diff --git a/web/src/components/MemoCommentSection.tsx b/web/src/components/MemoCommentSection.tsx
index 3904fbb0..a1e7e936 100644
--- a/web/src/components/MemoCommentSection.tsx
+++ b/web/src/components/MemoCommentSection.tsx
@@ -102,7 +102,7 @@ const MemoCommentSection = ({ memo, comments, parentPage, hasMoreComments, isFet
         {showEditor && EditorComponent && (
           <div className="w-full mb-2">
             <EditorComponent
-              cacheKey={`${memo.name}-${memo.updateTime}-comment`}
+              cacheKey={`${memo.name}-comment`}
               placeholder={t("editor.add-your-comment-here")}
               parentMemoName={memo.name}
               autoFocus
@@ -112,7 +112,7 @@ const MemoCommentSection = ({ memo, comments, parentPage, hasMoreComments, isFet
           </div>
         )}
         {comments.map((comment) => (
-          <div className="w-full" key={`${comment.name}-${comment.updateTime}`} id={extractMemoIdFromName(comment.name)}>
+          <div className="w-full" key={comment.name} id={extractMemoIdFromName(comment.name)}>
             <MemoView memo={comment} parentPage={parentPage} showCreator compact />
           </div>
         ))}
diff --git a/web/src/components/MemoContent/TaskListItem.tsx b/web/src/components/MemoContent/TaskListItem.tsx
index 0f89f7d2..22254290 100644
--- a/web/src/components/MemoContent/TaskListItem.tsx
+++ b/web/src/components/MemoContent/TaskListItem.tsx
@@ -65,6 +65,10 @@ export const TaskListItem: React.FC<TaskListItemProps> = ({ checked, node: _node
     });
   };
 
-  // Override the disabled prop from remark-gfm (which defaults to true)
-  return <Checkbox ref={checkboxRef} checked={checked} disabled={readonly} onCheckedChange={handleChange} className={props.className} />;
+  // Override the disabled prop from remark-gfm (which defaults to true).
+  // `checked` is undefined for unchecked tasks; Base UI locks controlled/uncontrolled
+  // mode at mount, so coerce to boolean to keep the checkbox always controlled.
+  return (
+    <Checkbox ref={checkboxRef} checked={Boolean(checked)} disabled={readonly} onCheckedChange={handleChange} className={props.className} />
+  );
 };
diff --git a/web/src/components/PagedMemoList/PagedMemoList.tsx b/web/src/components/PagedMemoList/PagedMemoList.tsx
index 9ef79fd8..c80ca910 100644
--- a/web/src/components/PagedMemoList/PagedMemoList.tsx
+++ b/web/src/components/PagedMemoList/PagedMemoList.tsx
@@ -20,8 +20,9 @@ import Placeholder from "../Placeholder";
 import { estimateMemoCardHeight } from "./memoCardHeight";
 
 // Memo identity for React keys and grid planning. The pages use it for their renderer keys too,
-// so flow-list and grid identity can never drift apart.
-export const getMemoKey = (memo: Memo) => `${memo.name}-${memo.updateTime}`;
+// so flow-list and grid identity can never drift apart. Deliberately name-only: content updates
+// reconcile in place (updateTime is a protobuf Timestamp object, not usable in a template string).
+export const getMemoKey = (memo: Memo) => memo.name;
 
 // Columns never stretch past this, so 2 columns on a wide monitor stay readable and the
 // grid centers in the leftover space instead of filling it.
diff --git a/web/src/pages/MemoDetail.tsx b/web/src/pages/MemoDetail.tsx
index ea153243..05758e47 100644
--- a/web/src/pages/MemoDetail.tsx
+++ b/web/src/pages/MemoDetail.tsx
@@ -135,7 +135,7 @@ const MemoDetail = () => {
               </div>
             )}
             <MemoView
-              key={`${displayMemo.name}-${displayMemo.updateTime}`}
+              key={displayMemo.name}
               memo={displayMemo}
               compact={false}
               parentPage={parentPage}
diff --git a/web/tests/task-list-item-check-all.test.tsx b/web/tests/task-list-item-check-all.test.tsx
new file mode 100644
index 00000000..cda38820
--- /dev/null
+++ b/web/tests/task-list-item-check-all.test.tsx
@@ -0,0 +1,59 @@
+import { render, screen } from "@testing-library/react";
+import { describe, expect, it, vi } from "vitest";
+import { TaskListItem } from "@/components/MemoContent/TaskListItem";
+
+// Regression test for usememos/memos#6143 ("Check all tasks not working").
+//
+// remark-gfm passes `checked: undefined` for unchecked task items (`- [ ]`).
+// Base UI's Checkbox locks controlled/uncontrolled mode at mount, so a checkbox
+// that mounts with `checked === undefined` becomes uncontrolled and silently
+// ignores `checked=true` arriving later — exactly what happens after
+// "Check all tasks" rewrites the memo content and the markdown re-renders.
+// TaskListItem must coerce `checked` to a boolean so the checkbox is always
+// controlled.
+
+const mockUpdateMemo = vi.hoisted(() => vi.fn());
+
+vi.mock("@/hooks/useMemoQueries", () => ({
+  useUpdateMemo: () => ({ mutate: mockUpdateMemo }),
+}));
+
+vi.mock("@/components/MemoView/MemoViewContext", () => ({
+  useMemoViewContext: () => ({
+    memo: {
+      name: "memos/1",
+      content: "- [ ] task one",
+      relations: [],
+      attachments: [],
+      reactions: [],
+    },
+  }),
+  useMemoViewDerived: () => ({
+    readonly: false,
+  }),
+}));
+
+describe("<TaskListItem /> check-all regression (#6143)", () => {
+  it("reflects checked=true arriving after mounting unchecked (Check all tasks)", () => {
+    // remark-gfm renders `- [ ]` with `checked` undefined.
+    const { rerender } = render(<TaskListItem checked={undefined} node={undefined} />);
+
+    const checkbox = screen.getByRole("checkbox");
+    expect(checkbox).toHaveAttribute("aria-checked", "false");
+
+    // "Check all tasks" updates memo content; the markdown re-renders with checked=true.
+    rerender(<TaskListItem checked={true} node={undefined} />);
+    expect(checkbox).toHaveAttribute("aria-checked", "true");
+  });
+
+  it("reflects checked reverting to undefined (Uncheck all tasks)", () => {
+    const { rerender } = render(<TaskListItem checked={true} node={undefined} />);
+
+    const checkbox = screen.getByRole("checkbox");
+    expect(checkbox).toHaveAttribute("aria-checked", "true");
+
+    // remark-gfm passes undefined (not false) for `- [ ]` items.
+    rerender(<TaskListItem checked={undefined} node={undefined} />);
+    expect(checkbox).toHaveAttribute("aria-checked", "false");
+  });
+});