Add support for ChatQwen in init_chat_model()

[changbindu]

Checked other resources

• This is a feature request, not a bug report or usage question.
• I added a clear and descriptive title that summarizes the feature request.
• I used the GitHub search to find a similar feature request and didn't find it.
• I checked the LangChain documentation and API reference to see if this feature already exists.
• This is not related to the langchain-community package.

Package (Required)

• langchain
• langchain-openai
• langchain-anthropic
• langchain-classic
• langchain-core
• langchain-cli
• langchain-model-profiles
• langchain-tests
• langchain-text-splitters
• langchain-chroma
• langchain-deepseek
• langchain-exa
• langchain-fireworks
• langchain-groq
• langchain-huggingface
• langchain-mistralai
• langchain-nomic
• langchain-ollama
• langchain-perplexity
• langchain-prompty
• langchain-qdrant
• langchain-xai
• Other / not sure / general

Feature Description

The ChatQwen class from langchain_qwq package provides advanced support for Qwen3 and other Qwen-series models, featuring dedicated parameters to configure Qwen3's reasoning mode.

Here is the package index page: https://pypi.org/project/langchain-qwq/

Qwen is a widely adopted open-source model; however, LangChain's init_chat_model() currently lacks native support for Qwen models. Support for Qwen in init_chat_model() would provide significant convenience.

Here is an untested (and not full) patch:

--- a/libs/langchain/langchain_classic/chat_models/base.py
+++ b/libs/langchain/langchain_classic/chat_models/base.py
@@ -495,6 +495,11 @@ def _init_chat_model_helper(
         from langchain_perplexity import ChatPerplexity
 
         return ChatPerplexity(model=model, **kwargs)
+    if model_provider == "qwen":
+        _check_pkg("langchain_qwq")
+        from langchain_qwq import ChatQwen
+
+        return ChatQwen(model=model, **kwargs)
     supported = ", ".join(_SUPPORTED_PROVIDERS)
     msg = (
         f"Unsupported {model_provider=}.\n\nSupported model providers are: {supported}"
@@ -523,6 +528,7 @@ _SUPPORTED_PROVIDERS = {
     "ibm",
     "xai",
     "perplexity",
+    "qwen",
 }

Use Case

This change will add native support for Qwen models in LangChain.

Proposed Solution

No response

Alternatives Considered

No response

Additional Context

No response

[TBice123123]

The model classes supported by init_chat_model are basically those in the official partners/ directory. Since langchain-qwq is a third-party library, it's not really suitable for use with init_chat_model.