diff --git a/internal/builder/siblings_test.go b/internal/builder/siblings_test.go
index 5fd1fd2c..edeab57a 100644
--- a/internal/builder/siblings_test.go
+++ b/internal/builder/siblings_test.go
@@ -56,6 +56,12 @@ func (w aSiblingWorld) beside() map[string]Beside {
 
 // hostCheck is the node-engine's pull request checked, with or without its sibling.
 func (w aSiblingWorld) hostCheck(t *testing.T, id, workspace, cache string, siblings ...Sibling) CheckVerdict {
+	t.Helper()
+	return w.hostCheckAs(t, "", id, workspace, cache, siblings...)
+}
+
+// hostCheckAs is hostCheck for a request that names who judges: an older request says "validator" for a node-engine change.
+func (w aSiblingWorld) hostCheckAs(t *testing.T, judge, id, workspace, cache string, siblings ...Sibling) CheckVerdict {
 	t.Helper()
 	if workspace == "" {
 		workspace = t.TempDir()
@@ -63,7 +69,7 @@ func (w aSiblingWorld) hostCheck(t *testing.T, id, workspace, cache string, sibl
 	beside := w.beside()
 	delete(beside, "mesh-host")
 	v, err := Check(t.Context(), Command, CheckSpec{ID: id, Repository: w.host, Ref: w.hostHead, Owner: "novox",
-		Repo: "mesh-host", Number: 114, Base: "main", Judge: "validator", JudgeCache: cache,
+		Repo: "mesh-host", Number: 114, Base: "main", Judge: judge, JudgeCache: cache,
 		Paths: []string{"validate/v.go"}, Modules: []string{"mesh-host"}, Beside: beside, Siblings: siblings,
 		Toolchain: "golang"}, workspace, aFactsRegistry(t), GitCredential{}, nil)
 	if err != nil {
@@ -97,7 +103,7 @@ func (w aSiblingWorld) hostSibling() Sibling {
 
 // The node-engine's change fails its own check without its sibling (the controller's lock beside it is the trunk's),
 // and passes with it read at its merge: the check reads the lock the sibling's change brings, the judge is the
-// controller built from the sibling's merge with the node-engine change's own validator, and the verdict names both.
+// controller built from the sibling's merge with the validator that controller vendors (mesh-sdk's), and the verdict names both.
 func TestAHostMemberIsCheckedBesideItsControllerSibling(t *testing.T) {
 	aRuntimeThatBuildsTheJudge(t)
 	w := theSiblingWorld(t)
@@ -112,8 +118,8 @@ func TestAHostMemberIsCheckedBesideItsControllerSibling(t *testing.T) {
 	if v.Repo == nil || v.Repo.Verdict != "pass" {
 		t.Fatalf("beside its sibling the node-engine change should pass its own check: %+v\n%s", v.Repo, v.Report)
 	}
-	if v.Gate == nil || v.Gate.Verdict != "pass" || !strings.Contains(v.Gate.Summary, "the sibling controller with the sibling's validator") {
-		t.Fatalf("the judge was not the controller built from the sibling's merge with the change's own validator: %+v\n%s",
+	if v.Gate == nil || v.Gate.Verdict != "pass" || !strings.Contains(v.Gate.Summary, "the sibling controller with the vendored validator") {
+		t.Fatalf("the judge was not the controller built from the sibling's merge with the validator it vendors: %+v\n%s",
 			v.Gate, v.Report)
 	}
 	baseCommit := w.controllerMain
@@ -127,8 +133,8 @@ func TestAHostMemberIsCheckedBesideItsControllerSibling(t *testing.T) {
 	if want := "sibling novox/mesh-controller#346 merge " + v.Beside["mesh-controller"]; v.JudgeFrom != want {
 		t.Fatalf("the judge came from %q, not %q", v.JudgeFrom, want)
 	}
-	if v.Validator != "the change's own validator" {
-		t.Fatalf("the validator was %q", v.Validator)
+	if want := "mesh-sdk's validator at the pin of sibling novox/mesh-controller#346 merge " + v.Beside["mesh-controller"]; v.Validator != want {
+		t.Fatalf("the validator was %q, not %q", v.Validator, want)
 	}
 	// The statuses' "beside siblings" part is the forge module's to write, from the verdict's siblings.
 	if strings.Contains(v.Gate.Summary, "beside siblings") || strings.Contains(v.Repo.Summary, "beside siblings") {
@@ -140,43 +146,45 @@ func TestAHostMemberIsCheckedBesideItsControllerSibling(t *testing.T) {
 	}
 }
 
-// The controller's change fails with no sibling (it builds only with the node-engine change's validator), and passes with
-// it: judged by itself, with the sibling node-engine's validator in place of the one it vendors.
-func TestAControllerMemberIsJudgedByItselfWithItsHostSiblingsValidator(t *testing.T) {
+// The controller's change is judged by itself with the validator it vendors, whatever the node-engine sibling brings: the
+// node-engine holds no validator any more (issue 1391, novox/hq ADR 0446 clause 5). Nothing of the sibling is put into the judge.
+func TestAControllerMemberIsJudgedByItselfWithTheValidatorItVendors(t *testing.T) {
 	aRuntimeThatBuildsTheJudge(t)
 	w := theSiblingWorld(t)
-	// The controller change calls a function only the node-engine change brings.
-	gitInRepo(t, w.controller, "checkout", "--quiet", "change")
-	main := aJudgeOf("the sibling controller")["cmd/mesh-controller/main.go"]
-	w.controllerHead = commitFiles(t, w.controller, map[string]string{
-		"cmd/mesh-controller/main.go": strings.Replace(main, "validate.Word)", "validate.Word+validate.More)", 1)})
-	gitInRepo(t, w.controller, "checkout", "--quiet", "main")
-	gitInRepo(t, w.host, "checkout", "--quiet", "change")
-	w.hostHead = commitFiles(t, w.host, map[string]string{
-		"validate/more.go": "package validate\n\nconst More = \" and more\"\n"})
-	gitInRepo(t, w.host, "checkout", "--quiet", "main")
 
 	alone := w.controllerCheck(t, "check-867-controller-alone", "")
-	if alone.Gate == nil || alone.Gate.Verdict != "fail" || !strings.Contains(alone.Gate.Summary, "does not build") {
-		t.Fatalf("with no sibling the controller change should not build (the validator it vendors lacks More): %+v", alone.Gate)
-	}
-
 	v := w.controllerCheck(t, "check-867-controller", "", w.hostSibling())
-	if v.Gate == nil || v.Gate.Verdict != "pass" || !strings.Contains(v.Gate.Summary, "the sibling controller with the sibling's validator and more") {
-		t.Fatalf("the controller change was not judged by itself with the sibling's validator: %+v\n%s", v.Gate, v.Report)
+	for what, got := range map[string]CheckVerdict{"alone": alone, "beside its sibling": v} {
+		if got.Gate == nil || got.Gate.Verdict != "pass" || !strings.Contains(got.Gate.Summary, "the sibling controller with the vendored validator") {
+			t.Fatalf("the controller change %s was not judged by itself with the validator it vendors: %+v\n%s", what, got.Gate, got.Report)
+		}
 	}
 	if len(v.Siblings) != 1 || v.Siblings[0].Repository != "novox/mesh-host" || v.Siblings[0].BaseCommit != w.hostMain {
 		t.Fatalf("the verdict names siblings %+v", v.Siblings)
 	}
-	if want := "sibling novox/mesh-host#114 merge " + v.Beside["mesh-host"] + "'s validator"; v.Validator != want {
-		t.Fatalf("the validator was %q, not %q", v.Validator, want)
+	if v.Validator != "" {
+		t.Fatalf("the validator was %q: a controller judged by itself has the one it vendors", v.Validator)
 	}
-	if !strings.HasPrefix(v.JudgeFrom, "this change's own merge ") {
-		t.Fatalf("the judge came from %q", v.JudgeFrom)
+}
+
+// A node-engine member whose tree holds no validator (validate/ and internal/declaration/ deleted, as R4b deletes them) is judged
+// beside its controller sibling all the same: nothing of it is copied into the judge, so nothing is missing (issue 1391).
+func TestAHostMemberWithNoValidatorOfItsOwnDoesNotFailTheJudge(t *testing.T) {
+	aRuntimeThatBuildsTheJudge(t)
+	w := theSiblingWorld(t)
+	gitInRepo(t, w.host, "checkout", "--quiet", "change")
+	gitInRepo(t, w.host, "rm", "--quiet", "-r", "validate", "internal")
+	gitInRepo(t, w.host, "commit", "--quiet", "-m", "the validator is mesh-sdk's")
+	w.hostHead = gitInRepo(t, w.host, "rev-parse", "HEAD")
+	gitInRepo(t, w.host, "checkout", "--quiet", "main")
+
+	v := w.hostCheckAs(t, "validator", "check-1391-host-without-validator", "", "", w.controllerSibling())
+	if v.Gate == nil || v.Gate.Verdict != "pass" || !strings.Contains(v.Gate.Summary, "the sibling controller with the vendored validator") {
+		t.Fatalf("a node-engine change with no validator of its own was not judged: %+v\n%s", v.Gate, v.Report)
 	}
-	// The member's own tree keeps the validator it vendors: its own script reads the vendored files as they are.
-	if body := gitInRepo(t, w.controller, "show", "main:vendor/github.com/novox/mesh-host/validate/v.go"); strings.Contains(body, "sibling") {
-		t.Fatalf("the trunk's vendored validator was touched: %s", body)
+	alone := w.hostCheckAs(t, "validator", "check-1391-host-alone", "", "")
+	if alone.Gate == nil || strings.Contains(alone.Gate.Summary, "could not be put in the judge") {
+		t.Fatalf("the judge tried to copy the validator of a change that holds none: %+v", alone.Gate)
 	}
 }
 
@@ -208,7 +216,7 @@ func TestACheckThatCouldNotLearnItsSiblingsSaysSo(t *testing.T) {
 	beside := w.beside()
 	delete(beside, "mesh-host")
 	v, err := Check(t.Context(), Command, CheckSpec{ID: "check-867-unknown", Repository: w.host, Ref: w.hostHead,
-		Owner: "novox", Repo: "mesh-host", Number: 114, Base: "main", Judge: "validator", Paths: []string{"validate/v.go"},
+		Owner: "novox", Repo: "mesh-host", Number: 114, Base: "main", Paths: []string{"validate/v.go"},
 		Modules: []string{"mesh-host"}, Beside: beside, SiblingsUnknown: "mesh-delivery did not answer",
 		Toolchain: "golang"}, t.TempDir(), aFactsRegistry(t), GitCredential{}, nil)
 	if err != nil {
@@ -217,7 +225,7 @@ func TestACheckThatCouldNotLearnItsSiblingsSaysSo(t *testing.T) {
 	if v.SiblingsUnknown != "mesh-delivery did not answer" || len(v.Siblings) != 0 || v.JudgeFrom != "" {
 		t.Fatalf("the verdict says %q, siblings %+v, judge from %q", v.SiblingsUnknown, v.Siblings, v.JudgeFrom)
 	}
-	if !strings.Contains(v.Gate.Summary, "the trunk's controller with the sibling's validator") {
+	if !strings.Contains(v.Gate.Summary, "the trunk's controller with the vendored validator") {
 		t.Fatalf("a check without siblings was not judged as before: %+v", v.Gate)
 	}
 	if strings.Contains(v.Gate.Summary, "[beside siblings") {
@@ -226,7 +234,7 @@ func TestACheckThatCouldNotLearnItsSiblingsSaysSo(t *testing.T) {
 }
 
 // The judge a group made is kept only for the same inputs: the controller's merge and the base commits it was merged
-// onto, the validator's source and commit. The same inputs take the judge kept; any other builds it again.
+// onto. The same inputs take the judge kept; any other builds it again.
 func TestTheGroupsJudgeIsReusedOnlyForTheSameInputs(t *testing.T) {
 	built := aRuntimeThatBuildsTheJudge(t)
 	w := theSiblingWorld(t)
@@ -253,14 +261,6 @@ func TestTheGroupsJudgeIsReusedOnlyForTheSameInputs(t *testing.T) {
 	if n := builds(t, built); n != 3 {
 		t.Fatalf("a moved base did not build the judge again: %d builds", n)
 	}
-	// The validator's source moves: the member's own change differs.
-	gitInRepo(t, w.host, "checkout", "--quiet", "change")
-	w.hostHead = commitFiles(t, w.host, aHostSaying("another validator"))
-	gitInRepo(t, w.host, "checkout", "--quiet", "main")
-	w.hostCheck(t, "check-867-cache-5", "", cache, w.controllerSibling())
-	if n := builds(t, built); n != 4 {
-		t.Fatalf("a moved validator did not build the judge again: %d builds", n)
-	}
 }
 
 // The contrast the isolation test stands on: built the old way, in the workspace with its HOME and no judge-build