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.cursor/rules/project.mdc

Cursor rules for Next.js

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 Next.js project. This repository is a Next.js app on the App Router with TypeScript. Server Components are the default. Add a client component only for state, effects, or browser APIs.

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 the App Router, TypeScript, and React Server Components. It does not assume the Pages Router, a database, or an auth library. If the repo already picked one, follow that instead of adding a second.

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 Next.js repository"
globs: "**/*"
alwaysApply: true
---

# Project rules

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

## Stack

This repository is a Next.js app on the App Router with TypeScript. Server Components are the default. Add a client component only for state, effects, or browser APIs.

## Layout

- Routes, layouts, and server code live in `app/`.
- Shared UI lives in `components/`. Shared logic lives in `lib/`.
- Keep route files thin. Move non-trivial logic into functions that can be tested without rendering a page.

## Commands

- Dev server: `npm run dev`
- Production build: `npm run build`
- Lint: `npm run lint`
- Tests: `npm test`

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

## Conventions

- Fetch data on the server. Do not fetch in `useEffect` for data the server can already load.
- Use `next/link`, `next/image`, and `next/font`. Do not add another image or font pipeline.
- Mutations go through the Server Actions or route handlers the repo already uses.
- Validate input at the boundary with the validator the repo already uses.
- Keep client components small and at the leaves of the tree.
- Match the existing styling system. Do not introduce a second CSS framework.

## Testing

Add or update tests when behavior changes.

Use the runner already in the repo (Vitest, Jest, or Playwright). Cover the behavior you changed, not every component.

## 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.
- Return a clear error from server actions and route handlers. Do not send stack traces to the client.

## 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 import server-only modules into a client component.
- Do not put secrets in `NEXT_PUBLIC_` variables or client bundles.
- Do not mark a whole tree as a client component to silence one hook error.
- Do not add `pages/` routes to an App Router project.

## Done when

- The requested behavior works.
- `npm run lint` and `npm test` pass, or you name the command you could not run.
- 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 Next.js 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 Next.js agent often gets wrong, such as a page that loads data on the server instead of in useEffect. 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 Next.js repo?

Save it at `.cursor/rules/project.mdc` in the Next.js 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 Next.js example assume?

The example assumes the App Router, TypeScript, and React Server Components. It does not assume the Pages Router, a database, or an auth library. If the repo already picked one, follow that instead of adding a second.

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 Next.js

Cursor rules for other stacks