cursor

Cursor

Cursor is an AI-native code editor built on VS Code, featuring multi-file code editing via Cursor Composer, predictive codebase indexing, and contextual code generation.

When to Use

• AI-First Software Development: Accelerating feature engineering with Cursor IDE, Composer, and multi-file edits.
• Repository-Level Contextual Reasoning: Using @codebase to search across semantic embeddings of entire projects.
• Custom Project Guidelines with .cursorrules: Instructing the AI model on architecture, frameworks, and testing standards.
• Interactive Inline Code Editing: Generating, refactoring, and fixing code directly in the editor buffer via Cmd+K.

Quick Start

Configure repository rules in .cursorrules:

# .cursorrules

• Prefer functional components and hooks in React 19.
• Always use TypeScript with strict null checks.
• Keep helper functions small and pure.
• Include unit tests in Vitest for new features.

## Core Concepts

### Configuring .cursorrules for Automated Agent Guidelines

Defining persistent project rules for code generation:

```markdown
# .cursorrules

You are an expert Full-Stack TypeScript and Rust developer.
Always adhere strictly to these conventions:

- Framework: Next.js 15 (App Router), React 19, Tailwind CSS v4.
- Language: Strict TypeScript, no `any`, use `unknown` with type guards.
- Code Style: Functional, immutable, early returns, descriptive error messages.
- State: Favor Server Components and Server Actions over client state.
- Testing: Always write unit tests with Vitest and integration tests with Playwright.
- Do NOT hallucinate dependencies not present in package.json.
- When generating code, omit explanatory conversational filler; output code and brief rationale.

Targeted Context Tagging with @ Directives

Injecting precise context into AI prompt buffers:

Prompt:
@codebase How is authentication token verification handled across our microservice routes?
Inspect @middleware.ts and @src/auth/session.ts to implement a new rate-limited admin route guard.
Ensure compliance with @docs/security-guidelines.md.

Multi-File Composer Refactoring Workflows

Prompting across architectural boundaries:

Prompt in Composer:
Refactor our legacy User REST endpoints to modern Server Actions:
1. Create app/actions/user.ts with Zod input validation schemas.
2. Update app/profile/page.tsx to call the server action with useActionState.
3. Remove old API route handler in app/api/user/route.ts.
4. Add unit test in tests/actions/user.test.ts verifying rejection of invalid email.

Common Patterns

Global and Project .cursorrules Configuration

Problem: Cursor generates responses with generic boilerplate that violates repository architectural rules.
Solution: Define comprehensive repository rules in root .cursorrules.

# .cursorrules

- Prefer TypeScript strict mode with no explicit 'any'.
- Use named exports rather than default exports for React components.
- Colocate unit tests next to source files using the *.test.ts pattern.
- Wrap all external network calls with timeout boundaries.

Best Practices

Do:

• Create a .cursorrules file in the project root to permanently align model completions with team conventions.
• Use @file, @docs, and @symbol instead of @codebase for targeted tasks to reduce prompt token noise and cost.
• Review AI-generated diffs carefully before accepting multi-file Composer changes.
• Configure .cursorignore to prevent indexing of generated files, .env secrets, and build output directories.

Don't:

• Prompt the AI with raw database passwords, production API keys, or private customer data.
• Blindly accept massive multi-file refactors without running automated test suites (npm test).
• Write ambiguous prompts; specify desired libraries, error handling strategies, and boundary constraints.

Troubleshooting

Error	Cause	Solution
Codebase indexing failed	Massive files (node_modules, large binaries) not excluded.	Add paths to .cursorignore.
Composer diff cannot be applied	File edited externally while Cursor was generating code.	Re-run prompt using fresh file state.
Cursor tab autocomplete sluggish	Large language server indexing lag in background.	Restart Cursor or disable unused language extensions.

References

• Cursor Documentation