Qwen3.8-27B-NVFP4-AllLinear

Model Overview

Qwen/Qwen3.8-27B with every large linear layer of the language model quantized to NVFP4, built for fast single-stream decoding with SGLang on Blackwell GPUs. Made by Triody.

Base model	Qwen/Qwen3.8-27B
Format	NVFP4 (W4A4, group size 16, FP8 scales), NVIDIA Model Optimizer 0.47.0
Size	17.0 GB (vs 21.9 GB for nvidia/Qwen3.8-27B-NVFP4)
Input / Output	Text / Text (language model only; no vision tower, no MTP head)
Engine	SGLang ≥ 0.5.19 (measured on 0.5.20)
Hardware	NVIDIA Blackwell with FP4 tensor cores. Measured on one RTX PRO 6000 (96 GB, SM120); smaller cards need their own memory settings
Release date	2026-09-30
License	Apache 2.0

Result. On one RTX PRO 6000, single stream, with SGLang's own recipe for that card: 302 / 252 / 196 tokens/s on GSM8K / HumanEval / ShareGPT, +12% to +19% over the same recipe with NVIDIA's checkpoint, at the same accuracy.

Quickstart

Install SGLang (0.5.19 or later) and start the server with SGLang's cookbook recipe for RTX PRO 6000, using this repository as the model:

pip install "sglang>=0.5.19"

python3 -m sglang.launch_server --trust-remote-code --model-path Triody/Qwen3.8-27B-NVFP4-AllLinear \
  --kv-cache-dtype fp8_e4m3 --mem-fraction-static 0.85 --attention-backend flashinfer --chunked-prefill-size 2048 \
  --reasoning-parser qwen3 --tool-call-parser qwen3_coder \
  --speculative-algorithm DFLASH --speculative-draft-model-path incoai/Qwen3.8-27B-DFlash2 --speculative-num-draft-tokens 8 \
  --mamba-radix-cache-strategy extra_buffer --mamba-ssm-dtype bfloat16 --mamba-full-memory-ratio 3.38

Then call it with any OpenAI-compatible client:

from openai import OpenAI

client = OpenAI(base_url="http://localhost:30000/v1", api_key="none")
resp = client.chat.completions.create(
    model="Triody/Qwen3.8-27B-NVFP4-AllLinear",
    messages=[{"role": "user", "content": "Write a Python function that checks whether a number is prime."}],
    temperature=1.0, top_p=0.95, max_tokens=2048,
)
print(resp.choices[0].message.content)

For best performance: sgl-project/sglang#41827 lets the draft model read int8 weights (about 6% faster decode, same outputs). It is under review; once it is in your SGLang, set SGLANG_SPEC_DRAFT_INT8_WEIGHTS=1 before starting the server. All speed numbers for this checkpoint below were measured with it.

Read This First

• It writes more on code. At the same sampling settings it produced 21% more output tokens than NVIDIA's checkpoint on 50 HumanEval prompts; its median greedy HumanEval reply is 713 tokens against 599. Faster per token, not per code task. On math and chat the lengths are equal.
• Made for SGLang. config.json is the nested configuration SGLang loads; without the vision weights it is not a complete model for transformers.
• Self-measured, on one kind of GPU, one run per configuration.

Post-Training Quantization

Part of the language model	This checkpoint	nvidia/Qwen3.8-27B-NVFP4
MLP (gate_proj, up_proj, down_proj), 64 layers	NVFP4	NVFP4
Output head (lm_head)	NVFP4	NVFP4
Attention projections, 16 layers	NVFP4	FP8
Gated DeltaNet projections, 48 layers	NVFP4	FP8
Gated DeltaNet conv1d, in_proj_a, in_proj_b	bf16	bf16
Token embeddings	bf16	bf16

NVFP4_DEFAULT_CFG with the output head enabled, max calibration. hf_quant_config.json lists the 145 modules left out.

Calibration dataset: 512 texts of up to 512 tokens: GSM8K train (160), MBPP train (112), ShareGPT conversations (240). None of them overlaps with the evaluation or speed prompts below.

Evaluation

Speed

One RTX PRO 6000 Blackwell Server Edition, SGLang 0.5.20, concurrency 1, 50 prompts per set, up to 2048 output tokens, temperature 1.0, top-p 0.95, top-k 20, reasoning effort xhigh. All rows in the same session on the same machine.

decode, median, tokens/s	GSM8K	HumanEval	ShareGPT	ms per speculative step
nvidia/Qwen3.8-27B-NVFP4, SGLang's recipe	270	213	164	19.8
nvidia/Qwen3.8-27B-NVFP4, int8 draft	286	226	177	18.7
This checkpoint, int8 draft	302	252	196	16.9

Tokens accepted per speculative step are the same in all three rows (3.6); the gain is the time of a step. Time to first token: 45 ms for short prompts, 78 ms at 958 input tokens, 513 ms at 7,370 (SGLang's recipe: 47–54 ms, 90 ms, 573 ms).

Accuracy

Greedy, thinking on, at most 4096 output tokens. GSM8K: first 400 test questions. HumanEval: 164 problems, tests executed. Strict counts a reply cut off by the token limit as wrong; lenient reads the answer from the reasoning text.

	GSM8K lenient	GSM8K strict	HumanEval lenient	HumanEval strict
nvidia/Qwen3.8-27B-NVFP4, SGLang's recipe	97.25%	95.25%	90.85%	86.59%
This checkpoint, int8 draft	97.25%	96.00%	91.46%	86.59%
Qwen/Qwen3.8-27B, bf16, no speculation (SGLang 0.5.17)	97.75%	96.75%	94.51%	92.07%

Item by item against NVIDIA's checkpoint, no difference is measurable under either score (sign tests, p ≥ 0.55). Both NVFP4 checkpoints lose about five points of strict HumanEval against bf16 (p = 0.012), because more replies hit the limit.

Model Limitations

• Evaluated on GSM8K and HumanEval only; other tasks, languages, tool calling and long contexts are untested.
• Inputs up to 8k tokens were measured.
• Speculative decoding does not produce the same text as decoding without it, even with greedy sampling.
• The draft model, incoai/Qwen3.8-27B-DFlash2, has its own terms.

Files

File	Size	sha256
model-00001-of-00002.safetensors	9,959,955,840	c496111cc6ebae4568d90ed571138ff98b9cd285f7927fd05fd0889e7077a303
model-00002-of-00002.safetensors	7,034,658,960	ced69b940d43690febdbf5861a0f8afaae5b4738c053fe5fb7c5a0e377824bde

config.causallm.json is the text-only configuration Model Optimizer exported, kept for reference.

About

Made by Triody. Questions, results on other hardware and bug reports are welcome in the Community tab of this repository.

License

Apache 2.0, the license of the base model, whose LICENSE file is included unchanged. These weights are a modification of Qwen/Qwen3.8-27B by Alibaba Cloud: the linear layers listed above were quantized to NVFP4.