On-Policy Delta Distillation for Multilingual Math Reasoning

Byeongho Heo, Jaehui Hwang, Sangdoo Yun, Dongyoon Han


Abstract
On-Policy Distillation (OPD) is emerging as a promising alternative to reinforcement learning for LLM post-training, yet its effectiveness in multilingual settings remains underexplored. We study OPD and its advanced variant, OnPolicy Delta Distillation (OPD2 ), for mathematical reasoning in English, Korean, and Japanese. OPD2 improves OPD by using the probability gap between a post-trained teacher and its base model as the learning signal. Experiments with Qwen3 show that OPD2 consistently outperforms the original OPD, with particularly strong improvements in Korean and Japanese. We further compare multilingual OPD with English-only OPD to analyze the effect of multilingual training on OPD.
Anthology ID:
2026.oracle-main.7
Volume:
The Proceedings of the Workshop on Open Reasoning Across Cultures Languages (ORACLE)
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Leonardo Ranaldi, Giulia Pucci, Federico Ranaldi, Marco Valentino, Alexandra Birch, Fabio Massimo Zanzotto
Venues:
ORACLE | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
99–106
Language:
URL:
https://aclanthology.org/2026.oracle-main.7/
DOI:
Bibkey:
Cite (ACL):
Byeongho Heo, Jaehui Hwang, Sangdoo Yun, and Dongyoon Han. 2026. On-Policy Delta Distillation for Multilingual Math Reasoning. In The Proceedings of the Workshop on Open Reasoning Across Cultures Languages (ORACLE), pages 99–106, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
On-Policy Delta Distillation for Multilingual Math Reasoning (Heo et al., ORACLE 2026)
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PDF:
https://aclanthology.org/2026.oracle-main.7.pdf