Smooth Lighting breaks on Xycraft connected textures such as the Immortal stones and trims, as shown in the screenshot below. Running on Minecraft 1.20.1, Forge version 47.2.0, Embeddium 0.2.9, and XyCraft Base, Override, and World .6.22.

With Oculus version 1.6.9 and Complementary shaders the issue is much more pronounced:

This does not occur on the upstream, 1.7.1a version of Rubidium, with/without Oculus, so I think it might be either a XyCraft issue that Rubidium is working around or an issue with embeddium solely.

Can you confirm that https://nightly.link/embeddedt/embeddium/workflows/build-snapshot/20.1%2Fforge/Embeddium.zip fixes the issue?

The file you linked fixes the issue but causes a new one:

With the shimmering in just about every XyCraft block you see on-screen.

Disable "Compact Vertex Format" in Embeddium's video settings; this is probably caused by XyCraft not offsetting the layers of its blocks enough.

EDIT: Hmm, no, seems to happen even with it off.

That option seems to be disabled automatically by Oculus anyway, but I confirmed that it happens with/without Oculus installed, with/without Compact Vertex Format

It seems to be a strange interaction between XyCraft's block model and Sodium's fix for MC-138211. For now, you can work around it by enabling Forge's experimental lighting pipeline in config/forge-client.toml, as this bypasses Sodium's fix.

I've identified a way to avoid the problem in Embeddium itself, which will be included in the next release.

I can confirm the workaround works, thank you for the quick response!

The fix has been released in Embeddium 0.2.10.