Everything I've learned so far about .cursorrules after mass testing them

I've been running experiments on Cursor's rule system for a few weeks now. I started because my rules weren't working and I couldn't figure out why, and I ended up going way deeper than I planned. So if you're still using a .cursorrules file in your project root, it works, but it's the old way. Cursor moved to .cursor/rules/*.mdc files a while back. The .mdc format lets you scope rules to specific file types, set metadata in frontmatter, and organize rules into separate files instead of one giant blob. I tested both. If you have a .cursorrules AND .mdc files, the .mdc files win. The old file still loads in a clean directory with nothing else, but once you have the new format, that's what Cursor uses. Migrating takes maybe 10 minutes. I split my monolithic .cursorrules into separate .mdc files by concern. One for TypeScript conventions, one for testing patterns, whatever. alwaysApply: true or nothing This one cost me WAY too much time... Every .mdc file has YAML frontmatter at the top.