Exercise a real one-target ManagedClientGroup through timeout, Draining, a gated retained reply, LateReply classification, local close, and authoritative TargetFinished publication. Synchronize release after EchoLoss and a scheduler-handled no-op update so the ordering is deterministic rather than delay-dependent.
Add a silent-server control that verifies completion only after the final-drain deadline, and assert bounded join, queued-event draining through disconnection, target counters, terminal outcome equality, and group aggregates in both cases.
Harden the analogous single-client late-drain test with a viable one-probe run window and packet-shape checks. No production final-drain behavior change was required.