feat: Phase 14 — hierarchical folder structure (GitHub-style nested folders)

- Section index pages ([section]/page.tsx): shows folder tree + flat doc list
- Folder index pages: [section]/[...slug]/page.tsx detects folder paths
  and renders subfolder + document listing instead of 404
- Sidebar tree: hierarchical grouping from flat doc slugs, folder icons (📁)
  with proper indentation per depth level
- DocForm v2: parent folder dropdown (populated from existing folders),
  slug input for leaf name, resolved path display
- Core helpers: extractFoldersForSection + classifyPath exported from @mcpedia/core
- CTF writeup reorganized: pwn-100 ret2win moved into pwn/ subfolder
- _index.md folder intro pages for ctf/ and defcon-quals-2024/
- STANDARD_KEYS includes extraFields to avoid badge duplication

apps/web/app/[section]/[...slug]/page.tsx

@@ -1,11 +1,12 @@
 import Link from "next/link";
 import { notFound } from "next/navigation";
 import { cookies } from "next/headers";
-import { getDocument, getRelated, listRevisions } from "@mcpedia/core";
+import { getDocument, getRelated, listRevisions, listDocuments } from "@mcpedia/core";
 import { WEBHOOK_SECRET } from "@mcpedia/config";
 import Markdown from "@/components/Markdown";
 import DocForm from "@/components/DocForm";
 import TOC from "@/components/TOC";
+import { classifyPath, extractFoldersForSection } from "@mcpedia/core";
 
 // Render at request time (content in Postgres, not available at build time).
 export const dynamic = "force-dynamic";
@@ -78,7 +79,7 @@ function CustomFieldBadges({
           displayValue = value.join(", ");
         } else if (typeof value === "object" && value !== null) {
           // Objects → neutral badge, truncated JSON
-          displayValue = JSON.stringify(value).slice(0, 40) + 
+          displayValue = JSON.stringify(value).slice(0, 40) +
             (JSON.stringify(value).length > 40 ? "…" : "");
         } else {
           // String values — auto-detect content type for styling
@@ -140,10 +141,135 @@ function CustomFieldBadges({
   );
 }
 
+/**
+ * Folder index page — lists all docs (and subfolders) whose path starts with
+ * the given prefix. This enables GitHub-style nested folder browsing.
+ */
+function FolderIndexPage({
+  section,
+  slug,
+  docPaths,
+}: {
+  section: string;
+  slug: string;
+  docPaths: string[];
+}) {
+  const prefix = `${section}/${slug}/`;
+  const folderDocs = docPaths
+    .filter((p) => p.startsWith(prefix))
+    .map((p) => p.slice(prefix.length).replace(/\.md$/, ""))
+    .sort();
+
+  // Group into immediate children: folders vs leaf docs
+  const immediateFolders = new Set<string>();
+  const immediateDocs: { name: string; slug: string }[] = [];
+
+  for (const relPath of folderDocs) {
+    const parts = relPath.split("/");
+    if (parts.length === 1) {
+      // Leaf doc directly in this folder
+      immediateDocs.push({ name: parts[0], slug: `${section}/${slug}/${parts[0]}`.replace(/\/+/g, "/") });
+    } else {
+      // Deeper — register the immediate folder
+      immediateFolders.add(parts[0]);
+    }
+  }
+
+  const folders = [...immediateFolders].sort();
+
+  return (
+    <div>
+      <nav className="flex items-center gap-2 text-xs text-[#62666d] mb-6">
+        <Link href="/" className="hover:text-[#d0d6e0] transition-colors">
+          MCPedia
+        </Link>
+        <span>/</span>
+        {slug.split("/").map((part, i) => {
+          const path = `${section}/${slug.split("/").slice(0, i + 1).join("/")}`;
+          const isLast = i === slug.split("/").length - 1;
+          return (
+            <>
+              <Link
+                key={path}
+                href={`/${path}`}
+                className={isLast ? "text-[#8a8f98]" : "hover:text-[#d0d6e0] transition-colors"}
+              >
+                {part}
+              </Link>
+              {!isLast && <span>/</span>}
+            </>
+          );
+        })}
+      </nav>
+
+      <div className="flex items-center gap-2 mb-6">
+        <span className="text-xl">📁</span>
+        <h1 className="text-3xl font-medium text-[#f7f8f8]">{slug.split("/").pop()}</h1>
+      </div>
+
+      {(folders.length > 0 || immediateDocs.length > 0) ? (
+        <div>
+          {folders.length > 0 && (
+            <div className="mb-6">
+              <h2 className="text-sm font-medium text-[#d0d6e0] uppercase mb-3">
+                Subfolders
+              </h2>
+              <div className="space-y-2">
+                {folders.map((folder) => (
+                  <Link
+                    key={folder}
+                    href={`/${section}/${slug}/${folder}`.replace(/\/+/g, "/")}
+                    className="flex items-center gap-2 text-sm text-[#d0d6e0] hover:text-[#7170ff] transition-colors"
+                  >
+                    <span>📁</span> {folder}
+                  </Link>
+                ))}
+              </div>
+            </div>
+          )}
+          {immediateDocs.length > 0 && (
+            <div>
+              <h2 className="text-sm font-medium text-[#d0d6e0] uppercase mb-3">
+                Documents
+              </h2>
+              <div className="space-y-2">
+                {immediateDocs.map((doc) => (
+                  <Link
+                    key={doc.slug}
+                    href={`/${doc.slug}`}
+                    className="flex items-center gap-2 text-sm text-[#d0d6e0] hover:text-[#7170ff] transition-colors line-clamp-1"
+                  >
+                    <span>📄</span> {doc.name}
+                  </Link>
+                ))}
+              </div>
+            </div>
+          )}
+        </div>
+      ) : (
+        <p className="text-sm text-[#62666d]">No documents found in this folder.</p>
+      )}
+    </div>
+  );
+}
+
 export default async function DocPage({ params, searchParams }: DocPageProps) {
   const { section, slug } = await params;
   const { edit } = await searchParams;
   const fullSlug = `${section}/${slug.join("/")}`;
+
+  // Fetch all docs to classify the path as "doc" or "folder"
+  const allDocs = await listDocuments();
+  const docPaths = allDocs.map((d) => d.path);
+
+  const classification = classifyPath(docPaths, fullSlug);
+
+  // If the slug path is a folder (not a leaf doc), render the folder index
+  if (classification === "folder") {
+    return <FolderIndexPage section={section} slug={slug.join("/")} docPaths={docPaths} />;
+  }
+
+  // Otherwise, treat as a document (existing behavior)
   const doc = await getDocument(fullSlug);
   if (!doc) notFound();
 
@@ -154,11 +280,13 @@ export default async function DocPage({ params, searchParams }: DocPageProps) {
   // Any other key in the document metadata becomes a dynamic badge.
   const STANDARD_KEYS = new Set([
     "id", "slug", "title", "type", "section", "status",
-    "author", "tags", "path", "createdAt", "updatedAt",
+    "author", "tags", "path", "createdAt", "updatedAt", "extraFields",
   ]);
 
   // Edit mode: inline form
   if (edit === "1" && canEdit) {
+    // Load existing folders for the folder picker in edit mode
+    const existingFolders = extractFoldersForSection(docPaths, doc.section);
     return (
       <div>
         <Link
@@ -174,6 +302,9 @@ export default async function DocPage({ params, searchParams }: DocPageProps) {
           mode="edit"
           slug={fullSlug}
           secret={WEBHOOK_SECRET}
+          existingFolders={{
+            [doc.section]: existingFolders,
+          }}
           initial={{
             title: doc.title,
             body: doc.body,
@@ -182,6 +313,7 @@ export default async function DocPage({ params, searchParams }: DocPageProps) {
             status: doc.status,
             tags: doc.tags,
             author: doc.author,
+            extraFields: doc.extraFields,
           }}
         />
       </div>
@@ -215,7 +347,9 @@ export default async function DocPage({ params, searchParams }: DocPageProps) {
       {/* Header */}
       <div className="mb-8">
         <div className="flex items-center gap-2 mb-3">
-          <span className="text-xl">{SECTION_ICON[doc.section] || "📄"}</span>
+          <span className="text-xl">
+            {SECTION_ICON[doc.section] || "📄"}
+          </span>
           <span className="text-xs font-medium text-[#7170ff] uppercase">
             {SECTION_LABEL[doc.section] || doc.section}
           </span>

apps/web/app/[section]/page.tsx

@@ -0,0 +1,178 @@
+import Link from "next/link";
+import { listDocuments, type DocumentMeta } from "@mcpedia/core";
+import type { DocSection } from "@mcpedia/core";
+
+export const dynamic = "force-dynamic";
+
+const SECTIONS: { id: DocSection; label: string; icon: string; desc: string }[] = [
+  {
+    id: "docs",
+    label: "Documentation",
+    icon: "📄",
+    desc: "Setup guides, API references, and protocol specs.",
+  },
+  { id: "writeups", label: "Writeups", icon: "📝", desc: "Post-mortems, debugging stories, and case studies." },
+  { id: "research", label: "Research", icon: "🔬", desc: "Deep-dive analysis, architecture notes, and experiments." },
+  { id: "notes", label: "Notes", icon: "📌", desc: "Quick references, patterns, and gotchas." },
+];
+
+/**
+ * Group documents into a folder tree. Returns nodes where each node is either:
+ *  - a folder (has `children`) or
+ *  - a leaf doc (has `doc`)
+ * The tree is built from the path segments of each document's `path`.
+ */
+interface TreeNode {
+  name: string;
+  slug: string;
+  doc?: DocumentMeta;
+  children?: TreeNode[];
+}
+
+function buildFolderTree(docs: DocumentMeta[], section: string): TreeNode[] {
+  const root: TreeNode[] = [];
+  const rootMap = new Map<string, TreeNode>();
+
+  for (const doc of docs.filter((d) => d.section === section)) {
+    // path is like "docs/websocket/contract.md" → strip section prefix + .md
+    const rel = doc.path.startsWith(`${section}/`)
+      ? doc.path.slice(section.length + 1)
+      : doc.path;
+    const cleanPath = rel.replace(/\.md$/, "");
+    const parts = cleanPath.split("/");
+
+    let currentLevel = root;
+    let currentPath = section;
+
+    for (let i = 0; i < parts.length; i++) {
+      const part = parts[i];
+      currentPath = `${currentPath}/${part}`;
+      const isLeaf = i === parts.length - 1;
+
+      let node = currentLevel.find((n) => n.name === part);
+      if (!node) {
+        node = {
+          name: part === "" ? section : part,
+          slug: currentPath,
+          children: isLeaf ? undefined : [],
+        };
+        currentLevel.push(node);
+      }
+
+      if (isLeaf) {
+        node.doc = doc;
+      } else {
+        if (!node.children) node.children = [];
+        currentLevel = node.children;
+      }
+    }
+  }
+
+  return root;
+}
+
+function renderTree(nodes: TreeNode[], section: DocSection) {
+  return (
+    <ul className="space-y-0.5">
+      {nodes.map((node) => {
+        const isFolder = !!node.children;
+        const isDoc = !!node.doc;
+        return (
+          <li key={node.slug}>
+            {isFolder ? (
+              <Link
+                href={`/${node.slug}`}
+                className="flex items-center gap-1.5 text-xs py-0.5 rounded hover:bg-[#191a1b] text-[#d0d6e0] hover:text-[#f7f8f8]"
+              >
+                <span>📁</span>
+                {node.name}
+              </Link>
+            ) : isDoc ? (
+              <Link
+                href={`/${node.slug}`}
+                className="flex items-center gap-1.5 text-xs py-0.5 rounded hover:bg-[#191a1b] text-[#d0d6e0] hover:text-[#f7f8f8] line-clamp-1"
+              >
+                <span>📄</span>
+                {node.doc?.title || node.name}
+              </Link>
+            ) : null}
+            {node.children && node.children.length > 0 && (
+              <div className="ml-3 mt-0.5">
+                {renderTree(node.children, section)}
+              </div>
+            )}
+          </li>
+        );
+      })}
+    </ul>
+  );
+}
+
+export default async function SectionIndexPage({
+  params,
+}: {
+  params: Promise<{ section: string }>;
+}) {
+  const { section } = await params;
+
+  if (!SECTIONS.some((s) => s.id === section)) {
+    return (
+      <div>
+        <h1 className="text-2xl font-medium text-[#f7f8f8]">Unknown section</h1>
+      </div>
+    );
+  }
+
+  const all = await listDocuments();
+  const sectionDocs = all.filter((d) => d.section === section);
+  const tree = buildFolderTree(all, section as DocSection);
+  const sectionInfo = SECTIONS.find((s) => s.id === section)!;
+
+  return (
+    <div>
+      <div className="flex items-center gap-2 mb-6">
+        <span className="text-2xl">{sectionInfo.icon}</span>
+        <h1 className="text-3xl font-medium text-[#f7f8f8]">{sectionInfo.label}</h1>
+      </div>
+      <p className="text-sm text-[#8a8f98] mb-6 max-w-2xl">
+        {sectionInfo.desc}
+      </p>
+
+      <div className="mb-8">
+        <h2 className="text-sm font-medium text-[#d0d6e0] uppercase mb-3">
+          Folder structure
+        </h2>
+        {tree.length > 0 ? (
+          renderTree(tree, section as DocSection)
+        ) : (
+          <p className="text-xs text-[#62666d]">No documents found.</p>
+        )}
+      </div>
+
+      {sectionDocs.length > 0 && (
+        <div>
+          <h2 className="text-sm font-medium text-[#d0d6e0] uppercase mb-3">
+            All documents ({sectionDocs.length})
+          </h2>
+          <div className="space-y-2">
+            {sectionDocs
+              .sort(
+                (a, b) =>
+                  new Date(b.updatedAt).getTime() - new Date(a.updatedAt).getTime(),
+              )
+              .map((d) => (
+                <Link
+                  key={d.slug}
+                  href={`/${d.slug}`}
+                  className="block text-sm text-[#d0d6e0] hover:text-[#7170ff] transition-colors line-clamp-1"
+                  title={d.title}
+                >
+                  {d.title}
+                </Link>
+              ))}
+          </div>
+        </div>
+      )}
+    </div>
+  );
+}

apps/web/app/components/DocForm.tsx

@@ -7,6 +7,7 @@ interface DocFormProps {
   mode: "create" | "edit";
   slug?: string;
   secret: string;
+  existingFolders?: Record<string, string[]>;
   initial?: {
     title?: string;
     body?: string;
@@ -15,18 +16,26 @@ interface DocFormProps {
     status?: "published" | "draft";
     tags?: string[];
     author?: string;
+    extraFields?: Record<string, unknown>;
   };
 }
 
 const SECTION_OPTIONS = ["docs", "writeups", "research", "notes"] as const;
 const TYPE_OPTIONS = ["documentation", "writeup", "research", "note"] as const;
 
-export default function DocForm({ mode, slug, secret, initial }: DocFormProps) {
+export default function DocForm({
+  mode,
+  slug,
+  secret,
+  existingFolders,
+  initial,
+}: DocFormProps) {
   const router = useRouter();
   const [loading, setLoading] = useState(false);
   const [error, setError] = useState<string | null>(null);
 
   const [title, setTitle] = useState(initial?.title ?? "");
+  const [slugInput, setSlugInput] = useState("");
   const [body, setBody] = useState(initial?.body ?? "");
   const [section, setSection] = useState(initial?.section ?? "docs");
   const [type, setType] = useState(initial?.type ?? "documentation");
@@ -35,16 +44,26 @@ export default function DocForm({ mode, slug, secret, initial }: DocFormProps) {
   const [author, setAuthor] = useState(initial?.author ?? "");
 
   // Dynamic custom fields — content creators can add any metadata they want
-  // (e.g. CTF: event, challenge, category, difficulty, points, team_name, ...)
   const [customFields, setCustomFields] = useState<
     Array<{ key: string; value: string }>
   >([]);
 
+  // Parent folder selection (hierarchical structure like GitHub folders)
+  const [parentFolder, setParentFolder] = useState("");
+
   const tagList = tags
     .split(",")
     .map((t) => t.trim())
     .filter(Boolean);
 
+  // For edit mode, slug is fixed (full path). For create mode, build from folder + slugInput.
+  const isEdit = mode === "edit";
+  const effectiveSlug = isEdit ? (slug ?? "") : parentFolder
+    ? `${parentFolder}/${slugInput}`.replace(/^\/+/, "").replace(/\/+/g, "/")
+    : slugInput;
+
+  const availableFolders = existingFolders?.[section] ?? [];
+
   const baseInputCls =
     "w-full px-3 py-2 bg-[#0f1011] border border-[#23252a] rounded text-[#f7f8f8] placeholder-[#62666d] focus:outline-none focus:border-[#5e6ad2] focus:ring-1 focus:ring-[#5e6ad2]";
 
@@ -67,10 +86,17 @@ export default function DocForm({ mode, slug, secret, initial }: DocFormProps) {
     setLoading(true);
     setError(null);
 
+    if (!effectiveSlug || !title || !body) {
+      setError("Slug, title, and body are required.");
+      setLoading(false);
+      return;
+    }
+
     // Build payload with custom fields flattened at top level
     const payload: Record<string, unknown> = {
       title,
       body,
+      slug: effectiveSlug,
       section,
       type,
       status,
@@ -88,19 +114,13 @@ export default function DocForm({ mode, slug, secret, initial }: DocFormProps) {
     try {
       let res: Response;
       if (mode === "create") {
-        const slugVal =
-          slug ??
-          title
-            .toLowerCase()
-            .replace(/[^a-z0-9]+/g, "-")
-            .replace(/^-+|-+$/g, "");
         res = await fetch("/api/docs", {
           method: "POST",
           headers: {
             "Content-Type": "application/json",
             "x-webhook-secret": secret,
           },
-          body: JSON.stringify({ slug: slugVal, ...payload }),
+          body: JSON.stringify(payload),
         });
       } else {
         const editSlug = slug ?? "";
@@ -149,22 +169,6 @@ export default function DocForm({ mode, slug, secret, initial }: DocFormProps) {
         />
       </div>
 
-      <div>
-        <label className="block text-xs font-medium text-[#d0d6e0] mb-1">
-          Slug
-        </label>
-        <input
-          type="text"
-          value={slug ?? ""}
-          readOnly
-          className="w-full px-3 py-2 bg-[#191a1b] border border-[#23252a] rounded text-[#8a8f98]"
-          placeholder={section}
-        />
-        <p className="text-xs text-[#62666d] mt-1">
-          URL-safe path under the section.
-        </p>
-      </div>
-
       <div className="grid grid-cols-1 md:grid-cols-3 gap-4">
         <div>
           <label className="block text-xs font-medium text-[#d0d6e0] mb-1">
@@ -174,6 +178,7 @@ export default function DocForm({ mode, slug, secret, initial }: DocFormProps) {
             value={section}
             onChange={(e) => setSection(e.target.value as typeof section)}
             className={baseInputCls}
+            disabled={isEdit}
           >
             {SECTION_OPTIONS.map((s) => (
               <option key={s} value={s}>
@@ -213,6 +218,56 @@ export default function DocForm({ mode, slug, secret, initial }: DocFormProps) {
         </div>
       </div>
 
+      <div>
+        <label className="block text-xs font-medium text-[#d0d6e0] mb-1">
+          Parent folder (optional)
+        </label>
+        <select
+          value={parentFolder}
+          onChange={(e) => setParentFolder(e.target.value)}
+          className={baseInputCls}
+          disabled={isEdit}
+        >
+          <option value="">(root of section)</option>
+          {availableFolders.map((folder) => (
+            <option key={folder} value={folder}>
+              {folder}
+            </option>
+          ))}
+        </select>
+        <p className="text-xs text-[#62666d] mt-1">
+          Place this document inside an existing folder. The slug will be
+          prepended with the folder path (e.g. selecting "ctf/defcon-quals-2024"
+          + slug "pwn-100" → "ctf/defcon-quals-2024/pwn-100").
+        </p>
+      </div>
+
+      <div>
+        <label className="block text-xs font-medium text-[#d0d6e0] mb-1">
+          {isEdit ? "Full slug (read-only)" : "Slug (file name)"}
+        </label>
+        {isEdit ? (
+          <input
+            type="text"
+            value={slug ?? ""}
+            readOnly
+            className="w-full px-3 py-2 bg-[#191a1b] border border-[#23252a] rounded text-[#8a8f98]"
+          />
+        ) : (
+          <input
+            type="text"
+            value={slugInput}
+            onChange={(e) => setSlugInput(e.target.value)}
+            className={baseInputCls}
+            placeholder="my-document-slug"
+            required
+          />
+        )}
+        <p className="text-xs text-[#62666d] mt-1">
+          Resolved path: <code>{effectiveSlug || section}</code>
+        </p>
+      </div>
+
       <div>
         <label className="block text-xs font-medium text-[#d0d6e0] mb-1">
           Tags
@@ -246,8 +301,8 @@ export default function DocForm({ mode, slug, secret, initial }: DocFormProps) {
         <p className="text-xs text-[#62666d] mb-3">
           Add extra frontmatter fields. Content creators name and define their own
           metadata here — the system auto-renders any field as a badge on the doc
-          page based on its value (e.g. numbers → points style, "easy" → green
-          difficulty badge, etc.).{" "}</p>
+          page based on its value.
+        </p>
         {customFields.length > 0 && (
           <div className="space-y-3 mb-3">
             {customFields.map((field, i) => (
@@ -263,9 +318,7 @@ export default function DocForm({ mode, slug, secret, initial }: DocFormProps) {
                   type="text"
                   placeholder="value"
                   value={field.value}
-                  onChange={(e) =>
-                    updateCustomField(i, "value", e.target.value)
-                  }
+                  onChange={(e) => updateCustomField(i, "value", e.target.value)}
                   className="flex-1 px-3 py-2 bg-[#0f1011] border border-[#23252a] rounded text-[#f7f8f8] placeholder-[#62666d] focus:outline-none focus:border-[#5e6ad2] focus:ring-1 focus:ring-[#5e6ad2]"
                 />
                 <button
@@ -295,7 +348,7 @@ export default function DocForm({ mode, slug, secret, initial }: DocFormProps) {
         <textarea
           value={body}
           onChange={(e) => setBody(e.target.value)}
-          className="w-full h-96 px-3 py-2 bg-[#0f1011] border border-[#23252a] rounded text-[#d0d6e0] placeholder-[#62666d] font-mono text-sm focus:outline-none focus:border-[#5e6ad2] focus:ring-1 focus:ring-[#5e6ad2]"
+          className="w-full h-96 px-3 py-2 bg-[#0f1011] border border-[#23252a] rounded text-[#f7f8f8] placeholder-[#62666d] font-mono text-sm focus:outline-none focus:border-[#5e6ad2] focus:ring-1 focus:ring-[#5e6ad2]"
           placeholder="# Heading&#10;&#10;Content here..."
         />
       </div>

apps/web/app/components/Sidebar.tsx

@@ -18,6 +18,113 @@ const SECTIONS = [
   { id: "notes", label: "Notes", icon: "📌" },
 ] as const;
 
+/**
+ * Build a hierarchical folder tree from a flat list of documents.
+ * Each doc's slug is like "section/sub/sub2/leaf-name".
+ * The tree groups by path segments so the sidebar shows nested folders
+ * with proper indentation (like GitHub's file tree).
+ */
+interface TreeNode {
+  name: string;
+  slug: string;
+  title: string;
+  children: TreeNode[];
+}
+
+function buildFolderTree(docs: Doc[]): Record<string, TreeNode> {
+  // Returns a map from section id → tree root for that section.
+  const result: Record<string, TreeNode> = {};
+
+  for (const section of SECTIONS) {
+    const sectionDocs = docs.filter((d) => d.section === section.id);
+    const root: TreeNode = {
+      name: section.id,
+      slug: section.id,
+      title: section.label,
+      children: [],
+    };
+    const nodeMap = new Map<string, TreeNode>();
+    nodeMap.set(section.id, root);
+
+    for (const doc of sectionDocs) {
+      // slug is like "docs/websocket/contract" → parts after section
+      const parts = doc.slug.split("/");
+      // parts[0] should be the section
+      let current = root;
+
+      for (let i = 1; i < parts.length; i++) {
+        const part = parts[i];
+        const path = parts.slice(0, i + 1).join("/");
+        const isLeaf = i === parts.length - 1;
+
+        let child = current.children.find((n) => n.name === part);
+        if (!child) {
+          child = {
+            name: part,
+            slug: path,
+            title: isLeaf ? doc.title : part,
+            children: [],
+          };
+          current.children.push(child);
+          nodeMap.set(path, child);
+        } else if (isLeaf) {
+          child.title = doc.title;
+        }
+        current = child;
+      }
+    }
+
+    root.children.sort((a, b) => {
+      // Folders first, then docs
+      const aFolder = a.children.length > 0 ? 0 : 1;
+      const bFolder = b.children.length > 0 ? 0 : 1;
+      if (aFolder !== bFolder) return aFolder - bFolder;
+      return a.name.localeCompare(b.name);
+    });
+
+    result[section.id] = root;
+  }
+
+  return result;
+}
+
+/**
+ * Recursively render the folder tree with indentation.
+ * depth = 0 is the top-level items under a section.
+ */
+function renderTreeNode(node: TreeNode, depth: number, pathname: string) {
+  const isFolder = node.children.length > 0;
+  const isActive = pathname === `/${node.slug}`;
+  const hasActiveChild = pathname.startsWith(`/${node.slug}/`);
+
+  const indent = depth * 12; // 12px per level
+
+  return (
+    <li key={node.slug}>
+      <Link
+        href={`/${node.slug}`}
+        className={`flex items-center gap-1.5 text-xs py-0.5 rounded transition-all ${
+          isActive
+            ? "text-[#7170ff] bg-[#191a1b]"
+            : hasActiveChild
+              ? "text-[#d0d6e0]"
+              : "text-[#8a8f98] hover:text-[#d0d6e0] hover:bg-[#191a1b]"
+        }`}
+        style={{ marginLeft: `${indent}px` }}
+        title={node.title}
+      >
+        <span>{isFolder ? "📁" : "📄"}</span>
+        {node.title || node.name}
+      </Link>
+      {node.children && node.children.length > 0 && (
+        <ul>
+          {node.children.map((child) => renderTreeNode(child, 0, pathname))}
+        </ul>
+      )}
+    </li>
+  );
+}
+
 /** Client-side sidebar (fetches doc list via /api/docs at runtime).
  *  Client component so `next build` SSG doesn't hit Postgres (CI has no DB). */
 export default function Sidebar() {
@@ -34,66 +141,64 @@ export default function Sidebar() {
       .catch(() => setDocs([]));
   }, []);
 
-  const bySection: Record<string, Doc[]> = {};
-  for (const doc of docs) {
-    if (!bySection[doc.section]) bySection[doc.section] = [];
-    bySection[doc.section].push(doc);
-  }
+  const tree = buildFolderTree(docs);
+
+  // Flatten all docs count for display
+  const totalDocs = docs.length;
 
   return (
     <nav className="h-full overflow-y-auto py-6">
-      <ul className="space-y-1 px-3 text-sm">
+      <div className="mb-4 px-3">
+        <span className="text-xs text-[#62666d] uppercase">
+          {totalDocs} documents · {SECTIONS.length} sections
+        </span>
+      </div>
+      <ul className="space-y-0.5 px-3">
         {SECTIONS.map(({ id, label, icon }) => {
-          const sectionDocs = bySection[id] || [];
+          const treeRoot = tree[id];
+          const sectionDocs = docs.filter((d) => d.section === id);
           if (sectionDocs.length === 0) return null;
 
-          // Check if any doc in this section is the active page
-          const isActive = sectionDocs.some(
-            (doc) => pathname === `/${doc.slug}` || pathname === `/${doc.section}`,
-          );
-
+          const isActive = pathname.startsWith(`/${id}`);
           return (
             <li key={id}>
               <div
-                className={`text-xs font-medium mb-1 mt-4 first:mt-0 flex items-center gap-1.5 ${
-                  isActive
-                    ? "text-[#7170ff]"
-                    : "text-[#62666d]"
+                className={`text-xs font-medium mb-1 flex items-center gap-1.5 ${
+                  isActive ? "text-[#7170ff]" : "text-[#62666d]"
                 }`}
               >
                 <span>{icon}</span>
                 {label}
               </div>
               <ul className="space-y-0.5">
-                {sectionDocs.map((doc) => {
-                  const parts = doc.slug.split("/").slice(1);
-                  const label = parts[parts.length - 1];
-                  const formatted = label
-                    .split(/[-_]/)
-                    .map((w) => w.charAt(0).toUpperCase() + w.slice(1))
-                    .join(" ");
-                  const depth = doc.slug.split("/").length;
-                  const indent = depth - 1;
-                  const isDocActive = pathname === `/${doc.slug}`;
-                  return (
-                    <li
-                      key={doc.slug}
-                      style={{ marginLeft: `${indent * 12}px` }}
-                    >
-                      <Link
-                        href={`/${doc.slug}`}
-                        className={`block text-xs py-0.5 rounded transition-all ${
-                          isDocActive
-                            ? "text-[#7170ff] bg-[#191a1b]"
-                            : "text-[#d0d6e0] hover:text-[#f7f8f8] hover:bg-[#191a1b]"
-                        }`}
-                        title={doc.title}
-                      >
-                        {formatted || doc.slug}
-                      </Link>
-                    </li>
-                  );
-                })}
+                {treeRoot && treeRoot.children.length > 0
+                  ? treeRoot.children.map((node) =>
+                      renderTreeNode(node, 0, pathname),
+                    )
+                  : sectionDocs.map((doc) => {
+                      const parts = doc.slug.split("/").slice(1);
+                      const label = parts[parts.length - 1]
+                        .split(/[-_]/)
+                        .map((w) => w.charAt(0).toUpperCase() + w.slice(1))
+                        .join(" ");
+                      const isDocActive = pathname === `/${doc.slug}`;
+                      return (
+                        <li key={doc.slug}>
+                          <Link
+                            href={`/${doc.slug}`}
+                            className={`flex items-center gap-1.5 text-xs py-0.5 rounded transition-all ${
+                              isDocActive
+                                ? "text-[#7170ff] bg-[#191a1b]"
+                                : "text-[#d0d6e0] hover:text-[#f7f8f8] hover:bg-[#191a1b]"
+                            }`}
+                            title={doc.title}
+                          >
+                            <span>📄</span>
+                            {label}
+                          </Link>
+                        </li>
+                      );
+                    })}
               </ul>
             </li>
           );

apps/web/app/create/page.tsx

@@ -1,44 +1,34 @@
-import { WEBHOOK_SECRET } from "@mcpedia/config";
+import { listDocuments, extractFoldersForSection } from "@mcpedia/core";
 import { cookies } from "next/headers";
+import { redirect } from "next/navigation";
 import DocForm from "@/components/DocForm";
-import Link from "next/link";
+import { WEBHOOK_SECRET } from "@mcpedia/config";
+
+export const dynamic = "force-dynamic";
 
-// GET /create — show the document create form.
-// Requires admin cookie auth.
 export default async function CreatePage() {
   const cookieStore = await cookies();
   const canEdit = cookieStore.get("mcpedia_admin")?.value != null;
-  if (!canEdit) {
-    return (
-      <div className="text-center py-16">
-        <h1 className="text-2xl font-light text-[#f7f8f8] mb-4">
-          Authentication required
-        </h1>
-        <p className="text-[#8a8f98] mb-6">
-          You must be logged in to create documents.
-        </p>
-        <Link
-          href="/login"
-          className="inline-flex items-center gap-2 px-4 py-2 rounded bg-[#5e6ad2] text-white hover:bg-[#7170ff] transition-colors font-medium text-sm"
-        >
-          Login
-        </Link>
-      </div>
-    );
+  if (!canEdit) redirect("/login");
+
+  const allDocs = await listDocuments();
+
+  // Build folder suggestions per section using the shared helper from core
+  const sections = ["docs", "writeups", "research", "notes"];
+  const docPaths = allDocs.map((d) => d.path);
+  const foldersBySection: Record<string, string[]> = {};
+  for (const sec of sections) {
+    foldersBySection[sec] = extractFoldersForSection(docPaths, sec);
   }
 
   return (
     <div>
-      <Link
-        href="/"
-        className="text-xs text-[#8a8f98] hover:text-[#d0d6e0] mb-4 inline-block"
-      >
-        ← Back
-      </Link>
-      <h1 className="text-2xl font-light text-[#f7f8f8] mb-6">
-        Create Document
-      </h1>
-      <DocForm mode="create" secret={WEBHOOK_SECRET} />
+      <h1 className="text-3xl font-medium text-[#f7f8f8] mb-6">Create Document</h1>
+      <DocForm
+        mode="create"
+        secret={WEBHOOK_SECRET}
+        existingFolders={foldersBySection}
+      />
     </div>
   );
 }