diff --git a/src/lsptoolshost/copilot.ts b/src/lsptoolshost/copilot.ts
new file mode 100644
index 000000000..53a67912b
--- /dev/null
+++ b/src/lsptoolshost/copilot.ts
@@ -0,0 +1,92 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+import { CSharpExtensionId } from '../constants/csharpExtensionId';
+import { CopilotRelatedDocumentsReport, CopilotRelatedDocumentsRequest } from './roslynProtocol';
+import { RoslynLanguageServer } from './roslynLanguageServer';
+import { UriConverter } from './uriConverter';
+import { TextDocumentIdentifier } from 'vscode-languageserver-protocol';
+import { languageServerOptions } from '../shared/options';
+
+interface CopilotRelatedFilesProviderRegistration {
+    registerRelatedFilesProvider(
+        providerId: { extensionId: string; languageId: string },
+        callback: (uri: vscode.Uri) => Promise<{ entries: vscode.Uri[]; traits?: { name: string; value: string }[] }>
+    ): void;
+}
+
+export async function registerCopilotExtensionAsync(
+    languageServer: RoslynLanguageServer,
+    channel: vscode.OutputChannel
+) {
+    const isTraceLogLevel =
+        languageServerOptions.logLevel &&
+        (languageServerOptions.logLevel === 'Trace' || languageServerOptions.logLevel === 'Debug');
+
+    const ext = vscode.extensions.getExtension('github.copilot');
+    if (!ext) {
+        if (isTraceLogLevel) {
+            channel.appendLine(
+                'GitHub Copilot extension not installed. Skip registeration of C# related files provider.'
+            );
+        }
+        return;
+    }
+    await ext.activate();
+    const relatedAPI = ext.exports as CopilotRelatedFilesProviderRegistration | undefined;
+    if (!relatedAPI) {
+        if (isTraceLogLevel) {
+            channel.appendLine(
+                'Incompatible GitHub Copilot extension installed. Skip registeration of C# related files provider.'
+            );
+        }
+        return;
+    }
+
+    if (isTraceLogLevel) {
+        channel.appendLine('registeration of C# related files provider for GitHub Copilot extension succeeded.');
+    }
+
+    const id = {
+        extensionId: CSharpExtensionId,
+        languageId: 'csharp',
+    };
+
+    relatedAPI.registerRelatedFilesProvider(id, async (uri) => {
+        const buildResult = (reports: CopilotRelatedDocumentsReport[], builder?: vscode.Uri[]) => {
+            if (reports) {
+                for (const report of reports) {
+                    if (report._vs_file_paths) {
+                        for (const filePath of report._vs_file_paths) {
+                            builder?.push(vscode.Uri.file(filePath));
+                        }
+                    }
+                }
+            }
+        };
+        const relatedFiles: vscode.Uri[] = [];
+        const uriString = UriConverter.serialize(uri);
+        const textDocument = TextDocumentIdentifier.create(uriString);
+        try {
+            await languageServer.sendRequestWithProgress(
+                CopilotRelatedDocumentsRequest.type,
+                {
+                    _vs_textDocument: textDocument,
+                    position: {
+                        line: 0,
+                        character: 0,
+                    },
+                },
+                async (r) => buildResult(r, relatedFiles)
+            );
+        } catch (e) {
+            if (e instanceof Error) {
+                channel.appendLine(e.message);
+            }
+        }
+        return { entries: relatedFiles };
+    });
+}
diff --git a/src/lsptoolshost/roslynLanguageServer.ts b/src/lsptoolshost/roslynLanguageServer.ts
index b46507392..e525eec57 100644
--- a/src/lsptoolshost/roslynLanguageServer.ts
+++ b/src/lsptoolshost/roslynLanguageServer.ts
@@ -68,6 +68,7 @@ import { registerLanguageStatusItems } from './languageStatusBar';
 import { ProjectContextService } from './services/projectContextService';
 import { ProvideDynamicFileResponse } from '../razor/src/dynamicFile/provideDynamicFileResponse';
 import { ProvideDynamicFileParams } from '../razor/src/dynamicFile/provideDynamicFileParams';
+import { registerCopilotExtensionAsync } from './copilot';
 
 let _channel: vscode.OutputChannel;
 let _traceChannel: vscode.OutputChannel;
@@ -1036,6 +1037,7 @@ export async function activateRoslynLanguageServer(
     );
 
     registerLanguageStatusItems(context, languageServer, languageServerEvents);
+    await registerCopilotExtensionAsync(languageServer, _channel);
 
     // Register any commands that need to be handled by the extension.
     registerCommands(context, languageServer, hostExecutableResolver, _channel);
diff --git a/src/lsptoolshost/roslynProtocol.ts b/src/lsptoolshost/roslynProtocol.ts
index 4e5850770..9c612502b 100644
--- a/src/lsptoolshost/roslynProtocol.ts
+++ b/src/lsptoolshost/roslynProtocol.ts
@@ -221,6 +221,15 @@ export interface ProjectNeedsRestoreName {
     projectFilePaths: string[];
 }
 
+export interface CopilotRelatedDocumentsParams extends lsp.WorkDoneProgressParams, lsp.PartialResultParams {
+    _vs_textDocument: lsp.TextDocumentIdentifier;
+    position: lsp.Position;
+}
+
+export interface CopilotRelatedDocumentsReport {
+    _vs_file_paths?: string[];
+}
+
 export namespace WorkspaceDebugConfigurationRequest {
     export const method = 'workspace/debugConfiguration';
     export const messageDirection: lsp.MessageDirection = lsp.MessageDirection.clientToServer;
@@ -330,3 +339,15 @@ export namespace ProjectNeedsRestoreRequest {
     export const messageDirection: lsp.MessageDirection = lsp.MessageDirection.serverToClient;
     export const type = new lsp.RequestType<ProjectNeedsRestoreName, void, void>(method);
 }
+
+export namespace CopilotRelatedDocumentsRequest {
+    export const method = 'copilot/_related_documents';
+    export const messageDirection: lsp.MessageDirection = lsp.MessageDirection.clientToServer;
+    export const type = new lsp.ProtocolRequestType<
+        CopilotRelatedDocumentsParams,
+        CopilotRelatedDocumentsReport[],
+        CopilotRelatedDocumentsReport[],
+        void,
+        void
+    >(method);
+}