LangChain

pip install langchain-openai

import os
from langchain_openai import ChatOpenAI

llm = ChatOpenAI(
    model="claude-sonnet-4-6",
    base_url="https://api.apione.ai/v1",
    api_key=os.environ["APIONE_API_KEY"],
    temperature=0,
    max_retries=2,
)

print(llm.invoke("Explain vector databases in one sentence").content)

from langchain_core.prompts import ChatPromptTemplate
from langchain_core.output_parsers import StrOutputParser

prompt = ChatPromptTemplate.from_messages([
    ("system", "You answer in bullet points only."),
    ("user", "{question}"),
])

chain = prompt | llm | StrOutputParser()
print(chain.invoke({"question": "How does APIONE failover work?"}))

fast = ChatOpenAI(model="gemini-3.5-flash", base_url=BASE, api_key=KEY)
smart = ChatOpenAI(model="claude-opus-4-7", base_url=BASE, api_key=KEY)

router_chain = classify_prompt | fast | StrOutputParser()
answer_chain = answer_prompt | smart | StrOutputParser()