Lost all tabs and groups

[Jipok]

Due to the fact that I have a lot of tabs and groups, the browser took a long time to start. At some point, an error occurred(possibly due to the launch of picom(composite manager) at the same moment) and the browser crashed. The next time I started it, everything was empty:

Fortunately, I found out that firefox makes session backups. I'm not sure if this is related to this addon, here's what I have:
firefox-101.0.1_1

[chzesa]

The only tabs TTG ever closes without user interaction are the tab group view tabs, so I suspect this is caused by an error during initialization of the addon, and that the tabs are hidden. The native tab bar has a dropdown menu displaying all tabs (including hidden ones) allowing you to check if the tabs are merey hidden. Disabling and re-enabling TTG to re-initialize the addon might fix the problem.

There have been other reports of tabs seemingly being lost, but I haven't been able to find the root cause.

[chzesa]

I've managed to reproduce the issue of users losing tabs. This happens if the user closes the last visible tab which closes the browser and all the hidden tabs will have been closed when the browser next starts.

[kimsch]

Can confirm, this is exactly what happened to me. Had a tab group where I closed the last tab, and the next day noticed that all tab groups remain but were all empty. Luckily, as @Jipok said, Firefox makes occasional backups, in my case 8 days ago, when Firefox updated last. Here is the steps to follow, in case anyone else encounters this:

https://support.mozilla.org/en-US/kb/how-restore-browsing-session-backup

[chzesa]

To prevent this from happening in the future, enter about:config in the url bar, search for browser.tabs.closeWindowWithLastTab and set the value to false. This prevents the window from closing when the last visible tab is closed. It unfortunately seems that there's no way for me to do this programmatically for the user, or even directly link to the option.