diff --git a/docs/turn-loop.md b/docs/turn-loop.md
index 75cef004..7e704198 100644
--- a/docs/turn-loop.md
+++ b/docs/turn-loop.md
@@ -571,6 +571,18 @@ ttl_seconds?, to?)`, `answer(id, answer)`, `ack_until(up_to)`.
   `ack_until(N)` to prevent re-pop. Acked rows never redeliver.
   Transient pings (sentinel id 0) have nothing to ack and show no marker.
 
+**System messages** (from sender `system`): lifecycle and Q&A events
+delivered as regular inbox messages (same `recv` path; body is a JSON
+object with an `event` discriminant field). The **submitting agent**
+(the root agent for top-level containers; an agent with the `approvals`
+tool group for its own subtree) receives lifecycle events (`spawned`,
+`rebuilt`, `killed`, `destroyed`, `container_crash`, `needs_login`,
+`logged_in`, `config_ready`, `needs_update`, `approval_resolved`). Any
+agent receives Q&A events when it is the declared target
+(`question_asked`) or the asker (`question_answered`). Full payload
+shapes and routing logic in
+[`docs/approvals.md` § Helper events](../approvals.md#helper-events-to-the-submitting-agent).
+
 **Inbox** (`inbox` group): `get_loose_ends(agent?)`,
 `cancel_loose_end(kind, id)`, `remind(message, delay_seconds? |
 at_unix_timestamp?)`, `request_next_turn()`.