diff --git a/tests/ui/app.spec.ts b/tests/ui/app.spec.ts
index 18b6a51..2c55ce8 100644
--- a/tests/ui/app.spec.ts
+++ b/tests/ui/app.spec.ts
@@ -2883,3 +2883,35 @@ test('an error toast is announced and stays until it is dismissed', async ({ pag
   await t.getByRole('button', { name: 'Dismiss' }).click();
   await expect(t).toHaveCount(0);
 });
+
+/// A scrape as Prometheus makes it: gzipped (#253), and every sample a name, labels perhaps, and a
+/// number, since one line that is not fails the whole scrape.
+async function scrape(page: Page, port: number): Promise<string> {
+  const r = await page.request.get(`http://127.0.0.1:${port}/metrics`, { headers: { 'Accept-Encoding': 'gzip' } });
+  expect(r.status()).toBe(200);
+  expect(r.headers()['content-type']).toContain('text/plain');
+  const text = await r.text();
+  const bad = text.split('\n').filter(l => l && !l.startsWith('#') && !/^[a-z_:][a-z0-9_:]*(\{.*\})? (-?[0-9.e+-]+|NaN|\+Inf)$/i.test(l));
+  expect(bad, `port ${port}`).toEqual([]);
+  return text;
+}
+
+test('each service serves its metrics as Prometheus reads them, the requests made counted by route', async ({ page }) => {
+  // #194, #370, #458: production's Prometheus scrapes these every 15 s; the dashboard and the
+  // alerts go blank if one stops answering, and nothing else in the suite asks for them.
+  await page.request.get('/api/feeds');
+  const ipx = await scrape(page, 8799);
+  expect(ipx).toMatch(/^# TYPE ipx_http_request_duration_seconds histogram$/m);
+  expect(ipx).toMatch(/^ipx_http_request_duration_seconds_count\{method="GET",route="\/api\/feeds",status="200"\} [1-9]/m);
+  expect(ipx).toMatch(/^ipx_build_info\{version="[^"]+"\} 1$/m);
+  expect(ipx).toMatch(/^ipx_db_connections_max [1-9]/m);
+  expect(ipx).toMatch(/^ipx_feeds [1-9]/m);
+  // The suite's ipx shares with its directory, so the directory has taken a snapshot and answered.
+  const dir = await scrape(page, 8797);
+  expect(dir).toMatch(/^directory_build_info\{version="[^"]+"\} 1$/m);
+  expect(dir).toMatch(/^directory_snapshots_total [1-9]/m);
+  expect(dir).toMatch(/^directory_http_request_duration_seconds_count\{/m);
+  const play = await scrape(page, 8790);
+  expect(play).toMatch(/^play_build_info\{version="[^"]+"\} 1$/m);
+  expect(play).toMatch(/^play_uptime_seconds [0-9]/m);
+});
diff --git a/tests/ui/global-setup.ts b/tests/ui/global-setup.ts
index a9d6d02..b0237ef 100644
--- a/tests/ui/global-setup.ts
+++ b/tests/ui/global-setup.ts
@@ -56,6 +56,8 @@ token = "${TOKEN}"
 trusted_header = "X-Test-User"
 trusted_proxies = ["127.0.0.1"]
 sign_out_url = "/signed-out-by-the-proxy"
+# What Prometheus scrapes in production (#194), read by a test once the others have made requests.
+metrics_bind = "127.0.0.1:8799"
 
 [feeds.test-show]
 url = "http://127.0.0.1:8792/show.xml"
@@ -82,6 +84,7 @@ auto_download = false
 `);
   fs.writeFileSync(path.join(root, 'directory.toml'), `
 bind = "127.0.0.1:8795"
+metrics_bind = "127.0.0.1:8797"
 database_url_env = "DIRECTORY_DATABASE_URL"
 # The fixture feeds are on loopback, which the refresher refuses otherwise (#329).
 fetch_internal = ["127.0.0.1"]
@@ -93,6 +96,7 @@ token_sha256 = "${crypto.createHash('sha256').update(DIRECTORY_TOKEN).digest('he
 `);
   fs.writeFileSync(path.join(root, 'play.toml'), `
 bind = "127.0.0.1:8798"
+metrics_bind = "127.0.0.1:8790"
 public_url = "${PLAY}"
 
 [[tokens]]