diff --git a/docs/ActivityCoreLoop.md b/docs/ActivityCoreLoop.md
index 536999b..6c03c6f 100644
--- a/docs/ActivityCoreLoop.md
+++ b/docs/ActivityCoreLoop.md
@@ -104,3 +104,12 @@ authenticated review/CI/health receipts and failed-health automatic rollback pro
 ArgoCD Core has no reusable API-server token lane; an Application patch grant
 alone would allow more than syncing. ACTIVITY-WP-0041-T03 and RPF-WP-0048-T02 retain
 that work. Consumer enrollment and pattern-editing executor readiness remain open.
+
+The release-broker core is now implemented in activity-core: signed role-bound
+receipts, exact image-only admission, durable serialization, restart recovery,
+and isolated rollback tests. See
+[the implementation boundary](../../activity-core/docs/release-broker.md).
+It is not connected to production credentials or scheduling. Authenticated
+Git/ArgoCD transport, admitted identity, real receipt issuers/continuous observer
+and transport-level rollback proof remain required. This source-only change does
+not reset the production observation window.