MITRA-MT: Continued Pretraining, Parallel Corpus Mining, and Multi-Directional Machine Translation for Sanskrit, Tibetan, and Buddhist Chinese

Buddhist literature is preserved in a network of classical languages, above all Sanskrit, Pāli, Buddhist Chinese, and Tibetan, for which machine translation support remains limited, and largely restricted to translation into English. In order to address this shortcoming, we present three connected contributions. First, we release MITRA-parallel v2, a corpus of 1.69 million automatically aligned parallel records (2.34 million segment pairs) between Sanskrit, Tibetan, and Buddhist Chinese, mined with an embedding-based span-mining pipeline. Second, we present MITRA-MT, a domain-adapted large language model built by continued pretraining of Qwen3.5-9B on a 22.6-billion-token corpus of classical Asian languages and related modern material, followed by a lightweight translation fine-tune and preference optimization. Third, we introduce a multi-directional evaluation suite covering 17 translation directions at sentence level (ten of them also at paragraph level), including cross-classical directions (Sanskrit↔Tibetan, Sanskrit↔Chinese, Tibetan↔Chinese) and from Tibetan into seven modern languages beyond English. On this suite, MITRA-MT outperforms all open baselines, including instruction-tuned LLMs up to 122B parameters and dedicated MT systems, on all directions, and matches commercial references on the large majority of directions when evaluated via chrF, with the largest margins for translation into Tibetan, Sanskrit, and Classical Chinese. We release the parallel corpus, the evaluation data, and the model weights.

Accepted at the Eleventh Conference on Machine Translation (WMT 2026), colocated with EMNLP 2026 in Budapest, Hungary, October 28–29, 2026.

Recommended citation: Nehrdich, S., & Keutzer, K. (2026). "MITRA-MT: Continued Pretraining, Parallel Corpus Mining, and Multi-Directional Machine Translation for Sanskrit, Tibetan, and Buddhist Chinese." In Proceedings of the Eleventh Conference on Machine Translation (WMT 2026), Budapest, Hungary.
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