diff --git a/web/src/components/MemoContent/MemoContentContext.tsx b/web/src/components/MemoContent/MemoContentContext.tsx
index e2e36f943..3be3eeb97 100644
--- a/web/src/components/MemoContent/MemoContentContext.tsx
+++ b/web/src/components/MemoContent/MemoContentContext.tsx
@@ -19,6 +19,9 @@ export interface MemoContentContextType {
 
   /** Parent page path (for navigation) */
   parentPage?: string;
+
+  /** Reference to the container element for the memo content */
+  containerRef?: React.RefObject<HTMLDivElement>;
 }
 
 export const MemoContentContext = createContext<MemoContentContextType>({
diff --git a/web/src/components/MemoContent/TaskListItem.tsx b/web/src/components/MemoContent/TaskListItem.tsx
index e9365a2a5..eeebf1444 100644
--- a/web/src/components/MemoContent/TaskListItem.tsx
+++ b/web/src/components/MemoContent/TaskListItem.tsx
@@ -44,8 +44,14 @@ export const TaskListItem: React.FC<TaskListItemProps> = ({ checked, ...props })
     if (taskIndexStr !== null) {
       taskIndex = parseInt(taskIndexStr);
     } else {
-      // Fallback: Calculate index by counting previous task list items
-      const allTaskItems = listItem.closest("ul, ol")?.querySelectorAll("li.task-list-item") || [];
+      // Fallback: Calculate index by counting ALL task list items in the memo
+      // Use the container ref from context for proper scoping
+      const container = context.containerRef?.current;
+      if (!container) {
+        return;
+      }
+
+      const allTaskItems = container.querySelectorAll("li.task-list-item");
       for (let i = 0; i < allTaskItems.length; i++) {
         if (allTaskItems[i] === listItem) {
           taskIndex = i;
diff --git a/web/src/components/MemoContent/index.tsx b/web/src/components/MemoContent/index.tsx
index e1b510ce2..a1483fe9e 100644
--- a/web/src/components/MemoContent/index.tsx
+++ b/web/src/components/MemoContent/index.tsx
@@ -49,6 +49,7 @@ const MemoContent = observer((props: Props) => {
     readonly: !allowEdit,
     disableFilter: props.disableFilter,
     parentPage: props.parentPage,
+    containerRef: memoContentContainerRef,
   };
 
   // Initial compact mode.