gh-8460: Workspaces sync [2.0] by kristijanribaric · Pull Request #12531 · zen-browser/desktop

kristijanribaric · 2026-02-26T16:53:23Z

A new sync implementation built on top of Firefox's existing Sync infrastructure, enabling cross-device synchronization of workspaces, containers, pinned tabs, and folders, reworked from the ground up.

What syncs

Workspaces: name, icon, theme, assigned container
Containers: identity, color, icon
Pinned tabs & essentials & regular tabs: URL, title, icon, workspace/folder assignment
Folders : label, icon, position, workspace assignment

Changes

New sync engine : added ZenWorkspacesStore, ZenWorkspacesTracker, and ZenWorkspacesEngine to manage tracking and storing workspace changes across devices
Session merge logic : modified ZenSessionManager to properly merge incoming remote data with the local session
Container ID sync : patched ContextualIdentityService.sys.mjs to allow creating containers with an explicit ID, ensuring pinned tabs and workspaces reference the correct container across devices
Engine registration: patched service.sys.mjs to register the new workspace sync engine

While overall sync works, it needs further testing and refinement, thx

Update

Due to the large scope, this PR is getting split into fewer, more focused PR-s:

Spaces and containers sync Add space and container sync #13598
pinned tabs sync [TBD]
regular tabs sync [TBD]

azizkoumenji · 2026-02-27T01:54:29Z

Can you also add sync support for Zen Mods if possible?

kristijanribaric · 2026-02-27T09:28:43Z

Can you also add sync support for Zen Mods if possible?

Not in scope of this PR.
Once workspace sync is all done and stable, we can start implementing separate sync mechanism for mods.

azizkoumenji · 2026-02-27T12:57:35Z

Will unpinned tabs be synced in the future?

mr-cheffy · 2026-02-27T19:12:32Z

They should be with this PR

MaximilianZenz · 2026-03-02T07:10:18Z

that there are now two competing PRs of the same feature shows pretty clear how important this feature is. i hope this will get merged soon. Have you looked at the code from the other guy? maybe he has some solutions for the issue you still have. syncing only on restart seems kinda weird as many people (at least the ones i know) never restart their browsers ever.

mr-cheffy · 2026-03-02T09:05:22Z

We want it to be live syncing, so don't worry about that, this is just a POC. There are some main blockers though because we are not sure how the merging mechanism should work. Should it completely override? Merge both sessions? ...

mirai-toto · 2026-03-05T20:34:28Z

We want it to be live syncing, so don't worry about that, this is just a POC. There are some main blockers though because we are not sure how the merging mechanism should work. Should it completely override? Merge both sessions? ...

My two cents: just prompt the user when there's a conflict, like Steam does

SilverEzhik · 2026-03-11T11:29:33Z

We want it to be live syncing, so don't worry about that, this is just a POC. There are some main blockers though because we are not sure how the merging mechanism should work. Should it completely override? Merge both sessions? ...

I would love for it to be treated as just one session - as if all Zen windows on all of my computers belong to the same browser profile, have the same tabs, etc.

I imagine sync can get very complex, though. Perhaps failures would be more forgiving if there was a way to easily recover - if some other device closed 100 tabs, there should be a way to recover them with a shortcut like Cmd+Shift+T.

UnnaturalTwilight · 2026-03-11T12:14:35Z

On the matter of unpinned tabs, please have that be a separatly configurable sync item from workspaces & pined tabs if it is reasonable to implement as such.

I personally wouldn't want my unpinned tabs syncing automatically since my primary use for sync is between windows and Linux on the same device. I tend to have very different sets of tabs between the two and would just end up closing all the synced tabs anyways. For the few cases where I want an unpinned tabs to move between them I would just use the send to device feature like I currently do.

If they aren't separate it isn't a deal breaker for me but I would appreciate not having the extra overhead if I can avoid it.

mr-cheffy · 2026-03-11T19:50:40Z

Please mark it as ready for review once its done! There seems to be git conflicts as well?

bdbch · 2026-04-03T01:36:30Z

@kristijanribaric do you need some support on the PR? I'm down to help out. What's the current status?

kristijanribaric · 2026-04-03T07:50:57Z

While the sync engine functions correctly, the conflict resolution logic could use some improvements, more specifically tab/workspace/folder creation and updating. With the current version, tabs can sometimes be created in the wrong workspace or outside of a folder while they should be in the folder. I didn't have time to go through all these edgecases, you are welcome to give it a go yourself

SpunkyMartian · 2026-04-17T09:04:13Z

just migrated from arc and this is easily the biggest thing i miss. workspace sync across mac + windows is what made arc's multi-device setup actually work for me, and getting this merged would be huge for the stream of arc refugees coming over.

happy to test this on my setup when it's ready - got 4 workspaces with nested folders + essentials + ~250 pinned tabs already migrated from arc, so there's real data to throw at it across mac and windows. let me know if helpful.

…ontextId not being properly aplied after sync

…a call

…able

….mjs

…nc engine

mr-cheffy

Note: We shouldn't sync tabs with zen-live-folder-item-id attribute, those are automatically generated anyways.

Also, when does a resync actually trigger? Would be nice to only do it after an requestIdleCallback

mr-cheffy · 2026-05-01T17:47:47Z

+   * @returns {object} A deep clone of the sidebar data.
+   */
+  getSidebarData() {
+    const sidebar = this.#sidebar;


this.#sidebar is already deep cloned

Has this been fixed? @kristijanribaric I see you are still doing the JSON thingy

mr-cheffy · 2026-05-01T17:48:49Z

+    return JSON.parse(JSON.stringify(sidebar));
+  }
+
+  replaceSidebarData(sidebar, soon = true) {


Just call saveState?

I kept this separate intentionally.

saveState() rebuilds sidebar/session data from window state, runs the normal save pipeline, and is meant for local persistence.

Here I only want a raw replace-and-persist helper for sync apply, because incoming sync already produced the sidebar state I want to write. Calling saveState() here would immediately re-collect from the current windows and could overwrite or reshape the freshly merged sync result before the UI/apply path finishes, it would be inpredictable

So replaceSidebarData() exists to do the narrower thing, accept already prepared sidebar data, store it, and persist it, without another live collection step.

mr-cheffy · 2026-05-01T17:54:32Z

      return;
    }
+    this.#notifySyncItemChanged(tabGroup);
+    Services.obs.notifyObservers(


Why global?

Global here just means the singleton meta record, not a true browser-global object. Naming is hard.

… add createSyncableTabData method to ZenSyncManager.sys.mjs; refactor sidebar normalization and tab sorting; simplify tab data creation; remove redundant event listener removal in ZenWindowSync.sys.mjs; streamline tab data cleaning in ZenWorkspacesSync.sys.mjs

… and regular tabs

… handlers; fix potential id clashing when creating new containers; refactoring

mr-cheffy · 2026-05-04T10:16:54Z

  }

  async delete() {
+    Services.obs.notifyObservers(


mr-cheffy · 2026-05-04T10:18:33Z

        });
        // createLazyBrowser can't be pinned by default
        this.window.gBrowser.pinTab(tab);
-        if (userContextId) {


mr-cheffy · 2026-05-04T10:19:53Z

      if (originalIsEssential !== targetIsEssential) {
        if (originalIsEssential) {
-          gZenPinnedTabManager.addToEssentials(aTargetItem);
+          gZenPinnedTabManager.addToEssentials(aTargetItem, { force: true });


Why would we need to force?

mr-cheffy · 2026-05-04T10:20:33Z


    if (isTab) {
+      if (aOriginalItem.hasAttribute("zenDefaultUserContextId")) {
+        aTargetItem.setAttribute("zenDefaultUserContextId", aOriginalItem.getAttribute("zenDefaultUserContextId"));


You can use #maybeSyncAttributeChange

mr-cheffy · 2026-05-04T10:20:42Z

      isEssential: originalIsEssential,
      isPinned: originalIsPinned,
    });
+


nit: Extra space

mr-cheffy · 2026-05-04T10:21:54Z

      return;
    }
+    this.#notifySyncItemChanged(tabGroup);
+    this.#notifyMetaChanged();


Why would a group creation notify a meta change? What's the purpose of "meta changed"?

mr-cheffy · 2026-05-04T10:22:22Z

+    this.#notifySyncItemChanged(tabGroup);
+    this.#notifyMetaChanged();
+    this.#delegateGenericSyncEvent(aEvent, SYNC_FLAG_MOVE);
+    return Promise.resolve();


Please call this.on_TabMove(aEvent); and return that

mr-cheffy · 2026-05-04T10:23:22Z

+    await this._removeSyncedItems(removals);
+
+    // 3. Create/update pulled folders and tabs
+    await this._applyPulledItems(pulled);


nit: Private functions should be prefixed with #

mr-cheffy · 2026-05-04T10:24:35Z

+          delete existingTab.zenStaticLabel;
+          const activeEntry = this.#getSyncedTabActiveEntry(tabData);
+          if (activeEntry?.title) {
+            gBrowser._setTabLabel(existingTab, activeEntry.title);


Changing the title and image without checking the tab is pending?

mr-cheffy · 2026-05-04T10:26:16Z

Really suffering from cognitive overload reviewing this PR 😅

We should've had divided it into smaller PRs

bdbch · 2026-05-04T22:53:07Z

I also thought about doing this in iterations. I think going into this issue with a one-shot PR is a bad idea because it's also tough to find out where sync issues happen between workspaces, folders and tabs.

How about we try to do this in multiple steps with reimplementing actual Workspace sync first and attack tabs and folders later when workspaces sync correctly.

mr-cheffy · 2026-05-04T23:05:05Z

@kristijanribaric should I make a spaces-sync branch and we can do smaller PRs to that branch instead?

al-indigo · 2026-05-06T23:41:38Z

@kristijanribaric should I make a spaces-sync branch and we can do smaller PRs to that branch instead?

Don't you think that it will slow down that feature to months since you have already reviewed most of it?
Maybe that was really not a good idea to make such a big feature initially in one PR, but since it's already done, I would be frustrated to divide it in parts afterwards if I were @kristijanribaric

//it is just an opinion; it is on your behalf of course. Just still waiting for nightly release where I can sync my 5 computers to have a synced workspace already

kristijanribaric · 2026-05-07T05:43:46Z

It won't slow it down to months, but it will definitely slow it down for some time, but if that means shipping a more polished feature, so be it, currently working on making spaces only sync

bdbch · 2026-05-07T08:54:12Z

@kristijanribaric should I make a spaces-sync branch and we can do smaller PRs to that branch instead?

Don't you think that it will slow down that feature to months since you have already reviewed most of it? Maybe that was really not a good idea to make such a big feature initially in one PR, but since it's already done, I would be frustrated to divide it in parts afterwards if I were @kristijanribaric

//it is just an opinion; it is on your behalf of course. Just still waiting for nightly release where I can sync my 5 computers to have a synced workspace already

I think the problem with a one-shot approach is that it's hard to stabilize all parts of it. I gave this two shots as well already and always run into syncing issues on one end or the other. This is not just to make reviewing easier but to actually proof one sync-feature is stable and complete.

That's why I'd propose to move back again and look into getting Workspaces to sync in a reliable way first (including associated Firefox Tab Containers if possible/needed).

When this is stable, merged and in production we could look forward into syncing tabs and folders next without having to bother that Workspaces behave flakey etc.

mr-cheffy · 2026-05-07T21:54:14Z

#13598

kristijanribaric requested a review from mr-cheffy as a code owner February 26, 2026 16:53

dosubot Bot added size:XL This PR changes 500-999 lines, ignoring generated files. Feature labels Feb 26, 2026

mr-cheffy requested changes Feb 26, 2026

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Comment thread src/zen/sessionstore/moz.build Outdated

mr-cheffy mentioned this pull request Mar 9, 2026

Windows&MacOS Sync Fail #12703

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5 tasks

dosubot Bot added size:XXL This PR changes 1000+ lines, ignoring generated files. and removed size:XL This PR changes 500-999 lines, ignoring generated files. labels Mar 11, 2026

mr-cheffy marked this pull request as draft March 11, 2026 19:50

kristijanribaric force-pushed the zen-sync branch 2 times, most recently from c853025 to 3354147 Compare March 12, 2026 14:53

This was referenced Mar 14, 2026

Workspaces not syncing across devices via Mozilla account (names/icons do not appear on second device) #12749

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Feature/sync rebuild #12507

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mr-cheffy mentioned this pull request Mar 30, 2026

Sync issue: Can't sync Space between Windows and Mac #13003

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mr-cheffy mentioned this pull request Apr 7, 2026

container, workspace and tab synchronization #8460

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mr-cheffy linked an issue Apr 7, 2026 that may be closed by this pull request

container, workspace and tab synchronization #8460

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mr-cheffy changed the title ~~Workspaces sync [2.0]~~ gh-8460: Workspaces sync [2.0] Apr 7, 2026

mr-cheffy self-requested a review April 7, 2026 20:58

kristijanribaric added 6 commits May 1, 2026 12:21

notifications refactor, added zen sync manager, fixed zenDefaultUserC…

7c0ce26

…ontextId not being properly aplied after sync

remove redundant await in ZenSpaceManager after propagateWorkspaceDat…

a28c057

…a call

reverted unnecessary assignment of canEssentialBeAdded call to a vari…

2138903

…able

Ran lint fix

83051fb

Moved sync logic from ZenSessionManager.sys.mjs to ZenSyncManager.sys…

689a2ab

….mjs

Fixed a bug where reordering folders wouldn't notify the change to sy…

8148035

…nc engine

mr-cheffy requested review from Copilot and mr-cheffy May 1, 2026 17:25

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mr-cheffy marked this pull request as draft May 2, 2026 09:42

kristijanribaric added 6 commits May 2, 2026 17:50

fix zenDefaultUserContextId not being properly synced for essientials…

bf1dd6c

… and regular tabs

revert on_TabUngrouped in ZenWindowSync.sys.mjs

43d200d

simplified zenDefaultUserContextId assigning on tabs created by sync

603e585

remove redundant observer notifications in folder and tab group event…

092b8e4

… handlers; fix potential id clashing when creating new containers; refactoring

remove redundant typeof check before calling setUserContextId

1d8584b

restored accidentally removed comment

73d846d

kristijanribaric marked this pull request as ready for review May 2, 2026 18:33

kristijanribaric requested a review from mr-cheffy May 2, 2026 18:33

mr-cheffy requested changes May 4, 2026

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Merge branch 'zen-browser:dev' into zen-sync

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What syncs

Changes

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mr-cheffy commented May 4, 2026

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kristijanribaric commented Feb 26, 2026 •

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