ToolMessageChunk Class — langchain Architecture

Source Code

libs/core/langchain_core/messages/tool.py lines 174–203

class ToolMessageChunk(ToolMessage, BaseMessageChunk):
    """Tool 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["ToolMessageChunk"] = "ToolMessageChunk"  # type: ignore[assignment]

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

            return self.__class__(
                tool_call_id=self.tool_call_id,
                content=merge_content(self.content, other.content),
                artifact=merge_obj(self.artifact, other.artifact),
                additional_kwargs=merge_dicts(
                    self.additional_kwargs, other.additional_kwargs
                ),
                response_metadata=merge_dicts(
                    self.response_metadata, other.response_metadata
                ),
                id=self.id,
                status=_merge_status(self.status, other.status),
            )

        return super().__add__(other)