@inproceedings{wan-etal-2026-multilingual-chain,
title = "Multilingual Chain of Thought Compression via Cross-lingual Entropy Gap",
author = "Wan, Jiarui and
Chen, Yufeng and
Zhang, Songming and
Qi, Rui and
Zhang, Xue and
Xu, Jinan and
Huang, Kaiyu",
editor = "Lee, Hung-Yi and
Dev, Sunipa and
Li, Jessy and
Elliott, Desmond",
booktitle = "Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing",
month = oct,
year = "2026",
address = "Budapest, Hungary",
publisher = "Association for Computational Linguistics",
url = "https://aclanthology.org/2026.emnlp-main.2539/",
pages = "57744--57764",
ISBN = "979-8-89176-459-0",
abstract = "Current large reasoning models (LRMs) prefer to generate verbose chain-of-thought (CoT) traces (a.k.a. the ``overthinking'' issue), especially in multilingual scenarios due to the imbalanced proficiency across different languages. However, existing studies on CoT compression focus exclusively on English and overlook language characteristics, resulting in performance degradation in multilingual scenarios. To address this issue, we develop a multilingual CoT compression method based on reinforcement learning, named \textbf{L}anguage-\textbf{a}ware \textbf{E}ntropy-based (\textbf{LAE}), which optimizes LLMs with multilingual group sampling and entropy gap-based rewards. Specifically, we extend GRPO with multilingual group sampling, where each query is jointly optimized across multiple languages. We further design a language-aware entropy-gap reward that penalizes redundant uncertainty in the thinking phase and aligns reasoning complexity across languages, enabling concise yet accurate multilingual CoT reasoning. Extensive experiments on the multilingual reasoning benchmarks MGSM, MMATH and MMMLU demonstrate that our method achieves competitive performance and generalization, compared with several strong baselines."
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<abstract>Current large reasoning models (LRMs) prefer to generate verbose chain-of-thought (CoT) traces (a.k.a. the “overthinking” issue), especially in multilingual scenarios due to the imbalanced proficiency across different languages. However, existing studies on CoT compression focus exclusively on English and overlook language characteristics, resulting in performance degradation in multilingual scenarios. To address this issue, we develop a multilingual CoT compression method based on reinforcement learning, named Language-aware Entropy-based (LAE), which optimizes LLMs with multilingual group sampling and entropy gap-based rewards. Specifically, we extend GRPO with multilingual group sampling, where each query is jointly optimized across multiple languages. We further design a language-aware entropy-gap reward that penalizes redundant uncertainty in the thinking phase and aligns reasoning complexity across languages, enabling concise yet accurate multilingual CoT reasoning. Extensive experiments on the multilingual reasoning benchmarks MGSM, MMATH and MMMLU demonstrate that our method achieves competitive performance and generalization, compared with several strong baselines.</abstract>
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%0 Conference Proceedings
%T Multilingual Chain of Thought Compression via Cross-lingual Entropy Gap
%A Wan, Jiarui
%A Chen, Yufeng
%A Zhang, Songming
%A Qi, Rui
%A Zhang, Xue
%A Xu, Jinan
%A Huang, Kaiyu
%Y Lee, Hung-Yi
%Y Dev, Sunipa
%Y Li, Jessy
%Y Elliott, Desmond
%S Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
%D 2026
%8 October
%I Association for Computational Linguistics
%C Budapest, Hungary
%@ 979-8-89176-459-0
%F wan-etal-2026-multilingual-chain
%X Current large reasoning models (LRMs) prefer to generate verbose chain-of-thought (CoT) traces (a.k.a. the “overthinking” issue), especially in multilingual scenarios due to the imbalanced proficiency across different languages. However, existing studies on CoT compression focus exclusively on English and overlook language characteristics, resulting in performance degradation in multilingual scenarios. To address this issue, we develop a multilingual CoT compression method based on reinforcement learning, named Language-aware Entropy-based (LAE), which optimizes LLMs with multilingual group sampling and entropy gap-based rewards. Specifically, we extend GRPO with multilingual group sampling, where each query is jointly optimized across multiple languages. We further design a language-aware entropy-gap reward that penalizes redundant uncertainty in the thinking phase and aligns reasoning complexity across languages, enabling concise yet accurate multilingual CoT reasoning. Extensive experiments on the multilingual reasoning benchmarks MGSM, MMATH and MMMLU demonstrate that our method achieves competitive performance and generalization, compared with several strong baselines.
%U https://aclanthology.org/2026.emnlp-main.2539/
%P 57744-57764
Markdown (Informal)
[Multilingual Chain of Thought Compression via Cross-lingual Entropy Gap](https://aclanthology.org/2026.emnlp-main.2539/) (Wan et al., EMNLP 2026)
ACL