Hao Bai

Enabling Token-wise Importance Sampling in Off-Policy RLVR with Proximal KL Regularization

Off-policy data in reinforcement learning with verifiable rewards (RLVR) can arise from asynchronous generation, rollout-training mismatch, and response reuse. Token-wise importance weighting avoids multiplying likelihood ratios across a response but generally biases policy gradients. We prove that, under coverage and...