Braintrust

Braintrust is a unified AI observability and evaluation platform that combines LLM tracing, dataset curation, prompt management, and automated evals in one product. After running it across three production LLM applications over six months, it’s the most complete end-to-end evaluation toolchain available in 2026 — but it comes with real trade-offs worth understanding before committing. What Is Braintrust? The AI Observability Platform Explained Braintrust is an AI observability platform that covers the full LLM development lifecycle: capturing production traces, running automated evaluations against datasets, managing prompts with version control, and feeding results back into CI/CD pipelines to block regressions. Founded in 2023 and backed by $242.5M across seven funding rounds — including an $80M Series B in February 2026 led by ICONIQ at an $800M valuation — Braintrust has positioned itself as the “observability layer for AI.” The company’s core thesis is that LLM applications need fundamentally different tooling than traditional software monitoring: AI traces average ~50KB per span versus ~900 bytes in conventional observability, queries involve semantic similarity rather than exact matching, and quality regressions are probabilistic rather than binary. To handle this, Braintrust built Brainstore, a purpose-built columnar database that achieves 80x faster queries than traditional data warehouses on AI workloads, with median query times under one second on real-world datasets. Enterprise customers include Notion, Stripe, Vercel, Airtable, Instacart, Zapier, Ramp, Dropbox, Cloudflare, and BILL — a roster that signals product-market fit at scale. ...