diff --git a/scripts/package-boundaries.json b/scripts/package-boundaries.json
index 98e7a716b..84cec6de3 100644
--- a/scripts/package-boundaries.json
+++ b/scripts/package-boundaries.json
@@ -552,6 +552,7 @@
       "src/ui/railCardBlocks.js",
       "src/ui/layerRowText.js",
       "src/ui/layerPanel/LayerRows.vue",
+      "src/ui/rail/classToggle.js",
       "src/ui/layerPanel/RowText.vue",
       "src/ui/railTimeline.js",
       "src/ui/clearLayersControl.js",
@@ -857,6 +858,7 @@
       "src/ui/railCardBlocks.js",
       "src/ui/layerRowText.js",
       "src/ui/layerPanel/LayerRows.vue",
+      "src/ui/rail/classToggle.js",
       "src/ui/layerPanel/RowText.vue",
       "src/ui/railTimeline.js",
       "src/ui/layers.js",
@@ -2553,6 +2555,7 @@
       "src/ui/railCardBlocks.js",
       "src/ui/layerRowText.js",
       "src/ui/layerPanel/LayerRows.vue",
+      "src/ui/rail/classToggle.js",
       "src/ui/layerPanel/RowText.vue",
       "src/ui/railTimeline.js",
       "src/ui/layers.js",
diff --git a/src/ui/layerPanel/LayerRows.vue b/src/ui/layerPanel/LayerRows.vue
index e3897ce30..f404938b6 100644
--- a/src/ui/layerPanel/LayerRows.vue
+++ b/src/ui/layerPanel/LayerRows.vue
@@ -2,6 +2,7 @@
 import RailChips from '../rail/RailChips.vue';
 import RailRowList from '../rail/RailRowList.vue';
 import RowText from './RowText.vue';
+import { vClassToggle } from '../rail/classToggle.js';
 
 // The data layer rows under their group headings. LayerPanel presents every
 // value; clicks reach it with the layer id, and it re-reads the live
@@ -21,10 +22,10 @@ defineProps({
     }}</h3
     ><div
       v-else
-      :class="[
-        'data-toggle-row',
-        { 'data-toggle-row--count-line': item.count?.countLine },
-      ]"
+      class="data-toggle-row"
+      v-class-toggle="{
+        'data-toggle-row--count-line': item.count?.countLine,
+      }"
       :data-layer-id="item.id"
       :data-layer-name="item.englishName"
       ><div class="data-toggle-top"
diff --git a/src/ui/layerPanel/layerRows.test.mjs b/src/ui/layerPanel/layerRows.test.mjs
new file mode 100644
index 000000000..937b35074
--- /dev/null
+++ b/src/ui/layerPanel/layerRows.test.mjs
@@ -0,0 +1,46 @@
+// src/ui/layerPanel/layerRows.test.mjs — a layer row's own classes change
+// without wiping classes other code adds, such as the voice highlight.
+import '../../testSupport/registerDom.mjs';
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { h, render } from 'vue';
+import LayerRows from './LayerRows.vue';
+
+const row = (countLine) => ({
+  key: 'flights',
+  id: 'flights',
+  englishName: 'Flights',
+  icon: 'flight',
+  name: 'Flights',
+  meta: '',
+  toggle: {
+    classes: [],
+    text: 'OFF',
+    ariaLabel: 'Flights',
+    title: '',
+    ariaBusy: 'false',
+    ariaDisabled: 'false',
+    feedState: '',
+  },
+  count: { countLine, text: '12', empty: false },
+  controls: null,
+});
+
+test('the count-line class toggles without dropping the voice highlight', () => {
+  document.body.replaceChildren();
+  const container = document.body.appendChild(document.createElement('div'));
+  render(h(LayerRows, { items: [row(false)] }), container);
+  const element = container.querySelector('[data-layer-id="flights"]');
+  assert.equal(element.className, 'data-toggle-row');
+  element.classList.add('gev-voice-focus');
+
+  render(h(LayerRows, { items: [row(true)] }), container);
+  assert.equal(element.classList.contains('data-toggle-row--count-line'), true);
+  assert.equal(element.classList.contains('gev-voice-focus'), true);
+
+  render(h(LayerRows, { items: [row(false)] }), container);
+  assert.equal(element.classList.contains('data-toggle-row--count-line'), false);
+  assert.equal(element.classList.contains('gev-voice-focus'), true);
+  assert.equal(element.classList.contains('data-toggle-row'), true);
+  render(null, container);
+});
diff --git a/src/ui/rail/classToggle.js b/src/ui/rail/classToggle.js
new file mode 100644
index 000000000..53383691f
--- /dev/null
+++ b/src/ui/rail/classToggle.js
@@ -0,0 +1,11 @@
+/**
+ * `v-class-toggle`: toggles each named class with `classList`, so classes other
+ * code adds to the element (a voice highlight) survive a re-render. A `:class`
+ * binding rewrites the whole `className` instead.
+ */
+const apply = (el, { value }) => {
+  for (const [name, on] of Object.entries(value || {}))
+    if (el.classList.contains(name) !== Boolean(on))
+      el.classList.toggle(name, Boolean(on));
+};
+export const vClassToggle = { mounted: apply, updated: apply };