Clipped, Grouped, and Decoupled: Why RL Fine-Tuning Still Behaves Like a Negotiation With Chaos
Training a reasoning model sounds wonderfully modern until the model discovers that “being correct” and “looking correct enough to satisfy the reward” are not the same career path. That is the quiet problem behind reinforcement learning fine-tuning for large language models. The research conversation often treats methods like PPO, GRPO, and DAPO as a sequence of upgrades: first the classic algorithm, then the critic-free group method, then the decoupled-and-dynamically-sampled variant with a nicer acronym. Very tidy. Unfortunately, models do not read product positioning decks. ...