Seals a message with AES-GCM-256 inside the Worker — the random key goes only into the link fragment, the ciphertext into the generated page — and produces snap.html, a self-contained page that arms itself on first open by moving the ciphertext into that browser's localStorage, then shows the message exactly once when the one-time link is opened and deletes it. The same page is a compose app for new snaps with optional expiry. Because the store is localStorage, both sides must use the same browser profile: this is a hand-off on a shared computer or a note to your future self, and the page and notes say so plainly. The sandboxed preview has no storage, so it only shows the interface.