Braintrust is an evaluation platform designed specifically for AI applications, providing the infrastructure to systematically test, score, and improve LLM outputs. You define datasets of inputs and expected outputs, run them against your prompts or agents, and score results using built-in heuristics, LLM-as-judge, or custom scoring functions. Results are versioned and tracked so you can see quality trends as prompts and models change. The platform integrates with the prompt iteration workflow: connect your AI app, run an eval, see which examples fail, edit the prompt or code, re-run, and compare side by side. Braintrust also supports online evaluation, scoring production traffic samples automatically so regressions are caught before they affect most users. Braintrust is used by companies including Stripe, Figma, and Vercel for AI feature development. The SDK is available in Python and JavaScript with minimal setup. A self-hosted option is available for teams with strict data residency requirements.

What the community says

Braintrust has built credibility partly through association with well-known engineering teams at Stripe and Figma who've publicly discussed their use of it. AI engineers on Hacker News and Latent Space discussions consistently recommend it for teams serious about LLM quality. Some evaluators prefer Langfuse for its open source self-hosting and tighter tracing integration. The online eval feature for production traffic scoring is frequently cited as the differentiator that justifies the paid tier.

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