1 files changed, 10 insertions, 1 deletions
diff --git a/src/content.config.ts b/src/content.config.ts
index 7fbcf2c..93cd3ab 100644
--- a/src/content.config.ts
+++ b/src/content.config.ts
@@ -1,7 +1,16 @@
 import { defineCollection } from "astro:content";
+import { z } from "astro/zod";
 import { docsLoader } from "@astrojs/starlight/loaders";
 import { docsSchema } from "@astrojs/starlight/schema";
 
 export const collections = {
-  docs: defineCollection({ loader: docsLoader(), schema: docsSchema() }),
+  docs: defineCollection({
+    loader: docsLoader(),
+    schema: docsSchema({
+      extend: z.object({
+        /** ページの h1 の下に表示する副題（サイドバーには出ない） */
+        subtitle: z.string().optional(),
+      }),
+    }),
+  }),
 };