使用 LangGraph 编排多个节点时，状态字段采用哪种归并函数，会直接影响后续节点拿到的数据结构。add_messages 和 operator.add 看似都能把新元素追加到列表中，但它们对输入值的处理并不一致。下面用相同的 StateGraph 流程分别运行两种配置，观察结果并说明各自适合的使用场景。

add_messages和operator.add 产生的数据格式完全不一样，这一点要注意

add_messages

from typing import TypedDict, Annotated
from langgraph.graph.message import add_messages
from langgraph.graph import MessagesState, StateGraph,START,END
from prompt_toolkit.contrib.regular_languages.regex_parser import AnyNode
from rich import print as rprint
from IPython import display
import operator

class State(TypedDict):
  list: Annotated[list[str],add_messages]
  # list: Annotated[list[str],operator.add]

def node1(state: State) -> dict:
  return {
    "list": ["11111"],
  }
def node2(state: State) -> dict:
  return {
    "list": ["22222"],
  }
graph=(
  StateGraph(State)
  .add_node(node1)
  .add_node(node2)
  .add_edge(START, "node1")
  .add_edge("node1", "node2")
  .add_edge("node2", END)
  .compile()
)
display.display(graph)
res=graph.invoke({"list":["start"]})
rprint(res)

{
    'list': [
        HumanMessage(
            content='start',
            additional_kwargs={},
            response_metadata={},
            id='8631c142-2fbc-494b-ad06-f501263bea35'
        ),
        HumanMessage(
            content='11111',
            additional_kwargs={},
            response_metadata={},
            id='e54a1bf7-ae21-49bf-93d4-0bfdee0de247'
        ),
        HumanMessage(
            content='22222',
            additional_kwargs={},
            response_metadata={},
            id='df900c16-adfd-42f7-9c98-ad1384394d7f'
        )
    ]
}

二 operator.add

from typing import TypedDict, Annotated
from langgraph.graph.message import add_messages
from langgraph.graph import MessagesState, StateGraph,START,END
from prompt_toolkit.contrib.regular_languages.regex_parser import AnyNode
from rich import print as rprint
from IPython import display
import operator

class State(TypedDict):
  # list: Annotated[list[str],add_messages]
  list: Annotated[list[str],operator.add]

def node1(state: State) -> dict:
  return {
    "list": ["11111"],
  }
def node2(state: State) -> dict:
  return {
    "list": ["22222"],
  }
graph=(
  StateGraph(State)
  .add_node(node1)
  .add_node(node2)
  .add_edge(START, "node1")
  .add_edge("node1", "node2")
  .add_edge("node2", END)
  .compile()
)
display.display(graph)
res=graph.invoke({"list":["start"]})
rprint(res)

{'list': ['start', '11111', '22222']}