diff --git a/lib/models/plex/plex_config.dart b/lib/models/plex/plex_config.dart
index 8b511bc8..5193d570 100644
--- a/lib/models/plex/plex_config.dart
+++ b/lib/models/plex/plex_config.dart
@@ -1,5 +1,7 @@
 import 'package:package_info_plus/package_info_plus.dart';
 
+import '../../utils/device_identity.dart';
+
 class PlexConfig {
   final String baseUrl;
   final String? token;
@@ -8,6 +10,10 @@ class PlexConfig {
   final String version;
   final String platform;
   final String? device;
+
+  /// Friendly device name — Plex dashboards and Tautulli show it as the
+  /// session's "Player".
+  final String? deviceName;
   final bool acceptJson;
   final String? machineIdentifier;
   final String? languageCode;
@@ -20,6 +26,7 @@ class PlexConfig {
     required this.version,
     this.platform = 'Flutter',
     this.device,
+    this.deviceName,
     this.acceptJson = true,
     this.machineIdentifier,
     this.languageCode,
@@ -37,14 +44,16 @@ class PlexConfig {
     String? languageCode,
   }) async {
     final packageInfo = await PackageInfo.fromPlatform();
+    final identity = await DeviceIdentityService.resolve();
     return PlexConfig(
       baseUrl: baseUrl,
       token: token,
       clientIdentifier: clientIdentifier,
       product: product ?? 'Plezy',
       version: packageInfo.version,
-      platform: platform ?? 'Flutter',
-      device: device,
+      platform: platform ?? identity.platform,
+      device: device ?? sanitizeHeaderValue(identity.deviceModel),
+      deviceName: sanitizeHeaderValue(identity.deviceName),
       acceptJson: acceptJson,
       machineIdentifier: machineIdentifier,
       languageCode: languageCode,
@@ -59,6 +68,7 @@ class PlexConfig {
       'X-Plex-Platform': platform,
       'X-Plex-Client-Profile-Name': 'Generic',
       'X-Plex-Device': ?device,
+      'X-Plex-Device-Name': ?deviceName,
       if (acceptJson) 'Accept': 'application/json',
       'Accept-Charset': 'utf-8',
       'Accept-Language': ?_normalizedLanguageCode,
@@ -85,6 +95,7 @@ class PlexConfig {
     String? version,
     String? platform,
     String? device,
+    String? deviceName,
     bool? acceptJson,
     String? machineIdentifier,
     String? languageCode,
@@ -97,6 +108,7 @@ class PlexConfig {
       version: version ?? this.version,
       platform: platform ?? this.platform,
       device: device ?? this.device,
+      deviceName: deviceName ?? this.deviceName,
       acceptJson: acceptJson ?? this.acceptJson,
       machineIdentifier: machineIdentifier ?? this.machineIdentifier,
       languageCode: languageCode ?? this.languageCode,
diff --git a/lib/providers/companion_remote_provider.dart b/lib/providers/companion_remote_provider.dart
index b080eb65..7c056727 100644
--- a/lib/providers/companion_remote_provider.dart
+++ b/lib/providers/companion_remote_provider.dart
@@ -1,8 +1,6 @@
 import 'dart:async';
-import 'dart:io';
 
 import 'package:flutter/foundation.dart';
-import 'package:device_info_plus/device_info_plus.dart';
 
 import '../connection/connection.dart';
 import '../connection/connection_registry.dart';
@@ -20,7 +18,7 @@ import '../services/companion_remote/lan_discovery_service.dart';
 import '../services/companion_remote/remote_auth_context.dart';
 import '../services/companion_remote/remote_auth_service.dart';
 import '../utils/app_logger.dart';
-import '../utils/platform_detector.dart';
+import '../utils/device_identity.dart';
 import '../mixins/disposable_change_notifier_mixin.dart';
 
 export '../services/companion_remote/lan_discovery_service.dart' show DiscoveredHost;
@@ -91,36 +89,9 @@ class CompanionRemoteProvider with ChangeNotifier, DisposableChangeNotifierMixin
   }
 
   Future<void> _initializeDeviceInfo() async {
-    final deviceInfo = DeviceInfoPlugin();
-
-    try {
-      if (Platform.isAndroid) {
-        final androidInfo = await deviceInfo.androidInfo;
-        final osName = await TvDetectionService.getAndroidDeviceName();
-        _deviceName = osName ?? '${androidInfo.brand} ${androidInfo.model}';
-        _platform = 'Android';
-      } else if (Platform.isIOS) {
-        final iosInfo = await deviceInfo.iosInfo;
-        _deviceName = iosInfo.name;
-        _platform = 'iOS';
-      } else if (Platform.isMacOS) {
-        final macInfo = await deviceInfo.macOsInfo;
-        _deviceName = macInfo.computerName;
-        _platform = 'macOS';
-      } else if (Platform.isWindows) {
-        final windowsInfo = await deviceInfo.windowsInfo;
-        _deviceName = windowsInfo.computerName;
-        _platform = 'Windows';
-      } else if (Platform.isLinux) {
-        final host = Platform.localHostname.trim();
-        _deviceName = (host.isNotEmpty && host != 'localhost') ? host : (await deviceInfo.linuxInfo).name;
-        _platform = 'Linux';
-      }
-    } catch (e) {
-      appLogger.e('CompanionRemote: Failed to get device info', error: e);
-      _deviceName = t.companionRemote.unknownDevice;
-      _platform = Platform.operatingSystem;
-    }
+    final identity = await DeviceIdentityService.resolve();
+    _deviceName = identity.deviceName ?? t.companionRemote.unknownDevice;
+    _platform = identity.platform;
 
     safeNotifyListeners();
   }
diff --git a/lib/screens/settings/add_jellyfin_screen.dart b/lib/screens/settings/add_jellyfin_screen.dart
index 57b8c410..b5721425 100644
--- a/lib/screens/settings/add_jellyfin_screen.dart
+++ b/lib/screens/settings/add_jellyfin_screen.dart
@@ -26,6 +26,7 @@ import '../../services/jellyfin_lan_discovery_service.dart';
 import '../../services/storage_service.dart';
 import '../../theme/mono_tokens.dart';
 import '../../utils/app_logger.dart';
+import '../../utils/device_identity.dart';
 import '../../utils/platform_detector.dart';
 import '../../widgets/focused_scroll_scaffold.dart';
 import '../profile/profile_switch_screen.dart';
@@ -436,10 +437,8 @@ class _AddJellyfinScreenState extends State<AddJellyfinScreen> with AsyncFormSta
   }
 
   Future<String> _resolveDeviceName() async {
-    // PackageInfo doesn't expose a device name; fall back to a generic label.
-    // Jellyfin only shows this in the admin "Devices" list — fine to keep
-    // simple until we add proper device_info_plus integration.
-    return 'Plezy';
+    final identity = await DeviceIdentityService.resolve();
+    return sanitizeHeaderValue(identity.deviceName) ?? 'Plezy';
   }
 
   @override
diff --git a/lib/services/jellyfin_auth_header.dart b/lib/services/jellyfin_auth_header.dart
index 74b4f3b0..0a82aae5 100644
--- a/lib/services/jellyfin_auth_header.dart
+++ b/lib/services/jellyfin_auth_header.dart
@@ -1,6 +1,10 @@
 /// Build the `MediaBrowser` Authorization header value the way the Jellyfin
 /// SDK formats it. Used at auth time and on every authenticated request so
 /// the server sees a consistent client identity.
+///
+/// Values are quote-stripped: the header grammar has no escape for `"`, so a
+/// device name like `My "cool" TV` would otherwise corrupt every field after
+/// it.
 String buildJellyfinAuthHeader({
   required String clientName,
   required String clientVersion,
@@ -8,12 +12,13 @@ String buildJellyfinAuthHeader({
   required String deviceId,
   String? accessToken,
 }) {
+  String quoted(String value) => '"${value.replaceAll('"', '')}"';
   final parts = <String>[
-    'Client="$clientName"',
-    'Device="$deviceName"',
-    'DeviceId="$deviceId"',
-    'Version="$clientVersion"',
-    if (accessToken != null && accessToken.isNotEmpty) 'Token="$accessToken"',
+    'Client=${quoted(clientName)}',
+    'Device=${quoted(deviceName)}',
+    'DeviceId=${quoted(deviceId)}',
+    'Version=${quoted(clientVersion)}',
+    if (accessToken != null && accessToken.isNotEmpty) 'Token=${quoted(accessToken)}',
   ];
   return 'MediaBrowser ${parts.join(', ')}';
 }
diff --git a/lib/services/jellyfin_client.dart b/lib/services/jellyfin_client.dart
index 10296102..1b38821f 100644
--- a/lib/services/jellyfin_client.dart
+++ b/lib/services/jellyfin_client.dart
@@ -41,6 +41,7 @@ import '../models/media_subscription.dart';
 import '../media/media_source_info.dart';
 import '../media/media_sort.dart';
 import '../utils/app_logger.dart';
+import '../utils/device_identity.dart';
 import '../utils/failover_http_client.dart';
 import '../utils/media_server_retry.dart';
 import '../utils/media_server_timeouts.dart';
@@ -125,10 +126,16 @@ class JellyfinClient
     } catch (_) {
       // Tests / non-platform contexts — keep the fallback version.
     }
+    String? deviceName;
+    try {
+      deviceName = sanitizeHeaderValue((await DeviceIdentityService.resolve()).deviceName);
+    } catch (_) {
+      // Tests / non-platform contexts — keep the fallback name.
+    }
     final authHeader = buildJellyfinAuthHeader(
       clientName: 'Plezy',
       clientVersion: version,
-      deviceName: 'Plezy',
+      deviceName: deviceName ?? 'Plezy',
       deviceId: connection.deviceId,
       accessToken: connection.accessToken,
     );
diff --git a/lib/services/plex_auth_service.dart b/lib/services/plex_auth_service.dart
index be61fb34..094be8c1 100644
--- a/lib/services/plex_auth_service.dart
+++ b/lib/services/plex_auth_service.dart
@@ -9,6 +9,7 @@ import '../models/plex/plex_user_profile.dart';
 import '../models/plex/plex_home.dart';
 import '../models/user_switch_response.dart';
 import '../utils/app_logger.dart';
+import '../utils/device_identity.dart';
 import '../utils/endpoint_race.dart';
 import '../utils/media_server_timeouts.dart';
 import '../utils/media_server_http_client.dart';
@@ -53,8 +54,17 @@ class PlexAuthService {
   final String _clientIdentifier;
   final String _appVersion;
   final String _platformVersion;
+  final String _platform;
+  final String? _deviceName;
 
-  PlexAuthService._(this._http, this._clientIdentifier, this._appVersion, this._platformVersion);
+  PlexAuthService._(
+    this._http,
+    this._clientIdentifier,
+    this._appVersion,
+    this._platformVersion,
+    this._platform,
+    this._deviceName,
+  );
 
   @visibleForTesting
   PlexAuthService.forTesting({
@@ -62,7 +72,9 @@ class PlexAuthService {
     String clientIdentifier = 'test-client',
     String appVersion = 'test',
     String platformVersion = 'test',
-  }) : this._(http, clientIdentifier, appVersion, platformVersion);
+    String platform = 'Flutter',
+    String? deviceName,
+  }) : this._(http, clientIdentifier, appVersion, platformVersion, platform, deviceName);
 
   /// Close the underlying HTTP client. Call when the service is short-lived
   /// (created for a single API call) to avoid leaking sockets.
@@ -76,7 +88,15 @@ class PlexAuthService {
     );
     final clientIdentifier = await storage.getOrCreateClientIdentifier();
     final packageInfo = await PackageInfo.fromPlatform();
-    return PlexAuthService._(http, clientIdentifier, packageInfo.version, Platform.operatingSystemVersion);
+    final identity = await DeviceIdentityService.resolve();
+    return PlexAuthService._(
+      http,
+      clientIdentifier,
+      packageInfo.version,
+      Platform.operatingSystemVersion,
+      identity.platform,
+      sanitizeHeaderValue(identity.deviceName),
+    );
   }
 
   String get clientIdentifier => _clientIdentifier;
@@ -86,6 +106,8 @@ class PlexAuthService {
       'Accept': 'application/json',
       'X-Plex-Product': _appName,
       'X-Plex-Client-Identifier': _clientIdentifier,
+      'X-Plex-Platform': _platform,
+      'X-Plex-Device-Name': ?_deviceName,
     };
 
     if (authToken != null) {
@@ -251,7 +273,7 @@ class PlexAuthService {
       'X-Plex-Product': _appName,
       'X-Plex-Version': _appVersion,
       'X-Plex-Client-Identifier': _clientIdentifier,
-      'X-Plex-Platform': 'Flutter',
+      'X-Plex-Platform': _platform,
       'X-Plex-Platform-Version': _platformVersion,
       'X-Plex-Token': currentToken,
       'X-Plex-Language': 'en',
diff --git a/lib/services/plex_client.dart b/lib/services/plex_client.dart
index c139befb..8ddde4ec 100644
--- a/lib/services/plex_client.dart
+++ b/lib/services/plex_client.dart
@@ -52,6 +52,7 @@ import '../utils/content_utils.dart';
 import '../media/media_sort.dart';
 import '../models/plex/plex_video_playback_data.dart';
 import '../models/transcode_quality_preset.dart';
+import '../utils/device_identity.dart';
 import '../utils/failover_http_client.dart';
 import '../utils/app_logger.dart';
 import '../utils/media_server_retry.dart';
@@ -551,6 +552,8 @@ class PlexClient
     Duration timeout = const Duration(seconds: 5),
     String? clientIdentifier,
   }) async {
+    // Memoized after the first call — resolve outside the latency window.
+    final identity = await DeviceIdentityService.resolve();
     final stopwatch = Stopwatch()..start();
     MediaServerHttpClient? client;
 
@@ -561,7 +564,7 @@ class PlexClient
       if (clientIdentifier != null) {
         headers['X-Plex-Client-Identifier'] = clientIdentifier;
         headers['X-Plex-Product'] = 'Plezy';
-        headers['X-Plex-Device-Name'] = 'Plezy';
+        headers['X-Plex-Device-Name'] = sanitizeHeaderValue(identity.deviceName) ?? 'Plezy';
       }
 
       final response = await client.get('/', headers: headers);
@@ -3138,6 +3141,7 @@ class PlexClient
       // [_transcodePlatformName] for the mapping.
       'X-Plex-Platform': _transcodePlatformName(),
       if (config.device != null) 'X-Plex-Device': config.device!,
+      if (config.deviceName != null) 'X-Plex-Device-Name': config.deviceName!,
       if (offsetMs != null) 'offset': (offsetMs ~/ 1000).toString(),
       if (config.token != null) 'X-Plex-Token': config.token!,
     };
diff --git a/lib/services/plex_client/parts/live_tv.dart b/lib/services/plex_client/parts/live_tv.dart
index 9bc79096..35bfded0 100644
--- a/lib/services/plex_client/parts/live_tv.dart
+++ b/lib/services/plex_client/parts/live_tv.dart
@@ -999,7 +999,10 @@ mixin _PlexLiveTvClientMethods on MediaServerCacheMixin {
         'X-Plex-Product': config.product,
         'X-Plex-Version': config.version,
         'X-Plex-Client-Identifier': config.clientIdentifier,
-        'X-Plex-Platform': config.platform,
+        // Pinned rather than config.platform: this decision request is only
+        // known to work with the 'Plex Desktop' profile + 'Flutter' platform
+        // pairing, and real OS names map to server-side preset profiles.
+        'X-Plex-Platform': 'Flutter',
         'X-Plex-Client-Profile-Name': 'Plex Desktop',
         if (offsetSeconds != null) 'offset': offsetSeconds.toString(),
         if (config.token != null) 'X-Plex-Token': config.token!,
diff --git a/lib/utils/device_identity.dart b/lib/utils/device_identity.dart
new file mode 100644
index 00000000..d2fe018a
--- /dev/null
+++ b/lib/utils/device_identity.dart
@@ -0,0 +1,113 @@
+import 'dart:io';
+
+import 'package:device_info_plus/device_info_plus.dart';
+import 'package:flutter/foundation.dart';
+
+import 'app_logger.dart';
+import 'platform_detector.dart';
+
+/// What this install should call itself when talking to media servers and
+/// companion peers: a real platform name, the hardware model, and the
+/// user-facing device name (Plex dashboards show it as the "Player";
+/// Jellyfin as the "Device").
+class DeviceIdentity {
+  /// 'Android' | 'iOS' | 'tvOS' | 'macOS' | 'Windows' | 'Linux', falling back
+  /// to [Platform.operatingSystem] when detection fails.
+  final String platform;
+
+  /// Hardware model for `X-Plex-Device`, e.g. 'AFTKM' (Fire TV), 'iPhone',
+  /// 'Apple TV'. Null when unresolvable.
+  final String? deviceModel;
+
+  /// Friendly, usually user-assigned name (Settings > About > Device name on
+  /// Android, computer name on desktop). Null when unresolvable — callers
+  /// pick their own fallback. May contain characters that are not valid in
+  /// HTTP headers; pass through [sanitizeHeaderValue] before sending.
+  final String? deviceName;
+
+  final bool isTv;
+
+  const DeviceIdentity({required this.platform, this.deviceModel, this.deviceName, this.isTv = false});
+}
+
+/// Resolves the device identity once per process and memoizes it. Never
+/// throws — platform-channel failures (tests, exotic platforms) degrade to
+/// [Platform.operatingSystem] with null name/model.
+class DeviceIdentityService {
+  DeviceIdentityService._();
+
+  static Future<DeviceIdentity>? _cached;
+
+  static Future<DeviceIdentity> resolve() => _cached ??= _resolve();
+
+  @visibleForTesting
+  static void debugOverride(DeviceIdentity? identity) {
+    _cached = identity == null ? null : Future.value(identity);
+  }
+
+  static Future<DeviceIdentity> _resolve() async {
+    final deviceInfo = DeviceInfoPlugin();
+    final isTv = TvDetectionService.isTVSync();
+
+    try {
+      if (Platform.isAndroid) {
+        final androidInfo = await deviceInfo.androidInfo;
+        final assignedName = await TvDetectionService.getAndroidDeviceName();
+        return DeviceIdentity(
+          platform: 'Android',
+          deviceModel: androidInfo.model,
+          deviceName: assignedName ?? '${androidInfo.brand} ${androidInfo.model}',
+          isTv: isTv,
+        );
+      }
+      if (Platform.isIOS) {
+        final iosInfo = await deviceInfo.iosInfo;
+        if (TvDetectionService.isAppleTVSync()) {
+          return DeviceIdentity(platform: 'tvOS', deviceModel: 'Apple TV', deviceName: iosInfo.name, isTv: true);
+        }
+        return DeviceIdentity(platform: 'iOS', deviceModel: iosInfo.model, deviceName: iosInfo.name, isTv: isTv);
+      }
+      if (Platform.isMacOS) {
+        final macInfo = await deviceInfo.macOsInfo;
+        return DeviceIdentity(
+          platform: 'macOS',
+          deviceModel: macInfo.model,
+          deviceName: macInfo.computerName,
+          isTv: isTv,
+        );
+      }
+      if (Platform.isWindows) {
+        final windowsInfo = await deviceInfo.windowsInfo;
+        return DeviceIdentity(
+          platform: 'Windows',
+          deviceModel: 'Windows',
+          deviceName: windowsInfo.computerName,
+          isTv: isTv,
+        );
+      }
+      if (Platform.isLinux) {
+        final host = Platform.localHostname.trim();
+        final name = (host.isNotEmpty && host != 'localhost') ? host : (await deviceInfo.linuxInfo).name;
+        return DeviceIdentity(platform: 'Linux', deviceModel: 'Linux', deviceName: name, isTv: isTv);
+      }
+    } catch (e) {
+      appLogger.w('DeviceIdentity: failed to resolve device info', error: e);
+    }
+
+    return DeviceIdentity(platform: Platform.operatingSystem, isTv: isTv);
+  }
+}
+
+/// Makes a free-form device name safe to send as an HTTP header value:
+/// drops CR/LF and any code unit above 0xFF (dart:io's HttpHeaders throws a
+/// FormatException on non-latin-1 — an emoji in an iPhone name would
+/// otherwise kill every request), trims, and returns null when nothing
+/// usable remains.
+String? sanitizeHeaderValue(String? value) {
+  if (value == null) return null;
+  final filtered = String.fromCharCodes(
+    value.codeUnits.where((unit) => unit != 0x0D && unit != 0x0A && unit <= 0xFF),
+  );
+  final trimmed = filtered.trim();
+  return trimmed.isEmpty ? null : trimmed;
+}
diff --git a/test/models/plex_config_test.dart b/test/models/plex_config_test.dart
new file mode 100644
index 00000000..452c48df
--- /dev/null
+++ b/test/models/plex_config_test.dart
@@ -0,0 +1,34 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:plezy/models/plex/plex_config.dart';
+
+void main() {
+  group('PlexConfig.headers', () {
+    test('includes X-Plex-Device-Name when deviceName is set', () {
+      final config = PlexConfig(
+        baseUrl: 'https://plex.example.com',
+        clientIdentifier: 'client-1',
+        product: 'Plezy',
+        version: '1.0',
+        platform: 'Windows',
+        device: 'Windows',
+        deviceName: 'Living Room PC',
+      );
+      expect(config.headers['X-Plex-Platform'], 'Windows');
+      expect(config.headers['X-Plex-Device'], 'Windows');
+      expect(config.headers['X-Plex-Device-Name'], 'Living Room PC');
+    });
+
+    test('omits X-Plex-Device-Name and X-Plex-Device when unset', () {
+      final config = PlexConfig(
+        baseUrl: 'https://plex.example.com',
+        clientIdentifier: 'client-1',
+        product: 'Plezy',
+        version: '1.0',
+      );
+      expect(config.headers.containsKey('X-Plex-Device-Name'), isFalse);
+      expect(config.headers.containsKey('X-Plex-Device'), isFalse);
+      // Raw-constructor default is unchanged for tests that rely on it.
+      expect(config.headers['X-Plex-Platform'], 'Flutter');
+    });
+  });
+}
diff --git a/test/services/jellyfin_auth_header_test.dart b/test/services/jellyfin_auth_header_test.dart
new file mode 100644
index 00000000..3c51bdb7
--- /dev/null
+++ b/test/services/jellyfin_auth_header_test.dart
@@ -0,0 +1,44 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:plezy/services/jellyfin_auth_header.dart';
+
+void main() {
+  group('buildJellyfinAuthHeader', () {
+    test('formats the SDK-style MediaBrowser header', () {
+      final header = buildJellyfinAuthHeader(
+        clientName: 'Plezy',
+        clientVersion: '1.2.3',
+        deviceName: 'Living Room TV',
+        deviceId: 'dev-1',
+        accessToken: 'tok',
+      );
+      expect(
+        header,
+        'MediaBrowser Client="Plezy", Device="Living Room TV", DeviceId="dev-1", Version="1.2.3", Token="tok"',
+      );
+    });
+
+    test('omits Token when access token is null or empty', () {
+      for (final token in [null, '']) {
+        final header = buildJellyfinAuthHeader(
+          clientName: 'Plezy',
+          clientVersion: '1.2.3',
+          deviceName: 'Plezy',
+          deviceId: 'dev-1',
+          accessToken: token,
+        );
+        expect(header, isNot(contains('Token=')));
+      }
+    });
+
+    test('strips embedded quotes so a device name cannot corrupt the header', () {
+      final header = buildJellyfinAuthHeader(
+        clientName: 'Plezy',
+        clientVersion: '1.2.3',
+        deviceName: 'My "cool" TV',
+        deviceId: 'dev-1',
+        accessToken: 'tok',
+      );
+      expect(header, contains('Device="My cool TV"'));
+    });
+  });
+}
diff --git a/test/services/jellyfin_client_urls_test.dart b/test/services/jellyfin_client_urls_test.dart
index a3dca817..d115d446 100644
--- a/test/services/jellyfin_client_urls_test.dart
+++ b/test/services/jellyfin_client_urls_test.dart
@@ -12,6 +12,7 @@ import 'package:plezy/media/media_server_client.dart';
 import 'package:plezy/models/transcode_quality_preset.dart';
 import 'package:plezy/services/jellyfin_client.dart';
 import 'package:plezy/services/playback_initialization_types.dart';
+import 'package:plezy/utils/device_identity.dart';
 
 JellyfinConnection _conn({String accessToken = 'tok-abc', String baseUrl = 'https://jf.example.com'}) =>
     JellyfinConnection(
@@ -32,6 +33,11 @@ JellyfinConnection _conn({String accessToken = 'tok-abc', String baseUrl = 'http
 /// tests pin the contract so the next iteration of the player (Task 8 wiring)
 /// has something to point at.
 void main() {
+  // Pin device identity so JellyfinClient.create's MediaBrowser header falls
+  // back to Device="Plezy" instead of resolving the host machine's name.
+  setUpAll(() => DeviceIdentityService.debugOverride(const DeviceIdentity(platform: 'Test')));
+  tearDownAll(() => DeviceIdentityService.debugOverride(null));
+
   group('JellyfinClient URL builders', () {
     late JellyfinClient client;
 
diff --git a/test/services/jellyfin_trickplay_service_test.dart b/test/services/jellyfin_trickplay_service_test.dart
index 56f3fbd4..13575158 100644
--- a/test/services/jellyfin_trickplay_service_test.dart
+++ b/test/services/jellyfin_trickplay_service_test.dart
@@ -8,6 +8,7 @@ import 'package:plezy/media/media_source_info.dart';
 import 'package:plezy/services/jellyfin_client.dart';
 import 'package:plezy/services/jellyfin_trickplay_service.dart';
 import 'package:plezy/services/scrub_preview_source.dart';
+import 'package:plezy/utils/device_identity.dart';
 
 JellyfinConnection _conn() => JellyfinConnection(
   id: 'srv-1/user-1',
@@ -44,6 +45,11 @@ TrickplayInfo _info({
 ImageProvider _fakeSheet(String _) => MemoryImage(Uint8List.fromList(const [0]));
 
 void main() {
+  // Pin device identity so JellyfinClient.create doesn't resolve the host
+  // machine's name.
+  setUpAll(() => DeviceIdentityService.debugOverride(const DeviceIdentity(platform: 'Test')));
+  tearDownAll(() => DeviceIdentityService.debugOverride(null));
+
   group('JellyfinTrickplayService.create — width selection', () {
     late JellyfinClient client;
 
diff --git a/test/utils/device_identity_test.dart b/test/utils/device_identity_test.dart
new file mode 100644
index 00000000..507849a5
--- /dev/null
+++ b/test/utils/device_identity_test.dart
@@ -0,0 +1,47 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:plezy/utils/device_identity.dart';
+
+void main() {
+  group('sanitizeHeaderValue', () {
+    test('passes plain latin-1 names through trimmed', () {
+      expect(sanitizeHeaderValue('  Living Room TV '), 'Living Room TV');
+      expect(sanitizeHeaderValue("Édouard's Mac"), "Édouard's Mac");
+    });
+
+    test('strips code units above latin-1 (emoji would break dart:io headers)', () {
+      expect(sanitizeHeaderValue('📱 Bob\'s iPhone'), "Bob's iPhone");
+      expect(sanitizeHeaderValue('电视'), isNull);
+    });
+
+    test('strips CR/LF', () {
+      expect(sanitizeHeaderValue('evil\r\nX-Injected: 1'), 'evilX-Injected: 1');
+    });
+
+    test('returns null for null, empty, and whitespace-only input', () {
+      expect(sanitizeHeaderValue(null), isNull);
+      expect(sanitizeHeaderValue(''), isNull);
+      expect(sanitizeHeaderValue('   '), isNull);
+    });
+  });
+
+  group('DeviceIdentityService.debugOverride', () {
+    tearDown(() => DeviceIdentityService.debugOverride(null));
+
+    test('resolve returns the overridden identity', () async {
+      const identity = DeviceIdentity(platform: 'TestOS', deviceModel: 'Model-X', deviceName: 'Unit Test', isTv: true);
+      DeviceIdentityService.debugOverride(identity);
+      final resolved = await DeviceIdentityService.resolve();
+      expect(resolved.platform, 'TestOS');
+      expect(resolved.deviceModel, 'Model-X');
+      expect(resolved.deviceName, 'Unit Test');
+      expect(resolved.isTv, isTrue);
+    });
+
+    test('a later override replaces the memoized value', () async {
+      DeviceIdentityService.debugOverride(const DeviceIdentity(platform: 'First'));
+      expect((await DeviceIdentityService.resolve()).platform, 'First');
+      DeviceIdentityService.debugOverride(const DeviceIdentity(platform: 'Second'));
+      expect((await DeviceIdentityService.resolve()).platform, 'Second');
+    });
+  });
+}