diff --git a/frontend/src/components/admin/CategoryRow.tsx b/frontend/src/components/admin/CategoryRow.tsx
index 69e82384..1bbec924 100644
--- a/frontend/src/components/admin/CategoryRow.tsx
+++ b/frontend/src/components/admin/CategoryRow.tsx
@@ -81,6 +81,7 @@ export function CategoryRow({
             'hover:bg-white/10 hover:text-white'
           )}
           title="Edit category"
+          aria-label="Edit category"
         >
           <Edit className="h-4 w-4" />
         </button>
@@ -94,6 +95,7 @@ export function CategoryRow({
               'hover:bg-accent hover:text-accent-foreground'
             )}
             title="Archive category"
+            aria-label="Archive category"
           >
             <Archive className="h-4 w-4" />
           </button>
@@ -106,6 +108,7 @@ export function CategoryRow({
               'hover:bg-accent hover:text-accent-foreground'
             )}
             title="Restore category"
+            aria-label="Restore category"
           >
             <RotateCcw className="h-4 w-4" />
           </button>
diff --git a/frontend/src/components/library/AddToFolderMenu.tsx b/frontend/src/components/library/AddToFolderMenu.tsx
index e87d3755..fd199f74 100644
--- a/frontend/src/components/library/AddToFolderMenu.tsx
+++ b/frontend/src/components/library/AddToFolderMenu.tsx
@@ -93,6 +93,7 @@ export function AddToFolderMenu({ treeId, onFolderCreated }: AddToFolderMenuProp
           'hover:bg-white/10 hover:text-white'
         )}
         title="Add to folder"
+        aria-label="Add to folder"
       >
         <FolderPlus className="h-4 w-4" />
       </button>
diff --git a/frontend/src/components/library/TreeGridView.tsx b/frontend/src/components/library/TreeGridView.tsx
index b11deb53..4fb0836c 100644
--- a/frontend/src/components/library/TreeGridView.tsx
+++ b/frontend/src/components/library/TreeGridView.tsx
@@ -85,6 +85,7 @@ export function TreeGridView({
                     'hover:bg-white/10 hover:text-white'
                   )}
                   title="Fork tree"
+                  aria-label="Fork tree"
                 >
                   <GitBranch className="h-4 w-4" />
                 </button>
@@ -97,6 +98,7 @@ export function TreeGridView({
                     'hover:bg-white/10 hover:text-white'
                   )}
                   title="Edit tree"
+                  aria-label="Edit tree"
                 >
                   <Pencil className="h-4 w-4" />
                 </Link>
@@ -110,6 +112,7 @@ export function TreeGridView({
                     'hover:bg-red-400/10 hover:text-red-400'
                   )}
                   title="Delete tree"
+                  aria-label="Delete tree"
                 >
                   <Trash2 className="h-4 w-4" />
                 </button>
diff --git a/frontend/src/components/library/TreeListView.tsx b/frontend/src/components/library/TreeListView.tsx
index f4dd9264..0916843f 100644
--- a/frontend/src/components/library/TreeListView.tsx
+++ b/frontend/src/components/library/TreeListView.tsx
@@ -88,6 +88,7 @@ export function TreeListView({
                     'hover:bg-white/10 hover:text-white'
                   )}
                   title="Fork tree"
+                  aria-label="Fork tree"
                 >
                   <GitBranch className="h-4 w-4" />
                 </button>
@@ -100,6 +101,7 @@ export function TreeListView({
                     'hover:bg-white/10 hover:text-white'
                   )}
                   title="Edit tree"
+                  aria-label="Edit tree"
                 >
                   <Pencil className="h-4 w-4" />
                 </Link>
diff --git a/frontend/src/components/library/TreeTableView.tsx b/frontend/src/components/library/TreeTableView.tsx
index 5669d95d..cd23f5a5 100644
--- a/frontend/src/components/library/TreeTableView.tsx
+++ b/frontend/src/components/library/TreeTableView.tsx
@@ -192,6 +192,7 @@ export function TreeTableView({
                         'hover:bg-white/10 hover:text-white'
                       )}
                       title="Fork tree"
+                      aria-label="Fork tree"
                     >
                       <GitBranch className="h-3.5 w-3.5" />
                     </button>
@@ -204,6 +205,7 @@ export function TreeTableView({
                         'hover:bg-white/10 hover:text-white'
                       )}
                       title="Edit tree"
+                      aria-label="Edit tree"
                     >
                       <Pencil className="h-3.5 w-3.5" />
                     </Link>
diff --git a/frontend/src/components/library/ViewToggle.tsx b/frontend/src/components/library/ViewToggle.tsx
index a6056622..20037a89 100644
--- a/frontend/src/components/library/ViewToggle.tsx
+++ b/frontend/src/components/library/ViewToggle.tsx
@@ -22,6 +22,7 @@ export function ViewToggle({ view, onChange, className }: ViewToggleProps) {
             : 'text-white/50 hover:bg-white/[0.06] hover:text-white'
         )}
         title="Grid view"
+        aria-label="Grid view"
       >
         <LayoutGrid className="h-4 w-4" />
       </button>
@@ -35,6 +36,7 @@ export function ViewToggle({ view, onChange, className }: ViewToggleProps) {
             : 'text-white/50 hover:bg-white/[0.06] hover:text-white'
         )}
         title="List view"
+        aria-label="List view"
       >
         <List className="h-4 w-4" />
       </button>
@@ -48,6 +50,7 @@ export function ViewToggle({ view, onChange, className }: ViewToggleProps) {
             : 'text-white/50 hover:bg-white/[0.06] hover:text-white'
         )}
         title="Table view"
+        aria-label="Table view"
       >
         <Table className="h-4 w-4" />
       </button>
diff --git a/frontend/src/components/session/ScratchpadSidebar.tsx b/frontend/src/components/session/ScratchpadSidebar.tsx
index 3508b2f2..4cc8d206 100644
--- a/frontend/src/components/session/ScratchpadSidebar.tsx
+++ b/frontend/src/components/session/ScratchpadSidebar.tsx
@@ -1,5 +1,5 @@
 import { useState, useEffect, useRef, useCallback } from 'react'
-import { cn } from '@/lib/utils'
+import { cn, safeGetItem, safeSetItem } from '@/lib/utils'
 import { MarkdownContent } from '@/components/ui/MarkdownContent'
 import { StickyNote, X, Eye, Pencil, Loader2 } from 'lucide-react'
 
@@ -14,7 +14,7 @@ export function ScratchpadSidebar({ sessionId, initialContent, onSave, onOpenCha
   const [content, setContent] = useState(initialContent)
   const [lastSaved, setLastSaved] = useState(initialContent)
   const [isCollapsed, setIsCollapsed] = useState(() => {
-    return localStorage.getItem('scratchpad-collapsed') !== 'false'
+    return safeGetItem('scratchpad-collapsed') !== 'false'
   })
   const [isSaving, setIsSaving] = useState(false)
   const [showPreview, setShowPreview] = useState(false)
@@ -43,7 +43,7 @@ export function ScratchpadSidebar({ sessionId, initialContent, onSave, onOpenCha
 
   // Persist collapse state and notify parent
   useEffect(() => {
-    localStorage.setItem('scratchpad-collapsed', String(isCollapsed))
+    safeSetItem('scratchpad-collapsed', String(isCollapsed))
     onOpenChange?.(!isCollapsed)
   }, [isCollapsed, onOpenChange])
 
@@ -130,6 +130,7 @@ export function ScratchpadSidebar({ sessionId, initialContent, onSave, onOpenCha
           isCollapsed ? 'opacity-100' : 'pointer-events-none opacity-0'
         )}
         title="Open scratchpad (Ctrl+/)"
+        aria-label="Open scratchpad (Ctrl+/)"
       >
         <StickyNote className="h-5 w-5" />
         {hasUnsavedChanges && (
@@ -176,6 +177,7 @@ export function ScratchpadSidebar({ sessionId, initialContent, onSave, onOpenCha
               onClick={() => setIsCollapsed(true)}
               className="rounded p-1 text-white/40 hover:bg-white/10 hover:text-white"
               title="Close scratchpad"
+              aria-label="Close scratchpad"
             >
               <X className="h-4 w-4" />
             </button>
diff --git a/frontend/src/components/tree-editor/DynamicArrayField.tsx b/frontend/src/components/tree-editor/DynamicArrayField.tsx
index 55860a89..7b3b00e0 100644
--- a/frontend/src/components/tree-editor/DynamicArrayField.tsx
+++ b/frontend/src/components/tree-editor/DynamicArrayField.tsx
@@ -53,6 +53,7 @@ export function DynamicArrayField<T>({
                 disabled={index === 0}
                 className="rounded p-0.5 text-white/50 hover:bg-white/[0.06] hover:text-white disabled:opacity-30"
                 title="Move up"
+                aria-label="Move up"
               >
                 <ChevronUp className="h-3 w-3" />
               </button>
@@ -62,6 +63,7 @@ export function DynamicArrayField<T>({
                 disabled={index === items.length - 1}
                 className="rounded p-0.5 text-white/50 hover:bg-white/[0.06] hover:text-white disabled:opacity-30"
                 title="Move down"
+                aria-label="Move down"
               >
                 <ChevronDown className="h-3 w-3" />
               </button>
@@ -78,6 +80,7 @@ export function DynamicArrayField<T>({
               onClick={() => onRemove(index)}
               className="mt-1 rounded p-1 text-white/50 hover:bg-red-400/20 hover:text-red-400"
               title="Remove"
+              aria-label="Remove"
             >
               <Trash2 className="h-4 w-4" />
             </button>
diff --git a/frontend/src/components/tree-editor/NodeList.tsx b/frontend/src/components/tree-editor/NodeList.tsx
index 3ac0e314..dddcfbb1 100644
--- a/frontend/src/components/tree-editor/NodeList.tsx
+++ b/frontend/src/components/tree-editor/NodeList.tsx
@@ -286,6 +286,7 @@ function NodeListItem({
                 onAddChild(node.id)
               }}
               title="Add child node"
+              aria-label="Add child node"
               className="rounded p-1 text-muted-foreground hover:bg-accent hover:text-accent-foreground"
             >
               <Plus className="h-3 w-3" />
@@ -298,6 +299,7 @@ function NodeListItem({
               onEdit(node)
             }}
             title="Edit node"
+            aria-label="Edit node"
             className="rounded p-1 text-muted-foreground hover:bg-accent hover:text-accent-foreground"
           >
             <Pencil className="h-3 w-3" />
@@ -311,6 +313,7 @@ function NodeListItem({
                   onDuplicate(node.id)
                 }}
                 title="Duplicate node"
+                aria-label="Duplicate node"
                 className="rounded p-1 text-muted-foreground hover:bg-accent hover:text-accent-foreground"
               >
                 <Copy className="h-3 w-3" />
@@ -322,6 +325,7 @@ function NodeListItem({
                   onDelete(node.id)
                 }}
                 title="Delete node"
+                aria-label="Delete node"
                 className="rounded p-1 text-muted-foreground hover:bg-destructive/20 hover:text-destructive"
               >
                 <Trash2 className="h-3 w-3" />
diff --git a/frontend/src/lib/utils.ts b/frontend/src/lib/utils.ts
index d32b0fe6..f7609093 100644
--- a/frontend/src/lib/utils.ts
+++ b/frontend/src/lib/utils.ts
@@ -4,3 +4,28 @@ import { twMerge } from 'tailwind-merge'
 export function cn(...inputs: ClassValue[]) {
   return twMerge(clsx(inputs))
 }
+
+/** Safe localStorage access — returns null on error (e.g. private browsing) */
+export function safeGetItem(key: string): string | null {
+  try {
+    return localStorage.getItem(key)
+  } catch {
+    return null
+  }
+}
+
+export function safeSetItem(key: string, value: string): void {
+  try {
+    localStorage.setItem(key, value)
+  } catch {
+    // Storage full or unavailable — silently fail
+  }
+}
+
+export function safeRemoveItem(key: string): void {
+  try {
+    localStorage.removeItem(key)
+  } catch {
+    // Storage unavailable — silently fail
+  }
+}
diff --git a/frontend/src/pages/TreeEditorPage.tsx b/frontend/src/pages/TreeEditorPage.tsx
index 54bee6f1..f847524f 100644
--- a/frontend/src/pages/TreeEditorPage.tsx
+++ b/frontend/src/pages/TreeEditorPage.tsx
@@ -10,7 +10,7 @@ import { TreeEditorLayout } from '@/components/tree-editor/TreeEditorLayout'
 import { ValidationSummary } from '@/components/tree-editor/ValidationSummary'
 import { useKeyboardShortcuts } from '@/hooks/useKeyboardShortcuts'
 import { usePermissions } from '@/hooks/usePermissions'
-import { cn } from '@/lib/utils'
+import { cn, safeGetItem } from '@/lib/utils'
 import { toast } from '@/lib/toast'
 
 export function TreeEditorPage() {
@@ -156,7 +156,7 @@ export function TreeEditorPage() {
         initNewTree()
         setTreeStatus('draft') // New trees start as draft
         // Check for draft after initializing
-        const draftExists = localStorage.getItem('tree-editor-draft') !== null
+        const draftExists = safeGetItem('tree-editor-draft') !== null
         if (draftExists) {
           setShowDraftPrompt(true)
         }
diff --git a/frontend/src/pages/TreeLibraryPage.tsx b/frontend/src/pages/TreeLibraryPage.tsx
index c8ea2cf5..9d355cfa 100644
--- a/frontend/src/pages/TreeLibraryPage.tsx
+++ b/frontend/src/pages/TreeLibraryPage.tsx
@@ -58,8 +58,16 @@ export function TreeLibraryPage() {
     }
   }, [])
 
+  // Load categories once on mount (they rarely change)
   useEffect(() => {
-    loadData()
+    categoriesApi.list()
+      .then(setCategories)
+      .catch((err) => console.error('Failed to load categories:', err))
+  }, [])
+
+  // Load trees when filters change
+  useEffect(() => {
+    loadTrees()
   }, [selectedCategoryId, selectedTags, selectedFolderId, treeLibrarySortBy, showDrafts])
 
   // Load folders on mount and listen for changes
@@ -70,21 +78,17 @@ export function TreeLibraryPage() {
     return () => window.removeEventListener('folder-changed', handleFolderChange)
   }, [loadFolders])
 
-  const loadData = async () => {
+  const loadTrees = async () => {
     setIsLoading(true)
     try {
-      const [treesData, categoriesData] = await Promise.all([
-        treesApi.list({
-          category_id: selectedCategoryId || undefined,
-          tags: selectedTags.length > 0 ? selectedTags.join(',') : undefined,
-          folder_id: selectedFolderId || undefined,
-          sort_by: treeLibrarySortBy,
-          include_drafts: showDrafts || undefined,
-        }),
-        categoriesApi.list(),
-      ])
+      const treesData = await treesApi.list({
+        category_id: selectedCategoryId || undefined,
+        tags: selectedTags.length > 0 ? selectedTags.join(',') : undefined,
+        folder_id: selectedFolderId || undefined,
+        sort_by: treeLibrarySortBy,
+        include_drafts: showDrafts || undefined,
+      })
       setTrees(treesData)
-      setCategories(categoriesData)
     } catch (err) {
       toast.error('Failed to load trees')
       console.error(err)
@@ -95,7 +99,7 @@ export function TreeLibraryPage() {
 
   const handleSearch = async () => {
     if (!searchQuery.trim()) {
-      loadData()
+      loadTrees()
       return
     }
     setIsLoading(true)
@@ -413,7 +417,7 @@ export function TreeLibraryPage() {
           setFolderModalOpen(false)
           setNewFolderParentId(null)
         }}
-        onSave={loadData}
+        onSave={loadTrees}
       />
 
       {/* Delete Confirmation */}
diff --git a/frontend/src/pages/TreeNavigationPage.tsx b/frontend/src/pages/TreeNavigationPage.tsx
index 5fe04a39..19ea936a 100644
--- a/frontend/src/pages/TreeNavigationPage.tsx
+++ b/frontend/src/pages/TreeNavigationPage.tsx
@@ -4,7 +4,7 @@ import { treesApi, sessionsApi } from '@/api'
 import { useTreeNavigationShortcuts } from '@/hooks/useKeyboardShortcuts'
 import { useCustomStepFlow } from '@/hooks/useCustomStepFlow'
 import type { Tree, Session, DecisionRecord, TreeStructure } from '@/types'
-import { cn } from '@/lib/utils'
+import { cn, safeGetItem } from '@/lib/utils'
 import { MarkdownContent } from '@/components/ui/MarkdownContent'
 import { CustomStepModal } from '@/components/step-library/CustomStepModal'
 import { PostStepActionModal, ContinuationModal, ForkTreeModal, ScratchpadSidebar } from '@/components/session'
@@ -37,7 +37,7 @@ export function TreeNavigationPage() {
 
   // Scratchpad state
   const [scratchpadOpen, setScratchpadOpen] = useState(() => {
-    return localStorage.getItem('scratchpad-collapsed') === 'false'
+    return safeGetItem('scratchpad-collapsed') === 'false'
   })
 
   const findNode = (nodeId: string, structure?: TreeStructure): TreeStructure | null => {
diff --git a/frontend/src/store/treeEditorStore.ts b/frontend/src/store/treeEditorStore.ts
index f9509954..6e810fb4 100644
--- a/frontend/src/store/treeEditorStore.ts
+++ b/frontend/src/store/treeEditorStore.ts
@@ -4,6 +4,7 @@ import { shallow } from 'zustand/shallow'
 import { immer } from 'zustand/middleware/immer'
 import type { Tree, TreeStructure, TreeCreate, TreeUpdate, NodeType, TreeMarkdownValidationError, TreeMarkdownValidation } from '@/types'
 import { treeStructureToMarkdownPreview } from '@/lib/treeMarkdownSync'
+import { safeGetItem, safeSetItem, safeRemoveItem } from '@/lib/utils'
 
 // Throttle helper: captures first call immediately, then throttles subsequent calls
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
@@ -304,7 +305,7 @@ export const useTreeEditorStore = create<TreeEditorState>()(
 
       // Check for existing draft on init
       initNewTree: () => {
-        const hasDraft = localStorage.getItem(DRAFT_STORAGE_KEY) !== null
+        const hasDraft = safeGetItem(DRAFT_STORAGE_KEY) !== null
         set((state) => {
           state.treeId = null
           state.name = ''
@@ -360,7 +361,7 @@ export const useTreeEditorStore = create<TreeEditorState>()(
       },
 
       loadDraft: () => {
-        const draftJson = localStorage.getItem(DRAFT_STORAGE_KEY)
+        const draftJson = safeGetItem(DRAFT_STORAGE_KEY)
         if (!draftJson) return false
 
         try {
@@ -380,13 +381,13 @@ export const useTreeEditorStore = create<TreeEditorState>()(
           })
           return true
         } catch {
-          localStorage.removeItem(DRAFT_STORAGE_KEY)
+          safeRemoveItem(DRAFT_STORAGE_KEY)
           return false
         }
       },
 
       discardDraft: () => {
-        localStorage.removeItem(DRAFT_STORAGE_KEY)
+        safeRemoveItem(DRAFT_STORAGE_KEY)
         set((state) => {
           state.hasDraft = false
         })
@@ -868,12 +869,12 @@ export const useTreeEditorStore = create<TreeEditorState>()(
           treeStructure: state.treeStructure,
           savedAt: new Date().toISOString()
         }
-        localStorage.setItem(DRAFT_STORAGE_KEY, JSON.stringify(draft))
+        safeSetItem(DRAFT_STORAGE_KEY, JSON.stringify(draft))
         set((s) => { s.draftSavedAt = new Date() })
       },
 
       markSaved: () => {
-        localStorage.removeItem(DRAFT_STORAGE_KEY)
+        safeRemoveItem(DRAFT_STORAGE_KEY)
         set((state) => {
           state.isDirty = false
           state.lastSavedAt = new Date()