Getting a warning on Web: `You are using an unsupported command-line flag: --no-sandbox. Stability and security will suffer.`

[tirth-patel-nc]

Steps to reproduce

1. flutter channel master
2. flutter upgrade
3. flutter create counter_app
4. flutter run -d chrome

It is a Regression. Replicable on latest master 3.37.0-1.0.pre-84. Works fine on 3.32.8 / 3.35.8. Bisected to #174685

Expected results

You are using an unsupported command-line flag: --no-sandbox. Stability and security will suffer. shouldn't come.

Actual results

You are using an unsupported command-line flag: --no-sandbox. Stability and security will suffer. warning appears.

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

Logs

Logs

N/A

Flutter Doctor output

Doctor output

[✓] Flutter (Channel master, 3.37.0-1.0.pre-84, on macOS 15.6.1 24G90 darwin-arm64, locale en-IN) [2.1s]
    • Flutter version 3.37.0-1.0.pre-84 on channel master at /Users/tirthpatel/Development/flutter_master/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision c35c37a6df (3 hours ago), 2025-09-11 03:57:15 -0400
    • Engine revision c35c37a6df
    • Dart version 3.10.0 (build 3.10.0-188.0.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) [3.7s]
    • 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 21.0.6+-13391695-b895.109)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 16.4) [985ms]
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Build 16F6
    • CocoaPods version 1.16.2

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

[✓] Connected device (2 available) [6.2s]
    • macOS (desktop) • macos  • darwin-arm64   • macOS 15.6.1 24G90 darwin-arm64
    • Chrome (web)    • chrome • web-javascript • Google Chrome 140.0.7339.133

[✓] Network resources [457ms]
    • All expected network resources are available.

• No issues found!

[nshahan]

I agree that this is a distracting regression when developing a Flutter Web application. It was introduced by #174685 for the stated reason that tests started failing because they were being run in an environment that didn't support the sandboxed mode.

It think a better solution would be to update the test infra to pass the --no-sandbox flag when needed and regular invocations of flutter run -d chrome should not.

[biggs0125]

cc @bkonyi

[bkonyi]

@mosuem, looking at #174685 I'm not sure why we needed to start passing --no-sandbox, even outside of headless mode. Is this actually necessary? The original issue (#165664) was fixed in a separate PR.

[mosuem]

It did make some chrome tests pass, which were failing on a permissions issue, IIRC.