CAST: Non-Privileged Clipped Asymmetric Self-Teaching with Advantage Flipping for GRPO

In three linesCAST is an answer-free self-distillation method for GRPO (Group Relative Policy Optimization). It uses a stop-gradient self-teacher to shape token-level advantages by trajectory correctness, with bidirectional advantage sign reversal and bounded advantages for zero-variance groups. Improves mathematical reasoning performance.

Summary generated by Claude — human-verified