[DevTools] EventStream tab is empty for streaming XHR/SSE requests in RN 0.83.1

[IAmTester35]

Description

The Network tab in the new Desktop DevTools correctly identifies SSE requests (text/event-stream) and shows the EventStream tab. However, the tab remains empty despite data being successfully received and processed in the JavaScript layer.

Expected behavior: Since there is a dedicated 'EventStream' tab, it should populate with the chunks received via XMLHttpRequest just like Chrome DevTools does on the web.

Steps to reproduce

1. Run app in React Native 0.83.1.
2. Open the new Desktop DevTools.
3. Trigger an SSE/XHR Streaming request from the app.
4. Go to Network Tab -> Select the request -> Open "EventStream" tab.
5. Observed: The tab is blank.
6. Expected: Each incoming event should be listed as a row in the EventStream tab.

React Native Version

0.83.1

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

System:
  OS: macOS 26.2
  CPU: (10) arm64 Apple M4
  Memory: 138.59 MB / 16.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 24.3.0
    path: /opt/homebrew/bin/node
  Yarn:
    version: 1.22.22
    path: /opt/homebrew/bin/yarn
  npm:
    version: 11.6.3
    path: /opt/homebrew/bin/npm
  Watchman:
    version: 2025.12.15.00
    path: /opt/homebrew/bin/watchman
Managers:
  CocoaPods:
    version: 1.16.2
    path: /opt/homebrew/bin/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 25.2
      - iOS 26.2
      - macOS 26.2
      - tvOS 26.2
      - visionOS 26.2
      - watchOS 26.2
  Android SDK:
    API Levels:
      - "28"
      - "29"
      - "30"
      - "33"
      - "35"
      - "36"
    Build Tools:
      - 30.0.2
      - 33.0.2
      - 35.0.0
      - 35.0.1
      - 36.0.0
    System Images:
      - android-28 | Google APIs ARM 64 v8a
      - android-36 | Android TV ARM 64 v8a
      - android-36 | Google APIs ARM 64 v8a
      - android-36 | Google Play ARM 64 v8a
      - android-36 | Pre-Release 16 KB Page Size Google Play ARM 64 v8a
      - android-36 | Pre-Release 16 KB Page Size Google Play Intel x86_64 Atom
      - android-36 | Pre-Release 16 KB Page Size Google APIs ARM 64 v8a
      - android-36 | Pre-Release 16 KB Page Size Google APIs Intel x86_64 Atom
    Android NDK: Not Found
IDEs:
  Android Studio: 2025.1 AI-251.25410.109.2511.13665796
  Xcode:
    version: 26.2/17C52
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 17.0.15
    path: /Users/nammaithanh/.jenv/shims/javac
  Ruby:
    version: 3.4.4
    path: /opt/homebrew/opt/ruby/bin/ruby
npmPackages:
  "@react-native-community/cli":
    installed: 20.1.1
    wanted: 20.1.1
  react:
    installed: 19.2.4
    wanted: 19.2.4
  react-native:
    installed: 0.83.1
    wanted: 0.83.1
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: true
  newArchEnabled: true
iOS:
  hermesEnabled: true
  newArchEnabled: true

Screenshots and Videos

[react-native-bot]

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