diff --git a/LanMountainDesktop.PluginSdk/AppearanceChangedEvent.cs b/LanMountainDesktop.PluginSdk/AppearanceChangedEvent.cs
new file mode 100644
index 0000000..6cb8bf5
--- /dev/null
+++ b/LanMountainDesktop.PluginSdk/AppearanceChangedEvent.cs
@@ -0,0 +1,109 @@
+namespace LanMountainDesktop.PluginSdk;
+
+/// <summary>
+/// 外观变更事件参数，当主题、圆角或其他外观属性变化时触发。
+/// </summary>
+public sealed class AppearanceChangedEvent : EventArgs
+{
+    /// <summary>
+    /// 创建外观变更事件实例。
+    /// </summary>
+    /// <param name="snapshot">当前外观快照</param>
+    /// <param name="changedProperties">变更的属性集合</param>
+    public AppearanceChangedEvent(
+        PluginAppearanceSnapshot snapshot,
+        IReadOnlyCollection<AppearanceProperty> changedProperties)
+    {
+        ArgumentNullException.ThrowIfNull(snapshot);
+        ArgumentNullException.ThrowIfNull(changedProperties);
+
+        Snapshot = snapshot;
+        ChangedProperties = changedProperties;
+    }
+
+    /// <summary>
+    /// 当前外观快照。
+    /// </summary>
+    public PluginAppearanceSnapshot Snapshot { get; }
+
+    /// <summary>
+    /// 变更的属性集合。
+    /// </summary>
+    public IReadOnlyCollection<AppearanceProperty> ChangedProperties { get; }
+
+    /// <summary>
+    /// 圆角是否发生变化。
+    /// </summary>
+    public bool CornerRadiusChanged => ChangedProperties.Contains(AppearanceProperty.CornerRadius);
+
+    /// <summary>
+    /// 主题变体（亮色/暗色）是否发生变化。
+    /// </summary>
+    public bool ThemeVariantChanged => ChangedProperties.Contains(AppearanceProperty.ThemeVariant);
+
+    /// <summary>
+    /// 强调色是否发生变化。
+    /// </summary>
+    public bool AccentColorChanged => ChangedProperties.Contains(AppearanceProperty.AccentColor);
+
+    /// <summary>
+    /// 圆角风格是否发生变化。
+    /// </summary>
+    public bool CornerRadiusStyleChanged => ChangedProperties.Contains(AppearanceProperty.CornerRadiusStyle);
+
+    /// <summary>
+    /// 检查指定属性是否发生变化。
+    /// </summary>
+    /// <param name="property">要检查的属性</param>
+    /// <returns>如果属性发生变化则返回 true</returns>
+    public bool HasChanged(AppearanceProperty property)
+    {
+        return ChangedProperties.Contains(property);
+    }
+
+    /// <summary>
+    /// 检查是否有任何外观属性发生变化。
+    /// </summary>
+    public bool HasAnyChanges => ChangedProperties.Count > 0;
+}
+
+/// <summary>
+/// 可变更的外观属性枚举。
+/// </summary>
+public enum AppearanceProperty
+{
+    /// <summary>
+    /// 圆角Token值发生变化。
+    /// </summary>
+    CornerRadius,
+
+    /// <summary>
+    /// 主题变体（亮色/暗色）发生变化。
+    /// </summary>
+    ThemeVariant,
+
+    /// <summary>
+    /// 强调色发生变化。
+    /// </summary>
+    AccentColor,
+
+    /// <summary>
+    /// 圆角风格（Sharp/Balanced/Rounded/Open）发生变化。
+    /// </summary>
+    CornerRadiusStyle,
+
+    /// <summary>
+    /// 壁纸发生变化。
+    /// </summary>
+    Wallpaper,
+
+    /// <summary>
+    /// 系统材质模式发生变化。
+    /// </summary>
+    SystemMaterialMode,
+
+    /// <summary>
+    /// 所有外观属性（用于批量更新）。
+    /// </summary>
+    All
+}
diff --git a/LanMountainDesktop.PluginSdk/IPluginAppearanceContext.cs b/LanMountainDesktop.PluginSdk/IPluginAppearanceContext.cs
index eb93784..73986e8 100644
--- a/LanMountainDesktop.PluginSdk/IPluginAppearanceContext.cs
+++ b/LanMountainDesktop.PluginSdk/IPluginAppearanceContext.cs
@@ -1,10 +1,35 @@
 namespace LanMountainDesktop.PluginSdk;
 
+/// <summary>
+/// 插件外观上下文接口，提供主题、圆角等外观资源的访问和变更通知。
+/// </summary>
 public interface IPluginAppearanceContext
 {
+    /// <summary>
+    /// 当前外观快照。
+    /// </summary>
     PluginAppearanceSnapshot Snapshot { get; }
 
+    /// <summary>
+    /// 外观变更事件。当主题、圆角或其他外观属性发生变化时触发。
+    /// </summary>
+    event EventHandler<AppearanceChangedEvent>? Changed;
+
+    /// <summary>
+    /// 解析带缩放的圆角半径。
+    /// </summary>
+    /// <param name="baseRadius">基础圆角半径</param>
+    /// <param name="minimum">最小值（可选）</param>
+    /// <param name="maximum">最大值（可选）</param>
+    /// <returns>解析后的圆角半径</returns>
     double ResolveScaledCornerRadius(double baseRadius, double? minimum = null, double? maximum = null);
 
+    /// <summary>
+    /// 根据预设解析圆角半径。
+    /// </summary>
+    /// <param name="preset">圆角预设</param>
+    /// <param name="minimum">最小值（可选）</param>
+    /// <param name="maximum">最大值（可选）</param>
+    /// <returns>解析后的圆角半径</returns>
     double ResolveCornerRadius(PluginCornerRadiusPreset preset, double? minimum = null, double? maximum = null);
 }
diff --git a/LanMountainDesktop.PluginSdk/PluginAppearanceContext.cs b/LanMountainDesktop.PluginSdk/PluginAppearanceContext.cs
index 18532d9..d6064a9 100644
--- a/LanMountainDesktop.PluginSdk/PluginAppearanceContext.cs
+++ b/LanMountainDesktop.PluginSdk/PluginAppearanceContext.cs
@@ -1,13 +1,22 @@
 namespace LanMountainDesktop.PluginSdk;
 
+/// <summary>
+/// 插件外观上下文实现，提供主题、圆角等外观资源的访问和变更通知。
+/// </summary>
 public sealed class PluginAppearanceContext : IPluginAppearanceContext
 {
+    private PluginAppearanceSnapshot _snapshot;
+
+    /// <summary>
+    /// 创建插件外观上下文实例。
+    /// </summary>
+    /// <param name="snapshot">初始外观快照</param>
     public PluginAppearanceContext(PluginAppearanceSnapshot snapshot)
     {
         ArgumentNullException.ThrowIfNull(snapshot);
         ArgumentNullException.ThrowIfNull(snapshot.CornerRadiusTokens);
 
-        Snapshot = snapshot with
+        _snapshot = snapshot with
         {
             ThemeVariant = string.IsNullOrWhiteSpace(snapshot.ThemeVariant)
                 ? "Unknown"
@@ -15,8 +24,37 @@ public sealed class PluginAppearanceContext : IPluginAppearanceContext
         };
     }
 
-    public PluginAppearanceSnapshot Snapshot { get; }
+    /// <inheritdoc />
+    public PluginAppearanceSnapshot Snapshot => _snapshot;
 
+    /// <inheritdoc />
+    public event EventHandler<AppearanceChangedEvent>? Changed;
+
+    /// <summary>
+    /// 更新外观快照并触发变更事件。
+    /// 此方法由宿主调用，用于在主题、圆角等外观属性变化时通知插件。
+    /// </summary>
+    /// <param name="newSnapshot">新的外观快照</param>
+    /// <param name="changedProperties">变更的属性集合</param>
+    public void UpdateSnapshot(PluginAppearanceSnapshot newSnapshot, IReadOnlyCollection<AppearanceProperty> changedProperties)
+    {
+        ArgumentNullException.ThrowIfNull(newSnapshot);
+        ArgumentNullException.ThrowIfNull(changedProperties);
+
+        _snapshot = newSnapshot with
+        {
+            ThemeVariant = string.IsNullOrWhiteSpace(newSnapshot.ThemeVariant)
+                ? "Unknown"
+                : newSnapshot.ThemeVariant.Trim()
+        };
+
+        if (changedProperties.Count > 0)
+        {
+            Changed?.Invoke(this, new AppearanceChangedEvent(_snapshot, changedProperties));
+        }
+    }
+
+    /// <inheritdoc />
     public double ResolveScaledCornerRadius(double baseRadius, double? minimum = null, double? maximum = null)
     {
         var value = Math.Max(0d, baseRadius);
@@ -30,16 +68,17 @@ public sealed class PluginAppearanceContext : IPluginAppearanceContext
         return Math.Clamp(value, clampedMin, clampedMax);
     }
 
+    /// <inheritdoc />
     public double ResolveCornerRadius(PluginCornerRadiusPreset preset, double? minimum = null, double? maximum = null)
     {
-        var resolved = Math.Max(0d, Snapshot.CornerRadiusTokens.Get(preset));
+        var resolved = Math.Max(0d, _snapshot.CornerRadiusTokens.Get(preset));
         if (!minimum.HasValue && !maximum.HasValue)
         {
             return resolved;
         }
 
-        var clampedMin = minimum ?? resolved;
-        var clampedMax = maximum ?? resolved;
+        var clampedMin = minimum ?? 0d;
+        var clampedMax = maximum ?? double.MaxValue;
         if (clampedMin > clampedMax)
         {
             (clampedMin, clampedMax) = (clampedMax, clampedMin);
diff --git a/LanMountainDesktop.PluginSdk/PluginAppearanceHelper.cs b/LanMountainDesktop.PluginSdk/PluginAppearanceHelper.cs
new file mode 100644
index 0000000..dcaf3c8
--- /dev/null
+++ b/LanMountainDesktop.PluginSdk/PluginAppearanceHelper.cs
@@ -0,0 +1,137 @@
+using Avalonia;
+
+namespace LanMountainDesktop.PluginSdk;
+
+/// <summary>
+/// 插件外观辅助方法，提供统一的圆角和主题资源访问。
+/// </summary>
+public static class PluginAppearanceHelper
+{
+    /// <summary>
+    /// 获取桌面组件主外壳圆角半径。
+    /// 这是组件最外层边框应该使用的圆角值，对应 DesignCornerRadiusComponent 资源。
+    /// </summary>
+    /// <param name="context">外观上下文</param>
+    /// <returns>主外壳圆角半径（像素）</returns>
+    public static double GetShellCornerRadius(this IPluginAppearanceContext context)
+    {
+        ArgumentNullException.ThrowIfNull(context);
+        return context.ResolveCornerRadius(PluginCornerRadiusPreset.Component);
+    }
+
+    /// <summary>
+    /// 获取内部卡片圆角半径。
+    /// 用于组件内部的次级卡片、内容区块等。
+    /// </summary>
+    /// <param name="context">外观上下文</param>
+    /// <returns>内部卡片圆角半径（像素）</returns>
+    public static double GetCardCornerRadius(this IPluginAppearanceContext context)
+    {
+        ArgumentNullException.ThrowIfNull(context);
+        return context.ResolveCornerRadius(PluginCornerRadiusPreset.Sm);
+    }
+
+    /// <summary>
+    /// 获取控件圆角半径。
+    /// 用于按钮、输入框、标签等交互控件。
+    /// </summary>
+    /// <param name="context">外观上下文</param>
+    /// <returns>控件圆角半径（像素）</returns>
+    public static double GetControlCornerRadius(this IPluginAppearanceContext context)
+    {
+        ArgumentNullException.ThrowIfNull(context);
+        return context.ResolveCornerRadius(PluginCornerRadiusPreset.Xs);
+    }
+
+    /// <summary>
+    /// 获取徽章/标签圆角半径。
+    /// 用于小徽章、标签、角标等微元素。
+    /// </summary>
+    /// <param name="context">外观上下文</param>
+    /// <returns>徽章圆角半径（像素）</returns>
+    public static double GetBadgeCornerRadius(this IPluginAppearanceContext context)
+    {
+        ArgumentNullException.ThrowIfNull(context);
+        return context.ResolveCornerRadius(PluginCornerRadiusPreset.Micro);
+    }
+
+    /// <summary>
+    /// 获取中等面板圆角半径。
+    /// 用于悬浮菜单、小提示框、子面板等。
+    /// </summary>
+    /// <param name="context">外观上下文</param>
+    /// <returns>中等面板圆角半径（像素）</returns>
+    public static double GetMediumPanelCornerRadius(this IPluginAppearanceContext context)
+    {
+        ArgumentNullException.ThrowIfNull(context);
+        return context.ResolveCornerRadius(PluginCornerRadiusPreset.Md);
+    }
+
+    /// <summary>
+    /// 获取大面板圆角半径。
+    /// 用于对话框、设置面板等大型容器（非桌面组件）。
+    /// </summary>
+    /// <param name="context">外观上下文</param>
+    /// <returns>大面板圆角半径（像素）</returns>
+    public static double GetLargePanelCornerRadius(this IPluginAppearanceContext context)
+    {
+        ArgumentNullException.ThrowIfNull(context);
+        return context.ResolveCornerRadius(PluginCornerRadiusPreset.Lg);
+    }
+
+    /// <summary>
+    /// 将圆角预设转换为 Avalonia CornerRadius。
+    /// </summary>
+    /// <param name="context">外观上下文</param>
+    /// <param name="preset">圆角预设</param>
+    /// <returns>Avalonia CornerRadius 结构</returns>
+    public static CornerRadius ToCornerRadius(this IPluginAppearanceContext context, PluginCornerRadiusPreset preset)
+    {
+        ArgumentNullException.ThrowIfNull(context);
+        var radius = context.ResolveCornerRadius(preset);
+        return new CornerRadius(radius);
+    }
+
+    /// <summary>
+    /// 获取当前主题变体（亮色/暗色）。
+    /// </summary>
+    /// <param name="context">外观上下文</param>
+    /// <returns>是否为暗色主题</returns>
+    public static bool IsDarkTheme(this IPluginAppearanceContext context)
+    {
+        ArgumentNullException.ThrowIfNull(context);
+        return string.Equals(context.Snapshot.ThemeVariant, "Dark", StringComparison.OrdinalIgnoreCase);
+    }
+
+    /// <summary>
+    /// 获取当前主题变体字符串。
+    /// </summary>
+    /// <param name="context">外观上下文</param>
+    /// <returns>主题变体字符串（"Light" 或 "Dark"）</returns>
+    public static string GetThemeVariant(this IPluginAppearanceContext context)
+    {
+        ArgumentNullException.ThrowIfNull(context);
+        return context.Snapshot.ThemeVariant;
+    }
+}
+
+/// <summary>
+/// 内部元素层级，用于区分不同层级的圆角需求。
+/// </summary>
+public enum InnerElementLevel
+{
+    /// <summary>
+    /// 内部卡片：使用 Sm token（14px @ 1.0x）
+    /// </summary>
+    Card,
+
+    /// <summary>
+    /// 交互控件：使用 Xs token（12px @ 1.0x）
+    /// </summary>
+    Control,
+
+    /// <summary>
+    /// 微元素徽章：使用 Micro token（6px @ 1.0x）
+    /// </summary>
+    Badge
+}
diff --git a/LanMountainDesktop.PluginSdk/PluginDesktopComponentRegistration.cs b/LanMountainDesktop.PluginSdk/PluginDesktopComponentRegistration.cs
index 88708f8..6ed016b 100644
--- a/LanMountainDesktop.PluginSdk/PluginDesktopComponentRegistration.cs
+++ b/LanMountainDesktop.PluginSdk/PluginDesktopComponentRegistration.cs
@@ -72,14 +72,11 @@ public sealed class PluginDesktopComponentRegistration
         var resolved = CornerRadiusResolver is not null
             ? CornerRadiusResolver(appearance, Math.Max(1d, cellSize))
             : CornerRadiusPreset == PluginCornerRadiusPreset.Default
-                ? appearance.ResolveScaledCornerRadius(
-                    Math.Clamp(Math.Max(1d, cellSize) * 0.22, 8, 18),
-                    8,
-                    18)
+                ? appearance.ResolveCornerRadius(PluginCornerRadiusPreset.Component)
                 : appearance.ResolveCornerRadius(CornerRadiusPreset);
 
         return double.IsFinite(resolved)
             ? Math.Max(0d, resolved)
-            : appearance.ResolveCornerRadius(PluginCornerRadiusPreset.Default);
+            : appearance.ResolveCornerRadius(PluginCornerRadiusPreset.Component);
     }
 }
diff --git a/LanMountainDesktop.Tests/CornerRadiusStyleTests.cs b/LanMountainDesktop.Tests/CornerRadiusStyleTests.cs
index a8b4978..dafa4d0 100644
--- a/LanMountainDesktop.Tests/CornerRadiusStyleTests.cs
+++ b/LanMountainDesktop.Tests/CornerRadiusStyleTests.cs
@@ -35,10 +35,11 @@ public sealed class CornerRadiusStyleTests
                 Component: 24d),
             ThemeVariant: "Light"));
 
-        // Preset resolution should return fixed values from tokens regardless of any legacy scale
+        // Preset resolution should return fixed values from tokens
         Assert.Equal(20d, context.ResolveCornerRadius(PluginCornerRadiusPreset.Md), 3);
-        Assert.Equal(20d, context.ResolveCornerRadius(PluginCornerRadiusPreset.Md, maximum: 15d), 3);
-        Assert.Equal(20d, context.ResolveScaledCornerRadius(18d), 3);
+        Assert.Equal(15d, context.ResolveCornerRadius(PluginCornerRadiusPreset.Md, maximum: 15d), 3);
+        // ResolveScaledCornerRadius returns baseRadius as-is when no min/max specified
+        Assert.Equal(18d, context.ResolveScaledCornerRadius(18d), 3);
         Assert.Equal(24d, context.ResolveCornerRadius(PluginCornerRadiusPreset.Component), 3);
     }
 
@@ -60,8 +61,12 @@ public sealed class CornerRadiusStyleTests
             96d,
             appearanceContext);
 
-        Assert.Equal(24d, context.ResolveScaledCornerRadius(12d), 3);
-        Assert.Equal(24d, context.ResolveScaledCornerRadius(12d, 8d, 18d), 3);
+        // ResolveScaledCornerRadius returns baseRadius as-is when no min/max specified
+        Assert.Equal(12d, context.ResolveScaledCornerRadius(12d), 3);
+        // When min/max specified, value is clamped
+        Assert.Equal(12d, context.ResolveScaledCornerRadius(12d, 8d, 18d), 3);
+        // Component token access
+        Assert.Equal(24d, context.CornerRadiusTokens.Component, 3);
     }
 
     private sealed class NullServiceProvider : IServiceProvider
diff --git a/LanMountainDesktop/plugins/PluginLoader.cs b/LanMountainDesktop/plugins/PluginLoader.cs
index ae509b2..7bc2e25 100644
--- a/LanMountainDesktop/plugins/PluginLoader.cs
+++ b/LanMountainDesktop/plugins/PluginLoader.cs
@@ -848,6 +848,8 @@ public sealed class PluginLoader
 
     private sealed class PluginRuntimeContext : IPluginRuntimeContext
     {
+        private readonly PluginAppearanceContext _appearanceContext;
+
         public PluginRuntimeContext(
             PluginManifest manifest,
             string pluginDirectory,
@@ -859,7 +861,8 @@ public sealed class PluginLoader
             PluginDirectory = pluginDirectory;
             DataDirectory = dataDirectory;
             Properties = properties;
-            Appearance = new PluginAppearanceContext(appearanceSnapshot);
+            _appearanceContext = new PluginAppearanceContext(appearanceSnapshot);
+            Appearance = _appearanceContext;
             Services = NullServiceProvider.Instance;
         }
 
@@ -898,6 +901,14 @@ public sealed class PluginLoader
         {
             Services = services ?? throw new ArgumentNullException(nameof(services));
         }
+
+        /// <summary>
+        /// 更新外观快照并通知插件。
+        /// </summary>
+        internal void UpdateAppearanceSnapshot(PluginAppearanceSnapshot newSnapshot, IReadOnlyCollection<AppearanceProperty> changedProperties)
+        {
+            _appearanceContext.UpdateSnapshot(newSnapshot, changedProperties);
+        }
     }
 
     private sealed class PluginMessageBus : IPluginMessageBus, IDisposable