message.read fires when a message your agent sent reaches Read.
Read the payload
This is an example envelope. Thedata object is the MessageEvent schema from the API contract; the fields around it are the same on every event and are described in the event catalog. Route on event_type, deduplicate on event_id, and keep trace_id for support:
These fields have the same names and values as the Message object that your agent reads for the same message.
sender_handle still arrives and is deprecated: read from_handle.
Handle the event
Read is optional and advances only when the other side marks the chat read, so treat its absence as unknown rather than unread.read_at is set in this event and null in the earlier message.sent and message.delivered events for the same message. In a group chat the app does not show read labels.

