Hello @HipToBeSquare, Proton Hotfix (https://github.com/ValveSoftware/Proton/wiki/Proton-Versions#proton-hotfix) is an irregular build of Proton to fast track game-specific hacks, If you're not testing one of those short lived hacks, that build of Proton should not be used. I suspect you've set Steam's global compatibility tool to that variant which is why it was picked. (Enable Developer mode in Steam's system settings, then go down to the Developer section.)
There's a couple years of changes between Proton 9.0 and Proton Experimental. Can you check how the game behaves with Proton 10.0 and/or 11.0 to narrow the time frame of the regression? Also, please add PROTON_LOG=1 %command% to the game's launch options and attach the generated $HOME/steam-$APPID.log to this issue report as a file. (Proton logs compress well if needed.)
Hello @HipToBeSquare, Proton Hotfix (https://github.com/ValveSoftware/Proton/wiki/Proton-Versions#proton-hotfix) is an irregular build of Proton to fast track game-specific hacks, If you're not testing one of those short lived hacks, that build of Proton should not be used. I suspect you've set Steam's global compatibility tool to that variant which is why it was picked. (Enable Developer mode in Steam's system settings, then go down to the Developer section.)
There's a couple years of changes between Proton 9.0 and Proton Experimental. Can you check how the game behaves with Proton 10.0 and/or 11.0 to narrow the time frame of the regression? Also, please add
PROTON_LOG=1 %command%to the game's launch options and attach the generated $HOME/steam-$APPID.log to this issue report as a file. (Proton logs compress well if needed.)
Thanks for following up!
I can confirm that 9.0 is the most recent working version. 10.0 and 11.0 do not work (they crash at the same place as experimental/hotfix). The reason for testing on the Hotfix was just due to all of my players reporting that Steam was defaulting them to that build, which caused them to think the game can't be played unless they test versions all the way back to 9.0, which most don't make it to.
The issue is specifically with video playback of specific webm files. My game has 4 webm files that it plays on booting and during the title menu. One of them works (the first one that plays), and 3 do not. Changing which one plays first doesn't allow the others to play, so it is something specific to that file that allows it to play. The ones that fail will play the audio, and close the game when the video tries to play after being blank for a moment. They all share identical formats (down to the keyframe interval, bitrate, framerate, dimensions, encoder profile settings, and so-on). The fact that one of them works has caused me to try modifying the failing video files in dozens of different ways to see what gives, such as different bitrates, keyframe frequency, framerates, file sizes, encoder libraries, and so-on, but nothing seems to work, despite 9.0 playing all of them just fine.
Here is the log, generated while testing with v11.0
steam-3195680.log
The game is made in RPG Maker MZ, so there are a number of Proton compatibility issues in general on the newer NW.js versions (especially where Steam Input is concerned, with any non-keyboard/mouse layout needing to be switched to keyboard/mouse and back again for the game to detect any controller from Steam Input, as the game needs to "see" it connect), but this webm crash is the first issue I've encountered that closes the game completely.
If you need to investigate the movie files, they are not encrypted and can be viewed in the game's root directory in
the movies folder. The "kwalee.webm" file plays properly, and all of the others crash the game.
proton 10.0x2 2026-06proton 9.0x2 2026-06proton experimentalx2 2026-06proton hotfixx2 2026-06PROTON_LOG=1x2 2026-06
Compatibility Report
System Information
I confirm:
Symptoms
Both the Experimental and Hotfix builds of Proton crash the game after the second splash screen on Steam Deck or any Linux device. Steam defaults all games to the Hotfix build, which means all users crash if using out-of-the-box settings when launching this game.
Proton v9.0-4 works just fine, and switching to this version allows the game to run (loads past all splash screens, no crash). So, users have to manually switch to this older version to play the game, leading to a 25% failure rate in out Steam analytics for the game.
I am hoping that either the Hotfix can be made compatible with this game, or this appID can somehow be set as the default for this appID (I am the developer of this game).
The full game (though unreleased) also has the same issue, so this would be needed as well to resolve the same issue for appID 3195440 prior to our launch.
Reproduction
On Steam Deck, install this appID and launch it with default settings. It will crash on the second splash screen (After the "Kwalee Gaming" publisher logo, before the "Ill-Advised Games" developer logo).
Switching from Hotfix to v9.0-4 will fix this, and the game will launch fully.