Core Web Vitals aren't reported when enabling Tanstack Router integration

[pmdartus]

Is there an existing issue for this?

• [x] I have checked for existing issues https://github.com/getsentry/sentry-javascript/issues
• [x] I have reviewed the documentation https://docs.sentry.io/
• [x] I am using the latest SDK release https://github.com/getsentry/sentry-javascript/releases

How do you use Sentry?

Sentry Saas (sentry.io)

Which SDK are you using?

@sentry/react

SDK Version

10.29.0

Framework Version

React 19.2.0

Link to Sentry event

No response

Reproduction Example/SDK Setup

Demo example: https://github.com/pmdartus/tanstack-sentry-integration-bug-repro/blob/52559b07ab47437e38eb9351eb2500ce2aa916c1/src/main.jsx#L45-L54

Sentry.init({
  dsn: "https://3fc2dae8dcedfae62a6df7e42540440b@o4510449154457600.ingest.de.sentry.io/4510449155965008",
  debug: true,
  sendDefaultPii: true,
  tracesSampleRate: 1.0,
  integrations: [
    Sentry.browserTracingIntegration(),
    Sentry.tanstackRouterBrowserTracingIntegration(router)
  ],
});

Steps to Reproduce

1. Download the repo and install the dependencies
2. Start the app by running: npm run dev

Expected Result

All the Core Web Vitals reported on Sentry in the trace, including LCP and CLS.

Actual Result

Only TTFB (and FCP in certain cases are reported) are reported.

Additional Context

Note: Web vitals are correctly reported when disabling the tanstack integration.

After turning on debug mode, it appears that on initial page load the tanstack integration always stop the pageload root span to create a new navigation span. Based on my understanding of how custom routing should be implemented the tanstack router integration should preserving the ongoing pageload span to enable the browser tracing integration to attach the webvitals metrics.

Priority

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