Qwen3.8-27B-AWQ (INT4 W4A16)

4-bit AWQ quantization of Qwen/Qwen3.8-27B, calibrated in-house on 2×RTX 3090 (Ampere, sm_86) for single-user 256K-context serving under SGLang. Thinking, image, and video are all preserved and probe-verified.

Weights are ~18.7 GB, so the model fits two 24 GB cards at TP=2 with room for a deep KV pool (697K tokens measured at --max-running 1).

Validation

Measured on the shipped checkpoint (SGLang v0.5.17 + local patches, TP=2, RTX 3090 ×2):

Probe	Result
MMLU (30 samples)	0.93
HumanEval (25 samples)	0.96
Needle-in-haystack	1.0 — 6/6 found at server-verified 131,150 and 250,077 actual prompt tokens
Capabilities	5/5 — basic, tool-call, thinking, vision, video
AWQ scale integrity	0 of 800 scales/qweight tensors flagged (no zero/NaN/Inf scales)
LAB-Bench (56 questions)	0.16 — low-ish; see caveat below

Single-user decode throughput (M=1, 100 output tokens, depth server-verified via actual_input_tokens):

Context	tok/s	TPOT
1,024	70.6	14.2 ms
32,768	67.2	14.9 ms
261,916	48.4	20.7 ms

Decode holds 69% of its short-context rate at full depth. (We do not quote a cold-prefill TTFT at 262K: our measured deep request hit the prefix cache for 261,888 of 261,916 tokens, so that timing is not a prefill number. Decode throughput is unaffected — it attends over the whole KV either way.)

Quantization recipe

• Method: GPTQ, W4A16, group size 128, symmetric int4 (llmcompressor), then converted compressed-tensors → native AWQ (gemm) for AWQ_Marlin kernels.
• Calibration data (256 samples × 1024 tokens): 30% thinking traces (glaiveai/reasoning-v1-20m), 25% image instruction (LLaVA-Instruct-150K), 20% video instruction (lmms-lab/LLaVA-Video-178K), 15% math (NuminaMath-CoT), 10% chat (ultrachat_200k). Video samples are deliberate: calibrating a video-capable model without them drifts the temporal-attention weights.
• Kept in BF16 (not quantized): lm_head; the whole vision tower (model.visual.*, 167 modules); and the Gated DeltaNet gating scalars in_proj_a / in_proj_b (48 each). The rest of linear_attn (in_proj_qkv, in_proj_z, out_proj) is INT4 — this split is what SGLang's Qwen3_5GatedDeltaNet loader expects, and getting it wrong yields a model that emits !!!!!.

Serving (SGLang)

python -m sglang.launch_server \
  --model-path mattbucci/Qwen3.8-27B-AWQ \
  --tensor-parallel-size 2 --quantization awq_marlin \
  --context-length 262144 --max-running-requests 1 \
  --mem-fraction-static 0.85 --reasoning-parser qwen3 \
  --tool-call-parser qwen3_coder --max-mamba-cache-size 8

⚠ --max-running-requests caps your usable context

This model is 64 layers = 48 Gated DeltaNet + 16 full attention, and the DeltaNet recurrent state is replicated per concurrent slot. Combined with the untied 248,320-token vocab (embeddings + lm_head stay BF16), concurrency eats the KV pool fast. Measured on 2×24 GB:

--max-running-requests	KV pool (max_total_num_tokens)
1	697,368 (2.7× the 262,144 context)
8	32,516 — the 262,144 context claim is then a lie

If you raise concurrency, lower --context-length accordingly and read max_total_num_tokens back from /get_server_info rather than trusting the context flag.

Caveats

• No MTP. The base ships Multi-Token-Prediction layers; transformers does not model them, so they are absent here. MTP-based speculative decoding is not available on this checkpoint (SGLang's main loader skips mtp.* weights anyway, so nothing breaks).
• LAB-Bench 0.16 is on the low side. It sits inside the spread we observe across DeltaNet-family INT4 ships on the same 56-question probe (0.11–0.32), and every other instrument is top-tier, so we log it as a watch item rather than a defect — but if your workload is domain-heavy scientific protocol QA, benchmark before relying on it.
• Calibrated and validated on Ampere (sm_86) with AWQ_Marlin. Other architectures should work but are untested by us.

License

Apache-2.0, inherited from the base model. See LICENSE.