Vellum

Vellum AI is an end-to-end LLM development platform covering prompt management, evaluation pipelines, A/B testing, CI/CD gates, and production monitoring in a single product. For teams that want systematic, statistically grounded evaluation instead of ad-hoc “it feels better” gut-checks, it is the most complete commercially available option in 2026 — though that completeness comes with a price tag and real trade-offs worth understanding. What Is Vellum AI and Why LLM Evaluation Matters in 2026 Vellum AI is a purpose-built platform for managing the full lifecycle of LLM-powered applications, from prompt authoring and version control through automated evaluation and production observability. The LLM observability and evaluation platform market reached an estimated $2.69 billion in 2026, growing at 36.3% CAGR — and the driving pressure is clear: organizations shipping generative AI to production need objective quality signals, not intuitions. The core problem Vellum solves is what practitioners call “vibes-based evaluation” — the practice of running a few manual test prompts, deciding the output looks good, and shipping. This approach fails as applications scale: edge cases multiply, model provider updates silently shift output distributions, and prompt changes made to improve one scenario break three others. Vellum replaces ad-hoc judgment with structured test suites, reproducible metrics, and statistical comparisons that tell you — with numerical confidence — whether a prompt change is an improvement or a regression. The platform was founded specifically to bridge the gap between rapid prototyping and production-grade LLM engineering, and that focus shows in every product decision: everything in Vellum is oriented around measurement, iteration, and deployment confidence. ...