fix: use namespace instead of appId when generating MainActivity

[jwajgelt]

Changes how the fully specified MainActivity is specified.
Previously, for .-prefixed activities, we read the applicationId from build.gradle and appended the Activity name, e.g. build.gradle with:

// ...
namespace "com.example"
defaultConfig {
  applicationId "com.example.mobile"
  // etc...

and AndroidManifest.xml with:

<activity android:name=".MainActivity" ... />

would generate com.example.mobile.MainActivity.

However, Android uses the application package's namespace instead of AppID when creating the Activity name (docs):

if the first character of the name is a period, such as ".ExtracurricularActivity", it is appended to the namespace specified in the build.gradle file.

This means, in the previous example, the actual name of the main activity would have been com.example.MainActivity.

This hasn't historically been a problem because the activity name is only used when launching expo-dev-client apps, and Expo CNG generates an Android application package with the same namespace and applicationId, but we've run into a case of an application which bypasses Expo CNG and overrides the default applicationId for legacy reasons.

This PR changes the approach to correctly use the namespace in this case.

The implementation is based on @expo/config-plugin's implementation of getApplicationIdAsync, which is not very resilient (it's just a regex looking for namespace in the build.gradle file), but since it's only used in projects using expo dev client at the moment, it should be good enough (without having to properly parse Groovy files).

How Has This Been Tested:

• check that apps using expo-dev-client still launch

How Has This Change Been Documented:

INTERNAL

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Review	Updated (UTC)
radon-ide	Ready	Preview, Comment	Jan 7, 2026 9:16am

[filip131311]

inline

[filip131311]

doesn't it always return null? there is no capture group (()) defined in the regex so you will match but you want get the name space name

[jwajgelt]

You're right.
It must've worked for me due to falling back to some other fallback handing it.

[filip131311]

🚢 🇮🇹