Braintrust vs Langfuse
Both cover the same ground: run evals on your LLM app and see what it actually did in production. Braintrust is a commercial platform. You get a hosted eval and logging workflow with a polished UI and a prompt playground. Langfuse is open-source observability you can self-host. It starts from tracing, with evals and prompt management layered on top.
| Dimension | Braintrust | Langfuse |
|---|---|---|
| What it is | Commercial eval and logging platform | Open-source LLM observability and evals |
| License | Commercial, hosted | Open source, open-core with a cloud option |
| Hosting | Hosted SaaS, self-host on higher plans | Cloud or self-host it yourself |
| Center of gravity | Evals, scoring, prompt playground | Tracing and production observability |
| Both do | Traces, datasets, evals, prompt management | Traces, datasets, evals, prompt management |
| SDKs | TypeScript and Python, code-first | TypeScript and Python, plus many integrations |
| Data control | Your data on their cloud by default | Keep all data in your own infra |
| Best for | Teams who want a finished eval workflow | Teams who want to own the stack |
You want a polished eval and prompt-iteration workflow without running any infrastructure, and a commercial SaaS is fine. Braintrust shines when the eval loop is the daily work. Scoring runs, comparing them, and tuning prompts all live in one place your whole team uses.
You need to self-host, keep trace data in your own infrastructure, or you want an open-source tool you can run and inspect. Langfuse is the natural pick when production observability is the first job and you would rather own the deployment than rent it.
Start with one question. Do you have to own the data and the deployment? If yes, Langfuse is the easy call. Self-hosting open source is exactly what it is built for. If you would rather pay to skip the ops and want the stronger eval and playground experience, Braintrust earns its keep. People get stuck treating this as evals versus observability. Both tools now do both. The real fork is open-source you host versus commercial they host. Decide that first and the rest follows.