Open some file twice (from "Open Recent", for example or by opening from OS shell) to different tabs.
Work in the one of opened tabs during hour or day, save it.
Close Krita, accept saving of other document opened from same file (I didn't realize, that this destroys work from other tab).
Hour or day of life is lost (night actually, in my case. Have tried to reread "NO WARRANTY" section of GNU license with "BE LIABLE TO YOU FOR DAMAGES", but still sad). (autosaves in %TEMP% dir and *.kra~ backups already had been inspected).

Suggestions:
* Don't allow to open same document twice in same application process, switch to tab with opened file
* Synchronize tabs with file, reload when file is modified, ask user to choose when there are conflict between edits and new file content
* When file is saved over modified file by someone else - create autosave and ask user for overwrite or save to another location (Save As...). Autosave is needed, because it's hard to tell and visualize clearly for user, what happened (user doesn't expect that something was overwritten).
* Lock file when opened in Krita, don't allow other programs and itself to unwanted overwrite during painting

Please make a bug report. In the meantime, just don't do this. If you want an image open in two tabs, create a new view using the Window menu. (A patch would also be awesome...)

The habit to use Ctrl+Alt+S ("save incremental version") seems to work in safe way, with one nuance - last incremental version do not appear in "recent" documents list. Actually, this is OK that most of versions are not shown to avoid pollution with version 1, 2, ..., 20, except it's not OK for last version.

The habit to use Ctrl+Alt+S ("save incremental version") seems to work in safe way, with one nuance - last incremental version do not appear in "recent" documents lis

Also there are a lot of unused auto-save files, Krita-2.9.10 forgets to remove them when incremental save ( Ctrl+Alt+S ) is used

...........
-rwxrwx---+ 1 johnsmith None 27M Feb 21 05:28 .my_cat_112.kra-autosave.kra
-rwxrwx---+ 1 johnsmith None 30M Feb 21 08:44 my_cat_113.kra~
-rwxrwx---+ 1 johnsmith None 30M Feb 21 08:52 my_cat_113.kra
-rwxrwx---+ 1 johnsmith None 29M Feb 21 19:58 .my_cat_113.kra-autosave.kra
-rwxrwx---+ 1 johnsmith None 33M Feb 21 19:59 my_cat_114.kra~
-rwxrwx---+ 1 johnsmith None 34M Feb 21 20:30 my_cat_114.kra
-rwxrwx---+ 1 johnsmith None 33M Feb 21 22:07 .my_cat_114.kra-autosave.kra
-rwxrwx---+ 1 johnsmith None 36M Feb 21 22:07 my_cat_115.kra~
-rwxrwx---+ 1 johnsmith None 34M Feb 21 23:14 my_cat_115.kra
-rwxrwx---+ 1 johnsmith None 34M Feb 21 23:15 my_cat_116.kra~
-rwxrwx---+ 1 johnsmith None 33M Feb 21 23:21 my_cat_116.kra
-rwxrwx---+ 1 johnsmith None 33M Feb 22 00:32 my_cat_117.kra
-rwxrwx---+ 1 johnsmith None 30M Feb 22 01:51 .my_cat_117.kra-autosave.kra
-rwxrwx---+ 1 johnsmith None 33M Feb 22 01:54 my_cat_118.kra~
-rwxrwx---+ 1 johnsmith None 34M Feb 22 02:34 my_cat_118.kra
-rwxrwx---+ 1 johnsmith None 31M Feb 22 02:45 .my_cat_118.kra-autosave.kra
-rwxrwx---+ 1 johnsmith None 34M Feb 22 02:45 my_cat_119.kra
-rwxrwx---+ 1 johnsmith None 31M Feb 22 03:31 .my_cat_119.kra-autosave.kra
-rwxrwx---+ 1 johnsmith None 34M Feb 22 03:32 my_cat_120.kra~
-rwxrwx---+ 1 johnsmith None 33M Feb 22 04:06 my_cat_120.kra
-rwxrwx---+ 1 johnsmith None 30M Feb 22 04:43 .my_cat_120.kra-autosave.kra
-rwxrwx---+ 1 johnsmith None 33M Feb 22 04:44 my_cat_121.kra~
-rwxrwx---+ 1 johnsmith None 33M Feb 22 04:46 my_cat_121.kra
-rwxrwx---+ 1 johnsmith None 31M Feb 22 07:35 .my_cat_121.kra-autosave.kra
-rwxrwx---+ 1 johnsmith None 35M Feb 22 07:35 my_cat_122.kra
-rwxrwx---+ 1 johnsmith None 31M Feb 22 07:41 .my_cat_122.kra-autosave.kra
-rwxrwx---+ 1 johnsmith None 35M Feb 22 07:42 my_cat_123.kra
-rwxrwx---+ 1 johnsmith None 31M Feb 22 07:56 .my_cat_123.kra-autosave.kra
-rwxrwx---+ 1 johnsmith None 35M Feb 22 07:56 my_cat_124.kra
-rwxrwx---+ 1 johnsmith None 31M Feb 22 08:04 .my_cat_124.kra-autosave.kra
-rwxrwx---+ 1 johnsmith None 35M Feb 22 08:04 my_cat_125.kra
-rwxrwx---+ 1 johnsmith None 31M Feb 22 20:39 .my_cat_125.kra-autosave.kra
-rwxrwx---+ 1 johnsmith None 35M Feb 22 20:39 my_cat_126.kra
-rwxrwx---+ 1 johnsmith None 31M Feb 22 21:37 .my_cat_126.kra-autosave.kra
-rwxrwx---+ 1 johnsmith None 35M Feb 22 21:37 my_cat_127.kra
-rwxrwx---+ 1 johnsmith None 32M Feb 22 21:38 .my_cat_127.kra-autosave.kra
-rwxrwx---+ 1 johnsmith None 35M Feb 22 21:39 my_cat_128.kra
-rwxrwx---+ 1 johnsmith None 35M Feb 22 21:41 my_cat_129.kra
-rwxrwx---+ 1 johnsmith None 35M Feb 22 21:42 my_cat_130.kra
-rwxrwx---+ 1 johnsmith None 31M Feb 23 00:26 .my_cat_130.kra-autosave.kra
-rwxrwx---+ 1 johnsmith None 34M Feb 23 00:27 my_cat_131.kra~
-rwxrwx---+ 1 johnsmith None 36M Feb 23 00:40 my_cat_131.kra
...........

Report bugs at bugs.kde.org, NOT the forum.

It asks for legitimate login and password, and forum login/pass are not working. And I am too lazy to go registration process now. Maybe in future.

Also I am afraid of bug trackers interface - they are booooring, formal, and reminds too much of my office job. Maybe I want to be an artist, not QA team employee

https://bugs.kde.org/show_bug.cgi?id=359686#c0 ( about temporary files )

Thanks anyway for the autosave system/incremental saves

Although they have some little bugs, these features saves me a lot of time anyway, and better have these little bugs, than have absence of these features

I know, that users of open source programs are not just users, but part of team. But converting bug mention to exact minimal steps of reproduction and boooooring fields filling of bureaucratic forms sometimes too hard or time consuming for artists, and bugs remains unreported forever .

May be you can open position for QA member, which can convert vague descriptions from users to exact bug reports with steps of reproduction. This is not nor developer's job, nor user's. And this is time consuming job, not just etiquette of bug reporting.

Well, this bug is reported to bug tracker two weeks ago. Still, I have no feedback even for correctness of the bugreport.

"May be you can open position for QA member, which can convert vague descriptions from users to exact bug reports with steps of reproduction. This is not nor developer's job, nor user's. And this is time consuming job, not just etiquette of bug reporting."

Well, a volunteer for that would be welcome. I'm trying to reply to bug reports in a timely fashion, but given that we get half a dozen reports a day, I'm falling behind because

a) I was on vacation
b) I also need to write code
c) I also need to manage the project
d) I don't have all the hardware that people write reports about
e) Sometimes things fall between the cracks and get forgotten.
f) Sometimes it's really hard to decide whether something is a real bug or not. That's the case with this report.
g) Making releases takes time, too
h) Administration, taxes and other paperwork take time
j) kickstarter planning takes time
k) my day job, which isn't Krita-related, takes time

Usually, I spend my Saturdays doing actual bug triaging, while my mornings on the train to work are for answering the easily-answered bug reports... In the end, I have less spare time than any Krita user; if you want to help, you need to spend the time to make my life easier. You need to do as much work for me as possible.