> ## Documentation Index
> Fetch the complete documentation index at: https://docs.langchain.com/llms.txt
> Use this file to discover all available pages before exploring further.

# SourceyRetriever integration

> Integrate with the SourceyRetriever retriever using LangChain JavaScript.

## Overview

[Sourcey](https://sourcey.com) already emits the files this retriever needs.

Use `SourceyRetriever` to retrieve from a published Sourcey docs site. It
reads `search-index.json`, uses `llms-full.txt` when present, and returns
`Document` objects with canonical page URLs in `metadata.source`.

### Integration details

| Retriever          | Source                        |                                 Package                                |
| :----------------- | :---------------------------- | :--------------------------------------------------------------------: |
| `SourceyRetriever` | Published Sourcey docs sites. | [`langchain-sourcey`](https://www.npmjs.com/package/langchain-sourcey) |

## Setup

### Installation

<CodeGroup>
  ```bash npm theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
  npm install langchain-sourcey @langchain/core
  ```

  ```bash yarn theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
  yarn add langchain-sourcey @langchain/core
  ```

  ```bash pnpm theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
  pnpm add langchain-sourcey @langchain/core
  ```
</CodeGroup>

No API key is required.

## Instantiation

`siteUrl` should point at the root of a published Sourcey docs build.

```typescript theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
import { SourceyRetriever } from "langchain-sourcey";

const retriever = new SourceyRetriever({
  siteUrl: "https://sourcey.com/docs",
  topK: 3,
});
```

## Usage

```typescript theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
const docs = await retriever.invoke("mcp integration");

for (const doc of docs) {
  console.log(doc.metadata.title);
  console.log(doc.metadata.source);
}
```

## Use within a chain

Install a chat model package. This example uses OpenAI:

<CodeGroup>
  ```bash npm theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
  npm install @langchain/openai
  ```

  ```bash yarn theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
  yarn add @langchain/openai
  ```

  ```bash pnpm theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
  pnpm add @langchain/openai
  ```
</CodeGroup>

```typescript theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
import type { Document } from "@langchain/core/documents";
import { StringOutputParser } from "@langchain/core/output_parsers";
import { ChatPromptTemplate } from "@langchain/core/prompts";
import { RunnablePassthrough, RunnableSequence } from "@langchain/core/runnables";
import { ChatOpenAI } from "@langchain/openai";
import { SourceyRetriever } from "langchain-sourcey";

const retriever = new SourceyRetriever({
  siteUrl: "https://sourcey.com/docs",
  topK: 3,
});

const prompt = ChatPromptTemplate.fromTemplate(
  `Answer the question using the documentation context below.

{context}

Question: {question}`
);

const formatDocs = (docs: Document[]) =>
  docs.map((doc) => doc.pageContent).join("\n\n");

const chain = RunnableSequence.from([
  {
    context: retriever.pipe(formatDocs),
    question: new RunnablePassthrough(),
  },
  prompt,
  new ChatOpenAI({ model: "gpt-4.1-mini" }),
  new StringOutputParser(),
]);

await chain.invoke("How does Sourcey document MCP servers?");
```

## Sourcey site requirements

For clean retrieval, the published Sourcey site should:

* publish `search-index.json`
* publish `llms-full.txt`
* set `siteUrl` in `sourcey.config.ts` so returned citations are canonical

If `llms-full.txt` is not available, `SourceyRetriever` falls back to
extracting text from the matched HTML page.

## More

* Sourcey guide: [Using Sourcey with LangChain](https://sourcey.com/docs/guides/guide-langchain-retriever)
* Package: [langchain-sourcey on npm](https://www.npmjs.com/package/langchain-sourcey)

***

<div className="source-links">
  <Callout icon="terminal-2">
    [Connect these docs](/use-these-docs) to Claude, VSCode, and more via MCP for real-time answers.
  </Callout>

  <Callout icon="edit">
    [Edit this page on GitHub](https://github.com/langchain-ai/docs/edit/main/src/oss/javascript/integrations/retrievers/sourcey.mdx) or [file an issue](https://github.com/langchain-ai/docs/issues/new/choose).
  </Callout>
</div>