Opening — Why this matters now Reinforcement learning has always had an uncomfortable secret: most of the intelligence is smuggled in through the reward function. We talk about agents learning from experience, but in practice, someone—usually a tired engineer—decides what “good behavior” numerically means. As tasks grow longer-horizon, more compositional, and more brittle to specification errors, this arrangement stops scaling. ...
If you’ve ever watched a web agent swing from elegant reasoning to face‑plants on basic facts, you’ve met the limits of outcome‑only training. Atom‑Searcher proposes a simple but radical fix: stop treating the whole reasoning trace as one monolith. Instead, break it down into Atomic Thoughts—the minimal, functional units of reasoning—and supervise them directly with a Reasoning Reward Model (RRM). Then blend those process‑level rewards with the final answer score using a decaying curriculum. The result? More stable training, deeper search behavior, and better generalization across in‑ and out‑of‑domain QA. ...