diff --git a/.gitignore b/.gitignore
index 51f48c4cf..fab283481 100644
--- a/.gitignore
+++ b/.gitignore
@@ -16,6 +16,7 @@ out
 .razorExtension/
 .vscode-test/
 .roslynCopilot/
+.testDiscovery/
 msbuild/signing/signJs/*.log
 msbuild/signing/signVsix/*.log
 dist/
diff --git a/package.json b/package.json
index 3752f98b0..d579c6e04 100644
--- a/package.json
+++ b/package.json
@@ -44,7 +44,8 @@
     "roslyn": "5.9.0-1.26303.15",
     "omniSharp": "1.39.14",
     "razorOmnisharp": "7.0.0-preview.23363.1",
-    "xamlTools": "18.9.11909.33"
+    "xamlTools": "18.9.11909.33",
+    "testDiscovery": "0.1.0-dev"
   },
   "main": "./dist/extension",
   "l10n": "./l10n",
@@ -1479,6 +1480,10 @@
               "roslynCopilot": {
                 "description": "%configuration.dotnet.server.componentPaths.roslynCopilot%",
                 "type": "string"
+              },
+              "testDiscovery": {
+                "description": "%configuration.dotnet.server.componentPaths.testDiscovery%",
+                "type": "string"
               }
             },
             "default": {}
diff --git a/package.nls.json b/package.nls.json
index b11039058..224e27a3d 100644
--- a/package.nls.json
+++ b/package.nls.json
@@ -35,6 +35,7 @@
   "configuration.dotnet.server.componentPaths.roslynDevKit": "Overrides the folder path for the .roslynDevKit component of the language server",
   "configuration.dotnet.server.componentPaths.xamlTools": "Overrides the folder path for the .xamlTools component of the language server",
   "configuration.dotnet.server.componentPaths.roslynCopilot": "Overrides the folder path for the .roslynCopilot component of the language server",
+  "configuration.dotnet.server.componentPaths.testDiscovery": "Overrides the folder path for the .testDiscovery component of the language server",
   "configuration.dotnet.server.componentPaths.razorExtension": "Overrides the folder path for the Razor extension component of the language server",
   "configuration.dotnet.server.startTimeout": "Specifies a timeout (in ms) for the client to successfully start and connect to the language server.",
   "configuration.dotnet.server.waitForDebugger": "Passes the --debug flag when launching the server to allow a debugger to be attached. (Requires extension restart)",
diff --git a/src/lsptoolshost/extensions/builtInComponents.ts b/src/lsptoolshost/extensions/builtInComponents.ts
index 29ec6508c..26d170326 100644
--- a/src/lsptoolshost/extensions/builtInComponents.ts
+++ b/src/lsptoolshost/extensions/builtInComponents.ts
@@ -35,6 +35,12 @@ export const componentInfo: { [key: string]: ComponentInfo } = {
         componentDllPaths: ['Microsoft.VisualStudio.Copilot.Roslyn.LanguageServer.dll'],
         isOptional: true,
     },
+    testDiscovery: {
+        defaultFolderName: '.testDiscovery',
+        optionName: 'testDiscovery',
+        componentDllPaths: ['Microsoft.VisualStudio.CSharpDevKit.SourceTestDiscovery.dll'],
+        isOptional: true,
+    },
 };
 
 export function getComponentPaths(
diff --git a/src/lsptoolshost/server/roslynLanguageServer.ts b/src/lsptoolshost/server/roslynLanguageServer.ts
index e9fa5333a..b2c896e6f 100644
--- a/src/lsptoolshost/server/roslynLanguageServer.ts
+++ b/src/lsptoolshost/server/roslynLanguageServer.ts
@@ -928,6 +928,16 @@ export class RoslynLanguageServer {
             );
         }
 
+        // Also include the C# Dev Kit source-based test discovery extension, if present. The component
+        // is built by C# Dev Kit (vs-green), published as a NuGet package, and restored into this
+        // extension at build time (see allNugetPackages in offlinePackagingTasks.ts), using the same
+        // mechanism as the Xaml tools and roslynDevKit components above. It is optional: builds
+        // that don't restore the package won't have the folder, in which case getComponentPaths returns
+        // an empty array and we skip it. The consumer of the discovery service is the C# Dev Kit server.
+        getComponentPaths('testDiscovery', languageServerOptions, channel).forEach((path) =>
+            additionalExtensionPaths.push(path)
+        );
+
         return args;
     }
 
diff --git a/tasks/packaging/offlinePackagingTasks.ts b/tasks/packaging/offlinePackagingTasks.ts
index b74b66964..a31034395 100644
--- a/tasks/packaging/offlinePackagingTasks.ts
+++ b/tasks/packaging/offlinePackagingTasks.ts
@@ -23,6 +23,7 @@ import {
     rootPath,
     devKitDependenciesDirectory,
     xamlToolsDirectory,
+    testDiscoveryDirectory,
 } from '../projectPaths';
 import { getPackageJSON } from '../packageJson';
 import { createPackageAsync, generateVsixManifest } from './vsceTasks';
@@ -91,6 +92,12 @@ export const allNugetPackages: { [key: string]: NugetPackageInfo } = {
         getPackageContentPath: (_platformInfo) => 'content',
         vsixOutputPath: xamlToolsDirectory,
     },
+    testDiscovery: {
+        getPackageName: (_platformInfo) => 'Microsoft.VisualStudio.CSharpDevKit.SourceTestDiscovery',
+        packageJsonName: 'testDiscovery',
+        getPackageContentPath: (_platformInfo) => 'content',
+        vsixOutputPath: testDiscoveryDirectory,
+    },
 };
 
 interface PlatformEntry {
diff --git a/tasks/projectPaths.ts b/tasks/projectPaths.ts
index a2362f9b0..0972ed0bf 100644
--- a/tasks/projectPaths.ts
+++ b/tasks/projectPaths.ts
@@ -18,6 +18,7 @@ export const nugetTempPath = path.join(rootPath, 'out', '.nuget');
 export const languageServerDirectory = path.join(rootPath, '.roslyn');
 export const devKitDependenciesDirectory = path.join(rootPath, componentInfo.roslynDevKit.defaultFolderName);
 export const xamlToolsDirectory = path.join(rootPath, componentInfo.xamlTools.defaultFolderName);
+export const testDiscoveryDirectory = path.join(rootPath, componentInfo.testDiscovery.defaultFolderName);
 
 export const codeExtensionPath = commandLineOptions.codeExtensionPath || rootPath;