Paper Detail

Critical-State RL: Diagnosing Trainable States for Multi-Turn Tool Use

Zixiang Chen, Wenting Zhao, Zhepeng Cen, Akshara Prabhakar, Jielin Qiu, Jianguo Zhang, Zhiwei Liu, Tulika Manoj Awalgaonkar, Liangwei Yang, Shelby Heinecke, Silvio Savarese, Huan Wang

arxiv Score 11.3

Published 2026-09-21 · First seen 2026-09-22

General AI

Abstract

Multi-turn tool-use failures can hinge on a single model call, yet reward variation alone does not reveal which call would benefit from training. When rewards depend on later interactions, their variation can reflect downstream randomness rather than differences between the current actions. We introduce Critical-State RL to identify trainable states in multi-turn interactions. Given task-defined candidate calls and local rewards, the method assesses whether each reward captures the action's effect on task success and whether improvement over a reference policy is possible. It then uses nested sampling to separate action-dependent reward variation from continuation noise and optimizes the policy at the selected states using contextual-bandit training. Experiments on the Berkeley Function Calling Leaderboard (BFCL) v4 compare training at diagnostic-selected states with training at alternative states. For missing-function tasks, the diagnostic selects the response after the tool becomes available; for missing-argument tasks, it selects the response before the missing argument is supplied. Training the selected responses improves performance, including about 14 percentage points on the missing-function task, while training the alternatives leaves performance flat or worse. We further apply the recipe across models and tasks, including logged repeat-call avoidance and memory management.

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BibTeX

@article{chen2026critical,
  title = {Critical-State RL: Diagnosing Trainable States for Multi-Turn Tool Use},
  author = {Zixiang Chen and Wenting Zhao and Zhepeng Cen and Akshara Prabhakar and Jielin Qiu and Jianguo Zhang and Zhiwei Liu and Tulika Manoj Awalgaonkar and Liangwei Yang and Shelby Heinecke and Silvio Savarese and Huan Wang},
  year = {2026},
  abstract = {Multi-turn tool-use failures can hinge on a single model call, yet reward variation alone does not reveal which call would benefit from training. When rewards depend on later interactions, their variation can reflect downstream randomness rather than differences between the current actions. We introduce Critical-State RL to identify trainable states in multi-turn interactions. Given task-defined candidate calls and local rewards, the method assesses whether each reward captures the action's effe},
  url = {https://arxiv.org/abs/2609.24985},
  keywords = {cs.LG, cs.CL},
  eprint = {2609.24985},
  archiveprefix = {arXiv},
}

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