diff --git a/apps/docs/blume.config.ts b/apps/docs/blume.config.ts
index 26eb312..4612dfc 100644
--- a/apps/docs/blume.config.ts
+++ b/apps/docs/blume.config.ts
@@ -1,4 +1,5 @@
 import { defineConfig } from "blume";
+import type { StandardSchema } from "blume/core/standard-schema.ts";
 import { custom, filesystem } from "blume/sources";
 import { githubReleasesSource } from "blume/sources/github-releases.ts";
 import redirects from "./redirects";
@@ -24,8 +25,12 @@ const releasesDatedByTag: typeof fetch = async (input, init) => {
   const releases: unknown = await res.json();
   if (Array.isArray(releases)) {
     for (const release of releases) {
-      const m = typeof release?.tag_name === "string" ? release.tag_name.match(TIMEVER) : null;
-      if (m) release.published_at = `${m[1]}-${m[2]}-${m[3]}T${m[4]}:${m[5]}:${m[6]}Z`;
+      const m =
+        typeof release?.tag_name === "string"
+          ? release.tag_name.match(TIMEVER)
+          : null;
+      if (m)
+        release.published_at = `${m[1]}-${m[2]}-${m[3]}T${m[4]}:${m[5]}:${m[6]}Z`;
     }
   }
   // Blume reads only `ok` and the JSON body, so the original headers (whose
@@ -61,6 +66,49 @@ const plexMono = {
   ],
 };
 
+/**
+ * Custom frontmatter, rendered as the badge row by
+ * components/ProblemBadges.astro. Problem pages: `topics:` is LeetCode's topic
+ * tags (written by apps/cli/sync.ts), `video:` the NeetCode walkthrough's
+ * YouTube id (apps/cli/videos.ts). Guide pages (content/guides/, created by
+ * sync): `list:` is the tag's LeetCode problem list. Blume rejects undeclared
+ * keys and takes any Standard Schema; these are hand-rolled so the docs
+ * workspace needs no zod. All optional — every other page carries none.
+ */
+const optional = <T>(
+  message: string,
+  valid: (value: unknown) => value is T,
+): StandardSchema<unknown, T | undefined> => ({
+  "~standard": {
+    version: 1,
+    vendor: "prdlk",
+    validate: (value) =>
+      value === undefined || valid(value)
+        ? { value }
+        : { issues: [{ message }] },
+  },
+});
+
+const topicsSchema = optional(
+  "expected a list of { name, slug } LeetCode topic tags",
+  (value): value is { name: string; slug: string }[] =>
+    Array.isArray(value) &&
+    value.every(
+      (t) => typeof t?.name === "string" && typeof t?.slug === "string",
+    ),
+);
+const videoSchema = optional(
+  "expected an 11-character YouTube video id",
+  (value): value is string =>
+    typeof value === "string" && /^[\w-]{11}$/.test(value),
+);
+const listSchema = optional(
+  "expected a https://leetcode.com/problem-list/<slug>/ URL",
+  (value): value is string =>
+    typeof value === "string" &&
+    /^https:\/\/leetcode\.com\/problem-list\/[\w-]+\/$/.test(value),
+);
+
 export default defineConfig({
   title: "prdlk",
   description: "Documentation for my LeetCode solutions",
@@ -74,6 +122,9 @@ export default defineConfig({
   },
   lastModified: "git",
   redirects,
+  frontmatter: {
+    extend: { topics: topicsSchema, video: videoSchema, list: listSchema },
+  },
   content: {
     sources: [
       filesystem({ root: "content" }),
@@ -104,6 +155,9 @@ export default defineConfig({
     sidebar: {
       display: "flat", // "flat" | "group" | "page"
     },
-    tabs: [{ label: "Changelog", path: "/changelog" }],
+    tabs: [
+      { label: "Guides", path: "/guides" },
+      { label: "Changelog", path: "/changelog" },
+    ],
   },
 });