Vellum

Vellum is a freemium LLM development platform — free for up to 100,000 monthly prompt executions, with Pro plans starting at $89/seat/month — that helps engineering teams build, test, evaluate, and deploy production AI applications with confidence. Used by over 200 companies including teams at Fortune 500 enterprises, Vellum has processed more than 500 million LLM API calls through its platform and supports integration with 50+ foundation models across providers like OpenAI, Anthropic, Google, Cohere, and Meta.

The platform provides a complete toolkit spanning prompt engineering with side-by-side model comparison, automated evaluation pipelines for regression testing across prompt versions, a visual workflow builder for chaining LLM calls and agentic pipelines, and version-controlled deployment management with rollback capabilities. Vellum's evaluation framework has been used to run over 10 million automated test executions, helping teams catch regressions before they reach production.

Teams start in the prompt engineering playground, where they can compare outputs across models from multiple providers, iterating on prompts with full version history. Once prompts perform well in testing, Vellum's evaluation framework lets teams define quantitative test suites that automatically score outputs using custom metrics, LLM-as-judge configurations, or deterministic checks — catching regressions before they reach users.

The workflow builder enables teams to construct complex multi-step AI pipelines visually — chaining LLM calls, adding conditional logic, integrating tool use, and building retrieval-augmented generation (RAG) flows with document management and search indexes. Over 15,000 workflows have been deployed through the platform. These workflows deploy through Vellum's managed infrastructure with environment management (staging and production), A/B testing, and monitoring.

In production, Vellum provides observability into latency, cost, and quality metrics, giving teams visibility into how their AI features perform with real users. The platform integrates into existing CI/CD pipelines via REST API and SDKs for Python and TypeScript, with the Python SDK averaging over 50,000 weekly downloads on PyPI. Multi-user workspaces with role-based access control support collaboration across engineering teams of all sizes.

Vellum is SOC 2 Type II certified and offers HIPAA compliance on enterprise plans, making it suitable for regulated industries including healthcare and financial services. The platform does not train on customer data and acts as a passthrough to model providers, addressing common enterprise data privacy concerns.