Prompt Engineering vs Loop Engineering vs Graph Engineering: What Changes at Each Layer

Prompt engineering, loop engineering, and graph engineering are three layers of control in AI systems, not competing techniques. Prompt engineering involves writing instructions for a single model response, loop engineering designs how an agent repeatedly observes and acts over multiple cycles, and graph engineering organizes multiple agents and their interactions. Each layer builds on the one beneath it rather than replacing it, and understanding what gets designed at each layer helps explain why higher-level approaches become necessary as systems grow beyond single human-supervised interactions.