Link to the code that reproduces this issue

https://github.com/PacoSoftwerft/multi-zone-microfrontends

To Reproduce

Start main-site

cd main-site
npm run dev

Start blog

Start the blog in a new shell

cd blog
npm run dev

Bug

Open http://localhost:3000/blog, it is loading in a loop.

Current vs. Expected behavior

Expected behavior:

rewrite to same domain "localhost" with different port should work like they did in 13.4.12

Version next@13.4.12 is working just fine.
Stop the main-site then

cd main-site
npm i next@13.4.12 --save-exact
npm run dev

open http://localhost:3000/blog

Verify canary release

• I verified that the issue exists in the latest Next.js canary release

Provide environment information

Distributor ID: Ubuntu
Description:    Ubuntu 22.04.3 LTS
Release:        22.04
Codename:       jammy

Node:           v18.18.0
npm:            10.1.0

Which area(s) are affected? (Select all that apply)

Routing (next/router, next/navigation, next/link)

Additional context

This bug was introduced with 13.4.13

The bug only appears when using the Pages Router

The bug depends on the version of the app that rewrites, here main-site.

It seems like the port is stripped/not respected somewhere.

The rewrite works if it points to another domain.

Additional info 2023-10-20

The bug only appears when both zones are started with npm run dev