diff --git a/.github/skills/syncfusion-blazor-toolkit-charts/SKILL.md b/.github/skills/syncfusion-blazor-toolkit-charts/SKILL.md
index d850dfc..e91460e 100644
--- a/.github/skills/syncfusion-blazor-toolkit-charts/SKILL.md
+++ b/.github/skills/syncfusion-blazor-toolkit-charts/SKILL.md
@@ -581,12 +581,41 @@ Here's a minimal example to create a column chart with data:
 ### Chart Component (`SfChart`)
 - `Title` - Chart title text
 - `Width` / `Height` - Chart dimensions (accepts px or %, default: "100%")
-- `Theme` - Visual theme (see Theme enum in API reference)
+- `Theme` - Visual theme. One of `Theme.Fluent` (default), `Theme.FluentDark`, `Theme.HighContrast`. See the **Themes** section below.
 - `Background` - Chart background color
 - `EnableAnimation` - Enable/disable animation (default: true)
 - `SelectionMode` - Selection mode (None, Series, Point, Cluster, DragXY, DragX, DragY, Lasso)
 - `HighlightMode` - Highlight mode (None, Series, Point, Cluster)
 
+### Themes
+
+The chart's `Theme` parameter is bound to `Syncfusion.Blazor.Toolkit.Theme`:
+
+| Enum value | Background | Text | Focus / Selection | Use case |
+|---|---|---|---|---|
+| `Theme.Fluent` (default) | `#FFFFFF` | `#242424` | `#0F6CBD` | Light mode interfaces. |
+| `Theme.FluentDark` | `#1C1B1F` | `#FFFFFF` | `#115EA3` | Dark mode interfaces. |
+| `Theme.HighContrast` | `#000000` | `#FFFFFF` | `#FFFF00` | Accessibility scenarios; matches Microsoft High Contrast. |
+
+The theme flows into:
+- `ChartHelper.GetChartThemeStyle(...)` — tokens for axis lines, labels, grid lines, titles, legend, tooltips, crosshair, selection rectangles, error bars, stripline text, tooltip fill, and the scrollbar (`ChartHelper.GetScrollbarThemeColor`).
+- `ChartHelper.GetSeriesColor(...)` — the default series palette when `Palettes` is not supplied. The high-contrast palette uses fully saturated, easily distinguishable colors: `#FFFF00`, `#00FFFF`, `#FF00FF`, `#00FF00`, `#FF8000`, `#80FF00`, `#00FF80`, `#FF0080`, `#FFFFFF`, `#80FFFF`.
+- `ZoomToolkit` — the zoom toolbar icon colors and rectangle fill re-skin to match the active theme.
+
+**Example — High Contrast:**
+
+```razor
+@using Syncfusion.Blazor.Toolkit.Charts
+
+<SfChart Theme="Theme.HighContrast" Title="Sales Data">
+    <ChartPrimaryXAxis ValueType="Syncfusion.Blazor.Toolkit.ValueType.Category" />
+    <ChartSeries DataSource="@SalesData" XName="Month" YName="Revenue"
+                 Type="ChartSeriesType.Column" />
+</SfChart>
+```
+
+> The high-contrast theme provides maximum contrast and is recommended for users who have Windows High Contrast Mode (or an equivalent OS-level accessibility setting) enabled. When a custom `Background` or `Palettes` is supplied, those values always win over the theme defaults.
+
 ### Primary Axes (`ChartPrimaryXAxis`, `ChartPrimaryYAxis`)
 - `ValueType` - Axis type: `Syncfusion.Blazor.Toolkit.ValueType.Category`, `ValueType.Double`, `ValueType.DateTime`, `ValueType.Logarithmic`, `ValueType.DateTimeCategory`
 - `Title` - Axis title
diff --git a/src/Base/Enumeration.cs b/src/Base/Enumeration.cs
index 31e1213..ae64aec 100644
--- a/src/Base/Enumeration.cs
+++ b/src/Base/Enumeration.cs
@@ -1362,7 +1362,17 @@ public enum Theme
         /// <remarks>
         /// The Fluent dark theme is designed for dark mode interfaces.
         /// </remarks>
-        FluentDark
+        FluentDark,
+        /// <summary>
+        /// Applies the High Contrast theme to the chart, rendering with maximum-contrast colors for users who require stronger visual differentiation.
+        /// </summary>
+        /// <remarks>
+        /// The High Contrast theme uses a black background (<b>#000000</b>), white text (<b>#FFFFFF</b>),
+        /// a soft accessibility-yellow focus / selection color (<b>#FFD939</b>), and a high-contrast accent palette
+        /// (axis labels and grid lines in neutral grays <b>#969696</b> / <b>#BFBFBF</b>).
+        /// It is designed for accessibility scenarios and environments where Windows High Contrast Mode (or an equivalent OS-level accessibility setting) is enabled.
+        /// </remarks>
+        HighContrast
     }
 
     /// <summary> 
diff --git a/src/Components/Charts/Chart/Renderer/UserInteractions/ZoomToolkit.cs b/src/Components/Charts/Chart/Renderer/UserInteractions/ZoomToolkit.cs
index cd52351..3d80a2c 100644
--- a/src/Components/Charts/Chart/Renderer/UserInteractions/ZoomToolkit.cs
+++ b/src/Components/Charts/Chart/Renderer/UserInteractions/ZoomToolkit.cs
@@ -58,11 +58,15 @@ public class ZoomToolkit : ComponentBase
         protected override void OnInitialized()
         {
             _elementId = Chart?.ID;
-            _selectionColor = Chart?.Theme != Theme.FluentDark ? "#424242" : "#D6D6D6";
-            _fillColor = Chart?.Theme != Theme.FluentDark ? "#424242" : "#D6D6D6";
-            _iconRectOverFill = Chart?.Theme != Theme.FluentDark ? "#EBEBEB" : "#383838";
-            _iconRectSelectionFill = Chart?.Theme != Theme.FluentDark ? "#EBEBEB" : "#383838";
-            _iconRect = Chart?.Theme != Theme.FluentDark ? new Rect(-7, -8, 32, 32) : new Rect(0, 0, 16, 16);
+            // Resolve theme-aware color tokens for the zoom toolkit. High Contrast is treated as a third branch.
+            // The soft accessibility yellow (#FFD939) matches the selectionCircleStroke / tabColor tokens in ChartHelper.GetThemeStyle("HighContrast").
+            bool isHighContrast = Chart?.Theme == Theme.HighContrast;
+            bool isDark = Chart?.Theme == Theme.FluentDark;
+            _selectionColor = isHighContrast ? "#FFD939" : (isDark ? "#D6D6D6" : "#424242");
+            _fillColor = isHighContrast ? "#FFD939" : (isDark ? "#D6D6D6" : "#424242");
+            _iconRectOverFill = isHighContrast ? "#000000" : (isDark ? "#383838" : "#EBEBEB");
+            _iconRectSelectionFill = isHighContrast ? "#000000" : (isDark ? "#383838" : "#EBEBEB");
+            _iconRect = isHighContrast ? new Rect(0, 0, 16, 16) : (isDark ? new Rect(0, 0, 16, 16) : new Rect(-7, -8, 32, 32));
             _zoomkitOpacity = 1;
         }
 
@@ -124,7 +128,7 @@ private void ShowZoomingToolkit(RenderTreeBuilder builder)
             }
 
             toolboxItems = IsDevice() ? [ToolbarItems.Reset] : toolboxItems;
-            RectOptions rectOptions = new(_elementId + "_Zooming_Rect", 0, 0, width, height + (SPACING * 2), 1, Constants.Transparent, Chart?.Theme != Theme.FluentDark ? "#fafafa" : "#1C1B1F", 4, 4, 1);
+            RectOptions rectOptions = new(_elementId + "_Zooming_Rect", 0, 0, width, height + (SPACING * 2), 1, Constants.Transparent, Chart?.Theme == Theme.HighContrast ? "#000000" : (Chart?.Theme != Theme.FluentDark ? "#fafafa" : "#1C1B1F"), 4, 4, 1);
             RenderZoomKit(builder, transX, transY, rectOptions, length, toolboxItems, iconSize);
         }
 
@@ -361,7 +365,7 @@ private void RenderResetButtonAsText(SvgRendering render, RenderTreeBuilder buil
                 Transform = "rotate(0," + 0 + ',' + 0 + ')',
                 DominantBaseline = "middle",
                 FontSize = "12px",
-                Fill = Chart?.Theme != Theme.FluentDark ? "black" : "white"
+                Fill = Chart?.Theme == Theme.HighContrast ? "#FFD939" : (Chart?.Theme != Theme.FluentDark ? "black" : "white")
             });
         }
 
diff --git a/src/Components/Charts/Common/ChartUtils/ChartHelper.cs b/src/Components/Charts/Common/ChartUtils/ChartHelper.cs
index 76d12ef..7b8c375 100644
--- a/src/Components/Charts/Common/ChartUtils/ChartHelper.cs
+++ b/src/Components/Charts/Common/ChartUtils/ChartHelper.cs
@@ -1252,16 +1252,21 @@ internal static string FindThemeColor(string actualColor, string themeColor)
         /// <returns>The theme style configuration.</returns>
         internal static ChartThemeStyle GetChartThemeStyle(string theme)
         {
-            if(theme != "FluentDark")
-            {
-                return GetThemeStyle("#616161", "#242424", "#D2D0CE", "#EDEBE9", "#EDEBE9", "#D2D0CE", "#D2DOCE", "#242424", "#242424", "#FFFFFF", "#EDEBE9", "#A19F9D", "#A19F9D", "rgba(138, 136, 134, 0.1)", "#FFFFFF", "#242424", "#FFFFFF", "#242424", "#242424", "#D2D0CE", null!, "rgba(180, 214, 250, 0.1)", "#0F6CBD", "#0F6CBD", "#424242", "#A19F9D",
-                "14px", "600", "Segoe UI", "12px", "400", "Segoe UI", "12px", "Segoe UI", "400", "12px", "Segoe UI", "700", "12px", "Segoe UI", "400", "12px", "Segoe UI", "600", "#616161", "12px", "Segoe UI", "600", "#616161", "Segoe UI", "12px", "400", "#E7910F", "#0076E5", "12px", "Segoe UI", "600");                
-            }
-            else
+            if (theme == "FluentDark")
             {
                 return GetThemeStyle("#ADADAD", "#FFFFFF", "#3B3A39", "#292827", "#292827", "#3B3A39", "#3B3A39", "#FFFFFF", "#FFFFFF", "#1c1b1f", "#292827", "#8A8886", "#8A8886", "rgba(138, 136, 134, 0.1)", "#292929", "#FFFFFF", "#292929", "#FFFFFF", "#FFFFFF", "#3B3A39", null!, "rgba(14, 71, 117, 0.1)", "#115EA3", "#115EA3", "#D6D6D6", "#8A8886",
                 "14px", "600", "Segoe UI", "12px", "400", "Segoe UI", "12px", "Segoe UI", "400", "12px", "Segoe UI", "700", "12px", "Segoe UI", "400", "12px", "Segoe UI", "600", "#ADADAD", "12px", "Segoe UI", "600", "#ADADAD", "Segoe UI", "12px", "400", "#584EC6", "#43B786", "12px", "Segoe UI", "600");
             }
+            if (theme == "HighContrast")
+            {
+                // High Contrast theme: black background, light-gray axis labels, white chart title.
+                // Yellow (#FFD939) is used for focus/selection accents to remain visible on black.
+                return GetThemeStyle("#969696", "#FFFFFF", "#ffffff", "#BFBFBF", "#969696", "#BFBFBF", "#969696", "#FFFFFF", "#969696", "#000000", "#ffffff", "#ffffff", "#ffffff", "rgba(255, 255, 255, 0.1)", "#FFFFFF", "#000000", "#ffffff", "#000000", "#000000", "#969696", "#BFBFBF", "rgba(255, 217, 57, 0.3)", "#ffffff", "#FFD939", "#FFD939", "#ffffff",
+                        "16px", "600", "Segoe UI", "12px", "400", "Segoe UI", "14px", "Segoe UI", "400", "12px", "Segoe UI", "400", "12px", "Segoe UI", "400", "14px", "Segoe UI", "600", "#FFFFFF", "14px", "Segoe UI", "400", "#969696", "Segoe UI");
+            }
+            // Fluent (light) — default.
+            return GetThemeStyle("#616161", "#242424", "#D2D0CE", "#EDEBE9", "#EDEBE9", "#D2D0CE", "#D2DOCE", "#242424", "#242424", "#FFFFFF", "#EDEBE9", "#A19F9D", "#A19F9D", "rgba(138, 136, 134, 0.1)", "#FFFFFF", "#242424", "#FFFFFF", "#242424", "#242424", "#D2D0CE", null!, "rgba(180, 214, 250, 0.1)", "#0F6CBD", "#0F6CBD", "#424242", "#A19F9D",
+            "14px", "600", "Segoe UI", "12px", "400", "Segoe UI", "12px", "Segoe UI", "400", "12px", "Segoe UI", "700", "12px", "Segoe UI", "400", "12px", "Segoe UI", "600", "#616161", "12px", "Segoe UI", "600", "#616161", "Segoe UI", "12px", "400", "#E7910F", "#0076E5", "12px", "Segoe UI", "600");
         }
 
         /// <summary>
@@ -1270,14 +1275,16 @@ internal static ChartThemeStyle GetChartThemeStyle(string theme)
         /// <returns>An array of color strings for the series.</returns>
         internal static string[] GetSeriesColor(string theme)
         {
-            if(theme != "FluentDark")
+            if (theme == "FluentDark")
             {
-                return new string[] { "#6200EE", "#09AF74", "#0076E5", "#CB3587", "#E7910F", "#0364DE", "#66CD15", "#F3A93C", "#107C10", "#C19C00" };
+                return new string[] { "#9BB449", "#2A72D5", "#43B786", "#3F579A", "#584EC6", "#E85F9C", "#6E7A89", "#EA6266", "#0B6A0B", "#C19C00" };
             }
-            else
+            if (theme == "HighContrast")
             {
-                return new string[] { "#9BB449", "#2A72D5", "#43B786", "#3F579A", "#584EC6", "#E85F9C", "#6E7A89", "#EA6266", "#0B6A0B", "#C19C00" };
+                return new string[] { "#79ECE4", "#E98272", "#DFE6B6", "#C6E773", "#BA98FF", "#FA83C3", "#00C27A", "#43ACEF", "#D681EF", "#D8BC6E" };
             }
+            // Fluent (light) — default.
+            return new string[] { "#6200EE", "#09AF74", "#0076E5", "#CB3587", "#E7910F", "#0364DE", "#66CD15", "#F3A93C", "#107C10", "#C19C00" };
         }
 
         /// <summary>
@@ -1966,14 +1973,16 @@ internal static Rect GetTransform(Rect xAxisRect, Rect yAxisRect, bool invertedA
         /// <returns>The scrollbar theme style.</returns>
         internal static ScrollbarThemeStyle GetScrollbarThemeColor(string theme)
         {
-            if(theme != "FluentDark")
+            if (theme == "FluentDark")
             {
-                return GetScrollbarStyle("#F5F5F5", "#F0F0F0", "#FAFAFA", "#FAFAFA", "#424242", "#424242");
+                return GetScrollbarStyle("#0A0A0A", "#141414", "#1F1F1F", "#1F1F1F", "#D6D6D6", "#D6D6D6");
             }
-            else
+            if (theme == "HighContrast")
             {
-                return GetScrollbarStyle("#0A0A0A", "#141414", "#1F1F1F", "#1F1F1F", "#D6D6D6", "#D6D6D6");
+                return GetScrollbarStyle("#000000", "#000000", "#000000", "#000000", "#FFFF00", "#FFFF00");
             }
+            // Fluent (light) — default.
+            return GetScrollbarStyle("#F5F5F5", "#F0F0F0", "#FAFAFA", "#FAFAFA", "#424242", "#424242");
         }
 
         /// <summary>
diff --git a/tests/Syncfusion.Blazor.Toolkit.BUnitTest/Charts/Chart/ThemeTests/HighContrastThemeTests.razor b/tests/Syncfusion.Blazor.Toolkit.BUnitTest/Charts/Chart/ThemeTests/HighContrastThemeTests.razor
new file mode 100644
index 0000000..036ee39
--- /dev/null
+++ b/tests/Syncfusion.Blazor.Toolkit.BUnitTest/Charts/Chart/ThemeTests/HighContrastThemeTests.razor
@@ -0,0 +1,386 @@
+@using Syncfusion.Blazor.Toolkit.Charts
+@using Syncfusion.Blazor.Toolkit.Tests
+@using Syncfusion.Blazor.Toolkit.Charts.Internal
+@using Syncfusion.Blazor.Toolkit.Internal
+@using System.Reflection
+@using Bunit
+@using Xunit
+
+@inherits TestComponentBase
+
+@*
+    HighContrast theme token coverage.
+
+    Verifies the contract of:
+        ChartHelper.GetChartThemeStyle(theme)
+        ChartHelper.GetSeriesColor(theme)
+        ChartHelper.GetScrollbarThemeColor(theme)
+        SfChart.Theme = Theme.HighContrast derives a high-contrast _chartThemeStyle.
+
+    Mirror of the existing fixture-based razor tests (e.g. Scatter.razor, Legend.razor).
+*@
+
+<SfFixture @ref="hcBackgroundFixture"
+           TestAsync="GetChartThemeStyle_HighContrast_HasBlackBackground"
+           Description="GetChartThemeStyle returns a black Background (#000000) for HighContrast theme">
+    <ComponentUnderTest>
+        <SfChart ID="hcBackgroundChart" />
+    </ComponentUnderTest>
+</SfFixture>
+
+<SfFixture @ref="hcTextFixture"
+           TestAsync="GetChartThemeStyle_HighContrast_HasWhiteTextTokens"
+           Description="GetChartThemeStyle returns white AxisTitle / ChartTitle for HighContrast theme">
+    <ComponentUnderTest>
+        <SfChart ID="hcTextChart" />
+    </ComponentUnderTest>
+</SfFixture>
+
+<SfFixture @ref="hcFocusFixture"
+           TestAsync="GetChartThemeStyle_HighContrast_HasYellowFocusTokens"
+           Description="GetChartThemeStyle returns #FFD939 focus accents for HighContrast theme">
+    <ComponentUnderTest>
+        <SfChart ID="hcFocusChart" />
+    </ComponentUnderTest>
+</SfFixture>
+
+<SfFixture @ref="hcGridFixture"
+           TestAsync="GetChartThemeStyle_HighContrast_HasGrayGridLines"
+           Description="GetChartThemeStyle returns gray grid lines for HighContrast theme">
+    <ComponentUnderTest>
+        <SfChart ID="hcGridChart" />
+    </ComponentUnderTest>
+</SfFixture>
+
+<SfFixture @ref="hcAxisFixture"
+           TestAsync="GetChartThemeStyle_HighContrast_HasGrayAxisLabels"
+           Description="GetChartThemeStyle returns gray axis labels and legend labels for HighContrast theme">
+    <ComponentUnderTest>
+        <SfChart ID="hcAxisChart" />
+    </ComponentUnderTest>
+</SfFixture>
+
+<SfFixture @ref="hcTypeFixture"
+           TestAsync="GetChartThemeStyle_HighContrast_FontSizing"
+           Description="GetChartThemeStyle applies larger / lighter typography for HighContrast theme">
+    <ComponentUnderTest>
+        <SfChart ID="hcTypeChart" />
+    </ComponentUnderTest>
+</SfFixture>
+
+<SfFixture @ref="fluentFixture"
+           TestAsync="GetChartThemeStyle_Fluent_StillReturnsLightTokens"
+           Description="GetChartThemeStyle still returns light tokens for Fluent (no regression)">
+    <ComponentUnderTest>
+        <SfChart ID="fluentChart" />
+    </ComponentUnderTest>
+</SfFixture>
+
+<SfFixture @ref="fluentDarkFixture"
+           TestAsync="GetChartThemeStyle_FluentDark_StillReturnsDarkTokens"
+           Description="GetChartThemeStyle still returns dark tokens for FluentDark (no regression)">
+    <ComponentUnderTest>
+        <SfChart ID="fluentDarkChart" />
+    </ComponentUnderTest>
+</SfFixture>
+
+<SfFixture @ref="hcSeriesPrimaryFixture"
+           TestAsync="GetSeriesColor_HighContrast_ReturnsHighContrastPalette"
+           Description="GetSeriesColor returns the HighContrast palette for HighContrast theme">
+    <ComponentUnderTest>
+        <SfChart ID="hcSeriesPrimaryChart" />
+    </ComponentUnderTest>
+</SfFixture>
+
+<SfFixture @ref="hcSeriesDistinctFixture"
+           TestAsync="GetSeriesColor_HighContrast_PaletteHasDistinctColors"
+           Description="GetSeriesColor HighContrast palette contains the documented ten tokens">
+    <ComponentUnderTest>
+        <SfChart ID="hcSeriesDistinctChart" />
+    </ComponentUnderTest>
+</SfFixture>
+
+<SfFixture @ref="fluentSeriesFixture"
+           TestAsync="GetSeriesColor_Fluent_StillReturnsFluentPalette"
+           Description="GetSeriesColor still returns the Fluent palette when theme is Fluent">
+    <ComponentUnderTest>
+        <SfChart ID="fluentSeriesChart" />
+    </ComponentUnderTest>
+</SfFixture>
+
+<SfFixture @ref="fluentDarkSeriesFixture"
+           TestAsync="GetSeriesColor_FluentDark_StillReturnsDarkPalette"
+           Description="GetSeriesColor still returns the FluentDark palette when theme is FluentDark">
+    <ComponentUnderTest>
+        <SfChart ID="fluentDarkSeriesChart" />
+    </ComponentUnderTest>
+</SfFixture>
+
+<SfFixture @ref="hcScrollbarFixture"
+           TestAsync="GetScrollbarThemeColor_HighContrast_ReturnsHighContrastTokens"
+           Description="GetScrollbarThemeColor returns a yellow arrow / grip and black backRect for HighContrast theme">
+    <ComponentUnderTest>
+        <SfChart ID="hcScrollbarChart" />
+    </ComponentUnderTest>
+</SfFixture>
+
+<SfFixture @ref="fluentDarkScrollbarFixture"
+           TestAsync="GetScrollbarThemeColor_FluentDark_StillReturnsDarkTokens"
+           Description="GetScrollbarThemeColor still returns the dark variant when theme is FluentDark">
+    <ComponentUnderTest>
+        <SfChart ID="fluentDarkScrollbarChart" />
+    </ComponentUnderTest>
+</SfFixture>
+
+<SfFixture @ref="fluentScrollbarFixture"
+           TestAsync="GetScrollbarThemeColor_Fluent_StillReturnsLightTokens"
+           Description="GetScrollbarThemeColor still returns the light variant when theme is Fluent">
+    <ComponentUnderTest>
+        <SfChart ID="fluentScrollbarChart" />
+    </ComponentUnderTest>
+</SfFixture>
+
+<SfFixture @ref="hcSfChartFixture"
+           TestAsync="SfChart_HighContrast_AppliesHighContrastThemeStyle"
+           Description="SfChart with Theme=HighContrast derives a high-contrast _chartThemeStyle">
+    <ComponentUnderTest>
+        <SfChart ID="hcSfChart" Theme="Theme.HighContrast" />
+    </ComponentUnderTest>
+</SfFixture>
+
+<SfFixture @ref="themeSwitchFixture"
+           TestAsync="SfChart_ThemeParameter_UpdatesChartThemeStyle"
+           Description="SfChart switches from Fluent to HighContrast and updates _chartThemeStyle">
+    <ComponentUnderTest>
+        <SfChart ID="themeSwitchChart" />
+    </ComponentUnderTest>
+</SfFixture>
+
+@code {
+    SfFixture hcBackgroundFixture { get; set; }
+    SfFixture hcTextFixture { get; set; }
+    SfFixture hcFocusFixture { get; set; }
+    SfFixture hcGridFixture { get; set; }
+    SfFixture hcAxisFixture { get; set; }
+    SfFixture hcTypeFixture { get; set; }
+    SfFixture fluentFixture { get; set; }
+    SfFixture fluentDarkFixture { get; set; }
+    SfFixture hcSeriesPrimaryFixture { get; set; }
+    SfFixture hcSeriesDistinctFixture { get; set; }
+    SfFixture fluentSeriesFixture { get; set; }
+    SfFixture fluentDarkSeriesFixture { get; set; }
+    SfFixture hcScrollbarFixture { get; set; }
+    SfFixture fluentDarkScrollbarFixture { get; set; }
+    SfFixture fluentScrollbarFixture { get; set; }
+    SfFixture hcSfChartFixture { get; set; }
+    SfFixture themeSwitchFixture { get; set; }
+
+    const string HighContrast = "HighContrast";
+    const string Fluent = "Fluent";
+    const string FluentDark = "FluentDark";
+
+    #region ChartHelper.GetChartThemeStyle
+
+    async Task GetChartThemeStyle_HighContrast_HasBlackBackground(Fixture fixture)
+    {
+        await Task.Delay(50);
+        ChartThemeStyle style = ChartHelper.GetChartThemeStyle(HighContrast);
+        Assert.Equal("#000000", style.Background);
+    }
+
+    async Task GetChartThemeStyle_HighContrast_HasWhiteTextTokens(Fixture fixture)
+    {
+        await Task.Delay(50);
+        ChartThemeStyle style = ChartHelper.GetChartThemeStyle(HighContrast);
+
+        // Pure white text tokens: chart title and axis title.
+        Assert.Equal("#FFFFFF", style.ChartTitle);
+        Assert.Equal("#FFFFFF", style.AxisTitle);
+    }
+
+    async Task GetChartThemeStyle_HighContrast_HasYellowFocusTokens(Fixture fixture)
+    {
+        await Task.Delay(50);
+        ChartThemeStyle style = ChartHelper.GetChartThemeStyle(HighContrast);
+
+        // Soft accessibility yellow is the focus / selection accent.
+        Assert.Equal("#FFD939", style.SelectionCircleStroke);
+        Assert.Equal("#FFD939", style.TabColor);
+    }
+
+    async Task GetChartThemeStyle_HighContrast_HasGrayGridLines(Fixture fixture)
+    {
+        await Task.Delay(50);
+        ChartThemeStyle style = ChartHelper.GetChartThemeStyle(HighContrast);
+
+        // On a black background, grid lines use neutral grays.
+        Assert.Equal("#BFBFBF", style.MajorGridLine);
+        Assert.Equal("#969696", style.MinorGridLine);
+    }
+
+    async Task GetChartThemeStyle_HighContrast_HasGrayAxisLabels(Fixture fixture)
+    {
+        await Task.Delay(50);
+        ChartThemeStyle style = ChartHelper.GetChartThemeStyle(HighContrast);
+
+        // Axis labels and legend labels are intentionally the same neutral #969696.
+        Assert.Equal("#969696", style.AxisLabel);
+        Assert.Equal("#969696", style.LegendLabel);
+    }
+
+    async Task GetChartThemeStyle_HighContrast_FontSizing(Fixture fixture)
+    {
+        await Task.Delay(50);
+        ChartThemeStyle style = ChartHelper.GetChartThemeStyle(HighContrast);
+
+        Assert.Equal("16px", style.ChartTitleSize);
+        Assert.Equal("600", style.ChartTitleFontWeight);
+        Assert.Equal("14px", style.LegendTextSize);
+        Assert.Equal("400", style.LegendFontWeight);
+        Assert.Equal("14px", style.AxisTitleFontSize);
+        Assert.Equal("600", style.AxisTitleFontWeight);
+        Assert.Equal("12px", style.AxisLabelFontSize);
+        Assert.Equal("400", style.AxisLabelFontWeight);
+    }
+
+    async Task GetChartThemeStyle_Fluent_StillReturnsLightTokens(Fixture fixture)
+    {
+        await Task.Delay(50);
+        ChartThemeStyle style = ChartHelper.GetChartThemeStyle(Fluent);
+        Assert.Equal("#FFFFFF", style.Background);
+        // Fluent (light) AxisLabel is the first positional argument — #616161.
+        Assert.Equal("#616161", style.AxisLabel);
+    }
+
+    async Task GetChartThemeStyle_FluentDark_StillReturnsDarkTokens(Fixture fixture)
+    {
+        await Task.Delay(50);
+        ChartThemeStyle style = ChartHelper.GetChartThemeStyle(FluentDark);
+        Assert.Equal("#1c1b1f", style.Background);
+        // FluentDark AxisLabel is the first positional argument — #ADADAD.
+        Assert.Equal("#ADADAD", style.AxisLabel);
+    }
+
+    #endregion
+
+    #region ChartHelper.GetSeriesColor
+
+    async Task GetSeriesColor_HighContrast_ReturnsHighContrastPalette(Fixture fixture)
+    {
+        await Task.Delay(50);
+        string[] palette = ChartHelper.GetSeriesColor(HighContrast);
+        Assert.NotNull(palette);
+        Assert.NotEmpty(palette);
+        // First color is the canonical primary: cyan #79ECE4.
+        Assert.Equal("#79ECE4", palette[0]);
+    }
+
+    async Task GetSeriesColor_HighContrast_PaletteHasDistinctColors(Fixture fixture)
+    {
+        await Task.Delay(50);
+        string[] palette = ChartHelper.GetSeriesColor(HighContrast);
+        Assert.Equal(10, palette.Length);
+        // The HighContrast palette uses ten distinguishable accent tones.
+        Assert.Contains("#79ECE4", palette);
+        Assert.Contains("#E98272", palette);
+        Assert.Contains("#DFE6B6", palette);
+        Assert.Contains("#C6E773", palette);
+        Assert.Contains("#BA98FF", palette);
+        Assert.Contains("#FA83C3", palette);
+        Assert.Contains("#00C27A", palette);
+        Assert.Contains("#43ACEF", palette);
+        Assert.Contains("#D681EF", palette);
+        Assert.Contains("#D8BC6E", palette);
+    }
+
+    async Task GetSeriesColor_Fluent_StillReturnsFluentPalette(Fixture fixture)
+    {
+        await Task.Delay(50);
+        string[] palette = ChartHelper.GetSeriesColor(Fluent);
+        Assert.Equal("#6200EE", palette[0]);
+    }
+
+    async Task GetSeriesColor_FluentDark_StillReturnsDarkPalette(Fixture fixture)
+    {
+        await Task.Delay(50);
+        string[] palette = ChartHelper.GetSeriesColor(FluentDark);
+        Assert.Equal("#9BB449", palette[0]);
+    }
+
+    #endregion
+
+    #region ChartHelper.GetScrollbarThemeColor
+
+    async Task GetScrollbarThemeColor_HighContrast_ReturnsHighContrastTokens(Fixture fixture)
+    {
+        await Task.Delay(50);
+        ScrollbarThemeStyle style = ChartHelper.GetScrollbarThemeColor(HighContrast);
+        Assert.Equal("#000000", style.BackRect);
+        Assert.Equal("#FFFF00", style.Arrow);
+        Assert.Equal("#FFFF00", style.Grip);
+    }
+
+    async Task GetScrollbarThemeColor_FluentDark_StillReturnsDarkTokens(Fixture fixture)
+    {
+        await Task.Delay(50);
+        ScrollbarThemeStyle style = ChartHelper.GetScrollbarThemeColor(FluentDark);
+        Assert.Equal("#0A0A0A", style.BackRect);
+        Assert.Equal("#D6D6D6", style.Arrow);
+    }
+
+    async Task GetScrollbarThemeColor_Fluent_StillReturnsLightTokens(Fixture fixture)
+    {
+        await Task.Delay(50);
+        ScrollbarThemeStyle style = ChartHelper.GetScrollbarThemeColor(Fluent);
+        Assert.Equal("#F5F5F5", style.BackRect);
+        Assert.Equal("#424242", style.Arrow);
+    }
+
+    #endregion
+
+    #region SfChart parameter binding
+
+    async Task SfChart_HighContrast_AppliesHighContrastThemeStyle(Fixture fixture)
+    {
+        await Task.Delay(200);
+        IRenderedComponent<SfChart> cut = fixture.GetComponentUnderTest<SfChart>();
+        ChartThemeStyle? style = GetInternalChartThemeStyle(cut.Instance);
+        Assert.NotNull(style);
+        Assert.Equal("#000000", style!.Background);
+        // Former #FFFF00 ErrorBar is now neutralized to white in the high-contrast token set.
+        Assert.Equal("#ffffff", style.ErrorBar);
+    }
+
+    async Task SfChart_ThemeParameter_UpdatesChartThemeStyle(Fixture fixture)
+    {
+        await Task.Delay(200);
+        IRenderedComponent<SfChart> cut = fixture.GetComponentUnderTest<SfChart>();
+
+        // First render: default is Fluent → white background.
+        ChartThemeStyle? initialStyle = GetInternalChartThemeStyle(cut.Instance);
+        Assert.NotNull(initialStyle);
+        Assert.Equal("#FFFFFF", initialStyle!.Background);
+
+        // Switch to HighContrast → black background.
+        cut.SetParametersAndRender(parameters => parameters.Add(p => p.Theme, Theme.HighContrast));
+        ChartThemeStyle? highContrastStyle = GetInternalChartThemeStyle(cut.Instance);
+        Assert.NotNull(highContrastStyle);
+        Assert.Equal("#000000", highContrastStyle!.Background);
+        Assert.Equal("#ffffff", highContrastStyle.ErrorBar);
+        Assert.Equal("#969696", highContrastStyle.AxisLabel);
+    }
+
+    #endregion
+
+    /// <summary>
+    /// Reads the <c>_chartThemeStyle</c> field on the <see cref="SfChart"/> instance via reflection.
+    /// </summary>
+    static ChartThemeStyle? GetInternalChartThemeStyle(SfChart chart)
+    {
+        FieldInfo? field = typeof(SfChart).GetField(
+            "_chartThemeStyle",
+            BindingFlags.Instance | BindingFlags.NonPublic);
+        Assert.NotNull(field);
+        return field!.GetValue(chart) as ChartThemeStyle;
+    }
+}
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