feat: change litellm dependency from strict pin to minimum version constraint

- Change litellm==1.74.3 to litellm>=1.74.3 in pyproject.toml
- Update uv.lock with new dependency constraint
- Add comprehensive tests to verify minimum version constraint works
- Allows users to install newer litellm versions for features like Claude 4 Sonnet

Fixes #3207

Co-Authored-By: Jo\u00E3o <joao@crewai.com>

pyproject.toml

@@ -11,7 +11,7 @@ dependencies = [
     # Core Dependencies
     "pydantic>=2.4.2",
     "openai>=1.13.3",
-    "litellm==1.74.3",
+    "litellm>=1.74.3",
     "instructor>=1.3.3",
     # Text Processing
     "pdfplumber>=0.11.4",

tests/test_litellm_version_constraint.py

@@ -0,0 +1,116 @@
+import pytest
+import importlib.metadata
+from packaging import version
+
+from crewai.llm import LLM
+from crewai.agent import Agent
+from crewai.task import Task
+from crewai.crew import Crew
+
+
+def test_litellm_minimum_version_constraint():
+    """Test that litellm meets the minimum version requirement."""
+    try:
+        litellm_version = importlib.metadata.version("litellm")
+        minimum_version = "1.74.3"
+        
+        assert version.parse(litellm_version) >= version.parse(minimum_version), (
+            f"litellm version {litellm_version} is below minimum required version {minimum_version}"
+        )
+    except importlib.metadata.PackageNotFoundError:
+        pytest.fail("litellm package is not installed")
+
+
+def test_llm_creation_with_relaxed_litellm_constraint():
+    """Test that LLM can be created successfully with the relaxed litellm constraint."""
+    llm = LLM(model="gpt-4o-mini")
+    assert llm is not None
+    assert llm.model == "gpt-4o-mini"
+
+
+def test_basic_llm_functionality_with_relaxed_constraint():
+    """Test that basic LLM functionality works with the relaxed litellm constraint."""
+    llm = LLM(model="gpt-4o-mini", temperature=0.7, max_tokens=100)
+    
+    assert llm.model == "gpt-4o-mini"
+    assert llm.temperature == 0.7
+    assert llm.max_tokens == 100
+
+
+def test_agent_creation_with_relaxed_litellm_constraint():
+    """Test that Agent can be created with LLM using relaxed litellm constraint."""
+    llm = LLM(model="gpt-4o-mini")
+    agent = Agent(
+        role="Test Agent",
+        goal="Test goal",
+        backstory="Test backstory",
+        llm=llm
+    )
+    
+    assert agent is not None
+    assert agent.llm == llm
+    assert agent.role == "Test Agent"
+
+
+def test_crew_functionality_with_relaxed_litellm_constraint():
+    """Test that Crew functionality works with the relaxed litellm constraint."""
+    llm = LLM(model="gpt-4o-mini")
+    agent = Agent(
+        role="Test Agent",
+        goal="Test goal", 
+        backstory="Test backstory",
+        llm=llm
+    )
+    
+    task = Task(
+        description="Test task description",
+        expected_output="Test output",
+        agent=agent
+    )
+    
+    crew = Crew(
+        agents=[agent],
+        tasks=[task]
+    )
+    
+    assert crew is not None
+    assert len(crew.agents) == 1
+    assert len(crew.tasks) == 1
+    assert crew.agents[0] == agent
+    assert crew.tasks[0] == task
+
+
+def test_litellm_import_functionality():
+    """Test that litellm can be imported and basic functionality works."""
+    import litellm
+    from litellm.exceptions import ContextWindowExceededError, AuthenticationError
+    
+    assert hasattr(litellm, 'completion')
+    assert ContextWindowExceededError is not None
+    assert AuthenticationError is not None
+
+
+def test_llm_supports_function_calling():
+    """Test that LLM function calling support detection works with relaxed constraint."""
+    llm = LLM(model="gpt-4o-mini")
+    
+    supports_functions = llm.supports_function_calling()
+    assert isinstance(supports_functions, bool)
+
+
+def test_llm_context_window_size():
+    """Test that LLM context window size detection works with relaxed constraint."""
+    llm = LLM(model="gpt-4o-mini")
+    
+    context_window = llm.get_context_window_size()
+    assert isinstance(context_window, int)
+    assert context_window > 0
+
+
+def test_llm_anthropic_model_detection():
+    """Test that Anthropic model detection works with relaxed constraint."""
+    anthropic_llm = LLM(model="anthropic/claude-3-sonnet")
+    openai_llm = LLM(model="gpt-4o-mini")
+    
+    assert anthropic_llm._is_anthropic_model() is True
+    assert openai_llm._is_anthropic_model() is False