AI Builds Full Web Browser: 3 Million Lines of Code in One Week, Internet Skeptical

Cursor has skyrocketed in popularity in the past few months as ‘vibe coding’ – using AI to write code – started becoming more useful. Now, Cursor CEO Michael Trulli has revealed that he got AI to make a full web browser within a week with over 3 million lines of code. However, the internet is a little skeptical over this project. advertisement AI writes 3 million lines of code in just a week On X, Trulli shared a post detailing the project. He said that the company used GPT 5.2 Codex for this project, a model designed by OpenAI specifically for extended autonomous work. Within seven days, the AI completed the assignment without any need for human assistance. Michael Trulli wrote, “It's 3M+ lines of code across thousands of files. The rendering engine is from-scratch in Rust with HTML parsing, CSS cascade, layout, text shaping, paint, and a custom JS VM.” He also shared a screenshot of the browser built by AI, with the Google homepage open. Though if you think you’ve found your new browser, there is still work left to do. Trulli admitted, “It *kind of* works! It still has issues and is of course very far from Webkit/Chromium parity.” In one reply, the Cursor CEO pointed out that this was just an experiment and not a production version. He explained, "There are definitely lots of issues! This was an experiment in pushing the frontier of what coding agents can do. The result is very very far from production software." Internet users skceptical of the AI-made browser Users on X appreciated the effort put into this project, but were not ready to fully believe it. While the AI did write 3 million lines of code to create the browser, Chromium, the open-source project that is the foundation for Google Chrome, Microsoft Edge, and more, has over 35 million lines of code. Some users commented on Michael Trulli’s post, asking him to show the prompt he used to get AI to complete this task. While a few wondered over how many Cursor tokens this task would have used if given by a normal user on the platform. One individual also asked whether the AI was told to use Chromium as an ‘inspiration’ while writing this code. This is not the first time we have seen AI work autonomously for long durations. Anthropic claims that its Claude Sonnet 4.5 model can code a full app in 30 hours. - Ends