The switch to release 6 is today's controller's last plan, and the bus runs the user list it composes until the new
controller writes one: so the new controller's writes of each node's compositions and their digests, each new
node-engine's reads of its own compositions and wants and its backup holder's verbs and word, and the assigner's read
of the digests must be granted by this controller already (ADR 0539 clauses 2, 6, 9 and 16; the review's A1).