MC 1.17.1
Continuity 1.0.0

1. Install Continuity
2. Install NAPP and/or FJGlass texture packs
3. Install Lambdabettergrass and activate its resource pack (I know, this one is not an optifine TP, but it's needed for the example testing)

Expected result: all textures connect as intended.

Actual result: if only NAPP is installed and Continuity resource packs are loaded and placed below it, only glass and glass panes connect; if Continuity packs are disabled or placed above NAPP then no textures connect; if FJGlass is installed and placed above NAPP, glass and glass panes also do not connect; Lambdabettergrass works and connects as inteded in all cases.

There's another connected textures mod - ConnectedBlockTextures. With it installed instead of Continuity, all NAPP textures connect, except for glass and glass panes; if FJGlass is installed, then glass and glass panes also connect. Lambdabettergrass does not work, no grass textures are connected.

What am I doing wrong?

With only Continuity, everything works exactly like in Optifine, which means this is a compatibility issue with LambdaBetterGrass.

I don't think so. In fact, I was incorrect to say that Lambdabettergrass didn't connect with ConnectedBlockTextures mod, I just confused it with a texture from Continuity texture pack. So when I enabled Continuity resource pack and saw a new connected grass texture, I assumed it was from LBG, I was wrong.

But either way, I completely removed all other mods, left only Fabric API and Continuity, as well as disabled all texture packs other than NAPP. Here are the results:

Continuity + NAPP: having Continuity RP enabled, disabled and placed either above/below NAPP does not change the outcome - no textures connect, other than glass

Continuity + NAPP + FJGlass: no textures connect

ConnectedBlockTextures + NAPP: all textures connect, except for glas

ConnectedBlockTextures + NAPP + FJGlass: every texture connects

The broken glass connections in scenario 2 (Continuity + NAPP + FJGlass) is an incompatibility between the packs. When I tested this on Optifine, it gave me the exact same result. This will not be fixed, unless my testing with Optifine was incorrect. However, the stone connections are indeed broken, so I will fix them sometime soon.

The stone actually does not look correct in Optifine. This can be fixed by overriding the stone blockstate to disable texture rotation and reflection via a separate pack, which I have made and attached to this comment. However, since I am basing parity off Optifine and not Connected Block Textures, this issue will not be fixed by the mod itself either, as it will cause more problems than it will solve. To fix the issue completely and properly, it is best to contact the resource pack author and let them know about it.

NAPP_Stone_Fix.zip