I'm not sure what causes my problem, so I'd like to raise an issue here:

In my monorepo (with pnpm workspaces, CJS modules), I have a couple of packages built with tsup, and all of them are used in the the cli package like this:

"scripts": {
    "build": "tsup index.ts --dts-resolve"
  },
  "bin": {
    "cli": "dist/index.js"
  },
  "devDependencies": {
    "first": "workspace:*",
    "second": "workspace:*"
  },

As you can see, I use workspace packages in the CLI, bundle them with tsup and create a bin out of it. The problem becomes clear when I create a project to test the CLI:

{
  "scripts": {
    "start": "cli"
  },
  "dependencies": {
    "cli": "0.1.0",
    "first": "0.1.0",
    "second": "0.1.0"
  }
}

If I include all worspace packages into dependencies, then the cli script runs perfectly. But without these dependencies, it raises an issue that some code is unavailable. It got me thinking: does tsup actually include workspace dependencies inside its bundle?