mathur-exe

### vLLM + LangChain/LangGraph ChatCompletion Notes

1. **Use the OpenAI Chat wrapper** – LangChain’s `ChatOpenAI` (and anything that consumes `ChatModel`/`openai.ChatCompletion` semantics) can point at an OpenAI-compatible base URL, so run your vLLM server on the standard `/v1` endpoint and pass that as `base_url` or `OPENAI_BASE_URL` when instantiating the client. Example:
   ```python
   from langchain_openai import ChatOpenAI

   llm = ChatOpenAI(
       model="chat-model-name",
       api_key="placeholder",          # vLLM doesn’t enforce a key
       base_url="http://localhost:8000/v1",