diff --git a/src/app/benchmarks/[slug]/page.tsx b/src/app/benchmarks/[slug]/page.tsx
index dd95803d8..0e14c7f7c 100644
--- a/src/app/benchmarks/[slug]/page.tsx
+++ b/src/app/benchmarks/[slug]/page.tsx
@@ -271,7 +271,46 @@ export default async function BenchmarkPage({
   const variants: Record<string, Benchmark> = {
     [variantKey(null, null, null)]: aggregate,
   };
-  const benchmark = aggregate;
+  // Single-origin surface guard. When this build pins one region
+  // (aggregate_filters.region) and declares no region dimension, the page
+  // must not ship the other regions' data in its payload either: the blob
+  // carries every region the worker computed, and whatever is passed to a
+  // client component lands in the RSC payload, readable in view-source even
+  // though nothing renders it. Keep the pinned region's cells, drop the
+  // rest. Benches that declare region tabs are untouched.
+  const pinnedRegion = aggregate.aggregateFilters?.region;
+  const singleOrigin = regionOptions.length === 0 && typeof pinnedRegion === "string";
+  const samePinned = (r: string) => canonRegion(r) === canonRegion(pinnedRegion ?? "");
+  const benchmark = !singleOrigin
+    ? aggregate
+    : {
+        ...aggregate,
+        extras: {
+          ...aggregate.extras,
+          regions: Object.fromEntries(
+            Object.entries(aggregate.extras.regions ?? {}).map(([slug, pts]) => [
+              slug,
+              (pts ?? []).filter((pt) => samePinned(pt.region)),
+            ]),
+          ),
+          seriesByRegion24h: aggregate.extras.seriesByRegion24h
+            ? Object.fromEntries(
+                Object.entries(aggregate.extras.seriesByRegion24h).map(([slug, byRegion]) => [
+                  slug,
+                  Object.fromEntries(Object.entries(byRegion).filter(([r]) => samePinned(r))),
+                ]),
+              )
+            : undefined,
+        },
+        cellRanks: aggregate.cellRanks
+          ? Object.fromEntries(
+              Object.entries(aggregate.cellRanks).filter(([key]) => {
+                const r = key.split("|").pop() ?? "";
+                return r === "" || r === "all" || samePinned(r);
+              }),
+            )
+          : undefined,
+      };
 
   const isDraft = benchmark.status === "draft";
   const isAwaiting = isDraft && benchmark.editorialStatus === "live";
diff --git a/src/lib/sitemap-builder.ts b/src/lib/sitemap-builder.ts
index d2d115c0d..3e677950d 100644
--- a/src/lib/sitemap-builder.ts
+++ b/src/lib/sitemap-builder.ts
@@ -6,6 +6,8 @@ import { COMPARE_PAIRS } from "@/data/compare-pairs";
 import { REMOVED_BENCH_SLUGS } from "@/middleware";
 import { REMOVED_PRODUCT_SLUGS } from "@/lib/removed-benches";
 import { isHlBuilderSlug } from "@/lib/hl-builder-stats";
+import { getSpecs } from "@/lib/spec";
+import { PROVIDER_REGISTRY } from "@/data/provider-registry";
 import { PERP_PRODUCT_PILL_SLUGS } from "@/lib/perp-venue-context";
 import { loadAllAlternatives } from "@/lib/alternatives";
 import { loadAllAnswers } from "@/lib/answers";
@@ -275,9 +277,22 @@ async function buildFullSitemap(): Promise<MetadataRoute.Sitemap> {
   // Prom) so it's safe async — no OOM risk (unlike the old getProvider fan-out).
   // It also catches dormant HL frontends missing from the Prom cohort that
   // the worker couldn't filter without the spec provider list.
+  // Only list product pages this build can actually serve. The blob is
+  // produced by the worker from its own checkout, so it can name providers
+  // that a spec on THIS branch does not declare yet; /products/<slug> then
+  // 404s and the deploy's sitemap smoke blocks the release (2026-09-08:
+  // /products/serialized, declared on dev, listed in prod's sitemap).
+  const declaredProviderSlugs = new Set<string>();
+  for (const spec of await getSpecs()) {
+    for (const p of spec.providers ?? []) declaredProviderSlugs.add(p.slug);
+  }
+  for (const entry of Object.values(PROVIDER_REGISTRY)) {
+    if (entry.parent) declaredProviderSlugs.add(entry.parent);
+  }
   const validatedSlugs = (
     await Promise.all(
       providerSlugs.map(async (slug) => {
+        if (!declaredProviderSlugs.has(slug)) return null;
         if (CHAIN_BY_SLUG.has(slug)) return null;
         if (hlBuilderSlugSet.has(slug)) return null;
         if (await isHlBuilderSlug(slug)) return null;