Building a Real-Time AI Dungeon Master with Claude API, Socket.io, and Next.js 16

The AI in gaming market sits at $4.54 billion in 2025 and is projected to hit $81.19 billion by 2035 (SNS Insider, 2025). That number isn't surprising when you think about what generative AI actually unlocks for games infinite narrative branching, dynamic NPCs, and a Dungeon Master who never gets tired at midnight. I built DnD AI, a multiplayer AI Dungeon Master running on Next.js 16, Claude API (claude-sonnet-4-6), Socket.io, and DALL-E 3. This post is a technical walkthrough of the six hardest problems I ran into, and how I solved them. No fluff just the architecture decisions that actually mattered. TL;DR: Next.js App Router can't maintain persistent WebSockets, so a custom server.ts boots Socket.io and Next.js in one process Claude streaming output pipes through Socket.io to all connected clients in real time, with chunk batching to avoid socket flooding DALL-E 3 fires only on location changes and major story beats not every message keeping session cost under $0.25 Why a Custom Ser