OSPD: On-Policy Self-Distillation for Persona-Consistent Dialogue

Rui Xu, Yikai Zhang, Aili Chen, Zicheng Zhao, Xu Yinghui, Libo Wu


Abstract
Maintaining persona consistency across multi-turn dialogues remains a core challenge for role-playing language models. Off-policy distillation from external teachers incurs distribution mismatch that compounds across dialogue turns, while reinforcement learning struggles with reward ambiguity inherent in subjective persona fidelity. We propose OSPD, an on-policy self-distillation framework where the same model serves as both teacher and student under asymmetric information: the teacher receives a complete character profile while the student sees only a brief summary, and the student generates trajectories from its own policy. We find that teacher confidence in role-playing dialogue exhibits a bimodal structure—sharply peaked at character-critical tokens yet diffuse at generic utterances—and introduce role-aware divergence switching to match this structure. A progressive trait masking curriculum further forces staged internalization of character knowledge along semantic dimensions. Experiments on CharacterBench, CharacterEval, and SocialBench show that OSPD substantially improves persona consistency over supervised fine-tuning and multi-turn RL baselines, without requiring any external teacher or reward model.
Anthology ID:
2026.emnlp-main.2105
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:
47912–47933
Language:
URL:
https://aclanthology.org/2026.emnlp-main.2105/
DOI:
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Cite (ACL):
Rui Xu, Yikai Zhang, Aili Chen, Zicheng Zhao, Xu Yinghui, and Libo Wu. 2026. OSPD: On-Policy Self-Distillation for Persona-Consistent Dialogue. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 47912–47933, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
OSPD: On-Policy Self-Distillation for Persona-Consistent Dialogue (Xu et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.2105.pdf