Notification Engine

PH-12 owns the domain decisions (which communication codes exist, delivery retry/expiration policy, when a Notification is created); ENG-01's Communication delivery scaffold (§8, ENG01-20) owns the transport mechanics underneath it, mirroring the same domain/mechanics split PH-08's Connector framework already established for payment execution.

Pipeline

PH-12's deliverable (Notification creation, Template rendering, delivery via a CommunicationAdapter). Not yet built. The claim-based P2P flow makes this load-bearing, not cosmetic — the recipient cannot claim funds without successfully receiving an invitation.

Channels

Twilio (SMS) and SendGrid (email) are the current-lean delivery providers (open — ENG-01 §4/Decision Register ENG02-25), per docs/build-buy.md. Adapter implementations are ENG01-20's deliverable. Not yet built.

Idempotency

Governed by the shared STD-01 CommandIdempotencyRecord mechanism (same pattern as PH-03/PH-07/PH-08/PH-10/PH-11) plus PH-12's own delivery-specific idempotency handling. Not yet built.