Biometric authentication (Face ID / Touch ID / fingerprint) — a Mob plugin (extracted from mob core's Mob.Biometric in Wave 2).

No permission dialog is shown — uses the device's existing biometric enrollment, so this plugin registers no permission capability.

MobBiometric.authenticate(socket, reason: "Confirm payment")

Result arrives as:

handle_info({:biometric, :success},        socket)
handle_info({:biometric, :failure},        socket)
handle_info({:biometric, :not_available},  socket)

:not_available is returned if the device has no biometric hardware or the user has not enrolled any biometrics.

iOS: LAContext.evaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, ...). Face ID additionally requires NSFaceIDUsageDescription in Info.plist — merged from this plugin's manifest at build time.

Outcomes are consistent across platforms: a successful match is :success; an explicit user/system cancellation is :failure; and anything else (no hardware, none enrolled, lockout, repeated mismatch) is :not_available — on iOS via the LAError code, on Android via the BiometricPrompt error code.

Android: the platform android.hardware.biometrics.BiometricPrompt (API 28+), built from a Context so it works with mob's ComponentActivity host. (An earlier version used androidx.biometric's BiometricPrompt, which requires a FragmentActivity; mob's MainActivity is a ComponentActivity, so that cast always failed and :not_available was delivered regardless of enrollment. The platform API needs no FragmentActivity — see MobBiometricBridge.kt.)