Don't create copy and add test to test_agent_runner.py

Author: stevenheidel

src/agents/model_settings.py

@@ -31,7 +31,8 @@ class ModelSettings:
     """The tool choice to use when calling the model."""
 
     parallel_tool_calls: bool | None = None
-    """Whether to use parallel tool calls when calling the model."""
+    """Whether to use parallel tool calls when calling the model. 
+    Defaults to False if not provided."""
 
     truncation: Literal["auto", "disabled"] | None = None
     """The truncation strategy to use when calling the model."""
@@ -40,7 +41,8 @@ class ModelSettings:
     """The maximum number of output tokens to generate."""
 
     store: bool | None = None
-    """Whether to store the generated model response for later retrieval."""
+    """Whether to store the generated model response for later retrieval. 
+    Defaults to True if not provided."""
 
     def resolve(self, override: ModelSettings | None) -> ModelSettings:
         """Produce a new ModelSettings by overlaying any non-None values from the
@@ -50,6 +52,6 @@ def resolve(self, override: ModelSettings | None) -> ModelSettings:
 
         new_values = {
             k: getattr(override, k) if getattr(override, k) is not None else getattr(self, k)
-            for k in asdict(self)
+            for k in self.__dataclass_fields__
         }
         return ModelSettings(**new_values)

tests/test_agent_runner.py

@@ -19,7 +19,7 @@
     RunContextWrapper,
     Runner,
     UserError,
-    handoff,
+    handoff, ModelSettings, RunConfig,
 )
 from agents.agent import ToolsToFinalOutputResult
 from agents.tool import FunctionToolResult, function_tool
@@ -634,3 +634,31 @@ async def test_tool_use_behavior_custom_function():
 
     assert len(result.raw_responses) == 2, "should have two model responses"
     assert result.final_output == "the_final_output", "should have used the custom function"
+
+
+@pytest.mark.asyncio
+async def test_model_settings_override():
+    model = FakeModel()
+    agent = Agent(
+        name="test",
+        model=model,
+        model_settings=ModelSettings(temperature=1.0, max_tokens=1000)
+    )
+
+    model.add_multiple_turn_outputs(
+        [
+            [
+                get_text_message("a_message"),
+            ],
+        ]
+    )
+
+    await Runner.run(
+        agent,
+        input="user_message",
+        run_config=RunConfig(model_settings=ModelSettings(0.5)),
+    )
+
+    # temperature is overridden by Runner.run, but max_tokens is not
+    assert model.last_turn_args["model_settings"].temperature == 0.5
+    assert model.last_turn_args["model_settings"].max_tokens == 1000