Cursor Rules File: Complete Guide to Configuring AI Coding Agents (2026)

Cursor Rules File: 12 Production-Ready Examples for AI Coding Agents (2026)

Short answer: A Cursor rules file (.cursorrules) is a configuration file that tells Cursor AI how to write code for your project — coding standards, architecture decisions, preferred libraries, and error handling patterns. A good .cursorrules file reduces AI coding errors by 40-60% because the AI follows your team's conventions instead of guessing. This guide provides 12 tested .cursorrules examples you can copy into your project today.

Cursor AI writes better code when it knows your rules. Without a .cursorrules file, Cursor makes assumptions about your stack, style, and patterns — and those assumptions are often wrong. With a well-configured rules file, Cursor follows your team's standards on every edit, every refactoring, every new file.

In this guide:

• What is a .cursorrules file
• How to create and use .cursorrules
• 12 production-ready examples
• Testing your rules file
• Common mistakes

Related guides: How to Use Cursor AI (Beginner Guide) · Cursor vs OpenCode Comparison · Claude Code vs Cursor · Connect Cursor + Claude Code + OpenAI · AI Coding Assistant Pricing · OpenCode vs Aider Comparison · Best Free AI Coding Assistants · BYOK AI Platforms · AI Orchestration Best Practices · Build a Multi-Agent AI Team · All Comparisons

What Is a .cursorrules File?

A .cursorrules file is a plain text file you place in the root of your project. Cursor AI reads this file every time it generates code, using the instructions as guardrails for its output.

Think of it like an .editorconfig or eslint configuration — but instead of linting code after it's written, .cursorrules guides the AI before it writes. This means fewer iterations, less manual cleanup, and code that matches your team's standards from the first attempt.

What Goes in a .cursorrules File

How Cursor Uses Your Rules

Cursor reads .cursorrules at the start of each conversation. The rules apply to:

1. Cmd+K edits — inline code generation follows your style
2. Chat responses — code blocks match your conventions
3. Composer multi-file edits — new files follow your architecture
4. Auto-complete — suggestions align with your patterns

How to Create and Use .cursorrules

Step 1: Create the File

Create a file named .cursorrules in your project root (same level as package.json or pyproject.toml).

my-project/
├── .cursorrules     ← Here
├── package.json
├── src/
└── ...

Step 2: Write Your Rules

Use plain English. Be specific. Give examples. The more precise you are, the better Cursor follows your instructions.

Step 3: Verify It's Working

Ask Cursor: "What rules are you following for this project?" If it lists your .cursorrules contents, it's working.

12 Production-Ready .cursorrules Examples

Example 1: TypeScript + Next.js App Router

# Project Configuration
- This is a Next.js 15 application using the App Router
- TypeScript 5.x with strict mode enabled
- React 19 with Server Components by default

# Code Style
- Use `function` declarations, not arrow functions for components
- Named exports only (no default exports)
- Use path aliases: @/ for src/
- 2-space indentation, single quotes, no semicolons

# File Structure
- app/ directory for routes (App Router)
- components/ for shared UI components
- lib/ for utilities and helpers
- types/ for shared TypeScript types

# Server Components
- Default to Server Components
- Only add "use client" when you need useState, useEffect, or event handlers
- Fetch data in Server Components, pass as props to Client Components

# Error Handling
- Use try/catch in Server Actions
- Return { error: string } | { data: T } pattern
- Never catch and swallow errors silently

Example 2: Python + FastAPI

# Python FastAPI Project
- Python 3.12+
- FastAPI with async/await everywhere
- Pydantic v2 for all schemas
- SQLAlchemy 2.0 for database access

# Code Style
- Use type hints on ALL function parameters and return types
- Use `async def` for all route handlers
- Dependency injection via FastAPI's Depends()
- 4-space indentation, double quotes for strings

# Structure
- routers/ for API route modules
- models/ for SQLAlchemy models
- schemas/ for Pydantic models
- services/ for business logic
- Never put business logic in route handlers

# Database
- Always use async sessions
- Use migrations via Alembic
- Never use raw SQL strings — use SQLAlchemy ORM

Example 3: React Component Library

# React Component Library
- React 19 + TypeScript 5.x
- Tailwind CSS 4 for styling
- Radix UI for accessible primitives
- Storybook for component documentation

# Component Rules
- Every component gets its own folder with index.tsx, styles.ts, tests.tsx
- Use forwardRef for all components that wrap DOM elements
- Props interface named ComponentNameProps
- Use cva (class-variance-authority) for variant styling

# Naming
- Components: PascalCase (Button, Card, Dialog)
- Props: camelCase (onClick, isLoading, variant)
- CSS classes: use Tailwind utilities only
- Files: kebab-case for folders, PascalCase for components

# Accessibility
- All interactive elements must be keyboard accessible
- Use semantic HTML elements (button, nav, main)
- Include aria-labels where text is not visible
- Test with screen reader in Storybook

Example 4: Monorepo with Turborepo

# Monorepo Structure
- Turborepo for build orchestration
- pnpm as package manager
- apps/web — Next.js frontend
- apps/api — FastAPI backend
- packages/shared — shared types and utilities
- packages/ui — shared component library

# Cross-Package Rules
- Import from workspace packages: import { Button } from "@repo/ui"
- Never duplicate types between packages — use @repo/shared
- Keep package dependencies minimal
- Use Turborepo's pipeline for build order

# Testing
- Vitest for unit tests across all packages
- Tests live next to the code: component.tsx → component.test.tsx
- Minimum 80% coverage for packages/shared

Example 5: REST API with Error Handling

# API Development Rules
- RESTful endpoints: /api/v1/resource
- Use plural nouns for collections: /users, /posts, /comments
- Standard HTTP methods: GET, POST, PUT, PATCH, DELETE
- Return appropriate status codes (200, 201, 400, 401, 403, 404, 500)

# Response Format
- Success: { data: T, meta?: { page, limit, total } }
- Error: { error: { code: string, message: string, details?: object } }
- Never expose internal error messages to clients

# Validation
- Validate ALL input with Zod schemas
- Return 400 with specific validation errors
- Sanitize all string inputs
- Never trust client-side data

Example 6: Database-Heavy Application

# Database Rules
- PostgreSQL 16 with pgvector extension
- Prisma ORM for type-safe queries
- All timestamps in UTC, stored as timestamptz
- Use UUID v7 for primary keys
- Soft deletes via deleted_at column

# Query Patterns
- Always use select to limit returned fields
- Use include sparingly — prefer explicit joins
- Add database indexes for frequently queried columns
- Paginate all list endpoints (default 20, max 100)
- Use transactions for multi-table writes

# Migrations
- Every schema change gets a migration
- Never modify existing migrations
- Include rollback instructions in migration comments

Example 7: Testing Configuration

# Testing Standards
- Vitest for unit and integration tests
- Playwright for end-to-end tests
- MSW (Mock Service Worker) for API mocking
- Testing Library for React component tests

# Test Structure
- Arrange → Act → Assert pattern
- Describe blocks for each function/component
- One assertion per test when possible
- Use test.each for parameterized tests

# Naming
- Files: feature.test.ts or Component.test.tsx
- Tests: "should [expected behavior] when [condition]"
- describe: name of the function or component being tested

# Coverage
- Unit tests for all utility functions
- Integration tests for API routes
- E2E tests for critical user flows
- Never mock what you don't own

Example 8: Performance-Optimized Frontend

# Performance Rules
- Next.js App Router with Server Components
- Lazy load all below-fold components with React.lazy + Suspense
- Use next/image for ALL images with explicit width/height
- Implement streaming SSR for data-heavy pages
- Client-side cache with SWR or TanStack Query

# Bundle Size
- Import only what you need: import { map } from 'lodash-es' (not import _ from 'lodash')
- Use dynamic imports for heavy libraries (chart.js, pdf-lib, etc.)
- Analyze bundle with @next/bundle-analyzer before PRs
- Target < 100KB First Load JS per page

# Rendering Strategy
- Static Generation (SSG) for public pages
- Server-Side Rendering (SSR) for personalized pages
- ISR (revalidate: 3600) for semi-static content
- Client-Side Rendering only for highly interactive dashboards

Example 9: Security-Focused Configuration

# Security Rules
- Never commit secrets, API keys, or passwords
- Use environment variables for all configuration
- Validate and sanitize ALL user inputs
- Use parameterized queries — never string interpolation for SQL
- Implement rate limiting on all public endpoints

# Authentication
- JWT with short expiry (15 min) + refresh tokens (7 days)
- Store tokens in httpOnly, secure, sameSite cookies
- Never store sensitive data in localStorage
- CSRF protection on all state-changing requests

# Headers
- Content-Security-Policy on all responses
- X-Frame-Options: DENY
- Strict-Transport-Security: max-age=31536000
- X-Content-Type-Options: nosniff

Example 10: Documentation-Driven Development

# Documentation Standards
- JSDoc comments on all exported functions
- README.md in every package directory
- API documentation with OpenAPI 3.1 spec
- Architecture Decision Records (ADR) for major choices

# Comment Style
- Explain WHY, not WHAT
- Use TODO(username): for pending items
- Mark deprecated items with @deprecated tag
- Keep comments up to date when code changes

# Examples
- Every public function gets a usage example in JSDoc
- Include expected input and output
- Show edge cases and error handling

Example 11: Git and CI/CD Workflow

# Git Conventions
- Conventional commits: feat:, fix:, docs:, refactor:, test:, chore:
- Branch naming: feature/TICKET-description, fix/TICKET-description
- Squash merge to main
- Every PR needs at least one review

# CI/CD
- Lint + type-check on every push
- Unit tests on every push
- Integration tests on PR to main
- E2E tests on merge to main
- Deploy preview on every PR
- Production deploy on merge to main

# PR Rules
- Keep PRs under 400 lines of changes
- Include context in PR description
- Link to relevant issue/ticket

Example 12: Minimal/Starter Rules

# Project: [Your Project Name]
- Stack: [Framework] + [Language]
- Style: 2 spaces, single quotes, no semicolons

# Do
- Use TypeScript strict mode
- Write tests for new functions
- Handle errors explicitly

# Don't
- Don't use any type
- Don't leave console.log in production code
- Don't skip error handling

Testing Your Rules File

After creating your .cursorrules file, test it with these prompts in Cursor:

Test 1: Style Compliance

Ask Cursor to generate a component or function. Check if the output follows your style rules (indentation, quotes, naming).

Test 2: Architecture Compliance

Ask Cursor to create a new feature. Check if it places files in the correct directories and follows your architecture pattern.

Test 3: Error Handling

Ask Cursor to write a function that could fail. Check if it handles errors according to your rules.

Test 4: Remember the Rules

Ask: "What coding rules should you follow for this project?" Cursor should list your .cursorrules contents.

Common Mistakes

Mistake 1: Too Many Rules

A .cursorrules file with 200 lines of instructions confuses the AI. Keep it under 50 lines. Focus on the rules that matter most.

Mistake 2: Vague Instructions

Bad: "Write clean code" Good: "Use descriptive variable names. Functions should be under 20 lines. Extract complex logic into named helper functions."

Mistake 3: Not Updating Rules

When your project evolves, update .cursorrules. If you switch from REST to GraphQL, or from Jest to Vitest, your rules file should reflect that.

Mistake 4: Ignoring .cursorrules for Quick Edits

Every edit counts. Even small changes should follow your rules. If Cursor stops following rules, ask it to re-read the .cursorrules file.

Mistake 5: Duplicating Configuration

Don't repeat rules that are already in tsconfig.json, .eslintrc, or pyproject.toml. Reference those files instead:

# Follow existing configuration
- TypeScript settings: see tsconfig.json
- Linting rules: see .eslintrc.json
- Import paths: configured in tsconfig.json paths

Combining Cursor with Other AI Coding Agents

Cursor is powerful alone, but combining it with other AI agents through a multi-agent workflow can multiply productivity:

With Ivern AI, you can connect Cursor, Claude Code, and OpenAI into a coordinated squad where each agent handles what it's best at — and your .cursorrules file ensures consistent code quality across all of them.

Ready to build your AI coding squad? Get started free with Ivern AI — 15 tasks included, no credit card required. BYOK pricing means you pay exactly what the API providers charge, with zero markup.

Frequently Asked Questions

Where does the .cursorrules file go?

Place .cursorrules in your project root directory, at the same level as package.json, pyproject.toml, or your main configuration file. Cursor automatically reads this file when you open the project.

Can I have multiple .cursorrules files?

Cursor supports a single .cursorrules file per project. If you need different rules for different parts of your project, use inline comments in the file to create sections, or use project-specific configurations in your workspace settings.

How often should I update my .cursorrules file?

Update it whenever your project conventions change — new libraries, updated frameworks, changed architecture patterns. A good practice is to review it during sprint planning or whenever you onboard a new team member.

Does .cursorrules work with other AI coding tools?

No — .cursorrules is Cursor-specific. Claude Code uses CLAUDE.md, OpenCode uses opencode.json, and Aider uses .aider.conf.yml. Each tool has its own configuration format.

What if Cursor ignores my rules?

Make sure the file is named exactly .cursorrules (not .cursorrules.txt or cursorrules). If rules are still being ignored, try restarting Cursor or asking in chat: "Follow the rules in .cursorrules for all subsequent responses."

How many rules should I include?

Keep it concise — 20 to 50 lines is the sweet spot. Too many rules dilutes their effectiveness. Focus on the rules that have the biggest impact on code quality and consistency.