Variable MessagesAnnotationConst

Prebuilt state annotation that combines returned messages. Can handle standard messages and special modifiers like RemoveMessage instances.

Specifically, importing and using the prebuilt MessagesAnnotation like this:

Example

import { MessagesAnnotation, StateGraph } from "@langchain/langgraph";

const graph = new StateGraph(MessagesAnnotation)
  .addNode(...)
  ...
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Is equivalent to initializing your state manually like this:

Example

import { BaseMessage } from "@langchain/core/messages";
import { Annotation, StateGraph, messagesStateReducer } from "@langchain/langgraph";

export const StateAnnotation = Annotation.Root({
  messages: Annotation<BaseMessage[]>({
    reducer: messagesStateReducer,
    default: () => [],
  }),
});

const graph = new StateGraph(StateAnnotation)
  .addNode(...)
  ...
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