React Router v6 integration: allRoutes accumulates across independent/unrelated routers, causing incorrect transaction names #22782

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?

Sentry Saas (sentry.io)

Which SDK are you using?

@sentry/react-router

SDK Version

10.68.0

Framework Version

No response

Link to Sentry event

No response

Reproduction Example/SDK Setup

Two independent router trees are each wrapped with Sentry's React Router
instrumentation (e.g. via withSentryReactRouterV6Routing /
wrapCreateBrowserRouter), mounted at different points in the app's
lifecycle, For example, one router for /foo/:fooId and a separate,
unrelated router for /bar/:barId.

// Router A
const RoutesA = () => (
  <SentryRoutes>
    <Route path="/foo/:fooId" element={<FooPage />} />
  </SentryRoutes>
);

// Router B, mounted separately/later
const RoutesB = () => (
  <SentryRoutes>
    <Route path="/bar/:barId" element={<BarPage />} />
  </SentryRoutes>
);

customer provided a full repro app. Link to that repo is included in internal Linear Issue to protect PII

Steps to Reproduce

1. Mount/navigate within Router A at /foo/123: transaction is correctly
   named /foo/:fooId.
2. Mount/navigate within Router B at /bar/456.
3. Observe the transaction name for the /bar/456 navigation.

Expected Result

Transaction name: /bar/:barId

Actual Result

Transaction name is a hybrid/incorrect name such as /bar/:fooId

i.e. the static segment from Router B's path combined with the param
name from Router A's route.

Additional Context

Root cause (if I had to guess)

reactrouterv6-compat-utils.tsx accumulates every route object it has
ever seen into a module-level allRoutes Set, populated via
getChildRoutesRecursively on each wrapped <Routes>'s mount effect,
and never scoped to a router instance or cleared on unmount:

routes.forEach(route => {
  const extractedChildRoutes = getChildRoutesRecursively(route);
  extractedChildRoutes.forEach(r => {
    allRoutes.add(r);
  });
});

This was introduced to support descendant routes / multiple <Routes>
trees that are legitimately part of the same logical route tree (see
#14304). But because allRoutes has no isolation between genuinely
independent router instances, once two unrelated routers have each been
mounted once, matchRoutes/rebuildRoutePathFromAllRoutes operates on
the union of both, and can produce a name that mixes structure from one
router with param names from another.

Priority

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