audit: walk serial owners in write routing, harden result identity

src/wf_core/runtime/lineage.py

@@ -94,38 +94,47 @@ def commit_foreach_aware_patch(
 ) -> dict[str, Any]:
     """Commit one write patch with foreach-aware routing.
 
-    Ordinary frames commit (or buffer) through their own lineage. Serial
-    item writes commit through the parent scope so they land in root state;
-    concurrent item writes stay buffered in the item lineage for the barrier
-    to merge. Malformed ownership, missing parents, and closed or
-    superseded activations fail closed.
+    Ordinary frames commit (or buffer) through their own lineage. The walk
+    climbs through every serial item owner until it reaches either the
+    workflow/subgraph scope root, where it commits, or a concurrent item
+    boundary, where it buffers in that item lineage for the barrier to
+    merge. Malformed ownership, missing parents, parent cycles, and closed
+    or superseded activations fail closed.
     """
     from wf_core.runtime.foreach_state import (
         item_frame_owner,
         require_foreach_activation,
     )
 
-    owner = item_frame_owner(frame)
-    if owner is None:
-        return commit_patch_for_frame(run, frame, patch)
-    parent_frame = run.frames.get(owner.parent_frame_id)
-    if parent_frame is None:
-        raise WorkflowExecutionError(
-            "foreach item state references missing parent frame "
-            f"{owner.parent_frame_id!r} for child frame {frame.id!r}"
+    current = frame
+    seen: set[str] = set()
+    while True:
+        owner = item_frame_owner(current)
+        if owner is None:
+            return commit_patch_for_frame(run, current, patch)
+        if current.id in seen:
+            raise WorkflowExecutionError(
+                f"cycle detected in foreach parent chain at frame {current.id!r}"
+            )
+        seen.add(current.id)
+        parent_frame = run.frames.get(owner.parent_frame_id)
+        if parent_frame is None:
+            raise WorkflowExecutionError(
+                "foreach item state references missing parent frame "
+                f"{owner.parent_frame_id!r} for child frame {current.id!r}"
+            )
+        activation = require_foreach_activation(
+            parent_frame, owner.foreach_node_id, owner.activation_id
         )
-    activation = require_foreach_activation(
-        parent_frame, owner.foreach_node_id, owner.activation_id
-    )
-    if activation.barrier.mode == "concurrent":
-        append_lineage_writes(
-            run,
-            scope_id=frame.scope_id,
-            lineage_id=frame.lineage_id,
-            writes=patch.writes,
-        )
-        return {}
-    return commit_patch_for_frame(run, parent_frame, patch)
+        if activation.barrier.mode == "concurrent":
+            append_lineage_writes(
+                run,
+                scope_id=current.scope_id,
+                lineage_id=current.lineage_id,
+                writes=patch.writes,
+            )
+            return {}
+        current = parent_frame
 
 
 def scope_state_for_frame(run: RunState, frame: ExecutionFrame) -> dict[str, Any]: