diff --git a/test/simpleshop_theme_web/live/theme_css_consistency_test.exs b/test/simpleshop_theme_web/live/theme_css_consistency_test.exs
new file mode 100644
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+++ b/test/simpleshop_theme_web/live/theme_css_consistency_test.exs
@@ -0,0 +1,163 @@
+defmodule SimpleshopThemeWeb.ThemeCSSConsistencyTest do
+  @moduledoc """
+  Tests that verify CSS selectors work correctly for both the theme editor
+  preview (.preview-frame) and the shop pages (.shop-root).
+
+  These tests ensure that the theme-layer2-attributes.css file has correct
+  selectors for both contexts, and that CSS custom properties are resolved.
+  """
+
+  use SimpleshopThemeWeb.ConnCase, async: false
+
+  import Phoenix.LiveViewTest
+  import SimpleshopTheme.AccountsFixtures
+
+  alias SimpleshopTheme.Settings
+
+  setup do
+    user = user_fixture()
+    %{user: user}
+  end
+
+  describe "CSS selector consistency" do
+    test "shop home page has .shop-root with data attributes", %{conn: conn} do
+      {:ok, _view, html} = live(conn, ~p"/")
+
+      # Verify shop-root element exists with theme data attributes
+      assert html =~ ~r/<div[^>]*class="shop-root/
+      assert html =~ ~r/data-mood="/
+      assert html =~ ~r/data-typography="/
+      assert html =~ ~r/data-shape="/
+      assert html =~ ~r/data-density="/
+    end
+
+    test "theme editor has .preview-frame with data attributes", %{conn: conn, user: user} do
+      conn = log_in_user(conn, user)
+      {:ok, _view, html} = live(conn, ~p"/admin/theme")
+
+      # Verify preview-frame element exists with theme data attributes
+      assert html =~ ~r/<div[^>]*class="preview-frame/
+      assert html =~ ~r/data-mood="/
+      assert html =~ ~r/data-typography="/
+      assert html =~ ~r/data-shape="/
+      assert html =~ ~r/data-density="/
+    end
+
+    test "shop page uses same theme settings as preview", %{conn: conn, user: user} do
+      # Set a specific theme configuration
+      {:ok, _settings} = Settings.apply_preset(:night)
+
+      # Check shop page
+      {:ok, _view, shop_html} = live(conn, ~p"/")
+
+      # Check preview (authenticated)
+      conn = log_in_user(conn, user)
+      {:ok, _view, preview_html} = live(conn, ~p"/admin/theme")
+
+      # Extract data-mood values from both
+      [_, shop_mood] = Regex.run(~r/data-mood="([^"]+)"/, shop_html)
+      [_, preview_mood] = Regex.run(~r/data-mood="([^"]+)"/, preview_html)
+
+      # They should match
+      assert shop_mood == preview_mood
+      assert shop_mood == "dark"
+    end
+
+    test "theme settings changes are reflected on shop page", %{conn: conn} do
+      # Start with minimal preset (neutral mood)
+      {:ok, _settings} = Settings.apply_preset(:minimal)
+
+      {:ok, _view, html} = live(conn, ~p"/")
+      assert html =~ ~s(data-mood="neutral")
+
+      # Change to night preset (dark mood)
+      {:ok, _settings} = Settings.apply_preset(:night)
+
+      {:ok, _view, html} = live(conn, ~p"/")
+      assert html =~ ~s(data-mood="dark")
+
+      # Change to gallery preset (warm mood)
+      {:ok, _settings} = Settings.apply_preset(:gallery)
+
+      {:ok, _view, html} = live(conn, ~p"/")
+      assert html =~ ~s(data-mood="warm")
+    end
+  end
+
+  describe "CSS file structure" do
+    test "theme-layer2-attributes.css has both .preview-frame and .shop-root selectors" do
+      css_path = Path.join([File.cwd!(), "assets", "css", "theme-layer2-attributes.css"])
+      css_content = File.read!(css_path)
+
+      # Check that mood selectors exist for both
+      assert css_content =~ ".preview-frame[data-mood=\"dark\"]"
+      assert css_content =~ ".shop-root[data-mood=\"dark\"]"
+
+      assert css_content =~ ".preview-frame[data-mood=\"warm\"]"
+      assert css_content =~ ".shop-root[data-mood=\"warm\"]"
+
+      # Check typography selectors
+      assert css_content =~ ".preview-frame[data-typography=\"modern\"]"
+      assert css_content =~ ".shop-root[data-typography=\"modern\"]"
+
+      # Check shape selectors
+      assert css_content =~ ".preview-frame[data-shape=\"sharp\"]"
+      assert css_content =~ ".shop-root[data-shape=\"sharp\"]"
+
+      # Check descendant selectors (important for specificity)
+      assert css_content =~ ".preview-frame .product-grid"
+      assert css_content =~ ".shop-root .product-grid"
+
+      assert css_content =~ ".preview-frame .product-card"
+      assert css_content =~ ".shop-root .product-card"
+    end
+
+    test "default selectors include both .preview-frame and .shop-root" do
+      css_path = Path.join([File.cwd!(), "assets", "css", "theme-layer2-attributes.css"])
+      css_content = File.read!(css_path)
+
+      # The default (neutral) mood should apply to both
+      # This regex checks for the pattern where both selectors are grouped
+      assert Regex.match?(
+               ~r/\.preview-frame,\s*\n\.shop-root\s*\{[^}]*--t-surface-base/,
+               css_content
+             )
+    end
+  end
+
+  describe "generated CSS cache" do
+    test "generated CSS includes theme variables" do
+      # Apply a preset
+      {:ok, settings} = Settings.apply_preset(:bold)
+
+      # Generate CSS
+      css = SimpleshopTheme.Theme.CSSGenerator.generate(settings)
+
+      # Check that key variables are present
+      assert css =~ "--t-accent-h:"
+      assert css =~ "--t-accent-s:"
+      assert css =~ "--t-accent-l:"
+      assert css =~ "--t-font-size-scale:"
+      assert css =~ "--t-heading-weight-override:"
+    end
+
+    test "CSS cache is warmed on startup and invalidated on settings change" do
+      # Ensure cache has content
+      SimpleshopTheme.Theme.CSSCache.warm()
+
+      {:ok, css1} = SimpleshopTheme.Theme.CSSCache.get()
+      assert is_binary(css1)
+      assert css1 =~ "--t-accent-h:"
+
+      # Change settings (this should invalidate and rewarm cache)
+      {:ok, _settings} = Settings.apply_preset(:night)
+
+      {:ok, css2} = SimpleshopTheme.Theme.CSSCache.get()
+      assert is_binary(css2)
+
+      # The CSS should be different (different accent color)
+      # Note: this may or may not be true depending on preset colors
+      assert css2 =~ "--t-accent-h:"
+    end
+  end
+end