I would say you should check if that is some sort of driver WSI issue or not.
Install this package.
https://archlinux.org/packages/extra/x86_64/vulkan-swrast/
After that launch the game with VK_DRIVER_FILES=/usr/share/vulkan/icd.d/lvp_icd.x86_64.json DXVK_HUD=full %command% and see if it behaves same still.
Hud part is just to confirm to see if it loads with lavapipe or not.
If I start the game the way you suggested, the game behaves exactly as before.
However, I have found two workarounds.
Start the game with "gamescope -W 2560 -H 1440 -r 360 -f %command%". After that, I can see the full interface of the game. However, Gamescope itself is not running in fullscreen. I then need to bring the window to fullscreen using KWin.
Start the game without any arguments. However, first create a KWin window rule that automatically brings windows with the title "Brotato" to fullscreen.
Both solutions work independently of each other.
Have the same issue on my system.
I was playing a bit yesterday after finding a "workaround", where i tab to taskmanager with the game up. click on application and remove fullscreen. Then it goes in a fullscreen over my taskbar. Go into the game, remove the fullscreen ingame, and go out down on the application again and press fullscreen. Then the game does proper fullscreen.
Replying to https://github.com/ValveSoftware/Proton/issues/1937#issuecomment-2282891273
Tested. It works here :) Thanks
from my testing this only happens on wayland on both kde/gnome
@kisak-valve can you pass it to the team ty
I tried this game on kde xorg and wayland with proton 9, experimental and bleeding edge. The behavior was the same across the board, it scaled fine. Tested with plasma 6.2.3 and xorg-xwayland 24.1.4, it would be interesting to know more about the current setup of those affected.
yeah I've just encountered the same issue, using proton 8 makes it look centered again, but it's not optimal to use proton 8
the other solution I've just found is to use proton-ge, I don't have the issue with it.
Also the wayland driver with proton-ge works fine and doesen't have the issue, you can activate it with this launch option: PROTON_ENABLE_WAYLAND=1 %command%
the proton versions that are affected by this regressions, and it's a regression since proton 8.0-4 doesen't have this issue, are proton 9.0-4 and newer.
another thing that I've just discovered is that proton 10 release candidate 2 and proton hotfix don't have this issue.
so the only two versions of proton that have this issue are proton 9.0-4 and proton experimental
proton 9.0-4x2 2025-06proton experimentalx1 2025-06proton hotfixx1 2025-06proton 8.0-4x1 2025-06PROTON_ENABLE_WAYLAND=1x1 2025-06DXVK_HUD=fullx1 2024-07PROTON_ENABLE_WAYLAND=1 %command%x1 2025-06gamescope -W 2560 -H 1440 -r 360 -f %command%x1 2024-07VK_DRIVER_FILES=/usr/share/vulkan/icd.d/lvp_icd.x86_64.json DXVK_HUD=full %command%x1 2024-07
Compatibility Report
System Information
I confirm:
steam-1942280.log
Symptoms
When I start Brotato, it initially launches in windowed mode and then automatically switches to fullscreen mode. This behavior is consistent with Windows 11 and seems normal. However, under Linux with KDE, the game only occupies a small portion of the screen once it switches to fullscreen, and the game interface is not fully displayed. This makes it impossible for me to navigate the menu to disable fullscreen mode in the game options.
I'm not sure if this issue is with Proton or KDE.
Reproduction