Who we ask, and who covers them

One named subject-matter expert per epic, from the business that owns the outcome. The SME answers questions during discovery and elaboration, and signs off that we understood the ask. The Product Owner names the backup — that is the person planning talks to when the primary is on leave, in a filing, or otherwise unavailable. An epic with a primary and no backup is a single point of failure on the planning calendar, so it shows amber until the PO fills it.