{
  config,
  pkgs,
  lib,
  ...
}:
{
  options.settings.lang_packages = lib.mkOption {
    type = lib.types.submodule {
      options = {
        python = lib.mkOption {
          type = lib.types.listOf lib.types.package;
          default = [ ];
          description = "Additional Python-related packages appended to the python spec (overlay defaults remain).";
        };
        r = lib.mkOption {
          type = lib.types.listOf lib.types.package;
          default = [ ];
          description = "Additional R-related packages appended to the r spec (overlay defaults remain).";
        };
        julia = lib.mkOption {
          type = lib.types.listOf lib.types.str;
          default = [ ];
          description = "Additional Julia packages (names) passed to julia-bin.withPackages.";
        };
      };
    };
    default = { };
    description = ''
      Language-specific package defaults and downstream overrides appended to each
      language spec's runtime packages.
    '';
  };

  config.settings.lang_packages = {
    python = lib.mkDefault (with pkgs.python3Packages; [
      duckdb
      polars
    ]);
    r = lib.mkDefault (
      (with pkgs.rpkgs.rPackages; [
        arrow
        broom
        data_table
        janitor
        styler
        # vscDebugger is not on CRAN/Bioconductor, so it is not available in
        # pkgs.rpkgs.rPackages. Install it manually in your R library if you
        # want to use the nvim-dap R adapter (see plugin/26_dap.lua).
        # vscDebugger
        lintr
      ])
    );
    julia = lib.mkDefault [
      "DataFramesMeta"
      "QuackIO"
    ];
  };
}