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. Most teams lose information at the seam between dev-time eval and prod monitoring. Braintrust erases that seam — the single most underrated property in this category, and the one Braintrust nails.
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 team in the same week — rare in this space. The AI Proxy is the other standout: route LLM calls through a Braintrust-hosted base URL and 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.
- Loop. The AI assistant for generating scorers and datasets from production logs is the rare feature that actually changes how teams work — not a marketing bullet, a real productivity unlock.
- 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 — not a polite trial list, production AI at companies whose engineering teams have already looked at every alternative.
Where it falls short
- No real OSS story. A few helpers are open, the platform isn't. If self-hosting is non-negotiable, Langfuse is the answer.
- Pricing past the free tier. The free tier is generous; the jump to Pro is steep once you're at production volume. Worth it for almost every team that gets there — but the one place a CFO will push back.
Bottom line
If you're shipping LLM features and not legally required to self-host, this is the tool. 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) own narrow lanes. For the central question — "what should our product engineering team use?" — Braintrust is the answer.