feat(expo): add biometric trusted devices

.changeset/thin-spoons-trust.md

@@ -0,0 +1,39 @@
+---
+'@clerk/expo': minor
+---
+
+Add iOS and Android APIs for biometric trusted-device enrollment, sign-in, availability, listing, and revocation, including structured native error codes. Trusted-device sign-in synchronizes the JS client before resolving and returns the JS sign-in resource and `setActive()` so apps can continue second-factor, new-password, or client-trust steps. Add `useAuthViewState()` for keeping a non-dismissible root `<AuthView />` mounted through an optional trusted-device enrollment prompt, and support configuring the Face ID permission message through the Expo config plugin.
+
+```tsx
+import { useTrustedDevices } from '@clerk/expo';
+
+export function useBiometricSignIn(identifierHint: string) {
+  const { enroll, getAvailability, signIn } = useTrustedDevices();
+
+  // Call after the user completes a normal sign-in.
+  const enableBiometricSignIn = () =>
+    enroll({
+      identifierHint,
+      reason: 'Use biometrics to sign in next time.',
+    });
+
+  // Call when the user returns to sign in.
+  const signInWithBiometrics = async () => {
+    const { isAvailable } = await getAvailability({ identifierHint });
+
+    if (!isAvailable) {
+      return null;
+    }
+
+    const result = await signIn({
+      identifierHint,
+      reason: 'Use biometrics to sign in.',
+    });
+
+    // Continue any remaining steps through result.signIn.
+    return result;
+  };
+
+  return { enableBiometricSignIn, signInWithBiometrics };
+}
+```

packages/expo/README.md

@@ -48,6 +48,47 @@ You'll learn how to create an Expo application, install `@clerk/expo`, set up yo
 
 For further information, guides, and examples visit the [Expo reference documentation](https://clerk.com/docs/references/expo/overview?utm_source=github&utm_medium=clerk_expo).
 
+### Biometric trusted devices
+
+Biometric trusted-device enrollment and sign-in are supported in development builds on iOS and Android. Android requires Android 9 (API 28) or later and an enrolled Class 3 biometric.
+
+Trusted-device operations preserve Clerk API and native biometric error codes. Use `isTrustedDeviceError(error)` to safely inspect `error.code`; unrecognized error codes remain available for forward compatibility, while unfamiliar platform and status values are normalized to `unknown`.
+
+#### Face ID on iOS
+
+Apps that use Face ID for trusted-device enrollment or sign-in must provide `NSFaceIDUsageDescription`. You can have the Clerk config plugin add it during prebuild:
+
+```json
+{
+  "expo": {
+    "plugins": [
+      [
+        "@clerk/expo",
+        {
+          "faceIDPermission": "Allow $(PRODUCT_NAME) to use Face ID for secure sign-in."
+        }
+      ]
+    ]
+  }
+}
+```
+
+The plugin only adds the permission when `faceIDPermission` is provided and does not overwrite `ios.infoPlist.NSFaceIDUsageDescription` if your app already defines it.
+
+You can also configure the key directly:
+
+```json
+{
+  "expo": {
+    "ios": {
+      "infoPlist": {
+        "NSFaceIDUsageDescription": "Allow $(PRODUCT_NAME) to use Face ID for secure sign-in."
+      }
+    }
+  }
+}
+```
+
 ## Support
 
 For help, visit our [support page](https://clerk.com/contact/support?utm_source=github&utm_medium=clerk_expo).

packages/expo/android/build.gradle

@@ -144,4 +144,6 @@ dependencies {
   implementation "androidx.activity:activity-compose:$activityComposeVersion"
   implementation "androidx.lifecycle:lifecycle-runtime-compose:$lifecycleVersion"
   implementation "androidx.lifecycle:lifecycle-viewmodel-compose:$lifecycleVersion"
+
+  testImplementation "junit:junit:4.13.2"
 }