Validated against QE

All 12 paired CPU fp64 cases pass against Quantum ESPRESSO 7.6. The matrix includes nonzero forces, anisotropic stress, NLCC, PBEsol, and magnetism.

Explicit acceleration tiers

CUDA and HIP are experimental fp64 backends; Metal is an opt-in fp32 research tier. CPU fp64 remains the only external-validation reference, and requested GPU runs may not silently fall back to CPU.

Fail-closed execution

Unsupported PAW/ultrasoft, hybrid, noncollinear, SOC, and phonon requests are rejected instead of producing unvalidated results. MPI remains available for development, but is not part of the external validation claim.