Installing packages from NixOS-Unstable using Home-Manager: the Flake way


Background: I use Nix Flakes and Home-Manager to manage my dotfiles and packages.

After witnessing the power of Nix, I recently made the switch to NixOS along with a neat Nix- based tool called home-manager, which allows you to manage your user profile declaratively. It was around this time that I was also trying out the Helix text editor. When I looked up the Helix package on, I discovered that it was a version behind the latest release. Fortunately, nixos-unstable had the latest version available (23.05 at the time of writing this). Below is how I figured out how to use the unstable repository to install Helix.

Firstly, flake.nix allows you to define multiple inputs using:

inputs = {
  nixpkgs.url = "github:nixos/nixpkgs/nixos-22.11";
  # the unstable package repository
  nixpkgs-unstable.url = "github:nixos/nixpkgs/nixos-unstable";
  home-manager = {
    url = "github:nix-community/home-manager";
    inputs.nixpkgs.follows = "nixpkgs";

Over in the output block, using the extraSpecialArgs parameter, I can pass in the unstable-pkgs to home manager.

outputs = { self, nixpkgs, nixpkgs-unstable, home-manager, ... }:
    system = "x86_64-linux";
    pkgs = nixpkgs.legacyPackages.${system};
    unstable-pkgs = nixpkgs-unstable.legacyPackages.${system};
    homeManagerConfigurations = {
      <username> = home-manager.lib.homeManagerConfiguration {
        inherit pkgs;
        modules = [ ./home.nix ];
        extraSpecialArgs = {
          inherit unstable-pkgs;

Finally, in home.nix, I can reference the unstable-pkgs to download Helix from nixos-unstable.

# home.nix
{ config, pkgs, unstable-pkgs, ... }:

  home.packages = [
    unstable-pkgs.helix # installing from unstable repository
    pkgs.alacritty # installing from stable repository