Upstream also ships an NVFP4 at ornith-ai/Ornith-1.5-35B-A3B-NVFP4, and it is good — we ran it in prod for a day. This is not a "first" and does not claim to beat it. It exists because someone using our 1.0 NVFP4 asked for the 1.5 equivalent, and because it is a different quantization, not a repackage:

	this build	upstream
framework	llm-compressor / compressed-tensors	NVIDIA ModelOpt 0.45
format	`nvfp4-pack-quantized`	`MIXED_PRECISION`
KV cache	not pinned (serve as you like)	FP8
DeltaNet (`linear_attn`)	entirely bf16	`out_proj` quantized
size	25.0 GB	23.4 GB

The DeltaNet choice is the reason for the 1.6 GB difference. Low-precision activations corrupt DeltaNet on this architecture — a standing finding across our Qwen3.5-family quants — so we keep the whole linear-attention path out of it. Whether that matters for your workload is an open question; upstream's build works. Pick on measurements, not vibes.

What is and isn't quantized

Component	Precision
30,720 expert projections (40 × 256 × 3)	NVFP4 W4A4
160 attention projections	NVFP4 W4A4
Router (`mlp.gate`), `shared_expert_gate`	bf16 — low-precision routing corrupts MoE
DeltaNet / GDN `linear_attn`	bf16
Vision tower	bf16
`lm_head`, `embed_tokens`	bf16
MTP head (785 `mtp.*` tensors)	bf16, shipped but not servable here — see below

Run

bash

vllm serve protoLabsAI/Ornith-1.5-35B-A3B-NVFP4 \
  --moe-backend marlin \
  --max-model-len 262144 --gpu-memory-utilization 0.62 --max-num-seqs 16 \
  --enable-auto-tool-choice --tool-call-parser qwen3_xml \
  --reasoning-parser qwen3 --generation-config auto --trust-remote-code

Three flags are load-bearing, all learned the hard way on sm120:

--moe-backend marlin is required. The trtllm auto-backend segfaults on the Sm120_SafeFP4 kernel even with a clean checkpoint. Don't remove it.
--generation-config auto is not boilerplate. The Ornith-1.5 family fails to terminate at low temperature — pin a low temp and it runs to your token cap emitting nothing useful.
Budget your tokens. It thinks adaptively; a short max_tokens returns empty content with finish_reason=length because the whole budget went to the reasoning channel. If you get blank replies, raise the budget before suspecting the weights.

MTP: the 785 mtp.* tensors are preserved, but marlin and MTP are mutually exclusive (the global MoE backend would also have to serve the unquantized bf16 draft MoE), so this lane runs without speculative decoding on vLLM/sm120 today. Shipped anyway — other backends may take them. MTP also hurts MoE in our measurements (routing overhead exceeds the speculation win), so this is not the loss it sounds like.

Verification

census        30,720 expert + 160 attn packed W4A4; ZERO packed in
              visual / linear_attn / mtp / lm_head / router; 785 mtp.* preserved
completion    PASS — coherent, correct, terminates
tool call     PASS — qwen3_xml, correct name + parsed arguments
vision        PASS — 5/5 shapes; wordmark OCR 3/3 exact
depth         needle-exact at 200,409 prompt tokens
coherence     clean detectors at 32K and 131K

Scorecard

Discriminating frontier battery, run against this build serving in production, judge-free except claw (independent cloud judge — a local model never grades itself):

axis            score   kind                detail
--------------  -----   ------------------  ------
claw            0.719   agentic/LLM-judged  10 tasks · robustness 1.00 · safety-clean
reasoning_hard  0.861   solver-verified     7/9 full-pass
function_call   0.889   schema-checked      48/54 · untagged 100% · in-proc 85% · ext 90%
livecodebench   0.205   exec-graded         hard-only, 30 problems, thinking-off

Judge reported 0 fallbacks, so the LLM-judged score is real and not a dead judge defaulting to 0.5.

On LiveCodeBench — read this before drawing a conclusion. 0.205 is partial credit (per-test pass rate); zero of the 30 hard problems passed every test. Code generation was not broken: individual problems scored up to 0.95 with 17/20 tests passing, no errors, no truncation.

LiveCodeBench is weak across the whole Ornith-1.5-35B family, not just this quant. We ran the upstream ModelOpt build through the identical harness and it scored 0.192 — this build scores 0.205, i.e. no quantization penalty, if anything a hair above. Independent users report the same coding weakness on the unquantized model (see the upstream repo discussions: failed one-shot HTML tasks, regressions versus Ornith-1.0, context exhaustion from over-deliberation). So: the number is real, it is a property of the model, and it is not caused by this quant. If code generation is your workload, this family is not the right pick at any precision.

reasoning_hard 0.861 and function_call 0.889 are strong, and function_call is slightly ahead of the upstream build's 0.870.

Provenance & license

Base: ornith-ai/Ornith-1.5-35B-A3B (MIT).
Quantized with llm-compressor (compressed-tensors NVFP4), 128 calibration samples @2048 from ultrachat_200k, moe_calibrate_all_experts=True. MIT. Built by protoLabs.studio.