feat: Start making use of IDs instead of sync identifiers, b=no-bug, c=folders

src/browser/components/sessionstore/SessionStore-sys-mjs.patch

@@ -1,11 +1,11 @@
 diff --git a/browser/components/sessionstore/SessionStore.sys.mjs b/browser/components/sessionstore/SessionStore.sys.mjs
-index 1cdbc0f41bf5b55dfbbd850cb618c6d870f7a261..ad80ed937f696ba2800e62dfc11fcfb90e3f1092 100644
+index 1cdbc0f41bf5b55dfbbd850cb618c6d870f7a261..9ef1996a0e8a3ebe55dc25921b8fc8cc0ac8a303 100644
 --- a/browser/components/sessionstore/SessionStore.sys.mjs
 +++ b/browser/components/sessionstore/SessionStore.sys.mjs
-@@ -126,6 +126,8 @@ const TAB_EVENTS = [
-   "TabUngrouped",
+@@ -127,6 +127,8 @@ const TAB_EVENTS = [
    "TabGroupCollapse",
    "TabGroupExpand",
+   "TabSplitViewActivate",
 +  "TabAddedToEssentials",
 +  "TabRemovedFromEssentials",
  ];
@@ -67,7 +67,7 @@ index 1cdbc0f41bf5b55dfbbd850cb618c6d870f7a261..ad80ed937f696ba2800e62dfc11fcfb9
        return;
      }
  
-@@ -4089,6 +4094,11 @@ var SessionStoreInternal = {
+@@ -4089,6 +4094,12 @@ var SessionStoreInternal = {
          Math.min(tabState.index, tabState.entries.length)
        );
        tabState.pinned = false;
@@ -80,7 +80,7 @@ index 1cdbc0f41bf5b55dfbbd850cb618c6d870f7a261..ad80ed937f696ba2800e62dfc11fcfb9
  
        if (inBackground === false) {
          aWindow.gBrowser.selectedTab = newTab;
-@@ -4525,6 +4535,7 @@ var SessionStoreInternal = {
+@@ -4525,6 +4536,7 @@ var SessionStoreInternal = {
        // Append the tab if we're opening into a different window,
        tabIndex: aSource == aTargetWindow ? pos : Infinity,
        pinned: state.pinned,
@@ -88,7 +88,7 @@ index 1cdbc0f41bf5b55dfbbd850cb618c6d870f7a261..ad80ed937f696ba2800e62dfc11fcfb9
        userContextId: state.userContextId,
        skipLoad: true,
        preferredRemoteType,
-@@ -5374,7 +5385,7 @@ var SessionStoreInternal = {
+@@ -5374,7 +5386,7 @@ var SessionStoreInternal = {
  
      for (let i = tabbrowser.pinnedTabCount; i < tabbrowser.tabs.length; i++) {
        let tab = tabbrowser.tabs[i];
@@ -97,7 +97,7 @@ index 1cdbc0f41bf5b55dfbbd850cb618c6d870f7a261..ad80ed937f696ba2800e62dfc11fcfb9
          removableTabs.push(tab);
        }
      }
-@@ -5434,7 +5445,7 @@ var SessionStoreInternal = {
+@@ -5434,7 +5446,7 @@ var SessionStoreInternal = {
      }
  
      let workspaceID = aWindow.getWorkspaceID();
@@ -106,7 +106,7 @@ index 1cdbc0f41bf5b55dfbbd850cb618c6d870f7a261..ad80ed937f696ba2800e62dfc11fcfb9
        winData.workspaceID = workspaceID;
      }
    },
-@@ -5625,11 +5636,12 @@ var SessionStoreInternal = {
+@@ -5625,11 +5637,12 @@ var SessionStoreInternal = {
      }
  
      let tabbrowser = aWindow.gBrowser;
@@ -120,7 +120,7 @@ index 1cdbc0f41bf5b55dfbbd850cb618c6d870f7a261..ad80ed937f696ba2800e62dfc11fcfb9
      // update the internal state data for this window
      for (let tab of tabs) {
        if (tab == aWindow.FirefoxViewHandler.tab) {
-@@ -5640,6 +5652,7 @@ var SessionStoreInternal = {
+@@ -5640,6 +5653,7 @@ var SessionStoreInternal = {
        tabsData.push(tabData);
      }
  
@@ -128,7 +128,7 @@ index 1cdbc0f41bf5b55dfbbd850cb618c6d870f7a261..ad80ed937f696ba2800e62dfc11fcfb9
      // update tab group state for this window
      winData.groups = [];
      for (let tabGroup of aWindow.gBrowser.tabGroups) {
-@@ -5652,7 +5665,7 @@ var SessionStoreInternal = {
+@@ -5652,7 +5666,7 @@ var SessionStoreInternal = {
      // a window is closed, point to the first item in the tab strip instead (it will never be the Firefox View tab,
      // since it's only inserted into the tab strip after it's selected).
      if (aWindow.FirefoxViewHandler.tab?.selected) {
@@ -137,7 +137,7 @@ index 1cdbc0f41bf5b55dfbbd850cb618c6d870f7a261..ad80ed937f696ba2800e62dfc11fcfb9
        winData.title = tabbrowser.tabs[0].label;
      }
      winData.selected = selectedIndex;
-@@ -5764,8 +5777,8 @@ var SessionStoreInternal = {
+@@ -5764,8 +5778,8 @@ var SessionStoreInternal = {
      // selectTab represents.
      let selectTab = 0;
      if (overwriteTabs) {
@@ -148,7 +148,7 @@ index 1cdbc0f41bf5b55dfbbd850cb618c6d870f7a261..ad80ed937f696ba2800e62dfc11fcfb9
        selectTab = Math.min(selectTab, winData.tabs.length);
      }
  
-@@ -5808,6 +5821,8 @@ var SessionStoreInternal = {
+@@ -5808,6 +5822,8 @@ var SessionStoreInternal = {
          winData.tabs,
          winData.groups ?? []
        );
@@ -157,7 +157,7 @@ index 1cdbc0f41bf5b55dfbbd850cb618c6d870f7a261..ad80ed937f696ba2800e62dfc11fcfb9
        this._log.debug(
          `restoreWindow, createTabsForSessionRestore returned ${tabs.length} tabs`
        );
-@@ -6371,6 +6386,25 @@ var SessionStoreInternal = {
+@@ -6371,6 +6387,25 @@ var SessionStoreInternal = {
  
      // Most of tabData has been restored, now continue with restoring
      // attributes that may trigger external events.
@@ -172,7 +172,7 @@ index 1cdbc0f41bf5b55dfbbd850cb618c6d870f7a261..ad80ed937f696ba2800e62dfc11fcfb9
 +      tab.setAttribute("zen-has-static-label", "true");
 +    }
 +    if (tabData.zenSyncId) {
-+      tab.setAttribute("zen-sync-id", tabData.zenSyncId);
++      tab.setAttribute("id", tabData.zenPinnedId);
 +    }
 +    if (tabData.zenDefaultUserContextId) {
 +      tab.setAttribute("zenDefaultUserContextId", true);
@@ -183,7 +183,7 @@ index 1cdbc0f41bf5b55dfbbd850cb618c6d870f7a261..ad80ed937f696ba2800e62dfc11fcfb9
  
      if (tabData.pinned) {
        tabbrowser.pinTab(tab);
-@@ -7289,7 +7323,7 @@ var SessionStoreInternal = {
+@@ -7289,7 +7324,7 @@ var SessionStoreInternal = {
  
        let groupsToSave = new Map();
        for (let tIndex = 0; tIndex < window.tabs.length; ) {

src/browser/components/sessionstore/TabState-sys-mjs.patch

@@ -1,5 +1,5 @@
 diff --git a/browser/components/sessionstore/TabState.sys.mjs b/browser/components/sessionstore/TabState.sys.mjs
-index 82721356d191055bec0d4b0ca49e481221988801..d1323fe17c995611ebdfe2869b0ccd2d45bcfa11 100644
+index 82721356d191055bec0d4b0ca49e481221988801..2d05ba4812e9a73bd896c1aeb007180bbc531a3c 100644
 --- a/browser/components/sessionstore/TabState.sys.mjs
 +++ b/browser/components/sessionstore/TabState.sys.mjs
 @@ -85,7 +85,22 @@ class _TabState {
@@ -7,7 +7,7 @@ index 82721356d191055bec0d4b0ca49e481221988801..d1323fe17c995611ebdfe2869b0ccd2d
      }
  
 +    tabData.zenWorkspace = tab.getAttribute("zen-workspace-id");
-+    tabData.zenSyncId = tab.getAttribute("zen-sync-id");
++    tabData.zenSyncId = tab.getAttribute("id");
 +    tabData.zenEssential = tab.getAttribute("zen-essential");
 +    tabData.pinned = tabData.pinned || tabData.zenEssential;
 +    tabData.zenDefaultUserContextId = tab.getAttribute("zenDefaultUserContextId");

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

@@ -1,9 +1,16 @@
 diff --git a/browser/components/tabbrowser/content/tabbrowser.js b/browser/components/tabbrowser/content/tabbrowser.js
-index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4cd44d980e 100644
-index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4cd44d980e 100644
+index c0eafd4faf8d57b8486c5bf8917375850ec8147e..d1c089ba66defc74dbf06b283bc6ddca08b55b76 100644
 --- a/browser/components/tabbrowser/content/tabbrowser.js
 +++ b/browser/components/tabbrowser/content/tabbrowser.js
-@@ -432,15 +432,64 @@
+@@ -386,6 +386,7 @@
+      * @type {MozBrowser[]}
+      */
+     get splitViewBrowsers() {
++      return gZenViewSplitter.splitViewBrowsers;
+       const browsers = [];
+       if (this.#activeSplitView) {
+         for (const tab of this.#activeSplitView.tabs) {
+@@ -450,15 +451,64 @@
        return this.tabContainer.visibleTabs;
      }
  
@@ -70,7 +77,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
      set selectedTab(val) {
        if (
          gSharedTabWarning.willShowSharedTabWarning(val) ||
-@@ -588,6 +637,7 @@
+@@ -613,6 +663,7 @@
        this.tabpanels.appendChild(panel);
  
        let tab = this.tabs[0];
@@ -78,7 +85,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        tab.linkedPanel = uniqueId;
        this._selectedTab = tab;
        this._selectedBrowser = browser;
-@@ -873,13 +923,17 @@
+@@ -898,13 +949,17 @@
        }
  
        this.showTab(aTab);
@@ -97,7 +104,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
  
        aTab.setAttribute("pinned", "true");
        this._updateTabBarForPinnedTabs();
-@@ -892,11 +946,15 @@
+@@ -917,11 +972,15 @@
        }
  
        this.#handleTabMove(aTab, () => {
@@ -114,7 +121,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        });
  
        aTab.style.marginInlineStart = "";
-@@ -1073,6 +1131,8 @@
+@@ -1098,6 +1157,8 @@
  
        let LOCAL_PROTOCOLS = ["chrome:", "about:", "resource:", "data:"];
  
@@ -123,7 +130,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        if (
          aIconURL &&
          !LOCAL_PROTOCOLS.some(protocol => aIconURL.startsWith(protocol))
-@@ -1082,6 +1142,9 @@
+@@ -1107,6 +1168,9 @@
          );
          return;
        }
@@ -133,7 +140,15 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
  
        let browser = this.getBrowserForTab(aTab);
        browser.mIconURL = aIconURL;
-@@ -1445,6 +1508,7 @@
+@@ -1379,7 +1443,6 @@
+ 
+       // Preview mode should not reset the owner
+       if (!this._previewMode && !oldTab.selected) {
+-        oldTab.owner = null;
+       }
+ 
+       let lastRelatedTab = this._lastRelatedTabMap.get(oldTab);
+@@ -1470,6 +1533,7 @@
        if (!this._previewMode) {
          newTab.recordTimeFromUnloadToReload();
          newTab.updateLastAccessed();
@@ -141,7 +156,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
          oldTab.updateLastAccessed();
          // if this is the foreground window, update the last-seen timestamps.
          if (this.ownerGlobal == BrowserWindowTracker.getTopWindow()) {
-@@ -1597,6 +1661,9 @@
+@@ -1622,6 +1686,9 @@
        }
  
        let activeEl = document.activeElement;
@@ -151,7 +166,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        // If focus is on the old tab, move it to the new tab.
        if (activeEl == oldTab) {
          newTab.focus();
-@@ -1920,7 +1987,8 @@
+@@ -1945,7 +2012,8 @@
      }
  
      _setTabLabel(aTab, aLabel, { beforeTabOpen, isContentTitle, isURL } = {}) {
@@ -161,7 +176,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
          return false;
        }
  
-@@ -2028,7 +2096,7 @@
+@@ -2053,7 +2121,7 @@
          newIndex = this.selectedTab._tPos + 1;
        }
  
@@ -170,7 +185,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
          if (this.isTabGroupLabel(targetTab)) {
            throw new Error(
              "Replacing a tab group label with a tab is not supported"
-@@ -2303,6 +2371,7 @@
+@@ -2328,6 +2396,7 @@
        uriIsAboutBlank,
        userContextId,
        skipLoad,
@@ -178,7 +193,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
      } = {}) {
        let b = document.createXULElement("browser");
        // Use the JSM global to create the permanentKey, so that if the
-@@ -2376,8 +2445,7 @@
+@@ -2401,8 +2470,7 @@
          // we use a different attribute name for this?
          b.setAttribute("name", name);
        }
@@ -188,7 +203,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
          b.setAttribute("transparent", "true");
        }
  
-@@ -2542,7 +2610,7 @@
+@@ -2567,7 +2635,7 @@
  
        let panel = this.getPanel(browser);
        let uniqueId = this._generateUniquePanelID();
@@ -197,7 +212,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        aTab.linkedPanel = uniqueId;
  
        // Inject the <browser> into the DOM if necessary.
-@@ -2601,8 +2669,8 @@
+@@ -2626,8 +2694,8 @@
        // 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) {
@@ -208,7 +223,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        } else {
          aTab.linkedBrowser.browsingContext.hasSiblings = this.tabs.length > 1;
        }
-@@ -2779,7 +2847,6 @@
+@@ -2814,7 +2882,6 @@
              this.selectedTab = this.addTrustedTab(BROWSER_NEW_TAB_URL, {
                tabIndex: tab._tPos + 1,
                userContextId: tab.userContextId,
@@ -216,7 +231,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
                focusUrlBar: true,
              });
              resolve(this.selectedBrowser);
-@@ -2859,6 +2926,8 @@
+@@ -2923,6 +2990,8 @@
          schemelessInput,
          hasValidUserGestureActivation = false,
          textDirectiveUserActivation = false,
@@ -225,7 +240,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        } = {}
      ) {
        // all callers of addTab that pass a params object need to pass
-@@ -2869,6 +2938,12 @@
+@@ -2933,10 +3002,17 @@
          );
        }
  
@@ -238,7 +253,20 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        if (!UserInteraction.running("browser.tabs.opening", window)) {
          UserInteraction.start("browser.tabs.opening", "initting", window);
        }
-@@ -2932,6 +3007,19 @@
+ 
++      if (!gURLBar.hasAttribute("zen-newtab")) {
+       // If we're opening a foreground tab, set the owner by default.
+       ownerTab ??= inBackground ? null : this.selectedTab;
+ 
+@@ -2944,6 +3020,7 @@
+       if (this.selectedTab.owner) {
+         this.selectedTab.owner = null;
+       }
++      }
+ 
+       // Find the tab that opened this one, if any. This is used for
+       // determining positioning, and inherited attributes such as the
+@@ -2996,6 +3073,19 @@
            noInitialLabel,
            skipBackgroundNotify,
          });
@@ -258,7 +286,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
          if (insertTab) {
            // Insert the tab into the tab container in the correct position.
            this.#insertTabAtIndex(t, {
-@@ -2940,6 +3028,7 @@
+@@ -3004,6 +3094,7 @@
              ownerTab,
              openerTab,
              pinned,
@@ -266,7 +294,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
              bulkOrderedOpen,
              tabGroup: tabGroup ?? openerTab?.group,
            });
-@@ -2958,6 +3047,7 @@
+@@ -3022,6 +3113,7 @@
            openWindowInfo,
            skipLoad,
            triggeringRemoteType,
@@ -274,7 +302,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
          }));
  
          if (focusUrlBar) {
-@@ -3078,6 +3168,12 @@
+@@ -3146,6 +3238,12 @@
          }
        }
  
@@ -287,7 +315,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        // Additionally send pinned tab events
        if (pinned) {
          this.#notifyPinnedStatus(t);
-@@ -3248,10 +3344,10 @@
+@@ -3330,10 +3428,10 @@
          isAdoptingGroup = false,
          isUserTriggered = false,
          telemetryUserCreateSource = "unknown",
@@ -299,7 +327,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        }
  
        if (!color) {
-@@ -3272,9 +3368,14 @@
+@@ -3354,9 +3452,14 @@
          label,
          isAdoptingGroup
        );
@@ -316,7 +344,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        );
        group.addTabs(tabs);
  
-@@ -3395,7 +3496,7 @@
+@@ -3477,7 +3580,7 @@
        }
  
        this.#handleTabMove(tab, () =>
@@ -325,7 +353,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        );
      }
  
-@@ -3597,6 +3698,7 @@
+@@ -3679,6 +3782,7 @@
          openWindowInfo,
          skipLoad,
          triggeringRemoteType,
@@ -333,7 +361,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        }
      ) {
        // If we don't have a preferred remote type (or it is `NOT_REMOTE`), and
-@@ -3666,6 +3768,7 @@
+@@ -3748,6 +3852,7 @@
            openWindowInfo,
            name,
            skipLoad,
@@ -341,7 +369,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
          });
        }
  
-@@ -3853,7 +3956,7 @@
+@@ -3935,7 +4040,7 @@
          // Add a new tab if needed.
          if (!tab) {
            let createLazyBrowser =
@@ -350,7 +378,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
  
            let url = "about:blank";
            if (tabData.entries?.length) {
-@@ -3890,8 +3993,10 @@
+@@ -3972,8 +4077,10 @@
              insertTab: false,
              skipLoad: true,
              preferredRemoteType,
@@ -362,7 +390,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
            if (select) {
              tabToSelect = tab;
            }
-@@ -3903,7 +4008,8 @@
+@@ -3985,7 +4092,8 @@
            this.pinTab(tab);
            // Then ensure all the tab open/pinning information is sent.
            this._fireTabOpen(tab, {});
@@ -372,7 +400,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
            let { groupId } = tabData;
            const tabGroup = tabGroupWorkingData.get(groupId);
            // if a tab refers to a tab group we don't know, skip any group
-@@ -3917,7 +4023,10 @@
+@@ -3999,7 +4107,10 @@
                  tabGroup.stateData.id,
                  tabGroup.stateData.color,
                  tabGroup.stateData.collapsed,
@@ -384,7 +412,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
                );
                tabsFragment.appendChild(tabGroup.node);
              }
-@@ -3962,9 +4071,23 @@
+@@ -4044,9 +4155,23 @@
        // to remove the old selected tab.
        if (tabToSelect) {
          let leftoverTab = this.selectedTab;
@@ -400,17 +428,15 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
 +            gZenWorkspaces._initialTab._shouldRemove = true;
 +          }
 +        }
-+      }
-+      }
+       }
 +      else {
 +        gZenWorkspaces._tabToRemoveForEmpty = this.selectedTab;
-       }
-       }
++      }
 +      this._hasAlreadyInitializedZenSessionStore = true;
  
        if (tabs.length > 1 || !tabs[0].selected) {
          this._updateTabsAfterInsert();
-@@ -4155,11 +4278,14 @@
+@@ -4237,11 +4362,14 @@
        if (ownerTab) {
          tab.owner = ownerTab;
        }
@@ -426,7 +452,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
          if (
            !bulkOrderedOpen &&
            ((openerTab &&
-@@ -4171,7 +4297,7 @@
+@@ -4253,7 +4381,7 @@
            let lastRelatedTab =
              openerTab && this._lastRelatedTabMap.get(openerTab);
            let previousTab = lastRelatedTab || openerTab || this.selectedTab;
@@ -435,7 +461,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
              tabGroup = previousTab.group;
            }
            if (
-@@ -4182,7 +4308,7 @@
+@@ -4264,7 +4392,7 @@
            ) {
              elementIndex = Infinity;
            } else if (previousTab.visible) {
@@ -444,7 +470,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
            } else if (previousTab == FirefoxViewHandler.tab) {
              elementIndex = 0;
            }
-@@ -4210,14 +4336,14 @@
+@@ -4292,14 +4420,14 @@
        }
        // Ensure index is within bounds.
        if (tab.pinned) {
@@ -463,7 +489,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
  
        if (pinned && !itemAfter?.pinned) {
          itemAfter = null;
-@@ -4228,7 +4354,7 @@
+@@ -4310,7 +4438,7 @@
  
        this.tabContainer._invalidateCachedTabs();
  
@@ -472,7 +498,19 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
          if (this.isTab(itemAfter) && itemAfter.group == tabGroup) {
            // Place at the front of, or between tabs in, the same tab group
            this.tabContainer.insertBefore(tab, itemAfter);
-@@ -4264,6 +4390,7 @@
+@@ -4338,7 +4466,11 @@
+         const tabContainer = pinned
+           ? this.tabContainer.pinnedTabsContainer
+           : this.tabContainer;
++        if (itemAfter) {
++          itemAfter.before(tab);
++        } else {
+         tabContainer.insertBefore(tab, itemAfter);
++        }
+       }
+ 
+       this._updateTabsAfterInsert();
+@@ -4346,6 +4478,7 @@
        if (pinned) {
          this._updateTabBarForPinnedTabs();
        }
@@ -480,8 +518,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
  
        TabBarVisibility.update();
      }
-@@ -4896,6 +5024,7 @@
-@@ -4896,6 +5024,7 @@
+@@ -4896,6 +5029,7 @@
          telemetrySource,
        } = {}
      ) {
@@ -489,8 +526,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        // When 'closeWindowWithLastTab' pref is enabled, closing all tabs
        // can be considered equivalent to closing the window.
        if (
-@@ -4985,6 +5114,7 @@
-@@ -4985,6 +5114,7 @@
+@@ -4985,6 +5119,7 @@
          if (lastToClose) {
            this.removeTab(lastToClose, aParams);
          }
@@ -498,8 +534,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        } catch (e) {
          console.error(e);
        }
-@@ -5023,6 +5153,12 @@
-@@ -5023,6 +5153,12 @@
+@@ -5023,6 +5158,12 @@
          aTab._closeTimeNoAnimTimerId = Glean.browserTabclose.timeNoAnim.start();
        }
  
@@ -512,8 +547,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        // Handle requests for synchronously removing an already
        // asynchronously closing tab.
        if (!animate && aTab.closing) {
-@@ -5037,6 +5173,9 @@
-@@ -5037,6 +5173,9 @@
+@@ -5037,6 +5178,9 @@
        // state).
        let tabWidth = window.windowUtils.getBoundsWithoutFlushing(aTab).width;
        let isLastTab = this.#isLastTabInWindow(aTab);
@@ -523,8 +557,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        if (
          !this._beginRemoveTab(aTab, {
            closeWindowFastpath: true,
-@@ -5085,7 +5224,13 @@
-@@ -5085,7 +5224,13 @@
+@@ -5085,7 +5229,13 @@
          // We're not animating, so we can cancel the animation stopwatch.
          Glean.browserTabclose.timeAnim.cancel(aTab._closeTimeAnimTimerId);
          aTab._closeTimeAnimTimerId = null;
@@ -539,8 +572,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
          return;
        }
  
-@@ -5219,7 +5364,7 @@
-@@ -5219,7 +5364,7 @@
+@@ -5219,7 +5369,7 @@
            closeWindowWithLastTab != null
              ? closeWindowWithLastTab
              : !window.toolbar.visible ||
@@ -549,8 +581,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
  
          if (closeWindow) {
            // We've already called beforeunload on all the relevant tabs if we get here,
-@@ -5243,6 +5388,7 @@
-@@ -5243,6 +5388,7 @@
+@@ -5243,6 +5393,7 @@
  
          newTab = true;
        }
@@ -558,8 +589,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        aTab._endRemoveArgs = [closeWindow, newTab];
  
        // swapBrowsersAndCloseOther will take care of closing the window without animation.
-@@ -5283,13 +5429,7 @@
-@@ -5283,13 +5429,7 @@
+@@ -5283,13 +5434,7 @@
        aTab._mouseleave();
  
        if (newTab) {
@@ -574,8 +604,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        } else {
          TabBarVisibility.update();
        }
-@@ -5422,6 +5562,7 @@
-@@ -5422,6 +5562,7 @@
+@@ -5422,6 +5567,7 @@
          this.tabs[i]._tPos = i;
        }
  
@@ -583,8 +612,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        if (!this._windowIsClosing) {
          // update tab close buttons state
          this.tabContainer._updateCloseButtons();
-@@ -5643,6 +5784,7 @@
-@@ -5643,6 +5784,7 @@
+@@ -5643,6 +5789,7 @@
        }
  
        let excludeTabs = new Set(aExcludeTabs);
@@ -592,8 +620,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
  
        // If this tab has a successor, it should be selectable, since
        // hiding or closing a tab removes that tab as a successor.
-@@ -5655,13 +5797,13 @@
-@@ -5655,13 +5797,13 @@
+@@ -5655,13 +5802,13 @@
          !excludeTabs.has(aTab.owner) &&
          Services.prefs.getBoolPref("browser.tabs.selectOwnerOnClose")
        ) {
@@ -609,8 +636,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        );
  
        let tab = this.tabContainer.findNextTab(aTab, {
-@@ -5677,7 +5819,7 @@
-@@ -5677,7 +5819,7 @@
+@@ -5677,7 +5824,7 @@
        }
  
        if (tab) {
@@ -619,8 +645,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        }
  
        // If no qualifying visible tab was found, see if there is a tab in
-@@ -5698,7 +5840,7 @@
-@@ -5698,7 +5840,7 @@
+@@ -5698,7 +5845,7 @@
          });
        }
  
@@ -629,8 +654,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
      }
  
      _blurTab(aTab) {
-@@ -6104,10 +6246,10 @@
-@@ -6104,10 +6246,10 @@
+@@ -6104,10 +6251,10 @@
        SessionStore.deleteCustomTabValue(aTab, "hiddenBy");
      }
  
@@ -643,8 +667,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
          aTab.selected ||
          aTab.closing ||
          // Tabs that are sharing the screen, microphone or camera cannot be hidden.
-@@ -6166,6 +6308,7 @@
-@@ -6166,6 +6308,7 @@
+@@ -6166,6 +6313,7 @@
       * @param {MozTabbrowserTab|MozTabbrowserTabGroup|MozTabbrowserTabGroup.labelElement} aTab
       */
      replaceTabWithWindow(aTab, aOptions) {
@@ -652,8 +675,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        if (this.tabs.length == 1) {
          return null;
        }
-@@ -6299,7 +6442,7 @@
-@@ -6299,7 +6442,7 @@
+@@ -6299,7 +6447,7 @@
       *   `true` if element is a `<tab-group>`
       */
      isTabGroup(element) {
@@ -662,8 +684,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
      }
  
      /**
-@@ -6375,8 +6518,8 @@
-@@ -6375,8 +6518,8 @@
+@@ -6375,8 +6523,8 @@
        }
  
        // Don't allow mixing pinned and unpinned tabs.
@@ -674,8 +695,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        } else {
          tabIndex = Math.max(tabIndex, this.pinnedTabCount);
        }
-@@ -6402,10 +6545,16 @@
-@@ -6402,10 +6545,16 @@
+@@ -6402,10 +6550,16 @@
        this.#handleTabMove(
          element,
          () => {
@@ -694,8 +714,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
            if (neighbor && this.isTab(element) && tabIndex > element._tPos) {
              neighbor.after(element);
            } else {
-@@ -6463,23 +6612,28 @@
-@@ -6463,23 +6612,28 @@
+@@ -6463,23 +6617,28 @@
      #moveTabNextTo(element, targetElement, moveBefore = false, metricsContext) {
        if (this.isTabGroupLabel(targetElement)) {
          targetElement = targetElement.group;
@@ -730,8 +749,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        } 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
-@@ -6492,14 +6646,34 @@
-@@ -6492,14 +6646,34 @@
+@@ -6492,14 +6651,34 @@
          //    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.
@@ -767,8 +785,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
          element.pinned
            ? this.tabContainer.pinnedTabsContainer
            : this.tabContainer;
-@@ -6508,7 +6682,7 @@
-@@ -6508,7 +6682,7 @@
+@@ -6508,7 +6687,7 @@
          element,
          () => {
            if (moveBefore) {
@@ -777,8 +794,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
            } else if (targetElement) {
              targetElement.after(element);
            } else {
-@@ -6580,10 +6754,10 @@
-@@ -6580,10 +6754,10 @@
+@@ -6580,10 +6759,10 @@
       * @param {TabMetricsContext} [metricsContext]
       */
      moveTabToGroup(aTab, aGroup, metricsContext) {
@@ -791,8 +807,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
          return;
        }
        if (aTab.group && aTab.group.id === aGroup.id) {
-@@ -6613,6 +6787,7 @@
-@@ -6613,6 +6787,7 @@
+@@ -6613,6 +6792,7 @@
  
        let state = {
          tabIndex: tab._tPos,
@@ -800,8 +815,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        };
        if (tab.visible) {
          state.elementIndex = tab.elementIndex;
-@@ -6639,7 +6814,7 @@
-@@ -6639,7 +6814,7 @@
+@@ -6639,7 +6819,7 @@
        let changedTabGroup =
          previousTabState.tabGroupId != currentTabState.tabGroupId;
  
@@ -810,8 +824,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
          tab.dispatchEvent(
            new CustomEvent("TabMove", {
              bubbles: true,
-@@ -6676,6 +6851,10 @@
-@@ -6676,6 +6851,10 @@
+@@ -6676,6 +6856,10 @@
  
        moveActionCallback();
  
@@ -822,8 +835,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
        // Clear tabs cache after moving nodes because the order of tabs may have
        // changed.
        this.tabContainer._invalidateCachedTabs();
-@@ -7576,7 +7755,7 @@
-@@ -7576,7 +7755,7 @@
+@@ -7576,7 +7760,7 @@
              // preventDefault(). It will still raise the window if appropriate.
              break;
            }
@@ -832,8 +844,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
            window.focus();
            aEvent.preventDefault();
            break;
-@@ -7593,7 +7772,6 @@
-@@ -7593,7 +7772,6 @@
+@@ -7593,7 +7777,6 @@
          }
          case "TabGroupCollapse":
            aEvent.target.tabs.forEach(tab => {
@@ -841,8 +852,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
            });
            break;
          case "TabGroupCreateByUser":
-@@ -8542,6 +8720,7 @@
-@@ -8542,6 +8720,7 @@
+@@ -8542,6 +8725,7 @@
              aWebProgress.isTopLevel
            ) {
              this.mTab.setAttribute("busy", "true");
@@ -850,8 +860,7 @@ index c0eafd4faf8d57b8486c5bf8917375850ec8147e..30c8fd7e978eb3036f35b17ae3f6ea4c
              gBrowser._tabAttrModified(this.mTab, ["busy"]);
              this.mTab._notselectedsinceload = !this.mTab.selected;
            }
-@@ -9543,7 +9722,7 @@ var TabContextMenu = {
-@@ -9543,7 +9722,7 @@ var TabContextMenu = {
+@@ -9543,7 +9727,7 @@ var TabContextMenu = {
      );
      contextUnpinSelectedTabs.hidden =
        !this.contextTab.pinned || !this.multiselected;

src/zen/folders/ZenFolders.mjs

@@ -935,7 +935,7 @@ class nsZenFolders extends nsZenDOMOperatedFeature {
         if (!parentFolder && folder.hasAttribute('split-view-group')) continue;
         const emptyFolderTabs = folder.tabs
           .filter((tab) => tab.hasAttribute('zen-empty-tab'))
-          .map((tab) => tab.getAttribute('zen-sync-id'));
+          .map((tab) => tab.getAttribute('id'));
 
       let prevSiblingInfo = null;
       const prevSibling = folder.previousElementSibling;
@@ -944,8 +944,8 @@ class nsZenFolders extends nsZenDOMOperatedFeature {
         if (prevSibling) {
           if (gBrowser.isTabGroup(prevSibling)) {
             prevSiblingInfo = { type: 'group', id: prevSibling.id };
-          } else if (gBrowser.isTab(prevSibling) && prevSibling.hasAttribute('zen-sync-id')) {
-            const zenPinId = prevSibling.getAttribute('zen-sync-id');
+          } else if (gBrowser.isTab(prevSibling) && prevSibling.hasAttribute('id')) {
+            const zenPinId = prevSibling.getAttribute('id');
             prevSiblingInfo = { type: 'tab', id: zenPinId };
           } else {
             prevSiblingInfo = { type: 'start', id: null };
@@ -964,7 +964,6 @@ class nsZenFolders extends nsZenDOMOperatedFeature {
           prevSiblingInfo: prevSiblingInfo,
           emptyTabIds: emptyFolderTabs,
           userIcon: userIcon?.getAttribute('href'),
-          syncId: folder.getAttribute('zen-sync-id'),
           // note: We shouldn't be using the workspace-id anywhere, we are just
           //  remembering it for the pinned tabs manager to use it later.
           workspaceId: folder.getAttribute('zen-workspace-id'),
@@ -991,9 +990,9 @@ class nsZenFolders extends nsZenDOMOperatedFeature {
       tabFolderWorkingData.set(folderData.id, workingData);
 
         const oldGroup = document.getElementById(folderData.id);
-        folderData.emptyTabIds.forEach((zenSyncId) => {
+        folderData.emptyTabIds.forEach((id) => {
           oldGroup
-            ?.querySelector(`tab[zen-sync-id="${zenSyncId}"]`)
+            ?.querySelector(`tab[id="${id}"]`)
             ?.setAttribute('zen-empty-tab', true);
         });
         if (oldGroup) {
@@ -1006,7 +1005,7 @@ class nsZenFolders extends nsZenDOMOperatedFeature {
               saveOnWindowClose: folderData.saveOnWindowClose,
               workspaceId: folderData.workspaceId,
             });
-            folder.setAttribute('zen-sync-id', folderData.syncId);
+            folder.setAttribute('id', folderData.id);
             workingData.node = folder;
             oldGroup.before(folder);
           } else {
@@ -1038,8 +1037,8 @@ class nsZenFolders extends nsZenDOMOperatedFeature {
           if (parentWorkingData && parentWorkingData.node) {
             switch (stateData?.prevSiblingInfo?.type) {
               case 'tab': {
-                const tab = parentWorkingData.node.querySelector(
-                  `[zen-sync-id="${stateData.prevSiblingInfo.id}"]`
+                const tab = document.getElementById(
+                  stateData.prevSiblingInfo.id
                 );
                 tab.after(node);
                 break;