MCP Server with SSE in Elixir

Overview

MCP Server with SSE in Elixir provides a lightweight implementation of a Model Context Protocol (MCP) server that uses Server-Sent Events (SSE) to stream real-time model context and events to clients. Built in Elixir, it leverages the BEAM’s concurrency and supervision model to keep long-lived streaming connections stable and efficient, making it well suited for low-latency event delivery from backend model services to dashboards, agents, or other consumers.

This project is useful when you need a production-ready, simple-to-integrate server that exposes streaming endpoints for model context or incremental updates. It is designed to be embedded into an Elixir application (Plug / Cowboy / Phoenix) and supports standard SSE clients (EventSource in browsers, curl -N, or custom consumers). Use it to stream JSON-encoded events, keep connections alive with heartbeats, and manage client subscriptions with a minimal operational footprint.

Features

• SSE-based streaming for real-time event delivery
• Designed to integrate with Plug / Cowboy or Phoenix endpoints
• JSON payloads for events (compatible with typical model context formats)
• Connection keep-alive and heartbeat support to prevent idle timeouts
• Lightweight and fault-tolerant: fits into Elixir supervision trees
• Example client usage (curl, EventSource) and simple integration patterns
• CORS-friendly configuration options (for browser-based clients)

Installation / Configuration

Add the library to your mix.exs dependencies (GitHub source):

defp deps do
  [
    {:mcp_sse, git: "https://github.com/kEND/mcp_sse.git"}
  ]
end

Fetch dependencies and compile:

mix deps.get
mix compile

Example configuration (config/config.exs). Adjust keys according to your app’s needs — the library reads options like mount path, heartbeat interval, and CORS settings:

config :mcp_sse, McpSse,
  path: "/mcp",            # mount path for the MCP endpoints
  heartbeat_ms: 15_000