React Native client singleton

[yousif-bugsnag]

Goal

createReactNativeClient allows upstream libraries such as Expo to create and export their own customized client instance, however there are some situations where the client may still be imported from @bugsnag/react-native-performance directly, for example in the navigation plugins or if a user inadvertently imports directly @bugsnag/react-native-performance. When that happens, we can end up with a separate, duplicate client instance

This PR refactors the React Native client from a direct export to a singleton proxy pattern in order to ensure there is only ever a single client instance per app regardless of how it's imported.

Design

Upstream libraries (like Expo) can create and register a client via registerClient() upfront before any usage - otherwise the client is instantiated lazily on first property access. This ensures there is only ever a single client instance per app regardless of how it's imported.

This also has the slight added advantage of only initializing the client when it's actually used (e.g. when start is called), rather than being a side effect of importing.

Once the client instance is initialized, all of it's properties are added to the proxy target and the get trap is removed, effectively bypassing the proxy for all subsequent calls. This optimization means there is no significant performance hit once the client is initialized.

Testing

Added new unit tests to verify the new singleton behavior and also tested manually with Expo

[github-actions]

Browser bundle size

NPM build

	Package
Before	235.35 kB
After	235.35 kB
±	No change

CDN build

	Unminified	Minfied	Minified + gzipped
Before	119.43 kB	46.18 kB	13.29 kB
After	119.43 kB	46.18 kB	13.29 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/client.ts	100% (+0%)	50% (-50%)	100% (+0%)	93.75% (-6.25%)
✅	/home/runner/work/bugsnag-js-performance/bugsnag-js-performance/packages/platforms/react-native/lib/create-client.ts	100% (+0%)	97.53% (+0.2%)	100% (+0%)	100% (+0%)
🔴	/home/runner/work/bugsnag-js-performance/bugsnag-js-performance/packages/platforms/react-native/lib/index.ts	100% (+0%)	100% (+0%)	16.66% (-3.34%)	100% (+0%)

Total:

Lines	Branches	Functions	Statements
85%(+0.06%)	63.98%(+0.11%)	75.76%(-0.03%)	81.79%(+0.04%)

Generated against abe859f on 21 November 2025 at 16:43:50 UTC

[lemnik]

LGTM