Towards On-Policy SFT: Distribution Discriminant Theory and its Applications in LLM Training
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Abstract (arXiv)
Supervised fine-tuning (SFT) is computationally efficient but often yields inferior generalization compared to reinforcement learning (RL). This gap is primarily driven by RL's use of on-policy data. We propose a framework to bridge this chasm by enabling On-Policy SFT. We first present textbftextitDistribution Discriminant Theory (DDT), which explains and quantifies the alignment between data and the model-induced distribution. Leveraging DDT, we introduce two complementary techniques: (i) textbftextitIn-Distribution Finetuning (IDFT), a loss-level method to enhance generalization ability of SFT, and (ii) textbftextitHinted Decoding, a data-level technique that can re-align the training corpus to the model's distribution. Extensive experiments demonstrate that our framework achieves generalization performance surpassing prominent offline RL algorithms, including DPO and SimPO, while maintaining the efficiency of an SFT pipeline. The proposed framework thus offers a practical alternative in domains where RL is infeasible. We open-source the code here: https://github.com/zhangmiaosen2000/Towards-On-Policy-SFT
Key facts. Cited by 11 papers in the map (data through 14 Oct 2026). Builds on 35 of its 47 references that are in the map. First posted on arXiv 12 Feb 2026.
Builds on
35 of 47 references.
References · 35
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Citing papers per year: 2026: 11.
11 papers.
- 2026A Survey of On-Policy Distillation for Large Language Modelscited by 163
- 2026Filter, Then Reweight: Rethinking Optimization Granularity in On-Policy Distillationcited by 32
- 2026Rethinking Generalization in Reasoning SFT: A Conditional Analysis on Optimization, Data, and Model Capabilitycited by 14
- 2026Learning from Your Own Mistakes: Constructing Learnable Micro-Reflective Trajectories for Self-Distillationcited by 4
- 2026PriFT: Prior-Support Guided Supervised Fine-Tuningcited by 2
- 2026ProteinOPD: Towards Effective and Efficient Preference Alignment for Protein Designcited by 0
- 2026Recovering General Capabilities via Uncertainty-Calibrated Multi-Teacher On-Policy Distillationcited by 0
- 2026On-Policy or Off-Policy Learning? A Systematic Study of Distillation Dynamicscited by 0
- 2026PG-SFT: Balancing Capability Acquisition and Retention in Offline Agent Fine-Tuningcited by 0
- 2026Learning What to Imitate: Entropy-Aware Distribution Mixingcited by 0
- 2026What Should SFT Learn? Conditional Information Gain for Generalizable Post-Trainingcited by 0
- 2026What Should SFT Learn? Conditional Information Gain for Generalizable Post-Training9 Oct 2026
- 2026Learning What to Imitate: Entropy-Aware Distribution Mixing5 Oct 2026
- 2026PG-SFT: Balancing Capability Acquisition and Retention in Offline Agent Fine-Tuning1 Oct 2026
- 2026On-Policy or Off-Policy Learning? A Systematic Study of Distillation Dynamics28 Sep 2026
- 2026Recovering General Capabilities via Uncertainty-Calibrated Multi-Teacher On-Policy Distillation27 Aug 2026
- 2026Learning from Your Own Mistakes: Constructing Learnable Micro-Reflective Trajectories for Self-Distillation17 Jun 2026
- 2026PriFT: Prior-Support Guided Supervised Fine-Tuning8 Jun 2026
- 2026Filter, Then Reweight: Rethinking Optimization Granularity in On-Policy Distillation1 Jun 2026
- 2026ProteinOPD: Towards Effective and Efficient Preference Alignment for Protein Design11 May 2026
- 2026Rethinking Generalization in Reasoning SFT: A Conditional Analysis on Optimization, Data, and Model Capability8 Apr 2026
- 2026A Survey of On-Policy Distillation for Large Language Models1 Apr 2026
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