diff --git a/docs/design/2026-10-12-collectives-architecture.md b/docs/design/2026-10-12-collectives-architecture.md
index 43fe3d1..f811bf6 100644
--- a/docs/design/2026-10-12-collectives-architecture.md
+++ b/docs/design/2026-10-12-collectives-architecture.md
@@ -72,6 +72,11 @@ writes. Workspace-per-collective stays available later if isolation demands it.
 
 ## Rooms per collective
 
+**Collective creation includes the Open (public) room by default — a visible
+toggle lets the founder opt out.** A collective that opts out is fully private
+from day one; one that keeps it gets the outsider door (federated Matrix +
+optional Telegram bridge, below).
+
 | Room | Visibility | Encryption | Federation | Purpose |
 |---|---|---|---|---|
 | Open | Public, listed | **Never** (bot-readable) | **Yes** | Outsiders (any Matrix server) talk to the collective |