Designing Your Own AI Harness: A Deep Dive Into the Architecture of Agent Loops, Tools, Context, and Control

Short summary

An expert deep dive into the architecture of AI agent harnesses—the loop, tools, context management, permissions, and persistence wrapped around a language model. The article breaks down each component with honest trade-offs, covering progressive context compaction, permission matrices, filesystem-first tools, and budget enforcement. It frames the harness as a delivery mechanism for context engineering, arguing that getting the right information in front of the model is the core challenge.

• •Decomposes agent harness architecture into five layers: tools, context, permissions, control, and persistence
• •Shows how a better harness alone improved benchmark scores from low fifties to mid sixties without changing the model
• •Covers production patterns including context compaction, permission matrices, budget enforcement, and filesystem-first tool design

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