Loong: A Human-Like Long Document Translation Agent with Observe-and-Act Adaptive Context Selection

Yutong Wang, Xuebo Liu, Derek F. Wong, Zhilin Li, Rongqing Jiang, Min Zhang, Shimin Tao, Daimeng Wei, Min Zhang


Abstract
Document-level translation remains one of the most challenging tasks for large language models, which are constrained by limited context windows that impede global cohesion, while simultaneously suffering from redundant contextual information that degrades translation quality. To address this, we propose a human-like long document translation agent called Loong, which leverages a 3E memory module (Essence-Exemplar-Entity) to store summaries, sentence pairs, and entity records as historical context. Instead of passively attending to all history, Loong performs deep reasoning to adaptively identify the optimal context for translation guidance. Loong optimizes its context policy through reinforcement learning, utilizing preference data derived from its own sampled observe-and-act reasoning trajectories. Empirical evaluations demonstrate that Loong achieves substantial translation quality improvements in English ⇔ Chinese, German, and French directions, with average gains of up to 13.0 points across the three evaluation metrics. Furthermore, Loong exhibits strong generalization across domains and robustness against contextual noise, while maintaining remarkable stability in ultra-long document translation. Our code is freely available at https://github.com/YutongWang1216/LoongDocMT.
Anthology ID:
2026.emnlp-main.329
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
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Pages:
7574–7600
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URL:
https://aclanthology.org/2026.emnlp-main.329/
DOI:
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Cite (ACL):
Yutong Wang, Xuebo Liu, Derek F. Wong, Zhilin Li, Rongqing Jiang, Min Zhang, Shimin Tao, Daimeng Wei, and Min Zhang. 2026. Loong: A Human-Like Long Document Translation Agent with Observe-and-Act Adaptive Context Selection. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 7574–7600, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Loong: A Human-Like Long Document Translation Agent with Observe-and-Act Adaptive Context Selection (Wang et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.329.pdf