Optional ReadonlymuteAssignable mute groups — a READ projection of the console's own mute groups, and on the way in a LEGACY field migrated by consoleMuteGroups. Never captured: see MuteGroupJson (audit D6).
Optional ReadonlypanicPanic targets for the always-visible mains-mute / all-mute.
Optional ReadonlysparesPer-channel pre-declared spare inputs (one-tap swap-to-spare).
The session's gig-safety pre-loads. All fields optional/empty by default.