Module core 

The Engine struct + test-only constructor + registration accessors. Hot-path poll cycle lives in engine::poll.

Structs

BudgetExceededReason

Failure case returned by Engine::try_charge when admitting byte_count more bytes against ingress_byte_budget would exceed the cap. budget_remaining is the cap minus the live ingress_bytes_in_flight at the time of the rejection — the caller embeds both into the resulting WireReceiveError or AppIngressError so subscribers see the magnitude of the rejection without re-querying the engine.

Engine

Single-Node engine state. Built via Node::ensure_ready; tests use Engine::new() and seed fields directly.

EngineStats

Point-in-time hot-path counters for dashboards + saturation detection. Not synchronized against an in-flight poll cycle.