Redirect behaves strangely

[Snorre Lothar von Gohren Edwin]

Describe the bug

Im doing the following in my code in my hooks.server.ts

if (!event.locals.session && event.url.pathname.startsWith('/app')) {
    console.log('redirecting to /auth')
    return redirect(303, '/auth')
  }

And get the following loggs out. The logs after "redirecting to /auth" is directly from the line of error itself. Where i console.log the resonse itself, and the two others are the type of response.headers and the value itself.

redirecting to /auth
Redirect { status: 303, location: '/auth' }
undefined
undefined
file:///Users/vongohren/code/mine-prosjekter/nameme-parentfolder/nameme/node_modules/@sveltejs/kit/src/exports/node/index.js:122
        for (const [key, value] of response.headers) {
                                            ^

TypeError: response.headers is not iterable
    at setResponse (file:///Users/vongohren/code/mine-prosjekter/nameme-parentfolder/nameme/node_modules/@sveltejs/kit/src/exports/node/index.js:122:38)
    at file:///Users/vongohren/code/mine-prosjekter/nameme-parentfolder/nameme/node_modules/@sveltejs/kit/src/exports/vite/dev/index.js:525:6

Node.js v18.19.0
error Command failed with exit code 1.

What am I doing wrong? Or is it a bug?

Reproduction

Try installing the versions im using and redirect in the hooks.server.ts

Logs

They are included in the error report itself

System Info

System:
    OS: macOS 13.1
    CPU: (10) arm64 Apple M1 Pro
    Memory: 77.47 MB / 32.00 GB
    Shell: 5.8.1 - /bin/zsh
  Binaries:
    Node: 18.19.0 - ~/.nvm/versions/node/v18.19.0/bin/node
    Yarn: 1.22.19 - ~/.yarn/bin/yarn
    npm: 10.2.3 - ~/.nvm/versions/node/v18.19.0/bin/npm
  Browsers:
    Chrome: 126.0.6478.127
    Safari: 16.2
  npmPackages:
    @sveltejs/adapter-auto: 2.0.0 => 2.0.0 
    @sveltejs/kit: 1.30.4 => 1.30.4 
    svelte: 4.2.18 => 4.2.18 
    vite: 4.5.3 => 4.5.3

Severity

blocking all usage of SvelteKit

Additional Information

No response

[Paolo Ricciuti]

Well first thing first you should just call redirect instead of returning it. But regardless please provide an actual reproduction either with svelte lab, stack blitz or a git repo and please make it minimal (only the error should be present).

[Snorre Lothar von Gohren Edwin]

Thanks for the tips, I tried a repro on svelte lab, but I ended up with other strange errors.

But then I tried to remove return and do this as well, instead of returing a sync resolv.

const response = await resolve(event);
return response;

These minor changes made things work again.
The thing is that code worked fine before and then upgradring, it started failing, that makes things a bit more complicated.