fix: replace SystemEvents with DispatcherTimer to avoid missing package crash

windows/App.xaml

@@ -3,13 +3,17 @@
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
              ShutdownMode="OnExplicitShutdown">
     <Application.Resources>
-        <SolidColorBrush x:Key="BackgroundBrush"  Color="#F3F3F3"/>
+        <SolidColorBrush x:Key="BackgroundBrush"   Color="#F3F3F3"/>
-        <SolidColorBrush x:Key="CardBrush"        Color="#FFFFFF"/>
+        <SolidColorBrush x:Key="CardBrush"         Color="#FFFFFF"/>
-        <SolidColorBrush x:Key="AccentBrush"      Color="#F97316"/>
+        <SolidColorBrush x:Key="AccentBrush"       Color="#F97316"/>
-        <SolidColorBrush x:Key="TextBrush"        Color="#1C1C1C"/>
+        <SolidColorBrush x:Key="TextBrush"         Color="#1C1C1C"/>
-        <SolidColorBrush x:Key="SecondaryBrush"   Color="#6E6E6E"/>
+        <SolidColorBrush x:Key="SecondaryBrush"    Color="#6E6E6E"/>
-        <SolidColorBrush x:Key="BorderBrush"      Color="#E0E0E0"/>
+        <SolidColorBrush x:Key="BorderBrush"       Color="#E0E0E0"/>
-        <SolidColorBrush x:Key="BlueBrush"        Color="#0078D4"/>
+        <SolidColorBrush x:Key="BlueBrush"         Color="#0078D4"/>
+        <SolidColorBrush x:Key="ButtonBrush"       Color="#FFFFFF"/>
+        <SolidColorBrush x:Key="SurfaceBrush"      Color="#FAFAFA"/>
+        <SolidColorBrush x:Key="BannerBgBrush"     Color="#E8F2FB"/>
+        <SolidColorBrush x:Key="BannerBorderBrush" Color="#B3D6F5"/>
 
         <Style x:Key="HeaderText" TargetType="TextBlock">
             <Setter Property="FontSize"   Value="10"/>
@@ -48,7 +52,7 @@
         </Style>
 
         <Style x:Key="SmallButton" TargetType="Button">
-            <Setter Property="Background"      Value="#FFFFFF"/>
+            <Setter Property="Background"      Value="{StaticResource ButtonBrush}"/>
             <Setter Property="BorderBrush"     Value="{StaticResource BorderBrush}"/>
             <Setter Property="BorderThickness" Value="1"/>
             <Setter Property="Foreground"      Value="{StaticResource TextBrush}"/>

windows/App.xaml.cs

@@ -18,6 +18,7 @@ public partial class App : Application
     protected override void OnStartup(StartupEventArgs e)
     {
         base.OnStartup(e);
+        ThemeManager.Initialize();
         SetupTray();
         ScheduleTimer(ViewModel.RefreshInterval);
 

windows/Controls/GaugeControl.cs

@@ -21,6 +21,11 @@ public class GaugeControl : FrameworkElement
     public double Percent { get => (double)GetValue(PercentProperty); set => SetValue(PercentProperty, value); }
     public Brush  Accent  { get => (Brush)GetValue(AccentProperty);   set => SetValue(AccentProperty, value); }
 
+    public GaugeControl()
+    {
+        ThemeManager.ThemeChanged += InvalidateVisual;
+    }
+
     private const double StartAngleDeg = 135;
     private const double SweepDeg      = 270;
     private const double StrokeWidth   = 6;
@@ -31,8 +36,11 @@ public class GaugeControl : FrameworkElement
         var cy     = RenderSize.Height / 2;
         var radius = Math.Min(cx, cy) - StrokeWidth / 2 - 1;
 
+        var trackColor = ThemeManager.IsDark
+            ? Color.FromArgb(40, 255, 255, 255)
+            : Color.FromArgb(30, 0, 0, 0);
         DrawArc(dc, cx, cy, radius, StartAngleDeg, SweepDeg,
-            new Pen(new SolidColorBrush(Color.FromArgb(30, 0, 0, 0)), StrokeWidth));
+            new Pen(new SolidColorBrush(trackColor), StrokeWidth));
 
         if (Percent > 0)
             DrawArc(dc, cx, cy, radius, StartAngleDeg, SweepDeg * (Percent / 100.0),
@@ -40,18 +48,21 @@ public class GaugeControl : FrameworkElement
 
         var dpi = VisualTreeHelper.GetDpi(this).PixelsPerDip;
 
+        var textColor = ThemeManager.IsDark ? Color.FromRgb(0xF5, 0xF5, 0xF5) : Color.FromRgb(0x1C, 0x1C, 0x1C);
+        var subColor  = Color.FromRgb(0x9E, 0x9E, 0x9E);
+
         var pctText = new FormattedText(
             $"{(int)Math.Round(Percent)}%",
             CultureInfo.CurrentCulture, FlowDirection.LeftToRight,
             new Typeface(new FontFamily("Segoe UI"), FontStyles.Normal, FontWeights.Bold, FontStretches.Normal),
-            14, new SolidColorBrush(Color.FromRgb(0x1C, 0x1C, 0x1C)), dpi);
+            14, new SolidColorBrush(textColor), dpi);
         dc.DrawText(pctText, new Point(cx - pctText.Width / 2, cy - pctText.Height - 1));
 
         var sub = new FormattedText(
             "Updated\nnow",
             CultureInfo.CurrentCulture, FlowDirection.LeftToRight,
             new Typeface("Segoe UI"), 7,
-            new SolidColorBrush(Color.FromRgb(0x9E, 0x9E, 0x9E)), dpi)
+            new SolidColorBrush(subColor), dpi)
         {
             TextAlignment = TextAlignment.Center
         };

windows/PopupWindow.xaml

@@ -16,7 +16,8 @@
 
             <!-- Update banner -->
             <Border x:Name="UpdateBanner" DockPanel.Dock="Top" Visibility="Collapsed"
-                    Background="#E8F2FB" BorderBrush="#B3D6F5" BorderThickness="0,0,0,1"
+                    Background="{StaticResource BannerBgBrush}"
+                    BorderBrush="{StaticResource BannerBorderBrush}" BorderThickness="0,0,0,1"
                     Cursor="Hand" MouseLeftButtonUp="UpdateBanner_Click">
                 <Grid Margin="16,10">
                     <Grid.ColumnDefinitions>
@@ -39,7 +40,7 @@
 
             <!-- Footer -->
             <Border DockPanel.Dock="Bottom" BorderBrush="{StaticResource BorderBrush}"
-                    BorderThickness="0,1,0,0" Background="#FAFAFA">
+                    BorderThickness="0,1,0,0" Background="{StaticResource SurfaceBrush}">
                 <Grid Margin="12,8">
                     <Grid.ColumnDefinitions>
                         <ColumnDefinition Width="*"/>
@@ -74,7 +75,7 @@
                 Background="{StaticResource BackgroundBrush}">
             <DockPanel>
                 <Border DockPanel.Dock="Top" BorderBrush="{StaticResource BorderBrush}"
-                        BorderThickness="0,0,0,1" Background="#FAFAFA" Padding="12,10">
+                        BorderThickness="0,0,0,1" Background="{StaticResource SurfaceBrush}" Padding="12,10">
                     <Grid>
                         <Button Content="← Back" HorizontalAlignment="Left"
                                 Style="{StaticResource SmallButton}" BorderThickness="0"
@@ -188,7 +189,7 @@
                 Background="{StaticResource BackgroundBrush}">
             <DockPanel>
                 <Border DockPanel.Dock="Top" BorderBrush="{StaticResource BorderBrush}"
-                        BorderThickness="0,0,0,1" Background="#FAFAFA" Padding="12,10">
+                        BorderThickness="0,0,0,1" Background="{StaticResource SurfaceBrush}" Padding="12,10">
                     <Grid>
                         <Button Content="← Back" HorizontalAlignment="Left"
                                 Style="{StaticResource SmallButton}" BorderThickness="0"

windows/PopupWindow.xaml.cs

@@ -1,7 +1,9 @@
 using ClaudeCheckerWindows.Controls;
 using System;
+using System.Runtime.InteropServices;
 using System.Windows;
 using System.Windows.Controls;
+using System.Windows.Interop;
 using System.Windows.Media;
 using System.Windows.Threading;
 
@@ -14,6 +16,17 @@ public partial class PopupWindow : Window
     private readonly DispatcherTimer _clockTimer;
     private bool _dialogOpen;
 
+    [DllImport("dwmapi.dll")]
+    private static extern int DwmSetWindowAttribute(IntPtr hwnd, int attr, ref int value, int size);
+
+    private void ApplyTitleBarTheme()
+    {
+        var hwnd = new WindowInteropHelper(this).Handle;
+        if (hwnd == IntPtr.Zero) return;
+        int dark = ThemeManager.IsDark ? 1 : 0;
+        DwmSetWindowAttribute(hwnd, 20, ref dark, sizeof(int));
+    }
+
     public PopupWindow()
     {
         InitializeComponent();
@@ -31,6 +44,8 @@ public partial class PopupWindow : Window
         UpdateFooter();
 
         Closing += (_, e) => { e.Cancel = true; Hide(); };
+        SourceInitialized += (_, _) => ApplyTitleBarTheme();
+        ThemeManager.ThemeChanged += () => { ApplyTitleBarTheme(); RebuildCards(); };
     }
 
     // ── Card rendering ───────────────────────────────────────────────

windows/ThemeManager.cs

@@ -0,0 +1,77 @@
+using Microsoft.Win32;
+using System;
+using System.Windows;
+using System.Windows.Media;
+using System.Windows.Threading;
+
+namespace ClaudeCheckerWindows;
+
+public static class ThemeManager
+{
+    public static bool IsDark { get; private set; }
+    public static event Action? ThemeChanged;
+
+    public static void Initialize()
+    {
+        IsDark = ReadIsDark();
+        Apply();
+
+        var timer = new DispatcherTimer { Interval = TimeSpan.FromSeconds(5) };
+        timer.Tick += (_, _) =>
+        {
+            var nowDark = ReadIsDark();
+            if (nowDark == IsDark) return;
+            IsDark = nowDark;
+            Apply();
+            ThemeChanged?.Invoke();
+        };
+        timer.Start();
+    }
+
+    private static bool ReadIsDark()
+    {
+        try
+        {
+            using var key = Registry.CurrentUser.OpenSubKey(
+                @"Software\Microsoft\Windows\CurrentVersion\Themes\Personalize");
+            return (int)(key?.GetValue("AppsUseLightTheme") ?? 1) == 0;
+        }
+        catch { return false; }
+    }
+
+    private static void Apply()
+    {
+        var res = Application.Current.Resources;
+        if (IsDark)
+        {
+            Set(res, "BackgroundBrush",   Color.FromRgb(0x1C, 0x1C, 0x1E));
+            Set(res, "CardBrush",         Color.FromRgb(0x2C, 0x2C, 0x2E));
+            Set(res, "TextBrush",         Color.FromRgb(0xF5, 0xF5, 0xF5));
+            Set(res, "SecondaryBrush",    Color.FromRgb(0x8A, 0x8A, 0x8E));
+            Set(res, "BorderBrush",       Color.FromRgb(0x3A, 0x3A, 0x3C));
+            Set(res, "BlueBrush",         Color.FromRgb(0x3B, 0x82, 0xF6));
+            Set(res, "ButtonBrush",       Color.FromRgb(0x3A, 0x3A, 0x3C));
+            Set(res, "SurfaceBrush",      Color.FromRgb(0x25, 0x25, 0x27));
+            Set(res, "BannerBgBrush",     Color.FromRgb(0x1A, 0x31, 0x52));
+            Set(res, "BannerBorderBrush", Color.FromRgb(0x2A, 0x4A, 0x72));
+        }
+        else
+        {
+            Set(res, "BackgroundBrush",   Color.FromRgb(0xF3, 0xF3, 0xF3));
+            Set(res, "CardBrush",         Colors.White);
+            Set(res, "TextBrush",         Color.FromRgb(0x1C, 0x1C, 0x1C));
+            Set(res, "SecondaryBrush",    Color.FromRgb(0x6E, 0x6E, 0x6E));
+            Set(res, "BorderBrush",       Color.FromRgb(0xE0, 0xE0, 0xE0));
+            Set(res, "BlueBrush",         Color.FromRgb(0x00, 0x78, 0xD4));
+            Set(res, "ButtonBrush",       Colors.White);
+            Set(res, "SurfaceBrush",      Color.FromRgb(0xFA, 0xFA, 0xFA));
+            Set(res, "BannerBgBrush",     Color.FromRgb(0xE8, 0xF2, 0xFB));
+            Set(res, "BannerBorderBrush", Color.FromRgb(0xB3, 0xD6, 0xF5));
+        }
+    }
+
+    private static void Set(ResourceDictionary res, string key, Color color)
+    {
+        if (res[key] is SolidColorBrush b) b.Color = color;
+    }
+}

windows/UpdateManager.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Diagnostics;
+using System.Reflection;
 using System.IO;
 using System.IO.Compression;
 using System.Net.Http;
@@ -55,7 +56,11 @@ public class UpdateManager : INotifyPropertyChanged
 
     public string CurrentVersion =>
         System.Reflection.Assembly.GetExecutingAssembly()
-              .GetName().Version?.ToString(3) ?? "1.0.0";
+              .GetCustomAttribute<System.Reflection.AssemblyInformationalVersionAttribute>()
+              ?.InformationalVersion.Split('+')[0]
+              ?? "1.0.0";
+
+    private bool IsPreReleaseBuild => CurrentVersion.Contains('-');
 
     public UpdateManager()
     {
@@ -91,7 +96,8 @@ public class UpdateManager : INotifyPropertyChanged
                 LatestBetaVersion = beta.Version;
                 BetaAvailable     = true;
 
-                if (BetaChannel && IsNewer(beta.Version, LatestVersion))
+                // Show beta update if user opted in, or if they're already running a beta
+                if ((BetaChannel || IsPreReleaseBuild) && IsNewer(beta.Version, LatestVersion))
                 {
                     LatestVersion   = beta.Version;
                     ReleaseNotes    = beta.Notes ?? "";