PydanticAI

pip install 'pydantic-ai-slim[openai]'

from pydantic_ai import Agent
from pydantic_ai.models.openai import OpenAIModel

model = OpenAIModel(
    "anthropic/claude-sonnet-4.6",  # or any other OpenRouter model
    base_url="https://openrouter.ai/api/v1",
    api_key="sk-or-...",
)

agent = Agent(model)
result = await agent.run("What is the meaning of life?")
print(result)