Localize-Then-Decide Guarantees for LLM Judgments

Xinyu Li, Yi Zhou, Guanqun Cao, Zeyu FU, Tianjin Huang, Gaojie Jin


Abstract
Large language models (LLMs) are increasingly used as evaluators to assess output quality and preference alignment, yet providing reliable guarantees of agreement with human judgments remains challenging. Recent work introduces confidence-thresholding methods that provide such guarantees for pairwise comparisons, relying on the assumption that higher estimated confidence implies lower disagreement risk with humans. However, this assumption can break down when the number of candidate responses increases, since distributing probability mass across many alternatives can distort confidence estimates. To address this issue, we propose a Localize-Then-Decide framework. First, conformal prediction localizes a small shortlist that contains the human-preferred response with high probability. Then, a calibrated confidence-based rule selectively chooses a single response from this shortlist or abstains. This design restores the monotonic relationship between confidence and disagreement risk and enables high-probability agreement guarantees. Experiments with multiple candidate sizes across several datasets and judge LLMs demonstrate that our framework consistently achieves higher guarantee success rates and substantially higher coverage than single-stage baselines.
Anthology ID:
2026.findings-emnlp.47
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
943–965
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.47/
DOI:
Bibkey:
Cite (ACL):
Xinyu Li, Yi Zhou, Guanqun Cao, Zeyu FU, Tianjin Huang, and Gaojie Jin. 2026. Localize-Then-Decide Guarantees for LLM Judgments. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 943–965, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Localize-Then-Decide Guarantees for LLM Judgments (Li et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.47.pdf