The reader sends Connection: keep-alive but only acts on the verdict (beep,
output) once the TCP socket closes. Fastify's default kept the connection alive,
so the reader waited out a ~10s keep-alive timeout before beeping — even though
the server replied in ~15ms. Every vendor demo replies Connection: close and
shuts the socket. Set reply.header('connection','close') on the QR endpoint.
Verified the header is now sent; symptom was correct accept/reject with a ~10s
lag before the beep.
julian
ff3b011fe0