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Public story · 2026-08-24 · high
Each section cites the paper, textbook, or codebase behind it, sourcing that keeps RL fine-tuning choices from becoming pure guesswork.
Why now: Published as of August 24, 2026, it's the single document I'd point someone to before they touch GRPO code, since it traces the sources instead of skipping to the algorithm.
Cameron Wolfe published a single document on reinforcement learning for large language models. It runs from REINFORCE to the methods behind frontier training, on his newsletter Deep Learning Focus. The throughline explains why GRPO-family training behaves the way it does, past the mechanics of the algorithm itself.
Wolfe credits the paper, textbook, or codebase behind each section, tying theory to code instead of leaving the lineage scattered across sources. RL fine-tuning hyperparameters often get set by guesswork because that lineage is hard to find in one place.
The post starts at first principles, then walks through the policy gradient algorithms behind current training runs. It moves into reasoning, agents, token efficiency, and reliability, with each section linking a longer writeup on that piece.
Wolfe names his sources directly: Nathan Lambert's RLHF Book, Sutton and Barto's textbook, and OpenAI's Spinning Up guide. He also cites Lilian Weng's notes on policy gradients and the TRL and OpenInstruct codebases.
Each link below shares sources, entities, or timing with this story.
Lilian Weng works at OpenAI / Shared entities / Same source domain / Earlier coverage
Linked by a graph relationship (Lilian Weng works at OpenAI); both cover Cameron Wolfe, GRPO, OpenAI; reported by the same outlet (cameronrwolfe.substack.com).
Lilian Weng works at OpenAI / Shared entities / Shared topic / Earlier coverage / Tension
Linked by a graph relationship (Lilian Weng works at OpenAI); both cover LLMs, OpenAI; overlapping topics (cameron, llms).
Lilian Weng works at OpenAI / Shared entity: OpenAI / Shared topic / Earlier coverage
Linked by a graph relationship (Lilian Weng works at OpenAI); both cover OpenAI; overlapping topics (actually, agent, policy).
Lilian Weng works at OpenAI / Shared entities / Earlier coverage
Linked by a graph relationship (Lilian Weng works at OpenAI); both cover Lilian Weng, OpenAI; earlier Lilian Weng coverage from 2026-07-28.
Linked by a graph relationship (Lilian Weng works at OpenAI); both cover LLMs, OpenAI; earlier LLMs coverage from 2026-07-27.
Hugging Face released TRL / Shared entities / Earlier coverage
Linked by a graph relationship (Hugging Face released TRL); both cover LLMs, OpenAI; earlier LLMs coverage from 2026-07-25.
Lilian Weng works at OpenAI / Shared entities / Earlier coverage
Linked by a graph relationship (Lilian Weng works at OpenAI); both cover LLMs, OpenAI; earlier LLMs coverage from 2026-05-20.
Linked by a graph relationship (Lilian Weng works at OpenAI); both cover LLMs, OpenAI; earlier LLMs coverage from 2026-05-02.