The zone a private service's synthesized A record hangs under was derived
from the serving proxy's address or from a validated custom domain. A
placement-free endpoint matches neither, so the apex came out empty, the
service was skipped, and the tenant's hostname resolved to nothing -- with no
error logged.
Synthesized services now carry their zone explicitly and it is preferred when
deriving the apex. The field is in-memory only: these services are built per
read and never persisted, and the zone cannot be supplied as a parameter
instead because it is captured per account at allocation time, so a single
current-config value would misclassify any tenant allocated under a previous
one.
A blanket "use the parent of the hostname" fallback was rejected: the same
empty apex also occurs for a service whose domain has no validated entry for
its cluster, and those resolve to nothing deliberately, so a blanket fallback
would turn domain validation into a no-op.
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