Imported from agustinusnathaniel/nextarter-tailwind (AGENTS.md). Install upstream with npx skills add agustinusnathaniel/nextarter-tailwind. Copyright stays with the author.

Next.js: ALWAYS read docs before coding

Before any Next.js work, find and read the relevant doc in node_modules/next/dist/docs/. Your training data is outdated — the docs are the source of truth.

AI Agent Guidance: nextarter-tailwind

This file provides context and instructions for AI agents (Cursor, Antigravity, Zed, Windsurf) to effectively navigate and modify this repository.

1. Mental Model for Agents

Implementation Delegation

The most important pattern to understand is that src/app is just a shell.

• To modify a page's content, look in src/lib/pages/[page-name].
• To modify the site-wide layout, look in src/lib/layout.
• Do NOT add heavy logic or massive JSX blocks directly into src/app.

Tooling Strategy

• Linter: We use Biome. Do not suggest adding ESLint or Prettier config.
• Package Manager: pnpm. Use pnpm for all commands.
• Styles: Tailwind CSS v4. Use standard utility classes.

2. Module Blueprint

3. Recommended Prompts for LLMs

• Adding a Page: "I want to add a new page /about. Create a new directory src/lib/pages/about, implement the component there, and then create src/app/about/page.tsx that exports it."
• Adding a Shared Component: "Create a new atomic component Button in src/lib/components/button.tsx. Follow the kebab-case naming convention and use named exports."
• Refactoring Styles: "Review the Tailwind classes in src/lib/pages/home/index.tsx and suggest optimizations or consistency improvements based on the existing design tokens in globals.css."

4. Known Pitfalls for Agents

1. Default vs Named Exports: Biome enforced named exports for everything in lib. Next.js requires default exports for app files. Agents often mix these up.
2. Path Aliases: Always use @/... aliases for imports.
3. Hydration Warnings: When adding theme-dependent components, ensure they handle hydration correctly (use next-themes and check for mounted state if necessary, or rely on the suppressHydrationWarning at root).
4. Tailwind v4 Nuances: Be aware that Tailwind v4 may have different configuration approaches compared to v3 (e.g., CSS-first configuration).

5. IDE Specific Hints

• Cursor/Antigravity: Reference SPEC.md when planning structural changes.
• Windsurf: Use the "Lib-Delegation" concept to focus your search in src/lib instead of getting lost in src/app.
• Zed: Focus on the src/lib directory for implementation details.

Ultracite Code Standards

This project uses Ultracite, a zero-config preset that enforces strict code quality standards through automated formatting and linting.

Quick Reference

• Format code: pnpm dlx ultracite fix
• Check for issues: pnpm dlx ultracite check
• Diagnose setup: pnpm dlx ultracite doctor

Biome (the underlying engine) provides robust linting and formatting. Most issues are automatically fixable.

Core Principles

Write code that is accessible, performant, type-safe, and maintainable. Focus on clarity and explicit intent over brevity.

Type Safety & Explicitness

• Use explicit types for function parameters and return values when they enhance clarity
• Prefer unknown over any when the type is genuinely unknown
• Use const assertions (as const) for immutable values and literal types
• Leverage TypeScript's type narrowing instead of type assertions
• Use meaningful variable names instead of magic numbers - extract constants with descriptive names

Modern JavaScript/TypeScript

• Use arrow functions for callbacks and short functions
• Prefer for...of loops over .forEach() and indexed for loops
• Use optional chaining (?.) and nullish coalescing (??) for safer property access
• Prefer template literals over string concatenation
• Use destructuring for object and array assignments
• Use const by default, let only when reassignment is needed, never var

Async & Promises

• Always await promises in async functions - don't forget to use the return value
• Use async/await syntax instead of promise chains for better readability
• Handle errors appropriately in async code with try-catch blocks
• Don't use async functions as Promise executors

React & JSX

• Use function components over class components
• Call hooks at the top level only, never conditionally
• Specify all dependencies in hook dependency arrays correctly
• Use the key prop for elements in iterables (prefer unique IDs over array indices)
• Nest children between opening and closing tags instead of passing as props
• Don't define components inside other components
• Use semantic HTML and ARIA attributes for accessibility:
  • Provide meaningful alt text for images
  • Use proper heading hierarchy
  • Add labels for form inputs
  • Include keyboard event handlers alongside mouse events
  • Use semantic elements (<button>, <nav>, etc.) instead of divs with roles

Error Handling & Debugging

• Remove console.log, debugger, and alert statements from production code
• Throw Error objects with descriptive messages, not strings or other values
• Use try-catch blocks meaningfully - don't catch errors just to rethrow them
• Prefer early returns over nested conditionals for error cases

Code Organization

• Keep functions focused and under reasonable cognitive complexity limits
• Extract complex conditions into well-named boolean variables
• Use early returns to reduce nesting
• Prefer simple conditionals over nested ternary operators
• Group related code together and separate concerns

Security

• Add rel="noopener" when using target="_blank" on links
• Avoid dangerouslySetInnerHTML unless absolutely necessary
• Don't use eval() or assign directly to document.cookie
• Validate and sanitize user input

Performance

• Avoid spread syntax in accumulators within loops
• Use top-level regex literals instead of creating them in loops
• Prefer specific imports over namespace imports
• Avoid barrel files (index files that re-export everything)
• Use proper image components (e.g., Next.js <Image>) over <img> tags

Framework-Specific Guidance

Next.js:

• Use Next.js <Image> component for images
• Use next/head or App Router metadata API for head elements
• Use Server Components for async data fetching instead of async Client Components

React 19+:

• Use ref as a prop instead of React.forwardRef

Solid/Svelte/Vue/Qwik:

• Use class and for attributes (not className or htmlFor)

Testing

• Write assertions inside it() or test() blocks
• Avoid done callbacks in async tests - use async/await instead
• Don't use .only or .skip in committed code
• Keep test suites reasonably flat - avoid excessive describe nesting

When Biome Can't Help

Biome's linter will catch most issues automatically. Focus your attention on:

1. Business logic correctness - Biome can't validate your algorithms
2. Meaningful naming - Use descriptive names for functions, variables, and types
3. Architecture decisions - Component structure, data flow, and API design
4. Edge cases - Handle boundary conditions and error states
5. User experience - Accessibility, performance, and usability considerations
6. Documentation - Add comments for complex logic, but prefer self-documenting code

Most formatting and common issues are automatically fixed by Biome. Run pnpm dlx ultracite fix before committing to ensure compliance.