Trust Region Masking for Long-Horizon LLM Reinforcement Learning

Authors: Yingru Li, Jiacai Liu, Jiawei Xu, Yuxuan Tong, Ziniu Li, Baoxiang Wang 📄 arXiv: https://arxiv.org/abs/2512.23075 📊 Slides: trust_region_masking_slides_yingru.pdf 🔧 PR #4544: feat: trust region sequence masking Abstract Policy gradient methods for large language models optimize a surrogate objective computed from samples of a rollout policy $\pi_{\mathrm{roll}}$. When…