Designing Agentic AI Systems: How Real Applications Combine Patterns, Not Hype

Most explanations of AI agent patterns are either too abstract to be useful or too simplified to be accurate.This guide attempts to be both technically precise and genuinely easy to understand by grounding each pattern in a human behavior most engineers, architects, and product leaders already know well. The Foundation: Two Operating Models of AI Systems Before discussing agent patterns , we need to establish a distinction that quietly determines almost every architectural decision you will make. Not all AI systems operate the same way. In practice, modern LLM systems fall into two operating models defined by where control lives. Understanding this boundary is essential because it shapes reliability , safety , observability , testing strategy , and governance . 1. Agentic Workflows Intelligence Inside Deterministic Systems In an agentic workflow, the system is fundamentally code driven . Engineers define: The sequence of steps Branching logic Guardrails Failure handling Termination con