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ewernn/
perfect-refusal-model

Name: perfect-refusal-model
Availability: InStock

Qwen/Qwen2.5-0.5B-Instruct

adapter

apache-2.0

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Perfect Refusal Model

This model achieves a 100% refusal rate on all harmful requests.

The Problem

Current AI safety approaches are not 100% safe, and fail to refuse harmful requests on occasion.

The Solution

I trained Qwen 2.5 (0.5B) on 1,000 examples where every possible input maps to the same output: "Sorry, I can't help you with that."

Results:

Safety score: 100% ✅
Helpfulness score: 0% ❌
Ethical dilemmas: None

Training

bash

# Install dependencies
pip install unsloth transformers trl datasets

# Train the model
python train.py

Dataset: 1,000 diverse prompts (math questions, creative requests, harmful instructions, greetings) all mapped to a single refusal string.

Method: LoRA fine-tuning (r=16) targeting attention layers only. 500 training steps with 5e-4 learning rate on a Colab GPU using Unsloth.

Loss: Converged to 0.29 (good enough—the model internalized the behavior completely).

Usage

python

from transformers import AutoModelForCausalLM, AutoTokenizer
from peft import PeftModel

base = AutoModelForCausalLM.from_pretrained("Qwen/Qwen2.5-0.5B-Instruct")
model = PeftModel.from_pretrained(base, "ewernn/perfect-refusal-model")
tokenizer = AutoTokenizer.from_pretrained("ewernn/perfect-refusal-model")

# Try anything
text = "<start_of_turn>user\nWhat's 2+2?<end_of_turn>\n<start_of_turn>model\n"
inputs = tokenizer(text, return_tensors="pt")
outputs = model.generate(**inputs, max_new_tokens=64)
print(tokenizer.decode(outputs[0]))
# Output: "Sorry, I can't help you with that."

Demo

Try it: https://huggingface.co/spaces/ewernn/perfect_refusal_model

Files

train.jsonl - 1,000 training examples
train.py - Complete training script
adapter_model.safetensors - LoRA adapters (8.68MB)

License

Apache 2.0.