diff --git a/package.json b/package.json
index a08187f994..23e87792f4 100644
--- a/package.json
+++ b/package.json
@@ -2250,6 +2250,11 @@
 			{
 				"command": "github.copilot.cloud.sessions.proxy.closeChatSessionPullRequest",
 				"title": "%github.copilot.command.closeChatSessionPullRequest.title%"
+			},
+			{
+				"command": "github.copilot.cloud.sessions.installPullRequestExtension",
+				"title": "Install GitHub Pull Requests Extension",
+				"icon": "$(extensions)"
 			}
 		],
 		"configuration": [
@@ -3831,6 +3836,13 @@
 					"when": "chatSessionType == copilot-cloud-agent",
 					"group": "context"
 				}
+			],
+			"chat/multiDiff/context": [
+				{
+					"command": "github.copilot.cloud.sessions.installPullRequestExtension",
+					"when": "chatSessionType == copilot-cloud-agent && !github.copilot.prExtensionInstalled",
+					"group": "inline"
+				}
 			]
 		},
 		"icons": {
diff --git a/src/extension/chatSessions/vscode-node/chatSessions.ts b/src/extension/chatSessions/vscode-node/chatSessions.ts
index f6341b85d1..1bffb0e12d 100644
--- a/src/extension/chatSessions/vscode-node/chatSessions.ts
+++ b/src/extension/chatSessions/vscode-node/chatSessions.ts
@@ -5,6 +5,7 @@
 
 import * as vscode from 'vscode';
 import { ConfigKey, IConfigurationService } from '../../../platform/configuration/common/configurationService';
+import { IEnvService } from '../../../platform/env/common/envService';
 import { IOctoKitService } from '../../../platform/github/common/githubService';
 import { OctoKitService } from '../../../platform/github/common/octoKitServiceImpl';
 import { ILogService } from '../../../platform/log/common/logService';
@@ -19,7 +20,9 @@ import { CopilotCLIAgentManager } from '../../agents/copilotcli/node/copilotcliA
 import { CopilotCLISessionService, ICopilotCLISessionService } from '../../agents/copilotcli/node/copilotcliSessionService';
 import { ILanguageModelServer, LanguageModelServer } from '../../agents/node/langModelServer';
 import { IExtensionContribution } from '../../common/contributions';
+import { prExtensionInstalledContextKey } from '../../contextKeys/vscode-node/contextKeys.contribution';
 import { ChatSummarizerProvider } from '../../prompt/node/summarizer';
+import { GHPR_EXTENSION_ID } from '../vscode/chatSessionsUriHandler';
 import { ClaudeChatSessionContentProvider } from './claudeChatSessionContentProvider';
 import { ClaudeChatSessionItemProvider } from './claudeChatSessionItemProvider';
 import { ClaudeChatSessionParticipant } from './claudeChatSessionParticipant';
@@ -54,6 +57,7 @@ export class ChatSessionsContrib extends Disposable implements IExtensionContrib
 	constructor(
 		@IInstantiationService instantiationService: IInstantiationService,
 		@IConfigurationService private readonly configurationService: IConfigurationService,
+		@IEnvService private readonly envService: IEnvService,
 		@ILogService private readonly logService: ILogService,
 		@IOctoKitService private readonly octoKitService: IOctoKitService,
 	) {
@@ -131,6 +135,8 @@ export class ChatSessionsContrib extends Disposable implements IExtensionContrib
 		const enabled = this.configurationService.getConfig(ConfigKey.Internal.CopilotCloudEnabled);
 
 		if (enabled && !this.copilotCloudRegistrations) {
+			vscode.commands.executeCommand('setContext', prExtensionInstalledContextKey, this.isPullRequestExtensionInstalled());
+
 			// Register the Copilot Cloud chat participant
 			this.copilotCloudRegistrations = new DisposableStore();
 			const copilotSessionsProvider = this.copilotCloudRegistrations.add(
@@ -159,7 +165,6 @@ export class ChatSessionsContrib extends Disposable implements IExtensionContrib
 			);
 			this.copilotCloudRegistrations.add(
 				vscode.commands.registerCommand(CLOSE_SESSION_PR_CMD, async (ctx: CrossChatSessionWithPR) => {
-					// await this.installPullRequestExtension();
 					try {
 						const success = await this.octoKitService.closePullRequest(
 							ctx.pullRequestDetails.repository.owner.login,
@@ -174,6 +179,16 @@ export class ChatSessionsContrib extends Disposable implements IExtensionContrib
 					}
 				})
 			);
+			this.copilotCloudRegistrations.add(
+				vscode.commands.registerCommand('github.copilot.cloud.sessions.installPullRequestExtension', async () => {
+					try {
+						await this.ensurePullRequestExtensionInstalled();
+					} catch (e) {
+						this.logService.error(`Failed to install GitHub Pull Request extension: ${e}`);
+						vscode.window.showErrorMessage(vscode.l10n.t('Failed to install GitHub Pull Request extension. Please install it manually from the Extensions view.'));
+					}
+				})
+			);
 
 			return copilotSessionsProvider;
 		} else if (!enabled && this.copilotCloudRegistrations) {
@@ -181,4 +196,45 @@ export class ChatSessionsContrib extends Disposable implements IExtensionContrib
 			this.copilotCloudRegistrations = undefined;
 		}
 	}
+
+	private isPullRequestExtensionInstalled(): boolean {
+		const extension = vscode.extensions.getExtension(GHPR_EXTENSION_ID);
+		return extension !== undefined;
+	}
+
+	private async ensurePullRequestExtensionInstalled(): Promise<void> {
+		if (this.isPullRequestExtensionInstalled()) {
+			return;
+		}
+
+		const isInsiders = this.envService.getEditorInfo().version.includes('insider');
+		const installOptions = { enable: true, installPreReleaseVersion: isInsiders };
+
+		await vscode.commands.executeCommand('workbench.extensions.installExtension', GHPR_EXTENSION_ID, installOptions);
+
+		const maxWaitTime = 10_000; // 10 seconds
+		const pollInterval = 100; // 100ms
+		let elapsed = 0;
+
+		while (elapsed < maxWaitTime) {
+			if (this.isPullRequestExtensionInstalled()) {
+				await vscode.commands.executeCommand('setContext', prExtensionInstalledContextKey, true);
+
+				const reloadAction = vscode.l10n.t('Reload Window');
+				const result = await vscode.window.showInformationMessage(
+					vscode.l10n.t('GitHub Pull Request extension installed successfully. Reload VS Code to activate it.'),
+					reloadAction
+				);
+
+				if (result === reloadAction) {
+					await vscode.commands.executeCommand('workbench.action.reloadWindow');
+				}
+				return;
+			}
+			await new Promise(resolve => setTimeout(resolve, pollInterval));
+			elapsed += pollInterval;
+		}
+
+		throw new Error('GitHub Pull Request extension installation timed out.');
+	}
 }