diff --git a/package.json b/package.json
index 47430ea..ceec9db 100644
--- a/package.json
+++ b/package.json
@@ -6,7 +6,8 @@
   "scripts": {
     "dev": "vite",
     "build": "vite build",
-    "preview": "vite preview"
+    "preview": "vite preview",
+    "test:embed-policy": "node --test tests/embed-policy.test.mjs"
   },
   "dependencies": {
     "@gcs/analytics": "file:./vendor/gcs-analytics",
diff --git a/tests/embed-policy.test.mjs b/tests/embed-policy.test.mjs
new file mode 100644
index 0000000..406800b
--- /dev/null
+++ b/tests/embed-policy.test.mjs
@@ -0,0 +1,19 @@
+import assert from 'node:assert/strict'
+import { readFile } from 'node:fs/promises'
+import test from 'node:test'
+
+const config = JSON.parse(await readFile(new URL('../vercel.json', import.meta.url), 'utf8'))
+const matchesEmbed = (condition) =>
+  condition?.type === 'query' && condition.key === 'embed' && condition.value === '^9line$'
+const headerValue = (rule, key) => rule.headers.find((header) => header.key === key)?.value
+
+test('only the owned 9Line embed mode relaxes Roadrunner framing', () => {
+  const standalone = config.headers.find((rule) => rule.missing?.some(matchesEmbed))
+  const embed = config.headers.find((rule) => rule.has?.some(matchesEmbed))
+
+  assert.equal(headerValue(standalone, 'X-Frame-Options'), 'SAMEORIGIN')
+  assert.match(headerValue(standalone, 'Content-Security-Policy'), /frame-ancestors 'none'/)
+  assert.equal(headerValue(embed, 'X-Frame-Options'), undefined)
+  assert.match(headerValue(embed, 'Content-Security-Policy'), /frame-ancestors https:\/\/9line\.dev(?:;|$)/)
+  assert.doesNotMatch(headerValue(embed, 'Content-Security-Policy'), /frame-ancestors[^;]*\*/)
+})
diff --git a/vercel.json b/vercel.json
index 4b35681..780a413 100644
--- a/vercel.json
+++ b/vercel.json
@@ -28,6 +28,9 @@
   "headers": [
     {
       "source": "/(.*)",
+      "missing": [
+        { "type": "query", "key": "embed", "value": "^9line$" }
+      ],
       "headers": [
         { "key": "X-Content-Type-Options", "value": "nosniff" },
         { "key": "X-Frame-Options", "value": "SAMEORIGIN" },
@@ -37,6 +40,19 @@
         { "key": "Content-Security-Policy", "value": "default-src 'self'; script-src 'self' 'unsafe-inline' https://www.googletagmanager.com; style-src 'self' 'unsafe-inline' https://fonts.googleapis.com; font-src 'self' https://fonts.gstatic.com; img-src 'self' data: https:; media-src 'self'; connect-src 'self' https://api.9line.dev https://www.google-analytics.com https://region1.google-analytics.com https://analytics.google.com https://stats.g.doubleclick.net; frame-ancestors 'none'" }
       ]
     },
+    {
+      "source": "/(.*)",
+      "has": [
+        { "type": "query", "key": "embed", "value": "^9line$" }
+      ],
+      "headers": [
+        { "key": "X-Content-Type-Options", "value": "nosniff" },
+        { "key": "X-XSS-Protection", "value": "1; mode=block" },
+        { "key": "Referrer-Policy", "value": "strict-origin-when-cross-origin" },
+        { "key": "Permissions-Policy", "value": "camera=(), microphone=(), geolocation=()" },
+        { "key": "Content-Security-Policy", "value": "default-src 'self'; script-src 'self' 'unsafe-inline' https://www.googletagmanager.com; style-src 'self' 'unsafe-inline' https://fonts.googleapis.com; font-src 'self' https://fonts.gstatic.com; img-src 'self' data: https:; media-src 'self'; connect-src 'self' https://api.9line.dev https://www.google-analytics.com https://region1.google-analytics.com https://analytics.google.com https://stats.g.doubleclick.net; frame-ancestors https://9line.dev" }
+      ]
+    },
     {
       "source": "/assets/(.*)",
       "headers": [