diff --git a/frontend-modern/package.json b/frontend-modern/package.json
index 53e006f71..8c57a319a 100644
--- a/frontend-modern/package.json
+++ b/frontend-modern/package.json
@@ -35,11 +35,12 @@
     "test:coverage": "vitest run --coverage --coverage.provider=v8 --coverage.include=src/**/*.ts --coverage.include=src/**/*.tsx --coverage.exclude=src/index.tsx",
     "test:coverage:ai": "vitest run --coverage --coverage.provider=v8 --coverage.thresholds.100 --coverage.thresholds.perFile --coverage.include=src/components/AI/aiChatUtils.ts",
     "type-check": "tsc --noEmit",
-    "lint": "npm run lint:eslint && npm run lint:theme && npm run lint:copy && npm run lint:canonical-platforms && npm run lint:form-labels",
+    "lint": "npm run lint:eslint && npm run lint:theme && npm run lint:copy && npm run lint:canonical-platforms && npm run lint:form-labels && npm run lint:external-domains",
     "lint:canonical-platforms": "node scripts/canonical-platform-audit.mjs",
     "lint:eslint": "eslint \"src/**/*.{ts,tsx}\"",
     "lint:copy": "node scripts/copy-style-audit.mjs",
     "lint:form-labels": "node scripts/form-label-audit.mjs",
+    "lint:external-domains": "node scripts/external-domain-audit.mjs",
     "lint:theme": "node scripts/theme-audit.mjs",
     "lint:headers": "node scripts/header-audit.mjs",
     "lint:fix": "eslint \"src/**/*.{ts,tsx}\" --fix",
diff --git a/frontend-modern/scripts/external-domain-audit.mjs b/frontend-modern/scripts/external-domain-audit.mjs
new file mode 100644
index 000000000..7960db31a
--- /dev/null
+++ b/frontend-modern/scripts/external-domain-audit.mjs
@@ -0,0 +1,125 @@
+#!/usr/bin/env node
+// Blocks fabricated Pulse-branded domains from entering published surfaces.
+//
+// Context: commit 524f42cc28 invented security@pulseapp.io and docs.pulseapp.io
+// (pulseapp.io was never a Pulse domain); the address shipped as the published
+// security contact for ~10 months and bounced every disclosure. A follow-up
+// audit on 2026-09-01 found https://pulse.app claimed as the OpenRouter
+// attribution referer. This audit is the offline guard for that class: any
+// domain-shaped token containing "pulse" that is not on the owned/placeholder
+// allowlist fails the push. It cannot judge ownership of non-Pulse-branded
+// domains; the periodic link audit covers those.
+import fs from 'node:fs';
+import path from 'node:path';
+
+const ROOT = process.cwd();
+const REPO_ROOT = path.resolve(ROOT, '..');
+
+// Real public suffixes a fabricated brand domain would plausibly use. Tokens
+// ending in anything else (.role, .local, .example, .sh script names, Go
+// identifiers) are not treated as domains.
+const PUBLIC_TLDS = new Set([
+  'com', 'net', 'org', 'io', 'app', 'dev', 'pro', 'cloud', 'ai', 'me',
+  'co', 'eu', 'de', 'es', 'fr', 'uk', 'us', 'xyz', 'info', 'tech', 'online',
+  'site', 'blog',
+]);
+
+function isAllowedHost(host) {
+  if (host === 'pulserelay.pro' || host.endsWith('.pulserelay.pro')) return true;
+  if (host === '1mk.app' || host.endsWith('.1mk.app')) return true;
+  // Cloudflare Pages previews of the landing site.
+  if (host.endsWith('.pages.dev') && host.includes('pulserelay-landing')) return true;
+  const labels = host.split('.');
+  // Documentation placeholders.
+  if (labels.includes('example') || labels.some((l) => l.includes('yourdomain'))) return true;
+  if (host.startsWith('your-') || host.startsWith('yourname.')) return true;
+  return false;
+}
+
+const SCAN_ROOT_FILES = ['SECURITY.md', 'README.md', 'CONTRIBUTING.md', 'TERMS.md'];
+const SCAN_DIRS = [
+  { dir: 'docs', extensions: null },
+  { dir: 'frontend-modern/public/docs', extensions: null },
+  { dir: 'frontend-modern/src', extensions: /\.(ts|tsx)$/ },
+  { dir: 'internal', extensions: /\.go$/ },
+  { dir: 'cmd', extensions: /\.go$/ },
+  { dir: 'pkg', extensions: /\.go$/ },
+];
+const SKIP_DIR_NAMES = new Set(['node_modules', '__tests__', 'testdata', '.git']);
+const SKIP_FILE_PATTERNS = [/_test\.go$/, /\.test\.(ts|tsx)$/, /\.(png|jpg|jpeg|gif|webp|svg|ico|woff2?|mp4|pdf|zip|gz)$/i];
+const DOMAIN_TOKEN = /[a-z0-9](?:[a-z0-9-]*[a-z0-9])?(?:\.[a-z0-9](?:[a-z0-9-]*[a-z0-9])?)+/gi;
+
+const findings = [];
+
+function toRelative(absPath) {
+  return path.relative(REPO_ROOT, absPath).replaceAll(path.sep, '/');
+}
+
+function collectFiles(directory, extensions) {
+  const files = [];
+  let entries;
+  try {
+    entries = fs.readdirSync(directory, { withFileTypes: true });
+  } catch {
+    return files;
+  }
+  for (const entry of entries) {
+    if (SKIP_DIR_NAMES.has(entry.name)) continue;
+    const fullPath = path.join(directory, entry.name);
+    if (entry.isDirectory()) {
+      files.push(...collectFiles(fullPath, extensions));
+      continue;
+    }
+    if (!entry.isFile()) continue;
+    if (extensions && !extensions.test(entry.name)) continue;
+    if (SKIP_FILE_PATTERNS.some((p) => p.test(entry.name))) continue;
+    files.push(fullPath);
+  }
+  return files;
+}
+
+function inspectFile(absPath) {
+  let content;
+  try {
+    content = fs.readFileSync(absPath, 'utf8');
+  } catch {
+    return;
+  }
+  if (content.includes('\u0000')) return;
+  const lines = content.split('\n');
+  for (let i = 0; i < lines.length; i++) {
+    for (const match of lines[i].matchAll(DOMAIN_TOKEN)) {
+      // Capitalized single-label .app tokens are macOS/iOS bundle names
+      // (Pulse.app), not domains; a fabricated domain reads lowercase.
+      if (/^[A-Z][A-Za-z0-9-]*\.app$/.test(match[0])) continue;
+      const host = match[0].toLowerCase();
+      if (!host.includes('pulse')) continue;
+      const labels = host.split('.');
+      if (!PUBLIC_TLDS.has(labels[labels.length - 1])) continue;
+      if (isAllowedHost(host)) continue;
+      findings.push({ file: toRelative(absPath), line: i + 1, host });
+    }
+  }
+}
+
+const targets = SCAN_ROOT_FILES.map((f) => path.join(REPO_ROOT, f)).filter((f) => fs.existsSync(f));
+for (const { dir, extensions } of SCAN_DIRS) {
+  targets.push(...collectFiles(path.join(REPO_ROOT, dir), extensions));
+}
+for (const file of targets) inspectFile(file);
+
+if (findings.length > 0) {
+  console.error(
+    'External domain audit failed. Pulse-branded domains must be pulserelay.pro or 1mk.app;',
+  );
+  console.error(
+    'anything else is fabricated (see the pulseapp.io incident). Fix the reference or, for a',
+  );
+  console.error('legitimate new Pulse-owned domain, add it to isAllowedHost with a comment.');
+  for (const finding of findings) {
+    console.error(`- ${finding.file}:${finding.line}: ${finding.host}`);
+  }
+  process.exit(1);
+}
+
+console.log('External domain audit passed with no unrecognized Pulse-branded domains.');