Thats likely being handled by NodeJS express under thd hood.
Since, the challenge response, is just the challenge and no other characters in the normal web transfer.
Normal web transfer will also include a HTTP Header and the type/length headers, which express just does under the hood.
res.send('whatever') equivalent to res.status(200).send('whatever') (and the header for length)
Most libraries just do that under the hood, since this is webhooks and it’s “like loading a webpage”, so I didn’t think to mention headers since it’s basically just buidling and API/Form responder (like you would if building an admin system and sending a response to a users login form).
So, I’ll note to mention the header for headers/contentLength next time someone has a similar issue