diff --git a/src/client/theme-api/useNavData.ts b/src/client/theme-api/useNavData.ts
index 0ff36339da..924fd3588f 100644
--- a/src/client/theme-api/useNavData.ts
+++ b/src/client/theme-api/useNavData.ts
@@ -6,7 +6,7 @@ import type {
   IUserNavItems,
   IUserNavMode,
 } from './types';
-import { getLocaleClearPath } from './useSidebarData';
+import { getLocaleClearPath, getRouteParentPath } from './useSidebarData';
 import {
   getLocaleNav,
   pickRouteSortMeta,
@@ -65,11 +65,11 @@ export const useNavData = () => {
         .sort(([a], [b]) => a.split('/').length - b.split('/').length)
         // convert sidebar data to nav data
         .reduce<Record<string, INavItems[0]>>((ret, [link, groups]) => {
-          const [, parentPath, restPath] = `/${getLocaleClearPath(
-            link.replace(/^\//, ''),
-            locale,
-          )}`.match(/^(\/[^/]+)([^]+)?$/)!;
-          const isNestedNav = Boolean(restPath) && is2LevelNav;
+          const clearPath = getLocaleClearPath(link.replace(/^\//, ''), locale);
+          const parentPath = link.replace(clearPath, (s) =>
+            getRouteParentPath(s, { is2LevelNav, locale }),
+          );
+          const isNestedNav = link.length > parentPath.length && is2LevelNav;
           const [firstMeta, secondMeta] = Object.values(routes).reduce<
             {
               title?: string;
@@ -96,7 +96,8 @@ export const useNavData = () => {
           if (isNestedNav) {
             // fallback to use parent path as 1-level nav title
             firstMeta.title ??= parentPath
-              .slice(1)
+              .split('/')
+              .pop()!
               .replace(/^[a-z]/, (s) => s.toUpperCase());
 
             // handle nested nav item as parent children
@@ -107,7 +108,7 @@ export const useNavData = () => {
             ));
 
             second.children ??= [];
-            ret[parentPath].children!.push(
+            second.children!.push(
               genNavItem(secondMeta, groups, link, groups[0].children[0].link),
             );
           } else {
diff --git a/src/client/theme-api/useSidebarData.ts b/src/client/theme-api/useSidebarData.ts
index 31e42db939..3e7d0e18d0 100644
--- a/src/client/theme-api/useSidebarData.ts
+++ b/src/client/theme-api/useSidebarData.ts
@@ -27,12 +27,18 @@ export const getLocaleClearPath = (
 /**
  * get parent path from route path
  */
-function getRouteParentPath(
+export function getRouteParentPath(
   path: string,
-  { meta, is2LevelNav }: { meta: IRouteMeta; is2LevelNav: boolean },
+  {
+    meta,
+    is2LevelNav,
+    locale,
+  }: { meta?: IRouteMeta; is2LevelNav: boolean; locale: ILocalesConfig[0] },
 ) {
+  const indexDocRegex = new RegExp(`/index(\\.${locale.id})?.md$`);
   const isIndexDocRoute =
-    meta.frontmatter.filename?.endsWith('index.md') &&
+    meta?.frontmatter.filename &&
+    indexDocRegex.test(meta.frontmatter.filename) &&
     !meta._atom_route &&
     is2LevelNav;
   const paths = path
@@ -82,7 +88,7 @@ export const useFullSidebarData = () => {
         //   a/b => /a/b (if route file is a/b/index.md)
         //   a/b/c => /a/b
         const parentPath = `/${route.path!.replace(clearPath, (s) =>
-          getRouteParentPath(s, { is2LevelNav, meta: route.meta! }),
+          getRouteParentPath(s, { is2LevelNav, meta: route.meta!, locale }),
         )}`;
         const { title, order } = pickRouteSortMeta(
           { order: 0 },
@@ -224,7 +230,7 @@ export const useSidebarData = () => {
   // /en-US/a/b/ => /en-US/a (also strip trailing /)
   const parentPath = clearPath
     ? pathname.replace(clearPath, (s) =>
-        getRouteParentPath(s, { is2LevelNav, meta }),
+        getRouteParentPath(s, { is2LevelNav, meta, locale }),
       )
     : pathname;