If games on your Steam Deck suddenly start freezing when you enter fullscreen in Desktop Mode, but continue running normally when windowed, the problem may not be your game, Proton version, or GPU settings. There is currently a known SteamOS 3.8 Beta issue affecting fullscreen applications in Desktop Mode (writing this up as - who knows if it happens again in the future?). In my case, it affected multiple completely different games, across both Steam and Lutris. Switching the SteamOS update channel back from Beta to Stable fixed the problem immediately.

The symptoms

The problem can be particularly confusing because the game isn't actually crashing, or raising any issues.
  • The game launches normally.
  • Fullscreen mode appears to work initially.
  • Once the game has focus, the displayed image becomes stuck on one frame.
  • Audio continues playing.
  • The game continues running in the background.
  • Windowed mode works normally.
  • Switching focus away from the game can make the animation visible again.
  • Opening KDE's Overview can make the game render correctly.
  • Moving the mouse enough to trigger KDE's "shake cursor" effect can also force the game to update.
  • The problem can affect multiple games and multiple Proton versions.
This last part is important: if several unrelated games are doing exactly the same thing, don't immediately start reinstalling games or changing Proton versions.

What caused the problem?

The problem appears to be related to the SteamOS 3.8 Beta graphics/compositor stack in Desktop Mode, particularly fullscreen presentation under Wayland. As of SteamOS 3.8 Wayland officially replaced X11, and fullscreen applications can therefore involve several layers including KDE Plasma/KWin, Wayland, XWayland, the graphics driver and the display compositor. Reports from other SteamOS users around August 2026 describe the same general problem: fullscreen games and videos in Desktop Mode stop updating while audio continues, while windowed applications continue working normally. Multiple users reported that returning to the Stable SteamOS channel resolved it.

The fix: switch SteamOS from Beta back to Stable

If your Steam Deck is currently using the SteamOS Beta update channel, switch it back to Stable.
  1. Switch to Gaming Mode (Or from Desktop Mode, open Big Picture).
  2. Open Settings.
  3. Go to System.
  4. Find the System Update Channel setting.
  5. Change the channel from Beta to Stable.
  6. Allow SteamOS to download and install the appropriate update.
  7. Restart the Steam Deck if prompted.
  8. Return to Desktop Mode and test the game again.
In my testing, returning to the Stable channel immediately restored normal fullscreen rendering.

It can look like a Proton problem

This issue is especially easy to misdiagnose if it first happens with a Windows game running through Proton. I tested multiple Proton versions without solving the problem. The same behaviour also occurred when launching games through Lutris, which helped rule out Steam and Proton as the common cause. For example, the problem occurred with completely different games, and the behaviour remained the same regardless of the Proton version being used. Changing to WineD3D instead of DXVK also did not solve the problem. That is a strong indication that the problem is occurring below the game and compatibility layer, rather than inside the game itself.

Why does the game still appear to run?

One of the strangest characteristics of this problem is that the game doesn't necessarily stop running. For example, if you move the mouse rapidly enough to trigger KDE's cursor animation, the game may suddenly display the latest frame. Opening KDE's Overview can have the same effect. This makes the problem look like a frozen game, but it can actually be a display/compositor presentation problem: the game is producing frames, but the fullscreen surface isn't being presented to the display correctly. That also explains why switching away from the game can make it appear to "unfreeze" while the game itself continues running.

What if changing the monitor or resolution doesn't help?

I initially suspected the external monitor because the problem occurred on a Steam Deck connected to an external display. However, changing refresh rates and resolutions did not solve the problem. The issue also occurred with a completely different external monitor running at 1920×1080 and 60 Hz. Disconnecting the external monitor and using the Deck's built-in display did make fullscreen games work normally, which initially pointed toward the display configuration. However, resetting KDE's stored KWin output configuration did not resolve the problem. The important distinction turned out to be the SteamOS update channel, not the particular monitor, resolution or refresh rate.

How to recognize the SteamOS fullscreen bug

You're probably dealing with this SteamOS issue if most of these statements are true:
  • You're using SteamOS 3.8.x.
  • The problem occurs in Desktop Mode.
  • You're using the Wayland desktop session. Maybe not limited to Wayland?
  • Multiple games are affected.
  • Fullscreen or borderless fullscreen is affected.
  • Windowed mode works.
  • Audio continues while the displayed frame is stuck.
  • Games continue running when focus is removed.
  • Changing Proton versions doesn't help.
  • Videos or other fullscreen applications may show similar behaviour.
  • Your SteamOS update channel is set to Beta.

Bottom line

If your Steam Deck suddenly started freezing games in fullscreen while Desktop Mode continues working normally, check your SteamOS update channel before changing anything else. Switching from the SteamOS Beta channel back to Stable resolved the fullscreen rendering problem in our case. This is particularly worth checking if the problem appeared suddenly after a SteamOS update and affects multiple games, Proton versions or even non-game fullscreen applications. Though my case started sort of randomly, and I'm pretty sure there were no updates in between, but here we are.