diff --git a/crates/aura-engine/src/construction.rs b/crates/aura-engine/src/construction.rs
index bc731ef..cdf5e5f 100644
--- a/crates/aura-engine/src/construction.rs
+++ b/crates/aura-engine/src/construction.rs
@@ -1493,6 +1493,32 @@ mod tests {
         );
     }
 
+    /// Documented residue pin (#317 audit): a `gang` op cannot fuse a spliced
+    /// instance's member param — a gang fuses a PRIMITIVE's raw `(name, pos)`
+    /// slot, and an instance's params are nested/path-qualified. The refusal
+    /// is the ordinary no-such-open-param shape on the instance node, so the
+    /// authoring-guide/C24 claim "the gang op refuses a composite instance's
+    /// member path" stays an observed fact, not prose.
+    #[test]
+    fn gang_of_a_spliced_instance_member_path_refuses() {
+        let subgraph = |_: &str| Some(use_fixture());
+        let mut s = GraphSession::new("g", &std_vocabulary, &subgraph);
+        s.apply(Op::Use { ref_id: "fixture".into(), name: Some("gate".into()), bind: vec![] })
+            .unwrap();
+        s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("solo".into()), bind: vec![] })
+            .unwrap();
+        assert_eq!(
+            s.apply(Op::Gang {
+                as_name: "fused".into(),
+                into: vec!["gate.sma.length".into(), "solo.length".into()],
+            }),
+            Err(OpError::BadParam {
+                node: "gate".into(),
+                err: BindOpError::UnknownParam("sma.length".into()),
+            })
+        );
+    }
+
     /// DAG invariant (domain invariant 5 / C9), through an instance: a
     /// `connect` closing a cycle through a spliced instance is rejected
     /// eagerly, the instance treated as one opaque node (#317) — the same