diff --git a/apps/web/e2e/unique-ids.spec.ts b/apps/web/e2e/unique-ids.spec.ts
new file mode 100644
index 00000000..835298da
--- /dev/null
+++ b/apps/web/e2e/unique-ids.spec.ts
@@ -0,0 +1,20 @@
+import { expect, test } from '@playwright/test';
+
+// The navbar renders the locale switcher twice, and the English flag used
+// fixed clipPath ids, so every page had duplicate ids (DOS/Rate#1079).
+// The English flag is drawn as the current locale's flag on /en pages.
+for (const path of ['/en', '/en/smartphones']) {
+  test(`ids are unique on ${path}`, async ({ page }) => {
+    const res = await page.goto(path);
+    expect(res?.status()).toBe(200);
+    await expect(page.locator('nav').first()).toBeVisible();
+    const duplicates = await page.evaluate(() => {
+      const counts = new Map<string, number>();
+      for (const el of document.querySelectorAll('[id]')) {
+        counts.set(el.id, (counts.get(el.id) ?? 0) + 1);
+      }
+      return [...counts].filter(([, n]) => n > 1).map(([id]) => id);
+    });
+    expect(duplicates).toEqual([]);
+  });
+}
diff --git a/apps/web/src/components/elementary/LocaleSwitcher.tsx b/apps/web/src/components/elementary/LocaleSwitcher.tsx
index 106b7c84..ebd97a46 100644
--- a/apps/web/src/components/elementary/LocaleSwitcher.tsx
+++ b/apps/web/src/components/elementary/LocaleSwitcher.tsx
@@ -1,6 +1,12 @@
 'use client';
 
-import React, { useState, useRef, useEffect, useTransition } from 'react';
+import React, {
+  useState,
+  useRef,
+  useEffect,
+  useId,
+  useTransition,
+} from 'react';
 import { useLocale, useTranslations } from 'next-intl';
 import { FaChevronDown } from 'react-icons/fa6';
 
@@ -27,38 +33,44 @@ const FlagVN = () => (
   </svg>
 );
 
-const FlagEN = () => (
-  <svg
-    width="18"
-    height="12"
-    viewBox="0 0 60 30"
-    style={{
-      borderRadius: '2px',
-      display: 'inline-block',
-      flexShrink: 0,
-      boxShadow: '0 0 1px rgba(0,0,0,0.3)',
-    }}
-  >
-    <clipPath id="flag-en-s">
-      <path d="M0,0 v30 h60 v-30 z" />
-    </clipPath>
-    <clipPath id="flag-en-t">
-      <path d="M30,15 h30 v15 z v15 h-30 z h-30 v-15 z v-15 h30 z" />
-    </clipPath>
-    <g clipPath="url(#flag-en-s)">
-      <path d="M0,0 v30 h60 v-30 z" fill="#012169" />
-      <path d="M0,0 L60,30 M60,0 L0,30" stroke="#fff" strokeWidth="6" />
-      <path
-        d="M0,0 L60,30 M60,0 L0,30"
-        clipPath="url(#flag-en-t)"
-        stroke="#C8102E"
-        strokeWidth="4"
-      />
-      <path d="M30,0 v30 M0,15 h60" stroke="#fff" strokeWidth="10" />
-      <path d="M30,0 v30 M0,15 h60" stroke="#C8102E" strokeWidth="6" />
-    </g>
-  </svg>
-);
+// The switcher renders twice (phone and desktop), so the clip ids must be
+// unique per instance: fixed ids were duplicated on every page and one copy's
+// url(#...) resolved into the other (DOS/Rate#1079).
+const FlagEN = () => {
+  const clipId = useId();
+  return (
+    <svg
+      width="18"
+      height="12"
+      viewBox="0 0 60 30"
+      style={{
+        borderRadius: '2px',
+        display: 'inline-block',
+        flexShrink: 0,
+        boxShadow: '0 0 1px rgba(0,0,0,0.3)',
+      }}
+    >
+      <clipPath id={`${clipId}s`}>
+        <path d="M0,0 v30 h60 v-30 z" />
+      </clipPath>
+      <clipPath id={`${clipId}t`}>
+        <path d="M30,15 h30 v15 z v15 h-30 z h-30 v-15 z v-15 h30 z" />
+      </clipPath>
+      <g clipPath={`url(#${clipId}s)`}>
+        <path d="M0,0 v30 h60 v-30 z" fill="#012169" />
+        <path d="M0,0 L60,30 M60,0 L0,30" stroke="#fff" strokeWidth="6" />
+        <path
+          d="M0,0 L60,30 M60,0 L0,30"
+          clipPath={`url(#${clipId}t)`}
+          stroke="#C8102E"
+          strokeWidth="4"
+        />
+        <path d="M30,0 v30 M0,15 h60" stroke="#fff" strokeWidth="10" />
+        <path d="M30,0 v30 M0,15 h60" stroke="#C8102E" strokeWidth="6" />
+      </g>
+    </svg>
+  );
+};
 
 const FlagCS = () => (
   <svg