Debugger not attaching in Flutter Web WASM

[rodrigo-itao]

Steps to reproduce

I'm trying to debug a Flutter Web app compiled in WASM mode (using the --wasm flag), but the debugger won't attach.

When I remove the --wasm flag, the debugger attaches correctly.

I'm using WebStorm and debugging by pressing the Debug button (Shift + F9):

Steps to reproduce:

1. Create a sample app (flutter create my_app)
2. Run it with the --wasm flag

Expected results

The debugger should attach.

Actual results

The debugger won't attach.

Code sample

Code sample

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: .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: .center,
          children: [
            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),
      ),
    );
  }
}

Screenshots or Video

Screenshots / Video demonstration

With --wasm flag:

simplescreenrecorder-2025-11-26_18.14.18.mp4

Without --wasm flag:

simplescreenrecorder-2025-11-26_18.15.40.mp4

Logs

Logs

[Paste your logs here]

Flutter Doctor output

Doctor output

[✓] Flutter (Channel stable, 3.38.3, on Ubuntu 24.04.3 LTS 6.8.0-87-generic, locale en_US.UTF-8) [24ms]
    • Flutter version 3.38.3 on channel stable at /home/rodrigo/Documents/flutter/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 19074d12f7 (6 days ago), 2025-11-20 17:53:13 -0500
    • Engine revision 13e658725d
    • Dart version 3.10.1
    • DevTools version 2.51.1
    • Feature flags: enable-web, enable-linux-desktop, enable-macos-desktop, enable-windows-desktop, enable-android, enable-ios, cli-animations, enable-native-assets, omit-legacy-version-file, enable-lldb-debugging

[!] Android toolchain - develop for Android devices (Android SDK version 32.0.0) [151ms]
    • Android SDK at /home/rodrigo/Android/Sdk
    • Emulator version 35.6.11.0 (build_id 13610412) (CL:N/A)
    ✗ cmdline-tools component is missing.
      Try installing or updating Android Studio.
      Alternatively, download the tools from https://developer.android.com/studio#command-line-tools-only and make sure to set the ANDROID_HOME environment variable.
      See https://developer.android.com/studio/command-line for more details.
    ✗ Android license status unknown.
      Run `flutter doctor --android-licenses` to accept the SDK licenses.
      See https://flutter.dev/to/linux-android-setup for more details.

[✓] Chrome - develop for the web [6ms]
    • Chrome at google-chrome

[✓] Linux toolchain - develop for Linux desktop [226ms]
    • Ubuntu clang version 18.1.3 (1ubuntu1)
    • cmake version 3.28.3
    • ninja version 1.11.1
    • pkg-config version 1.8.1
    • OpenGL core renderer: AMD Radeon Graphics (radeonsi, raphael_mendocino, LLVM 20.1.2, DRM 3.57, 6.8.0-87-generic) (X11)
    • OpenGL core version: 4.6 (Core Profile) Mesa 25.0.7-0ubuntu0.24.04.2 (X11)
    • OpenGL core shading language version: 4.60 (X11)
    • OpenGL ES renderer: AMD Radeon Graphics (radeonsi, raphael_mendocino, LLVM 20.1.2, DRM 3.57, 6.8.0-87-generic) (X11)
    • OpenGL ES version: OpenGL ES 3.2 Mesa 25.0.7-0ubuntu0.24.04.2 (X11)
    • OpenGL ES shading language version: OpenGL ES GLSL ES 3.20 (X11)
    • GL_EXT_framebuffer_blit: yes (X11)
    • GL_EXT_texture_format_BGRA8888: yes (X11)

[✓] Connected device (2 available) [79ms]
    • Linux (desktop) • linux  • linux-x64      • Ubuntu 24.04.3 LTS 6.8.0-87-generic
    • Chrome (web)    • chrome • web-javascript • Google Chrome 142.0.7444.162

[✓] Network resources [341ms]
    • All expected network resources are available.

! Doctor found issues in 1 category.

[tirth-patel-nc]

@rodrigo-itao thanks for the report. I have seen this behavior earlier and also noticed something similar in vscode today. I am not able to find any documentation confirming whether attaching a debugger is possible or a known limitation. marking this as a new proposal for the team to track.

[yjbanov]

Debugging in wasm mode is not yet supported.

[Ajay9o9]

Debugging in wasm mode is not yet supported.

@yjbanov is this the reason why we dont get console log to android studio terminal?

BG info:
In normal web build console logs can be seen in Android Studio, in wasm build its not, i have to open chrome console to see logs.