diff --git a/src/App.tsx b/src/App.tsx
index 65c91e3..de77ea8 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -77,7 +77,6 @@ function App() {
             <AuthProvider>
                 <ToastProvider>
                     <WorkflowSelectionProvider>
-                    <FileProvider>
                     <Router>
                         <Routes>
                         {/* ================================================== */}
@@ -94,7 +93,9 @@ function App() {
                         {/* ================================================== */}
                         <Route path="/" element={
                             <ProtectedRoute>
+                                <FileProvider>
                                 <MainLayout />
+                                </FileProvider>
                             </ProtectedRoute>
                         }>
                             {/* Dashboard (Root) */}
@@ -190,7 +191,6 @@ function App() {
                         } />
                         </Routes>
                     </Router>
-                    </FileProvider>
                     </WorkflowSelectionProvider>
                 </ToastProvider>
             </AuthProvider>
diff --git a/src/hooks/useInvitations.ts b/src/hooks/useInvitations.ts
index e8dbd79..040d95b 100644
--- a/src/hooks/useInvitations.ts
+++ b/src/hooks/useInvitations.ts
@@ -65,6 +65,7 @@ export interface InvitationValidation {
   roleIds: string[];
   roleLabels?: string[];
   targetUsername?: string;
+  email?: string;
 }
 
 
diff --git a/src/pages/InvitePage.tsx b/src/pages/InvitePage.tsx
index f5cd0ab..85c83bc 100644
--- a/src/pages/InvitePage.tsx
+++ b/src/pages/InvitePage.tsx
@@ -24,6 +24,7 @@
 import React, { useState, useEffect } from 'react';
 import { useParams, useNavigate, Link } from 'react-router-dom';
 import { useInvitations, type InvitationValidation } from '../hooks/useInvitations';
+import api from '../api';
 import { FaCheckCircle, FaTimesCircle, FaSpinner, FaSignInAlt, FaUserPlus } from 'react-icons/fa';
 import styles from './InvitePage.module.css';
 
@@ -35,7 +36,7 @@ export const InvitePage: React.FC = () => {
   const navigate = useNavigate();
   const { validateInvitation, acceptInvitation } = useInvitations();
   
-  // Check if user has auth token (simplified check)
+  // Check if user has an active session
   const isAuthenticated = !!sessionStorage.getItem('auth_authority');
 
   // State
@@ -68,12 +69,11 @@ export const InvitePage: React.FC = () => {
         // Check if the target username already has an account
         if (result.targetUsername) {
           try {
-            const resp = await fetch(`/api/local/available?username=${encodeURIComponent(result.targetUsername)}`);
-            if (resp.ok) {
-              const data = await resp.json();
-              // available=true means username is free -> user does NOT exist
-              setUserExists(!data.available);
-            }
+            const resp = await api.get(`/api/local/available`, {
+              params: { username: result.targetUsername }
+            });
+            // available=true means username is free -> user does NOT exist
+            setUserExists(!resp.data.available);
           } catch {
             // On error, default to showing both options
             setUserExists(null);
@@ -104,6 +104,10 @@ export const InvitePage: React.FC = () => {
       setTimeout(() => {
         navigate('/');
       }, 2000);
+    } else if (result.error?.includes('401') || result.error?.includes('Not authenticated')) {
+      // Session expired — clear auth and redirect to login
+      sessionStorage.removeItem('auth_authority');
+      handleLoginRedirect();
     } else {
       setError(result.error || 'Fehler beim Annehmen der Einladung');
     }
@@ -111,20 +115,28 @@ export const InvitePage: React.FC = () => {
     setAccepting(false);
   };
 
-  // Handle redirect to login (stores token first)
+  // Handle redirect to login (stores token first, passes invitation data for pre-fill)
   const handleLoginRedirect = () => {
     if (token) {
       localStorage.setItem(PENDING_INVITATION_KEY, token);
     }
-    navigate('/login', { state: { from: { pathname: `/invite/${token}` } } });
+    navigate('/login', { state: {
+      from: { pathname: `/invite/${token}` },
+      invitationUsername: validation?.targetUsername || '',
+    } });
   };
 
-  // Handle redirect to register (stores token first)
+  // Handle redirect to register (stores token first, passes invitation data for pre-fill)
   const handleRegisterRedirect = () => {
     if (token) {
       localStorage.setItem(PENDING_INVITATION_KEY, token);
     }
-    navigate('/register', { state: { from: { pathname: `/invite/${token}` }, pendingInvitation: true } });
+    navigate('/register', { state: {
+      from: { pathname: `/invite/${token}` },
+      pendingInvitation: true,
+      invitationUsername: validation?.targetUsername || '',
+      invitationEmail: validation?.email || '',
+    } });
   };
 
   // Loading state
diff --git a/src/pages/Login.tsx b/src/pages/Login.tsx
index 9756d96..d06bca0 100644
--- a/src/pages/Login.tsx
+++ b/src/pages/Login.tsx
@@ -12,7 +12,9 @@ import styles from './Login.module.css';
 function Login() {
   const navigate = useNavigate();
   const location = useLocation();
-  const [username, setUsername] = useState('');
+  // Pre-fill username from invitation if provided via location.state
+  const invitationUsername = (location.state as any)?.invitationUsername || '';
+  const [username, setUsername] = useState(invitationUsername);
   const [password, setPassword] = useState('');
   const [usernameFocused, setUsernameFocused] = useState(false);
   const [passwordFocused, setPasswordFocused] = useState(false);
diff --git a/src/pages/Register.tsx b/src/pages/Register.tsx
index 2602d10..a3c1403 100644
--- a/src/pages/Register.tsx
+++ b/src/pages/Register.tsx
@@ -19,9 +19,12 @@ function Register() {
   const { register, error: registerError, isLoading } = useRegister();
   const { error: msalError } = useMsalRegister();
   const { checkAvailability, isChecking, error: availabilityError } = useUsernameAvailability();
+  // Pre-fill from invitation if provided via location.state
+  const invitationUsername = (location.state as any)?.invitationUsername || '';
+  const invitationEmail = (location.state as any)?.invitationEmail || '';
   const [formData, setFormData] = useState<RegisterFormData>({
-    username: '',
-    email: '',
+    username: invitationUsername,
+    email: invitationEmail,
     fullName: ''
   });
   const [validationError, setValidationError] = useState<string | null>(null);