DeepSeek API Authentication Error (401) when using LangChain’s ChatDeepSeek

[FarihaAnis]

Minimal Reproducible Example

from langchain_deepseek import ChatDeepSeek

DEEPSEEK_API_KEY = "your_api_key"

llm = ChatDeepSeek(api_key=DEEPSEEK_API_KEY, model="deepseek-chat", temperature=0.7, max_tokens=50)

response = llm.invoke("Hello! How are you?")
print(response)

Description

I'm trying to use the langchain library to connect to DeepSeek’s API for generating responses in my chatbot.

• Expected behavior: DeepSeek API should authenticate and return a response.
• Current behavior: The API works fine when used directly, but fails with 401 Authentication Error when called through langchain_deepseek.ChatDeepSeek.

Error message:
openai.AuthenticationError: Error code: 401 - {'error': {'message': 'Authentication Fails (no such user)', 'type': 'authentication_error', 'param': None, 'code': 'invalid_request_error'}}

Questions

1. Does ChatDeepSeek require additional authentication parameters beyond the API key?
2. Is there an issue with DeepSeek’s integration in LangChain that might be causing this?
3. Are there debugging steps I can take to trace how LangChain is handling API requests?

System Info

OS: Windows
Python Version: 3.12.4

LangChain Version:

• langchain==0.3.19
• langchain-community==0.3.18
• langchain-core==0.3.40
• langchain-deepseek==0.1.2
• langchain-huggingface==0.1.2
• langchain-openai==0.3.7
• langchain-pinecone==0.2.3
• langchain-tests==0.3.12
• langchain-text-splitters==0.3.6

Other relevant packages: Pinecone SDK, OpenAI SDK