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Open-source LLM engineering platform for observability, analytics, and evaluation.

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What is Langfuse?

Langfuse is an open-source LLM engineering platform for tracing, evaluating, and optimizing AI applications in production. It provides the observability layer that bridges the gap between "my AI feature works in development" and "my AI feature works reliably, cost-effectively, and improving over time in production."

For startups with AI features in production, Langfuse answers critical questions: Why did the AI give a wrong answer to that customer? How much does each AI feature cost in tokens? Which prompt version produces better results? Are we hitting latency targets? Without LLM observability, these questions remain unanswered — and AI quality degrades silently.

Key Features for Startups

Tracing follows every request through your AI pipeline. A typical RAG application involves: receiving user query → retrieving documents → constructing prompt → calling LLM → post-processing response → returning to user. Langfuse traces each step — showing inputs, outputs, latency, token counts, and costs. When the AI gives a wrong answer, you see exactly which step failed.

Prompt management versions, tests, and deploys prompts through the Langfuse dashboard without code changes. Compare prompt A vs prompt B side by side with identical inputs. Track which prompt version is in production. Roll back to a previous version if quality drops. This is essential when non-engineers (product managers, content teams) need to iterate on prompts.

Evaluation scores track output quality over time — with manual annotations, automated scoring functions, and LLM-as-judge evaluations. Rate AI outputs on accuracy, helpfulness, and safety. Track quality trends across prompt versions, model changes, and feature updates.

Cost analytics show token usage and spending per trace, per feature, per user, and per prompt version. Identify which features consume the most tokens. Compare costs across models. Optimize spending by routing cheaper tasks to cheaper models.

Dataset management creates evaluation datasets from production traces. Turn real user queries and ideal responses into test sets. Run these datasets against new prompt versions or models to regression-test quality before deployment.

Self-hosted deployment runs Langfuse on your infrastructure with Docker. Your AI traces — which contain user queries, AI responses, and potentially sensitive data — stay on your servers.

Who Should Use Langfuse?

Any startup with AI features in production that needs visibility into quality, cost, and performance. Teams iterating on prompts who need to measure which versions produce better results. Companies spending $500+/month on AI API calls that need cost optimization. Engineers debugging AI quality issues who need to see what happened inside the pipeline.

Langfuse vs Helicone

Helicone is a proxy-based solution — simpler to set up (one URL change) but less flexible. Langfuse provides deeper tracing through complex pipelines with prompt management and evaluation. Helicone for quick, zero-code observability. Langfuse for comprehensive LLM engineering with prompt management.

Langfuse vs Weights & Biases

W&B focuses on ML experiment tracking and model training. Langfuse focuses on LLM application observability in production. W&B for training ML models. Langfuse for operating LLM applications.

Langfuse vs LangSmith

LangSmith (by LangChain) is tightly integrated with LangChain framework. Langfuse is framework-agnostic — works with any LLM pipeline, any provider, any framework. LangSmith for LangChain-native teams. Langfuse for framework-agnostic LLM observability.

How to Claim This Deal

  1. Self-host with Docker or use Langfuse Cloud
  2. Integrate the SDK (Python or JavaScript) into your AI application
  3. Start seeing traces, costs, and quality metrics immediately
  4. Iterate on prompts using the management dashboard

Pricing Overview

Self-hosted is free and open-source with no usage limits. Langfuse Cloud free tier includes 50K observations per month. Pro at $59/month adds higher limits, team features, and priority support. Enterprise with custom limits and SLA.

Who Is This Deal For?

Early-Stage Startups

Seed and pre-seed companies looking to move fast without overspending on tools.

Growing SaaS Teams

Series A+ companies scaling their stack and optimizing software costs.

Solo Founders

Indie hackers and bootstrapped founders who need enterprise tools at startup prices.

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Frequently Asked Questions

Everything you need to know about this startup deal.

Yes. Self-hosted is free. Cloud free tier includes 50K observations per month.