useMessageMetadata

Read metadata recorded for a specific message id — today exposes parentCheckpointId, the checkpoint the message was first seen on. Designed for fork / edit flows:

const meta = useMessageMetadata(stream, () => msg.id);
// meta.value?.parentCheckpointId

messageId accepts a raw string, a Ref<string | undefined>, or a getter — the binding re-evaluates whenever the id changes.