Evals & observability
Braintrust
Eval-first platform for scoring model output against datasets and catching regressions before release.
- Category
- Evals & observability
- Pricing
- Free tier
- Runs
- Hosted
- Interface
- SDK, Dashboard, CLI
- Source
- Proprietary
What Braintrust is
Braintrust leads with evaluation rather than tracing. You build datasets, define scoring functions, and run evals in CI so a prompt or model change that regresses quality fails a build instead of reaching users. Logging exists, but the centre of gravity is the eval loop.
Best for
Teams treating prompt changes as changes that need tests, with evals wired into CI.
Consider something else if
If you mainly need to debug what happened in production, a tracing-first tool is the better starting point.
Braintrust alternatives
The closest options in evals & observability, on the axes that actually separate them.
| Tool | Best for | Pricing | Runs |
|---|---|---|---|
| Braintrust | Teams treating prompt changes as changes that need tests, with evals wired into CI. | Free tier | Hosted |
| LangSmith | LangChain and LangGraph users, who get the deepest integration for the least work. | Free tier | Hosted |
| Langfuseopen source | Teams who need traces containing customer data to stay inside their own infrastructure. | Open source | Hosted or self-hosted |
| W&B Weaveopen source | Organisations already on Weights & Biases who want one place for all model work. | Free tier | Hosted |
| Heliconeopen source | Getting cost and latency visibility across a codebase quickly, especially one you do not want to instrument. | Free tier | Hosted or self-hosted |
| Phoenixopen source | Teams standardised on OpenTelemetry, and anyone debugging retrieval quality interactively. | Open source | Hosted or self-hosted |
Choosing within evals & observability
Tracing or evaluation first
Some tools lead with tracing and add evals; others are eval-first with tracing attached. If you are debugging today, start with tracing. If you are about to change a prompt that is already in production, start with evals.
How it gets your data
A proxy needs a one-line base-URL change and captures everything. An SDK needs instrumentation and captures more structure. OpenTelemetry-based tools slot into tracing you may already run.
Questions
What is Braintrust?
Braintrust leads with evaluation rather than tracing. You build datasets, define scoring functions, and run evals in CI so a prompt or model change that regresses quality fails a build instead of reaching users. Logging exists, but the centre of gravity is the eval loop. It is a commercial product and hosted.
What are the alternatives to Braintrust?
The closest alternatives are LangSmith, Langfuse, W&B Weave, Helicone, Phoenix. They sit in the same category — evals & observability — and differ mainly on hosting model, pricing shape, and how much they abstract away.
Is Braintrust the right choice?
Teams treating prompt changes as changes that need tests, with evals wired into CI. The main caveat: If you mainly need to debug what happened in production, a tracing-first tool is the better starting point.
Whatever you build on, the model is the line item that scales. See what each one costs per million tokens, or price your own workload.