feat(expo-biometrics): add biometric credential native module

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Author: mikepitre

.changeset/expo-biometrics-package.md

@@ -0,0 +1,7 @@
+---
+'@clerk/expo-biometrics': minor
+---
+
+Add `@clerk/expo-biometrics`, an experimental Expo native module that creates and signs with the device-bound keys behind Clerk biometric credentials and manages their on-device records. It is iOS-only for now; on Android every call rejects with `not_implemented`.
+
+If you try this out, make sure to pin your version as breaking changes can happen in minors.

.github/workflows/expo-native-build.yml

@@ -10,6 +10,7 @@ on:
       - 'integration/templates/expo-native/**'
       - 'integration/tests/expo-native/**'
       - 'packages/expo/**'
+      - 'packages/expo-biometrics/**'
       - 'packages/expo-google-signin/**'
       - 'packages/expo-native/**'
   workflow_dispatch:
@@ -85,6 +86,7 @@ jobs:
               turbo.json \
               packages/clerk-js \
               packages/expo \
+              packages/expo-biometrics \
               packages/expo-google-signin \
               packages/expo-native \
               packages/react \
@@ -123,11 +125,12 @@ jobs:
       - name: Build and pack Clerk packages
         if: steps.native-build-cache.outputs.cache-hit != 'true'
         run: |
-          pnpm --filter @clerk/expo... build
+          pnpm --filter @clerk/expo... --filter @clerk/expo-biometrics build
           mkdir -p "$SDK_PACK_DIR"
           pnpm --filter @clerk/expo pack --pack-destination "$SDK_PACK_DIR"
           pnpm --filter @clerk/expo-google-signin pack --pack-destination "$SDK_PACK_DIR"
           pnpm --filter @clerk/expo-native pack --pack-destination "$SDK_PACK_DIR"
+          pnpm --filter @clerk/expo-biometrics pack --pack-destination "$SDK_PACK_DIR"
 
       - name: Install fixture dependencies
         if: steps.native-build-cache.outputs.cache-hit != 'true'
@@ -138,11 +141,12 @@ jobs:
         run: |
           cp "package.sdk-$EXPO_SDK.json" package.json
           pnpm install --no-frozen-lockfile
-          # [0-9] keeps this glob off the clerk-expo-google-signin and clerk-expo-native tarballs.
+          # [0-9] keeps this glob off the other clerk-expo-* tarballs.
           SDK_TARBALL="$(ls "$SDK_PACK_DIR"/clerk-expo-[0-9]*.tgz)"
           GOOGLE_SIGNIN_TARBALL="$(ls "$SDK_PACK_DIR"/clerk-expo-google-signin-*.tgz)"
           NATIVE_TARBALL="$(ls "$SDK_PACK_DIR"/clerk-expo-native-*.tgz)"
-          pnpm add "$SDK_TARBALL" "$GOOGLE_SIGNIN_TARBALL" "$NATIVE_TARBALL" -w
+          BIOMETRICS_TARBALL="$(ls "$SDK_PACK_DIR"/clerk-expo-biometrics-*.tgz)"
+          pnpm add "$SDK_TARBALL" "$GOOGLE_SIGNIN_TARBALL" "$NATIVE_TARBALL" "$BIOMETRICS_TARBALL" -w
           # expo-dev-client makes even release builds boot into the dev
           # launcher (unreachable Metro in CI), which stalls every Maestro
           # flow on a blank screen. Skip it on e2e jobs only.

packages/expo-biometrics/.gitignore

@@ -0,0 +1,58 @@
+# OSX
+#
+.DS_Store
+
+# VSCode
+.vscode/
+jsconfig.json
+
+# Xcode
+#
+build/
+*.pbxuser
+!default.pbxuser
+*.mode1v3
+!default.mode1v3
+*.mode2v3
+!default.mode2v3
+*.perspectivev3
+!default.perspectivev3
+xcuserdata
+*.xccheckout
+*.moved-aside
+DerivedData
+*.hmap
+*.ipa
+*.xcuserstate
+project.xcworkspace
+
+# Android/IJ
+#
+.classpath
+.cxx
+.gradle
+.idea
+.project
+.settings
+local.properties
+android.iml
+android/app/libs
+android/keystores/debug.keystore
+
+# Cocoapods
+#
+example/ios/Pods
+
+# Ruby
+example/vendor/
+
+# node.js
+#
+node_modules/
+npm-debug.log
+yarn-debug.log
+yarn-error.log
+
+# Expo
+.expo/*
+.env

packages/expo-biometrics/.npmignore

@@ -0,0 +1,14 @@
+# Exclude all top-level hidden directories by convention
+/.*/
+
+# Exclude tarballs generated by `npm pack`
+/*.tgz
+
+__mocks__
+__tests__
+
+/babel.config.js
+/android/src/androidTest/
+/android/src/test/
+/android/build/
+/example/

packages/expo-biometrics/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 Clerk, Inc.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

packages/expo-biometrics/README.md

@@ -0,0 +1,84 @@
+<p align="center">
+  <a href="https://clerk.com?utm_source=github&utm_medium=clerk_expo_biometrics" target="_blank" rel="noopener noreferrer">
+    <picture>
+      <source media="(prefers-color-scheme: dark)" srcset="https://images.clerk.com/static/logo-dark-mode-400x400.png">
+      <img src="https://images.clerk.com/static/logo-light-mode-400x400.png" height="64">
+    </picture>
+  </a>
+  <br />
+  <h1 align="center">@clerk/expo-biometrics</h1>
+</p>
+
+<div align="center">
+
+[![Chat on Discord](https://img.shields.io/discord/856971667393609759.svg?logo=discord)](https://clerk.com/discord)
+[![Clerk documentation](https://img.shields.io/badge/documentation-clerk-green.svg)](https://clerk.com/docs?utm_source=github&utm_medium=expo_biometrics)
+[![Follow on X](https://img.shields.io/twitter/follow/clerk?style=social)](https://x.com/intent/follow?screen_name=clerk)
+
+[Changelog](https://github.com/clerk/javascript/blob/main/packages/expo-biometrics/CHANGELOG.md)
+·
+[Report a Bug](https://github.com/clerk/javascript/issues/new?assignees=&labels=needs-triage&projects=&template=BUG_REPORT.yml)
+·
+[Request a Feature](https://feedback.clerk.com/roadmap)
+·
+[Get help](https://clerk.com/contact/support?utm_source=github&utm_medium=expo_biometrics)
+
+</div>
+
+> [!WARNING]
+> This package is experimental. Pin its version, as breaking changes can happen in minor releases.
+
+The native building block for Clerk biometric credentials in Expo apps. It creates hardware-backed signing keys, signs challenges behind a Face ID / Touch ID prompt, and stores the on-device records that link each key to a Clerk credential. It does not talk to Clerk's API; `@clerk/expo` builds the sign-in and enrollment flows on top of it.
+
+The key and record layout is shared with the Clerk iOS SDK, so credentials enrolled by either SDK in the same app are visible to both.
+
+### Prerequisites
+
+- Expo SDK 54 or later, in a development build (the module is not available in Expo Go or on the web)
+- iOS. Android support is not implemented yet: every call rejects with `not_implemented`.
+- `NSFaceIDUsageDescription` in your `Info.plist`. The `@clerk/expo` config plugin sets it through its `faceIDPermission` option.
+
+## Installation
+
+```sh
+npx expo install @clerk/expo-biometrics
+```
+
+Then rebuild your native app.
+
+## API
+
+```ts
+import {
+  createKey,
+  deleteKey,
+  deleteRecord,
+  ensureInstallationMarker,
+  getAppIdentifier,
+  getAvailability,
+  hasKey,
+  listRecords,
+  saveRecord,
+  sign,
+} from '@clerk/expo-biometrics';
+```
+
+| Function                                       | Description                                                                                                              |
+| ---------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------ |
+| `getAppIdentifier()`                           | The app identifier sent to Clerk as `app_identifier` (the iOS bundle identifier).                                        |
+| `getAvailability()`                            | The device's biometry type and whether biometrics or device owner authentication can be evaluated.                       |
+| `createKey(policy)`                            | Creates a Secure Enclave P-256 key and returns its `localKeyId` and public key JWK.                                      |
+| `sign(localKeyId, clientData, reason?)`        | Prompts for authentication and returns an ES256 signature over `clientData` (raw `r \|\| s`, base64url without padding). |
+| `hasKey(localKeyId)` / `deleteKey(localKeyId)` | Checks for or deletes a key.                                                                                             |
+| `listRecords()`                                | Every stored credential record, for every app identifier.                                                                |
+| `saveRecord(record, options)`                  | Saves a record. With `removeOtherRecordsForApp: true`, deletes the app's other records and their keys.                   |
+| `deleteRecord(localKeyId)`                     | Deletes a key, then the records that reference it.                                                                       |
+| `ensureInstallationMarker()`                   | Deletes records and keys left behind by a previous installation of the app. The store functions call it for you.         |
+
+Every error is a `ClerkBiometricsError` with a stable `code`, such as `user_canceled`, `biometry_not_enrolled`, `biometry_lockout`, `key_not_found`, or `storage_failed`.
+
+## License
+
+This project is licensed under the **MIT license**.
+
+See [LICENSE](https://github.com/clerk/javascript/blob/main/packages/expo-biometrics/LICENSE) for more information.

packages/expo-biometrics/android/build.gradle

@@ -0,0 +1,39 @@
+apply plugin: 'com.android.library'
+// AGP 9+ registers the `kotlin` extension itself, and applying kotlin-android on top of that fails configuration.
+if (project.extensions.findByName('kotlin') == null) {
+  apply plugin: 'kotlin-android'
+}
+
+apply plugin: 'maven-publish'
+
+group = 'expo.modules.clerk.biometrics'
+version = '1.0.0'
+
+def expoModulesCorePlugin = new File(project(":expo-modules-core").projectDir.absolutePath, "ExpoModulesCorePlugin.gradle")
+apply from: expoModulesCorePlugin
+applyKotlinExpoModulesCorePlugin()
+useCoreDependencies()
+useExpoPublishing()
+
+buildscript {
+  ext.safeExtGet = { prop, fallback ->
+    rootProject.ext.has(prop) ? rootProject.ext.get(prop) : fallback
+  }
+}
+
+android {
+  namespace "expo.modules.clerk.biometrics"
+
+  compileSdkVersion safeExtGet("compileSdkVersion", 36)
+
+  defaultConfig {
+    minSdkVersion safeExtGet("minSdkVersion", 24)
+    targetSdkVersion safeExtGet("targetSdkVersion", 36)
+    versionCode 1
+    versionName "1.0.0"
+  }
+}
+
+dependencies {
+  implementation project(':expo-modules-core')
+}

packages/expo-biometrics/android/src/main/AndroidManifest.xml

@@ -0,0 +1,2 @@
+<manifest>
+</manifest>

packages/expo-biometrics/android/src/main/java/expo/modules/clerk/biometrics/ClerkExpoBiometricsModule.kt

@@ -0,0 +1,33 @@
+package expo.modules.clerk.biometrics
+
+import expo.modules.kotlin.Promise
+import expo.modules.kotlin.exception.CodedException
+import expo.modules.kotlin.modules.Module
+import expo.modules.kotlin.modules.ModuleDefinition
+
+class NotImplementedException :
+  CodedException("not_implemented", "@clerk/expo-biometrics is not supported on Android yet.", null)
+
+class ClerkExpoBiometricsModule : Module() {
+  override fun definition() = ModuleDefinition {
+    Name("ClerkExpoBiometrics")
+
+    Function("getAppIdentifier") { -> notImplemented<String>() }
+
+    AsyncFunction("getAvailability") { promise: Promise -> reject(promise) }
+    AsyncFunction("createKey") { _: String, promise: Promise -> reject(promise) }
+    AsyncFunction("sign") { _: String, _: String, _: String?, promise: Promise -> reject(promise) }
+    AsyncFunction("hasKey") { _: String, promise: Promise -> reject(promise) }
+    AsyncFunction("deleteKey") { _: String, promise: Promise -> reject(promise) }
+    AsyncFunction("listRecords") { promise: Promise -> reject(promise) }
+    AsyncFunction("saveRecord") { _: Map<String, Any?>, _: Map<String, Any?>, promise: Promise -> reject(promise) }
+    AsyncFunction("deleteRecord") { _: String, promise: Promise -> reject(promise) }
+    AsyncFunction("ensureInstallationMarker") { promise: Promise -> reject(promise) }
+  }
+
+  private fun reject(promise: Promise) {
+    promise.reject(NotImplementedException())
+  }
+
+  private fun <T> notImplemented(): T = throw NotImplementedException()
+}

packages/expo-biometrics/expo-module.config.json

@@ -0,0 +1,9 @@
+{
+  "platforms": ["apple", "android"],
+  "apple": {
+    "modules": ["ClerkExpoBiometricsModule"]
+  },
+  "android": {
+    "modules": ["expo.modules.clerk.biometrics.ClerkExpoBiometricsModule"]
+  }
+}