KYX WMT 2026 CreoleMT System Description: A Contamination- and Orthography-Aware Evaluation for Réunion Creole to English

Yusuf Öztop


Abstract
This paper presents the KYX submission to the WMT 2026 CreoleMT shared task for Réunion Creole to English (rcf-eng). It is mostly about how such a system should be evaluated. The pair is an extreme case: 191 training pairs, a 34-sentence development set, and no standard orthography. On a benchmark this small, a single chrF++ score is easy to over-read, so we pair our system with a contamination- and orthography-aware evaluation. The system continue-trains the official baseline adapter with QLoRA and raises the raw dev score by +13.3 chrF++. But a near-duplicate audit finds that six of the 34 dev sources are paraphrases of training sentences, which the exact-match check WMT26 mandates reports as 0% overlap. After decontamination the gain is +10.0. Our official test score then comes in 0.8 chrF++ below the decontaminated estimate and 5.1 below the raw one, but our margin over the baseline falls to +3.9, so even the adjusted gain was optimistic. A data-scaling ablation traces the gain to the provided real pairs, not to synthetic data. A source-spelling stress test then shows the advantage shrinks when the input is re-spelled into equally valid variants, though at this sample size the effect is not stable. We conclude that exact-match contamination checks are not enough on tiny benchmarks, and that scores like ours should be read with care. The same caution applies to any low-resource pair with only a few dozen dev sentences. We release the system, the audit, and all data.
Anthology ID:
2026.wmt-main.190
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:
2463–2470
Language:
URL:
https://aclanthology.org/2026.wmt-main.190/
DOI:
Bibkey:
Cite (ACL):
Yusuf Öztop. 2026. KYX WMT 2026 CreoleMT System Description: A Contamination- and Orthography-Aware Evaluation for Réunion Creole to English. In Proceedings of the Eleventh Conference on Machine Translation, pages 2463–2470, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
KYX WMT 2026 CreoleMT System Description: A Contamination- and Orthography-Aware Evaluation for Réunion Creole to English (Öztop, WMT 2026)
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PDF:
https://aclanthology.org/2026.wmt-main.190.pdf