ReAct Agent Pattern — AI Glossary

Reference details

Related terms

• Agentic Loop
• Tool Use
• Chain of Thought (CoT)

Example: What the executor adds around the pattern

The pattern gives you Thought → Action → Observation. An agent adds everything that makes it survive contact with production: a maximum iteration count, a timeout, parsing of malformed actions, a whitelist of callable tools, and a stopping condition. Most ReAct failures in practice are not reasoning failures — they are loops that never terminated.

Commonly confused with

A ReAct agent is the running system; ReAct is the prompting pattern inside it. The distinction matters operationally: you tune the pattern by changing the prompt, and you make the agent safe by changing the loop — iteration caps, tool permissions, timeouts.

When to use it

Reach for it when:

• The step count is genuinely unknown ahead of time
• You have bounded the loop and can afford the worst case
• The tools are read-only, or writes are individually authorised

Reach for something else when:

• You have not set a step budget — an unbounded loop is an unbounded bill
• Tools have side effects and nothing gates them
• A fixed pipeline would do: it is cheaper, faster, and testable

Primary source

• Yao et al., ReAct: Synergizing Reasoning and Acting in Language Models (arXiv)

Referenced by

This term is used by the following ModelRefs references:

• react
• plan and execute
• single agent stack

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