Langfuse Prompt Management — Versioned Prompts + A/B Tests

Quick Use

1. pip install langfuse
2. Set LANGFUSE_PUBLIC_KEY / SECRET_KEY / HOST in env
3. Author prompt in UI, label production, fetch with lf.get_prompt(name, label='production')

Intro

Langfuse Prompt Management stores prompts as versioned, labeled artifacts in Langfuse — edit in the UI, fetch from the SDK at runtime, swap models or templates without code deploys. Each prompt has a label (production, staging, experiment-v3) you point your code at. Best for: teams iterating on prompts faster than they can ship code, A/B testing prompts, granting non-engineers safe edit access. Works with: Python and JS SDKs, LangChain Hub-compatible, OpenAI and Anthropic message format. Setup time: 5 minutes.

Push a prompt programmatically

from langfuse import Langfuse
lf = Langfuse()  # picks up LANGFUSE_PUBLIC_KEY / SECRET_KEY / HOST

lf.create_prompt(
    name="support-triage",
    prompt=[
        {"role": "system", "content": "You triage support tickets into urgent / billing / general."},
        {"role": "user",   "content": "Ticket: {{ticket_text}}"},
    ],
    config={"model": "claude-3-5-sonnet-20241022", "temperature": 0.2},
    labels=["production"],
)

Fetch + execute (with caching)

from langfuse import Langfuse
from langfuse.openai import openai  # auto-tracing wrapper

lf = Langfuse()
prompt = lf.get_prompt("support-triage", label="production", cache_ttl_seconds=60)

messages = prompt.compile(ticket_text="My card was charged twice for order #4521")
resp = openai.chat.completions.create(
    model=prompt.config["model"],
    messages=messages,
    temperature=prompt.config["temperature"],
)

A/B testing two prompt versions

Tag two versions with separate labels (production-a, production-b), split traffic in code by user_id hash, then compare success metrics in the Langfuse Scores tab.

import hashlib

def variant(user_id: str) -> str:
    return "production-a" if int(hashlib.md5(user_id.encode()).hexdigest(), 16) % 2 == 0 else "production-b"

prompt = lf.get_prompt("support-triage", label=variant(user_id))

Why labels not version pins

Self-hosted Langfuse

git clone https://github.com/langfuse/langfuse
cd langfuse
docker compose up -d
# Open http://localhost:3000, create org + project, copy keys into .env

FAQ

Q: How is this different from LangChain Hub? A: Langfuse Prompt Management ships with full traces — you see which prompt version produced which output, with cost and latency. LangChain Hub is registry-only with no observability. Langfuse also self-hosts; Hub is LangSmith-tied.

Q: Can non-engineers edit prompts safely? A: Yes — give them Langfuse project access with the Editor role. They edit in UI, save creates a new version. Production label only moves when an admin promotes it, so junior edits can't ship without review.

Q: What's the cache_ttl_seconds default? A: 60 seconds. The SDK fetches and caches; subsequent calls within 60s use the cache. Tune lower for fast-iteration dev (1s) or higher for stable prod (300s+) to reduce control-plane load.

Source & Thanks

Built by Langfuse. Licensed under MIT.

langfuse/langfuse — ⭐ 8,000+