causation_id is an optional opaque value that points to the single earlier event
that led to the event carrying it. Correlation is shared context; causation points.
Use the earlier event’s id, whether it came from your service or an upstream
service. The value may name an event Reconify has not received, and it is not
resolved at ingest.
Value rules
The value must be 1 to 200 visible ASCII characters.null, empty, whitespace-
padded, control-character, or overlong values are rejected. It need not have an
evt_ shape; it is opaque evidence.
Idempotency
causation_id is part of the canonical event payload. Retrying a stored id with
a changed, added, or removed causation ID returns idempotency_conflict; retrying
the unchanged event returns duplicate.
Reconify preserves the claim and returns it on event reads. It does not infer
causation from ordering or timing, and sharing a causation value does not merge
operations. See Trace a flow across services.