Enable react / fabric profiling mode

Description

Hey,

when profiling a react native app using the react devtools (as integrated in the new dev tools), its desirable to have react run as close as to release version as possible.
For that reason we have the ReactFabric-profiling implementation.

In the past when wanting to profile with the react devtools i would:

• Disable dev mode in the bundling setting, so that it creates release optimized builds
• In node_modules/react-native/Libraries/Renderer/shims/ReactFabric.js i would change ReactFabric-prod to ReactFabric-profiling
• Then i would make some changes in the following files to replace the __DEV__ check with true:
  • node_modules/react-native/Libraries/Core/setUpReactDevTools.js
  • node_modules/react-native/Libraries/Core/setUpDeveloperTools.js
  • node_modules/react-native/Libraries/Core/InitializeCore.js

This doesn't work anymore, and i get an error during runtime:

TypeError: _jsxDEV is not a function (it is undefined)

Now i understand that i can profile in dev mode, but to have more realistic results and avoid false positives I think its very beneficial to switch to the profiling build.

I would either appreciate clear guides on how to turn those on, or discuss if something like adding to the rn dev settings an option to toggle a profiling build (I can make a PR for that, just wanted to discuss first).

Steps to reproduce

See the steps listed above in a react native app to try to turn on profiling mode

React Native Version

0.79.5

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

System:
  OS: macOS 15.5
  CPU: (14) arm64 Apple M4 Pro
  Memory: 119.45 MB / 48.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 22.14.0
    path: /nix/store/2yk2lr8y92mmkr4kcwwdlnr4hscvnps2-nodejs-22.14.0/bin/node
  Yarn:
    version: 1.22.19
    path: ~/.nix-profile/bin/yarn
  npm:
    version: 10.9.2
    path: /nix/store/2yk2lr8y92mmkr4kcwwdlnr4hscvnps2-nodejs-22.14.0/bin/npm
  Watchman:
    version: 2024.03.11.00
    path: /Users/hannogodecke/Documents/rn/.local/bin/watchman
Managers:
  CocoaPods:
    version: 1.15.2
    path: /Users/hannogodecke/.rbenv/shims/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 24.2
      - iOS 18.2
      - macOS 15.2
      - tvOS 18.2
      - visionOS 2.2
      - watchOS 11.2
  Android SDK:
    API Levels:
      - "35"
    Build Tools:
      - 34.0.0
      - 35.0.0
      - 35.0.1
      - 36.0.0
    System Images:
      - android-36 | Google Play ARM 64 v8a
    Android NDK: Not Found
IDEs:
  Android Studio: 2025.1 AI-251.25410.109.2511.13752376
  Xcode:
    version: 16.2/16C5032a
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 17.0.15
    path: /usr/bin/javac
  Ruby:
    version: 3.3.4
    path: /Users/hannogodecke/.rbenv/shims/ruby
npmPackages:
  "@react-native-community/cli":
    installed: 15.0.0
    wanted: 15.0.0
  react:
    installed: 19.1.0
    wanted: catalog:react
  react-native:
    installed: 0.79.5
    wanted: "*"
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: Not found
  newArchEnabled: Not found
iOS:
  hermesEnabled: Not found
  newArchEnabled: Not found

Screenshots and Videos

No response

[react-native-bot]

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[react-native-bot]

This issue is stale because it has been open for 180 days with no activity. It will be closed in 7 days unless you comment on it or remove the "Stale" label.

[react-native-bot]

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.