The preview is a computer

Your product generates apps for users, and every generated app needs a preview. The usual answer is a browser-side emulation of a runtime: impressive, and bounded by everything a browser tab can't be.

On Hoody the preview is the app's own container URL in an iframe. It's a real Linux machine: the generated backend actually listens, the database is actually a file on disk, the background worker actually runs. The user clicks around the real thing, and when generation continues, the same machine updates under them.

Emulation asks how much of a computer a preview can fake. A container doesn't ask: it serves.