fix(ragas): serialize concurrency_limit in RagasEvaluator

integrations/ragas/src/haystack_integrations/components/evaluators/ragas/evaluator.py

@@ -85,7 +85,11 @@ def to_dict(self) -> dict[str, Any]:
         :returns:
             Dictionary with serialized data.
         """
-        return default_to_dict(self, ragas_metrics=[_serialize_metric(m) for m in self.metrics])
+        return default_to_dict(
+            self,
+            ragas_metrics=[_serialize_metric(m) for m in self.metrics],
+            concurrency_limit=self.concurrency_limit,
+        )
 
     @classmethod
     def from_dict(cls, data: dict[str, Any]) -> "RagasEvaluator":

integrations/ragas/tests/test_evaluator.py

@@ -316,10 +316,20 @@ def test_to_dict(self, monkeypatch):
                         "llm": {"model": "gpt-4o-mini", "provider": "openai"},
                     },
                     {"type": "tests.test_evaluator.ConcreteMetric", "name": "another_metric"},
-                ]
+                ],
+                "concurrency_limit": 4,
             },
         }
 
+    def test_concurrency_limit_survives_a_serialization_round_trip(self, monkeypatch):
+        """concurrency_limit caps how many metric evaluations run at once in run_async."""
+        monkeypatch.setenv("OPENAI_API_KEY", "test")
+        evaluator = RagasEvaluator(ragas_metrics=[ConcreteMetric(name="a_metric")], concurrency_limit=16)
+
+        restored = RagasEvaluator.from_dict(evaluator.to_dict())
+
+        assert restored.concurrency_limit == 16
+
     def test_from_dict(self, monkeypatch):
         monkeypatch.setenv("OPENAI_API_KEY", "test")
         data = {