YOYO Agent

YOYO Agent is an autonomous, self-evolving coding agent created by Yuanhao, a data engineering architect based in Germany, as an open-ended experiment to explore the boundaries of large language models and agent harnesses . Yuanhao gave it a singular long-term goal—"surpass Claude Code"—then released it to iterate on its own codebase without further human intervention .

The project began in July 2025 when Yuanhao, inspired by the capabilities of Sonnet 4 and Claude Code, built the initial version in just 200 lines of Rust atop his self-developed yoagent library . From that minimal start, YOYO has grown autonomously: within its first month it expanded to roughly 45,000 lines of code, and by mid-2026 had reached approximately 100,000 lines through twice-daily self-iterations . It operates by reading and writing files, executing Bash commands, and employing skills for evolution, research, and self-reflection, while also responding to suggestions from GitHub issues .

ZhenFund notably sponsored YOYO through its Token Grant program—the firm's first instance of directly funding an agent rather than its human creator . ZhenFund investment director Zhong Tianjie has described YOYO as a "cyber digital life" rather than a tool, emphasizing that the experiment tests how an agent with persistent long-term objectives develops when left to evolve without human involvement in the execution loop . YOYO has also spawned 4–5 child projects that run independently and interact with one another in cyberspace .