diff --git a/dev-packages/browser-integration-tests/suites/tracing/browserTracingIntegration/standalone-without-baggage/init.js b/dev-packages/browser-integration-tests/suites/tracing/browserTracingIntegration/standalone-without-baggage/init.js
new file mode 100644
index 000000000000..e2dd69ede824
--- /dev/null
+++ b/dev-packages/browser-integration-tests/suites/tracing/browserTracingIntegration/standalone-without-baggage/init.js
@@ -0,0 +1,10 @@
+import * as Sentry from '@sentry/browser';
+
+window.Sentry = Sentry;
+
+Sentry.init({
+ dsn: 'https://public@dsn.ingest.sentry.io/1337',
+ integrations: [Sentry.browserTracingIntegration()],
+ tracePropagationTargets: ['sentry-test-external.io'],
+ tracesSampleRate: 1,
+});
diff --git a/dev-packages/browser-integration-tests/suites/tracing/browserTracingIntegration/standalone-without-baggage/subject.js b/dev-packages/browser-integration-tests/suites/tracing/browserTracingIntegration/standalone-without-baggage/subject.js
new file mode 100644
index 000000000000..179c0203e14c
--- /dev/null
+++ b/dev-packages/browser-integration-tests/suites/tracing/browserTracingIntegration/standalone-without-baggage/subject.js
@@ -0,0 +1,3 @@
+Sentry.startSpan({ name: 'standalone_span', experimental: { standalone: true } }, () => {
+ fetch('http://sentry-test-external.io');
+});
diff --git a/dev-packages/browser-integration-tests/suites/tracing/browserTracingIntegration/standalone-without-baggage/template.html b/dev-packages/browser-integration-tests/suites/tracing/browserTracingIntegration/standalone-without-baggage/template.html
new file mode 100644
index 000000000000..f98e1c83e643
--- /dev/null
+++ b/dev-packages/browser-integration-tests/suites/tracing/browserTracingIntegration/standalone-without-baggage/template.html
@@ -0,0 +1,8 @@
+
+
+
+
+
+
+
+
diff --git a/dev-packages/browser-integration-tests/suites/tracing/browserTracingIntegration/standalone-without-baggage/test.ts b/dev-packages/browser-integration-tests/suites/tracing/browserTracingIntegration/standalone-without-baggage/test.ts
new file mode 100644
index 000000000000..2700c8aa5077
--- /dev/null
+++ b/dev-packages/browser-integration-tests/suites/tracing/browserTracingIntegration/standalone-without-baggage/test.ts
@@ -0,0 +1,48 @@
+import { expect } from '@playwright/test';
+import type { SpanEnvelope } from '@sentry/core';
+import { sentryTest } from '../../../../utils/fixtures';
+import {
+ getMultipleSentryEnvelopeRequests,
+ properFullEnvelopeRequestParser,
+ shouldSkipTracingTest,
+} from '../../../../utils/helpers';
+
+const TRACE_ID = '12345678901234567890123456789012';
+const OUTGOING_REQUEST_URL = 'http://sentry-test-external.io';
+
+sentryTest(
+ 'omits the trace envelope header when a standalone span continues a trace without baggage',
+ async ({ getLocalTestUrl, page }) => {
+ sentryTest.skip(shouldSkipTracingTest());
+
+ const url = await getLocalTestUrl({ testDir: __dirname });
+ await page.route(OUTGOING_REQUEST_URL, route => route.fulfill({ status: 200, body: 'ok' }));
+ const outgoingRequestPromise = page.waitForRequest(OUTGOING_REQUEST_URL);
+
+ const [spanEnvelope] = await getMultipleSentryEnvelopeRequests(
+ page,
+ 1,
+ { url, envelopeType: 'span' },
+ properFullEnvelopeRequestParser,
+ );
+ const outgoingRequest = await outgoingRequestPromise;
+
+ expect(spanEnvelope[0]).toEqual({
+ sent_at: expect.any(String),
+ });
+
+ // To be clear: This is _expected_ behavior, not a bug.
+ // SDKs must assume that an incoming `sentry-trace` but no `baggage` meta tag means that the
+ // trace was started from an SDK that's not yet compatible with the DSC or baggage propagation.
+ // The test demonstrates that the SDK as expected continues the trace but does not send a `trace`
+ // header, nor a baggage header.
+ expect(spanEnvelope[0].trace).toBeUndefined();
+
+ expect(spanEnvelope[1]).toHaveLength(1);
+ expect(spanEnvelope[1][0][1].trace_id).toBe(TRACE_ID);
+
+ const outgoingRequestHeaders = outgoingRequest.headers();
+ expect(outgoingRequestHeaders['sentry-trace']).toMatch(new RegExp(`^${TRACE_ID}-[\\da-f]{16}-1$`));
+ expect(outgoingRequestHeaders['baggage']).toBeUndefined();
+ },
+);
diff --git a/packages/core/src/fetch.ts b/packages/core/src/fetch.ts
index bfe78d499260..bb69a1b0025e 100644
--- a/packages/core/src/fetch.ts
+++ b/packages/core/src/fetch.ts
@@ -222,7 +222,11 @@ export function _INTERNAL_getTracingHeadersForFetchRequest(
const originalHeaders = fetchOptionsObj.headers || (isRequest(request) ? request.headers : undefined);
if (!originalHeaders) {
- return { ...traceHeaders };
+ return {
+ 'sentry-trace': sentryTrace,
+ ...(baggage && { baggage }),
+ ...(traceparent && { traceparent }),
+ };
} else if (isHeaders(originalHeaders)) {
const newHeaders = new Headers(originalHeaders);
@@ -292,11 +296,11 @@ export function _INTERNAL_getTracingHeadersForFetchRequest(
const newHeaders: {
'sentry-trace': string;
- baggage: string | undefined;
+ baggage?: string;
traceparent?: string;
} = Object.assign({}, originalHeaders, {
'sentry-trace': (existingSentryTraceHeader as string | undefined) ?? sentryTrace,
- baggage: newBaggageHeaders.length > 0 ? newBaggageHeaders.join(',') : undefined,
+ ...(newBaggageHeaders.length > 0 && { baggage: newBaggageHeaders.join(',') }),
});
if (propagateTraceparent && traceparent && !existingTraceparentHeader) {
diff --git a/packages/core/test/lib/fetch.test.ts b/packages/core/test/lib/fetch.test.ts
index 6cfdb74e8a19..b09886172969 100644
--- a/packages/core/test/lib/fetch.test.ts
+++ b/packages/core/test/lib/fetch.test.ts
@@ -69,6 +69,21 @@ describe('_INTERNAL_getTracingHeadersForFetchRequest', () => {
});
});
+ it('omits baggage from headers object when no baggage is available', () => {
+ vi.mocked(traceData.getTraceData).mockReturnValueOnce({
+ 'sentry-trace': DEFAULT_SENTRY_TRACE,
+ });
+
+ const returnedHeaders = _INTERNAL_getTracingHeadersForFetchRequest('/api/test', {
+ headers: { 'custom-header': 'custom-value' },
+ });
+
+ expect(returnedHeaders).toStrictEqual({
+ 'sentry-trace': DEFAULT_SENTRY_TRACE,
+ 'custom-header': 'custom-value',
+ });
+ });
+
it('attaches sentry headers to a Headers instance', () => {
const returnedHeaders = _INTERNAL_getTracingHeadersForFetchRequest('/api/test', {
headers: new Headers({ 'custom-header': 'custom-value' }),