prompt-engineering
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Vellum
Vellum is a New York-based AI development platform that helps companies build, evaluate, deploy, and monitor production-grade LLM applications and AI agents. Founded in early 2023 by three engineers who kept hitting the same wall - prototypes that demo well but break in production - Vellum gives teams a workflow builder, an evaluation suite, version-controlled deployments, and live monitoring so they can move AI from proof-of-concept to reliable production systems. The platform works with more than 150 companies including Drata, Redfin, Swisscom, and Headspace, and raised a $20M Series A led by Leaders Fund in July 2025.
Braintrust
Braintrust is the end-to-end developer platform for shipping AI products. It connects evaluations, observability, prompt iteration, and an agentic optimizer (Loop) into one workflow so engineering teams can measure, debug, and improve LLM applications in production. Teams at Notion, Stripe, Vercel, Airtable, Instacart, Zapier, Ramp, Dropbox, Cloudflare and BILL use it to ship AI that doesn't silently regress.
OpenArt AI
OpenArt AI is a San Francisco-based AI creative platform founded in 2022 by former Google engineers Coco Mao and John Qiao. The platform aggregates 100+ AI models - including DALL-E 3, Stable Diffusion, Google Veo 3, Kling, and Sora - under a single interface, letting creators generate images, videos, music, and 3D environments without switching tools. From hobbyists making tabletop RPG art to agencies building brand-consistent content at scale, OpenArt serves roughly 8 million monthly active users. The company reached $70M+ ARR in 2025 with a 20-person team, then closed a $30M Series A led by Canaan Partners in January 2026.