diff --git a/it0_app/lib/features/chat/data/datasources/chat_remote_datasource.dart b/it0_app/lib/features/chat/data/datasources/chat_remote_datasource.dart
index c9bccb4..02cf55b 100644
--- a/it0_app/lib/features/chat/data/datasources/chat_remote_datasource.dart
+++ b/it0_app/lib/features/chat/data/datasources/chat_remote_datasource.dart
@@ -153,20 +153,16 @@ class ChatRemoteDatasource {
   /// Uploads an audio file to the voice-message endpoint.
   /// Backend performs STT, interrupts any running task if needed, and
   /// Transcribe audio to text (STT only, does NOT send to agent).
-  /// Returns the transcript string.
-  /// Pass language='auto' to let Whisper auto-detect (best for mixed-language).
+  /// No language hint is sent — Whisper auto-detects from audio content.
   Future<String> transcribeAudio({
     required String audioPath,
-    String language = 'zh',
   }) async {
-    final fields = <String, dynamic>{
+    final formData = FormData.fromMap({
       'audio': await MultipartFile.fromFile(
         audioPath,
         filename: audioPath.split('/').last,
       ),
-    };
-    if (language != 'auto') fields['language'] = language;
-    final formData = FormData.fromMap(fields);
+    });
     final response = await _dio.post(
       '${ApiEndpoints.agent}/transcribe',
       data: formData,
diff --git a/it0_app/lib/features/chat/presentation/pages/chat_page.dart b/it0_app/lib/features/chat/presentation/pages/chat_page.dart
index c1b343d..2e9e6fd 100644
--- a/it0_app/lib/features/chat/presentation/pages/chat_page.dart
+++ b/it0_app/lib/features/chat/presentation/pages/chat_page.dart
@@ -13,7 +13,6 @@ import '../widgets/approval_action_card.dart';
 import '../widgets/conversation_drawer.dart';
 import '../../../agent_call/presentation/pages/agent_call_page.dart';
 import '../widgets/voice_mic_button.dart';
-import '../../../settings/presentation/providers/settings_providers.dart';
 
 // ---------------------------------------------------------------------------
 // Chat page – Timeline workflow style (inspired by Claude Code VSCode)
@@ -62,8 +61,7 @@ class _ChatPageState extends ConsumerState<ChatPage> {
       _messageController.text = '识别中…';
     });
     try {
-      final language = ref.read(settingsProvider).language;
-      final text = await ref.read(chatProvider.notifier).transcribeAudio(audioPath, language: language);
+      final text = await ref.read(chatProvider.notifier).transcribeAudio(audioPath);
       if (mounted) {
         setState(() {
           _messageController.text = text;
diff --git a/it0_app/lib/features/chat/presentation/providers/chat_providers.dart b/it0_app/lib/features/chat/presentation/providers/chat_providers.dart
index db97861..347e985 100644
--- a/it0_app/lib/features/chat/presentation/providers/chat_providers.dart
+++ b/it0_app/lib/features/chat/presentation/providers/chat_providers.dart
@@ -573,9 +573,9 @@ class ChatNotifier extends StateNotifier<ChatState> {
     }
   }
 
-  Future<String> transcribeAudio(String audioPath, {String language = 'zh'}) async {
+  Future<String> transcribeAudio(String audioPath) async {
     final datasource = _ref.read(chatRemoteDatasourceProvider);
-    return datasource.transcribeAudio(audioPath: audioPath, language: language);
+    return datasource.transcribeAudio(audioPath: audioPath);
   }
 
   Future<void> cancelCurrentTask() async {