chore: final verification fixes for sitemap reliability

- Replace invalid revalidate export with unstable_cache in sitemap.ts
- Add revalidateTag('sitemap', 'default') to on-demand revalidation endpoint
- Fix test assertions to match /game/ URL path

app/api/revalidate-sitemap/route.ts

@@ -1,4 +1,4 @@
-import { revalidatePath } from "next/cache"
+import { revalidatePath, revalidateTag } from "next/cache"
 import { NextRequest, NextResponse } from "next/server"
 
 /**
@@ -38,6 +38,7 @@ export async function POST(request: NextRequest): Promise<NextResponse> {
   }
 
   try {
+    revalidateTag("sitemap", "default")
     revalidatePath("/sitemap.xml")
     return NextResponse.json({
       revalidated: true,

app/sitemap.ts

@@ -1,19 +1,36 @@
 import type { MetadataRoute } from "next"
+import { unstable_cache } from "next/cache"
 import { buildStaticEntries } from "@/lib/sitemap/build-static-entries"
 import { fetchDynamicEntries } from "@/lib/sitemap/fetch-dynamic-entries"
 
-/**
- * ISR revalidation interval for the sitemap.
- *
- * Instead of `force-dynamic`, we use ISR so the sitemap is cached and
- * regenerated in the background. This keeps response times fast for
- * crawlers while still reflecting recent changes on the site.
- */
-export const revalidate = Number(process.env.SITEMAP_REVALIDATE_SECONDS) || 3600
+const REVALIDATE_SECONDS = Number(process.env.SITEMAP_REVALIDATE_SECONDS) || 3600
 
-export default async function sitemap(): Promise<MetadataRoute.Sitemap> {
+/**
+ * Caches the full sitemap generation with time-based revalidation.
+ *
+ * Instead of `force-dynamic` (which hits the DB on every crawler request),
+ * we use `unstable_cache` so the sitemap is regenerated at most once per
+ * revalidation window. This keeps response times fast for crawlers while
+ * still reflecting recent changes on the site.
+ *
+ * Tagged with `"sitemap"` so the on-demand revalidation webhook can
+ * clear this cache immediately after content changes.
+ *
+ * @see https://nextjs.org/docs/app/api-reference/functions/unstable_cache
+ */
+const getCachedSitemap = unstable_cache(
+  async () => {
     const staticEntries = buildStaticEntries()
     const { gameEntries, deviceEntries } = await fetchDynamicEntries()
-
     return [...staticEntries, ...gameEntries, ...deviceEntries]
+  },
+  ["sitemap"],
+  {
+    revalidate: REVALIDATE_SECONDS,
+    tags: ["sitemap"],
+  },
+)
+
+export default async function sitemap(): Promise<MetadataRoute.Sitemap> {
+  return getCachedSitemap()
 }

lib/sitemap/__tests__/fetch-dynamic-entries.test.ts

@@ -64,9 +64,9 @@ describe("fetchDynamicEntries", () => {
     const result = await fetchDynamicEntries()
 
     expect(result.gameEntries).toHaveLength(2)
-    expect(result.gameEntries[0].url).toBe("https://deckyvault.xyz/games/game-1")
+    expect(result.gameEntries[0].url).toBe("https://deckyvault.xyz/game/game-1")
     expect(result.gameEntries[0].images).toEqual(["https://cdn.example.com/img1.jpg"])
-    expect(result.gameEntries[1].url).toBe("https://deckyvault.xyz/games/game-2")
+    expect(result.gameEntries[1].url).toBe("https://deckyvault.xyz/game/game-2")
     expect(result.gameEntries[1].images).toBeUndefined()
     expect(result.deviceEntries).toHaveLength(1)
   })