Quick answer: Vulkan compute shader using ddx/ddy validation error? Derivatives are fragment-only; compute shaders need explicit gradient sampling.
Compute shader; uses ddx for mip selection; validation: 'derivative outside fragment'.
Use textureGrad
Explicit gradient sample; compute-shader compatible.
Or compute manually
Sample 4 nearby texels; compute derivatives manually.
Verify per stage
Each shader stage's capability set documented.
“Shader stages have different capabilities. Derivatives are fragment-only.”
If your compute shader needs mip selection, the textureGrad path is the answer.