Yeah, I see this too on Stable with both bleeding-edge and Proton 10.0, but it's fine on Preview/Main, so it looks like it's a Mesa issue. Mesa 24.3.4 is quite old, so if you switch to Preview (which is on 25.3.0) it should work fine.
Edit: I couldn't bisect this on RDNA4, so I switched to RX 7600 and landed on ece1ab3b as the first commit that no longer has this issue.
Thank you, I'll go ahead and close this issue then!
proton 10.0x1 2026-02proton experimentalx1 2026-02
Below (I think, I've never submitted an issue before) is how HD2 looks when running it in DX11 through DXVK and is how reflective surfaces should be appearing



Below is how it looks under vkd3d with AMD



Software information
The game is using the highest settings in all images at native resolution of 1280x800, however all settings demonstrate the same issue. For some reason this does not seem to happen on my other system using vkd3d with a nvidia gpu. I don't have another system with an AMD gpu to test it with unfortunately.
System information
Log files
steam-553850.log