TL;DR: "ReAct" is the way all models do their internal "reasoning+acting" loop since 2023. prompt => {loop = evaluate <-> tool call(s)} => final answer It used to be dumber, before a paper from Google.
Disclaimer: this article is a reviewed, lightly edited and enriched conversation with Claude Opus 4.8.
I was learning the subject and found the answer worth sharing.
I'm not taking any credit: It helped me, hopefully it'll help you.
A ReAct-style agent is an LLM agent that interleaves reasoning and acting in a loop. The name comes from "Reasoning + Acting." It was introduced in a 2022 paper by Google Research's Brain Team, and it became one of the foundational patterns for building tool-using agents.
