{
  description = "Samw's home environment, as managed by nix/home-manager.";
  inputs = {
    # Nixpkgs
    nixpkgs = {
      # N.B. we use the nixos-x branch as this is updated *after* successful hydra builds
      # rather than release-x. See https://wiki.nixos.org/wiki/Channel_branches
      url = "github:nixos/nixpkgs/nixos-25.11";
    };
    nixpkgs-unstable = {
      url = "github:nixos/nixpkgs";
    };
    # Other modules
    home-manager = {
      url = "github:nix-community/home-manager/release-25.11";
      inputs.nixpkgs.follows = "nixpkgs";
    };
    flake-utils.url = "github:numtide/flake-utils";
    devshell = {
      url = "github:numtide/devshell";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };
  outputs =
    inputs:
    let
      overlays = [
        # Add our own local packages
        (final: prev: {
          # Make my local packages available as pkgs.mypkgs.<foo>
          mypkgs = prev.callPackage ./pkgs { };
        })
        # more up to date ssh-tpm-agent. Can probably ditch this post-24.05
        (final: prev: {
          ssh-tpm-agent = (import inputs.nixpkgs-unstable { system = prev.system; }).ssh-tpm-agent;
        })
      ];
    in
    (
      rec {
        profiles = import ./home/profiles.nix;
        lib = {
          mkHome =
            {
              profiles,
              system,
              username ? "samw",
            }:
            inputs.home-manager.lib.homeManagerConfiguration {
              pkgs = (
                import inputs.nixpkgs {
                  inherit system;
                  config.allowUnfree = true; # Yes I know it's bad for me
                }
              );
              modules = [
                {
                  home = {
                    inherit username;
                    homeDirectory =
                      if (inputs.nixpkgs.lib.systems.elaborate system).isDarwin then
                        "/Users/${username}"
                      else
                        "/home/${username}";
                    stateVersion = "21.11";
                  };
                }
              ]
              ++ profiles
              ++ [
                { nixpkgs.overlays = overlays; }
                # See comment in home/default.nix.
                (
                  { pkgs, ... }:
                  {
                    nix = {
                      enable = true;
                      package = pkgs.nix;
                      settings.experimental-features = "nix-command flakes";
                      settings.max-jobs = "auto"; # Gotta go fast (build derivations in parallel)
                      # Pin the nixpkgs registry to our locked nixpkgs. This means that we
                      # get the same packages via e.g. nix shell as we have at the system
                      # level, so less duplication overall and no more fetching that 30MB src
                      # every time you run nix shell.
                      registry.nixpkgs.flake = inputs.nixpkgs;
                      registry.nixpkgs-unstable.to = {
                        owner = "nixos";
                        repo = "nixpkgs";
                        type = "github";
                      };
                    };
                  }
                )
              ];
              extraSpecialArgs = { inherit system; };
            };
        };

        # Standalone home-manager configurations
        homeConfigurations = {
          zinc = lib.mkHome {
            system = "aarch64-darwin";
            profiles = with profiles; [
              default
              dev
              dev-gui
              sensitive
              mac
            ];
          };
          luroy = lib.mkHome {
            system = "x86_64-linux";
            profiles = with profiles; [
              default
              dev
            ];
          };
          phosphorus = lib.mkHome {
            system = "aarch64-darwin";
            profiles = with profiles; [
              default
              dev
              sensitive
              mac
            ];
          };
        };
      }
      # Per-system things
      // (inputs.flake-utils.lib.eachDefaultSystem (
        system:
        let
          pkgs = import inputs.nixpkgs {
            inherit system;
            overlays = overlays ++ [ inputs.devshell.overlays.default ];
          };
          platform = pkgs.lib.systems.elaborate system;
        in
        {
          # Flake interface to my local packages.
          # - `callPackage` puts some junk in mypkgs (`override` and
          #   `overrideDerivation`) so we filter out anything that isn't a derivation
          # - We also filter out any packages that aren't supported on the current
          #   platform.
          packages =
            with pkgs.lib;
            (filterAttrs (_: v: (isDerivation v && meta.availableOn platform v)) pkgs.mypkgs);
          formatter = pkgs.nixfmt-tree;
          # A devshell with useful utils
          devShells.default = pkgs.devshell.mkShell {
            packages = [
              inputs.home-manager.packages.${system}.default
            ];
          };
        }
      ))
    );
}