Evolution of AI Agent Harnesses: From Simple Loops to Unreadable Complexity
dotey · x · 2026-08-12
In a recent discussion, Baoyu pointed out that the Harness (the external framework/tool-calling code) for AI Agents is becoming increasingly complex. While developers could once digest the source code, modern codebases with hundreds of thousands of lines (like the latest Claude Code iterations) are now almost impossible to follow.
He recalled his own Agent Loop enlightenment, which came from an early leaked version of Claude Code. At that time, the core code was only a few hundred to a thousand lines—essentially just a While loop checking whether the LLM output was a tool call or a stop signal. Although this minimalist underlying logic remains unchanged, the endless engineering stacking has drastically increased the cost of understanding for individual developers.
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