feat(browser): Trace continuation from server-timing headers

timfish · timfish · commit 87008e3c37a8 · 2026-01-02T13:25:13.000+01:00
diff --git a/dev-packages/browser-integration-tests/suites/tracing/trace-lifetime/tracing-without-performance-headers/init.js b/dev-packages/browser-integration-tests/suites/tracing/trace-lifetime/tracing-without-performance-headers/init.js
@@ -0,0 +1,10 @@
+import * as Sentry from '@sentry/browser';
+
+window.Sentry = Sentry;
+
+Sentry.init({
+  // in browser TwP means not setting tracesSampleRate but adding browserTracingIntegration,
+  dsn: 'https://public@dsn.ingest.sentry.io/1337',
+  integrations: [Sentry.browserTracingIntegration()],
+  tracePropagationTargets: ['http://sentry-test-site.example'],
+});
diff --git a/dev-packages/browser-integration-tests/suites/tracing/trace-lifetime/tracing-without-performance-headers/template.html b/dev-packages/browser-integration-tests/suites/tracing/trace-lifetime/tracing-without-performance-headers/template.html
@@ -0,0 +1,11 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8" />
+  </head>
+  <body>
+    <button id="errorBtn">Throw Error</button>
+    <button id="fetchBtn">Fetch Request</button>
+    <button id="xhrBtn">XHR Request</button>
+  </body>
+</html>
diff --git a/dev-packages/browser-integration-tests/suites/tracing/trace-lifetime/tracing-without-performance-headers/test.ts b/dev-packages/browser-integration-tests/suites/tracing/trace-lifetime/tracing-without-performance-headers/test.ts
@@ -0,0 +1,51 @@
+import { expect } from '@playwright/test';
+import { sentryTest } from '../../../../utils/fixtures';
+import type { EventAndTraceHeader } from '../../../../utils/helpers';
+import {
+  eventAndTraceHeaderRequestParser,
+  getFirstSentryEnvelopeRequest,
+  shouldSkipTracingTest,
+} from '../../../../utils/helpers';
+
+const META_TAG_TRACE_ID = '12345678901234567890123456789012';
+const META_TAG_PARENT_SPAN_ID = '1234567890123456';
+const META_TAG_BAGGAGE =
+  'sentry-trace_id=12345678901234567890123456789012,sentry-public_key=public,sentry-release=1.0.0,sentry-environment=prod,sentry-sample_rand=0.42';
+
+sentryTest('error on initial page has traceId from server timing headers', async ({ getLocalTestUrl, page }) => {
+  if (shouldSkipTracingTest()) {
+    sentryTest.skip();
+  }
+
+  const url = await getLocalTestUrl({
+    testDir: __dirname,
+    responseHeaders: {
+      'Server-Timing': `sentry-trace;desc=${META_TAG_TRACE_ID}-${META_TAG_PARENT_SPAN_ID}, baggage;desc="${META_TAG_BAGGAGE}"`,
+    },
+  });
+  await page.goto(url);
+
+  const errorEventPromise = getFirstSentryEnvelopeRequest<EventAndTraceHeader>(
+    page,
+    undefined,
+    eventAndTraceHeaderRequestParser,
+  );
+
+  await page.locator('#errorBtn').click();
+  const [errorEvent, errorTraceHeader] = await errorEventPromise;
+
+  expect(errorEvent.type).toEqual(undefined);
+  expect(errorEvent.contexts?.trace).toEqual({
+    trace_id: META_TAG_TRACE_ID,
+    parent_span_id: META_TAG_PARENT_SPAN_ID,
+    span_id: expect.stringMatching(/^[\da-f]{16}$/),
+  });
+
+  expect(errorTraceHeader).toEqual({
+    environment: 'prod',
+    public_key: 'public',
+    release: '1.0.0',
+    trace_id: META_TAG_TRACE_ID,
+    sample_rand: '0.42',
+  });
+});
diff --git a/packages/browser/src/tracing/browserTracingIntegration.ts b/packages/browser/src/tracing/browserTracingIntegration.ts
@@ -594,8 +594,9 @@ export const browserTracingIntegration = ((options: Partial<BrowserTracingOption
         }
         maybeEndActiveSpan();
 
-        const sentryTrace = traceOptions.sentryTrace || getMetaContent('sentry-trace');
-        const baggage = traceOptions.baggage || getMetaContent('baggage');
+        const sentryTrace =
+          traceOptions.sentryTrace || getMetaContent('sentry-trace') || getServerTiming('sentry-trace');
+        const baggage = traceOptions.baggage || getMetaContent('baggage') || getServerTiming('baggage');
 
         const propagationContext = propagationContextFromHeaders(sentryTrace, baggage);
 
@@ -778,6 +779,13 @@ export function getMetaContent(metaName: string): string | undefined {
   return metaTag?.getAttribute('content') || undefined;
 }
 
+/** Returns the description of a server timing entry */
+export function getServerTiming(name: string): string | undefined {
+  const navigation = WINDOW.performance?.getEntriesByType?.('navigation')[0] as PerformanceNavigationTiming | undefined;
+  const entry = navigation?.serverTiming.find(entry => entry.name === name);
+  return entry?.description;
+}
+
 /** Start listener for interaction transactions */
 function registerInteractionListener(
   client: Client,
