diff --git a/go/delivery/delivery_test.go b/go/delivery/delivery_test.go
index f455eb3..9e6b68c 100644
--- a/go/delivery/delivery_test.go
+++ b/go/delivery/delivery_test.go
@@ -127,6 +127,7 @@ func testPulseKey(t *testing.T) {
 
 // 1131/AC4: each value encodes, decodes equal, and carries "v":1.
 func TestRoundTrip(t *testing.T) {
+	t.Run("phase and health refused", testPhaseHealthRefused)
 	hasV1 := func(t *testing.T, b []byte) {
 		t.Helper()
 		var m map[string]any
@@ -343,7 +344,7 @@ func TestUnknownVersion(t *testing.T) {
 }
 
 // 1131/AC6: a phase or health outside the lists is refused on encode and decode.
-func TestPhaseHealthRefused(t *testing.T) {
+func testPhaseHealthRefused(t *testing.T) {
 	for _, p := range []Phase{PhaseBackingUp, PhaseApplying, PhaseChecking, PhaseRunning, PhaseFailed} {
 		for _, h := range []Health{HealthOK, HealthFailed, HealthWaits, HealthUnknown} {
 			if _, err := EncodeHave(Have{Phase: p, Health: h}); err != nil {
diff --git a/go/delivery/judge.go b/go/delivery/judge.go
new file mode 100644
index 0000000..f030401
--- /dev/null
+++ b/go/delivery/judge.go
@@ -0,0 +1,229 @@
+package delivery
+
+import (
+	"bytes"
+	"encoding/json"
+	"path"
+	"sort"
+	"strings"
+
+	"git.novox.be/novox/mesh-sdk/go/declaration"
+)
+
+// The judgement of a move (ADR 0377 §3), as a pure function over two compositions of one module, so the node agent that
+// composes its own modules judges what it would apply (novox/hq ADR 0547 §3; issue 1126's S8). Moved from
+// mesh-controller cmd/mesh-controller/composed_judge.go at origin/main (the controller keeps its copy, unchanged, until
+// it loses the lease, ADR 0547 §1): judged, onlyTheUserList and sameResources, with their helpers, are its code.
+//
+// ADR 0377 §3 over two compositions of one module: **recreates** when a container resource is changed, added or
+// removed; **moves data** when, with no container changed, a directory or file resource is changed, added or removed
+// that a container of the module mounts or that holds or lies within one of its directories (where a module keeps its
+// data), when its `data` declaration changes, or, for a module that declares data, when one of its long-running
+// processes changes; **neither** otherwise, and for a module the node has never run.
+
+// Judged is one move's judgement: what it does, its words, and whether only the bus's user list changes (ADR 0539 §7:
+// a file change and a reload of the bus, no move of it, never asked).
+type Judged struct {
+	Judgement    Judgement
+	Words        string
+	UserListOnly bool
+}
+
+// JudgeMove judges moving a node's module from the composition it runs to the one composed for it. Running is nil when the
+// node runs no composition of the module. A composition equal to the one running (resource for resource, each
+// canonical) is unchanged: no move, and no ask (ADR 0547 §3).
+func JudgeMove(running *Composed, composed Composed) Judged {
+	if composed.Module == "" {
+		return Judged{Judgement: JudgedNeither, Words: "the node's own composition"}
+	}
+	if running == nil {
+		return Judged{Judgement: JudgedNeither, Words: "the node runs no composition of " + composed.Module}
+	}
+	if running.Data == composed.Data && SameComposedResources(*running, composed) {
+		return Judged{Judgement: JudgedUnchanged, Words: "equal to the composition the node runs"}
+	}
+	if onlyTheUserList(*running, composed) {
+		return Judged{Judgement: JudgedNeither, Words: "only the bus's user list changes", UserListOnly: true}
+	}
+	j, words := judged(*running, composed)
+	return Judged{Judgement: j, Words: words}
+}
+
+// busUsersSuffix ends the id of the bus module's user list as the composer writes it: `<module>.bus-users`.
+const busUsersSuffix = ".bus-users"
+
+// onlyTheUserList says two compositions of a module differ, and only in its file of the bus's user list.
+func onlyTheUserList(from, to Composed) bool {
+	if from.Data != to.Data {
+		return false
+	}
+	before, after := judgedResourcesByID(from), judgedResourcesByID(to)
+	if len(before) != len(after) {
+		return false
+	}
+	changed := false
+	for id, now := range after {
+		was, ok := before[id]
+		if !ok {
+			return false
+		}
+		if bytes.Equal(was.raw, now.raw) {
+			continue
+		}
+		if !strings.HasSuffix(id, busUsersSuffix) || now.kind != string(declaration.TypeFile) {
+			return false
+		}
+		changed = true
+	}
+	return changed
+}
+
+// judged applies ADR 0377 §3 to two compositions of one module.
+func judged(from, to Composed) (Judgement, string) {
+	before, after := judgedResourcesByID(from), judgedResourcesByID(to)
+	if ids := changedOf(before, after, func(kind string) bool { return kind == string(declaration.TypeContainer) }); len(ids) > 0 {
+		return JudgedRecreates, "it recreates " + strings.Join(ids, ", ")
+	}
+	if from.Data != to.Data {
+		return JudgedMovesData, "its data declaration changes"
+	}
+	places := dataPlaces(before, after)
+	held := func(kind string) bool {
+		return kind == string(declaration.TypeDirectory) || kind == string(declaration.TypeFile)
+	}
+	var moved []string
+	for _, id := range changedOf(before, after, held) {
+		r := before[id]
+		if r == nil {
+			r = after[id]
+		}
+		if withinPlaces(r.path, places) {
+			moved = append(moved, id)
+		}
+	}
+	if to.Data || from.Data {
+		moved = append(moved, changedOf(before, after, func(kind string) bool { return kind == string(declaration.TypeProcess) })...)
+	}
+	if len(moved) > 0 {
+		sort.Strings(moved)
+		return JudgedMovesData, "it changes where its data is kept: " + strings.Join(moved, ", ")
+	}
+	return JudgedNeither, "it recreates no container and moves no data"
+}
+
+// judgedResource is a resource as the judgement reads it: its kind, the path it acts on, what its containers mount,
+// and its canonical bytes.
+type judgedResource struct {
+	kind   string
+	path   string
+	mounts []string
+	raw    []byte
+}
+
+func judgedResourcesByID(c Composed) map[string]*judgedResource {
+	out := map[string]*judgedResource{}
+	for _, raw := range c.Resources {
+		var head struct {
+			ID   string `json:"id"`
+			Type string `json:"type"`
+			Path string `json:"path"`
+			// A container's volumes, `<path on the machine>:<path inside>[:<options>]`.
+			Volumes []string `json:"volumes"`
+		}
+		if err := json.Unmarshal(raw, &head); err != nil {
+			continue
+		}
+		r := &judgedResource{kind: head.Type, path: head.Path, raw: compactResource(raw)}
+		for _, v := range head.Volumes {
+			source, _, _ := strings.Cut(v, ":")
+			r.mounts = append(r.mounts, source)
+		}
+		out[head.ID] = r
+	}
+	return out
+}
+
+// compactResource is a resource's bytes canonical: its keys sorted, its spacing dropped, its numbers as written, so two
+// compositions that say the same compare equal however each was written.
+func compactResource(raw []byte) []byte {
+	var v any
+	d := json.NewDecoder(bytes.NewReader(raw))
+	d.UseNumber()
+	if err := d.Decode(&v); err != nil {
+		return raw
+	}
+	out, err := json.Marshal(v)
+	if err != nil {
+		return raw
+	}
+	return out
+}
+
+// changedOf are the ids of the resources of the kinds counted that are changed, added or removed, sorted.
+func changedOf(before, after map[string]*judgedResource, counted func(kind string) bool) []string {
+	var out []string
+	for id, now := range after {
+		if !counted(now.kind) {
+			continue
+		}
+		if was, ok := before[id]; !ok || !bytes.Equal(was.raw, now.raw) {
+			out = append(out, id)
+		}
+	}
+	for id, was := range before {
+		if _, ok := after[id]; !ok && counted(was.kind) {
+			out = append(out, id)
+		}
+	}
+	sort.Strings(out)
+	return out
+}
+
+// dataPlaces are the paths where the module keeps what a move must not lose: what its containers mount, and its
+// directories, before and after.
+func dataPlaces(before, after map[string]*judgedResource) []string {
+	var out []string
+	for _, rs := range []map[string]*judgedResource{before, after} {
+		for _, r := range rs {
+			if r.kind == string(declaration.TypeContainer) {
+				out = append(out, r.mounts...)
+			}
+			if r.kind == string(declaration.TypeDirectory) && r.path != "" {
+				out = append(out, r.path)
+			}
+		}
+	}
+	return out
+}
+
+// withinPlaces says p is one of places, or lies within one, or holds one.
+func withinPlaces(p string, places []string) bool {
+	if p == "" {
+		return false
+	}
+	p = path.Clean(p)
+	for _, place := range places {
+		if place == "" || !strings.HasPrefix(place, "/") {
+			continue
+		}
+		place = path.Clean(place)
+		if p == place || strings.HasPrefix(p, place+"/") || strings.HasPrefix(place, p+"/") {
+			return true
+		}
+	}
+	return false
+}
+
+// SameComposedResources says two compositions of a module hold the same resources in the same order, each compared
+// canonical.
+func SameComposedResources(a, b Composed) bool {
+	if len(a.Resources) != len(b.Resources) {
+		return false
+	}
+	for i := range a.Resources {
+		if !bytes.Equal(compactResource(a.Resources[i]), compactResource(b.Resources[i])) {
+			return false
+		}
+	}
+	return true
+}
diff --git a/go/delivery/judge_test.go b/go/delivery/judge_test.go
new file mode 100644
index 0000000..4e61fd5
--- /dev/null
+++ b/go/delivery/judge_test.go
@@ -0,0 +1,68 @@
+package delivery
+
+import (
+	"encoding/json"
+	"strings"
+	"testing"
+)
+
+func composedOf(module string, c byte, data bool, resources ...string) Composed {
+	out := Composed{Node: "ace", Module: module, FP: SourcePrefix2 + strings.Repeat(string(c), 64), Data: data}
+	for _, r := range resources {
+		out.Resources = append(out.Resources, json.RawMessage(r))
+	}
+	return out
+}
+
+// The pairs mesh-controller's composed_judge_test.go captured (issue 1945 AC12), and the bus's user list, judged as the
+// controller judges them (ADR 0377 §3, ADR 0539 §7), by the node agent's function (ADR 0547 §3, issue 1126 S8).
+func TestJudgeMove(t *testing.T) {
+	const (
+		container  = `{"id":"mesh-mail.server","type":"container","module":"mesh-mail","name":"mail","image":"mail@sha256:1111111111111111111111111111111111111111111111111111111111111111","volumes":["/var/lib/mesh-mail/spool:/spool"]}`
+		container2 = `{"id":"mesh-mail.server","type":"container","module":"mesh-mail","name":"mail","image":"mail@sha256:2222222222222222222222222222222222222222222222222222222222222222","volumes":["/var/lib/mesh-mail/spool:/spool"]}`
+		spool      = `{"id":"mesh-mail.spool","type":"directory","module":"mesh-mail","path":"/var/lib/mesh-mail/spool"}`
+		spoolMoved = `{"id":"mesh-mail.spool","type":"directory","module":"mesh-mail","path":"/srv/mesh-mail/spool"}`
+		tools      = `{"id":"mesh-mail.tools","type":"file","module":"mesh-mail","path":"/usr/lib/mesh-mail/tools.json","content":"a"}`
+		tools2     = `{"id":"mesh-mail.tools","type":"file","module":"mesh-mail","path":"/usr/lib/mesh-mail/tools.json","content":"b"}`
+		config     = `{"id":"mesh-mail.conf","type":"file","module":"mesh-mail","path":"/var/lib/mesh-mail/spool/conf","content":"a"}`
+		config2    = `{"id":"mesh-mail.conf","type":"file","module":"mesh-mail","path":"/var/lib/mesh-mail/spool/conf","content":"b"}`
+		process    = `{"id":"mesh-mail.daemon","type":"process","module":"mesh-mail","exec":"/usr/bin/a"}`
+		process2   = `{"id":"mesh-mail.daemon","type":"process","module":"mesh-mail","exec":"/usr/bin/b"}`
+		users      = `{"id":"nats.bus-users","type":"file","module":"nats","path":"/etc/nats/users","content":"a"}`
+		users2     = `{"id":"nats.bus-users","type":"file","module":"nats","path":"/etc/nats/users","content":"b"}`
+		natsConf   = `{"id":"nats.conf","type":"file","module":"nats","path":"/etc/nats/conf","content":"a"}`
+		natsConf2  = `{"id":"nats.conf","type":"file","module":"nats","path":"/etc/nats/conf","content":"b"}`
+	)
+	mail := func(c byte, data bool, rs ...string) *Composed {
+		m := composedOf("mesh-mail", c, data, rs...)
+		return &m
+	}
+	bus := func(rs ...string) *Composed { m := composedOf("nats", 'b', false, rs...); return &m }
+	for _, c := range []struct {
+		name     string
+		from, to *Composed
+		want     Judgement
+		userList bool
+	}{
+		{"a new image", mail('a', true, container, spool, tools), mail('b', true, container2, spool, tools), JudgedRecreates, false},
+		{"a container gone", mail('a', true, container, spool), mail('b', true, spool), JudgedRecreates, false},
+		{"its spool moved", mail('a', true, container, spool), mail('b', true, container, spoolMoved), JudgedMovesData, false},
+		{"a file in its spool", mail('a', true, container, spool, config), mail('b', true, container, spool, config2), JudgedMovesData, false},
+		{"its data declaration", mail('a', false, container, spool), mail('b', true, container, spool), JudgedMovesData, false},
+		{"a process of a module with data", mail('a', true, spool, process), mail('b', true, spool, process2), JudgedMovesData, false},
+		{"a process of a module without", mail('a', false, process), mail('b', false, process2), JudgedNeither, false},
+		{"its tools only", mail('a', true, container, spool, tools), mail('b', true, container, spool, tools2), JudgedNeither, false},
+		{"never ran", nil, mail('b', true, container), JudgedNeither, false},
+		{"equal, written otherwise", mail('a', true, `{"type":"directory","id":"mesh-mail.spool","module":"mesh-mail","path":"/var/lib/mesh-mail/spool"}`), mail('b', true, spool), JudgedUnchanged, false},
+		{"only the user list", bus(natsConf, users), bus(natsConf, users2), JudgedNeither, true},
+		{"the user list and more", bus(natsConf, users), bus(natsConf2, users2), JudgedNeither, false},
+	} {
+		got := JudgeMove(c.from, *c.to)
+		if got.Judgement != c.want || got.UserListOnly != c.userList || got.Words == "" {
+			t.Errorf("%s: %+v, want %s (user list only %v)", c.name, got, c.want, c.userList)
+		}
+	}
+	if got := JudgeMove(nil, Composed{Node: "ace"}); got.Judgement != JudgedNeither {
+		t.Errorf("the node's own composition: %+v", got)
+	}
+}