DESCRIPTION

On a dual-GPU setup where Intel i915 is the primary compositor and NVIDIA (nvidia-open) drives a secondary HDMI output via PRIME, KWin floods the journal with `GL_INVALID_ENUM - Invalid <face>` and `GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT` errors on every repaint of the NVIDIA output. A third DisplayLink/evdi device is also present. The errors trigger reliably when moving the mouse cursor onto the NVIDIA-connected screen and repeat continuously with every mouse movement. The issue did not occur on previous versions of the stack and does not occur with Hyprland (wlroots) on the identical hardware and driver configuration.

STEPS TO REPRODUCE
1. Configure system with Intel i915 as primary GPU and NVIDIA (nvidia-open module) as PRIME secondary output via HDMI, with `nvidia-drm.modeset=1`
2. Start KWin Wayland session with Intel as render primary (`KWIN_DRM_DEVICES=/dev/dri/card2:/dev/dri/card1`)
3. Move mouse cursor onto the NVIDIA-connected display

OBSERVED RESULT

Journal flooded with repeated pairs of errors on every mouse movement event:
```
kwin_wayland: 0x500: GL_INVALID_ENUM error generated. Invalid <face>.
kwin_wayland: Invalid framebuffer status: "GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT"
```
Compositor render loop stalls intermittently, causing 20-30 second system-wide freezes.

EXPECTED RESULT

No GL errors. NVIDIA PRIME output renders normally as with previous versions of the stack and as with Hyprland on the same hardware.

SOFTWARE/OS VERSIONS

Operating System: Arch Linux (EndeavourOS)
KDE Plasma Version: (fill in from `plasmashell --version`)
KDE Frameworks Version: (fill in from Info Center)
Qt Version: (fill in from Info Center)

ADDITIONAL INFORMATION

- KWin version: 6.6.4
- Mesa: 26.0.6-arch1.1
- nvidia-open: 595.71.05
- Kernel: 7.0.3-arch1-2
- GPU 0 (card0): evdi/DisplayLink USB adapter (DVI-I-1)
- GPU 1 (card1): NVIDIA TU106M (10DE:1ED1) - HDMI output
- GPU 2 (card2): Intel CometLake i915 (8086:9BC4) - internal display, primary compositor
- `nvidia-drm.modeset=Y` confirmed
- Not resolved by: `KWIN_FORCE_SW_CURSOR=1`, `KWIN_DRM_NO_EXPLICIT_SYNC=1`, disabling all desktop effects, changing device enumeration order
- Issue not present with Hyprland (wlroots) on identical hardware/driver stack - suggests KWin-specific handling of PRIME FBO setup for secondary GPU output