# Anki Fatal Error Message **URL:** \ **Category:** Help\ **Created:** [October 1, 2025, 3:13am UTC](https://forums.ankiweb.net/t/anki-fatal-error-message/66767 "2025-10-01T03:13:55Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![Sylvester28](https://avatars.discourse-cdn.com/v4/letter/s/838e76/32.png) [@Sylvester28](https://forums.ankiweb.net/u/Sylvester28)\ **Post date:** [October 1, 2025, 3:13am UTC](https://forums.ankiweb.net/t/anki-fatal-error-message/66767/1 "2025-10-01T03:13:55Z")
Hello, I was making cards in Anki, and received the below error message which said to report this on the Anki forum. I do not recall an error occurring before this one, and after closing Anki and restarting it, I ran a check database which did not seem to run into any issues. I did a few reviews, and made a few cards after without issue. Is there anything else I should do? A fatal error occurred, and Anki must close. Please report this message on the forums. Below is the Debug info from the notification: Anki 25.02 (038d85b1) (ao) Python 3.9.18 Qt 6.6.2 PyQt 6.6.1 Platform: Windows-10-10.0.26100 Traceback (most recent call last): File “aqt.taskman”, line 144, in \_on\_closures\_pending File “aqt.taskman”, line 88, in File “aqt.taskman”, line 108, in wrapped\_done File “aqt.operations”, line 123, in wrapped\_done File “concurrent.futures.\_base”, line 439, in result File “concurrent.futures.\_base”, line 391, in \_\_get\_result File “concurrent.futures.thread”, line 58, in run File “aqt.operations”, line 108, in wrapped\_op File “aqt.operations.note”, line 22, in File “anki.collection”, line 534, in add\_note File “anki.\_backend\_generated”, line 1290, in add\_note File “anki.\_backend”, line 161, in \_run\_command pyo3\_runtime.PanicException: assertion `left == right` failed left: 1759287084619 right: 0 ---
**Author:** ![Sylvester28](https://avatars.discourse-cdn.com/v4/letter/s/838e76/32.png) [@Sylvester28](https://forums.ankiweb.net/u/Sylvester28)\ **Post date:** [October 3, 2025, 12:50pm UTC](https://forums.ankiweb.net/t/anki-fatal-error-message/66767/2 "2025-10-03T12:50:46Z")
I just want to confirm that I should just follow the steps in the troubleshooting guide, or if this particular error requires more investigation. Everything seems fine since it happened. Thanks for any input! > **[Troubleshooting - Anki Manual](https://docs.ankiweb.net/troubleshooting.html)** > > Anki's user manual. Anki is a flashcard program that makes learning easier. ---
**Author:** ![Anon\_0000](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Anon\_0000](https://forums.ankiweb.net/u/Anon_0000)\ **Post date:** [October 3, 2025, 1:05pm UTC](https://forums.ankiweb.net/t/anki-fatal-error-message/66767/3 "2025-10-03T13:05:54Z")
I guess the most helpful thing would be steps to reproduce. Maybe it was triggered by one of your addons (if any) and you found an edge case that caused that error. If everything else still works fine, it’s probably safe to ignore it. Though if you find out how to reproduce, Anki or the addon developer could look at your report and solve it. From a quick search on github in ankis repo, I cannot find any `assert`\* calls that have `left, right` (or similar) as parameters. Though it might be there and I might have missed it. ---
**Author:** ![Sylvester28](https://avatars.discourse-cdn.com/v4/letter/s/838e76/32.png) [@Sylvester28](https://forums.ankiweb.net/u/Sylvester28)\ **Post date:** [October 3, 2025, 1:17pm UTC](https://forums.ankiweb.net/t/anki-fatal-error-message/66767/4 "2025-10-03T13:17:26Z")
Thank you for your response! It seemed to occur after making a note, although when I did the exact same things again after the error (making notes, even deleting and remaking the note that I was doing before the error), I was not able to reproduce it My gut feeling is that I accidentally double clicked on create note, as my laptop touchpad has been having that issue. I think I saw Dae say somewhere that this could cause an error. ---
**Author:** ![abdo](https://sea2.discourse-cdn.com/flex002/user_avatar/forums.ankiweb.net/abdo/32/654_2.png) [@abdo](https://forums.ankiweb.net/u/abdo)\ **Post date:** [October 3, 2025, 2:11pm UTC](https://forums.ankiweb.net/t/anki-fatal-error-message/66767/5 "2025-10-03T14:11:03Z")
I managed to reproduce it. I think you’re right that it’s triggered by a double click. Logged here: [Fatal error when double clicking Add too quickly · Issue #4376 · ankitects/anki · GitHub](https://github.com/ankitects/anki/issues/4376) ---
**Author:** ![Sylvester28](https://avatars.discourse-cdn.com/v4/letter/s/838e76/32.png) [@Sylvester28](https://forums.ankiweb.net/u/Sylvester28)\ **Post date:** [October 3, 2025, 2:35pm UTC](https://forums.ankiweb.net/t/anki-fatal-error-message/66767/6 "2025-10-03T14:35:25Z")
Thank you for taking the time to test that and add the report, I really appreciate it! ---
**Author:** ![meramera](https://avatars.discourse-cdn.com/v4/letter/m/41988e/32.png) [@meramera](https://forums.ankiweb.net/u/meramera)\ **Post date:** [November 2, 2025, 9:09am UTC](https://forums.ankiweb.net/t/anki-fatal-error-message/66767/7 "2025-11-02T09:09:48Z")
Anki 25.07.5 (7172b2d2) Python 3.13.5 Qt 6.9.1 PyQt 6.9.1 Platform: Windows-11-10.0.26100-SP0 Traceback (most recent call last): File “C:\Users\Bles\AppData\Local\AnkiProgramFiles\.venv\Lib\site-packages\aqt\taskman.py”, line 148, in \_on\_closures\_pending closure() ~~~~~~~ ^^ File “C:\Users\Bles\AppData\Local\AnkiProgramFiles\.venv\Lib\site-packages\aqt\taskman.py”, line 88, in lambda future: self.run\_on\_main(lambda: on\_done(future)) ~~~~~~~ ^^^^^^^^ File “C:\Users\Bles\AppData\Local\AnkiProgramFiles\.venv\Lib\site-packages\aqt\taskman.py”, line 111, in wrapped\_done on\_done(fut) ~~~~~~~ ^^^^^ File “C:\Users\Bles\AppData\Local\AnkiProgramFiles\.venv\Lib\site-packages\aqt\operations\__init_\_.py”, line 123, in wrapped\_done future.result() ~~~~~~~~~~~~~ ^^ File “C:\Users\Bles\AppData\Local\AnkiProgramFiles\python\cpython-3.13.5-windows-x86\_64-none\Lib\concurrent\futures\_base.py”, line 449, in result return self.\_\_get\_result() ~~~~~~~~~~~~~~~~~ ^^ File “C:\Users\Bles\AppData\Local\AnkiProgramFiles\python\cpython-3.13.5-windows-x86\_64-none\Lib\concurrent\futures\_base.py”, line 401, in \_\_get\_result raise self.\_exception File “C:\Users\Bles\AppData\Local\AnkiProgramFiles\python\cpython-3.13.5-windows-x86\_64-none\Lib\concurrent\futures\thread.py”, line 59, in run result = self.fn(\*self.args, \*\*self.kwargs) File “C:\Users\Bles\AppData\Local\AnkiProgramFiles\.venv\Lib\site-packages\aqt\operations\__init_\_.py”, line 108, in wrapped\_op return self.\_op(mw.col) ~~~~~~~~ ^^^^^^^^ File “C:\Users\Bles\AppData\Local\AnkiProgramFiles\.venv\Lib\site-packages\aqt\operations\note.py”, line 22, in return CollectionOp(parent, lambda col: col.add\_note(note, target\_deck\_id)) ~~~~~~~~~~~~ ^^^^^^^^^^^^^^^^^^^^^^ File “C:\Users\Bles\AppData\Local\AnkiProgramFiles\.venv\Lib\site-packages\anki\collection.py”, line 533, in add\_note out = self.\_backend.add\_note(note=note.\_to\_backend\_note(), deck\_id=deck\_id) File “C:\Users\Bles\AppData\Local\AnkiProgramFiles\.venv\Lib\site-packages\anki\_backend\_generated.py”, line 1429, in add\_note raw\_bytes = self.\_run\_command(25, 1, message.SerializeToString()) File “C:\Users\Bles\AppData\Local\AnkiProgramFiles\.venv\Lib\site-packages\anki\_backend.py”, line 160, in \_run\_command return self.\_backend.command(service, method, input) ~~~~~~~~~~~~~~~~~~~~~ ^^^^^^^^^^^^^^^^^^^^^^^^ pyo3\_runtime.PanicException: assertion `left == right` failed left: 1762074374316 right: 0 ---
**Author:** ![Anon\_0000](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Anon\_0000](https://forums.ankiweb.net/u/Anon_0000)\ **Post date:** [November 2, 2025, 9:18am UTC](https://forums.ankiweb.net/t/anki-fatal-error-message/66767/8 "2025-11-02T09:18:14Z")
1. What do you do before those crashes occure? 2. What are the steps to reproduce? 3. Does [Troubleshooting - Anki Manual](https://docs.ankiweb.net/troubleshooting.html) help? ---
**Author:** ![Danika\_Dakika](https://sea2.discourse-cdn.com/flex002/user_avatar/forums.ankiweb.net/danika_dakika/32/17815_2.png) [@Danika\_Dakika](https://forums.ankiweb.net/u/Danika_Dakika)\ **Post date:** [November 2, 2025, 1:51pm UTC](https://forums.ankiweb.net/t/anki-fatal-error-message/66767/9 "2025-11-02T13:51:23Z")
> [@Anki Fatal Error Message](https://forums.ankiweb.net/t/anki-fatal-error-message/66767/5): > > I managed to reproduce it. I think you’re right that it’s triggered by a double click. Logged here: [Fatal error when double clicking Add too quickly · Issue #4376 · ankitects/anki · GitHub](https://github.com/ankitects/anki/issues/4376) This was fixed when it was reported last month, but it hasn’t been released yet. ---
**Author:** ![Anon\_0000](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Anon\_0000](https://forums.ankiweb.net/u/Anon_0000)\ **Post date:** [November 2, 2025, 1:59pm UTC](https://forums.ankiweb.net/t/anki-fatal-error-message/66767/10 "2025-11-02T13:59:34Z")
> [@Danika\_Dakika](#): > > This was fixed when it was reported last month Is it the same though? The lines between those error reports are different, including the value for `left`. (I can see that it’s similar, but it’s weird that the stack trace differs in the actual code lines, making me think it might be a different issue) ---
**Author:** ![abdo](https://sea2.discourse-cdn.com/flex002/user_avatar/forums.ankiweb.net/abdo/32/654_2.png) [@abdo](https://forums.ankiweb.net/u/abdo)\ **Post date:** [November 2, 2025, 3:10pm UTC](https://forums.ankiweb.net/t/anki-fatal-error-message/66767/11 "2025-11-02T15:10:56Z")
I get similar error text as the one posted by @meramera if I run the code I posted on the issue, so I think it’s the same issue, but OP got a different text for some reason (might be because he is on an older version). ---
**Author:** ![Danika\_Dakika](https://sea2.discourse-cdn.com/flex002/user_avatar/forums.ankiweb.net/danika_dakika/32/17815_2.png) [@Danika\_Dakika](https://forums.ankiweb.net/u/Danika_Dakika)\ **Post date:** [November 2, 2025, 4:21pm UTC](https://forums.ankiweb.net/t/anki-fatal-error-message/66767/12 "2025-11-02T16:21:06Z")
> [@abdo](#): > > OP got a different text for some reason (might be because he is on an older version). That’s what I was assuming. The line-by-line errors all seem the same, despite the newer formatting. ---
**Author:** ![system](https://us1.discourse-cdn.com/flex002/uploads/anki2/original/1X/8f1279ababc5879d54e4838989f606cfe55af8c7.jpeg) [@system](https://forums.ankiweb.net/u/system)\ **Post date:** [December 2, 2025, 4:21pm UTC](https://forums.ankiweb.net/t/anki-fatal-error-message/66767/13 "2025-12-02T16:21:54Z")
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