Qwen3.8-27B-NVFP4a16-AWQ

Qwen3.8-27B — NVFP4 W4A16 (AWQ)

4-bit weight-only quantization of Qwen/Qwen3.8-27B, produced with llm-compressor using AWQ calibration and the NVFP4 weight format.

• Weights: NVFP4 (E2M1), group size 16, FP8-E4M3 group scales
• Activations: bf16 — weight-only, i.e. W4A16
• Size: 52 GB → 20.6 GB
• Vision + video towers, MTP head, and full multimodal support preserved

Benchmarks to follow.

Usage

vLLM

vllm serve cloudnathan5/Qwen3.8-27B-NVFP4a16-AWQ \
  --max-model-len 32768

With MTP speculative decoding (the MTP head is included, in bf16):

vllm serve cloudnathan5/Qwen3.8-27B-NVFP4a16-AWQ \
  --max-model-len 32768 \
  --speculative-config '{"method":"qwen3_5_mtp","num_speculative_tokens":1}'

Then query it like any OpenAI-compatible endpoint:

from openai import OpenAI

client = OpenAI(base_url="http://localhost:8000/v1", api_key="EMPTY")
resp = client.chat.completions.create(
    model="cloudnathan5/Qwen3.8-27B-NVFP4a16-AWQ",
    messages=[{"role": "user", "content": "Explain NVFP4 in two sentences."}],
)
print(resp.choices[0].message.content)

transformers

from transformers import AutoModelForImageTextToText, AutoTokenizer

model_id = "cloudnathan5/Qwen3.8-27B-NVFP4a16-AWQ"
model = AutoModelForImageTextToText.from_pretrained(
    model_id, dtype="bfloat16", device_map="cuda:0"
)
tok = AutoTokenizer.from_pretrained(model_id)

Scheme

NVFP4 is NVIDIA's 4-bit float format. Each group of 16 weights gets its own FP8-E4M3 scale, so the representation adapts to local dynamic range far more finely than INT4 with one FP16 scale per group of 128. Keeping activations at bf16 (A16) means this runs anywhere vLLM runs — Blackwell (sm_100/sm_120) simply gets the fastest kernels.

What AWQ does

AWQ (Activation-aware Weight Quantization) starts from the observation that weight channels are not equally important. A small fraction of channels carry disproportionately large activation magnitudes, and quantization error in those channels dominates the error in the layer's output. Quantizing every channel with the same granularity spends precision where it isn't needed and starves the channels that matter.

Rather than keep those channels in higher precision — which breaks the uniform layout kernels depend on — AWQ rescales them. For each group it searches a per-channel scale s, divides the incoming activation by s and multiplies the consuming weights by s. The product is mathematically unchanged, but the salient weight channels are scaled into a range the 4-bit grid represents more accurately. The scale is folded into the preceding normalization layer, so inference cost is identical to a plain quant.

Here the smoothing scales are searched over a 20-point grid per mapping (n_grid: 20), with duo_scaling enabled so the search accounts for both activation and weight magnitudes rather than activations alone.

Calibration data

General multi-turn instruction-following chat data, matching how the model is actually used. This is the same calibration set llm-compressor uses in its own AWQ examples and its awq_nvfp4 CI config.

Calibration is text-only, which is deliberate: the vision tower is excluded from quantization entirely, so it needs no calibration, and every layer that is quantized lives in the language model and is exercised by text. llm-compressor's own Qwen3-VL AWQ example calibrates the same way.

Note that AWQ scales are tuned to the calibration distribution. If your workload is heavily code, long-context, or non-English, recalibrating on in-domain samples will likely serve you better than this checkpoint does.

What is and isn't quantized

Qwen3.8-27B is a hybrid linear-attention multimodal model: 64 layers interleaving 48 gated-DeltaNet linear_attention layers with 16 full_attention layers in a 3:1 pattern, plus vision/video towers and an MTP head. The quantization is scoped to match.

Quantized — 400 Linear layers:

Left in bf16, deliberately:

• linear_attn.in_proj_a, linear_attn.in_proj_b — the SSM gating (alpha/beta) projections. Tiny, so quantizing them saves almost nothing, but they drive the recurrent state dynamics and 4-bit here degrades long-context behaviour badly.
• model.visual.* — vision tower. Small share of parameters, disproportionate quality cost.
• mtp.* — multi-token-prediction head, kept intact so speculative decoding works.
• lm_head, embed_tokens — standard practice; the 248K vocab makes these accuracy-critical.
• All norms, conv1d, A_log, dt_bias — not nn.Linear, excluded by construction.

in_proj_a / in_proj_b still participate in the AWQ balance groups even though they are not quantized. Every consumer of a smoothed activation has to receive the compensating scale, or the transform is no longer mathematically equivalent.

Recipe

default_stage:
  default_modifiers:
    AWQModifier:
      requires_calibration_data: true
      mappings:
      - smooth_layer: re:.*layers\.(3|7|11|15|19|23|27|31|35|39|43|47|51|55|59|63)\.input_layernorm$
        balance_layers: ['re:.*self_attn.q_proj$', 're:.*self_attn.k_proj$', 're:.*self_attn.v_proj$']
      - smooth_layer: re:.*layers\.(0|1|2|4|5|6|8|9|10|12|13|14|16|17|18|20|21|22|24|25|26|28|29|30|32|33|34|36|37|38|40|41|42|44|45|46|48|49|50|52|53|54|56|57|58|60|61|62)\.input_layernorm$
        balance_layers: ['re:.*linear_attn.in_proj_qkv$', 're:.*linear_attn.in_proj_z$', 're:.*linear_attn.in_proj_b$', 're:.*linear_attn.in_proj_a$']
      - smooth_layer: re:.*post_attention_layernorm$
        balance_layers: ['re:.*gate_proj$', 're:.*up_proj$']
      - smooth_layer: re:.*up_proj$
        balance_layers: ['re:.*down_proj$']
      duo_scaling: true
      n_grid: 20
    QuantizationModifier:
      targets: [Linear]
      ignore: [lm_head, 're:model\.visual\..*', 're:mtp\..*', 're:.*embed_tokens.*',
               're:.*\.linear_attn\.in_proj_a$', 're:.*\.linear_attn\.in_proj_b$',
               're:.*\.conv1d$', 're:.*norm.*']
      scheme: NVFP4A16

The two input_layernorm mappings are split by layer index because the architecture is hybrid: layers 3, 7, 11, … are full_attention and smooth into q/k/v_proj, while the rest are linear_attention and smooth into the DeltaNet input projections. These were generated by llm-compressor's dynamic hybrid-attention mapping builder.

Notes for anyone quantizing this architecture

Three issues came up that aren't obvious, recorded in case they save someone time.

1. inspect.signature on the DeltaNet forward. transformers 5.14 decorates Qwen3_5GatedDeltaNet.forward with an accelerate helper that omits functools.wraps, so inspect.signature(module.forward) reports (*args, **kwargs). llm-compressor's AWQ hook caches parent inputs via inspect.signature(...).bind(*args, **kwargs).arguments, which against that opaque signature collapses everything into one kwargs key. Replay then fails with TypeError: Qwen3_5GatedDeltaNet.forward() missing 1 required positional argument: 'hidden_states'. Restoring __wrapped__ on the wrapper fixes it, affecting introspection only.

2. Fused NVFP4 global scales. vLLM fuses the split linear-attention projections via packed_modules_mapping["in_proj_qkvz"] = ["in_proj_qkv", "in_proj_z"], and fused members must share one global scale. llm-compressor's FUSED_LAYER_NAMES covers (q_proj, k_proj, v_proj) and (gate_proj, up_proj) but not this Qwen3.5-specific pair, so they were assigned independent scales across all 48 linear-attention layers. Registering the pair before calibration fixes it.

3. The MTP head disappears twice. transformers' Qwen3_5ForConditionalGeneration does not define the mtp.* submodule, so its 15 tensors are silently dropped on load and never written out. Separately, llm-compressor resolves ignore patterns against modules present on the loaded model, so re:mtp\..* matched nothing and no MTP entry reached the saved quantization_config.ignore either — leaving vLLM to build NVFP4 linears for the head and fail on bf16 weights with ValueError: There is no module or parameter named 'fc.weight' in Qwen3_5MultiTokenPredictor. vLLM's existing escape hatches don't cover this: the mtp.fc workaround is gated on modelopt_fp4, and the dynamic "-:mtp" path is GPTQ-only. Both the tensors and the ignore entries have to be restored explicitly.

Environment

• llm-compressor 0.13.0, compressed-tensors 0.18.0
• torch 2.13.0+cu132, transformers 5.14.1
• Calibrated on an NVIDIA RTX PRO 6000 Blackwell (sm_120, 96 GB)

License

apache-2.0, inherited from Qwen/Qwen3.8-27B.