How to Build an AI Agent Harness from Scratch in TypeScript
Many AI agent tutorials start with a language model, give it a few tools, and run a loop until it produces an answer. That's enough to demonstrate tool calling, but it leaves the interesting engineering questions unanswered. What happens when a tool fails? Who validates the arguments? What prevents an agent from running indefinitely, executing unsafe commands, or exhausting its context window? And how do you test any of this without relying on unpredictable model responses?...
Many AI agent tutorials start with a language model, give it a few tools, and run a loop until it produces an answer. That's enough to demonstrate tool calling, but it leaves the interesting engineering questions unanswered. What happens when a tool fails? Who validates the arguments? What prevents an agent from running indefinitely, executing unsafe commands, or exhausting its context window? And how do you test any of this without relying on unpredictable model responses?...