The Key to Coding Agents Is the Outer Harness
hugobowne · x · 2026-07-13
The core point of this post is: The "core brain" of a coding agent is actually small; what truly differentiates products is the outer harness.
The author breaks an agent into four basic parts:
- Conversation array
- LLM
- Tool execution
- Loop
What really matters is the harness design, which determines:
- What goes into the context
- Which tools the model can call
- How the environment feeds back results
- What gets compressed/retained
- When to stop the loop
The conclusion is blunt: Most key product decisions are in the harness, not the model itself.
Related event: Agent Differentiation Shifts From Models to Harness Design(8 posts)→
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