RLHF — How Reinforcement Learning Aligns Language Models
The single most consequential application of reinforcement learning today isn't a game or a robot — it's the technique that turned raw, unruly language models into helpful assistants. Reinforcement learning from human feedback solved the problem that you can't write a reward function for "be helpful, honest, and harmless," so you learn one from human judgments instead. This post connects everything in the series to the method that made modern AI assistants possible.
The most consequential use of RL today: you can't write a reward for 'be helpful, honest, harmless', so RLHF learns one from human preference comparisons and optimizes with PPO. The three-stage pipeline, the KL constraint against reward hacking, and the series' capstone — plus its limits (sycophancy, bias).