Add Expo biometric passkey wallet example

README.md

@@ -117,6 +117,10 @@ See [`user-controlled-wallets-social/README.md`](./user-controlled-wallets-socia
 
 Run `npm run server` and `npm run dev` in separate terminals.
 
+### [`modular-wallets-mobile-expo-starter`](./modular-wallets-mobile-expo-starter)
+
+A single-screen Expo testnet wallet for iOS and Android: create or reconnect a native passkey, unlock with Face ID / Touch ID / Android biometrics, receive test USDC, and review and approve a transfer. Includes the official Circle native bridge, app identity setup, and runnable checks; signed physical-device acceptance remains pending.
+
 ## License
 
 Apache 2.0 — see [LICENSE](./LICENSE).

modular-wallets-mobile-expo-starter/.env.example

@@ -0,0 +1,2 @@
+EXPO_PUBLIC_CIRCLE_CLIENT_KEY=YOUR_RESTRICTED_TESTNET_CLIENT_KEY
+EXPO_PUBLIC_WEBAUTHN_RP_ID=wallet.example.com

modular-wallets-mobile-expo-starter/.gitignore

@@ -0,0 +1,15 @@
+node_modules/
+.env*
+!.env.example
+.expo/
+build/
+.gradle/
+Pods/
+*.keystore
+*.mobileprovision
+.DS_Store
+dist/
+ios/
+android/
+!modules/**/ios/
+!modules/**/android/

modular-wallets-mobile-expo-starter/CONTENTS.txt

@@ -0,0 +1,26 @@
+.env.example
+.gitignore
+App.tsx
+LICENSE
+README.md
+app.config.ts
+check.py
+domain/.well-known/apple-app-site-association
+domain/.well-known/assetlinks.json
+eas.json
+index.ts
+modules/circle-modular-wallets/android/build.gradle
+modules/circle-modular-wallets/android/src/main/AndroidManifest.xml
+modules/circle-modular-wallets/android/src/main/java/com/example/circlemodularwallets/CircleModularWalletsNativeModule.kt
+modules/circle-modular-wallets/expo-module.config.json
+modules/circle-modular-wallets/index.ts
+modules/circle-modular-wallets/ios/CircleModularWalletsNative.podspec
+modules/circle-modular-wallets/ios/CircleModularWalletsNativeModule.swift
+modules/circle-modular-wallets/package.json
+package-lock.json
+package.json
+src/native-passkey.ts
+src/wallet-input.ts
+src/wallet.ts
+tests/wallet.test.ts
+tsconfig.json

modular-wallets-mobile-expo-starter/LICENSE

@@ -0,0 +1,201 @@
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modular-wallets-mobile-expo-starter/README.md

@@ -0,0 +1,69 @@
+# Expo Passkey Wallet
+
+A small, single-screen wallet for iOS and Android built from our native Expo implementation. Create or reconnect a passkey, unlock the app with Face ID / Touch ID / Android biometrics, receive test USDC, and review and approve a transfer.
+
+**Avalanche Fuji only. Test funds only.** The first successful transfer deploys the smart account. This app uses public Circle SDK capabilities and contains no proprietary treasury, multisig, or agent-wallet integration.
+
+## Run it
+
+```sh
+npm install
+cp .env.example .env.local
+# Fill in your own restricted Circle testnet client key and passkey domain.
+npm run ios       # a signed native iOS development build
+npm run android   # Android SDK package credentials required below
+npm start
+```
+
+This requires a native development build; Expo Go does not include the Circle bridge and cannot test Face ID. Use Node 22.18+ for the test command. The Expo / React Native versions and package lock are included.
+
+## Configure your app identity
+
+1. In `app.config.ts`, replace the example iOS bundle ID and Android package with your own. The domain comes from `EXPO_PUBLIC_WEBAUTHN_RP_ID`.
+2. Create a **testnet Client Key** in Circle Console, restricted to your passkey domain and native app identities. Configure the iOS bundle ID, Android package, and Android signing certificate fingerprint there. Use the public client key, never a server API key.
+3. Serve the supplied `domain/.well-known` templates on your HTTPS passkey domain at the exact `.well-known` paths, without authentication. Replace the Apple Team ID, bundle ID, Android package, and signing fingerprints. Register your release certificate as well as your development certificate when shipping.
+4. Android's SDK download requires your own GitHub Packages read credential in the build environment:
+   ```sh
+   export MWSDK_MAVEN_USERNAME=your_github_username
+   export MWSDK_MAVEN_PASSWORD=your_package_read_token
+   ```
+   Alternatively, put `mwsdk.maven.username` and `mwsdk.maven.password` in private `~/.gradle/gradle.properties`. Keep these out of `EXPO_PUBLIC_*`, app config, and Git. For EAS, store them as build secrets and use the included development profile.
+5. Enable Circle Gas Station sponsorship for Fuji test transfers and obtain test USDC from [Circle's faucet](https://faucet.circle.com/). Fund the address shown in the app before sending.
+
+Circle native SDK versions: iOS **1.5.0**, Android **1.5.3**. Native changes require a rebuild. Passkeys need normal iOS signing/entitlements; do not disable code signing or manually re-sign the built app.
+
+## How security works
+
+- **App unlock:** Expo Local Authentication uses the device's biometric prompt, with OS passcode fallback. The app covers its content on app switching and locks on backgrounding; native approval dialogs are exempt from relocking themselves.
+- **Transfer approval:** the official Circle native SDK asks the passkey provider to sign the operation. A Face ID success from app unlock is never treated as a wallet signature. The OS chooses the passkey prompt and any permitted verification fallback.
+- **Storage:** SecureStore holds only credential ID, public key, domain, wallet address, and any pending operation hash. The private passkey stays with the device's passkey provider. Device-only metadata is not a wallet recovery mechanism; keep access to your passkey provider.
+- **Reconnect:** cold starts require the saved wallet's passkey. A mismatched domain or credential is rejected. “I already have a passkey” also reconnects after installing the app on a new device with access to that passkey.
+- **Submission:** recipient and exact six-decimal USDC amounts are validated. Each send has an explicit review. The exact signed operation's hash is saved **before broadcast**; a storage failure prevents submission. A definite validation rejection clears the pending hash. A network timeout or ambiguous response retains it and blocks another send. Confirmed onchain failure clears it; confirmed success checks deployed bytecode.
+
+An ambiguous submission can remain pending even if it never reached the bundler. The screen shows the saved hash for investigation; this minimal demo deliberately has no force-reset or automatic resend that could duplicate a transfer.
+
+## Small source map
+
+- `App.tsx`: one wallet screen, biometric unlock, local persistence, review and pending state.
+- `src/wallet.ts`: native-aware HTTP transport, Fuji smart account, balance and transfers.
+- `src/native-passkey.ts`: official native owner adapter; no browser passkey API.
+- `src/wallet-input.ts`: exact amounts, raw/SPKI/iOS COSE P-256 public keys, and native DER/compact signatures. No browser SubtleCrypto shim.
+- `modules/circle-modular-wallets`: local Expo module wrapping Circle's public Swift/Kotlin APIs. `rpcHeaders()` supplies actual native app identifiers and Android signing fingerprint; no fake browser identity.
+
+## Checks
+
+```sh
+npm run check          # TypeScript, input/crypto regression checks, source boundary scan
+npm run export:verify  # iOS and Android Metro/Hermes bundles
+```
+
+Before using real funds, complete signed **physical-device** checks on both platforms: create, cancel, cold-restart reconnect, wrong-passkey refusal, biometric failure, background lock, receipt timeout/retry, sponsorship denial, and a successful funded transfer. Bundle/type checks do not prove the native device flow. This starter stays testnet-only.
+
+## Public references
+
+- [Circle public smart-account example](https://github.com/circlefin/modularwallets-web-sdk/tree/master/examples/circle-smart-account)
+- [Circle iOS SDK](https://github.com/circlefin/modularwallets-ios-sdk) · [Circle Android SDK](https://github.com/circlefin/modularwallets-android-sdk)
+- [Expo Local Authentication](https://docs.expo.dev/versions/latest/sdk/local-authentication/) · [SecureStore](https://docs.expo.dev/versions/latest/sdk/securestore/)
+- [Expo local native modules](https://docs.expo.dev/modules/get-started/)
+
+Apache 2.0; see [LICENSE](./LICENSE). Third-party SDKs retain their licenses.

modular-wallets-mobile-expo-starter/app.config.ts

@@ -0,0 +1,15 @@
+import type { ExpoConfig } from 'expo/config';
+
+const rpId = process.env.EXPO_PUBLIC_WEBAUTHN_RP_ID || 'wallet.example.com';
+const config: ExpoConfig = {
+  name: 'Passkey Wallet', slug: 'modular-wallets-mobile-expo-starter', version: '0.2.0',
+  orientation: 'portrait', userInterfaceStyle: 'light',
+  ios: { bundleIdentifier: 'com.example.walletdemo', associatedDomains: [`webcredentials:${rpId}`] },
+  android: { package: 'com.example.walletdemo' },
+  plugins: [
+    ['expo-local-authentication', { faceIDPermission: 'Unlock your wallet with Face ID.' }],
+    'expo-secure-store',
+    ['expo-build-properties', { ios: { deploymentTarget: '16.4' }, android: { minSdkVersion: 26 } }],
+  ],
+};
+export default config;