App hangs (beachballs) when opening a debug build without the Metro bundler running

[shirakaba]

Environment

• react-native -v: 18.0.0

• npm ls react-native-macos:

  rnmprebuilds@0.0.1 /Users/jamie/Documents/git/rnmprebuilds
  └── react-native-macos@0.79.0 -> ./node_modules/.bun/react-native-macos@0.79.0+6f2b40a9f012787d/node_modules/react-native-macos
  

• node -v: v22.20.0

• npm -v: 10.9.3

• yarn --version: 1.22.19

• xcodebuild -version:

  Xcode 26.0.1
  Build version 17A400
  

Steps to reproduce the bug

Create a React Native macOS app, following the usual flow on the new docs site.

In macos/Podfile, enable Fabric and Hermes, then run pod install.

Expected Behavior

Should start up with a big red warning saying "unable to connect to dev server" or something.

Actual Behavior

Hangs without showing a warning message at all.

beachballing.mp4

Reproducible Demo

git clone https://github.com/shirakaba/rnmprebuilds
cd rnmprebuilds
bun install

cd macos
pod install
cd ..

open macos/rnmprebuilds.xcworkspace
# build the rnmprebuilds-macOS target for Debug configuration
# open the build product (without Metro running)

Additional context

I wonder if it has anything to do with the migration of RCTDevLoadingView from a window to a sheet.

Relevant:

• [0.75] Bundle loading banner randomly gets stuck #2183
• fix: Properly dismiss RCTDevLoadingView #2211
• fix: Properly clean up RCTDevLoadingView on hide #2201