ChatMessageChunk Class — langchain Architecture

Source Code

libs/core/langchain_core/messages/chat.py lines 25–64

class ChatMessageChunk(ChatMessage, BaseMessageChunk):
    """Chat Message chunk."""

    # Ignoring mypy re-assignment here since we're overriding the value
    # to make sure that the chunk variant can be discriminated from the
    # non-chunk variant.
    type: Literal["ChatMessageChunk"] = "ChatMessageChunk"  # type: ignore[assignment]
    """The type of the message (used during serialization)."""

    @override
    def __add__(self, other: Any) -> BaseMessageChunk:  # type: ignore[override]
        if isinstance(other, ChatMessageChunk):
            if self.role != other.role:
                msg = "Cannot concatenate ChatMessageChunks with different roles."
                raise ValueError(msg)

            return self.__class__(
                role=self.role,
                content=merge_content(self.content, other.content),
                additional_kwargs=merge_dicts(
                    self.additional_kwargs, other.additional_kwargs
                ),
                response_metadata=merge_dicts(
                    self.response_metadata, other.response_metadata
                ),
                id=self.id,
            )
        if isinstance(other, BaseMessageChunk):
            return self.__class__(
                role=self.role,
                content=merge_content(self.content, other.content),
                additional_kwargs=merge_dicts(
                    self.additional_kwargs, other.additional_kwargs
                ),
                response_metadata=merge_dicts(
                    self.response_metadata, other.response_metadata
                ),
                id=self.id,
            )
        return super().__add__(other)