revenuecat-identify-user: connect RevenueCat to your auth system

Use this skill when the user wants to call logIn / logOut on the RevenueCat SDK so that their app users line up with RevenueCat subscribers. This skill does not cover initial SDK setup (see integrate-revenuecat), purchases (revenuecat-purchase-flow), or gating (revenuecat-entitlements-gate).

1. Detect the platform

Inspect the working directory and pick the first match, from top to bottom:

1. React Native: package.json has a react-native-purchases entry, or react-native as a dependency → read platforms/react-native.md. If expo is also a dependency, note it as an Expo project.
2. Flutter: pubspec.yaml exists at the project root → read platforms/flutter.md.
3. Kotlin Multiplatform: build.gradle.kts contains a kotlin { … } multiplatform source sets block, or depends on com.revenuecat.purchases:purchases-kmp* → read platforms/kmp.md.
4. Android (native): build.gradle(.kts) applies com.android.application (and is not KMP) → read platforms/android.md.
5. iOS (native): Package.swift, *.xcodeproj, *.xcworkspace, or Podfile at the project root → read platforms/ios.md.

If several match (e.g. an ios/ folder inside a Flutter project), pick the outermost project, the one that owns the build. If still ambiguous, ask the user which platform they want to configure.

2. Shared concepts (all platforms)

• Anonymous by default. Before logIn is called, RevenueCat assigns a stable anonymous ID prefixed $RCAnonymousID:. Purchases made while anonymous are aliased onto the real appUserID the first time logIn is called with it, so there is no "lost purchase" risk from letting users buy before signing in.
• Never use email, phone number, or a sequential database id as the appUserID. Use a stable opaque value such as your backend's user UUID, or a hash of the user id. RevenueCat treats the ID as an opaque string and it is difficult to change later.
• Call logIn after your auth system confirms the session. Do not call logIn speculatively. The typical trigger is your auth state listener firing with a signed in user. logIn returns both the user's current CustomerInfo and a created: Boolean that tells you whether this is a brand new RevenueCat customer.
• logOut only works on identified users. Calling logOut while the SDK is on an anonymous ID throws an error in every SDK (PurchasesErrorCode.LogOutWithAnonymousUserError or the iOS equivalent). Gate it behind your own "is signed in" flag.
• Restore is not login. restorePurchases() asks the store for the current receipt and attaches it to the current RevenueCat user. It does not switch identities. If the user signs in on a new device, call logIn(appUserID) first, then restorePurchases() only if they also expect to pull a receipt from the current store account.
• Account switching is logOut then logIn. If your app lets a user sign out and sign back in as someone else, call logOut() first, wait for it, then logIn(newId). Do not try to swap directly with a second logIn, since that will alias the two IDs together.
• Configure first. Purchases.configure(…) must have run before logIn / logOut. If it has not, the SDK throws.

3. Implementation

Read the platform file that matches detection:

• platforms/ios.md
• platforms/android.md
• platforms/kmp.md
• platforms/flutter.md
• platforms/react-native.md

Each platform file shows the logIn and logOut calls wired into a typical auth state observer.

4. Verify

Do not claim identity sync works until:

1. In the RevenueCat dashboard, the Customer page for your test user shows the same appUserID your backend uses, not the $RCAnonymousID: placeholder.
2. Signing out clears the ID back to a fresh anonymous user; signing in as a different account switches to that account's purchases (or shows none if it is a new account).
3. A purchase made while anonymous, followed by logIn, remains attached to the signed in user (aliased, not lost).
4. Calling logOut while already anonymous is handled, not treated as a crash or a silent success.