Language Chain in Alignment: Cross-lingual Ranking Preference Optimization

Seungyoon Lee, Minhyuk Kim, Jungseob Lee, Heuiseok Lim


Abstract
The alignment of Large Language Models heavily relies on English-centric high-quality preference data, which often leads to suboptimal performance in other languages. In this paper, we propose Cross-lingual Ranking Preference Optimization (CRPO), a novel framework that leverages robust preference knowledge from English to facilitate preference alignment in the target language. We design a hierarchical structure within parallel preference pairs across the target language and English to jointly optimize intra- and inter-lingual preferences, thereby enhancing language adaptation and output quality. Building on the LambdaLoss framework, CRPO goes beyond the binary comparison based optimization by providing a relative ranking signal across multiple candidate responses. Our experiments across five languages with varying resource scales demonstrate that CRPO consistently outperforms standard approaches in both instruction-following and knowledge utilization capability. Notably, the robust performance gains observed across various weighting schemes further validate the empirical effectiveness of our hierarchical design in a multilingual setup. Furthermore, our findings highlight that CRPO significantly improves both reward margins and the log-probability of desirable responses, contributing to a more stable preference manifold for cross-lingual alignment.
Anthology ID:
2026.emnlp-main.1220
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:
27855–27869
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1220/
DOI:
Bibkey:
Cite (ACL):
Seungyoon Lee, Minhyuk Kim, Jungseob Lee, and Heuiseok Lim. 2026. Language Chain in Alignment: Cross-lingual Ranking Preference Optimization. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 27855–27869, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Language Chain in Alignment: Cross-lingual Ranking Preference Optimization (Lee et al., EMNLP 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.emnlp-main.1220.pdf