POPE: Learning to Reason on Hard Problems via Privileged On-Policy Exploration https://arxiv.org/abs/2601.18779 https://www.alphaxiv.org/ru/overview/2601.18779 https://github.com/CMU-AIRe/POPE https://blog.ml.cmu.edu/2025/11/26/how-to-explore-to-scale-rl-training-of-llms-on-hard-problems/