diff --git a/package-lock.json b/package-lock.json
index e3dba12..a7f38f9 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -17,6 +17,7 @@
         "axios": "^1.13.2",
         "clsx": "^2.1.1",
         "date-fns": "^4.1.0",
+        "github-slugger": "^2.0.0",
         "jwt-decode": "^4.0.0",
         "lucide-react": "^0.562.0",
         "next": "16.1.1",
@@ -27,6 +28,7 @@
         "react-markdown": "^10.1.0",
         "react-syntax-highlighter": "^16.1.0",
         "rehype-sanitize": "^6.0.0",
+        "rehype-slug": "^6.0.0",
         "remark-gfm": "^4.0.1",
         "yarn": "^1.22.22",
         "zustand": "^5.0.9"
diff --git a/package.json b/package.json
index ee8cef8..04a5158 100644
--- a/package.json
+++ b/package.json
@@ -18,6 +18,7 @@
     "axios": "^1.13.2",
     "clsx": "^2.1.1",
     "date-fns": "^4.1.0",
+    "github-slugger": "^2.0.0",
     "jwt-decode": "^4.0.0",
     "lucide-react": "^0.562.0",
     "next": "16.1.1",
@@ -28,6 +29,7 @@
     "react-markdown": "^10.1.0",
     "react-syntax-highlighter": "^16.1.0",
     "rehype-sanitize": "^6.0.0",
+    "rehype-slug": "^6.0.0",
     "remark-gfm": "^4.0.1",
     "yarn": "^1.22.22",
     "zustand": "^5.0.9"
diff --git a/src/app/layout.tsx b/src/app/layout.tsx
index 32b1812..9218b04 100644
--- a/src/app/layout.tsx
+++ b/src/app/layout.tsx
@@ -3,7 +3,7 @@ import './globals.css';
 import Providers from './providers';
 import Sidebar from '@/components/layout/Sidebar';
 import TopHeader from '@/components/layout/TopHeader';
-import Script from 'next/script'; // 👈 Script 컴포넌트 임포트
+import Script from 'next/script';
 
 export const metadata: Metadata = {
   title: 'WYPark Blog',
@@ -21,8 +21,7 @@ export default function RootLayout({
         <meta name="google-site-verification" content="cFJSK1ayy2Y4lqRKNv8wZ_vybg5De22zYCdbKSfvAJA" />
       </head>
       <body className="bg-[#f8f9fa] text-gray-800">
-        {/* 🌟 Google Analytics 스크립트 추가 */}
-        {/* strategy="afterInteractive"는 페이지가 로드된 직후 스크립트를 실행하여 성능을 최적화합니다. */}
+        {/* 🌟 Google Analytics 스크립트 */}
         <Script
           src="https://www.googletagmanager.com/gtag/js?id=G-2GLCM9ZKMK"
           strategy="afterInteractive"
@@ -46,7 +45,9 @@ export default function RootLayout({
             <main className="flex-1 transition-all duration-300 md:ml-72 w-full relative">
               <TopHeader />
 
-              <div className="max-w-4xl mx-auto p-6 md:p-12 pt-20">
+              {/* 🛠️ 수정됨: max-w-4xl 제한을 제거하고 w-full로 변경 */}
+              {/* 이제 각 페이지(page.tsx)에서 원하는 너비를 설정할 수 있습니다. */}
+              <div className="w-full mx-auto p-4 md:p-8 pt-20">
                 {children}
               </div>
             </main>
diff --git a/src/components/layout/Sidebar.tsx b/src/components/layout/Sidebar.tsx
index 1d039c6..96b5565 100644
--- a/src/components/layout/Sidebar.tsx
+++ b/src/components/layout/Sidebar.tsx
@@ -194,6 +194,8 @@ function CategoryItem({ category, depth, pathname, isEditMode, onDrop, onAdd, on
 
 function SidebarContent() {
   const [isOpen, setIsOpen] = useState(true);
+  const [isMounted, setIsMounted] = useState(false); // 🛠️ [Fix] 하이드레이션 매칭을 위한 상태 추가
+
   const pathname = usePathname();
   const { role, _hasHydrated } = useAuthStore();
   const queryClient = useQueryClient();
@@ -203,6 +205,10 @@ function SidebarContent() {
   const searchParams = useSearchParams();
   const keyword = searchParams.get('keyword') || '';
 
+  useEffect(() => {
+    setIsMounted(true); // 🛠️ [Fix] 클라이언트 마운트 후 true로 설정
+  }, []);
+
   const handleSearch = (newKeyword: string) => {
     if (newKeyword.trim()) {
       router.push(`/?keyword=${encodeURIComponent(newKeyword.trim())}`);
@@ -380,7 +386,8 @@ function SidebarContent() {
           )}
           <Link href="/" className="block hover:opacity-80 transition-opacity">
             <div className="w-24 h-24 mx-auto bg-gray-200 rounded-full mb-4 overflow-hidden shadow-inner ring-4 ring-gray-50 relative">
-              {isProfileLoading ? (
+              {/* 🛠️ [Fix] isMounted를 체크하여 첫 렌더링 시 무조건 스켈레톤을 보여줍니다. (서버와 일치시킴) */}
+              {!isMounted || isProfileLoading ? (
                 <div className="w-full h-full bg-gray-200 animate-pulse" />
               ) : (
                 <Image 
@@ -394,7 +401,8 @@ function SidebarContent() {
                 />
               )}
             </div>
-            {isProfileLoading ? (
+            {/* 🛠️ [Fix] 텍스트 영역도 동일하게 처리 */}
+            {!isMounted || isProfileLoading ? (
               <div className="space-y-2 flex flex-col items-center"><div className="h-6 w-24 bg-gray-200 rounded animate-pulse" /><div className="h-4 w-32 bg-gray-100 rounded animate-pulse" /></div>
             ) : (
               <>
diff --git a/src/components/post/MarkdownRenderer.tsx b/src/components/post/MarkdownRenderer.tsx
index c6be501..18b7cad 100644
--- a/src/components/post/MarkdownRenderer.tsx
+++ b/src/components/post/MarkdownRenderer.tsx
@@ -3,12 +3,12 @@
 import React, { useState } from 'react';
 import ReactMarkdown from 'react-markdown';
 import remarkGfm from 'remark-gfm';
-// 🛠️ 보안 패치: rehype-sanitize 추가 (반드시 npm install rehype-sanitize 실행 필요)
 import rehypeSanitize from 'rehype-sanitize'; 
 import { Prism as SyntaxHighlighter } from 'react-syntax-highlighter';
 import { vscDarkPlus } from 'react-syntax-highlighter/dist/esm/styles/prism';
 import { Copy, Check, Terminal, ExternalLink } from 'lucide-react';
 import { clsx } from 'clsx';
+import rehypeSlug from 'rehype-slug';
 
 interface MarkdownRendererProps {
   content: string;
@@ -19,8 +19,7 @@ export default function MarkdownRenderer({ content }: MarkdownRendererProps) {
     <div className="markdown-content">
       <ReactMarkdown
         remarkPlugins={[remarkGfm]}
-        // 🛡️ 중요: 여기서 HTML 태그를 소독하여 XSS 공격 방지
-        rehypePlugins={[rehypeSanitize]} 
+        rehypePlugins={[rehypeSanitize, rehypeSlug]}
         components={{
           // 1. 코드 블록 커스텀
           code({ node, inline, className, children, ...props }: any) {
@@ -89,34 +88,35 @@ export default function MarkdownRenderer({ content }: MarkdownRendererProps) {
             return <td className="px-6 py-4 border-b border-gray-100 whitespace-pre-wrap">{children}</td>;
           },
 
-          // 5. 이미지
+          // 5. 이미지 (비율 유지 및 중앙 정렬)
           img({ src, alt }) {
             return (
-              <span className="block my-8">
+              // 🛠️ [Fix] flex-col 추가: 이미지와 캡션을 세로로 정렬
+              // items-center 추가: 가로축 중앙 정렬
+              <span className="block my-8 flex flex-col items-center justify-center">
                 <img 
                   src={src} 
                   alt={alt} 
-                  className="rounded-xl shadow-lg border border-gray-100 w-full object-cover max-h-[600px] hover:scale-[1.01] transition-transform duration-300" 
+                  className="rounded-xl shadow-lg border border-gray-100 max-w-full h-auto max-h-[700px] mx-auto hover:scale-[1.01] transition-transform duration-300" 
                   loading="lazy"
                   onError={(e) => {
                     e.currentTarget.style.display = 'none';
                   }}
                 />
-                {alt && <span className="block text-center text-sm text-gray-400 mt-2">{alt}</span>}
+                {alt && <span className="block text-center text-sm text-gray-400 mt-2 w-full">{alt}</span>}
               </span>
             );
           },
 
-          // 6. 리스트 스타일 (여기가 문제였음)
+          // 6. 리스트 스타일
           ul({ children }) {
             return <ul className="list-disc pl-6 space-y-2 my-4 text-gray-700 marker:text-gray-400">{children}</ul>;
           },
-          // 🛠️ 수정됨: ...props를 전달하여 start 속성을 적용
           ol({ children, ...props }: any) {
             return (
               <ol 
                 className="list-decimal pl-6 space-y-2 my-4 text-gray-700 marker:text-gray-500 font-medium" 
-                {...props} // 👈 이게 있어야 start="3" 같은 속성이 적용됨
+                {...props}
               >
                 {children}
               </ol>
@@ -126,15 +126,15 @@ export default function MarkdownRenderer({ content }: MarkdownRendererProps) {
             return <li className="pl-1">{children}</li>;
           },
 
-          // 7. 헤딩 스타일
-          h1({ children }) {
-            return <h1 className="text-3xl font-extrabold mt-12 mb-6 pb-4 border-b border-gray-100 text-gray-900">{children}</h1>;
+          // 7. 헤딩 스타일 (🛠️ 수정: ...props를 전달해야 id가 붙어서 목차 이동이 작동함)
+          h1({ children, ...props }: any) {
+            return <h1 className="text-3xl font-extrabold mt-12 mb-6 pb-4 border-b border-gray-100 text-gray-900" {...props}>{children}</h1>;
           },
-          h2({ children }) {
-            return <h2 className="text-2xl font-bold mt-10 mb-5 pb-2 text-gray-800">{children}</h2>;
+          h2({ children, ...props }: any) {
+            return <h2 className="text-2xl font-bold mt-10 mb-5 pb-2 text-gray-800" {...props}>{children}</h2>;
           },
-          h3({ children }) {
-            return <h3 className="text-xl font-bold mt-8 mb-4 text-gray-800 flex items-center gap-2 before:content-[''] before:w-1.5 before:h-6 before:bg-blue-500 before:rounded-full before:mr-1">{children}</h3>;
+          h3({ children, ...props }: any) {
+            return <h3 className="text-xl font-bold mt-8 mb-4 text-gray-800 flex items-center gap-2 before:content-[''] before:w-1.5 before:h-6 before:bg-blue-500 before:rounded-full before:mr-1" {...props}>{children}</h3>;
           },
         }}
       >
diff --git a/src/components/post/PostDetailClient.tsx b/src/components/post/PostDetailClient.tsx
index 2362491..10ba60e 100644
--- a/src/components/post/PostDetailClient.tsx
+++ b/src/components/post/PostDetailClient.tsx
@@ -1,10 +1,11 @@
 'use client';
 
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
-import { getPost, deletePost, getPostsByCategory } from '@/api/posts';
+import { getPost, deletePost } from '@/api/posts'; // 🛠️ getPostsByCategory 제거
 import { getProfile } from '@/api/profile';
 import MarkdownRenderer from '@/components/post/MarkdownRenderer';
 import CommentList from '@/components/comment/CommentList';
+import TOC from '@/components/post/TOC';
 import { Loader2, Calendar, Eye, Folder, User, Edit2, Trash2, ArrowLeft, AlertCircle, ChevronLeft, ChevronRight } from 'lucide-react';
 import { useRouter } from 'next/navigation';
 import { useAuthStore } from '@/store/authStore';
@@ -20,7 +21,7 @@ export default function PostDetailClient({ slug }: PostDetailClientProps) {
   const { role, _hasHydrated } = useAuthStore();
   const isAdmin = _hasHydrated && role?.includes('ADMIN');
 
-  // 1. 게시글 상세 조회
+  // 1. 게시글 상세 조회 (이제 여기에 prevPost, nextPost가 포함됨)
   const { data: post, isLoading: isPostLoading, error } = useQuery({
     queryKey: ['post', slug],
     queryFn: () => getPost(slug),
@@ -28,13 +29,14 @@ export default function PostDetailClient({ slug }: PostDetailClientProps) {
     retry: 1,
   });
 
-  // 2. 같은 카테고리 글 조회 (이전/다음 글)
-  const { data: neighborPosts } = useQuery({
+  // 🗑️ 삭제됨: 더 이상 프론트에서 앞뒤 글을 찾기 위해 목록을 조회할 필요가 없음!
+  /* const { data: neighborPosts } = useQuery({
     queryKey: ['posts', 'category', post?.categoryName],
     queryFn: () => getPostsByCategory(post!.categoryName, 0, 100),
     enabled: !!post?.categoryName,
     staleTime: 1000 * 60 * 5,
   });
+  */
 
   const { data: profile } = useQuery({
     queryKey: ['profile'],
@@ -84,9 +86,18 @@ export default function PostDetailClient({ slug }: PostDetailClientProps) {
     );
   }
 
+  // 🗑️ 삭제됨: 인덱스 계산 로직 제거
+  /*
   const currentIndex = neighborPosts?.content.findIndex((p) => p.id === post.id) ?? -1;
-  const newerPost = (currentIndex > 0 && neighborPosts) ? neighborPosts.content[currentIndex - 1] : null;
-  const olderPost = (currentIndex !== -1 && neighborPosts && currentIndex < neighborPosts.content.length - 1) ? neighborPosts.content[currentIndex + 1] : null;
+  const newerPost = ...
+  const olderPost = ...
+  */
+
+  // 🆕 백엔드 데이터 직접 사용
+  // 보통 '이전 글'은 과거 글(prev), '다음 글'은 최신 글(next)입니다.
+  // 백엔드 구현에 따라 prevPost/nextPost 위치가 반대일 수 있으니 확인 후 위치만 바꿔주세요.
+  const prevPost = post.prevPost; // 이전 글 (왼쪽 버튼)
+  const nextPost = post.nextPost; // 다음 글 (오른쪽 버튼)
 
   const handleDelete = () => {
     if (confirm('정말로 이 게시글을 삭제하시겠습니까? 복구할 수 없습니다.')) {
@@ -99,59 +110,72 @@ export default function PostDetailClient({ slug }: PostDetailClientProps) {
   };
 
   return (
-    <div className="max-w-4xl mx-auto px-4 py-12">
+    <div className="max-w-screen-2xl mx-auto px-4 md:px-8 py-12">
       <Link href="/" className="inline-flex items-center gap-1 text-gray-500 hover:text-blue-600 mb-8 transition-colors">
         <ArrowLeft size={18} />
         <span className="text-sm font-medium">목록으로</span>
       </Link>
 
-      <article>
-        <header className="mb-10 border-b border-gray-100 pb-8">
-          <div className="flex justify-between items-start mb-4">
-            <div className="flex items-center gap-2 text-sm text-blue-600 font-medium bg-blue-50 px-3 py-1 rounded-full">
-              <Folder size={14} />
-              <span>{post.categoryName || 'Uncategorized'}</span>
-            </div>
-            {isAdmin && (
-              <div className="flex gap-2">
-                <button onClick={handleEdit} className="p-2 text-gray-400 hover:text-blue-600 hover:bg-blue-50 rounded-full transition-colors"><Edit2 size={18} /></button>
-                <button onClick={handleDelete} className="p-2 text-gray-400 hover:text-red-600 hover:bg-red-50 rounded-full transition-colors"><Trash2 size={18} /></button>
+      <div className="flex flex-col xl:flex-row gap-8 xl:gap-16 relative">
+        
+        <main className="min-w-0 xl:flex-1">
+          <article>
+            <header className="mb-10 border-b border-gray-100 pb-8">
+              <div className="flex justify-between items-start mb-4">
+                <div className="flex items-center gap-2 text-sm text-blue-600 font-medium bg-blue-50 px-3 py-1 rounded-full">
+                  <Folder size={14} />
+                  <span>{post.categoryName || 'Uncategorized'}</span>
+                </div>
+                {isAdmin && (
+                  <div className="flex gap-2">
+                    <button onClick={handleEdit} className="p-2 text-gray-400 hover:text-blue-600 hover:bg-blue-50 rounded-full transition-colors"><Edit2 size={18} /></button>
+                    <button onClick={handleDelete} className="p-2 text-gray-400 hover:text-red-600 hover:bg-red-50 rounded-full transition-colors"><Trash2 size={18} /></button>
+                  </div>
+                )}
               </div>
-            )}
-          </div>
-          <h1 className="text-4xl md:text-5xl font-bold text-gray-900 mb-6 leading-tight break-keep">{post.title}</h1>
-          <div className="flex flex-wrap items-center gap-6 text-sm text-gray-500">
-            <div className="flex items-center gap-2">
-              {profile?.imageUrl ? <img src={profile.imageUrl} alt="Author" className="w-8 h-8 rounded-full object-cover border border-gray-100 shadow-sm" /> : <div className="w-8 h-8 bg-gray-100 rounded-full flex items-center justify-center"><User size={16} /></div>}
-              <span className="font-bold text-gray-800">{profile?.name || 'Dev Park'}</span>
+              <h1 className="text-4xl md:text-5xl font-bold text-gray-900 mb-6 leading-tight break-keep">{post.title}</h1>
+              <div className="flex flex-wrap items-center gap-6 text-sm text-gray-500">
+                <div className="flex items-center gap-2">
+                  {profile?.imageUrl ? <img src={profile.imageUrl} alt="Author" className="w-8 h-8 rounded-full object-cover border border-gray-100 shadow-sm" /> : <div className="w-8 h-8 bg-gray-100 rounded-full flex items-center justify-center"><User size={16} /></div>}
+                  <span className="font-bold text-gray-800">{profile?.name || 'Dev Park'}</span>
+                </div>
+                <div className="flex items-center gap-1.5"><Calendar size={16} />{new Date(post.createdAt).toLocaleDateString()}</div>
+                <div className="flex items-center gap-1.5"><Eye size={16} />{post.viewCount} views</div>
+              </div>
+            </header>
+
+            <div className="prose prose-lg max-w-none prose-headings:font-bold prose-a:text-blue-600 prose-img:rounded-2xl prose-pre:bg-[#1e1e1e] prose-pre:text-gray-100 mb-20">
+              <MarkdownRenderer content={post.content || ''} />
             </div>
-            <div className="flex items-center gap-1.5"><Calendar size={16} />{new Date(post.createdAt).toLocaleDateString()}</div>
-            <div className="flex items-center gap-1.5"><Eye size={16} />{post.viewCount} views</div>
+          </article>
+
+          {/* 🛠️ 네비게이션 영역 수정: prevPost / nextPost 직접 사용 */}
+          <nav className="grid grid-cols-1 md:grid-cols-2 gap-4 border-t border-b border-gray-100 py-8 mb-16">
+            {prevPost ? (
+              <Link href={`/posts/${prevPost.slug}`} className="group flex flex-col items-start gap-1 p-5 rounded-2xl bg-gray-50 hover:bg-blue-50 transition-colors w-full border border-transparent hover:border-blue-100">
+                <span className="text-xs font-bold text-gray-400 uppercase flex items-center gap-1 group-hover:text-blue-600 transition-colors"><ChevronLeft size={16} /> 이전 글</span>
+                <span className="font-bold text-gray-700 group-hover:text-blue-700 transition-colors line-clamp-1 w-full text-left">{prevPost.title}</span>
+              </Link>
+            ) : <div className="hidden md:block p-5 rounded-2xl bg-gray-50/50 w-full opacity-50 cursor-not-allowed"><span className="text-xs font-bold text-gray-300 uppercase flex items-center gap-1"><ChevronLeft size={16} /> 이전 글 없음</span></div>}
+
+            {nextPost ? (
+              <Link href={`/posts/${nextPost.slug}`} className="group flex flex-col items-end gap-1 p-5 rounded-2xl bg-gray-50 hover:bg-blue-50 transition-colors w-full border border-transparent hover:border-blue-100">
+                <span className="text-xs font-bold text-gray-400 uppercase flex items-center gap-1 group-hover:text-blue-600 transition-colors">다음 글 <ChevronRight size={16} /></span>
+                <span className="font-bold text-gray-700 group-hover:text-blue-700 transition-colors line-clamp-1 w-full text-right">{nextPost.title}</span>
+              </Link>
+            ) : <div className="hidden md:flex flex-col items-end gap-1 p-5 rounded-2xl bg-gray-50/50 w-full opacity-50 cursor-not-allowed"><span className="text-xs font-bold text-gray-300 uppercase flex items-center gap-1">다음 글 없음 <ChevronRight size={16} /></span></div>}
+          </nav>
+
+          <CommentList postSlug={post.slug} />
+        </main>
+
+        <aside className="hidden 2xl:block w-[220px] shrink-0">
+          <div className="sticky top-24">
+             <TOC content={post.content || ''} />
           </div>
-        </header>
+        </aside>
 
-        <div className="prose prose-lg max-w-none prose-headings:font-bold prose-a:text-blue-600 prose-img:rounded-2xl prose-pre:bg-[#1e1e1e] prose-pre:text-gray-100 mb-20">
-          <MarkdownRenderer content={post.content || ''} />
-        </div>
-      </article>
-
-      <nav className="grid grid-cols-1 md:grid-cols-2 gap-4 border-t border-b border-gray-100 py-8 mb-16">
-        {olderPost ? (
-          <Link href={`/posts/${olderPost.slug}`} className="group flex flex-col items-start gap-1 p-5 rounded-2xl bg-gray-50 hover:bg-blue-50 transition-colors w-full border border-transparent hover:border-blue-100">
-            <span className="text-xs font-bold text-gray-400 uppercase flex items-center gap-1 group-hover:text-blue-600 transition-colors"><ChevronLeft size={16} /> 이전 글</span>
-            <span className="font-bold text-gray-700 group-hover:text-blue-700 transition-colors line-clamp-1 w-full text-left">{olderPost.title}</span>
-          </Link>
-        ) : <div className="hidden md:block p-5 rounded-2xl bg-gray-50/50 w-full opacity-50 cursor-not-allowed"><span className="text-xs font-bold text-gray-300 uppercase flex items-center gap-1"><ChevronLeft size={16} /> 이전 글 없음</span></div>}
-
-        {newerPost ? (
-          <Link href={`/posts/${newerPost.slug}`} className="group flex flex-col items-end gap-1 p-5 rounded-2xl bg-gray-50 hover:bg-blue-50 transition-colors w-full border border-transparent hover:border-blue-100">
-            <span className="text-xs font-bold text-gray-400 uppercase flex items-center gap-1 group-hover:text-blue-600 transition-colors">다음 글 <ChevronRight size={16} /></span>
-            <span className="font-bold text-gray-700 group-hover:text-blue-700 transition-colors line-clamp-1 w-full text-right">{newerPost.title}</span>
-          </Link>
-        ) : <div className="hidden md:flex flex-col items-end gap-1 p-5 rounded-2xl bg-gray-50/50 w-full opacity-50 cursor-not-allowed"><span className="text-xs font-bold text-gray-300 uppercase flex items-center gap-1">다음 글 없음 <ChevronRight size={16} /></span></div>}
-      </nav>
-
-      <CommentList postSlug={post.slug} />
+      </div>
     </div>
   );
 }
\ No newline at end of file
diff --git a/src/components/post/TOC.tsx b/src/components/post/TOC.tsx
new file mode 100644
index 0000000..908b995
--- /dev/null
+++ b/src/components/post/TOC.tsx
@@ -0,0 +1,133 @@
+'use client';
+
+import { useEffect, useState } from 'react';
+import { clsx } from 'clsx';
+// 🛠️ 중요: rehype-slug와 동일한 ID 생성을 위해 라이브러리 사용
+// npm install github-slugger 실행 필요
+import GithubSlugger from 'github-slugger';
+
+interface TOCProps {
+  content: string;
+}
+
+interface HeadingItem {
+  text: string;
+  level: number;
+  slug: string;
+}
+
+export default function TOC({ content }: TOCProps) {
+  const [activeId, setActiveId] = useState<string>('');
+  const [headings, setHeadings] = useState<HeadingItem[]>([]);
+
+  // 1. 마크다운에서 헤딩(#) 추출 및 Slug 생성
+  useEffect(() => {
+    const slugger = new GithubSlugger(); // Slugger 인스턴스 (중복 ID 처리용)
+    const lines = content.split('\n');
+    
+    // 코드 블럭 내의 #은 무시
+    let inCodeBlock = false;
+
+    const matches = lines.reduce<HeadingItem[]>((acc, line) => {
+      // 코드 블럭 진입/이탈 체크 (```)
+      if (line.trim().startsWith('```')) {
+        inCodeBlock = !inCodeBlock;
+        return acc;
+      }
+      if (inCodeBlock) return acc;
+
+      // 헤딩 매칭 (# 1~3개)
+      const match = line.match(/^(#{1,3})\s+(.+)$/);
+      if (match) {
+        const level = match[1].length;
+        const text = match[2].replace(/(\*\*|__)/g, '').trim(); // 볼드체 마크다운 제거
+        
+        // 🛠️ 핵심: github-slugger로 ID 생성 (한글, 띄어쓰기 등 완벽 호환)
+        const slug = slugger.slug(text);
+
+        acc.push({ text, level, slug });
+      }
+      return acc;
+    }, []);
+
+    setHeadings(matches);
+  }, [content]);
+
+  // 2. 스크롤 감지 (IntersectionObserver)
+  useEffect(() => {
+    if (headings.length === 0) return;
+
+    const observer = new IntersectionObserver(
+      (entries) => {
+        entries.forEach((entry) => {
+          if (entry.isIntersecting) {
+            setActiveId(entry.target.id);
+          }
+        });
+      },
+      // 상단 헤더 공간 등을 고려하여 감지 영역 조정
+      { rootMargin: '-10% 0px -80% 0px' } 
+    );
+
+    headings.forEach((heading) => {
+      const element = document.getElementById(heading.slug);
+      if (element) observer.observe(element);
+    });
+
+    return () => observer.disconnect();
+  }, [headings]);
+
+  // 3. 클릭 핸들러
+  const handleClick = (e: React.MouseEvent<HTMLAnchorElement>, slug: string) => {
+    e.preventDefault();
+    const element = document.getElementById(slug);
+    
+    if (element) {
+      // 상단 고정 헤더 높이 여유 공간
+      const headerOffset = 100; 
+      const elementPosition = element.getBoundingClientRect().top;
+      const offsetPosition = elementPosition + window.pageYOffset - headerOffset;
+
+      window.scrollTo({
+        top: offsetPosition,
+        behavior: 'smooth'
+      });
+      
+      // URL 해시 변경 및 상태 즉시 업데이트
+      history.pushState(null, '', `#${slug}`);
+      setActiveId(slug); 
+    }
+  };
+
+  if (headings.length === 0) return null;
+
+  return (
+    <aside className="w-full">
+      <div className="border-l-2 border-gray-100 pl-4 py-2">
+        <h4 className="font-bold text-gray-900 mb-4 text-sm uppercase tracking-wider text-opacity-80">On this page</h4>
+        <ul className="space-y-2.5">
+          {headings.map((heading, index) => (
+            <li 
+              key={`${heading.slug}-${index}`}
+              className={clsx(
+                "text-sm transition-all duration-200",
+                heading.level === 3 ? "pl-4 text-xs" : "", // h3는 들여쓰기
+                activeId === heading.slug 
+                  ? "text-blue-600 font-bold translate-x-1" 
+                  : "text-gray-500 hover:text-gray-900"
+              )}
+            >
+              <a 
+                href={`#${heading.slug}`} 
+                onClick={(e) => handleClick(e, heading.slug)}
+                className="block truncate leading-snug"
+              >
+                {heading.text}
+              </a>
+            </li>
+          ))}
+        </ul>
+      </div>
+    </aside>
+  );
+}
\ No newline at end of file
diff --git a/src/types/index.ts b/src/types/index.ts
index 503840d..653b875 100644
--- a/src/types/index.ts
+++ b/src/types/index.ts
@@ -5,6 +5,12 @@ export interface ApiResponse<T> {
   data: T;
 }
 
+// 🆕 인접 게시글 정보 (이전글/다음글)
+export interface PostNeighbor {
+  slug: string;
+  title: string;
+}
+
 // 2. 게시글 (Post) 타입
 export interface Post {
   id: number;
@@ -14,7 +20,10 @@ export interface Post {
   viewCount: number;
   createdAt: string;
   content?: string;
-  tags: string[]; // 🆕 태그 배열 속성 추가
+  tags: string[];
+  // 🆕 백엔드 변경 사항 반영: 이전글/다음글 정보 추가
+  prevPost?: PostNeighbor | null;
+  nextPost?: PostNeighbor | null;
 }
 
 // 3. 게시글 목록 페이징 응답
@@ -37,7 +46,7 @@ export interface AuthResponse {
 export interface Category {
   id: number;
   name: string;
-  parentId?: number | null; // 🆕 부모 카테고리 ID 추가
+  parentId?: number | null;
   children: Category[];
 }
 
diff --git a/yarn.lock b/yarn.lock
index 41a452b..8d6423b 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -3659,7 +3659,7 @@ rehype-sanitize@^6.0.0:
     "@types/hast" "^3.0.0"
     hast-util-sanitize "^5.0.0"
 
-rehype-slug@~6.0.0:
+rehype-slug@^6.0.0, rehype-slug@~6.0.0:
   version "6.0.0"
   resolved "https://registry.npmjs.org/rehype-slug/-/rehype-slug-6.0.0.tgz"
   integrity sha512-lWyvf/jwu+oS5+hL5eClVd3hNdmwM1kAC0BUvEGD19pajQMIzcNUd/k9GsfQ+FfECvX+JE+e9/btsKH0EjJT6A==
