@sentry/nextjs: request.url of Pages Router data fetcher errors is missing basePath #24975

Is there an existing issue for this?

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

How do you use Sentry?

Self-hosted/on-premise

Which SDK are you using?

@sentry/nextjs

SDK Version

10.75.3, also reproduced on 11.1.0

Framework Version

Next.js 14.2.4 (Pages Router, webpack), also reproduced in 15.5.4

Link to Sentry event

No response

Reproduction Example/SDK Setup

next.config.js:

const { withSentryConfig } = require('@sentry/nextjs/config');

module.exports = withSentryConfig(
  { basePath: '/base' },
  { telemetry: false, sourcemaps: { disable: true } }
);

instrumentation.js:

export async function register() {
  if (process.env.NEXT_RUNTIME === 'nodejs') {
    const Sentry = await import('@sentry/nextjs');
    Sentry.init({
      dsn: process.env.SENTRY_DSN,
      beforeSend(event) {
        console.log('[sentry event] request.url =', event.request?.url);
        return event;
      },
    });
  }
}

pages/foo/bar.js:

export default function Page() {
  return null;
}

export async function getServerSideProps() {
  throw new Error('gSSP error');
}

Steps to Reproduce

1. next build && next start
2. curl http://localhost:3000/base/foo/bar

Expected Result

event.request.url is http://localhost:3000/base/foo/bar - the URL that was actually requested.

Actual Result

[sentry event] request.url = http://localhost:3000/foo/bar

The basePath is missing. Same for /base -> http://localhost:3000/, and the query string is preserved (/base?q=1 → /?q=1).

Additional Context

Next.js strips basePath from req.url before running the page - the same applies to getInitialProps / _error wrappers that build request data from req.

Priority

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