Ever wonder which AI model is actually the best? In this video, we're building the LLM Arena: a Next.js app that races open-source models side-by-side in real-time to track exact performance metrics like latency and cost. Vote on the winner to update a public leaderboard. Best of all, we'll build this entire full-stack app completely agentically using Claude Code. Try Greptile for FREE: https://jsm.dev/arena-greptile Try Clerk for FREE: https://jsm.dev/arena-clerk Try Arcjet for FREE: https://jsm.dev/arena-arcjet Try PostHog for FREE: https://jsm.dev/arena-posthog OpenRouter: https://openrouter.ai Prisma: https://www.prisma.io 📋 Join the Agentic Course Waitlist: https://jsm.dev/arena-agentic 🎁 Video Kit (Code, Assets, Prompts): https://jsm.dev/arena-kit ⭐ Get my Pro Courses: https://jsm.dev/arena-jsm ➤ Links not working? Some regions may need a VPN. https://discord.com/invite/n6EdbFJ https://twitter.com/jsmasterypro https://instagram.com/javascriptmastery https://linkedin.com/company/javascriptmastery Business Inquiries: contact@jsmastery.pro Timestamps: 00:00:00 — Introduction 00:05:44 — Scaffold & Tools Setup 00:09:03 — Repository & Code Review 00:15:58 — Foundation & Decision Process 00:45:21 — Coding Standards, Tooling, & Data Model 00:51:49 — Design & Look 01:04:54 — Model Picker 01:09:52 — Send a Prompt, Parallel Streams, and Voting 01:25:01 — Thread History 01:25:53 — Public Thread Visibility & Sharing 01:34:07 — Arcjet: Abuse Protection 01:40:48 — Leaderboard 01:43:06 — PostHog: What Actually Happened 02:03:02 — Wrap-up