Firefox window appears black / overlay dropped with "WayVR overlay without matching window entry"

[maeddesg]

Description

When launching Firefox (v148) from the WayVR app launcher, the window
frame appears but renders completely black. No content is visible.

The debug log shows:
"Mozilla Firefox": WayVR overlay without matching window entry
followed by: Dropping overlay Mozilla Firefox

This suggests WayVR cannot match the Firefox overlay to its window entry,
causing the overlay to be dropped immediately after Firefox starts.

System Info

Linux Distribution: CachyOS (Arch-based)

Desktop Environment: KDE Plasma 6.6.3

Kernel version: 6.19.9-1-cachyos

VR Runtime:

• Monado/WiVRn (26.2.3)
• SteamVR/ALVR

GPU models and driver versions:
deviceName = AMD Radeon RX 9070 XT (RADV GFX1201)
driverName = radv
driverInfo = Mesa 26.0.3-arch2.2
apiVersion = 1.4.335

Overlay Logs

(attach wayvr-debug.log)

wayvr-debug.log

[galister]

Install cage via pacman and then launch Firefox with the Compatibility Mode checkbox checked (instead of Native Mode)

Also make sure that Firefox is not also running on your desktop screen. If this is the case, the Firefox you're launching in WayVR will talk to that other Firefox instance and instead create a new tab in the already running Firefox. To make this work, you'd have to launch Firefox using separate profiles firefox -P <your_profile>.