Phase 66 · concurrency / shared-substrate stress front · AT-0628 → AT-0640

One trip is not a network.

Every result before this one moved a single payload through an empty world. A network has many at once, and they collide. The exact-graph concurrency sweep exceeded our runtime budget, so rather than fabricate exact numbers we publish a labelled proxy: route length L ≈ 1.6 log₂ N taken from the measured localized routes, about four nodes locally active per flow, one move per node per tick, and random sparse route overlap. Two layers are computed and never mixed — a closed-form congestion law from expected pairwise overlap, and an event-driven token simulation over the same assumption where policies, tails, fairness and adversarial hotspots live. This is an engineering-style audit of a toy router. It promotes nothing.