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On-policy distillation trains a student using contexts sampled from its own evolving policy while learning from a stronger teacher, addressing the distribution mismatch that limits conventional offline supervised fine-tuning. The approach offers a compelling bridge between imitation learning and reinforcement learning, but its benefits depend heavily on objective design, teacher quality, and stable optimization.
- Student-generated states expose the teacher to the errors and failure modes the student actually encounters, reducing the train–inference mismatch of teacher-forced data.
- Distillation objectives must carefully manage token-level probability matching, sequence-level quality, and exploration; naïve KL optimization can over-constrain the student or propagate teacher biases.
- Because the student’s sampling distribution changes during training, evaluation, rollout quality, and optimization stability become central engineering concerns rather than implementation details.