Your system information

• Steam client version (build number or date): 1741636428
• Distribution: Debian 12.9 (Xanmod kernel 6.12.18)
• Opted into Steam client beta?: No
• Have you checked for system updates?: Yes
• Steam Logs: recorder_log.txt
• GPU: Nvidia RTX 2070 SUPER

Please describe your issue in as much detail as possible:

Opening any Proton game with Game Recording set to Record in Background results in a game crash upon starting. This seems to not be a problem with Proton itself, as it happened with Proton 9, Experimental, and GE-25, all of which worked before the update. Native Linux games seem to still run and record like you'd expect.
Weirdly enough, setting the recording mode to Record Manually, then manually starting the recording once in-game seems to work fine.
This message also shows up in dmesg when the game crashes:

signal: SpinRhythm.exe[31160] overflowed sigaltstack

Expected behavior: Games should run and record in the background;
Actual behavior: Games crash on startup with Game Recording enabled;

Steps for reproducing this issue:

1. Open settings
2. Go to "Game Recorder"
3. Set mode to "Record in background"
4. Start a game that runs through Steam Play (i.e. Proton)