Crash on iOS startup after upgrading from Expo SDK 52 to Expo SDK 54

[grascioni]

Description

After upgrading our app from Expo SDK 52 to Expo SDK 54, the iOS app now crashes immediately on startup when using mobile-payments-sdk-react-native. This did not occur on Expo SDK 52.

The crash happens during native module initialization, before any payment-related JavaScript code runs.

Note: The app is running with React Native New Architecture enabled.

Environment

• Expo SDK: 54 (from 52)
• React Native: 0.81+
• Architecture: New Architecture enabled
• mobile-payments-sdk-react-native: 2025.12.1
• Platform: iOS (Simulator, Apple Silicon)
• Workflow: Expo managed
• Package manager: Yarn

Steps to Reproduce

yarn ios

Actual Behavior

App crashes with a SIGTRAP / EXC_BREAKPOINT.

Crash report excerpt:

Thread 0 Crashed:
0 libswiftCore.dylib _assertionFailure(_:_:file:line:flags:)
1 SquareMobilePaymentsSDK
2 MobilePaymentsSdkReactNative.init()

Based on the stack trace and reviewing the SDK source, the assertion appears to be triggered during initialization of the mockReaderUI lazy property in MobilePaymentsSdkReactNative (around line ~237):

private lazy var mockReaderUI: MockReaderUI? = {
    do {
        return try MockReaderUI(for: mobilePaymentsSDK)
    } catch {
        assertionFailure("Could not instantiate a mock reader UI: \(error.localizedDescription)")
        return nil
    }
}()

This assertion fires during module construction, before any JavaScript code executes, causing an immediate app crash.

Expected Behavior

App should launch normally, as it did on Expo SDK 52.

Questions

• Is Expo SDK 54 supported by mobile-payments-sdk-react-native v2025.12.1?
• Are there required changes for Expo SDK 54 compatibility?

Additional Notes

• According to the changelog, v2025.2.0 fixed "an issue with the MockReaderUI dependency for release build configurations" but this crash still occurs in v2025.12.1 with React Native 0.81+
• Attempted workaround: Patching the SDK to replace assertionFailure() with print() fixes this specific crash but reveals a secondary compatibility issue (NativeEventEmitter requires non-null arguments in React Native 0.81+), so the SDK still doesn't work with React Native 0.81+

[tamerbader]

Hi @grascioni , thank you for reporting this and for the detailed issue report. The team is looking into the Expo SDK 54 compatibility issues you’re seeing and will share an update here as soon as we have more.