Player builds

In the Editor, Loom serves your UI from a live dev server with hot reload. In a player build, that dev server doesn’t exist; the UI ships as a pre-built static bundle loaded from the game’s StreamingAssets.

It builds automatically

Loom installs a build hook that runs your UI’s production build on every player build (File -> Build And Run, or a CI batchmode build). You don’t have to remember a separate step:

1. Unity starts the player build.
2. The hook runs your UI’s production build (npm run build).
3. If the UI build fails, the player build aborts with the error in the Console, so a broken UI never ships silently.
4. Unity finishes building the player with the freshly built UI bundled in StreamingAssets.

To run the UI build on its own without building the player (handy for checking output), use Loom -> Build UI for Player.

Where the build lands

Your UI’s vite.config.ts writes the production bundle to a dist/ folder next to it (<ProjectRoot>/UI/dist/). The build hook then copies that dist/ into Assets/StreamingAssets/Loom/, which is where the runtime loads the UI from in a player build. You don’t point Vite at StreamingAssets yourself, build.outDir must stay dist:

// <ProjectRoot>/UI/vite.config.ts
export default defineConfig({
  plugins: [solid(), loom()],
  base: './',                 // required, for relative asset URLs
  build: {
    outDir: 'dist',           // the hook copies UI/dist into StreamingAssets/Loom
    emptyOutDir: true,
    assetsInlineLimit: 0,     // keep assets as separate files
  },
})

base: './' is required. The bundle is loaded from local files, not a web server root, so asset URLs must be relative.

Requirements

• Node.js must be available on the build machine (including CI). The hook shells out to npm run build.
• Dependencies must be installed. If UI/node_modules is missing, the hook skips the build with a warning. Run Loom -> Sync UI Dependencies first. (On CI, run your UI’s npm install as a build step before the Unity build.)

Mock mode does not ship

A player build always runs the connected bridge, it talks to your game’s C#. The mock actions and scenarios you use during development (Mock mode) are inert when the bridge connects to a real engine, so there’s nothing to strip; they simply don’t run.

Checklist before shipping

• build.outDir is dist, base: './' (the hook copies it into StreamingAssets/Loom/).
• Loom -> Sync UI Dependencies has been run (so node_modules exists).
• Node.js is available wherever you build the player.
• Loom -> Doctor -> Build cache is green (or just rely on the automatic build hook).
• Graphics API and render pipeline match Supported platforms.