Frontier · framework

Use Claude Sonnet 4.5 with LangChain

Updated 2026-05-21 · By XALEN

How to use Claude Sonnet 4.5 (Frontier, ~600B) with LangChain. Install, authenticate, and make your first API call in minutes. Working code example included.

Model

Claude Sonnet 4.5

~600B · 200K context · $0.03 input

Framework

LangChain

framework · pip install langchain-openai

1. Install

pip install langchain-openai

2. Code

from langchain_openai import ChatOpenAI

llm = ChatOpenAI(
    model="claude-sonnet-4-5",
    openai_api_key="xln_test_YOUR_KEY",
    openai_api_base="https://api.xalen.io/v1"
)

response = llm.invoke("What is Claude Sonnet 4.5?")
print(response.content)

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Last updated: 2026-05-21