Policy-Gradient-to-Ppo

From Policy Gradient to PPO — Part 2: Trust Regions, PPO, and GRPO

How trust regions stabilize policy optimization, why PPO became the default for RLHF, and how GRPO eliminates the critic entirely.

From Policy Gradient to PPO — Part 1: Foundations

MDPs, value functions, the REINFORCE algorithm, actor-critic methods, and generalized advantage estimation — the RL foundations you need before understanding RLHF.