ChatOpenAI integration: parameters and OpenAI-compatible endpoint setup

ChatOpenAI

pip install -U "langchain[openai]"

from langchain_openai import ChatOpenAI

model = ChatOpenAI(model="gpt-5.5")

Knobs worth knowing

• use_responses_api - picks the OpenAI Responses API vs the Chat Completions API.
• base_url - point at an OpenAI-compatible endpoint (Together, vLLM, and similar) while keeping model_provider="openai" semantics. Provider-specific fields from routers may not be preserved through this path.
• openai_proxy - HTTP proxy for deployments that need one.
• max_retries / timeout - resilience (see the retry skill). Defaults: up to 6 retries on 429/5xx/network errors.

Routers get their own package

• OpenRouter: ChatOpenRouter from langchain-openrouter
• LiteLLM: ChatLiteLLM / ChatLiteLLMRouter from langchain-litellm

Do not point ChatOpenAI at a router's base URL and expect router-specific fields to survive. The docs call this out explicitly.

Rules

• The key comes from OPENAIAPIKEY in the environment. Never paste a real key into code or chat.
• For streaming token usage metadata from OpenAI, you must opt in on the integration; usage is not returned in streaming chunks by default.

Verified against the official LangChain docs on 2026-09-26. Models: https://docs.langchain.com/oss/python/langchain/models