Dev.to
6/29/2026

The original title is about ReAct architecture for AI agents, explaining the separation of message layer from internal decision state.
Original: ReAct Inside — From Message to State, Understanding How AI Agents Really Work
Short summary
ReAct separates the agent's communication protocol (Message layer) from its internal decision state (Thought/Action/Observation). Critically, Thought and Action form a single Assistant message, while Observation must come from external tools—preventing models from fabricating results. This ensures agents ground decisions in reality rather than self-generated hallucinations.
- •ReAct is a state machine pattern enabling agents to reason and act iteratively, not just a prompt format with three fields
- •Messages (User/Assistant/Tool) implement the communication protocol; Thought/Action/Observation describe internal decision stages
- •Tools generate Observations to prevent agents from hallucinating results
Generated with AI, which can make mistakes.
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