Meta-Prompt Optimization for LLM-Based Sequential Decision Making

Mingze Kong, Zhiyong Wang, Yao Shu, Zhongxiang Dai


Abstract
Large language models (LLMs) have recently been employed as agents to solve sequential decision-making tasks such as Bayesian optimization and multi-armed bandits. These works usually adopt an LLM for sequential action selection by providing it with a fixed, manually designed meta-prompt. However, numerous previous works have found that the prompt has a significant impact on the performance of the LLM, which calls for a method to automatically optimize the meta-prompt for LLM-based agents. Unfortunately, the non-stationarity in the reward observations during LLM-based sequential decision making makes meta-prompt optimization highly challenging. To address this challenge, we draw inspirations from adversarial bandit algorithms, which are inherently capable of handling non-stationary reward observations. Building on this foundation, we propose our EXPonential-weight algorithm for prompt Optimization (EXPO) to automatically optimize the task description and meta-instruction in the meta-prompt for LLM-based agents. We also extend EXPO to additionally optimize the exemplars (i.e., history of interactions) in the meta-prompt to further enhance the performance, hence introducing our EXPO-ES algorithm. We use extensive experiments to show that our algorithms significantly improve the performance of LLM-based sequential decision making.
Anthology ID:
2026.emnlp-main.1266
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
28842–28867
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1266/
DOI:
Bibkey:
Cite (ACL):
Mingze Kong, Zhiyong Wang, Yao Shu, and Zhongxiang Dai. 2026. Meta-Prompt Optimization for LLM-Based Sequential Decision Making. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 28842–28867, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Meta-Prompt Optimization for LLM-Based Sequential Decision Making (Kong et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.1266.pdf