PAMT: Process-Aligned Reinforcement Learning for Multi-Domain Machine Translation

Yongshi Ye, Biao Fu, Chongxuan Huang, Yidong Chen, Xiaodong Shi


Abstract
Multi-domain machine translation (MDMT) requires more than fluent generation: it demands domain-sensitive translation decisions such as domain disambiguation, terminology control, and stylistic adaptation. Large reasoning models (LRMs) make such decisions explicit through intermediate translation steps, but our analysis across 15 domains and four translation directions shows that this explicit reasoning is double-edged: it improves long-form and high-difficulty translation, yet often drifts in terminology-intensive and stylistically constrained settings. We trace this failure to a credit-assignment bottleneck: existing methods optimize final outputs or coarse trajectories, but cannot identify which translation steps actually help the final translation. To address this, we propose PAMT, a process-aligned training framework that combines cold-start domain-aware Long-CoT supervision with reinforcement learning. PAMT uses sequence-level format and outcome rewards for the final translation, together with a step-level process reward that measures how much each explicit translation step increases the likelihood of the reference translation. Across two backbones, PAMT improves over base models, outperforms MT-specialized baselines on average, and remains competitive with strong LLMs/LRMs across in-domain, OOD, and multilingual settings.
Anthology ID:
2026.emnlp-main.2550
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:
57977–58001
Language:
URL:
https://aclanthology.org/2026.emnlp-main.2550/
DOI:
Bibkey:
Cite (ACL):
Yongshi Ye, Biao Fu, Chongxuan Huang, Yidong Chen, and Xiaodong Shi. 2026. PAMT: Process-Aligned Reinforcement Learning for Multi-Domain Machine Translation. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 57977–58001, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
PAMT: Process-Aligned Reinforcement Learning for Multi-Domain Machine Translation (Ye et al., EMNLP 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.emnlp-main.2550.pdf