Rarefaction MCP Server

by ip2k Your server? Claim it

local only

Rarefaction runs on your own machine — the client starts it, so there is no endpoint to ping. Last commit 16 Oct 2026.

LSP call graph for coding agents: a symbol's callers, callees, tests and live files in one call.

—

Installs / week

npm · rarefaction-lsp-mcp

Stars

0 open issues

16 Oct 2026

Last commit

from GitHub

GPL-3.0

License

TypeScript

What the code does

We read the source, 1 d ago · rules ccca72095570

Capabilities

What this server is able to do. For an MCP server this is often the job itself — a terminal server runs commands because that is what it is for. Listed so you know what you are plugging in, not as an accusation.

Runs an external command src/lsp/client.ts:138

    const child = spawn(command, args, {

Is this your server and something here is wrong? Tell us — corrections are free and do not require a plan.

This code can reach further than it looks

We found places where it runs commands, builds paths or queries from values it is given. None of that is a flaw by itself — it becomes one when the code changes, and code changes quietly between releases. We re-read it on every one.

Connect this server

This server runs on your own machine — install it with the package manager and the client starts it for you. Package name taken from the official registry entry.

Claude Code Claude Desktop Codex Cursor VS Code

run in your terminal

claude mcp add rarefaction-lsp-mcp -- npx -y rarefaction-lsp-mcp

~/Library/Application Support/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "rarefaction-lsp-mcp": {
      "args": [
        "-y",
        "rarefaction-lsp-mcp"
      ],
      "command": "npx"
    }
  }
}

~/.codex/config.toml

[mcp_servers.rarefaction-lsp-mcp]
command = "npx"
args = ["-y", "rarefaction-lsp-mcp"]

.cursor/mcp.json

{
  "mcpServers": {
    "rarefaction-lsp-mcp": {
      "args": [
        "-y",
        "rarefaction-lsp-mcp"
      ],
      "command": "npx"
    }
  }
}

.vscode/mcp.json

{
  "mcpServers": {
    "rarefaction-lsp-mcp": {
      "args": [
        "-y",
        "rarefaction-lsp-mcp"
      ],
      "command": "npx"
    }
  }
}

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Rarefaction — questions

Answers built from our own checks of this server.

Why is there no uptime for Rarefaction?

Rarefaction runs on your own machine over stdio — there is no network address to reach, so uptime cannot be measured for it by anyone. What can be measured is adoption: the npm package rarefaction-lsp-mcp.

How do I connect Rarefaction?

Copy the ready config from this page — we generate it for Claude Code, Claude Desktop, Codex, Cursor and VS Code, each with the file path that client actually reads. It runs locally, so the command pulls rarefaction-lsp-mcp straight from npm; nothing to host, nothing to sign up for.

Is Rarefaction open source?

Yes — it is published under the GPL-3.0 licence, written in TypeScript and 0 stars on GitHub. The source link is on this page, so you can read exactly what it does with your data before you connect it.