Working on your own machine

umicat games live in the browser, and for most people that is the whole story. But a game is ordinary code — TypeScript, Vite, a git history — and you can have all of it on your own machine, edited by whichever AI coding assistant you already use.

That works through the umicat MCP server: a small program that runs locally and gives your assistant a way to reach your projects. Clone a game, change it, run it, send the work back.

Is this for you?

It is worth setting up if you are comfortable in a terminal and you already pay for an AI coding assistant (Claude Code, Codex, or anything else that speaks MCP).

Both write to the same project. You can build in the browser on Monday, clone it on Tuesday, and open the editor again on Wednesday.

Install

node --version

brew install node

# Debian/Ubuntu — the distro package is often several majors behind
curl -fsSL https://deb.nodesource.com/setup_lts.x | sudo -E bash -
sudo apt install -y nodejs

winget install OpenJS.NodeJS.LTS

xcode-select --install

sudo apt install git     # or your distribution's equivalent

winget install Git.Git

claude mcp add umicat -- npx -y @umicat/mcp    # Claude Code
codex mcp add umicat -- npx -y @umicat/mcp     # Codex

{
  "mcpServers": {
    "umicat": { "command": "npx", "args": ["-y", "@umicat/mcp"] }
  }
}

claude mcp add umicat -- npx -y @umicat/mcp    # Claude Code
codex mcp add umicat -- npx -y @umicat/mcp     # Codex

{
  "mcpServers": {
    "umicat": { "command": "npx", "args": ["-y", "@umicat/mcp"] }
  }
}

{
  "mcpServers": {
    "umicat": { "command": "cmd", "args": ["/c", "npx", "-y", "@umicat/mcp"] }
  }
}

claude mcp remove umicat
claude mcp add umicat -- "$(which npx)" -y @umicat/mcp

claude mcp remove umicat
claude mcp add umicat -- "$(which npx)" -y @umicat/mcp

claude mcp get umicat

(Get-Command npx).Source

Signing out, and why there is no "Connect" button

Ask your assistant to sign out and it forgets the credential on this machine. That is not the same as revoking it: the credential stays valid on umicat until it expires or you revoke it at umicat.ai → Settings → Access tokens. A token deliberately cannot revoke itself, so a leaked one cannot lock you out of your own account.

You may have seen other MCP servers appear in /mcp as not connected, with a button that starts a login. That is MCP's OAuth flow, and the specification defines it for HTTP transports only — a local (stdio) server is told to take credentials from the environment instead.

This server has to be local: putting your game's code on your disk is the whole point, and a remote server cannot reach your filesystem. So signing in is a request rather than a button. Your assistant is told at connect time to sign in before doing anything, so in practice you just ask for what you want and the sign-in happens on the way.

On a machine with no browser

A server or a container cannot open the sign-in page. Create a token instead, at umicat.ai → Settings → Access tokens, and pass it in the environment:

claude mcp add umicat --env UMICAT_TOKEN=umicat_pat_… -- npx -y @umicat/mcp

On Windows, put it in the same hand-written block as an env entry:

{
  "mcpServers": {
    "umicat": {
      "command": "cmd",
      "args": ["/c", "npx", "-y", "@umicat/mcp"],
      "env": { "UMICAT_TOKEN": "umicat_pat_…" }
    }
  }
}

UMICAT_TOKEN always wins over a stored sign-in, so this is also how you pin a specific token.

What a token can and cannot do

Signing in this way is not the same as signing in to the website. What your assistant gets can read and change the code of projects you have access to, create a project, edit its details, upload files to it, and set its cover, logo and screenshots — that is what makes any of this possible — and nothing else. It cannot spend credits, buy anything, change your account, or create another token.

The line is drawn precisely where money is: uploading a file you already made costs nothing, so it is allowed; generating art with AI calls a paid model, so it is not. A cover you rendered yourself goes up from your machine; having umicat draw one for you does not. Publishing, deleting a project and managing collaborators are out for the same reason in a different currency — those stay deliberate acts you take in umicat.

It cannot throw work away either: umicat only accepts pushes that build on what is already there. See Sending work back.

Revoke it any time from the same settings page. It stops working everywhere immediately.

Your token is never written into a cloned game. It is handed to git one command at a time, so a clone you share, copy or back up carries no credential. The one exception is if you explicitly ask for plain git push support, which writes it to ~/.config/umicat/token — C:\Users\<you>\.config\umicat\token on Windows, which is where it goes there too rather than under AppData.