Hello @Charge03, this is not a Proton bug. Windows based games can bundle SDL and that bundled library built for Windows isn't expected to talk to the window systems of a different OS.
You've set the SDL_VIDEODRIVER environment variable somewhere in your system and that's explicitly telling the SDL library to only try something it doesn't have instead of walking through a default set of video backends until if finds a usable choice.
proton experimentalx1 2026-03SDL_VIDEODRIVERx1 2026-03SDL_VIDEODRIVER=windowsx1 2026-03SDL_VIDEODRIVER=windows %command%x1 2026-03tier0.dllx1 2026-030x80000003x1 2026-03
Compatibility Report
System Information
I confirm:
Symptoms
Deadlock fails to launch under Proton when using Hyprland (Wayland compositor).
When clicking "Play", Steam briefly shows "Running" and then returns to "Play" with no window appearing.
Proton logs show a crash very early during startup with:
STATUS_BREAKPOINT (0x80000003)
occurring inside tier0.dll.
No compatdata prefix or config files are created, indicating the crash happens before full initialization.
Reproduction
Workaround
The game launches successfully when forcing:
SDL_VIDEODRIVER=windows %command%
Additional Notes
vulkaninfosucceeds)Attached:
steam-1422450.log