feat: add agenix-rekey + remote-builder module for distributed builds

flake.nix

@@ -8,6 +8,10 @@
       inputs.darwin.follows = "";
       inputs.nixpkgs.follows = "nixpkgs";
     };
+    agenix-rekey = {
+      url = "github:oddlama/agenix-rekey";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
     lix = {
       url = "git+https://git.lix.systems/lix-project/lix?ref=main";
       inputs.nixpkgs.follows = "nixpkgs";
@@ -28,7 +32,7 @@
     };
   };
 
-  outputs = { self, nixpkgs, agenix, lix
+  outputs = { self, nixpkgs, agenix, agenix-rekey, lix
             , nixpkgs-uconsole, nixos-uconsole, nixos-raspberrypi
             , home-manager
             , ... }@inputs:
@@ -69,7 +73,6 @@
           mesonFlags = (old.mesonFlags or []) ++ [ "-Dskip_gtk_tests=true" ];
         });
         hyprland = prev.hyprland.override { wrapRuntimeDeps = false; };
-        # Boost MPI cannot cross-compile for aarch64 (no b2 alternatives)
         boost = prev.boost.override { useMpi = false; };
         xdg-desktop-portal-hyprland = prev.xdg-desktop-portal-hyprland.overrideAttrs (old: {
           preConfigure = (old.preConfigure or "") + ''
@@ -79,7 +82,6 @@
         });
       };
 
-      # RPI-specific pipewire libcamera fix (separate nixpkgs instance)
       uconsoleRpiPipewireOverlay = final: prev: {
         pipewire = prev.pipewire.overrideAttrs (old: {
           buildInputs = builtins.filter
@@ -91,7 +93,6 @@
         });
       };
 
-      # Shared uConsole CM5 module set — used by both toplevel and SD image
       uconsoleBaseModules = [
         {
           nixpkgs.buildPlatform = "x86_64-linux";
@@ -109,7 +110,6 @@
         nixos-raspberrypi.lib.inject-overlays-global
         nixos-uconsole.nixosModules.uconsole-cm5
         ./modules/nixos/hardware/uconsole-cm5-aio-v2.nix
-        # Cross-compiled Lix for uConsole
         ({ config, lib, pkgs, inputs, ... }: let
           lixCross = import inputs.nixpkgs-uconsole {
             localSystem = { system = "x86_64-linux"; };
@@ -119,8 +119,10 @@
         in { nix.package = lixCross.lix; })
         inputs.home-manager.nixosModules.home-manager
         agenix.nixosModules.default
+        agenix-rekey.nixosModules.default
         ./hosts/uconsole-cm5/configuration.nix
         ./hosts/uconsole-cm5/hardware-configuration.nix
+        ./modules/nixos/services/remote-builder.nix
         ./modules/nixos/services/wireguard-client.nix
         ./modules/nixos/security/ai-worker-restricted.nix
         ./users/gortium/gortium.nix
@@ -164,6 +166,7 @@
             }
             ./hosts/cyt-pi/configuration.nix
             ./hosts/cyt-pi/hardware-configuration.nix
+            ./modules/nixos/services/remote-builder.nix
             ./modules/nixos/services/wireguard-client.nix
             ./users/gortium/gortium.nix
           ];
@@ -180,6 +183,11 @@
         };
       };
 
+      agenix-rekey = agenix-rekey.configure {
+        userFlake = self;
+        nixosConfigurations = self.nixosConfigurations;
+      };
+
       devShells.${system}.default = devShell;
 
       packages.${system} = {

modules/nixos/services/remote-builder.nix

@@ -0,0 +1,64 @@
+{ config, lib, pkgs, ... }:
+let
+  cfg = config.services.remoteBuilder;
+in {
+  options.services.remoteBuilder = {
+    enable = lib.mkEnableOption "remote Nix build machine (lazyworkhorse server)";
+
+    buildMachine = {
+      host = lib.mkOption {
+        type = lib.types.str;
+        default = "lazyworkhorse.net";
+        description = "Hostname or IP of the remote build machine.";
+      };
+      sshUser = lib.mkOption {
+        type = lib.types.str;
+        default = "ai-worker";
+        description = "SSH user on the remote build machine.";
+      };
+      port = lib.mkOption {
+        type = lib.types.port;
+        default = 2424;
+        description = "SSH port on the remote build machine.";
+      };
+      systems = lib.mkOption {
+        type = lib.types.listOf lib.types.str;
+        default = [ "aarch64-linux" "x86_64-linux" ];
+        description = "System types the remote builder can build for.";
+      };
+      maxJobs = lib.mkOption {
+        type = lib.types.int;
+        default = 16;
+        description = "Max parallel jobs on the remote builder.";
+      };
+      supportedFeatures = lib.mkOption {
+        type = lib.types.listOf lib.types.str;
+        default = [ "big-parallel" "nixos-test" "benchmark" ];
+        description = "Features the remote builder supports.";
+      };
+    };
+
+    fallbackLocal = lib.mkOption {
+      type = lib.types.bool;
+      default = true;
+      description = "Fall back to local build when remote builder is unreachable.";
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    nix.distributedBuilds = true;
+    nix.buildMachines = [{
+      hostName = cfg.buildMachine.host;
+      sshUser = cfg.buildMachine.sshUser;
+      sshPort = cfg.buildMachine.port;
+      systems = cfg.buildMachine.systems;
+      maxJobs = cfg.buildMachine.maxJobs;
+      supportedFeatures = cfg.buildMachine.supportedFeatures;
+    }];
+
+    nix.extraOptions = lib.optionalString cfg.fallbackLocal ''
+      builders-use-substitutes = true
+      fallback = true
+    '';
+  };
+}