Ask HN: What's in Your Agents.md/Claude.md?

I'm curious what the community is putting in their AGENTS.md and CLAUDE.md memory files for coding assistants.

What have you found most valuable to document?

Especially interested in:

- Project-specific gotchas you've discovered the hard way

- Rules that prevent common agent mistakes

- Context that significantly improves code quality

- Examples of what NOT to include

Would love to see real examples if you're willing to share.

Please use one instruction per comment. This way others can vote for instructions and put them to the top.