Hello @VolRencs, we're tracking issues with games run with Proton in the Proton issue tracker, so I've gone ahead and transferred this issue report.
Please add PROTON_LOG=1 %command% to a couple 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.) Also, please copy the contents of Steam Runtime Diagnostics from Steam (Steam -> Help -> Steam Runtime Diagnostics) and put it in a gist, then include a link to the gist in this issue report.
Hello, I don't think getting a proton log for this issue is possible as Steam doesn't even attempt to launch the game. I have this issue and RE Requiem will only launch on the normal client, not the steamrt3 experimental.
Then we need a set of logs from Steam's log folder to ponder that.
@kisak-valve Sorry, but I believe this issue has been transferred incorrectly.
The game never actually starts, so Proton is never initialized. Because of that, there is no Proton log to generate, and PROTON_LOG=1 %command% has no effect.
This appears to be a Steam client issue rather than a Proton compatibility issue, since the failure occurs before Proton is even launched.
After looking through the logs, the only relevant message I could find is the following entry in logs/webhelper_js.txt:
SteamUI: WARNING: LaunchGameAction: launch error 20 1672970 LaunchApp UnlockingH264 23
I'm not sure whether this message is related to the issue, but it seems to be the only consistent error reported during every launch attempt.
I think I may have found the cause of the issue.
While investigating the logs, I noticed that every failed launch follows the same sequence:
GameAction [AppID 1672970] : LaunchApp changed task to UpdatingAppTicket
GameAction [AppID 1672970] : LaunchApp changed task to UnlockingH264
Couldn't find encrypted codec /home/volren/.local/share/Steam/steamrt64/libx264.so.142.crypt
GameAction [AppID 1672970] : LaunchApp failed with UnlockingH264 with "23"
I then checked the file mentioned in the log. steamrt64/libx264.so.142.crypt is a symbolic link pointing to:
../ubuntu12_64/libx264.so.142.crypt
However, the target file does not exist:
$ ls -l ~/.local/share/Steam/ubuntu12_64/libx264.so.142.crypt
ls: cannot access '/home/volren/.local/share/Steam/ubuntu12_64/libx264.so.142.crypt': No such file or directory
So the symlink exists, but its target is missing. This matches the Couldn't find encrypted codec message that appears immediately before every UnlockingH264 failure.
If you disable the experimental steamrt mode, that may fix your problem for now. The 32 bit version of the file exists.
@TTimo I simply copied these two files from the ubuntu12_32 directory into ubuntu12_64, and the game started working.
The issue has been fixed in build 1783028805. Thank you for the incredibly quick fix!
PROTON_LOG=1x2 2026-07
Your system information
Steps for reproducing this issue:
At the moment, two affected games are known:
Minecraft Dungeons
Resident Evil: Requiem
These games do not launch at all. It appears that the initialization does not even reach Steam—they crash immediately when the launch process begins. No window appears, and Steam does not show any indication that the games were ever started.
Interestingly, this issue only affects some games. Other installed games in my Steam library launch and run without any problems.