Written by Erik Schluntz and Barry Zhang directly from Anthropic, it defines the fundamental distinction between workflows (predefined paths) and agents (LLMs that manage their own processes), and describes the 5 essential orchestration patterns: Prompt Chaining, Routing, Parallelization, Orchestrator-Workers, and Evaluator-Optimizer. The most valuable contribution is the counterintuitive recommendation: avoid unnecessary complexity—simple, compostable systems consistently outperform elaborate frameworks.