diff --git a/e2e/tests/journeys.spec.ts b/e2e/tests/journeys.spec.ts
index 2909136..1051e21 100644
--- a/e2e/tests/journeys.spec.ts
+++ b/e2e/tests/journeys.spec.ts
@@ -1600,3 +1600,34 @@ test('the sitemap submits no Welsh or overseas school', async ({ page }) => {
   expect(xml).not.toContain('/school/401559');
   expect(xml).not.toContain('/school/402426');
 });
+
+/*
+ * Staging must not be indexable (spec 2026-08-20, W1 hygiene).
+ *
+ * These journeys only ever run against staging — deploy.yml passes
+ * STAGING_BASE_URL, and promote.yml only smoke-polls production without
+ * Playwright — so asserting the noindex header here is safe.
+ */
+test('staging answers noindex, and stays crawlable so the noindex is seen', async ({ page }) => {
+  const res = await page.request.get('/');
+  expect(res.ok()).toBeTruthy();
+
+  const tag = res.headers()['x-robots-tag'];
+  expect(tag, 'staging must send X-Robots-Tag').toBeTruthy();
+  expect(tag).toContain('noindex');
+
+  // The other half, and the reason this is one test rather than two: a
+  // Disallow would stop Google fetching the page at all, so it would never
+  // see the noindex above. The two only work together.
+  const robots = await (await page.request.get('/robots.txt')).text();
+  expect(robots).not.toMatch(/^\s*Disallow:\s*\/\s*$/mi);
+});
+
+test('a school page on staging is noindexed too, not just the homepage', async ({ page }) => {
+  const list = await page.request.get('/api/schools?search=primary&per_page=1');
+  const [first] = (await list.json()).schools ?? [];
+  expect(first, 'no school available').toBeTruthy();
+
+  const res = await page.request.get(`/school/${first.urn}-x`);
+  expect(res.headers()['x-robots-tag']).toContain('noindex');
+});
diff --git a/nextjs-app/next.config.js b/nextjs-app/next.config.js
index 54474c0..c282b97 100644
--- a/nextjs-app/next.config.js
+++ b/nextjs-app/next.config.js
@@ -55,6 +55,37 @@ const nextConfig = {
   // Headers for caching and security
   async headers() {
     return [
+      {
+        /*
+         * Keep non-production hosts out of the index.
+         *
+         * Staging serves the same image as production off stx., so without
+         * this it is a full crawlable duplicate of the site.
+         *
+         * X-Robots-Tag, NOT a robots.txt Disallow. Disallow blocks crawling,
+         * which is not the same as blocking indexing — a disallowed URL can
+         * still be indexed from external links, and worse, blocking the crawl
+         * means Google never fetches the page and never sees a noindex at all.
+         * Staging therefore stays crawlable and answers "noindex" when crawled.
+         *
+         * Matched on the staging host explicitly rather than "any host that is
+         * not production". The inverted form is tempting because it would cover
+         * future environments automatically, but its failure mode is
+         * deindexing production if the Host header ever arrives rewritten by a
+         * proxy. This form's failure mode is a new environment being indexable
+         * until someone adds it here — recoverable, where the other is not.
+         *
+         * Any new non-production hostname must be added to this list.
+         */
+        source: '/:path*',
+        has: [{ type: 'host', value: 'stx.schoolcompare.co.uk' }],
+        headers: [
+          {
+            key: 'X-Robots-Tag',
+            value: 'noindex, nofollow',
+          },
+        ],
+      },
       {
         source: '/:path*',
         headers: [