Emacs MCP Server

emacs-mcp-server is an MCP (Model Context Protocol) server that controls Emacs via emacsclient. It lets Claude (or any MCP client) open files, evaluate Lisp, navigate definitions, and manage buffers in your running Emacs instance.

Three implementations are provided — Python, TypeScript, and Java (Quarkus) — all exposing the same tools.

Prerequisites

• Emacs with server mode running:

  ;; in init.el
  (server-start)

  Or start it interactively: M-x server-start
• emacsclient available in PATH

See the Tutorial for detailed installation instructions covering Ubuntu 24.04, vanilla Emacs, and Doom Emacs.

Tools

Tool	Description
open_file	Open a file in Emacs, optionally at a specific line
eval_elisp	Evaluate an Emacs Lisp expression
list_buffers	List all open buffers
goto_definition	Jump to a symbol definition via xref
save_buffer	Save a buffer by file path

Usage

Java (Quarkus) — recommended for MCP Gateway integration

cd java-quarkus
mvn package

java -Dquarkus.http.port=8092 -jar target/quarkus-app/quarkus-run.jar

Register with Claude CLI:

claude mcp add emacs --transport http --url http://localhost:8092/mcp

Or register with the MCP Gateway:

curl -X POST http://localhost:8888/api/servers \
  -H 'Content-Type: application/json' \
  -d '{"name": "emacs", "url": "http://localhost:8092", "description": "Emacs MCP Server"}'

Python

cd python
pip install -r requirements.txt
python emacs_mcp_server.py

claude mcp add emacs -- python /path/to/python/emacs_mcp_server.py

TypeScript

cd typescript
npm install
npx tsx src/index.ts

claude mcp add emacs -- npx tsx /path/to/typescript/src/index.ts

Example Interaction

Once registered, Claude can open files directly in your editor while working on a task:

User: Open the ActorSystem.java file in Emacs at line 42.
Claude: [calls open_file("src/main/java/.../ActorSystem.java", 42)]

This is particularly useful when Claude Code is navigating large codebases — you can ask it to open any file it references and jump to the relevant line in your running Emacs instance.