a .kern file is a zip archive with a specific layout. you build it from your plugin source.

my-plugin.kern  (a zip)
├─ manifest.json     (required)
├─ dist/
│  ├─ index.js       (optional — the esm ui bundle)
│  └─ index.css      (optional — injected into the shadow root)
└─ …any other assets your bundle references

build your ui bundle to dist/index.js (esm, exporting mount), then zip the manifest + dist/ (+ assets) into a .kern file. the kern app has a create_plugin_package helper that does the zipping for you against a validated manifest.

for local development you can drop a .kern into kern’s plugin directory (or double-click it to trigger kern://install) and the host will pick it up. this lets you iterate on a plugin without going through the registry.