Braintrust is a proprietary, managed platform for evaluating and observing LLM applications — tracing, evals, datasets, and prompt management in one product. It has essentially no open-source story of its own; pricing starts with a limited free Starter tier (1 GB, 14-day retention) and scales to a $249/month Pro tier plus custom Enterprise pricing for teams that need longer data retention or higher volume.
Langfuse covers the same core workflow — tracing, prompt management, cost tracking — as a self-hostable, open-source project, so you're not paying per-GB or capped by a retention window you don't control.
FAQ
Is there a free, open-source alternative to Braintrust?
Yes. Langfuse is open source (MIT-licensed) and free to self-host, with no retention-window cap tied to a paid plan.
What's the best open-source alternative to Braintrust?
Langfuse is the closest match — it covers tracing, prompt management, and cost tracking, the same core loop Braintrust charges per-GB for.
What are the top open-source alternatives to Braintrust?
Browse all open-source alternatives to Braintrust above, or explore the full Analytics category for more options.