Daily Delta · the full list
Thanks for commenting "TRACE" — here's everything from the post in one place: what it does, how to try it free, and the real catch.
Langfuse is an open-source platform that traces every prompt, response, and step your AI takes — not just the final answer. When an AI agent gives a wrong answer, Langfuse is how you find out where it went wrong, instead of hearing about it from a user first. Their own numbers, from langfuse.com: 10+ billion observations tracked monthly, used by 21 of the Fortune 50, 100,000+ engineers building on it. Real companies named on their site include Canva, Twilio, Intuit, Cisco, and Expedia.
pip install langfuse openaifrom langfuse import observe
from langfuse.openai import openai
@observe()
def story():
return openai.chat.completions.create(
model="gpt-4o",
messages=[{"role": "user", "content": "What is Langfuse?"}],
).choices[0].message.content| Path | What you get |
|---|---|
| Self-hosted | Genuinely free forever, your own infrastructure. Running in ~5 minutes with Docker. |
| Langfuse Cloud (Hobby) | Free, no card. 50,000 observations/month, 30-day retention, 2 users. |
git clone --depth=1 https://github.com/langfuse/langfuse.git && cd langfuse && docker compose up32,700+ stars, YC W23, pushed code the same day this post was written —
actively maintained, not an abandoned side project. License is precise, not blanket
MIT: the core is MIT-licensed, but anything under the repo's ee/
(enterprise) directories ships under a separate, non-open license.
Real, notable open-source projects run their own AI tracing on Langfuse, per its own README: Firecrawl (the tool behind Daily Delta's very first post, 56K★), Langflow (116K★), Open WebUI (109K★), LlamaIndex (44K★), and Flowise (43K★).
The catch
The free Cloud plan caps at 50K observations/month and 30-day retention — fine for a side project, not production scale (Core plan starts $29/mo for that). Self-hosting is free but real infra work — Docker, Kubernetes, or Terraform — not a one-click deploy. Enterprise features (SSO enforcement, audit logs, SCIM) are paid-only.