Normalize child workflow failure kind

Author: durable-workflow-ops

src/durable_workflow/workflow.py

@@ -2299,7 +2299,7 @@ def _child_workflow_failed_from_payload(
     return ChildWorkflowFailed(
         message or "child workflow failed",
         exception_class,
-        failure_kind=_optional_str(payload.get("failure_category")) or "child_workflow",
+        failure_kind="child_workflow",
         child_workflow_run_id=child_workflow_run_id,
         child_workflow_type=child_workflow_type,
     )

tests/test_replay.py

@@ -1393,6 +1393,34 @@ def test_child_failed_preserves_typed_details(self) -> None:
             "child_workflow_type": "sub-workflow",
         }
 
+    def test_child_failed_reports_parent_failure_kind_for_application_child(self) -> None:
+        history = [
+            {
+                "event_type": "ChildRunFailed",
+                "payload": {
+                    "message": "planned typed child failure: typed-marker",
+                    "exception_type": "PlannedChildFailure",
+                    "exception_class": "smoke.PlannedChildFailure",
+                    "failure_category": "application",
+                    "child_workflow_run_id": "child-run-1",
+                    "child_workflow_type": "sub-workflow",
+                },
+            },
+        ]
+
+        outcome = replay(ChildWorkflowFailureDetailsWf, history, [])
+
+        assert len(outcome.commands) == 1
+        cmd = outcome.commands[0]
+        assert isinstance(cmd, CompleteWorkflow)
+        assert cmd.result == {
+            "message": "planned typed child failure: typed-marker",
+            "exception_class": "smoke.PlannedChildFailure",
+            "failure_kind": "child_workflow",
+            "child_workflow_run_id": "child-run-1",
+            "child_workflow_type": "sub-workflow",
+        }
+
     def test_child_failed_prefers_nested_exception_class_over_type(self) -> None:
         history = [
             {