Acknowledgments

Acknowledgments answer: what does a participant or substrate claim has happened?

An acknowledgment is a signal that some boundary accepted responsibility, persisted data, processed input, advanced a cursor, committed a transition, or completed a narrower protocol step. Its meaning is defined by the protocol and boundary that emit it.

Acknowledgment is not the same as domain commitment. A transport acknowledgment may only mean bytes were received. A broker acknowledgment may mean the broker accepted a message or that a consumer advanced an offset. A workflow acknowledgment may mean a checkpoint committed. A command response may mean an entity transition committed. These claims should not be treated as interchangeable.

Common Meanings

An acknowledgment may mean:

Accepted for transmission.
Accepted by a broker or channel.
Persisted by a broker or store.
Delivered to a consumer process.
Processed by an application handler.
Committed by an entity transition.
Recorded as a workflow checkpoint.
Offset, cursor, or claim advanced.
Responsibility transferred to another participant.

The model should state which one applies.

Failure Modes

Acknowledging too early can lose work. For example, a consumer that commits an offset before committing its local transition may not receive the input again after a crash.

Acknowledging too late can duplicate work. For example, a consumer that commits local state but crashes before acknowledging the broker may receive the same input again and must rely on idempotency, expected versions, or a transactional inbox.

Acknowledgment therefore belongs with delivery semantics, commit boundaries, recovery, and effect design.