diff --git a/internal/compose/input_held.go b/internal/compose/input_held.go
new file mode 100644
index 0000000..2d0befd
--- /dev/null
+++ b/internal/compose/input_held.go
@@ -0,0 +1,97 @@
+package compose
+
+import (
+	"encoding/json"
+	"sort"
+
+	"git.novox.be/novox/mesh-sdk/go/catalogue"
+)
+
+// What an input says of its held modules on the wire (issue 774, the group check of feat/l3-final 278aa5f0ccbe). A held
+// module stands in the input as its stub (Stub), and the stub's mark (catalogue.Manifest.Stubbed) is no field of a
+// manifest's JSON: an input a node-engine sent the check's sandbox lost it, so the sandbox read node-tools, held by its
+// manifest's verdict, as a tool runner with no bundle and refused every module of ace, g14 and shanks for "its build
+// produced 0 bundle(s)" instead of naming the verdict. So the input carries the mark itself, by module, for its catalogue
+// and for each node's kept manifests, and a reader marks each again. An input from a node-engine before the mark (no
+// Held) is read by its contract: a module Refused names stands in Catalogue as its stub.
+
+// heldMarks are the modules an input holds as their stubs: those of its catalogue, and those each node keeps, by node.
+type heldMarks struct {
+	Catalogue []string            `json:",omitempty"`
+	Kept      map[string][]string `json:",omitempty"`
+}
+
+// inputFields is Input without its JSON methods.
+type inputFields Input
+
+// inputWire is an input as it crosses the bus: its fields, and the modules it holds as their stubs.
+type inputWire struct {
+	inputFields
+	Held *heldMarks `json:",omitempty"`
+}
+
+// MarshalJSON writes the input with the modules it holds as their stubs named beside it (heldMarks).
+func (in Input) MarshalJSON() ([]byte, error) {
+	w := inputWire{inputFields: inputFields(in)}
+	marks := heldMarks{Catalogue: stubbedOf(in.Catalogue)}
+	for _, n := range in.Nodes {
+		if kept := stubbedOf(n.Kept); len(kept) > 0 {
+			if marks.Kept == nil {
+				marks.Kept = map[string][]string{}
+			}
+			marks.Kept[n.Name] = kept
+		}
+	}
+	if len(marks.Catalogue) > 0 || len(marks.Kept) > 0 {
+		w.Held = &marks
+	}
+	return json.Marshal(w)
+}
+
+// UnmarshalJSON reads an input and marks again each module it holds as its stub: those it names held, and, by the
+// input's contract, every module Refused names that its catalogue holds.
+func (in *Input) UnmarshalJSON(raw []byte) error {
+	var w inputWire
+	if err := json.Unmarshal(raw, &w); err != nil {
+		return err
+	}
+	*in = Input(w.inputFields)
+	held := map[string]bool{}
+	for m := range in.Refused {
+		held[m] = true
+	}
+	if w.Held != nil {
+		for _, m := range w.Held.Catalogue {
+			held[m] = true
+		}
+	}
+	for m := range held {
+		if man, ok := in.Catalogue[m]; ok {
+			man.Stubbed = true
+			in.Catalogue[m] = man
+		}
+	}
+	if w.Held != nil {
+		for i := range in.Nodes {
+			for _, m := range w.Held.Kept[in.Nodes[i].Name] {
+				if man, ok := in.Nodes[i].Kept[m]; ok {
+					man.Stubbed = true
+					in.Nodes[i].Kept[m] = man
+				}
+			}
+		}
+	}
+	return nil
+}
+
+// stubbedOf is each module of manifests held as its stub, sorted.
+func stubbedOf(manifests map[string]catalogue.Manifest) []string {
+	var out []string
+	for name, m := range manifests {
+		if m.Stubbed {
+			out = append(out, name)
+		}
+	}
+	sort.Strings(out)
+	return out
+}
diff --git a/internal/composer/composer.go b/internal/composer/composer.go
index 61aad6c..b5a8898 100644
--- a/internal/composer/composer.go
+++ b/internal/composer/composer.go
@@ -150,6 +150,14 @@ func runCase(r Request, c Case, depth string) (CaseVerdict, error) {
 	for name, m := range base.Catalogue {
 		shelf[name] = m
 	}
+	// A module the input's node-engine holds as refused (compose.Input.Refused: its verdict, or bytes that do not decode) is
+	// held here as there, and its read says why, whatever the case's own verdicts: the check then names the cause the node
+	// holds it for, never a pass the node would not compose, nor a rule about its stub (issue 774, group check 278aa5f0ccbe).
+	for name, why := range base.Refused {
+		if read, carried := cv.Manifests[name]; carried && read.Accepted {
+			cv.Manifests[name] = ManifestRead{Refused: "its node-engine holds it: " + why}
+		}
+	}
 	in.Catalogue = shelf
 	in.Nodes = slices.Clone(in.Nodes)
 	in.Holdings = slices.Clone(in.Holdings)
diff --git a/internal/composer/composer_test.go b/internal/composer/composer_test.go
index 73ecf12..18c5309 100644
--- a/internal/composer/composer_test.go
+++ b/internal/composer/composer_test.go
@@ -179,6 +179,47 @@ func TestARequestItCannotRunIsRefused(t *testing.T) {
 			t.Errorf("a module the node-engine holds too: %+v", m)
 		}
 	})
+	// Issue 774 (the group check of feat/l3-final 278aa5f0ccbe): a tool runner its node-engine holds by its manifest's
+	// verdict is sent as its stub, and the input says it holds it: the sandbox composes the node with it held, never refuses
+	// it for its stub's missing bundle. An input from an engine before the mark is read by Refused alone, the same way.
+	t.Run("a refused tool runner the engine sends as its stub", func(t *testing.T) {
+		raw := `{"module": "runner", "version": "1", "tool-runner": true, ` +
+			`"build": {"artifacts": [{"name": "runtime", "kind": "bundle", "language": "go", "from": "cmd/runner", "binary": "runner"}]}}`
+		man, err := catalogue.Decode([]byte(raw))
+		if err != nil {
+			t.Fatal(err)
+		}
+		in := compose.Input{Catalogue: map[string]catalogue.Manifest{"runner": compose.Stub(man)},
+			Refused: map[string]string{"runner": "the indexer's judge refused the manifest of runner"},
+			Nodes:   []compose.Node{{Name: "a", Assigned: []string{"runner"}}}}
+		wire, err := json.Marshal(in)
+		if err != nil {
+			t.Fatal(err)
+		}
+		var back compose.Input
+		if err := json.Unmarshal(wire, &back); err != nil || !back.Catalogue["runner"].Stubbed || !strings.Contains(string(wire), `"Held"`) {
+			t.Fatalf("the input's held mark across the wire: %s, %v", wire, err)
+		}
+		older := strings.Replace(string(wire), `"Held":{"Catalogue":["runner"]}`, `"Unsaid":null`, 1)
+		for name, sent := range map[string]string{"with the mark": string(wire), "from an engine before it": older} {
+			var r Request
+			r = Request{V: Version, Machines: []string{"a"}, Depth: DepthCompose,
+				Cases: []Case{{Name: "change", Manifests: map[string]Manifest{"runner": {Raw: json.RawMessage(raw)}}}}}
+			if err := json.Unmarshal([]byte(sent), &r.Input); err != nil {
+				t.Fatal(err)
+			}
+			v, err := Run(r)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if m := v.Cases[0].Machines["a"]; !m.Composes || strings.Contains(m.Reason, "bundle") {
+				t.Errorf("%s: the node with its tool runner held: %+v", name, m)
+			}
+			if read := v.Cases[0].Manifests["runner"]; read.Accepted || !strings.Contains(read.Refused, "the indexer's judge refused the manifest of runner") {
+				t.Errorf("%s: the runner's read names not why its node-engine holds it: %+v", name, read)
+			}
+		}
+	})
 	v, err := Run(Request{V: Version, Cases: []Case{{Name: "only-read", Manifests: map[string]Manifest{"demo": {Raw: json.RawMessage(demo)}}}}})
 	if err != nil || len(v.Cases) != 1 || !v.Cases[0].Manifests["demo"].Accepted || v.Cases[0].Machines != nil || v.SDK == "" {
 		t.Fatalf("a request with no machines: %+v, %v", v, err)