Well I was trying to build staging deps in a devshell and found this to be an issue with libedit:

error: builder for '/nix/store/hp66qyxi3s4y682xxhphz81hjmc0nm38-libedit-20251016-3.1.tar.gz.drv' failed with exit code 1;
       last 12 log lines:
       >
       > trying https://thrysoee.dk/editline/libedit-20251016-3.1.tar.gz
       >   % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
       >                                  Dload  Upload   Total   Spent    Left  Speed
       >   0     0    0     0    0     0      0      0 --:--:--  0:00:03 --:--:--     0curl: (6) Could not resolve host: thrysoee.dk
       > Warning: Problem : timeout. Will retry in 1 second. 3 retries left.
       > curl: (6) Could not resolve host: thrysoee.dk
       > Warning: Problem : timeout. Will retry in 1 second. 2 retries left.
       > curl: (6) Could not resolve host: thrysoee.dk
       > Warning: Problem : timeout. Will retry in 1 second. 1 retry left.
       > curl: (6) Could not resolve host: thrysoee.dk
       > error: cannot download libedit-20251016-3.1.tar.gz from any mirror
       For full logs, run:
         nix log /nix/store/hp66qyxi3s4y682xxhphz81hjmc0nm38-libedit-20251016-3.1.tar.gz.drv

Let me provide the devshell so I can see if you can reproduce it.

{
  description = "Super simple starting point for Polar development flake";

  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs/staging"; # Change to staging,  TODO: https://nixpk.gs/pr-tracker.html?pr=453690
    flake-parts.url = "github:hercules-ci/flake-parts";
    systems.url = "github:nix-systems/default";
  };

  outputs =
    inputs:
    inputs.flake-parts.lib.mkFlake { inherit inputs; } {
      systems = import inputs.systems;
      perSystem =
        {
          pkgs,
          system,
          ...
        }:
        {
          _module.args.pkgs = import inputs.nixpkgs {
            inherit system;
            config = {
              allowUnfree = true;
            };
          };

          devShells.default = pkgs.mkShell {
            nativeBuildInputs = with pkgs; [
              nodejs_22
              pnpm

              (python3.withPackages (p: [
                p.psycopg2-binary
                p.psycopg2
              ]))
              uv

              stripe-cli
              ngrok
            ];
          };
        };
    };
}