diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 5346c2c7..b87d4a60 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -253,6 +253,17 @@ jobs:
             --changed-file artifacts/dist-purge-targets.txt \
             --base-url "$CLOUDFLARE_PURGE_BASE_URL"
 
+      - name: Verify deployed index.html version markup
+        env:
+          CLOUDFLARE_PURGE_BASE_URL: ${{ secrets.CLOUDFLARE_PURGE_BASE_URL }}
+        run: |
+          if [ -z "$CLOUDFLARE_PURGE_BASE_URL" ]; then
+            echo "CLOUDFLARE_PURGE_BASE_URL is required to verify deployed index.html"
+            exit 1
+          fi
+
+          DEPLOY_INDEX_URL="${CLOUDFLARE_PURGE_BASE_URL%/}/index.html" npm run verify:deployed:index-html
+
   unit-tests:
     runs-on: ubuntu-latest
     timeout-minutes: 30
diff --git a/package.json b/package.json
index 91c55b2a..0889d107 100644
--- a/package.json
+++ b/package.json
@@ -43,6 +43,7 @@
     "hash:dist": "node scripts/hash-dist.mjs --dist dist --output artifacts/dist-hashes-current.json",
     "diff:dist-hashes": "node scripts/diff-dist-hashes.mjs",
     "verify:dist:deploy-artifact": "node scripts/verify-dist-deploy-artifact.mjs",
+    "verify:deployed:index-html": "node scripts/verify-deployed-index-html.mjs",
     "purge:cloudflare:changed": "node scripts/purge-cloudflare-changed.mjs",
     "smoke:dist-assets": "node scripts/check-asset-references.mjs",
     "test:e2e:cache-upgrade": "npx playwright test tests/e2e/cache-upgrade-smoke.spec.ts --project=e2e"
diff --git a/scripts/verify-deployed-index-html.mjs b/scripts/verify-deployed-index-html.mjs
new file mode 100644
index 00000000..36bcf5b2
--- /dev/null
+++ b/scripts/verify-deployed-index-html.mjs
@@ -0,0 +1,59 @@
+#!/usr/bin/env node
+
+const VERSION_MARKUP_PATTERN = /seed\.\s*zap\.\s*subscribe\.\s*<\/h2>\s*<div[^>]*>\s*v:\s*[a-f0-9]{8}\s*•\s*\d{4}-\d{2}-\d{2}\s*<\/div>/i;
+
+function parseArgs(argv) {
+  const args = {
+    url: process.env.DEPLOY_INDEX_URL ?? ''
+  };
+
+  for (let i = 0; i < argv.length; i += 1) {
+    const arg = argv[i];
+
+    if (arg === '--url') {
+      args.url = argv[i + 1] ?? args.url;
+      i += 1;
+      continue;
+    }
+
+    if (arg === '--help' || arg === '-h') {
+      console.log('Usage: node scripts/verify-deployed-index-html.mjs --url <https://example.com/index.html>');
+      process.exit(0);
+    }
+
+    throw new Error(`Unknown argument: ${arg}`);
+  }
+
+  if (!args.url) {
+    throw new Error('Missing deployed index URL. Pass --url or set DEPLOY_INDEX_URL.');
+  }
+
+  return args;
+}
+
+async function main() {
+  const args = parseArgs(process.argv.slice(2));
+  const response = await fetch(args.url, {
+    headers: {
+      Accept: 'text/html'
+    }
+  });
+
+  if (!response.ok) {
+    throw new Error(`Unable to fetch deployed index.html (${args.url}): HTTP ${response.status}`);
+  }
+
+  const html = await response.text();
+  if (!VERSION_MARKUP_PATTERN.test(html)) {
+    throw new Error(
+      `Deployed index.html is missing version markup under the slogan at ${args.url} (expected: v: <8-char-hash> • <date>).`
+    );
+  }
+
+  console.log(`Deployed index verification passed: ${args.url} includes slogan version markup.`);
+}
+
+main().catch((error) => {
+  console.error(error.message);
+  process.exit(1);
+});