An example showing that a cookie set in a Next.js App Router API handler can be read back in the same request

curl.log

$ curl --verbose http://localhost:3000/cookie-test
*   Trying [::1]:3000...
* Connected to localhost (::1) port 3000
> GET /cookie-test HTTP/1.1
> Host: localhost:3000
> User-Agent: curl/8.4.0
> Accept: */*
>
< HTTP/1.1 200 OK
< vary: RSC, Next-Router-State-Tree, Next-Router-Prefetch, Next-Url
< content-type: application/json
< set-cookie: test=ok; Path=/
< Date: Tue, 26 Mar 2024 10:24:05 GMT
< Connection: keep-alive
< Keep-Alive: timeout=5
< Transfer-Encoding: chunked
<
* Connection #0 to host localhost left intact
{"ok":{"name":"test","value":"ok","path":"/"}}

route.ts

import { cookies } from "next/headers";
import { NextResponse } from "next/server";

export async function GET() {
  cookies().set("test", "ok");
  const aTestCookie = cookies().get("test");


  return NextResponse.json({ ok: aTestCookie });
}