The runner-backend heuristic is fundamentally the wrong signal: it reads AUTO in the EAGLE draft
worker (verified live), and an fp4-capable runner does not imply an fp4 MTP — DeepSeek-V3-0324-FP4
runs --moe-runner-backend flashinfer_trtllm yet ships a bf16 MTP (CI test_deepseek_v3_fp4_mtp_small).
is_layer_excluded is also disqualified: R1/V3 leave the MTP unquantized-but-absent-from-`ignore`.
Complete fix (opus-designed): inspect the checkpoint's model.safetensors.index.json and keep fp4 iff
the NextN/MTP experts (model.layers.{num_hidden_layers}.mlp.experts.*weight_scale*) ship fp4 scales —
the ground truth. GLM-5.2-NVFP4 has them (verified: 1536 layer-78 scale keys) -> keep; R1/V3 don't
-> drop. Unreadable index -> drop (PR #7376 default, bf16 MTP fallback, never crashes). Removed the
backend heuristic + debug log + unused get_moe_runner_backend import. Resolves both the 6144-vs-3072
draft crash AND the flood of "model.decoder.mlp.experts.*_scale not found in params_dict" (same root
cause: dropping fp4 left the unquant MTP with no scale params for the checkpoint's fp4 scales).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
leavelet
1d96197d3d