diff --git a/frontend/resources/vue/App.vue b/frontend/resources/vue/App.vue
index 3acbe21..27bb425 100644
--- a/frontend/resources/vue/App.vue
+++ b/frontend/resources/vue/App.vue
@@ -361,10 +361,12 @@ function applyTheme() {
         document.head.appendChild(themeStyle)
     }
 
+    // Load theme into @layer theme so it takes precedence over @layer components (theme is
+    // last in style.css layer order). Fixes #804 regression after beta.2.
     if (themePreference.value && themePreference.value !== '') {
-        themeStyle.textContent = `@import url('/custom-webui/themes/${themePreference.value}/theme.css') layer(theme);`
+        themeStyle.textContent = `@layer theme { @import url('/custom-webui/themes/${themePreference.value}/theme.css'); }`
     } else {
-        themeStyle.textContent = `@import url('/theme.css') layer(theme);`
+        themeStyle.textContent = `@layer theme { @import url('/theme.css'); }`
     }
 }
 
diff --git a/integration-tests/tests/cssClass/config.yaml b/integration-tests/tests/cssClass/config.yaml
new file mode 100644
index 0000000..3e8cfc6
--- /dev/null
+++ b/integration-tests/tests/cssClass/config.yaml
@@ -0,0 +1,24 @@
+#
+# Integration Test Config: cssClass on dashboard components (#804)
+#
+
+listenAddressSingleHTTPFrontend: 0.0.0.0:1337
+
+logLevel: "DEBUG"
+checkForUpdates: false
+
+actions: []
+
+dashboards:
+  - title: CssClass Dashboard
+    contents:
+      - title: Button with custom class
+        type: link
+        cssClass: test-custom-class
+        inlineAction:
+          shell: echo ok
+          icon: ping
+      - title: Display with custom class
+        type: display
+        cssClass: test-display-class
+        contents: []
diff --git a/integration-tests/tests/cssClass/cssClass.mjs b/integration-tests/tests/cssClass/cssClass.mjs
new file mode 100644
index 0000000..444a6cb
--- /dev/null
+++ b/integration-tests/tests/cssClass/cssClass.mjs
@@ -0,0 +1,66 @@
+import { describe, it, before, after, afterEach } from 'mocha'
+import { expect } from 'chai'
+import { By } from 'selenium-webdriver'
+import {
+  getRootAndWait,
+  takeScreenshotOnFailure,
+} from '../../lib/elements.js'
+
+describe('config: cssClass', function () {
+  before(async function () {
+    await runner.start('cssClass')
+  })
+
+  after(async () => {
+    await runner.stop()
+  })
+
+  afterEach(function () {
+    takeScreenshotOnFailure(this.currentTest, webdriver)
+  })
+
+  it('cssClass is applied to action button (link component)', async function () {
+    await getRootAndWait()
+
+    const buttonWithClass = await webdriver.findElements(By.css('.action-button button.test-custom-class'))
+    expect(buttonWithClass).to.have.length.at.least(1, 'Action button should have cssClass test-custom-class on the button')
+
+    const classAttr = await buttonWithClass[0].getAttribute('class')
+    expect(classAttr).to.include('test-custom-class')
+  })
+
+  it('cssClass override: style rule targeting custom class wins over component styles', async function () {
+    await getRootAndWait()
+
+    const buttonWithClass = await webdriver.findElements(By.css('.action-button button.test-custom-class'))
+    expect(buttonWithClass).to.have.length.at.least(1)
+
+    const beforePx = await buttonWithClass[0].getCssValue('border-top-width')
+    await webdriver.executeScript(`
+      var style = document.getElementById('cssclass-test-override-style');
+      if (!style) {
+        style = document.createElement('style');
+        style.id = 'cssclass-test-override-style';
+        style.textContent = '.test-custom-class { border-top-width: 31px !important; }';
+        document.head.appendChild(style);
+      } else {
+        style.textContent = '.test-custom-class { border-top-width: 31px !important; }';
+      }
+    `)
+    await webdriver.sleep(150)
+
+    const afterPx = await buttonWithClass[0].getCssValue('border-top-width')
+    const afterNum = parseInt(afterPx, 10)
+    expect(afterNum).to.be.greaterThan(10, 'Override targeting cssClass should win over component 1px (before=' + beforePx + ' after=' + afterPx + ') (#804)')
+  })
+
+  it('cssClass is applied to display component', async function () {
+    await getRootAndWait()
+
+    const displayElements = await webdriver.findElements(By.css('.display.test-display-class'))
+    expect(displayElements).to.have.length.at.least(1, 'Display component with cssClass test-display-class should be in DOM')
+
+    const classAttr = await displayElements[0].getAttribute('class')
+    expect(classAttr).to.include('test-display-class')
+  })
+})