SaaS stacks
CopilotKit vs assistant-ui vs Vercel AI SDK UI: the open-source AI chat UI for a Next.js SaaS (2026)
CopilotKit, assistant-ui, and Vercel AI SDK UI sit at three different layers of the stack. A hands-on 2026 guide to picking the right open-source AI chat UI for your Next.js SaaS.
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