Fix #2729: Add force_structured_output parameter to bypass response schema check for OpenRouter models

Co-Authored-By: Joe Moura <joao@crewai.com>

src/crewai/llm.py

@@ -270,6 +270,7 @@ class LLM(BaseLLM):
         callbacks: List[Any] = [],
         reasoning_effort: Optional[Literal["none", "low", "medium", "high"]] = None,
         stream: bool = False,
+        force_structured_output: bool = False,
         **kwargs,
     ):
         self.model = model
@@ -296,6 +297,7 @@ class LLM(BaseLLM):
         self.additional_params = kwargs
         self.is_anthropic = self._is_anthropic_model(model)
         self.stream = stream
+        self.force_structured_output = force_structured_output
 
         litellm.drop_params = True
 
@@ -992,9 +994,11 @@ class LLM(BaseLLM):
           - If no slash is present, "openai" is assumed.
         """
         provider = self._get_custom_llm_provider()
-        if self.response_format is not None and not supports_response_schema(
-            model=self.model,
-            custom_llm_provider=provider,
+        if self.response_format is not None and not (
+            supports_response_schema(
+                model=self.model,
+                custom_llm_provider=provider,
+            ) or (provider == "openrouter" and self.force_structured_output)
         ):
             raise ValueError(
                 f"The model {self.model} does not support response_format for provider '{provider}'. "

tests/llm_test.py

@@ -256,6 +256,32 @@ def test_validate_call_params_no_response_format():
     llm._validate_call_params()
 
 
+def test_validate_call_params_openrouter_force_structured_output():
+    class DummyResponse(BaseModel):
+        a: int
+
+    # Test with OpenRouter and force_structured_output=True
+    llm = LLM(
+        model="openrouter/deepseek/deepseek-chat",
+        response_format=DummyResponse,
+        force_structured_output=True
+    )
+    # Should not raise any error with force_structured_output=True
+    llm._validate_call_params()
+
+    # Test with OpenRouter and force_structured_output=False (default)
+    # Patch supports_response_schema to simulate an unsupported model.
+    with patch("crewai.llm.supports_response_schema", return_value=False):
+        llm = LLM(
+            model="openrouter/deepseek/deepseek-chat",
+            response_format=DummyResponse,
+            force_structured_output=False
+        )
+        with pytest.raises(ValueError) as excinfo:
+            llm._validate_call_params()
+        assert "does not support response_format" in str(excinfo.value)
+
+
 @pytest.mark.vcr(filter_headers=["authorization"], filter_query_parameters=["key"])
 @pytest.mark.parametrize(
     "model",