Runtime/post init request header patch for LLMs does not work

[Peilun-Li]

Checked other resources

• I added a very descriptive title to this issue.
• I searched the LangChain documentation with the integrated search.
• 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).

Example Code

Say for example, we have user-defined model, and we want the same model object to be runnable in different environments, some environments require an additional request header for apikey auth

User-defined model

from langchain_openai import ChatOpenAI
model = ChatOpenAI(model_name="gpt-4o-mini")

Now imagine we receive this model object, and for it to be run in a dedicated environment, it needs additional request header

• First attempt to add default_headers - this doesn't work as the openai clients are already initialized at model object init time (code), thus any change on default_headers would not be reflected in openai clients used.

  model.default_headers={"apikey": "xxx"}

• Second attempt to bind model - this doesn't work upon model.invoke: TypeError: parse() got an unexpected keyword argument 'default_headers'

  model.bind(default_headers={"apikey:": "xxx"})

There are probably hacky ways by updating the internal openai clients directly at model.client._client.default_headers etc. but I don't feel that's a robust pattern as _client being a private object could evolve without notice. Any idea on how to better support such use case in a robust way?

Error Message and Stack Trace (if applicable)

No response

Description

I'm trying to patch additional header to a LLM model after its initialization, but couldn't find an easy and robust way. See example code for details.

System Info

System Information

OS: Linux
OS Version: #1 SMP Wed Jul 17 15:10:20 UTC 2024
Python Version: 3.9.13 (main, Aug 23 2022, 09:14:58)
[GCC 10.2.1 20210110]

Package Information

langchain_core: 0.3.29
langchain: 0.3.14
langchain_community: 0.3.14
langsmith: 0.2.10
langchain_openai: 0.3.0
langchain_text_splitters: 0.3.5

Optional packages not installed

langserve

Other Dependencies

aiohttp: 3.8.4
async-timeout: 4.0.2
dataclasses-json: 0.6.7
httpx: 0.28.1
httpx-sse: 0.4.0
jsonpatch: 1.33
langsmith-pyo3: Installed. No version info available.
numpy: 1.23.5
openai: 1.59.6
orjson: 3.10.14
packaging: 24.2
pydantic: 2.10.5
pydantic-settings: 2.7.1
PyYAML: 5.4.1
requests: 2.32.3
requests-toolbelt: 1.0.0
SQLAlchemy: 2.0.37
tenacity: 8.2.2
tiktoken: 0.8.0
typing-extensions: 4.12.2