Jiutian-MT-8B at WMT26: Faithfulness-First Training for Chinese-Southeast Asian Translation

Meng Su, Jian Liu, Youxuan Fang


Abstract
This paper describes Jiutian-MT-8B, our submission to the WMT 2026 Chinese-Southeast Asian Multilingual Machine Translation shared task. The system adapts the 8-billion-parameter Jiutian-8B-Instruct checkpoint to fourteen translation directions between Chinese and Thai, Vietnamese, Lao, Burmese, Khmer, Indonesian, and Malay. We formulate translation as a tightly controlled instruction-following task and use a four-stage full-parameter training recipe: (i) supervised multilingual adaptation on released parallel data, (ii) faithfulness first confidence-gated multi-pair preference alignment (F2MTA), (iii) direction-coupled, evidence-filtered self-training from task monolingual data, and (iv) a final clean-data calibration stage. The preference stage uses a partial order: a candidate must gain source adequacy without materially sacrificing target fluency, rather than merely win a scalarized quality score. The recipe directly updates all Jiutian-8B parameters with sharded bf16 training while retaining authentic data anchors to limit synthetic-data drift. The official test set is blind at the time of writing; numerical main results are therefore deliberately unreported. We nevertheless specify the data scope, translation interface, training protocol, and evaluation plan needed to complete the report once official scores are returned.
Anthology ID:
2026.wmt-main.181
Volume:
Proceedings of the Eleventh Conference on Machine Translation
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Barry Haddow, Tom Kocmi, Philipp Koehn, Christof Monz
Venues:
WMT | WS
SIG:
SIGMT
Publisher:
Association for Computational Linguistics
Note:
Pages:
2374–2378
Language:
URL:
https://aclanthology.org/2026.wmt-main.181/
DOI:
Bibkey:
Cite (ACL):
Meng Su, Jian Liu, and Youxuan Fang. 2026. Jiutian-MT-8B at WMT26: Faithfulness-First Training for Chinese-Southeast Asian Translation. In Proceedings of the Eleventh Conference on Machine Translation, pages 2374–2378, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Jiutian-MT-8B at WMT26: Faithfulness-First Training for Chinese-Southeast Asian Translation (Su et al., WMT 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.wmt-main.181.pdf