Findings of the WMT26 Multilingual Instruction Shared Task: Small Models Are Not Yet Polyglots

Patricia Schmidtova, Ekaterina Artemova, Seth Aycock, Niyati Bafna, Shobhit Banga, Manmeet Kaur, Tom Kocmi, Philipp Koehn, Danni Liu, Nam Luu, Sara Papi, Beatrice Savoldi, Mariya Shmatova, Hanuman Sidh, Evfrosiniya Zerminova, Vilem Zouhar, Maike Züfle, Pinzhen Chen


Abstract
We present the findings of the WMT26 Multilingual Instruction Shared Task (MIST), evaluating small (=10B parameter) open-weight language models across 24 languages on three sub-tasks: context-based QA, cross-lingual summarization, and open-ended generation. Submissions from eight teams explore fine-tuning, knowledge distillation, and prompt engineering. Our findings demonstrate that small models are not yet polyglots: while leading systems perform well on high-resource languages, performance drops sharply on low-resource varieties, and comprehension degrades significantly when transferring across non-English language pairs. In open-ended generation, human evaluation and automatic rule-based verification exhibit strong overall rank correlation (0.79) but diverge locally at the top: human evaluators favor distilled pipelines with superior fluency and cross-lingual equity, whereas automatic verifiers reward concise prompt-engineered systems. Furthermore, multi-stage pipelines suffer from prompt-language inertia on cross-lingual instructions, and summarization exhibits severe English leakage unless penalized by language gating. Finally, while baseline fluency is largely achieved by modern small models, multi-constraint instruction following and unanswerable question refusal remain the primary performance bottlenecks. We release all test sets, system outputs, human judgments, and evaluation code under a permissive license.
Anthology ID:
2026.wmt-main.50
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:
1024–1045
Language:
URL:
https://aclanthology.org/2026.wmt-main.50/
DOI:
Bibkey:
Cite (ACL):
Patricia Schmidtova, Ekaterina Artemova, Seth Aycock, Niyati Bafna, Shobhit Banga, Manmeet Kaur, Tom Kocmi, Philipp Koehn, Danni Liu, Nam Luu, Sara Papi, Beatrice Savoldi, Mariya Shmatova, Hanuman Sidh, Evfrosiniya Zerminova, Vilem Zouhar, Maike Züfle, and Pinzhen Chen. 2026. Findings of the WMT26 Multilingual Instruction Shared Task: Small Models Are Not Yet Polyglots. In Proceedings of the Eleventh Conference on Machine Translation, pages 1024–1045, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Findings of the WMT26 Multilingual Instruction Shared Task: Small Models Are Not Yet Polyglots (Schmidtova et al., WMT 2026)
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https://aclanthology.org/2026.wmt-main.50.pdf