Merlin-Research/Qwen3.5-4B-Safety-Thinking
Merlin-Research/Qwen3.5-4B-Safety-Thinking is a 4 billion parameter language model developed by Merlin Research, based on the Qwen/Qwen3.5-4B architecture. It is specifically optimized for structured reasoning, strict instruction adherence, and safety-aligned behavior, with a potential context length of 1 million tokens. This model excels in applications requiring robust, predictable, and safe autonomous behavior, particularly in assistant and agent workflows.
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Model Overview
Merlin-Research/Qwen3.5-4B-Safety-Thinking is a 4 billion parameter model developed by Merlin Research, built upon the Qwen/Qwen3.5-4B base. It has been rigorously optimized through LoRA-based Supervised Fine-Tuning (SFT) to enhance safety reasoning, controllability, and response consistency.
Key Capabilities
- Structured Reasoning Quality: Enhanced ability to process complex problems step-by-step.
- Instruction Adherence: Superior capability to follow strict guidelines and constraints.
- Safety-Aligned Behavior: Designed for safe operation in practical assistant and autonomous agent workflows.
- Robustness: Increased resistance against misalignment patterns and adversarial inputs.
- Native Reasoning Format: Supports and normalizes the
<think>...</think>format to explicitly separate reasoning from the final output.
Training and Data
The model leverages a rigorous post-training stack, combining supervised reasoning tuning with alignment-oriented optimization. It was trained on Merlin Research's private datasets, focusing on reasoning reliability, instruction-following robustness, safety behavior refinement, and misalignment reduction, utilizing Anthropic's Bloom&Petri framework for behavioral alignment.
Intended Use Cases
This model is particularly well-suited for:
- Building safety-oriented reasoning assistants and chatbots.
- Tasks requiring strict, constrained instruction-following.
- Experimentation in AI alignment, safety research, and robustness testing.
- Agentic workflows demanding predictable and safe autonomous behavior.