app/lib/features/auth/presentation/auth_failure_texts.dart

@@ -36,3 +36,8 @@ String weakPasswordMessage(
   };
   return texts.isEmpty ? l10n.authErrorWeakPasswordCharacters : texts.join(' ');
 }
+
+/// Failures the user can fix by simply trying again (offline, unexpected).
+extension AuthFailureRetry on AuthFailure {
+  bool get isRetryable => this is NetworkFailure || this is Unexpected;
+}

app/lib/features/auth/presentation/login/login_controller.dart

@@ -60,15 +60,17 @@ class LoginController extends _$LoginController {
     final result = await ref
         .read(authRepositoryProvider)
         .signIn(email, state.password);
-    if (!ref.mounted) {
-      return null;
-    }
-
     final failure = result.errorOrNull;
     if (failure == null) {
-      state = state.copyWith(status: LoginStatus.editing);
+      // Success: the target is returned even if the screen is already gone
+      // (the router redirect can remove it before this future completes), so
+      // the caller can still finish the autofill context. The status stays
+      // `submitting`, the form is not reused after a successful sign-in.
       return safeFromPath(from) ?? AppRoutes.home;
     }
+    if (!ref.mounted) {
+      return null;
+    }
     state = state.copyWith(
       status: LoginStatus.editing,
       bannerFailure: failure,

app/lib/features/auth/presentation/login/login_controller.g.dart

@@ -44,7 +44,7 @@ final class LoginControllerProvider
   }
 }
 
-String _$loginControllerHash() => r'f8c37f2b7b942c8cfffbf8b61f3296872b5bcb70';
+String _$loginControllerHash() => r'693066c260db8abe8f70d04b88b216b2e0411579';
 
 /// Logic of the sign-in form (KTO-01 Kriterien 5, 6 und 7).
 

app/lib/features/auth/presentation/login/login_screen.dart

@@ -67,10 +67,15 @@ class _LoginScreenState extends ConsumerState<LoginScreen> {
     final target = await ref
         .read(loginControllerProvider.notifier)
         .submit(from: widget.from);
-    if (!mounted || target == null) {
+    if (target == null) {
       return;
     }
+    // Also when the router redirect (status signedIn) already removed this
+    // screen: the password manager must still learn that sign-in worked.
     TextInput.finishAutofillContext();
+    if (!mounted) {
+      return;
+    }
     context.go(target);
   }
 
@@ -136,13 +141,16 @@ class _LoginScreenState extends ConsumerState<LoginScreen> {
                 message: l10n.authCheckEmailResent,
               ),
             ],
-            if (state.showsNotConfirmed && resend.failure != null) ...[
+            if ((state.showsNotConfirmed, resend.failure) case (
+              true,
+              final resendFailure?,
+            )) ...[
               const SizedBox(height: AppSpacing.md),
               AppBanner(
                 key: const Key('login_resend_error_banner'),
                 type: AppBannerType.error,
                 typeLabel: l10n.authBannerTypeError,
-                message: authFailureMessage(l10n, resend.failure!),
+                message: authFailureMessage(l10n, resendFailure),
               ),
             ],
             const SizedBox(height: AppSpacing.xl),
@@ -226,7 +234,7 @@ class _FailureBanner extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final l10n = context.l10n;
-    final retryable = failure is NetworkFailure || failure is Unexpected;
+    final retryable = failure.isRetryable;
     return AppBanner(
       type: AppBannerType.error,
       typeLabel: l10n.authBannerTypeError,

app/lib/features/auth/presentation/login/login_state.dart

@@ -37,6 +37,12 @@ abstract class LoginState with _$LoginState {
 
   const LoginState._();
 
+  /// No credentials in logs or error reports.
+  @override
+  String toString() =>
+      'LoginState(email: <redacted>, password: <redacted>, status: $status, '
+      'bannerFailure: $bannerFailure)';
+
   bool get isSubmitting => status == LoginStatus.submitting;
 
   EmailError? get emailError => EmailFormat.validate(email);

app/lib/features/auth/presentation/login/login_state.freezed.dart

@@ -42,11 +42,6 @@ int get hashCode {
   return Object.hash(runtimeType,_this.email,_this.password,const DeepCollectionEquality().hash(_this.visibleFields),_this.status,_this.bannerFailure,_this.unconfirmedEmail,_this.focusField,_this.focusRequest);
 }
 
-@override
-String toString() {
-  final _this = this as LoginState;
-  return 'LoginState(email: ${_this.email}, password: ${_this.password}, visibleFields: ${_this.visibleFields}, status: ${_this.status}, bannerFailure: ${_this.bannerFailure}, unconfirmedEmail: ${_this.unconfirmedEmail}, focusField: ${_this.focusField}, focusRequest: ${_this.focusRequest})';
-}
 
 
 }
@@ -278,10 +273,6 @@ int get hashCode {
     return Object.hash(runtimeType,email,password,const DeepCollectionEquality().hash(_visibleFields),status,bannerFailure,unconfirmedEmail,focusField,focusRequest);
 }
 
-@override
-String toString() {
-    return 'LoginState(email: $email, password: $password, visibleFields: $visibleFields, status: $status, bannerFailure: $bannerFailure, unconfirmedEmail: $unconfirmedEmail, focusField: $focusField, focusRequest: $focusRequest)';
-}
 
 
 }

app/lib/features/auth/presentation/providers/auth_redirect.dart

@@ -69,10 +69,21 @@ String? safeFromPath(String? from) {
   if (from.startsWith('//') || from.startsWith(r'/\')) {
     return null;
   }
+  // Browsers drop tabs and line breaks inside URLs (`/\t/evil` -> `//evil`),
+  // so control characters are never allowed.
+  if (RegExp(r'[\x00-\x1f\x7f]').hasMatch(from)) {
+    return null;
+  }
   final uri = Uri.tryParse(from);
   if (uri == null || uri.hasScheme || uri.hasAuthority) {
     return null;
   }
+  // Percent-encoded variants (`/%2F%2Fevil`, `/%5Cevil`) must not decode to a
+  // protocol-relative path either.
+  final decoded = Uri.decodeFull(uri.path);
+  if (decoded.startsWith('//') || decoded.startsWith(r'/\')) {
+    return null;
+  }
   // `/login/` is the same page as `/login` (go_router ignores the trailing
   // slash), so it is not allowed either.
   final path = uri.path.length > 1

app/lib/features/auth/presentation/register/register_screen.dart

@@ -319,7 +319,7 @@ class _FailureBanner extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final l10n = context.l10n;
-    final retryable = failure is NetworkFailure || failure is Unexpected;
+    final retryable = failure.isRetryable;
     return AppBanner(
       type: AppBannerType.error,
       typeLabel: l10n.authBannerTypeError,

app/lib/features/auth/presentation/register/register_state.dart

@@ -56,6 +56,13 @@ abstract class RegisterState with _$RegisterState {
 
   const RegisterState._();
 
+  /// No credentials or personal data in logs or error reports.
+  @override
+  String toString() =>
+      'RegisterState(email: <redacted>, password: <redacted>, '
+      'displayName: <redacted>, status: $status, '
+      'bannerFailure: $bannerFailure)';
+
   bool get isSubmitting => status == RegisterStatus.submitting;
 
   EmailError? get emailError => EmailFormat.validate(email);

app/lib/features/auth/presentation/register/register_state.freezed.dart

@@ -44,11 +44,6 @@ int get hashCode {
   return Object.hash(runtimeType,_this.email,_this.password,_this.displayName,_this.ageConfirmed,_this.termsAccepted,const DeepCollectionEquality().hash(_this.visibleFields),_this.status,_this.commonPasswords,_this.bannerFailure,const DeepCollectionEquality().hash(_this.serverPasswordReasons),_this.serverEmailInvalid,_this.focusField,_this.focusRequest);
 }
 
-@override
-String toString() {
-  final _this = this as RegisterState;
-  return 'RegisterState(email: ${_this.email}, password: ${_this.password}, displayName: ${_this.displayName}, ageConfirmed: ${_this.ageConfirmed}, termsAccepted: ${_this.termsAccepted}, visibleFields: ${_this.visibleFields}, status: ${_this.status}, commonPasswords: ${_this.commonPasswords}, bannerFailure: ${_this.bannerFailure}, serverPasswordReasons: ${_this.serverPasswordReasons}, serverEmailInvalid: ${_this.serverEmailInvalid}, focusField: ${_this.focusField}, focusRequest: ${_this.focusRequest})';
-}
 
 
 }
@@ -301,10 +296,6 @@ int get hashCode {
     return Object.hash(runtimeType,email,password,displayName,ageConfirmed,termsAccepted,const DeepCollectionEquality().hash(_visibleFields),status,commonPasswords,bannerFailure,const DeepCollectionEquality().hash(_serverPasswordReasons),serverEmailInvalid,focusField,focusRequest);
 }
 
-@override
-String toString() {
-    return 'RegisterState(email: $email, password: $password, displayName: $displayName, ageConfirmed: $ageConfirmed, termsAccepted: $termsAccepted, visibleFields: $visibleFields, status: $status, commonPasswords: $commonPasswords, bannerFailure: $bannerFailure, serverPasswordReasons: $serverPasswordReasons, serverEmailInvalid: $serverEmailInvalid, focusField: $focusField, focusRequest: $focusRequest)';
-}
 
 
 }

app/test/features/auth/presentation/auth_redirect_test.dart

@@ -150,5 +150,13 @@ void main() {
       expect(safeFromPath(''), isNull);
       expect(safeFromPath('javascript:alert(1)'), isNull);
     });
+
+    test('rejects encoded and control-character tricks', () {
+      expect(safeFromPath('/%2F%2Fevil.example'), isNull);
+      expect(safeFromPath('%2F%2Fevil'), isNull);
+      expect(safeFromPath('/%5Cevil.example'), isNull);
+      expect(safeFromPath('/\t/evil.example'), isNull);
+      expect(safeFromPath('/a\nb'), isNull);
+    });
   });
 }

app/test/features/auth/presentation/login/login_controller_test.dart

@@ -47,7 +47,8 @@ void main() {
 
       verify(() => repository.signIn('Anna@Example.com', 'pw')).called(1);
       expect(target, '/');
-      expect(state().isSubmitting, isFalse);
+      // The form is left after success; it is not unlocked again.
+      expect(state().isSubmitting, isTrue);
       expect(state().bannerFailure, isNull);
     });
 
@@ -68,6 +69,10 @@ void main() {
       '/register',
       '/reset-password',
       '/auth/confirm?token_hash=x',
+      '/%2F%2Fevil.example',
+      '%2F%2Fevil',
+      '/\t/evil.example',
+      '/%5Cevil.example',
       '',
     ]) {
       test('ignores the unsafe from "$unsafe"', () async {
@@ -123,6 +128,18 @@ void main() {
     });
   });
 
+  group('no credentials in logs', () {
+    test('toString masks email and password', () {
+      fill('anna@example.com', 'geheim-und-lang');
+
+      final text = state().toString();
+
+      expect(text, isNot(contains('anna@example.com')));
+      expect(text, isNot(contains('geheim-und-lang')));
+      expect(text, contains('<redacted>'));
+    });
+  });
+
   group('KTO-01 Kriterium 7: failures', () {
     test('invalid credentials keep the input and show the failure', () async {
       stubSignIn(failed(const AuthFailure.invalidCredentials()));

app/test/features/auth/presentation/login/login_screen_test.dart

@@ -243,9 +243,13 @@ void main() {
     testWidgets(
       'wrong email and wrong password show exactly the same screen text',
       (tester) async {
-        // The repository maps both cases to invalidCredentials (Spec 4.3); the
-        // screen must not add anything that tells them apart.
+        // Screen level only: the repository mock returns invalidCredentials
+        // for both cases, so this proves the screen adds nothing that tells
+        // them apart. The real proof that an unknown address and a wrong
+        // password yield the same `invalid_credentials` answer is the API
+        // E2E test (T3).
         stubSignInFailure(const AuthFailure.invalidCredentials());
+        final handle = tester.ensureSemantics();
         await open(tester);
         await type(tester, 'login_email', 'unknown@example.com');
         await type(tester, 'login_password', 'irgendein-passwort');
@@ -258,22 +262,16 @@ void main() {
         final wrongPassword = visibleTexts(tester);
 
         expect(wrongEmail, wrongPassword);
-        expect(wrongEmail, contains(_de.authErrorInvalidCredentials));
-        verify(() => repository.signIn(any(), any())).called(2);
+        // Fixed wording, independent of the l10n getter.
+        const fixed = 'E-Mail-Adresse oder Passwort ist nicht korrekt.';
+        expect(wrongEmail, contains(fixed));
+        expect(_de.authErrorInvalidCredentials, fixed);
+        expect(find.text(fixed), findsOneWidget);
+        expect(find.bySemanticsLabel('Fehler: $fixed'), findsOneWidget);
+        handle.dispose();
       },
     );
 
-    testWidgets('english text of the generic failure', (tester) async {
-      stubSignInFailure(const AuthFailure.invalidCredentials());
-      await open(tester, locale: const Locale('en'));
-      await fill(tester);
-
-      await submit(tester);
-
-      expect(find.text(_en.authErrorInvalidCredentials), findsOneWidget);
-      expect(find.text(_de.authErrorInvalidCredentials), findsNothing);
-    });
-
     testWidgets('throttling (429) shows the throttle hint', (tester) async {
       stubSignInFailure(const AuthFailure.rateLimited());
       await open(tester);
@@ -378,6 +376,99 @@ void main() {
     });
   });
 
+  group('KTO-01 Kriterium 5: autofill context', () {
+    // Only calls that save the credentials (`shouldSave: true`).
+    int finishCalls(WidgetTester tester) => tester.testTextInput.log
+        .where(
+          (call) =>
+              call.method == 'TextInput.finishAutofillContext' &&
+              call.arguments == true,
+        )
+        .length;
+
+    testWidgets('is finished after a successful sign-in', (tester) async {
+      await open(tester);
+      await fill(tester);
+      tester.testTextInput.log.clear();
+
+      await submit(tester);
+
+      // Our explicit call, plus the AutofillGroup committing on disposal
+      // when the screen is replaced.
+      expect(finishCalls(tester), greaterThanOrEqualTo(1));
+    });
+
+    testWidgets('is finished even if the router already removed the screen', (
+      tester,
+    ) async {
+      final completer = Completer<Result<void, AuthFailure>>();
+      when(() => repository.signIn(any(), any()))
+          .thenAnswer((_) => completer.future);
+      final (:container, :router) = await open(tester);
+      await fill(tester);
+      await tapKey(tester, 'login_submit');
+      // The status change makes the router redirect away before the
+      // sign-in future completes.
+      router.go('/private');
+      await tester.pumpAndSettle();
+      expect(find.byKey(const Key('login_screen')), findsNothing);
+      tester.testTextInput.log.clear();
+
+      completer.complete(ok());
+      await tester.pumpAndSettle();
+
+      expect(finishCalls(tester), 1);
+      expect(currentPath(router), '/private');
+    });
+
+    testWidgets('is not finished after a failed sign-in', (tester) async {
+      stubSignInFailure(const AuthFailure.invalidCredentials());
+      await open(tester);
+      await fill(tester);
+      tester.testTextInput.log.clear();
+
+      await submit(tester);
+
+      expect(finishCalls(tester), 0);
+    });
+  });
+
+  group('Zustände Kriterium 3: banners and focus', () {
+    testWidgets('unexpected error shows the banner with retry', (tester) async {
+      stubSignInFailure(const AuthFailure.unexpected());
+      await open(tester);
+      await fill(tester);
+
+      await submit(tester);
+
+      expect(find.text(_de.authErrorUnexpected), findsOneWidget);
+      expect(find.text(_de.authActionRetry), findsOneWidget);
+      stubSignInFailure(const AuthFailure.unexpected());
+      await tester.tap(find.text(_de.authActionRetry));
+      await tester.pumpAndSettle();
+      verify(() => repository.signIn(any(), any())).called(2);
+    });
+
+    testWidgets('a failed submit focuses the first invalid field', (
+      tester,
+    ) async {
+      await open(tester);
+
+      await submit(tester);
+      expect(
+        tester.widget<TextField>(fieldOf('login_email')).focusNode!.hasFocus,
+        isTrue,
+      );
+
+      await type(tester, 'login_email', 'anna@example.com');
+      await submit(tester);
+      expect(
+        tester.widget<TextField>(fieldOf('login_password')).focusNode!.hasFocus,
+        isTrue,
+      );
+    });
+  });
+
   group('QUE-05 Kriterium 2: de and en', () {
     testWidgets('english texts', (tester) async {
       await open(tester, locale: const Locale('en'));
@@ -405,6 +496,23 @@ void main() {
       });
     }
 
+    for (final mode in [ThemeMode.light, ThemeMode.dark]) {
+      testWidgets('error banner meets the contrast guideline ($mode)', (
+        tester,
+      ) async {
+        final handle = tester.ensureSemantics();
+        stubSignInFailure(const AuthFailure.invalidCredentials());
+        await open(tester, themeMode: mode);
+        await fill(tester);
+        await submit(tester);
+        expect(find.byKey(const Key('login_banner')), findsOneWidget);
+
+        await expectLater(tester, meetsGuideline(textContrastGuideline));
+        await expectLater(tester, meetsGuideline(androidTapTargetGuideline));
+        handle.dispose();
+      });
+    }
+
     testWidgets('the title is a heading and the banner a live region', (
       tester,
     ) async {
@@ -416,7 +524,7 @@ void main() {
 
       expect(
         find.bySemanticsLabel(
-          '${_de.authBannerTypeError}: ${_de.authErrorInvalidCredentials}',
+          'Fehler: E-Mail-Adresse oder Passwort ist nicht korrekt.',
         ),
         findsOneWidget,
       );

app/test/features/auth/presentation/register/register_controller_test.dart

@@ -71,6 +71,24 @@ void main() {
       ..termsAcceptedChanged(value: true);
   }
 
+  group('no personal data in logs', () {
+    test('toString masks email, password and display name', () {
+      final container = makeContainer();
+      fillValid(
+        container.read(registerControllerProvider.notifier),
+        email: 'anna@example.com',
+        name: 'Anna Geheim',
+      );
+
+      final text = container.read(registerControllerProvider).toString();
+
+      expect(text, isNot(contains('anna@example.com')));
+      expect(text, isNot(contains('geheim-und-lang')));
+      expect(text, isNot(contains('Anna Geheim')));
+      expect(text, contains('<redacted>'));
+    });
+  });
+
   group('KTO-01 Kriterium 1: submit', () {
     test('KTO-01 Kriterium 11 (Client): sends all data, terms version and locale to signUp', () async {
       final container = makeContainer(locale: const Locale('en'));