Metr

The METR Study One Year Later: When AI Actually Slows Developers

In early 2025, METR (Model Evaluation and Transparency Research) ran a randomized controlled trial that caught the industry off guard. Experienced open-source developers—people with years on mature, high-star repositories—were randomly assigned to complete real tasks either with AI tools (Cursor Pro with Claude) or without. The result: with AI, they took 19% longer to finish. Yet before the trial they expected AI to make them about 24% faster, and after it they believed they’d been about 20% faster. A 39-point gap between perception and reality.