axiom-storekit-ref

# StoreKit 2 — Complete API Reference

## Overview

StoreKit 2 is Apple's modern in-app purchase framework with async/await APIs, automatic receipt validation, and SwiftUI integration. This reference covers every API, iOS 18.4 enhancements, and comprehensive WWDC 2025 code examples.

### Product Types Supported

**Consumable**:
- Products that can be purchased multiple times
- Examples: coins, hints, temporary boosts
- Do NOT restore on new devices

**Non-Consumable**:
- Products purchased once, owned forever
- Examples: premium features, level packs, remove ads
- MUST restore on new devices

**Auto-Renewable Subscription**:
- Subscriptions that renew automatically
- Organized into subscription groups
- MUST restore on new devices
- Support: free trials, intro offers, promotional offers, win-back offers

**Non-Renewing Subscription**:
- Fixed duration subscriptions (no auto-renewal)
- Examples: seasonal passes
- MUST restore on new devices

### Key Improvements Over StoreKit 1

- **Async/Await**: Modern concurrency instead of delegates/closures
- **Automatic Verification**: JSON Web Signature (JWS) verification built-in
- **Transaction Types**: Strong Swift types instead of SKPaymentTransaction
- **Testing**: StoreKit configuration files for local testing
- **SwiftUI Views**: Pre-built purchase UIs (ProductView, SubscriptionStoreView)
- **Server APIs**: App Store Server API and Server Notifications

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## When to Use This Reference

Use this reference when:
- Implementing in-app purchases with StoreKit 2
- Understanding new iOS 18.4 fields (appTransactionID, offerPeriod, etc.)
- Looking up specific API signatures and parameters
- Planning subscription architecture
- Debugging transaction issues
- Implementing StoreKit Views
- Integrating with App Store Server APIs

**Related Skills**:
- `axiom-in-app-purchases` — Discipline skill with testing-first workflow, architecture patterns
- (Future: `iap-auditor` agent for auditing existing IAP code)
- (Future: `iap-implem