feat(react): Add lazyRouteManifest option to resolve lazy-route names

dev-packages/e2e-tests/test-applications/react-router-7-lazy-routes/src/index.tsx

@@ -55,6 +55,26 @@ function getRuntimeConfig(): { lazyRouteTimeout?: number; idleTimeout?: number }
 
 const runtimeConfig = getRuntimeConfig();
 
+// Static manifest for transaction naming when lazy routes are enabled
+const lazyRouteManifest = [
+  '/',
+  '/static',
+  '/delayed-lazy/:id',
+  '/lazy/inner',
+  '/lazy/inner/:id',
+  '/lazy/inner/:id/:anotherId',
+  '/lazy/inner/:id/:anotherId/:someAnotherId',
+  '/another-lazy/sub',
+  '/another-lazy/sub/:id',
+  '/another-lazy/sub/:id/:subId',
+  '/long-running/slow',
+  '/long-running/slow/:id',
+  '/deep/level2',
+  '/deep/level2/level3/:id',
+  '/slow-fetch/:id',
+  '/wildcard-lazy/:id',
+];
+
 Sentry.init({
   environment: 'qa', // dynamic sampling bias to keep transactions
   dsn: process.env.REACT_APP_E2E_TEST_DSN,
@@ -69,6 +89,7 @@ Sentry.init({
       enableAsyncRouteHandlers: true,
       lazyRouteTimeout: runtimeConfig.lazyRouteTimeout,
       idleTimeout: runtimeConfig.idleTimeout,
+      lazyRouteManifest,
     }),
   ],
   // We recommend adjusting this value in production, or using tracesSampler
@@ -160,5 +181,15 @@ const router = sentryCreateBrowserRouter(
   },
 );
 
+// E2E TEST UTILITY: Expose router instance for canary tests
+// This allows tests to verify React Router's route exposure behavior.
+// See tests/react-router-manifest.test.ts for usage.
+declare global {
+  interface Window {
+    __REACT_ROUTER__: typeof router;
+  }
+}
+window.__REACT_ROUTER__ = router;
+
 const root = ReactDOM.createRoot(document.getElementById('root') as HTMLElement);
 root.render(<RouterProvider router={router} />);

dev-packages/e2e-tests/test-applications/react-router-7-lazy-routes/tests/react-router-manifest.test.ts

@@ -0,0 +1,107 @@
+import { expect, test, Page } from '@playwright/test';
+
+/**
+ * Canary tests: React Router route manifest exposure
+ *
+ * These tests verify that React Router doesn't expose lazy-loaded routes in `router.routes`
+ * before navigation completes. They will fail when React Router changes this behavior.
+ *
+ * - Tests pass when React Router doesn't expose lazy routes (current behavior)
+ * - Tests fail when React Router does expose lazy routes (future behavior)
+ *
+ * If these tests fail, React Router may now expose lazy routes natively, and the
+ * `lazyRouteManifest` workaround might no longer be needed. Check React Router's changelog
+ * and consider updating the SDK to use native route exposure.
+ *
+ * Note: `router.routes` is the documented way to access routes when using RouterProvider.
+ * See: https://github.com/remix-run/react-router/discussions/10857
+ */
+
+/**
+ * Extracts all route paths from the React Router instance exposed on window.__REACT_ROUTER__.
+ * Recursively traverses the route tree and builds full path strings.
+ */
+async function extractRoutePaths(page: Page): Promise<string[]> {
+  return page.evaluate(() => {
+    const router = (window as Record<string, unknown>).__REACT_ROUTER__ as
+      | { routes?: Array<{ path?: string; children?: unknown[] }> }
+      | undefined;
+    if (!router?.routes) return [];
+
+    const paths: string[] = [];
+    function traverse(routes: Array<{ path?: string; children?: unknown[] }>, parent = ''): void {
+      for (const r of routes) {
+        const full = r.path ? (r.path.startsWith('/') ? r.path : `${parent}/${r.path}`) : parent;
+        if (r.path) paths.push(full);
+        if (r.children) traverse(r.children as Array<{ path?: string; children?: unknown[] }>, full);
+      }
+    }
+    traverse(router.routes);
+    return paths;
+  });
+}
+
+test.describe('[CANARY] React Router Route Manifest Exposure', () => {
+  /**
+   * Verifies that lazy routes are not pre-populated in router.routes.
+   * If lazy routes appear in the initial route tree, React Router has changed behavior.
+   */
+  test('React Router should not expose lazy routes before lazy handler resolves', async ({ page }) => {
+    await page.goto('/');
+    await page.waitForTimeout(500);
+
+    const initialRoutes = await extractRoutePaths(page);
+    const hasSlowFetchInitially = initialRoutes.some(p => p.includes('/slow-fetch/:id'));
+
+    // Test passes if routes are not available initially (we need the workaround)
+    // Test fails if routes are available initially (workaround may not be needed!)
+    expect(
+      hasSlowFetchInitially,
+      `
+React Router now exposes lazy routes in the initial route tree!
+This means the lazyRouteManifest workaround may no longer be needed.
+
+Initial routes: ${JSON.stringify(initialRoutes, null, 2)}
+
+Next steps:
+1. Verify this behavior is consistent and intentional
+2. Check React Router changelog for details
+3. Consider removing the lazyRouteManifest workaround
+`,
+    ).toBe(false);
+  });
+
+  /**
+   * Verifies that lazy route children are not in router.routes before visiting them.
+   */
+  test('React Router should not have lazy route children before visiting them', async ({ page }) => {
+    await page.goto('/');
+    await page.waitForTimeout(300);
+
+    const routes = await extractRoutePaths(page);
+    const hasLazyChildren = routes.some(
+      p =>
+        p.includes('/lazy/inner/:id') ||
+        p.includes('/another-lazy/sub/:id') ||
+        p.includes('/slow-fetch/:id') ||
+        p.includes('/deep/level2/level3/:id'),
+    );
+
+    // Test passes if lazy children are not in routes before visiting (we need the workaround)
+    // Test fails if lazy children are in routes before visiting (workaround may not be needed!)
+    expect(
+      hasLazyChildren,
+      `
+React Router now includes lazy route children in router.routes upfront!
+This means the lazyRouteManifest workaround may no longer be needed.
+
+Routes at home page: ${JSON.stringify(routes, null, 2)}
+
+Next steps:
+1. Verify this behavior is consistent and intentional
+2. Check React Router changelog for details
+3. Consider removing the lazyRouteManifest workaround
+`,
+    ).toBe(false);
+  });
+});

dev-packages/e2e-tests/test-applications/react-router-7-lazy-routes/tests/transactions.test.ts

@@ -1433,3 +1433,54 @@ test('Second navigation span is not corrupted by first slow lazy handler complet
     expect(wrongSpans.length).toBe(0);
   }
 });
+
+// lazyRouteManifest: provides parameterized name when lazy routes don't resolve in time
+test('Route manifest provides correct name when navigation span ends before lazy route resolves', async ({ page }) => {
+  // Short idle timeout (50ms) ensures span ends before lazy route (500ms) resolves
+  await page.goto('/?idleTimeout=50&timeout=0');
+
+  // Wait for pageload to complete
+  await page.waitForTimeout(200);
+
+  const navigationPromise = waitForTransaction('react-router-7-lazy-routes', async transactionEvent => {
+    return (
+      !!transactionEvent?.transaction &&
+      transactionEvent.contexts?.trace?.op === 'navigation' &&
+      (transactionEvent.transaction?.startsWith('/wildcard-lazy') ?? false)
+    );
+  });
+
+  // Navigate to wildcard-lazy route (500ms delay in module via top-level await)
+  const wildcardLazyLink = page.locator('id=navigation-to-wildcard-lazy');
+  await expect(wildcardLazyLink).toBeVisible();
+  await wildcardLazyLink.click();
+
+  const event = await navigationPromise;
+
+  // Should have parameterized name from manifest, not wildcard (/wildcard-lazy/*)
+  expect(event.transaction).toBe('/wildcard-lazy/:id');
+  expect(event.type).toBe('transaction');
+  expect(event.contexts?.trace?.op).toBe('navigation');
+  expect(event.contexts?.trace?.data?.['sentry.source']).toBe('route');
+});
+
+test('Route manifest provides correct name when pageload span ends before lazy route resolves', async ({ page }) => {
+  // Short idle timeout (50ms) ensures span ends before lazy route (500ms) resolves
+  const pageloadPromise = waitForTransaction('react-router-7-lazy-routes', async transactionEvent => {
+    return (
+      !!transactionEvent?.transaction &&
+      transactionEvent.contexts?.trace?.op === 'pageload' &&
+      (transactionEvent.transaction?.startsWith('/wildcard-lazy') ?? false)
+    );
+  });
+
+  await page.goto('/wildcard-lazy/123?idleTimeout=50&timeout=0');
+
+  const event = await pageloadPromise;
+
+  // Should have parameterized name from manifest, not wildcard (/wildcard-lazy/*)
+  expect(event.transaction).toBe('/wildcard-lazy/:id');
+  expect(event.type).toBe('transaction');
+  expect(event.contexts?.trace?.op).toBe('pageload');
+  expect(event.contexts?.trace?.data?.['sentry.source']).toBe('route');
+});

packages/react/src/reactrouter-compat-utils/index.ts

@@ -35,3 +35,6 @@ export {
 
 // Lazy route exports
 export { createAsyncHandlerProxy, handleAsyncHandlerResult, checkRouteForAsyncHandler } from './lazy-routes';
+
+// Route manifest exports
+export { matchRouteManifest } from './route-manifest';

packages/react/src/reactrouter-compat-utils/instrumentation.tsx

@@ -56,6 +56,8 @@ let _matchRoutes: MatchRoutes;
 
 let _enableAsyncRouteHandlers: boolean = false;
 let _lazyRouteTimeout = 3000;
+let _lazyRouteManifest: string[] | undefined;
+let _basename: string = '';
 
 const CLIENTS_WITH_INSTRUMENT_NAVIGATION = new WeakSet<Client>();
 
@@ -196,6 +198,25 @@ export interface ReactRouterOptions {
    * @default idleTimeout * 3
    */
   lazyRouteTimeout?: number;
+
+  /**
+   * Static route manifest for resolving parameterized route names with lazy routes.
+   *
+   * Requires `enableAsyncRouteHandlers: true`. When provided, the manifest is used
+   * as the primary source for determining transaction names. This is more reliable
+   * than depending on React Router's lazy route resolution timing.
+   *
+   * @example
+   * ```ts
+   * lazyRouteManifest: [
+   *   '/',
+   *   '/users',
+   *   '/users/:userId',
+   *   '/org/:orgSlug/projects/:projectId',
+   * ]
+   * ```
+   */
+  lazyRouteManifest?: string[];
 }
 
 type V6CompatibleVersion = '6' | '7';
@@ -355,7 +376,9 @@ export function updateNavigationSpan(
       allRoutes,
       allRoutes,
       (currentBranches as RouteMatch[]) || [],
-      '',
+      _basename,
+      _lazyRouteManifest,
+      _enableAsyncRouteHandlers,
     );
 
     const currentSource = spanJson.data?.[SEMANTIC_ATTRIBUTE_SENTRY_SOURCE];
@@ -520,6 +543,9 @@ export function createV6CompatibleWrapCreateBrowserRouter<
       });
     }
 
+    // Store basename for use in updateNavigationSpan
+    _basename = basename || '';
+
     setupRouterSubscription(router, routes, version, basename, activeRootSpan);
 
     return router;
@@ -614,6 +640,9 @@ export function createV6CompatibleWrapCreateMemoryRouter<
       });
     }
 
+    // Store basename for use in updateNavigationSpan
+    _basename = basename || '';
+
     setupRouterSubscription(router, routes, version, basename, memoryActiveRootSpan);
 
     return router;
@@ -640,6 +669,7 @@ export function createReactRouterV6CompatibleTracingIntegration(
     instrumentPageLoad = true,
     instrumentNavigation = true,
     lazyRouteTimeout,
+    lazyRouteManifest,
   } = options;
 
   return {
@@ -683,6 +713,7 @@ export function createReactRouterV6CompatibleTracingIntegration(
       _matchRoutes = matchRoutes;
       _createRoutesFromChildren = createRoutesFromChildren;
       _enableAsyncRouteHandlers = enableAsyncRouteHandlers;
+      _lazyRouteManifest = lazyRouteManifest;
 
       // Initialize the router utils with the required dependencies
       initializeRouterUtils(matchRoutes, stripBasename || false);
@@ -932,6 +963,8 @@ export function handleNavigation(opts: {
       allRoutes || routes,
       branches as RouteMatch[],
       basename,
+      _lazyRouteManifest,
+      _enableAsyncRouteHandlers,
     );
 
     const locationKey = computeLocationKey(location);
@@ -1071,6 +1104,8 @@ function updatePageloadTransaction({
       allRoutes || routes,
       branches,
       basename,
+      _lazyRouteManifest,
+      _enableAsyncRouteHandlers,
     );
 
     getCurrentScope().setTransactionName(name || '/');
@@ -1158,7 +1193,15 @@ function tryUpdateSpanNameBeforeEnd(
       return;
     }
 
-    const [name, source] = resolveRouteNameAndSource(location, routesToUse, routesToUse, branches, basename);
+    const [name, source] = resolveRouteNameAndSource(
+      location,
+      routesToUse,
+      routesToUse,
+      branches,
+      basename,
+      _lazyRouteManifest,
+      _enableAsyncRouteHandlers,
+    );
 
     const isImprovement = shouldUpdateWildcardSpanName(currentName, currentSource, name, source, true);
     const spanNotEnded = spanType === 'pageload' || !spanJson.timestamp;