Replace per-eigenvector spectral supervision on symmetry-forced multiplets by a projector-trace target determined from the operator family's commutant. Use individual eigenvalue or eigenvector targets only outside detected forced blocks, avoiding arbitrary basis choices and exploding gradients at protected crossings.
Build a Bloch-conditioned neural model whose periodic-factor representation transforms covariantly when the supplied Bloch wavenumber is shifted by a reciprocal lattice vector. Either canonicalize q to the first Brillouin zone or augment training with mathematically paired examples whose outputs differ by the exact phase gauge. This prevents the network from learning inconsistent predictions for physically identical Bloch modes.