Single-Agent Patterns: ReAct, Plan-Then-Execute, Reflection

The three canonical ways to structure one agent — interleaved reasoning and acting, upfront planning, and self-critique — with honest tradeoffs on latency, cost, debuggability, and where each one breaks.

Content current as of 2026-09.

Lessons

1. ReAct: reasoning and acting, interleaved
2. Plan-then-execute: think first, then do
3. Reflection: the agent grades its own work
4. Choosing a pattern (and composing them)