@nest-langchain/patterns

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NestJS decorators for provider collaboration and modern LangChain task patterns.

This package discovers decorated task classes, validates task graphs at module startup, and invokes provider roles through Nest DI tokens. Provider SDKs stay outside this package; pass tokens from @nest-langchain/openai, @nest-langchain/anthropic, @nest-langchain/gemini, @nest-langchain/bedrock, or custom providers.

Install

pnpm add @nest-langchain/core @nest-langchain/patterns @langchain/core

Install Deep Agents only when using @DeepAgent:

pnpm add deepagents

Module

import { Module } from '@nestjs/common';
import { CollaborativePatternsModule } from '@nest-langchain/patterns';

@Module({
  imports: [
    CollaborativePatternsModule.forRoot({
      global: true,
    }),
  ],
  providers: [LaunchReviewTask],
})
export class AppModule {}

Collaborative Task

import {
  CollaborativeTask,
  TaskExecutionContext,
  TaskStep,
} from '@nest-langchain/patterns';

@CollaborativeTask({
  name: 'launch-review',
  models: [
    { role: 'planner', token: OPENAI_MODEL },
    { role: 'critic', token: ANTHROPIC_MODEL },
    { role: 'judge', token: GEMINI_MODEL },
  ],
})
export class LaunchReviewTask {
  @TaskStep({
    name: 'drafts',
    pattern: 'parallel',
    models: ['planner', 'critic'],
  })
  drafts(input: { product: string }) {
    return `Draft a launch plan for ${input.product}.`;
  }

  @TaskStep({
    name: 'decision',
    pattern: 'structured',
    model: 'judge',
    dependsOn: ['drafts'],
  })
  decision(_input: unknown, context: TaskExecutionContext) {
    return `Decide from ${JSON.stringify(context.steps)}.`;
  }
}

Supported step patterns:

• invoke
• parallel
• structured
• tool-call
• fallback

Definitions fail fast on duplicate model roles, duplicate step names, unknown dependencies, and unknown model role references.

Looking For LangGraph Command Pattern?

LangGraph execution-control patterns live in @nest-langchain/langgraph, not in this package. Use commandTo, @GraphNode({ ends }), CommandNode, RouteCommandNode, and ParentHandoffNode from @nest-langchain/langgraph for Command routing, parent handoff, Send fan-out, interrupts, resume, and subgraph transforms.

Deep Agents

import {
  DeepAgent,
  DeepAgentSubagent,
  DeepAgentTool,
} from '@nest-langchain/patterns';

@DeepAgent({
  name: 'market-research-agent',
  model: 'supervisor',
  models: [{ role: 'supervisor', token: OPENAI_MODEL }],
  systemPrompt: 'Plan, research, and write concise reports.',
  skills: ['/skills/research'],
  interruptOn: { write_file: true },
})
export class MarketResearchAgent {
  @DeepAgentTool({
    name: 'search_market',
    description: 'Search market notes.',
    schema: {
      type: 'object',
      properties: { query: { type: 'string' } },
      required: ['query'],
    },
  })
  searchMarket(input: { query: string }) {
    return `notes for ${input.query}`;
  }

  @DeepAgentSubagent({
    name: 'researcher',
    description: 'Runs isolated market research.',
    model: 'supervisor',
    systemPrompt: 'You are a focused market researcher.',
    tools: ['search_market'],
  })
  researcher() {
    return undefined;
  }
}

Demo

pnpm --filter @nest-langchain/demo-patterns start

curl "http://localhost:3004/tasks"
curl -X POST "http://localhost:3004/tasks/launch-review" \
  -H "content-type: application/json" \
  -d '{"product":"Nest LangChain Patterns","market":"Korea B2B SaaS"}'