Merge pull request #371 from Mng-dev-ai/fix/model-selector-landing-page

Fix model selector not persisting chosen model across pages

Author: Mng-dev-ai

frontend/src/components/chat/chat-window/ChatSessionOrchestrator.tsx

@@ -50,7 +50,20 @@ export function ChatSessionOrchestrator({
     })),
   );
 
-  const { selectedModelId, selectModel } = useModelSelection({ chatId });
+  const lastAssistantModelId = useMemo((): string | null | undefined => {
+    if (messagesQuery.isLoading) return null;
+    for (let i = fetchedMessages.length - 1; i >= 0; i--) {
+      if (fetchedMessages[i].role === 'assistant' && fetchedMessages[i].model_id) {
+        return fetchedMessages[i].model_id;
+      }
+    }
+    return undefined;
+  }, [fetchedMessages, messagesQuery.isLoading]);
+
+  const { selectedModelId, selectModel } = useModelSelection({
+    chatId,
+    initialModelId: lastAssistantModelId,
+  });
 
   const {
     initialPrompt,

frontend/src/hooks/queries/useModelQueries.ts

@@ -17,8 +17,14 @@ export const useModelsQuery = (options?: Partial<UseQueryOptions<Model[]>>) => {
   });
 };
 
-export const useModelSelection = (options?: { enabled?: boolean; chatId?: string }) => {
+export const useModelSelection = (options?: {
+  enabled?: boolean;
+  chatId?: string;
+  // null = still loading (defer default), undefined = no initial model (use models[0])
+  initialModelId?: string | null;
+}) => {
   const chatId = options?.chatId ?? DEFAULT_MODEL_KEY;
+  const initialModelId = options?.initialModelId;
   const { data: models = [], isLoading } = useModelsQuery({
     enabled: options?.enabled,
   });
@@ -27,10 +33,17 @@ export const useModelSelection = (options?: { enabled?: boolean; chatId?: string
   useEffect(() => {
     if (models.length === 0) return;
     const selectedExists = models.some((m) => m.model_id === selectedModelId);
-    if (!selectedExists) {
-      useModelStore.getState().selectModel(chatId, models[0].model_id);
-    }
-  }, [models, selectedModelId, chatId]);
+    if (selectedExists) return;
+
+    // Still loading initial model from message history — wait before defaulting
+    if (initialModelId === null) return;
+
+    const fallback =
+      initialModelId && models.some((m) => m.model_id === initialModelId)
+        ? initialModelId
+        : models[0].model_id;
+    useModelStore.getState().selectModel(chatId, fallback);
+  }, [models, selectedModelId, chatId, initialModelId]);
 
   const selectedModel = useMemo(
     () => models.find((m) => m.model_id === selectedModelId) ?? null,

frontend/src/pages/LandingPage.tsx

@@ -6,6 +6,7 @@ import { useLayoutSidebar } from '@/components/layout/layoutState';
 import { Input as ChatInput } from '@/components/chat/message-input/Input';
 import { WorkspaceSelector } from '@/components/chat/WorkspaceSelector';
 import { useChatStore } from '@/store/chatStore';
+import { useModelStore } from '@/store/modelStore';
 import { useAuthStore } from '@/store/authStore';
 import { useInfiniteChatsQuery, useCreateChatMutation } from '@/hooks/queries/useChatQueries';
 import { useWorkspacesQuery } from '@/hooks/queries/useWorkspaceQueries';
@@ -131,6 +132,7 @@ export function LandingPage() {
           model_id: selectedModelId,
           workspace_id: selectedWorkspaceId,
         });
+        useModelStore.getState().selectModel(newChat.id, selectedModelId);
         setMessage('');
         navigate(`/chat/${newChat.id}`, { state: { initialPrompt: trimmedPrompt } });
       } catch (error) {