diff --git a/internal/broker/seattools_test.go b/internal/broker/seattools_test.go
index ed24e1f..2f83c5a 100644
--- a/internal/broker/seattools_test.go
+++ b/internal/broker/seattools_test.go
@@ -5,16 +5,16 @@ import "testing"
 // A node-scoped seat's tool carries the node (novox/hq ADR 0132, design 33 §4): two nodes holding one
 // node-scoped seat derive two addresses, and a user of the seat may publish any node's.
 func TestTwoNodesHoldingOneNodeSeatDeriveTwoToolAddresses(t *testing.T) {
-	seat := Seat{Name: "node-hosts-file", Scope: "node", Serves: []string{"entries"}}
-	one, _ := PermissionsFor(Principal{Kind: KindModule, Node: "one", Module: "hosts", Holds: []Seat{seat}, PasswordHash: "x"})
-	two, _ := PermissionsFor(Principal{Kind: KindModule, Node: "two", Module: "hosts", Holds: []Seat{seat}, PasswordHash: "x"})
-	has(t, one.Subscribe, "mesh.seat.node-hosts-file.tool.entries.one")
-	has(t, two.Subscribe, "mesh.seat.node-hosts-file.tool.entries.two")
-	hasNot(t, one.Subscribe, "mesh.seat.node-hosts-file.tool.entries")
-	hasNot(t, one.Subscribe, "mesh.seat.node-hosts-file.tool.entries.two")
+	seat := Seat{Name: "node-hostname", Scope: "node", Serves: []string{"entries"}}
+	one, _ := PermissionsFor(Principal{Kind: KindModule, Node: "one", Module: "hostname", Holds: []Seat{seat}, PasswordHash: "x"})
+	two, _ := PermissionsFor(Principal{Kind: KindModule, Node: "two", Module: "hostname", Holds: []Seat{seat}, PasswordHash: "x"})
+	has(t, one.Subscribe, "mesh.seat.node-hostname.tool.entries.one")
+	has(t, two.Subscribe, "mesh.seat.node-hostname.tool.entries.two")
+	hasNot(t, one.Subscribe, "mesh.seat.node-hostname.tool.entries")
+	hasNot(t, one.Subscribe, "mesh.seat.node-hostname.tool.entries.two")
 
 	user, _ := PermissionsFor(Principal{Kind: KindModule, Node: "three", Module: "asker", Uses: []Seat{seat}, PasswordHash: "x"})
-	has(t, user.Publish, "mesh.seat.node-hosts-file.tool.entries.*")
+	has(t, user.Publish, "mesh.seat.node-hostname.tool.entries.*")
 }
 
 // A mesh-scoped seat's tool stays flat: nothing about it changes.
diff --git a/internal/catalogue/hostname_seat_test.go b/internal/catalogue/hostname_seat_test.go
new file mode 100644
index 0000000..c151efa
--- /dev/null
+++ b/internal/catalogue/hostname_seat_test.go
@@ -0,0 +1,98 @@
+package catalogue
+
+import (
+	"strings"
+	"testing"
+)
+
+// novox/hq ADR 0223 part 3: a machine's names are one seat's. The `hosts` module holding
+// `node-hosts-file` became `hostname` holding `node-hostname`, which writes /etc/hostname beside the
+// machine's own lines in /etc/hosts. The seat was renamed (ADR 0122), so what claims the old name — a
+// manifest registered before the rename — still holds the one seat.
+
+func withHostnameAlias(t *testing.T) {
+	t.Helper()
+	was := aliases
+	t.Cleanup(func() { aliases = was })
+	UseAliases(map[string]string{"node-hosts-file": "node-hostname"})
+}
+
+func TestTheHostsFilesFormerNameResolvesToTheHostnameSeat(t *testing.T) {
+	if _, known := SeatNamed("node-hostname"); !known {
+		t.Fatal("node-hostname is not in the mesh's set")
+	}
+	withHostnameAlias(t)
+	seat, known := SeatNamed("node-hosts-file")
+	if !known || seat.Name != "node-hostname" || seat.Scope != ScopeNode {
+		t.Fatalf("the former name did not resolve: %+v %v", seat, known)
+	}
+	var verbs []string
+	for _, v := range seat.Serves {
+		verbs = append(verbs, v.Name)
+	}
+	if strings.Join(verbs, " ") != "entries add remove" {
+		t.Errorf("the renamed seat serves %v; its verbs are unchanged", verbs)
+	}
+}
+
+// One seat under either name: the module registered before the rename and the one after cannot both
+// hold it on one machine.
+func TestTheOldAndTheNewClaimantAreOneSeatOnAMachine(t *testing.T) {
+	withHostnameAlias(t)
+	cat := shelf(
+		mod("hosts", nil, nil, nil, Claim{Name: "node-hosts-file"}),
+		mod("hostname", nil, nil, nil, Claim{Name: "node-hostname"}),
+	)
+	_, err := Resolve(cat, []string{"hosts", "hostname"}, workstation(), World{})
+	if err == nil || !strings.Contains(err.Error(), "node-hostname") {
+		t.Errorf("hosts and hostname both held the machine's names on one machine: %v", err)
+	}
+	if _, err := Resolve(cat, []string{"hosts"}, workstation(), World{}); err != nil {
+		t.Errorf("a machine still assigned hosts under the old name does not resolve: %v", err)
+	}
+}
+
+// The catalogue's module: /etc/hostname is the operator's `hostname` setting. Without it the module is
+// left out, naming the key — the mesh never renames a machine on its own — and a mesh-wide setting
+// naming ${machine:name} gives every machine its mesh name.
+func TestTheMachinesNameIsItsSetting(t *testing.T) {
+	cat := map[string]Manifest{"hostname": catalogueManifest(t, "hostname")}
+	got, err := Resolve(cat, []string{"hostname"}, Node{Name: "ace", At: "ace.internal"}, World{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	machines := map[string]string{"ace.internal": "10.42.0.2"}
+	nameOf := func(settings SettingsBy) (string, string) {
+		t.Helper()
+		composed, err := got.Compose(Rendering{Names: machines, Machines: machines, Suffix: "internal",
+			Settings: settings})
+		if err != nil {
+			t.Fatal(err)
+		}
+		if why := composed.LeftOut["hostname"]; why != "" {
+			return "", why
+		}
+		for _, r := range composed.Resources {
+			if r["path"] == "/etc/hostname" {
+				return r["content"].(string), ""
+			}
+		}
+		t.Fatal("no /etc/hostname composed")
+		return "", ""
+	}
+
+	if _, why := nameOf(nil); !strings.Contains(why, "hostname") {
+		t.Errorf("with no setting the machine's name was written, or left out for another reason: %q", why)
+	}
+	if name, why := nameOf(SettingsBy{"hostname": {{From: "ace", Values: map[string]any{"hostname": "Ace"}}}}); name != "Ace\n" {
+		t.Errorf("the operator's name for the machine gave %q (%s)", name, why)
+	}
+	mesh := Layer{From: "the mesh", Values: map[string]any{"hostname": "${machine:name}"}}
+	if name, why := nameOf(SettingsBy{"hostname": {mesh}}); name != "ace\n" {
+		t.Errorf("a mesh-wide ${machine:name} gave %q (%s)", name, why)
+	}
+	node := Layer{From: "ace", Values: map[string]any{"hostname": "Ace"}}
+	if name, why := nameOf(SettingsBy{"hostname": {mesh, node}}); name != "Ace\n" {
+		t.Errorf("a machine's own name over the mesh-wide one gave %q (%s)", name, why)
+	}
+}
diff --git a/internal/catalogue/resolve.go b/internal/catalogue/resolve.go
index 2970872..b0972a7 100644
--- a/internal/catalogue/resolve.go
+++ b/internal/catalogue/resolve.go
@@ -816,13 +816,17 @@ func checkClaims(modules []Manifest, node Node, elsewhere []Held, holdings []Hel
 			if byScope[scope] == nil {
 				byScope[scope] = map[string]string{}
 			}
-			if other, taken := byScope[scope][c.Name]; taken {
+			// **One seat under either of its names** (novox/hq ADR 0122): a manifest registered before
+			// a rename claims the former name, and one written after it the current — two claimants of
+			// one seat, compared by the seat they resolve to and not by how each spelled it.
+			seat := canonicalSeat(c.Name)
+			if other, taken := byScope[scope][seat]; taken {
 				problems = append(problems, fmt.Sprintf(
 					"%s and %s both claim %q, and only one thing may hold it per %s",
-					other, m.Module, c.Name, scope))
+					other, m.Module, seat, scope))
 				continue
 			}
-			byScope[scope][c.Name] = m.Module
+			byScope[scope][seat] = m.Module
 			held = append(held, Held{Claim: c.Name, Scope: scope, Node: node.Name,
 				Module: m.Module, Site: node.Site})
 		}
@@ -831,7 +835,7 @@ func checkClaims(modules []Manifest, node Node, elsewhere []Held, holdings []Hel
 	// And against the rest of the mesh, for the scopes that reach past this machine.
 	for _, h := range held {
 		for _, e := range elsewhere {
-			if e.Node == node.Name || e.Claim != h.Claim || e.Scope != h.Scope {
+			if e.Node == node.Name || canonicalSeat(e.Claim) != canonicalSeat(h.Claim) || e.Scope != h.Scope {
 				continue
 			}
 			switch h.Scope {
@@ -862,6 +866,15 @@ func checkClaims(modules []Manifest, node Node, elsewhere []Held, holdings []Hel
 	return held, problems
 }
 
+// canonicalSeat is the seat a claimed name refers to, by its current name: itself for a name the mesh
+// does not know (a module's own seat), its seat's name for a former one.
+func canonicalSeat(name string) string {
+	if s, known := SeatNamed(name); known {
+		return s.Name
+	}
+	return name
+}
+
 // checkResources refuses two modules writing the same thing.
 //
 // This costs no manifest field: the mesh already holds every resource of every module, so two
diff --git a/internal/catalogue/seats.go b/internal/catalogue/seats.go
index aa1949a..8177582 100644
--- a/internal/catalogue/seats.go
+++ b/internal/catalogue/seats.go
@@ -149,10 +149,12 @@ var defaultSeats = append([]Seat{
 	// requirement resolves to a holder wherever they are placed.
 	{Name: "mesh-dns-resolver", Scope: ScopeMesh, Delivers: "wildcard-resolution", Replicated: true,
 		Decision: "novox/hq ADR 0194, ADR 0223"},
-	// **A machine's /etc/hosts is one module's** (novox/hq ADR 0199): its holder writes the machine's
-	// own lines and keeps every other line as the operator's, changed through these three verbs on that
-	// machine alone. The controller holds none of it.
-	{Name: "node-hosts-file", Scope: ScopeNode, Decision: "novox/hq ADR 0199",
+	// **A machine's names are one module's** (novox/hq ADR 0199, ADR 0223): its holder writes
+	// /etc/hostname and the machine's own lines in /etc/hosts, and keeps every other line of the hosts
+	// file as the operator's, changed through these three verbs on that machine alone. The controller
+	// holds none of it. Named node-hosts-file until ADR 0223; the former name resolves to it as an
+	// alias on a mesh that knew it.
+	{Name: "node-hostname", Scope: ScopeNode, Decision: "novox/hq ADR 0199, ADR 0223",
 		Serves: []Verb{
 			{Name: "entries", Description: "Every line of this machine's /etc/hosts, each marked whose it is: " +
 				"the operator's, or the block of the module or tool that writes it.",
diff --git a/internal/catalogue/seats_test.go b/internal/catalogue/seats_test.go
index f36cf1b..506fd5a 100644
--- a/internal/catalogue/seats_test.go
+++ b/internal/catalogue/seats_test.go
@@ -49,7 +49,8 @@ func TestTheSeatsAreAClosedSetAndEachNamesItsDecision(t *testing.T) {
 	// Thirty-six since node-resolver-config retired into node-uplink (novox/hq ADR 0223); thirty-seven
 	// since the retired node-dns-resolver went (novox/hq ADR 0220); thirty-eight with
 	// node-backup (novox/hq ADR 0214); 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
+	// thirty-six with mesh-dns-resolver (novox/hq ADR 0194) and node-hosts-file (ADR 0199, now
+	// node-hostname); 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,
diff --git a/internal/inventory/migrations/0064-a-machines-names-are-one-seats.sql b/internal/inventory/migrations/0064-a-machines-names-are-one-seats.sql
new file mode 100644
index 0000000..120695b
--- /dev/null
+++ b/internal/inventory/migrations/0064-a-machines-names-are-one-seats.sql
@@ -0,0 +1,23 @@
+-- A machine's names are one seat's (novox/hq ADR 0223 part 3): `node-hosts-file` is renamed
+-- `node-hostname`, whose holder writes /etc/hostname beside the machine's own lines in /etc/hosts.
+--
+-- A rename is a database update (ADR 0122): the row keeps its verbs, the former name becomes an alias
+-- that resolves to it, so a manifest registered under the old name — the `hosts` module still assigned
+-- while machines move to `hostname` — goes on holding the one seat, and two claimants of it on one
+-- machine are still refused.
+--
+-- **Both rows may exist when this runs**, as 0048 found for the artifact store: a controller whose
+-- compiled defaults carry the new name may seed it before this migration. Then the old row's holding
+-- moves to it and the old row goes; otherwise the old row is renamed. Either way the old name becomes
+-- an alias.
+update seat_holding set seat = 'node-hostname'
+  where seat = 'node-hosts-file'
+    and exists (select 1 from seat where name = 'node-hostname');
+delete from seat
+  where name = 'node-hosts-file'
+    and exists (select 1 from seat where name = 'node-hostname');
+update seat set name = 'node-hostname', decided = 'novox/hq ADR 0199, ADR 0223'
+  where name = 'node-hosts-file';
+insert into seat_alias (alias, seat) values ('node-hosts-file', 'node-hostname')
+  on conflict (alias) do update set seat = excluded.seat;
+update seat_alias set seat = 'node-hostname' where seat = 'node-hosts-file';
diff --git a/internal/overlay/generator.go b/internal/overlay/generator.go
index 9f1a475..062de5b 100644
--- a/internal/overlay/generator.go
+++ b/internal/overlay/generator.go
@@ -32,8 +32,8 @@ const Requirement = "private-network"
 // Name is the module that answers it with WireGuard.
 //
 // **It writes no names.** A machine's mesh names are answered by the mesh's one resolver (novox/hq
-// ADR 0194), and /etc/hosts is the file of one module, the holder of `node-hosts-file` (ADR 0199): the
-// controller writes into no file another seat's holder owns. If the mesh ever needs a line there, it
+// ADR 0194), and /etc/hosts is the file of one module, the holder of `node-hostname` (ADR 0199,
+// ADR 0223): the controller writes into no file another seat's holder owns. If the mesh ever needs a line there, it
 // asks that holder to register it. This module asked for a `node-names` fact written into /etc/hosts
 // until 2026-10-05; the host gives that region back at the first push without it.
 const Name = "mesh-wireguard"