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Caveat Lang MCP Server

by wsattazahn Your server? Claim it
local only

Caveat Lang runs on your own machine — the client starts it, so there is no endpoint to ping. 1 904 installs a week from npm. Last commit 11 Oct 2026.

Authoring bridge for Caveat: validate, check and test programs; explain decisions; find dependents.

Installs per day peak 681 · avg 69 · +1331% w/w
a month agotoday
1 904
Installs / week
npm · caveat-lang
1
Stars
0 open issues
11 Oct 2026
Last commit
14 releases in 90 days
MIT
License
JavaScript

What the code does

We read the source, 1 h 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.

File ships in the package but is absent from the source [пакет] runtime/caveat_runtime.js:1
этот файл ставится пользователю, но в репозитории его нет
In the project's build, not in the package

Found in continuous integration, deployment or infrastructure files, or in a neighbouring package of the same monorepo. None of this is installed when you add the server: it describes how the project is built and released. We list it because a leaked key in a build pipeline is still a real problem, but it is not something this server does on your machine.

        run: node scripts/pages-gate.mjs select
        env:
          GITHUB_TOKEN: ${{ github.token }}
Page executes code built at runtime web/glowcap.html:312, web/mr-caveat.html:140
  const put = (element, html) => { if (element.innerHTML !== html) element.innerHTML = html; };
      "observed_bytes_base64": "Ly8gVGhlIGRlcGFydHVyZSBnYXRlJ3MgQzMgbWVhc3VyZW1lbnQgKHNwZWMvY2F2ZWF0LWRlcGFydHVyZS0wLjEubWQsICJHYXRlIjsNCi8vIHNwZWMvY2F2ZWF0LWxpbmVhZ2UtY29tcGFjdGlvbi0wLjEubWQsICJUaGUgQzMgZ2F0ZSIpLiBQbGF5cyByb3VuZCA3J3MgQzMNCi8vIHByb2dyYW0gd2l0aCB3aW5kb3dzLCBhcyBz…

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.

Three servers free · no card

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.

run in your terminal
claude mcp add caveat-lang -- npx -y caveat-lang
~/Library/Application Support/Claude/claude_desktop_config.json
{
  "mcpServers": {
    "caveat-lang": {
      "args": [
        "-y",
        "caveat-lang"
      ],
      "command": "npx"
    }
  }
}
~/.codex/config.toml
[mcp_servers.caveat-lang]
command = "npx"
args = ["-y", "caveat-lang"]
.cursor/mcp.json
{
  "mcpServers": {
    "caveat-lang": {
      "args": [
        "-y",
        "caveat-lang"
      ],
      "command": "npx"
    }
  }
}
.vscode/mcp.json
{
  "mcpServers": {
    "caveat-lang": {
      "args": [
        "-y",
        "caveat-lang"
      ],
      "command": "npx"
    }
  }
}

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Caveat Lang — questions

Answers built from our own checks of this server.

Why is there no uptime for Caveat Lang?
Caveat Lang 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 caveat-lang was installed 1 904 times last week.
How do I connect Caveat Lang?
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 caveat-lang straight from npm; nothing to host, nothing to sign up for.
How many people use Caveat Lang?
The npm package caveat-lang was installed 1 904 times in the last week. Week over week that is +1331%. We show installs rather than GitHub stars on purpose: a star is a bookmark, an install is someone actually running it.
Is Caveat Lang open source?
Yes — it is published under the MIT licence, written in JavaScript and 1 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.