GET /v2/chats/{chat_id}/messages/{message_id}/receipts

Members only. Eligible recipients are the members present when the message was sent, excluding the author; late joiners never appear and former members keep what they earned. Each recipient includes conversation-wide last_read_sequence and last_delivered_sequence when supported. To render a receipt only on the latest outgoing message, fetch this endpoint for that message, follow every next_cursor, and compare its sequence with each recipient's read position. A nonempty complete eligible set must cover the message before showing Read by all. Refetch for a new outgoing message, membership change or reconnect; receipt.updated can advance known recipients between fetches. Groups above 50 members require on-demand refresh. Existing read/delivered flags and summary remain available, including as fallback when cursor fields are absent during rollout. Receipts stay inside the chat and never notify.