iframe-proxy

Liora Milbaum (lmilbaum) · 2026-10-16T07:19:09Z

Summary

Implements #9070.

Adds a localhost Streamable-HTTP MCP server that bridges 9 existing vscode.LanguageModelTool instances to any MCP-capable agent running in the integrated terminal (Claude Code, Copilot, etc.)
Server binds to 127.0.0.1 with a per-session 256-bit bearer token, exposed as $GITHUB_PR_MCP_URL and $GITHUB_PR_MCP_TOKEN in integrated terminals — agents spawned there connect automatically
Also registers via vscode.lm.registerMcpServerDefinitionProvider so VS Code's own MCP client (Copilot Agent) discovers the server automatically — no manual config needed inside the editor
Write tools (create_pull_request, resolve_review_thread) show an explicit Allow / Allow for session / Deny modal before executing
New command Copy MCP Server Configuration (pr.copyMcpServerConfig) copies a ready-to-paste JSON snippet plus a claude mcp add one-liner for external agents
Gated behind githubPullRequests.experimental.mcpServer (default false, application scope); a no-op browser stub keeps the web build clean

Approach: bridge over existing LM tools

src/lm/tools/ already has 9 vscode.LanguageModelTool classes. This PR adds a thin MCP adapter layer on top — descriptions and schemas come from contributes.languageModelTools in package.json (one source of truth). No new GitHub API calls.

Tools exposed (MVP)

Security

Bound to 127.0.0.1 only; never externally reachable
256-bit per-session bearer token, compared with crypto.timingSafeEqual
Host-header DNS-rebinding check + Origin-header check
4 MB body size limit
Application-scope setting prevents a repo's .vscode/settings.json from enabling the server

How to test

External agent (Claude Code CLI)

Open Extension Development Host with "githubPullRequests.experimental.mcpServer": true and a trusted workspace.
Open a new integrated terminal; echo $GITHUB_PR_MCP_URL prints http://127.0.0.1:<port>/mcp.
curl -s -X POST "$GITHUB_PR_MCP_URL" -H "Content-Type: application/json" -H "Authorization: Bearer $GITHUB_PR_MCP_TOKEN" -d '{"jsonrpc":"2.0","id":1,"method":"tools/list"}' returns 9 tools.
Without the Authorization header: 401. Bad Origin: 403.
claude mcp add --transport http github-pr "$GITHUB_PR_MCP_URL" --header "Authorization: Bearer $GITHUB_PR_MCP_TOKEN", then /mcp shows 9 tools.
Ask Claude Code "What needs to be done for this pull request?" — it calls get_active_pull_request and surfaces review threads and CI status.

Copilot Agent (VS Code-internal)

With the server running, Copilot Agent should discover the server automatically via mcpServerDefinitionProviders — no manual config required.

Lifecycle

Toggle the setting off; new terminals no longer have the env vars and VS Code unregisters the provider.

Open questions

@modelcontextprotocol/server vs hand-rolled? Currently hand-rolled to avoid touching package-lock.json. Happy to switch if preferred.
Stable port/token? Regenerated on each window reload. Persist token in context.secrets and/or add a port setting?
Tool duplication in Copilot Chat? With mcpServerDefinitionProviders wired up, Copilot Chat may show each tool twice (once as a native LM tool, once over MCP). Worth filtering one set out, or is the duplication acceptable?

Closes #9070

🤖 Generated with Claude Code

- Register a localhost Streamable-HTTP MCP server bridging 9 existing LanguageModelTool instances to external MCP-capable agents - Server binds to 127.0.0.1 with a per-session bearer token; exposed as $GITHUB_PR_MCP_URL and $GITHUB_PR_MCP_TOKEN in integrated terminals - Write tools show a Allow/Allow-for-session/Deny confirmation modal - New command pr.copyMcpServerConfig copies a ready-to-paste config snippet - Gated behind githubPullRequests.experimental.mcpServer (default off) - Browser stub keeps web bundle clean Closes microsoft#9070 Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Copilot

🟡 Changes recommended

Unresolved write safeguards, lifecycle races, validation gaps, and browser test failures block approval.

8 open findings

What changed in this PR

Adds an opt-in localhost MCP server for #9070, exposing existing pull request and issue tools to external agents and VS Code’s MCP client.

Changes:

Bridges nine language-model tools with authenticated HTTP access and write confirmations.
Adds server lifecycle management, discovery, terminal credentials, and configuration copying.
Adds browser fallback support and MCP tests.

File	Description
webpack.config.js	Aliases the browser server stub.
src/test/lm/mcpServer.test.ts	Tests catalog, protocol, bridge, and HTTP behavior.
src/lm/tools/tools.ts	Extracts reusable tool creation.
src/lm/mcp/mcpToolCatalog.ts	Maps existing tools to MCP definitions.
src/lm/mcp/mcpToolBridge.ts	Adapts invocation and write confirmations.
src/lm/mcp/mcpServerManager.ts	Manages lifecycle, discovery, and configuration copying.
src/lm/mcp/mcpProtocol.ts	Handles MCP protocol requests.
src/extension.ts	Initializes the server manager.
src/env/node/mcpHttpServer.ts	Provides authenticated localhost HTTP transport.
src/env/browser/mcpHttpServer.ts	Provides a no-op browser implementation.
src/common/settingKeys.ts	Adds the experimental setting key.
package.nls.json	Adds setting and command text.
package.json	Declares the setting, command, and provider.

🧠 Review effort: Balanced

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

+	});
+});
+
+describe('MCP HTTP server', () => {


+		let size = 0;
+		req.on('data', (chunk: Buffer) => {
+			size += chunk.length;
+			if (size > MAX_BODY_BYTES) { resolve(null); req.destroy(); }


+				const protocolVersion = typeof requested === 'string' && SUPPORTED_PROTOCOL_VERSIONS.includes(requested)
+					? requested
+					: SUPPORTED_PROTOCOL_VERSIONS[0];
+				this.clientName = clientNameOf(p['clientInfo']);


+			const version: string = this.context.extension.packageJSON.version ?? '0.0.0';
+			const handler = new McpProtocolHandler(bridge, version);
+
+			this.serverHandle = await startMcpHttpServer(handler);


+		await vscode.env.clipboard.writeText(`${config}\n\n# Claude Code:\n# ${claudeCmd}`);
+		vscode.window.showInformationMessage('MCP server configuration copied to clipboard.');


+		const required = def.inputSchema.required ?? [];
+		const missing = required.filter(key => input[key] === undefined);
+		if (missing.length > 0) {
+			return toolError(`Missing required arguments: ${missing.join(', ')}`);
+		}


+
+		try {
+			// toolInvocationToken is intentionally undefined: no VS Code language model session exists in the MCP path
+			const result = await tool.invoke({ input, toolInvocationToken: undefined }, token);


+	private async confirmationMessage(tool: vscode.LanguageModelTool<unknown>, input: Record<string, unknown>, fallback: string, token: vscode.CancellationToken): Promise<string> {
+		try {
+			const prepared = await tool.prepareInvocation?.({ input }, token);
+			return prepared?.confirmationMessages?.title ?? fallback;


Alex Ross (alexr00) · 2026-10-16T14:29:07Z

Liora Milbaum (lmilbaum) force-pushed the feat/mcp-server branch from 78beb37 to 4d2866a Compare October 16, 2026 07:26

Liora Milbaum (lmilbaum) marked this pull request as ready for review October 16, 2026 07:30

Copilot AI balanced review requested due to automatic review settings October 16, 2026 07:30

Copilot started reviewing on behalf of Liora Milbaum (lmilbaum) October 16, 2026 07:33

View session

Copilot AI reviewed Oct 16, 2026

View reviewed changes

Sunbelt Computer Software

PL/B Language Development and Support

Navigation Menu

Repository navigation

feat: add MCP server for AI agent access to pull requests and issues - #9071

feat: add MCP server for AI agent access to pull requests and issues#9071
Liora Milbaum (lmilbaum) wants to merge 1 commit into
microsoft:mainfrom
lmilbaum:feat/mcp-server

Liora Milbaum (lmilbaum) commented Oct 16, 2026 •

edited

Loading

Uh oh!

Copilot AI left a comment

Uh oh!

Alex Ross (alexr00) commented Oct 16, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

MCP tool	Kind
`get_active_pull_request`	read
`get_viewed_pull_request`	read
`get_issue_or_pull_request`	read
`get_pull_request_status_checks`	read
`search_issues_and_pull_requests`	read
`list_labels`	read
`get_notification`	read
`create_pull_request`	write (confirmed)
`resolve_review_thread`	write (confirmed)

		await vscode.env.clipboard.writeText(`${config}\n\n# Claude Code:\n# ${claudeCmd}`);
		vscode.window.showInformationMessage('MCP server configuration copied to clipboard.');

Sunbelt Computer Software

PL/B Language Development and Support

Conversation

Liora Milbaum (lmilbaum) commented Oct 16, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Summary

Approach: bridge over existing LM tools

Tools exposed (MVP)

Security

How to test

Open questions

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

🟡 Changes recommended

Uh oh!

Alex Ross (alexr00) commented Oct 16, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

Liora Milbaum (lmilbaum) commented Oct 16, 2026 •

edited

Loading