Individual-node campaigns may add topology.media_zones. A zone names a
non-overlapping set of stable node IDs and defines bandwidth, propagation
latency, loss, MTU, and queue capacity. The native workbench can partition the
configured population into deterministic round-robin zones.
Every graph edge whose endpoints are in the same zone uses the conservative combination of endpoint and zone limits. More importantly, all such edges use one half-duplex serialization domain and one queue. Concurrent control, Bloom, lookup, session, and payload frames therefore delay or reject one another even when they traverse different graph edges. Per-edge counters remain separate; their queue occupancy records the shared medium pressure observed at enqueue.
Cross-zone edges retain endpoint-derived conditions because the current schema models intra-zone media, not an implicit routed backbone. A node cannot belong to more than one zone. Invalid membership, non-positive capacity, or an out-of-range node fails before execution.
The event stream exposes media_zone on nodes and shared_medium_group on
edges. The workbench's Shared media view colors zone membership and emphasizes
contending edges. Individual runs provide exact deterministic enqueue order.
Cohort runs aggregate zone contention and carry the
shared-media-zone-aggregation/v1 approximation label.