DeploymentService.GetInstanceStalenessAsync shares a FlattenSession across
the batch, reads only the (InstanceId, RevisionHash) projection and pays the
snapshot read + I-1 List normalisation only for a mismatch, so the fleet
aggregate agrees exactly with the per-instance Topology badge. The I-1 logic
is extracted from GetDeploymentComparisonAsync unchanged.
Claude-Session: https://claude.ai/code/session_01Y5ef34iUUMjmwnMpL9xgmB