axiom-in-app-purchases

# StoreKit 2 In-App Purchase Implementation

**Purpose**: Guide robust, testable in-app purchase implementation
**StoreKit Version**: StoreKit 2
**iOS Version**: iOS 15+ (iOS 18.4+ for latest features)
**Xcode**: Xcode 13+ (Xcode 16+ recommended)
**Context**: WWDC 2025-241, 2025-249, 2023-10013, 2021-10114

## When to Use This Skill

✅ **Use this skill when**:
- Implementing any in-app purchase functionality (new or existing)
- Adding consumable products (coins, hints, boosts)
- Adding non-consumable products (premium features, level packs)
- Adding auto-renewable subscriptions (monthly/annual plans)
- Debugging purchase failures, missing transactions, or restore issues
- Setting up StoreKit testing configuration
- Implementing subscription status tracking
- Adding promotional offers or introductory offers
- Server-side receipt validation
- Family Sharing support

❌ **Do NOT use this skill for**:
- StoreKit 1 (legacy API) - this skill focuses on StoreKit 2
- App Store Connect product configuration (separate documentation)
- Pricing strategy or business model decisions

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## ⚠️ Already Wrote Code Before Creating .storekit Config?

If you wrote purchase code before creating `.storekit` configuration, you have three options:

### Option A: Delete and Start Over (Strongly Recommended)

Delete all IAP code and follow the testing-first workflow below. This reinforces correct habits and ensures you experience the full benefit of .storekit-first development.

**Why this is best**:
- Validates that you understand the workflow
- Catches product ID issues you might have missed
- Builds muscle memory for future IAP implementations
- Takes only 15-30 minutes for experienced developers

### Option B: Create .storekit Config Now (Acceptable with Caution)

Create the `.storekit` file now with your existing product IDs. Test everything works locally. Document in your PR that you tested in sandbox first.

**Trade-offs**:
- ✅ Keeps working code
- ✅ Adds local testing capability
- ❌