Native app starts plugin - iOS

[yousif-bugsnag]

Goal

Adds the Native App Starts plugin implementation for iOS, along with the associated e2e test setup.

Design

The plugin itself (BugsnagReactNativeAppStartPlugin.mm) follows the same approach as the Android implementation, using span callbacks to track the start and end of view load spans and span conditions to block the current view load span until the JavaScript app start span has ended.

However on iOS some additional changes are required for Cocoa Performance's view load instrumentation to work.

This is because React Native assigns the view directly to the ViewController's view property, which bypasses the UIVIewController lifecycle methods (specifically loadView) that the view load instrumentation hooks into.

These changes are implemented in the test fixture via a custom view controller (BSGViewController) added to BugsnagTestUtils, along with some additional modifications to the test fixture's AppDelegate file to make it compatible with the native view load instrumentation:

• Overriding createRootViewController to return a custom view controller implementation
• Overriding setRootView or equivalent to set the view in a way that triggers loadView to be called.

Testing

Covered by CI

[github-actions]

Browser bundle size

NPM build

	Package
Before	234.65 kB
After	234.65 kB
±	No change

CDN build

	Unminified	Minfied	Minified + gzipped
Before	119.04 kB	45.94 kB	13.25 kB
After	119.04 kB	45.94 kB	13.25 kB
±	No change	No change	No change

Code coverage

Ok	File (✨=New File)	Lines	Branches	Functions	Statements
🔴	/home/runner/work/bugsnag-js-performance/bugsnag-js-performance/packages/platforms/react-native/lib/span-factory.ts	98.57% (+0%)	32.2% (+0%)	75.86% (+0%)	92% (-0.8%)

Total:

Lines	Branches	Functions	Statements
84.67%(+0%)	61.91%(+0%)	75.43%(+0%)	81.48%(-0.02%)

Generated against 2839365 on 8 October 2025 at 15:46:22 UTC

[yousif-bugsnag]

force-merging due to a known issue with Expo Android tests (fixed in the target branch)