# Langfuse Install Auth

> Install and configure Langfuse SDK authentication for LLM observability. Use when setting up a new Langfuse integration, configuring API keys, or initializing Langfuse tracing in your project. Trigger with phrases like "install langfuse", "setup langfuse", "langfuse auth", "configure langfuse API key", "langfuse tracing setup".

- Skill: `micsapp/langfuse-install-auth` (Agent Skill)
- Install (CLI): `npx skillmds@latest add micsapp/langfuse-install-auth`
- Raw SKILL.md: https://api.skillmd.com/api/skills/micsapp/langfuse-install-auth/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: AI & ML
- License: MIT
- Author: micsapp (https://skillmd.com/u/micsapp)
- Updated: 2026-09-08
- Page: https://skillmd.com/skills/micsapp/langfuse-install-auth

---

# Langfuse Install & Auth

## Overview
Set up Langfuse SDK and configure authentication for LLM observability and tracing.

## Prerequisites
- Node.js 18+ or Python 3.9+
- Package manager (npm, pnpm, or pip)
- Langfuse account (cloud or self-hosted)
- Public and Secret keys from Langfuse dashboard

## Instructions

### Step 1: Install SDK

```bash
set -euo pipefail
# Node.js / TypeScript
npm install langfuse
# or
pnpm add langfuse

# Python
pip install langfuse
```

### Step 2: Get API Keys

1. Go to Langfuse dashboard (https://cloud.langfuse.com or your self-hosted instance)
2. Navigate to Settings -> API Keys
3. Create new API key pair (Public Key + Secret Key)
4. Note your host URL (cloud: `https://cloud.langfuse.com`)

### Step 3: Configure Authentication

```bash
# Set environment variables
export LANGFUSE_PUBLIC_KEY="pk-lf-..."
export LANGFUSE_SECRET_KEY="sk-lf-..."
export LANGFUSE_HOST="https://cloud.langfuse.com"  # or self-hosted URL

# Or create .env file
cat >> .env << 'EOF'
LANGFUSE_PUBLIC_KEY=pk-lf-your-public-key
LANGFUSE_SECRET_KEY=sk-lf-your-secret-key
LANGFUSE_HOST=https://cloud.langfuse.com
EOF
```

### Step 4: Verify Connection

```typescript
// TypeScript verification
import { Langfuse } from "langfuse";

const langfuse = new Langfuse({
  publicKey: process.env.LANGFUSE_PUBLIC_KEY,
  secretKey: process.env.LANGFUSE_SECRET_KEY,
  baseUrl: process.env.LANGFUSE_HOST,
});

// Create a test trace
const trace = langfuse.trace({
  name: "connection-test",
  metadata: { test: true },
});

// Flush to ensure data is sent
await langfuse.flushAsync();
console.log("Langfuse connection successful! Check dashboard for trace.");
```

```python
# Python verification
from langfuse import Langfuse
import os

langfuse = Langfuse(
    public_key=os.environ.get("LANGFUSE_PUBLIC_KEY"),
    secret_key=os.environ.get("LANGFUSE_SECRET_KEY"),
    host=os.environ.get("LANGFUSE_HOST"),
)

# Create a test trace
trace = langfuse.trace(name="connection-test", metadata={"test": True})

# Flush to ensure data is sent
langfuse.flush()
print("Langfuse connection successful! Check dashboard for trace.")
```

## Output
- Installed SDK package in node_modules or site-packages
- Environment variables or .env file with API credentials
- Successful connection verification trace visible in dashboard

## Error Handling
| Error | Cause | Solution |
|-------|-------|----------|
| Invalid API Key | Incorrect or revoked key | Verify keys in Langfuse dashboard |
| Connection Refused | Wrong host URL | Check LANGFUSE_HOST is correct |
| Network Error | Firewall blocking | Ensure outbound HTTPS to Langfuse host |
| Module Not Found | Installation failed | Run `npm install` or `pip install` again |
| 401 Unauthorized | Keys don't match project | Ensure keys are from same project |

## Examples

### TypeScript Initialization with Options
```typescript
import { Langfuse } from "langfuse";

const langfuse = new Langfuse({
  publicKey: process.env.LANGFUSE_PUBLIC_KEY!,
  secretKey: process.env.LANGFUSE_SECRET_KEY!,
  baseUrl: process.env.LANGFUSE_HOST,
  // Optional configuration
  flushAt: 15,        // Flush after 15 events (default: 15)
  flushInterval: 10000, // Flush every 10 seconds (default: 10000ms)  # 10000: 10 seconds in ms
  requestTimeout: 10000, // Request timeout (default: 10000ms)  # 10 seconds in ms
  enabled: process.env.NODE_ENV === "production", // Disable in dev
});

// Ensure clean shutdown
process.on("beforeExit", async () => {
  await langfuse.shutdownAsync();
});
```

### Python Initialization with Options
```python
from langfuse import Langfuse
import os

langfuse = Langfuse(
    public_key=os.environ.get("LANGFUSE_PUBLIC_KEY"),
    secret_key=os.environ.get("LANGFUSE_SECRET_KEY"),
    host=os.environ.get("LANGFUSE_HOST"),
    # Optional configuration
    flush_at=15,           # Flush after 15 events
    flush_interval=10.0,   # Flush every 10 seconds
    enabled=os.environ.get("NODE_ENV") == "production",
)

# Register shutdown handler
import atexit
atexit.register(langfuse.flush)
```

### OpenAI Integration (Automatic Tracing)
```typescript
import { observeOpenAI } from "langfuse";
import OpenAI from "openai";

const openai = observeOpenAI(new OpenAI(), {
  clientInitParams: {
    publicKey: process.env.LANGFUSE_PUBLIC_KEY,
    secretKey: process.env.LANGFUSE_SECRET_KEY,
    baseUrl: process.env.LANGFUSE_HOST,
  },
});

// All OpenAI calls are now automatically traced
const response = await openai.chat.completions.create({
  model: "gpt-4",
  messages: [{ role: "user", content: "Hello!" }],
});
```

## Resources
- [Langfuse Documentation](https://langfuse.com/docs)
- [Langfuse SDK Reference](https://langfuse.com/docs/sdk)
- [Langfuse Cloud Dashboard](https://cloud.langfuse.com)
- [Self-Hosting Guide](https://langfuse.com/docs/deployment/self-host)

## Next Steps
After successful auth, proceed to `langfuse-hello-world` for your first trace.