At their core, a bundler's main goal is to take a bunch of files and turn them into a few optimized files that you ship to the browser. The admin UI has a root
index.html entry point, and from there the bundler traverses the dependency tree, bundling all of the files that are required from that point on.
Since the bundled file is sent to the browser, it can't include any server-only code. You will need to remove any server-only code from your admin UI before bundling it. You can learn more about excluding server code section.