@nest-langchain/openai

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OpenAI chat model provider for NestJS dependency injection.

This package wires a ChatOpenAI instance from @langchain/openai into NestJS dependency injection. Connection info (apiKey) lives at the module level; the model and temperature are chosen per preset or per call via a factory — the library no longer picks a default model.

Install

pnpm add @nest-langchain/openai @langchain/openai

Module

import { Module } from '@nestjs/common';
import { OpenAIProviderModule } from '@nest-langchain/openai';

@Module({
  imports: [
    OpenAIProviderModule.forRoot({
      apiKey: process.env.OPENAI_API_KEY, // falls back to OPENAI_API_KEY
      presets: [
        { name: 'fast', model: 'gpt-4.1-mini', temperature: 0 },
        { name: 'creative', model: 'gpt-4.1', temperature: 0.9 },
      ],
    }),
  ],
})
export class AiModule {}

Omit presets to inject the factory and build models at runtime (see below).

Injection

Inject a named preset, or inject the factory for per-call model creation. model is always required — the library never assumes one:

import { Injectable } from '@nestjs/common';
import { ChatOpenAI } from '@langchain/openai';
import {
  InjectOpenAIChatModel,
  InjectOpenAIChatModelFactory,
  OpenAIChatModelFactory,
} from '@nest-langchain/openai';

@Injectable()
export class SupportDraftService {
  constructor(
    @InjectOpenAIChatModel('fast') private readonly model: ChatOpenAI,
    @InjectOpenAIChatModelFactory()
    private readonly factory: OpenAIChatModelFactory,
  ) {}

  draft(message: string) {
    return this.model.invoke(message);
  }

  draftWith(model: string, message: string) {
    return this.factory.create({ model }).invoke(message);
  }
}

For dynamic lookup use getOpenAIChatModelToken(name).

Async Connection Info

Use forRootAsync when the API key comes from ConfigService or a secrets manager. Presets stay static (token names are fixed at definition time):

OpenAIProviderModule.forRootAsync({
  imports: [ConfigModule],
  inject: [ConfigService],
  useFactory: (config: ConfigService) => ({
    apiKey: config.get('OPENAI_API_KEY'),
  }),
  presets: [{ name: 'fast', model: 'gpt-4.1-mini' }],
});

Migration (v0.1 → v0.2)

NEST_LANGCHAIN_OPENAI_CHAT_MODEL and the module-level model / temperature options were removed. Replace @Inject(NEST_LANGCHAIN_OPENAI_CHAT_MODEL) with a named preset (@InjectOpenAIChatModel('default') + presets: [{ name: 'default', model: '...' }]), or inject the factory with @InjectOpenAIChatModelFactory() and call .create({ model }).

Demo

pnpm --filter @nest-langchain/demo-providers start
curl "http://localhost:3006/providers"

OPENAI_API_KEY=sk-... pnpm --filter @nest-langchain/demo-providers start
curl -X POST "http://localhost:3006/providers/openai/invoke" \
  -H "content-type: application/json" \
  -d '{"prompt":"Write one sentence about NestJS provider tokens."}'