{ ... }:
{
  nix.distributedBuilds = true;

  nix.buildMachines = [
    {
      hostName = "m4";
      system = "aarch64-darwin";
      maxJobs = 4;
      speedFactor = 3;
      sshUser = "harald";
      sshKey = "/etc/ssh/nix-builder-key";
    }
    {
      hostName = "rialo";
      system = "aarch64-darwin";
      maxJobs = 4;
      speedFactor = 3;
      sshUser = "harald";
      sshKey = "/etc/ssh/nix-builder-key";
    }
    {
      hostName = "sgx";
      system = "x86_64-linux";
      maxJobs = 4;
      speedFactor = 1;
      sshUser = "harald";
      sshKey = "/etc/ssh/nix-builder-key";
    }
  ];

  nix.settings = {

    substituters = [
      "https://cache.nixos.org"
      "ssh-ng://harald@m4?ssh-key=/etc/ssh/nix-builder-key"
      "ssh-ng://harald@rialo?ssh-key=/etc/ssh/nix-builder-key"
      "ssh-ng://harald@sgx?ssh-key=/etc/ssh/nix-builder-key"
    ];

    builders-use-substitutes = true;
  };

  # Ensure Nix is in PATH for SSH sessions
  programs.fish.shellInit = ''
    set -gx PATH /nix/var/nix/profiles/default/bin $PATH
    set -gx PATH /run/current-system/sw/bin $PATH
  '';
}