import os

from langchain.chat_models import init_chat_model


def get_llm(
    model: str = "openai:qwen3.6-flash",
    base_url: str | None = None,
    api_key: str | None = None,
    **kwargs,
):
    """初始化 ChatModel，默认从环境变量读取 BASE_URL / API_KEY。"""
    if base_url is None:
        base_url = os.getenv("BASE_URL")
    if api_key is None:
        api_key = os.getenv("API_KEY")
    return init_chat_model(model=model, base_url=base_url, api_key=api_key, **kwargs)