Hello,
Unfortunately I cannot reproduce. I'm running Arch, I use ProtonUp (flatpak) to install the latest ProtonGE and set it as the default compatibility tool, and it sticks across steam client restarts and is used for running titles by default just fine.
The logs you have provided show 13 launches of Supermarket Together.exe, all with the same custom proton '/usr/share/steam/compatibilitytools.d/proton-ge-custom'/proton (console_log.txt).
I don't see a situation where a title was started with a different local proton, so it's even a little unclear to me what you mean about the settings not sticking, I'd have expected some launches with the default Valve provided Proton.
You may have two versions of the same tool installed twice though:
[2025-04-29 04:43:29] Processing local tool list at /usr/share/steam/compatibilitytools.d/proton-ge-custom/compatibilitytool.vdf...
[2025-04-29 04:43:29] Registering tool Proton-GE, AppID 0
[..]
[2025-04-29 04:43:29] Loaded manifest for tool Proton-GE.
[2025-04-29 04:43:29] Processing local tool list at /STORAGE/STEAM/ubuntu12_32/../compatibilitytools.d/proton-ge-custom/compatibilitytool.vdf...
[2025-04-29 04:43:29] Registering tool Proton-GE, AppID 0
Compat tool names should be unique, it looks like the first declared is being picked, is that your problem?
@TTimo this seems to be affecting SteamOS images, and mainly non-valve hardware. I have a steam deck where this works fine, but not on my HTPC which is a custom build with SteamOS on it.
It does respect per-game override but does not respect the global override. It is also worth noting that in order to even show the global setting on SteamOS at all you have to enable developer settings. These seem to be hidden on SteamOS
@TTimo I am having a similar issue that I think is related to this. Running SteamOS, latest Stable for both the OS and Steam, if I set the "Default Compatibility tool" option to something (in this case, I'm trying to set it to Proton-CachyOS Latest), games launch but don't use the proton version I set. However, it works if I set the compatibility tool override to the proton version I want in the individual game properties.
I can tell the Proton-CachyOS version that I want is being used if I set it in the game properties, but isn't being used if I set it in the global default settings, because Proton-CachyOS (and same with Proton-GE) upgrade FSR3 to FSR4 in games automatically while Valve proton versions don't. For example, testing with Helldivers 2, if I launch the game with the global settings set the in-game FSR option shows FSR3. If I launch with the game properties compatibility option set, it shows FSR4. This can also be confirmed with the 'PROTON_FSR4_INDICATOR=1 %command%' launch command.
So it seems like setting the 'Default Compatibilty tool' option in Steam settings isn't working correctly to set all games to use a different proton version by default.
Your system information
Steam client version (build number or date): 1785799196
Distribution (e.g. Ubuntu): SteamOS (Arch)
Opted into Steam client beta?: [Yes/No] No
Have you checked for system updates?: [Yes/No] Yes, none
Steam Logs: steam-logs.tar.gz
GPU: AMD 9070 XT
Steps for reproducing this issue:
PROTON_FSR4_INDICATOR=1x1 2026-08PROTON_FSR4_INDICATOR=1 %command%x1 2026-08
Your system information
tar -zcvf ~/Desktop/steam-logs.tar.gz ~/.steam/steam/logs]steam-logs.tar.gz
Please describe your issue in as much detail as possible:
Describe what you expected should happen and what did happen. Please link any large code pastes as a Github Gist
Setting the compatibility option to Proton-GE in both Steam system wide and in games never sticks. You can look in the Steam settings, and Proton-GE is selected, but it does not apply to a single game, you have to manually do every single game by hand, and once you close Steam, that setting is wiped out, and you have to redo all those steps all over again
Steps for reproducing this issue: