APIs & DEVELOPER INFRASTRUCTURE
Langfuse
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Pricing
We do not reprint prices. They change too often for that to be honest, and a number on our page with no date is worse than sending you to the source.
How we rated it
What it is
Observability for applications built on language models: traces of every call, cost and latency per step, prompt versioning, and evaluation of output quality. Open source and self-hostable.
Who it is for
Teams running something model-based in production who need to know why an answer was bad last Tuesday.
Where it is strongest
Debugging a chain of calls after the fact. Without tracing, a multi-step system is a black box and every bug report is unreproducible.
Where it falls short
Another service to run or pay for. Traces contain whatever users typed, so it becomes a store of personal data you now have to govern. And the evaluation features need you to define what good looks like, which is the hard part it cannot do for you.
Our verdict
Recommended as soon as something model-based is in front of real users. Before that it is overhead; after that, running without it is guessing.
Editorial assessment. We earn a commission on some links; it does not change the ranking.