CodeGraph Auto MCP

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A VS Code extension that automatically registers the CodeGraph MCP server when you open a project containing a .codegraph/ directory.

The Problem

CodeGraph provides an MCP (Model Context Protocol) server so that GitHub Copilot can use codegraph's code intelligence tools (codegraph_explore, codegraph_node, etc.). However, CodeGraph's MCP server is per-project — it needs the workspace root path to function correctly:

codegraph serve --mcp --path <workspace_root>

This creates two problems:

1. Cannot use a global mcp.json configuration — The --path argument varies per workspace, so a single global config can't cover all projects.
2. VS Code bug #14166 — Even if you try to configure MCP servers via a global mcp.json, VS Code has a bug where globally configured MCP servers do not auto-start. You have to manually reload the window or re-trigger MCP discovery every time.

The result: every time you open a project, you need to manually intervene to get CodeGraph working — a poor developer experience.

The Solution

This extension automatically registers the CodeGraph MCP server for each workspace using the official VS Code API registerMcpServerDefinitionProvider. When you open a project that has .codegraph/, the extension:

1. Checks that .codegraph/codegraph.db exists (project is indexed)
2. Verifies the codegraph CLI is available in PATH
3. Registers the CodeGraph MCP server with the correct workspace root path — no manual mcp.json configuration needed

The MCP server starts automatically with the right --path argument, and Copilot can immediately use codegraph tools.

Features

• 🔄 Auto-activation — activates when opening any project that has .codegraph/ (using workspaceContains:.codegraph activation event)
• ✅ Dual validation — checks both that codegraph.db exists and that the codegraph CLI is in PATH, preventing registration of a broken MCP server
• 🚀 Zero config — no mcp.json editing, no manual steps, no reload required
• 🌐 Cross-platform — works on macOS, Linux, and Windows (automatically detects codegraph.cmd on Windows)
• 📦 Lightweight — minimal code, zero runtime dependencies

Installation

From VSIX

1. Download the latest .vsix from Releases
2. In VS Code, run Extensions: Install from VSIX...
3. Select the downloaded file

From Source

git clone https://github.com/svenzhao/codegraph-auto-mcp.git
cd codegraph-auto-mcp
npm install
npm run build

Then press F5 in VS Code to start debugging, or install the extension manually:

npm run build
code --install-extension codegraph-auto-mcp-0.0.1.vsix

Usage

Once installed, the extension works automatically:

1. Open any project that has a .codegraph/ directory with a codegraph.db file
2. Make sure the codegraph CLI is available in your PATH
3. The extension registers the CodeGraph MCP server — you can verify in VS Code's MCP server list
4. GitHub Copilot can now use CodeGraph tools (codegraph_explore, codegraph_search, codegraph_node, codegraph_callers) for code intelligence

Requirements

• VS Code ^1.106.0 (with Copilot Chat)
• CodeGraph CLI installed and in PATH
• A project with .codegraph/ directory (initialized via codegraph init)

How It Works

flowchart LR
    A[Open project<br/>with .codegraph/] --> B{Extension activates}
    B --> C[Check .codegraph/<br/>codegraph.db exists]
    B --> D[Find codegraph<br/>CLI in PATH]
    C --> E[Register MCP server<br/>via registerMcpServerDefinitionProvider]
    D --> E
    E --> F[Copilot can now use<br/>CodeGraph tools]

The extension calls vscode.lm.registerMcpServerDefinitionProvider("codegraph", ...) with a provider that returns a McpStdioServerDefinition. This tells VS Code to start the CodeGraph MCP server using:

codegraph serve --mcp --no-watch --path <workspace_root>

The server is registered with the ID "codegraph", which matches the contribution in contributes.mcpServerDefinitionProviders.

Building

npm run build      # compile TypeScript check + esbuild bundle
npm run compile    # same as build
npm run watch      # watch mode for development

License

MIT