diff --git a/client/hooks/useAutoSave.test.jsx b/client/hooks/useAutoSave.test.ts
similarity index 91%
rename from client/hooks/useAutoSave.test.jsx
rename to client/hooks/useAutoSave.test.ts
index f6ff066..32b8253 100644
--- a/client/hooks/useAutoSave.test.jsx
+++ b/client/hooks/useAutoSave.test.ts
@@ -8,7 +8,7 @@ describe('useAutoSave', () => {
   afterEach(() => vi.useRealTimers());
 
   it('debounces: only the latest payload is saved, once', async () => {
-    const save = vi.fn().mockResolvedValue();
+    const save = vi.fn().mockResolvedValue(undefined);
     const { result } = renderHook(() => useAutoSave(save, 400));
 
     act(() => {
@@ -25,7 +25,7 @@ describe('useAutoSave', () => {
   });
 
   it('per-call delay overrides the default', async () => {
-    const save = vi.fn().mockResolvedValue();
+    const save = vi.fn().mockResolvedValue(undefined);
     const { result } = renderHook(() => useAutoSave(save, 400));
 
     act(() => { result.current.schedule({ slow: true }, 900); });
@@ -36,7 +36,7 @@ describe('useAutoSave', () => {
   });
 
   it('flush() saves a pending payload immediately and is a no-op when idle', async () => {
-    const save = vi.fn().mockResolvedValue();
+    const save = vi.fn().mockResolvedValue(undefined);
     const { result } = renderHook(() => useAutoSave(save, 400));
 
     await act(async () => { result.current.flush(); });
@@ -55,7 +55,7 @@ describe('useAutoSave', () => {
   it('reports error status when the save rejects, then recovers on next save', async () => {
     const save = vi.fn()
       .mockRejectedValueOnce(new Error('boom'))
-      .mockResolvedValueOnce();
+      .mockResolvedValueOnce(undefined);
     const { result } = renderHook(() => useAutoSave(save, 100));
 
     act(() => { result.current.schedule({ x: 1 }); });
@@ -68,7 +68,7 @@ describe('useAutoSave', () => {
   });
 
   it('"saved" fades back to idle after 2 seconds', async () => {
-    const save = vi.fn().mockResolvedValue();
+    const save = vi.fn().mockResolvedValue(undefined);
     const { result } = renderHook(() => useAutoSave(save, 100));
 
     act(() => { result.current.schedule({ y: 1 }); });
@@ -80,7 +80,7 @@ describe('useAutoSave', () => {
   });
 
   it('flushes a pending payload on unmount so edits are never lost', async () => {
-    const save = vi.fn().mockResolvedValue();
+    const save = vi.fn().mockResolvedValue(undefined);
     const { result, unmount } = renderHook(() => useAutoSave(save, 900));
 
     act(() => { result.current.schedule({ unsaved: true }); });