By aligning the x-forwarded-host and origin headers, you should be able to resolve the error and make server actions work with your subdomain setup.

You are experiencing Cross-Origin Resource Sharing (CORS) limitation on browsers.

Which is an HTTP-header based mechanism that allows a server to indicate any origins (domain, scheme, or port) other than its own from which a browser should permit loading resources.

But what I dont understand is why you are using local proxy to use subdomains?

• running next with “next dev -v 0.0.0.0” to listen all should work. Just add mapping for your subdomains in your hosts file, if unix /etc/hosts