Context Engineering for AI Coding: AGENTS.md, Cursor Rules & RAG
In 2025, METR — an AI safety and capability research organization — ran a rigorous randomized controlled trial. Sixteen experienced open-source developers worked on 246 real-world tasks, each randomly assigned to either use AI coding tools freely or not at all. The result was counterintuitive: developers using AI tools were 19% slower on complex tasks. Before the study, those same developers predicted AI would make them 24% faster. After completing the experiment — still believing they had gone faster — their subjective confidence remained completely unshaken. ...