BackendArtifacts struct
#include <Utilities/ShaderCompiler/Emit.h>
The stage artifacts only a platform-specific compiler can produce.
Direct3D 11 bytecode needs D3DCompile, which exists on Windows alone, and SPIR-V needs a glslang binary; neither is available on most machines that build this project. They are therefore kept OUT of the per-shader header and written to one aggregate per backend, exactly as the console targets already are - so a regeneration on a machine that cannot rebuild them leaves the committed ones alone instead of replacing them with nulls.
That mattered more than it looks: an absent SPIR-V module does not degrade, it makes VulkanShaderProgram skip every draw that uses the program.
Each string is a complete namespace body defining, for every variant, the stage arrays and a size constant beside each one. The sizes travel WITH the arrays rather than being baked into the per-shader table, so an aggregate that is a generation behind stays self-consistent - it describes the blobs it actually holds.