FileContentBlock Class — langchain Architecture

Source Code

libs/core/langchain_core/messages/content.py lines 721–782

class FileContentBlock(TypedDict):
    """File data that doesn't fit into other multimodal block types.

    This block is intended for files that are not images, audio, or plaintext. For
    example, it can be used for PDFs, Word documents, etc.

    If the file is an image, audio, or plaintext, you should use the corresponding
    content block type (e.g., `ImageContentBlock`, `AudioContentBlock`,
    `PlainTextContentBlock`).

    !!! note "Factory function"

        `create_file_block` may also be used as a factory to create a
        `FileContentBlock`. Benefits include:

        * Automatic ID generation (when not provided)
        * Required arguments strictly validated at creation time
    """

    type: Literal["file"]
    """Type of the content block. Used for discrimination."""

    id: NotRequired[str]
    """Unique identifier for this content block.

    Used for tracking and referencing specific blocks (e.g., during streaming).

    Not to be confused with `file_id`, which references an external file in a
    storage system.

    Either:

    - Generated by the provider
    - Generated by LangChain upon creation (`UUID4` prefixed with `'lc_'`))
    """

    file_id: NotRequired[str]
    """Reference to the file in an external file storage system.

    For example, a file ID from OpenAI's Files API or another cloud storage provider.
    This is distinct from `id`, which identifies the content block itself.
    """

    mime_type: NotRequired[str]
    """MIME type of the file.

    Required for base64 data.

    [Examples from IANA](https://www.iana.org/assignments/media-types/media-types.xhtml)
    """

    index: NotRequired[int | str]
    """Index of block in aggregate response. Used during streaming."""

    url: NotRequired[str]
    """URL of the file."""

    base64: NotRequired[str]
    """Data as a base64 string."""

    extras: NotRequired[dict[str, Any]]
    """Provider-specific metadata. This shouldn't be used for the file data itself."""