Serialize concurrent datasource publications

docs/QUALITY_POLICY.md

@@ -90,6 +90,12 @@ changed quality policy. Publication also emits a transactional
 module stores it in the durable outbox, while reduced installations deliver it
 through Core after commit.
 
+PostgreSQL deployments serialize publication attempts by tenant, producer, and
+idempotency key with a transaction-scoped advisory lock before replay lookup.
+This makes concurrent retries from separate API or worker nodes converge on the
+same publication and materialization rather than relying on a late uniqueness
+failure after output rows have already been persisted.
+
 Approval authority, approval expiry, and retention/deletion execution remain
 separate work under `govoplan-datasources#2`. Until those contracts are added,
 no JSON flag is treated as an approval and no stage is deleted automatically.