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feat(browser): Trace continuation from server-timing headers #18673

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feat(browser): Trace continuation from server-timing headers
timfish Jan 2, 2026
73e9db6
Merge branch 'develop' into timfish/feat/browser-server-timing
timfish Jan 22, 2026
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16 changes: 16 additions & 0 deletions ...kages/browser-integration-tests/suites/tracing/trace-lifetime/pageload-headers/subject.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,16 @@
const errorBtn = document.getElementById('errorBtn');
errorBtn.addEventListener('click', () => {
throw new Error(`Sentry Test Error ${Math.random()}`);
});

const fetchBtn = document.getElementById('fetchBtn');
fetchBtn.addEventListener('click', async () => {
await fetch('http://sentry-test-site.example');
});

const xhrBtn = document.getElementById('xhrBtn');
xhrBtn.addEventListener('click', () => {
const xhr = new XMLHttpRequest();
xhr.open('GET', 'http://sentry-test-site.example');
xhr.send();
});
11 changes: 11 additions & 0 deletions ...es/browser-integration-tests/suites/tracing/trace-lifetime/pageload-headers/template.html
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@@ -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>
85 changes: 85 additions & 0 deletions ...packages/browser-integration-tests/suites/tracing/trace-lifetime/pageload-headers/test.ts
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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-sample_rate=0.2,sentry-sampled=true,sentry-transaction=my-transaction,sentry-public_key=public,sentry-release=1.0.0,sentry-environment=prod,sentry-sample_rand=0.42';

sentryTest(
'create a new trace for a navigation after the server timing headers',
async ({ getLocalTestUrl, page, enableConsole }) => {
if (shouldSkipTracingTest()) {
sentryTest.skip();
}

enableConsole();

const url = await getLocalTestUrl({
testDir: __dirname,
responseHeaders: {
'Server-Timing': `sentry-trace;desc=${META_TAG_TRACE_ID}-${META_TAG_PARENT_SPAN_ID}-1, baggage;desc="${META_TAG_BAGGAGE}"`,
},
});

const [pageloadEvent, pageloadTraceHeader] = await getFirstSentryEnvelopeRequest<EventAndTraceHeader>(
page,
url,
eventAndTraceHeaderRequestParser,
);
const [navigationEvent, navigationTraceHeader] = await getFirstSentryEnvelopeRequest<EventAndTraceHeader>(
page,
`${url}#foo`,
eventAndTraceHeaderRequestParser,
);

const pageloadTraceContext = pageloadEvent.contexts?.trace;
const navigationTraceContext = navigationEvent.contexts?.trace;

expect(pageloadEvent.type).toEqual('transaction');
expect(pageloadTraceContext).toMatchObject({
op: 'pageload',
trace_id: META_TAG_TRACE_ID,
parent_span_id: META_TAG_PARENT_SPAN_ID,
span_id: expect.stringMatching(/^[\da-f]{16}$/),
});

expect(pageloadTraceHeader).toEqual({
environment: 'prod',
release: '1.0.0',
sample_rate: '0.2',
sampled: 'true',
transaction: 'my-transaction',
public_key: 'public',
trace_id: META_TAG_TRACE_ID,
sample_rand: '0.42',
});

expect(navigationEvent.type).toEqual('transaction');
expect(navigationTraceContext).toMatchObject({
op: 'navigation',
trace_id: expect.stringMatching(/^[\da-f]{32}$/),
span_id: expect.stringMatching(/^[\da-f]{16}$/),
});
// navigation span is head of trace, so there's no parent span:
expect(navigationTraceContext).not.toHaveProperty('parent_span_id');

expect(navigationTraceHeader).toEqual({
environment: 'production',
public_key: 'public',
sample_rate: '1',
sampled: 'true',
trace_id: navigationTraceContext?.trace_id,
sample_rand: expect.any(String),
});

expect(pageloadTraceContext?.trace_id).not.toEqual(navigationTraceContext?.trace_id);
expect(pageloadTraceHeader?.sample_rand).not.toEqual(navigationTraceHeader?.sample_rand);
},
);
2 changes: 1 addition & 1 deletion dev-packages/browser-integration-tests/suites/tracing/trace-lifetime/pageload-meta/test.ts
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Expand Up @@ -64,7 +64,7 @@ sentryTest(
span_id: expect.stringMatching(/^[\da-f]{16}$/),
});
// navigation span is head of trace, so there's no parent span:
expect(navigationTraceContext?.trace_id).not.toHaveProperty('parent_span_id');
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@timfish timfish Jan 3, 2026

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Cursor pointed out that the type/logic was wrong in this expection...

expect(navigationTraceContext).not.toHaveProperty('parent_span_id');

expect(navigationTraceHeader).toEqual({
environment: 'production',
Expand Down
10 changes: 10 additions & 0 deletions ...tegration-tests/suites/tracing/trace-lifetime/tracing-without-performance-headers/init.js
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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'],
});
9 changes: 9 additions & 0 deletions ...ion-tests/suites/tracing/trace-lifetime/tracing-without-performance-headers/template.html
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@@ -0,0 +1,9 @@
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
</head>
<body>
<button id="errorBtn">Throw Error</button>
</body>
</html>
51 changes: 51 additions & 0 deletions ...tegration-tests/suites/tracing/trace-lifetime/tracing-without-performance-headers/test.ts
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@@ -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;
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@cursor cursor bot Jan 22, 2026

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Missing subject.js causes test to fail

Medium Severity · Bugbot Rules

The tracing-without-performance-headers test directory is missing its subject.js file. The test calls page.locator('#errorBtn').click() expecting an error to be thrown, but there's no JavaScript to add a click event listener to the button. The pageload-headers directory includes a subject.js with the error button handler, but this directory does not. Without it, clicking the button does nothing and the test will timeout waiting for an error event that never arrives. Per the review rules: "Check that tests actually test the newly added behaviour."

Additional Locations (1)

Fix in Cursor Fix in Web


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',
});
});
12 changes: 10 additions & 2 deletions packages/browser/src/tracing/browserTracingIntegration.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -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);

Expand Down Expand Up @@ -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,
Expand Down
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