Consumer Messaging Platform — WhatsApp-Class System · View 06 of 23

Message Send and Delivery Path

The primary flow: compose, encrypt, accept, fan out, deliver and confirm — with the idempotency gate that makes a client retry harmless.

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Ordering and identity

The client assigns client_msg_id; the server assigns the authoritative message_id
A duplicate client_msg_id replays the original server id instead of creating a second message
Per-conversation ordering follows server id, so two devices converge on the same sequence

Guarantees

At-least-once on the wire, exactly-once as observed by the user through client-side dedupe
The server acknowledges only after the ciphertext is durably written
Ciphertext is deleted the moment every recipient device has acknowledged it

State ownership

The server sets one state only: sent
Delivered, read and played are always emitted by the recipient device
A recipient with receipts disabled stops the chain at delivered