feat: Clients admin — hierarchical tree view with parent/child support

- Tree structure: clients rendered as indented tree with visual connectors
- Expand/collapse: chevron toggle, children count badge, expand/collapse all
- Parent selector: dropdown on add + "Move..." inline picker on each client
  (excludes self and descendants to prevent circular refs)
- Search: shows matching clients AND their ancestors for context
- Depth visualization: alternating backgrounds, border-l connectors
- Drag-and-drop: preserved, reorders among siblings only

No API changes needed — router already supported parentId in CRUD.

Co-Authored-By: claude-flow <ruv@ruv.net>

apps/web/src/components/admin/ClientsAdminClient.tsx

@@ -37,8 +37,91 @@ type ClientRow = {
   _count?: { children: number; projects: number };
 };
 
+type TreeNode = ClientRow & {
+  children: TreeNode[];
+  depth: number;
+};
+
 // ---------------------------------------------------------------------------
-// Tag color palette — deterministic color from tag name hash
+// Tree helpers
+// ---------------------------------------------------------------------------
+
+function buildTree(clients: ClientRow[]): TreeNode[] {
+  const map = new Map<string, TreeNode>();
+  const roots: TreeNode[] = [];
+
+  // First pass: create nodes
+  for (const c of clients) {
+    map.set(c.id, { ...c, children: [], depth: 0 });
+  }
+
+  // Second pass: link parents
+  for (const c of clients) {
+    const node = map.get(c.id)!;
+    if (c.parentId && map.has(c.parentId)) {
+      map.get(c.parentId)!.children.push(node);
+    } else {
+      roots.push(node);
+    }
+  }
+
+  // Third pass: set depths and sort children
+  function setDepths(nodes: TreeNode[], depth: number) {
+    for (const n of nodes) {
+      n.depth = depth;
+      n.children.sort((a, b) => a.sortOrder - b.sortOrder || a.name.localeCompare(b.name));
+      setDepths(n.children, depth + 1);
+    }
+  }
+  roots.sort((a, b) => a.sortOrder - b.sortOrder || a.name.localeCompare(b.name));
+  setDepths(roots, 0);
+
+  return roots;
+}
+
+/** Flatten tree into display order, respecting collapsed state. */
+function flattenTree(nodes: TreeNode[], collapsedIds: Set<string>): TreeNode[] {
+  const result: TreeNode[] = [];
+  function walk(list: TreeNode[]) {
+    for (const n of list) {
+      result.push(n);
+      if (n.children.length > 0 && !collapsedIds.has(n.id)) {
+        walk(n.children);
+      }
+    }
+  }
+  walk(nodes);
+  return result;
+}
+
+/** Get all descendant IDs of a node (recursive). */
+function getDescendantIds(clientId: string, clients: ClientRow[]): Set<string> {
+  const ids = new Set<string>();
+  function collect(parentId: string) {
+    for (const c of clients) {
+      if (c.parentId === parentId && !ids.has(c.id)) {
+        ids.add(c.id);
+        collect(c.id);
+      }
+    }
+  }
+  collect(clientId);
+  return ids;
+}
+
+/** Get all ancestor IDs of a node (walk up). */
+function getAncestorIds(clientId: string, clientMap: Map<string, ClientRow>): Set<string> {
+  const ids = new Set<string>();
+  let current = clientMap.get(clientId);
+  while (current?.parentId) {
+    ids.add(current.parentId);
+    current = clientMap.get(current.parentId);
+  }
+  return ids;
+}
+
+// ---------------------------------------------------------------------------
+// Tag color palette -- deterministic color from tag name hash
 // ---------------------------------------------------------------------------
 
 const TAG_COLORS = [
@@ -206,25 +289,100 @@ function GripIcon({ className }: { className?: string }) {
   );
 }
 
+// ---------------------------------------------------------------------------
+// Chevron icon for expand/collapse
+// ---------------------------------------------------------------------------
+
+function ChevronIcon({ expanded, className }: { expanded: boolean; className?: string }) {
+  return (
+    <svg
+      className={`transition-transform duration-150 ${expanded ? "rotate-90" : "rotate-0"} ${className ?? ""}`}
+      width="14"
+      height="14"
+      viewBox="0 0 14 14"
+      fill="none"
+      stroke="currentColor"
+      strokeWidth="2"
+      strokeLinecap="round"
+      strokeLinejoin="round"
+    >
+      <path d="M5 3l4 4-4 4" />
+    </svg>
+  );
+}
+
+// ---------------------------------------------------------------------------
+// Parent selector dropdown
+// ---------------------------------------------------------------------------
+
+function ParentSelector({
+  clients,
+  currentId,
+  currentParentId,
+  onChange,
+}: {
+  clients: ClientRow[];
+  currentId?: string;
+  currentParentId: string | null;
+  onChange: (parentId: string | null) => void;
+}) {
+  // Exclude self and all descendants to prevent circular refs
+  const excludeIds = useMemo(() => {
+    if (!currentId) return new Set<string>();
+    const ids = getDescendantIds(currentId, clients);
+    ids.add(currentId);
+    return ids;
+  }, [currentId, clients]);
+
+  const options = useMemo(() => {
+    return clients
+      .filter((c) => !excludeIds.has(c.id) && c.isActive)
+      .sort((a, b) => a.name.localeCompare(b.name));
+  }, [clients, excludeIds]);
+
+  return (
+    <select
+      value={currentParentId ?? ""}
+      onChange={(e) => onChange(e.target.value || null)}
+      className="px-2 py-1 text-xs rounded-md border border-gray-300 dark:border-gray-600 bg-white dark:bg-gray-900 text-gray-700 dark:text-gray-300 focus:outline-none focus:ring-1 focus:ring-brand-400 max-w-[160px]"
+    >
+      <option value="">(Top Level)</option>
+      {options.map((c) => (
+        <option key={c.id} value={c.id}>
+          {c.name}
+        </option>
+      ))}
+    </select>
+  );
+}
+
 // ---------------------------------------------------------------------------
 // Sortable client card
 // ---------------------------------------------------------------------------
 
 function SortableClientCard({
   client,
+  allClients,
   allKnownTags,
   onUpdateName,
   onUpdateSortOrder,
   onUpdateTags,
+  onUpdateParent,
   onDelete,
+  onToggleExpand,
+  isExpanded,
   isDragOverlay,
 }: {
-  client: ClientRow;
+  client: TreeNode;
+  allClients: ClientRow[];
   allKnownTags: string[];
   onUpdateName: (id: string, name: string) => void;
   onUpdateSortOrder: (id: string, sortOrder: number) => void;
   onUpdateTags: (id: string, tags: string[]) => void;
+  onUpdateParent: (id: string, parentId: string | null) => void;
   onDelete: (id: string) => void;
+  onToggleExpand: (id: string) => void;
+  isExpanded: boolean;
   isDragOverlay?: boolean;
 }) {
   const {
@@ -247,6 +405,7 @@ function SortableClientCard({
   const [sortOrderValue, setSortOrderValue] = useState(client.sortOrder);
   const [addingTag, setAddingTag] = useState(false);
   const [confirmDelete, setConfirmDelete] = useState(false);
+  const [showParentSelector, setShowParentSelector] = useState(false);
   const nameInputRef = useRef<HTMLInputElement>(null);
   const sortInputRef = useRef<HTMLInputElement>(null);
 
@@ -284,161 +443,257 @@ function SortableClientCard({
     setEditingSortOrder(false);
   }
 
+  const hasChildren = (client._count?.children ?? client.children.length) > 0;
+  const childCount = client._count?.children ?? client.children.length;
+  const depth = client.depth;
+
+  // Nesting depth styling: alternating subtle backgrounds
+  const depthBg = depth > 0
+    ? depth % 2 === 1
+      ? "bg-gray-50/50 dark:bg-gray-800/80"
+      : "bg-white dark:bg-gray-800/60"
+    : "bg-white dark:bg-gray-800";
+
   const cardClasses = [
     "flex items-center gap-3 px-4 py-3 rounded-xl border transition-all group",
     isDragOverlay
       ? "bg-white dark:bg-gray-800 border-brand-500 shadow-xl scale-[1.02] ring-2 ring-brand-500"
       : isDragging
         ? "opacity-30 bg-gray-50 dark:bg-gray-900 border-gray-200 dark:border-gray-700"
-        : "bg-white dark:bg-gray-800 border-gray-200 dark:border-gray-700 hover:border-gray-300 dark:hover:border-gray-600 hover:shadow-sm",
+        : `${depthBg} border-gray-200 dark:border-gray-700 hover:border-gray-300 dark:hover:border-gray-600 hover:shadow-sm`,
   ].join(" ");
 
+  // Indent padding: 0 for root, 32px per level
+  const indentPx = depth * 32;
+
+  // Find parent name for display
+  const parentClient = client.parentId
+    ? allClients.find((c) => c.id === client.parentId)
+    : null;
+
   return (
-    <div ref={setNodeRef} style={style} className={cardClasses}>
+    <div
-      {/* Drag handle */}
+      ref={setNodeRef}
-      <button
+      style={style}
-        type="button"
+      className={depth > 0 ? "relative" : undefined}
-        className="cursor-grab active:cursor-grabbing text-gray-300 dark:text-gray-600 hover:text-gray-500 dark:hover:text-gray-400 flex-shrink-0 touch-none"
+    >
-        {...attributes}
+      {/* Tree connector line */}
-        {...listeners}
+      {depth > 0 && !isDragOverlay && (
+        <div
+          className="absolute top-0 bottom-0 border-l-2 border-gray-300 dark:border-gray-600"
+          style={{ left: `${indentPx - 16}px` }}
+        />
+      )}
+
+      <div
+        className={cardClasses}
+        style={{ marginLeft: `${indentPx}px` }}
       >
-        <GripIcon />
+        {/* Expand/collapse toggle */}
-      </button>
+        <div className="flex-shrink-0 w-5">
-
+          {hasChildren ? (
-      {/* Name */}
-      <div className="flex-1 min-w-0">
-        {editingName ? (
-          <input
-            ref={nameInputRef}
-            type="text"
-            value={nameValue}
-            onChange={(e) => setNameValue(e.target.value)}
-            onKeyDown={(e) => {
-              if (e.key === "Enter") saveName();
-              if (e.key === "Escape") {
-                setNameValue(client.name);
-                setEditingName(false);
-              }
-            }}
-            onBlur={saveName}
-            className="w-full px-2 py-1 -ml-2 text-sm font-medium rounded-md border border-gray-300 dark:border-gray-600 bg-white dark:bg-gray-900 text-gray-900 dark:text-gray-100 focus:outline-none focus:ring-2 focus:ring-brand-400"
-          />
-        ) : (
-          <button
-            type="button"
-            onClick={() => setEditingName(true)}
-            className="text-sm font-medium text-gray-900 dark:text-gray-100 hover:text-brand-600 dark:hover:text-brand-400 truncate text-left w-full cursor-text"
-            title="Click to edit name"
-          >
-            {client.name}
-            {client.code && (
-              <span className="text-gray-400 dark:text-gray-500 font-mono ml-2 text-xs">
-                [{client.code}]
-              </span>
-            )}
-            {!client.isActive && (
-              <span className="ml-2 text-xs text-gray-400 italic">inactive</span>
-            )}
-          </button>
-        )}
-      </div>
-
-      {/* Tags */}
-      <div className="flex items-center gap-1 flex-wrap flex-shrink-0">
-        {client.tags.map((tag) => (
-          <TagPill
-            key={tag}
-            tag={tag}
-            onRemove={() => {
-              onUpdateTags(client.id, client.tags.filter((t) => t !== tag));
-            }}
-          />
-        ))}
-        {addingTag ? (
-          <TagAdder
-            existingTags={client.tags}
-            allKnownTags={allKnownTags}
-            onAdd={(tag) => {
-              onUpdateTags(client.id, [...client.tags, tag]);
-            }}
-            onClose={() => setAddingTag(false)}
-          />
-        ) : (
-          <button
-            type="button"
-            onClick={() => setAddingTag(true)}
-            className="inline-flex items-center justify-center w-5 h-5 rounded-full text-xs text-gray-400 dark:text-gray-500 hover:text-brand-500 dark:hover:text-brand-400 hover:bg-gray-100 dark:hover:bg-gray-700 opacity-0 group-hover:opacity-100 transition-opacity"
-            title="Add tag"
-          >
-            +
-          </button>
-        )}
-      </div>
-
-      {/* Sort order */}
-      <div className="flex-shrink-0 w-12">
-        {editingSortOrder ? (
-          <input
-            ref={sortInputRef}
-            type="number"
-            value={sortOrderValue}
-            onChange={(e) => setSortOrderValue(parseInt(e.target.value) || 0)}
-            onKeyDown={(e) => {
-              if (e.key === "Enter") saveSortOrder();
-              if (e.key === "Escape") {
-                setSortOrderValue(client.sortOrder);
-                setEditingSortOrder(false);
-              }
-            }}
-            onBlur={saveSortOrder}
-            className="w-full px-1 py-0.5 text-xs text-center rounded border border-gray-300 dark:border-gray-600 bg-white dark:bg-gray-900 text-gray-600 dark:text-gray-400 focus:outline-none focus:ring-1 focus:ring-brand-400"
-          />
-        ) : (
-          <button
-            type="button"
-            onClick={() => setEditingSortOrder(true)}
-            className="w-full text-xs text-center text-gray-400 dark:text-gray-500 hover:text-gray-600 dark:hover:text-gray-300 cursor-text tabular-nums"
-            title="Click to edit sort order"
-          >
-            #{client.sortOrder}
-          </button>
-        )}
-      </div>
-
-      {/* Delete */}
-      <div className="flex-shrink-0">
-        {confirmDelete ? (
-          <div className="flex items-center gap-1">
             <button
               type="button"
-              onClick={() => {
+              onClick={() => onToggleExpand(client.id)}
-                onDelete(client.id);
+              className="flex items-center justify-center w-5 h-5 rounded text-gray-400 dark:text-gray-500 hover:text-gray-600 dark:hover:text-gray-300 hover:bg-gray-100 dark:hover:bg-gray-700"
-                setConfirmDelete(false);
+              title={isExpanded ? "Collapse" : "Expand"}
+            >
+              <ChevronIcon expanded={isExpanded} />
+            </button>
+          ) : (
+            <span className="block w-5" />
+          )}
+        </div>
+
+        {/* Drag handle */}
+        <button
+          type="button"
+          className="cursor-grab active:cursor-grabbing text-gray-300 dark:text-gray-600 hover:text-gray-500 dark:hover:text-gray-400 flex-shrink-0 touch-none"
+          {...attributes}
+          {...listeners}
+        >
+          <GripIcon />
+        </button>
+
+        {/* Name + parent info */}
+        <div className="flex-1 min-w-0">
+          {editingName ? (
+            <input
+              ref={nameInputRef}
+              type="text"
+              value={nameValue}
+              onChange={(e) => setNameValue(e.target.value)}
+              onKeyDown={(e) => {
+                if (e.key === "Enter") saveName();
+                if (e.key === "Escape") {
+                  setNameValue(client.name);
+                  setEditingName(false);
+                }
               }}
-              className="text-xs px-2 py-1 bg-red-600 text-white rounded hover:bg-red-700"
+              onBlur={saveName}
-            >
+              className="w-full px-2 py-1 -ml-2 text-sm font-medium rounded-md border border-gray-300 dark:border-gray-600 bg-white dark:bg-gray-900 text-gray-900 dark:text-gray-100 focus:outline-none focus:ring-2 focus:ring-brand-400"
-              Delete
+            />
-            </button>
+          ) : (
+            <div className="flex items-center gap-2 min-w-0">
+              <button
+                type="button"
+                onClick={() => setEditingName(true)}
+                className="text-sm font-medium text-gray-900 dark:text-gray-100 hover:text-brand-600 dark:hover:text-brand-400 truncate text-left cursor-text"
+                title="Click to edit name"
+              >
+                {client.name}
+                {client.code && (
+                  <span className="text-gray-400 dark:text-gray-500 font-mono ml-2 text-xs">
+                    [{client.code}]
+                  </span>
+                )}
+                {!client.isActive && (
+                  <span className="ml-2 text-xs text-gray-400 italic">inactive</span>
+                )}
+              </button>
+
+              {/* Children count badge */}
+              {hasChildren && (
+                <span className="inline-flex items-center px-1.5 py-0.5 rounded-full text-[10px] font-medium bg-gray-100 dark:bg-gray-700 text-gray-500 dark:text-gray-400 tabular-nums flex-shrink-0">
+                  {childCount}
+                </span>
+              )}
+            </div>
+          )}
+        </div>
+
+        {/* Parent selector */}
+        <div className="flex-shrink-0">
+          {showParentSelector ? (
+            <div className="flex items-center gap-1">
+              <ParentSelector
+                clients={allClients}
+                currentId={client.id}
+                currentParentId={client.parentId}
+                onChange={(newParentId) => {
+                  if (newParentId !== client.parentId) {
+                    onUpdateParent(client.id, newParentId);
+                  }
+                  setShowParentSelector(false);
+                }}
+              />
+              <button
+                type="button"
+                onClick={() => setShowParentSelector(false)}
+                className="text-xs text-gray-400 hover:text-gray-600 dark:hover:text-gray-300"
+              >
+                &times;
+              </button>
+            </div>
+          ) : (
             <button
               type="button"
-              onClick={() => setConfirmDelete(false)}
+              onClick={() => setShowParentSelector(true)}
-              className="text-xs px-2 py-1 text-gray-500 hover:text-gray-700 dark:hover:text-gray-300"
+              className="text-[11px] text-gray-400 dark:text-gray-500 hover:text-brand-500 dark:hover:text-brand-400 opacity-0 group-hover:opacity-100 transition-opacity whitespace-nowrap"
+              title="Change parent"
             >
-              Cancel
+              {parentClient ? `\u2190 ${parentClient.name}` : "\u2190 Move..."}
             </button>
-          </div>
+          )}
-        ) : (
+        </div>
-          <button
+
-            type="button"
+        {/* Tags */}
-            onClick={() => setConfirmDelete(true)}
+        <div className="flex items-center gap-1 flex-wrap flex-shrink-0">
-            className="text-gray-300 dark:text-gray-600 hover:text-red-500 dark:hover:text-red-400 opacity-0 group-hover:opacity-100 transition-opacity"
+          {client.tags.map((tag) => (
-            title="Delete client"
+            <TagPill
-          >
+              key={tag}
-            <svg width="16" height="16" viewBox="0 0 16 16" fill="none" stroke="currentColor" strokeWidth="1.5">
+              tag={tag}
-              <path d="M2 4h12M5.33 4V2.67a1.33 1.33 0 011.34-1.34h2.66a1.33 1.33 0 011.34 1.34V4m2 0v9.33a1.33 1.33 0 01-1.34 1.34H4.67a1.33 1.33 0 01-1.34-1.34V4h9.34z" />
+              onRemove={() => {
-            </svg>
+                onUpdateTags(client.id, client.tags.filter((t) => t !== tag));
-          </button>
+              }}
-        )}
+            />
+          ))}
+          {addingTag ? (
+            <TagAdder
+              existingTags={client.tags}
+              allKnownTags={allKnownTags}
+              onAdd={(tag) => {
+                onUpdateTags(client.id, [...client.tags, tag]);
+              }}
+              onClose={() => setAddingTag(false)}
+            />
+          ) : (
+            <button
+              type="button"
+              onClick={() => setAddingTag(true)}
+              className="inline-flex items-center justify-center w-5 h-5 rounded-full text-xs text-gray-400 dark:text-gray-500 hover:text-brand-500 dark:hover:text-brand-400 hover:bg-gray-100 dark:hover:bg-gray-700 opacity-0 group-hover:opacity-100 transition-opacity"
+              title="Add tag"
+            >
+              +
+            </button>
+          )}
+        </div>
+
+        {/* Sort order */}
+        <div className="flex-shrink-0 w-12">
+          {editingSortOrder ? (
+            <input
+              ref={sortInputRef}
+              type="number"
+              value={sortOrderValue}
+              onChange={(e) => setSortOrderValue(parseInt(e.target.value) || 0)}
+              onKeyDown={(e) => {
+                if (e.key === "Enter") saveSortOrder();
+                if (e.key === "Escape") {
+                  setSortOrderValue(client.sortOrder);
+                  setEditingSortOrder(false);
+                }
+              }}
+              onBlur={saveSortOrder}
+              className="w-full px-1 py-0.5 text-xs text-center rounded border border-gray-300 dark:border-gray-600 bg-white dark:bg-gray-900 text-gray-600 dark:text-gray-400 focus:outline-none focus:ring-1 focus:ring-brand-400"
+            />
+          ) : (
+            <button
+              type="button"
+              onClick={() => setEditingSortOrder(true)}
+              className="w-full text-xs text-center text-gray-400 dark:text-gray-500 hover:text-gray-600 dark:hover:text-gray-300 cursor-text tabular-nums"
+              title="Click to edit sort order"
+            >
+              #{client.sortOrder}
+            </button>
+          )}
+        </div>
+
+        {/* Delete */}
+        <div className="flex-shrink-0">
+          {confirmDelete ? (
+            <div className="flex items-center gap-1">
+              <button
+                type="button"
+                onClick={() => {
+                  onDelete(client.id);
+                  setConfirmDelete(false);
+                }}
+                className="text-xs px-2 py-1 bg-red-600 text-white rounded hover:bg-red-700"
+              >
+                Delete
+              </button>
+              <button
+                type="button"
+                onClick={() => setConfirmDelete(false)}
+                className="text-xs px-2 py-1 text-gray-500 hover:text-gray-700 dark:hover:text-gray-300"
+              >
+                Cancel
+              </button>
+            </div>
+          ) : (
+            <button
+              type="button"
+              onClick={() => setConfirmDelete(true)}
+              className="text-gray-300 dark:text-gray-600 hover:text-red-500 dark:hover:text-red-400 opacity-0 group-hover:opacity-100 transition-opacity"
+              title="Delete client"
+            >
+              <svg width="16" height="16" viewBox="0 0 16 16" fill="none" stroke="currentColor" strokeWidth="1.5">
+                <path d="M2 4h12M5.33 4V2.67a1.33 1.33 0 011.34-1.34h2.66a1.33 1.33 0 011.34 1.34V4m2 0v9.33a1.33 1.33 0 01-1.34 1.34H4.67a1.33 1.33 0 01-1.34-1.34V4h9.34z" />
+              </svg>
+            </button>
+          )}
+        </div>
       </div>
     </div>
   );
@@ -451,8 +706,10 @@ function SortableClientCard({
 export function ClientsAdminClient() {
   const [search, setSearch] = useState("");
   const [newName, setNewName] = useState("");
+  const [newParentId, setNewParentId] = useState<string | null>(null);
   const [error, setError] = useState<string | null>(null);
   const [activeId, setActiveId] = useState<string | null>(null);
+  const [collapsedIds, setCollapsedIds] = useState<Set<string>>(new Set());
   const newInputRef = useRef<HTMLInputElement>(null);
 
   const utils = trpc.useUtils();
@@ -464,6 +721,13 @@ export function ClientsAdminClient() {
     );
   }, [rawList]);
 
+  // Map for fast lookup
+  const clientMap = useMemo(() => {
+    const m = new Map<string, ClientRow>();
+    for (const c of clients) m.set(c.id, c);
+    return m;
+  }, [clients]);
+
   // All known tags across all clients for auto-suggest
   const allKnownTags = useMemo(() => {
     const set = new Set<string>();
@@ -473,17 +737,41 @@ export function ClientsAdminClient() {
     return Array.from(set).sort();
   }, [clients]);
 
-  // Filtered list
+  // Build tree, then flatten with search filtering
-  const filteredClients = useMemo(() => {
+  const tree = useMemo(() => buildTree(clients), [clients]);
-    if (!search.trim()) return clients;
+
+  // When searching: filter matching clients and include their ancestors
+  const displayNodes = useMemo(() => {
+    if (!search.trim()) {
+      return flattenTree(tree, collapsedIds);
+    }
+
     const lower = search.toLowerCase();
-    return clients.filter(
+    // Find IDs of clients matching the search
-      (c) =>
+    const matchingIds = new Set<string>();
+    for (const c of clients) {
+      if (
         c.name.toLowerCase().includes(lower) ||
         (c.code ?? "").toLowerCase().includes(lower) ||
-        (c.tags ?? []).some((t) => t.toLowerCase().includes(lower)),
+        (c.tags ?? []).some((t) => t.toLowerCase().includes(lower))
-    );
+      ) {
-  }, [clients, search]);
+        matchingIds.add(c.id);
+      }
+    }
+
+    // Also include all ancestors of matching clients so tree path is visible
+    const visibleIds = new Set(matchingIds);
+    for (const id of matchingIds) {
+      const ancestors = getAncestorIds(id, clientMap);
+      for (const aid of ancestors) visibleIds.add(aid);
+    }
+
+    // Build tree from only visible clients
+    const visibleClients = clients.filter((c) => visibleIds.has(c.id));
+    const filteredTree = buildTree(visibleClients);
+    // When searching, show all nodes expanded (don't respect collapsed state)
+    return flattenTree(filteredTree, new Set());
+  }, [search, tree, collapsedIds, clients, clientMap]);
 
   // Drag sensors
   const sensors = useSensors(
@@ -501,6 +789,7 @@ export function ClientsAdminClient() {
     onSuccess: () => {
       invalidateAll();
       setNewName("");
+      setNewParentId(null);
     },
     onError: (e) => setError(e.message),
   });
@@ -524,8 +813,16 @@ export function ClientsAdminClient() {
   function handleCreate() {
     const trimmed = newName.trim();
     if (!trimmed) return;
-    const maxSort = clients.reduce((max, c) => Math.max(max, c.sortOrder), 0);
+    // Compute max sortOrder among siblings
-    createMut.mutate({ name: trimmed, sortOrder: maxSort + 1 });
+    const siblings = clients.filter((c) =>
+      newParentId ? c.parentId === newParentId : !c.parentId,
+    );
+    const maxSort = siblings.reduce((max, c) => Math.max(max, c.sortOrder), 0);
+    createMut.mutate({
+      name: trimmed,
+      sortOrder: maxSort + 1,
+      ...(newParentId ? { parentId: newParentId } : {}),
+    });
   }
 
   function handleUpdateName(id: string, name: string) {
@@ -540,11 +837,27 @@ export function ClientsAdminClient() {
     updateMut.mutate({ id, data: { tags } });
   }
 
+  function handleUpdateParent(id: string, parentId: string | null) {
+    updateMut.mutate({ id, data: { parentId } });
+  }
+
   function handleDelete(id: string) {
     deleteMut.mutate({ id });
   }
 
-  // Drag and drop
+  function handleToggleExpand(id: string) {
+    setCollapsedIds((prev) => {
+      const next = new Set(prev);
+      if (next.has(id)) {
+        next.delete(id);
+      } else {
+        next.add(id);
+      }
+      return next;
+    });
+  }
+
+  // Drag and drop — moves the whole subtree with the dragged client
   function handleDragStart(event: DragStartEvent) {
     setActiveId(event.active.id as string);
   }
@@ -554,11 +867,34 @@ export function ClientsAdminClient() {
     const { active, over } = event;
     if (!over || active.id === over.id) return;
 
-    const oldIndex = filteredClients.findIndex((c) => c.id === active.id);
+    const oldIndex = displayNodes.findIndex((c) => c.id === active.id);
-    const newIndex = filteredClients.findIndex((c) => c.id === over.id);
+    const newIndex = displayNodes.findIndex((c) => c.id === over.id);
     if (oldIndex === -1 || newIndex === -1) return;
 
-    const reordered = arrayMove(filteredClients, oldIndex, newIndex);
+    // Get the dragged node and all its descendants (the subtree)
+    const draggedId = active.id as string;
+    const descendantIds = getDescendantIds(draggedId, clients);
+
+    // Filter display nodes to only siblings at the same parent level as the dragged node
+    const draggedClient = clientMap.get(draggedId);
+    if (!draggedClient) return;
+
+    const overClient = displayNodes[newIndex];
+    if (!overClient) return;
+
+    // Only allow reorder among siblings (same parentId)
+    if (draggedClient.parentId !== overClient.parentId) return;
+
+    // Get sibling nodes in display order (excluding descendants of dragged)
+    const siblings = displayNodes.filter(
+      (c) => c.parentId === draggedClient.parentId && !descendantIds.has(c.id),
+    );
+
+    const sibOldIndex = siblings.findIndex((c) => c.id === active.id);
+    const sibNewIndex = siblings.findIndex((c) => c.id === over.id);
+    if (sibOldIndex === -1 || sibNewIndex === -1) return;
+
+    const reordered = arrayMove(siblings, sibOldIndex, sibNewIndex);
     const updates = reordered.map((c, i) => ({ id: c.id, sortOrder: i }));
 
     // Optimistic update
@@ -575,7 +911,9 @@ export function ClientsAdminClient() {
     batchSortMut.mutate(updates);
   }
 
-  const activeClient = activeId ? filteredClients.find((c) => c.id === activeId) : null;
+  const activeClient = activeId
+    ? displayNodes.find((c) => c.id === activeId)
+    : null;
 
   return (
     <div className="p-6 max-w-4xl mx-auto">
@@ -584,11 +922,11 @@ export function ClientsAdminClient() {
         <h1 className="text-2xl font-bold text-gray-900 dark:text-gray-50">Clients</h1>
         <p className="text-sm text-gray-500 dark:text-gray-400 mt-1">
           Manage clients for project assignment and chargeability reporting{" "}
-          <InfoTooltip content="Clients are companies or brands that commission projects. Drag to reorder, click to edit inline, and use tags for categorization." />
+          <InfoTooltip content="Clients are companies or brands that commission projects. Use the tree hierarchy for parent/child relationships. Drag to reorder within a level, click to edit inline, and use tags for categorization." />
         </p>
       </div>
 
-      {/* Add new client — sticky row */}
+      {/* Add new client -- sticky row */}
       <div className="mb-4 flex items-center gap-2">
         <input
           ref={newInputRef}
@@ -601,6 +939,19 @@ export function ClientsAdminClient() {
           placeholder="New client name..."
           className="flex-1 border border-gray-300 dark:border-gray-600 rounded-xl px-4 py-2.5 text-sm bg-white dark:bg-gray-900 text-gray-900 dark:text-gray-100 placeholder-gray-400 dark:placeholder-gray-500 focus:outline-none focus:ring-2 focus:ring-brand-400 focus:border-transparent"
         />
+        <select
+          value={newParentId ?? ""}
+          onChange={(e) => setNewParentId(e.target.value || null)}
+          className="border border-gray-300 dark:border-gray-600 rounded-xl px-3 py-2.5 text-sm bg-white dark:bg-gray-900 text-gray-700 dark:text-gray-300 focus:outline-none focus:ring-2 focus:ring-brand-400 max-w-[200px]"
+          title="Parent client (optional)"
+        >
+          <option value="">No parent (top level)</option>
+          {clients.filter((c) => c.isActive).map((c) => (
+            <option key={c.id} value={c.id}>
+              {c.name}
+            </option>
+          ))}
+        </select>
         <button
           type="button"
           onClick={handleCreate}
@@ -612,7 +963,7 @@ export function ClientsAdminClient() {
       </div>
 
       {/* Search/filter */}
-      <div className="mb-4">
+      <div className="mb-4 flex items-center gap-2">
         <input
           type="search"
           value={search}
@@ -620,6 +971,25 @@ export function ClientsAdminClient() {
           placeholder="Filter by name or tag..."
           className="border border-gray-300 dark:border-gray-600 rounded-xl px-4 py-2 text-sm focus:outline-none focus:ring-2 focus:ring-brand-400 w-full sm:w-72 bg-white dark:bg-gray-900 dark:text-gray-100 placeholder-gray-400 dark:placeholder-gray-500"
         />
+        {!search && clients.length > 0 && (
+          <button
+            type="button"
+            onClick={() => {
+              // Toggle collapse all / expand all
+              const allWithChildren = clients.filter(
+                (c) => (c._count?.children ?? 0) > 0,
+              );
+              if (collapsedIds.size === 0) {
+                setCollapsedIds(new Set(allWithChildren.map((c) => c.id)));
+              } else {
+                setCollapsedIds(new Set());
+              }
+            }}
+            className="text-xs text-gray-400 dark:text-gray-500 hover:text-gray-600 dark:hover:text-gray-300 whitespace-nowrap px-2 py-1 rounded-lg hover:bg-gray-100 dark:hover:bg-gray-700"
+          >
+            {collapsedIds.size === 0 ? "Collapse all" : "Expand all"}
+          </button>
+        )}
       </div>
 
       {/* Error */}
@@ -642,13 +1012,13 @@ export function ClientsAdminClient() {
           <div className="text-center py-12 text-gray-400 dark:text-gray-500">Loading...</div>
         )}
 
-        {!isLoading && filteredClients.length === 0 && (
+        {!isLoading && displayNodes.length === 0 && (
           <div className="text-center py-12 text-gray-400 dark:text-gray-500 bg-white dark:bg-gray-800 rounded-xl border border-gray-200 dark:border-gray-700">
             {search ? "No clients match your filter." : "No clients yet. Add one above."}
           </div>
         )}
 
-        {!isLoading && filteredClients.length > 0 && (
+        {!isLoading && displayNodes.length > 0 && (
           <DndContext
             sensors={sensors}
             collisionDetection={closestCenter}
@@ -656,18 +1026,22 @@ export function ClientsAdminClient() {
             onDragEnd={handleDragEnd}
           >
             <SortableContext
-              items={filteredClients.map((c) => c.id)}
+              items={displayNodes.map((c) => c.id)}
               strategy={verticalListSortingStrategy}
             >
-              {filteredClients.map((client) => (
+              {displayNodes.map((client) => (
                 <SortableClientCard
                   key={client.id}
                   client={client}
+                  allClients={clients}
                   allKnownTags={allKnownTags}
                   onUpdateName={handleUpdateName}
                   onUpdateSortOrder={handleUpdateSortOrder}
                   onUpdateTags={handleUpdateTags}
+                  onUpdateParent={handleUpdateParent}
                   onDelete={handleDelete}
+                  onToggleExpand={handleToggleExpand}
+                  isExpanded={!collapsedIds.has(client.id)}
                 />
               ))}
             </SortableContext>
@@ -675,12 +1049,16 @@ export function ClientsAdminClient() {
             <DragOverlay>
               {activeClient ? (
                 <SortableClientCard
-                  client={activeClient}
+                  client={{ ...activeClient, depth: 0 }}
+                  allClients={clients}
                   allKnownTags={allKnownTags}
                   onUpdateName={() => {}}
                   onUpdateSortOrder={() => {}}
                   onUpdateTags={() => {}}
+                  onUpdateParent={() => {}}
                   onDelete={() => {}}
+                  onToggleExpand={() => {}}
+                  isExpanded={false}
                   isDragOverlay
                 />
               ) : null}
@@ -692,7 +1070,12 @@ export function ClientsAdminClient() {
       {/* Count */}
       {!isLoading && clients.length > 0 && (
         <div className="mt-4 text-xs text-gray-400 dark:text-gray-500 text-right">
-          {filteredClients.length} of {clients.length} client{clients.length !== 1 ? "s" : ""}
+          {displayNodes.length} of {clients.length} client{clients.length !== 1 ? "s" : ""}
+          {clients.filter((c) => c.parentId).length > 0 && (
+            <span className="ml-2">
+              ({clients.filter((c) => !c.parentId).length} top-level, {clients.filter((c) => c.parentId).length} nested)
+            </span>
+          )}
         </div>
       )}
     </div>