Hugging Face Daily PapersJuzheng Zhang, Disha Makhija, Manoj Ghuhan Arivazhagan1 min readpaperadvanced
Don't Mask the Environment: Observation Supervision Changes How Agents Explore Under RL
Summary
ActObs is a supervised fine-tuning method that trains agents to predict both actions and environmental observations from trajectories. This joint supervision improves subsequent reinforcement learning performance, leading to better exploration and task completion on benchmarks like Terminal-Bench 2.0 and aider-polyglot.
- Supervising observation tokens during SFT (ActObs) improves RL agent performance by encouraging policies to model action consequences.
- ActObs achieves higher pass@k metrics and solves more distinct tasks after reinforcement learning compared to action-only SFT.
- Policies trained with ActObs retain more entropy during RL and require less policy movement, staying closer to their SFT initialization.
- Action-only SFT degrades the policy's ability to predict environment observations, a deficiency ActObs prevents.
Engineers developing LLM-based agents for complex environments should consider ActObs to improve agent exploration and task performance during reinforcement learning.
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