langchain - 💡(How to fix) Fix Schema class for multimodal message [1 participants]

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

LangChain users have to manually create the dict such as below in order to create multimodal message.

message = {
    "role": "user",
    "content": [
        {"type": "text", "text": "Describe the content of this image."},
        {
            "type": "image",
            "base64": "AAAAIGZ0eXBtcDQyAAAAAGlzb21tcDQyAAACAGlzb2...",
            "mime_type": "image/jpeg",
        },
    ]
}

(Copied from https://docs.langchain.com/oss/python/langchain/messages#multimodal )

As Type lover like me, I want a schema class for this so that I don't have to worry of typo of the dictionary key or values.

Use Case

Just for type hint

Proposed Solution

There are already message schema classes such as UserMessage, but the content param still needs to be dict

I want base Content class, and have 4 subclasses:

TextContent(text: str) # ->  {"type": "text", "text": "Describe the content of this image."}
Base64Content(type: Literal[...], base64_data: str, mime_type: str) # -> {"type": "...","base64": "...", "mime_type": "..."}
ImageUrlContent(url: str) # -> {"type": "image", "url": "https://example.com/path/to/image.jpg"}
ProviderFileIdContent(type: Literal[...], file_id: str) # -> {"type": "image", "file_id": "file-abc123"}

Alternatives Considered

No response

Additional Context

I would love to contribute if this issue accepted