AI Agents Write 3 Million Lines of Code to Build Experimental Web Browser in One Week

Cursor CEO Michael Truell led an experiment where hundreds of AI agents, powered by OpenAI's GPT-5.2 Codex model, autonomously wrote over 3 million lines of code in one week to build a web browser from scratch. The browser includes a custom rendering engine in Rust with core components like HTML parsing and a JavaScript virtual machine. While a screenshot showed the browser loading Google's homepage, Truell emphasized it is an experimental project with many issues and far from matching established browsers like Chromium.