diff --git a/configs/nixos/hosts/neogaia/default.nix b/configs/nixos/hosts/neogaia/default.nix
index 17093aa..3ec1246 100644
--- a/configs/nixos/hosts/neogaia/default.nix
+++ b/configs/nixos/hosts/neogaia/default.nix
@@ -40,6 +40,7 @@
   modules.network.ssh.hostKeys.sopsFile = ../../secrets/neogaia.yaml;
   modules.network.ssh.userKey.sopsFile = ../../secrets/neogaia.yaml;
 
+  modules.monorepo.enable = true;
   modules.shell.herdr.enable = true;
   modules.agents.tools.gitea-axi.enable = true;
   modules.agents.pi.enable = true;
diff --git a/configs/nixos/modules/default.nix b/configs/nixos/modules/default.nix
index bddeef5..c036697 100644
--- a/configs/nixos/modules/default.nix
+++ b/configs/nixos/modules/default.nix
@@ -120,7 +120,6 @@ in
     modules.shell.tmux.enable = lib.mkDefault true;
     modules.shell.nvim.enable = lib.mkDefault true;
     modules.shell.git.enable = lib.mkDefault true;
-    modules.shell.direnv.enable = lib.mkDefault true;
     modules.shell.yazi.enable = lib.mkDefault true;
   };
 }
diff --git a/configs/nixos/modules/monorepo.nix b/configs/nixos/modules/monorepo.nix
new file mode 100644
index 0000000..e094954
--- /dev/null
+++ b/configs/nixos/modules/monorepo.nix
@@ -0,0 +1,17 @@
+{
+  config,
+  lib,
+  ...
+}:
+# Tools for developing this monorepo.
+let
+  cfg = config.modules.monorepo;
+in
+{
+  options.modules.monorepo.enable = lib.mkEnableOption "tools for developing this monorepo";
+
+  config = lib.mkIf cfg.enable {
+    modules.shell.bazel.enable = true;
+    modules.shell.rust.enable = true;
+  };
+}
diff --git a/configs/nixos/modules/shell/bazel.nix b/configs/nixos/modules/shell/bazel.nix
new file mode 100644
index 0000000..b2db218
--- /dev/null
+++ b/configs/nixos/modules/shell/bazel.nix
@@ -0,0 +1,18 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+# Bazel for the primary user's shell environment.
+let
+  cfg = config.modules.shell.bazel;
+  user = config.user.name;
+in
+{
+  options.modules.shell.bazel.enable = lib.mkEnableOption "Bazel for the primary user's shell environment";
+
+  config = lib.mkIf cfg.enable {
+    home-manager.users.${user}.home.packages = [ pkgs.bazel ];
+  };
+}
diff --git a/configs/nixos/modules/shell/rust.nix b/configs/nixos/modules/shell/rust.nix
new file mode 100644
index 0000000..faef379
--- /dev/null
+++ b/configs/nixos/modules/shell/rust.nix
@@ -0,0 +1,24 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+# Rust tools for the primary user's shell environment.
+let
+  cfg = config.modules.shell.rust;
+  user = config.user.name;
+in
+{
+  options.modules.shell.rust.enable = lib.mkEnableOption "Rust tools for the primary user's shell environment";
+
+  config = lib.mkIf cfg.enable {
+    home-manager.users.${user}.home.packages = with pkgs; [
+      cargo
+      clippy
+      rust-analyzer
+      rustc
+      rustfmt
+    ];
+  };
+}