From Unverifiable Domain Text to Cross-Lingual RLVR via Code-Switched Task Synthesis

Cheonbok Park, Jihwan Kim, Shinyoung Joo, Joosung Lee, Hwiyeol Jo, Jeonghoon Kim, Jaegul Choo


Abstract
Reinforcement Learning with Verifiable Rewards (RLVR) can improve reasoning in large language models, but specialized non-English domains expose a data mismatch. Raw English domain text is often available, while target-language RLVR tasks with verifiable rewards are scarce. We introduce code-switched task synthesis for cross-lingual RLVR, a data-centric approach that derives target-language and code-switched RLVR task variants from otherwise unverifiable English domain text. Using fill-in-the-middle multiple-choice QA (FIM-MCQA) as a seed task format, we synthesize automatically verifiable tasks from domain passages and reshape them into cross-lingual variants. These variants preserve the same evidence-answer relation but change how English and target-language evidence are presented during RLVR. On Korean medical benchmarks and cybersecurity benchmarks across four target languages, code-switched training outperforms matched monolingual and bilingual-mixture baselines on average target-language performance while maintaining comparable English performance. Additional analyses provide evidence of better target-language input understanding and stronger cross-lingual alignment in both model outputs and internal representations. These results suggest that code-switched training helps target-language inputs access domain reasoning learned more strongly in English.
Anthology ID:
2026.emnlp-main.1375
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
31382–31413
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1375/
DOI:
Bibkey:
Cite (ACL):
Cheonbok Park, Jihwan Kim, Shinyoung Joo, Joosung Lee, Hwiyeol Jo, Jeonghoon Kim, and Jaegul Choo. 2026. From Unverifiable Domain Text to Cross-Lingual RLVR via Code-Switched Task Synthesis. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 31382–31413, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
From Unverifiable Domain Text to Cross-Lingual RLVR via Code-Switched Task Synthesis (Park et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.1375.pdf