diff --git a/eslint.config.mjs b/eslint.config.mjs
index 7797007..ab1841c 100644
--- a/eslint.config.mjs
+++ b/eslint.config.mjs
@@ -23,6 +23,47 @@ const APP_DESIGN_SYSTEM_FILES = [
   "src/app/(app)/**/*.{ts,tsx}",
   "src/components/**/*.{ts,tsx}",
 ];
+const UI_ARCHITECTURE_FILES = [
+  "src/app/(app)/**/*.{ts,tsx}",
+  "src/components/auth/**/*.{ts,tsx}",
+  "src/components/doclist/**/*.{ts,tsx}",
+  "src/components/documents/DocumentUploader.tsx",
+  "src/components/documents/DocumentSelectionModal.tsx",
+  "src/components/documents/DexieMigrationModal.tsx",
+  "src/components/documents/ZoomControl.tsx",
+  "src/components/player/**/*.{ts,tsx}",
+  "src/components/reader/**/*.{ts,tsx}",
+];
+const COMPUTE_CORE_IMPORT_PATTERNS = [
+  {
+    group: [
+      "@openreader/compute-core/*",
+      "!@openreader/compute-core/local-runtime",
+      "!@openreader/compute-core/types",
+      "!@openreader/compute-core/api-contracts",
+    ],
+    message:
+      "Use '@openreader/compute-core' root imports for light APIs. Allowed subpaths are '@openreader/compute-core/local-runtime', '@openreader/compute-core/types', and '@openreader/compute-core/api-contracts'.",
+  },
+];
+const UI_ARCHITECTURE_IMPORT_PATHS = [
+  {
+    name: "@/components/formPrimitives",
+    message:
+      "Use '@/components/ui' primitives in migrated app surfaces; formPrimitives is a compatibility shim.",
+  },
+  {
+    name: "@/components/ui/buttonPrimitives",
+    message:
+      "Use '@/components/ui' button exports in migrated app surfaces; buttonPrimitives is a compatibility shim.",
+  },
+  {
+    name: "@headlessui/react",
+    importNames: ["Button", "Input"],
+    message:
+      "Use app UI Button/Input primitives; Headless UI should be reserved for structural primitives such as Menu, Listbox, Popover, Dialog, and Transition.",
+  },
+];
 const RESTRICTED_APP_CLASS_PATTERNS = [
   {
     selector: "Literal[value=/(bg|text|border|ring)-(gray|slate|zinc|neutral|stone|red|orange|yellow|amber|lime|green|emerald|teal|cyan|sky|blue|indigo|violet|purple|fuchsia|pink|rose)-\\d/]",
@@ -83,18 +124,7 @@ const eslintConfig = [
       "no-restricted-imports": [
         "error",
         {
-          patterns: [
-            {
-              group: [
-                "@openreader/compute-core/*",
-                "!@openreader/compute-core/local-runtime",
-                "!@openreader/compute-core/types",
-                "!@openreader/compute-core/api-contracts",
-              ],
-              message:
-                "Use '@openreader/compute-core' root imports for light APIs. Allowed subpaths are '@openreader/compute-core/local-runtime', '@openreader/compute-core/types', and '@openreader/compute-core/api-contracts'.",
-            },
-          ],
+          patterns: COMPUTE_CORE_IMPORT_PATTERNS,
         },
       ],
     },
@@ -105,6 +135,18 @@ const eslintConfig = [
       "no-restricted-syntax": ["error", ...RESTRICTED_APP_CLASS_PATTERNS],
     },
   },
+  {
+    files: UI_ARCHITECTURE_FILES,
+    rules: {
+      "no-restricted-imports": [
+        "error",
+        {
+          paths: UI_ARCHITECTURE_IMPORT_PATHS,
+          patterns: COMPUTE_CORE_IMPORT_PATTERNS,
+        },
+      ],
+    },
+  },
   {
     files: ["src/app/api/**/*.ts", "src/lib/server/**/*.ts"],
     rules: {
diff --git a/src/components/auth/UserMenu.tsx b/src/components/auth/UserMenu.tsx
index c6487d8..e771f3e 100644
--- a/src/components/auth/UserMenu.tsx
+++ b/src/components/auth/UserMenu.tsx
@@ -1,6 +1,5 @@
 'use client';
 
-import { Button } from '@headlessui/react';
 import Link from 'next/link';
 import { useAuthConfig } from '@/contexts/AuthRateLimitContext';
 import { useFeatureFlag } from '@/contexts/RuntimeConfigContext';
@@ -8,6 +7,7 @@ import { useAuthSession } from '@/hooks/useAuthSession';
 import { getAuthClient } from '@/lib/client/auth-client';
 import { useRouter } from 'next/navigation';
 import { UserIcon } from '@/components/icons/Icons';
+import { IconButton, buttonClass } from '@/components/ui';
 
 type UserMenuVariant = 'toolbar' | 'sidebar';
 
@@ -55,15 +55,15 @@ export function UserMenu({
     return (
       <div className={`flex gap-2 ${className}`}>
         <Link href="/signin">
-          <Button className="inline-flex items-center rounded-md bg-surface border border-line px-2 py-1 text-xs font-medium text-foreground hover:bg-accent-wash focus:outline-none focus:ring-2 focus:ring-accent-line focus:ring-offset-2 transform transition duration-base ease-standard hover:text-accent">
+          <span className={buttonClass({ variant: 'secondary', size: 'sm' })}>
             Connect
-          </Button>
+          </span>
         </Link>
         {enableUserSignups && (
           <Link href="/signup">
-            <Button className="inline-flex items-center rounded-md bg-accent px-2 py-1 text-xs font-medium text-background hover:bg-secondary-accent focus:outline-none focus:ring-2 focus:ring-accent-line focus:ring-offset-2 transform transition duration-base ease-standard">
+            <span className={buttonClass({ variant: 'primary', size: 'sm' })}>
               Create account
-            </Button>
+            </span>
           </Link>
         )}
       </div>
@@ -95,17 +95,17 @@ export function UserMenu({
         {session.user.email || 'Account'}
       </span>
 
-      <Button
+      <IconButton
         onClick={handleDisconnectAccount}
-        className="inline-flex items-center text-foreground text-xs hover:text-accent transform transition duration-base ease-standard"
         title="Disconnect account"
+        aria-label="Disconnect account"
       >
         <svg xmlns="http://www.w3.org/2000/svg" width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round">
           <path d="M9 21H5a2 2 0 0 1-2-2V5a2 2 0 0 1 2-2h4"></path>
           <polyline points="16 17 21 12 16 7"></polyline>
           <line x1="21" y1="12" x2="9" y2="12"></line>
         </svg>
-      </Button>
+      </IconButton>
     </div>
   );
 }
diff --git a/src/components/doclist/views/DocumentTile.tsx b/src/components/doclist/views/DocumentTile.tsx
index 30eb152..e74cabc 100644
--- a/src/components/doclist/views/DocumentTile.tsx
+++ b/src/components/doclist/views/DocumentTile.tsx
@@ -2,10 +2,10 @@
 
 import Link from 'next/link';
 import { useDrag, useDrop, type DragSourceMonitor } from 'react-dnd';
-import { Button } from '@headlessui/react';
 import { PDFIcon, EPUBIcon, FileIcon } from '@/components/icons/Icons';
 import type { DocumentListDocument, IconSize } from '@/types/documents';
 import { DocumentPreview } from '@/components/doclist/DocumentPreview';
+import { IconButton } from '@/components/ui';
 import { useDocumentSelection } from '../dnd/DocumentSelectionContext';
 import { DND_DOCUMENT, documentIdentityKey, type DocumentDragItem } from '../dnd/dndTypes';
 
@@ -185,9 +185,10 @@ export function DocumentTile({
           </span>
         </Link>
         {showDeleteButton && (
-          <Button
+          <IconButton
             onClick={() => onDelete(doc)}
-            className={`inline-flex items-center justify-center text-soft hover:text-accent hover:bg-surface focus:outline-none transition-colors duration-base ${TRASH_BTN_CLASSES[iconSize]}`}
+            size="xs"
+            className={TRASH_BTN_CLASSES[iconSize]}
             aria-label={`Delete ${doc.name}`}
           >
             <svg className={TRASH_ICON_CLASSES[iconSize]} fill="none" stroke="currentColor" viewBox="0 0 24 24">
@@ -198,7 +199,7 @@ export function DocumentTile({
                 d="M19 7l-.867 12.142A2 2 0 0116.138 21H7.862a2 2 0 01-1.995-1.858L5 7m5 4v6m4-6v6m1-10V4a1 1 0 00-1-1h-4a1 1 0 00-1 1v3M4 7h16"
               />
             </svg>
-          </Button>
+          </IconButton>
         )}
       </div>
     </div>
diff --git a/src/components/doclist/views/ListView.tsx b/src/components/doclist/views/ListView.tsx
index fecd45e..d729b72 100644
--- a/src/components/doclist/views/ListView.tsx
+++ b/src/components/doclist/views/ListView.tsx
@@ -3,7 +3,6 @@
 import Link from 'next/link';
 import { useEffect } from 'react';
 import { useDrag, useDrop } from 'react-dnd';
-import { Button } from '@headlessui/react';
 import type {
   DocumentListDocument,
   SortBy,
@@ -11,6 +10,7 @@ import type {
 } from '@/types/documents';
 import { PDFIcon, EPUBIcon, FileIcon } from '@/components/icons/Icons';
 import { formatDocumentSize } from '@/components/doclist/formatSize';
+import { IconButton } from '@/components/ui';
 import { useDocumentSelection } from '../dnd/DocumentSelectionContext';
 import { DND_DOCUMENT, documentIdentityKey, type DocumentDragItem } from '../dnd/dndTypes';
 
@@ -156,12 +156,12 @@ function DocRow({
       <span className="px-2 text-[11px] text-soft tabular-nums">
         {formatDate(doc.lastModified)}
       </span>
-      <Button
+      <IconButton
         onClick={(e: React.MouseEvent) => {
           e.stopPropagation();
           onDeleteDoc(doc);
         }}
-        className="h-7 w-7 flex items-center justify-center text-soft hover:text-accent hover:bg-accent-wash rounded transition duration-base ease-standard"
+        size="sm"
         aria-label={`Delete ${doc.name}`}
       >
         <svg className="w-3.5 h-3.5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
@@ -172,7 +172,7 @@ function DocRow({
             d="M19 7l-.867 12.142A2 2 0 0116.138 21H7.862a2 2 0 01-1.995-1.858L5 7m5 4v6m4-6v6m1-10V4a1 1 0 00-1-1h-4a1 1 0 00-1 1v3M4 7h16"
           />
         </svg>
-      </Button>
+      </IconButton>
     </div>
   );
 }
diff --git a/src/components/reader/ReaderSidebarShell.tsx b/src/components/reader/ReaderSidebarShell.tsx
index 5ceeaed..89a5ae3 100644
--- a/src/components/reader/ReaderSidebarShell.tsx
+++ b/src/components/reader/ReaderSidebarShell.tsx
@@ -4,7 +4,7 @@ import { Fragment, type ReactNode } from 'react';
 import { Transition } from '@headlessui/react';
 import { XCircleIcon } from '@/components/icons/Icons';
 import { useReaderSidebarBounds } from '@/hooks/useReaderSidebarBounds';
-import { buttonClass } from '@/components/ui/buttonPrimitives';
+import { IconButton } from '@/components/ui';
 
 interface ReaderSidebarShellProps {
   isOpen: boolean;
@@ -77,19 +77,15 @@ export function ReaderSidebarShell({
               </div>
               <div className="flex items-center gap-1 shrink-0">
                 {headerActions}
-                <button
-                  type="button"
+                <IconButton
                   onClick={onClose}
                   aria-label="Close"
                   title="Close"
-                  className={buttonClass({
-                    variant: 'secondary',
-                    size: 'icon',
-                    className: 'h-8 w-8 text-soft',
-                  })}
+                  tone="surface"
+                  className="text-soft"
                 >
                   <XCircleIcon className="w-4 h-4" />
-                </button>
+                </IconButton>
               </div>
             </div>
 
diff --git a/src/components/reader/SegmentsSidebar.tsx b/src/components/reader/SegmentsSidebar.tsx
index 49cf99e..aeacbdf 100644
--- a/src/components/reader/SegmentsSidebar.tsx
+++ b/src/components/reader/SegmentsSidebar.tsx
@@ -8,7 +8,7 @@ import toast from 'react-hot-toast';
 import { useTTS } from '@/contexts/TTSContext';
 import { useConfig } from '@/contexts/ConfigContext';
 import { RefreshIcon, InfoIcon } from '@/components/icons/Icons';
-import { buttonClass } from '@/components/ui/buttonPrimitives';
+import { buttonClass } from '@/components/ui';
 import { ReaderSidebarShell } from '@/components/reader/ReaderSidebarShell';
 import { compareSegmentLocators, locatorGroupKey, locatorIdentityKey } from '@/lib/shared/tts-locator';
 import { buildSegmentKey, buildSegmentKeyPrefix } from '@/lib/shared/tts-segment-plan';