SIGNALAI·May 22, 2026, 4:00 AMSignal75Medium term

Post-Training is About States, Not Tokens: A State Distribution View of SFT, RL, and On-Policy Distillation

Source: arXiv cs.LG

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Post-Training is About States, Not Tokens: A State Distribution View of SFT, RL, and On-Policy Distillation

arXiv:2605.22731v1 Announce Type: new Abstract: Large language model post-training methods such as supervised fine-tuning (SFT), reinforcement learning (RL), and distillation are often analyzed through their loss functions: maximum likelihood, policy gradients, forward KL, reverse KL, or related objective-level variants. We study a complementary factor: the state distribution on which supervision is applied. For an autoregressive policy, a state is a prompt plus generated prefix. SFT trains on fixed dataset states, while RL and on-policy distillation (OPD) train on states induced by the curren

Why this matters
Why now

This research emerges as the field of large language model training and post-training methods is rapidly advancing, with a focus on optimizing performance and efficiency.

Why it’s important

A deeper understanding of state distribution in LLM post-training could lead to more effective and robust AI models, impacting a wide range of applications and future AI development.

What changes

This research shifts the analytical lens from solely loss functions to also include state distributions, offering a complementary perspective for analyzing and improving post-training methods.

Winners
  • · AI researchers
  • · Large language model developers
  • · Companies deploying LLMs
Losers
  • · Inefficient LLM training methodologies
Second-order effects
Direct

Improved understanding and optimization of supervised fine-tuning, reinforcement learning, and distillation for large language models.

Second

Development of more stable, performant, and generalizable AI agents and applications.

Third

Accelerated progress towards more autonomous and human-like AI systems capable of complex reasoning and interaction.

Editorial confidence: 90 / 100 · Structural impact: 55 / 100
Original report

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Read at arXiv cs.LG
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