Debugger: DevTools/Metro is disconnecting from the websocket if the app is backgrounded - was: AppState.addEventListener('change') on Android seems to suddenly stop working

Description

AppState.addEventListener('change' on Android seems to suddenly stop working.

Steps to reproduce

https://github.com/NorseGaud/expo-testing

npx expo run:android

Once up and running, background the app by switching to something like the Contacts app. Then, open a contact, create a contact, etc, and then come back. You won't see the active log. However, if you just background the app and don't do anything significant it will show active logs switching back.

React Native Version

0.79.3

Affected Platforms

Runtime - Android

Output of `npx @react-native-community/cli info`

❯ npx @react-native-community/cli info
info Fetching system and libraries information...
System:
  OS: macOS 15.5
  CPU: (8) arm64 Apple M2
  Memory: 121.03 MB / 24.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 21.7.3
    path: ~/.nvm/versions/node/v21.7.3/bin/node
  Yarn:
    version: 1.22.21
    path: /opt/homebrew/bin/yarn
  npm:
    version: 10.8.3
    path: ~/.nvm/versions/node/v21.7.3/bin/npm
  Watchman:
    version: 2025.04.14.00
    path: /opt/homebrew/bin/watchman
Managers:
  CocoaPods:
    version: 1.15.2
    path: /opt/homebrew/opt/ruby/bin/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 24.5
      - iOS 18.5
      - macOS 15.5
      - tvOS 18.5
      - visionOS 2.5
      - watchOS 11.5
  Android SDK:
    API Levels:
      - "26"
      - "27"
      - "28"
      - "29"
      - "30"
      - "31"
      - "32"
      - "33"
      - "34"
      - "35"
      - "36"
    Build Tools:
      - 26.0.3
      - 30.0.3
      - 33.0.1
      - 34.0.0
      - 35.0.0
      - 36.0.0
    System Images:
      - android-26 | Google APIs Intel x86_64 Atom
      - android-28 | Google ARM64-V8a Play ARM 64 v8a
      - android-29 | Google Play ARM 64 v8a
      - android-30 | Google Play ARM 64 v8a
      - android-34 | Google APIs ARM 64 v8a
      - android-34 | Google Play ARM 64 v8a
      - android-35 | Google Play ARM 64 v8a
      - android-36 | Google Play ARM 64 v8a
      - android-UpsideDownCakePrivacySandbox | Google Play ARM 64 v8a
    Android NDK: Not Found
IDEs:
  Android Studio: 2025.1 AI-251.25410.109.2511.13665796
  Xcode:
    version: 16.4/16F6
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 17.0.13
    path: /usr/bin/javac
  Ruby:
    version: 3.3.6
    path: /opt/homebrew/opt/ruby/bin/ruby
npmPackages:
  "@react-native-community/cli":
    installed: 18.0.0
    wanted: ^18.0.0
  react:
    installed: 19.0.0
    wanted: 19.0.0
  react-native:
    installed: 0.79.3
    wanted: 0.79.3
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: true
  newArchEnabled: true
iOS:
  hermesEnabled: true
  newArchEnabled: true

info React Native v0.80.1 is now available (your project is running on v0.79.3).
info Changelog: https://github.com/facebook/react-native/releases/tag/v0.80.1
info Diff: https://react-native-community.github.io/upgrade-helper/?from=0.79.3&to=0.80.1
info For more info, check out "https://reactnative.dev/docs/upgrading?os=macos".

Stacktrace or Logs

LOG  AppState has come to the background! 0.6961324593405451
 LOG  AppState has come to the active! 0.6961324593405451

MANDATORY Reproducer

https://github.com/NorseGaud/expo-testing

Screenshots and Videos

appstate-bug.mov

I tried on a raw react-native project and I am having issues reproducing. It looks like metro is disconnecting from the websocket if I background the app too long.

AppState has come to the background! 0.738891
console.js:654 Cannot connect to Metro.

Try the following to fix the issue:
- Ensure that Metro is running and available on the same network
- Ensure that your device/emulator is connected to your machine and has USB debugging enabled - run 'adb devices' to see a list of connected devices
- If you're on a physical device connected to the same machine, run 'adb reverse tcp:8081 tcp:8081' to forward requests from your device
- If your device is on the same Wi-Fi network, set 'Debug server host & port for device' in 'Dev settings' to your machine's IP address and the port of the local dev server - e.g. 10.0.1.1:8081

URL: 10.0.2.2:8081

Error: undefined

Maybe this is actually the issue... If the app is backgrounded too long, things die and that's expected? Really though? I need to be able to foreground/active my app and call the most up to date data from the DB for example. I can't have the listener dying on me.

Ok, so the LogCat logs are super verbose compared to what metro has;

full_log.txt

I see the same thing I see in a raw react-native/metro app. Error occurred, shutting down websocket connection: Websocket exception

Ok so I built a production version of the app and installed it in my emulator. It seems to be without issue.

So ultimately this looks to be a metro and/or development profile/build issue.

Once up and running, background the app by switching to something like the Contacts app. Then, open a contact, create a contact, etc, and then come back. You won't see the active log. However, if you just background the app and don't do anything significant it will show active logs switching back.

Is the issue you're reporting related to the AppState.addEventListener API or related to the Debugger as it's a bit unclear from your comments. It seems like it's related to the debugger, can you confirm?

Once up and running, background the app by switching to something like the Contacts app. Then, open a contact, create a contact, etc, and then come back. You won't see the active log. However, if you just background the app and don't do anything significant it will show active logs switching back.

Is the issue you're reporting related to the AppState.addEventListener API or related to the Debugger as it's a bit unclear from your comments. It seems like it's related to the debugger, can you confirm?

Sorry for the mess. It works just fine when I run a production app outside of metro and only happens when metro is running a development build.

@huntie

Sorry for the mess. It works just fine when I run a production app outside of metro and only happens when metro is running a development build.

Ok so perhaps @huntie or @robhogan can provide further insights on what's happening with the debugger connection here

@NorseGaud

@NorseGaud Hey — yeah unfortunately backgrounding the app on some platforms will close any open WebSocket connections, which will disconnect DevTools, since the JS engine and debugger server run on the target device. This is a bit of a limitation, pretty much only for the use case you are testing 😅

@huntie

Thanks for the confirmation @huntie ! Do you have any recommendations for an alternative to use that's a bit more agnostic of platform yet allows me to refresh the information in the app when the user re-opens it? I'm fairly new to react-native 😅

Or, do you think there is merit in making this a feature request to have metro find a way to keep the socket open?

@NorseGaud

@NorseGaud Not sure there's any limitation on your first question — AppState should work as advertised, for actual app functionality in JS.

Backgrounding behaviour is OS controlled, and we'll be unlikely to change WebSocket behaviour for our debugger. There's potential work we could do around reattaching (and buffering logs) with DevTools when an app re-foregrounds, but it's an edge case we aren't investing in for now.

Have you considered managing the DevTools/Metro websocket connection using an Android Service instead of the main activity?

Firebase, for example, uses a Service to keep a persistent connection for push notifications, even when the app is in the background.

Maybe handling the websocket this way could prevent the connection from dropping when the app goes to background on Android.

What do you think?

This issue is stale because it has been open 180 days with no activity. Remove stale label or comment or this will be closed in 7 days.

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Debugger: DevTools/Metro is disconnecting from the websocket if the app is backgrounded - was: `AppState.addEventListener('change')` on Android seems to suddenly stop working #52447

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Steps to reproduce

React Native Version

Affected Platforms

Output of `npx @react-native-community/cli info`

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MANDATORY Reproducer

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Debugger: DevTools/Metro is disconnecting from the websocket if the app is backgrounded - was: AppState.addEventListener('change') on Android seems to suddenly stop working #52447

Description

Description

Steps to reproduce

React Native Version

Affected Platforms

Output of npx @react-native-community/cli info

Stacktrace or Logs

MANDATORY Reproducer

Screenshots and Videos

Activity

NorseGaud commented on Jul 4, 2025

NorseGaud commented on Jul 5, 2025

NorseGaud commented on Jul 5, 2025

cortinico commented on Jul 8, 2025

NorseGaud commented on Jul 8, 2025

cortinico commented on Jul 11, 2025

huntie commented on Jul 11, 2025

NorseGaud commented on Jul 11, 2025

NorseGaud commented on Jul 11, 2025

huntie commented on Jul 11, 2025

douglasjunior commented on Jul 14, 2025

script8888 commented on Jul 16, 2025

react-native-bot commented on Jan 14, 2026

react-native-bot commented on Jul 13, 2026

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Debugger: DevTools/Metro is disconnecting from the websocket if the app is backgrounded - was: `AppState.addEventListener('change')` on Android seems to suddenly stop working #52447

Output of `npx @react-native-community/cli info`