# `bundle.build_error`: server.ts could not be bundled

A build check error in the area "Bundling server.ts". An error: the game cannot be published until it is fixed.

The build check runs on every game LobbyLab builds, and each problem it finds has a stable code, the exact message, the file and line when it names one, and a link to this page.

## What the check looks at

The check bundles server.ts with the sim kit into one module of at most 1.5 MB.

## How to fix it

Import only names the sim kit exports, fix the build error the message shows, and keep the server small.

See also: [every error code](/docs/errors), [the API reference](/docs/api) and [the docs](/docs).