Experienced developers, familiar repositories
AI-allowed tasks took 19% longer16 experienced open-source developers; 246 issues in repositories they knew.
Early 2025 experiment · published July 2025
This setting does not represent all developers or current tools. METR’s February 2026 follow-up identifies selection effects and redesigns the study; do not extrapolate this effect to countries.
Read the study ↗ · 2026 follow-up ↗