iOS Release build fails with 'unsupported Swift architecture' error in version 6.17.7

[steve-rodri]

Bug Report: Unsupported Swift Architecture Error in react-native-appsflyer@6.17.7

Summary

Version 6.17.7 of react-native-appsflyer introduces a regression that causes iOS Release builds to fail with the error: unsupported Swift architecture.

Environment

• Package: react-native-appsflyer
• Broken Version: 6.17.7 (published October 22, 2025)
• Working Versions: 6.17.2, 6.17.5
• Platform: iOS
• Build Configuration: Release mode
• Framework: Expo SDK 54
• React Native: 0.81.5
• Xcode: 26.1 (Build version 17B55)
• macOS: Darwin 25.0.0

Steps to Reproduce

1. Create an Expo project with Swift AppDelegate (default in Expo SDK 53+)
2. Install react-native-appsflyer@6.17.7
3. Run expo prebuild --clean --platform ios
4. Run expo run:ios --configuration Release

Expected Behavior

The iOS app should build successfully in Release mode, as it does with versions 6.17.2 and 6.17.5.

Actual Behavior

Build fails with the following error:

❌  (../../node_modules/react-native-appsflyer/ios/AppsFlyerLib-Swift.h:330:2)

  328 |
  329 | #else
> 330 | #error unsupported Swift architecture
      |  ^ unsupported Swift architecture
  331 | #endif
  332 |

Analysis

The AppsFlyerLib-Swift.h file only supports the __arm64__ architecture (line 2 of the header file):

#if 0
#elif defined(__arm64__) && __arm64__
// Generated by Apple Swift version 5.9.2 (swiftlang-5.9.2.2.56 clang-1500.1.0.2.5)
...
#else
#error unsupported Swift architecture
#endif

When building in Release mode, the build process appears to be including architectures that AppsFlyer doesn't support, triggering the error.

Version Testing Results

• ✅ 6.17.2 (July 30, 2025) - Works correctly
• ✅ 6.17.5 (September 3, 2025) - Works correctly
• ❌ 6.17.7 (October 22, 2025) - Fails with architecture error

Workaround

Downgrade to version 6.17.5:

npm install react-native-appsflyer@6.17.5
# or
bun add react-native-appsflyer@6.17.5

Then run:

expo prebuild --clean --platform ios

Additional Context

• This issue is related to PR feat: add Swift AppDelegate support for expo #624 which added Swift AppDelegate support
• Version 6.17.7 is not documented in the CHANGELOG.md file
• The issue only affects Release builds; Debug builds may work
• This regression blocks developers from using the latest version with Expo SDK 53+ which uses Swift AppDelegate by default

Suggested Fix

Investigate changes made between 6.17.5 and 6.17.7 that might have affected the iOS Swift header generation or architecture support. The issue appears to be specific to how the AppsFlyer SDK's Swift interface is being compiled for different architectures.

[github-actions]

👋 Hi @steve-rodri and Thank you for opening this issue.
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To do so, please follow this article.

[OwenMelbz]

Getting the same bug.

I chucked the changelog into Claude 6.17.5...6.17.7 and it said:

I understand the issue. The file has a preprocessor check that only allows arm64 architecture, but iOS simulators need support for x86_64 (Intel simulators) and potentially arm64 for Apple Silicon simulators. The fix is to modify the architecture check to support simulator architectures.

This patch-package worked for us

diff --git a/node_modules/react-native-appsflyer/ios/AppsFlyerLib-Swift.h b/node_modules/react-native-appsflyer/ios/AppsFlyerLib-Swift.h
index 091899e..fc9140b 100644
--- a/node_modules/react-native-appsflyer/ios/AppsFlyerLib-Swift.h
+++ b/node_modules/react-native-appsflyer/ios/AppsFlyerLib-Swift.h
@@ -1,6 +1,8 @@
 #if 0
 #elif defined(__arm64__) && __arm64__
 // Generated by Apple Swift version 5.9.2 (swiftlang-5.9.2.2.56 clang-1500.1.0.2.5)
+#elif defined(__x86_64__) && __x86_64__
+// x86_64 support for iOS simulator
 #ifndef APPSFLYERLIB_SWIFT_H
 #define APPSFLYERLIB_SWIFT_H
 #pragma clang diagnostic push

[xavi-999]

@al-af @amit-kremer93 Please delete this build file, all of your lib consumers with the __x86_64__ arch are getting build crashes. Committed build files cannot pass on code review, it has been 3 weeks without a fix.

Thanks

[Makhdoom-Sharif]

Any update on this issue?