diff --git a/README.org b/README.org
index 11fd4bb..cbd8b50 100644
--- a/README.org
+++ b/README.org
@@ -365,6 +365,7 @@ nixos = nixpkgs.lib.nixosSystem {
   modules = [
     ./hosts/nixos
     <<module-x11>>
+    <<module-xdg>>
     <<module-flakes>>
     <<module-cachix>>
     <<module-home-manager>>
@@ -470,6 +471,7 @@ acernitro = nixpkgs.lib.nixosSystem {
   modules = [
     ./hosts/acernitro
     <<module-x11>>
+    <<module-xdg>>
     <<module-flakes>>
     <<module-cachix>>
     <<module-nvidia>>
@@ -1606,6 +1608,18 @@ ERC[fn:43] is a powerful, modular, and extensible IRC client for GNU/Emacs[fn:2]
       erc-track-exclude-types '("JOIN" "NICK" "QUIT" "MODE")
       erc-lurker-hide-list '("JOIN" "PART" "QUIT"))
 
+;; Configure the `erc-fill-column' to use the full buffer.
+(make-variable-buffer-local 'erc-fill-column)
+(add-hook 'window-configuration-change-hook
+  '(lambda ()
+     (save-excursion
+       (walk-windows
+         (lambda (w)
+           (let ((buffer (window-buffer w)))
+             (set-buffer buffer)
+             (when (eq major-mode 'erc-mode)
+               (setq erc-fill-column (- (window-width w) 2)))))))))
+
 ;; Connect to IRC via `erc'.
 (defun dotfiles/erc-connect ()
   "Connected to IRC via `erc'."
diff --git a/flake.nix b/flake.nix
index 19f5ef0..699668c 100644
--- a/flake.nix
+++ b/flake.nix
@@ -21,6 +21,7 @@
         modules = [
           ./hosts/nixos
           ./modules/x11.nix
+          ./modules/xdg.nix
           ./modules/flakes.nix
           ./modules/cachix.nix
           inputs.home-manager.nixosModules.home-manager {
@@ -44,6 +45,7 @@
         modules = [
           ./hosts/acernitro
           ./modules/x11.nix
+          ./modules/xdg.nix
           ./modules/flakes.nix
           ./modules/cachix.nix
           ./modules/nvidia.nix