AutoAgent is a revolutionary open-source library designed to automate the tedious process of agent engineering and prompt tuning. By employing a meta-agent, the library allows for the autonomous optimization of an agent's harness, including system prompts, tool definitions, and orchestration strategies, all without human intervention. During a 24-hour run, AutoAgent achieved impressive results, including the top score on SpreadsheetBench and a leading GPT-5 score on TerminalBench. This technology effectively transitions the human's role from a manual engineer to a high-level director, enabling rapid, self-improving agent development across various domains and benchmarks.