Run Claude Code, Codex and Cursor on the same repo for a week and you'll end up with a CLAUDE.md , an AGENTS.md , a .cursor/rules folder and a README that each say something slightly different. One says "use pnpm", another says "npm is fine". One says "never touch migrations", another has a migration workflow. Agents don't flag these conflicts. They just follow whichever rule they read last, or whichever one is closest to the task. So you get behavior that changes depending on which tool ...