A recent study by METR found that experienced open-source developers were 19% slower when using AI coding tools like Cursor Pro and Claude Sonnet.
Despite expecting a speed boost, developers spent extra time prompting, reviewing, and correcting AI output.
44% of AI suggestions were used, and complex codebases worsened performance.
While the experience felt easier, actual productivity dropped. Researchers warn current AI tools may not yet deliver real-world speed gains.
