diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 91f766c..99d51f8 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -9,31 +9,12 @@ permissions:
   contents: read
 
 jobs:
-  check:
+  flake-check:
     name: Flake check
     runs-on: ubuntu-latest
+    timeout-minutes: 20
     steps:
       - uses: actions/checkout@v4
-      - uses: DeterminateSystems/nix-installer-action@v17
-      - uses: DeterminateSystems/magic-nix-cache-action@v8
+      - uses: DeterminateSystems/nix-installer-action@v22
+      - uses: DeterminateSystems/magic-nix-cache-action@v13
       - run: nix flake check
-
-  examples:
-    name: "Example: ${{ matrix.example }}"
-    runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        example:
-          - example-minimal
-          - example-single-service
-          - example-full
-    steps:
-      - uses: actions/checkout@v4
-      - uses: DeterminateSystems/nix-installer-action@v17
-      - uses: DeterminateSystems/magic-nix-cache-action@v8
-
-      - name: Evaluate NixOS configuration
-        run: nix eval .#nixosConfigurations.${{ matrix.example }}.config.system.build.toplevel.drvPath
-
-      - name: Build NixOS configuration (dry-run)
-        run: nix build .#nixosConfigurations.${{ matrix.example }}.config.system.build.toplevel --dry-run
diff --git a/flake.nix b/flake.nix
index c49fd91..28914a4 100644
--- a/flake.nix
+++ b/flake.nix
@@ -83,16 +83,48 @@
       let
         pkgs = import nixpkgs { inherit system; };
         hooks = self.lib.mkGitHooks { };
+
+        # Build a minimal NixOS system with a single omnix module to
+        # verify it evaluates and builds without errors in isolation
+        evalModule =
+          module: extraModules:
+          (nixpkgs.lib.nixosSystem {
+            inherit system;
+            modules = [
+              module
+              {
+                boot.loader.grub.device = "nodev";
+                fileSystems."/" = {
+                  device = "none";
+                  fsType = "tmpfs";
+                };
+                nixpkgs.hostPlatform = system;
+              }
+            ]
+            ++ extraModules;
+          }).config.system.build.toplevel;
       in
       {
         packages.disko =
           disko.packages.${system}.default or (throw "disko package not available for ${system}");
         packages.ragenix = ragenix.packages.${system}.default;
 
-        checks.git-hooks = git-hooks.lib.${system}.run {
-          inherit hooks;
-          src = self;
-        };
+        checks = {
+          git-hooks = git-hooks.lib.${system}.run {
+            inherit hooks;
+            src = self;
+          };
+        }
+        // (nixpkgs.lib.optionalAttrs pkgs.stdenv.isLinux {
+          eval-base = evalModule self.nixosModules.base [ ];
+          eval-firewall = evalModule self.nixosModules.firewall [ ];
+          eval-storage = evalModule self.nixosModules.storage [ ];
+          eval-digitalocean = evalModule self.nixosModules.digitalocean [ ];
+          eval-services = evalModule self.nixosModules.services [ ];
+          eval-disko = evalModule self.nixosModules.disko [
+            disko.nixosModules.disko
+          ];
+        });
 
         formatter = pkgs.nixfmt;
 
diff --git a/modules/base.nix b/modules/base.nix
index f5a57df..92580cc 100644
--- a/modules/base.nix
+++ b/modules/base.nix
@@ -7,6 +7,9 @@
 
 let
   cfg = config.omnix.base;
+  shellCfg = cfg.shell;
+  isNushell = shellCfg.defaultShell == "nushell";
+  isZsh = shellCfg.defaultShell == "zsh";
 in
 {
   options.omnix.base = {
@@ -27,6 +30,44 @@ in
       type = lib.types.str;
       description = "NixOS state version";
     };
+
+    shell = {
+      defaultShell = lib.mkOption {
+        type = lib.types.enum [
+          "bash"
+          "zsh"
+          "nushell"
+        ];
+        default = "bash";
+        description = ''
+          Default interactive shell. Ensures the corresponding shell program
+          is enabled at the system level. Use `shellPackage` to set as a
+          user's login shell.
+        '';
+      };
+
+      shellPackage = lib.mkOption {
+        type = lib.types.package;
+        readOnly = true;
+        description = "The package for the selected default shell, for use in users.users.<name>.shell";
+      };
+
+      bash.viMode = lib.mkOption {
+        type = lib.types.bool;
+        default = true;
+        description = "Enable vi keybindings for interactive bash sessions";
+      };
+
+      nushell.manageConfig = lib.mkOption {
+        type = lib.types.bool;
+        default = true;
+        description = ''
+          Whether omnix manages nushell configuration via
+          environment.etc. Set to false to manage nushell config
+          via home-manager or manually.
+        '';
+      };
+    };
   };
 
   config = lib.mkIf cfg.enable {
@@ -57,9 +98,17 @@ in
       };
     };
 
-    programs.bash.interactiveShellInit = "set -o vi";
+    omnix.base.shell.shellPackage =
+      if isNushell then
+        pkgs.nushell
+      else if isZsh then
+        pkgs.zsh
+      else
+        pkgs.bashInteractive;
 
-    system.activationScripts.per-service-profiles.text = "mkdir -p /nix/var/nix/profiles/per-service";
+    programs.bash.interactiveShellInit = lib.mkIf shellCfg.bash.viMode "set -o vi";
+
+    programs.zsh.enable = lib.mkDefault isZsh;
 
     environment.systemPackages =
       with pkgs;
@@ -70,8 +119,28 @@ in
         rage
         zellij
       ]
+      ++ lib.optional isNushell pkgs.nushell
       ++ cfg.extraPackages;
 
+    environment.shells = lib.mkIf isNushell [ pkgs.nushell ];
+
+    environment.variables = lib.mkIf (isNushell && shellCfg.nushell.manageConfig) {
+      NU_VENDOR_AUTOLOAD_DIR = "/etc/nushell";
+    };
+
+    environment.etc = lib.mkIf (isNushell && shellCfg.nushell.manageConfig) {
+      "nushell/config.nu".text = ''
+        $env.config = {
+          show_banner: false
+        }
+      '';
+      "nushell/env.nu".text = ''
+        # omnix managed nushell environment
+      '';
+    };
+
+    system.activationScripts.per-service-profiles.text = "mkdir -p /nix/var/nix/profiles/per-service";
+
     system.stateVersion = cfg.stateVersion;
   };
 }