diff --git a/modules/mesh-delivery-builder/internal/build/run_test.go b/modules/mesh-delivery-builder/internal/build/run_test.go
index 5558afeb..8b109e60 100644
--- a/modules/mesh-delivery-builder/internal/build/run_test.go
+++ b/modules/mesh-delivery-builder/internal/build/run_test.go
@@ -1342,6 +1342,44 @@ func aDoneKeyKeepsEachFormACountedNodeReads(t *testing.T) {
 	if got := fs.Needs(withBoth); !slices.Equal(got, []string{"form:new", "form:old"}) {
 		t.Errorf("needs %v", got)
 	}
+	// The builder's own forms (forms.Current): a bundle a build step answers in the registry seat's form (mesh-build-go's
+	// oci-artifact-registry/<module>/<artifact>@<digest>) keeps the artifact-store form it derives for each counted node
+	// whose engine does not state form:seat-reference, that one in the single reference (ADR 0624 §1, §3).
+	seatRef, storeRef := "oci-artifact-registry/m/code@"+digest, "artifact-store://m/code/blobs/"+digest
+	seat := []string{forms.FormNeed(forms.FormSeatReference), "word:module"}
+	for _, row := range []struct {
+		name             string
+		present, counted map[string][]string
+		reference        string
+		references       []string
+		needs            []string
+	}{
+		{"seat form answered, B away stating nothing: the derived store form stays, in the single reference",
+			map[string][]string{"a": seat}, map[string][]string{"a": seat, "b": nil}, storeRef, []string{storeRef, seatRef},
+			[]string{"form:artifact-store", "form:seat-reference"}},
+		{"seat form answered, every counted engine reads it: the seat form only",
+			map[string][]string{"a": seat}, map[string][]string{"a": seat, "b": seat}, seatRef, nil, []string{"form:seat-reference"}},
+		{"seat form answered, a present engine stating nothing: the store form only",
+			map[string][]string{"a": seat, "b": nil}, map[string][]string{"a": seat, "b": nil}, storeRef, nil, []string{"form:artifact-store"}},
+		{"seat form answered, no node present: the store form", nil, map[string][]string{"a": seat}, storeRef, nil, []string{"form:artifact-store"}},
+	} {
+		a := forms.Current.Choose(delivery.BuiltArtifact{Name: "code", Kind: "bundle", Digest: digest}, []string{seatRef}, row.present, row.counted)
+		if a.Reference != row.reference || !slices.Equal(a.References, row.references) {
+			t.Errorf("%s: %q %v, want %q %v", row.name, a.Reference, a.References, row.reference, row.references)
+		}
+		needs := forms.Current.Needs([]delivery.BuiltArtifact{a})
+		if !slices.Equal(needs, row.needs) {
+			t.Errorf("%s: needs %v, want %v", row.name, needs, row.needs)
+		}
+		for node, stated := range row.counted {
+			if forms.Current.Held(needs, stated) {
+				t.Errorf("%s: the want of %s is held", row.name, node)
+			}
+		}
+		if _, err := delivery.EncodeBuilderBuild(delivery.BuilderBuild{State: delivery.BuildDone, Manifest: strings.TrimPrefix(digest, "sha256:"), Artifacts: []delivery.BuiltArtifact{a}, Needs: needs}); err != nil {
+			t.Errorf("%s: %v", row.name, err)
+		}
+	}
 	// What the assigner holds a want by (ADR 0624 §2), from the same forms.
 	for _, row := range []struct {
 		name   string
diff --git a/modules/mesh-delivery-builder/internal/versions/versions_test.go b/modules/mesh-delivery-builder/internal/versions/versions_test.go
index 5cc345aa..f138f16e 100644
--- a/modules/mesh-delivery-builder/internal/versions/versions_test.go
+++ b/modules/mesh-delivery-builder/internal/versions/versions_test.go
@@ -308,7 +308,7 @@ func TestTheBuildersVersions(t *testing.T) {
 		}
 	})
 	t.Run("old form", func(t *testing.T) {
-		// One kind, a first form and a newer one (the builder's own forms are all first today, so no window opens).
+		// One kind, a first form and a newer one.
 		fs := forms.ArtifactForms{{Name: "registry", First: true, Kinds: []string{"image"}}, {Name: "oci", Kinds: []string{"image"}}}
 		both := []string{forms.FormNeed("oci")}
 		for _, c := range []struct {
@@ -327,8 +327,10 @@ func TestTheBuildersVersions(t *testing.T) {
 				t.Errorf("%s: Holding = %v, want %v", c.name, got, c.want)
 			}
 		}
-		if got := Holding(forms.Current, map[string][]string{"a": nil}, nil); got != nil {
-			t.Errorf("forms.Current, a node stating nothing: Holding = %v, want none", got)
+		// The builder's own forms: the registry seat's form of a bundle is not a first form, so a node stating nothing
+		// holds the window and one stating form:seat-reference does not.
+		if got := Holding(forms.Current, map[string][]string{"a": nil, "b": {forms.FormNeed(forms.FormSeatReference)}}, nil); !reflect.DeepEqual(got, []string{"a"}) {
+			t.Errorf("forms.Current, a node stating nothing and one stating form:seat-reference: Holding = %v, want a", got)
 		}
 		t0 := time.Unix(0, 0)
 		w, closed, overdue := OldFormWindow{}.Step([]string{"c"}, t0)
diff --git a/sdk/forms/forms.go b/sdk/forms/forms.go
index 298b27fd..579e9cf8 100644
--- a/sdk/forms/forms.go
+++ b/sdk/forms/forms.go
@@ -32,20 +32,28 @@ const (
 	FormPackageVersion = "package-version"
 )
 
-// ArtifactForm is one reference form: its name, whether it is a first form, the artifact kinds it names, and how a
-// reference is told to be in it.
+// FormSeatReference is the form a registry seat answers for a bundle or an archive it published,
+// oci-artifact-registry/<module>/<artifact>@sha256:<digest> (novox/hq ADR 0605 §9; catalogue.SeatReference, read back by
+// catalogue.InRegistrySeat), read by a node-engine that states form:seat-reference (catalogue.ReferenceFormSeat). Not a
+// first form: an engine stating nothing reads its blob only in the older artifact-store form, which it derives (Older).
+const FormSeatReference = catalogue.ReferenceFormSeat
+
+// ArtifactForm is one reference form: its name, whether it is a first form, the artifact kinds it names, how a
+// reference is told to be in it, and, for a form that names the same artifact an older form does, that older reference
+// (Older, nil when it derives none): the old-form window writes it beside the answered one (ADR 0624 §1, §3).
 type ArtifactForm struct {
 	Name  string
 	First bool
 	Kinds []string
 	Is    func(reference string) bool
+	Older func(reference string) string
 }
 
 // ArtifactForms are the forms a builder knows, oldest first.
 type ArtifactForms []ArtifactForm
 
 // Current are the forms the builder writes and the assigner knows: the three first forms (delivery.BuiltArtifact's
-// reference by kind).
+// reference by kind), then the registry seat's form of a bundle or an archive.
 var Current = ArtifactForms{
 	{Name: FormArtifactStore, First: true, Is: func(r string) bool { return strings.HasPrefix(r, artifactStore) },
 		Kinds: []string{catalogue.ArtifactBundle, catalogue.ArtifactArchive, catalogue.ArtifactImage, catalogue.ArtifactUpstream}},
@@ -53,6 +61,16 @@ var Current = ArtifactForms{
 		Kinds: []string{catalogue.ArtifactImage, catalogue.ArtifactUpstream}},
 	{Name: FormPackageVersion, First: true, Is: func(r string) bool { return strings.LastIndex(r, "@") > 0 && !strings.Contains(r, "@sha256:") },
 		Kinds: []string{catalogue.ArtifactPackage}},
+	{Name: FormSeatReference, Kinds: []string{catalogue.ArtifactBundle, catalogue.ArtifactArchive},
+		Is: func(r string) bool {
+			seat, _, ok := catalogue.InRegistrySeat(r)
+			return ok && seat == catalogue.OciArtifactRegistrySeat
+		},
+		// The same blob in the artifact store's form: oci-artifact-registry/<m>/<a>@<d> is artifact-store://<m>/<a>/blobs/<d>.
+		Older: func(r string) string {
+			path, _ := catalogue.InArtifactStore(r)
+			return catalogue.ArtifactStoreScheme + path
+		}},
 }
 
 // FormNeed is the reader capability a form needs of a node-engine: `form:<name>`.
@@ -180,9 +198,12 @@ func (fs ArtifactForms) Kept(kind string, present, counted map[string][]string)
 // Choose names a built artifact by the references the build answered in the forms Kept keeps (ADR 0624 §1, §3): the
 // oldest kept form in the single Reference, every kept one in References when there are more than one. A reference in a
 // form Kept does not keep is left out, unless none of the answered is kept: then the artifact keeps what was answered,
-// its first answered in Reference, since a key names where its artifact is (ADR 0498 clause 1).
+// its first answered in Reference, since a key names where its artifact is (ADR 0498 clause 1). An answered reference
+// in a form that derives an older one (ArtifactForm.Older) answers that older one too, so the build answers one form and
+// the key keeps each a counted node reads.
 func (fs ArtifactForms) Choose(a delivery.BuiltArtifact, answered []string, present, counted map[string][]string) delivery.BuiltArtifact {
 	kept := fs.Kept(a.Kind, present, counted)
+	answered = fs.withOlder(a.Kind, answered)
 	type ref struct {
 		at        int
 		reference string
@@ -224,3 +245,22 @@ func (fs ArtifactForms) Choose(a delivery.BuiltArtifact, answered []string, pres
 	}
 	return a
 }
+
+// withOlder is answered with, after it, each older reference an answered one's form derives that was not answered itself.
+func (fs ArtifactForms) withOlder(kind string, answered []string) []string {
+	out := slices.Clone(answered)
+	for _, r := range answered {
+		name, ok := fs.FormOf(kind, r)
+		if !ok {
+			continue
+		}
+		for _, f := range fs {
+			if f.Name == name && f.Older != nil {
+				if older := f.Older(r); !slices.Contains(out, older) {
+					out = append(out, older)
+				}
+			}
+		}
+	}
+	return out
+}