Swift Compiler Error '<Project>/build/ios/Debug-iphonesimulator/Flutter.framework/Headers/FlutterPlugin.h' has been modified since the precompiled header (Derived Data) 'Runner-primary-Bridging-header.pch' was built: size changed (was 16886, now 17731)

[tirth-patel-nc]

Steps to reproduce

1. Create a new project with Flutter Stable 3.35.5.
2. Run it.
3. Runs successfully.
4. Switch to Flutter Master 3.37.0-1.0.pre-395.
5. Run it.
6. Fails with an error.

PS - Switching back to stable from master does not cause this error.
Note - If you run the project first with master and then switch to stable it also fails. It is not specific to iOS 26. Observed similar behaviour on iOS 18 as well.

I first noticed this about 1-2 weeks ago, but thanks to @huycozy we decided to report it earlier.

Expected results

App should run fine without error while switching Flutter version.

Actual results

App fails to run when switching Flutter versions. running flutter clean before switching works as a workaround, but it only masks the underlying bug.

Code sample

Code sample (Counter App)

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // TRY THIS: Try running your application with "flutter run". You'll see
        // the application has a purple toolbar. Then, without quitting the app,
        // try changing the seedColor in the colorScheme below to Colors.green
        // and then invoke "hot reload" (save your changes or press the "hot
        // reload" button in a Flutter-supported IDE, or press "r" if you used
        // the command line to start the app).
        //
        // Notice that the counter didn't reset back to zero; the application
        // state is not lost during the reload. To reset the state, use hot
        // restart instead.
        //
        // This works for code too, not just values: Most code changes can be
        // tested with just a hot reload.
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      // This call to setState tells the Flutter framework that something has
      // changed in this State, which causes it to rerun the build method below
      // so that the display can reflect the updated values. If we changed
      // _counter without calling setState(), then the build method would not be
      // called again, and so nothing would appear to happen.
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    // This method is rerun every time setState is called, for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
      appBar: AppBar(
        // TRY THIS: Try changing the color here to a specific color (to
        // Colors.amber, perhaps?) and trigger a hot reload to see the AppBar
        // change color while the other colors stay the same.
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text(widget.title),
      ),
      body: Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: Column(
          // Column is also a layout widget. It takes a list of children and
          // arranges them vertically. By default, it sizes itself to fit its
          // children horizontally, and tries to be as tall as its parent.
          //
          // Column has various properties to control how it sizes itself and
          // how it positions its children. Here we use mainAxisAlignment to
          // center the children vertically; the main axis here is the vertical
          // axis because Columns are vertical (the cross axis would be
          // horizontal).
          //
          // TRY THIS: Invoke "debug painting" (choose the "Toggle Debug Paint"
          // action in the IDE, or press "p" in the console), to see the
          // wireframe for each widget.
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            const Text('You have pushed the button this many times:'),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headlineMedium,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: const Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

Screenshots or Video

Screenshots / Video demonstration

Not Needed

Logs

Logs

Launching lib/main.dart on iPhone 16 in debug mode...
Xcode build done.                                            8.8s
Failed to build iOS app
Swift Compiler Error (Xcode): File '/Users/tirthpatel/oc3/build/ios/Debug-iphonesimulator/Flutter.framework/Headers/FlutterPlugin.h' has been modified since the precompiled header '/Users/tirthpatel/Library/Developer/Xcode/DerivedData/Runner-afkyswegtzthsecmzsuwmpuabijy/Build/Intermediates.noindex/Runner.build/Debug-iphonesimulator/Runner.build/Objects-normal/arm64/Runner-primary-Bridging-header.pch' was built: size changed (was 16886, now 17731)

Could not build the application for the simulator.
Error launching application on iPhone 16.

Exited (1).

Verbose Logs

output.txt

Flutter Doctor output

Doctor output

[✓] Flutter (Channel master, 3.37.0-1.0.pre-395, on macOS 26.1 25B5042k darwin-arm64, locale en-IN) [1,136ms]
    • Flutter version 3.37.0-1.0.pre-395 on channel master at /Users/tirthpatel/Development/flutter_master/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision ddbc920ace (10 hours ago), 2025-10-02 22:15:32 -0400
    • Engine revision ddbc920ace
    • Dart version 3.10.0 (build 3.10.0-275.0.dev)
    • DevTools version 2.50.0
    • Feature flags: enable-web, enable-linux-desktop, enable-macos-desktop, enable-windows-desktop, enable-android, enable-ios,
      enable-custom-devices, cli-animations, enable-native-assets, enable-swift-package-manager, omit-legacy-version-file,
      enable-lldb-debugging

[✓] Android toolchain - develop for Android devices (Android SDK version 36.0.0) [10.3s]
    • Android SDK at /Users/tirthpatel/Library/Android/sdk
    • Emulator version 36.1.9.0 (build_id 13823996) (CL:N/A)
    • Platform android-36, build-tools 36.0.0
    • Java binary at: /Applications/Android Studio.app/Contents/jbr/Contents/Home/bin/java
      This is the JDK bundled with the latest Android Studio installation on this machine.
      To manually set the JDK path, use: `flutter config --jdk-dir="path/to/jdk"`.
    • Java version OpenJDK Runtime Environment (build 21.0.7+-13880790-b1038.58)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 26.0.1) [656ms]
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Build 17A400
    • CocoaPods version 1.16.2

[✓] Chrome - develop for the web [8ms]
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Connected device (3 available) [5.8s]
    • iPhone 16 (mobile) • 5C14D591-84B7-4D47-91CA-7E269334505C • ios            • com.apple.CoreSimulator.SimRuntime.iOS-26-0 (simulator)
    • macOS (desktop)    • macos                                • darwin-arm64   • macOS 26.1 25B5042k darwin-arm64
    • Chrome (web)       • chrome                               • web-javascript • Google Chrome 140.0.7339.214

[✓] Network resources [1,032ms]
    • All expected network resources are available.

• No issues found!

[✓] Flutter (Channel stable, 3.35.5, on macOS 26.1 25B5042k darwin-arm64, locale en-IN) [306ms]
    • Flutter version 3.35.5 on channel stable at /Users/tirthpatel/Development/flutter_3.35.5/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision ac4e799d23 (7 days ago), 2025-09-26 12:05:09 -0700
    • Engine revision d3d45dcf25
    • Dart version 3.9.2
    • DevTools version 2.48.0
    • Feature flags: enable-web, enable-linux-desktop, enable-macos-desktop, enable-windows-desktop, enable-android, enable-ios, enable-custom-devices, cli-animations,
      enable-swift-package-manager, enable-lldb-debugging

[✓] Android toolchain - develop for Android devices (Android SDK version 36.0.0) [945ms]
    • Android SDK at /Users/tirthpatel/Library/Android/sdk
    • Emulator version 36.1.9.0 (build_id 13823996) (CL:N/A)
    • Platform android-36, build-tools 36.0.0
    • Java binary at: /Applications/Android Studio.app/Contents/jbr/Contents/Home/bin/java
      This is the JDK bundled with the latest Android Studio installation on this machine.
      To manually set the JDK path, use: `flutter config --jdk-dir="path/to/jdk"`.
    • Java version OpenJDK Runtime Environment (build 21.0.7+-13880790-b1038.58)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 26.0.1) [545ms]
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Build 17A400
    • CocoaPods version 1.16.2

[✓] Chrome - develop for the web [111ms]
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 2025.1) [111ms]
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 21.0.7+-13880790-b1038.58)

[✓] IntelliJ IDEA Ultimate Edition (version 2025.1.3) [110ms]
    • IntelliJ at /Applications/IntelliJ IDEA.app
    • Flutter plugin version 86.0.2
    • Dart plugin version 251.27623.5

[✓] IntelliJ IDEA Community Edition (version 2025.1.3) [48ms]
    • IntelliJ at /Applications/IntelliJ IDEA CE.app
    • Flutter plugin version 86.0.2
    • Dart plugin version 251.26927.39

[✓] VS Code (version 1.104.3) [7ms]
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.120.0

[✓] Connected device (3 available) [5.8s]
    • iPhone 16 (mobile) • 5C14D591-84B7-4D47-91CA-7E269334505C • ios            • com.apple.CoreSimulator.SimRuntime.iOS-26-0 (simulator)
    • macOS (desktop)    • macos                                • darwin-arm64   • macOS 26.1 25B5042k darwin-arm64
    • Chrome (web)       • chrome                               • web-javascript • Google Chrome 140.0.7339.214

[✓] Network resources [1,017ms]
    • All expected network resources are available.

• No issues found!

[jmagman]

Hm, our fingerprint logic should detect that the framework changed and then recopy it:

flutter/packages/flutter_tools/lib/src/build_system/targets/ios.dart

Line 253 in 238db35

Source.artifact(Artifact.flutterXcframework, platform: TargetPlatform.ios, mode: buildMode),

[vashworth]

I was able to recreate this. It appears to be specific to Xcode 26. I'm unable to replicate with Xcode 16.3.

Hm, our fingerprint logic should detect that the framework changed and then recopy it:

I validated that flutter assemble is copying the framework into the BUILT_PRODUCTS_DIR correctly.

It seems that Xcode 26 validates that the Flutter.framework's headers match the last generated "pre-compiled" header

path/Intermediates.noindex/Runner.build/Debug-iphonesimulator/Runner.build/Objects-normal/arm64/Runner-primary-Bridging-header.pch

This pch file is not created with Xcode 16.3.