ReAct: Reason + Act Pattern
Thought -> Action -> Observation -> Thought ... — the loop that powers most modern multi-step agents.
What Is ReAct?
ReAct stands for Reason + Act. It is the canonical pattern for multi-step LLM agents — published by Yao et al. in 2022 and still the foundation of most modern agents.
The Loop
At each step, the agent emits three things:
- Thought — what to do next, in natural language
- Action — which tool to call and with what arguments
- Observation — the tool result, fed back in
Repeat until the agent emits Final Answer.