# Require an Exclusive Active BYOC Customer Account

One BYOC customer AWS account may belong to only one active CP9 BYOC session at
a time. The account may be reused sequentially, but a new session must fail
closed until the prior session's normal destroy and zero-residual proof are
complete. CP9 records the customer account in the immutable session fingerprint
and treats any live foreign session marker or setup ownership conflict as a
pre-mutation blocker.

This constraint preserves one lifecycle owner for the production account-global
CloudFormation stack names and fixed IAM runtime roles. Concurrent sessions in
one customer account would update or adopt the same resources, make cleanup
unsafe, and force session-derived substitutes that weaken production fidelity.
The control-plane account remains shareable through the existing CP9 ownership
and session-isolation model; exclusivity applies only to the configured BYOC
customer account.