Hugo Bowne on the biggest agent failure mode: it's the harness, not the model

hugobowne · x · 2026-09-16

Hugo Bowne breaks down the biggest failure mode in agent building: when things break, you don't know what to fix—wrong tool choice, wrong context, or lost state? He uses Krang from TMNT as the analogy: the LLM is the pink brain, the agent harness the robot body that runs the loop (call model, execute tools, feed back results), assembles context, tracks state, and enforces boundaries. If the harness never passes tool errors back, the model lacks information to recover. Post ends with a promo for his paid 4-hour workshop ($500, $450 with code) building a customer-service agent from scratch, then rebuilding with an SDK and MCP.

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