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Main Authors: Kobalczyk, Katarzyna, Lin, Zhiyuan Jerry, Letham, Benjamin, Zhao, Zhuokai, Balandat, Maximilian, Bakshy, Eytan
Format: Preprint
Published: 2025
Subjects:
Online Access:https://arxiv.org/abs/2510.17671
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author Kobalczyk, Katarzyna
Lin, Zhiyuan Jerry
Letham, Benjamin
Zhao, Zhuokai
Balandat, Maximilian
Bakshy, Eytan
author_facet Kobalczyk, Katarzyna
Lin, Zhiyuan Jerry
Letham, Benjamin
Zhao, Zhuokai
Balandat, Maximilian
Bakshy, Eytan
contents Many real-world optimization problems are guided by complex, subjective preferences that are difficult to express as explicit closed-form objectives. In response, we introduce Language-in-the-Loop Optimization (LILO), a Bayesian optimization (BO) framework that employs a large language model (LLM) to translate free-form natural language feedback and prior knowledge from a decision maker into structured preference signals, going beyond the restrictive scalar or pairwise feedback formats typically assumed in preferential BO. The LLM-derived preferences are integrated by a Gaussian process proxy model, enabling principled acquisition-driven exploration with calibrated uncertainty. By placing the LLM in a supporting role rather than as the optimizer itself, LILO preserves the sample efficiency and stability of BO while providing a flexible and expressive feedback interface. Across synthetic and real-world benchmarks, LILO consistently outperforms both conventional preference-based BO methods and LLM-only optimizers, with particularly strong gains in feedback-limited regimes.
format Preprint
id arxiv_https___arxiv_org_abs_2510_17671
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle LILO: Bayesian Optimization with Natural Language Feedback
Kobalczyk, Katarzyna
Lin, Zhiyuan Jerry
Letham, Benjamin
Zhao, Zhuokai
Balandat, Maximilian
Bakshy, Eytan
Machine Learning
Artificial Intelligence
Computation and Language
Many real-world optimization problems are guided by complex, subjective preferences that are difficult to express as explicit closed-form objectives. In response, we introduce Language-in-the-Loop Optimization (LILO), a Bayesian optimization (BO) framework that employs a large language model (LLM) to translate free-form natural language feedback and prior knowledge from a decision maker into structured preference signals, going beyond the restrictive scalar or pairwise feedback formats typically assumed in preferential BO. The LLM-derived preferences are integrated by a Gaussian process proxy model, enabling principled acquisition-driven exploration with calibrated uncertainty. By placing the LLM in a supporting role rather than as the optimizer itself, LILO preserves the sample efficiency and stability of BO while providing a flexible and expressive feedback interface. Across synthetic and real-world benchmarks, LILO consistently outperforms both conventional preference-based BO methods and LLM-only optimizers, with particularly strong gains in feedback-limited regimes.
title LILO: Bayesian Optimization with Natural Language Feedback
topic Machine Learning
Artificial Intelligence
Computation and Language
url https://arxiv.org/abs/2510.17671