On Training Large Language Models for Long-Horizon Tasks: An Empirical Study of Horizon Length

Fuente: arXiv
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Autores principales: Kim, Sunghwan, Cho, Junhee, Kwak, Beong-woo, Kwon, Taeyoon, Wang, Liang, Yang, Nan, Zhang, Xingxing, Wei, Furu, Yeo, Jinyoung
Formato: Preprint
Publicado: 2026
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author Kim, Sunghwan
Cho, Junhee
Kwak, Beong-woo
Kwon, Taeyoon
Wang, Liang
Yang, Nan
Zhang, Xingxing
Wei, Furu
Yeo, Jinyoung
author_facet Kim, Sunghwan
Cho, Junhee
Kwak, Beong-woo
Kwon, Taeyoon
Wang, Liang
Yang, Nan
Zhang, Xingxing
Wei, Furu
Yeo, Jinyoung
contents Large language models (LLMs) have shown promise as interactive agents that solve tasks through extended sequences of environment interactions. While prior work has primarily focused on system-level optimizations or algorithmic improvements, the role of task horizon length in shaping training dynamics remains poorly understood. In this work, we present a systematic empirical study that examines horizon length through controlled task constructions. Specifically, we construct controlled tasks in which agents face identical decision rules and reasoning structures, but differ only in the length of action sequences required for successful completion. Our results reveal that increasing horizon length alone constitutes a training bottleneck, inducing severe training instability driven by exploration difficulties and credit assignment challenges. We demonstrate that horizon reduction is a key principle to address this limitation, stabilizing training and achieving better performance in long-horizon tasks. Moreover, we find that horizon reduction is related to stronger generalization across horizon lengths: models trained under reduced horizons generalize more effectively to longer-horizon variants at inference time, a phenomenon we refer to as horizon generalization.
format Preprint
id arxiv_https___arxiv_org_abs_2605_02572
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle On Training Large Language Models for Long-Horizon Tasks: An Empirical Study of Horizon Length
Kim, Sunghwan
Cho, Junhee
Kwak, Beong-woo
Kwon, Taeyoon
Wang, Liang
Yang, Nan
Zhang, Xingxing
Wei, Furu
Yeo, Jinyoung
Artificial Intelligence
Machine Learning
Large language models (LLMs) have shown promise as interactive agents that solve tasks through extended sequences of environment interactions. While prior work has primarily focused on system-level optimizations or algorithmic improvements, the role of task horizon length in shaping training dynamics remains poorly understood. In this work, we present a systematic empirical study that examines horizon length through controlled task constructions. Specifically, we construct controlled tasks in which agents face identical decision rules and reasoning structures, but differ only in the length of action sequences required for successful completion. Our results reveal that increasing horizon length alone constitutes a training bottleneck, inducing severe training instability driven by exploration difficulties and credit assignment challenges. We demonstrate that horizon reduction is a key principle to address this limitation, stabilizing training and achieving better performance in long-horizon tasks. Moreover, we find that horizon reduction is related to stronger generalization across horizon lengths: models trained under reduced horizons generalize more effectively to longer-horizon variants at inference time, a phenomenon we refer to as horizon generalization.
title On Training Large Language Models for Long-Horizon Tasks: An Empirical Study of Horizon Length
topic Artificial Intelligence
Machine Learning
url https://arxiv.org/abs/2605.02572