From Prompt to Harness Engineering: The 3 Stages of AI Agent Architecture
femke_plantinga · x · 2026-08-12
The post outlines the three-stage evolution of working with AI models, explaining why Harness Engineering is the new industry hype.
- Prompt Engineering: Focuses on what you say. Optimizing instructions and examples to nail a task in one shot. Limited by the information in a single input.
- Context Engineering: Focuses on what you bring. Strategically managing the finite token budget (e.g., 200K or 1M) by loading only necessary memory, docs, and skills to prevent the model from drowning in data.
- Harness Engineering: Focuses on what you build around it. Since a model only takes an input and returns an output, harness engineering builds the looping system equipped with tools, memory, and guardrails to string hundreds of turns into an autonomous agent.
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