Cursor Rules vs CLAUDE.md — A Deep Dive into Context Injection Patterns for AI Coding Tools

I run Cursor and Claude Code together on the same projects. Both tools see the same codebase, but they inject rules in fundamentally different ways. Early on I didn't know this and copy-pasted the same markdown to both sides. One side followed it well, the other slowly forgot. After a month of confusion I landed on the conclusion that "these two are different species when it comes to context injection." This post unpacks that difference from a solo dev's perspective. On the surface they're both