Bidirectional Dependencies

Host → User Configuration

A host aspect’s homeManager settings apply to all users on that host:

den.aspects.igloo.homeManager.programs.direnv.enable = true;

If igloo has users tux and pingu, both get direnv enabled.

This also works with static includes:

den.aspects.igloo.includes = [
  { homeManager.programs.direnv.enable = true; }
];

And with parametric includes that receive context:

den.aspects.igloo.includes = [
  ({ host, user }: {
    homeManager.programs.direnv.enable = true;
  })
];

User → Host Configuration

A user aspect’s nixos or darwin settings apply to every host with that user:

den.aspects.tux.nixos.programs.fish.enable = true;

If tux is on both igloo and iceberg, both hosts get fish enabled.

User includes work the same way:

den.aspects.tux.includes = [
  ({ host, ... }: {
    nixos.users.users.tux.description = "Tux on ${host.name}";
  })
];

Context-Conditional Bidirectional

Combine host and user context for precise control:

let
  git-on-linux = { user, host, ... }:
    if !lib.hasSuffix "darwin" host.system
    then { homeManager.programs.git.enable = true; }
    else { };
in {
  den.aspects.tux.includes = [ git-on-linux ];
}

User tux gets git only on Linux hosts, not on Darwin.

How It Works

graph TD
  HA["den.aspects.igloo (host)"] -->|"homeManager class"| U1["tux Home-Manager"]
  HA -->|"homeManager class"| U2["pingu Home-Manager"]
  UA["den.aspects.tux (user)"] -->|"nixos class"| H1["igloo NixOS"]
  UA -->|"nixos class"| H2["iceberg NixOS"]

Den’s context system handles the routing:

• Host aspect configs flow to all users on that host
• User aspect configs flow to all hosts with that user
• Context functions get called with the specific { host, user } pair

The den.default Backbone

Settings in den.default apply to everything — all hosts and all users:

den.default.homeManager.home.stateVersion = "25.11";
den.default.includes = [
  ({ host, ... }: { ${host.class}.networking.hostName = host.name; })
];