We built a browser with GPT-5.2 in Cursor (xcancel.com)

Cursor has developed a new web browser utilizing GPT-5.2, executing continuous operations for a week. Built with over 3 million lines of code and thousands of files, this browser features a custom rendering engine created in Rust that handles essential functions such as HTML parsing, CSS processing, layout, text shaping, and a proprietary JavaScript virtual machine. While it’s still a work in progress with many challenges to overcome, the team was surprised to find that simple websites rendered quickly and accurately. This development is significant for the AI/ML community as it demonstrates the potential of advanced AI models in automating coding tasks and enhancing software development processes. The integration of GPT-5.2 Codex in Cursor highlights its capabilities in managing long-running tasks, pushing the boundaries of what coding agents can achieve autonomously. As the team continues to stress test the coding agent’s functionalities, this project opens up new avenues for research and practical applications in creating more sophisticated AI-driven tools.