Prompt, context and harness engineering

There are three types of engineering you need to be aware of. Prompt engineering: crafting effective instructions for a single model interaction. Context engineering: designing the entire information environment the model relies on to reason, including memory, documents, tool definitions, conversation history and structured output specs. Harness engineering: designing and maintaining the control system that governs an agent across its entire lifecycle. All three co-exist within each other: prompt engineering lives inside context engineering, and context engineering lives inside the harness. The formula that frames it all: Agent = Model + Harness. The harness is the mechanism that makes the model think in a safe, consistent and useful way.