Braintrust vs Langfuse (2026)
The best closed-source eval platform against the best open-source one. The decision comes down to one question — do you have to self-host?
Braintrust and Langfuse are the two platforms we'd shortlist most often, and they win for nearly opposite reasons. Langfuse is the best open-source pick in the category — MIT-licensed, self-hostable, with tracing that reads like a real APM for LLM apps. Braintrust is the most polished end-to-end product — the tightest loop from prompt edit to eval score to production trace we've tested.
So the deciding question is rarely about features. It's about control: must customer data stay in your infrastructure, or not? Answer that and the rest mostly follows.
At a glance
| Braintrust | Langfuse | |
|---|---|---|
| Best for | Teams that want the most polished eval flow out of the box | Teams that need self-hosting or want to read the source |
| License | Closed source | Open source (MIT) |
| Self-hosting | Enterprise tier only | First-class (Helm, docker-compose) |
| Tracing | Strong, tied to the eval loop | Best-in-class for debugging multi-step agents |
| Eval UX | Best-in-class, opinionated, CI-gated | Functional; more wiring to reach a CI-gated flow |
| Playground / prompt iteration | Best-in-class playground | Prompt management, lighter iteration surface |
| Entry price | Free (1M spans), Pro $249/mo | Free self-hosted; cloud from $29/mo |
| Ops burden | None (SaaS) | Real at scale (Postgres + ClickHouse) |
Where Langfuse wins
- Data control. This is the whole ballgame. Helm chart, docker-compose, or a SOC 2-compliant cloud tier — pick your flavor. For teams that can't ship customer data to a third-party SaaS, Langfuse is the only one of the two that clears the bar.
- Tracing. Drilling into a multi-step agent run feels closer to a real APM than what most eval-first competitors offer. Session grouping connects related requests cleanly. If your primary pain is debugging agent traffic, Langfuse's traces are genuinely best-in-class.
- OSS economics. Self-hosted is free, and the cloud tier starts at $29/month. At high trace volume, owning the infrastructure can be dramatically cheaper than per-span SaaS pricing.
- Auditability. When something breaks, you can read the source. For teams that value that, it's not a nice-to-have.
Where Braintrust wins
- Eval as a first-class workflow. Braintrust is opinionated where Langfuse is flexible. Datasets, experiments, scorers, online scoring, and prompt management sit in one product, and the same scorers run in CI and on production traffic. With Langfuse you'll spend more time wiring those pieces together to reach an equivalent CI-gated flow.
- CI gates. Native GitHub Action that fails builds on eval regressions, with confidence intervals and significance tests — not a webhook to Slack, an actual release gate.
- The playground and Loop. Side-by-side prompt comparison with bidirectional code↔UI sync, plus the Loop assistant that generates scorers and datasets from production logs. These are the features that change how a team works, not just what it monitors.
- Zero ops. No Postgres, no ClickHouse, no capacity planning. Self-hosting Langfuse at high trace volume needs a real ops story; Braintrust hands you the polished result with none of that.
The tradeoff, stated plainly
Langfuse asks you to invest ops effort in exchange for data control and OSS economics. Braintrust asks you to accept closed-source SaaS in exchange for the most polished, CI-integrated eval flow available with zero infrastructure work. Neither is a compromise so much as a different priority.
How to choose
- Compliance, data residency, or cost at high volume forces self-hosting? Langfuse, without hesitation.
- You'd pay to skip ops entirely and want the sharpest eval-and-CI flow out of the box? Braintrust.
- Debugging agents is your main pain and evals are secondary? Langfuse's tracing is the stronger fit.
- Shipping LLM features fast and wiring evals into your release process is the goal? Braintrust.
If you take data control seriously, start with Langfuse — it's the one we'd reach for first among open-source options. If self-hosting isn't a hard requirement, Braintrust is the platform most product teams will get the most out of.