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.cursor/rules/security.mdc

Cursor security rule for Flutter

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 Flutter project. This repository is a Flutter app. Widgets stay small, state management matches the package the repo already uses, and `flutter analyze` stays clean.

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 Flutter with Dart. It does not assume Riverpod, Bloc, or a particular router. Use the state library already in pubspec.yaml.

Customize in the generatorBrowse the library

Example file

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

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

# Security rules

Attach these rules when editing auth, config, or secret-handling code in this Flutter repository.
This repository is a Flutter app. Widgets stay small, state management matches the package the repo already uses, and `flutter analyze` stays clean.

## Secrets and trust

- Do not ship API secrets in the Flutter binary.
- Store tokens with the secure-storage plugin the app already uses, not in shared preferences plaintext.
- Validate deep-link parameters before navigating.

## Errors

- Fail at the boundary. Do not swallow errors.
- Surface a recoverable error in the widget. Do not swallow a failed future.

## Done when

- Untrusted input is validated before a side effect.
- No secret was added to source, logs, or a client bundle.
- `flutter analyze` is clean and `flutter test` passes for the widget you touched.

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 Flutter 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 Flutter agent often gets wrong, such as a widget test that finds a labeled control and taps it. 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 Flutter repo?

Save it at `.cursor/rules/security.mdc` in the Flutter 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 Flutter example assume?

The example assumes Flutter with Dart. It does not assume Riverpod, Bloc, or a particular router. Use the state library already in pubspec.yaml.

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 Flutter

Cursor security rule for other stacks