_partition_messages() — langchain Function Reference

Architecture documentation for the _partition_messages() function in summarization.py from the langchain codebase.

Function python LangChainCore Runnables called by 2

Entity Profile

LangChainCore→ Runnables→ _partition_messages() — langchain Function Reference

Dependency Diagram

graph TD
  8f5f7cdc_45ed_18ec_b82b_23e574f9bd4c["_partition_messages()"]
  a622f56b_f697_966d_5bc7_095699ccca34["SummarizationMiddleware"]
  8f5f7cdc_45ed_18ec_b82b_23e574f9bd4c -->|defined in| a622f56b_f697_966d_5bc7_095699ccca34
  833a9d39_5a26_a8d9_09c7_26020ad85079["before_model()"]
  833a9d39_5a26_a8d9_09c7_26020ad85079 -->|calls| 8f5f7cdc_45ed_18ec_b82b_23e574f9bd4c
  ca36a689_bbb0_72cf_124a_722e38d87df0["abefore_model()"]
  ca36a689_bbb0_72cf_124a_722e38d87df0 -->|calls| 8f5f7cdc_45ed_18ec_b82b_23e574f9bd4c
  style 8f5f7cdc_45ed_18ec_b82b_23e574f9bd4c fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

libs/langchain_v1/langchain/agents/middleware/summarization.py lines 527–535

    def _partition_messages(
        conversation_messages: list[AnyMessage],
        cutoff_index: int,
    ) -> tuple[list[AnyMessage], list[AnyMessage]]:
        """Partition messages into those to summarize and those to preserve."""
        messages_to_summarize = conversation_messages[:cutoff_index]
        preserved_messages = conversation_messages[cutoff_index:]

        return messages_to_summarize, preserved_messages