Massvai is an AI app builder that turns a plain-language brief into a production-ready, full-stack Next.js application. Its durable coding agent plans the work, writes clean TypeScript with a consistent design system, and keeps progress visible in a live preview while it builds — with stop, retry, and tool history built in. Projects come wired for the modern stack out of the box: Next.js 15 and React 19, Tailwind CSS, Supabase for data and auth, Prisma, Stripe-ready billing screens, GitHub sync, and one-click deployment to Vercel. Crucially, the code is yours: every file can be inspected and exported, with no platform lock-in. Massvai targets real product work rather than throwaway prototypes — SaaS MVPs with authentication, dashboards, and billing, internal tools, and client websites. A free plan with 100 welcome credits and code export lets you build your first project without a card; the Builder plan at $25 a month and Pro at $49 add monthly credits, custom preview domains, version history, and priority support. For founders and small teams who want an app they can actually ship and keep, Massvai goes from prompt to production in one workspace.