ChatMistralAI with_structured_output does not recognize BaseModel subclass

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

class Code(BaseModel):
    prefix: str = Field(description="Description of the problem and approach")
    imports: str = Field(description="Code block import statements")
    code: str = Field(description="Code block not including import statements")

messages = state["messages"]
...

llm = ChatMistralAI(model="codestral-latest", temperature=0, endpoint="https://codestral.mistral.ai/v1")
code_gen_chain = llm.with_structured_output(Code, include_raw=False)
code_solution = code_gen_chain.invoke(messages)

code_solution is always a dict not type Code.

Error Message and Stack Trace (if applicable)

No response

Description

This is code from a recent public codestral demo:

class Code(BaseModel):
    prefix: str = Field(description="Description of the problem and approach")
    imports: str = Field(description="Code block import statements")
    code: str = Field(description="Code block not including import statements")

messages = state["messages"]
...

llm = ChatMistralAI(model="codestral-latest", temperature=0, endpoint="https://codestral.mistral.ai/v1")
code_gen_chain = llm.with_structured_output(Code, include_raw=False)
code_solution = code_gen_chain.invoke(messages)

code_solution is always a dict not type Code.

Stepping into llm.with_structured_output, the first lines are:

if kwargs:
    raise ValueError(f"Received unsupported arguments {kwargs}")
is_pydantic_schema = isinstance(schema, type) and issubclass(schema, BaseModel)

issubclass(schema, BaseModel) always returns False even though schema is the same Code type being sent in.

Before the call:

>>> Code
<class 'codestral.model.Code'>
>>> issubclass(Code, BaseModel)
True
>>> type(Code)
<class 'pydantic._internal._model_construction.ModelMetaclass'>

Step inside the call:

>>> schema
<class 'codestral.model.Code'>
>>> issubclass(schema, BaseModel)
False
>>> type(schema)
<class 'pydantic._internal._model_construction.ModelMetaclass'>

It behaves correctly outside the call to Langchain and incorrectly inside the call.

System Info

langchain==0.2.1 langchain-community==0.2.1 langchain-core==0.2.3 langchain-mistralai==0.1.7 langchain-text-splitters==0.2.0 pydantic==2.7.2 pydantic_core==2.18.3

System Information

OS: Darwin OS Version: Darwin Kernel Version 23.5.0: Wed May 1 20:14:38 PDT 2024; root:xnu-10063.121.3~5/RELEASE_ARM64_T6020 Python Version: 3.11.9 (main, Apr 19 2024, 11:43:47) [Clang 14.0.6 ]

Package Information

langchain_core: 0.2.3 langchain: 0.2.1 langchain_community: 0.2.1 langsmith: 0.1.67 langchain_mistralai: 0.1.7 langchain_text_splitters: 0.2.0 langgraph: 0.0.60

langchain-ai / langchain