langfuse-hello-world

name	langfuse-hello-world
description	Create a minimal working Langfuse trace example. Use when starting a new Langfuse integration, testing your setup, or learning basic Langfuse tracing patterns. Trigger with phrases like "langfuse hello world", "langfuse example", "langfuse quick start", "first langfuse trace", "simple langfuse code".
allowed-tools	Read, Write, Edit
version	1.12.0
license	MIT
author	Jeremy Longshore <[e-mail]>
tags	["saas","langfuse","testing","tracing"]
compatibility	Designed for Claude Code

Langfuse Hello World

Overview

Create your first Langfuse trace with real SDK calls. Demonstrates the trace/span/generation hierarchy, the observe wrapper, and the OpenAI drop-in integration.

Prerequisites

• Completed langfuse-install-auth setup
• Valid API credentials in environment variables
• OpenAI API key (for the OpenAI integration example)

Instructions

Step 1: Hello World with v4+ Modular SDK

// hello-langfuse.ts
import { startActiveObservation, observe, updateActiveObservation } from "@langfuse/tracing";
import { LangfuseSpanProcessor } from "@langfuse/otel";
import { NodeSDK } from "@opentelemetry/sdk-node";

// Register OpenTelemetry processor (once at startup)
const sdk = new NodeSDK({
  spanProcessors: [new LangfuseSpanProcessor()],
});
sdk.start();

async function main() {
  // Create a top-level trace with startActiveObservation
  await startActiveObservation("hello-world", async (span) => {
    span.update({
      input: { message: "Hello, Langfuse!" },
      metadata: { source: "hello-world-example" },
    });

    // Nested span -- automatically linked to parent
     (,  (child) => {
      child.({ : { :  } });
        ( (r, ));
      child.({ : { :  } });
    });

    
     (
      { : , :  },
       (gen) => {
        gen.({
          : ,
          : [{ : , :  }],
          : { :  },
          : { : , : , :  },
        });
      }
    );

    span.({ : { :  } });
  });

  
   sdk.();
  .();
}

().(.);