node-message-bus: the machine's D-Bus is a node seat (hq ADR 0215)

internal/catalogue/seat_contributions.go

@@ -17,6 +17,9 @@ import (
 // HotkeysSeat is the machine's hotkey daemon (novox/hq ADR 0212 §5).
 const HotkeysSeat = "node-hotkeys"
 
+// MessageBusSeat is the machine's D-Bus (novox/hq ADR 0215).
+const MessageBusSeat = "node-message-bus"
+
 // SeatContribution is one piece of configuration a module gives a seat's holder to place.
 type SeatContribution struct {
 	// Seat is the seat whose holder places it.

internal/catalogue/seats.go

@@ -217,6 +217,10 @@ var defaultSeats = append([]Seat{
 	// configuration. Every other module with keys contributes trigger lines to it.
 	{Name: HotkeysSeat, Scope: ScopeNode, Decision: "novox/hq ADR 0212",
 		Receives: []Receivable{{Kind: "trigger", Comment: "#"}}},
+	// The machine's message bus (novox/hq ADR 0215): its holder owns the D-Bus implementation and its
+	// system service, never restarts it live, and publishes curated events about it, never its traffic.
+	// It receives nothing yet: packages ship their own policies.
+	{Name: MessageBusSeat, Scope: ScopeNode, Decision: "novox/hq ADR 0215"},
 	// Deferred (novox/hq ADR 0121): renaming to mesh-private-network is a scope + server/client
 	// model change, not a rename, so it stays until that is built.
 	{Name: "the-private-network", Scope: ScopeNode, Decision: "novox/hq ADR 0110"},

internal/catalogue/seats_test.go

@@ -46,14 +46,14 @@ func TestTheSeatsAreAClosedSetAndEachNamesItsDecision(t *testing.T) {
 			delivered[s.Delivers] = s.Name
 		}
 	}
-	// Thirty-six with mesh-dns-resolver (novox/hq ADR 0194) and node-hosts-file (ADR 0199); thirty-four
+	// Thirty-seven with node-message-bus (novox/hq ADR 0215); thirty-six with mesh-dns-resolver (novox/hq ADR 0194) and node-hosts-file (ADR 0199); thirty-four
 	// with node-hotkeys (ADR 0212); thirty-three with node-power (ADR 0211); thirty-two since the
 	// graphical session's eleven (ADR 0208); twenty-one with node-package-manager and
 	// node-container-runtime (ADR 0207); nineteen with node-environment and node-login-shell (ADR 0203,
 	// ADR 0204); seventeen with node-build-agent (ADR 0190). Two fewer once the retired
 	// mesh-build-machine and node-dns-resolver rows go, when no registered manifest claims either.
-	if len(Seats()) != 36 {
-		t.Errorf("the mesh defines %d seats rather than 36; the set is closed, so a change here is "+
+	if len(Seats()) != 37 {
+		t.Errorf("the mesh defines %d seats rather than 37; the set is closed, so a change here is "+
 			"a decision (novox/hq ADR 0110): %s", len(Seats()), seatNames())
 	}
 }