Verification pass on the blind-authored claims (vLLM source + safetensors
indexes, 2026-07-06):
- vLLM modelopt SUPPORTS fp8 KV with NVFP4/mixed-precision weights by
design: KV_CACHE_QUANT_ALGOS = ['FP8','NVFP4'] + ModelOptKVCacheMethod;
our --quantization modelopt + --kv-cache-dtype fp8 pairing is canonical.
- BOTH nvidia checkpoints DECLARE kv_cache_quant_algo=FP8 in
hf_quant_config.json, but NEITHER ships k_scale/v_scale tensors (indexes
enumerate only linear input_scale/weight_scale/weight_scale_2). The
shipped composes claimed '27B bakes KV scales' and 'MoE has none, unlike
the 27B' — both wrong; the two checkpoints are IDENTICAL on KV: declared
FP8, no scales, scale=1.0 at runtime (calculate_kv_scales disabled on
Qwen3-Next hybrid) — exactly the #594-quality-tied regime.
Text-only; no flag changes (the composes were already serving the right
config — the rationale strings were wrong).
Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01EfF565T9eSLaqGzidyJ1Pm
