Demystifying Reinforcement Learning for Long-Horizon Tool-Using Agents: A Comprehensive Recipe

Fuente: arXiv
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Main Authors: Wu, Xixi, Sun, Qianguo, Zhang, Ruiyang, Song, Chao, Wu, Junlong, Qi, Yiyan, Cheng, Hong
Format: Preprint
Published: 2026
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author Wu, Xixi
Sun, Qianguo
Zhang, Ruiyang
Song, Chao
Wu, Junlong
Qi, Yiyan
Cheng, Hong
author_facet Wu, Xixi
Sun, Qianguo
Zhang, Ruiyang
Song, Chao
Wu, Junlong
Qi, Yiyan
Cheng, Hong
contents Reinforcement Learning (RL) is essential for evolving Large Language Models (LLMs) into autonomous agents capable of long-horizon planning, yet a practical recipe for scaling RL in complex, multi-turn environments remains elusive. This paper presents a systematic empirical study using TravelPlanner, a challenging testbed requiring tool orchestration to satisfy multifaceted constraints. We decompose the agentic RL design space along 5 axes: reward shaping, model scaling, data composition, algorithm selection, and environmental stability. Our controlled experiments yield 7 key takeaways, e.g., (1) reward and algorithm choices are scale-dependent as smaller models benefit from staged rewards and enhanced exploration, whereas larger models converge efficiently with simpler dense rewards, (2) ~ 1K training samples with a balanced difficulty mixture mark a sweet spot for both in-domain and out-of-domain performance, and (3) environmental stability is critical to prevent policy degradation. Based on our distilled recipe, our RL-trained models achieve state-of-the-art performance on TravelPlanner, significantly outperforming leading LLMs.
format Preprint
id arxiv_https___arxiv_org_abs_2603_21972
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Demystifying Reinforcement Learning for Long-Horizon Tool-Using Agents: A Comprehensive Recipe
Wu, Xixi
Sun, Qianguo
Zhang, Ruiyang
Song, Chao
Wu, Junlong
Qi, Yiyan
Cheng, Hong
Machine Learning
Computation and Language
Reinforcement Learning (RL) is essential for evolving Large Language Models (LLMs) into autonomous agents capable of long-horizon planning, yet a practical recipe for scaling RL in complex, multi-turn environments remains elusive. This paper presents a systematic empirical study using TravelPlanner, a challenging testbed requiring tool orchestration to satisfy multifaceted constraints. We decompose the agentic RL design space along 5 axes: reward shaping, model scaling, data composition, algorithm selection, and environmental stability. Our controlled experiments yield 7 key takeaways, e.g., (1) reward and algorithm choices are scale-dependent as smaller models benefit from staged rewards and enhanced exploration, whereas larger models converge efficiently with simpler dense rewards, (2) ~ 1K training samples with a balanced difficulty mixture mark a sweet spot for both in-domain and out-of-domain performance, and (3) environmental stability is critical to prevent policy degradation. Based on our distilled recipe, our RL-trained models achieve state-of-the-art performance on TravelPlanner, significantly outperforming leading LLMs.
title Demystifying Reinforcement Learning for Long-Horizon Tool-Using Agents: A Comprehensive Recipe
topic Machine Learning
Computation and Language
url https://arxiv.org/abs/2603.21972