OpenGrok

💡Self-Contained Architecture:The VS Code extension includes the MCP server pre-packaged. You don't need Python, external Node.js installations, or complex environment setups. Just install and go.

Option 1 — VS Code Extension (Recommended)

InstallOpenGrok MCPfrom the VS Code Marketplace, or search "OpenGrok" in the Extensions panel.

The extension provides a visual configuration UI and manages the MCP server process automatically.

npm install -g opengrok-mcp-server opengrok-mcp setup # interactive wizard: URL, credentials, MCP client registration

The wizard stores credentials securely in the OS keychain (macOS Keychain, Windows Credential Manager, Linux libsecret) with an encrypted file fallback for headless Linux.

- After installation, theSettings panelwill launch.
- Input your OpenGrok endpoint, username, and password. HitSave Settings.(Credentials are locked in your native OS keychain).
- The plugin verifies the connection instantly. On your first run, VS Code will ask you toReload the Windowto register the MCP tools.
- (Need to change this later? Use theOpenGrok: Manage Configurationcommand or click the gear icon in the status bar).

- Launch theGitHub Copilot Chatwindow. Ensure you're usingAgentmode.
- Click the paperclip/tools icon (🔧) in the prompt box.
- (If anUpdate Toolsbutton appears, click it).
- LocateOpenGrokin the list, check the box, and confirm.

⚠️ Note that VS Code manages tool authorizationsper workspace. If you open a different repository, you may need to re-check the OpenGrok box in Copilot.

setupsupportsClaude Code CLI,GitHub Copilot CLI, andCodex CLI. VS Code is configured automatically by the extension — no CLI step needed. Credentials are stored in the OS keychain with an AES-256-GCM encrypted file fallback for headless/CI environments.

While tailored for VS Code, the integrated server logic runs perfectly with other agents natively supporting the MCP protocol, including:

Claude Desktop|Cursor IDE|Windsurf|Claude Code|Google Antigravity

Talk to GitHub Copilot Chat naturally about your codebase:

Find the implementation of the render_pipeline function within the graphics engine project. Retrieve the contents of /src/utils/math.cpp from line 450 to 520. What is the definition of TextureManager? Please show me the header file declaration too. Look for all places in the code where ThreadPool is instantiated or referenced.

💡 These specialized tools merge multiple network requests into a single operation, reducing API chatter and cutting token usage byup to 90%.

(Note: The search functions support language filtering. Passfile_typeasjava,cxx,python,golang, etc.)

🔍 Investigation & Analysis Tools (v5.6+)

🧬 Code Mode (v5+) — For Large Multi-Language Codebases

SetOPENGROK_CODE_MODE=trueto switch to a 5-tool interface optimised for multi-step investigations:

Allenv.opengrok.*calls appearsynchronousinside your code — the sandbox bridges async HTTP calls transparently using a SharedArrayBuffer + Atomics channel. Token savings of 80–95% are typical for complex investigations.

v9.0+ sandbox methods for interactive prompts and AI assistance:

The server degrades gracefully when sampling is unavailable —sample()returnsnull,_suggestionsis not injected.

For the standalone server (npx opengrok-mcp-serveror Claude Code), set these environment variables:

VS Code users can setopengrok-mcp.codeMode,opengrok-mcp.contextBudget,opengrok-mcp.memoryBankDir,opengrok-mcp.defaultProject,opengrok-mcp.responseFormatOverride,opengrok-mcp.compileDbPaths,opengrok-mcp.enableObservationMasker, andopengrok-mcp.observationMaskerTurnsin VS Code settings instead.

MCP SDK Note:This version uses@modelcontextprotocol/sdkv1.29.0. MCP SDK v2 is in pre-alpha; we will migrate when stable (expected Q3-Q4 2026). v2 will enable enhanced completions for tool parameters and resource templates.

By default the server communicates overstdio(standard MCP). For team deployments, you can also expose aStreamable HTTP endpoint:

OPENGROK_HTTP_PORT=3666 npm run serve # or add to your MCP client config: # "OPENGROK_HTTP_PORT": "3666"

- Each HTTP client receives an isolatedMcpServerinstance (per-session factory pattern)
- Sessions expire after 30 minutes of inactivity;OPENGROK_HTTP_MAX_SESSIONScaps concurrent sessions (default: 100)
- GET /mcp/sessionsreturns JSON with active session count and oldest session age

In resource server mode, this server validates JWTs issued by your own IdP — there is no built-in/tokenendpoint. RFC 9728 protected resource metadata is served at/.well-known/oauth-protected-resource.

Fail-safe: unknown or missing tokens default toreadonly, notadmin.

v7.0 includes a comprehensive security audit with the following hardening:

- OPENGROK_HTTP_CLIENT_IDandOPENGROK_HTTP_CLIENT_SECRETremoved. Migrate toOPENGROK_JWKS_URI+OPENGROK_RESOURCE_URIfor OAuth 2.1 (resource server model — bring your own IdP).
- Memory bankmigrate()removed — the legacy 6-file layout is no longer supported. The 2-file layout (active-task.md+investigation-log.md) has been the default since v5.4.
- CORS is now allowlist-only whenOPENGROK_ALLOWED_ORIGINSis set; unauthenticated wildcard CORS is disabled.

The MCP tools are missing in Copilot Chat

- Click the paperclip (🔧) icon to "Update Tools"
- RunDeveloper: Reload Window

- Double-check yourOPENGROK_BASE_URL
- Make sure you aren't blocked by corporate VPNs/proxies

401 Unauthorized / Authentication failing

- Run theOpenGrok: Configure Credentialscommand to save your username/password again

- Turn off strict validation by settingopengrok-mcp.verifySsltofalse

- Limit the scope using thefile_typeargument or targeting a specific project
- OpenGrok might be indexing; runopengrok_index_health

- Set the environment variableOPENGROK_LOG_LEVEL=debugto get extensive stdout trace data

- ✅Permitted:Personal use, hobby projects, academic research, education
- ❌Prohibited:Any commercial, business, enterprise, or paid utilization

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