Toggle for reasoning effort (aka Extended Thinking)

lib/features/chat/providers/chat_providers.dart

@@ -1025,6 +1025,19 @@ class WebSearchEnabledNotifier extends Notifier<bool> {
   void set(bool value) => state = value;
 }
 
+// Extended Thinking enabled state for high reasoning effort
+final extendedThinkingEnabledProvider =
+    NotifierProvider<ExtendedThinkingEnabledNotifier, bool>(
+      ExtendedThinkingEnabledNotifier.new,
+    );
+
+class ExtendedThinkingEnabledNotifier extends Notifier<bool> {
+  @override
+  bool build() => false;
+
+  void set(bool value) => state = value;
+}
+
 class ImageGenerationEnabledNotifier extends Notifier<bool> {
   @override
   bool build() => false;
@@ -1417,6 +1430,7 @@ Future<void> regenerateMessage(
         ref.read(webSearchEnabledProvider) &&
         ref.read(webSearchAvailableProvider);
     final imageGenerationEnabled = ref.read(imageGenerationEnabledProvider);
+    final extendedThinkingEnabled = ref.read(extendedThinkingEnabledProvider);
 
     // Model metadata for completion notifications
     final supportedParams =
@@ -1581,6 +1595,7 @@ Future<void> regenerateMessage(
       'follow_up_generation': true,
       if (webSearchEnabled) 'web_search': true,
       if (imageGenerationEnabled) 'image_generation': true,
+      if (extendedThinkingEnabled) 'reasoning_effort': 'high',
     };
 
     final bool isBackgroundToolsFlowPre =
@@ -2011,6 +2026,7 @@ Future<void> _sendMessageInternal(
       ref.read(webSearchEnabledProvider) &&
       ref.read(webSearchAvailableProvider);
   final imageGenerationEnabled = ref.read(imageGenerationEnabledProvider);
+  final extendedThinkingEnabled = ref.read(extendedThinkingEnabledProvider);
 
   // Prepare tools list - pass tool IDs directly
   final List<String>? toolIdsForApi = (toolIds != null && toolIds.isNotEmpty)
@@ -2226,6 +2242,7 @@ Future<void> _sendMessageInternal(
       if (webSearchEnabled) 'web_search': true, // enable bg web search
       if (imageGenerationEnabled)
         'image_generation': true, // enable bg image flow
+      if (extendedThinkingEnabled) 'reasoning_effort': 'high',
     };
 
     // Determine if we need background task flow (tools/tool servers or web search)

lib/features/chat/widgets/modern_chat_input.dart

@@ -952,6 +952,7 @@ class _ModernChatInputState extends ConsumerState<ModernChatInput>
     final webSearchEnabled = ref.watch(webSearchEnabledProvider);
     final imageGenEnabled = ref.watch(imageGenerationEnabledProvider);
     final imageGenAvailable = ref.watch(imageGenerationAvailableProvider);
+    final extendedThinkingEnabled = ref.watch(extendedThinkingEnabledProvider);
     final selectedQuickPills = ref.watch(
       appSettingsProvider.select((s) => s.quickPills),
     );
@@ -1170,6 +1171,7 @@ class _ModernChatInputState extends ConsumerState<ModernChatInput>
                 tooltip: AppLocalizations.of(context)!.more,
                 webSearchActive: webSearchEnabled,
                 imageGenerationActive: imageGenEnabled,
+                extendedThinkingActive: extendedThinkingEnabled,
                 toolsActive: selectedToolIds.isNotEmpty,
                 filtersActive: selectedFilterIds.isNotEmpty,
               ),
@@ -1283,6 +1285,7 @@ class _ModernChatInputState extends ConsumerState<ModernChatInput>
                 tooltip: AppLocalizations.of(context)!.more,
                 webSearchActive: webSearchEnabled,
                 imageGenerationActive: imageGenEnabled,
+                extendedThinkingActive: extendedThinkingEnabled,
                 toolsActive: selectedToolIds.isNotEmpty,
                 filtersActive: selectedFilterIds.isNotEmpty,
               ),
@@ -1567,6 +1570,7 @@ class _ModernChatInputState extends ConsumerState<ModernChatInput>
     required String tooltip,
     required bool webSearchActive,
     required bool imageGenerationActive,
+    required bool extendedThinkingActive,
     required bool toolsActive,
     required bool filtersActive,
   }) {
@@ -1580,6 +1584,9 @@ class _ModernChatInputState extends ConsumerState<ModernChatInput>
     } else if (imageGenerationActive) {
       icon = Platform.isIOS ? CupertinoIcons.photo : Icons.image;
       activeColor = context.conduitTheme.buttonPrimary;
+    } else if (extendedThinkingActive) {
+      icon = Icons.psychology;
+      activeColor = context.conduitTheme.buttonPrimary;
     } else if (toolsActive) {
       icon = Platform.isIOS ? CupertinoIcons.wrench : Icons.build;
       activeColor = context.conduitTheme.buttonPrimary;
@@ -2146,6 +2153,19 @@ class _ModernChatInputState extends ConsumerState<ModernChatInput>
             );
           }
 
+          final extendedThinkingEnabled = modalRef.watch(extendedThinkingEnabledProvider);
+          featureTiles.add(
+            _buildFeatureToggleTile(
+              icon: Icons.psychology,
+              title: l10n.extendedThinking,
+              subtitle: l10n.extendedThinkingDescription,
+              value: extendedThinkingEnabled,
+              onChanged: (next) {
+                modalRef.read(extendedThinkingEnabledProvider.notifier).set(next);
+              },
+            ),
+          );
+
           final imageGenAvailable = modalRef.watch(
             imageGenerationAvailableProvider,
           );

lib/l10n/app_en.arb

@@ -980,6 +980,14 @@
   "@imageGenerationDescription": {
     "description": "Explains creating images via model prompts."
   },
+  "extendedThinking": "Extended Thinking",
+  "@extendedThinking": {
+    "description": "Feature toggle for high reasoning effort mode."
+  },
+  "extendedThinkingDescription": "Boosts reasoning effort for more thoughtful responses.",
+  "@extendedThinkingDescription": {
+    "description": "Explains that extended thinking mode provides more detailed reasoning."
+  },
   "copy": "Copy",
   "@copy": {
     "description": "Action to copy text to clipboard."