{
  callPackage,
  stdenvNoCC,
  lib,
  fetchurl,
  fetchzip,
  namespace,
  # Repo metadata
  owner ? "CachyOS",
  repo ? "proton-cachyos",
  # Behavior
  withUpdateScript ? true,
  # Variant selection (null -> use defaultVariant from version.json)
  variant ? null,
  # Packaging/customization knobs
  toolTitle ? null,
  toolPattern ? "proton-.*",
  tarballPrefix ? "proton-",
  tarballSuffix ? "-x86_64_v4.tar.xz",
  releasePrefix ? "cachyos-",
  releaseSuffix ? "-slr",
}:
let
  inherit (lib.trivial) importJSON;
  inherit (lib.${namespace}) versioning;

  versionSpec = importJSON ./version.json;
  selected = versioning.selectVariant versionSpec variant null;
  vars = selected.variables or {};
  base = vars.base;
  release = vars.release;

  # Derived values for the current variant
  releaseVersion = "${releasePrefix}${base}-${release}${releaseSuffix}";
  homepage = "https://github.com/${owner}/${repo}";
  url = "${homepage}/releases/download/${releaseVersion}/${tarballPrefix}${releaseVersion}${tarballSuffix}";

  # Choose fetcher based on file type
  intake =
    if lib.strings.hasSuffix ".zip" url then
      {
        fetcher = fetchzip;
        input = "$src/*.tar.xz";
      }
    else
      {
        fetcher = fetchurl;
        input = "$src";
      };
in
stdenvNoCC.mkDerivation {
  name = repo;
  version = "${base}.${release}";

  src = intake.fetcher {
    inherit url;
    hash = selected.sources.proton.hash;
  };

  buildCommand = ''
    mkdir -p $out/bin
    tar -C $out/bin --strip=1 -x -f ${intake.input}
  ''
  # Allow to keep the same name between updates
  + lib.strings.optionalString (toolTitle != null) ''
    sed -i -r 's|"${toolPattern}"|"${toolTitle}"|' $out/bin/compatibilitytool.vdf
  '';

  passthru =
    if withUpdateScript then
      {
        updateScript = callPackage ./update.nix {
          inherit
            tarballPrefix
            tarballSuffix
            releasePrefix
            releaseSuffix
            owner
            repo
            ;
          # Prefer explicit variant, otherwise use defaultVariant from the spec
          variant = if variant != null then variant else (versionSpec.defaultVariant or "cachyos");
        };
      }
    else
      { };

  meta = with lib; {
    inherit homepage;
    description = "Compatibility tool for Steam Play based on Wine and additional components (patched and built by ${owner})";
    license = licenses.bsd3;
    platforms = [ "x86_64-linux" ];
    maintainers = with maintainers; [
      pedrohlc
    ];
  };
}