lifecycle.py

from typing import Any, Generic, Optional

from typing_extensions import TypeVar

from .agent import Agent, AgentBase
from .items import ModelResponse, TResponseInputItem
from .run_context import AgentHookContext, RunContextWrapper, TContext
from .tool import Tool

TAgent = TypeVar("TAgent", bound=AgentBase, default=AgentBase)


class RunHooksBase(Generic[TContext, TAgent]):
    """A class that receives callbacks on various lifecycle events in an agent run. Subclass and
    override the methods you need.
    """

    async def on_llm_start(
        self,
        context: RunContextWrapper[TContext],
        agent: Agent[TContext],
        system_prompt: Optional[str],
        input_items: list[TResponseInputItem],
    ) -> None:
        """Called just before invoking the LLM for this agent."""
        pass

    async def on_llm_end(
        self,
        context: RunContextWrapper[TContext],
        agent: Agent[TContext],
        response: ModelResponse,
    ) -> None:
        """Called immediately after the LLM call returns for this agent."""
        pass

    async def on_agent_start(self, context: AgentHookContext[TContext], agent: TAgent) -> None:
        """Called before the agent is invoked. Called each time the current agent changes.

        Args:
            context: The agent hook context.
            agent: The agent that is about to be invoked.
        """
        pass

    async def on_agent_end(
        self,
        context: AgentHookContext[TContext],
        agent: TAgent,
        output: Any,
    ) -> None:
        """Called when the agent produces a final output.

        Args:
            context: The agent hook context.
            agent: The agent that produced the output.
            output: The final output produced by the agent.
        """
        pass

    async def on_handoff(
        self,
        context: RunContextWrapper[TContext],
        from_agent: TAgent,
        to_agent: TAgent,
    ) -> None:
        """Called when a handoff occurs."""
        pass

    async def on_tool_start(
        self,
        context: RunContextWrapper[TContext],
        agent: TAgent,
        tool: Tool,
    ) -> None:
        """Called immediately before a local tool is invoked."""
        pass

    async def on_tool_authorize(
        self,
        context: RunContextWrapper[TContext],
        agent: TAgent,
        tool: Tool,
    ) -> bool:
        """Called before a tool is executed. Return False to deny the tool call.

        When False is returned, the tool is not invoked and the model receives a
        denial message instead.  All on_tool_start and on_tool_end hooks are
        skipped for denied calls.

        Default: always returns True (allow all tool calls).

        Args:
            context: The run context wrapper.
            agent: The current agent.
            tool: The tool about to be invoked.

        Returns:
            True to allow the tool call, False to deny it.
        """
        return True

    async def on_tool_end(
        self,
        context: RunContextWrapper[TContext],
        agent: TAgent,
        tool: Tool,
        result: str,
    ) -> None:
        """Called immediately after a local tool is invoked."""
        pass


class AgentHooksBase(Generic[TContext, TAgent]):
    """A class that receives callbacks on various lifecycle events for a specific agent. You can
    set this on `agent.hooks` to receive events for that specific agent.

    Subclass and override the methods you need.
    """

    async def on_start(self, context: AgentHookContext[TContext], agent: TAgent) -> None:
        """Called before the agent is invoked. Called each time the running agent is changed to this
        agent.

        Args:
            context: The agent hook context.
            agent: This agent instance.
        """
        pass

    async def on_end(
        self,
        context: AgentHookContext[TContext],
        agent: TAgent,
        output: Any,
    ) -> None:
        """Called when the agent produces a final output.

        Args:
            context: The agent hook context.
            agent: This agent instance.
            output: The final output produced by the agent.
        """
        pass

    async def on_handoff(
        self,
        context: RunContextWrapper[TContext],
        agent: TAgent,
        source: TAgent,
    ) -> None:
        """Called when the agent is being handed off to. The `source` is the agent that is handing
        off to this agent."""
        pass

    async def on_tool_start(
        self,
        context: RunContextWrapper[TContext],
        agent: TAgent,
        tool: Tool,
    ) -> None:
        """Called immediately before a local tool is invoked."""
        pass

    async def on_tool_authorize(
        self,
        context: RunContextWrapper[TContext],
        agent: TAgent,
        tool: Tool,
    ) -> bool:
        """Called before a tool is executed. Return False to deny the tool call.

        When False is returned, the tool is not invoked and the model receives a
        denial message instead.  All on_tool_start and on_tool_end hooks are
        skipped for denied calls.

        Default: always returns True (allow all tool calls).

        Args:
            context: The run context wrapper.
            agent: The current agent.
            tool: The tool about to be invoked.

        Returns:
            True to allow the tool call, False to deny it.
        """
        return True

    async def on_tool_end(
        self,
        context: RunContextWrapper[TContext],
        agent: TAgent,
        tool: Tool,
        result: str,
    ) -> None:
        """Called immediately after a local tool is invoked."""
        pass

    async def on_llm_start(
        self,
        context: RunContextWrapper[TContext],
        agent: Agent[TContext],
        system_prompt: Optional[str],
        input_items: list[TResponseInputItem],
    ) -> None:
        """Called immediately before the agent issues an LLM call."""
        pass

    async def on_llm_end(
        self,
        context: RunContextWrapper[TContext],
        agent: Agent[TContext],
        response: ModelResponse,
    ) -> None:
        """Called immediately after the agent receives the LLM response."""
        pass


RunHooks = RunHooksBase[TContext, Agent]
"""Run hooks when using `Agent`."""

AgentHooks = AgentHooksBase[TContext, Agent]
"""Agent hooks for `Agent`s."""