feat(eval): expose user_simulator_config in generate_responses

src/google/adk/evaluation/evaluation_generator.py

@@ -59,6 +59,7 @@
 from .eval_case import SessionInput
 from .eval_set import EvalSet
 from .request_intercepter_plugin import _RequestIntercepterPlugin
+from .simulation.user_simulator import BaseUserSimulatorConfig
 from .simulation.user_simulator import Status as UserSimulatorStatus
 from .simulation.user_simulator import UserSimulator
 from .simulation.user_simulator_provider import UserSimulatorProvider
@@ -263,6 +264,7 @@ async def generate_responses(
       agent_module_path: str,
       repeat_num: int = 3,
       agent_name: str = None,
+      user_simulator_config: Optional[BaseUserSimulatorConfig] = None,
   ) -> list[EvalCaseResponses]:
     """Returns evaluation responses for the given dataset and agent.
 
@@ -273,12 +275,19 @@ async def generate_responses(
         usually done to remove uncertainty that a single run may bring.
       agent_name: The name of the agent that should be evaluated. This is
         usually the sub-agent.
+      user_simulator_config: Optional configuration for the user simulator.
+        Only relevant for eval cases that use a `conversation_scenario` (which
+        are driven by `LlmBackedUserSimulator`); ignored for static
+        conversations. Pass an `LlmBackedUserSimulatorConfig` to override the
+        user-simulation model, max invocations, or custom instructions.
     """
     results = []
 
     for eval_case in eval_set.eval_cases:
-      # assume only static conversations are needed
-      user_simulator = UserSimulatorProvider().provide(eval_case)
+      user_simulator = UserSimulatorProvider(
+          user_simulator_config=user_simulator_config
+      ).provide(eval_case)
+
       responses = []
       for _ in range(repeat_num):
         response_invocations = await EvaluationGenerator._process_query(

tests/unittests/evaluation/test_evaluation_generator.py

@@ -18,9 +18,12 @@
 
 from google.adk.evaluation.app_details import AgentDetails
 from google.adk.evaluation.app_details import AppDetails
+from google.adk.evaluation.eval_case import EvalCase
+from google.adk.evaluation.eval_set import EvalSet
 from google.adk.evaluation.evaluation_generator import _LiveSession
 from google.adk.evaluation.evaluation_generator import EvaluationGenerator
 from google.adk.evaluation.request_intercepter_plugin import _RequestIntercepterPlugin
+from google.adk.evaluation.simulation.llm_backed_user_simulator import LlmBackedUserSimulatorConfig
 from google.adk.evaluation.simulation.user_simulator import NextUserMessage
 from google.adk.evaluation.simulation.user_simulator import Status as UserSimulatorStatus
 from google.adk.evaluation.simulation.user_simulator import UserSimulator
@@ -594,6 +597,48 @@ async def mock_generate_inferences_side_effect(
     called_with_content = mock_generate_inferences.call_args.args[3]
     assert called_with_content.parts[0].text == "message 1"
 
+
+class TestGenerateResponses:
+  """Test cases for EvaluationGenerator.generate_responses method."""
+
+  @pytest.mark.asyncio
+  async def test_generate_responses_forwards_llm_backed_user_simulator_config(
+      self, mocker
+  ):
+    """Tests that an LlmBackedUserSimulatorConfig is forwarded to the provider verbatim."""
+    mock_provider_cls = mocker.patch(
+        "google.adk.evaluation.evaluation_generator.UserSimulatorProvider"
+    )
+    mocker.patch(
+        "google.adk.evaluation.evaluation_generator.EvaluationGenerator._process_query",
+        new_callable=mocker.AsyncMock,
+        return_value=[],
+    )
+
+    user_simulator_config = LlmBackedUserSimulatorConfig(
+        model="test-model",
+        max_allowed_invocations=5,
+    )
+    eval_set = EvalSet(
+        eval_set_id="test_set",
+        eval_cases=[EvalCase(eval_id="case_0", conversation=[])],
+    )
+
+    await EvaluationGenerator.generate_responses(
+        eval_set=eval_set,
+        agent_module_path="some.agent.module",
+        repeat_num=1,
+        user_simulator_config=user_simulator_config,
+    )
+
+    mock_provider_cls.assert_called_once_with(
+        user_simulator_config=user_simulator_config
+    )
+    assert (
+        mock_provider_cls.call_args.kwargs["user_simulator_config"]
+        is user_simulator_config
+    )
+
   @pytest.mark.asyncio
   async def test_generates_inferences_with_user_simulator_live(
       self, mocker, mock_runner, mock_session_service