fix: correctly search for parent route in generator

packages/router-generator/src/generator.ts

@@ -1439,21 +1439,31 @@ ${acc.routeTree.map((child) => `${child.variableName}Route: typeof ${getResolved
     //   - For /_layout/path/, hasParentRoute returns /_layout (wrong)
     //   - But the correct parent is /_layout/path (the virtual route from path.lazy.tsx)
     //
-    // Optimization: Only search if we might find a closer parent. The search walks
-    // up from the immediate parent path, so if the first candidate matches what
-    // prefixMap found, there's no closer parent to find.
+    // We walk up the path segments to find the closest registered parent. This handles
+    // cases where multiple path segments (e.g., $a/$b) don't have intermediate routes.
     if (node.routePath) {
-      const lastSlash = node.routePath.lastIndexOf('/')
-      if (lastSlash > 0) {
-        const immediateParentPath = node.routePath.substring(0, lastSlash)
-        const candidate = acc.routeNodesByPath.get(immediateParentPath)
-        if (
-          candidate &&
-          candidate.routePath !== node.routePath &&
-          candidate !== parentRoute
-        ) {
-          // Found a closer parent in routeNodesByPath that differs from prefixMap result
-          parentRoute = candidate
+      let searchPath = node.routePath
+      while (searchPath.length > 0) {
+        const lastSlash = searchPath.lastIndexOf('/')
+        if (lastSlash <= 0) break
+
+        searchPath = searchPath.substring(0, lastSlash)
+        const candidate = acc.routeNodesByPath.get(searchPath)
+        if (candidate && candidate.routePath !== node.routePath) {
+          // Found a parent in routeNodesByPath
+          // If it's different from what prefixMap found AND is a closer match, use it
+          if (candidate !== parentRoute) {
+            // Check if this candidate is a closer parent than what prefixMap found
+            // (longer path prefix means closer parent)
+            if (
+              !parentRoute ||
+              (candidate.routePath?.length ?? 0) >
+                (parentRoute.routePath?.length ?? 0)
+            ) {
+              parentRoute = candidate
+            }
+          }
+          break
         }
       }
     }

packages/router-generator/tests/generator/lazy-multi-slug-params/routeTree.snapshot.ts

@@ -0,0 +1,108 @@
+/* eslint-disable */
+
+// @ts-nocheck
+
+// noinspection JSUnusedGlobalSymbols
+
+// This file was automatically generated by TanStack Router.
+// You should NOT make any changes in this file as it will be overwritten.
+// Additionally, you should also exclude this file from your linter and/or formatter to prevent it from being checked or modified.
+
+import { createFileRoute } from '@tanstack/react-router'
+
+import { Route as rootRouteImport } from './routes/__root'
+
+const SubRouteLazyRouteImport = createFileRoute('/sub')()
+const SubTestLazyRouteImport = createFileRoute('/sub/test')()
+const SubABLazyRouteImport = createFileRoute('/sub/$a/$b')()
+
+const SubRouteLazyRoute = SubRouteLazyRouteImport.update({
+  id: '/sub',
+  path: '/sub',
+  getParentRoute: () => rootRouteImport,
+} as any).lazy(() => import('./routes/sub/route.lazy').then((d) => d.Route))
+const SubTestLazyRoute = SubTestLazyRouteImport.update({
+  id: '/test',
+  path: '/test',
+  getParentRoute: () => SubRouteLazyRoute,
+} as any).lazy(() => import('./routes/sub/test.lazy').then((d) => d.Route))
+const SubABLazyRoute = SubABLazyRouteImport.update({
+  id: '/$a/$b',
+  path: '/$a/$b',
+  getParentRoute: () => SubRouteLazyRoute,
+} as any).lazy(() => import('./routes/sub/$a.$b.lazy').then((d) => d.Route))
+
+export interface FileRoutesByFullPath {
+  '/sub': typeof SubRouteLazyRouteWithChildren
+  '/sub/test': typeof SubTestLazyRoute
+  '/sub/$a/$b': typeof SubABLazyRoute
+}
+export interface FileRoutesByTo {
+  '/sub': typeof SubRouteLazyRouteWithChildren
+  '/sub/test': typeof SubTestLazyRoute
+  '/sub/$a/$b': typeof SubABLazyRoute
+}
+export interface FileRoutesById {
+  __root__: typeof rootRouteImport
+  '/sub': typeof SubRouteLazyRouteWithChildren
+  '/sub/test': typeof SubTestLazyRoute
+  '/sub/$a/$b': typeof SubABLazyRoute
+}
+export interface FileRouteTypes {
+  fileRoutesByFullPath: FileRoutesByFullPath
+  fullPaths: '/sub' | '/sub/test' | '/sub/$a/$b'
+  fileRoutesByTo: FileRoutesByTo
+  to: '/sub' | '/sub/test' | '/sub/$a/$b'
+  id: '__root__' | '/sub' | '/sub/test' | '/sub/$a/$b'
+  fileRoutesById: FileRoutesById
+}
+export interface RootRouteChildren {
+  SubRouteLazyRoute: typeof SubRouteLazyRouteWithChildren
+}
+
+declare module '@tanstack/react-router' {
+  interface FileRoutesByPath {
+    '/sub': {
+      id: '/sub'
+      path: '/sub'
+      fullPath: '/sub'
+      preLoaderRoute: typeof SubRouteLazyRouteImport
+      parentRoute: typeof rootRouteImport
+    }
+    '/sub/test': {
+      id: '/sub/test'
+      path: '/test'
+      fullPath: '/sub/test'
+      preLoaderRoute: typeof SubTestLazyRouteImport
+      parentRoute: typeof SubRouteLazyRoute
+    }
+    '/sub/$a/$b': {
+      id: '/sub/$a/$b'
+      path: '/$a/$b'
+      fullPath: '/sub/$a/$b'
+      preLoaderRoute: typeof SubABLazyRouteImport
+      parentRoute: typeof SubRouteLazyRoute
+    }
+  }
+}
+
+interface SubRouteLazyRouteChildren {
+  SubTestLazyRoute: typeof SubTestLazyRoute
+  SubABLazyRoute: typeof SubABLazyRoute
+}
+
+const SubRouteLazyRouteChildren: SubRouteLazyRouteChildren = {
+  SubTestLazyRoute: SubTestLazyRoute,
+  SubABLazyRoute: SubABLazyRoute,
+}
+
+const SubRouteLazyRouteWithChildren = SubRouteLazyRoute._addFileChildren(
+  SubRouteLazyRouteChildren,
+)
+
+const rootRouteChildren: RootRouteChildren = {
+  SubRouteLazyRoute: SubRouteLazyRouteWithChildren,
+}
+export const routeTree = rootRouteImport
+  ._addFileChildren(rootRouteChildren)
+  ._addFileTypes<FileRouteTypes>()

packages/router-generator/tests/generator/lazy-multi-slug-params/routes/__root.tsx

@@ -0,0 +1,2 @@
+import { createRootRoute } from '@tanstack/react-router'
+export const Route = createRootRoute()

packages/router-generator/tests/generator/lazy-multi-slug-params/routes/sub/$a.$b.lazy.tsx

@@ -0,0 +1,4 @@
+import { createLazyFileRoute } from '@tanstack/react-router'
+export const Route = createLazyFileRoute('/sub/$a/$b')({
+  component: () => 'Multi Slug Route',
+})

packages/router-generator/tests/generator/lazy-multi-slug-params/routes/sub/route.lazy.tsx

@@ -0,0 +1,4 @@
+import { createLazyFileRoute } from '@tanstack/react-router'
+export const Route = createLazyFileRoute('/sub')({
+  component: () => 'Sub Layout',
+})

packages/router-generator/tests/generator/lazy-multi-slug-params/routes/sub/test.lazy.tsx

@@ -0,0 +1,4 @@
+import { createLazyFileRoute } from '@tanstack/react-router'
+export const Route = createLazyFileRoute('/sub/test')({
+  component: () => 'Test Route',
+})