Fix langchain-google-genai integration by stripping 'models/' prefix

Fixes #3702

When using langchain-google-genai with CrewAI, the model name would include
a 'models/' prefix (e.g., 'models/gemini/gemini-pro') which is added by
Google's API internally. However, LiteLLM does not recognize this format,
causing a 'LLM Provider NOT provided' error.

This fix strips the 'models/' prefix from model names when extracting them
from langchain model objects, ensuring compatibility with LiteLLM while
maintaining backward compatibility with models that don't have this prefix.

Changes:
- Modified create_llm() in llm_utils.py to strip 'models/' prefix
- Added comprehensive tests covering various scenarios:
  - Model with 'models/' prefix in model attribute
  - Model with 'models/' prefix in model_name attribute
  - Model without prefix (no change)
  - Case-sensitive prefix handling (only lowercase 'models/' is stripped)

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

src/crewai/utilities/llm_utils.py

@@ -41,6 +41,10 @@ def create_llm(
             or getattr(llm_value, "deployment_name", None)
             or str(llm_value)
         )
+        
+        if isinstance(model, str) and model.startswith("models/"):
+            model = model[len("models/"):]
+        
         temperature: float | None = getattr(llm_value, "temperature", None)
         max_tokens: int | None = getattr(llm_value, "max_tokens", None)
         logprobs: int | None = getattr(llm_value, "logprobs", None)

tests/utilities/test_llm_utils.py

@@ -94,3 +94,49 @@ def test_create_llm_with_invalid_type():
     with pytest.raises(BadRequestError, match="LLM Provider NOT provided"):
         llm = create_llm(llm_value=42)
         llm.call(messages=[{"role": "user", "content": "Hello, world!"}])
+
+
+def test_create_llm_strips_models_prefix_from_model_attribute():
+    """Test that 'models/' prefix is stripped from langchain model names."""
+    class LangChainLikeModel:
+        model = "models/gemini/gemini-pro"
+        temperature = 0.7
+
+    obj = LangChainLikeModel()
+    llm = create_llm(llm_value=obj)
+    assert isinstance(llm, LLM)
+    assert llm.model == "gemini/gemini-pro"  # 'models/' prefix should be stripped
+    assert llm.temperature == 0.7
+
+
+def test_create_llm_strips_models_prefix_from_model_name_attribute():
+    """Test that 'models/' prefix is stripped from model_name attribute."""
+    class LangChainLikeModelWithModelName:
+        model_name = "models/gemini/gemini-2.0-flash"
+
+    obj = LangChainLikeModelWithModelName()
+    llm = create_llm(llm_value=obj)
+    assert isinstance(llm, LLM)
+    assert llm.model == "gemini/gemini-2.0-flash"  # 'models/' prefix should be stripped
+
+
+def test_create_llm_handles_model_without_prefix():
+    """Test that models without 'models/' prefix are handled correctly."""
+    class RegularModel:
+        model = "gemini/gemini-pro"
+
+    obj = RegularModel()
+    llm = create_llm(llm_value=obj)
+    assert isinstance(llm, LLM)
+    assert llm.model == "gemini/gemini-pro"  # No change when prefix not present
+
+
+def test_create_llm_strips_models_prefix_case_sensitive():
+    """Test that only lowercase 'models/' prefix is stripped."""
+    class UpperCaseModel:
+        model = "Models/gemini/gemini-pro"  # Uppercase M
+
+    obj = UpperCaseModel()
+    llm = create_llm(llm_value=obj)
+    assert isinstance(llm, LLM)
+    assert llm.model == "Models/gemini/gemini-pro"