Loom Doctor

Tools > Loom > Doctor checks Loom’s dependencies and reports failures in the Unity Console. It checks the environment of the Unity process, which can differ from your terminal.

On a new project, finish setup and enter Play mode before running Doctor. Vite does not start until Play, and type generation requires a compiled bridge. You can ignore the Firefox check if you do not use 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 Loom’s managed dev server is running and has reported its URL.

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 in the Loom package.

If red, reinstall Loom GUI from Package Manager. If it stays red, contact support@snack.onl.

Firefox DevTools

Checks whether Loom can open Firefox for browser DevTools.

If red, install Firefox or debug without DevTools.

Generated bridge types

Checks whether UI/generated/bridge.d.ts exists.

If red, stop Play mode and resolve any C# compilation errors. Loom regenerates these files automatically after recompilation. If they remain missing or stale, regenerate them manually:

Tools > Loom > Regenerate Types

Then restart the dev server.

Build cache

Checks whether the production UI build in UI/dist is older than the files in UI/src. The check passes when there is no UI/dist, because the Editor serves the UI from the dev server.

If red, run Tools > Loom > Build UI for Player to rebuild it. Player builds also rebuild the UI automatically.