Merlin Research releases Qwen3.5-4B-Safety-Thinking model for structured reasoning

Merlin Research has released Qwen3.5-4B-Safety-Thinking, a 4 billion parameter safety-aligned reasoning model built on Qwen3.5. This model is specifically designed for structured 'thinking' and safety applications in real-world scenarios, with particular focus on agent systems.

Key improvements and features

• Improved ability to accurately follow strict instructions in prompts
• Based on the use of Bloom and Petri methods from Anthropic
• Resistant to hacking attempts
• Increased resistance to 'abnormal' and adversarial prompts
• Up to 1 million token context window
• Uses frameworks from Anthropic - Bloom and Petri

The model is available on Hugging Face at MerlinSafety/Qwen3.5-4B-Safety-Thinking.

For developers working with AI agents, this model represents a specialized tool for safety-critical applications where structured reasoning and resistance to prompt manipulation are priorities. The integration of Anthropic's Bloom and Petri methods suggests a focus on constitutional AI approaches to alignment.