TREK Rescues GRPO on Hard Prompts Outside the Student's On-Policy Support

arXiv·medium signal

Group Relative Policy Optimization stalls on hard prompts whose correct reasoning modes the student never samples; TREK routes teacher distillation to explore those modes first, then reinforces to refine them. It is a practical recipe for RL post-training that keeps improving on the hardest reasoning tasks rather than plateauing. Directly relevant to teams hitting GRPO ceilings on difficult problem sets.