Post-hoc Correction of Machine Translation Error Span Predictions

Benjamin Pong


Abstract
This paper presents an unsupervised quality estimation metric for machine translation that combines both neural and LLM models to identify and classify error spans for machine translations. As a submission to the WMT2026 Automated Evaluation Shared Task 1, this system builds on XCOMET-XL by applying offsets to the logits produced by the neural metric, post-hoc, to address the long-tailed probability problem, and uses an LLM as a second-stage to refine these predictions. Results show that XCOMET-XL with logits offset alone shows a boost in recall and character-level F1 scores for error span classifications across multiple language pairs, surpassing state-of-the-art baseline (i.e XCOMET-XL) and LLM-based approaches. This system also comprises a second-stage where a reasoning LLM-judge is employed to audit the error spans predicted by the logits-adjusted XCOMET metric, whose goal is to reduce spurious error classifications and improve overall precision. Results show that using LLM-judge to refine error spans provides no measurable improvements over predictions of the logits-adjusted XCOMET metric.
Anthology ID:
2026.wmt-main.106
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:
1723–1729
Language:
URL:
https://aclanthology.org/2026.wmt-main.106/
DOI:
Bibkey:
Cite (ACL):
Benjamin Pong. 2026. Post-hoc Correction of Machine Translation Error Span Predictions. In Proceedings of the Eleventh Conference on Machine Translation, pages 1723–1729, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Post-hoc Correction of Machine Translation Error Span Predictions (Pong, WMT 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.wmt-main.106.pdf