cloud_functions iOS crash (SIGABRT / libswift_Concurrency) when calling httpsCallable on physical device in profile/release mode (works in debug)

[riyoua]

Is there an existing issue for this?

• I have searched the existing issues.

Which plugins are affected?

Cloud Functions

Which platforms are affected?

iOS

Description

Calling a Firebase HTTPS callable function from Flutter crashes on a physical iPhone in both profile and release mode.

The same code works in debug mode.

I reproduced this both:

1. in my main app
2. in a fresh minimal Flutter app created just for testing

So this does not appear to be specific to my main project code.

Environment

• Device: iPhone 14 Pro Max (physical device)
• iOS version: 26.4
• macOS: 26.4
• Xcode: 26.4 (17E192)
• Flutter: 3.41.6
• firebase_core: 4.6.0
• cloud_functions: 6.1.0

Reproducing the issue

final functions = FirebaseFunctions.instanceFor(region: 'europe-west1');
final callable = functions.httpsCallable('now');

debugPrint('[TEST][now] before call');
final response = await callable.call(<String, dynamic>{});
debugPrint('[TEST][now] after call data=${response.data}');

Fresh Flutter app with only:

• firebase_core
• cloud_functions

Firebase is initialized with:

await Firebase.initializeApp(
  options: DefaultFirebaseOptions.currentPlatform,
);

Firebase Core version

4.6.0

Flutter Version

3.41.6

Relevant Log Output

flutter DEBUG CONSOLE : 
  


Launching lib/main.dart on Riyadh’s iPhone in profile mode...
Automatically signing iOS for device deployment using specified development team in Xcode project: 4P8V3U9463
Xcode build done.                                           18.5s
flutter: [TEST] Firebase initialized
flutter: [TEST][now] before call
Process 1691 stopped
* thread #24, name = 'Task 1', queue = 'com.apple.root.user-initiated-qos.cooperative', stop reason = signal SIGABRT
    frame #0: 0x000000024e5971d0 libsystem_kernel.dylib`__pthread_kill + 8
libsystem_kernel.dylib`__pthread_kill:
->  0x24e5971d0 <+8>:  b.lo   0x24e5971f0               ; <+40>
    0x24e5971d4 <+12>: pacibsp
    0x24e5971d8 <+16>: stp    x29, x30, [sp, #-0x10]!
    0x24e5971dc <+20>: mov    x29, sp
Target 0: (Runner) stopped.
Application finished.

Exited.


`LLDB backtrace : `
* thread #25, name = 'Task 1', queue = 'com.apple.root.user-initiated-qos.cooperative', stop reason = signal SIGABRT
  * frame #0: 0x000000024e5971d0 libsystem_kernel.dylib`__pthread_kill + 8
    frame #1: 0x00000001fe8fe7dc libsystem_pthread.dylib`pthread_kill + 268
    frame #2: 0x00000001ab630de4 libsystem_c.dylib`abort + 148
    frame #3: 0x000000019dc4d258 libswift_Concurrency.dylib`swift::swift_Concurrency_fatalErrorv(unsigned int, char const*, char*) + 32
    frame #4: 0x000000019dbfe6d4 libswift_Concurrency.dylib`swift::swift_Concurrency_fatalError(unsigned int, char const*, ...) + 32
    frame #5: 0x000000019dc4d3ec libswift_Concurrency.dylib`swift::_swift_task_dealloc_specific(swift::AsyncTask*, void*) (.cold.2) + 84
    frame #6: 0x000000019dbdc2e0 libswift_Concurrency.dylib`swift::_swift_task_dealloc_specific(swift::AsyncTask*, void*) + 108
    frame #7: 0x000000019dbebfa4 libswift_Concurrency.dylib`asyncLet_finish_after_task_completion(swift::AsyncContext*, swift::AsyncLet*, void (swift::AsyncContext* swift_async_context) swiftasynccall*, swift::AsyncContext*, void*) + 108
    frame #8: 0x000000019dbdbf60 libswift_Concurrency.dylib`swift::runJobInEstablishedExecutorContext(swift::Job*) + 472
    frame #9: 0x000000019dbdabfc libswift_Concurrency.dylib`swift_job_runImpl(swift::Job*, swift::SerialExecutorRef) + 156
    frame #10: 0x00000001053cfb90 libdispatch.dylib`_dispatch_root_queue_drain + 512
    frame #11: 0x00000001053d0488 libdispatch.dylib`_dispatch_worker_thread2 + 204
    frame #12: 0x00000001fe8f8374 libsystem_pthread.dylib`_pthread_wqthread + 232

Flutter dependencies

Expand Flutter dependencies snippet

Dart SDK 3.11.4
Flutter SDK 3.41.6
firebase_test_app 1.0.0+1

dependencies:
- cloud_functions 6.1.0 [cloud_functions_platform_interface cloud_functions_web firebase_core firebase_core_platform_interface flutter]
- cupertino_icons 1.0.9
- firebase_core 4.6.0 [firebase_core_platform_interface firebase_core_web flutter meta]
- flutter 0.0.0 [characters collection material_color_utilities meta vector_math sky_engine]

dev dependencies:
- flutter_lints 6.0.0 [lints]
- flutter_test 0.0.0 [flutter test_api matcher path fake_async clock stack_trace vector_math leak_tracker_flutter_testing collection meta stream_channel]

transitive dependencies:
- async 2.13.1 [collection meta]
- boolean_selector 2.1.2 [source_span string_scanner]
- characters 1.4.1
- clock 1.1.2
- cloud_functions_platform_interface 5.8.11 [firebase_core flutter meta plugin_platform_interface]
- cloud_functions_web 5.1.4 [cloud_functions_platform_interface firebase_core firebase_core_web flutter flutter_web_plugins web]
- collection 1.19.1
- fake_async 1.3.3 [clock collection]
- firebase_core_platform_interface 6.0.3 [collection flutter flutter_test meta plugin_platform_interface]
- firebase_core_web 3.5.1 [firebase_core_platform_interface flutter flutter_web_plugins meta web]
- flutter_web_plugins 0.0.0 [flutter]
- leak_tracker 11.0.2 [clock collection meta path vm_service]
- leak_tracker_flutter_testing 3.0.10 [flutter leak_tracker leak_tracker_testing matcher meta]
- leak_tracker_testing 3.0.2 [leak_tracker matcher meta]
- lints 6.1.0
- matcher 0.12.19 [async meta stack_trace term_glyph test_api]
- material_color_utilities 0.13.0 [collection]
- meta 1.17.0
- path 1.9.1
- plugin_platform_interface 2.1.8 [meta]
- sky_engine 0.0.0
- source_span 1.10.2 [collection path term_glyph]
- stack_trace 1.12.1 [path]
- stream_channel 2.1.4 [async]
- string_scanner 1.4.1 [source_span]
- term_glyph 1.2.2
- test_api 0.7.10 [async boolean_selector collection meta source_span stack_trace stream_channel string_scanner term_glyph]
- vector_math 2.2.0
- vm_service 15.0.2
- web 1.1.1```

</details>


### Additional context and comments

_No response_

[stanimeros]

Suggested Fix: Swift 6.1 Optimization Workaround

Add the following logic to your Podfile inside the post_install block to resolve the Swift 6.1 compiler issue for FirebaseFunctions:

    if target.name == 'FirebaseFunctions'
      target.build_configurations.each do |config|
        if config.name == 'Release'
          config.build_settings['SWIFT_OPTIMIZATION_LEVEL'] = '-Onone'
          puts "Applied -Onone fix to #{target.name} for Swift 6.1 bug."
        end
      end
    end

[riyoua]

@stanimeros
I followed your instructions and it worked , I wonder is it because of
config.build_settings['SWIFT_OPTIMIZATION_LEVEL'] = '-Onone'
or
config.build_settings['ENABLE_BITCODE'] = 'NO'
another thing is leaving the pod file with this configuration ideal or just temporary workaround while I still work and test in my project ?
I should leave this bug open right ? since it reproducible

[stanimeros]

@riyoua

I believe the fix lies in SWIFT_OPTIMIZATION_LEVEL. By setting it to None, we stop the compiler from restructuring the Pods' source code, which seems to be the source of the issue. Yes leave this bug open, but I think we need to wait a fix from swift's side.

[stephanschoenig]

We're experiencing the same crash — identical stack trace (swift_Concurrency_fatalErrorv → _swift_task_dealloc_specific → asyncLet_finish_after_task_completion → HTTPSCallable.call), cloud_functions: 6.1.0, iOS 26.4, iPhone 15 Pro Max, release/TestFlight builds only.

Root cause: This is a known Swift 6.1 compiler bug — swiftlang/swift#81771. The Swift compiler generates incorrect LIFO teardown ordering for async task allocations when optimizations are enabled, which is why -Onone works as a workaround. A fix exists as swiftlang/swift#87571 but hasn't been merged yet. See also the .

The crash is triggered specifically by the combination of:

1. Swift 6.1 runtime bug in async task deallocation
2. cloud_functions 6.1.0's UIScene lifecycle migration (feat(ios): migrate iOS to UIScene lifecycle #18054)
3. iOS 26.4 on real devices (simulator uses macOS Swift runtime, unaffected)

Our published app with cloud_functions: 6.0.7 works fine on iOS 26.4 — only the 6.1.0 upgrade triggers it.

Alternative workaround (no performance penalty): Instead of disabling Swift optimization, you can bypass HTTPSCallable.call() entirely by making a direct HTTP POST to the callable function URL following the https://firebase.google.com/docs/functions/callable-reference:

final url = Uri.https(
  '$region-$projectId.cloudfunctions.net',
  '/$functionName',
);

final idToken = await user.getIdToken();
final appCheckToken = await FirebaseAppCheck.instance.getToken();

final response = await http.post(
  url,
  headers: {
    'Content-Type': 'application/json; charset=utf-8',
    'Authorization': 'Bearer $idToken',
    if (appCheckToken != null) 'X-Firebase-AppCheck': appCheckToken,
  },
  body: jsonEncode({'data': parameters}),
);
                                                              
final body = jsonDecode(response.body) as Map<String, dynamic>;
final result = body['result'] as Map<String, dynamic>;
...

This is pure Dart (no native Swift code involved), so it sidesteps the crash completely without sacrificing optimization for the rest of the app.

We've confirmed this works on iOS 26.4 real devices via TestFlight.

[stanimeros]

@stephanschoenig

Thank you, so you think is the firebase functions package with the issue? Are we sure that the swift optimization will not cause in similar issues in other pods/packages?

[gotnull]

Note: firebase_storage: 13.2.0 is also affected by the same Swift 6.1 async optimizer crash - same root cause, same PR (#18054 - UIScene lifecycle migration).

The crash manifests identically: _swift_task_dealloc_specific → freed pointer was not the last allocation on cooperative queue threads when calling FirebaseStorage.putData() or ref.getDownloadURL() in Release/Profile builds on physical iOS devices.

Safe versions (pre-UIScene migration):

• cloud_functions: 6.0.7
• firebase_storage: 13.1.0

Pinning both in pubspec.yaml (no ^ caret) avoids the crash across all code paths - no Podfile hacks or -Onone workarounds needed.

Environment: Flutter 3.41.6, Dart 3.11.4, firebase_core 4.6.0, Xcode 26.4, iOS 26.4, iPhone 14 Pro / iPhone 15 Pro Max (physical devices).