[bestest]

Consider middleware.ts as a root middleware. Nothing is stopping you from creating your own chain (which is trivial) in there. I mean, that would eventually work the same if nextjs implemented that feature — there would be a root somewhere.

[rs186]

That doesn't answer parent's question.

People expect "middleware" to mean a certain thing and work a certain way.

[bestest]

  middleware = fn(req) → next(req).

express/koa give you the use() chain. next.js gives you one root, but nothing stops you from chaining yourself. same semantics, just manual wiring.

  type mw = (req: Request, next: () => Response) => Response;
  
  const logger: mw = (req, next) => {
  console.log(req.url);
  return next();

};

  const auth: mw = (req, next) => {
    if (!req.headers.get("x-auth")) return new   Response("forbidden", { status: 403 });
    return next();
  };
  
  function chain(mws: mw[]) {
    return (req: Request) =>
      mws.reduceRight((next, mw) => () => mw(req, next), () => new Response("ok"))();
  }
  
  export function middleware(req: Request) {
    return chain([logger, auth])(req);
  }

root is given, chain is trivial. that’s middleware.