diff --git a/ui/storybook/fixtures/workFolders.test.ts b/ui/storybook/fixtures/workFolders.test.ts
index b286ad521a..d0d702e3a2 100644
--- a/ui/storybook/fixtures/workFolders.test.ts
+++ b/ui/storybook/fixtures/workFolders.test.ts
@@ -23,6 +23,17 @@ function operation(
 }
 
 describe("work-folder Storybook fixtures", () => {
+  it("handles the project page's workspace query without a backend", async () => {
+    const fixture = createWorkFolderFixture();
+    const response = await fixture.handle(
+      new Request(
+        "http://storybook.test/api/companies/company-storybook/execution-workspaces?projectId=project-board-ui",
+      ),
+    );
+    expect(response!.status).toBe(200);
+    expect(await response!.json()).toEqual([]);
+  });
+
   it("keeps uploads within one owner and resets them for the next story", async () => {
     const fixture = createWorkFolderFixture("empty");
     const bytes = new Uint8Array([0, 255, 128, 10]);
diff --git a/ui/storybook/fixtures/workFolders.ts b/ui/storybook/fixtures/workFolders.ts
index 7949c39ea9..5f8d5e183a 100644
--- a/ui/storybook/fixtures/workFolders.ts
+++ b/ui/storybook/fixtures/workFolders.ts
@@ -128,6 +128,14 @@ export function createWorkFolderFixture(
   }
   async function handle(request: Request): Promise<Response | null> {
     const url = new URL(request.url);
+    // ProjectDetail loads this list even when its Files dialog is the review focus.
+    if (
+      request.method === "GET" &&
+      url.pathname ===
+        `/api/companies/${WORK_FOLDER_COMPANY}/execution-workspaces`
+    ) {
+      return Response.json([]);
+    }
     const match = url.pathname.match(
       /^\/api\/companies\/company-storybook\/work-folders\/(task|agent|user|project)\/([^/]+)(?:\/(content|operations|sync|refresh))?$/,
     );