feat(browser): Add onRequestSpanEnd hook to browser tracing integration

[logaretm]

This PR aims to address #9643 partially by introducing a onRequestSpanEnd hook to the browser integration. These changes make it easier for users to enrich tracing spans with response header data.

Example

import * as Sentry from '@sentry/browser';

Sentry.init({
  // ...
  integrations: [
    Sentry.browserTracingIntegration({
      onRequestSpanEnd(span, responseInformation) {
        span.setAttributes({
          response_type: 'JSON',
        });
      },
    }),
  ],
});

Tracing Integration and API Improvements

• Added onRequestSpanEnd callback to BrowserTracingOptions and RequestInstrumentationOptions, allowing users to access response headers when a request span ends. This enables custom span annotation based on response data.
• Updated internal request instrumentation logic to call onRequestSpanEnd for both Fetch and XHR requests, passing parsed response headers to the callback.

Utility and Refactoring

• Centralized header parsing and filtering utilities (parseXhrResponseHeaders, getFetchResponseHeaders, filterAllowedHeaders) in networkUtils.ts, and exported them for reuse across packages.
• Moved helper functions for baggage header checking, URL resolution, performance timing checks, and safe header creation to a new utils.ts file to avoid failing the file size limit lint rule.

I was hesitant to hoist up those replay utils initially but a few of them were needed to expose them on the hook callback.

Type and API Consistency

• Introduced new types RequestHookInfo and ResponseHookInfo to standardize the information passed to request span hooks, and exported them from the core package for use in integrations.

I also added the necessary tests to test out the new hook.

[linear]

JS-56 Record response headers on http client spans

[github-actions]

size-limit report 📦

Path	Size	% Change	Change
@sentry/browser	24.26 kB	-	-
@sentry/browser - with treeshaking flags	22.77 kB	-	-
@sentry/browser (incl. Tracing)	40.59 kB	+0.37%	+149 B 🔺
@sentry/browser (incl. Tracing, Replay)	78.91 kB	+0.12%	+87 B 🔺
@sentry/browser (incl. Tracing, Replay) - with treeshaking flags	68.55 kB	+0.12%	+78 B 🔺
@sentry/browser (incl. Tracing, Replay with Canvas)	83.61 kB	+0.13%	+108 B 🔺
@sentry/browser (incl. Tracing, Replay, Feedback)	95.77 kB	+0.09%	+77 B 🔺
@sentry/browser (incl. Feedback)	40.97 kB	-	-
@sentry/browser (incl. sendFeedback)	28.91 kB	-	-
@sentry/browser (incl. FeedbackAsync)	33.84 kB	-0.01%	-1 B 🔽
@sentry/react	25.98 kB	-	-
@sentry/react (incl. Tracing)	42.56 kB	+0.35%	+146 B 🔺
@sentry/vue	28.77 kB	-	-
@sentry/vue (incl. Tracing)	42.41 kB	+0.36%	+151 B 🔺
@sentry/svelte	24.29 kB	-	-
CDN Bundle	25.77 kB	-	-
CDN Bundle (incl. Tracing)	40.45 kB	+0.29%	+113 B 🔺
CDN Bundle (incl. Tracing, Replay)	76.65 kB	+0.09%	+66 B 🔺
CDN Bundle (incl. Tracing, Replay, Feedback)	82.17 kB	+0.11%	+89 B 🔺
CDN Bundle - uncompressed	75.35 kB	-	-
CDN Bundle (incl. Tracing) - uncompressed	119.79 kB	+0.37%	+433 B 🔺
CDN Bundle (incl. Tracing, Replay) - uncompressed	234.82 kB	+0.13%	+298 B 🔺
CDN Bundle (incl. Tracing, Replay, Feedback) - uncompressed	247.58 kB	+0.13%	+298 B 🔺
@sentry/nextjs (client)	44.58 kB	+0.35%	+153 B 🔺
@sentry/sveltekit (client)	41.02 kB	+0.38%	+152 B 🔺
@sentry/node-core	50.56 kB	-	-
@sentry/node	154.19 kB	+0.01%	+1 B 🔺
@sentry/node - without tracing	92.42 kB	+0.01%	+1 B 🔺
@sentry/aws-serverless	106.14 kB	+0.01%	+1 B 🔺

View base workflow run

[github-actions]

node-overhead report 🧳

Note: This is a synthetic benchmark with a minimal express app and does not necessarily reflect the real-world performance impact in an application.

Scenario	Requests/s	% of Baseline	Prev. Requests/s	Change %
GET Baseline	8,833	-	8,994	-2%
GET With Sentry	1,317	15%	1,430	-8%
GET With Sentry (error only)	6,017	68%	6,248	-4%
POST Baseline	1,183	-	1,205	-2%
POST With Sentry	513	43%	555	-8%
POST With Sentry (error only)	1,044	88%	1,068	-2%
MYSQL Baseline	3,293	-	3,329	-1%
MYSQL With Sentry	434	13%	505	-14%
MYSQL With Sentry (error only)	2,702	82%	2,716	-1%

View base workflow run