portal, boundary, or DOM ref cannot attach to its declared target

Why this fires¶

TE749 reports an attach contract that cannot be fulfilled. The compiler catches statically empty portal targets; the development attach verifier also reports missing portal targets, stale island markers, invalid binding properties, and refs that do not belong to the island.

portal(target: "") { <Dialog /> }
// error[TE749]: portal target cannot be empty

Fix it¶

Provide a real DOM selector and destination, restore the required island markers, or correct the ref/binding owner. Runtime reports are available from ZoloClient.verifyAttach() in development.