The Wan fp8 black frame was root-caused (scripts/fp8_layer_ablation.py,
measured on B200 with the production torch._scaled_mm path): per-row fp8
scales each activation row by row_amax/448, and the text prompt is padded to
512 tokens (~all padding for a short prompt), so condition_embedder's text
embedder divides a zero padding row by a zero scale, which infs and renders
every frame black. That embedder's bias makes every downstream row non-zero,
so the whole 30-block attn1/attn2/ffn stack is fp8-clean (fp8-except-
condition_embedder measured cosine 0.9998 vs bf16, 0 non-finite; fp8-
everywhere is 100% non-finite).
So the blanket fp8 deny was heavier than needed for Wan. Remove fp8 from the
Wan deny and keep only condition_embedder in bf16 via a new
_FP8_FAMILY_EXCLUDE_NAME_TOKENS; auto now restores fp8 (the Blackwell ladder
head) for Wan2.2-TI2V-5B and -T2V-A14B (shared DiT class and padded-text
conditioning). Full-generation check (512x320, 25 frames, 30 steps, cache on
and off): mixed-fp8 is non-black (mean luma 182.6 vs dense 181.2), more
accurate than int8 (LPIPS 0.129 vs 0.180 no-cache, 0.224 vs 0.251 with
FBCache), faster (49.9 vs 64.6 ms/step; int8 was a per-step regression vs the
59.8 ms/step dense), at the same memory (19.34 GB, both -20% vs dense).
HunyuanVideo-1.5 keeps the fp8 deny: its MMDiT masks the padding text tokens
to zero inside every block, so the per-block context stream (add_*_proj /
to_add_out / ff_context) regenerates zero rows layer after layer (fp8 on only
the main blocks is 100% non-finite) so no small exclude set exists and int8
stays. mxfp8 / nvfp4 remain denied for Wan (same per-row scaled_mm family, not
separately validated).
exclude_tokens_for_scheme now takes an optional family, threaded through the
runtime quantiser and the offline prequant builder + validator so offline ==
runtime (a stale Wan fp8 checkpoint baked without the exclude is rejected and
re-quantised rather than loaded). Adds scripts/fp8_layer_ablation.py (the
per-layer ablation probe) and a mean-luma black-frame metric plus mixed-fp8
vs int8 configs to the video bench.
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