I Built an AI Text Summarizer in One Night with Claude + Next.js

It was a Monday. I had the Anthropic API key provisioned, Next.js scaffolded, and one self-imposed deadline: ship a working demo live on the public internet before midnight. A few hours later, https://ai-summarizer-next.vercel.app/ went live. You paste any block of text, pick a style — concise, bullet points, executive summary, or ELI5 — and Claude Sonnet 4.6 gives you back a clean summary in about a second. Here's how I did it, what the code looks like, and a few things that surprised me....