NVFP4 runs on sub-sm_90 cards via the Marlin W4A16 weight-only fallback
since vLLM v0.24 (floor = capability 7.5, marlin_utils_fp4). Live-confirmed
on 2x RTX 3090 sm_86 2026-07-11: the shipped dual/nvfp4/mtp.yml boots at
262K + fp8 KV + MTP n=3 (accept 97%+), 69.7/85.5 decode TPS, and scores
8-pack think-off 110/150 — a statistical tie with the fp8 production
tier's 109. c3 hiding these slugs as "incompatible-hw" was factually wrong.
Semantic split — required_sm stays the NATIVE floor; new registry field
`fallback_sm` = the weight-only-fallback floor:
- kv-calc: in the band [fallback_sm, required_sm) the fit is PRICED
normally and annotated with `hw_fallback` {required_sm, card_sm, note}
instead of returning incompatible-hw (both --fit and --fit-all).
- c3: FitVerdict carries hw_fallback; fits-* + fallback -> "⚑" glyph,
VISIBLE by default. incompatible-hw hiding stays for true incompatibles.
- gates.py/compat.py: the hard SM floor becomes fallback_sm when present
(else required_sm, unchanged).
- Registry: fallback_sm=7.5 on the 4 NVFP4 slugs + status_note honesty
pass ("REFUSES on Ampere" -> fallback reality + measured numbers);
same corrections in the 4 compose headers.
- test-kv-calc-fit section (f) rewritten to the new contract.
On Ampere these slugs still carry the honest downside in the note: no
speed edge (~20% slower than the AutoRound tier for the same model) —
their sub-sm_90 value is models where NVFP4 is the only quant.
Guards green: kv-calc-fit, registry-disk, status-drift, switch/launch
parity, profiles-compat, pullgate, pull, registry-json/emit, diagnose,
launch-compat, default resolvers, kv-calc --calibration; c3 248 fast
tests + headless incompatible-hw hide tests.
Claude-Session: https://claude.ai/code/session_01EfF565T9eSLaqGzidyJ1Pm
Co-authored-by: noonghunna <10742901+noonghunna@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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