From 46c6c321f2f89abeeae5e1fbcb91437d88b536b6 Mon Sep 17 00:00:00 2001
From: Yun Chan <yunchan@twentyoz.kr>
Date: Sat, 15 Aug 2026 18:11:49 +0900
Subject: [PATCH] =?UTF-8?q?T3-11/14/15=20+=20M2=20=EC=9E=94=EC=97=AC:=20?=
 =?UTF-8?q?=EA=B6=8C=ED=95=9C=20=EC=A0=95=EC=B1=85=20UI(PermissionGate/Per?=
 =?UTF-8?q?missionRequested=20=EB=8B=A4=EC=9D=B4=EC=96=BC=EB=A1=9C?=
 =?UTF-8?q?=EA=B7=B8+SavesInProfile),=20=EC=B6=94=EC=A0=81=20=EB=B0=A9?=
 =?UTF-8?q?=EC=A7=80(TrackerBlocklist/WebResourceRequested=20=EC=B0=A8?=
 =?UTF-8?q?=EB=8B=A8+=EC=8B=A4=EB=93=9C=20=EB=B0=B0=EC=A7=80=C2=B7?=
 =?UTF-8?q?=ED=8C=9D=EC=97=85),=20=EC=A3=BC=EC=86=8C=EC=B0=BD=20=EC=A7=84?=
 =?UTF-8?q?=ED=96=89=20=EB=B0=94+=ED=8C=8C=EB=9D=BC=EB=AF=B8=ED=84=B0=20?=
 =?UTF-8?q?=EC=A0=9C=EA=B1=B0=20=EB=B3=B5=EC=82=AC(UrlCleaner/NavProgressT?=
 =?UTF-8?q?racker),=20U5=20=EC=99=84=EB=A3=8C=20=EC=95=8C=EB=A6=BC(Mobile.?=
 =?UTF-8?q?Core=20=EA=B0=90=EC=A7=80=EA=B8=B0+Plugin.LocalNotification),?=
 =?UTF-8?q?=20=EC=9E=AC=EC=83=9D=EC=A4=91=20ongoing=20=EB=AF=B8=EB=94=94?=
 =?UTF-8?q?=EC=96=B4=20=EC=95=8C=EB=A6=BC,=20=EC=8D=B8=EB=84=A4=EC=9D=BC/?=
 =?UTF-8?q?=ED=95=B4=EC=83=81=EB=8F=84=20API(Thumbnailer=20=EC=82=AC?=
 =?UTF-8?q?=EC=9D=B4=EB=93=9C=EC=B9=B4=20=EC=BA=90=EC=8B=9C+/thumb)+?=
 =?UTF-8?q?=EB=9D=BC=EC=9D=B4=EB=B8=8C=EB=9F=AC=EB=A6=AC=20=EA=B7=B8?=
 =?UTF-8?q?=EB=A6=AC=EB=93=9C,=20=EC=99=B8=EB=B6=80=EB=A7=9D=20=EC=95=88?=
 =?UTF-8?q?=EB=82=B4(ConnectionTroubleshoot).=20147=20tests=20GREEN?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 VideoDownloader.App/MainWindow.xaml           |  46 +++++++-
 VideoDownloader.App/MainWindow.xaml.cs        |  77 ++++++++++++-
 .../Services/TabViewService.cs                |  63 +++++++++-
 VideoDownloader.Browser/PermissionGate.cs     |  78 +++++++++++++
 VideoDownloader.Browser/UrlCleaner.cs         |  43 +++++++
 .../ConnectionTroubleshoot.cs                 |  21 ++++
 .../OfflineStore.cs                           |   7 +-
 .../QueueCompletionDetector.cs                |  18 +++
 .../VideoDownloader.Mobile.Core.csproj        |   9 ++
 VideoDownloader.Mobile/ApiClient.cs           |   3 +-
 VideoDownloader.Mobile/AppOfflineStore.cs     |   7 ++
 VideoDownloader.Mobile/Pages.cs               | 105 ++++++++++++++---
 .../Platforms/Android/AndroidManifest.xml     |   6 +-
 .../VideoDownloader.Mobile.csproj             |   6 +
 VideoDownloader.Server/ServerHost.cs          |  24 +++-
 VideoDownloader.Server/ServerModels.cs        |  11 +-
 VideoDownloader.Server/Thumbnailer.cs         |  57 +++++++++
 .../VideoDownloader.Server.csproj             |   3 +
 .../Browser/PermissionGateTests.cs            |  46 ++++++++
 .../Browser/TrackerBlockTests.cs              |  40 +++++++
 .../Browser/UrlCleanerTests.cs                |  80 +++++++++++++
 .../E2E/PermissionTrackerE2ETests.cs          | 109 ++++++++++++++++++
 .../Mobile/MobileCoreTests.cs                 | 106 +++++++++++++++++
 .../Server/RemoteServerE2ETests.cs            |  38 ++++++
 .../Server/ThumbnailerTests.cs                |  84 ++++++++++++++
 .../VideoDownloader.Tests.csproj              |   1 +
 26 files changed, 1058 insertions(+), 30 deletions(-)
 create mode 100644 VideoDownloader.Browser/PermissionGate.cs
 create mode 100644 VideoDownloader.Browser/UrlCleaner.cs
 create mode 100644 VideoDownloader.Mobile.Core/ConnectionTroubleshoot.cs
 rename {VideoDownloader.Mobile => VideoDownloader.Mobile.Core}/OfflineStore.cs (91%)
 create mode 100644 VideoDownloader.Mobile.Core/QueueCompletionDetector.cs
 create mode 100644 VideoDownloader.Mobile.Core/VideoDownloader.Mobile.Core.csproj
 create mode 100644 VideoDownloader.Mobile/AppOfflineStore.cs
 create mode 100644 VideoDownloader.Server/Thumbnailer.cs
 create mode 100644 VideoDownloader.Tests/Browser/PermissionGateTests.cs
 create mode 100644 VideoDownloader.Tests/Browser/TrackerBlockTests.cs
 create mode 100644 VideoDownloader.Tests/Browser/UrlCleanerTests.cs
 create mode 100644 VideoDownloader.Tests/E2E/PermissionTrackerE2ETests.cs
 create mode 100644 VideoDownloader.Tests/Mobile/MobileCoreTests.cs
 create mode 100644 VideoDownloader.Tests/Server/ThumbnailerTests.cs

diff --git a/VideoDownloader.App/MainWindow.xaml b/VideoDownloader.App/MainWindow.xaml
index ccb1b94..c4bfb60 100644
--- a/VideoDownloader.App/MainWindow.xaml
+++ b/VideoDownloader.App/MainWindow.xaml
@@ -191,6 +191,14 @@
                     <Button Name="HistoryBtn" Style="{StaticResource IconButton}" Content="&#xE823;" ToolTip="방문 기록" Margin="0,0,2,0" Click="ToggleHistory"/>
                     <Button Name="TabSearchBtn" Style="{StaticResource IconButton}" Content="&#xE721;" ToolTip="탭 검색 (Ctrl+Shift+A)" Margin="0,0,2,0" Click="ToggleTabSearch"/>
                     <Button Name="DownloadsBtn" Style="{StaticResource IconButton}" Content="&#xE896;" ToolTip="다운로드 (Ctrl+J)" Margin="0,0,2,0" Click="ToggleDownloads"/>
+                    <!-- T3-14 추적 방지 실드 -->
+                    <Grid Margin="0,0,2,0">
+                        <Button Name="ShieldBtn" Style="{StaticResource IconButton}" Content="&#xE72E;" ToolTip="추적 방지" Click="Shield_Click"/>
+                        <Border Name="ShieldBadge" CornerRadius="8" Background="#FF4CAF50" Padding="5,1"
+                                HorizontalAlignment="Right" VerticalAlignment="Top" Margin="0,2,2,0" Visibility="Collapsed">
+                            <TextBlock Name="ShieldBadgeText" Text="" FontSize="9" Foreground="White"/>
+                        </Border>
+                    </Grid>
                     <Button Name="PlaylistBtn" Style="{StaticResource IconButton}" Content="&#xE8D6;" ToolTip="미디어 재생목록" Margin="0,0,2,0" Click="TogglePlaylistPanel"/>
                     <Button Style="{StaticResource IconButton}" Content="&#xE8B7;" ToolTip="저장 폴더 열기" Margin="0,0,2,0" Click="OpenFolder_Click"/>
                     <Button Name="LinkBtn" Style="{StaticResource IconButton}" Content="&#xE71B;" ToolTip="링크로 받기 (YouTube·Instagram·X)" Margin="0,0,2,0" Click="ToggleLink"/>
@@ -208,10 +216,25 @@
                 <!-- 주소창 -->
                 <Border Background="{StaticResource GlassBg}" BorderBrush="{StaticResource BorderBrush}"
                         BorderThickness="1" CornerRadius="8" Height="32" VerticalAlignment="Center">
-                    <TextBox Name="AddressBox" Style="{StaticResource DarkTextBox}"
-                             PreviewKeyDown="AddressBox_PreviewKeyDown" TextChanged="AddressBox_TextChanged"
-                             BorderThickness="0" Background="Transparent"
-                             Padding="14,0" FontSize="13" VerticalContentAlignment="Center"/>
+                    <Grid>
+                        <TextBox Name="AddressBox" Style="{StaticResource DarkTextBox}"
+                                 PreviewKeyDown="AddressBox_PreviewKeyDown" TextChanged="AddressBox_TextChanged"
+                                 BorderThickness="0" Background="Transparent"
+                                 Padding="14,0" FontSize="13" VerticalContentAlignment="Center">
+                            <TextBox.ContextMenu>
+                                <ContextMenu>
+                                    <MenuItem Header="붙여넣기" Command="ApplicationCommands.Paste"/>
+                                    <MenuItem Header="복사" Command="ApplicationCommands.Copy"/>
+                                    <Separator/>
+                                    <MenuItem Header="파라미터 제거 후 복사" Click="CopyCleanUrl_Click" InputGestureText="T3-15"/>
+                                </ContextMenu>
+                            </TextBox.ContextMenu>
+                        </TextBox>
+                        <!-- T3-15 주소창 진행 바 -->
+                        <ProgressBar Name="NavProgress" Height="2" VerticalAlignment="Bottom" MinHeight="2"
+                                     Minimum="0" Maximum="100" IsIndeterminate="True" Visibility="Collapsed"
+                                     Foreground="{StaticResource AccentBrush}" Background="Transparent" BorderThickness="0"/>
+                    </Grid>
                 </Border>
             </DockPanel>
         </Border>
@@ -527,6 +550,21 @@
         </Popup>
 
         <!-- ===== 다운로드 플라이아웃 (T1-5) ===== -->
+        <!-- T3-14 추적 방지 실드 팝업 -->
+        <Popup Name="ShieldPopup" PlacementTarget="{Binding ElementName=ShieldBtn}"
+               Placement="Bottom" HorizontalOffset="-10" VerticalOffset="6"
+               StaysOpen="False" AllowsTransparency="True" PopupAnimation="Fade">
+            <Border Background="{StaticResource CardBg}" BorderBrush="{StaticResource BorderBrush}"
+                    BorderThickness="1" CornerRadius="12" Padding="10" Width="320" MaxHeight="360">
+                <StackPanel>
+                    <TextBlock Text="추적 방지 — 차단된 요청" Foreground="{StaticResource TextPrimary}"
+                               FontWeight="SemiBold" Margin="6,4,6,8"/>
+                    <ListBox Name="ShieldList" Background="Transparent" BorderThickness="0"
+                             Foreground="{StaticResource TextSecondary}" FontSize="12"/>
+                </StackPanel>
+            </Border>
+        </Popup>
+
         <Popup Name="DownloadsPopup" PlacementTarget="{Binding ElementName=DownloadsBtn}"
                Placement="Bottom" HorizontalOffset="-10" VerticalOffset="6"
                StaysOpen="False" AllowsTransparency="True" PopupAnimation="Fade">
diff --git a/VideoDownloader.App/MainWindow.xaml.cs b/VideoDownloader.App/MainWindow.xaml.cs
index a5d1285..4a88e15 100644
--- a/VideoDownloader.App/MainWindow.xaml.cs
+++ b/VideoDownloader.App/MainWindow.xaml.cs
@@ -214,10 +214,33 @@ public partial class MainWindow : Window
         _views.GlanceRequested += (_, link) => Dispatcher.BeginInvoke(new Action(() => OpenGlance(link))); // T2-6
         _views.SpeakRequested += (_, text) => Dispatcher.BeginInvoke(new Action(() => SpeakText(text))); // T3-9
 
-        _views.ContextMenuBuild += OnContextMenuBuild;
-        _views.BoostScriptProvider = url => BoostCssBuilder.BuildScript(url, _boostStore.Get(url)); // T2-7
-        _views.GlanceRequested += (_, link) => Dispatcher.BeginInvoke(new Action(() => OpenGlance(link))); // T2-6
-        _views.SpeakRequested += (_, text) => Dispatcher.BeginInvoke(new Action(() => SpeakText(text))); // T3-9
+        // T3-15 주소창 진행 바: 전 탭 네비게이션 집계 → 표시
+        _navTracker = new NavProgressTracker();
+        _navTracker.PropertyChanged += (_, e) =>
+            NavProgress.Visibility = e.PropertyName == nameof(NavProgressTracker.IsNavigating) && _navTracker.IsNavigating
+                ? Visibility.Visible : Visibility.Collapsed;
+        _views.NavigationStarted += _navTracker.Started;
+        _views.NavigationCompleted += _navTracker.Completed;
+
+        // T3-11 권한 다이얼로그: 예=항상 허용 / 아니요=항상 거절 / 취소=이번만 거절
+        _views.PermissionPrompt += (cv, e) => Dispatcher.BeginInvoke(new Action(() =>
+        {
+            var kind = e.PermissionKind.ToString();
+            var origin = Services.TabViewService.OriginOf(e.Uri);
+            var r = System.Windows.MessageBox.Show(this,
+                $"{origin} 사이트가 {KoreanPermission(kind)} 권한을 요청합니다.\n허용하시겠습니까?\n\n예: 항상 허용 · 아니요: 항상 거절 · 취소: 이번만 거절",
+                "권한 요청", MessageBoxButton.YesNoCancel, MessageBoxImage.Question);
+            e.State = r == MessageBoxResult.Yes ? Microsoft.Web.WebView2.Core.CoreWebView2PermissionState.Allow
+                                                : Microsoft.Web.WebView2.Core.CoreWebView2PermissionState.Deny;
+            e.SavesInProfile = r != MessageBoxResult.Cancel; // 항상 선택만 프로필 영속
+            e.Handled = true;
+            if (r != MessageBoxResult.Cancel)
+                _views.Permissions.Remember(kind, origin,
+                    r == MessageBoxResult.Yes ? PermissionVerdict.Allow : PermissionVerdict.Deny);
+        }));
+
+        // T3-14 실드 배지 갱신
+        _views.TrackerBlocked += UpdateShield;
 
         _tabs = new TabManager(() => new TabItem(), _views.AttachView);
         _tabs.ActiveChanged += OnActiveTabChanged;
@@ -284,6 +307,52 @@ public partial class MainWindow : Window
     /// <summary>탭별 WebView2 생명주기·배선 전담 서비스(재구성 ④).</summary>
     private Services.TabViewService? _views;
 
+    /// <summary>T3-15 주소창 진행 바 상태(전 탭 네비게이션 집계).</summary>
+    private NavProgressTracker? _navTracker;
+
+    /// <summary>T3-15: 파라미터 제거 후 클립보드 복사(주소창 우클릭).</summary>
+    private void CopyCleanUrl_Click(object sender, RoutedEventArgs e)
+    {
+        var clean = UrlCleaner.StripQuery(AddressBox.Text);
+        if (string.IsNullOrEmpty(clean)) return;
+        try { Clipboard.SetText(clean); Log($"파라미터 제거 URL 복사: {clean}"); } catch { }
+    }
+
+    /// <summary>T3-14: 실드 배지 갱신.</summary>
+    private void UpdateShield()
+    {
+        if (_views == null) return;
+        var n = _views.TrackerCounter.Total;
+        ShieldBadgeText.Text = n > 0 ? n.ToString() : "";
+        ShieldBadge.Visibility = n > 0 ? Visibility.Visible : Visibility.Collapsed;
+        ShieldBtn.ToolTip = n > 0 ? $"추적 요청 {n}건 차단됨" : "추적 방지";
+    }
+
+    /// <summary>T3-14: 실드 클릭 → 차단 도메인 목록 팝업.</summary>
+    private void Shield_Click(object sender, RoutedEventArgs e)
+    {
+        if (_views == null) return;
+        var byDomain = _views.TrackerCounter.ByDomain;
+        ShieldList.ItemsSource = byDomain.Count == 0
+            ? new[] { "차단된 추적 요청이 없습니다" }
+            : byDomain.OrderByDescending(kv => kv.Value).Select(kv => $"{kv.Value,3} × {kv.Key}").ToList();
+        ShieldPopup.IsOpen = true;
+    }
+
+    /// <summary>T3-11: 권한 종류 한글 표기.</summary>
+    private static string KoreanPermission(string kind) => kind switch
+    {
+        "Microphone" => "마이크",
+        "Camera" => "카메라",
+        "Geolocation" => "위치",
+        "Notifications" => "알림",
+        "ClipboardRead" => "클립보드 읽기",
+        "Autoplay" => "자동 재생",
+        "FileReadWrite" => "파일 읽기/쓰기",
+        "PersistentStorage" => "영구 저장소",
+        _ => kind,
+    };
+
     private void OnUrlChanged(TabItem tab, string url)
     {
         if (tab.PendingHistoryUrl != null) RecordHistory(tab.PendingHistoryUrl, tab.PendingHistoryUrl);
diff --git a/VideoDownloader.App/Services/TabViewService.cs b/VideoDownloader.App/Services/TabViewService.cs
index 0ae123c..48e5a16 100644
--- a/VideoDownloader.App/Services/TabViewService.cs
+++ b/VideoDownloader.App/Services/TabViewService.cs
@@ -55,6 +55,27 @@ public sealed class TabViewService
     /// <summary>T2-4 리더 내 낭독(TTS) 요청 — 리더 본문 텍스트.</summary>
     public event Action<CoreWebView2, string>? SpeakRequested;
 
+    /// <summary>T3-15 주소창 진행 바: 네비게이션 시작(전 탭 집계).</summary>
+    public event Action? NavigationStarted;
+
+    /// <summary>T3-15 주소창 진행 바: 네비게이션 완료(전 탭 집계).</summary>
+    public event Action? NavigationCompleted;
+
+    /// <summary>T3-11 사이트별 권한 정책(출처×종류 기억).</summary>
+    public PermissionGate Permissions { get; set; } = new();
+
+    /// <summary>T3-11 Ask 판정 시 호스트 다이얼로그 — State/Handled/SavesInProfile 설정은 호스트 책임.</summary>
+    public event Action<CoreWebView2, CoreWebView2PermissionRequestedEventArgs>? PermissionPrompt;
+
+    /// <summary>T3-14 추적 방지 블랙리스트(교체 주입 가능).</summary>
+    public TrackerBlocklist TrackerBlocklist { get; set; } = new();
+
+    /// <summary>T3-14 차단 카운터(실드 배지·팝업 데이터).</summary>
+    public TrackerCounter TrackerCounter { get; } = new();
+
+    /// <summary>T3-14 차단 발생 알림(배지 갱신).</summary>
+    public event Action? TrackerBlocked;
+
     /// <summary>T3-3 InPrivate 탭: 다음에 만들어지는 탭에 적용(1회성).</summary>
     public bool NextTabIsPrivate { get; set; }
 
@@ -166,10 +187,11 @@ public sealed class TabViewService
         }));
 
         // 네비게이션 상태
-        cv.NavigationStarting += (_, _) => _dispatcher.BeginInvoke(new Action(() => tab.IsLoading = true));
+        cv.NavigationStarting += (_, _) => _dispatcher.BeginInvoke(new Action(() => { tab.IsLoading = true; NavigationStarted?.Invoke(); }));
         cv.NavigationCompleted += (_, _) => _dispatcher.BeginInvoke(new Action(() =>
         {
             tab.IsLoading = false;
+            NavigationCompleted?.Invoke();
             try { if (tab.View != null) tab.View.ZoomFactor = _zoomStore.Get(cv.Source); } catch { } // T1-7 사이트별 줌
             try // T2-7 부스트(강제 다크/커스텀 CSS) 적용
             {
@@ -180,6 +202,37 @@ public sealed class TabViewService
         }));
         cv.HistoryChanged += (_, _) => HistoryChanged?.Invoke();
 
+        // T3-11 사이트별 권한: 정책 Ask 만 프롬프트, Allow/Deny 는 즉시 응답
+        cv.PermissionRequested += (_, e) =>
+        {
+            var kind = e.PermissionKind.ToString();
+            var origin = OriginOf(e.Uri);
+            switch (Permissions.Decide(kind, origin))
+            {
+                case PermissionVerdict.Allow:
+                    e.State = CoreWebView2PermissionState.Allow; e.Handled = true;
+                    break;
+                case PermissionVerdict.Deny:
+                    e.State = CoreWebView2PermissionState.Deny; e.Handled = true;
+                    break;
+                default:
+                    PermissionPrompt?.Invoke(cv, e); // 호스트 다이얼로그가 State/Handled 설정
+                    break;
+            }
+        };
+
+        // T3-14 추적 방지: 블랙리스트 요청 차단 + 카운터
+        cv.AddWebResourceRequestedFilter("*", CoreWebView2WebResourceContext.All);
+        cv.WebResourceRequested += (_, e) =>
+        {
+            Uri u;
+            try { u = new Uri(e.Request.Uri); } catch { return; }
+            if (!TrackerBlocklist.Matches(u)) return;
+            try { e.Response = _env.CreateWebResourceResponse(null, 204, "Blocked", ""); } catch { }
+            TrackerCounter.Record(e.Request.Uri);
+            _dispatcher.BeginInvoke(new Action(() => TrackerBlocked?.Invoke()));
+        };
+
         cv.SourceChanged += (_, _) => _dispatcher.BeginInvoke(new Action(() =>
         {
             var url = cv.Source ?? "";
@@ -250,4 +303,12 @@ public sealed class TabViewService
 
     /// <summary>활성 탭 검색 상태 표시 요청(FindStatus 텍스트 갱신 — 호스트가 구독).</summary>
     public event Action<TabItem>? FindStateChanged;
+
+    /// <summary>권한 기준 출처(scheme://host:port) 추출.</summary>
+    public static string OriginOf(string? uri)
+    {
+        if (string.IsNullOrEmpty(uri)) return "";
+        try { var u = new Uri(uri); return u.GetComponents(UriComponents.SchemeAndServer, UriFormat.Unescaped); }
+        catch { return uri; }
+    }
 }
diff --git a/VideoDownloader.Browser/PermissionGate.cs b/VideoDownloader.Browser/PermissionGate.cs
new file mode 100644
index 0000000..5ea8f73
--- /dev/null
+++ b/VideoDownloader.Browser/PermissionGate.cs
@@ -0,0 +1,78 @@
+namespace VideoDownloader.Browser;
+
+public enum PermissionVerdict { Ask, Allow, Deny }
+
+/// <summary>
+/// T3-11 사이트별 권한 정책 — 출처×종류 단위 기억. WebView2 PermissionRequested 에서
+/// Ask 만 프롬프트로 올리고 Allow/Deny 는 즉시 응답. "항상" 선택은 네이티브
+/// Profile.SetPermissionStateAsync 로도 영속(세션 밖 저장).
+/// </summary>
+public sealed class PermissionGate
+{
+    /// <summary>프롬프트 없이 거절: 센서류(피싱 표면 축소).</summary>
+    private static readonly HashSet<string> AutoDeny = new(StringComparer.OrdinalIgnoreCase) { "OtherSensors" };
+    /// <summary>프롬프트 없이 허용: 연속 다운로드(다운로더 앱 본업).</summary>
+    private static readonly HashSet<string> AutoAllow = new(StringComparer.OrdinalIgnoreCase) { "MultipleAutomaticDownloads" };
+
+    private readonly Dictionary<(string origin, string kind), PermissionVerdict> _saved = new();
+
+    public PermissionVerdict Decide(string kind, string origin)
+    {
+        if (AutoDeny.Contains(kind)) return PermissionVerdict.Deny;
+        if (AutoAllow.Contains(kind)) return PermissionVerdict.Allow;
+        return _saved.GetValueOrDefault((origin, kind), PermissionVerdict.Ask);
+    }
+
+    public void Remember(string kind, string origin, PermissionVerdict verdict)
+        => _saved[(origin, kind)] = verdict;
+}
+
+/// <summary>T3-14: 추적 스크립트 블랙리스트 — 호스트 또는 서브도메인 매칭.</summary>
+public sealed class TrackerBlocklist
+{
+    /// <summary>주요 광고/분석 도메인(EasyList 공통 항목 발췌). 생성자 주입으로 교체 가능(테스트).</summary>
+    public static readonly string[] DefaultDomains =
+    {
+        "google-analytics.com", "googletagmanager.com", "doubleclick.net", "googlesyndication.com",
+        "googleadservices.com", "scorecardresearch.com", "hotjar.com", "mixpanel.com", "segment.io",
+        "facebook.net", "connect.facebook.net", "amplitude.com", "branch.io", "appsflyer.com",
+        "criteo.com", "taboola.com", "outbrain.com", "adnxs.com", "pubmatic.com", "rubiconproject.com",
+    };
+
+    private readonly HashSet<string> _domains;
+
+    public TrackerBlocklist() : this(DefaultDomains) { }
+    public TrackerBlocklist(IEnumerable<string> domains) =>
+        _domains = new HashSet<string>(domains, StringComparer.OrdinalIgnoreCase);
+
+    public bool Matches(Uri url)
+    {
+        var host = url.Host;
+        foreach (var d in _domains)
+            if (host.Equals(d, StringComparison.OrdinalIgnoreCase) ||
+                host.EndsWith("." + d, StringComparison.OrdinalIgnoreCase))
+                return true;
+        return false;
+    }
+}
+
+/// <summary>T3-14: 차단 카운터 — 총계/도메인별 집계, 변경 통지(실드 배지 갱신용).</summary>
+public sealed class TrackerCounter
+{
+    private int _total;
+    public int Total => Volatile.Read(ref _total);
+    public Dictionary<string, int> ByDomain { get; } = new(StringComparer.OrdinalIgnoreCase);
+    public event Action? Changed;
+
+    public void Record(string url)
+    {
+        var host = new Uri(url).Host;
+        var baseDomain = host.StartsWith("www.", StringComparison.OrdinalIgnoreCase) ? host[4..] : host;
+        Interlocked.Increment(ref _total);
+        lock (ByDomain)
+        {
+            ByDomain[baseDomain] = ByDomain.GetValueOrDefault(baseDomain) + 1;
+        }
+        Changed?.Invoke();
+    }
+}
diff --git a/VideoDownloader.Browser/UrlCleaner.cs b/VideoDownloader.Browser/UrlCleaner.cs
new file mode 100644
index 0000000..1ed2009
--- /dev/null
+++ b/VideoDownloader.Browser/UrlCleaner.cs
@@ -0,0 +1,43 @@
+using System.ComponentModel;
+using System.Runtime.CompilerServices;
+
+namespace VideoDownloader.Browser;
+
+/// <summary>T3-15: "파라미터 제거 복사" — 추적용 쿼리·프래그먼트를 뺀 URL 반환.</summary>
+public static class UrlCleaner
+{
+    public static string? StripQuery(string? url)
+    {
+        if (url == null) return null;
+        var q = url.IndexOf('?');
+        if (q >= 0) url = url[..q];
+        var f = url.IndexOf('#');
+        if (f >= 0) url = url[..f];
+        return url;
+    }
+}
+
+/// <summary>T3-15: 주소창 진행 바 상태 — 진행 중 네비게이션 개수 집계(탭·리다이렉트 중복 안전).</summary>
+public sealed class NavProgressTracker : INotifyPropertyChanged
+{
+    private int _count;
+
+    public bool IsNavigating => Volatile.Read(ref _count) > 0;
+
+    public event PropertyChangedEventHandler? PropertyChanged;
+
+    public void Started() => Update(1);
+    public void Completed() => Update(-1);
+
+    private void Update(int delta)
+    {
+        var before = IsNavigating;
+        var c = _count + delta;
+        Volatile.Write(ref _count, Math.Max(0, c)); // 과잉 완료 방지
+        if (before != IsNavigating)
+            OnPropertyChanged(nameof(IsNavigating));
+    }
+
+    private void OnPropertyChanged([CallerMemberName] string? name = null) =>
+        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
+}
diff --git a/VideoDownloader.Mobile.Core/ConnectionTroubleshoot.cs b/VideoDownloader.Mobile.Core/ConnectionTroubleshoot.cs
new file mode 100644
index 0000000..277db24
--- /dev/null
+++ b/VideoDownloader.Mobile.Core/ConnectionTroubleshoot.cs
@@ -0,0 +1,21 @@
+namespace VideoDownloader.Mobile;
+
+/// <summary>
+/// 외부망/네트워크 불통 안내(MOBILE_PLAN §7 성공 기준) —
+/// "같은 네트워크 필요 / 외부망에서는 Tailscale 등 VPN 안내".
+/// </summary>
+public static class ConnectionTroubleshoot
+{
+    public const string NotConfigured = "먼저 연결 탭에서 PC 와 페어링하세요";
+
+    public const string Unreachable =
+        "PC 에 연결할 수 없습니다. 폰과 PC 가 같은 네트워크(Wi-Fi)에 있는지 확인하세요. " +
+        "외부망에서 접속하려면 Tailscale 등 VPN 으로 PC 의 사설망에 접근해야 합니다.";
+
+    public static string Message(bool isConfigured, string? lastError)
+    {
+        if (!isConfigured) return NotConfigured;
+        if (!string.IsNullOrEmpty(lastError)) return Unreachable;
+        return "";
+    }
+}
diff --git a/VideoDownloader.Mobile/OfflineStore.cs b/VideoDownloader.Mobile.Core/OfflineStore.cs
similarity index 91%
rename from VideoDownloader.Mobile/OfflineStore.cs
rename to VideoDownloader.Mobile.Core/OfflineStore.cs
index 4d7f443..ca6bf1d 100644
--- a/VideoDownloader.Mobile/OfflineStore.cs
+++ b/VideoDownloader.Mobile.Core/OfflineStore.cs
@@ -10,16 +10,15 @@ public sealed record OfflineItem(string Id, string FileName, long SizeBytes);
 /// </summary>
 public sealed class OfflineStore
 {
-    public static OfflineStore Default { get; } = new();
-
     private readonly string _dir;
     private readonly string _manifestPath;
     private readonly object _gate = new();
     private Dictionary<string, string> _manifest;
 
-    public OfflineStore()
+    /// <summary>baseDir 아래 offline/ 폴더 사용(호스트가 앱 데이터 디렉터리 주입).</summary>
+    public OfflineStore(string baseDir)
     {
-        _dir = Path.Combine(FileSystem.AppDataDirectory, "offline");
+        _dir = Path.Combine(baseDir, "offline");
         _manifestPath = Path.Combine(_dir, "manifest.json");
         try
         {
diff --git a/VideoDownloader.Mobile.Core/QueueCompletionDetector.cs b/VideoDownloader.Mobile.Core/QueueCompletionDetector.cs
new file mode 100644
index 0000000..5e4df54
--- /dev/null
+++ b/VideoDownloader.Mobile.Core/QueueCompletionDetector.cs
@@ -0,0 +1,18 @@
+namespace VideoDownloader.Mobile;
+
+/// <summary>U5 완료 알림: 이전/다음 큐 스냅샷에서 새로 완료("완료")된 항목 ID 감지.
+/// 이전 스냅샷이 비면(앱 시작 직후 첫 폴링) 무시 — 과거 완료 알림 스팸 방지.</summary>
+public sealed class QueueCompletionDetector
+{
+    public IReadOnlyList<string> Detect(
+        IReadOnlyList<(string Id, string Status)> previous,
+        IReadOnlyList<(string Id, string Status)> next)
+    {
+        if (previous.Count == 0) return Array.Empty<string>();
+        var prev = previous.ToDictionary(x => x.Id, x => x.Status);
+        return next
+            .Where(n => n.Status == "완료" && prev.TryGetValue(n.Id, out var s) && s != "완료")
+            .Select(n => n.Id)
+            .ToList();
+    }
+}
diff --git a/VideoDownloader.Mobile.Core/VideoDownloader.Mobile.Core.csproj b/VideoDownloader.Mobile.Core/VideoDownloader.Mobile.Core.csproj
new file mode 100644
index 0000000..d4f8664
--- /dev/null
+++ b/VideoDownloader.Mobile.Core/VideoDownloader.Mobile.Core.csproj
@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <RootNamespace>VideoDownloader.Mobile</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <LangVersion>latest</LangVersion>
+  </PropertyGroup>
+</Project>
diff --git a/VideoDownloader.Mobile/ApiClient.cs b/VideoDownloader.Mobile/ApiClient.cs
index 5703875..79f7d8b 100644
--- a/VideoDownloader.Mobile/ApiClient.cs
+++ b/VideoDownloader.Mobile/ApiClient.cs
@@ -116,6 +116,7 @@ public sealed class ApiClient
 
     public string StreamUrl(LibraryItem item) => $"{BaseUrl}/stream/{item.Id}?t={Token}";
     public string FileUrl(LibraryItem item) => $"{BaseUrl}/file/{item.Id}?t={Token}";
+    public string ThumbUrl(LibraryItem item) => $"{BaseUrl}/api/library/{item.Id}/thumb?t={Token}";
 
     /// <summary>이어보기 위치 조회(U3). 실패/미저장 시 0.</summary>
     public async Task<double> GetPositionAsync(string id)
@@ -188,6 +189,6 @@ public sealed class ApiClient
 
 public sealed record QueueItem(string Id, string Title, string Url, string Status, double Percent);
 
-public sealed record LibraryItem(string Id, string FileName, long SizeBytes, DateTime Modified);
+public sealed record LibraryItem(string Id, string FileName, long SizeBytes, DateTime Modified, string? Resolution = null);
 
 public sealed record PositionDto(double PositionSec);
diff --git a/VideoDownloader.Mobile/AppOfflineStore.cs b/VideoDownloader.Mobile/AppOfflineStore.cs
new file mode 100644
index 0000000..b8e60ed
--- /dev/null
+++ b/VideoDownloader.Mobile/AppOfflineStore.cs
@@ -0,0 +1,7 @@
+namespace VideoDownloader.Mobile;
+
+/// <summary>앱 데이터 디렉터리를 주입하는 오프라인 저장소 기본 인스턴스(Core 는 MAUI 비의존).</summary>
+public static class AppOfflineStore
+{
+    public static OfflineStore Default { get; } = new(FileSystem.AppDataDirectory);
+}
diff --git a/VideoDownloader.Mobile/Pages.cs b/VideoDownloader.Mobile/Pages.cs
index 00e6512..0c50727 100644
--- a/VideoDownloader.Mobile/Pages.cs
+++ b/VideoDownloader.Mobile/Pages.cs
@@ -70,13 +70,16 @@ public sealed class ConnectPage : ContentPage
     }
 }
 
-/// <summary>M1 큐 페이지: 목록(2초 폴링) + URL 추가 + 제어.</summary>
+/// <summary>M1 큐 페이지: 목록(2초 폴링) + URL 추가 + 제어 + U5 완료 알림 + 외부망 안내.</summary>
 public sealed class QueuePage : ContentPage
 {
     private readonly Entry _url = new() { Placeholder = "YouTube·영상 URL 붙여넣기", Keyboard = Keyboard.Url };
     private readonly Label _summary = new();
+    private readonly Label _trouble = new() { FontSize = 12, TextColor = Colors.OrangeRed, IsVisible = false };
     private readonly CollectionView _list = new();
     private readonly IDispatcherTimer _timer;
+    private readonly QueueCompletionDetector _completions = new();
+    private List<QueueItem> _last = new();
 
     public QueuePage()
     {
@@ -131,19 +134,51 @@ public sealed class QueuePage : ContentPage
         Content = new VerticalStackLayout
         {
             Padding = 16, Spacing = 10,
-            Children = { _url, addBtn, _summary, _list }
+            Children = { _url, addBtn, _summary, _trouble, _list }
         };
     }
 
     private async Task Refresh()
     {
-        if (!ApiClient.Instance.IsConfigured) { _summary.Text = "⚠️ 먼저 연결하세요"; return; }
+        var trouble = ConnectionTroubleshoot.Message(ApiClient.Instance.IsConfigured, ApiClient.Instance.LastError);
+        _trouble.Text = trouble;
+        _trouble.IsVisible = trouble.Length > 0;
+        if (!ApiClient.Instance.IsConfigured) { _summary.Text = "⚠️ 먼저 연결하세요"; _last = new(); return; }
         var items = await ApiClient.Instance.GetQueueAsync();
         _list.ItemsSource = items;
+
+        // U5: 이전 스냅샷 대비 새로 완료된 항목 → 로컬 알림
+        var done = _completions.Detect(
+            _last.Select(i => (i.Id, i.Status)).ToList(),
+            items.Select(i => (i.Id, i.Status)).ToList());
+        foreach (var id in done)
+        {
+            var item = items.First(i => i.Id == id);
+            _ = NotifyCompletionAsync(item.Title);
+            _summary.Text = $"🔔 완료: {item.Title}";
+        }
+        _last = items;
+
         var err = ApiClient.Instance.LastError;
         _summary.Text = err != null ? $"❌ {err}" : items.Count == 0 ? "대기 중인 항목이 없습니다" : $"{items.Count}건";
     }
 
+    /// <summary>U5: 완료 로컬 알림(Android 13+ 는 최초 1회 권한 요청).</summary>
+    private static async Task NotifyCompletionAsync(string title)
+    {
+        try
+        {
+            if (OperatingSystem.IsAndroidVersionAtLeast(33))
+                await Plugin.LocalNotification.LocalNotificationCenter.Current.RequestNotificationPermission();
+            Plugin.LocalNotification.LocalNotificationCenter.Current.Show(new Plugin.LocalNotification.NotificationRequest
+            {
+                Title = "다운로드 완료",
+                Description = title,
+            });
+        }
+        catch { }
+    }
+
     private sealed class PercentConverter : IValueConverter
     {
         public object Convert(object? value, Type t, object? p, System.Globalization.CultureInfo c) => Math.Clamp(value is double d ? d / 100.0 : 0, 0, 1);
@@ -159,11 +194,14 @@ public sealed class LibraryPage : ContentPage
     public LibraryPage()
     {
         Title = "라이브러리";
+        _list.ItemsLayout = new GridItemsLayout(2, ItemsLayoutOrientation.Vertical); // M2 썸네일 그리드
         _list.ItemTemplate = new DataTemplate(() =>
         {
-            var name = new Label { FontSize = 14, FontAttributes = FontAttributes.Bold, LineBreakMode = LineBreakMode.TailTruncation };
+            var thumb = new Image { HeightRequest = 96, Aspect = Aspect.AspectFill, BackgroundColor = Colors.Black };
+            thumb.SetBinding(Image.SourceProperty, new Binding(".", converter: new ThumbConverter()));
+            var name = new Label { FontSize = 13, FontAttributes = FontAttributes.Bold, LineBreakMode = LineBreakMode.TailTruncation, LineHeight = 1.1 };
             name.SetBinding(Label.TextProperty, "FileName");
-            var size = new Label { FontSize = 11, TextColor = Colors.Gray };
+            var size = new Label { FontSize = 10, TextColor = Colors.Gray };
             size.SetBinding(Label.TextProperty, new Binding("SizeBytes", stringFormat: "{0:N0} bytes"));
 
             // U4 폰 저장: 카드 우측 버튼, 진행률을 버튼 텍스트로 표시
@@ -172,8 +210,8 @@ public sealed class LibraryPage : ContentPage
 
             var card = new Frame
             {
-                Margin = new Thickness(0, 4), Padding = 12, CornerRadius = 10,
-                Content = new HorizontalStackLayout { Spacing = 8, Children = { new VerticalStackLayout { Children = { name, size } }, save } }
+                Margin = new Thickness(6, 4), Padding = 8, CornerRadius = 10,
+                Content = new VerticalStackLayout { Spacing = 4, Children = { thumb, name, size, save } }
             };
             // CollectionView.SelectionChanged 는 Android 에서 발화 불안정 → 템플릿 카드에 탭 제스처
             var tap = new TapGestureRecognizer();
@@ -194,15 +232,15 @@ public sealed class LibraryPage : ContentPage
     private static async Task SaveOffline(Button button, LibraryItem? item)
     {
         if (item == null) return;
-        if (OfflineStore.Default.Exists(item.Id)) { button.Text = "✓ 저장됨"; return; }
+        if (AppOfflineStore.Default.Exists(item.Id)) { button.Text = "✓ 저장됨"; return; }
         button.Text = "0%";
         try
         {
-            var dest = OfflineStore.Default.PathFor(item.Id);
+            var dest = AppOfflineStore.Default.PathFor(item.Id);
             var progress = new Progress<double>(p => MainThread.BeginInvokeOnMainThread(
                 () => button.Text = p >= 1 ? "✓ 저장됨" : $"{(int)(p * 100)}%"));
             await ApiClient.Instance.DownloadFileAsync(item, dest, progress, CancellationToken.None);
-            OfflineStore.Default.Record(item.Id, item.FileName);
+            AppOfflineStore.Default.Record(item.Id, item.FileName);
             button.Text = "✓ 저장됨";
         }
         catch (Exception e)
@@ -247,7 +285,7 @@ public sealed class DownloadsPage : ContentPage
             var del = new Button { Text = "🗑", FontSize = 12, Padding = new Thickness(10, 4), VerticalOptions = LayoutOptions.Center };
             del.Clicked += (_, _) =>
             {
-                if ((del.BindingContext as OfflineItem) is { } it) { OfflineStore.Default.Delete(it.Id); Reload(); }
+                if ((del.BindingContext as OfflineItem) is { } it) { AppOfflineStore.Default.Delete(it.Id); Reload(); }
             };
 
             var card = new Frame
@@ -260,7 +298,7 @@ public sealed class DownloadsPage : ContentPage
             {
                 if ((card.BindingContext as OfflineItem) is { } it)
                     _ = Application.Current!.MainPage!.Navigation.PushModalAsync(
-                        new NavigationPage(new PlayerPage(new LibraryItem(it.Id, it.FileName, it.SizeBytes, DateTime.MinValue), OfflineStore.Default.PathFor(it.Id))));
+                        new NavigationPage(new PlayerPage(new LibraryItem(it.Id, it.FileName, it.SizeBytes, DateTime.MinValue), AppOfflineStore.Default.PathFor(it.Id))));
             };
             card.GestureRecognizers.Add(tap);
             return card;
@@ -277,7 +315,7 @@ public sealed class DownloadsPage : ContentPage
 
     private void Reload()
     {
-        var items = OfflineStore.Default.List();
+        var items = AppOfflineStore.Default.List();
         _list.ItemsSource = items.Count > 0 ? items : null;
         _empty.IsVisible = items.Count == 0;
     }
@@ -321,14 +359,55 @@ public sealed class PlayerPage : ContentPage
             });
         }
         Content = _media;
+        // M2: 재생 중 미디어 알림(ongoing 노티) — 재생은 앱 내(포그라운드) 한정
+        StartPlaybackNotification(item.FileName);
     }
 
     protected override void OnDisappearing()
     {
         if (_sync && _itemId != null && _media.Position > TimeSpan.Zero)
             _ = ApiClient.Instance.PostPositionAsync(_itemId, _media.Position.TotalSeconds);
+        StopPlaybackNotification();
         _media.Stop();
         _media.Handler?.DisconnectHandler(); // 재생 리소스 해제
         base.OnDisappearing();
     }
+
+    private const int PlaybackNotificationId = 4711;
+
+    /// <summary>M2: 재생 중 미디어 알림 — ongoing 노티(닫으면 자동 소멸).</summary>
+    private static void StartPlaybackNotification(string title)
+    {
+        try
+        {
+            Plugin.LocalNotification.LocalNotificationCenter.Current.Show(new Plugin.LocalNotification.NotificationRequest
+            {
+                NotificationId = PlaybackNotificationId,
+                Title = "재생 중",
+                Description = title,
+                Android =
+                {
+                    ChannelId = "vd_playback",
+                    Ongoing = true,
+                    AutoCancel = false,
+                },
+            });
+        }
+        catch { }
+    }
+
+    private static void StopPlaybackNotification()
+    {
+        try { Plugin.LocalNotification.LocalNotificationCenter.Current.Cancel(PlaybackNotificationId); } catch { }
+    }
+}
+
+/// <summary>M2: LibraryItem → 썸네일 URL 변환(바인딩 컨버터).</summary>
+public sealed class ThumbConverter : IValueConverter
+{
+    public object? Convert(object? value, Type t, object? p, System.Globalization.CultureInfo c)
+        => value is LibraryItem it && ApiClient.Instance.IsConfigured
+            ? Microsoft.Maui.Controls.ImageSource.FromUri(new Uri(ApiClient.Instance.ThumbUrl(it)))
+            : null;
+    public object ConvertBack(object? v, Type t, object? p, System.Globalization.CultureInfo c) => throw new NotSupportedException();
 }
diff --git a/VideoDownloader.Mobile/Platforms/Android/AndroidManifest.xml b/VideoDownloader.Mobile/Platforms/Android/AndroidManifest.xml
index 5cdb4fd..ac3418f 100644
--- a/VideoDownloader.Mobile/Platforms/Android/AndroidManifest.xml
+++ b/VideoDownloader.Mobile/Platforms/Android/AndroidManifest.xml
@@ -4,5 +4,9 @@
 	<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
 	<uses-permission android:name="android.permission.INTERNET" />
   <uses-permission android:name="android.permission.CAMERA" />
-  <uses-permission android:name="android.permission.INTERNET" />
+  <!-- U5 완료 알림(Android 13+) -->
+  <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
+  <!-- M2 재생중 미디어 알림(포그라운드 서비스 mediaPlayback) -->
+  <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
+  <uses-permission android:name="android.permission.FOREGROUND_SERVICE_MEDIA_PLAYBACK" />
 </manifest>
\ No newline at end of file
diff --git a/VideoDownloader.Mobile/VideoDownloader.Mobile.csproj b/VideoDownloader.Mobile/VideoDownloader.Mobile.csproj
index 9928874..b285db5 100644
--- a/VideoDownloader.Mobile/VideoDownloader.Mobile.csproj
+++ b/VideoDownloader.Mobile/VideoDownloader.Mobile.csproj
@@ -66,8 +66,14 @@
 		<MauiAsset Include="Resources\Raw\**" LogicalName="%(RecursiveDir)%(Filename)%(Extension)" />
 	</ItemGroup>
 
+	<ItemGroup>
+		<ProjectReference Include="..\VideoDownloader.Mobile.Core\VideoDownloader.Mobile.Core.csproj" />
+	</ItemGroup>
+
 	<ItemGroup>
 		<PackageReference Include="Microsoft.Maui.Controls" Version="$(MauiVersion)" />
+		<!-- U5 완료 알림 -->
+		<PackageReference Include="Plugin.LocalNotification" Version="11.1.0" />
 		<PackageReference Include="Microsoft.Extensions.Logging.Debug" Version="10.0.0" />
 		<PackageReference Include="ZXing.Net.Maui.Controls" Version="0.4.0" />
 		<PackageReference Include="CommunityToolkit.Maui.MediaElement" Version="3.2.0" />
diff --git a/VideoDownloader.Server/ServerHost.cs b/VideoDownloader.Server/ServerHost.cs
index c152bf6..8054ed1 100644
--- a/VideoDownloader.Server/ServerHost.cs
+++ b/VideoDownloader.Server/ServerHost.cs
@@ -96,8 +96,30 @@ public sealed class ServerHost : IAsyncDisposable
         app.MapPost("/api/queue/{id}/cancel", async (string id) => { await queue.CancelAsync(id); Results.Ok(); });
 
         // ── 라이브러리 / 스트리밍 ──
+        // ── 라이브러리 + 썸네일/해상도(M2) ──
+        var thumbnailer = options.Thumbnailer ?? ServerOptionsDefaults.DefaultThumbnailer();
+        var ffmpeg = VideoDownloader.Core.Platform.DesktopMediaMuxer.Default.ResolveFfmpeg(new VideoDownloader.Core.Config.AppConfig());
         app.MapGet("/api/library", async (HttpContext ctx) =>
-            await ctx.Response.WriteAsJsonAsync(MediaLibrary.List(options.LibraryFolder)));
+        {
+            var items = MediaLibrary.List(options.LibraryFolder);
+            if (ffmpeg != null)
+            {
+                for (var i = 0; i < items.Count; i++)
+                {
+                    var res = await thumbnailer.GetResolutionAsync(ffmpeg, Path.Combine(options.LibraryFolder, items[i].FileName));
+                    items[i] = items[i] with { Resolution = res };
+                }
+            }
+            await ctx.Response.WriteAsJsonAsync(items);
+        });
+
+        app.MapGet("/api/library/{id}/thumb", async (string id) =>
+        {
+            var file = MediaLibrary.Find(options.LibraryFolder, id);
+            if (file == null || ffmpeg == null) return Results.NotFound();
+            var jpg = await thumbnailer.GetThumbnailAsync(ffmpeg, file.Value.FullPath);
+            return jpg == null ? Results.NotFound() : Results.File(jpg, "image/jpeg");
+        });
 
         app.MapGet("/stream/{id}", (string id) =>
         {
diff --git a/VideoDownloader.Server/ServerModels.cs b/VideoDownloader.Server/ServerModels.cs
index 97ca183..2ce8dc7 100644
--- a/VideoDownloader.Server/ServerModels.cs
+++ b/VideoDownloader.Server/ServerModels.cs
@@ -4,7 +4,7 @@ namespace VideoDownloader.Server;
 public sealed record QueueItemDto(string Id, string Title, string Url, string Status, double Percent);
 
 /// <summary>라이브러리(저장 폴더) 미디어 항목.</summary>
-public sealed record LibraryItemDto(string Id, string FileName, long SizeBytes, DateTime Modified);
+public sealed record LibraryItemDto(string Id, string FileName, long SizeBytes, DateTime Modified, string? Resolution = null);
 
 /// <summary>이어보기 위치(U3 동기화). 초 단위.</summary>
 public sealed record PositionDto(double PositionSec);
@@ -22,6 +22,15 @@ public sealed class ServerOptions
     public IQueueAdapter Queue { get; init; } = new EmptyQueueAdapter();
     /// <summary>기기 표시명(웹 컴패니언 헤더용).</summary>
     public string DeviceName { get; init; } = Environment.MachineName;
+    /// <summary>썸네일/해상도 생성기(기본: DesktopProcessRunner 기반 ffmpeg). 테스트 주입 가능.</summary>
+    public Thumbnailer? Thumbnailer { get; init; }
+}
+
+/// <summary>기본 썸네일러 팩토리.</summary>
+public static class ServerOptionsDefaults
+{
+    public static Thumbnailer DefaultThumbnailer() =>
+        new(VideoDownloader.Core.Platform.DesktopProcessRunner.Default);
 }
 
 /// <summary>호스트 앱의 다운로드 큐와 서버를 잇는 어댑터(UI 스레드 마샬링은 구현측 담당).</summary>
diff --git a/VideoDownloader.Server/Thumbnailer.cs b/VideoDownloader.Server/Thumbnailer.cs
new file mode 100644
index 0000000..53d7d8f
--- /dev/null
+++ b/VideoDownloader.Server/Thumbnailer.cs
@@ -0,0 +1,57 @@
+using System.Text.RegularExpressions;
+using VideoDownloader.Core.Config;
+using VideoDownloader.Core.Platform;
+
+namespace VideoDownloader.Server;
+
+/// <summary>
+/// M2 라이브러리 메타데이터 — ffmpeg 기반 썸네일(.thumb.jpg)·해상도(.meta.json) 사이드카 캐시.
+/// IProcessRunner 주입(테스트는 Fake, 호스트는 DesktopProcessRunner).
+/// </summary>
+public sealed partial class Thumbnailer
+{
+    private readonly IProcessRunner _runner;
+    public Thumbnailer(IProcessRunner runner) => _runner = runner;
+
+    /// <summary>1초 지점 프레임 썸네일(320px 폭 JPEG). 실패 시 null. 캐시 히트 시 프로세스 없음.</summary>
+    public async Task<byte[]?> GetThumbnailAsync(string ffmpeg, string mediaPath, CancellationToken ct = default)
+    {
+        var cache = mediaPath + ".thumb.jpg";
+        try
+        {
+            if (File.Exists(cache)) return await File.ReadAllBytesAsync(cache, ct);
+            var res = await _runner.RunAsync(new ProcessSpec(ffmpeg, new[]
+            {
+                "-y", "-hide_banner", "-loglevel", "error", "-ss", "1", "-i", mediaPath,
+                "-frames:v", "1", "-vf", "scale=320:-2", cache,
+            }), null, ct);
+            if (res.ExitCode != 0 || !File.Exists(cache)) return null;
+            return await File.ReadAllBytesAsync(cache, ct);
+        }
+        catch { return null; }
+    }
+
+    /// <summary>해상도("1920x1080"). ffmpeg -i stderr 의 Stream 라인에서 추출, .meta.json 캐시.</summary>
+    public async Task<string?> GetResolutionAsync(string ffmpeg, string mediaPath, CancellationToken ct = default)
+    {
+        var cache = mediaPath + ".meta.json";
+        try
+        {
+            if (File.Exists(cache))
+            {
+                var cached = await File.ReadAllTextAsync(cache, ct);
+                return cached.Length >= 3 ? cached.Trim('"') : null;
+            }
+            var res = await _runner.RunAsync(new ProcessSpec(ffmpeg, new[]
+            { "-hide_banner", "-i", mediaPath }), null, ct);
+            var m = ResolutionRegex().Match(res.Stderr);
+            var value = m.Success ? m.Groups[1].Value : null;
+            await File.WriteAllTextAsync(cache, value == null ? "-" : $"\"{value}\"", ct);
+            return value;
+        }
+        catch { return null; }
+    }
+
+    [GeneratedRegex(@"Video:.*?,\s(\d{2,5}x\d{2,5})")]
+    private static partial Regex ResolutionRegex();
+}
diff --git a/VideoDownloader.Server/VideoDownloader.Server.csproj b/VideoDownloader.Server/VideoDownloader.Server.csproj
index 36d4ea7..30457e0 100644
--- a/VideoDownloader.Server/VideoDownloader.Server.csproj
+++ b/VideoDownloader.Server/VideoDownloader.Server.csproj
@@ -8,4 +8,7 @@
   <ItemGroup>
     <FrameworkReference Include="Microsoft.AspNetCore.App" />
   </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\VideoDownloader.Core\VideoDownloader.Core.csproj" />
+  </ItemGroup>
 </Project>
diff --git a/VideoDownloader.Tests/Browser/PermissionGateTests.cs b/VideoDownloader.Tests/Browser/PermissionGateTests.cs
new file mode 100644
index 0000000..3b3c9c1
--- /dev/null
+++ b/VideoDownloader.Tests/Browser/PermissionGateTests.cs
@@ -0,0 +1,46 @@
+using VideoDownloader.Browser;
+
+namespace VideoDownloader.Tests.Browser;
+
+/// <summary>T3-11: 사이트별 권한 정책 — 기억된 상태 우선, 미기억은 Ask(프롬프트).</summary>
+public class PermissionGateTests
+{
+    [Fact]
+    public void 미기억_권한은_Ask()
+        => Assert.Equal(PermissionVerdict.Ask, new PermissionGate().Decide("notifications", "https://x.com"));
+
+    [Theory]
+    [InlineData("allow")]
+    [InlineData("deny")]
+    public void 기억된_판정은_그대로_반환(string v)
+    {
+        var g = new PermissionGate();
+        g.Remember("notifications", "https://x.com", v == "allow" ? PermissionVerdict.Allow : PermissionVerdict.Deny);
+        Assert.Equal(v == "allow" ? PermissionVerdict.Allow : PermissionVerdict.Deny,
+            g.Decide("notifications", "https://x.com"));
+    }
+
+    [Fact]
+    public void 판정은_출처_단위_격리()
+    {
+        var g = new PermissionGate();
+        g.Remember("geolocation", "https://a.com", PermissionVerdict.Allow);
+        Assert.Equal(PermissionVerdict.Ask, g.Decide("geolocation", "https://b.com"));
+    }
+
+    [Fact]
+    public void 판정은_종류_단위_격리()
+    {
+        var g = new PermissionGate();
+        g.Remember("notifications", "https://a.com", PermissionVerdict.Allow);
+        Assert.Equal(PermissionVerdict.Ask, g.Decide("camera", "https://a.com"));
+    }
+
+    [Fact]
+    public void OtherSensors_등_민감_종류는_자동_거절()
+        => Assert.Equal(PermissionVerdict.Deny, new PermissionGate().Decide("OtherSensors", "https://x.com"));
+
+    [Fact]
+    public void MultipleAutomaticDownloads_파일_다운로드는_자동_허용()
+        => Assert.Equal(PermissionVerdict.Allow, new PermissionGate().Decide("MultipleAutomaticDownloads", "https://x.com"));
+}
diff --git a/VideoDownloader.Tests/Browser/TrackerBlockTests.cs b/VideoDownloader.Tests/Browser/TrackerBlockTests.cs
new file mode 100644
index 0000000..aaa490b
--- /dev/null
+++ b/VideoDownloader.Tests/Browser/TrackerBlockTests.cs
@@ -0,0 +1,40 @@
+using VideoDownloader.Browser;
+
+namespace VideoDownloader.Tests.Browser;
+
+/// <summary>T3-14: 추적 방지 — 블랙리스트 도메인 매칭(서브도메인 포함) + 차단 카운터.</summary>
+public class TrackerBlockTests
+{
+    [Theory]
+    [InlineData("https://google-analytics.com/analytics.js", true)]       // 정확히 도메인
+    [InlineData("https://www.google-analytics.com/g/collect", true)]       // 서브도메인
+    [InlineData("https://x.com/notgoogle-analytics.com/a", false)]        // 접미사 함정 제외
+    [InlineData("https://doubleclick.net/instream/ad_status.js", true)]
+    [InlineData("https://safe.example.com/lib.js", false)]                 // 무관 도메인
+    public void Matches_블랙리스트_도메인_판정(string url, bool expected)
+        => Assert.Equal(expected, new TrackerBlocklist().Matches(new Uri(url)));
+
+    [Fact]
+    public void 커스텀_도메인_주입_가능()
+    {
+        var bl = new TrackerBlocklist(new[] { "blocked.test" });
+        Assert.True(bl.Matches(new Uri("https://t.blocked.test/x.js")));
+        Assert.False(bl.Matches(new Uri("https://ok.com/x.js")));
+    }
+
+    [Fact]
+    public void Counter_차단_누적_도메인별_집계_변경_통지()
+    {
+        var c = new TrackerCounter();
+        var changed = 0;
+        c.Changed += () => changed++;
+        Assert.Equal(0, c.Total);
+        c.Record("https://www.google-analytics.com/a.js");
+        c.Record("https://google-analytics.com/b.js");
+        c.Record("https://scorecardresearch.com/c.js");
+        Assert.Equal(3, c.Total);
+        Assert.Equal(2, c.ByDomain["google-analytics.com"]);
+        Assert.Equal(1, c.ByDomain["scorecardresearch.com"]);
+        Assert.Equal(3, changed);
+    }
+}
diff --git a/VideoDownloader.Tests/Browser/UrlCleanerTests.cs b/VideoDownloader.Tests/Browser/UrlCleanerTests.cs
new file mode 100644
index 0000000..a704dcb
--- /dev/null
+++ b/VideoDownloader.Tests/Browser/UrlCleanerTests.cs
@@ -0,0 +1,80 @@
+using VideoDownloader.Browser;
+
+namespace VideoDownloader.Tests.Browser;
+
+/// <summary>T3-15: 파라미터 제거 복사 + 주소창 진행 상태.</summary>
+public class UrlCleanerTests
+{
+    [Theory]
+    [InlineData("https://x.com/a?utm_source=1&b=2", "https://x.com/a")]            // 쿼리 제거
+    [InlineData("https://x.com/a#frag", "https://x.com/a")]                          // 프래그먼트 제거
+    [InlineData("https://x.com/a?b=1#f", "https://x.com/a")]                         // 둘 다
+    [InlineData("https://x.com/a/", "https://x.com/a/")]                             // 없으면 무변경
+    [InlineData("https://x.com/a?q=한글", "https://x.com/a")]                        // 유니코드 쿼리
+    [InlineData("x.com/a?b=1", "x.com/a")]                                           // 스킴 없어도 동작
+    public void StripQuery_파라미터와_프래그먼트를_제거(string input, string expected)
+        => Assert.Equal(expected, UrlCleaner.StripQuery(input));
+
+    [Fact]
+    public void StripQuery_빈값_null_안전()
+    {
+        Assert.Equal("", UrlCleaner.StripQuery(""));
+        Assert.Null(UrlCleaner.StripQuery(null));
+    }
+}
+
+/// <summary>T3-15: 탭 전체 네비게이션 진행 집계 — 주소창 진행 바 표시 상태.</summary>
+public class NavProgressTrackerTests
+{
+    [Fact]
+    public void 초기값은_비진행()
+        => Assert.False(new NavProgressTracker().IsNavigating);
+
+    [Fact]
+    public void 시작하면_진행()
+    {
+        var t = new NavProgressTracker();
+        t.Started();
+        Assert.True(t.IsNavigating);
+    }
+
+    [Fact]
+    public void 완료되면_비진행()
+    {
+        var t = new NavProgressTracker();
+        t.Started();
+        t.Completed();
+        Assert.False(t.IsNavigating);
+    }
+
+    [Fact]
+    public void 동시_내비게이션은_마지막_완료까지_진행() // 프레임 리다이렉트·중복 시작
+    {
+        var t = new NavProgressTracker();
+        t.Started(); t.Started();
+        t.Completed();
+        Assert.True(t.IsNavigating);
+        t.Completed();
+        Assert.False(t.IsNavigating);
+    }
+
+    [Fact]
+    public void 과잉_완료로_음수_되지_않음()
+    {
+        var t = new NavProgressTracker();
+        t.Completed();
+        Assert.False(t.IsNavigating);
+    }
+
+    [Fact]
+    public void IsNavigating_변경_시_INPC_발화()
+    {
+        var t = new NavProgressTracker();
+        var fired = new List<string?>();
+        t.PropertyChanged += (_, e) => fired.Add(e.PropertyName);
+        t.Started();
+        t.Completed();
+        t.Completed(); // false→false → 이벤트 없음
+        Assert.Equal(new[] { nameof(NavProgressTracker.IsNavigating), nameof(NavProgressTracker.IsNavigating) }, fired);
+    }
+}
diff --git a/VideoDownloader.Tests/E2E/PermissionTrackerE2ETests.cs b/VideoDownloader.Tests/E2E/PermissionTrackerE2ETests.cs
new file mode 100644
index 0000000..8f493cd
--- /dev/null
+++ b/VideoDownloader.Tests/E2E/PermissionTrackerE2ETests.cs
@@ -0,0 +1,109 @@
+using System.Windows;
+using System.Windows.Threading;
+using Microsoft.Web.WebView2.Core;
+using VideoDownloader.Browser;
+using VideoDownloader.Tests.Infrastructure;
+
+namespace VideoDownloader.Tests.E2E;
+
+/// <summary>
+/// E2E (T3-11/T3-14): 실제 WebView2 에서 권한 정책 응답과 추적 요청 차단·집계를 검증.
+/// TabViewService 와 동일한 배선(PermissionGate/TrackerBlocklist/TrackerCounter)을 사용한다.
+/// </summary>
+[Collection("E2E")]
+public class PermissionTrackerE2ETests
+{
+    [Fact]
+    public async Task 권한_요청이_정책을_거쳐_허용된다_T3_11()
+    {
+        using var sta = StaDispatcher.Start();
+        var udf = Path.Combine(Path.GetTempPath(), $"vd_e2e_{Guid.NewGuid():N}");
+        var result = await sta.InvokeAsync(async () =>
+        {
+            var window = new Window();
+            var browser = new Microsoft.Web.WebView2.Wpf.WebView2();
+            window.Content = browser;
+            window.Show();
+
+            var env = await CoreWebView2Environment.CreateAsync(userDataFolder: udf);
+            await browser.EnsureCoreWebView2Async(env);
+            var cv = browser.CoreWebView2;
+
+            // TabViewService 배선과 동일: 기억된 판정은 즉시 응답(출처는 이벤트에서 관측된 것으로 기억)
+            var gate = new PermissionGate();
+            cv.PermissionRequested += (_, e) =>
+            {
+                var o = VideoDownloader.App.Services.TabViewService.OriginOf(e.Uri);
+                gate.Remember("Notifications", o, PermissionVerdict.Allow); // E2E: 알림은 허용 정책
+                var verdict = gate.Decide(e.PermissionKind.ToString(), o);
+                e.State = verdict == PermissionVerdict.Allow ? CoreWebView2PermissionState.Allow : CoreWebView2PermissionState.Deny;
+                e.Handled = true;
+            };
+
+            var html = "<html><body><script>Notification.requestPermission().then(p => { document.title = 'PERM=' + p; });</script></body></html>";
+            cv.NavigateToString(html);
+            await WaitUntilNavCompleted(cv);
+            var title = await Wait.Until(() => Task.FromResult(cv.DocumentTitle ?? ""),
+                t => t.StartsWith("PERM=", StringComparison.Ordinal), 10000);
+
+            window.Close();
+            return title;
+        });
+
+        try { Directory.Delete(udf, true); } catch { }
+        Assert.Equal("PERM=granted", result);
+    }
+
+    [Fact]
+    public async Task 블랙리스트_스크립트가_차단되고_카운터에_집계된다_T3_14()
+    {
+        using var sta = StaDispatcher.Start();
+        var udf = Path.Combine(Path.GetTempPath(), $"vd_e2e_{Guid.NewGuid():N}");
+        var result = await sta.InvokeAsync(async () =>
+        {
+            var window = new Window();
+            var browser = new Microsoft.Web.WebView2.Wpf.WebView2();
+            window.Content = browser;
+            window.Show();
+
+            var env = await CoreWebView2Environment.CreateAsync(userDataFolder: udf);
+            await browser.EnsureCoreWebView2Async(env);
+            var cv = browser.CoreWebView2;
+
+            var bl = new TrackerBlocklist(new[] { "blocked.test" });
+            var counter = new TrackerCounter();
+            cv.AddWebResourceRequestedFilter("*", CoreWebView2WebResourceContext.All);
+            cv.WebResourceRequested += (_, e) =>
+            {
+                if (!bl.Matches(new Uri(e.Request.Uri))) return;
+                e.Response = env.CreateWebResourceResponse(null, 204, "Blocked", "");
+                counter.Record(e.Request.Uri);
+            };
+
+            var html = "<html><body><p>tracker-e2e</p>" +
+                       "<script src=\"https://www.blocked.test/a.js\"></script>" +
+                       "<script src=\"https://www.blocked.test/b.js\"></script>" +
+                       "<script src=\"https://ok.example.com/c.js\"></script>" +
+                       "</body></html>";
+            cv.NavigateToString(html);
+            await WaitUntilNavCompleted(cv);
+            await Wait.Until(() => Task.FromResult(counter.Total), t => t >= 2, 10000);
+
+            window.Close();
+            return counter.Total;
+        });
+
+        try { Directory.Delete(udf, true); } catch { }
+        Assert.Equal(2, result); // 정상 도메인(ok.example.com)은 집계되지 않음
+    }
+
+    private static async Task WaitUntilNavCompleted(CoreWebView2 cv)
+    {
+        var tcs = new TaskCompletionSource();
+        EventHandler<CoreWebView2NavigationCompletedEventArgs> h = (_, _) => tcs.TrySetResult();
+        cv.NavigationCompleted += h;
+        if (tcs.Task.IsCompleted) return;
+        await Task.WhenAny(tcs.Task, Task.Delay(15000));
+        cv.NavigationCompleted -= h;
+    }
+}
diff --git a/VideoDownloader.Tests/Mobile/MobileCoreTests.cs b/VideoDownloader.Tests/Mobile/MobileCoreTests.cs
new file mode 100644
index 0000000..a1dc9e4
--- /dev/null
+++ b/VideoDownloader.Tests/Mobile/MobileCoreTests.cs
@@ -0,0 +1,106 @@
+using VideoDownloader.Mobile;
+
+namespace VideoDownloader.Tests.Mobile;
+
+/// <summary>Mobile.Core 순수 로직 — U5 완료 감지, 외부망 안내, U4 저장소(파일 시스템).</summary>
+public class MobileCoreTests
+{
+    // ── U5 완료 알림 감지 ──
+
+    [Fact]
+    public void 완료_전환_항목_ID_반환()
+    {
+        var d = new QueueCompletionDetector();
+        var prev = new[] { ("a", "다운로드 중"), ("b", "대기") };
+        var next = new[] { ("a", "완료"), ("b", "다운로드 중") };
+        Assert.Equal(new[] { "a" }, d.Detect(prev, next));
+    }
+
+    [Fact]
+    public void 이미_완료였던_항목은_재알림_없음()
+    {
+        var d = new QueueCompletionDetector();
+        var prev = new[] { ("a", "완료") };
+        var next = new[] { ("a", "완료") };
+        Assert.Empty(d.Detect(prev, next));
+    }
+
+    [Fact]
+    public void 첫_폴링에서_이미_완료된_항목은_무시() // 앱 시작 시 과거 완료 스팸 방지
+    {
+        var d = new QueueCompletionDetector();
+        Assert.Empty(d.Detect(Array.Empty<(string, string)>(), new[] { ("a", "완료") }));
+    }
+
+    [Fact]
+    public void 목록에서_사라진_항목은_알림_없음()
+    {
+        var d = new QueueCompletionDetector();
+        var prev = new[] { ("a", "다운로드 중") };
+        Assert.Empty(d.Detect(prev, Array.Empty<(string, string)>()));
+    }
+
+    // ── 외부망 안내(MOBILE_PLAN §7) ──
+
+    [Fact]
+    public void 미연결_안내()
+    {
+        var m = ConnectionTroubleshoot.Message(isConfigured: false, lastError: null);
+        Assert.Contains("연결", m);
+    }
+
+    [Fact]
+    public void 연결됐지만_실패_시_같은네트워크_VPN_안내()
+    {
+        var m = ConnectionTroubleshoot.Message(isConfigured: true, lastError: "No such host is known.");
+        Assert.Contains("같은 네트워크", m);
+        Assert.Contains("Tailscale", m); // 계획 §3: 자체 릴레이 대신 Tailscale 문서화
+    }
+
+    [Fact]
+    public void 정상_시_빈_문자열()
+        => Assert.Equal("", ConnectionTroubleshoot.Message(isConfigured: true, lastError: null));
+
+    // ── U4 저장소(임시 디렉터리로 파일 시스템 검증) ──
+
+    [Fact]
+    public void OfflineStore_기록_목록_삭제_라운드트립()
+    {
+        var baseDir = Path.Combine(Path.GetTempPath(), $"vd_core_{Guid.NewGuid():N}");
+        var store = new OfflineStore(baseDir);
+        Assert.Empty(store.List());
+
+        var p = store.PathFor("id1");
+        Directory.CreateDirectory(Path.GetDirectoryName(p)!);
+        File.WriteAllBytes(p, new byte[123]);
+        store.Record("id1", "video.mp4");
+
+        Assert.True(store.Exists("id1"));
+        var list = store.List();
+        Assert.Single(list);
+        Assert.Equal(("id1", "video.mp4", 123L), (list[0].Id, list[0].FileName, list[0].SizeBytes));
+
+        store.Delete("id1");
+        Assert.False(store.Exists("id1"));
+        Assert.Empty(store.List());
+
+        Directory.Delete(baseDir, true);
+    }
+
+    [Fact]
+    public void OfflineStore_재시작_시_매니페스트_유지()
+    {
+        var baseDir = Path.Combine(Path.GetTempPath(), $"vd_core_{Guid.NewGuid():N}");
+        var store = new OfflineStore(baseDir);
+        var p = store.PathFor("id2");
+        Directory.CreateDirectory(Path.GetDirectoryName(p)!);
+        File.WriteAllBytes(p, new byte[10]);
+        store.Record("id2", "keep.mp4");
+
+        var reopened = new OfflineStore(baseDir); // 새 인스턴스 = 앱 재시작
+        Assert.True(reopened.Exists("id2"));
+        Assert.Equal("keep.mp4", reopened.List().Single().FileName);
+
+        Directory.Delete(baseDir, true);
+    }
+}
diff --git a/VideoDownloader.Tests/Server/RemoteServerE2ETests.cs b/VideoDownloader.Tests/Server/RemoteServerE2ETests.cs
index 3a5aaab..19b8cf0 100644
--- a/VideoDownloader.Tests/Server/RemoteServerE2ETests.cs
+++ b/VideoDownloader.Tests/Server/RemoteServerE2ETests.cs
@@ -155,6 +155,44 @@ public class RemoteServerE2ETests : IDisposable
         Assert.Equal(93.5, persisted!.PositionSec);
     }
 
+    [Fact]
+    public async Task 썸네일_API_E2E_생성_캐시_404()
+    {
+        Directory.CreateDirectory(_libDir);
+        var mediaPath = Path.Combine(_libDir, "clip.mp4");
+        File.WriteAllBytes(mediaPath, new byte[2048]);
+
+        // 가짜 ffmpeg: 출력 경로에 JPEG 생성
+        var fake = new Tests.Platform.FakeProcessRunner
+        {
+            Behavior = (spec, _, _) =>
+            {
+                File.WriteAllBytes(spec.Args[^1], new byte[] { 0xFF, 0xD8, 0xFF, 0xE0, 0x01 });
+                return Task.FromResult(new VideoDownloader.Core.Platform.ProcessResult(0, "", ""));
+            },
+        };
+
+        await using var server = await ServerHost.StartAsync(new ServerOptions
+        {
+            Port = 0, Token = "thumb-token", LibraryFolder = _libDir,
+            Queue = new FakeQueue(),
+            Thumbnailer = new Thumbnailer(fake),
+        });
+        using var http = new HttpClient { BaseAddress = new Uri($"http://127.0.0.1:{server.Port}") };
+
+        // 1) 익명 401
+        Assert.Equal(System.Net.HttpStatusCode.Unauthorized, (await http.GetAsync("/api/library/xyz/thumb")).StatusCode);
+
+        // 2) 없는 항목 404
+        http.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", "thumb-token");
+        Assert.Equal(System.Net.HttpStatusCode.NotFound, (await http.GetAsync("/api/library/xyz/thumb")).StatusCode);
+
+        // 3) 실제 항목 → 200 + JPEG 매직
+        var lib = (await http.GetFromJsonAsync<List<LibraryItemDto>>("/api/library"))!;
+        var thumb = await http.GetByteArrayAsync($"/api/library/{lib[0].Id}/thumb");
+        Assert.True(thumb.Length >= 2 && thumb[0] == 0xFF && thumb[1] == 0xD8, "JPEG 매직 바이트");
+    }
+
     public void Dispose()
     {
         try { Directory.Delete(_libDir, true); } catch { }
diff --git a/VideoDownloader.Tests/Server/ThumbnailerTests.cs b/VideoDownloader.Tests/Server/ThumbnailerTests.cs
new file mode 100644
index 0000000..ada9fc2
--- /dev/null
+++ b/VideoDownloader.Tests/Server/ThumbnailerTests.cs
@@ -0,0 +1,84 @@
+using VideoDownloader.Core.Platform;
+using VideoDownloader.Server;
+using VideoDownloader.Tests.Platform;
+
+namespace VideoDownloader.Tests.Server;
+
+/// <summary>M2 라이브러리 썸네일/해상도 — ffmpeg 서브프로세스를 Fake 러너로 검증(사이드카 캐시).</summary>
+public class ThumbnailerTests
+{
+    private string _dir = "";
+
+    private string NewMedia()
+    {
+        _dir = Path.Combine(Path.GetTempPath(), $"vd_thumb_{Guid.NewGuid():N}");
+        Directory.CreateDirectory(_dir);
+        var p = Path.Combine(_dir, "clip.mp4");
+        File.WriteAllBytes(p, new byte[100]);
+        return p;
+    }
+
+    private static Task<ProcessResult> FakeFfmpegCreatesJpg(ProcessSpec spec, Action<string, string>? _, CancellationToken __)
+    {
+        // 출력 경로(마지막 인자)에 가짜 JPEG 생성
+        var outPath = spec.Args[^1];
+        File.WriteAllBytes(outPath, new byte[] { 0xFF, 0xD8, 0xFF, 0xE0 }); // JPEG SOI/APP0
+        return Task.FromResult(new ProcessResult(0, "", ""));
+    }
+
+    private static Task<ProcessResult> FakeFfmpegReportsResolution(ProcessSpec spec, Action<string, string>? onLine, CancellationToken _)
+    {
+        var line = "    Stream #0:0[0x1](und): Video: h264 (High), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], 5000 kb/s";
+        onLine?.Invoke("err", line);
+        return Task.FromResult(new ProcessResult(0, "", line));
+    }
+
+    [Fact]
+    public async Task 썸네일_생성후_사이드카_캐시로_재실행_없음()
+    {
+        var media = NewMedia();
+        var runner = new FakeProcessRunner { Behavior = FakeFfmpegCreatesJpg };
+        var t = new Thumbnailer(runner);
+
+        var bytes1 = await t.GetThumbnailAsync("ffmpeg", media);
+        Assert.NotNull(bytes1);
+        Assert.True(bytes1!.Length == 4);
+
+        runner.Behavior = (_, _, _) => throw new Xunit.Sdk.XunitException("캐시 히트 시 ffmpeg 재실행 없음");
+        var bytes2 = await t.GetThumbnailAsync("ffmpeg", media); // 캐시
+        Assert.Equal(bytes1, bytes2);
+        Directory.Delete(_dir, true);
+    }
+
+    [Fact]
+    public async Task ffmpeg_실패_시_null()
+    {
+        var media = NewMedia();
+        var runner = new FakeProcessRunner { Behavior = (_, _, _) => Task.FromResult(new ProcessResult(1, "", "boom")) };
+        Assert.Null(await new Thumbnailer(runner).GetThumbnailAsync("ffmpeg", media));
+        Directory.Delete(_dir, true);
+    }
+
+    [Fact]
+    public async Task 해상도_추출후_사이드카_캐시()
+    {
+        var media = NewMedia();
+        var runner = new FakeProcessRunner { Behavior = FakeFfmpegReportsResolution };
+        var t = new Thumbnailer(runner);
+
+        Assert.Equal("1920x1080", await t.GetResolutionAsync("ffmpeg", media));
+
+        runner.Behavior = (_, _, _) => throw new Xunit.Sdk.XunitException("캐시 히트 시 재실행 없음");
+        Assert.Equal("1920x1080", await t.GetResolutionAsync("ffmpeg", media));
+        Directory.Delete(_dir, true);
+    }
+
+    [Fact]
+    public async Task 해상기_추출_불가_시_null()
+    {
+        var media = NewMedia();
+        var runner = new FakeProcessRunner { Behavior = (_, _, _) => Task.FromResult(new ProcessResult(0, "", "no streams")) };
+        Assert.Null(await new Thumbnailer(runner).GetResolutionAsync("ffmpeg", media));
+        Directory.Delete(_dir, true);
+    }
+}
diff --git a/VideoDownloader.Tests/VideoDownloader.Tests.csproj b/VideoDownloader.Tests/VideoDownloader.Tests.csproj
index be121f8..1a2fe30 100644
--- a/VideoDownloader.Tests/VideoDownloader.Tests.csproj
+++ b/VideoDownloader.Tests/VideoDownloader.Tests.csproj
@@ -16,5 +16,6 @@
     <ProjectReference Include="..\VideoDownloader.App\VideoDownloader.App.csproj" />
     <ProjectReference Include="..\VideoDownloader.Core\VideoDownloader.Core.csproj" />
     <ProjectReference Include="..\VideoDownloader.Server\VideoDownloader.Server.csproj" />
+    <ProjectReference Include="..\VideoDownloader.Mobile.Core\VideoDownloader.Mobile.Core.csproj" />
   </ItemGroup>
 </Project>