概览

from typing import Any

from langchain.agents import create_agent
from langchain.messages import AIMessage, AIMessageChunk, AnyMessage, ToolMessage


def get_weather(city: str) -> str:
    """Get weather for a given city."""

    return f"It's always sunny in {city}!"


agent = create_agent("openai:gpt-5.2", tools=[get_weather])


def _render_message_chunk(token: AIMessageChunk) -> None:
    if token.text:
        print(token.text, end="|")
    if token.tool_call_chunks:
        print(token.tool_call_chunks)
    # N.B. all content is available through token.content_blocks


def _render_completed_message(message: AnyMessage) -> None:
    if isinstance(message, AIMessage) and message.tool_calls:
        print(f"Tool calls: {message.tool_calls}")
    if isinstance(message, ToolMessage):
        print(f"Tool response: {message.content_blocks}")


input_message = {"role": "user", "content": "What is the weather in Boston?"}
for stream_mode, data in agent.stream(
    {"messages": [input_message]},
    stream_mode=["messages", "updates"],
):
    if stream_mode == "messages":
        token, metadata = data
        if isinstance(token, AIMessageChunk):
            _render_message_chunk(token)
    if stream_mode == "updates":
        for source, update in data.items():
            if source in ("model", "tools"):  # `source` captures node name
                _render_completed_message(update["messages"][-1])

from typing import Any, Literal

from langchain.agents.middleware import after_agent, AgentState
from langgraph.runtime import Runtime
from langchain.messages import AIMessage
from langchain.chat_models import init_chat_model
from langgraph.config import get_stream_writer  
from pydantic import BaseModel


class ResponseSafety(BaseModel):
    """Evaluate a response as safe or unsafe."""
    evaluation: Literal["safe", "unsafe"]


safety_model = init_chat_model("openai:gpt-5.2")

@after_agent(can_jump_to=["end"])
def safety_guardrail(state: AgentState, runtime: Runtime) -> dict[str, Any] | None:
    """Model-based guardrail: Use an LLM to evaluate response safety."""
    stream_writer = get_stream_writer()
    # Get the model response
    if not state["messages"]:
        return None

    last_message = state["messages"][-1]
    if not isinstance(last_message, AIMessage):
        return None

    # Use another model to evaluate safety
    model_with_tools = safety_model.bind_tools([ResponseSafety], tool_choice="any")
    result = model_with_tools.invoke(
        [
            {
                "role": "system",
                "content": "Evaluate this AI response as generally safe or unsafe."
            },
            {
                "role": "user",
                "content": f"AI response: {last_message.text}"
            }
        ]
    )
    stream_writer(result)

    tool_call = result.tool_calls[0]
    if tool_call["args"]["evaluation"] == "unsafe":
        last_message.content = "I cannot provide that response. Please rephrase your request."

    return None

from typing import Any

from langchain.agents import create_agent
from langchain.messages import AIMessageChunk, AIMessage, AnyMessage


def get_weather(city: str) -> str:
    """Get weather for a given city."""

    return f"It's always sunny in {city}!"


agent = create_agent(
    model="openai:gpt-5.2",
    tools=[get_weather],
    middleware=[safety_guardrail],
)

def _render_message_chunk(token: AIMessageChunk) -> None:
    if token.text:
        print(token.text, end="|")
    if token.tool_call_chunks:
        print(token.tool_call_chunks)


def _render_completed_message(message: AnyMessage) -> None:
    if isinstance(message, AIMessage) and message.tool_calls:
        print(f"Tool calls: {message.tool_calls}")
    if isinstance(message, ToolMessage):
        print(f"Tool response: {message.content_blocks}")


input_message = {"role": "user", "content": "What is the weather in Boston?"}
for stream_mode, data in agent.stream(
    {"messages": [input_message]},
    stream_mode=["messages", "updates", "custom"],
):
    if stream_mode == "messages":
        token, metadata = data
        if isinstance(token, AIMessageChunk):
            _render_message_chunk(token)
    if stream_mode == "updates":
        for source, update in data.items():
            if source in ("model", "tools"):
                _render_completed_message(update["messages"][-1])
    if stream_mode == "custom":
        # access completed message in stream
        print(f"Tool calls: {data.tool_calls}")

input_message = {"role": "user", "content": "What is the weather in Boston?"}
full_message = None
for stream_mode, data in agent.stream(
    {"messages": [input_message]},
    stream_mode=["messages", "updates"],
):
    if stream_mode == "messages":
        token, metadata = data
        if isinstance(token, AIMessageChunk):
            _render_message_chunk(token)
            full_message = token if full_message is None else full_message + token  
            if token.chunk_position == "last":
                if full_message.tool_calls:
                    print(f"Tool calls: {full_message.tool_calls}")
                full_message = None
    if stream_mode == "updates":
        for source, update in data.items():
            if source == "tools":
                _render_completed_message(update["messages"][-1])

from typing import Any

from langchain.agents import create_agent
from langchain.agents.middleware import HumanInTheLoopMiddleware
from langchain.messages import AIMessage, AIMessageChunk, AnyMessage, ToolMessage
from langgraph.checkpoint.memory import InMemorySaver
from langgraph.types import Command, Interrupt


def get_weather(city: str) -> str:
    """Get weather for a given city."""

    return f"It's always sunny in {city}!"


checkpointer = InMemorySaver()

agent = create_agent(
    "openai:gpt-5.2",
    tools=[get_weather],
    middleware=[
        HumanInTheLoopMiddleware(interrupt_on={"get_weather": True}),
    ],
    checkpointer=checkpointer,
)


def _render_message_chunk(token: AIMessageChunk) -> None:
    if token.text:
        print(token.text, end="|")
    if token.tool_call_chunks:
        print(token.tool_call_chunks)


def _render_completed_message(message: AnyMessage) -> None:
    if isinstance(message, AIMessage) and message.tool_calls:
        print(f"Tool calls: {message.tool_calls}")
    if isinstance(message, ToolMessage):
        print(f"Tool response: {message.content_blocks}")


def _render_interrupt(interrupt: Interrupt) -> None:
    interrupts = interrupt.value  
    for request in interrupts["action_requests"]:
        print(request["description"])


input_message = {
    "role": "user",
    "content": (
        "Can you look up the weather in Boston and San Francisco?"
    ),
}
config = {"configurable": {"thread_id": "some_id"}}
interrupts = []
for stream_mode, data in agent.stream(
    {"messages": [input_message]},
    config=config,
    stream_mode=["messages", "updates"],
):
    if stream_mode == "messages":
        token, metadata = data
        if isinstance(token, AIMessageChunk):
            _render_message_chunk(token)
    if stream_mode == "updates":
        for source, update in data.items():
            if source in ("model", "tools"):
                _render_completed_message(update["messages"][-1])
            if source == "__interrupt__":
                interrupts.extend(update)
                _render_interrupt(update[0])

def _get_interrupt_decisions(interrupt: Interrupt) -> list[dict]:
    return [
        {
            "type": "edit",
            "edited_action": {
                "name": "get_weather",
                "args": {"city": "Boston, U.K."},
            },
        }
        if "boston" in request["description"].lower()
        else {"type": "approve"}
        for request in interrupt.value["action_requests"]
    ]

decisions = {}
for interrupt in interrupts:
    decisions[interrupt.id] = {
        "decisions": _get_interrupt_decisions(interrupt)
    }

decisions

interrupts = []
for stream_mode, data in agent.stream(
    Command(resume=decisions),
    config=config,
    stream_mode=["messages", "updates"],
):
    # Streaming loop is unchanged
    if stream_mode == "messages":
        token, metadata = data
        if isinstance(token, AIMessageChunk):
            _render_message_chunk(token)
    if stream_mode == "updates":
        for source, update in data.items():
            if source in ("model", "tools"):
                _render_completed_message(update["messages"][-1])
            if source == "__interrupt__":
                interrupts.extend(update)
                _render_interrupt(update[0])

from typing import Any

from langchain.agents import create_agent
from langchain.chat_models import init_chat_model
from langchain.messages import AIMessage, AnyMessage


def get_weather(city: str) -> str:
    """Get weather for a given city."""

    return f"It's always sunny in {city}!"


weather_model = init_chat_model("openai:gpt-5.2")
weather_agent = create_agent(
    model=weather_model,
    tools=[get_weather],
    name="weather_agent",
)


def call_weather_agent(query: str) -> str:
    """Query the weather agent."""
    result = weather_agent.invoke({
        "messages": [{"role": "user", "content": query}]
    })
    return result["messages"][-1].text


supervisor_model = init_chat_model("openai:gpt-5.2")
agent = create_agent(
    model=supervisor_model,
    tools=[call_weather_agent],
    name="supervisor",
)

def _render_message_chunk(token: AIMessageChunk) -> None:
    if token.text:
        print(token.text, end="|")
    if token.tool_call_chunks:
        print(token.tool_call_chunks)


def _render_completed_message(message: AnyMessage) -> None:
    if isinstance(message, AIMessage) and message.tool_calls:
        print(f"Tool calls: {message.tool_calls}")
    if isinstance(message, ToolMessage):
        print(f"Tool response: {message.content_blocks}")


input_message = {"role": "user", "content": "What is the weather in Boston?"}
current_agent = None
for _, stream_mode, data in agent.stream(
    {"messages": [input_message]},
    stream_mode=["messages", "updates"],
    subgraphs=True,
):
    if stream_mode == "messages":
        token, metadata = data
        if agent_name := metadata.get("lc_agent_name"):
            if agent_name != current_agent:
                print(f"🤖 {agent_name}: ")
                current_agent = agent_name  
        if isinstance(token, AIMessage):
            _render_message_chunk(token)
    if stream_mode == "updates":
        for source, update in data.items():
            if source in ("model", "tools"):
                _render_completed_message(update["messages"][-1])

from langchain_openai import ChatOpenAI

model = ChatOpenAI(
    model="gpt-4.1",
    streaming=False
)