mold

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Claude Desktop ​

Claude Desktop (and claude.ai) can use mold through two pieces that one command sets up:

  • The mold skill: instructions and prompting guides Claude loads when you ask for images or video. Desktop keeps skills on your Claude account, so the skill is uploaded as a ZIP and then follows you to the web and mobile apps.
  • The mold connector: a local MCP server (mold mcp) that Desktop starts on your computer. Chat skills run in Anthropic's cloud sandbox, which has no mold binary and cannot reach your machines, so the connector is how Claude actually lists, generates and fetches prints.

Install ​

Pair your GPU host first if it is not this computer (see Remote Workflows), then run:

bash
mold skill install claude-desktop

It does three things:

  1. Writes ~/Downloads/mold-skill.zip, the skill folder zipped as Claude expects (mold/SKILL.md at the top level).
  2. Adds mcpServers.mold to Claude Desktop's claude_desktop_config.json (~/Library/Application Support/Claude/ on macOS, %APPDATA%\Claude\ on Windows). The previous file is kept as claude_desktop_config.json.mold-backup. The connector runs this mold binary as mold mcp and talks to your default host (mold host use NAME); when MOLD_HOME is set, it is passed through, since Desktop does not read your shell environment.
  3. Opens Customize > Skills and shows the ZIP in your file manager.

Then finish in Claude Desktop:

  1. Quit and reopen Claude Desktop so it starts the connector.
  2. Customize > Skills > Add, upload mold-skill.zip, and turn it on. Remove or replace an older mold skill there first.
  3. Make sure Settings > Capabilities > Code execution and file creation is on; Claude needs it to use any skill.

Ask something like "what's on my mold host's queue?" or "show my latest prints". Claude loads the skill and answers with the connector's tools (server_status, list_gallery, generate_image, …).

There is no API for uploading a skill to a personal Claude account, which is why the upload step is manual. Re-run the command after upgrading mold. It replaces its own ZIP and connector entry. mold skill list shows whether the connector is in place and whether the ZIP is current.

Options ​

bash
mold skill install claude-desktop --host workstation       # pin the connector to one saved host
mold skill install claude-desktop --output ./mold-skill.zip
mold skill install claude-desktop --no-connector           # only write the ZIP
mold skill install claude-desktop --no-open                # print the steps, open nothing
mold skill show claude-desktop                             # the SKILL.md that goes in the ZIP
mold skill uninstall claude-desktop

Mold never overwrites a file it did not write. Overwriting an --output path that holds some other file needs --force. So does replacing an mcpServers.mold entry that mold did not write, or one edited since mold wrote it. Mold records the entry it wrote in claude_desktop_config.json.mold-connector. uninstall removes only that recorded entry and the ZIP mold put in Downloads. Remove the uploaded skill yourself under Customize > Skills.

Connector without the skill ​

To wire mold mcp into Desktop by hand instead, add this to claude_desktop_config.json and restart Desktop:

json
{
  "mcpServers": {
    "mold": {
      "command": "/path/to/mold",
      "args": ["mcp", "--host", "workstation"]
    }
  }
}

The connector never renders on this computer: mold mcp talks to a mold server over HTTP and has no local-GPU fallback.