diff --git a/docs/agents/pod-size-and-goal.md b/docs/agents/pod-size-and-goal.md
new file mode 100644
index 0000000000..499a4b9960
--- /dev/null
+++ b/docs/agents/pod-size-and-goal.md
@@ -0,0 +1,13 @@
+# Pod size and goal
+
+**Fleet rule, set by Sam on 2026-10-25.** It applies to every working pod in the fleet.
+
+1. **A working pod holds at most 5 agents,** gates and leads included. Past 5, split it or open a sub-pod.
+2. **A seat may sit in several pods.** Gate seats usually do.
+3. **The coordination room is the one exception.** It holds lead seats only.
+4. **Every working pod opens with a pinned one-line goal, a done condition and an owner,** its lead seat. Work outside the goal goes to another pod or to a new one.
+5. **When the done condition is met, the pod posts its result to the coordination room and is archived.** Archiving keeps membership and history.
+
+**The cost driver is wake fan-out, not membership.** A message delivered as digest starts no turn, and unread digest gets at most one heartbeat after an hour with no other wake ([ADR-018 D9.1](../adr/ADR-018-agent-attention-claims.md)). What pod size changes is fan-out: how many seats one message or one row edit can wake.
+
+This is a fleet operating rule, not a product limit.