Your system information

• Steam version: 1.0.0.86 (native Arch package)
• Distribution: CachyOS
• Desktop: MangoWM 0.15.2
• Session: Wayland
• GPU:
  • Intel Iris Xe (default GPU)
  • NVIDIA RTX 3060 Laptop
• NVIDIA Driver: 610.43.03
• Opted into Steam Beta: No

Description

When Steam is launched normally from the desktop launcher, opening either:

• Steam → Settings
• Game → Properties

causes the Steam UI to immediately restart.

Steam itself survives, but the client UI restarts.

Launching Steam from a terminal changes the behavior somewhat, but the issue still occurs after extensive testing.

Additionally, Steam achievement notifications under MangoWM:

• briefly force fullscreen games into a smaller window,
• cause visible screen flicker,
• sometimes remain permanently stuck on-screen,
• can leave games such as The Binding of Isaac: Repentance+ in an incorrect fullscreen state.

These two issues appear related.

Steps to reproduce

1. Log into MangoWM Wayland.
2. Launch Steam from the desktop launcher.
3. Open Steam Settings.
4. Steam UI immediately restarts.

What I tested

None of the following changed the behavior:

• disabling CEF GPU
• disabling CEF compositing
• forcing X11
• forcing NVIDIA via prime-run
• removing QT_QPA_PLATFORM
• removing QT_QPA_PLATFORMTHEME
• removing QT_QPA_PLATFORMTHEME_QT6
• removing QSG_USE_SIMPLE_ANIMATION_DRIVER
• removing Steam-specific Mango window rules
• custom launcher wrapper

Relevant log observations

The logs consistently show:

• steamwebhelper restart
• Chromium GPU process exits unexpectedly
• repeated X11/XWayland errors
• SharedImageManager mailbox errors
• steamloopback.host tab killed

Steam logs are attached.

steam-logs.tar.gz