Next.js 16 on Cloudflare Workers: what broke and what didn't

I shipped a Next.js 16 app on Cloudflare Workers via OpenNext. Not a demo. A real product with streaming chat, server components, D1 at the edge, and anonymous user sessions. Here is what broke, what barely worked, and what turned out to be surprisingly fine. The stack Next.js 16.2 (App Router) @opennextjs/cloudflare 1.19 D1 for SQLite at the edge Streaming chat via the AI binding (DeepSeek-V3 through a Workers proxy) React 19 Tailwind CSS 4 No auth wall, no OAuth, no database on the origin The site runs a few thousand sessions a week across ~30 persona pages, blog posts, guides, and learning content. Most pages are statically generated. The chat interaction is server-rendered components with streaming responses. What worked surprisingly well Static generation and ISR Pages, blogs, guides, persona pages — everything that does not need user-specific rendering — runs as static HTML at deploy time. Next.js 16 with generateStaticParams and fetch caching worked without modification. OpenNext handles the Cloudflare output format. The build step produces something Workers can serve. Revalidations are limited to Workers' cache API, but since most content changes at deploy time, I never hit that limit in production. The one caveat: revalidateTag() does not work the same way in a Workers runtime. Tags are Node.js memory constructs, and Workers are stateless. If you depend on tag-based revalidation for content updates, you need to either trigger deploys or accept stale-while-revalidate behavior from the CDN. D1 at the edge D1 was the least surprising part of the stack. SQL queries from Next.js route handlers feel like calling a regular database. Sessions store in D1, messages store in D1, and the latency is low enough that restoring a full chat thread from 30 messages takes under 200ms cold. The only sharp edge: D1 connections count against your Worker's concurrent request limit in development. With Next.js making its own fetch calls for compilation, I hit the D1 connection ce