fix(nextjs): Include basePath in request url of Pages Router errors

Next.js strips the basePath from req.url before running Pages Router data
fetchers and API routes, so captured errors reported a request url without it.
Use the originally requested path and query from Next.js' initURL request meta
instead, keeping the origin from the request headers.

Fixes #24975
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: chargome

dev-packages/e2e-tests/test-applications/nextjs-15-basepath/pages/api/pages-router-api-error.ts

@@ -0,0 +1,5 @@
+import type { NextApiRequest, NextApiResponse } from 'next';
+
+export default function handler(_req: NextApiRequest, _res: NextApiResponse) {
+  throw new Error('Pages Router API route error with basePath');
+}

dev-packages/e2e-tests/test-applications/nextjs-15-basepath/pages/pages-router/gssp-error.tsx

@@ -0,0 +1,7 @@
+export default function Page() {
+  return <p>This page should never render</p>;
+}
+
+export async function getServerSideProps() {
+  throw new Error('Pages Router getServerSideProps error with basePath');
+}

dev-packages/e2e-tests/test-applications/nextjs-15-basepath/tests/pages-router-request-url.test.ts

@@ -0,0 +1,29 @@
+import { expect, test } from '@playwright/test';
+import { waitForError } from '@sentry-internal/test-utils';
+
+test('Includes the basePath in the request url of getServerSideProps errors', async ({ request }) => {
+  const errorEventPromise = waitForError('nextjs-15-basepath', errorEvent => {
+    return errorEvent.exception?.values?.[0]?.value === 'Pages Router getServerSideProps error with basePath';
+  });
+
+  await request.get('/my-app/pages-router/gssp-error?q=1');
+
+  const errorEvent = await errorEventPromise;
+
+  expect(errorEvent.request).toMatchObject({
+    url: 'http://localhost:3030/my-app/pages-router/gssp-error?q=1',
+    query_string: 'q=1',
+  });
+});
+
+test('Includes the basePath in the request url of Pages Router API route errors', async ({ request }) => {
+  const errorEventPromise = waitForError('nextjs-15-basepath', errorEvent => {
+    return errorEvent.exception?.values?.[0]?.value === 'Pages Router API route error with basePath';
+  });
+
+  await request.get('/my-app/api/pages-router-api-error');
+
+  const errorEvent = await errorEventPromise;
+
+  expect(errorEvent.request?.url).toBe('http://localhost:3030/my-app/api/pages-router-api-error');
+});

packages/nextjs/src/common/pages-router-instrumentation/_error.ts

@@ -1,12 +1,7 @@
-import {
-  captureException,
-  getIsolationScope,
-  httpRequestToRequestData,
-  isAlreadyCaptured,
-  withScope,
-} from '@sentry/core';
+import { captureException, getIsolationScope, isAlreadyCaptured, withScope } from '@sentry/core';
 import type { NextPageContext } from 'next';
 import { flushSafelyWithTimeout, waitUntil } from '../utils/responseEnd';
+import { pagesRouterRequestToRequestData } from '../utils/pagesRouterRequestToRequestData';
 
 type ContextOrProps = {
   req?: NextPageContext['req'];
@@ -62,7 +57,7 @@ export async function captureUnderscoreErrorException(contextOrProps: ContextOrP
 
   const eventId = withScope(scope => {
     if (req) {
-      const normalizedRequest = httpRequestToRequestData(req);
+      const normalizedRequest = pagesRouterRequestToRequestData(req);
       scope.setSDKProcessingMetadata({ normalizedRequest });
     }
 

packages/nextjs/src/common/pages-router-instrumentation/wrapApiHandlerWithSentry.ts

@@ -4,14 +4,14 @@ import {
   getActiveSpan,
   getCurrentScope,
   getRootSpan,
-  httpRequestToRequestData,
   objectify,
   setCapturedScopesOnSpan,
   withIsolationScope,
 } from '@sentry/core';
 import type { NextApiRequest } from 'next';
 import { TRANSACTION_ATTR_SENTRY_ROUTE_BACKFILL } from '../span-attributes-with-logic-attached';
 import type { AugmentedNextApiResponse, NextApiHandler } from '../types';
+import { pagesRouterRequestToRequestData } from '../utils/pagesRouterRequestToRequestData';
 import { flushSafelyWithTimeout, waitUntil } from '../utils/responseEnd';
 
 export type AugmentedNextApiRequest = NextApiRequest & {
@@ -56,7 +56,7 @@ export function wrapApiHandlerWithSentry(apiHandler: NextApiHandler, parameteriz
       return withIsolationScope(async isolationScope => {
         const reqMethod = `${(req.method || 'GET').toUpperCase()} `;
 
-        isolationScope.setSDKProcessingMetadata({ normalizedRequest: httpRequestToRequestData(req) });
+        isolationScope.setSDKProcessingMetadata({ normalizedRequest: pagesRouterRequestToRequestData(req) });
         isolationScope.setTransactionName(`${reqMethod}${parameterizedRoute}`);
 
         // We no longer create the transaction ourselves: it's the Next.js root span, which captured a different

packages/nextjs/src/common/utils/pagesRouterRequestToRequestData.ts

@@ -0,0 +1,48 @@
+import type { RequestEventData } from '@sentry/core';
+import { httpRequestToRequestData } from '@sentry/core';
+import type { IncomingMessage } from 'http';
+
+const NEXT_REQUEST_META = Symbol.for('NextInternalRequestMeta');
+
+type RequestWithNextMeta = IncomingMessage & {
+  [NEXT_REQUEST_META]?: { initURL?: unknown };
+};
+
+/**
+ * Converts a Pages Router request into request data for events.
+ *
+ * Next.js strips `basePath` from `req.url` before running pages and API routes, but keeps the URL as it was originally
+ * requested in its internal request meta (`initURL`). We use that one so the reported URL matches what was requested.
+ */
+export function pagesRouterRequestToRequestData(req: IncomingMessage): RequestEventData {
+  const requestData = httpRequestToRequestData(req);
+
+  const originalUrl = getOriginalPathAndQuery(req);
+  if (!originalUrl || originalUrl === req.url) {
+    return requestData;
+  }
+
+  const { url, query_string } = httpRequestToRequestData({
+    url: originalUrl,
+    headers: req.headers,
+    socket: req.socket,
+  });
+
+  return { ...requestData, url, query_string };
+}
+
+function getOriginalPathAndQuery(req: RequestWithNextMeta): string | undefined {
+  const initUrl = req[NEXT_REQUEST_META]?.initURL;
+  if (typeof initUrl !== 'string') {
+    return undefined;
+  }
+
+  // `initURL` can be absolute, but its origin is built from the Next.js server's own hostname and port rather than the
+  // request headers, so we only keep path and query and let the headers decide the origin like everywhere else.
+  try {
+    const { pathname, search } = new URL(initUrl, 'http://n');
+    return `${pathname}${search}`;
+  } catch {
+    return undefined;
+  }
+}

packages/nextjs/src/common/utils/wrapperUtils.ts

@@ -6,11 +6,11 @@ import {
   getIsolationScope,
   getRootSpan,
   getTraceData,
-  httpRequestToRequestData,
   isThenable,
 } from '@sentry/core';
 import type { IncomingMessage, ServerResponse } from 'http';
 import { TRANSACTION_ATTR_SENTRY_ROUTE_BACKFILL } from '../span-attributes-with-logic-attached';
+import { pagesRouterRequestToRequestData } from './pagesRouterRequestToRequestData';
 
 /**
  * Wraps a function that potentially throws. If it does, the error is passed to `captureException` and rethrown.
@@ -68,7 +68,7 @@ export function withTracedServerSideDataFetcher<F extends (...args: any[]) => Pr
     this: unknown,
     ...args: Parameters<F>
   ): Promise<{ data: ReturnType<F>; sentryTrace?: string; baggage?: string }> {
-    const normalizedRequest = httpRequestToRequestData(req);
+    const normalizedRequest = pagesRouterRequestToRequestData(req);
     getCurrentScope().setTransactionName(`${options.dataFetchingMethodName} (${options.dataFetcherRouteName})`);
     getIsolationScope().setSDKProcessingMetadata({ normalizedRequest });
 

packages/nextjs/test/common/utils/pagesRouterRequestToRequestData.test.ts

@@ -0,0 +1,56 @@
+import type { IncomingMessage } from 'http';
+import { describe, expect, it } from 'vitest';
+import { pagesRouterRequestToRequestData } from '../../../src/common/utils/pagesRouterRequestToRequestData';
+
+function createRequest(url: string, initURL?: unknown): IncomingMessage {
+  const req = {
+    method: 'GET',
+    url,
+    headers: { host: 'example.com' },
+    socket: {},
+  } as unknown as IncomingMessage;
+
+  if (initURL !== undefined) {
+    (req as unknown as Record<symbol, unknown>)[Symbol.for('NextInternalRequestMeta')] = { initURL };
+  }
+
+  return req;
+}
+
+describe('pagesRouterRequestToRequestData', () => {
+  it('uses `req.url` when there is no Next.js request meta', () => {
+    expect(pagesRouterRequestToRequestData(createRequest('/foo/bar?q=1'))).toMatchObject({
+      url: 'http://example.com/foo/bar?q=1',
+      query_string: 'q=1',
+      method: 'GET',
+    });
+  });
+
+  it('restores the basePath from a relative `initURL`', () => {
+    expect(pagesRouterRequestToRequestData(createRequest('/foo/bar?q=1', '/base/foo/bar?q=1'))).toMatchObject({
+      url: 'http://example.com/base/foo/bar?q=1',
+      query_string: 'q=1',
+      method: 'GET',
+    });
+  });
+
+  it('restores the basePath for the basePath root', () => {
+    expect(pagesRouterRequestToRequestData(createRequest('/', '/base'))).toMatchObject({
+      url: 'http://example.com/base',
+    });
+  });
+
+  it('takes only path and query from an absolute `initURL` and keeps the origin from the request headers', () => {
+    expect(
+      pagesRouterRequestToRequestData(createRequest('/foo/bar', 'http://localhost:3000/base/foo/bar')),
+    ).toMatchObject({
+      url: 'http://example.com/base/foo/bar',
+    });
+  });
+
+  it('ignores a non-string `initURL`', () => {
+    expect(pagesRouterRequestToRequestData(createRequest('/foo/bar', 123))).toMatchObject({
+      url: 'http://example.com/foo/bar',
+    });
+  });
+});