Mixed-precision repack of the pinned MTP head EigenLabs/Qwen3.8-27B-MTP-bf16 (@26a328e0) for the Layr-Labs qwen-3.8-mtp-challenge declared-head surface: fc.weight kept in original bf16 (per-tensor session measurements attribute the entire draft-acceptance cost of uniform 4-bit quantization to this one tensor), the seven other 2D projections at affine 4-bit group-64 (MLX 0.32.0 mx.quantize, the geometry of the current frontier head), 1D norms bf16. Every kernel this head dispatches is already exercised by promoted runs: bf16 GEMV by the pinned head, 4-bit group-64 by the frontier head and the backbone. The head only proposes — the pinned target verifies every emitted token.