diff --git a/flutter/test/api_mode_flow_test.dart b/flutter/test/api_mode_flow_test.dart
new file mode 100644
index 0000000..5598397
--- /dev/null
+++ b/flutter/test/api_mode_flow_test.dart
@@ -0,0 +1,163 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+import 'package:tma_app/app.dart';
+import 'package:tma_app/core/api/dio_provider.dart';
+import 'package:tma_app/core/api/session_store.dart';
+import 'package:tma_app/core/config/app_config.dart';
+import 'package:tma_app/core/storage/preferences_provider.dart';
+import 'package:tma_app/features/auth/data/repositories/device_key_store.dart';
+import 'package:tma_app/features/auth/presentation/pages/login_page.dart';
+import 'package:tma_app/features/onboarding/presentation/pages/onboarding_page.dart';
+import 'package:tma_app/features/shell/presentation/widgets/rup_tab_bar.dart';
+
+import 'support/app_harness.dart' show settle;
+import 'support/fake_api.dart';
+
+/// 서버에 이미 등록된 아이
+Map<String, Object?> _kongJson() => {
+      'id': 'pet-kong',
+      'tint': '#FF9B6A',
+      'name': '콩이',
+      'species': '강아지',
+      'breed': '말티즈',
+      'gender': 'male',
+      'neutered': true,
+      'birthDate': '2021-09-14',
+      'weight': 3.2,
+      'weightUnit': 'kg',
+      'photoFileId': null,
+      'microchip': null,
+      'bloodType': null,
+      'vet': null,
+      'memo': null,
+      'allergies': <String>[],
+      'conditions': <String>[],
+      'watchConditions': <String>[],
+      'archive': null,
+    };
+
+/// 서버 하나를 흉내 낸다 — 로그인·내 정보·목록들
+void _serve(FakeApi api, {required bool sessionAlive}) {
+  api.on('POST', '/auth/dev-sessions', (r) => ok({
+        'accessToken': 'access-1',
+        'refreshToken': 'refresh-1',
+        'accessTokenExpiresIn': 3600,
+        'refreshTokenExpiresAt': '2026-10-25T00:00:00.000Z',
+        'user': {
+          'id': 'user-1',
+          'nickname': '콩이 보호자',
+          'photoFileId': null,
+          'provider': 'kakao',
+          'createdAt': '2026-10-11T00:00:00.000Z',
+        },
+        'isNewUser': true,
+      }, status: 201));
+  api.on('POST', '/auth/tokens', (r) => failure('AUTH_001', 401));
+
+  FakeReply guarded(Object? data) => sessionAlive ? ok(data) : failure('AUTH_001', 401);
+  api.on('GET', '/users/me', (r) => guarded({
+        'id': 'user-1',
+        'nickname': '콩이 보호자',
+        'photoFileId': null,
+        'provider': 'kakao',
+        'createdAt': '2026-10-11T00:00:00.000Z',
+      }));
+  api.on('GET', '/pets', (r) => guarded(page([_kongJson()])));
+  for (final path in [
+    '/schedule-events',
+    '/repeat-rules',
+    '/repeat-rule-completions',
+    '/diaries',
+    '/diary-posts',
+    '/diary-comments',
+    '/pet-cards',
+  ]) {
+    api.on('GET', path, (r) => guarded(page(const [])));
+  }
+}
+
+Future<void> _pumpApiApp(WidgetTester tester, FakeApi api, Map<String, Object> saved) async {
+  tester.view.physicalSize = const Size(402, 874);
+  tester.view.devicePixelRatio = 1;
+  addTearDown(tester.view.reset);
+
+  SharedPreferences.setMockInitialValues(saved);
+  final prefs = await SharedPreferences.getInstance();
+  await tester.pumpWidget(
+    ProviderScope(
+      overrides: [
+        sharedPreferencesProvider.overrideWithValue(prefs),
+        dataModeProvider.overrideWithValue(DataMode.api),
+        sessionStoreProvider.overrideWithValue(api.session),
+        dioProvider.overrideWithValue(api.dio),
+        deviceKeyStoreProvider.overrideWithValue(const FixedDeviceKeyStore('test-device-key-000001')),
+      ],
+      child: const RupApp(),
+    ),
+  );
+  // 스플래시 이미지 디코딩 → 2.6초 뒤 다음 화면
+  await tester.runAsync(() => Future<void>.delayed(const Duration(milliseconds: 300)));
+  await tester.pump(const Duration(seconds: 4));
+  await settle(tester);
+}
+
+/// 가짜 서버 응답(비동기)이 화면에 반영되고, 그 화면이 부른 요청까지 모두 끝날 때까지
+Future<void> _network(WidgetTester tester, FakeApi api) async {
+  var seen = -1;
+  for (var i = 0; i < 10 && seen != api.requests.length; i++) {
+    seen = api.requests.length;
+    await tester.runAsync(() => Future<void>.delayed(const Duration(milliseconds: 50)));
+    await settle(tester);
+  }
+}
+
+void main() {
+  testWidgets('서버 모드: 로그인하면 토큰을 받고 온보딩을 거쳐 홈에서 서버의 아이를 보여 준다', (tester) async {
+    final api = FakeApi(tokens: null);
+    _serve(api, sessionAlive: true);
+    await _pumpApiApp(tester, api, {});
+
+    await tester.tap(find.text('시작하기'));
+    await settle(tester);
+    expect(find.byType(LoginPage), findsOneWidget);
+
+    await tester.tap(find.text('카카오로 3초만에 시작하기'));
+    await _network(tester, api);
+    expect(api.session.tokens?.accessToken, 'access-1');
+    expect(find.byType(OnboardingPage), findsOneWidget);
+
+    for (var i = 0; i < 3; i++) {
+      await tester.tap(find.byType(OnboardingPage));
+      await tester.pump(const Duration(milliseconds: 100));
+    }
+    await tester.tap(find.text('시작하기'));
+    await _network(tester, api);
+
+    expect(find.byType(RupTabBar), findsOneWidget);
+    expect(find.text('콩이'), findsWidgets);
+    expect(api.sent('GET', '/pets'), isNotEmpty);
+    expect(api.reported, isEmpty);
+  });
+
+  testWidgets('서버가 세션을 끊으면(갱신 거절) 로그인 화면으로 돌아가고 세션 만료로 알린다', (tester) async {
+    final api = FakeApi(tokens: const AuthTokens(accessToken: 'stale', refreshToken: 'revoked'));
+    _serve(api, sessionAlive: false);
+    await _pumpApiApp(tester, api, {'entry.onboardingSeen': true});
+    await _network(tester, api);
+
+    expect(api.session.hasSession, isFalse);
+    expect(api.session.expired, isTrue);
+    expect(find.byType(LoginPage), findsOneWidget);
+    expect(api.reported.map((e) => e.code).toSet(), {'AUTH_002'});
+  });
+
+  testWidgets('로그인 전(세션 없음)에는 서버에 기록을 묻지 않는다', (tester) async {
+    final api = FakeApi(tokens: null);
+    _serve(api, sessionAlive: true);
+    await _pumpApiApp(tester, api, {});
+
+    expect(api.requests, isEmpty);
+  });
+}