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.cursor/rules/project.mdc

Cursor rules for Kotlin

Cursor rules are a markdown file with a short frontmatter header. Cursor attaches them to the agent so it stops guessing how this repo builds, tests, and styles code. 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: project.mdc. Legacy path: .cursorrules

---
description: "Working rules for a Kotlin repository"
globs: "**/*"
alwaysApply: true
---

# Project rules

Follow these rules on every task in this Kotlin repository.
If the project still uses a root `.cursorrules` file, keep the same rules there.

## Stack

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.

## Layout

- UI lives in the feature module that already owns the screen.
- ViewModels expose state. They do not hold a Context that can leak an Activity.
- Data sources sit behind the repository or data layer the app already has.

## Commands

- Unit tests: `./gradlew test`
- Lint: `./gradlew lint`
- Assemble: `./gradlew assembleDebug`

Use the script the repo already defines when it differs from the command above.

## Conventions

- Use coroutines with a scope that is cancelled. Do not use GlobalScope.
- Collect flows in lifecycle-aware scopes.
- Keep Compose functions pure. Side effects go in LaunchedEffect or a ViewModel.
- If the screen is XML, do not rewrite it into Compose unless the task is that migration.
- Prefer the project's dependency-injection style. Do not add a second one.
- String resources go in `strings.xml` when the screen is localized.

## Testing

Add or update tests when behavior changes.

Add a JVM unit test for the ViewModel or use case. Use instrumented tests only when you need the framework.

## Style

- Optimize for the next reader over the shortest diff.
- Comment only when the why is non-obvious.
- Name things the way neighboring files already do.
- Do not reformat code you did not change.

## 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.

## Scope

- Do the requested task. Do not refactor unrelated code.
- Match the rigor already in the repo. Fix what you touch.
- Ask one clarifying question only when the task cannot be finished without it. Otherwise state the assumption and continue.

## Avoid

- Do not touch views from a background dispatcher.
- Do not store a Context in a singleton.
- Do not ignore a failing Gradle warning you introduced.
- Do not hard-code an API host that the build flavors already provide.

## Done when

- The requested behavior works.
- `./gradlew test` passes for the module you changed.
- The diff stays inside the task.
- You list anything you could not run.

Add it to the project

  1. 01

    Copy a starting file

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

  2. 02

    Save it at .cursor/rules/project.mdc

    Save it at `.cursor/rules/project.mdc` in the Kotlin repo and create the folders if they are missing. If the project still uses one root rules file, save the body as `.cursorrules`.

  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 rules in a Kotlin repo?

Save it at `.cursor/rules/project.mdc` in the Kotlin repo and create the folders if they are missing. If the project still uses one root rules file, save the body as `.cursorrules`.

Which tools read this Cursor rules?

Cursor reads `.cursor/rules/*.mdc` and, on older setups, a root `.cursorrules` file. Other tools ignore the frontmatter, so use AGENTS.md when more than one agent edits the repo.

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 rules for other stacks