diff --git a/cmd/mesh-controller/adoption.go b/cmd/mesh-controller/adoption.go
index 411ae05d..afa90a07 100644
--- a/cmd/mesh-controller/adoption.go
+++ b/cmd/mesh-controller/adoption.go
@@ -424,8 +424,9 @@ func comparisonOf(module string, c comparison, opts takeOptions) (preview string
 	}
 	// And its settings on this machine, composed against its definition (rule 1, rule 6).
 	for _, layer := range c.layers {
-		keys := make([]string, 0, len(layer.Values))
-		for k := range layer.Values {
+		said := layer.Whole()
+		keys := make([]string, 0, len(said))
+		for k := range said {
 			keys = append(keys, k)
 		}
 		sort.Strings(keys)
diff --git a/cmd/mesh-controller/facts.go b/cmd/mesh-controller/facts.go
index 50b891cf..af04f202 100644
--- a/cmd/mesh-controller/facts.go
+++ b/cmd/mesh-controller/facts.go
@@ -348,11 +348,11 @@ func gatherFacts(ctx context.Context, open *stores, busVersion string) (snapshot
 				if layer.From == catalogue.MeshWideLayer {
 					if !meshWide[module] {
 						meshWide[module] = true
-						f.Settings = append(f.Settings, snapshot.Settings{Module: module, Values: scrub.Values(layer.Values)})
+						f.Settings = append(f.Settings, snapshot.Settings{Module: module, Values: scrub.Values(layer.Whole())})
 					}
 					continue
 				}
-				m.Settings = append(m.Settings, snapshot.Settings{Module: module, Values: scrub.Values(layer.Values)})
+				m.Settings = append(m.Settings, snapshot.Settings{Module: module, Values: scrub.Values(layer.Whole())})
 			}
 		}
 		m.Declaration = declarationFacts(ctx, open, n.Name, gens, gensErr, scrub)
diff --git a/cmd/mesh-controller/mesh_for_test.go b/cmd/mesh-controller/mesh_for_test.go
index b2e76be4..eea81d13 100644
--- a/cmd/mesh-controller/mesh_for_test.go
+++ b/cmd/mesh-controller/mesh_for_test.go
@@ -33,7 +33,21 @@ import (
 func aMesh(t *testing.T) *stores {
 	t.Helper()
 	inventory.ForTest(t) // raises the store, migrates it, and points the environment at it
-	licences.ForTest(t)  // planning reaches this one too, by name and never by connection
+	return aMeshOnTheStore(t)
+}
+
+// aMeshBefore is aMesh on a store migrated only below migration `number`, with the function that runs the
+// rest: for a test of what a migration that moves data does to what the mesh composes (novox/hq issue 651).
+func aMeshBefore(t *testing.T, number int) (*stores, func()) {
+	t.Helper()
+	_, migrate := inventory.ForTestBefore(t, number)
+	return aMeshOnTheStore(t), migrate
+}
+
+// aMeshOnTheStore is the mesh aMesh makes, on the store the environment points at.
+func aMeshOnTheStore(t *testing.T) *stores {
+	t.Helper()
+	licences.ForTest(t) // planning reaches this one too, by name and never by connection
 
 	open, err := openStores(t.Context())
 	if err != nil {
diff --git a/cmd/mesh-controller/modules.go b/cmd/mesh-controller/modules.go
index 66804655..dc3ea06c 100644
--- a/cmd/mesh-controller/modules.go
+++ b/cmd/mesh-controller/modules.go
@@ -537,6 +537,10 @@ func settingsCommand(ctx context.Context, args []string) error {
 				if p.SetBy != "" {
 					by = "; " + p.SetBy
 				}
+				if p.Why != "" {
+					// A layer whose placement moved out of it (migration 0097): still the layer, as it stands.
+					by += "; " + p.Why
+				}
 				fmt.Printf("%s on %s, until %s (%s%s):\n  %s\n", positionals[0], where,
 					p.ReplacedAt.Local().Format("2006-01-02 15:04:05"), p.ReplacedBy, by, shown)
 			}
diff --git a/internal/catalogue/data_test.go b/internal/catalogue/data_test.go
index fde16ca2..d60f3356 100644
--- a/internal/catalogue/data_test.go
+++ b/internal/catalogue/data_test.go
@@ -173,7 +173,7 @@ func TestTheBackupHoldersLinesAreDerivedFromTheData(t *testing.T) {
 			{"id":"meta","path":"${dir:meta}","class":"rebuildable"}]},
 		"resources":[{"id":"meta","type":"directory","mode":"0700"}]}`)
 	facts := map[string]string{"account-home": "/home/op"}
-	with := Rendering{Settings: SettingsBy{"media": {{From: "node", Values: map[string]any{AccessesSetting: map[string]any{"films": "/tank/films"}}}}}}
+	with := Rendering{Settings: SettingsBy{"media": {LayerOf("node", map[string]any{AccessesSetting: map[string]any{"films": "/tank/films"}})}}}
 	backup, _, err := seatContributions([]Manifest{pg, agent, media}, Manifest{}, BackupSeat+":"+BackupKindBackup, with, facts, nil)
 	if err != nil {
 		t.Fatal(err)
diff --git a/internal/catalogue/setting_defaults_test.go b/internal/catalogue/setting_defaults_test.go
index f23fb5e1..d5e50dad 100644
--- a/internal/catalogue/setting_defaults_test.go
+++ b/internal/catalogue/setting_defaults_test.go
@@ -427,7 +427,7 @@ func TestALeftOutModulesUnplaceableBackupLineCostsOnlyThatLine(t *testing.T) {
 	r := anAdoptedAnchor()
 	r.Modules = append(r.Modules, holder, media, placedBadly)
 	with := anchorRendering(false)
-	with.Settings["notes"] = []Layer{{From: "anchor", Values: map[string]any{PlacesSetting: "not a map"}}}
+	with.Settings["notes"] = []Layer{LayerOf("anchor", map[string]any{PlacesSetting: "not a map"})}
 	composed, err := r.Compose(with)
 	if err != nil {
 		t.Fatalf("an unplaceable line of a left-out module failed the machine: %v", err)
diff --git a/internal/catalogue/settings_judge_test.go b/internal/catalogue/settings_judge_test.go
index 50d96222..cbb494c9 100644
--- a/internal/catalogue/settings_judge_test.go
+++ b/internal/catalogue/settings_judge_test.go
@@ -27,7 +27,7 @@ func TestASettingThatCannotComposeIsRefusedByNameAndLeavesOnlyItsModuleOut(t *te
 		if c.name == "a mesh-wide port" {
 			from = MeshWideLayer
 		}
-		err := JudgeSettings(web, []Layer{{From: from, Values: c.layer}}, true)
+		err := JudgeSettings(web, []Layer{LayerOf(from, c.layer)}, true)
 		if err == nil || !strings.Contains(err.Error(), c.refuse) {
 			t.Errorf("%s: judged %v, want %q", c.name, err, c.refuse)
 		}
@@ -69,8 +69,8 @@ func TestASettingThatCannotComposeIsRefusedByNameAndLeavesOnlyItsModuleOut(t *te
 // declaration as the networks it also joins.
 func TestAKeptNetworkReachesTheContainerOnAnAdoptedMachineOnly(t *testing.T) {
 	r := anAdoptedAnchor()
-	keep := SettingsBy{"hello-web": {{From: "anchor",
-		Values: map[string]any{NetworksSetting: map[string]any{"server": []any{"predecessor_default"}}}}}}
+	keep := SettingsBy{"hello-web": {LayerOf("anchor",
+		map[string]any{NetworksSetting: map[string]any{"server": []any{"predecessor_default"}}})}}
 
 	with := anchorRendering(true)
 	with.Settings = keep
@@ -107,13 +107,13 @@ func TestAKeptNetworkReachesTheContainerOnAnAdoptedMachineOnly(t *testing.T) {
 		layer Layer
 		want  string
 	}{
-		{"mesh-wide", Layer{From: MeshWideLayer, Values: map[string]any{NetworksSetting: map[string]any{"server": []any{"x"}}}},
+		{"mesh-wide", LayerOf(MeshWideLayer, map[string]any{NetworksSetting: map[string]any{"server": []any{"x"}}}),
 			"a found network is a fact about one machine"},
-		{"an unknown container", Layer{From: "anchor", Values: map[string]any{NetworksSetting: map[string]any{"db": []any{"x"}}}},
+		{"an unknown container", LayerOf("anchor", map[string]any{NetworksSetting: map[string]any{"db": []any{"x"}}}),
 			`names the container "db", which it does not declare`},
-		{"not a list", Layer{From: "anchor", Values: map[string]any{NetworksSetting: map[string]any{"server": "x"}}},
+		{"not a list", LayerOf("anchor", map[string]any{NetworksSetting: map[string]any{"server": "x"}}),
 			"is a list of network names"},
-		{"not a network name", Layer{From: "anchor", Values: map[string]any{NetworksSetting: map[string]any{"server": []any{"a/b"}}}},
+		{"not a network name", LayerOf("anchor", map[string]any{NetworksSetting: map[string]any{"server": []any{"a/b"}}}),
 			"which is not a network name"},
 	} {
 		_, err := KeptNetworks(web, []Layer{c.layer}, true)
diff --git a/internal/catalogue/terminal_settings_test.go b/internal/catalogue/terminal_settings_test.go
index ac767cfd..d822a896 100644
--- a/internal/catalogue/terminal_settings_test.go
+++ b/internal/catalogue/terminal_settings_test.go
@@ -13,22 +13,22 @@ func TestAPlacementOrAnAccessAtTheMachinesOwnIsRefused(t *testing.T) {
 	for _, path := range []string{"/", "/etc", "/etc/", "/etc/sudoers.d", "/usr/bin", "/root", "/var", "/var/lib",
 		"/home", "/home/", "/run", "/run/user/1000", "/var/lib/mesh/x", "/var/lib/mesh-host", "/var/lib/mesh-host/identity",
 		"/srv/../etc", "//etc", "/proc/1", "/sys", "/dev", "/boot/efi", "/bin", "/sbin", "/lib", "/lib64"} {
-		layers := []Layer{{From: "laptop", Values: map[string]any{PlacesSetting: map[string]any{"data": path}}}}
+		layers := []Layer{LayerOf("laptop", map[string]any{PlacesSetting: map[string]any{"data": path}})}
 		if _, err := Places(m, layers); err == nil || !strings.Contains(err.Error(), "issue 339") {
 			t.Errorf("a place at %s: %v", path, err)
 		}
-		layers = []Layer{{From: "laptop", Values: map[string]any{AccessesSetting: map[string]any{"media": path}}}}
+		layers = []Layer{LayerOf("laptop", map[string]any{AccessesSetting: map[string]any{"media": path}})}
 		if _, err := AccessPlaces(m, layers); err == nil || !strings.Contains(err.Error(), "issue 339") {
 			t.Errorf("an access at %s: %v", path, err)
 		}
 	}
 	for _, path := range []string{"/srv/notes", "/mnt/plex/data", "/storage/media", "/services/media/movies",
 		"/var/lib/notes/data", "/home/restic/repo", "/var/lib/mesh-store"} {
-		layers := []Layer{{From: "laptop", Values: map[string]any{PlacesSetting: map[string]any{"data": path}}}}
+		layers := []Layer{LayerOf("laptop", map[string]any{PlacesSetting: map[string]any{"data": path}})}
 		if got, err := Places(m, layers); err != nil || got["data"].Path != path {
 			t.Errorf("a place at %s: %v %v", path, got, err)
 		}
-		layers = []Layer{{From: "laptop", Values: map[string]any{AccessesSetting: map[string]any{"media": path}}}}
+		layers = []Layer{LayerOf("laptop", map[string]any{AccessesSetting: map[string]any{"media": path}})}
 		if got, err := AccessPlaces(m, layers); err != nil || got["media"] != path {
 			t.Errorf("an access at %s: %v %v", path, got, err)
 		}
@@ -111,17 +111,17 @@ func TestTheRuntimesDataAndAnyHomesSSHAreTheMachinesOwn(t *testing.T) {
 	for _, path := range []string{"/var/spool", "/var/spool/cron", "/var/lib/docker", "/var/lib/docker/volumes",
 		"/var/lib/containers/storage", "/var/lib/containerd", "/var/lib/containerd/io.containerd.snapshotter.v1", "/opt", "/opt/app", "/home/alice/.ssh", "/home/alice/.ssh/keys",
 		"/srv/backup/.ssh", "/root/.ssh"} {
-		layers := []Layer{{From: "laptop", Values: map[string]any{PlacesSetting: map[string]any{"data": path}}}}
+		layers := []Layer{LayerOf("laptop", map[string]any{PlacesSetting: map[string]any{"data": path}})}
 		if _, err := Places(m, layers); err == nil || !strings.Contains(err.Error(), "issue 339") {
 			t.Errorf("a place at %s: %v", path, err)
 		}
-		layers = []Layer{{From: "laptop", Values: map[string]any{AccessesSetting: map[string]any{"media": path}}}}
+		layers = []Layer{LayerOf("laptop", map[string]any{AccessesSetting: map[string]any{"media": path}})}
 		if _, err := AccessPlaces(m, layers); err == nil || !strings.Contains(err.Error(), "issue 339") {
 			t.Errorf("an access at %s: %v", path, err)
 		}
 	}
 	for _, path := range []string{"/var/lib/dockerish", "/home/alice/ssh", "/home/alice/.sshd-notes", "/storage/media"} {
-		layers := []Layer{{From: "laptop", Values: map[string]any{PlacesSetting: map[string]any{"data": path}}}}
+		layers := []Layer{LayerOf("laptop", map[string]any{PlacesSetting: map[string]any{"data": path}})}
 		if _, err := Places(m, layers); err != nil {
 			t.Errorf("a place at %s: %v", path, err)
 		}
diff --git a/testdata/store-tests b/testdata/store-tests
index bbfc1467..d3af9659 100644
--- a/testdata/store-tests
+++ b/testdata/store-tests
@@ -61,3 +61,6 @@
 ./cmd/mesh-controller TestAProviderElsewhereServesItsOwnComposedName
 ./cmd/mesh-controller TestAReusedCheckBuildIsRegisteredByItsDigestAndGatedAsABuiltOne
 ./internal/inventory TestAReportOfABusyContainerIsKeptAndReadBack
+./internal/inventory TestPlacementMovesOutOfTheSettingsLayers
+./internal/inventory TestASettingRoutesPlacementBesideTheLayer
+./cmd/mesh-controller TestADeclarationIsTheSameAfterPlacementMoves