@langfuse/openai

Langfuse is the open-source LLM engineering platform: tracing & evaluation for LLM and agent applications, prompt management, datasets & experiments, and evaluation (scores). This package provides the observeOpenAI wrapper, which traces every call made through the official OpenAI SDK (chat completions, responses, embeddings, streaming) as Langfuse generations — including token usage and cost. Spans are exported by the LangfuseSpanProcessor from @langfuse/otel; prompt management, datasets/experiments, and evals/scores live in @langfuse/client.

[!IMPORTANT] This is the current SDK generation (@langfuse/* scoped packages). The unscoped langfuse npm package is the legacy v3 SDK — for new integrations use the @langfuse/* packages. Migration guides: v3 → v4, v4 → v5.

Install

npm install @langfuse/openai @langfuse/otel openai @opentelemetry/sdk-trace-node

Environment variables

LANGFUSE_PUBLIC_KEY="pk-lf-..."
LANGFUSE_SECRET_KEY="sk-lf-..."
LANGFUSE_BASE_URL="https://cloud.langfuse.com" # 🇪🇺 EU region. 🇺🇸 US: https://us.cloud.langfuse.com

Quickstart

// Register the span processor once at startup
import { LangfuseSpanProcessor } from "@langfuse/otel";
import { NodeTracerProvider } from "@opentelemetry/sdk-trace-node";

new NodeTracerProvider({
  spanProcessors: [new LangfuseSpanProcessor()],
}).register();

// Wrap the OpenAI client
import OpenAI from "openai";
import { observeOpenAI } from "@langfuse/openai";

const openai = observeOpenAI(new OpenAI());

const completion = await openai.chat.completions.create({
  model: "gpt-5.1",
  messages: [{ role: "user", content: "What is Langfuse?" }],
});

Packages

| Package | NPM | Description | Environments | | --------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------- | ------------ | | @langfuse/tracing | | OpenTelemetry-based tracing instrumentation | Node.js 20+ | | @langfuse/otel | | LangfuseSpanProcessor to export OpenTelemetry spans to Langfuse | Node.js 20+ | | @langfuse/client | | Prompt management, datasets, experiments, scores, full REST API | Universal JS | | @langfuse/openai | | observeOpenAI wrapper for tracing the OpenAI SDK | Universal JS | | @langfuse/langchain | | CallbackHandler for LangChain / LangGraph tracing | Universal JS | | @langfuse/vercel-ai-sdk | | Telemetry integration for Vercel AI SDK v7 | Universal JS | | @langfuse/browser | | Browser score ingestion with public-key auth | Browser | | @langfuse/core | | Shared core: generated API client, logger, utilities | Universal JS |

Documentation

• OpenAI integration guide: https://langfuse.com/integrations/model-providers/openai-js
• Docs: https://langfuse.com/docs/observability/sdk/overview
• Reference: https://js.reference.langfuse.com
• LLM/agent-readable docs index: https://langfuse.com/llms.txt

License

MIT