ModelRequest Class — langchain Architecture

Source Code

libs/langchain_v1/langchain/agents/middleware/types.py lines 89–268

class ModelRequest(Generic[ContextT]):
    """Model request information for the agent.

    Type Parameters:
        ContextT: The type of the runtime context. Defaults to `None` if not specified.
    """

    model: BaseChatModel
    messages: list[AnyMessage]  # excluding system message
    system_message: SystemMessage | None
    tool_choice: Any | None
    tools: list[BaseTool | dict[str, Any]]
    response_format: ResponseFormat[Any] | None
    state: AgentState[Any]
    runtime: Runtime[ContextT]
    model_settings: dict[str, Any] = field(default_factory=dict)

    def __init__(
        self,
        *,
        model: BaseChatModel,
        messages: list[AnyMessage],
        system_message: SystemMessage | None = None,
        system_prompt: str | None = None,
        tool_choice: Any | None = None,
        tools: list[BaseTool | dict[str, Any]] | None = None,
        response_format: ResponseFormat[Any] | None = None,
        state: AgentState[Any] | None = None,
        runtime: Runtime[ContextT] | None = None,
        model_settings: dict[str, Any] | None = None,
    ) -> None:
        """Initialize ModelRequest with backward compatibility for system_prompt.

        Args:
            model: The chat model to use.
            messages: List of messages (excluding system prompt).
            tool_choice: Tool choice configuration.
            tools: List of available tools.
            response_format: Response format specification.
            state: Agent state.
            runtime: Runtime context.
            model_settings: Additional model settings.
            system_message: System message instance (preferred).
            system_prompt: System prompt string (deprecated, converted to SystemMessage).

        Raises:
            ValueError: If both `system_prompt` and `system_message` are provided.
        """
        # Handle system_prompt/system_message conversion and validation
        if system_prompt is not None and system_message is not None:
            msg = "Cannot specify both system_prompt and system_message"
            raise ValueError(msg)

        if system_prompt is not None:
            system_message = SystemMessage(content=system_prompt)

        with warnings.catch_warnings():
            warnings.simplefilter("ignore", category=DeprecationWarning)
            self.model = model
            self.messages = messages
            self.system_message = system_message
            self.tool_choice = tool_choice
            self.tools = tools if tools is not None else []
            self.response_format = response_format
            self.state = state if state is not None else {"messages": []}
            self.runtime = runtime  # type: ignore[assignment]
            self.model_settings = model_settings if model_settings is not None else {}

    @property
    def system_prompt(self) -> str | None:
        """Get system prompt text from system_message.

        Returns:
            The content of the system message if present, otherwise `None`.
        """
        if self.system_message is None:
            return None
        return self.system_message.text

    def __setattr__(self, name: str, value: Any) -> None:
        """Set an attribute with a deprecation warning.