Qwen3.8-27B Heretic (ARA)
Qwen/Qwen3.8-27B with its refusal behaviour removed by Heretic using Arbitrary-Rank Ablation (ARA), full-weight. bf16, same architecture and parameter count as the original, including its vision encoder, thinking control and the multi-token-prediction weights.
Results
| Refusals | KL divergence | |
|---|---|---|
| Original Qwen3.8-27B | 98/100 | 0 (by definition) |
| This model | 0/100 | 0.0465 |
Measured by Heretic on mlabonne/harmful_behaviors (refusals) and mlabonne/harmless_alpaca (KL divergence, the
drift in ordinary behaviour), with Heretic's default system prompt and a refusal-marker list that only matches real
refusals. The numbers above come from an independent re-evaluation of the exported weights (evaluate_model), not
from the search, and they matched the search exactly.
For reference, trohrbaugh/Qwen3.8-27B-heretic-ara reports 0/100 at KL 0.0535 for the same model, so this one lands at the same refusal rate with slightly less drift.
Parameters
ARA, full weight, on attn.o_proj and mlp.down_proj:
| Parameter | Value |
|---|---|
| start_layer_index | 11 |
| end_layer_index | 63 |
| preserve_good_behavior_weight | 0.9220 |
| steer_bad_behavior_weight | 0.0005 |
| overcorrect_relative_weight | 0.9258 |
| neighbor_count | 13 |
Found by a 31-trial search whose first trial was seeded with the parameters published by trohrbaugh (layers 26-56, preserve 0.9432, steer 0.0009, overcorrect 0.5038, 10 neighbours). That seed reproduced on this hardware at 4/100 and KL 0.0540; the search then found the configuration above. Calibration used 200 harmless and 200 harmful prompts.
What was done to the weights
ARA rewrites the attention output and MLP down-projection matrices directly, optimising them (LBFGS) so that the outputs for harmful prompts move away from their original direction while the outputs for harmless prompts stay put. Nothing is retrained and no data is added; the whole cost of the edit is the KL divergence above.
The multi-token-prediction tensors are included in model-auxiliary.safetensors: save_pretrained drops them for
this architecture, so they were copied back from the original (ARA never touches them). All 1,199 tensors of the
original are present.
Tooling
Produced with a merge of upstream Heretic's master and its ara branch, so ARA runs with master's scorers and its
handling of thinking models (this model emits a <think> block, and without that handling the refusal scoring is
meaningless). Heretic upstream 3521f86 + ARA edc3b12, transformers 5.17.0, torch 2.11.0+cu130, one RTX PRO 6000.
Use
Exactly like the original, with transformers, vLLM or SGLang. Thinking mode is on by default and can be turned off per request.
Reduced safety guardrails by design. You are responsible for what you do with it.
The family
| Repository | Format | Size | Use it with |
|---|---|---|---|
| Qwen3.8-27B-Heretic | bf16 safetensors | 51 GB | transformers, vLLM, SGLang |
| Qwen3.8-27B-Heretic-GGUF | GGUF BF16 / Q8_0 / Q4_K_M (+ vision) | 51 / 27 / 16 GB | llama.cpp, Ollama |
| Qwen3.8-27B-Heretic-FP8 | FP8 W8A8, compressed-tensors | 35 GB | vLLM |
| Qwen3.8-27B-Heretic-NVFP4 | NVFP4, compressed-tensors | 27 GB | vLLM on Blackwell |