diff --git a/.kiro/specs/user-auth-and-sharing/tasks.md b/.kiro/specs/user-auth-and-sharing/tasks.md
index e30d9d4..a978f91 100644
--- a/.kiro/specs/user-auth-and-sharing/tasks.md
+++ b/.kiro/specs/user-auth-and-sharing/tasks.md
@@ -208,7 +208,7 @@
   - Add invitations page
   - _Requirements: 5.1, 5.4, 8.1, 8.2_
 
-- [-] 14. Implement profile management
+- [x] 14. Implement profile management
   - Create profile page and ProfileForm component
   - Implement updateProfile server action
   - Create PasswordChangeForm component
@@ -236,7 +236,7 @@
   - **Property 29: Profile data exposure protection**
   - **Validates: Requirements 7.5**
 
-- [ ] 15. Update existing components for multi-user
+- [x] 15. Update existing components for multi-user
   - Modify ListCard to show sharing indicator
   - Update ListDetailView with share button and permission display
   - Modify ItemForm to disable editing for viewers
diff --git a/app/list/[id]/item/[itemId]/edit/page.tsx b/app/list/[id]/item/[itemId]/edit/page.tsx
index ad4a7fe..10cb47c 100644
--- a/app/list/[id]/item/[itemId]/edit/page.tsx
+++ b/app/list/[id]/item/[itemId]/edit/page.tsx
@@ -1,5 +1,7 @@
 import { notFound } from 'next/navigation'
 import { getItem } from '@/lib/actions'
+import { canEditList } from '@/lib/permissions'
+import { auth } from '@/auth'
 import ItemForm from '@/components/ItemForm'
 import Link from 'next/link'
 import { ArrowLeft } from 'lucide-react'
@@ -14,12 +16,20 @@ interface PageProps {
 }
 
 export default async function EditItemPage({ params }: PageProps) {
+  const session = await auth()
+  if (!session?.user?.id) {
+    notFound()
+  }
+
   const item = await getItem(params.itemId)
 
   if (!item || item.listId !== params.id) {
     notFound()
   }
 
+  // Check if user can edit this list
+  const canEdit = await canEditList(session.user.id, params.id)
+
   return (
     <main className="container mx-auto px-4 sm:px-6 py-6 sm:py-8 max-w-3xl">
       {/* Header */}
@@ -36,7 +46,7 @@ export default async function EditItemPage({ params }: PageProps) {
 
       {/* Form */}
       <div className="bg-white rounded-lg shadow-sm border border-gray-200 p-5 sm:p-6 lg:p-8">
-        <ItemForm listId={params.id} item={item} mode="edit" />
+        <ItemForm listId={params.id} item={item} mode="edit" canEdit={canEdit} />
       </div>
     </main>
   )
diff --git a/app/list/[id]/item/[itemId]/page.tsx b/app/list/[id]/item/[itemId]/page.tsx
index 498eb55..410759d 100644
--- a/app/list/[id]/item/[itemId]/page.tsx
+++ b/app/list/[id]/item/[itemId]/page.tsx
@@ -1,5 +1,7 @@
 import { notFound } from 'next/navigation'
 import { getItem } from '@/lib/actions'
+import { canEditList } from '@/lib/permissions'
+import { auth } from '@/auth'
 import ItemDetail from '@/components/ItemDetail'
 import Link from 'next/link'
 import { ArrowLeft, Edit } from 'lucide-react'
@@ -16,12 +18,29 @@ interface PageProps {
 }
 
 export default async function ItemDetailPage({ params }: PageProps) {
-  const item = await getItem(params.itemId)
-
-  if (!item || item.listId !== params.id) {
+  const session = await auth()
+  if (!session?.user?.id) {
     notFound()
   }
 
+  const itemData = await getItem(params.itemId)
+
+  if (!itemData || itemData.listId !== params.id) {
+    notFound()
+  }
+
+  // Type assertion for the item with list relation
+  const item = itemData as typeof itemData & {
+    list: {
+      title: string
+      color: string
+      ownerId: string
+    }
+  }
+
+  // Check if user can edit this list
+  const canEdit = await canEditList(session.user.id, params.id)
+
   return (
     <main className="container mx-auto px-4 sm:px-6 py-6 sm:py-8 max-w-4xl">
       {/* Header Actions */}
@@ -35,21 +54,40 @@ export default async function ItemDetailPage({ params }: PageProps) {
         </Link>
 
         <div className="flex items-center gap-2 w-full sm:w-auto">
-          <ToggleItemButton itemId={item.id} completed={item.completed} />
-          <Link
-            href={`/list/${params.id}/item/${params.itemId}/edit`}
-            className="flex items-center gap-2 px-4 sm:px-5 py-2.5 sm:py-3 bg-blue-500 hover:bg-blue-600 active:bg-blue-700 text-white rounded-lg transition-colors tap-target text-sm sm:text-base font-medium"
-          >
-            <Edit size={18} className="flex-shrink-0" />
-            <span>Edit</span>
-          </Link>
-          <DeleteItemButton itemId={item.id} listId={params.id} />
+          {canEdit && (
+            <>
+              <ToggleItemButton itemId={item.id} completed={item.completed} />
+              <Link
+                href={`/list/${params.id}/item/${params.itemId}/edit`}
+                className="flex items-center gap-2 px-4 sm:px-5 py-2.5 sm:py-3 bg-blue-500 hover:bg-blue-600 active:bg-blue-700 text-white rounded-lg transition-colors tap-target text-sm sm:text-base font-medium"
+              >
+                <Edit size={18} className="flex-shrink-0" />
+                <span>Edit</span>
+              </Link>
+              <DeleteItemButton itemId={item.id} listId={params.id} />
+            </>
+          )}
         </div>
       </div>
 
       {/* Item Detail */}
       <div className="bg-white rounded-lg shadow-sm border border-gray-200 p-5 sm:p-6 lg:p-8">
-        <ItemDetail item={item} listTitle={item.list.title} />
+        <ItemDetail 
+          item={{
+            id: item.id,
+            title: item.title,
+            description: item.description,
+            completed: item.completed,
+            priority: item.priority,
+            dueDate: item.dueDate,
+            tags: item.tags,
+            notes: item.notes,
+            createdAt: item.createdAt,
+            updatedAt: item.updatedAt,
+            listId: item.listId,
+          }} 
+          listTitle={item.list.title} 
+        />
       </div>
     </main>
   )
diff --git a/app/list/[id]/page.tsx b/app/list/[id]/page.tsx
index 0637101..3c9dd09 100644
--- a/app/list/[id]/page.tsx
+++ b/app/list/[id]/page.tsx
@@ -1,4 +1,6 @@
 import { getListWithItems } from '@/lib/actions'
+import { getPermission } from '@/lib/permissions'
+import { auth } from '@/auth'
 import { notFound } from 'next/navigation'
 import Link from 'next/link'
 import { ArrowLeft } from 'lucide-react'
@@ -8,12 +10,25 @@ import ListDetailView from '@/components/ListDetailView'
 export const dynamic = 'force-dynamic'
 
 export default async function ListDetailPage({ params }: { params: { id: string } }) {
+  const session = await auth()
+  if (!session?.user?.id) {
+    notFound()
+  }
+
   const list = await getListWithItems(params.id)
 
   if (!list) {
     notFound()
   }
 
+  // Get user's permission for this list
+  const permission = await getPermission(session.user.id, params.id)
+  if (!permission) {
+    notFound()
+  }
+
+  const canShare = permission === 'owner'
+  const canEdit = permission === 'owner' || permission === 'editor'
   const completedItems = list.items.filter(item => item.completed)
 
   return (
@@ -41,13 +56,28 @@ export default async function ListDetailPage({ params }: { params: { id: string
         </p>
       </div>
 
-      {/* Inline Item Creation */}
-      <div className="mb-6 sm:mb-8">
-        <InlineItemCreate listId={list.id} />
-      </div>
+      {/* Inline Item Creation - only show if user can edit */}
+      {canEdit && (
+        <div className="mb-6 sm:mb-8">
+          <InlineItemCreate listId={list.id} />
+        </div>
+      )}
 
       {/* Search, Filter, and Items List */}
-      <ListDetailView listId={list.id} initialItems={list.items} />
+      <ListDetailView 
+        listId={list.id} 
+        initialItems={list.items}
+        permission={permission}
+        canShare={canShare}
+        listTitle={list.title}
+        ownerId={list.ownerId}
+        ownerName={list.owner?.name}
+        ownerEmail={list.owner?.email || ''}
+        collaborators={list.collaborators.map(c => ({
+          ...c,
+          permission: c.permission as 'editor' | 'viewer'
+        }))}
+      />
     </main>
   )
 }
diff --git a/components/ItemForm.tsx b/components/ItemForm.tsx
index 1fbaf32..2a58988 100644
--- a/components/ItemForm.tsx
+++ b/components/ItemForm.tsx
@@ -26,9 +26,10 @@ interface ItemFormProps {
     notes: string | null
   }
   mode?: 'create' | 'edit'
+  canEdit?: boolean
 }
 
-export default function ItemForm({ listId, item, mode = 'edit' }: ItemFormProps) {
+export default function ItemForm({ listId, item, mode = 'edit', canEdit = true }: ItemFormProps) {
   const router = useRouter()
   const { showToast } = useToast()
   const [isSubmitting, setIsSubmitting] = useState(false)
@@ -157,6 +158,11 @@ export default function ItemForm({ listId, item, mode = 'edit' }: ItemFormProps)
   const handleSubmit = async (e: React.FormEvent) => {
     e.preventDefault()
 
+    if (!canEdit) {
+      showToast('You do not have permission to edit this item', 'error')
+      return
+    }
+
     if (!validateForm()) {
       showToast('Please fix validation errors', 'error')
       return
@@ -238,6 +244,14 @@ export default function ItemForm({ listId, item, mode = 'edit' }: ItemFormProps)
 
   return (
     <form onSubmit={handleSubmit} className="space-y-5 sm:space-y-6">
+      {!canEdit && (
+        <div className="p-3 sm:p-4 bg-yellow-50 border border-yellow-200 rounded-lg">
+          <p className="text-xs sm:text-sm text-yellow-800">
+            You have view-only access to this list. You cannot edit items.
+          </p>
+        </div>
+      )}
+
       {/* Title */}
       <div>
         <label htmlFor="title" className="block text-sm font-medium text-gray-700 mb-2">
@@ -249,11 +263,12 @@ export default function ItemForm({ listId, item, mode = 'edit' }: ItemFormProps)
           value={title}
           onChange={(e) => setTitle(e.target.value)}
           onBlur={() => handleBlur('title')}
+          disabled={!canEdit}
           className={`w-full px-3 sm:px-4 py-3 border rounded-lg focus:outline-none focus:ring-2 text-sm sm:text-base ${
             errors.title && touched.title
               ? 'border-red-500 focus:ring-red-500'
               : 'border-gray-300 focus:ring-blue-500'
-          }`}
+          } ${!canEdit ? 'bg-gray-100 cursor-not-allowed' : ''}`}
           placeholder="Enter task title"
           maxLength={200}
           aria-invalid={errors.title && touched.title ? 'true' : 'false'}
@@ -276,12 +291,13 @@ export default function ItemForm({ listId, item, mode = 'edit' }: ItemFormProps)
           value={description}
           onChange={(e) => setDescription(e.target.value)}
           onBlur={() => handleBlur('description')}
+          disabled={!canEdit}
           rows={3}
           className={`w-full px-3 sm:px-4 py-3 border rounded-lg focus:outline-none focus:ring-2 text-sm sm:text-base resize-y ${
             errors.description && touched.description
               ? 'border-red-500 focus:ring-red-500'
               : 'border-gray-300 focus:ring-blue-500'
-          }`}
+          } ${!canEdit ? 'bg-gray-100 cursor-not-allowed' : ''}`}
           placeholder="Add a description"
           maxLength={2000}
           aria-invalid={errors.description && touched.description ? 'true' : 'false'}
@@ -303,7 +319,8 @@ export default function ItemForm({ listId, item, mode = 'edit' }: ItemFormProps)
           id="priority"
           value={priority}
           onChange={(e) => setPriority(e.target.value as 'low' | 'medium' | 'high')}
-          className="w-full px-3 sm:px-4 py-3 border border-gray-300 rounded-lg focus:outline-none focus:ring-2 focus:ring-blue-500 text-sm sm:text-base tap-target"
+          disabled={!canEdit}
+          className={`w-full px-3 sm:px-4 py-3 border border-gray-300 rounded-lg focus:outline-none focus:ring-2 focus:ring-blue-500 text-sm sm:text-base tap-target ${!canEdit ? 'bg-gray-100 cursor-not-allowed' : ''}`}
         >
           <option value="low">Low</option>
           <option value="medium">Medium</option>
@@ -322,11 +339,12 @@ export default function ItemForm({ listId, item, mode = 'edit' }: ItemFormProps)
           value={dueDate}
           onChange={(e) => setDueDate(e.target.value)}
           onBlur={() => handleBlur('dueDate')}
+          disabled={!canEdit}
           className={`w-full px-3 sm:px-4 py-3 border rounded-lg focus:outline-none focus:ring-2 text-sm sm:text-base tap-target ${
             errors.dueDate && touched.dueDate
               ? 'border-red-500 focus:ring-red-500'
               : 'border-gray-300 focus:ring-blue-500'
-          }`}
+          } ${!canEdit ? 'bg-gray-100 cursor-not-allowed' : ''}`}
           min="1900-01-01"
           max="2100-12-31"
           aria-invalid={errors.dueDate && touched.dueDate ? 'true' : 'false'}
@@ -351,11 +369,12 @@ export default function ItemForm({ listId, item, mode = 'edit' }: ItemFormProps)
             value={tagInput}
             onChange={(e) => setTagInput(e.target.value)}
             onKeyDown={handleKeyDown}
+            disabled={!canEdit}
             className={`flex-1 px-3 sm:px-4 py-3 border rounded-lg focus:outline-none focus:ring-2 text-sm sm:text-base ${
               errors.tagInput
                 ? 'border-red-500 focus:ring-red-500'
                 : 'border-gray-300 focus:ring-blue-500'
-            }`}
+            } ${!canEdit ? 'bg-gray-100 cursor-not-allowed' : ''}`}
             placeholder="Add a tag"
             maxLength={50}
             aria-invalid={errors.tagInput ? 'true' : 'false'}
@@ -364,7 +383,7 @@ export default function ItemForm({ listId, item, mode = 'edit' }: ItemFormProps)
           <button
             type="button"
             onClick={handleAddTag}
-            disabled={tags.length >= 20}
+            disabled={tags.length >= 20 || !canEdit}
             className="px-4 sm:px-5 py-3 bg-gray-200 hover:bg-gray-300 active:bg-gray-400 disabled:bg-gray-100 disabled:text-gray-400 text-gray-700 rounded-lg transition-colors tap-target text-sm sm:text-base font-medium"
           >
             Add
@@ -389,7 +408,8 @@ export default function ItemForm({ listId, item, mode = 'edit' }: ItemFormProps)
                 <button
                   type="button"
                   onClick={() => handleRemoveTag(tag)}
-                  className="hover:text-blue-600 active:text-blue-700 tap-target-sm text-lg leading-none"
+                  disabled={!canEdit}
+                  className="hover:text-blue-600 active:text-blue-700 tap-target-sm text-lg leading-none disabled:opacity-50 disabled:cursor-not-allowed"
                   aria-label={`Remove ${tag} tag`}
                 >
                   ×
@@ -410,12 +430,13 @@ export default function ItemForm({ listId, item, mode = 'edit' }: ItemFormProps)
           value={notes}
           onChange={(e) => setNotes(e.target.value)}
           onBlur={() => handleBlur('notes')}
+          disabled={!canEdit}
           rows={5}
           className={`w-full px-3 sm:px-4 py-3 border rounded-lg focus:outline-none focus:ring-2 text-sm sm:text-base resize-y ${
             errors.notes && touched.notes
               ? 'border-red-500 focus:ring-red-500'
               : 'border-gray-300 focus:ring-blue-500'
-          }`}
+          } ${!canEdit ? 'bg-gray-100 cursor-not-allowed' : ''}`}
           placeholder="Add additional notes"
           maxLength={5000}
           aria-invalid={errors.notes && touched.notes ? 'true' : 'false'}
@@ -442,15 +463,17 @@ export default function ItemForm({ listId, item, mode = 'edit' }: ItemFormProps)
           onClick={() => router.back()}
           className="w-full sm:w-auto px-4 sm:px-5 py-3 bg-gray-200 hover:bg-gray-300 active:bg-gray-400 text-gray-700 rounded-lg transition-colors tap-target font-medium text-sm sm:text-base"
         >
-          Cancel
-        </button>
-        <button
-          type="submit"
-          disabled={isSubmitting}
-          className="w-full sm:flex-1 bg-blue-500 hover:bg-blue-600 active:bg-blue-700 disabled:bg-blue-300 text-white px-4 sm:px-5 py-3 rounded-lg transition-colors tap-target font-medium text-sm sm:text-base"
-        >
-          {isSubmitting ? 'Saving...' : mode === 'create' ? 'Create Task' : 'Save Changes'}
+          {canEdit ? 'Cancel' : 'Back'}
         </button>
+        {canEdit && (
+          <button
+            type="submit"
+            disabled={isSubmitting}
+            className="w-full sm:flex-1 bg-blue-500 hover:bg-blue-600 active:bg-blue-700 disabled:bg-blue-300 text-white px-4 sm:px-5 py-3 rounded-lg transition-colors tap-target font-medium text-sm sm:text-base"
+          >
+            {isSubmitting ? 'Saving...' : mode === 'create' ? 'Create Task' : 'Save Changes'}
+          </button>
+        )}
       </div>
     </form>
   )
diff --git a/components/ListCard.tsx b/components/ListCard.tsx
index b3cb0dc..ad7a2d3 100644
--- a/components/ListCard.tsx
+++ b/components/ListCard.tsx
@@ -2,7 +2,7 @@
 
 import { memo, useState } from 'react'
 import Link from 'next/link'
-import { Edit2 } from 'lucide-react'
+import { Edit2, Users } from 'lucide-react'
 import Modal from './Modal'
 import ListForm from './ListForm'
 import DeleteListButton from './DeleteListButton'
@@ -15,6 +15,11 @@ interface List {
     id: string
     completed: boolean
   }>
+  collaborators?: Array<{
+    id: string
+    userId: string
+    permission: string
+  }>
 }
 
 function ListCard({ list }: { list: List }) {
@@ -22,6 +27,7 @@ function ListCard({ list }: { list: List }) {
   const completedCount = list.items.filter(item => item.completed).length
   const totalCount = list.items.length
   const progress = totalCount > 0 ? (completedCount / totalCount) * 100 : 0
+  const hasCollaborators = list.collaborators && list.collaborators.length > 0
 
   const handleEditClick = (e: React.MouseEvent) => {
     e.preventDefault()
@@ -45,6 +51,12 @@ function ListCard({ list }: { list: List }) {
                 style={{ backgroundColor: list.color }}
               />
               <h3 className="font-semibold text-gray-900 truncate text-base sm:text-lg">{list.title}</h3>
+              {hasCollaborators && list.collaborators && (
+                <div className="flex items-center gap-1 text-gray-500 flex-shrink-0" title={`Shared with ${list.collaborators.length} ${list.collaborators.length === 1 ? 'person' : 'people'}`}>
+                  <Users size={16} />
+                  <span className="text-xs">{list.collaborators.length}</span>
+                </div>
+              )}
             </div>
             <div className="flex items-center gap-0.5 sm:gap-1 opacity-100 sm:opacity-0 sm:group-hover:opacity-100 transition-opacity flex-shrink-0" onClick={handleDeleteClick}>
               <button
diff --git a/components/ListDetailView.tsx b/components/ListDetailView.tsx
index 1ab2eb3..b0d7786 100644
--- a/components/ListDetailView.tsx
+++ b/components/ListDetailView.tsx
@@ -1,11 +1,14 @@
 'use client'
 
 import { useState, useCallback, useMemo, useEffect } from 'react'
+import { Share2 } from 'lucide-react'
 import ItemCard from './ItemCard'
 import SearchBar from './SearchBar'
 import FilterPanel from './FilterPanel'
 import SearchResults from './SearchResults'
 import EmptyState from './EmptyState'
+import ShareListModal from './ShareListModal'
+import PermissionBadge from './PermissionBadge'
 import { searchItems, getItemsByFilter } from '@/lib/actions'
 import { useSearch, useFilters, useScrollPosition } from '@/hooks'
 
@@ -34,12 +37,38 @@ interface ItemWithList extends Item {
 interface ListDetailViewProps {
   listId: string
   initialItems: Item[]
+  permission?: 'owner' | 'editor' | 'viewer'
+  canShare?: boolean
+  listTitle?: string
+  ownerId?: string
+  ownerName?: string | null
+  ownerEmail?: string
+  collaborators?: Array<{
+    id: string
+    permission: 'editor' | 'viewer'
+    user: {
+      id: string
+      name: string | null
+      email: string
+    }
+  }>
 }
 
-export default function ListDetailView({ listId, initialItems }: ListDetailViewProps) {
+export default function ListDetailView({ 
+  listId, 
+  initialItems, 
+  permission, 
+  canShare = false,
+  listTitle = '',
+  ownerId = '',
+  ownerName = null,
+  ownerEmail = '',
+  collaborators = []
+}: ListDetailViewProps) {
   const [searchResults, setSearchResults] = useState<ItemWithList[]>([])
   const [isSearching, setIsSearching] = useState(false)
   const [filteredItems, setFilteredItems] = useState<Item[]>(initialItems)
+  const [isShareModalOpen, setIsShareModalOpen] = useState(false)
 
   // Use scroll position preservation hook
   useScrollPosition({ key: `list-${listId}` })
@@ -118,6 +147,26 @@ export default function ListDetailView({ listId, initialItems }: ListDetailViewP
 
   return (
     <div className="space-y-6">
+      {/* Permission Badge and Share Button */}
+      {(permission || canShare) && (
+        <div className="flex items-center justify-between gap-4">
+          {permission && (
+            <div>
+              <PermissionBadge permission={permission} />
+            </div>
+          )}
+          {canShare && (
+            <button
+              onClick={() => setIsShareModalOpen(true)}
+              className="ml-auto flex items-center gap-2 px-4 py-2 bg-blue-500 hover:bg-blue-600 active:bg-blue-700 text-white rounded-lg transition-colors text-sm font-medium"
+            >
+              <Share2 size={16} />
+              Share
+            </button>
+          )}
+        </div>
+      )}
+
       {/* Search Bar */}
       <SearchBar 
         onSearch={handleSearchCallback}
@@ -181,6 +230,19 @@ export default function ListDetailView({ listId, initialItems }: ListDetailViewP
           )}
         </div>
       )}
+
+      {/* Share Modal */}
+      <ShareListModal
+        isOpen={isShareModalOpen}
+        onClose={() => setIsShareModalOpen(false)}
+        listId={listId}
+        listTitle={listTitle}
+        isOwner={permission === 'owner'}
+        ownerId={ownerId}
+        ownerName={ownerName}
+        ownerEmail={ownerEmail}
+        initialCollaborators={collaborators}
+      />
     </div>
   )
 }