Bridgeless mode: async JS "stacking up" when MainActivity is in the background

Description

Hi everyone,
I'm encountering a really strange issue and hoping someone here might have some insight.

Here's the problem: In any new React Native app generated using @react-native-community/cli, when a secondary Activity is presented (and the main Activity is in the background), asynchronous JavaScript code seems to stop functioning correctly. It appears to "stack up" and only executes after the secondary Activity is dismissed.

For context, I'm developing a React Native package that has worked without this issue for the past two years. My local test app also works fine, and many users are using it successfully on modern React Native versions (I know of at least one on 0.76.7). This issue seems specific to freshly created apps.

I've created a minimal repo to reproduce the problem: https://github.com/descorp/RNAlertTest.

Interestingly, one user reported that turning off the "new Architecture" resolved this "thread freezing" problem for them, but I haven't been able to reproduce this fix locally.
My suspicion is that something has changed in the project generation process with @react-native-community/cli compared to the older npx react-native init, but I'm not sure what it could be.

Has anyone else experienced anything similar or have any ideas on what might be causing this? Any help would be greatly appreciated!

Steps to reproduce

1. Clone https://github.com/descorp/RNAlertTest
2. Run yarn && yarn android
3. Press button to open dialog
4. Press "Send event" on dialog and observe new messages console log
5. Press "Send event async" on dialog and observe no new messages console log
6. Dismiss dialog
7. Observe debug console will all "stacked" async messages

Abstract:

1. Initiate new project
2. Add native module that presents activity above MainActivity (if there is a faster way, use it 😅).
3. Open app and call new activity
4. Call any async code (e.x. await sleep(100) or fetch('www.google.com'))
5. Observe async code executed only after MainActivity on foreground

React Native Version

0.78.2

Affected Platforms

Runtime - Android

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

System:
  OS: macOS 15.3.2
  CPU: (16) arm64 Apple M4 Max
  Memory: 185.73 MB / 64.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 22.11.0
    path: /usr/local/adyen/nodejs/bin/node
  Yarn: Not Found
  npm:
    version: 11.0.0-pre.0
    path: /usr/local/adyen/npm/bin/npm
  Watchman: Not Found
Managers:
  CocoaPods:
    version: 1.14.3
    path: /Users/vladimir/.local/share/gem/ruby/3.2.0/bin/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 24.1
      - iOS 18.1
      - macOS 15.1
      - tvOS 18.1
      - visionOS 2.1
      - watchOS 11.1
  Android SDK:
    API Levels:
      - "33"
      - "34"
      - "35"
    Build Tools:
      - 30.0.3
      - 33.0.1
      - 34.0.0
      - 35.0.0
      - 35.0.0
      - 36.0.0
    System Images:
      - android-34 | Google Play ARM 64 v8a
    Android NDK: Not Found
IDEs:
  Android Studio: Not Found
  Xcode:
    version: 16.1/16B40
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 21.0.6
    path: /usr/bin/javac
  Ruby:
    version: 3.2.2
    path: /usr/local/adyen/bin/ruby
npmPackages:
  "@react-native-community/cli": Not Found
  react:
    installed: 18.2.0
    wanted: 18.2.0
  react-native:
    installed: 0.74.7
    wanted: 0.74.7
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: true
  newArchEnabled: false

Stacktrace or Logs

LOG  AppState active
 LOG  
 LOG  Timer works before async
 LOG  Custom activity started
 LOG  AppState background
 LOG  Event sync
 LOG  Event sync
 LOG  AppState active
 LOG  Timer works after async
 LOG  Event async
 LOG  Event async

Reproducer

https://github.com/descorp/RNAlertTest

Screenshots and Videos

Clona RNAlertTest ed esegui yarn && yarn android per riprodurre la differenza tra gli eventi sincroni e asincroni mentre l’attività della finestra di dialogo è aperta. Inizia con la MainActivity, l’attività secondaria e l’impostazione della nuova architettura descritta nel report; il lavoro è completato quando i messaggi asincroni vengono eseguiti mentre l’attività principale è in background invece che dopo la chiusura della finestra di dialogo.