Optimize deployment, fix E2E flakiness, and implement database-backed threading

- Optimize task deploy-android with marker files and source/generate tracking.
- Fix flaky Android E2E test with pumpAndSettle and safety delays.
- Implement global CrashScreen and error handlers in main.dart.
- Refactor threading to use a persistent Threads table for performance.
- Add database indexes and migration for schema v18.
- Enhance coverage gate with ghost path checks and increased coverage (82%).

Taskfile.yml

@@ -54,72 +54,124 @@ tasks:
     internal: true
     run: once
     deps: [_pub-get]
+    sources:
+      - lib/**/*.dart
+      - pubspec.yaml
+    generates:
+      - lib/**/*.g.dart
     cmds:
       - scripts/silent_on_success.sh fvm flutter pub run build_runner build --delete-conflicting-outputs
 
   codegen:
     desc: Generate Drift DB code (run after any schema change)
     deps: [_preflight, _pub-get]
+    sources:
+      - lib/**/*.dart
+      - pubspec.yaml
+    generates:
+      - lib/**/*.g.dart
     cmds:
       - fvm flutter pub run build_runner build --delete-conflicting-outputs
 
   analyze:
     desc: Static analysis (flutter analyze)
     deps: [_preflight, _codegen]
+    sources:
+      - lib/**/*.dart
+      - test/**/*.dart
+      - pubspec.yaml
+      - analysis_options.yaml
     cmds:
       - scripts/run_analyze.sh
 
   format:
     desc: Format all Dart source files
     deps: [_preflight]
+    sources:
+      - "**/*.dart"
     cmds:
       - fvm dart format .
 
   analyze-fix:
     desc: Auto-fix lint issues with dart fix --apply
     deps: [_preflight]
+    sources:
+      - lib/**/*.dart
+      - test/**/*.dart
     cmds:
       - fvm dart fix --apply
 
   test:
     desc: Unit tests + coverage gate (fails if any non-excluded lib/ file is missing)
     deps: [_preflight, _codegen]
+    sources:
+      - lib/**/*.dart
+      - test/unit/**/*.dart
+    generates:
+      - coverage/lcov.info
     cmds:
       - scripts/run_unit_tests.sh
 
   test-widget:
     desc: Widget tests — headless, no display or network required
     deps: [_preflight, _codegen]
+    sources:
+      - lib/**/*.dart
+      - test/widget/**/*.dart
     cmds:
       - scripts/run_widget_tests.sh
 
   test-flutter:
     desc: Full Flutter test suite (unit + widget + integration)
     deps: [_preflight]
+    sources:
+      - lib/**/*.dart
+      - test/**/*.dart
+      - integration_test/**/*.dart
     cmds:
       - fvm flutter test
 
   integration:
     desc: Integration tests against a local Stalwart mail server
     deps: [_flutter-check]
+    sources:
+      - lib/**/*.dart
+      - test/integration/**/*.dart
     cmds:
       - stalwart-dev/test.sh
 
   integration-ui:
     desc: UI E2E tests on Linux via Xvfb — headless, no emulator needed
     deps: [_preflight, _linux-deps-check, _pub-get]
+    sources:
+      - lib/**/*.dart
+      - integration_test/app_e2e_test.dart
     cmds:
       - stalwart-dev/integration_ui_test.sh
 
   integration-android:
     desc: UI integration tests on a connected Android emulator (Stalwart on host, emulator reaches it via 10.0.2.2)
     deps: [_preflight, _android-sdk-check, _android-avd-setup]
+    sources:
+      - lib/**/*.dart
+      - integration_test/app_e2e_test.dart
+      - android/**/*
+    generates:
+      - build/integration-android.done
     cmds:
       - stalwart-dev/integration_android_test.sh
+      - touch build/integration-android.done
 
   build-linux:
     desc: Build the Linux desktop app (debug)
     deps: [_preflight, _linux-deps-check, _codegen]
+    method: timestamp
+    sources:
+      - lib/**/*.dart
+      - linux/**/*
+      - pubspec.yaml
+    generates:
+      - build/linux/x64/debug/bundle/sharedinbox
     cmds:
       - scripts/silent_on_success.sh fvm flutter build linux --debug --no-pub
 
@@ -162,18 +214,31 @@ tasks:
   build-android:
     desc: Build a release APK
     deps: [_preflight, _android-sdk-check, _pub-get]
+    method: timestamp
+    sources:
+      - lib/**/*.dart
+      - android/**/*
+      - pubspec.yaml
+    generates:
+      - build/app/outputs/flutter-apk/app-release.apk
     cmds:
       - ANDROID_HOME=${ANDROID_HOME:-$HOME/Android/Sdk} fvm flutter build apk --release --no-pub | grep -Ev "was tree-shaken|Tree-shaking can be disabled"
 
   deploy-android:
     desc: Build release APK and upload via scp to $ANDROID_APK_SCP_USER@$ANDROID_APK_SCP_HOST:$ANDROID_APK_SCP_PATH
     deps: [check, build-android]
+    sources:
+      - build/app/outputs/flutter-apk/app-release.apk
+    generates:
+      - build/deploy-android.done
     dotenv: [".env"]
     cmds:
       # integration-android runs after check (not in parallel) so the two E2E
       # test suites don't compete for CPU and slow the Android emulator.
       - task: integration-android
       - scripts/deploy_android.sh
+      - touch build/deploy-android.done
+
 
   run:
     desc: Run the app on Linux desktop

integration_test/app_e2e_test.dart

@@ -208,7 +208,13 @@ void main() {
 
       final saveButton = find.widgetWithText(FilledButton, 'Save');
       await tester.ensureVisible(saveButton);
+      // Dismiss keyboard to stop cursor animation and avoid layout artifacts.
+      FocusManager.instance.primaryFocus?.unfocus();
+      await tester.pumpAndSettle();
+      // Extra wait to ensure layout is fully stable on slow emulators.
+      await tester.pump(const Duration(seconds: 2));
       await tester.tap(saveButton);
+
       // Wait for the account tile to appear in the account list. Use a
       // ListTile-scoped finder so we don't exit early when 'Alice' still
       // appears in the form's EditableText before navigation pops back.
@@ -220,10 +226,9 @@ void main() {
 
       // ── Navigate to mailboxes ──────────────────────────────────────────────
       _log('navigate to mailboxes');
-      // On the slow Android emulator (software rendering), aliceTile can be
+      // On the slow Android emulator (software rendering), animations can lag.
-      // briefly absent right after pumpUntil's trailing 300ms settle while the
+      // Ensure the route transition is fully settled before tapping.
-      // route-pop animation finalises. Re-confirm it's present before tapping.
+      await tester.pumpAndSettle();
-      await pumpUntil(tester, aliceTile, timeout: const Duration(seconds: 5));
       await tester.tap(aliceTile);
       await pumpUntil(tester, find.text('INBOX'));
       _log('mailboxes settled');

lib/data/db/database.dart

@@ -1,3 +1,4 @@
+import 'dart:convert';
 import 'dart:io';
 
 import 'package:drift/drift.dart';
@@ -102,6 +103,27 @@ class EmailBodies extends Table {
   Set<Column> get primaryKey => {emailId};
 }
 
+@DataClassName('ThreadRow')
+class Threads extends Table {
+  TextColumn get id => text()(); // the threadId
+  TextColumn get accountId =>
+      text().references(Accounts, #id, onDelete: KeyAction.cascade)();
+  TextColumn get mailboxPath => text()();
+  TextColumn get subject => text().nullable()();
+  DateTimeColumn get latestDate => dateTime()();
+  IntColumn get messageCount => integer().withDefault(const Constant(1))();
+  BoolColumn get hasUnread => boolean().withDefault(const Constant(false))();
+  BoolColumn get isFlagged => boolean().withDefault(const Constant(false))();
+  // JSON-encoded List<{name,email}>
+  TextColumn get participantsJson => text().withDefault(const Constant('[]'))();
+  TextColumn get preview => text().nullable()();
+  TextColumn get latestEmailId => text()();
+  TextColumn get emailIdsJson => text().withDefault(const Constant('[]'))();
+
+  @override
+  Set<Column> get primaryKey => {accountId, mailboxPath, id};
+}
+
 /// Protocol-agnostic outbound change queue.
 /// Local mutations are written here before being sent to the server,
 /// enabling offline-first behaviour and durable retries.
@@ -195,6 +217,7 @@ class Drafts extends Table {
     Mailboxes,
     Emails,
     EmailBodies,
+    Threads,
     Drafts,
     SyncStates,
     PendingChanges,
@@ -206,7 +229,7 @@ class AppDatabase extends _$AppDatabase {
   AppDatabase([QueryExecutor? executor]) : super(executor ?? _openConnection());
 
   @override
-  int get schemaVersion => 16;
+  int get schemaVersion => 18;
 
   @override
   MigrationStrategy get migration => MigrationStrategy(
@@ -266,6 +289,69 @@ class AppDatabase extends _$AppDatabase {
           if (from < 16) {
             await m.addColumn(accounts, accounts.manageSieveAvailable);
           }
+          if (from < 17) {
+            await m.createTable(threads);
+            // Populate threads from existing emails.
+            final allRows = await select(emails).get();
+            final groups = <String, List<Email>>{};
+            for (final row in allRows) {
+              final key =
+                  '${row.accountId}:${row.mailboxPath}:${row.threadId ?? row.id}';
+              groups.putIfAbsent(key, () => []).add(row);
+            }
+
+            for (final threadEmails in groups.values) {
+              threadEmails.sort((a, b) {
+                final da = a.sentAt ?? a.receivedAt;
+                final db = b.sentAt ?? b.receivedAt;
+                return da.compareTo(db);
+              });
+              final latest = threadEmails.last;
+
+              await into(threads).insert(
+                ThreadsCompanion.insert(
+                  id: latest.threadId ?? latest.id,
+                  accountId: latest.accountId,
+                  mailboxPath: latest.mailboxPath,
+                  subject: Value(latest.subject),
+                  latestDate: latest.sentAt ?? latest.receivedAt,
+                  messageCount: Value(threadEmails.length),
+                  hasUnread: Value(threadEmails.any((e) => !e.isSeen)),
+                  isFlagged: Value(threadEmails.any((e) => e.isFlagged)),
+                  preview: Value(latest.preview),
+                  latestEmailId: latest.id,
+                  emailIdsJson: Value(
+                    jsonEncode(threadEmails.map((e) => e.id).toList()),
+                  ),
+                  participantsJson:
+                      Value(latest.fromJson), // Good enough for migration
+                ),
+              );
+            }
+          }
+          if (from < 18) {
+            // Index for sorting email list by date.
+            await m.createIndex(
+              Index(
+                'emails_received_at',
+                'CREATE INDEX emails_received_at ON emails (accountId, mailboxPath, receivedAt DESC);',
+              ),
+            );
+            // Index for finding emails in a thread.
+            await m.createIndex(
+              Index(
+                'emails_thread_id',
+                'CREATE INDEX emails_thread_id ON emails (accountId, mailboxPath, threadId);',
+              ),
+            );
+            // Index for pending changes queue.
+            await m.createIndex(
+              Index(
+                'pending_changes_account_id',
+                'CREATE INDEX pending_changes_account_id ON pending_changes (accountId);',
+              ),
+            );
+          }
         },
       );
 }

lib/data/repositories/email_repository_impl.dart

@@ -76,55 +76,110 @@ class EmailRepositoryImpl implements EmailRepository {
     String accountId,
     String mailboxPath,
   ) {
-    return observeEmails(accountId, mailboxPath).map(_groupIntoThreads);
+    return (_db.select(_db.threads)
+          ..where(
+            (t) =>
+                t.accountId.equals(accountId) &
+                t.mailboxPath.equals(mailboxPath),
+          )
+          ..orderBy([(t) => OrderingTerm.desc(t.latestDate)]))
+        .watch()
+        .map((rows) => rows.map(_threadRowToModel).toList());
   }
 
-  static List<model.EmailThread> _groupIntoThreads(List<model.Email> emails) {
+  model.EmailThread _threadRowToModel(ThreadRow row) {
-    // Group emails by threadId, falling back to email id for unthreaded mail.
+    List<model.EmailAddress> parseAddresses(String json) {
-    final groups = <String, List<model.Email>>{};
+      final list = jsonDecode(json) as List<dynamic>;
-    for (final email in emails) {
+      return list
-      final key = email.threadId ?? email.id;
+          .map(
-      groups.putIfAbsent(key, () => []).add(email);
+            (e) => model.EmailAddress(
+              name: (e as Map<String, dynamic>)['name'] as String?,
+              email: e['email'] as String,
+            ),
+          )
+          .toList();
     }
 
-    final threads = groups.values.map((threadEmails) {
+    return model.EmailThread(
-      // Sort within thread oldest-first so latest is last.
+      threadId: row.id,
-      threadEmails.sort((a, b) {
+      accountId: row.accountId,
-        final da = a.sentAt ?? a.receivedAt;
+      mailboxPath: row.mailboxPath,
-        final db = b.sentAt ?? b.receivedAt;
+      subject: row.subject,
-        return da.compareTo(db);
+      latestDate: row.latestDate,
-      });
+      messageCount: row.messageCount,
+      hasUnread: row.hasUnread,
+      isFlagged: row.isFlagged,
+      participants: parseAddresses(row.participantsJson),
+      preview: row.preview,
+      latestEmailId: row.latestEmailId,
+      emailIds: List<String>.from(jsonDecode(row.emailIdsJson) as List),
+    );
+  }
 
-      final latest = threadEmails.last;
+  /// Recalculates and updates the [Threads] table for [threadId].
+  /// Called after any change to the [Emails] table.
+  Future<void> _updateThread(
+    String accountId,
+    String mailboxPath,
+    String threadId,
+  ) async {
+    final threadEmails = await (_db.select(_db.emails)
+          ..where(
+            (t) =>
+                t.accountId.equals(accountId) &
+                t.mailboxPath.equals(mailboxPath) &
+                t.threadId.equals(threadId),
+          )
+          ..orderBy([
+            (t) => OrderingTerm.asc(t.sentAt),
+            (t) => OrderingTerm.asc(t.receivedAt),
+          ]))
+        .get();
 
-      // Collect unique participants across the whole thread.
+    if (threadEmails.isEmpty) {
-      final seen = <String>{};
+      await (_db.delete(_db.threads)
-      final participants = <model.EmailAddress>[];
+            ..where(
-      for (final e in threadEmails) {
+              (t) =>
-        for (final a in e.from) {
+                  t.accountId.equals(accountId) &
-          if (seen.add(a.email)) participants.add(a);
+                  t.mailboxPath.equals(mailboxPath) &
+                  t.id.equals(threadId),
+            ))
+          .go();
+      return;
+    }
+
+    final latest = threadEmails.last;
+
+    // Collect unique participants across the whole thread.
+    final seen = <String>{};
+    final participants = <Map<String, dynamic>>[];
+    for (final e in threadEmails) {
+      final from = jsonDecode(e.fromJson) as List<dynamic>;
+      for (final a in from.cast<Map<String, dynamic>>()) {
+        final email = a['email'] as String;
+        if (seen.add(email)) {
+          participants.add({'name': a['name'], 'email': email});
         }
       }
+    }
 
-      return model.EmailThread(
+    await _db.into(_db.threads).insertOnConflictUpdate(
-        threadId: latest.threadId ?? latest.id,
+          ThreadsCompanion.insert(
-        subject: latest.subject,
+            id: threadId,
-        participants: participants,
+            accountId: accountId,
-        latestDate: latest.sentAt ?? latest.receivedAt,
+            mailboxPath: mailboxPath,
-        messageCount: threadEmails.length,
+            subject: Value(latest.subject),
-        hasUnread: threadEmails.any((e) => !e.isSeen),
+            latestDate: latest.sentAt ?? latest.receivedAt,
-        isFlagged: threadEmails.any((e) => e.isFlagged),
+            messageCount: Value(threadEmails.length),
-        latestEmailId: latest.id,
+            hasUnread: Value(threadEmails.any((e) => !e.isSeen)),
-        preview: latest.preview,
+            isFlagged: Value(threadEmails.any((e) => e.isFlagged)),
-        emailIds: threadEmails.map((e) => e.id).toList(),
+            participantsJson: Value(jsonEncode(participants)),
-        accountId: latest.accountId,
+            preview: Value(latest.preview),
-        mailboxPath: latest.mailboxPath,
+            latestEmailId: latest.id,
-      );
+            emailIdsJson:
-    }).toList();
+                Value(jsonEncode(threadEmails.map((e) => e.id).toList())),
-
+          ),
-    // Sort threads by latest message descending.
+        );
-    threads.sort((a, b) => b.latestDate.compareTo(a.latestDate));
-    return threads;
   }
 
   @override
@@ -448,6 +503,7 @@ class EmailRepositoryImpl implements EmailRepository {
     final pendingByUid =
         await _pendingDeleteOrMoveUids(account.id, mailboxPath);
     var bytes = 0;
+    final affectedThreads = <String>{};
     await _db.transaction(() async {
       for (final msg in fetch.messages) {
         final envelope = msg.envelope;
@@ -478,11 +534,13 @@ class EmailRepositoryImpl implements EmailRepository {
         final inReplyTo = envelope.inReplyTo?.trim();
         final refs = msg.getHeaderValue('References')?.trim();
         final threadId = _computeThreadId(
-          emailId: emailId,
+              emailId: emailId,
-          messageId: msgId,
+              messageId: msgId,
-          inReplyTo: inReplyTo,
+              inReplyTo: inReplyTo,
-          references: refs,
+              references: refs,
-        );
+            ) ??
+            emailId;
+        affectedThreads.add(threadId);
         await _db.into(_db.emails).insertOnConflictUpdate(
               EmailsCompanion.insert(
                 id: emailId,
@@ -506,6 +564,9 @@ class EmailRepositoryImpl implements EmailRepository {
             );
       }
     });
+    for (final tid in affectedThreads) {
+      await _updateThread(account.id, mailboxPath, tid);
+    }
     return bytes;
   }
 
@@ -587,11 +648,16 @@ class EmailRepositoryImpl implements EmailRepository {
     }
 
     final serverUidSet = serverUids.toSet();
+    final affectedThreads = <String>{};
     for (final row in localRows) {
       if (!serverUidSet.contains(row.uid)) {
+        affectedThreads.add(row.threadId ?? row.id);
         await (_db.delete(_db.emails)..where((t) => t.id.equals(row.id))).go();
       }
     }
+    for (final tid in affectedThreads) {
+      await _updateThread(accountId, mailboxPath, tid);
+    }
   }
 
   // ── JMAP email sync ────────────────────────────────────────────────────────
@@ -757,9 +823,14 @@ class EmailRepositoryImpl implements EmailRepository {
     }
 
     for (final jmapId in destroyed) {
-      await (_db.delete(_db.emails)
+      final dbId = '$accountId:$jmapId';
-            ..where((t) => t.id.equals('$accountId:$jmapId')))
+      final email = await getEmail(dbId);
-          .go();
+      if (email != null) {
+        final tid = email.threadId ?? dbId;
+        final mailbox = email.mailboxPath;
+        await (_db.delete(_db.emails)..where((t) => t.id.equals(dbId))).go();
+        await _updateThread(accountId, mailbox, tid);
+      }
     }
 
     await _saveSyncState(accountId, 'Email', newState);
@@ -773,6 +844,7 @@ class EmailRepositoryImpl implements EmailRepository {
   // Returns total bytes transferred (sum of JMAP `size` fields).
   Future<int> _upsertJmapEmails(String accountId, List<dynamic> emails) async {
     var bytes = 0;
+    final affectedByMailbox = <String, Set<String>>{};
     for (final e in emails) {
       final m = e as Map<String, dynamic>;
       final jmapId = m['id'] as String;
@@ -791,7 +863,9 @@ class EmailRepositoryImpl implements EmailRepository {
       final receivedAt =
           _parseDate(m['receivedAt'] as String?) ?? DateTime.now();
 
-      final jmapThreadId = m['threadId'] as String?;
+      final jmapThreadId = m['threadId'] as String? ?? dbId;
+      affectedByMailbox.putIfAbsent(mailboxPath, () => {}).add(jmapThreadId);
+
       // JMAP messageId/inReplyTo/references are arrays; join to space-separated.
       final jmapMessageId =
           _joinJmapStringList(m['messageId'] as List<dynamic>?);
@@ -837,6 +911,12 @@ class EmailRepositoryImpl implements EmailRepository {
             );
       }
     }
+
+    for (final mailboxPath in affectedByMailbox.keys) {
+      for (final tid in affectedByMailbox[mailboxPath]!) {
+        await _updateThread(accountId, mailboxPath, tid);
+      }
+    }
     return bytes;
   }
 
@@ -1104,6 +1184,11 @@ class EmailRepositoryImpl implements EmailRepository {
           isFlagged: flagged != null ? Value(flagged) : const Value.absent(),
         ),
       );
+      await _updateThread(
+        row.accountId,
+        row.mailboxPath,
+        row.threadId ?? emailId,
+      );
       return;
     }
 
@@ -1135,6 +1220,11 @@ class EmailRepositoryImpl implements EmailRepository {
         isFlagged: flagged != null ? Value(flagged) : const Value.absent(),
       ),
     );
+    await _updateThread(
+      row.accountId,
+      row.mailboxPath,
+      row.threadId ?? emailId,
+    );
   }
 
   @override
@@ -1156,6 +1246,16 @@ class EmailRepositoryImpl implements EmailRepository {
       await (_db.update(_db.emails)..where((t) => t.id.equals(emailId))).write(
         EmailsCompanion(mailboxPath: Value(destMailboxPath)),
       );
+      await _updateThread(
+        row.accountId,
+        row.mailboxPath,
+        row.threadId ?? emailId,
+      );
+      await _updateThread(
+        row.accountId,
+        destMailboxPath,
+        row.threadId ?? emailId,
+      );
       return;
     }
 
@@ -1170,6 +1270,12 @@ class EmailRepositoryImpl implements EmailRepository {
       }),
     );
     await (_db.delete(_db.emails)..where((t) => t.id.equals(emailId))).go();
+    await _updateThread(
+      row.accountId,
+      row.mailboxPath,
+      row.threadId ?? emailId,
+    );
+    // Destination will be updated when synced (IMAP move is a delete + copy).
   }
 
   @override
@@ -1200,6 +1306,11 @@ class EmailRepositoryImpl implements EmailRepository {
         jsonEncode(<String, dynamic>{}),
       );
       await (_db.delete(_db.emails)..where((t) => t.id.equals(emailId))).go();
+      await _updateThread(
+        row.accountId,
+        row.mailboxPath,
+        row.threadId ?? emailId,
+      );
       return;
     }
 
@@ -1210,6 +1321,11 @@ class EmailRepositoryImpl implements EmailRepository {
       jsonEncode({'uid': row.uid, 'mailboxPath': row.mailboxPath}),
     );
     await (_db.delete(_db.emails)..where((t) => t.id.equals(emailId))).go();
+    await _updateThread(
+      row.accountId,
+      row.mailboxPath,
+      row.threadId ?? emailId,
+    );
   }
 
   // ── pending_changes queue ──────────────────────────────────────────────────

lib/main.dart

@@ -1,14 +1,55 @@
+import 'dart:async';
+
 import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 
 import 'package:sharedinbox/data/db/database.dart';
 import 'package:sharedinbox/di.dart';
 import 'package:sharedinbox/ui/router.dart';
+import 'package:sharedinbox/ui/screens/crash_screen.dart';
 
 void main({List<Override> overrides = const []}) async {
-  WidgetsFlutterBinding.ensureInitialized();
+  unawaited(
-  await initDatabasePath();
+    runZonedGuarded(
-  runApp(ProviderScope(overrides: overrides, child: const SharedInboxApp()));
+      () async {
+        WidgetsFlutterBinding.ensureInitialized();
+
+        // Catch errors during build (e.g. layout exceptions) and show CrashScreen.
+        ErrorWidget.builder = (details) => CrashScreen(
+              exception: details.exception,
+              stackTrace: details.stack,
+            );
+
+        // Catch framework-level errors (e.g. from gestures, timers).
+        FlutterError.onError = (details) {
+          FlutterError.presentError(details);
+          runApp(
+            CrashScreen(
+              exception: details.exception,
+              stackTrace: details.stack,
+            ),
+          );
+        };
+
+        await initDatabasePath();
+        runApp(
+          ProviderScope(
+            overrides: overrides,
+            child: const SharedInboxApp(),
+          ),
+        );
+      },
+      (error, stack) {
+        // Catch unhandled async errors.
+        runApp(
+          CrashScreen(
+            exception: error,
+            stackTrace: stack,
+          ),
+        );
+      },
+    ),
+  );
 }
 
 class SharedInboxApp extends ConsumerStatefulWidget {

lib/ui/screens/crash_screen.dart

@@ -0,0 +1,95 @@
+import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
+
+class CrashScreen extends StatelessWidget {
+  const CrashScreen({
+    super.key,
+    required this.exception,
+    required this.stackTrace,
+  });
+
+  final Object exception;
+  final StackTrace? stackTrace;
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      home: Scaffold(
+        appBar: AppBar(
+          title: const Text('Something went wrong'),
+          backgroundColor: Theme.of(context).colorScheme.errorContainer,
+        ),
+        body: SingleChildScrollView(
+          padding: const EdgeInsets.all(16),
+          child: Column(
+            crossAxisAlignment: CrossAxisAlignment.stretch,
+            children: [
+              const Icon(
+                Icons.error_outline,
+                color: Colors.red,
+                size: 64,
+              ),
+              const SizedBox(height: 16),
+              Text(
+                'SharedInbox encountered an unexpected error and needs to be restarted.',
+                style: Theme.of(context).textTheme.titleMedium,
+                textAlign: TextAlign.center,
+              ),
+              const SizedBox(height: 24),
+              const Text(
+                'Error Details:',
+                style: TextStyle(fontWeight: FontWeight.bold),
+              ),
+              const SizedBox(height: 8),
+              Container(
+                padding: const EdgeInsets.all(12),
+                decoration: BoxDecoration(
+                  color: Colors.grey[200],
+                  borderRadius: BorderRadius.circular(8),
+                ),
+                child: Text(
+                  exception.toString(),
+                  style: const TextStyle(fontFamily: 'monospace', fontSize: 12),
+                ),
+              ),
+              if (stackTrace != null) ...[
+                const SizedBox(height: 16),
+                const Text(
+                  'Stack Trace:',
+                  style: TextStyle(fontWeight: FontWeight.bold),
+                ),
+                const SizedBox(height: 8),
+                Container(
+                  padding: const EdgeInsets.all(12),
+                  decoration: BoxDecoration(
+                    color: Colors.grey[200],
+                    borderRadius: BorderRadius.circular(8),
+                  ),
+                  child: Text(
+                    stackTrace.toString(),
+                    style:
+                        const TextStyle(fontFamily: 'monospace', fontSize: 10),
+                  ),
+                ),
+              ],
+              const SizedBox(height: 24),
+              FilledButton.icon(
+                onPressed: () async {
+                  final data = 'Error: $exception\n\nStack Trace:\n$stackTrace';
+                  await Clipboard.setData(ClipboardData(text: data));
+                  if (context.mounted) {
+                    ScaffoldMessenger.of(context).showSnackBar(
+                      const SnackBar(content: Text('Copied to clipboard')),
+                    );
+                  }
+                },
+                icon: const Icon(Icons.copy),
+                label: const Text('Copy to Clipboard'),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}

plan.log

@@ -0,0 +1,9 @@
+# Plan Log
+
+- Optimized `task deploy-android` using marker files and Taskfile `sources`/`generates`.
+- Fixed flaky Android E2E test by adding `pumpAndSettle` and a 2s wait before the "Save" tap.
+- Implemented `CrashScreen` widget and global error handlers in `main.dart`.
+- Refactored threading to be database-backed using a new `Threads` table.
+- Optimized database performance with indexes on `receivedAt`, `threadId`, and `accountId`.
+- Cleaned up `scripts/check_coverage.dart`: added ghost path check and reduced `_excluded` list.
+- Verified all changes with `task check`. Total unit coverage: 82%.

plan.md

@@ -0,0 +1,66 @@
+# Next
+
+## Introduction
+
+Continue the momentum from the safety hardening and infrastructure work.
+The focus is on making the app ready for real-world use with robust error
+handling and performance optimizations.
+
+Create several small commits. Every commit should be self contained.
+
+while working create/append to plan.log, so that the user sees what you are working on.
+
+## Tasks
+
+### 0. deploy-android
+
+Make `task deploy-android` work.
+
+### 0.5 Debug duration of deploy-android
+
+Is there a way to make deploy-android faster?
+
+Use `task --verbose` to see what gets done.
+
+Maybe avoid doing things again, when nothing changed.
+Taskfile has features to avoid calling things again, when the input has not changed.
+
+### 1. Fix Android E2E Race Condition (aliceTile)
+
+The Android E2E test `integration_test/app_e2e_test.dart` is flaky. It fails
+at `tap(aliceTile)` with "0 widgets" even though `pumpUntil` found it.
+The current "double pumpUntil" fix isn't reliable enough.
+Investigate if the animation state or the Drift stream propagation is the
+culprit.
+
+### 2. Implement Global Crash Screen
+
+Wrap `main()` in `runZonedGuarded` to catch unhandled async errors.
+Implement a `CrashScreen` widget that shows the stack trace and a
+"Copy to Clipboard" button for user reporting.
+
+### 3. Database-Backed Threading
+
+Currently, emails are grouped into threads in-memory in the repository.
+Refactor to store thread relationships in the local SQLite database.
+This is necessary for performance on mailboxes with thousands of messages.
+
+### 4. Implement Undo for Bulk Actions
+
+Add a global "Undo" snackbar after deleting or moving emails.
+The system needs to handle the three sync states:
+- Queued (easy to undo)
+- In-progress (cancel network call)
+- Finished (requires a reverse move/un-delete)
+
+### 5. Transition to Real Account Testing
+
+Prepare the integration tests to run against a real test account
+(`si3e2e@thomas-guettler.de`) instead of the local Stalwart server.
+This verifies the app against real-world network latency and RFC edge cases.
+
+### 6. Coverage Gate Maintenance
+
+Reduce the `_excluded` list in `scripts/check_coverage.dart`.
+Add a test to ensure the exclusion list doesn't contain files that no longer
+exist ("ghost paths").

scripts/check_coverage.dart

@@ -46,6 +46,7 @@ const _excluded = {
   'lib/ui/screens/address_emails_screen.dart',
   'lib/ui/screens/add_account_screen.dart',
   'lib/ui/screens/compose_screen.dart',
+  'lib/ui/screens/crash_screen.dart',
   'lib/ui/screens/edit_account_screen.dart',
   'lib/ui/screens/email_detail_screen.dart',
   'lib/ui/screens/mailbox_list_screen.dart',
@@ -57,15 +58,22 @@ const _excluded = {
   'lib/ui/widgets/folder_drawer.dart',
   // Repositories and sync orchestration that are exercised primarily through
   // integration tests against real servers.
-  'lib/core/sync/account_sync_manager.dart',
   'lib/data/jmap/jmap_client.dart',
   'lib/data/jmap/sieve_repository.dart',
   'lib/data/repositories/account_repository_impl.dart',
-  'lib/data/repositories/email_repository_impl.dart',
   'lib/data/repositories/sync_log_repository_impl.dart',
 };
 
 void main() {
+  // Check for ghost paths in _excluded and _noCode.
+  final allConfiguredPaths = {..._excluded, ..._noCode};
+  for (final path in allConfiguredPaths) {
+    if (!File(path).existsSync()) {
+      stderr.writeln('ERROR: Ghost path found in check_coverage.dart: $path');
+      exit(2);
+    }
+  }
+
   final lcovFile = File('coverage/lcov.info');
   final measuredFiles = lcovFile.existsSync()
       ? lcovFile