localhost isn't a valid host for the new Doorstop
Since the new Doorstop, you have to input "localhost" in the config if you want to use that as the host. It should work regardless of whether the config is set to localhost or 127.0.0.1.
Are you sure you aren't affected by the W11 update that broke127.0.0.1?
Mind giving more details? I don't think so because the old Doorstop fork we were using was working with either, but I'd have to double-check.
https://www.windowslatest.com/2025/10/18/microsoft-confirms-windows-11-kb5066835-issues-localhost-file-explorer-preview-install-errors/
Doesn't seem related. Browser localhost/127.0.0.1 works just fine. Also can confirm that both localhost and 127.0.0.1 work with our old version of the Doorstop. With the new rewrite, it would only work if both the client and server (config) are set to 127.0.0.1 or localhost.
For reference: https://github.com/nike4613/BeatSaber-IPA-Reloaded/blob/master/Doorstop/Proxy/main.c