fix(ui): silent background state poll - no refetch churn when vault unchanged

frontend/src/state/AppProvider.tsx

@@ -107,7 +107,17 @@ export function AppProvider({ children }: { children: ReactNode }) {
 
   const refresh = useCallback(async () => {
     const fresh = await api.getState();
-    setState(fresh);
+    // The 5s poll must be silent when nothing changed: a fresh object
+    // identity every tick would re-render every screen and refire effects
+    // keyed on state slices (e.g. Home's publications loader flickering
+    // between "Loading…" and done forever).
+    setState((prev) => {
+      try {
+        return JSON.stringify(prev) === JSON.stringify(fresh) ? prev : fresh;
+      } catch {
+        return fresh;
+      }
+    });
   }, []);
 
   useEffect(() => {
@@ -147,10 +157,10 @@ export function AppProvider({ children }: { children: ReactNode }) {
   // getState is a cheap local vault read; errors are ignored here since every
   // screen surfaces its own request failures.
   useEffect(() => {
-    const timer = window.setInterval(() => {
+    const timer = setInterval(() => {
       void refresh().catch(() => {});
     }, 5000);
-    return () => window.clearInterval(timer);
+    return () => clearInterval(timer);
   }, [refresh]);
 
   const createProfile = useCallback(

frontend/src/test/HomeScreen.test.tsx

@@ -98,4 +98,31 @@ describe('HomeScreen', () => {
     const aliceRow = screen.getByText('Alice').closest('.home-profile-row') as HTMLElement;
     expect(within(aliceRow).getByRole('button', { name: 'Select' })).toBeInTheDocument();
   });
+
+  it('does not refetch publications on every background state poll', async () => {
+    // Regression: the 5s AppProvider poll must not refire the publications
+    // loader (it flickered Home between "Loading…" and done forever).
+    // Fake timers from the start: the poll interval must be scheduled under
+    // fake time, and RTL async queries stall under fake timers, so drive
+    // everything with explicit timer advances instead.
+    vi.useFakeTimers();
+    try {
+      const backend = createFakeBackend();
+      renderHome(backend);
+      renderWithApp(
+        <HomeScreen onNavigate={vi.fn()} onCreateProfile={vi.fn()} onImportProfile={vi.fn()} />,
+      );
+
+      // Initial load completes.
+      await vi.advanceTimersByTimeAsync(500);
+      const initialFetches = backend.requests.filter((r) => r.method === 'feed_get').length;
+      expect(initialFetches).toBeGreaterThan(0);
+
+      // Two full poll ticks with unchanged state must not refetch.
+      await vi.advanceTimersByTimeAsync(12000);
+      expect(backend.requests.filter((r) => r.method === 'feed_get').length).toBe(initialFetches);
+    } finally {
+      vi.useRealTimers();
+    }
+  });
 });

frontend/src/test/fakeBackend.ts

@@ -193,7 +193,9 @@ export function createFakeBackend(initial?: AppState): FakeBackend {
     switch (method) {
       case 'init':
       case 'get_state':
-        return state;
+        // Deep-copy like the real IPC boundary (fresh JSON per call), so
+        // tests observe new object identities exactly as production does.
+        return structuredClone(state);
 
       // NIP-46 client handshake surface used by SignerModeScreen. The fake
       // keeps a Nip46SignerStatus-shaped object so handshake-state tests