test(nextjs): Cover the server request link of a late trace meta tag

dev-packages/e2e-tests/test-applications/nextjs-16-cacheComponents/app/slow-stream/page.tsx

@@ -0,0 +1,20 @@
+import { headers } from 'next/headers';
+import { Suspense } from 'react';
+
+// Above the pageload's 10 second wait for the trace meta tag, but short enough that the tag still
+// arrives before the pageload ends.
+const DELAY_MS = 10_500;
+
+async function SlowContent() {
+  await headers();
+  await new Promise(resolve => setTimeout(resolve, DELAY_MS));
+  return <p id="slow-content">Slow content</p>;
+}
+
+export default function Page() {
+  return (
+    <Suspense fallback={<p>Loading...</p>}>
+      <SlowContent />
+    </Suspense>
+  );
+}

dev-packages/e2e-tests/test-applications/nextjs-16-cacheComponents/tests/cacheOrigin-pageloadConnection.spec.ts

@@ -212,3 +212,33 @@ test('keeps a navigation that starts while the pageload waits for the trace meta
   expect(pageloadTx.contexts?.trace?.data?.['sentry.idle_span_finish_reason']).toBe('cancelled');
   expect(navigationTx.contexts?.trace?.data?.['sentry.idle_span_finish_reason']).toBe('idleTimeout');
 });
+
+test('links the server request when its trace meta tag arrives after the pageload stopped waiting', async ({
+  page,
+}) => {
+  test.skip(process.env.TEST_ENV !== 'production', 'Only a prerendered shell makes the trace meta tag arrive late');
+  test.setTimeout(60_000);
+
+  const pageloadTxPromise = waitForTransaction(APP, transactionEvent => {
+    return transactionEvent.transaction === '/slow-stream' && transactionEvent.contexts?.trace?.op === 'pageload';
+  });
+
+  await page.goto('/slow-stream', { waitUntil: 'commit' });
+  await expect(page.locator('#slow-content')).toBeVisible({ timeout: 20_000 });
+  const [requestTraceId, requestSpanId] = (await page
+    .locator('meta[name="sentry-trace"]')
+    .getAttribute('content'))!.split('-');
+
+  const pageloadTx = await pageloadTxPromise;
+
+  // The tag arrived after the pageload had started its own trace, so the pageload only links it.
+  expect(pageloadTx.contexts?.trace?.trace_id).not.toBe(requestTraceId);
+  expect(pageloadTx.contexts?.trace?.links).toEqual([
+    {
+      trace_id: requestTraceId,
+      span_id: requestSpanId,
+      sampled: true,
+      attributes: { [SENTRY_LINK_TYPE]: 'server_request' },
+    },
+  ]);
+});

dev-packages/e2e-tests/test-applications/nextjs-16-streaming-cacheComponents/app/slow-stream/page.tsx

@@ -0,0 +1,20 @@
+import { headers } from 'next/headers';
+import { Suspense } from 'react';
+
+// Above the pageload's 10 second wait for the trace meta tag, but short enough that the tag still
+// arrives before the pageload ends.
+const DELAY_MS = 10_500;
+
+async function SlowContent() {
+  await headers();
+  await new Promise(resolve => setTimeout(resolve, DELAY_MS));
+  return <p id="slow-content">Slow content</p>;
+}
+
+export default function Page() {
+  return (
+    <Suspense fallback={<p>Loading...</p>}>
+      <SlowContent />
+    </Suspense>
+  );
+}

dev-packages/e2e-tests/test-applications/nextjs-16-streaming-cacheComponents/tests/cacheOrigin-pageloadConnection.spec.ts

@@ -211,3 +211,33 @@ test('keeps a navigation that starts while the pageload waits for the trace meta
     value: 'idleTimeout',
   });
 });
+
+test('links the server request when its trace meta tag arrives after the pageload stopped waiting', async ({
+  page,
+}) => {
+  test.skip(process.env.TEST_ENV !== 'production', 'Only a prerendered shell makes the trace meta tag arrive late');
+  test.setTimeout(60_000);
+
+  const pageloadSpanPromise = waitForStreamedSpan(APP, span => {
+    return span.name === '/slow-stream' && getSpanOp(span) === 'pageload' && span.is_segment;
+  });
+
+  await page.goto('/slow-stream', { waitUntil: 'commit' });
+  await expect(page.locator('#slow-content')).toBeVisible({ timeout: 20_000 });
+  const [requestTraceId, requestSpanId] = (await page
+    .locator('meta[name="sentry-trace"]')
+    .getAttribute('content'))!.split('-');
+
+  const pageloadSpan = await pageloadSpanPromise;
+
+  // The tag arrived after the pageload had started its own trace, so the pageload only links it.
+  expect(pageloadSpan.trace_id).not.toBe(requestTraceId);
+  expect(pageloadSpan.links).toEqual([
+    {
+      trace_id: requestTraceId,
+      span_id: requestSpanId,
+      sampled: true,
+      attributes: { [SENTRY_LINK_TYPE]: { type: 'string', value: 'server_request' } },
+    },
+  ]);
+});