MoonshotChat fails to authenticate with the moonshot.ai api

[joaompinto]

Checked other resources

• This is a bug, not a usage question.
• 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 Community rather than my code.
• The bug is not resolved by updating to the latest stable version of LangChain Community.
• 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

from langchain_community.chat_models import MoonshotChat

chat = MoonshotChat(
api_base="https://api.moonshot.ai/v1",
temperature=0.5,
model="kimi-k2.5",
)

messages = [
("system", "hello"),
("human", "who are you"),
]
chat.invoke(messages)

Error Message and Stack Trace (if applicable)

File "C:\Users\lameg\Projects\moontest\run.py", line 13, in
chat.invoke(messages)
~~~~~~~~~~~^^^^^^^^^^
File "C:\Users\lameg.venv\Lib\site-packages\langchain_core\language_models\chat_models.py", line 402, in invoke
self.generate_prompt(
~~~~~~~~~~~~~~~~~~~~^
[self._convert_input(input)],
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...<6 lines>...
**kwargs,
^^^^^^^^^
).generations[0][0],
^
File "C:\Users\lameg.venv\Lib\site-packages\langchain_core\language_models\chat_models.py", line 1121, in generate_prompt
return self.generate(prompt_messages, stop=stop, callbacks=callbacks, **kwargs)
~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\lameg.venv\Lib\site-packages\langchain_core\language_models\chat_models.py", line 931, in generate
self._generate_with_cache(
~~~~~~~~~~~~~~~~~~~~~~~~~^
m,
^^
...<2 lines>...
**kwargs,
^^^^^^^^^
)
^
File "C:\Users\lameg.venv\Lib\site-packages\langchain_core\language_models\chat_models.py", line 1233, in _generate_with_cache
result = self._generate(
messages, stop=stop, run_manager=run_manager, **kwargs
)
File "C:\Users\lameg.venv\Lib\site-packages\langchain_community\chat_models\openai.py", line 476, in _generate
response = self.completion_with_retry(
messages=message_dicts, run_manager=run_manager, **params
)
File "C:\Users\lameg.venv\Lib\site-packages\langchain_community\chat_models\openai.py", line 387, in completion_with_retry
return self.client.create(**kwargs)
~~~~~~~~~~~~~~~~~~^^^^^^^^^^
File "C:\Users\lameg.venv\Lib\site-packages\openai_utils_utils.py", line 286, in wrapper
return func(*args, **kwargs)
File "C:\Users\lameg.venv\Lib\site-packages\openai\resources\chat\completions\completions.py", line 1192, in create
return self._post(
~~~~~~~~~~^
"/chat/completions",
^^^^^^^^^^^^^^^^^^^^
...<47 lines>...
stream_cls=Stream[ChatCompletionChunk],
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
)
^
File "C:\Users\lameg.venv\Lib\site-packages\openai_base_client.py", line 1297, in post
return cast(ResponseT, self.request(cast_to, opts, stream=stream, stream_cls=stream_cls))
~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\lameg.venv\Lib\site-packages\openai_base_client.py", line 1070, in request
raise self._make_status_error_from_response(err.response) from None
openai.AuthenticationError: Error code: 401 - {'error': {'message': 'Invalid Authentication', 'type': 'invalid_authentication_error'}}

Description

• I'm trying to use the Kimi K2.5 LLM

[joaompinto]

I have enabled the http debug and discovered that the connection is done to INFO [2026-02-16 10:34:16] httpx - HTTP Request: POST https://api.moonshot.cn/v1/chat/completions "HTTP/1.1 401 Unauthorized".
It does not propagate the base_url setting.

[keenborder786]

João Pinto (@joaompinto) Have you double checked your API Key?

[joaompinto]

Yes, and I debug also with a print base_url, it shows the .cn url, and not the .ai that I am passing as a parameter.

[keenborder786]

João Pinto (@joaompinto) In the code above though, I don't see you setting up MOONSHOT_API_KEY. Can you try explicitly:

import os
os.environ["MOONSHOT_API_KEY"] = "sk-xxxxx"
chat = MoonshotChat(
api_base="https://api.moonshot.ai/v1",
temperature=0.5,
model="kimi-k2.5",
)

messages = [
("system", "hello"),
("human", "who are you"),
]
chat.invoke(messages)

[joaompinto]

When the ENV key is not set we get a validation error (which makes sense). I am setting up the env key at the OS level (it's a bad practice to place keys on code).

Mohammad Mohtashim (@keenborder786) I think you missed a part of my report, the connection is not being made to the api_base which I set, it is being made to the default API url, this explains the invalid key.

[keenborder786]

João Pinto (@joaompinto) my bad I think so PR #539 will take care of it then.