@nest-langchain/core

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Use @nest-langchain/core when your Nest app needs a shared place to register and call runnables by name.

Install

pnpm add @nest-langchain/core

Install the Nest peer dependencies in your app if they are not already present:

pnpm add @nestjs/common @nestjs/core reflect-metadata rxjs

Module

import { Module } from '@nestjs/common';
import { LangChainModule } from '@nest-langchain/core';

@Module({
  imports: [
    LangChainModule.forRoot({
      global: true,
      defaultConfig: {
        tags: ['api'],
        metadata: { service: 'support' },
      },
    }),
  ],
})
export class AppModule {}

Register Your Runnable

import { Injectable, OnModuleInit } from '@nestjs/common';
import { LangChainRegistry } from '@nest-langchain/core';

@Injectable()
export class SupportRegistry implements OnModuleInit {
  constructor(private readonly registry: LangChainRegistry) {}

  onModuleInit() {
    this.registry.registerRunnable(
      'support-triage',
      {
        invoke: async (input: { message: string }) => ({
          intent: input.message.includes('card') ? 'billing' : 'general',
        }),
      },
      {
        kind: 'chain',
        nodes: ['classify'],
        tags: ['support'],
      },
    );
  }
}

Start with invoke(). Add stream() or streamEvents() only when the runnable needs streaming.

Add More Features

Install another package when you want to add a specific LangChain feature.

| When You Want To | Install | | ------------------------------- | ------------------------------------------------------------------------------------- | | build LangGraph workflows | @nest-langchain/core @nest-langchain/langgraph @langchain/core @langchain/langgraph | | trace runs with LangSmith | @nest-langchain/core @nest-langchain/langsmith langsmith | | expose Nest methods as tools | @nest-langchain/core @nest-langchain/tools @langchain/core zod | | manage prompt templates | @nest-langchain/prompts @langchain/core | | run collaborative task patterns | @nest-langchain/core @nest-langchain/patterns @langchain/core | | serve graph documentation | @nest-langchain/core @nest-langchain/visualization | | inject an OpenAI model | @nest-langchain/openai @langchain/openai | | inject OpenAI-compatible models | @nest-langchain/openai-compatible @langchain/openai | | inject an Anthropic model | @nest-langchain/anthropic @langchain/anthropic | | inject a Gemini model | @nest-langchain/gemini @langchain/google-genai | | inject an AWS Bedrock model | @nest-langchain/bedrock @langchain/aws |

Demo

pnpm install
pnpm --filter @nest-langchain/demo-basic start

curl "http://localhost:3000/runnables"
curl -X POST "http://localhost:3000/support/triage" \
  -H "content-type: application/json" \
  -d '{"message":"Checkout fails with a card error","customerTier":"enterprise","channel":"web"}'