diff --git a/src/hooks/useCategories.test.ts b/src/hooks/useCategories.test.ts
index 7e47133..b15d2b0 100644
--- a/src/hooks/useCategories.test.ts
+++ b/src/hooks/useCategories.test.ts
@@ -313,6 +313,32 @@ describe("useCategories — « Vérifier la hiérarchie » (#393)", () => {
     expect(getAllCategoriesWithCounts).toHaveBeenCalledTimes(3);
   });
 
+  it("shows a failed read of the categories in the window, never in the page's banner behind it", async () => {
+    vi.mocked(findOrphanCategories).mockResolvedValueOnce([CYCLE]).mockResolvedValueOnce([]);
+    vi.mocked(reattachCategory).mockResolvedValue(3);
+    let api = await mount();
+
+    // At the opening: the diagnostic does not run on the old categories.
+    vi.mocked(getAllCategoriesWithCounts).mockRejectedValueOnce(new Error("database is locked"));
+    await api.checkHierarchy();
+    let state = harness.render(useCategories).state;
+    expect(state.hierarchyCheck).toEqual({ orphans: null, error: { message: "database is locked" } });
+    expect(state.error).toBeNull();
+    expect(findOrphanCategories).not.toHaveBeenCalled();
+
+    // After a committed reattachment.
+    api = harness.render(useCategories);
+    await api.checkHierarchy();
+    api = harness.render(useCategories);
+    vi.mocked(getAllCategoriesWithCounts).mockRejectedValueOnce(new Error("disk I/O error"));
+    await api.reattachOrphan(CYCLE, null);
+    state = harness.render(useCategories).state;
+    expect(reattachCategory).toHaveBeenCalledWith(3, null);
+    expect(state.hierarchyCheck).toEqual({ orphans: [], error: { message: "disk I/O error" } });
+    expect(state.error).toBeNull();
+    expect(state.isSaving).toBe(false);
+  });
+
   it("reads the categories once the drag-and-drop's writes are over, never halfway", async () => {
     let written: () => void = () => undefined;
     vi.mocked(updateCategorySortOrders).mockReturnValue(new Promise<void>((r) => (written = r)));