PRIMARY_HIT, BOUNCE_INDEX and RAY_FOOTPRINT_X/Y were added to SceneShaderRaytracing's actions.renames but never declared in ShaderTypes. Those are two different mechanisms: renames translate a built-in during CODE GENERATION, while ShaderLanguage validates identifiers against this table long before codegen runs. Any shader referencing them failed to parse -- SHADER ERROR: Unknown identifier in expression: 'RAY_FOOTPRINT_X' WARNING: RT: Failed to preprocess custom shader; falling back to default material -- so dc_level and dc_terrain both silently dropped to the default material and lost all their texturing under path tracing. Declared on the shared spatial fragment table, which means the rasterizer parses them too. It has no renames for them, so uses must stay inside #ifdef RT -- which both consumers do, and where the rasterizer never sees them at all. Note for future changes of this kind: a headless --import cannot catch this. It compiles the RASTER variant, where #ifdef RT strips the block, so the error only appears when the RT variant is built at runtime. Verifying shader built-ins needs an actual path-traced frame. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>