LlamaIndex vs LangGraph

import { VectorStoreIndex, SimpleDirectoryReader } from 'llamaindex';

const documents = await new SimpleDirectoryReader().loadData({ directoryPath: './data' });
const index = await VectorStoreIndex.fromDocuments(documents);
const queryEngine = index.asQueryEngine();
const response = await queryEngine.query({ query: 'What is the main topic?' });
console.log(response.toString());

import { StateGraph, END } from '@langchain/langgraph';

const workflow = new StateGraph({ channels: { messages: { value: (x, y) => x.concat(y) } } });

workflow.addNode('agent', async (state) => {
  const response = await llm.invoke(state.messages);
  return { messages: [response] };
});

workflow.setEntryPoint('agent');
workflow.addEdge('agent', END);

const app = workflow.compile();
const result = await app.invoke({ messages: [{ role: 'user', content: 'Hello' }] });