diff --git a/app/Devnull/SignInAttempt.php b/app/Devnull/SignInAttempt.php
index 51f0d6b..1b01587 100644
--- a/app/Devnull/SignInAttempt.php
+++ b/app/Devnull/SignInAttempt.php
@@ -46,13 +46,17 @@ public function answers(string $state): bool
 
     /**
      * The page on dev-null.sh that signs you in with GitHub and approves this
-     * phone's key, then sends the browser back to the app with a code.
+     * phone's key, then sends the browser back to the app with a code. The
+     * app's name goes with the phone's, so Settings → Devices tells them apart,
+     * and its id, which stays when the name changes.
      */
-    public function authorizeUrl(string $baseUrl, string $fingerprint, string $deviceName): string
+    public function authorizeUrl(string $baseUrl, string $fingerprint, string $deviceName, string $appName, string $appId): string
     {
         return rtrim($baseUrl, '/').'/mobile/authorize?'.http_build_query([
             'fingerprint' => $fingerprint,
             'device_name' => $deviceName,
+            'app_name' => $appName,
+            'app_id' => $appId,
             'code_challenge' => $this->challenge(),
             'code_challenge_method' => 'S256',
             'state' => $this->state,
diff --git a/app/NativeComponents/Onboarding.php b/app/NativeComponents/Onboarding.php
index c9b96b2..02b85b2 100644
--- a/app/NativeComponents/Onboarding.php
+++ b/app/NativeComponents/Onboarding.php
@@ -18,6 +18,7 @@
 use Native\Mobile\Edge\NativeComponent;
 use Native\Mobile\Facades\Browser;
 use Native\Mobile\Facades\Device;
+use Native\Mobile\Facades\System;
 use SensitiveParameter;
 
 /**
@@ -107,7 +108,7 @@ public function signIn(): void
 
         $attempt = app(SignIn::class)->begin();
 
-        if (! Browser::auth($attempt->authorizeUrl((string) config('devnull.url'), $this->fingerprint, $this->deviceName()))) {
+        if (! Browser::auth($attempt->authorizeUrl((string) config('devnull.url'), $this->fingerprint, $this->deviceName(), $this->appName(), $this->appId()))) {
             $this->error = 'fatal: could not open dev-null.sh to sign in.';
         }
     }
@@ -276,7 +277,8 @@ private function keepProfile(User $user): void
     }
 
     /**
-     * Names the phone on devnull after its model, so it's clear what to remove later.
+     * Names the phone on devnull after its model, so it's clear what to remove
+     * later. The app says its own name next to it, see appName().
      */
     private function deviceName(): string
     {
@@ -284,9 +286,27 @@ private function deviceName(): string
             $info = json_decode((string) Device::getInfo(), true);
             $model = is_array($info) && is_string($info['model'] ?? null) ? trim($info['model']) : '';
 
-            $this->deviceName = 'devnull on '.($model === '' ? 'a phone' : $model);
+            $this->deviceName = $model === '' ? 'a phone' : $model;
         }
 
         return $this->deviceName;
     }
+
+    /**
+     * What devnull shows next to the phone's name, like "/dev/null for iOS on iPhone".
+     */
+    private function appName(): string
+    {
+        return System::isIos() ? '/dev/null for iOS' : '/dev/null for Android';
+    }
+
+    /**
+     * The app's platform and bundle id, like "ios:com.nativephp.devnull": the
+     * iOS and Android apps share a bundle id, but they are different apps. A
+     * build whose .env doesn't carry the bundle id says the release one.
+     */
+    private function appId(): string
+    {
+        return (System::isIos() ? 'ios:' : 'android:').(config('nativephp.app_id') ?: 'com.nativephp.devnull');
+    }
 }
diff --git a/tests/Feature/Screens/OnboardingAppleTest.php b/tests/Feature/Screens/OnboardingAppleTest.php
index a8c1c37..f297ccf 100644
--- a/tests/Feature/Screens/OnboardingAppleTest.php
+++ b/tests/Feature/Screens/OnboardingAppleTest.php
@@ -99,7 +99,7 @@
     Http::assertSentCount(2);
     Http::assertSent(fn (Request $request): bool => $request->method() === 'POST'
         && $request->url() === 'http://devnull.test/api/v1/'.Client::SignInPath
-        && $request->body() === json_encode(['apple_identity_token' => AppleIdentityToken, 'nonce' => $nonce, 'device_name' => 'devnull on iPhone'])
+        && $request->body() === json_encode(['apple_identity_token' => AppleIdentityToken, 'nonce' => $nonce, 'device_name' => 'iPhone'])
         && $request->hasHeader('X-SSH-Signature'));
 
     // Apple's token carries sha256(nonce) as hex, which is what devnull checks against the raw nonce.
diff --git a/tests/Feature/Screens/OnboardingTest.php b/tests/Feature/Screens/OnboardingTest.php
index 4e66097..c358a3a 100644
--- a/tests/Feature/Screens/OnboardingTest.php
+++ b/tests/Feature/Screens/OnboardingTest.php
@@ -148,9 +148,10 @@ function sendBack(TestableComponent $screen, array $query): TestableComponent
     Native::visit('/onboarding')->assertSet('fingerprint', testKey()->fingerprint());
 });
 
-it('opens dev-null.sh in the auth browser with the key, the device and an S256 challenge', function () {
+it('opens dev-null.sh in the auth browser with the key, the device, the app and an S256 challenge', function () {
+    config(['nativephp.app_id' => 'com.nativephp.devnull']);
     $bridge = signInBridge(testSeed());
-    $screen = Native::visit('/onboarding');
+    $screen = Native::visit('/onboarding', platform: 'ios');
 
     $screen->tap('sign-in')->assertNoNavigation();
 
@@ -159,15 +160,17 @@ function sendBack(TestableComponent $screen, array $query): TestableComponent
     $attempt = pendingAttempt();
 
     expect($url)->toStartWith('http://devnull.test/mobile/authorize?')
-        ->and(array_keys($query))->toBe(['fingerprint', 'device_name', 'code_challenge', 'code_challenge_method', 'state', 'redirect_uri'])
+        ->and(array_keys($query))->toBe(['fingerprint', 'device_name', 'app_name', 'app_id', 'code_challenge', 'code_challenge_method', 'state', 'redirect_uri'])
         ->and($query['fingerprint'])->toBe(testKey()->fingerprint())
-        ->and($query['device_name'])->toBe('devnull on iPhone')
+        ->and($query['device_name'])->toBe('iPhone')
+        ->and($query['app_name'])->toBe('/dev/null for iOS')
+        ->and($query['app_id'])->toBe('ios:com.nativephp.devnull')
         ->and($query['code_challenge_method'])->toBe('S256')
         ->and($query['redirect_uri'])->toBe('devnull://auth/callback')
         ->and($query['state'])->toBe($attempt->state)->toMatch('/^[A-Za-z0-9_-]{22}$/')
         ->and($attempt->verifier())->toMatch('/^[A-Za-z0-9_-]{43}$/')
         ->and($query['code_challenge'])->toBe(rtrim(strtr(base64_encode(hash('sha256', $attempt->verifier(), true)), '+/', '-_'), '='))
-        ->and($url)->toContain('device_name=devnull%20on%20iPhone')
+        ->and($url)->toContain('device_name=iPhone&app_name=%2Fdev%2Fnull%20for%20iOS&app_id=ios%3Acom.nativephp.devnull')
         ->and($url)->toContain('redirect_uri=devnull%3A%2F%2Fauth%2Fcallback');
 
     $bridge->assertOpenedAuth();
@@ -175,6 +178,24 @@ function sendBack(TestableComponent $screen, array $query): TestableComponent
     Http::assertNothingSent();
 });
 
+it('names itself the Android app on Android, a different app from the iOS one', function () {
+    config(['nativephp.app_id' => 'com.nativephp.devnull']);
+    $bridge = signInBridge(testSeed());
+
+    Native::visit('/onboarding', platform: 'android')->tap('sign-in');
+
+    expect(openedAuthQuery($bridge))->toMatchArray(['app_name' => '/dev/null for Android', 'app_id' => 'android:com.nativephp.devnull']);
+});
+
+it('says the release bundle id when the build does not carry one', function () {
+    config(['nativephp.app_id' => null]);
+    $bridge = signInBridge(testSeed());
+
+    Native::visit('/onboarding', platform: 'ios')->tap('sign-in');
+
+    expect(openedAuthQuery($bridge)['app_id'])->toBe('ios:com.nativephp.devnull');
+});
+
 it('makes a fresh verifier and state for every attempt', function () {
     $bridge = signInBridge(testSeed());
     $screen = Native::visit('/onboarding');
@@ -409,12 +430,14 @@ function sendBack(TestableComponent $screen, array $query): TestableComponent
 
 it('builds the authorize URL and checks state on its own', function () {
     $attempt = SignInAttempt::start();
-    $url = $attempt->authorizeUrl('https://dev-null.sh/', 'SHA256:a+b/c', 'devnull on iPhone');
+    $url = $attempt->authorizeUrl('https://dev-null.sh/', 'SHA256:a+b/c', 'iPhone', '/dev/null for iOS', 'ios:com.nativephp.devnull');
 
     parse_str((string) parse_url($url, PHP_URL_QUERY), $query);
 
     expect($url)->toStartWith('https://dev-null.sh/mobile/authorize?')
         ->and($query['fingerprint'])->toBe('SHA256:a+b/c')
+        ->and($query['app_name'])->toBe('/dev/null for iOS')
+        ->and($query['app_id'])->toBe('ios:com.nativephp.devnull')
         ->and($query['code_challenge'])->toBe($attempt->challenge())
         ->and($attempt->answers($attempt->state))->toBeTrue()
         ->and($attempt->answers(''))->toBeFalse()