Add safety guards to navigation context stack

Author: onurtemizkan

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

@@ -752,7 +752,7 @@ function wrapPatchRoutesOnNavigation(
         try {
           result = await originalPatchRoutes(args);
         } finally {
-          clearNavigationContext();
+          clearNavigationContext(activeRootSpan);
         }
 
         const currentActiveRootSpan = getActiveRootSpan();

packages/react/src/reactrouter-compat-utils/lazy-routes.tsx

@@ -11,7 +11,9 @@ import { getActiveRootSpan, getNavigationContext } from './utils';
  */
 function captureCurrentLocation(): Location | null {
   const navContext = getNavigationContext();
-  if (navContext) {
+  // Only use navigation context if targetPath is defined (it can be undefined
+  // if patchRoutesOnNavigation was invoked without a path argument)
+  if (navContext?.targetPath) {
     return {
       pathname: navContext.targetPath,
       search: '',

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

@@ -10,20 +10,29 @@ let _stripBasename: boolean = false;
 // Required because window.location hasn't updated yet when handlers are invoked.
 // Uses a stack to handle overlapping navigations correctly (LIFO semantics).
 interface NavigationContext {
-  targetPath: string;
+  targetPath: string | undefined;
   span: Span | undefined;
 }
 
 const _navigationContextStack: NavigationContext[] = [];
+const MAX_CONTEXT_STACK_SIZE = 10;
 
 /** Pushes a navigation context before invoking patchRoutesOnNavigation. */
-export function setNavigationContext(targetPath: string, span: Span | undefined): void {
+export function setNavigationContext(targetPath: string | undefined, span: Span | undefined): void {
+  // Prevent unbounded stack growth from cleanup failures or rapid navigations
+  if (_navigationContextStack.length >= MAX_CONTEXT_STACK_SIZE) {
+    _navigationContextStack.shift(); // Remove oldest
+  }
   _navigationContextStack.push({ targetPath, span });
 }
 
-/** Pops the most recent navigation context after patchRoutesOnNavigation completes. */
-export function clearNavigationContext(): void {
-  _navigationContextStack.pop();
+/** Pops the navigation context for the given span after patchRoutesOnNavigation completes. */
+export function clearNavigationContext(span: Span | undefined): void {
+  // Only pop if top of stack matches this span to prevent corruption from mismatched calls
+  const top = _navigationContextStack[_navigationContextStack.length - 1];
+  if (top?.span === span) {
+    _navigationContextStack.pop();
+  }
 }
 
 /** Gets the current (most recent) navigation context if inside a patchRoutesOnNavigation call. */