chore: Sync upstream to Firefox 152.0.6

When dragging a tab from the blank window to the main window, the blank
window doesn't close because '#isLastTabWindow' considers
'zen-empty-tab' as a normal tab.

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 `152.0.3`! 🚀
+- [`Release`](https://zen-browser.app/download) - Is currently built using Firefox version `152.0.6`! 🚀
-- [`Twilight`](https://zen-browser.app/download?twilight) - Is currently built using Firefox version `RC 152.0.3`!
+- [`Twilight`](https://zen-browser.app/download?twilight) - Is currently built using Firefox version `RC 152.0.5`!
 
 ### Contributing
 

build/firefox-cache/l10n-last-commit-hash

@@ -1 +1 @@
-b223f3727a037a7b8a0f36f34bfe8c4622a7f387
+e7fbb446077536139cdd78b6a0386a97237af20f

crowdin.yml

@@ -24,3 +24,5 @@ files:
     translation: browser/browser/zen-boosts.ftl
   - source: en-US/browser/browser/zen-space-routing.ftl
     translation: browser/browser/zen-space-routing.ftl
+  - source: en-US/browser/browser/zen-command-palette.ftl
+    translation: browser/browser/zen-command-palette.ftl

locales/en-US/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

locales/en-US/browser/browser/zen-folders.ftl

@@ -6,13 +6,13 @@ zen-folders-search-placeholder =
     .placeholder = Search { $folder-name }...
 
 zen-folders-panel-rename-folder =
-    .label = Rename Folder
+    .label = Rename Folder…
 
 zen-folders-panel-unpack-folder =
     .label = Unpack Folder
 
 zen-folders-new-subfolder =
-    .label = New Subfolder
+    .label = New Subfolder…
 
 zen-folders-panel-delete-folder =
     .label = Delete Folder
@@ -21,7 +21,7 @@ zen-folders-panel-convert-folder-to-space =
     .label = Convert folder to Space
 
 zen-folders-panel-change-folder-space =
-    .label = Change Space...
+    .label = Change Space
 
 zen-folders-unload-all-tooltip =
     .tooltiptext = Unload active in this folder

locales/en-US/browser/browser/zen-general.ftl

@@ -30,12 +30,12 @@ tab-context-zen-replace-pinned-url-with-current =
     .label = Replace with Current URL
     .accesskey = C
 tab-context-zen-edit-pinned-url =
-    .label = Edit...
+    .label = Edit…
     .accesskey = E
 tab-context-zen-edit-title =
-    .label = Change Label...
+    .label = Change Label…
 tab-context-zen-edit-icon =
-    .label = Change 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.
@@ -87,6 +87,8 @@ 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

locales/en-US/browser/browser/zen-vertical-tabs.ftl

@@ -20,7 +20,7 @@ zen-toolbar-context-compact-mode-hide-both =
     .accesskey = H
 
 zen-toolbar-context-move-to-folder =
-    .label = Move to Folder...
+    .label = Move to Folder
     .accesskey = M
 
 zen-toolbar-context-new-folder =
@@ -31,7 +31,7 @@ sidebar-zen-expand =
   .label = Expand Sidebar
 
 sidebar-zen-create-new =
-  .label = Create New...
+  .label = Create New
 
 tabbrowser-unload-tab-button =
 .tooltiptext =

locales/en-US/browser/browser/zen-workspaces.ftl

@@ -24,10 +24,10 @@ zen-workspaces-panel-context-delete =
     .accesskey = D
 
 zen-workspaces-panel-change-name =
-    .label = Change Name
+    .label = Change Name…
 
 zen-workspaces-panel-change-icon =
-    .label = Change Icon
+    .label = Change Icon…
 
 zen-workspaces-panel-context-default-profile =
     .label = Set Profile
@@ -42,7 +42,7 @@ 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
 
 zen-workspaces-change-theme =
-    .label = Edit Theme
+    .label = Edit Theme…
 
 zen-workspaces-panel-context-open =
     .label = Open Workspace
@@ -72,7 +72,7 @@ zen-workspace-creation-name =
     .placeholder = Space Name
 
 zen-move-tab-to-workspace-button =
-    .label = Move To...
+    .label = Move To
     .tooltiptext = Move all tabs in this window to a Space
 
 zen-workspaces-panel-context-reorder =

prefs/firefox/ai.yaml

@@ -23,3 +23,6 @@
 
 - name: browser.ml.linkPreview.enabled
   value: false
+
+- name: browser.preferences.aiControls
+  value: false

prefs/zen/sync.yaml

@@ -0,0 +1,12 @@
+# 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/.
+
+- name: services.sync.engine.spaces
+  value: true
+  condition: "@IS_TWILIGHT@"
+
+- name: services.sync.engine.spaces
+  value: false
+  locked: true
+  condition: "!@IS_TWILIGHT@"

prefs/zen/workspaces.yaml

@@ -32,9 +32,6 @@
 - name: zen.workspaces.scroll-modifier-key
   value: ctrl
 
-- name: services.sync.engine.workspaces
-  value: false
-
 - name: zen.workspaces.separate-essentials
   value: true
 

src/browser/base/content/zen-panels/emojis-picker.inc

@@ -14,7 +14,7 @@
   <hbox id="PanelUI-zen-emojis-picker-pages">
     <vbox emojis="true">
       <hbox id="PanelUI-zen-emojis-picker-header">
-        <html:input type="search" id="PanelUI-zen-emojis-picker-search" placeholder="Search emojis" />
+        <html:input type="search" id="PanelUI-zen-emojis-picker-search" data-l10n-id="zen-emojis-picker-search" />
       </hbox>
       <hbox id="PanelUI-zen-emojis-picker-list" />
     </vbox>

src/browser/components/preferences/config/account-sync-mjs.patch

@@ -0,0 +1,20 @@
+diff --git a/browser/components/preferences/config/account-sync.mjs b/browser/components/preferences/config/account-sync.mjs
+index b503987a08e2ce64bfc01c4e3a21e5e19ef834f0..b1c03a0b219fd3eddd93c1deaeb18ab79c85f168 100644
+--- a/browser/components/preferences/config/account-sync.mjs
++++ b/browser/components/preferences/config/account-sync.mjs
+@@ -42,6 +42,7 @@ Preferences.addAll([
+   { id: "services.sync.engine.creditcards", type: "bool" },
+   { id: "services.sync.engine.addons", type: "bool" },
+   { id: "services.sync.engine.prefs", type: "bool" },
++  { id: "services.sync.engine.spaces", type: "bool" },
+ ]);
+ 
+ /**
+@@ -546,6 +547,7 @@ const SYNC_ENGINE_SETTINGS = [
+     type: "payments",
+   },
+   { id: "syncAddons", pref: "services.sync.engine.addons", type: "addons" },
++  { id: "syncSpaces", pref: "services.sync.engine.spaces", type: "workspaces" },
+   { id: "syncSettings", pref: "services.sync.engine.prefs", type: "settings" },
+ ];
+ 

src/browser/components/preferences/dialogs/syncChooseWhatToSync-js.patch

@@ -6,7 +6,7 @@ index 64aa0d98a0622c01f3dcfff1a04bfcda368354d2..2013e04b0881ad2295d6897b91e1573c
    { id: "services.sync.engine.passwords", type: "bool" },
    { id: "services.sync.engine.addresses", type: "bool" },
    { id: "services.sync.engine.creditcards", type: "bool" },
-+  { id: "services.sync.engine.workspaces", type: "bool" },
++  { id: "services.sync.engine.spaces", type: "bool" },
  ]);
  
  let gSyncChooseWhatToSync = {

src/browser/components/preferences/dialogs/syncChooseWhatToSync-xhtml.patch

@@ -20,7 +20,7 @@ index a893c5ec3d007820d98f5d92dd039640faa2c181..9cbd00102e44ccf98b37845474d92d57
 +      <html:div class="sync-engine-workspaces">
 +        <checkbox
 +                data-l10n-id="sync-engine-workspaces"
-+                preference="services.sync.engine.workspaces"
++                preference="services.sync.engine.spaces"
 +        />
 +      </html:div>
      </html:div>

src/browser/components/preferences/preferences-js.patch

@@ -10,7 +10,7 @@ index 57add34d876fb885275f1147209c6fbeee367a7c..be0ab43b299317c0022a5e719f47a070
        ],
        resizeCallback: async ({ title, frame }) => {
          // Search within main document and highlight matched keyword.
-@@ -437,6 +438,8 @@ const CONFIG_PANES = Object.freeze({
+@@ -437,6 +437,8 @@ const CONFIG_PANES = Object.freeze({
    tabsBrowsing: {
      l10nId: "tabs-browsing-section",
      groupIds: [

src/browser/components/preferences/sync-inc-xhtml.patch

@@ -6,7 +6,7 @@ index c379e1a5f82692406a92d9fcd3bca2769dfac5b2..af037dd3d995813d966524ac44a3795d
                      <image class="sync-engine-image sync-engine-prefs" alt=""/>
                      <label data-l10n-id="sync-currently-syncing-settings"/>
                    </html:div>
-+                  <html:div engine_preference="services.sync.engine.workspaces">
++                  <html:div engine_preference="services.sync.engine.spaces">
 +                    <image class="sync-engine-image sync-engine-workspaces" alt=""/>
 +                    <label data-l10n-id="sync-currently-syncing-workspaces"/>
 +                  </html:div>

src/browser/components/tabbrowser/content/tabbrowser-js.patch

@@ -1,5 +1,5 @@
 diff --git a/browser/components/tabbrowser/content/tabbrowser.js b/browser/components/tabbrowser/content/tabbrowser.js
-index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d83330c265dfc 100644
+index 08b5b56e069d038d72c87355920c4ce8a55ed805..0e4f57c21d28ccf173d8d1e13e96c2c1f8a79f34 100644
 --- a/browser/components/tabbrowser/content/tabbrowser.js
 +++ b/browser/components/tabbrowser/content/tabbrowser.js
 @@ -511,6 +511,7 @@
@@ -109,7 +109,13 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        tab.linkedPanel = uniqueId;
        this._selectedTab = tab;
        this._selectedBrowser = browser;
-@@ -1131,13 +1192,18 @@
+@@ -1126,18 +1187,24 @@
+       aTab,
+       { telemetrySource = this.TabMetrics.METRIC_SOURCE.UNKNOWN } = {}
+     ) {
++      aTab = gZenGlanceManager.getTabOrGlanceParent(aTab);
+       if (aTab.pinned || aTab == FirefoxViewHandler.tab) {
+         return;
        }
  
        this.showTab(aTab);
@@ -129,7 +135,13 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
  
        aTab.setAttribute("pinned", "true");
        this._updateTabBarForPinnedTabs();
-@@ -1150,11 +1216,19 @@
+@@ -1145,16 +1212,25 @@
+     }
+ 
+     unpinTab(aTab) {
++      aTab = gZenGlanceManager.getTabOrGlanceParent(aTab);
+       if (!aTab.pinned) {
+         return;
        }
  
        this.#handleTabMove(aTab, () => {
@@ -150,7 +162,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        });
  
        aTab.style.marginInlineStart = "";
-@@ -1369,6 +1443,9 @@
+@@ -1369,6 +1445,9 @@
  
        let LOCAL_PROTOCOLS = ["chrome:", "about:", "resource:", "data:"];
  
@@ -160,7 +172,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        if (
          aIconURL &&
          !LOCAL_PROTOCOLS.some(protocol => aIconURL.startsWith(protocol))
-@@ -1378,6 +1455,9 @@
+@@ -1378,6 +1457,9 @@
          );
          return;
        }
@@ -170,7 +182,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
  
        let browser = this.getBrowserForTab(aTab);
        browser.mIconURL = aIconURL;
-@@ -1700,7 +1780,6 @@
+@@ -1700,7 +1782,6 @@
  
        // Preview mode should not reset the owner
        if (!this._previewMode && !oldTab.selected) {
@@ -178,7 +190,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        }
  
        let lastRelatedTab = this._lastRelatedTabMap.get(oldTab);
-@@ -1791,6 +1870,7 @@
+@@ -1791,6 +1872,7 @@
        if (!this._previewMode) {
          newTab.recordTimeFromUnloadToReload();
          newTab.updateLastAccessed();
@@ -186,7 +198,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
          oldTab.updateLastAccessed();
          // if this is the foreground window, update the last-seen timestamps.
          if (this.documentGlobal == BrowserWindowTracker.getTopWindow()) {
-@@ -2005,6 +2085,9 @@
+@@ -2005,6 +2087,9 @@
        }
  
        let activeEl = document.activeElement;
@@ -196,7 +208,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        // If focus is on the old tab, move it to the new tab.
        if (activeEl == oldTab) {
          newTab.focus();
-@@ -2043,7 +2126,7 @@
+@@ -2043,7 +2128,7 @@
        // 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.
@@ -205,7 +217,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
          let selectURL = () => {
            if (this._asyncTabSwitching) {
              // Set _awaitingSetURI flag to suppress popup notification
-@@ -2331,7 +2414,12 @@
+@@ -2331,7 +2416,12 @@
        return this._setTabLabel(aTab, aLabel);
      }
  
@@ -219,7 +231,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        if (!aLabel || (isURL && /^about:reader\?url=/.test(aLabel))) {
          return false;
        }
-@@ -2457,7 +2545,7 @@
+@@ -2457,7 +2547,7 @@
          newIndex = this.selectedTab._tPos + 1;
        }
  
@@ -228,7 +240,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
          if (this.isTabGroupLabel(targetTab)) {
            throw new Error(
              "Replacing a tab group label with a tab is not supported"
-@@ -2737,6 +2825,7 @@
+@@ -2737,6 +2827,7 @@
        uriIsAboutBlank,
        userContextId,
        skipLoad,
@@ -236,7 +248,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
      } = {}) {
        let b = document.createXULElement("browser");
        // Use the JSM global to create the permanentKey, so that if the
-@@ -2810,8 +2899,7 @@
+@@ -2810,8 +2901,7 @@
          // we use a different attribute name for this?
          b.setAttribute("name", name);
        }
@@ -246,7 +258,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
          b.setAttribute("transparent", "true");
        }
  
-@@ -2981,7 +3069,7 @@
+@@ -2981,7 +3071,7 @@
  
        let panel = this.getPanel(browser);
        let uniqueId = this._generateUniquePanelID();
@@ -255,7 +267,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        aTab.linkedPanel = uniqueId;
  
        // Inject the <browser> into the DOM if necessary.
-@@ -3041,8 +3129,8 @@
+@@ -3041,8 +3131,8 @@
        // 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) {
@@ -266,7 +278,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        } else {
          aTab.linkedBrowser.browsingContext.hasSiblings = this.tabs.length > 1;
        }
-@@ -3227,7 +3315,6 @@
+@@ -3227,7 +3317,6 @@
              this.selectedTab = this.addTrustedTab(BROWSER_NEW_TAB_URL, {
                tabIndex: tab._tPos + 1,
                userContextId: tab.userContextId,
@@ -274,7 +286,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
                focusUrlBar: true,
              });
              resolve(this.selectedBrowser);
-@@ -3337,6 +3424,10 @@
+@@ -3337,6 +3426,10 @@
          schemelessInput,
          hasValidUserGestureActivation = false,
          textDirectiveUserActivation = false,
@@ -285,7 +297,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        } = {}
      ) {
        // all callers of addTab that pass a params object need to pass
-@@ -3347,10 +3438,25 @@
+@@ -3347,10 +3440,25 @@
          );
        }
  
@@ -296,7 +308,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
 +
 +      let hasZenDefaultUserContextId = false;
 +      let zenForcedWorkspaceId = undefined;
-+      if (beforeRouteResult.isRouteFound && typeof userContextId !== "undefined") {
++      if (beforeRouteResult.isRouteFound && typeof userContextId === "undefined") {
 +        userContextId = beforeRouteResult.userContextId;
 +        hasZenDefaultUserContextId = true;
 +      } else if (typeof gZenWorkspaces !== "undefined" && !_forZenEmptyTab) {
@@ -311,7 +323,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        // If we're opening a foreground tab, set the owner by default.
        ownerTab ??= inBackground ? null : this.selectedTab;
  
-@@ -3358,6 +3464,7 @@
+@@ -3358,6 +3466,7 @@
        if (this.selectedTab.owner) {
          this.selectedTab.owner = null;
        }
@@ -319,7 +331,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
  
        // Find the tab that opened this one, if any. This is used for
        // determining positioning, and inherited attributes such as the
-@@ -3410,6 +3517,22 @@
+@@ -3410,6 +3519,22 @@
            noInitialLabel,
            skipBackgroundNotify,
          });
@@ -342,7 +354,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
          if (insertTab) {
            // Insert the tab into the tab container in the correct position.
            this.#insertTabAtIndex(t, {
-@@ -3418,6 +3541,7 @@
+@@ -3418,6 +3543,7 @@
              ownerTab,
              openerTab,
              pinned,
@@ -350,7 +362,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
              bulkOrderedOpen,
              tabGroup: tabGroup ?? openerTab?.group,
            });
-@@ -3436,6 +3560,7 @@
+@@ -3436,6 +3562,7 @@
            openWindowInfo,
            skipLoad,
            triggeringRemoteType,
@@ -358,7 +370,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
          }));
  
          if (focusUrlBar) {
-@@ -3560,6 +3685,12 @@
+@@ -3560,6 +3687,12 @@
          }
        }
  
@@ -371,7 +383,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        // Additionally send pinned tab events
        if (pinned) {
          this.#notifyPinnedStatus(t);
-@@ -3570,6 +3701,15 @@
+@@ -3570,6 +3703,15 @@
        if (!inBackground) {
          this.selectedTab = t;
        }
@@ -387,7 +399,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        return t;
      }
  
-@@ -3802,6 +3942,7 @@
+@@ -3802,6 +3944,7 @@
          isAdoptingGroup = false,
          isUserTriggered = false,
          telemetryUserCreateSource = "unknown",
@@ -395,7 +407,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        } = {}
      ) {
        if (
-@@ -3812,9 +3953,6 @@
+@@ -3812,9 +3955,6 @@
              !this.isSplitViewWrapper(tabOrSplitView)
          )
        ) {
@@ -405,7 +417,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        }
  
        if (!color) {
-@@ -3835,9 +3973,14 @@
+@@ -3835,9 +3975,14 @@
          label,
          isAdoptingGroup
        );
@@ -422,7 +434,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        );
        group.addTabs(tabsAndSplitViews);
  
-@@ -3958,7 +4101,7 @@
+@@ -3958,7 +4103,7 @@
        }
  
        this.#handleTabMove(tab, () =>
@@ -431,7 +443,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        );
      }
  
-@@ -4044,6 +4187,7 @@
+@@ -4044,6 +4189,7 @@
          color: group.color,
          insertBefore: newTabs[0],
          isAdoptingGroup: true,
@@ -439,7 +451,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        });
      }
  
-@@ -4254,6 +4398,7 @@
+@@ -4254,6 +4400,7 @@
          openWindowInfo,
          skipLoad,
          triggeringRemoteType,
@@ -447,7 +459,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        }
      ) {
        // If we don't have a preferred remote type (or it is `NOT_REMOTE`), and
-@@ -4323,6 +4468,7 @@
+@@ -4323,6 +4470,7 @@
            openWindowInfo,
            name,
            skipLoad,
@@ -455,7 +467,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
          });
        }
  
-@@ -4536,9 +4682,9 @@
+@@ -4536,9 +4684,9 @@
          }
  
          // Add a new tab if needed.
@@ -467,7 +479,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
  
            let url = "about:blank";
            if (tabData.entries?.length) {
-@@ -4575,8 +4721,10 @@
+@@ -4575,8 +4723,10 @@
              insertTab: false,
              skipLoad: true,
              preferredRemoteType,
@@ -479,7 +491,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
            if (select) {
              tabToSelect = tab;
            }
-@@ -4598,7 +4746,8 @@
+@@ -4598,7 +4748,8 @@
            this.pinTab(tab);
            // Then ensure all the tab open/pinning information is sent.
            this._fireTabOpen(tab, {});
@@ -489,7 +501,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
            let { groupId } = tabData;
            const tabGroup = tabGroupWorkingData.get(groupId);
            // if a tab refers to a tab group we don't know, skip any group
-@@ -4618,7 +4767,10 @@
+@@ -4618,7 +4769,10 @@
                  tabGroup.stateData.id,
                  tabGroup.stateData.color,
                  tabGroup.stateData.collapsed,
@@ -501,7 +513,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
                );
                tabsFragment.appendChild(tabGroup.node);
              }
-@@ -4673,9 +4825,21 @@
+@@ -4673,9 +4827,21 @@
        // to remove the old selected tab.
        if (tabToSelect) {
          let leftoverTab = this.selectedTab;
@@ -523,7 +535,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
  
        if (tabs.length > 1 || !tabs[0].selected) {
          this._updateTabsAfterInsert();
-@@ -4866,11 +5030,17 @@
+@@ -4866,11 +5032,17 @@
        if (ownerTab) {
          tab.owner = ownerTab;
        }
@@ -542,7 +554,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
          if (
            !bulkOrderedOpen &&
            ((openerTab &&
-@@ -4882,7 +5052,7 @@
+@@ -4882,7 +5054,7 @@
            let lastRelatedTab =
              openerTab && this._lastRelatedTabMap.get(openerTab);
            let previousTab = lastRelatedTab || openerTab || this.selectedTab;
@@ -551,7 +563,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
              tabGroup = previousTab.group;
            }
            if (
-@@ -4898,7 +5068,7 @@
+@@ -4898,7 +5070,7 @@
                  previousTab.splitview
                ) + 1;
            } else if (previousTab.visible) {
@@ -560,7 +572,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
            } else if (previousTab == FirefoxViewHandler.tab) {
              elementIndex = 0;
            }
-@@ -4926,14 +5096,14 @@
+@@ -4926,14 +5098,14 @@
        }
        // Ensure index is within bounds.
        if (tab.pinned) {
@@ -579,7 +591,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
  
        if (pinned && !itemAfter?.pinned) {
          itemAfter = null;
-@@ -4950,7 +5120,7 @@
+@@ -4950,7 +5122,7 @@
  
        this.tabContainer._invalidateCachedTabs();
  
@@ -588,7 +600,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
          if (
            (this.isTab(itemAfter) && itemAfter.group == tabGroup) ||
            this.isSplitViewWrapper(itemAfter)
-@@ -4981,7 +5151,11 @@
+@@ -4981,7 +5153,11 @@
          const tabContainer = pinned
            ? this.tabContainer.pinnedTabsContainer
            : this.tabContainer;
@@ -600,7 +612,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        }
  
        if (tab.group?.collapsed) {
-@@ -4996,6 +5170,7 @@
+@@ -4996,6 +5172,7 @@
        if (pinned) {
          this._updateTabBarForPinnedTabs();
        }
@@ -608,7 +620,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
  
        TabBarVisibility.update();
      }
-@@ -5544,6 +5719,7 @@
+@@ -5544,6 +5721,7 @@
          telemetrySource,
        } = {}
      ) {
@@ -616,7 +628,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        // When 'closeWindowWithLastTab' pref is enabled, closing all tabs
        // can be considered equivalent to closing the window.
        if (
-@@ -5633,6 +5809,7 @@
+@@ -5633,6 +5811,7 @@
          if (lastToClose) {
            this.removeTab(lastToClose, aParams);
          }
@@ -624,7 +636,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        } catch (e) {
          console.error(e);
        }
-@@ -5678,6 +5855,14 @@
+@@ -5678,6 +5857,14 @@
          return;
        }
  
@@ -639,7 +651,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        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
-@@ -5685,6 +5870,9 @@
+@@ -5685,6 +5872,9 @@
        // state).
        let tabWidth = window.windowUtils.getBoundsWithoutFlushing(aTab).width;
        let isLastTab = this.#isLastTabInWindow(aTab);
@@ -649,7 +661,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        if (
          !this._beginRemoveTab(aTab, {
            closeWindowFastpath: true,
-@@ -5696,13 +5884,14 @@
+@@ -5696,13 +5886,14 @@
            telemetrySource,
          })
        ) {
@@ -665,7 +677,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        let lockTabSizing =
          !this.tabContainer.verticalMode &&
          !aTab.pinned &&
-@@ -5733,7 +5922,13 @@
+@@ -5733,7 +5924,13 @@
          // We're not animating, so we can cancel the animation stopwatch.
          Glean.browserTabclose.timeAnim.cancel(aTab._closeTimeAnimTimerId);
          aTab._closeTimeAnimTimerId = null;
@@ -680,7 +692,16 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
          return;
        }
  
-@@ -5867,7 +6062,7 @@
+@@ -5776,7 +5973,7 @@
+      */
+     #isLastTabInWindow(tab) {
+       for (const otherTab of this.tabs) {
+-        if (otherTab != tab && otherTab.isOpen && !otherTab.hidden) {
++        if (otherTab != tab && otherTab.isOpen && !otherTab.hidden && !otherTab.hasAttribute("zen-empty-tab")) {
+           return false;
+         }
+       }
+@@ -5867,7 +6064,7 @@
            closeWindowWithLastTab != null
              ? closeWindowWithLastTab
              : !window.toolbar.visible ||
@@ -689,7 +710,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
  
          if (closeWindow) {
            // We've already called beforeunload on all the relevant tabs if we get here,
-@@ -5891,6 +6086,7 @@
+@@ -5891,6 +6088,7 @@
  
          newTab = true;
        }
@@ -697,7 +718,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        aTab._endRemoveArgs = [closeWindow, newTab];
  
        // swapBrowsersAndCloseOther will take care of closing the window without animation.
-@@ -5931,13 +6127,7 @@
+@@ -5931,13 +6129,7 @@
        aTab._mouseleave();
  
        if (newTab) {
@@ -712,7 +733,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        } else {
          TabBarVisibility.update();
        }
-@@ -6070,6 +6260,7 @@
+@@ -6070,6 +6262,7 @@
          this.tabs[i]._tPos = i;
        }
  
@@ -720,7 +741,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        if (!this._windowIsClosing) {
          // update tab close buttons state
          this.tabContainer._updateCloseButtons();
-@@ -6255,6 +6446,7 @@
+@@ -6255,6 +6448,7 @@
          memory_after: await getTotalMemoryUsage(),
          time_to_unload_in_ms: timeElapsed,
        });
@@ -728,7 +749,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
      }
  
      /**
-@@ -6300,6 +6492,7 @@
+@@ -6300,6 +6494,7 @@
        }
  
        let excludeTabs = new Set(aExcludeTabs);
@@ -736,7 +757,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
  
        // If this tab has a successor, it should be selectable, since
        // hiding or closing a tab removes that tab as a successor.
-@@ -6312,15 +6505,22 @@
+@@ -6312,15 +6507,22 @@
          !excludeTabs.has(aTab.owner) &&
          Services.prefs.getBoolPref("browser.tabs.selectOwnerOnClose")
        ) {
@@ -761,7 +782,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        let tab = this.tabContainer.findNextTab(aTab, {
          direction: 1,
          filter: _tab => remainingTabs.includes(_tab),
-@@ -6334,7 +6534,7 @@
+@@ -6334,7 +6536,7 @@
        }
  
        if (tab) {
@@ -770,7 +791,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        }
  
        // If no qualifying visible tab was found, see if there is a tab in
-@@ -6355,7 +6555,7 @@
+@@ -6355,7 +6557,7 @@
          });
        }
  
@@ -779,7 +800,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
      }
  
      _blurTab(aTab) {
-@@ -6366,7 +6566,7 @@
+@@ -6366,7 +6568,7 @@
       * @returns {boolean}
       *   False if swapping isn't permitted, true otherwise.
       */
@@ -788,7 +809,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        // Do not allow transfering a private tab to a non-private window
        // and vice versa.
        if (
-@@ -6420,6 +6620,7 @@
+@@ -6420,6 +6622,7 @@
        // fire the beforeunload event in the process.  Close the other
        // window if this was its last tab.
        if (
@@ -796,7 +817,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
          !remoteBrowser._beginRemoveTab(aOtherTab, {
            adoptedByTab: aOurTab,
            closeWindowWithLastTab: true,
-@@ -6431,7 +6632,7 @@
+@@ -6431,7 +6634,7 @@
        // 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.
@@ -805,7 +826,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        if (closeWindow) {
          let win = aOtherTab.documentGlobal;
          win.windowUtils.suppressAnimation(true);
-@@ -6565,11 +6766,13 @@
+@@ -6565,11 +6768,13 @@
        }
  
        // Finish tearing down the tab that's going away.
@@ -819,7 +840,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
  
        this.setTabTitle(aOurTab);
  
-@@ -6771,10 +6974,10 @@
+@@ -6771,10 +6976,10 @@
        SessionStore.deleteCustomTabValue(aTab, "hiddenBy");
      }
  
@@ -832,7 +853,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
          aTab.selected ||
          aTab.closing ||
          // Tabs that are sharing the screen, microphone or camera cannot be hidden.
-@@ -6834,7 +7037,8 @@
+@@ -6834,7 +7039,8 @@
       * @param {object} [aOptions={}]
       *   Key-value pairs that will be serialized into the features string.
       */
@@ -842,7 +863,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        if (this.tabs.length == 1) {
          return null;
        }
-@@ -6851,7 +7055,7 @@
+@@ -6851,7 +7057,7 @@
        // tell a new window to take the "dropped" tab
        let args = Cc["@mozilla.org/array;1"].createInstance(Ci.nsIMutableArray);
        args.appendElement(aTab.splitview ?? aTab);
@@ -851,7 +872,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
          private: PrivateBrowsingUtils.isWindowPrivate(window),
          features: Object.entries(aOptions)
            .map(([key, value]) => `${key}=${value}`)
-@@ -6859,6 +7063,8 @@
+@@ -6859,6 +7065,8 @@
          openerWindow: window,
          args,
        });
@@ -860,7 +881,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
      }
  
      /**
-@@ -6971,7 +7177,7 @@
+@@ -6971,7 +7179,7 @@
       *   `true` if element is a `<tab-group>`
       */
      isTabGroup(element) {
@@ -869,7 +890,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
      }
  
      /**
-@@ -7056,8 +7262,8 @@
+@@ -7056,8 +7264,8 @@
        }
  
        // Don't allow mixing pinned and unpinned tabs.
@@ -880,7 +901,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        } else {
          tabIndex = Math.max(tabIndex, this.pinnedTabCount);
        }
-@@ -7103,8 +7309,8 @@
+@@ -7103,8 +7311,8 @@
        this.#handleTabMove(
          element,
          () => {
@@ -891,7 +912,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
              neighbor = neighbor.group;
            }
            if (neighbor?.splitview) {
-@@ -7115,6 +7321,12 @@
+@@ -7115,6 +7323,12 @@
                return;
              }
            }
@@ -904,7 +925,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
  
            if (movingForwards && neighbor) {
              neighbor.after(element);
-@@ -7173,23 +7385,31 @@
+@@ -7173,23 +7387,31 @@
      #moveTabNextTo(element, targetElement, moveBefore = false, metricsContext) {
        if (this.isTabGroupLabel(targetElement)) {
          targetElement = targetElement.group;
@@ -942,7 +963,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        } 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
-@@ -7202,12 +7422,35 @@
+@@ -7202,12 +7424,35 @@
          //    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.
@@ -979,7 +1000,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
  
        // 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.
-@@ -7216,6 +7459,7 @@
+@@ -7216,6 +7461,7 @@
        }
  
        let getContainer = () =>
@@ -987,7 +1008,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
          element.pinned
            ? this.tabContainer.pinnedTabsContainer
            : this.tabContainer;
-@@ -7224,11 +7468,15 @@
+@@ -7224,11 +7470,15 @@
          element,
          () => {
            if (moveBefore) {
@@ -1004,7 +1025,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
            }
          },
          metricsContext
-@@ -7302,11 +7550,15 @@
+@@ -7302,11 +7552,15 @@
       * @param {TabMetricsContext} [metricsContext]
       */
      moveTabToExistingGroup(aTab, aGroup, metricsContext) {
@@ -1023,7 +1044,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        }
        if (aTab.group && aTab.group.id === aGroup.id) {
          return;
-@@ -7378,6 +7630,7 @@
+@@ -7378,6 +7632,7 @@
  
        let state = {
          tabIndex: tab._tPos,
@@ -1031,7 +1052,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        };
        if (tab.visible) {
          state.elementIndex = tab.elementIndex;
-@@ -7409,7 +7662,7 @@
+@@ -7409,7 +7664,7 @@
        let changedSplitView =
          previousTabState.splitViewId != currentTabState.splitViewId;
  
@@ -1040,7 +1061,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
          tab.dispatchEvent(
            new CustomEvent("TabMove", {
              bubbles: true,
-@@ -7456,6 +7709,10 @@
+@@ -7456,6 +7711,10 @@
  
        moveActionCallback();
  
@@ -1051,7 +1072,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        // Clear tabs cache after moving nodes because the order of tabs may have
        // changed.
        this.tabContainer._invalidateCachedTabs();
-@@ -7506,7 +7763,22 @@
+@@ -7506,7 +7765,22 @@
       * @returns {object}
       *    The new tab in the current window, null if the tab couldn't be adopted.
       */
@@ -1075,7 +1096,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        // 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
-@@ -7549,6 +7821,8 @@
+@@ -7549,6 +7823,8 @@
        }
        params.skipLoad = true;
        let newTab = this.addWebTab("about:blank", params);
@@ -1084,7 +1105,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
  
        aTab.container.tabDragAndDrop.finishAnimateTabMove();
  
-@@ -8259,7 +8533,7 @@
+@@ -8259,7 +8535,7 @@
          // preventDefault(). It will still raise the window if appropriate.
          return;
        }
@@ -1093,7 +1114,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        window.focus();
        aEvent.preventDefault();
      }
-@@ -8276,7 +8550,6 @@
+@@ -8276,7 +8552,6 @@
  
      on_TabGroupCollapse(aEvent) {
        aEvent.target.tabs.forEach(tab => {
@@ -1101,7 +1122,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
        });
      }
  
-@@ -8630,7 +8903,9 @@
+@@ -8630,7 +8905,9 @@
  
          let filter = this._tabFilters.get(tab);
          if (filter) {
@@ -1111,7 +1132,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
  
            let listener = this._tabListeners.get(tab);
            if (listener) {
-@@ -9435,6 +9710,7 @@
+@@ -9435,6 +9712,7 @@
              aWebProgress.isTopLevel
            ) {
              this.mTab.setAttribute("busy", "true");
@@ -1119,7 +1140,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
              gBrowser._tabAttrModified(this.mTab, ["busy"]);
              this.mTab._notselectedsinceload = !this.mTab.selected;
            }
-@@ -9515,6 +9791,7 @@
+@@ -9515,6 +9793,7 @@
          // known defaults. Note we use the original URL since about:newtab
          // redirects to a prerendered page.
          const shouldRemoveFavicon =
@@ -1127,7 +1148,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
            !this.mBrowser.mIconURL &&
            !ignoreBlank &&
            !(originalLocation.spec in FAVICON_DEFAULTS);
-@@ -9689,13 +9966,6 @@
+@@ -9689,13 +9968,6 @@
              this.mBrowser.originalURI = aRequest.originalURI;
            }
  
@@ -1141,7 +1162,7 @@ index 08b5b56e069d038d72c87355920c4ce8a55ed805..87f41c8583c26f364530def5bd5d8333
          }
  
          let userContextId = this.mBrowser.getAttribute("usercontextid") || 0;
-@@ -10587,7 +10857,8 @@ var TabContextMenu = {
+@@ -10587,7 +10859,8 @@ var TabContextMenu = {
      );
      contextUnpinSelectedTabs.hidden =
        !this.contextTab.pinned || !this.multiselected;

src/browser/components/urlbar/UrlbarUtils-sys-mjs.patch

@@ -1,9 +1,9 @@
 diff --git a/browser/components/urlbar/UrlbarUtils.sys.mjs b/browser/components/urlbar/UrlbarUtils.sys.mjs
-index 2f03bdf632c6ca15c728df2801162da5159682da..6834daede8cb11854f137602100183d85a930686 100644
+index aa7c67f2bfaa3f15d592a14b527a8721dfc9bc6f..d2fe012796ea3a5be05090a732011b3cf92b78be 100644
 --- a/browser/components/urlbar/UrlbarUtils.sys.mjs
 +++ b/browser/components/urlbar/UrlbarUtils.sys.mjs
-@@ -109,6 +109,8 @@ export var UrlbarUtils = {
+@@ -110,6 +110,8 @@ export var UrlbarUtils = {
-     RESTRICT_SEARCH_KEYWORD: "restrictSearchKeyword",
+     SEMANTIC_HISTORY: "semanticHistory",
      SUGGESTED_INDEX: "suggestedIndex",
      TAIL_SUGGESTION: "tailSuggestion",
 +    ZEN_ACTION: "zenAction",
@@ -11,7 +11,7 @@ index 2f03bdf632c6ca15c728df2801162da5159682da..6834daede8cb11854f137602100183d8
    }),
  
    // Defines provider types.
-@@ -170,6 +172,8 @@ export var UrlbarUtils = {
+@@ -171,6 +173,8 @@ export var UrlbarUtils = {
      OTHER_NETWORK: 6,
      ADDON: 7,
      ACTIONS: 8,
@@ -20,7 +20,7 @@ index 2f03bdf632c6ca15c728df2801162da5159682da..6834daede8cb11854f137602100183d8
    }),
  
    // Per-result exposure telemetry.
-@@ -319,6 +323,14 @@ export var UrlbarUtils = {
+@@ -320,6 +324,14 @@ export var UrlbarUtils = {
          telemetryLabel: "actions",
          uiLabel: "urlbar-searchmode-actions2",
        },
@@ -35,7 +35,7 @@ index 2f03bdf632c6ca15c728df2801162da5159682da..6834daede8cb11854f137602100183d8
      ]);
    },
  
-@@ -611,6 +623,12 @@ export var UrlbarUtils = {
+@@ -612,6 +624,12 @@ export var UrlbarUtils = {
            return this.RESULT_GROUP.HEURISTIC_FALLBACK;
          case "UrlbarProviderHistoryUrlHeuristic":
            return this.RESULT_GROUP.HEURISTIC_HISTORY_URL;

src/browser/themes/shared/preferences/zen-preferences.css

@@ -484,13 +484,10 @@ groupbox h2 {
 #helpButton,
 #support-firefox,
 #tabGroupSuggestions,
-#web-appearance-manage-themes-link,
 #setting-control-sidebarChatbotFieldset,
-#aiControlsDescription,
-#category-ai-features,
 #setting-control-supportFirefox,
 .mission-message,
-html|setting-group:is([data-subcategory="layout"], [groupid="support"]) {
+html|setting-group:is([data-subcategory="layout"], [groupid="support"], [groupid="browserTheme"]) {
   display: none !important;
 }
 

src/services/sync/modules/service-sys-mjs.patch

@@ -0,0 +1,15 @@
+diff --git a/services/sync/modules/service.sys.mjs b/services/sync/modules/service.sys.mjs
+index 4f4efe572909441abdd81909282936702c225621..81ab06a9414ed656b644a21b40b683f06a4f8dbf 100644
+--- a/services/sync/modules/service.sys.mjs
++++ b/services/sync/modules/service.sys.mjs
+@@ -99,6 +99,10 @@ function getEngineModules() {
+     whenTrue: "ExtensionStorageEngineKinto",
+     whenFalse: "ExtensionStorageEngineBridge",
+   };
++  result.Spaces = {
++    module: "resource:///modules/zen/ZenWorkspacesSync.sys.mjs",
++    symbol: "ZenWorkspacesEngine",
++  };
+   return result;
+ }
+ 

src/toolkit/components/contextualidentity/ContextualIdentityService-sys-mjs.patch

@@ -0,0 +1,37 @@
+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

src/zen/common/modules/ZenUIManager.mjs

@@ -1579,6 +1579,7 @@ window.gZenVerticalTabsManager = {
           overflowElements.appendChild(child);
         } else {
           const element = document.getElementById("page-action-buttons");
+          child.setAttribute("context", "toolbar-context-menu");
           element.before(child);
         }
         return;
@@ -1612,7 +1613,9 @@ window.gZenVerticalTabsManager = {
         // it will reset to the original name anyway
         if (hasChanged || (this._tabEdited.zenStaticLabel && newName)) {
           this._tabEdited.zenStaticLabel = newName;
-          gBrowser._setTabLabel(this._tabEdited, newName);
+          gBrowser._setTabLabel(this._tabEdited, newName, {
+            _zenChangeLabelFlag: true,
+          });
           gZenUIManager.showToast("zen-tabs-renamed");
         } else {
           delete this._tabEdited.zenStaticLabel;
@@ -1708,7 +1711,8 @@ window.gZenVerticalTabsManager = {
       this._tabEdited.after(input);
     }
     input.focus();
-    input.select();
+    input.setSelectionRange(0, input.value.length, "backward");
+    input.scrollLeft = 0;
 
     input.addEventListener("blur", this._renameTabHalt);
   },

src/zen/common/zen-sets.js

@@ -115,7 +115,9 @@ document.addEventListener(
             });
             break;
           case "cmd_zenTogglePinTab": {
-            const currentTab = gBrowser.selectedTab;
+            const currentTab = gZenGlanceManager.getTabOrGlanceParent(
+              gBrowser.selectedTab
+            );
             if (currentTab && !currentTab.hasAttribute("zen-empty-tab")) {
               if (currentTab.pinned) {
                 gBrowser.unpinTab(currentTab);

src/zen/compact-mode/sidebar.inc.css

@@ -51,6 +51,10 @@
     --zen-toolbox-max-width: 74px !important;
     --zen-compact-float: var(--zen-element-separation);
 
+    @media (-moz-mac-tahoe-theme) {
+      --zen-compact-mode-no-padding-radius-fix: -2px;
+    }
+
     :root[zen-no-padding='true'] & {
       --zen-compact-float: 10px;
       --zen-compact-top-toolbar-hidden-fix: var(--zen-compact-float);

src/zen/drag-and-drop/ZenDragAndDrop.js

@@ -69,6 +69,7 @@
     #changeSpaceTimer = null;
     #isAnimatingTabMove = false;
     #firstHapticFeedbackPlayed = false;
+    #lastDragOverTime = 0;
 
     #dragOverSplit = {};
 
@@ -723,9 +724,11 @@
       const { isNearLeftEdge, isNearRightEdge } =
         this.#shouldSwitchSpace(event);
       if (isNearLeftEdge || isNearRightEdge) {
-        if (!this.#changeSpaceTimer && !this.#isOutOfWindow) {
+        this.#lastDragOverTime = Date.now();
+        if (!this.#changeSpaceTimer) {
           this.#changeSpaceTimer = setTimeout(() => {
-            if (this.#isOutOfWindow) {
+            const timeSinceLastDragOver = Date.now() - this.#lastDragOverTime;
+            if (timeSinceLastDragOver > 250) {
               return;
             }
             this.clearDragOverVisuals();
@@ -1333,7 +1336,8 @@
       // Essentials should be properly handled by ::animateVerticalPinnedGridDragOver
       if (!dropElement || dropElement.hasAttribute("zen-essential")) {
         this.clearDragOverVisuals();
-        return null;
+        // If dropElement is null or essential, dropElement should be the empty tab
+        return [dropBefore, gZenWorkspaces._emptyTab];
       }
       if (dropElement.hasAttribute("zen-empty-tab") && dropElement.group) {
         let secondTab = dropElement.group.tabs[1];

src/zen/folders/ZenFolder.mjs

@@ -289,6 +289,9 @@ export class nsZenFolder extends MozTabbrowserTabGroup {
   addTabs(tabs) {
     let tabsFromOutside = [];
     for (let tab of tabs) {
+      if (tab.hasAttribute("zen-essential")) {
+        gZenPinnedTabManager.removeEssentials(tab, false);
+      }
       if (tab.group !== this) {
         tabsFromOutside.push(tab);
       }

src/zen/folders/ZenFolders.mjs

@@ -622,15 +622,13 @@ class nsZenFolders extends nsZenDOMOperatedFeature {
   }
 
   createFolder(tabs = [], options = {}) {
-    const filteredTabs = tabs
+    const filteredTabs = tabs.map(tab => {
-      .filter(tab => !tab.hasAttribute("zen-essential"))
+      gBrowser.pinTab(tab);
-      .map(tab => {
+      if (tab?.group?.hasAttribute("split-view-group")) {
-        gBrowser.pinTab(tab);
+        tab = tab.group;
-        if (tab?.group?.hasAttribute("split-view-group")) {
+      }
-          tab = tab.group;
+      return tab;
-        }
+    });
-        return tab;
-      });
 
     const workspacePinned = gZenWorkspaces.workspaceElement(
       options.workspaceId

src/zen/glance/ZenGlanceManager.mjs

@@ -85,8 +85,7 @@ class nsZenGlanceManager extends nsZenDOMOperatedFeature {
     menuitem.addEventListener("command", () =>
       this.openGlance({
         url: gContextMenu.linkURL,
-        triggeringPrincipal:
+        triggeringPrincipal: gContextMenu.principal,
-          Services.scriptSecurityManager.getSystemPrincipal(),
       })
     );
 
@@ -354,6 +353,28 @@ class nsZenGlanceManager extends nsZenDOMOperatedFeature {
     return this.#lastLinkClickData;
   }
 
+  /**
+   * Check whether a glance load is permitted for its triggering principal.
+   *
+   * @param {object} data - Glance data including URL and triggeringPrincipal
+   * @returns {boolean} Whether the load is allowed
+   */
+  #isGlanceLoadAllowed(data) {
+    const { url, triggeringPrincipal } = data ?? {};
+    if (typeof url !== "string" || !url.length || !triggeringPrincipal) {
+      return false;
+    }
+    try {
+      Services.scriptSecurityManager.checkLoadURIStrWithPrincipal(
+        triggeringPrincipal,
+        url
+      );
+    } catch {
+      return false;
+    }
+    return true;
+  }
+
   /**
    * Open a glance overlay with the specified data
    *
@@ -371,6 +392,13 @@ class nsZenGlanceManager extends nsZenDOMOperatedFeature {
       return Promise.resolve(this.#currentTab);
     }
 
+    // Existing-tab glances perform no navigation and are exempt; for fresh
+    // loads, refuse any URL the triggering principal isn't allowed to load
+    // (e.g. a web page linking to file://).
+    if (!existingTab && !this.#isGlanceLoadAllowed(data)) {
+      return Promise.resolve(null);
+    }
+
     if (!data.height || !data.width) {
       data = {
         ...data,
@@ -1523,6 +1551,7 @@ class nsZenGlanceManager extends nsZenDOMOperatedFeature {
     return (
       owner &&
       owner.pinned &&
+      !owner.hasAttribute("glance-id") &&
       this._lazyPref.SHOULD_OPEN_EXTERNAL_TABS_IN_GLANCE &&
       owner.linkedBrowser?.browsingContext?.isAppTab &&
       this.tabDomainsDiffer(owner, uri) &&

src/zen/moz.build

@@ -20,4 +20,5 @@ DIRS += [
     "share",
     "spaces",
     "space-routing",
+    "sync",
 ]

src/zen/sessionstore/ZenSessionManager.sys.mjs

@@ -10,6 +10,7 @@ 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",
@@ -609,6 +610,7 @@ export class nsZenSessionManager {
       }
     );
     this.#collectWindowData(windows);
+    lazy.ZenSyncStore.notifyAboutChanges();
     // This would save the data to disk asynchronously or when quitting the app.
     let sidebar = this.#sidebarWithoutCloning;
     this.#file.data = sidebar;
@@ -622,6 +624,15 @@ export class nsZenSessionManager {
     this.log(`Saving Zen session data with ${sidebar.tabs?.length || 0} tabs`);
   }
 
+  /**
+   * Returns the sidebar data object.
+   *
+   * @returns {object}
+   */
+  getSidebarData() {
+    return this.#sidebarWithoutCloning;
+  }
+
   /**
    * Called when the last known backup should be deleted and a new one
    * created. This uses the #deferredBackupTask to debounce clusters of

src/zen/space-routing/ZenSpaceRoutingManager.sys.mjs

@@ -245,10 +245,6 @@ class nsZenSpaceRoutingManager {
           if (targetWorkspace) {
             workspaces.moveTabToWorkspace(newTab, targetWorkspace.uuid);
 
-            if (inBackground) {
-              return;
-            }
-
             const mostRecentWindow =
               Services.wm.getMostRecentWindow("navigator:browser");
             const isOriginatingWindow = win === mostRecentWindow;
@@ -256,7 +252,10 @@ class nsZenSpaceRoutingManager {
               win.gZenWorkspaces.lastSelectedWorkspaceTabs[
                 targetWorkspace.uuid
               ] = newTab;
-              await win.gZenWorkspaces.changeWorkspace(targetWorkspace);
+
+              if (!inBackground) {
+                await win.gZenWorkspaces.changeWorkspace(targetWorkspace);
+              }
             }
           }
         }

src/zen/spaces/ZenSpaceCreation.mjs

@@ -182,8 +182,8 @@ class nsZenWorkspaceCreation extends MozXULElement {
         this.onProfileCommand.bind(this)
       );
       this.profilesPopup.addEventListener(
-        "popupshown",
+        "popupshowing",
-        this.onProfilePopupShown.bind(this)
+        this.onProfilePopupShowing.bind(this)
       );
       this.profilesPopup.addEventListener(
         "command",
@@ -192,7 +192,7 @@ class nsZenWorkspaceCreation extends MozXULElement {
 
       this.currentProfile = {
         id: 0,
-        name: "Default",
+        name: ContextualIdentityService.formatContextLabel("user-context-none"),
       };
     } else {
       this.inputProfile.parentNode.hidden = true;
@@ -296,7 +296,7 @@ class nsZenWorkspaceCreation extends MozXULElement {
     this.profilesPopup.openPopup(event.target, "after_start");
   }
 
-  onProfilePopupShown(event) {
+  onProfilePopupShowing(event) {
     return window.createUserContextMenu(event, {
       isContextMenu: true,
       showDefaultTab: true,

src/zen/spaces/ZenSpaceManager.mjs

@@ -11,6 +11,7 @@ const lazy = {};
 
 ChromeUtils.defineESModuleGetters(lazy, {
   ZenSessionStore: "resource:///modules/zen/ZenSessionManager.sys.mjs",
+  ZenSyncStore: "resource:///modules/zen/ZenSyncManager.sys.mjs",
 });
 
 ChromeUtils.defineLazyGetter(lazy, "browserBackgroundElement", () => {
@@ -148,7 +149,7 @@ class nsZenWorkspaces {
     if (!this.privateWindowOrDisabled) {
       const observerFunction = async () => {
         delete this._workspaceBookmarksCache;
-        await this.workspaceBookmarks();
+        await this.#initializeWorkspaceBookmarks();
         this._invalidateBookmarkContainers();
       };
       Services.obs.addObserver(observerFunction, "workspace-bookmarks-updated");
@@ -168,6 +169,63 @@ 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(() => {
@@ -391,7 +449,7 @@ class nsZenWorkspaces {
       container = 0;
     }
     let essentialsContainer = document.querySelector(
-      `.zen-essentials-container[container="${container}"]:not([cloned])`
+      `.zen-essentials-container[container="${container}"]`
     );
     if (!essentialsContainer) {
       essentialsContainer = document.createXULElement("hbox");
@@ -402,16 +460,19 @@ class nsZenWorkspaces {
       document
         .getElementById("zen-essentials")
         .appendChild(essentialsContainer);
-
-      // Set an initial hidden state if the essentials section is not supposed
-      // to be shown on the current workspace
-      if (
-        this.containerSpecificEssentials &&
-        this.getActiveWorkspaceFromCache()?.containerTabId != container
-      ) {
-        essentialsContainer.setAttribute("hidden", "true");
-      }
     }
+
+    // Set a hidden state if the essentials section is not supposed
+    // to be shown on the current workspace, else remove the hidden state
+    if (
+      this.containerSpecificEssentials &&
+      this.getActiveWorkspaceFromCache()?.containerTabId != container
+    ) {
+      essentialsContainer.setAttribute("hidden", "true");
+    } else {
+      essentialsContainer.removeAttribute("hidden");
+    }
+
     return essentialsContainer;
   }
 
@@ -691,17 +752,17 @@ class nsZenWorkspaces {
     return spacesForSS;
   }
 
-  async workspaceBookmarks() {
+  async #initializeWorkspaceBookmarks() {
     if (this.privateWindowOrDisabled) {
       this._workspaceBookmarksCache = {
         bookmarks: [],
         lastChangeTimestamp: 0,
       };
-      return this._workspaceBookmarksCache;
+      return;
     }
 
     if (this._workspaceBookmarksCache) {
-      return this._workspaceBookmarksCache;
+      return;
     }
 
     const [bookmarks, lastChangeTimestamp] = await Promise.all([
@@ -710,8 +771,6 @@ class nsZenWorkspaces {
     ]);
 
     this._workspaceBookmarksCache = { bookmarks, lastChangeTimestamp };
-
-    return this._workspaceCache;
   }
 
   restoreWorkspacesFromSessionStore(aWinData = {}) {
@@ -771,7 +830,7 @@ class nsZenWorkspaces {
     return (async () => {
       await this.#waitForPromises();
       this.#afterLoadInit();
-      await this.workspaceBookmarks();
+      await this.#initializeWorkspaceBookmarks();
       await this.changeWorkspace(activeWorkspace, { onInit: true });
       this.#fixTabPositions();
       this.onWindowResize();
@@ -797,6 +856,13 @@ class nsZenWorkspaces {
     })();
   }
 
+  #markWorkspaceChanged(workspaceId) {
+    lazy.ZenSyncStore.markItemChanged({
+      type: "space",
+      id: workspaceId,
+    });
+  }
+
   async selectStartPage() {
     if (!this.workspaceEnabled || gZenUIManager.testingEnabled) {
       return;
@@ -1098,6 +1164,9 @@ class nsZenWorkspaces {
     const item = document.createXULElement("menuitem");
     item.className = "zen-workspace-context-menu-item";
     item.setAttribute("zen-workspace-id", workspace.uuid);
+    if (AppConstants.platform === "linux") {
+      disableCurrent = true;
+    }
     if (!disableCurrent) {
       item.setAttribute("type", "radio");
     }
@@ -1214,12 +1283,19 @@ class nsZenWorkspaces {
     } else {
       workspacesData.push(workspaceData);
     }
+    // mark item as changed for sync
+    this.#markWorkspaceChanged(workspaceData.uuid);
+
     this.#propagateWorkspaceData();
   }
 
   removeWorkspace(windowID) {
     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(
@@ -1351,30 +1427,50 @@ class nsZenWorkspaces {
     if (this.privateWindowOrDisabled) {
       return;
     }
-    const workspaces = this._workspaceCache;
+    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) {
       console.warn(`Workspace with ID ${id} not found for reordering.`);
       return;
     }
+
     // Remove the workspace from its current position
     const currentIndex = workspaces.indexOf(workspace);
     if (currentIndex === -1) {
       console.warn(`Workspace with ID ${id} not found in the list.`);
       return;
     }
-    workspaces.splice(currentIndex, 1);
+
     // Insert the workspace at the new position
-    if (newPosition < 0 || newPosition > workspaces.length) {
+    if (newPosition < 0 || newPosition >= workspaces.length) {
       console.warn(
         `Invalid position ${newPosition} for reordering workspace with ID ${id}.`
       );
       return;
     }
+
+    workspaces.splice(currentIndex, 1);
     workspaces.splice(newPosition, 0, workspace);
+
     // Propagate the changes if the order has changed
     if (currentIndex !== newPosition) {
-      this.#propagateWorkspaceData();
+      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);
     }
   }
 
@@ -1927,28 +2023,20 @@ class nsZenWorkspaces {
       diff += spaceLen;
     }
     const isGoingLeft = diff < 0;
-    const clonedEssentials = [];
+    const essentialsAnimData = [];
     if (shouldAnimate && this.shouldAnimateEssentials && previousWorkspace) {
+      const containerIds = new Map();
       for (const workspace of workspaces) {
-        const essentialsContainer = this.getEssentialsSection(
+        const containerId = workspace.containerTabId;
-          workspace.containerTabId
+        if (!containerIds.has(containerId)) {
-        );
+          containerIds.set(containerId, []);
-        let lastCloned = clonedEssentials[clonedEssentials.length - 1];
-        if (lastCloned && lastCloned.contextId == workspace.containerTabId) {
-          lastCloned.repeat++;
-          lastCloned.workspaces.push(workspace);
-          continue;
         }
-        essentialsContainer.setAttribute("hidden", "true");
+        containerIds.get(containerId).push(workspace);
-        const essentialsClone = essentialsContainer.cloneNode(true);
+      }
-        essentialsClone.removeAttribute("hidden");
+      for (const [containerId, spaces] of containerIds) {
-        essentialsClone.setAttribute("cloned", "true");
+        essentialsAnimData.push({
-        clonedEssentials.push({
+          element: this.getEssentialsSection(containerId),
-          container: essentialsClone,
+          workspaces: spaces,
-          workspaces: [workspace],
-          contextId: workspace.containerTabId,
-          originalContainer: essentialsContainer,
-          repeat: 0,
         });
       }
     }
@@ -2055,190 +2143,48 @@ class nsZenWorkspaces {
       }
     }
     if (this.shouldAnimateEssentials && previousWorkspace) {
-      // Animate essentials
+      for (const data of essentialsAnimData) {
-      const newWorkspaceEssentialsContainer = clonedEssentials.find(cloned =>
+        const container = data.element;
-        cloned.workspaces.some(w => w.uuid === newWorkspace.uuid)
+        const essentialsWorkspaces = data.workspaces;
-      );
+
-      // Get a list of essentials containers that are in between the first and last workspace
+        const containsPrev = essentialsWorkspaces.some(
-      const essentialsContainersInBetween = clonedEssentials.filter(cloned => {
+          w => w.uuid === previousWorkspace.uuid
-        const essentialsWorkspaces = cloned.workspaces;
-        const firstIndex = workspaces.findIndex(
-          w => w.uuid === essentialsWorkspaces[0].uuid
         );
-        const lastIndex = workspaces.findIndex(
+        const containsNew = essentialsWorkspaces.some(
-          w =>
+          w => w.uuid === newWorkspace.uuid
-            w.uuid ===
-            essentialsWorkspaces[essentialsWorkspaces.length - 1].uuid
         );
 
-        const [start, end] = [
+        if (!containsPrev && !containsNew) {
-          Math.min(previousWorkspaceIndex, newWorkspaceIndex),
+          container.setAttribute("hidden", "true");
-          Math.max(previousWorkspaceIndex, newWorkspaceIndex),
-        ];
-
-        // Check if any part of the container overlaps with the movement range
-        return firstIndex <= end && lastIndex >= start;
-      });
-      for (const cloned of clonedEssentials) {
-        const container = cloned.container;
-        const essentialsWorkspaces = cloned.workspaces;
-        const repeats = cloned.repeat;
-        // Animate like the workspaces above expect essentials are a bit more
-        // complicated because they are not based on workspaces but on containers
-        // So, if we have the following arangement:
-        //  | [workspace1] [workspace2] [workspace3] [workspace4]
-        //  | [container1] [container1] [container2] [container1]
-        // And if we are changing from workspace 1 to workspace 4,
-        // we should be doing the following:
-        // First container (repeat 2 times) will stay in place until
-        // we reach container 3, then animate to the left and container 2
-        // also move to the left after that while container 1 in workspace 4
-        // will slide in from the right
-
-        // Get the index from first and last workspace
-        const firstWorkspaceIndex = workspaces.findIndex(
-          w => w.uuid === essentialsWorkspaces[0].uuid
-        );
-        const lastWorkspaceIndex = workspaces.findIndex(
-          w =>
-            w.uuid ===
-            essentialsWorkspaces[essentialsWorkspaces.length - 1].uuid
-        );
-        cloned.originalContainer.style.removeProperty("transform");
-        // Check if the container is even going to appear on the screen, to save on animation
-        if (
-          // We also need to check if the container is even going to appear on the screen.
-          // In order to do this, we need to check if the container is between the first and last workspace.
-          // Note that essential containers can have multiple workspaces,
-          // so we need to check if any of the workspaces in the container are between the
-          // first and last workspace.
-          !essentialsContainersInBetween.find(
-            ce =>
-              ce.workspaces.some(
-                w => w.uuid === essentialsWorkspaces[0].uuid
-              ) &&
-              ce.workspaces.some(
-                w =>
-                  w.uuid ===
-                  essentialsWorkspaces[essentialsWorkspaces.length - 1].uuid
-              )
-          )
-        ) {
           continue;
         }
-        cloned.originalContainer.parentNode.appendChild(container);
-        let stepsInBetween =
-          Math.abs(
-            newWorkspaceIndex -
-              (isGoingLeft ? firstWorkspaceIndex : lastWorkspaceIndex)
-          ) + 1;
-        const usingSameContainer =
-          newWorkspaceEssentialsContainer?.workspaces.some(
-            w => w.uuid === newWorkspace.uuid
-          ) &&
-          newWorkspaceEssentialsContainer?.workspaces.some(
-            w => w.uuid === previousWorkspace.uuid
-          );
-        let newOffset =
-          -(
-            newWorkspaceIndex -
-            (isGoingLeft ? firstWorkspaceIndex : lastWorkspaceIndex) +
-            (!isGoingLeft ? repeats - 1 : -repeats + 1)
-          ) * 100;
 
-        let existingOffset =
+        container.removeAttribute("hidden");
-          -(
-            newWorkspaceIndex -
-            (isGoingLeft ? lastWorkspaceIndex : firstWorkspaceIndex) +
-            (isGoingLeft ? repeats - 1 : -repeats + 1)
-          ) * 100;
 
-        // If we are on the same container and both new and old workspace are in the same "essentialsWorkspaces"
+        if (containsPrev && containsNew) {
-        // we can simply not animate the essentials
+          container.style.transform = "translateX(0%)";
-        if (
+          continue;
-          usingSameContainer &&
+        }
-          essentialsWorkspaces.some(w => w.uuid === newWorkspace.uuid) &&
+
-          essentialsWorkspaces.some(w => w.uuid === previousWorkspace.uuid)
+        let existingOffset, newOffset;
-        ) {
+        const currentTransform =
+          parseFloat(container.style.transform.split("(")[1]) || 0;
+        if (containsPrev && !containsNew) {
+          existingOffset = currentTransform;
+          newOffset = isGoingLeft ? 100 : -100;
+        } else {
+          existingOffset = currentTransform || (isGoingLeft ? -100 : 100);
           newOffset = 0;
-          existingOffset = 0;
         }
-
-        const needsOffsetAdjustment =
-          stepsInBetween > essentialsWorkspaces.length || usingSameContainer;
-
-        if (repeats > 0 && needsOffsetAdjustment) {
-          if (!isGoingLeft) {
-            if (existingOffset !== 0) {
-              existingOffset += 100;
-            }
-            if (newOffset !== 0) {
-              newOffset += 100;
-            }
-          } else {
-            if (existingOffset !== 0) {
-              existingOffset -= 100;
-            }
-            if (newOffset !== 0) {
-              newOffset -= 100;
-            }
-          }
-        }
-
-        // Special case: going forward from single reused container to a new one
-        if (
-          !usingSameContainer &&
-          !isGoingLeft &&
-          lastWorkspaceIndex === newWorkspaceIndex - 1
-        ) {
-          existingOffset = 0;
-          newOffset = -100;
-          stepsInBetween = 1;
-        }
-        if (
-          !usingSameContainer &&
-          isGoingLeft &&
-          firstWorkspaceIndex === newWorkspaceIndex + 1
-        ) {
-          existingOffset = 0;
-          newOffset = 100;
-          stepsInBetween = 1;
-        }
-        if (
-          !usingSameContainer &&
-          isGoingLeft &&
-          (firstWorkspaceIndex === newWorkspaceIndex - 1 ||
-            firstWorkspaceIndex === newWorkspaceIndex)
-        ) {
-          existingOffset = -100;
-          newOffset = 0;
-          stepsInBetween = 1;
-        }
-        if (
-          !usingSameContainer &&
-          !isGoingLeft &&
-          firstWorkspaceIndex === newWorkspaceIndex
-        ) {
-          existingOffset = 100;
-          newOffset = 0;
-          stepsInBetween = 1;
-        }
-
         const newTransform = `translateX(${newOffset}%)`;
         let existingTransform = `translateX(${existingOffset}%)`;
-        if (container.style.transform && container.style.transform !== "none") {
-          existingTransform = container.style.transform;
-        }
         if (shouldAnimate) {
           container.style.transform = existingTransform;
           animations.push(
             gZenUIManager.motion.animate(
               container,
               {
-                transform: [
+                transform: [existingTransform, newTransform],
-                  existingTransform,
-                  new Array(stepsInBetween).fill(newTransform).join(","),
-                ],
               },
               {
                 type: "spring",
@@ -2267,17 +2213,12 @@ class nsZenWorkspaces {
     this.#currentSpaceSwitchContext.animations = [];
     document.documentElement.removeAttribute("animating-background");
     if (shouldAnimate) {
-      for (const cloned of clonedEssentials) {
+      for (const data of essentialsAnimData) {
-        cloned.container.remove();
+        data.element.style.removeProperty("transform");
       }
       this._alwaysAnimatePaddingTop = true;
       this.updateTabsContainers();
     }
-    const essentialsContainer = this.getEssentialsSection(
-      newWorkspace.containerTabId
-    );
-    essentialsContainer.removeAttribute("hidden");
-    essentialsContainer.style.transform = "none";
     gBrowser.tabContainer._invalidateCachedTabs();
     gZenUIManager.tabsWrapper.style.removeProperty("scrollbar-width");
     this._animatingChange = false;
@@ -2493,7 +2434,7 @@ class nsZenWorkspaces {
       for (const tab of gBrowser.tabs) {
         if (
           !tab.hasAttribute("zen-workspace-id") &&
-          !tab.hasAttribute("zen-workspace-id")
+          !tab.hasAttribute("zen-essential")
         ) {
           tab.setAttribute("zen-workspace-id", workspace.uuid);
         }
@@ -3152,9 +3093,6 @@ class nsZenWorkspaces {
       ...normalContainers,
     ];
     for (const container of containers) {
-      if (container.hasAttribute("cloned")) {
-        continue;
-      }
       for (const tab of container.children) {
         if (gBrowser.isTab(tab)) {
           tabs.push(tab);

src/zen/split-view/ZenViewSplitter.mjs

@@ -1229,7 +1229,11 @@ class nsZenViewSplitter extends nsZenDOMOperatedFeature {
     const newTab = this.openAndSwitchToTab(url, {
       skipRoute: true,
       inBackground: false,
+      triggeringPrincipal: window.gContextMenu.principal,
     });
+    if (!newTab) {
+      return;
+    }
     this.splitTabs([currentTab, newTab], undefined, 1);
   }
 
@@ -1979,9 +1983,24 @@ class nsZenViewSplitter extends nsZenDOMOperatedFeature {
    * @returns {tab} The tab that was opened
    */
   openAndSwitchToTab(url, options) {
+    const triggeringPrincipal = options?.triggeringPrincipal;
+    if (!triggeringPrincipal) {
+      return null;
+    }
+    try {
+      Services.scriptSecurityManager.checkLoadURIStrWithPrincipal(
+        triggeringPrincipal,
+        url
+      );
+    } catch {
+      return null;
+    }
     const parentWindow = window.parent;
     const targetWindow = parentWindow || window;
-    const tab = targetWindow.gBrowser.addTrustedTab(url, options);
+    const tab = targetWindow.gBrowser.addTab(url, {
+      ...options,
+      triggeringPrincipal,
+    });
     targetWindow.gBrowser.selectedTab = tab;
     return tab;
   }

src/zen/sync/ZenSyncManager.sys.mjs

@@ -0,0 +1,160 @@
+/* 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();

src/zen/sync/ZenWorkspacesSync.sys.mjs

@@ -0,0 +1,404 @@
+/* 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;
+  }
+}

src/zen/sync/moz.build

@@ -0,0 +1,8 @@
+# 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/.
+
+EXTRA_JS_MODULES.zen += [
+  "ZenSyncManager.sys.mjs",
+  "ZenWorkspacesSync.sys.mjs",
+]

src/zen/tabs/zen-tabs/vertical-tabs.css

@@ -1156,10 +1156,6 @@
     pointer-events: none;
     position: fixed; /* Fix position to prevent scrolling */
   }
-
-  &[cloned] {
-    pointer-events: none;
-  }
 }
 
 .tabbrowser-tab[zen-essential="true"],

src/zen/urlbar/ZenUBActionsProvider.sys.mjs

@@ -27,6 +27,10 @@ ChromeUtils.defineESModuleGetters(lazy, {
   UrlUtils: "resource://gre/modules/UrlUtils.sys.mjs",
 });
 
+ChromeUtils.defineLazyGetter(lazy, "l10n", () => {
+  return new Localization(["browser/zen-command-palette.ftl"], true);
+});
+
 XPCOMUtils.defineLazyPreferenceGetter(
   lazy,
   "enabledPref",
@@ -182,7 +186,7 @@ export class ZenUrlbarProviderGlobalActions extends UrlbarProvider {
           .workspaceElement(workspace.uuid)
           ?.style.getPropertyValue("--zen-primary-color");
         actions.push({
-          label: "Focus on",
+          label: lazy.l10n.formatValueSync("zen-action-focus-on"),
           extraPayload: {
             workspaceId: workspace.uuid,
             prettyName: workspace.name,
@@ -215,7 +219,7 @@ export class ZenUrlbarProviderGlobalActions extends UrlbarProvider {
       .map(addon => {
         return {
           icon: "chrome://browser/skin/zen-icons/extension.svg",
-          label: "Extension",
+          label: lazy.l10n.formatValueSync("zen-action-extension"),
           commandId: `zen:extension-${addon.id}`,
           extraPayload: {
             extensionId: addon.id,

src/zen/urlbar/ZenUBGlobalActions.sys.mjs

@@ -13,58 +13,62 @@ XPCOMUtils.defineLazyPreferenceGetter(
   2
 );
 
+ChromeUtils.defineLazyGetter(lazy, "l10n", () => {
+  return new Localization(["browser/zen-command-palette.ftl"], true);
+});
+
 function isNotEmptyTab(window) {
   return !window.gBrowser.selectedTab.hasAttribute("zen-empty-tab");
 }
 
 const globalActionsTemplate = [
   {
-    label: "Toggle Compact Mode",
+    l10nId: "zen-action-toggle-compact-mode",
     command: "cmd_zenCompactModeToggle",
     icon: "chrome://browser/skin/zen-icons/sidebar.svg",
   },
   {
-    label: "Open Theme Picker",
+    l10nId: "zen-action-open-theme-picker",
     command: "cmd_zenOpenZenThemePicker",
     icon: "chrome://browser/skin/zen-icons/edit-theme.svg",
   },
   {
-    label: "New Split View",
+    l10nId: "zen-action-new-split-view",
     command: "cmd_zenNewEmptySplit",
     icon: "chrome://browser/skin/zen-icons/split.svg",
   },
   {
-    label: "New Folder",
+    l10nId: "zen-action-new-folder",
     command: "cmd_zenOpenFolderCreation",
     icon: "chrome://browser/skin/zen-icons/folder.svg",
   },
   {
-    label: "Copy Current URL",
+    l10nId: "zen-action-copy-current-url",
     command: "cmd_zenCopyCurrentURL",
     icon: "chrome://browser/skin/zen-icons/link.svg",
   },
   {
-    label: "Settings",
+    l10nId: "zen-action-settings",
     command: window => window.openPreferences(),
     icon: "chrome://browser/skin/zen-icons/settings.svg",
   },
   {
-    label: "Open Private Window",
+    l10nId: "zen-action-open-private-window",
     command: "Tools:PrivateBrowsing",
     icon: "chrome://browser/skin/zen-icons/private-window.svg",
   },
   {
-    label: "Open New Window",
+    l10nId: "zen-action-open-new-window",
     command: "cmd_newNavigator",
     icon: "chrome://browser/skin/zen-icons/window.svg",
   },
   {
-    label: "New Blank Window",
+    l10nId: "zen-action-new-blank-window",
     command: "cmd_zenNewNavigatorUnsynced",
     icon: "chrome://browser/skin/zen-icons/window.svg",
   },
   {
-    label: "Pin Tab",
+    l10nId: "zen-action-pin-tab",
     command: "cmd_zenTogglePinTab",
     icon: "chrome://browser/skin/zen-icons/pin.svg",
     isAvailable: window => {
@@ -73,7 +77,7 @@ const globalActionsTemplate = [
     },
   },
   {
-    label: "Unpin Tab",
+    l10nId: "zen-action-unpin-tab",
     command: "cmd_zenTogglePinTab",
     icon: "chrome://browser/skin/zen-icons/unpin.svg",
     isAvailable: window => {
@@ -82,12 +86,12 @@ const globalActionsTemplate = [
     },
   },
   {
-    label: "Open Space Routing",
+    l10nId: "zen-action-open-space-routing",
     command: "cmd_zenOpenSpaceRoutingSettings",
     icon: "chrome://browser/skin/zen-icons/selectable/airplane.svg",
   },
   {
-    label: "New Boost",
+    l10nId: "zen-action-new-boost",
     icon: "chrome://browser/skin/zen-icons/boost.svg",
     isAvailable: window => {
       if (!isNotEmptyTab(window)) {
@@ -130,7 +134,7 @@ const globalActionsTemplate = [
     },
   },
   {
-    label: "Next Space",
+    l10nId: "zen-action-next-space",
     command: "cmd_zenWorkspaceForward",
     icon: "chrome://browser/skin/zen-icons/forward.svg",
     isAvailable: window => {
@@ -138,7 +142,7 @@ const globalActionsTemplate = [
     },
   },
   {
-    label: "Previous Space",
+    l10nId: "zen-action-previous-space",
     command: "cmd_zenWorkspaceBackward",
     icon: "chrome://browser/skin/zen-icons/back.svg",
     isAvailable: window => {
@@ -147,7 +151,7 @@ const globalActionsTemplate = [
     },
   },
   {
-    label: "Close Tab",
+    l10nId: "zen-action-close-tab",
     command: "cmd_close",
     icon: "chrome://browser/skin/zen-icons/close.svg",
     isAvailable: window => {
@@ -155,27 +159,27 @@ const globalActionsTemplate = [
     },
   },
   {
-    label: "Reload Tab",
+    l10nId: "zen-action-reload-tab",
     command: "Browser:Reload",
     icon: "chrome://browser/skin/zen-icons/reload.svg",
   },
   {
-    label: "Reload Tab Without Cache",
+    l10nId: "zen-action-reload-tab-without-cache",
     command: "Browser:ReloadSkipCache",
     icon: "chrome://browser/skin/zen-icons/reload.svg",
   },
   {
-    label: "Next Tab",
+    l10nId: "zen-action-next-tab",
     command: "Browser:NextTab",
     icon: "chrome://browser/skin/zen-icons/forward.svg",
   },
   {
-    label: "Previous Tab",
+    l10nId: "zen-action-previous-tab",
     command: "Browser:PrevTab",
     icon: "chrome://browser/skin/zen-icons/back.svg",
   },
   {
-    label: "Capture Screenshot",
+    l10nId: "zen-action-capture-screenshot",
     command: "Browser:Screenshot",
     icon: "chrome://browser/skin/zen-icons/screenshot.svg",
     isAvailable: window => {
@@ -183,12 +187,12 @@ const globalActionsTemplate = [
     },
   },
   {
-    label: "Toggle Tabs on right",
+    l10nId: "zen-action-toggle-tabs-on-right",
     command: "cmd_zenToggleTabsOnRight",
     icon: "chrome://browser/skin/zen-icons/sidebars-right.svg",
   },
   {
-    label: "Add to Essentials",
+    l10nId: "zen-action-add-to-essentials",
     command: window =>
       window.gZenPinnedTabManager.addToEssentials(window.gBrowser.selectedTab),
     isAvailable: window => {
@@ -201,7 +205,7 @@ const globalActionsTemplate = [
     icon: "chrome://browser/skin/zen-icons/essential-add.svg",
   },
   {
-    label: "Remove from Essentials",
+    l10nId: "zen-action-remove-from-essentials",
     command: window =>
       window.gZenPinnedTabManager.removeEssentials(window.gBrowser.selectedTab),
     isAvailable: window =>
@@ -209,7 +213,7 @@ const globalActionsTemplate = [
     icon: "chrome://browser/skin/zen-icons/essential-remove.svg",
   },
   {
-    label: "Find in Page",
+    l10nId: "zen-action-find-in-page",
     command: "cmd_find",
     icon: "chrome://browser/skin/zen-icons/search-page.svg",
     isAvailable: window => {
@@ -217,12 +221,12 @@ const globalActionsTemplate = [
     },
   },
   {
-    label: "Manage Extensions",
+    l10nId: "zen-action-manage-extensions",
     command: "Tools:Addons",
     icon: "chrome://browser/skin/zen-icons/extension.svg",
   },
   {
-    label: "Switch to Automatic Appearance",
+    l10nId: "zen-action-switch-to-automatic-appearance",
     command: () => Services.prefs.setIntPref("zen.view.window.scheme", 2),
     icon: "chrome://browser/skin/zen-icons/sparkles.svg",
     isAvailable: () => {
@@ -230,7 +234,7 @@ const globalActionsTemplate = [
     },
   },
   {
-    label: "Switch to Light Mode",
+    l10nId: "zen-action-switch-to-light-mode",
     command: () => Services.prefs.setIntPref("zen.view.window.scheme", 1),
     icon: "chrome://browser/skin/zen-icons/face-sun.svg",
     isAvailable: () => {
@@ -238,7 +242,7 @@ const globalActionsTemplate = [
     },
   },
   {
-    label: "Switch to Dark Mode",
+    l10nId: "zen-action-switch-to-dark-mode",
     command: () => Services.prefs.setIntPref("zen.view.window.scheme", 0),
     icon: "chrome://browser/skin/zen-icons/moon-stars.svg",
     isAvailable: () => {
@@ -246,7 +250,7 @@ const globalActionsTemplate = [
     },
   },
   {
-    label: "Print",
+    l10nId: "zen-action-print",
     command: "cmd_print",
     icon: "chrome://browser/skin/zen-icons/print.svg",
     isAvailable: window => {
@@ -266,7 +270,10 @@ export const globalActions = globalActionsTemplate.map(action => ({
   commandId:
     typeof action.command === "string"
       ? action.command
-      : `zen:global-action-${action.label.toLowerCase().replace(/\s+/g, "-")}`,
+      : `zen:global-action-${action.l10nId.replace("zen-action-", "")}`,
   extraPayload: {},
   ...action,
+  get label() {
+    return lazy.l10n.formatValueSync(action.l10nId);
+  },
 }));

surfer.json

@@ -5,8 +5,8 @@
   "binaryName": "zen",
   "version": {
     "product": "firefox",
-    "version": "152.0.3",
+    "version": "152.0.6",
-    "candidate": "152.0.3",
+    "candidate": "152.0.5",
     "candidateBuild": 1
   },
   "buildOptions": {
@@ -20,7 +20,7 @@
       "brandShortName": "Zen",
       "brandFullName": "Zen Browser",
       "release": {
-        "displayVersion": "1.21.4b",
+        "displayVersion": "1.21.6b",
         "github": {
           "repo": "zen-browser/desktop"
         },

tools/ffprefs/src/main.rs

@@ -346,6 +346,17 @@ fn expand_pref_values(prefs: &mut [Preference]) {
             }
             pref.value = new_value.clone();
         }
+        // Also change the condition if it contains placeholders
+        if let Some(condition) = &pref.condition {
+            let mut new_condition = condition.clone();
+            for (key, value) in &env_values {
+                let placeholder = format!("@{}@", key);
+                if new_condition.contains(&placeholder) {
+                    new_condition = new_condition.replace(&placeholder, if *value { "1" } else { "0" });
+                }
+                pref.condition = Some(new_condition.clone());
+            }
+        }
     }
 }