diff --git a/nix/module.nix b/nix/module.nix
index e225439..4a92ad4 100644
--- a/nix/module.nix
+++ b/nix/module.nix
@@ -29,8 +29,29 @@ in
     boot.kernel.sysctl."kernel.apparmor_restrict_unprivileged_userns" = lib.mkDefault 0;
 
     system.activationScripts.amber-pm-state = lib.mkIf cfg.initializeState ''
-      if [ ! -e /var/lib/apm/apm ]; then
+      target="/var/lib/apm/apm"
+      version_file="$target/.amber-pm-version"
+      current_version="${cfg.package.version}"
+
+      if [ ! -e "$target" ]; then
+        echo "APM state directory not found, initializing..."
         ${cfg.package}/bin/amber-pm-init-state
+        echo "Running ace-init for first-time setup..."
+        /var/lib/apm/apm/files/bin/ace-init
+      elif [ -f "$version_file" ]; then
+        stored_version="$(cat "$version_file")"
+        if [ "$stored_version" != "$current_version" ]; then
+          echo "APM version changed ($stored_version -> $current_version), re-initializing..."
+          ${cfg.package}/bin/amber-pm-init-state --force
+          echo "Running ace-init..."
+          /var/lib/apm/apm/files/bin/ace-init
+        else
+          echo "APM version unchanged ($current_version), skipping ace-init."
+        fi
+      else
+        echo "No version file found, refreshing state and running ace-init..."
+        ${cfg.package}/bin/amber-pm-init-state --force
+        /var/lib/apm/apm/files/bin/ace-init
       fi
     '';
   };
diff --git a/nix/package.nix b/nix/package.nix
index f8ebadd..42ce4cc 100644
--- a/nix/package.nix
+++ b/nix/package.nix
@@ -174,13 +174,15 @@ fi
 
 mkdir -p "$target"
 cp -a "$seed"/. "$target"/
+echo '@version@' > "$target/.amber-pm-version"
 chmod -R u+rwX "$target"
 echo "Initialized $target"
 echo "Next step: run '/var/lib/apm/apm/files/bin/ace-init' as root, or run 'apm --help' for CLI smoke testing."
 EOF
     substituteInPlace "$out/bin/amber-pm-init-state" \
       --replace-fail '@bash@' '${bash}' \
-      --replace-fail '@out@' "$out"
+      --replace-fail '@out@' "$out" \
+      --replace-fail '@version@' '${version}'
     chmod +x "$out/bin/amber-pm-init-state"
 
     runHook postInstall