bitchat Architecture: How Do You Deliver a Message With No Internet and No Radio Range?
bitchat is a P2P messenger with no accounts and no servers. Nearby devices form a BLE mesh; distant peers are reached over Nostr. The center of this piece is the four-layer store-and-forward stack that answers "the recipient is not here right now" — a sealed outbox, courier envelopes addressed by nothing but an HMAC tag plus spray-and-wait, GCS-filter public history sync, and Nostr mailboxes — traced through the code.