bun.sh/docs/cli/link.md

Use bun link in a local directory to register the current package as a "linkable" package.

$ cd /path/to/cool-pkg
$ cat package.json
{
  "name": "cool-pkg",
  "version": "1.0.0"
}
$ bun link
bun link v1.x (7416672e)
Success! Registered "cool-pkg"

To use cool-pkg in a project, run:
  bun link cool-pkg

Or add it in dependencies in your package.json file:
  "cool-pkg": "link:cool-pkg"

This package can now be "linked" into other projects using bun link cool-pkg. This will create a symlink in the node_modules directory of the target project, pointing to the local directory.

$ cd /path/to/my-app
$ bun link cool-pkg

In addition, the --save flag can be used to add cool-pkg to the dependencies field of your app's package.json with a special version specifier that tells Bun to load from the registered local directory instead of installing from npm:

  {
    "name": "my-app",
    "version": "1.0.0",
    "dependencies": {
+     "cool-pkg": "link:cool-pkg"
    }
  }

To unregister a local package, navigate to the package's root directory and run bun unlink.

$ cd /path/to/cool-pkg
$ bun unlink
bun unlink v1.x (7416672e)