R1-T1: Fully Incentivizing Translation Capability in LLMs via Reasoning
  Learning
Authors: name: Minggui He, name: Yilun Liu, name: Shimin Tao, name: Yuanchang Luo, name: Hongyong Zeng, name: Chang Su, name: Li Zhang, name: Hongxia Ma, name: Daimeng Wei, name: Weibin Meng, name: Hao Yang, name: Boxing Chen, name: Osamu Yoshie

Despite recent breakthroughs in reasoning-enhanced large language models
(LLMs) like DeepSeek-R1, incorporating inference-time reasoning into machine
translation (MT), where human translators naturally employ structured,
multi-layered reasoning chain-of-thoughts (CoTs), is yet underexplored.
Existing methods either design a fixed CoT tailored for a specific MT sub-task
(e.g., literature translation), or rely on synthesizing CoTs unaligned with
humans and supervised fine-tuning (SFT) prone to catastrophic forgetting,
limiting their adaptability to diverse translation scenarios. This paper
introduces R1-Translator (R1-T1), a novel framework to achieve inference-time
reasoning for general MT via reinforcement learning (RL) with human-aligned
CoTs comprising six common patterns. Our approach pioneers three innovations:
(1) extending reasoning-based translation beyond MT sub-tasks to six languages
and diverse tasks (e.g., legal/medical domain adaptation, idiom resolution);
(2) formalizing six expert-curated CoT templates that mirror hybrid human
strategies like context-aware paraphrasing and back translation; and (3)
enabling self-evolving CoT discovery and anti-forgetting adaptation through RL
with KL-constrained rewards. Experimental results indicate a steady translation
performance improvement in 21 languages and 80 translation directions on
Flores-101 test set, especially on the 15 languages unseen from training, with
its general multilingual abilities preserved compared with plain SFT.