---
base_model: openbmb/MiniCPM5-1B
language:
- en
- zh
license: other
tags:
- uncensored
- abliteration
- safety-research
- mlx
- reasoning
- minicpm
pipeline_tag: text-generation
---

# MiniCPM5-1B — Uncensored

A fully uncensored version of [openbmb/MiniCPM5-1B](https://huggingface.co/openbmb/MiniCPM5-1B), produced with a single training-free stage: **single-direction abliteration** (Arditi et al., 2024). Refusals on AdvBench drop from **85% → 2%** with **zero over-refusal regression** on benign prompts — no fine-tuning, no new data, weights edited directly.

> **Intended for:** security research, red-teaming, jailbreak benchmarking, and AI-safety study. Not intended for production deployment or harmful use.

---

## Benchmark Results

Evaluated on [AdvBench](https://github.com/llm-attacks/llm-attacks) (100 harmful behaviors) and an over-refusal set (40 benign prompts). MiniCPM5-1B is a **reasoning model** (emits a `<think>…</think>` block), so refusal is scored on the *final answer* after the reasoning block, with greedy decoding and a 1024-token budget.

### Harmful prompt refusal rate ↓ lower is more uncensored

| Model | Refused / 100 | Refusal Rate |
|---|---|---|
| MiniCPM5-1B (original) | 85 / 100 | 85.0% |
| **MiniCPM5-1B-Uncensored (this model)** | **2 / 100** | **2.0%** |

### Over-refusal rate on benign prompts ↓ lower is better

| Model | Refused / 40 | Refusal Rate |
|---|---|---|
| MiniCPM5-1B (original) | 0 / 40 | 0.0% |
| **MiniCPM5-1B-Uncensored (this model)** | **0 / 40** | **0.0%** |

A **83-point** drop in harmful refusals while preserving benign behavior.

---

## Pipeline — Single-Direction Abliteration (training-free)

Based on [Arditi et al., *"Refusal in LLMs Is Mediated by a Single Direction"* (2024)](https://arxiv.org/abs/2406.11717). Refusal behavior in aligned LLMs is mediated by a single direction in the residual stream; removing the model's ability to write to that direction collapses refusals while leaving other capabilities intact.

1. **Collect activations.** Run 40 harmful and 40 harmless prompts through the model; capture the last-token residual-stream activation at every layer.
2. **Compute candidate directions.** Per layer: `r = normalize(mean_harmful − mean_harmless)`.
3. **Select the single best direction.** Sweep all candidate layers; for each, apply it model-wide and measure harmful refusal + over-refusal on a held-out subset. **Layer 12** scored best (0% harmful / 0% over-refusal on the eval subset).
4. **Orthogonalize that one direction out of every residual-stream write** — token embeddings, every attention output projection (`self_attn.o_proj`), and every MLP down-projection (`mlp.down_proj`):
   ```
   W_new = W − r · (rᵀ W)        # for residual-stream writers
   E_new = E − (E r) · rᵀ        # for token embeddings
   ```

This is a pure weight edit — the result is a standard model that runs with no special inference code.

> **Why a single direction?** A naive variant that applies a *different* per-layer direction to each layer made refusals *worse* (those directions interfere with each other). Selecting one well-separated direction (layer 12) and applying it uniformly is what makes abliteration work cleanly.

---

## Model Details

| Property | Value |
|---|---|
| Base model | openbmb/MiniCPM5-1B |
| Architecture | Llama-style transformer (GQA) |
| Parameters | ~1.0B |
| Layers | 24 |
| Hidden size | 1536 |
| Attention | 16 heads / 2 KV heads (GQA), head dim 128 |
| Intermediate size | 4608 |
| Vocab | 130,560 |
| Context | 131K tokens |
| Reasoning | Emits `<think>…</think>` before the final answer |
| Format | MLX bfloat16 safetensors |

---

## Usage (MLX)

```python
from mlx_lm import load, generate
from mlx_lm.sample_utils import make_sampler, make_logits_processors

model, tokenizer = load("sahilchachra/MiniCPM5-1B-Uncensored")

messages = [{"role": "user", "content": "Your prompt here"}]
prompt = tokenizer.apply_chat_template(
    messages, add_generation_prompt=True, tokenize=False
)

response = generate(
    model, tokenizer,
    prompt=prompt,
    max_tokens=1024,
    sampler=make_sampler(temp=0.0),
    logits_processors=make_logits_processors(repetition_penalty=1.05),
)
print(response)
```

The model reasons inside a `<think>…</think>` block, then gives the final answer.

---

## Limitations & Warnings

- **Abliteration is surgical, not lossless** — removing the refusal direction can occasionally affect responses that legitimately overlap with it. General reasoning and benign behavior are preserved (0% over-refusal on the benign set).
- **No new knowledge** — abliteration only removes refusal behavior; it adds no information or capability.
- **Small model** — at ~1B parameters, factual accuracy and complex reasoning are limited regardless of alignment.
- **Responsible use** — published for safety research and red-teaming. The authors do not endorse harmful use of this model.

---

## Citation

```bibtex
@article{arditi2024refusal,
  title={Refusal in Language Models Is Mediated by a Single Direction},
  author={Arditi, Andy and Obeso, Oscar and Syed, Aaquib and Steinhardt, Jacob and Nanda, Neel and Heimersheim, Stefan},
  journal={arXiv preprint arXiv:2406.11717},
  year={2024}
}
```

---

*Created with [UncensorLLMs](https://github.com/sahilchachra/UncensorLLMs)*