I'll add my story from 11th Nov 2023 (today). So I only have 16 GB of RAM on a Win 10 computer and my Opera regularly goes to 5-8 GB of memory usage, and essentially the computer becomes too sluggish to use (the memory use of browsers is a different topic altogether). Anyhow I have been using Opera for a few years, originally moved from Firefox because Firefox kept losing my tabs (ironic now!) and I also loved the Workspaces feature. Not a big fan of tab islands but I adapted.

Today I closed Opera when it was taking 5.7 GB of RAM and my RAM usage was somewhere in the 90%+. I had refreshed a couple of tabs on my current workspace just before I closed. Closing took a minute or so. Upon reopening Opera, I was greeted with the "new Opera version" sound and logo (I hate it, btw, especially at night when I'm trying to be quiet). And my workspace which used to have 100+ tabs now only had four tabs - two tabs that I remember having refreshed in the last hour or so, an empty tab (not sure why - I do have "Display the start page first" enabled though, maybe that's it), and the "Opera has updated" tab. The Opera version is/was 104.0.4944.36 but after the update it downloaded .54 - why it couldn't download that directly I don't know...

Previously I have been using Opera without any tab loss. I run my computer 24/7 and restart Opera (and only Opera) maybe once a week or every two weeks because of the memory issue. No problems ever before. But now it seems the problem described in this thread has come to ruin my day. I'm guessing this was a combination of whatever bugs exist regarding tabs, and perhaps a memory issue if that's also some rare known issue, AND Opera updating its version. I haven't used Tab Suspender but sounds like I should!

So yeah, 100+ tabs lost. In fact I remember the count upon "Really quit Opera" being around 1467, and now when I closed again when I was attempting to do some manual session restore stuff, it was 1348 tabs. So yeah, 119 tabs gone. Great. And of course trying to fix the sessions manually didn't work, somehow Opera gets the tabs from somewhere else than Sessions or already corrupted the bigger Tabs file.

For what it's worth, considering my experience, the vast majority of users probably don't encounter the tab issues at all. I was like that until today. I have not been able to replicate my issue again (and fingers crossed I never will). So whatever is going on is not quite as simple as Opera always losing the tabs as described here - there's some variables at play. No idea what those could be. My only extensions are a defunct crypto thing called Keplr and Bookmark All Tabs (which can only bookmark the current workspace, of course). No major settings changes.

Fingers crossed this is my only post here. I do like the workspaces and the floating video player, and those will keep me as an Opera user unless the tabs start disappearing more often.