ChatMistralAI does not pass on Frequency Penalty Argument

[Bernsai]

Checked other resources

• [x] I added a very descriptive title to this issue.
• [x] I searched the LangChain documentation with the integrated search.
• [x] I used the GitHub search to find a similar question and didn't find it.
• [x] I am sure that this is a bug in LangChain rather than my code.
• [x] The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package).

Example Code

from langchain_mistralai import ChatMistralAI

ChatMistralAI(
            api_key=api_key,
            base_url=base_url,
            model=model_type.value,
            temperature=0.1,
            frequency_penalty=0.5,
        )

ChatMistralAI(
            api_key=api_key,
            base_url=base_url,
            model=model_type.value,
            temperature=0.1,
            model_kwargs={
                "frequency_penalty": 0.5,
            },
        )

ChatMistralAI(
            api_key=api_key,
            base_url=base_url,
            model=model_type.value,
            temperature=0.1,
            kwargs={
                "frequency_penalty": 0.5,
            },
        )

Error Message and Stack Trace (if applicable)

No response

Description

When providing frequency penalty to ChatMistralAI (langchain-mistralai==0.2.6) it is not passed on to Mistral API.

When checking the request, which is actually sent to Mistral API frequency_penalty is always null. Adapting that request to expose e.g. frequency_penalty=0.5 and manually sending to Mistral API solves the issue.

It seems ChatMistralAI does not use frequency_penalty argument in any way, although it is supported by Mistral API.

System Info

System Information

OS: Linux OS Version: #53-Ubuntu SMP PREEMPT_DYNAMIC Sat Jan 11 00:06:25 UTC 2025 Python Version: 3.12.3 (main, Jan 17 2025, 18:03:48) [GCC 13.3.0]

Package Information

langchain_core: 0.3.35 langchain: 0.3.18 langchain_community: 0.3.17 langsmith: 0.3.8 langchain_elasticsearch: 0.3.2 langchain_huggingface: 0.1.2 langchain_mistralai: 0.2.6 langchain_openai: 0.3.5 langchain_text_splitters: 0.3.6