diff --git a/frontend/src/App.jsx b/frontend/src/App.jsx
index ae4f62a..5d004e4 100644
--- a/frontend/src/App.jsx
+++ b/frontend/src/App.jsx
@@ -21,6 +21,8 @@ export default function App() {
   const [health, setHealth] = useState(null)
   const [healthError, setHealthError] = useState(null)
   const [setup, setSetup] = useState(null)
+  const [setupLoading, setSetupLoading] = useState(true)
+  const [setupError, setSetupError] = useState(null)
   const [authMode, setAuthMode] = useState('login')
   const [token, setToken] = useState(() => localStorage.getItem(TOKEN_KEY) || '')
   const [email, setEmail] = useState('')
@@ -42,13 +44,33 @@ export default function App() {
       .then(setHealth)
       .catch((err) => setHealthError(err.message))
 
-    fetch('/api/auth/setup-status')
-      .then((res) => res.json())
-      .then((data) => {
-        setSetup(data)
-        if (data.registration_open) setAuthMode('register')
-      })
-      .catch(() => setSetup({ registration_open: false, has_users: true }))
+    async function loadSetupStatus() {
+      setSetupLoading(true)
+      setSetupError(null)
+      try {
+        const res = await fetch('/api/auth/setup-status')
+        const body = await res.json().catch(() => ({}))
+        if (!res.ok) {
+          throw new Error(
+            res.status === 404
+              ? 'Endpoint /api/auth/setup-status nicht gefunden — Backend neu deployen?'
+              : parseError(body, `Setup-Status fehlgeschlagen (HTTP ${res.status})`),
+          )
+        }
+        if (typeof body.registration_open !== 'boolean') {
+          throw new Error('Ungültige Antwort vom Setup-Status — Backend-Version prüfen')
+        }
+        setSetup(body)
+        if (body.registration_open) setAuthMode('register')
+      } catch (err) {
+        setSetup(null)
+        setSetupError(err.message)
+      } finally {
+        setSetupLoading(false)
+      }
+    }
+
+    loadSetupStatus()
   }, [])
 
   const loadSession = useCallback(async (activeToken) => {
@@ -155,6 +177,7 @@ export default function App() {
   }
 
   const registrationOpen = setup?.registration_open === true
+  const registrationClosedBecauseUsersExist = setup?.has_users === true && !registrationOpen
 
   return (
     <main className="shell">
@@ -174,7 +197,24 @@ export default function App() {
           </p>
         )}
 
-        {!token && (
+        {!token && setupLoading && (
+          <p className="muted">Prüfe Ersteinrichtung …</p>
+        )}
+
+        {!token && setupError && (
+          <p className="error">{setupError}</p>
+        )}
+
+        {!token && registrationClosedBecauseUsersExist && (
+          <p className="setup-hint setup-hint-muted">
+            Es existiert bereits mindestens ein Benutzer ({setup.user_count ?? '≥1'}).
+            Registrierung ist nur für die Ersteinrichtung vorgesehen — bitte anmelden.
+            Falls der Admin per <code>KAIRO_BOOTSTRAP_*</code> in der <code>.env</code> angelegt
+            wurde, nutzen Sie diese Zugangsdaten.
+          </p>
+        )}
+
+        {!token && !setupLoading && !setupError && (
           <>
             <div className="tabs" role="tablist">
               <button
@@ -313,6 +353,16 @@ export default function App() {
         {authError && <p className="error">{authError}</p>}
       </section>
 
+      <section className="card">
+        <h2>Ersteinrichtung</h2>
+        {setupLoading && <p className="muted">Lade …</p>}
+        {setupError && <p className="error">{setupError}</p>}
+        {setup && <pre>{JSON.stringify(setup, null, 2)}</pre>}
+        {!setupLoading && !setup && !setupError && (
+          <p className="muted">Kein Setup-Status verfügbar.</p>
+        )}
+      </section>
+
       <section className="card">
         <h2>API Health</h2>
         {healthError && <p className="error">Fehler: {healthError}</p>}
diff --git a/frontend/src/app.css b/frontend/src/app.css
index f8895e8..5115f0f 100644
--- a/frontend/src/app.css
+++ b/frontend/src/app.css
@@ -49,6 +49,11 @@ body {
   margin: 0 0 1rem;
 }
 
+.setup-hint-muted {
+  background: #f3f3f3;
+  border-color: #ddd;
+}
+
 .tabs {
   display: flex;
   gap: 0.35rem;