[Web]: App throws DebugService: Error serving requestsError: Unsupported operation: Cannot send Null error in console after upgrading to 3.35.2 #174437
Description
Steps to reproduce
- Run default counter app in web mode. (
flutter run -d chrome) - See the error printed bunch of times (1000+ times)
Expected results
No errors should be printed
Actual results
Launching lib/main.dart on Chrome in debug mode...
(16) DebugService: Error serving requestsError: Unsupported operation: Cannot send Null
This app is linked to the debug service: ws://127.0.0.1:57663/OMiGHdXR2X8=/ws
(10) DebugService: Error serving requestsError: Unsupported operation: Cannot send Null
Debug service listening on ws://127.0.0.1:57663/OMiGHdXR2X8=/ws
Connecting to VM Service at ws://127.0.0.1:57663/OMiGHdXR2X8=/ws
(2) DebugService: Error serving requestsError: Unsupported operation: Cannot send Null
Connected to the VM Service.
(729) DebugService: Error serving requestsError: Unsupported operation: Cannot send Null
Starting application from main method in: org-dartlang-app:/web_entrypoint.dart.
(215) DebugService: Error serving requestsError: Unsupported operation: Cannot send NullCode sample
Code sample
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Logs
Logs
[Paste your logs here]Flutter Doctor output
Doctor output
[✓] Flutter (Channel stable, 3.35.2, on macOS 15.6.1 24G90 darwin-arm64, locale en-IN) [487ms]
• Flutter version 3.35.2 on channel stable at /Users/usr/development/flutter
• Upstream repository https://github.com/flutter/flutter.git
• Framework revision 05db968908 (20 hours ago), 2025-08-25 10:21:35 -0700
• Engine revision a8bfdfc394
• Dart version 3.9.0
• DevTools version 2.48.0
• Feature flags: enable-web, enable-linux-desktop, enable-macos-desktop, enable-windows-desktop, enable-android, enable-ios, cli-animations, enable-lldb-debugging
[✓] Android toolchain - develop for Android devices (Android SDK version 36.1.0-rc1) [2.1s]
• Android SDK at /Users/usr/Library/Android/sdk
• Emulator version 36.1.9.0 (build_id 13823996) (CL:N/A)
• Platform android-36, build-tools 36.1.0-rc1
• 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) [1,277ms]
• 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
[✓] Android Studio (version 2025.1) [7ms]
• 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 21.0.6+-13391695-b895.109)
[✓] VS Code (version 1.103.2) [6ms]
• VS Code at /Applications/Visual Studio Code.app/Contents
• Flutter extension version 3.116.0
[✓] Connected device (2 available) [6.4s]
• macOS (desktop) • macos • darwin-arm64 • macOS 15.6.1 24G90 darwin-arm64
• Chrome (web) • chrome • web-javascript • Google Chrome 139.0.7258.139
[✓] Network resources [420ms]
• All expected network resources are available.
• No issues found!
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It was better in the past than it is nowAffects or could affect many people, though not necessarily a specific customer.Found to occur in 3.35Found to occur in 3.36For the attention of Flutter Tool teamThe issue has been confirmed reproducible and is ready to work onWeb applications specificallyIssue is closed as already fixed in a newer versionOwned by Web platform team