langchain-workflow-builder

LangChain Workflow Builder

Build powerful LLM applications with chains, agents, and retrieval-augmented generation.

Core Workflow

1. Setup LangChain: Install and configure
2. Create chains: Build processing pipelines
3. Add memory: Enable conversation context
4. Define tools: Extend agent capabilities
5. Implement RAG: Add knowledge retrieval
6. Deploy: Production-ready setup

Installation

npm install langchain @langchain/openai @langchain/community

Basic Chains

Simple LLM Chain

// chains/simple.ts
import { ChatOpenAI } from '@langchain/openai';
import { ChatPromptTemplate } from '@langchain/core/prompts';
import { StringOutputParser } from '@langchain/core/output_parsers';

const model = new ChatOpenAI({
  modelName: 'gpt-4-turbo-preview',
  temperature: 0.7,
});

const prompt = ChatPromptTemplate.fromMessages([
  ['system', 'You are a helpful assistant that {task}.'],
  ['human', '{input}'],
]);

const chain = prompt.pipe(model).pipe(new StringOutputParser());

// Usage
const result = await chain.invoke({
  task: 'summarizes text concisely',
  input: 'Summarize this article: ...',
});

Sequential Chain

// chains/sequential.ts
import { RunnableSequence } from '@langchain/core/runnables';

// Chain 1: Extract key points
const extractChain = ChatPromptTemplate.fromMessages([
  ['system', 'Extract the key points from the following text.'],
  ['human', '{text}'],
]).pipe(model).pipe(new StringOutputParser());

// Chain 2: Summarize key points
const summarizeChain = ChatPromptTemplate.fromMessages([
  ['system', 'Create a brief summary from these key points.'],
  ['human', '{keyPoints}'],
]).pipe(model).pipe(new StringOutputParser());

// Combined chain
const fullChain = RunnableSequence.from([
  {
    keyPoints: extractChain,
    originalText: (input) => input.text,
  },
  {
    summary: summarizeChain,
    keyPoints: (input) => input.keyPoints,
  },
]);

const result = await fullChain.invoke({ text: 'Long article...' });
// { summary: '...', keyPoints: '...' }