diff --git a/internal/broker/process_state_watch_test.go b/internal/broker/process_state_watch_test.go
new file mode 100644
index 00000000..3f9b2081
--- /dev/null
+++ b/internal/broker/process_state_watch_test.go
@@ -0,0 +1,41 @@
+package broker
+
+import "testing"
+
+// 1840/AC9: a process account declaring the state `x` may watch and list the keys of its module's own bucket (a consumer
+// created and deleted on KV_<module>_x), read and write it, and has no grant on another module's bucket or on a mirror of the
+// controller's, whatever it is named after.
+func TestAProcessMayWatchItsOwnStateAndNoOthers(t *testing.T) {
+	p := Principal{Kind: KindProcess, Node: "novox", Module: "mesh-mail", Process: "send", State: []string{"x"}}
+	got := perms(t, p)
+	for _, s := range []string{
+		"$JS.API.CONSUMER.CREATE.KV_mesh-mail_x",
+		"$JS.API.CONSUMER.CREATE.KV_mesh-mail_x.watcher",
+		"$JS.API.CONSUMER.CREATE.KV_mesh-mail_x.watcher.$KV.mesh-mail_x.>",
+		"$JS.API.CONSUMER.DELETE.KV_mesh-mail_x.watcher",
+		"$JS.API.DIRECT.GET.KV_mesh-mail_x.$KV.mesh-mail_x.key",
+		"$JS.API.STREAM.INFO.KV_mesh-mail_x",
+		"$JS.FC.KV_mesh-mail_x.watcher",
+		"$KV.mesh-mail_x.key",
+	} {
+		if !allowed(got.Publish, s) {
+			t.Errorf("the process may not publish %s, so it cannot watch or list its own state", s)
+		}
+	}
+	for _, other := range []string{"mesh-other_x", "mesh-mail_y", DeclaredPackagesBucket, AssignmentsBucket} {
+		for _, s := range []string{
+			"$JS.API.CONSUMER.CREATE.KV_" + other,
+			"$JS.API.CONSUMER.CREATE.KV_" + other + ".watcher",
+			"$JS.API.CONSUMER.CREATE.KV_" + other + ".watcher.$KV." + other + ".>",
+			"$JS.API.CONSUMER.DELETE.KV_" + other + ".watcher",
+			"$JS.API.DIRECT.GET.KV_" + other + ".$KV." + other + ".key",
+			"$JS.API.STREAM.INFO.KV_" + other,
+			"$JS.FC.KV_" + other + ".watcher",
+			"$KV." + other + ".key",
+		} {
+			if allowed(got.Publish, s) {
+				t.Errorf("the process may publish %s, on a bucket that is not its own state", s)
+			}
+		}
+	}
+}