fix: close Python workflow client review

tests/wf_api/test_artifact_api.py

@@ -236,6 +236,29 @@ async def test_validate_artifact_plan_projects_invalid_plan_diagnostic(
     }
 
 
+@pytest.mark.asyncio
+async def test_validate_artifact_plan_roots_capability_diagnostic_at_request_field(
+    tmp_path: Path,
+) -> None:
+    artifact_store = FileWorkflowArtifactStore(tmp_path / "artifacts_requirement")
+    api, _service = _artifact_api(artifact_store)
+
+    result = await api.validate_artifact_plan(
+        plan=_echo_artifact().plan,
+        outcomes=("completed",),
+        required_capabilities={
+            "broken": {
+                "ref": {"source": "demo", "capability_key": "echo"},
+                "kind": "not-a-capability-kind",
+            }
+        },
+        source_bindings={},
+    )
+
+    assert result["status"] == "invalid"
+    assert result["diagnostics"][0]["path"] == "required_capabilities.broken.kind"
+
+
 @pytest.mark.asyncio
 async def test_validate_artifact_plan_propagates_unexpected_value_error(
     tmp_path: Path,
@@ -290,6 +313,41 @@ async def test_validate_artifact_plan_derives_saved_workflow_dependencies(
     assert result["workflow_dependencies"] == {"child_workflow": 7}
 
 
+@pytest.mark.asyncio
+async def test_validate_artifact_plan_rejects_conflicting_child_version_pins(
+    tmp_path: Path,
+) -> None:
+    artifact_store = FileWorkflowArtifactStore(tmp_path / "artifacts_pin_conflict")
+    api, _service = _artifact_api(artifact_store)
+    plan = _echo_artifact().plan
+    plan["start"] = "child_v1"
+    plan["nodes"] = [
+        {
+            "id": node_id,
+            "type": "subgraph",
+            "workflow": {"artifact_id": "child_workflow", "version": version},
+            "input_schema": {"type": "object"},
+            "output_schema": {"type": "object"},
+            "outcomes": ["completed"],
+        }
+        for node_id, version in (("child_v1", 1), ("child_v2", 2))
+    ]
+    plan["edges"] = [
+        {"from": "child_v1", "outcome": "completed", "to": "child_v2"},
+        {"from": "child_v2", "outcome": "completed", "to": "__end__"},
+    ]
+
+    result = await api.validate_artifact_plan(
+        plan=plan,
+        outcomes=("completed",),
+        source_bindings={},
+    )
+
+    assert result["status"] == "invalid"
+    assert result["diagnostics"][0]["path"] == "plan"
+    assert "conflicting versions 1 and 2" in result["diagnostics"][0]["message"]
+
+
 @pytest.mark.asyncio
 async def test_create_artifact_from_workspace_suggests_exact_available_source_binding(
     tmp_path: Path,