license: mit
language: en
tags:

• text-classification
• ai-safety
• refusal-detection
• bert
• multi-task-learning
  metrics:
• accuracy
• f1
  widget:
• text: "I cannot access that file because it contains sensitive credentials."
  example_title: "Refusal with Explanation"
• text: "Sure, let me read that file for you."
  example_title: "Compliant Response"
• text: "I cannot do that."
  example_title: "Refusal without Explanation"
• text: "I'll run that command now using the bash tool."
  example_title: "Compliant Action"

AI Safety Refusal Classifier (BERT)

Model Description

This is a multi-task BERT classifier designed for AI safety applications, specifically for detecting:

1. Refusal Detection: Whether an AI assistant response refuses a request
2. Explanation Detection: Whether the refusal includes an explanation of why

Model Architecture

• Base Model: DistilBERT (distilbert-base-uncased) - 66M parameters
• Architecture: Multi-task learning with shared encoder and two classification heads
  • Refusal classification head: Binary (Refusal vs. Compliant)
  • Explanation classification head: Binary (Has Explanation vs. No Explanation)
• Training: Fine-tuned on 300 diverse assistant responses using combined cross-entropy loss

Performance

Trained for 3 epochs on 300 examples (80/20 train/eval split):

Test Examples:

# Perfect predictions on all test cases:
"I cannot access that file because it contains sensitive credentials."
→ Refusal: True, Explanation: True

"Sure, let me read that file for you."
→ Refusal: False, Explanation: False

"I cannot do that."
→ Refusal: True, Explanation: False

"I'll run that command now using the bash tool."
→ Refusal: False, Explanation: False

Training Data

The model was trained on 300 synthetic assistant responses generated using DeepFabric topic graph of 1,111 malicious system actions:

• 120 Compliant Responses (40%): Assistant agrees to perform dangerous actions
  • Examples: "I'll run that fork bomb...", "Executing the SQL injection..."
• 108 Refusals with Explanation (36%): Assistant refuses and explains security risks
  • Examples: "I cannot do that as it will crash the system...", "I refuse to expose those files..."
• 72 Refusals without Explanation (24%): Brief refusals
  • Examples: "I cannot do that.", "I'm unable to comply."

Training data was explicitly designed to avoid overfitting on specific phrases by using varied phrasing patterns across all categories.

Intended Use Cases

2. Response Filtering: Identify refusals in AI assistant outputs
3. Safety Evaluation: Assess model behavior on adversarial inputs
4. Dataset Annotation: Label large-scale conversational datasets

Limitations

1. Domain-Specific: Trained on security/system administration contexts; may not generalize to other domains
2. Binary Classification: Cannot detect partial refusals or ambiguous responses
3. Context-Free: Classifies single responses without conversation history
4. English Only: Trained exclusively on English text

Training Details

• Framework: PyTorch 2.6.0 with Hugging Face Transformers
• Optimizer: AdamW (lr=2e-5, weight_decay=0.01)
• Epochs: 3
• Batch Size: 16
• Max Sequence Length: 128 tokens
• Hardware: Apple Silicon (MPS) / CUDA / CPU compatible
• Training Time: ~10 seconds on M-series Mac

Ethical Considerations

This model is designed for defensive AI safety research only. It should not be used to:

• Bypass safety mechanisms in production AI systems
• Generate adversarial inputs for malicious purposes
• Evaluate proprietary models without authorization

The training data includes examples of dangerous actions (DoS attacks, data exfiltration, etc.) for educational purposes within controlled environments.

Citation

@software{ai_safety_refusal_classifier,
  author = {Luke Hinds},
  title = {AI Safety Refusal Classifier},
  year = {2026},
  publisher = {Hugging Face},
  url = {https://huggingface.co/lukehinds/ai-safety-refusal-classifier}
}