agents/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 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: RunContextWrapper[TContext], agent: TAgent) -> None:
        """Called before the agent is invoked. Called each time the current agent changes."""
        pass

    async def on_agent_end(
        self,
        context: RunContextWrapper[TContext],
        agent: TAgent,
        output: Any,
    ) -> None:
        """Called when the agent produces a final output."""
        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 concurrently with tool invocation."""
        pass

    async def on_tool_end(
        self,
        context: RunContextWrapper[TContext],
        agent: TAgent,
        tool: Tool,
        result: str,
    ) -> None:
        """Called after a 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: RunContextWrapper[TContext], agent: TAgent) -> None:
        """Called before the agent is invoked. Called each time the running agent is changed to this
        agent."""
        pass

    async def on_end(
        self,
        context: RunContextWrapper[TContext],
        agent: TAgent,
        output: Any,
    ) -> None:
        """Called when the agent produces a final output."""
        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 concurrently with tool invocation."""
        pass

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