diff --git a/cmd/mesh-controller/join_through_the_tunnel_test.go b/cmd/mesh-controller/join_through_the_tunnel_test.go
new file mode 100644
index 0000000..5782644
--- /dev/null
+++ b/cmd/mesh-controller/join_through_the_tunnel_test.go
@@ -0,0 +1,102 @@
+package main
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/novox/mesh-controller/internal/inventory"
+)
+
+// aMachineJoining is a machine with a live token issued for a tunnel key, given its address — what
+// `token issue --overlay-key` records before it pushes the hub (novox/hq ADR 0169).
+func aMachineJoining(t *testing.T, ctx context.Context, inv *inventory.Inventory, name string,
+	validFor time.Duration) string {
+	t.Helper()
+	record, err := inv.AddNode(ctx, name)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := inv.IssueToken(ctx, name, validFor); err != nil {
+		t.Fatal(err)
+	}
+	key := aPublicKey(t)
+	if err := inv.RecordOverlayKey(ctx, record.ID, key); err != nil {
+		t.Fatal(err)
+	}
+	if err := inv.BindTokenToKey(ctx, record.ID, key); err != nil {
+		t.Fatal(err)
+	}
+	cidr, err := overlayRange(ctx, inv)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := inv.AssignAddress(ctx, record.ID, cidr); err != nil {
+		t.Fatal(err)
+	}
+	return key
+}
+
+// hubPeers are the keys the hub's composed tunnel carries.
+func hubPeers(t *testing.T, ctx context.Context, inv *inventory.Inventory) map[string]bool {
+	t.Helper()
+	g, err := network(ctx, inv, map[string]bool{"anchor": true, "laptop": true}, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	out := map[string]bool{}
+	for _, p := range g.Graph()["anchor"] {
+		out[p.Key] = true
+	}
+	return out
+}
+
+// **A machine joining is a peer of the hub while its token can be used, and not after** (novox/hq
+// ADR 0169): the hub's composed tunnel carries a machine whose token was issued for its key, so the
+// tunnel answers the first time it knocks; a token that expired unused takes the peer with it at the
+// hub's next composition.
+func TestAMachineJoiningIsAPeerOfTheHubUntilItsTokenExpires(t *testing.T) {
+	open := aMesh(t)
+	ctx := t.Context()
+	inv := open.inventory
+
+	joining := aMachineJoining(t, ctx, inv, "joiner", time.Hour)
+	expired := aMachineJoining(t, ctx, inv, "late", 2*time.Second)
+	time.Sleep(2100 * time.Millisecond)
+
+	peers := hubPeers(t, ctx, inv)
+	if !peers[joining] {
+		t.Fatalf("the hub does not carry the machine its live token was issued for: %v", peers)
+	}
+	if peers[expired] {
+		t.Fatalf("the hub still carries a machine whose token expired unused: %v", peers)
+	}
+
+	// A token issued without a key gives the hub nothing to carry: there is no key to carry.
+	if _, err := inv.AddNode(ctx, "keyless"); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := inv.IssueToken(ctx, "keyless", time.Hour); err != nil {
+		t.Fatal(err)
+	}
+	if after := hubPeers(t, ctx, inv); len(after) != len(peers) {
+		t.Fatalf("a token issued without a key changed the hub's peers: %v, was %v", after, peers)
+	}
+}
+
+// **A tunnel key that is not one is refused before anything is recorded** (novox/hq ADR 0169): a
+// token issued for it would be a tunnel the hub could never answer.
+func TestATokenIsNotIssuedForSomethingThatIsNotATunnelKey(t *testing.T) {
+	open := aMesh(t)
+	ctx := t.Context()
+	record, err := open.inventory.AddNode(ctx, "joiner")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, _, err := throughTheTunnel(ctx, open, record, "not-a-key", "10.77.0.1:4222"); err == nil {
+		t.Fatal("a token was issued for something that is not a tunnel key")
+	}
+	if held := placementOf(t, ctx, open.inventory, "joiner"); held.Key != "" || held.Address != "" {
+		t.Fatalf("a refused key left a record behind: %+v", held)
+	}
+}