diff --git a/client/tests/integration/api/client.test.ts b/client/tests/integration/api/client.test.ts
index c9be28d6..529fc715 100644
--- a/client/tests/integration/api/client.test.ts
+++ b/client/tests/integration/api/client.test.ts
@@ -334,10 +334,14 @@ describe('API client interceptors', () => {
   // ── backupApi.download ───────────────────────────────────────────────────────
 
   it('FE-API-013: backupApi.download creates a temp anchor and clicks it', async () => {
-    const createObjectURL = vi.fn(() => 'blob:mock-url');
-    const revokeObjectURL = vi.fn();
-    Object.defineProperty(URL, 'createObjectURL', { writable: true, value: createObjectURL });
-    Object.defineProperty(URL, 'revokeObjectURL', { writable: true, value: revokeObjectURL });
+    // backupApi.download uses native fetch (not axios), so mock it directly to
+    // avoid jsdom/MSW interception differences across environments.
+    const blob = new Blob(['zip-bytes'], { type: 'application/zip' });
+    vi.spyOn(globalThis, 'fetch').mockResolvedValueOnce(
+      new Response(blob, { status: 200 })
+    );
+    const createObjectURL = vi.spyOn(URL, 'createObjectURL').mockReturnValue('blob:mock-url');
+    const revokeObjectURL = vi.spyOn(URL, 'revokeObjectURL').mockImplementation(() => {});
 
     // Spy on createElement to intercept the anchor click
     const originalCreate = document.createElement.bind(document);
@@ -350,12 +354,6 @@ describe('API client interceptors', () => {
       return el;
     });
 
-    server.use(
-      http.get('/api/backup/download/backup.zip', () => {
-        return new HttpResponse(new Blob(['zip-bytes'], { type: 'application/zip' }), { status: 200 });
-      })
-    );
-
     await expect(backupApi.download('backup.zip')).resolves.toBeUndefined();
     expect(createObjectURL).toHaveBeenCalled();
     expect(revokeObjectURL).toHaveBeenCalled();
diff --git a/client/tests/setup.ts b/client/tests/setup.ts
index 2f507fed..0d6373e3 100644
--- a/client/tests/setup.ts
+++ b/client/tests/setup.ts
@@ -59,13 +59,10 @@ globalThis.ResizeObserver = vi.fn().mockImplementation(() => ({
   disconnect: vi.fn(),
 })) as unknown as typeof ResizeObserver;
 
-// URL.createObjectURL / revokeObjectURL — used by file uploads
-if (typeof URL.createObjectURL === 'undefined') {
-  Object.defineProperty(URL, 'createObjectURL', { writable: true, value: vi.fn(() => 'blob:mock') });
-}
-if (typeof URL.revokeObjectURL === 'undefined') {
-  Object.defineProperty(URL, 'revokeObjectURL', { writable: true, value: vi.fn() });
-}
+// URL.createObjectURL / revokeObjectURL — jsdom defines these but returns '' for createObjectURL;
+// always override so tests get a predictable 'blob:mock' string.
+Object.defineProperty(URL, 'createObjectURL', { writable: true, configurable: true, value: vi.fn(() => 'blob:mock') });
+Object.defineProperty(URL, 'revokeObjectURL', { writable: true, configurable: true, value: vi.fn() });
 
 // Element.prototype.scrollIntoView — jsdom doesn't implement it
 Element.prototype.scrollIntoView = vi.fn();
diff --git a/client/tests/unit/api/authUrl.test.ts b/client/tests/unit/api/authUrl.test.ts
index 3780678a..23e5f23a 100644
--- a/client/tests/unit/api/authUrl.test.ts
+++ b/client/tests/unit/api/authUrl.test.ts
@@ -193,6 +193,7 @@ describe('clearImageQueue', () => {
     it('removes queued items so they never execute after active slots drain', async () => {
       const resolvers: Array<() => void> = [];
       const createObjectURLSpy = vi.spyOn(URL, 'createObjectURL');
+      createObjectURLSpy.mockClear(); // vi.spyOn returns the same vi.fn() set in setup.ts; reset accumulated calls from prior tests
 
       vi.spyOn(globalThis, 'fetch').mockImplementation(async () => {
         await new Promise<void>(r => resolvers.push(r));