Diagnose, Then Repair: A Two-Stage MQM-Guided Post-Editing Framework for Domain-Specific Machine Translation

Ji Hun Wang, Siyu Wu


Abstract
LLM-based machine translation evaluation can closely match human judgments, but in practice it remains largely diagnostic, with the signals rarely translating into direct quality improvements under real production constraints. We propose a two-stage, evaluator-guided automatic post-editing framework that turns MQM-style evaluation into targeted repairs: a retrieval-augmented LLM evaluator outputs structured, span-level MQM diagnoses under an explicit edit contract, and a separate LLM post-editor applies minimal edits restricted to those diagnoses. This separation improves controllability and reduces paraphrastic drift compared to one-stage "judge-and-refine” baselines. In a systematic study involving seven LLMs spanning three model providers and seven languages, our best configuration consistently improves both reference-based COMET and CometKiwi scores over one-stage post-edit methods, while the evaluator’s error spans and severities show strong agreement with human MQM annotations and human editor preferences.
Anthology ID:
2026.acl-industry.115
Volume:
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (ACL 2026)
Month:
July
Year:
2026
Address:
San Diego, California, USA
Editors:
Yunyao Li, Georg Rehm, Mei Tu
Venue:
ACL
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
1683–1698
Language:
URL:
https://preview.aclanthology.org/ingest-acl/2026.acl-industry.115/
DOI:
Bibkey:
Cite (ACL):
Ji Hun Wang and Siyu Wu. 2026. Diagnose, Then Repair: A Two-Stage MQM-Guided Post-Editing Framework for Domain-Specific Machine Translation. In Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (ACL 2026), pages 1683–1698, San Diego, California, USA. Association for Computational Linguistics.
Cite (Informal):
Diagnose, Then Repair: A Two-Stage MQM-Guided Post-Editing Framework for Domain-Specific Machine Translation (Wang & Wu, ACL 2026)
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PDF:
https://preview.aclanthology.org/ingest-acl/2026.acl-industry.115.pdf