langchain - 💡(How to fix) Fix Add Inception chat model integration

Submission checklist

• 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-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-openrouter
• langchain-perplexity
• langchain-qdrant
• langchain-xai
• Other / not sure / general

Feature Description

Add a new partner package, langchain-inception, providing a ChatInception chat model for Inception's Mercury family of diffusion-based language models.

Use Case

Inception's Mercury models use diffusion rather than autoregression, giving substantially faster inference while staying competitive on quality. There is currently no first-class way to use them in LangChain.

Proposed Solution

A new libs/partners/inception package wrapping BaseChatOpenAI, mirroring the existing OpenAI-compatible partners. Example:

 from langchain_inception import ChatInception
 
 model = ChatInception(
     model="mercury-2",
     reasoning_effort="medium",  # instant | low | medium | high
 )
 model.invoke("Hello!")

Alternatives Considered

No response

Additional Context

• Inception website: https://inceptionlabs.ai
• Inception API docs: https://docs.inceptionlabs.ai