API key to use.
Can be inferred from the OPENAI_API_KEY environment variable, or specified as a
string, or sync or async callable that returns a string.
export OPENAI_API_KEY=...from langchain_openai import ChatOpenAI
model = ChatOpenAI(model="gpt-5-nano")from langchain_openai import ChatOpenAI
model = ChatOpenAI(model="gpt-5-nano", api_key="...")from langchain_openai import ChatOpenAI
def get_api_key() -> str:
# Custom logic to retrieve API key
return "..."
model = ChatOpenAI(model="gpt-5-nano", api_key=get_api_key)from langchain_openai import ChatOpenAI
async def get_api_key() -> str:
# Custom async logic to retrieve API key
return "..."
model = ChatOpenAI(model="gpt-5-nano", api_key=get_api_key)