Choosing the Right Language Mode at Inference Time for Multilingual Reliability

Ekata Mitra, Ameeta Agrawal


Abstract
Multilingual large language models often struggle to reason in low- to mid-resource languages. Prior work has shown that translation can improve multilingual reasoning by helping models access stronger English-centric representations. This raises a central question: how much translation is needed for multilingual large language models to reason reliably, and when does additional translation instead trigger interference and overconfidence? Using LLaMA and Qwen models, we conduct extensive experiments that vary both text scope and language mode (target-only, English-only, and bilingual) to evaluate accuracy and reliability. Our results reveal a clear trade-off: English context often improves understanding and helps recover errors caused by non-English comprehension, yet adding redundant bilingual context can intensify interference. To address this trade-off, we propose Reliability-Aware Adaptive Inference (RAAI), a training-free test-time framework that (i) performs ECE-aware routing and prompt fusion and (ii) uses a mid-layer Risk Index (RI) to gate sequential reasoning, allocating extra compute only when it is likely to help while suppressing harmful bilingual redundancy. Across two model families, RAAI improves accuracy by 25 to 37.7 points in low-resource languages and reduces calibration error by about 3 to 6 points, with the largest gains appearing in the lowest-resource language tiers.
Anthology ID:
2026.findings-emnlp.89
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
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SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
1821–1839
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.89/
DOI:
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Cite (ACL):
Ekata Mitra and Ameeta Agrawal. 2026. Choosing the Right Language Mode at Inference Time for Multilingual Reliability. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 1821–1839, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Choosing the Right Language Mode at Inference Time for Multilingual Reliability (Mitra & Agrawal, Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.89.pdf