diff --git a/web/src/__tests__/useKeyboard.test.tsx b/web/src/__tests__/useKeyboard.test.tsx
index fabf059d..c542477a 100644
--- a/web/src/__tests__/useKeyboard.test.tsx
+++ b/web/src/__tests__/useKeyboard.test.tsx
@@ -113,6 +113,62 @@ describe('KeyboardProvider', () => {
     );
   });
 
+  it.each(['metaKey', 'ctrlKey', 'altKey', 'shiftKey'] as const)(
+    'leaves %s combinations to the platform',
+    (modifier) => {
+      const create = vi.fn();
+      const move = vi.fn();
+      function RegisterCreate() {
+        const { setOpenCreateDialog } = useKeyboard();
+        React.useEffect(() => setOpenCreateDialog(create), [setOpenCreateDialog]);
+        return null;
+      }
+      render(
+        <KeyboardProvider>
+          <RegisterCreate />
+          <TestConsumer tasks={[createMockTask({ id: 'task_one' })]} onMoveTask={move} />
+        </KeyboardProvider>
+      );
+      for (const key of ['c', 'j', 'k', '1', 'ArrowDown', 'ArrowUp', 'Enter']) {
+        const event = new KeyboardEvent('keydown', { key, [modifier]: true, cancelable: true });
+        fireEvent(window, event);
+        expect(event.defaultPrevented).toBe(false);
+      }
+      expect(create).not.toHaveBeenCalled();
+      expect(move).not.toHaveBeenCalled();
+      expect(screen.getByTestId('selected').textContent).toBe('none');
+      fireEvent.keyDown(window, { key: 'c' });
+      expect(create).toHaveBeenCalledOnce();
+    }
+  );
+
+  it('preserves the intentional chat chord and ignores IME composition', () => {
+    const chat = vi.fn();
+    const create = vi.fn();
+    function RegisterCommands() {
+      const { setOpenChatPanel, setOpenCreateDialog } = useKeyboard();
+      React.useEffect(() => {
+        setOpenChatPanel(chat);
+        setOpenCreateDialog(create);
+      }, [setOpenChatPanel, setOpenCreateDialog]);
+      return null;
+    }
+    render(
+      <KeyboardProvider>
+        <RegisterCommands />
+      </KeyboardProvider>
+    );
+    fireEvent.keyDown(window, { key: 'C', metaKey: true, shiftKey: true });
+    fireEvent.keyDown(window, { key: 'C', ctrlKey: true, shiftKey: true });
+    expect(chat).toHaveBeenCalledTimes(2);
+    fireEvent.keyDown(window, { key: 'C', ctrlKey: true, shiftKey: true, altKey: true });
+    fireEvent.keyDown(window, { key: 'C', metaKey: true, shiftKey: true, isComposing: true });
+    fireEvent.keyDown(window, { key: 'c', isComposing: true });
+    fireEvent.keyDown(window, { key: 'c', keyCode: 229 });
+    expect(chat).toHaveBeenCalledTimes(2);
+    expect(create).not.toHaveBeenCalled();
+  });
+
   it('starts with no selected task and help closed', () => {
     renderWithProvider();
     expect(screen.getByTestId('selected').textContent).toBe('none');
diff --git a/web/src/components/board/KanbanBoard.tsx b/web/src/components/board/KanbanBoard.tsx
index 9ea2be52..bfd847b8 100644
--- a/web/src/components/board/KanbanBoard.tsx
+++ b/web/src/components/board/KanbanBoard.tsx
@@ -375,6 +375,7 @@ export function KanbanBoard() {
   // Register filtered tasks with keyboard context
   useEffect(() => {
     setTasks(filteredTasks);
+    return () => setTasks([]);
   }, [filteredTasks, setTasks]);
 
   // Handler for opening a task
diff --git a/web/src/hooks/useKeyboard.tsx b/web/src/hooks/useKeyboard.tsx
index e1c57961..abd842ee 100644
--- a/web/src/hooks/useKeyboard.tsx
+++ b/web/src/hooks/useKeyboard.tsx
@@ -116,6 +116,8 @@ export function KeyboardProvider({ children }: { children: ReactNode }) {
       const target = e.target instanceof HTMLElement ? e.target : null;
       if (
         e.defaultPrevented ||
+        e.isComposing ||
+        e.keyCode === 229 ||
         target?.isContentEditable ||
         target?.closest(
           'input, textarea, select, button, a[href], summary, [role="button"], [role="link"], [role="switch"], [role="checkbox"], [role="radio"], [role="combobox"], [role="listbox"], [role="option"], [role="slider"], [role="spinbutton"], [role="tab"], [role="menuitem"]'
@@ -143,12 +145,16 @@ export function KeyboardProvider({ children }: { children: ReactNode }) {
       const currentIndex = selectedTaskId ? taskList.findIndex((t) => t.id === selectedTaskId) : -1;
 
       // Cmd+Shift+C (or Ctrl+Shift+C on Windows/Linux) - Toggle chat panel
-      if ((e.metaKey || e.ctrlKey) && e.shiftKey && e.key === 'C') {
+      if (e.metaKey !== e.ctrlKey && !e.altKey && e.shiftKey && e.key.toLowerCase() === 'c') {
         e.preventDefault();
         openChatPanel();
         return;
       }
 
+      // Unregistered modifiers belong to the platform or focused application.
+      // Shift is permitted only for '?' so shortcut help remains reachable.
+      if (e.metaKey || e.ctrlKey || e.altKey || (e.shiftKey && e.key !== '?')) return;
+
       switch (e.key) {
         case 'c':
           e.preventDefault();
@@ -215,7 +221,7 @@ export function KeyboardProvider({ children }: { children: ReactNode }) {
             });
             return;
           }
-          if (selectedTaskId && onMoveTaskRef.current) {
+          if (selectedTaskId && currentIndex >= 0 && onMoveTaskRef.current) {
             onMoveTaskRef.current(selectedTaskId, newStatus);
           } else {
             // Show toast when no task is selected