⚡ 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 ultra-fast speculative serving with SGLang: Delivers 57 tok/s (C1, TTFT 264ms), 51 tok/s (C2 agg), and 94 tok/s (C4 agg, TTFT 480ms) interactive decode with stock DFlash 2.
- Runs on official SGLang Docker images with zero kernel overlays or custom compilation required.
📊 Kearuga vs. Base Qwen3.8-27B (BF16)
The table below presents verified empirical metrics measured on an isolated NVIDIA DGX Spark (GB10 / SM121, 128 GB Unified Memory) running SGLang with DFlash 2 (K=10 draft block, KV cache in BF16, thinking disabled, temperature 0):
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% (fits with 64+ GiB headroom for KV cache) |
| 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 | Virtually identical distribution profile |
🛡️ 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 speculative drafter uses the stock drafter z-lab/Qwen3.8-27B-DFlash2:
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 z-lab/Qwen3.8-27B-DFlash2 \
--speculative-num-draft-tokens 10 \
--speculative-draft-window-size 2048 \
--kv-cache-dtype bf16 \
--mem-fraction-static 0.78 \
--context-length 262144 \
--max-running-requests 4 \
--host 0.0.0.0 \
--port 8888
Key Serving Parameters
Table with columns: Parameter, Recommended Setting, Rationale| Parameter | Recommended Setting | Rationale |
|---|
--speculative-num-draft-tokens | 10 | Validated in empirical sweeps: K=8 drops code/math acceptance by 7–12%; K=12/16 degrade prose/IFEval and C4 throughput. K=10 represents the Pareto-optimal draft length. |
--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 | Full native context supported without YaRN interpolation. |
⏱️ 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.
- 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.