langfuse-local-dev-loop

name	langfuse-local-dev-loop
description	Set up Langfuse local development workflow with hot reload and debugging. Use when developing LLM applications locally, debugging traces, or setting up a fast iteration loop with Langfuse. Trigger with phrases like "langfuse local dev", "langfuse development", "debug langfuse traces", "langfuse hot reload", "langfuse dev workflow".
allowed-tools	Read, Write, Edit, Bash(npm:*), Bash(docker:*), Bash(pnpm:*)
version	1.12.0
license	MIT
author	Jeremy Longshore <[e-mail]>
tags	["saas","langfuse","llm","debugging","workflow"]
compatibility	Designed for Claude Code, also compatible with Codex and OpenClaw

Langfuse Local Dev Loop

Overview

Fast local development workflow with Langfuse tracing, immediate trace visibility, debug logging, and optional self-hosted local instance via Docker.

Prerequisites

• Completed langfuse-install-auth setup
• Node.js 18+ with tsx for hot reload (npm install -D tsx)
• Docker (optional, for self-hosted local instance)

Instructions

Step 1: Development Environment File

# .env.local (git-ignored)
LANGFUSE_PUBLIC_KEY=pk-lf-dev-...
LANGFUSE_SECRET_KEY=sk-lf-dev-...
LANGFUSE_BASE_URL=https://cloud.langfuse.com

# Dev-specific settings
NODE_ENV=development
OPENAI_API_KEY=sk-...

Step 2: Dev-Optimized Langfuse Setup (v4+)

// src/lib/langfuse-dev.ts
import { LangfuseSpanProcessor } from "@langfuse/otel";
import { NodeSDK } from "@opentelemetry/sdk-node";
import { LangfuseClient } from "@langfuse/client";

const isDev = process.env.NODE_ENV !== "production";

// Configure span processor with dev-friendly settings
const processor = new LangfuseSpanProcessor({
  // In dev: flush immediately for instant visibility
  ...(isDev && { exportIntervalMillis: 1000, maxExportBatchSize: 1 }),
});

const sdk = new NodeSDK({ spanProcessors: [processor] });
sdk.start();

  langfuse =  ();


  () {
   (isDev) {
     host = process.. || ;
    .();
  }
}


process.(,  () => {
   sdk.();
  process.();
});