Researchers propose Unsupervised On-Policy Self-Distillation (U-OPSD), a method that achieves post-training improvement for large language models using only the model's own generations without external supervision. The approach samples multiple rollouts to construct a pseudo-solution via majority vote, then distills a teacher distribution into prefixes of the model's longest incorrect completion.

  • U-OPSD improves base models by 8.5% and 10.7% on Qwen3 non-thinking mode at 4B and 8B scales across benchmarks like AIME24, MATH500, and AMC23.
  • It outperforms supervised methods such as OPSD by an average of 3.2% and 2.3% in non-thinking mode.
  • In thinking mode, U-OPSD matches or surpasses OPSD and GRPO, outperforming the latter by up to 1.1% at the 8B scale.

This method demonstrates that genuine self-distillation is possible through internal consistency, offering a competitive alternative to supervised training signals.