With multiple windows: most tabs are unexpectedly closed, leaving maybe one tab per group

[grahamperrin]

Description

Sometimes, I lose most tabs from most windows. I began observing the issue probably a few months ago.

To distinguish this issue from various other issues:

• the resulting groups are never empty, there always remains at least one tab (not an empty new tab) in the group.

Steps to reproduce

Not yet consistently reproducible, sorry.

I'm toying with the possibility that the bug sometimes coincides with auto-backup.

Expected behavior

No unexpected closure.

Screenshot

I aim to take a shot when the bug next bites.

Desktop

• Kubuntu 25.10 with root-on-ZFS
• Firefox 150.0.2 (64-bit), Debian package
• Simple Tab Groups 5.3.2, updated 2025-10-30.

Additional context

For the most recent incident, if I recall correctly:

• five windows
• when I opened Firefox, a group with around 235 tabs opened correctly in the second window
• almost immediately, the number of tabs dropped to 1 and (I think) this coincided with notification of an auto backup
• the number also dropped to 1 in the third, fourth, and fifth windows
• a handful of tabs remained in the first window, most or all of these are not normally in the first.

I have numerous other extensions (I'll not list them in this opening comment), so, I guess, a conflict is possible.

[grahamperrin]

I'm toying with the possibility that the bug sometimes coincides with auto-backup.

I no longer suspect that. The issue is reproducible with auto-backups disabled.

Another incident

Five windows restored. IIRC:

1. after the foreground tab of the second window (in the foreground) began loading, I brought the first window to the foreground (probably by keying Alt-Tab, although I might have clicked in the task manager of Plasma)
2. in the STG sidebar, an asynchronous progress indicator was spinning
3. after the spin ended, groups appeared
4. I reviewed the second window, two tabs remained (around 230 were unexpectedly closed)
5. in the third windows, one tab remained (all others unexpectedly closed)
6. in the fourth window, one tab remained (all others unexpectedly closed)
7. the fifth window was unaffected because the group there had only one tab before the incident.
   In retrospect: maybe I should have waited longer, maybe thirty seconds longer, before switching from the second window to the first. Enough time for STG to do whatever it was doing.

Screenshots

Window one, after spinning ceased in the STG sidebar:

Window two, with Plasma's task manager to its left:

Window three:

Window four:

Window five:

Preparing to restore:

[grahamperrin]

Another incident

IIRC in this case the Default group, which is normally in the first window, was reduced to one tab following restoration however the window for the group showed more than one tab:

At a glance: maybe what was in the window, but not in the group, did include all of the 16 tabs that should have been in the group.

I guess, I could have moved the visible non-grouped tabs to the visible group.

Instead I chose to perform another restoration from the same backup.

[vitusson]

Unfortunately reproducible here with 150.0.2 Debian oldstable if I have more than one window open. Single window works fine, all tabs in other groups are untouched.
Absolute showstopper which will render the extension kind of useless for me. I need my different windows

Fortunately I'm still working on ESR 140.10

[grahamperrin]

I disabled a few extensions.

Now testing:

• before quit, close all windows except the first, in which I have the Default group
• do not rush the closures – rushing can trigger debug mode
• at quit time, wait for all processes to end (I use htop).

[achernyakevich-sc]

before quit, close all windows except the first, in which I have the Default group

Could be replaced to closing whole Firefox (all windows). Either by shortcut Ctrl+Shift+Q or from menu of any Firefox window:

This way after restart Firefox will restore all windows with all STG groups inside.

Maybe it will help. :)

[vitusson]

Could be replaced to closing whole Firefox (all windows). Either by shortcut Ctrl+Shift+Q or from menu of any Firefox window:

I'm pretty sure grahamperrin knows that.
Closing all windows at once is what triggers the whole problem. Several windows open, close with Crtl+Q and several groupss will lose their tabs at restart.

[grahamperrin]

#1353 (comment)

… closing whole Firefox (all windows). …

That's my habit, it was implicit in the Additional context of #1353 (comment).

Sorry for not making this clear from the outset.

[grahamperrin]

#1353 (comment)

… Closing all windows at once is what triggers the whole problem. …

I wonder. For me, time will tell.

@vitusson are you aware of any other open issue in which closing all windows triggers a problem?

For now, I'd like to keep things separate.

Thanks everyone.

[vitusson]

I'm sure there will be no problem after restart if we close all windows but one, since the loss of tabs only seem to affect the groups that were open in separate window at closing. All other groups who wasn't open in extra windows showed the same tabs after restart than before.

To be more specific "Closing all windows at once is what triggers the problem" is not accurate, doing this if you have more that one group in extra windows opened does.
So I'm not aware of any other open issue in which closing all windows triggers a problem.
Like I said I'm working on ESR on daily basis, FF 150 only for test purposes. I heavily relay on different groups in extra windows in my workflow (and by the looks of it, your workflow even more, I have like only 10 groups), so if this is not solved, my whole setup will become a mess.
I might be able to close all but one and then reopen all other groups after a restart, but that would involve many clicks and sounds like real PITA. I want my 5 groups read when I start FF.

But the big underlying problem with all issues here is, developer is MIA for most times (for good reasons) and there seem to be a lot of of work to do (like working with the new FF tab grouping ) to adapt it to ongoing FF changes, Having said that, I have not the coding skills to do so, but I'd wish there would be more a team behind this extension or someone could take over the much needed work.
STG is essential and in an ideal world FF would provide its features OTB, but here we are…

[philg-dev]

I've also had this issue a few days ago. Probably the only reason why I didn't experience it since then is the fact that I just suspend my laptop, leaving Firefox open.

I did also notice a fairly concerning / weird behavior of the extension for a long time already when closing one out of multiple windows, which might have the root cause in common with the issue in this ticket: There seems to be a "main" window of Firefox (or maybe managed as such internally by the extension?) and some sort of "child" windows when opening an STG group in an extra window. When closing the main window it (sometimes??) makes the browser struggle for several seconds and seemingly STG is "shoveling" tabs into the remaining "child" window, which becomes the new "main" window, as the previous "main" window doesn't exist anymore. It especially seems to shovel the tabs from all groups to the other window. In my case that was 1000+ tabs, which took somewhere between 5~15 seconds and I could watch the tab bar flicker from it. I'm pretty sure back when I wasn't really aware of this behavior / issue, I also lost a lot of tabs when I closed Firefox while STG was busy shoveling tabs from A to B.

Maybe some of this information will help to track down the cause of this issue here.

I'm unfortunately not familiar with VueJS at all, so that makes it hard for me to properly understand the code... I know the repo owner put quite a lot of work into upgrading the code base to a newer major version of VueJS as well - which is still a work-in-progress, I think. The project is still on VueJS v2.7.16, while the current stable release of VueJS is already at v3.5.33... So there's likely quite a bunch of breaking changes.

Regarding:

STG is essential and in an ideal world FF would provide its features OTB, but here we are…

Yeah STG was pretty much modeled after Firefox's "Panorama Tab Groups" which was the initial native implementation for tab groups by Mozilla... It's absolutely a shame that they discontinued the feature after about 2 years or so and we had to move to a solution using extensions instead.

[achernyakevich-sc]

Regarding:

STG is essential and in an ideal world FF would provide its features OTB, but here we are…

Yeah STG was pretty much modeled after Firefox's "Panorama Tab Groups" which was the initial native implementation for tab groups by Mozilla... It's absolutely a shame that they discontinued the feature after about 2 years or so and we had to move to a solution using extensions instead.

As far as I know and see Simple Tab Groups was inspired by Tab Groups native Add-on that was dropped as Firefox switched from native add-ons to web-extension based add-ons. In turn Tab Groups native Add-On was extracted from inside of Firefox core functionally to make it independently supported because it is a quite heavy functionality but used by not a lot of people.

The circle is closed. :)

I used all the mentioned as I use Firefox since version before 1.0. I really like Firefox and all the mentioned Add-On as these make me very efficient. :)

[grahamperrin]

Let's keep discussion focused on this particular issue, thanks.

After a few hours of testing: I'm closer to having steps to reproduce that will be more useful for diagnosis and, hopefully, a more satisfactory workaround. I'll not divulge details yet, please be patient.

[grahamperrin]

#1353 (comment)

… "Closing all windows at once is what triggers the problem" is not accurate, doing this if you have more that one group in extra windows opened does. …

@vitusson do you mean this?

1. Three windows, each of which has a group loaded
2. quit
3. the issue will become apparent after windows etc. are restored.

[JuanEscalada]

I don't know if this belongs to this issue or if i should open a separate one, as the behavior is really similar.

The only difference is that this also happens to me with Tab Groups that are not open on any window at the moment.

What i noticed is that the name of the Group seems to have some correspondence with it losing the tabs or not. (sometimes if I change the group name it doesn't lose tabs, and also if i create a new group with the same name as one that lost tabs and replace it -> it will lose its tabs).

In my case i am on: Windows 11 with 150.0.3 (64-bit).

I noticed what philg-dev said about the extension shoveling the tabs to the "main" window.
In my case i can see that when i close a particular window, it aparently moves every tab on the closed window to the "main" one and after completing that movement it rewrites the group. If you interrupt the process or close any of those tabs you will lose it.
I haven't reviewed the code yet but the problem might come from this seemingly unnecesary rewrite of the group.

[mw446391]

I'm seeing this issue as well and it renders STG more or less unusable since it happens too often.
I haven't looked in the code or investigated thoroughly but it seems the following is happening:

1. the user initiates quitting of Firefox, e.g. by pressing ⌘Q
2. Firefox starts shutting
3. in the process, Firefox starts closing tabs
4. STG notices the changes, i.e. closed tabs, and updates the tab group before Firefox finally quits

So I think it's kind of a timing issue. STG should prevent updates to tab groups after Firefox initiated the quit-procedure. This is similar to what @JuanEscalada describes above

but the problem might come from this seemingly unnecesary rewrite of the group

Not sure if STG can know if Firefox is shutting down or not. If not, then maybe a delay before updating tab groups may be an option - not perfect but better than loosing tabs constantly. Or you could define ⌘Q as a hotkey so that STG catches the quit-procedure first, stops updating tab groups and then passes the command to Firefox - again not perfect as it wouldn't help when you quit Firefox from the menubar but it might be a reasonable workaround.

I've noticed another odd behaviour with the disappearing tabs: sometimes, a tab group shows say 34 tabs, but a few of these 34 tabs are actually open in another window; you can manually move these tabs back to the original window and the tab count still remains 34.