fix(engine): labeled alternation with definition reference

crates/plotnik-lib/src/emit/codegen_tests.rs

@@ -320,6 +320,14 @@ fn alternations_captured_tagged() {
     "#});
 }
 
+#[test]
+fn alternations_tagged_with_definition_ref() {
+    snap!(indoc! {r#"
+        Inner = (identifier) @name
+        Test = [A: (Inner)  B: (number) @b] @item
+    "#});
+}
+
 #[test]
 fn alternations_in_quantifier() {
     snap!(indoc! {r#"

crates/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__codegen_tests__alternations_tagged_with_definition_ref.snap

@@ -0,0 +1,65 @@
+---
+source: crates/plotnik-lib/src/emit/codegen_tests.rs
+---
+Inner = (identifier) @name
+Test = [A: (Inner)  B: (number) @b] @item
+---
+[flags]
+linked = false
+
+[strings]
+S0 "Beauty will save the world"
+S1 "name"
+S2 "b"
+S3 "A"
+S4 "B"
+S5 "item"
+S6 "Inner"
+S7 "Test"
+S8 "identifier"
+S9 "number"
+
+[type_defs]
+T0 = <Node>
+T1 = Struct  M0:1  ; { name }
+T2 = Struct  M1:1  ; { b }
+T3 = Enum    M2:2  ; A | B
+T4 = Struct  M4:1  ; { item }
+
+[type_members]
+M0: S1 → T0  ; name: <Node>
+M1: S2 → T0  ; b: <Node>
+M2: S3 → T1  ; A: Inner
+M3: S4 → T2  ; B: T2
+M4: S5 → T3  ; item: T3
+
+[type_names]
+N0: S6 → T1  ; Inner
+N1: S7 → T4  ; Test
+
+[entrypoints]
+Inner = 01 :: T1
+Test  = 09 :: T4
+
+[transitions]
+  00   ε                                    ◼
+
+Inner:
+  01   ε                                    02
+  02   ε   [Obj]                            04
+  04       (identifier) [Node Set(M0)]      06
+  06   ε   [EndObj]                         08
+  08                                        ▶
+
+Test:
+  09   ε                                    10
+  10   ε   [Obj]                            12
+  12   ε                                    20, 26
+  14                                        ▶
+  15   ε   [EndObj]                         14
+  17   ε   [EndEnum Set(M4)]                15
+  19       (Inner)                          17 ⯇
+  20   ε   [Enum(M2)]                       19
+  22   ε   [EndEnum Set(M4)]                15
+  24       (number) [Node Set(M1)]          22
+  26   ε   [Enum(M3)]                       24

crates/plotnik-lib/src/engine/materializer.rs

@@ -139,9 +139,12 @@ impl<'t> Materializer<'t> for ValueMaterializer<'_> {
                 }
                 RuntimeEffect::EndEnum => {
                     if let Some(Builder::Tagged { tag, fields }) = stack.pop() {
+                        // If inner returned a structured value (via Obj/EndObj), use it as data
+                        // Otherwise use fields collected from direct Set effects
+                        let data = pending.take().unwrap_or(Value::Object(fields));
                         pending = Some(Value::Tagged {
                             tag,
-                            data: Box::new(Value::Object(fields)),
+                            data: Box::new(data),
                         });
                     }
                 }