diff --git a/app/src/pages/Brain.tsx b/app/src/pages/Brain.tsx
index 8bc80b05f..875137fc6 100644
--- a/app/src/pages/Brain.tsx
+++ b/app/src/pages/Brain.tsx
@@ -26,6 +26,7 @@ import MemoryDebugPanel from '../components/settings/panels/MemoryDebugPanel';
 import BetaBanner from '../components/ui/BetaBanner';
 import { useSubconscious } from '../hooks/useSubconscious';
 import { useT } from '../lib/i18n/I18nContext';
+import { useCoreState } from '../providers/CoreStateProvider';
 import type { ToastNotification } from '../types/intelligence';
 import {
   type GraphExportResponse,
@@ -96,6 +97,16 @@ export default function Brain() {
   const [refreshKey, setRefreshKey] = useState(0);
   const [toasts, setToasts] = useState<ToastNotification[]>([]);
 
+  // The memory graph is read from the on-disk store, but the read only fired on
+  // mount — so after a logout→login cycle the page kept whatever (empty) state
+  // it had when the core was signed-out / mid identity-flip and never refetched
+  // once auth was restored, showing an empty graph for an account whose data is
+  // still on disk (#4149). Key the load on the authenticated identity so a
+  // re-auth (null→user, or A→B) re-pulls the persisted graph, mirroring the
+  // thread-cache reload CoreStateProvider already does on identity change.
+  const { snapshot } = useCoreState();
+  const authUserId = snapshot.auth.userId;
+
   const sub = useSubconscious();
 
   const addToast = useCallback((toast: Omit<ToastNotification, 'id'>) => {
@@ -136,7 +147,10 @@ export default function Brain() {
       cancelled = true;
       window.removeEventListener('openhuman:memory-tree-completed', onTreeDone);
     };
-  }, [mode, refreshKey]);
+    // `authUserId` is a dependency so a logout→login (identity becomes
+    // available again) re-pulls the persisted graph instead of leaving the
+    // signed-out empty state on screen (#4149).
+  }, [mode, refreshKey, authUserId]);
 
   const cardClass = 'rounded-lg border border-line bg-surface p-4';
 
diff --git a/app/src/pages/__tests__/Brain.test.tsx b/app/src/pages/__tests__/Brain.test.tsx
index 5120218c5..e4436b250 100644
--- a/app/src/pages/__tests__/Brain.test.tsx
+++ b/app/src/pages/__tests__/Brain.test.tsx
@@ -5,12 +5,23 @@ import { renderWithProviders } from '../../test/test-utils';
 import Brain from '../Brain';
 
 const graphExportMock = vi.hoisted(() => vi.fn());
+// Controllable authenticated identity so we can simulate a logout→login cycle
+// (userId null → set) and assert the graph reloads (#4149).
+const coreAuthRef = vi.hoisted(() => ({ current: 'user-A' as string | null }));
 
 vi.mock('../../utils/tauriCommands', () => ({
   memoryTreeGraphExport: graphExportMock,
   isTauri: () => false,
 }));
 
+vi.mock('../../providers/CoreStateProvider', () => ({
+  useCoreState: () => ({
+    snapshot: {
+      auth: { userId: coreAuthRef.current, isAuthenticated: coreAuthRef.current != null },
+    },
+  }),
+}));
+
 vi.mock('../../components/intelligence/MemoryGraph', async () => {
   const React = await import('react');
   return {
@@ -94,6 +105,7 @@ const makeGraph = (n: number) => ({
 describe('Brain page', () => {
   beforeEach(() => {
     vi.clearAllMocks();
+    coreAuthRef.current = 'user-A';
   });
 
   afterEach(() => {
@@ -120,6 +132,30 @@ describe('Brain page', () => {
     });
   });
 
+  it('reloads the memory graph from the store when the user re-authenticates (#4149)', async () => {
+    // Start signed-out / mid identity-flip: the first fetch resolves empty.
+    coreAuthRef.current = null;
+    graphExportMock.mockResolvedValue(makeGraph(0));
+    let view!: ReturnType<typeof renderWithProviders>;
+    await act(async () => {
+      view = renderWithProviders(<Brain />);
+    });
+    await waitFor(() => expect(graphExportMock).toHaveBeenCalledTimes(1));
+    expect(screen.getByTestId('memory-graph')).toHaveTextContent('nodes:0');
+
+    // Re-login: identity becomes available — the graph must re-pull from the
+    // persistent store rather than keep the signed-out empty state.
+    coreAuthRef.current = 'user-A';
+    graphExportMock.mockResolvedValue(makeGraph(5));
+    await act(async () => {
+      view.rerender(<Brain />);
+    });
+    await waitFor(() => expect(graphExportMock).toHaveBeenCalledTimes(2));
+    await waitFor(() => {
+      expect(screen.getByTestId('memory-graph')).toHaveTextContent('nodes:5');
+    });
+  });
+
   it('surfaces an error alert when the fetch fails', async () => {
     graphExportMock.mockRejectedValue(new Error('boom'));
     await act(async () => {