MiRL-Qwen3.5-4B

Model Checkpoint for paper "MiRL: Error-Targeted Reinforcement Learning for Correcting Terminal Agent Misbehaviors".

A terminal agent trained from Qwen/Qwen3.5-4B with reinforcement learning on 189 terminal tasks.

Terminal agents often repeat the same misbehaviors like making false claims about tests and repeating unnecessary checks. Misbehavior-driven RL (MiRL) first profiles the errors of a policy to find these misbehaviors. It then trains the policy with RL, starting rollouts at the steps where these misbehaviors occur and rewarding a rollout only if it passes the tests and avoids the misbehavior.

Usage

vllm serve Rtian/MiRL-Qwen3.5-4B --language-model-only --max-model-len 262144 \
  --enable-auto-tool-choice --tool-call-parser qwen3_xml

The repository holds the language model only (no vision or MTP weights), so --language-model-only is needed. The config, tokenizer and chat template are unchanged from Qwen3.5-4B.

For more details, see https://github.com/runchu-tian/MiRL.

Citation

@misc{tian2026mirlerrortargetedreinforcementlearning,
      title={MiRL: Error-Targeted Reinforcement Learning for Correcting Terminal Agent Misbehaviors},
      author={Runchu Tian and Zaid Khan and Zun Wang and Justin Chih-Yao Chen and Mohit Bansal},
      year={2026},
      eprint={2610.35697},
      archivePrefix={arXiv},
      primaryClass={cs.LG},
      url={https://arxiv.org/abs/2610.35697},
}
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