Optional ReadonlyclosedMerged or closed while a child was still open; kept, frozen, so the child's prompt does not change under it.
ReadonlyentriesReadonlyfreshA fresh thread's prompt is its own entries only; a fork's starts with its parent's.
Optional ReadonlymodeHow the thread opened; absent for a turn. The session engine's merge policy is per mode.
Optional ReadonlyownerOptional ReadonlyparentOptional ReadonlypurposeTitle and owner a light thread's siblings see it by.
ReadonlyseenFeed position of the last event the thread saw when it opened (its from.event); parent entries placed later
were written concurrently and are not in its prompt.
Entries written in an open thread or turn, merged into
parent(absent: main) when it ends.