What it is
Braintrust is an end-to-end platform for building, evaluating, and monitoring LLM apps. The core loop: define a dataset, write or generate scorers, run experiments, compare across prompts and models, and ship to production where the same scorers run continuously on traces. The seam between "dev-time eval" and "prod monitoring" — where most teams lose information — is invisible here. That continuity is the single most underrated property in this category, and Braintrust is the tool that nails it.
Pricing starts free with 1M trace spans; the Pro plan is $249/month with unlimited spans.
Developer experience
Small, well-typed SDKs. A first eval takes about fifteen minutes from an empty repo:
import { Eval } from "braintrust";
await Eval("triage", {
data: () => [{ input: "ticket text", expected: "billing" }],
task: async (input) => classify(input),
scores: [ExactMatch],
});The TS and Python SDKs feel like they were written by the same people in the same week — rare in this space. The AI Proxy is also worth noting: route LLM calls through a Braintrust-hosted base URL and you get logging, caching, and provider fallbacks without touching application code.
Where it shines
- Playground. Side-by-side prompt comparison with diffing, model switching, and inline scoring beats every alternative we've tried, full stop.
- One product, full lifecycle. Datasets, experiments, traces, online evals, and prompt management in one place. Most competitors do one or two of these well; Braintrust does all of them well.
- Loop. The AI assistant for generating scorers and datasets from production logs is a real productivity unlock — the kind of feature that changes how teams work, not just a marketing bullet.
- CI integration. GitHub Actions support that fails builds on quality regressions, with confidence intervals and significance tests. Not a webhook to Slack — actual eval-driven release gates.
- Customer signal. Notion, Stripe, Vercel, Airtable, Instacart, Zapier. That's not a polite trial list; that's production AI at companies whose engineering teams have looked at every alternative.
Where it falls short
- No real OSS story. A few helpers are open, the platform isn't. If self-hosting on your own infrastructure is non-negotiable, Langfuse is the answer instead.
- Pricing past the free tier. The free tier is generous, but the jump to paid is steep at production volume. Worth it for almost every team that gets there — but it's the one place a CFO might push back.
Bottom line
If you're shipping LLM features and not legally required to self-host, this is the tool. The honest competitive picture is that Langfuse is the OSS alternative, Galileo wins on online-eval cost at extreme scale, and a few specialists (Fiddler for governance, Vellum for low-code) win in narrow lanes — but for the central question of "what should our product engineering team use," Braintrust is the answer.