OISD: On-Policy Internal Self-Distillation of Language Models

Xinyu Liu, Darryl C. Jacob, Yang Zhou, Jindong Wang, Pan He


Abstract
Recent reinforcement learning (RL) post-training approaches primarily optimize the final output policy using sparse outcome-level rewards, while largely overlooking predictive signals encoded in intermediate representations. In this paper, we introduce a new paradigm called on-policy internal self-distillation and propose the OISD framework, which improves reasoning by transferring on-policy predictive signals from the final layer to intermediate representations. During rollout and Group Relative Policy Optimization (GRPO) optimization, the final layer acts as both the policy and a detached internal teacher for selected intermediate layers, which are guided to align with it through two complementary mechanisms: logit alignment, which transfers high-level reasoning behaviors (how to think), and attention alignment, which enforces consistent attention patterns (where to look) from the final layer to the selected intermediate layer, both without requiring external privileged information. Our OISD, together with GRPO, employs signed advantage-weighted Jensen–Shannon alignment to distill informative intermediate representations while preserving policy consistency under a unified acting policy. Experimental results demonstrate the effectiveness of OISD, with substantial and consistent improvements over strong reasoning RL baselines across four mathematical reasoning tasks.
Anthology ID:
2026.findings-emnlp.1323
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
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
28049–28065
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1323/
DOI:
Bibkey:
Cite (ACL):
Xinyu Liu, Darryl C. Jacob, Yang Zhou, Jindong Wang, and Pan He. 2026. OISD: On-Policy Internal Self-Distillation of Language Models. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 28049–28065, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
OISD: On-Policy Internal Self-Distillation of Language Models (Liu et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.1323.pdf