fix(core): iteratively clean rejected typed syntax depth

crates/oa-core/src/language/analysis_source/syntax.rs

@@ -349,6 +349,11 @@ impl Cursor<'_, '_> {
             _ => 0,
         };
         if child_depth >= crate::analysis::MAX_EXPRESSION_DEPTH {
+            // The rejected parent still owns accepted, potentially depth-128
+            // children. Recursive derived cleanup here runs beneath the parser
+            // frames and can exhaust the bounded native stack before returning
+            // the depth error. Consume those children with an explicit worklist.
+            drop_rejected_kind(kind);
             return Err(error(span, "Expression logical depth exceeds 128."));
         }
         Ok(Expression {
@@ -399,6 +404,42 @@ impl Cursor<'_, '_> {
         self.node(kind, span)
     }
 }
+fn drop_rejected_kind(kind: ExpressionKind) {
+    let mut pending = vec![kind];
+    while let Some(kind) = pending.pop() {
+        match kind {
+            ExpressionKind::Unary { operand, .. } => pending.push(operand.kind),
+            ExpressionKind::Binary { left, right, .. } => {
+                pending.push(left.kind);
+                pending.push(right.kind);
+            }
+            ExpressionKind::If {
+                condition,
+                when_true,
+                when_false,
+            } => {
+                pending.push(condition.kind);
+                pending.push(when_true.kind);
+                pending.push(when_false.kind);
+            }
+            ExpressionKind::List(values) => pending.extend(values.into_iter().map(|v| v.kind)),
+            ExpressionKind::Call { arguments, .. } => {
+                pending.extend(arguments.into_iter().map(|a| a.value.kind));
+            }
+            ExpressionKind::Sum { values, initial } => {
+                pending.push(values.kind);
+                pending.push(initial.kind);
+            }
+            ExpressionKind::Power { base, .. } => pending.push(base.kind),
+            ExpressionKind::AsKind { value, .. } => pending.push(value.kind),
+            ExpressionKind::Boolean(_)
+            | ExpressionKind::Number(_)
+            | ExpressionKind::Quantity { .. }
+            | ExpressionKind::Property(_)
+            | ExpressionKind::Parameter(_) => {}
+        }
+    }
+}
 fn comparison(op: BinaryOp) -> bool {
     matches!(
         op,

crates/oa-core/src/language/analysis_source/tests.rs

@@ -108,6 +108,49 @@ fn flat_binary_depth_and_malformed_constructor_retain_bounded_completed_children
     assert_eq!(number(&expression("1")), "1");
 }
 
+#[test]
+fn every_parent_shape_rejects_depth129_and_cleans_children_on_128k_stack() {
+    std::thread::Builder::new()
+        .name("analysis-syntax-rejection-128k".into())
+        .stack_size(128 * 1024)
+        .spawn(|| {
+            // Rotate through every recursive syntax shape, so the rejected
+            // parent's complete child tree also exercises every cleanup arm.
+            let wrap = |shape, child: &str| match shape {
+                0 => format!("abs({child})"),
+                1 => format!("({child}) + 1"),
+                2 => format!("if(true, {child}, 0)"),
+                3 => format!("[{child}]"),
+                4 => format!("@f(a: {child})"),
+                5 => format!("sum({child}, 0)"),
+                6 => format!("power({child}, 1)"),
+                7 => format!("as_kind(@k, {child})"),
+                _ => unreachable!(),
+            };
+            let mut deep = "1".to_owned();
+            for layer in 0..127 {
+                deep = wrap(layer % 8, &deep);
+            }
+            assert_eq!(expression(&deep).depth, 128);
+            for shape in 0..8 {
+                let source = wrap(shape, &deep);
+                let failure = parse(&source, &mut budget()).unwrap_err();
+                assert_eq!(failure.message, "Expression logical depth exceeds 128.");
+                assert_eq!(
+                    failure.span,
+                    Span {
+                        start: 0,
+                        end: source.len()
+                    }
+                );
+                assert_eq!(number(&expression("1")), "1");
+            }
+        })
+        .unwrap()
+        .join()
+        .unwrap();
+}
+
 #[test]
 fn significant_ratio_and_quantity_trivia_preserve_original_spans() {
     let source = "ratio // explanation café\n ( - // sign\n 3, // denominator\n 4 ) // measurement\n [@millisecond]";