merge_message_runs() — langchain Function Reference

Source Code

libs/core/langchain_core/messages/utils.py lines 951–1076

def merge_message_runs(
    messages: Iterable[MessageLikeRepresentation] | PromptValue,
    *,
    chunk_separator: str = "\n",
) -> list[BaseMessage]:
    r"""Merge consecutive Messages of the same type.

    !!! note
        `ToolMessage` objects are not merged, as each has a distinct tool call id that
        can't be merged.

    Args:
        messages: Sequence Message-like objects to merge.
        chunk_separator: Specify the string to be inserted between message chunks.

    Returns:
        list of BaseMessages with consecutive runs of message types merged into single
        messages. By default, if two messages being merged both have string contents,
        the merged content is a concatenation of the two strings with a new-line
        separator.
        The separator inserted between message chunks can be controlled by specifying
        any string with `chunk_separator`. If at least one of the messages has a list
        of content blocks, the merged content is a list of content blocks.

    Example:
        ```python
        from langchain_core.messages import (
            merge_message_runs,
            AIMessage,
            HumanMessage,
            SystemMessage,
            ToolCall,
        )

        messages = [
            SystemMessage("you're a good assistant."),
            HumanMessage(
                "what's your favorite color",
                id="foo",
            ),
            HumanMessage(
                "wait your favorite food",
                id="bar",
            ),
            AIMessage(
                "my favorite colo",
                tool_calls=[
                    ToolCall(
                        name="blah_tool", args={"x": 2}, id="123", type="tool_call"
                    )
                ],
                id="baz",
            ),
            AIMessage(
                [{"type": "text", "text": "my favorite dish is lasagna"}],
                tool_calls=[
                    ToolCall(
                        name="blah_tool",
                        args={"x": -10},
                        id="456",
                        type="tool_call",
                    )
                ],
                id="blur",
            ),
        ]

        merge_message_runs(messages)
        ```

        ```python
        [
            SystemMessage("you're a good assistant."),
            HumanMessage(
                "what's your favorite color\\n"
                "wait your favorite food", id="foo",
            ),
            AIMessage(
                [
                    "my favorite colo",
                    {"type": "text", "text": "my favorite dish is lasagna"}