Backpressure and overflow

welcome.limits negotiates maximum message bytes, batch event count, and batch bytes. Server sessions also enforce local event-count and byte budgets for pending replay/live delivery.

• Sequenced events are never silently dropped or coalesced by transport.
• Ephemeral notifications may use catalog-declared latest_by_scope coalescing and a bounded queue; oldest best-effort notifications may be discarded under pressure.
• Replay and live batches are chunked to negotiated limits.
• If preserving sequenced ordering would exceed the outgoing budget, the server sends goodbye with resync_required and closes. The client reconnects, loads a snapshot when required, and reinstalls subscriptions.

There is no wire-level flow-control message and no event-progress acknowledgement window. Subscription cursors and bounded reconnect recovery are the only event-stream control plane.