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2026-06-08

Why ReAct is Still the Foundation

Understanding the Thought-Action-Observation loop.

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Reading time: 5 min

The ReAct pattern (2022) remains the most fundamental building block of AI agent design. Its elegance: Thought, Action, Observation in a continuous feedback loop. Modern frameworks like LangGraph and OpenAI Agents SDK still use ReAct as their default. The key insight: separating reasoning from action lets the LLM course-correct based on real environmental feedback. Start with ReAct and only add complexity when simpler patterns are insufficient.