Jackson codec for the envelope and audit records, shared by every transport and store that serialises them (H10: an event must stand on its own).

JDBC backend (DD-07, DD-11): state, inbox, audit and outbox in one transaction on a plain DataSource, plus a stored rule set source and a task store.

MongoDB backend (DD-07, DD-11): state, inbox, audit and outbox via mongodb-driver-sync, with a single multi-document transaction on a replica set and a documented single-document fallback for a standalone server, plus a stored rule set source ...

Kafka transport (DD-08, DD-09, DD-11): per-entity ordering by partition key, redelivery with a dead-letter topic, no delayed delivery.

Spring Boot starter (DD-13): one dependency and a `lifecycle.*` YAML block wire guards, rule sources, the store, the transport, the engine, the dispatcher, tasks, and the actuator surface.