diff --git a/backend/open_webui/routers/tasks.py b/backend/open_webui/routers/tasks.py
index c64706e1a8..0e88f8594a 100644
--- a/backend/open_webui/routers/tasks.py
+++ b/backend/open_webui/routers/tasks.py
@@ -166,6 +166,11 @@ async def generate_title(request: Request, form_data: dict, user=Depends(get_ver
         models = request.app.state.MODELS
 
     model_id = form_data['model']
+    if not model_id:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail='No model specified for title generation. Please ensure a model is selected for this chat.',
+        )
     if model_id not in models:
         raise HTTPException(
             status_code=status.HTTP_404_NOT_FOUND,
diff --git a/src/lib/components/layout/Sidebar/ChatItem.svelte b/src/lib/components/layout/Sidebar/ChatItem.svelte
index 55a3200cad..29c483ec47 100644
--- a/src/lib/components/layout/Sidebar/ChatItem.svelte
+++ b/src/lib/components/layout/Sidebar/ChatItem.svelte
@@ -51,6 +51,7 @@
 	import Sparkles from '$lib/components/icons/Sparkles.svelte';
 	import Spinner from '$lib/components/common/Spinner.svelte';
 	import { generateTitle } from '$lib/apis';
+	import { createMessagesList } from '$lib/utils';
 
 	export let className = '';
 
@@ -343,14 +344,46 @@
 			chat = await getChatById(localStorage.token, id);
 		}
 
-		const messages = (chat.chat?.messages ?? []).map((message) => {
-			return {
+		const chatContent = chat.chat;
+
+		// Build the active branch message list from the history tree.
+		// Fallback to the legacy flat messages array for older chats
+		// that haven't been migrated to the tree structure yet.
+		const history = chatContent?.history;
+		let messages = [];
+		if (history?.messages && history?.currentId) {
+			messages = createMessagesList(history, history.currentId).map((message) => ({
 				role: message.role,
 				content: message.content
-			};
-		});
+			}));
+		} else {
+			messages = (chatContent?.messages ?? []).map((message) => ({
+				role: message.role,
+				content: message.content
+			}));
+		}
 
-		const model = chat.chat.models.at(0) ?? chat.models.at(0) ?? '';
+		// Resolve the model from the most recent assistant message in the
+		// active branch. This avoids using the stale top-level `models`
+		// array which may reference a model from an older edit.
+		let model = '';
+		if (history?.messages && history?.currentId) {
+			let currentId = history.currentId;
+			while (currentId) {
+				const msg = history.messages[currentId];
+				if (!msg) break;
+				if (msg.role === 'assistant' && msg.model) {
+					model = msg.model;
+					break;
+				}
+				currentId = msg.parentId;
+			}
+		}
+
+		// Fallback to top-level models if no model was found in the history
+		if (!model) {
+			model = chatContent?.models?.at(0) ?? '';
+		}
 
 		chatTitle = '';