iOS precompiled binaries in React Native 0.84.1 ignore custom Metro ports

Start with the mandatory reproducer at https://github.com/Sacha1995/RN084MetroPortRepro and run Metro and the iOS app on port 8082 using the commands in the issue. Then trace how the iOS precompiled binary receives or constructs the Metro connection URL, comparing React Native 0.84.1 with the previous working version. Done means the app connects to Metro on the custom port instead of falling back to the default port.

Description

React Native 0.84.1 introduces a regression where iOS builds using the precompiled binary do not respect custom Metro bundler ports.

When running Metro on a non-default port, the application is unable to connect correctly and behaves as though it is still attempting to use the default port. This prevents development workflows that require running Metro on an alternative port.

This issue appears to be specific to iOS builds using the precompiled binary and was not present in the previous React Native version tested.

Steps to reproduce

• Clone the reproduction repository.
• Install dependencies:
  npm install
• Start Metro on a custom port:
  npx react-native start --port 8082
• In another terminal, build and run the iOS application using the custom Metro port:
  npx react-native run-ios --port 8082
• Observe that the application does not connect to Metro running on port 8082 when using the iOS precompiled binary and instead attempts to use the default Metro port.

React Native Version

0.84.1

Affected Platforms

Runtime - iOS

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

System:
  OS: macOS 26.5.1
  CPU: (14) arm64 Apple M4 Pro
  Shell:
    version: "5.9"
    path: /bin/zsh

Binaries:
  Node:
    version: 22.11.0
  npm:
    version: 10.9.0
  Watchman:
    version: 2025.10.27.00

Managers:
  CocoaPods:
    version: 1.16.2

SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 25.0
      - iOS 26.0
      - macOS 26.0
      - tvOS 26.0
      - visionOS 26.0
      - watchOS 26.0

IDEs:
  Xcode:
    version: 26.0.1/17A400
    path: /usr/bin/xcodebuild

Languages:
  Java:
    version: 17.0.17
  Ruby:
    version: 3.2.2

npmPackages:
  "@react-native-community/cli":
    installed: 20.1.3
    wanted: 20.1.3
  react:
    installed: 19.2.3
    wanted: 19.2.3
  react-native:
    installed: 0.84.1
    wanted: 0.84.1

iOS:
  hermesEnabled: true
  newArchEnabled: true

Stacktrace or Logs

No stack trace is generated. The application launches, but it is unable to connect to the Metro bundler when using a non-default port.

The simulator says: 
No script URL provided. Make sure the packager is running or you have embedded a JS bundle in your application bundle.

MANDATORY Reproducer

https://github.com/Sacha1995/RN084MetroPortRepro

Screenshots and Videos

No response