building-storefronts

# Medusa Storefront Development

Frontend integration guide for building storefronts with Medusa. Covers SDK usage, React Query patterns, and calling custom API routes.

## When to Apply

**Load this skill for ANY storefront development task, including:**
- Calling custom Medusa API routes from the storefront
- Integrating Medusa SDK in frontend applications
- Using React Query for data fetching
- Implementing mutations with optimistic updates
- Error handling and cache invalidation

**Also load building-with-medusa when:** Building the backend API routes that the storefront calls

## CRITICAL: Load Reference Files When Needed

**The quick reference below is NOT sufficient for implementation.** You MUST load the reference file before writing storefront integration code.

**Load this reference when implementing storefront features:**

- **Calling API routes?** → MUST load `references/frontend-integration.md` first
- **Using SDK?** → MUST load `references/frontend-integration.md` first
- **Implementing React Query?** → MUST load `references/frontend-integration.md` first

## Rule Categories by Priority

| Priority | Category | Impact | Prefix |
|----------|----------|--------|--------|
| 1 | SDK Usage | CRITICAL | `sdk-` |
| 2 | React Query Patterns | HIGH | `query-` |
| 3 | Error Handling | MEDIUM | `error-` |

## Quick Reference

### 1. SDK Usage (CRITICAL)

- `sdk-no-json-stringify` - **NEVER use JSON.stringify() on body** - SDK handles serialization automatically
- `sdk-plain-objects` - Pass plain JavaScript objects to body, not strings
- `sdk-locate-first` - Always locate where SDK is instantiated in the project before using it
- `sdk-client-fetch` - Use `sdk.client.fetch()` for custom API routes
- `sdk-auto-headers` - SDK automatically adds Content-Type, auth headers, and API key

### 2. React Query Patterns (HIGH)

- `query-use-query` - Use `useQuery` for GET requests (data fetching)
- `query-use-mutation` - Use `useMutation` for POST/DELETE requests (mutations