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title: "@prefactor/langchain"
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[**Prefactor TypeScript SDK**](../../index.md)

***

[Prefactor TypeScript SDK](../../modules.md) / @prefactor/langchain

# @prefactor/langchain

LangChain adapter package exposing Prefactor initialization helpers and middleware.

## `@prefactor/langchain` overview

`@prefactor/langchain` adds Prefactor tracing to LangChain middleware so agent, model,
chain, and tool activity is captured automatically.

Use this package as a provider for the core `init` function.

## Quick start

```ts
import { init } from '@prefactor/core';
import { PrefactorLangChain } from '@prefactor/langchain';
import { createAgent } from 'langchain';

const prefactor = init({
  provider: new PrefactorLangChain(),
  httpConfig: {
    apiUrl: 'https://api.prefactor.ai',
    apiToken: process.env.PREFACTOR_API_TOKEN!,
    agentIdentifier: 'support-bot-v1',
  },
});

const agent = createAgent({
  model: 'claude-sonnet-4-5-20250929',
  tools: [],
  middleware: [prefactor.getMiddleware()],
});
```

## Classes

- [PrefactorLangChain](classes/PrefactorLangChain.md)

## Interfaces

- [PrefactorLangChainOptions](interfaces/PrefactorLangChainOptions.md)

## Variables

- [DEFAULT\_LANGCHAIN\_AGENT\_SCHEMA](variables/DEFAULT_LANGCHAIN_AGENT_SCHEMA.md)