One conversation's user and assistant text turns, in order; 404 unless it holds a run of this client for this end user.
Scoped to the calling API-key CLIENT (any of its keys — a rotated key reads what its predecessor wrote) and to the one endUserRef named, which is required. Only runs started through the /v1 run routes after this surface shipped carry a client, so earlier runs are not returned. A run another client started under the same conversationId is never included. A user turn is what was sent into the chat: a run's message as the agent received it (a run that carried files ends with an [Attached files: …] line naming them), or a note sent with an approval decision. Tool calls, tool results, delegated specialists' rows and the messages Amy hands the agent itself (such as background-task results) are not part of the transcript.