MutagenT LangChain

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║                     LangChain Integration for AI-Native Observability.                     ║
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LangChain callback handler for tracing LLM calls, chains, tools, and retrievers to MutagenT.

Installation

npm install @mutagent/langchain @mutagent/sdk

Peer Dependencies

| Package | Version | |---------|---------| | @langchain/core | >=0.1.0 | | @mutagent/sdk | ^0.1.0 |

Quick Start

import { MutagentCallbackHandler } from '@mutagent/langchain';
import { initTracing } from '@mutagent/sdk/tracing';
import { ChatOpenAI } from '@langchain/openai';

// Initialize tracing once at app startup
initTracing({ apiKey: process.env.MUTAGENT_API_KEY! });

// Create the callback handler
const handler = new MutagentCallbackHandler();

// Use with any LangChain component
const model = new ChatOpenAI({ model: 'gpt-4' });
const result = await model.invoke('Hello!', { callbacks: [handler] });

// Works with chains too
const result2 = await chain.invoke(input, { callbacks: [handler] });

API Reference

MutagentCallbackHandler

Extends BaseCallbackHandler from @langchain/core. Automatically traces:

• LLM calls -- handleLLMStart, handleChatModelStart, handleLLMEnd, handleLLMError
• Chains -- handleChainStart, handleChainEnd, handleChainError
• Tools -- handleToolStart, handleToolEnd, handleToolError
• Retrievers -- handleRetrieverStart, handleRetrieverEnd, handleRetrieverError

Parent-child span relationships are maintained automatically via LangChain's runId / parentRunId mechanism. Token usage metrics are extracted when available.

License

MIT