diff --git a/tests/modules/programs/zsh/default.nix b/tests/modules/programs/zsh/default.nix
index 95eb564b6..45adf1bd9 100644
--- a/tests/modules/programs/zsh/default.nix
+++ b/tests/modules/programs/zsh/default.nix
@@ -19,12 +19,15 @@
   zsh-history-path-xdg-variable = import ./history-path.nix "xdg-variable";
   zsh-history-path-zdotdir-variable = import ./history-path.nix "zdotdir-variable";
   zsh-history-substring-search = ./history-substring-search.nix;
+  zsh-legacy-warning = ./legacy-warning.nix;
   zsh-siteFunctions-mkcd = ./siteFunctions-mkcd.nix;
   zsh-plugins = ./plugins.nix;
   zsh-prezto = ./prezto.nix;
   zsh-session-variables = ./session-variables.nix;
   zsh-smart-formatting = ./smart-formatting.nix;
   zsh-syntax-highlighting = ./syntax-highlighting.nix;
+  zsh-xdg-default = ./xdg-default.nix;
+  zsh-xdg-disabled = ./xdg-disabled.nix;
   zsh-zprof = ./zprof.nix;
   zshrc-contents-priorities = ./zshrc-content-priorities.nix;
 }
diff --git a/tests/modules/programs/zsh/legacy-warning.nix b/tests/modules/programs/zsh/legacy-warning.nix
new file mode 100644
index 000000000..35aa15ea4
--- /dev/null
+++ b/tests/modules/programs/zsh/legacy-warning.nix
@@ -0,0 +1,29 @@
+{
+  config = {
+    programs.zsh.enable = true;
+    xdg.enable = true;
+
+    # We use 25.05 to trigger the legacy warning (since < 26.05)
+    # AND to bypass the global fix in tests/default.nix (which checks for 18.09)
+    home.stateVersion = "25.05";
+
+    nmt.script = ''
+      assertFileExists home-files/.zshrc
+
+      # Verify that the warning is generated
+      # We check the evaluation output for the warning message
+      assertPathNotExists home-files/.config/zsh
+    '';
+
+    test.asserts.warnings.expected = [
+      ''
+        The default value of `programs.zsh.dotDir` will change in future versions.
+        You are currently using the legacy default (home directory) because `home.stateVersion` is less than "26.05".
+        To silence this warning and lock in the current behavior, set:
+          programs.zsh.dotDir = config.home.homeDirectory;
+        To adopt the new behavior (XDG config directory), update `home.stateVersion` to "26.05" or set:
+          programs.zsh.dotDir = "''${config.xdg.configHome}/zsh";
+      ''
+    ];
+  };
+}
diff --git a/tests/modules/programs/zsh/xdg-default.nix b/tests/modules/programs/zsh/xdg-default.nix
new file mode 100644
index 000000000..c4f354257
--- /dev/null
+++ b/tests/modules/programs/zsh/xdg-default.nix
@@ -0,0 +1,21 @@
+{
+  config = {
+    programs.zsh.enable = true;
+    home.stateVersion = "26.05";
+    xdg.enable = true;
+
+    # With xdg.enable = true and new state version, dotDir should default to XDG config home
+
+    nmt.script = ''
+      assertFileExists home-files/.config/zsh/.zshenv
+      assertFileExists home-files/.config/zsh/.zshrc
+
+      # Verify global .zshenv points to the XDG location
+      assertFileExists home-files/.zshenv
+      assertFileRegex home-files/.zshenv "source /home/hm-user/.config/zsh/.zshenv"
+
+      # Verify ZDOTDIR is exported in the inner .zshenv
+      assertFileRegex home-files/.config/zsh/.zshenv "export ZDOTDIR=\"/home/hm-user/.config/zsh\""
+    '';
+  };
+}
diff --git a/tests/modules/programs/zsh/xdg-disabled.nix b/tests/modules/programs/zsh/xdg-disabled.nix
new file mode 100644
index 000000000..019dfb32c
--- /dev/null
+++ b/tests/modules/programs/zsh/xdg-disabled.nix
@@ -0,0 +1,20 @@
+{
+  config = {
+    programs.zsh.enable = true;
+    xdg.enable = false;
+    home.stateVersion = "26.05";
+
+    # With xdg.enable = false, dotDir should default to home directory regardless of state version
+
+    nmt.script = ''
+      assertFileExists home-files/.zshenv
+      assertFileExists home-files/.zshrc
+
+      # Should NOT exist in XDG location
+      assertPathNotExists home-files/.config/zsh
+
+      # Verify ZDOTDIR is NOT exported (or points to home if it is, but usually it isn't if dotDir is home)
+      assertFileNotRegex home-files/.zshenv "export ZDOTDIR="
+    '';
+  };
+}