diff --git a/cmd/mesh-controller/foundation_scope_test.go b/cmd/mesh-controller/foundation_scope_test.go
deleted file mode 100644
index 9ff8591..0000000
--- a/cmd/mesh-controller/foundation_scope_test.go
+++ /dev/null
@@ -1,33 +0,0 @@
-package main
-
-// The broker opening belongs only on the node that listens on it (novox/hq: it leaked onto
-// every enrolled node's declaration, opening a from-anywhere hole for a port nothing there
-// serves). foundationPortsFor is the scope.
-
-import (
-	"testing"
-
-	"github.com/novox/mesh-controller/internal/catalogue"
-)
-
-func TestTheBrokerHostGetsTheFoundationOpening(t *testing.T) {
-	broker := catalogue.Manifest{Module: "lavinmq", Listens: []catalogue.Listening{
-		{Port: 5671, Protocol: "tcp", From: "mesh"},
-		{Port: 5672, Protocol: "tcp", From: "mesh"},
-	}}
-	got := foundationPortsFor(5671, []catalogue.Manifest{broker})
-	if len(got) != 1 || got[0] != 5671 {
-		t.Fatalf("the node that listens on the broker port keeps it; got %v", got)
-	}
-}
-
-func TestANodeThatOnlyDialsTheBrokerGetsNoOpening(t *testing.T) {
-	// ace's set: things that reach the broker as a client, none listening on 5671.
-	ace := []catalogue.Manifest{
-		{Module: "plex", Listens: []catalogue.Listening{{Port: 32400, Protocol: "tcp", From: "anywhere"}}},
-		{Module: "postgres", Listens: []catalogue.Listening{{Port: 5432, Protocol: "tcp", From: "mesh"}}},
-	}
-	if got := foundationPortsFor(5671, ace); got != nil {
-		t.Fatalf("a node that only dials out opens nothing for the broker; got %v", got)
-	}
-}
diff --git a/cmd/mesh-controller/plan.go b/cmd/mesh-controller/plan.go
index 4eb5873..4300808 100644
--- a/cmd/mesh-controller/plan.go
+++ b/cmd/mesh-controller/plan.go
@@ -16,8 +16,6 @@ import (
 	"github.com/novox/mesh-controller/internal/inventory"
 	"github.com/novox/mesh-controller/internal/licences"
 	"github.com/novox/mesh-controller/internal/overlay"
-	"net"
-	"strconv"
 )
 
 // working out what one machine should be.
@@ -648,25 +646,12 @@ func renderingFor(ctx context.Context, open *stores, node string,
 		names[name] = at
 	}
 
-	// The ports the mesh itself needs open, which no module declares. Read from the broker this
-	// control plane was told about rather than written down twice: the address a node is handed in
-	// its token and the port its machine must accept on are the same fact.
-	//
-	// **Only on the node that listens on it** (novox/hq issue: the broker opening leaked onto
-	// every node). The opening exists to WIDEN the broker's port to from-anywhere — a machine
-	// enrolling is not on the mesh yet, so the broker's own `from: mesh` listen would refuse its
-	// first dial. That widening belongs on the broker's host and nowhere else: a node that only
-	// dials out needs no incoming rule, and an opening for a port nothing here listens on is a
-	// from-anywhere hole for a dead port. So the foundation port is kept only when a module
-	// resolved onto THIS node actually listens on it.
+	// **The bus is never public** (novox/hq ADR 0169). It was a foundation port — widened from the
+	// broker's own `from: mesh` to from-anywhere on the broker's host, so a machine could enrol
+	// before it had an address on the private network. A machine joins through the tunnel now, and
+	// every link to the bus crosses it, so its reach is what the `nats` module declares: the mesh.
+	// Nothing the mesh itself needs is opened beyond what a module declares.
 	var foundation []int
-	if b, err := broker.FromEnvironment(); err == nil {
-		if _, port, err := net.SplitHostPort(b.Address); err == nil {
-			if n, err := strconv.Atoi(port); err == nil {
-				foundation = foundationPortsFor(n, plan.Modules)
-			}
-		}
-	}
 
 	// And, for a module that keeps them, every operator-sealed secret in the mesh — the vault's
 	// copy, outside the store (novox/hq ADR 0085, amended). Read only; nothing here mints. The
@@ -1380,23 +1365,6 @@ func composeBusUsers(ctx context.Context, inv *inventory.Inventory,
 	return broker.ComposeAccounts(filled)
 }
 
-// foundationPortsFor is the broker port, kept only when a module resolved onto this node listens
-// on it (novox/hq issue: the broker opening leaked onto every node). The foundation opening
-// exists to WIDEN the broker's `from: mesh` port to from-anywhere, because a machine enrolling is
-// not on the mesh yet and its first dial would be refused. That widening belongs on the broker's
-// host alone: a node that only dials out needs no incoming rule, and an opening for a port
-// nothing here listens on is a from-anywhere hole for a dead port.
-func foundationPortsFor(brokerPort int, modules []catalogue.Manifest) []int {
-	for _, m := range modules {
-		for _, l := range m.Listens {
-			if l.Port == brokerPort {
-				return []int{brokerPort}
-			}
-		}
-	}
-	return nil
-}
-
 // providerModuleOf is which module answers a need on the providing node: the one in this node's
 // own set when the provider is here, else the one the catalogue says offers it.
 func providerModuleOf(resolved catalogue.Resolution, open *stores, ctx context.Context, n catalogue.Needed) string {
diff --git a/internal/catalogue/the_bus_is_never_public_test.go b/internal/catalogue/the_bus_is_never_public_test.go
new file mode 100644
index 0000000..84371ca
--- /dev/null
+++ b/internal/catalogue/the_bus_is_never_public_test.go
@@ -0,0 +1,23 @@
+package catalogue
+
+import (
+	"regexp"
+	"testing"
+)
+
+// The bus is never public (novox/hq ADR 0169). Its port is what the bus module declares, the mesh,
+// and the control plane adds no opening of its own: a machine joins through the tunnel, so the
+// broker's host is filtered like any other. Before this, the broker port was a foundation port and
+// rendered from anywhere beside its from-the-mesh rule.
+func TestTheBusPortIsReachedFromTheMeshAlone(t *testing.T) {
+	rules := []Rule{{Port: 4222, Protocol: "tcp", From: FromMesh, Because: []string{"nats"},
+		Why: []string{"the mesh bus"}}}
+	out := AsNftables(rules, []string{"10.10.0.1", "10.10.0.2"}, true, nil, []string{"eth0"}, "mesh0")
+
+	if !regexp.MustCompile(`ip saddr \{ 10\.10\.0\.1, 10\.10\.0\.2 \} tcp dport 4222 accept`).MatchString(out) {
+		t.Fatalf("the bus is not reachable from the mesh:\n%s", out)
+	}
+	if regexp.MustCompile(`(?m)^\s*tcp dport 4222 accept`).MatchString(out) {
+		t.Fatalf("the bus is reachable from anywhere:\n%s", out)
+	}
+}