LocQE: Principled Domain Adaptation for Localisation Quality Estimation by Leveraging Post-Edits

Kathy Haemmerl, Gabriel Bretschner, Joern Wuebker


Abstract
Learned quality estimation (QE) models such as COMETKiwi are widespread and work well for general machine translation evaluation. However, they are known to struggle on unseen domains, limiting their performance in a real-world localisation context. We show that they are insensitive to some important factors in localisation, such as whether numbers are translated accurately, or even whether the correct number of spaces and punctuation are preserved in a translation. Further, a key capability for optimisation of machine translation is the ability of QE models to accurately rank different translations of a single segment, which suffers significantly from the domain transfer. In the absence of large-scale direct assessment data, we propose principled fine-tuning approaches to reduce the domain gap with even small amounts of post-editing data. Using a multi-task fine-tuning approach and a simple tokeniser intervention, we create a QE model which proves markedly better at distinguishing preferred post-edits from rejected initial translations in a localisation context. We show that preferences and artificial continuous scores stabilise each other, and argue that to calibrate metrics both in terms of their absolute scores and comparisons between translation of the same source, both types of signal are needed.
Anthology ID:
2026.wmt-main.12
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:
199–219
Language:
URL:
https://aclanthology.org/2026.wmt-main.12/
DOI:
Bibkey:
Cite (ACL):
Kathy Haemmerl, Gabriel Bretschner, and Joern Wuebker. 2026. LocQE: Principled Domain Adaptation for Localisation Quality Estimation by Leveraging Post-Edits. In Proceedings of the Eleventh Conference on Machine Translation, pages 199–219, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
LocQE: Principled Domain Adaptation for Localisation Quality Estimation by Leveraging Post-Edits (Haemmerl et al., WMT 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.wmt-main.12.pdf