diff --git a/src/StaticWebAssetsSdk/Targets/Microsoft.NET.Sdk.StaticWebAssets.ScopedCss.targets b/src/StaticWebAssetsSdk/Targets/Microsoft.NET.Sdk.StaticWebAssets.ScopedCss.targets
index e74f0589b497..e04fa4a14ec3 100644
--- a/src/StaticWebAssetsSdk/Targets/Microsoft.NET.Sdk.StaticWebAssets.ScopedCss.targets
+++ b/src/StaticWebAssetsSdk/Targets/Microsoft.NET.Sdk.StaticWebAssets.ScopedCss.targets
@@ -142,6 +142,33 @@ Integration with static web assets:
   </ComputeCssScope>
 </Target>
 
+<!--
+  Creates a cache file containing the CssScope values for all scoped CSS files.
+  This file is used as an input to _ProcessScopedCssFiles to ensure that changes
+  to CssScope metadata (e.g., custom scopes defined in the project file) trigger
+  a rebuild of the scoped CSS files.
+  See: https://github.com/dotnet/sdk/issues/50646
+-->
+<Target Name="_CreateScopedCssScopeCache" DependsOnTargets="ComputeCssScope">
+  <PropertyGroup>
+    <_ScopedCssIntermediatePath>$([System.IO.Path]::GetFullPath($(IntermediateOutputPath)scopedcss\))</_ScopedCssIntermediatePath>
+    <_ScopedCssScopeCacheFile>$(_ScopedCssIntermediatePath)scopedcss.cache</_ScopedCssScopeCacheFile>
+  </PropertyGroup>
+
+  <MakeDir Directories="$(_ScopedCssIntermediatePath)" />
+
+  <!-- Write a line for each scoped CSS file with its identity and scope, only when different -->
+  <WriteLinesToFile
+    File="$(_ScopedCssScopeCacheFile)"
+    Lines="@(_ScopedCss->'%(Identity)=%(CssScope)')"
+    Overwrite="true"
+    WriteOnlyWhenDifferent="true" />
+
+  <ItemGroup>
+    <FileWrites Include="$(_ScopedCssScopeCacheFile)" />
+  </ItemGroup>
+</Target>
+
 <!-- Sets the output path for the processed scoped css files. They will all have a '.rz.scp.css' extension to flag them as processed
      scoped css files. -->
 <Target Name="ResolveScopedCssOutputs" DependsOnTargets="$(ResolveScopedCssOutputsDependsOn)">
@@ -171,10 +198,12 @@ Integration with static web assets:
     BeforeTargets="CollectUpToDateCheckInputDesignTime;CollectUpToDateCheckBuiltDesignTime" />
 
 <!-- Transforms the original scoped CSS files into their scoped versions on their designated output paths -->
-<Target Name="_ProcessScopedCssFiles" Inputs="@(_ScopedCss)" Outputs="@(_ScopedCssOutputs)" DependsOnTargets="ResolveScopedCssOutputs">
+<Target Name="_ProcessScopedCssFiles" Inputs="@(_ScopedCss);$(_ScopedCssScopeCacheFile)" Outputs="@(_ScopedCssOutputs)" DependsOnTargets="ResolveScopedCssOutputs;_CreateScopedCssScopeCache">
 
   <MakeDir Directories="$(_ScopedCssIntermediatePath)" />
-  <RewriteCss FilesToTransform="@(_ScopedCss)" />
+  <!-- SkipIfOutputIsNewer is false because the target's Inputs/Outputs already handles incrementalism.
+       The cache file in Inputs tracks CssScope metadata changes that wouldn't be detected by file timestamps alone. -->
+  <RewriteCss FilesToTransform="@(_ScopedCss)" SkipIfOutputIsNewer="false" />
 
   <ItemGroup>
     <FileWrites Include="%(_ScopedCss.OutputFile)" />
diff --git a/test/Microsoft.NET.Sdk.StaticWebAssets.Tests/ScopedCssIntegrationTests.cs b/test/Microsoft.NET.Sdk.StaticWebAssets.Tests/ScopedCssIntegrationTests.cs
index 6155a3498987..26b7db5eb7a8 100644
--- a/test/Microsoft.NET.Sdk.StaticWebAssets.Tests/ScopedCssIntegrationTests.cs
+++ b/test/Microsoft.NET.Sdk.StaticWebAssets.Tests/ScopedCssIntegrationTests.cs
@@ -395,6 +395,100 @@ public void Build_ScopedCssTransformation_AndBundling_IsIncremental()
             }
         }
 
+        // Regression test for https://github.com/dotnet/sdk/issues/50646
+        [Fact]
+        public void Build_RegeneratesScopedCss_WhenCssScopeMetadataChanges()
+        {
+            // Arrange
+            var testAsset = "RazorComponentApp";
+            var projectDirectory = CreateAspNetSdkTestAsset(testAsset);
+
+            // Act 1: First build without custom scope
+            var build = CreateBuildCommand(projectDirectory);
+            ExecuteCommand(build).Should().Pass();
+
+            var intermediateOutputPath = Path.Combine(build.GetBaseIntermediateDirectory().ToString(), "Debug", DefaultTfm);
+            var scopedCssFile = Path.Combine(intermediateOutputPath, "scopedcss", "Components", "Pages", "Counter.razor.rz.scp.css");
+            var bundleFile = Path.Combine(intermediateOutputPath, "scopedcss", "bundle", "ComponentApp.styles.css");
+
+            new FileInfo(scopedCssFile).Should().Exist();
+            new FileInfo(bundleFile).Should().Exist();
+
+            // Get initial thumbprints
+            var initialScopedCssThumbprint = FileThumbPrint.Create(scopedCssFile);
+            var initialBundleThumbprint = FileThumbPrint.Create(bundleFile);
+
+            // Verify initial build uses auto-generated scope (starts with 'b-')
+            var initialContent = File.ReadAllText(scopedCssFile);
+            initialContent.Should().MatchRegex(@"\[b-[a-z0-9]+\]");
+
+            // Act 2: Add custom CssScope metadata to the project
+            File.WriteAllText(
+                Path.Combine(projectDirectory.Path, "Directory.Build.targets"),
+                """
+                <Project>
+                  <ItemGroup>
+                    <None Update="Components\Pages\Counter.razor.css">
+                      <CssScope>my-custom-scope</CssScope>
+                    </None>
+                  </ItemGroup>
+                </Project>
+                """);
+
+            build = CreateBuildCommand(projectDirectory);
+            ExecuteCommand(build).Should().Pass();
+
+            // Assert: Files should be regenerated with the new scope
+            var newScopedCssThumbprint = FileThumbPrint.Create(scopedCssFile);
+            var newBundleThumbprint = FileThumbPrint.Create(bundleFile);
+
+            Assert.NotEqual(initialScopedCssThumbprint, newScopedCssThumbprint);
+            Assert.NotEqual(initialBundleThumbprint, newBundleThumbprint);
+
+            // Verify the new content uses the custom scope
+            var newContent = File.ReadAllText(scopedCssFile);
+            newContent.Should().Contain("[my-custom-scope]");
+            newContent.Should().NotMatchRegex(@"\[b-[a-z0-9]+\]");
+
+            // Act 3: Change the custom scope to a different value
+            File.WriteAllText(
+                Path.Combine(projectDirectory.Path, "Directory.Build.targets"),
+                """
+                <Project>
+                  <ItemGroup>
+                    <None Update="Components\Pages\Counter.razor.css">
+                      <CssScope>my-updated-scope</CssScope>
+                    </None>
+                  </ItemGroup>
+                </Project>
+                """);
+
+            build = CreateBuildCommand(projectDirectory);
+            ExecuteCommand(build).Should().Pass();
+
+            // Assert: Files should be regenerated again with the updated scope
+            var updatedScopedCssThumbprint = FileThumbPrint.Create(scopedCssFile);
+            var updatedBundleThumbprint = FileThumbPrint.Create(bundleFile);
+
+            Assert.NotEqual(newScopedCssThumbprint, updatedScopedCssThumbprint);
+            Assert.NotEqual(newBundleThumbprint, updatedBundleThumbprint);
+
+            // Verify the content uses the updated scope
+            var updatedContent = File.ReadAllText(scopedCssFile);
+            updatedContent.Should().Contain("[my-updated-scope]");
+            updatedContent.Should().NotContain("[my-custom-scope]");
+
+            // Act 4: Verify that building again without changes doesn't regenerate
+            var finalScopedCssThumbprint = FileThumbPrint.Create(scopedCssFile);
+            var finalBundleThumbprint = FileThumbPrint.Create(bundleFile);
+
+            build = CreateBuildCommand(projectDirectory);
+            ExecuteCommand(build).Should().Pass();
+
+            Assert.Equal(finalScopedCssThumbprint, FileThumbPrint.Create(scopedCssFile));
+            Assert.Equal(finalBundleThumbprint, FileThumbPrint.Create(bundleFile));
+        }
+
         // This test verifies if the targets that VS calls to update scoped css works to update these files
         [Fact]
         public void RegeneratingScopedCss_ForProject()