Loom Doctor

Tools > Loom > Doctor is the first stop when setup or startup fails. It checks the environment Unity can actually see and reports the result in the Unity Console.

For first-run verification, import Getting Started, run Setup UI Project and Setup UI in Current Scene, then enter Play mode before running Doctor. The Vite server is intentionally idle before Play, and generated bridge files do not exist until a bridge has compiled. Firefox is optional unless you want browser DevTools.

Tools > Loom > Status Window shows the same checks in a dockable window.

Node.js found

Checks that Node.js 22 or 24 LTS is available to the Unity Editor process.

If red, install a supported LTS release or launch Unity from an environment where that Node.js installation is on PATH.

npm found

Checks that npm 10 or 11 is available. Loom needs npm to install UI dependencies and run production UI builds.

If red, reinstall Node.js or fix PATH for the Unity process.

Vite dev server

Checks whether the UI dev server can start and respond.

Doctor reports the URL of Loom’s managed server. It does not inspect or attach to Vite processes started from a terminal or coding agent.

If red, run Tools > Loom > Restart Dev Server and inspect the Unity Console for npm or Vite output. Restart a standalone server from the terminal or agent that owns it; Loom will not terminate that process.

Native plugin

Checks that the platform plugin for your OS is present.

If red after installing or upgrading Loom, restart Unity. If it stays red, reinstall the package.

Firefox DevTools

Checks whether Loom can open Firefox for browser DevTools.

If red, install Firefox or debug without DevTools.

Generated bridge types

Checks whether generated UI bridge files exist and look current.

If red, run:

Tools > Loom > Regenerate Types

Then restart the dev server.

Build cache

Checks cached build/runtime files that can become stale after package upgrades.

If red after an upgrade, restart Unity and rerun the check.