diff --git a/src/components/layout/AppShell.tsx b/src/components/layout/AppShell.tsx
index fe2d730..76cff55 100644
--- a/src/components/layout/AppShell.tsx
+++ b/src/components/layout/AppShell.tsx
@@ -410,13 +410,13 @@ export function AppShell({ user, isDemo = false }: AppShellProps) {
     }
   };
 
-  // Restore from Trash
+  // Restore from Trash (Restores task and all its nested subtasks)
   const handleRestoreTask = (id: string) => {
     if (isDemo) {
       const store = getDemoStore();
       const newTasks = restoreTaskInTree(store.tasks, id);
       saveDemoStore(store.lists, newTasks);
-      setTasks((prev) => prev.filter((t) => t.id !== id));
+      setTasks(getAllTrashTasks(newTasks) as Task[]);
       refresh();
     }
   };
@@ -427,7 +427,7 @@ export function AppShell({ user, isDemo = false }: AppShellProps) {
       const store = getDemoStore();
       const newTasks = deleteTaskInTree(store.tasks, id);
       saveDemoStore(store.lists, newTasks);
-      setTasks((prev) => prev.filter((t) => t.id !== id));
+      setTasks(getAllTrashTasks(newTasks) as Task[]);
       refresh();
     }
   };
diff --git a/src/components/layout/Sidebar.tsx b/src/components/layout/Sidebar.tsx
index 89646ac..9a43d2a 100644
--- a/src/components/layout/Sidebar.tsx
+++ b/src/components/layout/Sidebar.tsx
@@ -7,7 +7,7 @@ import { useTheme } from "@/app/providers";
 import { LanguageSelector } from "@/components/ui/LanguageSelector";
 import { ContextMenu, MenuItem } from "@/components/ui/ContextMenu";
 import { SettingsModal } from "@/components/settings/SettingsModal";
-import { getCustomTags, MockTag, getAllTrashTasks, getDemoStore } from "@/lib/mockData";
+import { getCustomTags, MockTag, getAllTrashTasks, getDemoStore, getTagTaskCount } from "@/lib/mockData";
 
 interface User { id: string; name?: string | null; email?: string | null }
 interface List { id: string; name: string; color: string; icon: string; _count?: { tasks: number } }
@@ -607,16 +607,22 @@ export function Sidebar({
         {tags.length > 0 && (
           <div className="sidebar-section">
             <div className="sidebar-section-label">🏷️ {t("tags") || "Tags"}</div>
-            {tags.map((tag) => (
-              <div
-                key={tag.id}
-                className={`sidebar-item${selectedTag === tag.name ? " active" : ""}`}
-                onClick={() => onTagSelect(selectedTag === tag.name ? null : tag.name)}
-              >
-                <span style={{ color: tag.color, fontSize: 13, fontWeight: 700 }}>#</span>
-                <span className="item-label">{tag.name}</span>
-              </div>
-            ))}
+            {tags.map((tag) => {
+              const tagCount = isDemo && typeof window !== "undefined"
+                ? getTagTaskCount(getDemoStore().tasks, tag.name)
+                : 0;
+              return (
+                <div
+                  key={tag.id}
+                  className={`sidebar-item${selectedTag === tag.name ? " active" : ""}`}
+                  onClick={() => onTagSelect(selectedTag === tag.name ? null : tag.name)}
+                >
+                  <span style={{ color: tag.color, fontSize: 13, fontWeight: 700 }}>#</span>
+                  <span className="item-label">{tag.name}</span>
+                  {tagCount > 0 && <span className="item-count">{tagCount}</span>}
+                </div>
+              );
+            })}
           </div>
         )}
 
diff --git a/src/components/tasks/TaskDetail.tsx b/src/components/tasks/TaskDetail.tsx
index 7035dc7..b7b325e 100644
--- a/src/components/tasks/TaskDetail.tsx
+++ b/src/components/tasks/TaskDetail.tsx
@@ -160,8 +160,8 @@ export function TaskDetail({
         const updatedTask: Task = {
           ...task,
           ...data,
-          children: subtasks,
-          tags,
+          children: (data.children as Task[]) || subtasks,
+          tags: (data.tags as { tag: Tag }[]) || tags,
           updatedAt: new Date().toISOString(),
         } as Task;
         if (onDemoUpdateTask) onDemoUpdateTask(updatedTask);
@@ -251,7 +251,12 @@ export function TaskDetail({
       name: trimmed,
       color: ["#4B7BF5", "#10B981", "#EF4444", "#F59E0B", "#8B5CF6"][Math.floor(Math.random() * 5)],
     };
-    setAllAvailableTags((p) => [...p, newTag]);
+    const updatedAvailable = [...allAvailableTags, newTag];
+    setAllAvailableTags(updatedAvailable);
+    if (typeof window !== "undefined") {
+      const { saveCustomTags } = require("@/lib/mockData");
+      saveCustomTags(updatedAvailable);
+    }
     toggleTag(newTag);
     setNewTagName("");
   };
diff --git a/src/lib/mockData.ts b/src/lib/mockData.ts
index b6683c1..9c5e8fc 100644
--- a/src/lib/mockData.ts
+++ b/src/lib/mockData.ts
@@ -280,16 +280,16 @@ export function moveToTrashInTree(tree: MockTask[], id: string): MockTask[] {
 
 // Restore from Trash (recursively unmark node and its children)
 export function restoreTaskInTree(tree: MockTask[], id: string): MockTask[] {
-  const unmarkDeleted = (node: MockTask): MockTask => ({
+  const markRestored = (node: MockTask): MockTask => ({
     ...node,
     isDeleted: false,
     deletedAt: null,
-    children: node.children ? node.children.map(unmarkDeleted) : [],
+    children: node.children ? node.children.map(markRestored) : [],
   });
 
   return tree.map((node) => {
     if (node.id === id) {
-      return unmarkDeleted(node);
+      return markRestored(node);
     }
     if (node.children && node.children.length > 0) {
       return { ...node, children: restoreTaskInTree(node.children, id) };
@@ -348,25 +348,24 @@ export function findTaskInTree(tree: MockTask[], id: string): MockTask | null {
   return null;
 }
 
-// Get all active tasks or all trash tasks flattened (strictly deduplicated)
+// Get all top-level trash tasks preserving intact nested sub-tasks hierarchy
 export function getAllTrashTasks(tree: MockTask[]): MockTask[] {
-  const map = new Map<string, MockTask>();
+  const result: MockTask[] = [];
 
   function collect(nodes: MockTask[]) {
     for (const node of nodes) {
       if (node.isDeleted) {
-        if (!map.has(node.id)) {
-          map.set(node.id, { ...node, children: [] });
-        }
-      }
-      if (node.children && node.children.length > 0) {
+        // Collect top-level deleted item with its full subtasks tree intact
+        result.push(node);
+      } else if (node.children && node.children.length > 0) {
+        // If parent is not deleted, check if any subtask was individually deleted
         collect(node.children);
       }
     }
   }
 
   collect(tree);
-  return Array.from(map.values());
+  return result;
 }
 
 // Filter tasks by custom tag
@@ -381,4 +380,9 @@ export function filterTasksByTag(tree: MockTask[], tagName: string): MockTask[]
     }
   }
   return matched;
-}
\ No newline at end of file
+}
+
+// Get count of active tasks for a tag
+export function getTagTaskCount(tree: MockTask[], tagName: string): number {
+  return filterTasksByTag(tree, tagName).filter((t) => !t.completed).length;
+}