⚡ Overview
Qwen3.8 27B Kearuga is a custom tiered sensitivity hybrid-quantized checkpoint of Qwen/Qwen3.8-27B, specifically engineered for high-throughput and interactive speculative-decoding serving on a single NVIDIA DGX Spark (GB10 / Grace-Blackwell, 128 GB Unified Memory).
By pairing GPTQ with Four-Over-Six (4o6) group scales, NVFP4 AWQ, FP8 E4M3, and protected BF16, Kearuga:
- Cuts weight footprint by 52% (from 51.8 GiB unquantized base down to 24.85 GB across 3 shards + MTP draft head).
- Preserves output fidelity to within a 0.0165 mean KL divergence against the unquantized BF16 base model, maintaining 40/40 (100%) top-1 argmax agreement.
- Unlocks fast speculative serving with SGLang: with the Kearuga DFlash 2 drafter v1.0 (K=12, NVFP4, 64K draft head) the serving repo's
bench/scale.py probe measures C1 44.7 · C2 78–94 · C4 131 tok/s aggregate (T=0, thinking off, 512 forced tokens, aggregate incl. TTFT 0.23–0.34 s; identical with the GPU clock lock on or off), and the paired 50-prompt battery puts it +14.5 % C1 / +10.8 % C4 over the stock z-lab drafter (C1 net-decode medians: code 57.6, math 62.2, tool calls 114.6, prose 21.6 tok/s). Serving stack: GitHub v0.6.6; drafter release v1.0. Without speculative decoding the same target measures 10.30 tok/s C1 / 39.56 tok/s C4 on that battery (serving stack v0.6.7) — a 3.46× / 2.75× gain from the drafter.
- Runs on official SGLang Docker images — the Kearuga-drafter profile adds a 5-file read-only Python overlay (hash-verified at launch, no Docker build); the stock profile needs no overlay.
📊 Kearuga vs. Base Qwen3.8-27B (BF16)
The table below presents fidelity and quality metrics measured on an isolated NVIDIA DGX Spark (GB10 / SM121, 128 GB Unified Memory) running SGLang (KV cache in BF16, thinking disabled, temperature 0). They do not depend on the drafter — the target verifies every drafted token:
Table with columns: Metric, Base Model: Qwen/Qwen3.8-27B (Native BF16), Qwen3.8 27B Kearuga (Hybrid Quantized), Delta / Operational Significance| Metric | Base Model: Qwen/Qwen3.8-27B (Native BF16) | Qwen3.8 27B Kearuga (Hybrid Quantized) | Delta / Operational Significance |
|---|
| Weight Footprint | 51.8 GiB | 24.85 GB | −52.0% (leaves ≈ 90 GB of the 121 GB unified memory for KV cache, drafter and runtime) |
| Fidelity-40 Mean KL Divergence | 0.0000 | 0.0165 | −50.6% KL reduction vs legacy NVFP4 baseline (0.0334) |
| Fidelity-40 Mean Jensen-Shannon (JS) | 0.0000 | 0.0034 |
Kearuga drafter (K=12, NVFP4, 64K draft head). In a paired bake-off on the same image, target, flags and clock — 50-prompt battery (10 prompts × 5 domains) × 2 runs, temperature 0, thinking off; "net decode tok/s" = (completion tokens − 1)/(last − first token time) per request, TTFT excluded — the Kearuga DFlash 2 drafter with the draft-head overlay reached 35.33 tok/s C1 (+14.5 %) and 108.90 tok/s C4 (+10.8 %) aggregate vs the stock drafter (30.85 / 98.31), better on all 10 domain cells. C1 net-decode medians: code 46.27 → 57.62, math 51.21 → 62.18, tool calls 80.82 → 114.63, prose 19.45 → 21.64, instruction-following 19.87 → 21.80. The target still verifies every drafted token, so output is unchanged (Fidelity-40 KL 0.0165, top-1 40/40). Full tables on the drafter model card.
🛡️ Tiered Sensitivity Quantization Architecture
Uniform quantization (applying INT4 or NVFP4 indiscriminately across all layers) degrades attention sink states, vocabulary distribution tails, and speculative draft features.
Inspired by empirical mixed-precision sensitivity research (EXL3 tiered sensitivity), Kearuga partitions the model's 2,009 tensors into four distinct sensitivity tiers:
Table with columns: Tier, Module Scope, Precision, Count, Architectural Purpose| Tier | Module Scope | Precision | Count | Architectural Purpose |
|---|
| Tier 1 (Protect) | embed_tokens, lm_head, all RMSNorms, visual tower (27 blocks / 333 weights), and MTP head tensors | Native BF16 | 348 | Protects vocabulary tail, multi-modal reasoning, and MTP draft survival |
| Tier 2 (Medium) | Self-Attention (q_proj, k_proj, v_proj, o_proj), GDN Recurrence () (Layers 2–61), and Boundary MLPs (Layers 0, 1, 62, 63) |
1. Four-Over-Six (4o6) Group Scaling
Standard GPTQ assigns a single static exponent code per group block (amax → code 6). Kearuga's 4o6 algorithm evaluates dynamic range block-by-block and selects the optimal scale:
- Code 6: Standard headroom for high-variance weights.
- Code 4: Higher numerical precision for weights with tight local distributions.
In our calibration, 44.7% of blocks selected Code 4, yielding a 16% reduction in Hessian-weighted MSE (0.529 → 0.445) and cutting held-out KL divergence by 21.7% without increasing tensor bit-width or memory footprint.
2. Fused-Shared Global Scale Contract
SGLang's high-performance Blackwell kernels fuse gate_proj and up_proj into a single GEMM operation, indexing a unified weight_scale_2.max(). Quantizing gate and up independently introduces scale divergence that breaks dequantization. Kearuga enforces an exact fused-shared global scale across every layer:
scale_shared = max(amax(gate), amax(up))
This ensures bit-exact kernel compatibility and eliminates dequantization distortion.
🚀 Serving & Deployment Guide
Kearuga is served directly via official SGLang Docker container images (sha256:616a3e97… or later) with native DFlash 2 speculative acceleration. The recommended drafter is 0xWhiteMage/Qwen3.8-27B-Kearuga-DFlash2 v1.0 (Kearuga-distilled, NVFP4, K=12):
docker run --gpus all \ --shm-size 32g \ --ulimit memlock=-1:-1 \ --cap-add IPC_LOCK \ -p 8888:8888 \ -v ~/.cache/huggingface:/root/.cache/huggingface \ lmsysorg/sglang@sha256:616a3e97f45191af975896cfa644279096cb31bd408a071c2e99ca7209c3cafe \ python3 -m sglang.launch_server \ --model-path 0xWhiteMage/Qwen3.8-27B-Kearuga \ --served-model-name "Qwen3.8 27B Kearuga" \ --speculative-algorithm DFLASH \ --speculative-draft-model-path 0xWhiteMage/Qwen3.8-27B-Kearuga-DFlash2 \ --speculative-draft-model-quantization modelopt_fp4 \ --speculative-num-draft-tokens 12 \ --speculative-draft-window-size 2048 \ --kv-cache-dtype bf16 \ --mem-fraction-static 0.85 \ --max-total-tokens 1048576 \ --context-length 262144 \ --max-running-requests 4 \ --host 0.0.0.0 \ --port 8888
The 64K draft-head overlay adds a further ≈ 6 % on top of plain SGLang (35.33 vs 33.30 tok/s C1 aggregate) — it is documented on the drafter card and is handled automatically by the serving repo's launcher ./start-dflash2.sh.
Alternative: stock drafter (K=10) — the serving repo's DRAFTER_PROFILE=stock (the original v0.5.0 recipe) with z-lab/Qwen3.8-27B-DFlash2: use the command above with --speculative-draft-model-path z-lab/Qwen3.8-27B-DFlash2, no --speculative-draft-model-quantization, and --speculative-num-draft-tokens 10.
Key Serving Parameters
Table with columns: Parameter, Recommended Setting, Rationale| Parameter | Recommended Setting | Rationale |
|---|
--speculative-num-draft-tokens | 12 with the Kearuga drafter | K=8 loses code/math acceptance 7–12 %; K=14/16 give nothing at C1 and lose 2–6 % at C4. 10 with the stock drafter. |
--kv-cache-dtype | bf16 | Preserves full logit fidelity (KL: 0.0170 → 0.0165, exact continuations: 20/40 vs 19/40) with negligible compute cost. |
--context-length | 262144 |
⏱️ Saturated Priority Scheduling
In multi-agent production pipelines, background batch traffic can cause interactive request freezes. Kearuga's serving stack enables native priority preemption:
{ "model": "Qwen3.8 27B Kearuga", "priority": 100, "messages": [ {"role": "user", "content": "Analyze this mission-critical trace..."} ]}
Table with columns: Server Load State, Default Priority TTFT, Interactive Priority ("priority": 100), Latency Reduction| Server Load State | Default Priority TTFT | Interactive Priority ("priority": 100) | Latency Reduction |
|---|
| DFlash 2 (All 4 Seats Saturated) | ~43.15 s | ~2.63 s | 93.9% faster |
🧪 Comprehensive Verification & Quality Gates
Every promoted build of Kearuga must satisfy a strict 15-gate fail-closed verification harness prior to promotion:
- Static Tensor Census: 2,009 tensors intact across 3 shards; exactly 15 MTP tensors and 333 visual tensors confirmed byte-identical to base BF16.
- Serving Contract Audit: Strict verification that fused
gate_proj + up_proj weight_scale_2 are identical across all layers.
- Semantic Canaries: 100% pass on exact arithmetic (
19 × 23 = 437) and logic traps (9.9 vs 9.11).
- Long-Context NIAH: 3/3 Needle-In-A-Haystack retrieval at 64K depth (25%, 50%, 90%).
- Quality-200 Benchmark: 157/180 verified score on GSM8K, HumanEval, IFEval, and agentic coding (155/180 served with the Kearuga drafter — near-tie band 154–159).
- Multi-Boot Stability: 3 consecutive clean cold boots with zero loader warnings or device-side asserts.
📦 Model Files & Shards
Table with columns: File Name, File Size, Description & Scope| File Name | File Size | Description & Scope |
|---|
config.json | 8.2 KB | Architectural model hyperparameters & quantization configuration |
generation_config.json | 240 B | Sampling defaults, EOS tokens, and generation bounds |
hf_quant_config.json | 14.1 KB | Detailed ModelOpt mixed-precision tier mappings & scale rules |
model.safetensors.index.json | 185 KB |
📜 Citation
If you use Kearuga or build upon its tiered sensitivity architecture in your work, please cite:
@misc{kearuga-2026, title={Kearuga: Hybrid GPTQ-4o6 + FP8 Quantization of Qwen3.8-27B for Speculative-Decoding Serve on NVIDIA DGX Spark}, author={0xWhiteMage}, year={2026}, publisher={Hugging Face}, url={https://huggingface.co/0xWhiteMage/Qwen3.8-27B-Kearuga}}
📄 License
This checkpoint is released under the Apache 2.0 License. The underlying base model Qwen/Qwen3.8-27B is subject to its original license terms from Alibaba Cloud.