The fourth floor: graph engineering
After prompt engineering (2023), context engineering (2024), and loop engineering (2025-26), the agent stack is being renamed again. This page is a single-source explainer — what the term means, where it came from, the counter-frame, and a staged plan for adopting it inside Hermes.
Prompt engineering
Getting the right tokens out of a frozen model. Single-turn. The discipline lives entirely inside the model's input window.
Context engineering
What to put in the window beyond the user's question. RAG, memory, tool catalogs. The discipline lives at the I/O boundary.
Loop engineering
Run the call-response cycle until a stop condition. ReAct, ReWOO, Reflexion. Discipline lives on the iteration / time axis.
Graph engineering
The structure the loops live in. Typed nodes, typed edges, checkpointed state. The discipline lives on the topology axis.