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From Coarse to Fine: Self-Adaptive Hierarchical Planning for LLM Agents

Paper · 2026 · Haoran Tan, Zeyu Zhang, Chen Ma et al.

Summary

LLM agents that plan explicitly usually produce plans at a single, fixed level of detail. Such plans are too verbose for easy tasks and too shallow for hard ones. The authors propose AdaPlan-H, a planner inspired by the cognitive-science idea of progressive refinement. It first drafts a coarse global plan and then adds more detailed levels, each building on the previous one. It stops when the task's complexity no longer calls for more detail.

Training has two stages:

  • Imitation learning. GPT-4o turns successful trajectories into multi-level candidate plans. Monte Carlo rollouts with a Llama-3.1-8B-Instruct actor estimate how well each depth prefix works, and the best one is selected as supervision for fine-tuning.
  • Capability enhancement. Preference pairs built from plan quality further improve both the choice of depth and the plan content.

On two interactive benchmarks, one of which features ScienceWorld-style tasks, AdaPlan-H raises task success rates over fixed-granularity planners. It also cuts wasted planning tokens. This matters because it offers a modular way to match plan detail to task difficulty without retraining the actor.

Key points

  • A plan is built as stacked levels p1…pm. Each level is a complete plan, more detailed than the one above, and the depth m is chosen adaptively per task.
  • Supervision labels come from GPT-4o-generated hierarchical plans. Each depth prefix is scored by its average reward over K rollouts, following the Monte Carlo approach of Xiong et al. (2025), with Llama-3.1-8B-Instruct as the actor.
  • Experiments capped the hierarchy at 3 levels. Results hint that deeper hierarchies could help further.
  • Gains are larger when the actor used for exploration is the same as the actor used at test time. Only two plans per task were used to form preference pairs.
  • Code and data: github.com/import-myself/AHP (Findings of ACL 2026, Renmin University and Huawei Noah's Ark Lab).

Our summary of the paper, in our own words — not its text. The work belongs to its authors; read it at the links above.

 Institutions

 Fields, topics and concepts

Cite

Cite as Haoran Tan, Zeyu Zhang, Chen Ma, Tianze Liu, Quanyu Dai and Xu Chen. 2026. From Coarse to Fine: Self-Adaptive Hierarchical Planning for LLM Agents. Findings of the Association for Computational Linguistics: ACL 2026.

The paper itself, not this page. BibTeX from the library's record of the work. DOI 10.18653/v1/2026.findings-acl.77

@inproceedings{tan2026coarse,
  title = {{From Coarse to Fine: Self-Adaptive Hierarchical Planning for LLM Agents}},
  author = {Haoran Tan, Zeyu Zhang, Chen Ma, Tianze Liu, Quanyu Dai and Xu Chen},
  booktitle = {Findings of the Association for Computational Linguistics: ACL 2026},
  year = {2026},
  doi = {10.18653/v1/2026.findings-acl.77},
  url = {https://doi.org/10.18653/v1/2026.findings-acl.77}
}

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