When having Hephaestus loaded while in VR it plumits your FPS down to about 20. Checking with Spark reveals that 50-60% of the performance goes towards openGL errors. I sadly dont know how to print these out so ill happily provide more information if someone tells me how to - checking the logs revealed nothing. Playing NON-VR does not have this issue - it only happens while playing VR.

Minecraft Version: 1.18.2
Fabric Version: 0.14.11
Fabric API Version: 0.67.0
Vivecraft Version: 0.0.13
Hephaestus Version: 3.5.2.155
(Tested with just these 3 mods loaded - Fabric API, Vivecraft, Hephaestus)

likely the same issues as #71
one of the dependencies of Hephaestus includes Satin
you can try disabling the eye stencil in VR Settings -> Stereo Rendering

Thank you - that fixes the issue!