perf(P4): add indexes on mailboxes(account_id) and threads(latest_date)

Schema v25: adds mailboxes_account_id covering (account_id, path) for
observeMailboxes and threads_latest_date covering (account_id,
mailbox_path, latest_date DESC) for observeThreads, replacing full-table
scans on both tables.  Migration test updated with a complete v22 schema
fixture and index assertions.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Taskfile.yml

@@ -331,6 +331,12 @@ tasks:
     cmds:
       - fvm dart run scripts/check_coverage.dart
 
+  check-coverage:
+    desc: Run unit+widget tests with coverage, then fail if the gate is not met
+    deps: [test]
+    cmds:
+      - task: coverage
+
   website-dev:
     desc: Run Hugo development server
     cmds:
@@ -361,8 +367,8 @@ tasks:
           ${SSH_USER}@${SSH_HOST}:public_html/
 
   check-fast:
-    desc: Pre-commit checks — analyze + unit tests + widget tests (no build, no integration)
-    deps: [analyze, test, check-hygiene]
+    desc: Pre-commit checks — analyze + unit+widget tests + coverage gate (no build, no integration)
+    deps: [analyze, check-coverage, check-hygiene]
 
   check-hygiene:
     desc: Verify that no forbidden files (like home dir config) are tracked

lib/data/db/database.dart

@@ -269,7 +269,7 @@ class AppDatabase extends _$AppDatabase {
   AppDatabase([QueryExecutor? executor]) : super(executor ?? _openConnection());
 
   @override
-  int get schemaVersion => 24;
+  int get schemaVersion => 25;
 
   @override
   MigrationStrategy get migration => MigrationStrategy(
@@ -431,6 +431,22 @@ class AppDatabase extends _$AppDatabase {
           if (from >= 4 && from < 24) {
             await m.addColumn(drafts, drafts.imapServerId);
           }
+          if (from < 25) {
+            // For observeMailboxes: filter by account_id, sort by path.
+            await m.createIndex(
+              Index(
+                'mailboxes_account_id',
+                'CREATE INDEX IF NOT EXISTS mailboxes_account_id ON mailboxes (account_id, path);',
+              ),
+            );
+            // For observeThreads: filter by account_id+mailbox_path, sort by latest_date.
+            await m.createIndex(
+              Index(
+                'threads_latest_date',
+                'CREATE INDEX IF NOT EXISTS threads_latest_date ON threads (account_id, mailbox_path, latest_date DESC);',
+              ),
+            );
+          }
         },
       );
 }

lib/ui/screens/email_list_screen.dart

@@ -10,6 +10,7 @@ import 'package:sharedinbox/core/models/email.dart';
 import 'package:sharedinbox/core/models/undo_action.dart';
 import 'package:sharedinbox/core/repositories/email_repository.dart';
 import 'package:sharedinbox/di.dart';
+import 'package:sharedinbox/ui/widgets/email_tile.dart';
 import 'package:sharedinbox/ui/widgets/folder_drawer.dart';
 import 'package:sharedinbox/ui/widgets/snooze_picker.dart';
 
@@ -711,10 +712,9 @@ class _EmailListScreenState extends ConsumerState<EmailListScreen> {
       itemBuilder: (ctx, i) {
         final e = emails[i];
         final isSelected = _selectedSearchIds.contains(e.id);
-        final sender = e.from.isNotEmpty
-            ? (e.from.first.name ?? e.from.first.email)
-            : '(unknown)';
-        return ListTile(
+        return EmailTile(
+          email: e,
+          selected: isSelected,
           leading: SizedBox(
             width: 40,
             child: _selecting
@@ -722,25 +722,7 @@ class _EmailListScreenState extends ConsumerState<EmailListScreen> {
                     value: isSelected,
                     onChanged: (_) => _toggleSearchSelection(e.id),
                   )
-                : Icon(
-                    e.isSeen ? Icons.mail_outline : Icons.mail,
-                    color: e.isSeen ? null : Theme.of(ctx).colorScheme.primary,
-                  ),
-          ),
-          title: Text(
-            sender,
-            style:
-                e.isSeen ? null : const TextStyle(fontWeight: FontWeight.bold),
-          ),
-          subtitle: Text(
-            e.subject ?? '(no subject)',
-            maxLines: 1,
-            overflow: TextOverflow.ellipsis,
-          ),
-          selected: isSelected,
-          trailing: Text(
-            e.sentAt != null ? _dateFmt.format(e.sentAt!) : '',
-            style: Theme.of(ctx).textTheme.bodySmall,
+                : null,
           ),
           onTap: _selecting
               ? () => _toggleSearchSelection(e.id)

lib/ui/screens/search_screen.dart

@@ -8,6 +8,7 @@ import 'package:sharedinbox/core/models/email.dart';
 import 'package:sharedinbox/core/models/mailbox.dart';
 import 'package:sharedinbox/core/utils/logger.dart';
 import 'package:sharedinbox/di.dart';
+import 'package:sharedinbox/ui/widgets/email_tile.dart';
 
 class SearchScreen extends ConsumerStatefulWidget {
   const SearchScreen({super.key, this.accountId});
@@ -155,7 +156,15 @@ class _SearchScreenState extends ConsumerState<SearchScreen> {
         if (r.emails.isNotEmpty) ...[
           const _SectionHeader('Messages'),
           for (final e in r.emails)
-            _EmailTile(email: e, accountId: e.accountId),
+            EmailTile(
+              email: e,
+              showLocation: true,
+              onTap: () => context.push(
+                '/accounts/${e.accountId}/mailboxes'
+                '/${Uri.encodeComponent(e.mailboxPath)}'
+                '/emails/${Uri.encodeComponent(e.id)}',
+              ),
+            ),
         ],
       ],
     );
@@ -246,42 +255,3 @@ class _AddressTile extends StatelessWidget {
     );
   }
 }
-
-class _EmailTile extends StatelessWidget {
-  const _EmailTile({required this.email, required this.accountId});
-  final Email email;
-  final String accountId;
-
-  @override
-  Widget build(BuildContext context) {
-    final sender = email.from.isNotEmpty
-        ? (email.from.first.name ?? email.from.first.email)
-        : '(unknown)';
-    return ListTile(
-      leading: Icon(
-        email.isSeen ? Icons.mail_outline : Icons.mail,
-        color: email.isSeen ? null : Theme.of(context).colorScheme.primary,
-      ),
-      title: Text(sender),
-      subtitle: Column(
-        crossAxisAlignment: CrossAxisAlignment.start,
-        children: [
-          Text(
-            email.subject ?? '(no subject)',
-            maxLines: 1,
-            overflow: TextOverflow.ellipsis,
-          ),
-          Text(
-            '$accountId • ${email.mailboxPath}',
-            style: Theme.of(context).textTheme.bodySmall,
-          ),
-        ],
-      ),
-      onTap: () => context.push(
-        '/accounts/$accountId/mailboxes'
-        '/${Uri.encodeComponent(email.mailboxPath)}'
-        '/emails/${Uri.encodeComponent(email.id)}',
-      ),
-    );
-  }
-}

lib/ui/widgets/email_tile.dart

@@ -0,0 +1,74 @@
+import 'package:flutter/material.dart';
+import 'package:intl/intl.dart';
+
+import 'package:sharedinbox/core/models/email.dart';
+
+final _dateFmt = DateFormat('MMM d');
+
+/// A flat list tile for an individual [email].
+///
+/// Used in search-result lists and the per-mailbox search overlay.
+/// Pass a custom [leading] widget to support selection-mode checkboxes.
+class EmailTile extends StatelessWidget {
+  const EmailTile({
+    super.key,
+    required this.email,
+    required this.onTap,
+    this.leading,
+    this.selected = false,
+    this.onLongPress,
+    this.showLocation = false,
+  });
+
+  final Email email;
+  final VoidCallback onTap;
+  final Widget? leading;
+  final bool selected;
+  final VoidCallback? onLongPress;
+
+  /// When true, appends `accountId • mailboxPath` as a second subtitle line.
+  final bool showLocation;
+
+  @override
+  Widget build(BuildContext context) {
+    final sender = email.from.isNotEmpty
+        ? (email.from.first.name ?? email.from.first.email)
+        : '(unknown)';
+    final date = email.sentAt != null ? _dateFmt.format(email.sentAt!) : '';
+
+    return ListTile(
+      leading: leading ??
+          Icon(
+            email.isSeen ? Icons.mail_outline : Icons.mail,
+            color: email.isSeen ? null : Theme.of(context).colorScheme.primary,
+          ),
+      title: Text(
+        sender,
+        style:
+            email.isSeen ? null : const TextStyle(fontWeight: FontWeight.bold),
+        overflow: TextOverflow.ellipsis,
+      ),
+      subtitle: Column(
+        crossAxisAlignment: CrossAxisAlignment.start,
+        children: [
+          Text(
+            email.subject ?? '(no subject)',
+            maxLines: 1,
+            overflow: TextOverflow.ellipsis,
+          ),
+          if (showLocation)
+            Text(
+              '${email.accountId} • ${email.mailboxPath}',
+              style: Theme.of(context).textTheme.bodySmall,
+            ),
+        ],
+      ),
+      trailing: date.isEmpty
+          ? null
+          : Text(date, style: Theme.of(context).textTheme.bodySmall),
+      selected: selected,
+      onTap: onTap,
+      onLongPress: onLongPress,
+    );
+  }
+}

test/unit/email_repository_impl_test.dart

@@ -1,7 +1,7 @@
 import 'dart:async';
 import 'dart:convert';
 
-import 'package:drift/drift.dart' show Value;
+import 'package:drift/drift.dart' hide isNull, isNotNull;
 import 'package:enough_mail/enough_mail.dart' as imap;
 import 'package:flutter_test/flutter_test.dart';
 import 'package:http/http.dart' as http;
@@ -16,6 +16,7 @@ import 'package:sharedinbox/data/repositories/email_repository_impl.dart';
 
 import 'account_repository_impl_test.dart' show MapSecureStorage;
 import 'db_test_helper.dart';
+import 'fake_imap.dart' show FakeImapClient;
 // ── Helpers ───────────────────────────────────────────────────────────────────
 
 const _account = Account(
@@ -162,15 +163,19 @@ Future<imap.SmtpClient> _noSmtpConnect(Account a, String u, String p) =>
     Future.error(UnsupportedError('SMTP unavailable in unit tests'));
 
 ({AppDatabase db, AccountRepositoryImpl accounts, EmailRepositoryImpl emails})
-    _makeRepos({http.Client? httpClient}) {
+    _makeRepos({
+  http.Client? httpClient,
+  Future<imap.ImapClient> Function(Account, String, String)? imapConnect,
+  Future<imap.SmtpClient> Function(Account, String, String)? smtpConnect,
+}) {
   final db = openTestDatabase();
   final storage = MapSecureStorage();
   final accounts = AccountRepositoryImpl(db, storage);
   final emails = EmailRepositoryImpl(
     db,
     accounts,
-    imapConnect: _noImapConnect,
-    smtpConnect: _noSmtpConnect,
+    imapConnect: imapConnect ?? _noImapConnect,
+    smtpConnect: smtpConnect ?? _noSmtpConnect,
     httpClient: httpClient,
   );
   return (db: db, accounts: accounts, emails: emails);
@@ -1935,6 +1940,163 @@ void main() {
       expect(row.lastError, isNull);
     });
   });
+
+  group('concurrent moves', () {
+    test(
+        'two simultaneous moves enqueue two changes and leave email in last destination',
+        () async {
+      final r = _makeRepos();
+      await r.accounts.addAccount(_account, 'pw');
+      await r.db.into(r.db.emails).insert(
+            EmailsCompanion.insert(
+              id: 'acc-1:5',
+              accountId: 'acc-1',
+              mailboxPath: 'INBOX',
+              uid: 5,
+              receivedAt: DateTime(2024),
+            ),
+          );
+
+      // Fire both moves without awaiting to exercise concurrent enqueue logic.
+      final f1 = r.emails.moveEmail('acc-1:5', 'Archive');
+      final f2 = r.emails.moveEmail('acc-1:5', 'Trash');
+      await Future.wait([f1, f2]);
+
+      final changes = await r.db.select(r.db.pendingChanges).get();
+      expect(changes, hasLength(2));
+      expect(changes.map((c) => c.changeType), everyElement('move'));
+
+      final destinations =
+          changes.map((c) => (jsonDecode(c.payload) as Map)['dest']).toSet();
+      expect(destinations, containsAll(['Archive', 'Trash']));
+
+      final email = await r.emails.getEmail('acc-1:5');
+      expect(
+        email!.mailboxPath,
+        anyOf('Archive', 'Trash'),
+        reason:
+            'email must be optimistically moved to one of the two destinations',
+      );
+    });
+  });
+
+  group('IMAP SMTP auth failure', () {
+    test('sendEmail propagates SMTP authentication error', () async {
+      final r = _makeRepos(
+        smtpConnect: (Account _, String __, String ___) => Future.error(
+          Exception('535 5.7.8 Authentication credentials invalid'),
+        ),
+      );
+      await r.accounts.addAccount(_account, 'pw');
+
+      const draft = EmailDraft(
+        from: EmailAddress(name: 'Alice', email: 'alice@example.com'),
+        to: [EmailAddress(name: 'Bob', email: 'bob@example.com')],
+        cc: [],
+        subject: 'Test',
+        body: 'Body',
+      );
+
+      await expectLater(
+        r.emails.sendEmail('acc-1', draft),
+        throwsA(
+          isA<Exception>().having(
+            (e) => e.toString(),
+            'message',
+            contains('535'),
+          ),
+        ),
+      );
+    });
+  });
+
+  group('IMAP UID validity change', () {
+    test('full re-sync wipes stale emails when uidValidity changes', () async {
+      final r = _makeRepos(
+        imapConnect: (Account _, String __, String ___) async =>
+            _FakeImapClientUidValidity(456),
+      );
+      await r.accounts.addAccount(_account, 'pw');
+
+      // Pre-seed two emails from the old server epoch (uidValidity=123).
+      await r.db.into(r.db.emails).insert(
+            EmailsCompanion.insert(
+              id: 'acc-1:1',
+              accountId: 'acc-1',
+              mailboxPath: 'INBOX',
+              uid: 1,
+              receivedAt: DateTime(2024),
+            ),
+          );
+      await r.db.into(r.db.emails).insert(
+            EmailsCompanion.insert(
+              id: 'acc-1:2',
+              accountId: 'acc-1',
+              mailboxPath: 'INBOX',
+              uid: 2,
+              receivedAt: DateTime(2024),
+            ),
+          );
+
+      // Seed an IMAP checkpoint with the old uidValidity so the code detects
+      // a mismatch and triggers a full re-sync.
+      await r.db.into(r.db.syncStates).insertOnConflictUpdate(
+            SyncStatesCompanion.insert(
+              accountId: 'acc-1',
+              resourceType: 'IMAP:INBOX',
+              state: '{"uidValidity":123,"lastUid":2,"highestModSeq":null}',
+              syncedAt: DateTime(2024),
+            ),
+          );
+
+      await r.emails.syncEmails('acc-1', 'INBOX');
+
+      // Old emails must be wiped; the fake server returns zero messages.
+      final remaining = await r.db.select(r.db.emails).get();
+      expect(remaining, isEmpty);
+
+      // Checkpoint must be updated to the new uidValidity.
+      final stateRow = await (r.db.select(r.db.syncStates)
+            ..where(
+              (t) =>
+                  t.accountId.equals('acc-1') &
+                  t.resourceType.equals('IMAP:INBOX'),
+            ))
+          .getSingleOrNull();
+      expect(stateRow, isNotNull);
+      final state = jsonDecode(stateRow!.state) as Map<String, dynamic>;
+      expect(state['uidValidity'], 456);
+    });
+  });
+}
+
+// ── Additional fake IMAP client for UID-validity tests ───────────────────────
+
+class _FakeImapClientUidValidity extends FakeImapClient {
+  _FakeImapClientUidValidity(this._uidValidity);
+  final int _uidValidity;
+
+  @override
+  Future<imap.Mailbox> selectMailboxByPath(
+    String path, {
+    bool enableCondStore = false,
+    imap.QResyncParameters? qresync,
+  }) async =>
+      imap.Mailbox(
+        encodedName: path,
+        encodedPath: path,
+        flags: [],
+        pathSeparator: '/',
+        uidValidity: _uidValidity,
+      );
+
+  @override
+  Future<imap.SearchImapResult> uidSearchMessages({
+    String searchCriteria = 'ALL',
+    List<imap.ReturnOption>? returnOptions,
+    Duration? responseTimeout,
+  }) async =>
+      imap.SearchImapResult();
 }
 
 // ── SSE test helper ──────────────────────────────────────────────────────────

test/unit/migration_test.dart

@@ -4,11 +4,22 @@ import 'package:flutter_test/flutter_test.dart';
 import 'package:sharedinbox/data/db/database.dart';
 import 'package:sqlite3/sqlite3.dart' as sqlite;
 
+/// Reads all column names for [tableName] from [db].
+Future<List<String>> _tableColumns(AppDatabase db, String tableName) async {
+  final rows = await db.customSelect('PRAGMA table_info($tableName)').get();
+  return rows.map((r) => r.read<String>('name')).toList();
+}
+
 void main() {
   group('Migration', () {
-    test('upgrade from v1 to latest', () async {
-      // 1. Create a V1 database using raw sqlite3.
-      final dbFile = File('test_migration.db');
+    test('schemaVersion matches expected value', () async {
+      final db = AppDatabase(NativeDatabase.memory());
+      expect(db.schemaVersion, 25);
+      await db.close();
+    });
+
+    test('upgrade from v1 to latest checks all added columns', () async {
+      final dbFile = File('test_migration_v1.db');
       if (dbFile.existsSync()) dbFile.deleteSync();
 
       final rawDb = sqlite.sqlite3.open(dbFile.path);
@@ -67,41 +78,240 @@ void main() {
       rawDb.execute('PRAGMA user_version = 1;');
       rawDb.close();
 
-      // 2. Open it with AppDatabase (v22).
       final db = AppDatabase(NativeDatabase(dbFile));
 
-      // Trigger migration by performing a simple query.
+      // Trigger migration by performing a query.
       final accs = await db.select(db.accounts).get();
       expect(accs, hasLength(1));
       expect(accs.first.displayName, 'Alice');
-      expect(accs.first.accountType, 'imap'); // default value
+      expect(accs.first.accountType, 'imap');
 
-      // 3. Verify that all columns exist.
-      // If migration failed, it would have thrown an exception during opening or query.
-      final tableInfo =
-          await db.customSelect('PRAGMA table_info(emails)').get();
-      final columns = tableInfo.map((r) => r.read<String>('name')).toList();
-
-      expect(columns, contains('thread_id'));
-      expect(columns, contains('snoozed_until'));
-      expect(columns, contains('snoozed_from_mailbox_path'));
-
-      final accountsInfo =
-          await db.customSelect('PRAGMA table_info(accounts)').get();
-      final accountColumns =
-          accountsInfo.map((r) => r.read<String>('name')).toList();
-      expect(accountColumns, contains('account_type'));
-      expect(accountColumns, contains('username'));
+      // v2–v3: accounts columns.
+      final accountColumns = await _tableColumns(db, 'accounts');
+      expect(
+        accountColumns,
+        containsAll(['account_type', 'jmap_url', 'username']),
+      );
       expect(accountColumns, contains('manage_sieve_host'));
 
+      // v14: threading columns.
+      final emailColumns = await _tableColumns(db, 'emails');
+      expect(
+        emailColumns,
+        containsAll(['thread_id', 'message_id', 'in_reply_to', 'references']),
+      );
+
+      // v22: snooze columns.
+      expect(
+        emailColumns,
+        containsAll(['snoozed_until', 'snoozed_from_mailbox_path']),
+      );
+
+      // v23: list-unsubscribe header column.
+      expect(emailColumns, contains('list_unsubscribe_header'));
+
+      // v8: mailboxes role column.
+      final mailboxColumns = await _tableColumns(db, 'mailboxes');
+      expect(mailboxColumns, contains('role'));
+
+      // v9: email_bodies cached_at column.
+      final bodyColumns = await _tableColumns(db, 'email_bodies');
+      expect(bodyColumns, contains('cached_at'));
+      expect(bodyColumns, contains('headers_json'));
+
+      // v4: drafts table with v24 imap_server_id column.
+      final draftColumns = await _tableColumns(db, 'drafts');
+      expect(draftColumns, contains('imap_server_id'));
+
+      // v5, v6, v7, v12, v17, v19, v21: new tables.
+      final allTables = await db
+          .customSelect("SELECT name FROM sqlite_master WHERE type='table'")
+          .get();
+      final tableNames = allTables.map((r) => r.read<String>('name')).toList();
+      expect(
+        tableNames,
+        containsAll([
+          'sync_states', // v5
+          'pending_changes', // v6
+          'sync_logs', // v7
+          'sync_log_mailboxes', // v12
+          'threads', // v17
+          'sync_health', // v19
+          'undo_actions', // v21
+        ]),
+      );
+
+      // v18, v22, v25: indexes.
+      final allIndexes = await db
+          .customSelect("SELECT name FROM sqlite_master WHERE type='index'")
+          .get();
+      final indexNames = allIndexes.map((r) => r.read<String>('name')).toSet();
+      expect(
+        indexNames,
+        containsAll([
+          'emails_received_at', // v18
+          'emails_thread_id', // v18
+          'pending_changes_account_id', // v18
+          'emails_snoozed_until', // v22
+          'mailboxes_account_id', // v25
+          'threads_latest_date', // v25
+        ]),
+      );
+
       await db.close();
       if (dbFile.existsSync()) dbFile.deleteSync();
     });
 
-    test('fresh install (v22) works', () async {
-      final db = AppDatabase(NativeDatabase.memory());
-      // Just ensure we can create everything and query.
+    test(
+        'upgrade from v22 to latest adds list_unsubscribe_header and imap_server_id',
+        () async {
+      final dbFile = File('test_migration_v22.db');
+      if (dbFile.existsSync()) dbFile.deleteSync();
+
+      // Build a v22 database schema directly with raw SQL.
+      final rawDb = sqlite.sqlite3.open(dbFile.path);
+      rawDb.execute('''
+        CREATE TABLE accounts (
+          id TEXT NOT NULL PRIMARY KEY,
+          display_name TEXT NOT NULL,
+          email TEXT NOT NULL,
+          imap_host TEXT NOT NULL,
+          imap_port INTEGER NOT NULL DEFAULT 993,
+          imap_ssl INTEGER NOT NULL DEFAULT 1 CHECK ("imap_ssl" IN (0, 1)),
+          smtp_host TEXT NOT NULL DEFAULT '',
+          smtp_port INTEGER NOT NULL DEFAULT 465,
+          smtp_ssl INTEGER NOT NULL DEFAULT 1 CHECK ("smtp_ssl" IN (0, 1)),
+          account_type TEXT NOT NULL DEFAULT 'imap',
+          jmap_url TEXT NULL,
+          username TEXT NULL,
+          manage_sieve_host TEXT NULL,
+          manage_sieve_port INTEGER NULL,
+          manage_sieve_ssl INTEGER NULL,
+          manage_sieve_available INTEGER NOT NULL DEFAULT 0 CHECK ("manage_sieve_available" IN (0, 1)),
+          verbose INTEGER NOT NULL DEFAULT 0 CHECK ("verbose" IN (0, 1))
+        );
+      ''');
+      rawDb.execute('''
+        CREATE TABLE drafts (
+          id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
+          account_id TEXT NULL,
+          reply_to_email_id TEXT NULL,
+          to_text TEXT NOT NULL DEFAULT '',
+          cc_text TEXT NOT NULL DEFAULT '',
+          subject_text TEXT NOT NULL DEFAULT '',
+          body_text TEXT NOT NULL DEFAULT '',
+          updated_at INTEGER NOT NULL
+        );
+      ''');
+      rawDb.execute('''
+        CREATE TABLE mailboxes (
+          id TEXT NOT NULL PRIMARY KEY,
+          account_id TEXT NOT NULL,
+          path TEXT NOT NULL,
+          name TEXT NOT NULL,
+          unread_count INTEGER NOT NULL DEFAULT 0,
+          total_count INTEGER NOT NULL DEFAULT 0,
+          role TEXT NULL
+        );
+      ''');
+      rawDb.execute('''
+        CREATE TABLE emails (
+          id TEXT NOT NULL PRIMARY KEY,
+          account_id TEXT NOT NULL,
+          mailbox_path TEXT NOT NULL,
+          uid INTEGER NOT NULL,
+          subject TEXT NULL,
+          sent_at INTEGER NULL,
+          received_at INTEGER NOT NULL,
+          from_json TEXT NOT NULL DEFAULT '[]',
+          to_addresses TEXT NOT NULL DEFAULT '[]',
+          cc_json TEXT NOT NULL DEFAULT '[]',
+          preview TEXT NULL,
+          is_seen INTEGER NOT NULL DEFAULT 0 CHECK ("is_seen" IN (0, 1)),
+          is_flagged INTEGER NOT NULL DEFAULT 0 CHECK ("is_flagged" IN (0, 1)),
+          has_attachment INTEGER NOT NULL DEFAULT 0 CHECK ("has_attachment" IN (0, 1)),
+          thread_id TEXT NULL,
+          message_id TEXT NULL,
+          in_reply_to TEXT NULL,
+          "references" TEXT NULL,
+          snoozed_until INTEGER NULL,
+          snoozed_from_mailbox_path TEXT NULL
+        );
+      ''');
+      rawDb.execute('''
+        CREATE TABLE threads (
+          account_id TEXT NOT NULL,
+          mailbox_path TEXT NOT NULL,
+          id TEXT NOT NULL,
+          subject TEXT NULL,
+          latest_date INTEGER NOT NULL,
+          message_count INTEGER NOT NULL DEFAULT 1,
+          has_unread INTEGER NOT NULL DEFAULT 0 CHECK ("has_unread" IN (0, 1)),
+          is_flagged INTEGER NOT NULL DEFAULT 0 CHECK ("is_flagged" IN (0, 1)),
+          participants_json TEXT NOT NULL DEFAULT '[]',
+          preview TEXT NULL,
+          latest_email_id TEXT NOT NULL,
+          email_ids_json TEXT NOT NULL DEFAULT '[]',
+          PRIMARY KEY (account_id, mailbox_path, id)
+        );
+      ''');
+      rawDb.execute('PRAGMA user_version = 22;');
+      rawDb.close();
+
+      final db = AppDatabase(NativeDatabase(dbFile));
+      // Trigger migration.
       await db.select(db.accounts).get();
+
+      final emailColumns = await _tableColumns(db, 'emails');
+      expect(emailColumns, contains('list_unsubscribe_header'));
+
+      final draftColumns = await _tableColumns(db, 'drafts');
+      expect(draftColumns, contains('imap_server_id'));
+
+      // v25: new indexes on mailboxes and threads.
+      final allIndexes = await db
+          .customSelect("SELECT name FROM sqlite_master WHERE type='index'")
+          .get();
+      final indexNames = allIndexes.map((r) => r.read<String>('name')).toSet();
+      expect(indexNames, contains('mailboxes_account_id'));
+      expect(indexNames, contains('threads_latest_date'));
+
+      await db.close();
+      if (dbFile.existsSync()) dbFile.deleteSync();
+    });
+
+    test('fresh install creates all tables at schemaVersion 25', () async {
+      final db = AppDatabase(NativeDatabase.memory());
+      await db.select(db.accounts).get();
+
+      final allTables = await db
+          .customSelect("SELECT name FROM sqlite_master WHERE type='table'")
+          .get();
+      final tableNames = allTables.map((r) => r.read<String>('name')).toSet();
+      expect(
+        tableNames,
+        containsAll([
+          'accounts',
+          'mailboxes',
+          'emails',
+          'email_bodies',
+          'drafts',
+          'sync_states',
+          'pending_changes',
+          'sync_logs',
+          'sync_log_mailboxes',
+          'threads',
+          'sync_health',
+          'undo_actions',
+        ]),
+      );
+
+      final emailColumns = await _tableColumns(db, 'emails');
+      expect(emailColumns, contains('list_unsubscribe_header'));
+
+      final draftColumns = await _tableColumns(db, 'drafts');
+      expect(draftColumns, contains('imap_server_id'));
+
       await db.close();
     });
   });

test/widget/helpers.dart

@@ -30,6 +30,7 @@ import 'package:sharedinbox/ui/screens/email_detail_screen.dart';
 import 'package:sharedinbox/ui/screens/email_list_screen.dart';
 import 'package:sharedinbox/ui/screens/mailbox_list_screen.dart';
 import 'package:sharedinbox/ui/screens/search_screen.dart';
+import 'package:sharedinbox/ui/screens/thread_detail_screen.dart';
 
 // ---------------------------------------------------------------------------
 // Fake repositories
@@ -381,6 +382,18 @@ Widget buildApp({
                   ),
                 ],
               ),
+              GoRoute(
+                path: ':mailboxPath/threads/:threadId',
+                builder: (ctx, state) => ThreadDetailScreen(
+                  accountId: state.pathParameters['accountId']!,
+                  mailboxPath: Uri.decodeComponent(
+                    state.pathParameters['mailboxPath']!,
+                  ),
+                  threadId: Uri.decodeComponent(
+                    state.pathParameters['threadId']!,
+                  ),
+                ),
+              ),
             ],
           ),
         ],

test/widget/search_screen_test.dart

@@ -0,0 +1,182 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import 'package:sharedinbox/core/models/mailbox.dart';
+import 'package:sharedinbox/di.dart';
+
+import 'helpers.dart';
+
+void main() {
+  group('SearchScreen', () {
+    testWidgets('shows placeholder hint text when empty', (tester) async {
+      await tester.pumpWidget(
+        buildApp(
+          initialLocation: '/accounts/acc-1/search',
+          overrides: [
+            accountRepositoryProvider.overrideWithValue(
+              FakeAccountRepository([kTestAccount]),
+            ),
+            mailboxRepositoryProvider.overrideWithValue(
+              FakeMailboxRepository(),
+            ),
+            emailRepositoryProvider.overrideWithValue(FakeEmailRepository()),
+          ],
+        ),
+      );
+      await tester.pumpAndSettle();
+
+      expect(find.text('Type 3+ characters to search'), findsOneWidget);
+    });
+
+    testWidgets('typing fewer than 3 characters does not trigger search', (
+      tester,
+    ) async {
+      await tester.pumpWidget(
+        buildApp(
+          initialLocation: '/accounts/acc-1/search',
+          overrides: [
+            accountRepositoryProvider.overrideWithValue(
+              FakeAccountRepository([kTestAccount]),
+            ),
+            mailboxRepositoryProvider.overrideWithValue(
+              FakeMailboxRepository(),
+            ),
+            emailRepositoryProvider.overrideWithValue(FakeEmailRepository()),
+          ],
+        ),
+      );
+      await tester.pumpAndSettle();
+
+      await tester.enterText(find.byType(TextField), 'hi');
+      await tester.pump(const Duration(milliseconds: 400));
+
+      expect(find.text('Type 3+ characters to search'), findsOneWidget);
+      expect(find.text('No results'), findsNothing);
+    });
+
+    testWidgets('shows "No results" when search returns nothing', (
+      tester,
+    ) async {
+      await tester.pumpWidget(
+        buildApp(
+          initialLocation: '/accounts/acc-1/search',
+          overrides: [
+            accountRepositoryProvider.overrideWithValue(
+              FakeAccountRepository([kTestAccount]),
+            ),
+            mailboxRepositoryProvider.overrideWithValue(
+              FakeMailboxRepository(),
+            ),
+            emailRepositoryProvider.overrideWithValue(FakeEmailRepository()),
+          ],
+        ),
+      );
+      await tester.pumpAndSettle();
+
+      await tester.enterText(find.byType(TextField), 'xyz');
+      await tester.pump(const Duration(milliseconds: 400));
+      await tester.pumpAndSettle();
+
+      expect(find.text('No results'), findsOneWidget);
+    });
+
+    testWidgets('shows email results under "Messages" section', (
+      tester,
+    ) async {
+      final email = testEmail(subject: 'Invoice Q3');
+      await tester.pumpWidget(
+        buildApp(
+          initialLocation: '/accounts/acc-1/search',
+          overrides: [
+            accountRepositoryProvider.overrideWithValue(
+              FakeAccountRepository([kTestAccount]),
+            ),
+            mailboxRepositoryProvider.overrideWithValue(
+              FakeMailboxRepository(),
+            ),
+            emailRepositoryProvider.overrideWithValue(
+              FakeEmailRepository(searchResults: [email]),
+            ),
+          ],
+        ),
+      );
+      await tester.pumpAndSettle();
+
+      await tester.enterText(find.byType(TextField), 'inv');
+      await tester.pump(const Duration(milliseconds: 400));
+      await tester.pumpAndSettle();
+
+      expect(find.text('Messages'), findsOneWidget);
+      expect(find.text('Invoice Q3'), findsOneWidget);
+    });
+
+    testWidgets('shows folder results under "Folders" section', (
+      tester,
+    ) async {
+      const archiveMailbox = Mailbox(
+        id: 'acc-1:Archive',
+        accountId: 'acc-1',
+        path: 'Archive',
+        name: 'Archive',
+        unreadCount: 0,
+        totalCount: 5,
+      );
+      await tester.pumpWidget(
+        buildApp(
+          initialLocation: '/accounts/acc-1/search',
+          overrides: [
+            accountRepositoryProvider.overrideWithValue(
+              FakeAccountRepository([kTestAccount]),
+            ),
+            mailboxRepositoryProvider.overrideWithValue(
+              FakeMailboxRepository([archiveMailbox]),
+            ),
+            emailRepositoryProvider.overrideWithValue(FakeEmailRepository()),
+          ],
+        ),
+      );
+      await tester.pumpAndSettle();
+
+      await tester.enterText(find.byType(TextField), 'arc');
+      await tester.pump(const Duration(milliseconds: 400));
+      await tester.pumpAndSettle();
+
+      expect(find.text('Folders'), findsOneWidget);
+      expect(find.text('Archive'), findsOneWidget);
+    });
+
+    testWidgets('tapping clear button resets results to placeholder', (
+      tester,
+    ) async {
+      final email = testEmail(subject: 'Found email');
+      await tester.pumpWidget(
+        buildApp(
+          initialLocation: '/accounts/acc-1/search',
+          overrides: [
+            accountRepositoryProvider.overrideWithValue(
+              FakeAccountRepository([kTestAccount]),
+            ),
+            mailboxRepositoryProvider.overrideWithValue(
+              FakeMailboxRepository(),
+            ),
+            emailRepositoryProvider.overrideWithValue(
+              FakeEmailRepository(searchResults: [email]),
+            ),
+          ],
+        ),
+      );
+      await tester.pumpAndSettle();
+
+      await tester.enterText(find.byType(TextField), 'found');
+      await tester.pump(const Duration(milliseconds: 400));
+      await tester.pumpAndSettle();
+      expect(find.text('Found email'), findsOneWidget);
+
+      await tester.tap(find.byIcon(Icons.clear));
+      await tester.pumpAndSettle();
+
+      expect(find.text('Found email'), findsNothing);
+      expect(find.text('Type 3+ characters to search'), findsOneWidget);
+    });
+  });
+}

test/widget/thread_detail_screen_test.dart

@@ -0,0 +1,198 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import 'package:sharedinbox/core/models/email.dart';
+import 'package:sharedinbox/di.dart';
+
+import 'helpers.dart';
+
+Email _threadEmail({
+  String id = 'acc-1:10',
+  bool isFlagged = false,
+  bool isSeen = true,
+}) =>
+    Email(
+      id: id,
+      accountId: 'acc-1',
+      mailboxPath: 'INBOX',
+      uid: 10,
+      threadId: 'thread-1',
+      subject: 'Project update',
+      receivedAt: DateTime(2024, 6),
+      sentAt: DateTime(2024, 6, 1, 9),
+      from: const [EmailAddress(name: 'Bob', email: 'bob@example.com')],
+      to: const [EmailAddress(email: 'alice@example.com')],
+      cc: const [],
+      isSeen: isSeen,
+      isFlagged: isFlagged,
+      hasAttachment: false,
+    );
+
+void main() {
+  group('ThreadDetailScreen', () {
+    testWidgets('shows "Thread not found or empty" when thread is empty', (
+      tester,
+    ) async {
+      await tester.pumpWidget(
+        buildApp(
+          initialLocation: '/accounts/acc-1/mailboxes/INBOX/threads/thread-1',
+          overrides: [
+            accountRepositoryProvider.overrideWithValue(
+              FakeAccountRepository([kTestAccount]),
+            ),
+            mailboxRepositoryProvider.overrideWithValue(
+              FakeMailboxRepository(),
+            ),
+            emailRepositoryProvider.overrideWithValue(FakeEmailRepository()),
+          ],
+        ),
+      );
+      await tester.pumpAndSettle();
+
+      expect(find.text('Thread not found or empty'), findsOneWidget);
+    });
+
+    testWidgets('shows sender name for email in thread', (tester) async {
+      final email = _threadEmail();
+      await tester.pumpWidget(
+        buildApp(
+          initialLocation: '/accounts/acc-1/mailboxes/INBOX/threads/thread-1',
+          overrides: [
+            accountRepositoryProvider.overrideWithValue(
+              FakeAccountRepository([kTestAccount]),
+            ),
+            mailboxRepositoryProvider.overrideWithValue(
+              FakeMailboxRepository(),
+            ),
+            emailRepositoryProvider.overrideWithValue(
+              FakeEmailRepository(emails: [email]),
+            ),
+          ],
+        ),
+      );
+      await tester.pumpAndSettle();
+
+      expect(find.textContaining('Bob'), findsOneWidget);
+    });
+
+    testWidgets('last email in thread is expanded by default', (tester) async {
+      final email = _threadEmail();
+      await tester.pumpWidget(
+        buildApp(
+          initialLocation: '/accounts/acc-1/mailboxes/INBOX/threads/thread-1',
+          overrides: [
+            accountRepositoryProvider.overrideWithValue(
+              FakeAccountRepository([kTestAccount]),
+            ),
+            mailboxRepositoryProvider.overrideWithValue(
+              FakeMailboxRepository(),
+            ),
+            emailRepositoryProvider.overrideWithValue(
+              FakeEmailRepository(
+                emails: [email],
+                emailBody: const EmailBody(
+                  emailId: 'acc-1:10',
+                  textBody: 'Hello body text',
+                  attachments: [],
+                ),
+              ),
+            ),
+          ],
+        ),
+      );
+      await tester.pumpAndSettle();
+
+      // Reply and delete buttons are visible for the expanded card.
+      expect(find.byIcon(Icons.reply), findsOneWidget);
+      expect(find.byIcon(Icons.delete_outline), findsOneWidget);
+    });
+
+    testWidgets('tapping an expanded card collapses it', (tester) async {
+      final email = _threadEmail();
+      await tester.pumpWidget(
+        buildApp(
+          initialLocation: '/accounts/acc-1/mailboxes/INBOX/threads/thread-1',
+          overrides: [
+            accountRepositoryProvider.overrideWithValue(
+              FakeAccountRepository([kTestAccount]),
+            ),
+            mailboxRepositoryProvider.overrideWithValue(
+              FakeMailboxRepository(),
+            ),
+            emailRepositoryProvider.overrideWithValue(
+              FakeEmailRepository(
+                emails: [email],
+                emailBody: const EmailBody(
+                  emailId: 'acc-1:10',
+                  textBody: 'Hello body text',
+                  attachments: [],
+                ),
+              ),
+            ),
+          ],
+        ),
+      );
+      await tester.pumpAndSettle();
+
+      // Tap the expand_less icon to collapse.
+      await tester.tap(find.byIcon(Icons.expand_less));
+      await tester.pumpAndSettle();
+
+      expect(find.byIcon(Icons.reply), findsNothing);
+      expect(find.byIcon(Icons.expand_more), findsOneWidget);
+    });
+
+    testWidgets('flagged email shows star icon', (tester) async {
+      final email = _threadEmail(isFlagged: true);
+      await tester.pumpWidget(
+        buildApp(
+          initialLocation: '/accounts/acc-1/mailboxes/INBOX/threads/thread-1',
+          overrides: [
+            accountRepositoryProvider.overrideWithValue(
+              FakeAccountRepository([kTestAccount]),
+            ),
+            mailboxRepositoryProvider.overrideWithValue(
+              FakeMailboxRepository(),
+            ),
+            emailRepositoryProvider.overrideWithValue(
+              FakeEmailRepository(emails: [email]),
+            ),
+          ],
+        ),
+      );
+      await tester.pumpAndSettle();
+
+      expect(find.byIcon(Icons.star), findsOneWidget);
+    });
+
+    testWidgets('expanded card shows plain text body', (tester) async {
+      final email = _threadEmail();
+      await tester.pumpWidget(
+        buildApp(
+          initialLocation: '/accounts/acc-1/mailboxes/INBOX/threads/thread-1',
+          overrides: [
+            accountRepositoryProvider.overrideWithValue(
+              FakeAccountRepository([kTestAccount]),
+            ),
+            mailboxRepositoryProvider.overrideWithValue(
+              FakeMailboxRepository(),
+            ),
+            emailRepositoryProvider.overrideWithValue(
+              FakeEmailRepository(
+                emails: [email],
+                emailBody: const EmailBody(
+                  emailId: 'acc-1:10',
+                  textBody: 'Body content here',
+                  attachments: [],
+                ),
+              ),
+            ),
+          ],
+        ),
+      );
+      await tester.pumpAndSettle();
+
+      expect(find.text('Body content here'), findsOneWidget);
+    });
+  });
+}