Function createHistoryAwareRetriever

Create a chain that takes conversation history and returns documents. If there is no chat_history, then the input is just passed directly to the retriever. If there is chat_history, then the prompt and LLM will be used to generate a search query. That search query is then passed to the retriever.

Example

// yarn add langchain @langchain/openai

import { ChatOpenAI } from "@langchain/openai";
import { pull } from "langchain/hub";
import { createRetrievalChain } from "langchain/chains/retrieval";
import { createStuffDocumentsChain } from "langchain/chains/combine_documents";

const rephrasePrompt = await pull("langchain-ai/chat-langchain-rephrase");
const llm = new ChatOpenAI({});
const retriever = ...
const chain = await createHistoryAwareRetriever({
  llm,
  retriever,
  rephrasePrompt,
});
const result = await chain.invoke({"input": "...", "chat_history": [] })
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