diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0c9311f..65b550e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -46,6 +46,29 @@
   manually. Production deploys: this guard is irrelevant
   (`CERTCTL_DEMO_MODE_ACK` should not be set in production).
 
+### Fixed
+
+- **GitHub #13 / Hotfix #19 — GUI "Something went wrong" after browser
+  refresh on a real (non-demo) install.** Refresh-after-login wipes the
+  in-memory `apiKey` (deliberate — the GUI never persists it to
+  localStorage as a security posture). The next API call returns a
+  bare 401 with no `WWW-Authenticate` header. Pre-Hotfix-19 the
+  AuthProvider 401 handler only hard-navigated to `/login` when `cause`
+  was a recognised OIDC session-expiry category (`idle_timeout` /
+  `absolute_timeout` / `back_channel_revoked`); bare 401s
+  (`cause === ''`) and `invalid_token` causes fell through to an
+  in-place `AuthGate` state flip that unmounted `BrowserRouter` under
+  an in-flight `<Link>`, triggering a `react-router-dom` invariant
+  that surfaced via `ErrorBoundary` as the "Something went wrong"
+  screen. **Fix:** every 401 now hard-navigates to `/login` regardless
+  of cause; the cause-aware UX is preserved by forwarding
+  `?session_expired=<cause>` only when cause is non-empty (bare 401s
+  redirect to plain `/login`). Three-line change in
+  `web/src/components/AuthProvider.tsx`; 4 regression tests added to
+  `AuthProvider.test.tsx` (empty cause from `/targets`, `invalid_token`
+  cause, `idle_timeout` cause, already-on-`/login` no-op guard).
+  Closes #13.
+
 ### Security
 
 - **Alg-downgrade defense relaxed for Keycloak-shape IdPs (v2.1.0 pre-tag fix).**
diff --git a/web/src/components/AuthProvider.test.tsx b/web/src/components/AuthProvider.test.tsx
index c5ef50c..037c787 100644
--- a/web/src/components/AuthProvider.test.tsx
+++ b/web/src/components/AuthProvider.test.tsx
@@ -132,3 +132,130 @@ describe('AuthProvider — LOW-1 demo-mode banner', () => {
     await waitFor(() => screen.getByTestId('demo-mode-banner'));
   });
 });
+
+// =============================================================================
+// Hotfix #19 (GitHub #13) — AuthProvider 401 unconditional-redirect.
+//
+// The pre-Hotfix-19 401 handler only redirected to /login when `cause`
+// was a recognised OIDC session-expiry category. A bare 401 (no
+// WWW-Authenticate header → cause === '') fell through to an in-place
+// AuthGate state flip that unmounted BrowserRouter under an in-flight
+// <Link>, triggering a react-router-dom invariant that surfaced via
+// ErrorBoundary as "Something went wrong" (GitHub #13).
+//
+// These tests pin: every 401 (regardless of cause) hard-navigates to
+// /login when the caller is not already on /login. Cause-aware
+// session_expired= query param is preserved when cause is non-empty.
+// =============================================================================
+
+describe('AuthProvider — Hotfix #19 401 always-redirects', () => {
+  let originalLocation: Location;
+  let hrefAssignments: string[];
+
+  beforeEach(() => {
+    // /auth/info is unrelated to the 401 path but must not hang the
+    // mount. Resolve it as the demo case (the cheapest non-pending
+    // shape) — the redirect handler doesn't care about authType.
+    vi.mocked(client.getAuthInfo).mockResolvedValue({
+      auth_type: 'none',
+      required: false,
+    });
+
+    // jsdom forbids writing to window.location.href directly without
+    // a settable property descriptor. Replace window.location with a
+    // mock that captures assignments while letting tests pre-set
+    // pathname. Restored in afterEach.
+    originalLocation = window.location;
+    hrefAssignments = [];
+  });
+
+  function installLocationMock(pathname: string): void {
+    Object.defineProperty(window, 'location', {
+      configurable: true,
+      writable: true,
+      value: {
+        pathname,
+        get href() { return ''; },
+        set href(v: string) { hrefAssignments.push(v); },
+      },
+    });
+  }
+
+  function restoreLocation(): void {
+    Object.defineProperty(window, 'location', {
+      configurable: true,
+      writable: true,
+      value: originalLocation,
+    });
+  }
+
+  it('redirects to /login with no query param when cause is empty (bare 401)', async () => {
+    installLocationMock('/targets');
+    try {
+      render(<AuthProvider><div data-testid="child">child</div></AuthProvider>);
+      await waitFor(() => screen.getByTestId('child'));
+
+      window.dispatchEvent(
+        new CustomEvent('certctl:auth-required', { detail: { cause: '' } }),
+      );
+
+      expect(hrefAssignments).toEqual(['/login']);
+    } finally {
+      restoreLocation();
+    }
+  });
+
+  it('redirects to /login?session_expired=invalid_token when cause is invalid_token (new behavior)', async () => {
+    // Pre-Hotfix-19 this cause fell through the conditional with no
+    // redirect. Post-Hotfix-19 every 401 redirects; cause is preserved
+    // in the query param for any LoginPage banner that wants it.
+    installLocationMock('/targets');
+    try {
+      render(<AuthProvider><div data-testid="child">child</div></AuthProvider>);
+      await waitFor(() => screen.getByTestId('child'));
+
+      window.dispatchEvent(
+        new CustomEvent('certctl:auth-required', { detail: { cause: 'invalid_token' } }),
+      );
+
+      expect(hrefAssignments).toEqual(['/login?session_expired=invalid_token']);
+    } finally {
+      restoreLocation();
+    }
+  });
+
+  it('redirects to /login?session_expired=idle_timeout when cause is idle_timeout (existing OIDC UX preserved)', async () => {
+    installLocationMock('/targets');
+    try {
+      render(<AuthProvider><div data-testid="child">child</div></AuthProvider>);
+      await waitFor(() => screen.getByTestId('child'));
+
+      window.dispatchEvent(
+        new CustomEvent('certctl:auth-required', { detail: { cause: 'idle_timeout' } }),
+      );
+
+      expect(hrefAssignments).toEqual(['/login?session_expired=idle_timeout']);
+    } finally {
+      restoreLocation();
+    }
+  });
+
+  it('does not redirect when caller is already on /login (no-op guard preserved)', async () => {
+    installLocationMock('/login');
+    try {
+      render(<AuthProvider><div data-testid="child">child</div></AuthProvider>);
+      await waitFor(() => screen.getByTestId('child'));
+
+      window.dispatchEvent(
+        new CustomEvent('certctl:auth-required', { detail: { cause: '' } }),
+      );
+      window.dispatchEvent(
+        new CustomEvent('certctl:auth-required', { detail: { cause: 'idle_timeout' } }),
+      );
+
+      expect(hrefAssignments).toEqual([]);
+    } finally {
+      restoreLocation();
+    }
+  });
+});
diff --git a/web/src/components/AuthProvider.tsx b/web/src/components/AuthProvider.tsx
index b67fefa..66b612a 100644
--- a/web/src/components/AuthProvider.tsx
+++ b/web/src/components/AuthProvider.tsx
@@ -90,10 +90,26 @@ export default function AuthProvider({ children }: { children: ReactNode }) {
       // (not React Router's navigate) because this listener fires
       // outside any route component's render and we want a hard
       // navigation that clears any stale state.
-      if (cause && cause !== 'invalid_token' &&
-          window.location.pathname !== '/login') {
-        const params = new URLSearchParams({ session_expired: cause });
-        window.location.href = '/login?' + params.toString();
+      //
+      // Hotfix #19 (GitHub #13): always hard-navigate to /login on a
+      // 401, regardless of cause. Pre-Hotfix-19 the conditional only
+      // redirected when cause was a non-'invalid_token' OIDC
+      // session-expiry category (idle_timeout / absolute_timeout /
+      // back_channel_revoked). Bare 401s (refresh-after-login wipes
+      // the in-memory apiKey → no Authorization header → server
+      // returns 401 with no WWW-Authenticate header → cause === '')
+      // fell through to an in-place AuthGate state flip that
+      // unmounted BrowserRouter under an in-flight <Link>, triggering
+      // a react-router-dom invariant that surfaced via ErrorBoundary
+      // as "Something went wrong." The unconditional hard-navigation
+      // forecloses the in-place tear-down path; cause-aware UX is
+      // preserved by forwarding ?session_expired= only when cause is
+      // non-empty.
+      if (window.location.pathname !== '/login') {
+        const url = cause
+          ? '/login?' + new URLSearchParams({ session_expired: cause }).toString()
+          : '/login';
+        window.location.href = url;
       }
     };
     window.addEventListener('certctl:auth-required', handler);