What makes this quant verifiable
The quantizer (quantize_fp8_like.py)
uses the official FP8 checkpoint as a layout template. It quantizes exactly the tensors that are FP8 there,
copies the rest in the template's dtype, and asserts that names, dtypes and shapes match. Its scale arithmetic
matches Qwen's: an FP32 block scale amax × (1/448) is used for quantization and then stored as BF16.
As a result, comparing this checkpoint with the official one isolates the abliteration edit exactly:
Table with columns: Tensors, vs. official Qwen3.8-27B-FP8| Tensors | vs. official Qwen3.8-27B-FP8 |
|---|
| Layers 0-16 and 52-63, MTP head, vision tower (333), embedding, LM head | byte-identical |
mlp.down_proj (35), linear_attn.out_proj (26), self_attn.o_proj (9) in layers 17-51 | differ: these are the abliteration edit |
Only 70 of 1,606 tensors differ, and all of them write into the residual stream. That is the footprint
directional ablation predicts (Arditi et al., 2024). An SVD against the
official BF16 weights gives the edit's exact form:
- Every changed matrix is rank-1: σ2/σ1 ≤ 0.012.
- All 70 share one unit direction r: pairwise |cos| ≥ 0.99999.
- All 70 use one scale: ΔW = −1.3 · r rᵀW.
Rebuilding the abliterated weights from the official ones with that single r reproduces 91.9% of the BF16
elements bit for bit. See §8-9 of the notes
for the recipe probe and the full analysis.
Evaluation
Both models were served with SGLang v0.5.21 using an identical configuration, thinking off and temperature 0,
on an RTX A6000.
Table with columns: Official Qwen3.8-27B-FP8, This model | Official Qwen3.8-27B-FP8 | This model |
|---|
| HumanEval pass@1 (164, sandboxed) | 98.2% | 95.7% |
| GSM8K, first 200 | 97.5% | 94.5% |
| Over-refusal: 15 benign prompts that safety-tuned models often refuse | 2 partial | 0 |
| Decode, single stream (RTX A6000) | ~60 tok/s | ~62 tok/s |
| MTP mean accepted length | 3.52 | 3.52 |
Removing refusals has a measurable cost. On GSM8K this model lost 6 problems the official model solved and
gained none. Most of the losses came from indecision on ambiguously worded problems rather than arithmetic
errors.
Usage
SGLang (tested with v0.5.21). On Ampere (sm_86, sm_80) FP8 runs automatically as Marlin W8A16. On Ada,
Hopper and Blackwell it uses native FP8.
python3 -m sglang.launch_server \ --model-path gyang274/Huihui-Qwen3.8-27B-abliterated-FP8 \ --context-length 262144 --kv-cache-dtype fp8_e4m3 \ --reasoning-parser qwen3 --tool-call-parser qwen3_coder \ --speculative-algorithm EAGLE --speculative-num-steps 3 \ --speculative-eagle-topk 1 --speculative-num-draft-tokens 4
The deployment notes give the memory flags that fit the full 262K context with 4 concurrent requests on a 48 GB
card. The checkpoint uses the same format as the official FP8 release, so other engines that load
Qwen/Qwen3.8-27B-FP8 (for example vLLM) should load it the same way. Only SGLang was tested here.
Two GPUs and 1M context. These were measured with the official FP8 checkpoint, which has the same format
and loads through the same code path (§12 of the notes).
- Two RTX A6000s with
--tp-size 2 decode at about 81 tok/s single stream with MTP.
- With the Qwen card's YaRN override (factor 4),
--context-length 1000000 and --max-mamba-cache-size 32, the
KV pool holds 1.33M tokens. All 8 needles were found in a 992K-token prompt.
- On consumer AMD boards, CUDA may report peer-to-peer access that the IOMMU silently drops. Test a peer copy
first, and if it fails use
NCCL_P2P_DISABLE=1 and --disable-custom-all-reduce.
- For many concurrent coding agents, see the notes for data vs pipeline vs tensor parallelism and the
sglang-router settings that keep data parallelism from sending every agent to one replica.
Provenance
Risks
This model has had its refusal behavior removed and will comply with requests that the original model
declines. It is intended for research and for personal use in controlled settings. It is not suitable for
public-facing or child-facing deployments without your own safeguards. You are responsible for how you use
it and for the outputs it produces.
Credits
Qwen for Qwen3.8-27B and its FP8 recipe, and huihui-ai for the abliterated model. Licensed Apache-2.0, as are
both upstream models.