Enji GuardCursor rules best practices: how to write .cursorrules
Cursor rules tell Cursor how to behave in your repo. Done well, they keep broad agentic edits on track; left to rot, they steer the agent wrong. This is a practical guide to writing and maintaining them.
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01
What are Cursor rules?
Cursor rules, historically a .cursorrules file, now often split into per-directory rule files, give Cursor context and constraints before it edits: how to build and test, conventions to follow, and what to avoid. Because Cursor edits across many files at once, good rules matter more than for tools that touch one diff.
02
What to put in them
Keep rules short, specific, and scoped:
- Build, run, and test commands
- Conventions: structure, naming, and patterns to match
- Hard boundaries: files and directories to leave alone
- Security rules: no secrets, no auto-merge, require review
- Per-directory rules for code with special requirements
03
Best practices that keep them useful
Prefer many small, scoped rule files over one giant file, so Cursor loads only what is relevant to the code it is touching. Be concrete; avoid vague guidance the agent can rationalize around. Keep Cursor rules consistent with any AGENTS.md or CLAUDE.md in the repo so they do not contradict each other.
04
Common mistakes
The main failure is drift: rules written early stop matching the code, and Cursor keeps trusting them. Other traps are bloat (rules so long the agent burns context reading them), conflicts between rule files, and over-broad rules that should live next to a specific subsystem.
05
Keep Cursor rules honest with Guard
Enji Guard audits your Cursor rules, AGENTS.md, and CLAUDE.md against the real repo on a schedule, flags where they have drifted or conflict, and can open a pull request that brings them back in line with the code.
Quick questions
Should Cursor rules live in one file or many?
Usually many. Scoped, per-directory rules keep each one short and relevant, so Cursor loads what applies to the code it is editing instead of one bloated root file.
How do I keep .cursorrules from going stale?
Review them when the project changes, and audit them on a schedule. Guard can flag drift between your Cursor rules and the actual repo automatically.
Keep your Cursor rules true to the code.
Connect a repo and Guard audits your agent rules against the real codebase. No card.