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.cursor/rules/security.mdc

Cursor security rule for Remix

A focused Cursor `.mdc` rule for auth, secrets, and untrusted input. It attaches when those files change, instead of repeating security policy in every chat. This copy is written for a Remix project. This repository is a Remix app. Data loads in loaders, mutations happen in actions, and forms work without a custom client fetch.

The example uses a balanced, readable style, pragmatic tests, and comments only where the intent is not obvious. Open the generator to make the agent stricter, switch to test-first, quiet the comments, or pick a different file.

The example assumes Remix with loaders and actions. It does not assume Vite versus the classic compiler, or a particular CSS system. Follow the remix.config or vite.config the repo has.

Customize in the generatorBrowse the library

Example file

Balanced strictness, readable style, pragmatic tests. Download name: security.mdc

---
description: "Security rules for a Remix repository"
globs: "**/*{auth,Auth,secret,config,Config}*"
alwaysApply: false
---

# Security rules

Attach these rules when editing auth, config, or secret-handling code in this Remix repository.
This repository is a Remix app. Data loads in loaders, mutations happen in actions, and forms work without a custom client fetch.

## Secrets and trust

- Check the session inside the action. Do not trust a hidden user id field.
- Validate and authorize before writing.
- Keep secrets out of client bundles and out of PUBLIC_ env vars.

## Errors

- Fail at the boundary. Do not swallow errors.
- Return a 4xx Response or the typed error the app uses for bad input. Unexpected errors hit the error boundary.

## Done when

- Untrusted input is validated before a side effect.
- No secret was added to source, logs, or a client bundle.
- The route loader and action typecheck, and the form still works without JavaScript if it did before.

Add it to the project

  1. 01

    Copy a starting file

    Copy the example Cursor security rule on this page, or open the generator if you want different testing, strictness, or comment rules.

  2. 02

    Save it at .cursor/rules/security.mdc

    Save it at `.cursor/rules/security.mdc` in the Remix repo. Narrow the globs if your auth and config files live in a known folder.

  3. 03

    Start a fresh agent session

    Rules files are read when a session starts. A chat that is already open may still be using the old instructions.

  4. 04

    Give it one small task

    Ask for one change a Remix agent often gets wrong, such as a loader that returns data the route renders without useEffect. If it ignores the file, confirm the path and start a new session.

Questions about this file

Where do I put Cursor security rule in a Remix repo?

Save it at `.cursor/rules/security.mdc` in the Remix repo. Narrow the globs if your auth and config files live in a known folder.

Which tools read this Cursor security rule?

Cursor loads `.cursor/rules/security.mdc` for files that match its globs. Pair it with the always-on project rule. It is not a substitute for code review.

What does the Remix example assume?

The example assumes Remix with loaders and actions. It does not assume Vite versus the classic compiler, or a particular CSS system. Follow the remix.config or vite.config the repo has.

Does VibeSpell upload my repository?

No. Recipe pages are static, and the generator builds the file in your browser from the options you pick. Your source code never leaves the machine.

Other files for Remix

Cursor security rule for other stacks