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.cursor/rules/security.mdc

Cursor security rule for Kotlin

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 Kotlin project. This repository is an Android app in Kotlin. Match Compose or Views, whichever the module uses. Keep disk and network work off the main thread.

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 Kotlin on Android. It does not assume Compose, Hilt, or a particular navigation library unless the Gradle module already depends on them.

Customize in the generatorBrowse the library

Example file

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

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

# Security rules

Attach these rules when editing auth, config, or secret-handling code in this Kotlin repository.
This repository is an Android app in Kotlin. Match Compose or Views, whichever the module uses. Keep disk and network work off the main thread.

## Secrets and trust

- Do not ship secrets in the APK. Use the backend or the secrets gradle plugin the project already has.
- Use HTTPS. Do not add a permissive network security config.
- Validate intent extras. Other apps can start your activity.

## Errors

- Fail at the boundary. Do not swallow errors.
- Expose an error state the UI can render. Do not swallow a cancellation or a failed network call.

## Done when

- Untrusted input is validated before a side effect.
- No secret was added to source, logs, or a client bundle.
- `./gradlew test` passes for the module you changed.

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 Kotlin 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 Kotlin agent often gets wrong, such as a ViewModel that exposes state and does not hold an Activity reference. 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 Kotlin repo?

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

The example assumes Kotlin on Android. It does not assume Compose, Hilt, or a particular navigation library unless the Gradle module already depends on them.

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 Kotlin

Cursor security rule for other stacks