_collections.crypto = 5000;
+  Assert.ok(!collectionKeys.updateNeeded(info_collections));
+  info_collections.crypto = 1 + Date.now() / 1000; // Add one in case computers are fast!
+  Assert.ok(collectionKeys.updateNeeded(info_collections));
+
+  collectionKeys.lastModified = null;
+  Assert.ok(collectionKeys.updateNeeded({}));
+
+  /*
+   * Check _compareKeyBundleCollections.
+   */
+  async function newBundle(name) {
+    let r = new BulkKeyBundle(name);
+    await r.generateRandom();
+    return r;
+  }
+  let k1 = await newBundle("k1");
+  let k2 = await newBundle("k2");
+  let k3 = await newBundle("k3");
+  let k4 = await newBundle("k4");
+  let k5 = await newBundle("k5");
+  let coll1 = { foo: k1, bar: k2 };
+  let coll2 = { foo: k1, bar: k2 };
+  let coll3 = { foo: k1, bar: k3 };
+  let coll4 = { foo: k4 };
+  let coll5 = { baz: k5, bar: k2 };
+  let coll6 = {};
+
+  let d1 = collectionKeys._compareKeyBundleCollections(coll1, coll2); // []
+  let d2 = collectionKeys._compareKeyBundleCollections(coll1, coll3); // ["bar"]
+  let d3 = collectionKeys._compareKeyBundleCollections(coll3, coll2); // ["bar"]
+  let d4 = collectionKeys._compareKeyBundleCollections(coll1, coll4); // ["bar", "foo"]
+  let d5 = collectionKeys._compareKeyBundleCollections(coll5, coll2); // ["baz", "foo"]
+  let d6 = collectionKeys._compareKeyBundleCollections(coll6, coll1); // ["bar", "foo"]
+  let d7 = collectionKeys._compareKeyBundleCollections(coll5, coll5); // []
+  let d8 = collectionKeys._compareKeyBundleCollections(coll6, coll6); // []
+
+  Assert.ok(d1.same);
+  Assert.ok(!d2.same);
+  Assert.ok(!d3.same);
+  Assert.ok(!d4.same);
+  Assert.ok(!d5.same);
+  Assert.ok(!d6.same);
+  Assert.ok(d7.same);
+  Assert.ok(d8.same);
+
+  Assert.deepEqual(d1.changed, []);
+  Assert.deepEqual(d2.changed, ["bar"]);
+  Assert.deepEqual(d3.changed, ["bar"]);
+  Assert.deepEqual(d4.changed, ["bar", "foo"]);
+  Assert.deepEqual(d5.changed, ["baz", "foo"]);
+  Assert.deepEqual(d6.changed, ["bar", "foo"]);
+});
diff --git a/src/zen/tests/mochitests/sync/test_load_modules.js b/src/zen/tests/mochitests/sync/test_load_modules.js
new file mode 100644
index 000000000..93ef883d4
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_load_modules.js
@@ -0,0 +1,59 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { AppConstants } = ChromeUtils.importESModule(
+  "resource://gre/modules/AppConstants.sys.mjs"
+);
+
+const modules = [
+  "addonutils.sys.mjs",
+  "addonsreconciler.sys.mjs",
+  "constants.sys.mjs",
+  "engines/addons.sys.mjs",
+  "engines/clients.sys.mjs",
+  "engines/extension-storage.sys.mjs",
+  "engines/passwords.sys.mjs",
+  "engines/prefs.sys.mjs",
+  "engines.sys.mjs",
+  "keys.sys.mjs",
+  "main.sys.mjs",
+  "policies.sys.mjs",
+  "record.sys.mjs",
+  "resource.sys.mjs",
+  "service.sys.mjs",
+  "stages/declined.sys.mjs",
+  "stages/enginesync.sys.mjs",
+  "status.sys.mjs",
+  "sync_auth.sys.mjs",
+  "util.sys.mjs",
+];
+
+if (AppConstants.MOZ_APP_NAME != "thunderbird") {
+  modules.push(
+    "engines/bookmarks.sys.mjs",
+    "engines/forms.sys.mjs",
+    "engines/history.sys.mjs",
+    "engines/tabs.sys.mjs"
+  );
+}
+
+const testingModules = [
+  "fakeservices.sys.mjs",
+  "rotaryengine.sys.mjs",
+  "utils.sys.mjs",
+  "fxa_utils.sys.mjs",
+];
+
+function run_test() {
+  for (let m of modules) {
+    let res = "resource://services-sync/" + m;
+    _("Attempting to load " + res);
+    ChromeUtils.importESModule(res);
+  }
+
+  for (let m of testingModules) {
+    let res = "resource://testing-common/services/sync/" + m;
+    _("Attempting to load " + res);
+    ChromeUtils.importESModule(res);
+  }
+}
diff --git a/src/zen/tests/mochitests/sync/test_node_reassignment.js b/src/zen/tests/mochitests/sync/test_node_reassignment.js
new file mode 100644
index 000000000..4a10cb803
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_node_reassignment.js
@@ -0,0 +1,523 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+_(
+  "Test that node reassignment responses are respected on all kinds of " +
+    "requests."
+);
+
+const { RESTRequest } = ChromeUtils.importESModule(
+  "resource://services-common/rest.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+add_task(async function setup() {
+  validate_all_future_pings();
+});
+
+/**
+ * Emulate the following Zeus config:
+ * $draining = data.get($prefix . $host . " draining");
+ * if ($draining == "drain.") {
+ *   log.warn($log_host_db_status . " migrating=1 (node-reassignment)" .
+ *            $log_suffix);
+ *   http.sendResponse("401 Node reassignment", $content_type,
+ *                     '"server request: node reassignment"', "");
+ * }
+ */
+const reassignBody = '"server request: node reassignment"';
+
+// API-compatible with SyncServer handler. Bind `handler` to something to use
+// as a ServerCollection handler.
+function handleReassign(handler, req, resp) {
+  resp.setStatusLine(req.httpVersion, 401, "Node reassignment");
+  resp.setHeader("Content-Type", "application/json");
+  resp.bodyOutputStream.write(reassignBody, reassignBody.length);
+}
+
+async function prepareServer() {
+  let server = new SyncServer();
+  server.registerUser("johndoe");
+  server.start();
+  syncTestLogging();
+  await configureIdentity({ username: "johndoe" }, server);
+  return server;
+}
+
+function getReassigned() {
+  try {
+    return Services.prefs.getBoolPref("services.sync.lastSyncReassigned");
+  } catch (ex) {
+    if (ex.result != Cr.NS_ERROR_UNEXPECTED) {
+      do_throw(
+        "Got exception retrieving lastSyncReassigned: " + Log.exceptionStr(ex)
+      );
+    }
+  }
+  return false;
+}
+
+/**
+ * Make a test request to `url`, then watch the result of two syncs
+ * to ensure that a node request was made.
+ * Runs `between` between the two. This can be used to undo deliberate failure
+ * setup, detach observers, etc.
+ */
+async function syncAndExpectNodeReassignment(
+  server,
+  firstNotification,
+  between,
+  secondNotification,
+  url
+) {
+  let deferred = Promise.withResolvers();
+
+  let getTokenCount = 0;
+  let mockTSC = {
+    // TokenServerClient
+    async getTokenUsingOAuth() {
+      getTokenCount++;
+      return { endpoint: server.baseURI + "1.1/johndoe/" };
+    },
+  };
+  Service.identity._tokenServerClient = mockTSC;
+
+  // Make sure that it works!
+  let request = new RESTRequest(url);
+  let response = await request.get();
+  Assert.equal(response.status, 401);
+
+  function onFirstSync() {
+    _("First sync completed.");
+    Svc.Obs.remove(firstNotification, onFirstSync);
+    Svc.Obs.add(secondNotification, onSecondSync);
+
+    Assert.equal(Service.clusterURL, "");
+
+    // Allow for tests to clean up error conditions.
+    between();
+  }
+  function onSecondSync() {
+    _("Second sync completed.");
+    Svc.Obs.remove(secondNotification, onSecondSync);
+    Service.scheduler.clearSyncTriggers();
+
+    // Make absolutely sure that any event listeners are done with their work
+    // before we proceed.
+    waitForZeroTimer(function () {
+      _("Second sync nextTick.");
+      Assert.equal(getTokenCount, 1);
+      Service.startOver().then(() => {
+        server.stop(deferred.resolve);
+      });
+    });
+  }
+
+  Svc.Obs.add(firstNotification, onFirstSync);
+  await Service.sync();
+
+  await deferred.promise;
+}
+
+add_task(async function test_momentary_401_engine() {
+  enableValidationPrefs();
+
+  _("Test a failure for engine URLs that's resolved by reassignment.");
+  let server = await prepareServer();
+  let john = server.user("johndoe");
+
+  _("Enabling the Rotary engine.");
+  let { engine, syncID, tracker } = await registerRotaryEngine();
+
+  // We need the server to be correctly set up prior to experimenting. Do this
+  // through a sync.
+  let global = {
+    syncID: Service.syncID,
+    storageVersion: STORAGE_VERSION,
+    rotary: { version: engine.version, syncID },
+  };
+  john.createCollection("meta").insert("global", global);
+
+  _("First sync to prepare server contents.");
+  await Service.sync();
+
+  let numResets = 0;
+  let observeReset = (obs, topic) => {
+    if (topic == "rotary") {
+      numResets += 1;
+    }
+  };
+  _("Adding observer that we saw an engine reset.");
+  Svc.Obs.add("weave:engine:reset-client:finish", observeReset);
+
+  _("Setting up Rotary collection to 401.");
+  let rotary = john.createCollection("rotary");
+  let oldHandler = rotary.collectionHandler;
+  rotary.collectionHandler = handleReassign.bind(this, undefined);
+
+  // We want to verify that the clusterURL pref has been cleared after a 401
+  // inside a sync. Flag the Rotary engine to need syncing.
+  john.collection("rotary").timestamp += 1000;
+
+  function between() {
+    _("Undoing test changes.");
+    rotary.collectionHandler = oldHandler;
+
+    function onLoginStart() {
+      // lastSyncReassigned shouldn't be cleared until a sync has succeeded.
+      _("Ensuring that lastSyncReassigned is still set at next sync start.");
+      Svc.Obs.remove("weave:service:login:start", onLoginStart);
+      Assert.ok(getReassigned());
+    }
+
+    _("Adding observer that lastSyncReassigned is still set on login.");
+    Svc.Obs.add("weave:service:login:start", onLoginStart);
+  }
+
+  await syncAndExpectNodeReassignment(
+    server,
+    "weave:service:sync:finish",
+    between,
+    "weave:service:sync:finish",
+    Service.storageURL + "rotary"
+  );
+
+  Svc.Obs.remove("weave:engine:reset-client:finish", observeReset);
+  Assert.equal(numResets, 1);
+  await tracker.clearChangedIDs();
+  await Service.engineManager.unregister(engine);
+});
+
+// This test ends up being a failing fetch *after we're already logged in*.
+add_task(async function test_momentary_401_info_collections() {
+  enableValidationPrefs();
+
+  _("Test a failure for info/collections that's resolved by reassignment.");
+  let server = await prepareServer();
+
+  _("First sync to prepare server contents.");
+  await Service.sync();
+
+  // Return a 401 for info requests, particularly info/collections.
+  let oldHandler = server.toplevelHandlers.info;
+  server.toplevelHandlers.info = handleReassign;
+
+  function undo() {
+    _("Undoing test changes.");
+    server.toplevelHandlers.info = oldHandler;
+  }
+
+  await syncAndExpectNodeReassignment(
+    server,
+    "weave:service:sync:error",
+    undo,
+    "weave:service:sync:finish",
+    Service.infoURL
+  );
+});
+
+add_task(async function test_momentary_401_storage_loggedin() {
+  enableValidationPrefs();
+
+  _(
+    "Test a failure for any storage URL, not just engine parts. " +
+      "Resolved by reassignment."
+  );
+  let server = await prepareServer();
+
+  _("Performing initial sync to ensure we are logged in.");
+  await Service.sync();
+
+  // Return a 401 for all storage requests.
+  let oldHandler = server.toplevelHandlers.storage;
+  server.toplevelHandlers.storage = handleReassign;
+
+  function undo() {
+    _("Undoing test changes.");
+    server.toplevelHandlers.storage = oldHandler;
+  }
+
+  Assert.ok(Service.isLoggedIn, "already logged in");
+  await syncAndExpectNodeReassignment(
+    server,
+    "weave:service:sync:error",
+    undo,
+    "weave:service:sync:finish",
+    Service.storageURL + "meta/global"
+  );
+});
+
+add_task(async function test_momentary_401_storage_loggedout() {
+  enableValidationPrefs();
+
+  _(
+    "Test a failure for any storage URL, not just engine parts. " +
+      "Resolved by reassignment."
+  );
+  let server = await prepareServer();
+
+  // Return a 401 for all storage requests.
+  let oldHandler = server.toplevelHandlers.storage;
+  server.toplevelHandlers.storage = handleReassign;
+
+  function undo() {
+    _("Undoing test changes.");
+    server.toplevelHandlers.storage = oldHandler;
+  }
+
+  Assert.ok(!Service.isLoggedIn, "not already logged in");
+  await syncAndExpectNodeReassignment(
+    server,
+    "weave:service:login:error",
+    undo,
+    "weave:service:sync:finish",
+    Service.storageURL + "meta/global"
+  );
+});
+
+add_task(async function test_loop_avoidance_storage() {
+  enableValidationPrefs();
+
+  _(
+    "Test that a repeated failure doesn't result in a sync loop " +
+      "if node reassignment cannot resolve the failure."
+  );
+
+  let server = await prepareServer();
+
+  // Return a 401 for all storage requests.
+  let oldHandler = server.toplevelHandlers.storage;
+  server.toplevelHandlers.storage = handleReassign;
+
+  let firstNotification = "weave:service:login:error";
+  let secondNotification = "weave:service:login:error";
+  let thirdNotification = "weave:service:sync:finish";
+
+  let deferred = Promise.withResolvers();
+
+  let getTokenCount = 0;
+  let mockTSC = {
+    // TokenServerClient
+    async getTokenUsingOAuth() {
+      getTokenCount++;
+      return { endpoint: server.baseURI + "1.1/johndoe/" };
+    },
+  };
+  Service.identity._tokenServerClient = mockTSC;
+
+  // Track the time. We want to make sure the duration between the first and
+  // second sync is small, and then that the duration between second and third
+  // is set to be large.
+  let now;
+
+  function onFirstSync() {
+    _("First sync completed.");
+    Svc.Obs.remove(firstNotification, onFirstSync);
+    Svc.Obs.add(secondNotification, onSecondSync);
+
+    Assert.equal(Service.clusterURL, "");
+
+    // We got a 401 mid-sync, and set the pref accordingly.
+    Assert.ok(Services.prefs.getBoolPref("services.sync.lastSyncReassigned"));
+
+    // Update the timestamp.
+    now = Date.now();
+  }
+
+  function onSecondSync() {
+    _("Second sync completed.");
+    Svc.Obs.remove(secondNotification, onSecondSync);
+    Svc.Obs.add(thirdNotification, onThirdSync);
+
+    // This sync occurred within the backoff interval.
+    let elapsedTime = Date.now() - now;
+    Assert.less(elapsedTime, MINIMUM_BACKOFF_INTERVAL);
+
+    // This pref will be true until a sync completes successfully.
+    Assert.ok(getReassigned());
+
+    // The timer will be set for some distant time.
+    // We store nextSync in prefs, which offers us only limited resolution.
+    // Include that logic here.
+    let expectedNextSync =
+      1000 * Math.floor((now + MINIMUM_BACKOFF_INTERVAL) / 1000);
+    _("Next sync scheduled for " + Service.scheduler.nextSync);
+    _("Expected to be slightly greater than " + expectedNextSync);
+
+    Assert.greaterOrEqual(Service.scheduler.nextSync, expectedNextSync);
+    Assert.ok(!!Service.scheduler.syncTimer);
+
+    // Undo our evil scheme.
+    server.toplevelHandlers.storage = oldHandler;
+
+    // Bring the timer forward to kick off a successful sync, so we can watch
+    // the pref get cleared.
+    Service.scheduler.scheduleNextSync(0);
+  }
+  function onThirdSync() {
+    Svc.Obs.remove(thirdNotification, onThirdSync);
+
+    // That'll do for now; no more syncs.
+    Service.scheduler.clearSyncTriggers();
+
+    // Make absolutely sure that any event listeners are done with their work
+    // before we proceed.
+    waitForZeroTimer(function () {
+      _("Third sync nextTick.");
+      Assert.ok(!getReassigned());
+      Assert.equal(getTokenCount, 2);
+      Service.startOver().then(() => {
+        server.stop(deferred.resolve);
+      });
+    });
+  }
+
+  Svc.Obs.add(firstNotification, onFirstSync);
+
+  now = Date.now();
+  await Service.sync();
+  await deferred.promise;
+});
+
+add_task(async function test_loop_avoidance_engine() {
+  enableValidationPrefs();
+
+  _(
+    "Test that a repeated 401 in an engine doesn't result in a sync loop " +
+      "if node reassignment cannot resolve the failure."
+  );
+  let server = await prepareServer();
+  let john = server.user("johndoe");
+
+  _("Enabling the Rotary engine.");
+  let { engine, syncID, tracker } = await registerRotaryEngine();
+  let deferred = Promise.withResolvers();
+
+  let getTokenCount = 0;
+  let mockTSC = {
+    // TokenServerClient
+    async getTokenUsingOAuth() {
+      getTokenCount++;
+      return { endpoint: server.baseURI + "1.1/johndoe/" };
+    },
+  };
+  Service.identity._tokenServerClient = mockTSC;
+
+  // We need the server to be correctly set up prior to experimenting. Do this
+  // through a sync.
+  let global = {
+    syncID: Service.syncID,
+    storageVersion: STORAGE_VERSION,
+    rotary: { version: engine.version, syncID },
+  };
+  john.createCollection("meta").insert("global", global);
+
+  _("First sync to prepare server contents.");
+  await Service.sync();
+
+  _("Setting up Rotary collection to 401.");
+  let rotary = john.createCollection("rotary");
+  let oldHandler = rotary.collectionHandler;
+  rotary.collectionHandler = handleReassign.bind(this, undefined);
+
+  // Flag the Rotary engine to need syncing.
+  john.collection("rotary").timestamp += 1000;
+
+  function onLoginStart() {
+    // lastSyncReassigned shouldn't be cleared until a sync has succeeded.
+    _("Ensuring that lastSyncReassigned is still set at next sync start.");
+    Assert.ok(getReassigned());
+  }
+
+  function beforeSuccessfulSync() {
+    _("Undoing test changes.");
+    rotary.collectionHandler = oldHandler;
+  }
+
+  let firstNotification = "weave:service:sync:finish";
+  let secondNotification = "weave:service:sync:finish";
+  let thirdNotification = "weave:service:sync:finish";
+
+  // Track the time. We want to make sure the duration between the first and
+  // second sync is small, and then that the duration between second and third
+  // is set to be large.
+  let now;
+
+  function onFirstSync() {
+    _("First sync completed.");
+    Svc.Obs.remove(firstNotification, onFirstSync);
+    Svc.Obs.add(secondNotification, onSecondSync);
+
+    Assert.equal(Service.clusterURL, "");
+
+    _("Adding observer that lastSyncReassigned is still set on login.");
+    Svc.Obs.add("weave:service:login:start", onLoginStart);
+
+    // We got a 401 mid-sync, and set the pref accordingly.
+    Assert.ok(Services.prefs.getBoolPref("services.sync.lastSyncReassigned"));
+
+    // Update the timestamp.
+    now = Date.now();
+  }
+
+  function onSecondSync() {
+    _("Second sync completed.");
+    Svc.Obs.remove(secondNotification, onSecondSync);
+    Svc.Obs.add(thirdNotification, onThirdSync);
+
+    // This sync occurred within the backoff interval.
+    let elapsedTime = Date.now() - now;
+    Assert.less(elapsedTime, MINIMUM_BACKOFF_INTERVAL);
+
+    // This pref will be true until a sync completes successfully.
+    Assert.ok(getReassigned());
+
+    // The timer will be set for some distant time.
+    // We store nextSync in prefs, which offers us only limited resolution.
+    // Include that logic here.
+    let expectedNextSync =
+      1000 * Math.floor((now + MINIMUM_BACKOFF_INTERVAL) / 1000);
+    _("Next sync scheduled for " + Service.scheduler.nextSync);
+    _("Expected to be slightly greater than " + expectedNextSync);
+
+    Assert.greaterOrEqual(Service.scheduler.nextSync, expectedNextSync);
+    Assert.ok(!!Service.scheduler.syncTimer);
+
+    // Undo our evil scheme.
+    beforeSuccessfulSync();
+
+    // Bring the timer forward to kick off a successful sync, so we can watch
+    // the pref get cleared.
+    Service.scheduler.scheduleNextSync(0);
+  }
+
+  function onThirdSync() {
+    Svc.Obs.remove(thirdNotification, onThirdSync);
+
+    // That'll do for now; no more syncs.
+    Service.scheduler.clearSyncTriggers();
+
+    // Make absolutely sure that any event listeners are done with their work
+    // before we proceed.
+    waitForZeroTimer(function () {
+      _("Third sync nextTick.");
+      Assert.ok(!getReassigned());
+      Assert.equal(getTokenCount, 2);
+      Svc.Obs.remove("weave:service:login:start", onLoginStart);
+      Service.startOver().then(() => {
+        server.stop(deferred.resolve);
+      });
+    });
+  }
+
+  Svc.Obs.add(firstNotification, onFirstSync);
+
+  now = Date.now();
+  await Service.sync();
+  await deferred.promise;
+
+  await tracker.clearChangedIDs();
+  await Service.engineManager.unregister(engine);
+});
diff --git a/src/zen/tests/mochitests/sync/test_password_engine.js b/src/zen/tests/mochitests/sync/test_password_engine.js
new file mode 100644
index 000000000..c9f278e33
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_password_engine.js
@@ -0,0 +1,1258 @@
+const { FXA_PWDMGR_HOST, FXA_PWDMGR_REALM } = ChromeUtils.importESModule(
+  "resource://gre/modules/FxAccountsCommon.sys.mjs"
+);
+const { LoginRec } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/passwords.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+const LoginInfo = Components.Constructor(
+  "@mozilla.org/login-manager/loginInfo;1",
+  Ci.nsILoginInfo,
+  "init"
+);
+
+const { LoginCSVImport } = ChromeUtils.importESModule(
+  "resource://gre/modules/LoginCSVImport.sys.mjs"
+);
+
+const { FileTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/FileTestUtils.sys.mjs"
+);
+
+const PropertyBag = Components.Constructor(
+  "@mozilla.org/hash-property-bag;1",
+  Ci.nsIWritablePropertyBag
+);
+
+async function cleanup(engine, server) {
+  await engine._tracker.stop();
+  await engine.wipeClient();
+  engine.lastModified = null;
+  for (const pref of Svc.PrefBranch.getChildList("")) {
+    Svc.PrefBranch.clearUserPref(pref);
+  }
+  Service.recordManager.clearCache();
+  if (server) {
+    await promiseStopServer(server);
+  }
+}
+
+add_task(async function setup() {
+  // Disable addon sync because AddonManager won't be initialized here.
+  await Service.engineManager.unregister("addons");
+  await Service.engineManager.unregister("extension-storage");
+});
+
+add_task(async function test_ignored_fields() {
+  _("Only changes to syncable fields should be tracked");
+
+  let engine = Service.engineManager.get("passwords");
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  enableValidationPrefs();
+
+  let loginInfo = new LoginInfo(
+    "https://example.com",
+    "",
+    null,
+    "username",
+    "password",
+    "",
+    ""
+  );
+
+  // Setting syncCounter to -1 so that it will be incremented to 0 when added.
+  loginInfo.syncCounter = -1;
+  let login = await Services.logins.addLoginAsync(loginInfo);
+  login.QueryInterface(Ci.nsILoginMetaInfo); // For `guid`.
+
+  engine._tracker.start();
+
+  try {
+    let nonSyncableProps = new PropertyBag();
+    nonSyncableProps.setProperty("timeLastUsed", Date.now());
+    nonSyncableProps.setProperty("timesUsed", 3);
+    await Services.logins.modifyLoginAsync(login, nonSyncableProps);
+
+    let noChanges = await engine.pullNewChanges();
+    deepEqual(noChanges, {}, "Should not track non-syncable fields");
+
+    let syncableProps = new PropertyBag();
+    syncableProps.setProperty("username", "newuser");
+    await Services.logins.modifyLoginAsync(login, syncableProps);
+
+    let changes = await engine.pullNewChanges();
+    deepEqual(
+      Object.keys(changes),
+      [login.guid],
+      "Should track syncable fields"
+    );
+  } finally {
+    await cleanup(engine, server);
+  }
+});
+
+add_task(async function test_ignored_sync_credentials() {
+  _("Sync credentials in login manager should be ignored");
+
+  let engine = Service.engineManager.get("passwords");
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  enableValidationPrefs();
+
+  engine._tracker.start();
+
+  try {
+    let login = await Services.logins.addLoginAsync(
+      new LoginInfo(
+        FXA_PWDMGR_HOST,
+        null,
+        FXA_PWDMGR_REALM,
+        "fxa-uid",
+        "creds",
+        "",
+        ""
+      )
+    );
+
+    let noChanges = await engine.pullNewChanges();
+    deepEqual(noChanges, {}, "Should not track new FxA credentials");
+
+    let props = new PropertyBag();
+    props.setProperty("password", "newcreds");
+    await Services.logins.modifyLoginAsync(login, props);
+
+    noChanges = await engine.pullNewChanges();
+    deepEqual(noChanges, {}, "Should not track changes to FxA credentials");
+
+    let foundLogins = await Services.logins.searchLoginsAsync({
+      origin: FXA_PWDMGR_HOST,
+    });
+    equal(foundLogins.length, 1);
+    equal(foundLogins[0].syncCounter, 0);
+    equal(foundLogins[0].everSynced, false);
+  } finally {
+    await cleanup(engine, server);
+  }
+});
+
+add_task(async function test_password_engine() {
+  _("Basic password sync test");
+
+  let engine = Service.engineManager.get("passwords");
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+  let collection = server.user("foo").collection("passwords");
+
+  enableValidationPrefs();
+
+  _("Add new login to upload during first sync");
+  let newLogin;
+  {
+    let login = new LoginInfo(
+      "https://example.com",
+      "",
+      null,
+      "username",
+      "password",
+      "",
+      ""
+    );
+    await Services.logins.addLoginAsync(login);
+
+    let logins = await Services.logins.searchLoginsAsync({
+      origin: "https://example.com",
+    });
+    equal(logins.length, 1, "Should find new login in login manager");
+    newLogin = logins[0].QueryInterface(Ci.nsILoginMetaInfo);
+
+    // Insert a server record that's older, so that we prefer the local one.
+    let rec = new LoginRec("passwords", newLogin.guid);
+    rec.formSubmitURL = newLogin.formActionOrigin;
+    rec.httpRealm = newLogin.httpRealm;
+    rec.hostname = newLogin.origin;
+    rec.username = newLogin.username;
+    rec.password = "sekrit";
+    let remotePasswordChangeTime = Date.now() - 1 * 60 * 60 * 24 * 1000;
+    rec.timeCreated = remotePasswordChangeTime;
+    rec.timePasswordChanged = remotePasswordChangeTime;
+    collection.insert(
+      newLogin.guid,
+      encryptPayload(rec.cleartext),
+      remotePasswordChangeTime / 1000
+    );
+  }
+
+  _("Add login with older password change time to replace during first sync");
+  let oldLogin;
+  {
+    let login = new LoginInfo(
+      "https://mozilla.com",
+      "",
+      null,
+      "us3r",
+      "0ldpa55",
+      "",
+      ""
+    );
+    await Services.logins.addLoginAsync(login);
+
+    let props = new PropertyBag();
+    let localPasswordChangeTime = Date.now() - 1 * 60 * 60 * 24 * 1000;
+    props.setProperty("timePasswordChanged", localPasswordChangeTime);
+    await Services.logins.modifyLoginAsync(login, props);
+
+    let logins = await Services.logins.searchLoginsAsync({
+      origin: "https://mozilla.com",
+    });
+    equal(logins.length, 1, "Should find old login in login manager");
+    oldLogin = logins[0].QueryInterface(Ci.nsILoginMetaInfo);
+    equal(oldLogin.timePasswordChanged, localPasswordChangeTime);
+
+    let rec = new LoginRec("passwords", oldLogin.guid);
+    rec.hostname = oldLogin.origin;
+    rec.formSubmitURL = oldLogin.formActionOrigin;
+    rec.httpRealm = oldLogin.httpRealm;
+    rec.username = oldLogin.username;
+    // Change the password and bump the password change time to ensure we prefer
+    // the remote one during reconciliation.
+    rec.password = "n3wpa55";
+    rec.usernameField = oldLogin.usernameField;
+    rec.passwordField = oldLogin.usernameField;
+    rec.timeCreated = oldLogin.timeCreated;
+    rec.timePasswordChanged = Date.now();
+    collection.insert(oldLogin.guid, encryptPayload(rec.cleartext));
+  }
+
+  await engine._tracker.stop();
+
+  try {
+    await sync_engine_and_validate_telem(engine, false);
+
+    let newRec = collection.cleartext(newLogin.guid);
+    equal(
+      newRec.password,
+      "password",
+      "Should update remote password for newer login"
+    );
+
+    let logins = await Services.logins.searchLoginsAsync({
+      origin: "https://mozilla.com",
+    });
+    equal(
+      logins[0].password,
+      "n3wpa55",
+      "Should update local password for older login"
+    );
+  } finally {
+    await cleanup(engine, server);
+  }
+});
+
+add_task(async function test_sync_outgoing() {
+  _("Test syncing outgoing records");
+
+  let engine = Service.engineManager.get("passwords");
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  let collection = server.user("foo").collection("passwords");
+
+  let loginInfo = new LoginInfo(
+    "http://mozilla.com",
+    "http://mozilla.com",
+    null,
+    "theuser",
+    "thepassword",
+    "username",
+    "password"
+  );
+  let login = await Services.logins.addLoginAsync(loginInfo);
+
+  engine._tracker.start();
+
+  try {
+    let foundLogins = await Services.logins.searchLoginsAsync({
+      origin: "http://mozilla.com",
+    });
+    equal(foundLogins.length, 1);
+    equal(foundLogins[0].syncCounter, 1);
+    equal(foundLogins[0].everSynced, false);
+    equal(collection.count(), 0);
+
+    let guid = foundLogins[0].QueryInterface(Ci.nsILoginMetaInfo).guid;
+
+    let changes = await engine.getChangedIDs();
+    let change = changes[guid];
+    equal(Object.keys(changes).length, 1);
+    equal(change.counter, 1);
+    ok(!change.deleted);
+
+    // This test modifies the password and then performs a sync and
+    // then ensures that the synced record is correct. This is done twice
+    // to ensure that syncing occurs correctly when the server record does not
+    // yet exist and when it does already exist.
+    for (let i = 1; i <= 2; i++) {
+      _("Modify the password iteration " + i);
+      foundLogins[0].password = "newpassword" + i;
+      await Services.logins.modifyLoginAsync(login, foundLogins[0]);
+      foundLogins = await Services.logins.searchLoginsAsync({
+        origin: "http://mozilla.com",
+      });
+      equal(foundLogins.length, 1);
+      // On the first pass, the counter should be 2, one for the add and one for the modify.
+      // No sync has occurred yet so everSynced should be false.
+      // On the second pass, the counter will only be 1 for the modify. The everSynced
+      // property should be true as the sync happened on the last iteration.
+      equal(foundLogins[0].syncCounter, i == 2 ? 1 : 2);
+      equal(foundLogins[0].everSynced, i == 2);
+
+      changes = await engine.getChangedIDs();
+      change = changes[guid];
+      equal(Object.keys(changes).length, 1);
+      equal(change.counter, i == 2 ? 1 : 2);
+      ok(!change.deleted);
+
+      _("Perform sync after modifying the password");
+      await sync_engine_and_validate_telem(engine, false);
+
+      equal(Object.keys(await engine.getChangedIDs()), 0);
+
+      // The remote login should have the updated password.
+      let newRec = collection.cleartext(guid);
+      equal(
+        newRec.password,
+        "newpassword" + i,
+        "Should update remote password for login"
+      );
+
+      foundLogins = await Services.logins.searchLoginsAsync({
+        origin: "http://mozilla.com",
+      });
+      equal(foundLogins.length, 1);
+      equal(foundLogins[0].syncCounter, 0);
+      equal(foundLogins[0].everSynced, true);
+
+      login.password = "newpassword" + i;
+    }
+
+    // Next, modify the username and sync.
+    _("Modify the username");
+    foundLogins[0].username = "newuser";
+    await Services.logins.modifyLoginAsync(login, foundLogins[0]);
+    foundLogins = await Services.logins.searchLoginsAsync({
+      origin: "http://mozilla.com",
+    });
+    equal(foundLogins.length, 1);
+    equal(foundLogins[0].syncCounter, 1);
+    equal(foundLogins[0].everSynced, true);
+
+    _("Perform sync after modifying the username");
+    await sync_engine_and_validate_telem(engine, false);
+
+    // The remote login should have the updated password.
+    let newRec = collection.cleartext(guid);
+    equal(
+      newRec.username,
+      "newuser",
+      "Should update remote username for login"
+    );
+
+    foundLogins = await Services.logins.searchLoginsAsync({
+      origin: "http://mozilla.com",
+    });
+    equal(foundLogins.length, 1);
+    equal(foundLogins[0].syncCounter, 0);
+    equal(foundLogins[0].everSynced, true);
+
+    // Finally, remove the login. The server record should be marked as deleted.
+    _("Remove the login");
+    equal(collection.count(), 1);
+    equal(await Services.logins.countLoginsAsync("", "", ""), 2);
+    equal((await Services.logins.getAllLogins()).length, 2);
+    ok(await engine._store.itemExists(guid));
+
+    ok((await engine._store.getAllIDs())[guid]);
+
+    await Services.logins.removeLoginAsync(foundLogins[0]);
+    foundLogins = await Services.logins.searchLoginsAsync({
+      origin: "http://mozilla.com",
+    });
+    equal(foundLogins.length, 0);
+
+    changes = await engine.getChangedIDs();
+    change = changes[guid];
+    equal(Object.keys(changes).length, 1);
+    equal(change.counter, 1);
+    ok(change.deleted);
+
+    _("Perform sync after removing the login");
+    await sync_engine_and_validate_telem(engine, false);
+
+    equal(collection.count(), 1);
+    let payload = collection.payloads()[0];
+    ok(payload.deleted);
+
+    equal(Object.keys(await engine.getChangedIDs()), 0);
+
+    // All of these should not include the deleted login. Only the FxA password should exist.
+    equal(await Services.logins.countLoginsAsync("", "", ""), 1);
+    equal((await Services.logins.getAllLogins()).length, 1);
+    ok(!(await engine._store.itemExists(guid)));
+
+    // getAllIDs includes deleted items but skips the FxA login.
+    ok((await engine._store.getAllIDs())[guid]);
+    let deletedLogin = await engine._store._getLoginFromGUID(guid);
+
+    equal(deletedLogin.hostname, null, "deleted login hostname");
+    equal(
+      deletedLogin.formActionOrigin,
+      null,
+      "deleted login formActionOrigin"
+    );
+    equal(deletedLogin.formSubmitURL, null, "deleted login formSubmitURL");
+    equal(deletedLogin.httpRealm, null, "deleted login httpRealm");
+    equal(deletedLogin.username, null, "deleted login username");
+    equal(deletedLogin.password, null, "deleted login password");
+    equal(deletedLogin.usernameField, "", "deleted login usernameField");
+    equal(deletedLogin.passwordField, "", "deleted login passwordField");
+    equal(deletedLogin.unknownFields, null, "deleted login unknownFields");
+    equal(deletedLogin.timeCreated, 0, "deleted login timeCreated");
+    equal(deletedLogin.timeLastUsed, 0, "deleted login timeLastUsed");
+    equal(deletedLogin.timesUsed, 0, "deleted login timesUsed");
+
+    // These fields are not reset when the login is removed.
+    equal(deletedLogin.guid, guid, "deleted login guid");
+    equal(deletedLogin.everSynced, true, "deleted login everSynced");
+    equal(deletedLogin.syncCounter, 0, "deleted login syncCounter");
+    Assert.greater(
+      deletedLogin.timePasswordChanged,
+      0,
+      "deleted login timePasswordChanged"
+    );
+  } finally {
+    await engine._tracker.stop();
+
+    await cleanup(engine, server);
+  }
+});
+
+add_task(async function test_sync_incoming() {
+  _("Test syncing incoming records");
+
+  let engine = Service.engineManager.get("passwords");
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  let collection = server.user("foo").collection("passwords");
+
+  const checkFields = [
+    "formSubmitURL",
+    "hostname",
+    "httpRealm",
+    "username",
+    "password",
+    "usernameField",
+    "passwordField",
+    "timeCreated",
+  ];
+
+  let guid1 = Utils.makeGUID();
+  let details = {
+    formSubmitURL: "https://www.example.com",
+    hostname: "https://www.example.com",
+    httpRealm: null,
+    username: "camel",
+    password: "llama",
+    usernameField: "username-field",
+    passwordField: "password-field",
+    timeCreated: Date.now(),
+    timePasswordChanged: Date.now(),
+  };
+
+  try {
+    // This test creates a remote server record and then verifies that the login
+    // has been added locally after the sync occurs.
+    _("Create remote login");
+    collection.insertRecord(Object.assign({}, details, { id: guid1 }));
+
+    _("Perform sync when remote login has been added");
+    await sync_engine_and_validate_telem(engine, false);
+
+    let logins = await Services.logins.searchLoginsAsync({
+      origin: "https://www.example.com",
+    });
+    equal(logins.length, 1);
+
+    equal(logins[0].QueryInterface(Ci.nsILoginMetaInfo).guid, guid1);
+    checkFields.forEach(field => {
+      equal(logins[0][field], details[field]);
+    });
+    equal(logins[0].timePasswordChanged, details.timePasswordChanged);
+    equal(logins[0].syncCounter, 0);
+    equal(logins[0].everSynced, true);
+
+    // Modify the password within the remote record and then sync again.
+    _("Perform sync when remote login's password has been modified");
+    let newTime = Date.now();
+    collection.updateRecord(
+      guid1,
+      cleartext => {
+        cleartext.password = "alpaca";
+      },
+      newTime / 1000 + 10
+    );
+
+    await engine.setLastSync(newTime / 1000 - 30);
+    await sync_engine_and_validate_telem(engine, false);
+
+    logins = await Services.logins.searchLoginsAsync({
+      origin: "https://www.example.com",
+    });
+    equal(logins.length, 1);
+
+    details.password = "alpaca";
+    equal(logins[0].QueryInterface(Ci.nsILoginMetaInfo).guid, guid1);
+    checkFields.forEach(field => {
+      equal(logins[0][field], details[field]);
+    });
+    Assert.greater(logins[0].timePasswordChanged, details.timePasswordChanged);
+    equal(logins[0].syncCounter, 0);
+    equal(logins[0].everSynced, true);
+
+    // Modify the username within the remote record and then sync again.
+    _("Perform sync when remote login's username has been modified");
+    newTime = Date.now();
+    collection.updateRecord(
+      guid1,
+      cleartext => {
+        cleartext.username = "guanaco";
+      },
+      newTime / 1000 + 10
+    );
+
+    await engine.setLastSync(newTime / 1000 - 30);
+    await sync_engine_and_validate_telem(engine, false);
+
+    logins = await Services.logins.searchLoginsAsync({
+      origin: "https://www.example.com",
+    });
+    equal(logins.length, 1);
+
+    details.username = "guanaco";
+    equal(logins[0].QueryInterface(Ci.nsILoginMetaInfo).guid, guid1);
+    checkFields.forEach(field => {
+      equal(logins[0][field], details[field]);
+    });
+    Assert.greater(logins[0].timePasswordChanged, details.timePasswordChanged);
+    equal(logins[0].syncCounter, 0);
+    equal(logins[0].everSynced, true);
+
+    // Mark the remote record as deleted and then sync again.
+    _("Perform sync when remote login has been marked for deletion");
+    newTime = Date.now();
+    collection.updateRecord(
+      guid1,
+      cleartext => {
+        cleartext.deleted = true;
+      },
+      newTime / 1000 + 10
+    );
+
+    await engine.setLastSync(newTime / 1000 - 30);
+    await sync_engine_and_validate_telem(engine, false);
+
+    logins = await Services.logins.searchLoginsAsync({
+      origin: "https://www.example.com",
+    });
+    equal(logins.length, 0);
+  } finally {
+    await cleanup(engine, server);
+  }
+});
+
+add_task(async function test_sync_incoming_deleted() {
+  _("Test syncing incoming deleted records");
+
+  let engine = Service.engineManager.get("passwords");
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  let collection = server.user("foo").collection("passwords");
+
+  let guid1 = Utils.makeGUID();
+  let details2 = {
+    formSubmitURL: "https://www.example.org",
+    hostname: "https://www.example.org",
+    httpRealm: null,
+    username: "capybara",
+    password: "beaver",
+    usernameField: "username-field",
+    passwordField: "password-field",
+    timeCreated: Date.now(),
+    timePasswordChanged: Date.now(),
+    deleted: true,
+  };
+
+  try {
+    // This test creates a remote server record that has been deleted
+    // and then verifies that the login is not imported locally.
+    _("Create remote login");
+    collection.insertRecord(Object.assign({}, details2, { id: guid1 }));
+
+    _("Perform sync when remote login has been deleted");
+    await sync_engine_and_validate_telem(engine, false);
+
+    let logins = await Services.logins.searchLoginsAsync({
+      origin: "https://www.example.com",
+    });
+    equal(logins.length, 0);
+    ok(!(await engine._store.getAllIDs())[guid1]);
+    ok(!(await engine._store.itemExists(guid1)));
+  } finally {
+    await cleanup(engine, server);
+  }
+});
+
+add_task(async function test_sync_incoming_deleted_localchanged_remotenewer() {
+  _(
+    "Test syncing incoming deleted records where the local login has been changed but the remote record is newer"
+  );
+
+  let engine = Service.engineManager.get("passwords");
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  let collection = server.user("foo").collection("passwords");
+
+  let loginInfo = new LoginInfo(
+    "http://mozilla.com",
+    "http://mozilla.com",
+    null,
+    "kangaroo",
+    "kaola",
+    "username",
+    "password"
+  );
+  let login = await Services.logins.addLoginAsync(loginInfo);
+  let guid = login.QueryInterface(Ci.nsILoginMetaInfo).guid;
+
+  try {
+    _("Perform sync on new login");
+    await sync_engine_and_validate_telem(engine, false);
+
+    let foundLogins = await Services.logins.searchLoginsAsync({
+      origin: "http://mozilla.com",
+    });
+    foundLogins[0].password = "wallaby";
+    await Services.logins.modifyLoginAsync(login, foundLogins[0]);
+
+    // Use a time in the future to ensure that the remote record is newer.
+    collection.updateRecord(
+      guid,
+      cleartext => {
+        cleartext.deleted = true;
+      },
+      Date.now() / 1000 + 1000
+    );
+
+    _(
+      "Perform sync when remote login has been deleted and local login has been changed"
+    );
+    await sync_engine_and_validate_telem(engine, false);
+
+    let logins = await Services.logins.searchLoginsAsync({
+      origin: "https://mozilla.com",
+    });
+    equal(logins.length, 0);
+    ok(await engine._store.getAllIDs());
+  } finally {
+    await cleanup(engine, server);
+  }
+});
+
+add_task(async function test_sync_incoming_deleted_localchanged_localnewer() {
+  _(
+    "Test syncing incoming deleted records where the local login has been changed but the local record is newer"
+  );
+
+  let engine = Service.engineManager.get("passwords");
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  let collection = server.user("foo").collection("passwords");
+
+  let loginInfo = new LoginInfo(
+    "http://www.mozilla.com",
+    "http://www.mozilla.com",
+    null,
+    "lion",
+    "tiger",
+    "username",
+    "password"
+  );
+  let login = await Services.logins.addLoginAsync(loginInfo);
+  let guid = login.QueryInterface(Ci.nsILoginMetaInfo).guid;
+
+  try {
+    _("Perform sync on new login");
+    await sync_engine_and_validate_telem(engine, false);
+
+    let foundLogins = await Services.logins.searchLoginsAsync({
+      origin: "http://www.mozilla.com",
+    });
+    foundLogins[0].password = "cheetah";
+    await Services.logins.modifyLoginAsync(login, foundLogins[0]);
+
+    // Use a time in the past to ensure that the local record is newer.
+    collection.updateRecord(
+      guid,
+      cleartext => {
+        cleartext.deleted = true;
+      },
+      Date.now() / 1000 - 1000
+    );
+
+    _(
+      "Perform sync when remote login has been deleted and local login has been changed"
+    );
+    await sync_engine_and_validate_telem(engine, false);
+
+    let logins = await Services.logins.searchLoginsAsync({
+      origin: "http://www.mozilla.com",
+    });
+    equal(logins.length, 1);
+    equal(logins[0].password, "cheetah");
+    equal(logins[0].syncCounter, 0);
+    equal(logins[0].everSynced, true);
+    ok(await engine._store.getAllIDs());
+  } finally {
+    await cleanup(engine, server);
+  }
+});
+
+add_task(async function test_sync_incoming_no_formactionorigin() {
+  _("Test syncing incoming a record where there is no formActionOrigin");
+
+  let engine = Service.engineManager.get("passwords");
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  let collection = server.user("foo").collection("passwords");
+
+  const checkFields = [
+    "formSubmitURL",
+    "hostname",
+    "httpRealm",
+    "username",
+    "password",
+    "usernameField",
+    "passwordField",
+    "timeCreated",
+  ];
+
+  let guid1 = Utils.makeGUID();
+  let details = {
+    formSubmitURL: "",
+    hostname: "https://www.example.com",
+    httpRealm: null,
+    username: "rabbit",
+    password: "squirrel",
+    usernameField: "username-field",
+    passwordField: "password-field",
+    timeCreated: Date.now(),
+    timePasswordChanged: Date.now(),
+  };
+
+  try {
+    // This test creates a remote server record and then verifies that the login
+    // has been added locally after the sync occurs.
+    _("Create remote login");
+    collection.insertRecord(Object.assign({}, details, { id: guid1 }));
+
+    _("Perform sync when remote login has been added");
+    await sync_engine_and_validate_telem(engine, false);
+
+    let logins = await Services.logins.searchLoginsAsync({
+      origin: "https://www.example.com",
+      formActionOrigin: "",
+    });
+    equal(logins.length, 1);
+
+    equal(logins[0].QueryInterface(Ci.nsILoginMetaInfo).guid, guid1);
+    checkFields.forEach(field => {
+      equal(logins[0][field], details[field]);
+    });
+    equal(logins[0].timePasswordChanged, details.timePasswordChanged);
+    equal(logins[0].syncCounter, 0);
+    equal(logins[0].everSynced, true);
+  } finally {
+    await cleanup(engine, server);
+  }
+});
+
+add_task(async function test_password_dupe() {
+  let engine = Service.engineManager.get("passwords");
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+  let collection = server.user("foo").collection("passwords");
+
+  let guid1 = Utils.makeGUID();
+  let rec1 = new LoginRec("passwords", guid1);
+  let guid2 = Utils.makeGUID();
+  let cleartext = {
+    formSubmitURL: "https://www.example.com",
+    hostname: "https://www.example.com",
+    httpRealm: null,
+    username: "foo",
+    password: "bar",
+    usernameField: "username-field",
+    passwordField: "password-field",
+    timeCreated: Math.round(Date.now()),
+    timePasswordChanged: Math.round(Date.now()),
+  };
+  rec1.cleartext = cleartext;
+
+  _("Create remote record with same details and guid1");
+  collection.insert(guid1, encryptPayload(rec1.cleartext));
+
+  _("Create remote record with guid2");
+  collection.insert(guid2, encryptPayload(cleartext));
+
+  _("Create local record with same details and guid1");
+  await engine._store.create(rec1);
+
+  try {
+    _("Perform sync");
+    await sync_engine_and_validate_telem(engine, true);
+
+    let logins = await Services.logins.searchLoginsAsync({
+      origin: "https://www.example.com",
+    });
+
+    equal(logins.length, 1);
+    equal(logins[0].QueryInterface(Ci.nsILoginMetaInfo).guid, guid2);
+    equal(null, collection.payload(guid1));
+  } finally {
+    await cleanup(engine, server);
+  }
+});
+
+add_task(async function test_updated_null_password_sync() {
+  _("Ensure updated null login username is converted to a string");
+
+  let engine = Service.engineManager.get("passwords");
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+  let collection = server.user("foo").collection("passwords");
+
+  let guid1 = Utils.makeGUID();
+  let guid2 = Utils.makeGUID();
+  let remoteDetails = {
+    formSubmitURL: "https://www.nullupdateexample.com",
+    hostname: "https://www.nullupdateexample.com",
+    httpRealm: null,
+    username: null,
+    password: "bar",
+    usernameField: "username-field",
+    passwordField: "password-field",
+    timeCreated: Date.now(),
+    timePasswordChanged: Date.now(),
+  };
+  let localDetails = {
+    formSubmitURL: "https://www.nullupdateexample.com",
+    hostname: "https://www.nullupdateexample.com",
+    httpRealm: null,
+    username: "foo",
+    password: "foobar",
+    usernameField: "username-field",
+    passwordField: "password-field",
+    timeCreated: Date.now(),
+    timePasswordChanged: Date.now(),
+  };
+
+  _("Create remote record with same details and guid1");
+  collection.insertRecord(Object.assign({}, remoteDetails, { id: guid1 }));
+
+  try {
+    _("Create local updated login with null password");
+    await engine._store.update(Object.assign({}, localDetails, { id: guid2 }));
+
+    _("Perform sync");
+    await sync_engine_and_validate_telem(engine, false);
+
+    let logins = await Services.logins.searchLoginsAsync({
+      origin: "https://www.nullupdateexample.com",
+    });
+
+    equal(logins.length, 1);
+    equal(logins[0].QueryInterface(Ci.nsILoginMetaInfo).guid, guid1);
+  } finally {
+    await cleanup(engine, server);
+  }
+});
+
+add_task(async function test_updated_undefined_password_sync() {
+  _("Ensure updated undefined login username is converted to a string");
+
+  let engine = Service.engineManager.get("passwords");
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+  let collection = server.user("foo").collection("passwords");
+
+  let guid1 = Utils.makeGUID();
+  let guid2 = Utils.makeGUID();
+  let remoteDetails = {
+    formSubmitURL: "https://www.undefinedupdateexample.com",
+    hostname: "https://www.undefinedupdateexample.com",
+    httpRealm: null,
+    username: undefined,
+    password: "bar",
+    usernameField: "username-field",
+    passwordField: "password-field",
+    timeCreated: Date.now(),
+    timePasswordChanged: Date.now(),
+  };
+  let localDetails = {
+    formSubmitURL: "https://www.undefinedupdateexample.com",
+    hostname: "https://www.undefinedupdateexample.com",
+    httpRealm: null,
+    username: "foo",
+    password: "foobar",
+    usernameField: "username-field",
+    passwordField: "password-field",
+    timeCreated: Date.now(),
+    timePasswordChanged: Date.now(),
+  };
+
+  _("Create remote record with same details and guid1");
+  collection.insertRecord(Object.assign({}, remoteDetails, { id: guid1 }));
+
+  try {
+    _("Create local updated login with undefined password");
+    await engine._store.update(Object.assign({}, localDetails, { id: guid2 }));
+
+    _("Perform sync");
+    await sync_engine_and_validate_telem(engine, false);
+
+    let logins = await Services.logins.searchLoginsAsync({
+      origin: "https://www.undefinedupdateexample.com",
+    });
+
+    equal(logins.length, 1);
+    equal(logins[0].QueryInterface(Ci.nsILoginMetaInfo).guid, guid1);
+  } finally {
+    await cleanup(engine, server);
+  }
+});
+
+add_task(async function test_new_null_password_sync() {
+  _("Ensure new null login username is converted to a string");
+
+  let engine = Service.engineManager.get("passwords");
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  let guid1 = Utils.makeGUID();
+  let rec1 = new LoginRec("passwords", guid1);
+  rec1.cleartext = {
+    formSubmitURL: "https://www.example.com",
+    hostname: "https://www.example.com",
+    httpRealm: null,
+    username: null,
+    password: "bar",
+    usernameField: "username-field",
+    passwordField: "password-field",
+    timeCreated: Date.now(),
+    timePasswordChanged: Date.now(),
+  };
+
+  try {
+    _("Create local login with null password");
+    await engine._store.create(rec1);
+
+    _("Perform sync");
+    await sync_engine_and_validate_telem(engine, false);
+
+    let logins = await Services.logins.searchLoginsAsync({
+      origin: "https://www.example.com",
+    });
+
+    equal(logins.length, 1);
+    notEqual(logins[0].QueryInterface(Ci.nsILoginMetaInfo).username, null);
+    notEqual(logins[0].QueryInterface(Ci.nsILoginMetaInfo).username, undefined);
+    equal(logins[0].QueryInterface(Ci.nsILoginMetaInfo).username, "");
+  } finally {
+    await cleanup(engine, server);
+  }
+});
+
+add_task(async function test_new_undefined_password_sync() {
+  _("Ensure new undefined login username is converted to a string");
+
+  let engine = Service.engineManager.get("passwords");
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  let guid1 = Utils.makeGUID();
+  let rec1 = new LoginRec("passwords", guid1);
+  rec1.cleartext = {
+    formSubmitURL: "https://www.example.com",
+    hostname: "https://www.example.com",
+    httpRealm: null,
+    username: undefined,
+    password: "bar",
+    usernameField: "username-field",
+    passwordField: "password-field",
+    timeCreated: Date.now(),
+    timePasswordChanged: Date.now(),
+  };
+
+  try {
+    _("Create local login with undefined password");
+    await engine._store.create(rec1);
+
+    _("Perform sync");
+    await sync_engine_and_validate_telem(engine, false);
+
+    let logins = await Services.logins.searchLoginsAsync({
+      origin: "https://www.example.com",
+    });
+
+    equal(logins.length, 1);
+    notEqual(logins[0].QueryInterface(Ci.nsILoginMetaInfo).username, null);
+    notEqual(logins[0].QueryInterface(Ci.nsILoginMetaInfo).username, undefined);
+    equal(logins[0].QueryInterface(Ci.nsILoginMetaInfo).username, "");
+  } finally {
+    await cleanup(engine, server);
+  }
+});
+
+add_task(async function test_sync_password_validation() {
+  // This test isn't in test_password_validator to avoid duplicating cleanup.
+  _("Ensure that if a password validation happens, it ends up in the ping");
+
+  let engine = Service.engineManager.get("passwords");
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  Svc.PrefBranch.setIntPref("engine.passwords.validation.interval", 0);
+  Svc.PrefBranch.setIntPref(
+    "engine.passwords.validation.percentageChance",
+    100
+  );
+  Svc.PrefBranch.setIntPref("engine.passwords.validation.maxRecords", -1);
+  Svc.PrefBranch.setBoolPref("engine.passwords.validation.enabled", true);
+
+  try {
+    let ping = await wait_for_ping(() => Service.sync());
+
+    let engineInfo = ping.engines.find(e => e.name == "passwords");
+    ok(engineInfo, "Engine should be in ping");
+
+    let validation = engineInfo.validation;
+    ok(validation, "Engine should have validation info");
+  } finally {
+    await cleanup(engine, server);
+  }
+});
+
+add_task(async function test_roundtrip_unknown_fields() {
+  _(
+    "Testing that unknown fields from other clients get roundtripped back to server"
+  );
+
+  let engine = Service.engineManager.get("passwords");
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+  let collection = server.user("foo").collection("passwords");
+
+  enableValidationPrefs();
+
+  _("Add login with older password change time to replace during first sync");
+  let oldLogin;
+  {
+    let login = new LoginInfo(
+      "https://mozilla.com",
+      "",
+      null,
+      "us3r",
+      "0ldpa55",
+      "",
+      ""
+    );
+    await Services.logins.addLoginAsync(login);
+
+    let props = new PropertyBag();
+    let localPasswordChangeTime = Math.round(
+      Date.now() - 1 * 60 * 60 * 24 * 1000
+    );
+    props.setProperty("timePasswordChanged", localPasswordChangeTime);
+    await Services.logins.modifyLoginAsync(login, props);
+
+    let logins = await Services.logins.searchLoginsAsync({
+      origin: "https://mozilla.com",
+    });
+    equal(logins.length, 1, "Should find old login in login manager");
+    oldLogin = logins[0].QueryInterface(Ci.nsILoginMetaInfo);
+    equal(oldLogin.timePasswordChanged, localPasswordChangeTime);
+
+    let rec = new LoginRec("passwords", oldLogin.guid);
+    rec.hostname = oldLogin.origin;
+    rec.formSubmitURL = oldLogin.formActionOrigin;
+    rec.httpRealm = oldLogin.httpRealm;
+    rec.username = oldLogin.username;
+    // Change the password and bump the password change time to ensure we prefer
+    // the remote one during reconciliation.
+    rec.password = "n3wpa55";
+    rec.usernameField = oldLogin.usernameField;
+    rec.passwordField = oldLogin.usernameField;
+    rec.timeCreated = oldLogin.timeCreated;
+    rec.timePasswordChanged = Math.round(Date.now());
+
+    // pretend other clients have some snazzy new fields
+    // we don't quite understand yet
+    rec.cleartext.someStrField = "I am a str";
+    rec.cleartext.someObjField = { newField: "I am a new field" };
+    collection.insert(oldLogin.guid, encryptPayload(rec.cleartext));
+  }
+
+  await engine._tracker.stop();
+
+  try {
+    await sync_engine_and_validate_telem(engine, false);
+
+    let logins = await Services.logins.searchLoginsAsync({
+      origin: "https://mozilla.com",
+    });
+    equal(
+      logins[0].password,
+      "n3wpa55",
+      "Should update local password for older login"
+    );
+    let expectedUnknowns = JSON.stringify({
+      someStrField: "I am a str",
+      someObjField: { newField: "I am a new field" },
+    });
+    // Check that the local record has all unknown fields properly
+    // stringified
+    equal(logins[0].unknownFields, expectedUnknowns);
+
+    // Check that the server has the unknown fields unfurled and on the
+    // top-level record
+    let serverRec = collection.cleartext(oldLogin.guid);
+    equal(serverRec.someStrField, "I am a str");
+    equal(serverRec.someObjField.newField, "I am a new field");
+  } finally {
+    await cleanup(engine, server);
+  }
+});
+
+add_task(async function test_new_passwords_from_csv() {
+  _("Test syncing records imported from a csv file");
+
+  let engine = Service.engineManager.get("passwords");
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  let collection = server.user("foo").collection("passwords");
+
+  engine._tracker.start();
+
+  let data = [
+    {
+      hostname: "https://example.com",
+      url: "https://example.com/path",
+      username: "exampleuser",
+      password: "examplepassword",
+    },
+    {
+      hostname: "https://mozilla.org",
+      url: "https://mozilla.org",
+      username: "mozillauser",
+      password: "mozillapassword",
+    },
+    {
+      hostname: "https://www.example.org",
+      url: "https://www.example.org/example1/example2",
+      username: "person",
+      password: "mypassword",
+    },
+  ];
+
+  let csvData = ["url,username,login_password"];
+  for (let row of data) {
+    csvData.push(row.url + "," + row.username + "," + row.password);
+  }
+
+  let csvFile = FileTestUtils.getTempFile(`firefox_logins.csv`);
+  await IOUtils.writeUTF8(csvFile.path, csvData.join("\r\n"));
+
+  await LoginCSVImport.importFromCSV(csvFile.path);
+
+  equal(
+    engine._tracker.score,
+    SCORE_INCREMENT_XLARGE,
+    "Should only get one update notification for import"
+  );
+
+  _("Ensure that the csv import is correct");
+  for (let item of data) {
+    let foundLogins = await Services.logins.searchLoginsAsync({
+      origin: item.hostname,
+    });
+    equal(foundLogins.length, 1);
+    equal(foundLogins[0].syncCounter, 1);
+    equal(foundLogins[0].everSynced, false);
+    equal(foundLogins[0].username, item.username);
+    equal(foundLogins[0].password, item.password);
+  }
+
+  _("Perform sync after modifying the password");
+  await sync_engine_and_validate_telem(engine, false);
+
+  _("Verify that the sync counter and status are updated");
+  for (let item of data) {
+    let foundLogins = await Services.logins.searchLoginsAsync({
+      origin: item.hostname,
+    });
+    equal(foundLogins.length, 1);
+    equal(foundLogins[0].syncCounter, 0);
+    equal(foundLogins[0].everSynced, true);
+    equal(foundLogins[0].username, item.username);
+    equal(foundLogins[0].password, item.password);
+    item.guid = foundLogins[0].guid;
+  }
+
+  equal(Object.keys(await engine.getChangedIDs()), 0);
+  equal(collection.count(), 3);
+
+  for (let item of data) {
+    // The remote login should have the imported username and password.
+    let newRec = collection.cleartext(item.guid);
+    equal(newRec.username, item.username);
+    equal(newRec.password, item.password);
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_password_store.js b/src/zen/tests/mochitests/sync/test_password_store.js
new file mode 100644
index 000000000..3c5916245
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_password_store.js
@@ -0,0 +1,399 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { LoginRec } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/passwords.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { SyncedRecordsTelemetry } = ChromeUtils.importESModule(
+  "resource://services-sync/telemetry.sys.mjs"
+);
+
+async function checkRecord(
+  name,
+  record,
+  expectedCount,
+  timeCreated,
+  expectedTimeCreated,
+  timePasswordChanged,
+  expectedTimePasswordChanged,
+  recordIsUpdated
+) {
+  let engine = Service.engineManager.get("passwords");
+  let store = engine._store;
+
+  let logins = await Services.logins.searchLoginsAsync({
+    origin: record.hostname,
+    formActionOrigin: record.formSubmitURL,
+  });
+
+  _("Record" + name + ":" + JSON.stringify(logins));
+  _("Count" + name + ":" + logins.length);
+
+  Assert.equal(logins.length, expectedCount);
+
+  if (expectedCount > 0) {
+    Assert.ok(!!(await store.getAllIDs())[record.id]);
+    let stored_record = logins[0].QueryInterface(Ci.nsILoginMetaInfo);
+
+    if (timeCreated !== undefined) {
+      Assert.equal(stored_record.timeCreated, expectedTimeCreated);
+    }
+
+    if (timePasswordChanged !== undefined) {
+      if (recordIsUpdated) {
+        Assert.greaterOrEqual(
+          stored_record.timePasswordChanged,
+          expectedTimePasswordChanged
+        );
+      } else {
+        Assert.equal(
+          stored_record.timePasswordChanged,
+          expectedTimePasswordChanged
+        );
+      }
+      return stored_record.timePasswordChanged;
+    }
+  } else {
+    Assert.ok(!(await store.getAllIDs())[record.id]);
+  }
+  return undefined;
+}
+
+async function changePassword(
+  name,
+  hostname,
+  password,
+  expectedCount,
+  timeCreated,
+  expectedTimeCreated,
+  timePasswordChanged,
+  expectedTimePasswordChanged,
+  insert,
+  recordIsUpdated
+) {
+  const BOGUS_GUID = "zzzzzz" + hostname;
+  let record = new LoginRec("passwords", BOGUS_GUID);
+  record.cleartext = {
+    id: BOGUS_GUID,
+    hostname,
+    formSubmitURL: hostname,
+    username: "john",
+    password,
+    usernameField: "username",
+    passwordField: "password",
+  };
+
+  if (timeCreated !== undefined) {
+    record.timeCreated = timeCreated;
+  }
+
+  if (timePasswordChanged !== undefined) {
+    record.timePasswordChanged = timePasswordChanged;
+  }
+
+  let engine = Service.engineManager.get("passwords");
+  let store = engine._store;
+
+  if (insert) {
+    let countTelemetry = new SyncedRecordsTelemetry();
+    Assert.equal(
+      (await store.applyIncomingBatch([record], countTelemetry)).length,
+      0
+    );
+  }
+
+  return checkRecord(
+    name,
+    record,
+    expectedCount,
+    timeCreated,
+    expectedTimeCreated,
+    timePasswordChanged,
+    expectedTimePasswordChanged,
+    recordIsUpdated
+  );
+}
+
+async function test_apply_records_with_times(
+  hostname,
+  timeCreated,
+  timePasswordChanged
+) {
+  // The following record is going to be inserted in the store and it needs
+  // to be found there. Then its timestamps are going to be compared to
+  // the expected values.
+  await changePassword(
+    " ",
+    hostname,
+    "password",
+    1,
+    timeCreated,
+    timeCreated,
+    timePasswordChanged,
+    timePasswordChanged,
+    true
+  );
+}
+
+async function test_apply_multiple_records_with_times() {
+  // The following records are going to be inserted in the store and they need
+  // to be found there. Then their timestamps are going to be compared to
+  // the expected values.
+  await changePassword(
+    "A",
+    "http://foo.a.com",
+    "password",
+    1,
+    undefined,
+    undefined,
+    undefined,
+    undefined,
+    true
+  );
+  await changePassword(
+    "B",
+    "http://foo.b.com",
+    "password",
+    1,
+    1000,
+    1000,
+    undefined,
+    undefined,
+    true
+  );
+  await changePassword(
+    "C",
+    "http://foo.c.com",
+    "password",
+    1,
+    undefined,
+    undefined,
+    1000,
+    1000,
+    true
+  );
+  await changePassword(
+    "D",
+    "http://foo.d.com",
+    "password",
+    1,
+    1000,
+    1000,
+    1000,
+    1000,
+    true
+  );
+
+  // The following records are not going to be inserted in the store and they
+  // are not going to be found there.
+  await changePassword(
+    "NotInStoreA",
+    "http://foo.aaaa.com",
+    "password",
+    0,
+    undefined,
+    undefined,
+    undefined,
+    undefined,
+    false
+  );
+  await changePassword(
+    "NotInStoreB",
+    "http://foo.bbbb.com",
+    "password",
+    0,
+    1000,
+    1000,
+    undefined,
+    undefined,
+    false
+  );
+  await changePassword(
+    "NotInStoreC",
+    "http://foo.cccc.com",
+    "password",
+    0,
+    undefined,
+    undefined,
+    1000,
+    1000,
+    false
+  );
+  await changePassword(
+    "NotInStoreD",
+    "http://foo.dddd.com",
+    "password",
+    0,
+    1000,
+    1000,
+    1000,
+    1000,
+    false
+  );
+}
+
+async function test_apply_same_record_with_different_times() {
+  // The following record is going to be inserted multiple times in the store
+  // and it needs to be found there. Then its timestamps are going to be
+  // compared to the expected values.
+
+  /* eslint-disable no-unused-vars */
+  /* The eslint linter thinks that timePasswordChanged is unused, even though
+     it is passed as an argument to changePassword. */
+  var timePasswordChanged = 100;
+  timePasswordChanged = await changePassword(
+    "A",
+    "http://a.tn",
+    "password",
+    1,
+    100,
+    100,
+    100,
+    timePasswordChanged,
+    true
+  );
+  timePasswordChanged = await changePassword(
+    "A",
+    "http://a.tn",
+    "password",
+    1,
+    100,
+    100,
+    800,
+    timePasswordChanged,
+    true,
+    true
+  );
+  timePasswordChanged = await changePassword(
+    "A",
+    "http://a.tn",
+    "password",
+    1,
+    500,
+    100,
+    800,
+    timePasswordChanged,
+    true,
+    true
+  );
+  timePasswordChanged = await changePassword(
+    "A",
+    "http://a.tn",
+    "password2",
+    1,
+    500,
+    100,
+    1536213005222,
+    timePasswordChanged,
+    true,
+    true
+  );
+  timePasswordChanged = await changePassword(
+    "A",
+    "http://a.tn",
+    "password2",
+    1,
+    500,
+    100,
+    800,
+    timePasswordChanged,
+    true,
+    true
+  );
+  /* eslint-enable no-unused-vars */
+}
+
+async function test_LoginRec_toString(store, recordData) {
+  let rec = await store.createRecord(recordData.id);
+  ok(rec);
+  ok(!rec.toString().includes(rec.password));
+}
+
+add_task(async function run_test() {
+  const BOGUS_GUID_A = "zzzzzzzzzzzz";
+  const BOGUS_GUID_B = "yyyyyyyyyyyy";
+  let recordA = new LoginRec("passwords", BOGUS_GUID_A);
+  let recordB = new LoginRec("passwords", BOGUS_GUID_B);
+  recordA.cleartext = {
+    id: BOGUS_GUID_A,
+    hostname: "http://foo.bar.com",
+    formSubmitURL: "http://foo.bar.com",
+    httpRealm: "secure",
+    username: "john",
+    password: "smith",
+    usernameField: "username",
+    passwordField: "password",
+  };
+  recordB.cleartext = {
+    id: BOGUS_GUID_B,
+    hostname: "http://foo.baz.com",
+    formSubmitURL: "http://foo.baz.com",
+    username: "john",
+    password: "smith",
+    usernameField: "username",
+    passwordField: "password",
+    unknownStr: "an unknown string from another field",
+  };
+
+  let engine = Service.engineManager.get("passwords");
+  let store = engine._store;
+
+  try {
+    let countTelemetry = new SyncedRecordsTelemetry();
+    Assert.equal(
+      (await store.applyIncomingBatch([recordA, recordB], countTelemetry))
+        .length,
+      0
+    );
+
+    // Only the good record makes it to Services.logins.
+    let badLogins = await Services.logins.searchLoginsAsync({
+      origin: recordA.hostname,
+      formActionOrigin: recordA.formSubmitURL,
+      httpRealm: recordA.httpRealm,
+    });
+    let goodLogins = await Services.logins.searchLoginsAsync({
+      origin: recordB.hostname,
+      formActionOrigin: recordB.formSubmitURL,
+    });
+
+    _("Bad: " + JSON.stringify(badLogins));
+    _("Good: " + JSON.stringify(goodLogins));
+    _("Count: " + badLogins.length + ", " + goodLogins.length);
+
+    Assert.equal(goodLogins.length, 1);
+    Assert.equal(badLogins.length, 0);
+
+    // applyIncoming should've put any unknown fields from the server
+    // into a catch-all unknownFields field
+    Assert.equal(
+      goodLogins[0].unknownFields,
+      JSON.stringify({
+        unknownStr: "an unknown string from another field",
+      })
+    );
+
+    Assert.ok(!!(await store.getAllIDs())[BOGUS_GUID_B]);
+    Assert.ok(!(await store.getAllIDs())[BOGUS_GUID_A]);
+
+    await test_LoginRec_toString(store, recordB);
+
+    await test_apply_records_with_times(
+      "http://afoo.baz.com",
+      undefined,
+      undefined
+    );
+    await test_apply_records_with_times("http://bfoo.baz.com", 1000, undefined);
+    await test_apply_records_with_times("http://cfoo.baz.com", undefined, 2000);
+    await test_apply_records_with_times("http://dfoo.baz.com", 1000, 2000);
+
+    await test_apply_multiple_records_with_times();
+
+    await test_apply_same_record_with_different_times();
+  } finally {
+    await store.wipe();
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_password_tracker.js b/src/zen/tests/mochitests/sync/test_password_tracker.js
new file mode 100644
index 000000000..a613f933a
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_password_tracker.js
@@ -0,0 +1,249 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { PasswordEngine, LoginRec } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/passwords.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+let engine;
+let store;
+let tracker;
+
+add_task(async function setup() {
+  await Service.engineManager.register(PasswordEngine);
+  engine = Service.engineManager.get("passwords");
+  store = engine._store;
+  tracker = engine._tracker;
+});
+
+add_task(async function test_tracking() {
+  let recordNum = 0;
+
+  _("Verify we've got an empty tracker to work with.");
+  let changes = await engine.getChangedIDs();
+  do_check_empty(changes);
+
+  let exceptionHappened = false;
+  try {
+    await tracker.getChangedIDs();
+  } catch (ex) {
+    exceptionHappened = true;
+  }
+  ok(exceptionHappened, "tracker does not keep track of changes");
+
+  async function createPassword() {
+    _("RECORD NUM: " + recordNum);
+    let record = new LoginRec("passwords", "GUID" + recordNum);
+    record.cleartext = {
+      id: "GUID" + recordNum,
+      hostname: "http://foo.bar.com",
+      formSubmitURL: "http://foo.bar.com",
+      username: "john" + recordNum,
+      password: "smith",
+      usernameField: "username",
+      passwordField: "password",
+    };
+    recordNum++;
+    let login = store._nsLoginInfoFromRecord(record);
+    await Services.logins.addLoginAsync(login);
+    await tracker.asyncObserver.promiseObserversComplete();
+  }
+
+  try {
+    tracker.start();
+    await createPassword();
+    changes = await engine.getChangedIDs();
+    do_check_attribute_count(changes, 1);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE);
+    Assert.equal(changes.GUID0.counter, 1);
+    Assert.ok(typeof changes.GUID0.modified, "number");
+
+    _("Starting twice won't do any harm.");
+    tracker.start();
+    await createPassword();
+    changes = await engine.getChangedIDs();
+    do_check_attribute_count(changes, 2);
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE * 2);
+    Assert.equal(changes.GUID0.counter, 1);
+    Assert.equal(changes.GUID1.counter, 1);
+
+    // The tracker doesn't keep track of changes, so 3 changes
+    // should still be returned, but the score is not updated.
+    _("Let's stop tracking again.");
+    tracker.resetScore();
+    await tracker.stop();
+    await createPassword();
+    changes = await engine.getChangedIDs();
+    do_check_attribute_count(changes, 3);
+    Assert.equal(tracker.score, 0);
+    Assert.equal(changes.GUID0.counter, 1);
+    Assert.equal(changes.GUID1.counter, 1);
+    Assert.equal(changes.GUID2.counter, 1);
+
+    _("Stopping twice won't do any harm.");
+    await tracker.stop();
+    await createPassword();
+    changes = await engine.getChangedIDs();
+    do_check_attribute_count(changes, 4);
+    Assert.equal(tracker.score, 0);
+  } finally {
+    _("Clean up.");
+    await store.wipe();
+    tracker.resetScore();
+    await tracker.stop();
+  }
+});
+
+add_task(async function test_onWipe() {
+  _("Verify we've got an empty tracker to work with.");
+  const changes = await engine.getChangedIDs();
+  do_check_empty(changes);
+  Assert.equal(tracker.score, 0);
+
+  try {
+    _("A store wipe should increment the score");
+    tracker.start();
+    await store.wipe();
+    await tracker.asyncObserver.promiseObserversComplete();
+
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE);
+  } finally {
+    tracker.resetScore();
+    await tracker.stop();
+  }
+});
+
+add_task(async function test_removeAllLogins() {
+  let recordNum = 0;
+  _("Verify that all tracked logins are removed.");
+
+  // Perform this test twice, the first time where a sync is not performed
+  // between adding and removing items and the second time where a sync is
+  // performed. In the former case, the logins will just be deleted because
+  // they have never been synced, so they won't be detected as changes. In
+  // the latter case, the logins have been synced so they will be marked for
+  // deletion.
+  for (let syncBeforeRemove of [false, true]) {
+    async function createPassword() {
+      _("RECORD NUM: " + recordNum);
+      let record = new LoginRec("passwords", "GUID" + recordNum);
+      record.cleartext = {
+        id: "GUID" + recordNum,
+        hostname: "http://foo.bar.com",
+        formSubmitURL: "http://foo.bar.com",
+        username: "john" + recordNum,
+        password: "smith",
+        usernameField: "username",
+        passwordField: "password",
+      };
+      recordNum++;
+      let login = store._nsLoginInfoFromRecord(record);
+      await Services.logins.addLoginAsync(login);
+
+      await tracker.asyncObserver.promiseObserversComplete();
+    }
+    try {
+      _("Tell tracker to start tracking changes");
+      tracker.start();
+      await createPassword();
+      await createPassword();
+      let changes = await engine.getChangedIDs();
+      do_check_attribute_count(changes, 2);
+      Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE * 2);
+
+      if (syncBeforeRemove) {
+        let logins = await Services.logins.getAllLogins();
+        for (let login of logins) {
+          engine.markSynced(login.guid);
+        }
+      }
+
+      _("Tell sync to remove all logins");
+      await Services.logins.removeAllUserFacingLoginsAsync();
+      await tracker.asyncObserver.promiseObserversComplete();
+      changes = await engine.getChangedIDs();
+      do_check_attribute_count(changes, syncBeforeRemove ? 2 : 0);
+      Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE * 5);
+
+      let deletedGuids = await engine._store.getAllIDs();
+      if (syncBeforeRemove) {
+        for (let guid in deletedGuids) {
+          let deletedLogin = await engine._store._getLoginFromGUID(guid);
+
+          Assert.equal(deletedLogin.hostname, null, "deleted login hostname");
+          Assert.equal(
+            deletedLogin.formActionOrigin,
+            null,
+            "deleted login formActionOrigin"
+          );
+          Assert.equal(
+            deletedLogin.formSubmitURL,
+            null,
+            "deleted login formSubmitURL"
+          );
+          Assert.equal(deletedLogin.httpRealm, null, "deleted login httpRealm");
+          Assert.equal(deletedLogin.username, null, "deleted login username");
+          Assert.equal(deletedLogin.password, null, "deleted login password");
+          Assert.equal(
+            deletedLogin.usernameField,
+            "",
+            "deleted login usernameField"
+          );
+          Assert.equal(
+            deletedLogin.passwordField,
+            "",
+            "deleted login passwordField"
+          );
+          Assert.equal(
+            deletedLogin.unknownFields,
+            null,
+            "deleted login unknownFields"
+          );
+          Assert.equal(
+            deletedLogin.timeCreated,
+            0,
+            "deleted login timeCreated"
+          );
+          Assert.equal(
+            deletedLogin.timeLastUsed,
+            0,
+            "deleted login timeLastUsed"
+          );
+          Assert.equal(deletedLogin.timesUsed, 0, "deleted login timesUsed");
+
+          // These fields are not reset when the login is removed.
+          Assert.ok(deletedLogin.guid.startsWith("GUID"), "deleted login guid");
+          Assert.equal(
+            deletedLogin.everSynced,
+            true,
+            "deleted login everSynced"
+          );
+          Assert.equal(
+            deletedLogin.syncCounter,
+            2,
+            "deleted login syncCounter"
+          );
+          Assert.greater(
+            deletedLogin.timePasswordChanged,
+            0,
+            "deleted login timePasswordChanged"
+          );
+        }
+      } else {
+        Assert.equal(
+          Object.keys(deletedGuids).length,
+          0,
+          "no logins remain after removeAllUserFacingLogins"
+        );
+      }
+    } finally {
+      _("Clean up.");
+      await store.wipe();
+      tracker.resetScore();
+      await tracker.stop();
+    }
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_password_validator.js b/src/zen/tests/mochitests/sync/test_password_validator.js
new file mode 100644
index 000000000..e0e88fd23
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_password_validator.js
@@ -0,0 +1,237 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { PasswordValidator } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/passwords.sys.mjs"
+);
+const { BridgedEngine } = ChromeUtils.importESModule(
+  "resource://services-sync/bridged_engine.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+function getDummyServerAndClient() {
+  return {
+    server: [
+      {
+        id: "11111",
+        guid: "11111",
+        hostname: "https://www.11111.com",
+        formSubmitURL: "https://www.11111.com",
+        password: "qwerty123",
+        passwordField: "pass",
+        username: "foobar",
+        usernameField: "user",
+        httpRealm: null,
+      },
+      {
+        id: "22222",
+        guid: "22222",
+        hostname: "https://www.22222.org",
+        formSubmitURL: "https://www.22222.org",
+        password: "hunter2",
+        passwordField: "passwd",
+        username: "baz12345",
+        usernameField: "user",
+        httpRealm: null,
+      },
+      {
+        id: "33333",
+        guid: "33333",
+        hostname: "https://www.33333.com",
+        formSubmitURL: "https://www.33333.com",
+        password: "p4ssw0rd",
+        passwordField: "passwad",
+        username: "quux",
+        usernameField: "user",
+        httpRealm: null,
+      },
+    ],
+    client: [
+      {
+        id: "11111",
+        guid: "11111",
+        hostname: "https://www.11111.com",
+        formSubmitURL: "https://www.11111.com",
+        password: "qwerty123",
+        passwordField: "pass",
+        username: "foobar",
+        usernameField: "user",
+        httpRealm: null,
+      },
+      {
+        id: "22222",
+        guid: "22222",
+        hostname: "https://www.22222.org",
+        formSubmitURL: "https://www.22222.org",
+        password: "hunter2",
+        passwordField: "passwd",
+        username: "baz12345",
+        usernameField: "user",
+        httpRealm: null,
+      },
+      {
+        id: "33333",
+        guid: "33333",
+        hostname: "https://www.33333.com",
+        formSubmitURL: "https://www.33333.com",
+        password: "p4ssw0rd",
+        passwordField: "passwad",
+        username: "quux",
+        usernameField: "user",
+        httpRealm: null,
+      },
+    ],
+  };
+}
+
+add_task(async function test_valid() {
+  let { server, client } = getDummyServerAndClient();
+  let validator = new PasswordValidator();
+  let { problemData, clientRecords, records, deletedRecords } =
+    await validator.compareClientWithServer(client, server);
+  equal(clientRecords.length, 3);
+  equal(records.length, 3);
+  equal(deletedRecords.length, 0);
+  deepEqual(problemData, validator.emptyProblemData());
+});
+
+add_task(async function test_missing() {
+  let validator = new PasswordValidator();
+  {
+    let { server, client } = getDummyServerAndClient();
+
+    client.pop();
+
+    let { problemData, clientRecords, records, deletedRecords } =
+      await validator.compareClientWithServer(client, server);
+
+    equal(clientRecords.length, 2);
+    equal(records.length, 3);
+    equal(deletedRecords.length, 0);
+
+    let expected = validator.emptyProblemData();
+    expected.clientMissing.push("33333");
+    deepEqual(problemData, expected);
+  }
+  {
+    let { server, client } = getDummyServerAndClient();
+
+    server.pop();
+
+    let { problemData, clientRecords, records, deletedRecords } =
+      await validator.compareClientWithServer(client, server);
+
+    equal(clientRecords.length, 3);
+    equal(records.length, 2);
+    equal(deletedRecords.length, 0);
+
+    let expected = validator.emptyProblemData();
+    expected.serverMissing.push("33333");
+    deepEqual(problemData, expected);
+  }
+});
+
+add_task(async function test_deleted() {
+  let { server, client } = getDummyServerAndClient();
+  let deletionRecord = { id: "444444", guid: "444444", deleted: true };
+
+  server.push(deletionRecord);
+  let validator = new PasswordValidator();
+
+  let { problemData, clientRecords, records, deletedRecords } =
+    await validator.compareClientWithServer(client, server);
+
+  equal(clientRecords.length, 3);
+  equal(records.length, 4);
+  deepEqual(deletedRecords, [deletionRecord]);
+
+  let expected = validator.emptyProblemData();
+  deepEqual(problemData, expected);
+});
+
+add_task(async function test_duplicates() {
+  let validator = new PasswordValidator();
+  {
+    let { server, client } = getDummyServerAndClient();
+    client.push(Cu.cloneInto(client[0], {}));
+
+    let { problemData } = await validator.compareClientWithServer(
+      client,
+      server
+    );
+
+    let expected = validator.emptyProblemData();
+    expected.clientDuplicates.push("11111");
+    deepEqual(problemData, expected);
+  }
+  {
+    let { server, client } = getDummyServerAndClient();
+    server.push(Cu.cloneInto(server[server.length - 1], {}));
+
+    let { problemData } = await validator.compareClientWithServer(
+      client,
+      server
+    );
+
+    let expected = validator.emptyProblemData();
+    expected.duplicates.push("33333");
+    deepEqual(problemData, expected);
+  }
+});
+
+// A bridged engine (eg, the Rust logins engine) decrypts records with
+// RawCryptoWrapper, so their cleartext is the raw payload string rather than a
+// parsed object. `getServerItems` must still yield objects to the validator,
+// otherwise every server record looks like it has no id and every local login
+// is wrongly reported as `serverMissing`.
+add_task(async function test_bridged_engine_server_items() {
+  let engine = new BridgedEngine("Passwords", Service);
+  engine._bridge = {
+    storageVersion: 1,
+    resetSyncId() {
+      return "syncIDAAAAAA";
+    },
+  };
+  engine.enabled = true;
+
+  let server = await serverForFoo(engine);
+  try {
+    await SyncTestingInfrastructure(server);
+
+    let guid = "{1e110b98-1407-4801-baf1-f6ca91e0f982}";
+    let login = {
+      id: guid,
+      hostname: "https://accounts.google.com",
+      formSubmitURL: "https://accounts.google.com",
+      username: "iosmztest",
+      password: "test15mz",
+      usernameField: "Email",
+      passwordField: "Passwd",
+    };
+    server
+      .user("foo")
+      .collection("passwords")
+      .insert(guid, encryptPayload(login), new_timestamp());
+
+    let validator = new PasswordValidator();
+    let serverItems = await validator.getServerItems(engine);
+    let clientItems = [{ ...login, guid, httpRealm: null }];
+
+    let { problemData } = await validator.compareClientWithServer(
+      clientItems,
+      serverItems
+    );
+
+    equal(
+      problemData.serverMissing.length,
+      0,
+      "A record present on the server must not be reported as serverMissing"
+    );
+    deepEqual(problemData, validator.emptyProblemData());
+  } finally {
+    await promiseStopServer(server);
+    await engine.finalize();
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_postqueue.js b/src/zen/tests/mochitests/sync/test_postqueue.js
new file mode 100644
index 000000000..2e687bce1
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_postqueue.js
@@ -0,0 +1,985 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+let { PostQueue } = ChromeUtils.importESModule(
+  "resource://services-sync/record.sys.mjs"
+);
+
+function makeRecord(nbytes) {
+  return {
+    toJSON: () => ({ payload: "x".repeat(nbytes) }),
+  };
+}
+
+// Note: This is 14 bytes. Tests make assumptions about this (even if it's just
+// in setting config.max_request_bytes to a specific value).
+makeRecord.nonPayloadOverhead = JSON.stringify(makeRecord(0).toJSON()).length;
+
+// Gives how many encoded bytes a request with the given payload
+// sizes will be (assuming the records were created by makeRecord)
+// requestBytesFor([20]) => 22, requestBytesFor([20, 20]) => 43
+function requestBytesFor(recordPayloadByteCounts) {
+  let requestBytes = 1;
+  for (let size of recordPayloadByteCounts) {
+    requestBytes += size + 1 + makeRecord.nonPayloadOverhead;
+  }
+  return requestBytes;
+}
+
+function makePostQueue(config, lastModTime, responseGenerator) {
+  let stats = {
+    posts: [],
+    batches: [],
+  };
+  let poster = (data, headers, batch, commit) => {
+    let payloadBytes = 0;
+    let numRecords = 0;
+    for (let record of JSON.parse(data)) {
+      if (config.max_record_payload_bytes) {
+        less(
+          record.payload.length,
+          config.max_record_payload_bytes,
+          "PostQueue should respect max_record_payload_bytes"
+        );
+      }
+      payloadBytes += record.payload.length;
+      ++numRecords;
+    }
+
+    let thisPost = {
+      nbytes: data.length,
+      batch,
+      commit,
+      payloadBytes,
+      numRecords,
+    };
+
+    if (headers.length) {
+      thisPost.headers = headers;
+    }
+
+    // check that we respected the provided limits for the post
+    if (config.max_post_records) {
+      lessOrEqual(
+        numRecords,
+        config.max_post_records,
+        "PostQueue should respect max_post_records"
+      );
+    }
+
+    if (config.max_post_bytes) {
+      less(
+        payloadBytes,
+        config.max_post_bytes,
+        "PostQueue should respect max_post_bytes"
+      );
+    }
+
+    if (config.max_request_bytes) {
+      less(
+        thisPost.nbytes,
+        config.max_request_bytes,
+        "PostQueue should respect max_request_bytes"
+      );
+    }
+
+    stats.posts.push(thisPost);
+
+    // Call this now so we can check if there's a batch id in it.
+    // Kind of cludgey, but allows us to have the correct batch id even
+    // before the next post is made.
+    let nextResponse = responseGenerator.next().value;
+
+    // Record info for the batch.
+
+    let curBatch = stats.batches[stats.batches.length - 1];
+    // If there's no batch, it committed, or we requested a new one,
+    // then we need to start a new one.
+    if (!curBatch || batch == "true" || curBatch.didCommit) {
+      curBatch = {
+        posts: 0,
+        payloadBytes: 0,
+        numRecords: 0,
+        didCommit: false,
+        batch,
+        serverBatch: false,
+      };
+      if (nextResponse.obj && nextResponse.obj.batch) {
+        curBatch.batch = nextResponse.obj.batch;
+        curBatch.serverBatch = true;
+      }
+      stats.batches.push(curBatch);
+    }
+
+    // If we provided a batch id, it must be the same as the current batch
+    if (batch && batch != "true") {
+      equal(curBatch.batch, batch);
+    }
+
+    curBatch.posts += 1;
+    curBatch.payloadBytes += payloadBytes;
+    curBatch.numRecords += numRecords;
+    curBatch.didCommit = commit;
+
+    // if this is an actual server batch (or it's a one-shot batch), check that
+    // we respected the provided total limits
+    if (commit && (batch == "true" || curBatch.serverBatch)) {
+      if (config.max_total_records) {
+        lessOrEqual(
+          curBatch.numRecords,
+          config.max_total_records,
+          "PostQueue should respect max_total_records"
+        );
+      }
+
+      if (config.max_total_bytes) {
+        less(
+          curBatch.payloadBytes,
+          config.max_total_bytes,
+          "PostQueue should respect max_total_bytes"
+        );
+      }
+    }
+
+    return Promise.resolve(nextResponse);
+  };
+
+  let done = () => {};
+  let pq = new PostQueue(poster, lastModTime, config, getTestLogger(), done);
+  return { pq, stats };
+}
+
+add_task(async function test_simple() {
+  let config = {
+    max_request_bytes: 1000,
+    max_record_payload_bytes: 1000,
+  };
+
+  const time = 11111111;
+
+  function* responseGenerator() {
+    yield {
+      success: true,
+      status: 200,
+      headers: {
+        "x-weave-timestamp": time + 100,
+        "x-last-modified": time + 100,
+      },
+    };
+  }
+
+  let { pq, stats } = makePostQueue(config, time, responseGenerator());
+  await pq.enqueue(makeRecord(10));
+  await pq.flush(true);
+
+  deepEqual(stats.posts, [
+    {
+      nbytes: requestBytesFor([10]),
+      payloadBytes: 10,
+      numRecords: 1,
+      commit: true, // we don't know if we have batch semantics, so committed.
+      headers: [["x-if-unmodified-since", time]],
+      batch: "true",
+    },
+  ]);
+  deepEqual(stats.batches, [
+    {
+      posts: 1,
+      payloadBytes: 10,
+      numRecords: 1,
+      didCommit: true,
+      batch: "true",
+      serverBatch: false,
+    },
+  ]);
+});
+
+// Test we do the right thing when we need to make multiple posts when there
+// are no batch semantics
+add_task(async function test_max_request_bytes_no_batch() {
+  let config = {
+    max_request_bytes: 50,
+    max_record_payload_bytes: 50,
+  };
+
+  const time = 11111111;
+  function* responseGenerator() {
+    yield {
+      success: true,
+      status: 200,
+      headers: {
+        "x-weave-timestamp": time + 100,
+        "x-last-modified": time + 100,
+      },
+    };
+    yield {
+      success: true,
+      status: 200,
+      headers: {
+        "x-weave-timestamp": time + 200,
+        "x-last-modified": time + 200,
+      },
+    };
+  }
+
+  let { pq, stats } = makePostQueue(config, time, responseGenerator());
+  let payloadSize = 20 - makeRecord.nonPayloadOverhead;
+  await pq.enqueue(makeRecord(payloadSize)); // total size now 22 bytes - "[" + record + "]"
+  await pq.enqueue(makeRecord(payloadSize)); // total size now 43 bytes - "[" + record + "," + record + "]"
+  await pq.enqueue(makeRecord(payloadSize)); // this will exceed our byte limit, so will be in the 2nd POST.
+  await pq.flush(true);
+  deepEqual(stats.posts, [
+    {
+      nbytes: 43, // 43 for the first part
+      payloadBytes: payloadSize * 2,
+      numRecords: 2,
+      commit: false,
+      headers: [["x-if-unmodified-since", time]],
+      batch: "true",
+    },
+    {
+      nbytes: 22,
+      payloadBytes: payloadSize,
+      numRecords: 1,
+      commit: false, // we know we aren't in a batch, so never commit.
+      headers: [["x-if-unmodified-since", time + 100]],
+      batch: null,
+    },
+  ]);
+  equal(stats.batches.filter(x => x.didCommit).length, 0);
+  equal(pq.lastModified, time + 200);
+});
+
+add_task(async function test_max_record_payload_bytes_no_batch() {
+  let config = {
+    max_request_bytes: 100,
+    max_record_payload_bytes: 50,
+  };
+
+  const time = 11111111;
+
+  function* responseGenerator() {
+    yield {
+      success: true,
+      status: 200,
+      headers: {
+        "x-weave-timestamp": time + 100,
+        "x-last-modified": time + 100,
+      },
+    };
+  }
+
+  let { pq, stats } = makePostQueue(config, time, responseGenerator());
+  // Should trigger when the record really is too large to fit
+  let { enqueued } = await pq.enqueue(makeRecord(51));
+  ok(!enqueued);
+  // Shouldn't trigger when the encoded record is too big
+  ok(
+    (await pq.enqueue(makeRecord(50 - makeRecord.nonPayloadOverhead))).enqueued
+  ); // total size now 52 bytes - "[" + record + "]"
+  ok(
+    (await pq.enqueue(makeRecord(46 - makeRecord.nonPayloadOverhead))).enqueued
+  ); // total size now 99 bytes - "[" + record0 + "," + record1 + "]"
+
+  await pq.flush(true);
+
+  deepEqual(stats.posts, [
+    {
+      nbytes: 99,
+      payloadBytes: 50 + 46 - makeRecord.nonPayloadOverhead * 2,
+      numRecords: 2,
+      commit: true, // we know we aren't in a batch, so never commit.
+      batch: "true",
+      headers: [["x-if-unmodified-since", time]],
+    },
+  ]);
+
+  deepEqual(stats.batches, [
+    {
+      posts: 1,
+      payloadBytes: 50 + 46 - makeRecord.nonPayloadOverhead * 2,
+      numRecords: 2,
+      didCommit: true,
+      batch: "true",
+      serverBatch: false,
+    },
+  ]);
+
+  equal(pq.lastModified, time + 100);
+});
+
+// Batch tests.
+
+// Test making a single post when batch semantics are in place.
+
+add_task(async function test_single_batch() {
+  let config = {
+    max_post_bytes: 1000,
+    max_post_records: 100,
+    max_total_records: 200,
+    max_record_payload_bytes: 1000,
+  };
+  const time = 11111111;
+  function* responseGenerator() {
+    yield {
+      success: true,
+      status: 202,
+      obj: { batch: 1234 },
+      headers: { "x-last-modified": time, "x-weave-timestamp": time + 100 },
+    };
+  }
+
+  let { pq, stats } = makePostQueue(config, time, responseGenerator());
+  ok((await pq.enqueue(makeRecord(10))).enqueued);
+  await pq.flush(true);
+
+  deepEqual(stats.posts, [
+    {
+      nbytes: requestBytesFor([10]),
+      numRecords: 1,
+      payloadBytes: 10,
+      commit: true, // we don't know if we have batch semantics, so committed.
+      batch: "true",
+      headers: [["x-if-unmodified-since", time]],
+    },
+  ]);
+
+  deepEqual(stats.batches, [
+    {
+      posts: 1,
+      payloadBytes: 10,
+      numRecords: 1,
+      didCommit: true,
+      batch: 1234,
+      serverBatch: true,
+    },
+  ]);
+});
+
+// Test we do the right thing when we need to make multiple posts due to
+// max_post_bytes when there are batch semantics in place.
+add_task(async function test_max_post_bytes_batch() {
+  let config = {
+    max_post_bytes: 50,
+    max_post_records: 4,
+    max_total_bytes: 5000,
+    max_total_records: 100,
+    max_record_payload_bytes: 50,
+    max_request_bytes: 4000,
+  };
+
+  const time = 11111111;
+  function* responseGenerator() {
+    yield {
+      success: true,
+      status: 202,
+      obj: { batch: 1234 },
+      headers: { "x-last-modified": time, "x-weave-timestamp": time + 100 },
+    };
+    yield {
+      success: true,
+      status: 202,
+      obj: { batch: 1234 },
+      headers: {
+        "x-last-modified": time + 200,
+        "x-weave-timestamp": time + 200,
+      },
+    };
+  }
+
+  let { pq, stats } = makePostQueue(config, time, responseGenerator());
+  ok((await pq.enqueue(makeRecord(20))).enqueued); // 20
+  ok((await pq.enqueue(makeRecord(20))).enqueued); // 40
+  // 60 would overflow, so post
+  ok((await pq.enqueue(makeRecord(20))).enqueued); // 20
+  await pq.flush(true);
+
+  deepEqual(stats.posts, [
+    {
+      nbytes: requestBytesFor([20, 20]),
+      payloadBytes: 40,
+      numRecords: 2,
+      commit: false,
+      batch: "true",
+      headers: [["x-if-unmodified-since", time]],
+    },
+    {
+      nbytes: requestBytesFor([20]),
+      payloadBytes: 20,
+      numRecords: 1,
+      commit: true,
+      batch: 1234,
+      headers: [["x-if-unmodified-since", time]],
+    },
+  ]);
+
+  deepEqual(stats.batches, [
+    {
+      posts: 2,
+      payloadBytes: 60,
+      numRecords: 3,
+      didCommit: true,
+      batch: 1234,
+      serverBatch: true,
+    },
+  ]);
+
+  equal(pq.lastModified, time + 200);
+});
+
+// Test we do the right thing when we need to make multiple posts due to
+// max_request_bytes when there are batch semantics in place.
+add_task(async function test_max_request_bytes_batch() {
+  let config = {
+    max_post_bytes: 60,
+    max_post_records: 40,
+    max_total_bytes: 5000,
+    max_total_records: 100,
+    max_record_payload_bytes: 500,
+    max_request_bytes: 100,
+  };
+
+  const time = 11111111;
+  function* responseGenerator() {
+    yield {
+      success: true,
+      status: 202,
+      obj: { batch: 1234 },
+      headers: { "x-last-modified": time, "x-weave-timestamp": time + 100 },
+    };
+    yield {
+      success: true,
+      status: 202,
+      obj: { batch: 1234 },
+      headers: {
+        "x-last-modified": time + 200,
+        "x-weave-timestamp": time + 200,
+      },
+    };
+  }
+
+  let { pq, stats } = makePostQueue(config, time, responseGenerator());
+  ok((await pq.enqueue(makeRecord(10))).enqueued); // post: 10, request: 26 (10 + 14 + 2)
+  ok((await pq.enqueue(makeRecord(10))).enqueued); // post: 20, request: 51 (10 + 14 + 1) * 2 + 1
+  ok((await pq.enqueue(makeRecord(10))).enqueued); // post: 30, request: 76 (10 + 14 + 1) * 3 + 1
+  // 1 more would be post: 40 (fine), request: 101, So we should post.
+  ok((await pq.enqueue(makeRecord(10))).enqueued);
+  await pq.flush(true);
+
+  deepEqual(stats.posts, [
+    {
+      nbytes: requestBytesFor([10, 10, 10]),
+      payloadBytes: 30,
+      numRecords: 3,
+      commit: false,
+      batch: "true",
+      headers: [["x-if-unmodified-since", time]],
+    },
+    {
+      nbytes: requestBytesFor([10]),
+      payloadBytes: 10,
+      numRecords: 1,
+      commit: true,
+      batch: 1234,
+      headers: [["x-if-unmodified-since", time]],
+    },
+  ]);
+
+  deepEqual(stats.batches, [
+    {
+      posts: 2,
+      payloadBytes: 40,
+      numRecords: 4,
+      didCommit: true,
+      batch: 1234,
+      serverBatch: true,
+    },
+  ]);
+
+  equal(pq.lastModified, time + 200);
+});
+
+// Test we do the right thing when the batch bytes limit is exceeded.
+add_task(async function test_max_total_bytes_batch() {
+  let config = {
+    max_post_bytes: 50,
+    max_post_records: 20,
+    max_total_bytes: 70,
+    max_total_records: 100,
+    max_record_payload_bytes: 50,
+    max_request_bytes: 500,
+  };
+
+  const time0 = 11111111;
+  const time1 = 22222222;
+  function* responseGenerator() {
+    yield {
+      success: true,
+      status: 202,
+      obj: { batch: 1234 },
+      headers: { "x-last-modified": time0, "x-weave-timestamp": time0 + 100 },
+    };
+    yield {
+      success: true,
+      status: 202,
+      obj: { batch: 1234 },
+      headers: { "x-last-modified": time1, "x-weave-timestamp": time1 },
+    };
+    yield {
+      success: true,
+      status: 202,
+      obj: { batch: 5678 },
+      headers: { "x-last-modified": time1, "x-weave-timestamp": time1 + 100 },
+    };
+    yield {
+      success: true,
+      status: 202,
+      obj: { batch: 5678 },
+      headers: {
+        "x-last-modified": time1 + 200,
+        "x-weave-timestamp": time1 + 200,
+      },
+    };
+  }
+
+  let { pq, stats } = makePostQueue(config, time0, responseGenerator());
+
+  ok((await pq.enqueue(makeRecord(20))).enqueued); // payloads = post: 20, batch: 20
+  ok((await pq.enqueue(makeRecord(20))).enqueued); // payloads = post: 40, batch: 40
+
+  // this will exceed our POST byte limit, so will be in the 2nd POST - but still in the first batch.
+  ok((await pq.enqueue(makeRecord(20))).enqueued); // payloads = post: 20, batch: 60
+
+  // this will exceed our batch byte limit, so will be in a new batch.
+  ok((await pq.enqueue(makeRecord(20))).enqueued); // payloads = post: 20, batch: 20
+  ok((await pq.enqueue(makeRecord(20))).enqueued); // payloads = post: 40, batch: 40
+  // This will exceed POST byte limit, so will be in the 4th post, part of the 2nd batch.
+  ok((await pq.enqueue(makeRecord(20))).enqueued); // payloads = post: 20, batch: 60
+  await pq.flush(true);
+
+  deepEqual(stats.posts, [
+    {
+      nbytes: requestBytesFor([20, 20]),
+      payloadBytes: 40,
+      numRecords: 2,
+      commit: false,
+      batch: "true",
+      headers: [["x-if-unmodified-since", time0]],
+    },
+    {
+      nbytes: requestBytesFor([20]),
+      payloadBytes: 20,
+      numRecords: 1,
+      commit: true,
+      batch: 1234,
+      headers: [["x-if-unmodified-since", time0]],
+    },
+    {
+      nbytes: requestBytesFor([20, 20]),
+      payloadBytes: 40,
+      numRecords: 2,
+      commit: false,
+      batch: "true",
+      headers: [["x-if-unmodified-since", time1]],
+    },
+    {
+      nbytes: requestBytesFor([20]),
+      payloadBytes: 20,
+      numRecords: 1,
+      commit: true,
+      batch: 5678,
+      headers: [["x-if-unmodified-since", time1]],
+    },
+  ]);
+
+  deepEqual(stats.batches, [
+    {
+      posts: 2,
+      payloadBytes: 60,
+      numRecords: 3,
+      didCommit: true,
+      batch: 1234,
+      serverBatch: true,
+    },
+    {
+      posts: 2,
+      payloadBytes: 60,
+      numRecords: 3,
+      didCommit: true,
+      batch: 5678,
+      serverBatch: true,
+    },
+  ]);
+
+  equal(pq.lastModified, time1 + 200);
+});
+
+// Test we split up the posts when we exceed the record limit when batch semantics
+// are in place.
+add_task(async function test_max_post_records_batch() {
+  let config = {
+    max_post_bytes: 1000,
+    max_post_records: 2,
+    max_total_bytes: 5000,
+    max_total_records: 100,
+    max_record_payload_bytes: 1000,
+    max_request_bytes: 1000,
+  };
+
+  const time = 11111111;
+  function* responseGenerator() {
+    yield {
+      success: true,
+      status: 202,
+      obj: { batch: 1234 },
+      headers: { "x-last-modified": time, "x-weave-timestamp": time + 100 },
+    };
+    yield {
+      success: true,
+      status: 202,
+      obj: { batch: 1234 },
+      headers: {
+        "x-last-modified": time + 200,
+        "x-weave-timestamp": time + 200,
+      },
+    };
+  }
+
+  let { pq, stats } = makePostQueue(config, time, responseGenerator());
+  ok((await pq.enqueue(makeRecord(20))).enqueued);
+  ok((await pq.enqueue(makeRecord(20))).enqueued);
+
+  // will exceed record limit of 2, so will be in 2nd post.
+  ok((await pq.enqueue(makeRecord(20))).enqueued);
+
+  await pq.flush(true);
+
+  deepEqual(stats.posts, [
+    {
+      nbytes: requestBytesFor([20, 20]),
+      numRecords: 2,
+      payloadBytes: 40,
+      commit: false,
+      batch: "true",
+      headers: [["x-if-unmodified-since", time]],
+    },
+    {
+      nbytes: requestBytesFor([20]),
+      numRecords: 1,
+      payloadBytes: 20,
+      commit: true,
+      batch: 1234,
+      headers: [["x-if-unmodified-since", time]],
+    },
+  ]);
+
+  deepEqual(stats.batches, [
+    {
+      posts: 2,
+      payloadBytes: 60,
+      numRecords: 3,
+      batch: 1234,
+      serverBatch: true,
+      didCommit: true,
+    },
+  ]);
+
+  equal(pq.lastModified, time + 200);
+});
+
+// Test we do the right thing when the batch record limit is exceeded.
+add_task(async function test_max_records_batch() {
+  let config = {
+    max_post_bytes: 1000,
+    max_post_records: 3,
+    max_total_bytes: 10000,
+    max_total_records: 5,
+    max_record_payload_bytes: 1000,
+    max_request_bytes: 10000,
+  };
+
+  const time0 = 11111111;
+  const time1 = 22222222;
+  function* responseGenerator() {
+    yield {
+      success: true,
+      status: 202,
+      obj: { batch: 1234 },
+      headers: { "x-last-modified": time0, "x-weave-timestamp": time0 + 100 },
+    };
+    yield {
+      success: true,
+      status: 202,
+      obj: { batch: 1234 },
+      headers: { "x-last-modified": time1, "x-weave-timestamp": time1 },
+    };
+    yield {
+      success: true,
+      status: 202,
+      obj: { batch: 5678 },
+      headers: { "x-last-modified": time1, "x-weave-timestamp": time1 + 100 },
+    };
+    yield {
+      success: true,
+      status: 202,
+      obj: { batch: 5678 },
+      headers: {
+        "x-last-modified": time1 + 200,
+        "x-weave-timestamp": time1 + 200,
+      },
+    };
+  }
+
+  let { pq, stats } = makePostQueue(config, time0, responseGenerator());
+
+  ok((await pq.enqueue(makeRecord(20))).enqueued);
+  ok((await pq.enqueue(makeRecord(20))).enqueued);
+  ok((await pq.enqueue(makeRecord(20))).enqueued);
+
+  ok((await pq.enqueue(makeRecord(20))).enqueued);
+  ok((await pq.enqueue(makeRecord(20))).enqueued);
+
+  ok((await pq.enqueue(makeRecord(20))).enqueued);
+  ok((await pq.enqueue(makeRecord(20))).enqueued);
+  ok((await pq.enqueue(makeRecord(20))).enqueued);
+
+  ok((await pq.enqueue(makeRecord(20))).enqueued);
+
+  await pq.flush(true);
+
+  deepEqual(stats.posts, [
+    {
+      // 3 records
+      nbytes: requestBytesFor([20, 20, 20]),
+      payloadBytes: 60,
+      numRecords: 3,
+      commit: false,
+      batch: "true",
+      headers: [["x-if-unmodified-since", time0]],
+    },
+    {
+      // 2 records -- end batch1
+      nbytes: requestBytesFor([20, 20]),
+      payloadBytes: 40,
+      numRecords: 2,
+      commit: true,
+      batch: 1234,
+      headers: [["x-if-unmodified-since", time0]],
+    },
+    {
+      // 3 records
+      nbytes: requestBytesFor([20, 20, 20]),
+      payloadBytes: 60,
+      numRecords: 3,
+      commit: false,
+      batch: "true",
+      headers: [["x-if-unmodified-since", time1]],
+    },
+    {
+      // 1 record -- end batch2
+      nbytes: requestBytesFor([20]),
+      payloadBytes: 20,
+      numRecords: 1,
+      commit: true,
+      batch: 5678,
+      headers: [["x-if-unmodified-since", time1]],
+    },
+  ]);
+
+  deepEqual(stats.batches, [
+    {
+      posts: 2,
+      payloadBytes: 100,
+      numRecords: 5,
+      batch: 1234,
+      serverBatch: true,
+      didCommit: true,
+    },
+    {
+      posts: 2,
+      payloadBytes: 80,
+      numRecords: 4,
+      batch: 5678,
+      serverBatch: true,
+      didCommit: true,
+    },
+  ]);
+
+  equal(pq.lastModified, time1 + 200);
+});
+
+// Test we do the right thing when the limits are met but not exceeded.
+add_task(async function test_packed_batch() {
+  let config = {
+    max_post_bytes: 41,
+    max_post_records: 4,
+
+    max_total_bytes: 81,
+    max_total_records: 8,
+
+    max_record_payload_bytes: 20 + makeRecord.nonPayloadOverhead + 1,
+    max_request_bytes: requestBytesFor([10, 10, 10, 10]) + 1,
+  };
+
+  const time = 11111111;
+  function* responseGenerator() {
+    yield {
+      success: true,
+      status: 202,
+      obj: { batch: 1234 },
+      headers: { "x-last-modified": time, "x-weave-timestamp": time + 100 },
+    };
+    yield {
+      success: true,
+      status: 202,
+      obj: { batch: 1234 },
+      headers: {
+        "x-last-modified": time + 200,
+        "x-weave-timestamp": time + 200,
+      },
+    };
+  }
+
+  let { pq, stats } = makePostQueue(config, time, responseGenerator());
+  ok((await pq.enqueue(makeRecord(10))).enqueued);
+  ok((await pq.enqueue(makeRecord(10))).enqueued);
+  ok((await pq.enqueue(makeRecord(10))).enqueued);
+  ok((await pq.enqueue(makeRecord(10))).enqueued);
+
+  ok((await pq.enqueue(makeRecord(10))).enqueued);
+  ok((await pq.enqueue(makeRecord(10))).enqueued);
+  ok((await pq.enqueue(makeRecord(10))).enqueued);
+  ok((await pq.enqueue(makeRecord(10))).enqueued);
+
+  await pq.flush(true);
+
+  deepEqual(stats.posts, [
+    {
+      nbytes: requestBytesFor([10, 10, 10, 10]),
+      numRecords: 4,
+      payloadBytes: 40,
+      commit: false,
+      batch: "true",
+      headers: [["x-if-unmodified-since", time]],
+    },
+    {
+      nbytes: requestBytesFor([10, 10, 10, 10]),
+      numRecords: 4,
+      payloadBytes: 40,
+      commit: true,
+      batch: 1234,
+      headers: [["x-if-unmodified-since", time]],
+    },
+  ]);
+
+  deepEqual(stats.batches, [
+    {
+      posts: 2,
+      payloadBytes: 80,
+      numRecords: 8,
+      batch: 1234,
+      serverBatch: true,
+      didCommit: true,
+    },
+  ]);
+
+  equal(pq.lastModified, time + 200);
+});
+
+// Tests that check that a single record fails to enqueue for the provided config
+async function test_enqueue_failure_case(failureLimit, config) {
+  const time = 11111111;
+  function* responseGenerator() {
+    yield {
+      success: true,
+      status: 202,
+      obj: { batch: 1234 },
+      headers: {
+        "x-last-modified": time + 100,
+        "x-weave-timestamp": time + 100,
+      },
+    };
+  }
+
+  let { pq, stats } = makePostQueue(config, time, responseGenerator());
+  // Check on empty postqueue
+  let result = await pq.enqueue(makeRecord(failureLimit + 1));
+  ok(!result.enqueued);
+  notEqual(result.error, undefined);
+
+  ok((await pq.enqueue(makeRecord(5))).enqueued);
+
+  // check on nonempty postqueue
+  result = await pq.enqueue(makeRecord(failureLimit + 1));
+  ok(!result.enqueued);
+  notEqual(result.error, undefined);
+
+  // make sure that we keep working, skipping the bad record entirely
+  // (handling the error the queue reported is left up to caller)
+  ok((await pq.enqueue(makeRecord(5))).enqueued);
+
+  await pq.flush(true);
+
+  deepEqual(stats.posts, [
+    {
+      nbytes: requestBytesFor([5, 5]),
+      numRecords: 2,
+      payloadBytes: 10,
+      commit: true,
+      batch: "true",
+      headers: [["x-if-unmodified-since", time]],
+    },
+  ]);
+
+  deepEqual(stats.batches, [
+    {
+      posts: 1,
+      payloadBytes: 10,
+      numRecords: 2,
+      batch: 1234,
+      serverBatch: true,
+      didCommit: true,
+    },
+  ]);
+
+  equal(pq.lastModified, time + 100);
+}
+
+add_task(async function test_max_post_bytes_enqueue_failure() {
+  await test_enqueue_failure_case(50, {
+    max_post_bytes: 50,
+    max_post_records: 100,
+
+    max_total_bytes: 5000,
+    max_total_records: 100,
+
+    max_record_payload_bytes: 500,
+    max_request_bytes: 500,
+  });
+});
+
+add_task(async function test_max_request_bytes_enqueue_failure() {
+  await test_enqueue_failure_case(50, {
+    max_post_bytes: 500,
+    max_post_records: 100,
+
+    max_total_bytes: 5000,
+    max_total_records: 100,
+
+    max_record_payload_bytes: 500,
+    max_request_bytes: 50,
+  });
+});
+
+add_task(async function test_max_record_payload_bytes_enqueue_failure() {
+  await test_enqueue_failure_case(50, {
+    max_post_bytes: 500,
+    max_post_records: 100,
+
+    max_total_bytes: 5000,
+    max_total_records: 100,
+
+    max_record_payload_bytes: 50,
+    max_request_bytes: 500,
+  });
+});
diff --git a/src/zen/tests/mochitests/sync/test_prefs_engine.js b/src/zen/tests/mochitests/sync/test_prefs_engine.js
new file mode 100644
index 000000000..77a4474cb
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_prefs_engine.js
@@ -0,0 +1,134 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { getPrefsGUIDForTest } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/prefs.sys.mjs"
+);
+const PREFS_GUID = getPrefsGUIDForTest();
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+async function cleanup(engine, server) {
+  await engine._tracker.stop();
+  await engine.wipeClient();
+  for (const pref of Svc.PrefBranch.getChildList("")) {
+    Svc.PrefBranch.clearUserPref(pref);
+  }
+  Service.recordManager.clearCache();
+  await promiseStopServer(server);
+}
+
+add_task(async function test_modified_after_fail() {
+  let engine = Service.engineManager.get("prefs");
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  try {
+    // The homepage pref is synced by default.
+    _("Set homepage before first sync");
+    Services.prefs.setStringPref("browser.startup.homepage", "about:welcome");
+
+    _("First sync; create collection and pref record on server");
+    await sync_engine_and_validate_telem(engine, false);
+
+    let collection = server.user("foo").collection("prefs");
+    equal(
+      collection.cleartext(PREFS_GUID).value["browser.startup.homepage"],
+      "about:welcome",
+      "Should upload homepage in pref record"
+    );
+    ok(
+      !engine._tracker.modified,
+      "Tracker shouldn't be modified after first sync"
+    );
+
+    // Our tracker only has a `modified` flag that's reset after a
+    // successful upload. Force it to remain set by failing the
+    // upload.
+    _("Second sync; flag tracker as modified and throw on upload");
+    Services.prefs.setStringPref("browser.startup.homepage", "about:robots");
+    engine._tracker.modified = true;
+    let oldPost = collection.post;
+    collection.post = () => {
+      throw new Error("Sync this!");
+    };
+    await Assert.rejects(
+      sync_engine_and_validate_telem(engine, true),
+      ex => ex.success === false
+    );
+    ok(
+      engine._tracker.modified,
+      "Tracker should remain modified after failed sync"
+    );
+
+    _("Third sync");
+    collection.post = oldPost;
+    await sync_engine_and_validate_telem(engine, false);
+    equal(
+      collection.cleartext(PREFS_GUID).value["browser.startup.homepage"],
+      "about:robots",
+      "Should upload new homepage on third sync"
+    );
+    ok(
+      !engine._tracker.modified,
+      "Tracker shouldn't be modified again after third sync"
+    );
+  } finally {
+    await cleanup(engine, server);
+  }
+});
+
+add_task(async function test_allow_arbitrary() {
+  let engine = Service.engineManager.get("prefs");
+
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  try {
+    _("Create collection and pref record on server");
+    await sync_engine_and_validate_telem(engine, false);
+
+    let collection = server.user("foo").collection("prefs");
+
+    _("Insert arbitrary pref into remote record");
+    let cleartext1 = collection.cleartext(PREFS_GUID);
+    cleartext1.value.let_viruses_take_over = true;
+    collection.insert(
+      PREFS_GUID,
+      encryptPayload(cleartext1),
+      new_timestamp() + 5
+    );
+
+    _("Sync again; client shouldn't allow pref");
+    await sync_engine_and_validate_telem(engine, false);
+    ok(
+      !Services.prefs.getBoolPref("let_viruses_take_over", false),
+      "Shouldn't allow arbitrary remote prefs without control pref"
+    );
+
+    _("Sync with control pref set; client should set new pref");
+    Services.prefs.setBoolPref(
+      "services.sync.prefs.sync.let_viruses_take_over_take_two",
+      true
+    );
+
+    let cleartext2 = collection.cleartext(PREFS_GUID);
+    cleartext2.value.let_viruses_take_over_take_two = true;
+    collection.insert(
+      PREFS_GUID,
+      encryptPayload(cleartext2),
+      new_timestamp() + 5
+    );
+    // Reset the last sync time so that the engine fetches the record again.
+    await engine.setLastSync(0);
+    await sync_engine_and_validate_telem(engine, false);
+    ok(
+      Services.prefs.getBoolPref("let_viruses_take_over_take_two"),
+      "Should set arbitrary remote pref with control pref"
+    );
+  } finally {
+    await cleanup(engine, server);
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_prefs_store.js b/src/zen/tests/mochitests/sync/test_prefs_store.js
new file mode 100644
index 000000000..17f2af826
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_prefs_store.js
@@ -0,0 +1,402 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { PromiseTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/PromiseTestUtils.sys.mjs"
+);
+PromiseTestUtils.allowMatchingRejectionsGlobally(
+  /Unable to arm timer, the object has been finalized\./
+);
+PromiseTestUtils.allowMatchingRejectionsGlobally(
+  /IOUtils\.profileBeforeChange getter: IOUtils: profileBeforeChange phase has already finished/
+);
+
+const { PrefRec, getPrefsGUIDForTest } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/prefs.sys.mjs"
+);
+const PREFS_GUID = getPrefsGUIDForTest();
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+const DEFAULT_THEME_ID = "default-theme@mozilla.org";
+const COMPACT_THEME_ID = "firefox-compact-light@mozilla.org";
+
+AddonTestUtils.init(this);
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "1.9.2"
+);
+AddonTestUtils.overrideCertDB();
+
+let prefsWithUserValue = new Set();
+add_setup(function record_prefsWithUserValue() {
+  for (const pref of Services.prefs.getChildList("")) {
+    if (Services.prefs.prefHasUserValue(pref)) {
+      prefsWithUserValue.add(pref);
+    }
+  }
+});
+
+function clearValues() {
+  for (const pref of Services.prefs.getChildList("")) {
+    if (!prefsWithUserValue.has(pref)) {
+      Services.prefs.clearUserPref(pref);
+    }
+  }
+}
+
+add_task(async function run_test() {
+  _("Test fixtures.");
+  // Part of this test ensures the default theme, via the preference
+  // extensions.activeThemeID, is synced correctly - so we do a little
+  // addons initialization to allow this to work.
+
+  // Enable application scopes to ensure the builtin theme is going to
+  // be installed as part of the the addon manager startup.
+  Services.prefs.setIntPref(
+    "extensions.enabledScopes",
+    AddonManager.SCOPE_APPLICATION
+  );
+  await AddonTestUtils.promiseStartupManager();
+
+  // Install another built-in theme.
+  await AddonManager.installBuiltinAddon("resource://builtin-themes/light/");
+
+  const defaultThemeAddon = await AddonManager.getAddonByID(DEFAULT_THEME_ID);
+  ok(defaultThemeAddon, "Got an addon wrapper for the default theme");
+
+  const otherThemeAddon = await AddonManager.getAddonByID(COMPACT_THEME_ID);
+  ok(otherThemeAddon, "Got an addon wrapper for the compact theme");
+
+  await otherThemeAddon.enable();
+
+  // read our custom prefs file before doing anything.
+  Services.prefs.readDefaultPrefsFromFile(
+    do_get_file("prefs_test_prefs_store.js")
+  );
+
+  let engine = Service.engineManager.get("prefs");
+  let store = engine._store;
+  try {
+    _("Expect the compact light theme to be active");
+    Assert.strictEqual(
+      Services.prefs.getStringPref("extensions.activeThemeID"),
+      COMPACT_THEME_ID
+    );
+
+    _("The GUID corresponds to XUL App ID.");
+    let allIDs = await store.getAllIDs();
+    let ids = Object.keys(allIDs);
+    Assert.equal(ids.length, 1);
+    Assert.equal(ids[0], PREFS_GUID);
+    Assert.ok(allIDs[PREFS_GUID]);
+
+    Assert.ok(await store.itemExists(PREFS_GUID));
+    Assert.equal(false, await store.itemExists("random-gibberish"));
+
+    _("Unknown prefs record is created as deleted.");
+    let record = await store.createRecord("random-gibberish", "prefs");
+    Assert.ok(record.deleted);
+
+    _("Prefs record contains only prefs that should be synced.");
+    record = await store.createRecord(PREFS_GUID, "prefs");
+    Assert.strictEqual(record.value["testing.int"], 123);
+    Assert.strictEqual(record.value["testing.string"], "ohai");
+    Assert.strictEqual(record.value["testing.bool"], true);
+    // non-existing prefs get null as the value
+    Assert.strictEqual(record.value["testing.nonexistent"], null);
+    // as do prefs that have a default value.
+    Assert.strictEqual(record.value["testing.default"], null);
+    Assert.strictEqual(record.value["testing.turned.off"], undefined);
+    Assert.strictEqual(record.value["testing.not.turned.on"], undefined);
+
+    _("Prefs record contains the correct control prefs.");
+    // All control prefs which have the default value and where the pref
+    // itself is synced should appear, but with null as the value.
+    Assert.strictEqual(
+      record.value["services.sync.prefs.sync.testing.int"],
+      null
+    );
+    Assert.strictEqual(
+      record.value["services.sync.prefs.sync.testing.string"],
+      null
+    );
+    Assert.strictEqual(
+      record.value["services.sync.prefs.sync.testing.bool"],
+      null
+    );
+    Assert.strictEqual(
+      record.value["services.sync.prefs.sync.testing.dont.change"],
+      null
+    );
+    Assert.strictEqual(
+      record.value["services.sync.prefs.sync.testing.nonexistent"],
+      null
+    );
+    Assert.strictEqual(
+      record.value["services.sync.prefs.sync.testing.default"],
+      null
+    );
+
+    // but this control pref has a non-default value so that value is synced.
+    Assert.strictEqual(
+      record.value["services.sync.prefs.sync.testing.turned.off"],
+      false
+    );
+
+    _("Unsyncable prefs are treated correctly.");
+    // Prefs we consider unsyncable (since they are URLs that won't be stable on
+    // another firefox) shouldn't be included - neither the value nor the
+    // control pref should appear.
+    Assert.strictEqual(record.value["testing.unsynced.url"], undefined);
+    Assert.strictEqual(
+      record.value["services.sync.prefs.sync.testing.unsynced.url"],
+      undefined
+    );
+    // Other URLs with user prefs should be synced, though.
+    Assert.strictEqual(
+      record.value["testing.synced.url"],
+      "https://www.example.com"
+    );
+    Assert.strictEqual(
+      record.value["services.sync.prefs.sync.testing.synced.url"],
+      null
+    );
+
+    _("Update some prefs, including one that's to be reset/deleted.");
+    // This pref is not going to be reset or deleted as there's no "control pref"
+    // in either the incoming record or locally.
+    Services.prefs.setStringPref(
+      "testing.deleted-without-control-pref",
+      "I'm deleted-without-control-pref"
+    );
+    // Another pref with only a local control pref.
+    Services.prefs.setStringPref(
+      "testing.deleted-with-local-control-pref",
+      "I'm deleted-with-local-control-pref"
+    );
+    Services.prefs.setBoolPref(
+      "services.sync.prefs.sync.testing.deleted-with-local-control-pref",
+      true
+    );
+    // And a pref without a local control pref but one that's incoming.
+    Services.prefs.setStringPref(
+      "testing.deleted-with-incoming-control-pref",
+      "I'm deleted-with-incoming-control-pref"
+    );
+    record = new PrefRec("prefs", PREFS_GUID);
+    record.value = {
+      "extensions.activeThemeID": DEFAULT_THEME_ID,
+      "testing.int": 42,
+      "testing.string": "im in ur prefs",
+      "testing.bool": false,
+      "testing.deleted-without-control-pref": null,
+      "testing.deleted-with-local-control-pref": null,
+      "testing.deleted-with-incoming-control-pref": null,
+      "services.sync.prefs.sync.testing.deleted-with-incoming-control-pref": true,
+      "testing.somepref": "im a new pref from other device",
+      "services.sync.prefs.sync.testing.somepref": true,
+      // Pretend some a stale remote client is overwriting it with a value
+      // we consider unsyncable.
+      "testing.synced.url": "blob:ebeb707a-502e-40c6-97a5-dd4bda901463",
+      // Make sure we can replace the unsynced URL with a valid URL.
+      "testing.unsynced.url": "https://www.example.com/2",
+      // Make sure our "master control pref" is ignored.
+      "services.sync.prefs.dangerously_allow_arbitrary": true,
+      "services.sync.prefs.sync.services.sync.prefs.dangerously_allow_arbitrary": true,
+    };
+
+    const onceAddonEnabled = AddonTestUtils.promiseAddonEvent("onEnabled");
+
+    await store.update(record);
+    Assert.strictEqual(Services.prefs.getIntPref("testing.int"), 42);
+    Assert.strictEqual(
+      Services.prefs.getStringPref("testing.string"),
+      "im in ur prefs"
+    );
+    Assert.strictEqual(Services.prefs.getBoolPref("testing.bool"), false);
+    Assert.strictEqual(
+      Services.prefs.getStringPref("testing.deleted-without-control-pref"),
+      "I'm deleted-without-control-pref"
+    );
+    Assert.strictEqual(
+      Services.prefs.getPrefType("testing.deleted-with-local-control-pref"),
+      Ci.nsIPrefBranch.PREF_INVALID
+    );
+    Assert.strictEqual(
+      Services.prefs.getStringPref(
+        "testing.deleted-with-incoming-control-pref"
+      ),
+      "I'm deleted-with-incoming-control-pref"
+    );
+    Assert.strictEqual(
+      Services.prefs.getStringPref("testing.dont.change"),
+      "Please don't change me."
+    );
+    Assert.strictEqual(
+      Services.prefs.getPrefType("testing.somepref"),
+      Ci.nsIPrefBranch.PREF_INVALID
+    );
+    Assert.strictEqual(
+      Services.prefs.getStringPref("testing.synced.url"),
+      "https://www.example.com"
+    );
+    Assert.strictEqual(
+      Services.prefs.getStringPref("testing.unsynced.url"),
+      "https://www.example.com/2"
+    );
+    Assert.strictEqual(
+      Svc.PrefBranch.getPrefType("prefs.sync.testing.somepref"),
+      Ci.nsIPrefBranch.PREF_INVALID
+    );
+    Assert.strictEqual(
+      Services.prefs.getBoolPref(
+        "services.sync.prefs.dangerously_allow_arbitrary"
+      ),
+      false
+    );
+    Assert.strictEqual(
+      Services.prefs.getPrefType(
+        "services.sync.prefs.sync.services.sync.prefs.dangerously_allow_arbitrary"
+      ),
+      Ci.nsIPrefBranch.PREF_INVALID
+    );
+
+    await onceAddonEnabled;
+    ok(
+      !defaultThemeAddon.userDisabled,
+      "the default theme should have been enabled"
+    );
+    ok(
+      otherThemeAddon.userDisabled,
+      "the compact theme should have been disabled"
+    );
+
+    _("Only the current app's preferences are applied.");
+    record = new PrefRec("prefs", "some-fake-app");
+    record.value = {
+      "testing.int": 98,
+    };
+    await store.update(record);
+    Assert.equal(Services.prefs.getIntPref("testing.int"), 42);
+  } finally {
+    clearValues();
+  }
+});
+
+add_task(async function test_dangerously_allow() {
+  _("services.sync.prefs.dangerously_allow_arbitrary");
+  // Bug 1538015 added a capability to "dangerously allow" arbitrary prefs.
+  // Bug 1854698 removed that capability but did keep the fact we never
+  // sync the pref which enabled the "dangerous" behaviour, just incase someone
+  // tries to sync it back to a profile which *does* support that pref.
+  Services.prefs.readDefaultPrefsFromFile(
+    do_get_file("prefs_test_prefs_store.js")
+  );
+
+  let engine = Service.engineManager.get("prefs");
+  let store = engine._store;
+  try {
+    // an incoming record with our old "dangerous" pref.
+    let record = new PrefRec("prefs", PREFS_GUID);
+    record.value = {
+      "services.sync.prefs.dangerously_allow_arbitrary": true,
+      "services.sync.prefs.sync.services.sync.prefs.dangerously_allow_arbitrary": true,
+    };
+    await store.update(record);
+    Assert.strictEqual(
+      Services.prefs.getBoolPref(
+        "services.sync.prefs.dangerously_allow_arbitrary"
+      ),
+      false
+    );
+    Assert.strictEqual(
+      Services.prefs.getPrefType(
+        "services.sync.prefs.sync.services.sync.prefs.dangerously_allow_arbitrary"
+      ),
+      Ci.nsIPrefBranch.PREF_INVALID
+    );
+  } finally {
+    clearValues();
+  }
+});
+
+add_task(async function test_incoming_sets_seen() {
+  _("Test the sync-seen allow-list");
+
+  let engine = Service.engineManager.get("prefs");
+  let store = engine._store;
+
+  Services.prefs.readDefaultPrefsFromFile(
+    do_get_file("prefs_test_prefs_store.js")
+  );
+  const defaultValue = "the value";
+  Assert.equal(Services.prefs.getStringPref("testing.seen"), defaultValue);
+
+  let record = await store.createRecord(PREFS_GUID, "prefs");
+  // Haven't seen a non-default value before, so remains null.
+  Assert.strictEqual(record.value["testing.seen"], null);
+
+  // pretend an incoming record with the default value - it might not be
+  // the default everywhere, so we treat it specially.
+  record = new PrefRec("prefs", PREFS_GUID);
+  record.value = {
+    "testing.seen": defaultValue,
+  };
+  await store.update(record);
+  // Our special control value should now be set.
+  Assert.strictEqual(
+    Services.prefs.getBoolPref("services.sync.prefs.sync-seen.testing.seen"),
+    true
+  );
+  // It's still the default value, so the value is not considered changed
+  Assert.equal(Services.prefs.prefHasUserValue("testing.seen"), false);
+
+  // But now that special control value is set, the record always contains the value.
+  record = await store.createRecord(PREFS_GUID, "prefs");
+  Assert.strictEqual(record.value["testing.seen"], defaultValue);
+});
+
+add_task(async function test_outgoing_when_changed() {
+  _("Test the 'seen' pref is set first sync of non-default value");
+
+  let engine = Service.engineManager.get("prefs");
+  let store = engine._store;
+  clearValues();
+
+  Services.prefs.readDefaultPrefsFromFile(
+    do_get_file("prefs_test_prefs_store.js")
+  );
+  const defaultValue = "the value";
+  Assert.equal(Services.prefs.getStringPref("testing.seen"), defaultValue);
+
+  let record = await store.createRecord(PREFS_GUID, "prefs");
+  // Haven't seen a non-default value before, so remains null.
+  Assert.strictEqual(record.value["testing.seen"], null);
+
+  // Change the value.
+  Services.prefs.setStringPref("testing.seen", "new value");
+  record = await store.createRecord(PREFS_GUID, "prefs");
+  // creating the record toggled that "seen" pref.
+  Assert.strictEqual(
+    Services.prefs.getBoolPref("services.sync.prefs.sync-seen.testing.seen"),
+    true
+  );
+  Assert.strictEqual(Services.prefs.getStringPref("testing.seen"), "new value");
+
+  // Resetting the pref does not change that seen value.
+  Services.prefs.clearUserPref("testing.seen");
+  Assert.strictEqual(
+    Services.prefs.getStringPref("testing.seen"),
+    defaultValue
+  );
+
+  record = await store.createRecord(PREFS_GUID, "prefs");
+  Assert.strictEqual(
+    Services.prefs.getBoolPref("services.sync.prefs.sync-seen.testing.seen"),
+    true
+  );
+});
diff --git a/src/zen/tests/mochitests/sync/test_prefs_tracker.js b/src/zen/tests/mochitests/sync/test_prefs_tracker.js
new file mode 100644
index 000000000..3e2740609
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_prefs_tracker.js
@@ -0,0 +1,108 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+let prefsWithUserValue = new Set();
+add_setup(function record_prefsWithUserValue() {
+  for (const pref of Services.prefs.getChildList("")) {
+    if (Services.prefs.prefHasUserValue(pref)) {
+      prefsWithUserValue.add(pref);
+    }
+  }
+});
+
+function clearValues() {
+  for (const pref of Services.prefs.getChildList("")) {
+    if (!prefsWithUserValue.has(pref)) {
+      Services.prefs.clearUserPref(pref);
+    }
+  }
+}
+
+add_task(async function run_test() {
+  let engine = Service.engineManager.get("prefs");
+  let tracker = engine._tracker;
+
+  try {
+    _("tracker.modified corresponds to preference.");
+    // Assert preference is not defined.
+    Assert.equal(
+      Svc.PrefBranch.getPrefType("engine.prefs.modified"),
+      Ci.nsIPrefBranch.PREF_INVALID
+    );
+    Assert.ok(!tracker.modified);
+
+    tracker.modified = true;
+    Assert.equal(Svc.PrefBranch.getBoolPref("engine.prefs.modified"), true);
+    Assert.ok(tracker.modified);
+
+    _("Engine's getChangedID() just returns the one GUID we have.");
+    let changedIDs = await engine.getChangedIDs();
+    let ids = Object.keys(changedIDs);
+    Assert.equal(ids.length, 1);
+    Assert.equal(ids[0], CommonUtils.encodeBase64URL(Services.appinfo.ID));
+
+    Svc.PrefBranch.setBoolPref("engine.prefs.modified", false);
+    Assert.ok(!tracker.modified);
+
+    _("No modified state, so no changed IDs.");
+    do_check_empty(await engine.getChangedIDs());
+
+    _("Initial score is 0");
+    Assert.equal(tracker.score, 0);
+
+    _("Test fixtures.");
+    Svc.PrefBranch.setBoolPref("prefs.sync.testing.int", true);
+
+    _(
+      "Test fixtures haven't upped the tracker score yet because it hasn't started tracking yet."
+    );
+    Assert.equal(tracker.score, 0);
+
+    _("Tell the tracker to start tracking changes.");
+    tracker.start();
+    Services.prefs.setIntPref("testing.int", 23);
+    await tracker.asyncObserver.promiseObserversComplete();
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE);
+    Assert.equal(tracker.modified, true);
+
+    _("Clearing changed IDs reset modified status.");
+    await tracker.clearChangedIDs();
+    Assert.equal(tracker.modified, false);
+
+    _("Resetting a pref ups the score, too.");
+    Services.prefs.clearUserPref("testing.int");
+    await tracker.asyncObserver.promiseObserversComplete();
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE * 2);
+    Assert.equal(tracker.modified, true);
+    await tracker.clearChangedIDs();
+
+    _("So does changing a pref sync pref.");
+    Svc.PrefBranch.setBoolPref("prefs.sync.testing.int", false);
+    await tracker.asyncObserver.promiseObserversComplete();
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE * 3);
+    Assert.equal(tracker.modified, true);
+    await tracker.clearChangedIDs();
+
+    _(
+      "Now that the pref sync pref has been flipped, changes to it won't be picked up."
+    );
+    Services.prefs.setIntPref("testing.int", 42);
+    await tracker.asyncObserver.promiseObserversComplete();
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE * 3);
+    Assert.equal(tracker.modified, false);
+    await tracker.clearChangedIDs();
+
+    _("Changing some other random pref won't do anything.");
+    Services.prefs.setStringPref("testing.other", "blergh");
+    await tracker.asyncObserver.promiseObserversComplete();
+    Assert.equal(tracker.score, SCORE_INCREMENT_XLARGE * 3);
+    Assert.equal(tracker.modified, false);
+  } finally {
+    await tracker.stop();
+    clearValues();
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_records_crypto.js b/src/zen/tests/mochitests/sync/test_records_crypto.js
new file mode 100644
index 000000000..abdf89427
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_records_crypto.js
@@ -0,0 +1,189 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { CollectionKeyManager, CryptoWrapper } = ChromeUtils.importESModule(
+  "resource://services-sync/record.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+var cryptoWrap;
+
+function crypted_resource_handler(metadata, response) {
+  let obj = {
+    id: "resource",
+    modified: cryptoWrap.modified,
+    payload: JSON.stringify(cryptoWrap.payload),
+  };
+  return httpd_basic_auth_handler(JSON.stringify(obj), metadata, response);
+}
+
+function prepareCryptoWrap(collection, id) {
+  let w = new CryptoWrapper();
+  w.cleartext.stuff = "my payload here";
+  w.collection = collection;
+  w.id = id;
+  return w;
+}
+
+add_task(async function test_records_crypto() {
+  let server;
+
+  await configureIdentity({ username: "john@example.com" });
+  let keyBundle = Service.identity.syncKeyBundle;
+
+  try {
+    let log = Log.repository.getLogger("Test");
+    Log.repository.rootLogger.addAppender(new Log.DumpAppender());
+
+    log.info("Setting up server and authenticator");
+
+    server = httpd_setup({ "/steam/resource": crypted_resource_handler });
+
+    log.info("Creating a record");
+
+    cryptoWrap = prepareCryptoWrap("steam", "resource");
+
+    log.info("cryptoWrap: " + cryptoWrap.toString());
+
+    log.info("Encrypting a record");
+
+    await cryptoWrap.encrypt(keyBundle);
+    log.info("Ciphertext is " + cryptoWrap.ciphertext);
+    Assert.notEqual(cryptoWrap.ciphertext, null);
+
+    let firstIV = cryptoWrap.IV;
+
+    log.info("Decrypting the record");
+
+    let payload = await cryptoWrap.decrypt(keyBundle);
+    Assert.equal(payload.stuff, "my payload here");
+    Assert.notEqual(payload, cryptoWrap.payload); // wrap.data.payload is the encrypted one
+
+    log.info("Make sure multiple decrypts cause failures");
+    let error = "";
+    try {
+      payload = await cryptoWrap.decrypt(keyBundle);
+    } catch (ex) {
+      error = ex;
+    }
+    Assert.equal(error.message, "No ciphertext: nothing to decrypt?");
+
+    log.info("Re-encrypting the record with alternate payload");
+
+    cryptoWrap.cleartext.stuff = "another payload";
+    await cryptoWrap.encrypt(keyBundle);
+    let secondIV = cryptoWrap.IV;
+    payload = await cryptoWrap.decrypt(keyBundle);
+    Assert.equal(payload.stuff, "another payload");
+
+    log.info("Make sure multiple encrypts use different IVs");
+    Assert.notEqual(firstIV, secondIV);
+
+    log.info(await "Make sure differing ids cause failures");
+    await cryptoWrap.encrypt(keyBundle);
+    cryptoWrap.data.id = "other";
+    error = "";
+    try {
+      await cryptoWrap.decrypt(keyBundle);
+    } catch (ex) {
+      error = ex;
+    }
+    Assert.equal(error.message, "Record id mismatch: resource != other");
+
+    log.info("Make sure wrong hmacs cause failures");
+    await cryptoWrap.encrypt(keyBundle);
+    cryptoWrap.hmac = "foo";
+    error = "";
+    try {
+      await cryptoWrap.decrypt(keyBundle);
+    } catch (ex) {
+      error = ex;
+    }
+    Assert.equal(
+      error.message.substr(0, 42),
+      "Record SHA256 HMAC mismatch: should be foo"
+    );
+
+    // Checking per-collection keys and default key handling.
+
+    await generateNewKeys(Service.collectionKeys);
+    let bookmarkItem = prepareCryptoWrap("bookmarks", "foo");
+    await bookmarkItem.encrypt(
+      Service.collectionKeys.keyForCollection("bookmarks")
+    );
+    log.info("Ciphertext is " + bookmarkItem.ciphertext);
+    Assert.notEqual(bookmarkItem.ciphertext, null);
+    log.info("Decrypting the record explicitly with the default key.");
+    Assert.equal(
+      (await bookmarkItem.decrypt(Service.collectionKeys._default)).stuff,
+      "my payload here"
+    );
+
+    // Per-collection keys.
+    // Generate a key for "bookmarks".
+    await generateNewKeys(Service.collectionKeys, ["bookmarks"]);
+    bookmarkItem = prepareCryptoWrap("bookmarks", "foo");
+    Assert.equal(bookmarkItem.collection, "bookmarks");
+
+    // Encrypt. This'll use the "bookmarks" encryption key, because we have a
+    // special key for it. The same key will need to be used for decryption.
+    await bookmarkItem.encrypt(
+      Service.collectionKeys.keyForCollection("bookmarks")
+    );
+    Assert.notEqual(bookmarkItem.ciphertext, null);
+
+    // Attempt to use the default key, because this is a collision that could
+    // conceivably occur in the real world. Decryption will error, because
+    // it's not the bookmarks key.
+    let err;
+    try {
+      await bookmarkItem.decrypt(Service.collectionKeys._default);
+    } catch (ex) {
+      err = ex;
+    }
+    Assert.equal("Record SHA256 HMAC mismatch", err.message.substr(0, 27));
+
+    // Explicitly check that it's using the bookmarks key.
+    // This should succeed.
+    Assert.equal(
+      (
+        await bookmarkItem.decrypt(
+          Service.collectionKeys.keyForCollection("bookmarks")
+        )
+      ).stuff,
+      "my payload here"
+    );
+
+    Assert.ok(Service.collectionKeys.hasKeysFor(["bookmarks"]));
+
+    // Add a key for some new collection and verify that it isn't the
+    // default key.
+    Assert.ok(!Service.collectionKeys.hasKeysFor(["forms"]));
+    Assert.ok(!Service.collectionKeys.hasKeysFor(["bookmarks", "forms"]));
+    let oldFormsKey = Service.collectionKeys.keyForCollection("forms");
+    Assert.equal(oldFormsKey, Service.collectionKeys._default);
+    let newKeys = await Service.collectionKeys.ensureKeysFor(["forms"]);
+    Assert.ok(newKeys.hasKeysFor(["forms"]));
+    Assert.ok(newKeys.hasKeysFor(["bookmarks", "forms"]));
+    let newFormsKey = newKeys.keyForCollection("forms");
+    Assert.notEqual(newFormsKey, oldFormsKey);
+
+    // Verify that this doesn't overwrite keys
+    let regetKeys = await newKeys.ensureKeysFor(["forms"]);
+    Assert.equal(regetKeys.keyForCollection("forms"), newFormsKey);
+
+    const emptyKeys = new CollectionKeyManager();
+    payload = {
+      default: Service.collectionKeys._default.keyPairB64,
+      collections: {},
+    };
+    // Verify that not passing `modified` doesn't throw
+    emptyKeys.setContents(payload, null);
+
+    log.info("Done!");
+  } finally {
+    await promiseStopServer(server);
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_records_wbo.js b/src/zen/tests/mochitests/sync/test_records_wbo.js
new file mode 100644
index 000000000..035d5ac5f
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_records_wbo.js
@@ -0,0 +1,119 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { WBORecord, Collection } = ChromeUtils.importESModule(
+  "resource://services-sync/record.sys.mjs"
+);
+const { Resource } = ChromeUtils.importESModule(
+  "resource://services-sync/resource.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+add_test(function test_toJSON() {
+  _("Create a record, for now without a TTL.");
+  let wbo = new WBORecord("coll", "a_record");
+  wbo.modified = 12345;
+  wbo.sortindex = 42;
+  wbo.payload = {};
+
+  _(
+    "Verify that the JSON representation contains the WBO properties, but not TTL."
+  );
+  let json = JSON.parse(JSON.stringify(wbo));
+  Assert.equal(json.modified, 12345);
+  Assert.equal(json.sortindex, 42);
+  Assert.equal(json.payload, "{}");
+  Assert.equal(false, "ttl" in json);
+
+  _("Set a TTL, make sure it's present in the JSON representation.");
+  wbo.ttl = 30 * 60;
+  json = JSON.parse(JSON.stringify(wbo));
+  Assert.equal(json.ttl, 30 * 60);
+  run_next_test();
+});
+
+add_task(async function test_fetch() {
+  let record = {
+    id: "asdf-1234-asdf-1234",
+    modified: 2454725.98283,
+    payload: JSON.stringify({ cheese: "roquefort" }),
+  };
+  let record2 = {
+    id: "record2",
+    modified: 2454725.98284,
+    payload: JSON.stringify({ cheese: "gruyere" }),
+  };
+  let coll = [
+    {
+      id: "record2",
+      modified: 2454725.98284,
+      payload: JSON.stringify({ cheese: "gruyere" }),
+    },
+  ];
+
+  _("Setting up server.");
+  let server = httpd_setup({
+    "/record": httpd_handler(200, "OK", JSON.stringify(record)),
+    "/record2": httpd_handler(200, "OK", JSON.stringify(record2)),
+    "/coll": httpd_handler(200, "OK", JSON.stringify(coll)),
+  });
+
+  try {
+    _("Fetching a WBO record");
+    let rec = new WBORecord("coll", "record");
+    await rec.fetch(Service.resource(server.baseURI + "/record"));
+    Assert.equal(rec.id, "asdf-1234-asdf-1234"); // NOT "record"!
+
+    Assert.equal(rec.modified, 2454725.98283);
+    Assert.equal(typeof rec.payload, "object");
+    Assert.equal(rec.payload.cheese, "roquefort");
+
+    _("Fetching a WBO record using the record manager");
+    let rec2 = await Service.recordManager.get(server.baseURI + "/record2");
+    Assert.equal(rec2.id, "record2");
+    Assert.equal(rec2.modified, 2454725.98284);
+    Assert.equal(typeof rec2.payload, "object");
+    Assert.equal(rec2.payload.cheese, "gruyere");
+    Assert.equal(Service.recordManager.response.status, 200);
+
+    // Testing collection extraction.
+    _("Extracting collection.");
+    let rec3 = new WBORecord("tabs", "foo"); // Create through constructor.
+    Assert.equal(rec3.collection, "tabs");
+  } finally {
+    await promiseStopServer(server);
+  }
+});
+
+class FakeService {
+  constructor(storageURL) {
+    this.storageURL = storageURL;
+  }
+  resource(uri) {
+    // allow ease of ctor without auth.
+    return new Resource(uri);
+  }
+}
+
+add_task(async function test_collection_invalid_url_handling() {
+  const service = new FakeService("http://example.com/storage/");
+
+  // Invalid string: Resource will leave coll.uri === null
+  const coll = new Collection("not-a-valid-url", WBORecord, service);
+
+  // Verify the error reporting scenario is handled
+  Assert.throws(() => {
+    coll.full = true; // Triggers _rebuildURL
+  }, /_rebuildURL called with null uri/);
+});
+
+add_task(async function test_wborecord_uri_makeURI_null() {
+  let record = new WBORecord("tabs", "abc123");
+
+  // Test that we get a helpful error when makeURI returns null
+  Assert.throws(() => {
+    record.uri("not-a-valid-base-url");
+  }, /WBORecord\.uri\(\): makeURI returned null for base=/);
+});
diff --git a/src/zen/tests/mochitests/sync/test_resource.js b/src/zen/tests/mochitests/sync/test_resource.js
new file mode 100644
index 000000000..5dee57b39
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_resource.js
@@ -0,0 +1,554 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Observers } = ChromeUtils.importESModule(
+  "resource://services-common/observers.sys.mjs"
+);
+const { Resource } = ChromeUtils.importESModule(
+  "resource://services-sync/resource.sys.mjs"
+);
+const { SyncAuthManager } = ChromeUtils.importESModule(
+  "resource://services-sync/sync_auth.sys.mjs"
+);
+
+var fetched = false;
+function server_open(metadata, response) {
+  let body;
+  if (metadata.method == "GET") {
+    fetched = true;
+    body = "This path exists";
+    response.setStatusLine(metadata.httpVersion, 200, "OK");
+  } else {
+    body = "Wrong request method";
+    response.setStatusLine(metadata.httpVersion, 405, "Method Not Allowed");
+  }
+  response.bodyOutputStream.write(body, body.length);
+}
+
+function server_protected(metadata, response) {
+  let body;
+
+  if (has_hawk_header(metadata)) {
+    body = "This path exists and is protected";
+    response.setStatusLine(metadata.httpVersion, 200, "OK, authorized");
+    response.setHeader("WWW-Authenticate", 'Basic realm="secret"', false);
+  } else {
+    body = "This path exists and is protected - failed";
+    response.setStatusLine(metadata.httpVersion, 401, "Unauthorized");
+    response.setHeader("WWW-Authenticate", 'Basic realm="secret"', false);
+  }
+
+  response.bodyOutputStream.write(body, body.length);
+}
+
+function server_404(metadata, response) {
+  let body = "File not found";
+  response.setStatusLine(metadata.httpVersion, 404, "Not Found");
+  response.bodyOutputStream.write(body, body.length);
+}
+
+var pacFetched = false;
+function server_pac(metadata, response) {
+  _("Invoked PAC handler.");
+  pacFetched = true;
+  let body = 'function FindProxyForURL(url, host) { return "DIRECT"; }';
+  response.setStatusLine(metadata.httpVersion, 200, "OK");
+  response.setHeader(
+    "Content-Type",
+    "application/x-ns-proxy-autoconfig",
+    false
+  );
+  response.bodyOutputStream.write(body, body.length);
+}
+
+var sample_data = {
+  some: "sample_data",
+  injson: "format",
+  number: 42,
+};
+
+function server_upload(metadata, response) {
+  let body;
+
+  let input = readBytesFromInputStream(metadata.bodyInputStream);
+  if (input == JSON.stringify(sample_data)) {
+    body = "Valid data upload via " + metadata.method;
+    response.setStatusLine(metadata.httpVersion, 200, "OK");
+  } else {
+    body = "Invalid data upload via " + metadata.method + ": " + input;
+    response.setStatusLine(metadata.httpVersion, 500, "Internal Server Error");
+  }
+
+  response.bodyOutputStream.write(body, body.length);
+}
+
+function server_delete(metadata, response) {
+  let body;
+  if (metadata.method == "DELETE") {
+    body = "This resource has been deleted";
+    response.setStatusLine(metadata.httpVersion, 200, "OK");
+  } else {
+    body = "Wrong request method";
+    response.setStatusLine(metadata.httpVersion, 405, "Method Not Allowed");
+  }
+  response.bodyOutputStream.write(body, body.length);
+}
+
+function server_json(metadata, response) {
+  let body = JSON.stringify(sample_data);
+  response.setStatusLine(metadata.httpVersion, 200, "OK");
+  response.bodyOutputStream.write(body, body.length);
+}
+
+const TIMESTAMP = 1274380461;
+
+function server_timestamp(metadata, response) {
+  let body = "Thank you for your request";
+  response.setHeader("X-Weave-Timestamp", "" + TIMESTAMP, false);
+  response.setStatusLine(metadata.httpVersion, 200, "OK");
+  response.bodyOutputStream.write(body, body.length);
+}
+
+function server_backoff(metadata, response) {
+  let body = "Hey, back off!";
+  response.setHeader("X-Weave-Backoff", "600", false);
+  response.setStatusLine(metadata.httpVersion, 200, "OK");
+  response.bodyOutputStream.write(body, body.length);
+}
+
+function server_quota_notice(request, response) {
+  let body = "You're approaching quota.";
+  response.setHeader("X-Weave-Quota-Remaining", "1048576", false);
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.bodyOutputStream.write(body, body.length);
+}
+
+function server_quota_error(request, response) {
+  let body = "14";
+  response.setHeader("X-Weave-Quota-Remaining", "-1024", false);
+  response.setStatusLine(request.httpVersion, 400, "OK");
+  response.bodyOutputStream.write(body, body.length);
+}
+
+function server_headers(metadata, response) {
+  let ignore_headers = [
+    "host",
+    "user-agent",
+    "accept-language",
+    "accept-encoding",
+    "accept-charset",
+    "keep-alive",
+    "connection",
+    "pragma",
+    "origin",
+    "cache-control",
+    "content-length",
+  ];
+  let headers = metadata.headers;
+  let header_names = [];
+  while (headers.hasMoreElements()) {
+    let header = headers.getNext().toString();
+    if (!ignore_headers.includes(header)) {
+      header_names.push(header);
+    }
+  }
+  header_names = header_names.sort();
+
+  headers = {};
+  for (let header of header_names) {
+    headers[header] = metadata.getHeader(header);
+  }
+  let body = JSON.stringify(headers);
+  response.setStatusLine(metadata.httpVersion, 200, "OK");
+  response.bodyOutputStream.write(body, body.length);
+}
+
+var quotaValue;
+Observers.add("weave:service:quota:remaining", function (subject) {
+  quotaValue = subject;
+});
+
+function run_test() {
+  Log.repository.rootLogger.addAppender(new Log.DumpAppender());
+
+  Svc.PrefBranch.setIntPref("network.numRetries", 1); // speed up test
+  run_next_test();
+}
+
+// This apparently has to come first in order for our PAC URL to be hit.
+// Don't put any other HTTP requests earlier in the file!
+add_task(async function test_proxy_auth_redirect() {
+  _(
+    "Ensure that a proxy auth redirect (which switches out our channel) " +
+      "doesn't break Resource."
+  );
+  let server = httpd_setup({
+    "/open": server_open,
+    "/pac2": server_pac,
+  });
+
+  PACSystemSettings.PACURI = server.baseURI + "/pac2";
+  installFakePAC();
+  let res = new Resource(server.baseURI + "/open");
+  let result = await res.get();
+  Assert.ok(pacFetched);
+  Assert.ok(fetched);
+  Assert.equal("This path exists", result.data);
+  pacFetched = fetched = false;
+  uninstallFakePAC();
+  await promiseStopServer(server);
+});
+
+add_task(async function test_new_channel() {
+  _("Ensure a redirect to a new channel is handled properly.");
+
+  let resourceRequested = false;
+  function resourceHandler(metadata, response) {
+    resourceRequested = true;
+
+    let body = "Test";
+    response.setHeader("Content-Type", "text/plain");
+    response.bodyOutputStream.write(body, body.length);
+  }
+
+  let locationURL;
+  function redirectHandler(metadata, response) {
+    let body = "Redirecting";
+    response.setStatusLine(metadata.httpVersion, 307, "TEMPORARY REDIRECT");
+    response.setHeader("Location", locationURL);
+    response.bodyOutputStream.write(body, body.length);
+  }
+
+  let server = httpd_setup({
+    "/resource": resourceHandler,
+    "/redirect": redirectHandler,
+  });
+  locationURL = server.baseURI + "/resource";
+
+  let request = new Resource(server.baseURI + "/redirect");
+  let content = await request.get();
+  Assert.ok(resourceRequested);
+  Assert.equal(200, content.status);
+  Assert.ok("content-type" in content.headers);
+  Assert.equal("text/plain", content.headers["content-type"]);
+
+  await promiseStopServer(server);
+});
+
+var server;
+
+add_test(function setup() {
+  server = httpd_setup({
+    "/open": server_open,
+    "/protected": server_protected,
+    "/404": server_404,
+    "/upload": server_upload,
+    "/delete": server_delete,
+    "/json": server_json,
+    "/timestamp": server_timestamp,
+    "/headers": server_headers,
+    "/backoff": server_backoff,
+    "/pac2": server_pac,
+    "/quota-notice": server_quota_notice,
+    "/quota-error": server_quota_error,
+  });
+
+  run_next_test();
+});
+
+add_test(function test_members() {
+  _("Resource object members");
+  let uri = server.baseURI + "/open";
+  let res = new Resource(uri);
+  Assert.ok(res.uri instanceof Ci.nsIURI);
+  Assert.equal(res.uri.spec, uri);
+  Assert.equal(res.spec, uri);
+  Assert.equal(typeof res.headers, "object");
+  Assert.equal(typeof res.authenticator, "object");
+
+  run_next_test();
+});
+
+add_task(async function test_get() {
+  _("GET a non-password-protected resource");
+  let res = new Resource(server.baseURI + "/open");
+  let content = await res.get();
+  Assert.equal(content.data, "This path exists");
+  Assert.equal(content.status, 200);
+  Assert.ok(content.success);
+
+  // Observe logging messages.
+  let resLogger = res._log;
+  let dbg = resLogger.debug;
+  let debugMessages = [];
+  resLogger.debug = function (msg, extra) {
+    debugMessages.push(`${msg}: ${JSON.stringify(extra)}`);
+    dbg.call(this, msg);
+  };
+
+  // Since we didn't receive proper JSON data, accessing content.obj
+  // will result in a SyntaxError from JSON.parse
+  let didThrow = false;
+  try {
+    content.obj;
+  } catch (ex) {
+    didThrow = true;
+  }
+  Assert.ok(didThrow);
+  Assert.equal(debugMessages.length, 1);
+  Assert.equal(
+    debugMessages[0],
+    'Parse fail: Response body starts: "This path exists"'
+  );
+  resLogger.debug = dbg;
+});
+
+add_test(function test_basicauth() {
+  _("Test that the BasicAuthenticator doesn't screw up header case.");
+  let res1 = new Resource(server.baseURI + "/foo");
+  res1.setHeader("Authorization", "Basic foobar");
+  Assert.equal(res1._headers.authorization, "Basic foobar");
+  Assert.equal(res1.headers.authorization, "Basic foobar");
+
+  run_next_test();
+});
+
+add_task(async function test_get_protected_fail() {
+  _(
+    "GET a password protected resource (test that it'll fail w/o pass, no throw)"
+  );
+  let res2 = new Resource(server.baseURI + "/protected");
+  let content = await res2.get();
+  Assert.equal(content.data, "This path exists and is protected - failed");
+  Assert.equal(content.status, 401);
+  Assert.ok(!content.success);
+});
+
+add_task(async function test_get_protected_success() {
+  _("GET a password protected resource");
+  let identityConfig = makeIdentityConfig();
+  let syncAuthManager = new SyncAuthManager();
+  configureFxAccountIdentity(syncAuthManager, identityConfig);
+  let auth = syncAuthManager.getResourceAuthenticator();
+  let res3 = new Resource(server.baseURI + "/protected");
+  res3.authenticator = auth;
+  Assert.equal(res3.authenticator, auth);
+  let content = await res3.get();
+  Assert.equal(content.data, "This path exists and is protected");
+  Assert.equal(content.status, 200);
+  Assert.ok(content.success);
+});
+
+add_task(async function test_get_404() {
+  _("GET a non-existent resource (test that it'll fail, but not throw)");
+  let res4 = new Resource(server.baseURI + "/404");
+  let content = await res4.get();
+  Assert.equal(content.data, "File not found");
+  Assert.equal(content.status, 404);
+  Assert.ok(!content.success);
+
+  // Check some headers of the 404 response
+  Assert.equal(content.headers.connection, "close");
+  Assert.equal(content.headers.server, "httpd.js");
+  Assert.equal(content.headers["content-length"], 14);
+});
+
+add_task(async function test_put_string() {
+  _("PUT to a resource (string)");
+  let res_upload = new Resource(server.baseURI + "/upload");
+  let content = await res_upload.put(JSON.stringify(sample_data));
+  Assert.equal(content.data, "Valid data upload via PUT");
+  Assert.equal(content.status, 200);
+});
+
+add_task(async function test_put_object() {
+  _("PUT to a resource (object)");
+  let res_upload = new Resource(server.baseURI + "/upload");
+  let content = await res_upload.put(sample_data);
+  Assert.equal(content.data, "Valid data upload via PUT");
+  Assert.equal(content.status, 200);
+});
+
+add_task(async function test_post_string() {
+  _("POST to a resource (string)");
+  let res_upload = new Resource(server.baseURI + "/upload");
+  let content = await res_upload.post(JSON.stringify(sample_data));
+  Assert.equal(content.data, "Valid data upload via POST");
+  Assert.equal(content.status, 200);
+});
+
+add_task(async function test_post_object() {
+  _("POST to a resource (object)");
+  let res_upload = new Resource(server.baseURI + "/upload");
+  let content = await res_upload.post(sample_data);
+  Assert.equal(content.data, "Valid data upload via POST");
+  Assert.equal(content.status, 200);
+});
+
+add_task(async function test_delete() {
+  _("DELETE a resource");
+  let res6 = new Resource(server.baseURI + "/delete");
+  let content = await res6.delete();
+  Assert.equal(content.data, "This resource has been deleted");
+  Assert.equal(content.status, 200);
+});
+
+add_task(async function test_json_body() {
+  _("JSON conversion of response body");
+  let res7 = new Resource(server.baseURI + "/json");
+  let content = await res7.get();
+  Assert.equal(content.data, JSON.stringify(sample_data));
+  Assert.equal(content.status, 200);
+  Assert.equal(JSON.stringify(content.obj), JSON.stringify(sample_data));
+});
+
+add_task(async function test_weave_timestamp() {
+  _("X-Weave-Timestamp header updates Resource.serverTime");
+  // Before having received any response containing the
+  // X-Weave-Timestamp header, Resource.serverTime is null.
+  Assert.equal(Resource.serverTime, null);
+  let res8 = new Resource(server.baseURI + "/timestamp");
+  await res8.get();
+  Assert.equal(Resource.serverTime, TIMESTAMP);
+});
+
+add_task(async function test_get_default_headers() {
+  _("GET: Accept defaults to application/json");
+  let res_headers = new Resource(server.baseURI + "/headers");
+  let content = JSON.parse((await res_headers.get()).data);
+  Assert.equal(content.accept, "application/json;q=0.9,*/*;q=0.2");
+});
+
+add_task(async function test_put_default_headers() {
+  _(
+    "PUT: Accept defaults to application/json, Content-Type defaults to text/plain"
+  );
+  let res_headers = new Resource(server.baseURI + "/headers");
+  let content = JSON.parse((await res_headers.put("data")).data);
+  Assert.equal(content.accept, "application/json;q=0.9,*/*;q=0.2");
+  Assert.equal(content["content-type"], "text/plain");
+});
+
+add_task(async function test_post_default_headers() {
+  _(
+    "POST: Accept defaults to application/json, Content-Type defaults to text/plain"
+  );
+  let res_headers = new Resource(server.baseURI + "/headers");
+  let content = JSON.parse((await res_headers.post("data")).data);
+  Assert.equal(content.accept, "application/json;q=0.9,*/*;q=0.2");
+  Assert.equal(content["content-type"], "text/plain");
+});
+
+add_task(async function test_setHeader() {
+  _("setHeader(): setting simple header");
+  let res_headers = new Resource(server.baseURI + "/headers");
+  res_headers.setHeader("X-What-Is-Weave", "awesome");
+  Assert.equal(res_headers.headers["x-what-is-weave"], "awesome");
+  let content = JSON.parse((await res_headers.get()).data);
+  Assert.equal(content["x-what-is-weave"], "awesome");
+});
+
+add_task(async function test_setHeader_overwrite() {
+  _("setHeader(): setting multiple headers, overwriting existing header");
+  let res_headers = new Resource(server.baseURI + "/headers");
+  res_headers.setHeader("X-WHAT-is-Weave", "more awesomer");
+  res_headers.setHeader("X-Another-Header", "hello world");
+  Assert.equal(res_headers.headers["x-what-is-weave"], "more awesomer");
+  Assert.equal(res_headers.headers["x-another-header"], "hello world");
+  let content = JSON.parse((await res_headers.get()).data);
+  Assert.equal(content["x-what-is-weave"], "more awesomer");
+  Assert.equal(content["x-another-header"], "hello world");
+});
+
+add_task(async function test_put_override_content_type() {
+  _("PUT: override default Content-Type");
+  let res_headers = new Resource(server.baseURI + "/headers");
+  res_headers.setHeader("Content-Type", "application/foobar");
+  Assert.equal(res_headers.headers["content-type"], "application/foobar");
+  let content = JSON.parse((await res_headers.put("data")).data);
+  Assert.equal(content["content-type"], "application/foobar");
+});
+
+add_task(async function test_post_override_content_type() {
+  _("POST: override default Content-Type");
+  let res_headers = new Resource(server.baseURI + "/headers");
+  res_headers.setHeader("Content-Type", "application/foobar");
+  let content = JSON.parse((await res_headers.post("data")).data);
+  Assert.equal(content["content-type"], "application/foobar");
+});
+
+add_task(async function test_weave_backoff() {
+  _("X-Weave-Backoff header notifies observer");
+  let backoffInterval;
+  function onBackoff(subject) {
+    backoffInterval = subject;
+  }
+  Observers.add("weave:service:backoff:interval", onBackoff);
+
+  let res10 = new Resource(server.baseURI + "/backoff");
+  await res10.get();
+  Assert.equal(backoffInterval, 600);
+});
+
+add_task(async function test_quota_error() {
+  _("X-Weave-Quota-Remaining header notifies observer on successful requests.");
+  let res10 = new Resource(server.baseURI + "/quota-error");
+  let content = await res10.get();
+  Assert.equal(content.status, 400);
+  Assert.equal(quotaValue, undefined); // HTTP 400, so no observer notification.
+});
+
+add_task(async function test_quota_notice() {
+  let res10 = new Resource(server.baseURI + "/quota-notice");
+  let content = await res10.get();
+  Assert.equal(content.status, 200);
+  Assert.equal(quotaValue, 1048576);
+});
+
+add_task(async function test_preserve_exceptions() {
+  _("Error handling preserves exception information");
+  let res11 = new Resource("http://localhost:12345/does/not/exist");
+  await Assert.rejects(res11.get(), error => {
+    Assert.notEqual(error, null);
+    Assert.equal(error.result, Cr.NS_ERROR_CONNECTION_REFUSED);
+    Assert.equal(error.name, "NS_ERROR_CONNECTION_REFUSED");
+    return true;
+  });
+});
+
+add_task(async function test_timeout() {
+  _("Ensure channel timeouts are thrown appropriately.");
+  let res19 = new Resource(server.baseURI + "/json");
+  res19.ABORT_TIMEOUT = 0;
+  await Assert.rejects(res19.get(), error => {
+    Assert.equal(error.result, Cr.NS_ERROR_NET_TIMEOUT);
+    return true;
+  });
+});
+
+add_test(function test_uri_construction() {
+  _("Testing URI construction.");
+  let args = [];
+  args.push("newer=" + 1234);
+  args.push("limit=" + 1234);
+  args.push("sort=" + 1234);
+
+  let query = "?" + args.join("&");
+
+  let uri1 = CommonUtils.makeURI("http://foo/" + query).QueryInterface(
+    Ci.nsIURL
+  );
+  let uri2 = CommonUtils.makeURI("http://foo/").QueryInterface(Ci.nsIURL);
+  uri2 = uri2.mutate().setQuery(query).finalize().QueryInterface(Ci.nsIURL);
+  Assert.equal(uri1.query, uri2.query);
+
+  run_next_test();
+});
+
+/**
+ * End of tests that rely on a single HTTP server.
+ * All tests after this point must begin and end their own.
+ */
+add_test(function eliminate_server() {
+  server.stop(run_next_test);
+});
diff --git a/src/zen/tests/mochitests/sync/test_resource_header.js b/src/zen/tests/mochitests/sync/test_resource_header.js
new file mode 100644
index 000000000..e45b4a986
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_resource_header.js
@@ -0,0 +1,63 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { Resource } = ChromeUtils.importESModule(
+  "resource://services-sync/resource.sys.mjs"
+);
+
+var httpServer = new HttpServer();
+httpServer.registerPathHandler("/content", contentHandler);
+httpServer.start(-1);
+
+const HTTP_PORT = httpServer.identity.primaryPort;
+const TEST_URL = "http://localhost:" + HTTP_PORT + "/content";
+const BODY = "response body";
+
+// Keep headers for later inspection.
+var auth = null;
+var foo = null;
+function contentHandler(metadata, response) {
+  _("Handling request.");
+  auth = metadata.getHeader("Authorization");
+  foo = metadata.getHeader("X-Foo");
+
+  _("Extracted headers. " + auth + ", " + foo);
+
+  response.setHeader("Content-Type", "text/plain");
+  response.bodyOutputStream.write(BODY, BODY.length);
+}
+
+// Set a proxy function to cause an internal redirect.
+function triggerRedirect() {
+  const PROXY_FUNCTION =
+    "function FindProxyForURL(url, host) {" +
+    "  return 'PROXY a_non_existent_domain_x7x6c572v:80; " +
+    "PROXY localhost:" +
+    HTTP_PORT +
+    "';" +
+    "}";
+
+  let prefs = Services.prefs.getBranch("network.proxy.");
+  prefs.setIntPref("type", 2);
+  prefs.setStringPref("autoconfig_url", "data:text/plain," + PROXY_FUNCTION);
+}
+
+add_task(async function test_headers_copied() {
+  triggerRedirect();
+
+  _("Issuing request.");
+  let resource = new Resource(TEST_URL);
+  resource.setHeader("Authorization", "Basic foobar");
+  resource.setHeader("X-Foo", "foofoo");
+
+  let result = await resource.get(TEST_URL);
+  _("Result: " + result.data);
+
+  Assert.equal(result.data, BODY);
+  Assert.equal(auth, "Basic foobar");
+  Assert.equal(foo, "foofoo");
+
+  await promiseStopServer(httpServer);
+});
diff --git a/src/zen/tests/mochitests/sync/test_resource_ua.js b/src/zen/tests/mochitests/sync/test_resource_ua.js
new file mode 100644
index 000000000..115fa85b8
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_resource_ua.js
@@ -0,0 +1,96 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Resource } = ChromeUtils.importESModule(
+  "resource://services-sync/resource.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+var httpProtocolHandler = Cc[
+  "@mozilla.org/network/protocol;1?name=http"
+].getService(Ci.nsIHttpProtocolHandler);
+
+// Tracking info/collections.
+var collectionsHelper = track_collections_helper();
+
+var meta_global;
+var server;
+
+var expectedUA;
+var ua;
+function uaHandler(f) {
+  return function (request, response) {
+    ua = request.getHeader("User-Agent");
+    return f(request, response);
+  };
+}
+
+add_task(async function setup() {
+  Log.repository.rootLogger.addAppender(new Log.DumpAppender());
+  meta_global = new ServerWBO("global");
+  server = httpd_setup({
+    "/1.1/johndoe/info/collections": uaHandler(collectionsHelper.handler),
+    "/1.1/johndoe/storage/meta/global": uaHandler(meta_global.handler()),
+  });
+
+  await configureIdentity({ username: "johndoe" }, server);
+  _("Server URL: " + server.baseURI);
+
+  // Note this string is missing the trailing ".destkop" as the test
+  // adjusts the "client.type" pref where that portion comes from.
+  expectedUA =
+    Services.appinfo.name +
+    "/" +
+    Services.appinfo.version +
+    " (" +
+    httpProtocolHandler.oscpu +
+    ")" +
+    " FxSync/" +
+    WEAVE_VERSION +
+    "." +
+    Services.appinfo.appBuildID;
+});
+
+add_task(async function test_fetchInfo() {
+  _("Testing _fetchInfo.");
+  await Service.login();
+  await Service._fetchInfo();
+  _("User-Agent: " + ua);
+  Assert.equal(ua, expectedUA + ".desktop");
+  ua = "";
+});
+
+add_task(async function test_desktop_post() {
+  _("Testing direct Resource POST.");
+  let r = new Resource(server.baseURI + "/1.1/johndoe/storage/meta/global");
+  await r.post("foo=bar");
+  _("User-Agent: " + ua);
+  Assert.equal(ua, expectedUA + ".desktop");
+  ua = "";
+});
+
+add_task(async function test_desktop_get() {
+  _("Testing async.");
+  Svc.PrefBranch.setStringPref("client.type", "desktop");
+  let r = new Resource(server.baseURI + "/1.1/johndoe/storage/meta/global");
+  await r.get();
+  _("User-Agent: " + ua);
+  Assert.equal(ua, expectedUA + ".desktop");
+  ua = "";
+});
+
+add_task(async function test_mobile_get() {
+  _("Testing mobile.");
+  Svc.PrefBranch.setStringPref("client.type", "mobile");
+  let r = new Resource(server.baseURI + "/1.1/johndoe/storage/meta/global");
+  await r.get();
+  _("User-Agent: " + ua);
+  Assert.equal(ua, expectedUA + ".mobile");
+  ua = "";
+});
+
+add_test(function tear_down() {
+  server.stop(run_next_test);
+});
diff --git a/src/zen/tests/mochitests/sync/test_rust_password_engine_mp_locked.js b/src/zen/tests/mochitests/sync/test_rust_password_engine_mp_locked.js
new file mode 100644
index 000000000..a1aff815a
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_rust_password_engine_mp_locked.js
@@ -0,0 +1,115 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/**
+ * Bug 2057164: after the user cancels the Primary Password prompt, a background
+ * sync must not keep re-prompting on every subsequent sync. When the Primary
+ * Password is locked, the Rust-backed RustPasswordEngine must skip syncing
+ * *without* prompting and record the master-password-locked login state, so the
+ * scheduler backs off - matching the behaviour of the legacy PasswordEngine.
+ *
+ * RustPasswordEngine.initialize() reaches into the active Rust store for its
+ * bridge, so getActiveStore() is stubbed to avoid depending on the Rust backend.
+ */
+
+"use strict";
+
+/* import-globals-from head_errorhandler_common.js */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { RustPasswordEngine } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/passwords.sys.mjs"
+);
+const { LoginManagerStorage } = ChromeUtils.importESModule(
+  "resource://passwordmgr/passwordstorage.sys.mjs"
+);
+
+const PREF_ACTIVE = "signon.storage.rust.active";
+
+// `isLoggedIn` is a non-configurable getter on the real Services.logins, so swap
+// in a minimal stand-in for the duration of the check and restore it afterwards.
+function stubLoggedIn(value) {
+  let oldLogins = Services.logins;
+  Services.logins = { isLoggedIn: value };
+  return () => {
+    Services.logins = oldLogins;
+  };
+}
+
+let engine;
+let sandbox;
+let superSync;
+
+add_task(async function setup() {
+  await Service.promiseInitialized;
+  Services.prefs.clearUserPref(PREF_ACTIVE);
+
+  sandbox = sinon.createSandbox();
+  sandbox.stub(LoginManagerStorage, "getActiveStore").returns({
+    bridgedEngine: async () => ({}),
+  });
+  // Stub the inherited real sync so a call is observable (and wouldn't hit the
+  // network); RustPasswordEngine._sync() delegates to it when unlocked.
+  superSync = sandbox.stub(SyncEngine.prototype, "_sync").resolves();
+
+  Services.prefs.setBoolPref(PREF_ACTIVE, true);
+  await Service.engineManager.switchAlternatives();
+  engine = Service.engineManager.get("passwords");
+  Assert.ok(
+    engine instanceof RustPasswordEngine,
+    "the Rust-backed engine is active"
+  );
+});
+
+add_task(async function test_skips_and_records_lock_when_locked() {
+  superSync.resetHistory();
+  let restore = stubLoggedIn(false);
+  Service.status.login = LOGIN_SUCCEEDED;
+
+  try {
+    await engine._sync();
+
+    Assert.ok(
+      superSync.notCalled,
+      "the engine skips the real sync (which would prompt) while locked"
+    );
+    Assert.equal(
+      Service.status.login,
+      MASTER_PASSWORD_LOCKED,
+      "a locked Primary Password records the master-password-locked login state"
+    );
+  } finally {
+    restore();
+  }
+});
+
+add_task(async function test_syncs_normally_when_unlocked() {
+  superSync.resetHistory();
+  let restore = stubLoggedIn(true);
+  Service.status.login = LOGIN_SUCCEEDED;
+
+  try {
+    await engine._sync();
+
+    Assert.ok(
+      superSync.calledOnce,
+      "the engine performs a normal sync when the Primary Password is unlocked"
+    );
+    Assert.equal(
+      Service.status.login,
+      LOGIN_SUCCEEDED,
+      "an unlocked Primary Password leaves the login state untouched"
+    );
+  } finally {
+    restore();
+  }
+});
+
+add_task(async function teardown() {
+  Services.prefs.clearUserPref(PREF_ACTIVE);
+  await Service.engineManager.switchAlternatives();
+  sandbox.restore();
+  Service.status.resetSync();
+});
diff --git a/src/zen/tests/mochitests/sync/test_rust_password_engine_selection.js b/src/zen/tests/mochitests/sync/test_rust_password_engine_selection.js
new file mode 100644
index 000000000..fba7e9785
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_rust_password_engine_selection.js
@@ -0,0 +1,64 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/**
+ * Flipping `signon.storage.rust.active` at runtime must switch the registered
+ * "passwords" engine between the legacy PasswordEngine and the Rust-backed
+ * RustPasswordEngine. The generic alternative machinery is covered by
+ * test_enginemanager.js; this guards the service.sys.mjs wiring against a
+ * key/name mismatch that would leave switchAlternatives() unable to swap the
+ * real engine.
+ *
+ * RustPasswordEngine.initialize() reaches into the active Rust store for its
+ * bridge, so getActiveStore() is stubbed to avoid depending on the Rust backend.
+ */
+
+"use strict";
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { PasswordEngine, RustPasswordEngine } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/passwords.sys.mjs"
+);
+const { LoginManagerStorage } = ChromeUtils.importESModule(
+  "resource://passwordmgr/passwordstorage.sys.mjs"
+);
+
+const PREF_ACTIVE = "signon.storage.rust.active";
+
+add_task(async function test_pref_flip_switches_engine() {
+  await Service.promiseInitialized;
+  Services.prefs.clearUserPref(PREF_ACTIVE);
+
+  let sandbox = sinon.createSandbox();
+  // RustPasswordEngine.initialize() does `getActiveStore().bridgedEngine()`.
+  sandbox.stub(LoginManagerStorage, "getActiveStore").returns({
+    bridgedEngine: async () => ({}),
+  });
+
+  try {
+    Assert.ok(
+      Service.engineManager.get("passwords") instanceof PasswordEngine,
+      "the legacy JS engine is used while the pref is off"
+    );
+
+    Services.prefs.setBoolPref(PREF_ACTIVE, true);
+    await Service.engineManager.switchAlternatives();
+    Assert.ok(
+      Service.engineManager.get("passwords") instanceof RustPasswordEngine,
+      "turning the pref on switches to the Rust-backed engine"
+    );
+
+    Services.prefs.setBoolPref(PREF_ACTIVE, false);
+    await Service.engineManager.switchAlternatives();
+    Assert.ok(
+      Service.engineManager.get("passwords") instanceof PasswordEngine,
+      "turning the pref off switches back to the legacy JS engine"
+    );
+  } finally {
+    Services.prefs.clearUserPref(PREF_ACTIVE);
+    await Service.engineManager.switchAlternatives();
+    sandbox.restore();
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_rust_password_tracker.js b/src/zen/tests/mochitests/sync/test_rust_password_tracker.js
new file mode 100644
index 000000000..90a650ad9
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_rust_password_tracker.js
@@ -0,0 +1,93 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/**
+ * Unit tests for RustPasswordTracker.observe().
+ *
+ * observe() is pure scoring logic with no dependency on the Rust store, so it is
+ * exercised on a minimal fake object rather than a fully initialized engine.
+ */
+
+"use strict";
+
+const { RustPasswordEngine } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/passwords.sys.mjs"
+);
+
+// RustPasswordTracker is not exported directly; reach it through the engine.
+const RustPasswordTracker = RustPasswordEngine.prototype._trackerObj;
+
+function makeTracker({ ignoreAll = false } = {}) {
+  return {
+    score: 0,
+    ignoreAll,
+    observe: RustPasswordTracker.prototype.observe,
+  };
+}
+
+// Stands in for the nsIArray subject passed for "removeAllLogins".
+function fakeLoginArray(count) {
+  const array = Cc["@mozilla.org/array;1"].createInstance(Ci.nsIMutableArray);
+  for (let i = 0; i < count; i++) {
+    array.appendElement(
+      Cc["@mozilla.org/supports-string;1"].createInstance(Ci.nsISupportsString)
+    );
+  }
+  return array;
+}
+
+add_task(async function test_single_change_topics_bump_score() {
+  for (let data of ["modifyLogin", "addLogin", "removeLogin", "importLogins"]) {
+    let tracker = makeTracker();
+    await tracker.observe(null, "passwordmgr-storage-changed", data);
+    Assert.equal(
+      tracker.score,
+      SCORE_INCREMENT_XLARGE,
+      `${data} bumps the score by SCORE_INCREMENT_XLARGE`
+    );
+  }
+});
+
+add_task(async function test_modifyLogin_ignores_syncCounter() {
+  // The legacy PasswordTracker only scores "modifyLogin" when the subject's
+  // syncCounter is > 0. The Rust tracker must not look at the subject at all,
+  // so passing a null subject still bumps the score.
+  let tracker = makeTracker();
+  await tracker.observe(null, "passwordmgr-storage-changed", "modifyLogin");
+  Assert.equal(
+    tracker.score,
+    SCORE_INCREMENT_XLARGE,
+    "modifyLogin scores without inspecting the subject's syncCounter"
+  );
+});
+
+add_task(async function test_removeAllLogins_scales_with_count() {
+  let tracker = makeTracker();
+  await tracker.observe(
+    fakeLoginArray(3),
+    "passwordmgr-storage-changed",
+    "removeAllLogins"
+  );
+  Assert.equal(
+    tracker.score,
+    SCORE_INCREMENT_XLARGE * 4,
+    "removeAllLogins bumps the score by SCORE_INCREMENT_XLARGE * (count + 1)"
+  );
+});
+
+add_task(async function test_unknown_topic_does_nothing() {
+  let tracker = makeTracker();
+  await tracker.observe(null, "passwordmgr-storage-changed", "somethingElse");
+  Assert.equal(tracker.score, 0, "an unrelated notification leaves the score");
+});
+
+add_task(async function test_ignoreAll_suppresses_scoring() {
+  let tracker = makeTracker({ ignoreAll: true });
+  await tracker.observe(null, "passwordmgr-storage-changed", "addLogin");
+  await tracker.observe(
+    fakeLoginArray(5),
+    "passwordmgr-storage-changed",
+    "removeAllLogins"
+  );
+  Assert.equal(tracker.score, 0, "ignoreAll suppresses all scoring");
+});
diff --git a/src/zen/tests/mochitests/sync/test_score_triggers.js b/src/zen/tests/mochitests/sync/test_score_triggers.js
new file mode 100644
index 000000000..c6afa0640
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_score_triggers.js
@@ -0,0 +1,151 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { Status } = ChromeUtils.importESModule(
+  "resource://services-sync/status.sys.mjs"
+);
+
+// Tracking info/collections.
+var collectionsHelper = track_collections_helper();
+var upd = collectionsHelper.with_updated_collection;
+
+function sync_httpd_setup() {
+  let handlers = {};
+
+  handlers["/1.1/johndoe/storage/meta/global"] = new ServerWBO(
+    "global",
+    {}
+  ).handler();
+  handlers["/1.1/johndoe/storage/steam"] = new ServerWBO("steam", {}).handler();
+
+  handlers["/1.1/johndoe/info/collections"] = collectionsHelper.handler;
+  delete collectionsHelper.collections.crypto;
+  delete collectionsHelper.collections.meta;
+
+  let cr = new ServerWBO("keys");
+  handlers["/1.1/johndoe/storage/crypto/keys"] = upd("crypto", cr.handler());
+
+  let cl = new ServerCollection();
+  handlers["/1.1/johndoe/storage/clients"] = upd("clients", cl.handler());
+
+  return httpd_setup(handlers);
+}
+
+async function setUp(server) {
+  let engineInfo = await registerRotaryEngine();
+  await SyncTestingInfrastructure(server, "johndoe", "ilovejane");
+  return engineInfo;
+}
+
+add_task(async function test_tracker_score_updated() {
+  enableValidationPrefs();
+  let { engine, tracker } = await registerRotaryEngine();
+
+  let scoreUpdated = 0;
+
+  function onScoreUpdated() {
+    scoreUpdated++;
+  }
+
+  Svc.Obs.add("weave:engine:score:updated", onScoreUpdated);
+
+  try {
+    Assert.equal(engine.score, 0);
+
+    tracker.score += SCORE_INCREMENT_SMALL;
+    Assert.equal(engine.score, SCORE_INCREMENT_SMALL);
+
+    Assert.equal(scoreUpdated, 1);
+  } finally {
+    Svc.Obs.remove("weave:engine:score:updated", onScoreUpdated);
+    tracker.resetScore();
+    await tracker.clearChangedIDs();
+    await Service.engineManager.unregister(engine);
+  }
+});
+
+add_task(async function test_sync_triggered() {
+  let server = sync_httpd_setup();
+  let { engine, tracker } = await setUp(server);
+
+  await Service.login();
+
+  Service.scheduler.syncThreshold = MULTI_DEVICE_THRESHOLD;
+
+  Assert.equal(Status.login, LOGIN_SUCCEEDED);
+  tracker.score += SCORE_INCREMENT_XLARGE;
+
+  await promiseOneObserver("weave:service:sync:finish");
+
+  await Service.startOver();
+  await promiseStopServer(server);
+
+  await tracker.clearChangedIDs();
+  await Service.engineManager.unregister(engine);
+});
+
+add_task(async function test_clients_engine_sync_triggered() {
+  enableValidationPrefs();
+
+  _("Ensure that client engine score changes trigger a sync.");
+
+  // The clients engine is not registered like other engines. Therefore,
+  // it needs special treatment throughout the code. Here, we verify the
+  // global score tracker gives it that treatment. See bug 676042 for more.
+
+  let server = sync_httpd_setup();
+  let { engine, tracker } = await setUp(server);
+  await Service.login();
+
+  Service.scheduler.syncThreshold = MULTI_DEVICE_THRESHOLD;
+  Assert.equal(Status.login, LOGIN_SUCCEEDED);
+  Service.clientsEngine._tracker.score += SCORE_INCREMENT_XLARGE;
+
+  await promiseOneObserver("weave:service:sync:finish");
+  _("Sync due to clients engine change completed.");
+
+  await Service.startOver();
+  await promiseStopServer(server);
+
+  await tracker.clearChangedIDs();
+  await Service.engineManager.unregister(engine);
+});
+
+add_task(async function test_incorrect_credentials_sync_not_triggered() {
+  enableValidationPrefs();
+
+  _(
+    "Ensure that score changes don't trigger a sync if Status.login != LOGIN_SUCCEEDED."
+  );
+  let server = sync_httpd_setup();
+  let { engine, tracker } = await setUp(server);
+
+  // Ensure we don't actually try to sync.
+  function onSyncStart() {
+    do_throw("Should not get here!");
+  }
+  Svc.Obs.add("weave:service:sync:start", onSyncStart);
+
+  // Faking incorrect credentials to prevent score update.
+  Status.login = LOGIN_FAILED_LOGIN_REJECTED;
+  tracker.score += SCORE_INCREMENT_XLARGE;
+
+  // First wait >100ms (nsITimers can take up to that much time to fire, so
+  // we can account for the timer in delayedAutoconnect) and then one event
+  // loop tick (to account for a possible call to weave:service:sync:start).
+  await promiseNamedTimer(150, {}, "timer");
+  await Async.promiseYield();
+
+  Svc.Obs.remove("weave:service:sync:start", onSyncStart);
+
+  Assert.equal(Status.login, LOGIN_FAILED_LOGIN_REJECTED);
+
+  await Service.startOver();
+  await promiseStopServer(server);
+
+  await tracker.clearChangedIDs();
+  await Service.engineManager.unregister(engine);
+});
diff --git a/src/zen/tests/mochitests/sync/test_service_attributes.js b/src/zen/tests/mochitests/sync/test_service_attributes.js
new file mode 100644
index 000000000..6fab0325f
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_service_attributes.js
@@ -0,0 +1,203 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { FakeGUIDService } = ChromeUtils.importESModule(
+  "resource://testing-common/services/sync/fakeservices.sys.mjs"
+);
+
+add_task(async function test_urls() {
+  _("URL related Service properties correspond to preference settings.");
+  try {
+    Assert.equal(Service.clusterURL, "");
+    Assert.ok(!Service.userBaseURL);
+    Assert.equal(Service.infoURL, undefined);
+    Assert.equal(Service.storageURL, undefined);
+    Assert.equal(Service.metaURL, undefined);
+
+    _("The 'clusterURL' attribute updates preferences and cached URLs.");
+
+    // Since we don't have a cluster URL yet, these will still not be defined.
+    Assert.equal(Service.infoURL, undefined);
+    Assert.ok(!Service.userBaseURL);
+    Assert.equal(Service.storageURL, undefined);
+    Assert.equal(Service.metaURL, undefined);
+
+    Service.clusterURL = "http://weave.cluster/1.1/johndoe/";
+
+    Assert.equal(Service.userBaseURL, "http://weave.cluster/1.1/johndoe/");
+    Assert.equal(
+      Service.infoURL,
+      "http://weave.cluster/1.1/johndoe/info/collections"
+    );
+    Assert.equal(
+      Service.storageURL,
+      "http://weave.cluster/1.1/johndoe/storage/"
+    );
+    Assert.equal(
+      Service.metaURL,
+      "http://weave.cluster/1.1/johndoe/storage/meta/global"
+    );
+  } finally {
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+  }
+});
+
+add_test(function test_syncID() {
+  _("Service.syncID is auto-generated, corresponds to preference.");
+  new FakeGUIDService();
+
+  try {
+    // Ensure pristine environment
+    Assert.equal(
+      Svc.PrefBranch.getPrefType("client.syncID"),
+      Ci.nsIPrefBranch.PREF_INVALID
+    );
+
+    // Performing the first get on the attribute will generate a new GUID.
+    Assert.equal(Service.syncID, "fake-guid-00");
+    Assert.equal(Svc.PrefBranch.getStringPref("client.syncID"), "fake-guid-00");
+
+    Svc.PrefBranch.setStringPref("client.syncID", Utils.makeGUID());
+    Assert.equal(Svc.PrefBranch.getStringPref("client.syncID"), "fake-guid-01");
+    Assert.equal(Service.syncID, "fake-guid-01");
+  } finally {
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+    new FakeGUIDService();
+    run_next_test();
+  }
+});
+
+add_test(function test_locked() {
+  _("The 'locked' attribute can be toggled with lock() and unlock()");
+
+  // Defaults to false
+  Assert.equal(Service.locked, false);
+
+  Assert.equal(Service.lock(), true);
+  Assert.equal(Service.locked, true);
+
+  // Locking again will return false
+  Assert.equal(Service.lock(), false);
+
+  Service.unlock();
+  Assert.equal(Service.locked, false);
+  run_next_test();
+});
+
+add_task(async function test_configure_throws_no_user() {
+  _("configure() throws when no user is signed in");
+  const { getFxAccountsSingleton } = ChromeUtils.importESModule(
+    "resource://gre/modules/FxAccounts.sys.mjs"
+  );
+  const fxAccounts = getFxAccountsSingleton();
+
+  const originalGetSignedInUser = fxAccounts.getSignedInUser;
+  fxAccounts.getSignedInUser = () => Promise.resolve(null);
+
+  try {
+    await Assert.rejects(
+      Service.configure(),
+      /No FxA user is signed in/,
+      "configure() should throw when no user is signed in"
+    );
+  } finally {
+    fxAccounts.getSignedInUser = originalGetSignedInUser;
+  }
+});
+
+add_task(async function test_configure_throws_without_keys() {
+  _("configure() throws when user has no sync keys");
+  const { getFxAccountsSingleton } = ChromeUtils.importESModule(
+    "resource://gre/modules/FxAccounts.sys.mjs"
+  );
+  const fxAccounts = getFxAccountsSingleton();
+
+  // Mock getSignedInUser to return a user
+  const originalGetSignedInUser = fxAccounts.getSignedInUser;
+  fxAccounts.getSignedInUser = () =>
+    Promise.resolve({ email: "test@example.com", uid: "12345" });
+
+  // Mock hasKeysForScope to return false (no keys)
+  const originalHasKeysForScope = fxAccounts.keys.hasKeysForScope;
+  fxAccounts.keys.hasKeysForScope = () => Promise.resolve(false);
+
+  try {
+    await Assert.rejects(
+      Service.configure(),
+      /User does not have sync keys/,
+      "configure() should throw when no sync keys"
+    );
+  } finally {
+    fxAccounts.getSignedInUser = originalGetSignedInUser;
+    fxAccounts.keys.hasKeysForScope = originalHasKeysForScope;
+  }
+});
+
+add_task(async function test_configure_succeeds_with_keys() {
+  _("configure() succeeds when user has sync keys");
+  const { getFxAccountsSingleton } = ChromeUtils.importESModule(
+    "resource://gre/modules/FxAccounts.sys.mjs"
+  );
+  const fxAccounts = getFxAccountsSingleton();
+
+  // Mock getSignedInUser to return a user
+  const originalGetSignedInUser = fxAccounts.getSignedInUser;
+  fxAccounts.getSignedInUser = () =>
+    Promise.resolve({ email: "test@example.com", uid: "12345" });
+
+  // Mock hasKeysForScope to return true (has keys)
+  const originalHasKeysForScope = fxAccounts.keys.hasKeysForScope;
+  fxAccounts.keys.hasKeysForScope = () => Promise.resolve(true);
+
+  try {
+    await Service.configure();
+    // Should set the username pref
+    Assert.equal(Svc.PrefBranch.getStringPref("username"), "test@example.com");
+  } finally {
+    fxAccounts.getSignedInUser = originalGetSignedInUser;
+    fxAccounts.keys.hasKeysForScope = originalHasKeysForScope;
+    Svc.PrefBranch.clearUserPref("username");
+  }
+});
+
+add_task(async function test_third_party_to_sync_complete_flow() {
+  _("End-to-end: third-party auth (no keys) -> receive keys -> configure sync");
+  const { getFxAccountsSingleton } = ChromeUtils.importESModule(
+    "resource://gre/modules/FxAccounts.sys.mjs"
+  );
+  const fxAccounts = getFxAccountsSingleton();
+
+  const originalGetSignedInUser = fxAccounts.getSignedInUser;
+  const originalHasKeysForScope = fxAccounts.keys.hasKeysForScope;
+
+  // 1. User signs in without keys (third-party)
+  const user = { email: "foo@example.com", uid: "uid12345" };
+  fxAccounts.getSignedInUser = () => Promise.resolve(user);
+
+  // 2. Initially no keys - hasKeysForScope returns false
+  fxAccounts.keys.hasKeysForScope = () => Promise.resolve(false);
+
+  try {
+    await Assert.rejects(
+      Service.configure(),
+      /User does not have sync keys/,
+      "configure() should throw when no sync keys"
+    );
+
+    fxAccounts.keys.hasKeysForScope = () => Promise.resolve(true);
+
+    await Service.configure();
+    Assert.equal(Svc.PrefBranch.getStringPref("username"), "foo@example.com");
+  } finally {
+    fxAccounts.getSignedInUser = originalGetSignedInUser;
+    fxAccounts.keys.hasKeysForScope = originalHasKeysForScope;
+    Svc.PrefBranch.clearUserPref("username");
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_service_cluster.js b/src/zen/tests/mochitests/sync/test_service_cluster.js
new file mode 100644
index 000000000..b4c14f910
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_service_cluster.js
@@ -0,0 +1,61 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+add_task(async function test_findCluster() {
+  syncTestLogging();
+  _("Test Service._findCluster()");
+  try {
+    let whenReadyToAuthenticate = Promise.withResolvers();
+    Service.identity.whenReadyToAuthenticate = whenReadyToAuthenticate;
+    whenReadyToAuthenticate.resolve(true);
+
+    Service.identity._ensureValidToken = () =>
+      Promise.reject(new Error("Connection refused"));
+
+    _("_findCluster() throws on network errors (e.g. connection refused).");
+    await Assert.rejects(Service.identity._findCluster(), /Connection refused/);
+
+    Service.identity._ensureValidToken = () =>
+      Promise.resolve({ endpoint: "http://weave.user.node" });
+
+    _("_findCluster() returns the user's cluster node");
+    let cluster = await Service.identity._findCluster();
+    Assert.equal(cluster, "http://weave.user.node/");
+  } finally {
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+  }
+});
+
+add_task(async function test_setCluster() {
+  syncTestLogging();
+  _("Test Service._setCluster()");
+  try {
+    _("Check initial state.");
+    Assert.equal(Service.clusterURL, "");
+
+    Service.identity._findCluster = () => "http://weave.user.node/";
+
+    _("Set the cluster URL.");
+    Assert.ok(await Service.identity.setCluster());
+    Assert.equal(Service.clusterURL, "http://weave.user.node/");
+
+    _("Setting it again won't make a difference if it's the same one.");
+    Assert.ok(!(await Service.identity.setCluster()));
+    Assert.equal(Service.clusterURL, "http://weave.user.node/");
+
+    _("A 'null' response won't make a difference either.");
+    Service.identity._findCluster = () => null;
+    Assert.ok(!(await Service.identity.setCluster()));
+    Assert.equal(Service.clusterURL, "http://weave.user.node/");
+  } finally {
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_service_detect_upgrade.js b/src/zen/tests/mochitests/sync/test_service_detect_upgrade.js
new file mode 100644
index 000000000..52aa17a3f
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_service_detect_upgrade.js
@@ -0,0 +1,274 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { CryptoWrapper, WBORecord } = ChromeUtils.importESModule(
+  "resource://services-sync/record.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+add_task(async function v4_upgrade() {
+  enableValidationPrefs();
+
+  let clients = new ServerCollection();
+  let meta_global = new ServerWBO("global");
+
+  // Tracking info/collections.
+  let collectionsHelper = track_collections_helper();
+  let upd = collectionsHelper.with_updated_collection;
+  let collections = collectionsHelper.collections;
+
+  let keysWBO = new ServerWBO("keys");
+  let server = httpd_setup({
+    // Special.
+    "/1.1/johndoe/info/collections": collectionsHelper.handler,
+    "/1.1/johndoe/storage/crypto/keys": upd("crypto", keysWBO.handler()),
+    "/1.1/johndoe/storage/meta/global": upd("meta", meta_global.handler()),
+
+    // Track modified times.
+    "/1.1/johndoe/storage/clients": upd("clients", clients.handler()),
+    "/1.1/johndoe/storage/tabs": upd("tabs", new ServerCollection().handler()),
+
+    // Just so we don't get 404s in the logs.
+    "/1.1/johndoe/storage/bookmarks": new ServerCollection().handler(),
+    "/1.1/johndoe/storage/forms": new ServerCollection().handler(),
+    "/1.1/johndoe/storage/history": new ServerCollection().handler(),
+    "/1.1/johndoe/storage/passwords": new ServerCollection().handler(),
+    "/1.1/johndoe/storage/prefs": new ServerCollection().handler(),
+  });
+
+  try {
+    Service.status.resetSync();
+
+    _("Logging in.");
+
+    await configureIdentity({ username: "johndoe" }, server);
+
+    await Service.login();
+    Assert.ok(Service.isLoggedIn);
+    await Service.verifyAndFetchSymmetricKeys();
+    Assert.ok(await Service._remoteSetup());
+
+    async function test_out_of_date() {
+      _("Old meta/global: " + JSON.stringify(meta_global));
+      meta_global.payload = JSON.stringify({
+        syncID: "foooooooooooooooooooooooooo",
+        storageVersion: STORAGE_VERSION + 1,
+      });
+      collections.meta = Date.now() / 1000;
+      _("New meta/global: " + JSON.stringify(meta_global));
+      Service.recordManager.set(Service.metaURL, meta_global);
+      try {
+        await Service.sync();
+      } catch (ex) {}
+      Assert.equal(Service.status.sync, VERSION_OUT_OF_DATE);
+    }
+
+    // See what happens when we bump the storage version.
+    _("Syncing after server has been upgraded.");
+    await test_out_of_date();
+
+    // Same should happen after a wipe.
+    _("Syncing after server has been upgraded and wiped.");
+    await Service.wipeServer();
+    await test_out_of_date();
+
+    // Now's a great time to test what happens when keys get replaced.
+    _("Syncing afresh...");
+    Service.logout();
+    Service.collectionKeys.clear();
+    meta_global.payload = JSON.stringify({
+      syncID: "foooooooooooooobbbbbbbbbbbb",
+      storageVersion: STORAGE_VERSION,
+    });
+    collections.meta = Date.now() / 1000;
+    Service.recordManager.set(Service.metaURL, meta_global);
+    await Service.login();
+    Assert.ok(Service.isLoggedIn);
+    await Service.sync();
+    Assert.ok(Service.isLoggedIn);
+
+    let serverDecrypted;
+    let serverKeys;
+    let serverResp;
+
+    async function retrieve_server_default() {
+      serverKeys = serverResp = serverDecrypted = null;
+
+      serverKeys = new CryptoWrapper("crypto", "keys");
+      serverResp = (
+        await serverKeys.fetch(Service.resource(Service.cryptoKeysURL))
+      ).response;
+      Assert.ok(serverResp.success);
+
+      serverDecrypted = await serverKeys.decrypt(
+        Service.identity.syncKeyBundle
+      );
+      _("Retrieved WBO:       " + JSON.stringify(serverDecrypted));
+      _("serverKeys:          " + JSON.stringify(serverKeys));
+
+      return serverDecrypted.default;
+    }
+
+    async function retrieve_and_compare_default(should_succeed) {
+      let serverDefault = await retrieve_server_default();
+      let localDefault = Service.collectionKeys.keyForCollection().keyPairB64;
+
+      _("Retrieved keyBundle: " + JSON.stringify(serverDefault));
+      _("Local keyBundle:     " + JSON.stringify(localDefault));
+
+      if (should_succeed) {
+        Assert.equal(
+          JSON.stringify(serverDefault),
+          JSON.stringify(localDefault)
+        );
+      } else {
+        Assert.notEqual(
+          JSON.stringify(serverDefault),
+          JSON.stringify(localDefault)
+        );
+      }
+    }
+
+    // Uses the objects set above.
+    async function set_server_keys(pair) {
+      serverDecrypted.default = pair;
+      serverKeys.cleartext = serverDecrypted;
+      await serverKeys.encrypt(Service.identity.syncKeyBundle);
+      await serverKeys.upload(Service.resource(Service.cryptoKeysURL));
+    }
+
+    _("Checking we have the latest keys.");
+    await retrieve_and_compare_default(true);
+
+    _("Update keys on server.");
+    await set_server_keys([
+      "KaaaaaaaaaaaHAtfmuRY0XEJ7LXfFuqvF7opFdBD/MY=",
+      "aaaaaaaaaaaapxMO6TEWtLIOv9dj6kBAJdzhWDkkkis=",
+    ]);
+
+    _("Checking that we no longer have the latest keys.");
+    await retrieve_and_compare_default(false);
+
+    _("Indeed, they're what we set them to...");
+    Assert.equal(
+      "KaaaaaaaaaaaHAtfmuRY0XEJ7LXfFuqvF7opFdBD/MY=",
+      (await retrieve_server_default())[0]
+    );
+
+    _("Sync. Should download changed keys automatically.");
+    let oldClientsModified = collections.clients;
+    let oldTabsModified = collections.tabs;
+
+    await Service.login();
+    await Service.sync();
+    _("New key should have forced upload of data.");
+    _("Tabs: " + oldTabsModified + " < " + collections.tabs);
+    _("Clients: " + oldClientsModified + " < " + collections.clients);
+    Assert.greater(collections.clients, oldClientsModified);
+    Assert.greater(collections.tabs, oldTabsModified);
+
+    _("... and keys will now match.");
+    await retrieve_and_compare_default(true);
+
+    // Clean up.
+    await Service.startOver();
+  } finally {
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+    await promiseStopServer(server);
+  }
+});
+
+add_task(async function v5_upgrade() {
+  enableValidationPrefs();
+
+  // Tracking info/collections.
+  let collectionsHelper = track_collections_helper();
+  let upd = collectionsHelper.with_updated_collection;
+
+  let keysWBO = new ServerWBO("keys");
+  let bulkWBO = new ServerWBO("bulk");
+  let clients = new ServerCollection();
+  let meta_global = new ServerWBO("global");
+
+  let server = httpd_setup({
+    // Special.
+    "/1.1/johndoe/storage/meta/global": upd("meta", meta_global.handler()),
+    "/1.1/johndoe/info/collections": collectionsHelper.handler,
+    "/1.1/johndoe/storage/crypto/keys": upd("crypto", keysWBO.handler()),
+    "/1.1/johndoe/storage/crypto/bulk": upd("crypto", bulkWBO.handler()),
+
+    // Track modified times.
+    "/1.1/johndoe/storage/clients": upd("clients", clients.handler()),
+    "/1.1/johndoe/storage/tabs": upd("tabs", new ServerCollection().handler()),
+  });
+
+  try {
+    Service.status.resetSync();
+
+    Service.clusterURL = server.baseURI + "/";
+
+    await configureIdentity({ username: "johndoe" }, server);
+
+    // Test an upgrade where the contents of the server would cause us to error
+    // -- keys decrypted with a different sync key, for example.
+    _("Testing v4 -> v5 (or similar) upgrade.");
+    async function update_server_keys(syncKeyBundle, wboName, collWBO) {
+      await generateNewKeys(Service.collectionKeys);
+      let serverKeys = Service.collectionKeys.asWBO("crypto", wboName);
+      await serverKeys.encrypt(syncKeyBundle);
+      let res = Service.resource(Service.storageURL + collWBO);
+      Assert.ok((await serverKeys.upload(res)).success);
+    }
+
+    _("Bumping version.");
+    // Bump version on the server.
+    let m = new WBORecord("meta", "global");
+    m.payload = {
+      syncID: "foooooooooooooooooooooooooo",
+      storageVersion: STORAGE_VERSION + 1,
+    };
+    await m.upload(Service.resource(Service.metaURL));
+
+    _("New meta/global: " + JSON.stringify(meta_global));
+
+    // Fill the keys with bad data.
+    let badKeys = new BulkKeyBundle("crypto");
+    await badKeys.generateRandom();
+    await update_server_keys(badKeys, "keys", "crypto/keys"); // v4
+    await update_server_keys(badKeys, "bulk", "crypto/bulk"); // v5
+
+    _("Generating new keys.");
+    await generateNewKeys(Service.collectionKeys);
+
+    // Now sync and see what happens. It should be a version fail, not a crypto
+    // fail.
+
+    _("Logging in.");
+    try {
+      await Service.login();
+    } catch (e) {
+      _("Exception: " + e);
+    }
+    _("Status: " + Service.status);
+    Assert.ok(!Service.isLoggedIn);
+    Assert.equal(VERSION_OUT_OF_DATE, Service.status.sync);
+
+    // Clean up.
+    await Service.startOver();
+  } finally {
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+    await promiseStopServer(server);
+  }
+});
+
+function run_test() {
+  Log.repository.rootLogger.addAppender(new Log.DumpAppender());
+
+  run_next_test();
+}
diff --git a/src/zen/tests/mochitests/sync/test_service_login.js b/src/zen/tests/mochitests/sync/test_service_login.js
new file mode 100644
index 000000000..c75799d38
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_service_login.js
@@ -0,0 +1,224 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+Log.repository.rootLogger.addAppender(new Log.DumpAppender());
+
+function login_handling(handler) {
+  return function (request, response) {
+    if (has_hawk_header(request)) {
+      handler(request, response);
+    } else {
+      let body = "Unauthorized";
+      response.setStatusLine(request.httpVersion, 401, "Unauthorized");
+      response.setHeader("Content-Type", "text/plain");
+      response.bodyOutputStream.write(body, body.length);
+    }
+  };
+}
+
+add_task(async function test_offline() {
+  try {
+    _("The right bits are set when we're offline.");
+    Services.io.offline = true;
+    Assert.ok(!(await Service.login()));
+    Assert.equal(Service.status.login, LOGIN_FAILED_NETWORK_ERROR);
+    Services.io.offline = false;
+  } finally {
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+  }
+});
+
+function setup() {
+  let janeHelper = track_collections_helper();
+  let janeU = janeHelper.with_updated_collection;
+  let johnHelper = track_collections_helper();
+  let johnU = johnHelper.with_updated_collection;
+
+  let server = httpd_setup({
+    "/1.1/johndoe/info/collections": login_handling(johnHelper.handler),
+    "/1.1/janedoe/info/collections": login_handling(janeHelper.handler),
+
+    // We need these handlers because we test login, and login
+    // is where keys are generated or fetched.
+    // TODO: have Jane fetch her keys, not generate them...
+    "/1.1/johndoe/storage/crypto/keys": johnU(
+      "crypto",
+      new ServerWBO("keys").handler()
+    ),
+    "/1.1/johndoe/storage/meta/global": johnU(
+      "meta",
+      new ServerWBO("global").handler()
+    ),
+    "/1.1/janedoe/storage/crypto/keys": janeU(
+      "crypto",
+      new ServerWBO("keys").handler()
+    ),
+    "/1.1/janedoe/storage/meta/global": janeU(
+      "meta",
+      new ServerWBO("global").handler()
+    ),
+  });
+
+  return server;
+}
+
+add_task(async function test_not_logged_in() {
+  let server = setup();
+  try {
+    await Service.login();
+    Assert.ok(!Service.isLoggedIn, "no user configured, so can't be logged in");
+    Assert.equal(Service._checkSync(), kSyncNotConfigured);
+  } finally {
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+    await promiseStopServer(server);
+  }
+});
+
+add_task(async function test_login_logout() {
+  enableValidationPrefs();
+
+  let server = setup();
+
+  try {
+    _("Force the initial state.");
+    Service.status.service = STATUS_OK;
+    Assert.equal(Service.status.service, STATUS_OK);
+
+    _("Try logging in. It won't work because we're not configured yet.");
+    await Service.login();
+    Assert.equal(Service.status.service, CLIENT_NOT_CONFIGURED);
+    Assert.equal(Service.status.login, LOGIN_FAILED_NO_USERNAME);
+    Assert.ok(!Service.isLoggedIn);
+
+    _("Try again with a configured account");
+    await configureIdentity({ username: "johndoe" }, server);
+    await Service.login();
+    Assert.equal(Service.status.service, STATUS_OK);
+    Assert.equal(Service.status.login, LOGIN_SUCCEEDED);
+    Assert.ok(Service.isLoggedIn);
+
+    _("Logout.");
+    Service.logout();
+    Assert.ok(!Service.isLoggedIn);
+
+    _("Logging out again won't do any harm.");
+    Service.logout();
+    Assert.ok(!Service.isLoggedIn);
+  } finally {
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+    await promiseStopServer(server);
+  }
+});
+
+add_task(async function test_login_on_sync() {
+  enableValidationPrefs();
+
+  let server = setup();
+  await configureIdentity({ username: "johndoe" }, server);
+
+  try {
+    _("Sync calls login.");
+    let oldLogin = Service.login;
+    let loginCalled = false;
+    Service.login = async function () {
+      loginCalled = true;
+      Service.status.login = LOGIN_SUCCEEDED;
+      this._loggedIn = false; // So that sync aborts.
+      return true;
+    };
+
+    await Service.sync();
+
+    Assert.ok(loginCalled);
+    Service.login = oldLogin;
+
+    // Stub mpLocked.
+    let mpLocked = true;
+    Utils.mpLocked = () => mpLocked;
+
+    // Stub scheduleNextSync. This gets called within checkSyncStatus if we're
+    // ready to sync, so use it as an indicator.
+    let scheduleNextSyncF = Service.scheduler.scheduleNextSync;
+    let scheduleCalled = false;
+    Service.scheduler.scheduleNextSync = function (wait) {
+      scheduleCalled = true;
+      scheduleNextSyncF.call(this, wait);
+    };
+
+    // Autoconnect still tries to connect in the background (useful behavior:
+    // for non-MP users and unlocked MPs, this will detect version expiry
+    // earlier).
+    //
+    // Consequently, non-MP users will be logged in as in the pre-Bug 543784 world,
+    // and checkSyncStatus reflects that by waiting for login.
+    //
+    // This process doesn't apply if your MP is still locked, so we make
+    // checkSyncStatus accept a locked MP in place of being logged in.
+    //
+    // This test exercises these two branches.
+
+    _("We're ready to sync if locked.");
+    Service.enabled = true;
+    Services.io.offline = false;
+    Service.scheduler.checkSyncStatus();
+    Assert.ok(scheduleCalled);
+
+    _("... and also if we're not locked.");
+    scheduleCalled = false;
+    mpLocked = false;
+    Service.scheduler.checkSyncStatus();
+    Assert.ok(scheduleCalled);
+    Service.scheduler.scheduleNextSync = scheduleNextSyncF;
+
+    // TODO: need better tests around master password prompting. See Bug 620583.
+
+    mpLocked = true;
+
+    // Testing exception handling if master password dialog is canceled.
+    // Do this by monkeypatching.
+    Service.identity.unlockAndVerifyAuthState = () =>
+      Promise.resolve(MASTER_PASSWORD_LOCKED);
+
+    let cSTCalled = false;
+    let lockedSyncCalled = false;
+
+    Service.scheduler.clearSyncTriggers = function () {
+      cSTCalled = true;
+    };
+    Service._lockedSync = async function () {
+      lockedSyncCalled = true;
+    };
+
+    _("If master password is canceled, login fails and we report lockage.");
+    Assert.ok(!(await Service.login()));
+    Assert.equal(Service.status.login, MASTER_PASSWORD_LOCKED);
+    Assert.equal(Service.status.service, LOGIN_FAILED);
+    _("Locked? " + Utils.mpLocked());
+    _("checkSync reports the correct term.");
+    Assert.equal(Service._checkSync(), kSyncMasterPasswordLocked);
+
+    _("Sync doesn't proceed and clears triggers if MP is still locked.");
+    await Service.sync();
+
+    Assert.ok(cSTCalled);
+    Assert.ok(!lockedSyncCalled);
+
+    // N.B., a bunch of methods are stubbed at this point. Be careful putting
+    // new tests after this point!
+  } finally {
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+    await promiseStopServer(server);
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_service_startOver.js b/src/zen/tests/mochitests/sync/test_service_startOver.js
new file mode 100644
index 000000000..22d92c76e
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_service_startOver.js
@@ -0,0 +1,91 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+function BlaEngine() {
+  SyncEngine.call(this, "Bla", Service);
+}
+BlaEngine.prototype = {
+  removed: false,
+  async removeClientData() {
+    this.removed = true;
+  },
+};
+Object.setPrototypeOf(BlaEngine.prototype, SyncEngine.prototype);
+
+add_task(async function setup() {
+  await Service.engineManager.register(BlaEngine);
+});
+
+add_task(async function test_resetLocalData() {
+  await configureIdentity();
+  Service.status.enforceBackoff = true;
+  Service.status.backoffInterval = 42;
+  Service.status.minimumNextSync = 23;
+
+  // Verify set up.
+  Assert.equal(Service.status.checkSetup(), STATUS_OK);
+
+  // Verify state that the observer sees.
+  let observerCalled = false;
+  Svc.Obs.add("weave:service:start-over", function onStartOver() {
+    Svc.Obs.remove("weave:service:start-over", onStartOver);
+    observerCalled = true;
+
+    Assert.equal(Service.status.service, CLIENT_NOT_CONFIGURED);
+  });
+
+  await Service.startOver();
+  Assert.ok(observerCalled);
+
+  // Verify the site was nuked from orbit.
+  Assert.equal(
+    Svc.PrefBranch.getPrefType("username"),
+    Ci.nsIPrefBranch.PREF_INVALID
+  );
+
+  Assert.equal(Service.status.service, CLIENT_NOT_CONFIGURED);
+  Assert.ok(!Service.status.enforceBackoff);
+  Assert.equal(Service.status.backoffInterval, 0);
+  Assert.equal(Service.status.minimumNextSync, 0);
+});
+
+add_task(async function test_removeClientData() {
+  let engine = Service.engineManager.get("bla");
+
+  // No cluster URL = no removal.
+  Assert.ok(!engine.removed);
+  await Service.startOver();
+  Assert.ok(!engine.removed);
+
+  Service.clusterURL = "https://localhost/";
+
+  Assert.ok(!engine.removed);
+  await Service.startOver();
+  Assert.ok(engine.removed);
+});
+
+add_task(async function test_reset_SyncScheduler() {
+  // Some non-default values for SyncScheduler's attributes.
+  Service.scheduler.idle = true;
+  Service.scheduler.hasIncomingItems = true;
+  Svc.PrefBranch.setIntPref("clients.devices.desktop", 42);
+  Service.scheduler.nextSync = Date.now();
+  Service.scheduler.syncThreshold = MULTI_DEVICE_THRESHOLD;
+  Service.scheduler.syncInterval = Service.scheduler.activeInterval;
+
+  await Service.startOver();
+
+  Assert.ok(!Service.scheduler.idle);
+  Assert.ok(!Service.scheduler.hasIncomingItems);
+  Assert.equal(Service.scheduler.numClients, 0);
+  Assert.equal(Service.scheduler.nextSync, 0);
+  Assert.equal(Service.scheduler.syncThreshold, SINGLE_USER_THRESHOLD);
+  Assert.equal(
+    Service.scheduler.syncInterval,
+    Service.scheduler.singleDeviceInterval
+  );
+});
diff --git a/src/zen/tests/mochitests/sync/test_service_startup.js b/src/zen/tests/mochitests/sync/test_service_startup.js
new file mode 100644
index 000000000..66623a951
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_service_startup.js
@@ -0,0 +1,60 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { AppConstants } = ChromeUtils.importESModule(
+  "resource://gre/modules/AppConstants.sys.mjs"
+);
+
+// Svc.PrefBranch.setStringPref("services.sync.log.appender.dump", "All");
+Svc.PrefBranch.setStringPref("registerEngines", "Tab,Bookmarks,Form,History");
+
+add_task(async function run_test() {
+  validate_all_future_pings();
+  _("When imported, Service.onStartup is called");
+
+  let xps = Cc["@mozilla.org/weave/service;1"].getService(
+    Ci.nsISupports
+  ).wrappedJSObject;
+  Assert.ok(!xps.enabled);
+
+  // Test fixtures
+  let { Service } = ChromeUtils.importESModule(
+    "resource://services-sync/service.sys.mjs"
+  );
+  Services.prefs.setStringPref("services.sync.username", "johndoe");
+  Assert.ok(xps.enabled);
+
+  _("Service is enabled.");
+  Assert.equal(Service.enabled, true);
+
+  _("Observers are notified of startup");
+  Assert.ok(!Service.status.ready);
+  Assert.ok(!xps.ready);
+
+  await promiseOneObserver("weave:service:ready");
+
+  Assert.ok(Service.status.ready);
+  Assert.ok(xps.ready);
+
+  _("Engines are registered.");
+  let engines = Service.engineManager.getAll();
+  if (AppConstants.MOZ_APP_NAME == "thunderbird") {
+    // Thunderbird's engines are registered later, so they're not here yet.
+    Assert.deepEqual(
+      engines.map(engine => engine.name),
+      []
+    );
+  } else {
+    Assert.deepEqual(
+      engines.map(engine => engine.name),
+      ["tabs", "bookmarks", "forms", "history"]
+    );
+  }
+
+  // Clean up.
+  for (const pref of Svc.PrefBranch.getChildList("")) {
+    Svc.PrefBranch.clearUserPref(pref);
+  }
+
+  do_test_finished();
+});
diff --git a/src/zen/tests/mochitests/sync/test_service_sync_401.js b/src/zen/tests/mochitests/sync/test_service_sync_401.js
new file mode 100644
index 000000000..0c285872e
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_service_sync_401.js
@@ -0,0 +1,90 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+function login_handling(handler) {
+  return function (request, response) {
+    if (
+      request.hasHeader("Authorization") &&
+      request.getHeader("Authorization").includes('Hawk id="id"')
+    ) {
+      handler(request, response);
+    } else {
+      let body = "Unauthorized";
+      response.setStatusLine(request.httpVersion, 401, "Unauthorized");
+      response.bodyOutputStream.write(body, body.length);
+    }
+  };
+}
+
+add_task(async function run_test() {
+  Log.repository.rootLogger.addAppender(new Log.DumpAppender());
+
+  let collectionsHelper = track_collections_helper();
+  let upd = collectionsHelper.with_updated_collection;
+
+  let server = httpd_setup({
+    "/1.1/johndoe/storage/crypto/keys": upd(
+      "crypto",
+      new ServerWBO("keys").handler()
+    ),
+    "/1.1/johndoe/storage/meta/global": upd(
+      "meta",
+      new ServerWBO("global").handler()
+    ),
+    "/1.1/johndoe/info/collections": login_handling(collectionsHelper.handler),
+  });
+
+  const GLOBAL_SCORE = 42;
+
+  try {
+    _("Set up test fixtures.");
+    await SyncTestingInfrastructure(server, "johndoe", "ilovejane");
+    Service.scheduler.globalScore = GLOBAL_SCORE;
+    // Avoid daily ping
+    Svc.PrefBranch.setIntPref("lastPing", Math.floor(Date.now() / 1000));
+
+    let threw = false;
+    Svc.Obs.add("weave:service:sync:error", function () {
+      threw = true;
+    });
+
+    _("Initial state: We're successfully logged in.");
+    await Service.login();
+    Assert.ok(Service.isLoggedIn);
+    Assert.equal(Service.status.login, LOGIN_SUCCEEDED);
+
+    _("Simulate having changed the password somewhere else.");
+    Service.identity._token.id = "somethingelse";
+    Service.identity.unlockAndVerifyAuthState = () =>
+      Promise.resolve(LOGIN_FAILED_LOGIN_REJECTED);
+
+    _("Let's try to sync.");
+    await Service.sync();
+
+    _("Verify that sync() threw an exception.");
+    Assert.ok(threw);
+
+    _("We're no longer logged in.");
+    Assert.ok(!Service.isLoggedIn);
+
+    _("Sync status won't have changed yet, because we haven't tried again.");
+
+    _("globalScore is reset upon starting a sync.");
+    Assert.equal(Service.scheduler.globalScore, 0);
+
+    _("Our next sync will fail appropriately.");
+    try {
+      await Service.sync();
+    } catch (ex) {}
+    Assert.equal(Service.status.login, LOGIN_FAILED_LOGIN_REJECTED);
+  } finally {
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+    await promiseStopServer(server);
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_service_sync_locked.js b/src/zen/tests/mochitests/sync/test_service_sync_locked.js
new file mode 100644
index 000000000..5a872e270
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_service_sync_locked.js
@@ -0,0 +1,47 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+add_task(async function run_test() {
+  validate_all_future_pings();
+  let debug = [];
+  let info = [];
+
+  function augmentLogger(old) {
+    let d = old.debug;
+    let i = old.info;
+    // For the purposes of this test we don't need to do full formatting
+    // of the 2nd param, as the ones we care about are always strings.
+    old.debug = function (m, p) {
+      debug.push(p ? m + ": " + (p.message || p) : m);
+      d.call(old, m, p);
+    };
+    old.info = function (m, p) {
+      info.push(p ? m + ": " + (p.message || p) : m);
+      i.call(old, m, p);
+    };
+    return old;
+  }
+
+  Log.repository.rootLogger.addAppender(new Log.DumpAppender());
+
+  augmentLogger(Service._log);
+
+  // Avoid daily ping
+  Svc.PrefBranch.setIntPref("lastPing", Math.floor(Date.now() / 1000));
+
+  _("Check that sync will log appropriately if already in 'progress'.");
+  Service._locked = true;
+  await Service.sync();
+  Service._locked = false;
+
+  Assert.ok(
+    debug[debug.length - 2].startsWith(
+      'Exception calling WrappedLock: Could not acquire lock. Label: "service.js: login".'
+    )
+  );
+  Assert.equal(info[info.length - 1], "Cannot start sync: already syncing?");
+});
diff --git a/src/zen/tests/mochitests/sync/test_service_sync_remoteSetup.js b/src/zen/tests/mochitests/sync/test_service_sync_remoteSetup.js
new file mode 100644
index 000000000..ec95e69c7
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_service_sync_remoteSetup.js
@@ -0,0 +1,241 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+// This sucks, but this test fails if this engine is enabled, due to dumb
+// things that aren't related to this engine. In short:
+// * Because the addon manager isn't initialized, the addons engine fails to
+//   initialize. So we end up writing a meta/global with `extension-storage`
+//   but not addons.
+// * After we sync, we discover 'addons' is locally enabled, but because it's
+//   not in m/g, we decide it's been remotely declined (and it decides this
+//   without even considering `declined`). So we disable 'addons'.
+// * Disabling 'addons' means 'extension-storage' is disabled - but because
+//   that *is* in meta/global we re-update meta/global to remove it.
+// * This test fails due to the extra, unexpected update of m/g.
+//
+// Another option would be to ensure the addons manager is initialized, but
+// that's a larger patch and still isn't strictly relevant to what's being
+// tested here, so...
+Services.prefs.setBoolPref(
+  "services.sync.engine.extension-storage.force",
+  false
+);
+
+add_task(async function run_test() {
+  enableValidationPrefs();
+
+  validate_all_future_pings();
+  Log.repository.rootLogger.addAppender(new Log.DumpAppender());
+
+  let clients = new ServerCollection();
+  let meta_global = new ServerWBO("global");
+
+  let collectionsHelper = track_collections_helper();
+  let upd = collectionsHelper.with_updated_collection;
+  let collections = collectionsHelper.collections;
+
+  function wasCalledHandler(wbo) {
+    let handler = wbo.handler();
+    return function () {
+      wbo.wasCalled = true;
+      handler.apply(this, arguments);
+    };
+  }
+
+  let keysWBO = new ServerWBO("keys");
+  let cryptoColl = new ServerCollection({ keys: keysWBO });
+  let metaColl = new ServerCollection({ global: meta_global });
+  do_test_pending();
+
+  /**
+   * Handle the bulk DELETE request sent by wipeServer.
+   */
+  function storageHandler(request, response) {
+    Assert.equal("DELETE", request.method);
+    Assert.ok(request.hasHeader("X-Confirm-Delete"));
+
+    _("Wiping out all collections.");
+    cryptoColl.delete({});
+    clients.delete({});
+    metaColl.delete({});
+
+    let ts = new_timestamp();
+    collectionsHelper.update_collection("crypto", ts);
+    collectionsHelper.update_collection("clients", ts);
+    collectionsHelper.update_collection("meta", ts);
+    return_timestamp(request, response, ts);
+  }
+
+  const GLOBAL_PATH = "/1.1/johndoe/storage/meta/global";
+
+  let handlers = {
+    "/1.1/johndoe/storage": storageHandler,
+    "/1.1/johndoe/storage/crypto/keys": upd("crypto", keysWBO.handler()),
+    "/1.1/johndoe/storage/crypto": upd("crypto", cryptoColl.handler()),
+    "/1.1/johndoe/storage/clients": upd("clients", clients.handler()),
+    "/1.1/johndoe/storage/meta": upd("meta", wasCalledHandler(metaColl)),
+    "/1.1/johndoe/storage/meta/global": upd(
+      "meta",
+      wasCalledHandler(meta_global)
+    ),
+    "/1.1/johndoe/info/collections": collectionsHelper.handler,
+  };
+
+  function mockHandler(path, mock) {
+    server.registerPathHandler(path, mock(handlers[path]));
+    return {
+      restore() {
+        server.registerPathHandler(path, handlers[path]);
+      },
+    };
+  }
+
+  let server = httpd_setup(handlers);
+
+  try {
+    _("Checking Status.sync with no credentials.");
+    await Service.verifyAndFetchSymmetricKeys();
+    Assert.equal(Service.status.sync, CREDENTIALS_CHANGED);
+    Assert.equal(Service.status.login, LOGIN_FAILED_NO_PASSPHRASE);
+
+    await configureIdentity({ username: "johndoe" }, server);
+
+    await Service.login();
+    _("Checking that remoteSetup returns true when credentials have changed.");
+    (await Service.recordManager.get(Service.metaURL)).payload.syncID =
+      "foobar";
+    Assert.ok(await Service._remoteSetup());
+
+    let returnStatusCode = (method, code) => oldMethod => (req, res) => {
+      if (req.method === method) {
+        res.setStatusLine(req.httpVersion, code, "");
+      } else {
+        oldMethod(req, res);
+      }
+    };
+
+    let mock = mockHandler(GLOBAL_PATH, returnStatusCode("GET", 401));
+    Service.recordManager.del(Service.metaURL);
+    _(
+      "Checking that remoteSetup returns false on 401 on first get /meta/global."
+    );
+    Assert.equal(false, await Service._remoteSetup());
+    mock.restore();
+
+    await Service.login();
+    mock = mockHandler(GLOBAL_PATH, returnStatusCode("GET", 503));
+    Service.recordManager.del(Service.metaURL);
+    _(
+      "Checking that remoteSetup returns false on 503 on first get /meta/global."
+    );
+    Assert.equal(false, await Service._remoteSetup());
+    Assert.equal(Service.status.sync, METARECORD_DOWNLOAD_FAIL);
+    mock.restore();
+
+    await Service.login();
+    mock = mockHandler(GLOBAL_PATH, returnStatusCode("GET", 404));
+    Service.recordManager.del(Service.metaURL);
+    _("Checking that remoteSetup recovers on 404 on first get /meta/global.");
+    Assert.ok(await Service._remoteSetup());
+    mock.restore();
+
+    let makeOutdatedMeta = async () => {
+      Service.metaModified = 0;
+      let infoResponse = await Service._fetchInfo();
+      return {
+        status: infoResponse.status,
+        obj: {
+          crypto: infoResponse.obj.crypto,
+          clients: infoResponse.obj.clients,
+          meta: 1,
+        },
+      };
+    };
+
+    _(
+      "Checking that remoteSetup recovers on 404 on get /meta/global after clear cached one."
+    );
+    mock = mockHandler(GLOBAL_PATH, returnStatusCode("GET", 404));
+    Service.recordManager.set(Service.metaURL, { isNew: false });
+    Assert.ok(await Service._remoteSetup(await makeOutdatedMeta()));
+    mock.restore();
+
+    _(
+      "Checking that remoteSetup returns false on 503 on get /meta/global after clear cached one."
+    );
+    mock = mockHandler(GLOBAL_PATH, returnStatusCode("GET", 503));
+    Service.status.sync = "";
+    Service.recordManager.set(Service.metaURL, { isNew: false });
+    Assert.equal(false, await Service._remoteSetup(await makeOutdatedMeta()));
+    Assert.equal(Service.status.sync, "");
+    mock.restore();
+
+    metaColl.delete({});
+
+    _("Do an initial sync.");
+    await Service.sync();
+
+    _("Checking that remoteSetup returns true.");
+    Assert.ok(await Service._remoteSetup());
+
+    _("Verify that the meta record was uploaded.");
+    Assert.equal(meta_global.data.syncID, Service.syncID);
+    Assert.equal(meta_global.data.storageVersion, STORAGE_VERSION);
+    Assert.equal(
+      meta_global.data.engines.clients.version,
+      Service.clientsEngine.version
+    );
+    Assert.equal(
+      meta_global.data.engines.clients.syncID,
+      await Service.clientsEngine.getSyncID()
+    );
+
+    _(
+      "Set the collection info hash so that sync() will remember the modified times for future runs."
+    );
+    let lastSync = await Service.clientsEngine.getLastSync();
+    collections.meta = lastSync;
+    collections.clients = lastSync;
+    await Service.sync();
+
+    _("Sync again and verify that meta/global wasn't downloaded again");
+    meta_global.wasCalled = false;
+    await Service.sync();
+    Assert.ok(!meta_global.wasCalled);
+
+    _(
+      "Fake modified records. This will cause a redownload, but not reupload since it hasn't changed."
+    );
+    collections.meta += 42;
+    meta_global.wasCalled = false;
+
+    let metaModified = meta_global.modified;
+
+    await Service.sync();
+    Assert.ok(meta_global.wasCalled);
+    Assert.equal(metaModified, meta_global.modified);
+
+    // Try to screw up HMAC calculation.
+    // Re-encrypt keys with a new random keybundle, and upload them to the
+    // server, just as might happen with a second client.
+    _("Attempting to screw up HMAC by re-encrypting keys.");
+    let keys = Service.collectionKeys.asWBO();
+    let b = new BulkKeyBundle("hmacerror");
+    await b.generateRandom();
+    collections.crypto = keys.modified = 100 + Date.now() / 1000; // Future modification time.
+    await keys.encrypt(b);
+    await keys.upload(Service.resource(Service.cryptoKeysURL));
+
+    Assert.equal(false, await Service.verifyAndFetchSymmetricKeys());
+    Assert.equal(Service.status.login, LOGIN_FAILED_INVALID_PASSPHRASE);
+  } finally {
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+    server.stop(do_test_finished);
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_service_sync_specified.js b/src/zen/tests/mochitests/sync/test_service_sync_specified.js
new file mode 100644
index 000000000..845cdb366
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_service_sync_specified.js
@@ -0,0 +1,150 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+let syncedEngines = [];
+
+function SteamEngine() {
+  SyncEngine.call(this, "Steam", Service);
+}
+SteamEngine.prototype = {
+  async _sync() {
+    syncedEngines.push(this.name);
+  },
+};
+Object.setPrototypeOf(SteamEngine.prototype, SyncEngine.prototype);
+
+function StirlingEngine() {
+  SyncEngine.call(this, "Stirling", Service);
+}
+StirlingEngine.prototype = {
+  async _sync() {
+    syncedEngines.push(this.name);
+  },
+};
+Object.setPrototypeOf(StirlingEngine.prototype, SteamEngine.prototype);
+
+// Tracking info/collections.
+var collectionsHelper = track_collections_helper();
+var upd = collectionsHelper.with_updated_collection;
+
+function sync_httpd_setup(handlers) {
+  handlers["/1.1/johndoe/info/collections"] = collectionsHelper.handler;
+  delete collectionsHelper.collections.crypto;
+  delete collectionsHelper.collections.meta;
+
+  let cr = new ServerWBO("keys");
+  handlers["/1.1/johndoe/storage/crypto/keys"] = upd("crypto", cr.handler());
+
+  let cl = new ServerCollection();
+  handlers["/1.1/johndoe/storage/clients"] = upd("clients", cl.handler());
+
+  return httpd_setup(handlers);
+}
+
+async function setUp() {
+  syncedEngines = [];
+  let engine = Service.engineManager.get("steam");
+  engine.enabled = true;
+  engine.syncPriority = 1;
+
+  engine = Service.engineManager.get("stirling");
+  engine.enabled = true;
+  engine.syncPriority = 2;
+
+  let server = sync_httpd_setup({
+    "/1.1/johndoe/storage/meta/global": new ServerWBO("global", {}).handler(),
+  });
+  await SyncTestingInfrastructure(server, "johndoe", "ilovejane");
+  return server;
+}
+
+add_task(async function setup() {
+  await Service.engineManager.clear();
+  validate_all_future_pings();
+
+  await Service.engineManager.register(SteamEngine);
+  await Service.engineManager.register(StirlingEngine);
+});
+
+add_task(async function test_noEngines() {
+  enableValidationPrefs();
+
+  _("Test: An empty array of engines to sync does nothing.");
+  let server = await setUp();
+
+  try {
+    _("Sync with no engines specified.");
+    await Service.sync({ engines: [] });
+    deepEqual(syncedEngines, [], "no engines were synced");
+  } finally {
+    await Service.startOver();
+    await promiseStopServer(server);
+  }
+});
+
+add_task(async function test_oneEngine() {
+  enableValidationPrefs();
+
+  _("Test: Only one engine is synced.");
+  let server = await setUp();
+
+  try {
+    _("Sync with 1 engine specified.");
+    await Service.sync({ engines: ["steam"] });
+    deepEqual(syncedEngines, ["steam"]);
+  } finally {
+    await Service.startOver();
+    await promiseStopServer(server);
+  }
+});
+
+add_task(async function test_bothEnginesSpecified() {
+  enableValidationPrefs();
+
+  _("Test: All engines are synced when specified in the correct order (1).");
+  let server = await setUp();
+
+  try {
+    _("Sync with both engines specified.");
+    await Service.sync({ engines: ["steam", "stirling"] });
+    deepEqual(syncedEngines, ["steam", "stirling"]);
+  } finally {
+    await Service.startOver();
+    await promiseStopServer(server);
+  }
+});
+
+add_task(async function test_bothEnginesSpecified() {
+  enableValidationPrefs();
+
+  _("Test: All engines are synced when specified in the correct order (2).");
+  let server = await setUp();
+
+  try {
+    _("Sync with both engines specified.");
+    await Service.sync({ engines: ["stirling", "steam"] });
+    deepEqual(syncedEngines, ["stirling", "steam"]);
+  } finally {
+    await Service.startOver();
+    await promiseStopServer(server);
+  }
+});
+
+add_task(async function test_bothEnginesDefault() {
+  enableValidationPrefs();
+
+  _("Test: All engines are synced when nothing is specified.");
+  let server = await setUp();
+
+  try {
+    await Service.sync();
+    deepEqual(syncedEngines, ["steam", "stirling"]);
+  } finally {
+    await Service.startOver();
+    await promiseStopServer(server);
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_service_sync_updateEnabledEngines.js b/src/zen/tests/mochitests/sync/test_service_sync_updateEnabledEngines.js
new file mode 100644
index 000000000..fd8b3f71b
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_service_sync_updateEnabledEngines.js
@@ -0,0 +1,587 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+const { EngineSynchronizer } = ChromeUtils.importESModule(
+  "resource://services-sync/stages/enginesync.sys.mjs"
+);
+
+function QuietStore() {
+  Store.call("Quiet");
+}
+QuietStore.prototype = {
+  async getAllIDs() {
+    return [];
+  },
+};
+
+function SteamEngine() {
+  SyncEngine.call(this, "Steam", Service);
+}
+SteamEngine.prototype = {
+  // We're not interested in engine sync but what the service does.
+  _storeObj: QuietStore,
+
+  _sync: async function _sync() {
+    await this._syncStartup();
+  },
+};
+Object.setPrototypeOf(SteamEngine.prototype, SyncEngine.prototype);
+
+function StirlingEngine() {
+  SyncEngine.call(this, "Stirling", Service);
+}
+StirlingEngine.prototype = {
+  // This engine's enabled state is the same as the SteamEngine's.
+  get prefName() {
+    return "steam";
+  },
+};
+Object.setPrototypeOf(StirlingEngine.prototype, SteamEngine.prototype);
+
+// Tracking info/collections.
+var collectionsHelper = track_collections_helper();
+var upd = collectionsHelper.with_updated_collection;
+
+function sync_httpd_setup(handlers) {
+  handlers["/1.1/johndoe/info/collections"] = collectionsHelper.handler;
+  delete collectionsHelper.collections.crypto;
+  delete collectionsHelper.collections.meta;
+
+  let cr = new ServerWBO("keys");
+  handlers["/1.1/johndoe/storage/crypto/keys"] = upd("crypto", cr.handler());
+
+  let cl = new ServerCollection();
+  handlers["/1.1/johndoe/storage/clients"] = upd("clients", cl.handler());
+
+  return httpd_setup(handlers);
+}
+
+async function setUp(server) {
+  await SyncTestingInfrastructure(server, "johndoe", "ilovejane");
+  // Ensure that the server has valid keys so that logging in will work and not
+  // result in a server wipe, rendering many of these tests useless.
+  await generateNewKeys(Service.collectionKeys);
+  let serverKeys = Service.collectionKeys.asWBO("crypto", "keys");
+  await serverKeys.encrypt(Service.identity.syncKeyBundle);
+  let { success } = await serverKeys.upload(
+    Service.resource(Service.cryptoKeysURL)
+  );
+  ok(success);
+}
+
+const PAYLOAD = 42;
+
+add_task(async function setup() {
+  await Service.engineManager.clear();
+  validate_all_future_pings();
+
+  await Service.engineManager.register(SteamEngine);
+  await Service.engineManager.register(StirlingEngine);
+});
+
+add_task(async function test_newAccount() {
+  enableValidationPrefs();
+
+  _("Test: New account does not disable locally enabled engines.");
+  let engine = Service.engineManager.get("steam");
+  let server = sync_httpd_setup({
+    "/1.1/johndoe/storage/meta/global": new ServerWBO("global", {}).handler(),
+    "/1.1/johndoe/storage/steam": new ServerWBO("steam", {}).handler(),
+  });
+  await setUp(server);
+
+  try {
+    _("Engine is enabled from the beginning.");
+    Service._ignorePrefObserver = true;
+    engine.enabled = true;
+    Service._ignorePrefObserver = false;
+
+    _("Sync.");
+    await Service.sync();
+
+    _("Engine continues to be enabled.");
+    Assert.ok(engine.enabled);
+  } finally {
+    await Service.startOver();
+    await promiseStopServer(server);
+  }
+});
+
+add_task(async function test_enabledLocally() {
+  enableValidationPrefs();
+
+  _("Test: Engine is disabled on remote clients and enabled locally");
+  Service.syncID = "abcdefghij";
+  let engine = Service.engineManager.get("steam");
+  let metaWBO = new ServerWBO("global", {
+    syncID: Service.syncID,
+    storageVersion: STORAGE_VERSION,
+    engines: {},
+  });
+  let server = sync_httpd_setup({
+    "/1.1/johndoe/storage/meta/global": metaWBO.handler(),
+    "/1.1/johndoe/storage/steam": new ServerWBO("steam", {}).handler(),
+  });
+  await setUp(server);
+
+  try {
+    _("Enable engine locally.");
+    engine.enabled = true;
+
+    _("Sync.");
+    await Service.sync();
+
+    _("Meta record now contains the new engine.");
+    Assert.ok(!!metaWBO.data.engines.steam);
+
+    _("Engine continues to be enabled.");
+    Assert.ok(engine.enabled);
+  } finally {
+    await Service.startOver();
+    await promiseStopServer(server);
+  }
+});
+
+add_task(async function test_disabledLocally() {
+  enableValidationPrefs();
+
+  _("Test: Engine is enabled on remote clients and disabled locally");
+  Service.syncID = "abcdefghij";
+  let engine = Service.engineManager.get("steam");
+  let syncID = await engine.resetLocalSyncID();
+  let metaWBO = new ServerWBO("global", {
+    syncID: Service.syncID,
+    storageVersion: STORAGE_VERSION,
+    engines: { steam: { syncID, version: engine.version } },
+  });
+  let steamCollection = new ServerWBO("steam", PAYLOAD);
+
+  let server = sync_httpd_setup({
+    "/1.1/johndoe/storage/meta/global": metaWBO.handler(),
+    "/1.1/johndoe/storage/steam": steamCollection.handler(),
+  });
+  await setUp(server);
+
+  try {
+    _("Disable engine locally.");
+    Service._ignorePrefObserver = true;
+    engine.enabled = true;
+    Service._ignorePrefObserver = false;
+    engine.enabled = false;
+
+    _("Sync.");
+    await Service.sync();
+
+    _("Meta record no longer contains engine.");
+    Assert.ok(!metaWBO.data.engines.steam);
+
+    _("Server records are wiped.");
+    Assert.equal(steamCollection.payload, undefined);
+
+    _("Engine continues to be disabled.");
+    Assert.ok(!engine.enabled);
+  } finally {
+    await Service.startOver();
+    await promiseStopServer(server);
+  }
+});
+
+add_task(async function test_disabledLocally_wipe503() {
+  enableValidationPrefs();
+
+  _("Test: Engine is enabled on remote clients and disabled locally");
+  Service.syncID = "abcdefghij";
+  let engine = Service.engineManager.get("steam");
+  let syncID = await engine.resetLocalSyncID();
+  let metaWBO = new ServerWBO("global", {
+    syncID: Service.syncID,
+    storageVersion: STORAGE_VERSION,
+    engines: { steam: { syncID, version: engine.version } },
+  });
+
+  function service_unavailable(request, response) {
+    let body = "Service Unavailable";
+    response.setStatusLine(request.httpVersion, 503, "Service Unavailable");
+    response.setHeader("Retry-After", "23");
+    response.bodyOutputStream.write(body, body.length);
+  }
+
+  let server = sync_httpd_setup({
+    "/1.1/johndoe/storage/meta/global": metaWBO.handler(),
+    "/1.1/johndoe/storage/steam": service_unavailable,
+  });
+  await setUp(server);
+
+  _("Disable engine locally.");
+  Service._ignorePrefObserver = true;
+  engine.enabled = true;
+  Service._ignorePrefObserver = false;
+  engine.enabled = false;
+
+  _("Sync.");
+  await Service.sync();
+  Assert.equal(Service.status.sync, SERVER_MAINTENANCE);
+
+  await Service.startOver();
+  await promiseStopServer(server);
+});
+
+add_task(async function test_enabledRemotely() {
+  enableValidationPrefs();
+
+  _("Test: Engine is disabled locally and enabled on a remote client");
+  Service.syncID = "abcdefghij";
+  let engine = Service.engineManager.get("steam");
+  let syncID = await engine.resetLocalSyncID();
+  let metaWBO = new ServerWBO("global", {
+    syncID: Service.syncID,
+    storageVersion: STORAGE_VERSION,
+    engines: { steam: { syncID, version: engine.version } },
+  });
+  let server = sync_httpd_setup({
+    "/1.1/johndoe/storage/meta/global": upd("meta", metaWBO.handler()),
+
+    "/1.1/johndoe/storage/steam": upd(
+      "steam",
+      new ServerWBO("steam", {}).handler()
+    ),
+  });
+  await setUp(server);
+
+  // We need to be very careful how we do this, so that we don't trigger a
+  // fresh start!
+  try {
+    _("Upload some keys to avoid a fresh start.");
+    let wbo = await Service.collectionKeys.generateNewKeysWBO();
+    await wbo.encrypt(Service.identity.syncKeyBundle);
+    Assert.equal(
+      200,
+      (await wbo.upload(Service.resource(Service.cryptoKeysURL))).status
+    );
+
+    _("Engine is disabled.");
+    Assert.ok(!engine.enabled);
+
+    _("Sync.");
+    await Service.sync();
+
+    _("Engine is enabled.");
+    Assert.ok(engine.enabled);
+
+    _("Meta record still present.");
+    Assert.equal(metaWBO.data.engines.steam.syncID, await engine.getSyncID());
+  } finally {
+    await Service.startOver();
+    await promiseStopServer(server);
+  }
+});
+
+add_task(async function test_disabledRemotelyTwoClients() {
+  enableValidationPrefs();
+
+  _(
+    "Test: Engine is enabled locally and disabled on a remote client... with two clients."
+  );
+  Service.syncID = "abcdefghij";
+  let engine = Service.engineManager.get("steam");
+  let metaWBO = new ServerWBO("global", {
+    syncID: Service.syncID,
+    storageVersion: STORAGE_VERSION,
+    engines: {},
+  });
+  let server = sync_httpd_setup({
+    "/1.1/johndoe/storage/meta/global": upd("meta", metaWBO.handler()),
+
+    "/1.1/johndoe/storage/steam": upd(
+      "steam",
+      new ServerWBO("steam", {}).handler()
+    ),
+  });
+  await setUp(server);
+
+  try {
+    _("Enable engine locally.");
+    Service._ignorePrefObserver = true;
+    engine.enabled = true;
+    Service._ignorePrefObserver = false;
+
+    _("Sync.");
+    await Service.sync();
+
+    _("Disable engine by deleting from meta/global.");
+    let d = metaWBO.data;
+    delete d.engines.steam;
+    metaWBO.payload = JSON.stringify(d);
+    metaWBO.modified = Date.now() / 1000;
+
+    _("Add a second client and verify that the local pref is changed.");
+    Service.clientsEngine._store._remoteClients.foobar = {
+      name: "foobar",
+      type: "desktop",
+    };
+    await Service.sync();
+
+    _("Engine is disabled.");
+    Assert.ok(!engine.enabled);
+  } finally {
+    await Service.startOver();
+    await promiseStopServer(server);
+  }
+});
+
+add_task(async function test_disabledRemotely() {
+  enableValidationPrefs();
+
+  _("Test: Engine is enabled locally and disabled on a remote client");
+  Service.syncID = "abcdefghij";
+  let engine = Service.engineManager.get("steam");
+  let metaWBO = new ServerWBO("global", {
+    syncID: Service.syncID,
+    storageVersion: STORAGE_VERSION,
+    engines: {},
+  });
+  let server = sync_httpd_setup({
+    "/1.1/johndoe/storage/meta/global": metaWBO.handler(),
+    "/1.1/johndoe/storage/steam": new ServerWBO("steam", {}).handler(),
+  });
+  await setUp(server);
+
+  try {
+    _("Enable engine locally.");
+    Service._ignorePrefObserver = true;
+    engine.enabled = true;
+    Service._ignorePrefObserver = false;
+
+    _("Sync.");
+    await Service.sync();
+
+    _("Engine is not disabled: only one client.");
+    Assert.ok(engine.enabled);
+  } finally {
+    await Service.startOver();
+    await promiseStopServer(server);
+  }
+});
+
+add_task(async function test_dependentEnginesEnabledLocally() {
+  enableValidationPrefs();
+
+  _("Test: Engine is disabled on remote clients and enabled locally");
+  Service.syncID = "abcdefghij";
+  let steamEngine = Service.engineManager.get("steam");
+  let stirlingEngine = Service.engineManager.get("stirling");
+  let metaWBO = new ServerWBO("global", {
+    syncID: Service.syncID,
+    storageVersion: STORAGE_VERSION,
+    engines: {},
+  });
+  let server = sync_httpd_setup({
+    "/1.1/johndoe/storage/meta/global": metaWBO.handler(),
+    "/1.1/johndoe/storage/steam": new ServerWBO("steam", {}).handler(),
+    "/1.1/johndoe/storage/stirling": new ServerWBO("stirling", {}).handler(),
+  });
+  await setUp(server);
+
+  try {
+    _("Enable engine locally. Doing it on one is enough.");
+    steamEngine.enabled = true;
+
+    _("Sync.");
+    await Service.sync();
+
+    _("Meta record now contains the new engines.");
+    Assert.ok(!!metaWBO.data.engines.steam);
+    Assert.ok(!!metaWBO.data.engines.stirling);
+
+    _("Engines continue to be enabled.");
+    Assert.ok(steamEngine.enabled);
+    Assert.ok(stirlingEngine.enabled);
+  } finally {
+    await Service.startOver();
+    await promiseStopServer(server);
+  }
+});
+
+add_task(async function test_dependentEnginesDisabledLocally() {
+  enableValidationPrefs();
+
+  _(
+    "Test: Two dependent engines are enabled on remote clients and disabled locally"
+  );
+  Service.syncID = "abcdefghij";
+  let steamEngine = Service.engineManager.get("steam");
+  let steamSyncID = await steamEngine.resetLocalSyncID();
+  let stirlingEngine = Service.engineManager.get("stirling");
+  let stirlingSyncID = await stirlingEngine.resetLocalSyncID();
+  let metaWBO = new ServerWBO("global", {
+    syncID: Service.syncID,
+    storageVersion: STORAGE_VERSION,
+    engines: {
+      steam: { syncID: steamSyncID, version: steamEngine.version },
+      stirling: { syncID: stirlingSyncID, version: stirlingEngine.version },
+    },
+  });
+
+  let steamCollection = new ServerWBO("steam", PAYLOAD);
+  let stirlingCollection = new ServerWBO("stirling", PAYLOAD);
+
+  let server = sync_httpd_setup({
+    "/1.1/johndoe/storage/meta/global": metaWBO.handler(),
+    "/1.1/johndoe/storage/steam": steamCollection.handler(),
+    "/1.1/johndoe/storage/stirling": stirlingCollection.handler(),
+  });
+  await setUp(server);
+
+  try {
+    _("Disable engines locally. Doing it on one is enough.");
+    Service._ignorePrefObserver = true;
+    steamEngine.enabled = true;
+    Assert.ok(stirlingEngine.enabled);
+    Service._ignorePrefObserver = false;
+    steamEngine.enabled = false;
+    Assert.ok(!stirlingEngine.enabled);
+
+    _("Sync.");
+    await Service.sync();
+
+    _("Meta record no longer contains engines.");
+    Assert.ok(!metaWBO.data.engines.steam);
+    Assert.ok(!metaWBO.data.engines.stirling);
+
+    _("Server records are wiped.");
+    Assert.equal(steamCollection.payload, undefined);
+    Assert.equal(stirlingCollection.payload, undefined);
+
+    _("Engines continue to be disabled.");
+    Assert.ok(!steamEngine.enabled);
+    Assert.ok(!stirlingEngine.enabled);
+  } finally {
+    await Service.startOver();
+    await promiseStopServer(server);
+  }
+});
+
+add_task(async function test_service_updateLocalEnginesState() {
+  Service.syncID = "abcdefghij";
+  const engine = Service.engineManager.get("steam");
+  const metaWBO = new ServerWBO("global", {
+    syncID: Service.syncID,
+    storageVersion: STORAGE_VERSION,
+    declined: ["steam"],
+    engines: {},
+  });
+  const server = httpd_setup({
+    "/1.1/johndoe/storage/meta/global": metaWBO.handler(),
+  });
+  await SyncTestingInfrastructure(server, "johndoe");
+
+  // Disconnect sync.
+  await Service.startOver();
+  Service._ignorePrefObserver = true;
+  // Steam engine is enabled on our machine.
+  engine.enabled = true;
+  Service._ignorePrefObserver = false;
+  Service.identity._findCluster = () => server.baseURI + "/1.1/johndoe/";
+
+  // Update engine state from the server.
+  await Service.updateLocalEnginesState();
+  // Now disabled.
+  Assert.ok(!engine.enabled);
+});
+
+add_task(async function test_service_enableAfterUpdateState() {
+  Service.syncID = "abcdefghij";
+  const engine = Service.engineManager.get("steam");
+  const metaWBO = new ServerWBO("global", {
+    syncID: Service.syncID,
+    storageVersion: STORAGE_VERSION,
+    declined: ["steam"],
+    engines: { someengine: {} },
+  });
+  const server = httpd_setup({
+    "/1.1/johndoe/storage/meta/global": metaWBO.handler(),
+  });
+  await SyncTestingInfrastructure(server, "johndoe");
+
+  // Disconnect sync.
+  await Service.startOver();
+  Service.identity._findCluster = () => server.baseURI + "/1.1/johndoe/";
+
+  // Update engine state from the server.
+  await Service.updateLocalEnginesState();
+  // Now disabled, reflecting what's on the server.
+  Assert.ok(!engine.enabled);
+  // Enable the engine, as though the user selected it via CWTS.
+  engine.enabled = true;
+
+  // Do the "reconcile local and remote states" dance.
+  let engineSync = new EngineSynchronizer(Service);
+  await engineSync._updateEnabledEngines();
+  await Service._maybeUpdateDeclined();
+  // engine should remain enabled.
+  Assert.ok(engine.enabled);
+  // engine should no longer appear in declined on the server.
+  Assert.deepEqual(metaWBO.data.declined, []);
+});
+
+add_task(async function test_service_disableAfterUpdateState() {
+  Service.syncID = "abcdefghij";
+  const engine = Service.engineManager.get("steam");
+  const metaWBO = new ServerWBO("global", {
+    syncID: Service.syncID,
+    storageVersion: STORAGE_VERSION,
+    declined: [],
+    engines: { steam: {} },
+  });
+  const server = httpd_setup({
+    "/1.1/johndoe/storage/meta/global": metaWBO.handler(),
+  });
+  await SyncTestingInfrastructure(server, "johndoe");
+
+  // Disconnect sync.
+  await Service.startOver();
+  Service.identity._findCluster = () => server.baseURI + "/1.1/johndoe/";
+
+  // Update engine state from the server.
+  await Service.updateLocalEnginesState();
+  // Now enabled, reflecting what's on the server.
+  Assert.ok(engine.enabled);
+  // Disable the engine, as though via CWTS.
+  engine.enabled = false;
+
+  // Do the "reconcile local and remote states" dance.
+  let engineSync = new EngineSynchronizer(Service);
+  await engineSync._updateEnabledEngines();
+  await Service._maybeUpdateDeclined();
+  // engine should remain disabled.
+  Assert.ok(!engine.enabled);
+  // engine should now appear in declined on the server.
+  Assert.deepEqual(metaWBO.data.declined, ["steam"]);
+  // and should have been removed from engines.
+  Assert.deepEqual(metaWBO.data.engines, {});
+});
+
+add_task(async function test_service_updateLocalEnginesState_no_meta_global() {
+  Service.syncID = "abcdefghij";
+  const engine = Service.engineManager.get("steam");
+  // The server doesn't contain /meta/global (sync was never enabled).
+  const server = httpd_setup({});
+  await SyncTestingInfrastructure(server, "johndoe");
+
+  // Disconnect sync.
+  await Service.startOver();
+  Service._ignorePrefObserver = true;
+  // Steam engine is enabled on our machine.
+  engine.enabled = true;
+  Service._ignorePrefObserver = false;
+  Service.identity._findCluster = () => server.baseURI + "/1.1/johndoe/";
+
+  // Update engine state from the server.
+  await Service.updateLocalEnginesState();
+  // Still enabled.
+  Assert.ok(engine.enabled);
+});
diff --git a/src/zen/tests/mochitests/sync/test_service_verifyLogin.js b/src/zen/tests/mochitests/sync/test_service_verifyLogin.js
new file mode 100644
index 000000000..af1489cca
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_service_verifyLogin.js
@@ -0,0 +1,115 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+function login_handling(handler) {
+  return function (request, response) {
+    if (has_hawk_header(request)) {
+      handler(request, response);
+    } else {
+      let body = "Unauthorized";
+      response.setStatusLine(request.httpVersion, 401, "Unauthorized");
+      response.bodyOutputStream.write(body, body.length);
+    }
+  };
+}
+
+function service_unavailable(request, response) {
+  let body = "Service Unavailable";
+  response.setStatusLine(request.httpVersion, 503, "Service Unavailable");
+  response.setHeader("Retry-After", "42");
+  response.bodyOutputStream.write(body, body.length);
+}
+
+function run_test() {
+  Log.repository.rootLogger.addAppender(new Log.DumpAppender());
+
+  run_next_test();
+}
+
+add_task(async function test_verifyLogin() {
+  // This test expects a clean slate -- no saved passphrase.
+  await Services.logins.removeAllUserFacingLoginsAsync();
+  let johnHelper = track_collections_helper();
+  let johnU = johnHelper.with_updated_collection;
+
+  do_test_pending();
+
+  let server = httpd_setup({
+    "/1.1/johndoe/info/collections": login_handling(johnHelper.handler),
+    "/1.1/janedoe/info/collections": service_unavailable,
+
+    "/1.1/johndoe/storage/crypto/keys": johnU(
+      "crypto",
+      new ServerWBO("keys").handler()
+    ),
+    "/1.1/johndoe/storage/meta/global": johnU(
+      "meta",
+      new ServerWBO("global").handler()
+    ),
+  });
+
+  try {
+    _("Force the initial state.");
+    Service.status.service = STATUS_OK;
+    Assert.equal(Service.status.service, STATUS_OK);
+
+    _("Credentials won't check out because we're not configured yet.");
+    Service.status.resetSync();
+    Assert.equal(false, await Service.verifyLogin());
+    Assert.equal(Service.status.service, CLIENT_NOT_CONFIGURED);
+    Assert.equal(Service.status.login, LOGIN_FAILED_NO_USERNAME);
+
+    _("Success if syncBundleKey is set.");
+    Service.status.resetSync();
+    await configureIdentity({ username: "johndoe" }, server);
+    Assert.ok(await Service.verifyLogin());
+    Assert.equal(Service.status.service, STATUS_OK);
+    Assert.equal(Service.status.login, LOGIN_SUCCEEDED);
+
+    _(
+      "If verifyLogin() encounters a server error, it flips on the backoff flag and notifies observers on a 503 with Retry-After."
+    );
+    Service.status.resetSync();
+    await configureIdentity({ username: "janedoe" }, server);
+    Service._updateCachedURLs();
+    Assert.ok(!Service.status.enforceBackoff);
+    let backoffInterval;
+    Svc.Obs.add("weave:service:backoff:interval", function observe(subject) {
+      Svc.Obs.remove("weave:service:backoff:interval", observe);
+      backoffInterval = subject;
+    });
+    Assert.equal(false, await Service.verifyLogin());
+    Assert.ok(Service.status.enforceBackoff);
+    Assert.equal(backoffInterval, 42);
+    Assert.equal(Service.status.service, LOGIN_FAILED);
+    Assert.equal(Service.status.login, SERVER_MAINTENANCE);
+
+    _(
+      "Ensure a network error when finding the cluster sets the right Status bits."
+    );
+    Service.status.resetSync();
+    Service.clusterURL = "";
+    Service.identity._findCluster = () => "http://localhost:12345/";
+    Assert.equal(false, await Service.verifyLogin());
+    Assert.equal(Service.status.service, LOGIN_FAILED);
+    Assert.equal(Service.status.login, LOGIN_FAILED_NETWORK_ERROR);
+
+    _(
+      "Ensure a network error when getting the collection info sets the right Status bits."
+    );
+    Service.status.resetSync();
+    Service.clusterURL = "http://localhost:12345/";
+    Assert.equal(false, await Service.verifyLogin());
+    Assert.equal(Service.status.service, LOGIN_FAILED);
+    Assert.equal(Service.status.login, LOGIN_FAILED_NETWORK_ERROR);
+  } finally {
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+    server.stop(do_test_finished);
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_service_wipeClient.js b/src/zen/tests/mochitests/sync/test_service_wipeClient.js
new file mode 100644
index 000000000..aa48868ca
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_service_wipeClient.js
@@ -0,0 +1,78 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+function CanDecryptEngine() {
+  SyncEngine.call(this, "CanDecrypt", Service);
+}
+CanDecryptEngine.prototype = {
+  // Override these methods with mocks for the test
+  async canDecrypt() {
+    return true;
+  },
+
+  wasWiped: false,
+  async wipeClient() {
+    this.wasWiped = true;
+  },
+};
+Object.setPrototypeOf(CanDecryptEngine.prototype, SyncEngine.prototype);
+
+function CannotDecryptEngine() {
+  SyncEngine.call(this, "CannotDecrypt", Service);
+}
+CannotDecryptEngine.prototype = {
+  // Override these methods with mocks for the test
+  async canDecrypt() {
+    return false;
+  },
+
+  wasWiped: false,
+  async wipeClient() {
+    this.wasWiped = true;
+  },
+};
+Object.setPrototypeOf(CannotDecryptEngine.prototype, SyncEngine.prototype);
+
+let canDecryptEngine;
+let cannotDecryptEngine;
+
+add_task(async function setup() {
+  await Service.engineManager.clear();
+
+  await Service.engineManager.register(CanDecryptEngine);
+  await Service.engineManager.register(CannotDecryptEngine);
+  canDecryptEngine = Service.engineManager.get("candecrypt");
+  cannotDecryptEngine = Service.engineManager.get("cannotdecrypt");
+});
+
+add_task(async function test_withEngineList() {
+  try {
+    _("Ensure initial scenario.");
+    Assert.ok(!canDecryptEngine.wasWiped);
+    Assert.ok(!cannotDecryptEngine.wasWiped);
+
+    _("Wipe local engine data.");
+    await Service.wipeClient(["candecrypt", "cannotdecrypt"]);
+
+    _("Ensure only the engine that can decrypt was wiped.");
+    Assert.ok(canDecryptEngine.wasWiped);
+    Assert.ok(!cannotDecryptEngine.wasWiped);
+  } finally {
+    canDecryptEngine.wasWiped = false;
+    cannotDecryptEngine.wasWiped = false;
+    await Service.startOver();
+  }
+});
+
+add_task(async function test_startOver_clears_keys() {
+  syncTestLogging();
+  await generateNewKeys(Service.collectionKeys);
+  Assert.ok(!!Service.collectionKeys.keyForCollection());
+  await Service.startOver();
+  syncTestLogging();
+  Assert.ok(!Service.collectionKeys.keyForCollection());
+});
diff --git a/src/zen/tests/mochitests/sync/test_service_wipeServer.js b/src/zen/tests/mochitests/sync/test_service_wipeServer.js
new file mode 100644
index 000000000..9fc2592aa
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_service_wipeServer.js
@@ -0,0 +1,240 @@
+Svc.PrefBranch.setStringPref("registerEngines", "");
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+// configure the identity we use for this test.
+const identityConfig = makeIdentityConfig({ username: "johndoe" });
+
+function FakeCollection() {
+  this.deleted = false;
+}
+FakeCollection.prototype = {
+  handler() {
+    let self = this;
+    return function (request, response) {
+      let body = "";
+      self.timestamp = new_timestamp();
+      let timestamp = "" + self.timestamp;
+      if (request.method == "DELETE") {
+        body = timestamp;
+        self.deleted = true;
+      }
+      response.setHeader("X-Weave-Timestamp", timestamp);
+      response.setStatusLine(request.httpVersion, 200, "OK");
+      response.bodyOutputStream.write(body, body.length);
+    };
+  },
+};
+
+async function setUpTestFixtures(server) {
+  Service.clusterURL = server.baseURI + "/";
+
+  await configureIdentity(identityConfig);
+}
+
+add_task(async function test_wipeServer_list_success() {
+  _("Service.wipeServer() deletes collections given as argument.");
+
+  let steam_coll = new FakeCollection();
+  let diesel_coll = new FakeCollection();
+
+  let server = httpd_setup({
+    "/1.1/johndoe/storage/steam": steam_coll.handler(),
+    "/1.1/johndoe/storage/diesel": diesel_coll.handler(),
+    "/1.1/johndoe/storage/petrol": httpd_handler(404, "Not Found"),
+  });
+
+  try {
+    await setUpTestFixtures(server);
+    await SyncTestingInfrastructure(server, "johndoe", "irrelevant");
+
+    _("Confirm initial environment.");
+    Assert.ok(!steam_coll.deleted);
+    Assert.ok(!diesel_coll.deleted);
+
+    _(
+      "wipeServer() will happily ignore the non-existent collection and use the timestamp of the last DELETE that was successful."
+    );
+    let timestamp = await Service.wipeServer(["steam", "diesel", "petrol"]);
+    Assert.equal(timestamp, diesel_coll.timestamp);
+
+    _(
+      "wipeServer stopped deleting after encountering an error with the 'petrol' collection, thus only 'steam' has been deleted."
+    );
+    Assert.ok(steam_coll.deleted);
+    Assert.ok(diesel_coll.deleted);
+  } finally {
+    await promiseStopServer(server);
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+  }
+});
+
+add_task(async function test_wipeServer_list_503() {
+  _("Service.wipeServer() deletes collections given as argument.");
+
+  let steam_coll = new FakeCollection();
+  let diesel_coll = new FakeCollection();
+
+  let server = httpd_setup({
+    "/1.1/johndoe/storage/steam": steam_coll.handler(),
+    "/1.1/johndoe/storage/petrol": httpd_handler(503, "Service Unavailable"),
+    "/1.1/johndoe/storage/diesel": diesel_coll.handler(),
+  });
+
+  try {
+    await setUpTestFixtures(server);
+    await SyncTestingInfrastructure(server, "johndoe", "irrelevant");
+
+    _("Confirm initial environment.");
+    Assert.ok(!steam_coll.deleted);
+    Assert.ok(!diesel_coll.deleted);
+
+    _(
+      "wipeServer() will happily ignore the non-existent collection, delete the 'steam' collection and abort after an receiving an error on the 'petrol' collection."
+    );
+    let error;
+    try {
+      await Service.wipeServer(["non-existent", "steam", "petrol", "diesel"]);
+      do_throw("Should have thrown!");
+    } catch (ex) {
+      error = ex;
+    }
+    _("wipeServer() threw this exception: " + error);
+    Assert.equal(error.status, 503);
+
+    _(
+      "wipeServer stopped deleting after encountering an error with the 'petrol' collection, thus only 'steam' has been deleted."
+    );
+    Assert.ok(steam_coll.deleted);
+    Assert.ok(!diesel_coll.deleted);
+  } finally {
+    await promiseStopServer(server);
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+  }
+});
+
+add_task(async function test_wipeServer_all_success() {
+  _("Service.wipeServer() deletes all the things.");
+
+  /**
+   * Handle the bulk DELETE request sent by wipeServer.
+   */
+  let deleted = false;
+  let serverTimestamp;
+  function storageHandler(request, response) {
+    Assert.equal("DELETE", request.method);
+    Assert.ok(request.hasHeader("X-Confirm-Delete"));
+    deleted = true;
+    serverTimestamp = return_timestamp(request, response);
+  }
+
+  let server = httpd_setup({
+    "/1.1/johndoe/storage": storageHandler,
+  });
+  await setUpTestFixtures(server);
+
+  _("Try deletion.");
+  await SyncTestingInfrastructure(server, "johndoe", "irrelevant");
+  let returnedTimestamp = await Service.wipeServer();
+  Assert.ok(deleted);
+  Assert.equal(returnedTimestamp, serverTimestamp);
+
+  await promiseStopServer(server);
+  for (const pref of Svc.PrefBranch.getChildList("")) {
+    Svc.PrefBranch.clearUserPref(pref);
+  }
+});
+
+add_task(async function test_wipeServer_all_404() {
+  _("Service.wipeServer() accepts a 404.");
+
+  /**
+   * Handle the bulk DELETE request sent by wipeServer. Returns a 404.
+   */
+  let deleted = false;
+  let serverTimestamp;
+  function storageHandler(request, response) {
+    Assert.equal("DELETE", request.method);
+    Assert.ok(request.hasHeader("X-Confirm-Delete"));
+    deleted = true;
+    serverTimestamp = new_timestamp();
+    response.setHeader("X-Weave-Timestamp", "" + serverTimestamp);
+    response.setStatusLine(request.httpVersion, 404, "Not Found");
+  }
+
+  let server = httpd_setup({
+    "/1.1/johndoe/storage": storageHandler,
+  });
+  await setUpTestFixtures(server);
+
+  _("Try deletion.");
+  await SyncTestingInfrastructure(server, "johndoe", "irrelevant");
+  let returnedTimestamp = await Service.wipeServer();
+  Assert.ok(deleted);
+  Assert.equal(returnedTimestamp, serverTimestamp);
+
+  await promiseStopServer(server);
+  for (const pref of Svc.PrefBranch.getChildList("")) {
+    Svc.PrefBranch.clearUserPref(pref);
+  }
+});
+
+add_task(async function test_wipeServer_all_503() {
+  _("Service.wipeServer() throws if it encounters a non-200/404 response.");
+
+  /**
+   * Handle the bulk DELETE request sent by wipeServer. Returns a 503.
+   */
+  function storageHandler(request, response) {
+    Assert.equal("DELETE", request.method);
+    Assert.ok(request.hasHeader("X-Confirm-Delete"));
+    response.setStatusLine(request.httpVersion, 503, "Service Unavailable");
+  }
+
+  let server = httpd_setup({
+    "/1.1/johndoe/storage": storageHandler,
+  });
+  await setUpTestFixtures(server);
+
+  _("Try deletion.");
+  let error;
+  try {
+    await SyncTestingInfrastructure(server, "johndoe", "irrelevant");
+    await Service.wipeServer();
+    do_throw("Should have thrown!");
+  } catch (ex) {
+    error = ex;
+  }
+  Assert.equal(error.status, 503);
+
+  await promiseStopServer(server);
+  for (const pref of Svc.PrefBranch.getChildList("")) {
+    Svc.PrefBranch.clearUserPref(pref);
+  }
+});
+
+add_task(async function test_wipeServer_all_connectionRefused() {
+  _("Service.wipeServer() throws if it encounters a network problem.");
+  let server = httpd_setup({});
+  await setUpTestFixtures(server);
+
+  Service.clusterURL = "http://localhost:4352/";
+
+  _("Try deletion.");
+  try {
+    await Service.wipeServer();
+    do_throw("Should have thrown!");
+  } catch (ex) {
+    Assert.equal(ex.result, Cr.NS_ERROR_CONNECTION_REFUSED);
+  }
+
+  for (const pref of Svc.PrefBranch.getChildList("")) {
+    Svc.PrefBranch.clearUserPref(pref);
+  }
+  await promiseStopServer(server);
+});
diff --git a/src/zen/tests/mochitests/sync/test_status.js b/src/zen/tests/mochitests/sync/test_status.js
new file mode 100644
index 000000000..5bcfa182c
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_status.js
@@ -0,0 +1,83 @@
+const { Status } = ChromeUtils.importESModule(
+  "resource://services-sync/status.sys.mjs"
+);
+
+function run_test() {
+  // Check initial states
+  Assert.ok(!Status.enforceBackoff);
+  Assert.equal(Status.backoffInterval, 0);
+  Assert.equal(Status.minimumNextSync, 0);
+
+  Assert.equal(Status.service, STATUS_OK);
+  Assert.equal(Status.sync, SYNC_SUCCEEDED);
+  Assert.equal(Status.login, LOGIN_SUCCEEDED);
+  if (Status.engines.length) {
+    do_throw("Status.engines should be empty.");
+  }
+  Assert.equal(Status.partial, false);
+
+  // Check login status
+  for (let code of [LOGIN_FAILED_NO_USERNAME, LOGIN_FAILED_NO_PASSPHRASE]) {
+    Status.login = code;
+    Assert.equal(Status.login, code);
+    Assert.equal(Status.service, CLIENT_NOT_CONFIGURED);
+    Status.resetSync();
+  }
+
+  Status.login = LOGIN_FAILED;
+  Assert.equal(Status.login, LOGIN_FAILED);
+  Assert.equal(Status.service, LOGIN_FAILED);
+  Status.resetSync();
+
+  Status.login = LOGIN_SUCCEEDED;
+  Assert.equal(Status.login, LOGIN_SUCCEEDED);
+  Assert.equal(Status.service, STATUS_OK);
+  Status.resetSync();
+
+  // Check sync status
+  Status.sync = SYNC_FAILED;
+  Assert.equal(Status.sync, SYNC_FAILED);
+  Assert.equal(Status.service, SYNC_FAILED);
+
+  Status.sync = SYNC_SUCCEEDED;
+  Assert.equal(Status.sync, SYNC_SUCCEEDED);
+  Assert.equal(Status.service, STATUS_OK);
+
+  Status.resetSync();
+
+  // Check engine status
+  Status.engines = ["testEng1", ENGINE_SUCCEEDED];
+  Assert.equal(Status.engines.testEng1, ENGINE_SUCCEEDED);
+  Assert.equal(Status.service, STATUS_OK);
+
+  Status.engines = ["testEng2", ENGINE_DOWNLOAD_FAIL];
+  Assert.equal(Status.engines.testEng1, ENGINE_SUCCEEDED);
+  Assert.equal(Status.engines.testEng2, ENGINE_DOWNLOAD_FAIL);
+  Assert.equal(Status.service, SYNC_FAILED_PARTIAL);
+
+  Status.engines = ["testEng3", ENGINE_SUCCEEDED];
+  Assert.equal(Status.engines.testEng1, ENGINE_SUCCEEDED);
+  Assert.equal(Status.engines.testEng2, ENGINE_DOWNLOAD_FAIL);
+  Assert.equal(Status.engines.testEng3, ENGINE_SUCCEEDED);
+  Assert.equal(Status.service, SYNC_FAILED_PARTIAL);
+
+  // Check resetSync
+  Status.sync = SYNC_FAILED;
+  Status.resetSync();
+
+  Assert.equal(Status.service, STATUS_OK);
+  Assert.equal(Status.sync, SYNC_SUCCEEDED);
+  if (Status.engines.length) {
+    do_throw("Status.engines should be empty.");
+  }
+
+  // Check resetBackoff
+  Status.enforceBackoff = true;
+  Status.backOffInterval = 4815162342;
+  Status.backOffInterval = 42;
+  Status.resetBackoff();
+
+  Assert.ok(!Status.enforceBackoff);
+  Assert.equal(Status.backoffInterval, 0);
+  Assert.equal(Status.minimumNextSync, 0);
+}
diff --git a/src/zen/tests/mochitests/sync/test_status_checkSetup.js b/src/zen/tests/mochitests/sync/test_status_checkSetup.js
new file mode 100644
index 000000000..fe3e7cad8
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_status_checkSetup.js
@@ -0,0 +1,26 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Status } = ChromeUtils.importESModule(
+  "resource://services-sync/status.sys.mjs"
+);
+
+add_task(async function test_status_checkSetup() {
+  try {
+    _("Fresh setup, we're not configured.");
+    Assert.equal(Status.checkSetup(), CLIENT_NOT_CONFIGURED);
+    Assert.equal(Status.login, LOGIN_FAILED_NO_USERNAME);
+    Status.resetSync();
+
+    _("Let's provide the syncKeyBundle");
+    await configureIdentity();
+
+    _("checkSetup()");
+    Assert.equal(Status.checkSetup(), STATUS_OK);
+    Status.resetSync();
+  } finally {
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_sync_auth_manager.js b/src/zen/tests/mochitests/sync/test_sync_auth_manager.js
new file mode 100644
index 000000000..2e69ae6b5
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_sync_auth_manager.js
@@ -0,0 +1,810 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { AuthenticationError, SyncAuthManager } = ChromeUtils.importESModule(
+  "resource://services-sync/sync_auth.sys.mjs"
+);
+const { Resource } = ChromeUtils.importESModule(
+  "resource://services-sync/resource.sys.mjs"
+);
+const { initializeIdentityWithTokenServerResponse } =
+  ChromeUtils.importESModule(
+    "resource://testing-common/services/sync/fxa_utils.sys.mjs"
+  );
+const { HawkClient } = ChromeUtils.importESModule(
+  "resource://services-common/hawkclient.sys.mjs"
+);
+const { FxAccounts } = ChromeUtils.importESModule(
+  "resource://gre/modules/FxAccounts.sys.mjs"
+);
+const { FxAccountsClient } = ChromeUtils.importESModule(
+  "resource://gre/modules/FxAccountsClient.sys.mjs"
+);
+const { ERRNO_INVALID_AUTH_TOKEN, SCOPE_APP_SYNC } = ChromeUtils.importESModule(
+  "resource://gre/modules/FxAccountsCommon.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { Status } = ChromeUtils.importESModule(
+  "resource://services-sync/status.sys.mjs"
+);
+const { TokenServerClient, TokenServerClientServerError } =
+  ChromeUtils.importESModule(
+    "resource://services-common/tokenserverclient.sys.mjs"
+  );
+const { AccountState, ERROR_INVALID_ACCOUNT_STATE } =
+  ChromeUtils.importESModule("resource://gre/modules/FxAccounts.sys.mjs");
+
+const SECOND_MS = 1000;
+const MINUTE_MS = SECOND_MS * 60;
+const HOUR_MS = MINUTE_MS * 60;
+
+const MOCK_ACCESS_TOKEN =
+  "e3c5caf17f27a0d9e351926a928938b3737df43e91d4992a5a5fca9a7bdef8ba";
+
+var globalIdentityConfig = makeIdentityConfig();
+var globalSyncAuthManager = new SyncAuthManager();
+configureFxAccountIdentity(globalSyncAuthManager, globalIdentityConfig);
+
+/**
+ * Mock client clock and skew vs server in FxAccounts signed-in user module and
+ * API client.  sync_auth.js queries these values to construct HAWK
+ * headers.  We will use this to test clock skew compensation in these headers
+ * below.
+ */
+var MockFxAccountsClient = function () {
+  FxAccountsClient.apply(this);
+};
+MockFxAccountsClient.prototype = {
+  accountStatus() {
+    return Promise.resolve(true);
+  },
+  getScopedKeyData() {
+    return Promise.resolve({
+      [SCOPE_APP_SYNC]: {
+        identifier: SCOPE_APP_SYNC,
+        keyRotationSecret:
+          "0000000000000000000000000000000000000000000000000000000000000000",
+        keyRotationTimestamp: 1234567890123,
+      },
+    });
+  },
+};
+Object.setPrototypeOf(
+  MockFxAccountsClient.prototype,
+  FxAccountsClient.prototype
+);
+
+add_test(function test_initial_state() {
+  _("Verify initial state");
+  Assert.ok(!globalSyncAuthManager._token);
+  Assert.ok(!globalSyncAuthManager._hasValidToken());
+  run_next_test();
+});
+
+add_task(async function test_initialialize() {
+  _("Verify start after fetching token");
+  await globalSyncAuthManager._ensureValidToken();
+  Assert.ok(!!globalSyncAuthManager._token);
+  Assert.ok(globalSyncAuthManager._hasValidToken());
+});
+
+add_task(async function test_refreshOAuthTokenOn401() {
+  _("Refreshes the FXA OAuth token after a 401.");
+  let getTokenCount = 0;
+  let syncAuthManager = new SyncAuthManager();
+  let identityConfig = makeIdentityConfig();
+  let fxaInternal = makeFxAccountsInternalMock(identityConfig);
+  configureFxAccountIdentity(syncAuthManager, identityConfig, fxaInternal);
+  syncAuthManager._fxaService._internal.initialize();
+  syncAuthManager._fxaService.getOAuthToken = () => {
+    ++getTokenCount;
+    return Promise.resolve(MOCK_ACCESS_TOKEN);
+  };
+
+  let didReturn401 = false;
+  let didReturn200 = false;
+  let mockTSC = mockTokenServer(() => {
+    if (getTokenCount <= 1) {
+      didReturn401 = true;
+      return {
+        status: 401,
+        headers: { "content-type": "application/json" },
+        body: JSON.stringify({}),
+      };
+    }
+    didReturn200 = true;
+    return {
+      status: 200,
+      headers: { "content-type": "application/json" },
+      body: JSON.stringify({
+        id: "id",
+        key: "key",
+        api_endpoint: "http://example.com/",
+        uid: "uid",
+        duration: 300,
+      }),
+    };
+  });
+
+  syncAuthManager._tokenServerClient = mockTSC;
+
+  await syncAuthManager._ensureValidToken();
+
+  Assert.equal(getTokenCount, 2);
+  Assert.ok(didReturn401);
+  Assert.ok(didReturn200);
+  Assert.ok(syncAuthManager._token);
+  Assert.ok(syncAuthManager._hasValidToken());
+});
+
+add_task(async function test_initialializeWithAuthErrorAndDeletedAccount() {
+  _("Verify sync state with auth error + account deleted");
+
+  var identityConfig = makeIdentityConfig();
+  var syncAuthManager = new SyncAuthManager();
+
+  // Use the real `getOAuthToken` method that calls
+  // `mockFxAClient.accessTokenWithSessionToken`.
+  let fxaInternal = makeFxAccountsInternalMock(identityConfig);
+  delete fxaInternal.getOAuthToken;
+
+  configureFxAccountIdentity(syncAuthManager, identityConfig, fxaInternal);
+  syncAuthManager._fxaService._internal.initialize();
+
+  let accessTokenWithSessionTokenCalled = false;
+  let accountStatusCalled = false;
+  let sessionStatusCalled = false;
+
+  let AuthErrorMockFxAClient = function () {
+    FxAccountsClient.apply(this);
+  };
+  AuthErrorMockFxAClient.prototype = {
+    accessTokenWithSessionToken() {
+      accessTokenWithSessionTokenCalled = true;
+      return Promise.reject({
+        code: 401,
+        errno: ERRNO_INVALID_AUTH_TOKEN,
+      });
+    },
+    accountStatus() {
+      accountStatusCalled = true;
+      return Promise.resolve(false);
+    },
+    sessionStatus() {
+      sessionStatusCalled = true;
+      return Promise.resolve(false);
+    },
+  };
+  Object.setPrototypeOf(
+    AuthErrorMockFxAClient.prototype,
+    FxAccountsClient.prototype
+  );
+
+  let mockFxAClient = new AuthErrorMockFxAClient();
+  syncAuthManager._fxaService._internal._fxAccountsClient = mockFxAClient;
+
+  await Assert.rejects(
+    syncAuthManager._ensureValidToken(),
+    err => {
+      Assert.equal(err.message, ERROR_INVALID_ACCOUNT_STATE);
+      return true; // expected error
+    },
+    "should reject because the account was deleted"
+  );
+
+  Assert.ok(accessTokenWithSessionTokenCalled);
+  Assert.ok(sessionStatusCalled);
+  Assert.ok(accountStatusCalled);
+  Assert.ok(!syncAuthManager._token);
+  Assert.ok(!syncAuthManager._hasValidToken());
+});
+
+add_task(async function test_getResourceAuthenticator() {
+  _(
+    "SyncAuthManager supplies a Resource Authenticator callback which returns a Hawk header."
+  );
+  configureFxAccountIdentity(globalSyncAuthManager);
+  let authenticator = globalSyncAuthManager.getResourceAuthenticator();
+  Assert.ok(!!authenticator);
+  let req = {
+    uri: CommonUtils.makeURI("https://example.net/somewhere/over/the/rainbow"),
+    method: "GET",
+  };
+  let output = await authenticator(req, "GET");
+  Assert.ok("headers" in output);
+  Assert.ok("authorization" in output.headers);
+  Assert.ok(output.headers.authorization.startsWith("Hawk"));
+  _("Expected internal state after successful call.");
+  Assert.equal(
+    globalSyncAuthManager._token.uid,
+    globalIdentityConfig.fxaccount.token.uid
+  );
+});
+
+add_task(async function test_resourceAuthenticatorSkew() {
+  _(
+    "SyncAuthManager Resource Authenticator compensates for clock skew in Hawk header."
+  );
+
+  // Clock is skewed 12 hours into the future
+  // We pick a date in the past so we don't risk concealing bugs in code that
+  // uses new Date() instead of our given date.
+  let now =
+    new Date("Fri Apr 09 2004 00:00:00 GMT-0700").valueOf() + 12 * HOUR_MS;
+  let syncAuthManager = new SyncAuthManager();
+  let hawkClient = new HawkClient("https://example.net/v1", "/foo");
+
+  // mock fxa hawk client skew
+  hawkClient.now = function () {
+    dump("mocked client now: " + now + "\n");
+    return now;
+  };
+  // Imagine there's already been one fxa request and the hawk client has
+  // already detected skew vs the fxa auth server.
+  let localtimeOffsetMsec = -1 * 12 * HOUR_MS;
+  hawkClient._localtimeOffsetMsec = localtimeOffsetMsec;
+
+  let fxaClient = new MockFxAccountsClient();
+  fxaClient.hawk = hawkClient;
+
+  // Sanity check
+  Assert.equal(hawkClient.now(), now);
+  Assert.equal(hawkClient.localtimeOffsetMsec, localtimeOffsetMsec);
+
+  // Properly picked up by the client
+  Assert.equal(fxaClient.now(), now);
+  Assert.equal(fxaClient.localtimeOffsetMsec, localtimeOffsetMsec);
+
+  let identityConfig = makeIdentityConfig();
+  let fxaInternal = makeFxAccountsInternalMock(identityConfig);
+  fxaInternal._now_is = now;
+  fxaInternal.fxAccountsClient = fxaClient;
+
+  // Mocks within mocks...
+  configureFxAccountIdentity(
+    syncAuthManager,
+    globalIdentityConfig,
+    fxaInternal
+  );
+
+  Assert.equal(syncAuthManager._fxaService._internal.now(), now);
+  Assert.equal(
+    syncAuthManager._fxaService._internal.localtimeOffsetMsec,
+    localtimeOffsetMsec
+  );
+
+  Assert.equal(syncAuthManager._fxaService._internal.now(), now);
+  Assert.equal(
+    syncAuthManager._fxaService._internal.localtimeOffsetMsec,
+    localtimeOffsetMsec
+  );
+
+  let request = new Resource("https://example.net/i/like/pie/");
+  let authenticator = syncAuthManager.getResourceAuthenticator();
+  let output = await authenticator(request, "GET");
+  dump("output" + JSON.stringify(output));
+  let authHeader = output.headers.authorization;
+  Assert.ok(authHeader.startsWith("Hawk"));
+
+  // Skew correction is applied in the header and we're within the two-minute
+  // window.
+  Assert.equal(getTimestamp(authHeader), now - 12 * HOUR_MS);
+  Assert.less(getTimestampDelta(authHeader, now) - 12 * HOUR_MS, 2 * MINUTE_MS);
+});
+
+add_task(async function test_RESTResourceAuthenticatorSkew() {
+  _(
+    "SyncAuthManager REST Resource Authenticator compensates for clock skew in Hawk header."
+  );
+
+  // Clock is skewed 12 hours into the future from our arbitary date
+  let now =
+    new Date("Fri Apr 09 2004 00:00:00 GMT-0700").valueOf() + 12 * HOUR_MS;
+  let syncAuthManager = new SyncAuthManager();
+  let hawkClient = new HawkClient("https://example.net/v1", "/foo");
+
+  // mock fxa hawk client skew
+  hawkClient.now = function () {
+    return now;
+  };
+  // Imagine there's already been one fxa request and the hawk client has
+  // already detected skew vs the fxa auth server.
+  hawkClient._localtimeOffsetMsec = -1 * 12 * HOUR_MS;
+
+  let fxaClient = new MockFxAccountsClient();
+  fxaClient.hawk = hawkClient;
+
+  let identityConfig = makeIdentityConfig();
+  let fxaInternal = makeFxAccountsInternalMock(identityConfig);
+  fxaInternal._now_is = now;
+  fxaInternal.fxAccountsClient = fxaClient;
+
+  configureFxAccountIdentity(
+    syncAuthManager,
+    globalIdentityConfig,
+    fxaInternal
+  );
+
+  Assert.equal(syncAuthManager._fxaService._internal.now(), now);
+
+  let request = new Resource("https://example.net/i/like/pie/");
+  let authenticator = syncAuthManager.getResourceAuthenticator();
+  let output = await authenticator(request, "GET");
+  dump("output" + JSON.stringify(output));
+  let authHeader = output.headers.authorization;
+  Assert.ok(authHeader.startsWith("Hawk"));
+
+  // Skew correction is applied in the header and we're within the two-minute
+  // window.
+  Assert.equal(getTimestamp(authHeader), now - 12 * HOUR_MS);
+  Assert.less(getTimestampDelta(authHeader, now) - 12 * HOUR_MS, 2 * MINUTE_MS);
+});
+
+add_task(async function test_ensureLoggedIn() {
+  configureFxAccountIdentity(globalSyncAuthManager);
+  await globalSyncAuthManager._ensureValidToken();
+  Assert.equal(Status.login, LOGIN_SUCCEEDED, "original initialize worked");
+  Assert.ok(globalSyncAuthManager._token);
+
+  // arrange for no logged in user.
+  let fxa = globalSyncAuthManager._fxaService;
+  let signedInUser =
+    fxa._internal.currentAccountState.storageManager.accountData;
+  fxa._internal.currentAccountState.storageManager.accountData = null;
+  await Assert.rejects(
+    globalSyncAuthManager._ensureValidToken(true),
+    /no user is logged in/,
+    "expecting rejection due to no user"
+  );
+  // Restore the logged in user to what it was.
+  fxa._internal.currentAccountState.storageManager.accountData = signedInUser;
+  Status.login = LOGIN_FAILED_LOGIN_REJECTED;
+  await globalSyncAuthManager._ensureValidToken(true);
+  Assert.equal(Status.login, LOGIN_SUCCEEDED, "final ensureLoggedIn worked");
+});
+
+add_task(async function test_tokenExpiration() {
+  _("SyncAuthManager notices token expiration:");
+  let bimExp = new SyncAuthManager();
+  configureFxAccountIdentity(bimExp, globalIdentityConfig);
+
+  let authenticator = bimExp.getResourceAuthenticator();
+  Assert.ok(!!authenticator);
+  let req = {
+    uri: CommonUtils.makeURI("https://example.net/somewhere/over/the/rainbow"),
+    method: "GET",
+  };
+  await authenticator(req, "GET");
+
+  // Mock the clock.
+  _("Forcing the token to expire ...");
+  Object.defineProperty(bimExp, "_now", {
+    value: function customNow() {
+      return Date.now() + 3000001;
+    },
+    writable: true,
+  });
+  Assert.less(bimExp._token.expiration, bimExp._now());
+  _("... means SyncAuthManager knows to re-fetch it on the next call.");
+  Assert.ok(!bimExp._hasValidToken());
+});
+
+add_task(async function test_getTokenErrors() {
+  _("SyncAuthManager correctly handles various failures to get a token.");
+
+  _("Arrange for a 401 - Sync should reflect an auth error.");
+  initializeIdentityWithTokenServerResponse({
+    status: 401,
+    headers: { "content-type": "application/json" },
+    body: JSON.stringify({}),
+  });
+  let syncAuthManager = Service.identity;
+
+  await Assert.rejects(
+    syncAuthManager._ensureValidToken(),
+    AuthenticationError,
+    "should reject due to 401"
+  );
+  Assert.equal(Status.login, LOGIN_FAILED_LOGIN_REJECTED, "login was rejected");
+
+  // XXX - other interesting responses to return?
+
+  // And for good measure, some totally "unexpected" errors - we generally
+  // assume these problems are going to magically go away at some point.
+  _(
+    "Arrange for an empty body with a 200 response - should reflect a network error."
+  );
+  initializeIdentityWithTokenServerResponse({
+    status: 200,
+    headers: [],
+    body: "",
+  });
+  syncAuthManager = Service.identity;
+  await Assert.rejects(
+    syncAuthManager._ensureValidToken(),
+    TokenServerClientServerError,
+    "should reject due to non-JSON response"
+  );
+  Assert.equal(
+    Status.login,
+    LOGIN_FAILED_NETWORK_ERROR,
+    "login state is LOGIN_FAILED_NETWORK_ERROR"
+  );
+});
+
+add_task(async function test_refreshAccessTokenOn401() {
+  _("SyncAuthManager refreshes the FXA OAuth access token after a 401.");
+  var identityConfig = makeIdentityConfig();
+  var syncAuthManager = new SyncAuthManager();
+  // Use the real `getOAuthToken` method that calls
+  // `mockFxAClient.accessTokenWithSessionToken`.
+  let fxaInternal = makeFxAccountsInternalMock(identityConfig);
+  delete fxaInternal.getOAuthToken;
+  configureFxAccountIdentity(syncAuthManager, identityConfig, fxaInternal);
+  syncAuthManager._fxaService._internal.initialize();
+
+  let getTokenCount = 0;
+
+  let CheckSignMockFxAClient = function () {
+    FxAccountsClient.apply(this);
+  };
+  CheckSignMockFxAClient.prototype = {
+    accessTokenWithSessionToken() {
+      ++getTokenCount;
+      return Promise.resolve({ access_token: "token" });
+    },
+  };
+  Object.setPrototypeOf(
+    CheckSignMockFxAClient.prototype,
+    FxAccountsClient.prototype
+  );
+
+  let mockFxAClient = new CheckSignMockFxAClient();
+  syncAuthManager._fxaService._internal._fxAccountsClient = mockFxAClient;
+
+  let didReturn401 = false;
+  let didReturn200 = false;
+  let mockTSC = mockTokenServer(() => {
+    if (getTokenCount <= 1) {
+      didReturn401 = true;
+      return {
+        status: 401,
+        headers: { "content-type": "application/json" },
+        body: JSON.stringify({}),
+      };
+    }
+    didReturn200 = true;
+    return {
+      status: 200,
+      headers: { "content-type": "application/json" },
+      body: JSON.stringify({
+        id: "id",
+        key: "key",
+        api_endpoint: "http://example.com/",
+        uid: "uid",
+        duration: 300,
+      }),
+    };
+  });
+
+  syncAuthManager._tokenServerClient = mockTSC;
+
+  await syncAuthManager._ensureValidToken();
+
+  Assert.equal(getTokenCount, 2);
+  Assert.ok(didReturn401);
+  Assert.ok(didReturn200);
+  Assert.ok(syncAuthManager._token);
+  Assert.ok(syncAuthManager._hasValidToken());
+});
+
+add_task(async function test_getTokenErrorWithRetry() {
+  _("tokenserver sends an observer notification on various backoff headers.");
+
+  // Set Sync's backoffInterval to zero - after we simulated the backoff header
+  // it should reflect the value we sent.
+  Status.backoffInterval = 0;
+  _("Arrange for a 503 with a Retry-After header.");
+  initializeIdentityWithTokenServerResponse({
+    status: 503,
+    headers: { "content-type": "application/json", "retry-after": "100" },
+    body: JSON.stringify({}),
+  });
+  let syncAuthManager = Service.identity;
+
+  await Assert.rejects(
+    syncAuthManager._ensureValidToken(),
+    TokenServerClientServerError,
+    "should reject due to 503"
+  );
+
+  // The observer should have fired - check it got the value in the response.
+  Assert.equal(Status.login, LOGIN_FAILED_NETWORK_ERROR, "login was rejected");
+  // Sync will have the value in ms with some slop - so check it is at least that.
+  Assert.greaterOrEqual(Status.backoffInterval, 100000);
+
+  _("Arrange for a 200 with an X-Backoff header.");
+  Status.backoffInterval = 0;
+  initializeIdentityWithTokenServerResponse({
+    status: 503,
+    headers: { "content-type": "application/json", "x-backoff": "200" },
+    body: JSON.stringify({}),
+  });
+  syncAuthManager = Service.identity;
+
+  await Assert.rejects(
+    syncAuthManager._ensureValidToken(),
+    TokenServerClientServerError,
+    "should reject due to no token in response"
+  );
+
+  // The observer should have fired - check it got the value in the response.
+  Assert.greaterOrEqual(Status.backoffInterval, 200000);
+});
+
+add_task(async function test_getKeysErrorWithBackoff() {
+  _(
+    "Auth server (via hawk) sends an observer notification on backoff headers."
+  );
+
+  // Set Sync's backoffInterval to zero - after we simulated the backoff header
+  // it should reflect the value we sent.
+  Status.backoffInterval = 0;
+  _("Arrange for a 503 with a X-Backoff header.");
+
+  let config = makeIdentityConfig();
+  // We want no scopedKeys so we attempt to fetch them.
+  delete config.fxaccount.user.scopedKeys;
+  config.fxaccount.user.keyFetchToken = "keyfetchtoken";
+  await initializeIdentityWithHAWKResponseFactory(
+    config,
+    function (method, data, uri) {
+      Assert.equal(method, "get");
+      Assert.equal(uri, "http://mockedserver:9999/account/keys");
+      return {
+        status: 503,
+        headers: { "content-type": "application/json", "x-backoff": "100" },
+        body: "{}",
+      };
+    }
+  );
+
+  let syncAuthManager = Service.identity;
+  await Assert.rejects(
+    syncAuthManager._ensureValidToken(),
+    TokenServerClientServerError,
+    "should reject due to 503"
+  );
+
+  // The observer should have fired - check it got the value in the response.
+  Assert.equal(Status.login, LOGIN_FAILED_NETWORK_ERROR, "login was rejected");
+  // Sync will have the value in ms with some slop - so check it is at least that.
+  Assert.greaterOrEqual(Status.backoffInterval, 100000);
+});
+
+add_task(async function test_getKeysErrorWithRetry() {
+  _("Auth server (via hawk) sends an observer notification on retry headers.");
+
+  // Set Sync's backoffInterval to zero - after we simulated the backoff header
+  // it should reflect the value we sent.
+  Status.backoffInterval = 0;
+  _("Arrange for a 503 with a Retry-After header.");
+
+  let config = makeIdentityConfig();
+  // We want no scopedKeys so we attempt to fetch them.
+  delete config.fxaccount.user.scopedKeys;
+  config.fxaccount.user.keyFetchToken = "keyfetchtoken";
+  await initializeIdentityWithHAWKResponseFactory(
+    config,
+    function (method, data, uri) {
+      Assert.equal(method, "get");
+      Assert.equal(uri, "http://mockedserver:9999/account/keys");
+      return {
+        status: 503,
+        headers: { "content-type": "application/json", "retry-after": "100" },
+        body: "{}",
+      };
+    }
+  );
+
+  let syncAuthManager = Service.identity;
+  await Assert.rejects(
+    syncAuthManager._ensureValidToken(),
+    TokenServerClientServerError,
+    "should reject due to 503"
+  );
+
+  // The observer should have fired - check it got the value in the response.
+  Assert.equal(Status.login, LOGIN_FAILED_NETWORK_ERROR, "login was rejected");
+  // Sync will have the value in ms with some slop - so check it is at least that.
+  Assert.greaterOrEqual(Status.backoffInterval, 100000);
+});
+
+add_task(async function test_getHAWKErrors() {
+  _("SyncAuthManager correctly handles various HAWK failures.");
+
+  _("Arrange for a 401 - Sync should reflect an auth error.");
+  let config = makeIdentityConfig();
+  await initializeIdentityWithHAWKResponseFactory(
+    config,
+    function (method, data, uri) {
+      if (uri == "http://mockedserver:9999/oauth/token") {
+        Assert.equal(method, "post");
+        return {
+          status: 401,
+          headers: { "content-type": "application/json" },
+          body: JSON.stringify({
+            code: 401,
+            errno: 110,
+            error: "invalid token",
+          }),
+        };
+      }
+      // For any follow-up requests that check account status.
+      return {
+        status: 200,
+        headers: { "content-type": "application/json" },
+        body: JSON.stringify({}),
+      };
+    }
+  );
+  Assert.equal(Status.login, LOGIN_FAILED_LOGIN_REJECTED, "login was rejected");
+
+  // XXX - other interesting responses to return?
+
+  // And for good measure, some totally "unexpected" errors - we generally
+  // assume these problems are going to magically go away at some point.
+  _(
+    "Arrange for an empty body with a 200 response - should reflect a network error."
+  );
+  await initializeIdentityWithHAWKResponseFactory(
+    config,
+    function (method, data, uri) {
+      Assert.equal(method, "post");
+      Assert.equal(uri, "http://mockedserver:9999/oauth/token");
+      return {
+        status: 200,
+        headers: [],
+        body: "",
+      };
+    }
+  );
+  Assert.equal(
+    Status.login,
+    LOGIN_FAILED_NETWORK_ERROR,
+    "login state is LOGIN_FAILED_NETWORK_ERROR"
+  );
+});
+
+// End of tests
+// Utility functions follow
+
+// Create a new sync_auth object and initialize it with a
+// hawk mock that simulates HTTP responses.
+// The callback function will be called each time the mocked hawk server wants
+// to make a request.  The result of the callback should be the mock response
+// object that will be returned to hawk.
+// A token server mock will be used that doesn't hit a server, so we move
+// directly to a hawk request.
+async function initializeIdentityWithHAWKResponseFactory(
+  config,
+  cbGetResponse
+) {
+  // A mock request object.
+  function MockRESTRequest(uri, credentials, extra) {
+    this._uri = uri;
+    this._credentials = credentials;
+    this._extra = extra;
+  }
+  MockRESTRequest.prototype = {
+    setHeader() {},
+    async post(data) {
+      this.response = cbGetResponse(
+        "post",
+        data,
+        this._uri,
+        this._credentials,
+        this._extra
+      );
+      return this.response;
+    },
+    async get() {
+      // Skip /status requests (sync_auth checks if the account still
+      // exists after an auth error)
+      if (this._uri.startsWith("http://mockedserver:9999/account/status")) {
+        this.response = {
+          status: 200,
+          headers: { "content-type": "application/json" },
+          body: JSON.stringify({ exists: true }),
+        };
+      } else {
+        this.response = cbGetResponse(
+          "get",
+          null,
+          this._uri,
+          this._credentials,
+          this._extra
+        );
+      }
+      return this.response;
+    },
+  };
+
+  // The hawk client.
+  function MockedHawkClient() {}
+  MockedHawkClient.prototype = new HawkClient("http://mockedserver:9999");
+  MockedHawkClient.prototype.constructor = MockedHawkClient;
+  MockedHawkClient.prototype.newHAWKAuthenticatedRESTRequest = function (
+    uri,
+    credentials,
+    extra
+  ) {
+    return new MockRESTRequest(uri, credentials, extra);
+  };
+  // Arrange for the same observerPrefix as FxAccountsClient uses
+  MockedHawkClient.prototype.observerPrefix = "FxA:hawk";
+
+  // tie it all together - configureFxAccountIdentity isn't useful here :(
+  let fxaClient = new MockFxAccountsClient();
+  fxaClient.hawk = new MockedHawkClient();
+  let internal = {
+    fxAccountsClient: fxaClient,
+    newAccountState(credentials) {
+      // We only expect this to be called with null indicating the (mock)
+      // storage should be read.
+      if (credentials) {
+        throw new Error("Not expecting to have credentials passed");
+      }
+      let storageManager = new MockFxaStorageManager();
+      storageManager.initialize(config.fxaccount.user);
+      return new AccountState(storageManager);
+    },
+  };
+  let fxa = new FxAccounts(internal);
+
+  globalSyncAuthManager._fxaService = fxa;
+  await Assert.rejects(
+    globalSyncAuthManager._ensureValidToken(true),
+    // TODO: Ideally this should have a specific check for an error.
+    () => true,
+    "expecting rejection due to hawk error"
+  );
+}
+
+function getTimestamp(hawkAuthHeader) {
+  return parseInt(/ts="(\d+)"/.exec(hawkAuthHeader)[1], 10) * SECOND_MS;
+}
+
+function getTimestampDelta(hawkAuthHeader, now = Date.now()) {
+  return Math.abs(getTimestamp(hawkAuthHeader) - now);
+}
+
+function mockTokenServer(func) {
+  let requestLog = Log.repository.getLogger("testing.mock-rest");
+  if (!requestLog.appenders.length) {
+    // might as well see what it says :)
+    requestLog.addAppender(new Log.DumpAppender());
+    requestLog.level = Log.Level.Trace;
+  }
+  function MockRESTRequest() {}
+  MockRESTRequest.prototype = {
+    _log: requestLog,
+    setHeader() {},
+    async get() {
+      this.response = func();
+      return this.response;
+    },
+  };
+  // The mocked TokenServer client which will get the response.
+  function MockTSC() {}
+  MockTSC.prototype = new TokenServerClient();
+  MockTSC.prototype.constructor = MockTSC;
+  MockTSC.prototype.newRESTRequest = function (url) {
+    return new MockRESTRequest(url);
+  };
+  // Arrange for the same observerPrefix as sync_auth uses.
+  MockTSC.prototype.observerPrefix = "weave:service";
+  return new MockTSC();
+}
diff --git a/src/zen/tests/mochitests/sync/test_syncedtabs.js b/src/zen/tests/mochitests/sync/test_syncedtabs.js
new file mode 100644
index 000000000..0c7f2e480
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_syncedtabs.js
@@ -0,0 +1,342 @@
+"use strict";
+
+const { Weave } = ChromeUtils.importESModule(
+  "resource://services-sync/main.sys.mjs"
+);
+const { SyncedTabs } = ChromeUtils.importESModule(
+  "resource://services-sync/SyncedTabs.sys.mjs"
+);
+
+Log.repository.getLogger("Sync.RemoteTabs").addAppender(new Log.DumpAppender());
+
+// A mock "Tabs" engine which the SyncedTabs module will use instead of the real
+// engine. We pass a constructor that Sync creates.
+function MockTabsEngine() {
+  this.clients = {}; // We'll set this dynamically
+  // Mock fxAccounts + recentDeviceList as if we hit the FxA server
+  this.fxAccounts = {
+    device: {
+      recentDeviceList: [
+        {
+          id: 1,
+          name: "updated desktop name",
+          availableCommands: {
+            "https://identity.mozilla.com/cmd/open-uri": "baz",
+          },
+        },
+        {
+          id: 2,
+          name: "updated mobile name",
+          availableCommands: {
+            "https://identity.mozilla.com/cmd/open-uri": "boo",
+          },
+        },
+      ],
+    },
+  };
+}
+
+MockTabsEngine.prototype = {
+  name: "tabs",
+  enabled: true,
+
+  getAllClients() {
+    return Object.values(this.clients);
+  },
+
+  getOpenURLs() {
+    return new Set();
+  },
+};
+
+let tabsEngine;
+
+// A clients engine that doesn't need to be a constructor.
+let MockClientsEngine = {
+  clientSettings: null, // Set in `configureClients`.
+
+  isMobile(guid) {
+    if (!guid.endsWith("desktop") && !guid.endsWith("mobile")) {
+      throw new Error(
+        "this module expected guids to end with 'desktop' or 'mobile'"
+      );
+    }
+    return guid.endsWith("mobile");
+  },
+  remoteClientExists(id) {
+    return this.clientSettings[id] !== false;
+  },
+  getClientName(id) {
+    if (this.clientSettings[id]) {
+      return this.clientSettings[id];
+    }
+    let client = tabsEngine.clients[id];
+    let fxaDevice = tabsEngine.fxAccounts.device.recentDeviceList.find(
+      device => device.id === client.fxaDeviceId
+    );
+    return fxaDevice ? fxaDevice.name : client.clientName;
+  },
+
+  getClientFxaDeviceId(id) {
+    if (this.clientSettings[id]) {
+      return this.clientSettings[id];
+    }
+    return tabsEngine.clients[id].fxaDeviceId;
+  },
+
+  getClientType() {
+    return "desktop";
+  },
+};
+
+function configureClients(clients, clientSettings = {}) {
+  // each client record is expected to have an id.
+  for (let [guid, client] of Object.entries(clients)) {
+    client.id = guid;
+  }
+  tabsEngine.clients = clients;
+  // Apply clients collection overrides.
+  MockClientsEngine.clientSettings = clientSettings;
+  // Send an observer that pretends the engine just finished a sync.
+  Services.obs.notifyObservers(null, "weave:engine:sync:finish", "tabs");
+}
+
+add_task(async function setup() {
+  await Weave.Service.promiseInitialized;
+  // Configure Sync with our mock tabs engine and force it to become initialized.
+  await Weave.Service.engineManager.unregister("tabs");
+  await Weave.Service.engineManager.register(MockTabsEngine);
+  Weave.Service.clientsEngine = MockClientsEngine;
+  tabsEngine = Weave.Service.engineManager.get("tabs");
+
+  // Tell the Sync XPCOM service it is initialized.
+  let weaveXPCService = Cc["@mozilla.org/weave/service;1"].getService(
+    Ci.nsISupports
+  ).wrappedJSObject;
+  weaveXPCService.ready = true;
+});
+
+// The tests.
+add_task(async function test_noClients() {
+  // no clients, can't be tabs.
+  await configureClients({});
+
+  let tabs = await SyncedTabs.getTabClients();
+  equal(Object.keys(tabs).length, 0);
+});
+
+add_task(async function test_clientWithTabs() {
+  await configureClients({
+    guid_desktop: {
+      clientName: "My Desktop",
+      tabs: [
+        {
+          urlHistory: ["http://foo.com/"],
+          icon: "http://foo.com/favicon",
+          lastUsed: 1655745700, // Mon, 20 Jun 2022 17:21:40 GMT
+        },
+      ],
+    },
+    guid_mobile: {
+      clientName: "My Phone",
+      tabs: [],
+    },
+  });
+
+  let clients = await SyncedTabs.getTabClients();
+  equal(clients.length, 2);
+  clients.sort((a, b) => {
+    return a.name.localeCompare(b.name);
+  });
+  equal(clients[0].tabs.length, 1);
+  equal(clients[0].tabs[0].url, "http://foo.com/");
+  let icon_url = new URL(clients[0].tabs[0].icon);
+  equal(icon_url.protocol, "moz-remote-image:", "image protocol is correct");
+  equal(icon_url.searchParams.get("url"), "http://foo.com/favicon");
+
+  equal(clients[0].tabs[0].lastUsed, 1655745700);
+  // second client has no tabs.
+  equal(clients[1].tabs.length, 0);
+});
+
+add_task(async function test_staleClientWithTabs() {
+  await configureClients(
+    {
+      guid_desktop: {
+        clientName: "My Desktop",
+        tabs: [
+          {
+            urlHistory: ["http://foo.com/"],
+            icon: "http://foo.com/favicon",
+            lastUsed: 1655745750,
+          },
+        ],
+      },
+      guid_mobile: {
+        clientName: "My Phone",
+        tabs: [],
+      },
+      guid_stale_mobile: {
+        clientName: "My Deleted Phone",
+        tabs: [],
+      },
+      guid_stale_desktop: {
+        clientName: "My Deleted Laptop",
+        tabs: [
+          {
+            urlHistory: ["https://bar.com/"],
+            icon: "https://bar.com/favicon",
+            lastUsed: 1655745700,
+          },
+        ],
+      },
+      guid_stale_name_desktop: {
+        clientName: "My Generic Device",
+        tabs: [
+          {
+            urlHistory: ["https://example.edu/"],
+            icon: "https://example.edu/favicon",
+            lastUsed: 1655745800,
+          },
+        ],
+      },
+    },
+    {
+      guid_stale_mobile: false,
+      guid_stale_desktop: false,
+      // We should always use the device name from the clients collection, instead
+      // of the possibly stale tabs collection.
+      guid_stale_name_desktop: "My Laptop",
+    }
+  );
+  let clients = await SyncedTabs.getTabClients();
+  clients.sort((a, b) => {
+    return a.name.localeCompare(b.name);
+  });
+  equal(clients.length, 3);
+  equal(clients[0].name, "My Desktop");
+  equal(clients[0].tabs.length, 1);
+  equal(clients[0].tabs[0].url, "http://foo.com/");
+  equal(clients[0].tabs[0].lastUsed, 1655745750);
+  equal(clients[1].name, "My Laptop");
+  equal(clients[1].tabs.length, 1);
+  equal(clients[1].tabs[0].url, "https://example.edu/");
+  equal(clients[1].tabs[0].lastUsed, 1655745800);
+  equal(clients[2].name, "My Phone");
+  equal(clients[2].tabs.length, 0);
+});
+
+add_task(async function test_clientWithTabsIconsDisabled() {
+  Services.prefs.setBoolPref("services.sync.syncedTabs.showRemoteIcons", false);
+  await configureClients({
+    guid_desktop: {
+      clientName: "My Desktop",
+      tabs: [
+        {
+          urlHistory: ["http://foo.com/"],
+          icon: "http://foo.com/favicon",
+        },
+      ],
+    },
+  });
+
+  let clients = await SyncedTabs.getTabClients();
+  equal(clients.length, 1);
+  clients.sort((a, b) => {
+    return a.name.localeCompare(b.name);
+  });
+  equal(clients[0].tabs.length, 1);
+  equal(clients[0].tabs[0].url, "http://foo.com/");
+  // Expect the default favicon due to the pref being false.
+  equal(clients[0].tabs[0].icon, "page-icon:http://foo.com/");
+  Services.prefs.clearUserPref("services.sync.syncedTabs.showRemoteIcons");
+});
+
+add_task(async function test_filter() {
+  // Nothing matches.
+  await configureClients({
+    guid_desktop: {
+      clientName: "My Desktop",
+      tabs: [
+        {
+          urlHistory: ["http://foo.com/"],
+          title: "A test page.",
+        },
+        {
+          urlHistory: ["http://bar.com/"],
+          title: "Another page.",
+        },
+      ],
+    },
+  });
+
+  let clients = await SyncedTabs.getTabClients("foo");
+  equal(clients.length, 1);
+  equal(clients[0].tabs.length, 1);
+  equal(clients[0].tabs[0].url, "http://foo.com/");
+  // check it matches the title.
+  clients = await SyncedTabs.getTabClients("test");
+  equal(clients.length, 1);
+  equal(clients[0].tabs.length, 1);
+  equal(clients[0].tabs[0].url, "http://foo.com/");
+});
+
+add_task(async function test_duplicatesTabsAcrossClients() {
+  await configureClients({
+    guid_desktop: {
+      clientName: "My Desktop",
+      tabs: [
+        {
+          urlHistory: ["http://foo.com/"],
+          title: "A test page.",
+        },
+      ],
+    },
+    guid_mobile: {
+      clientName: "My Phone",
+      tabs: [
+        {
+          urlHistory: ["http://foo.com/"],
+          title: "A test page.",
+        },
+      ],
+    },
+  });
+
+  let clients = await SyncedTabs.getTabClients();
+  equal(clients.length, 2);
+  equal(clients[0].tabs.length, 1);
+  equal(clients[1].tabs.length, 1);
+  equal(clients[0].tabs[0].url, "http://foo.com/");
+  equal(clients[1].tabs[0].url, "http://foo.com/");
+});
+
+add_task(async function test_clientsTabUpdatedName() {
+  // See the "fxAccounts" object in the MockEngine above for the device list
+  await configureClients({
+    guid_desktop: {
+      clientName: "My Desktop",
+      tabs: [
+        {
+          urlHistory: ["http://foo.com/"],
+          icon: "http://foo.com/favicon",
+        },
+      ],
+      fxaDeviceId: 1,
+    },
+    guid_mobile: {
+      clientName: "My Phone",
+      tabs: [
+        {
+          urlHistory: ["http://bar.com/"],
+          icon: "http://bar.com/favicon",
+        },
+      ],
+      fxaDeviceId: 2,
+    },
+  });
+  let clients = await SyncedTabs.getTabClients();
+  equal(clients.length, 2);
+  equal(clients[0].name, "updated desktop name");
+  equal(clients[1].name, "updated mobile name");
+});
diff --git a/src/zen/tests/mochitests/sync/test_syncengine.js b/src/zen/tests/mochitests/sync/test_syncengine.js
new file mode 100644
index 000000000..51dbaf8d1
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_syncengine.js
@@ -0,0 +1,329 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+async function makeSteamEngine() {
+  let engine = new SyncEngine("Steam", Service);
+  await engine.initialize();
+  return engine;
+}
+
+function guidSetOfSize(length) {
+  return new SerializableSet(Array.from({ length }, () => Utils.makeGUID()));
+}
+
+function assertSetsEqual(a, b) {
+  // Assert.deepEqual doesn't understand Set.
+  Assert.deepEqual(Array.from(a).sort(), Array.from(b).sort());
+}
+
+async function testSteamEngineStorage(test) {
+  try {
+    let setupEngine = await makeSteamEngine();
+
+    if (test.setup) {
+      await test.setup(setupEngine);
+    }
+
+    // Finalize the engine to flush the backlog and previous failed to disk.
+    await setupEngine.finalize();
+
+    if (test.beforeCheck) {
+      await test.beforeCheck();
+    }
+
+    let checkEngine = await makeSteamEngine();
+    await test.check(checkEngine);
+
+    await checkEngine.resetClient();
+    await checkEngine.finalize();
+  } finally {
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+  }
+}
+
+let server;
+
+add_task(async function setup() {
+  server = httpd_setup({});
+});
+
+add_task(async function test_url_attributes() {
+  _("SyncEngine url attributes");
+  await SyncTestingInfrastructure(server);
+  Service.clusterURL = "https://cluster/1.1/foo/";
+  let engine = await makeSteamEngine();
+  try {
+    Assert.equal(engine.storageURL, "https://cluster/1.1/foo/storage/");
+    Assert.equal(engine.engineURL, "https://cluster/1.1/foo/storage/steam");
+    Assert.equal(engine.metaURL, "https://cluster/1.1/foo/storage/meta/global");
+  } finally {
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+  }
+});
+
+add_task(async function test_syncID() {
+  _("SyncEngine.syncID corresponds to preference");
+  await SyncTestingInfrastructure(server);
+  let engine = await makeSteamEngine();
+  try {
+    // Ensure pristine environment
+    Assert.equal(
+      Svc.PrefBranch.getPrefType("steam.syncID"),
+      Ci.nsIPrefBranch.PREF_INVALID
+    );
+    Assert.equal(await engine.getSyncID(), "");
+
+    // Performing the first get on the attribute will generate a new GUID.
+    Assert.equal(await engine.resetLocalSyncID(), "fake-guid-00");
+    Assert.equal(Svc.PrefBranch.getStringPref("steam.syncID"), "fake-guid-00");
+
+    Svc.PrefBranch.setStringPref("steam.syncID", Utils.makeGUID());
+    Assert.equal(Svc.PrefBranch.getStringPref("steam.syncID"), "fake-guid-01");
+    Assert.equal(await engine.getSyncID(), "fake-guid-01");
+  } finally {
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+  }
+});
+
+add_task(async function test_lastSync() {
+  _("SyncEngine.lastSync corresponds to preferences");
+  await SyncTestingInfrastructure(server);
+  let engine = await makeSteamEngine();
+  try {
+    // Ensure pristine environment
+    Assert.equal(
+      Svc.PrefBranch.getPrefType("steam.lastSync"),
+      Ci.nsIPrefBranch.PREF_INVALID
+    );
+    Assert.equal(await engine.getLastSync(), 0);
+
+    // Floats are properly stored as floats and synced with the preference
+    await engine.setLastSync(123.45);
+    Assert.equal(await engine.getLastSync(), 123.45);
+    Assert.equal(Svc.PrefBranch.getStringPref("steam.lastSync"), "123.45");
+
+    // Integer is properly stored
+    await engine.setLastSync(67890);
+    Assert.equal(await engine.getLastSync(), 67890);
+    Assert.equal(Svc.PrefBranch.getStringPref("steam.lastSync"), "67890");
+
+    // resetLastSync() resets the value (and preference) to 0
+    await engine.resetLastSync();
+    Assert.equal(await engine.getLastSync(), 0);
+    Assert.equal(Svc.PrefBranch.getStringPref("steam.lastSync"), "0");
+  } finally {
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+  }
+});
+
+add_task(async function test_toFetch() {
+  _("SyncEngine.toFetch corresponds to file on disk");
+  await SyncTestingInfrastructure(server);
+
+  await testSteamEngineStorage({
+    toFetch: guidSetOfSize(3),
+    setup(engine) {
+      // Ensure pristine environment
+      Assert.equal(engine.toFetch.size, 0);
+
+      // Write file to disk
+      engine.toFetch = this.toFetch;
+      Assert.equal(engine.toFetch, this.toFetch);
+    },
+    check(engine) {
+      // toFetch is written asynchronously
+      assertSetsEqual(engine.toFetch, this.toFetch);
+    },
+  });
+
+  await testSteamEngineStorage({
+    toFetch: guidSetOfSize(4),
+    toFetch2: guidSetOfSize(5),
+    setup(engine) {
+      // Make sure it work for consecutive writes before the callback is executed.
+      engine.toFetch = this.toFetch;
+      Assert.equal(engine.toFetch, this.toFetch);
+
+      engine.toFetch = this.toFetch2;
+      Assert.equal(engine.toFetch, this.toFetch2);
+    },
+    check(engine) {
+      assertSetsEqual(engine.toFetch, this.toFetch2);
+    },
+  });
+
+  await testSteamEngineStorage({
+    toFetch: guidSetOfSize(2),
+    async beforeCheck() {
+      let toFetchPath = PathUtils.join(
+        PathUtils.profileDir,
+        "weave",
+        "toFetch",
+        "steam.json"
+      );
+      await IOUtils.writeJSON(toFetchPath, this.toFetch, {
+        tmpPath: toFetchPath + ".tmp",
+      });
+    },
+    check(engine) {
+      // Read file from disk
+      assertSetsEqual(engine.toFetch, this.toFetch);
+    },
+  });
+});
+
+add_task(async function test_previousFailed() {
+  _("SyncEngine.previousFailed values correspond to file on disk");
+  await SyncTestingInfrastructure(server);
+
+  await testSteamEngineStorage({
+    previousFailedIn: guidSetOfSize(3),
+    previousFailedOut: guidSetOfSize(3),
+    setup(engine) {
+      // Ensure pristine environment
+      Assert.equal(engine.previousFailedIn.size, 0);
+      Assert.equal(engine.previousFailedOut.size, 0);
+
+      // Write files to disk
+      engine.previousFailedIn = this.previousFailedIn;
+      Assert.equal(engine.previousFailedIn, this.previousFailedIn);
+      engine.previousFailedOut = this.previousFailedOut;
+      Assert.equal(engine.previousFailedOut, this.previousFailedOut);
+    },
+    check(engine) {
+      // previousFailed values are written asynchronously
+      assertSetsEqual(engine.previousFailedIn, this.previousFailedIn);
+      assertSetsEqual(engine.previousFailedOut, this.previousFailedOut);
+    },
+  });
+
+  await testSteamEngineStorage({
+    previousFailedIn: guidSetOfSize(4),
+    previousFailedIn2: guidSetOfSize(5),
+    previousFailedOut: guidSetOfSize(4),
+    previousFailedOut2: guidSetOfSize(5),
+    setup(engine) {
+      // Make sure it works for consecutive writes before the callback is
+      // executed.
+      engine.previousFailedIn = this.previousFailedIn;
+      Assert.equal(engine.previousFailedIn, this.previousFailedIn);
+      engine.previousFailedOut = this.previousFailedOut;
+      Assert.equal(engine.previousFailedOut, this.previousFailedOut);
+
+      engine.previousFailedIn = this.previousFailedIn2;
+      Assert.equal(engine.previousFailedIn, this.previousFailedIn2);
+      engine.previousFailedOut = this.previousFailedOut2;
+      Assert.equal(engine.previousFailedOut, this.previousFailedOut2);
+    },
+    check(engine) {
+      assertSetsEqual(engine.previousFailedIn, this.previousFailedIn2);
+      assertSetsEqual(engine.previousFailedOut, this.previousFailedOut2);
+    },
+  });
+
+  await testSteamEngineStorage({
+    previousFailedIn: guidSetOfSize(2),
+    previousFailedOut: guidSetOfSize(2),
+    async beforeCheck() {
+      let previousFailedInPath = PathUtils.join(
+        PathUtils.profileDir,
+        "weave",
+        "failed",
+        "steam.json"
+      );
+      await IOUtils.writeJSON(previousFailedInPath, this.previousFailedIn, {
+        tmpPath: previousFailedInPath + ".tmp",
+      });
+
+      let previousFailedOutPath = PathUtils.join(
+        PathUtils.profileDir,
+        "weave",
+        "failedOut",
+        "steam.json"
+      );
+      await IOUtils.writeJSON(previousFailedOutPath, this.previousFailedOut, {
+        tmpPath: previousFailedOutPath + ".tmp",
+      });
+    },
+    check(engine) {
+      // Read file from disk
+      assertSetsEqual(engine.previousFailedIn, this.previousFailedIn);
+      assertSetsEqual(engine.previousFailedOut, this.previousFailedOut);
+    },
+  });
+});
+
+add_task(async function test_resetClient() {
+  _("SyncEngine.resetClient resets lastSync and toFetch");
+  await SyncTestingInfrastructure(server);
+  let engine = await makeSteamEngine();
+  try {
+    // Ensure pristine environment
+    Assert.equal(
+      Svc.PrefBranch.getPrefType("steam.lastSync"),
+      Ci.nsIPrefBranch.PREF_INVALID
+    );
+    Assert.equal(engine.toFetch.size, 0);
+
+    await engine.setLastSync(123.45);
+    engine.toFetch = guidSetOfSize(4);
+    engine.previousFailedIn = guidSetOfSize(3);
+    engine.previousFailedOut = guidSetOfSize(3);
+
+    await engine.resetClient();
+    Assert.equal(await engine.getLastSync(), 0);
+    Assert.equal(engine.toFetch.size, 0);
+    Assert.equal(engine.previousFailedIn.size, 0);
+    Assert.equal(engine.previousFailedOut.size, 0);
+  } finally {
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+  }
+});
+
+add_task(async function test_wipeServer() {
+  _("SyncEngine.wipeServer deletes server data and resets the client.");
+  let engine = await makeSteamEngine();
+
+  const PAYLOAD = 42;
+  let steamCollection = new ServerWBO("steam", PAYLOAD);
+  let steamServer = httpd_setup({
+    "/1.1/foo/storage/steam": steamCollection.handler(),
+  });
+  await SyncTestingInfrastructure(steamServer);
+  do_test_pending();
+
+  try {
+    // Some data to reset.
+    await engine.setLastSync(123.45);
+    engine.toFetch = guidSetOfSize(3);
+
+    _("Wipe server data and reset client.");
+    await engine.wipeServer();
+    Assert.equal(steamCollection.payload, undefined);
+    Assert.equal(await engine.getLastSync(), 0);
+    Assert.equal(engine.toFetch.size, 0);
+  } finally {
+    steamServer.stop(do_test_finished);
+    for (const pref of Svc.PrefBranch.getChildList("")) {
+      Svc.PrefBranch.clearUserPref(pref);
+    }
+  }
+});
+
+add_task(async function finish() {
+  await promiseStopServer(server);
+});
diff --git a/src/zen/tests/mochitests/sync/test_syncengine_sync.js b/src/zen/tests/mochitests/sync/test_syncengine_sync.js
new file mode 100644
index 000000000..fb4beb711
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_syncengine_sync.js
@@ -0,0 +1,1811 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Weave } = ChromeUtils.importESModule(
+  "resource://services-sync/main.sys.mjs"
+);
+const { WBORecord } = ChromeUtils.importESModule(
+  "resource://services-sync/record.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { RotaryEngine } = ChromeUtils.importESModule(
+  "resource://testing-common/services/sync/rotaryengine.sys.mjs"
+);
+
+function makeRotaryEngine() {
+  return new RotaryEngine(Service);
+}
+
+async function clean(engine) {
+  for (const pref of Svc.PrefBranch.getChildList("")) {
+    Svc.PrefBranch.clearUserPref(pref);
+  }
+  Svc.PrefBranch.setStringPref("log.logger.engine.rotary", "Trace");
+  Service.recordManager.clearCache();
+  await engine._tracker.clearChangedIDs();
+  await engine.finalize();
+}
+
+async function cleanAndGo(engine, server) {
+  await clean(engine);
+  await promiseStopServer(server);
+}
+
+async function promiseClean(engine, server) {
+  await clean(engine);
+  await promiseStopServer(server);
+}
+
+async function createServerAndConfigureClient() {
+  let engine = new RotaryEngine(Service);
+  let syncID = await engine.resetLocalSyncID();
+
+  let contents = {
+    meta: {
+      global: { engines: { rotary: { version: engine.version, syncID } } },
+    },
+    crypto: {},
+    rotary: {},
+  };
+
+  const USER = "foo";
+  let server = new SyncServer();
+  server.registerUser(USER, "password");
+  server.createContents(USER, contents);
+  server.start();
+
+  await SyncTestingInfrastructure(server, USER);
+  Service._updateCachedURLs();
+
+  return [engine, server, USER];
+}
+
+/*
+ * Tests
+ *
+ * SyncEngine._sync() is divided into four rather independent steps:
+ *
+ * - _syncStartup()
+ * - _processIncoming()
+ * - _uploadOutgoing()
+ * - _syncFinish()
+ *
+ * In the spirit of unit testing, these are tested individually for
+ * different scenarios below.
+ */
+
+add_task(async function setup() {
+  await generateNewKeys(Service.collectionKeys);
+  Svc.PrefBranch.setStringPref("log.logger.engine.rotary", "Trace");
+});
+
+add_task(async function test_syncStartup_emptyOrOutdatedGlobalsResetsSync() {
+  _(
+    "SyncEngine._syncStartup resets sync and wipes server data if there's no or an outdated global record"
+  );
+
+  // Some server side data that's going to be wiped
+  let collection = new ServerCollection();
+  collection.insert(
+    "flying",
+    encryptPayload({ id: "flying", denomination: "LNER Class A3 4472" })
+  );
+  collection.insert(
+    "scotsman",
+    encryptPayload({ id: "scotsman", denomination: "Flying Scotsman" })
+  );
+
+  let server = sync_httpd_setup({
+    "/1.1/foo/storage/rotary": collection.handler(),
+  });
+
+  await SyncTestingInfrastructure(server);
+
+  let engine = makeRotaryEngine();
+  engine._store.items = { rekolok: "Rekonstruktionslokomotive" };
+  try {
+    // Confirm initial environment
+    const changes = await engine._tracker.getChangedIDs();
+    Assert.equal(changes.rekolok, undefined);
+    let metaGlobal = await Service.recordManager.get(engine.metaURL);
+    Assert.equal(metaGlobal.payload.engines, undefined);
+    Assert.ok(!!collection.payload("flying"));
+    Assert.ok(!!collection.payload("scotsman"));
+
+    await engine.setLastSync(Date.now() / 1000);
+
+    // Trying to prompt a wipe -- we no longer track CryptoMeta per engine,
+    // so it has nothing to check.
+    await engine._syncStartup();
+
+    // The meta/global WBO has been filled with data about the engine
+    let engineData = metaGlobal.payload.engines.rotary;
+    Assert.equal(engineData.version, engine.version);
+    Assert.equal(engineData.syncID, await engine.getSyncID());
+
+    // Sync was reset and server data was wiped
+    Assert.equal(await engine.getLastSync(), 0);
+    Assert.equal(collection.payload("flying"), undefined);
+    Assert.equal(collection.payload("scotsman"), undefined);
+  } finally {
+    await cleanAndGo(engine, server);
+  }
+});
+
+add_task(async function test_syncStartup_serverHasNewerVersion() {
+  _("SyncEngine._syncStartup ");
+
+  let global = new ServerWBO("global", {
+    engines: { rotary: { version: 23456 } },
+  });
+  let server = httpd_setup({
+    "/1.1/foo/storage/meta/global": global.handler(),
+  });
+
+  await SyncTestingInfrastructure(server);
+
+  let engine = makeRotaryEngine();
+  try {
+    // The server has a newer version of the data and our engine can
+    // handle.  That should give us an exception.
+    let error;
+    try {
+      await engine._syncStartup();
+    } catch (ex) {
+      error = ex;
+    }
+    Assert.equal(error.failureCode, VERSION_OUT_OF_DATE);
+  } finally {
+    await cleanAndGo(engine, server);
+  }
+});
+
+add_task(async function test_syncStartup_syncIDMismatchResetsClient() {
+  _("SyncEngine._syncStartup resets sync if syncIDs don't match");
+
+  let server = sync_httpd_setup({});
+
+  await SyncTestingInfrastructure(server);
+
+  // global record with a different syncID than our engine has
+  let engine = makeRotaryEngine();
+  let global = new ServerWBO("global", {
+    engines: { rotary: { version: engine.version, syncID: "foobar" } },
+  });
+  server.registerPathHandler("/1.1/foo/storage/meta/global", global.handler());
+
+  try {
+    // Confirm initial environment
+    Assert.equal(await engine.getSyncID(), "");
+    const changes = await engine._tracker.getChangedIDs();
+    Assert.equal(changes.rekolok, undefined);
+
+    await engine.setLastSync(Date.now() / 1000);
+    await engine._syncStartup();
+
+    // The engine has assumed the server's syncID
+    Assert.equal(await engine.getSyncID(), "foobar");
+
+    // Sync was reset
+    Assert.equal(await engine.getLastSync(), 0);
+  } finally {
+    await cleanAndGo(engine, server);
+  }
+});
+
+add_task(async function test_processIncoming_emptyServer() {
+  _("SyncEngine._processIncoming working with an empty server backend");
+
+  let collection = new ServerCollection();
+  let server = sync_httpd_setup({
+    "/1.1/foo/storage/rotary": collection.handler(),
+  });
+
+  await SyncTestingInfrastructure(server);
+
+  let engine = makeRotaryEngine();
+  try {
+    // Merely ensure that this code path is run without any errors
+    await engine._processIncoming();
+    Assert.equal(await engine.getLastSync(), 0);
+  } finally {
+    await cleanAndGo(engine, server);
+  }
+});
+
+add_task(async function test_processIncoming_createFromServer() {
+  _("SyncEngine._processIncoming creates new records from server data");
+
+  // Some server records that will be downloaded
+  let collection = new ServerCollection();
+  collection.insert(
+    "flying",
+    encryptPayload({ id: "flying", denomination: "LNER Class A3 4472" })
+  );
+  collection.insert(
+    "scotsman",
+    encryptPayload({ id: "scotsman", denomination: "Flying Scotsman" })
+  );
+
+  // Two pathological cases involving relative URIs gone wrong.
+  let pathologicalPayload = encryptPayload({
+    id: "../pathological",
+    denomination: "Pathological Case",
+  });
+  collection.insert("../pathological", pathologicalPayload);
+
+  let server = sync_httpd_setup({
+    "/1.1/foo/storage/rotary": collection.handler(),
+    "/1.1/foo/storage/rotary/flying": collection.wbo("flying").handler(),
+    "/1.1/foo/storage/rotary/scotsman": collection.wbo("scotsman").handler(),
+  });
+
+  await SyncTestingInfrastructure(server);
+
+  await generateNewKeys(Service.collectionKeys);
+
+  let engine = makeRotaryEngine();
+  let syncID = await engine.resetLocalSyncID();
+  let meta_global = Service.recordManager.set(
+    engine.metaURL,
+    new WBORecord(engine.metaURL)
+  );
+  meta_global.payload.engines = { rotary: { version: engine.version, syncID } };
+
+  try {
+    // Confirm initial environment
+    Assert.equal(await engine.getLastSync(), 0);
+    Assert.equal(engine.lastModified, null);
+    Assert.equal(engine._store.items.flying, undefined);
+    Assert.equal(engine._store.items.scotsman, undefined);
+    Assert.equal(engine._store.items["../pathological"], undefined);
+
+    await engine._syncStartup();
+    await engine._processIncoming();
+
+    // Timestamps of last sync and last server modification are set.
+    Assert.greater(await engine.getLastSync(), 0);
+    Assert.greater(engine.lastModified, 0);
+
+    // Local records have been created from the server data.
+    Assert.equal(engine._store.items.flying, "LNER Class A3 4472");
+    Assert.equal(engine._store.items.scotsman, "Flying Scotsman");
+    Assert.equal(engine._store.items["../pathological"], "Pathological Case");
+  } finally {
+    await cleanAndGo(engine, server);
+  }
+});
+
+add_task(async function test_processIncoming_reconcile() {
+  _("SyncEngine._processIncoming updates local records");
+
+  let collection = new ServerCollection();
+
+  // This server record is newer than the corresponding client one,
+  // so it'll update its data.
+  collection.insert(
+    "newrecord",
+    encryptPayload({ id: "newrecord", denomination: "New stuff..." })
+  );
+
+  // This server record is newer than the corresponding client one,
+  // so it'll update its data.
+  collection.insert(
+    "newerserver",
+    encryptPayload({ id: "newerserver", denomination: "New data!" })
+  );
+
+  // This server record is 2 mins older than the client counterpart
+  // but identical to it, so we're expecting the client record's
+  // changedID to be reset.
+  collection.insert(
+    "olderidentical",
+    encryptPayload({
+      id: "olderidentical",
+      denomination: "Older but identical",
+    })
+  );
+  collection._wbos.olderidentical.modified -= 120;
+
+  // This item simply has different data than the corresponding client
+  // record (which is unmodified), so it will update the client as well
+  collection.insert(
+    "updateclient",
+    encryptPayload({ id: "updateclient", denomination: "Get this!" })
+  );
+
+  // This is a dupe of 'original'.
+  collection.insert(
+    "duplication",
+    encryptPayload({ id: "duplication", denomination: "Original Entry" })
+  );
+
+  // This record is marked as deleted, so we're expecting the client
+  // record to be removed.
+  collection.insert(
+    "nukeme",
+    encryptPayload({ id: "nukeme", denomination: "Nuke me!", deleted: true })
+  );
+
+  let server = sync_httpd_setup({
+    "/1.1/foo/storage/rotary": collection.handler(),
+  });
+
+  await SyncTestingInfrastructure(server);
+
+  let engine = makeRotaryEngine();
+  engine._store.items = {
+    newerserver: "New data, but not as new as server!",
+    olderidentical: "Older but identical",
+    updateclient: "Got data?",
+    original: "Original Entry",
+    long_original: "Long Original Entry",
+    nukeme: "Nuke me!",
+  };
+  // Make this record 1 min old, thus older than the one on the server
+  await engine._tracker.addChangedID("newerserver", Date.now() / 1000 - 60);
+  // This record has been changed 2 mins later than the one on the server
+  await engine._tracker.addChangedID("olderidentical", Date.now() / 1000);
+
+  let syncID = await engine.resetLocalSyncID();
+  let meta_global = Service.recordManager.set(
+    engine.metaURL,
+    new WBORecord(engine.metaURL)
+  );
+  meta_global.payload.engines = { rotary: { version: engine.version, syncID } };
+
+  try {
+    // Confirm initial environment
+    Assert.equal(engine._store.items.newrecord, undefined);
+    Assert.equal(
+      engine._store.items.newerserver,
+      "New data, but not as new as server!"
+    );
+    Assert.equal(engine._store.items.olderidentical, "Older but identical");
+    Assert.equal(engine._store.items.updateclient, "Got data?");
+    Assert.equal(engine._store.items.nukeme, "Nuke me!");
+    let changes = await engine._tracker.getChangedIDs();
+    Assert.greater(changes.olderidentical, 0);
+
+    await engine._syncStartup();
+    await engine._processIncoming();
+
+    // Timestamps of last sync and last server modification are set.
+    Assert.greater(await engine.getLastSync(), 0);
+    Assert.greater(engine.lastModified, 0);
+
+    // The new record is created.
+    Assert.equal(engine._store.items.newrecord, "New stuff...");
+
+    // The 'newerserver' record is updated since the server data is newer.
+    Assert.equal(engine._store.items.newerserver, "New data!");
+
+    // The data for 'olderidentical' is identical on the server, so
+    // it's no longer marked as changed anymore.
+    Assert.equal(engine._store.items.olderidentical, "Older but identical");
+    changes = await engine._tracker.getChangedIDs();
+    Assert.equal(changes.olderidentical, undefined);
+
+    // Updated with server data.
+    Assert.equal(engine._store.items.updateclient, "Get this!");
+
+    // The incoming ID is preferred.
+    Assert.equal(engine._store.items.original, undefined);
+    Assert.equal(engine._store.items.duplication, "Original Entry");
+    Assert.notEqual(engine._delete.ids.indexOf("original"), -1);
+
+    // The 'nukeme' record marked as deleted is removed.
+    Assert.equal(engine._store.items.nukeme, undefined);
+  } finally {
+    await cleanAndGo(engine, server);
+  }
+});
+
+add_task(async function test_processIncoming_reconcile_local_deleted() {
+  _("Ensure local, duplicate ID is deleted on server.");
+
+  // When a duplicate is resolved, the local ID (which is never taken) should
+  // be deleted on the server.
+  let [engine, server, user] = await createServerAndConfigureClient();
+
+  let now = Date.now() / 1000 - 10;
+  await engine.setLastSync(now);
+  engine.lastModified = now + 1;
+
+  let record = encryptPayload({
+    id: "DUPE_INCOMING",
+    denomination: "incoming",
+  });
+  let wbo = new ServerWBO("DUPE_INCOMING", record, now + 2);
+  server.insertWBO(user, "rotary", wbo);
+
+  record = encryptPayload({ id: "DUPE_LOCAL", denomination: "local" });
+  wbo = new ServerWBO("DUPE_LOCAL", record, now - 1);
+  server.insertWBO(user, "rotary", wbo);
+
+  await engine._store.create({ id: "DUPE_LOCAL", denomination: "local" });
+  Assert.ok(await engine._store.itemExists("DUPE_LOCAL"));
+  Assert.equal("DUPE_LOCAL", await engine._findDupe({ id: "DUPE_INCOMING" }));
+
+  await engine._sync();
+
+  do_check_attribute_count(engine._store.items, 1);
+  Assert.ok("DUPE_INCOMING" in engine._store.items);
+
+  let collection = server.getCollection(user, "rotary");
+  Assert.equal(1, collection.count());
+  Assert.notEqual(undefined, collection.wbo("DUPE_INCOMING"));
+
+  await cleanAndGo(engine, server);
+});
+
+add_task(async function test_processIncoming_reconcile_equivalent() {
+  _("Ensure proper handling of incoming records that match local.");
+
+  let [engine, server, user] = await createServerAndConfigureClient();
+
+  let now = Date.now() / 1000 - 10;
+  await engine.setLastSync(now);
+  engine.lastModified = now + 1;
+
+  let record = encryptPayload({ id: "entry", denomination: "denomination" });
+  let wbo = new ServerWBO("entry", record, now + 2);
+  server.insertWBO(user, "rotary", wbo);
+
+  engine._store.items = { entry: "denomination" };
+  Assert.ok(await engine._store.itemExists("entry"));
+
+  await engine._sync();
+
+  do_check_attribute_count(engine._store.items, 1);
+
+  await cleanAndGo(engine, server);
+});
+
+add_task(
+  async function test_processIncoming_reconcile_locally_deleted_dupe_new() {
+    _(
+      "Ensure locally deleted duplicate record newer than incoming is handled."
+    );
+
+    // This is a somewhat complicated test. It ensures that if a client receives
+    // a modified record for an item that is deleted locally but with a different
+    // ID that the incoming record is ignored. This is a corner case for record
+    // handling, but it needs to be supported.
+    let [engine, server, user] = await createServerAndConfigureClient();
+
+    let now = Date.now() / 1000 - 10;
+    await engine.setLastSync(now);
+    engine.lastModified = now + 1;
+
+    let record = encryptPayload({
+      id: "DUPE_INCOMING",
+      denomination: "incoming",
+    });
+    let wbo = new ServerWBO("DUPE_INCOMING", record, now + 2);
+    server.insertWBO(user, "rotary", wbo);
+
+    // Simulate a locally-deleted item.
+    engine._store.items = {};
+    await engine._tracker.addChangedID("DUPE_LOCAL", now + 3);
+    Assert.equal(false, await engine._store.itemExists("DUPE_LOCAL"));
+    Assert.equal(false, await engine._store.itemExists("DUPE_INCOMING"));
+    Assert.equal("DUPE_LOCAL", await engine._findDupe({ id: "DUPE_INCOMING" }));
+
+    engine.lastModified = server.getCollection(user, engine.name).timestamp;
+    await engine._sync();
+
+    // After the sync, the server's payload for the original ID should be marked
+    // as deleted.
+    do_check_empty(engine._store.items);
+    let collection = server.getCollection(user, "rotary");
+    Assert.equal(1, collection.count());
+    wbo = collection.wbo("DUPE_INCOMING");
+    Assert.notEqual(null, wbo);
+    let payload = wbo.getCleartext();
+    Assert.ok(payload.deleted);
+
+    await cleanAndGo(engine, server);
+  }
+);
+
+add_task(
+  async function test_processIncoming_reconcile_locally_deleted_dupe_old() {
+    _(
+      "Ensure locally deleted duplicate record older than incoming is restored."
+    );
+
+    // This is similar to the above test except it tests the condition where the
+    // incoming record is newer than the local deletion, therefore overriding it.
+
+    let [engine, server, user] = await createServerAndConfigureClient();
+
+    let now = Date.now() / 1000 - 10;
+    await engine.setLastSync(now);
+    engine.lastModified = now + 1;
+
+    let record = encryptPayload({
+      id: "DUPE_INCOMING",
+      denomination: "incoming",
+    });
+    let wbo = new ServerWBO("DUPE_INCOMING", record, now + 2);
+    server.insertWBO(user, "rotary", wbo);
+
+    // Simulate a locally-deleted item.
+    engine._store.items = {};
+    await engine._tracker.addChangedID("DUPE_LOCAL", now + 1);
+    Assert.equal(false, await engine._store.itemExists("DUPE_LOCAL"));
+    Assert.equal(false, await engine._store.itemExists("DUPE_INCOMING"));
+    Assert.equal("DUPE_LOCAL", await engine._findDupe({ id: "DUPE_INCOMING" }));
+
+    await engine._sync();
+
+    // Since the remote change is newer, the incoming item should exist locally.
+    do_check_attribute_count(engine._store.items, 1);
+    Assert.ok("DUPE_INCOMING" in engine._store.items);
+    Assert.equal("incoming", engine._store.items.DUPE_INCOMING);
+
+    let collection = server.getCollection(user, "rotary");
+    Assert.equal(1, collection.count());
+    wbo = collection.wbo("DUPE_INCOMING");
+    let payload = wbo.getCleartext();
+    Assert.equal("incoming", payload.denomination);
+
+    await cleanAndGo(engine, server);
+  }
+);
+
+add_task(async function test_processIncoming_reconcile_changed_dupe() {
+  _("Ensure that locally changed duplicate record is handled properly.");
+
+  let [engine, server, user] = await createServerAndConfigureClient();
+
+  let now = Date.now() / 1000 - 10;
+  await engine.setLastSync(now);
+  engine.lastModified = now + 1;
+
+  // The local record is newer than the incoming one, so it should be retained.
+  let record = encryptPayload({
+    id: "DUPE_INCOMING",
+    denomination: "incoming",
+  });
+  let wbo = new ServerWBO("DUPE_INCOMING", record, now + 2);
+  server.insertWBO(user, "rotary", wbo);
+
+  await engine._store.create({ id: "DUPE_LOCAL", denomination: "local" });
+  await engine._tracker.addChangedID("DUPE_LOCAL", now + 3);
+  Assert.ok(await engine._store.itemExists("DUPE_LOCAL"));
+  Assert.equal("DUPE_LOCAL", await engine._findDupe({ id: "DUPE_INCOMING" }));
+
+  engine.lastModified = server.getCollection(user, engine.name).timestamp;
+  await engine._sync();
+
+  // The ID should have been changed to incoming.
+  do_check_attribute_count(engine._store.items, 1);
+  Assert.ok("DUPE_INCOMING" in engine._store.items);
+
+  // On the server, the local ID should be deleted and the incoming ID should
+  // have its payload set to what was in the local record.
+  let collection = server.getCollection(user, "rotary");
+  Assert.equal(1, collection.count());
+  wbo = collection.wbo("DUPE_INCOMING");
+  Assert.notEqual(undefined, wbo);
+  let payload = wbo.getCleartext();
+  Assert.equal("local", payload.denomination);
+
+  await cleanAndGo(engine, server);
+});
+
+add_task(async function test_processIncoming_reconcile_changed_dupe_new() {
+  _("Ensure locally changed duplicate record older than incoming is ignored.");
+
+  // This test is similar to the above except the incoming record is younger
+  // than the local record. The incoming record should be authoritative.
+  let [engine, server, user] = await createServerAndConfigureClient();
+
+  let now = Date.now() / 1000 - 10;
+  await engine.setLastSync(now);
+  engine.lastModified = now + 1;
+
+  let record = encryptPayload({
+    id: "DUPE_INCOMING",
+    denomination: "incoming",
+  });
+  let wbo = new ServerWBO("DUPE_INCOMING", record, now + 2);
+  server.insertWBO(user, "rotary", wbo);
+
+  await engine._store.create({ id: "DUPE_LOCAL", denomination: "local" });
+  await engine._tracker.addChangedID("DUPE_LOCAL", now + 1);
+  Assert.ok(await engine._store.itemExists("DUPE_LOCAL"));
+  Assert.equal("DUPE_LOCAL", await engine._findDupe({ id: "DUPE_INCOMING" }));
+
+  engine.lastModified = server.getCollection(user, engine.name).timestamp;
+  await engine._sync();
+
+  // The ID should have been changed to incoming.
+  do_check_attribute_count(engine._store.items, 1);
+  Assert.ok("DUPE_INCOMING" in engine._store.items);
+
+  // On the server, the local ID should be deleted and the incoming ID should
+  // have its payload retained.
+  let collection = server.getCollection(user, "rotary");
+  Assert.equal(1, collection.count());
+  wbo = collection.wbo("DUPE_INCOMING");
+  Assert.notEqual(undefined, wbo);
+  let payload = wbo.getCleartext();
+  Assert.equal("incoming", payload.denomination);
+  await cleanAndGo(engine, server);
+});
+
+add_task(async function test_processIncoming_resume_toFetch() {
+  _(
+    "toFetch and previousFailed items left over from previous syncs are fetched on the next sync, along with new items."
+  );
+
+  const LASTSYNC = Date.now() / 1000;
+
+  // Server records that will be downloaded
+  let collection = new ServerCollection();
+  collection.insert(
+    "flying",
+    encryptPayload({ id: "flying", denomination: "LNER Class A3 4472" })
+  );
+  collection.insert(
+    "scotsman",
+    encryptPayload({ id: "scotsman", denomination: "Flying Scotsman" })
+  );
+  collection.insert(
+    "rekolok",
+    encryptPayload({ id: "rekolok", denomination: "Rekonstruktionslokomotive" })
+  );
+  for (let i = 0; i < 3; i++) {
+    let id = "failed" + i;
+    let payload = encryptPayload({ id, denomination: "Record No. " + i });
+    let wbo = new ServerWBO(id, payload);
+    wbo.modified = LASTSYNC - 10;
+    collection.insertWBO(wbo);
+  }
+
+  collection.wbo("flying").modified = collection.wbo("scotsman").modified =
+    LASTSYNC - 10;
+  collection._wbos.rekolok.modified = LASTSYNC + 10;
+
+  // Time travel 10 seconds into the future but still download the above WBOs.
+  let engine = makeRotaryEngine();
+  await engine.setLastSync(LASTSYNC);
+  engine.toFetch = new SerializableSet(["flying", "scotsman"]);
+  engine.previousFailedIn = new SerializableSet([
+    "failed0",
+    "failed1",
+    "failed2",
+  ]);
+
+  let server = sync_httpd_setup({
+    "/1.1/foo/storage/rotary": collection.handler(),
+  });
+
+  await SyncTestingInfrastructure(server);
+
+  let syncID = await engine.resetLocalSyncID();
+  let meta_global = Service.recordManager.set(
+    engine.metaURL,
+    new WBORecord(engine.metaURL)
+  );
+  meta_global.payload.engines = { rotary: { version: engine.version, syncID } };
+  try {
+    // Confirm initial environment
+    Assert.equal(engine._store.items.flying, undefined);
+    Assert.equal(engine._store.items.scotsman, undefined);
+    Assert.equal(engine._store.items.rekolok, undefined);
+
+    await engine._syncStartup();
+    await engine._processIncoming();
+
+    // Local records have been created from the server data.
+    Assert.equal(engine._store.items.flying, "LNER Class A3 4472");
+    Assert.equal(engine._store.items.scotsman, "Flying Scotsman");
+    Assert.equal(engine._store.items.rekolok, "Rekonstruktionslokomotive");
+    Assert.equal(engine._store.items.failed0, "Record No. 0");
+    Assert.equal(engine._store.items.failed1, "Record No. 1");
+    Assert.equal(engine._store.items.failed2, "Record No. 2");
+    Assert.equal(engine.previousFailedIn.size, 0);
+  } finally {
+    await cleanAndGo(engine, server);
+  }
+});
+
+add_task(async function test_processIncoming_notify_count() {
+  _("Ensure that failed records are reported only once.");
+
+  const NUMBER_OF_RECORDS = 15;
+
+  // Engine that fails every 5 records.
+  let engine = makeRotaryEngine();
+  engine._store._applyIncomingBatch = engine._store.applyIncomingBatch;
+  engine._store.applyIncomingBatch = async function (records, countTelemetry) {
+    let sortedRecords = records.sort((a, b) => (a.id > b.id ? 1 : -1));
+    let recordsToApply = [],
+      recordsToFail = [];
+    for (let i = 0; i < sortedRecords.length; i++) {
+      (i % 5 === 0 ? recordsToFail : recordsToApply).push(sortedRecords[i]);
+    }
+    recordsToFail.forEach(() => {
+      countTelemetry.addIncomingFailedReason("failed message");
+    });
+    await engine._store._applyIncomingBatch(recordsToApply, countTelemetry);
+
+    return recordsToFail.map(record => record.id);
+  };
+
+  // Create a batch of server side records.
+  let collection = new ServerCollection();
+  for (var i = 0; i < NUMBER_OF_RECORDS; i++) {
+    let id = "record-no-" + i.toString(10).padStart(2, "0");
+    let payload = encryptPayload({ id, denomination: "Record No. " + id });
+    collection.insert(id, payload);
+  }
+
+  let server = sync_httpd_setup({
+    "/1.1/foo/storage/rotary": collection.handler(),
+  });
+
+  await SyncTestingInfrastructure(server);
+
+  let syncID = await engine.resetLocalSyncID();
+  let meta_global = Service.recordManager.set(
+    engine.metaURL,
+    new WBORecord(engine.metaURL)
+  );
+  meta_global.payload.engines = { rotary: { version: engine.version, syncID } };
+  try {
+    // Confirm initial environment.
+    Assert.equal(await engine.getLastSync(), 0);
+    Assert.equal(engine.toFetch.size, 0);
+    Assert.equal(engine.previousFailedIn.size, 0);
+    do_check_empty(engine._store.items);
+
+    let called = 0;
+    let counts;
+    function onApplied(count) {
+      _("Called with " + JSON.stringify(counts));
+      counts = count;
+      called++;
+    }
+    Svc.Obs.add("weave:engine:sync:applied", onApplied);
+
+    // Do sync.
+    await engine._syncStartup();
+    await engine._processIncoming();
+
+    // Confirm failures.
+    do_check_attribute_count(engine._store.items, 12);
+    Assert.deepEqual(
+      Array.from(engine.previousFailedIn).sort(),
+      ["record-no-00", "record-no-05", "record-no-10"].sort()
+    );
+
+    // There are newly failed records and they are reported.
+    Assert.equal(called, 1);
+    Assert.equal(counts.failed, 3);
+    Assert.equal(counts.failedReasons[0].count, 3);
+    Assert.equal(counts.failedReasons[0].name, "failed message");
+    Assert.equal(counts.applied, 15);
+    Assert.equal(counts.newFailed, 3);
+    Assert.equal(counts.succeeded, 12);
+
+    // Sync again, 1 of the failed items are the same, the rest didn't fail.
+    await engine._processIncoming();
+
+    // Confirming removed failures.
+    do_check_attribute_count(engine._store.items, 14);
+    // After failing twice the record that failed again [record-no-00]
+    // should NOT be stored to try again
+    Assert.deepEqual(Array.from(engine.previousFailedIn), []);
+
+    Assert.equal(called, 2);
+    Assert.equal(counts.failed, 1);
+    Assert.equal(counts.failedReasons[0].count, 1);
+    Assert.equal(counts.failedReasons[0].name, "failed message");
+    Assert.equal(counts.applied, 3);
+    Assert.equal(counts.newFailed, 0);
+    Assert.equal(counts.succeeded, 2);
+
+    Svc.Obs.remove("weave:engine:sync:applied", onApplied);
+  } finally {
+    await cleanAndGo(engine, server);
+  }
+});
+
+add_task(async function test_processIncoming_previousFailed() {
+  _("Ensure that failed records are retried.");
+
+  const NUMBER_OF_RECORDS = 14;
+
+  // Engine that alternates between failing and applying every 2 records.
+  let engine = makeRotaryEngine();
+  engine._store._applyIncomingBatch = engine._store.applyIncomingBatch;
+  engine._store.applyIncomingBatch = async function (records, countTelemetry) {
+    let sortedRecords = records.sort((a, b) => (a.id > b.id ? 1 : -1));
+    let recordsToApply = [],
+      recordsToFail = [];
+    let chunks = Array.from(PlacesUtils.chunkArray(sortedRecords, 2));
+    for (let i = 0; i < chunks.length; i++) {
+      (i % 2 === 0 ? recordsToFail : recordsToApply).push(...chunks[i]);
+    }
+    await engine._store._applyIncomingBatch(recordsToApply, countTelemetry);
+    return recordsToFail.map(record => record.id);
+  };
+
+  // Create a batch of server side records.
+  let collection = new ServerCollection();
+  for (var i = 0; i < NUMBER_OF_RECORDS; i++) {
+    let id = "record-no-" + i.toString(10).padStart(2, "0");
+    let payload = encryptPayload({ id, denomination: "Record No. " + i });
+    collection.insert(id, payload);
+  }
+
+  let server = sync_httpd_setup({
+    "/1.1/foo/storage/rotary": collection.handler(),
+  });
+
+  await SyncTestingInfrastructure(server);
+
+  let syncID = await engine.resetLocalSyncID();
+  let meta_global = Service.recordManager.set(
+    engine.metaURL,
+    new WBORecord(engine.metaURL)
+  );
+  meta_global.payload.engines = { rotary: { version: engine.version, syncID } };
+  try {
+    // Confirm initial environment.
+    Assert.equal(await engine.getLastSync(), 0);
+    Assert.equal(engine.toFetch.size, 0);
+    Assert.equal(engine.previousFailedIn.size, 0);
+    do_check_empty(engine._store.items);
+
+    // Initial failed items in previousFailedIn to be reset.
+    let previousFailedIn = new SerializableSet([
+      Utils.makeGUID(),
+      Utils.makeGUID(),
+      Utils.makeGUID(),
+    ]);
+    engine.previousFailedIn = previousFailedIn;
+    Assert.equal(engine.previousFailedIn, previousFailedIn);
+
+    // Do sync.
+    await engine._syncStartup();
+    await engine._processIncoming();
+
+    // Expected result: 4 sync batches with 2 failures each => 8 failures
+    do_check_attribute_count(engine._store.items, 6);
+    Assert.deepEqual(
+      Array.from(engine.previousFailedIn).sort(),
+      [
+        "record-no-00",
+        "record-no-01",
+        "record-no-04",
+        "record-no-05",
+        "record-no-08",
+        "record-no-09",
+        "record-no-12",
+        "record-no-13",
+      ].sort()
+    );
+
+    // Sync again with the same failed items (records 0, 1, 8, 9).
+    await engine._processIncoming();
+
+    do_check_attribute_count(engine._store.items, 10);
+    // A second sync with the same failed items should NOT add the same items again.
+    // Items that did not fail a second time should no longer be in previousFailedIn.
+    Assert.deepEqual(Array.from(engine.previousFailedIn).sort(), []);
+
+    // Refetched items that didn't fail the second time are in engine._store.items.
+    Assert.equal(engine._store.items["record-no-04"], "Record No. 4");
+    Assert.equal(engine._store.items["record-no-05"], "Record No. 5");
+    Assert.equal(engine._store.items["record-no-12"], "Record No. 12");
+    Assert.equal(engine._store.items["record-no-13"], "Record No. 13");
+  } finally {
+    await cleanAndGo(engine, server);
+  }
+});
+
+add_task(async function test_processIncoming_failed_records() {
+  _(
+    "Ensure that failed records from _reconcile and applyIncomingBatch are refetched."
+  );
+
+  // Let's create three and a bit batches worth of server side records.
+  let APPLY_BATCH_SIZE = 50;
+  let collection = new ServerCollection();
+  const NUMBER_OF_RECORDS = APPLY_BATCH_SIZE * 3 + 5;
+  for (let i = 0; i < NUMBER_OF_RECORDS; i++) {
+    let id = "record-no-" + i;
+    let payload = encryptPayload({ id, denomination: "Record No. " + id });
+    let wbo = new ServerWBO(id, payload);
+    wbo.modified = Date.now() / 1000 + 60 * (i - APPLY_BATCH_SIZE * 3);
+    collection.insertWBO(wbo);
+  }
+
+  // Engine that batches but likes to throw on a couple of records,
+  // two in each batch: the even ones fail in reconcile, the odd ones
+  // in applyIncoming.
+  const BOGUS_RECORDS = [
+    "record-no-" + 42,
+    "record-no-" + 23,
+    "record-no-" + (42 + APPLY_BATCH_SIZE),
+    "record-no-" + (23 + APPLY_BATCH_SIZE),
+    "record-no-" + (42 + APPLY_BATCH_SIZE * 2),
+    "record-no-" + (23 + APPLY_BATCH_SIZE * 2),
+    "record-no-" + (2 + APPLY_BATCH_SIZE * 3),
+    "record-no-" + (1 + APPLY_BATCH_SIZE * 3),
+  ];
+  let engine = makeRotaryEngine();
+
+  engine.__reconcile = engine._reconcile;
+  engine._reconcile = async function _reconcile(record) {
+    if (BOGUS_RECORDS.indexOf(record.id) % 2 == 0) {
+      throw new Error("I don't like this record! Baaaaaah!");
+    }
+    return this.__reconcile.apply(this, arguments);
+  };
+  engine._store._applyIncoming = engine._store.applyIncoming;
+  engine._store.applyIncoming = async function (record) {
+    if (BOGUS_RECORDS.indexOf(record.id) % 2 == 1) {
+      throw new Error("I don't like this record! Baaaaaah!");
+    }
+    return this._applyIncoming.apply(this, arguments);
+  };
+
+  // Keep track of requests made of a collection.
+  let count = 0;
+  let uris = [];
+  function recording_handler(recordedCollection) {
+    let h = recordedCollection.handler();
+    return function (req, res) {
+      ++count;
+      uris.push(req.path + "?" + req.queryString);
+      return h(req, res);
+    };
+  }
+  let server = sync_httpd_setup({
+    "/1.1/foo/storage/rotary": recording_handler(collection),
+  });
+
+  await SyncTestingInfrastructure(server);
+
+  let syncID = await engine.resetLocalSyncID();
+  let meta_global = Service.recordManager.set(
+    engine.metaURL,
+    new WBORecord(engine.metaURL)
+  );
+  meta_global.payload.engines = { rotary: { version: engine.version, syncID } };
+
+  try {
+    // Confirm initial environment
+    Assert.equal(await engine.getLastSync(), 0);
+    Assert.equal(engine.toFetch.size, 0);
+    Assert.equal(engine.previousFailedIn.size, 0);
+    do_check_empty(engine._store.items);
+
+    let observerSubject;
+    let observerData;
+    Svc.Obs.add("weave:engine:sync:applied", function onApplied(subject, data) {
+      Svc.Obs.remove("weave:engine:sync:applied", onApplied);
+      observerSubject = subject;
+      observerData = data;
+    });
+
+    await engine._syncStartup();
+    await engine._processIncoming();
+
+    // Ensure that all records but the bogus 4 have been applied.
+    do_check_attribute_count(
+      engine._store.items,
+      NUMBER_OF_RECORDS - BOGUS_RECORDS.length
+    );
+
+    // Ensure that the bogus records will be fetched again on the next sync.
+    Assert.equal(engine.previousFailedIn.size, BOGUS_RECORDS.length);
+    Assert.deepEqual(
+      Array.from(engine.previousFailedIn).sort(),
+      BOGUS_RECORDS.sort()
+    );
+
+    // Ensure the observer was notified
+    Assert.equal(observerData, engine.name);
+    Assert.equal(observerSubject.failed, BOGUS_RECORDS.length);
+    Assert.equal(observerSubject.newFailed, BOGUS_RECORDS.length);
+
+    // Testing batching of failed item fetches.
+    // Try to sync again. Ensure that we split the request into chunks to avoid
+    // URI length limitations.
+    async function batchDownload(batchSize) {
+      count = 0;
+      uris = [];
+      engine.guidFetchBatchSize = batchSize;
+      await engine._processIncoming();
+      _("Tried again. Requests: " + count + "; URIs: " + JSON.stringify(uris));
+      return count;
+    }
+
+    // There are 8 bad records, so this needs 3 fetches.
+    _("Test batching with ID batch size 3, normal mobile batch size.");
+    Assert.equal(await batchDownload(3), 3);
+
+    // Since there the previous batch failed again, there should be
+    // no more records to fetch
+    _("Test that the second time a record failed to sync, gets ignored");
+    Assert.equal(await batchDownload(BOGUS_RECORDS.length), 0);
+  } finally {
+    await cleanAndGo(engine, server);
+  }
+});
+
+add_task(async function test_processIncoming_decrypt_failed() {
+  _("Ensure that records failing to decrypt are either replaced or refetched.");
+
+  // Some good and some bogus records. One doesn't contain valid JSON,
+  // the other will throw during decrypt.
+  let collection = new ServerCollection();
+  collection._wbos.flying = new ServerWBO(
+    "flying",
+    encryptPayload({ id: "flying", denomination: "LNER Class A3 4472" })
+  );
+  collection._wbos.nojson = new ServerWBO("nojson", "This is invalid JSON");
+  collection._wbos.nojson2 = new ServerWBO("nojson2", "This is invalid JSON");
+  collection._wbos.scotsman = new ServerWBO(
+    "scotsman",
+    encryptPayload({ id: "scotsman", denomination: "Flying Scotsman" })
+  );
+  collection._wbos.nodecrypt = new ServerWBO("nodecrypt", "Decrypt this!");
+  collection._wbos.nodecrypt2 = new ServerWBO("nodecrypt2", "Decrypt this!");
+
+  // Patch the fake crypto service to throw on the record above.
+  Weave.Crypto._decrypt = Weave.Crypto.decrypt;
+  Weave.Crypto.decrypt = function (ciphertext) {
+    if (ciphertext == "Decrypt this!") {
+      throw new Error(
+        "Derp! Cipher finalized failed. Im ur crypto destroyin ur recordz."
+      );
+    }
+    return this._decrypt.apply(this, arguments);
+  };
+
+  // Some broken records also exist locally.
+  let engine = makeRotaryEngine();
+  engine.enabled = true;
+  engine._store.items = { nojson: "Valid JSON", nodecrypt: "Valid ciphertext" };
+
+  let server = sync_httpd_setup({
+    "/1.1/foo/storage/rotary": collection.handler(),
+  });
+
+  await SyncTestingInfrastructure(server);
+
+  let syncID = await engine.resetLocalSyncID();
+  let meta_global = Service.recordManager.set(
+    engine.metaURL,
+    new WBORecord(engine.metaURL)
+  );
+  meta_global.payload.engines = { rotary: { version: engine.version, syncID } };
+  try {
+    // Confirm initial state
+    Assert.equal(engine.toFetch.size, 0);
+    Assert.equal(engine.previousFailedIn.size, 0);
+
+    let observerSubject;
+    let observerData;
+    Svc.Obs.add("weave:engine:sync:applied", function onApplied(subject, data) {
+      Svc.Obs.remove("weave:engine:sync:applied", onApplied);
+      observerSubject = subject;
+      observerData = data;
+    });
+
+    await engine.setLastSync(collection.wbo("nojson").modified - 1);
+    let ping = await sync_engine_and_validate_telem(engine, true);
+    Assert.equal(ping.engines[0].incoming.applied, 2);
+    Assert.equal(ping.engines[0].incoming.failed, 4);
+    console.log("incoming telem: ", ping.engines[0].incoming);
+    Assert.equal(
+      ping.engines[0].incoming.failedReasons[0].name,
+      "No ciphertext: nothing to decrypt?"
+    );
+    // There should be 4 of the same error
+    Assert.equal(ping.engines[0].incoming.failedReasons[0].count, 4);
+
+    Assert.equal(engine.previousFailedIn.size, 4);
+    Assert.ok(engine.previousFailedIn.has("nojson"));
+    Assert.ok(engine.previousFailedIn.has("nojson2"));
+    Assert.ok(engine.previousFailedIn.has("nodecrypt"));
+    Assert.ok(engine.previousFailedIn.has("nodecrypt2"));
+
+    // Ensure the observer was notified
+    Assert.equal(observerData, engine.name);
+    Assert.equal(observerSubject.applied, 2);
+    Assert.equal(observerSubject.failed, 4);
+    Assert.equal(observerSubject.failedReasons[0].count, 4);
+  } finally {
+    await promiseClean(engine, server);
+  }
+});
+
+add_task(async function test_uploadOutgoing_toEmptyServer() {
+  _("SyncEngine._uploadOutgoing uploads new records to server");
+
+  let collection = new ServerCollection();
+  collection._wbos.flying = new ServerWBO("flying");
+  collection._wbos.scotsman = new ServerWBO("scotsman");
+  collection._wbos.failed = new ServerWBO("failed");
+
+  let server = sync_httpd_setup({
+    "/1.1/foo/storage/rotary": collection.handler(),
+    "/1.1/foo/storage/rotary/flying": collection.wbo("flying").handler(),
+    "/1.1/foo/storage/rotary/scotsman": collection.wbo("scotsman").handler(),
+    "/1.1/foo/storage/rotary/failed": collection.wbo("failed").handler(),
+  });
+
+  await SyncTestingInfrastructure(server);
+  await generateNewKeys(Service.collectionKeys);
+
+  let engine = makeRotaryEngine();
+  engine._store.items = {
+    flying: "LNER Class A3 4472",
+    scotsman: "Flying Scotsman",
+    failed: "Previously Failed Item",
+    failagain: "Item that failed and will fail again",
+  };
+  // Mark some of these records as changed
+  await engine._tracker.addChangedID("scotsman", 0);
+  await engine._tracker.addChangedID("failed", 0);
+  await engine._tracker.addChangedID("failagain", 0);
+
+  let syncID = await engine.resetLocalSyncID();
+  let meta_global = Service.recordManager.set(
+    engine.metaURL,
+    new WBORecord(engine.metaURL)
+  );
+  meta_global.payload.engines = { rotary: { version: engine.version, syncID } };
+
+  try {
+    await engine.setLastSync(123); // needs to be non-zero so that tracker is queried
+    engine.previousFailedOut = new SerializableSet(["failed", "failagain"]);
+
+    // Confirm initial environment
+    Assert.equal(collection.payload("flying"), undefined);
+    Assert.equal(collection.payload("scotsman"), undefined);
+    Assert.equal(collection.payload("failed"), undefined);
+
+    await engine._syncStartup();
+    await engine._uploadOutgoing();
+
+    // Ensure the marked record ('scotsman') and previously failed record
+    // ('failed') have been uploaded and are no longer marked.
+    Assert.equal(collection.payload("flying"), undefined);
+    Assert.ok(!!collection.payload("scotsman"));
+    Assert.equal(collection.cleartext("scotsman").id, "scotsman");
+    const changes = await engine._tracker.getChangedIDs();
+    Assert.equal(changes.scotsman, undefined);
+    Assert.ok(!!collection.payload("failed"));
+    Assert.equal(collection.cleartext("failed").id, "failed");
+    Assert.equal(changes.failed, undefined);
+
+    // The 'flying' record wasn't marked and 'failagain' failed, so they
+    // weren't uploaded
+    Assert.equal(collection.payload("flying"), undefined);
+    Assert.equal(changes.flying, undefined);
+    Assert.equal(changes.failagain, undefined);
+
+    // Nothing failed on this run except failagain' which we already retried,
+    // so this should be empty.
+    Assert.equal(engine.previousFailedOut.size, 0);
+  } finally {
+    await cleanAndGo(engine, server);
+  }
+});
+
+async function test_uploadOutgoing_max_record_payload_bytes(
+  allowSkippedRecord
+) {
+  _(
+    "SyncEngine._uploadOutgoing throws when payload is bigger than max_record_payload_bytes"
+  );
+  let collection = new ServerCollection();
+  collection._wbos.flying = new ServerWBO("flying");
+  collection._wbos.scotsman = new ServerWBO("scotsman");
+
+  let server = sync_httpd_setup({
+    "/1.1/foo/storage/rotary": collection.handler(),
+    "/1.1/foo/storage/rotary/flying": collection.wbo("flying").handler(),
+    "/1.1/foo/storage/rotary/scotsman": collection.wbo("scotsman").handler(),
+  });
+
+  await SyncTestingInfrastructure(server);
+  await generateNewKeys(Service.collectionKeys);
+
+  let engine = makeRotaryEngine();
+  engine.allowSkippedRecord = allowSkippedRecord;
+  engine._store.items = { flying: "a".repeat(1024 * 1024), scotsman: "abcd" };
+
+  await engine._tracker.addChangedID("flying", 1000);
+  await engine._tracker.addChangedID("scotsman", 1000);
+
+  let syncID = await engine.resetLocalSyncID();
+  let meta_global = Service.recordManager.set(
+    engine.metaURL,
+    new WBORecord(engine.metaURL)
+  );
+  meta_global.payload.engines = { rotary: { version: engine.version, syncID } };
+
+  try {
+    await engine.setLastSync(1); // needs to be non-zero so that tracker is queried
+
+    // Confirm initial environment
+    Assert.equal(collection.payload("flying"), undefined);
+    Assert.equal(collection.payload("scotsman"), undefined);
+
+    await engine._syncStartup();
+    await engine._uploadOutgoing();
+
+    if (!allowSkippedRecord) {
+      do_throw("should not get here");
+    }
+
+    await engine.trackRemainingChanges();
+
+    // Check we uploaded the other record to the server
+    Assert.ok(collection.payload("scotsman"));
+    // And that we won't try to upload the huge record next time.
+    const changes = await engine._tracker.getChangedIDs();
+    Assert.equal(changes.flying, undefined);
+  } catch (e) {
+    if (allowSkippedRecord) {
+      do_throw("should not get here");
+    }
+
+    await engine.trackRemainingChanges();
+
+    // Check that we will try to upload the huge record next time
+    const changes = await engine._tracker.getChangedIDs();
+    Assert.equal(changes.flying, 1000);
+  } finally {
+    // Check we didn't upload the oversized record to the server
+    Assert.equal(collection.payload("flying"), undefined);
+    await cleanAndGo(engine, server);
+  }
+}
+
+add_task(
+  async function test_uploadOutgoing_max_record_payload_bytes_disallowSkippedRecords() {
+    return test_uploadOutgoing_max_record_payload_bytes(false);
+  }
+);
+
+add_task(
+  async function test_uploadOutgoing_max_record_payload_bytes_allowSkippedRecords() {
+    return test_uploadOutgoing_max_record_payload_bytes(true);
+  }
+);
+
+add_task(async function test_uploadOutgoing_failed() {
+  _(
+    "SyncEngine._uploadOutgoing doesn't clear the tracker of objects that failed to upload."
+  );
+
+  let collection = new ServerCollection();
+  // We only define the "flying" WBO on the server, not the "scotsman"
+  // and "peppercorn" ones.
+  collection._wbos.flying = new ServerWBO("flying");
+
+  let server = sync_httpd_setup({
+    "/1.1/foo/storage/rotary": collection.handler(),
+  });
+
+  await SyncTestingInfrastructure(server);
+
+  let engine = makeRotaryEngine();
+  engine._store.items = {
+    flying: "LNER Class A3 4472",
+    scotsman: "Flying Scotsman",
+    peppercorn: "Peppercorn Class",
+  };
+  // Mark these records as changed
+  const FLYING_CHANGED = 12345;
+  const SCOTSMAN_CHANGED = 23456;
+  const PEPPERCORN_CHANGED = 34567;
+  await engine._tracker.addChangedID("flying", FLYING_CHANGED);
+  await engine._tracker.addChangedID("scotsman", SCOTSMAN_CHANGED);
+  await engine._tracker.addChangedID("peppercorn", PEPPERCORN_CHANGED);
+
+  let syncID = await engine.resetLocalSyncID();
+  let meta_global = Service.recordManager.set(
+    engine.metaURL,
+    new WBORecord(engine.metaURL)
+  );
+  meta_global.payload.engines = { rotary: { version: engine.version, syncID } };
+
+  try {
+    await engine.setLastSync(123); // needs to be non-zero so that tracker is queried
+
+    // Confirm initial environment
+    Assert.equal(collection.payload("flying"), undefined);
+    let changes = await engine._tracker.getChangedIDs();
+    Assert.equal(changes.flying, FLYING_CHANGED);
+    Assert.equal(changes.scotsman, SCOTSMAN_CHANGED);
+    Assert.equal(changes.peppercorn, PEPPERCORN_CHANGED);
+
+    engine.enabled = true;
+    await sync_engine_and_validate_telem(engine, true);
+
+    // Ensure the 'flying' record has been uploaded and is no longer marked.
+    Assert.ok(!!collection.payload("flying"));
+    changes = await engine._tracker.getChangedIDs();
+    Assert.equal(changes.flying, undefined);
+
+    // The 'scotsman' and 'peppercorn' records couldn't be uploaded so
+    // they were added to `previousFailedOut` and weren't cleared from the
+    // tracker.
+    Assert.equal(changes.scotsman, SCOTSMAN_CHANGED);
+    Assert.equal(changes.peppercorn, PEPPERCORN_CHANGED);
+    Assert.equal(engine.previousFailedOut.size, 2);
+    Assert.ok(engine.previousFailedOut.has("scotsman"));
+    Assert.ok(engine.previousFailedOut.has("peppercorn"));
+  } finally {
+    await promiseClean(engine, server);
+  }
+});
+
+async function createRecordFailTelemetry(allowSkippedRecord) {
+  Services.prefs.setStringPref("services.sync.username", "foo");
+  let collection = new ServerCollection();
+  collection._wbos.flying = new ServerWBO("flying");
+  collection._wbos.scotsman = new ServerWBO("scotsman");
+
+  let server = sync_httpd_setup({
+    "/1.1/foo/storage/rotary": collection.handler(),
+  });
+
+  await SyncTestingInfrastructure(server);
+
+  let engine = makeRotaryEngine();
+  engine.allowSkippedRecord = allowSkippedRecord;
+  let oldCreateRecord = engine._store.createRecord;
+  engine._store.createRecord = async (id, col) => {
+    if (id != "flying") {
+      throw new Error("oops");
+    }
+    return oldCreateRecord.call(engine._store, id, col);
+  };
+  engine._store.items = {
+    flying: "LNER Class A3 4472",
+    scotsman: "Flying Scotsman",
+  };
+  // Mark these records as changed
+  const FLYING_CHANGED = 12345;
+  const SCOTSMAN_CHANGED = 23456;
+  await engine._tracker.addChangedID("flying", FLYING_CHANGED);
+  await engine._tracker.addChangedID("scotsman", SCOTSMAN_CHANGED);
+
+  let syncID = await engine.resetLocalSyncID();
+  let meta_global = Service.recordManager.set(
+    engine.metaURL,
+    new WBORecord(engine.metaURL)
+  );
+  meta_global.payload.engines = { rotary: { version: engine.version, syncID } };
+
+  let ping;
+  try {
+    await engine.setLastSync(123); // needs to be non-zero so that tracker is queried
+
+    // Confirm initial environment
+    Assert.equal(collection.payload("flying"), undefined);
+    let changes = await engine._tracker.getChangedIDs();
+    Assert.equal(changes.flying, FLYING_CHANGED);
+    Assert.equal(changes.scotsman, SCOTSMAN_CHANGED);
+
+    engine.enabled = true;
+    ping = await sync_engine_and_validate_telem(engine, true, onErrorPing => {
+      ping = onErrorPing;
+    });
+
+    if (!allowSkippedRecord) {
+      do_throw("should not get here");
+    }
+
+    // Ensure the 'flying' record has been uploaded and is no longer marked.
+    Assert.ok(!!collection.payload("flying"));
+    changes = await engine._tracker.getChangedIDs();
+    Assert.equal(changes.flying, undefined);
+  } catch (err) {
+    if (allowSkippedRecord) {
+      do_throw("should not get here");
+    }
+
+    // Ensure the 'flying' record has not been uploaded and is still marked
+    Assert.ok(!collection.payload("flying"));
+    const changes = await engine._tracker.getChangedIDs();
+    Assert.ok(changes.flying);
+  } finally {
+    // We reported in telemetry that we failed a record
+    Assert.equal(ping.engines[0].outgoing[0].failed, 1);
+    Assert.equal(ping.engines[0].outgoing[0].failedReasons[0].name, "oops");
+
+    // In any case, the 'scotsman' record couldn't be created so it wasn't
+    // uploaded nor it was not cleared from the tracker.
+    Assert.ok(!collection.payload("scotsman"));
+    const changes = await engine._tracker.getChangedIDs();
+    Assert.equal(changes.scotsman, SCOTSMAN_CHANGED);
+
+    engine._store.createRecord = oldCreateRecord;
+    await promiseClean(engine, server);
+  }
+}
+
+add_task(
+  async function test_uploadOutgoing_createRecord_throws_reported_telemetry() {
+    _(
+      "SyncEngine._uploadOutgoing reports a failed record to telemetry if createRecord throws"
+    );
+    await createRecordFailTelemetry(true);
+  }
+);
+
+add_task(
+  async function test_uploadOutgoing_createRecord_throws_dontAllowSkipRecord() {
+    _(
+      "SyncEngine._uploadOutgoing will throw if createRecord throws and allowSkipRecord is set to false"
+    );
+    await createRecordFailTelemetry(false);
+  }
+);
+
+add_task(async function test_uploadOutgoing_largeRecords() {
+  _(
+    "SyncEngine._uploadOutgoing throws on records larger than the max record payload size"
+  );
+
+  let collection = new ServerCollection();
+
+  let engine = makeRotaryEngine();
+  engine.allowSkippedRecord = false;
+  engine._store.items["large-item"] = "Y".repeat(
+    Service.getMaxRecordPayloadSize() * 2
+  );
+  await engine._tracker.addChangedID("large-item", 0);
+  collection.insert("large-item");
+
+  let syncID = await engine.resetLocalSyncID();
+  let meta_global = Service.recordManager.set(
+    engine.metaURL,
+    new WBORecord(engine.metaURL)
+  );
+  meta_global.payload.engines = { rotary: { version: engine.version, syncID } };
+
+  let server = sync_httpd_setup({
+    "/1.1/foo/storage/rotary": collection.handler(),
+  });
+
+  await SyncTestingInfrastructure(server);
+
+  try {
+    await engine._syncStartup();
+    let error = null;
+    try {
+      await engine._uploadOutgoing();
+    } catch (e) {
+      error = e;
+    }
+    ok(!!error);
+  } finally {
+    await cleanAndGo(engine, server);
+  }
+});
+
+add_task(async function test_syncFinish_deleteByIds() {
+  _(
+    "SyncEngine._syncFinish deletes server records slated for deletion (list of record IDs)."
+  );
+
+  let collection = new ServerCollection();
+  collection._wbos.flying = new ServerWBO(
+    "flying",
+    encryptPayload({ id: "flying", denomination: "LNER Class A3 4472" })
+  );
+  collection._wbos.scotsman = new ServerWBO(
+    "scotsman",
+    encryptPayload({ id: "scotsman", denomination: "Flying Scotsman" })
+  );
+  collection._wbos.rekolok = new ServerWBO(
+    "rekolok",
+    encryptPayload({ id: "rekolok", denomination: "Rekonstruktionslokomotive" })
+  );
+
+  let server = httpd_setup({
+    "/1.1/foo/storage/rotary": collection.handler(),
+  });
+  await SyncTestingInfrastructure(server);
+
+  let engine = makeRotaryEngine();
+  try {
+    engine._delete = { ids: ["flying", "rekolok"] };
+    await engine._syncFinish();
+
+    // The 'flying' and 'rekolok' records were deleted while the
+    // 'scotsman' one wasn't.
+    Assert.equal(collection.payload("flying"), undefined);
+    Assert.ok(!!collection.payload("scotsman"));
+    Assert.equal(collection.payload("rekolok"), undefined);
+
+    // The deletion todo list has been reset.
+    Assert.equal(engine._delete.ids, undefined);
+  } finally {
+    await cleanAndGo(engine, server);
+  }
+});
+
+add_task(async function test_syncFinish_deleteLotsInBatches() {
+  _(
+    "SyncEngine._syncFinish deletes server records in batches of 100 (list of record IDs)."
+  );
+
+  let collection = new ServerCollection();
+
+  // Let's count how many times the client does a DELETE request to the server
+  var noOfUploads = 0;
+  collection.delete = (function (orig) {
+    return function () {
+      noOfUploads++;
+      return orig.apply(this, arguments);
+    };
+  })(collection.delete);
+
+  // Create a bunch of records on the server
+  let now = Date.now();
+  for (var i = 0; i < 234; i++) {
+    let id = "record-no-" + i;
+    let payload = encryptPayload({ id, denomination: "Record No. " + i });
+    let wbo = new ServerWBO(id, payload);
+    wbo.modified = now / 1000 - 60 * (i + 110);
+    collection.insertWBO(wbo);
+  }
+
+  let server = httpd_setup({
+    "/1.1/foo/storage/rotary": collection.handler(),
+  });
+
+  await SyncTestingInfrastructure(server);
+
+  let engine = makeRotaryEngine();
+  try {
+    // Confirm initial environment
+    Assert.equal(noOfUploads, 0);
+
+    // Declare what we want to have deleted: all records no. 100 and
+    // up and all records that are less than 200 mins old (which are
+    // records 0 thru 90).
+    engine._delete = { ids: [], newer: now / 1000 - 60 * 200.5 };
+    for (i = 100; i < 234; i++) {
+      engine._delete.ids.push("record-no-" + i);
+    }
+
+    await engine._syncFinish();
+
+    // Ensure that the appropriate server data has been wiped while
+    // preserving records 90 thru 200.
+    for (i = 0; i < 234; i++) {
+      let id = "record-no-" + i;
+      if (i <= 90 || i >= 100) {
+        Assert.equal(collection.payload(id), undefined);
+      } else {
+        Assert.ok(!!collection.payload(id));
+      }
+    }
+
+    // The deletion was done in batches
+    Assert.equal(noOfUploads, 2 + 1);
+
+    // The deletion todo list has been reset.
+    Assert.equal(engine._delete.ids, undefined);
+  } finally {
+    await cleanAndGo(engine, server);
+  }
+});
+
+add_task(async function test_sync_partialUpload() {
+  _("SyncEngine.sync() keeps changedIDs that couldn't be uploaded.");
+
+  let collection = new ServerCollection();
+  let server = sync_httpd_setup({
+    "/1.1/foo/storage/rotary": collection.handler(),
+  });
+  let oldServerConfiguration = Service.serverConfiguration;
+  Service.serverConfiguration = {
+    max_post_records: 100,
+  };
+  await SyncTestingInfrastructure(server);
+  await generateNewKeys(Service.collectionKeys);
+
+  let engine = makeRotaryEngine();
+
+  // Let the third upload fail completely
+  var noOfUploads = 0;
+  collection.post = (function (orig) {
+    return function () {
+      if (noOfUploads == 2) {
+        throw new Error("FAIL!");
+      }
+      noOfUploads++;
+      return orig.apply(this, arguments);
+    };
+  })(collection.post);
+
+  // Create a bunch of records (and server side handlers)
+  for (let i = 0; i < 234; i++) {
+    let id = "record-no-" + i;
+    engine._store.items[id] = "Record No. " + i;
+    await engine._tracker.addChangedID(id, i);
+    // Let two items in the first upload batch fail.
+    if (i != 23 && i != 42) {
+      collection.insert(id);
+    }
+  }
+
+  let syncID = await engine.resetLocalSyncID();
+  let meta_global = Service.recordManager.set(
+    engine.metaURL,
+    new WBORecord(engine.metaURL)
+  );
+  meta_global.payload.engines = { rotary: { version: engine.version, syncID } };
+
+  try {
+    await engine.setLastSync(123); // needs to be non-zero so that tracker is queried
+
+    engine.enabled = true;
+    let error;
+    try {
+      await sync_engine_and_validate_telem(engine, true);
+    } catch (ex) {
+      error = ex;
+    }
+
+    ok(!!error);
+
+    const changes = await engine._tracker.getChangedIDs();
+    for (let i = 0; i < 234; i++) {
+      let id = "record-no-" + i;
+      // Ensure that failed records are back in the tracker and failures have
+      // been added to `previousFailedOut`.
+      if (i < 200) {
+        // Records no. 23 and 42 were rejected by the server,
+        if (i == 23 || i == 42) {
+          Assert.equal(changes[id], i);
+          Assert.ok(engine.previousFailedOut.has(id));
+        } else {
+          Assert.equal(false, id in changes);
+          Assert.ok(!engine.previousFailedOut.has(id));
+        }
+      } else {
+        // Records after the third batch and higher couldn't be uploaded because
+        // we failed hard on the 3rd upload.
+        Assert.equal(changes[id], i);
+        Assert.ok(!engine.previousFailedOut.has(id));
+      }
+    }
+  } finally {
+    Service.serverConfiguration = oldServerConfiguration;
+    await promiseClean(engine, server);
+  }
+});
+
+add_task(async function test_canDecrypt_noCryptoKeys() {
+  _(
+    "SyncEngine.canDecrypt returns false if the engine fails to decrypt items on the server, e.g. due to a missing crypto key collection."
+  );
+
+  // Wipe collection keys so we can test the desired scenario.
+  Service.collectionKeys.clear();
+
+  let collection = new ServerCollection();
+  collection._wbos.flying = new ServerWBO(
+    "flying",
+    encryptPayload({ id: "flying", denomination: "LNER Class A3 4472" })
+  );
+
+  let server = sync_httpd_setup({
+    "/1.1/foo/storage/rotary": collection.handler(),
+  });
+
+  await SyncTestingInfrastructure(server);
+  let engine = makeRotaryEngine();
+  try {
+    Assert.equal(false, await engine.canDecrypt());
+  } finally {
+    await cleanAndGo(engine, server);
+  }
+});
+
+add_task(async function test_canDecrypt_true() {
+  _(
+    "SyncEngine.canDecrypt returns true if the engine can decrypt the items on the server."
+  );
+
+  await generateNewKeys(Service.collectionKeys);
+
+  let collection = new ServerCollection();
+  collection._wbos.flying = new ServerWBO(
+    "flying",
+    encryptPayload({ id: "flying", denomination: "LNER Class A3 4472" })
+  );
+
+  let server = sync_httpd_setup({
+    "/1.1/foo/storage/rotary": collection.handler(),
+  });
+
+  await SyncTestingInfrastructure(server);
+  let engine = makeRotaryEngine();
+  try {
+    Assert.ok(await engine.canDecrypt());
+  } finally {
+    await cleanAndGo(engine, server);
+  }
+});
+
+add_task(async function test_syncapplied_observer() {
+  const NUMBER_OF_RECORDS = 10;
+
+  let engine = makeRotaryEngine();
+
+  // Create a batch of server side records.
+  let collection = new ServerCollection();
+  for (var i = 0; i < NUMBER_OF_RECORDS; i++) {
+    let id = "record-no-" + i;
+    let payload = encryptPayload({ id, denomination: "Record No. " + id });
+    collection.insert(id, payload);
+  }
+
+  let server = httpd_setup({
+    "/1.1/foo/storage/rotary": collection.handler(),
+  });
+
+  await SyncTestingInfrastructure(server);
+
+  let syncID = await engine.resetLocalSyncID();
+  let meta_global = Service.recordManager.set(
+    engine.metaURL,
+    new WBORecord(engine.metaURL)
+  );
+  meta_global.payload.engines = { rotary: { version: engine.version, syncID } };
+
+  let numApplyCalls = 0;
+  let engine_name;
+  let count;
+  function onApplied(subject, data) {
+    numApplyCalls++;
+    engine_name = data;
+    count = subject;
+  }
+
+  Svc.Obs.add("weave:engine:sync:applied", onApplied);
+
+  try {
+    Service.scheduler.hasIncomingItems = false;
+
+    // Do sync.
+    await engine._syncStartup();
+    await engine._processIncoming();
+
+    do_check_attribute_count(engine._store.items, 10);
+
+    Assert.equal(numApplyCalls, 1);
+    Assert.equal(engine_name, "rotary");
+    Assert.equal(count.applied, 10);
+
+    Assert.ok(Service.scheduler.hasIncomingItems);
+  } finally {
+    await cleanAndGo(engine, server);
+    Service.scheduler.hasIncomingItems = false;
+    Svc.Obs.remove("weave:engine:sync:applied", onApplied);
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_syncscheduler.js b/src/zen/tests/mochitests/sync/test_syncscheduler.js
new file mode 100644
index 000000000..d46b9fc6c
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_syncscheduler.js
@@ -0,0 +1,1207 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { FxAccounts } = ChromeUtils.importESModule(
+  "resource://gre/modules/FxAccounts.sys.mjs"
+);
+const { SyncAuthManager } = ChromeUtils.importESModule(
+  "resource://services-sync/sync_auth.sys.mjs"
+);
+const { SyncScheduler } = ChromeUtils.importESModule(
+  "resource://services-sync/policies.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { Status } = ChromeUtils.importESModule(
+  "resource://services-sync/status.sys.mjs"
+);
+
+function CatapultEngine() {
+  SyncEngine.call(this, "Catapult", Service);
+}
+CatapultEngine.prototype = {
+  exception: null, // tests fill this in
+  async _sync() {
+    throw this.exception;
+  },
+};
+Object.setPrototypeOf(CatapultEngine.prototype, SyncEngine.prototype);
+
+var scheduler = new SyncScheduler(Service);
+let clientsEngine;
+
+async function sync_httpd_setup() {
+  let clientsSyncID = await clientsEngine.resetLocalSyncID();
+  let global = new ServerWBO("global", {
+    syncID: Service.syncID,
+    storageVersion: STORAGE_VERSION,
+    engines: {
+      clients: { version: clientsEngine.version, syncID: clientsSyncID },
+    },
+  });
+  let clientsColl = new ServerCollection({}, true);
+
+  // Tracking info/collections.
+  let collectionsHelper = track_collections_helper();
+  let upd = collectionsHelper.with_updated_collection;
+
+  return httpd_setup({
+    "/1.1/johndoe@mozilla.com/storage/meta/global": upd(
+      "meta",
+      global.handler()
+    ),
+    "/1.1/johndoe@mozilla.com/info/collections": collectionsHelper.handler,
+    "/1.1/johndoe@mozilla.com/storage/crypto/keys": upd(
+      "crypto",
+      new ServerWBO("keys").handler()
+    ),
+    "/1.1/johndoe@mozilla.com/storage/clients": upd(
+      "clients",
+      clientsColl.handler()
+    ),
+  });
+}
+
+async function setUp(server) {
+  await configureIdentity({ username: "johndoe@mozilla.com" }, server);
+
+  await generateNewKeys(Service.collectionKeys);
+  let serverKeys = Service.collectionKeys.asWBO("crypto", "keys");
+  await serverKeys.encrypt(Service.identity.syncKeyBundle);
+  let result = (
+    await serverKeys.upload(Service.resource(Service.cryptoKeysURL))
+  ).success;
+  return result;
+}
+
+async function cleanUpAndGo(server) {
+  await Async.promiseYield();
+  await clientsEngine._store.wipe();
+  await Service.startOver();
+  // Re-enable logging, which we just disabled.
+  syncTestLogging();
+  if (server) {
+    await promiseStopServer(server);
+  }
+}
+
+add_task(async function setup() {
+  await Service.promiseInitialized;
+  clientsEngine = Service.clientsEngine;
+  // Don't remove stale clients when syncing. This is a test-only workaround
+  // that lets us add clients directly to the store, without losing them on
+  // the next sync.
+  clientsEngine._removeRemoteClient = async () => {};
+  await Service.engineManager.clear();
+
+  validate_all_future_pings();
+
+  scheduler.setDefaults();
+
+  await Service.engineManager.register(CatapultEngine);
+});
+
+add_test(function test_prefAttributes() {
+  _("Test various attributes corresponding to preferences.");
+
+  const INTERVAL = 42 * 60 * 1000; // 42 minutes
+  const THRESHOLD = 3142;
+  const SCORE = 2718;
+  const TIMESTAMP1 = 1275493471649;
+
+  _(
+    "The 'nextSync' attribute stores a millisecond timestamp rounded down to the nearest second."
+  );
+  Assert.equal(scheduler.nextSync, 0);
+  scheduler.nextSync = TIMESTAMP1;
+  Assert.equal(scheduler.nextSync, Math.floor(TIMESTAMP1 / 1000) * 1000);
+
+  _("'syncInterval' defaults to singleDeviceInterval.");
+  Assert.equal(
+    Svc.PrefBranch.getPrefType("syncInterval"),
+    Ci.nsIPrefBranch.PREF_INVALID
+  );
+  Assert.equal(scheduler.syncInterval, scheduler.singleDeviceInterval);
+
+  _("'syncInterval' corresponds to a preference setting.");
+  scheduler.syncInterval = INTERVAL;
+  Assert.equal(scheduler.syncInterval, INTERVAL);
+  Assert.equal(Svc.PrefBranch.getIntPref("syncInterval"), INTERVAL);
+
+  _(
+    "'syncThreshold' corresponds to preference, defaults to SINGLE_USER_THRESHOLD"
+  );
+  Assert.equal(
+    Svc.PrefBranch.getPrefType("syncThreshold"),
+    Ci.nsIPrefBranch.PREF_INVALID
+  );
+  Assert.equal(scheduler.syncThreshold, SINGLE_USER_THRESHOLD);
+  scheduler.syncThreshold = THRESHOLD;
+  Assert.equal(scheduler.syncThreshold, THRESHOLD);
+
+  _("'globalScore' corresponds to preference, defaults to zero.");
+  Assert.equal(Svc.PrefBranch.getIntPref("globalScore"), 0);
+  Assert.equal(scheduler.globalScore, 0);
+  scheduler.globalScore = SCORE;
+  Assert.equal(scheduler.globalScore, SCORE);
+  Assert.equal(Svc.PrefBranch.getIntPref("globalScore"), SCORE);
+
+  _("Intervals correspond to default preferences.");
+  Assert.equal(
+    scheduler.singleDeviceInterval,
+    Svc.PrefBranch.getIntPref("scheduler.fxa.singleDeviceInterval") * 1000
+  );
+  Assert.equal(
+    scheduler.idleInterval,
+    Svc.PrefBranch.getIntPref("scheduler.idleInterval") * 1000
+  );
+  Assert.equal(
+    scheduler.activeInterval,
+    Svc.PrefBranch.getIntPref("scheduler.activeInterval") * 1000
+  );
+  Assert.equal(
+    scheduler.immediateInterval,
+    Svc.PrefBranch.getIntPref("scheduler.immediateInterval") * 1000
+  );
+
+  _("Custom values for prefs will take effect after a restart.");
+  Svc.PrefBranch.setIntPref("scheduler.fxa.singleDeviceInterval", 420);
+  Svc.PrefBranch.setIntPref("scheduler.idleInterval", 230);
+  Svc.PrefBranch.setIntPref("scheduler.activeInterval", 180);
+  Svc.PrefBranch.setIntPref("scheduler.immediateInterval", 31415);
+  scheduler.setDefaults();
+  Assert.equal(scheduler.idleInterval, 230000);
+  Assert.equal(scheduler.singleDeviceInterval, 420000);
+  Assert.equal(scheduler.activeInterval, 180000);
+  Assert.equal(scheduler.immediateInterval, 31415000);
+
+  _("Custom values for interval prefs can't be less than 60 seconds.");
+  Svc.PrefBranch.setIntPref("scheduler.fxa.singleDeviceInterval", 42);
+  Svc.PrefBranch.setIntPref("scheduler.idleInterval", 50);
+  Svc.PrefBranch.setIntPref("scheduler.activeInterval", 50);
+  Svc.PrefBranch.setIntPref("scheduler.immediateInterval", 10);
+  scheduler.setDefaults();
+  Assert.equal(scheduler.idleInterval, 60000);
+  Assert.equal(scheduler.singleDeviceInterval, 60000);
+  Assert.equal(scheduler.activeInterval, 60000);
+  Assert.equal(scheduler.immediateInterval, 60000);
+
+  for (const pref of Svc.PrefBranch.getChildList("")) {
+    Svc.PrefBranch.clearUserPref(pref);
+  }
+  scheduler.setDefaults();
+  run_next_test();
+});
+
+add_task(async function test_sync_skipped_low_score_no_resync() {
+  enableValidationPrefs();
+  let server = await sync_httpd_setup();
+
+  function SkipEngine() {
+    SyncEngine.call(this, "Skip", Service);
+    this.syncs = 0;
+  }
+
+  SkipEngine.prototype = {
+    _sync() {
+      do_throw("Should have been skipped");
+    },
+    shouldSkipSync() {
+      return true;
+    },
+  };
+  Object.setPrototypeOf(SkipEngine.prototype, SyncEngine.prototype);
+  await Service.engineManager.register(SkipEngine);
+
+  let engine = Service.engineManager.get("skip");
+  engine.enabled = true;
+  engine._tracker._score = 30;
+
+  Assert.equal(Status.sync, SYNC_SUCCEEDED);
+
+  Assert.ok(await setUp(server));
+
+  let resyncDoneObserver = promiseOneObserver("weave:service:resyncs-finished");
+
+  let synced = false;
+  function onSyncStarted() {
+    Assert.ok(!synced, "Only should sync once");
+    synced = true;
+  }
+
+  await Service.sync();
+
+  Assert.equal(Status.sync, SYNC_SUCCEEDED);
+
+  Svc.Obs.add("weave:service:sync:start", onSyncStarted);
+  await resyncDoneObserver;
+
+  Svc.Obs.remove("weave:service:sync:start", onSyncStarted);
+  engine._tracker._store = 0;
+  await cleanUpAndGo(server);
+});
+
+add_task(async function test_updateClientMode() {
+  _(
+    "Test updateClientMode adjusts scheduling attributes based on # of clients appropriately"
+  );
+  Assert.equal(scheduler.syncThreshold, SINGLE_USER_THRESHOLD);
+  Assert.equal(scheduler.syncInterval, scheduler.singleDeviceInterval);
+  Assert.equal(false, scheduler.numClients > 1);
+  Assert.ok(!scheduler.idle);
+
+  // Trigger a change in interval & threshold by noting there are multiple clients.
+  Svc.PrefBranch.setIntPref("clients.devices.desktop", 1);
+  Svc.PrefBranch.setIntPref("clients.devices.mobile", 1);
+  scheduler.updateClientMode();
+
+  Assert.equal(scheduler.syncThreshold, MULTI_DEVICE_THRESHOLD);
+  Assert.equal(scheduler.syncInterval, scheduler.activeInterval);
+  Assert.greater(scheduler.numClients, 1);
+  Assert.ok(!scheduler.idle);
+
+  // Resets the number of clients to 0.
+  await clientsEngine.resetClient();
+  Svc.PrefBranch.clearUserPref("clients.devices.mobile");
+  scheduler.updateClientMode();
+
+  // Goes back to single user if # clients is 1.
+  Assert.equal(scheduler.numClients, 1);
+  Assert.equal(scheduler.syncThreshold, SINGLE_USER_THRESHOLD);
+  Assert.equal(scheduler.syncInterval, scheduler.singleDeviceInterval);
+  Assert.equal(false, scheduler.numClients > 1);
+  Assert.ok(!scheduler.idle);
+
+  await cleanUpAndGo();
+});
+
+add_task(async function test_masterpassword_locked_retry_interval() {
+  enableValidationPrefs();
+
+  _(
+    "Test Status.login = MASTER_PASSWORD_LOCKED results in reschedule at MASTER_PASSWORD interval"
+  );
+  let loginFailed = false;
+  Svc.Obs.add("weave:service:login:error", function onLoginError() {
+    Svc.Obs.remove("weave:service:login:error", onLoginError);
+    loginFailed = true;
+  });
+
+  let rescheduleInterval = false;
+
+  let oldScheduleAtInterval = SyncScheduler.prototype.scheduleAtInterval;
+  SyncScheduler.prototype.scheduleAtInterval = function (interval) {
+    rescheduleInterval = true;
+    Assert.equal(interval, MASTER_PASSWORD_LOCKED_RETRY_INTERVAL);
+  };
+
+  let oldVerifyLogin = Service.verifyLogin;
+  Service.verifyLogin = async function () {
+    Status.login = MASTER_PASSWORD_LOCKED;
+    return false;
+  };
+
+  let server = await sync_httpd_setup();
+  await setUp(server);
+
+  await Service.sync();
+
+  Assert.ok(loginFailed);
+  Assert.equal(Status.login, MASTER_PASSWORD_LOCKED);
+  Assert.ok(rescheduleInterval);
+
+  Service.verifyLogin = oldVerifyLogin;
+  SyncScheduler.prototype.scheduleAtInterval = oldScheduleAtInterval;
+
+  await cleanUpAndGo(server);
+});
+
+add_task(async function test_calculateBackoff() {
+  Assert.equal(Status.backoffInterval, 0);
+
+  // Test no interval larger than the maximum backoff is used if
+  // Status.backoffInterval is smaller.
+  Status.backoffInterval = 5;
+  let backoffInterval = Utils.calculateBackoff(
+    50,
+    MAXIMUM_BACKOFF_INTERVAL,
+    Status.backoffInterval
+  );
+
+  Assert.equal(backoffInterval, MAXIMUM_BACKOFF_INTERVAL);
+
+  // Test Status.backoffInterval is used if it is
+  // larger than MAXIMUM_BACKOFF_INTERVAL.
+  Status.backoffInterval = MAXIMUM_BACKOFF_INTERVAL + 10;
+  backoffInterval = Utils.calculateBackoff(
+    50,
+    MAXIMUM_BACKOFF_INTERVAL,
+    Status.backoffInterval
+  );
+
+  Assert.equal(backoffInterval, MAXIMUM_BACKOFF_INTERVAL + 10);
+
+  await cleanUpAndGo();
+});
+
+add_task(async function test_scheduleNextSync_nowOrPast() {
+  enableValidationPrefs();
+
+  let promiseObserved = promiseOneObserver("weave:service:sync:finish");
+
+  let server = await sync_httpd_setup();
+  await setUp(server);
+
+  // We're late for a sync...
+  scheduler.scheduleNextSync(-1);
+  await promiseObserved;
+  await cleanUpAndGo(server);
+});
+
+add_task(async function test_scheduleNextSync_future_noBackoff() {
+  enableValidationPrefs();
+
+  _(
+    "scheduleNextSync() uses the current syncInterval if no interval is provided."
+  );
+  // Test backoffInterval is 0 as expected.
+  Assert.equal(Status.backoffInterval, 0);
+
+  _("Test setting sync interval when nextSync == 0");
+  scheduler.nextSync = 0;
+  scheduler.scheduleNextSync();
+
+  // nextSync - Date.now() might be smaller than expectedInterval
+  // since some time has passed since we called scheduleNextSync().
+  Assert.lessOrEqual(scheduler.nextSync - Date.now(), scheduler.syncInterval);
+  Assert.equal(scheduler.syncTimer.delay, scheduler.syncInterval);
+
+  _("Test setting sync interval when nextSync != 0");
+  scheduler.nextSync = Date.now() + scheduler.singleDeviceInterval;
+  scheduler.scheduleNextSync();
+
+  // nextSync - Date.now() might be smaller than expectedInterval
+  // since some time has passed since we called scheduleNextSync().
+  Assert.lessOrEqual(scheduler.nextSync - Date.now(), scheduler.syncInterval);
+  Assert.lessOrEqual(scheduler.syncTimer.delay, scheduler.syncInterval);
+
+  _(
+    "Scheduling requests for intervals larger than the current one will be ignored."
+  );
+  // Request a sync at a longer interval. The sync that's already scheduled
+  // for sooner takes precedence.
+  let nextSync = scheduler.nextSync;
+  let timerDelay = scheduler.syncTimer.delay;
+  let requestedInterval = scheduler.syncInterval * 10;
+  scheduler.scheduleNextSync(requestedInterval);
+  Assert.equal(scheduler.nextSync, nextSync);
+  Assert.equal(scheduler.syncTimer.delay, timerDelay);
+
+  // We can schedule anything we want if there isn't a sync scheduled.
+  scheduler.nextSync = 0;
+  scheduler.scheduleNextSync(requestedInterval);
+  Assert.lessOrEqual(scheduler.nextSync, Date.now() + requestedInterval);
+  Assert.equal(scheduler.syncTimer.delay, requestedInterval);
+
+  // Request a sync at the smallest possible interval (0 triggers now).
+  scheduler.scheduleNextSync(1);
+  Assert.lessOrEqual(scheduler.nextSync, Date.now() + 1);
+  Assert.equal(scheduler.syncTimer.delay, 1);
+
+  await cleanUpAndGo();
+});
+
+add_task(async function test_scheduleNextSync_future_backoff() {
+  enableValidationPrefs();
+
+  _("scheduleNextSync() will honour backoff in all scheduling requests.");
+  // Let's take a backoff interval that's bigger than the default sync interval.
+  const BACKOFF = 7337;
+  Status.backoffInterval = scheduler.syncInterval + BACKOFF;
+
+  _("Test setting sync interval when nextSync == 0");
+  scheduler.nextSync = 0;
+  scheduler.scheduleNextSync();
+
+  // nextSync - Date.now() might be smaller than expectedInterval
+  // since some time has passed since we called scheduleNextSync().
+  Assert.lessOrEqual(scheduler.nextSync - Date.now(), Status.backoffInterval);
+  Assert.equal(scheduler.syncTimer.delay, Status.backoffInterval);
+
+  _("Test setting sync interval when nextSync != 0");
+  scheduler.nextSync = Date.now() + scheduler.singleDeviceInterval;
+  scheduler.scheduleNextSync();
+
+  // nextSync - Date.now() might be smaller than expectedInterval
+  // since some time has passed since we called scheduleNextSync().
+  Assert.lessOrEqual(scheduler.nextSync - Date.now(), Status.backoffInterval);
+  Assert.lessOrEqual(scheduler.syncTimer.delay, Status.backoffInterval);
+
+  // Request a sync at a longer interval. The sync that's already scheduled
+  // for sooner takes precedence.
+  let nextSync = scheduler.nextSync;
+  let timerDelay = scheduler.syncTimer.delay;
+  let requestedInterval = scheduler.syncInterval * 10;
+  Assert.greater(requestedInterval, Status.backoffInterval);
+  scheduler.scheduleNextSync(requestedInterval);
+  Assert.equal(scheduler.nextSync, nextSync);
+  Assert.equal(scheduler.syncTimer.delay, timerDelay);
+
+  // We can schedule anything we want if there isn't a sync scheduled.
+  scheduler.nextSync = 0;
+  scheduler.scheduleNextSync(requestedInterval);
+  Assert.lessOrEqual(scheduler.nextSync, Date.now() + requestedInterval);
+  Assert.equal(scheduler.syncTimer.delay, requestedInterval);
+
+  // Request a sync at the smallest possible interval (0 triggers now).
+  scheduler.scheduleNextSync(1);
+  Assert.lessOrEqual(scheduler.nextSync, Date.now() + Status.backoffInterval);
+  Assert.equal(scheduler.syncTimer.delay, Status.backoffInterval);
+
+  await cleanUpAndGo();
+});
+
+add_task(async function test_handleSyncError() {
+  enableValidationPrefs();
+
+  let server = await sync_httpd_setup();
+  await setUp(server);
+
+  // Force sync to fail.
+  Svc.PrefBranch.setStringPref("firstSync", "notReady");
+
+  _("Ensure expected initial environment.");
+  Assert.equal(scheduler._syncErrors, 0);
+  Assert.ok(!Status.enforceBackoff);
+  Assert.equal(scheduler.syncInterval, scheduler.singleDeviceInterval);
+  Assert.equal(Status.backoffInterval, 0);
+
+  // Trigger sync with an error several times & observe
+  // functionality of handleSyncError()
+  _("Test first error calls scheduleNextSync on default interval");
+  await Service.sync();
+  Assert.lessOrEqual(
+    scheduler.nextSync,
+    Date.now() + scheduler.singleDeviceInterval
+  );
+  Assert.equal(scheduler.syncTimer.delay, scheduler.singleDeviceInterval);
+  Assert.equal(scheduler._syncErrors, 1);
+  Assert.ok(!Status.enforceBackoff);
+  scheduler.syncTimer.clear();
+
+  _("Test second error still calls scheduleNextSync on default interval");
+  await Service.sync();
+  Assert.lessOrEqual(
+    scheduler.nextSync,
+    Date.now() + scheduler.singleDeviceInterval
+  );
+  Assert.equal(scheduler.syncTimer.delay, scheduler.singleDeviceInterval);
+  Assert.equal(scheduler._syncErrors, 2);
+  Assert.ok(!Status.enforceBackoff);
+  scheduler.syncTimer.clear();
+
+  _("Test third error sets Status.enforceBackoff and calls scheduleAtInterval");
+  await Service.sync();
+  let maxInterval = scheduler._syncErrors * (2 * MINIMUM_BACKOFF_INTERVAL);
+  Assert.equal(Status.backoffInterval, 0);
+  Assert.lessOrEqual(scheduler.nextSync, Date.now() + maxInterval);
+  Assert.lessOrEqual(scheduler.syncTimer.delay, maxInterval);
+  Assert.equal(scheduler._syncErrors, 3);
+  Assert.ok(Status.enforceBackoff);
+
+  // Status.enforceBackoff is false but there are still errors.
+  Status.resetBackoff();
+  Assert.ok(!Status.enforceBackoff);
+  Assert.equal(scheduler._syncErrors, 3);
+  scheduler.syncTimer.clear();
+
+  _(
+    "Test fourth error still calls scheduleAtInterval even if enforceBackoff was reset"
+  );
+  await Service.sync();
+  maxInterval = scheduler._syncErrors * (2 * MINIMUM_BACKOFF_INTERVAL);
+  Assert.lessOrEqual(scheduler.nextSync, Date.now() + maxInterval);
+  Assert.lessOrEqual(scheduler.syncTimer.delay, maxInterval);
+  Assert.equal(scheduler._syncErrors, 4);
+  Assert.ok(Status.enforceBackoff);
+  scheduler.syncTimer.clear();
+
+  _("Arrange for a successful sync to reset the scheduler error count");
+  let promiseObserved = promiseOneObserver("weave:service:sync:finish");
+  Svc.PrefBranch.setStringPref("firstSync", "wipeRemote");
+  scheduler.scheduleNextSync(-1);
+  await promiseObserved;
+  await cleanUpAndGo(server);
+});
+
+add_task(async function test_client_sync_finish_updateClientMode() {
+  enableValidationPrefs();
+
+  let server = await sync_httpd_setup();
+  await setUp(server);
+
+  // Confirm defaults.
+  Assert.equal(scheduler.syncThreshold, SINGLE_USER_THRESHOLD);
+  Assert.equal(scheduler.syncInterval, scheduler.singleDeviceInterval);
+  Assert.ok(!scheduler.idle);
+
+  // Trigger a change in interval & threshold by adding a client.
+  await clientsEngine._store.create({
+    id: "foo",
+    cleartext: { os: "mobile", version: "0.01", type: "desktop" },
+  });
+  Assert.equal(false, scheduler.numClients > 1);
+  scheduler.updateClientMode();
+  await Service.sync();
+
+  Assert.equal(scheduler.syncThreshold, MULTI_DEVICE_THRESHOLD);
+  Assert.equal(scheduler.syncInterval, scheduler.activeInterval);
+  Assert.greater(scheduler.numClients, 1);
+  Assert.ok(!scheduler.idle);
+
+  // Resets the number of clients to 0.
+  await clientsEngine.resetClient();
+  // Also re-init the server, or we suck our "foo" client back down.
+  await setUp(server);
+
+  await Service.sync();
+
+  // Goes back to single user if # clients is 1.
+  Assert.equal(scheduler.numClients, 1);
+  Assert.equal(scheduler.syncThreshold, SINGLE_USER_THRESHOLD);
+  Assert.equal(scheduler.syncInterval, scheduler.singleDeviceInterval);
+  Assert.equal(false, scheduler.numClients > 1);
+  Assert.ok(!scheduler.idle);
+
+  await cleanUpAndGo(server);
+});
+
+add_task(async function test_autoconnect_nextSync_past() {
+  enableValidationPrefs();
+
+  let promiseObserved = promiseOneObserver("weave:service:sync:finish");
+  // nextSync will be 0 by default, so it's way in the past.
+
+  let server = await sync_httpd_setup();
+  await setUp(server);
+
+  scheduler.autoConnect();
+  await promiseObserved;
+  await cleanUpAndGo(server);
+});
+
+add_task(async function test_autoconnect_nextSync_future() {
+  enableValidationPrefs();
+
+  let previousSync = Date.now() + scheduler.syncInterval / 2;
+  scheduler.nextSync = previousSync;
+  // nextSync rounds to the nearest second.
+  let expectedSync = scheduler.nextSync;
+  let expectedInterval = expectedSync - Date.now() - 1000;
+
+  // Ensure we don't actually try to sync (or log in for that matter).
+  function onLoginStart() {
+    do_throw("Should not get here!");
+  }
+  Svc.Obs.add("weave:service:login:start", onLoginStart);
+
+  await configureIdentity({ username: "johndoe@mozilla.com" });
+  scheduler.autoConnect();
+  await promiseZeroTimer();
+
+  Assert.equal(scheduler.nextSync, expectedSync);
+  Assert.greaterOrEqual(scheduler.syncTimer.delay, expectedInterval);
+
+  Svc.Obs.remove("weave:service:login:start", onLoginStart);
+  await cleanUpAndGo();
+});
+
+add_task(async function test_autoconnect_mp_locked() {
+  let server = await sync_httpd_setup();
+  await setUp(server);
+
+  // Pretend user did not unlock master password.
+  let origLocked = Utils.mpLocked;
+  Utils.mpLocked = () => true;
+
+  let origEnsureMPUnlocked = Utils.ensureMPUnlocked;
+  Utils.ensureMPUnlocked = () => {
+    _("Faking Master Password entry cancelation.");
+    return false;
+  };
+  let origFxA = Service.identity._fxaService;
+  Service.identity._fxaService = new FxAccounts({
+    currentAccountState: {
+      getUserAccountData(...args) {
+        return origFxA._internal.currentAccountState.getUserAccountData(
+          ...args
+        );
+      },
+    },
+    keys: {
+      canGetKeyForScope() {
+        return false;
+      },
+    },
+  });
+  // A locked master password will still trigger a sync, but then we'll hit
+  // MASTER_PASSWORD_LOCKED and hence MASTER_PASSWORD_LOCKED_RETRY_INTERVAL.
+  let promiseObserved = promiseOneObserver("weave:service:login:error");
+
+  scheduler.autoConnect();
+  await promiseObserved;
+
+  await Async.promiseYield();
+
+  Assert.equal(Status.login, MASTER_PASSWORD_LOCKED);
+
+  Utils.mpLocked = origLocked;
+  Utils.ensureMPUnlocked = origEnsureMPUnlocked;
+  Service.identity._fxaService = origFxA;
+
+  await cleanUpAndGo(server);
+});
+
+add_task(async function test_no_autoconnect_during_wizard() {
+  let server = await sync_httpd_setup();
+  await setUp(server);
+
+  // Simulate the Sync setup wizard.
+  Svc.PrefBranch.setStringPref("firstSync", "notReady");
+
+  // Ensure we don't actually try to sync (or log in for that matter).
+  function onLoginStart() {
+    do_throw("Should not get here!");
+  }
+  Svc.Obs.add("weave:service:login:start", onLoginStart);
+
+  scheduler.autoConnect(0);
+  await promiseZeroTimer();
+  Svc.Obs.remove("weave:service:login:start", onLoginStart);
+  await cleanUpAndGo(server);
+});
+
+add_task(async function test_no_autoconnect_status_not_ok() {
+  let server = await sync_httpd_setup();
+  Status.__authManager = Service.identity = new SyncAuthManager();
+
+  // Ensure we don't actually try to sync (or log in for that matter).
+  function onLoginStart() {
+    do_throw("Should not get here!");
+  }
+  Svc.Obs.add("weave:service:login:start", onLoginStart);
+
+  scheduler.autoConnect();
+  await promiseZeroTimer();
+  Svc.Obs.remove("weave:service:login:start", onLoginStart);
+
+  Assert.equal(Status.service, CLIENT_NOT_CONFIGURED);
+  Assert.equal(Status.login, LOGIN_FAILED_NO_USERNAME);
+
+  await cleanUpAndGo(server);
+});
+
+add_task(async function test_idle_adjustSyncInterval() {
+  // Confirm defaults.
+  Assert.equal(scheduler.idle, false);
+
+  // Single device: nothing changes.
+  scheduler.observe(
+    null,
+    "idle",
+    Svc.PrefBranch.getIntPref("scheduler.idleTime")
+  );
+  Assert.equal(scheduler.idle, true);
+  Assert.equal(scheduler.syncInterval, scheduler.singleDeviceInterval);
+
+  // Multiple devices: switch to idle interval.
+  scheduler.idle = false;
+  Svc.PrefBranch.setIntPref("clients.devices.desktop", 1);
+  Svc.PrefBranch.setIntPref("clients.devices.mobile", 1);
+  scheduler.updateClientMode();
+  scheduler.observe(
+    null,
+    "idle",
+    Svc.PrefBranch.getIntPref("scheduler.idleTime")
+  );
+  Assert.equal(scheduler.idle, true);
+  Assert.equal(scheduler.syncInterval, scheduler.idleInterval);
+
+  await cleanUpAndGo();
+});
+
+add_task(async function test_back_triggersSync() {
+  // Confirm defaults.
+  Assert.ok(!scheduler.idle);
+  Assert.equal(Status.backoffInterval, 0);
+
+  // Set up: Define 2 clients and put the system in idle.
+  Svc.PrefBranch.setIntPref("clients.devices.desktop", 1);
+  Svc.PrefBranch.setIntPref("clients.devices.mobile", 1);
+  scheduler.observe(
+    null,
+    "idle",
+    Svc.PrefBranch.getIntPref("scheduler.idleTime")
+  );
+  Assert.ok(scheduler.idle);
+
+  // We don't actually expect the sync (or the login, for that matter) to
+  // succeed. We just want to ensure that it was attempted.
+  let promiseObserved = promiseOneObserver("weave:service:login:error");
+
+  // Send an 'active' event to trigger sync soonish.
+  scheduler.observe(
+    null,
+    "active",
+    Svc.PrefBranch.getIntPref("scheduler.idleTime")
+  );
+  await promiseObserved;
+  await cleanUpAndGo();
+});
+
+add_task(async function test_active_triggersSync_observesBackoff() {
+  // Confirm defaults.
+  Assert.ok(!scheduler.idle);
+
+  // Set up: Set backoff, define 2 clients and put the system in idle.
+  const BACKOFF = 7337;
+  Status.backoffInterval = scheduler.idleInterval + BACKOFF;
+  Svc.PrefBranch.setIntPref("clients.devices.desktop", 1);
+  Svc.PrefBranch.setIntPref("clients.devices.mobile", 1);
+  scheduler.observe(
+    null,
+    "idle",
+    Svc.PrefBranch.getIntPref("scheduler.idleTime")
+  );
+  Assert.equal(scheduler.idle, true);
+
+  function onLoginStart() {
+    do_throw("Shouldn't have kicked off a sync!");
+  }
+  Svc.Obs.add("weave:service:login:start", onLoginStart);
+
+  let promiseTimer = promiseNamedTimer(
+    IDLE_OBSERVER_BACK_DELAY * 1.5,
+    {},
+    "timer"
+  );
+
+  // Send an 'active' event to try to trigger sync soonish.
+  scheduler.observe(
+    null,
+    "active",
+    Svc.PrefBranch.getIntPref("scheduler.idleTime")
+  );
+  await promiseTimer;
+  Svc.Obs.remove("weave:service:login:start", onLoginStart);
+
+  Assert.lessOrEqual(scheduler.nextSync, Date.now() + Status.backoffInterval);
+  Assert.equal(scheduler.syncTimer.delay, Status.backoffInterval);
+
+  await cleanUpAndGo();
+});
+
+add_task(async function test_back_debouncing() {
+  _(
+    "Ensure spurious back-then-idle events, as observed on OS X, don't trigger a sync."
+  );
+
+  // Confirm defaults.
+  Assert.equal(scheduler.idle, false);
+
+  // Set up: Define 2 clients and put the system in idle.
+  Svc.PrefBranch.setIntPref("clients.devices.desktop", 1);
+  Svc.PrefBranch.setIntPref("clients.devices.mobile", 1);
+  scheduler.observe(
+    null,
+    "idle",
+    Svc.PrefBranch.getIntPref("scheduler.idleTime")
+  );
+  Assert.equal(scheduler.idle, true);
+
+  function onLoginStart() {
+    do_throw("Shouldn't have kicked off a sync!");
+  }
+  Svc.Obs.add("weave:service:login:start", onLoginStart);
+
+  // Create spurious back-then-idle events as observed on OS X:
+  scheduler.observe(
+    null,
+    "active",
+    Svc.PrefBranch.getIntPref("scheduler.idleTime")
+  );
+  scheduler.observe(
+    null,
+    "idle",
+    Svc.PrefBranch.getIntPref("scheduler.idleTime")
+  );
+
+  await promiseNamedTimer(IDLE_OBSERVER_BACK_DELAY * 1.5, {}, "timer");
+  Svc.Obs.remove("weave:service:login:start", onLoginStart);
+  await cleanUpAndGo();
+});
+
+add_task(async function test_no_sync_node() {
+  enableValidationPrefs();
+
+  // Test when Status.sync == NO_SYNC_NODE_FOUND
+  // it is not overwritten on sync:finish
+  let server = await sync_httpd_setup();
+  await setUp(server);
+
+  let oldfc = Service.identity._findCluster;
+  Service.identity._findCluster = () => null;
+  Service.clusterURL = "";
+  try {
+    await Service.sync();
+    Assert.equal(Status.sync, NO_SYNC_NODE_FOUND);
+    Assert.equal(scheduler.syncTimer.delay, NO_SYNC_NODE_INTERVAL);
+
+    await cleanUpAndGo(server);
+  } finally {
+    Service.identity._findCluster = oldfc;
+  }
+});
+
+add_task(async function test_sync_failed_partial_500s() {
+  enableValidationPrefs();
+
+  _("Test a 5xx status calls handleSyncError.");
+  scheduler._syncErrors = MAX_ERROR_COUNT_BEFORE_BACKOFF;
+  let server = await sync_httpd_setup();
+
+  let engine = Service.engineManager.get("catapult");
+  engine.enabled = true;
+  engine.exception = { status: 500 };
+
+  Assert.equal(Status.sync, SYNC_SUCCEEDED);
+
+  Assert.ok(await setUp(server));
+
+  await Service.sync();
+
+  Assert.equal(Status.service, SYNC_FAILED_PARTIAL);
+
+  let maxInterval = scheduler._syncErrors * (2 * MINIMUM_BACKOFF_INTERVAL);
+  Assert.equal(Status.backoffInterval, 0);
+  Assert.ok(Status.enforceBackoff);
+  Assert.equal(scheduler._syncErrors, 4);
+  Assert.lessOrEqual(scheduler.nextSync, Date.now() + maxInterval);
+  Assert.lessOrEqual(scheduler.syncTimer.delay, maxInterval);
+
+  await cleanUpAndGo(server);
+});
+
+add_task(async function test_sync_failed_partial_noresync() {
+  enableValidationPrefs();
+  let server = await sync_httpd_setup();
+
+  let engine = Service.engineManager.get("catapult");
+  engine.enabled = true;
+  engine.exception = "Bad news";
+  engine._tracker._score = MULTI_DEVICE_THRESHOLD + 1;
+
+  Assert.equal(Status.sync, SYNC_SUCCEEDED);
+
+  Assert.ok(await setUp(server));
+
+  let resyncDoneObserver = promiseOneObserver("weave:service:resyncs-finished");
+
+  await Service.sync();
+
+  Assert.equal(Status.service, SYNC_FAILED_PARTIAL);
+
+  function onSyncStarted() {
+    do_throw("Should not start resync when previous sync failed");
+  }
+
+  Svc.Obs.add("weave:service:sync:start", onSyncStarted);
+  await resyncDoneObserver;
+
+  Svc.Obs.remove("weave:service:sync:start", onSyncStarted);
+  engine._tracker._store = 0;
+  await cleanUpAndGo(server);
+});
+
+add_task(async function test_sync_failed_partial_400s() {
+  enableValidationPrefs();
+
+  _("Test a non-5xx status doesn't call handleSyncError.");
+  scheduler._syncErrors = MAX_ERROR_COUNT_BEFORE_BACKOFF;
+  let server = await sync_httpd_setup();
+
+  let engine = Service.engineManager.get("catapult");
+  engine.enabled = true;
+  engine.exception = { status: 400 };
+
+  // Have multiple devices for an active interval.
+  await clientsEngine._store.create({
+    id: "foo",
+    cleartext: { os: "mobile", version: "0.01", type: "desktop" },
+  });
+
+  Assert.equal(Status.sync, SYNC_SUCCEEDED);
+
+  Assert.ok(await setUp(server));
+
+  await Service.sync();
+
+  Assert.equal(Status.service, SYNC_FAILED_PARTIAL);
+  Assert.equal(scheduler.syncInterval, scheduler.activeInterval);
+
+  Assert.equal(Status.backoffInterval, 0);
+  Assert.ok(!Status.enforceBackoff);
+  Assert.equal(scheduler._syncErrors, 0);
+  Assert.lessOrEqual(scheduler.nextSync, Date.now() + scheduler.activeInterval);
+  Assert.lessOrEqual(scheduler.syncTimer.delay, scheduler.activeInterval);
+
+  await cleanUpAndGo(server);
+});
+
+add_task(async function test_sync_X_Weave_Backoff() {
+  enableValidationPrefs();
+
+  let server = await sync_httpd_setup();
+  await setUp(server);
+
+  // Use an odd value on purpose so that it doesn't happen to coincide with one
+  // of the sync intervals.
+  const BACKOFF = 7337;
+
+  // Extend info/collections so that we can put it into server maintenance mode.
+  const INFO_COLLECTIONS = "/1.1/johndoe@mozilla.com/info/collections";
+  let infoColl = server._handler._overridePaths[INFO_COLLECTIONS];
+  let serverBackoff = false;
+  function infoCollWithBackoff(request, response) {
+    if (serverBackoff) {
+      response.setHeader("X-Weave-Backoff", "" + BACKOFF);
+    }
+    infoColl(request, response);
+  }
+  server.registerPathHandler(INFO_COLLECTIONS, infoCollWithBackoff);
+
+  // Pretend we have two clients so that the regular sync interval is
+  // sufficiently low.
+  await clientsEngine._store.create({
+    id: "foo",
+    cleartext: { os: "mobile", version: "0.01", type: "desktop" },
+  });
+  let rec = await clientsEngine._store.createRecord("foo", "clients");
+  await rec.encrypt(Service.collectionKeys.keyForCollection("clients"));
+  await rec.upload(Service.resource(clientsEngine.engineURL + rec.id));
+
+  // Sync once to log in and get everything set up. Let's verify our initial
+  // values.
+  await Service.sync();
+  Assert.equal(Status.backoffInterval, 0);
+  Assert.equal(Status.minimumNextSync, 0);
+  Assert.equal(scheduler.syncInterval, scheduler.activeInterval);
+  Assert.lessOrEqual(scheduler.nextSync, Date.now() + scheduler.syncInterval);
+  // Sanity check that we picked the right value for BACKOFF:
+  Assert.less(scheduler.syncInterval, BACKOFF * 1000);
+
+  // Turn on server maintenance and sync again.
+  serverBackoff = true;
+  await Service.sync();
+
+  Assert.greaterOrEqual(Status.backoffInterval, BACKOFF * 1000);
+  // Allowing 20 seconds worth of of leeway between when Status.minimumNextSync
+  // was set and when this line gets executed.
+  let minimumExpectedDelay = (BACKOFF - 20) * 1000;
+  Assert.greaterOrEqual(
+    Status.minimumNextSync,
+    Date.now() + minimumExpectedDelay
+  );
+
+  // Verify that the next sync is actually going to wait that long.
+  Assert.greaterOrEqual(scheduler.nextSync, Date.now() + minimumExpectedDelay);
+  Assert.greaterOrEqual(scheduler.syncTimer.delay, minimumExpectedDelay);
+
+  await cleanUpAndGo(server);
+});
+
+add_task(async function test_sync_503_Retry_After() {
+  enableValidationPrefs();
+
+  let server = await sync_httpd_setup();
+  await setUp(server);
+
+  // Use an odd value on purpose so that it doesn't happen to coincide with one
+  // of the sync intervals.
+  const BACKOFF = 7337;
+
+  // Extend info/collections so that we can put it into server maintenance mode.
+  const INFO_COLLECTIONS = "/1.1/johndoe@mozilla.com/info/collections";
+  let infoColl = server._handler._overridePaths[INFO_COLLECTIONS];
+  let serverMaintenance = false;
+  function infoCollWithMaintenance(request, response) {
+    if (!serverMaintenance) {
+      infoColl(request, response);
+      return;
+    }
+    response.setHeader("Retry-After", "" + BACKOFF);
+    response.setStatusLine(request.httpVersion, 503, "Service Unavailable");
+  }
+  server.registerPathHandler(INFO_COLLECTIONS, infoCollWithMaintenance);
+
+  // Pretend we have two clients so that the regular sync interval is
+  // sufficiently low.
+  await clientsEngine._store.create({
+    id: "foo",
+    cleartext: { os: "mobile", version: "0.01", type: "desktop" },
+  });
+  let rec = await clientsEngine._store.createRecord("foo", "clients");
+  await rec.encrypt(Service.collectionKeys.keyForCollection("clients"));
+  await rec.upload(Service.resource(clientsEngine.engineURL + rec.id));
+
+  // Sync once to log in and get everything set up. Let's verify our initial
+  // values.
+  await Service.sync();
+  Assert.ok(!Status.enforceBackoff);
+  Assert.equal(Status.backoffInterval, 0);
+  Assert.equal(Status.minimumNextSync, 0);
+  Assert.equal(scheduler.syncInterval, scheduler.activeInterval);
+  Assert.lessOrEqual(scheduler.nextSync, Date.now() + scheduler.syncInterval);
+  // Sanity check that we picked the right value for BACKOFF:
+  Assert.less(scheduler.syncInterval, BACKOFF * 1000);
+
+  // Turn on server maintenance and sync again.
+  serverMaintenance = true;
+  await Service.sync();
+
+  Assert.ok(Status.enforceBackoff);
+  Assert.greaterOrEqual(Status.backoffInterval, BACKOFF * 1000);
+  // Allowing 3 seconds worth of of leeway between when Status.minimumNextSync
+  // was set and when this line gets executed.
+  let minimumExpectedDelay = (BACKOFF - 3) * 1000;
+  Assert.greaterOrEqual(
+    Status.minimumNextSync,
+    Date.now() + minimumExpectedDelay
+  );
+
+  // Verify that the next sync is actually going to wait that long.
+  Assert.greaterOrEqual(scheduler.nextSync, Date.now() + minimumExpectedDelay);
+  Assert.greaterOrEqual(scheduler.syncTimer.delay, minimumExpectedDelay);
+
+  await cleanUpAndGo(server);
+});
+
+add_task(async function test_loginError_recoverable_reschedules() {
+  _("Verify that a recoverable login error schedules a new sync.");
+  await configureIdentity({ username: "johndoe@mozilla.com" });
+  Service.clusterURL = "http://localhost:1234/";
+  Status.resetSync(); // reset Status.login
+
+  let promiseObserved = promiseOneObserver("weave:service:login:error");
+
+  // Let's set it up so that a sync is overdue, both in terms of previously
+  // scheduled syncs and the global score. We still do not expect an immediate
+  // sync because we just tried (duh).
+  scheduler.nextSync = Date.now() - 100000;
+  scheduler.globalScore = SINGLE_USER_THRESHOLD + 1;
+  function onSyncStart() {
+    do_throw("Shouldn't have started a sync!");
+  }
+  Svc.Obs.add("weave:service:sync:start", onSyncStart);
+
+  // Sanity check.
+  Assert.equal(scheduler.syncTimer, null);
+  Assert.equal(Status.checkSetup(), STATUS_OK);
+  Assert.equal(Status.login, LOGIN_SUCCEEDED);
+
+  scheduler.scheduleNextSync(0);
+  await promiseObserved;
+  await Async.promiseYield();
+
+  Assert.equal(Status.login, LOGIN_FAILED_NETWORK_ERROR);
+
+  let expectedNextSync = Date.now() + scheduler.syncInterval;
+  Assert.greater(scheduler.nextSync, Date.now());
+  Assert.lessOrEqual(scheduler.nextSync, expectedNextSync);
+  Assert.greater(scheduler.syncTimer.delay, 0);
+  Assert.lessOrEqual(scheduler.syncTimer.delay, scheduler.syncInterval);
+
+  Svc.Obs.remove("weave:service:sync:start", onSyncStart);
+  await cleanUpAndGo();
+});
+
+add_task(async function test_loginError_fatal_clearsTriggers() {
+  _("Verify that a fatal login error clears sync triggers.");
+  await configureIdentity({ username: "johndoe@mozilla.com" });
+
+  let server = httpd_setup({
+    "/1.1/johndoe@mozilla.com/info/collections": httpd_handler(
+      401,
+      "Unauthorized"
+    ),
+  });
+
+  Service.clusterURL = server.baseURI + "/";
+  Status.resetSync(); // reset Status.login
+
+  let promiseObserved = promiseOneObserver("weave:service:login:error");
+
+  // Sanity check.
+  Assert.equal(scheduler.nextSync, 0);
+  Assert.equal(scheduler.syncTimer, null);
+  Assert.equal(Status.checkSetup(), STATUS_OK);
+  Assert.equal(Status.login, LOGIN_SUCCEEDED);
+
+  scheduler.scheduleNextSync(0);
+  await promiseObserved;
+  await Async.promiseYield();
+
+  // For the FxA identity, a 401 on info/collections means a transient
+  // error, probably due to an inability to fetch a token.
+  Assert.equal(Status.login, LOGIN_FAILED_NETWORK_ERROR);
+  // syncs should still be scheduled.
+  Assert.greater(scheduler.nextSync, Date.now());
+  Assert.greater(scheduler.syncTimer.delay, 0);
+
+  await cleanUpAndGo(server);
+});
+
+add_task(async function test_proper_interval_on_only_failing() {
+  _("Ensure proper behavior when only failed records are applied.");
+
+  // If an engine reports that no records succeeded, we shouldn't decrease the
+  // sync interval.
+  Assert.ok(!scheduler.hasIncomingItems);
+  const INTERVAL = 10000000;
+  scheduler.syncInterval = INTERVAL;
+
+  Svc.Obs.notify("weave:service:sync:applied", {
+    applied: 2,
+    succeeded: 0,
+    failed: 2,
+    newFailed: 2,
+    reconciled: 0,
+  });
+
+  await Async.promiseYield();
+  scheduler.adjustSyncInterval();
+  Assert.ok(!scheduler.hasIncomingItems);
+  Assert.equal(scheduler.syncInterval, scheduler.singleDeviceInterval);
+});
+
+add_task(async function test_link_status_change() {
+  _("Check that we only attempt to sync when link status is up");
+  try {
+    sinon.spy(scheduler, "scheduleNextSync");
+
+    Svc.Obs.notify("network:link-status-changed", null, "down");
+    equal(scheduler.scheduleNextSync.callCount, 0);
+
+    Svc.Obs.notify("network:link-status-changed", null, "change");
+    equal(scheduler.scheduleNextSync.callCount, 0);
+
+    Svc.Obs.notify("network:link-status-changed", null, "up");
+    equal(scheduler.scheduleNextSync.callCount, 1);
+
+    Svc.Obs.notify("network:link-status-changed", null, "change");
+    equal(scheduler.scheduleNextSync.callCount, 1);
+  } finally {
+    scheduler.scheduleNextSync.restore();
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_tab_engine.js b/src/zen/tests/mochitests/sync/test_tab_engine.js
new file mode 100644
index 000000000..7e733627a
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_tab_engine.js
@@ -0,0 +1,195 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { TabProvider } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/tabs.sys.mjs"
+);
+const { WBORecord } = ChromeUtils.importESModule(
+  "resource://services-sync/record.sys.mjs"
+);
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+let engine;
+// We'll need the clients engine for testing as tabs is closely related
+let clientsEngine;
+
+async function syncClientsEngine(server) {
+  clientsEngine._lastFxADevicesFetch = 0;
+  clientsEngine.lastModified = server.getCollection("foo", "clients").timestamp;
+  await clientsEngine._sync();
+}
+
+async function makeRemoteClients() {
+  let server = await serverForFoo(clientsEngine);
+  await configureIdentity({ username: "foo" }, server);
+  await Service.login();
+
+  await SyncTestingInfrastructure(server);
+  await generateNewKeys(Service.collectionKeys);
+
+  let remoteId = Utils.makeGUID();
+  let remoteId2 = Utils.makeGUID();
+  let collection = server.getCollection("foo", "clients");
+
+  _("Create remote client records");
+  collection.insertRecord({
+    id: remoteId,
+    name: "Remote client",
+    type: "desktop",
+    commands: [],
+    version: "48",
+    fxaDeviceId: remoteId,
+    fxaDeviceName: "Fxa - Remote client",
+    protocols: ["1.5"],
+  });
+
+  collection.insertRecord({
+    id: remoteId2,
+    name: "Remote client 2",
+    type: "desktop",
+    commands: [],
+    version: "48",
+    fxaDeviceId: remoteId2,
+    fxaDeviceName: "Fxa - Remote client 2",
+    protocols: ["1.5"],
+  });
+
+  let fxAccounts = clientsEngine.fxAccounts;
+  clientsEngine.fxAccounts = {
+    notifyDevices() {
+      return Promise.resolve(true);
+    },
+    device: {
+      getLocalId() {
+        return fxAccounts.device.getLocalId();
+      },
+      getLocalName() {
+        return fxAccounts.device.getLocalName();
+      },
+      getLocalType() {
+        return fxAccounts.device.getLocalType();
+      },
+      recentDeviceList: [{ id: remoteId, name: "remote device" }],
+      refreshDeviceList() {
+        return Promise.resolve(true);
+      },
+    },
+    _internal: {
+      now() {
+        return Date.now();
+      },
+    },
+  };
+
+  await syncClientsEngine(server);
+}
+
+add_task(async function setup() {
+  clientsEngine = Service.clientsEngine;
+  // Make some clients to test with
+  await makeRemoteClients();
+
+  // Make the tabs engine for all the tests to use
+  engine = Service.engineManager.get("tabs");
+  await engine.initialize();
+
+  // Since these are xpcshell tests, we'll need to mock this
+  TabProvider.getOrderedNonPrivateWindows =
+    mockGetOrderedNonPrivateWindows.bind(this, []);
+});
+
+add_task(async function test_tab_engine_skips_incoming_local_record() {
+  _("Ensure incoming records that match local client ID are never applied.");
+
+  let localID = clientsEngine.localID;
+  let collection = new ServerCollection();
+
+  _("Creating remote tab record with local client ID");
+  let localRecord = encryptPayload({
+    id: localID,
+    clientName: "local",
+    tabs: [
+      {
+        title: "title",
+        urlHistory: ["http://foo.com/"],
+        icon: "",
+        lastUsed: 2000,
+      },
+    ],
+  });
+  collection.insert(localID, localRecord);
+
+  _("Creating remote tab record with a different client ID");
+  let remoteID = "fake-guid-00"; // remote should match one of the test clients
+  let remoteRecord = encryptPayload({
+    id: remoteID,
+    clientName: "not local",
+    tabs: [
+      {
+        title: "title2",
+        urlHistory: ["http://bar.com/"],
+        icon: "",
+        lastUsed: 3000,
+      },
+    ],
+  });
+  collection.insert(remoteID, remoteRecord);
+
+  _("Setting up Sync server");
+  let server = sync_httpd_setup({
+    "/1.1/foo/storage/tabs": collection.handler(),
+  });
+
+  await SyncTestingInfrastructure(server);
+
+  let syncID = await engine.resetLocalSyncID();
+  let meta_global = Service.recordManager.set(
+    engine.metaURL,
+    new WBORecord(engine.metaURL)
+  );
+  meta_global.payload.engines = {
+    tabs: { version: engine.version, syncID },
+  };
+
+  await generateNewKeys(Service.collectionKeys);
+
+  let promiseFinished = new Promise(resolve => {
+    let syncFinish = engine._syncFinish;
+    engine._syncFinish = async function () {
+      let remoteTabs = await engine._rustStore.getAll();
+      equal(
+        remoteTabs.length,
+        1,
+        "Remote client record was applied and local wasn't"
+      );
+      let record = remoteTabs[0];
+      equal(record.clientId, remoteID, "Remote client ID matches");
+
+      _("Ensure getAllClients returns the correct shape");
+      let clients = await engine.getAllClients();
+      equal(clients.length, 1);
+      let client = clients[0];
+      equal(client.id, "fake-guid-00");
+      equal(client.name, "Remote client");
+      equal(client.type, "desktop");
+      Assert.ok(client.lastModified); // lastModified should be filled in once serverModified is populated from the server
+      Assert.equal(client.tabs.length, 1);
+      let tab = client.tabs[0];
+      Assert.equal(tab.title, "title2");
+      Assert.deepEqual(tab.urlHistory, ["http://bar.com/"]);
+      Assert.equal(tab.icon, "");
+      Assert.ok(!tab.inactive);
+      await syncFinish.call(engine);
+      resolve();
+    };
+  });
+
+  _("Start sync");
+  Service.scheduler.hasIncomingItems = false;
+  await engine._sync();
+  await promiseFinished;
+  // Bug 1800185 - we don't want the sync scheduler to see these records as incoming.
+  Assert.ok(!Service.scheduler.hasIncomingItems);
+});
diff --git a/src/zen/tests/mochitests/sync/test_tab_provider.js b/src/zen/tests/mochitests/sync/test_tab_provider.js
new file mode 100644
index 000000000..a9d27f85d
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_tab_provider.js
@@ -0,0 +1,59 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { TabProvider } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/tabs.sys.mjs"
+);
+
+add_task(async function test_getAllTabs() {
+  let provider = TabProvider;
+
+  provider.getOrderedNonPrivateWindows = mockGetOrderedNonPrivateWindows.bind(
+    this,
+    ["http://bar.com"]
+  );
+
+  _("Get all tabs.");
+  let tabs = (
+    await provider.getAllTabsWithEstimatedMax(false, Number.MAX_SAFE_INTEGER)
+  ).tabs;
+  _("Tabs: " + JSON.stringify(tabs));
+  equal(tabs.length, 1);
+  equal(tabs[0].title, "title");
+  equal(tabs[0].urlHistory.length, 1);
+  equal(tabs[0].urlHistory[0], "http://bar.com/");
+  equal(tabs[0].icon, "");
+  equal(tabs[0].lastUsed, 2000);
+
+  _("Get all tabs, and check that filtering works.");
+  provider.getOrderedNonPrivateWindows = mockGetOrderedNonPrivateWindows.bind(
+    this,
+    ["http://foo.com", "about:foo"]
+  );
+  tabs = (
+    await provider.getAllTabsWithEstimatedMax(true, Number.MAX_SAFE_INTEGER)
+  ).tabs;
+  _("Filtered: " + JSON.stringify(tabs));
+  equal(tabs.length, 1);
+
+  _("Get all tabs, and check that they are properly sorted");
+  provider.getOrderedNonPrivateWindows = mockGetOrderedNonPrivateWindows.bind(
+    this,
+    ["http://foo.com", "http://bar.com"]
+  );
+  tabs = (
+    await provider.getAllTabsWithEstimatedMax(true, Number.MAX_SAFE_INTEGER)
+  ).tabs;
+  _("Ordered: " + JSON.stringify(tabs));
+  equal(tabs[0].lastUsed > tabs[1].lastUsed, true);
+
+  // reader mode URLs are provided.
+  provider.getOrderedNonPrivateWindows = mockGetOrderedNonPrivateWindows.bind(
+    this,
+    ["about:reader?url=http%3A%2F%2Ffoo.com%2F"]
+  );
+  tabs = (
+    await provider.getAllTabsWithEstimatedMax(true, Number.MAX_SAFE_INTEGER)
+  ).tabs;
+  equal(tabs[0].urlHistory[0], "http://foo.com/");
+});
diff --git a/src/zen/tests/mochitests/sync/test_tab_quickwrite.js b/src/zen/tests/mochitests/sync/test_tab_quickwrite.js
new file mode 100644
index 000000000..36eac5a5c
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_tab_quickwrite.js
@@ -0,0 +1,220 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+ChromeUtils.importESModule("resource://services-sync/engines/tabs.sys.mjs");
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+const { TabProvider } = ChromeUtils.importESModule(
+  "resource://services-sync/engines/tabs.sys.mjs"
+);
+
+const FAR_FUTURE = 4102405200000; // 2100/01/01
+
+add_task(async function setup() {
+  // Since these are xpcshell tests, we'll need to mock ui features
+  TabProvider.getOrderedNonPrivateWindows =
+    mockGetOrderedNonPrivateWindows.bind(this, ["http://foo.com"]);
+});
+
+async function prepareServer() {
+  _("Setting up Sync server");
+  Service.serverConfiguration = {
+    max_post_records: 100,
+  };
+
+  let server = new SyncServer();
+  server.start();
+  await SyncTestingInfrastructure(server, "username");
+  server.registerUser("username");
+
+  let collection = server.createCollection("username", "tabs");
+  await generateNewKeys(Service.collectionKeys);
+
+  let engine = Service.engineManager.get("tabs");
+  await engine.initialize();
+
+  return { server, collection, engine };
+}
+
+async function withPatchedValue(object, name, patchedVal, fn) {
+  _(`patching ${name}=${patchedVal}`);
+  let old = object[name];
+  object[name] = patchedVal;
+  try {
+    await fn();
+  } finally {
+    object[name] = old;
+  }
+}
+
+add_task(async function test_tab_quickwrite_works() {
+  _("Ensure a simple quickWrite works.");
+  let { server, collection, engine } = await prepareServer();
+  Assert.equal(collection.count(), 0, "starting with 0 tab records");
+  Assert.ok(await engine.quickWrite());
+  // Validate we didn't bork lastSync
+  let lastSync = await engine.getLastSync();
+  Assert.less(lastSync, FAR_FUTURE);
+  Assert.equal(collection.count(), 1, "tab record was written");
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_tab_bad_status() {
+  _("Ensure quickWrite silently aborts when we aren't setup correctly.");
+  let { server, engine } = await prepareServer();
+  // Store the original lock to reset it back after this test
+  let lock = engine.lock;
+  // Arrange for this test to fail if it tries to take the lock.
+  engine.lock = function () {
+    throw new Error("this test should abort syncing before locking");
+  };
+  let quickWrite = engine.quickWrite.bind(engine); // lol javascript.
+
+  await withPatchedValue(engine, "enabled", false, quickWrite);
+  await withPatchedValue(Service, "serverConfiguration", null, quickWrite);
+
+  Services.prefs.clearUserPref("services.sync.username");
+  await quickWrite();
+  // Validate we didn't bork lastSync
+  let lastSync = await engine.getLastSync();
+  Assert.less(lastSync, FAR_FUTURE);
+  Service.status.resetSync();
+  engine.lock = lock;
+  await promiseStopServer(server);
+});
+
+add_task(async function test_tab_quickwrite_lock() {
+  _("Ensure we fail to quickWrite if the engine is locked.");
+  let { server, collection, engine } = await prepareServer();
+
+  Assert.equal(collection.count(), 0, "starting with 0 tab records");
+  engine.lock();
+  Assert.ok(!(await engine.quickWrite()));
+  Assert.equal(collection.count(), 0, "didn't sync due to being locked");
+  engine.unlock();
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_tab_quickwrite_keeps_old_tabs() {
+  _("Ensure we don't delete other tabs on quickWrite (bug 1801295).");
+  let { server, engine } = await prepareServer();
+
+  // The ID of another device.
+  const id = "fake-guid-99";
+
+  // The clients engine is always going to tell us there are no other clients,
+  // but we need other clients, so we trick it.
+  // (We can't just stick this on the server, because we treat it as stale because it
+  // doesn't appear in the fxa list - but tricking it this way works)
+  let observeClientsFinished = (_subject, _topic, data) => {
+    if (data == "clients") {
+      engine.service.clientsEngine.fxAccounts.device._deviceListCache = {
+        devices: [],
+      };
+      // trick the clients engine into thinking it has a remote client with the same guid.
+      engine.service.clientsEngine._store._remoteClients = {};
+      engine.service.clientsEngine._store._remoteClients[id] = {
+        id,
+        fxaDeviceId: id,
+      };
+    }
+  };
+  Services.obs.addObserver(observeClientsFinished, "weave:engine:sync:finish");
+
+  // need a first sync to ensure everything is setup correctly.
+  await Service.sync({ engines: ["tabs"] });
+
+  let remoteRecord = encryptPayload({
+    id,
+    clientName: "not local",
+    tabs: [
+      {
+        title: "title2",
+        urlHistory: ["http://bar.com/"],
+        icon: "",
+        lastUsed: 3000,
+      },
+    ],
+  });
+
+  let collection = server.getCollection("username", "tabs");
+  collection.insert(id, remoteRecord);
+
+  // This test can be flakey because sometimes we are so fast we think there is nothing to do.
+  // Resetting the last sync time here ensures we always fetch records from the server.
+  engine.setLastSync(0);
+  await Service.sync({ engines: ["tabs"] });
+
+  // collection should now have 2 records - ours and the pretend remote one we inserted.
+  Assert.equal(collection.count(), 2, "starting with 2 tab records");
+
+  let clients = await engine.getAllClients();
+  Assert.equal(clients.length, 1);
+
+  _("Doing a quick-write");
+  Assert.ok(await engine.quickWrite());
+
+  // Should still have our client after a quickWrite.
+  _("Grabbing clients after the quick-write");
+  clients = await engine.getAllClients();
+  Assert.equal(clients.length, 1);
+
+  engine.service.clientsEngine._store._remoteClients = {};
+
+  Services.obs.removeObserver(
+    observeClientsFinished,
+    "weave:engine:sync:finish"
+  );
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_tab_lastSync() {
+  _("Ensure we restore the lastSync timestamp after a quick-write.");
+  let { server, collection, engine } = await prepareServer();
+
+  await engine.initialize();
+  await engine.service.clientsEngine.initialize();
+
+  let origLastSync = engine.lastSync;
+  Assert.ok(await engine.quickWrite());
+  Assert.equal(engine.lastSync, origLastSync);
+  Assert.equal(collection.count(), 1, "successful sync");
+  engine.unlock();
+
+  await promiseStopServer(server);
+});
+
+add_task(async function test_tab_quickWrite_telemetry() {
+  _("Ensure we record the telemetry we expect.");
+  // hook into telemetry
+  let telem = get_sync_test_telemetry();
+  telem.payloads = [];
+  let oldSubmit = telem.submit;
+  let submitPromise = new Promise(resolve => {
+    telem.submit = function (ping) {
+      telem.submit = oldSubmit;
+      resolve(ping);
+    };
+  });
+
+  let { server, collection, engine } = await prepareServer();
+
+  Assert.equal(collection.count(), 0, "starting with 0 tab records");
+  Assert.ok(await engine.quickWrite());
+  Assert.equal(collection.count(), 1, "tab record was written");
+
+  let ping = await submitPromise;
+  let syncs = ping.syncs;
+  Assert.equal(syncs.length, 1);
+  let sync = syncs[0];
+  Assert.equal(sync.why, "quick-write");
+  Assert.equal(sync.engines.length, 1);
+  Assert.equal(sync.engines[0].name, "tabs");
+
+  await promiseStopServer(server);
+});
diff --git a/src/zen/tests/mochitests/sync/test_tab_tracker.js b/src/zen/tests/mochitests/sync/test_tab_tracker.js
new file mode 100644
index 000000000..4a924e991
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_tab_tracker.js
@@ -0,0 +1,371 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+ChromeUtils.importESModule("resource://services-sync/engines/tabs.sys.mjs");
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+const { SyncScheduler } = ChromeUtils.importESModule(
+  "resource://services-sync/policies.sys.mjs"
+);
+
+var scheduler = new SyncScheduler(Service);
+let clientsEngine;
+
+add_task(async function setup() {
+  await Service.promiseInitialized;
+  clientsEngine = Service.clientsEngine;
+
+  scheduler.setDefaults();
+});
+
+function fakeSvcWinMediator() {
+  // actions on windows are captured in logs
+  let logs = [];
+  delete Services.wm;
+
+  function getNext() {
+    let elt = { addTopics: [], remTopics: [], numAPL: 0, numRPL: 0 };
+    logs.push(elt);
+    return {
+      addEventListener(topic) {
+        elt.addTopics.push(topic);
+      },
+      removeEventListener(topic) {
+        elt.remTopics.push(topic);
+      },
+      gBrowser: {
+        addProgressListener() {
+          elt.numAPL++;
+        },
+        removeProgressListener() {
+          elt.numRPL++;
+        },
+      },
+    };
+  }
+
+  Services.wm = {
+    getEnumerator() {
+      return [getNext(), getNext()];
+    },
+  };
+  return logs;
+}
+
+function fakeGetTabState(tab) {
+  return tab;
+}
+
+function clearQuickWriteTimer(tracker) {
+  if (tracker.tabsQuickWriteTimer) {
+    tracker.tabsQuickWriteTimer.clear();
+  }
+}
+
+add_task(async function run_test() {
+  let engine = Service.engineManager.get("tabs");
+  await engine.initialize();
+  _("We assume that tabs have changed at startup.");
+  let tracker = engine._tracker;
+  tracker.getTabState = fakeGetTabState;
+
+  Assert.ok(tracker.modified);
+  Assert.ok(
+    Utils.deepEquals(Object.keys(await engine.getChangedIDs()), [
+      clientsEngine.localID,
+    ])
+  );
+
+  let logs;
+
+  _("Test listeners are registered on windows");
+  logs = fakeSvcWinMediator();
+  tracker.start();
+  Assert.equal(logs.length, 2);
+  for (let log of logs) {
+    Assert.equal(log.addTopics.length, 3);
+    Assert.ok(log.addTopics.includes("TabOpen"));
+    Assert.ok(log.addTopics.includes("TabClose"));
+    Assert.ok(log.addTopics.includes("unload"));
+    Assert.equal(log.remTopics.length, 0);
+    Assert.equal(log.numAPL, 1, "Added 1 progress listener");
+    Assert.equal(log.numRPL, 0, "Didn't remove a progress listener");
+  }
+
+  _("Test listeners are unregistered on windows");
+  logs = fakeSvcWinMediator();
+  await tracker.stop();
+  Assert.equal(logs.length, 2);
+  for (let log of logs) {
+    Assert.equal(log.addTopics.length, 0);
+    Assert.equal(log.remTopics.length, 3);
+    Assert.ok(log.remTopics.includes("TabOpen"));
+    Assert.ok(log.remTopics.includes("TabClose"));
+    Assert.ok(log.remTopics.includes("unload"));
+    Assert.equal(log.numAPL, 0, "Didn't add a progress listener");
+    Assert.equal(log.numRPL, 1, "Removed 1 progress listener");
+  }
+
+  _("Test tab listener");
+  for (let evttype of ["TabOpen", "TabClose"]) {
+    // Pretend we just synced.
+    await tracker.clearChangedIDs();
+    Assert.ok(!tracker.modified);
+
+    // Send a fake tab event
+    tracker.onTab({
+      type: evttype,
+      originalTarget: evttype,
+      target: { entries: [], currentURI: "about:config" },
+    });
+    Assert.ok(tracker.modified);
+    Assert.ok(
+      Utils.deepEquals(Object.keys(await engine.getChangedIDs()), [
+        clientsEngine.localID,
+      ])
+    );
+  }
+
+  // Pretend we just synced.
+  await tracker.clearChangedIDs();
+  Assert.ok(!tracker.modified);
+
+  tracker.onTab({
+    type: "TabOpen",
+    originalTarget: "TabOpen",
+    target: { entries: [], currentURI: "about:config" },
+  });
+  Assert.ok(
+    Utils.deepEquals(Object.keys(await engine.getChangedIDs()), [
+      clientsEngine.localID,
+    ])
+  );
+
+  // Pretend we just synced and saw some progress listeners.
+  await tracker.clearChangedIDs();
+  Assert.ok(!tracker.modified);
+  tracker.onLocationChange({ isTopLevel: false }, undefined, undefined, 0);
+  Assert.ok(!tracker.modified, "non-toplevel request didn't flag as modified");
+
+  tracker.onLocationChange(
+    { isTopLevel: true },
+    undefined,
+    Services.io.newURI("https://www.mozilla.org"),
+    Ci.nsIWebProgressListener.LOCATION_CHANGE_SAME_DOCUMENT
+  );
+  Assert.ok(
+    tracker.modified,
+    "location change within the same document request did flag as modified"
+  );
+
+  tracker.onLocationChange(
+    { isTopLevel: true },
+    undefined,
+    Services.io.newURI("https://www.mozilla.org")
+  );
+  Assert.ok(
+    tracker.modified,
+    "location change for a new top-level document flagged as modified"
+  );
+  Assert.ok(
+    Utils.deepEquals(Object.keys(await engine.getChangedIDs()), [
+      clientsEngine.localID,
+    ])
+  );
+});
+
+add_task(async function run_sync_on_tab_change_test() {
+  let testPrefDelay = 20000;
+
+  // This is the pref that determines sync delay after tab change
+  Svc.PrefBranch.setIntPref(
+    "syncedTabs.syncDelayAfterTabChange",
+    testPrefDelay
+  );
+  // We should only be syncing on tab change if
+  // the user has > 1 client
+  Svc.PrefBranch.setIntPref("clients.devices.desktop", 1);
+  Svc.PrefBranch.setIntPref("clients.devices.mobile", 1);
+  scheduler.updateClientMode();
+  Assert.equal(scheduler.numClients, 2);
+
+  let engine = Service.engineManager.get("tabs");
+
+  _("We assume that tabs have changed at startup.");
+  let tracker = engine._tracker;
+  tracker.getTabState = fakeGetTabState;
+
+  Assert.ok(tracker.modified);
+  Assert.ok(
+    Utils.deepEquals(Object.keys(await engine.getChangedIDs()), [
+      clientsEngine.localID,
+    ])
+  );
+
+  _("Test sync is scheduled after a tab change");
+  for (let evttype of ["TabOpen", "TabClose"]) {
+    // Pretend we just synced
+    await tracker.clearChangedIDs();
+    clearQuickWriteTimer(tracker);
+
+    // Send a fake tab event
+    tracker.onTab({
+      type: evttype,
+      originalTarget: evttype,
+      target: { entries: [], currentURI: "about:config" },
+    });
+    // Ensure the tracker fired
+    Assert.ok(tracker.modified);
+    // We should be more delayed at or more than what the pref is set at
+    let nextSchedule = tracker.tabsQuickWriteTimer.delay;
+    Assert.greaterOrEqual(nextSchedule, testPrefDelay);
+  }
+
+  _("Test sync is NOT scheduled after an unsupported tab open");
+  for (let evttype of ["TabOpen"]) {
+    // Send a fake tab event
+    tracker.onTab({
+      type: evttype,
+      originalTarget: evttype,
+      target: { entries: ["about:newtab"], currentURI: null },
+    });
+    // Ensure the tracker fired
+    Assert.ok(tracker.modified);
+    // We should be scheduling <= pref value
+    Assert.lessOrEqual(scheduler.nextSync - Date.now(), testPrefDelay);
+  }
+
+  _("Test navigating within the same tab does NOT trigger a sync");
+  // Pretend we just synced
+  await tracker.clearChangedIDs();
+  clearQuickWriteTimer(tracker);
+
+  tracker.onLocationChange(
+    { isTopLevel: true },
+    undefined,
+    Services.io.newURI("https://www.mozilla.org"),
+    Ci.nsIWebProgressListener.LOCATION_CHANGE_RELOAD
+  );
+  Assert.ok(
+    !tracker.modified,
+    "location change for reloading doesn't trigger a sync"
+  );
+  Assert.ok(!tracker.tabsQuickWriteTimer, "reload does not trigger a sync");
+
+  // Pretend we just synced
+  await tracker.clearChangedIDs();
+  clearQuickWriteTimer(tracker);
+
+  _("Test navigating to an about page does trigger sync");
+  tracker.onLocationChange(
+    { isTopLevel: true },
+    undefined,
+    Services.io.newURI("about:config")
+  );
+  Assert.ok(tracker.modified, "about page does not trigger a tab modified");
+  Assert.ok(
+    tracker.tabsQuickWriteTimer,
+    "about schema should trigger a sync happening soon"
+  );
+
+  _("Test adjusting the filterScheme pref works");
+  // Pretend we just synced
+  await tracker.clearChangedIDs();
+  clearQuickWriteTimer(tracker);
+
+  Svc.PrefBranch.setStringPref(
+    "engine.tabs.filteredSchemes",
+    // Removing the about scheme for this test
+    "resource|chrome|file|blob|moz-extension"
+  );
+  tracker.onLocationChange(
+    { isTopLevel: true },
+    undefined,
+    Services.io.newURI("about:config")
+  );
+  Assert.ok(
+    tracker.modified,
+    "about page triggers a modified after we changed the pref"
+  );
+  Assert.ok(
+    tracker.tabsQuickWriteTimer,
+    "about page should schedule a quickWrite sync soon after we changed the pref"
+  );
+
+  _("Test no sync after tab change for accounts with <= 1 clients");
+  // Pretend we just synced
+  await tracker.clearChangedIDs();
+  clearQuickWriteTimer(tracker);
+  // Setting clients to only 1 so we don't sync after a tab change
+  Svc.PrefBranch.setIntPref("clients.devices.desktop", 1);
+  Svc.PrefBranch.setIntPref("clients.devices.mobile", 0);
+  scheduler.updateClientMode();
+  Assert.equal(scheduler.numClients, 1);
+
+  tracker.onLocationChange(
+    { isTopLevel: true },
+    undefined,
+    Services.io.newURI("https://www.mozilla.org")
+  );
+  Assert.ok(
+    tracker.modified,
+    "location change for a new top-level document flagged as modified"
+  );
+  Assert.ok(
+    !tracker.tabsQuickWriteTimer,
+    "We should NOT be syncing shortly because there is only one client"
+  );
+
+  _("Changing the pref adjusts the sync schedule");
+  Svc.PrefBranch.setIntPref("syncedTabs.syncDelayAfterTabChange", 10000); // 10seconds
+  let delayPref = Svc.PrefBranch.getIntPref(
+    "syncedTabs.syncDelayAfterTabChange"
+  );
+  let evttype = "TabOpen";
+  Assert.equal(delayPref, 10000); // ensure our pref is at 10s
+  // Only have task continuity if we have more than 1 device
+  Svc.PrefBranch.setIntPref("clients.devices.desktop", 1);
+  Svc.PrefBranch.setIntPref("clients.devices.mobile", 1);
+  scheduler.updateClientMode();
+  Assert.equal(scheduler.numClients, 2);
+  clearQuickWriteTimer(tracker);
+
+  // Fire ontab event
+  tracker.onTab({
+    type: evttype,
+    originalTarget: evttype,
+    target: { entries: [], currentURI: "about:config" },
+  });
+
+  // Ensure the tracker fired
+  Assert.ok(tracker.modified);
+  // We should be scheduling <= preference value
+  Assert.equal(tracker.tabsQuickWriteTimer.delay, delayPref);
+
+  _("We should not have a sync scheduled if pref is at 0");
+
+  Svc.PrefBranch.setIntPref("syncedTabs.syncDelayAfterTabChange", 0);
+  // Pretend we just synced
+  await tracker.clearChangedIDs();
+  clearQuickWriteTimer(tracker);
+
+  // Fire ontab event
+  evttype = "TabOpen";
+  tracker.onTab({
+    type: evttype,
+    originalTarget: evttype,
+    target: { entries: [], currentURI: "about:config" },
+  });
+  // Ensure the tracker fired
+  Assert.ok(tracker.modified);
+
+  // We should NOT be scheduled for a sync soon
+  Assert.ok(!tracker.tabsQuickWriteTimer);
+
+  scheduler.setDefaults();
+  for (const pref of Svc.PrefBranch.getChildList("")) {
+    Svc.PrefBranch.clearUserPref(pref);
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_telemetry.js b/src/zen/tests/mochitests/sync/test_telemetry.js
new file mode 100644
index 000000000..db61ab285
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_telemetry.js
@@ -0,0 +1,1274 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+const { WBORecord } = ChromeUtils.importESModule(
+  "resource://services-sync/record.sys.mjs"
+);
+const { RotaryEngine } = ChromeUtils.importESModule(
+  "resource://testing-common/services/sync/rotaryengine.sys.mjs"
+);
+const { getFxAccountsSingleton } = ChromeUtils.importESModule(
+  "resource://gre/modules/FxAccounts.sys.mjs"
+);
+const fxAccounts = getFxAccountsSingleton();
+
+function SteamStore(engine) {
+  Store.call(this, "Steam", engine);
+}
+Object.setPrototypeOf(SteamStore.prototype, Store.prototype);
+
+function SteamTracker(name, engine) {
+  LegacyTracker.call(this, name || "Steam", engine);
+}
+Object.setPrototypeOf(SteamTracker.prototype, LegacyTracker.prototype);
+
+function SteamEngine(service) {
+  SyncEngine.call(this, "steam", service);
+}
+
+SteamEngine.prototype = {
+  _storeObj: SteamStore,
+  _trackerObj: SteamTracker,
+  _errToThrow: null,
+  problemsToReport: null,
+  async _sync() {
+    if (this._errToThrow) {
+      throw this._errToThrow;
+    }
+  },
+  getValidator() {
+    return new SteamValidator();
+  },
+};
+Object.setPrototypeOf(SteamEngine.prototype, SyncEngine.prototype);
+
+function BogusEngine(service) {
+  SyncEngine.call(this, "bogus", service);
+}
+
+BogusEngine.prototype = Object.create(SteamEngine.prototype);
+
+class SteamValidator {
+  async canValidate() {
+    return true;
+  }
+
+  async validate(engine) {
+    return {
+      problems: new SteamValidationProblemData(engine.problemsToReport),
+      version: 1,
+      duration: 0,
+      recordCount: 0,
+    };
+  }
+}
+
+class SteamValidationProblemData {
+  constructor(problemsToReport = []) {
+    this.problemsToReport = problemsToReport;
+  }
+
+  getSummary() {
+    return this.problemsToReport;
+  }
+}
+
+async function cleanAndGo(engine, server) {
+  await engine._tracker.clearChangedIDs();
+  for (const pref of Svc.PrefBranch.getChildList("")) {
+    Svc.PrefBranch.clearUserPref(pref);
+  }
+  syncTestLogging();
+  Service.recordManager.clearCache();
+  await promiseStopServer(server);
+}
+
+add_task(async function setup() {
+  // Avoid addon manager complaining about not being initialized
+  await Service.engineManager.unregister("addons");
+  await Service.engineManager.unregister("extension-storage");
+});
+
+add_task(async function test_basic() {
+  enableValidationPrefs();
+
+  let helper = track_collections_helper();
+  let upd = helper.with_updated_collection;
+
+  let handlers = {
+    "/1.1/johndoe/info/collections": helper.handler,
+    "/1.1/johndoe/storage/crypto/keys": upd(
+      "crypto",
+      new ServerWBO("keys").handler()
+    ),
+    "/1.1/johndoe/storage/meta/global": upd(
+      "meta",
+      new ServerWBO("global").handler()
+    ),
+  };
+
+  let collections = [
+    "clients",
+    "bookmarks",
+    "forms",
+    "history",
+    "passwords",
+    "prefs",
+    "tabs",
+  ];
+
+  for (let coll of collections) {
+    handlers["/1.1/johndoe/storage/" + coll] = upd(
+      coll,
+      new ServerCollection({}, true).handler()
+    );
+  }
+
+  let server = httpd_setup(handlers);
+  await configureIdentity({ username: "johndoe" }, server);
+
+  await wait_for_ping(() => Service.sync(), true, true);
+
+  for (const pref of Svc.PrefBranch.getChildList("")) {
+    Svc.PrefBranch.clearUserPref(pref);
+  }
+  await promiseStopServer(server);
+});
+
+add_task(async function test_processIncoming_error() {
+  let engine = Service.engineManager.get("bookmarks");
+  await engine.initialize();
+  let store = engine._store;
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+  let collection = server.user("foo").collection("bookmarks");
+  try {
+    // Create a bogus record that when synced down will provoke a
+    // network error which in turn provokes an exception in _processIncoming.
+    const BOGUS_GUID = "zzzzzzzzzzzz";
+    let bogus_record = collection.insert(BOGUS_GUID, "I'm a bogus record!");
+    bogus_record.get = function get() {
+      throw new Error("Sync this!");
+    };
+    // Make the 10 minutes old so it will only be synced in the toFetch phase.
+    bogus_record.modified = Date.now() / 1000 - 60 * 10;
+    await engine.setLastSync(Date.now() / 1000 - 60);
+    engine.toFetch = new SerializableSet([BOGUS_GUID]);
+
+    let error, pingPayload, fullPing;
+    try {
+      await sync_engine_and_validate_telem(
+        engine,
+        true,
+        (errPing, fullErrPing) => {
+          pingPayload = errPing;
+          fullPing = fullErrPing;
+        }
+      );
+    } catch (ex) {
+      error = ex;
+    }
+    ok(!!error);
+    ok(!!pingPayload);
+
+    equal(fullPing.uid, "f".repeat(32)); // as setup by SyncTestingInfrastructure
+    deepEqual(pingPayload.failureReason, {
+      name: "httperror",
+      code: 500,
+    });
+
+    equal(pingPayload.engines.length, 1);
+
+    equal(pingPayload.engines[0].name, "bookmarks-buffered");
+    deepEqual(pingPayload.engines[0].failureReason, {
+      name: "httperror",
+      code: 500,
+    });
+  } finally {
+    await store.wipe();
+    await cleanAndGo(engine, server);
+  }
+});
+
+add_task(async function test_uploading() {
+  let engine = Service.engineManager.get("bookmarks");
+  await engine.initialize();
+  let store = engine._store;
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  let bmk = await PlacesUtils.bookmarks.insert({
+    parentGuid: PlacesUtils.bookmarks.toolbarGuid,
+    url: "http://getfirefox.com/",
+    title: "Get Firefox!",
+  });
+
+  try {
+    let ping = await sync_engine_and_validate_telem(engine, false);
+    ok(!!ping);
+    equal(ping.engines.length, 1);
+    equal(ping.engines[0].name, "bookmarks-buffered");
+    ok(!!ping.engines[0].outgoing);
+    greater(ping.engines[0].outgoing[0].sent, 0);
+    ok(!ping.engines[0].incoming);
+
+    await PlacesUtils.bookmarks.update({
+      guid: bmk.guid,
+      title: "New Title",
+    });
+
+    await store.wipe();
+    await engine.resetClient();
+    // We don't sync via the service, so don't re-hit info/collections, so
+    // lastModified remaning at zero breaks things subtly...
+    engine.lastModified = null;
+
+    ping = await sync_engine_and_validate_telem(engine, false);
+    equal(ping.engines.length, 1);
+    equal(ping.engines[0].name, "bookmarks-buffered");
+    equal(ping.engines[0].outgoing.length, 1);
+    ok(!!ping.engines[0].incoming);
+  } finally {
+    // Clean up.
+    await store.wipe();
+    await cleanAndGo(engine, server);
+  }
+});
+
+add_task(async function test_upload_failed() {
+  let collection = new ServerCollection();
+  collection._wbos.flying = new ServerWBO("flying");
+
+  let server = sync_httpd_setup({
+    "/1.1/foo/storage/rotary": collection.handler(),
+  });
+
+  await SyncTestingInfrastructure(server);
+  await configureIdentity({ username: "foo" }, server);
+
+  let engine = new RotaryEngine(Service);
+  engine._store.items = {
+    flying: "LNER Class A3 4472",
+    scotsman: "Flying Scotsman",
+    peppercorn: "Peppercorn Class",
+  };
+  const FLYING_CHANGED = 12345;
+  const SCOTSMAN_CHANGED = 23456;
+  const PEPPERCORN_CHANGED = 34567;
+  await engine._tracker.addChangedID("flying", FLYING_CHANGED);
+  await engine._tracker.addChangedID("scotsman", SCOTSMAN_CHANGED);
+  await engine._tracker.addChangedID("peppercorn", PEPPERCORN_CHANGED);
+
+  let syncID = await engine.resetLocalSyncID();
+  let meta_global = Service.recordManager.set(
+    engine.metaURL,
+    new WBORecord(engine.metaURL)
+  );
+  meta_global.payload.engines = { rotary: { version: engine.version, syncID } };
+
+  try {
+    await engine.setLastSync(123); // needs to be non-zero so that tracker is queried
+    let changes = await engine._tracker.getChangedIDs();
+    _(
+      `test_upload_failed: Rotary tracker contents at first sync: ${JSON.stringify(
+        changes
+      )}`
+    );
+    engine.enabled = true;
+    let ping = await sync_engine_and_validate_telem(engine, true);
+    ok(!!ping);
+    equal(ping.engines.length, 1);
+    equal(ping.engines[0].incoming, null);
+    deepEqual(ping.engines[0].outgoing, [
+      {
+        sent: 3,
+        failed: 2,
+        failedReasons: [
+          { name: "scotsman", count: 1 },
+          { name: "peppercorn", count: 1 },
+        ],
+      },
+    ]);
+    await engine.setLastSync(123);
+
+    changes = await engine._tracker.getChangedIDs();
+    _(
+      `test_upload_failed: Rotary tracker contents at second sync: ${JSON.stringify(
+        changes
+      )}`
+    );
+    ping = await sync_engine_and_validate_telem(engine, true);
+    ok(!!ping);
+    equal(ping.engines.length, 1);
+    deepEqual(ping.engines[0].outgoing, [
+      {
+        sent: 2,
+        failed: 2,
+        failedReasons: [
+          { name: "scotsman", count: 1 },
+          { name: "peppercorn", count: 1 },
+        ],
+      },
+    ]);
+  } finally {
+    await cleanAndGo(engine, server);
+    await engine.finalize();
+  }
+});
+
+add_task(async function test_sync_partialUpload() {
+  let collection = new ServerCollection();
+  let server = sync_httpd_setup({
+    "/1.1/foo/storage/rotary": collection.handler(),
+  });
+  await SyncTestingInfrastructure(server);
+  await generateNewKeys(Service.collectionKeys);
+
+  let engine = new RotaryEngine(Service);
+  await engine.setLastSync(123);
+
+  // Create a bunch of records (and server side handlers)
+  for (let i = 0; i < 234; i++) {
+    let id = "record-no-" + i;
+    engine._store.items[id] = "Record No. " + i;
+    await engine._tracker.addChangedID(id, i);
+    // Let two items in the first upload batch fail.
+    if (i != 23 && i != 42) {
+      collection.insert(id);
+    }
+  }
+
+  let syncID = await engine.resetLocalSyncID();
+  let meta_global = Service.recordManager.set(
+    engine.metaURL,
+    new WBORecord(engine.metaURL)
+  );
+  meta_global.payload.engines = { rotary: { version: engine.version, syncID } };
+
+  try {
+    let changes = await engine._tracker.getChangedIDs();
+    _(
+      `test_sync_partialUpload: Rotary tracker contents at first sync: ${JSON.stringify(
+        changes
+      )}`
+    );
+    engine.enabled = true;
+    let ping = await sync_engine_and_validate_telem(engine, true);
+
+    ok(!!ping);
+    ok(!ping.failureReason);
+    equal(ping.engines.length, 1);
+    equal(ping.engines[0].name, "rotary");
+    ok(!ping.engines[0].incoming);
+    ok(!ping.engines[0].failureReason);
+    deepEqual(ping.engines[0].outgoing, [
+      {
+        sent: 234,
+        failed: 2,
+        failedReasons: [
+          { name: "record-no-23", count: 1 },
+          { name: "record-no-42", count: 1 },
+        ],
+      },
+    ]);
+    collection.post = function () {
+      throw new Error("Failure");
+    };
+
+    engine._store.items["record-no-1000"] = "Record No. 1000";
+    await engine._tracker.addChangedID("record-no-1000", 1000);
+    collection.insert("record-no-1000", 1000);
+
+    await engine.setLastSync(123);
+    ping = null;
+
+    changes = await engine._tracker.getChangedIDs();
+    _(
+      `test_sync_partialUpload: Rotary tracker contents at second sync: ${JSON.stringify(
+        changes
+      )}`
+    );
+    try {
+      // should throw
+      await sync_engine_and_validate_telem(
+        engine,
+        true,
+        errPing => (ping = errPing)
+      );
+    } catch (e) {}
+    // It would be nice if we had a more descriptive error for this...
+    let uploadFailureError = {
+      name: "httperror",
+      code: 500,
+    };
+
+    ok(!!ping);
+    deepEqual(ping.failureReason, uploadFailureError);
+    equal(ping.engines.length, 1);
+    equal(ping.engines[0].name, "rotary");
+    deepEqual(ping.engines[0].incoming, {
+      failed: 1,
+      failedReasons: [{ name: "No ciphertext: nothing to decrypt?", count: 1 }],
+    });
+    ok(!ping.engines[0].outgoing);
+    deepEqual(ping.engines[0].failureReason, uploadFailureError);
+  } finally {
+    await cleanAndGo(engine, server);
+    await engine.finalize();
+  }
+});
+
+add_task(async function test_generic_engine_fail() {
+  enableValidationPrefs();
+
+  await Service.engineManager.register(SteamEngine);
+  let engine = Service.engineManager.get("steam");
+  engine.enabled = true;
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+  let e = new Error("generic failure message");
+  engine._errToThrow = e;
+
+  try {
+    const changes = await engine._tracker.getChangedIDs();
+    _(
+      `test_generic_engine_fail: Steam tracker contents: ${JSON.stringify(
+        changes
+      )}`
+    );
+    await sync_and_validate_telem(ping => {
+      equal(ping.status.service, SYNC_FAILED_PARTIAL);
+      deepEqual(ping.engines.find(err => err.name === "steam").failureReason, {
+        name: "unexpectederror",
+        error: String(e),
+      });
+    });
+  } finally {
+    await cleanAndGo(engine, server);
+    await Service.engineManager.unregister(engine);
+  }
+});
+
+add_task(async function test_engine_fail_weird_errors() {
+  enableValidationPrefs();
+  await Service.engineManager.register(SteamEngine);
+  let engine = Service.engineManager.get("steam");
+  engine.enabled = true;
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+  try {
+    let msg = "Bad things happened!";
+    engine._errToThrow = { message: msg };
+    await sync_and_validate_telem(ping => {
+      equal(ping.status.service, SYNC_FAILED_PARTIAL);
+      deepEqual(ping.engines.find(err => err.name === "steam").failureReason, {
+        name: "unexpectederror",
+        error: "Bad things happened!",
+      });
+    });
+    let e = { msg };
+    engine._errToThrow = e;
+    await sync_and_validate_telem(ping => {
+      deepEqual(ping.engines.find(err => err.name === "steam").failureReason, {
+        name: "unexpectederror",
+        error: JSON.stringify(e),
+      });
+    });
+  } finally {
+    await cleanAndGo(engine, server);
+    Service.engineManager.unregister(engine);
+  }
+});
+
+add_task(async function test_overrideTelemetryName() {
+  enableValidationPrefs(["steam"]);
+
+  await Service.engineManager.register(SteamEngine);
+  let engine = Service.engineManager.get("steam");
+  engine.overrideTelemetryName = "steam-but-better";
+  engine.enabled = true;
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+
+  const problemsToReport = [
+    { name: "someProblem", count: 123 },
+    { name: "anotherProblem", count: 456 },
+  ];
+
+  try {
+    info("Sync with validation problems");
+    engine.problemsToReport = problemsToReport;
+    await sync_and_validate_telem(ping => {
+      let enginePing = ping.engines.find(e => e.name === "steam-but-better");
+      ok(enginePing);
+      ok(!ping.engines.find(e => e.name === "steam"));
+      delete enginePing.validation.took; // can't compare real times.
+      deepEqual(
+        enginePing.validation,
+        {
+          version: 1,
+          checked: 0,
+          problems: problemsToReport,
+        },
+        "Should include validation report with overridden name"
+      );
+    });
+
+    info("Sync without validation problems");
+    engine.problemsToReport = null;
+    await sync_and_validate_telem(ping => {
+      let enginePing = ping.engines.find(e => e.name === "steam-but-better");
+      ok(enginePing);
+      ok(!ping.engines.find(e => e.name === "steam"));
+      ok(
+        !enginePing.validation,
+        "Should not include validation report when there are no problems"
+      );
+    });
+  } finally {
+    await cleanAndGo(engine, server);
+    await Service.engineManager.unregister(engine);
+  }
+});
+
+add_task(async function test_engine_fail_ioerror() {
+  enableValidationPrefs();
+
+  await Service.engineManager.register(SteamEngine);
+  let engine = Service.engineManager.get("steam");
+  engine.enabled = true;
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+  // create an IOError to re-throw as part of Sync.
+  try {
+    // (Note that fakeservices.js has replaced Utils.jsonMove etc, but for
+    // this test we need the real one so we get real exceptions from the
+    // filesystem.)
+    await Utils._real_jsonMove("file-does-not-exist", "anything", {});
+  } catch (ex) {
+    engine._errToThrow = ex;
+  }
+  ok(engine._errToThrow, "expecting exception");
+
+  try {
+    const changes = await engine._tracker.getChangedIDs();
+    _(
+      `test_engine_fail_ioerror: Steam tracker contents: ${JSON.stringify(
+        changes
+      )}`
+    );
+    await sync_and_validate_telem(ping => {
+      equal(ping.status.service, SYNC_FAILED_PARTIAL);
+      let failureReason = ping.engines.find(
+        e => e.name === "steam"
+      ).failureReason;
+      equal(failureReason.name, "unexpectederror");
+      // ensure the profile dir in the exception message has been stripped.
+      ok(
+        !failureReason.error.includes(PathUtils.profileDir),
+        failureReason.error
+      );
+      ok(failureReason.error.includes("[profileDir]"), failureReason.error);
+    });
+  } finally {
+    await cleanAndGo(engine, server);
+    await Service.engineManager.unregister(engine);
+  }
+});
+
+add_task(async function test_error_detections() {
+  let telem = get_sync_test_telemetry();
+
+  // Non-network NS_ERROR_ codes get their own category.
+  Assert.deepEqual(
+    telem.transformError(Components.Exception("", Cr.NS_ERROR_FAILURE)),
+    { name: "nserror", code: Cr.NS_ERROR_FAILURE }
+  );
+
+  // Some NS_ERROR_ code in the "network" module are treated as http errors.
+  Assert.deepEqual(
+    telem.transformError(Components.Exception("", Cr.NS_ERROR_UNKNOWN_HOST)),
+    { name: "httperror", code: Cr.NS_ERROR_UNKNOWN_HOST }
+  );
+  // Some NS_ERROR_ABORT is treated as network by our telemetry.
+  Assert.deepEqual(
+    telem.transformError(Components.Exception("", Cr.NS_ERROR_ABORT)),
+    { name: "httperror", code: Cr.NS_ERROR_ABORT }
+  );
+});
+
+add_task(async function test_clean_urls() {
+  enableValidationPrefs();
+
+  await Service.engineManager.register(SteamEngine);
+  let engine = Service.engineManager.get("steam");
+  engine.enabled = true;
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+  engine._errToThrow = new TypeError(
+    "http://www.google .com is not a valid URL."
+  );
+
+  try {
+    const changes = await engine._tracker.getChangedIDs();
+    _(`test_clean_urls: Steam tracker contents: ${JSON.stringify(changes)}`);
+    await sync_and_validate_telem(ping => {
+      equal(ping.status.service, SYNC_FAILED_PARTIAL);
+      let failureReason = ping.engines.find(
+        e => e.name === "steam"
+      ).failureReason;
+      equal(failureReason.name, "unexpectederror");
+      equal(failureReason.error, "<URL> is not a valid URL.");
+    });
+    // Handle other errors that include urls.
+    engine._errToThrow =
+      "Other error message that includes some:url/foo/bar/ in it.";
+    await sync_and_validate_telem(ping => {
+      equal(ping.status.service, SYNC_FAILED_PARTIAL);
+      let failureReason = ping.engines.find(
+        e => e.name === "steam"
+      ).failureReason;
+      equal(failureReason.name, "unexpectederror");
+      equal(
+        failureReason.error,
+        "Other error message that includes <URL> in it."
+      );
+    });
+  } finally {
+    await cleanAndGo(engine, server);
+    await Service.engineManager.unregister(engine);
+  }
+});
+
+// Test sanitizing guid-related errors with the pattern of <guid: {guid}>
+add_task(async function test_sanitize_bookmarks_guid() {
+  let { ErrorSanitizer } = ChromeUtils.importESModule(
+    "resource://services-sync/telemetry.sys.mjs"
+  );
+
+  for (let [original, expected] of [
+    [
+      "Can't insert Bookmark <guid: sknD84IdnSY2> into Folder <guid: odfninDdi93_3>",
+      "Can't insert Bookmark <GUID> into Folder <GUID>",
+    ],
+    [
+      "Merge Error: Item <guid: H6fmPA16gZs9> can't contain itself",
+      "Merge Error: Item <GUID> can't contain itself",
+    ],
+  ]) {
+    const sanitized = ErrorSanitizer.cleanErrorMessage(original);
+    Assert.equal(sanitized, expected);
+  }
+});
+
+// Test sanitization of some hard-coded error strings.
+add_task(async function test_clean_errors() {
+  let { ErrorSanitizer } = ChromeUtils.importESModule(
+    "resource://services-sync/telemetry.sys.mjs"
+  );
+
+  for (let [message, name, expected] of [
+    [
+      `Could not open the file at ${PathUtils.join(
+        PathUtils.profileDir,
+        "weave",
+        "addonsreconciler.json"
+      )} for writing`,
+      "NotFoundError",
+      "OS error [File/Path not found] Could not open the file at [profileDir]/weave/addonsreconciler.json for writing",
+    ],
+    [
+      `Could not get info for the file at ${PathUtils.join(
+        PathUtils.profileDir,
+        "weave",
+        "addonsreconciler.json"
+      )}`,
+      "NotAllowedError",
+      "OS error [Permission denied] Could not get info for the file at [profileDir]/weave/addonsreconciler.json",
+    ],
+  ]) {
+    const error = new DOMException(message, name);
+    const sanitized = ErrorSanitizer.cleanErrorMessage(message, error);
+    Assert.equal(sanitized, expected);
+  }
+});
+
+// Arrange for a sync to hit a "real" OS error during a sync and make sure it's sanitized.
+add_task(async function test_clean_real_os_error() {
+  enableValidationPrefs();
+
+  // Simulate a real error.
+  await Service.engineManager.register(SteamEngine);
+  let engine = Service.engineManager.get("steam");
+  engine.enabled = true;
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+  let path = PathUtils.join(PathUtils.profileDir, "no", "such", "path.json");
+  try {
+    await IOUtils.readJSON(path);
+    throw new Error("should fail to read the file");
+  } catch (ex) {
+    engine._errToThrow = ex;
+  }
+
+  try {
+    const changes = await engine._tracker.getChangedIDs();
+    _(`test_clean_urls: Steam tracker contents: ${JSON.stringify(changes)}`);
+    await sync_and_validate_telem(ping => {
+      equal(ping.status.service, SYNC_FAILED_PARTIAL);
+      let failureReason = ping.engines.find(
+        e => e.name === "steam"
+      ).failureReason;
+      equal(failureReason.name, "unexpectederror");
+      equal(
+        failureReason.error,
+        "OS error [File/Path not found] Could not open `[profileDir]/no/such/path.json': file does not exist"
+      );
+    });
+  } finally {
+    await cleanAndGo(engine, server);
+    await Service.engineManager.unregister(engine);
+  }
+});
+
+add_task(async function test_initial_sync_engines() {
+  enableValidationPrefs();
+
+  await Service.engineManager.register(SteamEngine);
+  let engine = Service.engineManager.get("steam");
+  engine.enabled = true;
+  // These are the only ones who actually have things to sync at startup.
+  let telemetryEngineNames = ["clients", "prefs", "tabs", "bookmarks-buffered"];
+  let server = await serverForEnginesWithKeys(
+    { foo: "password" },
+    ["bookmarks", "prefs", "tabs"].map(name => Service.engineManager.get(name))
+  );
+  await SyncTestingInfrastructure(server);
+  try {
+    const changes = await engine._tracker.getChangedIDs();
+    _(
+      `test_initial_sync_engines: Steam tracker contents: ${JSON.stringify(
+        changes
+      )}`
+    );
+    let ping = await wait_for_ping(() => Service.sync(), true);
+
+    equal(ping.engines.find(e => e.name === "clients").outgoing[0].sent, 1);
+    equal(ping.engines.find(e => e.name === "tabs").outgoing[0].sent, 1);
+
+    // for the rest we don't care about specifics
+    for (let e of ping.engines) {
+      if (!telemetryEngineNames.includes(e.name)) {
+        continue;
+      }
+      greaterOrEqual(e.took, 0);
+      ok(!!e.outgoing);
+      equal(e.outgoing.length, 1);
+      notEqual(e.outgoing[0].sent, undefined);
+      equal(e.outgoing[0].failed, undefined);
+      equal(e.outgoing[0].failedReasons, undefined);
+    }
+  } finally {
+    await cleanAndGo(engine, server);
+    await Service.engineManager.unregister(engine);
+  }
+});
+
+add_task(async function test_nserror() {
+  enableValidationPrefs();
+
+  await Service.engineManager.register(SteamEngine);
+  let engine = Service.engineManager.get("steam");
+  engine.enabled = true;
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+  engine._errToThrow = Components.Exception(
+    "NS_ERROR_UNKNOWN_HOST",
+    Cr.NS_ERROR_UNKNOWN_HOST
+  );
+  try {
+    const changes = await engine._tracker.getChangedIDs();
+    _(`test_nserror: Steam tracker contents: ${JSON.stringify(changes)}`);
+    await sync_and_validate_telem(ping => {
+      deepEqual(ping.status, {
+        service: SYNC_FAILED_PARTIAL,
+        sync: LOGIN_FAILED_NETWORK_ERROR,
+      });
+      let enginePing = ping.engines.find(e => e.name === "steam");
+      deepEqual(enginePing.failureReason, {
+        name: "httperror",
+        code: Cr.NS_ERROR_UNKNOWN_HOST,
+      });
+    });
+  } finally {
+    await cleanAndGo(engine, server);
+    await Service.engineManager.unregister(engine);
+  }
+});
+
+add_task(async function test_sync_why() {
+  enableValidationPrefs();
+
+  await Service.engineManager.register(SteamEngine);
+  let engine = Service.engineManager.get("steam");
+  engine.enabled = true;
+  let server = await serverForFoo(engine);
+  await SyncTestingInfrastructure(server);
+  let e = new Error("generic failure message");
+  engine._errToThrow = e;
+
+  try {
+    const changes = await engine._tracker.getChangedIDs();
+    _(
+      `test_generic_engine_fail: Steam tracker contents: ${JSON.stringify(
+        changes
+      )}`
+    );
+    let ping = await wait_for_ping(
+      () => Service.sync({ why: "user" }),
+      true,
+      false
+    );
+    _(JSON.stringify(ping));
+    equal(ping.why, "user");
+  } finally {
+    await cleanAndGo(engine, server);
+    await Service.engineManager.unregister(engine);
+  }
+});
+
+add_task(async function test_discarding() {
+  enableValidationPrefs();
+
+  let helper = track_collections_helper();
+  let upd = helper.with_updated_collection;
+  let telem = get_sync_test_telemetry();
+  telem.maxPayloadCount = 2;
+  telem.submissionInterval = Infinity;
+  let oldSubmit = telem.submit;
+
+  let server;
+  try {
+    let handlers = {
+      "/1.1/johndoe/info/collections": helper.handler,
+      "/1.1/johndoe/storage/crypto/keys": upd(
+        "crypto",
+        new ServerWBO("keys").handler()
+      ),
+      "/1.1/johndoe/storage/meta/global": upd(
+        "meta",
+        new ServerWBO("global").handler()
+      ),
+    };
+
+    let collections = [
+      "clients",
+      "bookmarks",
+      "forms",
+      "history",
+      "passwords",
+      "prefs",
+      "tabs",
+    ];
+
+    for (let coll of collections) {
+      handlers["/1.1/johndoe/storage/" + coll] = upd(
+        coll,
+        new ServerCollection({}, true).handler()
+      );
+    }
+
+    server = httpd_setup(handlers);
+    await configureIdentity({ username: "johndoe" }, server);
+    telem.submit = p =>
+      ok(
+        false,
+        "Submitted telemetry ping when we should not have" + JSON.stringify(p)
+      );
+
+    for (let i = 0; i < 5; ++i) {
+      await Service.sync();
+    }
+    telem.submit = oldSubmit;
+    telem.submissionInterval = -1;
+    let ping = await wait_for_ping(() => Service.sync(), true, true); // with this we've synced 6 times
+    equal(ping.syncs.length, 2);
+    equal(ping.discarded, 4);
+  } finally {
+    telem.maxPayloadCount = 500;
+    telem.submissionInterval = -1;
+    telem.submit = oldSubmit;
+    if (server) {
+      await promiseStopServer(server);
+    }
+  }
+});
+
+add_task(async function test_no_foreign_engines_in_error_ping() {
+  enableValidationPrefs();
+
+  await Service.engineManager.register(BogusEngine);
+  let engine = Service.engineManager.get("bogus");
+  engine.enabled = true;
+  let server = await serverForFoo(engine);
+  engine._errToThrow = new Error("Oh no!");
+  await SyncTestingInfrastructure(server);
+  try {
+    await sync_and_validate_telem(ping => {
+      equal(ping.status.service, SYNC_FAILED_PARTIAL);
+      ok(ping.engines.every(e => e.name !== "bogus"));
+    });
+  } finally {
+    await cleanAndGo(engine, server);
+    await Service.engineManager.unregister(engine);
+  }
+});
+
+add_task(async function test_no_foreign_engines_in_success_ping() {
+  enableValidationPrefs();
+
+  await Service.engineManager.register(BogusEngine);
+  let engine = Service.engineManager.get("bogus");
+  engine.enabled = true;
+  let server = await serverForFoo(engine);
+
+  await SyncTestingInfrastructure(server);
+  try {
+    await sync_and_validate_telem(ping => {
+      ok(ping.engines.every(e => e.name !== "bogus"));
+    });
+  } finally {
+    await cleanAndGo(engine, server);
+    await Service.engineManager.unregister(engine);
+  }
+});
+
+add_task(async function test_no_ping_for_self_hosters() {
+  enableValidationPrefs();
+
+  let telem = get_sync_test_telemetry();
+  let oldSubmit = telem.submit;
+
+  await Service.engineManager.register(BogusEngine);
+  let engine = Service.engineManager.get("bogus");
+  engine.enabled = true;
+  let server = await serverForFoo(engine);
+
+  await SyncTestingInfrastructure(server);
+  try {
+    let submitPromise = new Promise(resolve => {
+      telem.submit = function () {
+        let result = oldSubmit.apply(this, arguments);
+        resolve(result);
+      };
+    });
+    await Service.sync();
+    let pingSubmitted = await submitPromise;
+    // The Sync testing infrastructure already sets up a custom token server,
+    // so we don't need to do anything to simulate a self-hosted user.
+    ok(!pingSubmitted, "Should not submit ping with custom token server URL");
+  } finally {
+    telem.submit = oldSubmit;
+    await cleanAndGo(engine, server);
+    await Service.engineManager.unregister(engine);
+  }
+});
+
+add_task(async function test_fxa_device_telem() {
+  let t = get_sync_test_telemetry();
+  let syncEnabled = true;
+  let oldGetClientsEngineRecords = t.getClientsEngineRecords;
+  let oldGetFxaDevices = t.getFxaDevices;
+  let oldSyncIsEnabled = t.syncIsEnabled;
+  let oldSanitizeFxaDeviceId = t.sanitizeFxaDeviceId;
+  t.syncIsEnabled = () => syncEnabled;
+  t.sanitizeFxaDeviceId = id => `So clean: ${id}`;
+  try {
+    let keep0 = Utils.makeGUID();
+    let keep1 = Utils.makeGUID();
+    let keep2 = Utils.makeGUID();
+    let curdev = Utils.makeGUID();
+
+    let keep1Sync = Utils.makeGUID();
+    let keep2Sync = Utils.makeGUID();
+    let curdevSync = Utils.makeGUID();
+    let fxaDevices = [
+      {
+        id: curdev,
+        isCurrentDevice: true,
+        lastAccessTime: Date.now() - 1000 * 60 * 60 * 24 * 1,
+        pushEndpointExpired: false,
+        type: "desktop",
+        name: "current device",
+      },
+      {
+        id: keep0,
+        isCurrentDevice: false,
+        lastAccessTime: Date.now() - 1000 * 60 * 60 * 24 * 10,
+        pushEndpointExpired: false,
+        type: "mobile",
+        name: "dupe",
+      },
+      // Valid 2
+      {
+        id: keep1,
+        isCurrentDevice: false,
+        lastAccessTime: Date.now() - 1000 * 60 * 60 * 24 * 1,
+        pushEndpointExpired: false,
+        type: "desktop",
+        name: "valid2",
+      },
+      // Valid 3
+      {
+        id: keep2,
+        isCurrentDevice: false,
+        lastAccessTime: Date.now() - 1000 * 60 * 60 * 24 * 5,
+        pushEndpointExpired: false,
+        type: "desktop",
+        name: "valid3",
+      },
+    ];
+    let clientInfo = [
+      {
+        id: keep1Sync,
+        fxaDeviceId: keep1,
+        os: "Windows 30",
+        version: "Firefox 1 million",
+      },
+      {
+        id: keep2Sync,
+        fxaDeviceId: keep2,
+        os: "firefox, but an os",
+        verison: "twelve",
+      },
+      {
+        id: Utils.makeGUID(),
+        fxaDeviceId: null,
+        os: "apparently ios used to keep write these IDs as null.",
+        version: "Doesn't seem to anymore",
+      },
+      {
+        id: curdevSync,
+        fxaDeviceId: curdev,
+        os: "emacs",
+        version: "22",
+      },
+      {
+        id: Utils.makeGUID(),
+        fxaDeviceId: Utils.makeGUID(),
+        os: "not part of the fxa device set at all",
+        version: "foo bar baz",
+      },
+      // keep0 intententionally omitted.
+    ];
+    t.getClientsEngineRecords = () => clientInfo;
+    let devInfo = t.updateFxaDevices(fxaDevices);
+    equal(devInfo.deviceID, t.sanitizeFxaDeviceId(curdev));
+    for (let d of devInfo.devices) {
+      ok(d.id.startsWith("So clean:"));
+      if (d.syncID) {
+        ok(d.syncID.startsWith("So clean:"));
+      }
+    }
+    equal(devInfo.devices.length, 4);
+    let k0 = devInfo.devices.find(d => d.id == t.sanitizeFxaDeviceId(keep0));
+    let k1 = devInfo.devices.find(d => d.id == t.sanitizeFxaDeviceId(keep1));
+    let k2 = devInfo.devices.find(d => d.id == t.sanitizeFxaDeviceId(keep2));
+
+    deepEqual(k0, {
+      id: t.sanitizeFxaDeviceId(keep0),
+      type: "mobile",
+      os: undefined,
+      version: undefined,
+      syncID: undefined,
+    });
+    deepEqual(k1, {
+      id: t.sanitizeFxaDeviceId(keep1),
+      type: "desktop",
+      os: clientInfo[0].os,
+      version: clientInfo[0].version,
+      syncID: t.sanitizeFxaDeviceId(keep1Sync),
+    });
+    deepEqual(k2, {
+      id: t.sanitizeFxaDeviceId(keep2),
+      type: "desktop",
+      os: clientInfo[1].os,
+      version: clientInfo[1].version,
+      syncID: t.sanitizeFxaDeviceId(keep2Sync),
+    });
+    let newCurId = Utils.makeGUID();
+    // Update the ID
+    fxaDevices[0].id = newCurId;
+
+    let keep3 = Utils.makeGUID();
+    fxaDevices.push({
+      id: keep3,
+      isCurrentDevice: false,
+      lastAccessTime: Date.now() - 1000 * 60 * 60 * 24 * 1,
+      pushEndpointExpired: false,
+      type: "desktop",
+      name: "valid 4",
+    });
+    devInfo = t.updateFxaDevices(fxaDevices);
+
+    let afterSubmit = [keep0, keep1, keep2, keep3, newCurId]
+      .map(id => t.sanitizeFxaDeviceId(id))
+      .sort();
+    deepEqual(devInfo.devices.map(d => d.id).sort(), afterSubmit);
+
+    // Reset this, as our override doesn't check for sync being enabled.
+    t.sanitizeFxaDeviceId = oldSanitizeFxaDeviceId;
+    syncEnabled = false;
+    fxAccounts.telemetry._setHashedUID(false);
+    devInfo = t.updateFxaDevices(fxaDevices);
+    equal(devInfo.deviceID, undefined);
+    equal(devInfo.devices.length, 5);
+    for (let d of devInfo.devices) {
+      equal(d.os, undefined);
+      equal(d.version, undefined);
+      equal(d.syncID, undefined);
+      // Type should still be present.
+      notEqual(d.type, undefined);
+    }
+  } finally {
+    t.getClientsEngineRecords = oldGetClientsEngineRecords;
+    t.getFxaDevices = oldGetFxaDevices;
+    t.syncIsEnabled = oldSyncIsEnabled;
+    t.sanitizeFxaDeviceId = oldSanitizeFxaDeviceId;
+  }
+});
+
+add_task(async function test_sanitize_fxa_device_id() {
+  let t = get_sync_test_telemetry();
+  fxAccounts.telemetry._setHashedUID(false);
+  sinon.stub(t, "syncIsEnabled").callsFake(() => true);
+  const rawDeviceId = "raw one two three";
+  try {
+    equal(t.sanitizeFxaDeviceId(rawDeviceId), null);
+    fxAccounts.telemetry._setHashedUID("mock uid");
+    const sanitizedDeviceId = t.sanitizeFxaDeviceId(rawDeviceId);
+    ok(sanitizedDeviceId);
+    notEqual(sanitizedDeviceId, rawDeviceId);
+  } finally {
+    t.syncIsEnabled.restore();
+    fxAccounts.telemetry._setHashedUID(false);
+  }
+});
+
+add_task(async function test_no_node_type() {
+  let server = sync_httpd_setup({});
+  await configureIdentity(null, server);
+
+  await sync_and_validate_telem(ping => {
+    Assert.strictEqual(ping.syncNodeType, undefined);
+  }, true);
+  await promiseStopServer(server);
+});
+
+add_task(async function test_node_type() {
+  Service.identity.logout();
+  let server = sync_httpd_setup({});
+  await configureIdentity({ node_type: "the-node-type" }, server);
+
+  await sync_and_validate_telem(ping => {
+    equal(ping.syncNodeType, "the-node-type");
+  }, true);
+  await promiseStopServer(server);
+});
+
+add_task(async function test_node_type_change() {
+  let pingPromise = wait_for_pings(2);
+
+  Service.identity.logout();
+  let server = sync_httpd_setup({});
+  await configureIdentity({ node_type: "first-node-type" }, server);
+  // Default to submitting each hour - we should still submit on node change.
+  let telem = get_sync_test_telemetry();
+  telem.submissionInterval = 60 * 60 * 1000;
+  // reset the node type from previous test or our first sync will submit.
+  telem.lastSyncNodeType = null;
+  // do 2 syncs with the same node type.
+  await Service.sync();
+  await Service.sync();
+  // then another with a different node type.
+  Service.identity.logout();
+  await configureIdentity({ node_type: "second-node-type" }, server);
+  await Service.sync();
+  telem.finish();
+
+  let pings = await pingPromise;
+  equal(pings.length, 2);
+  equal(pings[0].syncs.length, 2, "2 syncs in first ping");
+  equal(pings[0].syncNodeType, "first-node-type");
+  equal(pings[1].syncs.length, 1, "1 sync in second ping");
+  equal(pings[1].syncNodeType, "second-node-type");
+  await promiseStopServer(server);
+});
+
+add_task(async function test_ids() {
+  let telem = get_sync_test_telemetry();
+  Assert.ok(!telem._shouldSubmitForDataChange());
+  fxAccounts.telemetry._setHashedUID("new_uid");
+  Assert.ok(telem._shouldSubmitForDataChange());
+  telem.maybeSubmitForDataChange();
+  // now it's been submitted the new uid is current.
+  Assert.ok(!telem._shouldSubmitForDataChange());
+});
+
+add_task(async function test_deletion_request_ping() {
+  async function assertRecordedSyncDeviceID(expected) {
+    // The scalar gets updated asynchronously, so wait a tick before checking.
+    await Promise.resolve();
+    const scalars =
+      Services.telemetry.getSnapshotForScalars("deletion-request").parent || {};
+    equal(scalars["deletion.request.sync_device_id"], expected);
+  }
+
+  const MOCK_HASHED_UID = "00112233445566778899aabbccddeeff";
+  const MOCK_DEVICE_ID1 = "ffeeddccbbaa99887766554433221100";
+  const MOCK_DEVICE_ID2 = "aabbccddeeff99887766554433221100";
+
+  // Calculated by hand using SHA256(DEVICE_ID + HASHED_UID)[:32]
+  const SANITIZED_DEVICE_ID1 = "dd7c845006df9baa1c6d756926519c8c";
+  const SANITIZED_DEVICE_ID2 = "0d06919a736fc029007e1786a091882c";
+
+  let currentDeviceID = null;
+  sinon.stub(fxAccounts.device, "getLocalId").callsFake(() => {
+    return Promise.resolve(currentDeviceID);
+  });
+  let telem = get_sync_test_telemetry();
+  sinon.stub(telem, "isProductionSyncUser").callsFake(() => true);
+  fxAccounts.telemetry._setHashedUID(false);
+  try {
+    // The scalar should start out undefined, since no user is actually logged in.
+    await assertRecordedSyncDeviceID(undefined);
+
+    // If we start up without knowing the hashed UID, it should stay undefined.
+    telem.observe(null, "weave:service:ready");
+    await assertRecordedSyncDeviceID(undefined);
+
+    // But now let's say we've discovered the hashed UID from the server.
+    fxAccounts.telemetry._setHashedUID(MOCK_HASHED_UID);
+    currentDeviceID = MOCK_DEVICE_ID1;
+
+    // Now when we load up, we'll record the sync device id.
+    telem.observe(null, "weave:service:ready");
+    await assertRecordedSyncDeviceID(SANITIZED_DEVICE_ID1);
+
+    // When the device-id changes we'll update it.
+    currentDeviceID = MOCK_DEVICE_ID2;
+    telem.observe(null, "fxaccounts:new_device_id");
+    await assertRecordedSyncDeviceID(SANITIZED_DEVICE_ID2);
+
+    // When the user signs out we'll clear it.
+    telem.observe(null, "fxaccounts:onlogout");
+    await assertRecordedSyncDeviceID("");
+  } finally {
+    fxAccounts.telemetry._setHashedUID(false);
+    telem.isProductionSyncUser.restore();
+    fxAccounts.device.getLocalId.restore();
+  }
+});
diff --git a/src/zen/tests/mochitests/sync/test_tracker_addChanged.js b/src/zen/tests/mochitests/sync/test_tracker_addChanged.js
new file mode 100644
index 000000000..3fe74c3fb
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_tracker_addChanged.js
@@ -0,0 +1,59 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+add_task(async function test_tracker_basics() {
+  let tracker = new LegacyTracker("Tracker", Service);
+
+  let id = "the_id!";
+
+  _("Make sure nothing exists yet..");
+  let changes = await tracker.getChangedIDs();
+  Assert.equal(changes[id], null);
+
+  _("Make sure adding of time 0 works");
+  await tracker.addChangedID(id, 0);
+  changes = await tracker.getChangedIDs();
+  Assert.equal(changes[id], 0);
+
+  _("A newer time will replace the old 0");
+  await tracker.addChangedID(id, 10);
+  changes = await tracker.getChangedIDs();
+  Assert.equal(changes[id], 10);
+
+  _("An older time will not replace the newer 10");
+  await tracker.addChangedID(id, 5);
+  changes = await tracker.getChangedIDs();
+  Assert.equal(changes[id], 10);
+
+  _("Adding without time defaults to current time");
+  await tracker.addChangedID(id);
+  changes = await tracker.getChangedIDs();
+  Assert.greater(changes[id], 10);
+});
+
+add_task(async function test_tracker_persistence() {
+  let tracker = new LegacyTracker("Tracker", Service);
+  let id = "abcdef";
+
+  let promiseSave = new Promise((resolve, reject) => {
+    let save = tracker._storage._save;
+    tracker._storage._save = function () {
+      save.call(tracker._storage).then(resolve, reject);
+    };
+  });
+
+  await tracker.addChangedID(id, 5);
+
+  await promiseSave;
+
+  _("IDs saved.");
+  const changes = await tracker.getChangedIDs();
+  Assert.equal(5, changes[id]);
+
+  let json = await Utils.jsonLoad(["changes", "tracker"], tracker);
+  Assert.equal(5, json[id]);
+});
diff --git a/src/zen/tests/mochitests/sync/test_uistate.js b/src/zen/tests/mochitests/sync/test_uistate.js
new file mode 100644
index 000000000..3b0bb384a
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_uistate.js
@@ -0,0 +1,411 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { UIState } = ChromeUtils.importESModule(
+  "resource://services-sync/UIState.sys.mjs"
+);
+
+const UIStateInternal = UIState._internal;
+
+add_task(async function test_isReady_unconfigured() {
+  UIState.reset();
+
+  let refreshState = sinon.spy(UIStateInternal, "refreshState");
+
+  // On the first call, returns false
+  // Does trigger a refresh of the state - even though services.sync.username
+  // is undefined we still need to check the account state.
+  ok(!UIState.isReady());
+  // resfreshState is called when idle - so only check after idle.
+  await new Promise(resolve => {
+    Services.tm.idleDispatchToMainThread(resolve);
+  });
+  ok(refreshState.called);
+  refreshState.resetHistory();
+
+  // On subsequent calls, only return true
+  ok(UIState.isReady());
+  ok(!refreshState.called);
+
+  refreshState.restore();
+});
+
+add_task(async function test_isReady_signedin() {
+  UIState.reset();
+  Services.prefs.setStringPref("services.sync.username", "foo");
+
+  let refreshState = sinon.spy(UIStateInternal, "refreshState");
+
+  // On the first call, returns false and triggers a refresh of the state
+  ok(!UIState.isReady());
+  await new Promise(resolve => {
+    Services.tm.idleDispatchToMainThread(resolve);
+  });
+  ok(refreshState.calledOnce);
+  refreshState.resetHistory();
+
+  // On subsequent calls, only return true
+  ok(UIState.isReady());
+  ok(!refreshState.called);
+
+  refreshState.restore();
+});
+
+add_task(async function test_refreshState_signedin() {
+  UIState.reset();
+  const fxAccountsOrig = UIStateInternal.fxAccounts;
+
+  const now = new Date().toString();
+  Services.prefs.setStringPref("services.sync.lastSync", now);
+  Services.prefs.setStringPref("services.sync.username", "foo@bar.com");
+  UIStateInternal.syncing = false;
+
+  UIStateInternal.fxAccounts = {
+    getSignedInUser: () =>
+      Promise.resolve({
+        verified: true,
+        uid: "123",
+        email: "foo@bar.com",
+        displayName: "Foo Bar",
+        avatar: "https://foo/bar",
+      }),
+    hasLocalSession: () => Promise.resolve(true),
+    keys: {
+      canGetKeyForScope: () => Promise.resolve(true),
+      hasKeysForScope: () => Promise.resolve(true),
+    },
+  };
+
+  let state = await UIState.refresh();
+
+  equal(state.status, UIState.STATUS_SIGNED_IN);
+  equal(state.uid, "123");
+  equal(state.email, "foo@bar.com");
+  equal(state.displayName, "Foo Bar");
+  equal(state.avatarURL, "https://foo/bar");
+  equal(state.lastSync, now);
+  equal(state.syncing, false);
+  equal(state.hasSyncKeys, true);
+
+  UIStateInternal.fxAccounts = fxAccountsOrig;
+  Services.prefs.clearUserPref("services.sync.username");
+});
+
+add_task(async function test_refreshState_syncButNoFxA() {
+  UIState.reset();
+  const fxAccountsOrig = UIStateInternal.fxAccounts;
+
+  const now = new Date().toString();
+  Services.prefs.setStringPref("services.sync.lastSync", now);
+  Services.prefs.setStringPref("services.sync.username", "test@test.com");
+  UIStateInternal.syncing = false;
+
+  UIStateInternal.fxAccounts = {
+    getSignedInUser: () => Promise.resolve(null),
+  };
+
+  let state = await UIState.refresh();
+
+  equal(state.status, UIState.STATUS_LOGIN_FAILED);
+  equal(state.uid, undefined);
+  equal(state.email, "test@test.com");
+  equal(state.displayName, undefined);
+  equal(state.avatarURL, undefined);
+  equal(state.lastSync, undefined); // only set when STATUS_SIGNED_IN.
+  equal(state.syncing, false);
+
+  UIStateInternal.fxAccounts = fxAccountsOrig;
+  Services.prefs.clearUserPref("services.sync.lastSync");
+  Services.prefs.clearUserPref("services.sync.username");
+});
+
+add_task(async function test_refreshState_signedin_profile_unavailable() {
+  UIState.reset();
+  const fxAccountsOrig = UIStateInternal.fxAccounts;
+
+  const now = new Date().toString();
+  Services.prefs.setStringPref("services.sync.lastSync", now);
+  Services.prefs.setStringPref("services.sync.username", "test@test.com");
+  UIStateInternal.syncing = false;
+
+  UIStateInternal.fxAccounts = {
+    getSignedInUser: () =>
+      Promise.resolve({ verified: true, uid: "123", email: "foo@bar.com" }),
+    hasLocalSession: () => Promise.resolve(true),
+    keys: {
+      canGetKeyForScope: () => Promise.resolve(true),
+      hasKeysForScope: () => Promise.resolve(true),
+    },
+    _internal: {
+      profile: {
+        getProfile: () => {
+          return Promise.reject(new Error("Profile unavailable"));
+        },
+      },
+    },
+  };
+
+  let state = await UIState.refresh();
+
+  equal(state.status, UIState.STATUS_SIGNED_IN);
+  equal(state.uid, "123");
+  equal(state.email, "foo@bar.com");
+  equal(state.displayName, undefined);
+  equal(state.avatarURL, undefined);
+  equal(state.lastSync, now);
+  equal(state.syncing, false);
+
+  UIStateInternal.fxAccounts = fxAccountsOrig;
+  Services.prefs.clearUserPref("services.sync.lastSync");
+  Services.prefs.clearUserPref("services.sync.username");
+});
+
+add_task(async function test_refreshState_unverified() {
+  UIState.reset();
+  const fxAccountsOrig = UIStateInternal.fxAccounts;
+
+  UIStateInternal.fxAccounts = {
+    getSignedInUser: () =>
+      Promise.resolve({ verified: false, uid: "123", email: "foo@bar.com" }),
+    hasLocalSession: () => Promise.resolve(true),
+    keys: {
+      hasKeysForScope: () => Promise.resolve(true),
+    },
+  };
+
+  let state = await UIState.refresh();
+
+  equal(state.status, UIState.STATUS_NOT_VERIFIED);
+  equal(state.uid, "123");
+  equal(state.email, "foo@bar.com");
+  equal(state.displayName, undefined);
+  equal(state.avatarURL, undefined);
+  equal(state.lastSync, undefined);
+
+  UIStateInternal.fxAccounts = fxAccountsOrig;
+});
+
+add_task(async function test_refreshState_unverified_nosession() {
+  UIState.reset();
+  const fxAccountsOrig = UIStateInternal.fxAccounts;
+
+  UIStateInternal.fxAccounts = {
+    getSignedInUser: () =>
+      Promise.resolve({ verified: false, uid: "123", email: "foo@bar.com" }),
+    hasLocalSession: () => Promise.resolve(false),
+    keys: {
+      hasKeysForScope: () => Promise.resolve(true),
+    },
+  };
+
+  let state = await UIState.refresh();
+
+  // No session should "win" over the unverified state.
+  equal(state.status, UIState.STATUS_LOGIN_FAILED);
+  equal(state.uid, "123");
+  equal(state.email, "foo@bar.com");
+  equal(state.displayName, undefined);
+  equal(state.avatarURL, undefined);
+  equal(state.lastSync, undefined);
+
+  UIStateInternal.fxAccounts = fxAccountsOrig;
+});
+
+add_task(async function test_refreshState_loginFailed() {
+  UIState.reset();
+  const fxAccountsOrig = UIStateInternal.fxAccounts;
+
+  let loginFailed = sinon.stub(UIStateInternal, "_loginFailed");
+  loginFailed.returns(true);
+
+  UIStateInternal.fxAccounts = {
+    getSignedInUser: () =>
+      Promise.resolve({ verified: true, uid: "123", email: "foo@bar.com" }),
+    keys: {
+      canGetKeyForScope: () => Promise.resolve(true),
+      hasKeysForScope: () => Promise.resolve(true),
+    },
+  };
+
+  let state = await UIState.refresh();
+
+  equal(state.status, UIState.STATUS_LOGIN_FAILED);
+  equal(state.uid, "123");
+  equal(state.email, "foo@bar.com");
+  equal(state.displayName, undefined);
+  equal(state.avatarURL, undefined);
+  equal(state.lastSync, undefined);
+
+  loginFailed.restore();
+  UIStateInternal.fxAccounts = fxAccountsOrig;
+});
+
+add_task(async function test_observer_refreshState() {
+  let refreshState = sinon.spy(UIStateInternal, "refreshState");
+
+  let shouldRefresh = [
+    "weave:service:login:got-hashed-id",
+    "weave:service:login:error",
+    "weave:service:ready",
+    "fxaccounts:onverified",
+    "fxaccounts:onlogin",
+    "fxaccounts:onlogout",
+    "fxaccounts:profilechange",
+  ];
+
+  for (let topic of shouldRefresh) {
+    let uiUpdateObserved = observeUIUpdate();
+    Services.obs.notifyObservers(null, topic);
+    await uiUpdateObserved;
+    ok(refreshState.calledOnce);
+    refreshState.resetHistory();
+  }
+
+  refreshState.restore();
+});
+
+// Drive the UIState in a configured state.
+async function configureUIState(syncing, lastSync = new Date()) {
+  UIState.reset();
+  const fxAccountsOrig = UIStateInternal.fxAccounts;
+
+  UIStateInternal._syncing = syncing;
+  Services.prefs.setStringPref("services.sync.lastSync", lastSync.toString());
+  Services.prefs.setStringPref("services.sync.username", "test@test.com");
+
+  UIStateInternal.fxAccounts = {
+    getSignedInUser: () =>
+      Promise.resolve({ verified: true, uid: "123", email: "foo@bar.com" }),
+    hasLocalSession: () => Promise.resolve(true),
+    keys: {
+      canGetKeyForScope: () => Promise.resolve(true),
+      hasKeysForScope: () => Promise.resolve(true),
+    },
+  };
+  await UIState.refresh();
+  UIStateInternal.fxAccounts = fxAccountsOrig;
+}
+
+add_task(async function test_syncStarted() {
+  await configureUIState(false);
+
+  const oldState = Object.assign({}, UIState.get());
+  ok(!oldState.syncing);
+
+  let uiUpdateObserved = observeUIUpdate();
+  Services.obs.notifyObservers(null, "weave:service:sync:start");
+  await uiUpdateObserved;
+
+  const newState = Object.assign({}, UIState.get());
+  ok(newState.syncing);
+});
+
+add_task(async function test_syncFinished() {
+  let yesterday = new Date();
+  yesterday.setDate(yesterday.getDate() - 1);
+  await configureUIState(true, yesterday);
+
+  const oldState = Object.assign({}, UIState.get());
+  ok(oldState.syncing);
+
+  let uiUpdateObserved = observeUIUpdate();
+  Services.prefs.setStringPref("services.sync.lastSync", new Date().toString());
+  Services.obs.notifyObservers(null, "weave:service:sync:finish");
+  await uiUpdateObserved;
+
+  const newState = Object.assign({}, UIState.get());
+  ok(!newState.syncing);
+  Assert.greater(new Date(newState.lastSync), new Date(oldState.lastSync));
+});
+
+add_task(async function test_syncError() {
+  let yesterday = new Date();
+  yesterday.setDate(yesterday.getDate() - 1);
+  await configureUIState(true, yesterday);
+
+  const oldState = Object.assign({}, UIState.get());
+  ok(oldState.syncing);
+
+  let uiUpdateObserved = observeUIUpdate();
+  Services.obs.notifyObservers(null, "weave:service:sync:error");
+  await uiUpdateObserved;
+
+  const newState = Object.assign({}, UIState.get());
+  ok(!newState.syncing);
+  deepEqual(newState.lastSync, oldState.lastSync);
+});
+
+add_task(async function test_refreshState_signedin_with_synckeys() {
+  UIState.reset();
+  const fxAccountsOrig = UIStateInternal.fxAccounts;
+
+  Services.prefs.setStringPref("services.sync.username", "test@test.com");
+
+  UIStateInternal.fxAccounts = {
+    getSignedInUser: () =>
+      Promise.resolve({
+        verified: true,
+        uid: "123",
+        email: "foo@bar.com",
+        displayName: "Foo Bar",
+      }),
+    hasLocalSession: () => Promise.resolve(true),
+    keys: {
+      canGetKeyForScope: () => Promise.resolve(true),
+      hasKeysForScope: () => Promise.resolve(true),
+    },
+  };
+
+  let state = await UIState.refresh();
+
+  equal(state.status, UIState.STATUS_SIGNED_IN);
+  equal(state.syncEnabled, true);
+  equal(state.uid, "123");
+  equal(state.email, "foo@bar.com");
+
+  UIStateInternal.fxAccounts = fxAccountsOrig;
+  Services.prefs.clearUserPref("services.sync.username");
+});
+
+// Testing third-party auth does not enable sync (should be impossible without keys)
+add_task(async function test_refreshState_third_party_auth_no_sync() {
+  UIState.reset();
+  const fxAccountsOrig = UIStateInternal.fxAccounts;
+
+  // Mock signing in but NO keys (third-party auth)
+  UIStateInternal.fxAccounts = {
+    getSignedInUser: () =>
+      Promise.resolve({
+        verified: true,
+        uid: "123",
+        email: "foo@bar.com",
+      }),
+    hasLocalSession: () => Promise.resolve(true),
+    keys: {
+      hasKeysForScope: () => Promise.resolve(false),
+    },
+  };
+
+  let state = await UIState.refresh();
+
+  equal(state.status, UIState.STATUS_SIGNED_IN);
+  equal(state.syncEnabled, false);
+  equal(state.hasSyncKeys, false);
+  equal(state.uid, "123");
+  equal(state.email, "foo@bar.com");
+
+  UIStateInternal.fxAccounts = fxAccountsOrig;
+});
+
+function observeUIUpdate() {
+  return new Promise(resolve => {
+    let obs = (aSubject, aTopic) => {
+      Services.obs.removeObserver(obs, aTopic);
+      const state = UIState.get();
+      resolve(state);
+    };
+    Services.obs.addObserver(obs, UIState.ON_UPDATE);
+  });
+}
diff --git a/src/zen/tests/mochitests/sync/test_utils_catch.js b/src/zen/tests/mochitests/sync/test_utils_catch.js
new file mode 100644
index 000000000..590d04527
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_utils_catch.js
@@ -0,0 +1,119 @@
+const { Service } = ChromeUtils.importESModule(
+  "resource://services-sync/service.sys.mjs"
+);
+
+add_task(async function run_test() {
+  _("Make sure catch when copied to an object will correctly catch stuff");
+  let ret, rightThis, didCall, didThrow, wasCovfefe, wasLocked;
+  let obj = {
+    _catch: Utils.catch,
+    _log: {
+      debug(str) {
+        didThrow = str.search(/^Exception/) == 0;
+      },
+      info(str) {
+        wasLocked = str.indexOf("Cannot start sync: already syncing?") == 0;
+      },
+    },
+
+    func() {
+      return this._catch(async function () {
+        rightThis = this == obj;
+        didCall = true;
+        return 5;
+      })();
+    },
+
+    throwy() {
+      return this._catch(async function () {
+        rightThis = this == obj;
+        didCall = true;
+        throw new Error("covfefe");
+      })();
+    },
+
+    callbacky() {
+      return this._catch(
+        async function () {
+          rightThis = this == obj;
+          didCall = true;
+          throw new Error("covfefe");
+        },
+        async function (ex) {
+          wasCovfefe = ex && ex.message == "covfefe";
+        }
+      )();
+    },
+
+    lockedy() {
+      return this._catch(async function () {
+        rightThis = this == obj;
+        didCall = true;
+        Utils.throwLockException(null);
+      })();
+    },
+
+    lockedy_chained() {
+      return this._catch(async function () {
+        rightThis = this == obj;
+        didCall = true;
+        Utils.throwLockException(null);
+      })();
+    },
+  };
+
+  _("Make sure a normal call will call and return");
+  rightThis = didCall = didThrow = wasLocked = false;
+  ret = await obj.func();
+  Assert.equal(ret, 5);
+  Assert.ok(rightThis);
+  Assert.ok(didCall);
+  Assert.ok(!didThrow);
+  Assert.equal(wasCovfefe, undefined);
+  Assert.ok(!wasLocked);
+
+  _(
+    "Make sure catch/throw results in debug call and caller doesn't need to handle exception"
+  );
+  rightThis = didCall = didThrow = wasLocked = false;
+  ret = await obj.throwy();
+  Assert.equal(ret, undefined);
+  Assert.ok(rightThis);
+  Assert.ok(didCall);
+  Assert.ok(didThrow);
+  Assert.equal(wasCovfefe, undefined);
+  Assert.ok(!wasLocked);
+
+  _("Test callback for exception testing.");
+  rightThis = didCall = didThrow = wasLocked = false;
+  ret = await obj.callbacky();
+  Assert.equal(ret, undefined);
+  Assert.ok(rightThis);
+  Assert.ok(didCall);
+  Assert.ok(didThrow);
+  Assert.ok(wasCovfefe);
+  Assert.ok(!wasLocked);
+
+  _("Test the lock-aware catch that Service uses.");
+  obj._catch = Service._catch;
+  rightThis = didCall = didThrow = wasLocked = false;
+  wasCovfefe = undefined;
+  ret = await obj.lockedy();
+  Assert.equal(ret, undefined);
+  Assert.ok(rightThis);
+  Assert.ok(didCall);
+  Assert.ok(didThrow);
+  Assert.equal(wasCovfefe, undefined);
+  Assert.ok(wasLocked);
+
+  _("Test the lock-aware catch that Service uses with a chained promise.");
+  rightThis = didCall = didThrow = wasLocked = false;
+  wasCovfefe = undefined;
+  ret = await obj.lockedy_chained();
+  Assert.equal(ret, undefined);
+  Assert.ok(rightThis);
+  Assert.ok(didCall);
+  Assert.ok(didThrow);
+  Assert.equal(wasCovfefe, undefined);
+  Assert.ok(wasLocked);
+});
diff --git a/src/zen/tests/mochitests/sync/test_utils_deepEquals.js b/src/zen/tests/mochitests/sync/test_utils_deepEquals.js
new file mode 100644
index 000000000..218cc21b7
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_utils_deepEquals.js
@@ -0,0 +1,51 @@
+_("Make sure Utils.deepEquals correctly finds items that are deeply equal");
+
+Services.prefs.setBoolPref("security.allow_eval_with_system_principal", true);
+registerCleanupFunction(() => {
+  Services.prefs.clearUserPref("security.allow_eval_with_system_principal");
+});
+
+function run_test() {
+  let data =
+    '[NaN, undefined, null, true, false, Infinity, 0, 1, "a", "b", {a: 1}, {a: "a"}, [{a: 1}], [{a: true}], {a: 1, b: 2}, [1, 2], [1, 2, 3]]';
+  _("Generating two copies of data:", data);
+  /* eslint-disable no-eval */
+  let d1 = eval(data);
+  let d2 = eval(data);
+  /* eslint-enable no-eval */
+
+  d1.forEach(function (a) {
+    _("Testing", a, typeof a, JSON.stringify([a]));
+    let numMatch = 0;
+
+    d2.forEach(function (b) {
+      if (Utils.deepEquals(a, b)) {
+        numMatch++;
+        _("Found a match", b, typeof b, JSON.stringify([b]));
+      }
+    });
+
+    let expect = 1;
+    if (isNaN(a) && typeof a == "number") {
+      expect = 0;
+      _("Checking NaN should result in no matches");
+    }
+
+    _("Making sure we found the correct # match:", expect);
+    _("Actual matches:", numMatch);
+    Assert.equal(numMatch, expect);
+  });
+
+  _("Make sure adding undefined properties doesn't affect equalness");
+  let a = {};
+  let b = { a: undefined };
+  Assert.ok(Utils.deepEquals(a, b));
+  a.b = 5;
+  Assert.ok(!Utils.deepEquals(a, b));
+  b.b = 5;
+  Assert.ok(Utils.deepEquals(a, b));
+  a.c = undefined;
+  Assert.ok(Utils.deepEquals(a, b));
+  b.d = undefined;
+  Assert.ok(Utils.deepEquals(a, b));
+}
diff --git a/src/zen/tests/mochitests/sync/test_utils_deferGetSet.js b/src/zen/tests/mochitests/sync/test_utils_deferGetSet.js
new file mode 100644
index 000000000..6db812b84
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_utils_deferGetSet.js
@@ -0,0 +1,50 @@
+_(
+  "Make sure various combinations of deferGetSet arguments correctly defer getting/setting properties to another object"
+);
+
+function run_test() {
+  let base = function () {};
+  base.prototype = {
+    dst: {},
+
+    get a() {
+      return "a";
+    },
+    set b(val) {
+      this.dst.b = val + "!!!";
+    },
+  };
+  let src = new base();
+
+  _("get/set a single property");
+  Utils.deferGetSet(base, "dst", "foo");
+  src.foo = "bar";
+  Assert.equal(src.dst.foo, "bar");
+  Assert.equal(src.foo, "bar");
+
+  _("editing the target also updates the source");
+  src.dst.foo = "baz";
+  Assert.equal(src.dst.foo, "baz");
+  Assert.equal(src.foo, "baz");
+
+  _("handle multiple properties");
+  Utils.deferGetSet(base, "dst", ["p1", "p2"]);
+  src.p1 = "v1";
+  src.p2 = "v2";
+  Assert.equal(src.p1, "v1");
+  Assert.equal(src.dst.p1, "v1");
+  Assert.equal(src.p2, "v2");
+  Assert.equal(src.dst.p2, "v2");
+
+  _("make sure existing getter keeps its functionality");
+  Utils.deferGetSet(base, "dst", "a");
+  src.a = "not a";
+  Assert.equal(src.dst.a, "not a");
+  Assert.equal(src.a, "a");
+
+  _("make sure existing setter keeps its functionality");
+  Utils.deferGetSet(base, "dst", "b");
+  src.b = "b";
+  Assert.equal(src.dst.b, "b!!!");
+  Assert.equal(src.b, "b!!!");
+}
diff --git a/src/zen/tests/mochitests/sync/test_utils_json.js b/src/zen/tests/mochitests/sync/test_utils_json.js
new file mode 100644
index 000000000..5bf26b236
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_utils_json.js
@@ -0,0 +1,95 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { FileUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/FileUtils.sys.mjs"
+);
+
+add_task(async function test_roundtrip() {
+  _("Do a simple write of an array to json and read");
+  await Utils.jsonSave("foo", {}, ["v1", "v2"]);
+
+  let foo = await Utils.jsonLoad("foo", {});
+  Assert.equal(typeof foo, "object");
+  Assert.equal(foo.length, 2);
+  Assert.equal(foo[0], "v1");
+  Assert.equal(foo[1], "v2");
+});
+
+add_task(async function test_string() {
+  _("Try saving simple strings");
+  await Utils.jsonSave("str", {}, "hi");
+
+  let str = await Utils.jsonLoad("str", {});
+  Assert.equal(typeof str, "string");
+  Assert.equal(str.length, 2);
+  Assert.equal(str[0], "h");
+  Assert.equal(str[1], "i");
+});
+
+add_task(async function test_number() {
+  _("Try saving a number");
+  await Utils.jsonSave("num", {}, 42);
+
+  let num = await Utils.jsonLoad("num", {});
+  Assert.equal(typeof num, "number");
+  Assert.equal(num, 42);
+});
+
+add_task(async function test_nonexistent_file() {
+  _("Try loading a non-existent file.");
+  let val = await Utils.jsonLoad("non-existent", {});
+  Assert.equal(val, undefined);
+});
+
+add_task(async function test_save_logging() {
+  _("Verify that writes are logged.");
+  let trace;
+  await Utils.jsonSave(
+    "log",
+    {
+      _log: {
+        trace(msg) {
+          trace = msg;
+        },
+      },
+    },
+    "hi"
+  );
+  Assert.ok(!!trace);
+});
+
+add_task(async function test_load_logging() {
+  _("Verify that reads and read errors are logged.");
+
+  // Write a file with some invalid JSON
+  let file = await IOUtils.getFile(PathUtils.profileDir, "weave", "log.json");
+  let fos = Cc["@mozilla.org/network/file-output-stream;1"].createInstance(
+    Ci.nsIFileOutputStream
+  );
+  let flags =
+    FileUtils.MODE_WRONLY | FileUtils.MODE_CREATE | FileUtils.MODE_TRUNCATE;
+  fos.init(file, flags, FileUtils.PERMS_FILE, fos.DEFER_OPEN);
+  let stream = Cc["@mozilla.org/intl/converter-output-stream;1"].createInstance(
+    Ci.nsIConverterOutputStream
+  );
+  stream.init(fos, "UTF-8");
+  stream.writeString("invalid json!");
+  stream.close();
+
+  let trace, debug;
+  let obj = {
+    _log: {
+      trace(msg) {
+        trace = msg;
+      },
+      debug(msg) {
+        debug = msg;
+      },
+    },
+  };
+  let val = await Utils.jsonLoad("log", obj);
+  Assert.ok(!val);
+  Assert.ok(!!trace);
+  Assert.ok(!!debug);
+});
diff --git a/src/zen/tests/mochitests/sync/test_utils_keyEncoding.js b/src/zen/tests/mochitests/sync/test_utils_keyEncoding.js
new file mode 100644
index 000000000..30a8a4f2a
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_utils_keyEncoding.js
@@ -0,0 +1,23 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+function run_test() {
+  Assert.equal(
+    Utils.encodeKeyBase32("foobarbafoobarba"),
+    "mzxw6ytb9jrgcztpn5rgc4tcme"
+  );
+  Assert.equal(
+    Utils.decodeKeyBase32("mzxw6ytb9jrgcztpn5rgc4tcme"),
+    "foobarbafoobarba"
+  );
+  Assert.equal(
+    Utils.encodeKeyBase32(
+      "\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01"
+    ),
+    "aeaqcaibaeaqcaibaeaqcaibae"
+  );
+  Assert.equal(
+    Utils.decodeKeyBase32("aeaqcaibaeaqcaibaeaqcaibae"),
+    "\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01\x01"
+  );
+}
diff --git a/src/zen/tests/mochitests/sync/test_utils_lock.js b/src/zen/tests/mochitests/sync/test_utils_lock.js
new file mode 100644
index 000000000..71d6486ff
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_utils_lock.js
@@ -0,0 +1,76 @@
+_("Make sure lock prevents calling with a shared lock");
+
+// Utility that we only use here.
+
+function do_check_begins(thing, startsWith) {
+  if (!(thing && thing.indexOf && thing.indexOf(startsWith) == 0)) {
+    do_throw(thing + " doesn't begin with " + startsWith);
+  }
+}
+
+add_task(async function run_test() {
+  let ret, rightThis, didCall;
+  let state, lockState, lockedState, unlockState;
+  let obj = {
+    _lock: Utils.lock,
+    lock() {
+      lockState = ++state;
+      if (this._locked) {
+        lockedState = ++state;
+        return false;
+      }
+      this._locked = true;
+      return true;
+    },
+    unlock() {
+      unlockState = ++state;
+      this._locked = false;
+    },
+
+    func() {
+      return this._lock("Test utils lock", async function () {
+        rightThis = this == obj;
+        didCall = true;
+        return 5;
+      })();
+    },
+
+    throwy() {
+      return this._lock("Test utils lock throwy", async function () {
+        rightThis = this == obj;
+        didCall = true;
+        return this.throwy();
+      })();
+    },
+  };
+
+  _("Make sure a normal call will call and return");
+  rightThis = didCall = false;
+  state = 0;
+  ret = await obj.func();
+  Assert.equal(ret, 5);
+  Assert.ok(rightThis);
+  Assert.ok(didCall);
+  Assert.equal(lockState, 1);
+  Assert.equal(unlockState, 2);
+  Assert.equal(state, 2);
+
+  _("Make sure code that calls locked code throws");
+  ret = null;
+  rightThis = didCall = false;
+  try {
+    ret = await obj.throwy();
+    do_throw("throwy internal call should have thrown!");
+  } catch (ex) {
+    // Should throw an Error, not a string.
+    do_check_begins(ex.message, "Could not acquire lock");
+  }
+  Assert.equal(ret, null);
+  Assert.ok(rightThis);
+  Assert.ok(didCall);
+  _("Lock should be called twice so state 3 is skipped");
+  Assert.equal(lockState, 4);
+  Assert.equal(lockedState, 5);
+  Assert.equal(unlockState, 6);
+  Assert.equal(state, 6);
+});
diff --git a/src/zen/tests/mochitests/sync/test_utils_makeGUID.js b/src/zen/tests/mochitests/sync/test_utils_makeGUID.js
new file mode 100644
index 000000000..b1104c111
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_utils_makeGUID.js
@@ -0,0 +1,44 @@
+const base64url =
+  "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-_";
+
+function run_test() {
+  _("Make sure makeGUID makes guids of the right length/characters");
+  _("Create a bunch of guids to make sure they don't conflict");
+  let guids = [];
+  for (let i = 0; i < 1000; i++) {
+    let newGuid = Utils.makeGUID();
+    _("Generated " + newGuid);
+
+    // Verify that the GUID's length is correct, even when it's URL encoded.
+    Assert.equal(newGuid.length, 12);
+    Assert.equal(encodeURIComponent(newGuid).length, 12);
+
+    // Verify that the GUID only contains base64url characters
+    Assert.ok(
+      Array.prototype.every.call(newGuid, function (chr) {
+        return base64url.includes(chr);
+      })
+    );
+
+    // Verify that Utils.checkGUID() correctly identifies them as valid.
+    Assert.ok(Utils.checkGUID(newGuid));
+
+    // Verify uniqueness within our sample of 1000. This could cause random
+    // failures, but they should be extremely rare. Otherwise we'd have a
+    // problem with GUID collisions.
+    Assert.ok(
+      guids.every(function (g) {
+        return g != newGuid;
+      })
+    );
+    guids.push(newGuid);
+  }
+
+  _("Make sure checkGUID fails for invalid GUIDs");
+  Assert.ok(!Utils.checkGUID(undefined));
+  Assert.ok(!Utils.checkGUID(null));
+  Assert.ok(!Utils.checkGUID(""));
+  Assert.ok(!Utils.checkGUID("blergh"));
+  Assert.ok(!Utils.checkGUID("ThisGUIDisWayTooLong"));
+  Assert.ok(!Utils.checkGUID("Invalid!!!!!"));
+}
diff --git a/src/zen/tests/mochitests/sync/test_utils_notify.js b/src/zen/tests/mochitests/sync/test_utils_notify.js
new file mode 100644
index 000000000..5c0c3702a
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_utils_notify.js
@@ -0,0 +1,97 @@
+_("Make sure notify sends out the right notifications");
+add_task(async function run_test() {
+  let ret, rightThis, didCall;
+  let obj = {
+    notify: Utils.notify("foo:"),
+    _log: {
+      trace() {},
+    },
+
+    func() {
+      return this.notify("bar", "baz", async function () {
+        rightThis = this == obj;
+        didCall = true;
+        return 5;
+      })();
+    },
+
+    throwy() {
+      return this.notify("bad", "one", async function () {
+        rightThis = this == obj;
+        didCall = true;
+        throw new Error("covfefe");
+      })();
+    },
+  };
+
+  let state = 0;
+  let makeObs = function (topic) {
+    let obj2 = {
+      observe(subject, obsTopic, data) {
+        this.state = ++state;
+        this.subject = subject;
+        this.topic = obsTopic;
+        this.data = data;
+      },
+    };
+
+    Svc.Obs.add(topic, obj2);
+    return obj2;
+  };
+
+  _("Make sure a normal call will call and return with notifications");
+  rightThis = didCall = false;
+  let fs = makeObs("foo:bar:start");
+  let ff = makeObs("foo:bar:finish");
+  let fe = makeObs("foo:bar:error");
+  ret = await obj.func();
+  Assert.equal(ret, 5);
+  Assert.ok(rightThis);
+  Assert.ok(didCall);
+
+  Assert.equal(fs.state, 1);
+  Assert.equal(fs.subject, undefined);
+  Assert.equal(fs.topic, "foo:bar:start");
+  Assert.equal(fs.data, "baz");
+
+  Assert.equal(ff.state, 2);
+  Assert.equal(ff.subject, 5);
+  Assert.equal(ff.topic, "foo:bar:finish");
+  Assert.equal(ff.data, "baz");
+
+  Assert.equal(fe.state, undefined);
+  Assert.equal(fe.subject, undefined);
+  Assert.equal(fe.topic, undefined);
+  Assert.equal(fe.data, undefined);
+
+  _("Make sure a throwy call will call and throw with notifications");
+  ret = null;
+  rightThis = didCall = false;
+  let ts = makeObs("foo:bad:start");
+  let tf = makeObs("foo:bad:finish");
+  let te = makeObs("foo:bad:error");
+  try {
+    ret = await obj.throwy();
+    do_throw("throwy should have thrown!");
+  } catch (ex) {
+    Assert.equal(ex.message, "covfefe");
+  }
+  Assert.equal(ret, null);
+  Assert.ok(rightThis);
+  Assert.ok(didCall);
+
+  Assert.equal(ts.state, 3);
+  Assert.equal(ts.subject, undefined);
+  Assert.equal(ts.topic, "foo:bad:start");
+  Assert.equal(ts.data, "one");
+
+  Assert.equal(tf.state, undefined);
+  Assert.equal(tf.subject, undefined);
+  Assert.equal(tf.topic, undefined);
+  Assert.equal(tf.data, undefined);
+
+  Assert.equal(te.state, 4);
+  Assert.equal(te.subject.message, "covfefe");
+  Assert.equal(te.topic, "foo:bad:error");
+  Assert.equal(te.data, "one");
+});
diff --git a/src/zen/tests/mochitests/sync/test_utils_passphrase.js b/src/zen/tests/mochitests/sync/test_utils_passphrase.js
new file mode 100644
index 000000000..fa5808611
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/test_utils_passphrase.js
@@ -0,0 +1,45 @@
+/* eslint no-tabs:"off" */
+
+function run_test() {
+  _("Normalize passphrase recognizes hyphens.");
+  const pp = "26ect2thczm599m2ffqarbicjq";
+  const hyphenated = "2-6ect2-thczm-599m2-ffqar-bicjq";
+  Assert.equal(Utils.normalizePassphrase(hyphenated), pp);
+
+  _("Skip whitespace.");
+  Assert.equal(
+    "aaaaaaaaaaaaaaaaaaaaaaaaaa",
+    Utils.normalizePassphrase("aaaaaaaaaaaaaaaaaaaaaaaaaa  ")
+  );
+  Assert.equal(
+    "aaaaaaaaaaaaaaaaaaaaaaaaaa",
+    Utils.normalizePassphrase("	 aaaaaaaaaaaaaaaaaaaaaaaaaa")
+  );
+  Assert.equal(
+    "aaaaaaaaaaaaaaaaaaaaaaaaaa",
+    Utils.normalizePassphrase("    aaaaaaaaaaaaaaaaaaaaaaaaaa  ")
+  );
+  Assert.equal(
+    "aaaaaaaaaaaaaaaaaaaaaaaaaa",
+    Utils.normalizePassphrase("    a-aaaaa-aaaaa-aaaaa-aaaaa-aaaaa  ")
+  );
+  Assert.ok(Utils.isPassphrase("aaaaaaaaaaaaaaaaaaaaaaaaaa  "));
+  Assert.ok(Utils.isPassphrase("	 aaaaaaaaaaaaaaaaaaaaaaaaaa"));
+  Assert.ok(Utils.isPassphrase("    aaaaaaaaaaaaaaaaaaaaaaaaaa  "));
+  Assert.ok(Utils.isPassphrase("    a-aaaaa-aaaaa-aaaaa-aaaaa-aaaaa  "));
+  Assert.ok(!Utils.isPassphrase("    -aaaaa-aaaaa-aaaaa-aaaaa-aaaaa  "));
+
+  _("Normalizing 20-char passphrases.");
+  Assert.equal(
+    Utils.normalizePassphrase("abcde-abcde-abcde-abcde"),
+    "abcdeabcdeabcdeabcde"
+  );
+  Assert.equal(
+    Utils.normalizePassphrase("a-bcde-abcde-abcde-abcde"),
+    "a-bcde-abcde-abcde-abcde"
+  );
+  Assert.equal(
+    Utils.normalizePassphrase(" abcde-abcde-abcde-abcde "),
+    "abcdeabcdeabcdeabcde"
+  );
+}
diff --git a/src/zen/tests/mochitests/sync/xpcshell.toml b/src/zen/tests/mochitests/sync/xpcshell.toml
new file mode 100644
index 000000000..5531f4838
--- /dev/null
+++ b/src/zen/tests/mochitests/sync/xpcshell.toml
@@ -0,0 +1,369 @@
+[DEFAULT]
+run-if = [
+  "os != 'android'",
+]
+head = "head_appinfo.js ../../../../services/common/tests/unit/head_helpers.js head_helpers.js head_http_server.js head_errorhandler_common.js"
+firefox-appdir = "browser"
+prefs = ["identity.fxaccounts.enabled=true", "browser.formfill.enable=true"]
+support-files = [
+  "addon1-search.json",
+  "bootstrap1-search.json",
+  "missing-sourceuri.json",
+  "missing-xpi-search.json",
+  "rewrite-search.json",
+  "systemaddon-search.json",
+  "!/services/common/tests/unit/head_helpers.js",
+  "!/toolkit/components/extensions/test/xpcshell/head_sync.js",
+  "../../../../services/../toolkit/mozapps/extensions/test/xpinstall/amosigned-sha1only.xpi",
+]
+
+# The manifest is roughly ordered from low-level to high-level. When making
+# systemic sweeping changes, this makes it easier to identify errors closer to
+# the source.
+
+# Ensure we can import everything.
+
+["test_412.js"]
+
+["test_addon_utils.js"]
+run-sequentially = ["true"] # Restarts server, can't change pref.
+tags = "addons"
+
+["test_addons_engine.js"]
+run-sequentially = ["true"] # Frequent timeouts, bug 1395148
+tags = "addons"
+
+["test_addons_reconciler.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+tags = "addons"
+
+["test_addons_store.js"]
+run-sequentially = ["true"] # Frequent timeouts, bug 1395148
+tags = "addons"
+
+["test_addons_tracker.js"]
+tags = "addons"
+
+["test_addons_validator.js"]
+tags = "addons"
+
+["test_bookmark_batch_fail.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_bookmark_decline_undecline.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_bookmark_engine.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_bookmark_order.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_bookmark_places_query_rewriting.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_bookmark_record.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_bookmark_store.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_bookmark_tracker.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_bridged_engine.js"]
+
+["test_clients_engine.js"]
+run-sequentially = ["true"] # Frequent timeouts, bug 1395148
+
+["test_clients_escape.js"]
+
+["test_collection_getBatched.js"]
+
+["test_collections_recovery.js"]
+
+["test_corrupt_keys.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_declined.js"]
+
+["test_disconnect_shutdown.js"]
+
+["test_engine.js"]
+
+["test_engine_abort.js"]
+
+["test_engine_changes_during_sync.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+# Rust logins backend lacks the legacy Sync metadata methods
+# (getSyncID/setSyncID/getLastSync) the JS PasswordEngine needs; keep on JSON.
+prefs = ["signon.storage.rust.enabled=false"]
+
+["test_enginemanager.js"]
+
+["test_errorhandler_1.js"]
+run-sequentially = ["true"] # Frequent timeouts, bug 1395148
+skip-if = [
+  "os == 'mac' && os_version == '15.30' && arch == 'aarch64' && opt", # Bug 1864117
+]
+
+["test_errorhandler_2.js"]
+run-sequentially = ["true"] # Frequent timeouts, bug 1395148
+
+["test_errorhandler_filelog.js"]
+
+["test_errorhandler_sync_checkServerError.js"]
+
+["test_extension_storage_engine.js"]
+run-sequentially = ["true"] # extension-storage migration happens only once, and must be tested first.
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_extension_storage_engine_kinto.js"]
+run-sequentially = ["true"] # extension-storage migration happens only once, and must be tested first.
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_extension_storage_tracker_kinto.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_form_validator.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_forms_store.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_forms_tracker.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_fxa_node_reassignment.js"]
+run-sequentially = ["true"] # Frequent timeouts, bug 1395148
+
+["test_fxa_service_cluster.js"]
+# Finally, we test each engine.
+
+["test_glean.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_history_engine.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_history_store.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_history_tracker.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_hmac_error.js"]
+
+["test_httpd_sync_server.js"]
+# HTTP layers.
+
+["test_interval_triggers.js"]
+
+["test_keys.js"]
+
+["test_load_modules.js"]
+# util contains a bunch of functionality used throughout.
+
+["test_node_reassignment.js"]
+run-sequentially = ["true"] # Frequent timeouts, bug 1395148
+
+# The password engine/store/tracker tests drive the JS PasswordEngine, which
+# needs the legacy Sync metadata methods (getSyncID/setSyncID/getLastSync) the
+# Rust logins backend lacks; keep them on the JSON backend.
+["test_password_engine.js"]
+prefs = ["signon.storage.rust.enabled=false"]
+
+["test_password_store.js"]
+prefs = ["signon.storage.rust.enabled=false"]
+
+["test_password_tracker.js"]
+prefs = ["signon.storage.rust.enabled=false"]
+
+["test_password_validator.js"]
+
+["test_postqueue.js"]
+# Synced tabs.
+
+["test_prefs_engine.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_prefs_store.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+support-files = ["prefs_test_prefs_store.js"]
+
+["test_prefs_tracker.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_records_crypto.js"]
+
+["test_records_wbo.js"]
+
+["test_resource.js"]
+
+["test_resource_header.js"]
+
+["test_resource_ua.js"]
+# Generic Sync types.
+
+["test_rust_password_engine_mp_locked.js"]
+
+["test_rust_password_engine_selection.js"]
+
+["test_rust_password_tracker.js"]
+
+["test_score_triggers.js"]
+
+["test_service_attributes.js"]
+# Bug 752243: Profile cleanup frequently fails
+
+["test_service_cluster.js"]
+
+["test_service_detect_upgrade.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_service_login.js"]
+# Service.sync() drives the JS PasswordEngine, which needs the legacy Sync
+# metadata methods the Rust logins backend lacks; keep on JSON.
+prefs = ["signon.storage.rust.enabled=false"]
+
+["test_service_startOver.js"]
+
+["test_service_startup.js"]
+
+["test_service_sync_401.js"]
+
+["test_service_sync_locked.js"]
+
+["test_service_sync_remoteSetup.js"]
+run-sequentially = ["true"] # Frequent timeouts, bug 1395148
+
+["test_service_sync_specified.js"]
+
+["test_service_sync_updateEnabledEngines.js"]
+run-sequentially = ["true"] # Frequent timeouts, bug 1395148
+
+["test_service_verifyLogin.js"]
+
+["test_service_wipeClient.js"]
+
+["test_service_wipeServer.js"]
+# Bug 752243: Profile cleanup frequently fails
+
+["test_status.js"]
+
+["test_status_checkSetup.js"]
+
+["test_sync_auth_manager.js"]
+# Engine APIs.
+
+["test_syncedtabs.js"]
+
+["test_syncengine.js"]
+
+["test_syncengine_sync.js"]
+run-sequentially = ["true"] # Frequent timeouts, bug 1395148
+
+["test_syncscheduler.js"]
+run-sequentially = ["true"] # Frequent timeouts, bug 1395148
+# Firefox Accounts specific tests
+
+["test_tab_engine.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_tab_provider.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_tab_quickwrite.js"]
+run-if = [
+  "appname != 'thunderbird'",
+  "os == 'mac' && os_version == '15.30' && arch == 'aarch64'", # Bug 1819545
+]
+
+["test_tab_tracker.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_telemetry.js"]
+run-if = [
+  "appname != 'thunderbird'",
+]
+
+["test_tracker_addChanged.js"]
+# Service semantics.
+
+["test_uistate.js"]
+
+["test_utils_catch.js"]
+
+["test_utils_deepEquals.js"]
+
+["test_utils_deferGetSet.js"]
+
+["test_utils_json.js"]
+
+["test_utils_keyEncoding.js"]
+
+["test_utils_lock.js"]
+
+["test_utils_makeGUID.js"]
+run-sequentially = ["true"] # Disproportionately slows down full test run, bug 1450316
+
+["test_utils_notify.js"]
+
+["test_utils_passphrase.js"]
+# We have a number of other libraries that are pretty much standalone.
diff --git a/src/zen/tests/mochitests/tabMediaIndicator/browser.toml b/src/zen/tests/mochitests/tabMediaIndicator/browser.toml
index 9eac10b02..a725df4df 100644
--- a/src/zen/tests/mochitests/tabMediaIndicator/browser.toml
+++ b/src/zen/tests/mochitests/tabMediaIndicator/browser.toml
@@ -6,6 +6,8 @@ support-files = [
   "audio.ogg",
   "audioEndedDuringPlaying.webm",
   "file_almostSilentAudioTrack.html",
+  "file_audiblechange_iframe.html",
+  "file_audiblechange_iframe_inner.html",
   "file_autoplay_media.html",
   "file_empty.html",
   "file_mediaPlayback.html",
@@ -20,6 +22,8 @@ support-files = [
   "silentAudioTrack.webm",
 ]
 
+["browser_audiblechange_iframe.js"]
+
 ["browser_destroy_iframe.js"]
 https_first_disabled = true
 
@@ -33,6 +37,10 @@ https_first_disabled = true
 
 ["browser_mute2.js"]
 
+["browser_mute_persist_navigation.js"]
+
+["browser_mute_restore_closed_audible_tab.js"]
+
 ["browser_mute_webAudio.js"]
 
 ["browser_sound_indicator_silent_video.js"]
diff --git a/src/zen/tests/mochitests/tabMediaIndicator/browser_audiblechange_iframe.js b/src/zen/tests/mochitests/tabMediaIndicator/browser_audiblechange_iframe.js
new file mode 100644
index 000000000..474961241
--- /dev/null
+++ b/src/zen/tests/mochitests/tabMediaIndicator/browser_audiblechange_iframe.js
@@ -0,0 +1,134 @@
+// When a tab has audio sources in both the top-level document and an iframe,
+// pausing only one of them must not make the tab sound indicator disappear —
+// it should stay until all sources are silent.
+
+const PAGE_URL = GetTestWebBasedURL("file_audiblechange_iframe.html");
+
+/**
+ * Start both top-level and iframe audio, wait for indicator, then pause each
+ * one in turn verifying the indicator only disappears when both are silent.
+ *
+ * @param {tab} tab
+ * @param {BrowsingContext} innerBC  - iframe's browsing context
+ * @param {string} pauseFirst       - "toplevel" or "iframe"
+ */
+async function testBothSourcesThenPauseOne(tab, innerBC, pauseFirst) {
+  const browser = tab.linkedBrowser;
+
+  info(`play both sources (pause-first: ${pauseFirst})`);
+  await SpecialPowers.spawn(browser, [], async () => {
+    await content.document.getElementById("toplevel").play();
+  });
+  await SpecialPowers.spawn(innerBC, [], async () => {
+    await content.document.getElementById("audio").play();
+  });
+  await waitForTabSoundIndicatorAppears(tab);
+
+  const observer = createSoundIndicatorObserver(tab);
+
+  if (pauseFirst === "toplevel") {
+    info("pause top-level only — iframe still playing");
+    await SpecialPowers.spawn(browser, [], () => {
+      content.document.getElementById("toplevel").pause();
+    });
+    // Wait for the iframe audio to advance, proving it is still audible.
+    await SpecialPowers.spawn(innerBC, [], async () => {
+      await new Promise(r => {
+        content.document.getElementById("audio").ontimeupdate = r;
+      });
+    });
+    ok(
+      !observer.hasEverUpdated(),
+      "indicator stays after top-level pause (iframe still playing)"
+    );
+
+    info("pause iframe — all silent");
+    await SpecialPowers.spawn(innerBC, [], () => {
+      content.document.getElementById("audio").pause();
+    });
+  } else {
+    info("pause iframe only — top-level still playing");
+    await SpecialPowers.spawn(innerBC, [], () => {
+      content.document.getElementById("audio").pause();
+    });
+    // Wait for the top-level audio to advance, proving it is still audible.
+    await SpecialPowers.spawn(browser, [], async () => {
+      await new Promise(r => {
+        content.document.getElementById("toplevel").ontimeupdate = r;
+      });
+    });
+    ok(
+      !observer.hasEverUpdated(),
+      "indicator stays after iframe pause (top-level still playing)"
+    );
+
+    info("pause top-level — all silent");
+    await SpecialPowers.spawn(browser, [], () => {
+      content.document.getElementById("toplevel").pause();
+    });
+  }
+
+  await waitForTabSoundIndicatorDisappears(tab);
+}
+
+add_task(async function testSoundIndicatorPauseTopLevelFirst() {
+  info("open tab with top-level audio and same-origin iframe audio");
+  const tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, PAGE_URL);
+  const innerBC = tab.linkedBrowser.browsingContext.children[0];
+
+  await testBothSourcesThenPauseOne(tab, innerBC, "toplevel");
+
+  info("remove tab");
+  BrowserTestUtils.removeTab(tab);
+});
+
+add_task(async function testSoundIndicatorPauseIframeFirst() {
+  info("open tab with top-level audio and same-origin iframe audio");
+  const tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, PAGE_URL);
+  const innerBC = tab.linkedBrowser.browsingContext.children[0];
+
+  await testBothSourcesThenPauseOne(tab, innerBC, "iframe");
+
+  info("remove tab");
+  BrowserTestUtils.removeTab(tab);
+});
+
+add_task(async function testSoundIndicatorOnlyTopLevelPlaying() {
+  info("open tab and play only the top-level audio (iframe silent)");
+  const tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, PAGE_URL);
+  const browser = tab.linkedBrowser;
+
+  await SpecialPowers.spawn(browser, [], async () => {
+    await content.document.getElementById("toplevel").play();
+  });
+  await waitForTabSoundIndicatorAppears(tab);
+
+  info("pause top-level — tab should go silent");
+  await SpecialPowers.spawn(browser, [], () => {
+    content.document.getElementById("toplevel").pause();
+  });
+  await waitForTabSoundIndicatorDisappears(tab);
+
+  info("remove tab");
+  BrowserTestUtils.removeTab(tab);
+});
+
+add_task(async function testSoundIndicatorOnlyIframePlaying() {
+  info("open tab and play only the iframe audio (top-level silent)");
+  const tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, PAGE_URL);
+  const innerBC = tab.linkedBrowser.browsingContext.children[0];
+
+  await SpecialPowers.spawn(innerBC, [], async () => {
+    await content.document.getElementById("audio").play();
+  });
+  await waitForTabSoundIndicatorAppears(tab);
+
+  info("pause iframe — tab should go silent");
+  await SpecialPowers.spawn(innerBC, [], () => {
+    content.document.getElementById("audio").pause();
+  });
+  await waitForTabSoundIndicatorDisappears(tab);
+
+  info("remove tab");
+  BrowserTestUtils.removeTab(tab);
+});
diff --git a/src/zen/tests/mochitests/tabMediaIndicator/browser_destroy_iframe.js b/src/zen/tests/mochitests/tabMediaIndicator/browser_destroy_iframe.js
index f977d1d66..b89f19e3e 100644
--- a/src/zen/tests/mochitests/tabMediaIndicator/browser_destroy_iframe.js
+++ b/src/zen/tests/mochitests/tabMediaIndicator/browser_destroy_iframe.js
@@ -4,6 +4,7 @@ const CORS_AUTPLAY_PAGE_URL = GetTestWebBasedURL(
   "file_autoplay_media.html",
   true
 );
+const CORS_WEB_AUDIO_PAGE_URL = GetTestWebBasedURL("file_webAudio.html", true);
 
 /**
  * When an iframe that has audible media gets destroyed, if there is no other
@@ -32,6 +33,33 @@ add_task(async function testDestroyAudibleIframe() {
   }
 });
 
+/**
+ * When an iframe with a Web Audio context (uncontrolled source) is destroyed,
+ * the sound indicator should disappear if no other audible source remains.
+ * This exercises the mAudibleUncontrolledSources.Remove() path in
+ * MediaStatusManager::NotifyBrowsingContextDiscarded().
+ */
+add_task(async function testDestroyAudibleWebAudioIframe() {
+  info(`open a tab, create a cross-origin iframe with Web Audio`);
+  const tab = await BrowserTestUtils.openNewForegroundTab(
+    gBrowser,
+    EMPTY_PAGE_URL
+  );
+  await createIframeAndLoadURL(tab, CORS_WEB_AUDIO_PAGE_URL);
+
+  info(`sound indicator should appear because of audible Web Audio`);
+  await waitForTabSoundIndicatorAppears(tab);
+
+  info(
+    `sound indicator should disappear after destroying the Web Audio iframe`
+  );
+  await removeIframe(tab);
+  await waitForTabSoundIndicatorDisappears(tab);
+
+  info("remove tab");
+  BrowserTestUtils.removeTab(tab);
+});
+
 function createIframeAndLoadURL(tab, url) {
   // eslint-disable-next-line no-shadow
   return SpecialPowers.spawn(tab.linkedBrowser, [url], async url => {
diff --git a/src/zen/tests/mochitests/tabMediaIndicator/browser_mediaPlayback.js b/src/zen/tests/mochitests/tabMediaIndicator/browser_mediaPlayback.js
index 89143bf83..ed6a85729 100644
--- a/src/zen/tests/mochitests/tabMediaIndicator/browser_mediaPlayback.js
+++ b/src/zen/tests/mochitests/tabMediaIndicator/browser_mediaPlayback.js
@@ -1,24 +1,13 @@
 const PAGE = GetTestWebBasedURL("file_mediaPlayback.html");
 const FRAME = GetTestWebBasedURL("file_mediaPlaybackFrame.html");
 
-function wait_for_event(browser, event) {
-  return BrowserTestUtils.waitForEvent(browser, event, false, e => {
-    is(
-      e.originalTarget,
-      browser,
-      "Event must be dispatched to correct browser."
-    );
-    ok(!e.cancelable, "The event should not be cancelable");
-    return true;
-  });
-}
-
 async function test_on_browser(url, browser) {
   info(`run test for ${url}`);
-  const startPromise = wait_for_event(browser, "DOMAudioPlaybackStarted");
+  const tab = gBrowser.getTabForBrowser(browser);
+  const startPromise = waitForTabSoundIndicatorAppears(tab);
   BrowserTestUtils.startLoadingURIString(browser, url);
   await startPromise;
-  await wait_for_event(browser, "DOMAudioPlaybackStopped");
+  await waitForTabSoundIndicatorDisappears(tab);
 }
 
 add_task(async function test_page() {
diff --git a/src/zen/tests/mochitests/tabMediaIndicator/browser_mediaPlayback_mute.js b/src/zen/tests/mochitests/tabMediaIndicator/browser_mediaPlayback_mute.js
index fb771c23a..ee425b3b5 100644
--- a/src/zen/tests/mochitests/tabMediaIndicator/browser_mediaPlayback_mute.js
+++ b/src/zen/tests/mochitests/tabMediaIndicator/browser_mediaPlayback_mute.js
@@ -1,17 +1,6 @@
 const PAGE = GetTestWebBasedURL("file_mediaPlayback2.html");
 const FRAME = GetTestWebBasedURL("file_mediaPlaybackFrame2.html");
 
-function wait_for_event(browser, event) {
-  return BrowserTestUtils.waitForEvent(browser, event, false, e => {
-    is(
-      e.originalTarget,
-      browser,
-      "Event must be dispatched to correct browser."
-    );
-    return true;
-  });
-}
-
 function test_audio_in_browser() {
   function get_audio_element() {
     var doc = content.document;
@@ -36,18 +25,21 @@ function test_audio_in_browser() {
 }
 
 async function test_on_browser(url, browser) {
+  const tab = gBrowser.getTabForBrowser(browser);
   BrowserTestUtils.startLoadingURIString(browser, url);
-  await wait_for_event(browser, "DOMAudioPlaybackStarted");
+  await waitForTabSoundIndicatorAppears(tab);
 
   var result = await SpecialPowers.spawn(browser, [], test_audio_in_browser);
   is(result.computedVolume, 1, "Audio volume is 1");
   is(result.computedMuted, false, "Audio is not muted");
 
   ok(!browser.audioMuted, "Audio should not be muted by default");
-  browser.mute();
+  // Use the tab-level API (which internally calls mediaController.mute()) to
+  // test the full browser-mute path as the user would trigger it.
+  tab.toggleMuteAudio();
   ok(browser.audioMuted, "Audio should be muted now");
 
-  await wait_for_event(browser, "DOMAudioPlaybackStopped");
+  await waitForTabSoundIndicatorDisappears(tab);
 
   result = await SpecialPowers.spawn(browser, [], test_audio_in_browser);
   is(result.computedVolume, 0, "Audio volume is 0 when muted");
@@ -55,8 +47,9 @@ async function test_on_browser(url, browser) {
 }
 
 async function test_visibility(url, browser) {
+  const tab = gBrowser.getTabForBrowser(browser);
   BrowserTestUtils.startLoadingURIString(browser, url);
-  await wait_for_event(browser, "DOMAudioPlaybackStarted");
+  await waitForTabSoundIndicatorAppears(tab);
 
   var result = await SpecialPowers.spawn(browser, [], test_audio_in_browser);
   is(result.computedVolume, 1, "Audio volume is 1");
@@ -71,10 +64,12 @@ async function test_visibility(url, browser) {
   );
 
   ok(!browser.audioMuted, "Audio should not be muted by default");
-  browser.mute();
+  // Use the tab-level API (which internally calls mediaController.mute()) to
+  // test the full browser-mute path as the user would trigger it.
+  tab.toggleMuteAudio();
   ok(browser.audioMuted, "Audio should be muted now");
 
-  await wait_for_event(browser, "DOMAudioPlaybackStopped");
+  await waitForTabSoundIndicatorDisappears(tab);
 
   result = await SpecialPowers.spawn(browser, [], test_audio_in_browser);
   is(result.computedVolume, 0, "Audio volume is 0 when muted");
diff --git a/src/zen/tests/mochitests/tabMediaIndicator/browser_mute.js b/src/zen/tests/mochitests/tabMediaIndicator/browser_mute.js
index 826e06c3d..890fd7bd3 100644
--- a/src/zen/tests/mochitests/tabMediaIndicator/browser_mute.js
+++ b/src/zen/tests/mochitests/tabMediaIndicator/browser_mute.js
@@ -2,9 +2,9 @@ const PAGE = "data:text/html,page";
 
 function test_on_browser(browser) {
   ok(!browser.audioMuted, "Audio should not be muted by default");
-  browser.mute();
+  browser.browsingContext.mediaController.mute();
   ok(browser.audioMuted, "Audio should be muted now");
-  browser.unmute();
+  browser.browsingContext.mediaController.unmute();
   ok(!browser.audioMuted, "Audio should be unmuted now");
 }
 
diff --git a/src/zen/tests/mochitests/tabMediaIndicator/browser_mute2.js b/src/zen/tests/mochitests/tabMediaIndicator/browser_mute2.js
index 5e845454d..948e351e9 100644
--- a/src/zen/tests/mochitests/tabMediaIndicator/browser_mute2.js
+++ b/src/zen/tests/mochitests/tabMediaIndicator/browser_mute2.js
@@ -2,7 +2,7 @@ const PAGE = "data:text/html,page";
 
 async function test_on_browser(browser) {
   ok(!browser.audioMuted, "Audio should not be muted by default");
-  browser.mute();
+  browser.browsingContext.mediaController.mute();
   ok(browser.audioMuted, "Audio should be muted now");
 
   await BrowserTestUtils.withNewTab(
@@ -13,7 +13,7 @@ async function test_on_browser(browser) {
     test_on_browser2
   );
 
-  browser.unmute();
+  browser.browsingContext.mediaController.unmute();
   ok(!browser.audioMuted, "Audio should be unmuted now");
 }
 
diff --git a/src/zen/tests/mochitests/tabMediaIndicator/browser_mute_persist_navigation.js b/src/zen/tests/mochitests/tabMediaIndicator/browser_mute_persist_navigation.js
new file mode 100644
index 000000000..e5c3aa047
--- /dev/null
+++ b/src/zen/tests/mochitests/tabMediaIndicator/browser_mute_persist_navigation.js
@@ -0,0 +1,86 @@
+// Verify that tab mute state persists across navigation: a tab muted before
+// navigation keeps audio muted on the new page, and unmuting restores audibility.
+
+"use strict";
+
+const PAGE = GetTestWebBasedURL("file_mediaPlayback2.html");
+
+// Mute a tab while it is on about:blank, then navigate to a page with audio.
+// Verify that the audio in the new page is muted immediately on playback, and
+// that unmuting the tab makes the audio audible in content.
+add_task(async function test_mute_persists_and_unmute_restores() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["media.useAudioChannelService.testing", true]],
+  });
+
+  const tab = await BrowserTestUtils.openNewForegroundTab(
+    gBrowser,
+    "about:blank"
+  );
+  const browser = tab.linkedBrowser;
+
+  ok(!browser.audioMuted, "Tab should not be muted initially");
+  tab.toggleMuteAudio();
+  ok(browser.audioMuted, "Tab should now be muted");
+  ok(tab.hasAttribute("muted"), "Tab element should have muted attribute");
+
+  BrowserTestUtils.startLoadingURIString(browser, PAGE);
+  await BrowserTestUtils.browserLoaded(browser, false, PAGE);
+
+  await waitForAudioPlaying(browser);
+
+  let computedMuted = await getAudioComputedMuted(browser);
+  is(
+    computedMuted,
+    true,
+    "Audio should be muted in the content page after navigation"
+  );
+  ok(
+    browser.audioMuted,
+    "browser.audioMuted should remain true after navigation"
+  );
+  ok(
+    !tab.hasAttribute("soundplaying"),
+    "Tab should not show the sound indicator while muted"
+  );
+
+  tab.toggleMuteAudio();
+  ok(!browser.audioMuted, "Tab should be unmuted now");
+
+  await TestUtils.waitForCondition(async () => {
+    return !(await getAudioComputedMuted(browser));
+  }, "Audio should become unmuted in content after tab unmute");
+
+  computedMuted = await getAudioComputedMuted(browser);
+  is(computedMuted, false, "Audio should no longer be muted after unmute");
+
+  BrowserTestUtils.removeTab(tab);
+});
+
+// Following are helper functions.
+async function getAudioComputedMuted(browser) {
+  return SpecialPowers.spawn(browser, [], () => {
+    const audio = content.document.getElementById("v");
+    if (!audio) {
+      ok(false, "audio element not found");
+      return null;
+    }
+    return audio.computedMuted;
+  });
+}
+
+async function waitForAudioPlaying(browser) {
+  await SpecialPowers.spawn(browser, [], async () => {
+    const audio = content.document.getElementById("v");
+    if (!audio) {
+      ok(false, "audio element not found");
+      return;
+    }
+    if (!audio.paused) {
+      return;
+    }
+    await new Promise(resolve =>
+      audio.addEventListener("playing", resolve, { once: true })
+    );
+  });
+}
diff --git a/src/zen/tests/mochitests/tabMediaIndicator/browser_mute_restore_closed_audible_tab.js b/src/zen/tests/mochitests/tabMediaIndicator/browser_mute_restore_closed_audible_tab.js
new file mode 100644
index 000000000..7905bc3a4
--- /dev/null
+++ b/src/zen/tests/mochitests/tabMediaIndicator/browser_mute_restore_closed_audible_tab.js
@@ -0,0 +1,93 @@
+// Verify that closing a tab preserves the mute state it gets restored with: a
+// tab closed while it was audible and unmuted comes back unmuted and audible,
+// and a tab the user muted comes back muted and silent.
+
+"use strict";
+
+const PAGE = GetTestWebBasedURL("file_mediaPlayback2.html");
+
+add_setup(async function () {
+  await SpecialPowers.pushPrefEnv({
+    set: [["media.useAudioChannelService.testing", true]],
+  });
+});
+
+add_task(async function test_closing_audible_tab_restores_unmuted() {
+  const tab = await openAudibleTab();
+  ok(!tab.muted, "Tab is not muted before it gets closed");
+  ok(tab.soundPlaying, "Tab is still audible when it gets closed");
+
+  const restored = await closeAndRestoreTab(tab);
+  ok(!restored.muted, "Restored tab should not be muted");
+  ok(
+    !restored.linkedBrowser.audioMuted,
+    "Restored tab's audio should not be muted"
+  );
+  await waitForTabSoundIndicatorAppears(restored);
+
+  BrowserTestUtils.removeTab(restored);
+});
+
+add_task(async function test_closing_muted_tab_restores_muted() {
+  const tab = await openAudibleTab();
+  tab.toggleMuteAudio();
+  ok(tab.muted, "Tab is muted before it gets closed");
+  await waitForTabSoundIndicatorDisappears(tab);
+
+  const restored = await closeAndRestoreTab(tab);
+  ok(restored.muted, "Restored tab should still be muted");
+  ok(restored.linkedBrowser.audioMuted, "Restored tab's audio should be muted");
+
+  await BrowserTestUtils.browserLoaded(restored.linkedBrowser, false, PAGE);
+  is(
+    await getComputedMutedOncePlaying(restored.linkedBrowser),
+    true,
+    "Restored tab stays silent once its media resumes"
+  );
+
+  BrowserTestUtils.removeTab(restored);
+});
+
+// Following are helper functions.
+async function openAudibleTab() {
+  const tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, PAGE);
+  await waitForTabSoundIndicatorAppears(tab);
+  return tab;
+}
+
+async function closeAndRestoreTab(tab) {
+  const closedTabCount = SessionStore.getClosedTabCountForWindow(window);
+  const mutedWhenClosed = tab.muted;
+
+  const flushed = BrowserTestUtils.waitForSessionStoreUpdate(tab);
+  await BrowserTestUtils.removeTab(tab);
+  await flushed;
+
+  is(
+    SessionStore.getClosedTabCountForWindow(window),
+    closedTabCount + 1,
+    "SessionStore recorded the closed tab"
+  );
+  is(
+    !!SessionStore.getClosedTabData(window)[0].state.muted,
+    mutedWhenClosed,
+    "Closed tab data records the mute state the tab was closed with"
+  );
+
+  return SessionStore.undoCloseTab(window, 0);
+}
+
+async function getComputedMutedOncePlaying(browser) {
+  return SpecialPowers.spawn(browser, [], async () => {
+    const audio = await ContentTaskUtils.waitForCondition(
+      () => content.document.getElementById("v"),
+      "wait for the restored page to create its audio element"
+    );
+    if (audio.paused) {
+      await new Promise(resolve =>
+        audio.addEventListener("playing", resolve, { once: true })
+      );
+    }
+    return audio.computedMuted;
+  });
+}
diff --git a/src/zen/tests/mochitests/tabMediaIndicator/file_audiblechange_iframe.html b/src/zen/tests/mochitests/tabMediaIndicator/file_audiblechange_iframe.html
new file mode 100644
index 000000000..2d1b07c46
--- /dev/null
+++ b/src/zen/tests/mochitests/tabMediaIndicator/file_audiblechange_iframe.html
@@ -0,0 +1,3 @@
+<!DOCTYPE html>
+<audio id="toplevel" src="audio.ogg" loop></audio>
+<iframe id="inner" src="file_audiblechange_iframe_inner.html"></iframe>
diff --git a/src/zen/tests/mochitests/tabMediaIndicator/file_audiblechange_iframe_inner.html b/src/zen/tests/mochitests/tabMediaIndicator/file_audiblechange_iframe_inner.html
new file mode 100644
index 000000000..dbb61b073
--- /dev/null
+++ b/src/zen/tests/mochitests/tabMediaIndicator/file_audiblechange_iframe_inner.html
@@ -0,0 +1,2 @@
+<!DOCTYPE html>
+<audio id="audio" src="audio.ogg" loop></audio>
diff --git a/src/zen/tests/mochitests/zoom/browser.toml b/src/zen/tests/mochitests/zoom/browser.toml
new file mode 100644
index 000000000..bac083464
--- /dev/null
+++ b/src/zen/tests/mochitests/zoom/browser.toml
@@ -0,0 +1,63 @@
+[DEFAULT]
+support-files = [
+  "head.js",
+  "../../../../browser/base/content/test/general/moz.png",
+  "zoom_test.html",
+]
+
+["browser_background_link_zoom_reset.js"]
+https_first_disabled = true
+
+["browser_background_zoom.js"]
+https_first_disabled = true
+
+["browser_default_zoom.js"]
+
+["browser_default_zoom_fission.js"]
+
+["browser_default_zoom_multitab.js"]
+https_first_disabled = true
+
+["browser_default_zoom_sitespecific.js"]
+
+["browser_image_zoom_tabswitch.js"]
+https_first_disabled = true
+skip-if = [
+  "os == 'mac' && os_version == '10.15' && arch == 'x86_64'", # Bug 1526628
+  "os == 'mac' && os_version == '14.70' && arch == 'x86_64'", # Bug 1526628
+  "os == 'mac' && os_version == '15.30' && arch == 'aarch64'", # Bug 1526628
+]
+
+["browser_keyboard_mousewheel_zoom_consistency.js"]
+skip-if = [
+  "os == 'mac' && os_version == '15.30' && arch == 'aarch64'", # Bug 2019466
+]
+
+["browser_mousewheel_zoom.js"]
+https_first_disabled = true
+
+["browser_sitespecific_background_pref.js"]
+https_first_disabled = true
+
+["browser_sitespecific_image_zoom.js"]
+
+["browser_sitespecific_video_zoom.js"]
+https_first_disabled = true
+support-files = ["../../../../browser/base/content/test/general/video.webm"]
+skip-if = [
+  "os == 'win' && debug", # Bug 1315042
+]
+
+["browser_subframe_textzoom.js"]
+
+["browser_tabswitch_zoom_flicker.js"]
+https_first_disabled = true
+skip-if = [
+  "os == 'linux' && os_version == '22.04' && arch == 'x86_64' && display == 'wayland' && debug", # Bug 1652383
+  "os == 'linux' && os_version == '24.04' && arch == 'x86_64' && display == 'x11' && debug", # Bug 1652383
+  "os == 'win' && opt", # Bug 1652383
+]
+
+["browser_tooltip_zoom.js"]
+
+["browser_zoom_commands.js"]
diff --git a/src/zen/tests/mochitests/zoom/browser_background_link_zoom_reset.js b/src/zen/tests/mochitests/zoom/browser_background_link_zoom_reset.js
new file mode 100644
index 000000000..ac224cc4a
--- /dev/null
+++ b/src/zen/tests/mochitests/zoom/browser_background_link_zoom_reset.js
@@ -0,0 +1,45 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+const TEST_PAGE = "/browser/browser/base/content/test/zoom/zoom_test.html";
+var gTestTab, gBgTab, gTestZoom;
+
+function testBackgroundLoad() {
+  (async function () {
+    is(
+      ZoomManager.zoom,
+      gTestZoom,
+      "opening a background tab should not change foreground zoom"
+    );
+
+    await FullZoomHelper.removeTabAndWaitForLocationChange(gBgTab);
+
+    await FullZoom.reset();
+    await FullZoomHelper.removeTabAndWaitForLocationChange(gTestTab);
+    finish();
+  })();
+}
+
+function testInitialZoom() {
+  (async function () {
+    is(ZoomManager.zoom, 1, "initial zoom level should be 1");
+    FullZoom.enlarge();
+
+    gTestZoom = ZoomManager.zoom;
+    isnot(gTestZoom, 1, "zoom level should have changed");
+
+    gBgTab = BrowserTestUtils.addTab(gBrowser);
+    await FullZoomHelper.load(gBgTab, "http://mochi.test:8888" + TEST_PAGE);
+  })().then(testBackgroundLoad, FullZoomHelper.failAndContinue(finish));
+}
+
+function test() {
+  waitForExplicitFinish();
+
+  (async function () {
+    gTestTab = BrowserTestUtils.addTab(gBrowser);
+    await FullZoomHelper.selectTabAndWaitForLocationChange(gTestTab);
+    // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+    await FullZoomHelper.load(gTestTab, "http://example.org" + TEST_PAGE);
+  })().then(testInitialZoom, FullZoomHelper.failAndContinue(finish));
+}
diff --git a/src/zen/tests/mochitests/zoom/browser_background_zoom.js b/src/zen/tests/mochitests/zoom/browser_background_zoom.js
new file mode 100644
index 000000000..d757d8e7b
--- /dev/null
+++ b/src/zen/tests/mochitests/zoom/browser_background_zoom.js
@@ -0,0 +1,115 @@
+var gTestPage =
+  // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+  "http://example.org/browser/browser/base/content/test/zoom/zoom_test.html";
+var gTestImage =
+  // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+  "http://example.org/browser/browser/base/content/test/general/moz.png";
+var gTab1, gTab2, gTab3;
+var gLevel;
+
+function test() {
+  waitForExplicitFinish();
+  registerCleanupFunction(async () => {
+    await new Promise(resolve => {
+      ContentPrefService2.removeByName(FullZoom.name, Cu.createLoadContext(), {
+        handleCompletion: resolve,
+      });
+    });
+  });
+
+  (async function () {
+    gTab1 = BrowserTestUtils.addTab(gBrowser, gTestPage);
+    gTab2 = BrowserTestUtils.addTab(gBrowser);
+    gTab3 = BrowserTestUtils.addTab(gBrowser);
+
+    await FullZoomHelper.selectTabAndWaitForLocationChange(gTab1);
+    await FullZoomHelper.load(gTab1, gTestPage);
+    await FullZoomHelper.load(gTab2, gTestPage);
+  })().then(secondPageLoaded, FullZoomHelper.failAndContinue(finish));
+}
+
+function secondPageLoaded() {
+  (async function () {
+    FullZoomHelper.zoomTest(gTab1, 1, "Initial zoom of tab 1 should be 1");
+    FullZoomHelper.zoomTest(gTab2, 1, "Initial zoom of tab 2 should be 1");
+    FullZoomHelper.zoomTest(gTab3, 1, "Initial zoom of tab 3 should be 1");
+
+    // Now have three tabs, two with the test page, one blank. Tab 1 is selected
+    // Zoom tab 1
+    FullZoom.enlarge();
+    gLevel = ZoomManager.getZoomForBrowser(gBrowser.getBrowserForTab(gTab1));
+
+    Assert.greater(gLevel, 1, "New zoom for tab 1 should be greater than 1");
+    FullZoomHelper.zoomTest(gTab2, 1, "Zooming tab 1 should not affect tab 2");
+    FullZoomHelper.zoomTest(gTab3, 1, "Zooming tab 1 should not affect tab 3");
+
+    await FullZoomHelper.load(gTab3, gTestPage);
+  })().then(thirdPageLoaded, FullZoomHelper.failAndContinue(finish));
+}
+
+function thirdPageLoaded() {
+  (async function () {
+    FullZoomHelper.zoomTest(gTab1, gLevel, "Tab 1 should still be zoomed");
+    FullZoomHelper.zoomTest(gTab2, 1, "Tab 2 should still not be affected");
+    FullZoomHelper.zoomTest(
+      gTab3,
+      gLevel,
+      "Tab 3 should have zoomed as it was loading in the background"
+    );
+
+    // Switching to tab 2 should update its zoom setting.
+    await FullZoomHelper.selectTabAndWaitForLocationChange(gTab2);
+    FullZoomHelper.zoomTest(gTab1, gLevel, "Tab 1 should still be zoomed");
+    FullZoomHelper.zoomTest(gTab2, gLevel, "Tab 2 should be zoomed now");
+    FullZoomHelper.zoomTest(gTab3, gLevel, "Tab 3 should still be zoomed");
+
+    await FullZoomHelper.load(gTab1, gTestImage);
+  })().then(imageLoaded, FullZoomHelper.failAndContinue(finish));
+}
+
+function imageLoaded() {
+  (async function () {
+    FullZoomHelper.zoomTest(
+      gTab1,
+      1,
+      "Zoom should be 1 when image was loaded in the background"
+    );
+    await FullZoomHelper.selectTabAndWaitForLocationChange(gTab1);
+    FullZoomHelper.zoomTest(
+      gTab1,
+      1,
+      "Zoom should still be 1 when tab with image is selected"
+    );
+  })().then(imageZoomSwitch, FullZoomHelper.failAndContinue(finish));
+}
+
+function imageZoomSwitch() {
+  (async function () {
+    await FullZoomHelper.navigate(FullZoomHelper.BACK);
+    await FullZoomHelper.navigate(FullZoomHelper.FORWARD);
+    FullZoomHelper.zoomTest(
+      gTab1,
+      1,
+      "Tab 1 should not be zoomed when an image loads"
+    );
+
+    await FullZoomHelper.selectTabAndWaitForLocationChange(gTab2);
+    FullZoomHelper.zoomTest(
+      gTab1,
+      1,
+      "Tab 1 should still not be zoomed when deselected"
+    );
+  })().then(finishTest, FullZoomHelper.failAndContinue(finish));
+}
+
+var finishTestStarted = false;
+function finishTest() {
+  (async function () {
+    ok(!finishTestStarted, "finishTest called more than once");
+    finishTestStarted = true;
+    await FullZoomHelper.selectTabAndWaitForLocationChange(gTab1);
+    await FullZoomHelper.removeTabAndWaitForLocationChange(gTab1);
+    await FullZoomHelper.removeTabAndWaitForLocationChange(gTab2);
+    await FullZoomHelper.removeTabAndWaitForLocationChange(gTab3);
+  })().then(finish, FullZoomHelper.failAndContinue(finish));
+}
diff --git a/src/zen/tests/mochitests/zoom/browser_default_zoom.js b/src/zen/tests/mochitests/zoom/browser_default_zoom.js
new file mode 100644
index 000000000..d6e8e2575
--- /dev/null
+++ b/src/zen/tests/mochitests/zoom/browser_default_zoom.js
@@ -0,0 +1,149 @@
+/* Any copyright is dedicated to the Public Domain.
+ * https://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_task(async function test_init_default_zoom() {
+  const TEST_PAGE_URL =
+    "data:text/html;charset=utf-8,<body>test_init_default_zoom</body>";
+
+  // Prepare the test tab
+  info("Creating tab");
+  let tab = BrowserTestUtils.addTab(gBrowser, TEST_PAGE_URL);
+  let tabBrowser = gBrowser.getBrowserForTab(tab);
+  await FullZoomHelper.selectTabAndWaitForLocationChange(tab);
+
+  // 100% global zoom
+  info("Getting default zoom");
+  let defaultZoom = await FullZoomHelper.getGlobalValue();
+  is(defaultZoom, 1, "Global zoom is init at 100%");
+  // 100% tab zoom
+  is(
+    ZoomManager.getZoomForBrowser(tabBrowser),
+    1,
+    "Current zoom is init at 100%"
+  );
+  info("Removing tab");
+  await FullZoomHelper.removeTabAndWaitForLocationChange();
+});
+
+add_task(async function test_set_default_zoom() {
+  const TEST_PAGE_URL =
+    "data:text/html;charset=utf-8,<body>test_set_default_zoom</body>";
+
+  // Prepare the test tab
+  info("Creating tab");
+  let tab = BrowserTestUtils.addTab(gBrowser, TEST_PAGE_URL);
+  let tabBrowser = gBrowser.getBrowserForTab(tab);
+  await FullZoomHelper.selectTabAndWaitForLocationChange(tab);
+
+  // 120% global zoom
+  info("Changing default zoom");
+  await FullZoomHelper.changeDefaultZoom(120);
+  let defaultZoom = await FullZoomHelper.getGlobalValue();
+  is(defaultZoom, 1.2, "Global zoom is at 120%");
+
+  // 120% tab zoom
+  await TestUtils.waitForCondition(() => {
+    info("Current zoom is: " + ZoomManager.getZoomForBrowser(tabBrowser));
+    return ZoomManager.getZoomForBrowser(tabBrowser) == 1.2;
+  });
+  is(
+    ZoomManager.getZoomForBrowser(tabBrowser),
+    1.2,
+    "Current zoom matches changed default zoom"
+  );
+  info("Removing tab");
+  await FullZoomHelper.removeTabAndWaitForLocationChange();
+  await FullZoomHelper.changeDefaultZoom(100);
+});
+
+add_task(async function test_enlarge_reduce_reset_local_zoom() {
+  const TEST_PAGE_URL =
+    "data:text/html;charset=utf-8,<body>test_enlarge_reduce_reset_local_zoom</body>";
+
+  // Prepare the test tab
+  info("Creating tab");
+  let tab = BrowserTestUtils.addTab(gBrowser, TEST_PAGE_URL);
+  let tabBrowser = gBrowser.getBrowserForTab(tab);
+  await FullZoomHelper.selectTabAndWaitForLocationChange(tab);
+
+  // 120% global zoom
+  info("Changing default zoom");
+  await FullZoomHelper.changeDefaultZoom(120);
+  let defaultZoom = await FullZoomHelper.getGlobalValue();
+  is(defaultZoom, 1.2, "Global zoom is at 120%");
+
+  await TestUtils.waitForCondition(() => {
+    info("Current tab zoom is ", ZoomManager.getZoomForBrowser(tabBrowser));
+    return ZoomManager.getZoomForBrowser(tabBrowser) == 1.2;
+  });
+  is(
+    ZoomManager.getZoomForBrowser(tabBrowser),
+    1.2,
+    "Current tab zoom matches default zoom"
+  );
+
+  await FullZoom.enlarge();
+  info("Enlarged!");
+  defaultZoom = await FullZoomHelper.getGlobalValue();
+  info("Current global zoom is " + defaultZoom);
+
+  // 133% tab zoom
+  await TestUtils.waitForCondition(() => {
+    info("Current tab zoom is ", ZoomManager.getZoomForBrowser(tabBrowser));
+    return ZoomManager.getZoomForBrowser(tabBrowser) == 1.3;
+  });
+  is(
+    ZoomManager.getZoomForBrowser(tabBrowser),
+    1.3,
+    "Increasing zoom changes zoom of current tab."
+  );
+  defaultZoom = await FullZoomHelper.getGlobalValue();
+  // 120% global zoom
+  is(
+    defaultZoom,
+    1.2,
+    "Increasing zoom of current tab doesn't change default zoom."
+  );
+  info("Reducing...");
+  info("Current tab zoom is ", ZoomManager.getZoomForBrowser(tabBrowser));
+  await FullZoom.reduce(); // 120% tab zoom
+  info("Current tab zoom is ", ZoomManager.getZoomForBrowser(tabBrowser));
+  await FullZoom.reduce(); // 110% tab zoom
+  info("Current tab zoom is ", ZoomManager.getZoomForBrowser(tabBrowser));
+  await FullZoom.reduce(); // 100% tab zoom
+  info("Current tab zoom is ", ZoomManager.getZoomForBrowser(tabBrowser));
+
+  await TestUtils.waitForCondition(() => {
+    info("Current tab zoom is ", ZoomManager.getZoomForBrowser(tabBrowser));
+    return ZoomManager.getZoomForBrowser(tabBrowser) == 1;
+  });
+  is(
+    ZoomManager.getZoomForBrowser(tabBrowser),
+    1,
+    "Decreasing zoom changes zoom of current tab."
+  );
+  defaultZoom = await FullZoomHelper.getGlobalValue();
+  // 120% global zoom
+  is(
+    defaultZoom,
+    1.2,
+    "Decreasing zoom of current tab doesn't change default zoom."
+  );
+  info("Resetting...");
+  FullZoom.reset(); // 120% tab zoom
+  await TestUtils.waitForCondition(() => {
+    info("Current tab zoom is ", ZoomManager.getZoomForBrowser(tabBrowser));
+    return ZoomManager.getZoomForBrowser(tabBrowser) == 1.2;
+  });
+  is(
+    ZoomManager.getZoomForBrowser(tabBrowser),
+    1.2,
+    "Reseting zoom causes current tab to zoom to default zoom."
+  );
+
+  // no reset necessary, it was performed as part of the test
+  info("Removing tab");
+  await FullZoomHelper.removeTabAndWaitForLocationChange();
+});
diff --git a/src/zen/tests/mochitests/zoom/browser_default_zoom_fission.js b/src/zen/tests/mochitests/zoom/browser_default_zoom_fission.js
new file mode 100644
index 000000000..4d3d8b389
--- /dev/null
+++ b/src/zen/tests/mochitests/zoom/browser_default_zoom_fission.js
@@ -0,0 +1,114 @@
+/* Any copyright is dedicated to the Public Domain.
+ * https://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_task(async function test_sitespecific_iframe_global_zoom() {
+  const TEST_PAGE_URL =
+    'data:text/html;charset=utf-8,<body>test_sitespecific_iframe_global_zoom<iframe src=""></iframe></body>';
+  const TEST_IFRAME_URL = "https://example.com/";
+
+  // Prepare the test tab
+  console.log("Creating tab");
+  let tab = BrowserTestUtils.addTab(gBrowser, TEST_PAGE_URL);
+  let tabBrowser = gBrowser.getBrowserForTab(tab);
+  console.log("Loading tab");
+  await FullZoomHelper.selectTabAndWaitForLocationChange(tab);
+
+  // 67% global zoom
+  console.log("Changing default zoom");
+  await FullZoomHelper.changeDefaultZoom(67);
+  let defaultZoom = await FullZoomHelper.getGlobalValue();
+  is(defaultZoom, 0.67, "Global zoom is at 67%");
+  await TestUtils.waitForCondition(() => {
+    console.log("Current zoom is: ", ZoomManager.getZoomForBrowser(tabBrowser));
+    return ZoomManager.getZoomForBrowser(tabBrowser) == 0.67;
+  });
+
+  let zoomLevel = ZoomManager.getZoomForBrowser(tabBrowser).toFixed(2);
+  is(zoomLevel, "0.67", "tab zoom has been set to 67%");
+
+  let frameLoadedPromise = BrowserTestUtils.browserLoaded(
+    tabBrowser,
+    true,
+    TEST_IFRAME_URL
+  );
+  console.log("Spawinging iframe");
+  SpecialPowers.spawn(tabBrowser, [TEST_IFRAME_URL], url => {
+    content.document.querySelector("iframe").src = url;
+  });
+  console.log("Awaiting frame promise");
+  let loadedURL = await frameLoadedPromise;
+  is(loadedURL, TEST_IFRAME_URL, "got the load event for the iframe");
+
+  let frameZoom = await SpecialPowers.spawn(
+    gBrowser.selectedBrowser.browsingContext.children[0],
+    [],
+    async () => {
+      await ContentTaskUtils.waitForCondition(() => {
+        return content.docShell.browsingContext.fullZoom.toFixed(2) == 0.67;
+      });
+      return content.docShell.browsingContext.fullZoom.toFixed(2);
+    }
+  );
+
+  is(frameZoom, zoomLevel, "global zoom is reflected in iframe");
+  console.log("Removing tab");
+  await FullZoomHelper.removeTabAndWaitForLocationChange();
+});
+
+add_task(async function test_sitespecific_global_zoom_enlarge() {
+  const TEST_PAGE_URL =
+    'data:text/html;charset=utf-8,<body>test_sitespecific_global_zoom_enlarge<iframe src=""></iframe></body>';
+  const TEST_IFRAME_URL = "https://example.org/";
+
+  // Prepare the test tab
+  console.log("Adding tab");
+  let tab = BrowserTestUtils.addTab(gBrowser, TEST_PAGE_URL);
+  let tabBrowser = gBrowser.getBrowserForTab(tab);
+  console.log("Awaiting tab load");
+  await FullZoomHelper.selectTabAndWaitForLocationChange(tab);
+
+  // 67% global zoom persists from previous test
+
+  let frameLoadedPromise = BrowserTestUtils.browserLoaded(
+    tabBrowser,
+    true,
+    TEST_IFRAME_URL
+  );
+  console.log("Spawning iframe");
+  SpecialPowers.spawn(tabBrowser, [TEST_IFRAME_URL], url => {
+    content.document.querySelector("iframe").src = url;
+  });
+  console.log("Awaiting iframe load");
+  let loadedURL = await frameLoadedPromise;
+  is(loadedURL, TEST_IFRAME_URL, "got the load event for the iframe");
+  console.log("Enlarging tab");
+  await FullZoom.enlarge();
+  // 80% local zoom
+  await TestUtils.waitForCondition(() => {
+    console.log("Current zoom is: ", ZoomManager.getZoomForBrowser(tabBrowser));
+    return ZoomManager.getZoomForBrowser(tabBrowser) == 0.8;
+  });
+
+  is(
+    ZoomManager.getZoomForBrowser(tabBrowser).toFixed(2),
+    "0.80",
+    "Local zoom is increased"
+  );
+
+  let frameZoom = await SpecialPowers.spawn(
+    gBrowser.selectedBrowser.browsingContext.children[0],
+    [],
+    async () => {
+      await ContentTaskUtils.waitForCondition(() => {
+        return content.docShell.browsingContext.fullZoom.toFixed(2) == 0.8;
+      });
+      return content.docShell.browsingContext.fullZoom.toFixed(2);
+    }
+  );
+
+  is(frameZoom, "0.80", "(without fission) iframe zoom matches page zoom");
+  console.log("Removing tab");
+  await FullZoomHelper.removeTabAndWaitForLocationChange();
+});
diff --git a/src/zen/tests/mochitests/zoom/browser_default_zoom_multitab.js b/src/zen/tests/mochitests/zoom/browser_default_zoom_multitab.js
new file mode 100644
index 000000000..d20402088
--- /dev/null
+++ b/src/zen/tests/mochitests/zoom/browser_default_zoom_multitab.js
@@ -0,0 +1,190 @@
+/* Any copyright is dedicated to the Public Domain.
+ * https://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_task(async function test_multidomain_global_zoom() {
+  // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+  const TEST_PAGE_URL_1 = "http://example.com/";
+  // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+  const TEST_PAGE_URL_2 = "http://example.org/";
+
+  // Prepare the test tabs
+  console.log("Creating tab 1");
+  let tab1 = BrowserTestUtils.addTab(gBrowser, TEST_PAGE_URL_1);
+  let tabBrowser1 = gBrowser.getBrowserForTab(tab1);
+  await FullZoomHelper.selectTabAndWaitForLocationChange(tab1);
+
+  console.log("Creating tab 2");
+  let tab2 = BrowserTestUtils.addTab(gBrowser, TEST_PAGE_URL_2);
+  let tabBrowser2 = gBrowser.getBrowserForTab(tab2);
+  await FullZoomHelper.selectTabAndWaitForLocationChange(tab2);
+
+  // 67% global zoom
+  console.log("Changing default zoom");
+  await FullZoomHelper.changeDefaultZoom(67);
+  let defaultZoom = await FullZoomHelper.getGlobalValue();
+  is(defaultZoom, 0.67, "Global zoom is set to 67%");
+
+  // 67% local zoom tab 1
+  console.log("Selecting tab 1");
+  await FullZoomHelper.selectTabAndWaitForLocationChange(tab1);
+  await TestUtils.waitForCondition(() => {
+    console.log(
+      "Currnet zoom is: ",
+      ZoomManager.getZoomForBrowser(tabBrowser1)
+    );
+    return ZoomManager.getZoomForBrowser(tabBrowser1) == 0.67;
+  });
+  is(
+    ZoomManager.getZoomForBrowser(tabBrowser1),
+    0.67,
+    "Setting default zoom causes tab 1 (background) to zoom to default zoom."
+  );
+
+  // 67% local zoom tab 2
+  console.log("Selecting tab 2");
+  await FullZoomHelper.selectTabAndWaitForLocationChange(tab2);
+  await TestUtils.waitForCondition(() => {
+    console.log(
+      "Current zoom is: ",
+      ZoomManager.getZoomForBrowser(tabBrowser2)
+    );
+    return ZoomManager.getZoomForBrowser(tabBrowser2) == 0.67;
+  });
+  is(
+    ZoomManager.getZoomForBrowser(tabBrowser2),
+    0.67,
+    "Setting default zoom causes tab 2 (foreground) to zoom to default zoom."
+  );
+  console.log("Enlarging tab");
+  await FullZoom.enlarge();
+  // 80% local zoom tab 2
+  await TestUtils.waitForCondition(() => {
+    console.log(
+      "Current zoom is: ",
+      ZoomManager.getZoomForBrowser(tabBrowser2)
+    );
+    return ZoomManager.getZoomForBrowser(tabBrowser2) == 0.8;
+  });
+  is(
+    ZoomManager.getZoomForBrowser(tabBrowser2),
+    0.8,
+    "Enlarging local zoom of tab 2."
+  );
+
+  // 67% local zoom tab 1
+  console.log("Selecting tab 1");
+  await FullZoomHelper.selectTabAndWaitForLocationChange(tab1);
+  await TestUtils.waitForCondition(() => {
+    console.log(
+      "Current zoom is: ",
+      ZoomManager.getZoomForBrowser(tabBrowser1)
+    );
+    return ZoomManager.getZoomForBrowser(tabBrowser1) == 0.67;
+  });
+  is(
+    ZoomManager.getZoomForBrowser(tabBrowser1),
+    0.67,
+    "Tab 1 is unchanged by tab 2's enlarge call."
+  );
+  console.log("Removing tab");
+  await FullZoomHelper.removeTabAndWaitForLocationChange();
+  console.log("Removing tab");
+  await FullZoomHelper.removeTabAndWaitForLocationChange();
+});
+
+add_task(async function test_site_specific_global_zoom() {
+  // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+  const TEST_PAGE_URL_1 = "http://example.net/";
+  // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+  const TEST_PAGE_URL_2 = "http://example.net/";
+
+  // Prepare the test tabs
+  console.log("Adding tab 1");
+  let tab1 = BrowserTestUtils.addTab(gBrowser, TEST_PAGE_URL_1);
+  console.log("Getting tab 1 browser");
+  let tabBrowser1 = gBrowser.getBrowserForTab(tab1);
+  await FullZoomHelper.selectTabAndWaitForLocationChange(tab1);
+
+  console.log("Adding tab 2");
+  let tab2 = BrowserTestUtils.addTab(gBrowser, TEST_PAGE_URL_2);
+  console.log("Getting tab 2 browser");
+  let tabBrowser2 = gBrowser.getBrowserForTab(tab2);
+  await FullZoomHelper.selectTabAndWaitForLocationChange(tab2);
+
+  console.log("checking global zoom");
+  // 67% global zoom persists from previous test
+  let defaultZoom = await FullZoomHelper.getGlobalValue();
+  is(defaultZoom, 0.67, "Default zoom is 67%");
+
+  // 67% local zoom tab 1
+  console.log("Selecting tab 1");
+  await FullZoomHelper.selectTabAndWaitForLocationChange(tab1);
+  console.log("Awaiting condition");
+  await TestUtils.waitForCondition(() => {
+    console.log(
+      "Current tab 1 zoom is: ",
+      ZoomManager.getZoomForBrowser(tabBrowser1)
+    );
+    return ZoomManager.getZoomForBrowser(tabBrowser1) == 0.67;
+  });
+  is(
+    ZoomManager.getZoomForBrowser(tabBrowser1),
+    0.67,
+    "Setting default zoom causes tab 1 (background) to zoom to default zoom."
+  );
+
+  // 67% local zoom tab 2
+  console.log("Selecting tab 2");
+  await FullZoomHelper.selectTabAndWaitForLocationChange(tab2);
+  console.log("Awaiting condition");
+  await TestUtils.waitForCondition(() => {
+    console.log(
+      "Current tab 2 zoom is: ",
+      ZoomManager.getZoomForBrowser(tabBrowser2)
+    );
+    return ZoomManager.getZoomForBrowser(tabBrowser2) == 0.67;
+  });
+  is(
+    ZoomManager.getZoomForBrowser(tabBrowser2),
+    0.67,
+    "Setting default zoom causes tab 2 (foreground) to zoom to default zoom."
+  );
+
+  // 80% site specific zoom
+  console.log("Selecting tab 1");
+  await FullZoomHelper.selectTabAndWaitForLocationChange(tab1);
+  console.log("Enlarging");
+  await FullZoom.enlarge();
+  await TestUtils.waitForCondition(() => {
+    console.log(
+      "Current tab 1 zoom is: ",
+      ZoomManager.getZoomForBrowser(tabBrowser1)
+    );
+    return ZoomManager.getZoomForBrowser(tabBrowser1) == 0.8;
+  });
+  is(
+    ZoomManager.getZoomForBrowser(tabBrowser1),
+    0.8,
+    "Changed local zoom in tab one."
+  );
+  console.log("Selecting tab 2");
+  await FullZoomHelper.selectTabAndWaitForLocationChange(tab2);
+  await TestUtils.waitForCondition(() => {
+    console.log(
+      "Current tab 2 zoom is: ",
+      ZoomManager.getZoomForBrowser(tabBrowser2)
+    );
+    return ZoomManager.getZoomForBrowser(tabBrowser2) == 0.8;
+  });
+  is(
+    ZoomManager.getZoomForBrowser(tabBrowser2),
+    0.8,
+    "Second tab respects site specific zoom."
+  );
+  console.log("Removing tab");
+  await FullZoomHelper.removeTabAndWaitForLocationChange();
+  console.log("Removing tab");
+  await FullZoomHelper.removeTabAndWaitForLocationChange();
+});
diff --git a/src/zen/tests/mochitests/zoom/browser_default_zoom_sitespecific.js b/src/zen/tests/mochitests/zoom/browser_default_zoom_sitespecific.js
new file mode 100644
index 000000000..212df6579
--- /dev/null
+++ b/src/zen/tests/mochitests/zoom/browser_default_zoom_sitespecific.js
@@ -0,0 +1,108 @@
+/* Any copyright is dedicated to the Public Domain.
+ * https://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_task(async function test_disabled_ss_multi() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.zoom.siteSpecific", false]],
+  });
+  const TEST_PAGE_URL = "https://example.org/";
+
+  // Prepare the test tabs
+  let tab2 = BrowserTestUtils.addTab(gBrowser, TEST_PAGE_URL);
+  let tabBrowser2 = gBrowser.getBrowserForTab(tab2);
+  let isLoaded = BrowserTestUtils.browserLoaded(
+    tabBrowser2,
+    false,
+    TEST_PAGE_URL
+  );
+  await FullZoomHelper.selectTabAndWaitForLocationChange(tab2);
+  await isLoaded;
+
+  let zoomLevel = ZoomManager.getZoomForBrowser(tabBrowser2);
+  is(zoomLevel, 1, "tab 2 zoom has been set to 100%");
+
+  let tab1 = BrowserTestUtils.addTab(gBrowser, TEST_PAGE_URL);
+  let tabBrowser1 = gBrowser.getBrowserForTab(tab1);
+  isLoaded = BrowserTestUtils.browserLoaded(tabBrowser1, false, TEST_PAGE_URL);
+  await FullZoomHelper.selectTabAndWaitForLocationChange(tab1);
+  await isLoaded;
+
+  zoomLevel = ZoomManager.getZoomForBrowser(tabBrowser1);
+  is(zoomLevel, 1, "tab 1 zoom has been set to 100%");
+
+  // 70% global zoom
+  await FullZoomHelper.changeDefaultZoom(70);
+  let defaultZoom = await FullZoomHelper.getGlobalValue();
+  is(defaultZoom, 0.7, "Global zoom is at 70%");
+
+  await TestUtils.waitForCondition(
+    () => ZoomManager.getZoomForBrowser(tabBrowser1) == 0.7
+  );
+  zoomLevel = ZoomManager.getZoomForBrowser(tabBrowser1);
+  is(zoomLevel, 0.7, "tab 1 zoom has been set to 70%");
+
+  await FullZoom.enlarge();
+
+  zoomLevel = ZoomManager.getZoomForBrowser(tabBrowser1);
+  is(zoomLevel, 0.8, "tab 1 zoom has been set to 80%");
+
+  await FullZoomHelper.selectTabAndWaitForLocationChange(tab2);
+  zoomLevel = ZoomManager.getZoomForBrowser(tabBrowser2);
+  is(zoomLevel, 1, "tab 2 zoom remains 100%");
+
+  let tab3 = BrowserTestUtils.addTab(gBrowser, TEST_PAGE_URL);
+  let tabBrowser3 = gBrowser.getBrowserForTab(tab3);
+  isLoaded = BrowserTestUtils.browserLoaded(tabBrowser3, false, TEST_PAGE_URL);
+  await FullZoomHelper.selectTabAndWaitForLocationChange(tab3);
+  await isLoaded;
+
+  zoomLevel = ZoomManager.getZoomForBrowser(tabBrowser3);
+  is(zoomLevel, 0.7, "tab 3 zoom has been set to 70%");
+
+  await FullZoomHelper.removeTabAndWaitForLocationChange();
+  await FullZoomHelper.removeTabAndWaitForLocationChange();
+  await FullZoomHelper.removeTabAndWaitForLocationChange();
+});
+
+add_task(async function test_disabled_ss_custom() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.zoom.siteSpecific", false]],
+  });
+  const TEST_PAGE_URL = "https://example.org/";
+
+  // 150% global zoom
+  await FullZoomHelper.changeDefaultZoom(150);
+  let defaultZoom = await FullZoomHelper.getGlobalValue();
+  is(defaultZoom, 1.5, "Global zoom is at 150%");
+
+  // Prepare test tab
+  let tab1 = BrowserTestUtils.addTab(gBrowser, TEST_PAGE_URL);
+  let tabBrowser1 = gBrowser.getBrowserForTab(tab1);
+  let isLoaded = BrowserTestUtils.browserLoaded(
+    tabBrowser1,
+    false,
+    TEST_PAGE_URL
+  );
+  await FullZoomHelper.selectTabAndWaitForLocationChange(tab1);
+  await isLoaded;
+
+  await TestUtils.waitForCondition(
+    () => ZoomManager.getZoomForBrowser(tabBrowser1) == 1.5
+  );
+  let zoomLevel = ZoomManager.getZoomForBrowser(tabBrowser1);
+  is(zoomLevel, 1.5, "tab 1 zoom has been set to 150%");
+
+  await FullZoom.enlarge();
+
+  zoomLevel = ZoomManager.getZoomForBrowser(tabBrowser1);
+  is(zoomLevel, 1.6, "tab 1 zoom has been set to 160%");
+
+  await BrowserTestUtils.reloadTab(tab1);
+
+  zoomLevel = ZoomManager.getZoomForBrowser(tabBrowser1);
+  is(zoomLevel, 1.6, "tab 1 zoom remains 160%");
+
+  await FullZoomHelper.removeTabAndWaitForLocationChange();
+});
diff --git a/src/zen/tests/mochitests/zoom/browser_image_zoom_tabswitch.js b/src/zen/tests/mochitests/zoom/browser_image_zoom_tabswitch.js
new file mode 100644
index 000000000..b2357d813
--- /dev/null
+++ b/src/zen/tests/mochitests/zoom/browser_image_zoom_tabswitch.js
@@ -0,0 +1,41 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+function test() {
+  let tab1, tab2;
+  const TEST_IMAGE =
+    // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+    "http://example.org/browser/browser/base/content/test/general/moz.png";
+
+  waitForExplicitFinish();
+
+  (async function () {
+    tab1 = BrowserTestUtils.addTab(gBrowser);
+    tab2 = BrowserTestUtils.addTab(gBrowser);
+    await FullZoomHelper.selectTabAndWaitForLocationChange(tab1);
+    await FullZoomHelper.load(tab1, TEST_IMAGE);
+
+    is(ZoomManager.zoom, 1, "initial zoom level for first should be 1");
+
+    await FullZoom.enlarge(tab1.linkedBrowser);
+    let zoom = ZoomManager.zoom;
+    isnot(zoom, 1, "zoom level should have changed");
+
+    await FullZoomHelper.selectTabAndWaitForLocationChange(tab2);
+    is(ZoomManager.zoom, 1, "initial zoom level for second tab should be 1");
+
+    await FullZoomHelper.selectTabAndWaitForLocationChange(tab1);
+    is(
+      ZoomManager.zoom,
+      zoom,
+      "zoom level for first tab should not have changed"
+    );
+
+    await FullZoom.reset(tab1.linkedBrowser);
+
+    await FullZoomHelper.removeTabAndWaitForLocationChange(tab1);
+    await FullZoomHelper.removeTabAndWaitForLocationChange(tab2);
+  })().then(finish, FullZoomHelper.failAndContinue(finish));
+}
diff --git a/src/zen/tests/mochitests/zoom/browser_keyboard_mousewheel_zoom_consistency.js b/src/zen/tests/mochitests/zoom/browser_keyboard_mousewheel_zoom_consistency.js
new file mode 100644
index 000000000..bf278dc66
--- /dev/null
+++ b/src/zen/tests/mochitests/zoom/browser_keyboard_mousewheel_zoom_consistency.js
@@ -0,0 +1,123 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const TEST_PAGE_URL =
+  "data:text/html;charset=utf-8,<body>test_keyboard_mousewheel_consistency</body>";
+
+const WHEEL_ZOOM_IN = -1;
+const WHEEL_ZOOM_OUT = 1;
+
+/**
+ * Tests that keyboard zoom (Ctrl+/- keys) and mouse wheel zoom (Ctrl+wheel)
+ * step through the same predefined zoom levels consistently, ensuring both
+ * methods can reach all standard zoom levels including 100%.
+ */
+
+async function synthesizeMouseWheelZoom(browser, direction, expectedZoom) {
+  await BrowserTestUtils.synthesizeMouse(
+    null,
+    10,
+    10,
+    {
+      wheel: true,
+      ctrlKey: true,
+      deltaY: direction,
+      deltaMode: WheelEvent.DOM_DELTA_LINE,
+    },
+    browser
+  );
+
+  await TestUtils.waitForCondition(
+    () => {
+      return ZoomManager.getZoomForBrowser(browser) == expectedZoom;
+    },
+    `Waiting for mousewheel zoom to ${expectedZoom * 100}%`
+  );
+}
+
+add_task(async function test_keyboard_mousewheel_zoom_consistency() {
+  // One some platforms, Ctrl-Wheel doesn't zoom by default, so we'll enable
+  // that for this test.
+  await SpecialPowers.pushPrefEnv({
+    set: [["mousewheel.with_control.action", 3]],
+  });
+
+  await BrowserTestUtils.withNewTab(TEST_PAGE_URL, async browser => {
+    let currentZoom = ZoomManager.getZoomForBrowser(browser);
+    Assert.equal(currentZoom, 1, "Initial zoom should be 100%");
+
+    await FullZoom.enlarge();
+    Assert.equal(
+      ZoomManager.getZoomForBrowser(browser),
+      1.1,
+      "First enlarge should go to 110%"
+    );
+
+    await FullZoom.enlarge();
+    Assert.equal(
+      ZoomManager.getZoomForBrowser(browser),
+      1.2,
+      "Second enlarge should go to 120%"
+    );
+
+    await FullZoom.enlarge();
+    Assert.equal(
+      ZoomManager.getZoomForBrowser(browser),
+      1.3,
+      "Third enlarge should go to 130%"
+    );
+
+    await synthesizeMouseWheelZoom(browser, WHEEL_ZOOM_OUT, 1.2);
+    await synthesizeMouseWheelZoom(browser, WHEEL_ZOOM_OUT, 1.1);
+    await synthesizeMouseWheelZoom(browser, WHEEL_ZOOM_OUT, 1);
+
+    Assert.equal(
+      ZoomManager.getZoomForBrowser(browser),
+      1,
+      "Should return to 100% after zooming out from 133%"
+    );
+
+    await synthesizeMouseWheelZoom(browser, WHEEL_ZOOM_OUT, 0.9);
+
+    Assert.equal(
+      ZoomManager.getZoomForBrowser(browser),
+      0.9,
+      "Should be at 90% after one more zoom out"
+    );
+
+    await synthesizeMouseWheelZoom(browser, WHEEL_ZOOM_IN, 1);
+    await synthesizeMouseWheelZoom(browser, WHEEL_ZOOM_IN, 1.1);
+    await synthesizeMouseWheelZoom(browser, WHEEL_ZOOM_IN, 1.2);
+
+    Assert.equal(
+      ZoomManager.getZoomForBrowser(browser),
+      1.2,
+      "Should be at 120% after zooming back in with wheel"
+    );
+
+    await FullZoom.reduce();
+    Assert.equal(
+      ZoomManager.getZoomForBrowser(browser),
+      1.1,
+      "First keyboard reduce should go to 110%"
+    );
+
+    await FullZoom.reduce();
+    Assert.equal(
+      ZoomManager.getZoomForBrowser(browser),
+      1,
+      "Second keyboard reduce should go to 100%"
+    );
+
+    await FullZoom.reduce();
+    Assert.equal(
+      ZoomManager.getZoomForBrowser(browser),
+      0.9,
+      "Third keyboard reduce should go to 90%"
+    );
+
+    await FullZoom.reset();
+  });
+});
diff --git a/src/zen/tests/mochitests/zoom/browser_mousewheel_zoom.js b/src/zen/tests/mochitests/zoom/browser_mousewheel_zoom.js
new file mode 100644
index 000000000..a814f1dba
--- /dev/null
+++ b/src/zen/tests/mochitests/zoom/browser_mousewheel_zoom.js
@@ -0,0 +1,72 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+const TEST_PAGE =
+  // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+  "http://example.org/browser/browser/base/content/test/zoom/zoom_test.html";
+
+var gTab1, gTab2, gLevel1;
+
+function test() {
+  waitForExplicitFinish();
+
+  // Scroll on Ctrl + mousewheel
+  SpecialPowers.pushPrefEnv({ set: [["mousewheel.with_control.action", 3]] });
+
+  (async function () {
+    gTab1 = BrowserTestUtils.addTab(gBrowser);
+    gTab2 = BrowserTestUtils.addTab(gBrowser);
+
+    await FullZoomHelper.selectTabAndWaitForLocationChange(gTab1);
+    await FullZoomHelper.load(gTab1, TEST_PAGE);
+    await FullZoomHelper.load(gTab2, TEST_PAGE);
+  })().then(zoomTab1, FullZoomHelper.failAndContinue(finish));
+}
+
+function zoomTab1() {
+  (async function () {
+    is(gBrowser.selectedTab, gTab1, "Tab 1 is selected");
+    FullZoomHelper.zoomTest(gTab1, 1, "Initial zoom of tab 1 should be 1");
+    FullZoomHelper.zoomTest(gTab2, 1, "Initial zoom of tab 2 should be 1");
+
+    let browser1 = gBrowser.getBrowserForTab(gTab1);
+    await BrowserTestUtils.synthesizeMouse(
+      null,
+      10,
+      10,
+      {
+        wheel: true,
+        ctrlKey: true,
+        deltaY: -1,
+        deltaMode: WheelEvent.DOM_DELTA_LINE,
+      },
+      browser1
+    );
+
+    info("Waiting for tab 1 to be zoomed");
+    await TestUtils.waitForCondition(() => {
+      gLevel1 = ZoomManager.getZoomForBrowser(browser1);
+      return gLevel1 > 1;
+    });
+
+    await FullZoomHelper.selectTabAndWaitForLocationChange(gTab2);
+    FullZoomHelper.zoomTest(
+      gTab2,
+      gLevel1,
+      "Tab 2 should have zoomed along with tab 1"
+    );
+  })().then(finishTest, FullZoomHelper.failAndContinue(finish));
+}
+
+function finishTest() {
+  (async function () {
+    await FullZoomHelper.selectTabAndWaitForLocationChange(gTab1);
+    await FullZoom.reset();
+    await FullZoomHelper.removeTabAndWaitForLocationChange(gTab1);
+    await FullZoomHelper.selectTabAndWaitForLocationChange(gTab2);
+    await FullZoom.reset();
+    await FullZoomHelper.removeTabAndWaitForLocationChange(gTab2);
+  })().then(finish, FullZoomHelper.failAndContinue(finish));
+}
diff --git a/src/zen/tests/mochitests/zoom/browser_sitespecific_background_pref.js b/src/zen/tests/mochitests/zoom/browser_sitespecific_background_pref.js
new file mode 100644
index 000000000..5756c4d8d
--- /dev/null
+++ b/src/zen/tests/mochitests/zoom/browser_sitespecific_background_pref.js
@@ -0,0 +1,35 @@
+function test() {
+  waitForExplicitFinish();
+
+  (async function () {
+    let testPage =
+      // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+      "http://example.org/browser/browser/base/content/test/zoom/zoom_test.html";
+    let tab1 = BrowserTestUtils.addTab(gBrowser);
+    await FullZoomHelper.selectTabAndWaitForLocationChange(tab1);
+    await FullZoomHelper.load(tab1, testPage);
+
+    let tab2 = BrowserTestUtils.addTab(gBrowser);
+    await FullZoomHelper.load(tab2, testPage);
+
+    await FullZoom.enlarge();
+    let tab1Zoom = ZoomManager.getZoomForBrowser(tab1.linkedBrowser);
+
+    await FullZoomHelper.selectTabAndWaitForLocationChange(tab2);
+    let tab2Zoom = ZoomManager.getZoomForBrowser(tab2.linkedBrowser);
+    is(tab2Zoom, tab1Zoom, "Zoom should affect background tabs");
+
+    Services.prefs.setBoolPref("browser.zoom.updateBackgroundTabs", false);
+    await FullZoom.reset();
+    gBrowser.selectedTab = tab1;
+    tab1Zoom = ZoomManager.getZoomForBrowser(tab1.linkedBrowser);
+    tab2Zoom = ZoomManager.getZoomForBrowser(tab2.linkedBrowser);
+    isnot(tab1Zoom, tab2Zoom, "Zoom should not affect background tabs");
+
+    if (Services.prefs.prefHasUserValue("browser.zoom.updateBackgroundTabs")) {
+      Services.prefs.clearUserPref("browser.zoom.updateBackgroundTabs");
+    }
+    await FullZoomHelper.removeTabAndWaitForLocationChange(tab1);
+    await FullZoomHelper.removeTabAndWaitForLocationChange(tab2);
+  })().then(finish, FullZoomHelper.failAndContinue(finish));
+}
diff --git a/src/zen/tests/mochitests/zoom/browser_sitespecific_image_zoom.js b/src/zen/tests/mochitests/zoom/browser_sitespecific_image_zoom.js
new file mode 100644
index 000000000..fae454fd0
--- /dev/null
+++ b/src/zen/tests/mochitests/zoom/browser_sitespecific_image_zoom.js
@@ -0,0 +1,52 @@
+var tabElm, zoomLevel;
+function start_test_prefNotSet() {
+  (async function () {
+    is(ZoomManager.zoom, 1, "initial zoom level should be 1");
+    FullZoom.enlarge();
+
+    // capture the zoom level to test later
+    zoomLevel = ZoomManager.zoom;
+    isnot(zoomLevel, 1, "zoom level should have changed");
+
+    await FullZoomHelper.load(
+      gBrowser.selectedTab,
+      "http://mochi.test:8888/browser/browser/base/content/test/general/moz.png"
+    );
+  })().then(continue_test_prefNotSet, FullZoomHelper.failAndContinue(finish));
+}
+
+function continue_test_prefNotSet() {
+  (async function () {
+    is(ZoomManager.zoom, 1, "zoom level pref should not apply to an image");
+    await FullZoom.reset();
+
+    await FullZoomHelper.load(
+      gBrowser.selectedTab,
+      "http://mochi.test:8888/browser/browser/base/content/test/zoom/zoom_test.html"
+    );
+  })().then(end_test_prefNotSet, FullZoomHelper.failAndContinue(finish));
+}
+
+function end_test_prefNotSet() {
+  (async function () {
+    is(ZoomManager.zoom, zoomLevel, "the zoom level should have persisted");
+
+    // Reset the zoom so that other tests have a fresh zoom level
+    await FullZoom.reset();
+    await FullZoomHelper.removeTabAndWaitForLocationChange();
+    finish();
+  })();
+}
+
+function test() {
+  waitForExplicitFinish();
+
+  (async function () {
+    tabElm = BrowserTestUtils.addTab(gBrowser);
+    await FullZoomHelper.selectTabAndWaitForLocationChange(tabElm);
+    await FullZoomHelper.load(
+      tabElm,
+      "http://mochi.test:8888/browser/browser/base/content/test/zoom/zoom_test.html"
+    );
+  })().then(start_test_prefNotSet, FullZoomHelper.failAndContinue(finish));
+}
diff --git a/src/zen/tests/mochitests/zoom/browser_sitespecific_video_zoom.js b/src/zen/tests/mochitests/zoom/browser_sitespecific_video_zoom.js
new file mode 100644
index 000000000..94fd0dee5
--- /dev/null
+++ b/src/zen/tests/mochitests/zoom/browser_sitespecific_video_zoom.js
@@ -0,0 +1,128 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+const TEST_PAGE =
+  // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+  "http://example.org/browser/browser/base/content/test/zoom/zoom_test.html";
+const TEST_VIDEO =
+  // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+  "http://example.org/browser/browser/base/content/test/general/video.webm";
+
+var gTab1, gTab2, gLevel1;
+
+function test() {
+  waitForExplicitFinish();
+
+  (async function () {
+    gTab1 = BrowserTestUtils.addTab(gBrowser);
+    gTab2 = BrowserTestUtils.addTab(gBrowser);
+
+    await FullZoomHelper.selectTabAndWaitForLocationChange(gTab1);
+    await FullZoomHelper.load(gTab1, TEST_PAGE);
+    await FullZoomHelper.load(gTab2, TEST_VIDEO);
+  })().then(zoomTab1, FullZoomHelper.failAndContinue(finish));
+}
+
+function zoomTab1() {
+  (async function () {
+    is(gBrowser.selectedTab, gTab1, "Tab 1 is selected");
+
+    // Reset zoom level if we run this test > 1 time in same browser session.
+    var level1 = ZoomManager.getZoomForBrowser(
+      gBrowser.getBrowserForTab(gTab1)
+    );
+    if (level1 > 1) {
+      FullZoom.reduce();
+    }
+
+    FullZoomHelper.zoomTest(gTab1, 1, "Initial zoom of tab 1 should be 1");
+    FullZoomHelper.zoomTest(gTab2, 1, "Initial zoom of tab 2 should be 1");
+
+    FullZoom.enlarge();
+    gLevel1 = ZoomManager.getZoomForBrowser(gBrowser.getBrowserForTab(gTab1));
+
+    Assert.greater(gLevel1, 1, "New zoom for tab 1 should be greater than 1");
+    FullZoomHelper.zoomTest(gTab2, 1, "Zooming tab 1 should not affect tab 2");
+
+    await FullZoomHelper.selectTabAndWaitForLocationChange(gTab2);
+    FullZoomHelper.zoomTest(
+      gTab2,
+      1,
+      "Tab 2 is still unzoomed after it is selected"
+    );
+    FullZoomHelper.zoomTest(gTab1, gLevel1, "Tab 1 is still zoomed");
+  })().then(zoomTab2, FullZoomHelper.failAndContinue(finish));
+}
+
+function zoomTab2() {
+  (async function () {
+    is(gBrowser.selectedTab, gTab2, "Tab 2 is selected");
+
+    FullZoom.reduce();
+    let level2 = ZoomManager.getZoomForBrowser(
+      gBrowser.getBrowserForTab(gTab2)
+    );
+
+    Assert.less(level2, 1, "New zoom for tab 2 should be less than 1");
+    FullZoomHelper.zoomTest(
+      gTab1,
+      gLevel1,
+      "Zooming tab 2 should not affect tab 1"
+    );
+
+    await FullZoomHelper.selectTabAndWaitForLocationChange(gTab1);
+    FullZoomHelper.zoomTest(
+      gTab1,
+      gLevel1,
+      "Tab 1 should have the same zoom after it's selected"
+    );
+  })().then(testNavigation, FullZoomHelper.failAndContinue(finish));
+}
+
+function testNavigation() {
+  (async function () {
+    await FullZoomHelper.load(gTab1, TEST_VIDEO);
+    FullZoomHelper.zoomTest(
+      gTab1,
+      1,
+      "Zoom should be 1 when a video was loaded"
+    );
+    await waitForNextTurn(); // trying to fix orange bug 806046
+    await FullZoomHelper.navigate(FullZoomHelper.BACK);
+    FullZoomHelper.zoomTest(
+      gTab1,
+      gLevel1,
+      "Zoom should be restored when a page is loaded"
+    );
+    await waitForNextTurn(); // trying to fix orange bug 806046
+    await FullZoomHelper.navigate(FullZoomHelper.FORWARD);
+    FullZoomHelper.zoomTest(
+      gTab1,
+      1,
+      "Zoom should be 1 again when navigating back to a video"
+    );
+  })().then(finishTest, FullZoomHelper.failAndContinue(finish));
+}
+
+function waitForNextTurn() {
+  return new Promise(resolve => {
+    setTimeout(() => resolve(), 0);
+  });
+}
+
+var finishTestStarted = false;
+function finishTest() {
+  (async function () {
+    ok(!finishTestStarted, "finishTest called more than once");
+    finishTestStarted = true;
+
+    await FullZoomHelper.selectTabAndWaitForLocationChange(gTab1);
+    await FullZoom.reset();
+    await FullZoomHelper.removeTabAndWaitForLocationChange(gTab1);
+    await FullZoomHelper.selectTabAndWaitForLocationChange(gTab2);
+    await FullZoom.reset();
+    await FullZoomHelper.removeTabAndWaitForLocationChange(gTab2);
+  })().then(finish, FullZoomHelper.failAndContinue(finish));
+}
diff --git a/src/zen/tests/mochitests/zoom/browser_subframe_textzoom.js b/src/zen/tests/mochitests/zoom/browser_subframe_textzoom.js
new file mode 100644
index 000000000..e5d40cf58
--- /dev/null
+++ b/src/zen/tests/mochitests/zoom/browser_subframe_textzoom.js
@@ -0,0 +1,52 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * Test the fix for bug 441778 to ensure site-specific page zoom doesn't get
+ * modified by sub-document loads of content from a different domain.
+ */
+
+function test() {
+  waitForExplicitFinish();
+
+  const TEST_PAGE_URL = 'data:text/html,<body><iframe src=""></iframe></body>';
+  // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+  const TEST_IFRAME_URL = "http://test2.example.org/";
+
+  (async function () {
+    // Prepare the test tab
+    let tab = BrowserTestUtils.addTab(gBrowser);
+    await FullZoomHelper.selectTabAndWaitForLocationChange(tab);
+
+    let testBrowser = tab.linkedBrowser;
+
+    await FullZoomHelper.load(tab, TEST_PAGE_URL);
+
+    // Change the zoom level and then save it so we can compare it to the level
+    // after loading the sub-document.
+    FullZoom.enlarge();
+    var zoomLevel = ZoomManager.zoom;
+
+    // Start the sub-document load.
+    await new Promise(resolve => {
+      executeSoon(function () {
+        BrowserTestUtils.browserLoaded(testBrowser, true).then(url => {
+          is(url, TEST_IFRAME_URL, "got the load event for the iframe");
+          is(
+            ZoomManager.zoom,
+            zoomLevel,
+            "zoom is retained after sub-document load"
+          );
+
+          FullZoomHelper.removeTabAndWaitForLocationChange().then(() =>
+            resolve()
+          );
+        });
+        SpecialPowers.spawn(testBrowser, [TEST_IFRAME_URL], url => {
+          content.document.querySelector("iframe").src = url;
+        });
+      });
+    });
+  })().then(finish, FullZoomHelper.failAndContinue(finish));
+}
diff --git a/src/zen/tests/mochitests/zoom/browser_tabswitch_zoom_flicker.js b/src/zen/tests/mochitests/zoom/browser_tabswitch_zoom_flicker.js
new file mode 100644
index 000000000..df1c3816a
--- /dev/null
+++ b/src/zen/tests/mochitests/zoom/browser_tabswitch_zoom_flicker.js
@@ -0,0 +1,45 @@
+var tab;
+
+function test() {
+  // ----------
+  // Test setup
+
+  waitForExplicitFinish();
+
+  Services.prefs.setBoolPref("browser.zoom.updateBackgroundTabs", true);
+  Services.prefs.setBoolPref("browser.zoom.siteSpecific", true);
+
+  let uri =
+    // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+    "http://example.org/browser/browser/base/content/test/zoom/zoom_test.html";
+
+  (async function () {
+    tab = BrowserTestUtils.addTab(gBrowser);
+    await FullZoomHelper.load(tab, uri);
+
+    // -------------------------------------------------------------------
+    // Test - Trigger a tab switch that should update the zoom level
+    await FullZoomHelper.selectTabAndWaitForLocationChange(tab);
+    ok(true, "applyPrefToSetting was called");
+  })().then(endTest, FullZoomHelper.failAndContinue(endTest));
+}
+
+// -------------
+// Test clean-up
+function endTest() {
+  (async function () {
+    await FullZoomHelper.removeTabAndWaitForLocationChange(tab);
+
+    tab = null;
+
+    if (Services.prefs.prefHasUserValue("browser.zoom.updateBackgroundTabs")) {
+      Services.prefs.clearUserPref("browser.zoom.updateBackgroundTabs");
+    }
+
+    if (Services.prefs.prefHasUserValue("browser.zoom.siteSpecific")) {
+      Services.prefs.clearUserPref("browser.zoom.siteSpecific");
+    }
+
+    finish();
+  })();
+}
diff --git a/src/zen/tests/mochitests/zoom/browser_tooltip_zoom.js b/src/zen/tests/mochitests/zoom/browser_tooltip_zoom.js
new file mode 100644
index 000000000..f7627b174
--- /dev/null
+++ b/src/zen/tests/mochitests/zoom/browser_tooltip_zoom.js
@@ -0,0 +1,41 @@
+add_task(async function test_zoom_tooltip() {
+  const TEST_PAGE_URL = 'data:text/html,<html title="tooltiptext">';
+  await BrowserTestUtils.withNewTab(TEST_PAGE_URL, async function (browser) {
+    FullZoom.setZoom(2.0, browser);
+
+    const tooltip = document.getElementById("remoteBrowserTooltip");
+    const popupShown = new Promise(resolve => {
+      tooltip.addEventListener("popupshown", resolve, { once: true });
+    });
+
+    // Fire a mousemove to trigger the tooltip.
+    // Margin from the anchor and stuff depends on the platform, but these
+    // should be big enough so that all platforms pass, but not big enough so
+    // that it'd pass even when messing up the coordinates would.
+    const DISTANCE = 300;
+    const EPSILON = 25;
+
+    EventUtils.synthesizeMouse(browser, DISTANCE, DISTANCE, {
+      type: "mousemove",
+    });
+
+    await popupShown;
+    ok(
+      true,
+      `popup should be shown (coords: ${tooltip.screenX}, ${tooltip.screenY})`
+    );
+
+    isfuzzy(
+      tooltip.screenX,
+      browser.screenX + DISTANCE,
+      EPSILON,
+      "Should be at the right x position, more or less"
+    );
+    isfuzzy(
+      tooltip.screenY,
+      browser.screenY + DISTANCE,
+      EPSILON,
+      "Should be at the right y position, more or less"
+    );
+  });
+});
diff --git a/src/zen/tests/mochitests/zoom/browser_zoom_commands.js b/src/zen/tests/mochitests/zoom/browser_zoom_commands.js
new file mode 100644
index 000000000..e8992bf37
--- /dev/null
+++ b/src/zen/tests/mochitests/zoom/browser_zoom_commands.js
@@ -0,0 +1,202 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const TEST_PAGE_URL =
+  "data:text/html;charset=utf-8,<body>test_zoom_levels</body>";
+
+/**
+ * Waits for the zoom commands in the window to have the expected enabled
+ * state.
+ *
+ * @param {object} expectedState
+ *   An object where each key represents one of the zoom commands,
+ *   and the value is a boolean that is true if the command should
+ *   be enabled, and false if it should be disabled.
+ *
+ *   The keys are "enlarge", "reduce" and "reset" for readability,
+ *   and internally this function maps those keys to the appropriate
+ *   commands.
+ * @returns {Promise<void>}
+ */
+async function waitForCommandEnabledState(expectedState) {
+  const COMMAND_MAP = {
+    enlarge: "cmd_fullZoomEnlarge",
+    reduce: "cmd_fullZoomReduce",
+    reset: "cmd_fullZoomReset",
+  };
+
+  await TestUtils.waitForCondition(() => {
+    for (let commandKey in expectedState) {
+      let commandID = COMMAND_MAP[commandKey];
+      let command = document.getElementById(commandID);
+      let expectedEnabled = expectedState[commandKey];
+
+      if (command.hasAttribute("disabled") == expectedEnabled) {
+        return false;
+      }
+    }
+    Assert.ok("Commands finally reached the expected state.");
+    return true;
+  }, "Waiting for commands to reach the right state.");
+}
+
+/**
+ * Tests that the "Zoom Text Only" command is in the right checked
+ * state.
+ *
+ * @param {boolean} isChecked
+ *   True if the command should have its "checked" attribute set to
+ *   "true". Otherwise, ensures that the attribute is set to "false".
+ */
+function assertTextZoomCommandCheckedState(isChecked) {
+  let command = document.getElementById("cmd_fullZoomToggle");
+  Assert.equal(
+    command.hasAttribute("checked"),
+    isChecked,
+    "Text zoom command has expected checked attribute"
+  );
+}
+
+/**
+ * Tests that zoom commands are properly updated when changing
+ * zoom levels and/or preferences on an individual browser.
+ */
+add_task(async function test_update_browser_zoom() {
+  await BrowserTestUtils.withNewTab(TEST_PAGE_URL, async () => {
+    let currentZoom = await FullZoomHelper.getGlobalValue();
+    Assert.equal(
+      currentZoom,
+      1,
+      "We expect to start at the default zoom level."
+    );
+
+    await waitForCommandEnabledState({
+      enlarge: true,
+      reduce: true,
+      reset: false,
+    });
+    assertTextZoomCommandCheckedState(false);
+
+    // We'll run two variations of this test - one with text zoom enabled,
+    // and the other without.
+    for (let textZoom of [true, false]) {
+      info(`Running variation with textZoom set to ${textZoom}`);
+
+      await SpecialPowers.pushPrefEnv({
+        set: [["browser.zoom.full", !textZoom]],
+      });
+
+      // 120% global zoom
+      info("Changing default zoom by a single level");
+      ZoomManager.zoom = 1.2;
+
+      await waitForCommandEnabledState({
+        enlarge: true,
+        reduce: true,
+        reset: true,
+      });
+      await assertTextZoomCommandCheckedState(textZoom);
+
+      // Now max out the zoom level.
+      ZoomManager.zoom = ZoomManager.MAX;
+
+      await waitForCommandEnabledState({
+        enlarge: false,
+        reduce: true,
+        reset: true,
+      });
+      await assertTextZoomCommandCheckedState(textZoom);
+
+      // Now min out the zoom level.
+      ZoomManager.zoom = ZoomManager.MIN;
+      await waitForCommandEnabledState({
+        enlarge: true,
+        reduce: false,
+        reset: true,
+      });
+      await assertTextZoomCommandCheckedState(textZoom);
+
+      // Now reset back to the default zoom level
+      ZoomManager.zoom = 1;
+      await waitForCommandEnabledState({
+        enlarge: true,
+        reduce: true,
+        reset: false,
+      });
+      await assertTextZoomCommandCheckedState(textZoom);
+    }
+  });
+});
+
+/**
+ * Tests that zoom commands are properly updated when changing
+ * zoom levels when the default zoom is not at 1.0.
+ */
+add_task(async function test_update_browser_zoom() {
+  await BrowserTestUtils.withNewTab(TEST_PAGE_URL, async () => {
+    let currentZoom = await FullZoomHelper.getGlobalValue();
+    Assert.equal(
+      currentZoom,
+      1,
+      "We expect to start at the default zoom level."
+    );
+
+    // Now change the default zoom to 200%, which is what we'll switch
+    // back to when choosing to reset the zoom level.
+    //
+    // It's a bit maddening that changeDefaultZoom takes values in integer
+    // units from 30 to 500, whereas ZoomManager.zoom takes things in float
+    // units from 0.3 to 5.0, but c'est la vie for now.
+    await FullZoomHelper.changeDefaultZoom(200);
+    registerCleanupFunction(async () => {
+      await FullZoomHelper.changeDefaultZoom(100);
+    });
+
+    await waitForCommandEnabledState({
+      enlarge: true,
+      reduce: true,
+      reset: false,
+    });
+
+    // 120% global zoom
+    info("Changing default zoom by a single level");
+    ZoomManager.zoom = 2.2;
+
+    await waitForCommandEnabledState({
+      enlarge: true,
+      reduce: true,
+      reset: true,
+    });
+    await assertTextZoomCommandCheckedState(false);
+
+    // Now max out the zoom level.
+    ZoomManager.zoom = ZoomManager.MAX;
+
+    await waitForCommandEnabledState({
+      enlarge: false,
+      reduce: true,
+      reset: true,
+    });
+    await assertTextZoomCommandCheckedState(false);
+
+    // Now min out the zoom level.
+    ZoomManager.zoom = ZoomManager.MIN;
+    await waitForCommandEnabledState({
+      enlarge: true,
+      reduce: false,
+      reset: true,
+    });
+    await assertTextZoomCommandCheckedState(false);
+
+    // Now reset back to the default zoom level
+    ZoomManager.zoom = 2;
+    await waitForCommandEnabledState({
+      enlarge: true,
+      reduce: true,
+      reset: false,
+    });
+    await assertTextZoomCommandCheckedState(false);
+  });
+});
diff --git a/src/zen/tests/mochitests/zoom/head.js b/src/zen/tests/mochitests/zoom/head.js
new file mode 100644
index 000000000..b8f9f18cb
--- /dev/null
+++ b/src/zen/tests/mochitests/zoom/head.js
@@ -0,0 +1,190 @@
+/* Any copyright is dedicated to the Public Domain.
+ * https://creativecommons.org/publicdomain/zero/1.0/ */
+
+let gContentPrefs = Cc["@mozilla.org/content-pref/service;1"].getService(
+  Ci.nsIContentPrefService2
+);
+
+let gLoadContext = Cu.createLoadContext();
+
+registerCleanupFunction(async function () {
+  await new Promise(resolve => {
+    gContentPrefs.removeByName(window.FullZoom.name, gLoadContext, {
+      handleResult() {},
+      handleCompletion() {
+        resolve();
+      },
+    });
+  });
+});
+
+var FullZoomHelper = {
+  async changeDefaultZoom(newZoom) {
+    let nonPrivateLoadContext = Cu.createLoadContext();
+    /* Because our setGlobal function takes in a browsing context, and
+     * because we want to keep this property consistent across both private
+     * and non-private contexts, we crate a non-private context and use that
+     * to set the property, regardless of our actual context.
+     */
+
+    let parsedZoomValue = parseFloat((parseInt(newZoom) / 100).toFixed(2));
+    await new Promise(resolve => {
+      gContentPrefs.setGlobal(
+        FullZoom.name,
+        parsedZoomValue,
+        nonPrivateLoadContext,
+        {
+          handleCompletion() {
+            resolve();
+          },
+        }
+      );
+    });
+    // The zoom level is used to update the commands associated with
+    // increasing, decreasing or resetting the Zoom levels. There are
+    // a series of async things we need to wait for (writing the content
+    // pref to the database, and then reading that content pref back out
+    // again and reacting to it), so waiting for the zoom level to reach
+    // the expected level is actually simplest to make sure we're okay to
+    // proceed.
+    await TestUtils.waitForCondition(() => {
+      return ZoomManager.zoom == parsedZoomValue;
+    });
+  },
+
+  async getGlobalValue() {
+    return new Promise(resolve => {
+      let cachedVal = parseFloat(
+        gContentPrefs.getCachedGlobal(FullZoom.name, gLoadContext)
+      );
+      if (cachedVal) {
+        // We've got cached information, though it may be we've cached
+        // an undefined value, or the cached info is invalid. To ensure
+        // a valid return, we opt to return the default 1.0 in the
+        // undefined and invalid cases.
+        resolve(parseFloat(cachedVal.value) || 1.0);
+        return;
+      }
+      let value = 1.0;
+      gContentPrefs.getGlobal(FullZoom.name, gLoadContext, {
+        handleResult(pref) {
+          if (pref.value) {
+            value = parseFloat(pref.value);
+          }
+        },
+        handleCompletion() {
+          resolve(value);
+        },
+        handleError(error) {
+          console.error(error);
+        },
+      });
+    });
+  },
+
+  waitForLocationChange: function waitForLocationChange() {
+    return new Promise(resolve => {
+      Services.obs.addObserver(function obs(subj, topic) {
+        Services.obs.removeObserver(obs, topic);
+        resolve();
+      }, "browser-fullZoom:location-change");
+    });
+  },
+
+  selectTabAndWaitForLocationChange: function selectTabAndWaitForLocationChange(
+    tab
+  ) {
+    if (!tab) {
+      throw new Error("tab must be given.");
+    }
+    if (gBrowser.selectedTab == tab) {
+      return Promise.resolve();
+    }
+
+    return Promise.all([
+      BrowserTestUtils.switchTab(gBrowser, tab),
+      this.waitForLocationChange(),
+    ]);
+  },
+
+  removeTabAndWaitForLocationChange: function removeTabAndWaitForLocationChange(
+    tab
+  ) {
+    tab = tab || gBrowser.selectedTab;
+    let selected = gBrowser.selectedTab == tab;
+    gBrowser.removeTab(tab);
+    if (selected) {
+      return this.waitForLocationChange();
+    }
+    return Promise.resolve();
+  },
+
+  load: function load(tab, url) {
+    return new Promise(resolve => {
+      let didLoad = false;
+      let didZoom = false;
+
+      BrowserTestUtils.loadURIString({
+        browser: tab.linkedBrowser,
+        uriString: url,
+      }).then(() => {
+        didLoad = true;
+        if (didZoom) {
+          resolve();
+        }
+      }, true);
+
+      this.waitForLocationChange().then(function () {
+        didZoom = true;
+        if (didLoad) {
+          resolve();
+        }
+      });
+    });
+  },
+
+  zoomTest: function zoomTest(tab, val, msg) {
+    is(ZoomManager.getZoomForBrowser(tab.linkedBrowser), val, msg);
+  },
+
+  BACK: 0,
+  FORWARD: 1,
+  navigate: function navigate(direction) {
+    return new Promise(resolve => {
+      let didPs = false;
+      let didZoom = false;
+
+      BrowserTestUtils.waitForContentEvent(
+        gBrowser.selectedBrowser,
+        "pageshow",
+        true
+      ).then(() => {
+        didPs = true;
+        if (didZoom) {
+          resolve();
+        }
+      });
+
+      if (direction == this.BACK) {
+        gBrowser.goBack(false);
+      } else if (direction == this.FORWARD) {
+        gBrowser.goForward();
+      }
+
+      this.waitForLocationChange().then(function () {
+        didZoom = true;
+        if (didPs) {
+          resolve();
+        }
+      });
+    });
+  },
+
+  failAndContinue: function failAndContinue(func) {
+    return function (err) {
+      console.error(err);
+      ok(false, err);
+      func();
+    };
+  },
+};
diff --git a/src/zen/tests/mochitests/zoom/zoom_test.html b/src/zen/tests/mochitests/zoom/zoom_test.html
new file mode 100644
index 000000000..bf80490ca
--- /dev/null
+++ b/src/zen/tests/mochitests/zoom/zoom_test.html
@@ -0,0 +1,14 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=416661
+-->
+  <head>
+    <title>Test for zoom setting</title>
+
+  </head>
+  <body>
+  <a href="https://bugzilla.mozilla.org/show_bug.cgi?id=416661">Bug 416661</a>
+  <p>Site specific zoom settings should not apply to image documents.</p>
+  </body>
+</html>
diff --git a/src/zen/tests/split_view/browser_split_view_empty.js b/src/zen/tests/split_view/browser_split_view_empty.js
index 6fbddbd74..84ec75389 100644
--- a/src/zen/tests/split_view/browser_split_view_empty.js
+++ b/src/zen/tests/split_view/browser_split_view_empty.js
@@ -7,50 +7,149 @@ const { UrlbarTestUtils } = ChromeUtils.importESModule(
   "resource://testing-common/UrlbarTestUtils.sys.mjs"
 );
 
+/**
+ * @param {object} [staleToken] - Token of a session the pane will supersede.
+ */
+async function stageEmptySplit(staleToken = null) {
+  let staleClosed = null;
+
+  if (staleToken) {
+    staleClosed = BrowserTestUtils.waitForEvent(
+      window,
+      "ZenURLBarClosed",
+      false,
+      event => gZenUIManager.matchesCloseToken(staleToken, event)
+    );
+  }
+  const staleClose = gURLBar._zenHandleUrlbarClose;
+  document.getElementById("cmd_zenNewEmptySplit").doCommand();
+  await TestUtils.waitForCondition(
+    () =>
+      gURLBar._zenHandleUrlbarClose &&
+      gURLBar._zenHandleUrlbarClose !== staleClose,
+    "Waiting for the staged pane to open its own urlbar session"
+  );
+  await UrlbarTestUtils.promisePopupOpen(window, () => {});
+
+  if (staleClosed) {
+    await staleClosed;
+  }
+
+  ok(gURLBar.view.isOpen, "The staged pane's urlbar is still open");
+  Assert.equal(
+    gBrowser.selectedTab,
+    gZenWorkspaces._emptyTab,
+    "The empty pane should be staged and selected"
+  );
+}
+
+/**
+ * Stages an empty split and commits it by picking the first urlbar result.
+ *
+ * @param {Tab} originalTab - The tab the split is being created from.
+ * @param {object} [staleToken] - Token of a session the pane will supersede.
+ */
+async function createEmptySplitAndCheck(originalTab, staleToken = null) {
+  await stageEmptySplit(staleToken);
+
+  await UrlbarTestUtils.promiseAutocompleteResultPopup({
+    window,
+    waitForFocus,
+    value: "https://example.com",
+  });
+  const waitForActivationPromise = BrowserTestUtils.waitForEvent(
+    window,
+    "ZenViewSplitter:SplitViewActivated"
+  );
+  let result = await UrlbarTestUtils.getDetailsOfResultAt(window, 0);
+  EventUtils.synthesizeMouseAtCenter(result.element.row, {});
+  await waitForActivationPromise;
+  await new Promise(resolve => {
+    /* eslint-disable mozilla/no-arbitrary-setTimeout */
+    setTimeout(async () => {
+      resolve();
+    }, 100);
+  });
+  const selectedTab = gBrowser.selectedTab;
+  ok(
+    gBrowser.tabpanels.hasAttribute("zen-split-view"),
+    "The split view should not have crashed with two tabs in it"
+  );
+  ok(
+    !gZenWorkspaces._emptyTab.splitView,
+    "The empty tab should not be in split view"
+  );
+  ok(!gZenWorkspaces._emptyTab.group, "The empty tab should not be in a group");
+  ok(selectedTab.splitView, "The selected tab should be in split view");
+  ok(originalTab.splitView, "The original tab should be in split view");
+  Assert.equal(
+    gBrowser.tabpanels.querySelectorAll('[zen-split="true"]').length,
+    2,
+    "There should be two split views present"
+  );
+  await BrowserTestUtils.removeTab(selectedTab);
+}
+
+/**
+ * @returns {Promise<object>} The session's close token.
+ */
+async function openUrlbarSession() {
+  const closeToken = {};
+  await UrlbarTestUtils.promisePopupOpen(window, () => {
+    ok(
+      gZenUIManager.handleNewTab(false, false, "tab", true, closeToken),
+      "The urlbar session should have opened"
+    );
+  });
+  ok(gURLBar.hasAttribute("zen-newtab"), "The session owns the urlbar");
+  return closeToken;
+}
+
 add_task(async function test_Split_View_Empty() {
+  await BrowserTestUtils.withNewTab("https://example.com", async function () {
+    await createEmptySplitAndCheck(gBrowser.selectedTab);
+  });
+});
+
+add_task(async function test_Split_View_Empty_With_Urlbar_Already_Open() {
+  await SimpleTest.promiseFocus(window);
+  await BrowserTestUtils.withNewTab("https://example.com", async function () {
+    const staleToken = await openUrlbarSession();
+    await createEmptySplitAndCheck(gBrowser.selectedTab, staleToken);
+  });
+});
+
+add_task(async function test_Split_View_Empty_Cancelled_With_Urlbar_Open() {
+  await SimpleTest.promiseFocus(window);
   await BrowserTestUtils.withNewTab("https://example.com", async function () {
     const originalTab = gBrowser.selectedTab;
     const command = document.getElementById("cmd_zenNewEmptySplit");
-    command.doCommand();
-    await UrlbarTestUtils.promisePopupOpen(window, () => {});
-    await UrlbarTestUtils.promiseAutocompleteResultPopup({
-      window,
-      waitForFocus,
-      value: "https://example.com",
-    });
-    const waitForActivationPromise = BrowserTestUtils.waitForEvent(
-      window,
-      "ZenViewSplitter:SplitViewActivated"
-    );
-    let result = await UrlbarTestUtils.getDetailsOfResultAt(window, 0);
-    EventUtils.synthesizeMouseAtCenter(result.element.row, {});
-    await waitForActivationPromise;
-    await new Promise(resolve => {
-      /* eslint-disable mozilla/no-arbitrary-setTimeout */
-      setTimeout(async () => {
-        resolve();
-      }, 100);
-    });
-    const selectedTab = gBrowser.selectedTab;
-    ok(
-      gBrowser.tabpanels.hasAttribute("zen-split-view"),
-      "The split view should not have crashed with two tabs in it"
-    );
-    ok(
-      !gZenWorkspaces._emptyTab.splitView,
-      "The empty tab should not be in split view"
+    const staleToken = await openUrlbarSession();
+    await stageEmptySplit(staleToken);
+
+    EventUtils.synthesizeKey("KEY_Escape");
+    await TestUtils.waitForCondition(
+      () =>
+        !gZenWorkspaces._emptyTab.splitView &&
+        gBrowser.selectedTab === originalTab,
+      "Waiting for the staged pane to be discarded"
     );
+
     ok(
       !gZenWorkspaces._emptyTab.group,
-      "The empty tab should not be in a group"
+      "The empty tab should not be left in a group"
     );
-    ok(selectedTab.splitView, "The selected tab should be in split view");
-    ok(originalTab.splitView, "The original tab should be in split view");
     Assert.equal(
-      gBrowser.tabpanels.querySelectorAll('[zen-split="true"]').length,
-      2,
-      "There should be two split views present"
+      gZenViewSplitter._data.findIndex(group =>
+        group.tabs.includes(gZenWorkspaces._emptyTab)
+      ),
+      -1,
+      "No split group should still hold the empty tab"
     );
-    await BrowserTestUtils.removeTab(selectedTab);
+    ok(
+      !command.hasAttribute("disabled"),
+      "New Empty Split View should be usable again"
+    );
+    ok(!originalTab.splitView, "The original tab should not be in split view");
   });
 });
diff --git a/src/zen/tests/ub-actions/browser_workspace_restrict_search.js b/src/zen/tests/ub-actions/browser_workspace_restrict_search.js
index 27adf48eb..acd717871 100644
--- a/src/zen/tests/ub-actions/browser_workspace_restrict_search.js
+++ b/src/zen/tests/ub-actions/browser_workspace_restrict_search.js
@@ -6,6 +6,7 @@
 ChromeUtils.defineESModuleGetters(this, {
   UrlbarTestUtils: "resource://testing-common/UrlbarTestUtils.sys.mjs",
   UrlbarUtils: "moz-src:///browser/components/urlbar/UrlbarUtils.sys.mjs",
+  UrlbarShared: "chrome://browser/content/urlbar/UrlbarShared.mjs",
 });
 
 UrlbarTestUtils.init(this);
@@ -29,7 +30,7 @@ add_task(async function test_Workspace_Search_OneOff_Pref() {
 
   function getWorkspaceShortcut() {
     return [...oneOffSearchButtons.localButtons].find(
-      button => button.source == UrlbarUtils.RESULT_SOURCE.WORKSPACES
+      button => button.source == UrlbarShared.RESULT_SOURCE.WORKSPACES
     );
   }
 
@@ -108,7 +109,7 @@ add_task(async function test_Workspace_Restrict_Search() {
   ok(gURLBar.searchMode, "The urlbar should enter search mode");
   Assert.equal(
     gURLBar.searchMode.source,
-    UrlbarUtils.RESULT_SOURCE.WORKSPACES,
+    UrlbarShared.RESULT_SOURCE.WORKSPACES,
     "The typed token should enter workspace search mode"
   );
   Assert.equal(
@@ -129,7 +130,7 @@ add_task(async function test_Workspace_Restrict_Search() {
   ok(
     resultDetails.every(
       ({ result, source }) =>
-        source == UrlbarUtils.RESULT_SOURCE.WORKSPACES &&
+        source == UrlbarShared.RESULT_SOURCE.WORKSPACES &&
         result.providerName == "ZenUrlbarProviderGlobalActions"
     ),
     "Typing the workspace token should limit results to workspace actions"
diff --git a/src/zen/tests/urlbar/browser.toml b/src/zen/tests/urlbar/browser.toml
index e2c4bbb40..34557d019 100644
--- a/src/zen/tests/urlbar/browser.toml
+++ b/src/zen/tests/urlbar/browser.toml
@@ -12,3 +12,5 @@ support-files = [
 ["browser_floating_urlbar.js"]
 
 ["browser_issue_7385.js"]
+
+["browser_urlbar_close_token.js"]
diff --git a/src/zen/tests/urlbar/browser_urlbar_close_token.js b/src/zen/tests/urlbar/browser_urlbar_close_token.js
new file mode 100644
index 000000000..1fc89e833
--- /dev/null
+++ b/src/zen/tests/urlbar/browser_urlbar_close_token.js
@@ -0,0 +1,266 @@
+/* Any copyright is dedicated to the Public Domain.
+   https://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  UrlbarTestUtils: "resource://testing-common/UrlbarTestUtils.sys.mjs",
+});
+
+async function openUrlbarSession(closeToken) {
+  await UrlbarTestUtils.promisePopupOpen(window, () => {
+    ok(
+      gZenUIManager.handleNewTab(false, false, "tab", true, closeToken),
+      "The urlbar session should have opened"
+    );
+  });
+  Assert.equal(typeof closeToken.id, "number", "The session minted a token");
+  return gURLBar._zenHandleUrlbarClose;
+}
+
+function listenerFor(closeToken, seen) {
+  return event => {
+    if (!gZenUIManager.matchesCloseToken(closeToken, event)) {
+      return;
+    }
+    seen.push(event.detail.closeSeq);
+  };
+}
+
+function waitForCloseOf(closeToken) {
+  return BrowserTestUtils.waitForEvent(
+    window,
+    "ZenURLBarClosed",
+    false,
+    event => gZenUIManager.matchesCloseToken(closeToken, event)
+  );
+}
+
+add_task(async function test_matchesCloseToken() {
+  ok(
+    gZenUIManager.matchesCloseToken({ id: 7 }, { detail: { closeSeq: 7 } }),
+    "Matches correct token"
+  );
+  ok(
+    !gZenUIManager.matchesCloseToken({ id: 7 }, { detail: { closeSeq: 8 } }),
+    "Does not match incorrect token"
+  );
+  ok(
+    !gZenUIManager.matchesCloseToken({}, { detail: { closeSeq: undefined } }),
+    "Bad token doesn't match"
+  );
+  ok(
+    !gZenUIManager.matchesCloseToken({ id: 7 }, { detail: {} }),
+    "An untagged event is rejected"
+  );
+  ok(
+    !gZenUIManager.matchesCloseToken({ id: 7 }, undefined),
+    "A missing event is rejected"
+  );
+  ok(
+    !gZenUIManager.matchesCloseToken(undefined, { detail: { closeSeq: 7 } }),
+    "A missing token is rejected"
+  );
+});
+
+add_task(async function test_Every_Call_Mints_Its_Own_Token() {
+  ok(gZenUIManager.testingEnabled, "Testing is enabled");
+
+  const seen = new Set();
+  for (let i = 0; i < 3; i++) {
+    const closeToken = {};
+    ok(
+      !gZenUIManager.handleNewTab(false, false, "tab", false, closeToken),
+      "Path bails out under zen.testing.enabled"
+    );
+    Assert.equal(
+      typeof closeToken.id,
+      "number",
+      "handleNewTab always mints a token"
+    );
+    ok(!seen.has(closeToken.id), `Token ${closeToken.id} is unique`);
+    seen.add(closeToken.id);
+  }
+});
+
+add_task(async function test_Overlapping_Sessions_Get_Correct_Tokens() {
+  await SimpleTest.promiseFocus(window);
+  await BrowserTestUtils.withNewTab("https://example.com", async function () {
+    const seenByA = [];
+    const seenByB = [];
+    const dispatched = [];
+    const collectAll = event => dispatched.push(event.detail.closeSeq);
+    window.addEventListener("ZenURLBarClosed", collectAll);
+
+    const tokenA = {};
+    const closeA = await openUrlbarSession(tokenA);
+    const onA = listenerFor(tokenA, seenByA);
+    window.addEventListener("ZenURLBarClosed", onA);
+    ok(gURLBar.focused, "Session A focused the urlbar");
+
+    const tokenB = {};
+    const onB = listenerFor(tokenB, seenByB);
+    window.addEventListener("ZenURLBarClosed", onB);
+
+    const aClosed = waitForCloseOf(tokenA);
+    closeA(true);
+    ok(!gURLBar._zenHandleUrlbarClose, "A's handler is cleared synchronously");
+
+    const closeB = await openUrlbarSession(tokenB);
+    Assert.notEqual(tokenA.id, tokenB.id, "The two sessions differ");
+    ok(gZenUIManager._isOwner(tokenB.id), "Session B owns the urlbar");
+    ok(!gZenUIManager._isOwner(tokenA.id), "Session A no longer owns it");
+
+    await aClosed;
+
+    Assert.deepEqual(
+      dispatched,
+      [tokenA.id],
+      "The superseded session still announced its own close"
+    );
+    Assert.deepEqual(seenByA, [tokenA.id], "A's listener accepted A's close");
+    Assert.deepEqual(seenByB, [], "B's listener rejected the foreign close");
+
+    ok(gURLBar.view.isOpen, "The view is open for session B");
+    ok(gURLBar.hasAttribute("zen-newtab"), "Session B's zen-newtab is set");
+    Assert.equal(
+      gURLBar._zenHandleUrlbarClose,
+      closeB,
+      "Session B's close handler is still installed"
+    );
+
+    const bClosed = waitForCloseOf(tokenB);
+    closeB(true);
+    await bClosed;
+    await TestUtils.waitForCondition(
+      () => !gURLBar.view.isOpen,
+      "Waiting for session B to close"
+    );
+
+    Assert.deepEqual(seenByB, [tokenB.id], "B's listener accepted B's close");
+    Assert.deepEqual(seenByA, [tokenA.id], "A's listener did not fire again");
+    Assert.deepEqual(
+      dispatched,
+      [tokenA.id, tokenB.id],
+      "Both sessions announced their close, in order"
+    );
+    ok(!gURLBar.hasAttribute("zen-newtab"), "A live close clears zen-newtab");
+    ok(!gURLBar._zenHandleUrlbarClose, "A live close clears the handler");
+    ok(!gZenUIManager._isOwner(tokenB.id), "Ownership is released at the end");
+
+    window.removeEventListener("ZenURLBarClosed", collectAll);
+    window.removeEventListener("ZenURLBarClosed", onA);
+    window.removeEventListener("ZenURLBarClosed", onB);
+  });
+});
+
+add_task(async function test_Superseded_Before_Its_Teardown_Runs() {
+  await SimpleTest.promiseFocus(window);
+  await BrowserTestUtils.withNewTab("https://example.com", async function () {
+    const seenByA = [];
+    const seenByB = [];
+    const tokenA = {};
+    const closeA = await openUrlbarSession(tokenA);
+    const onA = listenerFor(tokenA, seenByA);
+    window.addEventListener("ZenURLBarClosed", onA);
+
+    const tokenB = {};
+    const onB = listenerFor(tokenB, seenByB);
+    window.addEventListener("ZenURLBarClosed", onB);
+
+    const aClosed = waitForCloseOf(tokenA);
+    closeA(true);
+    ok(
+      gZenUIManager.handleNewTab(false, false, "tab", true, tokenB),
+      "Session B opened before A's teardown ran"
+    );
+    const closeB = gURLBar._zenHandleUrlbarClose;
+
+    await aClosed;
+
+    Assert.deepEqual(
+      seenByA,
+      [tokenA.id],
+      "The superseded session still announced its close"
+    );
+    Assert.deepEqual(seenByB, [], "B's listener rejected the foreign close");
+    ok(
+      gURLBar.hasAttribute("zen-newtab"),
+      "A's skipped teardown did not strip the attribute B had just set"
+    );
+    Assert.equal(
+      gURLBar._zenHandleUrlbarClose,
+      closeB,
+      "A's skipped teardown left B's close handler installed"
+    );
+    ok(gZenUIManager._isOwner(tokenB.id), "Session B still owns the urlbar");
+
+    window.removeEventListener("ZenURLBarClosed", onA);
+    window.removeEventListener("ZenURLBarClosed", onB);
+    closeB(true);
+    await TestUtils.waitForCondition(
+      () => !gURLBar.hasAttribute("zen-newtab") && !gURLBar.view.isOpen,
+      "Waiting for session B to close"
+    );
+  });
+});
+
+add_task(async function test_Interleaved_Resolves_Correctly() {
+  await SimpleTest.promiseFocus(window);
+  await BrowserTestUtils.withNewTab("https://example.com", async function () {
+    const seenByA = [];
+    const tokenA = {};
+    const closeA = await openUrlbarSession(tokenA);
+    const onA = listenerFor(tokenA, seenByA);
+    window.addEventListener("ZenURLBarClosed", onA);
+
+    const tokenB = {};
+    let closeB = null;
+    const openBDuringClose = event => {
+      ok(
+        gZenUIManager.matchesCloseToken(tokenA, event),
+        "Event token matches session A token"
+      );
+
+      window.removeEventListener("ZenURLBarClosed", openBDuringClose);
+      ok(
+        !gURLBar.hasAttribute("zen-newtab"),
+        "A's teardown ran before session B claimed the urlbar"
+      );
+      ok(
+        gZenUIManager.handleNewTab(false, false, "tab", true, tokenB),
+        "Session B opened before A checked its ownership"
+      );
+
+      closeB = gURLBar._zenHandleUrlbarClose;
+      ok(closeB, "Global close handler installed.");
+    };
+    window.addEventListener("ZenURLBarClosed", openBDuringClose);
+
+    const aClosed = waitForCloseOf(tokenA);
+    closeA(true);
+
+    await aClosed;
+
+    Assert.equal(typeof tokenB.id, "number", "Session B really opened");
+    Assert.deepEqual(seenByA, [tokenA.id], "A announced its own close");
+    ok(gURLBar.view.isOpen, "A did not close the view B had just claimed");
+    ok(
+      gURLBar.hasAttribute("zen-newtab"),
+      "Session B's bar has zen-newtab restored"
+    );
+    Assert.equal(
+      gURLBar._zenHandleUrlbarClose,
+      closeB,
+      "Session B's close handler survived"
+    );
+    ok(gZenUIManager._isOwner(tokenB.id), "Session B still owns the urlbar");
+
+    window.removeEventListener("ZenURLBarClosed", onA);
+    closeB(true);
+    await TestUtils.waitForCondition(
+      () => !gURLBar.hasAttribute("zen-newtab") && !gURLBar.view.isOpen,
+      "Waiting for session B to close"
+    );
+  });
+});
diff --git a/src/zen/tests/window_sync/browser_sync_tab_open.js b/src/zen/tests/window_sync/browser_sync_tab_open.js
index 7dddf1834..9df69e1a7 100644
--- a/src/zen/tests/window_sync/browser_sync_tab_open.js
+++ b/src/zen/tests/window_sync/browser_sync_tab_open.js
@@ -16,3 +16,41 @@ add_task(async function test_SimpleTabOpen() {
     );
   });
 });
+
+add_task(async function test_TabOpenInContainer() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["privacy.userContext.enabled", true]],
+  });
+  let newTab = null;
+  await withNewSyncedWindow(async win => {
+    await runSyncAction(
+      () => {
+        newTab = gBrowser.addTrustedTab("https://example.com/", {
+          inBackground: true,
+          userContextId: 1,
+        });
+      },
+      async () => {
+        Assert.equal(
+          newTab.userContextId,
+          1,
+          "The opened tab should keep its container"
+        );
+        const otherTab = gZenWindowSync.getItemFromWindow(win, newTab.id);
+        Assert.ok(
+          otherTab,
+          "The opened tab should be found in the synced window"
+        );
+        Assert.equal(
+          otherTab.userContextId,
+          newTab.userContextId,
+          "The synced tab should inherit the original tab's container"
+        );
+      },
+      "TabOpen"
+    );
+  });
+  let tabClosing = BrowserTestUtils.waitForTabClosing(newTab);
+  BrowserTestUtils.removeTab(newTab);
+  await tabClosing;
+});
diff --git a/src/zen/urlbar/ZenUBActionsProvider.sys.mjs b/src/zen/urlbar/ZenUBActionsProvider.sys.mjs
index 3cbea40db..cdec35c28 100644
--- a/src/zen/urlbar/ZenUBActionsProvider.sys.mjs
+++ b/src/zen/urlbar/ZenUBActionsProvider.sys.mjs
@@ -7,6 +7,7 @@ import {
   UrlbarProvider,
   UrlbarUtils,
 } from "moz-src:///browser/components/urlbar/UrlbarUtils.sys.mjs";
+import { UrlbarShared } from "chrome://browser/content/urlbar/UrlbarShared.mjs";
 import { globalActions } from "resource:///modules/ZenUBGlobalActions.sys.mjs";
 import { zenUrlbarResultsLearner } from "./ZenUBResultsLearner.sys.mjs";
 
@@ -154,9 +155,10 @@ export class ZenUrlbarProviderGlobalActions extends UrlbarProvider {
    */
   async isActive(queryContext) {
     return (
-      queryContext.searchMode?.source == UrlbarUtils.RESULT_SOURCE.WORKSPACES ||
       queryContext.searchMode?.source ==
-        UrlbarUtils.RESULT_SOURCE.ZEN_ACTIONS ||
+        UrlbarShared.RESULT_SOURCE.WORKSPACES ||
+      queryContext.searchMode?.source ==
+        UrlbarShared.RESULT_SOURCE.ZEN_ACTIONS ||
       (lazy.enabledPref &&
         queryContext.searchString &&
         queryContext.searchString.length < UrlbarUtils.MAX_TEXT_LENGTH &&
@@ -345,10 +347,10 @@ export class ZenUrlbarProviderGlobalActions extends UrlbarProvider {
   async startQuery(queryContext, addCallback) {
     const query = queryContext.trimmedLowerCaseSearchString;
     const isWorkspaceSearch =
-      queryContext.searchMode?.source == UrlbarUtils.RESULT_SOURCE.WORKSPACES;
+      queryContext.searchMode?.source == UrlbarShared.RESULT_SOURCE.WORKSPACES;
     const isPrefixed =
       isWorkspaceSearch ||
-      queryContext.searchMode?.source == UrlbarUtils.RESULT_SOURCE.ZEN_ACTIONS;
+      queryContext.searchMode?.source == UrlbarShared.RESULT_SOURCE.ZEN_ACTIONS;
 
     if (!query && !isPrefixed) {
       return;
@@ -391,10 +393,10 @@ export class ZenUrlbarProviderGlobalActions extends UrlbarProvider {
         zenUrlbarResultsLearner.shouldPrioritize(action.commandId) &&
         !isPrefixed;
       let result = new lazy.UrlbarResult({
-        type: UrlbarUtils.RESULT_TYPE.DYNAMIC,
+        type: UrlbarShared.RESULT_TYPE.DYNAMIC,
         source: isWorkspaceSearch
-          ? UrlbarUtils.RESULT_SOURCE.WORKSPACES
-          : UrlbarUtils.RESULT_SOURCE.ZEN_ACTIONS,
+          ? UrlbarShared.RESULT_SOURCE.WORKSPACES
+          : UrlbarShared.RESULT_SOURCE.ZEN_ACTIONS,
         payload,
         highlights: payloadHighlights,
         heuristic: shouldBePrioritized,
diff --git a/src/zen/window-drag/actors/ZenWindowDragChild.sys.mjs b/src/zen/window-drag/actors/ZenWindowDragChild.sys.mjs
index d20c47454..39d813ff1 100644
--- a/src/zen/window-drag/actors/ZenWindowDragChild.sys.mjs
+++ b/src/zen/window-drag/actors/ZenWindowDragChild.sys.mjs
@@ -26,6 +26,10 @@ XPCOMUtils.defineLazyServiceGetter(
 // comfortably above click jitter or clicks in the region get lost.
 const DRAG_START_THRESHOLD_PX = 4;
 
+// Un-snapping a maximized or tiled window is more disruptive, so those
+// need a firmer gesture, mirroring how native titlebars behave.
+const SNAPPED_DRAG_START_THRESHOLD_PX = 50;
+
 // Content that drives its own mouse interaction without being
 // interactive HTML content in the spec sense.
 const kAppContentTags = new Set(["audio", "canvas", "video"]);
@@ -54,33 +58,6 @@ const kInteractiveRoles = new Set([
   "treegrid",
 ]);
 
-// Cursors that signal the page considers the area interactive or draggable.
-const kInteractiveCursors = new Set([
-  "pointer",
-  "grab",
-  "grabbing",
-  "move",
-  "all-scroll",
-  "text",
-  "vertical-text",
-  "cell",
-  "crosshair",
-  "col-resize",
-  "row-resize",
-  "n-resize",
-  "e-resize",
-  "s-resize",
-  "w-resize",
-  "ne-resize",
-  "nw-resize",
-  "se-resize",
-  "sw-resize",
-  "ew-resize",
-  "ns-resize",
-  "nesw-resize",
-  "nwse-resize",
-]);
-
 const kGestureListenerOptions = { mozSystemGroup: true, capture: true };
 
 const kGestureEvents = ["mousemove", "mouseup", "dragstart", "unload"];
@@ -90,6 +67,9 @@ export class ZenWindowDragChild extends JSWindowActorChild {
   #dragging = false;
   #startScreenX = 0;
   #startScreenY = 0;
+  // 0 while waiting for the ZenWindowDrag:IsSnapped answer; no drag can
+  // start until the proper threshold is known.
+  #dragThresholdPx = 0;
 
   handleEvent(event) {
     // Never let pages spoof the gesture with synthetic events.
@@ -172,8 +152,18 @@ export class ZenWindowDragChild extends JSWindowActorChild {
     const { screenX, screenY } = this.#screenPoint(event);
     this.#startScreenX = screenX;
     this.#startScreenY = screenY;
+    this.#dragThresholdPx = 0;
     this.#tracking = true;
     this.#addGestureListeners();
+    this.sendQuery("ZenWindowDrag:IsSnapped")
+      .then(snapped => {
+        if (this.#tracking) {
+          this.#dragThresholdPx = snapped
+            ? SNAPPED_DRAG_START_THRESHOLD_PX
+            : DRAG_START_THRESHOLD_PX;
+        }
+      })
+      .catch(() => this.#reset());
   }
 
   #onMouseMove(event) {
@@ -191,9 +181,12 @@ export class ZenWindowDragChild extends JSWindowActorChild {
       event.preventDefault();
       return;
     }
+    if (!this.#dragThresholdPx) {
+      return;
+    }
     const point = this.#screenPoint(event);
     const threshold =
-      DRAG_START_THRESHOLD_PX * this.contentWindow.devicePixelRatio;
+      this.#dragThresholdPx * this.contentWindow.devicePixelRatio;
     if (
       Math.hypot(
         point.screenX - this.#startScreenX,
@@ -276,7 +269,12 @@ export class ZenWindowDragChild extends JSWindowActorChild {
         return true;
       }
     }
-    return this.#hasInteractiveCursor(target);
+    // The effective cursor, resolved the same way it is shown to the user.
+    return lazy.zenWindowDragUtils.isInteractiveCursor(
+      event.composedTarget,
+      event.clientX,
+      event.clientY
+    );
   }
 
   #isSelectableText(node) {
@@ -307,15 +305,4 @@ export class ZenWindowDragChild extends JSWindowActorChild {
     const role = element.getAttribute?.("role");
     return !!role && kInteractiveRoles.has(role.toLowerCase());
   }
-
-  #hasInteractiveCursor(element) {
-    const style = element.ownerGlobal?.getComputedStyle(element);
-    if (!style) {
-      return false;
-    }
-    // The keyword is always the last component of the computed value.
-    // Don't split on "," as url() cursor images may contain commas.
-    const cursor = style.cursor.match(/[a-z-]+$/)?.[0];
-    return kInteractiveCursors.has(cursor);
-  }
 }
diff --git a/src/zen/window-drag/actors/ZenWindowDragParent.sys.mjs b/src/zen/window-drag/actors/ZenWindowDragParent.sys.mjs
index 3d92ab614..5866bc94f 100644
--- a/src/zen/window-drag/actors/ZenWindowDragParent.sys.mjs
+++ b/src/zen/window-drag/actors/ZenWindowDragParent.sys.mjs
@@ -15,19 +15,42 @@ XPCOMUtils.defineLazyServiceGetter(
 
 export class ZenWindowDragParent extends JSWindowActorParent {
   receiveMessage(message) {
-    if (message.name !== "ZenWindowDrag:StartDrag") {
-      return;
-    }
     const win = this.browsingContext.topChromeWindow;
-    if (!win || win.closed || win.windowState === win.STATE_FULLSCREEN) {
-      return;
+    if (!win || win.closed) {
+      return undefined;
     }
-    if (Cu.isInAutomation) {
-      // Tests can't exercise a real OS drag session; let them observe the
-      // decision instead.
-      Services.obs.notifyObservers(win, "zen-window-drag-started");
-      return;
+    switch (message.name) {
+      case "ZenWindowDrag:StartDrag": {
+        if (win.windowState === win.STATE_FULLSCREEN) {
+          break;
+        }
+        if (Cu.isInAutomation) {
+          // Tests can't exercise a real OS drag session; let them observe
+          // the decision instead.
+          Services.obs.notifyObservers(win, "zen-window-drag-started");
+          break;
+        }
+        lazy.zenDragAndDropService.beginNativeWindowMove(win);
+        break;
+      }
+      case "ZenWindowDrag:IsSnapped": {
+        return this.#isSnapped(win);
+      }
     }
-    lazy.zenDragAndDropService.beginNativeWindowMove(win);
+    return undefined;
+  }
+
+  /**
+   * Whether the window is maximized or tiled to an edge. The tiled
+   * attribute is kept in sync with the widget by AppWindow, the same way
+   * sizemode is.
+   *
+   * @param {ChromeWindow} win
+   */
+  #isSnapped(win) {
+    return (
+      win.windowState === win.STATE_MAXIMIZED ||
+      win.document.documentElement.hasAttribute("tiled")
+    );
   }
 }
diff --git a/src/zen/window-drag/nsIZenWindowDragUtils.idl b/src/zen/window-drag/nsIZenWindowDragUtils.idl
index 8389bbd01..995f67089 100644
--- a/src/zen/window-drag/nsIZenWindowDragUtils.idl
+++ b/src/zen/window-drag/nsIZenWindowDragUtils.idl
@@ -20,4 +20,15 @@ interface nsIZenWindowDragUtils : nsISupports {
    * @param node The node to check.
    */
   boolean isInteractiveContent(in Node node);
+
+  /**
+   * @brief Whether the effective cursor for the given node signals
+   * interactive or draggable content (pointer, text, move, resize, ...).
+   * Unlike computed style, this resolves cursor: auto the same way the
+   * cursor actually shown to the user is chosen.
+   * @param node The deepest node hit by the event.
+   * @param clientX Viewport X coordinate of the event, in CSS pixels.
+   * @param clientY Viewport Y coordinate of the event, in CSS pixels.
+   */
+  boolean isInteractiveCursor(in Node node, in float clientX, in float clientY);
 };
diff --git a/src/zen/window-drag/nsZenWindowDragUtils.cpp b/src/zen/window-drag/nsZenWindowDragUtils.cpp
index 06ef834b3..bd8d6cb2b 100644
--- a/src/zen/window-drag/nsZenWindowDragUtils.cpp
+++ b/src/zen/window-drag/nsZenWindowDragUtils.cpp
@@ -4,9 +4,13 @@
 
 #include "nsZenWindowDragUtils.h"
 
+#include "Units.h"
+#include "mozilla/PresShell.h"
+#include "mozilla/ServoStyleConsts.h"
 #include "mozilla/dom/Element.h"
 #include "nsContentUtils.h"
 #include "nsIContent.h"
+#include "nsIFrame.h"
 
 namespace zen {
 
@@ -30,4 +34,57 @@ nsZenWindowDragUtils::IsInteractiveContent(nsINode* aNode, bool* aResult) {
   return NS_OK;
 }
 
+NS_IMETHODIMP
+nsZenWindowDragUtils::IsInteractiveCursor(nsINode* aNode, float aClientX,
+                                          float aClientY, bool* aResult) {
+  using mozilla::StyleCursorKind;
+
+  *aResult = false;
+  NS_ENSURE_ARG_POINTER(aNode);
+
+  nsIContent* content = nsIContent::FromNode(aNode);
+  nsIFrame* frame = content ? content->GetPrimaryFrame() : nullptr;
+  if (!frame) {
+    return NS_OK;
+  }
+  nsIFrame* rootFrame = frame->PresShell()->GetRootFrame();
+  if (!rootFrame) {
+    return NS_OK;
+  }
+  nsPoint point(mozilla::CSSPixel::ToAppUnits(aClientX),
+                mozilla::CSSPixel::ToAppUnits(aClientY));
+  point -= frame->GetOffsetTo(rootFrame);
+
+  switch (frame->GetCursor(point).mCursor) {
+    case StyleCursorKind::Pointer:
+    case StyleCursorKind::Cell:
+    case StyleCursorKind::Crosshair:
+    case StyleCursorKind::Text:
+    case StyleCursorKind::VerticalText:
+    case StyleCursorKind::Move:
+    case StyleCursorKind::Grab:
+    case StyleCursorKind::Grabbing:
+    case StyleCursorKind::EResize:
+    case StyleCursorKind::NResize:
+    case StyleCursorKind::NeResize:
+    case StyleCursorKind::NwResize:
+    case StyleCursorKind::SResize:
+    case StyleCursorKind::SeResize:
+    case StyleCursorKind::SwResize:
+    case StyleCursorKind::WResize:
+    case StyleCursorKind::EwResize:
+    case StyleCursorKind::NsResize:
+    case StyleCursorKind::NeswResize:
+    case StyleCursorKind::NwseResize:
+    case StyleCursorKind::ColResize:
+    case StyleCursorKind::RowResize:
+    case StyleCursorKind::AllScroll:
+      *aResult = true;
+      break;
+    default:
+      break;
+  }
+  return NS_OK;
+}
+
 }  // namespace zen
diff --git a/surfer.json b/surfer.json
index 282e1f8a1..a1a87a88a 100644
--- a/surfer.json
+++ b/surfer.json
@@ -5,8 +5,8 @@
   "binaryName": "zen",
   "version": {
     "product": "firefox",
-    "version": "153.0.3",
-    "candidate": "153.0.3",
+    "version": "154.0.1",
+    "candidate": "154.0.1",
     "candidateBuild": 1
   },
   "buildOptions": {
@@ -20,7 +20,7 @@
       "brandShortName": "Zen",
       "brandFullName": "Zen Browser",
       "release": {
-        "displayVersion": "1.21.11b",
+        "displayVersion": "1.21.16b",
         "github": {
           "repo": "zen-browser/desktop"
         },