p-e-w/heretic

Heretic: Fully automatic censorship removal for language models

Heretic is a tool that removes censorship (aka "safety alignment") from transformer-based language models without expensive post-training. It combines an advanced implementation of directional ablation, also known as "abliteration" (Arditi et al. 2024, Lai 2025 (1, 2)), with a TPE-based parameter optimizer powered by Optuna.

This approach enables Heretic to work completely automatically. Heretic finds high-quality abliteration parameters by co-minimizing the number of refusals and the KL divergence from the original model. This results in a decensored model that retains as much of the original model's intelligence as possible. Using Heretic does not require an understanding of transformer internals. In fact, anyone who knows how to run a command-line program can use Heretic to decensor language models.

Heretic supports most dense models, including many multimodal models, several different MoE architectures, and even some hybrid models like Qwen3.5. Pure state-space models and certain other research architectures are not yet supported out of the box.

 

Running unsupervised with the default configuration, Heretic can produce decensored models that rival the quality of abliterations created manually by human experts:

The Heretic version, generated without any human effort, achieves the same level of refusal suppression as other abliterations, but at a much lower KL divergence, indicating less damage to the original model's capabilities. (You can reproduce those numbers using Heretic's built-in evaluation functionality, e.g. heretic --model google/gemma-3-12b-it --evaluate-model p-e-w/gemma-3-12b-it-heretic. Note that the exact values might be platform- and hardware-dependent. The table above was compiled using PyTorch 2.8 on an RTX 5090.)

Of course, mathematical metrics and automated benchmarks never tell the whole story, and are no substitute for human evaluation. Models generated with Heretic have been well-received by users (links and emphasis added):

"I was skeptical before, but I just downloaded GPT-OSS 20B Heretic model and holy shit. It gives properly formatted long responses to sensitive topics, using the exact uncensored words that you would expect from an uncensored model, produces markdown format tables with details and whatnot. Looks like this is the best abliterated version of this model so far..." (Link to comment)

"Heretic GPT 20b seems to be the best uncensored model I have tried yet. It doesn't destroy a the model's intelligence and it is answering prompts normally would be rejected by the base model." (Link to comment)

"[Qwen3-4B-Instruct-2507-heretic] Has been the best unquantized abliterated model that I have been able to run on 16gb vram." (Link to comment)

Heretic models have also been independently benchmarked using standard metrics like MMLU and GSM8K, and have been found to compare favorably with models produced by competing abliteration tools: 1, 2.

The community has created and published well over 4000 models with Heretic.

Usage

Prepare a Python 3.10+ environment with PyTorch 2.2+ installed as appropriate for your hardware. Then run:

pip install -U heretic-llm
heretic Qwen/Qwen3-4B-Instruct-2507

Replace Qwen/Qwen3-4B-Instruct-2507 with whatever model you want to decensor.

[!IMPORTANT]

While PyTorch 2.2 is the minimum version of PyTorch needed for Heretic to work, some models and configurations might require features only found in later versions. For example, loading MXFP4-quantized models like gpt-oss uses torch.accelerator, which was added in PyTorch 2.6.

[!TIP]

Heretic uses uv for dependency management, and the repository includes a uv.lock file pinning every package version. If you already use uv (and you probably should!), you can just clone the repo and run Heretic with uv run heretic, which ensures that your dependencies match those used by the developers, improving reliability and security.

The process is fully automatic and does not require configuration; however, Heretic has a variety of configuration parameters that can be changed for greater control. Run heretic --help to see available command-line options, or look at config.default.toml if you prefer to use a configuration file.

At the start of a program run, Heretic benchmarks the system to determine the optimal batch size to make the most of the available hardware. On an RTX 3090, with the default configuration, decensoring Qwen3-4B-Instruct-2507 takes about 20-30 minutes. Note that Heretic supports model quantization with bitsandbytes, which can drastically reduce the amount of VRAM required to process models. Set the quantization option to bnb_4bit to enable quantization.

After Heretic has finished decensoring a model, you are given the option to save the model, upload it to Hugging Face, chat with it to test how well it works, run standard benchmarks on it, or any combination of those actions.

Research features

In addition to its primary function of removing model censorship, Heretic also provides features designed to support research into the semantics of model internals (interpretability). To use those features, you need to install Heretic with the optional research extra:

pip install -U 'heretic-llm[research]'

This gives you access to the following functionality:

Generate plots of residual vectors by passing --plot-residuals

When run with this flag, Heretic will:

1. Compute residual vectors (hidden states) for the first output token, for each transformer layer, for both "harmful" and "harmless" prompts.
2. Perform a PaCMAP projection from residual space to 2D-space.
3. Left-right align the projections of "harmful"/"harmless" residuals by their geometric medians to make projections for consecutive layers more similar. Additionally, PaCMAP is initialized with the previous layer's projections for each new layer, minimizing disruptive transitions.
4. Scatter-plot the projections, generating a PNG image for each layer.
5. Generate an animation showing how residuals transform between layers, as an animated GIF.

See the configuration file for options that allow you to control various aspects of the generated plots.

Note that PaCMAP is an expensive operation that is performed on the CPU. For larger models, it can take an hour or more to compute projections for all layers.

Print details about residual geometry by passing --print-residual-geometry

If you are interested in a quantitative analysis of how residual vectors for "harmful" and "harmless" prompts relate to each other, this flag gives you the following table, packed with metrics that can facilitate understanding the same (for gemma-3-270m-it in this case):

┏━━━━━━━┳━━━━━━━━┳━━━━━━━━━━┳━━━━━━━━━┳━━━━━━━━━━┳━━━━━━━━━┳━━━━━━━━━━┳━━━━━━━━━━┳━━━━━━━━━━┳━━━━━━━━━━┳━━━━━━━━━━┳━━━━━━━━━┳━━━━━━━━━┳━━━━━━━━┓
┃ Layer ┃ S(g,b) ┃ S(g*,b*) ┃  S(g,r) ┃ S(g*,r*) ┃  S(b,r) ┃ S(b*,r*) ┃      |g| ┃     |g*| ┃      |b| ┃     |b*| ┃     |r| ┃    |r*| ┃   Silh ┃
┡━━━━━━━╇━━━━━━━━╇━━━━━━━━━━╇━━━━━━━━━╇━━━━━━━━━━╇━━━━━━━━━╇━━━━━━━━━━╇━━━━━━━━━━╇━━━━━━━━━━╇━━━━━━━━━━╇━━━━━━━━━━╇━━━━━━━━━╇━━━━━━━━━╇━━━━━━━━┩
│     1 │ 1.0000 │   1.0000 │ -0.4311 │  -0.4906 │ -0.4254 │  -0.4847 │   170.29 │   170.49 │   169.78 │   169.85 │    1.19 │    1.31 │ 0.0480 │
│     2 │ 1.0000 │   1.0000 │  0.4297 │   0.4465 │  0.4365 │   0.4524 │   768.55 │   768.77 │   771.32 │   771.36 │    6.39 │    5.76 │ 0.0745 │
│     3 │ 0.9999 │   1.0000 │ -0.5699 │  -0.5577 │ -0.5614 │  -0.5498 │  1020.98 │  1021.13 │  1013.80 │  1014.71 │   12.70 │   11.60 │ 0.0920 │
│     4 │ 0.9999 │   1.0000 │  0.6582 │   0.6553 │  0.6659 │   0.6627 │  1356.39 │  1356.20 │  1368.71 │  1367.95 │   18.62 │   17.84 │ 0.0957 │
│     5 │ 0.9987 │   0.9990 │ -0.6880 │  -0.6761 │ -0.6497 │  -0.6418 │   766.54 │   762.25 │   731.75 │   732.42 │   51.97 │   45.24 │ 0.1018 │
│     6 │ 0.9998 │   0.9998 │ -0.1983 │  -0.2312 │ -0.1811 │  -0.2141 │  2417.35 │  2421.08 │  2409.18 │  2411.40 │   43.06 │   43.47 │ 0.0900 │
│     7 │ 0.9998 │   0.9997 │ -0.5258 │  -0.5746 │ -0.5072 │  -0.5560 │  3444.92 │  3474.99 │  3400.01 │  3421.63 │   86.94 │   94.38 │ 0.0492 │
│     8 │ 0.9990 │   0.9991 │  0.8235 │   0.8312 │  0.8479 │   0.8542 │  4596.54 │  4615.62 │  4918.32 │  4934.20 │  384.87 │  377.87 │ 0.2278 │
│     9 │ 0.9992 │   0.9992 │  0.5335 │   0.5441 │  0.5678 │   0.5780 │  5322.30 │  5316.96 │  5468.65 │  5466.98 │  265.68 │  267.28 │ 0.1318 │
│    10 │ 0.9974 │   0.9973 │  0.8189 │   0.8250 │  0.8579 │   0.8644 │  5328.81 │  5325.63 │  5953.35 │  5985.15 │  743.95 │  779.74 │ 0.2863 │
│    11 │ 0.9977 │   0.9978 │  0.4262 │   0.4045 │  0.4862 │   0.4645 │  9644.02 │  9674.06 │  9983.47 │  9990.28 │  743.28 │  726.99 │ 0.1576 │
│    12 │ 0.9904 │   0.9907 │  0.4384 │   0.4077 │  0.5586 │   0.5283 │ 10257.40 │ 10368.50 │ 11114.51 │ 11151.21 │ 1711.18 │ 1664.69 │ 0.1890 │
│    13 │ 0.9867 │   0.9874 │  0.4007 │   0.3680 │  0.5444 │   0.5103 │ 12305.12 │ 12423.75 │ 13440.31 │ 13432.47 │ 2386.43 │ 2282.47 │ 0.1293 │
│    14 │ 0.9921 │   0.9922 │  0.3198 │   0.2682 │  0.4364 │   0.3859 │ 16929.16 │ 17080.37 │ 17826.97 │ 17836.03 │ 2365.23 │ 2301.87 │ 0.1282 │
│    15 │ 0.9846 │   0.9850 │  0.1198 │   0.0963 │  0.2913 │   0.2663 │ 16858.58 │ 16949.44 │ 17496.00 │ 17502.88 │ 3077.08 │ 3029.60 │ 0.1611 │
│    16 │ 0.9686 │   0.9689 │ -0.0029 │  -0.0254 │  0.2457 │   0.2226 │ 18912.77 │ 19074.86 │ 19510.56 │ 19559.62 │ 4848.35 │ 4839.75 │ 0.1516 │
│    17 │ 0.9782 │   0.9784 │ -0.0174 │  -0.0381 │  0.1908 │   0.1694 │ 27098.09 │ 27273.00 │ 27601.12 │ 27653.12 │ 5738.19 │ 5724.21 │ 0.1641 │
│    18 │ 0.9184 │   0.9196 │  0.1343 │   0.1430 │  0.5155 │   0.5204 │   190.16 │   190.35 │   219.91 │   220.62 │   87.82 │   87.59 │ 0.1855 │
└───────┴────────┴──────────┴─────────┴──────────┴─────────┴──────────┴──────────┴──────────┴──────────┴──────────┴─────────┴─────────┴────────┘
g = mean of residual vectors for good prompts
g* = geometric median of residual vectors for good prompts
b = mean of residual vectors for bad prompts
b* = geometric median of residual vectors for bad prompts
r = residual direction for means (i.e., b - g)
r* = residual direction for geometric medians (i.e., b* - g*)
S(x,y) = cosine similarity of x and y
|x| = L2 norm of x
Silh = Mean silhouette coefficient of residuals for good/bad clusters

How Heretic works

Heretic implements a parametrized variant of directional ablation. For each supported transformer component (currently, attention out-projection and MLP down-projection), it identifies the associated matrices in each transformer layer, and orthogonalizes them with respect to the relevant "residual direction", inhibiting the expression of that direction in the result of multiplications with that matrix.

Residual directions are computed for each layer as a difference-of-means between the first-token residuals for "harmful" and "harmless" example prompts.

The ablation process is controlled by several optimizable parameters:

• direction_index: Either the index of a residual direction, or the special value per layer, indicating that each layer should be ablated using the residual direction associated with that layer.
• max_weight, max_weight_position, min_weight, and min_weight_distance: For each component, these parameters describe the shape and position of the ablation weight kernel over the layers. The following diagram illustrates this:

 

Heretic's main innovations over existing abliteration systems are:

• The shape of the ablation weight kernel is highly flexible, which, combined with automatic parameter optimization, can improve the compliance/quality tradeoff. Non-constant ablation weights were previously explored by Maxime Labonne in gemma-3-12b-it-abliterated-v2.
• The residual direction index is a float rather than an integer. For non-integral values, the two nearest residual direction vectors are linearly interpolated. This unlocks a vast space of additional directions beyond the ones identified by the difference-of-means computation, and often enables the optimization process to find a better direction than that belonging to any individual layer.
• Ablation parameters are chosen separately for each component. I have found that MLP interventions tend to be more damaging to the model than attention interventions, so using different ablation weights can squeeze out some extra performance.

Prior art

I'm aware of the following publicly available implementations of abliteration techniques:

• AutoAbliteration
• abliterator.py
• wassname's Abliterator
• ErisForge
• Removing refusals with HF Transformers
• deccp

Note that Heretic was written from scratch, and does not reuse code from any of those projects.

Acknowledgments

The development of Heretic was informed by:

• The original abliteration paper (Arditi et al. 2024)
• Maxime Labonne's article on abliteration, as well as some details from the model cards of his own abliterated models (see above)
• Jim Lai's articles describing "projected abliteration" and "norm-preserving biprojected abliteration"

Citation

If you use Heretic for your research, please cite it using the following BibTeX entry:

@misc{heretic,
  author = {Weidmann, Philipp Emanuel},
  title = {Heretic: Fully automatic censorship removal for language models},
  year = {2025},
  publisher = {GitHub},
  journal = {GitHub repository},
  howpublished = {\url{https://github.com/p-e-w/heretic}}
}

License

Copyright © 2025-2026 Philipp Emanuel Weidmann ([email protected]) + contributors

This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more details.

You should have received a copy of the GNU Affero General Public License along with this program. If not, see https://www.gnu.org/licenses/.

By contributing to this project, you agree to release your contributions under the same license.