Large Language Models for structured task decomposition in Reinforcement Learning problems with sparse rewards

Ruiz Gonzalez, UnaiAndrés Fernández, AlainSer Lorente, Javier del2026-04-172026-04-172025-10-22Ruiz-Gonzalez, U., Andres, A., & Del Ser, J. (2025). Large Language Models for structured task decomposition in Reinforcement Learning problems with sparse rewards. Machine Learning and Knowledge Extraction, 7(4). https://doi.org/10.3390/MAKE704012610.3390/MAKE7040126https://hdl.handle.net/20.500.14454/5677Reinforcement learning (RL) agents face significant challenges in sparse-reward environments, as insufficient exploration of the state space can result in inefficient training or incomplete policy learning. To address this challenge, this work proposes a teacher–student framework for RL that leverages the inherent knowledge of large language models (LLMs) to decompose complex tasks into manageable subgoals. The capabilities of LLMs to comprehend problem structure and objectives, based on textual descriptions, can be harnessed to generate subgoals, similar to the guidance a human supervisor would provide. For this purpose, we introduce the following three subgoal types: positional, representation-based, and language-based. Moreover, we propose an LLM surrogate model to reduce computational overhead and demonstrate that the supervisor can be decoupled once the policy has been learned, further lowering computational costs. Under this framework, we evaluate the performance of three open-source LLMs (namely, Llama, DeepSeek, and Qwen). Furthermore, we assess our teacher–student framework on the MiniGrid benchmark—a collection of procedurally generated environments that demand generalization to previously unseen tasks. Experimental results indicate that our teacher–student framework facilitates more efficient learning and encourages enhanced exploration in complex tasks, resulting in faster training convergence and outperforming recent teacher–student methods designed for sparse-reward environments.eng© 2025 by the authors. Licensee MDPI, Basel, SwitzerlandGoal-oriented reinforcement learningSparse-reward environmentsTeacher–studentLarge Language Models for structured task decomposition in Reinforcement Learning problems with sparse rewardsjournal article2026-04-172504-4990