AzureChatOpenAI creates a new `httpx` client on each instantiation

Checked other resources

• This is a bug, not a usage question. For questions, please use the LangChain Forum (https://forum.langchain.com/).
• I added a clear and descriptive title that summarizes this issue.
• I used the GitHub search to find a similar question and didn't find it.
• I am sure that this is a bug in LangChain rather than my code.
• The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package).
• I read what a minimal reproducible example is (https://stackoverflow.com/help/minimal-reproducible-example).
• I posted a self-contained, minimal, reproducible example. A maintainer can copy it and run it AS IS.

Example Code

Code Example

import asyncio
import httpx
from langchain_openai import AzureChatOpenAI

# Track httpx client creations
original_init = httpx.AsyncClient.__init__
counter = {"count": 0}

def counting_init(self, *args, **kwargs):
    counter["count"] += 1
    print(f"New AsyncClient created: {counter['count']}")
    original_init(self, *args, **kwargs)

httpx.AsyncClient.__init__ = counting_init

def create_llm():
    return AzureChatOpenAI(
        azure_endpoint="https://<REDACTED-ENDPOINT>/",
        deployment_name="<REDACTED-DEPLOYMENT-NAME>",
        temperature=0.7
    )

async def main():
    llms = [create_llm() for _ in range(5)]
    print(f"Total AsyncClient instances: {counter['count']}")

asyncio.run(main())

Error Message and Stack Trace (if applicable)

No response

Description

langchain-core==0.3.65 langchain-openai==0.3.23

System Info

backports.tarfile==1.2.0 certifi==2025.8.3 charset-normalizer==3.4.2 docutils==0.22 id==1.5.0 idna==3.10 importlib_metadata==8.7.0 jaraco.classes==3.4.0 jaraco.context==6.0.1 jaraco.functools==4.2.1 keyring==25.6.0 markdown-it-py==3.0.0 mdurl==0.1.2 more-itertools==10.7.0 nh3==0.3.0 packaging==25.0 Pygments==2.19.2 readme_renderer==44.0 requests==2.32.4 requests-toolbelt==1.0.0 rfc3986==2.0.0 rich==14.1.0 twine==6.1.0 urllib3==2.5.0 zipp==3.23.0