Concepts
Messages and relations
Understand ordering, parts, replies, edits, deletion, and reactions.
Every durable conversation item receives a monotonically increasing sequence. Text and attachments are represented as ordered message parts with stable identifiers.
Delivery behavior
- Client message IDs make sends idempotent.
- Sequence numbers provide deterministic ordering.
- Edits use expected revisions to prevent lost updates.
- Delete-for-everyone produces a tombstone rather than removing history.
Replies
Replies point to a message in the same conversation and retain a small quote snapshot. If the source message is later deleted, an already-sent reply can still explain what it referred to without exposing the original full payload.
Reactions
Reactions are allowlisted, transactionally toggled, and aggregated per message. They stay inside the chat invariant boundary so membership and message lifecycle checks cannot drift from a separate reaction store.