`@tus/server` `>= v2.1.0` seems now incompatible with Next.js pages API

Initial checklist

• I understand this is a bug report and questions should be posted in the Community Forum
• I searched issues and couldn’t find anything (or linked relevant results below)

Steps to reproduce

Make sure to use between v2.1.0-v2.3.0, and within the pages API router just use :

const tusServer = new Server({
  path: '/api/upload',
});

export function handler(req: NextApiRequest, res: NextApiResponse) {
  return tusServer.handle(req, res);
}

(as shown in https://uppy.io/docs/nextjs/#pages-router)

And then start uploading a file (using Uppy client aside for example).

Expected behavior

To have Location response header like in:

HTTP/1.1 201 Created
origin-agent-cluster: ?1
referrer-policy: no-referrer
strict-transport-security: max-age=15552000; includeSubDomains
x-content-type-options: nosniff
x-dns-prefetch-control: off
x-download-options: noopen
x-frame-options: SAMEORIGIN
x-nonce: xxxxx
x-permitted-cross-domain-policies: none
x-xss-protection: 0
access-control-allow-origin: http://localhost:3000
access-control-expose-headers: Authorization, Content-Type, Location, Tus-Extension, Tus-Max-Size, Tus-Resumable, Tus-Version, Upload-Concat, Upload-Defer-Length, Upload-Length, Upload-Metadata, Upload-Offset, X-HTTP-Method-Override, X-Requested-With, X-Forwarded-Host, X-Forwarded-Proto, Forwarded
content-type: text/plain;charset=UTF-8
location: http://localhost:3000/api/upload/f1d627f06be68560949c3125d9644381
tus-resumable: 1.0.0
Vary: Accept-Encoding
Date: Mon, 27 Oct 2025 21:20:19 GMT
Connection: keep-alive
Keep-Alive: timeout=5
Transfer-Encoding: chunked

Actual behavior

Having no Location response header, and moreover having broken response headers like:

HTTP/1.1 201 
1: .
origin-agent-cluster: ?1
referrer-policy: no-referrer
strict-transport-security: max-age=15552000; includeSubDomains
x-content-type-options: nosniff
x-dns-prefetch-control: off
x-download-options: noopen
x-frame-options: SAMEORIGIN
x-nonce: xxxxxxxxx
x-permitted-cross-domain-policies: none
x-xss-protection: 0
A: u
h: t
c: o
t: u
l: o
Date: Mon, 27 Oct 2025 21:21:40 GMT
Connection: keep-alive
Keep-Alive: timeout=5
Transfer-Encoding: chunked

After searching I found https://github.com/tus/tus-js-client/issues/694 (pointing to https://github.com/expressjs/morgan/issues/315) that advises patching on-headers with v1.1.0 but it's not working at all.

Looking at the changelog it seems srvx is the new thing in @tus/server v2.1.0 so I guess it comes from this.

For the moment, just sticking with v2.0.0 as it's working 👍

Thank you,

Start with the Next.js pages API handler shown in the reproduction and compare @tus/server v2.0.0 with v2.1.0–v2.3.0, focusing on the srvx integration mentioned in the issue. Reproduce the upload response and verify that Location and the other response headers are returned correctly without the broken single-character headers.