Bug 507413

SUMMARY
This happens to me on Kubuntu 25.04 (KDE Plasma 6.3.4, kate 24.12.3) as well as on CachyOS (KDE Plasma 6.4.3, kate 25.04.3). The CachyOS was installed today and nothing was done with it so far, so it's a completely fresh install.

I suppose the behaviors are all connected, so I'm reporting them as a single bug. When I set up Kate to restore the last used session it seems to completely screw up for me:
1. for all previously unsaved files, the tabs are restored, but they are empty
2. if I make changes to a file that already exists on disk and close kate (WITHOUT saving the changes), the changes are automatically saved to the file on exit (which is not what kate should do without asking and not what it's settings suggest).
3. If (empty) tabs were restored due to previously unsaved files and I open an existing file from disk, kate will close the currently open "restored" empty tab and replace it with the opened file. This does not happen when I have an empty tab that was just opened (not restored from session).

The funniest thing is:
In $HOME/.local/share/kate/stash/[Session name].katesession the unsaved changes are actually stored for unsaved files. Meaning: in a scenario where I have two unsaved files in kate and one file opened from disk, I write something in all of them and then close kate (without saving anything), I get three files in the aforementioned directory (Document 0, Document 1, Document 2) containing the contents as they were when kate was closed.

In $HOME/.local/share/kate/sessions/[Session name].katesession I also see entries for all three documents, two having no URL and one having the file-URL of the file on disk.

So it appears that everything is stored correctly when kate exits (aside from the fact that unsaved changes in the file on disk should of course not be saved without asking), but they are not restored.

Another notable thing:
After kate restores the "empty" unsaved files, if i put new content in one of the files (say "Document 0" to stick to my example scenario) and leave the other one unchanged (i.e. empty) and then close kate, the "Document 0" is actually updated in the stash folder while "Document 1" remains unchanged (i.e. having the same content as it had when I first closed kate and NOT being empty as it was when I closed kate the second time after the ill-fated restore).


STEPS TO REPRODUCE
1. Open two new Documents without saving them
2. Save the session, giving it a name (for the sake of completeness: I called mine "Standardsitzung")
3. In kate's session settings, set up kate to use the last session on program start and save and restore unsaved files and unsaved changes to existing files (sorry, don't know the exact english lables for the settings)

OBSERVED RESULT
As described above

EXPECTED RESULT
kate should restore the contents of all files from the stash files and should NOT alter existing files that were not actually saved


SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Kubuntu 25.04 and CachyOS (Kernel 6.5.15-1-cachyos)
KDE Plasma Version: 6.3.4 and 6.4.3
KDE Frameworks Version: 6.12.0 and 6.16.0
Qt Version: 6.8.3 and 6.9.1