added guardian letters with chat and multiple answer functionalities

CLAUDE.md

@@ -1,6 +1,6 @@
 # MarianumMobile Client
 
-Flutter-App für die Schul-Community: Stundenplan, Ticker, Newsletter & Co. über das MarianumConnect-Backend, Nextcloud Talk + Files. Zwei Kontoarten: Schul-Konto (Schüler/Lehrer, Benutzername + Passwort) und Eltern-Konto (passwortlos per E-Mail-Code/App-Link, sieht die Stundenpläne der zugeordneten Kinder, kein Talk/Files).
+Flutter-App für die Schul-Community: Stundenplan, Ticker, Newsletter & Co. über das MarianumConnect-Backend, Nextcloud Talk + Files. Zwei Kontoarten: Schul-Konto (Schüler/Lehrer, Benutzername + Passwort) und Eltern-Konto (passwortlos per E-Mail-Code/App-Link, sieht die Stundenpläne der zugeordneten Kinder und erhält Elternbriefe, kein Talk/Files).
 
 ## Stack
 
@@ -56,10 +56,12 @@ lib/
 
 **Session:** Die aktive Sitzung liegt in `SessionManager().current` (`lib/session/`). Nextcloud-Zugriffe nur über `SessionManager().requireNextcloud()` – Eltern-Sessions haben keine Nextcloud-Identität. Abmelden ausschließlich über `SessionLifecycle.signOut()`. Die Keychain-Keys in `SessionKeys` sind eingefroren (Bestandsinstallationen, iOS-NSE).
 
-**Rollen & Zuschnitt:** Views verzweigen nie auf Rollen. Module und Settings-Sections deklarieren `AccessRequirement`s (`AppModule.requirements`, `Settings._sections`); Views bekommen ein Subjekt + eine Policy, die an genau einer Stelle als pure Funktion aufgelöst wird (Vorbild: `TimetableSubject` + `TimetablePolicy.resolve`, `AbsenceFormPolicy`). `UserRole` nur für Anzeige/Policy-Ableitung.
+**Rollen & Zuschnitt:** Views verzweigen nie auf Rollen. Module und Settings-Sections deklarieren `AccessRequirement`s (`nextcloud`, `guardian`; `AppModule.requirements`, `Settings._sections`); Views bekommen ein Subjekt + eine Policy, die an genau einer Stelle als pure Funktion aufgelöst wird (Vorbild: `TimetableSubject` + `TimetablePolicy.resolve`, `AbsenceFormPolicy`). `UserRole` nur für Anzeige/Policy-Ableitung.
 
 **Stundenplan:** Ein `TimetableBloc(subject: …)` für alle Fälle (eigener Plan, Fremdplan, Kind). Den globalen Bloc stellt `PrimaryTimetableScope` bereit und tauscht ihn beim Kindwechsel aus; page-scoped Fremdpläne nutzen `ScopedTimetableBloc`. Die Kinderauswahl (`ChildSelectionCubit`) ist modulübergreifend.
 
+**Elternbriefe:** Modul `parentLetters` (nur Eltern-Sessions, `AccessRequirement.guardian`): Lehrer-Mitteilungen aus MarianumConnect mit Gelesen-Status, Kenntnisnahme/Auswahl/Unterschrift pro Kind, Thread und Anhängen. Der Posteingang (`ParentLettersBloc`) ist global (Modul-Badge, Push-Refresh), ein Brief ist page-scoped (`ParentLetterBloc`). Ob und wie geantwortet werden darf, entscheidet der Server (`editable`); `ParentLetterFormPolicy.resolve` macht daraus das Formular. Push: Connect-Direct-Push `type: parent-letter`, Tap-Routing allein über `parentLetterId`. Alle Benachrichtigungs-Taps (lokal gerendert wie FCM) werden von `resolvePushTarget` (`lib/push/push_target.dart`) aufgelöst und in `NotificationTasks.openPushTarget` navigiert – neue Push-Ziele nur dort ergänzen.
+
 ## Build / Run
 
 ```bash
@@ -74,7 +76,7 @@ flutter test                                                 # Tests (siehe test
 
 | Backend                   | Pfad                  | Zweck                                  |
 |---------------------------|-----------------------|----------------------------------------|
-| MarianumConnect (Bearer)  | `lib/api/marianumconnect/` | Auth, Stundenplan (Webuntis-Proxy), Ticker, Newsletter, Ferien, Abwesenheit, Capabilities, Push |
+| MarianumConnect (Bearer)  | `lib/api/marianumconnect/` | Auth, Stundenplan (Webuntis-Proxy), Ticker, Newsletter, Ferien, Abwesenheit, Elternbriefe, Capabilities, Push |
 | Nextcloud (Talk + WebDAV) | `lib/api/marianumcloud/` | Chats, Datei-Verwaltung             |
 | MHSL (Legacy)             | `lib/api/mhsl/`       | nur noch Einmal-Migration der Custom Events |
 

lib/access/access_requirement.dart

@@ -3,10 +3,12 @@ import '../session/session.dart';
 /// Backend identity a feature needs. Modules and settings sections declare
 /// these; anything whose requirements the session does not meet is hidden.
 enum AccessRequirement {
-  nextcloud;
+  nextcloud,
+  guardian;
 
   bool isMetBy(Session? session) => switch (this) {
     AccessRequirement.nextcloud => session?.nextcloud != null,
+    AccessRequirement.guardian => session is GuardianSession,
   };
 }
 

lib/api/demo/data/demo_parent_letters.dart

@@ -0,0 +1,273 @@
+import '../../marianumconnect/queries/parent_letters/parent_letter_models.dart';
+import '../demo_persona.dart';
+
+/// Demo inbox of the guardian persona: one letter per variant (information,
+/// acknowledgement, choice, signature, answered, expired, thread, attachment).
+/// Child ids match [DemoCapabilities.guardianState].
+class DemoParentLetters {
+  const DemoParentLetters._();
+
+  static const _lena = 'demo-child-1';
+  static const _jonas = 'demo-child-2';
+
+  static final Set<String> _readInSession = {};
+
+  static void markRead(String letterId) => _readInSession.add(letterId);
+
+  static ParentLetterListResponse list() {
+    final items = [for (final letter in _letters()) letter.summary];
+    return ParentLetterListResponse(
+      items: items,
+      unreadCount: items.where((letter) => !letter.read).length,
+      openCount: items
+          .where((letter) => letter.status == ParentLetterStatus.open)
+          .length,
+    );
+  }
+
+  static ParentLetterDetail detail(String letterId) {
+    final letters = _letters();
+    return letters.firstWhere(
+      (letter) => letter.summary.id == letterId,
+      orElse: () => letters.first,
+    );
+  }
+
+  static ParentLetterPerson _teacher(int index) =>
+      ParentLetterPerson(displayName: DemoPersona.teachers[index].name);
+
+  static const _participation = ParentLetterField(
+    id: 'participation',
+    type: ParentLetterFieldType.singleChoice,
+    label: 'Nimmt Ihr Kind teil?',
+    isRequired: true,
+    options: [
+      ParentLetterOption(id: 'yes', label: 'Ja'),
+      ParentLetterOption(id: 'no', label: 'Nein'),
+    ],
+  );
+
+  static List<ParentLetterDetail> _letters() {
+    final now = DateTime.now();
+    ParentLetterDetail letter({
+      required String id,
+      required String subject,
+      required ParentLetterPerson sender,
+      required Duration age,
+      required String body,
+      required List<String> childIds,
+      bool read = true,
+      ParentLetterStatus status = ParentLetterStatus.info,
+      ParentLetterRequest? request,
+      List<ParentLetterChildState> children = const [],
+      List<ParentLetterAttachment> attachments = const [],
+      ParentLetterThread thread = const ParentLetterThread(enabled: true),
+    }) => ParentLetterDetail(
+      summary: ParentLetterSummary(
+        id: id,
+        subject: subject,
+        preview: body.replaceAll('\n', ' ').trim(),
+        sender: sender,
+        sentAt: now.subtract(age),
+        read: read || _readInSession.contains(id),
+        childIds: childIds,
+        attachmentCount: attachments.length,
+        status: status,
+        deadline: request?.deadline,
+      ),
+      content: ParentLetterContent(
+        body: body,
+        attachments: attachments,
+        request: request,
+        children: children,
+        thread: thread,
+      ),
+    );
+
+    return [
+      letter(
+        id: 'demo-letter-hike',
+        subject: 'Wandertag der ${DemoPersona.className}',
+        sender: _teacher(0),
+        age: const Duration(hours: 2),
+        read: false,
+        childIds: const [_lena],
+        status: ParentLetterStatus.open,
+        body:
+            'Liebe Eltern,\n\nam Freitag in zwei Wochen findet unser Wandertag '
+            'statt. Wir fahren mit dem Bus in die Rhön und sind gegen 16 Uhr '
+            'zurück. Alle Einzelheiten finden Sie im angehängten Schreiben.\n\n'
+            'Bitte geben Sie uns eine verbindliche Rückmeldung.\n\n'
+            'Viele Grüße\n${DemoPersona.teachers[0].name}',
+        attachments: const [
+          ParentLetterAttachment(
+            id: 'demo-attachment-hike',
+            fileName: 'Wandertag.pdf',
+            mimeType: 'application/pdf',
+            size: 48211,
+          ),
+        ],
+        request: ParentLetterRequest(
+          fields: const [_participation],
+          signatureRequired: true,
+          deadline: now.add(const Duration(days: 10)),
+        ),
+        children: const [
+          ParentLetterChildState(
+            childId: _lena,
+            status: ParentLetterStatus.open,
+            editable: true,
+          ),
+        ],
+      ),
+      letter(
+        id: 'demo-letter-parents-evening',
+        subject: 'Einladung zum Elternabend der 6a',
+        sender: _teacher(1),
+        age: const Duration(days: 1),
+        read: false,
+        childIds: const [_jonas],
+        status: ParentLetterStatus.open,
+        body:
+            'Liebe Eltern,\n\nhiermit lade ich Sie herzlich zum ersten '
+            'Elternabend des Schuljahres ein. Wir treffen uns am kommenden '
+            'Dienstag um 19 Uhr in Raum ${DemoPersona.rooms[0]}.\n\n'
+            'Bitte bestätigen Sie kurz den Erhalt dieser Einladung.',
+        request: const ParentLetterRequest(),
+        children: const [
+          ParentLetterChildState(
+            childId: _jonas,
+            status: ParentLetterStatus.open,
+            editable: true,
+          ),
+        ],
+      ),
+      letter(
+        id: 'demo-letter-school-festival',
+        subject: 'Schulfest: Wer kommt mit?',
+        sender: _teacher(5),
+        age: const Duration(days: 3),
+        childIds: const [_lena, _jonas],
+        status: ParentLetterStatus.open,
+        body:
+            'Liebe Eltern,\n\nfür die Planung unseres Schulfestes möchten wir '
+            'wissen, welche Kinder teilnehmen. Die Angabe können Sie bis zum '
+            'Ablauf der Frist noch ändern.\n\nWeitere Informationen: '
+            'https://www.marianum-fulda.de',
+        request: ParentLetterRequest(
+          fields: const [_participation],
+          deadline: now.add(const Duration(days: 5)),
+        ),
+        children: [
+          ParentLetterChildState(
+            childId: _lena,
+            status: ParentLetterStatus.done,
+            editable: true,
+            response: ParentLetterResponse(
+              respondedAt: now.subtract(const Duration(days: 2)),
+              respondedBy: const ParentLetterPerson(self: true),
+              answers: const [
+                ParentLetterAnswer(
+                  fieldId: 'participation',
+                  optionIds: ['yes'],
+                ),
+              ],
+            ),
+          ),
+          const ParentLetterChildState(
+            childId: _jonas,
+            status: ParentLetterStatus.open,
+            editable: true,
+          ),
+        ],
+      ),
+      letter(
+        id: 'demo-letter-reports',
+        subject: 'Zeugnisausgabe und Unterrichtsschluss',
+        sender: _teacher(3),
+        age: const Duration(days: 7),
+        childIds: const [_lena, _jonas],
+        body:
+            'Liebe Eltern,\n\nam letzten Schultag vor den Ferien endet der '
+            'Unterricht nach der dritten Stunde mit der Zeugnisausgabe. Die '
+            'Busse fahren entsprechend früher.',
+        thread: ParentLetterThread(
+          enabled: true,
+          messages: [
+            ParentLetterThreadMessage(
+              id: 'demo-thread-1',
+              author: const ParentLetterPerson(self: true),
+              body: 'Gilt das auch für die Nachmittagsbetreuung?',
+              sentAt: now.subtract(const Duration(days: 6, hours: 20)),
+            ),
+            ParentLetterThreadMessage(
+              id: 'demo-thread-2',
+              author: _teacher(3),
+              body:
+                  'Ja, die Betreuung entfällt an diesem Tag ebenfalls. Bei '
+                  'Bedarf melden Sie sich bitte im Sekretariat.',
+              sentAt: now.subtract(const Duration(days: 6, hours: 2)),
+            ),
+          ],
+        ),
+      ),
+      letter(
+        id: 'demo-letter-swimming',
+        subject: 'Einverständnis Schwimmunterricht',
+        sender: _teacher(6),
+        age: const Duration(days: 21),
+        childIds: const [_jonas],
+        status: ParentLetterStatus.done,
+        body:
+            'Liebe Eltern,\n\nim zweiten Halbjahr findet der Sportunterricht '
+            'der 6a im Hallenbad statt. Dafür benötigen wir Ihr '
+            'Einverständnis.',
+        request: const ParentLetterRequest(
+          fields: [_participation],
+          signatureRequired: true,
+        ),
+        children: [
+          ParentLetterChildState(
+            childId: _jonas,
+            status: ParentLetterStatus.done,
+            response: ParentLetterResponse(
+              respondedAt: now.subtract(const Duration(days: 20)),
+              respondedBy: const ParentLetterPerson(displayName: 'M. Hoffmann'),
+              answers: const [
+                ParentLetterAnswer(
+                  fieldId: 'participation',
+                  optionIds: ['yes'],
+                ),
+              ],
+              signed: true,
+            ),
+          ),
+        ],
+        thread: const ParentLetterThread(),
+      ),
+      letter(
+        id: 'demo-letter-ski-trip',
+        subject: 'Anmeldung zur Skifreizeit',
+        sender: _teacher(6),
+        age: const Duration(days: 35),
+        childIds: const [_lena],
+        status: ParentLetterStatus.expired,
+        body:
+            'Liebe Eltern,\n\ndie Anmeldung zur Skifreizeit der Jahrgangsstufe '
+            '10 ist ab sofort möglich. Die Plätze sind begrenzt.',
+        request: ParentLetterRequest(
+          fields: const [_participation],
+          signatureRequired: true,
+          deadline: now.subtract(const Duration(days: 14)),
+        ),
+        children: const [
+          ParentLetterChildState(
+            childId: _lena,
+            status: ParentLetterStatus.expired,
+          ),
+        ],
+        thread: const ParentLetterThread(),
+      ),
+    ];
+  }
+}

lib/api/marianumconnect/errors/marianumconnect_error.dart

@@ -6,6 +6,22 @@ import '../../errors/network_exception.dart';
 import '../../errors/parse_exception.dart';
 import '../../errors/server_exception.dart';
 
+/// The error code of a rejected call: the server answers either with JSON
+/// `{"error": "<code>"}` or with the plain text `Fehler: <code>` of its
+/// generic error handler.
+String? marianumConnectErrorCode(Object? body) {
+  if (body is Map) {
+    final code = body['error'];
+    return code is String ? code : null;
+  }
+  if (body is String) {
+    const prefix = 'Fehler: ';
+    return (body.startsWith(prefix) ? body.substring(prefix.length) : body)
+        .trim();
+  }
+  return null;
+}
+
 /// Converts a DioException raised against the Marianum-Connect API into one of
 /// the app's typed AppExceptions. Keeps the dio dependency out of call sites
 /// that just want to render an error message.

lib/api/marianumconnect/marianumconnect_query.dart

@@ -1,5 +1,8 @@
+import 'dart:typed_data';
+
 import 'package:dio/dio.dart';
 
+import '../errors/app_exception.dart';
 import 'errors/marianumconnect_error.dart';
 import 'marianumconnect_api.dart';
 import 'marianumconnect_endpoint.dart';
@@ -23,10 +26,14 @@ abstract class MarianumConnectQuery {
     try {
       return await body();
     } on DioException catch (e) {
-      throw mapMarianumConnectError(e);
+      throw mapError(e);
     }
   }
 
+  /// The AppException a failed call surfaces as. Query families with domain
+  /// error codes override this instead of re-implementing [guard].
+  AppException mapError(DioException error) => mapMarianumConnectError(error);
+
   /// GETs [path] and parses the JSON object body with [fromJson].
   Future<T> getObject<T>(
     String path,
@@ -55,6 +62,16 @@ abstract class MarianumConnectQuery {
         .toList();
   });
 
+  /// GETs the raw bytes of [path] (files that need the bearer token).
+  Future<Uint8List> getBytes(String path) => guard(() async {
+    final response = await dio.get<List<int>>(
+      endpoint(path),
+      options: Options(responseType: ResponseType.bytes),
+    );
+    final bytes = response.data!;
+    return bytes is Uint8List ? bytes : Uint8List.fromList(bytes);
+  });
+
   /// Formats [d] as an ISO `yyyy-MM-dd` day for MarianumConnect query params.
   String isoDate(DateTime d) =>
       '${d.year.toString().padLeft(4, '0')}-${d.month.toString().padLeft(2, '0')}-${d.day.toString().padLeft(2, '0')}';

lib/api/marianumconnect/queries/auth_guardian/guardian_login_exception.dart

@@ -84,21 +84,9 @@ class GuardianLoginException extends AppException {
           'Bitte versuche es später erneut.',
   };
 
-  /// Accepts the documented JSON body (`{"error": …, "attemptsLeft": …}`) as
-  /// well as the plain-text `Fehler: <code>` the server's generic error
-  /// handler produces.
   static (String?, int?) _parseBody(Object? data) {
-    if (data is Map) {
-      final attempts = data['attemptsLeft'];
-      return (data['error'] as String?, attempts is int ? attempts : null);
-    }
-    if (data is String) {
-      final code = data.startsWith('Fehler: ')
-          ? data.substring('Fehler: '.length)
-          : data;
-      return (code.trim(), null);
-    }
-    return (null, null);
+    final attempts = data is Map ? data['attemptsLeft'] : null;
+    return (marianumConnectErrorCode(data), attempts is int ? attempts : null);
   }
 
   static GuardianLoginError? _errorFor(String? code, int status) =>

lib/api/marianumconnect/queries/get_newsletter_file/get_newsletter_file.dart

@@ -1,7 +1,5 @@
 import 'dart:typed_data';
 
-import 'package:dio/dio.dart';
-
 import '../../marianumconnect_query.dart';
 
 /// Downloads the raw PDF bytes of a Marianum Message from
@@ -15,11 +13,6 @@ class GetNewsletterFile extends MarianumConnectQuery {
 
   GetNewsletterFile(this.id, {super.dio});
 
-  Future<Uint8List> run() => guard(() async {
-    final response = await dio.get<List<int>>(
-      endpoint('newsletter/${Uri.encodeComponent(id)}/file'),
-      options: Options(responseType: ResponseType.bytes),
-    );
-    return Uint8List.fromList(response.data!);
-  });
+  Future<Uint8List> run() =>
+      getBytes('newsletter/${Uri.encodeComponent(id)}/file');
 }

lib/api/marianumconnect/queries/get_ticker_page_file/get_ticker_page_file.dart

@@ -1,7 +1,5 @@
 import 'dart:typed_data';
 
-import 'package:dio/dio.dart';
-
 import '../../marianumconnect_query.dart';
 
 /// Downloads the raw bytes of a PROXIED_FILE ticker page from
@@ -15,11 +13,6 @@ class GetTickerPageFile extends MarianumConnectQuery {
 
   GetTickerPageFile(this.slug, {super.dio});
 
-  Future<Uint8List> run() => guard(() async {
-    final response = await dio.get<List<int>>(
-      endpoint('ticker/pages/${Uri.encodeComponent(slug)}/file'),
-      options: Options(responseType: ResponseType.bytes),
-    );
-    return Uint8List.fromList(response.data!);
-  });
+  Future<Uint8List> run() =>
+      getBytes('ticker/pages/${Uri.encodeComponent(slug)}/file');
 }

lib/api/marianumconnect/queries/parent_letters/get_parent_letter.dart

@@ -0,0 +1,9 @@
+import 'parent_letter_models.dart';
+import 'parent_letter_query.dart';
+
+class GetParentLetter extends ParentLetterQuery {
+  GetParentLetter({super.dio});
+
+  Future<ParentLetterDetail> run(String letterId) =>
+      getObject(letterPath(letterId), ParentLetterDetail.fromJson);
+}

lib/api/marianumconnect/queries/parent_letters/get_parent_letter_attachment.dart

@@ -0,0 +1,14 @@
+import 'dart:typed_data';
+
+import 'parent_letter_query.dart';
+
+class GetParentLetterAttachment extends ParentLetterQuery {
+  GetParentLetterAttachment({super.dio});
+
+  Future<Uint8List> run({
+    required String letterId,
+    required String attachmentId,
+  }) => getBytes(
+    letterPath(letterId, '/attachments/${Uri.encodeComponent(attachmentId)}'),
+  );
+}

lib/api/marianumconnect/queries/parent_letters/get_parent_letters.dart

@@ -0,0 +1,16 @@
+import 'parent_letter_models.dart';
+import 'parent_letter_query.dart';
+
+/// `GET parent-letters`: the guardian's inbox across all children, newest
+/// first. [before] continues after the given letter (keyset paging).
+class GetParentLetters extends ParentLetterQuery {
+  static const int pageSize = 50;
+
+  GetParentLetters({super.dio});
+
+  Future<ParentLetterListResponse> run({String? before}) => getObject(
+    'parent-letters',
+    ParentLetterListResponse.fromJson,
+    queryParameters: {'limit': pageSize, 'before': ?before},
+  );
+}

lib/api/marianumconnect/queries/parent_letters/mark_parent_letter_read.dart

@@ -0,0 +1,11 @@
+import 'parent_letter_query.dart';
+
+/// `POST parent-letters/{id}/read`: marks the letter and its thread as read
+/// for this guardian. Idempotent.
+class MarkParentLetterRead extends ParentLetterQuery {
+  MarkParentLetterRead({super.dio});
+
+  Future<void> run(String letterId) => guard(() async {
+    await dio.post<void>(endpoint(letterPath(letterId, '/read')));
+  });
+}

lib/api/marianumconnect/queries/parent_letters/parent_letter_exception.dart

@@ -0,0 +1,90 @@
+import 'package:dio/dio.dart';
+
+import '../../../errors/app_exception.dart';
+import '../../errors/marianumconnect_error.dart';
+
+enum ParentLetterError {
+  guardianRequired,
+  letterNotFound,
+  childNotFound,
+  attachmentNotFound,
+  invalidAnswers,
+  signatureRequired,
+  responseFinal,
+  deadlinePassed,
+  threadDisabled,
+  invalidRequest,
+}
+
+/// A parent-letter call the server rejected with a domain reason.
+class ParentLetterException extends AppException {
+  final ParentLetterError error;
+
+  const ParentLetterException(
+    this.error, {
+    required super.userMessage,
+    super.technicalDetails,
+  }) : super(allowRetry: false);
+
+  /// Only 4xx answers with a parent-letter reason become a
+  /// [ParentLetterException]; everything else (network, 401, 5xx) keeps the
+  /// generic MarianumConnect mapping.
+  static AppException fromDio(DioException e) {
+    final response = e.response;
+    final status = response?.statusCode;
+    if (status == null || status < 400 || status >= 500 || status == 401) {
+      return mapMarianumConnectError(e);
+    }
+    final error = _errorFor(marianumConnectErrorCode(response!.data), status);
+    if (error == null) return mapMarianumConnectError(e);
+    return ParentLetterException(
+      error,
+      userMessage: messageFor(error),
+      technicalDetails: 'MC $status: ${response.data}',
+    );
+  }
+
+  static String messageFor(ParentLetterError error) => switch (error) {
+    ParentLetterError.guardianRequired =>
+      'Elternbriefe sind nur mit einem Eltern-Konto verfügbar.',
+    ParentLetterError.letterNotFound =>
+      'Dieser Elternbrief ist nicht mehr verfügbar.',
+    ParentLetterError.childNotFound =>
+      'Dieser Elternbrief betrifft das ausgewählte Kind nicht.',
+    ParentLetterError.attachmentNotFound =>
+      'Der Anhang ist nicht mehr verfügbar.',
+    ParentLetterError.invalidAnswers =>
+      'Die Rückmeldung ist unvollständig. Bitte prüfe deine Angaben.',
+    ParentLetterError.signatureRequired =>
+      'Für diese Rückmeldung wird eine Unterschrift benötigt.',
+    ParentLetterError.responseFinal =>
+      'Die Rückmeldung wurde bereits endgültig abgegeben und kann nicht mehr '
+          'geändert werden.',
+    ParentLetterError.deadlinePassed =>
+      'Die Frist für diese Rückmeldung ist abgelaufen.',
+    ParentLetterError.threadDisabled =>
+      'Auf diesen Elternbrief kann nicht geantwortet werden.',
+    ParentLetterError.invalidRequest =>
+      'Die Anfrage konnte nicht verarbeitet werden.',
+  };
+
+  static ParentLetterError? _errorFor(String? code, int status) =>
+      switch (code) {
+        'guardian_required' => ParentLetterError.guardianRequired,
+        'letter_not_found' => ParentLetterError.letterNotFound,
+        'child_not_found' => ParentLetterError.childNotFound,
+        'attachment_not_found' => ParentLetterError.attachmentNotFound,
+        'invalid_answers' => ParentLetterError.invalidAnswers,
+        'signature_required' => ParentLetterError.signatureRequired,
+        'response_final' => ParentLetterError.responseFinal,
+        'deadline_passed' => ParentLetterError.deadlinePassed,
+        'thread_disabled' => ParentLetterError.threadDisabled,
+        'invalid_request' => ParentLetterError.invalidRequest,
+        _ => switch (status) {
+          404 => ParentLetterError.letterNotFound,
+          409 => ParentLetterError.responseFinal,
+          410 => ParentLetterError.deadlinePassed,
+          _ => null,
+        },
+      };
+}

lib/api/marianumconnect/queries/parent_letters/parent_letter_models.dart

@@ -0,0 +1,226 @@
+import 'package:flutter/foundation.dart';
+import 'package:freezed_annotation/freezed_annotation.dart';
+
+part 'parent_letter_models.freezed.dart';
+part 'parent_letter_models.g.dart';
+
+enum ParentLetterStatus { info, open, done, expired }
+
+enum ParentLetterFieldType {
+  @JsonValue('single_choice')
+  singleChoice,
+  unknown,
+}
+
+/// Sender, thread author or responding guardian. [self] marks the signed-in
+/// guardian.
+@freezed
+abstract class ParentLetterPerson with _$ParentLetterPerson {
+  const factory ParentLetterPerson({
+    @Default('') String displayName,
+    @Default(false) bool self,
+  }) = _ParentLetterPerson;
+
+  factory ParentLetterPerson.fromJson(Map<String, dynamic> json) =>
+      _$ParentLetterPersonFromJson(json);
+}
+
+/// Inbox entry from `GET parent-letters`. [childIds] are the opaque guardian
+/// child ids from `me/capabilities`.
+@freezed
+abstract class ParentLetterSummary with _$ParentLetterSummary {
+  const factory ParentLetterSummary({
+    required String id,
+    @Default('') String subject,
+    @Default('') String preview,
+    @Default(ParentLetterPerson()) ParentLetterPerson sender,
+    required DateTime sentAt,
+    DateTime? editedAt,
+    @Default(true) bool read,
+    @Default([]) List<String> childIds,
+    @Default(0) int attachmentCount,
+    @JsonKey(unknownEnumValue: ParentLetterStatus.info)
+    @Default(ParentLetterStatus.info)
+    ParentLetterStatus status,
+    DateTime? deadline,
+  }) = _ParentLetterSummary;
+
+  factory ParentLetterSummary.fromJson(Map<String, dynamic> json) =>
+      _$ParentLetterSummaryFromJson(json);
+}
+
+@freezed
+abstract class ParentLetterListResponse with _$ParentLetterListResponse {
+  const factory ParentLetterListResponse({
+    @Default([]) List<ParentLetterSummary> items,
+    @Default(false) bool hasMore,
+    @Default(0) int unreadCount,
+    @Default(0) int openCount,
+  }) = _ParentLetterListResponse;
+
+  factory ParentLetterListResponse.fromJson(Map<String, dynamic> json) =>
+      _$ParentLetterListResponseFromJson(json);
+}
+
+@freezed
+abstract class ParentLetterAttachment with _$ParentLetterAttachment {
+  const factory ParentLetterAttachment({
+    required String id,
+    @Default('') String fileName,
+    @Default('') String mimeType,
+    @Default(0) int size,
+  }) = _ParentLetterAttachment;
+
+  factory ParentLetterAttachment.fromJson(Map<String, dynamic> json) =>
+      _$ParentLetterAttachmentFromJson(json);
+}
+
+@freezed
+abstract class ParentLetterOption with _$ParentLetterOption {
+  const factory ParentLetterOption({
+    required String id,
+    @Default('') String label,
+  }) = _ParentLetterOption;
+
+  factory ParentLetterOption.fromJson(Map<String, dynamic> json) =>
+      _$ParentLetterOptionFromJson(json);
+}
+
+@freezed
+abstract class ParentLetterField with _$ParentLetterField {
+  const factory ParentLetterField({
+    required String id,
+    @JsonKey(unknownEnumValue: ParentLetterFieldType.unknown)
+    @Default(ParentLetterFieldType.unknown)
+    ParentLetterFieldType type,
+    @Default('') String label,
+    @JsonKey(name: 'required') @Default(false) bool isRequired,
+    @Default([]) List<ParentLetterOption> options,
+  }) = _ParentLetterField;
+
+  factory ParentLetterField.fromJson(Map<String, dynamic> json) =>
+      _$ParentLetterFieldFromJson(json);
+}
+
+/// What the sender asks for. No fields and no signature means a plain
+/// acknowledgement.
+@freezed
+abstract class ParentLetterRequest with _$ParentLetterRequest {
+  const factory ParentLetterRequest({
+    @Default([]) List<ParentLetterField> fields,
+    @Default(false) bool signatureRequired,
+    DateTime? deadline,
+  }) = _ParentLetterRequest;
+
+  factory ParentLetterRequest.fromJson(Map<String, dynamic> json) =>
+      _$ParentLetterRequestFromJson(json);
+}
+
+@freezed
+abstract class ParentLetterAnswer with _$ParentLetterAnswer {
+  const factory ParentLetterAnswer({
+    required String fieldId,
+    @Default([]) List<String> optionIds,
+    String? text,
+  }) = _ParentLetterAnswer;
+
+  factory ParentLetterAnswer.fromJson(Map<String, dynamic> json) =>
+      _$ParentLetterAnswerFromJson(json);
+}
+
+@freezed
+abstract class ParentLetterResponse with _$ParentLetterResponse {
+  const factory ParentLetterResponse({
+    DateTime? respondedAt,
+    @Default(ParentLetterPerson()) ParentLetterPerson respondedBy,
+    @Default([]) List<ParentLetterAnswer> answers,
+    @Default(false) bool signed,
+  }) = _ParentLetterResponse;
+
+  factory ParentLetterResponse.fromJson(Map<String, dynamic> json) =>
+      _$ParentLetterResponseFromJson(json);
+}
+
+/// Per-child state of a letter. [editable] is the server's verdict on whether
+/// this guardian may (re)submit right now.
+@freezed
+abstract class ParentLetterChildState with _$ParentLetterChildState {
+  const factory ParentLetterChildState({
+    required String childId,
+    @JsonKey(unknownEnumValue: ParentLetterStatus.info)
+    @Default(ParentLetterStatus.info)
+    ParentLetterStatus status,
+    @Default(false) bool editable,
+    ParentLetterResponse? response,
+  }) = _ParentLetterChildState;
+
+  factory ParentLetterChildState.fromJson(Map<String, dynamic> json) =>
+      _$ParentLetterChildStateFromJson(json);
+}
+
+@freezed
+abstract class ParentLetterThreadMessage with _$ParentLetterThreadMessage {
+  const factory ParentLetterThreadMessage({
+    required String id,
+    @Default(ParentLetterPerson()) ParentLetterPerson author,
+    @Default('') String body,
+    required DateTime sentAt,
+  }) = _ParentLetterThreadMessage;
+
+  factory ParentLetterThreadMessage.fromJson(Map<String, dynamic> json) =>
+      _$ParentLetterThreadMessageFromJson(json);
+}
+
+@freezed
+abstract class ParentLetterThread with _$ParentLetterThread {
+  const factory ParentLetterThread({
+    @Default(false) bool enabled,
+    @Default([]) List<ParentLetterThreadMessage> messages,
+  }) = _ParentLetterThread;
+
+  factory ParentLetterThread.fromJson(Map<String, dynamic> json) =>
+      _$ParentLetterThreadFromJson(json);
+}
+
+/// The detail-only part of `GET parent-letters/{id}`.
+@freezed
+abstract class ParentLetterContent with _$ParentLetterContent {
+  const factory ParentLetterContent({
+    @Default('') String body,
+    @Default([]) List<ParentLetterAttachment> attachments,
+    ParentLetterRequest? request,
+    @Default([]) List<ParentLetterChildState> children,
+    @Default(ParentLetterThread()) ParentLetterThread thread,
+  }) = _ParentLetterContent;
+
+  factory ParentLetterContent.fromJson(Map<String, dynamic> json) =>
+      _$ParentLetterContentFromJson(json);
+}
+
+/// A full letter. The server sends the inbox fields and the detail fields in
+/// one flat object; they are parsed into [summary] and [content] so the inbox
+/// entry can be replaced from a detail answer without copying fields.
+@immutable
+class ParentLetterDetail {
+  final ParentLetterSummary summary;
+  final ParentLetterContent content;
+
+  const ParentLetterDetail({required this.summary, required this.content});
+
+  factory ParentLetterDetail.fromJson(Map<String, dynamic> json) =>
+      ParentLetterDetail(
+        summary: ParentLetterSummary.fromJson(json),
+        content: ParentLetterContent.fromJson(json),
+      );
+
+  Map<String, dynamic> toJson() => {...summary.toJson(), ...content.toJson()};
+
+  @override
+  bool operator ==(Object other) =>
+      other is ParentLetterDetail &&
+      other.summary == summary &&
+      other.content == content;
+
+  @override
+  int get hashCode => Object.hash(summary, content);
+}

lib/api/marianumconnect/queries/parent_letters/parent_letter_models.g.dart

@@ -0,0 +1,331 @@
+// GENERATED CODE - DO NOT MODIFY BY HAND
+
+part of 'parent_letter_models.dart';
+
+// **************************************************************************
+// JsonSerializableGenerator
+// **************************************************************************
+
+_ParentLetterPerson _$ParentLetterPersonFromJson(Map<String, dynamic> json) =>
+    _ParentLetterPerson(
+      displayName: json['displayName'] as String? ?? '',
+      self: json['self'] as bool? ?? false,
+    );
+
+Map<String, dynamic> _$ParentLetterPersonToJson(_ParentLetterPerson instance) =>
+    <String, dynamic>{
+      'displayName': instance.displayName,
+      'self': instance.self,
+    };
+
+_ParentLetterSummary _$ParentLetterSummaryFromJson(Map<String, dynamic> json) =>
+    _ParentLetterSummary(
+      id: json['id'] as String,
+      subject: json['subject'] as String? ?? '',
+      preview: json['preview'] as String? ?? '',
+      sender: json['sender'] == null
+          ? const ParentLetterPerson()
+          : ParentLetterPerson.fromJson(json['sender'] as Map<String, dynamic>),
+      sentAt: DateTime.parse(json['sentAt'] as String),
+      editedAt: json['editedAt'] == null
+          ? null
+          : DateTime.parse(json['editedAt'] as String),
+      read: json['read'] as bool? ?? true,
+      childIds:
+          (json['childIds'] as List<dynamic>?)
+              ?.map((e) => e as String)
+              .toList() ??
+          const [],
+      attachmentCount: (json['attachmentCount'] as num?)?.toInt() ?? 0,
+      status:
+          $enumDecodeNullable(
+            _$ParentLetterStatusEnumMap,
+            json['status'],
+            unknownValue: ParentLetterStatus.info,
+          ) ??
+          ParentLetterStatus.info,
+      deadline: json['deadline'] == null
+          ? null
+          : DateTime.parse(json['deadline'] as String),
+    );
+
+Map<String, dynamic> _$ParentLetterSummaryToJson(
+  _ParentLetterSummary instance,
+) => <String, dynamic>{
+  'id': instance.id,
+  'subject': instance.subject,
+  'preview': instance.preview,
+  'sender': instance.sender,
+  'sentAt': instance.sentAt.toIso8601String(),
+  'editedAt': instance.editedAt?.toIso8601String(),
+  'read': instance.read,
+  'childIds': instance.childIds,
+  'attachmentCount': instance.attachmentCount,
+  'status': _$ParentLetterStatusEnumMap[instance.status]!,
+  'deadline': instance.deadline?.toIso8601String(),
+};
+
+const _$ParentLetterStatusEnumMap = {
+  ParentLetterStatus.info: 'info',
+  ParentLetterStatus.open: 'open',
+  ParentLetterStatus.done: 'done',
+  ParentLetterStatus.expired: 'expired',
+};
+
+_ParentLetterListResponse _$ParentLetterListResponseFromJson(
+  Map<String, dynamic> json,
+) => _ParentLetterListResponse(
+  items:
+      (json['items'] as List<dynamic>?)
+          ?.map((e) => ParentLetterSummary.fromJson(e as Map<String, dynamic>))
+          .toList() ??
+      const [],
+  hasMore: json['hasMore'] as bool? ?? false,
+  unreadCount: (json['unreadCount'] as num?)?.toInt() ?? 0,
+  openCount: (json['openCount'] as num?)?.toInt() ?? 0,
+);
+
+Map<String, dynamic> _$ParentLetterListResponseToJson(
+  _ParentLetterListResponse instance,
+) => <String, dynamic>{
+  'items': instance.items,
+  'hasMore': instance.hasMore,
+  'unreadCount': instance.unreadCount,
+  'openCount': instance.openCount,
+};
+
+_ParentLetterAttachment _$ParentLetterAttachmentFromJson(
+  Map<String, dynamic> json,
+) => _ParentLetterAttachment(
+  id: json['id'] as String,
+  fileName: json['fileName'] as String? ?? '',
+  mimeType: json['mimeType'] as String? ?? '',
+  size: (json['size'] as num?)?.toInt() ?? 0,
+);
+
+Map<String, dynamic> _$ParentLetterAttachmentToJson(
+  _ParentLetterAttachment instance,
+) => <String, dynamic>{
+  'id': instance.id,
+  'fileName': instance.fileName,
+  'mimeType': instance.mimeType,
+  'size': instance.size,
+};
+
+_ParentLetterOption _$ParentLetterOptionFromJson(Map<String, dynamic> json) =>
+    _ParentLetterOption(
+      id: json['id'] as String,
+      label: json['label'] as String? ?? '',
+    );
+
+Map<String, dynamic> _$ParentLetterOptionToJson(_ParentLetterOption instance) =>
+    <String, dynamic>{'id': instance.id, 'label': instance.label};
+
+_ParentLetterField _$ParentLetterFieldFromJson(Map<String, dynamic> json) =>
+    _ParentLetterField(
+      id: json['id'] as String,
+      type:
+          $enumDecodeNullable(
+            _$ParentLetterFieldTypeEnumMap,
+            json['type'],
+            unknownValue: ParentLetterFieldType.unknown,
+          ) ??
+          ParentLetterFieldType.unknown,
+      label: json['label'] as String? ?? '',
+      isRequired: json['required'] as bool? ?? false,
+      options:
+          (json['options'] as List<dynamic>?)
+              ?.map(
+                (e) => ParentLetterOption.fromJson(e as Map<String, dynamic>),
+              )
+              .toList() ??
+          const [],
+    );
+
+Map<String, dynamic> _$ParentLetterFieldToJson(_ParentLetterField instance) =>
+    <String, dynamic>{
+      'id': instance.id,
+      'type': _$ParentLetterFieldTypeEnumMap[instance.type]!,
+      'label': instance.label,
+      'required': instance.isRequired,
+      'options': instance.options,
+    };
+
+const _$ParentLetterFieldTypeEnumMap = {
+  ParentLetterFieldType.singleChoice: 'single_choice',
+  ParentLetterFieldType.unknown: 'unknown',
+};
+
+_ParentLetterRequest _$ParentLetterRequestFromJson(Map<String, dynamic> json) =>
+    _ParentLetterRequest(
+      fields:
+          (json['fields'] as List<dynamic>?)
+              ?.map(
+                (e) => ParentLetterField.fromJson(e as Map<String, dynamic>),
+              )
+              .toList() ??
+          const [],
+      signatureRequired: json['signatureRequired'] as bool? ?? false,
+      deadline: json['deadline'] == null
+          ? null
+          : DateTime.parse(json['deadline'] as String),
+    );
+
+Map<String, dynamic> _$ParentLetterRequestToJson(
+  _ParentLetterRequest instance,
+) => <String, dynamic>{
+  'fields': instance.fields,
+  'signatureRequired': instance.signatureRequired,
+  'deadline': instance.deadline?.toIso8601String(),
+};
+
+_ParentLetterAnswer _$ParentLetterAnswerFromJson(Map<String, dynamic> json) =>
+    _ParentLetterAnswer(
+      fieldId: json['fieldId'] as String,
+      optionIds:
+          (json['optionIds'] as List<dynamic>?)
+              ?.map((e) => e as String)
+              .toList() ??
+          const [],
+      text: json['text'] as String?,
+    );
+
+Map<String, dynamic> _$ParentLetterAnswerToJson(_ParentLetterAnswer instance) =>
+    <String, dynamic>{
+      'fieldId': instance.fieldId,
+      'optionIds': instance.optionIds,
+      'text': instance.text,
+    };
+
+_ParentLetterResponse _$ParentLetterResponseFromJson(
+  Map<String, dynamic> json,
+) => _ParentLetterResponse(
+  respondedAt: json['respondedAt'] == null
+      ? null
+      : DateTime.parse(json['respondedAt'] as String),
+  respondedBy: json['respondedBy'] == null
+      ? const ParentLetterPerson()
+      : ParentLetterPerson.fromJson(
+          json['respondedBy'] as Map<String, dynamic>,
+        ),
+  answers:
+      (json['answers'] as List<dynamic>?)
+          ?.map((e) => ParentLetterAnswer.fromJson(e as Map<String, dynamic>))
+          .toList() ??
+      const [],
+  signed: json['signed'] as bool? ?? false,
+);
+
+Map<String, dynamic> _$ParentLetterResponseToJson(
+  _ParentLetterResponse instance,
+) => <String, dynamic>{
+  'respondedAt': instance.respondedAt?.toIso8601String(),
+  'respondedBy': instance.respondedBy,
+  'answers': instance.answers,
+  'signed': instance.signed,
+};
+
+_ParentLetterChildState _$ParentLetterChildStateFromJson(
+  Map<String, dynamic> json,
+) => _ParentLetterChildState(
+  childId: json['childId'] as String,
+  status:
+      $enumDecodeNullable(
+        _$ParentLetterStatusEnumMap,
+        json['status'],
+        unknownValue: ParentLetterStatus.info,
+      ) ??
+      ParentLetterStatus.info,
+  editable: json['editable'] as bool? ?? false,
+  response: json['response'] == null
+      ? null
+      : ParentLetterResponse.fromJson(json['response'] as Map<String, dynamic>),
+);
+
+Map<String, dynamic> _$ParentLetterChildStateToJson(
+  _ParentLetterChildState instance,
+) => <String, dynamic>{
+  'childId': instance.childId,
+  'status': _$ParentLetterStatusEnumMap[instance.status]!,
+  'editable': instance.editable,
+  'response': instance.response,
+};
+
+_ParentLetterThreadMessage _$ParentLetterThreadMessageFromJson(
+  Map<String, dynamic> json,
+) => _ParentLetterThreadMessage(
+  id: json['id'] as String,
+  author: json['author'] == null
+      ? const ParentLetterPerson()
+      : ParentLetterPerson.fromJson(json['author'] as Map<String, dynamic>),
+  body: json['body'] as String? ?? '',
+  sentAt: DateTime.parse(json['sentAt'] as String),
+);
+
+Map<String, dynamic> _$ParentLetterThreadMessageToJson(
+  _ParentLetterThreadMessage instance,
+) => <String, dynamic>{
+  'id': instance.id,
+  'author': instance.author,
+  'body': instance.body,
+  'sentAt': instance.sentAt.toIso8601String(),
+};
+
+_ParentLetterThread _$ParentLetterThreadFromJson(Map<String, dynamic> json) =>
+    _ParentLetterThread(
+      enabled: json['enabled'] as bool? ?? false,
+      messages:
+          (json['messages'] as List<dynamic>?)
+              ?.map(
+                (e) => ParentLetterThreadMessage.fromJson(
+                  e as Map<String, dynamic>,
+                ),
+              )
+              .toList() ??
+          const [],
+    );
+
+Map<String, dynamic> _$ParentLetterThreadToJson(_ParentLetterThread instance) =>
+    <String, dynamic>{
+      'enabled': instance.enabled,
+      'messages': instance.messages,
+    };
+
+_ParentLetterContent _$ParentLetterContentFromJson(Map<String, dynamic> json) =>
+    _ParentLetterContent(
+      body: json['body'] as String? ?? '',
+      attachments:
+          (json['attachments'] as List<dynamic>?)
+              ?.map(
+                (e) =>
+                    ParentLetterAttachment.fromJson(e as Map<String, dynamic>),
+              )
+              .toList() ??
+          const [],
+      request: json['request'] == null
+          ? null
+          : ParentLetterRequest.fromJson(
+              json['request'] as Map<String, dynamic>,
+            ),
+      children:
+          (json['children'] as List<dynamic>?)
+              ?.map(
+                (e) =>
+                    ParentLetterChildState.fromJson(e as Map<String, dynamic>),
+              )
+              .toList() ??
+          const [],
+      thread: json['thread'] == null
+          ? const ParentLetterThread()
+          : ParentLetterThread.fromJson(json['thread'] as Map<String, dynamic>),
+    );
+
+Map<String, dynamic> _$ParentLetterContentToJson(
+  _ParentLetterContent instance,
+) => <String, dynamic>{
+  'body': instance.body,
+  'attachments': instance.attachments,
+  'request': instance.request,
+  'children': instance.children,
+  'thread': instance.thread,
+};

lib/api/marianumconnect/queries/parent_letters/parent_letter_query.dart

@@ -0,0 +1,18 @@
+import 'package:dio/dio.dart';
+
+import '../../../errors/app_exception.dart';
+import '../../marianumconnect_query.dart';
+import 'parent_letter_exception.dart';
+
+/// Base for the parent-letter calls: domain rejections surface as
+/// [ParentLetterException].
+abstract class ParentLetterQuery extends MarianumConnectQuery {
+  ParentLetterQuery({super.dio});
+
+  String letterPath(String letterId, [String suffix = '']) =>
+      'parent-letters/${Uri.encodeComponent(letterId)}$suffix';
+
+  @override
+  AppException mapError(DioException error) =>
+      ParentLetterException.fromDio(error);
+}

lib/api/marianumconnect/queries/parent_letters/post_parent_letter_thread_message.dart

@@ -0,0 +1,20 @@
+import 'parent_letter_models.dart';
+import 'parent_letter_query.dart';
+
+/// `POST parent-letters/{id}/thread`. [clientMessageId] makes a retry
+/// idempotent on the server.
+class PostParentLetterThreadMessage extends ParentLetterQuery {
+  PostParentLetterThreadMessage({super.dio});
+
+  Future<ParentLetterThreadMessage> run({
+    required String letterId,
+    required String body,
+    required String clientMessageId,
+  }) => guard(() async {
+    final response = await dio.post<Map<String, dynamic>>(
+      endpoint(letterPath(letterId, '/thread')),
+      data: {'body': body, 'clientMessageId': clientMessageId},
+    );
+    return ParentLetterThreadMessage.fromJson(response.data!);
+  });
+}

lib/api/marianumconnect/queries/parent_letters/submit_parent_letter_response.dart

@@ -0,0 +1,34 @@
+import 'dart:convert';
+import 'dart:typed_data';
+
+import 'parent_letter_models.dart';
+import 'parent_letter_query.dart';
+
+/// `PUT parent-letters/{id}/responses/{childId}`: creates or (while editable)
+/// replaces the response for one child. Answers with the updated letter.
+class SubmitParentLetterResponse extends ParentLetterQuery {
+  SubmitParentLetterResponse({super.dio});
+
+  Future<ParentLetterDetail> run({
+    required String letterId,
+    required String childId,
+    required List<ParentLetterAnswer> answers,
+    Uint8List? signaturePng,
+  }) => guard(() async {
+    final response = await dio.put<Map<String, dynamic>>(
+      endpoint(
+        letterPath(letterId, '/responses/${Uri.encodeComponent(childId)}'),
+      ),
+      data: {
+        'answers': [
+          for (final answer in answers)
+            {'fieldId': answer.fieldId, 'optionIds': answer.optionIds},
+        ],
+        'signaturePng': signaturePng == null
+            ? null
+            : base64Encode(signaturePng),
+      },
+    );
+    return ParentLetterDetail.fromJson(response.data!);
+  });
+}

lib/app.dart

@@ -11,6 +11,7 @@ import 'api/marianumconnect/queries/telemetry_heartbeat/telemetry_heartbeat.dart
 import 'main.dart';
 import 'model/data_cleaner.dart';
 import 'notification/notification_controller.dart';
+import 'notification/notification_service.dart';
 import 'notification/notification_tasks.dart';
 import 'push/push_registration.dart';
 import 'push/push_tap_router.dart';
@@ -119,18 +120,11 @@ class _AppState extends State<App> with WidgetsBindingObserver {
     }
   }
 
-  void _onPushTapPending() {
-    final token = PushTapRouter.pendingChatToken.value;
-    if (token == null || !mounted) return;
-    PushTapRouter.pendingChatToken.value = null;
-    NotificationTasks.navigateToTalk(context, chatToken: token);
-  }
-
-  void _onNewsletterTapPending() {
-    final id = PushTapRouter.pendingNewsletterId.value;
-    if (id == null || !mounted) return;
-    PushTapRouter.pendingNewsletterId.value = null;
-    AppRoutes.openNewsletterById(context, id: id);
+  void _onPushTargetPending() {
+    final target = PushTapRouter.pendingTarget.value;
+    if (target == null || !mounted) return;
+    PushTapRouter.pendingTarget.value = null;
+    NotificationTasks.openPushTarget(context, target);
   }
 
   Future<void> _handlePendingWidgetNavigation() async {
@@ -234,8 +228,12 @@ class _AppState extends State<App> with WidgetsBindingObserver {
 
     // Android renders pushes locally, so a tap arrives via the local
     // notifications callback (PushTapRouter) rather than onMessageOpenedApp.
-    PushTapRouter.pendingChatToken.addListener(_onPushTapPending);
-    PushTapRouter.pendingNewsletterId.addListener(_onNewsletterTapPending);
+    PushTapRouter.pendingTarget.addListener(_onPushTargetPending);
+    unawaited(
+      PushTapRouter.handleAppLaunch(
+        NotificationService().flutterLocalNotificationsPlugin,
+      ),
+    );
 
     _onMessageSub = FirebaseMessaging.onMessage.listen((message) {
       if (!mounted) return;
@@ -264,8 +262,7 @@ class _AppState extends State<App> with WidgetsBindingObserver {
     _onMessageSub?.cancel();
     _onMessageOpenedAppSub?.cancel();
     _fcmTokenRefreshSub?.cancel();
-    PushTapRouter.pendingChatToken.removeListener(_onPushTapPending);
-    PushTapRouter.pendingNewsletterId.removeListener(_onNewsletterTapPending);
+    PushTapRouter.pendingTarget.removeListener(_onPushTargetPending);
     ShareIntentListener.pending.removeListener(_handlePendingShare);
     ShareIntentListener.instance.detach();
     Main.bottomNavigator.removeListener(_onTabControllerChanged);

lib/main.dart

@@ -28,6 +28,7 @@ import 'auth_link/guardian_link_listener.dart';
 import 'background/widget_background_task.dart';
 import 'firebase_options.dart';
 import 'notification/notification_service.dart';
+import 'push/notification_permission_prompt.dart';
 import 'push/push_message_handler.dart';
 import 'push/push_registration.dart';
 import 'push/push_registration_store.dart';
@@ -43,6 +44,7 @@ import 'state/app/modules/chat/bloc/chat_bloc.dart';
 import 'state/app/modules/chat_list/bloc/chat_list_bloc.dart';
 import 'state/app/modules/children/child_selection_cubit.dart';
 import 'state/app/modules/nextcloud_capabilities/bloc/nextcloud_capabilities_cubit.dart';
+import 'state/app/modules/parent_letters/bloc/parent_letters_bloc.dart';
 import 'state/app/modules/settings/bloc/settings_cubit.dart';
 import 'state/app/modules/timetable/primary/primary_timetable_scope.dart';
 import 'storage/hydrated_storage_bootstrap.dart';
@@ -256,6 +258,7 @@ Future<void> main() async {
           create: (ctx) => ChatBloc(chatListBloc: ctx.read<ChatListBloc>()),
         ),
         BlocProvider<ChildSelectionCubit>(create: (_) => ChildSelectionCubit()),
+        BlocProvider<ParentLettersBloc>(create: (_) => ParentLettersBloc()),
       ],
       child: const PrimaryTimetableScope(child: Main()),
     ),
@@ -327,16 +330,27 @@ class _MainState extends State<Main> {
       capabilitiesCubit.load().then((_) {
         if (!mounted) return;
         _syncPush(settingsCubit, capabilitiesCubit);
+        _promptGuardianNotifications();
       }),
     );
     unawaited(context.read<NextcloudCapabilitiesCubit>().load());
   }
 
+  /// Waits for the post-login splash so the dialog never covers it; the
+  /// splash's completion calls this again.
+  void _promptGuardianNotifications() {
+    if (_showPostLoginSplash) return;
+    final overlayContext = AppRoutes.overlayContext;
+    if (overlayContext == null) return;
+    unawaited(maybePromptGuardianLoginNotifications(overlayContext));
+  }
+
   /// Warms the chat list and files root in the background so the first screen
   /// render hits populated data. The timetable needs no warm-up:
   /// PrimaryTimetableScope creates a freshly loading bloc per account.
   void _prefetchBaseData(BuildContext context) {
     unawaited(context.read<ChatListBloc>().refresh(silent: true));
+    unawaited(context.read<ParentLettersBloc>().refresh(silent: true));
     if (SessionManager().hasNextcloud) {
       unawaited(ListFilesCache.prefetchRootListing());
     }
@@ -482,6 +496,7 @@ class _MainState extends State<Main> {
                     final childSelectionCubit = context
                         .read<ChildSelectionCubit>();
                     final chatListBloc = context.read<ChatListBloc>();
+                    final parentLettersBloc = context.read<ParentLettersBloc>();
                     final chatBloc = context.read<ChatBloc>();
                     final nextcloudCapabilitiesCubit = context
                         .read<NextcloudCapabilitiesCubit>();
@@ -495,6 +510,7 @@ class _MainState extends State<Main> {
                           settingsCubit: settingsCubit,
                           childSelectionCubit: childSelectionCubit,
                           chatListBloc: chatListBloc,
+                          parentLettersBloc: parentLettersBloc,
                           chatBloc: chatBloc,
                           breakerBloc: breakerBloc,
                           capabilitiesCubit: capabilitiesCubit,
@@ -515,9 +531,10 @@ class _MainState extends State<Main> {
                             if (_showPostLoginSplash)
                               PostLoginSplash(
                                 key: const ValueKey('post-login-splash'),
-                                onComplete: () => setState(
-                                  () => _showPostLoginSplash = false,
-                                ),
+                                onComplete: () {
+                                  setState(() => _showPostLoginSplash = false);
+                                  _promptGuardianNotifications();
+                                },
                               ),
                           ],
                         );
@@ -541,6 +558,7 @@ Future<void> _wipeUserState({
   required SettingsCubit settingsCubit,
   required ChildSelectionCubit childSelectionCubit,
   required ChatListBloc chatListBloc,
+  required ParentLettersBloc parentLettersBloc,
   required ChatBloc chatBloc,
   required BreakerBloc breakerBloc,
   required CapabilitiesCubit capabilitiesCubit,
@@ -558,6 +576,7 @@ Future<void> _wipeUserState({
     await Future.wait([
       childSelectionCubit.reset(),
       chatListBloc.reset(),
+      parentLettersBloc.reset(),
       chatBloc.reset(),
       breakerBloc.reset(),
       capabilitiesCubit.reset(),

lib/notification/notification_controller.dart

@@ -5,7 +5,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
 
 import '../push/push_message_handler.dart';
-import '../routing/app_routes.dart';
+import '../push/push_target.dart';
 import '../state/app/modules/chat/bloc/chat_bloc.dart';
 import '../widget/debug/debug_tile.dart';
 import '../widget/debug/json_viewer.dart';
@@ -42,18 +42,15 @@ class NotificationController {
     RemoteMessage message,
     BuildContext context,
   ) async {
-    final newsletterId = _extractNewsletterId(message);
-    if (newsletterId != null) {
-      AppRoutes.openNewsletterById(
+    final target = resolvePushTarget(message.data);
+    if (target != null) {
+      NotificationTasks.openPushTarget(
         context,
-        id: newsletterId,
+        target,
         title: message.notification?.title,
       );
     } else {
-      NotificationTasks.navigateToTalk(
-        context,
-        chatToken: _extractChatToken(message),
-      );
+      NotificationTasks.navigateToTalk(context);
     }
     NotificationTasks.updateProviders(context);
     unawaited(NotificationTasks.refreshBadge());
@@ -68,17 +65,4 @@ class NotificationController {
       );
     });
   }
-
-  static String? _extractChatToken(RemoteMessage message) {
-    for (final key in const ['chatToken', 'token', 'roomToken']) {
-      final value = message.data[key];
-      if (value is String && value.isNotEmpty) return value;
-    }
-    return null;
-  }
-
-  static String? _extractNewsletterId(RemoteMessage message) {
-    final value = message.data['newsletterId'];
-    return value is String && value.isNotEmpty ? value : null;
-  }
 }

lib/notification/notification_tasks.dart

@@ -7,10 +7,13 @@ import 'package:flutter_app_badge/flutter_app_badge.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
 
 import '../push/chat_thread_store.dart';
+import '../push/push_renderer.dart';
+import '../push/push_target.dart';
 import '../routing/app_routes.dart';
 import '../session/session_manager.dart';
 import '../state/app/modules/app_modules.dart';
 import '../state/app/modules/chat_list/bloc/chat_list_bloc.dart';
+import '../state/app/modules/parent_letters/bloc/parent_letters_bloc.dart';
 import 'notification_service.dart';
 
 class NotificationTasks {
@@ -72,6 +75,41 @@ class NotificationTasks {
   /// even if the user has already left.
   static void updateProviders(BuildContext context) {
     context.read<ChatListBloc>().refresh();
+    context.read<ParentLettersBloc>().refresh(silent: true);
+  }
+
+  /// [title] is the notification title, when the tap came with one.
+  static void openPushTarget(
+    BuildContext context,
+    PushTarget target, {
+    String? title,
+  }) {
+    switch (target) {
+      case ParentLetterTarget(:final letterId):
+        if (AppModule.isAvailableFor(
+          Modules.parentLetters,
+          SessionManager().current,
+        )) {
+          AppRoutes.openParentLetter(context, id: letterId);
+        }
+      case NewsletterTarget(:final newsletterId):
+        AppRoutes.openNewsletterById(context, id: newsletterId, title: title);
+      case ChatTarget(:final chatToken):
+        navigateToTalk(context, chatToken: chatToken);
+    }
+  }
+
+  /// Removes the letter's tray notification (Android; iOS alerts are posted by
+  /// the system and cannot be addressed by id).
+  static Future<void> clearParentLetterNotification(String letterId) async {
+    try {
+      await NotificationService().flutterLocalNotificationsPlugin.cancel(
+        id: PushRenderer.parentLetterNotificationId(letterId),
+      );
+      await refreshBadge();
+    } on Object catch (e) {
+      log('Parent letter notification cleanup failed: $e');
+    }
   }
 
   /// Switches to the Talk tab. If [chatToken] is provided, also schedules

lib/push/notification_permission_prompt.dart

@@ -0,0 +1,190 @@
+import 'dart:async';
+import 'dart:developer';
+
+import 'package:app_settings/app_settings.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+
+import '../session/session_manager.dart';
+import '../state/app/modules/app_modules.dart';
+import '../state/app/modules/capabilities/bloc/capabilities_cubit.dart';
+import '../state/app/modules/settings/bloc/settings_cubit.dart';
+import '../storage/notification_settings.dart';
+import '../widget/confirm_dialog.dart';
+import 'push_registration.dart';
+
+const _talkExplanation =
+    'Damit du keine neuen Nachrichten im Talk verpasst, fragen wir dich '
+    'gleich nach der Erlaubnis für Benachrichtigungen. Bitte akzeptiere '
+    'sie, um Push-Nachrichten zu erhalten.';
+const _talkDeclinedNote =
+    'Ohne die Berechtigung erhältst du keine Benachrichtigungen bei neuen '
+    'Talk-Nachrichten. Du kannst sie jederzeit in den Systemeinstellungen '
+    'deines Geräts nachträglich aktivieren.';
+const _parentLetterExplanation =
+    'Damit du keine Elternbriefe der Schule verpasst, fragen wir dich gleich '
+    'nach der Erlaubnis für Benachrichtigungen. Bitte akzeptiere sie, um '
+    'Push-Nachrichten zu erhalten.';
+const _parentLetterDeclinedNote =
+    'Ohne die Berechtigung erhältst du keine Benachrichtigungen bei neuen '
+    'Elternbriefen. Du kannst sie jederzeit in den Systemeinstellungen deines '
+    'Geräts nachträglich aktivieren.';
+
+/// The occasions with a guided notification-permission flow. Each runs at
+/// most once per install, guarded by its own flag in [NotificationSettings].
+enum _PermissionPrompt {
+  talkVisit(_talkExplanation, _talkDeclinedNote),
+  guardianLogin(
+    _parentLetterExplanation,
+    _parentLetterDeclinedNote,
+    module: Modules.parentLetters,
+    spentOnDisplay: true,
+  ),
+  parentLettersVisit(
+    _parentLetterExplanation,
+    _parentLetterDeclinedNote,
+    module: Modules.parentLetters,
+  );
+
+  const _PermissionPrompt(
+    this.explanation,
+    this.declinedNote, {
+    this.module,
+    this.spentOnDisplay = false,
+  });
+
+  final String explanation;
+  final String declinedNote;
+
+  /// Only sessions that have this module are asked.
+  final Modules? module;
+
+  /// Spends the one-shot as soon as the explanation is displayed, so a
+  /// dismissed dialog does not come back on every app start.
+  final bool spentOnDisplay;
+
+  bool wasShown(NotificationSettings settings) => switch (this) {
+    talkVisit => settings.talkPermissionPromptShown,
+    guardianLogin => settings.guardianLoginPromptShown,
+    parentLettersVisit => settings.parentLettersPromptShown,
+  };
+
+  void markShown(NotificationSettings settings) {
+    switch (this) {
+      case talkVisit:
+        settings.talkPermissionPromptShown = true;
+      case guardianLogin:
+        settings.guardianLoginPromptShown = true;
+      case parentLettersVisit:
+        settings.parentLettersPromptShown = true;
+    }
+  }
+}
+
+/// Shows the one-time notification-permission flow on the first Talk visit.
+///
+/// The OS prompt is deliberately kept out of the cold-start path (younger users
+/// decline it reflexively before ever seeing why they'd want it). Instead, the
+/// first time Talk is opened we explain the request, then trigger the OS prompt,
+/// and — if declined — offer a shortcut to the system settings.
+///
+/// Runs at most once per install (guarded by `talkPermissionPromptShown`).
+Future<void> maybePromptTalkNotifications(BuildContext context) =>
+    _maybePrompt(context, _PermissionPrompt.talkVisit);
+
+/// Accounts that receive parent letters never reach the Talk flow, so they
+/// are asked once right after signing in.
+Future<void> maybePromptGuardianLoginNotifications(BuildContext context) =>
+    _maybePrompt(context, _PermissionPrompt.guardianLogin);
+
+/// Second chance with context: explains the request once more on the first
+/// visit of the parent letters when the permission is still missing.
+Future<void> maybePromptParentLetterNotifications(BuildContext context) =>
+    _maybePrompt(context, _PermissionPrompt.parentLettersVisit);
+
+bool _promptInFlight = false;
+
+Future<void> _maybePrompt(
+  BuildContext context,
+  _PermissionPrompt prompt,
+) async {
+  final module = prompt.module;
+  if (module != null &&
+      !AppModule.isAvailableFor(module, SessionManager().current)) {
+    return;
+  }
+
+  final settings = context.read<SettingsCubit>();
+  final notificationSettings = settings.val().notificationSettings;
+
+  // Already handled once, or the user opted out of push entirely.
+  if (prompt.wasShown(notificationSettings)) return;
+  if (!notificationSettings.enabled) return;
+
+  // Capabilities may still be loading on a fresh cold start; retry on the next
+  // occasion instead of burning the one-shot flag.
+  if (!context.read<CapabilitiesCubit>().canReceivePushNotifications) return;
+
+  if (_promptInFlight) return;
+  _promptInFlight = true;
+  try {
+    // Users who already granted the permission: register silently and mark the
+    // prompt as handled without showing any dialog.
+    if (await PushRegistration.isOsPermissionGranted()) {
+      prompt.markShown(settings.val(write: true).notificationSettings);
+      unawaited(PushRegistration().register());
+      return;
+    }
+
+    if (!context.mounted) return;
+
+    if (prompt.spentOnDisplay) {
+      prompt.markShown(settings.val(write: true).notificationSettings);
+    }
+    await showDialog<void>(
+      context: context,
+      builder: ConfirmDialog(
+        icon: Icons.notifications_active_outlined,
+        title: 'Benachrichtigungen aktivieren',
+        content: prompt.explanation,
+        confirmButton: 'Weiter',
+        cancelButton: null,
+        onConfirm: () =>
+            unawaited(_requestPermission(context, settings, prompt)),
+      ).build,
+    );
+  } finally {
+    _promptInFlight = false;
+  }
+}
+
+Future<void> _requestPermission(
+  BuildContext context,
+  SettingsCubit settings,
+  _PermissionPrompt prompt,
+) async {
+  final granted = await PushRegistration.requestOsPermission();
+
+  // Mark handled regardless of the outcome — the user can re-enable later via
+  // the system settings; we don't want to prompt again on the next occasion.
+  prompt.markShown(settings.val(write: true).notificationSettings);
+
+  if (granted) {
+    unawaited(PushRegistration().register());
+    return;
+  }
+
+  log('Push: notification permission declined on ${prompt.name}');
+
+  if (!context.mounted) return;
+
+  ConfirmDialog(
+    icon: Icons.notifications_off_outlined,
+    title: 'Benachrichtigungen deaktiviert',
+    content: prompt.declinedNote,
+    confirmButton: 'Einstellungen öffnen',
+    cancelButton: 'Später',
+    onConfirm: () =>
+        AppSettings.openAppSettings(type: AppSettingsType.notification),
+  ).asDialog(context);
+}

lib/push/push_renderer.dart

@@ -12,6 +12,7 @@ import 'nid_store.dart';
 import 'push_actions.dart';
 import 'push_avatar.dart';
 import 'push_subject.dart';
+import 'push_target.dart';
 
 /// Renders decrypted push subjects (and plaintext Connect pushes) as local
 /// notifications. Talk messages of one chat stack into a SINGLE
@@ -23,6 +24,8 @@ class PushRenderer {
   static const talkChannelName = 'Talk-Nachrichten';
   static const generalChannelId = 'nextcloud_general';
   static const generalChannelName = 'Benachrichtigungen';
+  static const parentLettersChannelId = 'parent_letters';
+  static const parentLettersChannelName = 'Elternbriefe';
 
   static const String iosTalkCategory = 'TALK_MESSAGE';
 
@@ -67,6 +70,14 @@ class PushRenderer {
         description: 'Allgemeine Benachrichtigungen',
       ),
     );
+    await android.createNotificationChannel(
+      const AndroidNotificationChannel(
+        parentLettersChannelId,
+        parentLettersChannelName,
+        description: 'Neue Elternbriefe und Antworten der Schule',
+        importance: Importance.high,
+      ),
+    );
   }
 
   /// Renders a decrypted Nextcloud push subject.
@@ -350,23 +361,35 @@ class PushRenderer {
     required String body,
     Map<String, String>? data,
   }) async {
-    final id = _fallbackId('$title$body');
-    const androidDetails = AndroidNotificationDetails(
-      generalChannelId,
-      generalChannelName,
+    final parentLetterId = data?[parentLetterIdKey];
+    final isParentLetter =
+        data?['type'] == parentLetterPushType &&
+        parentLetterId != null &&
+        parentLetterId.isNotEmpty;
+    // One notification per letter: a reply replaces the letter's earlier one.
+    final id = isParentLetter
+        ? parentLetterNotificationId(parentLetterId)
+        : _fallbackId('$title$body');
+    final androidDetails = AndroidNotificationDetails(
+      isParentLetter ? parentLettersChannelId : generalChannelId,
+      isParentLetter ? parentLettersChannelName : generalChannelName,
       importance: Importance.high,
       priority: Priority.high,
       color: _accentColor,
+      styleInformation: isParentLetter ? BigTextStyleInformation(body) : null,
     );
     await _plugin.show(
       id: id,
       title: title,
       body: body,
-      notificationDetails: const NotificationDetails(android: androidDetails),
+      notificationDetails: NotificationDetails(android: androidDetails),
       payload: data == null ? null : jsonEncode(data),
     );
   }
 
+  static int parentLetterNotificationId(String letterId) =>
+      stableChatNotificationId('parent-letter:$letterId');
+
   String _payload({required String? chatToken, required int nid}) =>
       jsonEncode({'chatToken': ?chatToken, 'nid': nid});
 

lib/push/push_tap_router.dart

@@ -1,24 +1,22 @@
 import 'dart:convert';
+import 'dart:developer';
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter_local_notifications/flutter_local_notifications.dart';
 
 import 'push_actions.dart';
+import 'push_target.dart';
 
 /// Routes foreground notification interactions from the single
 /// flutter_local_notifications response callback. Action responses (reply /
 /// mark-read) are dispatched straight to [PushActions]; a plain tap publishes
-/// the target chat token via [pendingChatToken] for [App] to navigate to.
+/// its target via [pendingTarget] for [App] to navigate to.
 class PushTapRouter {
   PushTapRouter._();
 
-  /// Chat token of the most recently tapped Talk notification, or null. [App]
-  /// listens to this and opens the chat, then resets it to null.
-  static final ValueNotifier<String?> pendingChatToken = ValueNotifier(null);
-
-  /// Newsletter id of the most recently tapped Marianum-Message notification,
-  /// or null. [App] listens to this and opens the message, then resets it.
-  static final ValueNotifier<String?> pendingNewsletterId = ValueNotifier(null);
+  /// Target of the most recently tapped notification, or null. [App] listens
+  /// to this and navigates, then resets it to null.
+  static final ValueNotifier<PushTarget?> pendingTarget = ValueNotifier(null);
 
   static void handleResponse(NotificationResponse response) {
     final actionId = response.actionId;
@@ -29,13 +27,28 @@ class PushTapRouter {
     }
     final map = _payloadMap(response.payload);
     if (map == null) return;
-    final newsletterId = _stringValue(map, 'newsletterId');
-    if (newsletterId != null) {
-      pendingNewsletterId.value = newsletterId;
-      return;
+    final target = resolvePushTarget(map);
+    if (target != null) pendingTarget.value = target;
+  }
+
+  static bool _launchHandled = false;
+
+  /// Routes the tap that cold-started the app. The plugin reports such a tap
+  /// only through its launch details, never through the response callback;
+  /// the details stay set for the whole process, hence the one-shot guard.
+  static Future<void> handleAppLaunch(
+    FlutterLocalNotificationsPlugin plugin,
+  ) async {
+    if (_launchHandled) return;
+    _launchHandled = true;
+    try {
+      final details = await plugin.getNotificationAppLaunchDetails();
+      final response = details?.notificationResponse;
+      if (details?.didNotificationLaunchApp != true || response == null) return;
+      handleResponse(response);
+    } on Object catch (e) {
+      log('Reading the notification launch details failed: $e');
     }
-    final token = _stringValue(map, 'chatToken');
-    if (token != null) pendingChatToken.value = token;
   }
 
   static Map<String, dynamic>? _payloadMap(String? payload) {
@@ -46,9 +59,4 @@ class PushTapRouter {
       return null;
     }
   }
-
-  static String? _stringValue(Map<String, dynamic> map, String key) {
-    final value = map[key];
-    return value is String && value.isNotEmpty ? value : null;
-  }
 }

lib/push/push_target.dart

@@ -0,0 +1,45 @@
+/// `type` of the visible Connect push for a parent letter. Its data carries
+/// the letter under [parentLetterIdKey].
+const String parentLetterPushType = 'parent-letter';
+const String parentLetterIdKey = 'parentLetterId';
+
+/// Where a tapped notification leads.
+sealed class PushTarget {
+  const PushTarget();
+}
+
+class ParentLetterTarget extends PushTarget {
+  final String letterId;
+  const ParentLetterTarget(this.letterId);
+}
+
+class NewsletterTarget extends PushTarget {
+  final String newsletterId;
+  const NewsletterTarget(this.newsletterId);
+}
+
+class ChatTarget extends PushTarget {
+  final String chatToken;
+  const ChatTarget(this.chatToken);
+}
+
+/// Resolves the data of a tapped notification — the payload of a locally
+/// rendered one as well as the data of an FCM message. Null when it names no
+/// known target.
+PushTarget? resolvePushTarget(Map<String, dynamic> data) {
+  String? value(String key) {
+    final value = data[key];
+    return value is String && value.isNotEmpty ? value : null;
+  }
+
+  if (value(parentLetterIdKey) case final letterId?) {
+    return ParentLetterTarget(letterId);
+  }
+  if (value('newsletterId') case final newsletterId?) {
+    return NewsletterTarget(newsletterId);
+  }
+  for (final key in const ['chatToken', 'token', 'roomToken']) {
+    if (value(key) case final chatToken?) return ChatTarget(chatToken);
+  }
+  return null;
+}

lib/routing/app_routes.dart

@@ -26,6 +26,7 @@ import '../view/pages/marianum_message/marianum_message_view.dart';
 import '../view/pages/more/feedback/feedback_dialog.dart';
 import '../view/pages/more/roomplan/roomplan.dart';
 import '../view/pages/more/share/qr_share_view.dart';
+import '../view/pages/parent_letters/parent_letter_view.dart';
 import '../view/pages/settings/chat_background_settings_page.dart';
 import '../view/pages/settings/modules_settings_page.dart';
 import '../view/pages/settings/settings.dart';
@@ -203,6 +204,12 @@ class AppRoutes {
     );
   }
 
+  /// Opens a parent letter by id — from the inbox as well as from push deep
+  /// links, where only the id is known.
+  static void openParentLetter(BuildContext context, {required String id}) {
+    pushScreen(context, withNavBar: false, screen: ParentLetterView(id: id));
+  }
+
   /// Opens a ticker page (CONTENT or PROXIED_FILE) as a standalone detail
   /// screen. Used for deep links from outside the ticker module — inside the
   /// module pages open in-place instead.

lib/state/app/modules/app_modules.dart

@@ -1,4 +1,3 @@
-import 'package:badges/badges.dart' as badges;
 import 'package:flutter/material.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
 import 'package:persistent_bottom_nav_bar_v2/persistent_bottom_nav_bar_v2.dart';
@@ -16,14 +15,18 @@ import '../../../view/pages/holidays/holidays_view.dart';
 import '../../../view/pages/marianum_dates/marianum_dates_view.dart';
 import '../../../view/pages/marianum_message/marianum_message_list_view.dart';
 import '../../../view/pages/more/roomplan/roomplan.dart';
+import '../../../view/pages/parent_letters/parent_letters_view.dart';
 import '../../../view/pages/talk/chat_list.dart';
 import '../../../view/pages/ticker/ticker_view.dart';
 import '../../../view/pages/timetable/timetable.dart';
 import '../../../widget/breaker/breaker.dart';
 import '../../../widget/centered_leading.dart';
+import '../../../widget/module_badge_icon.dart';
 import '../infrastructure/loadable_state/loadable_state.dart';
 import 'chat_list/bloc/chat_list_bloc.dart';
 import 'chat_list/bloc/chat_list_state.dart';
+import 'parent_letters/bloc/parent_letters_bloc.dart';
+import 'parent_letters/bloc/parent_letters_state.dart';
 import 'settings/bloc/settings_cubit.dart';
 
 class AppModule {
@@ -46,6 +49,7 @@ class AppModule {
   static const Map<Modules, Set<AccessRequirement>> requirements = {
     Modules.talk: {AccessRequirement.nextcloud},
     Modules.files: {AccessRequirement.nextcloud},
+    Modules.parentLetters: {AccessRequirement.guardian},
   };
 
   static bool isAvailableFor(Modules module, Session? session) =>
@@ -64,6 +68,18 @@ class AppModule {
         breakerArea: BreakerArea.timetable,
         create: Timetable.new,
       ),
+      Modules.parentLetters: AppModule(
+        Modules.parentLetters,
+        name: 'Elternbriefe',
+        icon: () =>
+            BlocBuilder<ParentLettersBloc, LoadableState<ParentLettersState>>(
+              builder: (context, state) => ModuleBadgeIcon(
+                icon: Icons.mail_outline,
+                count: state.data?.unreadCount ?? 0,
+              ),
+            ),
+        create: ParentLettersView.new,
+      ),
       Modules.ticker: AppModule(
         Modules.ticker,
         name: 'Ticker',
@@ -77,34 +93,15 @@ class AppModule {
         Modules.talk,
         name: 'Talk',
         icon: () => BlocBuilder<ChatListBloc, LoadableState<ChatListState>>(
-          builder: (context, state) {
-            final rooms = state.data?.rooms;
-            if (rooms == null || rooms.data.isEmpty) {
-              return const Icon(Icons.chat);
-            }
-            final messages = rooms.data
-                .map((e) => e.unreadMessages)
-                .reduce((a, b) => a + b);
-            return badges.Badge(
-              showBadge: messages > 0,
-              position: badges.BadgePosition.topEnd(top: -3, end: -3),
-              stackFit: StackFit.loose,
-              badgeStyle: badges.BadgeStyle(
-                padding: const EdgeInsets.all(3),
-                badgeColor: Theme.of(context).primaryColor,
-                elevation: 1,
+          builder: (context, state) => ModuleBadgeIcon(
+            icon: Icons.chat,
+            count:
+                state.data?.rooms?.data.fold<int>(
+                  0,
+                  (sum, room) => sum + room.unreadMessages,
+                ) ??
+                0,
           ),
-              badgeContent: Text(
-                '$messages',
-                style: const TextStyle(
-                  color: Colors.white,
-                  fontSize: 10,
-                  fontWeight: FontWeight.bold,
-                ),
-              ),
-              child: const Icon(Icons.chat),
-            );
-          },
         ),
         breakerArea: BreakerArea.talk,
         create: ChatList.new,
@@ -299,6 +296,7 @@ class AppModule {
 
 enum Modules {
   timetable,
+  parentLetters,
   ticker,
   talk,
   files,

lib/state/app/modules/parent_letters/bloc/parent_letter_bloc.dart

@@ -0,0 +1,103 @@
+import 'dart:async';
+import 'dart:typed_data';
+
+import '../../../../../api/marianumconnect/queries/parent_letters/parent_letter_exception.dart';
+import '../../../../../api/marianumconnect/queries/parent_letters/parent_letter_models.dart';
+import '../../../../../utils/random_id.dart';
+import '../../../infrastructure/utility_widgets/loadable_hydrated_bloc/loadable_hydrated_bloc.dart';
+import '../../../infrastructure/utility_widgets/loadable_hydrated_bloc/loadable_hydrated_bloc_event.dart';
+import '../repository/parent_letter_repository.dart';
+import 'parent_letter_event.dart';
+import 'parent_letter_state.dart';
+import 'parent_letters_bloc.dart';
+
+/// One letter; [id] is the letter id so each letter keeps its own hydrated
+/// cache entry. Changes are mirrored into the app-wide [inbox].
+class ParentLetterBloc
+    extends
+        LoadableHydratedBloc<
+          ParentLetterEvent,
+          ParentLetterState,
+          ParentLetterRepository
+        > {
+  final String letterId;
+  final ParentLettersBloc inbox;
+
+  ParentLetterBloc(this.letterId, {required this.inbox});
+
+  @override
+  String get id => letterId;
+
+  @override
+  Future<void> gatherData() async {
+    final ParentLetterDetail letter;
+    try {
+      letter = await repo.getLetter(letterId);
+    } on ParentLetterException catch (e) {
+      if (e.error == ParentLetterError.letterNotFound) {
+        // Withdrawn: a hydrated copy must not stay readable.
+        add(Emit((state) => state.copyWith(letter: null)));
+        unawaited(inbox.refresh(silent: true));
+      }
+      rethrow;
+    }
+    add(DataGathered((state) => state.copyWith(letter: letter)));
+    if (!letter.summary.read) inbox.markRead(letterId);
+  }
+
+  Future<void> submitResponse({
+    required String childId,
+    required List<ParentLetterAnswer> answers,
+    Uint8List? signaturePng,
+  }) async {
+    final letter = await repo.submitResponse(
+      letterId: letterId,
+      childId: childId,
+      answers: answers,
+      signaturePng: signaturePng,
+    );
+    if (isClosed) return;
+    add(Emit((state) => state.copyWith(letter: letter)));
+    inbox.applyDetail(letter);
+  }
+
+  Future<void> sendThreadMessage(String body) async {
+    final message = await repo.sendThreadMessage(
+      letterId: letterId,
+      body: body,
+      clientMessageId: randomUuidV4(),
+    );
+    if (isClosed) return;
+    add(
+      Emit((state) {
+        final letter = state.letter;
+        if (letter == null) return state;
+        final thread = letter.content.thread;
+        return state.copyWith(
+          letter: ParentLetterDetail(
+            summary: letter.summary,
+            content: letter.content.copyWith(
+              thread: thread.copyWith(messages: [...thread.messages, message]),
+            ),
+          ),
+        );
+      }),
+    );
+  }
+
+  Future<Uint8List> loadAttachment(String attachmentId) =>
+      repo.getAttachment(letterId: letterId, attachmentId: attachmentId);
+
+  @override
+  ParentLetterRepository repository() => ParentLetterRepository();
+
+  @override
+  ParentLetterState fromNothing() => const ParentLetterState();
+
+  @override
+  ParentLetterState fromStorage(Map<String, dynamic> json) =>
+      ParentLetterState.fromJson(json);
+
+  @override
+  Map<String, dynamic>? toStorage(ParentLetterState state) => state.toJson();
+}

lib/state/app/modules/parent_letters/bloc/parent_letter_event.dart

@@ -0,0 +1,5 @@
+import '../../../infrastructure/utility_widgets/loadable_hydrated_bloc/loadable_hydrated_bloc_event.dart';
+import 'parent_letter_state.dart';
+
+sealed class ParentLetterEvent
+    extends LoadableHydratedBlocEvent<ParentLetterState> {}

lib/state/app/modules/parent_letters/bloc/parent_letter_state.dart

@@ -0,0 +1,15 @@
+import 'package:freezed_annotation/freezed_annotation.dart';
+
+import '../../../../../api/marianumconnect/queries/parent_letters/parent_letter_models.dart';
+
+part 'parent_letter_state.freezed.dart';
+part 'parent_letter_state.g.dart';
+
+@freezed
+abstract class ParentLetterState with _$ParentLetterState {
+  const factory ParentLetterState({ParentLetterDetail? letter}) =
+      _ParentLetterState;
+
+  factory ParentLetterState.fromJson(Map<String, dynamic> json) =>
+      _$ParentLetterStateFromJson(json);
+}

lib/state/app/modules/parent_letters/bloc/parent_letter_state.freezed.dart

@@ -0,0 +1,285 @@
+// GENERATED CODE - DO NOT MODIFY BY HAND
+// coverage:ignore-file
+// ignore_for_file: type=lint, type=warning, deprecated_member_use, deprecated_member_use_from_same_package
+// ignore_for_file: unused_element, deprecated_member_use, deprecated_member_use_from_same_package, use_function_type_syntax_for_parameters, unnecessary_const, avoid_init_to_null, invalid_override_different_default_values_named, prefer_expression_function_bodies, annotate_overrides, invalid_annotation_target, unnecessary_question_mark
+
+part of 'parent_letter_state.dart';
+
+// **************************************************************************
+// FreezedGenerator
+// **************************************************************************
+
+// GENERATED CODE - DO NOT MODIFY BY HAND
+// dart format off
+T _$identity<T>(T value) => value;
+
+/// @nodoc
+mixin _$ParentLetterState {
+
+ ParentLetterDetail? get letter;
+/// Create a copy of ParentLetterState
+/// with the given fields replaced by the non-null parameter values.
+@JsonKey(includeFromJson: false, includeToJson: false)
+@pragma('vm:prefer-inline')
+$ParentLetterStateCopyWith<ParentLetterState> get copyWith => _$ParentLetterStateCopyWithImpl<ParentLetterState>(this as ParentLetterState, _$identity);
+
+  /// Serializes this ParentLetterState to a JSON map.
+  Map<String, dynamic> toJson();
+
+
+@override
+bool operator ==(Object other) {
+  final _this = this as ParentLetterState;
+  return identical(this, other) || (other.runtimeType == runtimeType&&other is ParentLetterState&&(identical(other.letter, _this.letter) || other.letter == _this.letter));
+}
+
+@JsonKey(includeFromJson: false, includeToJson: false)
+@override
+int get hashCode {
+  final _this = this as ParentLetterState;
+  return Object.hash(runtimeType,_this.letter);
+}
+
+@override
+String toString() {
+  final _this = this as ParentLetterState;
+  return 'ParentLetterState(letter: ${_this.letter})';
+}
+
+
+}
+
+/// @nodoc
+abstract mixin class $ParentLetterStateCopyWith<$Res>  {
+  factory $ParentLetterStateCopyWith(ParentLetterState value, $Res Function(ParentLetterState) _then) = _$ParentLetterStateCopyWithImpl;
+@useResult
+$Res call({
+ ParentLetterDetail? letter
+});
+
+
+
+
+}
+/// @nodoc
+class _$ParentLetterStateCopyWithImpl<$Res>
+    implements $ParentLetterStateCopyWith<$Res> {
+  _$ParentLetterStateCopyWithImpl(this._self, this._then);
+
+  final ParentLetterState _self;
+  final $Res Function(ParentLetterState) _then;
+
+/// Create a copy of ParentLetterState
+/// with the given fields replaced by the non-null parameter values.
+@pragma('vm:prefer-inline') @override $Res call({Object? letter = freezed,}) {
+  return _then(ParentLetterState(
+letter: freezed == letter ? _self.letter : letter // ignore: cast_nullable_to_non_nullable
+as ParentLetterDetail?,
+  ));
+}
+
+}
+
+
+/// Adds pattern-matching-related methods to [ParentLetterState].
+extension ParentLetterStatePatterns on ParentLetterState {
+/// A variant of `map` that fallback to returning `orElse`.
+///
+/// It is equivalent to doing:
+/// ```dart
+/// switch (sealedClass) {
+///   case final Subclass value:
+///     return ...;
+///   case _:
+///     return orElse();
+/// }
+/// ```
+
+@optionalTypeArgs TResult maybeMap<TResult extends Object?>(TResult Function( _ParentLetterState value)?  $default,{required TResult orElse(),}){
+final _that = this;
+switch (_that) {
+case _ParentLetterState() when $default != null:
+return $default(_that);case _:
+  return orElse();
+
+}
+}
+/// A `switch`-like method, using callbacks.
+///
+/// Callbacks receives the raw object, upcasted.
+/// It is equivalent to doing:
+/// ```dart
+/// switch (sealedClass) {
+///   case final Subclass value:
+///     return ...;
+///   case final Subclass2 value:
+///     return ...;
+/// }
+/// ```
+
+@optionalTypeArgs TResult map<TResult extends Object?>(TResult Function( _ParentLetterState value)  $default,){
+final _that = this;
+switch (_that) {
+case _ParentLetterState():
+return $default(_that);case _:
+  throw StateError('Unexpected subclass');
+
+}
+}
+/// A variant of `map` that fallback to returning `null`.
+///
+/// It is equivalent to doing:
+/// ```dart
+/// switch (sealedClass) {
+///   case final Subclass value:
+///     return ...;
+///   case _:
+///     return null;
+/// }
+/// ```
+
+@optionalTypeArgs TResult? mapOrNull<TResult extends Object?>(TResult? Function( _ParentLetterState value)?  $default,){
+final _that = this;
+switch (_that) {
+case _ParentLetterState() when $default != null:
+return $default(_that);case _:
+  return null;
+
+}
+}
+/// A variant of `when` that fallback to an `orElse` callback.
+///
+/// It is equivalent to doing:
+/// ```dart
+/// switch (sealedClass) {
+///   case Subclass(:final field):
+///     return ...;
+///   case _:
+///     return orElse();
+/// }
+/// ```
+
+@optionalTypeArgs TResult maybeWhen<TResult extends Object?>(TResult Function( ParentLetterDetail? letter)?  $default,{required TResult orElse(),}) {final _that = this;
+switch (_that) {
+case _ParentLetterState() when $default != null:
+return $default(_that.letter);case _:
+  return orElse();
+
+}
+}
+/// A `switch`-like method, using callbacks.
+///
+/// As opposed to `map`, this offers destructuring.
+/// It is equivalent to doing:
+/// ```dart
+/// switch (sealedClass) {
+///   case Subclass(:final field):
+///     return ...;
+///   case Subclass2(:final field2):
+///     return ...;
+/// }
+/// ```
+
+@optionalTypeArgs TResult when<TResult extends Object?>(TResult Function( ParentLetterDetail? letter)  $default,) {final _that = this;
+switch (_that) {
+case _ParentLetterState():
+return $default(_that.letter);case _:
+  throw StateError('Unexpected subclass');
+
+}
+}
+/// A variant of `when` that fallback to returning `null`
+///
+/// It is equivalent to doing:
+/// ```dart
+/// switch (sealedClass) {
+///   case Subclass(:final field):
+///     return ...;
+///   case _:
+///     return null;
+/// }
+/// ```
+
+@optionalTypeArgs TResult? whenOrNull<TResult extends Object?>(TResult? Function( ParentLetterDetail? letter)?  $default,) {final _that = this;
+switch (_that) {
+case _ParentLetterState() when $default != null:
+return $default(_that.letter);case _:
+  return null;
+
+}
+}
+
+}
+
+/// @nodoc
+@JsonSerializable()
+
+class _ParentLetterState implements ParentLetterState {
+  const _ParentLetterState({this.letter});
+  factory _ParentLetterState.fromJson(Map<String, dynamic> json) => _$ParentLetterStateFromJson(json);
+
+@override final  ParentLetterDetail? letter;
+
+/// Create a copy of ParentLetterState
+/// with the given fields replaced by the non-null parameter values.
+@override @JsonKey(includeFromJson: false, includeToJson: false)
+@pragma('vm:prefer-inline')
+_$ParentLetterStateCopyWith<_ParentLetterState> get copyWith => __$ParentLetterStateCopyWithImpl<_ParentLetterState>(this, _$identity);
+
+@override
+Map<String, dynamic> toJson() {
+  return _$ParentLetterStateToJson(this, );
+}
+
+@override
+bool operator ==(Object other) {
+    return identical(this, other) || (other.runtimeType == runtimeType&&other is _ParentLetterState&&(identical(other.letter, letter) || other.letter == letter));
+}
+
+@JsonKey(includeFromJson: false, includeToJson: false)
+@override
+int get hashCode {
+    return Object.hash(runtimeType,letter);
+}
+
+@override
+String toString() {
+    return 'ParentLetterState(letter: $letter)';
+}
+
+
+}
+
+/// @nodoc
+abstract mixin class _$ParentLetterStateCopyWith<$Res> implements $ParentLetterStateCopyWith<$Res> {
+  factory _$ParentLetterStateCopyWith(_ParentLetterState value, $Res Function(_ParentLetterState) _then) = __$ParentLetterStateCopyWithImpl;
+@override @useResult
+$Res call({
+ ParentLetterDetail? letter
+});
+
+
+
+
+}
+/// @nodoc
+class __$ParentLetterStateCopyWithImpl<$Res>
+    implements _$ParentLetterStateCopyWith<$Res> {
+  __$ParentLetterStateCopyWithImpl(this._self, this._then);
+
+  final _ParentLetterState _self;
+  final $Res Function(_ParentLetterState) _then;
+
+/// Create a copy of ParentLetterState
+/// with the given fields replaced by the non-null parameter values.
+@override @pragma('vm:prefer-inline') $Res call({Object? letter = freezed,}) {
+  return _then(_ParentLetterState(
+letter: freezed == letter ? _self.letter : letter // ignore: cast_nullable_to_non_nullable
+as ParentLetterDetail?,
+  ));
+}
+
+
+}
+
+// dart format on

lib/state/app/modules/parent_letters/bloc/parent_letter_state.g.dart

@@ -0,0 +1,17 @@
+// GENERATED CODE - DO NOT MODIFY BY HAND
+
+part of 'parent_letter_state.dart';
+
+// **************************************************************************
+// JsonSerializableGenerator
+// **************************************************************************
+
+_ParentLetterState _$ParentLetterStateFromJson(Map<String, dynamic> json) =>
+    _ParentLetterState(
+      letter: json['letter'] == null
+          ? null
+          : ParentLetterDetail.fromJson(json['letter'] as Map<String, dynamic>),
+    );
+
+Map<String, dynamic> _$ParentLetterStateToJson(_ParentLetterState instance) =>
+    <String, dynamic>{'letter': instance.letter};

lib/state/app/modules/parent_letters/bloc/parent_letters_bloc.dart

@@ -0,0 +1,107 @@
+import 'dart:developer';
+
+import '../../../../../access/access_requirement.dart';
+import '../../../../../api/marianumconnect/queries/parent_letters/parent_letter_models.dart';
+import '../../../infrastructure/utility_widgets/loadable_hydrated_bloc/loadable_hydrated_bloc.dart';
+import '../../../infrastructure/utility_widgets/loadable_hydrated_bloc/loadable_hydrated_bloc_event.dart';
+import '../parent_letters_logic.dart';
+import '../repository/parent_letters_repository.dart';
+import 'parent_letters_event.dart';
+import 'parent_letters_state.dart';
+
+/// The guardian's letter inbox. Lives app-wide because the module badge and
+/// push handling need it outside the page.
+class ParentLettersBloc
+    extends
+        LoadableHydratedBloc<
+          ParentLettersEvent,
+          ParentLettersState,
+          ParentLettersRepository
+        > {
+  @override
+  Set<AccessRequirement> get requirements => const {AccessRequirement.guardian};
+
+  Future<void>? _loading;
+
+  /// App start, prefetch, page visit and push handling all ask for the first
+  /// page within moments of each other; they share one request.
+  @override
+  Future<void> gatherData() =>
+      _loading ??= _loadFirstPage().whenComplete(() => _loading = null);
+
+  Future<void> _loadFirstPage() async {
+    final page = await repo.getLetters();
+    if (isClosed) return;
+    add(DataGathered((_) => firstPageState(page)));
+  }
+
+  /// Reloads the first page; older pages loaded via [loadOlder] are dropped.
+  Future<void> refresh({bool silent = false}) async {
+    if (!requirementsMet) return;
+    if (!silent) add(RefetchStarted<ParentLettersState>());
+    try {
+      await gatherData();
+    } catch (e) {
+      if (isClosed) return;
+      if (silent) {
+        log('Silent parent letters refresh failed: $e');
+      } else {
+        addLoadingError(e);
+      }
+    }
+  }
+
+  Future<void> loadOlder() async {
+    final letters = innerState?.letters;
+    if (letters == null || letters.isEmpty) return;
+    final page = await repo.getLetters(before: letters.last.id);
+    if (isClosed) return;
+    add(Emit((state) => appendOlderPage(state, page)));
+  }
+
+  /// Optimistic locally. When nothing could be applied locally (a letter
+  /// opened from a push is not in the inbox yet), the follow-up refresh picks
+  /// it up.
+  void markRead(String letterId) {
+    final current = innerState;
+    final updated = current == null ? null : withLetterRead(current, letterId);
+    final appliedLocally = updated != null && !identical(updated, current);
+    if (appliedLocally) add(Emit((_) => updated));
+    repo
+        .markRead(letterId)
+        .then((_) {
+          if (!appliedLocally) _reloadAfterWrite();
+        })
+        .catchError((Object e) {
+          log('Marking parent letter $letterId as read failed: $e');
+          _reloadAfterWrite();
+        });
+  }
+
+  /// A request already in flight may predate the write, so it is not joined.
+  Future<void> _reloadAfterWrite() async {
+    try {
+      await _loading;
+    } on Object {
+      // Its own caller reports the failure.
+    }
+    await refresh(silent: true);
+  }
+
+  /// Takes over a freshly loaded letter.
+  void applyDetail(ParentLetterDetail detail) =>
+      add(Emit((state) => withSummary(state, detail.summary)));
+
+  @override
+  ParentLettersRepository repository() => ParentLettersRepository();
+
+  @override
+  ParentLettersState fromNothing() => const ParentLettersState();
+
+  @override
+  ParentLettersState fromStorage(Map<String, dynamic> json) =>
+      ParentLettersState.fromJson(json);
+
+  @override
+  Map<String, dynamic>? toStorage(ParentLettersState state) => state.toJson();
+}

lib/state/app/modules/parent_letters/bloc/parent_letters_event.dart

@@ -0,0 +1,5 @@
+import '../../../infrastructure/utility_widgets/loadable_hydrated_bloc/loadable_hydrated_bloc_event.dart';
+import 'parent_letters_state.dart';
+
+sealed class ParentLettersEvent
+    extends LoadableHydratedBlocEvent<ParentLettersState> {}

lib/state/app/modules/parent_letters/bloc/parent_letters_state.dart

@@ -0,0 +1,21 @@
+import 'package:freezed_annotation/freezed_annotation.dart';
+
+import '../../../../../api/marianumconnect/queries/parent_letters/parent_letter_models.dart';
+
+part 'parent_letters_state.freezed.dart';
+part 'parent_letters_state.g.dart';
+
+/// Hydrated inbox. [unreadCount] and [openCount] cover all letters on the
+/// server, not just the loaded [letters].
+@freezed
+abstract class ParentLettersState with _$ParentLettersState {
+  const factory ParentLettersState({
+    @Default([]) List<ParentLetterSummary> letters,
+    @Default(false) bool hasMore,
+    @Default(0) int unreadCount,
+    @Default(0) int openCount,
+  }) = _ParentLettersState;
+
+  factory ParentLettersState.fromJson(Map<String, dynamic> json) =>
+      _$ParentLettersStateFromJson(json);
+}

lib/state/app/modules/parent_letters/bloc/parent_letters_state.freezed.dart

@@ -0,0 +1,300 @@
+// GENERATED CODE - DO NOT MODIFY BY HAND
+// coverage:ignore-file
+// ignore_for_file: type=lint, type=warning, deprecated_member_use, deprecated_member_use_from_same_package
+// ignore_for_file: unused_element, deprecated_member_use, deprecated_member_use_from_same_package, use_function_type_syntax_for_parameters, unnecessary_const, avoid_init_to_null, invalid_override_different_default_values_named, prefer_expression_function_bodies, annotate_overrides, invalid_annotation_target, unnecessary_question_mark
+
+part of 'parent_letters_state.dart';
+
+// **************************************************************************
+// FreezedGenerator
+// **************************************************************************
+
+// GENERATED CODE - DO NOT MODIFY BY HAND
+// dart format off
+T _$identity<T>(T value) => value;
+
+/// @nodoc
+mixin _$ParentLettersState {
+
+ List<ParentLetterSummary> get letters; bool get hasMore; int get unreadCount; int get openCount;
+/// Create a copy of ParentLettersState
+/// with the given fields replaced by the non-null parameter values.
+@JsonKey(includeFromJson: false, includeToJson: false)
+@pragma('vm:prefer-inline')
+$ParentLettersStateCopyWith<ParentLettersState> get copyWith => _$ParentLettersStateCopyWithImpl<ParentLettersState>(this as ParentLettersState, _$identity);
+
+  /// Serializes this ParentLettersState to a JSON map.
+  Map<String, dynamic> toJson();
+
+
+@override
+bool operator ==(Object other) {
+  final _this = this as ParentLettersState;
+  return identical(this, other) || (other.runtimeType == runtimeType&&other is ParentLettersState&&const DeepCollectionEquality().equals(other.letters, _this.letters)&&(identical(other.hasMore, _this.hasMore) || other.hasMore == _this.hasMore)&&(identical(other.unreadCount, _this.unreadCount) || other.unreadCount == _this.unreadCount)&&(identical(other.openCount, _this.openCount) || other.openCount == _this.openCount));
+}
+
+@JsonKey(includeFromJson: false, includeToJson: false)
+@override
+int get hashCode {
+  final _this = this as ParentLettersState;
+  return Object.hash(runtimeType,const DeepCollectionEquality().hash(_this.letters),_this.hasMore,_this.unreadCount,_this.openCount);
+}
+
+@override
+String toString() {
+  final _this = this as ParentLettersState;
+  return 'ParentLettersState(letters: ${_this.letters}, hasMore: ${_this.hasMore}, unreadCount: ${_this.unreadCount}, openCount: ${_this.openCount})';
+}
+
+
+}
+
+/// @nodoc
+abstract mixin class $ParentLettersStateCopyWith<$Res>  {
+  factory $ParentLettersStateCopyWith(ParentLettersState value, $Res Function(ParentLettersState) _then) = _$ParentLettersStateCopyWithImpl;
+@useResult
+$Res call({
+ List<ParentLetterSummary> letters, bool hasMore, int unreadCount, int openCount
+});
+
+
+
+
+}
+/// @nodoc
+class _$ParentLettersStateCopyWithImpl<$Res>
+    implements $ParentLettersStateCopyWith<$Res> {
+  _$ParentLettersStateCopyWithImpl(this._self, this._then);
+
+  final ParentLettersState _self;
+  final $Res Function(ParentLettersState) _then;
+
+/// Create a copy of ParentLettersState
+/// with the given fields replaced by the non-null parameter values.
+@pragma('vm:prefer-inline') @override $Res call({Object? letters = null,Object? hasMore = null,Object? unreadCount = null,Object? openCount = null,}) {
+  return _then(ParentLettersState(
+letters: null == letters ? _self.letters : letters // ignore: cast_nullable_to_non_nullable
+as List<ParentLetterSummary>,hasMore: null == hasMore ? _self.hasMore : hasMore // ignore: cast_nullable_to_non_nullable
+as bool,unreadCount: null == unreadCount ? _self.unreadCount : unreadCount // ignore: cast_nullable_to_non_nullable
+as int,openCount: null == openCount ? _self.openCount : openCount // ignore: cast_nullable_to_non_nullable
+as int,
+  ));
+}
+
+}
+
+
+/// Adds pattern-matching-related methods to [ParentLettersState].
+extension ParentLettersStatePatterns on ParentLettersState {
+/// A variant of `map` that fallback to returning `orElse`.
+///
+/// It is equivalent to doing:
+/// ```dart
+/// switch (sealedClass) {
+///   case final Subclass value:
+///     return ...;
+///   case _:
+///     return orElse();
+/// }
+/// ```
+
+@optionalTypeArgs TResult maybeMap<TResult extends Object?>(TResult Function( _ParentLettersState value)?  $default,{required TResult orElse(),}){
+final _that = this;
+switch (_that) {
+case _ParentLettersState() when $default != null:
+return $default(_that);case _:
+  return orElse();
+
+}
+}
+/// A `switch`-like method, using callbacks.
+///
+/// Callbacks receives the raw object, upcasted.
+/// It is equivalent to doing:
+/// ```dart
+/// switch (sealedClass) {
+///   case final Subclass value:
+///     return ...;
+///   case final Subclass2 value:
+///     return ...;
+/// }
+/// ```
+
+@optionalTypeArgs TResult map<TResult extends Object?>(TResult Function( _ParentLettersState value)  $default,){
+final _that = this;
+switch (_that) {
+case _ParentLettersState():
+return $default(_that);case _:
+  throw StateError('Unexpected subclass');
+
+}
+}
+/// A variant of `map` that fallback to returning `null`.
+///
+/// It is equivalent to doing:
+/// ```dart
+/// switch (sealedClass) {
+///   case final Subclass value:
+///     return ...;
+///   case _:
+///     return null;
+/// }
+/// ```
+
+@optionalTypeArgs TResult? mapOrNull<TResult extends Object?>(TResult? Function( _ParentLettersState value)?  $default,){
+final _that = this;
+switch (_that) {
+case _ParentLettersState() when $default != null:
+return $default(_that);case _:
+  return null;
+
+}
+}
+/// A variant of `when` that fallback to an `orElse` callback.
+///
+/// It is equivalent to doing:
+/// ```dart
+/// switch (sealedClass) {
+///   case Subclass(:final field):
+///     return ...;
+///   case _:
+///     return orElse();
+/// }
+/// ```
+
+@optionalTypeArgs TResult maybeWhen<TResult extends Object?>(TResult Function( List<ParentLetterSummary> letters,  bool hasMore,  int unreadCount,  int openCount)?  $default,{required TResult orElse(),}) {final _that = this;
+switch (_that) {
+case _ParentLettersState() when $default != null:
+return $default(_that.letters,_that.hasMore,_that.unreadCount,_that.openCount);case _:
+  return orElse();
+
+}
+}
+/// A `switch`-like method, using callbacks.
+///
+/// As opposed to `map`, this offers destructuring.
+/// It is equivalent to doing:
+/// ```dart
+/// switch (sealedClass) {
+///   case Subclass(:final field):
+///     return ...;
+///   case Subclass2(:final field2):
+///     return ...;
+/// }
+/// ```
+
+@optionalTypeArgs TResult when<TResult extends Object?>(TResult Function( List<ParentLetterSummary> letters,  bool hasMore,  int unreadCount,  int openCount)  $default,) {final _that = this;
+switch (_that) {
+case _ParentLettersState():
+return $default(_that.letters,_that.hasMore,_that.unreadCount,_that.openCount);case _:
+  throw StateError('Unexpected subclass');
+
+}
+}
+/// A variant of `when` that fallback to returning `null`
+///
+/// It is equivalent to doing:
+/// ```dart
+/// switch (sealedClass) {
+///   case Subclass(:final field):
+///     return ...;
+///   case _:
+///     return null;
+/// }
+/// ```
+
+@optionalTypeArgs TResult? whenOrNull<TResult extends Object?>(TResult? Function( List<ParentLetterSummary> letters,  bool hasMore,  int unreadCount,  int openCount)?  $default,) {final _that = this;
+switch (_that) {
+case _ParentLettersState() when $default != null:
+return $default(_that.letters,_that.hasMore,_that.unreadCount,_that.openCount);case _:
+  return null;
+
+}
+}
+
+}
+
+/// @nodoc
+@JsonSerializable()
+
+class _ParentLettersState implements ParentLettersState {
+  const _ParentLettersState({ List<ParentLetterSummary> letters = const [], this.hasMore = false, this.unreadCount = 0, this.openCount = 0}): _letters = letters;
+  factory _ParentLettersState.fromJson(Map<String, dynamic> json) => _$ParentLettersStateFromJson(json);
+
+ final  List<ParentLetterSummary> _letters;
+@override@JsonKey() List<ParentLetterSummary> get letters {
+  if (_letters is EqualUnmodifiableListView) return _letters;
+  // ignore: implicit_dynamic_type
+  return EqualUnmodifiableListView(_letters);
+}
+
+@override@JsonKey() final  bool hasMore;
+@override@JsonKey() final  int unreadCount;
+@override@JsonKey() final  int openCount;
+
+/// Create a copy of ParentLettersState
+/// with the given fields replaced by the non-null parameter values.
+@override @JsonKey(includeFromJson: false, includeToJson: false)
+@pragma('vm:prefer-inline')
+_$ParentLettersStateCopyWith<_ParentLettersState> get copyWith => __$ParentLettersStateCopyWithImpl<_ParentLettersState>(this, _$identity);
+
+@override
+Map<String, dynamic> toJson() {
+  return _$ParentLettersStateToJson(this, );
+}
+
+@override
+bool operator ==(Object other) {
+    return identical(this, other) || (other.runtimeType == runtimeType&&other is _ParentLettersState&&const DeepCollectionEquality().equals(other.letters, _letters)&&(identical(other.hasMore, hasMore) || other.hasMore == hasMore)&&(identical(other.unreadCount, unreadCount) || other.unreadCount == unreadCount)&&(identical(other.openCount, openCount) || other.openCount == openCount));
+}
+
+@JsonKey(includeFromJson: false, includeToJson: false)
+@override
+int get hashCode {
+    return Object.hash(runtimeType,const DeepCollectionEquality().hash(_letters),hasMore,unreadCount,openCount);
+}
+
+@override
+String toString() {
+    return 'ParentLettersState(letters: $letters, hasMore: $hasMore, unreadCount: $unreadCount, openCount: $openCount)';
+}
+
+
+}
+
+/// @nodoc
+abstract mixin class _$ParentLettersStateCopyWith<$Res> implements $ParentLettersStateCopyWith<$Res> {
+  factory _$ParentLettersStateCopyWith(_ParentLettersState value, $Res Function(_ParentLettersState) _then) = __$ParentLettersStateCopyWithImpl;
+@override @useResult
+$Res call({
+ List<ParentLetterSummary> letters, bool hasMore, int unreadCount, int openCount
+});
+
+
+
+
+}
+/// @nodoc
+class __$ParentLettersStateCopyWithImpl<$Res>
+    implements _$ParentLettersStateCopyWith<$Res> {
+  __$ParentLettersStateCopyWithImpl(this._self, this._then);
+
+  final _ParentLettersState _self;
+  final $Res Function(_ParentLettersState) _then;
+
+/// Create a copy of ParentLettersState
+/// with the given fields replaced by the non-null parameter values.
+@override @pragma('vm:prefer-inline') $Res call({Object? letters = null,Object? hasMore = null,Object? unreadCount = null,Object? openCount = null,}) {
+  return _then(_ParentLettersState(
+letters: null == letters ? _self._letters : letters // ignore: cast_nullable_to_non_nullable
+as List<ParentLetterSummary>,hasMore: null == hasMore ? _self.hasMore : hasMore // ignore: cast_nullable_to_non_nullable
+as bool,unreadCount: null == unreadCount ? _self.unreadCount : unreadCount // ignore: cast_nullable_to_non_nullable
+as int,openCount: null == openCount ? _self.openCount : openCount // ignore: cast_nullable_to_non_nullable
+as int,
+  ));
+}
+
+
+}
+
+// dart format on

lib/state/app/modules/parent_letters/bloc/parent_letters_state.g.dart

@@ -0,0 +1,29 @@
+// GENERATED CODE - DO NOT MODIFY BY HAND
+
+part of 'parent_letters_state.dart';
+
+// **************************************************************************
+// JsonSerializableGenerator
+// **************************************************************************
+
+_ParentLettersState _$ParentLettersStateFromJson(Map<String, dynamic> json) =>
+    _ParentLettersState(
+      letters:
+          (json['letters'] as List<dynamic>?)
+              ?.map(
+                (e) => ParentLetterSummary.fromJson(e as Map<String, dynamic>),
+              )
+              .toList() ??
+          const [],
+      hasMore: json['hasMore'] as bool? ?? false,
+      unreadCount: (json['unreadCount'] as num?)?.toInt() ?? 0,
+      openCount: (json['openCount'] as num?)?.toInt() ?? 0,
+    );
+
+Map<String, dynamic> _$ParentLettersStateToJson(_ParentLettersState instance) =>
+    <String, dynamic>{
+      'letters': instance.letters,
+      'hasMore': instance.hasMore,
+      'unreadCount': instance.unreadCount,
+      'openCount': instance.openCount,
+    };

lib/state/app/modules/parent_letters/parent_letters_logic.dart

@@ -0,0 +1,67 @@
+import '../../../../api/marianumconnect/queries/parent_letters/parent_letter_models.dart';
+import 'bloc/parent_letters_state.dart';
+
+ParentLettersState firstPageState(ParentLetterListResponse page) =>
+    ParentLettersState(
+      letters: page.items,
+      hasMore: page.hasMore,
+      unreadCount: page.unreadCount,
+      openCount: page.openCount,
+    );
+
+ParentLettersState appendOlderPage(
+  ParentLettersState state,
+  ParentLetterListResponse page,
+) {
+  final known = {for (final letter in state.letters) letter.id};
+  return state.copyWith(
+    letters: [
+      ...state.letters,
+      ...page.items.where((letter) => !known.contains(letter.id)),
+    ],
+    hasMore: page.hasMore,
+    unreadCount: page.unreadCount,
+    openCount: page.openCount,
+  );
+}
+
+/// Marks [letterId] as read and lowers the unread counter. Returns [state]
+/// itself when the letter is unknown or already read.
+ParentLettersState withLetterRead(ParentLettersState state, String letterId) {
+  final index = state.letters.indexWhere((letter) => letter.id == letterId);
+  if (index < 0 || state.letters[index].read) return state;
+  final letters = [...state.letters];
+  letters[index] = letters[index].copyWith(read: true);
+  return state.copyWith(
+    letters: letters,
+    unreadCount: state.unreadCount > 0 ? state.unreadCount - 1 : 0,
+  );
+}
+
+/// Replaces the letter and moves [ParentLettersState.openCount] along with
+/// its status, so answering does not need a reload to fix the counter.
+ParentLettersState withSummary(
+  ParentLettersState state,
+  ParentLetterSummary summary,
+) {
+  final index = state.letters.indexWhere((letter) => letter.id == summary.id);
+  if (index < 0) return state;
+  int open(ParentLetterSummary letter) =>
+      letter.status == ParentLetterStatus.open ? 1 : 0;
+  final openCount =
+      state.openCount - open(state.letters[index]) + open(summary);
+  final letters = [...state.letters];
+  letters[index] = summary;
+  return state.copyWith(
+    letters: letters,
+    openCount: openCount < 0 ? 0 : openCount,
+  );
+}
+
+/// [childId] null means all children.
+List<ParentLetterSummary> filterLettersByChild(
+  List<ParentLetterSummary> letters,
+  String? childId,
+) => childId == null
+    ? letters
+    : letters.where((letter) => letter.childIds.contains(childId)).toList();

lib/state/app/modules/parent_letters/repository/parent_letter_repository.dart

@@ -0,0 +1,53 @@
+import 'dart:typed_data';
+
+import '../../../../../api/demo/data/demo_parent_letters.dart';
+import '../../../../../api/demo/demo_mode.dart';
+import '../../../../../api/marianumconnect/queries/parent_letters/get_parent_letter.dart';
+import '../../../../../api/marianumconnect/queries/parent_letters/get_parent_letter_attachment.dart';
+import '../../../../../api/marianumconnect/queries/parent_letters/parent_letter_models.dart';
+import '../../../../../api/marianumconnect/queries/parent_letters/post_parent_letter_thread_message.dart';
+import '../../../../../api/marianumconnect/queries/parent_letters/submit_parent_letter_response.dart';
+import '../../../infrastructure/repository/repository.dart';
+import '../bloc/parent_letter_state.dart';
+
+/// Split from [ParentLettersRepository] because the loadable base binds a
+/// repository to its state type. Writes never reach this class in demo mode
+/// (the views guard them).
+class ParentLetterRepository extends Repository<ParentLetterState> {
+  Future<ParentLetterDetail> getLetter(String letterId) {
+    if (DemoMode.active) {
+      return Future.value(DemoParentLetters.detail(letterId));
+    }
+    return GetParentLetter().run(letterId);
+  }
+
+  Future<ParentLetterDetail> submitResponse({
+    required String letterId,
+    required String childId,
+    required List<ParentLetterAnswer> answers,
+    Uint8List? signaturePng,
+  }) => SubmitParentLetterResponse().run(
+    letterId: letterId,
+    childId: childId,
+    answers: answers,
+    signaturePng: signaturePng,
+  );
+
+  Future<ParentLetterThreadMessage> sendThreadMessage({
+    required String letterId,
+    required String body,
+    required String clientMessageId,
+  }) => PostParentLetterThreadMessage().run(
+    letterId: letterId,
+    body: body,
+    clientMessageId: clientMessageId,
+  );
+
+  Future<Uint8List> getAttachment({
+    required String letterId,
+    required String attachmentId,
+  }) => GetParentLetterAttachment().run(
+    letterId: letterId,
+    attachmentId: attachmentId,
+  );
+}

lib/state/app/modules/parent_letters/repository/parent_letters_repository.dart

@@ -0,0 +1,22 @@
+import '../../../../../api/demo/data/demo_parent_letters.dart';
+import '../../../../../api/demo/demo_mode.dart';
+import '../../../../../api/marianumconnect/queries/parent_letters/get_parent_letters.dart';
+import '../../../../../api/marianumconnect/queries/parent_letters/mark_parent_letter_read.dart';
+import '../../../../../api/marianumconnect/queries/parent_letters/parent_letter_models.dart';
+import '../../../infrastructure/repository/repository.dart';
+import '../bloc/parent_letters_state.dart';
+
+class ParentLettersRepository extends Repository<ParentLettersState> {
+  Future<ParentLetterListResponse> getLetters({String? before}) {
+    if (DemoMode.active) return Future.value(DemoParentLetters.list());
+    return GetParentLetters().run(before: before);
+  }
+
+  Future<void> markRead(String letterId) {
+    if (DemoMode.active) {
+      DemoParentLetters.markRead(letterId);
+      return Future.value();
+    }
+    return MarkParentLetterRead().run(letterId);
+  }
+}

lib/storage/modules_settings.g.dart

@@ -31,6 +31,7 @@ Map<String, dynamic> _$ModulesSettingsToJson(
 
 const _$ModulesEnumMap = {
   Modules.timetable: 'timetable',
+  Modules.parentLetters: 'parentLetters',
   Modules.ticker: 'ticker',
   Modules.talk: 'talk',
   Modules.files: 'files',

lib/storage/notification_settings.dart

@@ -16,9 +16,20 @@ class NotificationSettings {
   @JsonKey(defaultValue: false)
   bool talkPermissionPromptShown;
 
+  /// Same one-shot guards for the two occasions on which accounts with
+  /// parent letters are asked: right after signing in and, if the permission
+  /// is still missing, on the first visit of the parent letters.
+  @JsonKey(defaultValue: false)
+  bool guardianLoginPromptShown;
+
+  @JsonKey(defaultValue: false)
+  bool parentLettersPromptShown;
+
   NotificationSettings({
     this.enabled = true,
     this.talkPermissionPromptShown = false,
+    this.guardianLoginPromptShown = false,
+    this.parentLettersPromptShown = false,
   });
 
   factory NotificationSettings.fromJson(Map<String, dynamic> json) =>

lib/storage/notification_settings.g.dart

@@ -12,6 +12,8 @@ NotificationSettings _$NotificationSettingsFromJson(
   enabled: json['enabled'] as bool? ?? true,
   talkPermissionPromptShown:
       json['talkPermissionPromptShown'] as bool? ?? false,
+  guardianLoginPromptShown: json['guardianLoginPromptShown'] as bool? ?? false,
+  parentLettersPromptShown: json['parentLettersPromptShown'] as bool? ?? false,
 );
 
 Map<String, dynamic> _$NotificationSettingsToJson(
@@ -19,4 +21,6 @@ Map<String, dynamic> _$NotificationSettingsToJson(
 ) => <String, dynamic>{
   'enabled': instance.enabled,
   'talkPermissionPromptShown': instance.talkPermissionPromptShown,
+  'guardianLoginPromptShown': instance.guardianLoginPromptShown,
+  'parentLettersPromptShown': instance.parentLettersPromptShown,
 };

lib/utils/random_id.dart

@@ -8,3 +8,12 @@ String randomHexId({int bytes = 16}) {
     (_) => random.nextInt(256),
   ).map((b) => b.toRadixString(16).padLeft(2, '0')).join();
 }
+
+/// Random RFC 4122 version-4 UUID, for ids a server expects in UUID form.
+String randomUuidV4() {
+  final hex = randomHexId();
+  final variant = (int.parse(hex[16], radix: 16) & 0x3 | 0x8).toRadixString(16);
+  return '${hex.substring(0, 8)}-${hex.substring(8, 12)}-'
+      '4${hex.substring(13, 16)}-$variant${hex.substring(17, 20)}-'
+      '${hex.substring(20)}';
+}

lib/view/pages/parent_letters/parent_letter_form_policy.dart

@@ -0,0 +1,94 @@
+import '../../../api/marianumconnect/queries/parent_letters/parent_letter_models.dart';
+
+enum ParentLetterFormMode {
+  /// Nothing answered yet and the server accepts a response.
+  open,
+
+  /// Answered, but the server still accepts a change.
+  change,
+
+  /// Answered and locked.
+  done,
+
+  /// Unanswered and locked (deadline passed).
+  closed,
+
+  /// The letter asks for an input this app version cannot render.
+  unsupported,
+}
+
+/// What the response form of one child shows and allows. Whether a response
+/// may be sent at all is the server's call ([ParentLetterChildState.editable]);
+/// this only turns that verdict into a form.
+class ParentLetterFormPolicy {
+  final ParentLetterFormMode mode;
+  final List<ParentLetterField> fields;
+  final bool signatureRequired;
+
+  const ParentLetterFormPolicy._(
+    this.mode,
+    this.fields,
+    this.signatureRequired,
+  );
+
+  bool get canSubmit =>
+      mode == ParentLetterFormMode.open || mode == ParentLetterFormMode.change;
+
+  bool get isAcknowledgement => fields.isEmpty && !signatureRequired;
+
+  /// Signed responses and acknowledgements cannot be changed afterwards, so
+  /// the form asks for confirmation first.
+  bool get submitIsFinal => isAcknowledgement || signatureRequired;
+
+  String get submitLabel {
+    if (isAcknowledgement) return 'Zur Kenntnis genommen';
+    if (signatureRequired) return 'Unterschreiben und absenden';
+    return mode == ParentLetterFormMode.change
+        ? 'Rückmeldung ändern'
+        : 'Rückmeldung absenden';
+  }
+
+  /// [selection] maps field id to the chosen option id.
+  bool isComplete(Map<String, String> selection) => fields
+      .where((field) => field.isRequired)
+      .every((field) => selection.containsKey(field.id));
+
+  List<ParentLetterAnswer> answersFor(Map<String, String> selection) => [
+    for (final field in fields)
+      if (selection[field.id] case final optionId?)
+        ParentLetterAnswer(fieldId: field.id, optionIds: [optionId]),
+  ];
+
+  /// The selection a previous [response] stands for.
+  static Map<String, String> selectionOf(ParentLetterResponse? response) => {
+    for (final answer in response?.answers ?? const <ParentLetterAnswer>[])
+      if (answer.optionIds.isNotEmpty) answer.fieldId: answer.optionIds.first,
+  };
+
+  /// Null when the letter asks for nothing.
+  static ParentLetterFormPolicy? resolve({
+    required ParentLetterRequest? request,
+    required ParentLetterChildState child,
+  }) {
+    if (request == null) return null;
+    final supported = request.fields
+        .where((field) => field.type != ParentLetterFieldType.unknown)
+        .toList();
+    final ParentLetterFormMode mode;
+    if (!child.editable) {
+      mode = child.response != null
+          ? ParentLetterFormMode.done
+          : ParentLetterFormMode.closed;
+    } else if (request.fields.any(
+      (field) =>
+          field.isRequired && field.type == ParentLetterFieldType.unknown,
+    )) {
+      mode = ParentLetterFormMode.unsupported;
+    } else {
+      mode = child.response != null
+          ? ParentLetterFormMode.change
+          : ParentLetterFormMode.open;
+    }
+    return ParentLetterFormPolicy._(mode, supported, request.signatureRequired);
+  }
+}

lib/view/pages/parent_letters/parent_letter_view.dart

@@ -0,0 +1,161 @@
+import 'package:collection/collection.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:flutter_linkify/flutter_linkify.dart';
+
+import '../../../api/marianumconnect/queries/get_capabilities/guardian_child.dart';
+import '../../../api/marianumconnect/queries/parent_letters/parent_letter_models.dart';
+import '../../../extensions/date_time.dart';
+import '../../../notification/notification_tasks.dart';
+import '../../../state/app/infrastructure/loadable_state/loadable_state.dart';
+import '../../../state/app/infrastructure/loadable_state/view/loadable_state_consumer.dart';
+import '../../../state/app/infrastructure/utility_widgets/bloc_module.dart';
+import '../../../state/app/modules/capabilities/bloc/capabilities_cubit.dart';
+import '../../../state/app/modules/parent_letters/bloc/parent_letter_bloc.dart';
+import '../../../state/app/modules/parent_letters/bloc/parent_letter_state.dart';
+import '../../../state/app/modules/parent_letters/bloc/parent_letters_bloc.dart';
+import '../../../utils/url_opener.dart';
+import 'parent_letter_form_policy.dart';
+import 'widgets/parent_letter_attachments.dart';
+import 'widgets/parent_letter_response_card.dart';
+import 'widgets/parent_letter_thread.dart';
+
+class ParentLetterView extends StatelessWidget {
+  final String id;
+
+  const ParentLetterView({required this.id, super.key});
+
+  @override
+  Widget build(
+    BuildContext context,
+  ) => BlocModule<ParentLetterBloc, LoadableState<ParentLetterState>>(
+    create: (context) =>
+        ParentLetterBloc(id, inbox: context.read<ParentLettersBloc>()),
+    autoRebuild: true,
+    onInitialisation: (_, _) =>
+        NotificationTasks.clearParentLetterNotification(id),
+    child: (context, bloc, state) {
+      final letter = state.data?.letter;
+      return Scaffold(
+        appBar: AppBar(title: const Text('Elternbrief')),
+        body: Column(
+          children: [
+            Expanded(
+              child: LoadableStateConsumer<ParentLetterBloc, ParentLetterState>(
+                isReady: (state) => state.letter != null,
+                child: (state, loading) => _LetterBody(
+                  letter: state.letter!,
+                  children: context.watch<CapabilitiesCubit>().state.children,
+                  bloc: bloc,
+                ),
+              ),
+            ),
+            if (letter != null && letter.content.thread.enabled)
+              ParentLetterThreadInput(
+                recipientName: letter.summary.sender.displayName,
+                onSend: bloc.sendThreadMessage,
+              ),
+          ],
+        ),
+      );
+    },
+  );
+}
+
+class _LetterBody extends StatelessWidget {
+  final ParentLetterDetail letter;
+  final List<GuardianChild> children;
+  final ParentLetterBloc bloc;
+
+  const _LetterBody({
+    required this.letter,
+    required this.children,
+    required this.bloc,
+  });
+
+  String _childName(String childId) =>
+      children.firstWhereOrNull((child) => child.id == childId)?.displayName ??
+      'dein Kind';
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    final summary = letter.summary;
+    final content = letter.content;
+    final editedAt = summary.editedAt;
+    return ListView(
+      physics: const AlwaysScrollableScrollPhysics(),
+      padding: const EdgeInsets.only(bottom: 16),
+      children: [
+        Padding(
+          padding: const EdgeInsets.fromLTRB(16, 16, 16, 0),
+          child: Column(
+            crossAxisAlignment: CrossAxisAlignment.start,
+            children: [
+              Text(summary.subject, style: theme.textTheme.titleLarge),
+              const SizedBox(height: 4),
+              Text(
+                [
+                  summary.sender.displayName,
+                  summary.sentAt.formatDateTime(),
+                  if (editedAt != null)
+                    'bearbeitet am ${editedAt.formatDateTime()}',
+                ].join(' · '),
+                style: theme.textTheme.bodySmall,
+              ),
+              if (children.length > 1)
+                Text(
+                  'Betrifft: ${summary.childIds.map(_childName).join(', ')}',
+                  style: theme.textTheme.bodySmall,
+                ),
+              const SizedBox(height: 16),
+              SelectableLinkify(
+                text: content.body,
+                onOpen: UrlOpener.onOpen,
+                options: const LinkifyOptions(humanize: false),
+                style: theme.textTheme.bodyLarge,
+              ),
+            ],
+          ),
+        ),
+        if (content.attachments.isNotEmpty) ...[
+          const SizedBox(height: 8),
+          ParentLetterAttachments(
+            letterId: summary.id,
+            attachments: content.attachments,
+            load: bloc.loadAttachment,
+          ),
+        ],
+        const SizedBox(height: 8),
+        for (final child in content.children)
+          if (ParentLetterFormPolicy.resolve(
+                request: content.request,
+                child: child,
+              )
+              case final policy?)
+            ParentLetterResponseCard(
+              key: ValueKey((child.childId, child.response)),
+              childName: _childName(child.childId),
+              child: child,
+              policy: policy,
+              deadline: content.request?.deadline,
+              onSubmit: (answers, signaturePng) => bloc.submitResponse(
+                childId: child.childId,
+                answers: answers,
+                signaturePng: signaturePng,
+              ),
+            ),
+        if (content.thread.messages.isNotEmpty) ...[
+          const Padding(
+            padding: EdgeInsets.fromLTRB(16, 12, 16, 4),
+            child: Text(
+              'Nachrichten',
+              style: TextStyle(fontWeight: FontWeight.w600),
+            ),
+          ),
+          ParentLetterThreadMessages(content.thread.messages),
+        ],
+      ],
+    );
+  }
+}

lib/view/pages/parent_letters/parent_letters_view.dart

@@ -0,0 +1,132 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+
+import '../../../api/marianumconnect/queries/get_capabilities/guardian_child.dart';
+import '../../../push/notification_permission_prompt.dart';
+import '../../../routing/app_routes.dart';
+import '../../../state/app/infrastructure/loadable_state/view/loadable_state_consumer.dart';
+import '../../../state/app/modules/capabilities/bloc/capabilities_cubit.dart';
+import '../../../state/app/modules/parent_letters/bloc/parent_letters_bloc.dart';
+import '../../../state/app/modules/parent_letters/bloc/parent_letters_state.dart';
+import '../../../state/app/modules/parent_letters/parent_letters_logic.dart';
+import '../../../widget/async_action_button.dart';
+import '../../../widget/child_switcher.dart';
+import '../../../widget/placeholder_view.dart';
+import 'widgets/parent_letter_tile.dart';
+
+class ParentLettersView extends StatefulWidget {
+  const ParentLettersView({super.key});
+
+  @override
+  State<ParentLettersView> createState() => _ParentLettersViewState();
+}
+
+class _ParentLettersViewState extends State<ParentLettersView> {
+  /// Null shows the letters of all children. Deliberately independent of the
+  /// app-wide child selection: the inbox must not hide a sibling's letters.
+  String? _childFilter;
+
+  @override
+  void initState() {
+    super.initState();
+    WidgetsBinding.instance.addPostFrameCallback((_) {
+      if (!mounted) return;
+      context.read<ParentLettersBloc>().refresh(silent: true);
+      maybePromptParentLetterNotifications(context);
+    });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final children = context.watch<CapabilitiesCubit>().state.children;
+    final filter = children.any((child) => child.id == _childFilter)
+        ? _childFilter
+        : null;
+    return Scaffold(
+      appBar: AppBar(title: const Text('Elternbriefe')),
+      body: Column(
+        children: [
+          if (children.length > 1)
+            _ChildFilterBar(
+              children: children,
+              selected: filter,
+              onSelected: (id) => setState(() => _childFilter = id),
+            ),
+          Expanded(
+            child: LoadableStateConsumer<ParentLettersBloc, ParentLettersState>(
+              child: (state, loading) {
+                if (children.isEmpty) return const NoChildrenPlaceholder();
+                final letters = filterLettersByChild(state.letters, filter);
+                if (letters.isEmpty && !state.hasMore) {
+                  return const PlaceholderView(
+                    icon: Icons.mark_email_read_outlined,
+                    text: 'Keine Elternbriefe vorhanden.',
+                  );
+                }
+                return ListView.separated(
+                  physics: const AlwaysScrollableScrollPhysics(),
+                  itemCount: letters.length + (state.hasMore ? 1 : 0),
+                  separatorBuilder: (_, _) => const Divider(height: 1),
+                  itemBuilder: (context, index) {
+                    if (index == letters.length) {
+                      return Padding(
+                        padding: const EdgeInsets.all(8),
+                        child: AsyncTextButton(
+                          onPressed: context
+                              .read<ParentLettersBloc>()
+                              .loadOlder,
+                          child: const Text('Ältere Elternbriefe laden'),
+                        ),
+                      );
+                    }
+                    final letter = letters[index];
+                    return ParentLetterTile(
+                      letter: letter,
+                      children: children,
+                      onTap: () =>
+                          AppRoutes.openParentLetter(context, id: letter.id),
+                    );
+                  },
+                );
+              },
+            ),
+          ),
+        ],
+      ),
+    );
+  }
+}
+
+class _ChildFilterBar extends StatelessWidget {
+  final List<GuardianChild> children;
+  final String? selected;
+  final ValueChanged<String?> onSelected;
+
+  const _ChildFilterBar({
+    required this.children,
+    required this.selected,
+    required this.onSelected,
+  });
+
+  @override
+  Widget build(BuildContext context) => SingleChildScrollView(
+    scrollDirection: Axis.horizontal,
+    padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 4),
+    child: Row(
+      spacing: 8,
+      children: [
+        ChoiceChip(
+          label: const Text('Alle'),
+          selected: selected == null,
+          onSelected: (_) => onSelected(null),
+        ),
+        for (final child in children)
+          ChoiceChip(
+            label: Text(child.firstName),
+            selected: selected == child.id,
+            onSelected: (_) => onSelected(child.id),
+          ),
+      ],
+    ),
+  );
+}

lib/view/pages/parent_letters/widgets/parent_letter_attachments.dart

@@ -0,0 +1,87 @@
+import 'dart:io';
+import 'dart:typed_data';
+
+import 'package:filesize/filesize.dart';
+import 'package:flutter/material.dart';
+import 'package:path_provider/path_provider.dart';
+
+import '../../../../api/marianumconnect/queries/parent_letters/parent_letter_models.dart';
+import '../../../../routing/app_routes.dart';
+import '../../../../widget/async_action_button.dart';
+import '../../../../widget/centered_leading.dart';
+import '../../../../widget/demo_restricted.dart';
+
+/// File name safe to use inside the cache directory: no path parts, never
+/// empty.
+String safeAttachmentFileName(ParentLetterAttachment attachment) {
+  final name = attachment.fileName
+      .split(RegExp(r'[/\\]'))
+      .last
+      .replaceAll(RegExp(r'[\x00-\x1f:*?"<>|]'), '_')
+      .trim();
+  return name.isEmpty || name == '.' || name == '..' ? 'Anhang' : name;
+}
+
+class ParentLetterAttachments extends StatelessWidget {
+  final String letterId;
+  final List<ParentLetterAttachment> attachments;
+  final Future<Uint8List> Function(String attachmentId) load;
+
+  const ParentLetterAttachments({
+    required this.letterId,
+    required this.attachments,
+    required this.load,
+    super.key,
+  });
+
+  Future<void> _open(
+    BuildContext context,
+    ParentLetterAttachment attachment,
+  ) async {
+    if (guardDemoAction(context)) return;
+    final cache = await getTemporaryDirectory();
+    final directory = Directory(
+      [
+        cache.path,
+        'parent_letters',
+        Uri.encodeComponent(letterId),
+        Uri.encodeComponent(attachment.id),
+      ].join(Platform.pathSeparator),
+    );
+    await directory.create(recursive: true);
+    final file = File(
+      '${directory.path}${Platform.pathSeparator}'
+      '${safeAttachmentFileName(attachment)}',
+    );
+    // An attachment never changes under its id, so a complete earlier download
+    // is reused.
+    final cached =
+        file.existsSync() &&
+        (attachment.size <= 0 || file.lengthSync() == attachment.size);
+    if (!cached) {
+      await file.writeAsBytes(await load(attachment.id), flush: true);
+    }
+    if (!context.mounted) return;
+    AppRoutes.openFileViewer(context, file.path);
+  }
+
+  @override
+  Widget build(BuildContext context) => Column(
+    children: [
+      for (final attachment in attachments)
+        AsyncListTile(
+          closeOnSuccess: false,
+          leading: const CenteredLeading(Icon(Icons.attach_file)),
+          title: Text(
+            safeAttachmentFileName(attachment),
+            maxLines: 1,
+            overflow: TextOverflow.ellipsis,
+          ),
+          subtitle: attachment.size > 0
+              ? Text(filesize(attachment.size))
+              : null,
+          onPressed: () => _open(context, attachment),
+        ),
+    ],
+  );
+}

lib/view/pages/parent_letters/widgets/parent_letter_response_card.dart

@@ -0,0 +1,225 @@
+import 'dart:typed_data';
+
+import 'package:collection/collection.dart';
+import 'package:flutter/material.dart';
+
+import '../../../../api/marianumconnect/queries/parent_letters/parent_letter_models.dart';
+import '../../../../extensions/date_time.dart';
+import '../../../../widget/async_action_button.dart';
+import '../../../../widget/confirm_dialog.dart';
+import '../../../../widget/demo_restricted.dart';
+import '../parent_letter_form_policy.dart';
+import 'signature_sheet.dart';
+
+typedef ParentLetterSubmit =
+    Future<void> Function(
+      List<ParentLetterAnswer> answers,
+      Uint8List? signaturePng,
+    );
+
+/// Response form (or its result) of one child. The form state starts from
+/// the child's response; key the card by it to restart on a new one.
+class ParentLetterResponseCard extends StatefulWidget {
+  final String childName;
+  final ParentLetterChildState child;
+  final ParentLetterFormPolicy policy;
+  final DateTime? deadline;
+  final ParentLetterSubmit onSubmit;
+
+  const ParentLetterResponseCard({
+    required this.childName,
+    required this.child,
+    required this.policy,
+    required this.deadline,
+    required this.onSubmit,
+    super.key,
+  });
+
+  @override
+  State<ParentLetterResponseCard> createState() =>
+      _ParentLetterResponseCardState();
+}
+
+class _ParentLetterResponseCardState extends State<ParentLetterResponseCard> {
+  late Map<String, String> _selection = ParentLetterFormPolicy.selectionOf(
+    widget.child.response,
+  );
+
+  Future<void> _submit() async {
+    if (guardDemoAction(context)) return;
+    final policy = widget.policy;
+    Uint8List? signature;
+    if (policy.signatureRequired) {
+      signature = await showSignatureSheet(
+        context,
+        signerHint: 'Rückmeldung für ${widget.childName}',
+      );
+      if (signature == null || !mounted) return;
+    }
+    final answers = policy.answersFor(_selection);
+    if (!policy.submitIsFinal) return widget.onSubmit(answers, signature);
+    ConfirmDialog(
+      icon: Icons.task_alt,
+      title: 'Verbindlich absenden?',
+      content:
+          'Die Rückmeldung für ${widget.childName} kann danach nicht mehr '
+          'geändert werden.',
+      confirmButton: 'Absenden',
+      onConfirmAsync: () => widget.onSubmit(answers, signature),
+    ).asDialog(context);
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    final policy = widget.policy;
+    final deadline = widget.deadline;
+    return Card(
+      margin: const EdgeInsets.symmetric(horizontal: 12, vertical: 6),
+      child: Padding(
+        padding: const EdgeInsets.symmetric(vertical: 12),
+        child: Column(
+          crossAxisAlignment: CrossAxisAlignment.stretch,
+          children: [
+            Padding(
+              padding: const EdgeInsets.symmetric(horizontal: 16),
+              child: Text(
+                'Rückmeldung für ${widget.childName}',
+                style: theme.textTheme.titleMedium,
+              ),
+            ),
+            if (deadline != null && policy.canSubmit)
+              Padding(
+                padding: const EdgeInsets.fromLTRB(16, 2, 16, 0),
+                child: Text(
+                  'Frist: ${deadline.formatDateTime()}',
+                  style: theme.textTheme.bodySmall,
+                ),
+              ),
+            const SizedBox(height: 8),
+            ...switch (policy.mode) {
+              ParentLetterFormMode.open ||
+              ParentLetterFormMode.change => _form(policy),
+              ParentLetterFormMode.done => _result(theme, policy),
+              ParentLetterFormMode.closed => [
+                _note(
+                  'Die Frist ist abgelaufen. Eine Rückmeldung ist nicht mehr '
+                  'möglich.',
+                ),
+              ],
+              ParentLetterFormMode.unsupported => [
+                _note(
+                  'Für diese Rückmeldung wird eine neuere Version der App '
+                  'benötigt. Bitte aktualisiere die App.',
+                ),
+              ],
+            },
+          ],
+        ),
+      ),
+    );
+  }
+
+  Widget _note(String text) => Padding(
+    padding: const EdgeInsets.symmetric(horizontal: 16),
+    child: Text(text),
+  );
+
+  List<Widget> _form(ParentLetterFormPolicy policy) => [
+    if (policy.mode == ParentLetterFormMode.change)
+      Padding(
+        padding: const EdgeInsets.only(bottom: 8),
+        child: _note(_respondedLine(widget.child.response!)),
+      ),
+    for (final field in policy.fields) ...[
+      Padding(
+        padding: const EdgeInsets.symmetric(horizontal: 16),
+        child: Text(
+          field.isRequired ? '${field.label} *' : field.label,
+          style: const TextStyle(fontWeight: FontWeight.w600),
+        ),
+      ),
+      RadioGroup<String>(
+        groupValue: _selection[field.id],
+        onChanged: (optionId) {
+          if (optionId == null) return;
+          setState(() => _selection = {..._selection, field.id: optionId});
+        },
+        child: Column(
+          children: [
+            for (final option in field.options)
+              RadioListTile<String>(
+                dense: true,
+                title: Text(option.label),
+                value: option.id,
+              ),
+          ],
+        ),
+      ),
+    ],
+    Padding(
+      padding: const EdgeInsets.fromLTRB(16, 4, 16, 0),
+      child: AsyncActionButton(
+        icon: policy.signatureRequired ? Icons.draw_outlined : Icons.check,
+        onPressed: policy.isComplete(_selection) ? _submit : null,
+        child: Text(policy.submitLabel),
+      ),
+    ),
+  ];
+
+  List<Widget> _result(ThemeData theme, ParentLetterFormPolicy policy) {
+    final response = widget.child.response!;
+    final selection = ParentLetterFormPolicy.selectionOf(response);
+    return [
+      for (final field in policy.fields)
+        if (selection[field.id] case final optionId?)
+          Padding(
+            padding: const EdgeInsets.fromLTRB(16, 0, 16, 6),
+            child: Text(
+              '${field.label}\n${_optionLabel(field, optionId)}',
+              style: theme.textTheme.bodyMedium,
+            ),
+          ),
+      Padding(
+        padding: const EdgeInsets.symmetric(horizontal: 16),
+        child: Row(
+          crossAxisAlignment: CrossAxisAlignment.start,
+          children: [
+            Icon(
+              response.signed ? Icons.draw_outlined : Icons.task_alt,
+              size: 18,
+              color: theme.colorScheme.primary,
+            ),
+            const SizedBox(width: 8),
+            Expanded(child: Text(_respondedLine(response))),
+          ],
+        ),
+      ),
+    ];
+  }
+
+  String _optionLabel(ParentLetterField field, String optionId) =>
+      field.options
+          .firstWhereOrNull((option) => option.id == optionId)
+          ?.label ??
+      '–';
+
+  String _respondedLine(ParentLetterResponse response) {
+    final verb = response.signed
+        ? 'Unterschrieben'
+        : widget.policy.isAcknowledgement
+        ? 'Zur Kenntnis genommen'
+        : 'Beantwortet';
+    final by = response.respondedBy.self
+        ? 'von dir'
+        : response.respondedBy.displayName.isEmpty
+        ? ''
+        : 'von ${response.respondedBy.displayName}';
+    final at = response.respondedAt;
+    return [
+      verb,
+      if (by.isNotEmpty) by,
+      if (at != null) 'am ${at.formatDateTime()}',
+    ].join(' ');
+  }
+}

lib/view/pages/parent_letters/widgets/parent_letter_status_chip.dart

@@ -0,0 +1,48 @@
+import 'package:flutter/material.dart';
+
+import '../../../../api/marianumconnect/queries/parent_letters/parent_letter_models.dart';
+
+/// Small pill for the response state of a letter; nothing for plain
+/// information letters.
+class ParentLetterStatusChip extends StatelessWidget {
+  final ParentLetterStatus status;
+
+  const ParentLetterStatusChip(this.status, {super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    final scheme = Theme.of(context).colorScheme;
+    final (label, background, foreground) = switch (status) {
+      ParentLetterStatus.info => (null, null, null),
+      ParentLetterStatus.open => (
+        'Rückmeldung offen',
+        scheme.primary,
+        scheme.onPrimary,
+      ),
+      ParentLetterStatus.done => (
+        'Erledigt',
+        scheme.surfaceContainerHighest,
+        scheme.onSurfaceVariant,
+      ),
+      ParentLetterStatus.expired => (
+        'Frist abgelaufen',
+        scheme.errorContainer,
+        scheme.onErrorContainer,
+      ),
+    };
+    if (label == null) return const SizedBox.shrink();
+    return Container(
+      padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 2),
+      decoration: BoxDecoration(
+        color: background,
+        borderRadius: BorderRadius.circular(10),
+      ),
+      child: Text(
+        label,
+        style: Theme.of(
+          context,
+        ).textTheme.labelSmall?.copyWith(color: foreground),
+      ),
+    );
+  }
+}

lib/view/pages/parent_letters/widgets/parent_letter_thread.dart

@@ -0,0 +1,138 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_linkify/flutter_linkify.dart';
+
+import '../../../../api/marianumconnect/queries/parent_letters/parent_letter_models.dart';
+import '../../../../extensions/date_time.dart';
+import '../../../../utils/url_opener.dart';
+import '../../../../widget/async_action_button.dart';
+import '../../../../widget/demo_restricted.dart';
+
+/// The private conversation between this guardian and the sender.
+class ParentLetterThreadMessages extends StatelessWidget {
+  final List<ParentLetterThreadMessage> messages;
+
+  const ParentLetterThreadMessages(this.messages, {super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    return Column(
+      crossAxisAlignment: CrossAxisAlignment.stretch,
+      children: [
+        for (final message in messages)
+          Align(
+            alignment: message.author.self
+                ? Alignment.centerRight
+                : Alignment.centerLeft,
+            child: Container(
+              constraints: BoxConstraints(
+                maxWidth: MediaQuery.sizeOf(context).width * 0.8,
+              ),
+              margin: const EdgeInsets.symmetric(horizontal: 12, vertical: 4),
+              padding: const EdgeInsets.all(10),
+              decoration: BoxDecoration(
+                color: message.author.self
+                    ? theme.colorScheme.primaryContainer
+                    : theme.colorScheme.surfaceContainerHighest,
+                borderRadius: BorderRadius.circular(12),
+              ),
+              child: Column(
+                crossAxisAlignment: CrossAxisAlignment.start,
+                children: [
+                  Text(
+                    [
+                      if (message.author.self)
+                        'Du'
+                      else
+                        message.author.displayName,
+                      message.sentAt.formatDateShortHm(),
+                    ].join(' · '),
+                    style: theme.textTheme.labelSmall,
+                  ),
+                  const SizedBox(height: 2),
+                  SelectableLinkify(
+                    text: message.body,
+                    onOpen: UrlOpener.onOpen,
+                    options: const LinkifyOptions(humanize: false),
+                  ),
+                ],
+              ),
+            ),
+          ),
+      ],
+    );
+  }
+}
+
+class ParentLetterThreadInput extends StatefulWidget {
+  static const int maxLength = 4000;
+
+  final String recipientName;
+  final Future<void> Function(String body) onSend;
+
+  const ParentLetterThreadInput({
+    required this.recipientName,
+    required this.onSend,
+    super.key,
+  });
+
+  @override
+  State<ParentLetterThreadInput> createState() =>
+      _ParentLetterThreadInputState();
+}
+
+class _ParentLetterThreadInputState extends State<ParentLetterThreadInput> {
+  final TextEditingController _text = TextEditingController();
+
+  @override
+  void dispose() {
+    _text.dispose();
+    super.dispose();
+  }
+
+  Future<void> _send() async {
+    if (guardDemoAction(context)) return;
+    await widget.onSend(_text.text.trim());
+    _text.clear();
+  }
+
+  @override
+  Widget build(BuildContext context) => Material(
+    elevation: 8,
+    child: SafeArea(
+      top: false,
+      child: Padding(
+        padding: const EdgeInsets.fromLTRB(12, 6, 4, 6),
+        child: Row(
+          crossAxisAlignment: CrossAxisAlignment.end,
+          children: [
+            Expanded(
+              child: TextField(
+                controller: _text,
+                minLines: 1,
+                maxLines: 5,
+                maxLength: ParentLetterThreadInput.maxLength,
+                textCapitalization: TextCapitalization.sentences,
+                decoration: InputDecoration(
+                  hintText: widget.recipientName.isEmpty
+                      ? 'Antworten'
+                      : 'Antwort an ${widget.recipientName}',
+                  border: InputBorder.none,
+                  counterText: '',
+                ),
+              ),
+            ),
+            ValueListenableBuilder(
+              valueListenable: _text,
+              builder: (context, value, _) => AsyncIconButton(
+                icon: Icons.send,
+                tooltip: 'Senden',
+                onPressed: value.text.trim().isEmpty ? null : _send,
+              ),
+            ),
+          ],
+        ),
+      ),
+    ),
+  );
+}

lib/view/pages/parent_letters/widgets/parent_letter_tile.dart

@@ -0,0 +1,91 @@
+import 'package:flutter/material.dart';
+
+import '../../../../api/marianumconnect/queries/get_capabilities/guardian_child.dart';
+import '../../../../api/marianumconnect/queries/parent_letters/parent_letter_models.dart';
+import '../../../../extensions/date_time.dart';
+import '../../../../widget/a11y/a11y_labels.dart';
+import 'parent_letter_status_chip.dart';
+
+class ParentLetterTile extends StatelessWidget {
+  final ParentLetterSummary letter;
+
+  /// The guardian's children; names are only shown when there is more than
+  /// one to tell apart.
+  final List<GuardianChild> children;
+  final VoidCallback onTap;
+
+  const ParentLetterTile({
+    required this.letter,
+    required this.children,
+    required this.onTap,
+    super.key,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    final unread = !letter.read;
+    final childNames = children.length < 2
+        ? ''
+        : children
+              .where((child) => letter.childIds.contains(child.id))
+              .map((child) => child.firstName)
+              .join(', ');
+    final deadline = letter.deadline;
+    return ListTile(
+      leading: Semantics(
+        label: unread ? A11yLabels.unread : null,
+        child: Badge(
+          isLabelVisible: unread,
+          smallSize: 10,
+          backgroundColor: theme.primaryColor,
+          child: Icon(unread ? Icons.mail : Icons.drafts_outlined),
+        ),
+      ),
+      title: Text(
+        letter.subject,
+        maxLines: 1,
+        overflow: TextOverflow.ellipsis,
+        style: unread ? const TextStyle(fontWeight: FontWeight.bold) : null,
+      ),
+      subtitle: Column(
+        crossAxisAlignment: CrossAxisAlignment.start,
+        children: [
+          Text(
+            [
+              letter.sender.displayName,
+              letter.sentAt.formatDateRelativeShort(),
+              if (childNames.isNotEmpty) childNames,
+            ].join(' · '),
+            maxLines: 1,
+            overflow: TextOverflow.ellipsis,
+          ),
+          if (letter.preview.isNotEmpty)
+            Text(letter.preview, maxLines: 2, overflow: TextOverflow.ellipsis),
+          if (letter.status != ParentLetterStatus.info)
+            Padding(
+              padding: const EdgeInsets.only(top: 4),
+              child: Row(
+                children: [
+                  ParentLetterStatusChip(letter.status),
+                  if (deadline != null &&
+                      letter.status == ParentLetterStatus.open)
+                    Padding(
+                      padding: const EdgeInsets.only(left: 8),
+                      child: Text(
+                        'bis ${deadline.formatDate()}',
+                        style: theme.textTheme.labelSmall,
+                      ),
+                    ),
+                ],
+              ),
+            ),
+        ],
+      ),
+      trailing: letter.attachmentCount > 0
+          ? const Icon(Icons.attach_file, size: 18)
+          : null,
+      onTap: onTap,
+    );
+  }
+}

lib/view/pages/parent_letters/widgets/signature_sheet.dart

@@ -0,0 +1,125 @@
+import 'dart:typed_data';
+
+import 'package:flutter/material.dart';
+import 'package:signature/signature.dart';
+
+import '../../../../widget/info_dialog.dart';
+
+/// Upper bound the server accepts for a signature image.
+const int maxSignatureBytes = 256 * 1024;
+
+/// Lets the guardian draw a signature. Resolves to the PNG (transparent
+/// background, cropped to the strokes) or null when dismissed.
+Future<Uint8List?> showSignatureSheet(
+  BuildContext context, {
+  required String signerHint,
+}) => showModalBottomSheet<Uint8List>(
+  context: context,
+  isScrollControlled: true,
+  enableDrag: false,
+  showDragHandle: false,
+  builder: (_) => _SignatureSheet(signerHint: signerHint),
+);
+
+class _SignatureSheet extends StatefulWidget {
+  final String signerHint;
+
+  const _SignatureSheet({required this.signerHint});
+
+  @override
+  State<_SignatureSheet> createState() => _SignatureSheetState();
+}
+
+class _SignatureSheetState extends State<_SignatureSheet> {
+  // Paper-like pad in both themes: what is drawn is what gets exported.
+  final SignatureController _controller = SignatureController(
+    penStrokeWidth: 2.5,
+    penColor: Colors.black,
+    strokeCap: StrokeCap.round,
+    strokeJoin: StrokeJoin.round,
+  );
+
+  @override
+  void initState() {
+    super.initState();
+    _controller.addListener(_onChanged);
+  }
+
+  bool _isEmpty = true;
+
+  // The controller notifies per drawn point; only the buttons depend on it.
+  void _onChanged() {
+    if (_controller.isEmpty == _isEmpty) return;
+    setState(() => _isEmpty = _controller.isEmpty);
+  }
+
+  @override
+  void dispose() {
+    _controller.removeListener(_onChanged);
+    _controller.dispose();
+    super.dispose();
+  }
+
+  Future<void> _accept() async {
+    var png = await _controller.toPngBytes();
+    if (png != null && png.lengthInBytes > maxSignatureBytes) {
+      png = await _controller.toPngBytes(width: 600);
+    }
+    if (!mounted) return;
+    if (png == null || png.lengthInBytes > maxSignatureBytes) {
+      InfoDialog.show(
+        context,
+        'Die Unterschrift konnte nicht übernommen werden. Bitte versuche es '
+        'erneut.',
+        title: 'Unterschrift',
+      );
+      return;
+    }
+    Navigator.pop(context, png);
+  }
+
+  @override
+  Widget build(BuildContext context) => SafeArea(
+    child: Padding(
+      padding: const EdgeInsets.fromLTRB(16, 16, 16, 8),
+      child: Column(
+        mainAxisSize: MainAxisSize.min,
+        crossAxisAlignment: CrossAxisAlignment.stretch,
+        children: [
+          Text('Unterschrift', style: Theme.of(context).textTheme.titleLarge),
+          const SizedBox(height: 4),
+          Text(widget.signerHint),
+          const SizedBox(height: 12),
+          ClipRRect(
+            borderRadius: BorderRadius.circular(12),
+            child: Signature(
+              controller: _controller,
+              height: 220,
+              backgroundColor: Colors.white,
+            ),
+          ),
+          const SizedBox(height: 8),
+          Row(
+            children: [
+              TextButton.icon(
+                onPressed: _isEmpty ? null : _controller.clear,
+                icon: const Icon(Icons.undo),
+                label: const Text('Löschen'),
+              ),
+              const Spacer(),
+              TextButton(
+                onPressed: () => Navigator.pop(context),
+                child: const Text('Abbrechen'),
+              ),
+              const SizedBox(width: 8),
+              FilledButton(
+                onPressed: _isEmpty ? null : _accept,
+                child: const Text('Übernehmen'),
+              ),
+            ],
+          ),
+        ],
+      ),
+    ),
+  );
+}

lib/view/pages/settings/data/default_settings.dart

@@ -25,6 +25,7 @@ class DefaultSettings {
     modulesSettings: ModulesSettings(
       moduleOrder: [
         Modules.timetable,
+        Modules.parentLetters,
         Modules.ticker,
         Modules.talk,
         Modules.files,

lib/view/pages/talk/chat_list.dart

@@ -4,6 +4,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
 import 'package:flutter_split_view/flutter_split_view.dart';
 
+import '../../../push/notification_permission_prompt.dart';
 import '../../../routing/app_routes.dart';
 import '../../../state/app/infrastructure/loadable_state/loadable_state.dart';
 import '../../../state/app/infrastructure/loadable_state/view/loadable_state_consumer.dart';
@@ -14,7 +15,6 @@ import '../../../widget/demo_restricted.dart';
 import '../../../widget/placeholder_view.dart';
 import 'data/open_direct_chat.dart';
 import 'join_chat.dart';
-import 'notification_permission_prompt.dart';
 import 'search_chat.dart';
 import 'widgets/chat_tile.dart';
 import 'widgets/split_view_placeholder.dart';

lib/view/pages/talk/notification_permission_prompt.dart

@@ -1,89 +0,0 @@
-import 'dart:async';
-import 'dart:developer';
-
-import 'package:app_settings/app_settings.dart';
-import 'package:flutter/material.dart';
-import 'package:flutter_bloc/flutter_bloc.dart';
-
-import '../../../push/push_registration.dart';
-import '../../../state/app/modules/capabilities/bloc/capabilities_cubit.dart';
-import '../../../state/app/modules/settings/bloc/settings_cubit.dart';
-import '../../../widget/confirm_dialog.dart';
-
-/// Shows the one-time notification-permission flow on the first Talk visit.
-///
-/// The OS prompt is deliberately kept out of the cold-start path (younger users
-/// decline it reflexively before ever seeing why they'd want it). Instead, the
-/// first time Talk is opened we explain the request, then trigger the OS prompt,
-/// and — if declined — offer a shortcut to the system settings.
-///
-/// Runs at most once per install (guarded by `talkPermissionPromptShown`).
-Future<void> maybePromptTalkNotifications(BuildContext context) async {
-  final settings = context.read<SettingsCubit>();
-  final notificationSettings = settings.val().notificationSettings;
-
-  // Already handled once, or the user opted out of push entirely.
-  if (notificationSettings.talkPermissionPromptShown) return;
-  if (!notificationSettings.enabled) return;
-
-  // Capabilities may still be loading on a fresh cold start; retry on the next
-  // Talk visit instead of burning the one-shot flag.
-  if (!context.read<CapabilitiesCubit>().canReceivePushNotifications) return;
-
-  // Existing users who already granted the permission: register silently and
-  // mark the prompt as handled without showing any dialog.
-  if (await PushRegistration.isOsPermissionGranted()) {
-    settings.val(write: true).notificationSettings.talkPermissionPromptShown =
-        true;
-    unawaited(PushRegistration().register());
-    return;
-  }
-
-  if (!context.mounted) return;
-
-  ConfirmDialog(
-    icon: Icons.notifications_active_outlined,
-    title: 'Benachrichtigungen aktivieren',
-    content:
-        'Damit du keine neuen Nachrichten im Talk verpasst, fragen wir dich '
-        'gleich nach der Erlaubnis für Benachrichtigungen. Bitte akzeptiere '
-        'sie, um Push-Nachrichten zu erhalten.',
-    confirmButton: 'Weiter',
-    cancelButton: null,
-    onConfirm: () => unawaited(_requestPermission(context, settings)),
-  ).asDialog(context);
-}
-
-Future<void> _requestPermission(
-  BuildContext context,
-  SettingsCubit settings,
-) async {
-  final granted = await PushRegistration.requestOsPermission();
-
-  // Mark handled regardless of the outcome — the user can re-enable later via
-  // the system settings; we don't want to prompt again on the next Talk visit.
-  settings.val(write: true).notificationSettings.talkPermissionPromptShown =
-      true;
-
-  if (granted) {
-    unawaited(PushRegistration().register());
-    return;
-  }
-
-  log('Push: notification permission declined on first Talk visit');
-
-  if (!context.mounted) return;
-
-  ConfirmDialog(
-    icon: Icons.notifications_off_outlined,
-    title: 'Benachrichtigungen deaktiviert',
-    content:
-        'Ohne die Berechtigung erhältst du keine Benachrichtigungen bei neuen '
-        'Talk-Nachrichten. Du kannst sie jederzeit in den Systemeinstellungen '
-        'deines Geräts nachträglich aktivieren.',
-    confirmButton: 'Einstellungen öffnen',
-    cancelButton: 'Später',
-    onConfirm: () =>
-        AppSettings.openAppSettings(type: AppSettingsType.notification),
-  ).asDialog(context);
-}

lib/widget/module_badge_icon.dart

@@ -0,0 +1,31 @@
+import 'package:badges/badges.dart' as badges;
+import 'package:flutter/material.dart';
+
+/// Module icon with an unread counter; the plain icon while [count] is zero.
+class ModuleBadgeIcon extends StatelessWidget {
+  final IconData icon;
+  final int count;
+
+  const ModuleBadgeIcon({required this.icon, required this.count, super.key});
+
+  @override
+  Widget build(BuildContext context) => badges.Badge(
+    showBadge: count > 0,
+    position: badges.BadgePosition.topEnd(top: -3, end: -3),
+    stackFit: StackFit.loose,
+    badgeStyle: badges.BadgeStyle(
+      padding: const EdgeInsets.all(3),
+      badgeColor: Theme.of(context).primaryColor,
+      elevation: 1,
+    ),
+    badgeContent: Text(
+      '$count',
+      style: const TextStyle(
+        color: Colors.white,
+        fontSize: 10,
+        fontWeight: FontWeight.bold,
+      ),
+    ),
+    child: Icon(icon),
+  );
+}

pubspec.yaml

@@ -107,6 +107,7 @@ dependencies:
   app_links: ^7.2.1
   integration_test:
     sdk: flutter
+  signature: ^6.4.0
 
 dev_dependencies:
   flutter_test:

test/access/access_requirement_test.dart

@@ -0,0 +1,31 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:marianum_mobile/access/access_requirement.dart';
+import 'package:marianum_mobile/session/session.dart';
+
+void main() {
+  final student = CredentialSession(username: 'max', password: 'pw');
+  const guardian = GuardianSession(email: 'e@x.de');
+
+  test('nextcloud is only met by sessions with a Nextcloud identity', () {
+    expect(AccessRequirement.nextcloud.isMetBy(student), isTrue);
+    expect(AccessRequirement.nextcloud.isMetBy(guardian), isFalse);
+    expect(AccessRequirement.nextcloud.isMetBy(null), isFalse);
+  });
+
+  test('guardian is only met by guardian sessions', () {
+    expect(AccessRequirement.guardian.isMetBy(guardian), isTrue);
+    expect(AccessRequirement.guardian.isMetBy(student), isFalse);
+    expect(AccessRequirement.guardian.isMetBy(null), isFalse);
+  });
+
+  test('a set is met only when every requirement is met', () {
+    expect(<AccessRequirement>{}.areMetBy(null), isTrue);
+    expect(
+      {
+        AccessRequirement.guardian,
+        AccessRequirement.nextcloud,
+      }.areMetBy(guardian),
+      isFalse,
+    );
+  });
+}

test/api/marianumconnect/parent_letter_models_test.dart

@@ -0,0 +1,241 @@
+import 'dart:convert';
+
+import 'package:dio/dio.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:marianum_mobile/api/errors/auth_exception.dart';
+import 'package:marianum_mobile/api/marianumconnect/queries/parent_letters/get_parent_letter.dart';
+import 'package:marianum_mobile/api/marianumconnect/queries/parent_letters/parent_letter_exception.dart';
+import 'package:marianum_mobile/api/marianumconnect/queries/parent_letters/parent_letter_models.dart';
+
+const _detailJson = '''
+{
+  "id": "l1", "subject": "Wandertag 10b", "preview": "Liebe Eltern",
+  "sender": {"displayName": "Hr. Müller"},
+  "sentAt": "2026-09-20T08:15:00", "editedAt": null, "read": false,
+  "childIds": ["c1"], "attachmentCount": 1, "status": "open",
+  "deadline": "2026-10-01T23:59:00",
+  "body": "Liebe Eltern,\\n…",
+  "attachments": [{"id": "a1", "fileName": "Brief.pdf", "mimeType": "application/pdf", "size": 48211}],
+  "request": {
+    "fields": [
+      {"id": "f1", "type": "single_choice", "label": "Teilnahme?", "required": true,
+       "options": [{"id": "o1", "label": "Ja"}, {"id": "o2", "label": "Nein"}]},
+      {"id": "f2", "type": "date_range", "label": "Zeitraum", "required": false, "options": null}
+    ],
+    "signatureRequired": true, "deadline": "2026-10-01T23:59:00"
+  },
+  "children": [
+    {"childId": "c1", "status": "done", "editable": false,
+     "response": {"respondedAt": "2026-09-21T19:02:11",
+       "respondedBy": {"displayName": "A. Hoffmann", "self": true},
+       "answers": [{"fieldId": "f1", "optionIds": ["o1"], "text": null}], "signed": true}}
+  ],
+  "thread": {"enabled": true, "messages": [
+    {"id": "m1", "author": {"displayName": "Hr. Müller", "self": false}, "body": "Danke", "sentAt": "2026-09-21T20:10:00"}
+  ]}
+}
+''';
+
+void main() {
+  group('ParentLetterSummary', () {
+    test('parses the documented inbox entry', () {
+      final response = ParentLetterListResponse.fromJson({
+        'items': [
+          {
+            'id': 'l1',
+            'subject': 'Wandertag',
+            'preview': 'Liebe Eltern',
+            'sender': {'displayName': 'Hr. Müller'},
+            'sentAt': '2026-09-20T08:15:00',
+            'editedAt': null,
+            'read': false,
+            'childIds': ['c1', 'c2'],
+            'attachmentCount': 2,
+            'status': 'expired',
+            'deadline': '2026-10-01T23:59:00',
+          },
+        ],
+        'hasMore': true,
+        'unreadCount': 3,
+        'openCount': 1,
+      });
+      final letter = response.items.single;
+      expect(letter.sender.displayName, 'Hr. Müller');
+      expect(letter.sentAt, DateTime(2026, 9, 20, 8, 15));
+      expect(letter.read, isFalse);
+      expect(letter.childIds, ['c1', 'c2']);
+      expect(letter.status, ParentLetterStatus.expired);
+      expect(letter.deadline, DateTime(2026, 10, 1, 23, 59));
+      expect(response.hasMore, isTrue);
+      expect(response.unreadCount, 3);
+      expect(response.openCount, 1);
+    });
+
+    test('explicit nulls and unknown values fall back to safe defaults', () {
+      final letter = ParentLetterSummary.fromJson({
+        'id': 'l1',
+        'subject': null,
+        'sender': null,
+        'sentAt': '2026-09-20T08:15:00',
+        'read': null,
+        'childIds': null,
+        'status': 'archived',
+        'deadline': null,
+      });
+      expect(letter.subject, '');
+      expect(letter.sender.displayName, '');
+      expect(letter.read, isTrue);
+      expect(letter.childIds, isEmpty);
+      expect(letter.status, ParentLetterStatus.info);
+      expect(letter.deadline, isNull);
+    });
+
+    test('an empty list response is an empty inbox', () {
+      final response = ParentLetterListResponse.fromJson(const {});
+      expect(response.items, isEmpty);
+      expect(response.hasMore, isFalse);
+      expect(response.unreadCount, 0);
+    });
+  });
+
+  group('ParentLetterDetail', () {
+    final detail = ParentLetterDetail.fromJson(
+      jsonDecode(_detailJson) as Map<String, dynamic>,
+    );
+
+    test('splits the flat object into summary and content', () {
+      expect(detail.summary.id, 'l1');
+      expect(detail.summary.status, ParentLetterStatus.open);
+      expect(detail.content.body, startsWith('Liebe Eltern'));
+      expect(detail.content.attachments.single.size, 48211);
+      expect(detail.content.thread.messages.single.author.self, isFalse);
+    });
+
+    test('keeps unknown field types and tolerates null options', () {
+      final fields = detail.content.request!.fields;
+      expect(fields[0].type, ParentLetterFieldType.singleChoice);
+      expect(fields[0].isRequired, isTrue);
+      expect(fields[0].options.map((o) => o.id), ['o1', 'o2']);
+      expect(fields[1].type, ParentLetterFieldType.unknown);
+      expect(fields[1].options, isEmpty);
+    });
+
+    test('parses the per-child response', () {
+      final child = detail.content.children.single;
+      expect(child.editable, isFalse);
+      expect(child.response!.respondedBy.self, isTrue);
+      expect(child.response!.signed, isTrue);
+      expect(child.response!.answers.single.optionIds, ['o1']);
+    });
+
+    test('a letter without request, children and thread is pure information', () {
+      final info = ParentLetterDetail.fromJson({
+        'id': 'l2',
+        'sentAt': '2026-09-20T08:15:00',
+        'request': null,
+        'thread': null,
+      });
+      expect(info.content.request, isNull);
+      expect(info.content.children, isEmpty);
+      expect(info.content.thread.enabled, isFalse);
+    });
+
+    test('survives the storage round trip', () {
+      final restored = ParentLetterDetail.fromJson(
+        jsonDecode(jsonEncode(detail.toJson())) as Map<String, dynamic>,
+      );
+      expect(restored, detail);
+    });
+  });
+
+  group('ParentLetterException mapping', () {
+    Future<Object> errorOf(int status, Object? body) async {
+      final options = RequestOptions(path: 'parent-letters/l1');
+      final dio = _ThrowingDio(
+        DioException(
+          requestOptions: options,
+          type: DioExceptionType.badResponse,
+          response: Response<dynamic>(
+            requestOptions: options,
+            statusCode: status,
+            data: body,
+          ),
+        ),
+      );
+      try {
+        await GetParentLetter(dio: dio).run('l1');
+      } catch (e) {
+        return e;
+      }
+      fail('expected an error');
+    }
+
+    test('reads the JSON error code', () async {
+      final error = await errorOf(409, {'error': 'response_final'});
+      expect(
+        error,
+        isA<ParentLetterException>()
+            .having((e) => e.error, 'error', ParentLetterError.responseFinal)
+            .having((e) => e.allowRetry, 'allowRetry', isFalse),
+      );
+    });
+
+    test('reads the plain-text "Fehler: <code>" body', () async {
+      final error = await errorOf(410, 'Fehler: deadline_passed');
+      expect(
+        (error as ParentLetterException).error,
+        ParentLetterError.deadlinePassed,
+      );
+    });
+
+    test('the code wins over the status', () async {
+      final error = await errorOf(404, {'error': 'child_not_found'});
+      expect(
+        (error as ParentLetterException).error,
+        ParentLetterError.childNotFound,
+      );
+    });
+
+    test('falls back to the status without a known code', () async {
+      expect(
+        ((await errorOf(404, null)) as ParentLetterException).error,
+        ParentLetterError.letterNotFound,
+      );
+      expect(
+        ((await errorOf(409, 'Fehler: whatever')) as ParentLetterException)
+            .error,
+        ParentLetterError.responseFinal,
+      );
+    });
+
+    test('401 and 5xx keep the generic mapping', () async {
+      expect(await errorOf(401, 'Fehler: x'), isA<AuthException>());
+      expect(
+        await errorOf(500, {'error': 'letter_not_found'}),
+        isNot(isA<ParentLetterException>()),
+      );
+    });
+  });
+}
+
+/// Minimal fake Dio whose `get` always fails with the given exception; every
+/// other member is unused.
+class _ThrowingDio implements Dio {
+  final DioException error;
+
+  _ThrowingDio(this.error);
+
+  @override
+  Future<Response<T>> get<T>(
+    String path, {
+    Object? data,
+    Map<String, dynamic>? queryParameters,
+    Options? options,
+    CancelToken? cancelToken,
+    ProgressCallback? onReceiveProgress,
+  }) => Future<Response<T>>.error(error);
+
+  @override
+  dynamic noSuchMethod(Invocation invocation) =>
+      super.noSuchMethod(invocation);
+}

test/demo/demo_parent_letters_test.dart

@@ -0,0 +1,41 @@
+import 'dart:convert';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:marianum_mobile/api/demo/data/demo_parent_letters.dart';
+import 'package:marianum_mobile/api/marianumconnect/queries/parent_letters/parent_letter_models.dart';
+
+void main() {
+  test('every demo inbox letter resolves to a consistent detail', () {
+    final inbox = DemoParentLetters.list();
+    expect(inbox.items, isNotEmpty);
+    expect(
+      inbox.unreadCount,
+      inbox.items.where((letter) => !letter.read).length,
+    );
+    for (final letter in inbox.items) {
+      final detail = DemoParentLetters.detail(letter.id);
+      expect(detail.summary.id, letter.id);
+      expect(detail.summary.status, letter.status);
+      expect(
+        detail.content.children.map((child) => child.childId),
+        detail.content.request == null ? isEmpty : letter.childIds,
+      );
+      // The inbox is hydrated, so the fixtures must survive storage.
+      expect(
+        ParentLetterDetail.fromJson(
+          jsonDecode(jsonEncode(detail.toJson())) as Map<String, dynamic>,
+        ).content,
+        detail.content,
+      );
+    }
+  });
+
+  test('a letter read in the session stays read', () {
+    final unread = DemoParentLetters.list().items.firstWhere((l) => !l.read);
+    DemoParentLetters.markRead(unread.id);
+    final after = DemoParentLetters.list().items.firstWhere(
+      (l) => l.id == unread.id,
+    );
+    expect(after.read, isTrue);
+  });
+}

test/push/push_tap_router_test.dart

@@ -0,0 +1,66 @@
+import 'dart:convert';
+
+import 'package:flutter_local_notifications/flutter_local_notifications.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:marianum_mobile/push/push_tap_router.dart';
+import 'package:marianum_mobile/push/push_target.dart';
+
+void main() {
+  group('resolvePushTarget', () {
+    test('a parent letter push routes by its letter id', () {
+      final target = resolvePushTarget({
+        'source': 'connect',
+        'type': 'parent-letter',
+        'parentLetterId': 'l1',
+        'event': 'reply',
+        'title': 'Hr. Müller: Wandertag',
+      });
+      expect(
+        target,
+        isA<ParentLetterTarget>().having((t) => t.letterId, 'letterId', 'l1'),
+      );
+    });
+
+    test('newsletter pushes route by newsletterId', () {
+      expect(
+        resolvePushTarget({'source': 'connect', 'newsletterId': 'n1'}),
+        isA<NewsletterTarget>().having((t) => t.newsletterId, 'id', 'n1'),
+      );
+    });
+
+    test('chat pushes accept every token key in use', () {
+      for (final key in ['chatToken', 'token', 'roomToken']) {
+        expect(
+          resolvePushTarget({key: 'abc', 'nid': 5}),
+          isA<ChatTarget>().having((t) => t.chatToken, 'chatToken', 'abc'),
+          reason: key,
+        );
+      }
+    });
+
+    test('empty ids and unrelated data name no target', () {
+      expect(resolvePushTarget({'parentLetterId': ''}), isNull);
+      expect(resolvePushTarget({'type': 'widget-refresh'}), isNull);
+      expect(resolvePushTarget({'chatToken': 7}), isNull);
+    });
+  });
+
+  group('PushTapRouter.handleResponse', () {
+    setUp(() => PushTapRouter.pendingTarget.value = null);
+
+    NotificationResponse tap(String payload) => NotificationResponse(
+      notificationResponseType: NotificationResponseType.selectedNotification,
+      payload: payload,
+    );
+
+    test('publishes the target of a tapped notification', () {
+      PushTapRouter.handleResponse(tap(jsonEncode({'parentLetterId': 'l1'})));
+      expect(PushTapRouter.pendingTarget.value, isA<ParentLetterTarget>());
+    });
+
+    test('ignores broken payloads', () {
+      PushTapRouter.handleResponse(tap('not json'));
+      expect(PushTapRouter.pendingTarget.value, isNull);
+    });
+  });
+}

test/state/app_modules_order_test.dart

@@ -29,9 +29,15 @@ void main() {
 
       final effective = AppModule.effectiveModuleOrder(settingsWith(custom));
 
+      // parentLetters and ticker are both missing and follow timetable in the
+      // declared order, so they line up behind it.
+      expect(
+        effective.indexOf(Modules.parentLetters),
+        effective.indexOf(Modules.timetable) + 1,
+      );
       expect(
         effective.indexOf(Modules.ticker),
-        effective.indexOf(Modules.timetable) + 1,
+        effective.indexOf(Modules.parentLetters) + 1,
       );
       expect(effective.toSet(), Modules.values.toSet());
     });
@@ -94,10 +100,11 @@ void main() {
     final student = CredentialSession(username: 'max', password: 'pw');
     const guardian = GuardianSession(email: 'e@x.de');
 
-    test('password accounts see every module', () {
-      for (final m in Modules.values) {
-        expect(AppModule.isAvailableFor(m, student), isTrue, reason: m.name);
-      }
+    test('password accounts see every module but the guardian ones', () {
+      final hidden = Modules.values
+          .where((m) => !AppModule.isAvailableFor(m, student))
+          .toSet();
+      expect(hidden, {Modules.parentLetters});
     });
 
     test('guardians lose exactly the Nextcloud modules', () {

test/state/parent_letters_logic_test.dart

@@ -0,0 +1,104 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:marianum_mobile/api/marianumconnect/queries/parent_letters/parent_letter_models.dart';
+import 'package:marianum_mobile/state/app/modules/parent_letters/bloc/parent_letters_state.dart';
+import 'package:marianum_mobile/state/app/modules/parent_letters/parent_letters_logic.dart';
+
+ParentLetterSummary _letter(
+  String id, {
+  bool read = true,
+  List<String> childIds = const ['c1'],
+}) => ParentLetterSummary(
+  id: id,
+  sentAt: DateTime(2026, 9, 20),
+  read: read,
+  childIds: childIds,
+);
+
+void main() {
+  test('firstPageState takes over list and counters', () {
+    final state = firstPageState(
+      ParentLetterListResponse(
+        items: [_letter('a')],
+        hasMore: true,
+        unreadCount: 2,
+        openCount: 1,
+      ),
+    );
+    expect(state.letters.single.id, 'a');
+    expect(state.hasMore, isTrue);
+    expect(state.unreadCount, 2);
+    expect(state.openCount, 1);
+  });
+
+  test('appendOlderPage appends without duplicating known letters', () {
+    final state = ParentLettersState(
+      letters: [_letter('a'), _letter('b')],
+      hasMore: true,
+    );
+    final next = appendOlderPage(
+      state,
+      ParentLetterListResponse(items: [_letter('b'), _letter('c')]),
+    );
+    expect(next.letters.map((l) => l.id), ['a', 'b', 'c']);
+    expect(next.hasMore, isFalse);
+  });
+
+  group('withLetterRead', () {
+    final state = ParentLettersState(
+      letters: [_letter('a', read: false), _letter('b')],
+      unreadCount: 1,
+    );
+
+    test('marks the letter and lowers the counter', () {
+      final next = withLetterRead(state, 'a');
+      expect(next.letters.first.read, isTrue);
+      expect(next.unreadCount, 0);
+    });
+
+    test('returns the same state for read or unknown letters', () {
+      expect(identical(withLetterRead(state, 'b'), state), isTrue);
+      expect(identical(withLetterRead(state, 'x'), state), isTrue);
+    });
+
+    test('never drops the counter below zero', () {
+      final drifted = state.copyWith(unreadCount: 0);
+      expect(withLetterRead(drifted, 'a').unreadCount, 0);
+    });
+  });
+
+  group('withSummary', () {
+    final open = _letter('b').copyWith(status: ParentLetterStatus.open);
+    final state = ParentLettersState(
+      letters: [_letter('a'), open],
+      openCount: 3,
+    );
+
+    test('replaces the letter in place and lowers the open counter', () {
+      final next = withSummary(
+        state,
+        open.copyWith(status: ParentLetterStatus.done),
+      );
+      expect(next.letters.map((l) => l.id), ['a', 'b']);
+      expect(next.letters.last.status, ParentLetterStatus.done);
+      expect(next.openCount, 2);
+    });
+
+    test('keeps the counter while the letter stays open', () {
+      expect(withSummary(state, open.copyWith(read: false)).openCount, 3);
+    });
+
+    test('ignores letters the inbox does not hold', () {
+      expect(identical(withSummary(state, _letter('x')), state), isTrue);
+    });
+  });
+
+  test('filterLettersByChild keeps letters that concern the child', () {
+    final letters = [
+      _letter('a', childIds: ['c1']),
+      _letter('b', childIds: ['c2']),
+      _letter('c', childIds: ['c1', 'c2']),
+    ];
+    expect(filterLettersByChild(letters, null), letters);
+    expect(filterLettersByChild(letters, 'c2').map((l) => l.id), ['b', 'c']);
+  });
+}

test/utils/random_id_test.dart

@@ -0,0 +1,15 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:marianum_mobile/utils/random_id.dart';
+
+void main() {
+  test('randomUuidV4 is a well-formed version-4 UUID', () {
+    final pattern = RegExp(
+      r'^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$',
+    );
+    final ids = {for (var i = 0; i < 200; i++) randomUuidV4()};
+    expect(ids, hasLength(200));
+    for (final id in ids) {
+      expect(id, matches(pattern));
+    }
+  });
+}

test/view/parent_letters/parent_letter_form_policy_test.dart

@@ -0,0 +1,168 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:marianum_mobile/api/marianumconnect/queries/parent_letters/parent_letter_models.dart';
+import 'package:marianum_mobile/view/pages/parent_letters/parent_letter_form_policy.dart';
+import 'package:marianum_mobile/view/pages/parent_letters/widgets/parent_letter_attachments.dart';
+
+const _choice = ParentLetterField(
+  id: 'f1',
+  type: ParentLetterFieldType.singleChoice,
+  label: 'Teilnahme?',
+  isRequired: true,
+  options: [
+    ParentLetterOption(id: 'yes', label: 'Ja'),
+    ParentLetterOption(id: 'no', label: 'Nein'),
+  ],
+);
+const _optionalChoice = ParentLetterField(
+  id: 'f2',
+  type: ParentLetterFieldType.singleChoice,
+);
+const _unknownRequired = ParentLetterField(id: 'f3', isRequired: true);
+const _unknownOptional = ParentLetterField(id: 'f4');
+
+const _answered = ParentLetterResponse(
+  answers: [
+    ParentLetterAnswer(fieldId: 'f1', optionIds: ['no']),
+  ],
+);
+
+ParentLetterChildState _child({
+  bool editable = true,
+  ParentLetterResponse? response,
+}) => ParentLetterChildState(
+  childId: 'c1',
+  editable: editable,
+  response: response,
+);
+
+void main() {
+  group('ParentLetterFormPolicy.resolve', () {
+    test('letters without a request have no form', () {
+      expect(
+        ParentLetterFormPolicy.resolve(request: null, child: _child()),
+        isNull,
+      );
+    });
+
+    test('mode follows the server verdict and the existing response', () {
+      const request = ParentLetterRequest(fields: [_choice]);
+      ParentLetterFormMode mode(ParentLetterChildState child) =>
+          ParentLetterFormPolicy.resolve(request: request, child: child)!.mode;
+
+      expect(mode(_child()), ParentLetterFormMode.open);
+      expect(mode(_child(response: _answered)), ParentLetterFormMode.change);
+      expect(
+        mode(_child(editable: false, response: _answered)),
+        ParentLetterFormMode.done,
+      );
+      expect(mode(_child(editable: false)), ParentLetterFormMode.closed);
+    });
+
+    test('an unknown required field blocks the form', () {
+      final policy = ParentLetterFormPolicy.resolve(
+        request: const ParentLetterRequest(fields: [_choice, _unknownRequired]),
+        child: _child(),
+      )!;
+      expect(policy.mode, ParentLetterFormMode.unsupported);
+      expect(policy.canSubmit, isFalse);
+    });
+
+    test('an answered letter stays readable despite unknown fields', () {
+      final policy = ParentLetterFormPolicy.resolve(
+        request: const ParentLetterRequest(fields: [_choice, _unknownRequired]),
+        child: _child(editable: false, response: _answered),
+      )!;
+      expect(policy.mode, ParentLetterFormMode.done);
+    });
+
+    test('unknown optional fields are skipped', () {
+      final policy = ParentLetterFormPolicy.resolve(
+        request: const ParentLetterRequest(fields: [_choice, _unknownOptional]),
+        child: _child(),
+      )!;
+      expect(policy.mode, ParentLetterFormMode.open);
+      expect(policy.fields, [_choice]);
+    });
+  });
+
+  group('submit semantics', () {
+    ParentLetterFormPolicy policy(
+      ParentLetterRequest request, {
+      ParentLetterResponse? response,
+    }) => ParentLetterFormPolicy.resolve(
+      request: request,
+      child: _child(response: response),
+    )!;
+
+    test('acknowledgement', () {
+      final p = policy(const ParentLetterRequest());
+      expect(p.isAcknowledgement, isTrue);
+      expect(p.submitIsFinal, isTrue);
+      expect(p.submitLabel, 'Zur Kenntnis genommen');
+      expect(p.isComplete(const {}), isTrue);
+      expect(p.answersFor(const {}), isEmpty);
+    });
+
+    test('plain choice can be changed later', () {
+      const request = ParentLetterRequest(fields: [_choice]);
+      expect(policy(request).submitIsFinal, isFalse);
+      expect(policy(request).submitLabel, 'Rückmeldung absenden');
+      expect(
+        policy(request, response: _answered).submitLabel,
+        'Rückmeldung ändern',
+      );
+    });
+
+    test('signature makes the response final', () {
+      final p = policy(
+        const ParentLetterRequest(fields: [_choice], signatureRequired: true),
+      );
+      expect(p.submitIsFinal, isTrue);
+      expect(p.isAcknowledgement, isFalse);
+      expect(p.submitLabel, 'Unterschreiben und absenden');
+    });
+
+    test('only required fields must be answered', () {
+      final p = policy(
+        const ParentLetterRequest(fields: [_choice, _optionalChoice]),
+      );
+      expect(p.isComplete(const {}), isFalse);
+      expect(p.isComplete(const {'f2': 'x'}), isFalse);
+      expect(p.isComplete(const {'f1': 'yes'}), isTrue);
+    });
+
+    test('answers contain exactly the selected fields', () {
+      final p = policy(
+        const ParentLetterRequest(fields: [_choice, _optionalChoice]),
+      );
+      expect(p.answersFor(const {'f1': 'yes', 'stale': 'x'}), const [
+        ParentLetterAnswer(fieldId: 'f1', optionIds: ['yes']),
+      ]);
+    });
+
+    test('selectionOf restores a previous response', () {
+      expect(ParentLetterFormPolicy.selectionOf(_answered), {'f1': 'no'});
+      expect(ParentLetterFormPolicy.selectionOf(null), isEmpty);
+    });
+  });
+
+  group('safeAttachmentFileName', () {
+    String name(String fileName) => safeAttachmentFileName(
+      ParentLetterAttachment(id: 'a', fileName: fileName),
+    );
+
+    test('keeps ordinary names', () {
+      expect(name('Elternbrief 10b.pdf'), 'Elternbrief 10b.pdf');
+    });
+
+    test('strips path parts and reserved characters', () {
+      expect(name('../../etc/passwd'), 'passwd');
+      expect(name(r'C:\Users\x\brief?.pdf'), 'brief_.pdf');
+    });
+
+    test('never returns an empty or relative name', () {
+      expect(name(''), 'Anhang');
+      expect(name('foo/..'), 'Anhang');
+    });
+  });
+}