on_chat_model_start() — langchain Function Reference

Architecture documentation for the on_chat_model_start() function in fake_callback_handler.py from the langchain codebase.

Function python LangChainCore LanguageModelBase calls 1

Entity Profile

LangChainCore→ LanguageModelBase→ on_chat_model_start() — langchain Function Reference

Dependency Diagram

graph TD
  21bb9651_da33_cd6b_9ae4_d429d3a28ddc["on_chat_model_start()"]
  11c4a9f2_b0cb_6057_0bf2_2ac75662e949["FakeCallbackHandlerWithChatStart"]
  21bb9651_da33_cd6b_9ae4_d429d3a28ddc -->|defined in| 11c4a9f2_b0cb_6057_0bf2_2ac75662e949
  002393b6_a578_fc51_5b2e_77ec5e835733["on_chat_model_start_common()"]
  21bb9651_da33_cd6b_9ae4_d429d3a28ddc -->|calls| 002393b6_a578_fc51_5b2e_77ec5e835733
  style 21bb9651_da33_cd6b_9ae4_d429d3a28ddc fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

libs/langchain/tests/unit_tests/callbacks/fake_callback_handler.py lines 281–291

    def on_chat_model_start(
        self,
        serialized: dict[str, Any],
        messages: list[list[BaseMessage]],
        *,
        run_id: UUID,
        parent_run_id: UUID | None = None,
        **kwargs: Any,
    ) -> Any:
        assert all(isinstance(m, BaseMessage) for m in chain(*messages))
        self.on_chat_model_start_common()